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Search Results: 1 - 10 of 191777 matches for " D. Rudolph "
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Lamsiekte (botulism): Solving the aetiology riddle
Rudolph D. Bigalke
Journal of the South African Veterinary Association , 2012,
Abstract: The reason or reasons why it took Sir Arnold Theiler so many years to unravel the riddle of the aetiology of lamsiekte in cattle and whether P.R. Viljoen’s lifelong grudge for receiving insufficient credit from Theiler for his research contribution was justified are analysed in this paper. By 1912, Theiler knew that Duncan Hutcheon had advocated the use of bonemeal as a prophylactic against the disease in the early 1880s. Hutcheon’s colleague, J.D. Borthwick, had shown conclusively in a field experiment in 1895 that lamsiekte did not occur in cattle fed a liberal allowance of bonemeal; and bone-craving had been identified by Hutcheon and several farmers as being associated with the occurrence of the disease (a ‘premonitory’ sign). Hutcheon regarded a phosphate deficiency of the pastures as the direct cause of lamsiekte. However, Theiler did not accept this, was convinced that intoxication was involved and developed a ‘grass toxin’ theory. Viljoen (1918) also latched onto the grass toxin theory. He did not believe that osteophagia existed, stating categorically that he had not observed it on the experimental farm Armoedsvlakte where > 100 cases of lamsiekte had occurred during the > 3 years that he spent there. Moreover, he did not believe in the prophylactic value of bonemeal. However, careful analysis of a subsequent publication, of which he was a co-author, revealed that in late 1918 and early 1919 he reproduced the disease by drenching cattle with blowfly pupae and larvae as well as with crushed bones from decomposing bovine carcasses. For this breakthrough he did not get proper credit from Theiler. Reappointed to study lamsiekte on Armoedsvlakte in the autumn of 1919, Theiler, probably already aware that the toxin he was seeking was in the decomposing bones or carcass material rather than the grass, deliberately ‘walked with the cattle’ on the farm to encounter a classic manifestation of bone-craving (osteophagia). The penny then immediately dropped. Theiler, actually rationalising an hypothesis that was about four decades old, did so with a vengeance. Within less than two years he had reproduced lamsiekte by exposing cattle with natural bone-craving to rotten carcass material, had chemical proof that the grazing was phosphorus-deficient, had developed a satisfactory bonemeal prophylactic dosage programme, and the bacterial toxin concerned – perhaps the trickiest contribution – had been produced in culture. Hence the table was set for the later development of an excellent lamsiekte vaccine.
Distance- versus patch-based movements of woodland caribou during spring dispersion in northern Quebec
Tyler D. Rudolph et al.
Rangifer , 2011,
The trade-offs of emotional reactivity for youths' social information processing in the context of maternal depression
Megan Flynn,Karen D. Rudolph
Frontiers in Integrative Neuroscience , 2012, DOI: 10.3389/fnint.2012.00043
Abstract: Although research demonstrates that emotional experiences can influence cognitive processing, little is known about individual differences in this association, particularly in youth. The present study examined how the emotional backdrop of the caregiving environment, as reflected in exposure to maternal depression and anxiety, was linked to biases in youths' cognitive processing of mother-referent information. Further, we investigated whether this association differed according to variation in youths' emotional reactivity to stress. Youth (50 boys, 46 girls; M age = 12.36, SD = 1.05) completed a behavioral task assessing cognitive bias. Semi-structured interviews were administered to assess (a) youths' emotional reactivity to naturally occurring stressors, and (b) maternal depression and anxiety. Hierarchical multiple regression analyses revealed that emotional reactivity to interpersonal stressors moderated the linkage between maternal depression and cognitive bias such that maternal depression predicted a greater negative bias in youth exhibiting high and average, but not low, levels of emotional reactivity. At low levels of maternal depression, youth with heightened interpersonal emotional reactivity showed a greater positive cognitive bias. This pattern of effects was specific to interpersonal (but not non-interpersonal) emotional reactivity and to maternal depression (but not anxiety). These findings illuminate one personal characteristic of youth that moderates emotion-cognition linkages, and reveal that emotional reactivity both enhances and impairs youths' cognitive processing as a function of socialization context.
Polynomial super-gl(n) algebras
P. D. Jarvis,G. Rudolph
Physics , 2003, DOI: 10.1088/0305-4470/36/20/311
Abstract: We introduce a class of finite dimensional nonlinear superalgebras $L = L_{\bar{0}} + L_{\bar{1}}$ providing gradings of $L_{\bar{0}} = gl(n) \simeq sl(n) + gl(1)$. Odd generators close by anticommutation on polynomials (of degree $>1$) in the $gl(n)$ generators. Specifically, we investigate `type I' super-$gl(n)$ algebras, having odd generators transforming in a single irreducible representation of $gl(n)$ together with its contragredient. Admissible structure constants are discussed in terms of available $gl(n)$ couplings, and various special cases and candidate superalgebras are identified and exemplified via concrete oscillator constructions. For the case of the $n$-dimensional defining representation, with odd generators $Q_{a}, \bar{Q}{}^{b}$, and even generators ${E^{a}}_{b}$, $a,b = 1,...,n$, a three parameter family of quadratic super-$gl(n)$ algebras (deformations of $sl(n/1)$) is defined. In general, additional covariant Serre-type conditions are imposed, in order that the Jacobi identities be fulfilled. For these quadratic super-$gl(n)$ algebras, the construction of Kac modules, and conditions for atypicality, are briefly considered. Applications in quantum field theory, including Hamiltonian lattice QCD and space-time supersymmetry, are discussed.
A simple nearest-neighbor two-body Hamiltonian system for which the ground state is a universal resource for quantum computation
Stephen D. Bartlett,Terry Rudolph
Physics , 2006, DOI: 10.1103/PhysRevA.74.040302
Abstract: We present a simple quantum many-body system - a two-dimensional lattice of qubits with a Hamiltonian composed of nearest-neighbor two-body interactions - such that the ground state is a universal resource for quantum computation using single-qubit measurements. This ground state approximates a cluster state that is encoded into a larger number of physical qubits. The Hamiltonian we use is motivated by the projected entangled pair states, which provide a transparent mechanism to produce such approximate encoded cluster states on square or other lattice structures (as well as a variety of other quantum states) as the ground state. We show that the error in this approximation takes the form of independent errors on bonds occurring with a fixed probability. The energy gap of such a system, which in part determines its usefulness for quantum computation, is shown to be independent of the size of the lattice. In addition, we show that the scaling of this energy gap in terms of the coupling constants of the Hamiltonian is directly determined by the lattice geometry. As a result, the approximate encoded cluster state obtained on a hexagonal lattice (a resource that is also universal for quantum computation) can be shown to have a larger energy gap than one on a square lattice with an equivalent Hamiltonian.
Die Behandlung von lteren Patienten mit benignen oder malignen Hirntumoren
Krex D,Rudolph K,Schackert G
Journal für Neurologie, Neurochirurgie und Psychiatrie , 2011,
Abstract: Der demographische Wandel spiegelt sich zunehmend in unserem klinischen Alltag wider. Der Anteil an alten Patienten wird auch in der Neurochirurgie stetig gr er. Menschen jenseits des 65. Lebensjahres wurden bisher nur vereinzelt in klinischen Studien berücksichtigt, sodass die Datenlage zu evidenzbasierten Therapieempfehlungen dieser Altersgruppe entsprechend dürftig ist. Die vorliegende retrospektive Analyse besch ftigt sich mit der Frage, ob bei Patienten jenseits des 75. Lebensjahres mit einem Glioblastom oder einem Meningeom generell die gleiche operative und adjuvante Therapie angewendet werden sollte wie bei jüngeren Patienten, und ob h ufiger oder schwerwiegendere Komplikationen in dieser Altersgruppe auftreten. 105 Patienten mit Glioblastomen oder Meningeomen 75 Jahre wurden 97 Patienten mit gleichen Diagnosen und einem Alter 50 Jahre gegenübergestellt. Der Allgemein- und neurologische Zustand war bei den lteren initial schlechter als bei den Jüngeren. Die OP-assoziierten Komplikationen waren in beiden Gruppen gleich verteilt. Auff llig war jedoch ein erh hter Anteil an Patienten mit Antriebs- und Hirnleistungsst rungen in der Gruppe der 75-J hrigen, was zu einer vorübergehenden Pflegebedürftigkeit führte. Maligne Gliome wurden bei den lteren deutlich weniger adjuvant behandelt und das überleben war in dieser Gruppe signifikant schlechter. Daraus resultiert, dass auch alte Patienten mit malignen Gliomen oder Meningeomen in gleichem Ma e neurochirurgisch behandelt werden sollten wie jüngere Patienten. Auch sollte über eine intensivere adjuvante Therapie nachgedacht werden, um das überleben zu verbessern, was aber letztlich in klinischen Studien beurteilt werden muss, die auch diese Altersgruppe berücksichtigen.
Homogeneous decoherence functionals in standard and history quantum mechanics
Oliver Rudolph,J. D. M. Wright
Physics , 1998, DOI: 10.1007/s002200050645
Abstract: General history quantum theories are quantum theories without a globally defined notion of time. Decoherence functionals represent the states in the history approach and are defined as certain bivariate complex-valued functionals on the space of all histories. However, in practical situations -- for instance in the history formulation of standard quantum mechanics -- there often is a global time direction and the homogeneous decoherence functionals are specified by their values on the subspace of homogeneous histories. In this work we study the analytic properties of (i) the standard decoherence functional in the history version of standard quantum mechanics and (ii) homogeneous decoherence functionals in general history theories. We restrict ourselves to the situation where the space of histories is given by the lattice of projections on some Hilbert space H. Among other things we prove the non-existence of a finitely valued extension for the standard decoherence functional to the space of all histories, derive a representation for the standard decoherence functional as an unbounded quadratic form with a natural representation on a Hilbert space and prove the existence of an Isham-Linden-Schreckenberg (ILS) type representation for the standard decoherence functional.
How good must single photon sources and detectors be for efficient linear optical quantum computation?
M. Varnava,D. E. Browne,T. Rudolph
Physics , 2007, DOI: 10.1103/PhysRevLett.100.060502
Abstract: We present a scheme for linear optical quantum computation (LOQC) which is highly robust to imperfect single photon sources and inefficient detectors. In particular we show that if the product of the detector efficiency with the source efficiency is greater than 2/3, then efficient LOQC is possible. This threshold is many orders of magnitude more relaxed than those which could be inferred by application of standard results in fault tolerance. The result is achieved within the cluster state paradigm for quantum computation.
On unentangled Gleason theorems for quantum information theory
Oliver Rudolph,J. D. M. Wright
Physics , 2000,
Abstract: It is shown here that a strengthening of Wallach's Unentangled Gleason Theorem can be obtained by applying results of the present authors on generalised Gleason theorems for quantum multi-measures arising from investigations of quantum decoherence functionals.
On Tracial Operator Representations of Quantum Decoherence Functionals
Oliver Rudolph,J. D. Maitland Wright
Physics , 1997, DOI: 10.1063/1.532157
Abstract: A general `quantum history theory' can be characterised by the space of histories and by the space of decoherence functionals. In this note we consider the situation where the space of histories is given by the lattice of projection operators on an infinite dimensional Hilbert space $H$. We study operator representations for decoherence functionals on this space of histories. We first give necessary and sufficient conditions for a decoherence functional being representable by a trace class operator on $H \otimes H$, an infinite dimensional analogue of the Isham-Linden-Schreckenberg representation for finite dimensions. Since this excludes many decoherence functionals of physical interest, we then identify the large and physically important class of decoherence functionals which can be represented, canonically, by bounded operators on $H \otimes H$.
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