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Systems pharmacology is the application of systems biology principles to the field of pharmacology . It seeks to understand how drugs affect the human body as a single complex biological system .
Instead of considering the effect of a drug to be the result of one specific drug-protein interaction , systems pharmacology considers the effect of a drug to be the outcome of the network of interactions a drug may have. In 1992, an article on systems medicine and pharmacology was published in China. [ 1 ] Networks of interaction may include chemical-protein, protein–protein , genetic, signalling and physiological (at cellular, tissue, organ and whole body levels). Systems pharmacology uses bioinformatics and statistics techniques to integrate and interpret these networks.
Systems pharmacology can be applied to drug safety studies as a complement to pharmacoepidemiology . [ 2 ]
This pharmacology -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Systems_pharmacology |
Computers are used to generate numeric models for the purpose of describing or displaying complex interaction among multiple variables within a system. The complexity of the system arises from the stochastic (probabilistic) nature of the events, rules for the interaction of the elements and the difficulty in perceiving the behavior of the systems as a whole with the passing of time.
One of the most notable video games to incorporate systems simulation is Sim City , [ 1 ] which simulates the multiple systems of a functioning city including but not limited to: electricity, water, sewage, public transportation, population growth, social interactions (including, but not limited to jobs, education and emergency response).
This systems -related article is a stub . You can help Wikipedia by expanding it .
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Systems_simulation |
In astronomy , a syzygy ( / ˈ s ɪ z ə dʒ i / SIZ -ə-jee ; from Ancient Greek συζυγία (suzugía) ' union, yoking ' , expressing the sense of σύν ( syn- "together") and ζυγ- ( zug- "a yoke") [ 1 ] [ 2 ] )
is a roughly straight-line configuration of three or more celestial bodies in a gravitational system. [ 3 ]
The word is often used in reference to the Sun , Earth , and either the Moon or a planet , where the latter is in conjunction or opposition . Solar and lunar eclipses occur at times of syzygy, as do transits and occultations . The term is often applied when the Sun and Moon are in conjunction ( new moon ) or in opposition ( full moon ). [ 4 ]
A syzygy sometimes results in an occultation, transit, or an eclipse.
As electromagnetic rays are affected by gravitation, when they pass by a heavy mass they are bent. As a result, the heavy mass acts as a form of gravitational lens. If the light source, the gravitating mass and the observer stand in a line, one sees what is termed an Einstein ring.
A syzygy causes the fortnightly phenomena of spring tides . At the new and full moon, the Sun and Moon are in syzygy. Their tidal forces act to reinforce each other, and the ocean both rises higher and falls lower than the average. [ 6 ] Tidal variations can also be measured in the Earth's crust , and these Earth tide influences may affect the frequency of earthquakes .
The word syzygy is often used to describe interesting configurations of astronomical objects in general. For example, one such case occurred on March 21, 1894, around 23:00 GMT , when Mercury transited the Sun as would have been seen from Venus, and Mercury and Venus both simultaneously transited the Sun as seen from Saturn .
On June 3, 2014, the Curiosity rover on Mars observed the planet Mercury transiting the Sun , marking the first time a planetary transit has been observed from a celestial body besides Earth . [ 7 ]
The term is also used to describe situations when all the planets are on the same side of the Sun although they are not necessarily in a straight line, such as on March 10, 1982. [ 8 ]
Because the orbits of all the planets in the Solar System (as well as the Moon) are inclined by only a few degrees, they always appear very near the ecliptic in our sky. Therefore, although an apparent planetary alignment known as a planetary parade may appear as a line (actually, a great arc ), the planets are not necessarily aligned in space. | https://en.wikipedia.org/wiki/Syzygy_(astronomy) |
The Sz.-Nagy dilation theorem (proved by Béla Szőkefalvi-Nagy ) states that every contraction T {\displaystyle T} on a Hilbert space H {\displaystyle H} has a unitary dilation U {\displaystyle U} to a Hilbert space K {\displaystyle K} , containing H {\displaystyle H} , with
where P H {\displaystyle P_{H}} is the projection from K {\displaystyle K} onto H {\displaystyle H} .
Moreover, such a dilation is unique (up to unitary equivalence) when one assumes K is minimal, in the sense that the linear span of ⋃ n ∈ N U n H {\displaystyle \bigcup \nolimits _{n\in \mathbb {N} }\,U^{n}H} is dense in K . When this minimality condition holds, U is called the minimal unitary dilation of T .
For a contraction T (i.e., ( ‖ T ‖ ≤ 1 {\displaystyle \|T\|\leq 1} ), its defect operator D T is defined to be the (unique) positive square root D T = ( I - T*T ) ½ . In the special case that S is an isometry, D S* is a projector and D S =0 , hence the following is an Sz. Nagy unitary dilation of S with the required polynomial functional calculus property:
Returning to the general case of a contraction T , every contraction T on a Hilbert space H has an isometric dilation, again with the calculus property, on
given by
Substituting the S thus constructed into the previous Sz.-Nagy unitary dilation for an isometry S , one obtains a unitary dilation for a contraction T :
The Schaffer form of a unitary Sz. Nagy dilation can be viewed as a beginning point for the characterization of all unitary dilations, with the required property, for a given contraction.
A generalisation of this theorem, by Berger, Foias and Lebow, shows that if X is a spectral set for T , and
is a Dirichlet algebra , then T has a minimal normal δX dilation, of the form above. A consequence of this is that any operator with a simply connected spectral set X has a minimal normal δX dilation.
To see that this generalises Sz.-Nagy's theorem, note that contraction operators have the unit disc D as a spectral set, and that normal operators with spectrum in the unit circle δ D are unitary. | https://en.wikipedia.org/wiki/Sz.-Nagy's_dilation_theorem |
In chemical graph theory , the Szeged index is a topological index of a molecule , used in biochemistry . The Szeged index, introduced by Iván Gutman , [ 1 ] generalizes the concept of the Wiener index introduced by Harry Wiener .
The Szeged index of a connected graph G is defined as
If e is an edge of G connecting vertices u and v , then we write e = uv or e = vu . For e = u v ∈ E ( G ) {\displaystyle e=uv\in E(G)} , let n 1 ( e ∣ G ) {\displaystyle n_{1}(e\mid G)} and n 2 ( e ∣ G ) {\displaystyle n_{2}(e\mid G)} be respectively the number of vertices of G lying closer to vertex u than to vertex v and the number of vertices of G lying closer to vertex v than to vertex u .
Szeged index plays an important role in information theory . One way to measure a network structure is through the so-called topological indices . Szeged index has been shown to correlate well with numerous biological and physicochemical properties.
The Szeged index of Dendrimer Nanostar of the following figure can be calculated by [ 2 ] | https://en.wikipedia.org/wiki/Szeged_index |
In mathematical analysis , the Szegő limit theorems describe the asymptotic behaviour of the determinants of large Toeplitz matrices . [ 1 ] [ 2 ] [ 3 ] They were first proved by Gábor Szegő .
Let w {\displaystyle w} be a Fourier series with Fourier coefficients c k {\displaystyle c_{k}} , relating to each other as
such that the n × n {\displaystyle n\times n} Toeplitz matrices T n ( w ) = ( c k − l ) 0 ≤ k , l ≤ n − 1 {\displaystyle T_{n}(w)=\left(c_{k-l}\right)_{0\leq k,l\leq n-1}} are Hermitian , i.e., if T n ( w ) = T n ( w ) ∗ {\displaystyle T_{n}(w)=T_{n}(w)^{\ast }} then c − k = c k ¯ {\displaystyle c_{-k}={\overline {c_{k}}}} . Then both w {\displaystyle w} and eigenvalues ( λ m ( n ) ) 0 ≤ m ≤ n − 1 {\displaystyle (\lambda _{m}^{(n)})_{0\leq m\leq n-1}} are real-valued and the determinant of T n ( w ) {\displaystyle T_{n}(w)} is given by
Under suitable assumptions the Szegő theorem states that
for any function F {\displaystyle F} that is continuous on the range of w {\displaystyle w} . In particular
such that the arithmetic mean of λ ( n ) {\displaystyle \lambda ^{(n)}} converges to the integral of w {\displaystyle w} . [ 4 ]
The first Szegő theorem [ 1 ] [ 3 ] [ 5 ] states that, if right-hand side of ( 1 ) holds and w ≥ 0 {\displaystyle w\geq 0} , then
holds for w > 0 {\displaystyle w>0} and w ∈ L 1 {\displaystyle w\in L_{1}} . The RHS of ( 2 ) is the geometric mean of w {\displaystyle w} (well-defined by the arithmetic-geometric mean inequality ).
Let c ^ k {\displaystyle {\widehat {c}}_{k}} be the Fourier coefficient of log w ∈ L 1 {\displaystyle \log w\in L^{1}} , written as
The second (or strong) Szegő theorem [ 1 ] [ 6 ] states that, if w ≥ 0 {\displaystyle w\geq 0} , then | https://en.wikipedia.org/wiki/Szegő_limit_theorems |
In arithmetic combinatorics , Szemerédi's theorem is a result concerning arithmetic progressions in subsets of the integers. In 1936, Erdős and Turán conjectured [ 1 ] that every set of integers A with positive natural density contains a k -term arithmetic progression for every k . Endre Szemerédi proved the conjecture in 1975.
A subset A of the natural numbers is said to have positive upper density if
Szemerédi's theorem asserts that a subset of the natural numbers with positive upper density contains an arithmetic progression of length k for all positive integers k .
An often-used equivalent finitary version of the theorem states that for every positive integer k and real number δ ∈ ( 0 , 1 ] {\displaystyle \delta \in (0,1]} , there exists a positive integer
such that every subset of {1, 2, ..., N } of size at least δ N {\displaystyle \delta N} contains an arithmetic progression of length k .
Another formulation uses the function r k ( N ), the size of the largest subset of {1, 2, ..., N } without an arithmetic progression of length k . Szemerédi's theorem is equivalent to the asymptotic bound
That is, r k ( N ) grows less than linearly with N .
Van der Waerden's theorem , a precursor of Szemerédi's theorem, was proved in 1927.
The cases k = 1 and k = 2 of Szemerédi's theorem are trivial. The case k = 3, known as Roth's theorem , was established in 1953 by Klaus Roth [ 2 ] via an adaptation of the Hardy–Littlewood circle method . Szemerédi [ 3 ] next proved the case k = 4 through combinatorics. Using an approach similar to the one he used for the case k = 3, Roth [ 4 ] gave a second proof for k = 4 in 1972.
The general case was settled in 1975, also by Szemerédi, [ 5 ] who developed an ingenious and complicated extension of his previous combinatorial argument for k = 4 (called "a masterpiece of combinatorial reasoning" by Erdős [ 6 ] ). Several other proofs are now known, the most important being those by Hillel Furstenberg [ 7 ] [ 8 ] in 1977, using ergodic theory , and by Timothy Gowers [ 9 ] in 2001, using both Fourier analysis and combinatorics while also introducing what is now called the Gowers norm . Terence Tao has called the various proofs of Szemerédi's theorem a " Rosetta stone " for connecting disparate fields of mathematics. [ 10 ]
It is an open problem to determine the exact growth rate of r k ( N ). The best known general bounds are
where n = ⌈ log k ⌉ {\displaystyle n=\lceil \log k\rceil } . The lower bound is due to O'Bryant [ 11 ] building on the work of Behrend , [ 12 ] Rankin , [ 13 ] and Elkin. [ 14 ] [ 15 ] The upper bound is due to Gowers. [ 9 ]
For small k , there are tighter bounds than the general case. When k = 3, Bourgain , [ 16 ] [ 17 ] Heath-Brown, [ 18 ] Szemerédi, [ 19 ] Sanders , [ 20 ] and Bloom [ 21 ] established progressively smaller upper bounds, and Bloom and Sisask then proved the first bound that broke the so-called "logarithmic barrier". [ 22 ] The current best bounds are
respectively due to O'Bryant, [ 11 ] and Bloom and Sisask [ 23 ] (the latter built upon the breakthrough result of Kelley and Meka, [ 24 ] who obtained the same upper bound, with "1/9" replaced by "1/12").
For k = 4, Green and Tao [ 25 ] [ 26 ] proved that
For k=5 in 2023 and k≥5 in 2024 Leng, Sah and Sawhney proved in preprints [ 27 ] [ 28 ] [ 29 ] that:
A multidimensional generalization of Szemerédi's theorem was first proven by Hillel Furstenberg and Yitzhak Katznelson using ergodic theory. [ 30 ] Timothy Gowers , [ 31 ] Vojtěch Rödl and Jozef Skokan [ 32 ] [ 33 ] with Brendan Nagle, Rödl, and Mathias Schacht , [ 34 ] and Terence Tao [ 35 ] provided combinatorial proofs.
Alexander Leibman and Vitaly Bergelson [ 36 ] generalized Szemerédi's to polynomial progressions: If A ⊂ N {\displaystyle A\subset \mathbb {N} } is a set with positive upper density and p 1 ( n ) , p 2 ( n ) , … , p k ( n ) {\displaystyle p_{1}(n),p_{2}(n),\dotsc ,p_{k}(n)} are integer-valued polynomials such that p i ( 0 ) = 0 {\displaystyle p_{i}(0)=0} , then there are infinitely many u , n ∈ Z {\displaystyle u,n\in \mathbb {Z} } such that u + p i ( n ) ∈ A {\displaystyle u+p_{i}(n)\in A} for all 1 ≤ i ≤ k {\displaystyle 1\leq i\leq k} . Leibman and Bergelson's result also holds in a multidimensional setting.
The finitary version of Szemerédi's theorem can be generalized to finite additive groups including vector spaces over finite fields . [ 37 ] The finite field analog can be used as a model for understanding the theorem in the natural numbers. [ 38 ] The problem of obtaining bounds in the k=3 case of Szemerédi's theorem in the vector space F 3 n {\displaystyle \mathbb {F} _{3}^{n}} is known as the cap set problem.
The Green–Tao theorem asserts the prime numbers contain arbitrarily long arithmetic progressions. It is not implied by Szemerédi's theorem because the primes have density 0 in the natural numbers. As part of their proof, Ben Green and Tao introduced a "relative" Szemerédi theorem which applies to subsets of the integers (even those with 0 density) satisfying certain pseudorandomness conditions. A more general relative Szemerédi theorem has since been given by David Conlon , Jacob Fox , and Yufei Zhao . [ 39 ] [ 40 ]
The Erdős conjecture on arithmetic progressions would imply both Szemerédi's theorem and the Green–Tao theorem. | https://en.wikipedia.org/wiki/Szemerédi's_theorem |
In extremal graph theory , Szemerédi’s regularity lemma states that a graph can be partitioned into a bounded number of parts so that the edges between parts are regular (in the sense defined below). The lemma shows that certain properties of random graphs can be applied to dense graphs like counting the copies of a given subgraph within graphs. Endre Szemerédi proved the lemma over bipartite graphs for his theorem on arithmetic progressions in 1975 and for general graphs in 1978. Variants of the lemma use different notions of regularity and apply to other mathematical objects like hypergraphs .
To state Szemerédi's regularity lemma formally, we must formalize what the edge distribution between parts behaving 'almost randomly' really means. By 'almost random', we're referring to a notion called ε -regularity . To understand what this means, we first state some definitions. In what follows G is a graph with vertex set V .
Definition 1. Let X , Y be disjoint subsets of V . The edge density of the pair ( X , Y ) is defined as:
where E ( X , Y ) denotes the set of edges having one end vertex in X and one in Y .
We call a pair of parts ε -regular if, whenever you take a large subset of each part, their edge density isn't too far off the edge density of the pair of parts. Formally,
Definition 2. For ε > 0 , a pair of vertex sets X and Y is called ε -regular , if for all subsets A ⊆ X , B ⊆ Y satisfying | A | ≥ ε| X | , | B | ≥ ε| Y | , we have
The natural way to define an ε -regular partition should be one where each pair of parts is ε -regular. However, some graphs, such as the half graphs , require many pairs of partitions (but a small fraction of all pairs) to be irregular. [ 1 ] So we shall define ε -regular partitions to be one where most pairs of parts are ε -regular.
Definition 3. A partition of V {\displaystyle V} into k {\displaystyle k} sets P = { V 1 , … , V k } {\displaystyle {\mathcal {P}}=\{V_{1},\ldots ,V_{k}\}} is called an ε {\displaystyle \varepsilon } -regular partition if
Now we can state the lemma:
Szemerédi's regularity Lemma. For every ε > 0 and positive integer m there exists an integer M such that if G is a graph with at least M vertices, there exists an integer k in the range m ≤ k ≤ M and an ε -regular partition of the vertex set of G into k sets.
The bound M for the number of parts in the partition of the graph given by the proofs of Szemeredi's regularity lemma is very large, given by a O(ε −5 ) -level iterated exponential of m . At one time it was hoped that the true bound was much smaller, which would have had several useful applications. However Gowers (1997) found examples of graphs for which M does indeed grow very fast and is at least as large as a ε −1/16 -level iterated exponential of m . [ 2 ]
We shall find an ε-regular partition for a given graph following an algorithm:
We apply a technique called the energy increment argument to show that this process stops after a bounded number of steps. To do this, we define a measure which must increase by a certain amount in each step, but it's bounded above and thus cannot increase indefinitely. This measure is called 'energy' as it's an L 2 {\displaystyle L^{2}} quantity.
Definition 4. Let U , W be subsets of V . Set | V | = n {\displaystyle |V|=n} . The energy of the pair ( U , W ) is defined as:
For partitions P U = { U 1 , … , U k } {\displaystyle {\mathcal {P}}_{U}=\{U_{1},\ldots ,U_{k}\}} of U and P W = { W 1 , … , W l } {\displaystyle {\mathcal {P}}_{W}=\{W_{1},\ldots ,W_{l}\}} of W , we define the energy to be the sum of the energies between each pair of parts:
Finally, for a partition P = { V 1 , … , V k } {\displaystyle {\mathcal {P}}=\{V_{1},\ldots ,V_{k}\}} of V , define the energy of P {\displaystyle {\mathcal {P}}} to be q ( P , P ) {\displaystyle q({\mathcal {P}},{\mathcal {P}})} . Specifically,
Note that energy is between 0 and 1 because edge density is bounded above by 1:
Now, we start by proving that energy does not decrease upon refinement.
Lemma 1. (Energy is nondecreasing under partitioning) For any partitions P U {\displaystyle {\mathcal {P}}_{U}} and P W {\displaystyle {\mathcal {P}}_{W}} of vertex sets U {\displaystyle U} and W {\displaystyle W} , q ( P U , P W ) ≥ q ( U , W ) {\displaystyle q({\mathcal {P}}_{U},{\mathcal {P}}_{W})\geq q(U,W)} .
Proof: Let P U = { U 1 , … , U k } {\displaystyle {\mathcal {P}}_{U}=\{U_{1},\ldots ,U_{k}\}} and P W = { W 1 , … , W l } {\displaystyle {\mathcal {P}}_{W}=\{W_{1},\ldots ,W_{l}\}} . Choose vertices x {\displaystyle x} uniformly from U {\displaystyle U} and y {\displaystyle y} uniformly from W {\displaystyle W} , with x {\displaystyle x} in part U i {\displaystyle U_{i}} and y {\displaystyle y} in part W j {\displaystyle W_{j}} . Then define the random variable Z = d ( U i , W j ) {\displaystyle Z=d(U_{i},W_{j})} . Let us look at properties of Z {\displaystyle Z} . The expectation is
The second moment is
By convexity, E [ Z 2 ] ≥ E [ Z ] 2 {\displaystyle \mathbb {E} [Z^{2}]\geq \mathbb {E} [Z]^{2}} . Rearranging, we get that q ( P U , P W ) ≥ q ( U , W ) {\displaystyle q({\mathcal {P}}_{U},{\mathcal {P}}_{W})\geq q(U,W)} for all U , W {\displaystyle U,W} . ◻ {\displaystyle \square }
If each part of P {\displaystyle {\mathcal {P}}} is further partitioned, the new partition is called a refinement of P {\displaystyle {\mathcal {P}}} . Now, if P = { V 1 , … , V m } {\displaystyle {\mathcal {P}}=\{V_{1},\ldots ,V_{m}\}} , applying Lemma 1 to each pair ( V i , V j ) {\displaystyle (V_{i},V_{j})} proves that for every refinement P ′ {\displaystyle {\mathcal {P'}}} of P {\displaystyle {\mathcal {P}}} , q ( P ′ ) ≥ q ( P ) {\displaystyle q({\mathcal {P'}})\geq q({\mathcal {P}})} . Thus the refinement step in the algorithm doesn't lose any energy.
Lemma 2. (Energy boost lemma) If ( U , W ) {\displaystyle (U,W)} is not ε {\displaystyle \varepsilon } -regular as witnessed by U 1 ⊂ U , W 1 ⊂ W {\displaystyle U_{1}\subset U,W_{1}\subset W} , then,
Proof: Define Z {\displaystyle Z} as above. Then,
But observe that | Z − E [ Z ] | = | d ( U 1 , W 1 ) − d ( U , W ) | {\displaystyle |Z-\mathbb {E} [Z]|=|d(U_{1},W_{1})-d(U,W)|} with probability | U 1 | | U | | W 1 | | W | {\displaystyle {\frac {|U_{1}|}{|U|}}{\frac {|W_{1}|}{|W|}}} (corresponding to x ∈ U 1 {\displaystyle x\in U_{1}} and y ∈ W 1 {\displaystyle y\in W_{1}} ), so
Now we can prove the energy increment argument, which shows that energy increases substantially in each iteration of the algorithm.
Lemma 3 (Energy increment lemma) If a partition P = { V 1 , … , V k } {\displaystyle {\mathcal {P}}=\{V_{1},\ldots ,V_{k}\}} of V ( G ) {\displaystyle V(G)} is not ε {\displaystyle \varepsilon } -regular, then there exists a refinement Q {\displaystyle {\mathcal {Q}}} of P {\displaystyle {\mathcal {P}}} where every V i {\displaystyle V_{i}} is partitioned into at most 2 k {\displaystyle 2^{k}} parts such that
Proof: For all ( i , j ) {\displaystyle (i,j)} such that ( V i , V j ) {\displaystyle (V_{i},V_{j})} is not ε {\displaystyle \varepsilon } -regular, find A i , j ⊂ V i {\displaystyle A^{i,j}\subset V_{i}} and A j , i ⊂ V j {\displaystyle A^{j,i}\subset V_{j}} that witness irregularity (do this simultaneously for all irregular pairs). Let Q {\displaystyle {\mathcal {Q}}} be a common refinement of P {\displaystyle {\mathcal {P}}} by A i , j {\displaystyle A^{i,j}} 's. Each V i {\displaystyle V_{i}} is partitioned into at most 2 k {\displaystyle 2^{k}} parts as desired. Then,
Where Q V i {\displaystyle {\mathcal {Q}}_{V_{i}}} is the partition of V i {\displaystyle V_{i}} given by Q {\displaystyle {\mathcal {Q}}} . By Lemma 1, the above quantity is at least
Since V i {\displaystyle V_{i}} is cut by A i , j {\displaystyle A^{i,j}} when creating Q {\displaystyle {\mathcal {Q}}} , so Q V i {\displaystyle {\mathcal {Q}}_{V_{i}}} is a refinement of { A i , j , V i ∖ A i , j } {\displaystyle \{A^{i,j},V_{i}\backslash A^{i,j}\}} . By lemma 2, the above sum is at least
But the second sum is at least ε 5 {\displaystyle \varepsilon ^{5}} since P {\displaystyle {\mathcal {P}}} is not ε {\displaystyle \varepsilon } -regular, so we deduce the desired inequality. ◻ {\displaystyle \square }
Now, starting from any partition, we can keep applying Lemma 3 as long as the resulting partition isn't ε {\displaystyle \varepsilon } -regular. But in each step energy increases by ε 5 {\displaystyle \varepsilon ^{5}} , and it's bounded above by 1. Then this process can be repeated at most ε − 5 {\displaystyle \varepsilon ^{-5}} times, before it terminates and we must have an ε {\displaystyle \varepsilon } -regular partition.
If we have enough information about the regularity of a graph, we can count the number of copies of a specific subgraph within the graph up to small error.
Graph Counting Lemma. Let H {\displaystyle H} be a graph with V ( H ) = [ k ] {\displaystyle V(H)=[k]} , and let ε > 0 {\displaystyle \varepsilon >0} . Let G {\displaystyle G} be an n {\displaystyle n} -vertex graph with vertex sets V 1 , … , V k ⊆ V ( G ) {\displaystyle V_{1},\dots ,V_{k}\subseteq V(G)} such that ( V i , V j ) {\displaystyle (V_{i},V_{j})} is ε {\displaystyle \varepsilon } -regular whenever { i , j } ∈ E ( H ) {\displaystyle \{i,j\}\in E(H)} . Then, the number of labeled copies of H {\displaystyle H} in G {\displaystyle G} is within e ( H ) ε | V 1 | ⋯ | V k | {\displaystyle e(H)\varepsilon |V_{1}|\cdots |V_{k}|} of
This can be combined with Szemerédi's regularity lemma to prove the Graph removal lemma . The graph removal lemma can be used to prove Roth's Theorem on Arithmetic Progressions , [ 3 ] and a generalization of it, the hypergraph removal lemma , can be used to prove Szemerédi's theorem . [ 4 ]
The graph removal lemma generalizes to induced subgraphs , by considering edge edits instead of only edge deletions. This was proved by Alon, Fischer, Krivelevich, and Szegedy in 2000. [ 5 ] However, this required a stronger variation of the regularity lemma.
Szemerédi's regularity lemma does not provide meaningful results in sparse graphs . Since sparse graphs have subconstant edge densities, ε {\displaystyle \varepsilon } -regularity is trivially satisfied. Even though the result seems purely theoretical, some attempts [ 6 ] [ 7 ] have been made to use the regularity method as compression technique for large graphs.
A different notion of regularity was introduced by Frieze and Kannan, known as the weak regularity lemma. [ 8 ] This lemma defines a weaker notion of regularity than that of Szemerédi which uses better bounds and can be used in efficient algorithms.
Given a graph G = ( V , E ) {\displaystyle G=(V,E)} , a partition of its vertices P = { V 1 , … , V k } {\displaystyle {\mathcal {P}}=\{V_{1},\ldots ,V_{k}\}} is said to be Frieze-Kannan ϵ {\displaystyle \epsilon } -regular if for any pair of sets S , T ⊆ V {\displaystyle S,T\subseteq V} :
The weak regularity lemma for graphs states that every graph has a weak ϵ {\displaystyle \epsilon } -regular partition into at most 4 ϵ − 2 {\displaystyle 4^{\epsilon ^{-2}}} parts.
This notion can be extended to graphons by defining a stepping operator. Given a graphon W {\displaystyle W} and a partition P {\displaystyle {\mathcal {P}}} of [ 0 , 1 ] {\displaystyle [0,1]} , we can define W P {\displaystyle W_{\mathcal {P}}} as a step-graphon with steps given by P {\displaystyle {\mathcal {P}}} and values given by averaging W {\displaystyle W} over each step.
A partition P {\displaystyle {\mathcal {P}}} is weak ϵ {\displaystyle \epsilon } -regular if:
The weak regularity lemma for graphons states that every graphon has a weak ϵ {\displaystyle \epsilon } -regular partition into at most 4 ϵ − 2 {\displaystyle 4^{\epsilon ^{-2}}} parts. As with Szemerédi's regularity lemma, the weak regularity also induces a counting lemma.
One of the initial motivations for the development of the weak regularity lemma was the search for an efficient algorithm for estimating the maximum cut in a dense graph . [ 8 ] It has been shown that approximating the max-cut problem beyond 16/17 is NP-hard , [ 9 ] however an algorithmic version of the weak regularity lemma gives an efficient algorithm for approximating the max-cut for dense graphs within an ϵ n 2 {\displaystyle \epsilon n^{2}} additive error. [ 8 ] These ideas have been further developed into efficient sampling algorithms for estimating max-cut in dense graphs. [ 10 ]
The smaller bounds of the weak regularity lemma allow for efficient algorithms to find an ϵ {\displaystyle \epsilon } -regular partition. [ 11 ] Graph regularity has further been used in various area of theoretical computer science , such as matrix multiplication [ 12 ] and communication complexity . [ 13 ]
The strong regularity lemma is a stronger variation of the regularity lemma proven by Alon , Fischer, Krivelevich , and Szegedy in 2000. [ 5 ] Intuitively, it provides information between non-regular pairs and could be applied to prove the induced graph removal lemma .
For any infinite sequence of constants ϵ 0 ≥ ϵ 1 ≥ . . . > 0 {\displaystyle \epsilon _{0}\geq \epsilon _{1}\geq ...>0} , there exists an integer M {\displaystyle M} such that for any graph G {\displaystyle G} , we can obtain two (equitable) partitions P {\displaystyle {\mathcal {P}}} and Q {\displaystyle {\mathcal {Q}}} such that the following properties are satisfied:
We apply the regularity lemma repeatedly to prove the stronger version. A rough outline:
We start with P 0 {\displaystyle {\mathcal {P}}_{0}} be an ϵ 0 {\displaystyle \epsilon _{0}} regular partition of G {\displaystyle G} with ≤ M ( ϵ 0 ) {\displaystyle \leq M(\epsilon _{0})} parts. Here M ( t ) {\displaystyle M(t)} corresponds to the bound of parts in regularity lemma when ϵ = t {\displaystyle \epsilon =t} .
Now for i = 0 , 1 , ⋯ {\displaystyle i=0,1,\cdots } , we set P i + 1 {\displaystyle {\mathcal {P_{i+1}}}} to be an ϵ | P i | {\displaystyle \epsilon _{|P_{i}|}} regular refinement of P i {\displaystyle {\mathcal {P_{i}}}} with ≤ M ( ϵ | P i | ) | P i | {\displaystyle \leq M(\epsilon _{|P_{i}|})|{\mathcal {P}}_{i}|} parts. By the energy increment argument, q ( P i + 1 ) ≥ q ( P i ) {\displaystyle q({\mathcal {P}}_{i+1})\geq q({\mathcal {P}}_{i})} . Since the energy is bounded in [ 0 , 1 ] {\displaystyle [0,1]} , there must be some i ≤ 1 / ϵ 0 + 1 {\displaystyle i\leq 1/\epsilon _{0}+1} such that q ( P i + 1 ) − q ( P i ) < ϵ 0 {\displaystyle q({\mathcal {P}}_{i+1})-q({\mathcal {P}}_{i})<\epsilon _{0}} . We return ( P i , P i + 1 ) {\displaystyle ({\mathcal {P}}_{i},{\mathcal {P}}_{i+1})} as ( P , Q ) {\displaystyle ({\mathcal {P}},{\mathcal {Q}})} .
By our choice of P i + 1 , {\displaystyle {\mathcal {P}}_{i+1},} the regular and refinement conditions hold. The energy condition holds trivially. Now we argue for the number of parts. We use induction to show that ∀ i {\displaystyle \forall i} , there exists M i {\displaystyle M_{i}} such that | P i | ≤ M i {\displaystyle |{\mathcal {P}}_{i}|\leq M_{i}} . By setting M 0 = M ( ϵ 0 ) {\displaystyle M_{0}=M(\epsilon _{0})} , we have | P 0 | ≤ M 0 {\displaystyle |{\mathcal {P}}_{0}|\leq M_{0}} . Note that when | P i | ≤ M i {\displaystyle |P_{i}|\leq M_{i}} , | P i + 1 | ≤ M ( ϵ | P i | ) | P i | ≤ M ( ϵ | M i | ) M i {\displaystyle |P_{i+1}|\leq M(\epsilon _{|P_{i}|})|{\mathcal {P}}_{i}|\leq M(\epsilon _{|M_{i}|})M_{i}} , so we could set M i + 1 = M ( ϵ | M i | ) M i {\displaystyle M_{i+1}=M(\epsilon _{|M_{i}|})M_{i}} and the statement is true for i + 1 {\displaystyle i+1} . By setting M = max i ≤ 1 / ϵ 0 + 2 M i {\displaystyle M=\max _{i\leq 1/\epsilon _{0}+2}M_{i}} , we have | P | , | Q | ≤ M . {\displaystyle |P|,|Q|\leq M.}
A partition is equitable if the sizes of any two sets differ by at most 1 {\displaystyle 1} . By equitizing in each round of iteration, the proof of regularity lemma could be accustomed to prove the equitable version of regularity lemma. And by replacing the regularity lemma with its equitable version, the proof above could prove the equitable version of strong regularity lemma where P {\displaystyle {\mathcal {P}}} and Q {\displaystyle {\mathcal {Q}}} are equitable partitions.
For any infinite sequence of constants ϵ 0 ≥ ϵ 1 ≥ . . . > 0 {\displaystyle \epsilon _{0}\geq \epsilon _{1}\geq ...>0} , there exists δ > 0 {\displaystyle \delta >0} such that there exists a partition P = V 1 , . . . , V k {\displaystyle {\mathcal {P}}={V_{1},...,V_{k}}} and subsets W i ⊂ V i {\displaystyle W_{i}\subset V_{i}} for each i {\displaystyle i} where the following properties are satisfied:
The corollary explores deeper the small energy increment. It gives us a partition together with subsets with large sizes from each part, which are pairwise regular. In addition, the density between the corresponding subset pairs differs "not much" from the density between the corresponding parts.
We'll only prove the weaker result where the second condition only requires ( W i , W j ) {\displaystyle (W_{i},W_{j})} to be ϵ | P | {\displaystyle \epsilon _{|{\mathcal {P}}|}} -regular for 1 ≤ i < j ≤ k {\displaystyle 1\leq i<j\leq k} . The full version can be proved by picking more subsets from each part that are mostly pairwise regular and combine them together.
Let r = ϵ 0 3 / 20 {\displaystyle r=\epsilon _{0}^{3}/20} . We apply the strong regularity lemma to find equitable P {\displaystyle {\mathcal {P}}} that is a r {\displaystyle r} regular partition and equitable Q {\displaystyle {\mathcal {Q}}} that is a r / | P | 4 {\displaystyle r/|P|^{4}} regular refinement of P {\displaystyle {\mathcal {P}}} , such that q ( Q ) − q ( P ) ≤ r {\displaystyle q({\mathcal {Q}})-q({\mathcal {P}})\leq r} and | Q | ≤ M {\displaystyle |{\mathcal {Q}}|\leq M} .
Now assume that P = { V 1 , ⋯ , V k } {\displaystyle P=\{V_{1},\cdots ,V_{k}\}} , we randomly pick a vertex v i {\displaystyle v_{i}} from each V i {\displaystyle V_{i}} and let W i {\displaystyle W_{i}} to be the set that contains v i {\displaystyle v_{i}} in Q {\displaystyle {\mathcal {Q}}} . We argue that the subsets W i {\displaystyle W_{i}} satisfy all the conditions with probability > 0 {\displaystyle >0} .
By setting δ = 1 2 M {\displaystyle \delta ={\frac {1}{2M}}} the first condition is trivially true since Q {\displaystyle {\mathcal {Q}}} is an equitable partition. Since at most r | P | 4 ( n 2 ) ≤ ϵ 0 | V i | | V j | 3 | P | 2 {\displaystyle {\frac {r}{|P|^{4}}}{\binom {n}{2}}\leq \epsilon _{0}{\frac {|V_{i}||V_{j}|}{3|P|^{2}}}} vertex pairs live between irregular pairs in Q {\displaystyle {\mathcal {Q}}} , the probability that the pair W i {\displaystyle W_{i}} and W j {\displaystyle W_{j}} is irregular ≤ 1 3 | P | 2 {\displaystyle \leq {\frac {1}{3|P|^{2}}}} , by union bound, the probability that at least one pair W i {\displaystyle W_{i}} , W i {\displaystyle W_{i}} is irregular ≤ 1 / 3 {\displaystyle \leq 1/3} . Note that
r ≥ q ( Q ) − q ( P ) = ∑ i , j | V i | | V j | n 2 E | d ( W i , W j ) − d ( V i , V j ) | 2 ≥ ∑ i , j 1 4 | P | 2 E | d ( W i , W j ) − d ( V i , V j ) | 2 = 1 4 | P | 2 E ∑ i , j | d ( W i , W j ) − d ( V i , V j ) | 2 {\displaystyle {\begin{aligned}r&\geq q({\mathcal {Q}})-q({\mathcal {P}})\\&=\sum _{i,j}{\frac {|V_{i}||V_{j}|}{n^{2}}}\mathbb {E} |d(W_{i},W_{j})-d(V_{i},V_{j})|^{2}\\&\geq \sum _{i,j}{\frac {1}{4|P|^{2}}}\mathbb {E} |d(W_{i},W_{j})-d(V_{i},V_{j})|^{2}\\&={\frac {1}{4|P|^{2}}}\mathbb {E} \sum _{i,j}|d(W_{i},W_{j})-d(V_{i},V_{j})|^{2}\end{aligned}}}
So by Markov's inequality P ( ∑ i , j | d ( W i , W j ) − d ( V i , V j ) | 2 ≥ 8 | P | 2 r ) ≤ 1 / 2 {\displaystyle P(\sum _{i,j}|d(W_{i},W_{j})-d(V_{i},V_{j})|^{2}\geq 8|P|^{2}r)\leq 1/2} , so with probability ≥ 1 / 2 {\displaystyle \geq 1/2} , at most ϵ 0 | P | 2 {\displaystyle \epsilon _{0}|P|^{2}} pairs could have d ( W i , W j ) − d ( V i , V j ) ≥ ϵ 0 {\displaystyle d(W_{i},W_{j})-d(V_{i},V_{j})\geq \epsilon _{0}} . By union bound, the probability that all conditions hold ≥ 1 − 1 / 2 − 1 / 3 > 0 {\displaystyle \geq 1-1/2-1/3>0} .
Szemerédi (1975) first introduced a weaker version of this lemma, restricted to bipartite graphs, in order to prove Szemerédi's theorem , [ 14 ] and in ( Szemerédi 1978 ) he proved the full lemma. [ 15 ] Extensions of the regularity method to hypergraphs were obtained by Rödl and his collaborators [ 16 ] [ 17 ] [ 18 ] and Gowers . [ 19 ] [ 20 ]
János Komlós , Gábor Sárközy and Endre Szemerédi later (in 1997) proved in the blow-up lemma [ 21 ] [ 22 ] that the regular pairs in Szemerédi regularity lemma behave like complete bipartite graphs under the correct conditions. The lemma allowed for deeper exploration into the nature of embeddings of large sparse graphs into dense graphs.
The first constructive version was provided by Alon, Duke, Lefmann, Rödl and Yuster . [ 23 ] Subsequently, Frieze and Kannan gave a different version and extended it to hypergraphs. [ 24 ] They later produced a different construction due to Alan Frieze and Ravi Kannan that uses singular values of matrices. [ 25 ] One can find more efficient non-deterministic algorithms, as formally detailed in Terence Tao 's blog [ 26 ] and implicitly mentioned in various papers. [ 27 ] [ 28 ] [ 29 ]
An inequality of Terence Tao extends the Szemerédi regularity lemma, by revisiting it from the perspective of probability theory and information theory instead of graph theory. [ 30 ] Terence Tao has also provided a proof of the lemma based on spectral theory, using the adjacency matrices of graphs. [ 31 ]
It is not possible to prove a variant of the regularity lemma in which all pairs of partition sets are regular. Some graphs, such as the half graphs , require many pairs of partitions (but a small fraction of all pairs) to be irregular. [ 1 ]
It is a common variant in the definition of an ε {\displaystyle \varepsilon } -regular partition to require that the vertex sets all have the same size, while collecting the leftover vertices in an "error"-set V 0 {\displaystyle V_{0}} whose size is at most an ε {\displaystyle \varepsilon } -fraction of the size of the vertex set of G {\displaystyle G} .
A stronger variation of the regularity lemma was proven by Alon, Fischer, Krivelevich, and Szegedy while proving the induced graph removal lemma. This works with a sequence of ε {\displaystyle \varepsilon } instead of just one, and shows that there exists a partition with an extremely regular refinement, where the refinement doesn't have too large of an energy increment.
Szemerédi's regularity lemma can be interpreted as saying that the space of all graphs is totally bounded (and hence precompact ) in a suitable metric (the cut distance ). Limits in this metric can be represented by graphons ; another version of the regularity lemma simply states that the space of graphons is compact . [ 32 ] | https://en.wikipedia.org/wiki/Szemerédi_regularity_lemma |
The Szemerédi–Trotter theorem is a mathematical result in the field of Discrete geometry . It asserts that given n points and m lines in the Euclidean plane , the number of incidences ( i.e. , the number of point-line pairs, such that the point lies on the line) is
O ( n 2 / 3 m 2 / 3 + n + m ) . {\displaystyle O\left(n^{2/3}m^{2/3}+n+m\right).}
This bound cannot be improved, except in terms of the implicit constants in its big O notation . An equivalent formulation of the theorem is the following. Given n points and an integer k ≥ 2 , the number of lines which pass through at least k of the points is
O ( n 2 k 3 + n k ) . {\displaystyle O\left({\frac {n^{2}}{k^{3}}}+{\frac {n}{k}}\right).}
The original proof of Endre Szemerédi and William T. Trotter was somewhat complicated, using a combinatorial technique known as cell decomposition . [ 1 ] [ 2 ] Later, László Székely discovered a much simpler proof using the crossing number inequality for graphs . [ 3 ] This method has been used to produce the explicit upper bound 2.5 n 2 / 3 m 2 / 3 + n + m {\displaystyle 2.5n^{2/3}m^{2/3}+n+m} on the number of incidences. [ 4 ] Subsequent research has lowered the constant, coming from the crossing lemma, from 2.5 to 2.44. [ 5 ] On the other hand, this bound would not remain valid if one replaces the coefficient 2.44 with 0.42. [ 6 ]
The Szemerédi–Trotter theorem has a number of consequences, including Beck's theorem in incidence geometry and the Erdős-Szemerédi sum-product problem in additive combinatorics .
We may discard the lines which contain two or fewer of the points, as they can contribute at most 2 m incidences to the total number. Thus we may assume that every line contains at least three of the points.
If a line contains k points, then it will contain k − 1 line segments which connect two consecutive points along the line. Because k ≥ 3 after discarding the two-point lines, it follows that k − 1 ≥ k /2 , so the number of these line segments on each line is at least half the number of incidences on that line. Summing over all of the lines, the number of these line segments is again at least half the total number of incidences. Thus if e denotes the number of such line segments, it will suffice to show that
e = O ( n 2 / 3 m 2 / 3 + n + m ) . {\displaystyle e=O\left(n^{2/3}m^{2/3}+n+m\right).}
Now consider the graph formed by using the n points as vertices, and the e line segments as edges. Since each line segment lies on one of m lines, and any two lines intersect in at most one point, the crossing number of this graph is at most the number of points where two lines intersect, which is at most m ( m − 1)/2 . The crossing number inequality implies that either e ≤ 7.5 n , or that m ( m − 1)/2 ≥ e 3 / 33.75 n 2 . In either case e ≤ 3.24( nm ) 2/3 + 7.5 n , giving the desired bound
Since every pair of points can be connected by at most one line, there can be at most n ( n − 1)/2 lines which can connect at k or more points, since k ≥ 2 . This bound will prove the theorem when k is small (e.g. if k ≤ C for some absolute constant C ). Thus, we need only consider the case when k is large, say k ≥ C .
Suppose that there are m lines that each contain at least k points. These lines generate at least mk incidences, and so by the first formulation of the Szemerédi–Trotter theorem, we have
m k = O ( n 2 / 3 m 2 / 3 + n + m ) , {\displaystyle mk=O\left(n^{2/3}m^{2/3}+n+m\right),}
and so at least one of the statements m k = O ( n 2 / 3 m 2 / 3 ) , m k = O ( n ) {\displaystyle mk=O(n^{2/3}m^{2/3}),mk=O(n)} , or m k = O ( m ) {\displaystyle mk=O(m)} is true. The third possibility is ruled out since k was assumed to be large, so we are left with the first two. But in either of these two cases, some elementary algebra will give the bound m = O ( n 2 / k 3 + n / k ) {\displaystyle m=O(n^{2}/k^{3}+n/k)} as desired.
Except for its constant, the Szemerédi–Trotter incidence bound cannot be improved. To see this, consider for any positive integer N ∈ N {\displaystyle N\in \mathbb {N} } a set of points on the integer lattice
P = { ( a , b ) ∈ Z 2 : 1 ≤ a ≤ N ; 1 ≤ b ≤ 2 N 2 } , {\displaystyle P=\left\{(a,b)\in \mathbb {Z} ^{2}\ :\ 1\leq a\leq N;1\leq b\leq 2N^{2}\right\},}
and a set of lines
L = { ( x , m x + b ) : m , b ∈ Z ; 1 ≤ m ≤ N ; 1 ≤ b ≤ N 2 } . {\displaystyle L=\left\{(x,mx+b)\ :\ m,b\in \mathbb {Z} ;1\leq m\leq N;1\leq b\leq N^{2}\right\}.}
Clearly, | P | = 2 N 3 {\displaystyle |P|=2N^{3}} and | L | = N 3 {\displaystyle |L|=N^{3}} . Since each line is incident to N points (i.e., once for each x ∈ { 1 , ⋯ , N } {\displaystyle x\in \{1,\cdots ,N\}} ), the number of incidences is N 4 {\displaystyle N^{4}} which matches the upper bound. [ 7 ]
One generalization of this result to arbitrary dimension, R d {\displaystyle \mathbb {R} ^{d}} , was found by Agarwal and Aronov. [ 8 ] Given a set of n points, S , and the set of m hyperplanes, H , which are each spanned by S , the number of incidences between S and H is bounded above by
O ( m 2 / 3 n d / 3 + n d − 1 ) , {\displaystyle O\left(m^{2/3}n^{d/3}+n^{d-1}\right),}
provided n d − 2 < m < n d {\displaystyle n^{d-2}<m<n^{d}} . Equivalently, the number of hyperplanes in H containing k or more points is bounded above by
O ( n d k 3 + n d − 1 k ) . {\displaystyle O\left({\frac {n^{d}}{k^{3}}}+{\frac {n^{d-1}}{k}}\right).}
A construction due to Edelsbrunner shows this bound to be asymptotically optimal. [ 9 ]
József Solymosi and Terence Tao obtained near sharp upper bounds for the number of incidences between points and algebraic varieties in higher dimensions, when the points and varieties satisfy "certain pseudo-line type axioms". Their proof uses the Polynomial Ham Sandwich Theorem . [ 10 ]
Many proofs of the Szemerédi–Trotter theorem over R {\displaystyle \mathbb {R} } rely in a crucial way on the topology of Euclidean space , so do not extend easily to other fields . e.g. the original proof of Szemerédi and Trotter; the polynomial partitioning proof and the crossing number proof do not extend to the complex plane .
Tóth successfully generalized the original proof of Szemerédi and Trotter to the complex plane C 2 {\displaystyle \mathbb {C} ^{2}} by introducing additional ideas. [ 11 ] This result was also obtained independently and through a different method by Zahl. [ 12 ] The implicit constant in the bound is not the same in the complex numbers : in Tóth's proof the constant can be taken to be 10 60 {\displaystyle 10^{60}} ; the constant is not explicit in Zahl's proof.
When the point set is a Cartesian product , Solymosi and Tardos show that the Szemerédi-Trotter bound holds using a much simpler argument. [ 13 ]
Let F {\displaystyle \mathbb {F} } be a field .
A Szemerédi-Trotter bound is impossible in general due to the following example, stated here in F p {\displaystyle \mathbb {F} _{p}} : let P = F p × F p {\displaystyle {\mathcal {P}}=\mathbb {F} _{p}\times \mathbb {F} _{p}} be the set of all p 2 {\displaystyle p^{2}} points and let L {\displaystyle {\mathcal {L}}} be the set of all p 2 {\displaystyle p^{2}} lines in the plane. Since each line contains p {\displaystyle p} points, there are p 3 {\displaystyle p^{3}} incidences. On the other hand, a Szemerédi-Trotter bound would give O ( ( p 2 ) 2 / 3 ( p 2 ) 2 / 3 + p 2 ) = O ( p 8 / 3 ) {\displaystyle O((p^{2})^{2/3}(p^{2})^{2/3}+p^{2})=O(p^{8/3})} incidences. This example shows that the trivial, combinatorial incidence bound is tight.
Bourgain , Katz and Tao [ 14 ] show that if this example is excluded, then an incidence bound that is an improvement on the trivial bound can be attained.
Incidence bounds over finite fields are of two types: (i) when at least one of the set of points or lines is `large' in terms of the characteristic of the field; (ii) both the set of points and the set of lines are `small' in terms of the characteristic.
Let q {\displaystyle q} be an odd prime power. Then Vinh [ 15 ] showed that the number of incidences between n {\displaystyle n} points and m {\displaystyle m} lines in F q 2 {\displaystyle \mathbb {F} _{q}^{2}} is at most
n m q + q n m . {\displaystyle {\frac {nm}{q}}+{\sqrt {qnm}}.}
Note that there is no implicit constant in this bound.
Let F {\displaystyle \mathbb {F} } be a field of characteristic p ≠ 2 {\displaystyle p\neq 2} . Stevens and de Zeeuw [ 16 ] show that the number of incidences between n {\displaystyle n} points and m {\displaystyle m} lines in F 2 {\displaystyle \mathbb {F} ^{2}} is
O ( m 11 / 15 n 11 / 15 ) {\displaystyle O\left(m^{11/15}n^{11/15}\right)}
under the condition m − 2 n 13 ≤ p 15 {\displaystyle m^{-2}n^{13}\leq p^{15}} in positive characteristic. (In a field of characteristic zero, this condition is not necessary.) This bound is better than the trivial incidence estimate when m 7 / 8 < n < m 8 / 7 {\displaystyle m^{7/8}<n<m^{8/7}} .
If the point set is a Cartesian Product, then they show an improved incidence bound: let P = A × B ⊆ F 2 {\displaystyle {\mathcal {P}}=A\times B\subseteq \mathbb {F} ^{2}} be a finite set of points with | A | ≤ | B | {\displaystyle |A|\leq |B|} and let L {\displaystyle {\mathcal {L}}} be a set of lines in the plane. Suppose that | A | | B | 2 ≤ | L | 3 {\displaystyle |A||B|^{2}\leq |{\mathcal {L}}|^{3}} and in positive characteristic that | A | | L | ≤ p 2 {\displaystyle |A||{\mathcal {L}}|\leq p^{2}} . Then the number of incidences between P {\displaystyle {\mathcal {P}}} and L {\displaystyle {\mathcal {L}}} is
O ( | A | 3 / 4 | B | 1 / 2 | L | 3 / 4 + | L | ) . {\displaystyle O\left(|A|^{3/4}|B|^{1/2}|{\mathcal {L}}|^{3/4}+|{\mathcal {L}}|\right).}
This bound is optimal. Note that by point-line duality in the plane, this incidence bound can be rephrased for an arbitrary point set and a set of lines having a Cartesian product structure.
In both the reals and arbitrary fields, Rudnev and Shkredov [ 17 ] show an incidence bound for when both the point set and the line set has a Cartesian product structure. This is sometimes better than the above bounds. | https://en.wikipedia.org/wiki/Szemerédi–Trotter_theorem |
The Sznajd model or United we stand, divided we fall ( USDF ) model is a sociophysics model introduced in 2000 [ 1 ] to gain fundamental understanding about opinion dynamics. The Sznajd model implements a phenomenon called social validation and thus extends the Ising spin model . In simple words, the model states:
For simplicity, one assumes that each individual i {\displaystyle i} has
an opinion S i which might be Boolean ( S i = − 1 {\displaystyle S_{i}=-1} for no , S i = 1 {\displaystyle S_{i}=1} for yes ) in its simplest formulation, which means that each individual either agrees or disagrees to a given question.
In the original 1D-formulation, each individual has exactly two neighbors just like beads on a bracelet . At each time step a pair of individual S i {\displaystyle S_{i}} and S i + 1 {\displaystyle S_{i+1}} is chosen at random to change their nearest neighbors' opinion (or: Ising spins ) S i − 1 {\displaystyle S_{i-1}} and S i + 2 {\displaystyle S_{i+2}} according to two dynamical rules:
In a closed (1 dimensional) community, two steady states are always reached, namely complete consensus (which is called ferromagnetic state in physics) or stalemate (the antiferromagnetic state ).
Furthermore, Monte Carlo simulations showed that these simple rules lead to complicated dynamics, in particular to a power law in the decision time distribution with an exponent of -1.5. [ 2 ]
The final (antiferromagnetic) state of alternating all-on and all-off is unrealistic to represent the behavior of a community. It would mean that the complete population uniformly changes their opinion from one time step to the next. For this reason an alternative dynamical rule was proposed. One possibility is that two spins S i {\displaystyle S_{i}} and S i + 1 {\displaystyle S_{i+1}} change their nearest neighbors according to the two following rules: [ 3 ]
In recent years, statistical physics has been accepted as modeling framework for phenomena outside the traditional physics. Fields as econophysics or sociophysics formed, and many quantitative analysts in finance are physicists. The Ising model in statistical physics has been a very important step in the history of studying collective (critical) phenomena . The Sznajd model is a simple but yet important variation of prototypical Ising system. [ 4 ]
In 2007, Katarzyna Sznajd-Weron has been recognized by the Young Scientist Award for Socio- and Econophysics of the Deutsche Physikalische Gesellschaft (German Physical Society) for an outstanding original contribution using physical methods to develop a better understanding of socio-economic problems. [ 5 ]
The Sznajd model belongs to the class of binary-state dynamics on a networks also referred to as Boolean networks . This class of systems includes the Ising model , the voter model and the q-voter model , the Bass diffusion model , threshold models and others. [ 6 ] The Sznajd model can be applied to various fields: | https://en.wikipedia.org/wiki/Sznajd_model |
In order theory , the Szpilrajn extension theorem (also called the order-extension principle ), proved by Edward Szpilrajn in 1930, [ 1 ] states that every partial order is contained in a total order . Intuitively, the theorem says that any method of comparing elements that leaves some pairs incomparable can be extended in such a way that every pair becomes comparable. The theorem is one of many examples of the use of the axiom of choice in the form of Zorn's lemma to find a maximal set with certain properties.
A binary relation R {\displaystyle R} on a set X {\displaystyle X} is formally defined as a set of ordered pairs ( x , y ) {\displaystyle (x,y)} of elements of X , {\displaystyle X,} and ( x , y ) ∈ R {\displaystyle (x,y)\in R} is often abbreviated as x R y . {\displaystyle xRy.}
A relation is reflexive if x R x {\displaystyle xRx} holds for every element x ∈ X ; {\displaystyle x\in X;} it is transitive if x R y and y R z {\displaystyle xRy{\text{ and }}yRz} imply x R z {\displaystyle xRz} for all x , y , z ∈ X ; {\displaystyle x,y,z\in X;} it is antisymmetric if x R y and y R x {\displaystyle xRy{\text{ and }}yRx} imply x = y {\displaystyle x=y} for all x , y ∈ X ; {\displaystyle x,y\in X;} and it is a connex relation if x R y or y R x {\displaystyle xRy{\text{ or }}yRx} holds for all x , y ∈ X . {\displaystyle x,y\in X.} A partial order is, by definition, a reflexive, transitive and antisymmetric relation. A total order is a partial order that is connex.
A relation R {\displaystyle R} is contained in another relation S {\displaystyle S} when all ordered pairs in R {\displaystyle R} also appear in S ; {\displaystyle S;} that is, x R y {\displaystyle xRy} implies x S y {\displaystyle xSy} for all x , y ∈ X . {\displaystyle x,y\in X.} The extension theorem states that every relation R {\displaystyle R} that is reflexive, transitive and antisymmetric (that is, a partial order) is contained in another relation S {\displaystyle S} which is reflexive, transitive, antisymmetric and connex (that is, a total order).
The theorem is proved in two steps. First, one shows that, if a partial order does not compare some two elements, it can be extended to an order with a superset of comparable pairs. A maximal partial order cannot be extended, by definition, so it follows from this step that a maximal partial order must be a total order. In the second step, Zorn's lemma is applied to find a maximal partial order that extends any given partial order.
For the first step, suppose that a given partial order does not compare x {\displaystyle x} and y {\displaystyle y} . Then the order is extended by first adding the pair x R y {\displaystyle xRy} to the relation, which may result in a non-transitive relation, and then restoring transitivity by adding all pairs q R p {\displaystyle qRp} such that q R x and y R p . {\displaystyle qRx{\text{ and }}yRp.} This produces a relation that is still reflexive, antisymmetric and transitive and that strictly contains the original one. It follows that if the partial orders extending R {\displaystyle R} are themselves partially ordered by extension, then any maximal element of this extension order must be a total order.
Next it is shown that the poset of partial orders extending R {\displaystyle R} , ordered by extension, has a maximal element. The existence of such a maximal element is proved by applying Zorn's lemma to this poset. Zorn's lemma states that a partial order in which every chain has an upper bound has a maximal element. A chain in this poset is a set of relations in which, for every two relations, one extends the other. An upper bound for a chain C {\displaystyle {\mathcal {C}}} can be found as the union of the relations in the chain, ⋃ C {\displaystyle \textstyle \bigcup {\mathcal {C}}} . This union is a relation that extends R {\displaystyle R} , since every element of C {\displaystyle {\mathcal {C}}} is a partial order having R {\displaystyle R} as a subset. Next, it is shown that ⋃ C {\displaystyle \textstyle \bigcup {\mathcal {C}}} is a transitive relation. Suppose that ( x , y ) {\displaystyle (x,y)} and ( y , z ) {\displaystyle (y,z)} are in ⋃ C , {\displaystyle \textstyle \bigcup {\mathcal {C}},} so that there exist S , T ∈ C {\displaystyle S,T\in {\mathcal {C}}} such that ( x , y ) ∈ S {\displaystyle (x,y)\in S} and ( y , z ) ∈ T {\displaystyle (y,z)\in T} . Because C {\displaystyle {\mathcal {C}}} is a chain, one of S {\displaystyle S} or T {\displaystyle T} must extend the other and contain both ( x , y ) {\displaystyle (x,y)} and ( y , z ) {\displaystyle (y,z)} ,
and by its transitivity it also contains ( x , z ) {\displaystyle (x,z)} , as does the union. Similarly, it can be shown that ⋃ C {\displaystyle \textstyle \bigcup {\mathcal {C}}} is antisymmetric. Thus, ⋃ C {\displaystyle \textstyle \bigcup {\mathcal {C}}} is an extension of R {\displaystyle R} , so it belongs to the poset of extensions of R {\displaystyle R} , and is an upper bound for C {\displaystyle {\mathcal {C}}} .
This argument shows that Zorn's lemma may be applied to the poset of extensions of R {\displaystyle R} , producing a maximal element Q {\displaystyle Q} . By the first step this maximal element must be a total order, completing the proof.
Some form of the axiom of choice is necessary in proving the Szpilrajn extension theorem. The extension theorem implies the axiom of finite choice : if the union of a family of finite sets is given the empty partial order, and this is extended to a total order, the extension defines a choice from each finite set, its minimum element in the total order. Although finite choice is a weak version of the axiom of choice, it is independent of Zermelo–Fraenkel set theory without choice. [ 2 ]
The Szpilrajn extension theorem together with another consequence of the axiom of choice, the principle that every total order has a cofinal well-order , can be combined to prove the full axiom of choice. With these assumptions, one can choose an element from any given set by extending its empty partial order, finding a cofinal well-order, and choosing the minimum element from that well-ordering. [ 3 ]
Arrow stated that every preorder (reflexive and transitive relation) can be extended to a total preorder (transitive and connex relation). [ 4 ] This claim was later proved by Hansson. [ 5 ] [ 6 ]
Suzumura proved that a binary relation can be extended to a total preorder if and only if it is Suzumura-consistent , which means that there is no cycle of elements such that x R y {\displaystyle xRy} for every pair of consecutive elements ( x , y ) , {\displaystyle (x,y),} and there is some pair of consecutive elements ( x , y ) {\displaystyle (x,y)} in the cycle for which y R x {\displaystyle yRx} does not hold. [ 6 ] | https://en.wikipedia.org/wiki/Szpilrajn_extension_theorem |
Szymon Suckewer (born April 10, 1938, in Warsaw) is a Polish-born American physicist, and professor emeritus at Princeton University . His primary fields of interest include X-ray lasers , and X-ray microscopy , particularly the generation of ultrashort laser pulses which are applied in plasma diagnostics .
Suckewer completed his degree in physics at the Lomonosov Moscow State University in 1962. He went on to receive a doctorate in physics from the Institute for Nuclear Research at the University of Warsaw in 1966. Suckewer received his habilitation in 1971 after which he was a lecturer at the Institute for Nuclear Research in Warsaw until 1975. In the same year, he went to Princeton University where he was the Senior Research Physicist in the Laboratory for Plasma Physics. From 1987 he worked as a professor and leader of a research team tasked to discover lasers with wavelengths of under 30 nm .
In 1984 Suckewer's team succeeded in creating a laser with a wavelength of 18.2 nm in plasma composed of carbon ions. [ 1 ] This was the first successful demonstration of laser operation in the soft X-ray range, almost at the same time as Peter Hagelstein's group at Lawrence Livermore National Laboratory succeeded in doing so too. For the next years, he tasked himself with the need for developing laser pulses of shorter wavelengths and inventing new techniques for producing high-intensity laser pulses.
In 1987 he managed to create ultrashort laser pulses within intensities of 2 × 10 18 {\textstyle 2\times 10^{18}} W × c m − 2 {\displaystyle W\times cm^{-2}} with a krypton-fluoride laser . With these pulses he managed to induce laser activity in lithium-ion plasma with wavelengths of 13.5 nm. [ 2 ] He continued working with laser pulses of even shorter wavelengths into the 21st century. This led Suckewer to investigate applications of his lasers in fields such as bioengineering. He applied his laser technologies in the carrying out of incision-free eye surgery as well as using high-intensity lasers in the safe and efficient removal of tattoos. [ 3 ]
In 1990 he received the American Physical Society's Award for Excellence in Plasma Physics Research. In 2005 Suckewer was presented the Willis E. Lamb Award for Laser Science and Quantum Optics. [ 4 ] In 2007 he received the Arthur L. Schawlow Award f or pioneering contributions to the generation of ultra-short wavelength and femtosecond lasers and X-ray laser microscopy . [ 5 ]
Suckewer is a fellow of the American Physical Society and the Optical Society of America and holds numerous patents in The United States Patent and Trademark Office . He transferred to professor emeritus status on July 1, 2016. [ 6 ]
attribution translated from de:Szymon Suckewer | https://en.wikipedia.org/wiki/Szymon_Suckewer |
The Szyszkowski Equation [ 1 ] has been used by Meissner and Michaels [ 2 ] to describe the decrease in surface tension of aqueous solutions of carboxylic acids , alcohols and esters at varying mole fractions. It describes the exponential decrease of the surface tension at low concentrations reasonably but should be used only at concentrations below 1 mole%. [ 3 ]
with:
The equation can be rearranged to be explicit in a :
This allows the direct calculation of that component specific parameter a from experimental data.
The equation can also be written as:
with:
The surface tension of pure water is dependent on temperature. At room temperature (298 K), it is equal to 71.97 mN/m [ 4 ]
Meissner and Michaels published the following a constants:
The following table and diagram show experimentally determined surface tensions in the mixture of water and propionic acid.
This example shows a good agreement between the published value a=2.6*10 −3 and the calculated value a=2.59*10 −3 at the smallest given mole fraction of 0.00861 but at higher concentrations of propionic acid the value of an increases considerably, showing deviations from the predicted value. | https://en.wikipedia.org/wiki/Szyszkowski_equation |
The Sérsic profile (or Sérsic model or Sérsic's law ) is a mathematical function that describes how the intensity I {\displaystyle I} of a galaxy varies with distance R {\displaystyle R} from its center. It is a generalization of de Vaucouleurs' law . José Luis Sérsic first published his law in 1963. [ 1 ]
The Sérsic profile has the form ln I ( R ) = ln I 0 − k R 1 / n , {\displaystyle \ln I(R)=\ln I_{0}-kR^{1/n},} or I ( R ) = I 0 exp ( − k R 1 / n ) , {\displaystyle I(R)=I_{0}\exp {\!\left(-kR^{1/n}\right)},}
where I 0 {\displaystyle I_{0}} is the intensity at R = 0 {\displaystyle R=0} .
The parameter n {\displaystyle n} , called the "Sérsic index," controls the degree of curvature of the profile (see figure). The smaller the value of n {\displaystyle n} , the less centrally concentrated the profile is and the shallower (steeper) the logarithmic slope at small (large) radii is. The equation for describing this is: d ln I d ln R = − ( k / n ) R 1 / n . {\displaystyle {\frac {\mathrm {d} \ln I}{\mathrm {d} \ln R}}=-(k/n)\ R^{1/n}.}
Today, it is more common to write this function in terms of the half-light radius , R e , and the intensity at that radius, I e , such that
where b n {\displaystyle b_{n}} is approximately 2 n − 1 / 3 {\displaystyle 2n-1/3} for n > 8 {\displaystyle n>8} . b n {\displaystyle b_{n}} can also be approximated to be 2 n − 1 / 3 + 4 405 n + 46 25515 n 2 + 131 1148175 n 3 − 2194697 30690717750 n 4 {\displaystyle 2n-1/3+{\frac {4}{405n}}+{\frac {46}{25515n^{2}}}+{\frac {131}{1148175n^{3}}}-{\frac {2194697}{30690717750n^{4}}}} , for n > 0.36 {\displaystyle n>0.36} . [ 2 ] It can be shown that b n {\displaystyle b_{n}} satisfies γ ( 2 n ; b n ) = 1 2 Γ ( 2 n ) {\textstyle \gamma (2n;b_{n})={\frac {1}{2}}\Gamma (2n)} , where Γ {\displaystyle \Gamma } and γ {\displaystyle \gamma } are respectively the Gamma function and lower incomplete Gamma function .
Many related expressions, in terms of the surface brightness, also exist. [ 3 ]
Most galaxies are fit by Sérsic profiles with indices in the range 1/2 < n < 10.
The best-fit value of n correlates with galaxy size and luminosity, such that bigger and brighter galaxies tend to be fit with larger n . [ 5 ] [ 6 ] Setting n = 4 gives the de Vaucouleurs profile : I ( R ) ∝ e − b R 1 / 4 {\displaystyle I(R)\propto e^{-bR^{1/4}}} which is a rough approximation of ordinary elliptical galaxies .
Setting n = 1 gives the exponential profile: I ( R ) ∝ e − b R {\displaystyle I(R)\propto e^{-bR}} which is a good approximation of spiral galaxy disks and a rough approximation of dwarf elliptical galaxies . The correlation of Sérsic index (i.e. galaxy concentration [ 7 ] ) with galaxy morphology is sometimes used in automated schemes to determine the Hubble type of distant galaxies. [ 8 ] Sérsic indices have also been shown to correlate with the mass of the supermassive black hole at the centers of the galaxies. [ 9 ]
Sérsic profiles can also be used to describe dark matter halos , where the Sérsic index correlates with halo mass. [ 10 ] [ 11 ]
The brightest elliptical galaxies often have low-density cores that are not well described by Sérsic's law. The core-Sérsic family of models was introduced [ 12 ] [ 13 ] [ 14 ] to describe such galaxies. Core-Sérsic models have an additional set of parameters that describe the core.
Dwarf elliptical galaxies and bulges often have point-like nuclei that are also not well described by Sérsic's law. These galaxies are often fit by a Sérsic model with an added central component representing the nucleus. [ 15 ] [ 16 ]
The Einasto profile is mathematically identical to the Sérsic profile, except that I {\displaystyle I} is replaced by ρ {\displaystyle \rho } , the volume density, and R {\displaystyle R} is replaced by r {\displaystyle r} , the internal (not projected on the sky) distance from the center. | https://en.wikipedia.org/wiki/Sérsic_profile |
Sødring & Co. was a Danish manufacturer of artificial mineral water and soft drinks based in Copenhagen , Denmark. The company was initially based in Rabeshave in Christianshavn , then at Kompagnistræde 20 from 1860 and finally at Østerbrogade 48 (now No. 70) in Østerbro from 1886. A branch in Aalborg was established in 1870 and from 1926 continued as an independent company under the name Sødring & Co.'sEftf. . The remainder of the company was in 1929 acquired by Rosenborg Brøndanstalt .
Christopher Hansen Sødring (1822–1881), a cousin of the painter Frederik Hansen Sødring , graduated in Applied Sciences from the College of Advanced Technology in 1847. He then worked first as an assistant for professor Johan Georg Forchhammer and then from 1849 as an assistant at Rosenborg Brøndanstalt . [ 1 ] He was the same year married to the actress Julie Sødring . [ 2 ]
On 19 November 1855. Sødring went into a partnership with Frederik Marchus, Count Knuth til Knuthenborg aimed at establishing and operating a mineral water factory in Copenhagen. Knut contributed with the needed premises in Rabeshave in Christianshavn as well as up to 6,000 Danish rigsdaler in funding for the necessary materials and installationswhile Sødring according to their contract would be responsible for the daily operations of the enterprise. [ 3 ]
The mineral water factory opened at Rabeshave the following year. The factory and the production methods had been approved by Sundhedskollegiet prior to its opening. It produced artificial mineral water with alleged medicinal properties based on extracts from natural springs. [ 4 ]
Sødring was from 1860 the sole owner of the company. In October 1860, Sødring & Co. relocated to new premises at Kompagnistræde 20 and steam power was at the same time introduced in the operations. [ 3 ] A second factory was opened in Aalborg in 1870.
Sødring's son Christian Sødring joined the company in 1872 and became its sole owner following his father's death in 1881. He constructed a new factory at Østerbrogade 47 in 1885–86. [ 5 ]
The Aalborg factory was on 1 January 1926 sold to Arnold Sørensen (born 18 July 1879) and continued by him under the name Sødring & Co's Edtf. (S'dring & Co.'s Successor). [ 5 ] In 1929, Sødring & Co.'s remaining activities in Copenhagen were acquired by Rosenborg Brøndanstalt . The activities of the two companies were the same year moved to a new factory at Bispevej 25in Bispebjerg . [ 4 ] The company was in 1950 headed by Svend Sørensen. Board members were professor Carl Faurholt, director L. Tholstrup and lawyer J. C. Bang. [ 6 ]
Brands and products owned by Sødring & Co. included: [ 7 ] | https://en.wikipedia.org/wiki/Sødring_&_Co. |
The Sørensen formol titration(SFT) invented by S. P. L. Sørensen in 1907 [ 1 ] is a titration of an amino acid with potassium hydroxide in the presence of formaldehyde . [ 2 ] It is used in the determination of protein content in samples. [ 3 ]
If instead of an amino acid an ammonium salt is used the reaction product with formaldehyde is hexamethylenetetramine :
The liberated hydrochloric acid is then titrated with the base and the amount of ammonium salt used can be determined.
With an amino acid the formaldehyde reacts with the amino group to form a methylene amino (R-N=CH 2 ) group. The remaining acidic carboxylic acid group can then again be titrated with base. [ 3 ]
Formol titration is one of the methods used in winemaking to measure yeast assimilable nitrogen needed by wine yeast in order to successfully complete fermentation . [ 4 ]
There has been some inaccuracies of the SFT caused by the differences in the basicity of the nitrogen in different amino acids which were explained by S. L. Jodidi. For instances, proline(an amino acid), histidine, and lysine yields too low values compared to the theory. Unlike alpha, monobasic (containing one amino group per molecule) amino acids, these amino (or imino) acids' nitrogens have inconstant basicity, which results in partial reaction with formaldehyde. [ 5 ]
In case of tyrosine, the actual results are too high due to the negative hydroxyl group (-OH), which acts as a base. This explanation is supported by the fact that phenylalanine can be accurately titrated. [ 5 ]
This article about analytical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Sørensen_formol_titration |
Sławomir Kołodziej ( Polish : [swaˈvɔmir kɔˈwɔd͡ʑɛj] ; born 12 March 1961, Bielsko-Biała ) is a Polish mathematician and Professor at the Faculty of Mathematics and Computer Science of the Jagiellonian University in Kraków . His research interests include complex analysis and theoretical mathematics including Monge–Ampère equation and plurisubharmonic functions . [ 1 ]
He graduated in mathematics from the Jagiellonian University and continued his scientific career there obtaining his doctoral degree written under the supervision of Józef Siciak in 1989. [ 2 ] He further received his habilitation in 1998 and the title of professor in 2005. He assumed the chair of Mathematical Analysis at the Institute of Mathematics and Computer Science of the Jagiellonian University. His doctoral students include Rafał Czyż and Sławomir Dinew . [ 2 ]
He published his scientific papers in such journals as Acta Mathematica , Proceedings of the American Mathematical Society , Indiana University Mathematics Journal , Michigan Mathematical Journal , Mathematische Zeitschrift and Advances in Mathematics . [ 3 ] [ 4 ] He serves as editor-in-chief of the Annales Polonici Mathematici . [ 5 ] He is a member of the Polish Mathematical Society (PTM), having served as the organization's deputy director between 2014–2016.
In 1998, he was awarded the Stanisław Zaremba Prize of the Polish Mathematical Society. [ 6 ] In 2014, he became the joint recipient of the Stefan Bergman Prize of the American Mathematical Society , together with Takeo Oshawa, "for his seminal contributions to the complex Monge-Ampère equation and pluripotential theory, including necessary and sufficient conditions for the existence of bounded solutions, stability, and other sharp estimates." [ 7 ] | https://en.wikipedia.org/wiki/Sławomir_Kołodziej |
T-1123 is a carbamate -based acetylcholinesterase inhibitor . It was investigated as a chemical warfare agent starting in 1940. It does not go through the blood-brain barrier due to the charge on quaternary nitrogen. The antidote is atropine . [ 3 ] T-1123 is a quaternary ammonium ion. A phenyl carbamate ester is bonded in the meta position to the nitrogen on a diethylmethyl amine. The chloride and methylsulfate salt of T-1123 is TL-1299 and TL-1317, respectively.
T-1123 can be produced from m-diethylaminophenol , methyl isocyanate and methyl iodide . First, m-diethylaminophenol is reacted with methyl isocyanate to produce a methylcarbamate. The resulting methylcarbamate is then reacted with methyl iodide to produce T-1123. [ 1 ]
This article about an organic compound is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T-1123 |
TMOS is a type of thermal sensor consisting in a micromachined thermally isolated transistor fabricated using CMOS -SOI( Silicon on Insulator ) MEMS( Micro electro-mechanical system ) technology. It has been developed in the last decade by the Technion - Israel Institute of Technology . [ 1 ] A thermal sensor is a device able to detect the thermal radiation emitted by an object located in the FOV (Field Of View) of the sensor. Infrared radiation ( IR ) striking the sensor produces a change in the temperature of the device that as a consequence generates an electric output signal proportional to the incident IR power. The sensor is able to approximate the temperature of the object radiating thanks to the information contained in the impinging radiation, assuming a black-body radiator based on the Stefan - Boltzmann law . [ 2 ] [ 3 ] TMOS detector has two important characteristics that make it different from others: it's an active and uncooled sensor. [ 4 ] [ 5 ]
A TMOS detector consists in a mosaic structure composed of several sub-pixels, which are electrically connected in parallel or in series or in a mixed combination, and are thermally isolated. In each sub-pixels the sensitive element is the TMOS sensor, that is suspended in vacuum, fabricated in CMOS - SOI technology and dry released. [ 6 ] [ 1 ] The mosaic structure includes: the pixel frame, the suspended transistor, that absorbs IR radiation and that could also be embedded in an absorbing IR membrane which determine the thermal capacitance of the sensor, and two folding arms that determine the sensor thermal conductivity .
TMOS fabrication is based on built - in masks and dry bulk micromachining. [ 1 ] [ 4 ] In TMOS fabrication to the standard CMOS - SOI technology, used to produce MOS transistor, is added a MEMS post process necessary to realize the folded arms and the suspension of the transistor. In standard CMOS process there are several metallization layers. In TMOS production the upper ones, made in aluminum or copper , are used as built - in masks. Both metals are not affected by the fluorine plasma , used to dry etch silicon and interlevel dielectrics . The use of built- in mask grants high alignment accuracy and resolution while reducing fabrication costs. [ 1 ] Final step of MEMS post process is the metal mask removal. This step is performed using standard wet etchant of aluminum or copper. [ 4 ]
At present 130 nm CMOS - SOI technology implemented on 8 inch wafers is used to produce TMOS sensors, employing wafer level processing in standard CMOS facilities, allowing cost reduction and large production volumes. [ 1 ] [ 4 ]
To improve sensor's performance and to protect it from the surrounding environment, especially from moisture, TMOS sensor are packaged under vacuum. The wafer-level production enables also wafer-level packaging, allowing the possibility to integrate optical windows and filters to improve their efficiency and widening their applicability. [ 1 ] [ 6 ] [ 7 ]
TMOS package contains two devices: one "active", that sense and is exposed to external radiation, and another one "blind", that is shielded from the outside through an aluminum mirror deposited on the package. [ 1 ] [ 8 ] [ 7 ]
The working principle of TMOS sensor provides that when thermal IR radiation is absorbed in the sensitive area heats up the TMOS causing a variation in its temperature. The temperature change produces a current or a voltage output signal proportional to the absorbed radiation.
TMOS performance depends on the transistor operating region and configuration: two terminals component, diode-like configuration, or three terminals component. Two terminals configuration is characterized by a grater thermal isolation. On the other side the three-terminal configuration has an higher internal voltage gain, given by the higher output resistivity. [ 7 ] [ 9 ]
Subthreshold region is the preferred one because avoids self heating effects and leads to higher sensitivity. Another reason to work in subthreshold region is that TMOS is an active device so requires a bias, however in this operating region the power consumption is lower than in other ones. [ 4 ] [ 10 ]
From a circuit point of view the produced TMOS signal can be modelled as a temperature dependent current source i s i g {\displaystyle i_{sig}} in parallel with the g m V g s {\displaystyle g_{m}V_{gs}} generator for small signal equivalent circuit. The value of i s i g {\displaystyle i_{sig}} is directly proportional to the drain source current variation with respect to TMOS operating temperature and to the temperature variation induced on the TMOS by the radiation absorbed from target object. This temperature has a direct dependence on the absorbing efficiency, the incident radiation power and on the thermal conductance of the sensor. [ 1 ] [ 7 ]
As mentioned in the previous section TMOS sensor package contains two devices, so the signal is read in a differential configuration. In this way the blind TMOS represents a reference relative to which the measure [ 10 ] is done. This configuration is useful because allows to reject the common mode signal and reduce self heating effects. [ 1 ] [ 10 ] [ 11 ]
The most important figure of merit of every kind of sensor is its responsivity. The responsivity is defined as the ratio between the output electrical parameters, both current or voltage, and the incident power on the detector. For TMOS sensor working in subthreshold region is 1,25 x 10 7 V/W. [ 1 ]
R = V o u t P i n {\displaystyle R={V_{out} \over P_{in}}}
TMOS sensitivity depends if the device is working in current or voltage mode. [ 11 ] In current mode a bias voltage is applied, the current increases by an increment, which is the signal current. In the first case sensitivity corresponds to the temperature coefficient of current TCC, that is inversely proportional to drain source current and directly proportional to the derivative of drain source current respect to the operating temperature. In contrast, at voltage mode, where a bias current is applied, the voltage decreases by an increment, which is the voltage signal. In voltage mode the sensitivity is the temperature coefficient of voltage TCV and is inversely proportional to the voltage bias and directly proportional to the derivative of voltage respect to temperature for the considered operating temperature. TCC values above 4%/K are achieved working in the subthreshold region. [ 1 ] [ 7 ]
TMOS thermal sensor presents several advantages compared to other thermal sensors such as thermopiles , bolometers , and also microbolometers , which have a very similar structure. Both thermopile and bolometer are passive detectors while microbolometers can also have an active structure, but the transistor used is a TFT ( thin-film transistor ).
The main advantages of using TMOS sensor are:
The main disadvantage is in the limited sensitivity compared with cooled IR detectors. Quantum photon detectors, for example, reach higher sensitivity but they need to work at cryogenic temperatures, so require a cooling system which consumes a lot of power.
Thermal sensors may have a lot of different applications. They respond to thermal IR radiation so their main application is for the production of thermal IR cameras . The other possible applications regard different fields from gas analysis, human detection for autonomous driving, presence detection, people counting, security system, or thermal monitoring during the fabrication process. [ 1 ]
Until now the main TMOS application has been as a high-sensitivity detector for motion and presence. [ 12 ] [ 13 ] When an object enters the FOV of the sensor there is a change in the radiation power that reaches the detector. This changing cause a temperature variation concerning the previous case and so coming from this difference the presence or motion is detected. This changing cause a temperature variation respect to previous case and so coming from this difference the presence or motion is detected. TMOS presence commercial products are available.
The low power consumption typical of the TMOS sensor means that it can also be powered by a common ion battery, making it suitable for IOT, wearable devices, mobile phone integration, and smart homes. [ 1 ]
The human body emitted radiation falls in the mid-infrared range peaking around 12 μm, so one of the applications of thermal sensors is fever detection. TMOS high performance, in terms of high sensitivity and low power consumption, and low costs fabrication process make it a promising candidate to implement contactless thermometer. [ 1 ] | https://en.wikipedia.org/wiki/T-MOS_thermal_sensor |
The T-Mobile 4G LTE CellSpot is a femtocell released by T-Mobile US in 2015. [ 1 ]
In 2016, Qualcomm announced a collaboration with T-Mobile and Nokia for the development of femtocells. [ 2 ]
The original version [ 3 ] and version 2 [ 4 ] have been released.
This article related to telephony is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T-Mobile_4G_LTE_CellSpot |
T-Mobile MDA (Mobile Digital Assistant) is a series of T-Mobile -branded phones manufactured by HTC Corporation of Taiwan :
This mobile technology –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T-Mobile_MDA |
T-Platforms was a Russian supercomputer company. Their main competitor was RSC Group.
Founded in 2002, T-Platforms Group was headquartered in Moscow , Russia with regional offices in Hanover , Germany , Hong Kong , China and Taipei , Taiwan . The company has implemented more than 300 integrated projects, six of which were included in the Top500 list of the world’s most powerful supercomputers. T-Platforms owns patents on a number of supercomputer technologies and electronic components. T-Platforms’ solutions are used for fundamental and applied research in various fields of science, including life sciences, physics, chemistry and mathematics, as well as for calculation-intensive tasks in engineering, computer graphics and many other disciplines. In 2011, HPCWire named Vsevolod Opanasenko, CEO of T-Platforms, one of 12 most famous and respected people of the global HPC community. [ 1 ]
In November 2011, the 33,072 processor Lomonosov supercomputer in Moscow developed by T-Platforms ranked number 18 in the world, and the fastest in Russia. [ 2 ] It placed 3rd in Europe. [ 3 ] In October 2012, T-Platforms delivered its first supercomputer in the US to the State University of New York at Stony Brook (SBU). [ 4 ] [ 5 ]
T-Platforms is part of the plan of the Russian government to focus on larger supercomputers by 2020. [ 6 ] [ 7 ] [ 8 ]
In April 2013, the United States Department of Commerce added T-Platforms to their "list of organizations and individuals acting contrary to the national security or foreign policy interests of the United States", preventing the company from buying computer chips produced anywhere in the world if the factories producing them use American technology. The decision was based on US concerns that T-Platforms work includes "the development of computer systems for military end-users, and the production of computers for nuclear research". [ 4 ] [ 9 ] [ 10 ]
T-Platforms was delisted from the list in December 2013/January 2014, [ 11 ] [ 12 ] [ 13 ] after removal request from the company. [ 14 ] On March 31, 2022 the company was once again added to the US Government SDN list in an effort to limit the capacity of Russian Aerospace, Marine and Electronics sectors for the war against Ukraine. [ 15 ] In August 2023, the company declared bankruptcy. [ 16 ] | https://en.wikipedia.org/wiki/T-Platforms |
T-Square is an early drafting program written by Peter Samson assisted by Alan Kotok and possibly Robert A. Saunders while they were students at the Massachusetts Institute of Technology and members of the Tech Model Railroad Club .
T-Square was written for the PDP-1 computer and its Type 30 precision CRT that Digital Equipment Corporation donated to MIT in 1961. It is unlikely that many people have had the opportunity to use T-Square although Samson has said the group drew some schematics .
Students of Jack Dennis and John McCarthy discovered a stunning array of uses for the very expensive room-sized computers that were given to MIT. They were privileged to be enrolled when the school's first programming courses were taught.
They negotiated with their advisors and the operations manager John McKenzie for time and became single-users long before personal computers were available. About 1959 or 1960, some of this group of students became support staff and wrote software for about $1.75 USD per hour. [ 1 ] They wrote the programming software which is used to build application software . Later Samson and Kotok became architects of DEC computers.
During this period Samson created other "firsts" in application software for music , games and page layout so it is perhaps not surprising he wrote what may be the first drafting program. Based on this experience, later in life Samson worked on an electronic drafting program with 80,000 lines of code. He received a patent [ 2 ] in virtual reality at Autodesk , a vendor of CAD and CAM software.
To move the cursor , T-Square used a Spacewar! game controller built by Kotok and Saunders in 1962. It is not known if Saunders was involved in repurposing it for T-Square. Kotok, who was about 20 years old, did participate. He was known for doing what needed to be done and for taking an interest in "all things ingenious or intriguing." [ 3 ]
The Spacewar! control boxes were cobbled together with wood, Bakelite and toggle switches . Although they are often considered to be the first joysticks , Kotok did not accept credit for coinventing them with Saunders. [ 4 ]
T-Square is a small part of the reason people use today's computers for drafting, architecture, drawing and illustration and engineering. Prior to this revolution and in some places to this day, draftsmen and women used triangles , wood or metal T-squares , pencils and technical pens on film and paper . The beginning of this change can be seen in a video of Sutherland demonstrating Sketchpad . [ 5 ]
In his 1963 MIT Ph.D. thesis, Sutherland explains he completed an early version that could draw parallel and perpendicular lines in November 1961. He goes on to say, "Somewhat before my first effort was working, Welden Clark of Bolt, Beranek and Newman ..." showed him a "similar program" running on a PDP-1. [ 6 ] T-Square and Sketchpad were developed in the same location a year or two apart but their influence on each other is unknown. | https://en.wikipedia.org/wiki/T-Square_(software) |
A T-beam (or tee beam ), used in construction , is a load-bearing structure of reinforced concrete , wood or metal , with a capital 'T'-shaped cross section . The top of the T-shaped cross section serves as a flange or compression member in resisting compressive stresses . The web (vertical section) of the beam below the compression flange serves to resist shear stress . When used for highway bridges [ 1 ] the beam incorporates reinforcing bars in the bottom of the beam to resist the tensile stresses which occur during bending . [ 2 ]
The T-beam has a big disadvantage compared to an I-beam (with 'Ɪ' shape) because it has no bottom flange with which to deal with tensile forces , applicable for steel section. One way to make a T-beam more efficient structurally is to use an inverted T-beam with a floor slab or bridge deck joining the tops of the beams. Done properly, the slab acts as the compression flange.
A T-beam is a structural element able to withstand large loads by resistance in the beam or by internal reinforcements. In some respects, the T-beam dates back to the first time a human formed a bridge with a pier and a deck. After all, a T-beam is, in one sense, no more than a pillar with a horizontal bed on top, or, in the case of the inverted T-beam, on the bottom. [ 3 ] The upright portion carrying the tension of the beam is termed a web or stem, and the horizontal part that carries the compression is termed a flange. However, the materials used have changed over the years but the basic structure is the same. T-beams structures such as highway overpasses, buildings and parking garages, have extra material added on the underside where the web joins the flange to reduce the T-beam’s vulnerability to shear stress. [ 4 ] However, when one investigates more deeply into the design of T-beams, some distinctions appear.
Unlike an I-beam, a T-beam lacks a bottom flange, which carries savings in terms of materials, but at the loss of resistance to tensile forces. [ 5 ] T- beam designs come in many sizes, lengths and widths to suit where they are to be used (eg highway bridge, underground parking garage) and how they have to resist the tension, compression and shear stresses associated with beam bending in their particular application. However, the simplicity of the T-beam is in question by some who investigate more complex beam structures; for example, a group of researchers tested pretension inverted T-beams with circular web openings, [ 6 ] with mixed but generally favorable results. The extra time and effort invested in creating a more complex structure may prove worthwhile if it is subsequently used in construction . The most suitable materials also have to be selected for a particular T-beam application.
Steel T-beams manufacturing process includes: hot rolling, extrusion, plate welding and pressure fitting. A process of large rollers connecting two steel plates by pinching them together called pressure fitting is a common process for non-load bearing beams. The reality is that for most roadways and bridges today, it is more practical to bring concrete into the design as well. Most T-beam construction is not with steel or concrete alone, but rather with the composite of the two, namely, reinforced concrete. [ 7 ] Though the term could refer to any one of a number of means of reinforcement, generally, the definition is limited to concrete poured around rebar. This shows that in considering materials available for a task, engineers need to consider the possibility that no one single material is adequate for the job; rather, combining multiple materials together may be the best solution. Thus, steel and concrete together can prove ideal.
Concrete alone is brittle and thus overly subject to the shear stresses a T-beam faces where the web and flange meet. This is the reason that steel is combined with concrete in T-beams. A problem of shear stress can lead to failures of flanges detaching from webs when under load. [ 8 ] This could prove catastrophic if allowed to occur in real life; hence, the very real need to mitigate that possibility with reinforcement for concrete T-beams. In such composite structures, many questions arise as to the particulars of the design, including what the ideal distribution of concrete and steel might be: “To evaluate an objective function, a ratio of steel to concrete costs is necessary”. [ 9 ] This demonstrates that for all aspects of the design of composite T-beams, equations are made only if one has adequate information. Still, there are aspects of design that some may not even have considered, such as the possibility of using external fabric-based reinforcement, as described by Chajes et al., who say of their tested beams, “All the beams failed in shear and those with composite reinforcement displayed excellent bond characteristics. For the beams with external reinforcement, increases in ultimate strength of 60 to 150 percent were achieved”. [ 4 ] When it comes to resistance to shear forces, external reinforcement is a valid option to consider. Thus, overall, the multiple important aspects of T-beam design impress themselves upon the student of engineering.
An issue with the T-beam compared to the I-beam is the lack of the bottom flange. In addition, this makes the beam not as versatile because of the weaker side not having the flange making it have less tensile strength.
Concrete beams are often poured integrally with the slab, forming a much stronger T–shaped beam. These beams are very efficient because the slab portion carries the compressive loads and the reinforcing bars placed at the bottom of the stem carry the tension. A T-beam typically has a narrower stem than an ordinary rectangular beam. These stems are typically spaced from 4’-0” apart to more than
12’-0”. The slab portion above the stem is designed as a one-way slab spanning between stems. [ citation needed ]
A double-T beam or double tee beam is a load-bearing structure that resemble two T-beams connected to each other. Double tees are manufactured from prestressed concrete using pretensioning beds of about 200-foot (61 m) to 500-foot (150 m) long. The strong bond of the flange (horizontal section) and the two webs (vertical members) creates a structure that is capable of withstanding high loads while having a long span. The typical sizes of double tees are up to 15 feet (4.6 m) for flange width, up to 5 feet (1.5 m) for web depth and up to 80 feet (24 m) or more for span length. [ 10 ] | https://en.wikipedia.org/wiki/T-beam |
T-cell growth factors acronym: TCGF(s) are signaling molecules collectively called growth factors which stimulate the production and development of T-cells . A number of them have been discovered, among them many members of the interleukin family. The thymus is one organ which releases TCGFs. TCGFs have been able to induce T-cell production outside the body for injection. | https://en.wikipedia.org/wiki/T-cell_growth_factor |
T-cell vaccination is immunization with inactivated autoreactive T cells . The concept of T-cell vaccination is, at least partially, analogous to classical vaccination against infectious disease. However, the agents to be eliminated or neutralized are not foreign microbial agents but a pathogenic autoreactive T-cell population. Research on T-cell vaccination so far has focused mostly on multiple sclerosis and to a lesser extent on rheumatoid arthritis , Crohn's disease and AIDS . [ 1 ] [ 2 ] [ 3 ]
This article about vaccines or vaccination is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T-cell_vaccination |
The T-failure criterion is a set of material failure criteria that can be used to predict both brittle and ductile failure. [ 1 ] [ 2 ]
These criteria were designed as a replacement for the von Mises yield criterion which predicts the unphysical result that pure hydrostatic tensile loading of metals never leads to failure. The T-criteria use the volumetric stress in addition to the deviatoric stress used by the von Mises criterion and are similar to the Drucker Prager yield criterion . T-criteria have been designed on the basis of energy considerations and the observation that the reversible elastic energy density storage process has a limit which can be used to determine when a material has failed.
Only in the case of pure shear does the strain energy density stored in the material and calculated by the area under the σ ¯ {\displaystyle {\bar {\sigma }}} - ϵ ¯ {\displaystyle {\bar {\epsilon }}} curve, represent the total amount of energy stored. In all other cases, there is a divergence between the actual and calculated stored energy in the material, which is maximum in the case of pure hydrostatic loading, where, according to the von Mises criterion, no energy is stored. This paradox is resolved if a second constitutive equation is introduced, that relates hydrostatic pressure p with the volume change Θ {\displaystyle \Theta } . These two curves, namely σ ¯ − ϵ ¯ {\displaystyle {\bar {\sigma }}-{\bar {\epsilon }}} and (p- Θ {\displaystyle \Theta } ) are essential for a complete description of material behaviour up to failure. Thus, two criteria must be accounted for when considering failure and two constitutive equations that describe material response. According to this criterion, an upper limit to allowable strains is set either by a critical value Τ V,0 of the elastic energy density due to volume change ( dilatational energy ) or by a critical value Τ D,0 of the elastic energy density due to change in shape ( distortional energy ). The volume of material is considered to have failed by extensive plastic flow when the distortional energy Τ d reaches the critical value Τ D,0 or by extensive dilatation when the dilatational energy Τ v reaches a critical value Τ V,0 . The two critical values Τ D,0 and Τ V,0 are considered material constants independent of the shape of the volume of material considered and the induced loading, but dependent on the strain rate and temperature.
For the development of the criterion, a continuum mechanics approach is adopted. The material volume is considered to be a continuous medium with no particular form or manufacturing defect. It is also considered to behave as a linear elastic isotropically hardening material, where stresses and strains are related by the generalized Hooke’s law and by the incremental theory of plasticity with the von Mises flow rule. For such materials, the following assumptions are considered to hold: (a) The total increment of a strain component d ϵ i , j {\displaystyle d\epsilon _{i,j}} is decomposed into the elastic and the plastic d ϵ i , j e {\displaystyle d\epsilon _{i,j}^{e}} increment and d ϵ i , j p {\displaystyle d\epsilon _{i,j}^{p}} respectively: d ϵ i , j = d ϵ i , j e + d ϵ i , j p {\displaystyle d\epsilon _{i,j}=d\epsilon _{i,j}^{e}+d\epsilon _{i,j}^{p}} (1) (b) The elastic strain increment d ϵ i , j e {\displaystyle d\epsilon _{i,j}^{e}} is given by Hooke’s law: d ϵ i , j e = 1 2 G ( d σ i , j − 3 ν 1 + ν δ i , j d p ) {\displaystyle d\epsilon _{i,j}^{e}={\cfrac {1}{2G}}(d{\sigma }_{i,j}-{\cfrac {3\nu }{1+{\nu }}}{\delta }_{i,j}dp)} (2) where G = E 2 ( 1 + ν ) {\displaystyle G={\cfrac {E}{2(1+\nu )}}} the shear modulus , ν {\displaystyle \nu } the Poisson’s ratio and δ i , j {\displaystyle {\delta }_{i,j}} the Krönecker delta . (c) The plastic strain increment d ϵ i , j p {\displaystyle d\epsilon _{i,j}^{p}} is proportional to the respective deviatoric stress: d ϵ i , j p = s i , j d λ {\displaystyle d\epsilon _{i,j}^{p}=s_{i,j}d{\lambda }} (3) where s i , j = σ i , j − δ i , j p {\displaystyle s_{i,j}={\sigma }_{i,j}-{\delta }_{i,j}p} and d λ {\displaystyle d{\lambda }} an infinitesimal scalar. (3) implies that the plastic strain increment:
(d) The increment in plastic work per unit volume using (4.16) is: d w p = σ i , j d ϵ i , j p = σ i , j s i , j d λ {\displaystyle dw_{p}={\sigma }_{i,j}d{\epsilon }_{i,j}^{p}={\sigma }_{i,j}s_{i,j}d{\lambda }} (4) and the increment in strain energy, d T {\displaystyle dT} , equals to the total differential of the potential Π {\displaystyle {\Pi }} : d T = d Π = p d Θ + σ d ϵ = d T V + d T D ∗ {\displaystyle dT=d{\Pi }=pd{\Theta }+{\sigma }d{\epsilon }=dT_{V}+dT_{D}^{*}} (5) where Θ = ϵ 11 + ϵ 22 + ϵ 33 {\displaystyle {\Theta }={\epsilon }_{11}+{\epsilon }_{22}+{\epsilon }_{33}} , p = 1 3 ( σ 11 + σ 22 + σ 33 ) {\displaystyle p={\cfrac {1}{3}}({\sigma }_{11}+{\sigma }_{22}+{\sigma }_{33})} and for metals following the von Mises yield law, by definition σ ¯ = 1 2 2 [ ( σ 11 − σ 22 ) 2 + ( σ 22 − σ 33 ) 2 + ( σ 33 − σ 11 ) 2 ] 1 / 2 {\displaystyle {\bar {\sigma }}={\cfrac {1}{2}}{\sqrt {2}}[({\sigma }_{11}-{\sigma }_{22})^{2}+({\sigma }_{22}-{\sigma }_{33})^{2}+({\sigma }_{33}-{\sigma }_{11})^{2}]^{1/2}} (6) ϵ ¯ = 1 ‴ 2 2 [ ( ϵ 11 − ϵ 22 ) 2 + ( ϵ 22 − ϵ 33 ) 2 + ( ϵ 33 − ϵ 11 ) 2 ] 1 / 2 {\displaystyle {\bar {\epsilon }}={\cfrac {1'''}{2}}{\sqrt {2}}[({\epsilon }_{11}-{\epsilon }_{22})^{2}+({\epsilon }_{22}-{\epsilon }_{33})^{2}+({\epsilon }_{33}-{\epsilon }_{11})^{2}]^{1/2}} (7) are the equivalent stress and strain respectively.
In (5) the first term of the right hand side, d T V = p d Θ {\displaystyle dT_{V}=pd\Theta } is the increment in elastic energy for unit volume change due to hydrostatic pressure. Its integral over a load path is the total amount of dilatational strain energy density stored in the material. The second term d T D ∗ = σ ¯ d ϵ ¯ {\displaystyle dT_{D}^{*}={\bar {\sigma }}d{\bar {\epsilon }}} is the energy required for an infinitesimal distortion of the material. The integral of this quantity is the distortional strain energy density. The theory of plastic flow permits the evaluation of stresses, strains and strain energy densities along a path provided that d λ {\displaystyle d{\lambda }} in (3) is known. In elasticity, linear or nonlinear, d λ {\displaystyle d{\lambda }} . In the case of strain hardening materials, d λ {\displaystyle d{\lambda }} can be evaluated by recording the σ ¯ = σ ¯ ( ϵ ¯ ) {\displaystyle {\bar {\sigma }}={\bar {\sigma }}({\bar {\epsilon }})} curve in a pure shear experiment. The hardening function after point “y” in Figure 1 is then: H ( σ ¯ , ϵ ¯ ) = d σ ¯ d ϵ ¯ {\displaystyle H({\bar {\sigma }},{\bar {\epsilon }})={\cfrac {d{\bar {\sigma }}}{d{\bar {\epsilon }}}}} (8) and the infinitesimal scalar d λ {\displaystyle d{\lambda }} is: d λ = 3 2 σ ¯ 2 d w p ( H ) {\displaystyle d{\lambda }={\cfrac {3}{2{\bar {\sigma }}^{2}}}dw_{p}(H)} (9) where d w p ( H ) {\displaystyle dw_{p}(H)} is the infinitesimal increase in plastic work (see Figure 1). The elastic part of the total distortional strain energy density is: d T D = σ ¯ d ϵ ¯ e {\displaystyle dT_{D}={\bar {\sigma }}d{\bar {\epsilon }}^{e}} (10) where ϵ ¯ e {\displaystyle {\bar {\epsilon }}^{e}} is the elastic part of the equivalent strain. When there is no nonlinear elastic behaviour, by integrating (4.22) the elastic distortional strain energy density is: T D = ∫ σ ¯ d ϵ ¯ e = 1 6 G σ ¯ 2 {\displaystyle T_{D}=\int {\bar {\sigma }}d{\bar {\epsilon }}^{e}={\cfrac {1}{6G}}{\bar {\sigma }}^{2}} (11) Similarly, by integrating the increment in elastic energy for unit volume change due to hydrostatic pressure, d T V = p d Θ {\displaystyle dT_{V}=pd\Theta } , the dilatational strain energy density is: T V = ∫ p d Θ = 1 2 K p 2 = 1 2 K Θ 2 {\displaystyle T_{V}=\int {pd\Theta }={\cfrac {1}{2K}}p^{2}={\cfrac {1}{2}}K{\Theta }^{2}} (12) assuming that the unit volume change Θ {\displaystyle {\Theta }} is the elastic straining, proportional to the hydrostatic pressure, p (Figure 2): Θ = 1 2 K p {\displaystyle {\Theta }={\cfrac {1}{2K}}p} or d Θ = 1 K d p {\displaystyle d{\Theta }={\cfrac {1}{K}}dp} (13) where Θ = ϵ 11 + ϵ 22 + ϵ 33 {\displaystyle {\Theta }={\epsilon }_{11}+{\epsilon }_{22}+{\epsilon }_{33}} , p = 1 3 ( σ 11 + σ 22 + σ 33 ) {\displaystyle p={\cfrac {1}{3}}({\sigma }_{11}+{\sigma }_{22}+{\sigma }_{33})} and K = E 3 ( 1 − 2 ν ) {\displaystyle K={\cfrac {E}{3(1-2\nu )}}} the bulk modulus of the material. In summary, in order to use (12) and (13) to determine the failure of a material volume, the following assumptions hold:
The criterion will not predict any failure due to distortion for elastic-perfectly plastic, rigid-plastic, or strain softening materials. For the case of nonlinear elasticity, appropriate calculations for the integrals in and (12) and (13) accounting for the nonlinear elastic material properties must be performed. The two threshold values for the elastic strain energy T V , 0 {\displaystyle T_{V,0}} and T D , 0 {\displaystyle T_{D,0}} are derived from experimental data. A drawback of the criterion is that elastic strain energy densities are small and comparatively hard to derive. Nevertheless, example values are presented in the literature as well as applications where the T-criterion appears to perform quite well. | https://en.wikipedia.org/wiki/T-criterion |
The Transition Matrix Method ( T-matrix method , TMM ) is a computational technique of light scattering by nonspherical particles originally formulated by Peter C. Waterman (1928–2012) in 1965. [ 1 ] [ 2 ] The technique is also known as null field method and extended boundary condition method (EBCM). [ 3 ] In the method, matrix elements are obtained by matching boundary conditions for solutions of Maxwell equations . It has been greatly extended to incorporate diverse types of linear media occupying the region enclosing the scatterer. [ 4 ] T-matrix method proves to be highly efficient and has been widely used in computing electromagnetic scattering of single and compound particles. [ 5 ]
The incident and scattered electric field are expanded into spherical vector wave functions (SVWF), which are also encountered in Mie scattering . They are the fundamental solutions of the vector Helmholtz equation and can be generated from the scalar fundamental solutions in spherical coordinates , the spherical Bessel functions of the first kind and the spherical Hankel functions. Accordingly, there are two linearly independent sets of solutions denoted as M 1 , N 1 {\displaystyle \mathbf {M} ^{1},\mathbf {N} ^{1}} and M 3 , N 3 {\displaystyle \mathbf {M} ^{3},\mathbf {N} ^{3}} , respectively. They are also called regular and outgoing SVWFs, respectively. With this, we can write the incident field as
The scattered field is expanded into radiating SVWFs:
The T-matrix relates the expansion coefficients of the incident field to those of the scattered field.
The T-matrix is determined by the scatterer shape and material and for a given incident field allows one to calculate the scattered field.
The standard way to calculate the T-matrix is the null-field method , which relies on the Stratton–Chu equations. [ 6 ] They basically state that the electromagnetic fields outside a given volume can be expressed as integrals over the surface enclosing the volume involving only the tangential components of the fields on the surface. If the observation point is located inside this volume, the integrals vanish.
By making use of the boundary conditions for the tangential field components on the scatterer surface,
and
where n {\displaystyle \mathbf {n} } is the normal vector to the scatterer surface, one can derive an integral representation of the scattered field in terms of the tangential components of the internal fields on the scatterer surface. A similar representation can be derived for the incident field.
By expanding the internal field in terms of SVWFs and exploiting their orthogonality on spherical surfaces, one arrives at an expression for the T-matrix. The T-matrix can also be computed from far field data. [ 7 ] This approach avoids numerical stability issues associated with the null-field method. [ 8 ]
Several numerical codes for the evaluation of the T-matrix can be found online [1] [2] [3] .
The T matrix can be found with methods other than null field method and extended boundary condition method (EBCM); therefore, the term "T-matrix method" is infelicitous.
Improvement of traditional T-matrix includes Invariant-imbedding T-matrix Method (IITM) by B. R. Johnson. [ 9 ] The numerical code of IITM is developed by Lei Bi, based on Mishchenko's EBCM code. [ 3 ] [ 10 ] It is more powerful than EBCM as it is more efficient and increases the upper limit of particle size during the computation. | https://en.wikipedia.org/wiki/T-matrix_method |
The T-schema ("truth schema ", not to be confused with " Convention T ") is used to check if an inductive definition of truth is valid, which lies at the heart of any realisation of Alfred Tarski 's semantic theory of truth . Some authors refer to it as the "Equivalence Schema", a synonym introduced by Michael Dummett . [ 1 ]
The T-schema is often expressed in natural language , but it can be formalized in many-sorted predicate logic or modal logic ; such a formalisation is called a " T-theory ." [ citation needed ] T-theories form the basis of much fundamental work in philosophical logic , where they are applied in several important controversies in analytic philosophy .
As expressed in semi-natural language (where 'S' is the name of the sentence abbreviated to S): 'S' is true if and only if S.
Example: 'snow is white' is true if and only if snow is white.
By using the schema one can give an inductive definition for the truth of compound sentences. Atomic sentences are assigned truth values disquotationally . For example, the sentence "'Snow is white' is true" becomes materially equivalent with the sentence "snow is white", i.e. 'snow is white' is true if and only if snow is white. Said again, a sentence of the form "A" is true if and only if A is true. The truth of more complex sentences is defined in terms of the components of the sentence:
Predicates for truth that meet all of these criteria are called "satisfaction classes", a notion often defined with respect to a fixed language (such as the language of Peano arithmetic ); these classes are considered acceptable definitions for the notion of truth. [ 2 ]
Joseph Heath points out that "the analysis of the truth predicate provided by Tarski's Schema T is not capable of handling all occurrences of the truth predicate in natural language. In particular, Schema T treats only "freestanding" uses of the predicate—cases when it is applied to complete sentences." [ 3 ] He gives as an "obvious problem" the sentence:
Heath argues that analyzing this sentence using T-schema generates the sentence fragment —"everything that Bill believes"—on the righthand side of the logical biconditional . | https://en.wikipedia.org/wiki/T-schema |
In chemistry, T-shaped molecular geometry describes the structures of some molecules where a central atom has three ligands . Ordinarily, three-coordinated compounds adopt trigonal planar or pyramidal geometries. Examples of T-shaped molecules are the halogen trifluorides, such as ClF 3 . [ 1 ]
According to VSEPR theory , T-shaped geometry results when three ligands and two lone pairs of electrons are bonded to the central atom, written in AXE notation as AX 3 E 2 . The T-shaped geometry is related to the trigonal bipyramidal molecular geometry for AX 5 molecules with three equatorial and two axial ligands. In an AX 3 E 2 molecule, the two lone pairs occupy two equatorial positions, and the three ligand atoms occupy the two axial positions as well as one equatorial position. The three atoms bond at 90° angles on one side of the central atom, producing the T shape. [ 2 ]
The trifluoroxenate(II) anion, XeF − 3 , has been investigated as a possible first example of an AX 3 E 3 molecule, which might be expected by VSEPR reasoning to have six electron pairs in an octahedral arrangement with both the three lone pairs and the three ligands in a mer or T-shaped orientations. [ 3 ] Although this anion has been detected in the gas phase, attempts at synthesis in solution and experimental structure determination were unsuccessful. A computational chemistry study showed a distorted planar Y-shaped geometry with the smallest F–Xe–F bond angle equal to 69°, rather than 90° as in a T-shaped geometry. [ 3 ]
This stereochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T-shaped_molecular_geometry |
T-slot structural framing is a framing system consisting of lengths of square or rectangular extruded aluminium, typically 6105-T5 aluminium alloy , with a T-slot down the centerline of one or more sides.
It is also known under several generic names, such as aluminium extrusion, aluminium profile and 2020 extrusion if the cross-section is 20x20 mm, alongside brand names, such as 80/20 framing. [ 1 ]
While the precise history of the T-slot framing system is not known, advancement in extrusion press technology in the early 1950s allowed for economic production of aluminium profiles, [ 2 ] and examples of use can be found from the early 1960s. [ 3 ]
Although no published standard defines the system, it is produced in a series of conventional sizes which allows for compatibility between manufacturers.
There is a variation on T-slot profiles known as V-slot rails where V-slot wheels are slotted into the V-shaped channels of the framing for linear motion in a 3D printer or other CNC machine .
T-slot framing is divided into metric and fractional (imperial) categories. The T-slot is always centered along the long-axis of the piece. Pieces are available in each series with a square cross-section. Rectangular cross sections are also available which measure x by 2x (where x is the defined width) - e.g. 40mm by 80mm for 40 series. | https://en.wikipedia.org/wiki/T-slot_structural_framing |
T-symmetry or time reversal symmetry is the theoretical symmetry of physical laws under the transformation of time reversal,
Since the second law of thermodynamics states that entropy increases as time flows toward the future, in general, the macroscopic universe does not show symmetry under time reversal. In other words, time is said to be non-symmetric, or asymmetric, except for special equilibrium states when the second law of thermodynamics predicts the time symmetry to hold. However, quantum noninvasive measurements are predicted to violate time symmetry even in equilibrium, [ 1 ] contrary to their classical counterparts, although this has not yet been experimentally confirmed.
Time asymmetries (see Arrow of time ) generally are caused by one of three categories:
Daily experience shows that T-symmetry does not hold for the behavior of bulk materials. Of these macroscopic laws, most notable is the second law of thermodynamics . Many other phenomena, such as the relative motion of bodies with friction, or viscous motion of fluids, reduce to this, because the underlying mechanism is the dissipation of usable energy (for example, kinetic energy) into heat.
The question of whether this time-asymmetric dissipation is really inevitable has been considered by many physicists, often in the context of Maxwell's demon . The name comes from a thought experiment described by James Clerk Maxwell in which a microscopic demon guards a gate between two halves of a room. It only lets slow molecules into one half, only fast ones into the other. By eventually making one side of the room cooler than before and the other hotter, it seems to reduce the entropy of the room, and reverse the arrow of time. Many analyses have been made of this; all show that when the entropy of room and demon are taken together, this total entropy does increase. Modern analyses of this problem have taken into account Claude E. Shannon 's relation between entropy and information . Many interesting results in modern computing are closely related to this problem— reversible computing , quantum computing and physical limits to computing , are examples. These seemingly metaphysical questions are today, in these ways, slowly being converted into hypotheses of the physical sciences.
The current consensus hinges upon the Boltzmann–Shannon identification of the logarithm of phase space volume with the negative of Shannon information , and hence to entropy . In this notion, a fixed initial state of a macroscopic system corresponds to relatively low entropy because the coordinates of the molecules of the body are constrained. As the system evolves in the presence of dissipation , the molecular coordinates can move into larger volumes of phase space, becoming more uncertain, and thus leading to increase in entropy.
One resolution to irreversibility is to say that the constant increase of entropy we observe happens only because of the initial state of our universe. Other possible states of the universe (for example, a universe at heat death equilibrium) would actually result in no increase of entropy. In this view, the apparent T-asymmetry of our universe is a problem in cosmology : why did the universe start with a low entropy? This view, supported by cosmological observations (such as the isotropy of the cosmic microwave background ) connects this problem to the question of initial conditions of the universe.
The laws of gravity seem to be time reversal invariant in classical mechanics; however, specific solutions need not be.
An object can cross through the event horizon of a black hole from the outside, and then fall rapidly to the central region where our understanding of physics breaks down. Since within a black hole the forward light-cone is directed towards the center and the backward light-cone is directed outward, it is not even possible to define time-reversal in the usual manner. The only way anything can escape from a black hole is as Hawking radiation .
The time reversal of a black hole would be a hypothetical object known as a white hole . From the outside they appear similar. While a black hole has a beginning and is inescapable, a white hole has an ending and cannot be entered. The forward light-cones of a white hole are directed outward; and its backward light-cones are directed towards the center.
The event horizon of a black hole may be thought of as a surface moving outward at the local speed of light and is just on the edge between escaping and falling back. The event horizon of a white hole is a surface moving inward at the local speed of light and is just on the edge between being swept outward and succeeding in reaching the center. They are two different kinds of horizons—the horizon of a white hole is like the horizon of a black hole turned inside-out.
The modern view of black hole irreversibility is to relate it to the second law of thermodynamics, since black holes are viewed as thermodynamic objects . For example, according to the gauge–gravity duality conjecture, all microscopic processes in a black hole are reversible, and only the collective behavior is irreversible, as in any other macroscopic, thermal system. [ citation needed ]
In physical and chemical kinetics , T-symmetry of the mechanical microscopic equations implies two important laws: the principle of detailed balance and the Onsager reciprocal relations . T-symmetry of the microscopic description together with its kinetic consequences are called microscopic reversibility .
Classical variables that do not change upon time reversal include:
Classical variables that time reversal negates include:
Let us consider the example of a system of charged particles subject to a constant external magnetic field: in this case the canonical time reversal operation that reverses the velocities and the time t {\displaystyle t} and keeps the coordinates untouched is no more a symmetry for the system. Under this consideration, it seems that only Onsager–Casimir reciprocal relations could hold; [ 2 ] these equalities relate two different systems, one subject to B → {\displaystyle {\vec {B}}} and another to − B → {\displaystyle -{\vec {B}}} , and so their utility is limited. However, it was proved that it is possible to find other time reversal operations which preserve the dynamics and so Onsager reciprocal relations; [ 3 ] [ 4 ] [ 5 ] in conclusion, one cannot state that the presence of a magnetic field always breaks T-symmetry.
Most systems are asymmetric under time reversal, but there may be phenomena with symmetry. In classical mechanics, a velocity v reverses under the operation of T , but an acceleration does not. [ 6 ] Therefore, one models dissipative phenomena through terms that are odd in v . However, delicate experiments in which known sources of dissipation are removed reveal that the laws of mechanics are time reversal invariant. Dissipation itself is originated in the second law of thermodynamics .
The motion of a charged body in a magnetic field, B involves the velocity through the Lorentz force term v × B , and might seem at first to be asymmetric under T . A closer look assures us that B also changes sign under time reversal. This happens because a magnetic field is produced by an electric current, J , which reverses sign under T . Thus, the motion of classical charged particles in electromagnetic fields is also time reversal invariant. (Despite this, it is still useful to consider the time-reversal non-invariance in a local sense when the external field is held fixed, as when the magneto-optic effect is analyzed. This allows one to analyze the conditions under which optical phenomena that locally break time-reversal, such as Faraday isolators and directional dichroism , can occur.)
In physics one separates the laws of motion, called kinematics , from the laws of force, called dynamics . Following the classical kinematics of Newton's laws of motion , the kinematics of quantum mechanics is built in such a way that it presupposes nothing about the time reversal symmetry of the dynamics. In other words, if the dynamics are invariant, then the kinematics will allow it to remain invariant; if the dynamics is not, then the kinematics will also show this. The structure of the quantum laws of motion are richer, and we examine these next.
This section contains a discussion of the three most important properties of time reversal in quantum mechanics; chiefly,
The strangeness of this result is clear if one compares it with parity. If parity transforms a pair of quantum states into each other, then the sum and difference of these two basis states are states of good parity. Time reversal does not behave like this. It seems to violate the theorem that all abelian groups be represented by one-dimensional irreducible representations. The reason it does this is that it is represented by an anti-unitary operator. It thus opens the way to spinors in quantum mechanics.
On the other hand, the notion of quantum-mechanical time reversal turns out to be a useful tool for the development of physically motivated quantum computing and simulation settings, providing, at the same time, relatively simple tools to assess their complexity . For instance, quantum-mechanical time reversal was used to develop novel boson sampling schemes [ 7 ] and to prove the duality between two fundamental optical operations, beam splitter and squeezing transformations. [ 8 ]
In formal mathematical presentations of T-symmetry, three different kinds of notation for T need to be carefully distinguished: the T that is an involution , capturing the actual reversal of the time coordinate, the T that is an ordinary finite dimensional matrix, acting on spinors and vectors, and the T that is an operator on an infinite-dimensional Hilbert space .
For a real (not complex ) classical (unquantized) scalar field ϕ {\displaystyle \phi } , the time reversal involution can simply be written as
as time reversal leaves the scalar value at a fixed spacetime point unchanged, up to an overall sign s = ± 1 {\displaystyle s=\pm 1} . A slightly more formal way to write this is
which has the advantage of emphasizing that T {\displaystyle {\mathsf {T}}} is a map , and thus the "mapsto" notation ↦ , {\displaystyle \mapsto ~,} whereas ϕ ′ ( − t , x → ) = s ϕ ( t , x → ) {\displaystyle \phi ^{\prime }(-t,{\vec {x}})=s\phi (t,{\vec {x}})} is a factual statement relating the old and new fields to one-another.
Unlike scalar fields, spinor and vector fields ψ {\displaystyle \psi } might have a non-trivial behavior under time reversal. In this case, one has to write
where T {\displaystyle T} is just an ordinary matrix . For complex fields, complex conjugation may be required, for which the mapping K : ( x + i y ) ↦ ( x − i y ) {\displaystyle K:(x+iy)\mapsto (x-iy)} can be thought of as a 2×2 matrix. For a Dirac spinor , T {\displaystyle T} cannot be written as a 4×4 matrix, because, in fact, complex conjugation is indeed required; however, it can be written as an 8×8 matrix, acting on the 8 real components of a Dirac spinor.
In the general setting, there is no ab initio value to be given for T {\displaystyle T} ; its actual form depends on the specific equation or equations which are being examined. In general, one simply states that the equations must be time-reversal invariant, and then solves for the explicit value of T {\displaystyle T} that achieves this goal. In some cases, generic arguments can be made. Thus, for example, for spinors in three-dimensional Euclidean space , or four-dimensional Minkowski space , an explicit transformation can be given. It is conventionally given as
where J y {\displaystyle J_{y}} is the y-component of the angular momentum operator and K {\displaystyle K} is complex conjugation, as before. This form follows whenever the spinor can be described with a linear differential equation that is first-order in the time derivative, which is generally the case in order for something to be validly called "a spinor".
The formal notation now makes it clear how to extend time-reversal to an arbitrary tensor field ψ a b c ⋯ {\displaystyle \psi _{abc\cdots }} In this case,
Covariant tensor indexes will transform as T a b = ( T − 1 ) b a {\displaystyle {T_{a}}^{b}={(T^{-1})_{b}}^{a}} and so on. For quantum fields, there is also a third T , written as T , {\displaystyle {\mathcal {T}},} which is actually an infinite dimensional operator acting on a Hilbert space. It acts on quantized fields Ψ {\displaystyle \Psi } as
This can be thought of as a special case of a tensor with one covariant, and one contravariant index, and thus two T {\displaystyle {\mathcal {T}}} 's are required.
All three of these symbols capture the idea of time-reversal; they differ with respect to the specific space that is being acted on: functions, vectors/spinors, or infinite-dimensional operators. The remainder of this article is not cautious to distinguish these three; the T that appears below is meant to be either T {\displaystyle {\mathsf {T}}} or T {\displaystyle T} or T , {\displaystyle {\mathcal {T}},} depending on context, left for the reader to infer.
Eugene Wigner showed that a symmetry operation S of a Hamiltonian is represented, in quantum mechanics either by a unitary operator , S = U , or an antiunitary one, S = UK where U is unitary, and K denotes complex conjugation . These are the only operations that act on Hilbert space so as to preserve the length of the projection of any one state-vector onto another state-vector.
Consider the parity operator. Acting on the position, it reverses the directions of space, so that PxP −1 = − x . Similarly, it reverses the direction of momentum , so that PpP −1 = − p , where x and p are the position and momentum operators. This preserves the canonical commutator [ x , p ] = iħ , where ħ is the reduced Planck constant , only if P is chosen to be unitary, PiP −1 = i .
On the other hand, the time reversal operator T , it does nothing to the x-operator, TxT −1 = x , but it reverses the direction of p, so that TpT −1 = − p . The canonical commutator is invariant only if T is chosen to be anti-unitary, i.e., TiT −1 = − i .
Another argument involves energy, the time-component of the four-momentum. If time reversal were implemented as a unitary operator, it would reverse the sign of the energy just as space-reversal reverses the sign of the momentum. This is not possible, because, unlike momentum, energy is always positive. Since energy in quantum mechanics is defined as the phase factor exp(− iEt ) that one gets when one moves forward in time, the way to reverse time while preserving the sign of the energy is to also reverse the sense of " i ", so that the sense of phases is reversed.
Similarly, any operation that reverses the sense of phase, which changes the sign of i , will turn positive energies into negative energies unless it also changes the direction of time. So every antiunitary symmetry in a theory with positive energy must reverse the direction of time. Every antiunitary operator can be written as the product of the time reversal operator and a unitary operator that does not reverse time.
For a particle with spin J , one can use the representation
where J y is the y -component of the spin, and use of TJT −1 = − J has been made.
This has an interesting consequence on the electric dipole moment (EDM) of any particle. The EDM is defined through the shift in the energy of a state when it is put in an external electric field: Δ e = d· E + E ·δ· E , where d is called the EDM and δ, the induced dipole moment. One important property of an EDM is that the energy shift due to it changes sign under a parity transformation. However, since d is a vector, its expectation value in a state |ψ⟩ must be proportional to ⟨ψ| J |ψ⟩, that is the expected spin. Thus, under time reversal, an invariant state must have vanishing EDM. In other words, a non-vanishing EDM signals both P and T symmetry-breaking. [ 9 ]
Some molecules, such as water, must have EDM irrespective of whether T is a symmetry. This is correct; if a quantum system has degenerate ground states that transform into each other under parity, then time reversal need not be broken to give EDM.
Experimentally observed bounds on the electric dipole moment of the nucleon currently set stringent limits on the violation of time reversal symmetry in the strong interactions , and their modern theory: quantum chromodynamics . Then, using the CPT invariance of a relativistic quantum field theory , this puts strong bounds on strong CP violation .
Experimental bounds on the electron electric dipole moment also place limits on theories of particle physics and their parameters. [ 10 ] [ 11 ]
For T , which is an anti-unitary Z 2 symmetry generator
where Φ is a diagonal matrix of phases. As a result, U = Φ U T and U T = U Φ , showing that
This means that the entries in Φ are ±1, as a result of which one may have either T 2 = ±1 . This is specific to the anti-unitarity of T . For a unitary operator, such as the parity , any phase is allowed.
Next, take a Hamiltonian invariant under T . Let | a ⟩ and T | a ⟩ be two quantum states of the same energy. Now, if T 2 = −1 , then one finds that the states are orthogonal: a result called Kramers' theorem . This implies that if T 2 = −1 , then there is a twofold degeneracy in the state. This result in non-relativistic quantum mechanics presages the spin statistics theorem of quantum field theory .
Quantum states that give unitary representations of time reversal, i.e., have T 2 = 1 , are characterized by a multiplicative quantum number , sometimes called the T-parity .
Particle physics codified the basic laws of dynamics into the standard model . This is formulated as a quantum field theory that has CPT symmetry , i.e., the laws are invariant under simultaneous operation of time reversal, parity and charge conjugation . However, time reversal itself is seen not to be a symmetry (this is usually called CP violation ). There are two possible origins of this asymmetry, one through the mixing of different flavours of quarks in their weak decays , the second through a direct CP violation in strong interactions. The first is seen in experiments, the second is strongly constrained by the non-observation of the EDM of a neutron .
Time reversal violation is unrelated to the second law of thermodynamics , because due to the conservation of the CPT symmetry , the effect of time reversal is to rename particles as antiparticles and vice versa . Thus the second law of thermodynamics is thought to originate in the initial conditions in the universe.
Strong measurements (both classical and quantum) are certainly disturbing, causing asymmetry due to the second law of thermodynamics . However, noninvasive measurements should not disturb the evolution, so they are expected to be time-symmetric. Surprisingly, it is true only in classical physics but not in quantum physics, even in a thermodynamically invariant equilibrium state. [ 1 ] This type of asymmetry is independent of CPT symmetry but has not yet been confirmed experimentally due to extreme conditions of the checking proposal.
In 2024, experiments by the University of Toronto showed that under certain quantum conditions, photons can exhibit "negative time" behavior. When interacting with atomic clouds, photons appeared to exit the medium before entering it, indicating a negative group delay, especially near atomic resonance. Using the cross- Kerr effect , the team measured atomic excitation by observing phase shifts in a weak probe beam. The results showed that atomic excitation times varied from negative to positive, depending on the pulse width. For narrow pulses, the excitation time was approximately −0.82 times the non-post-selected excitation time (τ₀), while for broader pulses, it was around 0.54 times τ₀. These findings align with theoretical predictions and highlight the non-classical nature of quantum mechanics, opening new possibilities for quantum computing and photonics . [ 12 ] | https://en.wikipedia.org/wiki/T-symmetry |
T.C. Mits (acronym for " the celebrated man in the street "), [ 1 ] is a term coined by Lillian Rosanoff Lieber to refer to an everyman . In Lieber's works, T.C. Mits was a character who made scientific topics more approachable to the public audience.
The phrase has enjoyed sparse use by authors in fields such as molecular biology , [ 2 ] secondary education, [ 3 ] and general semantics. [ 4 ]
Dr. Lillian Rosanoff Lieber wrote this treatise on mathematical thinking in twenty chapters. The writing took a form that resembled free-verse poetry, though Lieber included an introduction stating that the form was meant only to facilitate rapid reading, rather than emulate free-verse. Lieber's husband, a fellow professor at Long Island University , Hugh Gray Lieber, provided illustrations for the book. [ 5 ] The title of the book was meant to emphasize that mathematics can be understood by anyone, which was further shown when a special "Overseas edition for the Armed Forces" was published in 1942, and approved by the Council on Books in Wartime to be sent to American troops fighting in World War II. [ 6 ] | https://en.wikipedia.org/wiki/T.C._Mits |
Trivandrum Ramakrishnan " T. R. " Ramadas (born 30 March 1955) is an Indian mathematician who specializes in algebraic and differential geometry, and mathematical physics. He was awarded the Shanti Swarup Bhatnagar Prize for Science and Technology in 1998, the highest science award in India , in the mathematical sciences category. [ 1 ] [ 2 ]
He studied engineering in IIT Kanpur then joined TIFR as a graduate student in physics finally changing to mathematics after his interactions with M S Narasimhan .
He is currently a professor at Chennai Mathematical Institute , Chennai, Tamil Nadu. [ 3 ]
This article about an Indian scientist is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T._R._Ramadas |
T.V. (Babu) RajanBabu is an organic chemist who holds the position of Distinguished Professor of Chemistry in the College of Arts and Sciences at the Ohio State University . His laboratory traditionally focuses on developing transition metal-catalyzed reactions. RajanBabu is known for helping develop the Nugent-RajanBabu reagent ( Bis(cyclopentadienyl)titanium(III) chloride ), a chemical reagent used in synthetic organic chemistry as a single electron reductant . [ 1 ]
RajanBabu received his B. Sc (Special) from Kerala University in 1969 and M. Sc. degree from The Indian Institute of Technology ( IIT, Madras ) in 1971. He obtained his Ph.D. from The Ohio State University in 1979 working with Professor Harold Shechter, and was a postdoctoral fellow at Harvard University with Professor R. B. Woodward from 1978 to 1979. Notable work during his postdoctoral career includes the total synthesis of erythromycin . [ 2 ] RajanBabu was a Member of Research Staff and Research Fellow at DuPont Central Research from 1980 to 1994 until joining the Ohio State University faculty as a Professor of Chemistry in 1995. [ 3 ]
Research in the RajanBabu lab is focused on development of new methodology for stereoselective synthesis. [ 4 ] Major research areas include:
Asymmetric Hydrovinylation
RajanBabu developed methodology surrounding C-C bond formation via metal-catalyzed hydroformylation . They reported several asymmetric examples through the usage of chiral phosphine ligand with a hemilabile coordinating group. [ 5 ] [ 6 ] This method was applicable using vinylarenes, 1,3-dienes [ 7 ] and strained olefins as substrates. Applications of this chemistry include a new synthesis of (S)- ibuprofen [ 8 ] and a new approach to controlling the exocyclic side-chain stereochemistry in helioporin D [ 9 ] and pseudopterocins. [ 10 ] Related to this methodology, RajanBabu also developed a tandem [2+2] cycloaddition/asymmetric hydrovinylation reaction to allow conversion of simple precursors ( ethylene , enynes) to structurally complex cyclobutanes. [ 11 ]
Asymmetric Hydrocyanation
The RajanBabu group developed methodology in the area of hydrocyanation , leveraging the reaction of vinylarenes with HCN in the presence of Ni(0) complexes. Based on the phosphorus ligands within the Ni complex, the reaction can be rendered asymmetric. [ 12 ] [ 13 ] The enantioselectivity could be further improved by tuning the electronics of the phosphine ligands to electronically differentiate the phosphorus chelates. Electronic tuning was accomplished, for example, using widely available sugars such as D-glucose and D-fructose.
Radical Epoxide Opening
For further information on the Nugent-RajanBabu reagent, please see Bis(cyclopentadienyl)titanium(III) chloride .
Multicomponent Cyclization
One area of interest to the RajanBabu group is catalytic multicomponent addition/cyclization reactions. This methodology allows for formation of carbocyclic and heterocyclic compounds from acyclic precursors including unactivated olefins and acetylenes. [ 14 ] This method leverages the reactivity of bifunctional reagents (X-Y) where X-Y in above scheme can represent R 3 Si−SiR‘ 3 , R 3 Si−SnR‘ 3 , R 3 Si−BR‘ 2 , R 3 Sn−BR‘ 2 , and trialkylsilicon- and trialkyltin- hydrides. The reactions are palladium-catalyzed, and incorporation of the X and Y species allows for vast diversification of the end products. [ 15 ] [ 16 ] [ 17 ] Application of this methodology afforded syntheses of highly alkylated indolizidines such as IND-223A. [ 18 ]
Additional Methods
RajanBabu has evaluated asymmetric aziridine openings with high enantioselectivity using yttrium- and lanthanide- salen complexes. [ 19 ] The RajanBabu group has also developed water-soluble Rhodium(I) complexes, allowing for reactions to be run in aqueous media. [ 20 ]
RajanBabu has over 160 publications to date and has co-authored several reviews and patents. His H-index is 56. [ 21 ]
Notable publications include: | https://en.wikipedia.org/wiki/T._V._Rajan_Babu |
A T1 process (or topological rearrangement process of the first kind) [ 1 ] [ 2 ] is one of the main processes by which cellular materials such as foams or biological tissues change shapes. It involves four discrete objects such as bubbles , drops , cells , etc. The four objects are initially arranged in a plane in the following way. Objects A and B are in contact and objects C and D are on either side of the AB group and touching both A and B. The T1 process consists in breaking the contact between A and B and establishing the contact between C and D.
When a significant number of rearrangement events such as T1 processes with similar orientations occur inside a foam or a tissue, the material correspondingly undergoes a deformation: it elongates in the direction in which neighbours depart (here, AB) while it contracts in the direction in which new neighbour pairs form (here, CD).
As a result of the existence of the T1 and similar processes, materials made of these objects have a number of similar rheological properties . Among these, plasticity allows them to be deformed irreversibly. For such materials, such irreversible deformations arise from the ability to rearrange their constitutive objects. Thus, the T1 process is the major mesoscopic ingredient of plasticity for these materials. | https://en.wikipedia.org/wiki/T1_process |
[ 4 ] [ 5 ]
Tritiated water is a radioactive form of water in which the usual protium atoms are replaced with tritium atoms. In its pure form it may be called tritium oxide ( T 2 O or 3 H 2 O ) or super-heavy water . Pure T 2 O is a colorless liquid, [ 1 ] and it is corrosive due to self- radiolysis . Diluted, tritiated water is mainly H 2 O plus some HTO ( 3 HOH). It is also used as a tracer for water transport studies in life-science research. Furthermore, since it naturally occurs in minute quantities, it can be used to determine the age of various water-based liquids, such as vintage wines .
The name super-heavy water helps distinguish the tritiated material from heavy water , which contains deuterium instead.
Tritiated water is primarily studied as a dilute solution within light water. Here, the proportion of the light, hydrogen tritium oxide is strongly favoured versus the more negligible heavy, double tritium oxide, as the conversion reaction has an equilibrium constant of 3.42 at room temperature. [ 6 ]
H 2 O + T 2 O ↽ − ⇀ 2 HTO {\displaystyle {\ce {H2O + T2O <=>> 2HTO}}}
The molecules then experience beta decay and formation of the hydroxyl or tritoxyl radical via:
HTO ⟶ 3 He + + β + − ν ¯ + OH ⋅ {\displaystyle {\ce {HTO->\ ^{3}He^{+}\ +\ \beta ^{-}+\ {\bar {\nu }}\ +\ OH^{.}}}}
T 2 O ⟶ 3 He + + β + − ν ¯ + OT ⋅ {\displaystyle {\ce {T2O->\ ^{3}He^{+}\ +\ \beta ^{-}+\ {\bar {\nu }}\ +\ OT^{.}}}}
The average electron energy of the beta decay is 5.7 keV . The energy required to break hydrogen-oxygen bonds in water is three orders of magnitude lower at 5.2 eV. This leads to many radiolysis events:
H 2 O → beta rays e aq − , HO ⋅ , H ⋅ , HO 2 ⋅ , H 3 O + , OH − , H 2 O 2 , H 2 {\displaystyle {\ce {H2O\;->[{\text{beta rays}}]\;e_{aq}^{-},HO*,H*,HO2*,H3O^{+},OH^{-},H2O2,H2}}}
Many subsequent reactions occur, but primarily result in recombination to water, or the escape of molecular hydrogen and oxygen gas, alongside the helium-3 .
Studies of tritiated water often prefer describe the concentration by the measurable radiation level in curies per liter (Ci/L) or terabecquerels per liter (TBq/L), rather than the species proportion.
In one CEA study, relatively highly tritiated water at 1,800 Ci/L or 74 TBq/L (0.12% HTO, negligible T 2 O) was left to self-radiolyze for 56 days in three volumes. In the 300 mL volume, the primary gases collected were H 2 at 2.54 mmol , O 2 at 1.31 mmol, and 3 He at 0.13 mmol. Thus in this geometry, for each tritium decay, roughly twenty water molecules were permanently dissociated . [ 6 ]
Tritiated water can be used to measure an organism's total body water (TBW). Unlike doubly labeled water this method relies on scintillation counting . Tritiated water distributes itself into all body compartments relatively quickly. The concentration of tritiated water in urine is assumed to be similar to the concentration of tritiated water in the body. TBW is determined from the following relation:
body water volume = mass ingested − mass excreted concentration {\displaystyle {\text{body water volume}}={\frac {{\text{mass ingested}}-{\text{mass excreted}}}{\text{concentration}}}}
Tritium is radioactive and a low energy beta emitter .
While HTO is produced naturally by cosmic ray interactions in the stratosphere, it is also produced by human activities and can increase local concentrations and be considered an air and water pollutant. Anthropogenic sources of tritiated water include nuclear weapons testing , nuclear power plants , nuclear reprocessing and consumer products such as self-illuminating watches and signs.
HTO has a short biological half-life in the human body of 7 to 14 days, which both reduces the total effects of single-incident ingestion and precludes long-term bioaccumulation of HTO from the environment. The biological half life of tritiated water in the human body, which is a measure of body water turn-over, varies with the season. Studies on the biological half life of occupational radiation workers for free water tritium in a coastal region of Karnataka , India, show that the biological half life in the winter season is twice that of the summer season.
If tritium exposure is suspected or known, drinking uncontaminated water will help replace the tritium from the body. Increasing sweating, urination or breathing can help the body expel water and thereby the tritium contained in it. However, care should be taken that neither dehydration nor a depletion of the body's electrolytes results as the health consequences of those things (particularly in the short term) can be more severe than those of tritium exposure. [ citation needed ] | https://en.wikipedia.org/wiki/T2O |
T2 is a financial market infrastructure that provides real-time gross settlement (RTGS) of payments, mostly in euros . It is operated by the European Central Bank and is the critical payments infrastructure of the euro area . With turnover in the trillions of euros every day, it is one of the largest payment systems in the world. [ 1 ] It is one of three so-called TARGET Services , together with TARGET2-Securities (T2S) for securities and TARGET Instant Payment Settlement (TIPS) for fast payments. [ 2 ] The acronym TARGET stands for Trans-European Automated Real-time Gross-Settlement Express Transfer.
T2 replaced its predecessor RTGS system, TARGET2 (itself introduced in 2007-2008), on 20 March 2023. [ 3 ]
Like other RTGS systems, T2 allows individual banks to submit payment orders and have them settled in central bank money , namely the euro. T2 settles payments between banks as well as those related to the Eurosystem 's own operations. [ 1 ] Member banks can connect to T2 either via SWIFT or via NEXI-Colt, a service of Nexi . In legal terms, the relationship is between the member bank and the relevant National Central Bank within the Eurosystem. [ 2 ]
In addition to payments in euros, T2 allows settlements in other currencies of the EU if the respective central bank opts for it. [ 1 ] This is a new feature of T2 compared with TARGET2, as is the adoption of the ISO 20022 messaging standard. [ 2 ] T2 also integrates a Central Liquidity Management (CLM) functionality which extends to T2S and TIPS. [ 4 ] The transition to T2 also entailed the phasing out of national settlement systems that had been kept e.g. for overnight deposit and intraday credit provision. [ 5 ] : Box 1
T2 was developed jointly with T2S by four central banks of the Eurosystem: the Bank of France , Bank of Italy , Bank of Spain , and Deutsche Bundesbank . [ 2 ] It is planned to be complemented by a new Eurosystem Collateral Management System (ECMS), which will the single collateral management system for collateralising the Eurosystem's monetary policy operations. [ 4 ]
Like its predecessors TARGET and TARGET2, T2 is used for the end-of-day settlement of EURO1 (operated by the Euro Banking Association ) and payments in euros between CLS Bank and its members. [ 6 ] : 6
On 21 March 2024, the Eurosystem and Danmarks Nationalbank signed an agreement that provides for Denmark to join T2 (as well as TIPS) in March 2025, allowing for T2 to settle transactions in Danish krones as well as euros. [ 7 ]
In the course of 2023, TARGET2 (until 20 March) and T2 (after that date) settled 104 million transactions for a total turnover of €559 trillion, with daily turnover fluctuating between €1.4 trillion (29 May) and €4.7 trillion (20 March). That places TARGET2/T2 turnover below CLS and Fedwire but above BOJ-NET (Japan) and CHAPS (United Kingdom), as has been the case throughout the previous decade. [ 5 ] : 1.1 The system suffered no outages during 2023; 90 percent of transactions were settled within 38 seconds, whereas 0.09 percent took more than five minutes. [ 5 ] : 2
As of end-2023, T2 had 956 direct participants holding an RTGS account, opening access to T2 settlement to 5,368 correspondents worldwide. In total, T2 was accessible to nearly 40,000 participants, including branches and subsidiaries of direct participants and correspondents. [ 5 ] : 3.1
This bank and insurance -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T2_(settlement_system) |
T5 retrofit conversion is a means of converting light fittings designed to use T8 format lamps , so that they can use more energy-efficient T5 lamps. [ 1 ] This is done by electronically converting the luminaires to high frequency operation. [ 2 ]
T5 lamps are approximately 40% smaller than T8 Lamps . T5 lamps have a G5 base while T8 lamps use a G13 base . [ 3 ]
Conversion kits are available which will work in existing fittings containing switch start, mains frequency fluorescent lamp ballasts. The kits convert the fittings to use energy efficient, high frequency ballasts and accommodate the smaller diameter T5 lamp. [ 1 ]
The magnetic ballast remains in place but it is bypassed, rendering it ineffective as a conductor. The new high-frequency ballast draws only 2 W , rather than the 6-10 W of the old ballast, increasing the efficiency of the system. [ 4 ] Changing to this type of lamp without taking the ballast out of operation (rather than simply bypassing it) results in an increased power factor for the fitting. This increase in power is a result of the separate coils used in an electric ballast, as opposed to the single coil in a magnetic ballast, because it allows the electricity to flow more consistently. [ 5 ]
There are tree main types of conversion kits:
T5 retrofit conversion can maintain existing lighting levels with the higher efficiency of the T5 lamp. However, with kits that operates the lamp on the existing magnetic ballast, the efficiency drops and the lamp life is considerably shortened, as T5 lamps aren't designed to be operated on mains frequency but only on high frequency. | https://en.wikipedia.org/wiki/T5_retrofit_conversion |
T790M , also known as Thr790Met , is a gatekeeper mutation of the epidermal growth factor receptor (EGFR). The mutation substitutes a threonine (T) with a methionine (M) at position 790 of exon 20, [ 1 ] affecting the ATP binding pocket of the EGFR kinase domain. Threonine is a small polar amino acid ; methionine is a larger nonpolar amino acid. Rather than directly blocking inhibitor binding to the active site, T790M increases the affinity for ATP so that the inhibitors are outcompeted; irreversible covalent inhibitors such as osimertinib can overcome this resistance. [ 2 ] [ 3 ]
Over 50% of acquired resistance to EGFR tyrosine kinase inhibitors (TKI) is caused by a mutation in the ATP binding pocket of the EGFR kinase domain involving substitution of a small polar threonine residue with a large nonpolar methionine residue, T790M. [ 4 ] [ 5 ]
In November 2015, the US FDA granted accelerated approval to osimertinib (Tagrisso) for the treatment of patients with metastatic epidermal growth factor receptor (EGFR) T790M mutation -positive non-small cell lung cancer (NSCLC), as detected by an FDA-approved test, which progressed on or after EGFR TKI therapy. [ 6 ] [ 7 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it .
This genetics article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/T790M |
T7 DNA helicase (gp4) is a hexameric motor protein encoded by T7 phages that uses energy from dTTP hydrolysis to process unidirectionally along single stranded DNA , separating ( helicase ) the two strands as it progresses. It is also a primase , making short stretches of RNA that initiates DNA synthesis . [ 2 ] It forms a complex with T7 DNA polymerase . Its homologs are found in mitochondria (as Twinkle ) and chloroplasts . [ 3 ] [ 4 ]
The crystal structure was solved to 3.0 Å resolution in 2000, as shown in the figure in the reference. [ 5 ] In (A), notice that the separate subunits appear to be anchored through interactions between an alpha helix and an adjacent subunit. In (B), there are six sets of three loops. The red loop, known as loop II, contains three lysine residues and is thought to be involved in binding the ssDNA that is fed through the center of the enzyme .
Crampton et al. have proposed a mechanism for the ssDNA-dependent hydrolysis of dTTP by T7 DNA helicase as shown in the figure below. [ 6 ] In their model, protein loops located on each hexameric subunit, each of which contain three lysine residues, sequentially interact with the negatively charged phosphate backbone of ssDNA. This interaction presumably causes a conformational change in the actively bound subunit, providing for the efficient release of dTDP from its dTTP binding site. In the process of dTDP release, the ssDNA is transferred to the neighboring subunit, which undergoes a similar process. Previous studies have already suggested that ssDNA is able to bind to two hexameric subunits simultaneously. [ 7 ] | https://en.wikipedia.org/wiki/T7_DNA_helicase |
The T7 expression system is utilized in the field of microbiology to clone recombinant DNA using strains of E. coli . [ 1 ] It is the most popular system for expressing recombinant proteins in E. coli. [ 2 ]
By 2021, this system had been described in over 220,000 research publications. [ 3 ]
The sequencing and annotating of the genome of the T7 bacteriophage took place in the 1980s at the U.S. Department of Energy 's Brookhaven National Laboratory , under the senior biophysicist F. William Studier . Soon, the lab was able to clone the T7 RNA polymerase and use it, along with the powerful T7 promoter, to transcribe copious amounts of almost any gene. [ 4 ] The development of the T7 expression system has been considered the most successful biotechnology developed at the Brookhaven National Laboratory, being licensed by over 900 companies which has generated over $55 million for the lab. [ 5 ]
An expression vector, most commonly the pET expression vector, is engineered to integrate two essential components: a T7 promoter and a gene of interest downstream of the promoter and under its control. The expression vector is transformed into one of several relevant strains of E. coli, most frequently BL21(DE3). The E. coli cell also has its own chromosome, which possesses a gene that is expressed to produce T7 RNA polymerase . (This polymerase originates from the T7 phage , a bacteriophage virus which infects E. coli bacterial cells and is capable of integrating its DNA into the host DNA, as well as overriding its cellular machinery to produce more copies of itself.) T7 RNA polymerase is responsible for beginning transcription at the T7 promoter of the transformed vector. The T7 gene is itself under the control of a lac promoter. Normally, both the lac promoter and the T7 promoter are repressed in the E. coli cell by the Lac repressor . In order to initiate transcription, an inducer must bind to the lac repressor and prevent it from inhibiting the gene expression of the T7 gene. Once this happens, the gene can be normally transcribed to produce T7 RNA polymerase. T7 RNA polymerase, in turn, can bind to the T7 promoter on the expression vector and begin transcribing its downstream gene of interest. To stimulate this process, the inducer IPTG can be added to the system. IPTG is a reagent that mimics the structure of allolactose , and can therefore bind to the lac repressor and prevent it from inhibiting gene expression. Once enough IPTG is added, the T7 gene is normally transcribed, and so transcription of the gene of interest downstream of the T7 promoter also begins. [ 6 ] Expression of a recombinant protein under the control of the T7 promoter is 8x faster than protein expression under the control of E. coli RNA polymerase. [ 7 ] Basal levels of expression of T7 RNA polymerase in the cell are also inhibited by the bacteriophage T7 lysozyme, which results in a delay of the accumulation of T7 RNA polymerase until after lysozymic activity is saturated. [ 8 ]
During the COVID-19 pandemic , mRNA vaccines have been developed by Moderna and Pfizer to combat the spread of the virus. Both Moderna and Pfizer have relied on the T7 expression system to generate the large quantities of mRNA needed to manufacture the vaccines. [ 9 ] [ 4 ] | https://en.wikipedia.org/wiki/T7_expression_system |
The M3 Stuart / light tank M3, was a US light tank of World War II , first entered service in the British Army in early 1941 and saw action in the North African campaign in July 1941. [ 4 ] Later an improved version of the tank entered service as the M5 in 1942 to be supplied to British and other allied Commonwealth forces under lend-lease prior to the entry of the United States into the war.
The British service name "Stuart" came from the U.S. Civil War Confederate general J. E. B. Stuart and was used for both the M3 and the derivative M5 light tank. Unofficially, they were also often called "Honeys" by the British, because of their smooth ride. [ 5 ] In U.S. use, the tanks were officially known as "light tank M3" and "light tank M5".
Stuarts were first used in combat in the North African campaign ; about 170 were used by the British forces in Operation Crusader (18 November – 30 December 1941). Stuarts were the first American-crewed tanks in World War II to engage the enemy in tank versus tank combat when used in the Philippines in December 1941 against the Japanese. [ 6 ] [ 7 ] Outside of the Pacific War, in later years of WWII the M3 was used for reconnaissance and screening.
Observing events in Europe and Asia during World War II , American tank designers realized that the light tank M2 was becoming obsolete and set about improving it. The upgraded design, with thicker armor , modified suspension and new gun recoil system was called "light tank M3". Production of the vehicle started in March 1941 and continued until October 1943.
By the standards of the era for light tanks, the Stuart was fairly heavily armored. It had 38 mm of armor on the upper front hull, 44 mm on the lower front hull, 51 mm on the gun mantlet, 38 mm on the turret sides, 25 mm on the hull sides, and 25 mm on the hull rear. [ 8 ] Like its direct predecessor, the M2A4, the M3 was initially armed with a 37 mm M5 gun and five .30-06 Browning M1919A4 machine guns: one coaxial with the main gun, one on top of the turret in an M20 anti-aircraft mount, another in a ball mount in right bow, and two more in the right and left hull sponsons . Later, the main gun was replaced with the slightly longer M6, and the sponson machine guns were removed.
The M3 and M3A1 variants were powered by an air-cooled radial engine , either a gasoline-fueled 7- cylinder Continental W-670 (8,936 built) or a 9-cylinder Guiberson T-1020 diesel (1,496 built). [ 9 ] Both of these powerplants were originally developed as aircraft engines . Internally, the radial engine was at the rear and the transmission at the front of the tank's hull. The driveshaft connecting the engine and transmission ran through the middle of the fighting compartment. The radial engine's crankshaft was positioned high off the hull bottom and contributed to the tank's relatively tall profile. [ 10 ] When a revolving turret floor was introduced in the M3 hybrid and M3A1, the crew had less room. A further 3,427 M3A3 variants were built with modified hull (similar to the M5), new turret and the Continental W-670 gasoline engine. [ 11 ] In contrast to the M2A4, all M3/M5 series tanks had a trailing rear idler wheel for increased ground contact, whereas on the M2 the idler wheel was off the ground and did not aid in suspension.
To relieve wartime demand for the radial aero-engines used in the M3, a new version was developed using twin Cadillac V8 automobile engines and twin Hydra-Matic transmissions operating through a transfer case . This version of the tank was quieter, cooler and roomier; the automatic transmission also simplified crew training. The new model (initially called M4 but redesignated M5 to avoid confusion with the M4 Sherman [ 12 ] ) featured a redesigned hull with a raised rear deck over the engine compartment, sloped glacis plate and driver's hatches moved to the top. Although the main criticism from units using the Stuarts was that it lacked firepower, the improved M5 series kept the same 37 mm gun. The M5 gradually replaced the M3 in production from 1942 and, after the M7 project proved unsatisfactory, was succeeded by the light tank M24 in 1944. Total M5 and M5A1 tank production was 8,884; an additional 1,778 M8 75 mm howitzer motor carriages based on the M5 chassis with an open-top turret were produced.
Light tanks were issued to tank battalions (one of the four companies was a light tank company), light tank battalions and cavalry reconnaissance squadrons. The original role of the light tank in these formations was similar to medium tanks and they were expected to engage enemy armor with AP rounds and enemy positions with HE rounds. As a result, tank gunnery training for light and medium tankers was common. [ 14 ]
US Army Field Manuals written before 1944 clearly show that light tanks were to be part of an armored assault on enemy positions, and examples of fire on enemy armor were in these manuals. [ 15 ] When pursuing an enemy, light tank battalions were expected to move parallel with enemy columns and, together with accompanying infantry and engineer units, seize "critical terrain that will block hostile retreat". [ 16 ] Despite the fact that light tank platoons were not expected to function as a reconnaissance unit, they could be used for reconnaissance purposes. [ 17 ] In this role, they were expected to remain behind the main reconnaissance force as the support element and augment the firepower whenever enemy contact was made. [ 18 ]
[It] is apparent that a Light Tank Battalion, armed with only 37mm guns, unless very skillfully employed with Infantry, will suffer severe casualties in men and material. The Light Tank still has to depend on speed, maneuver, and selection of suitable targets if it is to be of very much use. In spite of the fact that the training of this Battalion was not pointed toward reconnaissance lines, we have been able to accomplish our missions with a Cavalry Reconnaissance Group with a much greater degree of success than in any other assignment to date.
British and other Commonwealth armies were the first to use the light tank M3, as the "Stuart", in combat. [ 20 ] From mid-November 1941 to the end of the year, about 170 Stuarts (in a total force of over 700 tanks) took part in Operation Crusader during the North Africa Campaign , with poor results. This is despite the fact that the M3 was superior or comparable in most regards to most of the tanks used by the Axis forces. The most numerous German tank, the Panzer III Ausf G, had nearly identical armor and speed to the M3, [ a ] and both tanks' guns could penetrate the other tank's front armor from beyond 1,000 m (3,300 ft). [ 21 ] The most numerous Italian tank (and second most numerous Axis tank overall), the Fiat M13/40 , was much slower than the Stuart, had slightly weaker armor all around, and could not penetrate the Stuart's front hull or turret armor at 1,000 meters, whereas the Stuart's gun could penetrate any spot on the M13/40. Although the high losses suffered by Stuart-equipped units during the operation had more to do with the better tactics and training of the Afrika Korps than the apparent superiority of German armored fighting vehicles used in the North African campaign, [ 21 ] the operation revealed that the M3 had several technical faults. Mentioned in the British complaints were the 37 mm M5 gun and poor internal layout. The two-man turret crew was a significant weakness, and some British units tried to fight with three-man turret crews. The Stuart also had a limited range, which was a severe problem in the highly mobile desert warfare as units often outpaced their supplies and were stranded when they ran out of fuel.
On the positive side, crews liked its relatively high speed and mechanical reliability, especially compared to the Crusader tank , [ 22 ] [ 23 ] which comprised a large portion of the British tank force in Africa up until 1942. The Crusader had similar armament and armor to the Stuart while being slower, less reliable, and several tons heavier. The Stuart also had the advantage of a gun that could deliver high-explosive shells; HE shells were not available for the 40 mm QF 2-pdr gun mounted by most Crusaders, severely limiting their use against emplaced anti-tank guns or infantry. [ 24 ] [ b ] The main drawback of the Stuart was its low fuel capacity and range; its operational range was only 75 miles (121 km) cross country, [ 25 ] roughly half that of the Crusader.
In the summer of 1942, the British usually kept Stuarts out of tank-to-tank combat, using them primarily for reconnaissance. The turret was removed from some examples to save weight and improve speed and range. These became known as "Stuart Recce". Some others were converted to armored personnel carriers known as the "Stuart Kangaroo ", and some were converted into command vehicles and known as "Stuart Command". M3s, M3A3s, and M5s continued in British service until the end of the war, but British units had a smaller proportion of these light tanks than U.S. units. [ citation needed ]
The other major Lend-Lease recipient of the M3, the Soviet Union , was less happy with the tank, considering it under-gunned, under-armored, likely to catch fire, and too sensitive to fuel quality. The M3's radial aircraft engine required high-octane fuel, which complicated Soviet logistics as most of their tanks used diesel or low-octane fuel. High fuel consumption led to a poor range characteristic, especially sensitive for use as a reconnaissance vehicle. In the letter sent to Franklin Roosevelt (18 July 1942), Stalin wrote: "I consider it my duty to warn you that, according to our experts at the front, U.S. tanks catch fire very easily when hit from behind or from the side by anti-tank rifle bullets. The reason is that the high-grade gasoline used forms inside the tank a thick layer of highly inflammable fumes. " [ 26 ] [ check quotation syntax ] Also, compared to Soviet tanks, the M3's narrower tracks resulted in a higher ground pressure, getting them more easily stuck in the Rasputitsa muddy conditions of spring and autumn and winter snow conditions on the Eastern Front. In 1943, the Red Army tried out the M5 and decided that the upgraded design was not much better than the M3. Being less desperate than in 1941, the Soviets turned down an American offer to supply the M5. M3s continued in Red Army service at least until 1944. [ citation needed ]
One of the more successful uses of the M5 in combat came during the Battle of Anzio when breaking through German forces surrounding the beachhead. The tactics called for an initial breakthrough by a medium tank company to destroy the heavier defenses, followed by an infantry battalion who would attack the German troops who were being left behind the medium tanks. Since many hidden fortifications and positions would have survived the initial medium tank assault, the infantry would then be confronted by any remaining fortified German troops. Behind the infantry came the M5s of a light tank company, who would attack these positions when directed to by the Infantry, usually by the use of green smoke grenades . [ 27 ]
In the 1944 Liri Valley campaign, the official history of the 18th Battalion (New Zealand) notes that in the campaign (a war of movement) the regiment discovered that the Stuart recce tanks were an enormous advance on scout cars, and could go where not even jeeps could go. They carried commanders and engineers, and medical orderlies, and they could explore flanks while the Shermans forged ahead. They carried mobile wireless links and transported supplies up hilltops; they had a dozen different uses. [ 28 ]
The U.S. Army initially deployed 108 Stuart light tanks to the Philippines in September 1941, equipping the U.S. Army's 194th and 192nd Tank Battalions . The first U.S. tank versus tank combat to occur in World War II happened on 22 December 1941 during the Philippines campaign (1941–1942) when a platoon of five M3s led by Lieutenant Ben R. Morin engaged the Imperial Japanese Army (IJA) 4th Tank Regiment's Type 95 Ha-Go light tanks north of Damortis. Morin, with his 37mm cannon locked in recoil maneuvered his M3 off the road, but took a direct hit while doing so, and his tank began to burn. The other four M3s were also hit, but managed to leave the field under their own power. Lt. Morin was wounded, and he and his crew were captured by the enemy. [ 29 ] M3s of the 194th and 192nd Tank Battalions continued to skirmish with the 4th Tank Regiment's tanks as they continued their retreat down the Bataan Peninsula, with the last tank versus tank combat occurring on 7 April 1942. [ 30 ] [ 31 ]
As the Japanese 15th Army was threatening southern Burma toward the end of February 1942, 7th Armoured Brigade of the British Army landed at Rangoon with 114 M3 Stuarts bearing the green rodent of the "Desert Rats". They supported 17th Indian Division and 1st Burma Division on the retreat until they managed to escape to India in April. [ 32 ]
Due to the naval nature of the Pacific campaign, steel for warship production took precedence over tanks for the IJA, [ 33 ] creating by default an IJA light tank that performed admirably in the jungle terrain of the South Pacific. By the same measure, although the US was not hampered by industrial restrictions, the M3 proved to be an effective armored vehicle for fighting in jungle environments. [ 34 ] At least one was captured in the Philippines. [ 35 ]
With the IJA's drive toward India within the South-East Asian theatre of World War II , the United Kingdom hastily withdrew their 2nd Royal Tank Regiment and 7th Hussars Stuart tank units (which also contained some M2A4 light tanks [ 36 ] ) from North Africa, and deployed them against the Japanese 14th Tank Regiment. By the time the Japanese had been stopped at Imphal , only one British Stuart remained operational. [ 37 ] When the U.S. entered the war in 1941, it began to supply China with AFVs, including M3 Stuarts, and later M4 Sherman medium tanks and M18 Hellcat tank destroyers , which trickled in through Burma.
Although the M3/M5 had proven effective in jungle warfare, by late 1943, U.S. Marine Corps tank battalions were transitioning from their M3/M5 light tanks to M4 medium tanks, mostly for the much greater high-explosive blast effect of the M4's 75mm gun, which fired a much larger shell with a heavier explosive payload. [ 38 ]
When the U.S. Army joined the North African Campaign in late 1942, Stuart units still formed a large part of its armor strength. After the disastrous Battle of Kasserine Pass , the U.S. quickly followed the British in disbanding most of their light tank battalions and reorganizing medium tank battalions to include one company of light tanks, where the Stuarts mostly performed the traditional cavalry missions of scouting and screening; for the rest of the war, most U.S. tank battalions had three companies of M4 Shermans and one company of M3s or M5/M5A1s. [ 39 ]
In Europe, Allied light tanks were given cavalry and infantry fire support roles since their light main armament was not competitive against heavier enemy armored fighting vehicles. However, the Stuart was still effective in combat in the Pacific Theater , as Japanese tanks were both relatively rare and were lighter in armor than even Allied light tanks. [ 40 ] [ 41 ] Japanese infantrymen were not well equipped with anti-tank weapons, and as such had to use close assault tactics. In this environment, the Stuart was only moderately more vulnerable than medium tanks. [ citation needed ] [ check quotation syntax ] Though the Stuart was to be completely replaced by the newer M24 Chaffee, the number of M3s/M5s produced was so great (over 25,000 including the 75mm HMC M8) that the tank remained in service until the end of the war, and well after. In addition to the U.S, UK and Soviet Union, who were the primary users, it was also used by France (M3A3 and M5A1), China (M3A3s and, immediately post-war, M5A1s) and Josip Broz Tito 's Partisans in Yugoslavia (M3A3s and few M3A1).
With the limitations of both the main gun (see below) and armor, the Stuart's intended combat role in Western Europe was changed significantly. Light tank companies were often paired with cavalry reconnaissance units, or else used for guarding or screening, and even used in supply or messenger roles for medium tank units. [ c ]
On 9 December 1944, the 759th Tank Battalion advanced on a hill near Bogheim but was subjected to a counter-attack by German forces, including a heavy self-propelled assault gun , which took "over 100 direct hits" at ranges as low as 75 yd (69 m) with "no appreciable damage". [ 43 ]
In January 1945, a report to General Eisenhower concluded that the Stuart was "obsolete in every respect as a fighting tank" and that it would not "turn the German fire [n]or [would] the 37mm gun damage the German tanks or SP guns". [ 44 ]
After the war, some countries chose to equip their armies with cheap and reliable war surplus Stuarts. The Chinese Nationalist Army having suffered great attrition as a result of the ensuing civil war, rebuilt their armored forces by acquiring surplus vehicles left behind in the Philippines by the U.S. forces, including 21 M5A1s to equip two tank companies.
The M5 played a significant role in the First Kashmir War (1947) between India and Pakistan, including the battle of Zoji-la pass fought at an elevation of nearly 12,000 ft (3,700 m).
M3A1 and M3A3s were used by British forces in Indonesia during the Indonesian National Revolution , where they suffered heavy losses due to the Stuart's thin armor plating. [ 45 ] They were used until 1946, when the British left. The M3A1 and M3A3s were then passed on to the Royal Netherlands East Indies Army , which used them until the end of the fighting before passing on the tanks to the Indonesian Army . The tank saw action during the Darul Islam rebellions in Aceh and Java, Republic of South Maluku rebellions in South Maluku, PRRI rebellions in Sumatra, Permesta rebellions in Northern Sulawesi and the fighting against the 30 September Movement . [ 46 ]
During the 1960s and 1970s, the Portuguese Army also used a small number of M5A1 light tanks, out of a total of 90 received as military aid from Canada in 1956, in the war in Angola , where its all-terrain capability (compared to wheeled vehicles) was greatly appreciated. In 1967, the Portuguese Army deployed three M5A1 light tanks – nicknamed "Milocas", "Licas", and "Gina" by their crews – to northern Angola , which served with the 1927th Cavalry Battalion commanded by Cavalry Major João Mendes Paulo, stationed at Nambuangongo . The vehicles were mostly employed for convoy escort and recovery duties and limited counterinsurgency operations against National Liberation Front of Angola (FNLA) guerrillas, who dubbed them "Elefante Dundum". "Milocas" was destroyed by an accidental fire in 1969, while "Gina" and "Licas" were withdrawn from active service in 1972, the former being sent to Luanda and the latter ended up in 1973 as an airfield security pillbox in the Portuguese Air Force 's Zala airfield. [ 47 ] Period photographs show some modifications to the basic design, namely the omission of the bow machine gun, re-installed on a pintle mount in the roof of the turret, and a small searchlight fitted in front of the commander's cupola. [ 48 ]
During the four-day long Football War of 1969, El Salvador invaded Honduras in an all-out-war strike using the M3 Stuart as the main battle tank. El Salvador captured eight major cities before the Organization of American States arranged a ceasefire.
The South African Armoured Corps continued to use M3A1s in a reserve role until 1955. Some were refurbished locally in 1962 and remained in service as late as 1964. The fleet was withdrawn in 1968, owing to parts shortage. [ 49 ]
The M3 Stuart is still on the active list in the Armed Forces of Paraguay , with ten of the tanks being overhauled in 2014 to provide a training capability. [ 50 ] [ 51 ] Ecuador also still has a number in service. [ 51 ]
The amphibious Landing Vehicle Tracked LVT(A)-1 had a turret that was nearly identical to that of the M3 Stuart. [ 55 ]
In the 1970s, the Brazilian company Bernardini developed a series of radical Stuart upgrades for the Brazilian Army .
Yugoslav partisans received Stuarts from the British Army. In 1945, obsolete as tanks, many were modified to carry specialized armament:
Current operators
Former operators
Notes
Background: British armoured fighting vehicle production during World War II , Tanks in the British Army | https://en.wikipedia.org/wiki/T81_Chemical_Mortar_Motor_Carriage |
T9 is a predictive text technology for mobile phones (specifically those that contain a 3×4 numeric keypad ), originally developed by Tegic Communications , now part of Nuance Communications . T9 stands for Text on 9 keys. [ 1 ]
T9 was used on phones from Verizon , NEC , Nokia , Samsung Electronics , Siemens , Sony Mobile , Sanyo , SAGEM and others, as well as PDAs such as Avigo during the late 1990s. The main competing technologies include iTap created by Motorola , SureType created by RIM , Eatoni's LetterWise and WordWise , and Intelab's Tauto . It still is used on niche products as Punkt mp-02.
T9 is available on certain phones without a touchscreen, and is available on Apple iPhone (as of iOS 18 ) [ 2 ] and Android phones as a custom keyboard.
T9's objective is to make it easier to enter text messages . It allows words to be formed by a single keypress for each letter, which is an improvement over the multi-tap approach used in conventional mobile phone text entry at the time, in which several letters are associated with each key, and selecting one letter often requires multiple keypresses.
T9 combines the groups of letters on each phone key with a fast-access dictionary of words. It will then look up in the dictionary all words corresponding to the sequence of keypresses and order them by frequency of use. As T9 "gains familiarity" with the words and phrases the user commonly uses, it speeds up the process by offering the most frequently used words first and then letting the user access other choices with one or more presses of a predefined "Next" key.
The dictionary is expandable. After introducing a new word, the next time the user tries to produce that word, T9 adds it to the predictive dictionary. The user database (UDB) can be expanded via multi-tap . The implementation of the user database is dependent on the version of T9 and how T9 is actually integrated on the device. Some phone manufacturers supply a permanent user database, while others do so for the duration of the session.
Some T9 implementations feature smart punctuation . This feature allows the user to insert sentence and word punctuation using the '1'-key. Depending on the context, smart punctuation inserts sentence punctuation (period or 'full stop') or embedded punctuation (period or hyphen) or word punctuation (apostrophe in can't, won't, isn't, and the possessive 's ). Depending on the language, T9 also supports word breaking after punctuation to support clitics such as l' and n' in French and 's in English.
For words entered by the user, word completion can be enabled. When the user enters matching keypresses, in addition to words and stems, the system also provides completions.
In later versions of T9, the user can select a primary and secondary language and access matches from both languages. This enables users to write messages in their native language, as well as a foreign one.
Some implementations learn commonly used word pairs and provide word prediction (e.g. if one often writes "eat food", after entering "eat" the phone will suggest "food", which can be confirmed by pressing Next).
T9 can automatically recognize and correct typing/texting errors, by looking at neighboring keys on the keypad to determine an incorrect keypress. For example, the word "testing" is entered with the key combination "8378464". Entering the same number but with two incorrect keypresses of neighboring keys, e.g. "8278494", results in T9 suggesting the words "tasting" (8278464), "testing" (8378464), and "tapping" (8277464).
In order to achieve compression ratios of close to 1 byte per word, T9 uses an optimized algorithm that maintains word order and partial words (also known as stems); however, because of this compression, it over-generates words that are sometimes visible as "junk words". This is a side effect of the requirements for small database sizes on the lower end embedded devices. [ citation needed ]
On a phone with a numeric keypad, each time a key (1-9) is pressed (when in a text field), the algorithm returns a guess for what letters are most likely for the keys pressed to that point. For example, to enter the word 'the', the user would press 8 then 4 then 3, and the display would display 't' then 'th' then 'the'. If the less-common word 'fore' is intended (3673) the predictive algorithm may select 'Ford'. Pressing the 'next' key (typically the '*' key) might bring up 'dose', and finally 'fore'. If 'fore' is selected, then the next time the user presses the sequence 3673, fore will be more likely to be the first word displayed. If the word "Felix" is intended, however, when entering 33549, the display shows ' E ', then 'De', 'Del', 'Deli', and ' F elix.' This is an example of a letter changing while entering words.
Many smart keyboards now exist, such as Gboard or Swiftkey , that have taken the idea of T9 and combined it with the advanced touchscreen technology found in Android phones and iPhones . These advances have made T9 obsolete in newer cellphones for many users, since it is predicated on the use of a keypad with nothing besides numbers, the asterisk and the hash sign (known by various different names depending on the country, e.g. the hash sign in the UK , Australia , and various other Commonwealth nations; the pound sign in the USA (not to be confused with the currency symbol ); and the number sign in Canada ). Many features, such as predictive text, have been adopted by and improved by future generations of keyboard software. However, T9 remains viable. For example, those with larger fingertips still use the T9 based keyboard on smartphones for text entry, because key press accuracy increases with the larger screen area per key on a numeric-style 4×3 keyboard. Such T9 formats for text entry therefore remain available in all latest [as of August 2020] iterations of LG keyboards, certain Samsung keyboards, and third party T9 keyboards such as Go keyboard for Androids and Type Nine for iPhones, as shown on this LG V60. | https://en.wikipedia.org/wiki/T9_(predictive_text) |
The Foundation for Technology Assessment TA-SWISS is a Centre of Competence of the Swiss Academies of Arts and Sciences , based on a mandate in the Swiss federal law on research. It is an advisory body, financed by public money, and devoted to technology assessment . (The abbreviation «TA» which is used to describe TA-SWISS stands for Technology Assessment , and reflects the activities of the Centre.)
The object of the Foundation for Technology Assessment TA-SWISS is to follow technological changes and developments and to identify the social, legal and ethical consequences of new technologies. Another element of its mission is to encourage the discussion of scientific and technological challenges.
The recommendations that result from TA-SWISS projects are used to assist the decision making process, and are intended for the Swiss Parliament and the Federal Council. Depending on the topics covered, these recommendations may also be of interest to other groups, such as professional associations, commercial enterprises, universities and stakeholder groups, as well as public administrations. The media, in their role as disseminators of information, are also kept regularly informed about the activities of TA-SWISS.
TA-Swiss is full member of the European Parliamentary Technology Assessment (EPTA) network [ 1 ] and is a founding member of the German speaking Network NTA (Netzwerk Technikfolgenabschätzung). [ 2 ]
The activities of the Foundation for Technology Assessment TA-SWISS are further divided into two areas:
1. Studies (interdisciplinary scientific analyses)
Recent studies have covered the following topics:
2. Participative projects (consultations aimed at gathering the views of citizens)
Numerous events have been organised within the scope of the participative projects – PubliForums, publifocus and other forms of dialogue, for example:
Experimental beginnings: TA-SWISS began its work in 1992. Following a number of parliamentary interventions, the Federal Council assigned the Swiss Science and Technology Council the task of developing a system of technology assessment for Switzerland over a four-year pilot phase (1992–1995).
Institutionalisation of technology assessment: In its Message relating to the promotion of training, research and technology for the years 1996-1999, the Federal Council defined the bases for the institutionalisation and financing of technology assessment in Switzerland. In 1999, technology assessment was firmly fixed in the law on research. In this way, the Federal Council reinforced the independence of TA-SWISS, which until 2007 was affiliated to the Swiss Science and Technology Council.
In 2008 a change in the law on research conferred the legal basis on the incorporation of the mandate for TA-SWISS within the Association of Swiss Academies of Arts and Sciences. Accordingly, since 1 January 2008 TA-SWISS has been a Centre for Excellence of the Swiss Academies of Arts and Sciences. | https://en.wikipedia.org/wiki/TA-SWISS |
Threat Agent Cloud Tactical Intercept & Countermeasure , or TACTIC , is a United States military research program whose goal is to detect, classify, and neutralize airborne biological and chemical warfare agents .
As Dr. Karen Wood, program manager of TACTIC in the Tactical Technology Office of DARPA , explains:
The purpose of the Threat Agent Cloud Tactical Intercept and Countermeasure (TACTIC) Program is to provide the United States (US) military with the capability to protect the warfighter from CWA/BWA threat clouds on the battlefield. The goal of the program is to provide a system that can rapidly detect and identify the presence of a typical threat cloud and provide a countermeasure to that cloud that will kill it before it reaches the intended target. [ 1 ]
The program's goal is to be able to detect and identify CWA/BWA threats within the time frame of one minute. Research includes such methodologies as:
Upon successfully determining the nature of the CWA/BWA threat, "technologies that mimic the seeding of rain clouds will be developed for particulate bio-agents, and technologies that react with chemical agent vapor will be investigated." [ 2 ] When an effective system for both identifying and countering the CWA/BWA threat is engineered, DARPA will then provide a prototype which will be vigorously tested in aerosol chambers. Only after completion of chamber testing will full-scale field testing commence. | https://en.wikipedia.org/wiki/TACTIC_(military_program) |
TADIG code is a number uniquely identifying network operators in a GSM mobile network. The acronym TADIG expands to " Transferred Account Data Interchange Group ". According to the GSM specification, the codes are used as "primary identifiers within file contents and file names" in multiple file formats defined by the GSMA . [ 1 ] Network operators are required to register new codes and limit themselves to using code already registered with the GSMA. [ 2 ]
TADIG codes are generally used by bilateral agreement for the purposes of billing roaming telephone calls.
A TADIG code is 5 characters long, consisting of
TADIG code: CANGW (for Freedom Mobile, formerly WIND Mobile)
TADIG code: SWE01 (for the Sweden1 bilateral Roaming Hub)
TADIG code: USAHI (for Mobi )
The GSMA specification lists the following in their list of "known issues" as discrepancies between codes registered with them against ones actually being used
This article related to telecommunications is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TADIG_code |
TAG Heuer S.A. , founded Heuer AG [ a ] ( / ˌ t æ ɡ ˈ h ɔɪ . ər / TAG HOY -ər ) is a Swiss luxury watchmaker . Founded in 1860 by Edouard Heuer in St-Imier , Switzerland, it was acquired by Techniques d'Avant Garde (TAG) in 1985, which purchased a majority stake in the company, forming TAG Heuer . [ 1 ] In 1999, French luxury goods conglomerate LVMH bought nearly 100 percent of the Swiss company. [ 1 ] The name TAG Heuer combines the initials of "Techniques d'Avant Garde" and the founder's surname. Although best known for its chronographs , it has also manufactured stopwatches .
TAG Heuer is based in La Chaux-de-Fonds , Switzerland, and is led by CEO Frédéric Arnault. Jack Heuer, great-grandson of the founder, is the honorary chairman. TAG Heuer maintains a watchmaking workshop in Cornol , Switzerland, and a watchmaking factory in La Chaux-de-Fonds. TAG Heuer's slogan is "Swiss Avant-Garde Since 1860".
In 1860 Edouard Heuer founded Uhrenmanufaktur Heuer AG (English: Heuer Watchmaking Inc.) in St-Imier , Switzerland. [ 2 ]
Edouard Heuer patented his first chronograph in 1882 and in 1887 patented an "oscillating pinion" still used by major watchmakers of mechanical chronographs. [ 3 ] [ 4 ]
In 1911, Heuer received a patent for the "Time of Trip", the first dashboard chronograph. Designed for use in automobiles and aircraft, two large hands mounted from the center pinion indicate the time of day, as on a traditional clock. A small pair of hands mounted at the top of the dial (12 o'clock position) indicates the duration of the trip (up to 12 hours). A top-mounted crown allows the user to set the time; a button mounted in that crown operates the start/stop/reset functions of the "duration of trip" counter.
Heuer introduced its first wrist chronograph in 1914. The crown was at the 12 o'clock position, as these first wrist chronographs were adapted from pocket chronographs. In 1916 Edward Heuer's son, Charles-Auguste, introduced the "Mikrograph", the first stopwatch accurate to 1/100 of a second. This model was soon followed by the "Semikrograph", a stopwatch that offered 1/50 of a second timing, as well as a split-second function (which allows the user to determine the interval between two contestants or events).
In 1933, Heuer introduced the "Autavia", a dashboard timer used for automobiles and aviation (whence its name, from "AUTos" and "AVIAtion"). The companion "Hervue" was a clock that could run for eight days without being wound. Over the period from 1935 through the early 1940s, Heuer manufactured chronographs for pilots in the Luftwaffe , known as "Flieger" (pilot) chronographs. The earlier version featured a hinged-back case and one pusher (for start/stop/reset); the later version had a snap-back case and added a second pusher (for time-in and time-out). All these Flieger chronographs had two-registers, with a capacity of 30 minutes." [ 5 ]
In the mid-1940s, Heuer expanded its line of chronographs to include two- and three-register models and a three-register chronograph that had a full calendar function (day/date/month). As the highest development of Heuer's chronographs, these "triple calendar" chronographs came in stainless steel and 14, 18, and 22 karat gold cases. Dial colors were white, black, or copper.
In the early-1950s, Heuer produced watches for the American retailer Abercrombie & Fitch . The "Seafarer" and "Auto-Graph" were chronographs produced by Heuer to be sold by Abercrombie & Fitch. The "Seafarers" had special dials—with blue, green, and yellow patterns—that showed the high and low tides. This dial could also be used to track the phases of the moon. Heuer produced a version of the "Seafarer" for sale under the Heuer name, with this model called the "Mareographe". Heuer produced the "Auto-Graph" in 1953 and 1954, which featured a tachymeter scale on the dial and a hand that could be preset to a specific point on the scale. This complication allowed a rally driver or navigator to determine whether the car achieved the desired pace over a measured mile. Advertisements and literature also pointed out that this hand could be rotated to count golf scores or other events. [ 6 ]
From 1911, Heuer manufactured timepieces to be mounted on the dashboards of automobiles, aircraft, and boats. These clocks and timers included a variety of models designed to address the specific needs of racers and rallyists. In 1958, Heuer introduced a new line of dashboard timepieces, which included the Master Time (8-day clock), the Monte Carlo (12-hour stopwatch), the Super Autavia (full chronograph), Sebring (60-minute, split-second timer), and Auto-Rallye (60-minute stopwatch). Heuer continued to manufacture these dashboard timepieces into the 1980s when Heuer discontinued them. Heuer also introduced timing devices for ski and motor racing events, including Formula One .
From the 1950s to the 1970s, Heuers were popular watches among automobile racers, both professionals and amateurs. [ 7 ] Heuer was a leading producer of stopwatches and timing equipment, based on the volume of its sales, so it was only natural that racers, their crews and event sponsors began to wear Heuer chronographs. Heuer produced special chronograph versions with the logo of the Indianapolis Motor Speedway , as well as the names or logos of racing teams or sponsors (for example, Shelby Cobra , MG and Champion Sparkplugs). [ 8 ]
In 1962, Heuer became the first Swiss watchmaker in space. John Glenn wore a Heuer stopwatch when he piloted the Mercury Atlas 6 spacecraft on the first US crewed space flight to orbit the Earth. [ 9 ] This stopwatch was the backup clock for the mission. It was started manually by Glenn 20 seconds into the flight. It is currently on display at the San Diego Air and Space Museum .
The Autavia chronograph was introduced in 1962 and featured a rotating bezel, marked in either hours, minutes, decimal minutes (1/100 minute increments), or with a tachymeter scale. All manual-wind Autavias from the 1960s had a black dial with white registers. Early cases had a screw-back, and later models (from and after 1968) had snap-backs. Heuer had previously used the "Autavia" name for its dashboard timers.
In 1963, Heuer introduced the Carrera chronograph, designed by Jack Heuer, great-grandson of Edouard. The Carrera had a very simple design, with only the registers and applied markers on the dial. The fixed inner bezel is divided into 1/5 second increments. In the 1960s, Carreras were available with a variety of dials, including all-white, all-black, white registers on a black dial, and black registers on a black dial. A three-register, triple calendar version of the Carrera was introduced around 1968.
Most of Heuer chronographs from this period—including the Autavias and Carreras—used movements manufactured by Valjoux , including the Valjoux 72 movement (for a 12-hour chronograph) and the Valjoux 92 movement (for a 30-minute or 45-minute chronograph). The Valjoux 72 movement utilized a "tri-compax" design, with three registers on the dial—one register for the chronograph hours (at the bottom), one register for the chronograph minutes (at the right), and a third register for a continuously running second hand (at the left). The second hand for the chronograph was mounted on the center pinion, along with the time-of-day hands.
Heuer acquired the "Leonidas" brand in the early 1960s, with the combined company marketing watches under the "Heuer-Leonidas" name. One of the designs that Heuer acquired from Leonidas was the "Bundeswehr" chronograph, used by the German air force. These "BWs" feature a "fly-back" mechanism, so that when the chronograph is reset to zero, it immediately begins running again, to time the next segment or event.
In the mid-1960s, Heuer partnered with Breitling and Hamilton (and in competition with Seiko and Zenith ) to introduce an automatic chronograph. These projects were conducted in secret, as none of the competitors wanted the other companies to be aware of their efforts. Heuer-Breitling-Hamilton held press conferences in Geneva and New York, on 3 March 1969 to show their new lines of chronographs. [ 10 ]
Heuer's first automatic chronographs were the Autavia, Carrera, and Monaco . These were powered by the Cal 11 and Cal 12 movements (12-hour chronograph); Cal 14 movement (12-hour chronograph and additional hand for GMT/second time-zone) and the Cal 15 movement (30-minute chronograph). The winding crown was on the left, with the pushers for the chronograph on the right. The earliest of Heuer's Cal 11 chronographs (from 1969) were named "Chrono-Matic". In the early-1970s, Heuer expanded its line of automatic chronographs to include the Daytona, Montreal, Silverstone, Calculator, Monza, and Jarama models, all powered by the Calibre 11 movement.
In 1975, Heuer introduced the Chronosplit, a digital chronograph with dual LED and LCD displays. Later versions featured two LCD displays.
Heuer began using the Valjoux 7750 movement in its automatic chronographs, with the Kentucky and Pasadena models (both introduced in 1977). The Valjoux 7750 movement was a three-register chronograph (with seconds, minutes, and hours), that also offered day/date windows.
In the mid-1970s, Heuer introduced a series of chronographs powered by the Lemania 5100 movement. The Lemania 5100 movements have the minute hand for the chronograph on the center pinion (rather than on a smaller register), greatly improving legibility. The Lemania 5100 movement is considered very rugged and has been used in a variety of chronographs issued to military pilots. There are ten models of Heuer chronographs powered by the Lemania 5100—Reference 510.500 (stainless steel), 510.501 (black coated), 510.502 (olive drab coated), 510.503 (pewter-coated), 510.511 (Carrera dialed acrylic crystal PVD finish), 510.523 (Carrera dialed acrylic crystal stainless steel), as well as models with the names Silverstone (steel case with black dial) and Cortina (steel case with blue dial); the Reference 510.543 was made for the A.M.I. (Italian Air Force) and a special edition (with no reference number marked on the case) was made for AudiSport. [ 11 ]
TAG Heuer was formed in 1985 when TAG Group (Holdings) S.A. , manufacturers of high-tech items such as ceramic turbochargers for Formula One cars, acquired Heuer. Akram Ojjeh , the owner of TAG Heuer sold a significant stake of the company to British businessman Ron Dennis . [ 12 ]
In 1999 TAG Heuer accepted a bid from LVMH Moët Hennessy Louis Vuitton S.A. of CHF 1.15 billion (£452.15 million, USD 739 million), contingent upon a transfer of 50.1 percent of stock. [ 13 ]
In 2010, TAG Heuer introduced the "Pendulum Concept", the first magnetic oscillator without hairspring capable of providing restoring torque comparable to that of hairspring.
In 2013, TAG Heuer celebrated the 50th anniversary of the Carrera, the racing-inspired chronograph that is a key part of the TAG Heuer range today. There have been ten generations of Carrera since its introduction, with models launched in every decade since 1963. [ 14 ]
In 2017 TAG Heuer released limited edition Muhammad Ali watch. [ 15 ]
A company slogan of TAG Heuer is "Don't Crack Under Pressure". [ 16 ] [ 17 ] The slogan was originally introduced in 1991. [ 17 ]
TAG Heuer's current lines include Formula One, Aquaracer, Link, Carrera, Monaco , Connected, Autavia, and Heuer Heritage.
Some of the more recently [ when? ] announced models include the Monaco V4 (the movement of which is driven by belts rather than gears); [ 18 ] the Carrera Calibre 360 (the first mechanical wrist chronograph to measure and display time to 1/100 of a second [ 19 ] ) and the Monaco 69 (with both a digital chronograph accurate to a millisecond and a traditional mechanical movement, with a hinged mechanism allowing wearers to flip the watch between its two separate dials). [ 20 ]
London-based Christoph Behling has been the lead designer for TAG Heuer since 2004. The collaboration has resulted in some of the brand's most celebrated pieces including the world's fastest chronograph, the Mikrogirder 1/2000, launched in 2012. [ 21 ]
Many TAG Heuer watches feature chronographs . In January 2011 TAG Heuer announced the new Carrera Mikrograph, [ 22 ] the first TAG Heuer to use the in-house Mikrograph movement, which is accurate to 1/100 of a second. Additionally, TAG Heuer has also released the limited edition Carrera MP4-12C to commemorate the launch of the McLaren MP4-12C supercar. TAG Heuer has been a partner of the McLaren F1 team for over 26 years. [ 23 ]
At the Basel 2011 show in March 2011, TAG Heuer announced the Mikrotimer Flying 1000, a concept mechanical watch capable of accuracy of 1/1000 of a second—ten times more accurate than the Mikrograph. [ 24 ]
This mark was superseded in January 2012 with the Mikrogirder model, precise to 1/2,000 of a second. [ 25 ]
On November 9, 2015, TAG Heuer announced the launch of their first smartwatch which they named Tag Heuer Connected . [ 26 ] The watch runs on the Android Wear operating system which is used by many smartwatch brands. It uses Intel chips. [ 27 ]
TAG Heuer Connected also offers its own app which principally offers several custom TAG Heuer watch faces which include "Three-Hand", "Chronograph", "GMT", "Themed", "Ambassador" and "Exclusive" watch faces. Each watch face (other than Ambassador and Exclusive) offer black, blue and white backgrounds. The app also provides three smart functions which are a stopwatch , alarm and timer .
All other smartwatch functions and apps are driven via the Android Wear operating system.
In March 2017, TAG Heuer introduced a new smartwatch, TAG Heuer's Connected Modular 45, which allows its owners to switch between connected and mechanical modules. [ 28 ]
In May 2017, TAG Heuer partnered with 20th Century Fox to make the TAG Heuer Connected the official watch of Kingsman: The Golden Circle . [ 29 ]
In 2022, the Connected Calibre line of smartwatches was introduced.
Morez, France-based Groupe Logo manufactures TAG Heuer-branded eyewear under a licence acquired in 2002. [ 30 ]
Paris, France-based ModeLabs Group manufactures TAG Heuer-branded mobile phone under licence. ModeLabs acquired the license in late-2007 and marketed the first TAG Heuer branded mobile phone in late 2008. [ 31 ]
The company also markets a line of men's accessories including wallets, belts, bags, jackets, bracelets, and cuff-links.
In 2007, TAG Heuer won the iF product design award [ 32 ] for its Monaco Calibre 360 LS Concept Chronograph. The award was given away by the International Forum Design Hannover GmbH, held in Hanover , Germany. The watch received the award in the Leisure/Lifestyle category. It was chosen among more than 2,200 timepieces presented by watchmakers from 35 countries. TAG Heuer received the iF product design award for the second time in two years. In 2006, another TAG Heuer watch, entitled Professional Golf Watch, won in the same Leisure/Lifestyle category. The design of the Professional Golf Watch was developed with Tiger Woods . [ 33 ]
In 2010 the Carrera 1887 won La Petite Aiguille ("the small hand") award for watches retailing for less than CHF5,000 at the Grand Prix d'Horlogerie de Genève. [ 34 ]
In December 2018, World Wide Fund for Nature (WWF) released an official report giving environmental ratings for 15 major watch manufacturers and jewelers in Switzerland . [ 35 ] [ 36 ] TAG Heuer, along with Chopard , was given a below-average environmental rating as "Lower Midfield", suggesting that the manufacturer has only taken a few actions addressing the impact of its manufacturing activities on the environment and climate change . [ 35 ]
In the jewelry and watchmaking industries, there are general concerns over the lack of transparency in manufacturing activities and the sourcing of precious raw materials, such as gold , which is a major cause of environmental issues , such as pollution , soil degradation and deforestation . [ 35 ] [ 36 ] The situation is especially serious in the developing countries which are top producers of gold, including China , Russia and South Africa . [ 37 ] [ 38 ] [ 39 ] [ 40 ] It is estimated that the watch and jewelry sector uses over 50% of world's annual gold production (over 2,000 tons), but in most cases the watch companies are not able to or are unwilling to demonstrate where their raw materials come from and if the material suppliers use eco-friendly sourcing technologies. [ 35 ]
TAG Heuer, in keeping with its image as a luxury brand with an innovative spirit, has long-standing links with the world of sport and Hollywood. The brand has had a long list of sports and Hollywood ambassadors. [ 41 ] In addition, TAG Heuer has paid numerous celebrities to endorse its products, including: Tom Brady , Ayrton Senna , Kevin Richardson , Cristiano Ronaldo , Chris Hemsworth , Jessica Michibata , Tiger Woods , Leonardo DiCaprio , Brad Pitt , Sarah Fisher , Louis Koo , Chen Daoming , G.E.M. Tang , Jeff Gordon , Maria Sharapova , Jeremy Lin , Juan Pablo Montoya , Kimi Räikkönen , Uma Thurman , Fernando Alonso , Summer McIntosh , Lewis Hamilton , [ 42 ] Max Verstappen , Sergio Pérez , Therese Johaug , Shah Rukh Khan , Priyanka Chopra , Cameron Diaz , Sydney McLaughlin , [ 43 ] Steve McQueen , Ranbir Kapoor , Mary Kom , Alexander Rossi , Alexandra Daddario and Li Yifeng . [ 44 ] [ 45 ] [ 46 ]
Steve McQueen wore a blue Monaco in the 1971 movie Le Mans (this model is now referred to as the "McQueen Monaco"), [ 47 ] and Swiss Formula One star Jo Siffert customarily wore a white-dialed Autavia with black registers. In 1974, Heuer produced a special version of the black-dialed Autavia that was offered by the Viceroy cigarette company for US$88. [ 48 ] This version of the Autavia was called the "Viceroy" and advertisements for this promotion featured racer Parnelli Jones . [ 49 ]
In the past, TAG Heuer has been the official timekeeper of the three Summer Olympic Games of the 1920s, [ 4 ] the Skiing World Championships and the Formula One World Championship . They have returned to the role of Formula One timekeeper from 2025 onwards, resuming the role they held prior to 2013. [ 50 ]
TAG Heuer is the official time keeper and sponsor of La Liga , Bundesliga , Ligue 1 , Serie A , J1 League , and Major League Soccer .
Since 2011, TAG Heuer has sponsored the Monaco Grand Prix .
From 2017 to 2020, TAG Heuer was the official timekeeper for Gran Turismo Sport , a racing video game that was released on PlayStation 4 . [ 51 ] [ 52 ]
TAG Heuer is an official partner of the Red Bull Racing in Formula One, and sponsored Red Bull's Renault -manufactured power units from 2016 to 2018. [ 53 ] TAG , now known as TAG Group which is no longer affiliated with TAG Heuer, sponsored Williams during the early 1980s. TAG also gave its name to the Porsche engines used by McLaren from 1983 through 1987, and remained a sponsor until 2015. [ 54 ] TAG Group continues to hold a stake in McLaren until 2024. [ 55 ] Heuer was the official timepiece of the Scuderia Ferrari in the 1970s, prior to the TAG acquisition. [ 56 ]
The endorsement with Red Bull was part of a larger promotional outreach program by former TAG Heuer CEO Jean-Claude Biver to enter into markets that may not necessarily be traditional markets for the company, an idea Biver calls "Universes", which include sport, heritage, lifestyle and art and music. Other brand ambassadors in the "Universes" program include David Guetta , OneRepublic , Martin Garrix , Cara Delevingne , Chris Hemsworth , Manchester United F.C. and Muhammad Ali . [ 57 ]
Starting in May 2018, TAG Heuer picked up the sponsorship of the pagoda at the Indianapolis Motor Speedway and also sponsors the IndyCar Series . [ 58 ]
In September 2023, TAG Heuer is became the title sponsor of Porsche Formula E Team . [ 59 ]
In February 2025, TAG Heuer became the official timekeeper of F1 Academy . TAG Heuer will also support Aiva Anagnostiadis for the 2025 season . [ 60 ]
Complete Formula One results
( key ) (results in bold indicate pole position; races in italics indicate fastest lap)
† The driver did not finish the Grand Prix, but was classified as he completed over 90% of the race distance. | https://en.wikipedia.org/wiki/TAG_Heuer_Connected |
TAP Pharmaceuticals was formed in 1977 as a joint venture between the two global pharmaceutical companies, Abbott Laboratories and Takeda Pharmaceutical Co. and was dissolved in 2008; its two most lucrative products were proton-pump inhibitor lansoprazole (Prevacid) and the prostate cancer drug, leuprorelin (Lupron). [ 1 ] The intention of the joint venture was to get products that Takeda had discovered developed , approved, and marketed in the US and Canada. [ 2 ]
The company was established at a time when Japanese pharmaceutical companies were seeking partnerships to access the US market. [ 1 ] These efforts were supported by the Japanese government at the time to help the national economy compete in higher technology, as countries like South Korea, Taiwan were beginning to catch up with Japan in commodity production. [ 2 ] Japanese pharmaceutical companies were especially strong in the fields of generating analogs of known cephalosporin antibiotics, cancer drugs, and cardiovascular drugs. [ 2 ]
The first products TAP file new drug applications for, were two cephalosporins, cefmenoxime (Cefmax) and cefsulodin (Cefonomil), estazolam for sleep disorders, and leuprorelin; leuprorelin was the first one approved, in 1985. [ 3 ]
In 1998 Takeda established its own US R&D and sales force, for the diabetes drug pioglitazone (Actos). [ 1 ]
In 2000, TAP's withdrew its new drug application for apomorphine (branded as "Uprima") as a treatment for erectile dysfunction after an FDA review panel raised questions about the drug's safety, due to many clinical trial subjects fainting after taking the drug. [ 4 ]
In 2001, the US Department of Justice, states attorneys general, and TAP Pharmaceutical Products settled criminal and civil charges against TAP related to federal and state medicare fraud and illegal marketing of the drug leuprorelin . TAP paid a total of $875 million, which was a record high at the time . [ 5 ] [ 6 ]
The $875 million settlement broke down to $290 million for violating the Prescription Drug Marketing Act, $559.5 million to settle federal fraud charges for overcharging Medicare, and $25.5 million reimbursement to 50 states and Washington, D.C., for filing false claims with the states' Medicaid programs. [ 6 ] The case arose under the False Claims Act with claims filed by Douglas Durand, a former TAP vice president of sales, and Joseph Gerstein, a doctor at Tufts University 's HMO practice. [ 5 ] Durand, Gerstein, and Tufts shared $95 million of the settlement. [ 5 ]
When the settlement was announced, the Department of Justice also announced that seven people were indicted on criminal charges by a grand jury; the DoJ also said that four doctors pleaded guilty for receiving kickbacks. [ 6 ] As of 2003 around 12 TAP employees had been indicted and were contested the charges, and one pleaded guilty. [ 7 ] However, in July 2004 a federal jury in Boston declared all the defendants not guilty. [ 8 ]
Abbott and Takeda agreed to end the partnership in 2008, with Abbott keeping the rights to leuprorelin, which had sales in 2007 of $600 million and a patent expiring in 2015 and the approximately 300 employees who worked on the product, and Takeda keeping the rights to lansoprazole, which had sales of $2.3 billion in 2007 but was facing imminent generic competition, along with 800 employees in the U.S. and all the drugs in the TAP pipeline. [ 1 ] [ 9 ] [ 10 ] Takeda was also obligated to pay Abbott about $1.5 billion over several years. [ 9 ] By 2008, Takeda's own sales in the US outside of TAP had grown to $3 billion, mostly from sales of pioglitazone which by then was the best-selling diabetes drug in the world. [ 10 ] | https://en.wikipedia.org/wiki/TAP_Pharmaceuticals |
TARDIS , Temperature And Radiative Diffusion In Supernovae , is an open-source 1D Monte Carlo radiative-transfer spectral synthesis program used for numerical modelling and analysis of supernovae . [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ]
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TARDIS_(software) |
TARGET2 was the real-time gross settlement (RTGS) system for the Eurozone from its phased introduction in 2007-2008 until its replacement with T2 in March 2023. As such, it was one of the Eurosystem 's TARGET Services , replacing the original TARGET (Trans-European Automated Real-time Gross Settlement Express Transfer System) RTGS introduced in 1999. Like the other TARGET Services, it was developed and owned by the Eurosystem.
TARGET2 was based on an integrated central technical infrastructure, known as the Single Shared Platform (SSP). [ 1 ] SSP was operated by three providing central banks : France ( Banque de France ), Germany ( Deutsche Bundesbank ) and Italy ( Banca d'Italia ). It started to replace the predecessor system TARGET in November 2007.
TARGET2 was also an interbank RTGS payment system for the clearing of cross-border transfers in the eurozone. Participants in the system were either direct or indirect. Direct participants held an RTGS account and had access to real-time information and control tools. They were responsible for all payments sent from or received on their accounts by themselves or any indirect participants operating through them. Indirect participation meant that payment orders were always sent to and received from the system via a direct participant, with only the relevant direct participant having a legal relationship with the Eurosystem. Finally, bank branches and subsidiaries could choose to participate in TARGET2 as multi-addressee access or addressable BICs .
The Eurosystem in March 2023 switched its real-time gross settlement from TARGET2 to T2, which follows ISO 20022 . The switch involved transactions for settling payments related to the Eurosystem's monetary policy operations, as well as bank‑to‑bank and commercial transactions. TARGET2 previously handled transactions for over €2.2 trillion per day. [ 2 ]
Since the establishment of the European Economic Community in 1958, there has been movement towards an integrated European financial market. This movement has been marked by several events: In the field of payments, the most visible were the launch of the euro in 1999 and the cash changeover in the euro area countries in 2002. The establishment of the large-value central bank payment system TARGET was less visible, but also of great importance. It formed an integral part of the introduction of the euro and facilitated the rapid integration of the euro area money market.
The implementation of TARGET2 was based on a decision of the ECB Council of autumn 2002. TARGET2 started operations on 19 November 2007, when the first group of countries (Austria, Cyprus, Germany, Latvia, Lithuania, Luxembourg, Malta and Slovenia) migrated to the SSP. This first migration was successful and confirmed the reliability of SSP. After this initial migration, TARGET2 already settled around 50% of overall traffic in terms of volume and 30% in terms of value.
On 18 February 2008, the second migration successfully migrated to TARGET2, comprising Belgium, Finland, France, Ireland, the Netherlands, Portugal and Spain.
On 19 May 2008, the final group migrated to TARGET2, comprising Denmark, Estonia, Greece, Italy, Poland and the ECB. The six-month migration process went smoothly and did not cause any operational disruptions.
Slovakia joined TARGET2 on 1 January 2009, Bulgaria joined in February 2010, Romania on 4 July 2011, and Croatia in February 2016.
The use of TARGET2 was mandatory for the settlement of any euro operations involving the Eurosystem , consisting of the European Central Bank (ECB) and the national central banks of the 20 European Union member states that were part of the Eurozone by the end of the TARGET2 period. [ 3 ] Participation in TARGET2 was mandatory for new member states joining the Eurozone.
TARGET2 services in euro were available to non-Eurozone states. National central banks of states which have not yet adopted the euro could also participate in TARGET2 to facilitate the settlement of transactions in euro. Central banks from four non-Eurozone states Bulgaria, Denmark, Poland and Romania also participated in TARGET2.
In 2012, TARGET2 had 999 direct participants, 3,386 indirect participants and 13,313 correspondents.
There was no upper or lower limit on the value of payments. TARGET2 had to be used for all payments involving the Eurosystem, as well as for the settlement of operations of all large-value net settlement systems and securities settlement systems handling the euro. TARGET2 was operated on a single technical platform. The business relationships were established between the TARGET2 users and their national central bank. In terms of the value processed, TARGET2 was one of the largest payment systems in the world. [ 4 ]
In 2012, TARGET2:
There were two pricing schemes: [ 6 ]
The TARGET2 system was closed on Saturdays and Sundays and on the following public holidays in all participating countries: 1 January, Good Friday and Easter Monday (according to the calendar used by Western Christianity), 1 May, 25 December and 26 December. [ 7 ] [ 8 ]
In October 2020, the system and TARGET2 Securities experienced an almost-11-hour outage, attributed to a "software glitch in a third-party network device" by the ECB, per a report. Much shorter service interruptions of different sorts have hit Target2 in July 2019, November 2018 and December 2017, and in October 2020 Euronext NV, a stock market on the continent, also experienced some outages, per the report. [ 9 ]
[ needs update ]
Starting during the 2007–2008 financial crisis and the European debt crisis , the main subjects of criticism were the unlimited financial balances made available since the establishment of the TARGET system by the national central banks of the Eurosystem on the one hand and by the ECB on the other.
The issue of the increasing TARGET balances was brought to public attention for the first time in early 2011 by Hans-Werner Sinn , president of the Munich-based Ifo Institute for Economic Research . In an article in Wirtschaftswoche , he drew attention to the enormous increase in TARGET claims held by Germany's Bundesbank, from €5 billion at the end of 2006 to €326 billion at the end of 2010, and to the attendant liability risk. [ 10 ] In the German daily Süddeutsche Zeitung he put the entire volume of the TARGET liabilities of Greece, Ireland, Portugal, and Spain at €340 billion at the end of February 2011. Moreover, he pointed out that if these countries should exit the Eurozone and declare insolvency, Germany's liability risk would amount to 33% of that sum, or €114 billion, relating these sums to the other rescue facilities of euro countries and the International Monetary Fund . Before he made them public, TARGET deficits or surpluses were not the subject of major public attention even though they were disclosed by Eurosystem central banks. [ 11 ]
Shortly thereafter, Sinn interpreted the TARGET balances for the first time within the context of current account deficits, international private capital movements and the international shifting of the refinancing credit that the national central banks of the Eurosystem grant to the commercial banks in their jurisdiction . He proved that the ECB system compensated the interruption and reversal in capital flows triggered by the 2007–2008 financial crisis by shifting refinancing credit among national central banks. The increase in TARGET liabilities is a direct measure of net payment orders across borders, i.e. of the portion of the current account deficit that is not counterbalanced by capital imports, or, equivalently, the sum of the current account deficit and net capital exports. Indirectly, they also measure a country's amount of central bank money created and lent out beyond what is needed for domestic circulation. Since every country needs a relatively steady amount of central bank money for its domestic transactions, payment orders to other countries, which reduce the domestic stock of money, must be offset by a continuous issuing of new refinancing credit, i.e., the creation of new central bank money. Similarly, the increase in money balances in the country whose central bank honours the payment orders reduces the demand for fresh refinancing credit. Hence, a country's TARGET liabilities also indicate the extent to which its central bank has replaced the capital markets to finance its current account deficit, as well as any possible capital flight, by creating new central bank money through corresponding refinancing credit. Sinn illustrated that from an economic perspective, TARGET credit and formal rescue facilities serve the same purpose and involve similar liability risks. [ 12 ] [ 13 ] Sinn's presentation on 19 May 2011 at the Munich Economic Summit motivated an op-ed column in the Financial Times . They reconstructed the data on the basis of the balance sheets of the Eurosystem's national central banks and the balance-sheet statistics of the International Monetary Fund.
Later, in June 2011, Hans-Werner Sinn and Timo Wollmershaeuser compiled the first panel database of the Eurozone's TARGET balances. [ 14 ] [ 15 ] [ 16 ] The authors point out that the additional creation of money by the central banks of the crisis-stricken countries was provided by a lowering of the standards for the collateral that commercial banks have to provide to their national central banks to obtain refinancing credit. Furthermore, they showed that the commercial banks of the Eurozone's core countries used the incoming liquidity to reduce the refinancing credit they drew from their national central bank, even lending the surplus liquidity to this central bank, which implies that the TARGET balances indirectly also measure the reallocation of refinancing credit among the countries of the Eurozone. The authors showed that the national central banks of the northern countries became net debtors to their own banking systems. Sinn and Wollmershaeuser argue that the euro crisis is a balance-of-payments crisis, which in its substance is similar to the Bretton Woods crisis . Moreover, they show the extent to which TARGET credit financed current account deficits or capital flight in Greece, Ireland, Portugal, Spain and Italy. They also show that the current account deficits of Greece and Portugal were financed for years by refinancing credits of their national central banks and the concomitant TARGET credit. They also document the Irish capital flight and the capital flight from Spain and Italy, which began in earnest in summer 2011. Following Sinn, [ 17 ] the authors compare the TARGET balances of the Eurosystem with the corresponding balances in the US settlement system ( Interdistrict Settlement Account ) and point out that US balances relative to US GDP have decreased thanks to a regularly performed settlement procedure in which ownership shares in a common Fed clearing portfolio are reallocated among the various district Feds comprising the US Federal Reserve System. They advocate the establishment of a similar system in Europe to end the ECB's role as a provider of international public credit that undercuts private market conditions.
Hans-Werner Sinn addressed the TARGET balances issue again in a special edition of ifo Schnelldienst and made it the main topic of his book Die Target-Falle ("The Target Trap"), published in early October 2012. [ 18 ] [ 19 ]
A number of economists took a stand on the issue of the TARGET balances in a publication of the Ifo Institute, confirming Sinn's analysis. [ 20 ] Financial commentator David Marsh , writing in early 2012, noted that TARGET2 provides "automatic central bank funding for EMU countries suffering capital outflows provided through it" and that the balances would "have to be shared out by central banks throughout the Eurosystem ... if EMU fragments into its constituent parts. So the pressure on Germany is to keep the balances growing, in order to avoid crystallization of losses that would be hugely damaging not just to Berlin but also to central banks and governments in Paris and Rome". [ 21 ]
The official reactions to Sinn's research findings were mixed. At first, in February and March 2011, the Bundesbank downplayed the TARGET balances as an irrelevant statistical position. [ 22 ] [ 23 ] However, in early 2012, Bundesbank chief Jens Weidmann wrote a letter to ECB head Mario Draghi on the subject which "found its way into the columns of the conservative Frankfurter Allgemeine Zeitung newspaper. It appeared to suggest more secure collateralisation for the overall ECB credits to weaker EMU central banks, which now amount to more than €800 billion under the ECB's TARGET2 electronic payment system," Marsh noted in a subsequent column. [ 24 ]
Jens Ulbrich and Alexander Lipponer (economists at the Bundesbank) justified the policy of the ECB during the European balance-of-payments crisis as follows: In the crisis, the Eurosystem consciously assumed a larger intermediation function in view of the massive disruptions in the interbank market by extending its liquidity control instruments. With this greater role in the provision of central bank money – essentially by changing to a full allotment procedure in refinancing operations and the extension of longer-term refinancing operations – the total volume of refinancing credits provided has increased (temporarily even markedly). At the same time, the quality requirements for the underlying collateral were reduced in the crisis. The higher risk was accepted to maintain the functioning of the financial system under more difficult conditions. [ 25 ]
The Ifo Institute's regularly updated "Exposure level indicator" ('Haftungspegel') shows Germany's potential financial burden should the crisis-stricken euro countries exit the currency union and declare insolvency. [ 26 ] In another development, the Institute of Empirical Economic Research at the University of Osnabrueck collects and publishes TARGET2 data from all euro countries on the basis of the balance sheets of each central bank. [ 27 ]
Nevertheless, there are also some economists who contradict some points of Sinn's analysis. Paul De Grauwe and Yuemei Ji argue that Germany's and other countries' TARGET claims could be made void, without suffering any losses, since the value of the central bank money, being " fiat money ", is independent of a central bank's assets. [ 28 ] Sinn, in his rejoinder, showed that the TARGET balances represent the shift of refinancing credit to the crisis-stricken countries, representing thus the claim on the interest returns from these countries. Eliminating the TARGET balances would thus entail a real loss of resources amounting to the present value of this interest income, which is reflected exactly by the amount of TARGET claims. This loss would result in a smaller transfer of Bundesbank's revenues to the German budget and, should the situation arise, in the necessity to recapitalise the Bundesbank through increased taxation. [ 29 ] Sinn uses the same reasoning in his book Die Target-Falle . [ 30 ] Sinn points out that the option of self-rescue for the crisis-affected countries by drawing TARGET credit forces Germany to approve the formal rescue facilities and eventually to accept eurobonds as well. He considers the resulting path dependence in policy-making a "trap". Analysis of TARGET2 balances countering the Ifo conclusions have been advanced by economist Karl Whelan at University College Dublin . In summer 2012, Thomas A. Lubik, a senior economist and research advisor, and Karl Rhodes, a writer, both at the Federal Reserve Bank of Richmond (Virginia, US), cited Whelan's work and also drew parallels and distinctions between the US Fed and the ECB in analysing the balances. Lubik and Rhodes argued that:
"TARGET2 merely reflects persistent imbalances in current accounts and capital accounts. It does not cause them ... [and does not represent] a 'stealth bailout' of the periphery nations". [ 31 ]
Sinn countered that he was misinterpreted in this point insofar as he was just "saying that the current-account deficits were sustained with the extra refinancing credit behind the TARGET balances" and this would "not equate to claiming that current-account deficits and TARGET deficits were positively correlated". [ 29 ]
Alexander L. Wolman believes that rising Interdistrict Settlement Account (ISA) balances – the US-equivalent of rising TARGET balances, if there were no yearly rebalancing – would not be a reason for concern in the US, because the borderlines of the Federal Reserve Districts do not follow national, not even state borders. Further, a rising ISA balance of the Federal Reserve District of New York would be regarded as not surprising, as New York is the financial center of the United States. Until 1975 there was no rebalancing between Federal Reserve districts, a fact which did not lead to major discussions. [ 32 ]
Finally, in late 2016, after some years of relative improvement but with rising worries over Italy, the level of TARGET2 intra-eurozone balances at the ECB had surpassed 2012's record levels. The claims represented half of the Germany's net foreign assets and were on track shortly to reach €1 trillion if trends continued unchecked. [ 33 ]
This article incorporates text from the corresponding German Wikipedia articles on TARGET and TARGET2 as of 4 April 2008. More text also from the website of the European Central Bank which provides and maintains information on TARGET2 both for the general public as for professional users of TARGET2 | https://en.wikipedia.org/wiki/TARGET2 |
TARGET Services (for Transeuropean Automated Real-time Gross-settlement Express Transfer ) are payment services operated by the Eurosystem for the euro area and beyond on its proprietary financial market infrastructures .
As of late 2024, TARGET Services included T2 for large payments (which replaced TARGET2 in 2023), TARGET2-Securities (T2S) for securities transactions, and TARGET Instant Payment Settlement (TIPS) for instant payments. [ 1 ] [ 2 ] A fourth service, the Eurosystem Collateral Management System (ECMS), is to complement the TARGET suite in mid-June 2025. [ 3 ]
In 1993, as the Maastricht Treaty entered into force, central banks of the EU agreed that all of them should have an real-time gross settlement (RTGS) system, as some had already done in the previous decade. In 1995, they decided to interlink these national infrastructures through a pan-European system that they called TARGET. That original TARGET system duly began operations on 4 January 1999. [ 4 ] : 61 Its first version had a decentralized structure that consisted of the national RTGS systems of the 12 euro area member states plus those of Denmark (KRONOS), Sweden (E-RIX), and the UK (CHAPS) together with the ECB Payment Mechanism (EPM). [ 5 ] : 4 On 7 March 2005, Poland was the first new EU member state following the 2004 enlargement to connect to TARGET, via its SORBNET-EURO RTGS system operated by the National Bank of Poland . [ 5 ] : 14
The first TARGET was replaced with TARGET2 , a more centralized system based on a Single Shared Platform (SSP), in stages from November 2007 to May 2008. [ 6 ] In addition to euro area countries and those that would adopt the euro in subsequent years (namely Cyprus, Malta, Slovakia and the Baltic countries), Denmark and Poland participated in the migration to TARGET2, [ 7 ] : 99 whereas Sweden and the UK did not. [ 4 ] : 66, 79 On 4 July 2011, Romania also connected to TARGET2. [ 8 ]
In June 2015, TARGET2 participants were first allowed to open a Dedicated Cash Account (DCA) on the T2S platform, marking the start of the T2S service. [ 6 ] In October 2018, T2S allowed settlements in Danish krones (DKK) in addition to those in euros. [ 9 ]
TIPS was introduced in November 2018. [ 10 ] On 19 February 2024, Sweden completed its integration into TIPS, allowing for TIPS to also settle instant payments in Swedish kronas . [ 11 ]
TARGET2 was replaced with T2 in March 2023. [ 6 ] T2 and TIPS will also allow settlements of DKK payments in March 2025. [ 12 ]
While technically integrated at the European level since the transition to TARGET2 in 2008, TARGET Services are based on contractual arrangements between participants and national entities known as TARGET components. [ 7 ] : 100 The contractual conditions are harmonized in a formal Eurosystem document known as the TARGET Guideline last updated in 2022. [ 13 ]
During the euro area crisis of the 2010s, cross-country imbalances within the TARGET2 system became an object of heated discussion, particularly in Germany.
In October 2020, TARGET2 and T2S experienced an outage for nearly 11 hours. [ 14 ]
This bank and insurance -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TARGET_Services |
The TARIC code (TARif Intégré Communautaire; Integrated Tariff of the European Communities) is designed to show the various rules applying to specific products when imported into the EU . This includes the provisions of the harmonised system and the combined nomenclature but also additional provisions specified in Community legislation such as tariff suspensions , tariff quotas and tariff preferences , which exist for the majority of the Community’s trading partners. In trade with third countries, the 10-digit Taric code must be used in customs and statistical declarations.
A proper classification can save huge amount of money for the company, which is why nowadays importers and exporters strive to find a perfect way to solve those problems:
TARIC builds upon the international harmonised system | https://en.wikipedia.org/wiki/TARIC_code |
The TASF reagent or tris(dimethylamino)sulfonium difluorotrimethylsilicate is a reagent in organic chemistry with structural formula [((CH 3 ) 2 N) 3 S] + [F 2 Si(CH 3 ) 3 ] − . It is an anhydrous source of fluoride and is used to cleave silyl ether protective groups . Many other fluoride reagents are known, but few are truly anhydrous, because of the extraordinary basicity of "naked" F − . In TASF, the fluoride is masked as an adduct with the weak Lewis acid trimethylsilylfluoride (FSi(CH 3 ) 3 ). The sulfonium cation ((CH 3 ) 2 N) 3 S + is unusually non-electrophilic due to the electron-donating properties of the three (CH 3 ) 2 N substituents.
This compound is prepared from sulfur tetrafluoride :
The colorless salt precipitates from the reaction solvent, diethyl ether . [ 1 ]
The cation [((CH 3 ) 2 N) 3 S] + is a sulfonium ion . The S-N distances are 1.612 and 1.675 pm. The N-S-N angles are 99.6°. The anion is [F 2 Si(CH 3 ) 3 ] − . It is trigonal bipyramidal with mutually trans fluorides. The Si-F distances are 176 picometers. The Si-C distances are 188 pm. [ 2 ] | https://en.wikipedia.org/wiki/TASF_reagent |
TATB , triaminotrinitrobenzene or 2,4,6-triamino-1,3,5-trinitrobenzene is an aromatic explosive, based on the basic six-carbon benzene ring structure with three nitro functional groups (NO 2 ) and three amine (NH 2 ) groups attached, alternating around the ring.
TATB is a very powerful explosive (somewhat less powerful than RDX , but more than TNT ), but it is extremely insensitive to shock , vibration , fire , or impact . Because it is so difficult to detonate by accident, even under severe conditions, it has become preferred for applications where extreme safety is required, such as the explosives used in nuclear weapons , where accidental detonation during an airplane crash or rocket misfiring could potentially detonate the fissile core. All British nuclear warheads use TATB-based explosives in their primary stage . [ 1 ] According to David Albright , South Africa's nuclear weapons used TATB to increase their safety. [ 2 ]
TATB is normally used as the explosive ingredient in plastic bonded explosive compositions, such as PBX-9502, LX-17-0, and PBX-9503 (with 15% HMX ). These formulations are described as insensitive high explosives (IHEs) in nuclear weapons literature.
Though it could theoretically be mixed with other explosive compounds in castable mixtures or other use forms, the applications for such forms would be unclear since they would largely undo the insensitivity of pure TATB.
At a pressed density of 1.80, TATB has a velocity of detonation of 7,350 meters per second.
TATB has a crystal density of 1.93 grams/cm 3 , though most forms currently in use have no higher density than 1.80 grams/cm 3 . TATB melts at 350 °C. The chemical formula for TATB is C 6 (NO 2 ) 3 (NH 2 ) 3 .
Pure TATB has a bright yellow color.
TATB has been found to remain stable at temperatures at least as high as 250 °C for prolonged periods of time.
TATB is produced by nitration of 1,3,5-trichlorobenzene to 1,3,5-trichloro-2,4,6-trinitrobenzene , then the chlorine atoms are substituted with amine groups using ammonolysis.
However, it is likely that the production of TATB will be switched over to a process involving the nitration and transamination of phloroglucinol , since this process is milder, cheaper, and reduces the amount of ammonium chloride salt produced in waste effluents (greener). [ citation needed ]
Still, another process has been found for the production of TATB from materials that are surplus to military use. 1,1,1-trimethylhydrazinium iodide (TMHI) is formed from the rocket fuel unsymmetrical dimethylhydrazine ( UDMH ) and methyl iodide , and acts as a vicarious nucleophilic substitution (VNS) amination reagent. When picramide , which is easily produced from Explosive D , is reacted with TMHI it is aminated to TATB. [ 3 ] Thus, materials that would have to be destroyed when no longer needed are converted into a high value explosive. [ 4 ] | https://en.wikipedia.org/wiki/TATB |
The Tel Aviv University Ultraviolet Explorer , or TAUVEX ( Hebrew : טאווקס ), is a space telescope array conceived by Noah Brosch of Tel Aviv University and designed and constructed in Israel for Tel Aviv University by El-Op, [ 1 ] Electro-Optical Industries, Ltd. (a division of Elbit systems) acting as Prime Contractor, for the exploration of the ultraviolet (UV) sky. TAUVEX was selected in 1988 by the Israel Space Agency (ISA) as its first priority scientific payload. Although originally slated to fly on a national Israeli satellite of the Ofeq series, TAUVEX was shifted in 1991 to fly as part of a Spektr-RG international observatory, a collaboration of many countries with the Soviet Union ( Space Research Institute ) leading.
Due to repeated delays of the Spektr project, caused by the economic situation in the post-Soviet Russia, ISA decided to shift TAUVEX to a different satellite. In early-2004 ISA signed an agreement with the Indian Space Research Organisation (ISRO) to launch TAUVEX on board the Indian technology demonstrator satellite GSAT-4 . The launch vehicle slated to be used was the GSLV with a new, cryogenic, upper stage. TAUVEX was a scientific collaboration between Tel Aviv University and the Indian Institute of Astrophysics in Bangalore . Its Principal Investigators were Noah Brosch at Tel Aviv University and Jayant Murthy at the Indian Institute of Astrophysics. Originally, TAUVEX was scheduled to be launched in 2008, [ 2 ] but various delays caused the integration with GSAT-4 to take place only in November 2009 for a launch the following year. ISRO decided in January 2010 to remove TAUVEX [ 3 ] from the satellite since the Indian-built cryogenic upper stage for GSLV was deemed under-powered to bring GSAT-4 to a geosynchronous orbit. [ 4 ] GSAT-4 was subsequently lost in the 15 April 2010 launch failure of GSLV . [ 5 ] On 13 March 2011 TAUVEX was returned to Israel and was stored at the Prime Contractor facility pending an ISA decision about its future. In 2012 ISA decided to terminate the TAUVEX project, against the recommendation of a committee it formed to consider its future that recommended its release for a high-altitude balloon flight.
TAUVEX consists of three bore-sighted 20 cm diameter telescopes on a single bezel, called telescopes A, B, and C. Each telescope images the same sky area of 0.9 degree, with an angular resolution of 7-11 arcseconds . The imaging is onto position-sensitive detectors (CsTe cathodes on calcium fluoride windows) equipped with multi-channel plate electron intensifiers. The detectors oversample the point-spread-function by a factor of approximately three. The output is detected by position-sensitive anodes (wedge-and-strip) and is digitized to 12 bits. The full image of each telescope has about 300 resolution elements across its diameter.
The type of cathode (CsTe) assures sensitivity from longward of Lyman α to the atmospheric limit with a peak quantum efficiency of approximately 10%. The operating spectral range is separated in a number of segments selectable with filters. Each telescope [T] is equipped with a four-position filter wheel. Each wheel contains one blocked position (shutter) and three band-selection filters [Fn]. The filter complement, and its distribution among the three telescopes, is as follows:
The approximate characteristics of each filter type are summarized below:
TAUVEX was mounted to the GSAT-4 spacecraft on a plate that could rotate around its axis (the MDP), enabling to point the telescopes' line-of-sight to any desired declination. Being on a geostationary satellite , the observation would therefore have been of a scanning type. A 'ribbon' of a constant declination, 0.9 degree wide, would have been scanned as time advanced, completing an entire 360 degree circuit during one sidereal day . In this mode of operation, the dwell time of a source within the detector field of view is a function of the pointing declination and of the exact location in the FOV relative to the detector diameter. The closer a source is to one of the celestial poles, the longer it resides in the TAUVEX field of view during a single scan. The longest theoretically possible exposure is for sources at |δ|>89°30'; these could be observed all day.
The interface with GSAT-4 ensured that each photon event hitting the detectors would have been transmitted to the ground in real time and processed in a near-real-time pipeline. In-between the photon events a time tag is added every 128 ms. The time between the adjacent time tags is sufficiently short so that the orbital motion of the nadir-pointing platform is much smaller than the TAUVEX virtual pixel.
Given that TAUVEX on GSAT-4 was planned to operate from a geo-synchronous platform that is, essentially, a telecommunications satellite, it is clear that up and downlink telemetry are much less problematic that with other astronomical satellites. In fact, TAUVEX was allowed a dedicated 1 Mbit/s downlink to the ISRO Master Control Facility (MCF) at Hassan , near Bangalore . Command sequences were planned to be uplinked after being generated by IIA and ISRO and the downlink to be analyzed on-line to monitor the payload state of health.
In most situations, TAUVEX would have been able to download all the detected photon events. However, in case of strong straylight or of many bright sources in the field of view, the collected event rate could overload the capacity of the telemetry link. In this case, TAUVEX would have stored the photon events in a solid state memory module (4 GB ), from which the events are transmitted at the nominal 1 Mbit/s rate.
The science of TAUVEX is based on its unique characteristics: three bore-sighted and independent telescopes able to operate independently, with different filters but measuring the same sources, and reasonably fine time resolution as every detected photon is time-tagged. A unique possibility allows the study of the interstellar dust band at 217.4 nm ; the two TAUVEX filters SF2 and NBF3 are centered on this wavelength but have different widths. As the filters are located on different telescopes, it is possible to measure the same sky region with both filters simultaneously, deriving the equivalent width of the band for every star in the field of view. [ 6 ] The use of TAUVEX as a scientific instrument is the result of calibration on the ground. [ 7 ] This calibration was very difficult and produced unreliable results [ 8 ] possibly indicating a significantly reduced performance. Given the uncertain results, the Principal Investigators planned to repeat and improve the calibration in space, in the months following the launch. | https://en.wikipedia.org/wiki/TAUVEX |
TA cloning (also known as rapid cloning or T cloning ) is a subcloning technique that avoids the use of restriction enzymes [ 1 ] and is easier and quicker than traditional subcloning. The technique relies on the ability of adenine (A) and thymine (T) (complementary basepairs) on different DNA fragments to hybridize and, in the presence of ligase , become ligated together. PCR products are usually amplified using Taq DNA polymerase which preferentially adds an adenine to the 3' end of the product. Such PCR amplified inserts are cloned into linearized vectors that have complementary 3' thymine overhangs. [ 2 ]
The insert is created by PCR using Taq polymerase . This polymerase lacks 3' to 5' proofreading activity and, with a high probability, adds a single, 3'- adenine overhang to each end of the PCR product. It is best if the PCR primers have guanines at the 5' end as this maximizes probability of Taq DNA polymerase adding the terminal adenosine overhang. [ 3 ] Thermostable polymerases containing extensive 3´ to 5´ exonuclease activity should not be used as they do not leave the 3´ adenine-overhangs. [ 4 ]
The target vector is linearized and cut with a blunt-end restriction enzyme. This vector is then tailed with dideoxythymidine triphosphate (ddTTP) using terminal transferase . It is important to use ddTTP to ensure the addition of only one T residue. This tailing leaves the vector with a single 3'-overhanging thymine residue on each blunt end. [ 5 ] Manufacturers commonly sell TA Cloning "kits" with a wide range of prepared vectors that have already been linearized and tagged with an overhanging thymine.
Given that there is no need for restriction enzymes other than for generating the linearized vector, the procedure is much simpler and faster than traditional subcloning . There is also no need to add restriction sites when designing primers and thus shorter primers can be used saving time and money. In addition, in instances where there are no viable restriction sites that can be used for traditional cloning, TA cloning is often used as an alternative. The major downside of TA cloning is that directional cloning is not possible, so the gene has a 50% chance of getting cloned in the reverse direction. [ 1 ] | https://en.wikipedia.org/wiki/TA_cloning |
Thiobarbituric acid reactive substances ( TBARS ) are formed as a byproduct of lipid peroxidation (i.e. as degradation products of fats) which can be detected by the TBARS assay using thiobarbituric acid as a reagent. TBARS can be upregulated, for example, by heart attack [ 1 ] or by certain kinds of stroke. [ 2 ]
Because reactive oxygen species (ROS) have extremely short half-lives, they are difficult to measure directly. Instead, what can be measured are several products of the damage produced by oxidative stress, such as TBARS. [ 3 ]
Assay of TBARS measures malondialdehyde (MDA) present in the sample, as well as malondialdehyde generated from lipid hydroperoxides by the hydrolytic conditions of the reaction. [ 4 ] MDA is one of several low-molecular-weight end products formed via the decomposition of certain primary and secondary lipid peroxidation products. However, only certain lipid peroxidation products generate MDA, and MDA is neither the sole end product of fatty peroxide formation and decomposition, nor a substance generated exclusively through lipid peroxidation. These and other considerations from the extensive literature on MDA, TBA reactivity, and oxidative lipid degradation support the conclusion that MDA determination and the TBA test can offer, at best, a narrow and somewhat empirical window on the complex process of lipid peroxidation. Use of MDA analysis and/or the TBA test and interpretation of sample MDA content and TBA test response in studies of lipid peroxidation require caution, discretion, and (especially in biological systems) correlative data from other indices of fatty peroxide formation and decomposition. [ 5 ]
Malondialdehyde reacts with both barbiturate and thiobarbiturate, [ 6 ] and the end-product of the TBARS assay is almost identical to the end product of the pyridine-barbiturate cyanide assay. This suggests that some cyanide poisoning cases that relied on the pyridine-barbiturate diagnostic could be false positives with elevated blood malondialdehyde, and no cyanide present at all. The cases of Urooj Khan, lottery winner of Chicago, and Autumn Klein, doctor of Pittsburgh, both fit these characteristics, since neither patient exhibited cyanide poisoning symptoms, yet both appeared to have suffered heart attacks, with Urooj Khan's blocked arteries noted at autopsy [ 7 ] and Autumn Klein's evidence for heart abnormalities noted at trial and as a central part of her husband's conviction appeal. [ 8 ] [ citation needed ] | https://en.wikipedia.org/wiki/TBARS |
In molecular biology , TBST (or TTBS ) is a mixture of tris-buffered saline (TBS) (a buffer solution ) and Polysorbate 20 (a polysorbate -type nonionic surfactant ). Polysorbate 20 is also known as Tween 20, a commercial brand name. It is a common detergent used in many buffers for washing nitrocellulose membrane in western blotting and microtiter plate wells in ELISA assays. Tris is a buffer that maintains a pH of 7–9.2.
The following is a sample recipe for TBST:
Adjust pH with HCl to pH 7.4–7.6
The simplest way to prepare a TBS-Tween solution is to use TBS-T tablets. They are formulated to give a ready to use TBST solution upon dissolution in 500 ml of deionized water. [ 1 ]
https://www.gbiosciences.com/Buffers-Reagents-Chemicals/Electrophoresis-Related-Buffers-Chemicals/TBST-10X
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TBST |
TCEP ( tris(2-carboxyethyl)phosphine ) is a reducing agent frequently used in biochemistry and molecular biology applications. It is often prepared and used as a hydrochloride salt (TCEP-HCl) with a molecular weight of 286.65 gram/mol. It is soluble in water and available as a stabilized solution at neutral pH and immobilized onto an agarose support to facilitate removal of the reducing agent.
TCEP can be prepared by the acid hydrolysis of tris(cyanoethyl)phosphine . [ 1 ]
TCEP is often used as a reducing agent to break disulfide bonds within and between proteins as a preparatory step for gel electrophoresis .
Compared to the other two most common agents used for this purpose ( dithiothreitol and β-mercaptoethanol ), TCEP has the advantages of being odorless, a more powerful reducing agent, an irreversible reducing agent (in the sense that TCEP does not regenerate—the end product of TCEP-mediated disulfide cleavage is in fact two free thiols/cysteines), more hydrophilic, and more resistant to oxidation in air. [ 2 ] It also does not reduce metals used in immobilized metal affinity chromatography .
TCEP is particularly useful when labeling cysteine residues with maleimides . TCEP can keep the cysteines from forming di-sulfide bonds and, unlike dithiothreitol and β-mercaptoethanol , it will not react as readily with the maleimide. [ 2 ] However, TCEP has been reported to react with maleimide under certain conditions. [ 3 ] [ 4 ]
TCEP is also used in the tissue homogenization process for RNA isolation. [ 5 ]
For Ultraviolet–visible spectroscopy applications, TCEP is useful when it is important to avoid interfering absorbance from 250 to 285 nanometers which can occur with dithiothreitol . Dithiothreitol will slowly over time absorb more and more light in this spectrum as various redox reactions occur.
Reduction of biomolecules with trialkyphosphines received little attention for decades because historically available phosphines were extremely malodorous and/or insoluble in water. [ 6 ] In 1969, TCEP was reported as an odorless and water-soluble trialkyphosphine suitable for biochemical use, [ 7 ] however the potential use of TCEP for biochemical applications was almost totally ignored for decades. In 1991, Burns reported a new convenient synthetic procedure for TCEP, [ 8 ] which set off TCEP becoming more widely available and marketed as a "new" reducing agent for biochemical use, & thus TCEP came into more widespread use throughout the 1990s. [ 6 ]
TCEP will reduce disulfides to thiols in the presence of water:
Via a similar process it can also reduce sulfoxides and N-oxides . [ 9 ] Some other side reactions have also been reported:
TCEP is available from various chemical suppliers as the hydrochloride salt. When dissolved in water, TCEP-HCl is acidic. A reported preparation is a 0.5 M TCEP-HCl aqueous stock solution that is pH adjusted to near-neutral pH and stored frozen at -20˚C. [ 12 ] TCEP is reportedly less stable in phosphate buffers. [ 12 ] | https://en.wikipedia.org/wiki/TCEP |
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NM_001361129
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NP_001348058
Transcription factor 4 (TCF-4) also known as immunoglobulin transcription factor 2 (ITF-2) is a protein that in humans is encoded by the TCF4 gene located on chromosome 18q 21.2. [ 5 ]
TCF4 proteins act as transcription factors which will bind to the immunoglobulin enhancer mu-E5/kappa-E2 motif. TCF4 activates transcription by binding to the E-box (5’-CANNTG-3’) found usually on SSTR2 -INR, or somatostatin receptor 2 initiator element. TCF4 is primarily involved in neurological development of the fetus during pregnancy by initiating neural differentiation by binding to DNA. It is found in the central nervous system, somites, and gonadal ridge during early development. Later in development it will be found in the thyroid, thymus, and kidneys while in adulthood TCF4 it is found in lymphocytes , muscles, mature neurons, and gastrointestinal system. [ 6 ] [ 7 ] [ 8 ]
Mutations in TCF4 cause Pitt-Hopkins Syndrome (PTHS). These mutations cause TCF4 proteins to not bind to DNA properly and control the differentiation of the nervous system. It has been suggested that TCF4 loss-of-function leads to decreased Wnt signaling and, consequently, a reduced neural progenitor proliferation. [ 9 ] In most cases that have been studied, the mutations were de novo , meaning it was a new mutation not found in other family members of the patient. Common symptoms of Pitt-Hopkins Syndrome include a wide mouth, gastrointestinal problems, developmental delay of fine motor skills, speech and breathing problems, epilepsy, and other brain defects. [ 10 ] [ 11 ]
This article incorporates text from the United States National Library of Medicine , which is in the public domain .
This article on a gene on human chromosome 18 is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TCF4 |
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Transcription factor 7-like 2 (T-cell specific, HMG-box) , also known as TCF7L2 or TCF4 , is a protein acting as a transcription factor that, in humans, is encoded by the TCF7L2 gene . [ 5 ] [ 6 ] The TCF7L2 gene is located on chromosome 10q25.2–q25.3, contains 19 exons . [ 7 ] [ 8 ] As a member of the TCF family , TCF7L2 can form a bipartite transcription factor and influence several biological pathways, including the Wnt signalling pathway . [ 9 ]
Single-nucleotide polymorphisms (SNPs) in this gene are especially known to be linked to higher risk to develop type 2 diabetes , [ 9 ] gestational diabetes , [ 10 ] multiple neurodevelopmental disorders [ 11 ] [ 12 ] including schizophrenia [ 13 ] [ 14 ] and autism spectrum disorder , [ 15 ] [ 16 ] as well as other diseases. [ 17 ] [ 18 ] The SNP rs7903146 , within the TCF7L2 gene, is, to date, the most significant genetic marker associated with type 2 diabetes risk. [ 19 ]
TCF7L2 is a transcription factor influencing the transcription of several genes thereby exerting a large variety of functions within the cell. It is a member of the TCF family that can form a bipartite transcription factor ( β-catenin / TCF ) alongside β-catenin. [ 9 ] Bipartite transcription factors can have large effects on the Wnt signalling pathway . [ 9 ] Stimulation of the Wnt signaling pathway leads to the association of β-catenin with BCL9 , translocation to the nucleus, and association with TCF7L2, [ 21 ] which in turn results in the activation of Wnt target genes. The activation of the Wnt target genes specifically represses proglucagon synthesis in enteroendocrine cells. [ 9 ] [ 8 ] The repression of TCF7L2 using HMG-box repressor (HBP1) inhibits Wnt signalling. [ 9 ] Therefore, TCF7L2 is an effector in the Wnt signalling pathway. TCF7L2's role in glucose metabolism is expressed in many tissues such as gut, brain, liver, and skeletal muscle. However, TCF7L2 does not directly regulate glucose metabolism in β-cells , but regulates glucose metabolism in pancreatic and liver tissues. [ 22 ] That said, TCF7L2 directly regulates the expression of multiple transcription factors, axon guidance cues, cell adhesion molecules and ion channels in the thalamus. [ 23 ]
The TCF7L2 gene encoding the TCF7L2 transcription factor, exhibits multiple functions through its polymorphisms and thus, is known as a pleiotropic gene. Type 2 diabetes T2DM susceptibility is exhibited in carriers of TCF7L2 rs7903146C>T [ 24 ] [ 25 ] and rs290481T>C [ 25 ] polymorphisms. [ 24 ] [ 25 ] TCF7L2 rs290481T>C polymorphism, however, has shown no significant correlation to the susceptibility to gestational diabetes mellitus (GDM) in a Chinese Han population, whereas the T alleles of rs7903146 [ 25 ] and rs1799884 [ 10 ] increase susceptibility to GDM in the Chinese Han population. [ 25 ] [ 10 ] The difference in effects of the different polymorphisms of the gene indicate that the gene is indeed pleiotropic.
The TCF7L2 gene, encoding the TCF7L2 protein, is located on chromosome 10q25.2-q25.3. The gene contains 19 exons. [ 7 ] [ 8 ] Of the 19 exons, 5 are alternative . [ 8 ] The TCF7L2 protein contains 619 amino acids and its molecular mass is 67919 Da . [ 26 ] TCF7L2's secondary structure is a helix-turn-helix structure. [ 27 ]
TCF7L2 is primarily expressed in brain (mainly in the diencephalon , including especially high in the thalamus [ 23 ] [ 28 ] [ 29 ] ), liver, intestine and fat cells. It does not primarily operate in the β-cells in the pancreas. [ 30 ]
Several single nucleotide polymorphisms within the TCF7L2 gene have been associated with type 2 diabetes. Studies conducted by Ravindranath Duggirala and Michael Stern at The University of Texas Health Science Center at San Antonio were the first to identify strong linkage for type 2 diabetes at a region on Chromosome 10 in Mexican Americans [ 31 ] This signal was later refined by Struan Grant and colleagues at DeCODE genetics and isolated to the TCF7L2 gene. [ 32 ] The molecular and physiological mechanisms underlying the association of TCF7L2 with type 2 diabetes are under active investigation, but it is likely that TCF7L2 has important biological roles in multiple metabolic tissues, including the pancreas, liver and adipose tissue. [ 30 ] [ 33 ] TCF7L2 polymorphisms can increase susceptibility to type 2 diabetes by decreasing the production of glucagon-like peptide-1 (GLP-1) . [ 9 ]
TCF7L2 modulates pancreatic islet β-cell function strongly implicating its significant association with GDM risk. [ 10 ] T alleles of rs7903146 [ 25 ] and rs1799884 [ 10 ] TCF7L2 polymorphisms increase susceptibility to GDM in the Chinese Han population. [ 25 ] [ 10 ]
TCF7L2 plays a role in colorectal cancer . [ 17 ] A frameshift mutation of TCF7L2 provided evidence that TCF7L2 is implicated in colorectal cancer. [ 34 ] [ 35 ] The silencing of TCF7L2 in KM12 colorectal cancer cells provided evidence that TCF7L2 played a role in proliferation and metastasis of cancer cells in colorectal cancer. [ 17 ]
Variants of the gene are most likely involved in many other cancer types. [ 36 ] TCF7L2 is indirectly involved in prostate cancer through its role in activating the PI3K/Akt pathway , a pathway involved in prostate cancer. [ 37 ]
Single nucleotide polymorphisms (SNPs) in TCF7L2 gene have shown an increase in susceptibility to schizophrenia in Arab, European and Chinese Han populations. [ citation needed ] In the Chinese Han population, SNP rs12573128 [ 14 ] in TCF7L2 is the variant that was associated with an increase in schizophrenia risk. This marker is used as a pre-diagnostic marker for schizophrenia. [ 14 ] TCF7L2 has also been reported as a risk gene in autism spectrum disorder [ 38 ] and has been linked to it in recent large-scale genetic studies. [ 15 ] [ 16 ]
The mechanism behind TCF7L2's involvement in the emergence of neurodevelopmental disorders is not fully understood, as there have been few studies characterizing its role in brain development in detail. It was shown that during embryogenesis TCF7L2 is involved in the development of fish-specific habenula asymmetry in Danio rerio , [ 39 ] [ 40 ] and that the dominant negative TCF7L2 isoform influences cephalic separation in the embryo by inhibiting the posteriorizing effect of the Wnt pathway. [ 41 ] It was also shown that in Tcf7l2 knockout mice the number of proliferating cells in cortical neural progenitor cells is reduced. [ 42 ] In contrast, no such effect was found in the midbrain. [ 43 ]
More recently it was shown that TCF7L2 plays a crucial role in both the embryonic development and postnatal maturation of the thalamus through direct and indirect regulation of many genes previously reported to be important for both processes. [ 23 ] In late gestation TCF7L2 regulates the expression of many thalamus-enriched transcription factors (e.g. Foxp2 , Rora , Mef2a , Lef1 , Prox1 ), axon guidance molecules (e.g. Epha1 , Epha4 , Ntng1 , Epha8 ) and cell adhesion molecules (e.g. Cdh6 , Cdh8 , Cdhr1). Accordingly, a total knockout of Tcf7l2 in mice leads to improper growth of thalamocortical axons, changed anatomy and improper sorting of the cells in the thalamo-habenular region. [ 23 ] In the early postnaral period TCF7L2 starts to regulate the expression of many genes necessary for the acquisition of characteristic excitability patterns in the thalamus, mainly ion channels, neurotransmitters and their receptors and synaptic vescicle proteins (e.g. Cacna1g , Kcnc2 , Slc17a7 , Grin2b ), and an early postnatal knockout of Tcf7l2 in mouse thalamus leads to significant reduction in the number and frequency of action potentials generated by the thalamocortical neurons . [ 23 ] The mechanism that leads to the change in TCF7L2 target genes between gestation and early postnatal period is unknown. It is likely that a perinatal change in the proportion of TCF7L2 isoforms expressed in the thalamus is partially responsible. [ 28 ] Abnormalities in the anatomy of the thalamus and the activity of its connections to the cerebral cortex are frequently detected in patients with schizophrenia [ 44 ] [ 45 ] [ 46 ] [ 47 ] and autism. [ 48 ] [ 49 ] [ 50 ] [ 51 ] Such abnormalities could arise from developmental aberrations in patients with unfavorable mutations of TCF7L2, further strengthening the link between TCF7L2 and neurodevelopmental disorders.
TCF7L2 is downstream of the WNT / β-catenin pathways. The activation of the WNT/β-catenin pathways have been associated demyelination in multiple sclerosis . [ 18 ] TCF7L2 is unregulated during early remyelination , leading scientists to believe that it is involved in remyelination . [ 18 ] TCF7L2 could act in dependence or independent of the WNT/β-catenin pathways. [ 18 ]
Model organisms have been used in the study of TCF7L2 function. A conditional knockout mouse line called Tcf7l2 tm1a(EUCOMM)Wtsi was generated at the Wellcome Trust Sanger Institute . [ 52 ] Male and female animals underwent a standardized phenotypic screen [ 53 ] to determine the effects of deletion. [ 54 ] [ 55 ] [ 56 ] [ 57 ] Additional screens performed: - In-depth immunological phenotyping [ 58 ]
Variations of the protein encoding gene are found in rats, zebra fish, drosophila, and budding yeast. [ 59 ] Therefore, all of those organisms can be used as model organisms in the study of TCF7L2 function.
TCF7L2 is the symbol officially approved by the HUGO Gene Nomenclature Committee for the Transcription Factor 7-Like 2 gene. | https://en.wikipedia.org/wiki/TCF7L2 |
TCFH ( N , N , N ’, N ’-tetramethylchloroformamidinium hexafluorophosphate ) is an electrophilic amidine reagent used to activate a number of functional groups for reaction with nucleophilies . TCFH is most commonly used to activate carboxylic acids for reaction with amines in the context of amide bond formation and peptide synthesis .
TCFH is commercially available. It may be prepared from tetramethylurea using a chlorinating agent such as oxalyl chloride , thionyl chloride or phosphorus oxychloride followed by salt exchange. [ 2 ]
TCFH itself is a common reagent used in the preparation of uronium and guanidinium salts used for amide bond formation and peptide synthesis, such as HATU . [ 3 ] [ 4 ] [ 5 ]
Amide bond formation with TCFH can be performed in a wide range of organic solvents, most commonly acetonitrile , but also water [ 6 ] and in the solid state. [ 7 ] Reactions typically require an added Brønsted base , and a wide range can be employed including N,N -diisopropylethylamine (DIPEA). In reactions of carboxylic acids with TCFH and a weakly Lewis basic amine like DIPEA, formation of an acid chloride or anhydride as the active acylating agent occurs. [ 8 ] Use of N -methylimidazole (NMI) as a base, with both Brønsted and Lewis basic properties, provides some unique advantages. Reactions of carboxylic acids with TCFH and a strongly Lewis basic amine like NMI lead to in situ formation of an N -acyl imidazolium ion (NAI) as the active acylating agent.
These strongly electrophilic NAIs [ 9 ] [ 10 ] allow for reactions with a wide range of nitrogen nucleophiles, including hindered and electron-deficient amines. [ 11 ] An added benefit of the use of NMI as the base, due to its low p K a (H 2 O) of 7, [ 12 ] is that the epimerization of labile stereogenic centers is minimized. The reaction by-products have high water solubility, facilitating reaction workup and isolation.
TCFH can also be used in other reactions involving activation of carboxylic acids from reactions with oxygen-, sulfur- and carbon- nucleophiles for the preparation of esters , thioesters and ketones . [ 13 ] [ 14 ] Extending beyond reactions with carboxylic acids, TCFH has been shown to be an activator for other oxygen centered nucleophiles, including heterocyclic alcohols , ketooximes , and even alcohols . [ 15 ] [ 16 ] Reactivity with sulfur centered nucleophiles like thioureas has also been demonstrated.
TCFH does not exhibit dermal corrosion or irritation but irritates eyes. [ 17 ] The sensitization potential of TCFH was shown to be low compared to other common amide bond forming agents (non-sensitizing at 1% in LLNA testing according to OECD 429 [ 18 ] ). The by-product of the reactions of TCFH is tetramethylurea , which has demonstrated embryotoxic and teratogenic activity in several animal species. [ 19 ] | https://en.wikipedia.org/wiki/TCFH |
TCL is a small (~21 kDa) signaling G protein (more specifically a GTPase ), and is a member of the Rho family of GTPases . [ 1 ] [ 2 ]
TCL (TC10-like) shares 85% and 78% amino acid similarity to TC10 and Cdc42, respectively. TCL mRNA is 2.5 kb long and is mainly expressed in heart. In vitro, TCL shows rapid GDP/GTP exchange and displays higher GTP dissociation and hydrolysis rates than TC10. Like other Rac/Cdc42/RhoUV members, GTP-bound TCL interacts with CRIB domains, such as those found in PAK and WASP. TCL produces large and dynamic F-actin-rich ruffles on the dorsal cell membrane in REF-52 fibroblasts. TCL activity is blocked by dominant negative Rac1 and Cdc42 mutants, suggesting a cross-talk between these three Rho GTPases. [ 3 ]
TCL is unrelated to TCL1A , a proto-oncogene implicated in the development of T-Cell Leukemias.
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TCL_(GTPase) |
(Benzothiazol-2-ylthio)methyl thiocyanate ( TCMTB ) is a chemical compound classified as a benzothiazole .
TCMTB is an oily, flammable, red to brown liquid with a pungent odor that is very slightly soluble in water. It decomposes on heating producing hydrogen cyanide , sulfur oxides , and nitrogen oxides . [ 2 ] The degradation products are 2-mercaptobenzothiazole (2-MBT) and 2-benzothiazolesulfonic acid . [ 3 ]
TCMTB is used as wideband microbicide , paint fungicide , and paint gallicide . [ 2 ] The active substance approved in 1980 in the United States. [ 3 ] It is used, for example, in leather preservation, [ 4 ] for the protection of paper products, in wood preservatives, and against germs in industrial water. [ 3 ]
In the US, TCMTB is used as a fungicide for seed dressing in cereals, safflower , cotton and sugar beet.
It is also used when dealing with fungal problems when extracting hydrocarbons via fracking. [ 5 ]
TCMTB is not an authorized plant protection product in the European Union. [ 6 ] In Germany, Austria and Switzerland, no plant protection products containing this active substance are authorized. [ 7 ]
TCMTB contributes to health problems in tannery workers as it is a potential carcinogen , and is a hepatotoxin . It is also a skin sensitizer, and may cause contact dermatitis in those exposed to the poisonous compound. [ 8 ] Hence, it is mainly used in developing countries. | https://en.wikipedia.org/wiki/TCMTB |
Translation complex profile sequencing ( TCP-seq ) is a molecular biology method for obtaining snapshots of momentary distribution of protein synthesis complexes along messenger RNA (mRNA) chains. [ 1 ]
Expression of genetic code in all life forms consists of two major processes, synthesis of copies of the genetic code recorded in DNA into the form of mRNA ( transcription ), and protein synthesis itself ( translation ), whereby the code copies in mRNA are decoded into amino acid sequences of the respective proteins. Both transcription and translation are highly regulated processes essentially controlling everything of what happens in live cells (and multicellular organisms, consequently).
Control of translation is especially important in eukaryotic cells where it forms part of post-transcriptional regulatory networks of genes expression. This additional functionality is reflected in the increased complexity of the translation process , making it a hard object to investigate. Yet details on when and what mRNA is translated and what mechanisms are responsible for this control are key to understanding of normal and pathological cell functionality. TCP-seq can be used to obtain this information.
With the advent of the high-throughput DNA and RNA sequence identification methods (such as Illumina sequencing ), it became possible to efficiently analyse nucleotide sequences of large numbers of relatively short DNA and RNA fragments. Sequences of these fragments can be superimposed to reconstruct the source. Alternatively, if the source sequence is already known, the fragments can be found within it (“mapped”), and their individual numbers counted. Thus, if an initial stage exists whereby the fragments are differentially present or selected (“enriched”), this approach can be used to quantitatively describe such stage over even a very large number or length of the input sequences, most usually encompassing the entire DNA or RNA of the cell.
TCP-seq is based on these capabilities of the high-throughput RNA sequencing and further uses the nucleic acid protection phenomenon . The protection is manifested as resistance to depolymerisation or modification of stretches of nucleic acids (particularly, RNA) that are tightly bound to or engulfed with other biomolecules, which thus leave their “footprints” over the nucleic acid strand. These “footprint” fragments therefore represent location on nucleic acid chain where the interaction occurs. By sequencing and mapping the fragments back to the source sequence, it is possible to precisely identify the locations and counts of these intermolecular contacts.
In case of TCP-seq, ribosomes and ribosomal subunits engaged in interaction with mRNA are first fast chemically crosslinked to it with formaldehyde to preserve existing state of interactions (“snapshot” of distribution) and to block any possible non-equilibrium processes. The crosslinking can be performed directly in, but not restricted to, live cells. The RNA is then partially degraded ( e.g. with ribonuclease ) so that only fragments protected by the ribosomes or ribosomal subunits are left. The protected fragments are then purified according to the sedimentation dynamics of the attached ribosomes or ribosomal subunits, de-blocked, sequenced and mapped to the source transcriptome , giving the original locations of the translation complexes over mRNA.
TCP-seq merges several elements typical to other transcriptome-wide analyses of its kind. In particular, polysome profiling [ 2 ] [ 3 ] and ribosome (translation) profiling [ 4 ] approaches are also employed to identify mRNA involved in polysome formation and locations of elongating ribosomes over coding regions of transcripts, correspondingly. These methods, however, do not use chemical stabilisation of translation complexes and purification of the covalently bound intermediates from the live cells. TCP-seq thus can be considered more as a functional equivalent of ChIP-seq and similar methods of investigating momentary interactions of DNA that are redesigned to be applicable for translation.
The advantages of the method include:
The disadvantages include:
The method is currently being developed and was applied to investigate translation dynamics in live yeast cells and is extending, rather than simply combining, the capabilities of the previous techniques. [ 1 ] The only other transcriptome-wide method for mapping ribosome positions over mRNA with nucleotide precision is ribosome (translation) profiling. However, it captures positions of only elongating ribosomes, and most dynamic and functionally important intermediates of translation at the initiation stage are not detected.
TCP-seq was designed to specifically target these blind spots. It can essentially provide the same level of details for elongation phase as ribosome (translation) profiling, but also includes recording of initiation, termination and recycling intermediates (and basically any other possible translation complexes as long as the ribosome or its subunits are contacting and protecting the mRNA) of protein synthesis that previously remained out of the reach. Therefore, TCP-seq provides a single approach for a complete insight into the translation process of a biological sample. This particular aspect of the method can be expected to be developed further as the dynamics of ribosomal scanning on mRNA during translation initiation is generally unknown for the most of life. Current dataset containing TCP-seq data for translation initiation is available for yeast Saccharomyces cerevisiae , [ 5 ] [ 6 ] and likely to be extended for other organisms in the future. | https://en.wikipedia.org/wiki/TCP-seq |
Transmission Control Protocol (TCP) uses a congestion control algorithm that includes various aspects of an additive increase/multiplicative decrease (AIMD) scheme, along with other schemes including slow start [ 1 ] and a congestion window (CWND), to achieve congestion avoidance. The TCP congestion-avoidance algorithm is the primary basis for congestion control in the Internet. [ 2 ] [ 3 ] [ 4 ] Per the end-to-end principle , congestion control is largely a function of internet hosts , not the network itself. There are several variations and versions of the algorithm implemented in protocol stacks of operating systems of computers that connect to the Internet .
To avoid congestive collapse , TCP uses a multi-faceted congestion-control strategy. For each connection, TCP maintains a CWND, limiting the total number of unacknowledged packets that may be in transit end-to-end. This is somewhat analogous to TCP's sliding window used for flow control .
The additive increase/multiplicative decrease (AIMD) algorithm is a closed-loop control algorithm . AIMD combines linear growth of the congestion window with an exponential reduction when congestion occurs. Multiple flows using AIMD congestion control will eventually converge to use equal amounts of a contended link. [ 5 ]
This is the algorithm that is described in RFC 5681 for the "congestion avoidance" state. [ 6 ]
In TCP, the congestion window (CWND) is one of the factors that determines the number of bytes that can be sent out at any time. The congestion window is maintained by the sender and is a means of preventing a link between the sender and the receiver from becoming overloaded with too much traffic. This should not be confused with the sliding window maintained by the sender which exists to prevent the receiver from becoming overloaded. The congestion window is calculated by estimating how much congestion there is on the link.
When a connection is set up, the congestion window, a value maintained independently at each host, is set to a small multiple of the maximum segment size ( MSS ) allowed on that connection. Further variance in the congestion window is dictated by an additive increase/multiplicative decrease (AIMD) approach. This means that if all segments are received and the acknowledgments reach the sender on time, some constant is added to the window size. It will follow different algorithms.
A system administrator may adjust the maximum window size limit, or adjust the constant added during additive increase, as part of TCP tuning .
The flow of data over a TCP connection is also controlled by the use of the receive window advertised by the receiver. A sender can send data less than its own congestion window and the receive window .
Slow start, defined by RFC 5681 . [ 7 ] is part of the congestion control strategy used by TCP in conjunction with other algorithms to avoid sending more data than the network is capable of forwarding, that is, to avoid causing network congestion.
Slow start begins initially with a congestion window size (CWND) of 1, 2, 4 or 10 MSS. [ 8 ] [ 3 ] : 1 The value for the congestion window size can be increased by 1 MSS with each acknowledgment (ACK) received, effectively doubling the window size each RTT . [ a ]
The transmission rate will be increased by the slow-start algorithm until either a packet loss is detected, the receiver's advertised window (rwnd) becomes the limiting factor, or slow start threshold (ssthresh) is reached, which is used to determine whether the slow start or congestion avoidance algorithm is used, a value set to limit slow start.
If the CWND reaches ssthresh , TCP switches to the congestion avoidance algorithm. It should be increased by up to 1 MSS for each RTT. A common formula is that each new ACK increases the CWND by MSS * MSS / CWND. It increases almost linearly and provides an acceptable approximation.
If a loss event occurs, TCP assumes that it is due to network congestion and takes steps to reduce the offered load on the network. These measures depend on the exact TCP congestion avoidance algorithm used.
When a TCP sender detects segment loss using the retransmission timer and the given segment has not yet been resent, the value of ssthresh must be set to no more than half of the amount of data that has been sent but not yet cumulatively acknowledged or 2 * MSS , whichever value is greater.
Slow start assumes that unacknowledged segments are due to network congestion. While this is an acceptable assumption for many networks, segments may be lost for other reasons, such as poor data link layer transmission quality. Thus, slow start can perform poorly in situations with poor reception, such as wireless networks .
The slow start protocol also performs badly for short-lived connections. Older web browsers would create many consecutive short-lived connections to the web server, and would open and close the connection for each file requested. This kept most connections in the slow start mode, which resulted in poor response time. To avoid this problem, modern browsers either open multiple connections simultaneously or reuse one connection for all files requested from a particular web server. Connections, however, cannot be reused for the multiple third-party servers used by web sites to implement web advertising , sharing features of social networking services , [ 9 ] and counter scripts of web analytics .
Fast retransmit is an enhancement to TCP that reduces the time a sender waits before retransmitting a lost segment. A TCP sender normally uses a simple timer to recognize lost segments. If an acknowledgment is not received for a particular segment within a specified time (a function of the estimated round-trip delay time ), the sender will assume the segment was lost in the network and will retransmit the segment.
Duplicate acknowledgment is the basis for the fast retransmit mechanism. After receiving a packet an acknowledgement is sent for the last in-order byte of data received. For an in-order packet, this is effectively the last packet's sequence number plus the current packet's payload length. If the next packet in the sequence is lost but a third packet in the sequence is received, then the receiver can only acknowledge the last in-order byte of data, which is the same value as was acknowledged for the first packet. The second packet is lost and the third packet is not in order, so the last in-order byte of data remains the same as before. Thus a Duplicate acknowledgment occurs. The sender continues to send packets, and a fourth and fifth packet are received by the receiver. Again, the second packet is missing from the sequence, so the last in-order byte has not changed. Duplicate acknowledgments are sent for both of these packets.
When a sender receives three duplicate acknowledgments, it can be reasonably confident that the segment carrying the data that followed the last in-order byte specified in the acknowledgment was lost. A sender with fast retransmit will then retransmit this packet immediately without waiting for its timeout. On receipt of the retransmitted segment, the receiver can acknowledge the last in-order byte of data received. In the above example, this would acknowledge to the end of the payload of the fifth packet. There is no need to acknowledge intermediate packets since TCP uses cumulative acknowledgments by default.
The names Reno and Tahoe are the names of releases of the BSD UNIX operating system, and were used to refer to the congestion control algorithms (CCAs) at least as early a 1996 paper by Kevin Fall and Sally Floyd. [ 10 ] [ failed verification ]
The following is one possible classification according to the following properties:
Some well-known congestion avoidance mechanisms are classified by this scheme as follows:
TCP Tahoe and Reno algorithms were retrospectively named after the versions or flavors of the 4.3BSD operating system in which each first appeared (which were themselves named after Lake Tahoe and the nearby city of Reno, Nevada ). The Tahoe algorithm first appeared in 4.3BSD-Tahoe (which was made to support the CCI Power 6/32 "Tahoe" minicomputer ), and was later made available to non-AT&T licensees as part of the 4.3BSD Networking Release 1; this ensured its wide distribution and implementation. Improvements were made in 4.3BSD-Reno and subsequently released to the public as Networking Release 2 and later 4.4BSD-Lite.
While both consider retransmission timeout (RTO) and duplicate ACKs as packet loss events, the behavior of Tahoe and Reno differ primarily in how they react to duplicate ACKs:
In both Tahoe and Reno, if an ACK times out (RTO timeout), slow start is used, and both algorithms reduce the congestion window to 1 MSS. [ citation needed ]
TCP New Reno, defined by RFC 6582 (which obsolesces previous definitions in RFC 3782 and RFC 2582 ), improves retransmission during the fast-recovery phase of TCP Reno.
During fast recovery, to keep the transmit window full, for every duplicate ACK that is returned, a new unsent packet from the end of the congestion window is sent.
The difference from Reno is that New Reno does not halve ssthresh immediately which may reduce the window too much if multiple packet losses occur. It does not exit fast-recovery and reset ssthresh until it acknowledges all of the data.
After retransmission, newly acknowledged data have two cases:
It uses a variable called "recover" to record how much data needs to be recovered. After a retransmit timeout, it records the highest sequence number transmitted in the recover variable and exits the fast recovery procedure. If this sequence number is acknowledged, TCP returns to the congestion avoidance state.
A problem occurs with New Reno when there are no packet losses but instead, packets are reordered by more than 3 packet sequence numbers. In this case, New Reno mistakenly enters fast recovery. When the reordered packet is delivered, duplicate and needless retransmissions are immediately sent.
New Reno performs as well as SACK at low packet error rates and substantially outperforms Reno at high error rates. [ 19 ]
Until the mid-1990s, all of TCP's set timeouts and measured round-trip delays were based upon only the last transmitted packet in the transmit buffer. University of Arizona researchers Larry Peterson and Lawrence Brakmo introduced TCP Vegas in which timeouts were set and round-trip delays were measured for every packet in the transmit buffer. In addition, TCP Vegas uses additive increases in the congestion window. In a comparison study of various TCP CCA s, TCP Vegas appeared to be the smoothest followed by TCP CUBIC. [ 20 ]
TCP Vegas was not widely deployed outside Peterson's laboratory but was selected as the default congestion control method for DD-WRT firmware v24 SP2. [ 21 ]
TCP Hybla [ 22 ] [ 23 ] aims to eliminate penalties to TCP connections that use high-latency terrestrial or satellite radio links. Hybla improvements are based on analytical evaluation of the congestion window dynamics. [ 24 ]
Binary Increase Congestion control (BIC) is a TCP implementation with an optimized CCA for high-speed networks with high latency, known as long fat networks (LFNs). [ 25 ] BIC is used by default in Linux kernels 2.6.8 through 2.6.18. [ citation needed ]
CUBIC is a less aggressive and more systematic derivative of BIC, in which the window is a cubic function of time since the last congestion event, with the inflection point set to the window prior to the event. CUBIC is used by default in Linux kernels since version 2.6.19.
Agile-SD is a Linux-based CCA which is designed for the real Linux kernel. It is a receiver-side algorithm that employs a loss-based approach using a novel mechanism, called agility factor (AF). to increase the bandwidth utilization over high-speed and short-distance networks (low bandwidth-delay product networks) such as local area networks or fiber-optic network, especially when the applied buffer size is small. [ 26 ] It has been evaluated by comparing its performance to Compound TCP (the default CCA in MS Windows) and CUBIC (the default of Linux) using NS-2 simulator. It improves the total performance up to 55% in term of average throughput.
Westwood+ is a sender-only modification of TCP Reno that optimizes the performance of TCP congestion control over both wired and wireless networks . TCP Westwood+ is based on end-to-end bandwidth estimation to set the congestion window and slow-start threshold after a congestion episode, that is, after three duplicate acknowledgments or a timeout. The bandwidth is estimated by averaging the rate of returning acknowledgment packets. In contrast with TCP Reno, which blindly halves the congestion window after three duplicate ACKs, TCP Westwood+ adaptively sets a slow-start threshold and a congestion window that takes into account an estimate of bandwidth available at the time congestion is experienced. Compared to Reno and New Reno, Westwood+ significantly increases throughput over wireless links and improves fairness in wired networks. [ citation needed ]
Compound TCP is a Microsoft implementation of TCP which maintains two different congestion windows simultaneously, with the goal of achieving good performance on LFNs while not impairing fairness . It has been widely deployed in Windows versions since Microsoft Windows Vista and Windows Server 2008 and has been ported to older Microsoft Windows versions as well as Linux .
TCP Proportional Rate Reduction (PRR) [ 27 ] is an algorithm designed to improve the accuracy of data sent during recovery. The algorithm ensures that the window size after recovery is as close as possible to the slow start threshold. In tests performed by Google , PRR resulted in a 3–10% reduction in average latency and recovery timeouts were reduced by 5%. [ 28 ] PRR is available in Linux kernels since version 3.2. [ 29 ]
Bottleneck Bandwidth and Round-trip propagation time (BBR) is a CCA developed at Google in 2016. [ 30 ] While most CCAs are loss-based, in that they rely on packet loss to detect congestion and lower rates of transmission, BBR, like TCP Vegas , is model-based. The algorithm uses the maximum bandwidth and round-trip time at which the network delivered the most recent flight of outbound data packets to build a model of the network. Each cumulative or selective acknowledgment of packet delivery produces a rate sample that records the amount of data delivered over the time interval between the transmission of a data packet and the acknowledgment of that packet. [ 31 ]
When implemented at YouTube , BBRv1 yielded an average of 4% higher network throughput and up to 14% in some countries. [ 32 ] BBR has been available for Linux TCP since Linux 4.9. [ 33 ] It is also available for QUIC . [ 34 ]
BBR version 1 (BBRv1) fairness to non-BBR streams is disputed. While Google's presentation shows BBRv1 co-existing well with CUBIC, [ 30 ] researchers like Geoff Huston and Hock, Bless and Zitterbart found it unfair to other streams and not scalable. [ 35 ] Hock et al. also found "some severe inherent issues such as increased queuing delays, unfairness, and massive packet loss" in the BBR implementation of Linux 4.9. [ 36 ] Soheil Abbasloo et al. (authors of C2TCP) show that BBRv1 doesn't perform well in dynamic environments such as cellular networks. [ 11 ] [ 12 ] They have also shown that BBR has an unfairness issue. For instance, when a CUBIC flow (which is the default TCP implementation in Linux, Android, and MacOS) coexists with a BBR flow in the network, the BBR flow can dominate the CUBIC flow and get the whole link bandwidth from it (see figure 16 in [ 11 ] ).
Version 2 attempts to deal with the issue of unfairness when operating alongside loss-based congestion management such as CUBIC. [ 37 ] In BBRv2 the model used by BBRv1 is augmented to include information about packet loss and information from Explicit Congestion Notification (ECN). [ 38 ] Whilst BBRv2 may at times have lower throughput than BBRv1 it is generally considered to have better goodput . [ citation needed ]
Version 3 (BBRv3) fixes two bugs in BBRv2 (premature end of bandwidth probing, bandwidth convergence) and performs some performance tuning. There is also a variant, termed BBR.Swift, optimized for datacenter-internal links: it uses network_RTT (excluding receiver delay) as the main congestion control signal. [ 38 ]
Cellular Controlled Delay TCP (C2TCP) [ 11 ] [ 12 ] was motivated by the lack of a flexible end-to-end TCP approach that can satisfy various QoS requirements for different applications without requiring any changes in the network devices. C2TCP aims to satisfy ultra-low latency and high-bandwidth requirements of applications such as virtual reality , video conferencing , online gaming , vehicular communication systems , etc. in a highly dynamic environment such as current LTE and future 5G cellular networks . C2TCP works as an add-on on top of loss-based TCP (e.g. Reno, NewReno, CUBIC , BIC , ...), it is only required to be installed on the server-side and makes the average delay of packets bounded to the desired delays set by the applications.
Researchers at NYU [ 39 ] showed that C2TCP outperforms the delay and delay-variation performance of various state-of-the-art TCP schemes. For instance, they showed that compared to BBR, CUBIC, and Westwood on average, C2TCP decreases the average delay of packets by about 250%, 900%, and 700% respectively on various cellular network environments. [ 11 ]
Elastic-TCP was proposed in February 2019 to increase bandwidth utilization over high-BDP networks in support of cloud computing. It is a Linux-based CCA that is designed for the Linux kernel. It is a receiver-side algorithm that employs a loss-delay-based approach using a novel mechanism called a window-correlated weighting function (WWF). It has a high level of elasticity to deal with different network characteristics without the need for human tuning. It has been evaluated by comparing its performance to Compound TCP (the default CCA in MS Windows), CUBIC (the default for Linux) and TCP-BBR (the default of Linux 4.9 used by Google) using the NS-2 simulator and testbed. Elastic-TCP significantly improves the total performance in terms of average throughput, loss ratio, and delay. [ 40 ]
Soheil Abbasloo et al. proposed NATCP (Network-Assisted TCP) [ 13 ] a controversial [ according to whom? ] TCP design targeting multi-access edge computing (MEC). The key idea of NATCP is that if the characteristics of the network were known beforehand, TCP would have been designed differently. Therefore, NATCP employs the available features and properties in the current MEC-based cellular architectures to push the performance of TCP close to the optimal performance. NATCP uses out-of-band feedback from the network to the servers located nearby. The feedback from the network, which includes the capacity of the cellular access link and the minimum RTT of the network, guides the servers to adjust their sending rates. As preliminary results show, NATCP outperforms the state-of-the-art TCP schemes. [ 13 ] [ 41 ]
TCP New Reno was the most commonly implemented algorithm, [ citation needed ] SACK support is very common [ citation needed ] and is an extension to Reno/New Reno. Most others are competing proposals that still need evaluation. Starting with 2.6.8 the Linux kernel switched the default implementation from New Reno to BIC . The default implementation was again changed to CUBIC in the 2.6.19 version. FreeBSD from version 14.X onwards also uses CUBIC as the default algorithm. [ 53 ] Previous version used New Reno. However, FreeBSD supports a number of other choices. [ 54 ]
When the per-flow product of bandwidth and latency increases, regardless of the queuing scheme, TCP becomes inefficient and prone to instability. This becomes increasingly important as the Internet evolves to incorporate very high-bandwidth optical links.
TCP Interactive (iTCP) [ 55 ] allows applications to subscribe to TCP events and respond accordingly enabling various functional extensions to TCP from outside TCP layer. Most TCP congestion schemes work internally. iTCP additionally enables advanced applications to directly participate in congestion control such as to control the source generation rate.
Zeta-TCP detects congestion from both latency and loss rate measures. To maximize the goodput Zeta-TCP and applies different congestion window backoff strategies based on the likelihood of congestion. It also has other improvements to accurately detect packet losses, avoiding retransmission timeout retransmission; and accelerate and control the inbound (download) traffic. [ 56 ]
CCAs may be classified in relation to network awareness, meaning the extent to which these algorithms are aware of the state of the network. This consist of three primary categories: black box, grey box, and green box. [ 57 ]
Black box algorithms offer blind methods of congestion control. They operate only on the binary feedback received upon congestion and do not assume any knowledge concerning the state of the networks which they manage.
Grey box algorithms use time-based measurement, such as RTT variation and rate of packet arrival, in order to obtain measurements and estimations of bandwidth, flow contention, and other knowledge of network conditions.
Green box algorithms offer bimodal methods of congestion control which measures the fair share of total bandwidth which should be allocated for each flow, at any point, during the system's execution.
The following algorithms require custom fields to be added to the TCP packet structure: | https://en.wikipedia.org/wiki/TCP_congestion_control |
In the field of computer networking , TCP pacing is the denomination of a set of techniques to make the pattern of packet transmission generated by the Transmission Control Protocol less bursty. Where there could be insufficient buffers in switches and routers, TCP Pacing is intended to avoid packet loss due to exhaustion of buffer memory in network devices along the path. [ 1 ] It can be conducted by the network scheduler .
Bursty traffic can lead to higher queuing delays, more packet losses and lower throughput. [ 2 ] However it has been observed that TCP's congestion control mechanisms may lead to bursty traffic on high bandwidth and highly multiplexed networks, [ 3 ] a proposed solution to this problem is TCP pacing. TCP pacing involves evenly spacing data transmissions across a round-trip time. [1] | https://en.wikipedia.org/wiki/TCP_pacing |
A TCP reset attack , also known as a forged TCP reset or spoofed TCP reset , is a way to terminate a TCP connection by sending a forged TCP reset packet. This tampering technique can be used by a firewall or abused by a malicious attacker to interrupt Internet connections.
As of 2006, the The Great Firewall of China and Iranian Internet censors are known to use TCP reset attacks to interfere with and block connections as a major method to carry out Internet censorship. [ 1 ]
The Internet is a system for individual computers to exchange electronic messages, or packets of data. This system includes hardware to carry the messages (such as copper and fiber optics cables) and a formalized system for formatting the messages, called "protocols". The basic protocol used on the Internet is the Internet Protocol (IP), which is usually coupled with additional protocols such as TCP ( Transmission Control Protocol [ 2 ] ) or UDP ( User Datagram Protocol ). TCP/IP is the protocol set used for email and web browsing. Each protocol has a block of information, called a header, included near the front of each packet. Headers contain information about which computer sent the packet, which computer should receive it, the packet size, etc.
TCP is commonly employed alongside IP (Internet Protocol) to establish a two-way virtual connection between two computers. As a connection-oriented protocol, TCP necessitates the establishment of a logical connection between two processes prior to the exchange of data. This is in contrast to UDP, which is a connection-less protocol within the IP suite. TCP/IP sockets facilitate communication between computers, such as between a workstation with a browser and a web server , through the exchange of a stream of data packets. The use of a TCP connection enables the transfer of large data items, which exceed the size limits of a single packet, including video clips, email attachments, or music files. Although certain web pages are sufficiently small to fit within a single packet, they are typically transmitted over TCP connections for enhanced reliability and error control.
In a stream of packets of a TCP connection, each packet contains a TCP header. Each of these headers contains a bit known as the "reset" (RST) flag. [ 3 ] In most packets, this bit is set to 0 and has no effect. However, if this bit is set to 1, it indicates to the receiving computer that the computer should immediately stop using the TCP connection; it should not send any more packets using the connection's identifying numbers, called ports, and discard any further packets it receives with headers indicating they belong to that connection. A TCP reset kills a TCP connection near instantly.
This tool serves a specific function within the realm of computer networking, particularly in managing TCP connections. A notable use case arises when a computer, referred to as 'Computer A,' experiences a system crash during an active TCP connection. Consequently, the corresponding computer on the other end of the connection, designated as 'Computer B,' remains unaware of the crash and continues to transmit TCP packets. Upon rebooting, Computer A receives these residual packets from the disrupted connection. However, lacking the original context and unable to process them appropriately, Computer A typically issues a TCP reset signal to Computer B. This reset informs Computer B of the failure in the connection, prompting the user at Computer B to either attempt reestablishing the connection or take alternative actions as necessary.
In the scenario above, the TCP reset bit was sent by a computer that was one of the connection endpoints. It is possible for a third computer to monitor the TCP packets on the connection and then send a "forged" packet containing a TCP reset to one or both endpoints. The headers in the forged packet must indicate, falsely, that it came from an endpoint, not the forger. This information includes the endpoint IP addresses and port numbers. Every field in the IP and TCP headers must be set to a convincing forged value for the fake reset to trick the endpoint into closing the TCP connection. Properly formatted forged TCP resets can be a very effective way to disrupt any TCP connection that the forger can monitor.
One application of a forged TCP reset is to maliciously disrupt TCP connections without the consent of the two parties that own the endpoints. However, network security systems using forged TCP resets have been designed as well. A prototype "Buster" software package was demonstrated in 1995 that would send forged resets to any TCP connection that used port numbers in a short list. Linux volunteers proposed doing something similar with Linux firewalls in 2000, [ 3 ] and open source software, such as Snort used TCP resets to disrupt suspicious connections as early as 2003. [ 4 ]
By late 2007, Comcast began using forged TCP resets to cripple peer-to-peer and certain groupware applications on their customers' computers. [ 5 ] This started a controversy, which was followed by the creation of the Network Neutrality Squad (NNSquad) by Lauren Weinstein , Vint Cerf , David Farber , Craig Newmark and other well-known founders and champions of openness on the Internet. [ 6 ] In 2008, the NNSquad released the NNSquad Network Measurement Agent, a Windows software program written by John Bartas, which could detect Comcast's forged TCP resets and distinguish them from real endpoint-generated resets. The technology to detect the resets was developed from the earlier open-source "Buster" software which used forged resets to block malware and ads in web pages.
In January 2008, the FCC announced it would investigate Comcast's use of forged resets, and, on August 21, 2008, it ordered Comcast to terminate the practice. [ 7 ]
By encrypting connections through the utilization of a VPN , the attacker has to do a TCP reset attack on all encrypted connections, causing collateral damage . [ citation needed ] | https://en.wikipedia.org/wiki/TCP_reset_attack |
TCP tuning techniques adjust the network congestion avoidance parameters of Transmission Control Protocol (TCP) connections over high- bandwidth , high- latency networks. Well-tuned networks can perform up to 10 times faster in some cases. [ 1 ] However, blindly following instructions without understanding their real consequences can hurt performance as well.
Bandwidth-delay product (BDP) is a term primarily used in conjunction with TCP to refer to the number of bytes necessary to fill a TCP "path", i.e. it is equal to the maximum number of simultaneous bits in transit between the transmitter and the receiver.
High performance networks have very large BDPs. To give a practical example, two nodes communicating over a geostationary satellite link with a round-trip delay time (or round-trip time, RTT) of 0.5 seconds and a bandwidth of 10 Gbit/s can have up to 0.5×10 Gbits , i.e., 5 Gbit of unacknowledged data in flight. Despite having much lower latencies than satellite links, even terrestrial fiber links can have very high BDPs because their link capacity is so large. Operating systems and protocols designed as recently as a few years ago when networks were slower were tuned for BDPs of orders of magnitude smaller, with implications for limited achievable performance.
The original TCP configurations supported TCP receive window size buffers of up to 65,535 (64 KiB - 1) bytes, which was adequate for slow links or links with small RTTs. Larger buffers are required by the high performance options described below.
Buffering is used throughout high performance network systems to handle delays in the system. In general, buffer size will need to be scaled proportionally to the amount of data "in flight" at any time. For very high performance applications that are not sensitive to network delays, it is possible to interpose large end to end buffering delays by putting in intermediate data storage points in an end to end system, and then to use automated and scheduled non-real-time data transfers to get the data to their final endpoints.
Maximum achievable throughput for a single TCP connection is determined by different factors. One trivial limitation is the maximum bandwidth of the slowest link in the path. But there are also other, less obvious limits for TCP throughput. Bit errors can create a limitation for the connection as well as RTT.
In computer networking , RWIN (TCP Receive Window) is the amount of data that a computer can accept without acknowledging the sender. If the sender has not received acknowledgement for the first packet it sent, it will stop and wait and if this wait exceeds a certain limit, it may even retransmit . This is how TCP achieves reliable data transmission .
Even if there is no packet loss in the network, windowing can limit throughput. Because TCP transmits data up to the window size before waiting for the acknowledgements, the full bandwidth of the network may not always get used. The limitation caused by window size can be calculated as follows:
T h r o u g h p u t ≤ R W I N R T T {\displaystyle \mathrm {Throughput} \leq {\frac {\mathrm {RWIN} }{\mathrm {RTT} }}\,\!}
where RWIN is the TCP Receive Window and RTT is the round-trip time for the path.
At any given time, the window advertised by the receive side of TCP corresponds to the amount of free receive memory it has allocated for this connection. Otherwise it would risk dropping received packets due to lack of space.
The sending side should also allocate the same amount of memory as the receive side for good performance. That is because, even after data has been sent on the network, the sending side must hold it in memory until it has been acknowledged as successfully received, just in case it would have to be retransmitted. If the receiver is far away, acknowledgments will take a long time to arrive. If the send memory is small, it can saturate and block emission. A simple computation gives the same optimal send memory size as for the receive memory size given above.
When packet loss occurs in the network, an additional limit is imposed on the connection. [ 2 ] In the case of light to moderate packet loss when the TCP rate is limited by the congestion avoidance algorithm , the limit can be calculated according to the formula (Mathis, et al.):
T h r o u g h p u t ≤ M S S R T T P l o s s {\displaystyle \mathrm {Throughput} \leq {\frac {\mathrm {MSS} }{\mathrm {RTT} {\sqrt {P_{\mathrm {loss} }}}}}}
where MSS is the maximum segment size and P loss is the probability of packet loss. If packet loss is so rare that the TCP window becomes regularly fully extended, this formula doesn't apply.
A number of extensions have been made to TCP over the years to increase its performance over fast high-RTT links ("long fat networks" or LFNs).
TCP timestamps (RFC 1323) play a double role: they avoid ambiguities due to the 32-bit sequence number field wrapping around, and they allow more precise RTT estimation in the presence of multiple losses per RTT. With those improvements, it becomes reasonable to increase the TCP window beyond 64 kB, which can be done using the window scaling option (RFC 1323).
The TCP selective acknowledgment option (SACK, RFC 2018) allows a TCP receiver to precisely inform the TCP sender about which segments have been lost. This increases performance on high-RTT links, when multiple losses per window are possible.
Path MTU Discovery avoids the need for in-network fragmentation , increasing the performance in the presence of packet loss.
The default IP queue length is 1000, which is generally too large. Imagine a Wi-Fi base station having a speed of 20 Mbit/s and an average packet size of 750 byte. How large should the IP queue be? A voice over IP client should be able to transmit a packet every 20 ms. The estimated maximum number of packets in transit would then be:
A better queue length would be: | https://en.wikipedia.org/wiki/TCP_tuning |
TD/SMP , short for Terminal Device/Session Management Protocol , was a terminal multiplexer system introduced by DEC on their VT330/340 terminals in 1987. The terminal-side was referred to as SSU . TD/SMP allowed data from two separate host sessions to be sent to a compatible computer terminal over a single serial port . The format was patented [ 1 ] and never described in depth, limiting it to DEC's own terminal servers and terminals.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TD/SMP |
The time-dependent Ginzburg-Landau ( TDGL ) equations give the evolution in time of the steady-state equations of the Ginzburg-Landau theory (GL). Although phenomenological, these equations can be very useful in making qualitative predictions about the time evolution of superconductors, particularly in the mixed state where Abrikosov vortices or Pearl vortices may appear. [ 1 ]
Because of the phenomenological nature of GL theory, there are a number of different ways to expand its time dependence including different corrections and approximations. For example, in their seminal paper using TDGL to describe the time scale of fluctuations in one-dimensional superconducting wires, McCumber and Halperin adopt the following form (note units are CGS): [ 2 ]
τ ( T ) ( ∂ ∂ t + i 2 e V ℏ ) ψ = ( 1 − | ψ | 2 ) ψ + ξ ( T ) ( ∂ ∂ x − i 2 e ℏ c A x ) 2 ψ {\displaystyle \tau (T)({\frac {\partial }{\partial t}}+i{\frac {2eV}{\hbar }})\psi =(1-|\psi |^{2})\psi +\xi (T)({\frac {\partial }{\partial x}}-i{\frac {2e}{\hbar c}}A_{x})^{2}\psi }
With ψ {\displaystyle \psi } the order parameter describing the degree of superconducting order; τ {\displaystyle \tau } the temperature-dependent GL relaxation time of the order parameter; V {\displaystyle V} the electrochemical potential; A x {\displaystyle A_{x}} the magnetic vector potential ; and ξ {\displaystyle \xi } the superconducting coherence length . However, other forms exist. Sometimes the electrochemical potential is dropped for convenience, even though it increases the quantitative accuracy of the TDGL equations, and sometimes other correction terms are added. [ 3 ] | https://en.wikipedia.org/wiki/TDGL |
A TDM Fabric to Framer Interface is a type of interface used in optical networking. TDM refers to time division multiplexing . Some commonly used TDM variants include:
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TDM_Fabric_to_Framer_Interface |
The TDR Targets database is a bioinformatics project that seeks to exploit the availability of diverse genomic and chemical datasets to facilitate the identification and prioritization of drugs and drug targets in neglected disease pathogens . [ 2 ] TDR in the name of the database stands from the popular abbreviation for a special programme within the World Health Organization , whose focus is T ropical D isease R esearch . The project was jumpstarted by funds from this programme (see Special Programme for Research and Training in Tropical Diseases ), and the initial focus of the resource was on organisms/diseases of high priority for this Programme.
The database functions both as a website, where researchers can look for information on targets or compounds of interest, or as a tool for prioritization of targets in whole genomes . [ 3 ] When prioritizing genes, individual database queries are used to specify one or more desirable or undesirable criteria. The output of each query will be a set of genes (e.g. all genes that produce a lethal phenotype upon a genetic knockout); and different combinations of gene sets can be obtained using standard set operators (Union, Intersection, Subtraction), including the possibility of weighting genes present in more than one set (this is particularly useful when calculating Unions). A number of prioritizations obtained with this tool have been published, [ 4 ] demonstrating a number of use cases.
The database currently hosts information for 21 bacterial and eukaryotic pathogens, and for > 2 million bioactive compounds . Information integrated into the TDR Targets database comes from disparate data sources, and therefore cannot be considered a primary data repository.
The database has seen six major releases since its launch in 2007, which coincided with expansion of phylogenetic coverage (e.g. inclusion of helminth genomes in release 2), incorporation of new functionalities (e.g. chemical similarity and substructure searches in release 4), major data updates to keep the database in sync with upstream data providers (in release 5), and the incorporation of a multilayer network model [ 5 ] to guide Drug repositioning through nice user-friendly visualizations (in release 6).
ChEMBL
This database -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TDR_Targets |
A spatial TDR moisture sensor employs time-domain reflectometry (TDR) to measure moisture content indirectly based on the correlation to electric and dielectric properties of materials, such as soil , agrarian products , snow , wood or concrete .
Measurement usually involves inserting a sensor into the substance to be tested and then applying either Standard Waveform Analysis to determine the average moisture content along the sensor or Profile Analysis to provide moisture content at discrete points along the sensor. A spatial location can be achieved by appropriate installation of several sensors.
In the waveform analysis a sensor (usually a probe) is placed in the material to be tested. The sensor contains a waveguide consisting of two, three, or more parallel wires which is connected via a coaxial cable to a voltage pulse generator which sends precisely defined voltage pulses into the sensor. As the pulse travels along the waveguide its progress varies depending on the moisture content of the material being examined. When the pulse reaches the end of the waveguide it is reflected . This reflection is visualised in a TDR waveform using an oscilloscope connected to the sensor. The rate of travel of the pulse in the probe is measured and related to moisture content, with slower travel indicating an increase of moisture. By measuring the time from the initial pulse until the reflection is received the average moisture content and relative permitivity of the sample can be calculated by using an equivalent circuit as a reference.
Standard waveform analysis can be used either manually (hand held instruments) or automatically for monitoring moisture content in several areas such as hydrology , agriculture and construction .
Standard Waveform Analysis is unable to provide a spatial moisture profile. More sophisticated methods such as Profile Analysis are required. This method uses a variety of techniques to add spatial information to the measurement results.
Profile analysis allows fully automatic measurement and monitoring of spatial moisture content and thus a leak monitoring of building foundations , landfill barriers and geological repositories in salt mines . | https://en.wikipedia.org/wiki/TDR_moisture_sensor |
Total dissolved solids ( TDS ) is a measure of the dissolved combined content of all inorganic and organic substances present in a liquid in molecular , ionized , or micro-granular ( colloidal sol ) suspended form. TDS are often measured in parts per million (ppm). TDS in water can be measured using a digital meter. [ 1 ]
Generally, the operational definition is that the solids must be small enough to survive filtration through a filter with 2-micrometer (nominal size, or smaller) pores. Total dissolved solids are normally discussed only for freshwater systems, as salinity includes some of the ions constituting the definition of TDS. The principal application of TDS is in the study of water quality for streams , rivers , and lakes . Although TDS is not generally considered a primary pollutant (e.g. it is not deemed to be associated with health effects), it is used as an indication of aesthetic characteristics of drinking water and as an aggregate indicator of the presence of a broad array of chemical contaminants.
Primary sources for TDS in receiving waters are agricultural runoff and residential (urban) runoff , clay-rich mountain waters, leaching of soil contamination , and point source water pollution discharge from industrial or sewage treatment plants. The most common chemical constituents are calcium , phosphates , nitrates , sodium , potassium , and chloride , which are found in nutrient runoff, general stormwater runoff and runoff from snowy climates where road de-icing salts are applied. The chemicals may be cations , anions , molecules or agglomerations on the order of one thousand or fewer molecules, so long as a soluble micro- granule is formed. More exotic and harmful elements of TDS are pesticides arising from surface runoff . Certain naturally occurring total dissolved solids arise from the weathering and dissolution of rocks and soils. The United States has established a secondary water quality standard of 500 mg/L to provide for palatability of drinking water.
Total dissolved solids are differentiated from total suspended solids (TSS), in that the latter cannot pass through a sieve of 2 micrometers and yet are indefinitely suspended in solution. The term settleable solids refers to material of any size that will not remain suspended or dissolved in a holding tank not subject to motion, and excludes both TDS and TSS. [ 2 ] Settleable solids may include larger particulate matter or insoluble molecules.
Total dissolved solids include both volatile and non-volatile solids. Volatile solids are ones that can easily go from a solid to a gaseous state. Non-volatile solids must be heated to a high temperature, typically 550 °C, in order to achieve this state change. Examples of non-volatile substances include salts and sugars. [ 3 ]
The two principal methods of measuring total dissolved solids are gravimetric analysis and conductivity . [ 4 ] Gravimetric methods are the most accurate and involve evaporating the liquid solvent and measuring the mass of residues left. This method is generally the best, although it is time-consuming. If inorganic salts comprise the great majority of TDS, conductivity-based methods are appropriate.
Conductivity of water is directly related to the concentration of dissolved ionized solids. These ions allow the water to conduct electric current . This electric current can be measured using a conventional conductivity meter or TDS meter . When correlated with laboratory TDS measurements, conductivity provides an approximate value for the TDS concentration , with around 10% accuracy.
The relationship of TDS and specific conductance of groundwater can be approximated by the following equation:
where TDS is expressed in mg/L and EC is the electrical conductivity in microsiemens per centimeter at 25 °C. The conversion factor k e varies between 0.55 and 0.8. [ 5 ]
Some TDS meters use an electrical conductivity measurement to the ppm using the above formula. Regarding units, 1 ppm indicates 1 mg of dissolved solids per 1,000 g of water. [ 6 ]
Hydrologic transport models are used to mathematically analyze movement of TDS within river systems. The most common models address surface runoff, allowing variation in land use type, topography , soil type, vegetative cover, precipitation , and land management practice (e.g. the application rate of a fertilizer ). Runoff models have evolved to a good degree of accuracy and permit the evaluation of alternative land management practices upon impacts to stream water quality.
Basin models are used to more comprehensively evaluate total dissolved solids within a catchment basin and dynamically along various stream reaches. The DSSAM model was developed by the U.S. Environmental Protection Agency (EPA). [ 7 ] This hydrology transport model is actually based upon the pollutant-loading metric called " Total Maximum Daily Load " (TMDL), which addresses TDS and other specific chemical pollutants. The success of this model contributed to the Agency's broadened commitment to the use of the underlying TMDL protocol in its national policy for management of many river systems in the United States. [ 8 ]
When measuring water treated with water softeners , high levels of total dissolved solids do not correlate to hard water, as water softeners do not reduce TDS; rather, they replace magnesium and calcium ions, which cause hard water, with an equal charge of sodium or potassium ions, e.g. Ca 2+ ⇌ 2 Na + , leaving overall TDS unchanged [ 9 ] or even increased. Hard water can cause scale buildup in pipes, valves , and filters , reducing performance and adding to system maintenance costs. These effects can be seen in aquariums , spas , swimming pools , and reverse osmosis water treatment systems. Typically, total dissolved solids are tested frequently in these applications, and filtration membranes are checked to prevent adverse effects.
In the case of hydroponics and aquaculture , TDS is often monitored to create a water quality environment favorable for organism productivity. For freshwater, oysters , trouts , and other high-value seafood , the highest productivity and economic returns are achieved by mimicking the TDS and pH levels of each species ' native environment. For hydroponic uses, total dissolved solids are considered one of the best indices of nutrient availability for the aquatic plants being grown.
Because the threshold of acceptable aesthetic criteria for human drinking water is 500 mg/L, there is no general concern for odor , taste, and color at a level much lower than is required for harm. Several studies have been conducted that indicate various species' reactions range from intolerance to outright toxicity due to elevated TDS. The numerical results must be interpreted cautiously, as accurate toxicity outcomes relate to specific chemical constituents. Nevertheless, some numerical information is a helpful guide to the nature of risks in exposing aquatic organisms or terrestrial animals to high TDS levels. Most aquatic ecosystems involving mixed fish fauna can tolerate TDS levels of 1000 mg/L. [ 10 ]
The fathead minnow ( Pimephales promelas ), for example, realizes an LD 50 concentration of 5,600 ppm based upon a 96-hour exposure. LD50 is the concentration required to produce a lethal effect on 50 percent of the exposed population . Daphnia magna , a good example of a primary member of the food chain , is a small planktonic crustacean , about 0.5 mm (0.020 in) in length, having an LD50 of about 10,000 ppm TDS for a 96-hour exposure. [ 11 ]
Spawning fishes and juveniles appear to be more sensitive to high TDS levels. For example, it was found that concentrations of 350 mg/L TDS reduced spawning of Striped bass ( Morone saxatilis ) in the San Francisco Bay -Delta region, and that concentrations below 200 mg/L promoted even healthier spawning conditions. [ 12 ] In the Truckee River , EPA found that juvenile Lahontan cutthroat trout were subject to higher mortality when exposed to thermal pollution stress combined with high total dissolved solids concentrations. [ 7 ]
For terrestrial animals, poultry typically possess a safe upper limit of TDS exposure of approximately 2,900 mg/L, whereas dairy cattle are measured to have a safe upper limit of about 7,100 mg/L. Research has shown that exposure to TDS is compounded in toxicity when other stressors are present, such as abnormal pH, high turbidity , or reduced dissolved oxygen with the latter stressor acting only in the case of Animalia. [ 13 ]
In countries with often unsafe/unclean tap water supplies, technicians frequently check the TDS of drinking water to gauge how effectively their RO/Water Filtration devices are working. While TDS readings will not provide the number of microorganisms present in a sample of water, they can indicate how efficient the filter is by the presence of TDS.
[ 14 ] Water can be classified by the level of total dissolved solids (TDS) in the water:
Drinking water generally has a TDS below 500 ppm. Higher TDS Fresh Water is drinkable but taste may be objectionable. | https://en.wikipedia.org/wiki/TDS_meter |
TECO ( / ˈ t iː k oʊ / [ 1 ] ), short for Text Editor & Corrector , [ 2 ] [ 3 ] [ 4 ] is both a character-oriented text editor and a programming language , [ 5 ] [ 6 ] that was developed in 1962 for use on Digital Equipment Corporation computers, and has since become available on PCs and Unix . Dan Murphy developed TECO while a student at the Massachusetts Institute of Technology (MIT). [ 5 ]
According to Murphy, the initial acronym was Tape Editor and Corrector because " punched paper tape was the only medium for the storage of program source on our PDP-1. There was no hard disk, floppy disk, magnetic tape (magtape), or network." [ 5 ] By the time TECO was made available for general use, the name had become "Text Editor and Corrector", [ 4 ] since even the PDP-1 version
by then supported other media. [ 5 ] It was subsequently modified by many other people [ 7 ] and is a direct ancestor of Emacs , which was originally implemented in TECO macros. [ 8 ] [ 9 ] [ 10 ]
TECO is not only an editor but also an interpreted programming language for text manipulation. Arbitrary programs (called "macros") for searching and modifying text give it great power. Unlike regular expressions , however, the language was imperative , though some versions had an "or" operator in string search.
TECO does not really have syntax ; each character in a program is an imperative command, dispatched to its corresponding routine. That routine may read further characters from the program stream (giving the effect of string arguments), change the position of the "program counter" (giving the effect of control structures), or push values onto a value stack (giving the effect of nested parentheses). But there is nothing to prevent operations like jumping into the middle of a comment, since there is no syntax and no parsing.
TECO ignores case and whitespace (except tab , which is an insertion command). [ 11 ]
A satirical essay on computer programming, " Real Programmers Don't Use Pascal ", suggested that a common game for TECO fans was to enter their name as a command sequence, and then try to work out what would happen. The same essay in describing TECO coined the acronym YAFIYGI , meaning "You Asked For It You Got It" (in contrast to WYSIWYG ).
The EMACS editor originally started by David A. Moon and Guy L. Steele Jr. was implemented in TECO as a set of Editor MACroS. TECO became more widely used following a Digital Equipment Corporation (DEC) PDP-6 implementation developed at MIT's Project MAC in 1964. This implementation continuously displayed the edited text visually on a CRT screen , and was used as an interactive online editor. Later versions of TECO were capable of driving full-screen mode on various DEC RS-232 video terminals such as the VT52 or VT100 .
TECO was available for several operating systems and computers, including the PDP-1 computer, the PDP-8 (under OS/8), [ 12 ] [ 13 ] the Incompatible Timesharing System (ITS) on the PDP-6 and PDP-10 , and TOPS-10 and TOPS-20 on the PDP-10 . A version of TECO was provided with all DEC operating systems; the version available for RT11 was able to drive the GT40 graphics display while the version available for RSTS/E was implemented as a multi-user run-time system and could be used as the user's complete operating environment; the user never actually had to exit TECO. The VTEDIT (Video Terminal Editor) TECO macro was commonly used on RSTS/E and VAX systems with terminals capable of direct-cursor control (e.g. VT52 and VT100 ) to provide a full-screen visual editor similar in function to the contemporaneously developed Emacs .
TECO continues to be included in OpenVMS by VSI, and is invoked with the EDIT/TECO command. [ 14 ]
A descendant of the version DEC distributed for the PDP-10 is still available on the Internet, along with several partial implementations for the MS-DOS / Microsoft Windows environment.
TECO was originally developed at MIT [ 15 ] in around 1963 by Daniel L. Murphy for use on two PDP-1 computers, belonging to different departments, both housed in MIT's Building 26. [ 16 ] On these machines, the normal development process involved the use of a Friden Flexowriter to prepare source code offline on a continuous strip of punched paper tape. Programmers of the big IBM mainframes customarily punched their source code on cards , using key punches which printed human-readable dot-matrix characters along the top of every card at the same time as they punched each machine-readable character. Thus IBM programmers could read, insert, delete, and move lines of code by physically manipulating the cards in the deck. Punched paper tape offered no such amenities, leading to the development of online editing.
An early editor for the PDP-1 was named " Expensive Typewriter ". Written by Stephen D. Piner, it was the most rudimentary imaginable line-oriented editor, lacking even search-and-replace capabilities. Its name was chosen as a wry poke at an earlier, rather bloated, editor called " Colossal Typewriter ". Even in those days, online editing could save time in the debugging cycle. Another program written by the PDP-1 hackers was Expensive Desk Calculator , in a similar vein.
The original stated purpose of TECO was to make more efficient use of the PDP-1. As envisioned in the manual, rather than performing editing "expensively" by sitting at a console , one would simply examine the faulty text and prepare a "correction tape" describing the editing operations to be performed on the text. One would efficiently feed the source tape and the correction tape into the PDP-1 via its high-speed (200 characters per second) reader. Running TECO, it immediately would punch an edited tape with its high-speed (60 characters per second) punch. One could then immediately proceed to load and run the assembler, with no time wasted in online editing.
TECO's sophisticated searching operations were motivated by the fact that the offline Flexowriter printouts were not line-numbered. Editing locations therefore needed to be specified by context rather than by line number. The various looping and conditional constructs (which made TECO Turing-complete ) were included in order to provide sufficient descriptive power for the correction tape. The terse syntax minimized the number of keystrokes needed to prepare the correction tape.
The correction tape was a program, and required debugging just like any other program. The pitfalls of even the simplest global search-and-replace soon became evident. In practice, TECO editing was performed online just as it had been with Expensive Typewriter (although TECO was certainly a more feature-complete editor than Expensive Typewriter, so editing was much more efficient with TECO). The original PDP-1 version had no screen display. The only way to observe the state of the text during the editing process was to type in commands that would cause the text (or portions thereof) to be typed out on the console typewriter.
By 1964, a special Version of TECO ( TECO-6 ) had been implemented on the PDP-6 at MIT. That version supported visual editing, using a screen display that showed the contents of the editing buffer in real time, updating as it changed. [ 17 ] Amongst the creators of TECO-6 were Richard Greenblatt and Stewart Nelson . [ 18 ]
At MIT, TECO development continued in the fall of 1971. [ citation needed ] Carl Mikkelsen had implemented a real-time edit mode loosely based on the TECO-6 graphic console commands, but working with the newly installed Datapoint -3300 CRT text displays. [ 19 ] The TECO buffer implementation, however, was terribly inefficient for processing single character insert or delete functions—editing consumed 100% of the PDP-10. With Richard Greenblatt 's support, in summer of 1972 Carl reimplemented the TECO buffer storage and reformed the macros as native PDP-10 code. [ citation needed ] As entering the real-time mode was by typing cntl + R , this was known as control-R mode. At the same time, Rici Liknaitski added input-time macros ( cntl + ] ), which operated as the command string was read rather than when executed. [ citation needed ] Read-time macros made the TECO auxiliary text buffers, called Q-registers, more useful. [ citation needed ] Carl expanded the Q-register name space. With read-time macros, a large Q-register name space, and efficient buffer operations, the stage was set for binding each key to a macro. [ 20 ] These edit macros evolved into Emacs . [ 21 ]
The VMS implementation has a long history - it began as TECO-8, implemented in PDP-8 assembly. This code was translated into PDP-11 assembly to produce TECO-11. TECO-11 was used in early versions of VAX/VMS in PDP-11 compatibility mode. It was later translated from PDP-11 assembly into VAX assembly to produce TECO32. TECO32 was then converted with the VEST and AEST binary translation utilities to make it compatible with OpenVMS on the Alpha and Itanium respectively. [ 22 ] [ 23 ] [ 24 ]
The OS/8 CCL MUNG command invoked TECO to read and execute the specified .TE TECO macro. Optional command line parameters gave added adaptability. [ 25 ]
During and shortly following the years of the punched card era , there were source programs that had begun as punched card -based. Comments were often a series of lines that included single marginal asterisks and top/bottom full lines of asterisks. Once the cards were transferred online, it was difficult to realign the marginal stars. TECO aimed to solve this problem. [ 26 ] [ 27 ]
The obscurity of the TECO programming language is described in the following quote from " Real Programmers Don't Use Pascal ", a letter from Ed Post to Datamation, July 1983:
It has been observed that a TECO command sequence more closely resembles transmission line noise than readable text. One of the more entertaining games to play with TECO is to type your name in as a command line and try to guess what it does. Just about any possible typing error while talking with TECO will probably destroy your program, or even worse - introduce subtle and mysterious bugs in a once working subroutine. [ 28 ]
According to Craig Finseth, author of The Craft of Text Editing , [ 29 ] TECO has been described as a "write-only" language, implying that once a program is written in TECO, it is extremely difficult to comprehend what it did without appropriate documentation.
Despite its syntax, the TECO command language was tremendously powerful, and clones are still available for MS-DOS and for Unix .
TECO commands are characters (including control-characters), and the prompt is a single asterisk:
The escape key displays as a dollar sign, pressed once it delineates the end of a command requiring an argument and pressed twice initiates the execution of the entered commands:
Given a file named hello.c with the following contents:
one could use the following TECO session (noting that the prompt is "*" and "$" is how ESC is echoed) to change "Hello" into "Goodbye":
These two example programs are a simple interchange sort of the current text buffer, based on the 1st character of each line, taken from the PDP-11 TECO User's Guide. [ 12 ] A " goto " and " structured " version are shown. The second program originally had a bug that prevented the program terminating and the fixed version is used here instead.
This article is based in part on the Jargon File , which is in the public domain. | https://en.wikipedia.org/wiki/TECO_(text_editor) |
In petroleum engineering , TEM (true effective mobility), also called TEM-function is a criterion to characterize dynamic two-phase flow characteristics of rocks (or dynamic rock quality). [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] TEM is a function of relative permeability , porosity , absolute permeability and fluid viscosity , and can be determined for each fluid phase separately. TEM-function has been derived from Darcy's law for multiphase flow. [ 1 ]
in which k {\displaystyle k} is the absolute permeability, k r {\displaystyle k_{\mathit {r}}} is the relative permeability, φ is the porosity, and μ is the fluid viscosity.
Rocks with better fluid dynamics (i.e., experiencing a lower pressure drop in conducting a fluid phase) have higher TEM versus saturation curves. Rocks with lower TEM versus saturation curves resemble low quality systems. [ 1 ]
TEM-function in analyzing relative permeability data is analogous with Leverett J-function in analyzing capillary pressure data. Furthermore, TEM-function in two-phase flow systems is an extension of RQI (rock quality index) for single-phase systems. [ 1 ]
Also, TEM-function can be used for averaging relative permeability curves (for each fluid phase separately, i.e., water, oil, gas, CO 2 ). [ 1 ]
This fluid dynamics –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TEM-function |
(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl , commonly known as TEMPO , is a chemical compound with the formula (CH 2 ) 3 (CMe 2 ) 2 NO. This heterocyclic compound is a red-orange, sublimable solid. As a stable aminoxyl radical , it has applications in chemistry and biochemistry. [ 1 ] TEMPO is used as a radical marker, as a structural probe for biological systems in conjunction with electron spin resonance spectroscopy, as a reagent in organic synthesis , and as a mediator in controlled radical polymerization . [ 2 ]
TEMPO was discovered by Lebedev and Kazarnowskii in 1960. [ 3 ] It is prepared by oxidation of 2,2,6,6-tetramethylpiperidine .
The structure has been confirmed by X-ray crystallography . The reactive radical is well shielded by the four methyl groups.
The stability of this radical can be attributed to the delocalization of the radical to form a two-center three-electron N–O bond. The stability is reminiscent of the stability of nitric oxide and nitrogen dioxide . Additional stability is attributed to the steric protection provided by the four methyl groups adjacent to the aminoxyl group . These methyl groups serve as inert substituents, whereas any CH center adjacent to the aminoxyl would be subject to abstraction by the aminoxyl. [ 5 ]
Regardless of the reasons for the stability of the radical, the O–H bond in the hydrogenated derivative (the hydroxylamine 1-hydroxy-2,2,6,6-tetramethylpiperidine ) TEMPO–H is weak. With an O–H bond dissociation energy of about 70 kcal/mol (290 kJ/mol), this bond is about 30% weaker than a typical O–H bond. [ 6 ]
TEMPO is employed in organic synthesis as a catalyst for the oxidation of primary alcohols to aldehydes . The actual oxidant is the N -oxoammonium salt . In a catalytic cycle with sodium hypochlorite as the stoichiometric oxidant, hypochlorous acid generates the N -oxoammonium salt from TEMPO.
One typical reaction example is the oxidation of ( S )-(−)-2-methyl-1-butanol to ( S )-(+)-2-methylbutanal: [ 7 ] 4-Methoxyphenethyl alcohol is oxidized to the corresponding carboxylic acid in a system of catalytic TEMPO and sodium hypochlorite and a stoichiometric amount of sodium chlorite . [ 8 ] TEMPO oxidations also exhibit chemoselectivity , being inert towards secondary alcohols, but the reagent will convert aldehydes to carboxylic acids.
The oxidation of TEMPO can be highly selective. It has been proven that secondary alcohols are more likely to be oxidized by TEMPO under an acidic environment. The reason is when in this condition, secondary alcohols are more easily able to provide an H − ion. [ 9 ]
In cases where secondary oxidizing agents cause side reactions, it is possible to stoichiometrically convert TEMPO to the oxoammonium salt in a separate step. For example, in the oxidation of geraniol to geranial , 4-acetamido-TEMPO is first oxidized to the oxoammonium tetrafluoroborate. [ 10 ]
TEMPO can also be employed in nitroxide-mediated radical polymerization (NMP), a controlled free radical polymerization technique that allows better control over the final molecular weight distribution. The TEMPO free radical can be added to the end of a growing polymer chain, creating a "dormant" chain that stops polymerizing. However, the linkage between the polymer chain and TEMPO is weak, and can be broken upon heating, which then allows the polymerization to continue. Thus, the chemist can control the extent of polymerization and also synthesize narrowly distributed polymer chains.
TEMPO is sufficiently inexpensive for use on a laboratory scale. [ 11 ] There is also industrial-scale manufacturer which can provide TEMPO at a reasonable price in large quantity. [ 12 ] Structurally related analogues do exist, which are largely based on 4-hydroxy-TEMPO (TEMPOL). This is produced from acetone and ammonia, via triacetone amine , making it much less expensive. Other alternatives include polymer-supported TEMPO catalysts, which are economic due to their recyclability. [ 13 ]
Industrial-scale examples of TEMPO-like compounds include hindered amine light stabilizers and polymerisation inhibitors . | https://en.wikipedia.org/wiki/TEMPO |
TEOS-10 (Thermodynamic Equation of Seawater - 2010) is the international standard for the use and calculation of the thermodynamic properties of seawater, humid air and ice. It supersedes the former standard EOS-80 (Equation of State of Seawater 1980). [ 1 ] TEOS-10 is used by oceanographers and climate scientists to calculate and model properties of the oceans such as heat content in an internationally comparable way.
TEOS-10 was developed by the SCOR(Scientific Committee on Oceanic Research) / IAPSO(International Association for the Physical Sciences of the Oceans) Working Group 127 [ 2 ] which was chaired by Trevor McDougall . It has been approved as the official description of the thermodynamic properties of seawater, humid air and ice in 2009 by the Intergovernmental Oceanographic Commission (IOC) [ 3 ] and in 2011 by the International Union of Geodesy and Geophysics (IUGG) . [ 4 ]
TEOS-10 is based on thermodynamic potentials . Fluids like humid air and liquid water in TEOS-10 are therefore described by the Helmholtz energy F(m,T,V)=F(m,T,m/ρ) or the specific Helmholtz-energy f(T,ρ)=F(m,T,m/ρ)/m . The Helmholtz energy has a unique value across phase boundaries. [ 5 ] For the calculation of the thermodynamic properties of seawater and ice, TEOS-10 uses the specific Gibbs potential g(T,P)=G/m, G=F+pV, because the pressure is a more easily measurable property than density in a geophysical context. Gibbs energies are multivalued around phase boundaries and need to be defined for each phase separately. [ 6 ]
The thermodynamic potential functions are determined by a set of adjustable parameters which are tuned to fit experimental data and theoretical laws of physics like the ideal gas equation . Since absolute energy and entropy cannot be directly measured, arbitrary reference states for liquid water, seawater and dry air in TEOS-10 are defined in a way that
TEOS-10 covers all thermodynamic properties of liquid water, seawater, ice, water vapour and humid air within their particular ranges of validity as well as their mutual equilibrium composites such as sea ice or cloudy (wet and icy) air.
Additionally, TEOS-10 covers derived properties, for example the potential temperature and Conservative Temperature , the buoyancy frequency , the planetary vorticity and the Montgomery and Cunningham geostrophic streamfunctions . A complete list of featured properties can be found in the TEOS-10 Manual .
The handling of salinity was one of the novelties in TEOS-10. It defines the relationship between Reference Salinity and Practical Salinity, Chlorinity or Absolute Salinity and accounts for the different chemical compositions by adding a regionally variable 𝛿 S A (see Figure). [ 7 ] TEOS-10 is valid for Vienna Standard Mean Ocean Water which accounts for different hydrogen- and oxygen-isotope compositions in water which affects the triple point and therefore phase transitions of water.
TEOS-10 includes the Gibbs Seawater (GSW) Oceanographic Toolbox which is available as open source software in MATLAB , Fortran , Python , C , C++ , R , Julia and PHP . While TEOS-10 is generally expressed in basic SI-units, the GSW package uses input and output data in commonly used oceanographic units (such as g/kg for Absolute Salinity S A and dbar for pressure p ). [ 8 ]
In addition to the GSW Oceanographic Toolbox, the Seawater-Ice-Air (SIA) Library is available for Fortran and VBA (for the use in Excel ), and covers the thermodynamic properties of seawater, ice and (moist) air. In contrast to the GSW Toolbox, the SIA-Library exclusively uses basic SI-units . [ 9 ]
EOS-80 (Equation of State of Seawater -1980) uses Practical Salinity measured on the PSS-78 (Practical Salinity Scale of 1978) scale that itself is based on measurements of temperature, pressure and electrical conductivity. Thus, EOS-80 did not account for different chemical compositions of seawater. [ 2 ]
EOS-80 consisted of separate equations for density, sound speed, freezing temperature and heat capacity but did not provide expressions for entropy or chemical potentials. [ 10 ] Therefore, it was not a complete and consistent description of the thermodynamic properties of seawater. Inconsistencies in EOS-80 appear for example in the heat content at high pressure, depending on which equation is used for the calculation. Furthermore, EOS-80 was not consistent with meteorological equations while TEOS-10 is valid for humid air as well as for seawater.
EOS-80 provided expressions for potential temperature , which removes the effect of pressure on temperature but not for Conservative Temperature, [ 11 ] which is a direct measure for potential enthalpy and therefore heat content. [ 2 ]
In TEOS-10 the current standard for temperature scales, ITS-90 (International Temperature Scale of 1990) is used, while EOS-80 used the IPTS-68 (International Practical Temperature of 1968). [ 12 ] In the SIA-Library of TEOS-10 implementations to convert outdated into current scales are included. [ 11 ]
TEOS-10 was derived using absolute pressure P while EOS-80 used the pressure relative to the sea surface 𝑝 sea . They can be converted by: P /Pa = 101325 + 10000 ∙ 𝑝 sea /dbar (see Atmospheric Pressure ). | https://en.wikipedia.org/wiki/TEOS-10 |
Terrain contour matching , or TERCOM , is a navigation system used primarily by cruise missiles . It uses a contour map of the terrain that is compared with measurements made during flight by an on-board radar altimeter . A TERCOM system considerably increases the accuracy of a missile compared with inertial navigation systems (INS). The increased accuracy allows a TERCOM-equipped missile to fly closer to obstacles and at generally lower altitudes, making it harder to detect by ground radar. [ citation needed ]
The Goodyear Aircraft Corporation ATRAN ( Automatic Terrain Recognition And Navigation ) system for the MGM-13 Mace was the earliest known TERCOM system. In August 1952, Air Materiel Command initiated the mating of the Goodyear ATRAN with the MGM-1 Matador . This mating resulted in a production contract in June 1954. ATRAN was difficult to jam and was not range-limited by line-of sight, but its range was restricted by the availability of radar maps. In time, it became possible to construct radar maps from topographic maps . [ citation needed ]
Preparation of the maps required the route to be flown by an aircraft. A radar on the aircraft was set to a fixed angle and made horizontal scans of the land in front. The timing of the return signal indicated the range to the landform and produced an amplitude modulated (AM) signal. This was sent to a light source and recorded on 35 mm film , advancing the film and taking a picture at indicated times. The film could then be processed and copied for use in multiple missiles. [ citation needed ]
In the missile, a similar radar produced the same signal. A second system scanned the frames of film against a photocell and produced a similar AM signal. By comparing the points along the scan where the brightness changed rapidly, which could be picked out easily by simple electronics, the system could compare the left-right path of the missile compared with that of the pathfinding aircraft. Errors between the two signals drove corrections in the autopilot needed to bring the missile back onto its programmed flight path. [ citation needed ]
Modern TERCOM systems use a different concept, based on the altitude of the ground over which missile flies and measure by radar altimeter of the missile and comparing that to measurements of prerecorded terrain altitude maps stored in missile avionics memory. TERCOM "maps" consist of a series of squares of a selected size. Using a smaller number of larger squares saves memory, at the cost of decreasing accuracy. A series of such maps are produced, typically from data from radar mapping satellites.
As a radar altimeter measures the distance between the missile and the terrain, not the absolute altitude compared to sea level, the important measure in the data is the change in altitude from square to square. The missile's radar altimeter feeds measurements into a small buffer that periodically "gates" the measurements over a period of time and averages them out to produce a single measurement. The series of such numbers held in the buffer produce a strip of measurements similar to those held in the maps. The series of changes in the buffer is then compared with the values in the map, looking for areas where the changes in altitude are identical. This produces a location and direction. The guidance system can then use this information to correct the flight path of the missile. [ citation needed ]
During the cruise portion of the flight to the target, the accuracy of the system has to be enough only to avoid terrain features. This allows the maps to be a relatively low resolution in these areas. Only the portion of the map for the terminal approach has to be higher resolution, and would normally be encoded at the highest resolutions available to the satellite mapping system. [ citation needed ]
Due to the limited amount of memory available in mass storage devices of the 1960s and 70s, and their slow access times, the amount of terrain data that could be stored in a missile-sized package was far too small to encompass the entire flight. Instead, small patches of terrain information were stored and periodically used to update a conventional inertial platform . These systems, combining TERCOM and inertial navigation, are sometimes known as TAINS , for TERCOM-Aided Inertial Navigation System. [ citation needed ]
TERCOM systems have the advantage of offering accuracy that is not based on the length of the flight; an inertial system slowly drifts after a "fix", and its accuracy is lower for longer distances. TERCOM systems receive constant fixes during the flight, and thus do not have any drift. Their absolute accuracy, however, is based on the accuracy of the radar mapping information, which is typically in the range of meters, and the ability of the processor to compare the altimeter data to the map quickly enough as the resolution increases. This generally limits first generation TERCOM systems to targets on the order of hundreds of meters, limiting them to the use of nuclear warheads . Use of conventional warheads requires further accuracy, which in turn demands additional terminal guidance systems. [ citation needed ]
The limited data storage and computing systems of the time meant that the entire route had to be pre-planned, including its launch point. If the missile was launched from an unexpected location or flew too far off-course, it would never fly over the features included in the maps, and would become lost. The INS system can help, allowing it to fly to the general area of the first patch, but gross errors simply cannot be corrected. This made early TERCOM-based systems much less flexible than more modern systems like GPS , which can be set to attack any location from any location, and do not require pre-recorded information which means they can be given their targets immediately before launch. [ citation needed ]
Improvements in computing and memory, combined with the availability of global digital elevation maps , have reduced this problem, as TERCOM data is no longer limited to small patches, and the availability of side-looking radar allows much larger areas of landscape contour data to be acquired for comparison with the stored contour data. [ citation needed ]
DSMAC was an early form of AI which could guide missiles in real time by using camera inputs to determine location. DSMAC was used in Tomahawk Block II onward, and proved itself successfully during the first Gulf War. The system worked by comparing camera inputs during flight to maps computed from spy satellite images. The DSMAC AI system computed contrast maps of images, which it then combined in a buffer and then averaged. It then compared the averages to stored maps computed beforehand by a large mainframe computer , which converted spy satellite pictures to simulate what routes and targets would look like from low level. Since the data were not identical and would change by season and from other unexpected changes and visual effects, the DSMAC system within the missiles had to be able to compare and determine if maps were the same, regardless of changes. It could successfully filter out differences in maps and use the remaining map data to determine its location. Due to its ability to visually identify targets instead of simply attacking estimated coordinates, its accuracy exceeded GPS guided weapons during the first Gulf War. [ 1 ]
The massive improvements in memory and processing power from the 1950s, when these scene comparison systems were first invented, to the 1980s, when TERCOM was widely deployed, changed the nature of the problem considerably. Modern systems can store numerous images of a target as seen from different directions, and often the imagery can be calculated using image synthesis techniques. Likewise, the complexity of the live imaging systems has been greatly reduced through the introduction of solid-state technologies like CCDs . The combination of these technologies produced the digitized scene-mapping area correlator (DSMAC) . DSMAC systems are often combined with TERCOM as a terminal guidance system, allowing point attack with conventional warheads. [ citation needed ]
MGM-31 Pershing II , SS-12 Scaleboard Temp-SM and OTR-23 Oka used an active radar homing version of DSMAC (digitized correlator unit DCU), which compared radar topographic maps taken by satellites or aircraft with information received from the onboard active radar regarding target topography, for terminal guidance. [ citation needed ]
Yet another way to navigate a cruise missile is by using a satellite positioning system as they are precise and cheap. Unfortunately, they rely on satellites. If the satellites are interfered with (e.g. destroyed) or if the satellite signal is interfered with (e.g. jammed), the satellite navigation system becomes inoperable. Therefore, the GPS/GLONASS/BeiDou/Galileo-based navigation is useful in a conflict with a technologically unsophisticated adversary. On the other hand, to be ready for a conflict with a technologically advanced adversary, one needs missiles equipped with TAINS and DSMAC. [ citation needed ]
The cruise missiles that employ a TERCOM system include: | https://en.wikipedia.org/wiki/TERCOM |
TERRA in biology is an abbreviation for "TElomeric Repeat-containing RNA". [ 1 ] TERRA is RNA that is transcribed from telomeres — the repeating 6- nucleotide sequences that cap the ends of chromosomes . TERRA functions with shelterin to inhibit telomere lengthening by enzyme telomerase . [ 1 ] However, other studies have shown that under certain conditions TERRA can recruit telomerase to telomeres. [ 2 ]
TERRAs are essential for telomere length and maintenance. [ 3 ] [ 2 ] At least four factors contribute to telomere maintenance: telomerase, shelterin, TERRA and the CST Complex . [ 4 ]
TERRA can also regulate telomere length by increasing euchromatin formation. [ 5 ] On the other hand, nonsense-mediated decay factor enrichment at telomeres may exist to prevent TERRA inhibition of telomerase. [ 1 ] TERRA levels vary during the cell cycle , decreasing during S phase , and increasing in the transition from G2 phase to G1 phase . [ 5 ] | https://en.wikipedia.org/wiki/TERRA_(biology) |
TESCREAL is an acronym neologism proposed by computer scientist Timnit Gebru and philosopher Émile P. Torres that stands for Transhumanism , Extropianism , Singularitarianism , (modern) Cosmism , Rationalist ideology, Effective Altruism , and Longtermism . [ 1 ] [ 2 ] Gebru and Torres argue that these ideologies should be treated as an "interconnected and overlapping" group with shared origins. [ 1 ] They claim these constitute a movement that allows its proponents to use the threat of human extinction to justify expensive or detrimental projects and consider it pervasive in social and academic circles in Silicon Valley centered around artificial intelligence . [ 3 ] As such, the acronym is sometimes used to criticize a perceived belief system associated with Big Tech . [ 3 ] [ 4 ] [ 5 ]
Gebru and Torres proposed the term "TESCREAL" in 2023, first using it in a draft of a paper titled "The TESCREAL bundle: Eugenics and the promise of utopia through artificial general intelligence". [ 1 ] [ 4 ] First Monday published the paper in April 2024, though Torres and Gebru popularized the term elsewhere [ 3 ] before the paper's publication. According to Gebru and Torres, transhumanism, extropianism, singularitarianism, (modern) cosmism, rationalism, effective altruism, and longtermism are a "bundle" of "interconnected and overlapping ideologies" that emerged from 20th-century eugenics , with shared progenitors. [ 1 ] They use the term "TESCREAList" to refer to people who in their judgment subscribe to, or appear to endorse, any or all of the ideologies captured in the acronym. [ 1 ] [ 3 ]
According to critics of these philosophies, TESCREAL describes overlapping movements endorsed by prominent people in the tech industry to provide intellectual backing to pursue and prioritize projects including artificial general intelligence (AGI), life extension , and space colonization . [ 1 ] [ 4 ] [ 6 ] Science fiction author Charles Stross , using the example of space colonization, argued that the ideologies allow billionaires to pursue massive personal projects driven by a right-wing interpretation of science fiction by arguing that not to pursue such projects poses an existential risk to society. [ 7 ] Gebru and Torres write that, using the threat of extinction, TESCREALists can justify "attempts to build unscoped systems which are inherently unsafe". [ 1 ] Media scholar Ethan Zuckerman argues that by only considering goals that are valuable to the TESCREAL movement, futuristic projects with more immediate drawbacks, such as racial inequity, algorithmic bias , and environmental degradation, can be justified. [ 8 ]
Philosopher Yogi Hale Hendlin has argued that by both ignoring the human causes of societal problems and over-engineering solutions, TESCREALists ignore the context in which many problems arise. [ 9 ] Camille Sojit Pejcha wrote in Document Journal that TESCREAL is a tool for tech elites to concentrate power. [ 6 ] In The Washington Spectator , Dave Troy called TESCREAL an " ends justifies the means " movement that is antithetical to "democratic, inclusive, fair, patient, and just governance". [ 4 ] Gil Duran wrote that "TESCREAL", "authoritarian technocracy", and "techno-optimism" were phrases used in early 2024 to describe a new ideology emerging in the tech industry. [ 10 ]
Gebru, Torres, and others have likened TESCREAL to a secular religion due to its parallels to Christian theology and eschatology . [ 1 ] [ 3 ] [ 11 ] [ 7 ] [ 12 ] Writers in Current Affairs compared these philosophies and the ensuing techno-optimism to "any other monomaniacal faith... in which doubters are seen as enemies and beliefs are accepted without evidence". They argue pursuing TESCREAL would prevent an actual equitable shared future. [ 13 ]
Much of the discourse about existential risk from AGI occurs among those whom Gebru and Torres identify as supporters of the TESCREAL ideologies. [ 8 ] [ 14 ] [ 15 ] TESCREALists are either considered "AI accelerationists", who consider AI the only way to pursue a utopian future where problems are solved, or "AI doomers ", who consider AI likely to be unaligned to human survival and likely to cause human extinction. [ 8 ] [ 12 ] Despite the risk, many doomers consider the development of AGI inevitable and argue that only by developing and aligning AGI first can existential risk be averted. [ 16 ] [ 15 ]
Gebru has likened the conflict between accelerationists and doomers to a "secular religion selling AGI enabled utopia and apocalypse". [ 12 ] Torres and Gebru argue that both groups use hypothetical AI-driven apocalypses and utopian futures to justify unlimited research, development, and deregulation of technology. By considering only far-reaching future consequences, creating hype for unproven technology, and fear-mongering, Torres and Gebru allege TESCREALists distract from the impacts of technology that may adversely affect society, disproportionately harm minorities through algorithmic bias , and have a detrimental impact on the environment . [ 5 ] [ 11 ] [ 15 ]
Neşe Devenot has used the TESCREAL acronym to refer to "global financial and tech elites" who promote new uses of psychedelic drugs as mental health treatments, not because they want to help people, but so that they can make money on the sale of these pharmaceuticals as part of a plan to increase inequality. [ 17 ]
Gebru and Torres claim that TESCREAL ideologies directly originate from 20th-century eugenics [ 1 ] and that the bundle of ideologies advocates a new eugenics . [ 1 ] [ 18 ] Others have similarly argued that the TESCREAL ideologies developed from earlier philosophies that were used to justify mass murder and genocide. [ 6 ] [ 16 ] Some prominent figures who have contributed to TESCREAL ideologies have been alleged to be racist and sexist. [ 14 ] [ 19 ] [ 20 ]
Writing in Asterisk , a magazine related to effective altruism, Ozy Brennan criticized Gebru's and Torres's grouping of different philosophies as if they were a "monolithic" movement. Brennan argues Torres has misunderstood these different philosophies, and has taken philosophical thought experiments out of context. [ 21 ] Similarly, Oliver Habryka of LessWrong has criticized the concept, saying: "I've never in my life met a cosmist; apparently I'm great friends with them. Apparently, I'm like in cahoots [with them]." [ 22 ]
At Radio New Zealand , politics writer Danyl McLauchlan said that while some members of these groups want to engineer superhumans, others, like the effective altruists (who generally want to help the poor), are astounded to be lumped into a malevolent eugenics conspiracy. [ 23 ]
James Pethokoukis, of the American Enterprise Institute , disagrees with criticizing proponents of TESCREAL. He argues that the tech billionaires criticized in a Scientific American article for allegedly espousing TESCREAL have significantly advanced society. [ 24 ] In the blog for the technoprogressive Institute for Ethics and Emerging Technologies , Eli Sennesh and James Hughes have argued that TESCREAL is a left-wing conspiracy theory that groups disparate philosophies together without understanding their mutually exclusive tenets. [ 25 ]
In 2023, venture capitalist Marc Andreessen published the " Techno-Optimist Manifesto ", which Jag Bhalla and Nathan J. Robinson have called a "perfect example" of TESCREAL ideologies. [ 13 ] In it, he argues that more advanced artificial intelligence could save countless future potential lives, and that those working to slow or prevent its development should be condemned as murderers. [ 6 ] [ 8 ]
Elon Musk has been described as sympathetic to some TESCREAL ideologies. [ 5 ] [ 11 ] [ 19 ] [ 17 ] In August 2022, Musk tweeted that William MacAskill 's longtermist book What We Owe the Future was a "close match for my philosophy". [ 26 ] Some writers believe Musk's Neuralink pursues TESCREAList goals. [ 5 ] [ 27 ] Some AI experts have complained about the focus of Musk's XAI company on existential risk, arguing that it and other AI companies have ties to TESCREAL movements. [ 28 ] [ 29 ] Dave Troy believes Musk's natalist views originate from TESCREAL ideals. [ 4 ]
It has also been suggested that Peter Thiel is sympathetic to TESCREAL ideas. [ 5 ] [ 11 ] [ 30 ] Benjamin Svetkey wrote in The Hollywood Reporter that Thiel and other Silicon Valley CEOs who support the Donald Trump 2024 presidential campaign are pushing for policies that would shut down "regulators whose outdated restrictions on things like human experimentation are slowing down progress toward a technotopian paradise". [ 30 ]
Sam Altman and much of the OpenAI board has been described as supporting TESCREAL movements, especially in the context of his attempted firing in 2023. [ 11 ] [ 31 ] [ 12 ] Gebru and Torres have urged Altman not to pursue TESCREAL ideals. [ 32 ] Lorraine Redaud writing in Charlie Hebdo described Sam Altman and multiple other Silicon Valley executives as supporting TESCREAL ideals. [ 11 ]
Self-identified transhumanists Nick Bostrom and Eliezer Yudkowsky , both influential in discussions of existential risk from AI, [ 20 ] have also been described as leaders of the TESCREAL movement. [ 5 ] [ 14 ] [ 20 ]
Sam Bankman-Fried , former CEO of the FTX cryptocurrency exchange, was a prominent and self-identified member of the effective altruist community. [ 33 ] According to The Guardian , since FTX's collapse , administrators of the bankruptcy estate have been trying to recoup about $5 million that they allege was transferred to a nonprofit to help secure the purchase of a historic hotel that has been rented out for conferences and workshops associated with longtermism, Rationalism, and effective altruism. In attendance at one such conference were one person who self-identifies as a "liberal eugenicist" and speakers The Guardian said had racist and misogynistic connections. [ 19 ] : 1
Longtermist and effective altruist William MacAskill , who frequently collaborated with Bankman-Fried to coordinate philanthropic initiatives, has been described [ by whom? ] as a TESCREAList. [ 1 ] [ 4 ] [ 8 ] [ 17 ]
Torres and Gebru have said that Trump's 2024 presidential campaign and second presidency support TESCREAL ideals, especially due to his close collaboration with Musk. [ 30 ] [ 34 ] [ 35 ] | https://en.wikipedia.org/wiki/TESCREAL |
In the x86 assembly language , the TEST instruction performs a bitwise AND on two operands . The flags SF , ZF , PF are modified while the numerical result of the AND is discarded. The OF and CF flags are set to 0 , while AF flag is undefined. There are 9 different opcodes for the TEST instruction depending on the type and size of the operands . It can test 8-bit, 16-bit, 32-bit, or 64-bit values. It can also test registers and memory against registers and immediate values. [ 1 ]
The TEST operation clears the flags CF and OF to zero. The SF is set to the most significant bit of the result of the AND . If the result is 0 , the ZF is set to 1 , otherwise set to 0 . The parity flag is set to the bitwise XNOR of the least significant byte of the result, 1 if the number of ones in that byte is even, 0 otherwise. The value of AF is undefined.
This computer hardware article is a stub . You can help Wikipedia by expanding it .
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TEST_(x86_instruction) |
TET-assisted pyridine borane sequencing or TAPS is a laboratory technique in epigenetics for high-throughput profiling of DNA methylation at a single base-pair resolution. It uses a two-step enzymatic conversion of methylated cytosines , 5mC and 5hmC, to uracil which is read as a thymine after sequencing. [ 1 ] Due to direct conversion of methylated bases, TAPS is a mC-to-T chemistry unlike traditional method such as bisulfite sequencing or EM-Seq which are C-to-T chemistries and convert un-methylated cytosines. [ 2 ] TAPS was developed by Chunxiao Song and Benjamin Schuster-Böckler and their groups affiliated with Ludwig Cancer Research at the University of Oxford in 2019 and published in Nature Biotechnology . [ 3 ] TAPS is patented in US and its technology is licensed to Exact sciences and its exclusive partner Watchmaker Genomics. [ 4 ] [ 5 ]
While the enzymatic conversion mitigates DNA damage and degradation, similar to EM-Seq, direct conversion of methylated cytosines without affecting unmodified cytosines further improves the sensitivity and specificity of DNA methylation profiling. [ 2 ] [ 6 ]
Unlike bisulfite sequencing, which converts unmodified cytosine (C) to uracil (U) (read as thymine , T, after PCR ) while leaving 5mC and 5hmC largely unchanged (read as C), TAPS uses a different chemical approach. It employs Ten-eleven translocation (TET) enzymes to oxidize both 5mC and 5hmC to 5-carboxylcytosine (5caC). Subsequently, pyridine borane selectively reduces 5caC to dihydrouracil (DHU), which, like uracil, is read as thymine (T) during PCR amplification . Critically, unmodified cytosine (C) remains unaffected by this process and is read as C. Therefore, the TAPS readout is C → C, while 5mC → T and 5hmC → T. [ 7 ] [ 2 ]
The TAPS method involves two main chemical steps followed by PCR amplification and sequencing:
During subsequent PCR amplification, DNA polymerase reads DHU as if it were thymine (T). Unmodified cytosine bases, which were unaffected by the TAPS chemistry, are read as cytosine (C). Therefore, sites originally containing 5mC or 5hmC appear as T in the final sequencing reads, while original C bases appear as C. The resulting sequencing data can then be aligned to a reference genome, and the methylation status (presence of 5mC or 5hmC) at each cytosine position can be inferred by comparing the sequenced reads to the reference. A C-to-T conversion at a cytosine site indicates the original presence of either 5mC or 5hmC. [ 8 ] [ 2 ]
Standard TAPS detects both 5mC and 5hmC as T, and cannot distinguish between them. To specifically map 5hmC, a variation called TAPSβ (TAPS-beta) was developed. TAPSβ incorporates an initial enzymatic step before the TET oxidation which protects the 5hmC by binding a glucose moiety to the hydroxyl group of 5hmC through a β-Glucosyl transferase enzyme, forming 5-glucosylated hydroxymethylcytosine (5ghmC). [ 8 ] The standard TAPS procedure (TET oxidation followed by pyridine borane reduction) is then performed. The bulky glucose group on 5ghmC effectively blocks the TET enzyme from oxidizing it to 5caC. Therefore, 5hmC bases protected by glucosylation are not converted to DHU/T.
CAPS protocol, developed with TAPSβ, allows direct detection of the oxidized methylcytosine derivatives 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). [ 8 ] CAPS uses pyridine borane reduction directly on genomic DNA without the initial TET oxidation step. Pyridine borane reduces 5fC and 5caC to DHU (read as T), while unmodified C, 5mC, and 5hmC are unaffected (read as C). This allows for the specific mapping of 5fC and 5caC. [ 9 ] | https://en.wikipedia.org/wiki/TET-assisted_pyridine_borane_sequencing |
The TET enzymes are a family of ten-eleven translocation (TET) methylcytosine dioxygenases. They are instrumental in DNA demethylation . 5-Methylcytosine (see first Figure) is a methylated form of the DNA base cytosine (C) that often regulates gene transcription and has several other functions in the genome. [ 1 ]
Demethylation by TET enzymes (see second Figure), can alter the regulation of transcription. The TET enzymes catalyze the hydroxylation of DNA 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), and can further catalyse oxidation of 5hmC to 5-formylcytosine (5fC) and then to 5-carboxycytosine (5caC). [ 2 ] 5fC and 5caC can be removed from the DNA base sequence by base excision repair and replaced by cytosine in the base sequence.
TET enzymes have central roles in DNA demethylation required during embryogenesis, gametogenesis, memory, learning , addiction and pain perception . [ 3 ]
The three related TET genes, TET1 , TET2 and TET3 code respectively for three related mammalian proteins TET1, TET2, and TET3. All three proteins possess 5mC oxidase activity, but they differ in terms of domain architecture. [ 4 ] TET proteins are large (~180- to 230-kDa) multidomain enzymes. All TET proteins contain a conserved double-stranded β-helix (DSBH) domain, a cysteine-rich domain, and binding sites for the cofactors Fe(II) and 2-oxoglutarate (2-OG) that together form the core catalytic region in the C terminus . In addition to their catalytic domain , full-length TET1 and TET3 proteins have an N-terminal CXXC zinc finger domain that can bind DNA. [ 5 ] The TET2 protein lacks a CXXC domain, but the IDAX gene, that's a neighbor of the TET2 gene, encodes a CXXC4 protein. IDAX is thought to play a role in regulating TET2 activity by facilitating its recruitment to unmethylated CpGs.
The three TET genes are expressed as different isoforms , including at least two isoforms of TET1, three of TET2 and three of TET3. [ 2 ] [ 6 ] Different isoforms of the TET genes are expressed in different cells and tissues. The full-length canonical TET1 isoform appears virtually restricted to early embryos, embryonic stem cells and primordial germ cells (PGCs). The dominant TET1 isoform in most somatic tissues, at least in the mouse, arises from alternative promoter usage which gives rise to a short transcript and a truncated protein designated TET1s. The three isoforms of TET2 arise from different promoters. They are expressed and active in embryogenesis and differentiation of hematopoietic cells . The isoforms of TET3 are the full length form TET3FL, a short form splice variant TET3s, and a form that occurs in oocytes designated TET3o. TET3o is created by alternative promoter use and contains an additional first N-terminal exon coding for 11 amino acids. TET3o only occurs in oocytes and the one cell stage of the zygote and is not expressed in embryonic stem cells or in any other cell type or adult mouse tissue tested. Whereas TET1 expression can barely be detected in oocytes and zygotes, and TET2 is only moderately expressed, the TET3 variant TET3o shows extremely high levels of expression in oocytes and zygotes, but is nearly absent at the 2-cell stage. It appears that TET3o, high in oocytes and zygotes at the one cell stage, is the major TET enzyme utilized when almost 100% rapid demethylation occurs in the paternal genome just after fertilization and before DNA replication begins (see DNA demethylation ).
Many different proteins bind to particular TET enzymes and recruit the TETs to specific genomic locations. In some studies, further analysis is needed to determine whether the interaction per se mediates the recruitment or instead the interacting partner helps to establish a favourable chromatin environment for TET binding. TET1‑depleted and TET2‑depleted cells revealed distinct target preferences of these two enzymes, with TET1‑preferring promoters and TET2‑preferring gene bodies of highly expressed genes and enhancers. [ 7 ]
The three mammalian DNA methyltransferases (DNMTs) show a strong preference for adding a methyl group to the 5 carbon of a cytosine where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5' → 3' direction (at CpG sites ). [ 8 ] This forms a 5mCpG site. More than 98% of DNA methylation occurs at CpG sites in mammalian somatic cells . [ 9 ] Thus TET enzymes largely initiate demethylation at 5mCpG sites.
Oxoguanine glycosylase (OGG1) is one example of a protein that recruits a TET enzyme. TET1 is able to act on 5mCpG if an ROS has first acted on the guanine to form 8-hydroxy-2'-deoxyguanosine (8-OHdG or its tautomer 8-oxo-dG), resulting in a 5mCp-8-OHdG dinucleotide (see Figure). [ 10 ] After formation of 5mCp-8-OHdG, the base excision repair enzyme OGG1 binds to the 8-OHdG lesion without immediate excision (see Figure). Adherence of OGG1 to the 5mCp-8-OHdG site recruits TET1 , allowing TET1 to oxidize the 5mC adjacent to 8-OHdG. This initiates the demethylation pathway.
EGR1 is another example of a protein that recruits a TET enzyme. [ 11 ] EGR1 has an important role in learning and memory. [ 12 ] [ 13 ] When a new event such as fear conditioning causes a memory to be formed, EGR1 messenger RNA is rapidly and selectively up-regulated in subsets of neurons in specific brain regions associated with learning and memory formation. [ 14 ] TET1s is the predominant isoform of TET1 that is expressed in neurons. [ 15 ] When EGR1 proteins are expressed, they appear to bring TET1s to about 600 sites in the neuron genome. [ 11 ] Then EGR1 and TET1 appear to cooperate in demethylating and thereby activating the expression of genes downstream of the EGR1 binding sites in DNA. [ 11 ]
TET processivity can be viewed at three levels, the physical, chemical and genetic levels. Physical processivity refers to the ability of a TET protein to slide along the DNA from one CpG site to another. An in vitro study showed that DNA-bound TET does not preferentially oxidize other CpG sites on the same DNA molecule, indicating that TET is not physically processive. Chemical processivity refers to the ability of TET to catalyze the oxidation of 5mC iteratively to 5caC without releasing its substrate. It appears that TET can work through both chemically processive and non‑processive mechanisms depending on reaction conditions. Genetic processivity refers to the genetic outcome of TET‑mediated oxidation in the genome, as shown by mapping of the oxidized bases. In mouse embryonic stem cells, many genomic regions or CpG sites are modified so that 5mC is changed to 5hmC but not to 5fC or 5caC, whereas at many otherCpG sites 5mCs are modified to 5fC or 5caC but not 5hmC, suggesting that 5mC is processed to different states at different genomic regions or CpG sites. [ 7 ]
TET enzymes are dioxygenases in the family of alpha-ketoglutarate-dependent hydroxylases . A TET enzyme is an alpha-ketoglutarate (α-KG) dependent dioxygenase that catalyses an oxidation reaction by incorporating a single oxygen atom from molecular oxygen (O 2 ) into its substrate, 5-methylcytosine in DNA (5mC), to produce the product 5-hydroxymethylcytosine in DNA. This conversion is coupled with the oxidation of the co-substrate α-KG to succinate and carbon dioxide (see Figure).
The first step involves the binding of α-KG and 5-methylcytosine to the TET enzyme active site. The TET enzymes each harbor a core catalytic domain with a double-stranded β-helix fold that contains the crucial metal-binding residues found in the family of Fe(II)/α-KG- dependent oxygenases. [ 16 ] α-KG coordinates as a bidentate ligand (connected at two points) to Fe(II) (see Figure), while the 5mC is held by a noncovalent force in close proximity. The TET active site contains a highly conserved triad motif, in which the catalytically-essential Fe(II) is held by two histidine residues and one aspartic acid residue (see Figure). The triad binds to one face of the Fe center, leaving three labile sites available for binding α-KG and O 2 (see Figure). TET then acts to convert 5-methylcytosine to 5-hydroxymethylcytosine while α-ketoglutarate is converted to succinate and CO 2 .
The TET proteins also have activities that are independent of DNA demethylation. [ 17 ] These include, for instance, TET2 interaction with O -linked N -acetylglucosamine ( O-GlcNAc ) transferase to promote histone O-GlcN acylation to affect transcription of target genes. [ 18 ]
The mouse sperm genome is 80–90% methylated at its CpG sites in DNA, amounting to about 20 million methylated sites. [ 20 ] After fertilization , early in the first day of embryogenesis , the paternal chromosomes are almost completely demethylated in six hours by an active TET-dependent process, before DNA replication begins (blue line in Figure).
Demethylation of the maternal genome occurs by a different process. In the mature oocyte , about 40% of its CpG sites in DNA are methylated. In the pre- implantation embryo up to the blastocyst stage (see Figure), the only methyltransferase present is an isoform of DNMT1 designated DNMT1o. [ 21 ] It appears that demethylation of the maternal chromosomes largely takes place by blockage of the methylating enzyme DNMT1o from entering the nucleus except briefly at the 8 cell stage (see DNA demethylation ). The maternal-origin DNA thus undergoes passive demethylation by dilution of the methylated maternal DNA during replication (red line in Figure). The morula (at the 16 cell stage), has only a small amount of DNA methylation (black line in Figure).
The newly formed primordial germ cells (PGC) in the implanted embryo devolve from the somatic cells at about day 7 of embryogenesis in the mouse. At this point the PGCs have high levels of methylation. These cells migrate from the epiblast toward the gonadal ridge . As reviewed by Messerschmidt et al., [ 22 ] the majority of PGCs are arrested in the G 2 phase of the cell cycle while they migrate toward the hindgut during embryo days 7.5 to 8.5. Then demethylation of the PGCs takes place in two waves. [ 22 ] There is both passive and active, TET-dependent demethylation of the primordial germ cells. At day 9.5 the primordial germ cells begin to rapidly replicate going from about 200 PGCs at embryo day 9.5 to about 10,000 PGCs at day 12.5. [ 23 ] During days 9.5 to 12.5 DNMT3a and DNMT3b are repressed and DNMT1 is present in the nucleus at a high level. But DNMT1 is unable to methylate cytosines during days 9.5 to 12.5 because the UHRF1 gene (also known as NP95 ) is repressed and UHRF1 is an essential protein needed to recruit DNMT1 to replication foci where maintenance DNA methylation takes place. [ 23 ] This is a passive, dilution form of demethylation.
In addition, from embryo day 9.5 to 13.5 there is an active form of demethylation. As indicated in the Figure of the demethylation pathway above, two enzymes are central to active demethylation. These are a ten-eleven translocation (TET) methylcytosine dioxygenase and thymine-DNA glycosylase (TDG). One particular TET enzyme, TET1, and TDG are present at high levels from embryo day 9.5 to 13.5, [ 23 ] and are employed in active TET-dependent demethylation during gametogenesis. [ 22 ] PGC genomes display the lowest levels of DNA methylation of any cells in the entire life cycle of the mouse by embryonic day 13.5. [ 24 ]
Learning and memory have levels of permanence, differing from other mental processes such as thought, language, and consciousness, which are temporary in nature. Learning and memory can be either accumulated slowly (multiplication tables) or rapidly (touching a hot stove), but once attained, can be recalled into conscious use for a long time. Rats subjected to one instance of contextual fear conditioning create an especially strong long-term memory. At 24 hours after training, 9.17% of the genes in the genomes of rat hippocampus neurons were found to be differentially methylated . This included more than 2,000 differentially methylated genes at 24 hours after training, with over 500 genes being demethylated. [ 25 ] Similar results to that in the rat hippocampus were also obtained in mice with contextual fear conditioning. [ 26 ]
The hippocampus region of the brain is where contextual fear memories are first stored (see Figure), but this storage is transient and does not remain in the hippocampus. In rats contextual fear conditioning is abolished when the hippocampus is subjected to hippocampectomy just one day after conditioning, but rats retain a considerable amount of contextual fear when hippocampectomy is delayed by four weeks. [ 27 ] In mice, examined at 4 weeks after conditioning, the hippocampus methylations and demethylations were reversed (the hippocampus is needed to form memories but memories are not stored there) while substantial differential CpG methylation and demethylation occurred in cortical neurons during memory maintenance. There were 1,223 differentially methylated genes in the anterior cingulate cortex (see Figure) of mice four weeks after contextual fear conditioning. Thus, while there were many methylations in the hippocampus shortly after memory was formed, all these hippocampus methylations were demethylated as soon as four weeks later.
Li et al. [ 28 ] reported one example of the relationship between expression of a TET protein, demethylation and memory while using extinction training . Extinction training is the disappearance of a previously learned behavior when the behavior is not reinforced.
A comparison between infralimbic prefrontal cortex (ILPFC) neuron samples derived from mice trained to fear an auditory cue and extinction-trained mice revealed dramatic experience-dependent genome-wide differences in the accumulation of 5-hmC in the ILPFC in response to learning. Extinction training led to a significant increase in TET3 messenger RNA levels within cortical neurons. TET3 was selectively activated within the adult neo-cortex in an experience-dependent manner.
A short hairpin RNA (shRNA) is an artificial RNA molecule with a tight hairpin turn that can be used to silence target gene expression via RNA interference . Mice trained in the presence of TET3-targeted shRNA showed a significant impairment in fear extinction memory. [ 28 ]
The nucleus accumbens (NAc) has a significant role in addiction . In the nucleus accumbens of mice, repeated cocaine exposure resulted in reduced TET1 messenger RNA (mRNA) and reduced TET1 protein expression. Similarly, there was a ~40% decrease in TET1 mRNA in the NAc of human cocaine addicts examined postmortem. [ 29 ]
As indicated above in learning and memory, a short hairpin RNA (shRNA) is an artificial RNA molecule with a tight hairpin turn that can be used to silence target gene expression via RNA interference . Feng et al. [ 29 ] injected shRNA targeted to TET1 in the NAc of mice. This could reduce TET1 expression in the same manner as reduction of TET1 expression with cocaine exposure. They then used an indirect measure of addiction, conditioned place preference . Conditioned place preference can measure the amount of time an animal spends in an area that has been associated with cocaine exposure, and this can indicate an addiction to cocaine. Reduced Tet1 expression caused by shRNA injected into the NAc robustly enhanced cocaine place conditioning.
As described in the article Nociception , nociception is the sensory nervous system's response to harmful stimuli, such as a toxic chemical applied to a tissue. In nociception, chemical stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain . Nociception triggers a variety of physiological and behavioral responses and usually results in a subjective experience, or perception , of pain .
Work by Pan et al. [ 3 ] first showed that TET1 and TET3 proteins are normally present in the spinal cords of mice. They used a pain inducing model of intra plantar injection of 5% formalin into the dorsal surface of the mouse hindpaw and measured time of licking of the hindpaw as a measure of induced pain. Protein expression of TET1 and TET3 increased by 152% and 160%, respectively, by 2 hours after formalin injection. Forced reduction of expression of TET1 or TET3 by spinal injection of Tet1-siRNA or Tet3-siRNA for three consecutive days before formalin injection alleviated the mouse perception of pain. On the other hand, forced overexpression of TET1 or TET3 for 2 consecutive days significantly produced pain-like behavior as evidenced by a decrease in the mouse of the thermal pain threshold.
They further showed that the nociceptive pain effects occurred through TET mediated conversion of 5-methylcytosine to 5-hydroxymethylcytosine in the promoter of a microRNA designated miR-365-3p , thus increasing its expression. This microRNA, in turn, ordinarily targets (decreases expression of) the messenger RNA of Kcnh2 , that codes for a protein known as K v 11.1 or KCNH2. KCNH2 is the alpha subunit of a potassium ion channel in the central nervous system . Forced decrease in expression of TET1 or TET3 through pre-injection of siRNA reversed the decrease of KCNH2 protein in formalin-treated mice. | https://en.wikipedia.org/wiki/TET_enzymes |
TEX (chemical name 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0 5,9 .0 3,11 ]-dodecane ) is a dense (ρ = 1.985 g cm −3 ) nitramine high explosive , that derives from the very powerful and sensitive high explosive CL-20 . Though related to CL-20 in that is shares the same cage structure, TEX is more easily synthesized in good yield from inexpensive starting materials. [ 1 ] Unlike CL-20, TEX is friction insensitive, bears a low impact sensitivity, and possesses a very low shock sensitivity and large critical diameter, making it an interesting explosive filler for insensitive munitions . [ 2 ] Its systematic name, 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0 5,9 .0 3,11 ]-dodecane derives from its tetracyclic structure.
Unlike CL-20, which requires a cumbersome and even costly procedure, TEX is obtained in moderate yield (40 wt.-%) in a one-pot synthesis from 1,4-diformyl-2,3,5,6-tetrahydroxypiperazine (DFTHP) and mixed acid ( H 2 SO 4 / HNO 3 ). The DFTHP undergoes proton-catalyzed hydrolysis and yields glyoxal which reacts as with an intermediate to give TEX. [ 2 ]
Based on the Kamlet-Jacobs method, the formal idealistic detonation of TEX
at ambient temperature and density of TEX (1.985 g/cm 3 ) yields a detonation velocity of 8170 m/s and a CJ pressure of 31.4 GPa. Calculations with advanced computational algorithms like EXPLO and CHEETAH [ further explanation needed ] predict even higher detonation velocity but about similar values for the detonation pressure, definitely superseding insensitive high explosive NTO . Experimental determination with plastic bonded formulations at high theoretical maximum density exceed the predicted detonation pressures but fall a little short with regards to the detonation velocity if the charge diameter is below 90 mm. [ 2 ]
TEX is not friction sensitive and requires some 40 Joules energy to react in the BAM impact tester. In the autoignition test it yields a mild burn response at 252 °C onset temperature. TEX is also mildly shock sensitive in the Large Scale Gap Test (LSGT). [ 2 ]
TEX has a similar water solubility as RDX and hence will be equally mobile in soil and groundwater. However, in comparison to insensitive explosive NTO, which is highly soluble in water (16 g/L), it should pose a lower level of concern when considering the environmental effects of unexploded or partially exploded charges. Preliminary investigation of the effects of TEX on daphnia and cell cultures show slightly lower toxicity than RDX. [ 2 ]
Though known since 1990, [ 3 ] TEX is still an experimental explosive. However, given its large critical diameter and low shock sensitivity, it is an ideal candidate for insensitive large-calibre ammunition such as general-purpose bombs , artillery shells , torpedoes and depth charges . [ 2 ] | https://en.wikipedia.org/wiki/TEX_(explosive) |
TGCC (Très Grand Centre de Calcul) is a new " green infrastructure " for high computing performance, able to host petascale supercomputers at French Alternative Energies and Atomic Energy Commission .
This supercomputing center has been planned to welcome the first French Petascale machine Curie , [ 1 ] funded by GENCI for the PRACE Research Infrastructure, and the next generation of the CCRT Computing Center . [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/TGCC |
1KLA , 1KLC , 1KLD , 3KFD , 4KV5
7041
21804
ENSG00000140682
ENSMUSG00000030782
O43294
Q62219
NM_015927 NM_001042454 NM_001164719
NM_001289550 NM_001289551 NM_001289552 NM_001289553 NM_009365
NP_001035919 NP_001158191 NP_057011 NP_001158191.1 NP_057011.2
NP_001276479 NP_001276480 NP_001276481 NP_001276482
Transforming growth factor beta-1-induced transcript 1 protein is a protein that in humans is encoded by the TGFB1I1 gene . [ 5 ] [ 6 ] Often put together with and studied alongside TGFB1I1 is the mouse homologue HIC-5 ( Hydrogen Peroxide-Inducible Clone-5). As the name suggests, TGFB1I1 is an induced form of the larger family of TGFB1 . Studies suggest TGFB1I1 plays a role in processes of cell growth, proliferation, [ 7 ] migration, differentiation [ 8 ] and senescence. [ 9 ] TGFB1I1 is most localized at focal adhesion complexes of cells, [ 5 ] although it may be found active in the cytosol, nucleus and cell membrane as well. [ 7 ] [ 10 ] [ 11 ]
Transforming growth factor beta-1-induced transcript 1 plays a role in a number of cell functions. Originally, TGFB1I1 was isolated as a senescence-inducing gene from mouse osteoblastic cells through treatment with transforming growth factor beta-1 and hydrogen peroxide. [ 9 ] During this, TGFB1I1 was also being independently discovered by numerous other groups and was characterized as a focal adhesion protein, [ 12 ] [ 13 ] an androgen and glucocorticoid receptor co-activator, [ 10 ] [ 14 ] a negative regulator of muscle differentiation, [ 8 ] and major player in the recovery of arterial media. [ 15 ] [ 16 ]
TGFB1I1 has been shown to interact with:
This article incorporates text from the United States National Library of Medicine , which is in the public domain . | https://en.wikipedia.org/wiki/TGFB1I1 |
Theoretical Microscopic Anomalous Titration Curve Shapes ( THEMATICS ) is a computational method for predicting the biochemically active amino acids in a protein three-dimensional structure. [ 1 ] [ 2 ] [ 3 ]
The method was developed by Mary Jo Ondrechen , James Clifton, and Dagmar Ringe . [ 4 ] It is based on computed electrostatic and chemical properties of the individual amino acids in a protein structure. Specifically it identifies anomalous shapes in the theoretical titration curves of the ionizable amino acids. Biochemically active amino acids tend to have wide buffer ranges and non-sigmoidal titration patterns.
While the method predicts biochemically active amino acids successfully, it also provides input features to a machine learning predictor, Partial Order Optimum Likelihood (POOL). [ 5 ] [ 6 ]
This computational chemistry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/THEMATICS |
Transient High-Energy Sky and Early Universe Surveyor ( THESEUS ) is a space telescope mission proposal by the European Space Agency that would study gamma-ray bursts and X-rays for investigating the early universe . [ 1 ] [ 3 ] If developed, the mission would investigate star formation rates and metallicity evolution, as well as studying the sources and physics of reionization .
THESEUS is a mission concept that would monitor transient events in the high-energy Universe across the whole sky and over the entirety of cosmic history . In particular, it expects to make a complete census of gamma-ray bursts (GRBs) from the Universe's first billion years, to help understand the life cycle of the first stars. [ 4 ] THESEUS would provide real-time triggers and accurate locations of the sources, which could also be followed up by other space- or ground-based telescopes operating at complementary wavelengths.
The concept was selected in May 2018 as a finalist to become the fifth Medium-class mission (M5) of the Cosmic Vision programme by the European Space Agency (ESA). The other finalist was EnVision , a Venus orbiter. The winner, EnVision , was selected in June 2021 for launch in 2031. [ 5 ]
In November 2023, following a new selection process (2022) and a Phase-0 study (2023), THESEUS was selected by ESA for a new 2.5 year Phase-A study as one of the three candidates M7 missions (together with M-Matisse and Plasma Observatory).
The space observatory would study GRBs and X-rays and their association with the explosive death of massive stars, supernova shock break-outs, black hole tidal disruption events , and magnetar flares. This can provide fundamental information on the cosmic star formation rate, the number density and properties of low-mass galaxies, the neutral hydrogen fraction, and the escape fraction of ultraviolet photons from galaxies. [ 1 ]
The conceptual payload of THESEUS includes: [ 1 ] | https://en.wikipedia.org/wiki/THESEUS |
Borane–tetrahydrofuran is an adduct derived from borane and tetrahydrofuran (THF). These solutions, which are colorless, are used for reductions and hydroboration , reactions that are useful in synthesis of organic compounds . A common alternative to BH 3 •THF is borane–dimethylsulfide , which has a longer shelf life and effects similar transformations. [ 1 ]
The complex is commercially available but can also be generated by the dissolution of diborane in THF. Alternatively, it can be prepared by the oxidation of sodium borohydride with iodine in THF. [ 2 ]
The complex can reduce carboxylic acids to alcohols and is a common route for the reduction of amino acids to amino alcohols [ 3 ] (e.g. valinol ). It adds across alkenes to give organoboron compounds that are useful intermediates. [ 4 ] The following organoboron reagents are prepared from borane-THF: 9-borabicyclo[3.3.1]nonane , Alpine borane , diisopinocampheylborane . It is also used as a source of borane (BH 3 ) for the formation of adducts. [ 5 ]
The solution is highly sensitive to air, requiring the use of air-free techniques . [ 1 ] | https://en.wikipedia.org/wiki/THFBH3 |
TI-BASIC 83 , TI-BASIC Z80 or simply TI-BASIC , is the built-in programming language for the Texas Instruments programmable calculators in the TI-83 series . [ 1 ] Calculators that implement TI-BASIC have a built in editor for writing programs. While the considerably faster Z80 assembly language [ 2 ] : 120 is supported for the calculators, TI-BASIC's in-calculator editor and more user friendly syntax make it easier to use. TI-BASIC is interpreted. [ 2 ] : 155
The syntax for TI-BASIC 83 is significantly different compared to most dialects of BASIC . For example, the language does not permit indentation with whitespace characters . It also depends on the TI calculator character set because it is tokenized . [ 2 ] : 25 Aside from these differences, TI-BASIC retains most control flow statements: conditionals, various loops, GOTOs and Labels . Conditionals and loops use End to denote the end of their bodies.
Each command can be placed on a new line, or separated by a colon for brevity. As such, the following snippets are identical in function.
In the above example the closing double quotes can be omitted because the colon causes all open markers to be closed.
Unlike many high-level programming languages , TI-BASIC has only one assignment operator: → . The rightward arrow (Known as "STO" on most calculators) assigns the value on the left to the variable on the right.
TI-BASIC includes simple constructs using the If statement. When the If token does not have a Then token on the following line it will only execute the next single command.
Where condition is any boolean statement. One benefit of this format is brevity as it does not include Then and End . An If statement may have more than one command in its body if, instead of a command, a Then token is placed.
When using Then , the body must be closed by an End token. One more construct utilizes Else . This allows one of two bodies to be executed.
In this case the calculator evaluates condition , if it evaluates to true body one is executed, however, if condition evaluates to false, body two is executed. Unlike many other programming languages, TI-BASIC has no else if construct, or any switch statement .
It does, however, have a Menu( statement which allows a user to select one of a number of options. Similar to a switch menus do have fallthrough. The general syntax is Menu( , a quoted title string, and followed by quoted option name and label name. An example:
The image is how the calculator renders the example above.
In terms of functionality, the Menu( 's flow is similar to some switch statement and cases, with a key difference that the user supplies the switch's usual expression. Like many switches and cases, the Lbl allows fall-through. For example, in the code above, if a user selects "FIRST", all three bodies are executed. However, selecting "SECOND" means only the second and third bodies are executed.
TI-BASIC includes three types of loops: For( , While , and Repeat .
For( is similar to many other languages. It will repeat commands either a set number of times, or a variable number.
While takes a single argument, a condition which must be fulfilled, without parentheses. Repeat functions the same way except that it loops when the given condition is false. [ 3 ]
DS<( and IS>( are specialized conditionals that are similar in overall function to If statements. However, they have the unique property of changing the value of the given variable.
TI-BASIC is strongly and mostly statically typed. Most variables, besides lists and programs, have predefined names and allowed types. Each variable can usually only hold one data type, the exceptions are the numeric and all list variables which can hold either real or complex values.
There are 27 numeric variables, A through Z , and θ . [ 2 ] : 28 These can hold two types of values, real and complex. All numbers are stored in the RAM as floating-point numbers with 14-digit mantissa, or significand , and an exponent range of -128 to 127. Complex numbers are stored as two consecutive reals.
Lists are also supported through the use of six built-in lists, and user created lists with up to five characters as the name. They are capable of holding up to 999 elements. A list may hold entirely real numbers or entirely imaginary numbers. Some functions in the calculator are able to operate over entire lists, via Array programming .
Matrices are supported through the use of ten built-in matrices. Matrices do not support user created names or complex numbers.
There are ten built-in strings for storing variable text, named Str1 through Str0 .
The TI-83 family supports several more data types other than numeric, list, and matrix types: token based data, screen image data, and graph database data. These data types cannot be directly manipulated by TI-BASIC. | https://en.wikipedia.org/wiki/TI-BASIC_83 |
2MJN , 3BS9
7072
21841
ENSG00000116001
ENSMUSG00000071337
P31483
P52912
NM_022037 NM_022173
NM_001164078 NM_001164079 NM_011585
NP_001338440 NP_001338441 NP_001338443 NP_001338444 NP_001338445 NP_001338446 NP_001338447 NP_001338448 NP_001338449 NP_001338450 NP_001338451 NP_001338452 NP_001338453 NP_001338454 NP_001338442
NP_001157550 NP_001157551 NP_035715
TIA1 or Tia1 cytotoxic granule-associated rna binding protein is a 3'UTR mRNA binding protein that can bind the 5'TOP sequence of 5'TOP mRNAs. It is associated with programmed cell death ( apoptosis ) and regulates alternative splicing of the gene encoding the Fas receptor , an apoptosis-promoting protein. [ 4 ] Under stress conditions, TIA1 localizes to cellular RNA-protein conglomerations called stress granules . [ 5 ] It is encoded by the TIA1 gene . [ 6 ]
Mutations in the TIA1 gene have been associated with amyotrophic lateral sclerosis , frontotemporal dementia , and Welander distal myopathy . [ 7 ] [ 8 ] [ 9 ] It also plays a crucial role in the development of toxic oligomeric tau in Alzheimer's disease . [ 10 ]
This protein is a member of a RNA-binding protein family that regulates transcription and RNA translation . It was first identified in cytotoxic lymphocyte (CTL) target cells. TIA1 acts in the nucleus to regulate splicing and transcription. [ 11 ] TIA1 helps to recruit the splicesome to regulate RNA splicing, and it inhibits transcription of multiple genes, such as the cytokine Tumor necrosis factor alpha . [ 11 ] In response to stress, TIA1 translocates from the nucleus to the cytoplasm, where it nucleates a type of RNA granule, termed the stress granule , and participates in the translational stress response. [ 12 ] As part of the translational stress response, TIA1 works in cooperation with other RNA binding proteins to sequester RNA transcripts away from the ribosome, which allows the cell to focus its protein synthesis/RNA translation machinery on producing proteins that will address the particular stress. [ 13 ] It has been suggested that this protein may be involved in the induction of apoptosis as it preferentially recognizes poly(A) homopolymers and induces DNA fragmentation in CTL targets. [ 14 ] The major granule-associated species is a 15-kDa protein that is thought to be derived from the carboxyl terminus of the 40-kDa product by proteolytic processing. Alternative splicing resulting in different isoforms of this gene product have been described.
This article incorporates text from the United States National Library of Medicine , which is in the public domain .
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TIA1 |
The Integrated Archive of Short-Read and Array ( TIARA ) database contains personal genomic information obtained from next generation sequencing techniques and ultra-high-resolution comparative genomic hybridization . [ 1 ]
This Biological database -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TIARA_(database) |
TIFRAC ( Tata Institute of Fundamental Research Automatic Calculator ) was the first computer developed in India , at the Tata Institute of Fundamental Research in Mumbai . Initially a TIFR Pilot Machine was developed in the 1950s (operational in 1956). [ 1 ] Based on the IAS machine design, [ 2 ] the development of the final machine was started in 1955 [ 2 ] and was formally commissioned (and named TIFRAC, by Jawaharlal Nehru ) [ 2 ] in 1960. The full machine was in use until 1965. [ citation needed ]
TIFRAC included 2,700 vacuum tubes , 1,700 germanium diodes and 12,500 resistors . It had 2,048 40-bit words of ferrite core memory . This machine was an early adopter of ferrite core memory. [ citation needed ]
The main assembly of TIFRAC, which had vacuum tubes was housed in a massive steel rack measuring 18 feet x 2.5 feet x 8 feet. It was fabricated from modules of 4 feet x 2.5 feet x 8 feet. Each module had steel doors on either side for accessing the circuits. [ citation needed ]
A cathode ray tube display system was developed to serve as an auxiliary output to the computer for analogue and digital display of both graphs and alpha-numeric symbols.
A manual console served as the input/output control unit of the computer. The software of TIFRAC were written in a series of commands of 0s and 1s ( machine code ).
A British-built HEC 2M computer, happened to be the first digital computer in India, which was imported and installed in Indian Statistical Institute , Kolkata, during 1955. Prior to that, this institute had developed a small analog computer in 1953, which is technically the first computer in India. [ 3 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TIFRAC |
TILLING ( Targeting Induced Local Lesions in Genomes ) is a method in molecular biology that allows directed identification of mutations in a specific gene . TILLING was introduced in 2000, using the model plant Arabidopsis thaliana , and expanded on into other uses and methodologies by a small group of scientists including Luca Comai . TILLING has since been used as a reverse genetics method in other organisms such as zebrafish , maize , wheat , rice , soybean , tomato and lettuce .
The method combines a standard and efficient technique of mutagenesis using a chemical mutagen such as ethyl methanesulfonate (EMS) with a sensitive DNA screening-technique that identifies single base mutations (also called point mutations) in a target gene. The TILLING method relies on the formation of DNA heteroduplexes that are formed when multiple alleles are amplified by PCR and are then heated and slowly cooled. A “ bubble ” forms at the mismatch of the two DNA strands, which is then cleaved by a single stranded nuclease . The products are then separated by size on several different platforms (see below).
Mismatches may be due to induced mutation, heterozygosity within an individual, or natural variation between individuals.
EcoTILLING [ 1 ] [ 2 ] [ 3 ] [ 4 ] is a method that uses TILLING techniques to look for natural mutations in individuals, usually for population genetics analysis. DEcoTILLING [ 5 ] is a modification of TILLING and EcoTILLING which uses an inexpensive method to identify fragments. Since the advent of NGS sequencing technologies, TILLING-by-sequencing [ 6 ] has been developed based on Illumina sequencing of target genes amplified from multidimensionally pooled templates to identify possible single-nucleotide changes.
There are several sources for single strand nucleases. The first widely used enzyme was mung bean nuclease , but this nuclease has been shown to have high non-specific activity, and only works at low pH, which can degrade PCR products and dye-labeled primers. The original source for single strand nuclease was from CEL1, or CJE (celery juice extract), but other products have entered the market including Frontier Genomics’ SNiPerase enzymes, which have been optimized for use on platforms that use labeled and unlabeled PCR products (see next section). Transgenomic isolated the single strand nuclease protein and sells it as a recombinant form. The advantage of the recombinant form is that unlike the enzyme mixtures, it does not contain non-specific nuclease activity, which can degrade the dyes on the PCR primers. The disadvantage is a substantially higher cost.
The first paper describing TILLING used HPLC to identify mutations (McCallum et al., 2000a). The method was made more high throughput by using the restriction enzyme Cel-I combined with the LICOR gel based system to identify mutations (Colbert et al., 2001). Advantages to using this system are that mutation sites can be easily confirmed and differentiated from noise. This is because different colored dyes can be used for the forward and reverse primers. Once the cleavage products have been run on a gel, it can be viewed in separate channels, and much like an RFLP, the fragment sizes within a lane in each channel should add up to the full length product size. Advantages to the LICOR system are separation of large fragments (~ 2kb), high sample throughput (96 samples loaded on paper combs), and freeware to identify the mutations (GelBuddy). Drawbacks to the LICOR system is having to pour slab gels and long run times (~4 hours). TILLING and EcoTILLING methods are now being used on capillary systems from, Advanced Analytical Technologies, ABI and Beckman.
Several systems can be used to separate PCR products that are not labeled with dyes. Simple agarose electrophoresis systems will separate cleavage products inexpensively and with standard lab equipment. This was used to discover SNPs in chum salmon and was referred to as DEcoTILLING. The disadvantage of this system is reduced resolution compared to polyacrylamide systems. Elchrom Scientific sells Spreadex gels which are precast, can be high throughput and are more sensitive than standard polyacrylamide gels. Advanced Analytical Technologies Inc sells the AdvanCE FS96 dsDNA Fluorescent System which is a 96 capillary electrophoresis system that has several advantages over traditional methods; including ability to separate large fragments (up to 40kb), no desalting or precipitation step required, short run times (~30 minutes), sensitivity to 5pg/ul and no need for fluorescent labeled primers.
Several TILLING centers exist over the world that focus on agriculturally important species: | https://en.wikipedia.org/wiki/TILLING_(molecular_biology) |
2Y92 , 3UB2 , 3UB3 , 3UB4 , 4FZ5 , 4LQD
114609
117149
ENSG00000150455
ENSMUSG00000032041
P58753
Q99JY1
NM_001039661 NM_052887 NM_148910 NM_001318776 NM_001318777
NM_001177845 NM_001177846 NM_001177847 NM_054096
NP_001034750 NP_001305705 NP_001305706 NP_683708
NP_001171316 NP_001171317 NP_001171318 NP_473437
TIRAP ( TIR domain containing adaptor protein ) is an adapter molecule associated with toll-like receptors . The innate immune system recognizes microbial pathogens through Toll-like receptors (TLRs), which identify pathogen-associated molecular patterns. Different TLRs recognize different pathogen-associated molecular patterns and all TLRs have a Toll-interleukin 1 receptor (TIR) domain, which is responsible for signal transduction. The protein encoded by this gene is a TIR adaptor protein involved in the TLR4 signaling pathway of the immune system. It activates NF-kappa-B , MAPK1 , MAPK3 and JNK , which then results in cytokine secretion and the inflammatory response. Alternative splicing of this gene results in several transcript variants; however, not all variants have been fully described.
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TIRAP |
TJ-2 ( Type Justifying Program ) was published by Peter Samson in May 1963 and is thought to be the first page layout program. Although it lacks page numbering , page headers and footers , TJ-2 is the first word processor to provide a number of essential typographic alignment and automatic typesetting features:
Developed from two earlier Samson programs, Justify [ 1 ] and TJ-1, [ 2 ] TJ-2 was written for the PDP-1 that was donated to the Massachusetts Institute of Technology in 1961 by Digital Equipment Corporation .
Taking English text as input, TJ-2 aligns left and right margins, justifying the output using white space and word hyphenation. Text is marked-up with single lowercase characters combined with the PDP-1's overline character, carriage returns, and internal concise codes. The computer's six toggle switches control the input and output devices, enable and disable hyphenation and stop the session. Words can be hyphenated with a light pen on the computer's CRT display and from the session's dictionary in memory. On-screen hyphenation has SAVE and FORGET commands and OOPS , the undo .
Comments in the code were quoted thirty years later: "The ways of God are just and can be justified to man" [ 3 ] and "Girls who wear pants should be sure that the end justifies the jeans." [ 4 ]
TJ-2 was succeeded by TYPSET and RUNOFF , a pair of complementary programs written in 1964 for the CTSS operating system. [ 5 ] TYPSET and RUNOFF soon evolved into runoff for Multics , which was in turn ported to Unix in the 1970s as roff . [ 6 ]
A similar program for the ITS PDP-6 and later the PDP-10 was TJ6 . [ 7 ] | https://en.wikipedia.org/wiki/TJ-2 |
The TK83 was a home computer produced by the Brazilian company Microdigital Eletrônica Ltda. and introduced in August 1982. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] By December 1984, it was no longer being advertised by Microdigital, being discontinued in 1985. [ 6 ] [ 7 ]
The TK83 was a clone of the Sinclair ZX81 , [ 8 ] [ 5 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] and can for all practical purposes, be considered a version of the TK82C with repagged memory and including the SLOW function which permitted the video be shown during processing. [ 3 ]
The TK83 had the Zilog Z80A processor running at 3.25 MHz, 2 KB RAM (expandable to 64 KB) and 8 KB of ROM that included the BASIC interpreter. [ 3 ] [ 11 ] [ 9 ]
The keyboard was made of layers of conductive (membrane) material and followed the Sinclair layout with 40 keys.
Video output was sent via a RF modulator to a TV set tuned at VHF channel 3, and featured black characters on a white background. The maximum resolution was 64 x 44 pixels , based on semigraphic characters useful for games and basic images (see ZX81 character set ).
There was one expansion slot at the side of the machine, a cassette interface (data storage in tapes at 300 to 4200 baud , [ 5 ] with audio cables were supplied with the computer for connection with a regular tape recorder) [ 3 ] and a DIN joystick connector. [ 1 ]
This computing article is a stub . You can help Wikipedia by expanding it .
This computer hardware article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/TK83 |
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