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002f7b238666396489e855316fa943dc12a864f0
suppose firstly that γ and δ are two
suppose firstly that γ and δ are two geodesic rays with busemann functions differing by a constant. shifting the argument of one of the geodesics by a constant, it may be assumed that b = b = b, say. let c be the closed convex set on which b (x) ≤ − r. then b (γ(t)) = b (γ(t)) = − t and similarly b (δ(t)) = − t. then f...
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6b4b272adaee10d09e95485aeb7924e0519bbfa2
hence h (y) = 0. similarly h (x)
hence h (y) = 0. similarly h (x) = 0. hence h (y) = 0 on the level surface of h containing x. now for t ≥ 0 and z in x, let α (z) = γ (t) the geodesic ray starting at z. then α = α ∘ α and h ∘ α = h − t. moreover, by boundedness, d (α (u),α (v)) ≤ d (u, v). the flow α can be used to transport this result to all the lev...
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ab716735c16fd1a335868f2b3bf306b6fea0d64d
fix x in x. let γ (s) be
fix x in x. let γ (s) be the geodesic ray starting at x. let g (z) = h (z), the busemann function for γ with base point x. in particular g (x) = 0. it suffices to show that g = h – h (y)1. now take y with h (x) = h (y) and let δ (t) be the geodesic ray starting at y corresponding to h. then
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da079fce593aa3b97a915034fefa807e16bae063
let c be the closed convex set of
let c be the closed convex set of points z with h (z) ≤ − r. since x is a hadamard space for every point y in x there is a unique closest point p (y) to y in c. it depends continuously on y and if y lies outside c, then p (y) lies on the hypersurface h (z) = − r —the boundary ∂ c of c —and p (y) satisfies the inequalit...
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f0f0bc4fe1e7bae7b7c14695ea86f64f533123e5
to prove the first assertion, it is enough
to prove the first assertion, it is enough to check this for t sufficiently large. in that case γ(t) and δ (t − h (y)) are the projections of x and y onto the closed convex set h ≤ − t. therefore, d (γ (t), δ (t − h (y))) ≤ d (x, y). hence d (γ (t), δ (t)) ≤ d (γ (t), δ (t − h (y))) + d (δ (t − h (y)), δ (t)) ≤ d (x, y...
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58187a5e1376fd8444d84b0fded7c2fdac0ebc3d
the third condition implies that v is the
the third condition implies that v is the closest point to y in the closed convex set c of points u {\displaystyle u} such that h (u) ≤ h (y) – r. let δ (t) for 0 ≤ t ≤ r be the geodesic joining y to v. then k (t) = h (δ (t)) - h (y) is a convex lipschitz function on with lipschitz constant 1 satisfying k (t) ≤ – t and...
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7f6a45094cea5b9d74ce663c1c6f91123e625b24
comment. note that, since any closed convex subset
comment. note that, since any closed convex subset of a hadamard subset of a hadamard space is also a hadamard space, any closed ball in a hadamard space is a hadamard space. in particular it need not be the case that every geodesic segment is contained in a geodesic defined on the whole of r or even a semi-infinite in...
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3c2e0e86a062234b5eb4b4d4c826a5b7d9b717f1
uniform limits. the above argument proves more generally
uniform limits. the above argument proves more generally that if d (x, x) tends to infinity and the functions h (x) = d (x, x) – d (x, x) tend uniformly on bounded sets to h (x), then h is convex, lipschitz with lipschitz constant 1 and, given y in x and r > 0, there is a unique point v with d (y, v) = r such that h (v...
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7a8b2eb701abf485c236cf749621a367ab794c3e
so that u is a cauchy sequence. if
so that u is a cauchy sequence. if u is its limit, then d (y, u) = r and h (u) = h (y) − r. by uniqueness it follows that u = v and hence d (y, v) = r, as required.
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a8b9faf3850e928a1ec5db7a24261e5f88bcced3
let v be the closest point to y
let v be the closest point to y in c. then h (v) = h (y) − r and so h is minimised by v in b (y, r) where r = d (y, v) and v is the unique point where h is minimised. by the lipschitz condition r = | h (y) − h (v)| ≤ r. to prove the assertion, it suffices to show that r = r, i.e. d (y, v) = r. on the other hand, h is t...
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eac7c0b434f063fa383036a4dfb9ffbcc86cb01a
this condition persists for busemann functions. the statement
this condition persists for busemann functions. the statement and proof of the property for busemann functions relies on a fundamental theorem on closed convex subsets of a hadamard space, which generalises orthogonal projection in a hilbert space: if c is a closed convex set in a hadamard space x, then every point x i...
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3a7562af550b24fd2d6861dc8d78eb9c07a6c7d2
next suppose that x, y are points in
next suppose that x, y are points in a hadamard space, and let δ (s) be the geodesic through x with δ (0) = y and δ (t) = x, where t = d (x, y). this geodesic cuts the boundary of the closed ball b (y, r) at the point δ (r). thus if d (x, y) > r, there is a point v with d (y, v) = r such that d (x, v) = d (x, y) − r.
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75bb690bf489387b12a94a626e2a6b5bf21b1877
note that the inequality above for | f
note that the inequality above for | f s (y) − f t (y) | {\displaystyle |f_{s}(y)-f_{t}(y)|} (together with its proof) also holds for geodesic segments: if γ (t) is a geodesic segment starting at x and parametrised by arclength then
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311c6903d813a9d8b42e013ba49a1d4e0f456123
let h (t) = d (y,γ(t)) − t
let h (t) = d (y,γ(t)) − t = f (y). since γ (t) {\displaystyle \gamma (t)} is parametrised by arclength, alexandrov's first comparison theorem for hadamard spaces implies that the function g (t) = d (y,γ(t)) − t is convex. hence for 0< s < t
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f0cf3dab39cd16981adac5c1621a27a2443ecb2f
in a hadamard space, where any two points
in a hadamard space, where any two points are joined by a unique geodesic segment, the function f = f t {\displaystyle f=f_{t}} is convex, i.e. convex on geodesic segments {\displaystyle }. explicitly this means that if z (s) {\displaystyle z(s)} is the point which divides {\displaystyle } in the ratio s : (1 − s), the...
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c79cb1782c625060ad8b5dd8fdb5845c3528348a
where the term in brackets on the right
where the term in brackets on the right hand side is the poisson kernel for the unit disk and ζ {\displaystyle \zeta } corresponds to the radial geodesic γ {\displaystyle \gamma } from the origin towards ζ {\displaystyle \zeta }, γ (t) = ζ tanh (t / 2) {\displaystyle \gamma (t)=\zeta \tanh(t/2)}. the computation of d (...
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fad45188ff373924c31882a810033d8424227fc9
by dini's theorem, the functions f t (x)
by dini's theorem, the functions f t (x) = d (x, γ (t)) − t {\displaystyle f_{t}(x)=d(x,\gamma (t))-t} tend to b γ (x) {\displaystyle b_{\gamma }(x)} uniformly on compact sets as t tends to infinity.
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17eb8593465869597c2b80aae3462a1062414a95
thus, when t is very large, the distance
thus, when t is very large, the distance d (γ (t), x) {\displaystyle d{\big (}\gamma (t),x{\big)}} is approximately equal to b γ (x) + t {\displaystyle b_{\gamma }(x)+t}. given a ray γ, its busemann function is always well-defined: indeed the right hand side above f t (x) = def d (γ (t), x) − t {\displaystyle f_{t}(x){...
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90c57b1506e09681869861e75b0da844dd47ca59
let (x, d) {\displaystyle (x,d)} be a metric
let (x, d) {\displaystyle (x,d)} be a metric space. a geodesic ray is a path γ: [ 0, ∞) → x {\displaystyle \gamma :[0,\infty)\to x} which minimizes distance everywhere along its length. i.e., for all t, t ′ ∈ [ 0, ∞) {\displaystyle t,t'\in [0,\infty)},
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d8acb88d694e8c674713f5a5f285b2059b6bc9c8
in geometric topology, busemann functions are used to
in geometric topology, busemann functions are used to study the large-scale geometry of geodesics in hadamard spaces and in particular hadamard manifolds (simply connected complete riemannian manifolds of nonpositive curvature). they are named after herbert busemann, who introduced them; he gave an extensive treatment ...
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21183507adcaf7430da0b661ba0a02a558d2db4e
the bridge at nimreh is a roman bridge
the bridge at nimreh is a roman bridge in the vicinity of shahba, syria, dating to the 3rd or 4th century ad. its transversal arch construction derives from old building traditions of the hauran region and is arguably unique in roman bridge building.
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38a4441b9c345239fa39561ec377252c3ad0aaa1
presumably, the bridge was built directly onto the
presumably, the bridge was built directly onto the solid stone. its almost unadorned masonry walls consist of rectangular, roughly smoothed basalt blocks of varying size without mortar (opus quasi-quadratum). since roman bridges rarely featured basalt, its use is undoubtedly due to the availability of the material in s...
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7f94ce36a21686e6bf52f2eb4dfeec110309271a
the vault was made of three parallel, transversal
the vault was made of three parallel, transversal arches standing at intervals of 1.20 m; the arches were built of 60 cm long, 30 cm wide and just as high ashlar, while the spaces in between are covered with longish basalt blocks. this design principle – transversal arches with lintels – seems to be unique among roman ...
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994e912cd4064bf7da9bff52051764cf5f2b808f
the bridge is situated 10 km southeast from
the bridge is situated 10 km southeast from shahba, close to the modern road at the foot of the mountain village nimreh, which was known in the onomastikon of eusebius by the name namara and regarded as an important place (vicus grandis). here, the bridge crosses the wadi al-liwa almost right-angled, making a small ben...
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0f9a34356b6841f93300598ebf5d6591e646ae0b
after the annexation by emperor trajan in 106
after the annexation by emperor trajan in 106 ad, the infrastructure of the newly established provincia arabia was greatly expanded by the construction of roman forts and military roads to ward off nomadic incursions; in bostra the legio iii cyrenaica was stationed. the rugged terrain, with many wadis crisscrossing it,...
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9d804d7c456751473044c4304758d89b2c05f80b
the bridge at nimreh is located in the
the bridge at nimreh is located in the hauran (ancient name: auranitis), a mountainous volcanic region c. 80 km southeast from damascus in the transitional zone between agricultural land and the desert. due to fertile soils and sufficient rainfalls, the area yielded in roman times particularly high returns, which could...
wikipedia
580f5c44d307c3709cf639e9fb6d84c7d4856560
the bridge at nimreh is a roman bridge
the bridge at nimreh is a roman bridge in the vicinity of shahba (ancient philippopolis), syria, dating to the 3rd or 4th century ad. its transversal arch construction derives from old building traditions of the hauran region and is arguably unique in roman bridge building.
wikipedia
ec3467bc51522a3720290b43d8e720f593429ba9
brochosomes are intricately structured microscopic granules secreted by
brochosomes are intricately structured microscopic granules secreted by leafhoppers and typically found on their body surface and, more rarely, eggs. brochosomes were first described in 1952 with the aid of an electron microscope. brochosomes are hydrophobic and help keep the insect cuticle clean. these particles have ...
wikipedia
877ec8086e86bf6a63d792b35ba87975a84235c2
in several new world genera of the leafhopper
in several new world genera of the leafhopper subfamily cicadellinae (including the glassy-winged sharpshooter and related species) brochosomes are also used as a coating on egg masses. in gravid females from these genera, the malpighian tubules switch over from production of regular brochosomes, described above, to pr...
wikipedia
f11ddb48c9b827e90a62a822152e543cc20d39fc
after each molt, most leafhopper species release droplets
after each molt, most leafhopper species release droplets of the brochosome-containing fluid through the anus and actively spread them over the newly formed integument. this behavior is called anointing. dry brochosomes are further distributed across the body and appendages in repeated bouts of grooming, in which leafh...
wikipedia
04f8de0f60dadd33fef400f716c7ded89c996b90
brochosomes are produced within cells of specialized glandular
brochosomes are produced within cells of specialized glandular segments of the malpighian tubules – the primary excretory organs of insects, which often serve additional functions. each cell simultaneously manufactures a large number of brochosomes within its golgi complexes and eventually releases them into the lumen ...
wikipedia
d43d97267065776374b54521685ce232a76876b9
most species of leafhoppers produce hollow spherical brochosomes,
most species of leafhoppers produce hollow spherical brochosomes, 0.2–0.7 micrometres in diameter, with a honeycombed outer wall. they often consist of 20 hexagonal and 12 pentagonal cells, making the outline of each brochosome approximating a truncated icosahedron – the geometry of a soccer ball and a c buckminsterful...
wikipedia
af1ea011e8dce091402571e325e77e66935c7d87
brochosomes are intricately structured microscopic granules secreted by
brochosomes are intricately structured microscopic granules secreted by leafhoppers (the family cicadellidae of the insect order hemiptera) and typically found on their body surface and, more rarely, eggs. brochosomes were first described in 1952 with the aid of an electron microscope. brochosomes are hydrophobic and h...
wikipedia
be18f4819b069027c3c259816413cc4e018a44d1
cleidson rodrigues dos santos or simply cleidson is
cleidson rodrigues dos santos or simply cleidson is a brazilian footballer who plays primarily as a left back. he currently plays for itumbiara esporte clube. a strong, versatile player who can deputise at centre back should the need arise, cleidson was linked with several european clubs during the 2012 summer transfer...
wikipedia
e12c5ff675562275887eb9fabc7218100beded80
a strong, versatile player who can deputise at
a strong, versatile player who can deputise at centre back should the need arise, cleidson was linked with several european clubs during the 2012 summer transfer window: most notably vfb stuttgart of the german bundesliga as well as queens park rangers and swansea city, then both of the english premier league.
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f39ce10e9e358b28dd11b75139e6b5e21f394c62
cleidson rodrigues dos santos or simply cleidson (born
cleidson rodrigues dos santos or simply cleidson (born 13 august 1988) is a brazilian footballer who plays primarily as a left back. he currently plays for itumbiara esporte clube.
wikipedia
85739f92f29b7e855a8472bc6c617d50a2653b93
dean edward martin is an english football manager,
dean edward martin is an english football manager, coach and former player who is assistant coach of Ía. a midfielder, martin spent much of his playing career in iceland with ka and Ía and he also played in england, hong kong and the republic of ireland. he moved into coaching and management whilst still a player and h...
wikipedia
74a3801b0687cf8707151715187ba0604c5a9bef
in international football, martin has assisted and coached
in international football, martin has assisted and coached iceland at youth level and in january 2017 he was appointed the ksÍ's head of talent identification. he departed his roles to become assistant manager of china women in november 2017, but he left the setup after manager sigurður ragnar eyjólfsson was sacked in ...
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a59d902f45d63cad94d555d450253ccdcb3c698c
martin completed his ksÍ 'a' coaching badges in
martin completed his ksÍ 'a' coaching badges in 2009 and has a bsc in sports science from reykjavík university. he has held management roles at ka, breiðablik u19 and hk u19. he has worked as an assistant manager at club sides Ía, Íbv and hk. on 26 september 2018, martin was appointed as manager of newly-relegated 2. d...
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51f1b330ba19e95f3e23e415b82593173a6848ab
between 1995 and 2001, martin spent the autumn
between 1995 and 2001, martin spent the autumn and winter months playing for clubs outside iceland. he returned to england to play for brentford (1995–96), hereford united (1998–99) and stevenage borough during the 1999–00 and 2000–01 seasons. he also played in hong kong for eastern aa and hong kong rangers and in the ...
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6384d988e1b25421db7924327baf3e262ac73bd3
martin moved to iceland to join 1. deild
martin moved to iceland to join 1. deild karla club ka in 1995. martin's icelandic career stretched from 1995 to 2014 and he played in the top two divisions, principally for ka and Ía. he won a promotion from the 1. deild karla with each club and played european football for both. martin retired at age 42, after spendi...
wikipedia
7eed3dbe875249c2539a05d34d6e3665b4bd1913
a midfielder, martin began his career in sunday
a midfielder, martin began his career in sunday league football, before moving to conference club fisher athletic. he returned to first division club west ham united, with whom he had spent a period as a youth, for a £25,000 fee in may 1991. martin made three appearances during the second half of the 1991–92 season, wh...
wikipedia
5fd0a50f6de174ee7c1da2822183d9e5bb3eb632
a midfielder, martin spent much of his playing
a midfielder, martin spent much of his playing career in iceland with ka and Ía and he also played in england, hong kong and the republic of ireland. he moved into coaching and management whilst still a player and has held senior and youth roles with club and international teams in iceland.
wikipedia
739df42b7f12b5f0947617ba7d9aff15277afed2
notation: | x ⟩ - position eigenstate |
notation: | x ⟩ - position eigenstate | α ⟩ , | β ⟩ , | γ ⟩ . . . - wave function of the state of the system Ψ - total wave function of a system ψ - wave function of a system ψ α - wave function of a particle in position representation, equal to ⟨ x | α ⟩
wikipedia
ba795f8b506559c1bd60dce2e9712b48e9ee2e53
it can be derived from (1) by considering
it can be derived from (1) by considering Ψ α (x, t):= ⟨ x | α ⟩ {\displaystyle \psi _{\alpha }(x,t):=\langle x|\alpha \rangle } and h ^:= − ℏ 2 2 m ∇ 2 + v ^ {\displaystyle {\hat {h}}:=-{\frac {\hbar ^{2}}{2m}}\nabla ^{2}+{\hat {v}}}
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8245cc2226b9cf039b7f97a5e7f61eb08ef2392f
calvin blackman bridges was an american scientist known
calvin blackman bridges was an american scientist known for his contributions to the field of genetics. along with alfred sturtevant and h.j. muller, bridges was part of thomas hunt morgan's famous "fly room" at columbia university.
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745e4a529f26344f1ce46b1fddc0e06f9daa0842
2. muhlrad, paul j. "fruit fly: drosophila." genetics.
2. muhlrad, paul j. "fruit fly: drosophila." genetics. ed. richard robinson. vol. 2. new york: macmillan reference usa, 2003. 42-45. gale virtual reference library. web. 26 january 2015.
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40e8516f1f1b5d2e48b2c5351373809a7819bd4a
1. "bridges, calvin blackman." complete dictionary of scientific
1. "bridges, calvin blackman." complete dictionary of scientific biography. vol. 2. detroit: charles scribner's sons, 2008. 455-457. gale virtual reference library. web. 26 january 2015.
wikipedia
7978610430f9e41cd0f2340b64849b22d2bbab74
bridges married gertrude ives, with whom he had
bridges married gertrude ives, with whom he had four children. he was known to be both brilliant and very kind and considerate, though he was equally well-known for his womanizing and his struggles to keep up with family obligations. he was an atheist. in 1938, bridges died from what is believed to have been a case of ...
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6c18dc81c46b1556ebba0ab86850d21365fcc0f9
after his death, bridges' student katherine brehme warren
after his death, bridges' student katherine brehme warren completed work on the mutants of drosophila melanogaster (1944), a classic book which was for two decades an indispensable resource for geneticists, with information from the "red book" later being transferred to the flybase database. morgan and sturtevant destr...
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18d9ed4b33b036e94b0ae17444826fd35f11cf65
bridges' phd thesis on " non-disjunction as proof
bridges' phd thesis on " non-disjunction as proof of the chromosome theory of heredity" appeared as the first paper in the first issue of the journal genetics in 1916. in this paper, he also established that the y chromosome does not determine gender in drosophila. bridges' best-known contribution among drosophila rese...
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9f118a2fd7e2ea0a0706239f15112c70ac8aa37d
bridges published many works, one of his most
bridges published many works, one of his most famous being "sex in relation to chromosomes and genes". he also contributed many items to the journal of experimental zoology and science. his work with sex-linked traits suggested that chromosomes contained genes; nettie maria stevens was later able to support this hypoth...
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2f9f0c9f5556295765c138308df52202ab217275
bridges in particular was responsible for many improvements
bridges in particular was responsible for many improvements regarding the techniques and the equipment used in the experiments. he suggested the use binocular microscopes instead of hand lenses that had been using before, which improved data quality and convenience. bridges also developed temperature controls for the e...
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0bc08ed9f7edd9c7d764eda16079fe8e40127665
the "fly room" experiments began in 1910 and
the "fly room" experiments began in 1910 and continued for seventeen years, with thomas hunt morgan being the project's lead experimental developer. among many others working alongside bridges and morgan in the laboratory were alfred sturtevant and hermann joseph muller. the "fly room" experiments were the first to use...
wikipedia
6e0da03e44b6ad3dafa7f50a1c7857040cb23a93
calvin blackman bridges was born in schuyler falls,
calvin blackman bridges was born in schuyler falls, new york in 1889 to the parents of leonard bridges and charlotte blackman. tragically, calvin's mother died when he was two years old, and his father died a year later, leaving the young calvin an orphan. bridges was subsequently taken in and raised by his grandmother...
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16517200685c859789ea6ca53deb621abf7290a0
calvin blackman bridges (january 11, 1889 – december
calvin blackman bridges (january 11, 1889 – december 27, 1938) was an american scientist known for his contributions to the field of genetics. along with alfred sturtevant and h.j. muller, bridges was part of thomas hunt morgan 's famous "fly room" at columbia university.
wikipedia
dba4c118cf50ded8906c22433eafbb9b2628b256
the bristol cherub is a british two-cylinder, air-cooled,
the bristol cherub is a british two-cylinder, air-cooled, aircraft engine designed and built by the bristol aeroplane company. introduced in 1923 it was a popular engine for ultralight and small aircraft in the 1930s.
wikipedia
dba4c118cf50ded8906c22433eafbb9b2628b256
the bristol cherub is a british two-cylinder, air-cooled,
the bristol cherub is a british two-cylinder, air-cooled, aircraft engine designed and built by the bristol aeroplane company. introduced in 1923 it was a popular engine for ultralight and small aircraft in the 1930s.
wikipedia
e831e911e84e3169ee3601cad13cd5e90baa716f
conor ramsay is a scottish professional footballer who
conor ramsay is a scottish professional footballer who plays for arthurlie in the scottish junior football association, west region. he is a former scotland youth international and has previously played in the scottish premier league for st mirren.
wikipedia
17dc99c460e12584399564dba3e3c25b052bfbf4
a midfielder, ramsay started his career with hometown
a midfielder, ramsay started his career with hometown team st mirren. he made five appearances in the scottish premier league under the management of gus macpherson at the age of sixteen while also featuring for the scotland u17 international team. injury restricted his progress at st mirren and ramsay moved to rivals ...
wikipedia
e3315a16b192d0bf5a725fff254b4b3a9b445009
conor ramsay (born 9 march 1993) is a
conor ramsay (born 9 march 1993) is a scottish professional footballer who plays for arthurlie in the scottish junior football association, west region. he is a former scotland youth international and has previously played in the scottish premier league for st mirren.
wikipedia
9e88f4bad434697ba5f0619b5bf72256ad645f94
gudrun kadereit is a german botanist, the princess
gudrun kadereit is a german botanist, the princess therese von bayern chair of systematics, biodiversity and evolution of plants at the ludwig maximilians university of munich and the director of both the botanical garden munich-nymphenburg and the botanical state collection munich.
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3a58b46288152ef1de2937b4496ae26cf302c993
her research focuses on angiosperm phylogenetics, systematics and
her research focuses on angiosperm phylogenetics, systematics and biogeography, in particular on the families amaranthaceae, melastomataceae, crassulaceae, aizoaceae and zygophyllaceae but also on the evolution of c4 photosynthesis and crassulacean acid metabolism (cam) and the evolution of seed traits.
wikipedia
f857b8566b445e7a375265bc093ce91116730780
gudrun kadereit (born 1969) is a german botanist,
gudrun kadereit (born 1969) is a german botanist, the princess therese von bayern chair of systematics, biodiversity and evolution of plants at the ludwig maximilians university of munich and the director of both the botanical garden munich-nymphenburg and the botanical state collection munich. her research focuses on ...
wikipedia
4ff95e1b5e87d6ae1ac5006aca4745c44cb710a4
branko grünbaum was a croatian-born mathematician of jewish
branko grünbaum was a croatian-born mathematician of jewish descent and a professor emeritus at the university of washington in seattle. he received his ph.d. in 1957 from hebrew university of jerusalem in israel.
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635957ea6dfd7796face1727f8817207cd422e31
in 1976 grünbaum won a lester r. ford
in 1976 grünbaum won a lester r. ford award for his expository article venn diagrams and independent families of sets. in 2004, gil kalai and victor klee edited a special issue of discrete and computational geometry in his honor, the "grünbaum festschrift". in 2005, grünbaum was awarded the leroy p. steele prize for ma...
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778eda38e739a2fff229e9bd3b5a2073c0452170
grünbaum's classic monograph convex polytopes, first published in
grünbaum's classic monograph convex polytopes, first published in 1967, became the main textbook on the subject. his monograph tilings and patterns, coauthored with g. c. shephard, helped to rejuvenate interest in this classic field, and has proved popular with nonmathematical audiences, as well as with mathematicians.
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dde9737d9c3c4312bb9e73883a4d1a224c0d3797
his paper on line arrangements may have inspired
his paper on line arrangements may have inspired a paper by n. g. de bruijn on quasiperiodic tilings (the most famous example of which is the penrose tiling of the plane). this paper is also cited by the authors of a monograph on hyperplane arrangements as having inspired their research.
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2d869126d24c5bce5d87668c7cbf6305069db68a
grünbaum remained affiliated with the hebrew university until
grünbaum remained affiliated with the hebrew university until 1966, taking long research visits to the university of washington and in 1965–1966 to michigan state university. however, during the michigan visit, learning of another case similar to their marriage annulment, he and zdenka decided to stay in the us instead...
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c52d713cdec45557363d3abc26a2f013d55cfe74
after finishing his military service in 1958, grünbaum
after finishing his military service in 1958, grünbaum and his family came to the us so that grünbaum could become a postdoctoral researcher at the institute for advanced study. he then became a visiting researcher at the university of washington in 1960. he agreed to return to israel as a lecturer at the hebrew univer...
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ba730828329606a57096ff321580470b93be89df
in israel, grünbaum found a job in tel
in israel, grünbaum found a job in tel aviv, but in 1950 returned to the study of mathematics, at the hebrew university of jerusalem. he earned a master's degree in 1954 and in the same year married zdenka, who continued as a master's student in chemistry. he served a tour of duty as an operations researcher in the isr...
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c38e5473372a18a45cf4bfb0132634afd3e0fbad
grünbaum was born in osijek, then part of
grünbaum was born in osijek, then part of the kingdom of yugoslavia, on 2 october 1929. his father was jewish and his mother was catholic, so during world war ii the family survived the holocaust by living at his catholic grandmother's home. after the war, as a high school student, he met zdenka bienenstock, a jew who ...
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c28a10b98ff481658a3604d7f7544d9a121c26f4
branko grünbaum (hebrew: ברנקו גרונבאום; 2 october 1929
branko grünbaum (hebrew: ברנקו גרונבאום; 2 october 1929 – 14 september 2018) was a croatian-born mathematician of jewish descent and a professor emeritus at the university of washington in seattle. he received his ph.d. in 1957 from hebrew university of jerusalem in israel.
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49553a05860ff0431b88d8710971858cfc42aa32
joseph hector "hec" lépine was a canadian professional
joseph hector "hec" lépine was a canadian professional ice hockey forward who played 33 games in the national hockey league for the montreal canadiens during the 1925–26 season. the rest of his career, which lasted from 1917 to 1927, was spent in minor leagues. he was born in sainte-anne-de-bellevue, quebec. hector is ...
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3e7394c1310019f7fa984daead0bb76ddeb835c4
joseph hector "hec" lépine (december 7, 1897 —
joseph hector "hec" lépine (december 7, 1897 — march 29, 1951) was a canadian professional ice hockey forward who played 33 games in the national hockey league for the montreal canadiens during the 1925–26 season. the rest of his career, which lasted from 1917 to 1927, was spent in minor leagues. he was born in sainte-...
wikipedia
44dc5fa18dbfa19075c0752aabbf75f8e9acf86c
in mathematics, a higher spin alternating sign matrix
in mathematics, a higher spin alternating sign matrix is a generalisation of the alternating sign matrix (asm), where the columns and rows sum to an integer r rather than simply summing to 1 as in the usual alternating sign matrix definition. hsasms are square matrices whose elements may be integers in the range −r to ...
wikipedia
45fa579977c9c3c3ea91a8cbe0981ace5b2aa0dd
in mathematics, a higher spin alternating sign matrix
in mathematics, a higher spin alternating sign matrix is a generalisation of the alternating sign matrix (asm), where the columns and rows sum to an integer r (the spin) rather than simply summing to 1 as in the usual alternating sign matrix definition. hsasms are square matrices whose elements may be integers in the r...
wikipedia
9a6b01a9da74fed65627038dd17f4ec0232fb617
smith joined convair in 1941, working extensively in
smith joined convair in 1941, working extensively in the area of fatigue with a focus on aluminum aircraft structures. he contributed work on fatigue in support of the us air force, us navy, and nasa. smith was an early adopter of photoelasticity to determining stress concentrations due to notches, corner fillets, and ...
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867c43833bf575bb1c4f6936c4481aba61120de8
assuming that the bully algorithm messages are of
assuming that the bully algorithm messages are of a fixed (known, invariant) sizes, the most number of messages are exchanged in the group when the process with the lowest id initiates an election. this process sends (n−1) election messages, the next higher id sends (n−2) messages, and so on, resulting in Θ (n 2) {\dis...
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2641415f02bed88549d205eedccf6f9fb4a5b03e
liveness is also guaranteed in the synchronous, crash-recovery
liveness is also guaranteed in the synchronous, crash-recovery model. consider the would-be leader failing after sending an answer (alive) message but before sending a coordinator (victory) message. if it does not recover before the set timeout on lower id processes, one of them will become leader eventually (even if s...
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d4e1b6ce6bf8584eea17c438a4524023e0a9d435
the safety property expected of leader election protocols
the safety property expected of leader election protocols is that every non-faulty process either elects a process q, or elects none at all. note that all processes that elect a leader must decide on the same process q as the leader. the bully algorithm satisfies this property (under the system model specified), and at...
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e8f9005ca67c41b7944a2ef735f771e280fa4fc3
in public key cryptography, a certificate may be
in public key cryptography, a certificate may be revoked before it expires, which signals that it is no longer valid. without revocation, an attacker could exploit such a compromised or misissued certificate until expiry. hence, revocation is an important part of a public key infrastructure. revocation is performed by ...
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50a3e0e888b996fd1685e5ba2c08fa242ebf299b
private information retrieval techniques can allay the privacy
private information retrieval techniques can allay the privacy concern with pull-based checks. rather than clients performing revocation checks, a middlebox could instead, centralising the cost of revocation checking and amortising it across many connections; the clients need to dedicate no storage to revocation inform...
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e2a2e911b30ef637e4ffda8bef4a56fae7f8c526
let's revoke has not yet been widely deployed.
let's revoke has not yet been widely deployed. besides client implementations, it requires cas to make operational changes, and does not provide as much information as crls or ocsp (only a bit per certificate for validity); crls or ocsp may still be used to supplement let's revoke and provide that additional informatio...
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d2531fc0e3c5779ce4088a2af6f95d03c6bd2d00
crvs are expected to be small enough to
crvs are expected to be small enough to enable push-based checking, but more constrained clients may still perform pull-based checks, only accessing select crvs, or deferring retrieval of crvs until certificate validation. a client using let's revoke with push-based checking is able to fail-hard for any certificate wit...
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5904392da925f7946be335f0e38b05573f7387fb
let's revoke uses bit vectors of revocation statuses
let's revoke uses bit vectors of revocation statuses (called certificate revocation vectors, or crvs) to allow large amounts of revocation statuses to be efficiently retrieved by clients. cas generate crvs for their own certificates, with one crv per expiration date. crv maintenance for cas is linear in the number of c...
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8b6ebb64acd1f9d324bf4b86d1d682745ab4115c
crlite has not yet been widely deployed. it
crlite has not yet been widely deployed. it is, however, deployable, only requiring an aggregator to retrieve crls from cas and then provide the filter cascade and updates to it, and for clients to use it; no action from cas is needed, and nor is any needed from certificate holders. the aggregator does not need to be a...
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9034c76e3bdb831778843e9e91a24648738ddb9e
the revocation status of all certificates in the
the revocation status of all certificates in the web pki in january was estimated to be 10 mb in size when using the bloom filter cascade, with updates of 580 kb per day. in march 2018, this had grown to 18 mb. in a simulation with 100 million certificates, a 1% daily expiration rate, and a 2% revocation rate, crlite r...
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50186713fe28a7ec93fc77c19e2b024c4aa0c015
crlite provides revocation statuses by a cascade of
crlite provides revocation statuses by a cascade of bloom filters. a single filter constructed from a list of revoked certificates produces false positives. with an open domain, this is an insuperable problem for revocation checking. however, by using certificate transparency to enumerate all unexpired certificates, an...
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a30e933c9a15ab36aafcb8542a178551e982d5b5
beyond clients and cas enabling stapling and the
beyond clients and cas enabling stapling and the must-staple extension, server administrators must also take action to support stapling by regularly retrieving responses and then providing them to clients during the handshake. in 2018, only firefox supported must-staple, and neither of the two most-used web servers (ap...
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8d2f370bbbca47faf4b8bb1e5bcf940460c40695
ocsp stapling can solve the operational challenges of
ocsp stapling can solve the operational challenges of ocsp, namely additional network requests causing latency and privacy degradation. however, it can be susceptible to downgrade attacks by an on-path attacker. rfc 7633 defines an extension that embeds a requirement into a certificate to be stapled to a valid ocsp res...
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22e892fd5c625c6075f0f6828ee03f26e4fb5991
a 2018 study found that 1.7% of requests
a 2018 study found that 1.7% of requests to responders were unavailable at the network level, and a further c. 2% produced unusable ocsp responses, with significant hetereogeneity across cas and client vantage points.
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6bdf1916ea6b68082753ea89d2345d6bbcc82294
as requests to the responder are made in
as requests to the responder are made in response to users' browsing, ocsp responders can learn about the users' browsing, which is a privacy issue. it also introduces latency to connections, as the responder must be queried before a new connection can be used.
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b40e9f4189fea075c7e1a453e46aeb47ae9bbfe3
ocsp suffers from scalability issues. it relies on
ocsp suffers from scalability issues. it relies on the client having network access at the time of checking the certificate's revocation status; further, the ocsp responder must be accessible and produce usable responses, or else the check will fail and the client must choose between failing-soft and failing-hard. many...
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9fae1769b0ea55e0de9aa675aa8e4fcecb41697d
the online certificate status protocol (ocsp) allows clients
the online certificate status protocol (ocsp) allows clients to interactively ask a server (an ocsp responder) about a certificate's status, receiving a response that is cryptographically authenticated by the issuing ca. it was designed to address issues with crls. a typical ocsp response is less than 1 kb.
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4a88121f133d39af7c4c11cb81045edde35d7753
a crl contains information about all of the
a crl contains information about all of the certificates revoked by a ca, which means distributors and clients must incur transfer costs for information that is likely irrelevant. a 2015 study found that the median certificate had a crl with size 51 kb, and the largest crl was 76 mb.
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0a127234508b18e3d8237585d508d836947fd4b1
push-based checking is less bandwidth efficient than pull-based
push-based checking is less bandwidth efficient than pull-based checking, but gains availability and privacy. different methods may be used on a certificate-by-certificate basis, allowing for fine-tuning the trade-off: both google chrome and mozilla firefox perform push-based checks on a small set of critical certifica...
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1a593d68cbed665fcfb5a7cc9263e8249c22c6db
there are three broad architectures for how clients
there are three broad architectures for how clients access revocation status: pull-based, where clients retrieve revocation status at validation time; push-based, where clients retrieve revocation status ahead of validation and cache it; and network-assisted, where revocation checking is tightly integrated with the tls...
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8b4e415815bf0522677f01eeb89283ce34bffbe2
a revocation status distribution that places heavy burdens
a revocation status distribution that places heavy burdens on cas may not succeed, especially if the ca is unable to derive countervailing benefits from implementation. reducing the number of parties that must make changes to adopt it also eases deployability: potentially involved are cas, clients, server administrator...
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17d8398a3e72be9da9f18f5865a9374bdd58da28
if revocation status is not freshly retrieved for
if revocation status is not freshly retrieved for every check (e.g., due to caching or periodic retrievals), there is a delay between a certificate being revoked and all clients being guaranteed to be aware of the revocation. this presents a trade-off between latency, efficiency, and security: longer cache times or les...
wikipedia