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Search Results: 1 - 10 of 462460 matches for " Royal A; Mel DeJarnette "
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Bull spermatozoa express receptors for platelet-activating factor
Bosch,Pablo; Roudebush,William E; McGraw,Royal A; Mel DeJarnette,J; Marshall,Clifton E; Massey,Joe B; Brackett,Benjamin G;
Revista Científica , 2009,
Abstract: platelet-activating factor (paf; 1-o-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is a ubiquitous phospholipid that is implicated in the mediation of a wide variety of reproductive processes. to better understand the role of paf in bovine reproduction, it was designed experiments to: (a) determine whether bull spermatozoa express receptors for paf and (b) study the effect of exogenous paf on in vitro sperm physiology (i.e., capacitation, acrosome reaction, motility, and fertilizing ability). bull sperm express paf receptor as determined by two approaches: rt-pcr and immunofluorescence. however, exposure of spermatozoa to different concentrations of exogenous paf (10-11-10-6 m) did not affect capacitation, acrosome reaction or motility. consistent with these findings, coculture of gametes in medium containing increasing concentrations of paf (1 x 10-8-8 x 10-6 m) did not improve in vitro fertilization outcome as measured by percentage of inseminated oocytes reaching 2-cell stage 48 h after fertilization. in contrast, paf at 8 x 10-6 m concentration significantly inhibited ivf. in conclusion, although bull sperm have paf receptors, exposure of bull spermatozoa to exogenous paf failed to enhance the sperm function parameters measured in this study. additional studies are warranted to elucidate the biological role of paf on bull spermatozoa.
Polishing compound residues in gold jewellery alloys
Helen Royal
Gold Bulletin , 1989, DOI: 10.1007/BF03214706
Abstract: The assaying of gold jewellery before hallmarking is generally carried out on samples scraped from the surface. But the assay result may not necessarily be representative of the bulk composition. Analyses reported here have shown the presence of polishing compound residues on, and just below, the surface of some of the jewellery tested.
Quantum Analogical Modeling: A General Quantum Computing Algorithm for Predicting Language Behavior
Royal Skousen
Physics , 2005,
Abstract: This paper proposes a general quantum algorithm that can be applied to any classical computer program. Each computational step is written using reversible operators, but the operators remain classical in that the qubits take on values of only zero and one. This classical restriction on the quantum states allows the copying of qubits, a necessary requirement for doing general classical computation. Parallel processing of the quantum algorithm proceeds because of the superpositioning of qubits, the only aspect of the algorithm that is strictly quantum mechanical. Measurement of the system collapses the superposition, leaving only one state that can be observed. In most instances, the loss of information as a result of measurement would be unacceptable. But the linguistically motivated theory of Analogical Modeling (AM) proposes that the probabilistic nature of language behavior can be accurately modeled in terms of the simultaneous analysis of all possible contexts (referred to as supracontexts) providing one selects a single supracontext from those supracontexts that are homogeneous in behavior (namely, supracontexts that allow no increase in uncertainty). The amplitude for each homogeneous supracontext is proportional to its frequency of occurrence, with the result that the probability of selecting one particular supracontext to predict the behavior of the system is proportional to the square of its frequency.
Quantum Analogical Modeling with Homogeneous Pointers
Royal Skousen
Physics , 2010,
Abstract: Quantum Analogical Modeling (QAM) works under the assumption that the correct exemplar-based description for a system of behavior minimizes the overall uncertainty of the system. The measure used in QAM differs from the traditional logarithmic measure of uncertainty; instead QAM uses a quadratic measure of disagreement between pairs of exemplars. (This quadratic measure parallels the squaring function holding between the amplitude and the probability for a state function in quantum mechanics.) QAM eliminates all supracontexts (contextual groupings of exemplars) that fail to minimize the number of disagreements. The resulting system thus distinguishes between homogeneous and heterogeneous supracontexts and uses only exemplars in homogeneous supracontexts to predict behavior. This paper revises earlier work on QAM (in 2005) by showing that homogeneity for a supracontext can be most simply determined by discovering whether there are any heterogeneous pointers between any of the supracontext's exemplars. A pointer for a pair of exemplars is heterogeneous whenever those two exemplars are found in different subcontexts of the supracontext and take different outcomes.
Analogical Modeling and Quantum Computing
Royal Skousen
Physics , 2000,
Abstract: This paper serves as a bridge between quantum computing and analogical modeling (a general theory for predicting categories of behavior in varying contexts). Since its formulation in the early 1980s, analogical modeling has been successfully applied to a variety of problems in language. Several striking similarities between quantum mechanics and analogical modeling have recently been noted: (1) traditional statistics can be derived from a non-statistical basis by assuming data occurrences are accessed through a spin-up state (given two equally probable quantum states, spin-up and spin-down); (2) the probability of predicting a particular outcome is determined by the squaring of an underlying linear measure and is the result of decoherence (which occurs when a quantum system is observed); and (3) a natural measure of certainty (called the agreement) is based on one chance of guessing the right outcome and corresponds to the integrated squaring of Schroedinger's wave equation. Analogical modeling considers all possible combiantions of a given context of n variables, which is classical terms leads to an exponential explosion on the order of 2**n. This paper proposes a quantum computational solution to this exponentiality by applying a cycle of reversible quantum operators to all 2**n possibilities, thus reducing the time and space of analogical modeling to a polynomial order.
Dynamics of 2D pancake vortices in layered superconductors
A. S. Mel'nikov
Physics , 1995, DOI: 10.1103/PhysRevB.53.449
Abstract: The dynamics of 2D pancake vortices in Josephson-coupled superconducting/normal - metal multilayers is considered within the time-dependent Ginzburg-Landau theory. For temperatures close to $T_{c}$ a viscous drag force acting on a moving 2D vortex is shown to depend strongly on the conductivity of normal metal layers. For a tilted vortex line consisting of 2D vortices the equation of viscous motion in the presence of a transport current parallel to the layers is obtained. The specific structure of the vortex line core leads to a new dynamic behavior and to substantial deviations from the Bardeen-Stephen theory. The viscosity coefficient is found to depend essentially on the angle $\gamma$ between the magnetic field ${\bf B}$ and the ${\bf c}$ axis normal to the layers. For field orientations close to the layers the nonlinear effects in the vortex motion appear even for slowly moving vortex lines (when the in-plane transport current is much smaller than the Ginzburg-Landau critical current). In this nonlinear regime the viscosity coefficient depends logarithmically on the vortex velocity $V$.
Inertial Mass and Viscosity of Tilted Vortex Lines in Layered Superconductors
A. S. Mel'nikov
Physics , 1996, DOI: 10.1103/PhysRevLett.77.2786
Abstract: The dynamics of tilted vortex lines in Josephson-coupled layered superconductors is considered within the time-dependent Ginzburg-Landau theory. The frequency and angular dependences of the complex-valued vortex mobility $\mu$ are studied. The components of the viscosity and inertial mass tensors are found to increase essentially for magnetic field orientations close to the layers. For superconducting/normal metal multilayers the frequency ($\omega$) range is shown to exist where the $\mu^{-1}$ value depends logarithmically on $\omega$.
Peculiar Features of the Velocity Field of OB Associations and the Spiral Structure of the Galaxy
A. M. Mel'nik
Physics , 2003, DOI: 10.1134/1.1573279
Abstract: Some of the peculiar features of the periodic velocity-field structure for OB associations can be explained by using the model of Roberts and Hausman (1984), in which the behavior of a system of dense clouds is considered in a perturbed potential. The absence of statistically significant variations in the azimuthal velocity across the Carina arm, probably, results from its sharp increase behind the shock front, which is easily blurred by distance errors. The existence of a shock wave in the spiral arms and, at the same time, the virtually free motion of OB associations in epicycles can be reconciled in the model of particle clouds with a mean free path of 0.2-2 kpc. The velocity field of OB associations exhibits two appreciable nonrandom deviations from an ideal spiral pattern: a 0.5-kpc displacement of the Cygnus- and Carina-arm fragments from one another and a weakening of the Perseus arm in quadrant III. However, the identified fragments of the Carina, Cygnus, and Perseus arms do not belong to any of the known types of spurs.
Theory of vortex lattice effects on STM spectra in d-wave superconductors
A. S. Mel'nikov
Physics , 1999, DOI: 10.1134/1.568343
Abstract: Theory of scanning tunneling spectroscopy of low energy quasiparticle (QP) states in vortex lattices of d-wave superconductors is developed taking account of the effects caused by an extremely large extension of QP wavefunctions in the nodal directions and the band structure in the QP spectrum. The oscillatory structures in STM spectra, which correspond to van Hove singularities are analysed. Theoretical calculations carried out for finite temperatures and scattering rates are compared with recent experimental data for high temperature cuprates.
Quasiparticle spectrum near the gap node directions in the mixed state of d-wave superconductors
A. S. Mel'nikov
Physics , 1998,
Abstract: We report on a calculation of the quantized energy spectrum and quasiparticle eigenfunctions for low lying excitations in the mixed state of clean d-wave superconductors. Our study is based on an approximate analytical solution of the Bogolubov-de Gennes equations for both rectangular and triangular flux lattices with one of the primitive translations chosen parallel to the gap node direction. For excitations with momenta close to a certain gap node we have obtained a set of eigenfunctions which appear to be extended along the chosen gap node direction and localized along the perpendicular one on a scale determined by the intervortex distance. The periodic superfluid velocity field induces a band structure in the spectrum, which depends essentially on the vortex lattice geometry.
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