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4ab781ed0104e2680e43397adb56944bd1e9dd57 | in december 2023 the malaysian government rescinded its | in december 2023 the malaysian government rescinded its permit for zim to use their ports, responding to "israel's actions that ignore basic humanitarian principles and violate international law" in the 2023 israel-hamas war. | wikipedia |
784a79c99bb740b327305dfac95acb682dccd9ee | in july 2014, by which time the company | in july 2014, by which time the company was almost wholly owned by israel corporation, zim was restructured with 68% of the group's shares owned by its creditors and bondholders, and 32% retained by israel corporation, and starting early 2015 by kenon holdings, a spin-off company of israel corporation. in mid-to-late 2... | wikipedia |
1b3a470b7812732822f091faf22b8056a7b389a7 | in 2014, unloading of a zim ship at | in 2014, unloading of a zim ship at the port of oakland was delayed by anti-israel protesters. longshoremen declined to load the ship out of safety concerns, taking no position on the underlying dispute, but unloaded the ship after their safety was assured. other protests in los angeles and tacoma, washington failed to... | wikipedia |
c5605120382989d2db7a967ca1dcd4a1bc36d703 | in 2010, zim regained profitability and in early | in 2010, zim regained profitability and in early 2011 zim renewed its plans for a flotation on the hong kong stock exchange, but again had to postpone it due to the economic downturn and the drop in container shipping rates. | wikipedia |
f682d7cd5c19d592263af08ce3be2761989779d5 | in 2008, zim planned to launch an initial | in 2008, zim planned to launch an initial public offering and selling 25% of its shares on the hong kong stock exchange, but due to the onset of the global economic crisis it was called off. in 2009, zim required a cash injection of $450 million by the ofer family and debt restructuring following the world's container ... | wikipedia |
dd1625ac65f4e96e13d1790c539452d88cb38dea | in 2004, the israel corporation (which is controlled | in 2004, the israel corporation (which is controlled by the ofer brothers group) purchased 49% of zim's shares held by the israeli government, becoming the sole owner of the company. the new official name after privatization became zim integrated shipping services. the purchase deal for about five hundred million new i... | wikipedia |
565a14c9ea0b44715cf1a81b28caf01ad8715e3c | during the 1960s, zim started to turn its | during the 1960s, zim started to turn its focus to cargo ships, and obtained several special-purpose vessels, including refrigerated ships and oil tankers. zim transported crude oil from iran to israel and oil byproducts from israel to europe. | wikipedia |
ec20e0468012da268aaf845051a25dafc2378466 | due to rising airline competition and the market | due to rising airline competition and the market failure of the expensive new shalom, passenger services were gradually phased out between 1966-1969, as zim refocused on cargo shipping. jerusalem was chartered out to british-based p&o cruises in 1966 to become their miami, then sold entirely in 1968. the sisters israel... | wikipedia |
47e3e61f527ca1872d98d1929fad2015338fe370 | in 1950s and 1960s, zim concentrated on passenger | in 1950s and 1960s, zim concentrated on passenger ships, alongside a constant expansion of the cargo shipping business. passenger liners were a common means of international transport before the emergence of cheap air transport, and pleasure cruises were also popular. zim sailed the mediterranean sea, as well as having... | wikipedia |
19fd0c83c166164cbd21b1ae4891349b0b46af99 | zim was invited in 1957 by the government | zim was invited in 1957 by the government of ghana to assist the setting up and management of a national shipping line. black star line was formed with a 40% participation by zim and principally operated cargo services from west africa. a similar joint venture - burma five star line - was made with the burmese governme... | wikipedia |
ddae42533b4fe8c9f88d4e98427ee7f22d257dd8 | 1957 saw the delivery of two more new | 1957 saw the delivery of two more new ocean liners, the 10,000 ton sister ships ss jerusalem and ss theodor herzl, followed by the more modest, 7,800 ton ss moledet in 1961, which featured an all-tourist class layout, targeted principally to american tourists looking for affordable transportation to the holy land. | wikipedia |
6fa4f8aa09b51114f10257be2b7b293e87f55a6b | in 1953, some of the money from the | in 1953, some of the money from the reparations agreement between israel and west germany was allocated to the purchase and construction of new ships. the ss bergensfjord, renamed jerusalem, sailed the israel-new york route, another ship purchased with reparations money was the ss theodor herzl. | wikipedia |
053426f50b3f0ac1a65a0e96313b6cb0a22b5444 | zim was founded on june 7, 1945, as | zim was founded on june 7, 1945, as the zim palestine navigation company ltd, by the jewish agency, the israel maritime league and the histadrut (general federation of laborers in the land of israel). the first ship was purchased in partnership with harris and dixon (based in london) in 1947. this vessel was refurbishe... | wikipedia |
92a94f3bb718eaec6a3363b422b9fbdfbdbfa887 | zim integrated shipping services ltd., commonly known as | zim integrated shipping services ltd., commonly known as zim (hebrew: צים, tsim; a biblical word meaning "a fleet of ships", numbers 24:24), is a publicly held israeli international cargo shipping company, and one of the top 20 global carriers. the company's headquarters are in haifa, israel; founded in 1945, zim has t... | wikipedia |
73ef2db993ec28a5b78742688c9e708e6894a168 | in mathematics, and more specifically in linear algebra, | in mathematics, and more specifically in linear algebra, a linear map is a mapping v → w between two vector spaces that preserves the operations of vector addition and scalar multiplication. the same names and the same definition are also used for the more general case of modules over a ring; see module homomorphism. i... | wikipedia |
58155f6356fc225075e87ca3da0010f09c91f1d2 | a specific application of linear maps is for | a specific application of linear maps is for geometric transformations, such as those performed in computer graphics, where the translation, rotation and scaling of 2d or 3d objects is performed by the use of a transformation matrix. linear mappings also are used as a mechanism for describing change: for example in cal... | wikipedia |
62ee40cad9e60060591f6f28c2978bd5d9e3a464 | an example of an unbounded, hence discontinuous, linear | an example of an unbounded, hence discontinuous, linear transformation is differentiation on the space of smooth functions equipped with the supremum norm (a function with small values can have a derivative with large values, while the derivative of 0 is 0). for a specific example, sin(nx)/ n converges to 0, but its de... | wikipedia |
818e700efee817ad0c898fe3484cf1d0d131f55f | a linear transformation between topological vector spaces, for | a linear transformation between topological vector spaces, for example normed spaces, may be continuous. if its domain and codomain are the same, it will then be a continuous linear operator. a linear operator on a normed linear space is continuous if and only if it is bounded, for example, when the domain is finite-di... | wikipedia |
a631667ddbd3dce275db59f870eca944807cd9b8 | substituting this in the first expression b = | substituting this in the first expression b = a b {\displaystyle b\left=ab\left} hence = b − 1 a b = a ′. {\displaystyle \left=b^{-1}ab\left=a'\left.} | wikipedia |
1a0c8f289bd05813fe53c747c07f93302eb2932b | given a linear map which is an endomorphism | given a linear map which is an endomorphism whose matrix is a, in the basis b of the space it transforms vector coordinates as = a. as vectors change with the inverse of b (vectors coordinates are contravariant) its inverse transformation is = b. | wikipedia |
317fb61253e2b60cb2ab6e70d606b1f1f13bceee | t is said to be an isomorphism if | t is said to be an isomorphism if it is both left- and right-invertible. this is equivalent to t being both one-to-one and onto (a bijection of sets) or also to t being both epic and monic, and so being a bimorphism. | wikipedia |
df188c82de8725abb440808756732bf71e950f44 | the index of an operator is precisely the | the index of an operator is precisely the euler characteristic of the 2-term complex 0 → v → w → 0. in operator theory, the index of fredholm operators is an object of study, with a major result being the atiyah–singer index theorem. | wikipedia |
575206c75d9db3cd00ce4b3c51c65275ab6718ce | for a transformation between finite-dimensional vector spaces, this | for a transformation between finite-dimensional vector spaces, this is just the difference dim(v) − dim(w), by rank–nullity. this gives an indication of how many solutions or how many constraints one has: if mapping from a larger space to a smaller one, the map may be onto, and thus will have degrees of freedom even wi... | wikipedia |
1efc09116226db00013a4431b9fc600199cc5e4e | for a linear operator with finite-dimensional kernel and | for a linear operator with finite-dimensional kernel and co-kernel, one may define index as: ind (f):= dim (ker (f)) − dim (coker (f)), {\displaystyle \operatorname {ind} (f):=\dim(\ker(f))-\dim(\operatorname {coker} (f)),} namely the degrees of freedom minus the number of constraints. | wikipedia |
fe1dd78ae1b2cb4ca23caf576c299ff2a94780a8 | an example illustrating the infinite-dimensional case is afforded | an example illustrating the infinite-dimensional case is afforded by the map f: r → r, { a n } ↦ { b n } {\textstyle \left\{a_{n}\right\}\mapsto \left\{b_{n}\right\}} with b = 0 and b = a for n > 0. its image consists of all sequences with first element 0, and thus its cokernel consists of the classes of sequences with... | wikipedia |
ca1e2835dbb976aaae9203140a3ed86249a9c865 | as a simple example, consider the map f: | as a simple example, consider the map f: r → r, given by f (x, y) = (0, y). then for an equation f (x, y) = (a, b) to have a solution, we must have a = 0 (one constraint), and in that case the solution space is (x, b) or equivalently stated, (0, b) + (x, 0), (one degree of freedom). the kernel may be expressed as the s... | wikipedia |
86b0b5a24f42f3b96bdb56e63768c9ef1d7ca068 | the dimension of the co-kernel and the dimension | the dimension of the co-kernel and the dimension of the image (the rank) add up to the dimension of the target space. for finite dimensions, this means that the dimension of the quotient space w / f (v) is the dimension of the target space minus the dimension of the image. | wikipedia |
51d064eb0740c7dec352b31c756c39b30f3573e9 | this is the dual notion to the kernel: | this is the dual notion to the kernel: just as the kernel is a sub space of the domain, the co-kernel is a quotient space of the target. formally, one has the exact sequence 0 → ker (f) → v → w → coker (f) → 0. {\displaystyle 0\to \ker(f)\to v\to w\to \operatorname {coker} (f)\to 0.} | wikipedia |
8dfd91457c9e7a43bea8c5be5837585154b59c08 | a subtler invariant of a linear transformation f: | a subtler invariant of a linear transformation f: v → w {\textstyle f:v\to w} is the co kernel, which is defined as coker (f):= w / f (v) = w / im (f). {\displaystyle \operatorname {coker} (f):=w/f(v)=w/\operatorname {im} (f).} | wikipedia |
c873939a98b2c2fa525898c818324d392e64b6f2 | the number dim (im (f)) {\textstyle \dim(\operatorname {im} | the number dim (im (f)) {\textstyle \dim(\operatorname {im} (f))} is also called the rank of f {\textstyle f} and written as rank (f) {\textstyle \operatorname {rank} (f)}, or sometimes, ρ (f) {\textstyle \rho (f)}; the number dim (ker (f)) {\textstyle \dim(\ker(f))} is called the nullity of f {\textstyle f} and writte... | wikipedia |
46d6b0ea7d7336c971ad1b7eea8b50bca2376096 | ker (f) {\textstyle \ker(f)} is a subspace of | ker (f) {\textstyle \ker(f)} is a subspace of v {\textstyle v} and im (f) {\textstyle \operatorname {im} (f)} is a subspace of w {\textstyle w}. the following dimension formula is known as the rank–nullity theorem: dim (ker (f)) + dim (im (f)) = dim (v). {\displaystyle \dim(\ker(f))+\dim(\operatorname {im} (f))=\dim(v)... | wikipedia |
ec22d6c890111bf007f0ddd58df74d45f6fbaa1d | if f: v → w {\textstyle f:v\to w} | if f: v → w {\textstyle f:v\to w} is linear, we define the kernel and the image or range of f {\textstyle f} by ker (f) = { x ∈ v: f (x) = 0 } im (f) = { w ∈ w: w = f (x), x ∈ v } {\displaystyle {\begin{aligned}\ker(f)&=\{\,\mathbf {x} \in v:f(\mathbf {x})=\mathbf {0} \,\}\\\operatorname {im} (f)&=\{\,\mathbf {w} \in w... | wikipedia |
10615704fb63eb838d47419c0a59ba6422c8a40a | if v {\textstyle v} has finite dimension n | if v {\textstyle v} has finite dimension n {\textstyle n}, then end (v) {\textstyle \operatorname {end} (v)} is isomorphic to the associative algebra of all n × n {\textstyle n\times n} matrices with entries in k {\textstyle k}. the automorphism group of v {\textstyle v} is isomorphic to the general linear group gl (n,... | wikipedia |
71c1faffa3b0567a3684b7c6c06ff23cb53ce83f | an endomorphism of v {\textstyle v} that is | an endomorphism of v {\textstyle v} that is also an isomorphism is called an automorphism of v {\textstyle v}. the composition of two automorphisms is again an automorphism, and the set of all automorphisms of v {\textstyle v} forms a group, the automorphism group of v {\textstyle v} which is denoted by aut (v) {\texts... | wikipedia |
a25f71b059f6343e85a053eb51e61c27fe1dfbe9 | a linear transformation f: v → v {\textstyle | a linear transformation f: v → v {\textstyle f:v\to v} is an endomorphism of v {\textstyle v}; the set of all such endomorphisms end (v) {\textstyle \operatorname {end} (v)} together with addition, composition and scalar multiplication as defined above forms an associative algebra with identity element over the field k... | wikipedia |
771fb8d2efd9cf8da1c432bcb9ac51f5e5a9ef2b | given again the finite-dimensional case, if bases have | given again the finite-dimensional case, if bases have been chosen, then the composition of linear maps corresponds to the matrix multiplication, the addition of linear maps corresponds to the matrix addition, and the multiplication of linear maps with scalars corresponds to the multiplication of matrices with scalars. | wikipedia |
fceed689a3b1200397f81690d5edaa12e89ea559 | thus the set l (v, w) {\textstyle {\mathcal | thus the set l (v, w) {\textstyle {\mathcal {l}}(v,w)} of linear maps from v {\textstyle v} to w {\textstyle w} itself forms a vector space over k {\textstyle k}, sometimes denoted hom (v, w) {\textstyle \operatorname {hom} (v,w)}. furthermore, in the case that v = w {\textstyle v=w}, this vector space, denoted end (v)... | wikipedia |
5d6bfdd1bbd244d3397b66c72ce045040ca430f4 | if f: v → w {\textstyle f:v\to w} | if f: v → w {\textstyle f:v\to w} is linear and α {\textstyle \alpha } is an element of the ground field k {\textstyle k}, then the map α f {\textstyle \alpha f}, defined by (α f) (x) = α (f (x)) {\textstyle (\alpha f)(\mathbf {x})=\alpha (f(\mathbf {x}))}, is also linear. | wikipedia |
d42d18b0550244456897e65396ec3d5e00df199f | if f 1: v → w {\textstyle f_{1}:v\to | if f 1: v → w {\textstyle f_{1}:v\to w} and f 2: v → w {\textstyle f_{2}:v\to w} are linear, then so is their pointwise sum f 1 + f 2 {\displaystyle f_{1}+f_{2}}, which is defined by (f 1 + f 2) (x) = f 1 (x) + f 2 (x) {\displaystyle (f_{1}+f_{2})(\mathbf {x})=f_{1}(\mathbf {x})+f_{2}(\mathbf {x})}. | wikipedia |
2117f786225c9d070f9cf2976b76564ed1fb6d99 | the composition of linear maps is linear: if | the composition of linear maps is linear: if f: v → w {\displaystyle f:v\to w} and g: w → z {\textstyle g:w\to z} are linear, then so is their composition g ∘ f: v → z {\textstyle g\circ f:v\to z}. it follows from this that the class of all vector spaces over a given field k, together with k -linear maps as morphisms, ... | wikipedia |
0e94f30a8a365c7b2a98325d0dedd3c634bf5d85 | such that starting in the bottom left corner | such that starting in the bottom left corner b ′ {\textstyle \left_{b'}} and looking for the bottom right corner b ′ {\textstyle \left_{b'}}, one would left-multiply—that is, a ′ b ′ = b ′ {\textstyle a'\left_{b'}=\left_{b'}}. the equivalent method would be the "longer" method going clockwise from the same point such t... | wikipedia |
3bec2d52b9ef339eb1b3de5d89ecb25236e60668 | thus, the function f {\displaystyle f} is entirely | thus, the function f {\displaystyle f} is entirely determined by the values of a i j {\displaystyle a_{ij}}. if we put these values into an m × n {\displaystyle m\times n} matrix m {\displaystyle m}, then we can conveniently use it to compute the vector output of f {\displaystyle f} for any vector in v {\displaystyle v... | wikipedia |
7e9dfee3ace30301f94aabdc3002005c8bcef9c6 | which implies that the function f is entirely | which implies that the function f is entirely determined by the vectors f (v 1), …, f (v n) {\displaystyle f(\mathbf {v} _{1}),\ldots,f(\mathbf {v} _{n})}. now let { w 1, …, w m } {\displaystyle \{\mathbf {w} _{1},\ldots,\mathbf {w} _{m}\}} be a basis for w {\displaystyle w}. then we can represent each vector f (v j) {... | wikipedia |
a16cb7b19ee774bf819b470742780f64b364f74c | if f: v → w {\textstyle f:v\to w} | if f: v → w {\textstyle f:v\to w} is a linear map, f (v) = f (c 1 v 1 + ⋯ + c n v n) = c 1 f (v 1) + ⋯ + c n f (v n), {\displaystyle f(\mathbf {v})=f(c_{1}\mathbf {v} _{1}+\cdots +c_{n}\mathbf {v} _{n})=c_{1}f(\mathbf {v} _{1})+\cdots +c_{n}f\left(\mathbf {v} _{n}\right),} | wikipedia |
ccf8b6eb985af35036a7e262b6eeedff22d0738e | let { v 1, …, v n } | let { v 1, …, v n } {\displaystyle \{\mathbf {v} _{1},\ldots,\mathbf {v} _{n}\}} be a basis for v {\displaystyle v}. then every vector v ∈ v {\displaystyle \mathbf {v} \in v} is uniquely determined by the coefficients c 1, …, c n {\displaystyle c_{1},\ldots,c_{n}} in the field r {\displaystyle \mathbb {r} }: v = c 1 v ... | wikipedia |
18e0f0444fed445ad3afef3c9ec8e7123d71ec45 | if v {\displaystyle v} and w {\displaystyle w} | if v {\displaystyle v} and w {\displaystyle w} are finite-dimensional vector spaces and a basis is defined for each vector space, then every linear map from v {\displaystyle v} to w {\displaystyle w} can be represented by a matrix. this is useful because it allows concrete calculations. matrices yield examples of linea... | wikipedia |
7221ca32df668ad59d0ead656105b2c81e5541f4 | every (scalar-valued) linear functional f {\displaystyle f} defined | every (scalar-valued) linear functional f {\displaystyle f} defined on a vector subspace of a real or complex vector space x {\displaystyle x} has a linear extension to all of x. {\displaystyle x.} indeed, the hahn–banach dominated extension theorem even guarantees that when this linear functional f {\displaystyle f} i... | wikipedia |
94532bb0cae8dc53555a8af8f29ca7e927ac50a7 | for example, if x = r 2 {\displaystyle | for example, if x = r 2 {\displaystyle x=\mathbb {r} ^{2}} and y = r {\displaystyle y=\mathbb {r} } then the assignment (1, 0) → − 1 {\displaystyle (1,0)\to -1} and (0, 1) → 2 {\displaystyle (0,1)\to 2} can be linearly extended from the linearly independent set of vectors s:= { (1, 0), (0, 1) } {\displaystyle s:=\{(1,0... | wikipedia |
4c929e8ca9a22f544daa906541c447391411a1bb | the map f: s → y {\displaystyle f:s\to | the map f: s → y {\displaystyle f:s\to y} can be extended to a linear map f: span s → y {\displaystyle f:\operatorname {span} s\to y} if and only if whenever n > 0 {\displaystyle n>0} is an integer, c 1, …, c n {\displaystyle c_{1},\ldots,c_{n}} are scalars, and s 1, …, s n ∈ s {\displaystyle s_{1},\ldots,s_{n}\in s} a... | wikipedia |
02b646a70c8f8feb2b19faea7f793276e01b2364 | the map f: s → y {\displaystyle f:s\to | displaystyle n,c_{1},\ldots,c_{n},} and s 1, …, s n {\displaystyle s_{1},\ldots,s_{n}} as above. if s {\displaystyle s} is linearly independent then every function f: s → y {\displaystyle f:s\to y} into any vector space has a linear extension to a (linear) map span s → y {\displaystyle \;\operatorname {span} s\to y} (t... | wikipedia |
06978d7d184f13679fff6d5c932b41239c6ba7ad | often, a linear map is constructed by defining | often, a linear map is constructed by defining it on a subset of a vector space and then extending by linearity to the linear span of the domain. suppose x {\displaystyle x} and y {\displaystyle y} are vector spaces and f: s → y {\displaystyle f:s\to y} is a function defined on some subset s ⊆ x. {\displaystyle s\subse... | wikipedia |
5109fc13bd1e86b0f68b66423d0acf183c9fb98f | denoting the zero elements of the vector spaces | denoting the zero elements of the vector spaces v {\displaystyle v} and w {\displaystyle w} by 0 v {\textstyle \mathbf {0} _{v}} and 0 w {\textstyle \mathbf {0} _{w}} respectively, it follows that f (0 v) = 0 w. {\textstyle f(\mathbf {0} _{v})=\mathbf {0} _{w}.} let c = 0 {\displaystyle c=0} and v ∈ v {\textstyle \math... | wikipedia |
0392a4dd59684fbf1e873f5f61ea794d747f424a | by the associativity of the addition operation denoted | by the associativity of the addition operation denoted as +, for any vectors u 1, …, u n ∈ v {\textstyle \mathbf {u} _{1},\ldots,\mathbf {u} _{n}\in v} and scalars c 1, …, c n ∈ k, {\textstyle c_{1},\ldots,c_{n}\in k,} the following equality holds: f (c 1 u 1 + ⋯ + c n u n) = c 1 f (u 1) + ⋯ + c n f (u n). {\displaysty... | wikipedia |
c077058d602ddb18780ee9674eb257bd3dfdb6b4 | thus, a linear map is said to be | thus, a linear map is said to be operation preserving. in other words, it does not matter whether the linear map is applied before (the right hand sides of the above examples) or after (the left hand sides of the examples) the operations of addition and scalar multiplication. | wikipedia |
f3eb8f0931fa4c83bbbbf86759d4b73642b2fcad | let v {\displaystyle v} and w {\displaystyle w} | let v {\displaystyle v} and w {\displaystyle w} be vector spaces over the same field k {\displaystyle k}. a function f: v → w {\displaystyle f:v\to w} is said to be a linear map if for any two vectors u, v ∈ v {\textstyle \mathbf {u},\mathbf {v} \in v} and any scalar c ∈ k {\displaystyle c\in k} the following two condi... | wikipedia |
7f2f4b6056184b651ae1e4e2f4de37e4dc999390 | a linear map from v {\displaystyle v} to | a linear map from v {\displaystyle v} to w {\displaystyle w} always maps the origin of v {\displaystyle v} to the origin of w {\displaystyle w}. moreover, it maps linear subspaces in v {\displaystyle v} onto linear subspaces in w {\displaystyle w} (possibly of a lower dimension); for example, it maps a plane through th... | wikipedia |
c897d66210e991596992d62fbf3f474942cb9568 | if a linear map is a bijection then | if a linear map is a bijection then it is called a linear isomorphism. in the case where v = w {\displaystyle v=w}, a linear map is called a linear endomorphism. sometimes the term linear operator refers to this case, but the term "linear operator" can have different meanings for different conventions: for example, it ... | wikipedia |
f35e707e255b7452fe9282009fcd84d5731d92b8 | in mathematics, and more specifically in linear algebra, | in mathematics, and more specifically in linear algebra, a linear map (also called a linear mapping, linear transformation, vector space homomorphism, or in some contexts linear function) is a mapping v → w {\displaystyle v\to w} between two vector spaces that preserves the operations of vector addition and scalar mult... | wikipedia |
113a471def838787fea34ed4b67a13288b2ca06c | kenneth w. witwer is an associate professor of | kenneth w. witwer is an associate professor of molecular and comparative pathobiology and neurology at the johns hopkins university school of medicine in baltimore, maryland, united states. he is president of the international society for extracellular vesicles (isev) and previously served as secretary general and exec... | wikipedia |
2dd3469a563d8b7be0fef1d1a5037ca1e7127e3f | witwer has contributed to scientific standardization and rigor | witwer has contributed to scientific standardization and rigor efforts. he was corresponding author in 2013 of the first position paper of the international society for extracellular vesicles, on standardization of isolation and characterization of evs in rna studies. with clotilde théry, he coordinated the minimal inf... | wikipedia |
e395106c5fab45a91f4dff2c8cb1b1cfa67e6d9b | witwer chaired the organizing committee of the isev2015 | witwer chaired the organizing committee of the isev2015 annual meeting (bethesda, united states). he has since filled several leadership roles with isev and become president of the society in 2024. witwer has organized or co-organized workshops and other meetings on five continents. responding in 2020 to the restrictio... | wikipedia |
f92bf9c6f0454ad84a5df9cc4984c707d8d9ff35 | the witwer laboratory studies the roles of evs, | the witwer laboratory studies the roles of evs, exrna, and ncrna in hiv disease of the central nervous system and in other neurodegenerative diseases, such as alzheimer's and parkinson's. another focus of the group is on how inflammatory insults like cigarette smoking affect progression of disease. beginning in 2013, w... | wikipedia |
920da912503dcecb86995df6fa7bdcae840e2359 | witwer's phd dissertation research was on retroviruses and | witwer's phd dissertation research was on retroviruses and innate immune system responses to pathogens such as visna virus and simian immunodeficiency virus (siv) as models of human immunodeficiency virus (hiv) disease, specifically regulation of micrornas, cytokines, and the promyelocytic leukemia protein (trim19). he... | wikipedia |
113a471def838787fea34ed4b67a13288b2ca06c | kenneth w. witwer is an associate professor of | kenneth w. witwer is an associate professor of molecular and comparative pathobiology and neurology at the johns hopkins university school of medicine in baltimore, maryland, united states. he is president of the international society for extracellular vesicles (isev) and previously served as secretary general and exec... | wikipedia |
2cceb47c37f7c59d10f2c9b3dacd3384bdeb7bbc | the paxman hi-dyne engine was a form of | the paxman hi-dyne engine was a form of experimental diesel engine developed for rail transport use by the british engine makers paxman of colchester. they used variable supercharging to give a constant power output across their speed range. the name "hi-dyne" is a reference to dyne, a cgs unit of force, and implicitly... | wikipedia |
566f1eba1bf694bba34ec626adb02b1aba324d72 | paxman was not alone in trying to develop | paxman was not alone in trying to develop diesel engines which gave high torque at low speed. italian inventors enrico hocke and fausto zarlatti patented a "diesel type locomotive with direct transmission and with automatically supercharged motor when decreasing the velocity" in 1938, patent us2115525. | wikipedia |
0b60917302a0a99f2d5801e0f9fe6fbf55d64ea3 | paxman subsequently supplied sixteen hi-dyne engines, based on | paxman subsequently supplied sixteen hi-dyne engines, based on the 6 cylinder rphxl (contracts 55096-103 and 55721-8) to hudswell clarke for locomotives for sierra leone government railways. | wikipedia |
9381a6185edca1cb42a17324b340c923169521e0 | one of the more lasting, although obscure, legacies | one of the more lasting, although obscure, legacies of this locomotive was due to its name. this locomotive first appeared in 1954, during the construction of dp1, the prototype class 55 deltic. dp1 already had the internal project name enterprise and it had been intended to name the locomotive similarly on its deliver... | wikipedia |
e8d76cd94106f5660f9cdd85d59ad10e9358422b | in 1954 the first prototype hi-dyne was installed | in 1954 the first prototype hi-dyne was installed in enterprise, a 48-ton hudswell clarke industrial locomotive. this was tested for a range of industrial uses, particularly for colliery traffic on the stockton to darlington line. unusually for the testing of a small locomotive, the test trains also included a dynamome... | wikipedia |
d135e5819c4a323705887f6f956c97f0ad698e1d | engine fuel supply through the injection pump was | engine fuel supply through the injection pump was controlled by a governor. rather than the usual arrangement where a control input from the driver's lever sets an engine speed that is maintained by a governor, in the hi-dyne engine the control input selected an output power level, which was maintained by the governor. | wikipedia |
832a665256ff8aa0237df7e436e0b2917c18b626 | the same concept of a constant-power diesel engine | the same concept of a constant-power diesel engine by variable supercharging had earlier been used in the multi-engined 2,000 bhp mechanical transmission fell locomotive (british rail 10100). this used six engines in total: four paxman 12rph power engines and two aec a210d engines solely to drive the holmes-connersvill... | wikipedia |
6532f30f9455d7290615677d940492e124461535 | by applying a turbocharger, it is possible to | by applying a turbocharger, it is possible to increase the torque (and thus power) at low speeds, so as to match the naturally-aspirated maximum power at the torque peak. if the turbocharger and its inlet manifold are carefully sized to provide the necessary boost at low pressure, but for the volume delivered to stay r... | wikipedia |
9e26b184d1b75e7a526620d7c8138804d0519f88 | experiments in supercharging diesel engines from the 1930s | experiments in supercharging diesel engines from the 1930s onwards, initially by sulzer and saurer, had shown that a robustly constructed diesel engine could be supercharged heavily, such that its output torque could become several times greater. the eventual limitation on this process became the engine's ability to ex... | wikipedia |
e775e23940097e17e0f5f75c56021e8df302a42d | the hi-dyne principle was to produce an engine | the hi-dyne principle was to produce an engine where the torque curve was the inverse of the usual: a maximum at low revolutions and decreasing gradually with increasing speed, so that the overall power (the product of torque and power) would remain constant, whatever the speed. such an engine cannot be achieved by nor... | wikipedia |
111002b9d59f527b20e8b405fd814836e65e250a | the output power of an engine is the | the output power of an engine is the product of its torque and speed. the torque varies with speed, increasing to a peak value and falling away both above and below this. the range for which the torque is a useful proportion of the maximum is described as the 'power band'. diesel engines generally have a broader band t... | wikipedia |
2368a6c2a0f5230cd166d22a0313ce1d4e46a90b | one of the main needs for a transmission | one of the main needs for a transmission is to match the speed of the engine to the speed of the locomotive, so that the engine can work in its useful operating speed range. all locomotives need to deliver high torque from zero rail speed for startup. the overall range of gear ratios required from the transmission thus... | wikipedia |
7959c03427656f3ccc88e300058a7d4f7edcc250 | diesel locomotives appeared in the 1930s, after the | diesel locomotives appeared in the 1930s, after the availability of reliable, compact diesel engines. the first were low-speed shunters with mechanical transmissions. these were followed by more powerful high-speed express locomotives with diesel-electric transmissions. these electric transmissions and their traction m... | wikipedia |
3aac1f8a1e1053f6c23cd1e5a3b6a504919ffb78 | magnetic reconnection is a physical process occurring in | magnetic reconnection is a physical process occurring in electrically conducting plasmas, in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle acceleration. magnetic reconnection involves plasma flows at a substantial fraction of the alfvén wave s... | wikipedia |
b17bbba5436f8e5cec5279ccac547afe4271eb63 | magnetic reconnection is a physical process occurring in | sweet and eugene parker at a conference in 1956. sweet pointed out that by pushing two plasmas with oppositely directed magnetic fields together, resistive diffusion is able to occur on a length scale much shorter than a typical equilibrium length scale. parker was in attendance at this conference and developed scalin... | wikipedia |
ebb8306c19d83959ec2f45be13d9821540472610 | sawtooth oscillations are periodic mixing events occurring in | sawtooth oscillations are periodic mixing events occurring in the tokamak plasma core. the kadomtsev model describes sawtooth oscillations as a consequence of magnetic reconnection due to displacement of the central region with safety factor q < 1 {\displaystyle q<1} caused by the internal kink mode. | wikipedia |
84b9e7cfc7c541e092bb89b11849d1a5a5f524c0 | magnetic reconnection has also been observed in numerous | magnetic reconnection has also been observed in numerous laboratory experiments. for example, studies on the large plasma device (lapd) at ucla have observed and mapped quasi-separatrix layers near the magnetic reconnection region of a two flux rope system, while experiments on the magnetic reconnection experiment (mrx... | wikipedia |
a8d5ce3af03dc0b8894c1e45c6739990cab7555b | on 26 february 2008, themis probes were able | on 26 february 2008, themis probes were able to determine the triggering event for the onset of magnetospheric substorms. two of the five probes, positioned approximately one third the distance to the moon, measured events suggesting a magnetic reconnection event 96 seconds prior to auroral intensification. dr. vassili... | wikipedia |
dbfdd8d184fbc229627b75e3d747302005249d7a | magnetic reconnection events that occur in the earth's | magnetic reconnection events that occur in the earth's magnetosphere (in the dayside magnetopause and in the magnetotail) were for many years inferred because they uniquely explained many aspects of the large-scale behaviour of the magnetosphere and its dependence on the orientation of the near-earth interplanetary mag... | wikipedia |
a0c8a829a11f5cb843135069c5ced8a07870adbf | magnetic reconnection occurs during solar flares, coronal mass | magnetic reconnection occurs during solar flares, coronal mass ejections, and many other events in the solar atmosphere. the observational evidence for solar flares includes observations of inflows/outflows, downflowing loops, and changes in the magnetic topology. in the past, observations of the solar atmosphere were ... | wikipedia |
5a95a9286809f13d301d7141514b85a7b10d40c4 | on length scales shorter than the ion inertial | on length scales shorter than the ion inertial length c / ω p i {\displaystyle c/\omega _{pi}} (where ω p i ≡ n i z 2 e 2 ϵ 0 m i {\displaystyle \omega _{pi}\equiv {\sqrt {\frac {n_{i}z^{2}e^{2}}{\epsilon _{0}m_{i}}}}} is the ion plasma frequency), ions decouple from electrons and the magnetic field becomes frozen into... | wikipedia |
b4a93adc26139244091e6fc286f009eefaff3c8e | where v turb = v l 2 / | where v turb = v l 2 / v a {\displaystyle v_{\text{turb}}=v_{l}^{2}/v_{a}}. here l {\displaystyle l}, and v l {\displaystyle v_{l}} are turbulence injection length scale and velocity respectively and v a {\displaystyle v_{a}} is the alfvén velocity. this model has been successfully tested by numerical simulations. | wikipedia |
90e79d0e9c13ba170a169184fae3172c81fc7628 | in stochastic reconnection, magnetic field has a small | in stochastic reconnection, magnetic field has a small scale random component arising because of turbulence. for the turbulent flow in the reconnection region, a model for magnetohydrodynamic turbulence should be used such as the model developed by goldreich and sridhar in 1995. this stochastic model is independent of ... | wikipedia |
1295dfbf8d41d9f5a8949b801f9f57f768de66c8 | another proposed mechanism is known as the bohm | another proposed mechanism is known as the bohm diffusion across the magnetic field. this replaces the ohmic resistivity with v a 2 (m c / e b) {\displaystyle v_{a}^{2}(mc/eb)}, however, its effect, similar to the anomalous resistivity, is still too small compared with the observations. | wikipedia |
638cf6886af5d356b43dccff18821fc712d19b78 | nevertheless, if the drift velocity of electrons exceeds | nevertheless, if the drift velocity of electrons exceeds the thermal velocity of plasma, a steady state cannot be achieved and magnetic diffusivity should be much larger than what is given in the above. this is called anomalous resistivity, η anom {\displaystyle \eta _{\text{anom}}}, which can enhance the reconnection ... | wikipedia |
96025791efee2f866779a0e5f63e06ac93ea8992 | where ν {\displaystyle \nu } is the collision | where ν {\displaystyle \nu } is the collision frequency. since in the steady state, d v / d t = 0 {\displaystyle d{\mathbf {v} }/dt=0}, then the above equation along with the definition of electric current, j = e n v {\displaystyle {\mathbf {j} }=en{\mathbf {v} }}, where n {\displaystyle n} is the electron number densi... | wikipedia |
8f861b92a7ce01cdae77b913275db766af5f5c68 | in the sweet–parker model, the common assumption is | in the sweet–parker model, the common assumption is that the magnetic diffusivity is constant. this can be estimated using the equation of motion for an electron with mass m {\displaystyle m} and electric charge e {\displaystyle e}: | wikipedia |
b44c26a689d4ae910cd257d7df2e7a8a0e12d849 | simulations of resistive mhd reconnection with uniform resistivity | simulations of resistive mhd reconnection with uniform resistivity showed the development of elongated current sheets in agreement with the sweet–parker model rather than the petschek model. when a localized anomalously large resistivity is used, however, petschek reconnection can be realized in resistive mhd simulatio... | wikipedia |
8582f6b72dcd9453095fc55c56dc41df32a13d8a | this expression allows for fast reconnection and is | this expression allows for fast reconnection and is almost independent of the lundquist number. theory and numerical simulations show that most of the actions of the shocks that were proposed by petschek can be carried out by alfvén waves and in particular rotational discontinuities (rds). in cases of asymmetric plasma... | wikipedia |
88351922980e26c782a4535d3628c6ca8af73efd | the fundamental reason that petschek reconnection is faster | the fundamental reason that petschek reconnection is faster than parker-sweet is that it broadens the outflow region and thereby removes some of the limitation caused by the build up in plasma pressure. the inflow velocity, and thus the reconnection rate, can only be very small if the outflow region is narrow. in 1964,... | wikipedia |
dc4327b925133360653d8bf92934cc1a5da5dba3 | sweet–parker reconnection allows for reconnection rates much faster | sweet–parker reconnection allows for reconnection rates much faster than global diffusion, but is not able to explain the fast reconnection rates observed in solar flares, the earth's magnetosphere, and laboratory plasmas. additionally, sweet–parker reconnection neglects three-dimensional effects, collisionless physics... | wikipedia |
ec234a357fc526c7c8fc78bac4c911f13ee8557d | the two different expressions of r {\displaystyle r} | the two different expressions of r {\displaystyle r} are multiplied by each other and then square-rooted, giving a simple relation between the reconnection rate r {\displaystyle r} and the lundquist number s {\displaystyle s} r ∼ η v a l = 1 s 1 2. {\displaystyle r~\sim {\sqrt {\frac {\eta }{v_{a}l}}}={\frac {1}{s^{\fr... | wikipedia |
a7a8bf4144e23bad802cb19662292e972853a644 | where v a {\displaystyle v_{a}} is the alfvén | where v a {\displaystyle v_{a}} is the alfvén velocity. with the above relations, the dimensionless reconnection rate r {\displaystyle r} can then be written in two forms, the first in terms of (η, δ, v a) {\displaystyle (\eta,\delta,v_{a})} using the result earlier derived from ohm's law, the second in terms of (δ, l)... | wikipedia |
154060be37cea9545521d763dc5a5b860d52b302 | where ρ {\displaystyle \rho } is the mass | where ρ {\displaystyle \rho } is the mass density of the plasma. solving for the outflow velocity then gives v out ∼ b in μ 0 ρ ≡ v a {\displaystyle v_{\text{out}}\sim {\frac {b_{\text{in}}}{\sqrt {\mu _{0}\rho }}}\equiv v_{a}} | wikipedia |
ba347f52ba18bb85e3490070f52de24980e393bb | where l {\displaystyle l} is the half-length of | where l {\displaystyle l} is the half-length of the current sheet and v out {\displaystyle v_{\text{out}}} is the outflow velocity. the left and right hand sides of the above relation represent the mass flux into the layer and out of the layer, respectively. equating the upstream magnetic pressure with the downstream d... | wikipedia |
a27b2fd0790915f9799798d77ab48f986b05343d | where η {\displaystyle \eta } is the magnetic | where η {\displaystyle \eta } is the magnetic diffusivity. when the inflow density is comparable to the outflow density, conservation of mass yields the relationship v in l ∼ v out δ, {\displaystyle v_{\text{in}}l\sim v_{\text{out}}\delta,} | wikipedia |
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