The 16-vertex model and its even and odd 8-vertex subcases on the square lattice
NASA Astrophysics Data System (ADS)
Assis, Michael
2017-09-01
We survey and enlarge the known mappings of the 16-vertex model, with emphasis on mappings between the even and odd 8-vertex subcases of the general model, also giving new mappings between these models, valid on finite toroidal lattices. In particular, we find new mappings between the models by using their algebraic invariants with respect to the SL(2)× SL(2) symmetry of the 16-vertex model; we also find a larger set of weak-graph transformations. We show many examples of models with negative weights which map to models with only positive weights. Using the algebraic invariant relations of the even and odd 8-vertex models, we find the complete set of points in the complex field plane of the square lattice Ising model in a field which map to the even or odd 8-vertex models; these points also correspond to the set of free-fermionic points of the model. We do not find any new integrable points, but we find a new mapping between the odd 8-vertex model and the square lattice Ising model at magnetic field H= iπ/(2β) , valid on finite toroidal lattices. We also show directly through various examples that mappings via algebraic invariants do not fully exhaust the possible mappings a model may have with another model. We construct a new solution to the odd 8-vertex free-fermion model which is valid on the finite lattice, since the previous known solution resulted from a mapping valid only in the thermodynamic limit. Finally, we detail for the first time the phase transitions of the column staggered free-fermion 8-vertex model, and show that it can be mapped to the bi-partite staggered free-fermion model.
Vertex Models of Epithelial Morphogenesis
Fletcher, Alexander G.; Osterfield, Miriam; Baker, Ruth E.; Shvartsman, Stanislav Y.
2014-01-01
The dynamic behavior of epithelial cell sheets plays a central role during numerous developmental processes. Genetic and imaging studies of epithelial morphogenesis in a wide range of organisms have led to increasingly detailed mechanisms of cell sheet dynamics. Computational models offer a useful means by which to investigate and test these mechanisms, and have played a key role in the study of cell-cell interactions. A variety of modeling approaches can be used to simulate the balance of forces within an epithelial sheet. Vertex models are a class of such models that consider cells as individual objects, approximated by two-dimensional polygons representing cellular interfaces, in which each vertex moves in response to forces due to growth, interfacial tension, and pressure within each cell. Vertex models are used to study cellular processes within epithelia, including cell motility, adhesion, mitosis, and delamination. This review summarizes how vertex models have been used to provide insight into developmental processes and highlights current challenges in this area, including progressing these models from two to three dimensions and developing new tools for model validation. PMID:24896108
Quantum search on the two-dimensional lattice using the staggered model with Hamiltonians
NASA Astrophysics Data System (ADS)
Portugal, R.; Fernandes, T. D.
2017-04-01
Quantum search on the two-dimensional lattice with one marked vertex and cyclic boundary conditions is an important problem in the context of quantum algorithms with an interesting unfolding. It avails to test the ability of quantum walk models to provide efficient algorithms from the theoretical side and means to implement quantum walks in laboratories from the practical side. In this paper, we rigorously prove that the recent-proposed staggered quantum walk model provides an efficient quantum search on the two-dimensional lattice, if the reflection operators associated with the graph tessellations are used as Hamiltonians, which is an important theoretical result for validating the staggered model with Hamiltonians. Numerical results show that on the two-dimensional lattice staggered models without Hamiltonians are not as efficient as the one described in this paper and are, in fact, as slow as classical random-walk-based algorithms.
Quantum vertex model for reversible classical computing
NASA Astrophysics Data System (ADS)
Chamon, C.; Mucciolo, E. R.; Ruckenstein, A. E.; Yang, Z.-C.
2017-05-01
Mappings of classical computation onto statistical mechanics models have led to remarkable successes in addressing some complex computational problems. However, such mappings display thermodynamic phase transitions that may prevent reaching solution even for easy problems known to be solvable in polynomial time. Here we map universal reversible classical computations onto a planar vertex model that exhibits no bulk classical thermodynamic phase transition, independent of the computational circuit. Within our approach the solution of the computation is encoded in the ground state of the vertex model and its complexity is reflected in the dynamics of the relaxation of the system to its ground state. We use thermal annealing with and without `learning' to explore typical computational problems. We also construct a mapping of the vertex model into the Chimera architecture of the D-Wave machine, initiating an approach to reversible classical computation based on state-of-the-art implementations of quantum annealing.
Quantum vertex model for reversible classical computing.
Chamon, C; Mucciolo, E R; Ruckenstein, A E; Yang, Z-C
2017-05-12
Mappings of classical computation onto statistical mechanics models have led to remarkable successes in addressing some complex computational problems. However, such mappings display thermodynamic phase transitions that may prevent reaching solution even for easy problems known to be solvable in polynomial time. Here we map universal reversible classical computations onto a planar vertex model that exhibits no bulk classical thermodynamic phase transition, independent of the computational circuit. Within our approach the solution of the computation is encoded in the ground state of the vertex model and its complexity is reflected in the dynamics of the relaxation of the system to its ground state. We use thermal annealing with and without 'learning' to explore typical computational problems. We also construct a mapping of the vertex model into the Chimera architecture of the D-Wave machine, initiating an approach to reversible classical computation based on state-of-the-art implementations of quantum annealing.
Quantum vertex model for reversible classical computing
Chamon, C.; Mucciolo, E. R.; Ruckenstein, A. E.; Yang, Z.-C.
2017-01-01
Mappings of classical computation onto statistical mechanics models have led to remarkable successes in addressing some complex computational problems. However, such mappings display thermodynamic phase transitions that may prevent reaching solution even for easy problems known to be solvable in polynomial time. Here we map universal reversible classical computations onto a planar vertex model that exhibits no bulk classical thermodynamic phase transition, independent of the computational circuit. Within our approach the solution of the computation is encoded in the ground state of the vertex model and its complexity is reflected in the dynamics of the relaxation of the system to its ground state. We use thermal annealing with and without ‘learning' to explore typical computational problems. We also construct a mapping of the vertex model into the Chimera architecture of the D-Wave machine, initiating an approach to reversible classical computation based on state-of-the-art implementations of quantum annealing. PMID:28497790
A staggered-grid convolutional differentiator for elastic wave modelling
NASA Astrophysics Data System (ADS)
Sun, Weijia; Zhou, Binzhong; Fu, Li-Yun
2015-11-01
The computation of derivatives in governing partial differential equations is one of the most investigated subjects in the numerical simulation of physical wave propagation. An analytical staggered-grid convolutional differentiator (CD) for first-order velocity-stress elastic wave equations is derived in this paper by inverse Fourier transformation of the band-limited spectrum of a first derivative operator. A taper window function is used to truncate the infinite staggered-grid CD stencil. The truncated CD operator is almost as accurate as the analytical solution, and as efficient as the finite-difference (FD) method. The selection of window functions will influence the accuracy of the CD operator in wave simulation. We search for the optimal Gaussian windows for different order CDs by minimizing the spectral error of the derivative and comparing the windows with the normal Hanning window function for tapering the CD operators. It is found that the optimal Gaussian window appears to be similar to the Hanning window function for tapering the same CD operator. We investigate the accuracy of the windowed CD operator and the staggered-grid FD method with different orders. Compared to the conventional staggered-grid FD method, a short staggered-grid CD operator achieves an accuracy equivalent to that of a long FD operator, with lower computational costs. For example, an 8th order staggered-grid CD operator can achieve the same accuracy of a 16th order staggered-grid FD algorithm but with half of the computational resources and time required. Numerical examples from a homogeneous model and a crustal waveguide model are used to illustrate the superiority of the CD operators over the conventional staggered-grid FD operators for the simulation of wave propagations.
Random matrix model for QCD{sub 3} staggered fermions
Bialas, P.; Burda, Z.; Petersson, B.
2011-01-01
We show that the lowest part of the eigenvalue density of the staggered fermion operator in lattice QCD{sub 3} at small lattice coupling constant {beta} has exactly the same shape as in QCD{sub 4}. This observation is quite surprising, since universal properties of the QCD{sub 3} Dirac operator are expected to be described by a nonchiral matrix model. We show that this effect is related to the specific nature of the staggered fermion discretization and that the eigenvalue density evolves toward the nonchiral random matrix prediction when {beta} is increased and the continuum limit is approached. We propose a two-matrix model with one free parameter which interpolates between the two limits and very well mimics the pattern of evolution with {beta} of the eigenvalue density of the staggered fermion operator in QCD{sub 3}.
Artificial Spin-Ice and Vertex Models
NASA Astrophysics Data System (ADS)
Cugliandolo, Leticia F.
2017-01-01
In classical and quantum frustrated magnets the interactions in combination with the lattice structure impede the spins to order in optimal configurations at zero temperature. The theoretical interest in their classical realisations has been boosted by the artificial manufacture of materials with these properties, that are of flexible design. This note summarises work on the use of vertex models to study bidimensional spin-ices samples, done in collaboration with R. A. Borzi, M. V. Ferreyra, L. Foini, G. Gonnella, S. A. Grigera, P. Guruciaga, D. Levis, A. Pelizzola and M. Tarzia, in recent years. It is an invited contribution to a J. Stat. Mech. special issue dedicated to the memory of Leo P. Kadanoff.
Artificial Spin-Ice and Vertex Models
NASA Astrophysics Data System (ADS)
Cugliandolo, Leticia F.
2017-05-01
In classical and quantum frustrated magnets the interactions in combination with the lattice structure impede the spins to order in optimal configurations at zero temperature. The theoretical interest in their classical realisations has been boosted by the artificial manufacture of materials with these properties, that are of flexible design. This note summarises work on the use of vertex models to study bidimensional spin-ices samples, done in collaboration with R. A. Borzi, M. V. Ferreyra, L. Foini, G. Gonnella, S. A. Grigera, P. Guruciaga, D. Levis, A. Pelizzola and M. Tarzia, in recent years. It is an invited contribution to a J. Stat. Mech. special issue dedicated to the memory of Leo P. Kadanoff.
Dynamical Vertex Approximation for the Hubbard Model
NASA Astrophysics Data System (ADS)
Toschi, Alessandro
A full understanding of correlated electron systems in the physically relevant situations of three and two dimensions represents a challenge for the contemporary condensed matter theory. However, in the last years considerable progress has been achieved by means of increasingly more powerful quantum many-body algorithms, applied to the basic model for correlated electrons, the Hubbard Hamiltonian. Here, I will review the physics emerging from studies performed with the dynamical vertex approximation, which includes diagrammatic corrections to the local description of the dynamical mean field theory (DMFT). In particular, I will first discuss the phase diagram in three dimensions with a special focus on the commensurate and incommensurate magnetic phases, their (quantum) critical properties, and the impact of fluctuations on electronic lifetimes and spectral functions. In two dimensions, the effects of non-local fluctuations beyond DMFT grow enormously, determining the appearance of a low-temperature insulating behavior for all values of the interaction in the unfrustrated model: Here the prototypical features of the Mott-Hubbard metal-insulator transition, as well as the existence of magnetically ordered phases, are completely overwhelmed by antiferromagnetic fluctuations of exponentially large extension, in accordance with the Mermin-Wagner theorem. Eventually, by a fluctuation diagnostics analysis of cluster DMFT self-energies, the same magnetic fluctuations are identified as responsible for the pseudogap regime in the holed-doped frustrated case, with important implications for the theoretical modeling of the cuprate physics.
Superstring vertex operators in type IIB matrix model
Kitazawa, Yoshihisa; Nagaoka, Satoshi
2008-06-15
We clarify the relation between the vertex operators in type IIB matrix model and superstring. Green-Schwarz light-cone closed superstring theory is obtained from IIB matrix model on two-dimensional noncommutative backgrounds. Superstring vertex operators should be reproduced from those of IIB matrix model through this connection. Indeed, we confirm that supergravity vertex operators in IIB matrix model on the two-dimensional backgrounds reduce to those in superstring theory. Noncommutativity plays an important role in our identification. Through this correspondence, we can reproduce superstring scattering amplitudes from IIB matrix model.
Quark-gluon vertex model and lattice-QCD data
Bhagwat, M.S.; Tandy, P.C.
2004-11-01
A model for the dressed-quark-gluon vertex, at zero gluon momentum, is formed from a nonperturbative extension of the two Feynman diagrams that contribute at one loop in perturbation theory. The required input is an existing ladder-rainbow model Bethe-Salpeter kernel from an approach based on the Dyson-Schwinger equations; no new parameters are introduced. The model includes an Ansatz for the triple-gluon vertex. Two of the three vertex amplitudes from the model provide a pointwise description of the recent quenched-lattice-QCD data. An estimate of the effects of quenching is made.
Vertex models: from cell mechanics to tissue morphogenesis.
Alt, Silvanus; Ganguly, Poulami; Salbreux, Guillaume
2017-05-19
Tissue morphogenesis requires the collective, coordinated motion and deformation of a large number of cells. Vertex model simulations for tissue mechanics have been developed to bridge the scales between force generation at the cellular level and tissue deformation and flows. We review here various formulations of vertex models that have been proposed for describing tissues in two and three dimensions. We discuss a generic formulation using a virtual work differential, and we review applications of vertex models to biological morphogenetic processes. We also highlight recent efforts to obtain continuum theories of tissue mechanics, which are effective, coarse-grained descriptions of vertex models.This article is part of the themed issue 'Systems morphodynamics: understanding the development of tissue hardware'.
Vertex models: from cell mechanics to tissue morphogenesis
Alt, Silvanus; Ganguly, Poulami
2017-01-01
Tissue morphogenesis requires the collective, coordinated motion and deformation of a large number of cells. Vertex model simulations for tissue mechanics have been developed to bridge the scales between force generation at the cellular level and tissue deformation and flows. We review here various formulations of vertex models that have been proposed for describing tissues in two and three dimensions. We discuss a generic formulation using a virtual work differential, and we review applications of vertex models to biological morphogenetic processes. We also highlight recent efforts to obtain continuum theories of tissue mechanics, which are effective, coarse-grained descriptions of vertex models. This article is part of the themed issue ‘Systems morphodynamics: understanding the development of tissue hardware’. PMID:28348254
Compressibility enhancement in an almost staggered interacting Harper model
NASA Astrophysics Data System (ADS)
Friedman, Bat-el; Berkovits, Richard
2015-03-01
We discuss the compressibility in the almost staggered fermionic Harper model with repulsive interactions in the vicinity of half-filling. It has been shown by Kraus et al. [Phys. Rev. B 89, 161106(R) (2014)], 10.1103/PhysRevB.89.161106 that for spinless electrons and nearest neighbors electron-electron interactions the compressibility in the central band is enhanced by repulsive interactions. Here we would like to investigate the sensitivity of this conclusion to the spin degree of freedom and longer range interactions. We use the Hartree-Fock (HF) approximation, as well as the density matrix renormalization group (DMRG) calculation to evaluate the compressibility. In the almost staggered Harper model, the central energy band is essentially flat and separated from the other bands by a large gap and therefore, the HF approximation is rather accurate. In both cases the compressibility of the system is enhanced compared to the noninteracting case, although the enhancement is weaker due to the inclusion of Hubbard and longer ranged interactions. We also show that the entanglement entropy is suppressed when the compressibility of the system is enhanced.
Persistent current in an almost staggered Harper model
NASA Astrophysics Data System (ADS)
Vasserman, A.; Berkovits, R.
2015-08-01
In this paper we study the persistent current (PC) of a staggered Harper model, close to the half-filling. The Harper model is different than other one dimensional disordered systems which are always localized, since it is a quasi-periodic system with correlated disorder resulting in the fact that it can be in the metallic regime. Nevertheless, the PC for a wide range of parameters of the Harper model does not show typical metallic behavior, although the system is in the metallic regime. This is a result of the nature of the central band states, which are a hybridization of Gaussian states localized in superlattice points. When the superlattice is not commensurate with the system length, the PC behaves as an insulator. Thus even in the metallic regime a typical finite Harper model may exhibit a PC expected from an insulator.
Arrow-arrow correlations for the six-vertex model.
Falco, P
2013-09-01
The six-vertex model on a square lattice is "exactly solvable" because an exact formula for the free energy can be obtained by the Bethe ansatz. However, exact formulas for the correlations of local bulk observables, such as the orientation of the arrow at a given edge, are, in general, not available. In this Rapid Communication, we consider the isotropic "zero-field" six-vertex model at small Δ. We derive the long-distance asymptotic formula of arrow-arrow correlations, which display power law decays with one anomalous exponent. Our method is based on an interacting fermion representation of the six-vertex model and does not use any information obtained from the exact solution.
Three-dimensional vertex model for simulating multicellular morphogenesis
Okuda, Satoru; Inoue, Yasuhiro; Adachi, Taiji
2015-01-01
During morphogenesis, various cellular activities are spatiotemporally coordinated on the protein regulatory background to construct the complicated, three-dimensional (3D) structures of organs. Computational simulations using 3D vertex models have been the focus of efforts to approach the mechanisms underlying 3D multicellular constructions, such as dynamics of the 3D monolayer or multilayer cell sheet like epithelia as well as the 3D compacted cell aggregate, including dynamic changes in layer structures. 3D vertex models enable the quantitative simulation of multicellular morphogenesis on the basis of single-cell mechanics, with complete control of various cellular activities such as cell contraction, growth, rearrangement, division, and death. This review describes the general use of the 3D vertex model, along with its applications to several simplified problems of developmental phenomena. PMID:27493850
Network Unfolding Map by Vertex-Edge Dynamics Modeling.
Verri, Filipe Alves Neto; Urio, Paulo Roberto; Zhao, Liang
2016-11-29
The emergence of collective dynamics in neural networks is a mechanism of the animal and human brain for information processing. In this paper, we develop a computational technique using distributed processing elements in a complex network, which are called particles, to solve semisupervised learning problems. Three actions govern the particles' dynamics: generation, walking, and absorption. Labeled vertices generate new particles that compete against rival particles for edge domination. Active particles randomly walk in the network until they are absorbed by either a rival vertex or an edge currently dominated by rival particles. The result from the model evolution consists of sets of edges arranged by the label dominance. Each set tends to form a connected subnetwork to represent a data class. Although the intrinsic dynamics of the model is a stochastic one, we prove that there exists a deterministic version with largely reduced computational complexity; specifically, with linear growth. Furthermore, the edge domination process corresponds to an unfolding map in such way that edges "stretch" and "shrink" according to the vertex-edge dynamics. Consequently, the unfolding effect summarizes the relevant relationships between vertices and the uncovered data classes. The proposed model captures important details of connectivity patterns over the vertex-edge dynamics evolution, in contrast to the previous approaches, which focused on only vertex or only edge dynamics. Computer simulations reveal that the new model can identify nonlinear features in both real and artificial data, including boundaries between distinct classes and overlapping structures of data.
Integrability of Limit Shapes of the Six Vertex Model
NASA Astrophysics Data System (ADS)
Reshetikhin, Nicolai; Sridhar, Ananth
2017-09-01
The main result of this paper is the construction of infinitely many conserved quantities (corresponding to commuting transfer-matrices) for the limit shape equation for the six vertex model on a cylinder. This suggests that the limit shape equation is an integrable PDE with gradient constraints. At the free fermionic point this equation becomes the complex Burgers equation.
3-state Hamiltonians associated to solvable 33-vertex models
NASA Astrophysics Data System (ADS)
Crampé, N.; Frappat, L.; Ragoucy, E.; Vanicat, M.
2016-09-01
Using the nested coordinate Bethe ansatz, we study 3-state Hamiltonians with 33 non-vanishing entries, or 33-vertex models, where only one global charge with degenerate eigenvalues exists and each site possesses three internal degrees of freedom. In the context of Markovian processes, they correspond to diffusing particles with two possible internal states which may be exchanged during the diffusion (transmutation). The first step of the nested coordinate Bethe ansatz is performed providing the eigenvalues in terms of rapidities. We give the constraints ensuring the consistency of the computations. These rapidities also satisfy Bethe equations involving 4 × 4 R-matrices, solutions of the Yang-Baxter equation which implies new constraints on the models. We solve them allowing us to list all the solvable 33-vertex models.
Six-vertex model and Schramm-Loewner evolution
NASA Astrophysics Data System (ADS)
Kenyon, Richard; Miller, Jason; Sheffield, Scott; Wilson, David B.
2017-05-01
Square ice is a statistical mechanics model for two-dimensional ice, widely believed to have a conformally invariant scaling limit. We associate a Peano (space-filling) curve to a square ice configuration, and more generally to a so-called six-vertex model configuration, and argue that its scaling limit is a space-filling version of the random fractal curve SL E κ, Schramm-Loewner evolution with parameter κ , where 4 <κ ≤12 +8 √{2 } . For square ice, κ =12 . At the "free-fermion point" of the six-vertex model, κ =8 +4 √{3 } . These unusual values lie outside the classical interval 2 ≤κ ≤8 .
Staggered Flux State in Two-Dimensional Hubbard Models
NASA Astrophysics Data System (ADS)
Yokoyama, Hisatoshi; Tamura, Shun; Ogata, Masao
2016-12-01
The stability and other properties of a staggered flux (SF) state or a correlated d-density wave state are studied for the Hubbard (t-t'-U) model on extended square lattices, as a low-lying state that competes with the dx2 - y2-wave superconductivity (d-SC) and possibly causes the pseudogap phenomena in underdoped high-Tc cuprates and organic κ-BEDT-TTF salts. In calculations, a variational Monte Carlo method is used. In the trial wave function, a configuration-dependent phase factor, which is vital to treat a current-carrying state for a large U/t, is introduced in addition to ordinary correlation factors. Varying U/t, t'/t, and the doping rate (δ) systematically, we show that the SF state becomes more stable than the normal state (projected Fermi sea) for a strongly correlated (U/t ≳ 5) and underdoped (δ ≲ 0.16) area. The decrease in energy is sizable, particularly in the area where Mott physics prevails and the circular current (order parameter) is strongly suppressed. These features are consistent with those for the t-J model. The effect of the frustration t'/t plays a crucial role in preserving charge homogeneity and appropriately describing the behavior of hole- and electron-doped cuprates and κ-BEDT-TTF salts. We argue that the SF state does not coexist with d-SC and is not a "normal state" from which d-SC arises. We also show that a spin current (flux or nematic) state is never stabilized in the same regime.
An unenumerative DNA computing model for vertex coloring problem.
Xu, Jin; Qiang, Xiaoli; Yang, Yan; Wang, Baoju; Yang, Dongliang; Luo, Liang; Pan, Linqiang; Wang, Shudong
2011-06-01
The solution space exponential explosion caused by the enumeration of the candidate solutions maybe is the biggest obstacle in DNA computing. In the paper, a new unenumerative DNA computing model for graph vertex coloring problem is presented based on two techniques: 1) ordering the vertex sequence for a given graph in such a way that any two consecutive labeled vertices i and i+1 should be adjacent in the graph as much as possible; 2) reducing the number of encodings representing colors according to the construture of the given graph. A graph with 12 vertices without triangles is solved and its initial solution space includes only 283 DNA strands, which is 0.0532 of 3(12) (the worst complexity).
NASA Astrophysics Data System (ADS)
Hoelbling, Christian; Zielinski, Christian
2016-07-01
We follow up on a suggestion by Adams and construct explicit domain wall fermion operators with staggered kernels. We compare different domain wall formulations, namely the standard construction as well as Boriçi's modified and Chiu's optimal construction, utilizing both Wilson and staggered kernels. In the process, we generalize the staggered kernels to arbitrary even dimensions and introduce both truncated and optimal staggered domain wall fermions. Some numerical investigations are carried out in the (1 +1 )-dimensional setting of the Schwinger model, where we explore spectral properties of the bulk, effective and overlap Dirac operators in the free-field case, on quenched thermalized gauge configurations and on smooth topological configurations. We compare different formulations using the effective mass, deviations from normality and violations of the Ginsparg-Wilson relation as measures of chirality.
cellGPU: Massively parallel simulations of dynamic vertex models
NASA Astrophysics Data System (ADS)
Sussman, Daniel M.
2017-10-01
Vertex models represent confluent tissue by polygonal or polyhedral tilings of space, with the individual cells interacting via force laws that depend on both the geometry of the cells and the topology of the tessellation. This dependence on the connectivity of the cellular network introduces several complications to performing molecular-dynamics-like simulations of vertex models, and in particular makes parallelizing the simulations difficult. cellGPU addresses this difficulty and lays the foundation for massively parallelized, GPU-based simulations of these models. This article discusses its implementation for a pair of two-dimensional models, and compares the typical performance that can be expected between running cellGPU entirely on the CPU versus its performance when running on a range of commercial and server-grade graphics cards. By implementing the calculation of topological changes and forces on cells in a highly parallelizable fashion, cellGPU enables researchers to simulate time- and length-scales previously inaccessible via existing single-threaded CPU implementations. Program Files doi:http://dx.doi.org/10.17632/6j2cj29t3r.1 Licensing provisions: MIT Programming language: CUDA/C++ Nature of problem: Simulations of off-lattice "vertex models" of cells, in which the interaction forces depend on both the geometry and the topology of the cellular aggregate. Solution method: Highly parallelized GPU-accelerated dynamical simulations in which the force calculations and the topological features can be handled on either the CPU or GPU. Additional comments: The code is hosted at https://gitlab.com/dmsussman/cellGPU, with documentation additionally maintained at http://dmsussman.gitlab.io/cellGPUdocumentation
The eight-vertex model with quasi-periodic boundary conditions
NASA Astrophysics Data System (ADS)
Niccoli, G.; Terras, V.
2016-01-01
We study the inhomogeneous eight-vertex model (or equivalently the XYZ Heisenberg spin-1/2 chain) with all kinds of integrable quasi-periodic boundary conditions: periodic, {σ }x-twisted, {σ }y-twisted or {σ }z-twisted. We show that in all these cases but the periodic one with an even number of sites {N}, the transfer matrix of the model is related, by the vertex-IRF transformation, to the transfer matrix of the dynamical six-vertex model with antiperiodic boundary conditions, which we have recently solved by means of Sklyanin's separation of variables approach. We show moreover that, in all the twisted cases, the vertex-IRF transformation is bijective. This allows us to completely characterize, from our previous results on the antiperiodic dynamical six-vertex model, the twisted eight-vertex transfer matrix spectrum (proving that it is simple) and eigenstates. We also consider the periodic case for {N} odd. In this case we can define two independent vertex-IRF transformations, both not bijective, and by using them we show that the eight-vertex transfer matrix spectrum is doubly degenerate, and that it can, as well as the corresponding eigenstates, also be completely characterized in terms of the spectrum and eigenstates of the dynamical six-vertex antiperiodic transfer matrix. In all these cases we can adapt to the eight-vertex case the reformulations of the dynamical six-vertex transfer matrix spectrum and eigenstates that had been obtained by T-Q functional equations, where the Q-functions are elliptic polynomials with twist-dependent quasi-periods. Such reformulations enable one to characterize the eight-vertex transfer matrix spectrum by the solutions of some Bethe-type equations, and to rewrite the corresponding eigenstates as the multiple action of some operators on a pseudo-vacuum state, in a similar way as in the algebraic Bethe ansatz framework.
Implementation of Newton-Rapshon iterations for parallel staggered-grid geodynamic models
NASA Astrophysics Data System (ADS)
Popov, A. A.; Kaus, B. J. P.
2012-04-01
Staggered-grid finite differences discretization has a good potential for solving highly heterogeneous geodynamic models on parallel computers (e.g. Tackey, 2008; Gerya &Yuen, 2007). They are inherently stable, computationally inexpensive and relatively easy to implement. However, currently used staggered-grid geodynamic codes employ almost exclusively the sub-optimal Picard linearization scheme to deal with nonlinearities. It was shown that Newton-Rapshon linearization can lead to substantial improvements of the solution quality in geodynamic problems, simultaneously with reduction of computer time (e.g. Popov & Sobolev, 2008). This work is aimed at implementation of the Newton-Rapshon linearization in the parallel geodynamic code LaMEM together with staggered-grid discretization and viso-(elasto)-plastic rock rheologies. We present the expressions for the approximate Jacobian matrix, and give detailed comparisons with the currently employed Picard linearization scheme, in terms of solution quality and number of iterations.
Odd-even staggering in the neutron-proton interaction and nuclear mass models
NASA Astrophysics Data System (ADS)
Cheng, Y. Y.; Zhao, Y. M.; Arima, A.
2015-02-01
In this paper we study odd-even staggering of the empirical neutron-proton interaction between the last neutron and the last proton, denoted as δ V1 n -1 p , and its consequence in the Garvey-Kelson mass relations (GKs) and nuclear mass models. The root-mean-squared deviations of predicted masses respectively for even-A and odd-A nuclei by using two combinatorial GKs suggest a large odd-even staggering of δ V1 n -1 p between even-odd and odd-even nuclei, while the odd-even difference of δ V1 n -1 p between even-even and odd-odd nuclei is much smaller. The contribution of the odd-even staggering of δ V1 n -1 p between even-A and odd-A nuclei in deviations of theoretical δ V1 n -1 p values of the Duflo-Zuker model and the improved Weizs a ̈cker -Skyrme model are well represented by an isospin-dependent term. The consideration of this odd-even staggering improves our description of binding energies and one-neutron separation energies in both the Duflo-Zuker model and the improved Weizs a ̈cker -Skyrme model.
A dynamic cellular vertex model of growing epithelial tissues
NASA Astrophysics Data System (ADS)
Lin, Shao-Zhen; Li, Bo; Feng, Xi-Qiao
2017-03-01
Intercellular interactions play a significant role in a wide range of biological functions and processes at both the cellular and tissue scales, for example, embryogenesis, organogenesis, and cancer invasion. In this paper, a dynamic cellular vertex model is presented to study the morphomechanics of a growing epithelial monolayer. The regulating role of stresses in soft tissue growth is revealed. It is found that the cells originating from the same parent cell in the monolayer can orchestrate into clustering patterns as the tissue grows. Collective cell migration exhibits a feature of spatial correlation across multiple cells. Dynamic intercellular interactions can engender a variety of distinct tissue behaviors in a social context. Uniform cell proliferation may render high and heterogeneous residual compressive stresses, while stress-regulated proliferation can effectively release the stresses, reducing the stress heterogeneity in the tissue. The results highlight the critical role of mechanical factors in the growth and morphogenesis of epithelial tissues and help understand the development and invasion of epithelial tumors.
A dynamic cellular vertex model of growing epithelial tissues
NASA Astrophysics Data System (ADS)
Lin, Shao-Zhen; Li, Bo; Feng, Xi-Qiao
2017-04-01
Intercellular interactions play a significant role in a wide range of biological functions and processes at both the cellular and tissue scales, for example, embryogenesis, organogenesis, and cancer invasion. In this paper, a dynamic cellular vertex model is presented to study the morphomechanics of a growing epithelial monolayer. The regulating role of stresses in soft tissue growth is revealed. It is found that the cells originating from the same parent cell in the monolayer can orchestrate into clustering patterns as the tissue grows. Collective cell migration exhibits a feature of spatial correlation across multiple cells. Dynamic intercellular interactions can engender a variety of distinct tissue behaviors in a social context. Uniform cell proliferation may render high and heterogeneous residual compressive stresses, while stress-regulated proliferation can effectively release the stresses, reducing the stress heterogeneity in the tissue. The results highlight the critical role of mechanical factors in the growth and morphogenesis of epithelial tissues and help understand the development and invasion of epithelial tumors.
On the staggered scheme for shallow water model down an inclined channel
NASA Astrophysics Data System (ADS)
Fauzi, Rifky; Wiryanto, L. H.
2017-08-01
The goal of this paper is to establish a staggered scheme for the shallow water model. The model is taken from [1], which include energy dissipation term. The study examines the temporal stability of the uniform flow using monochromatic waves. The result shows that the roll-waves occur and stable if and only if the Froude number is less than four. We simulate roll-waves by using finite difference in staggered grid. For the linear case this method is capable validating this condition. Moreover, momentum conservative scheme is used to handle advection term thus the evolution of roll-waves can be investigated. We found that this method is able to capture shock discontinuity. From the result, we investigate the effect of Froude number, Reynold and the value of σ. We also found that for supercritical Froude number (F > 1) with low Reynold number the shocks appear faster than the higher number.
NASA Astrophysics Data System (ADS)
Zhang, Pu; Heyne, Mary A.; To, Albert C.
2015-10-01
We investigate the damping enhancement in a class of biomimetic staggered composites via a combination of design, modeling, and experiment. In total, three kinds of staggered composites are designed by mimicking the structure of bone and nacre. These composite designs are realized by 3D printing a rigid plastic and a viscous elastomer simultaneously. Greatly-enhanced energy dissipation in the designed composites is observed from both the experimental results and theoretical prediction. The designed polymer composites have loss modulus up to ~500 MPa, higher than most of the existing polymers. In addition, their specific loss modulus (up to 0.43 km2/s2) is among the highest of damping materials. The damping enhancement is attributed to the large shear deformation of the viscous soft matrix and the large strengthening effect from the rigid inclusion phase.
A high-order staggered finite-element vertical discretization for non-hydrostatic atmospheric models
NASA Astrophysics Data System (ADS)
Guerra, Jorge E.; Ullrich, Paul A.
2016-06-01
Atmospheric modeling systems require economical methods to solve the non-hydrostatic Euler equations. Two major differences between hydrostatic models and a full non-hydrostatic description lies in the vertical velocity tendency and numerical stiffness associated with sound waves. In this work we introduce a new arbitrary-order vertical discretization entitled the staggered nodal finite-element method (SNFEM). Our method uses a generalized discrete derivative that consistently combines the discontinuous Galerkin and spectral element methods on a staggered grid. Our combined method leverages the accurate wave propagation and conservation properties of spectral elements with staggered methods that eliminate stationary (2Δx) modes. Furthermore, high-order accuracy also eliminates the need for a reference state to maintain hydrostatic balance. In this work we demonstrate the use of high vertical order as a means of improving simulation quality at relatively coarse resolution. We choose a test case suite that spans the range of atmospheric flows from predominantly hydrostatic to nonlinear in the large-eddy regime. Our results show that there is a distinct benefit in using the high-order vertical coordinate at low resolutions with the same robust properties as the low-order alternative.
A high-order staggered finite-element vertical discretization for non-hydrostatic atmospheric models
Guerra, Jorge E.; Ullrich, Paul A.
2016-06-01
Atmospheric modeling systems require economical methods to solve the non-hydrostatic Euler equations. Two major differences between hydrostatic models and a full non-hydrostatic description lies in the vertical velocity tendency and numerical stiffness associated with sound waves. In this work we introduce a new arbitrary-order vertical discretization entitled the staggered nodal finite-element method (SNFEM). Our method uses a generalized discrete derivative that consistently combines the discontinuous Galerkin and spectral element methods on a staggered grid. Our combined method leverages the accurate wave propagation and conservation properties of spectral elements with staggered methods that eliminate stationary (2Δx) modes. Furthermore, high-order accuracy alsomore » eliminates the need for a reference state to maintain hydrostatic balance. In this work we demonstrate the use of high vertical order as a means of improving simulation quality at relatively coarse resolution. We choose a test case suite that spans the range of atmospheric flows from predominantly hydrostatic to nonlinear in the large-eddy regime. Our results show that there is a distinct benefit in using the high-order vertical coordinate at low resolutions with the same robust properties as the low-order alternative.« less
Computational dispersion properties of horizontal staggered grids for atmospheric and ocean models
NASA Technical Reports Server (NTRS)
Fox-Rabinovitz, Michael S.
1991-01-01
The computational dispersion properties of horizontally and time-horizontally staggered grids utilizing corresponding centered-difference techniques for approximation of the adjustment, or gravity wave equations, are examined in terms of their group velocity characteristics. Results are acquired for oceanic and atmospheric models, the former being characterized by a much smaller Rossby radius of deformation. For all grids considered additional filtering is required to control and even eliminate waves with poor computational dispersion characteristics. Computational dispersion properties along with other computational characteristics and requirements give some guidance for an optimal selection of an appropriate grid for an ocean or atmospheric model.
Staggered-grid PSTD on local Fourier basis and its applications to surface tissue modeling.
Ding, Ming; Chen, Kun
2010-04-26
We introduce a high performance parallelization to the PSTD solution of Maxwell equations by employing the fast Fourier transform on local Fourier basis. Meanwhile a reformatted derivative operator allows the adoption of a staggered-grid such as the Yee lattice in PSTD, which can overcome the numerical errors in a collocated-grid when spatial discontinuities are present. The accuracy and capability of our method are confirmed by two analytical models. In two applications to surface tissue optics, an ultra wide coherent backscattering cone from the surface layer is found, and the penetration depth of polarization gating identified. Our development prepares a tool for investigating the optical properties of surface tissue structures.
Parametric modeling and stagger angle optimization of an axial flow fan
NASA Astrophysics Data System (ADS)
Li, M. X.; Zhang, C. H.; Liu, Y.; Y Zheng, S.
2013-12-01
Axial flow fans are widely used in every field of social production. Improving their efficiency is a sustained and urgent demand of domestic industry. The optimization of stagger angle is an important method to improve fan performance. Parametric modeling and calculation process automation are realized in this paper to improve optimization efficiency. Geometric modeling and mesh division are parameterized based on GAMBIT. Parameter setting and flow field calculation are completed in the batch mode of FLUENT. A control program is developed in Visual C++ to dominate the data exchange of mentioned software. It also extracts calculation results for optimization algorithm module (provided by Matlab) to generate directive optimization control parameters, which as feedback are transferred upwards to modeling module. The center line of the blade airfoil, based on CLARK y profile, is constructed by non-constant circulation and triangle discharge method. Stagger angles of six airfoil sections are optimized, to reduce the influence of inlet shock loss as well as gas leak in blade tip clearance and hub resistance at blade root. Finally an optimal solution is obtained, which meets the total pressure requirement under given conditions and improves total pressure efficiency by about 6%.
Modeling & Informatics at Vertex Pharmaceuticals Incorporated: our philosophy for sustained impact.
McGaughey, Georgia; Patrick Walters, W
2017-03-01
Molecular modelers and informaticians have the unique opportunity to integrate cross-functional data using a myriad of tools, methods and visuals to generate information. Using their drug discovery expertise, information is transformed to knowledge that impacts drug discovery. These insights are often times formulated locally and then applied more broadly, which influence the discovery of new medicines. This is particularly true in an organization where the members are exposed to projects throughout an organization, such as in the case of the global Modeling & Informatics group at Vertex Pharmaceuticals. From its inception, Vertex has been a leader in the development and use of computational methods for drug discovery. In this paper, we describe the Modeling & Informatics group at Vertex and the underlying philosophy, which has driven this team to sustain impact on the discovery of first-in-class transformative medicines.
Modeling & Informatics at Vertex Pharmaceuticals Incorporated: our philosophy for sustained impact
NASA Astrophysics Data System (ADS)
McGaughey, Georgia; Patrick Walters, W.
2017-03-01
Molecular modelers and informaticians have the unique opportunity to integrate cross-functional data using a myriad of tools, methods and visuals to generate information. Using their drug discovery expertise, information is transformed to knowledge that impacts drug discovery. These insights are often times formulated locally and then applied more broadly, which influence the discovery of new medicines. This is particularly true in an organization where the members are exposed to projects throughout an organization, such as in the case of the global Modeling & Informatics group at Vertex Pharmaceuticals. From its inception, Vertex has been a leader in the development and use of computational methods for drug discovery. In this paper, we describe the Modeling & Informatics group at Vertex and the underlying philosophy, which has driven this team to sustain impact on the discovery of first-in-class transformative medicines.
Modeling & Informatics at Vertex Pharmaceuticals Incorporated: our philosophy for sustained impact
NASA Astrophysics Data System (ADS)
McGaughey, Georgia; Patrick Walters, W.
2016-11-01
Molecular modelers and informaticians have the unique opportunity to integrate cross-functional data using a myriad of tools, methods and visuals to generate information. Using their drug discovery expertise, information is transformed to knowledge that impacts drug discovery. These insights are often times formulated locally and then applied more broadly, which influence the discovery of new medicines. This is particularly true in an organization where the members are exposed to projects throughout an organization, such as in the case of the global Modeling & Informatics group at Vertex Pharmaceuticals. From its inception, Vertex has been a leader in the development and use of computational methods for drug discovery. In this paper, we describe the Modeling & Informatics group at Vertex and the underlying philosophy, which has driven this team to sustain impact on the discovery of first-in-class transformative medicines.
Thermodynamics of the Six-Vertex Model in an L-Shaped Domain
NASA Astrophysics Data System (ADS)
Colomo, Filippo; Pronko, Andrei G.
2015-10-01
We consider the six-vertex model in an L-shaped domain of the square lattice, with domain wall boundary conditions. For free-fermion vertex weights the partition function can be expressed in terms of some Hankel determinant, or equivalently as a Coulomb gas with discrete measure and a non-polynomial potential with two hard walls. We use Coulomb gas methods to study the partition function in the thermodynamic limit. We obtain the free energy of the six-vertex model as a function of the parameters describing the geometry of the scaled L-shaped domain. Under variations of these parameters the system undergoes a third-order phase transition. The result can also be considered in the context of dimer models, for the perfect matchings of the Aztec diamond graph with a cut-off corner.
The monodromy matrix in the F-basis for arbitrary six-vertex models
NASA Astrophysics Data System (ADS)
Martins, M. J.; Zuparic, M.
2011-10-01
We present the expressions for the monodromy matrix elements of the six-vertex model in the F-basis for arbitrary Boltzmann weights. The results rely solely on the property of unitarity and Yang-Baxter relations, avoiding any specific parameterization of the weights. This allows us to write complete algebraic expressions for the inner products and the underlying domain wall partition functions in the case of arbitrary rapidities. We then apply our results for the trigonometric six-vertex model in the presence of inhomogeneous electric fields and obtain a determinant formula for the respective on-shell scalar products.
Anderson, R W; Pember, R B; Elliot, N S
2000-09-26
A new method for the solution of the unsteady Euler equations has been developed. The method combines staggered grid Lagrangian techniques with structured local adaptive mesh refinement (AMR). This method is a precursor to a more general adaptive arbitrary Lagrangian Eulerian (ALE-AMR) algorithm under development, which will facilitate the solution of problems currently at and beyond the boundary of soluble problems by traditional ALE methods by focusing computational resources where they are required. Many of the core issues involved in the development of the ALE-AMR method hinge upon the integration of AMR with a Lagrange step, which is the focus of the work described here. The novel components of the method are mainly driven by the need to reconcile traditional AMR techniques, which are typically employed on stationary meshes with cell-centered quantities, with the staggered grids and grid motion employed by Lagrangian methods. These new algorithmic components are first developed in one dimension and are then generalized to two dimensions. Solutions of several model problems involving shock hydrodynamics are presented and discussed.
Maximum group velocity in a one-dimensional model with a sinusoidally varying staggered potential
NASA Astrophysics Data System (ADS)
Nag, Tanay; Sen, Diptiman; Dutta, Amit
2015-06-01
We use Floquet theory to study the maximum value of the stroboscopic group velocity in a one-dimensional tight-binding model subjected to an on-site staggered potential varying sinusoidally in time. The results obtained by numerically diagonalizing the Floquet operator are analyzed using a variety of analytical schemes. In the low-frequency limit we use adiabatic theory, while in the high-frequency limit the Magnus expansion of the Floquet Hamiltonian turns out to be appropriate. When the magnitude of the staggered potential is much greater or much less than the hopping, we use degenerate Floquet perturbation theory; we find that dynamical localization occurs in the former case when the maximum group velocity vanishes. Finally, starting from an "engineered" initial state where the particles (taken to be hard-core bosons) are localized in one part of the chain, we demonstrate that the existence of a maximum stroboscopic group velocity manifests in a light-cone-like spreading of the particles in real space.
Variational Study on Loop Currents in Bose Hubbard model with Staggered Flux
NASA Astrophysics Data System (ADS)
Toga, Y.; Yokoyama, H.
In view of strongly interacting bosons in an optical lattice with a large gauge field, we study phase transitions in a two-dimensional Bose-Hubbard model with a staggered flux, on the basis of variational Monte Carlo calculations. Inthe trial states,besides typical onsite and intersite correlation factors, we introduce a configuration-dependent phase factor,which was recently found essential for treating current-carrying states. It is found that this phase factor is qualitativelyvitalfordescribing a Mott insulating (MI) state in the present model. Thereby, the Peierls phasesattached in relevant hopping processes are cancelled out. As a result, local currents completely suppressed in MI states, namely, a chiral Mott state does not appear for the square lattice, in contrast tothecorresponding two-leg ladder model. In addition, we discuss other features of the first-order superfluid-MI transition in this model.
The Stagger-grid: A grid of 3D stellar atmosphere models. IV. Limb darkening coefficients
NASA Astrophysics Data System (ADS)
Magic, Z.; Chiavassa, A.; Collet, R.; Asplund, M.
2015-01-01
Aims: We compute the emergent stellar spectra from the UV to far infrared for different viewing angles using realistic 3D model atmospheres for a large range in stellar parameters to predict the stellar limb darkening. Methods: We have computed full 3D LTE synthetic spectra based on 3D radiative hydrodynamic atmosphere models from the Stagger-grid in the ranges: Teff from 4000 to 7000 K, log g from 1.5 to 5.0, and [Fe/H], from -4.0 to +0.5. From the resulting intensities, we derived coefficients for the standard limb darkening laws considering a number of often-used photometric filters. Furthermore, we calculated theoretical transit light curves, in order to quantify the differences between predictions by the widely used 1D model atmosphere and our 3D models. Results: The 3D models are often found to predict steeper darkening towards the limb compared to the 1D models, mainly due to the temperature stratifications and temperature gradients being different in the 3D models compared to those predicted with 1D models based on the mixing length theory description of convective energy transport. The resulting differences in the transit light curves are rather small; however, these can be significant for high-precision observations of extrasolar transits, and are able to lower the residuals from the fits with 1D limb darkening profiles. Conclusions: We advocate the use of the new limb darkening coefficients provided for the standard four-parameter non-linear power law, which can fit the limb darkening more accurately than other choices. Full Table A.1 and the grid of spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/573/A90, as well as at http://www.stagger-stars.net
Liu, X. M.; Cheng, W. W.; Liu, J. -M.
2016-01-01
We investigate the quantum Fisher information and quantum phase transitions of an XY spin chain with staggered Dzyaloshinskii-Moriya interaction using the quantum renormalization-group method. The quantum Fisher information, its first-derivatives, and the finite-size scaling behaviors are rigorously calculated respectively. The singularity of the derivatives at the phase transition point as a function of lattice size is carefully discussed and it is revealed that the scaling exponent for quantum Fisher information at the critical point can be used to describe the correlation length of this model, addressing the substantial role of staggered Dzyaloshinskii-Moriya interaction in modulating quantum phase transitions. PMID:26780973
Liu, X M; Cheng, W W; Liu, J-M
2016-01-19
We investigate the quantum Fisher information and quantum phase transitions of an XY spin chain with staggered Dzyaloshinskii-Moriya interaction using the quantum renormalization-group method. The quantum Fisher information, its first-derivatives, and the finite-size scaling behaviors are rigorously calculated respectively. The singularity of the derivatives at the phase transition point as a function of lattice size is carefully discussed and it is revealed that the scaling exponent for quantum Fisher information at the critical point can be used to describe the correlation length of this model, addressing the substantial role of staggered Dzyaloshinskii-Moriya interaction in modulating quantum phase transitions.
Conserved currents in the six-vertex and trigonometric solid-on-solid models
NASA Astrophysics Data System (ADS)
Ikhlef, Yacine; Weston, Robert
2017-04-01
We construct quasi-local conserved currents in the six-vertex model with anisotropy parameter η by making use of the quantum-group approach of Bernard and Felder. From these currents, we construct parafermionic operators with spin 1+\\text{i}η /π that obey a discrete-integral condition around lattice plaquettes embedded into the complex plane. These operators are identified with primary fields in a c = 1 compactified free Boson conformal field theory. We then consider a vertex-face correspondence that takes the six-vertex model to a trigonometric SOS model, and construct SOS operators that are the image of the six-vertex currents under this correspondence. We define corresponding SOS parafermionic operators with spins s = 1 and s=1+2\\text{i}η /π that obey discrete integral conditions around SOS plaquettes embedded into the complex plane. We consider in detail the cyclic-SOS case corresponding to the choice η =\\text{i}π ≤ft( p-{{p}\\prime}\\right)/p , with {{p}\\prime} coprime. We identify our SOS parafermionic operators in terms of the screening operators and primary fields of the associated c=1-6≤ft( p-{{p}\\prime}\\right){{}2}/p{{p}\\prime} conformal field theory.
Designing Type-II staggered model ternary copolymers using ant algorithm
NASA Astrophysics Data System (ADS)
Garg, Aparna; Bakhshi, A. K.
2010-12-01
Ant algorithm has been applied in combination with the simple negative factor counting (NFC) method and the inverse iteration method (IIM) to the designing of Type-II staggered model ternary copolymers. Two types of copolymers have been studied, one in which the band widths of the homopolymers were identical and their band-gaps were different and vice versa. On the basis of the optimized results obtained in both the cases it has been found that (i) the band-gap of the copolymer is closest to that of the lowest band-gap component and (ii) the component having the lowest ionization potential has the maximum amount in the optimum solution. Further, the optimized results are found to be nearly independent of the seed used. The density of states has also been investigated for all the copolymers. The results obtained are expected to be important guidelines for molecular designing of copolymers with tailor-made conduction properties.
Interplay between staggered flux and d-wave superconducting states in Hubbard model
NASA Astrophysics Data System (ADS)
Kobayashi, Kenji; Yokoyama, Hisatoshi
2017-07-01
With cuprate superconductors in mind, we check whether the d-wave superconducting (dSC) state coexists with or excludes the staggered flux (SF) state, which was revealed to be the strong candidate for the pseudogap state. To this end, we use a variational Monte Carlo method for the square Hubbard model with diagonal transfer t‧. In the trial wave function, dSC and SF orders coexist, which allows a continuous description of their interplay; essential factors for Mott physics and band renormalization are also included. It is found that the SF state does not coexist with dSC and is unstable for U/t = 12 regardless of the value of t‧/t within the present work.
VizieR Online Data Catalog: STAGGER-grid of 3D stellar models. I. (Magic+, 2013)
NASA Astrophysics Data System (ADS)
Magic, Z.; Collet, R.; Asplund, M.; Trampedach, R.; Hayek, W.; Chiavassa, A.; Stein, R. F.; Nordlund, A.
2013-07-01
The 3D model atmospheres presented here were constructed with a custom version of the Stagger-code, a state-of-the-art, multipurpose, radiative-magnetohydrodynamics (R-MHD) code originally developed by Nordlund & Galsgaard (1995, http://www.astro.ku.dk/~kg/Papers/MHD_code.ps.gz), and continuously improved over the years by its user community. (1 data file).
Computational analysis of three-dimensional epithelial morphogenesis using vertex models
Du, XinXin; Osterfield, Miriam; Shvartsman, Stanislav Y.
2014-01-01
The folding of epithelial sheets, accompanied by cell shape changes and rearrangements, gives rise to three-dimensional structures during development. Recently, some aspects of epithelial morphogenesis have been modeled using vertex models, in which each cell is approximated by a polygon; however, these models have been largely confined to two dimensions. Here, we describe an adaptation of these models in which the classical two-dimensional vertex model is embedded in three dimensions. This modification allows for the construction of complex three-dimensional shapes from simple sheets of cells. We describe algorithmic, computational, and biophysical aspects of our model, with the view that it may be useful for formulating and testing hypotheses regarding the mechanical forces underlying a wide range of morphogenetic processes. PMID:25410646
Kendall, William L.; Hines, James E.; Nichols, James D.; Grant, Evan H. Campbell
2013-01-01
Occupancy statistical models that account for imperfect detection have proved very useful in several areas of ecology, including species distribution and spatial dynamics, disease ecology, and ecological responses to climate change. These models are based on the collection of multiple samples at each of a number of sites within a given season, during which it is assumed the species is either absent or present and available for detection while each sample is taken. However, for some species, individuals are only present or available for detection seasonally. We present a statistical model that relaxes the closure assumption within a season by permitting staggered entry and exit times for the species of interest at each site. Based on simulation, our open model eliminates bias in occupancy estimators and in some cases increases precision. The power to detect the violation of closure is high if detection probability is reasonably high. In addition to providing more robust estimation of occupancy, this model permits comparison of phenology across sites, species, or years, by modeling variation in arrival or departure probabilities. In a comparison of four species of amphibians in Maryland we found that two toad species arrived at breeding sites later in the season than a salamander and frog species, and departed from sites earlier.
NASA Astrophysics Data System (ADS)
Yong, Peng; Huang, Jianping; Li, Zhenchun; Liao, Wenyuan; Qu, Luping; Li, Qingyang; Liu, Peijun
2016-12-01
In finite difference (FD) method, numerical dispersion is the dominant factor influencing the accuracy of seismic modeling. Various optimized FD schemes for scalar wave modeling have been proposed to reduce grid dispersion, while the optimized time-space domain FD schemes for elastic wave modeling have not been fully investigated yet. In this paper, an optimized FD scheme with Equivalent Staggered Grid (ESG) for elastic modelling has been developed. We start from the constant P- and S-wave speed elastic wave equations and then deduce analytical plane wave solutions in the wavenumber domain with eigenvalue decomposition method. Based on the elastic plane wave solutions, three new time-space domain dispersion relations of ESG elastic modeling are obtained, which are represented by three equations corresponding to P-, S- and converted wave terms in the elastic equations, respectively. By using these new relations, we can study the dispersion errors of different spatial FD terms independently. The dispersion analysis showed that different spatial FD terms have different errors. It is therefore suggested that different FD coefficients to be used to approximate the three spatial derivative terms. In addition, the relative dispersion error in L2-norm is minimized through optimizing FD coefficients using Newton's method. Synthetic examples have demonstrated that this new optimal FD schemes have superior accuracy for elastic wave modeling compared to Taylor-series expansion and optimized space domain FD schemes.
NASA Astrophysics Data System (ADS)
Yong, Peng; Huang, Jianping; Li, Zhenchun; Liao, Wenyuan; Qu, Luping; Li, Qingyang; Liu, Peijun
2017-02-01
In finite-difference (FD) method, numerical dispersion is the dominant factor influencing the accuracy of seismic modelling. Various optimized FD schemes for scalar wave modelling have been proposed to reduce grid dispersion, while the optimized time-space domain FD schemes for elastic wave modelling have not been fully investigated yet. In this paper, an optimized FD scheme with Equivalent Staggered Grid (ESG) for elastic modelling has been developed. We start from the constant P- and S-wave speed elastic wave equations and then deduce analytical plane wave solutions in the wavenumber domain with eigenvalue decomposition method. Based on the elastic plane wave solutions, three new time-space domain dispersion relations of ESG elastic modelling are obtained, which are represented by three equations corresponding to P-, S- and converted-wave terms in the elastic equations, respectively. By using these new relations, we can study the dispersion errors of different spatial FD terms independently. The dispersion analysis showed that different spatial FD terms have different errors. It is therefore suggested that different FD coefficients to be used to approximate the three spatial derivative terms. In addition, the relative dispersion error in L2-norm is minimized through optimizing FD coefficients using Newton's method. Synthetic examples have demonstrated that this new optimal FD schemes have superior accuracy for elastic wave modelling compared to Taylor-series expansion and optimized space domain FD schemes.
A new computation method for a staggered grid of 3D EM field conservative modeling
NASA Astrophysics Data System (ADS)
Fomenko, Elena Yu.; Mogi, Toru
2002-05-01
A new three-dimensional (3D) MT modeling scheme conserving electric current and magnetic flux is developed. The scheme is based on finite difference (FD) staggered rectangular non-uniform grid formulation for the secondary electric field with continuous components of tangential electric and normal magnetic fields, in contrast to existing FD algorithms with a discontinuous E-field at the face of the cells. The scheme leads to a sparse 13-band complex symmetrical system of linear equations, which is effectively solved by fast and stable conjugate gradient (CG) methods. The preconditioning procedure was used to decrease the condition of a number of an ill-conditioned matrix system by several orders and stably and quickly solves the matrix system. The special module for the correction of divergence-free current J greatly increased the speed of convergence and accuracy, especially at low frequencies and for high-contrast resistivity or conductivity structures. A special procedure was developed to improve the accuracy of tangential magnetic and vertical electrical components at the Earth's surface and at the interface with a large conductivity contrast. The validity of the new algorithm was demonstrated for difficult models with high-contrast resistivity structures including topography and for COMMEMI project models.
Active Vertex Model for cell-resolution description of epithelial tissue mechanics
Barton, Daniel L.; Henkes, Silke
2017-01-01
We introduce an Active Vertex Model (AVM) for cell-resolution studies of the mechanics of confluent epithelial tissues consisting of tens of thousands of cells, with a level of detail inaccessible to similar methods. The AVM combines the Vertex Model for confluent epithelial tissues with active matter dynamics. This introduces a natural description of the cell motion and accounts for motion patterns observed on multiple scales. Furthermore, cell contacts are generated dynamically from positions of cell centres. This not only enables efficient numerical implementation, but provides a natural description of the T1 transition events responsible for local tissue rearrangements. The AVM also includes cell alignment, cell-specific mechanical properties, cell growth, division and apoptosis. In addition, the AVM introduces a flexible, dynamically changing boundary of the epithelial sheet allowing for studies of phenomena such as the fingering instability or wound healing. We illustrate these capabilities with a number of case studies. PMID:28665934
Vertex expansion for the Bianchi type I model
Campiglia, Miguel; Henderson, Adam; Nelson, William
2010-09-15
A perturbative expansion of loop quantum cosmological transitions amplitudes of Bianchi I models is performed. Following the procedure outlined in [1,2] for isotropic models, it is shown that the resulting expansion can be written in the form of a series of amplitudes each with a fixed number of transitions mimicking a spin foam expansion. This analogy is more complete than in the isotropic case, since there are now the additional anisotropic degrees of freedom which play the role of 'coloring' of the spin foams. Furthermore, the isotropic expansion is recovered by integrating out the anisotropies.
A new Q-matrix in the eight-vertex model
NASA Astrophysics Data System (ADS)
Fabricius, Klaus
2007-04-01
We construct a Q-matrix for the eight-vertex model at roots of unity for crossing parameter η = 2mK/L with odd L, a case for which the existing constructions do not work. The new Q-matrix {\\skew3\\hat{Q}} depends on the spectral parameter v and also on a free parameter t. For t=0, {\\skew3\\hat{Q}} has the standard properties. For t ≠ 0, however, it does not commute with the operator S nor with itself for different values of the spectral parameter. We show that the six-vertex limit of {\\skew3\\hat{Q}}(v,t=iK^{\\prime}/2) exists.
NASA Astrophysics Data System (ADS)
Engwirda, Darren
2017-06-01
An algorithm for the generation of non-uniform, locally orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered Voronoi-Delaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a priori bounds on element size and shape. Grid quality is further improved through the application of hill-climbing-type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid-type finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution-type studies is discussed in detail.
NASA Technical Reports Server (NTRS)
Engwirda, Darren
2017-01-01
An algorithm for the generation of non-uniform, locally orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered VoronoiDelaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a priori bounds on element size and shape. Grid quality is further improved through the application of hill-climbing-type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid-type finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution-type studies is discussed in detail.
Mapping of (1+1) D-Crystal Growth onto a 14-Vertex Model
NASA Astrophysics Data System (ADS)
Hontinfinde, F.; Levi, A. C.
1996-07-01
A restricted solid-on-solid (SOS) single- and double-step model is introduced and studied with Glauber dynamics. Kinetics and roughness of the growing crystal are described in terms of a Markov process whose states are given by the crystal upper edge profile that we map onto a 14-vertex model. We solve exactly the kinetic equation for small-size versions of the model. Extensive simulations are performed to derive the large scale properties. The present study appears as a further extension of Gates and Westcott's investigation of the single-step model.
The loop-cluster algorithm for the case of the 6 vertex model
NASA Astrophysics Data System (ADS)
Evertz, Hans Gerd; Marcu, Mihai
1993-03-01
We present the loop algorithm, a new type of cluster algorithm that we recently introduced for the F model. Using the framework of Kandel and Domany, we show how to generalize the algorithm to the arrow flip symmetric 6 vertex model. We propose the principle of least possible freezing as the guide to choosing the values of free parameters in the algorithm. Finally, we briefly discuss the application of our algorithm to simulations of quantum spin systems. In particular, all necessary information is provided for the simulation of spin {1}/{2} Heisenberg and ¢x¢x z models.
Vertex-element models for anisotropic growth of elongated plant organs
Fozard, John A.; Lucas, Mikaël; King, John R.; Jensen, Oliver E.
2013-01-01
New tools are required to address the challenge of relating plant hormone levels, hormone responses, wall biochemistry and wall mechanical properties to organ-scale growth. Current vertex-based models (applied in other contexts) can be unsuitable for simulating the growth of elongated organs such as roots because of the large aspect ratio of the cells, and these models fail to capture the mechanical properties of cell walls in sufficient detail. We describe a vertex-element model which resolves individual cells and includes anisotropic non-linear viscoelastic mechanical properties of cell walls and cell division whilst still being computationally efficient. We show that detailed consideration of the cell walls in the plane of a 2D simulation is necessary when cells have large aspect ratio, such as those in the root elongation zone of Arabidopsis thaliana, in order to avoid anomalous transverse swelling. We explore how differences in the mechanical properties of cells across an organ can result in bending and how cellulose microfibril orientation affects macroscale growth. We also demonstrate that the model can be used to simulate growth on realistic geometries, for example that of the primary root apex, using moderate computational resources. The model shows how macroscopic root shape can be sensitive to fine-scale cellular geometries. PMID:23847638
Symmetry classes of alternating sign matrices in a nineteen-vertex model
NASA Astrophysics Data System (ADS)
Hagendorf, Christian; Morin-Duchesne, Alexi
2016-05-01
The nineteen-vertex model of Fateev and Zamolodchikov on a periodic lattice with an anti-diagonal twist is investigated. Its inhomogeneous transfer matrix is shown to have a simple eigenvalue, with the corresponding eigenstate displaying intriguing combinatorial features. Similar results were previously found for the same model with a diagonal twist. The eigenstate for the anti-diagonal twist is explicitly constructed using the quantum separation of variables technique. A number of sum rules and special components are computed and expressed in terms of Kuperberg’s determinants for partition functions of the inhomogeneous six-vertex model. The computations of some components of the special eigenstate for the diagonal twist are also presented. In the homogeneous limit, the special eigenstates become eigenvectors of the Hamiltonians of the integrable spin-one XXZ chain with twisted boundary conditions. Their sum rules and special components for both twists are expressed in terms of generating functions arising in the weighted enumeration of various symmetry classes of alternating sign matrices (ASMs). These include half-turn symmetric ASMs, quarter-turn symmetric ASMs, vertically symmetric ASMs, vertically and horizontally perverse ASMs and double U-turn ASMs. As side results, new determinant and pfaffian formulas for the weighted enumeration of various symmetry classes of alternating sign matrices are obtained.
Time evolution of three-dimensional cellular systems: Computer modeling based on vertex-type models
NASA Astrophysics Data System (ADS)
Kazuhiro Fuchizaki; Kyozi Kawasaki
1995-02-01
An effective computer modeling of time evolution of three-dimensional cellular systems like soap froths and crystalline grain aggregates has been devised, which captures the essence of difficult correlation effects of neighboring cells. This can be achieved by eliminating the continuous degrees of freedom besides the immediate vicinity of the center of a singular region of space, that is, an intersection of interfaces from the original full-curvature drien equation of motion of interfaces, thus leaving a set of equations of motion for such intersections, i.e. vertices. To actually carry out this projection operation each interface is divided intoa set of two-dimensional simplexes. A derivation of the model equations is given in the most general possible form. Various results including topological characteristics of three-dimensional cellular patterns were obtained using the simpler version of these vertex equations, among which the result for the average growth rate of f-sided cells is presented. An application to some specific cellular systems is also discussed.
Chiral Potts rapidity curve descended from six-vertex model and symmetry group of rapidities
NASA Astrophysics Data System (ADS)
Roan, Shi-shyr
2005-08-01
In this paper, we present a systematical account of the descending procedure from the six-vertex model to the N-state chiral Potts model through fusion relations of τ(j)-operators, following the works of Bazhanov-Stroganov and Baxter-Bazhanov-Perk. A careful analysis of the descending process leads to the appearance of the high genus curve as the rapidity constraint for the chiral Potts models. Full symmetries of the rapidity curve are identified, as is its symmetry group structure. By normalized transfer matrices of the chiral Potts model, the τ(2)T relation can be reduced to functional equations over a hyperelliptic curve associated with rapidities, by which the degeneracy of τ(2)-eigenvalues is revealed in the case of the superintegrable chiral Potts model.
Electron-phonon vertex in the two-dimensional one-band Hubbard model
NASA Astrophysics Data System (ADS)
Huang, Z. B.; Hanke, W.; Arrigoni, E.; Scalapino, D. J.
2003-12-01
Using quantum Monte Carlo techniques, we study the effects of electronic correlations on the effective electron-phonon (el-ph) coupling in a two-dimensional one-band Hubbard model. We consider a momentum-independent bare ionic el-ph coupling. In the weak- and intermediate-correlation regimes, we find that the on-site Coulomb interaction U acts to effectively suppress the ionic el-ph coupling at all electron and phonon momenta. In this regime, our numerical simulations are in good agreement with the results of perturbation theory to order U2. However, entering the strong-correlation regime, we find that the forward-scattering process stops decreasing and begins to substantially increase as a function of U, leading to an effective el-ph coupling which is peaked in the forward direction. Whereas at weak and intermediate Coulomb interactions, screening is the dominant correlation effect suppressing the el-ph coupling, at larger U values irreducible vertex corrections become more important and give rise to this increase. These vertex corrections depend crucially on the renormalized electronic structure of the strongly correlated system.
NASA Astrophysics Data System (ADS)
Mellbin, Y.; Hallberg, H.; Ristinmaa, M.
2015-06-01
A mesoscale model of microstructure evolution is formulated in the present work by combining a crystal plasticity model with a graph-based vertex algorithm. This provides a versatile formulation capable of capturing finite-strain deformations, development of texture and microstructure evolution through recrystallization. The crystal plasticity model is employed in a finite element setting and allows tracing of stored energy build-up in the polycrystal microstructure and concurrent reorientation of the crystal lattices in the grains. This influences the progression of recrystallization as nucleation occurs at sites with sufficient stored energy and since the grain boundary mobility and energy is allowed to vary with crystallographic misorientation across the boundaries. The proposed graph-based vertex model describes the topological changes to the grain microstructure and keeps track of the grain inter-connectivity. Through homogenization, the macroscopic material response is also obtained. By the proposed modeling approach, grain structure evolution at large deformations as well as texture development are captured. This is in contrast to most other models of recrystallization which are usually limited by assumptions of one or the other of these factors. In simulation examples, the model is in the present study shown to capture the salient features of dynamic recrystallization, including the effects of varying initial grain size and strain rate on the transitions between single-peak and multiple-peak oscillating flow stress behavior. Also the development of recrystallization texture and the influence of different assumptions on orientation of recrystallization nuclei are investigated. Further, recrystallization kinetics are discussed and compared to classical JMAK theory. To promote computational efficiency, the polycrystal plasticity algorithm is parallelized through a GPU implementation that was recently proposed by the authors.
Connecting dark matter annihilation to the vertex functions of Standard Model fermions
NASA Astrophysics Data System (ADS)
Kumar, Jason; Light, Christopher
2017-07-01
We consider scenarios in which dark matter is a Majorana fermion which couples to Standard Model fermions through the exchange of charged mediating particles. The matrix elements for various dark matter annihilation processes are then related to one-loop corrections to the fermion-photon vertex, where dark matter and the charged mediators run in the loop. In particular, in the limit where Standard Model fermion helicity mixing is suppressed, the cross section for dark matter annihilation to various final states is related to corrections to the Standard Model fermion charge form factor. These corrections can be extracted in a gauge-invariant manner from collider cross sections. Although current measurements from colliders are not precise enough to provide useful constraints on dark matter annihilation, improved measurements at future experiments, such as the International Linear Collider, could improve these constraints by several orders of magnitude, allowing them to surpass the limits obtainable by direct observation.
Staggered quantum walks with Hamiltonians
NASA Astrophysics Data System (ADS)
Portugal, R.; de Oliveira, M. C.; Moqadam, J. K.
2017-01-01
Quantum walks are recognizably useful for the development of new quantum algorithms, as well as for the investigation of several physical phenomena in quantum systems. Actual implementations of quantum walks face technological difficulties similar to the ones for quantum computers, though. Therefore, there is a strong motivation to develop new quantum-walk models which might be easier to implement. In this work we present an extension of the staggered quantum walk model that is fitted for physical implementations in terms of time-independent Hamiltonians. We demonstrate that this class of quantum walk includes the entire class of staggered quantum walk model, Szegedy's model, and an important subset of the coined model.
Lueth, V.
1992-07-01
The purpose of a vertex detector is to measure position and angles of charged particle tracks to sufficient precision so as to be able to separate tracks originating from decay vertices from those produced at the interaction vertex. Such measurements are interesting because they permit the detection of weakly decaying particles with lifetimes down to 10{sup {minus}13} s, among them the {tau} lepton and charm and beauty hadrons. These two lectures are intended to introduce the reader to the different techniques for the detection of secondary vertices that have been developed over the past decades. The first lecture includes a brief introduction to the methods used to detect secondary vertices and to estimate particle lifetimes. It describes the traditional technologies, based on photographic recording in emulsions and on film of bubble chambers, and introduces fast electronic registration of signals derived from scintillating fibers, drift chambers and gaseous micro-strip chambers. The second lecture is devoted to solid state detectors. It begins with a brief introduction into semiconductor devices, and then describes the application of large arrays of strip and pixel diodes for charged particle tracking. These lectures can only serve as an introduction the topic of vertex detectors. Time and space do not allow for an in-depth coverage of many of the interesting aspects of vertex detector design and operation.
tbW vertex in the littlest Higgs model with T parity
Penunuri, F.; Larios, F.
2009-01-01
A study of the effective tbW vertex is done in the littlest Higgs model with T parity that includes the one-loop induced weak dipole coefficient f{sub 2R}. The top's width and the W-boson helicity in the t{yields}bW{sup +} decay as well as the t-channel and the s-channel modes of single top quark production at the LHC are then obtained for the tbW coupling. Our calculation is done in the Feynman-'t Hooft gauge, and we provide details of the analysis, like exact formulas (to all orders of the expansion variable v/f) of masses and mixing angles of all of the particles involved. Also, a complete and exact diagonalization (and normalization) of the scalar sector of the model is made.
Prediction of least-scattered photons traversing turbid medium: a vertex/propagator model
NASA Astrophysics Data System (ADS)
Wang, Ruikang K.; Wilson, Michael J.
2000-04-01
The least scattered photons that arrive at a detector through the highly scattering tissues have the potential for imaging internal structures, functions and status with high imaging resolution. In contrast optical diffusing tomography is based on the use of the late arriving photons, which have been diffusely scattered, leading to very low imaging resolution. A good model of the early arriving photons, i.e. the least scattered photons may have a significant impact on the development of imaging algorithms and the further understanding of imaging mechanisms within current high resolution optical imaging techniques. This paper describes a vertex/propagator approach, which attempts to find the probabilities for least scattered photons traversing a scattering medium, based on analytical expressions for photon histories. The basic mathematical derivations for the model are outlined, and the results are discussed and found to be in very good agreement with those from the Monte-Carlo simulations.
Genome sequencing supports a multi-vertex model for Brassiceae species.
Cheng, Feng; Liang, Jianli; Cai, Chengcheng; Cai, Xu; Wu, Jian; Wang, Xiaowu
2017-02-24
The economically important Brassica genus is a good system for studying the evolution of polyploids. Brassica genomes have undergone whole genome triplication (WGT). Subgenome dominance phenomena such as biased gene fractionation and dominant gene expression were observed in tripled genomes of Brassica. The genome of radish (Raphanus sativus), another important crop of tribe Brassiceae, was derived from the same WGT event and shows similar subgenome dominance. These findings and molecular dating indicate that radish occupies a similar evolutionary origin as that of Brassica species. Here, we extended the Brassica "triangle of U" to a multi-vertex model. This model describes the relationships or the potential of using more Brassiceae mesohexaploids in the creation of new allotetraploid oil or vegetable crop species.
Vertex/propagator model for least-scattered photons traversing a turbid medium.
Wang, R K; Wilson, M
2001-01-01
The least-scattered photons that arrive at a detector through highly scattering tissues have the potential to image internal structures, functions, and status with high imaging resolution. In contrast, optical diffusing tomography is based on the use of the late-arriving photons, which have been diffusely scattered, leading to very low imaging resolution. A good model of the early-arriving photons, i.e., the least-scattered photons, may have a significant effect on the development of imaging algorithms and a further understanding of imaging mechanisms within current high-resolution optical-imaging techniques. We describe a vertex/propagator approach that attempts to find the probabilities for least-scattered photons traversing a scattering medium, based on analytical expressions for photon histories. The basic mathematical derivations for the model are outlined, and the results are discussed and found to be in very good agreement with those from the Monte Carlo simulations.
Reflection K-matrices for a nineteen vertex model with Uq [ osp (2 | 2) (2) ] symmetry
NASA Astrophysics Data System (ADS)
Vieira, R. S.; Lima Santos, A.
2017-09-01
We derive the solutions of the boundary Yang-Baxter equation associated with a supersymmetric nineteen vertex model constructed from the three-dimensional representation of the twisted quantum affine Lie superalgebra Uq [ osp (2 | 2) (2) ]. We found three classes of solutions. The type I solution is characterized by three boundary free-parameters and all elements of the corresponding reflection K-matrix are different from zero. In the type II solution, the reflection K-matrix is even (every element of the K-matrix with an odd parity is null) and it has only one boundary free-parameter. Finally, the type III solution corresponds to a diagonal reflection K-matrix with two boundary free-parameters.
W W V (V =γ , Z ) vertex in the Georgi-Machacek model
NASA Astrophysics Data System (ADS)
Arroyo-Ureña, M. A.; Hernández-Tomé, G.; Tavares-Velasco, G.
2016-11-01
The C P -even static form factors Δ κV' and Δ QV (V =γ , Z ) associated with the W W V vertex are studied in the context of the Georgi-Machacek model (GMM), which predicts nine new scalar bosons accommodated in a singlet, a triplet, and a fiveplet. General expressions for the one-loop contributions to Δ κV' and Δ QV arising from neutral, singly, and doubly charged scalar bosons are obtained in terms of both parametric integrals and Passarino-Veltman scalar functions, which can be numerically evaluated. It is found that the GMM yields 15 (28) distinct contributions to Δ κγ' and Δ Qγ (Δ κZ' and Δ QZ), though several of them are naturally suppressed. A numerical analysis is done in the region of parameter space still consistent with current experimental data and it is found that the largest contributions to Δ κV' arise from Feynman diagrams with two nondegenerate scalar bosons in the loop, with values of the order of a =g2/(96 π2) reached when there is a large splitting between the masses of these scalar bosons. As for Δ QV, it reaches values as large as 10-2a for the lightest allowed scalar bosons, but it decreases rapidly as one of the masses of the scalar bosons becomes large. Among the new contributions of the GMM to the Δ κV' and Δ QV form factors are those induced by the H5±W∓Z vertex, which arises at the tree level and is a unique prediction of this model.
Modeling one-mode projection of bipartite networks by tagging vertex information
NASA Astrophysics Data System (ADS)
Qiao, Jian; Meng, Ying-Ying; Chen, Hsinchun; Huang, Hong-Qiao; Li, Guo-Ying
2016-09-01
Traditional one-mode projection models are less informative than their original bipartite networks. Hence, using such models cannot control the projection's structure freely. We proposed a new method for modeling the one-mode projection of bipartite networks, which thoroughly breaks through the limitations of the available one-mode projecting methods by tagging the vertex information of bipartite networks in their one-mode projections. We designed a one-mode collaboration network model by using the method presented in this paper. The simulation results show that our model matches three real networks very well and outperforms the available collaboration network models significantly, which reflects the idea that our method is ideal for modeling one-mode projection models of bipartite graphs and that our one-mode collaboration network model captures the crucial mechanisms of the three real systems. Our study reveals that size growth, individual aging, random collaboration, preferential collaboration, transitivity collaboration and multi-round collaboration are the crucial mechanisms of collaboration networks, and the lack of some of the crucial mechanisms is the main reason that the other available models do not perform as well as ours.
Symeonidis, Vasileios; Karniadakis, George Em . E-mail: gk@dam.brown.edu
2006-10-10
We propose new schemes for integrating the stochastic differential equations of dissipative particle dynamics (DPD) in simulations of dilute polymer solutions. The hybrid DPD models consist of hard potentials that describe the microscopic dynamics of polymers and soft potentials that describe the mesoscopic dynamics of the solvent. In particular, we develop extensions to the velocity-Verlet and Lowe's approaches - two representative DPD time-integrators - following a subcycling procedure whereby the solvent is advanced with a timestep much larger than the one employed in the polymer time-integration. The introduction of relaxation parameters allows optimization studies for accuracy while maintaining the low computational complexity of standard DPD algorithms. We demonstrate through equilibrium simulations that a 10-fold gain in efficiency can be obtained with the time-staggered algorithms without loss of accuracy compared to the non-staggered schemes. We then apply the new approach to investigate the scaling response of polymers in equilibrium as well as the dynamics of {lambda}-phage DNA molecules subjected to shear.
NASA Astrophysics Data System (ADS)
Symeonidis, Vasileios; Karniadakis, George Em
2006-10-01
We propose new schemes for integrating the stochastic differential equations of dissipative particle dynamics (DPD) in simulations of dilute polymer solutions. The hybrid DPD models consist of hard potentials that describe the microscopic dynamics of polymers and soft potentials that describe the mesoscopic dynamics of the solvent. In particular, we develop extensions to the velocity-Verlet and Lowe's approaches - two representative DPD time-integrators - following a subcycling procedure whereby the solvent is advanced with a timestep much larger than the one employed in the polymer time-integration. The introduction of relaxation parameters allows optimization studies for accuracy while maintaining the low computational complexity of standard DPD algorithms. We demonstrate through equilibrium simulations that a 10-fold gain in efficiency can be obtained with the time-staggered algorithms without loss of accuracy compared to the non-staggered schemes. We then apply the new approach to investigate the scaling response of polymers in equilibrium as well as the dynamics of λ-phage DNA molecules subjected to shear.
NASA Astrophysics Data System (ADS)
Hui, Ning-Ju; Xu, Yang-Yang; Wang, Jicheng; Zhang, Yixin; Hu, Zheng-Da
2017-04-01
We investigate the properties of geometric quantum coherence in the XY spin-1/2 chain with staggered Dzyaloshinsky-Moriya interaction via the quantum renormalization-group approach. It is shown that the geometric quantum coherence and its coherence susceptibility are effective to detect the quantum phase transition. In the thermodynamic limit, the geometric quantum coherence exhibits a sudden jump. The coherence susceptibilities versus the anisotropy parameter and the Dzyaloshinsky-Moriya interaction are infinite and vanishing, respectively, illustrating the distinct roles of the anisotropy parameter and the Dzyaloshinsky-Moriya interaction in quantum phase transition. Moreover, we also explore the finite-size scaling behaviors of the coherence susceptibilities. For a finite-size chain, the coherence susceptibility versus the phase-transition parameter is always maximal at the critical point, indicating the dramatic quantum fluctuation. Besides, we show that the correlation length can be revealed by the scaling exponent for the coherence susceptibility versus the Dzyaloshinsky-Moriya interaction.
Fletcher, Alexander G; Osborne, James M; Maini, Philip K; Gavaghan, David J
2013-11-01
The dynamic behaviour of epithelial cell sheets plays a central role during development, growth, disease and wound healing. These processes occur as a result of cell adhesion, migration, division, differentiation and death, and involve multiple processes acting at the cellular and molecular level. Computational models offer a useful means by which to investigate and test hypotheses about these processes, and have played a key role in the study of cell-cell interactions. However, the necessarily complex nature of such models means that it is difficult to make accurate comparison between different models, since it is often impossible to distinguish between differences in behaviour that are due to the underlying model assumptions, and those due to differences in the in silico implementation of the model. In this work, an approach is described for the implementation of vertex dynamics models, a discrete approach that represents each cell by a polygon (or polyhedron) whose vertices may move in response to forces. The implementation is undertaken in a consistent manner within a single open source computational framework, Chaste, which comprises fully tested, industrial-grade software that has been developed using an agile approach. This framework allows one to easily change assumptions regarding force generation and cell rearrangement processes within these models. The versatility and generality of this framework is illustrated using a number of biological examples. In each case we provide full details of all technical aspects of our model implementations, and in some cases provide extensions to make the models more generally applicable.
NASA Astrophysics Data System (ADS)
Avila-Marin, Antonio L.; Fernandez-Reche, Jesús; Casanova, Marina; Caliot, Cyril; Flamant, Gilles
2017-06-01
Volumetric receivers made of metallic wire meshes are a promising technology that allows different designs and configurations. In this paper the local volumetric heat transfer coefficient for a volumetric absorber with two extreme arrangements, inline and stagger, is presented. The results show that the heat transfer rates for the stagger stack is nearly two times higher than the inline stack. Moreover, the local volumetric heat transfer coefficient is implemented in a Homogeneous Equivalent Model using a Local Thermal Non-Equilibrium model to compare the results. The stagger stack performs better than the inline stack despite their higher frontal losses and pressure drop. Finally, a validation of the Homogeneous Equivalent Model is carried out with experimental data showing a good agreement.
Aldridge, David Franklin; Collier, Sandra L.; Marlin, David H.; Ostashev, Vladimir E.; Symons, Neill Phillip; Wilson, D. Keith
2005-05-01
This document is intended to serve as a users guide for the time-domain atmospheric acoustic propagation suite (TDAAPS) program developed as part of the Department of Defense High-Performance Modernization Office (HPCMP) Common High-Performance Computing Scalable Software Initiative (CHSSI). TDAAPS performs staggered-grid finite-difference modeling of the acoustic velocity-pressure system with the incorporation of spatially inhomogeneous winds. Wherever practical the control structure of the codes are written in C++ using an object oriented design. Sections of code where a large number of calculations are required are written in C or F77 in order to enable better compiler optimization of these sections. The TDAAPS program conforms to a UNIX style calling interface. Most of the actions of the codes are controlled by adding flags to the invoking command line. This document presents a large number of examples and provides new users with the necessary background to perform acoustic modeling with TDAAPS.
Duerr, Stephan; Hoelbling, Christian; Wenger, Urs
2004-11-01
We study the infrared part of the spectrum for UV-filtered staggered Dirac operators and compare them to the overlap counterpart. With sufficient filtering and at small enough lattice spacing the staggered spectra manage to 'mimic' the overlap version. They show a 4-fold near degeneracy, and a clear separation between would-be zero modes and nonzero modes. This suggests an approximate index theorem for filtered staggered fermions and a correct sensitivity to the topology of QCD. Moreover, it supports square-rooting the staggered determinant to obtain dynamical ensembles with N{sub f}=2.
NASA Astrophysics Data System (ADS)
Mellbin, Y.; Hallberg, H.; Ristinmaa, M.
2016-10-01
A multiscale modeling framework, combining a graph-based vertex model of microstructure evolution with a GPU-parallelized crystal plasticity model, was recently proposed by the authors. Considering hot rolling of copper, the full capabilities of the model are demonstrated in the present work. The polycrystal plasticity model captures the plastic response and the texture evolution during materials processing while the vertex model provides central features of grain structure evolution through dynamic recrystallization, such as nucleation and growth of individual crystals. The multiscale model makes it possible to obtain information regarding grain size and texture development throughout the workpiece, capturing the effects of recrystallization and heterogeneous microstructure evolution. Recognizing that recrystallization is a highly temperature dependent phenomenon, simulations are performed at different process temperatures. The results show that the proposed modeling framework is capable of simultaneously capturing central aspects of material behavior at both the meso- and macrolevel. Detailed investigation of the evolution of texture, grain size distribution and plastic deformation during the different processing conditions are performed, using the proposed model. The results show a strong texture development, but almost no recrystallization, for the lower of the investigated temperatures, while at higher temperatures an increased recrystallization is shown to weaken the development of a typical rolling texture. The simulations also show the influence of the shear deformation close to the rolling surface on both texture development and recrystallization.
Properties of Linear Integral Equations Related to the Six-Vertex Model with Disorder Parameter
NASA Astrophysics Data System (ADS)
Boos, Hermann; Göhmann, Frank
2011-10-01
One of the key steps in recent work on the correlation functions of the XXZ chain was to regularize the underlying six-vertex model by a disorder parameter α. For the regularized model it was shown that all static correlation functions are polynomials in only two functions. It was further shown that these two functions can be written as contour integrals involving the solutions of a certain type of linear and non-linear integral equations. The linear integral equations depend parametrically on α and generalize linear integral equations known from the study of the bulk thermodynamic properties of the model. In this note we consider the generalized dressed charge and a generalized magnetization density. We express the generalized dressed charge as a linear combination of two quotients of Q-functions, the solutions of Baxter's t-Q-equation. With this result we give a new proof of a lemma on the asymptotics of the generalized magnetization density as a function of the spectral parameter.
The Stagger-grid: A grid of 3D stellar atmosphere models. I. Methods and general properties
NASA Astrophysics Data System (ADS)
Magic, Z.; Collet, R.; Asplund, M.; Trampedach, R.; Hayek, W.; Chiavassa, A.; Stein, R. F.; Nordlund, Å.
2013-09-01
Aims: We present the Stagger-grid, a comprehensive grid of time-dependent, three-dimensional (3D), hydrodynamic model atmospheres for late-type stars with realistic treatment of radiative transfer, covering a wide range in stellar parameters. This grid of 3D models is intended for various applications besides studies of stellar convection and atmospheres per se, including stellar parameter determination, stellar spectroscopy and abundance analysis, asteroseismology, calibration of stellar evolution models, interferometry, and extrasolar planet search. In this introductory paper, we describe the methods we applied for the computation of the grid and discuss the general properties of the 3D models as well as of their temporal and spatial averages (here denoted ⟨3D⟩ models). Methods: All our models were generated with the Stagger-code, using realistic input physics for the equation of state (EOS) and for continuous and line opacities. Our ~ 220 grid models range in effective temperature, Teff, from 4000 to 7000 K in steps of 500 K, in surface gravity, log g, from 1.5 to 5.0 in steps of 0.5 dex, and metallicity, [Fe/H], from - 4.0 to + 0.5 in steps of 0.5 and 1.0 dex. Results: We find a tight scaling relation between the vertical velocity and the surface entropy jump, which itself correlates with the constant entropy value of the adiabatic convection zone. The range in intensity contrast is enhanced at lower metallicity. The granule size correlates closely with the pressure scale height sampled at the depth of maximum velocity. We compare the ⟨3D⟩ models with currently widely applied one-dimensional (1D) atmosphere models, as well as with theoretical 1D hydrostatic models generated with the same EOS and opacity tables as the 3D models, in order to isolate the effects of using self-consistent and hydrodynamic modeling of convection, rather than the classical mixing length theory approach. For the first time, we are able to quantify systematically over a broad
Investigation of deformation mechanisms of staggered nanocomposites using molecular dynamics
NASA Astrophysics Data System (ADS)
Mathiazhagan, S.; Anup, S.
2016-08-01
Biological materials with nanostructure of regularly or stair-wise staggered arrangements of hard platelets reinforced in a soft protein matrix have superior mechanical properties. Applications of these nanostructures to ceramic matrix composites could enhance their toughness. Using molecular dynamics simulations, mechanical behaviour of the bio-inspired nanocomposites is studied. Regularly staggered model shows better flow behaviour compared to stair-wise staggered model due to the symmetrical crack propagation along the interface. Though higher stiffness and strength are obtained for stair-wise staggered models, rapid crack propagation reduces the toughness. Arresting this crack propagation could lead to superior mechanical properties in stair-wise staggered models.
NASA Astrophysics Data System (ADS)
Salas, Jesús; Sokal, Alan D.
2011-09-01
We study, using transfer-matrix methods, the partition-function zeros of the square-lattice q-state Potts antiferromagnet at zero temperature (= square-lattice chromatic polynomial) for the boundary conditions that are obtained from an m× n grid with free boundary conditions by adjoining one new vertex adjacent to all the sites in the leftmost column and a second new vertex adjacent to all the sites in the rightmost column. We provide numerical evidence that the partition-function zeros are becoming dense everywhere in the complex q-plane outside the limiting curve {B}_{infty}(sq) for this model with ordinary (e.g. free or cylindrical) boundary conditions. Despite this, the infinite-volume free energy is perfectly analytic in this region.
NASA Astrophysics Data System (ADS)
Li, Y.; Han, B.; Métivier, L.; Brossier, R.
2016-09-01
We investigate an optimal fourth-order staggered-grid finite-difference scheme for 3D frequency-domain viscoelastic wave modeling. An anti-lumped mass strategy is incorporated to minimize the numerical dispersion. The optimal finite-difference coefficients and the mass weighting coefficients are obtained by minimizing the misfit between the normalized phase velocities and the unity. An iterative damped least-squares method, the Levenberg-Marquardt algorithm, is utilized for the optimization. Dispersion analysis shows that the optimal fourth-order scheme presents less grid dispersion and anisotropy than the conventional fourth-order scheme with respect to different Poisson's ratios. Moreover, only 3.7 grid-points per minimum shear wavelength are required to keep the error of the group velocities below 1%. The memory cost is then greatly reduced due to a coarser sampling. A parallel iterative method named CARP-CG is used to solve the large ill-conditioned linear system for the frequency-domain modeling. Validations are conducted with respect to both the analytic viscoacoustic and viscoelastic solutions. Compared with the conventional fourth-order scheme, the optimal scheme generates wavefields having smaller error under the same discretization setups. Profiles of the wavefields are presented to confirm better agreement between the optimal results and the analytic solutions.
NASA Astrophysics Data System (ADS)
Etemadsaeed, Leila; Moczo, Peter; Kristek, Jozef; Ansari, Anooshiravan; Kristekova, Miriam
2016-10-01
We investigate the problem of finite-difference approximations of the velocity-stress formulation of the equation of motion and constitutive law on the staggered grid (SG) and collocated grid (CG). For approximating the first spatial and temporal derivatives, we use three approaches: Taylor expansion (TE), dispersion-relation preserving (DRP), and combined TE-DRP. The TE and DRP approaches represent two fundamental extremes. We derive useful formulae for DRP and TE-DRP approximations. We compare accuracy of the numerical wavenumbers and numerical frequencies of the basic TE, DRP and TE-DRP approximations. Based on the developed approximations, we construct and numerically investigate 14 basic TE, DRP and TE-DRP finite-difference schemes on SG and CG. We find that (1) the TE second-order in time, TE fourth-order in space, 2-point in time, 4-point in space SG scheme (that is the standard (2,4) VS SG scheme, say TE-2-4-2-4-SG) is the best scheme (of the 14 investigated) for large fractions of the maximum possible time step, or, in other words, in a homogeneous medium; (2) the TE second-order in time, combined TE-DRP second-order in space, 2-point in time, 4-point in space SG scheme (say TE-DRP-2-2-2-4-SG) is the best scheme for small fractions of the maximum possible time step, or, in other words, in models with large velocity contrasts if uniform spatial grid spacing and time step are used. The practical conclusion is that in computer codes based on standard TE-2-4-2-4-SG, it is enough to redefine the values of the approximation coefficients by those of TE-DRP-2-2-2-4-SG for increasing accuracy of modelling in models with large velocity contrast between rock and sediments.
Ab initio dynamical vertex approximation
NASA Astrophysics Data System (ADS)
Galler, Anna; Thunström, Patrik; Gunacker, Patrik; Tomczak, Jan M.; Held, Karsten
2017-03-01
Diagrammatic extensions of dynamical mean-field theory (DMFT) such as the dynamical vertex approximation (DΓ A) allow us to include nonlocal correlations beyond DMFT on all length scales and proved their worth for model calculations. Here, we develop and implement an Ab initio DΓ A approach (AbinitioDΓ A ) for electronic structure calculations of materials. The starting point is the two-particle irreducible vertex in the two particle-hole channels which is approximated by the bare nonlocal Coulomb interaction and all local vertex corrections. From this, we calculate the full nonlocal vertex and the nonlocal self-energy through the Bethe-Salpeter equation. The AbinitioDΓ A approach naturally generates all local DMFT correlations and all nonlocal G W contributions, but also further nonlocal correlations beyond: mixed terms of the former two and nonlocal spin fluctuations. We apply this new methodology to the prototypical correlated metal SrVO3.
3D change detection in staggered voxels model for robotic sensing and navigation
NASA Astrophysics Data System (ADS)
Liu, Ruixu; Hampshire, Brandon; Asari, Vijayan K.
2016-05-01
3D scene change detection is a challenging problem in robotic sensing and navigation. There are several unpredictable aspects in performing scene change detection. A change detection method which can support various applications in varying environmental conditions is proposed. Point cloud models are acquired from a RGB-D sensor, which provides the required color and depth information. Change detection is performed on robot view point cloud model. A bilateral filter smooths the surface and fills the holes as well as keeps the edge details on depth image. Registration of the point cloud model is implemented by using Random Sample Consensus (RANSAC) algorithm. It uses surface normal as the previous stage for the ground and wall estimate. After preprocessing the data, we create a point voxel model which defines voxel as surface or free space. Then we create a color model which defines each voxel that has a color by the mean of all points' color value in this voxel. The preliminary change detection is detected by XOR subtract on the point voxel model. Next, the eight neighbors for this center voxel are defined. If they are neither all `changed' voxels nor all `no changed' voxels, a histogram of location and hue channel color is estimated. The experimental evaluations performed to evaluate the capability of our algorithm show promising results for novel change detection that indicate all the changing objects with very limited false alarm rate.
Dynamic inversion method based on the time-staggered stereo-modeling scheme and its acceleration
NASA Astrophysics Data System (ADS)
Jing, Hao; Yang, Dinghui; Wu, Hao
2016-12-01
A set of second-order differential equations describing the space-time behaviour of derivatives of displacement with respect to model parameters (i.e. waveform sensitivities) is obtained via taking the derivative of the original wave equations. The dynamic inversion method obtains sensitivities of the seismic displacement field with respect to earth properties directly by solving differential equations for them instead of constructing sensitivities from the displacement field itself. In this study, we have taken a new perspective on the dynamic inversion method and used acceleration approaches to reduce the computational time and memory usage to improve its ability of performing high-resolution imaging. The dynamic inversion method, which can simultaneously use different waves and multicomponent observation data, is appropriate for directly inverting elastic parameters, medium density or wave velocities. Full wavefield information is utilized as much as possible at the expense of a larger amount of calculations. To mitigate the computational burden, two ways are proposed to accelerate the method from a computer-implementation point of view. One is source encoding which uses a linear combination of all shots, and the other is to reduce the amount of calculations on forward modeling. We applied a new finite-difference (FD) method to the dynamic inversion to improve the computational accuracy and speed up the performance. Numerical experiments indicated that the new FD method can effectively suppress the numerical dispersion caused by the discretization of wave equations, resulting in enhanced computational efficiency with less memory cost for seismic modeling and inversion based on the full wave equations. We present some inversion results to demonstrate the validity of this method through both checkerboard and Marmousi models. It shows that this method is also convergent even with big deviations for the initial model. Besides, parallel calculations can be easily
Altmeyer, Michaela; Guterding, Daniel; Hirschfeld, P. J.; Maier, Thomas A.; Valentí, Roser; Scalapino, Douglas J.
2016-12-21
In the framework of a multiorbital Hubbard model description of superconductivity, a matrix formulation of the superconducting pairing interaction that has been widely used is designed to treat spin, charge, and orbital fluctuations within a random phase approximation (RPA). In terms of Feynman diagrams, this takes into account particle-hole ladder and bubble contributions as expected. It turns out, however, that this matrix formulation also generates additional terms which have the diagrammatic structure of vertex corrections. As a result we examine these terms and discuss the relationship between the matrix-RPA superconducting pairing interaction and the Feynman diagrams that it sums.
NASA Astrophysics Data System (ADS)
Altmeyer, Michaela; Guterding, Daniel; Hirschfeld, P. J.; Maier, Thomas A.; Valentí, Roser; Scalapino, Douglas J.
2016-12-01
In the framework of a multiorbital Hubbard model description of superconductivity, a matrix formulation of the superconducting pairing interaction that has been widely used is designed to treat spin, charge, and orbital fluctuations within a random phase approximation (RPA). In terms of Feynman diagrams, this takes into account particle-hole ladder and bubble contributions as expected. It turns out, however, that this matrix formulation also generates additional terms which have the diagrammatic structure of vertex corrections. Here we examine these terms and discuss the relationship between the matrix-RPA superconducting pairing interaction and the Feynman diagrams that it sums.
Staggered fermions, zero modes, and flavor-singlet mesons
Donald, Gordon C; Davies, Christine T.H.; Follana, Eduardo; Kronfeld, Andreas S.
2011-09-12
We examine the taste structure of eigenvectors of the staggered-fermion Dirac operator. We derive a set of conditions on the eigenvectors of modes with small eigenvalues (near-zero modes), such that staggered fermions reproduce the 't Hooft vertex in the continuum limit. We also show that, assuming these conditions, the correlators of flavor-singlet mesons are free of contributions singular in 1/m, where m is the quark mass. This conclusion holds also when a single flavor of sea quark is represented by the fourth root of the staggered-fermion determinant. We then test numerically, using the HISQ action, whether these conditions hold on realistic lattice gauge fields. We find that the needed structure does indeed emerge.
Staggered fermions, zero modes, and flavor-singlet mesons
Donald, Gordon C; Davies, Christine T.H.; Follana, Eduardo; ...
2011-09-12
We examine the taste structure of eigenvectors of the staggered-fermion Dirac operator. We derive a set of conditions on the eigenvectors of modes with small eigenvalues (near-zero modes), such that staggered fermions reproduce the 't Hooft vertex in the continuum limit. We also show that, assuming these conditions, the correlators of flavor-singlet mesons are free of contributions singular in 1/m, where m is the quark mass. This conclusion holds also when a single flavor of sea quark is represented by the fourth root of the staggered-fermion determinant. We then test numerically, using the HISQ action, whether these conditions hold onmore » realistic lattice gauge fields. We find that the needed structure does indeed emerge.« less
NASA Astrophysics Data System (ADS)
Magic, Z.; Weiss, A.; Asplund, M.
2015-01-01
Aims: We investigate the relation between 1D atmosphere models that rely on the mixing length theory and models based on full 3D radiative hydrodynamic (RHD) calculations to describe convection in the envelopes of late-type stars. Methods: The adiabatic entropy value of the deep convection zone, sbot, and the entropy jump, Δs, determined from the 3D RHD models, were matched with the mixing length parameter, αMLT, from 1D hydrostatic atmosphere models with identical microphysics (opacities and equation-of-state). We also derived the mass mixing length parameter, αm, and the vertical correlation length of the vertical velocity, C[vz,vz], directly from the 3D hydrodynamical simulations of stellar subsurface convection. Results: The calibrated mixing length parameter for the Sun is α๏MLT (Sbot) = 1.98. . For different stellar parameters, αMLT varies systematically in the range of 1.7 - 2.4. In particular, αMLT decreases towards higher effective temperature, lower surface gravity and higher metallicity. We find equivalent results for α๏MLT (ΔS). In addition, we find a tight correlation between the mixing length parameter and the inverse entropy jump. We derive an analytical expression from the hydrodynamic mean-field equations that motivates the relation to the mass mixing length parameter, αm, and find that it qualitatively shows a similar variation with stellar parameter (between 1.6 and 2.4) with the solar value of α๏m = 1.83.. The vertical correlation length scaled with the pressure scale height yields 1.71 for the Sun, but only displays a small systematic variation with stellar parameters, the correlation length slightly increases with Teff. Conclusions: We derive mixing length parameters for various stellar parameters that can be used to replace a constant value. Within any convective envelope, αm and related quantities vary strongly. Our results will help to replace a constant αMLT. Appendices are available in electronic form at http
NASA Astrophysics Data System (ADS)
Freedman, Avraham; Levanon, Nadav
1986-11-01
A radar signal, based on coherent processing of a train of staggered Costas (1984) bursts is based on a minimum number of collocation of their individual ambiguity function sidelobe peaks. The resulting ambiguity function combines qualities of both 'thumbtack' and 'bed of nails' signals. Comparison with linear-FM, V-FM, and complementary phase coded signals is given, as well as comparison with hybrid signals consisting of both phase and frequency coding.
Vertex upgrading problems for VLSI
Paik, D.
1991-01-01
The author examines vertex modification (splitting, deleting and upgrading) problems that arise in VLSI CAD and other application areas. The problems he considers differ from previously studied vertex-deletion problems in that he is interested in modifying vertices in a dag so that the resulting dag has no path whose length exceeds a prespecified amount. Vertex-modification problems can be used to model the scan register placement problem in VLSI design, placement of signal boosters in lossy circuits, satellite uplink/downlink placement in communication networks, etc. The approach adopted is to first determine which of these problems are NP-hard. Pseudo polynomial time algorithms and fast heuristics for the NP-hard versions are explored. Fast polynomial time algorithms for other versions are developed. Experimentation using the ISCAS benchmark circuits are also performed.
NASA Astrophysics Data System (ADS)
Bohlen, Thomas; Wittkamp, Florian
2016-03-01
We analyse the performance of a higher order accurate staggered viscoelastic time-domain finite-difference method, in which the staggered Adams-Bashforth (ABS) third-order and fourth-order accurate time integrators are used for temporal discretization. ABS is a multistep method that uses previously calculated wavefields to increase the order of accuracy in time. The analysis shows that the numerical dispersion is much lower than that of the widely used second-order leapfrog method. Numerical dissipation is introduced by the ABS method which is significantly smaller for fourth-order than third-order accuracy. In 1-D and 3-D simulation experiments, we verify the convincing improvements of simulation accuracy of the fourth-order ABS method. In a realistic elastic 3-D scenario, the computing time reduces by a factor of approximately 2.4, whereas the memory requirements increase by approximately a factor of 2.2. The ABS method thus provides an alternative strategy to increase the simulation accuracy in time by investing computer memory instead of computing time.
Strube, Jan; Graf, Norman; /SLAC
2006-03-03
This document describes the implementation of the topological vertex finding algorithm ZVTOP within the org.lcsim reconstruction and analysis framework. At the present date, Java vertexing tools allow users to perform topological vertexing on tracks that have been obtained from a Fast MC simulation. An implementation that will be able to handle fully reconstructed events is being designed from the ground up for longevity and maintainability.
NASA Astrophysics Data System (ADS)
Bergeron, Dominic; Hankevych, Vasyl; Kyung, Bumsoo; Tremblay, A.-M. S.
2011-08-01
The conductivity of the two-dimensional Hubbard model is particularly relevant for high-temperature superconductors. Vertex corrections are expected to be important because of strongly momentum-dependent self-energies. To attack this problem, one must also take into account the Mermin-Wagner theorem, the Pauli principle, and crucial sum rules in order to reach nonperturbative regimes. Here, we use the two-particle self-consistent approach that satisfies these constraints. This approach is reliable from weak to intermediate coupling. A functional derivative approach ensures that vertex corrections are included in a way that satisfies the f-sum rule. The two types of vertex corrections that we find are the antiferromagnetic analogs of the Maki-Thompson and Aslamasov-Larkin contributions of superconducting fluctuations to the conductivity but, contrary to the latter, they include nonperturbative effects. The resulting analytical expressions must be evaluated numerically. The calculations are impossible unless a number of advanced numerical algorithms are used. These algorithms make extensive use of fast Fourier transforms, cubic splines, and asymptotic forms. A maximum entropy approach is specially developed for analytical continuation of our results. These algorithms are explained in detail in the appendices. The numerical results are for nearest-neighbor hoppings. In the pseudogap regime induced by two-dimensional antiferromagnetic fluctuations, the effect of vertex corrections is dramatic. Without vertex corrections the resistivity increases as we enter the pseudogap regime. Adding vertex corrections leads to a drop in resistivity, as observed in some high-temperature superconductors. At high temperatures, the resistivity saturates at the Ioffe-Regel limit. At the quantum critical point and beyond, the resistivity displays both linear and quadratic temperature dependence and there is a correlation between the linear term and the superconducting transition
Staggered chiral random matrix theory
Osborn, James C.
2011-02-01
We present a random matrix theory for the staggered lattice QCD Dirac operator. The staggered random matrix theory is equivalent to the zero-momentum limit of the staggered chiral Lagrangian and includes all taste breaking terms at their leading order. This is an extension of previous work which only included some of the taste breaking terms. We will also present some results for the taste breaking contributions to the partition function and the Dirac eigenvalues.
NASA Astrophysics Data System (ADS)
Magic, Z.; Collet, R.; Hayek, W.; Asplund, M.
2013-12-01
Aims: We study the implications of averaging methods with different reference depth scales for 3D hydrodynamical model atmospheres computed with the Stagger-code. The temporally and spatially averaged (hereafter denoted as ⟨3D⟩) models are explored in the light of local thermodynamic equilibrium (LTE) spectral line formation by comparing spectrum calculations using full 3D atmosphere structures with those from ⟨3D⟩ averages. Methods: We explored methods for computing mean ⟨3D⟩ stratifications from the Stagger-grid time-dependent 3D radiative hydrodynamical atmosphere models by considering four different reference depth scales (geometrical depth, column-mass density, and two optical depth scales). Furthermore, we investigated the influence of alternative averages (logarithmic, enforced hydrostatic equilibrium, flux-weighted temperatures). For the line formation we computed curves of growth for Fe i and Fe ii lines in LTE. Results: The resulting ⟨3D⟩ stratifications for the four reference depth scales can be very different. We typically find that in the upper atmosphere and in the superadiabatic region just below the optical surface, where the temperature and density fluctuations are highest, the differences become considerable and increase for higher Teff, lower log g, and lower [Fe / H]. The differential comparison of spectral line formation shows distinctive differences depending on which ⟨3D⟩ model is applied. The averages over layers of constant column-mass density yield the best mean ⟨3D⟩ representation of the full 3D models for LTE line formation, while the averages on layers at constant geometrical height are the least appropriate. Unexpectedly, the usually preferred averages over layers of constant optical depth are prone to increasing interference by reversed granulation towards higher effective temperature, in particular at low metallicity. Appendix A is available in electronic form at http://www.aanda.orgMean ⟨3D⟩ models are
NASA Astrophysics Data System (ADS)
Moortgat, Joachim; Firoozabadi, Abbas
2016-06-01
Problems of interest in hydrogeology and hydrocarbon resources involve complex heterogeneous geological formations. Such domains are most accurately represented in reservoir simulations by unstructured computational grids. Finite element methods accurately describe flow on unstructured meshes with complex geometries, and their flexible formulation allows implementation on different grid types. In this work, we consider for the first time the challenging problem of fully compositional three-phase flow in 3D unstructured grids, discretized by any combination of tetrahedra, prisms, and hexahedra. We employ a mass conserving mixed hybrid finite element (MHFE) method to solve for the pressure and flux fields. The transport equations are approximated with a higher-order vertex-based discontinuous Galerkin (DG) discretization. We show that this approach outperforms a face-based implementation of the same polynomial order. These methods are well suited for heterogeneous and fractured reservoirs, because they provide globally continuous pressure and flux fields, while allowing for sharp discontinuities in compositions and saturations. The higher-order accuracy improves the modeling of strongly non-linear flow, such as gravitational and viscous fingering. We review the literature on unstructured reservoir simulation models, and present many examples that consider gravity depletion, water flooding, and gas injection in oil saturated reservoirs. We study convergence rates, mesh sensitivity, and demonstrate the wide applicability of our chosen finite element methods for challenging multiphase flow problems in geometrically complex subsurface media.
NASA Astrophysics Data System (ADS)
Kaus, B.; Popov, A.
2014-12-01
The complexity of lithospheric rheology and the necessity to resolve the deformation patterns near the free surface (faults and folds) sufficiently well places a great demand on a stable and scalable modeling tool that is capable of efficiently handling nonlinearities. Our code LaMEM (Lithosphere and Mantle Evolution Model) is an attempt to satisfy this demand. The code utilizes a stable and numerically inexpensive finite difference discretization with the spatial staggering of velocity, pressure, and temperature unknowns (a so-called staggered grid). As a time discretization method the forward Euler, or a combination of the predictor-corrector and the fourth-order Runge-Kutta can be chosen. Elastic stresses are rotated on the markers, which are also used to track all relevant material properties and solution history fields. The Newtonian nonlinear iteration, however, is handled at the level of the grid points to avoid spurious averaging between markers and grid. Such an arrangement required us to develop a non-standard discretization of the effective strain-rate second invariant. Important feature of the code is its ability to handle stress-free and open-box boundary conditions, in which empty cells are simply eliminated from the discretization, which also solves the biggest problem of the sticky-air approach - namely large viscosity jumps near the free surface. We currently support an arbitrary combination of linear elastic, nonlinear viscous with multiple creep mechanisms, and plastic rheologies based on either a depth-dependent von Mises or pressure-dependent Drucker-Prager yield criteria.LaMEM is being developed as an inherently parallel code. Structurally all its parts are based on the building blocks provided by PETSc library. These include Jacobian-Free Newton-Krylov nonlinear solvers with convergence globalization techniques (line search), equipped with different linear preconditioners. We have also implemented the coupled velocity-pressure multigrid
Modeling of low-frequency seismic waves in a shallow sea using the staggered grid difference method
NASA Astrophysics Data System (ADS)
Lu, Zaihua; Zhang, Zhihong; Gu, Jiannong
2017-09-01
Elastic waves in the seabed generated by low-frequency noise radiating from ships are known as ship seismic waves and can be used to detect and identify ships. To obtain the propagation characteristics of ship seismic waves, an algorithm for calculating seismic waves at the seafloor is presented based on the staggered-grid finite difference method. The accuracy of the algorithm was tested by comparison with analytical solutions. Numerical simulation of seismic waves generated by a low-frequency point sound source in a typical shallow sea environment was carried out. Using various source frequencies and locations in the numerical simulation, we show that the seismic waves in the near field are composed mostly of transmitted S-waves and interface waves while transmitted P-waves are weak near the seafloor. However, in the far field, the wave components of the seismic wave are mainly normal modes and interface waves, with the latter being relatively strong in the waveforms. As the source frequency decreases, the normal modes become smaller and the interface waves dominate the time series of the seismic waves.
Medical Imaging Inspired Vertex Reconstruction at LHC
NASA Astrophysics Data System (ADS)
Hageböck, S.; von Toerne, E.
2012-12-01
Three-dimensional image reconstruction in medical applications (PET or X-ray CT) utilizes sophisticated filter algorithms to linear trajectories of coincident photon pairs or x-rays. The goal is to reconstruct an image of an emitter density distribution. In a similar manner, tracks in particle physics originate from vertices that need to be distinguished from background track combinations. In this study it is investigated if vertex reconstruction in high energy proton collisions may benefit from medical imaging methods. A new method of vertex finding, the Medical Imaging Vertexer (MIV), is presented based on a three-dimensional filtered backprojection algorithm. It is compared to the open-source RAVE vertexing package. The performance of the vertex finding algorithms is evaluated as a function of instantaneous luminosity using simulated LHC collisions. Tracks in these collisions are described by a simplified detector model which is inspired by the tracking performance of the LHC experiments. At high luminosities (25 pileup vertices and more), the medical imaging approach finds vertices with a higher efficiency and purity than the RAVE “Adaptive Vertex Reconstructor” algorithm. It is also much faster if more than 25 vertices are to be reconstructed because the amount of CPU time rises linearly with the number of tracks whereas it rises quadratically for the adaptive vertex fitter AVR.
Rouvroye, Jan L; Wiegerinck, Jan A M
2006-10-01
In industry, potentially hazardous (technical) structures are equipped with safety systems in order to protect people, the environment, and assets from the consequences of accidents by reducing the probability of incidents occurring. Not only companies but also society will want to know what the effect of these safety measures is: society in terms of "likelihood of undesired events" and companies in addition in terms of "value for money," the expected benefits per dollar or euro invested that these systems provide. As a compromise between demands from society (the safer the better) and industry (but against what cost), in many countries government has decided to impose standards to industry with respect to safety requirements. These standards use the average probability of failure on demand as the main performance indicator for these systems, and require, for the societal reason given before, that this probability remain below a certain value depending on a given risk. The main factor commonly used in industry to "fine-tune" the average probability of failure on demand for a given system configuration in order to comply with these standards against financial risk for the company is "optimizing" the test strategy (interval, coverage, and procedure). In industry, meeting the criterion on the average probability of failure on demand is often demonstrated by using well accepted mathematical models such as Markov models from literature and adapting them for the actual situation. This paper shows the implications and potential pitfalls when using this commonly used practical approach for a situation where the test strategy is changed. Adapting an existing Markov model can lead to unexpected results, and this paper will demonstrate that a different model has to be developed. In addition, the authors propose an approach that can be applied in industry without suffering from the problems mentioned above.
NASA Astrophysics Data System (ADS)
Wang, Y.; Vogt, B.
2001-05-01
Recent worldwide earthquakes have resulted in staggering losses. The Northridge, California; Kobe, Japan; Loma Prieta, California; Izmit, Turkey; Chi-Chi, Taiwan; and Bhuj, India earthquakes, which range from magnitudes 6.7 to 7.7, have all occurred near populated areas. These earthquakes have resulted in estimated losses between \\3 and \\300 billion, with tens to tens of thousands of fatalities. Subduction zones are capable of producing the largest earthquakes. The 1939 M7.8 Chilean, the 1960 M9.5 Chilean, the 1964 M9.2 Alaskan, the 1970 M7.8 Peruvian, the 1985 M7.9 Mexico City and the 2001 M7.7 Bhuj earthquakes are damaging subduction zone quakes. The Cascadia fault zone poses a tremendous hazard in the Pacific Northwest due to the ground shaking and tsunami inundation hazards combined with the population. To address the Cascadia subduction zone threat, the Oregon Department of Geology and Mineral Industries conducted a preliminary statewide loss study. The 1998 Oregon study incorporated a M8.5 quake, the influence of near surface soil effects and default building, social and economic data available in FEMA's HAZUS97 software. Direct financial losses are projected at over \\$12 billion. Casualties are estimated at about 13,000. Over 5,000 of the casualties are estimated to result in fatalities from hazards relating to tsunamis and unreinforced masonry buildings.
NASA Astrophysics Data System (ADS)
Ramírez-Zavaleta, F.; Tavares-Velasco, G.; Toscano, J. J.
2007-04-01
In a recent paper [J. Montano, F. Ramírez-Zavaleta, G. Tavares-Velasco, and J. J. Toscano, Phys. Rev. D 72, 055023 (2005).PRVDAQ0556-282110.1103/PhysRevD.72.055023], we investigated the effects of the massive charged gauge bosons (bileptons) predicted by the minimal 331 model on the off-shell vertex WWV* (V=γ, Z) using a SUL(2)×UY(1) covariant gauge-fixing term for the bileptons. We proceed along the same lines and calculate the effects of the gauge bosons predicted by the 331 model with right-handed neutrinos. It is found that the bilepton effects on the WWV* vertex are of the same order of magnitude as those arising from the standard model and several of its extensions, provided that the bilepton mass is of the order of a few hundred of GeVs. For heavier bileptons, their effects on the WWV* vertex are negligible. The behavior of the form factors at high energies is also discussed as it is a reflection of the gauge invariance and gauge independence of the WWV* Green function obtained via our quantization method.
Thermodynamics of spin chains of Haldane-Shastry type and one-dimensional vertex models
Enciso, Alberto; Finkel, Federico; Gonzalez-Lopez, Artemio
2012-11-15
We study the thermodynamic properties of spin chains of Haldane-Shastry type associated with the A{sub N-1} root system in the presence of a uniform external magnetic field. To this end, we exactly compute the partition function of these models for an arbitrary finite number of spins. We then show that these chains are equivalent to a suitable inhomogeneous classical Ising model in a spatially dependent magnetic field, generalizing the results of Basu-Mallick et al. for the zero magnetic field case. Using the standard transfer matrix approach, we are able to compute in closed form the free energy per site in the thermodynamic limit. We perform a detailed analysis of the chains' thermodynamics in a unified way, with special emphasis on the zero field and zero temperature limits. Finally, we provide a novel interpretation of the thermodynamic quantities of spin chains of Haldane-Shastry type as weighted averages of the analogous quantities over an ensemble of classical Ising models. - Highlights: Black-Right-Pointing-Pointer Partition function of spin chains of Haldane-Shastry type in magnetic field. Black-Right-Pointing-Pointer Equivalence to classical inhomogeneous Ising models. Black-Right-Pointing-Pointer Free energy per site, other thermodynamic quantities in thermodynamic limit. Black-Right-Pointing-Pointer Zero field, zero temperature limits. Black-Right-Pointing-Pointer Thermodynamic equivalence with ensemble of classical Ising models.
Vertex shading of the three-dimensional model based on ray-tracing algorithm
NASA Astrophysics Data System (ADS)
Hu, Xiaoming; Sang, Xinzhu; Xing, Shujun; Yan, Binbin; Wang, Kuiru; Dou, Wenhua; Xiao, Liquan
2016-10-01
Ray Tracing Algorithm is one of the research hotspots in Photorealistic Graphics. It is an important light and shadow technology in many industries with the three-dimensional (3D) structure, such as aerospace, game, video and so on. Unlike the traditional method of pixel shading based on ray tracing, a novel ray tracing algorithm is presented to color and render vertices of the 3D model directly. Rendering results are related to the degree of subdivision of the 3D model. A good light and shade effect is achieved by realizing the quad-tree data structure to get adaptive subdivision of a triangle according to the brightness difference of its vertices. The uniform grid algorithm is adopted to improve the rendering efficiency. Besides, the rendering time is independent of the screen resolution. In theory, as long as the subdivision of a model is adequate, cool effects as the same as the way of pixel shading will be obtained. Our practical application can be compromised between the efficiency and the effectiveness.
NASA Astrophysics Data System (ADS)
Yan, Hongyong; Yang, Lei; Li, Xiang-Yang
2016-12-01
High-order staggered-grid finite-difference (SFD) schemes have been universally used to improve the accuracy of wave equation modeling. However, the high-order SFD coefficients on spatial derivatives are usually determined by the Taylor-series expansion (TE) method, which just leads to great accuracy at small wavenumbers for wave equation modeling. Some conventional optimization methods can achieve high accuracy at large wavenumbers, but they hardly guarantee the small numerical dispersion error at small wavenumbers. In this paper, we develop new optimal explicit SFD (ESFD) and implicit SFD (ISFD) schemes for wave equation modeling. We first derive the optimal ESFD and ISFD coefficients for the first-order spatial derivatives by applying the combination of the TE and the sampling approximation to the dispersion relation, and then analyze their numerical accuracy. Finally, we perform elastic wave modeling with the ESFD and ISFD schemes based on the TE method and the optimal method, respectively. When the appropriate number and interval for the sampling points are chosen, these optimal schemes have extremely high accuracy at small wavenumbers, and can also guarantee small numerical dispersion error at large wavenumbers. Numerical accuracy analyses and modeling results demonstrate the optimal ESFD and ISFD schemes can efficiently suppress the numerical dispersion and significantly improve the modeling accuracy compared to the TE-based ESFD and ISFD schemes.
Karmanov, V. A.; Smirnov, A. V.; Mathiot, J.-F.
2007-02-15
In light-front dynamics, the regularization of amplitudes by traditional cutoffs imposed on the transverse and longitudinal components of particle momenta corresponds to restricting the integration volume by a nonrotationally invariant domain. The result depends not only on the size of this domain (i.e., on the cutoff values), but also on its orientation determined by the position of the light-front plane. Explicitly covariant formulation of light-front dynamics allows us to parametrize the latter dependence in a very transparent form. If we decompose the regularized amplitude in terms of independent invariant amplitudes, extra (nonphysical) terms should appear, with spin structures which explicitly depend on the orientation of the light-front plane. The number of form factors, i.e., the coefficients of this decomposition, therefore also increases. The spin-1/2 fermion self-energy is determined by three scalar functions, instead of the two standard ones, while for the elastic electromagnetic vertex the number of form factors increases from two to five. In the present paper we calculate perturbatively all these form factors in the Yukawa model. Then we compare the results obtained in the two following ways: (i) by using the light-front dynamics graph technique rules directly; (ii) by integrating the corresponding Feynman amplitudes in terms of the light-front variables. For each of these methods, we use two types of regularization: the transverse and longitudinal cutoffs, and the Pauli-Villars regularization. In the latter case, the dependence of amplitudes on the light-front plane orientation vanishes completely provided enough Pauli-Villars subtractions are made.
CDF - Secondary vertex trigger
D. Lucchesi
2002-10-25
At the beginning of 2002 a new data taking with an upgraded trigger system started for the CDF collaboration. One of the major improvements is the track trigger. A fast processor reconstructs tracks in the central drift chamber and the Silicon Vertex Tracker combines these tracks with the silicon vertex detector information to have track parameters with a precision as good as the offine reconstruction. This system allows CDF to trigger on tracks significantly displaced from the primary vertex with high efficiency for signal events like charm and beauty and to keep low background rates. The performances, in terms of resolution and efficiency, of both the processors are illustrated and the firsts physics results are discussed.
Gao, Kai; Huang, Lianjie
2017-08-31
The rotated staggered-grid (RSG) finite-difference method is a powerful tool for elastic-wave modeling in 2D anisotropic media where the symmetry axes of anisotropy are not aligned with the coordinate axes. We develop an improved RSG scheme with fourth-order temporal accuracy to reduce the numerical dispersion associated with prolonged wave propagation or a large temporal step size. The high-order temporal accuracy is achieved by including high-order temporal derivatives, which can be converted to high-order spatial derivatives to reduce computational cost. Dispersion analysis and numerical tests show that our method exhibits very low temporal dispersion even with a large temporal step sizemore » for elastic-wave modeling in complex anisotropic media. Using the same temporal step size, our method is more accurate than the conventional RSG scheme. In conclusion, our improved RSG scheme is therefore suitable for prolonged modeling of elastic-wave propagation in 2D anisotropic media.« less
STAGGERS IN SHEEP IN PATAGONIA
Jones, F. S.; Arnold, J. F.
1917-01-01
After observations and experimental work both in the field and laboratory, the following conclusions seem justified. 1. Staggers is a non-infectious disorder affecting horses, cattle, and sheep. 2. The disease is characterized by weakness, muscular twitching, irregular movements of the head, stiffness of the limbs, and transient motor paralysis, accompanied with spastic spasms on excitement. There is also a derangement of vision and conjunctivitis. 3. The postmortem lesions are not characteristic. 4. We readily produced the disease by feeding susceptible sheep on a coarse tuft grass commonly known as coiron or pampa grass (Poa argentina). 5. The time required to produce definite symptoms by feeding the grass varied. Two animals developed typical staggers after two feedings; in another instance a period of 21 days of feeding was required. The average time for the production of unmistakable symptoms in our experiments was 10 days. 6. Many sheep recover from staggers spontaneously. A complete change of diet will usually effect a cure within 2 weeks. 7. Older .animals that have pastured for long periods on lands where the grass grows become tolerant and are rarely affected with staggers. 8. The grass is toxic to sheep at all seasons of the year. We fed late winter and early spring grass and grass in flower, and produced staggers in every instance. The young green grass is as toxic as any edible portion of the plant. PMID:19868185
NASA Astrophysics Data System (ADS)
Yang, Lei; Yan, Hongyong; Liu, Hong
2017-03-01
Implicit staggered-grid finite-difference (ISFD) scheme is competitive for its great accuracy and stability, whereas its coefficients are conventionally determined by the Taylor-series expansion (TE) method, leading to a loss in numerical precision. In this paper, we modify the TE method using the minimax approximation (MA), and propose a new optimal ISFD scheme based on the modified TE (MTE) with MA method. The new ISFD scheme takes the advantage of the TE method that guarantees great accuracy at small wavenumbers, and keeps the property of the MA method that keeps the numerical errors within a limited bound at the same time. Thus, it leads to great accuracy for numerical solution of the wave equations. We derive the optimal ISFD coefficients by applying the new method to the construction of the objective function, and using a Remez algorithm to minimize its maximum. Numerical analysis is made in comparison with the conventional TE-based ISFD scheme, indicating that the MTE-based ISFD scheme with appropriate parameters can widen the wavenumber range with high accuracy, and achieve greater precision than the conventional ISFD scheme. The numerical modeling results also demonstrate that the MTE-based ISFD scheme performs well in elastic wave simulation, and is more efficient than the conventional ISFD scheme for elastic modeling.
NASA Astrophysics Data System (ADS)
Jahandari, Hormoz; Ansari, SeyedMasoud; Farquharson, Colin G.
2017-03-01
This study compares two finite-element (FE) and three finite-volume (FV) schemes which use unstructured tetrahedral grids for the modelling of electromagnetic (EM) data. All these schemes belong to a group of differential methods where the electric field is defined along the edges of the elements. The FE and FV schemes are based on both the EM-field and the potential formulations of Maxwell's equations. The EM-field FE scheme uses edge-based (vector) basis functions while the potential FE scheme uses vector and scalar basis functions. All the FV schemes use staggered tetrahedral-Voronoï grids. Three examples are used for comparisons in terms of accuracy and in terms of the computation resources required by generic iterative and direct solvers for solving the problems. Two of these examples represent survey scenarios with electric and magnetic sources and the results are compared with those from the literature while the third example is a comparison against analytical solutions for an electric dipole source. Exactly the same mesh is used for all examples to allow for direct comparison of the various schemes. The results show that while the FE and FV schemes are comparable in terms of accuracy and computation resources, the FE schemes are slightly more accurate but also more expensive than the FV schemes.
Taste changing in staggered quarks
Quentin Mason et al.
2004-01-05
The authors present results from a systematic perturbative investigation of taste-changing in improved staggered quarks. They show one-loop taste-changing interactions can be removed perturbatively by an effective four-quark term and calculate the necessary coefficients.
On staggered indecomposable Virasoro modules
NASA Astrophysics Data System (ADS)
Kytölä, Kalle; Ridout, David
2009-12-01
In this article, certain indecomposable Virasoro modules are studied. Specifically, the Virasoro mode L0 is assumed to be nondiagonalizable, possessing Jordan blocks of rank 2. Moreover, the module is further assumed to have a highest weight submodule, the "left module," and that the quotient by this submodule yields another highest weight module, the "right module." Such modules, which have been called staggered, have appeared repeatedly in the logarithmic conformal field theory literature, but their theory has not been explored in full generality. Here, such a theory is developed for the Virasoro algebra using rather elementary techniques. The focus centers on two different but related questions typically encountered in practical studies: How can one identify a given staggered module, and how can one demonstrate the existence of a proposed staggered module. Given just the values of the highest weights of the left and right modules, themselves subject to simple necessary conditions, invariants are defined which together with the knowledge of the left and right modules uniquely identify a staggered module. The possible values of these invariants form a vector space of dimension 0, 1, or 2, and the structures of the left and right modules limit the isomorphism classes of the corresponding staggered modules to an affine subspace (possibly empty). The number of invariants and affine restrictions is purely determined by the structures of the left and right modules. Moreover, in order to facilitate applications, the expressions for the invariants and restrictions are given by formulas as explicit as possible (they generally rely on expressions for Virasoro singular vectors). Finally, the text is liberally peppered throughout with examples illustrating the general concepts. These have been carefully chosen for their physical relevance or for the novel features they exhibit.
VizieR Online Data Catalog: STAGGER-grid of 3D stellar models. III. (Magic+, 2015)
NASA Astrophysics Data System (ADS)
Magic, Z.; Weiss, A.; Asplund, M.
2014-10-01
We investigate the relation between 1D atmosphere models that rely on the mixing length theory and models based on full 3D radiative hydrodynamic (RHD) calculations to describe convection in the envelopes of late-type stars. The adiabatic entropy value of the deep convection zone, sbot, and the entropy jump, Δs, determined from the 3D RHD models, are matched with the mixing length parameter, αMLT, from 1D hydrostatic atmosphere models with identical microphysics (opacities and equation-of-state). We also derive the mass mixing length, αm, and the vertical correlation length of the vertical velocity, C[Vz,Vz], directly from the 3D hydrodynamical simulations of stellar subsurface convection. (1 data file).
NASA Astrophysics Data System (ADS)
Zhang, Yan; Fu, Li-Yun; Zhang, Luxin; Wei, Wei; Guan, Xizhu
2014-05-01
Ultrasonic wave propagation in heterogeneous porous cores under laboratory studies is an extremely complex process involved with strong scattering by microscale heterogeneous structures. The resulting coda waves, as an index to measure scattering attenuation, are recorded as continuous waveforms in the tail portion of wavetrains. Because of the contamination of reflections from the side ends and reverberations between the sample surfaces, it is difficult to extract pure coda waves from ultrasonic measurements for the estimation of the P- and S-coda attenuation quality factors. Comparisons of numerical and experimental ultrasonic wave propagation in heterogeneous porous cores can give important insight into understanding the effect of boundary reflections on the P- and S-codas in the laboratory experiment. It challenges numerical modeling techniques by three major issues: the creation of a digital core model to map heterogeneous rock properties in detail, the perfect simulation with a controllable and accurate absorbing boundary, and overcoming the numerical dispersions resulting from high-frequency propagation and strong heterogeneity in material. A rotated staggered-grid finite-difference method of Biot's poroelastic equations is presented with an unsplit convolutional perfectly matched layer (CPML) absorbing boundary to simulate poroelastic wave propagation in isotropic and fluid-saturated porous media. The contamination of boundary reflections on coda waves is controlled by the CPML absorbing coefficients for the comparison between numerical and experimental ultrasonic waveforms. Numerical examples with a digital porous core demonstrate that the boundary reflections contaminate coda waves seriously, causing much larger coda quality factors and thus underestimating scattering attenuation.
Sau, Jay D; Tewari, Sumanta
2011-10-21
We study the diamagnetism of the six-vertex model with the arrows as directed bond currents. To our knowledge, this is the first study of the diamagnetism of this model. A special version of this model, called the F model, describes the thermal disordering transition of an orbital antiferromagnet, known as d-density wave, a proposed state for the pseudogap phase of the high-T(c) cuprates. We find that the F model is strongly diamagnetic and the susceptibility may diverge in the high-temperature critical phase with power-law arrow correlations. These results may explain the surprising recent observation of a diverging low-field diamagnetic susceptibility seen in some optimally doped cuprates within the d-density wave model of the pseudogap phase.
Vertex Detector Cable Considerations
Cooper, William E.; /Fermilab
2009-02-01
Vertex detector cable requirements are considered within the context of the SiD concept. Cable material should be limited so that the number of radiation lengths represented is consistent with the material budget. In order to take advantage of the proposed accelerator beam structure and allow cooling by flow of dry gas, 'pulsed power' is assumed. Potential approaches to power distribution, cable paths, and cable design for operation in a 5 T magnetic field are described.
NASA Astrophysics Data System (ADS)
Dannheim, D.
2015-03-01
The precision physics needs at TeV-scale linear electron-positron colliders (ILC and CLIC) require a vertex-detector system with excellent flavour-tagging capabilities through a measurement of displaced vertices. This is essential, for example, for an explicit measurement of the Higgs decays to pairs of b-quarks, c-quarks and gluons. Efficient identification of top quarks in the decay t → Wb will give access to the ttH-coupling measurement. In addition to those requirements driven by physics arguments, the CLIC bunch structure calls for hit timing at the few-ns level. As a result, the CLIC vertex-detector system needs to have excellent spatial resolution, full geometrical coverage extending to low polar angles, extremely low material budget, low occupancy facilitated by time-tagging, and sufficient heat removal from sensors and readout. These considerations challenge current technological limits. A detector concept based on hybrid pixel-detector technology is under development for the CLIC vertex detector. It comprises fast, low-power and small-pitch readout ASICs implemented in 65 nm CMOS technology (CLICpix) coupled to ultra-thin planar or active HV-CMOS sensors via low-mass interconnects. The power dissipation of the readout chips is reduced by means of power pulsing, allowing for a cooling system based on forced gas flow. This contribution reviews the requirements and design optimisation for the CLIC vertex detector and gives an overview of recent R&D achievements in the domains of sensors, readout and detector integration.
Biricodar. Vertex Pharmaceuticals.
Dey, Saibal
2002-05-01
Vertex is developing biricodar as a chemosensitizing agent designed to restore the effectiveness of chemotherapeutic agents in tumor multidrug resistance. By November 1998, phase II trials had commenced for biricodar, in combination with chemotherapy, for five common cancer indications: breast, ovarian, soft-tissue sarcomas, small cell lung cancer and prostate cancer. Phase II trials were ongoing in January 2002. By March 2000, Vertex was the sole developer of biricodar, as an agreement made in 1996 with BioChem Pharma (now Shire Pharmaceuticals), for the development and marketing of biricodar in Canada was terminated. Biricodar is the free base compound, which also has a citrate salt analog known as VX-710-3. Vertex has published three patents, WO-09615101, WO-09636630 and WO-09736869, disclosing derivatives of biricodar that are claimed for the treatment of multidrug resistant protein and P-glycoprotein-mediated multidrug resistant tumors. In January 2002, a Banc of America analyst report forecast that biricodar had a 30% chance of reaching the market with a launch date in the second half of 2005, with peak sales estimated at $250 million.
Ovarian abnormalities in the staggerer mutant mouse.
Guastavino, Jean-Marie; Boufares, Salima; Crusio, Wim E
2005-08-24
Disturbances in several reproductive functions of the staggerer cerebellar mutant mouse have been observed. In this study, reproductive efficiency of staggerer mice was compared to normal mice by recording the number of pups produced and the number of oocytes occurring. It was found that staggerer mothers produced smaller litters than controls and the number of oocytes produced in their ovaries was reduced by the staggerer mutation. These results indicate a pleiotropic effect on fertility of the Rora(sg) gene underlying the cerebellar abnormalities of the staggerer mutant.
Jaspers, Stijn; Verbeke, Geert; Böhning, Dankmar; Aerts, Marc
2016-01-01
In the last decades, considerable attention has been paid to the collection of antimicrobial resistance data, with the aim of monitoring non-wild-type isolates. This monitoring is performed based on minimum inhibition concentration (MIC) values, which are collected through dilution experiments. We present a semi-parametric mixture model to estimate the entire MIC density on the continuous scale. The parametric first component is extended with a non-parametric second component and a new back-fitting algorithm, based on the Vertex Exchange Method, is proposed. Our data example shows how to estimate the MIC density for Escherichia coli tested for ampicillin and how to use this estimate for model-based classification. A simulation study was performed, showing the promising behavior of the new method, both in terms of density estimation as well as classification.
An improved failure criterion for biological and engineered staggered composites.
Barthelat, Francois; Dastjerdi, Ahmad Khayer; Rabiei, Reza
2013-02-01
High-performance biological materials such as nacre, spider silk or bone have evolved a staggered microstructure consisting of stiff and strong elongated inclusions aligned with the direction of loading. This structure leads to useful combinations of stiffness, strength and toughness, and it is therefore increasingly mimicked in bio-inspired composites. The performance of staggered composites can be tuned; for example, their mechanical properties increase when the overlap between the inclusions is increased. However, larger overlaps may lead to excessive tensile stress and fracture of the inclusions themselves, a highly detrimental failure mode. Fracture of the inclusions has so far only been predicted using highly simplified models, which hinder our ability to properly design and optimize engineered staggered composites. In this work, we develop a new failure criterion that takes into account the complex stress field within the inclusions as well as initial defects. The model leads to an 'optimum criterion' for cases where the shear tractions on the inclusions is uniform, and a 'conservative' criterion for which the tractions are modelled as point forces at the ends of the overlap regions. The criterion can therefore be applied for a wide array of material behaviour at the interface, even if the details of the shear load transfer is not known. The new criterion is validated with experiments on staggered structures made of millimetre-thick alumina tablets, and by comparison with data on nacre. Formulated in a non-dimensional form, our new criterion can be applied on a wide variety of engineered staggered composites at any length scale. It also reveals new design guidelines, for example high aspect ratio inclusions with weak interfaces are preferable over inclusions with low aspect ratio and stronger interfaces. Together with existing models, this new criterion will lead to optimal designs that harness the full potential of bio-inspired staggered composites.
Packing Vertex Data into Hardware-Decompressible Textures.
Kwan, Kin Chung; Xu, Xuemiao; Wan, Liang; Wong, Tien-Tsin; Pang, Wai-Man
2017-04-18
Most graphics hardware features memory to store textures and vertex data for rendering. However, because of the irreversible trend of increasing complexity of scenes, rendering a scene can easily reach the limit of memory resources. Thus, vertex data are preferably compressed, with a requirement that they can be decompressed during rendering. In this paper, we present a novel method to exploit existing hardware texture compression circuits to facilitate the decompression of vertex data in graphics processing unit (GPUs). This built-in hardware allows real-time, random-order decoding of data. However, vertex data must be packed into textures, and careless packing arrangements can easily disrupt data coherence. Hence, we propose an optimization approach for the best vertex data permutation that minimizes compression error. All of these result in fast and high-quality vertex data decompression for real-time rendering. To further improve the visual quality, we introduce vertex clustering to reduce the dynamic range of data during quantization. Our experiments demonstrate the effectiveness of our method for various vertex data of 3D models during rendering with the advantages of a minimized memory footprint and high frame rate.
Magnetic wormholes and vertex operators
Singh, H. )
1994-10-15
We consider wormhole solutions in 2+1 Euclidean dimensions. A duality transformation is introduced to derive a new action from the magnetic wormhole action of Gupta, Hughes, Preskill, and Wise. The classical solution is presented. The vertex operators corresponding to the wormhole are derived. Conformally coupled scalars and spinors are considered in the wormhole background and the vertex operators are computed.
On Making a Distinguished Vertex Minimum Degree by Vertex Deletion
NASA Astrophysics Data System (ADS)
Betzler, Nadja; Bredereck, Robert; Niedermeier, Rolf; Uhlmann, Johannes
For directed and undirected graphs, we study the problem to make a distinguished vertex the unique minimum-(in)degree vertex through deletion of a minimum number of vertices. The corresponding NP-hard optimization problems are motivated by applications concerning control in elections and social network analysis. Continuing previous work for the directed case, we show that the problem is W[2]-hard when parameterized by the graph's feedback arc set number, whereas it becomes fixed-parameter tractable when combining the parameters "feedback vertex set number" and "number of vertices to delete". For the so far unstudied undirected case, we show that the problem is NP-hard and W[1]-hard when parameterized by the "number of vertices to delete". On the positive side, we show fixed-parameter tractability for several parameterizations measuring tree-likeness, including a vertex-linear problem kernel with respect to the parameter "feedback edge set number". On the contrary, we show a non-existence result concerning polynomial-size problem kernels for the combined parameter "vertex cover number and number of vertices to delete", implying corresponding nonexistence results when replacing vertex cover number by treewidth or feedback vertex set number.
The CDF silicon vertex tracker
A. Cerri et al.
2000-10-10
Real time pattern recognition is becoming a key issue in many position sensitive detector applications. The CDF collaboration is building SVT: a specialized electronic device designed to perform real time track reconstruction using the silicon vertex detector (SVX II). This will strongly improve the CDF capability of triggering on events containing b quarks, usually characterized by the presence of a secondary vertex. SVT is designed to reconstruct in real time charged particles trajectories using data coming from the Silicon Vertex detector and the Central Outer Tracker drift chamber. The SVT architecture and algorithm have been specially tuned to minimize processing time without degrading parameter resolution.
Possible Aoki phase for staggered fermions
Aubin, C.; Wang Qinghai
2004-12-01
The phase diagram for staggered fermions is discussed in the context of the staggered chiral Lagrangian, extending previous work on the subject. When the discretization errors are significant, there may be an Aoki-like phase for staggered fermions, where the remnant SO(4) taste-symmetry is broken down to SO(3). We solve explicitly for the mass spectrum in the 3-flavor degenerate mass case and discuss qualitatively the 2+1-flavor case. From numerical results we find that current simulations are outside the staggered-Aoki phase. As for near-future simulations with more-improved versions of the staggered action, it seems unlikely that these will be in the Aoki phase for any realistic value of the quark mass, although the evidence is not conclusive.
Effect of initial stagger selection on the handedness of Amyloid beta helical fibrils
Ghattyvenkatakrishna, Pavan K; Cheng, Xiaolin; Uberbacher, Edward C
2013-01-01
Various structural models for Amyloid $\\beta$ fibrils derived from a variety of experimental techniques are currently available. However, this data cannot differentiate between the relative position of the two arms of the $\\beta$ hairpin called the stagger. Amyloid fibrils of various heirarchical levels form left--handed helices composed of $\\beta$ sheets. However it is unclear if positive, negative and neutral staggers all form the macroscopic left--handed helices. Studying this is important since the success of computational approaches to develop drugs for amyloidic diseases will depend on selecting the physiologically relevant structure of the sheets. To address this issue we have conducted extensive molecular dynamics simulations of Amyloid$\\beta$ sheets of various staggers and show that only negative staggers generate the experimentally observed left--handed helices while positive staggers generate the incorrect right--handed helices. The implications of this result extend in to all amyloidic--aggregation type diseases.
Complex growing networks with intrinsic vertex fitness
Bedogne, C.; Rodgers, G. J.
2006-10-15
One of the major questions in complex network research is to identify the range of mechanisms by which a complex network can self organize into a scale-free state. In this paper we investigate the interplay between a fitness linking mechanism and both random and preferential attachment. In our models, each vertex is assigned a fitness x, drawn from a probability distribution {rho}(x). In Model A, at each time step a vertex is added and joined to an existing vertex, selected at random, with probability p and an edge is introduced between vertices with fitnesses x and y, with a rate f(x,y), with probability 1-p. Model B differs from Model A in that, with probability p, edges are added with preferential attachment rather than randomly. The analysis of Model A shows that, for every fixed fitness x, the network's degree distribution decays exponentially. In Model B we recover instead a power-law degree distribution whose exponent depends only on p, and we show how this result can be generalized. The properties of a number of particular networks are examined.
The STAR Vertex Position Detector
NASA Astrophysics Data System (ADS)
Llope, W. J.; Zhou, J.; Nussbaum, T.; Hoffmann, G. W.; Asselta, K.; Brandenburg, J. D.; Butterworth, J.; Camarda, T.; Christie, W.; Crawford, H. J.; Dong, X.; Engelage, J.; Eppley, G.; Geurts, F.; Hammond, J.; Judd, E.; McDonald, D. L.; Perkins, C.; Ruan, L.; Scheblein, J.; Schambach, J. J.; Soja, R.; Xin, K.; Yang, C.
2014-09-01
The 2×3 channel pseudo Vertex Position Detector (pVPD) in the STAR experiment at RHIC has been upgraded to a 2×19 channel detector in the same acceptance, called the Vertex Position Detector (VPD). This detector is fully integrated into the STAR trigger system and provides the primary input to the minimum-bias trigger in Au+Au collisions. The information from the detector is used both in the STAR Level-0 trigger and offline to measure the location of the primary collision vertex along the beam pipe and the event "start time" needed by other fast-timing detectors in STAR. The offline timing resolution of single detector channels in full-energy Au+Au collisions is ~100 ps, resulting in a start time resolution of a few tens of picoseconds and a resolution on the primary vertex location of ~1 cm.
Belle II Silicon Vertex Detector
NASA Astrophysics Data System (ADS)
Dutta, D.; Adamczyk, K.; Aihara, H.; Angelini, C.; Aziz, T.; Babu, V.; Bacher, S.; Bahinipati, S.; Barberio, E.; Baroncelli, Ti.; Baroncelli, To.; Basith, A. K.; Batignani, G.; Bauer, A.; Behera, P. K.; Bergauer, T.; Bettarini, S.; Bhuyan, B.; Bilka, T.; Bosi, F.; Bosisio, L.; Bozek, A.; Buchsteiner, F.; Bulla, L.; Caria, G.; Casarosa, G.; Ceccanti, M.; Červenkov, D.; Chendvankar, S. R.; Dash, N.; De Pietro, G.; Divekar, S. T.; Doležal, Z.; Forti, F.; Friedl, M.; Hara, K.; Higuchi, T.; Horiguchi, T.; Irmler, C.; Ishikawa, A.; Jeon, H. B.; Joo, C.; Kandra, J.; Kambara, N.; Kang, K. H.; Kawasaki, T.; Kodyš, P.; Kohriki, T.; Koike, S.; Kolwalkar, M. M.; Kumar, R.; Kun, W.; Kvasnička, P.; La Licata, C.; Lanceri, L.; Lettenbicher, J.; Libby, J.; Lueck, T.; Maki, M.; Mammini, P.; Mayekar, S. N.; Mohanty, G. B.; Mohanty, S.; Morii, T.; Nakamura, K. R.; Natkaniec, Z.; Onuki, Y.; Ostrowicz, W.; Paladino, A.; Paoloni, E.; Park, H.; Pilo, F.; Profeti, A.; Rashevskaya, I.; Rao, K. K.; Rizzo, G.; Resmi, P. K.; Rozanska, M.; Sasaki, J.; Sato, N.; Schultschik, S.; Schwanda, C.; Seino, Y.; Shimizu, N.; Stypula, J.; Suzuki, J.; Tanaka, S.; Taylor, G. N.; Thalmeier, R.; Thomas, R.; Tsuboyama, T.; Uozumi, S.; Urquijo, P.; Vitale, L.; Watanuki, S.; Watanabe, M.; Watson, I. J.; Webb, J.; Wiechczynski, J.; Williams, S.; Würkner, B.; Yamamoto, H.; Yin, H.; Yoshinobu, T.; Zani, L.
2017-02-01
The Belle II experiment at the SuperKEKB asymmetric energy e+e‑ collider in KEK, Japan will operate at an instantaneous luminosity 40 times larger than that of its predecessor, Belle. It is built with an aim of collecting a huge amount of data (50 ab‑1 by 2025) for precise CP violation measurements and new physics search. Thus, we need an accurate vertex determination and reconstruction of low momentum tracks which will be achieved with the help of vertex detector (VXD). The Belle II VXD consists of two layers of DEPFET pixels (`Pixel Detector') and four layers of double-sided silicon microstrip sensors (`Silicon Vertex Detector'), assembled over carbon fibre ribs. In this paper, we discuss about the Belle II Silicon Vertex Detector, especially its design and key features; we also present its module (`ladder') assembly and testing procedures.
The formation of a yield-surface vertex in rock
Olsson, W.A.
1992-01-01
Microstructural models of deformation of polycrystalline materials suggest that inelastic deformation leads to the formation of a corner or vertex at the current load point. This vertex can cause the response to non-proportional loading to be more compliant than predicted by the smooth yield-surface idealization. Combined compression-torsion experiments on Tennessee marble indicate that a vertex forms during inelastic flow. An important implication is that strain localization by bifurcation occurs earlier than predicted by bifurcation analysis using isotropic hardening.
Spin wave Feynman diagram vertex computation package
NASA Astrophysics Data System (ADS)
Price, Alexander; Javernick, Philip; Datta, Trinanjan
Spin wave theory is a well-established theoretical technique that can correctly predict the physical behavior of ordered magnetic states. However, computing the effects of an interacting spin wave theory incorporating magnons involve a laborious by hand derivation of Feynman diagram vertices. The process is tedious and time consuming. Hence, to improve productivity and have another means to check the analytical calculations, we have devised a Feynman Diagram Vertex Computation package. In this talk, we will describe our research group's effort to implement a Mathematica based symbolic Feynman diagram vertex computation package that computes spin wave vertices. Utilizing the non-commutative algebra package NCAlgebra as an add-on to Mathematica, symbolic expressions for the Feynman diagram vertices of a Heisenberg quantum antiferromagnet are obtained. Our existing code reproduces the well-known expressions of a nearest neighbor square lattice Heisenberg model. We also discuss the case of a triangular lattice Heisenberg model where non collinear terms contribute to the vertex interactions.
Lorentzian proper vertex amplitude: Asymptotics
NASA Astrophysics Data System (ADS)
Engle, Jonathan; Vilensky, Ilya; Zipfel, Antonia
2016-09-01
In previous work, the Lorentzian proper vertex amplitude for a spin-foam model of quantum gravity was derived. In the present work, the asymptotics of this amplitude are studied in the semiclassical limit. The starting point of the analysis is an expression for the amplitude as an action integral with action differing from that in the Engle-Pereira-Rovelli-Livine (EPRL) case by an extra "projector" term. This extra term scales linearly with spins only in the asymptotic limit, and is discontinuous on a (lower dimensional) submanifold of the integration domain in the sense that its value at each such point depends on the direction of approach. New tools are introduced to generalize stationary phase methods to this case. For the case of boundary data which can be glued to a nondegenerate Lorentzian 4-simplex, the asymptotic limit of the amplitude is shown to equal the single Feynman term, showing that the extra term in the asymptotics of the EPRL amplitude has been eliminated.
Silicon technologies for the CLIC vertex detector
NASA Astrophysics Data System (ADS)
Spannagel, S.
2017-06-01
CLIC is a proposed linear e+e- collider designed to provide particle collisions at center-of-mass energies of up to 3 TeV. Precise measurements of the properties of the top quark and the Higgs boson, as well as searches for Beyond the Standard Model physics require a highly performant CLIC detector. In particular the vertex detector must provide a single point resolution of only a few micrometers while not exceeding the envisaged material budget of around 0.2% X0 per layer. Beam-beam interactions and beamstrahlung processes impose an additional requirement on the timestamping capabilities of the vertex detector of about 10 ns. These goals can only be met by using novel techniques in the sensor and ASIC design as well as in the detector construction. The R&D program for the CLIC vertex detector explores various technologies in order to meet these demands. The feasibility of planar sensors with a thickness of 50-150 μm, including different active edge designs, are evaluated using Timepix3 ASICs. First prototypes of the CLICpix readout ASIC, implemented in 65 nm CMOS technology and with a pixel size of 25×25μm 2, have been produced and tested in particle beams. An updated version of the ASIC with a larger pixel matrix and improved precision of the time-over-threshold and time-of-arrival measurements has been submitted. Different hybridization concepts have been developed for the interconnection between the sensor and readout ASIC, ranging from small-pitch bump bonding of planar sensors to capacitive coupling of active HV-CMOS sensors. Detector simulations based on Geant 4 and TCAD are compared with experimental results to assess and optimize the performance of the various designs. This contribution gives an overview of the R&D program undertaken for the CLIC vertex detector and presents performance measurements of the prototype detectors currently under investigation.
Hessian and graviton propagator of the proper vertex
NASA Astrophysics Data System (ADS)
Chaharsough Shirazi, Atousa; Engle, Jonathan; Vilensky, Ilya
2016-10-01
The proper spin-foam vertex amplitude is obtained from the EPRL vertex by projecting out all but a single gravitational sector, in order to achieve correct semi-classical behavior. In this paper we calculate the gravitational two-point function predicted by the proper spin-foam vertex to lowest order in the vertex expansion. We find the same answer as in the EPRL case in the ‘continuum spectrum’ limit, so that the theory is consistent with the predictions of linearized gravity in the regime of small curvature. The method for calculating the two-point function is similar to that used in prior works: we cast it in terms of an action integral and use stationary phase methods. Thus, the calculation of the Hessian matrix plays a key role. Once the Hessian is calculated, it is used not only to calculate the two-point function, but also to calculate the coefficient appearing in the semi-classical limit of the proper vertex amplitude itself. This coefficient is the effective discrete ‘measure factor’ encoded in the spin-foam model. Through a non-trivial cancellation of different factors, we find that this coefficient is the same as the coefficient in front of the term in the asymptotics of the EPRL vertex corresponding to the selected gravitational sector.
Anomalous pseudoscalar-photon vertex in and out of equilibrium
Kumar, S. Prem; Boyanovsky, Daniel; Vega, Hector J. de
2000-03-15
The anomalous pseudoscalar-photon vertex is studied in real time in and out of equilibrium in a constituent quark model. The goal is to understand the in-medium modifications of this vertex, exploring the possibility of enhanced isospin breaking by electromagnetic effects as well as the formation of neutral pion condensates in a rapid chiral phase transition in peripheral, ultrarelativistic heavy-ion collisions. In equilibrium the effective vertex is afflicted by infrared and pinch singularities that require hard thermal loop and width corrections of the quark propagator. The resumed effective equilibrium vertex vanishes near the chiral transition in the chiral limit. In a strongly out of equilibrium chiral phase transition we find that the chiral condensate drastically modifies the quark propagators and the effective vertex. The ensuing dynamics for the neutral pion results in a potential enhancement of isospin breaking and the formation of {pi}{sup 0} condensates. While the anomaly equation and the axial Ward identity are not modified by the medium in or out of equilibrium, the effective real-time pseudoscalar-photon vertex is sensitive to low energy physics. (c) 2000 The American Physical Society.
A Macdonald refined topological vertex
NASA Astrophysics Data System (ADS)
Foda, Omar; Wu, Jian-Feng
2017-07-01
We consider the refined topological vertex of Iqbal et al (2009 J. High Energy Phys. JHEP10(2009)069), as a function of two parameters ≤ft\\lgroup x, y \\right\\rgroup , and deform it by introducing the Macdonald parameters ≤ft\\lgroup q, t \\right\\rgroup , as in the work of Vuletić on plane partitions (Vuletić M 2009 Trans. Am. Math. Soc. 361 2789-804), to obtain ‘a Macdonald refined topological vertex’. In the limit q → t , we recover the refined topological vertex of Iqbal et al and in the limit x → y , we obtain a qt-deformation of the original topological vertex of Aganagic et al (2005 Commun. Math. Phys. 25 425-78). Copies of the vertex can be glued to obtain qt-deformed 5D instanton partition functions that have well-defined 4D limits and, for generic values of ≤ft\\lgroup q, t\\right\\rgroup , contain infinite-towers of poles for every pole present in the limit q → t .
Loop-quantum-gravity vertex amplitude.
Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo
2007-10-19
Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.
Staggered heavy baryon chiral perturbation theory
Bailey, Jon A.
2008-03-01
Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms of O(m{sub {pi}}{sup 3}), which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms of O(a{sup 2}). The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in detail. The resulting chiral forms are appropriate to lattice results obtained with operators already in use and could be used to study the restoration of taste symmetry in the continuum limit. I assume that the fourth root of the fermion determinant can be incorporated in staggered chiral perturbation theory using the replica method.
Strecka, Jozef; Canová, Lucia; Minami, Kazuhiko
2009-05-01
The spin-1/2 Ising-Heisenberg model with the pair XYZ Heisenberg interaction and quartic Ising interactions is exactly solved by establishing a precise mapping relationship with the corresponding zero-field (symmetric) eight-vertex model. It is shown that the Ising-Heisenberg model with the ferromagnetic Heisenberg interaction exhibits a striking critical behavior, which manifests itself through re-entrant phase transitions as well as continuously varying critical exponents. The changes in critical exponents are in accordance with the weak universality hypothesis in spite of a peculiar singular behavior that emerges at a quantum critical point of the infinite order, which occurs at the isotropic limit of the Heisenberg interaction. On the other hand, the Ising-Heisenberg model with the antiferromagnetic Heisenberg interaction surprisingly exhibits less significant changes in both critical temperatures and critical exponents upon varying the strength of the exchange anisotropy in the Heisenberg interaction.
Examining B(M1) staggering as a fingerprint for chiral doublet bands
Qi, B.; Yao, J. M.; Zhang, S. Q.; Wang, S. Y.; Meng, J.
2009-04-15
The electromagnetic transitions of the doublet bands with different triaxiality parameter {gamma} are discussed in the particle rotor model with {pi}h{sub 11/2} x {nu}h{sub 11/2}{sup -1} configuration. It is found that B(M1) staggering as well as the resulting B(M1)/B(E2) and B(M1){sub in}/B(M1){sub out} staggering are sensitive to the triaxiality parameter {gamma}, and they associate strongly with the characters of nuclear chirality for 15 deg. {<=}{gamma}{<=}30 deg., i.e., the staggering is weak in the chiral vibration region while strong in the static chirality region. For partner bands with near degenerate energy spectra and similar B(M1) and B(E2) transitions, the strong B(M1) staggering can be used as a fingerprint for the static chirality.
NASA Astrophysics Data System (ADS)
Tomiwa, K. G.
2017-09-01
The search for new physics in the H → γγ+met relies on how well the missing transverse energy is reconstructed. The Met algorithm used by the ATLAS experiment in turns uses input variables like photon and jets which depend on the reconstruction of the primary vertex. This document presents the performance of di-photon vertex reconstruction algorithms (hardest vertex method and Neural Network method). Comparing the performance of these algorithms for the nominal Standard Model sample and the Beyond Standard Model sample, we see the overall performance of the Neural Network method of primary vertex selection performed better than the Hardest vertex method.
An optimal staggered harvesting strategy for herbaceous biomass energy crops
Bhat, M.G.; English, B.C.
1993-12-31
Biofuel research over the past two decades indicates lignocellulosic crops are a reliable source of feedstock for alternative energy. However, under the current technology of producing, harvesting and converting biomass crops, the cost of biofuel is not competitive with conventional biofuel. Cost of harvesting biomass feedstock is a single largest component of feedstock cost so there is a cost advantage in designing a biomass harvesting system. Traditional farmer-initiated harvesting operation causes over investment. This study develops a least-cost, time-distributed (staggered) harvesting system for example switch grass, that calls for an effective coordination between farmers, processing plant and a single third-party custom harvester. A linear programming model explicitly accounts for the trade-off between yield loss and benefit of reduced machinery overhead cost, associated with the staggered harvesting system. Total cost of producing and harvesting switch grass will decline by 17.94 percent from conventional non-staggered to proposed staggered harvesting strategy. Harvesting machinery cost alone experiences a significant reduction of 39.68 percent from moving from former to latter. The net return to farmers is estimated to increase by 160.40 percent. Per tonne and per hectare costs of feedstock production will decline by 17.94 percent and 24.78 percent, respectively. These results clearly lend support to the view that the traditional system of single period harvesting calls for over investment on agricultural machinery which escalates the feedstock cost. This social loss to the society in the form of escalated harvesting cost can be avoided if there is a proper coordination among farmers, processing plant and custom harvesters as to when and how biomass crop needs to be planted and harvested. Such an institutional arrangement benefits producers, processing plant and, in turn, end users of biofuels.
A Novel Vertex Affinity for Community Detection
Yoo, Andy; Sanders, Geoffrey; Henson, Van; Vassilevski, Panayot
2015-10-05
We propose a novel vertex affinity measure in this paper. The new vertex affinity quantifies the proximity between two vertices in terms of their clustering strength and is ideal for such graph analytics applications as community detection. We also developed a framework that combines simple graph searches and resistance circuit formulas to compute the vertex affinity efficiently. We study the properties of the new affinity measure empirically in comparison to those of other popular vertex proximity metrics. Our results show that the existing metrics are ill-suited for community detection due to their lack of fundamental properties that are essential for correctly capturing inter- and intra-cluster vertex proximity.
A nonperturbative fermion-boson vertex
NASA Astrophysics Data System (ADS)
Bashir, A.; Raya, A.
2002-07-01
We calculate the massive fermion propagator at one-loop order in QED3. The Ward-Takahashi identity (WTI) relates the propagator to the vertex. This allows us to split the vertex into its longitudinal and transverse parts. The former is fixed by the WTI. Following the scheme of Ball and Chiu later modified by Kizilersu et. al., we calculate the full vertex at one-loop order. A mere subtraction of the longitudinal part of the vertex gives us the transverse part. The alpha dependence in the transverse vertex can be eliminated by making use of the perturbative expressions for the wavefunction renormalization function and the mass function of complicated arguments of the incoming and outgoing fermion momenta. This leads us to a vertex which is nonperturbative in nature. We also calculate an effective vertex for which the arguments of the unknown functions have no angular dependence, making it particularly suitable for numerical studies of dynamical symmetry breaking.
Belle II silicon vertex detector
NASA Astrophysics Data System (ADS)
Adamczyk, K.; Aihara, H.; Angelini, C.; Aziz, T.; Babu, V.; Bacher, S.; Bahinipati, S.; Barberio, E.; Baroncelli, Ti.; Baroncelli, To.; Basith, A. K.; Batignani, G.; Bauer, A.; Behera, P. K.; Bergauer, T.; Bettarini, S.; Bhuyan, B.; Bilka, T.; Bosi, F.; Bosisio, L.; Bozek, A.; Buchsteiner, F.; Casarosa, G.; Ceccanti, M.; Červenkov, D.; Chendvankar, S. R.; Dash, N.; Divekar, S. T.; Doležal, Z.; Dutta, D.; Enami, K.; Forti, F.; Friedl, M.; Hara, K.; Higuchi, T.; Horiguchi, T.; Irmler, C.; Ishikawa, A.; Jeon, H. B.; Joo, C. W.; Kandra, J.; Kang, K. H.; Kato, E.; Kawasaki, T.; Kodyš, P.; Kohriki, T.; Koike, S.; Kolwalkar, M. M.; Kvasnička, P.; Lanceri, L.; Lettenbicher, J.; Maki, M.; Mammini, P.; Mayekar, S. N.; Mohanty, G. B.; Mohanty, S.; Morii, T.; Nakamura, K. R.; Natkaniec, Z.; Negishi, K.; Nisar, N. K.; Onuki, Y.; Ostrowicz, W.; Paladino, A.; Paoloni, E.; Park, H.; Pilo, F.; Profeti, A.; Rashevskaya, I.; Rao, K. K.; Rizzo, G.; Rozanska, M.; Sandilya, S.; Sasaki, J.; Sato, N.; Schultschik, S.; Schwanda, C.; Seino, Y.; Shimizu, N.; Stypula, J.; Suzuki, J.; Tanaka, S.; Tanida, K.; Taylor, G. N.; Thalmeier, R.; Thomas, R.; Tsuboyama, T.; Uozumi, S.; Urquijo, P.; Vitale, L.; Volpi, M.; Watanuki, S.; Watson, I. J.; Webb, J.; Wiechczynski, J.; Williams, S.; Würkner, B.; Yamamoto, H.; Yin, H.; Yoshinobu, T.
2016-09-01
The Belle II experiment at the SuperKEKB collider in Japan is designed to indirectly probe new physics using approximately 50 times the data recorded by its predecessor. An accurate determination of the decay-point position of subatomic particles such as beauty and charm hadrons as well as a precise measurement of low-momentum charged particles will play a key role in this pursuit. These will be accomplished by an inner tracking device comprising two layers of pixelated silicon detector and four layers of silicon vertex detector based on double-sided microstrip sensors. We describe herein the design, prototyping and construction efforts of the Belle-II silicon vertex detector.
Three-point vertex functions in Yang-Mills Theory and QCD in Landau gauge
NASA Astrophysics Data System (ADS)
Blum, Adrian L.; Alkofer, Reinhard; Huber, Markus Q.; Windisch, Andreas
2017-03-01
Solutions for the three-gluon and quark-gluon vertices from Dyson-Schwinger equations and the three-particle irreducible formalism are discussed. Dynamical quarks ("unquenching") change the three-gluon vertex via the quark-triangle diagrams which themselves include fully dressed quark-gluon vertex functions. On the other hand, the quark-swordfish diagram is, at least with the model used for the two-quark-two-gluon vertex employed here, of minor importance. For the leading tensor structure of the threegluon vertex the "unquenching" effect can be summarized for the nonperturbative part as a shift of the related dressing function towards the infrared.
Refining the shifted topological vertex
Drissi, L. B.; Jehjouh, H.; Saidi, E. H.
2009-01-15
We study aspects of the refining and shifting properties of the 3d MacMahon function C{sub 3}(q) used in topological string theory and BKP hierarchy. We derive the explicit expressions of the shifted topological vertex S{sub {lambda}}{sub {mu}}{sub {nu}}(q) and its refined version T{sub {lambda}}{sub {mu}}{sub {nu}}(q,t). These vertices complete results in literature.
STAR Vertex Detector Upgrade Development
Greiner, Leo C.; Matis, Howard S.; Stezelberger, Thorsten; Vu,Chinh Q.; Wieman, Howard; Szelezniak, Michal; Sun, Xiangming
2008-01-28
We report on the development and prototyping efforts undertaken with the goal of producing a micro-vertex detector for the STAR experiment at the RHIC accelerator at BNL. We present the basic detector requirements and show a sensor development path, conceptual mechanical design candidates and readout architecture. Prototyping and beam test results with current generation MimoSTAR-2 sensors and a readout system featuring FPGA based on-the-fly hit finding and data sparsification are also presented.
Scalar meson spectroscopy with lattice staggered fermions
Bernard, Claude; DeTar, Carleton; Fu Ziwen; Prelovsek, Sasa
2007-11-01
With sufficiently light up and down quarks the isovector (a{sub 0}) and isosinglet (f{sub 0}) scalar meson propagators are dominated at large distance by two-meson states. In the staggered-fermion formulation of lattice quantum chromodynamics, taste-symmetry breaking causes a proliferation of two-meson states that further complicates the analysis of these channels. Many of them are unphysical artifacts of the lattice approximation. They are expected to disappear in the continuum limit. The staggered-fermion fourth-root procedure has its purported counterpart in rooted staggered chiral perturbation theory (rS{chi}PT). Fortunately, the rooted theory provides a strict framework that permits the analysis of scalar meson correlators in terms of only a small number of low-energy couplings. Thus the analysis of the point-to-point scalar meson correlators in this context gives a useful consistency check of the fourth-root procedure and its proposed chiral realization. Through numerical simulation we have measured correlators for both the a{sub 0} and f{sub 0} channels in the 'Asqtad' improved staggered-fermion formulation in a lattice ensemble with lattice spacing a=0.12 fm. We analyze those correlators in the context of rS{chi}PT and obtain values of the low-energy chiral couplings that are reasonably consistent with previous determinations.
Staggered Multiple-PRF Ultrafast Color Doppler.
Posada, Daniel; Poree, Jonathan; Pellissier, Arnaud; Chayer, Boris; Tournoux, Francois; Cloutier, Guy; Garcia, Damien
2016-06-01
Color Doppler imaging is an established pulsed ultrasound technique to visualize blood flow non-invasively. High-frame-rate (ultrafast) color Doppler, by emissions of plane or circular wavefronts, allows severalfold increase in frame rates. Conventional and ultrafast color Doppler are both limited by the range-velocity dilemma, which may result in velocity folding (aliasing) for large depths and/or large velocities. We investigated multiple pulse-repetition-frequency (PRF) emissions arranged in a series of staggered intervals to remove aliasing in ultrafast color Doppler. Staggered PRF is an emission process where time delays between successive pulse transmissions change in an alternating way. We tested staggered dual- and triple-PRF ultrafast color Doppler, 1) in vitro in a spinning disc and a free jet flow, and 2) in vivo in a human left ventricle. The in vitro results showed that the Nyquist velocity could be extended to up to 6 times the conventional limit. We found coefficients of determination r(2) ≥ 0.98 between the de-aliased and ground-truth velocities. Consistent de-aliased Doppler images were also obtained in the human left heart. Our results demonstrate that staggered multiple-PRF ultrafast color Doppler is efficient for high-velocity high-frame-rate blood flow imaging. This is particularly relevant for new developments in ultrasound imaging relying on accurate velocity measurements.
Hessian and graviton propagator of the proper vertex
NASA Astrophysics Data System (ADS)
Chaharsough Shirazi, Atousa; Engle, Jonathan; Vilenskiy, Ilya
2015-04-01
The proper spin-foam vertex amplitude was obtained from the EPRL vertex by projecting out all but a single gravitational sector, in order to enable correct semi-classical behavior. In this paper we calculate the gravitational two-point function predicted by the proper spin-foam vertex to lowest order in the vertex expansion. We find the same answer as in the EPRL case, so that the theory is consistent with the predictions of linearized gravity in the regime of small curvature. The method for calculating the two-point function is again to cast it in terms of an action integral and to use stationary phase methods. Thus, the calculation of the Hessian matrix plays a key role. Once the Hessian is calculated, it is used not only to calculate the two-point function, but also to calculate the coefficient appearing in the semi-classical limit of the proper vertex amplitude itself. This coefficient can be thought of as the effective discrete ``measure factor'' encoded in the spin-foam model.
Evaluation of new spin foam vertex amplitudes
NASA Astrophysics Data System (ADS)
Khavkine, Igor
2009-06-01
The Christensen-Egan algorithm is extended and generalized to efficiently evaluate new spin foam vertex amplitudes proposed by Engle, Pereira and Rovelli and Freidel and Krasnov, with or without (factored) boundary states. A concrete pragmatic proposal is made for comparing the different models using uniform methodologies, applicable to the behavior of large spin asymptotics and of expectation values of specific semiclassical observables. The asymptotics of the new models exhibit non-oscillatory, power-law decay similar to that of the Barrett-Crane model, though with different exponents. Also, an analysis of the semiclassical wave packet propagation problem indicates that the Magliaro, Rovelli and Perini's conjecture of good semiclassical behavior of the new models does not hold for generic factored states, which neglect spin-spin correlations.
Spinfoam Cosmology with the Proper Vertex
NASA Astrophysics Data System (ADS)
Vilensky, Ilya
2017-01-01
A modification of the EPRL vertex amplitude in the spin-foam framework of quantum gravity - so-called ``proper vertex amplitude'' - has been developed to enable correct semi-classical behavior to conform to the classical Regge calculus. The proper vertex amplitude is defined by projecting to the single gravitational sector. The amplitude is recast into an exponentiated form and we derive the asymptotic form of the projector part of the action. This enables us to study the asymptotics of the proper vertex by applying extended stationary phase methods. We use the proper vertex amplitude to investigate transition amplitudes between coherent quantum boundary states of cosmological geometries. In particular, Hartle-Hawking no-boundary states are computed in the proper vertex framework. We confirm that in the classical limit the Hartle-Hawking wavefunction satisfies the Hamiltonian constraint. Partly supported by NSF grants PHY-1205968 and PHY-1505490.
NASA Astrophysics Data System (ADS)
Alipour Tehrani, Niloufar
2016-07-01
A vertex detector concept is under development for the proposed multi-TeV linear e+e- Compact Linear Collider (CLIC). To perform precision physics measurements in a challenging environment, the CLIC vertex detector pushes the technological requirements to the limits. This paper reviews the requirements for the CLIC vertex detector and gives an overview of recent R&D achievements in the domains of sensor, readout, powering and cooling.
The CDF Silicon Vertex Detector
Tkaczyk, S.; Carter, H.; Flaugher, B.
1993-09-01
A silicon strip vertex detector was designed, constructed and commissioned at the CDF experiment at the Tevatron collider at Fermilab. The mechanical design of the detector, its cooling and monitoring are presented. The front end electronics employing a custom VLSI chip, the readout electronics and various components of the SVX system are described. The system performance and the experience with the operation of the detector in the radiation environment are discussed. The device has been taking colliding beams data since May of 1992, performing at its best design specifications and enhancing the physics program of CDF.
A practical guide to the staggered herringbone mixer
Williams, Manda S.; Longmuir, Kenneth J.; Yager, Paul
2009-01-01
An analytical model of mixing in the staggered herringbone mixer (SHM) was derived to estimate mixing parameters and provide practical expressions to guide mixer design and operation for a wide range of possible solutes and flow conditions. Mixing in microfluidic systems has historically been characterized by the mixing of a specific solute system or by the redistribution of flow streams; this approach does not give any insight into the ideal operational parameters of the mixer with an arbitrary real system. For Stokes-flow mixers, mixing can be computed from a relationship between solute diffusivity, flow rate, and mixer length. Confocal microscopy and computational fluid dynamics (CFD) modeling were used to directly determine the extent of mixing for several solutes in the staggered herringbone mixer over a range of Reynolds numbers (Re) and Péclet numbers (Pe); the results were used to develop and evaluate an analytical model of its behavior. Mixing was found to be a function of only Pe and downstream position in the mixer. Required mixer length was proportional to Log(Pe); this analytical model matched well with the confocal data and CFD model for Pe < 5×104, at which point the experiments reached the limit of resolution. For particular solutes, required length and mixing time depend upon Re and diffusivity. This analytical model is applicable to other solute systems, and possibly to other embodiments of the mixer, to enable optimal design, operation, and estimation of performance. PMID:18584088
Vertex representations of quantum affine algebras.
Frenkel, I B; Jing, N
1988-12-01
We construct vertex representations of quantum affine algebras of ADE type, which were first introduced in greater generality by Drinfeld and Jimbo. The limiting special case of our construction is the untwisted vertex representation of affine Lie algebras of Frenkel-Kac and Segal. Our representation is given by means of a new type of vertex operator corresponding to the simple roots and satisfying the defining relations. In the case of the quantum affine algebra of type A, we introduce vertex operators corresponding to all the roots and determine their commutation relations. This provides an analogue of a Chevalley basis of the affine Lie algebra [unk](n) in the basic representation.
Fan Stagger Angle for Dirt Rejection
NASA Technical Reports Server (NTRS)
Gallagher, Edward J. (Inventor); Rose, Becky E. (Inventor); Brilliant, Lisa I. (Inventor)
2015-01-01
A gas turbine engine includes a spool, a turbine coupled to drive the spool, a propulsor coupled to be rotated about an axis by the turbine through the spool, and a gear assembly coupled between the propulsor and the spool such that rotation of the turbine drives the propulsor at a different speed than the spool. The propulsor includes a hub and a row of propulsor blades that extend from the hub. Each of the propulsor blades has a span between a root at the hub and a tip, and a chord between a leading edge and a trailing edge. The chord forms a stagger angle alpha with the axis, and the stagger angle alpha is less than 15 deg. at a position along the propulsor blade that is within an inboard 20% of the span.
Spin glass approach to the feedback vertex set problem
NASA Astrophysics Data System (ADS)
Zhou, Hai-Jun
2013-11-01
A feedback vertex set (FVS) of an undirected graph is a set of vertices that contains at least one vertex of each cycle of the graph. The feedback vertex set problem consists of constructing a FVS of size less than a certain given value. This combinatorial optimization problem has many practical applications, but it is in the nondeterministic polynomial-complete class of worst-case computational complexity. In this paper we define a spin glass model for the FVS problem and then study this model on the ensemble of finite-connectivity random graphs. In our model the global cycle constraints are represented through the local constraints on all the edges of the graph, and they are then treated by distributed message-passing procedures such as belief propagation. Our belief propagation-guided decimation algorithm can construct nearly optimal feedback vertex sets for single random graph instances and regular lattices. We also design a spin glass model for the FVS problem on a directed graph. Our work will be very useful for identifying the set of vertices that contribute most significantly to the dynamical complexity of a large networked system.
Tan, Sirui; Huang, Lianjie
2014-11-01
For modeling scalar-wave propagation in geophysical problems using finite-difference schemes, optimizing the coefficients of the finite-difference operators can reduce numerical dispersion. Most optimized finite-difference schemes for modeling seismic-wave propagation suppress only spatial but not temporal dispersion errors. We develop a novel optimized finite-difference scheme for numerical scalar-wave modeling to control dispersion errors not only in space but also in time. Our optimized scheme is based on a new stencil that contains a few more grid points than the standard stencil. We design an objective function for minimizing relative errors of phase velocities of waves propagating in all directions within a given range of wavenumbers. Dispersion analysis and numerical examples demonstrate that our optimized finite-difference scheme is computationally up to 2.5 times faster than the optimized schemes using the standard stencil to achieve the similar modeling accuracy for a given 2D or 3D problem. Compared with the high-order finite-difference scheme using the same new stencil, our optimized scheme reduces 50 percent of the computational cost to achieve the similar modeling accuracy. This new optimized finite-difference scheme is particularly useful for large-scale 3D scalar-wave modeling and inversion.
Vertex Separators for Partitioning a Graph
Evrendilek, Cem
2008-01-01
Finite Element Method (FEM) is a well known technique extensively studied for spatial and temporal modeling of environmental processes, weather prediction computations, and intelligent signal processing for wireless sensors. The need for huge computational power arising in such applications to simulate physical phenomenon correctly mandates the use of massively parallel computers to distribute the workload evenly. In this study, a novel heuristic algorithm called Line Graph Bisection which partitions a graph via vertex separators so as to balance the workload amongst the processors and to minimize the communication overhead is proposed. The proposed algorithm is proved to be computationally feasible and makes cost-effective parallel implementations possible to speed up the solution process. PMID:27879727
The CDF silicon vertex trigger
B. Ashmanskas; A. Barchiesi; A. Bardi
2003-06-23
The CDF experiment's Silicon Vertex Trigger is a system of 150 custom 9U VME boards that reconstructs axial tracks in the CDF silicon strip detector in a 15 {mu}sec pipeline. SVT's 35 {mu}m impact parameter resolution enables CDF's Level 2 trigger to distinguish primary and secondary particles, and hence to collect large samples of hadronic bottom and charm decays. We review some of SVT's key design features. Speed is achieved with custom VLSI pattern recognition, linearized track fitting, pipelining, and parallel processing. Testing and reliability are aided by built-in logic state analysis and test-data sourcing at each board's input and output, a common inter-board data link, and a universal ''Merger'' board for data fan-in/fan-out. Speed and adaptability are enhanced by use of modern FPGAs.
Numerical simulation and experiment on multilayer stagger-split die.
Liu, Zhiwei; Li, Mingzhe; Han, Qigang; Yang, Yunfei; Wang, Bolong; Sui, Zhou
2013-05-01
A novel ultra-high pressure device, multilayer stagger-split die, has been constructed based on the principle of "dividing dies before cracking." Multilayer stagger-split die includes an encircling ring and multilayer assemblages, and the mating surfaces of the multilayer assemblages are mutually staggered between adjacent layers. In this paper, we investigated the stressing features of this structure through finite element techniques, and the results were compared with those of the belt type die and single split die. The contrast experiments were also carried out to test the bearing pressure performance of multilayer stagger-split die. It is concluded that the stress distributions are reasonable and the materials are utilized effectively for multilayer stagger-split die. And experiments indicate that the multilayer stagger-split die can bear the greatest pressure.
Proposed proper Engle-Pereira-Rovelli-Livine vertex amplitude
NASA Astrophysics Data System (ADS)
Engle, Jonathan
2013-04-01
As established in a prior work of the author, the linear simplicity constraints used in the construction of the so-called “new” spin-foam models mix three of the five sectors of Plebanski theory as well as two dynamical orientations, and this is the reason for multiple terms in the asymptotics of the Engle-Pereira-Rovelli-Livine vertex amplitude as calculated by Barrett et al. Specifically, the term equal to the usual exponential of i times the Regge action corresponds to configurations either in sector (II+) with positive orientation or sector (II-) with negative orientation. The presence of the other terms beyond this cause problems in the semiclassical limit of the spin-foam model when considering multiple 4-simplices due to the fact that the different terms for different 4-simplices mix in the semiclassical limit, leading in general to a non-Regge action and hence non-Regge and nongravitational configurations persisting in the semiclassical limit. To correct this problem, we propose to modify the vertex so its asymptotics include only the one term of the form eiSRegge. To do this, an explicit classical discrete condition is derived that isolates the desired gravitational sector corresponding to this one term. This condition is quantized and used to modify the vertex amplitude, yielding what we call the “proper Engle-Pereira-Rovelli-Livine vertex amplitude.” This vertex still depends only on standard SU(2) spin-network data on the boundary, is SU(2) gauge-invariant, and is linear in the boundary state, as required. In addition, the asymptotics now consist in the single desired term of the form eiSRegge, and all degenerate configurations are exponentially suppressed. A natural generalization to the Lorentzian signature is also presented.
Wu, Qing-Qiu; Ni, Wei-Hai; You, Wen-Long
2017-06-07
We consider a class of one-dimensional compass models with staggered Dzyaloshinskii-Moriya exchange interactions in an external transverse magnetic field. Based on the exact solution derived from Jordan-Wigner approach, we study the excitation gap, energy spectra, spin correlations and critical properties at phase transitions. We explore mutual effects of the staggered Dzyaloshinskii-Moriya interaction and the magnetic field on the energy spectra and the ground-state phase diagram. Thermodynamic quantities including the entropy and the specific heat are discussed, and their universal scalings at low temperature are demonstrated.
NASA Astrophysics Data System (ADS)
Wu, Qing-Qiu; Ni, Wei-Hai; You, Wen-Long
2017-06-01
We consider a class of one-dimensional compass models with staggered Dzyaloshinskii-Moriya exchange interactions in an external transverse magnetic field. Based on the exact solution derived from Jordan-Wigner approach, we study the excitation gap, energy spectra, spin correlations and critical properties at phase transitions. We explore mutual effects of the staggered Dzyaloshinskii-Moriya interaction and the magnetic field on the energy spectra and the ground-state phase diagram. Thermodynamic quantities including the entropy and the specific heat are discussed, and their universal scalings at low temperature are demonstrated.
Domination Number of Vertex Amalgamation of Graphs
NASA Astrophysics Data System (ADS)
Wahyuni, Y.; Utoyo, M. I.; Slamin
2017-06-01
For a graph G = (V, E), a subset S of V is called a dominating set if every vertex x in V is either in S or adjacent to a vertex in S. The domination number γ ( G ) is the minimum cardinality of the dominating set of G. The dominating set of G with a minimum cardinality denoted by γ ( G )-set. Let G 1, G 2, …, Gt be subgraphs of the graph G. If the union of all these subgraphs is G and their intersection is {v}, then we say that G is the vertex-amalgamation of G 1, G 2, …, Gt at vertex v. Based on the membership of the common vertex v in the γ ( Gi )-set, there exist three conditions to be considered. First, if v elements of every γ ( Gi )-set, second if there is no γ ( Gi )-set containing v, and third if either v is element of γ ( Gi )-set for 1 ≤ i ≤ p or there is no γ ( Gi )-set containing v for p < i ≤ t . For these three conditions, the domination number of G as vertex-amalgamation of G 1, G 2, …, Gt at vertex v can be determined.
Vertex finding with deformable templates at LHC
NASA Astrophysics Data System (ADS)
Stepanov, Nikita; Khanov, Alexandre
1997-02-01
We present a novel vertex finding technique. The task is formulated as a discrete-continuous optimisation problem in a way similar to the deformable templates approach for the track finding. Unlike the track finding problem, "elastic hedgehogs" rather than elastic arms are used as deformable templates. They are initialised by a set of procedures which provide zero level approximation for vertex positions and track parameters at the vertex point. The algorithm was evaluated using the simulated events for the LHC CMS detector and demonstrated good performance.
Edge union of networks on the same vertex set
NASA Astrophysics Data System (ADS)
Loe, Chuan Wen; Jeldtoft Jensen, Henrik
2013-06-01
Random network generators such as Erdős-Rényi, Watts-Strogatz and Barabási-Albert models are used as models to study real-world networks. Let G1(V, E1) and G2(V, E2) be two such networks on the same vertex set V. This paper studies the degree distribution and clustering coefficient of the resultant networks, G(V, E1∪E2).
Exploratory analysis of longitudinal trials with staggered intervention times.
Sousa, Inês; Chetwynd, Amanda G; Diggle, Peter J
2005-07-01
Longitudinal trials involving surgical interventions commonly have subject-specific intervention times, due to constraints on the availability of surgeons and operating theatres. Moreover, the intervention often effects a discontinuous change in the mean response. We propose a nonparametric estimator for the mean response profile of longitudinal data with staggered intervention times and a discontinuity at the times of intervention, as an exploratory tool to assist the formulation of a suitable parametric model. We use an adaptation of the standard generalized additive model algorithm for estimation, with smoothing constants chosen by a cross-validation criterion. We illustrate the method using longitudinal data from a trial to assess the effect of lung resection surgery in the treatment of emphysema patients.
The Vertex Algebra M(1)+ and Certain Affine Vertex Algebras of Level -1
NASA Astrophysics Data System (ADS)
Adamović, Dražen; Perše, Ozren
2012-07-01
We give a coset realization of the vertex operator algebra M(1)^+ with central charge ℓ. We realize M(1) ^+ as a commutant of certain affine vertex algebras of level -1 in the vertex algebra L_{C_{ℓ} ^{(1)}}(-1/2 Λ_0) ⊗ L_{C_{ℓ} ^{(1)}}(-1/2 Λ_0). We show that the simple vertex algebra L_{C_{ℓ} ^{(1)}}(-Λ_0) can be (conformally) embedded into L_{A_{2 ℓ -1} ^{(1)}} (-Λ_0) and find the corresponding decomposition. We also study certain coset subalgebras inside L_{C_{ℓ} ^{(1)}}(-Λ_0).
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
Matevosyan, Hrayr H.; Thomas, Anthony W.; Tandy, Peter C.
2007-04-15
We include a generalized infinite class of quark-gluon vertex dressing diagrams in a study of how dynamics beyond the ladder-rainbow truncation influences the Bethe-Salpeter description of light-quark pseudoscalar and vector mesons. The diagrammatic specification of the vertex is mapped into a corresponding specification of the Bethe-Salpeter kernel, which preserves chiral symmetry. This study adopts the algebraic format afforded by the simple interaction kernel used in previous work on this topic. The new feature of the present work is that in every diagram summed for the vertex and the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be the self-consistent vertex solution. We also adopt from previous work the effective accounting for the role of the explicitly non-Abelian three-gluon coupling in a global manner through one parameter determined from recent lattice-QCD data for the vertex. Within the current model, the more consistent dressed vertex limits the ladder-rainbow truncation error for vector mesons to be never more than 10% as the current quark mass is varied from the u/d region to the b region.
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
NASA Astrophysics Data System (ADS)
Matevosyan, Hrayr H.; Thomas, Anthony W.; Tandy, Peter C.
2007-04-01
We include a generalized infinite class of quark-gluon vertex dressing diagrams in a study of how dynamics beyond the ladder-rainbow truncation influences the Bethe-Salpeter description of light-quark pseudoscalar and vector mesons. The diagrammatic specification of the vertex is mapped into a corresponding specification of the Bethe-Salpeter kernel, which preserves chiral symmetry. This study adopts the algebraic format afforded by the simple interaction kernel used in previous work on this topic. The new feature of the present work is that in every diagram summed for the vertex and the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be the self-consistent vertex solution. We also adopt from previous work the effective accounting for the role of the explicitly non-Abelian three-gluon coupling in a global manner through one parameter determined from recent lattice-QCD data for the vertex. Within the current model, the more consistent dressed vertex limits the ladder-rainbow truncation error for vector mesons to be never more than 10% as the current quark mass is varied from the u/d region to the b region.
A spin glass approach to the directed feedback vertex set problem
NASA Astrophysics Data System (ADS)
Zhou, Hai-Jun
2016-07-01
A directed graph (digraph) is formed by vertices and arcs (directed edges) from one vertex to another. A feedback vertex set (FVS) is a set of vertices that contains at least one vertex of every directed cycle in this digraph. The directed feedback vertex set problem aims at constructing a FVS of minimum cardinality. This is a fundamental cycle-constrained hard combinatorial optimization problem with wide practical applications. In this paper we construct a spin glass model for the directed FVS problem by converting the global cycle constraints into local arc constraints, and study this model through the replica-symmetric (RS) mean field theory of statistical physics. We then implement a belief propagation-guided decimation (BPD) algorithm for single digraph instances. The BPD algorithm slightly outperforms the simulated annealing algorithm on large random graph instances. The RS mean field results and algorithmic results can be further improved by working on a more restrictive (and more difficult) spin glass model.
Vertex amplitudes in spin foam loop quantum cosmology
NASA Astrophysics Data System (ADS)
Craig, David
2016-03-01
We discuss properties of the vertex expansion for homogeneous, isotropic loop quantum cosmological models sourced by a massless, minimally coupled scalar field, which in this model plays the role of an internal matter ``clock''. We show that the vertex expansion, first written down by Ashtekar, Campiglia and Henderson, must be thought of as a short-time expansion in the sense that the amplitude for volume transitions is constrained both by the order of the expansion and by the elapsed scalar field. To calculate the amplitude for significant volume changes or between large differences in the value of the scalar field requires the expansion be evaluated to very high order. This contribution describes work in collaboration with P. Singh.
Vertex micromagnetic energy in artificial square ice
NASA Astrophysics Data System (ADS)
Perrin, Yann; Canals, Benjamin; Rougemaille, Nicolas
2016-10-01
Artificial arrays of interacting magnetic elements provide an uncharted arena in which the physics of magnetic frustration and magnetic monopoles can be observed in real space and in real time. These systems offer the formidable opportunity to investigate a wide range of collective magnetic phenomena with a lab-on-chip approach and to explore various theoretical predictions from spin models. Here, we study artificial square ice systems numerically and use micromagnetic simulations to understand how the geometrical parameters of the individual magnetic elements affect the energy levels of an isolated square vertex. More specifically, we address the question of whether the celebrated square ice model could be made relevant for artificial square ice systems. Our work reveals that tuning the geometry alone should not allow the experimental realization of the square ice model when using nanomagnets coupled through the magnetostatic interaction. However, low-aspect ratios combined with small gaps separating neighboring magnetic elements of moderated thickness might permit approaching the ideal case where the degeneracy of the ice rule states is recovered.
String loop corrections from fusion of handles and vertex operators
NASA Astrophysics Data System (ADS)
Ooguri, H.; Sakai, N.
1987-10-01
Handle operators are introduced to describe nonlinear sigma models on higher genus surfaces by an operator formalism. Operator product expansions (fusions) among handle and vertex operators provide new sources of conformal symmetry breakings. Through the renormalization group equations, string-loop corrected equations of motion without one-particle reducible parts are derived to one-loop order. Work supported in part by Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture (No. 61540200).
Penguin diagrams for improved staggered fermions
Lee, Weonjong
2005-01-01
We calculate, at the one-loop level, penguin diagrams for improved staggered fermion operators constructed using various fat links. The main result is that diagonal mixing coefficients with penguin operators are identical between the unimproved operators and the improved operators using such fat links as Fat7, Fat7+Lepage, Fat7, HYP (I) and HYP (II). In addition, it turns out that the off-diagonal mixing vanishes for those constructed using fat links of Fat7, Fat7 and HYP (II). This is a consequence of the fact that the improvement by various fat links changes only the mixing with higher dimension operators and off-diagonal operators. The results of this paper, combined with those for current-current diagrams, provide complete matching at the one-loop level with all corrections of O(g{sup 2}) included.
Thermal Protection System with Staggered Joints
NASA Technical Reports Server (NTRS)
Simon, Xavier D. (Inventor); Robinson, Michael J. (Inventor); Andrews, Thomas L. (Inventor)
2014-01-01
The thermal protection system disclosed herein is suitable for use with a spacecraft such as a reentry module or vehicle, where the spacecraft has a convex surface to be protected. An embodiment of the thermal protection system includes a plurality of heat resistant panels, each having an outer surface configured for exposure to atmosphere, an inner surface opposite the outer surface and configured for attachment to the convex surface of the spacecraft, and a joint edge defined between the outer surface and the inner surface. The joint edges of adjacent ones of the heat resistant panels are configured to mate with each other to form staggered joints that run between the peak of the convex surface and the base section of the convex surface.
Power module assemblies with staggered coolant channels
Herron, Nicholas Hayden; Mann, Brooks S; Korich, Mark D
2013-07-16
A manifold is provided for supporting a power module assembly with a plurality of power modules. The manifold includes a first manifold section. The first face of the first manifold section is configured to receive the first power module, and the second face of the first manifold section defines a first cavity with a first baseplate thermally coupled to the first power module. The first face of the second manifold section is configured to receive the second power module, and the second face of the second manifold section defines a second cavity with a second baseplate thermally coupled to the second power module. The second face of the first manifold section and the second face of the second manifold section are coupled together such that the first cavity and the second cavity form a coolant channel. The first cavity is at least partially staggered with respect to second cavity.
Proposal of a Bulk HTSC Staggered Array Undulator
Kii, Toshiteru; Kinjo, Ryota; Bakr, Mahmoud A.; Sonobe, Taro; Higashimura, Keisuke; Masuda, Kai; Ohgaki, Hideaki; Yoshida, Kyohei; Zen, Heisyun
2010-06-23
We proposed a new type of undulator based on bulk high-T{sub c} superconductors (HTSC) which consists of a single solenoid and a stacked array of bulk HTSC. The main advantage of this configuration is that a mechanical structure is not required to produce and control the undulator field. In order to perform a proof of principle experiment, we have developed a prototype of bulk HTSC staggered array undulator using 11 pairs of DyBaCuO bulk superconductors and a normal conducting solenoid. Experimental results obtained by using the prototype undulator and numerical results obtained by a loop current model based on the Bean mode for a type-II superconductor were compared.
Staggering Inflation To Stabilize Attitude of a Solar Sail
NASA Technical Reports Server (NTRS)
Quadrelli, Marco; West, John
2007-01-01
A document presents computational-simulation studies of a concept for stabilizing the attitude of a spacecraft during deployment of such structures as a solar sail or other structures supported by inflatable booms. Specifically, the solar sail considered in this paper is a square sail with inflatable booms and attitude control vanes at the corners. The sail inflates from its stowed configuration into a square sail with four segments and four vanes at the tips. Basically, the concept is one of controlling the rates of inflation of the booms to utilize in mass-distribution properties to effect changes in the system s angular momentum. More specifically, what was studied were the effects of staggering inflation of each boom by holding it at constant length for specified intervals between intervals of increasing length until full length is reached. The studies included sensitivity analyses of effects of variations in mass properties, boom lengths, rates of increase in boom length, initial rates of rotation of the spacecraft, and several asymmetries that could arise during deployment. The studies led to the conclusion that the final attitude of the spacecraft could be modified by varying the parameters of staggered inflation. Computational studies also showed that by feeding back attitude and attitude-rate measurements so that corrective action is taken during the deployment, the final attitude can be maintained very closely to the initial attitude, thus mitigating the attitude changes incurred during deployment and caused by modeling errors. Moreover, it was found that by optimizing the ratio between the holding and length-increasing intervals in deployment of a boom, one could cause deployment to track a desired deployment profile to place the entire spacecraft in a desired attitude at the end of deployment.
Duality, gauged supergravities and vertex operators in string theory
NASA Astrophysics Data System (ADS)
Langham, Michael Charles
2000-10-01
We first examine a conjectured S-duality between the type IIA on R6 × K3 and the Heterotic string on R6 × T4, and compare their perturbative spectra. The partition function of type II strings on R6 × K3, in the orbifold limit, is computed as a modular invariant sum of spin structures or sectors, required by perturbative unitarity. Secondly, we analyze type II strings on R6 × W4, where W4 is associated with the tube metric conformal field theory, given by the degrees of freedom transverse to the Neveu- Schwarz fivebrane solution. The tube metric generates partition functions and perturbative spectra of string theories in six space-time dimensions, associated with the modular invariants of the level k affine SU(2) Kac-Moody algebra. We then study maximally supersymmetric gauged supergravities; i.e. low-energy limits of superstrings and M theory in anti-deSitter space times a sphere (AdSxS). We show how the gauge symmetry representation of the massless particle content of gauged supergravities can be derived from symmetric subgroups to be carried by string theory vertex operators in these compactified models. Lastly, for a non-maximally supersymmetric case, type IIB in AdS3 × S 3 background with NS-NS flux, we calculate explicit vertex operators using the Berkovits-Vafa-Witten formalism. From these, with suitable field definitions, the linearized field equations for six-dimensional supergravity and a tensor multiplet on AdS3 × S3 are recovered. We also discuss the three dimensional massless degrees of freedom that survive the S3 Kaluza-Klein compactification and show how our vertex operators are related to the vertex operators introduced by Giveon, Kutasov, and Seiberg.
NASA Astrophysics Data System (ADS)
Ismail, Kamal, Samsul; Purnomo, Sarjiya
2016-06-01
This investigation was conducted to identify the influences of the two positions (non-staggered and staggered) of wind turbine arrays. Identification on down-scaled size wind turbine arrays was carried out in an open circuit, suction-type wind tunnel. Based on the results of the experiment, empirical relations for the centreline velocity deficit, tipline velocity deficit and wake radius are proposed. The non-staggered position results are larger power generated than that of the staggered position, this influenced by the trend deficit in velocity that makes wind turbine generated power difference between staggered position and non-stagger position. The area used non-staggered position larger than staggered position. Result staggered position has become one of the solutions to harness wind farms confined areas.
Optimal Designs of Staggered Dean Vortex Micromixers
Chen, Jyh Jian; Chen, Chun Huei; Shie, Shian Ruei
2011-01-01
A novel parallel laminar micromixer with a two-dimensional staggered Dean Vortex micromixer is optimized and fabricated in our study. Dean vortices induced by centrifugal forces in curved rectangular channels cause fluids to produce secondary flows. The split-and-recombination (SAR) structures of the flow channels and the impinging effects result in the reduction of the diffusion distance of two fluids. Three different designs of a curved channel micromixer are introduced to evaluate the mixing performance of the designed micromixer. Mixing performances are demonstrated by means of a pH indicator using an optical microscope and fluorescent particles via a confocal microscope at different flow rates corresponding to Reynolds numbers (Re) ranging from 0.5 to 50. The comparison between the experimental data and numerical results shows a very reasonable agreement. At a Re of 50, the mixing length at the sixth segment, corresponding to the downstream distance of 21.0 mm, can be achieved in a distance 4 times shorter than when the Re equals 1. An optimization of this micromixer is performed with two geometric parameters. These are the angle between the lines from the center to two intersections of two consecutive curved channels, θ, and the angle between two lines of the centers of three consecutive curved channels, ϕ. It can be found that the maximal mixing index is related to the maximal value of the sum of θ and ϕ, which is equal to 139.82°. PMID:21747691
Efficiency and optimal allocation in the staggered entry design
Link, W.A.
1993-01-01
The staggered entry design for survival analysis specifies that r left-truncated samples are to be used in estimation of a population survival function. The ith sample is taken at time Bi, from the subpopulation of individuals having survival time exceeding Bi. This paper investigates the performance of the staggered entry design relative to the usual design in which all samples have a common time origin. The staggered entry design is shown to be an attractive alternative, even when not necessitated by logistical constraints. The staggered entry design allows for increased precision in estimation of the right tail of the survival function, especially when some of the data may be censored. A trade-off between the range of values for which the increased precision occurs and the magnitude of the increased precision is demonstrated.
Structural insight for chain selection and stagger control in collagen
Boudko, Sergei P.; Bächinger, Hans Peter
2016-01-01
Collagen plays a fundamental role in all known metazoans. In collagens three polypeptides form a unique triple-helical structure with a one-residue stagger to fit every third glycine residue in the inner core without disturbing the poly-proline type II helical conformation of each chain. There are homo- and hetero-trimeric types of collagen consisting of one, two or three distinct chains. Thus there must be mechanisms that control composition and stagger during collagen folding. Here, we uncover the structural basis for both chain selection and stagger formation of a collagen molecule. Three distinct chains (α1, α2 and α3) of the non-collagenous domain 2 (NC2) of type IX collagen are assembled to guide triple-helical sequences in the leading, middle and trailing positions. This unique domain opens the door for generating any fragment of collagen in its native composition and stagger. PMID:27897211
Topological susceptibility in staggered fermion chiral perturbation theory
Billeter, Brian; DeTar, Carleton; Osborn, James
2004-10-01
The topological susceptibility of the vacuum in quantum chromodynamics has been simulated numerically using the Asqtad improved staggered fermion formalism. At nonzero lattice spacing, the residual fermion doublers (fermion tastes) in the staggered fermion formalism give contributions to the susceptibility that deviate from conventional continuum chiral perturbation theory. In this brief report, we estimate the taste-breaking artifact and compare it with results of recent simulations, finding that it accounts for roughly half of the scaling violation.
Turbulent flow and scalar flux through and over aligned and staggered wind farms
NASA Astrophysics Data System (ADS)
Markfort, C. D.; Zhang, W.; Porté-Agel, F.
2012-04-01
Wind farm-atmosphere interaction is complicated by the effect of turbine array configuration on momentum, scalar and kinetic energy fluxes. Wind turbine arrays are often arranged in rectilinear grids and, depending on the wind direction, may be perfectly aligned or perfectly staggered. The two extreme configurations make up the end members of a spectrum of infinite possible layouts. A wind farm of finite length may be modeled as an added roughness or as a canopy in large-scale weather and climate models. However, it is not clear which analogy is physically more appropriate. Also, surface scalar flux, including heat, evaporation and trace gas (e.g. CO2) fluxes affected by wind farms, need to be properly parameterized in large-scale models. Experiments involving model wind farms in aligned and staggered configurations, consisting of 13 rows with equivalent turbine density, were conducted in a thermally-controlled boundary-layer wind tunnel. Measurements of the turbulent flow were made using a custom x-wire/cold wire within and over the wind farms. Particular focus was placed on studying the effect of wind farm layout on flow adjustment, momentum and scalar fluxes, and turbulent kinetic energy distribution. Results show that the turbulence statistics of the flow exhibit similar turbulent transport properties to those of canopy flows, but retain some characteristic surface layer properties in a limited region above the wind farms as well. The initial wake growth over columns of turbines in the aligned wind farm is faster. However, the overall wake adjusts within and grows more rapidly over the staggered farm. The effective roughness of the staggered farm was found to be significantly larger than that of the aligned farm. The flow equilibrates faster, and the overall momentum absorption is higher for the staggered compared to the aligned farm, which is consistent with canopy scaling. Lower surface heat flux was found for the wind farms compared to the boundary
Effective field theories for QCD with rooted staggered fermions
Bernard, Claude; Golterman, Maarten; Shamir, Yigal
2008-04-01
Even highly improved variants of lattice QCD with staggered fermions show significant violations of taste symmetry at currently accessible lattice spacings. In addition, the 'rooting trick' is used in order to simulate with the correct number of light sea quarks, and this makes the lattice theory nonlocal, even though there is good reason to believe that the continuum limit is in the correct universality class. In order to understand scaling violations, it is thus necessary to extend the construction of the Symanzik effective theory to include rooted staggered fermions. We show how this can be done, starting from a generalization of the renormalization-group approach to rooted staggered fermions recently developed by one of us. We then explain how the chiral effective theory follows from the Symanzik action, and show that it leads to 'rooted' staggered chiral perturbation theory as the correct chiral theory for QCD with rooted staggered fermions. We thus establish a direct link between the renormalization-group based arguments for the correctness of the continuum limit and the success of rooted staggered chiral perturbation theory in fitting numerical results obtained with the rooting trick. In order to develop our argument, we need to assume the existence of a standard partially-quenched chiral effective theory for any local partially-quenched theory. Other technical, but standard, assumptions are also required.
Lifetime tests for MAC vertex chamber
Nelson, H.N.
1986-07-01
A vertex chamber for MAC was proposed to increase precision in the measurement of the B hadron and tau lepton lifetimes. Thin-walled aluminized mylar drift tubes were used for detector elements. A study of radiation hardness was conducted under the conditions of the proposed design using different gases and different operating conditions. (LEW)
Investigation and improvement of the staggered labyrinth seal
NASA Astrophysics Data System (ADS)
Lin, Zhirong; Wang, Xudong; Yuan, Xin; Shibukawa, Naoki; Noguchi, Taro
2015-03-01
Recent studies on staggered labyrinth seals have focused on the effects of different parameters, such as the pressure ratio and rotational speed on the leakage flow rate. However, few investigations pay sufficient attention to flow details and the sealing mechanism, which would be of practical importance in designing seals having higher performance. This paper establishes a theoretical model to study the seal mechanism, thus revealing that leakage is determined by the pressure ratio and geometric structure. Numerical simulation is implemented to illustrate details of the flow field within the seal structure. Viscous dissipation is used to quantitatively investigate the contribution that each location makes to the seal performance, revealing that orifices and stagnation points are the most important positions in the seal structure, generating the most dissipation. The orifice is carefully studied by using the theoretical model. Experiments for different pressure ratios are conducted and the results match well with those of the theoretical model and numerical simulation, verifying the theoretical model and analysis of the seal mechanism. Three new designs, based on a good understanding of the seal mechanism, are presented, with one reducing leakage by 24.5%.
Battaglia, Marco; Bussat, Jean-Marie; Contarato, Devis; Denes,Peter; Glesener, Lindsay; Greiner, Leo; Hooberman, Benjamin; Shuman,Derek; Tompkins, Lauren; Vu, Chinh; Bisello, Dario; Giubilato, Piero; Pantano, Devis; Costa, Marco; La Rosa, Alessandro; Bolla, Gino; Bortoletto, Daniela; Children, Isaac
2007-10-01
This document summarizes past achievements, current activities and future goals of the R&D program aimed at the design, prototyping and characterization of a full detector module, equipped with monolithic pixel sensors, matching the requirements for the Vertex Tracker at the ILC. We provide a plan of activities to obtain a demonstrator multi-layered vertex tracker equipped with sensors matching the ILC requirements and realistic lightweight ladders in FY11, under the assumption that ILC detector proto-collaborations will be choosing technologies and designs for the Vertex Tracker by that time. The R&D program discussed here started at LBNL in 2004, supported by a Laboratory Directed R&D (LDRD) grant and by funding allocated from the core budget of the LBNL Physics Division and from the Department of Physics at UC Berkeley. Subsequently additional funding has been awarded under the NSF-DOE LCRD program and also personnel have become available through collaborative research with other groups. The aim of the R&D program carried out by our collaboration is to provide a well-integrated, inclusive research effort starting from physics requirements for the ILC Vertex Tracker and addressing Si sensor design and characterization, engineered ladder design, module system issues, tracking and vertex performances and beam test validation. The broad scope of this program is made possible by important synergies with existing know-how and concurrent programs both at LBNL and at the other collaborating institutions. In particular, significant overlaps with LHC detector design, SLHC R&D as well as prototyping for the STAR upgrade have been exploited to optimize the cost per deliverable of our program. This activity is carried out as a collaborative effort together with Accelerator and Fusion Research, the Engineering and the Nuclear Science Divisions at LBNL, INFN and the Department of Physics in Padova, Italy, INFN and the Department of Physics in Torino, Italy and the Department
Experimental Measurement of the Staggered Magnetization Curve for a Haldane Spin Chain
NASA Astrophysics Data System (ADS)
Zheludev, A.; Ressouche, E.; Maslov, S.; Yokoo, T.; Raymond, S.; Akimitsu, J.
1998-04-01
Long-range magnetic ordering in R2BaNiO5 ( R = magnetic rare earth) quasi-one-dimensional mixed-spin antiferromagnets is described by a simple mean-field model that is based on the intrinsic staggered magnetization function of isolated Haldane spin chains for the Ni subsystem, and single-ion magnetization functions for the rare earth ions. The model is applied to new experimental results obtained in powder diffraction experiments on Nd2BaNiO5 and NdYBaNiO5, and to previously published diffraction data for Er2BaNiO5. From this analysis we extract the bare staggered magnetization curve for Haldane spin chains in these compounds.
Staggered chiral perturbation theory and the fourth-root trick
Bernard, C.
2006-06-01
Staggered chiral perturbation theory (S{chi}PT) takes into account the 'fourth-root trick' for reducing unwanted (taste) degrees of freedom with staggered quarks by multiplying the contribution of each sea quark loop by a factor of 1/4. In the special case of four staggered fields (four flavors, n{sub F}=4), I show here that certain assumptions about analyticity and phase structure imply the validity of this procedure for representing the rooting trick in the chiral sector. I start from the observation that, when the four flavors are degenerate, the fourth root simply reduces n{sub F}=4 to n{sub F}=1. One can then treat nondegenerate quark masses by expanding around the degenerate limit. With additional assumptions on decoupling, the result can be extended to the more interesting cases of n{sub F}=3, 2, or 1. An apparent paradox associated with the one-flavor case is resolved. Coupled with some expected features of unrooted staggered quarks in the continuum limit, in particular, the restoration of taste symmetry, S{chi}PT then implies that the fourth-root trick induces no problems (for example, a violation of unitarity that persists in the continuum limit) in the lowest energy sector of staggered lattice QCD. It also says that the theory with staggered valence quarks and rooted staggered sea quarks behaves like a simple, partially-quenched theory, not like a mixed theory in which sea and valence quarks have different lattice actions. In most cases, the assumptions made in this paper are not only sufficient but also necessary for the validity of S{chi}PT, so that a variety of possible new routes for testing this validity are opened.
NASA Astrophysics Data System (ADS)
Murtazaev, A. K.; Babaev, A. B.; Ataeva, G. Ya.
2017-01-01
The thermodynamic properties and phase transitions in a two-dimensional strongly diluted threevertex antiferromagnetic Potts model on a triangular lattice have been investigated using the Monte Carlo method. The systems with linear dimensions of L × L = N, where L = 18-48, have been considered. It has been shown using the method of fourth-order Binder cumulants that, upon the introduction of nonmagnetic impurities into the spin system described by the two-dimensional antiferromagnetic Potts model, the firstorder phase transition changes to a second-order phase transition.
NASA Astrophysics Data System (ADS)
Verdier, Maxime; Anufriev, Roman; Ramiere, Aymeric; Termentzidis, Konstantinos; Lacroix, David
2017-05-01
The in-plane thermal conductivity of silicon phononic membranes is investigated by micro time domain thermoreflectance and Monte Carlo simulations. Strong reduction of thermal conductivity is observed mainly due to phonon boundary scattering for both aligned and staggered lattices of holes. The measured and calculated thermal conductivities of the porous membranes with cylindrical holes are found to be in good quantitative agreement (at 4 K and 300 K). A significant difference between thermal conductivities of aligned and staggered lattice of identical porosities is observed. This difference is shown to arise from ballistic phonons that acquired directionality by propagating between the holes. The directionality effect strengthens when the temperature is decreased or when the diameter of the holes becomes close to the period. Finally, we propose a model, which quantifies and explains the difference between thermal conductivities of aligned and staggered lattices based on geometric considerations.
Numerical simulation of dam-break problem using staggered finite volume method
NASA Astrophysics Data System (ADS)
Budiasih, L. K.; Wiryanto, L. H.
2016-02-01
A problem in a dam-break is when a wall separating two sides of water is removed. A shock wave occurs and propagates. The behavior of the wave is interesting to be investigated with respect to the water depth and its wave speed. The aim of this research is to model dam-break problem using the non-linear shallow water equations and solve them numerically using staggered finite volume method. The solution is used to simulate the dam-break on a wet bed. Our numerical solution will be compared to the analytical solution of shallow water equations for dam-break problem. The momentum non-conservative finite volume scheme on a staggered grid will give a good agreement for dam-break problem on a wet bed, for depth ratios greater than 0.25.
Internal Alignment of the SLD Vertex Detector
Jackson, D.J.; Wickens, F.J.; Su, D.; /SLAC
2007-12-03
The tracking resolution and vertex finding capabilities of the SLD experiment depended upon a precise knowledge of the location and orientation of the elements of the SLD pixel vertex detector (VXD3) in 3D space. At the heart of the procedure described here to align the 96 CCDs is the matrix inversion technique of singular value decomposition (SVD). This tool was employed to unfold the detector geometry corrections from the track data in the VXD3. The algorithm was adapted to perform an optimal {chi}{sup 2} minimization by careful treatment of the track hit residual measurement errors. The tracking resolution obtained with the aligned geometry achieved the design performance. Comments are given on how this method could be used for other trackers.
Optimized Vertex Method and Hybrid Reliability
NASA Technical Reports Server (NTRS)
Smith, Steven A.; Krishnamurthy, T.; Mason, B. H.
2002-01-01
A method of calculating the fuzzy response of a system is presented. This method, called the Optimized Vertex Method (OVM), is based upon the vertex method but requires considerably fewer function evaluations. The method is demonstrated by calculating the response membership function of strain-energy release rate for a bonded joint with a crack. The possibility of failure of the bonded joint was determined over a range of loads. After completing the possibilistic analysis, the possibilistic (fuzzy) membership functions were transformed to probability density functions and the probability of failure of the bonded joint was calculated. This approach is called a possibility-based hybrid reliability assessment. The possibility and probability of failure are presented and compared to a Monte Carlo Simulation (MCS) of the bonded joint.
The HERA-B vertex detector system
NASA Astrophysics Data System (ADS)
Bauer, C.; Bräuer, M.; Glebe, T.; Hofmann, W.; Jagla, T.; Klefenz, F.; Knöpfle, K. T.; Pugatch, V.; Schmelling, M.; Schwingenheuer, B.; Sexauer, E.; Trunk, U.; Wanke, R.; Zurheide, F.; Abt, I.; Dressel, M.; Kisel, I.; Masciocchi, S.; Moshous, B.; Perschke, T.; Sang, M.; Schaller, S.; Wagner, W.
2000-10-01
The HERA-B experiment is being built to measure CP violation in the B-system using internal targets at the HERA proton storage ring at DESY. This paper presents an overview of its vertex detector which - apart from an additional superlayer - is realized by a system of 20 Roman pots containing seven superlayers of double-sided silicon microstrip detectors that are operated at 10 mm distance from the proton beam in a high-radiation environment.
B Decay Charm Counting via Topological Vertexing
Chou, Aaron S
2001-10-15
We present a new and unique measurement of the branching fractions of b hadrons to states with 0, 1, and 2 open charm hadrons, using a sample of 350,000 hadronic Z{sup 0} decays collected during the SLD/SLC 97-98 run. The method takes advantage of the excellent vertexing resolution of the VXD3, a pixel-based CCD vertex detector, which allows the separation of B and cascade D decay vertices. A fit of the vertex count and the decay length distributions to distribution shapes predicted by Monte Carlo simulation allows the extraction of the inclusive branching fractions. We measure: BR(B {yields} (0D)X) = (3.7{+-}1.1(stat) {+-} 2.1(syst))%; and BR(B {yields} (2D)X) = (17.9{+-}1.4(stat) {+-} 3.3(syst))% where B and D represent mixtures of open b and open c hadrons. The corresponding charm count, N{sub c} = 1.188 {+-} 0.010 {+-} 0.040 {+-} 0.006 is consistent with previous measurement averages but slightly closer to theoretical expectations.
Effect of Stagger on the Vibroacoustic Loads from Clustered Rockets
NASA Technical Reports Server (NTRS)
Rojo, Raymundo; Tinney, Charles E.; Ruf, Joseph H.
2016-01-01
The effect of stagger startup on the vibro-acoustic loads that form during the end- effects-regime of clustered rockets is studied using both full-scale (hot-gas) and laboratory scale (cold gas) data. Both configurations comprise three nozzles with thrust optimized parabolic contours that undergo free shock separated flow and restricted shock separated flow as well as an end-effects regime prior to flowing full. Acoustic pressure waveforms recorded at the base of the nozzle clusters are analyzed using various statistical metrics as well as time-frequency analysis. The findings reveal a significant reduction in end- effects-regime loads when engine ignition is staggered. However, regardless of stagger, both the skewness and kurtosis of the acoustic pressure time derivative elevate to the same levels during the end-effects-regime event thereby demonstrating the intermittence and impulsiveness of the acoustic waveforms that form during engine startup.
Staggered chiral perturbation theory in the two-flavor case
Du Xining
2010-07-01
I study two-flavor staggered chiral perturbation theory in the light pseudoscalar sector. The pion mass and decay constant are calculated through next-to-leading order in the partially-quenched case. In the limit where the strange quark mass is large compared to the light quark masses and the taste splittings, I show that the SU(2) staggered chiral theory emerges from the SU(3) staggered chiral theory, as expected. Explicit relations between SU(2) and SU(3) low energy constants and taste-violating parameters are given. The results are useful for SU(2) chiral fits to asqtad data and allow one to incorporate effects from varying strange quark masses.
B_K in unquenched QCD using improved staggered fermions
NASA Astrophysics Data System (ADS)
Kim, Jongjeong
2006-12-01
We present preliminary results for BK calculated using improved staggered fermions with a mixed action (HYP-smeared staggered valence quarks and AsqTad staggered sea quarks). We investigate £¡ ¢ a2¤ effect due to non- the effect of non-degenerate quarks on BK and attempt to estimate the Goldstone pions in loops. We fit the data to continuum partially quenched chiral perturbation theory. We find that the quality of fit for BK improves if we include non-degenerate quark mass combinations. We also observe, however, that the fitting curve deviates from the data points in the light quark mass region. This may indicate the need to include taste-breaking in pion loops.
Upgrade of the LHCb Vertex Locator
NASA Astrophysics Data System (ADS)
Leflat, A.
2014-08-01
The upgrade of the LHCb experiment, planned for 2018, will transform the entire readout to a trigger-less system operating at 40 MHz. All data reduction algorithms will be executed in a high-level software farm, with access to all event information. This will enable the detector to run at luminosities of 1-2 × 1033/cm2/s and probe physics beyond the Standard Model in the heavy sector with unprecedented precision. The upgraded VELO must be low mass, radiation hard and vacuum compatible. It must be capable of fast pattern recognition and track reconstruction and will be required to drive data to the outside world at speeds of up to 2.5 Tbit/s. This challenge is being met with a new Vertex Locator (VELO) design based on hybrid pixel detectors positioned to within 5 mm of the LHC colliding beams. The sensors have 55 × 55 μm square pixels and the VELOPix ASIC which is being developed for the readout is based on the Timepix/Medipix family of chips. The hottest ASIC will have to cope with pixel hit rates of up to 900 MHz. The material budget will be optimised with the use of evaporative CO2 coolant circulating in microchannels within a thin silicon substrate. Microchannel cooling brings many advantages: very efficient heat transfer with almost no temperature gradients across the module, no CTE mismatch with silicon components, and low material contribution. This is a breakthrough technology being developed for LHCb. LHCb is also focussing effort on the construction of a lightweight foil to separate the primary and secondary LHC vacua, the development of high speed cables and radiation qualification of the module. The 40 MHz readout will also bring significant conceptual changes to the way in which the upgrade trigger is operated. Work is in progress to incorporate momentum and impact parameter information into the trigger at the earliest possible stage, using the fast pattern recognition capabilities of the upgraded detector. The current status of the VELO upgrade will
NASA Astrophysics Data System (ADS)
Hale, Simon; Freericks, Jim
2010-03-01
In the bulk, dynamical mean-field theory has no vertex corrections to dc transport, as proved by Khurana in 1990. The proof does not hold for inhomogeneous systems like multilayers with current flow perpendicular to the layers. We examine the effect of vertex corrections on the transport for multilayered inhomogeneous devices composed of semi-infinite metallic leads coupled via a strongly correlated material barrier region. The barrier region can be adjusted from a metallic regime to a Mott insulator through adjusting the interaction strength. We use the Falicov-Kimball model because the exact expression for the vertex corrections is known and it displays a Mott like metal to insulator transition. The resistance is calculated and we find the effects of the vertex correction are relatively small manifesting in a small reduction in the resistance-area product. This as expected this reduction saturates as the barrier layer grows towards the bulk limit. Overall, the effect of vertex corrections is smaller than about 5% of the total resistance and relatively decreases.
Developing new fluorescent proteins with stagger extension process
NASA Astrophysics Data System (ADS)
Yang, Jie; Lu, Jinling; Luo, Haiming; Luo, Qingming; Zhang, Zhihong
2009-02-01
The Stagger Extension Process (StEP), a recombination of DNA technique, has been used as a rapid molecular mutagenesis strategy. In this study, for obtaining the fluorescence proteins with new properties, six fluorescence proteins (EYFP, EGFP, ECFP, mCitrine, mCerulean and Venus) were used as the templates to recombine the mutation library by the Stagger Extension Process (StEP) technique. Through screening this mutation library, we have obtained some useful new FPs which are different fluorescent properties with ancestor. These protein will extend fluorescent proteins application.
The Vertex Version of Weighted Wiener Number for Bicyclic Molecular Structures
Gao, Wei; Wang, Weifan
2015-01-01
Graphs are used to model chemical compounds and drugs. In the graphs, each vertex represents an atom of molecule and edges between the corresponding vertices are used to represent covalent bounds between atoms. We call such a graph, which is derived from a chemical compound, a molecular graph. Evidence shows that the vertex-weighted Wiener number, which is defined over this molecular graph, is strongly correlated to both the melting point and boiling point of the compounds. In this paper, we report the extremal vertex-weighted Wiener number of bicyclic molecular graph in terms of molecular structural analysis and graph transformations. The promising prospects of the application for the chemical and pharmacy engineering are illustrated by theoretical results achieved in this paper. PMID:26640513
Vertex cover problem studied by cavity method: Analytics and population dynamics
NASA Astrophysics Data System (ADS)
Zhou, Haijun
2003-03-01
We study the vertex cover problem on finite connectivity random graphs by zero-temperature cavity method. The minimum vertex cover corresponds to the ground state(s) of a proposed Ising spin model. When the connectivity c > e = 2.718282, there is no state for this system as the reweighting parameter y, which takes a similar role as the inverse temperature β in conventional statistical physics, approaches infinity; consequently the ground state energy is obtained at a finite value of y when the free energy function attains its maximum value. The minimum vertex cover size at given c is estimated using population dynamics and compared with known rigorous bounds and numerical results. The backbone size is also calculated.
Building a non-perturbative quark-gluon vertex from a perturbative one
NASA Astrophysics Data System (ADS)
Bermudez, Rocio
2016-10-01
The quark-gluon vertex describes the electromagnetic and the strong interaction among these particles. The description of this interaction at high precision in both regimes, perturbative and non-perturbative, continues being a matter of interest in the context of QCD and Hadron Physics. There exist very helpful models in the literature that explain perturbative aspects of the theory but they fail describing non-perturbative phenomena, as confinement and dynamic chiral symmetry breaking. In this work we study the structure of the quark-gluon vertex in a non-perturbative regime examining QCD, checking results with QED, and working in the Schwinger-Dyson formalism.
Natural constraints on the gluon-quark vertex
NASA Astrophysics Data System (ADS)
Binosi, Daniele; Chang, Lei; Papavassiliou, Joannis; Qin, Si-Xue; Roberts, Craig D.
2017-02-01
In principle, the strong-interaction sector of the standard model is characterized by a unique renormalization-group-invariant (RGI) running interaction and a unique form for the dressed-gluon-quark vertex, Γμ; but, whilst much has been learnt about the former, the latter is still obscure. In order to improve this situation, we use a RGI running-interaction that reconciles top-down and bottom-up analyses of the gauge sector in quantum chromodynamics (QCD) to compute dressed-quark gap equation solutions with 1,660,000 distinct Ansätze for Γμ. Each one of the solutions is then tested for compatibility with three physical criteria and, remarkably, we find that merely 0.55% of the solutions survive the test. Evidently, even a small selection of observables places extremely tight bounds on the domain of realistic vertex Ansätze. This analysis and its results should prove useful in constraining insightful contemporary studies of QCD and hadronic phenomena.
Electronics cooling of Phenix multiplicity and vertex detector
Chen, Z.; Gregory, W.S.
1996-08-01
The Multiplicity and Vertex Detector (MVD) uses silicon strip sensors arranged in two concentric barrels around the beam pipe of the PHENIX detector that will be installed at Brookhaven National Laboratory. Each silicon sensor is connected by a flexible kapton cable to its own front-end electronics printed circuit board that is a multi-chip module or MCM. The MCMs are the main heat source in the system. To maintain the MVD at optimized operational status, the maximum temperature of the multi-chip modules must be below 40 C. Using COSMOS/M HSTAR for the Heat Transfer analysis, a finite element model of a typical MCM plate was created to simulate a 9m/s airflow and 9m/s mixed flow composed of 50% helium and 50% air respectively, with convective heat transfer on both sides of the plate. The results using a mixed flow of helium and air show that the average maximum temperature reached by the MCMs is 37.5 C. The maximum temperature which is represented by the hot spots on the MCM is 39.43 C for the helium and air mixture which meets the design temperature requirement 40 C. To maintain the Multiplicity and Vertex Detector at optimized operational status, the configuration of the plenum chamber, the power dissipated by the silicon chips, the fluid flow velocity and comparison on the MCM design parameters will be discussed.
The Belle II Silicon Vertex Detector
NASA Astrophysics Data System (ADS)
Friedl, M.; Ackermann, K.; Aihara, H.; Aziz, T.; Bergauer, T.; Bozek, A.; Campbell, A.; Dingfelder, J.; Drasal, Z.; Frankenberger, A.; Gadow, K.; Gfall, I.; Haba, J.; Hara, K.; Hara, T.; Higuchi, T.; Himori, S.; Irmler, C.; Ishikawa, A.; Joo, C.; Kah, D. H.; Kang, K. H.; Kato, E.; Kiesling, C.; Kodys, P.; Kohriki, T.; Koike, S.; Kvasnicka, P.; Marinas, C.; Mayekar, S. N.; Mibe, T.; Mohanty, G. B.; Moll, A.; Negishi, K.; Nakayama, H.; Natkaniec, Z.; Niebuhr, C.; Onuki, Y.; Ostrowicz, W.; Park, H.; Rao, K. K.; Ritter, M.; Rozanska, M.; Saito, T.; Sakai, K.; Sato, N.; Schmid, S.; Schnell, M.; Shimizu, N.; Steininger, H.; Tanaka, S.; Tanida, K.; Taylor, G.; Tsuboyama, T.; Ueno, K.; Uozumi, S.; Ushiroda, Y.; Valentan, M.; Yamamoto, H.
2013-12-01
The KEKB machine and the Belle experiment in Tsukuba (Japan) are now undergoing an upgrade, leading to an ultimate luminosity of 8×1035 cm-2 s-1 in order to measure rare decays in the B system with high statistics. The previous vertex detector cannot cope with this 40-fold increase of luminosity and thus needs to be replaced. Belle II will be equipped with a two-layer Pixel Detector surrounding the beam pipe, and four layers of double-sided silicon strip sensors at higher radii than the old detector. The Silicon Vertex Detector (SVD) will have a total sensitive area of 1.13 m2 and 223,744 channels-twice as many as its predecessor. All silicon sensors will be made from 150 mm wafers in order to maximize their size and thus to reduce the relative contribution of the support structure. The forward part has slanted sensors of trapezoidal shape to improve the measurement precision and to minimize the amount of material as seen by particles from the vertex. Fast-shaping front-end amplifiers will be used in conjunction with an online hit time reconstruction algorithm in order to reduce the occupancy to the level of a few percent at most. A novel “Origami” chip-on-sensor scheme is used to minimize both the distance between strips and amplifier (thus reducing the electronic noise) as well as the overall material budget. This report gives an overview on the status of the Belle II SVD and its components, including sensors, front-end detector ladders, mechanics, cooling and the readout electronics.
Mechanical design of the CDF SVX II silicon vertex detector
Skarha, J.E.
1994-08-01
A next generation silicon vertex detector is planned at CDF for the 1998 Tevatron collider run with the Main Injector. The SVX II silicon vertex detector will allow high luminosity data-taking, enable online triggering of secondary vertex production, and greatly increase the acceptance for heavy flavor physics at CDF. The design specifications, geometric layout, and early mechanical prototyping work for this detector are discussed.
Construction of the CDF silicon vertex detector
Skarha, J.; Barnett, B.; Boswell, C.; Snider, F.; Spies, A.; Tseng, J.; Vejcik, S. ); Carter, H.; Flaugher, B.; Gonzales, B.; Hrycyk, M.; Nelson, C.; Segler, S.; Shaw, T.; Tkaczyk, S.; Turner, K.; Wesson, T. ); Carithers, W.; Ely, R.; Haber, C.; Holland, S.; Kleinfelder, S.; Merrick, T.; Schneider, O.; Wester
1992-04-01
Technical details and methods used in constructing the CDF silicon vertex detector are presented. This description includes a discussion of the foam-carbon fiber composite structure used to silicon microstrip detectors and the procedure for achievement of 5 {mu}m detector alignment. The construction of the beryllium barrel structure, which houses the detector assemblies, is also described. In addition, the 10 {mu}m placement accuracy of the detectors in the barrel structure is discussed and the detector cooling and mounting systems are described. 12 refs.
The Mark II Vertex Drift Chamber
Alexander, J.P.; Baggs, R.; Fujino, D.; Hayes, K.; Hoard, C.; Hower, N.; Hutchinson, D.; Jaros, J.A.; Koetke, D.; Kowalski, L.A.
1989-03-01
We have completed constructing and begun operating the Mark II Drift Chamber Vertex Detector. The chamber, based on a modified jet cell design, achieves 30 {mu}m spatial resolution and <1000 {mu}m track-pair resolution in pressurized CO{sub 2} gas mixtures. Special emphasis has been placed on controlling systematic errors including the use of novel construction techniques which permit accurate wire placement. Chamber performance has been studied with cosmic ray tracks collected with the chamber located both inside and outside the Mark II. Results on spatial resolution, average pulse shape, and some properties of CO{sub 2} mixtures are presented. 10 refs., 12 figs., 1 tab.
Complete LQG propagator: Difficulties with the Barrett-Crane vertex
Alesci, Emanuele; Rovelli, Carlo
2007-11-15
Some components of the graviton two-point function have been recently computed in the context of loop quantum gravity, using the spinfoam Barrett-Crane vertex. We complete the calculation of the remaining components. We find that, under our assumptions, the Barrett-Crane vertex does not yield the correct long-distance limit. We argue that the problem is general and can be traced to the intertwiner independence of the Barrett-Crane vertex, and therefore to the well-known mismatch between the Barrett-Crane formalism and the standard canonical spin networks. In another paper we illustrate the asymptotic behavior of a vertex amplitude that can correct this difficulty.
Jia, Yun-Fei; Xuan, Fu-Zhen; Tu, Shan-Tung
2012-12-01
The thermal-mechanical stress distributions and equivalent coefficient of thermal expansion (CTE) of the staggered arrangement of mineral platelets wrapped by soft matrix are analyzed, which exist in numerous natural biological and biomimetic materials. Two analytical models, 'Stress model' and 'Displacement model', were established from the ways of stress and displacement solution based on the modification of classical shear-lag model. Complementary finite element analysis (FEA) was used to verify the analytical models. Results reveal that, compared to 'Displacement model', 'Stress model' gives a better prediction of the stress distributions within the staggered structure referring to FEA. The equivalent CTE predicted by both models reach constant as the aspect ratio and volume fraction of platelets exceeding the critical values. Nevertheless, the relative error between the results from different models increases with the increase of the ratio of overlap to length of platelets. These provide a benchmark to the optimum design of micro/nano-structure in bio-inspired materials suffering to temperature fluctuation and applied loading. Copyright © 2012 Elsevier Ltd. All rights reserved.
{kappa}K*{sup 0}{gamma}-vertex in light cone QCD sum rules
Gokalp, A.; Yilmaz, O.; Sarac, Y.
2008-06-01
We investigate the {kappa}K*{sup 0}{gamma}-vertex in the framework of light cone QCD sum rules. We estimate the coupling constant g{sub {kappa}}{sub K*{sup 0}}{sub {gamma}}, and compare our result with that used in the nonlinear chiral Lagrangian approach using the vector-meson dominance model in the SU(3) limit.
Drift chamber vertex detectors for SLC/LEP
Hayes, K.G.
1987-03-01
The short but measurable lifetimes of the b and c quarks and the tau lepton have motivated the development of high precision tracking detectors capable of providing information on the decay vertex topology of events containing these particles. This paper reviews the OPAL, L3, and MARK II experiments vertex drift chambers.
Calculation of the Nucleon Axial Form Factor Using Staggered Lattice QCD
Meyer, Aaron S.; Hill, Richard J.; Kronfeld, Andreas S.; Li, Ruizi; Simone, James N.
2016-10-14
The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice QCD calculations can help control theory errors by providing first-principles information on nucleon form factors. In these proceedings, we present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered baryons with 2+1+1 flavors of sea quarks. Calculations are done using physical light quark masses and are absolutely normalized. We discuss fitting form factor data with the model-independent $z$ expansion parametrization.
Emergent reduced dimensionality by vertex frustration in artificial spin ice
Gilbert, Ian; Lao, Yuyang; Carrasquillo, Isaac; O’Brien, Liam; Watts, Justin D.; Manno, Michael; Leighton, Chris; Scholl, Andreas; Nisoli, Cristiano; Schiffer, Peter
2015-10-26
Reducing the dimensionality of a physical system can have a profound effect on its properties, as in the ordering of low-dimensional magnetic materials, phonon dispersion in mercury chain salts, sliding phases, and the electronic states of graphene. Here we explore the emergence of quasi-one-dimensional behaviour in two-dimensional artificial spin ice, a class of lithographically fabricated nanomagnet arrays used to study geometrical frustration. We extend the implementation of artificial spin ice by fabricating a new array geometry, the so-called tetris lattice. We demonstrate that the ground state of the tetris lattice consists of alternating ordered and disordered bands of nanomagnetic moments. The disordered bands can be mapped onto an emergent thermal one-dimensional Ising model. Furthermore, we show that the level of degeneracy associated with these bands dictates the susceptibility of island moments to thermally induced reversals, thus establishing that vertex frustration can reduce the relevant dimensionality of physical behaviour in a magnetic system.
Displaced vertex searches for sterile neutrinos at future lepton colliders
NASA Astrophysics Data System (ADS)
Antusch, Stefan; Cazzato, Eros; Fischer, Oliver
2016-12-01
We investigate the sensitivity of future lepton colliders to displaced vertices from the decays of long-lived heavy (almost sterile) neutrinos with electroweak scale masses and detectable time of flight. As future lepton colliders we consider the FCC-ee, the CEPC, and the ILC, searching at the Z-pole and at the center-of-mass energies of 240, 350 and 500 GeV. For a realistic discussion of the detector response to the displaced vertex signal and the Standard Model background we consider the ILC's Silicon Detector (SiD) as benchmark for the future lepton collider detectors. We find that displaced vertices constitute a powerful search channel for sterile neutrinos, sensitive to squared active-sterile mixing angles as small as 10-11.
Vertex Sensitivity in the Schwinger-Dyson Equations of QCD
David J. Wilson, Michael R. Pennington
2012-01-01
The nonperturbative gluon and ghost propagators in Landau gauge QCD are obtained using the Schwinger-Dyson equation approach. The propagator equations are solved in Euclidean space using Landau gauge with a range of vertex inputs. Initially we solve for the ghost alone, using a model gluon input, which leads us to favour a finite ghost dressing in the nonperturbative region. In order to then solve the gluon and ghost equations simultaneously, we find that non-trivial vertices are required, particularly for the gluon propagator in the small momentum limit. We focus on the properties of a number vertices and how these differences influence the final solutions. The self-consistent solutions we obtain are all qualitatively similar and contain a mass-like term in the gluon propagator dressing in agreement with related studies, supporting the long-held proposal of Cornwall.
Emergent reduced dimensionality by vertex frustration in artificial spin ice
NASA Astrophysics Data System (ADS)
Gilbert, Ian; Lao, Yuyang; Carrasquillo, Isaac; O'Brien, Liam; Watts, Justin D.; Manno, Michael; Leighton, Chris; Scholl, Andreas; Nisoli, Cristiano; Schiffer, Peter
2016-02-01
Reducing the dimensionality of a physical system can have a profound effect on its properties, as in the ordering of low-dimensional magnetic materials, phonon dispersion in mercury chain salts, sliding phases, and the electronic states of graphene. Here we explore the emergence of quasi-one-dimensional behaviour in two-dimensional artificial spin ice, a class of lithographically fabricated nanomagnet arrays used to study geometrical frustration. We extend the implementation of artificial spin ice by fabricating a new array geometry, the so-called tetris lattice. We demonstrate that the ground state of the tetris lattice consists of alternating ordered and disordered bands of nanomagnetic moments. The disordered bands can be mapped onto an emergent thermal one-dimensional Ising model. Furthermore, we show that the level of degeneracy associated with these bands dictates the susceptibility of island moments to thermally induced reversals, thus establishing that vertex frustration can reduce the relevant dimensionality of physical behaviour in a magnetic system.
Small Vertex Cover Makes Petri Net Coverability and Boundedness Easier
NASA Astrophysics Data System (ADS)
Praveen, M.
The coverability and boundedness problems for Petri nets are known to be Expspace-complete. Given a Petri net, we associate a graph with it. With the vertex cover number k of this graph and the maximum arc weight W as parameters, we show that coverability and boundedness are in ParaPspace. This means that these problems can be solved in space O(ef(k,W)poly(n)) where ef(k,W) is some exponential function and poly(n) is some polynomial in the size of the input. We then extend the ParaPspace result to model checking a logic that can express some generalizations of coverability and boundedness.
Twisted vertex algebras, bicharacter construction and boson-fermion correspondences
NASA Astrophysics Data System (ADS)
Anguelova, Iana I.
2013-12-01
The boson-fermion correspondences are an important phenomena on the intersection of several areas in mathematical physics: representation theory, vertex algebras and conformal field theory, integrable systems, number theory, cohomology. Two such correspondences are well known: the types A and B (and their super extensions). As a main result of this paper we present a new boson-fermion correspondence of type D-A. Further, we define a new concept of twisted vertex algebra of order N, which generalizes super vertex algebra. We develop the bicharacter construction which we use for constructing classes of examples of twisted vertex algebras, as well as for deriving formulas for the operator product expansions, analytic continuations, and normal ordered products. By using the underlying Hopf algebra structure we prove general bicharacter formulas for the vacuum expectation values for two important groups of examples. We show that the correspondences of types B, C, and D-A are isomorphisms of twisted vertex algebras.
Twisted vertex algebras, bicharacter construction and boson-fermion correspondences
Anguelova, Iana I.
2013-12-15
The boson-fermion correspondences are an important phenomena on the intersection of several areas in mathematical physics: representation theory, vertex algebras and conformal field theory, integrable systems, number theory, cohomology. Two such correspondences are well known: the types A and B (and their super extensions). As a main result of this paper we present a new boson-fermion correspondence of type D-A. Further, we define a new concept of twisted vertex algebra of order N, which generalizes super vertex algebra. We develop the bicharacter construction which we use for constructing classes of examples of twisted vertex algebras, as well as for deriving formulas for the operator product expansions, analytic continuations, and normal ordered products. By using the underlying Hopf algebra structure we prove general bicharacter formulas for the vacuum expectation values for two important groups of examples. We show that the correspondences of types B, C, and D-A are isomorphisms of twisted vertex algebras.
Witnessing macroscopic entanglement in a staggered magnetic field
NASA Astrophysics Data System (ADS)
Hide, Jenny; Son, Wonmin; Lawrie, Ian; Vedral, Vlatko
2007-08-01
We investigate macroscopic entanglement in an infinite XX spin- (1)/(2) chain with staggered magnetic field, Bl=B+e-iπlb . Using single-site entropy and by constructing an entanglement witness, we search for the existence of entanglement when the system is at absolute zero, as well as in thermal equilibrium. Although the role of the alternating magnetic field b is, in general, to suppress entanglement as do B and T , we find that when T=0 , introducing b allows the existence of entanglement even when the uniform magnetic field B is arbitrarily large. We find that the region and the amount of entanglement in the spin chain can be enhanced by a staggered magnetic field.
Future of Lattice Calculations with Staggered Sea Quarks
Gottlieb, Steven
2011-05-23
The MILC collaboration for some years has been creating gauge ensembles with 2+1 flavors of asqtad or improved staggered quarks. There are some 40 ensembles covering a wide range of quark mass and lattice spacing, thus allowing control of the chiral and continuum limits. An extensive review of that program has been published in Reviews of Modern Physics. Recently, MILC has begun a new program using HPQCD's highly improved staggered quark (HISQ) action. This action has smaller taste symmetry breaking than asqtad and improved scaling properties. We also include a dynamical charm quark in these calculations. We summarize the achievements of the asqtad program, what has been done so far with HISQ quarks, and then consider what future ensembles will be created and their impact.
B{sub K} in staggered chiral perturbation theory
Water, Ruth S. van de; Sharpe, Stephen R.
2006-01-01
We calculate the kaon B parameter, B{sub K}, to next-to-leading order in staggered chiral perturbation theory. We find expressions for partially quenched QCD with three sea quarks, quenched QCD, and full QCD with m{sub u}=m{sub d}{ne}m{sub s}. We extend the usual power counting to include the effects of using perturbative (rather than nonperturbative) matching factors. Taste breaking enters through the O(a{sup 2}) terms in the effective action, through O(a{sup 2}) terms from the discretization of operators, and through the truncation of matching factors. These effects cause mixing with several additional operators, complicating the chiral and continuum extrapolations. In addition to the staggered expressions, we present B{sub K} at next-to-leading order in continuum PQ{chi}PT for N{sub f}=3 sea quarks with m{sub u}=m{sub d}{ne}m{sub s}.
Weight Representations of Admissible Affine Vertex Algebras
NASA Astrophysics Data System (ADS)
Arakawa, Tomoyuki; Futorny, Vyacheslav; Ramirez, Luis Enrique
2017-08-01
For an admissible affine vertex algebra {V_k{(\\mathfrak{g})}} of type A, we describe a new family of relaxed highest weight representations of {V_k{(\\mathfrak{g})}}. They are simple quotients of representations of the affine Kac-Moody algebra {\\widehat{\\mathfrak{g}}} induced from the following {\\mathfrak{g}}-modules: (1) generic Gelfand-Tsetlin modules in the principal nilpotent orbit, in particular all such modules induced from {\\mathfrak{sl}_2}; (2) all Gelfand-Tsetlin modules in the principal nilpotent orbit that are induced from {\\mathfrak{sl}_3}; (3) all simple Gelfand-Tsetlin modules over {\\mathfrak{sl}_3}. This in particular gives the classification of all simple positive energy weight representations of {V_k{(\\mathfrak{g})}} with finite dimensional weight spaces for {\\mathfrak{g}=\\mathfrak{sl}_3}.
The upgrade of the LHCb Vertex Locator
NASA Astrophysics Data System (ADS)
Bird, T.
2014-12-01
The LHCb experiment is set for a significant upgrade, which will be ready for Run 3 of the LHC in 2020. This upgrade will allow LHCb to run at a significantly higher instantaneous luminosity and collect an integrated luminosity of 50fb-1 by the end of Run 4. In this process the Vertex Locator (VELO) detector will be upgraded to a pixel-based silicon detector. The upgraded VELO will improve upon the current detector by being closer to the beams and having lower material modules with microchannel cooling and a thinner RF-foil. Simulations have shown that it will maintain its excellent performance, even after the radiation damage caused by collecting an integrated luminosity of 50fb-1.
Quarkonium decays: Testing the 3-gluon vertex
NASA Astrophysics Data System (ADS)
Koller, K.; Streng, K. H.; Walsh, T. F.; Zerwas, P. M.
1981-12-01
We study the 3-jet decays of S- and P-wave quarkonia with C=+. If observed, some of these will offer a way of seeing the 3G vertex of QCD via 1S 0, 3P 0, 3P 2(Q overlineQ) → GGG + Gq overlineq → 3 jets. (As is well-known, cancellations reduce 3P1( Q overlineQ)→ GGG.) We elaborate in detail the S-wave decay, as it is expected to show all the characteristic features of orthoquarkonium decays into 4 jets, 3S 1(Q overlineQ) → GGGG + GGq overlineq → 4 jets, which we will comment upon. These quarkonium decays offer a very clear signal for QCD as a non-abelian local gauge field theory with color-charged gluons.
Compton scattering vertex for massive scalar QED
Bashir, A.; Concha-Sanchez, Y.; Delbourgo, R.; Tejeda-Yeomans, M. E.
2009-08-15
We investigate the Compton scattering vertex of charged scalars and photons in scalar quantum electrodynamics (SQED). We carry out its nonperturbative construction consistent with Ward-Fradkin-Green-Takahashi identity which relates 3-point vertices to the 4-point ones. There is an undetermined part which is transverse to one or both the external photons, and needs to be evaluated through perturbation theory. We present in detail how the transverse part at the 1-loop order can be evaluated for completely general kinematics of momenta involved in covariant gauges and dimensions. This involves the calculation of genuine 4-point functions with three massive propagators, the most nontrivial integrals reported in this paper. We also discuss possible applications of our results.
On the Quality of Velocity Interpolation Schemes for Marker-in-Cell Method and Staggered Grids
NASA Astrophysics Data System (ADS)
Pusok, Adina E.; Kaus, Boris J. P.; Popov, Anton A.
2017-03-01
The marker-in-cell method is generally considered a flexible and robust method to model the advection of heterogenous non-diffusive properties (i.e., rock type or composition) in geodynamic problems. In this method, Lagrangian points carrying compositional information are advected with the ambient velocity field on an Eulerian grid. However, velocity interpolation from grid points to marker locations is often performed without considering the divergence of the velocity field at the interpolated locations (i.e., non-conservative). Such interpolation schemes can induce non-physical clustering of markers when strong velocity gradients are present (Journal of Computational Physics 166:218-252, 2001) and this may, eventually, result in empty grid cells, a serious numerical violation of the marker-in-cell method. To remedy this at low computational costs, Jenny et al. (Journal of Computational Physics 166:218-252, 2001) and Meyer and Jenny (Proceedings in Applied Mathematics and Mechanics 4:466-467, 2004) proposed a simple, conservative velocity interpolation scheme for 2-D staggered grid, while Wang et al. (Geochemistry, Geophysics, Geosystems 16(6):2015-2023, 2015) extended the formulation to 3-D finite element methods. Here, we adapt this formulation for 3-D staggered grids (correction interpolation) and we report on the quality of various velocity interpolation methods for 2-D and 3-D staggered grids. We test the interpolation schemes in combination with different advection schemes on incompressible Stokes problems with strong velocity gradients, which are discretized using a finite difference method. Our results suggest that a conservative formulation reduces the dispersion and clustering of markers, minimizing the need of unphysical marker control in geodynamic models.
On the Quality of Velocity Interpolation Schemes for Marker-in-Cell Method and Staggered Grids
NASA Astrophysics Data System (ADS)
Pusok, Adina E.; Kaus, Boris J. P.; Popov, Anton A.
2016-11-01
The marker-in-cell method is generally considered a flexible and robust method to model the advection of heterogenous non-diffusive properties (i.e., rock type or composition) in geodynamic problems. In this method, Lagrangian points carrying compositional information are advected with the ambient velocity field on an Eulerian grid. However, velocity interpolation from grid points to marker locations is often performed without considering the divergence of the velocity field at the interpolated locations (i.e., non-conservative). Such interpolation schemes can induce non-physical clustering of markers when strong velocity gradients are present (Journal of Computational Physics 166:218-252, 2001) and this may, eventually, result in empty grid cells, a serious numerical violation of the marker-in-cell method. To remedy this at low computational costs, Jenny et al. (Journal of Computational Physics 166:218-252, 2001) and Meyer and Jenny (Proceedings in Applied Mathematics and Mechanics 4:466-467, 2004) proposed a simple, conservative velocity interpolation scheme for 2-D staggered grid, while Wang et al. (Geochemistry, Geophysics, Geosystems 16(6):2015-2023, 2015) extended the formulation to 3-D finite element methods. Here, we adapt this formulation for 3-D staggered grids (correction interpolation) and we report on the quality of various velocity interpolation methods for 2-D and 3-D staggered grids. We test the interpolation schemes in combination with different advection schemes on incompressible Stokes problems with strong velocity gradients, which are discretized using a finite difference method. Our results suggest that a conservative formulation reduces the dispersion and clustering of markers, minimizing the need of unphysical marker control in geodynamic models.
Calculating weak matrix elements using HYP staggered fermions
T. Bhattacharya; G. T. Fleming; G. Kilcup; R. Gupta; W. Lee; S. Sharpe
2004-03-01
We present preliminary results of weak matrix elements relevant to CP violation calculated using the HYP (II) staggered fermions. Since the complete set of matching coefficients at the one-loop level became available recently, we have constructed lattice operators with all the g{sup 2} corrections included. The main results include both {Delta}I = 3/2 and {Delta}I = 1/2 contributions.
Baryons with Ginsparg-Wilson quarks in a staggered sea
Tiburzi, Brian C.
2005-11-01
We determine the masses and magnetic moments of the octet baryons in chiral perturbation theory formulated for a mixed lattice action of Ginsparg-Wilson valence quarks and staggered sea quarks. Taste-symmetry breaking does not occur at next-to-leading order in the combined lattice spacing and chiral expansion. Expressions derived for masses and magnetic moments are required for addressing lattice artifacts in mixed-action simulations of these observables.
The PHENIX Forward Silicon Vertex Detector
NASA Astrophysics Data System (ADS)
Aidala, C.; Anaya, L.; Anderssen, E.; Bambaugh, A.; Barron, A.; Boissevain, J. G.; Bok, J.; Boose, S.; Brooks, M. L.; Butsyk, S.; Cepeda, M.; Chacon, P.; Chacon, S.; Chavez, L.; Cote, T.; D'Agostino, C.; Datta, A.; DeBlasio, K.; DelMonte, L.; Desmond, E. J.; Durham, J. M.; Fields, D.; Finger, M.; Gingu, C.; Gonzales, B.; Haggerty, J. S.; Hawke, T.; van Hecke, H. W.; Herron, M.; Hoff, J.; Huang, J.; Jiang, X.; Johnson, T.; Jonas, M.; Kapustinsky, J. S.; Key, A.; Kunde, G. J.; Kurtz, J.; LaBounty, J.; Lee, D. M.; Lee, K. B.; Leitch, M. J.; Lenz, M.; Lenz, W.; Liu, M. X.; Lynch, D.; Mannel, E.; McGaughey, P. L.; Meles, A.; Meredith, B.; Nguyen, H.; O'Brien, E.; Pak, R.; Papavassiliou, V.; Pate, S.; Pereira, H.; Perera, G. D. N.; Phillips, M.; Pisani, R.; Polizzo, S.; Poncione, R. J.; Popule, J.; Prokop, M.; Purschke, M. L.; Purwar, A. K.; Ronzhina, N.; Silva, C. L.; Slunečka, M.; Smith, R.; Sondheim, W. E.; Spendier, K.; Stoffer, M.; Tennant, E.; Thomas, D.; Tomášek, M.; Veicht, A.; Vrba, V.; Wang, X. R.; Wei, F.; Winter, D.; Yarema, R.; You, Z.; Younus, I.; Zimmerman, A.; Zimmerman, T.
2014-08-01
A new silicon detector has been developed to provide the PHENIX experiment with precise charged particle tracking at forward and backward rapidity. The Forward Silicon Vertex Tracker (FVTX) was installed in PHENIX prior to the 2012 run period of the Relativistic Heavy Ion Collider (RHIC). The FVTX is composed of two annular endcaps, each with four stations of silicon mini-strip sensors, covering a rapidity range of 1.2<|η|<2.2 that closely matches the two existing PHENIX muon arms. Each station consists of 48 individual silicon sensors, each of which contains two columns of mini-strips with 75 μm pitch in the radial direction and lengths in the ϕ direction varying from 3.4 mm at the inner radius to 11.5 mm at the outer radius. The FVTX has approximately 0.54 million strips in each endcap. These are read out with FPHX chips, developed in collaboration with Fermilab, which are wire bonded directly to the mini-strips. The maximum strip occupancy reached in central Au-Au collisions is approximately 2.8%. The precision tracking provided by this device makes the identification of muons from secondary vertices away from the primary event vertex possible. The expected distance of closest approach (DCA) resolution of 200 μm or better for particles with a transverse momentum of 5 GeV/c will allow identification of muons from relatively long-lived particles, such as D and B mesons, through their broader DCA distributions.
Staggered baryon operators with flavor SU(3) quantum numbers
Bailey, Jon A.
2007-06-01
The construction of the first baryon operators for staggered lattice QCD exploited the taste symmetry to emulate physical quark flavor; contemporary 2+1 flavor simulations explicitly include three physical quark flavors and necessitate interpreting a valence sector with 12 quarks. After discussing expected features of the resulting baryon spectrum, I consider the spectra of operators transforming irreducibly under SU(3){sub F}xGTS, the direct product of flavor SU(3){sub F} and the geometrical time-slice group of the 1-flavor staggered theory. I then describe the construction of a set of maximally local baryon operators transforming irreducibly under SU(3){sub F}xGTS and enumerate this set. In principle, the operators listed here could be used to extract the masses of all the lightest spin-(1/2) and spin-(3/2) baryon resonances of staggered QCD. Using appropriate operators from this set in partially quenched simulations should allow for particularly clean 2+1 flavor calculations of the masses of the nucleon, {delta}, {sigma}*, {xi}*, and {omega}{sup -}.
Staggered chiral perturbation theory at next-to-leading order
Sharpe, Stephen R.; Van de Water, Ruth S.
2005-06-01
We study taste and Euclidean rotational symmetry violation for staggered fermions at nonzero lattice spacing using staggered chiral perturbation theory. We extend the staggered chiral Lagrangian to O(a{sup 2}p{sup 2}), O(a{sup 4}), and O(a{sup 2}m), the orders necessary for a full next-to-leading order calculation of pseudo-Goldstone boson masses and decay constants including analytic terms. We then calculate a number of SO(4) taste-breaking quantities, which involve only a small subset of these next-to-leading order operators. We predict relationships between SO(4) taste-breaking splittings in masses, pseudoscalar decay constants, and dispersion relations. We also find predictions for a few quantities that are not SO(4) breaking. All these results hold also for theories in which the fourth root of the fermionic determinant is taken to reduce the number of quark tastes; testing them will therefore provide evidence for or against the validity of this trick.
Taste symmetry breaking with hypercubic-smeared staggered fermions
Bae, Taegil; Adams, David H.; Kim, Hyung-Jin; Kim, Jongjeong; Kim, Kwangwoo; Lee, Weonjong; Jung, Chulwoo; Sharpe, Stephen R.
2008-05-01
We study the impact of hypercubic (HYP) smearing on the size of taste-breaking for staggered fermions, comparing to unimproved and to asqtad-improved staggered fermions. As in previous studies, we find a substantial reduction in taste-breaking compared to unimproved staggered fermions (by a factor of 4-7 on lattices with spacing a{approx_equal}0.1 fm). In addition, we observe that discretization effects of next-to-leading order in the chiral expansion (O(a{sup 2}p{sup 2})) are markedly reduced by HYP smearing. Compared to asqtad valence fermions, we find that taste-breaking in the pion spectrum is reduced by a factor of 2.5-3, down to a level comparable to the expected size of generic O(a{sup 2}) effects. Our results suggest that, once one reaches a lattice spacing of a{approx_equal}0.09 fm, taste-breaking will be small enough after HYP smearing that one can use a modified power counting in which O(a{sup 2})<
Staggered chiral perturbation theory for heavy-light mesons
Aubin, C.; Bernard, C.
2006-01-01
We incorporate heavy-light mesons into staggered chiral perturbation theory (S{chi}PT), working to leading order in 1/m{sub Q}, where m{sub Q} is the heavy-quark mass. At first nontrivial order in the chiral expansion, staggered taste violations affect the chiral logarithms for heavy-light quantities only through the light-meson propagators in loops. There are also new analytic contributions coming from additional terms in the Lagrangian involving heavy-light and light mesons. Using this heavy-light S{chi}PT, we perform the one-loop calculation of the B (or D) meson leptonic decay constant in the partially quenched and full QCD cases. In our treatment, we assume the validity both of the 'fourth root trick' to reduce four staggered tastes to one, and of the S{chi}PT prescription to represent this trick by insertions of factors of 1/4 for each sea-quark loop.
NASA Astrophysics Data System (ADS)
Khalaf, A. M.; Kotb, M.; Awwad, T. M.
Two-way cross-talk transitions between pairs of signature partners superdeformed (SD) bands in 191Hg (SD2,SD3), 193Hg (SD3,SD4) and 193T1(SD1,SD2) built on the configurations ν3/2 + [642],ν7/2 + [624],π5/2 + [642], respectively, are proposed. The ΔI = 1 energy staggering presented in these odd SD nuclei are investigated and parametrized by proposing two staggering functions depending on the dipole transitions linking the signature partners. These staggering functions differ from the conventional staggering functions employed in previous works which depend on the quadruple transitions within each band. For parametrization, we used the two-term formula of Bohr-Mottelson collective rotational model. The model parameters and the bandhead spins of the considered signature partners are determined by using a simulated fitting search program and the values of the adopted parameters are used to calculate transition energies Eγ, rotational frequencies ℏω, kinematic J(1) and dynamic J(2) moments of inertia. The calculated results agree very well with the experimental ones. The bands exhibit the usual increasing trend. Large amplitude staggering has been found in the considered three signature partner pairs in 191,193Hg and 193T1 nuclei.
Locking mechanisms in degree-4 vertex origami structures
NASA Astrophysics Data System (ADS)
Fang, Hongbin; Li, Suyi; Xu, Jian; Wang, K. W.
2016-04-01
Origami has emerged as a potential tool for the design of mechanical metamaterials and metastructures whose novel properties originate from their crease patterns. Most of the attention in origami engineering has focused on the wellknown Miura-Ori, a folded tessellation that is flat-foldable for folded sheet and stacked blocks. This study advances the state of the art and expands the research field to investigate generic degree-4 vertex (4-vertex) origami, with a focus on facet-binding. In order to understand how facet-binding attributes to the mechanical properties of 4-vertex origami structures, geometries of the 4-vertex origami cells are analyzed and analytically expressed. Through repeating and stacking 4-vertex cells, origami sheets and stacked origami blocks can be constructed. Geometry analyses discover four mechanisms that will lead to the self-locking of 4-vertex origami cells, sheets, and stacked blocks: in-cell facet-binding, inlayer facet-binding, inter-layer facet binding, and in-layer and inter-layer facet-bindings. These mechanisms and the predicted self-locking phenomena are verified through 3D simulations and prototype experiments. Finally, this paper briefly introduces the unusual mechanical properties caused by the locking of 4-vertex origami structures. The research reported in this paper could foster a new breed of self-locking structures with various engineering applications.
RAVE—a Detector-independent vertex reconstruction toolkit
NASA Astrophysics Data System (ADS)
Waltenberger, Wolfgang; Mitaroff, Winfried; Moser, Fabian
2007-10-01
A detector-independent toolkit for vertex reconstruction (RAVE ) is being developed, along with a standalone framework (VERTIGO ) for testing, analyzing and debugging. The core algorithms represent state of the art for geometric vertex finding and fitting by both linear (Kalman filter) and robust estimation methods. Main design goals are ease of use, flexibility for embedding into existing software frameworks, extensibility, and openness. The implementation is based on modern object-oriented techniques, is coded in C++ with interfaces for Java and Python, and follows an open-source approach. A beta release is available. VERTIGO = "vertex reconstruction toolkit and interface to generic objects".
Quark-gluon vertex in arbitrary gauge and dimension
NASA Astrophysics Data System (ADS)
Davydychev, A. I.; Osland, P.; Saks, L.
2001-01-01
One-loop off-shell contributions to the quark-gluon vertex are calculated, in an arbitrary covariant gauge and in arbitrary space-time dimension, including quark-mass effects. It is shown how one can get results for all on-shell limits of interest directly from the off-shell expressions. In order to demonstrate that the Ward-Slavnov-Taylor identity for the quark-gluon vertex is satisfied, we have also calculated the corresponding one-loop contribution involving the quark-quark-ghost-ghost vertex.
Poves, A.; Nowacki, F.; Caurier, E.
2005-10-01
In an effort to understand the magical status of N=32 and N=34 at the very neutron rich edge, experiments have been carried out in the titanium isotopes up to A=56. The measured staggering of the B(E2)'s is not reproduced by the shell model calculations using the best effective interactions. We argue that this may be related to the choice of the isovector effective charge and to the value of the N=34 neutron gap.
Ghost story. II. The midpoint ghost vertex
NASA Astrophysics Data System (ADS)
Bonora, L.; Maccaferri, C.; Santos, R. J. Scherer; Tolla, D. D.
2009-11-01
We construct the ghost number 9 three strings vertex for OSFT in the natural normal ordering. We find two versions, one with a ghost insertion at z = i and a twist-conjugate one with insertion at z = -i. For this reason we call them midpoint vertices. We show that the relevant Neumann matrices commute among themselves and with the matrix G representing the operator K1. We analyze the spectrum of the latter and find that beside a continuous spectrum there is a (so far ignored) discrete one. We are able to write spectral formulas for all the Neumann matrices involved and clarify the important role of the integration contour over the continuous spectrum. We then pass to examine the (ghost) wedge states. We compute the discrete and continuous eigenvalues of the corresponding Neumann matrices and show that they satisfy the appropriate recursion relations. Using these results we show that the formulas for our vertices correctly define the star product in that, starting from the data of two ghost number 0 wedge states, they allow us to reconstruct a ghost number 3 state which is the expected wedge state with the ghost insertion at the midpoint, according to the star recursion relation.
Linear Time Vertex Partitioning on Massive Graphs.
Mell, Peter; Harang, Richard; Gueye, Assane
The problem of optimally removing a set of vertices from a graph to minimize the size of the largest resultant component is known to be NP-complete. Prior work has provided near optimal heuristics with a high time complexity that function on up to hundreds of nodes and less optimal but faster techniques that function on up to thousands of nodes. In this work, we analyze how to perform vertex partitioning on massive graphs of tens of millions of nodes. We use a previously known and very simple heuristic technique: iteratively removing the node of largest degree and all of its edges. This approach has an apparent quadratic complexity since, upon removal of a node and adjoining set of edges, the node degree calculations must be updated prior to choosing the next node. However, we describe a linear time complexity solution using an array whose indices map to node degree and whose values are hash tables indicating the presence or absence of a node at that degree value. This approach also has a linear growth with respect to memory usage which is surprising since we lowered the time complexity from quadratic to linear. We empirically demonstrate linear scalability and linear memory usage on random graphs of up to 15000 nodes. We then demonstrate tractability on massive graphs through execution on a graph with 34 million nodes representing Internet wide router connectivity.
The Belle II Silicon Vertex Detector
NASA Astrophysics Data System (ADS)
Friedl, M.; Bergauer, T.; Dolejschi, P.; Frankenberger, A.; Gfall, I.; Irmler, C.; Obermayer, T.; Onuki, Y.; Smiljic, D.; Tsuboyama, T.; Valentan, M.
The KEKB factory (Tsukuba, Japan) has been shut down in mid-2010 after reaching a total integrated luminosity of 1ab-1. Recently, the work on an upgrade of the collider (SuperKEKB), aiming at an ultimate luminosity of 8×1035 cm-2s-1, has started. This is 40 times the peak value of the previous system and thus also requires a redesign of the Belle detector (leading to Belle II), especially its Silicon Vertex Detector (SVD), which surrounds the beam pipe. Similar to its predecessor, the future Belle II SVD will again consist of four layers of double-sided silicon strip sensors (DSSD), but at higher radii. Moreover, a double-layer PiXel Detector (PXD) will complement the SVD as the innermost sensing device. All DSSDs will be made from 6" silicon wafers and read out by APV25 chips, which were originally developed for the CMS experiment. That system was proven to meet the requirements for Belle II in matters of occupancy and dead time. Since the KEKB factory operates at relatively low energy, material inside the active volume has to be minimized in order to reduce multiple scattering. This can be achieved by the Origami chip-on-sensor concept, including a very light-weight mechanical support structure made from carbon fiber reinforced Airex foam. Moreover, CO2 cooling for the front-end chips will ensure high efficiency at minimum material budget.
Linear Time Vertex Partitioning on Massive Graphs
Mell, Peter; Harang, Richard; Gueye, Assane
2016-01-01
The problem of optimally removing a set of vertices from a graph to minimize the size of the largest resultant component is known to be NP-complete. Prior work has provided near optimal heuristics with a high time complexity that function on up to hundreds of nodes and less optimal but faster techniques that function on up to thousands of nodes. In this work, we analyze how to perform vertex partitioning on massive graphs of tens of millions of nodes. We use a previously known and very simple heuristic technique: iteratively removing the node of largest degree and all of its edges. This approach has an apparent quadratic complexity since, upon removal of a node and adjoining set of edges, the node degree calculations must be updated prior to choosing the next node. However, we describe a linear time complexity solution using an array whose indices map to node degree and whose values are hash tables indicating the presence or absence of a node at that degree value. This approach also has a linear growth with respect to memory usage which is surprising since we lowered the time complexity from quadratic to linear. We empirically demonstrate linear scalability and linear memory usage on random graphs of up to 15000 nodes. We then demonstrate tractability on massive graphs through execution on a graph with 34 million nodes representing Internet wide router connectivity. PMID:27336059
Efficient variants of the vertex space domain decomposition algorithm
Chan, T.F.; Shao, J.P. . Dept. of Mathematics); Mathew, T.P. . Dept. of Mathematics)
1994-11-01
Several variants of the vertex space algorithm of Smith for two-dimensional elliptic problems are described. The vertex space algorithm is a domain decomposition method based on nonoverlapping subregions, in which the reduced Schur complement system on the interface is solved using a generalized block Jacobi-type preconditioner, with the blocks corresponding to the vertex space, edges, and a coarse grid. Two kinds of approximations are considered for the edge and vertex space subblocks, one based on Fourier approximation, and another based on an algebraic probing technique in which sparse approximations to these subblocks are computed. The motivation is to improve the efficiency of the algorithm without sacrificing the optimal convergence rate. Numerical and theoretical results on the performance of these algorithms, including variants of an algorithm of Bramble, Pasciak, and Schatz are presented.
NASA Astrophysics Data System (ADS)
Hasunuma, Takumi; Kaneko, Tatsuya; Miyakoshi, Shohei; Ohta, Yukinori
2016-07-01
The variational cluster approximation is used to study the ground-state properties and single-particle spectra of the three-component fermionic Hubbard model defined on the two-dimensional square lattice at half filling. First, we show that either a paired Mott state or color-selective Mott state is realized in the paramagnetic system, depending on the anisotropy in the interaction strengths, except around the SU(3) symmetric point, where a paramagnetic metallic state is maintained. Then, by introducing Weiss fields to observe spontaneous symmetry breakings, we show that either a color-density-wave state or color-selective antiferromagnetic state is realized depending on the interaction anisotropy and that the first-order phase transition between these two states occurs at the SU(3) point. We moreover show that these staggered orders originate from the gain in potential energy (or Slater mechanism) near the SU(3) point but originate from the gain in kinetic energy (or Mott mechanism) when the interaction anisotropy is strong. The staggered orders near the SU(3) point disappear when the next-nearest-neighbor hopping parameters are introduced, indicating that these orders are fragile, protected only by the Fermi surface nesting.
A staggered approach for the coupling of Cahn-Hilliard type diffusion and finite strain elasticity
NASA Astrophysics Data System (ADS)
Areias, P.; Samaniego, E.; Rabczuk, T.
2016-02-01
We develop an algorithm and computational implementation for simulation of problems that combine Cahn-Hilliard type diffusion with finite strain elasticity. We have in mind applications such as the electro-chemo-mechanics of lithium ion (Li-ion) batteries. We concentrate on basic computational aspects. A staggered algorithm is proposed for the coupled multi-field model. For the diffusion problem, the fourth order differential equation is replaced by a system of second order equations to deal with the issue of the regularity required for the approximation spaces. Low order finite elements are used for discretization in space of the involved fields (displacement, concentration, nonlocal concentration). Three (both 2D and 3D) extensively worked numerical examples show the capabilities of our approach for the representation of (i) phase separation, (ii) the effect of concentration in deformation and stress, (iii) the effect of strain in concentration, and (iv) lithiation. We analyze convergence with respect to spatial and time discretization and found that very good results are achievable using both a staggered scheme and approximated strain interpolation.
Film cooling: case of double rows of staggered jets.
Dorignac, E; Vullierme, J J; Noirault, P; Foucault, E; Bousgarbiès, J L
2001-05-01
An experimental investigation of film cooling of a wall in a case of double rows of staggered hot jets (65 degrees C) in an ambient air flow. The wall is heated at a temperature value between the one of the jets and the one of the main flow. Experiments have been carried out for different injection rates, the main flow velocity is maintained at 32 m/s. Association of the measures of temperature profiles by cold wire and the measures of wall temperature by infrared thermography allows us to describe the behaviour of the flows and to propose the best injection which assures a good cooling of the plate.
Survival analysis in telemetry studies: The staggered entry design
Pollock, K.H.; Winterstein, S.R.; Bunck, C.M.; Curtis, P.D.
1989-01-01
A simple description of the Kaplan-Meier procedure is presented with an example using northern bobwhite quail survival data. The Kaplan- Meier procedure was then generalized to allow gradual (or staggered) entry of animals into the study, allowing animals being lost (or censored) due to radio failure, radio loss, or emigration of the animal from the study area. Additionally, the applicability and generalization of the log rank test, a test to compare two survival distributions, was demonstrated. Computer program was developed and is available from authors.
Observations on staggered fermions at nonzero lattice spacing
Bernard, Claude; Golterman, Maarten; Shamir, Yigal
2006-06-01
We show that the use of the fourth-root trick in lattice QCD with staggered fermions corresponds to a nonlocal theory at nonzero lattice spacing, but argue that the nonlocal behavior is likely to go away in the continuum limit. We give examples of this nonlocal behavior in the free theory, and for the case of a fixed topologically nontrivial background gauge field. In both special cases, the nonlocal behavior indeed disappears in the continuum limit. Our results invalidate a recent claim that at nonzero lattice spacing an additive mass renormalization is needed because of taste-symmetry breaking.
Distinct failure modes in bio-inspired 3D-printed staggered composites under non-aligned loadings
NASA Astrophysics Data System (ADS)
Slesarenko, Viacheslav; Kazarinov, Nikita; Rudykh, Stephan
2017-03-01
The superior mechanical properties of biological materials originate in their complex hierarchical microstructures, combining stiff and soft constituents at different length scales. In this work, we employ a three-dimensional multi-materials printing to fabricate the bio-inspired staggered composites, and study their mechanical properties and failure mechanisms. We observe that bio-inspired staggered composites with inclined stiff tablets are able to undergo two different failure modes, depending on the inclination angle. We find that such artificial structure demonstrates high toughness only under loading applied at relatively small angle to the tablets stacking direction, while for higher angles the composites fail catastrophically. This aspect of the failure behavior was captured experimentally as well as by means of the finite element analysis. We show that even a relatively simple failure model with a strain energy limiter, can be utilized to qualitatively distinguish these two different modes of failure, occurring in the artificial bio-inspired composites.
Hagino, K.; Sagawa, H.
2011-07-15
We investigate the spatial extension of weakly bound Ne and C isotopes by taking into account the pairing correlation with the Hartree-Fock-Bogoliubov (HFB) method and a three-body model, respectively. We show that the odd-even staggering in the reaction cross sections of {sup 30,31,32}Ne and {sup 14,15,16}C are successfully reproduced, and thus the staggering can be attributed to the pairing anti-halo effect. A correlation between a one-neutron separation energy and the anti-halo effect is demonstrated for s and p waves using the HFB wave functions.
The vertex detector for the Lepton/Photon collaboration
Sullivan, J.P.; Boissevain, J.G.; Fox, D.; Hecke, H. van; Jacak, B.V.; Kapustinsky, J.S.; Leitch, M.J.; McGaughey, P.L.; Moss, J.M.; Sondheim, W.E.
1991-12-31
The conceptual design of the vertex detector for the Lepton/Photon Collaboration at RHIC is described, including simulations of its expected performance. The design consists of two con- centric layers of single-sided Si strips. The expected performance as a multiplicity detector and in measuring the pseudo-rapidity ({nu}) distribution is discussed as well as the expected vertex finding efficiency and accuracy. Various options which could be used to reduce the cost of the detector are also discussed.
NASA Astrophysics Data System (ADS)
Janiš, V.; Pokorný, V.
2014-07-01
We use the dynamical mean-field approximation to study singularities in the self-energy and a two-particle irreducible vertex induced by the metal-insulator transition of the disordered Falicov-Kimball model. We set general conditions for the existence of a critical metal-insulator transition caused by a divergence of the imaginary part of the self-energy. We calculate explicitly the critical behavior of the self-energy for the symmetric and asymmetric disorder distributions. We demonstrate that the metal-insulator transition is preceded by a pole in a two-particle irreducible vertex. We show that unlike the singularity in the self-energy the divergence in the irreducible vertex does not lead to nonanalyticities in measurable physical quantities. We reveal universal features of the critical metal-insulator transition that are transferable also to the Mott-Hubbard transition in the models of the local Fermi liquid.
Phase Transition of Bosons Driven by a Staggered Gauge Field in AN Optical Lattice
NASA Astrophysics Data System (ADS)
Cha, Min-Chul
2013-06-01
We have studied the ground state properties of hard-core bosons in a two-leg optical ladder in the presence of uniform and staggered frustrations due to an artificial gauge field. By calculating the ground state via the Lanczos method, we find first-order phase transitions tuned by the staggered gauge field between the Meissner and the vortex states. The momentum distributions show that the Meissner state has edge and staggered currents, while the vortex states have vortex-solid or vortex-glass phases in the presence of a staggered field.
Covariant and self-consistent vertex corrections for pions and isobars in nuclear matter
Korpa, C. L.; Lutz, M. F. M.; Riek, F.
2009-08-15
We evaluate the pion and isobar propagators in cold nuclear matter self-consistently applying a covariant form of the isobar-hole model. Migdal's vertex correction effects are considered systematically in the absence of phenomenological soft form factors. Saturated nuclear matter is modeled by scalar and vector mean fields for the nucleon. It is shown that the short-range dressing of the {pi}N{delta} vertex has a significant effect on the pion and isobar properties. Using realistic parameters sets we predict a downward shift of about 50 MeV for the {delta} resonance at nuclear saturation density. The pionic soft modes are much less pronounced than in previous studies.
Continuous-time quantum Monte Carlo calculation of multiorbital vertex asymptotics
NASA Astrophysics Data System (ADS)
Kaufmann, Josef; Gunacker, Patrik; Held, Karsten
2017-07-01
We derive the equations for calculating the high-frequency asymptotics of the local two-particle vertex function for a multiorbital impurity model. These relate the asymptotics for a general local interaction to equal-time two-particle Green's functions, which we sample using continuous-time quantum Monte Carlo simulations with a worm algorithm. As specific examples we study the single-orbital Hubbard model and the three t2 g orbitals of SrVO3 within dynamical mean-field theory (DMFT). We demonstrate how the knowledge of the high-frequency asymptotics reduces the statistical uncertainties of the vertex and further eliminates finite-box-size effects. The proposed method benefits the calculation of nonlocal susceptibilities in DMFT and diagrammatic extensions of DMFT.
Magnetic-free non-reciprocity based on staggered commutation
Reiskarimian, Negar; Krishnaswamy, Harish
2016-01-01
Lorentz reciprocity is a fundamental characteristic of the vast majority of electronic and photonic structures. However, non-reciprocal components such as isolators, circulators and gyrators enable new applications ranging from radio frequencies to optical frequencies, including full-duplex wireless communication and on-chip all-optical information processing. Such components today dominantly rely on the phenomenon of Faraday rotation in magneto-optic materials. However, they are typically bulky, expensive and not suitable for insertion in a conventional integrated circuit. Here we demonstrate magnetic-free linear passive non-reciprocity based on the concept of staggered commutation. Commutation is a form of parametric modulation with very high modulation ratio. We observe that staggered commutation enables time-reversal symmetry breaking within very small dimensions (λ/1,250 × λ/1,250 in our device), resulting in a miniature radio-frequency circulator that exhibits reduced implementation complexity, very low loss, strong non-reciprocity, significantly enhanced linearity and real-time reconfigurability, and is integrated in a conventional complementary metal–oxide–semiconductor integrated circuit for the first time. PMID:27079524
Magnetic-free non-reciprocity based on staggered commutation.
Reiskarimian, Negar; Krishnaswamy, Harish
2016-04-15
Lorentz reciprocity is a fundamental characteristic of the vast majority of electronic and photonic structures. However, non-reciprocal components such as isolators, circulators and gyrators enable new applications ranging from radio frequencies to optical frequencies, including full-duplex wireless communication and on-chip all-optical information processing. Such components today dominantly rely on the phenomenon of Faraday rotation in magneto-optic materials. However, they are typically bulky, expensive and not suitable for insertion in a conventional integrated circuit. Here we demonstrate magnetic-free linear passive non-reciprocity based on the concept of staggered commutation. Commutation is a form of parametric modulation with very high modulation ratio. We observe that staggered commutation enables time-reversal symmetry breaking within very small dimensions (λ/1,250 × λ/1,250 in our device), resulting in a miniature radio-frequency circulator that exhibits reduced implementation complexity, very low loss, strong non-reciprocity, significantly enhanced linearity and real-time reconfigurability, and is integrated in a conventional complementary metal-oxide-semiconductor integrated circuit for the first time.
A subzone reconstruction algorithm for efficient staggered compatible remapping
Starinshak, D.P. Owen, J.M.
2015-09-01
Staggered-grid Lagrangian hydrodynamics algorithms frequently make use of subzonal discretization of state variables for the purposes of improved numerical accuracy, generality to unstructured meshes, and exact conservation of mass, momentum, and energy. For Arbitrary Lagrangian–Eulerian (ALE) methods using a geometric overlay, it is difficult to remap subzonal variables in an accurate and efficient manner due to the number of subzone–subzone intersections that must be computed. This becomes prohibitive in the case of 3D, unstructured, polyhedral meshes. A new procedure is outlined in this paper to avoid direct subzonal remapping. The new algorithm reconstructs the spatial profile of a subzonal variable using remapped zonal and nodal representations of the data. The reconstruction procedure is cast as an under-constrained optimization problem. Enforcing conservation at each zone and node on the remapped mesh provides the set of equality constraints; the objective function corresponds to a quadratic variation per subzone between the values to be reconstructed and a set of target reference values. Numerical results for various pure-remapping and hydrodynamics tests are provided. Ideas for extending the algorithm to staggered-grid radiation-hydrodynamics are discussed as well as ideas for generalizing the algorithm to include inequality constraints.
Qwamizadeh, Mahan; Zhang, Zuoqi; Zhou, Kun; Zhang, Yong Wei
2016-07-01
One of the key functions of load-bearing biological materials, such as bone, dentin and sea shell, is to protect their inside fragile organs by effectively damping dynamic impact. How those materials achieve this remarkable function remains largely unknown. Using systematic finite element analyses, we study the stress wave propagation and attenuation in cortical bone at the nanoscale as a model material to examine the effects of protein viscosity, mineral fraction and staggered architecture on the elastic wave decay. It is found that the staggered arrangement, protein viscosity and mineral fraction work cooperatively to effectively attenuate the stress wave. For a typical mineral volume fraction and protein viscosity, an optimal staggered nanostructure with specific feature sizes and layouts is able to give rise to the fastest stress wave decay, and the optimal aspect ratio and thickness of mineral platelets are in excellent agreement with experimental measurements. In contrary, as the mineral volume fraction or the protein viscosity goes much higher, the structural arrangement is seen having trivial effect on the stress wave decay, suggesting that the damping properties of the composites go into the structure-insensitive regime from the structure-sensitive regime. These findings not only significantly add to our understanding of the structure-function relationship of load-bearing biological materials, and but also provide useful guidelines for the design of bio-inspired materials with superior resistance to impact loading.
NASA Astrophysics Data System (ADS)
Calleya, N. L.; Souza, S. R.; Carlson, B. V.; Donangelo, R.; Lynch, W. G.; Tsang, M. B.; Winkelbauer, J. R.
2014-11-01
The fragmentation of thermalized sources is studied using a version of the Statistical Multifragmentation Model which employs state densities that take the pairing gap in the nuclear levels into account. Attention is focused on the properties of the charge distributions observed in the breakup of the source. Since the microcanonical version of the model used in this study provides the primary fragment excitation energy distribution, one may correlate the reduction of the odd-even staggering in the charge distribution with the increasing occupation of high-energy states. Thus, in the framework of this model, such staggering tends to disappear as a function of the total excitation energy of the source, although the energy per particle may be small for large systems. We also find that, although the deexcitation of the primary fragments should, in principle, blur these odd-even effects as the fragments follow their decay chains, the consistent treatment of pairing may significantly enhance these staggering effects on the final yields. In the framework of this model, we find that odd-even effects in the charge distributions should be observed in the fragmentation of relatively light systems at very low excitation energies. Our results also suggest that the odd-even staggering may provide useful information on the nuclear state density.
A free surface capturing discretization for the staggered grid finite difference scheme
NASA Astrophysics Data System (ADS)
Duretz, T.; May, D. A.; Yamato, P.
2016-03-01
The coupling that exists between surface processes and deformation within both the shallow crust and the deeper mantle-lithosphere has stimulated the development of computational geodynamic models that incorporate a free surface boundary condition. We introduce a treatment of this boundary condition that is suitable for staggered grid, finite difference schemes employing a structured Eulerian mesh. Our interface capturing treatment discretizes the free surface boundary condition via an interface that conforms with the edges of control volumes (e.g. a `staircase' representation) and requires only local stencil modifications to be performed. Comparisons with analytic solutions verify that the method is first-order accurate. Additional intermodel comparisons are performed between known reference models to further validate our free surface approximation. Lastly, we demonstrate the applicability of a multigrid solver to our free surface methodology and demonstrate that the local stencil modifications do not strongly influence the convergence of the iterative solver.
Isospin Dependence in the Odd-Even Staggering of Nuclear Binding Energies
Litvinov, Yu.A.; Geissel, H.; Buervenich, T.J.; Novikov, Yu.N.; Patyk, Z.; Scheidenberger, C.; Attallah, F.; Beckert, K.; Bosch, F.; Franzke, B.; Klepper, O.; Kluge, H.-J.; Kozhuharov, C.; Muenzenberg, G.; Nolden, F.; Radon, T.; Steck, M.; Typel, S.; Audi, G.; Falch, M.
2005-07-22
The FRS-ESR facility at GSI provides unique conditions for precision measurements of large areas on the nuclear mass surface in a single experiment. Values for masses of 604 neutron-deficient nuclides (30{<=}Z{<=}92) were obtained with a typical uncertainty of 30 {mu}u. The masses of 114 nuclides were determined for the first time. The odd-even staggering (OES) of nuclear masses was systematically investigated for isotopic chains between the proton shell closures at Z=50 and Z=82. The results were compared with predictions of modern nuclear models. The comparison revealed that the measured trend of OES is not reproduced by the theories fitted to masses only. The spectral pairing gaps extracted from models adjusted to both masses, and density related observables of nuclei agree better with the experimental data.
A 3D staggered-grid finite difference scheme for poroelastic wave equation
NASA Astrophysics Data System (ADS)
Zhang, Yijie; Gao, Jinghuai
2014-10-01
Three dimensional numerical modeling has been a viable tool for understanding wave propagation in real media. The poroelastic media can better describe the phenomena of hydrocarbon reservoirs than acoustic and elastic media. However, the numerical modeling in 3D poroelastic media demands significantly more computational capacity, including both computational time and memory. In this paper, we present a 3D poroelastic staggered-grid finite difference (SFD) scheme. During the procedure, parallel computing is implemented to reduce the computational time. Parallelization is based on domain decomposition, and communication between processors is performed using message passing interface (MPI). Parallel analysis shows that the parallelized SFD scheme significantly improves the simulation efficiency and 3D decomposition in domain is the most efficient. We also analyze the numerical dispersion and stability condition of the 3D poroelastic SFD method. Numerical results show that the 3D numerical simulation can provide a real description of wave propagation.
ERIC Educational Resources Information Center
Childers, Annie Burns; Vidakovic, Draga
2014-01-01
This paper explores sixty-six students' personal meaning and interpretation of the vertex of a quadratic function in relation to their understanding of quadratic functions in two different representations, algebraic and word problem. Several categories emerged from students' personal meaning of the vertex including vertex as maximum or minimum…
ERIC Educational Resources Information Center
Childers, Annie Burns; Vidakovic, Draga
2014-01-01
This paper explores sixty-six students' personal meaning and interpretation of the vertex of a quadratic function in relation to their understanding of quadratic functions in two different representations, algebraic and word problem. Several categories emerged from students' personal meaning of the vertex including vertex as maximum or minimum…
An image matching method based on closed edges incorporated with vertex angles
NASA Astrophysics Data System (ADS)
Zhang, Baoming; Chen, Xiaowei; Lu, Jun; Gong, Zhihui; Guo, Haitao
2015-10-01
An image matching method based on closed edges incorporated with vertex angles is proposed in this paper. Based on edge detection results by Edison operator, invariant moments of closed edges and angles between the two branches for edge vertexes are used as matching entities to determine conjugate features candidates. The transformation relationship between images is approximated by similarity transformation model, and a set of transformation parameters can be determined by each pair of conjugate features after combining conjugate feature candidates in pair-wise. Furthermore, considering that the difference among transformation parameters which calculated by real conjugate features are minor, K-d tree method and K-means Spatial clustering method are used in succession to eliminate pairs which contain mismatching features. Therefore, conjugate features can be obtained from the similarity transformation parameters. Experimental results turn out that this method shows a stable performance and presents a satisfactory matching result.
VERTEX: manganese transport through oxygen minima
NASA Astrophysics Data System (ADS)
Martin, John H.; Knauer, George A.
1984-01-01
Manganese transport through a well-developed oxygen minimum was studied off central Mexico (18°N, 108°W) in October-November 1981 as part of the VERTEX (Vertical Transport and Exchange) research program. Refractory, leachable and dissolved Mn fractions associated with particulates caught in traps set at eight depths (120-1950 m) were analyzed. Particles entering the oxygen minimum had relatively large Mn loads; however, as the particulates sank further into the minimum, total Mn fluxes steadily decreased from 190 nmol m -2 day -1 at 120 m to 36 nmol m -2 day -1 at 400 m. Manganese fluxes then steadily increased in the remaining 800-1950 m, reaching rates of up to 230 nmol m -2 day -1 at 1950 m. Manganese concentrations were also measured in the water column. Dissolved Mn levels < 3.0 nmol kg -1 were consistently observed within the 150-600 m depth interval. In contrast, suspended particulate leachable Mn amounts were especially low at those depths, and never exceeded 0.04 nmol kg -1. The combined water column and particle trap data clearly indicate that Mn is released from particles as they sink through the oxygen minimum. Rate-of-change estimates based on trap flux data yield regeneration rates of up to 0.44 nmol kg -1 yr -1 in the upper oxygen minimum (120-200 m). However, only 30% of the dissolved Mn in the oxygen minimum appears to be from sinking particulate regeneration; the other 70% probably results from continental-slope-release-horizontal-transport processes. Dissolved Mn scavenges back onto particles as oxygen levels begin to increase with depth. Scavenging rates ranging from -0.03 to -0.09 nmol kg -1 yr -1 were observed at depths from 700 to 1950 m. These scavenging rates result in Mn residence times of 16-19 years, and scavenging rate constants on the order of 0.057 yr -1. Manganese removal via scavenging on sinking particles below the oxygen minimum is balanced by Mn released along continental boundaries and transported horizontally via advective
A vertex trigger based on cylindrical multiwire proportional chambers
NASA Astrophysics Data System (ADS)
Becker, J.; Bösiger, K.; Lindfeld, L.; Müller, K.; Robmann, P.; Schmitt, S.; Schmitz, C.; Steiner, S.; Straumann, U.; Szeker, K.; Truöl, P.; Urban, M.; Vollhardt, A.; Werner, N.; Baumeister, D.; Löchner, S.; Hildebrandt, M.
2008-02-01
This article describes the technical implementation and the performance of the z-vertex trigger (CIP2k), which is part of the H1-experiment at HERA. The HERA storage ring and collider was designed to investigate electron (and positron) proton scattering at a center-of-mass energy of 320 GeV. To improve the sensitivity for detecting non-standard model physics and other high momentum transfer phenomena, the HERA ring has been ungraded between 2000 and 2003 to increase the specific luminosity for the experiments. In order to cope with the increased event and background rate the experiments were upgraded, too. The CIP2k trigger system is based on a set of five cylindrical multiwire proportional chambers with cathode pad readout, and allows to distinguish between events induced by beam background and ep-interactions at the first trigger stage. The trigger decision is calculated dead-time free with a latency of 1.5 μs in parallel to the beam clock at 10.4 MHz. The trigger-logic is realized in large field programmable gate arrays (FPGA) using the hardware description language Verilog. The system is operational since October 2003. It suppresses background events with high efficiency and provides event timing information, as designed.
Emergent reduced dimensionality by vertex frustration in artificial spin ice
Gilbert, Ian; Lao, Yuyang; Carrasquillo, Isaac; ...
2015-10-26
Reducing the dimensionality of a physical system can have a profound effect on its properties, as in the ordering of low-dimensional magnetic materials, phonon dispersion in mercury chain salts, sliding phases, and the electronic states of graphene. Here we explore the emergence of quasi-one-dimensional behaviour in two-dimensional artificial spin ice, a class of lithographically fabricated nanomagnet arrays used to study geometrical frustration. We extend the implementation of artificial spin ice by fabricating a new array geometry, the so-called tetris lattice. We demonstrate that the ground state of the tetris lattice consists of alternating ordered and disordered bands of nanomagnetic moments.more » The disordered bands can be mapped onto an emergent thermal one-dimensional Ising model. Furthermore, we show that the level of degeneracy associated with these bands dictates the susceptibility of island moments to thermally induced reversals, thus establishing that vertex frustration can reduce the relevant dimensionality of physical behaviour in a magnetic system.« less
Genus Ranges of 4-Regular Rigid Vertex Graphs.
Buck, Dorothy; Dolzhenko, Egor; Jonoska, Nataša; Saito, Masahico; Valencia, Karin
2015-01-01
A rigid vertex of a graph is one that has a prescribed cyclic order of its incident edges. We study orientable genus ranges of 4-regular rigid vertex graphs. The (orientable) genus range is a set of genera values over all orientable surfaces into which a graph is embedded cellularly, and the embeddings of rigid vertex graphs are required to preserve the prescribed cyclic order of incident edges at every vertex. The genus ranges of 4-regular rigid vertex graphs are sets of consecutive integers, and we address two questions: which intervals of integers appear as genus ranges of such graphs, and what types of graphs realize a given genus range. For graphs with 2n vertices (n > 1), we prove that all intervals [a, b] for all a < b ≤ n, and singletons [h, h] for some h ≤ n, are realized as genus ranges. For graphs with 2n - 1 vertices (n ≥ 1), we prove that all intervals [a, b] for all a < b ≤ n except [0, n], and [h, h] for some h ≤ n, are realized as genus ranges. We also provide constructions of graphs that realize these ranges.
Genus Ranges of 4-Regular Rigid Vertex Graphs
Buck, Dorothy; Dolzhenko, Egor; Jonoska, Nataša; Saito, Masahico; Valencia, Karin
2016-01-01
A rigid vertex of a graph is one that has a prescribed cyclic order of its incident edges. We study orientable genus ranges of 4-regular rigid vertex graphs. The (orientable) genus range is a set of genera values over all orientable surfaces into which a graph is embedded cellularly, and the embeddings of rigid vertex graphs are required to preserve the prescribed cyclic order of incident edges at every vertex. The genus ranges of 4-regular rigid vertex graphs are sets of consecutive integers, and we address two questions: which intervals of integers appear as genus ranges of such graphs, and what types of graphs realize a given genus range. For graphs with 2n vertices (n > 1), we prove that all intervals [a, b] for all a < b ≤ n, and singletons [h, h] for some h ≤ n, are realized as genus ranges. For graphs with 2n − 1 vertices (n ≥ 1), we prove that all intervals [a, b] for all a < b ≤ n except [0, n], and [h, h] for some h ≤ n, are realized as genus ranges. We also provide constructions of graphs that realize these ranges. PMID:27807395
't Hooft vertices, partial quenching, and rooted staggered QCD
Bernard, Claude; Golterman, Maarten; Shamir, Yigal; Sharpe, Stephen R.
2008-06-01
We discuss the properties of 't Hooft vertices in partially quenched and rooted versions of QCD in the continuum. These theories have a physical subspace, equivalent to ordinary QCD, that is contained within a larger space that includes many unphysical correlation functions. We find that the 't Hooft vertices in the physical subspace have the expected form, despite the presence of unphysical 't Hooft vertices appearing in correlation functions that have an excess of valence quarks (or ghost quarks). We also show that, due to the singular behavior of unphysical correlation functions as the massless limit is approached, order parameters for nonanomalous symmetries can be nonvanishing in finite volume if these symmetries act outside of the physical subspace. Using these results, we demonstrate that arguments recently given by Creutz - claiming to disprove the validity of rooted staggered QCD - are incorrect. In particular, the unphysical 't Hooft vertices do not present an obstacle to the recovery of taste symmetry in the continuum limit.
Vertex dynamics simulations of viscosity-dependent deformation during tissue morphogenesis.
Okuda, Satoru; Inoue, Yasuhiro; Eiraku, Mototsugu; Adachi, Taiji; Sasai, Yoshiki
2015-04-01
In biological development, multiple cells cooperate to form tissue morphologies based on their mechanical interactions; namely active force generation and passive viscoelastic response. In particular, the dynamic processes of tissue deformations are governed by the viscous properties of the tissues. These properties are spatially inhomogeneous because they depend on the tissue constituents, such as cytoplasm, cytoskeleton, basement membrane and extracellular matrix. The multicellular mechanics of tissue morphogenesis have been investigated in vertex dynamics models. However, conventional models are applicable only to quasi-static deformation processes, which do not account for tissue viscosities. We propose a vertex dynamics model that simulates the viscosity-dependent dynamic deformation processes during tissue morphogenesis. By incorporating local velocity fields into the governing equation of vertex movements, the model turns Galilean invariant. In addition, the viscous properties of tissue components are newly expressed by formulating friction forces on vertices as functions of the relative velocities among the vertices. The advantages of the proposed model are examined by epithelial growth simulations under the employed condition for quasi-static processes. As a result, the epithelial vesicle simulated by the proposed model is linearly elongated with nearly free stress, while that simulated by the conventional model is undulated with compressive residual stress. Therefore, the proposed model is able to reflect the timescale of deformations by satisfying Galilean invariance. Next, the applicability of the proposed model is assessed in epithelial growth simulations of viscous extracellular materials. In this test, the epithelial vesicles are deformed into tubular shapes by oriented cell divisions, and their morphologies are extremely sensitive to extracellular viscosity. Therefore, the dynamic deformations in the proposed model depend on the viscous properties
Plethystic vertex operators and boson-fermion correspondences
NASA Astrophysics Data System (ADS)
Fauser, Bertfried; Jarvis, Peter D.; King, Ronald C.
2016-10-01
We study the algebraic properties of plethystic vertex operators, introduced in (2010 J. Phys. A: Math. Theor. 43 405202), underlying the structure of symmetric functions associated with certain generalized universal character rings of subgroups of the general linear group, defined to stabilize tensors of Young symmetry type characterized by a partition of arbitrary shape π. Here we establish an extension of the well-known boson-fermion correspondence involving Schur functions and their associated (Bernstein) vertex operators: for each π, the modes generated by the plethystic vertex operators and their suitably constructed duals, satisfy the anticommutation relations of a complex Clifford algebra. The combinatorial manipulations underlying the results involve exchange identities exploiting the Hopf-algebraic structure of certain symmetric function series and their plethysms.
The RAVE/VERTIGO vertex reconstruction toolkit and framework
NASA Astrophysics Data System (ADS)
Waltenberger, W.; Mitaroff, W.; Moser, F.; Pflugfelder, B.; Riedel, H. V.
2008-07-01
A detector-independent toolkit for vertex reconstruction (RAVE1) is being developed, along with a standalone framework (VERTIGO2) for testing, analyzing and debugging. The core algorithms represent state-of-the-art for geometric vertex finding and fitting by both linear (Kalman filter) and robust estimation methods. Main design goals are ease of use, flexibility for embedding into existing software frameworks, extensibility, and openness. The implementation is based on modern object-oriented techniques, is coded in C++ with interfaces for Java and Python, and follows an open-source approach. A beta release is available.
A GPU algorithm for minimum vertex cover problems
NASA Astrophysics Data System (ADS)
Toume, Kouta; Kinjo, Daiki; Nakamura, Morikazu
2014-10-01
The minimum vertex cover problem is one of the fundamental problems in graph theory and is known to be NP-hard. For data mining in large-scale structured systems, we proposes a GPU algorithm for the minimum vertex cover problem. The algorithm is designed to derive sufficient parallelism of the problem for the GPU architecture and also to arrange data on the device memory for efficient coalesced accessing. Through the experimental evaluation, we demonstrate that our GPU algorithm is quite faster than CPU programs and the speedup becomes much evident when the graph size is enlarged.
q-vertex operator from 5D Nekrasov function
NASA Astrophysics Data System (ADS)
Itoyama, H.; Oota, T.; Yoshioka, R.
2016-08-01
The five-dimensional AGT correspondence implies the connection between the q-deformed Virasoro block and the 5d Nekrasov partition function. In this paper, we determine a q-deformation of the four-point block in the Coulomb gas representation from the 5d Nekrasov function, and obtain an expression of the q-deformed vertex operator. If we use only one kind of the q-vertex operators, one of the insertion points of them must be modified in order to hold the 2d/5d correspondence.
The Virasoro vertex algebra and factorization algebras on Riemann surfaces
NASA Astrophysics Data System (ADS)
Williams, Brian
2017-08-01
This paper focuses on the connection of holomorphic two-dimensional factorization algebras and vertex algebras which has been made precise in the forthcoming book of Costello-Gwilliam. We provide a construction of the Virasoro vertex algebra starting from a local Lie algebra on the complex plane. Moreover, we discuss an extension of this factorization algebra to a factorization algebra on the category of Riemann surfaces. The factorization homology of this factorization algebra is computed as the correlation functions. We provide an example of how the Virasoro factorization algebra implements conformal symmetry of the beta-gamma system using the method of effective BV quantization.
Simulations of silicon vertex tracker for star experiment at RHIC
Odyniec, G.; Cebra, D.; Christie, W.; Naudet, C.; Schroeder, L.; Wilson, W.; Liko, D.; Cramer, J.; Prindle, D.; Trainor, T.; Braithwaite, W.
1991-12-31
The first computer simulations to optimize the Silicon Vertex Tracker (SVT) designed for the STAR experiment at RHIC are presented. The physics goals and the expected complexity of the events at RHIC dictate the design of a tracking system for the STAR experiment. The proposed tracking system will consist of a silicon vertex tracker (SVT) to locate the primary interaction and secondary decay vertices and to improve the momentum resolution, and a time projection chamber (TPC), positioned inside a solenoidal magnet, for continuous tracking.
Cellular uptake of magnetite nanoparticles enhanced by NdFeB magnets in staggered arrangement
NASA Astrophysics Data System (ADS)
Lu, Yi-Ching; Chang, Fan-Yu; Tu, Shu-Ju; Chen, Jyh-Ping; Ma, Yunn-Hwa
2017-04-01
Magnetic force may greatly enhance uptake of magnetic nanoparticles (MNPs) by cultured cells; however, the effects of non-uniformity of magnetic field/ magnetic gradient on MNP internalization in culture has not been elucidated. Cellular uptake of polyacrylic acid coated-MNP by LN229 cells was measured with cylindrical NdFeB magnets arranged in a staggered pattern. The magnetic field generated by placing a magnet underneath (H-field) elicited a homogenous distribution of MNPs on the cells in culture; whereas the field without magnet underneath (L-field) resulted in MNP distribution along the edge of the wells. Cell-associated MNP (MNPcell) appeared to be magnetic field- and concentration-dependent. In H-field, MNPcell reached plateau within one hour of exposure to MNP with only one-min application of the magnetic force in the beginning of incubation; continuous presence of the magnet for 2 h did not further increase MNPcell, suggesting that magnetic force-induced uptake may be primarily contributed to enhanced MNP sedimentation. Although MNP distribution was much inhomogeneous in L-field, averaged MNPcell in the L-field may reach as high as 80% of that in H-field during 1-6 h incubation, suggesting high capacity of MNP internalization. In addition, no significant difference was observed in MNPcell analyzed by flow cytometry with the application of H-field of staggered plate vs. filled magnet plate. Therefore, biological variation may dominate MNP internalization even under relatively uniformed magnetic field; whereas non-uniformed magnetic field may serve as a model for tumor targeting with MNPs in vivo.
Yang, Q; Wen, S W; Chen, Y; Krewski, D; Fung Kee Fung, K; Walker, M
2006-01-01
To assess the risk of neonatal mortality and morbidity in vertex-vertex second twins according to mode of delivery and birth weight. Data from a historical cohort study based on a twin registry in the US (1995-1997) were used. Multivariate logistic regression was used to control for maternal age, race, marital status, cigarette smoking during pregnancy, parity, medical complications, gestational age, and other confounders. A total of 86 041 vertex-vertex second twins were classified into two groups: second twins delivered by cesarean section after cesarean delivery of first twin (C-C) (43.0%), second twins whose co-twins delivered vaginally (V-X) (57.0%). In infants of birth weight>or=2500 g group, the risks of noncongenital anomaly-related death (adjusted odds ratio (aOR): 4.64, 95% confidence interval (95% CI): 1.90, 13.92), low Apgar score (aOR: 2.39, 95% CI: 1.43, 4.14), and ventilation use (aOR: 1.31, 95% CI: 1.18, 1.47) were higher in the V-X group compared with the C-C group. No asphyxia-related neonatal deaths occurred in C-C group, whereas the incidence of this death was 0.04% in the V-X group. The risks of neonatal mortality and morbidity are increased in vertex-vertex second twins with birth weight>or=2500 g whose co-twins delivered vaginally compared with second twins delivered by cesarean section after cesarean delivery of first twin.
LOGISTIC NETWORK REGRESSION FOR SCALABLE ANALYSIS OF NETWORKS WITH JOINT EDGE/VERTEX DYNAMICS.
Almquist, Zack W; Butts, Carter T
2014-08-01
Change in group size and composition has long been an important area of research in the social sciences. Similarly, interest in interaction dynamics has a long history in sociology and social psychology. However, the effects of endogenous group change on interaction dynamics are a surprisingly understudied area. One way to explore these relationships is through social network models. Network dynamics may be viewed as a process of change in the edge structure of a network, in the vertex set on which edges are defined, or in both simultaneously. Although early studies of such processes were primarily descriptive, recent work on this topic has increasingly turned to formal statistical models. Although showing great promise, many of these modern dynamic models are computationally intensive and scale very poorly in the size of the network under study and/or the number of time points considered. Likewise, currently used models focus on edge dynamics, with little support for endogenously changing vertex sets. Here, the authors show how an existing approach based on logistic network regression can be extended to serve as a highly scalable framework for modeling large networks with dynamic vertex sets. The authors place this approach within a general dynamic exponential family (exponential-family random graph modeling) context, clarifying the assumptions underlying the framework (and providing a clear path for extensions), and they show how model assessment methods for cross-sectional networks can be extended to the dynamic case. Finally, the authors illustrate this approach on a classic data set involving interactions among windsurfers on a California beach.
LOGISTIC NETWORK REGRESSION FOR SCALABLE ANALYSIS OF NETWORKS WITH JOINT EDGE/VERTEX DYNAMICS
Almquist, Zack W.; Butts, Carter T.
2015-01-01
Change in group size and composition has long been an important area of research in the social sciences. Similarly, interest in interaction dynamics has a long history in sociology and social psychology. However, the effects of endogenous group change on interaction dynamics are a surprisingly understudied area. One way to explore these relationships is through social network models. Network dynamics may be viewed as a process of change in the edge structure of a network, in the vertex set on which edges are defined, or in both simultaneously. Although early studies of such processes were primarily descriptive, recent work on this topic has increasingly turned to formal statistical models. Although showing great promise, many of these modern dynamic models are computationally intensive and scale very poorly in the size of the network under study and/or the number of time points considered. Likewise, currently used models focus on edge dynamics, with little support for endogenously changing vertex sets. Here, the authors show how an existing approach based on logistic network regression can be extended to serve as a highly scalable framework for modeling large networks with dynamic vertex sets. The authors place this approach within a general dynamic exponential family (exponential-family random graph modeling) context, clarifying the assumptions underlying the framework (and providing a clear path for extensions), and they show how model assessment methods for cross-sectional networks can be extended to the dynamic case. Finally, the authors illustrate this approach on a classic data set involving interactions among windsurfers on a California beach. PMID:26120218
Edwards, R.G.; Heller, U.M.; Narayanan, R.
1999-10-01
The low-lying spectrum of the Dirac operator is predicted to be universal, within three classes, depending on symmetry properties specified according to random matrix theory. The three universal classes are the orthogonal, unitary and symplectic ensembles. Lattice gauge theory with staggered fermions has verified two of the cases so far, unitary and symplectic, with staggered fermions in the fundamental representation of SU(3) and SU(2). We verify the missing case here, namely orthogonal, with staggered fermions in the adjoint representation of SU(N{sub c}), N{sub c}=2,3. {copyright} {ital 1999} {ital The American Physical Society}
Symmetric point quartic gluon vertex and momentum subtraction
NASA Astrophysics Data System (ADS)
Gracey, J. A.
2014-07-01
We compute the full one loop correction to the quartic vertex of QCD at the fully symmetric point. This allows us to define a new momentum subtraction (MOM) scheme in the class of schemes introduced by Celmaster and Gonsalves. Hence using properties of the renormalization group equation, the two loop renormalization group functions for this scheme are given.
A Cohomology Theory of Grading-Restricted Vertex Algebras
NASA Astrophysics Data System (ADS)
Huang, Yi-Zhi
2014-04-01
We introduce a cohomology theory of grading-restricted vertex algebras. To construct the correct cohomologies, we consider linear maps from tensor powers of a grading-restricted vertex algebra to "rational functions valued in the algebraic completion of a module for the algebra," instead of linear maps from tensor powers of the algebra to a module for the algebra. One subtle complication arising from such functions is that we have to carefully address the issue of convergence when we compose these linear maps with vertex operators. In particular, for each , we have an inverse system of nth cohomologies and an additional nth cohomology of a grading-restricted vertex algebra V with coefficients in a V-module W such that is isomorphic to the inverse limit of the inverse system . In the case of n = 2, there is an additional second cohomology denoted by which will be shown in a sequel to the present paper to correspond to what we call square-zero extensions of V and to first order deformations of V when W = V.
The role of geometry in 4-vertex origami mechanics
NASA Astrophysics Data System (ADS)
Waitukaitis, Scott; Dieleman, Peter; van Hecke, Martin
Origami offers an interesting design platform metamaterials because it strongly couples mechanics with geometry. Even so, most research carried out so far has been limited to one or two particular patterns. I will discuss the full geometrical space of the most common origami building block, the 4-vertex, and show how exotic geometries can have dramatic effects on the mechanics.
Self-locking degree-4 vertex origami structures.
Fang, Hongbin; Li, Suyi; Wang, K W
2016-11-01
A generic degree-4 vertex (4-vertex) origami possesses one continuous degree-of-freedom for rigid folding, and this folding process can be stopped when two of its facets bind together. Such facet-binding will induce self-locking so that the overall structure stays at a pre-specified configuration without additional locking elements or actuators. Self-locking offers many promising properties, such as programmable deformation ranges and piecewise stiffness jumps, that could significantly advance many adaptive structural systems. However, despite its excellent potential, the origami self-locking features have not been well studied, understood, and used. To advance the state of the art, this research conducts a comprehensive investigation on the principles of achieving and harnessing self-locking in 4-vertex origami structures. Especially, for the first time, this study expands the 4-vertex structure construction from single-component to dual-component designs and investigates their self-locking behaviours. By exploiting various tessellation designs, this research discovers that the dual-component designs offer the origami structures with extraordinary attributes that the single-component structures do not have, which include the existence of flat-folded locking planes, programmable locking points and deformability. Finally, proof-of-concept experiments investigate how self-locking can effectively induce piecewise stiffness jumps. The results of this research provide new scientific knowledge and a systematic framework for the design, analysis and utilization of self-locking origami structures for many potential engineering applications.
AN ONLINE LONGITUDINAL VERTEX AND BUNCH SPECTRUM MONITOR FOR RHIC.
VAN ZEIJTS,J.
2004-07-05
The longitudinal bunch profile acquisition system at RHIC was recently upgraded to allow on-line measurements of the bunch spectrum, and collision vertex location and shape. The system allows monitoring the evolution of these properties along the ramp, at transition and rebucketing, and at store conditions. We describe some of the hardware and software changes, and show some applications of the system.
A neural network z-vertex trigger for Belle II
NASA Astrophysics Data System (ADS)
Neuhaus, S.; Skambraks, S.; Abudinen, F.; Chen, Y.; Feindt, M.; Frühwirth, R.; Heck, M.; Kiesling, C.; Knoll, A.; Paul, S.; Schieck, J.
2015-05-01
We present the concept of a track trigger for the Belle II experiment, based on a neural network approach, that is able to reconstruct the z (longitudinal) position of the event vertex within the latency of the first level trigger. The trigger will thus be able to suppress a large fraction of the dominating background from events outside of the interaction region. The trigger uses the drift time information of the hits from the Central Drift Chamber (CDC) of Belle II within narrow cones in polar and azimuthal angle as well as in transverse momentum (sectors), and estimates the z-vertex without explicit track reconstruction. The preprocessing for the track trigger is based on the track information provided by the standard CDC trigger. It takes input from the 2D (r — φ) track finder, adds information from the stereo wires of the CDC, and finds the appropriate sectors in the CDC for each track in a given event. Within each sector, the z-vertex of the associated track is estimated by a specialized neural network, with a continuous output corresponding to the scaled z-vertex. The input values for the neural network are calculated from the wire hits of the CDC.
Tests of track segment and vertex finding with neural networks
Denby, B.; Lessner, E. ); Lindsey, C.S. )
1990-04-01
Feed forward neural networks have been trained, using back-propagation, to find the slopes of simulated track segments in a straw chamber and to find the vertex of tracks from both simulated and real events in a more conventional drift chamber geometry. Network architectures, training, and performance are presented. 12 refs., 7 figs.
Self-locking degree-4 vertex origami structures
NASA Astrophysics Data System (ADS)
Fang, Hongbin; Li, Suyi; Wang, K. W.
2016-11-01
A generic degree-4 vertex (4-vertex) origami possesses one continuous degree-of-freedom for rigid folding, and this folding process can be stopped when two of its facets bind together. Such facet-binding will induce self-locking so that the overall structure stays at a pre-specified configuration without additional locking elements or actuators. Self-locking offers many promising properties, such as programmable deformation ranges and piecewise stiffness jumps, that could significantly advance many adaptive structural systems. However, despite its excellent potential, the origami self-locking features have not been well studied, understood, and used. To advance the state of the art, this research conducts a comprehensive investigation on the principles of achieving and harnessing self-locking in 4-vertex origami structures. Especially, for the first time, this study expands the 4-vertex structure construction from single-component to dual-component designs and investigates their self-locking behaviours. By exploiting various tessellation designs, this research discovers that the dual-component designs offer the origami structures with extraordinary attributes that the single-component structures do not have, which include the existence of flat-folded locking planes, programmable locking points and deformability. Finally, proof-of-concept experiments investigate how self-locking can effectively induce piecewise stiffness jumps. The results of this research provide new scientific knowledge and a systematic framework for the design, analysis and utilization of self-locking origami structures for many potential engineering applications.
SVT: an online silicon vertex tracker for the CDF upgrade
Bardi, A.; Belforte, S.; Berryhill, J.; CDF Collaboration
1997-07-01
The SVT is an online tracker for the CDF upgrade which will reconstruct 2D tracks using information from the Silicon VerteX detector (SVXII) and Central Outer Tracker (COT). The precision measurement of the track impact parameter will then be used to select and record large samples of B hadrons. We discuss the overall architecture, algorithms, and hardware implementation of the system.
Conservation laws, vertex corrections, and screening in Raman spectroscopy
NASA Astrophysics Data System (ADS)
Maiti, Saurabh; Chubukov, Andrey V.; Hirschfeld, P. J.
2017-07-01
We present a microscopic theory for the Raman response of a clean multiband superconductor, with emphasis on the effects of vertex corrections and long-range Coulomb interaction. The measured Raman intensity, R (Ω ) , is proportional to the imaginary part of the fully renormalized particle-hole correlator with Raman form factors γ (k ⃗) . In a BCS superconductor, a bare Raman bubble is nonzero for any γ (k ⃗) and diverges at Ω =2 Δmax , where Δmax is the largest gap along the Fermi surface. However, for γ (k ⃗) = constant, the full R (Ω ) is expected to vanish due to particle number conservation. It was sometimes stated that this vanishing is due to the singular screening by long-range Coulomb interaction. In our general approach, we show diagrammatically that this vanishing actually holds due to vertex corrections from the same short-range interaction that gives rise to superconductivity. We further argue that long-range Coulomb interaction does not affect the Raman signal for any γ (k ⃗) . We argue that vertex corrections eliminate the divergence at 2 Δmax . We also argue that vertex corrections give rise to sharp peaks in R (Ω ) at Ω <2 Δmin (the minimum gap along the Fermi surface), when Ω coincides with the frequency of one of the collective modes in a superconductor, e.g., Leggett and Bardasis-Schrieffer modes in the particle-particle channel, and an excitonic mode in the particle-hole channel.
Status and upgrade plans of the Belle silicon vertex detector
NASA Astrophysics Data System (ADS)
Aihara, H.; Arakawa, T.; Asano, Y.; Aso, T.; Bakich, A.; Barbero, M.; Browder, T.; Chang, M. C.; Chao, Y.; Chen, K. F.; Chidzik, S.; Chouvikov, A.; Choi, Y. K.; Das, A.; Dalseno, J.; Fratina, S.; Friedl, M.; Fujiyama, Y.; Haba, J.; Hara, K.; Hara, T.; Harrop, B.; Hayashi, K.; Hazumi, M.; Heffernan, D.; Higuchi, T.; Hirakawa, T.; Irmler, C.; Ishino, H.; Joshi, N. K.; Kajiwara, S.; Kakuno, H.; Kameshima, T.; Kawasaki, T.; Kibayashi, A.; Kim, Y. J.; Koike, S.; Korpar, S.; Križan, P.; Kurashiro, H.; Kusaka, A.; Marlow, D.; Miyake, H.; Moloney, G. R.; Nakahama, Y.; Natkaniec, Z.; Okuno, S.; Ono, S.; Ostrowicz, W.; Ozaki, H.; Peak, L.; Pernicka, M.; Rosen, M.; Rozanska, M.; Sato, N.; Schmid, S.; Schümann, J.; Stanič, S.; Steininger, H.; Sumisawa, K.; Tajima, O.; Takahashi, T.; Tamura, N.; Tanaka, M.; Tani, N.; Taylor, G. N.; Trabelsi, K.; Tsuboyama, T.; Uchida, K.; Ueno, K.; Ushiroda, Y.; Varner, G.; Varvell, K.; Velikzhanin, Y. S.; Wang, C. C.; Wang, M. Z.; Watanabe, M.; Watanabe, Y.; Yamamoto, H.; Yamashita, Y.; Ziegler, T.
2007-12-01
The second generation of Belle Silicon Vertex Detector (SVD) has been efficiently operated for more than three years. With increasing beam-induced background, a degradation of the detector performance is expected. To avoid such a difficulty, we are planing a next upgrade, the third generation of the SVD. Currently, its design is almost finalized.
Recent developments in high precision vertex chambers at SLAC
Rust, D.R.
1984-04-01
Three detectors MARK II, MAC, AND HRS are using or planning small drift chambers placed as close as possible to the interaction print at PEP. There is also a program of development for a gaseous vertex detector for MARK II at SLC. All these programs are reviewed. 13 references.
SVX{prime}, the new CDF silicon vertex detector
Cihangir, S.; Gillespie, G.; Gonzalez, H.
1994-08-26
The Collider Detector at Fermilab (CDF) radiation hardened silicon vertex detector (SVX{prime}) is described. The new detector has several improvements over its predecessor such as better signal to noise and higher efficiency. It`s expected to have a radiation tolerance in excess of 1 Mrad. It has been taking data for several months and some preliminary results are shown.
Gap and stagger effects on the aerodynamic performance and the wake behind a biplane with endplates
NASA Astrophysics Data System (ADS)
Kang, Hantae
Modern flow diagnostics applied to a very old aerodynamic problem has produced a number of intriguing new results and new insight into previous results. The aerodynamic performance and associated flow physics of the biplane with endplates as a function of variation in gap and stagger were analytically and experimentally investigated. A combination of vortex lattice method, integrated force measurement, streamwise PIV, and Trefftz plane Stereo PIV were used to better understand the flowfield around the biplane with endplates. This study was performed to determine the configuration with the optimal aerodynamic performance and to understand the fluid mechanics behind optimal and suboptimal performance of the configuration. The Vortex Lattice code (AVL) shows that the gap and stagger have the most dramatic effects out of the six parameters studied: gap, stagger, dihedral, decalage, sweep and overhang. The force balance measurements with fourteen biplane configurations of different gaps and staggers show that as gap and stagger increase, the lift efficiency also increases at all angles of attack tested at both Re 60,000 and 120,000. Using the force balance data, a generalized empirical method for the prediction of lift coefficient as a function of gap, stagger and angle of attack has been determined and validated when combined with existing relations for CL--α adjustments for AR and taper effects. The resulting empirical approach allows for a rapid determination of CL for a biplane having different gap, stagger, AR and taper without the need for a complete flowfield analysis. Two Dimensional PIV results show a distinctive pattern in the downwash angle for the different gap and stagger configurations tested. The downwash angle increases with increasing gap and stagger. It is also evident that the change in downwash angle is directly proportional to the change in lift coefficient as would be expected. Increasing gap spacing increases the downwash angle as well. Based on
Nisoli, Cristiano; Li, Jiie; Ke, Xianglin; Lammert, Paul E; Schiffer, Peter; Crespi, Vincent H
2009-01-01
Frustrated arrays of interacting single-domain nanomagnets provide important model systems for statistical mechanics, because they map closely onto well-studied vertex models and are amenable to direct imaging and custom engineering. Although these systems are manifestly athermal, they demonstrate that the statistical properties of both hexagonal and square lattices can be described by an effective temperature based on the magnetostatic energy of the arrays. This temperature has predictive power for the moment configurations and is intimately related to how the moments are driven by an oscillating external field.
NASA Astrophysics Data System (ADS)
Li, Chuan-Yao; Huang, Hai-Jun; Tang, Tie-Qiao
2017-03-01
This paper investigates the traffic flow dynamics under the social optimum (SO) principle in a single-entry traffic corridor with staggered shifts from the analytical and numerical perspectives. The LWR (Lighthill-Whitham and Richards) model and the Greenshield's velocity-density function are utilized to describe the dynamic properties of traffic flow. The closed-form SO solution is analytically derived and some numerical examples are used to further testify the analytical solution. The optimum proportion of the numbers of commuters with different desired arrival times is further discussed, where the analytical and numerical results both indicate that the cumulative outflow curve under the SO principle is piecewise smooth.
Empty versus filled polyhedra: 11 vertex bare germanium clusters.
Uţă, Matei-Maria; King, Robert Bruce
2014-04-01
The structures and energetics of centered 10-vertex Ge@Ge₁₀(z) (z = -4, -2, 0, +2, +4) clusters have been investigated by density functional theory (DFT) for comparison with the previously studied isomeric empty 11-vertex Ge₁₁(z) clusters. For the cationic species (z = +2, +4) such centered Ge@Ge₁₀(z) structures are shown to be energetically competitive (within ∼1 kcal mol⁻¹) to the lowest energy isomeric empty Ge₁₁(z) structures. These Ge@Ge₁₀(z) structures can be derived from the lowest energy empty 10-vertex Ge₁₀(z-4) structures by inserting a Ge⁴⁺ ion in the center. The outer 10-vertex polyhedron in the lowest energy Ge@Ge₁₀²⁺ dication structure is the most spherical D(4d) bicapped square antiprism, which is also the lowest energy structure of the empty Ge₁₀²⁻ dianion, as expected from the Wade-Mingos skeletal electron counting rules. For the tetracationic Ge₁₁⁴⁺ /Ge@Ge₁₀⁴⁺ system the lowest energy centered Ge@Ge₁₀⁴⁺ structure can be obtained by inserting a Ge⁴⁺ ion in the center of a C(3v) deltahedral empty Ge10 cluster. Centered 10-vertex polyhedral Ge@Ge₁₀(z) structures were also found for the neutral (z = 0) and dianionic (z = -2) systems but at significantly higher energies than the lowest energy isomeric empty Ge₁₁(z) structures.
An Adaptive Staggered Dose Design for a Normal Endpoint.
Wu, Joseph; Menon, Sandeep; Chang, Mark
2015-01-01
In a clinical trial where several doses are compared to a control, a multi-stage design that combines both the selection of the best dose and the confirmation of this selected dose is desirable. An example is the two-stage drop-the-losers or pick-the-winner design, where inferior doses are dropped after interim analysis. Selection of target dose(s) can be based on ranking of observed effects, hypothesis testing with adjustment for multiplicity, or other criteria at interim stages. A number of methods have been proposed and have made significant gains in trial efficiency. However, many of these designs started off with all doses with equal allocation and did not consider prioritizing the doses using existing dose-response information. We propose an adaptive staggered dose procedure that allows explicit prioritization of doses and applies error spending scheme that favors doses with assumed better responses. This design starts off with only a subset of the doses and adaptively adds new doses depending on interim results. Using simulation, we have shown that this design performs better in terms of increased statistical power than the drop-the-losers design given strong prior information of dose response.
Heat transfer coefficients for staggered arrays of short pin fins
NASA Technical Reports Server (NTRS)
Vanfossen, G. J.
1981-01-01
Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).
Axially staggered seed-blanket reactor fuel module construction
Cowell, Gary K.; DiGuiseppe, Carl P.
1985-01-01
A heterogeneous nuclear reactor of the seed-blanket type is provided wher the fissile (seed) and fertile (blanket) nuclear fuels are segregated axially within each fuel element such that fissile and fertile regions occur in an alternating pattern along the length of the fuel element. Further, different axial stacking patterns are used for the fuel elements of at least two module types such that when modules of different types are positioned adjacent to one another, the fertile regions of the modules are offset or staggered. Thus, when a module of one type is surrounded by modules of the second type the fertile regions thereof will be surrounded on all sides by fissile material. This provides enhanced neutron communication both radially and axially, thereby resulting in greater power oscillation stability than other axial arrangements. The arrangements of the fissile and fertile regions in an alternating axial manner minimizes the radial power peaking factors and provides a more optional thermal-hydraulic design than is afforded by radial arrangements.
Heat transfer coefficients for staggered arrays of short pin fins
NASA Technical Reports Server (NTRS)
Vanfossen, G. J.
1981-01-01
Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).
Rashba coupling amplification by a staggered crystal field
NASA Astrophysics Data System (ADS)
Santos-Cottin, David; Casula, Michele; Lantz, Gabriel; Klein, Yannick; Petaccia, Luca; Le Fèvre, Patrick; Bertran, François; Papalazarou, Evangelos; Marsi, Marino; Gauzzi, Andrea
2016-04-01
There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications. One example is the splitting of bands with opposite spin chirality produced by the Rashba spin-orbit coupling in asymmetric potentials. Sizable splittings have been hitherto obtained using either heavy elements, where this coupling is intrinsically strong, or large surface electric fields. Here by means of angular resolved photoemission spectroscopy and first-principles calculations, we give evidence of a large Rashba coupling of 0.25 eV Å, leading to a remarkable band splitting up to 0.15 eV with hidden spin-chiral polarization in centrosymmetric BaNiS2. This is explained by a huge staggered crystal field of 1.4 V Å-1, produced by a gliding plane symmetry, that breaks inversion symmetry at the Ni site. This unexpected result in the absence of heavy elements demonstrates an effective mechanism of Rashba coupling amplification that may foster spin-orbit band engineering.
Rashba coupling amplification by a staggered crystal field
Santos-Cottin, David; Casula, Michele; Lantz, Gabriel; Klein, Yannick; Petaccia, Luca; Le Fèvre, Patrick; Bertran, François; Papalazarou, Evangelos; Marsi, Marino; Gauzzi, Andrea
2016-01-01
There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications. One example is the splitting of bands with opposite spin chirality produced by the Rashba spin-orbit coupling in asymmetric potentials. Sizable splittings have been hitherto obtained using either heavy elements, where this coupling is intrinsically strong, or large surface electric fields. Here by means of angular resolved photoemission spectroscopy and first-principles calculations, we give evidence of a large Rashba coupling of 0.25 eV Å, leading to a remarkable band splitting up to 0.15 eV with hidden spin-chiral polarization in centrosymmetric BaNiS2. This is explained by a huge staggered crystal field of 1.4 V Å−1, produced by a gliding plane symmetry, that breaks inversion symmetry at the Ni site. This unexpected result in the absence of heavy elements demonstrates an effective mechanism of Rashba coupling amplification that may foster spin-orbit band engineering. PMID:27089869
Phalaris arundinacea (reed canarygrass) grass staggers in beef cattle.
Binder, Ellen M; Blodgett, Dennis J; Currin, John F; Caudell, David; Cherney, Jerry H; LeRoith, Tanya
2010-09-01
Four adult mixed-breed beef cows from a cow-calf operation in West Virginia were referred to the Virginia-Maryland Regional College of Veterinary Medicine in March 2009 with weakness, ataxia, hind limb paresis progressing to lateral recumbency, and death within 2-3 days. Histologically, there was accumulation of light brown, granular pigment in neurons of the ventral gray horns of the spinal cord (more severe in thoracic and lumbar sections), brain stem, and pons, resulting in distortion and bulging of the cell body and displacement of the Nissl substance, suggestive of Phalaris sp. grass toxicosis. The most severely affected cow had accumulation of dark green-brown pigment in renal tubular epithelial cells. Reed canarygrass (Phalaris arundinacea) was identified in pastures, and the concentration of tryptamine alkaloids in new leaf blades was approximately 0.2% on a wet weight basis. These alkaloids are serotonergic receptor agonists, resulting in neurologic "staggers" in ruminants. Delayed onset times of up to 4-5 months have been reported in sheep after removal from Phalaris sp. pastures. Distribution of pigment in serotonergic tracts of the midbrain, brain stem, and spinal cord with Phalaris sp. toxicoses is distinct and differs from lipofuscin. Electron microscopy confirmed that the pigment was not lipofuscin. From these findings, a diagnosis of delayed P. arundinacea toxicosis was made. Over a 2-month period, 18 cows died with similar clinical signs.
The limitations of staggered grid finite differences in plasticity problems
NASA Astrophysics Data System (ADS)
Pranger, Casper; Herrendörfer, Robert; Le Pourhiet, Laetitia
2017-04-01
Most crustal-scale applications operate at grid sizes much larger than those at which plasticity occurs in nature. As a consequence, plastic shear bands often localize to the scale of one grid cell, and numerical ploys — like introducing an artificial length scale — are needed to counter this. If for whatever reasons (good or bad) this is not done, we find that problems may arise due to the fact that in the staggered grid finite difference discretization, unknowns like components of the stress tensor and velocity vector are located in physically different positions. This incurs frequent interpolation, reducing the accuracy of the discretization. For purely stress-dependent plasticity problems the adverse effects might be contained because the magnitude of the stress discontinuity across a plastic shear band is limited. However, we find that when rate-dependence of friction is added in the mix, things become ugly really fast and the already hard-to-solve and highly nonlinear problem of plasticity incurs an extra penalty.
A quantum hybrid with a thin antenna at the vertex of a wedge
NASA Astrophysics Data System (ADS)
Carlone, Raffaele; Posilicano, Andrea
2017-03-01
We study the spectrum, resonances and scattering matrix of a quantum Hamiltonian on a "hybrid surface" consisting of a half-line attached by its endpoint to the vertex of a concave planar wedge. At the boundary of the wedge, outside the vertex, homogeneous Dirichlet conditions are imposed. The system is tunable by varying the measure of the angle at the vertex.
Masses and decay constants of pions and kaons in mixed-action staggered chiral perturbation theory
NASA Astrophysics Data System (ADS)
Bailey, Jon A.; Kim, Jongjeong; Lee, Weonjong; Kim, Hyung-Jin; Yoon, Boram
2017-08-01
Lattice QCD calculations with different staggered valence and sea quarks can be used to improve determinations of quark masses, Gasser-Leutwyler couplings, and other parameters relevant to phenomenology. We calculate the masses and decay constants of flavored pions and kaons through next-to-leading order in staggered-valence, staggered-sea mixed-action chiral perturbation theory. We present the results in the valence-valence and valence-sea sectors, for all tastes. As in unmixed theories, the taste-pseudoscalar, valence-valence mesons are exact Goldstone bosons in the chiral limit, at nonzero lattice spacing. The results reduce correctly when the valence and sea quark actions are identical, connect smoothly to the continuum limit, and provide a way to control light quark and gluon discretization errors in lattice calculations performed with different staggered actions for the valence and sea quarks.
Superconductor magnets used for stagger-tuning traveling-wave maser
NASA Technical Reports Server (NTRS)
1965-01-01
Superconducting materials reduce size and weight of magnets used for stagger-tuning individual traveling-wave maser crystals. The invention is useful in microwave communication systems requiring a high information rate.
An analytical solution for contact resistance of staggered organic field-effect transistors
NASA Astrophysics Data System (ADS)
Karimi-Alavijeh, Hamidreza; Katebi-Jahromi, Alireza
2017-03-01
We have developed analytical models for bias dependent contact resistance (RC) and output characteristics of staggered organic field-effect transistors (OFETS) based on a bulk resistance-approximated and mobility-modified current-crowding method. Numerical evaluations of RC and its resistive components show that the bias dependency of the bulk resistance is negligible. Consequently, the properties of the active layer interfaces determine RC and its characteristics. Effective parameters include a normally constant charge injection barrier at the organic-metal interface (Eb) and a gate induced surface carrier-concentration (PS0) at the organic-insulator boundary. The energy barrier pertains to the fabrication process, and its related resistance (rc) can be determined as the fitting parameter of the theoretical model. However, PS0 is strongly gate bias dependent and the results of the numerical model indicate that the resulting component (rch) is dominant and has a considerable effect on RC and its characteristics. More importantly, PS0 as the key parameter of the contact resistance is analytically expressible and by using a proposed mobility-modified current-crowding model, the contact resistance can be analytically formulated. Accordingly, the output characteristics of the OFETs in the triode region can be also analytically modeled using the developed relation of RC.
NASA Technical Reports Server (NTRS)
Farhat, Charbel; Park, K. C.; Dubois-Pelerin, Yves
1991-01-01
An unconditionally stable second order accurate implicit-implicit staggered procedure for the finite element solution of fully coupled thermoelasticity transient problems is proposed. The procedure is stabilized with a semi-algebraic augmentation technique. A comparative cost analysis reveals the superiority of the proposed computational strategy to other conventional staggered procedures. Numerical examples of one- and two-dimensional thermomechanical coupled problems demonstrate the accuracy of the proposed numerical solution algorithm.
{Delta}I = 2 energy staggering in normal deformed dysprosium nuclei
Riley, M.A.; Brown, T.B.; Archer, D.E.
1996-12-31
Very high spin states (I{ge}50{Dirac_h}) have been observed in {sup 155,156,157}Dy. The long regular band sequences, free from sharp backbending effects, observed in these dysprosium nuclei offer the possibility of investigating the occurence of any {Delta}I = 2 staggering in normal deformed nuclei. Employing the same analysis techniques as used in superdeformed nuclei, certain bands do indeed demonstrate an apparent staggering and this is discussed.
Theoretical and practical considerations for staggered production of crops in a BLSS
NASA Astrophysics Data System (ADS)
Stutte, G. W.; Mackowiak, C. L.; Yorio, N. C.; Wheeler, A.
1997-01-01
A functional Bioregenerative Life Support System (BLSS) will generate oxygen, remove excess carbon dioxide, purify water, and produce food on a continuous basis for long periods of operation. In order to minimize fluctuations in gas exchange, water purification, and yield that are inherent in batch systems, staggered planting and harvesting of the crop is desirable. A 418-d test of staggered production of potato cv. Norland (26-d harvest cycles) using nutrients recovered from inedible biomass was recently completed at Kennedy Space Center. The results indicate that staggered production can be sustained without detrimental effects on life support functions in a CELSS. System yields of H_2O, O_2 and food were higher in staggered than batch plantings. Plants growing in staggered production or batch production on ``aged'' solution initiated tubers earlier, and were shorter than plants grown on ``fresh'' solution. This morphological response required an increase in planting density to maintain full canopy coverage. Plants grown in staggered production used available light more efficiently than the batch planting due to increased sidelighting.
Theoretical and practical considerations for staggered production of crops in a BLSS.
Stutte, G W; Mackowiak, C L; Yorio, N C; Wheeler, R M
1997-01-01
A functional Bioregenerative Life Support System (BLSS) will generate oxygen, remove excess carbon dioxide, purify water, and produce food on a continuous basis for long periods of operation. In order to minimize fluctuations in gas exchange, water purification, and yield that are inherent in batch systems, staggered planting and harvesting of the crop is desirable. A 418-d test of staggered production of potato cv. Norland (26-d harvest cycles) using nutrients recovered from inedible biomass was recently completed at Kennedy Space Center. The results indicate that staggered production can be sustained without detrimental effects on life support functions in a CELSS. System yields of H2O, O2 and food were higher in staggered than batch plantings. Plants growing in staggered production or batch production on "aged" solution initiated tubers earlier, and were shorter than plants grown on "fresh" solution. This morphological response required an increase in planting density to maintain full canopy coverage. Plants grown in staggered production used available light more efficiently than the batch planting due to increased sidelighting.
Theoretical and practical considerations of staggered crop production in a BLSS.
Stutte, G W; Mackowiak, C L; Yorio, N C; Wheeler, R M
1999-01-01
A functional Bioregenerative Life Support System (BLSS) will generate oxygen, remove excess carbon dioxide, purify water, and produce food on a continuous basis for long periods of operation. In order to minimize fluctuations in gas exchange, water purification, and yield that are inherent in batch systems, staggered planting and harvesting of the crop is desirable. A 418-day test of staggered production of potato cv. Norland (26-day harvest cycles) using nutrients recovered from inedible biomass was conducted at Kennedy Space Center. The results indicate that staggered production can be sustained without detrimental effects on BLSS life support functions. System yields of H2O, O2 and food were higher in staggered than batch plantings. Plants growing in staggered production or batch production on "aged" solution initiated tubers earlier, and were shorter than plants grown on "fresh" solution. This morphological response required an increase in planting density to maintain full canopy coverage. Plants grown in staggered production used available light more efficiently than the batch planting due to increased side lighting.
Design and construction of a Vertex Chamber and measurement of the average B-Hadron lifetime
Nelson, H.N.
1987-10-01
Four parameters describe the mixing of the three quark generations in the Standard Model of the weak charged current interaction. These four parameters are experimental inputs to the model. A measurement of the mean lifetime of hadrons containing b-quarks, or B-Hadrons, constrains the magnitudes of two of these parameters. Measurement of the B-Hadron lifetime requires a device that can measure the locations of the stable particles that result from B-Hadron decay. This device must function reliably in an inaccessible location, and survive high radiation levels. We describe the design and construction of such a device, a gaseous drift chamber. Tubes of 6.9 mm diameter, having aluminized mylar walls of 100 ..mu..m thickness are utilized in this Vertex Chamber. It achieves a spatial resolution of 45 ..mu..m, and a resolution in extrapolation to the B-Hadron decay location of 87 ..mu..m. Its inner layer is 4.6 cm from e/sup +/e/sup -/ colliding beams. The Vertex Chamber is situated within the MAC detector at PEP. We have analyzed botht he 94 pb/sup -1/ of integrated luminosity accumulated at ..sqrt..s = 29 GeV with the Vertex Chamber in place as well as the 210 pb/sup -1/ accumulated previously. We require a lepton with large momentum transverse to the event thrust axis to obtain a sample of events enriched in B-Hadron decays. The distribution of signed impact parameters of all tracks in these events is used to measure the B-Hadron flight distance, and hence lifetime. 106 refs., 79 figs., 20 tabs.
Vertex detectors: The state of the art and future prospects
Damerell, C.J.S.
1997-01-01
We review the current status of vertex detectors (tracking microscopes for the recognition of charm and bottom particle decays). The reasons why silicon has become the dominant detector medium are explained. Energy loss mechanisms are reviewed, as well as the physics and technology of semiconductor devices, emphasizing the areas of most relevance for detectors. The main design options (microstrips and pixel devices, both CCD`s and APS`s) are discussed, as well as the issue of radiation damage, which probably implies the need to change to detector media beyond silicon for some vertexing applications. Finally, the evolution of key performance parameters over the past 15 years is reviewed, and an attempt is made to extrapolate to the likely performance of detectors working at the energy frontier ten years from now.
On the zero crossing of the three-gluon vertex
NASA Astrophysics Data System (ADS)
Athenodorou, A.; Binosi, D.; Boucaud, Ph.; De Soto, F.; Papavassiliou, J.; Rodríguez-Quintero, J.; Zafeiropoulos, S.
2016-10-01
We report on new results on the infrared behavior of the three-gluon vertex in quenched Quantum Chromodynamics, obtained from large-volume lattice simulations. The main focus of our study is the appearance of the characteristic infrared feature known as 'zero crossing', the origin of which is intimately connected with the nonperturbative masslessness of the Faddeev-Popov ghost. The appearance of this effect is clearly visible in one of the two kinematic configurations analyzed, and its theoretical origin is discussed in the framework of Schwinger-Dyson equations. The effective coupling in the momentum subtraction scheme that corresponds to the three-gluon vertex is constructed, revealing the vanishing of the effective interaction at the exact location of the zero crossing.
Performance of the CDF Online Silicon Vertex Tracker
R. Carosi et al.
2002-03-27
The Online Silicon Vertex Tracker (SVT) is the new trigger processor dedicated to the 2-D reconstruction of charged particle trajectories at the Level 2 of the CDF trigger. The SVT links the digitized pulse heights found within the Silicon Vertex detector to the tracks reconstructed in the Central Outer Tracker by the Level 1 fast track finder. Preliminary tests of the system took place during the October 2000 commissioning run of the Tevatron Collider. During the April-October 2001 data taking it was possible to evaluate the performance of the system. In this paper we review the tracking algorithms implemented in the SVT and we report on the performance achieved during the early phase of run II.
Vertex topological indices and tree expressions, generalizations of continued fractions
2010-01-01
We expand on the work of Hosoya to describe a generalization of continued fractions called “tree expressions.” Each rooted tree will be shown to correspond to a unique tree expression which can be evaluated as a rational number (not necessarily in lowest terms) whose numerator is equal to the Hosoya index of the entire tree and whose denominator is equal to the tree with the root deleted. In the development, we use Z(G) to define a natural candidate ζ(G, v) for a “vertex topological index” which is a value applied to each vertex of a graph, rather than a value assigned to the graph overall. Finally, we generalize the notion of tree expression to “labeled tree expressions” that correspond to labeled trees and show that such expressions can be evaluated as quotients of determinants of matrices that resemble adjacency matrices. PMID:20490285
Worldline calculation of the three-gluon vertex
Ahmadiniaz, N.; Schubert, C.
2012-10-23
The three-gluon vertex is a basic object of interest in nonabelian gauge theory. At the one-loop level, it has been calculated and analyzed by a number of authors. Here we use the worldline formalism to unify the calculations of the scalar, spinor and gluon loop contributions to the one-loop vertex, leading to an extremely compact representation in terms of field strength tensors. We verify its equivalence with previously obtained representations, and explain the relation of its structure to the low-energy effective action. The sum rule found by Binger and Brodsky for the scalar, spinor and gluon loop contributions in the present approach relates to worldline supersymmetry.
Silicon vertex detector upgrade in the ALPHA experiment
NASA Astrophysics Data System (ADS)
Amole, C.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Burrows, C.; Butler, E.; Capra, A.; Cesar, C. L.; Chapman, S.; Charlton, M.; Deller, A.; Eriksson, S.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Isaac, C. A.; Jonsell, S.; Kurchaninov, L.; Little, A.; Madsen, N.; McKenna, J. T. K.; Menary, S.; Napoli, S. C.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sacramento, R. L.; Stracka, S.; Sampson, J. A.; Sarid, E.; Seddon, D.; Silveira, D. M.; So, C.; Thompson, R. I.; Tharp, T.; Thornhill, J.; Tooley, M. P.; van der Werf, D. P.; Wells, D.
2013-12-01
The Silicon Vertex Detector (SVD) is the main diagnostic tool in the ALPHA-experiment. It provides precise spatial and timing information of antiproton (antihydrogen) annihilation events (vertices), and most importantly, the SVD is capable of directly identifying and analysing single annihilation events, thereby forming the basis of ALPHA's analysis. This paper describes the ALPHA SVD and its upgrade, installed in the ALPHA's new neutral atom trap.
The SVX II Silicon Vertex Detector at CDF
NASA Astrophysics Data System (ADS)
Valls, Juan A.
1999-08-01
The Silicon VerteX detector (SVX II) for the CDF experiment at the Tevatron p overlinep collider is a 3-barrel 5-layer device with double-sided, AC-coupled silicon strip detectors. The readout is based on a custom IC, the SVX3 chip, capable of simultaneous acquisition, digitization and readout operation (dead-timeless). In this paper we report on the SVX II design and project status including mechanical design, frontend electronics, and data acquisition.
Nucleon contribution to the neutrino electromagnetic vertex in matter
DOlivo, J.C.; Nieves, J.F.
1997-11-01
We calculate the nucleon contribution to the electromagnetic vertex of a neutrino in a background of particles, including the effect of the anomalous magnetic moment of the nucleons. Explicit formulas for the form factors are given in various physical limits of practical interest. Several applications of the results are mentioned, including the effect of an external magnetic field on the dispersion relation of a neutrino in matter. {copyright} {ital 1997} {ital The American Physical Society}
Organization mechanism and counting algorithm on vertex-cover solutions
NASA Astrophysics Data System (ADS)
Wei, Wei; Zhang, Renquan; Niu, Baolong; Guo, Binghui; Zheng, Zhiming
2015-04-01
Counting the solution number of combinational optimization problems is an important topic in the study of computational complexity, which is concerned with Vertex-Cover in this paper. First, we investigate organizations of Vertex-Cover solution spaces by the underlying connectivity of unfrozen vertices and provide facts on the global and local environment. Then, a Vertex-Cover Solution Number Counting Algorithm is proposed and its complexity analysis is provided, the results of which fit very well with the simulations and have a better performance than those by 1-RSB in the neighborhood of c = e for random graphs. Based on the algorithm, variation and fluctuation on the solution number the statistics are studied to reveal the evolution mechanism of the solution numbers. Furthermore, the marginal probability distributions on the solution space are investigated on both the random graph and scale-free graph to illustrate the different evolution characteristics of their solution spaces. Thus, doing solution number counting based on the graph expression of the solution space should be an alternative and meaningful way to study the hardness of NP-complete and #P-complete problems and the appropriate algorithm design can help to achieve better approximations of solving combinational optimization problems and the corresponding counting problems.
Automatically generated algorithms for the vertex coloring problem.
Contreras Bolton, Carlos; Gatica, Gustavo; Parada, Víctor
2013-01-01
The vertex coloring problem is a classical problem in combinatorial optimization that consists of assigning a color to each vertex of a graph such that no adjacent vertices share the same color, minimizing the number of colors used. Despite the various practical applications that exist for this problem, its NP-hardness still represents a computational challenge. Some of the best computational results obtained for this problem are consequences of hybridizing the various known heuristics. Automatically revising the space constituted by combining these techniques to find the most adequate combination has received less attention. In this paper, we propose exploring the heuristics space for the vertex coloring problem using evolutionary algorithms. We automatically generate three new algorithms by combining elementary heuristics. To evaluate the new algorithms, a computational experiment was performed that allowed comparing them numerically with existing heuristics. The obtained algorithms present an average 29.97% relative error, while four other heuristics selected from the literature present a 59.73% error, considering 29 of the more difficult instances in the DIMACS benchmark.
Automatically Generated Algorithms for the Vertex Coloring Problem
Contreras Bolton, Carlos; Gatica, Gustavo; Parada, Víctor
2013-01-01
The vertex coloring problem is a classical problem in combinatorial optimization that consists of assigning a color to each vertex of a graph such that no adjacent vertices share the same color, minimizing the number of colors used. Despite the various practical applications that exist for this problem, its NP-hardness still represents a computational challenge. Some of the best computational results obtained for this problem are consequences of hybridizing the various known heuristics. Automatically revising the space constituted by combining these techniques to find the most adequate combination has received less attention. In this paper, we propose exploring the heuristics space for the vertex coloring problem using evolutionary algorithms. We automatically generate three new algorithms by combining elementary heuristics. To evaluate the new algorithms, a computational experiment was performed that allowed comparing them numerically with existing heuristics. The obtained algorithms present an average 29.97% relative error, while four other heuristics selected from the literature present a 59.73% error, considering 29 of the more difficult instances in the DIMACS benchmark. PMID:23516506
Staggered-grid split-node method for spontaneous rupture simulation
NASA Astrophysics Data System (ADS)
Dalguer, Luis A.; Day, Steven M.
2007-02-01
We adapt the traction-at-split-node method for spontaneous rupture simulations to the velocity-stress staggered-grid finite difference scheme. The staggered-grid implementation introduces both velocity and stress discontinuities via split nodes. The staggered traction components on the fault plane are interpolated to form the traction vector at split nodes, facilitating alignment of the vectors of sliding friction and slip velocity. To simplify the split-node partitioning of the equations of motion, spatial differencing is reduced from fourth to second order along the fault plane, but in the remainder of the grid the spatial differencing scheme remains identical to conventional spatially fourth-order three-dimensional staggered-grid schemes. The resulting staggered-grid split node (SGSN) method has convergence rates relative to rupture-time, final-slip, and peak-slip-velocity metrics that are very similar to the corresponding rates for both a partly staggered split-node code (DFM) and the boundary integral method. The SGSN method gives very accurate solutions (in the sense that errors are comparable to the uncertainties in the reference solution) when the median resolution of the cohesive zone is 4.4 grid points. Combined with previous results for other grid types and other fault-discontinuity approximations, the SGSN results demonstrate that accuracy in finite difference solutions to the spontaneous rupture problem is controlled principally by the scheme used to represent the fault discontinuity, and is relatively insensitive to the grid geometry used to represent the continuum. The method provides an efficient and accurate means of adding spontaneous rupture capability to velocity-stress staggered-grid finite difference codes, while retaining the computational advantages of those codes for problems of wave propagation in complex media.
NASA Astrophysics Data System (ADS)
OświÈ©cimka, Paweł; Livi, Lorenzo; DroŻdŻ, Stanisław
2016-10-01
We investigate the scaling of the cross-correlations calculated for two-variable time series containing vertex properties in the context of complex networks. Time series of such observables are obtained by means of stationary, unbiased random walks. We consider three vertex properties that provide, respectively, short-, medium-, and long-range information regarding the topological role of vertices in a given network. In order to reveal the relation between these quantities, we applied the multifractal cross-correlation analysis technique, which provides information about the nonlinear effects in coupling of time series. We show that the considered network models are characterized by unique multifractal properties of the cross-correlation. In particular, it is possible to distinguish between Erdös-Rényi, Barabási-Albert, and Watts-Strogatz networks on the basis of fractal cross-correlation. Moreover, the analysis of protein contact networks reveals characteristics shared with both scale-free and small-world models.
FAS multigrid calculations of three dimensional flow using non-staggered grids
NASA Technical Reports Server (NTRS)
Matovic, D.; Pollard, A.; Becker, H. A.; Grandmaison, E. W.
1993-01-01
Grid staggering is a well known remedy for the problem of velocity/pressure coupling in incompressible flow calculations. Numerous inconveniences occur, however, when staggered grids are implemented, particularly when a general-purpose code, capable of handling irregular three-dimensional domains, is sought. In several non-staggered grid numerical procedures proposed in the literature, the velocity/pressure coupling is achieved by either pressure or velocity (momentum) averaging. This approach is not convenient for simultaneous (block) solvers that are preferred when using multigrid methods. A new method is introduced in this paper that is based upon non-staggered grid formulation with a set of virtual cell face velocities used for pressure/velocity coupling. Instead of pressure or velocity averaging, a momentum balance at the cell face is used as a link between the momentum and mass balance constraints. The numerical stencil is limited to 9 nodes (in 2D) or 27 nodes (in 3D), both during the smoothing and inter-grid transfer, which is a convenient feature when a block point solver is applied. The results for a lid-driven cavity and a cube in a lid-driven cavity are presented and compared to staggered grid calculations using the same multigrid algorithm. The method is shown to be stable and produce a smooth (wiggle-free) pressure field.
NASA Astrophysics Data System (ADS)
Wang, Y.-J.
2003-12-01
In the weak-coupling regime of the continuous theories, two sets of one-loop renormalization-group equations are derived and solved to disclose the phase diagrams of the antiferromagnetic generalized two-leg spin-1/2 ladder under the effect of (I) a staggered external magnetic field and (II) an explicit dimerization. In model (I), the splitting of the SU(2)2 critical line into U(1) and Z2 critical surfaces is observed, while in model (II), two critical surfaces arising from their underlying critical lines with SU(2)2 and Z2 characteristics merge into an SU(2)1 critical surface on the line where the model attains its highest symmetry.
Perturbative matching of the staggered four-fermion operators for {epsilon}'/{epsilon}
Lee, Weonjong
2001-09-01
Using staggered fermions, we calculate the perturbative corrections to the bilinear and four-fermion operators that are used in the numerical study of weak matrix elements for {epsilon}'/{epsilon}. We present results for one-loop matching coefficients between continuum operators, calculated in the naive dimensional regularization (NDR) scheme, and gauge invariant staggered fermion operators. In particular, we concentrate on Feynman diagrams of the current-current insertion type. We also present results for the tadpole improved operators. These results, combined with existing results for penguin diagrams, provide a complete one-loop renormalization of the staggered four-fermion operators. Therefore, using our results, it is possible to match a lattice calculation of K{sup 0}-{bar K}{sup 0} mixing and K{yields}{pi}{pi} decays to the continuum NDR results with all corrections of O(g{sup 2}) included.
Coal mining with Triple-section extraction process in stagger arrangement roadway layout method
NASA Astrophysics Data System (ADS)
Cui, Zimo; Liu, Baozhu; Zhao, Jingli; Chanda, Emmanuel
2017-03-01
This paper introduces the Triple-section extraction process in the three-dimensional roadway layout of stagger arrangement method for longwall top-coal caving mining. This 3-D roadway layout of stagger arrangement method without coal pillars, which arranged the air intake roadway and air return roadway in different horizons, realizing the design theory transformation of roadway layout from 2D system to 3D system. And the paper makes systematic analysis to the geological, technical and economic factors, applies this new mining roadway layout technology for raising coal recovery ratio and solving the problems about full-seam mining in thick coal seam synthetically according to theoretical study and mining practice. Furthermore, the paper presents a physical simulation about inner staggered roadway layout of this particular longwall top-coal caving method.
Lanigan, G W; Payne, A L; Cockrum, P A
1979-02-01
Topsoil, herbage and faeces collected during an outbreak of ryegrass staggers in sheep were examined for tremorgenic penicillia. No such fungi were recovered from the plant material, but they were found among the predominant fungi in the soil and faecal samples. The commonest species of Penicillium, and almost the only tremorgenic species encountered, was Penicillium janthinellum Biourge. When fed to sheep, the mycelium of this fungus evoked a number of the clinical signs seen in field cases of ryegrass staggers. Two tremorgenic toxins were isolated from the mycelial felts and available evidence indicates that they are verruculogen and fumitremorgin A. P. janthinellum also produced these tremorgens when cultured in moist, autoclaved soil, but not in unheated soil. The results obtained from this study are in accord with the hypothesis that ryegrass staggers is caused by tremorgenic mycotoxins.
Single-molecule observation of helix staggering, sliding, and coiled coil misfolding
Xi, Zhiqun; Gao, Ying; Sirinakis, George; Guo, Honglian; Zhang, Yongli
2012-01-01
The biological functions of coiled coils generally depend on efficient folding and perfect pairing of their α-helices. Dynamic changes in the helical registry that lead to staggered helices have only been proposed for a few special systems and not found in generic coiled coils. Here, we report our observations of multiple staggered helical structures of two canonical coiled coils. The partially folded structures are formed predominantly by coiled coil misfolding and occasionally by helix sliding. Using high-resolution optical tweezers, we characterized their energies and transition kinetics at a single-molecule level. The staggered states occur less than 2% of the time and about 0.1% of the time at zero force. We conclude that dynamic changes in helical registry may be a general property of coiled coils. Our findings should have broad and unique implications in functions and dysfunctions of proteins containing coiled coils. PMID:22451899
Studies with staggered starts: multiple baseline designs and group-randomized trials.
Rhoda, Dale A; Murray, David M; Andridge, Rebecca R; Pennell, Michael L; Hade, Erinn M
2011-11-01
Multiple baseline designs (MBDs) have been suggested as alternatives to group-randomized trials (GRT). We reviewed structural features of MBDs and considered their potential effectiveness in public health research. We also reviewed the effect of staggered starts on statistical power. We reviewed the MBD literature to identify key structural features, recent suggestions that MBDs be adopted in public health research, and the literature on power in GRTs with staggered starts. We also computed power for MBDs and GRTs. The features that have contributed to the success of small MBDs in some fields are not likely to translate well to public health research. MBDs can be more powerful than GRTs under some conditions, but those conditions involve assumptions that require careful evaluation in practice. MBDs will often serve better as a complement of rather than as an alternative to GRTs. GRTs may employ staggered starts for logistical or ethical reasons, but this will always increase their duration and will often increase their cost.
Energy stable and high-order-accurate finite difference methods on staggered grids
NASA Astrophysics Data System (ADS)
O'Reilly, Ossian; Lundquist, Tomas; Dunham, Eric M.; Nordström, Jan
2017-10-01
For wave propagation over distances of many wavelengths, high-order finite difference methods on staggered grids are widely used due to their excellent dispersion properties. However, the enforcement of boundary conditions in a stable manner and treatment of interface problems with discontinuous coefficients usually pose many challenges. In this work, we construct a provably stable and high-order-accurate finite difference method on staggered grids that can be applied to a broad class of boundary and interface problems. The staggered grid difference operators are in summation-by-parts form and when combined with a weak enforcement of the boundary conditions, lead to an energy stable method on multiblock grids. The general applicability of the method is demonstrated by simulating an explosive acoustic source, generating waves reflecting against a free surface and material discontinuity.
Zeng, Hong-Cheng; Chen, Jie; Liu, Wei; Yang, Wei
2015-02-05
In this work, the staggered SAR technique is employed for high-speed platform highly-squint SAR by varying the pulse repetition interval (PRI) as a linear function of range-walk. To focus the staggered SAR data more efficiently, a low-complexity modified Omega-k algorithm is proposed based on a novel method for optimal azimuth non-uniform interpolation, avoiding zero padding in range direction for recovering range cell migration (RCM) and saving in both data storage and computational load. An approximate model on continuous PRI variation with respect to sliding receive-window is employed in the proposed algorithm, leaving a residual phase error only due to the effect of a time-varying Doppler phase caused by staggered SAR. Then, azimuth non-uniform interpolation (ANI) at baseband is carried out to compensate the azimuth non-uniform sampling (ANS) effect resulting from continuous PRI variation, which is further followed by the modified Omega-k algorithm. The proposed algorithm has a significantly lower computational complexity, but with an equally effective imaging performance, as shown in our simulation results.
Zeng, Hong-Cheng; Chen, Jie; Liu, Wei; Yang, Wei
2015-01-01
In this work, the staggered SAR technique is employed for high-speed platform highly-squint SAR by varying the pulse repetition interval (PRI) as a linear function of range-walk. To focus the staggered SAR data more efficiently, a low-complexity modified Omega-k algorithm is proposed based on a novel method for optimal azimuth non-uniform interpolation, avoiding zero padding in range direction for recovering range cell migration (RCM) and saving in both data storage and computational load. An approximate model on continuous PRI variation with respect to sliding receive-window is employed in the proposed algorithm, leaving a residual phase error only due to the effect of a time-varying Doppler phase caused by staggered SAR. Then, azimuth non-uniform interpolation (ANI) at baseband is carried out to compensate the azimuth non-uniform sampling (ANS) effect resulting from continuous PRI variation, which is further followed by the modified Omega-k algorithm. The proposed algorithm has a significantly lower computational complexity, but with an equally effective imaging performance, as shown in our simulation results. PMID:25664433
Low-mass materials and vertex detector systems
Cooper, William E.
2014-01-01
Physics requirements set the material budget and the precision and stability necessary in low-mass vertex detector systems. Operational considerations, along with physics requirements, set the operating environment to be provided and determine the heat to be removed. Representative materials for fulfilling those requirements are described and properties of the materials are tabulated. A figure of merit is proposed to aid in material selection. Multi-layer structures are examined as a method to allow material to be used effectively, thereby reducing material contributions. Lastly, comments are made on future directions to be considered in using present materials effectively and in developing newmore » materials.« less
Low-mass materials and vertex detector systems
Cooper, William E.
2014-01-01
Physics requirements set the material budget and the precision and stability necessary in low-mass vertex detector systems. Operational considerations, along with physics requirements, set the operating environment to be provided and determine the heat to be removed. Representative materials for fulfilling those requirements are described and properties of the materials are tabulated. A figure of merit is proposed to aid in material selection. Multi-layer structures are examined as a method to allow material to be used effectively, thereby reducing material contributions. Lastly, comments are made on future directions to be considered in using present materials effectively and in developing new materials.
Multijet decays of quarkonia: Testing the three-gluon vertex
NASA Astrophysics Data System (ADS)
Koller, K.; Streng, K. H.; Walsh, T. F.; Zerwas, P. M.
1982-10-01
We study the 4-jet and photon plus 3-jet decays of orthoquarkonia, 3S1( Q overlineQ)→ GGGG+ GGq overlineq→4 jets, 3S1( Q overlineQ→γ GGG+γ Gq overlineq→γ+3 jets. We show that the characteristic features of the jet distributions in the final state are determined by the 3-gluon vertex of quantum chromodynamics. These decays of a heavy quarkonium resonance (toponium) will offer clear signals for the gluons' self-coupling which can establish QCD as a local non-abelian gauge theory.
Anomalous ω-Z-γ vertex from hidden local symmetry
NASA Astrophysics Data System (ADS)
Harada, Masayasu; Matsuzaki, Shinya; Yamawaki, Koichi
2011-08-01
We formulate the general form of the ω-Z-γ vertex in the framework based on the hidden local symmetry, which arises from the gauge-invariant terms for intrinsic parity-odd part of the effective action. Those terms are given as the homogeneous part of the general solution (having free parameters) to the Wess-Zumino anomaly equation and hence are not determined by the anomaly, in sharp contrast to the Harvey-Hill-Hill (HHH) action where the relevant vertex is claimed to be uniquely determined by the anomaly. We show that, even in the framework that HHH was based on, the ω-Z-γ vertex is actually not determined by the anomaly but by the homogeneous (anomaly-free) part of the general solution to the Wess-Zumino anomaly equation having free parameters in the same way as in the hidden local symmetry formulation: The HHH action is just a particular choice of the free parameters in the general solution. We further show that the ω-Z-γ vertex related to the neutrino (ν)-nucleon (N) scattering cross section σ(νN→νN(N')γ) is determined not by the anomaly but by the anomaly-free part of the general solution having free parameters. Nevertheless, we find that the cross section σ(νN→νN(N')γ) is related through the Ward-Takahashi identity to Γ(ω→π0γ) which has the same parameter dependence as that of σ(νN→νN(N')γ) and hence the ratio σ(νN→νN(N')γ)/Γ(ω→π0γ) is fixed independently of these free parameters. Other set of the free parameters of the general solution can be fixed to make the best fit of the ω→π0l+l- process, which substantially differs from the HHH action. This gives a prediction of the cross section σ(νN→νN(N')γ*(l+l-)) to be tested at ν-N collision experiments in the future.
Vertex Operators Arising from Jacobi-Trudi Identities
NASA Astrophysics Data System (ADS)
Jing, Naihuan; Rozhkovskaya, Natasha
2016-09-01
We give an interpretation of the boson-fermion correspondence as a direct consequence of the Jacobi-Trudi identity. This viewpoint enables us to construct from a generalized version of the Jacobi-Trudi identity the action of a Clifford algebra on the polynomial algebras that arrive as analogues of the algebra of symmetric functions. A generalized Giambelli identity is also proved to follow from that identity. As applications, we obtain explicit formulas for vertex operators corresponding to characters of the classical Lie algebras, shifted Schur functions, and generalized Schur symmetric functions associated to linear recurrence relations.
Petreczky P.; Bazavov, A.
2011-10-11
We report preliminary results on the chiral and deconfinement aspects of the QCD transition at finite temperature using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent of N{sub {tau}} = 6 and 8. The chiral aspects of the transition are studied in terms of quark condensates and the disconnected chiral susceptibility. We study the deconfinement transition in terms of the strange quark number susceptibility and the renormalized Polyakov loop. We made continuum estimates for some quantities and find reasonably good agreement between our results and the recent continuum extrapolated results obtained with the stout staggered quark action.
Ma, Hongcai; Wu, Lin
2015-07-10
We present the design of a horizontally staggered lightguide solar concentrator with lateral displacement tracking for high concentration applications. This solar concentrator consists of an array of telecentric primary concentrators, a horizontally staggered lightguide layer, and a vertically tapered lightguide layer. The primary concentrator is realized by two plano-aspheric lenses with lateral movement and maintains a high F-number over an angle range of ±23.5°. The results of the simulations show that the solar concentrator achieves a high concentration ratio of 500× with ±0.5° of acceptance angle by a single-axis tracker and dual lateral translation stages.
Numerical simulation of multilayer stagger-split die and experiment on the bearing capacity
NASA Astrophysics Data System (ADS)
Wang, Bolong; Li, Mingzhe; Yang, Yunfei; Liu, Zhiwei; Liu, Hongwei
2015-10-01
A high pressure device, multilayer stagger-split die, is investigated by finite-element analysis. We simulated the process of compressing pyrophyllite according to the Drucker-Prager criterion. Simulated results of both dies in the axial and radial directions are displayed and compared using the contour and path plots. We obtained the rate of pressure decay in the radial and axial directions, and analyzed the pressure distribution of the pressed pyrophyllite. The results demonstrate that in almost the same condition, the pressure of the multilayer stagger-split die is about 13.6% higher than that of the belt die, and the experimental result is higher.
Topological index theorem on the lattice through the spectral flow of staggered fermions
NASA Astrophysics Data System (ADS)
Azcoiti, V.; Follana, E.; Vaquero, A.; Di Carlo, G.
2015-05-01
We investigate numerically the spectral flow introduced by Adams for the staggered Dirac operator on realistic (quenched) gauge configurations. We obtain clear numerical evidence that the definition works as expected: there is a clear separation between crossings near and far away from the origin, and the topological charge defined through the crossings near the origin agrees, for most configurations, with the one defined through the near-zero modes of large taste-singlet chirality of the staggered Dirac operator. The crossings are much closer to the origin if we improve the Dirac operator used in the definition, and they move towards the origin as we decrease the lattice spacing.
Kaon BSM B -parameters using improved staggered fermions from Nf=2 +1 unquenched QCD
NASA Astrophysics Data System (ADS)
Choi, Benjamin J.; Jang, Yong-Chull; Jung, Chulwoo; Jeong, Hwancheol; Kim, Jangho; Kim, Jongjeong; Kim, Sunghee; Lee, Weonjong; Leem, Jaehoon; Pak, Jeonghwan; Park, Sungwoo; Sharpe, Stephen R.; Yoon, Boram; SWME Collaboration
2016-01-01
We present results for the matrix elements of the additional Δ S =2 operators that appear in models of physics beyond the Standard Model (BSM), expressed in terms of four BSM B -parameters. Combined with experimental results for Δ MK and ɛK, these constrain the parameters of BSM models. We use improved staggered fermions, with valence hypercubic blocking transfromation (HYP)-smeared quarks and Nf=2 +1 flavors of "asqtad" sea quarks. The configurations have been generated by the MILC Collaboration. The matching between lattice and continuum four-fermion operators and bilinears is done perturbatively at one-loop order. We use three lattice spacings for the continuum extrapolation: a ≈0.09 , 0.06 and 0.045 fm. Valence light-quark masses range down to ≈msphys/13 while the light sea-quark masses range down to ≈msphys/20 . Compared to our previous published work, we have added four additional lattice ensembles, leading to better controlled extrapolations in the lattice spacing and sea-quark masses. We report final results for two renormalization scales, μ =2 and 3 GeV, and compare them to those obtained by other collaborations. Agreement is found for two of the four BSM B -parameters (B2 and B3SUSY). The other two (B4 and B5) differ significantly from those obtained using regularization independent momentum subtraction (RI-MOM) renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD Collaboration using regularization independent symmetric momentum subtraction (RI-SMOM) intermediate schemes.
Kaon BSM B -parameters using improved staggered fermions from Nf=2+1 unquenched QCD
Choi, Benjamin J.
2016-01-28
In this paper, we present results for the matrix elements of the additional ΔS = 2 operators that appear in models of physics beyond the Standard Model (BSM), expressed in terms of four BSM B -parameters. Combined with experimental results for ΔMK and εK, these constrain the parameters of BSM models. We use improved staggered fermions, with valence hypercubic blocking transfromation (HYP)-smeared quarks and Nf = 2 + 1 flavors of “asqtad” sea quarks. The configurations have been generated by the MILC Collaboration. The matching between lattice and continuum four-fermion operators and bilinears is done perturbatively at one-loop order. We use three lattice spacings for the continuum extrapolation: a ≈ 0.09 , 0.06 and 0.045 fm. Valence light-quark masses range down to ≈ mmore » $$phys\\atop{s}$$ /13 while the light sea-quark masses range down to ≈ m$$phys\\atop{s}$$ / 20 . Compared to our previous published work, we have added four additional lattice ensembles, leading to better controlled extrapolations in the lattice spacing and sea-quark masses. We report final results for two renormalization scales, μ = 2 and 3 GeV, and compare them to those obtained by other collaborations. Agreement is found for two of the four BSM B-parameters (B2 and B$$SUSY\\atop{3}$$ ). The other two (B4 and B5) differ significantly from those obtained using regularization independent momentum subtraction (RI-MOM) renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD Collaboration using regularization independent symmetric momentum subtraction (RI-SMOM) intermediate schemes.« less
Heavy flavour physics at colliders with silicon strip vertex detectors
NASA Astrophysics Data System (ADS)
Schwarz, Andreas S.
1994-03-01
The physics of heavy flavours has played a dominant role in high energy physics research ever since the discovery of charm in 1974, followed by the τ lepton in 1975 and bottom in 1977. With the startup of the large experiments at the e+e- colliders LEP and the SLC a new type of detector system has now come into operation which has a major impact on the studies of heavy flavours: the silicon strip vertex detector. The basic design priciples of these novel detector systems are outlined and three representative experimental realizations are discussed. The impact of these detectors on the studies of the properties of heavy flavours is just emerging and focuses on the measurement of lifetimes and the tagging of the presence of heavy flavour hadrons in hadronic events. The tools that are being developed for these studies are described as well as details of representative analyses. The potential of these devices and the associated technological developments that were necessary for their application in the colding beam environment is reflected in a plethora of new proposals to build sophisticated silicon detector systems for a large variety of future high energy physics applications. Two examples will be briefly sketched, a vertex detector for an asymmetric e+e- bottom factory and a large scale tracking system for a multipurpose detector at one of the new large hadron colliders.
Quark-gluon vertex: A perturbation theory primer and beyond
NASA Astrophysics Data System (ADS)
Bermudez, R.; Albino, L.; Gutiérrez-Guerrero, L. X.; Tejeda-Yeomans, M. E.; Bashir, A.
2017-02-01
There has been growing evidence that the infrared enhancement of the form factors defining the full quark-gluon vertex plays an important role in realizing a dynamical breakdown of chiral symmetry in quantum chromodynamics, leading to the observed spectrum and properties of hadrons. Both the lattice and the Schwinger-Dyson communities have begun to calculate these form factors in various kinematical regimes of momenta involved. A natural consistency check for these studies is that they should match onto the perturbative predictions in the ultraviolet, where nonperturbative effects mellow down. In this article, we carry out a numerical analysis of the one-loop result for all the form factors of the quark-gluon vertex. Interestingly, even the one-loop results qualitatively encode most of the infrared enhancement features expected of their nonperturbative counter parts. We analyze various kinematical configurations of momenta: symmetric, on shell, and asymptotic. The on-shell limit enables us to compute anomalous chromomagnetic moment of quarks. The asymptotic results have implications for the multiplicative renormalizability of the quark propagator and its connection with the Landau-Khalatnikov-Fradkin transformations, allowing us to analyze and compare various Ansätze proposed so far.
Vertex epidural hematoma: An analysis of a large series
Ramesh, Vengalathur Ganesan; Kodeeswaran, Marappan; Deiveegan, Kunjithapatham; Sundar, Venkataraman; Sriram, Kuchalambal
2017-01-01
Context: Vertex epidural hematoma (VEDH) is uncommon. A high index of suspicion is required to suspect and diagnose this condition, and the surgical management is a challenge to neurosurgeons. There are only isolated case reports or small series of VEDH in the literature. Aims: We have tried to analyze a large series of VEDH seen in our institute. Settings and Design: Retrospective observational study. Subjects and Methods: This is an analysis of case records of patients with VEDH during 17 years period from 1995 to 2012. Statistical Analysis Used: Nil. Results: Twenty nine cases of VEDH encountered over a period of 17 years have been analyzed, including 26 males and 3 females. Majority were due to road accidents. Headache, papilledema and lower limb weakness have been the major presenting features in these cases. The diagnosis was by direct coronal computerized tomography (CT) scan in most of them. Majority were managed conservatively with observation and serial imaging. Four patients who had large VEDH with altered sensorium were managed surgically. The source of bleeding was mainly from superior sagittal sinus. Conclusions: VEDH has to be suspected when a patient presents with impact over the vertex and features of raised intracranial pressure. Direct coronal CT or magnetic resonance imaging is useful in the diagnosis. Surgery is required when the patient develops progressive deterioration in sensorium and/or with the hematoma volume more than 30 ml. The present series of 29 cases is the largest reported so far. PMID:28484524
The Belle II silicon vertex detector assembly and mechanics
NASA Astrophysics Data System (ADS)
Adamczyk, K.; Aihara, H.; Angelini, C.; Aziz, T.; Babu, V.; Bacher, S.; Bahinipati, S.; Barberio, E.; Baroncelli, Ti.; Baroncelli, To.; Basith, A. K.; Batignani, G.; Bauer, A.; Behera, P. K.; Bergauer, T.; Bettarini, S.; Bhuyan, B.; Bilka, T.; Bosi, F.; Bosisio, L.; Bozek, A.; Buchsteiner, F.; Bulla, L.; Casarosa, G.; Ceccanti, M.; Červenkov, D.; Chendvankar, S. R.; Dash, N.; Divekar, S. T.; Doležal, Z.; Dutta, D.; Forti, F.; Friedl, M.; Hara, K.; Higuchi, T.; Horiguchi, T.; Irmler, C.; Ishikawa, A.; Jeon, H. B.; Joo, C. W.; Kandra, J.; Kang, K. H.; Kato, E.; Kawasaki, T.; Kodyš, P.; Kohriki, T.; Koike, S.; Kolwalkar, M. M.; Kvasnička, P.; Lanceri, L.; Lettenbicher, J.; Lueck, T.; Maki, M.; Mammini, P.; Mayekar, S. N.; Mohanty, G. B.; Mohanty, S.; Morii, T.; Nakamura, K. R.; Natkaniec, Z.; Negishi, K.; Nisar, N. K.; Onuki, Y.; Ostrowicz, W.; Paladino, A.; Paoloni, E.; Park, H.; Pilo, F.; Profeti, A.; Rashevskaya, I.; Rao, K. K.; Rizzo, G.; Rozanska, M.; Sasaki, J.; Sato, N.; Schultschik, S.; Schwanda, C.; Seino, Y.; Shimizu, N.; Stypula, J.; Suzuki, J.; Tanaka, S.; Tanida, K.; Taylor, G. N.; Thalmeier, R.; Thomas, R.; Tsuboyama, T.; Uozumi, S.; Urquijo, P.; Vitale, L.; Watanuki, S.; Watson, I. J.; Webb, J.; Wiechczynski, J.; Williams, S.; Würkner, B.; Yamamoto, H.; Yin, H.; Yoshinobu, T.
2017-02-01
The Belle II experiment at the asymmetric SuperKEKB collider in Japan will operate at an instantaneous luminosity approximately 50 times greater than its predecessor (Belle). The central feature of the experiment is a vertex detector comprising two layers of pixelated silicon detectors (PXD) and four layers of double-sided silicon microstrip detectors (SVD). One of the key measurements for Belle II is CP violation asymmetry in the decays of beauty and charm hadrons, which hinges on a precise charged-track vertex determination and low-momentum track measurement. Towards this goal, a proper assembly of the SVD components with precise alignment ought to be performed and the geometrical tolerances should be checked to fall within the design limits. We present an overview of the assembly procedure that is being followed, which includes the precision gluing of the SVD module components, wire-bonding of the various electrical components, and precision 3D coordinate measurements of the final SVD modules. Finally, some results from the latest test-beam are reported.
A cell-vertex multigrid method for the Navier-Stokes equations
NASA Technical Reports Server (NTRS)
Radespiel, R.
1989-01-01
A cell-vertex scheme for the Navier-Stokes equations, which is based on central difference approximations and Runge-Kutta time stepping, is described. Using local time stepping, implicit residual smoothing, a multigrid method, and carefully controlled artificial dissipative terms, very good convergence rates are obtained for a wide range of two- and three-dimensional flows over airfoils and wings. The accuracy of the code is examined by grid refinement studies and comparison with experimental data. For an accurate prediction of turbulent flows with strong separations, a modified version of the nonequilibrium turbulence model of Johnson and King is introduced, which is well suited for an implementation into three-dimensional Navier-Stokes codes. It is shown that the solutions for three-dimensional flows with strong separations can be dramatically improved, when a nonequilibrium model of turbulence is used.
Vertex intrinsic fitness: How to produce arbitrary scale-free networks
Servedio, Vito D.P.; Caldarelli, Guido; Butta, Paolo
2004-11-01
We study a recent model of random networks based on the presence of an intrinsic character of the vertices called fitness. The vertex fitnesses are drawn from a given probability distribution density. The edges between pairs of vertices are drawn according to a linking probability function depending on the fitnesses of the two vertices involved. We study here different choices for the probability distribution densities and the linking functions. We find that, irrespective of the particular choices, the generation of scale-free networks is straightforward. We then derive the general conditions under which scale-free behavior appears. This model could then represent a possible explanation for the ubiquity and robustness of such structures.
Hasenfratz, Anna; Hoffmann, Roland
2006-12-01
Growing evidence indicates that in the continuum limit the rooted staggered action is in the correct QCD universality class, the nonlocal terms arising from taste breaking can be viewed as lattice artifacts. In this paper we consider the 2-flavor Asqtad staggered action at lattice spacing a{approx_equal}0.13 fm and probe the properties of the staggered configurations by an overlap valence Dirac operator. By comparing the distribution of the overlap eigenmodes to continuum QCD predictions we investigate if/when the lattice artifacts are small as a function of the staggered quark mass. We define a matching overlap quark mass where the lattice corrections are minimal for the topological susceptibility and from the eigenmode distribution we predict the 2-flavor chiral condensate. Our results indicate that the staggered configurations are consistent with 2-flavor continuum QCD up to small lattice artifacts, and predict a consistent value for the infinite volume chiral condensate.
Magnetic property of a staggered-array undulator using a bulk high-temperature superconductor
NASA Astrophysics Data System (ADS)
Kinjo, Ryota; Mishima, Kenta; Choi, Yong-Woon; Omer, Mohamed; Yoshida, Kyohei; Negm, Hani; Torgasin, Konstantin; Shibata, Marie; Shimahashi, Kyohei; Imon, Hidekazu; Okumura, Kensuke; Inukai, Motoharu; Zen, Heishun; Kii, Toshiteru; Masuda, Kai; Nagasaki, Kazunobu; Ohgaki, Hideaki
2014-02-01
The magnetic field of a staggered-array undulator using a bulk high-temperature superconductor is calculated by analytical and numerical methods. Analytical formulas for the undulator field and the solenoid field required to generate the undulator field are derived from a simple two-dimensional model. The analytical calculation shows the degree of dependence of these fields on the undulator parameters, the generation of a high undulator field proportional to the critical current density of the bulk superconductor, and the good tunability of the undulator field over a wide range of values. The numerical calculation is performed in a three-dimensional geometry by two methods: the center field and energy minimization methods. The latter treats the current distribution inside the bulk, whereas the former neglects it as a natural extension of the analytical model. The calculation also reveals the dependence of the fields on the undulator parameters arising from the current distribution. From the comparison with experimental results, we find that the latter method reproduces the experimental results well, which indicates the importance of the current distribution inside the bulk. Therefore, we derive a semiempirical formula for the required solenoid field by modifying the analytical formula using the numerical results so as to include the effect of the current distribution. The semiempirical formula reproduces the numerical result with an error of 3%. Finally, we estimate the magnetic performance of the undulator as an example of using the formulas and values presented in this paper. The estimation shows that an undulator field twice as large as that of the present in-vacuum undulator but with an equal period and gap can be obtained at a temperature of approximately 20-40 K, and that deflection parameters (K values) of 1 and 2 can be achieved with periods of 5 and 10 mm at approximately 4-20 K.
NASA Technical Reports Server (NTRS)
Florschuetz, L. W.; Metzger, D. E.; Takeuchi, D. I.; Berry, R. A.
1980-01-01
Heat transfer characteristics were obtained for configurations designed to model the impingement cooled midchord region of air cooled gas turbine airfoils. The configurations tested were inline and staggered two-dimensional arrays of circular jets with ten spanwise rows of holes. The cooling air was constrained to exit in the chordwise direction along the channel formed by the jet orifice plate and the heat transfer surface. Tests were run for chordwise jet hole spacings of five, ten, and fifteen hole diameters; spanwise spacings of four, six, and eight diameters; and channel heights of one, two, three, and six diameters. Mean jet Reynolds numbers ranged from 5000 to 50,000. The thermal boundary condition at the heat transfer test surface was isothermal. Tests were run for sets of geometrically similar configurations of different sizes. Mean and chordwise resolved Nusselt numbers were determined utilizing a specially constructed test surface which was segmented in the chordwise direction.
NASA Astrophysics Data System (ADS)
Li, Chuan-Yao; Huang, Hai-Jun; Tang, Tie-Qiao
2017-05-01
In this paper, we investigate the effects of staggered shifts on the user equilibrium (UE) state in a single-entry traffic corridor with no late arrivals from the analytical and numerical perspective. The LWR (Lighthill-Whitham-Richards) model and the Greenshields' velocity-density function are used to describe the dynamic properties of traffic flow. Propositions for the properties of flow patterns in UE, and the quasi-analytic solutions for three possible situations in UE are deduced. Numerical tests are carried out to testify the analytical results, where the three-dimensional evolution diagram of traffic flow illustrates that shock and rarefaction wave exist in UE and the space-time diagram indicates that UE solutions satisfy the propagation properties of traffic flow. In addition, the cost curves show that the UE solutions satisfy the UE trip-timing condition.
NASA Astrophysics Data System (ADS)
Yefet, Amir; Petropoulos, Peter G.
2001-04-01
We consider a model explicit fourth-order staggered finite-difference method for the hyperbolic Maxwell's equations. Appropriate fourth-order accurate extrapolation and one-sided difference operators are derived in order to complete the scheme near metal boundaries and dielectric interfaces. An eigenvalue analysis of the overall scheme provides a necessary, but not sufficient, stability condition and indicates long-time stability. Numerical results verify both the stability analysis, and the scheme's fourth-order convergence rate over complex domains that include dielectric interfaces and perfectly conducting surfaces. For a fixed error level, we find the fourth-order scheme is computationally cheaper in comparison to the Yee scheme by more than an order of magnitude. Some open problems encountered in the application of such high-order schemes are also discussed.
NASA Astrophysics Data System (ADS)
Kumar, Sanjay; Narayan, Jay
2008-12-01
This article presents the implementation of two well known absorbing boundary conditions in a fourth-order accurate staggered grid SH-wave finite difference (FD) algorithm with variable grid size, in a very simplified manner. Based on simulated results, it was confirmed that the Clayton and Engquist absorbing boundary condition causes edge-reflections in case of larger angle of incidence of body waves on the model edges. The results of various numerical experiments revealed that the Israeli and Orszag sponge boundary condition is efficient enough to avoid edge-reflections for any angle of incidence of the body. We recommend the use of both the Clayton and Engquist and Israeli and Orszag absorbing boundary conditions simultaneously to avoid any edge-reflections.
Nam, Young Gyu; Najera, Maria Alejandra; Lee, Sang Woo; Strickler, J. Rudi; Chang, Woo-Jin
2016-01-01
The liquid streams in a microchannel are hardly mixed to form laminar flow, and the mixing issue is well described by a low Reynolds number scheme. The staggered herringbone mixer (SHM) using repeated patterns of grooves in the microchannel have been proved to be an efficient passive micro-mixer. However, only a negative pattern of the staggered herringbone mixer has been used so far after it was first suggested, to the best of our knowledge. In this study, the mixing efficiencies from negative and positive staggered herringbone mixer patterns as well as from opposite flow directions were tested to investigate the effect of the micro-structure geometry on the surrounding laminar flow. The positive herringbone pattern showed better mixing efficiency than the conventionally used negative pattern. Also, generally used forward flow gives better mixing efficiency than reverse flow. The mixing was completed after two cycles of staggered herringbone mixer with both forward and reverse flow in a positive pattern. The traditional negative pattern showed complete mixing after four and five cycles in forward and reverse flow direction, respectively. The mixing effect in all geometries was numerically simulated, and the results confirmed more efficient mixing in the positive pattern than the negative. The results can further enable the design of a more efficient microfluidic mixer, as well as in depth understanding of the phenomena of positive and negative patterns existing in nature with regards to the surrounding fluids. PMID:27814386
An evaluation of torque (moment) on implant/prosthesis with staggered buccal and lingual offset.
Weinberg, L A; Kruger, B
1996-06-01
The supposition that staggered buccal and lingual implant offset is biomechanically advantageous was examined mathematically. The method of evaluation utilized a standard hypothetical geometric configuration from which implants could be staggered buccally and/or lingually in both arches. Torque (moment) values were calculated at the gold screw, abutment screw, and 3.5 mm apical to the head of the implant. Comparisons were made in percentages of change from the hypothetical standard to the buccal and/or lingual implant offset. In the maxillary arch, buccal offset decreased the torque (moment) while lingual offset increased it. If more lingually offset implants were present in the maxillary restoration, the total torque would be greater than if they were all in a straight line. Staggered buccolingual implant alignment often requires abutment reangulation. The resultant line of force produced by occlusal anatomy usually results in buccal inclination in the maxillary arch and lingual inclination in the mandibular arch. As a result, mandibular implant/prostheses are greatly favored over similar maxillary configurations because the mandibular resultant line of force usually passes lingually, closer to the components and supporting bone and considerably less torque is produced. Therefore, the concept of staggered offset for multiple implant-supported prostheses can be utilized on the mandible but is not recommended for the maxilla where maximum uniform buccal implant orientation is advised.
Gündüz, İslam; Pollock, Christianne L.; Giménez, Mabel D.; Förster, Daniel W.; White, Thomas A.; Sans-Fuentes, Maria A.; Hauffe, Heidi C.; Ventura, Jacint; López-Fuster, María José; Searle, Jeremy B.
2010-01-01
In the house mouse there are numerous chromosomal races distinguished by different combinations of metacentric chromosomes. These may come into contact with each other and with the ancestral all-acrocentric race, and form hybrid zones. The chromosomal clines that make up these hybrid zones may be coincident or separated from each other (staggered). Such staggered hybrid zones are interesting because they may include populations of individuals homozygous for a mix of features of the hybridising races. We review the characteristics of four staggered hybrid zones in the house mouse and discuss whether they are examples of primary or secondary contact and whether they represent reticulate evolution or not. However, the most important aspect of staggered hybrid zones is that the homozygous populations within the zones have the potential to expand their distributions and become new races (a process termed ‘zonal raciation’). In this way they can add to the total ‘stock’ of chromosomal races in the species concerned. Speciation is an infrequent phenomenon that may involve an unusual set of circumstances. Each one of the products of zonal raciation has the potential to become a new species and by having more races increases the chance of a speciation event. PMID:24710041
The use of staggered scheme and an absorbing buffer zone for computational aeroacoustics
NASA Technical Reports Server (NTRS)
Nark, Douglas M.
1995-01-01
Various problems from those proposed for the Computational Aeroacoustics (CAA) workshop were studied using second and fourth order staggered spatial discretizations in conjunction with fourth order Runge-Kutta time integration. In addition, an absorbing buffer zone was used at the outflow boundaries. Promising results were obtained and provide a basis for application of these techniques to a wider variety of problems.
Ye, Longfang; Xiao, Yifan; Liu, Yanhui; Zhang, Liang; Cai, Guoxiong; Liu, Qing Huo
2016-01-01
We demonstrate a novel route to achieving highly efficient and strongly confined spoof surface plasmon polaritons (SPPs) waveguides at subwavelength scale enabled by planar staggered plasmonic waveguides (PSPWs). The structure of these new waveguides consists of an ultrathin metallic strip with periodic subwavelength staggered double groove arrays supported by a flexible dielectric substrate, leading to unique staggered EM coupling and waveguiding phenomenon. The spoof SPP propagation properties, including dispersion relations and near field distributions, are numerically investigated. Furthermore, broadband coplanar waveguide (CPW) to planar staggered plasmonic waveguide (PSPW) transitions are designed to achieve smooth momentum matching and highly efficient spoof SPP mode conversion. By applying these transitions, a CPW-PSPW-CPW structure is designed, fabricated and measured to verify the PSPW’s propagation performance at microwave frequencies. The investigation results show the proposed PSPWs have excellent performance of deep subwavelength spoof SPPs confinement, long propagation length and low bend loss, as well as great design flexibility to engineer the propagation properties by adjusting their geometry dimensions and material parameters. Our work opens up a new avenue for development of various advanced planar integrated plasmonic devices and circuits in microwave and terahertz regimes. PMID:27917930
Kwak, Tae Joon; Nam, Young Gyu; Najera, Maria Alejandra; Lee, Sang Woo; Strickler, J Rudi; Chang, Woo-Jin
2016-01-01
The liquid streams in a microchannel are hardly mixed to form laminar flow, and the mixing issue is well described by a low Reynolds number scheme. The staggered herringbone mixer (SHM) using repeated patterns of grooves in the microchannel have been proved to be an efficient passive micro-mixer. However, only a negative pattern of the staggered herringbone mixer has been used so far after it was first suggested, to the best of our knowledge. In this study, the mixing efficiencies from negative and positive staggered herringbone mixer patterns as well as from opposite flow directions were tested to investigate the effect of the micro-structure geometry on the surrounding laminar flow. The positive herringbone pattern showed better mixing efficiency than the conventionally used negative pattern. Also, generally used forward flow gives better mixing efficiency than reverse flow. The mixing was completed after two cycles of staggered herringbone mixer with both forward and reverse flow in a positive pattern. The traditional negative pattern showed complete mixing after four and five cycles in forward and reverse flow direction, respectively. The mixing effect in all geometries was numerically simulated, and the results confirmed more efficient mixing in the positive pattern than the negative. The results can further enable the design of a more efficient microfluidic mixer, as well as in depth understanding of the phenomena of positive and negative patterns existing in nature with regards to the surrounding fluids.
NASA Astrophysics Data System (ADS)
Ye, Longfang; Xiao, Yifan; Liu, Yanhui; Zhang, Liang; Cai, Guoxiong; Liu, Qing Huo
2016-12-01
We demonstrate a novel route to achieving highly efficient and strongly confined spoof surface plasmon polaritons (SPPs) waveguides at subwavelength scale enabled by planar staggered plasmonic waveguides (PSPWs). The structure of these new waveguides consists of an ultrathin metallic strip with periodic subwavelength staggered double groove arrays supported by a flexible dielectric substrate, leading to unique staggered EM coupling and waveguiding phenomenon. The spoof SPP propagation properties, including dispersion relations and near field distributions, are numerically investigated. Furthermore, broadband coplanar waveguide (CPW) to planar staggered plasmonic waveguide (PSPW) transitions are designed to achieve smooth momentum matching and highly efficient spoof SPP mode conversion. By applying these transitions, a CPW-PSPW-CPW structure is designed, fabricated and measured to verify the PSPW’s propagation performance at microwave frequencies. The investigation results show the proposed PSPWs have excellent performance of deep subwavelength spoof SPPs confinement, long propagation length and low bend loss, as well as great design flexibility to engineer the propagation properties by adjusting their geometry dimensions and material parameters. Our work opens up a new avenue for development of various advanced planar integrated plasmonic devices and circuits in microwave and terahertz regimes.
Enhancement of Radiative Efficiency with Staggered InGaN Quantum Well Light Emitting Diodes
Tansu, Nelson; Dierolf, Volkmar; Huang, Gensheng; Penn, Samson; Zhao, Hongping; Liu, Guangyu; Li, Xiaohang; Poplawsky, Jonathan
2011-07-14
The technology on the large overlap InGaN QWs developed in this program is currently implemented in commercial technology in enhancing the internal quantum efficiency in major LED industry in US and Asia. The scientific finding from this work supported by the DOE enabled the implementation of this step-like staggered quantum well in the commercial LEDs.
Strategic Alliances between Chinese and Foreign Universities: Was a Staggered Form of Entry Used?
ERIC Educational Resources Information Center
Willis, Mike
2001-01-01
Explored whether foreign universities moved through levels of alliance with China as a form of staggered market entry. Found almost no movement between levels of alliance, and that high levels of commitment were required at all levels to make an alliance successful. This indicates that foreign universities should be careful to establish alliances…
The use of staggered scheme and an absorbing buffer zone for computational aeroacoustics
NASA Technical Reports Server (NTRS)
Nark, Douglas M.
1995-01-01
Various problems from those proposed for the Computational Aeroacoustics (CAA) workshop were studied using second and fourth order staggered spatial discretizations in conjunction with fourth order Runge-Kutta time integration. In addition, an absorbing buffer zone was used at the outflow boundaries. Promising results were obtained and provide a basis for application of these techniques to a wider variety of problems.
Stagger/Destagger Modification for the Air Traffic Control Radar Beacon System
1976-01-01
various interlace ratios. A-3 The six type 74L00 logic gates (B2B through B2G ) connected in series from the junction of divider networks RI and R2 are used...at B2G is delayed approximately 120 rns from the input trigger and is then processed through the DL circuitry. The staggered trigger output of the DL
On the Quality of Velocity Interpolation Schemes for Marker-In-Cell Methods on 3-D Staggered Grids
NASA Astrophysics Data System (ADS)
Kaus, B.; Pusok, A. E.; Popov, A.
2015-12-01
The marker-in-cell method is generally considered to be a flexible and robust method to model advection of heterogenous non-diffusive properties (i.e. rock type or composition) in geodynamic problems or incompressible Stokes problems. In this method, Lagrangian points carrying compositional information are advected with the ambient velocity field on an immobile, Eulerian grid. However, velocity interpolation from grid points to marker locations is often performed without preserving the zero divergence of the velocity field at the interpolated locations (i.e. non-conservative). Such interpolation schemes can induce non-physical clustering of markers when strong velocity gradients are present (Jenny et al., 2001) and this may, eventually, result in empty grid cells, a serious numerical violation of the marker-in-cell method. Solutions to this problem include: using larger mesh resolutions and/or marker densities, or repeatedly controlling the marker distribution (i.e. inject/delete), but which does not have an established physical background. To remedy this at low computational costs, Jenny et al. (2001) and Meyer and Jenny (2004) proposed a simple, conservative velocity interpolation (CVI) scheme for 2-D staggered grid, while Wang et al. (2015) extended the formulation to 3-D finite element methods. Here, we follow up with these studies and report on the quality of velocity interpolation methods for 2-D and 3-D staggered grids. We adapt the formulations from both Jenny et al. (2001) and Wang et al. (2015) for use on 3-D staggered grids, where the velocity components have different node locations as compared to finite element, where they share the same node location. We test the different interpolation schemes (CVI and non-CVI) in combination with different advection schemes (Euler, RK2 and RK4) and with/out marker control on Stokes problems with strong velocity gradients, which are discretized using a finite difference method. We show that a conservative formulation
Lemmens, Sofie G; Martens, Eveline A; Born, Jurriaan M; Martens, Mieke J; Westerterp-Plantenga, Margriet S
2011-03-01
Meal pattern may influence hormone and appetite dynamics and food intake. The objective of the study was to determine the effects of staggered compared with nonstaggered meal consumption on hormone and appetite dynamics, food reward (i.e. "liking," "wanting"), and subsequent energy intake. The study was conducted in a randomized cross-over design. Participants (n = 38, age = 24 ± 6 y, BMI = 25.0 ± 3.1 kg/m(2)) came to the university twice for consumption of a 4-course lunch (40% of the daily energy requirements) in 0.5 h (nonstaggered) or in 2 h with 3 within-meal pauses (staggered) followed by ad libitum food intake. Throughout the test sessions, glucagon-like peptide (GLP)-1, peptide tyrosine-tyrosine (PYY(3-36)), ghrelin, appetite, and food reward were measured. In the staggered compared with nonstaggered meal condition, peak values of GLP-1, PYY(3-36), and satiety were lower and time to peak values were higher (P < 0.02); the nadir value of hunger was higher, and time to nadir values of ghrelin and hunger were higher (P < 0.0001). Prior to ad libitum food intake, GLP-1 concentrations and satiety ratings were greater, ghrelin concentrations and hunger ratings were smaller, and food "wanting" was less in the staggered compared with nonstaggered meal condition (P < 0.05). However, this did not affect ad libitum energy intake (1.7 ± 0.3 vs. 1.9 ± 0.2 MJ). In conclusion, staggered compared with nonstaggered meal consumption induces less pronounced hormone and appetite dynamics. Moreover, it results in higher final GLP-1 concentrations and satiety ratings, lower ghrelin concentrations and hunger ratings, and lower food "wanting" prior to ad libitum food intake. However, this was not translated into lower energy intake.
Odd-even staggering in yields of neutron-deficient nuclei produced by projectile fragmentation
NASA Astrophysics Data System (ADS)
Mei, B.; Xu, H. S.; Zhang, Y. H.; Wang, M.; Tu, X. L.; Schmidt, K.-H.; Litvinov, Yu. A.; Sun, Z. Y.; Zhou, X. H.; Yuan, Y. J.; Blaum, K.; Ricciardi, M. V.; Kelić-Heil, A.; Mao, R. S.; Hu, Z. G.; Shuai, P.; Zang, Y. D.; Ma, X. W.; Zhang, X. Y.; Xia, J. W.; Xiao, G. Q.; Guo, Z. Y.; Yang, J. C.; Zhang, X. H.; Xu, X.; Yan, X. L.; Zhang, W.; Zhan, W. L.
2016-10-01
Background: Fragment yields exhibit a strong odd-even staggering (OES). This OES has been experimentally observed in different fragmentation reactions with different projectile-target combinations. However, the experimental data are still scarce for fragments close to drip lines and the origin of this OES is not well understood. Purpose: More experimental data are needed to explore the origin of this OES in fragment yields and to validate fragmentation reaction models, especially for nuclei close to the drip lines. To study the pronounced OES near the proton drip line, we measured the yields of Tz=-1 and Tz=-3 /2 nuclei over a wide range of mass number. Methods: The combination of a fragment separator and a storage ring at the Heavy Ion Research Facility in Lanzhou has been used to measure the yields of Tz=-1 and Tz=-3 /2 fragments, produced by 58Ni projectiles impinging on a beryllium target at an energy of about 463 MeV/nucleon. Results: A very strong OES is observed in the measured yields of both Tz=-1 and Tz=-3 /2 fragments. Our experimental data demonstrate that the shell structure has a significant impact on the magnitude of this OES. A comparison of different fragmentation reaction data indicates that this OES is almost independent of the projectile-target combinations and the fragmentation energy between 140 and 650 MeV/nucleon. Conclusions: Our study reveals that the OES of fragment yields originates mainly from the OES of particle-emission threshold energies, which is very close to the OES of fragment yields when the Coulomb barrier is considered in particle-emission threshold energies.
NASA Astrophysics Data System (ADS)
Baumgärtel, M.; Ghanem, K.; Kiani, A.; Koch, E.; Pavarini, E.; Sims, H.; Zhang, G.
2017-07-01
We discuss the efficient implementation of general impurity solvers for dynamical mean-field theory. We show that both Lanczos and quantum Monte Carlo in different flavors (Hirsch-Fye, continuous-time hybridization- and interaction-expansion) exhibit excellent scaling on massively parallel supercomputers. We apply these algorithms to simulate realistic model Hamiltonians including the full Coulomb vertex, crystal-field splitting, and spin-orbit interaction. We discuss how to remove the sign problem in the presence of non-diagonal crystal-field and hybridization matrices. We show how to extract the physically observable quantities from imaginary time data, in particular correlation functions and susceptibilities. Finally, we present benchmarks and applications for representative correlated systems.
The scalar-photon 3-point vertex in massless quenched scalar QED
NASA Astrophysics Data System (ADS)
Concha-Sánchez, Y.; Gutiérrez-Guerrero, L. X.; Fernández-Rangel, L. A.
2016-10-01
Non perturbative studies of Schwinger-Dyson equations (SDEs) require their infinite, coupled tower to be truncated in order to reduce them to a practically solvable set. In this connection, a physically acceptable ansatz for the three point vertex is the most favorite choice. Scalar quantum electrodynamics (sQED) provides a simple and neat platform to address this problem. The most general form of the scalar-photon three point vertex can be expressed in terms of only two independent form factors, longitudinal and transverse. Ball and Chiu have demonstrated that the longitudinal vertex is fixed by requiring the Ward-Fradkin-Green- Takahashi identity (WFGTI), while the transverse vertex remains undetermined. In massless quenched sQED, we propose the transverse part of the non perturbative scalar-photon vertex.
NASA Astrophysics Data System (ADS)
Janiš, Václav; Pokorný, Vladislav
2012-12-01
We propose a renormalization scheme of the Kubo formula for the electrical conductivity with multiple backscatterings contributing to the electron-hole irreducible vertex derived from the asymptotic limit to high spatial dimensions. We use this vertex to represent the two-particle Green function via a symmetrized Bethe-Salpeter equation in momentum space. We further utilize the dominance of a pole in the irreducible vertex to an approximate diagonalization of the Bethe-Salpeter equation and a non-perturbative representation of the electron-hole correlation function. The latter function is then used to derive a compact representation for the electrical conductivity at zero temperature without the necessity to evaluate separately the Drude term and vertex corrections. The electrical conductivity calculated in this way remains nonnegative also in the strongly disordered regime where the localization effects become significant and the negative vertex corrections in the standard Kubo formula overweight the Drude term.
Performance of the ALICE secondary vertex b-tagging algorithm
NASA Astrophysics Data System (ADS)
Eyyubova, G.; Kramarik, L.
2016-11-01
The identification of jets originating from beauty quarks in heavy-ion collisions is important to study the properties of the hot and dense matter produced in such collisions. A variety of algorithms for b-jet tagging was elaborated at the LHC experments. They rely on the properties of B hadrons, i.e. their long lifetime, large mass and large multiplicity of decay products. In this work, the b-tagging algorithm based on displaced secondary-vertex topologies is described. We present Monte Carlo based performance studies of the algorithm for charged jets reconstructed with the ALICE tracking system in p-Pb collisions at √sNN = 5.02 TeV. The tagging efficiency, rejection rate and the correction of the smearing effects of non-ideal detector response are presented.
The LHCb Vertex Locator (VELO) Pixel Detector Upgrade
NASA Astrophysics Data System (ADS)
Buchanan, E.
2017-01-01
The LHCb experiment is designed to perform high-precision measurements of CP violation and the decays of beauty and charm hadrons at the Large Hadron Collider (LHC) at CERN. There is a planned upgrade during Long Shutdown 2 (LS2), expected in 2019, which will allow the detector to run at higher luminosities by transforming the entire readout to a trigger-less system. This will include a substantial upgrade of the Vertex Locator (VELO), the silicon tracker that surrounds the LHCb interaction region. The VELO is moving from silicon strip technology to hybrid pixel sensors, where silicon sensors are bonded to VeloPix ASICs. Sensor prototypes have undergone rigorous testing using the Timepix3 Telescope at the SPS, CERN. The main components of the upgrade are summarised and testbeam results presented.
STAR Vertex Detector Upgrade-HFT Pixel Development
Szelezniak, Michal; Greiner, Leo C.; Matis, Howard S.; Ritter, Hans Georg; Sun Xiangming; Thomas, James H.; Wieman, Howard H.; Anderssen, Eric; Stezelberger, Thorsten; Vu, Chinh Q.
2009-03-10
Development and prototyping efforts directed towards construction of a new vertex detector for the STAR experiment at the RHIC accelerator at BNL are presented. This new detector will extend the physics range of STAR by allowing for precision measurements of yields and spectra of particles containing heavy quarks. The innermost central part of the new detector is a high resolution pixel-type detector (PIXEL). PIXEL requirements are discussed as well as a conceptual mechanical design, a sensor development path, and a detector readout architecture. Selected progress with sensor prototypes dedicated to the PIXEL detector is summarized and the approach chosen for the readout system architecture validated in tests of hardware prototypes is discussed.
A vertex similarity index for better personalized recommendation
NASA Astrophysics Data System (ADS)
Chen, Ling-Jiao; Zhang, Zi-Ke; Liu, Jin-Hu; Gao, Jian; Zhou, Tao
2017-01-01
Recommender systems benefit us in tackling the problem of information overload by predicting our potential choices among diverse niche objects. So far, a variety of personalized recommendation algorithms have been proposed and most of them are based on similarities, such as collaborative filtering and mass diffusion. Here, we propose a novel vertex similarity index named CosRA, which combines advantages of both the cosine index and the resource-allocation (RA) index. By applying the CosRA index to real recommender systems including MovieLens, Netflix and RYM, we show that the CosRA-based method has better performance in accuracy, diversity and novelty than some benchmark methods. Moreover, the CosRA index is free of parameters, which is a significant advantage in real applications. Further experiments show that the introduction of two turnable parameters cannot remarkably improve the overall performance of the CosRA index.
The FIRST experiment: interaction region and MAPS vertex detector
NASA Astrophysics Data System (ADS)
Spiriti, E.; de Napoli, M.; Romano, F.; FIRST Collaboration
2011-06-01
The improvement of the precision of the measurement of the nuclear cross-section, in order to fulfill the requirements of the actual Monte Carlo simulations for hadrontherapy and space radioprotection, is the main goal of the FIRST experiment. After a brief introduction on the treatment planning in hadrontherapy, this paper describes main characteristics and components of the experiment. The features of the interaction region detectors and their main needs (low material budget, high angular coverage, two tracks resolution and large trigger rate) are discussed. Special emphasis is devoted in discussing the new silicon pixel vertex detector, in particular its new developed data acquisition and its characterization with the first test results obtained with a prototype of the detector.
Limits on anomalous contributions to the Wtb vertex
NASA Astrophysics Data System (ADS)
Pease, Christopher; Fiolhais, Miguel; Onofre, Antonio
2017-01-01
Recent LHC results on the measurements of the W-boson helicity fractions and single top quark production cross section at a center-of-mass energy of 13 TeV are combined in order to establish new limits on anomalous contributions to the Wtb vertex. The allowed regions for these limits are presented in three-dimensional graphics, for both real and imaginary components of the different anomalous couplings, allowing all the other anomalous couplings to vary at the same time. These results are combined with the prospected future measurement of the single top quark production cross section and W-boson helicity fractions at the LHC. When compared with the previous most precise limits, these results show a significant improvement, larger than 10%.
The silicon vertex detector of HERA-B
Moshous, Basil
1998-02-01
HERA-B is an experiment to study CP violation in the B system using an internal target at the DESY HERA proton ring(820 GeV). The main goal is to measure the asymmetry in the 'gold plated' decays of B{sup 0}, B-bar{sup 0}{yields}J/{psi}K{sub s}{sup 0} yielding a measurement of the angle {beta} of the unitarity triangle. From the semileptonic decay channels of the b, b-bar-hadron produced in association with the B{sup 0},B-bar{sup 0} can be used to tag the flavor of the B{sup 0}. The purpose of the Vertex Detector System is to provide the track coordinates for reconstructing the J/{psi}{yields}e{sup +}e{sup -}, {mu}{sup +}{mu}{sup -} secondary decay vertices and the impact parameters of all tagging particles.
Performance of the CLAS12 Silicon Vertex Tracker modules
Antonioli, Mary Ann; Boiarinov, Serguie; Bonneau, Peter R.; Elouadrhiri, Latifa; Eng, Brian J.; Gotra, Yuri N.; Kurbatov, Evgeny O.; Leffel, Mindy A.; Mandal, Saptarshi; McMullen, Marc E.; Merkin, Mikhail M.; Raydo, Benjamin J.; Teachey, Robert W,; Tucker, Ross J.; Ungaro, Maurizio; Yegneswaran, Amrit S.; Ziegler, Veronique
2013-12-01
For the 12 GeV upgrade, the CLAS12 experiment has designed a Silicon Vertex Tracker (SVT) using single sided microstrip sensors fabricated by Hamamatsu. The sensors have graded angle design to minimize dead areas and a readout pitch of 156{micro}m, with intermediate strip. Double sided SVT module hosts three daisy-chained sensors on each side with a full strip length of 33 cm. There are 512 channels per module read out by four Fermilab Silicon Strip Readout (FSSR2) chips featuring data driven architecture, mounted on a rigid-flex hybrid. Modules are assembled on the barrel using unique cantilevered geometry to minimize the amount of material in the tracking volume. Design and performance of the SVT modules are presented, focusing on results of electrical measurements.
The silicon vertex detector of the Belle II experiment
NASA Astrophysics Data System (ADS)
Adamczyk, K.; Aihara, H.; Angelini, C.; Aziz, T.; Babu, V.; Bacher, S.; Bahinipati, S.; Barberio, E.; Baroncelli, T.; Basith, A. K.; Batignani, G.; Bauer, A.; Behera, P. K.; Bergauer, T.; Bettarini, S.; Bhuyan, B.; Bilka, T.; Bosi, F.; Bosisio, L.; Bozek, A.; Buchsteiner, F.; Casarosa, G.; Ceccanti, M.; Červenkov, D.; Chendvankar, S. R.; Dash, N.; Divekar, S. T.; Doležal, Z.; Dutta, D.; Forti, F.; Friedl, M.; Hara, K.; Higuchi, T.; Horiguchi, T.; Irmler, C.; Ishikawa, A.; Jeon, H. B.; Joo, C. W.; Kandra, J.; Kang, K. H.; Kato, E.; Kawasaki, T.; Kodyš, P.; Kohriki, T.; Koike, S.; Kolwalkar, M. M.; Kvasnička, P.; Lanceri, L.; Lettenbicher, J.; Mammini, P.; Mayekar, S. N.; Mohanty, G. B.; Mohanty, S.; Morii, T.; Nakamura, K. R.; Natkaniec, Z.; Negishi, K.; Nisar, N. K.; Onuki, Y.; Ostrowicz, W.; Paladino, A.; Paoloni, E.; Park, H.; Pilo, F.; Profeti, A.; Rao, K. K.; Rashevskaya, I.; Rizzo, G.; Rozanska, M.; Sandilya, S.; Sasaki, J.; Sato, N.; Schultschik, S.; Schwanda, C.; Seino, Y.; Shimizu, N.; Stypula, J.; Tanaka, S.; Tanida, K.; Taylor, G. N.; Thalmeier, R.; Thomas, R.; Tsuboyama, T.; Uozumi, S.; Urquijo, P.; Vitale, L.; Volpi, M.; Watanuki, S.; Watson, I. J.; Webb, J.; Wiechczynski, J.; Williams, S.; Würkner, B.; Yamamoto, H.; Yin, H.; Yoshinobu, T.; Belle SVD Collaboration, II
2016-07-01
The silicon vertex detector of the Belle II experiment, structured in a lantern shape, consists of four layers of ladders, fabricated from two to five silicon sensors. The APV25 readout ASIC chips are mounted on one side of the ladder to minimize the signal path for reducing the capacitive noise; signals from the sensor backside are transmitted to the chip by bent flexible fan-out circuits. The ladder is assembled using several dedicated jigs. Sensor motion on the jig is minimized by vacuum chucking. The gluing procedure provides such a rigid foundation that later leads to the desired wire bonding performance. The full ladder with electrically functional sensors is consistently completed with a fully developed assembly procedure, and its sensor offsets from the design values are found to be less than 200 μm. The potential functionality of the ladder is also demonstrated by the radioactive source test.
Cutaneous paraganglioma of the vertex in a child.
Kim; Lee, Il Jae; Park, Myong Chul; Kim, Joo Hyoung; Lim, Hyoseob
2012-07-01
Paraganglioma is a neuroendocrine neoplasm that may develop at various body sites, including the head, neck, thorax, and abdomen. Approximately 85% of paragangliomas develop on the abdomen, 12% develop on the chest, and only 3% develop on the head and neck. These tumors are found in locations that parallel the sympathetic chain ganglion in the thoracolumbar regions and parasympathetic nervous system in craniosacral regions, and all head and neck paragangliomas arise from the parasympathetic nervous system. Although the skin has a rich neural network, it is devoid of ganglia. There has been only 1 report of a paraganglioma on the scalp of a child. We describe a 3-year-old child with a primary cutaneous paraganglioma of the vertex scalp and review the literature on paragangliomas.
Performance of the CLAS12 Silicon Vertex Tracker modules
NASA Astrophysics Data System (ADS)
Antonioli, M. A.; Boiarinov, S.; Bonneau, P.; Elouadrhiri, L.; Eng, B.; Gotra, Y.; Kurbatov, E.; Leffel, M.; Mandal, S.; McMullen, M.; Merkin, M.; Raydo, B.; Teachey, W.; Tucker, R.; Ungaro, M.; Yegneswaran, A.; Ziegler, V.
2013-12-01
For the 12 GeV upgrade, the CLAS12 experiment has designed a Silicon Vertex Tracker (SVT) using single sided microstrip sensors fabricated by Hamamatsu. The sensors have graded angle design to minimize dead areas and a readout pitch of 156 μm, with intermediate strip. Double sided SVT module hosts three daisy-chained sensors on each side with a full strip length of 33 cm. There are 512 channels per module read out by four Fermilab Silicon Strip Readout (FSSR2) chips featuring data driven architecture, mounted on a rigid-flex hybrid. Modules are assembled on the barrel using unique cantilevered geometry to minimize the amount of material in the tracking volume. Design and performance of the SVT modules are presented, focusing on results of electrical measurements.
Testing the RRPP vertex of effective Regge action
NASA Astrophysics Data System (ADS)
Kuraev, E. A.; Bytev, V. V.; Bakmaev, S.; Antonov, E. N.
2008-06-01
We discuss the possibility of checking the vertex with creation of two real gluons in collision of two reggeized ones (RRPP) which can reveal themselves in process of scalar meson production in high energy peripheral nucleon collisions. Numerical estimations of the cross section of a pair of charged pion production for the LHC facility give the value of an order of 10 mb. We also estimate the excess of production of positively charged muons (as a decay of pions) created by cosmic ray proton collisions with the atmosphere gas nuclei to be in reasonable agreement with modern data. The effects of higher orders which reveal themselves as a screening factor are considered in terms of impact parameter representation. We estimate the cross section of pion pair production in central region to fall faster than factorial σn ∼ 1 / (n2 n !).
Photoabsorption off nuclei with self-consistent vertex corrections
Riek, F.; Lutz, M. F. M.; Korpa, C. L.
2009-08-15
We study photoproduction off nuclei based on a self-consistent and covariant many-body approach for the pion and isobar propagation in infinite nuclear matter. For the first time the t-channel exchange of an in-medium pion is evaluated in the presence of vertex correction effects consistently. In particular the interference pattern with the s-channel in-medium nucleon and isobar exchange contribution is considered. Electromagnetic gauge invariance is kept as a consequence of various Ward identities obeyed by the computation. Adjusting the set of Migdal parameters to the data set we predict an attractive mass shift for the isobar of about 50 MeV at nuclear saturation density.
NASA Astrophysics Data System (ADS)
Sun, Jie; Sun, Huiqing; Yi, Xinyan; Yang, Xian; Liu, Tianyi; Wang, Xin; Zhang, Xiu; Fan, Xuancong; Zhang, Zhuding; Guo, Zhiyou
2017-07-01
Ultraviolet light-emitting diodes (UVLEDs) with staggered barriers have been studied. The energy band diagrams, internal quantum efficiency, total output power and radiative recombination rate are investigated by APSYS software. The simulation results show that the UVLED with staggered barriers get a little enhancement comparing to the conventional one, on the contrary the structure with p-doped staggered barriers has higher efficiency and power due to enhancement of the holes' injection and the electrons' confinement. Then structures with different Al content in the Mg-doped barriers have been studied numerically and that confirmed the best.
Impact of nonlocal correlations over different energy scales: A dynamical vertex approximation study
NASA Astrophysics Data System (ADS)
Rohringer, G.; Toschi, A.
2016-09-01
In this paper, we investigate how nonlocal correlations affect, selectively, the physics of correlated electrons over different energy scales, from the Fermi level to the band edges. This goal is achieved by applying a diagrammatic extension of dynamical mean field theory (DMFT), the dynamical vertex approximation (D Γ A ), to study several spectral and thermodynamic properties of the unfrustrated Hubbard model in two and three dimensions. Specifically, we focus first on the low-energy regime by computing the electronic scattering rate and the quasiparticle mass renormalization for decreasing temperatures at a fixed interaction strength. This way, we obtain a precise characterization of the several steps through which the Fermi-liquid physics is progressively destroyed by nonlocal correlations. Our study is then extended to a broader energy range, by analyzing the temperature behavior of the kinetic and potential energy, as well as of the corresponding energy distribution functions. Our findings allow us to identify a smooth but definite evolution of the nature of nonlocal correlations by increasing interaction: They either increase or decrease the kinetic energy w.r.t. DMFT depending on the interaction strength being weak or strong, respectively. This reflects the corresponding evolution of the ground state from a nesting-driven (Slater) to a superexchange-driven (Heisenberg) antiferromagnet (AF), whose fingerprints are, thus, recognizable in the spatial correlations of the paramagnetic phase. Finally, a critical analysis of our numerical results of the potential energy at the largest interaction allows us to identify possible procedures to improve the ladder-based algorithms adopted in the dynamical vertex approximation.
Cross flow induced vibrations in staggered arrays of cylindrical structures
Marn, J.
1991-12-31
Flow induced vibrations cause by instability is the subject of this investigation. The bulk of the work performed is theoretical in nature, the comparison with some of existing experimental data is given for each of four models described. First model encompasses the effects of prescribed motion on the cylinder. Such circumstances occur in the case of vortex shedding initiated instability. The reduced velocity within the cylinder array is low and there is no coupling between the adjacent cylinders. Second model assumes certain form of vibration and corresponding behavior of the perturbed velocity field in temporal and one of spatial coordinates thus transforming partial differential equations into ordinary differential equations and takes into account the motion of the neighboring cylinder. This corresponds to fluid elastic controlled instabilities. The resulting equations are solved analytically. The model is used for better understanding of the equations of cylinder motion as well as for quick estimates of threshold of instability. Third model relaxes an assumption about the form of vibration in spatial direction and uses the vorticity formulation of equation of fluid motion to account for fluid-solid interaction. This model analysis is of two phase (air-water mixture) flow. The void fraction distribution is found to be the single most decisive factor to determine the onset of instability for such a domain. In conclusion, two distinct mechanism were found to be responsible for flow induced vibration caused instabilities, (1) outside source controlled periodic excitation (such as vortex shedding) -- described by the first model and (2) fluid elastic forces -- described by second, third and fourth models. For the values of reduced velocity below 0.7 first model is proposed, for the values above 0.7, the rest.
NASA Astrophysics Data System (ADS)
Tan, D.-R.; Jiang, F.-J.
2017-02-01
The Néel temperature, staggered magnetization density, as well as the spin-wave velocity of a three-dimensional (3D) quantum Heisenberg model with antiferromagnetic disorder (randomness) are calculated using first-principles nonperturbative quantum Monte Carlo simulations. In particular, we examine the validity of universal scaling relations that are related to these three studied physical quantities. These relations are relevant to experimental data and are firmly established for clean (regular) 3D dimerized spin-1/2 Heisenberg models. Remarkably, our numerical results show that the considered scaling relations remain true for the investigated model with the introduced disorder. In addition, while the presence of disorder may change the physical properties of regular dimerized models, hence leading to different critical theories, both the obtained data of Néel temperature and staggered magnetization density in our study are fully compatible with the expected critical behavior for clean dimerized systems. As a result, it is persuasive to conclude that the related quantum phase transitions of the considered disordered model and its clean analogues are governed by the same critical theory, which is not always the case in general. Finally, we also find smooth scaling curves even emerging when both the data of the investigated disordered model as well as its associated clean system are taken into account concurrently. This in turn implies that, while in a restricted sense, the considered scaling relations for 3D spin-1/2 antiferromagnets are indeed universal.
Lim, Chi Wan; Su, Yi; Yeo, Si Yong; Ng, Gillian Maria; Nguyen, Vinh Tan; Zhong, Liang; Tan, Ru San; Poh, Kian Keong; Chai, Ping
2014-01-01
We propose an automatic algorithm for the reconstruction of patient-specific cardiac mesh models with 1-to-1 vertex correspondence. In this framework, a series of 3D meshes depicting the endocardial surface of the heart at each time step is constructed, based on a set of border delineated magnetic resonance imaging (MRI) data of the whole cardiac cycle. The key contribution in this work involves a novel reconstruction technique to generate a 4D (i.e., spatial–temporal) model of the heart with 1-to-1 vertex mapping throughout the time frames. The reconstructed 3D model from the first time step is used as a base template model and then deformed to fit the segmented contours from the subsequent time steps. A method to determine a tree-based connectivity relationship is proposed to ensure robust mapping during mesh deformation. The novel feature is the ability to handle intra- and inter-frame 2D topology changes of the contours, which manifests as a series of merging and splitting of contours when the images are viewed either in a spatial or temporal sequence. Our algorithm has been tested on five acquisitions of cardiac MRI and can successfully reconstruct the full 4D heart model in around 30 minutes per subject. The generated 4D heart model conforms very well with the input segmented contours and the mesh element shape is of reasonably good quality. The work is important in the support of downstream computational simulation activities. PMID:24743555
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
Hrayr Matevosyan; Anthony Thomas; Peter Tandy
2007-04-01
We include a generalized infinite class of quark-gluon vertex dressing diagrams in a study of how dynamics beyond the ladder-rainbow truncation influences the Bethe-Salpeter description of light quark pseudoscalar and vector mesons. The diagrammatic specification of the vertex is mapped into a corresponding specification of the Bethe-Salpeter kernel, which preserves chiral symmetry. This study adopts the algebraic format afforded by the simple interaction kernel used in previous work on this topic. The new feature of the present work is that in every diagram summed for the vertex and the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be the self-consistent vertex solution. We also adopt from previous work the effective accounting for the role of the explicitly non-Abelian three gluon coupling in a global manner through one parameter determined from recent lattice-QCD data for the vertex. With the more consistent vertex used here, the error in ladder-rainbow truncation for vector mesons is never more than 10% as the current quark mass is varied from the u/d region to the b region.
Characterizing general scale-free networks by vertex-degree sequences
NASA Astrophysics Data System (ADS)
Xiao, Wenjun; Lai, Zhengwen; Chen, Guanrong
2015-11-01
Many complex networks possess a scale-free vertex-degree distribution in a power-law form of c k-γ , where k is the vertex-degree variable and c and γ are constants. To better understand the mechanism of the power-law formation in scale-free networks, it is important to understand and analyze their vertex-degree sequences. We had shown before that, for a scale-free network of size N , if its vertex-degree sequence is k1
Characterizing general scale-free networks by vertex-degree sequences.
Xiao, Wenjun; Lai, Zhengwen; Chen, Guanrong
2015-11-01
Many complex networks possess a scale-free vertex-degree distribution in a power-law form of ck(-γ), where k is the vertex-degree variable and c and γ are constants. To better understand the mechanism of the power-law formation in scale-free networks, it is important to understand and analyze their vertex-degree sequences. We had shown before that, for a scale-free network of size N, if its vertex-degree sequence is k1
3D Staggered-Grid Finite-Difference Simulation of Acoustic Waves in Turbulent Moving Media
NASA Astrophysics Data System (ADS)
Symons, N. P.; Aldridge, D. F.; Marlin, D.; Wilson, D. K.; Sullivan, P.; Ostashev, V.
2003-12-01
Acoustic wave propagation in a three-dimensional heterogeneous moving atmosphere is accurately simulated with a numerical algorithm recently developed under the DOD Common High Performance Computing Software Support Initiative (CHSSI). Sound waves within such a dynamic environment are mathematically described by a set of four, coupled, first-order partial differential equations governing small-amplitude fluctuations in pressure and particle velocity. The system is rigorously derived from fundamental principles of continuum mechanics, ideal-fluid constitutive relations, and reasonable assumptions that the ambient atmospheric motion is adiabatic and divergence-free. An explicit, time-domain, finite-difference (FD) numerical scheme is used to solve the system for both pressure and particle velocity wavefields. The atmosphere is characterized by 3D gridded models of sound speed, mass density, and the three components of the wind velocity vector. Dependent variables are stored on staggered spatial and temporal grids, and centered FD operators possess 2nd-order and 4th-order space/time accuracy. Accurate sound wave simulation is achieved provided grid intervals are chosen appropriately. The gridding must be fine enough to reduce numerical dispersion artifacts to an acceptable level and maintain stability. The algorithm is designed to execute on parallel computational platforms by utilizing a spatial domain-decomposition strategy. Currently, the algorithm has been validated on four different computational platforms, and parallel scalability of approximately 85% has been demonstrated. Comparisons with analytic solutions for uniform and vertically stratified wind models indicate that the FD algorithm generates accurate results with either a vanishing pressure or vanishing vertical-particle velocity boundary condition. Simulations are performed using a kinematic turbulence wind profile developed with the quasi-wavelet method. In addition, preliminary results are presented
Test of {Delta}I = 2 staggering in the superdeformed bands of {sup 194}Hg
Kruecken, R.; Deleplanque, M.A.; Lee, I.Y.; Asztalos, S.
1996-06-05
The presence of {Delta}I = 2 staggering in the three known superdeformed bands of {sup 194}Hg has been reexamined in a new experiment with Gammasphere. A relative accuracy of better than 30 eV was achieved for most transition energies. No statistically significant oscillations in the transition energies were found for band 1 while staggering patterns were observed in bands 2 and 3. The statistical significance of the observed effects was analyzed. The patterns display some similarities with expectations based on a band crossing picture, even though such a picture cannot reproduce the observations in a straightforward way. No evidence was found for additional superdeformed bands in {sup 194}Hg which could account for possible band-crossings.
Adams, David H.
2008-05-15
To investigate the viability of the 4th root trick for the staggered fermion determinant in a simpler setting, we consider a 2-taste (flavor) lattice fermion formulation with no taste mixing but with exact taste-nonsinglet chiral symmetries analogous to the taste-nonsinglet U(1){sub A} symmetry of staggered fermions. Creutz's objections to the rooting trick apply just as much in this setting. To counter them we show that the formulation has robust would-be zero modes in topologically nontrivial gauge backgrounds, and that these manifest themselves in a viable way in the rooted fermion determinant and also in the disconnected piece of the pseudoscalar meson propagator as required to solve the U(1) problem. Also, our rooted theory is heuristically seen to be in the right universality class for QCD if the same is true for an unrooted mixed fermion action theory.
Index theorem and universality properties of the low-lying eigenvalues of improved staggered quarks.
Follana, E; Hart, A; Davies, C T H
2004-12-10
We study various improved staggered quark Dirac operators on quenched gluon backgrounds in lattice QCD generated using a Symanzik-improved gluon action. We find a clear separation of the spectrum into would-be zero modes and others. The number of would-be zero modes depends on the topological charge as expected from the index theorem, and their chirality expectation value is large ( approximately 0.7). The remaining modes have low chirality and show clear signs of clustering into quartets and approaching the random matrix theory predictions for all topological charge sectors. We conclude that improvement of the fermionic and gauge actions moves the staggered quarks closer to the continuum limit where they respond correctly to QCD topology.
A METHOD OF TREATING UNSTRUCTURED CONCAVE CELLS IN STAGGERED-GRID LAGRANGIAN HYDRODYNAMICS
C. ROUSCULP; D. BURTON
2000-12-01
A method is proposed for the treatment of concave cells in staggered-grid Lagrangian hydrodynamics. The method is general enough to be applied to two- and three-dimensional unstructured cells. Instead of defining a cell-point as the geometric average of its nodes (a cell-center), the cell-point is that which equalizes the triangular/tetrahedral area/volume in two/three dimensions. Examples are given.
A conservative staggered-grid Chebyshev multidomain method for compressible flows
NASA Technical Reports Server (NTRS)
Kopriva, David A.; Kolias, John H.
1995-01-01
We present a new multidomain spectral collocation method that uses staggered grids for the solution of compressible flow problems. The solution unknowns are defined at the nodes of a Gauss quadrature rule. The fluxes are evaluated at the nodes of a Gauss-Lobatto rule. The method is conservative, free-stream preserving, and exponentially accurate. A significant advantage of the method is that subdomain corners are not included in the approximation, making solutions in complex geometries easier to compute.
Numerical study of super-resolved optical microscopy with partly staggered beams
NASA Astrophysics Data System (ADS)
He, Jinping; Wang, Nan; Kobayashi, Takayoshi
2016-12-01
The resolving power of optical microscopy involving two or even more beams, such as pump-probe microscopy and nonlinear optical microscopy, can be enhanced both laterally and longitudinally with partly staggered beams. A numerical study of the new super-resolution imaging technology is performed with vector diffraction theory. The influence of polarization is discussed. A resolving power of sub-100 nm and sub-300 nm in the lateral and longitudinal directions, respectively, is achievable.
D(S) spectrum and leptonic decays with Fermilab heavy quarks and improved staggered light quarks
Massimo Di Pierro et al.
2004-03-12
We present preliminary results for the D{sub s} meson spectrum and decay constants in unquenched lattice QCD. Simulations are carried out with 2 + 1 dynamical quarks using gauge configurations generated by the MILC collaboration. We use the ''asqtad'' a{sup 2} improved staggered action for the light quarks, and the clover heavy quark action with the Fermilab interpretation. We compare our spectrum results with the newly discovered 0{sup +} and 1{sup +} states in the D{sub s} system.
A MAPS based vertex detector for the STAR experiment at RHIC
Anderssen, E; Ritter, H G; Schambach, J; Sun, X; Szelezniak, M; Thomas, J; Vu, C; Wieman, H
2011-09-11
The STAR experiment at RHIC is in the process of upgrading the inner detector region of the experiment to improve the vertex resolution. We describe the current design of a MAPS based vertex detector, which is the innermost and highest resolution detector of the set of three planned upgrade detectors. This detector will enable the identification of decay vertices displaced from the interaction vertex by 100-150 {micro}m and extend the capabilities of the STAR detector in the heavy flavor domain. We present selected detector design characteristics and prototyping results, which help to validate the design in preparation for the construction of the detector.
Vertex corrections and the Korringa ratio in strongly correlated electron materials
NASA Astrophysics Data System (ADS)
Yusuf, Eddy; Powell, B. J.; McKenzie, Ross H.
2009-05-01
We show that the Korringa ratio, associated with nuclear magnetic resonance in metals, is unity if vertex corrections to the dynamic spin susceptibility are negligible, the hyperfine coupling is momentum independent, and there exists an energy scale below which the density of states is constant. In the absence of vertex corrections we also find a Korringa behaviour for T1, the nuclear spin relaxation rate, i.e., 1/T_1\\propto T , and a temperature independent Knight shift. These results are independent of the form and magnitude of the self-energy (so far as is consistent with neglecting vertex corrections) and of the dimensionality of the system.
NASA Astrophysics Data System (ADS)
Boucaud, Ph.; De Soto, F.; Rodríguez-Quintero, J.; Zafeiropoulos, S.
2017-06-01
This article reports on the detailed study of the three-gluon vertex in four-dimensional S U (3 ) Yang-Mills theory employing lattice simulations with large physical volumes and high statistics. A meticulous scrutiny of the so-called symmetric and asymmetric kinematical configurations is performed, and it is shown that the associated form factor changes sign at a given range of momenta. The lattice results are compared to the model-independent predictions of Schwinger-Dyson equations, and a very good agreement between the two is found.
Adjacent-vertex-distinguishing proper total colouring number of {\\bar{K}}_{m}\\vee {P}_{n}
NASA Astrophysics Data System (ADS)
Liu, Shunqin
2017-08-01
Coloring is a fundamental problem in scientific computation and engineering design. In recent years, a variety of colorings frequently appeared and solved many problems in production. For example, adjacent-vertex-distinguishing proper total coloring, adjacent-vertex-distinguishing proper edge coloring, smarandachely-adjacent-vertex-distinguishing proper edge coloring. It is an important also difficult problem to discuss the coloring numbers of a given graph class. And we focus on the adjacent-vertex-distinguishing proper total coloring numbers in this paper. We study the adjacent-vertex-distinguishing proper total coloring numbers of joint graphs {\\bar{K}}m\\vee {P}n.
NASA Technical Reports Server (NTRS)
Carpenter, Mark H.; Parsani, Matteo; Fisher, Travis C.; Nielsen, Eric J.
2015-01-01
Staggered grid, entropy stable discontinuous spectral collocation operators of any order are developed for Burgers' and the compressible Navier-Stokes equations on unstructured hexahedral elements. This generalization of previous entropy stable spectral collocation work [1, 2], extends the applicable set of points from tensor product, Legendre-Gauss-Lobatto (LGL) to a combination of tensor product Legendre-Gauss (LG) and LGL points. The new semi-discrete operators discretely conserve mass, momentum, energy and satisfy a mathematical entropy inequality for both Burgers' and the compressible Navier-Stokes equations in three spatial dimensions. They are valid for smooth as well as discontinuous flows. The staggered LG and conventional LGL point formulations are compared on several challenging test problems. The staggered LG operators are significantly more accurate, although more costly to implement. The LG and LGL operators exhibit similar robustness, as is demonstrated using test problems known to be problematic for operators that lack a nonlinearly stability proof for the compressible Navier-Stokes equations (e.g., discontinuous Galerkin, spectral difference, or flux reconstruction operators).
Effects of staggered fermions and mixed actions on the scalar correlator
Prelovsek, S.
2006-01-01
We provide the analytic predictions for the flavor nonsinglet scalar correlator, which will enable determination of the scalar meson mass from the lattice scalar correlator. We consider simulations with 2+1 staggered sea quarks and staggered or chiral valence quarks. At small u/d masses the correlator is dominated by the bubble contribution, which is the intermediate state with two pseudoscalar mesons. We determine the bubble contribution within staggered and mixed chiral perturbation theory. Its effective mass is smaller than the mass of {pi}{eta}, which is the lightest intermediate state in proper 2+1 QCD. The unphysical effective mass is a consequence of the taste breaking that makes possible the intermediate state with mass 2M{sub {pi}}. We find that the scalar correlator can be negative in the simulations with mixed quark actions if the sea- and valence-quark masses are tuned by matching the pion masses M{sub val,val}=M{sub {pi}{sub 5}}.
Studies With Staggered Starts: Multiple Baseline Designs and Group-Randomized Trials
Murray, David M.; Andridge, Rebecca R.; Pennell, Michael L.; Hade, Erinn M.
2011-01-01
Objectives. Multiple baseline designs (MBDs) have been suggested as alternatives to group-randomized trials (GRT). We reviewed structural features of MBDs and considered their potential effectiveness in public health research. We also reviewed the effect of staggered starts on statistical power. Methods. We reviewed the MBD literature to identify key structural features, recent suggestions that MBDs be adopted in public health research, and the literature on power in GRTs with staggered starts. We also computed power for MBDs and GRTs. Results. The features that have contributed to the success of small MBDs in some fields are not likely to translate well to public health research. MBDs can be more powerful than GRTs under some conditions, but those conditions involve assumptions that require careful evaluation in practice. Conclusions. MBDs will often serve better as a complement of rather than as an alternative to GRTs. GRTs may employ staggered starts for logistical or ethical reasons, but this will always increase their duration and will often increase their cost. PMID:21940928
NASA Technical Reports Server (NTRS)
Holdeman, James D.
2016-01-01
The purpose of this article is to explain why the extension of the previously published C = (S/Ho)sqrt(J) scaling for opposed rows of staggered jets wasn't directly successful in the study by Choi et al. (2016). It is not surprising that staggered jets from opposite sides do not pass each other at the expected C value, because Ho/D and sqrt(J) are much larger than the maximum in previous studies. These, and large x/D's, tend to suggest development of 2-dimensional flow. Although there are distinct optima for opposed rows of in-line jets, single-side injection, and opposed rows of staggered jets based on C, opposed rows of staggered jets provide as good or better mixing performance, at any C value, than opposed rows of in-line jets or jets from single-side injection.
NASA Astrophysics Data System (ADS)
Weiss, C. J.; Schultz, A.
2011-12-01
The high computational cost of the forward solution for modeling low-frequency electromagnetic induction phenomena is one of the primary impediments against broad-scale adoption by the geoscience community of exploration techniques, such as magnetotellurics and geomagnetic depth sounding, that rely on fast and cheap forward solutions to make tractable the inverse problem. As geophysical observables, electromagnetic fields are direct indicators of Earth's electrical conductivity - a physical property independent of (but in some cases correlative with) seismic wavespeed. Electrical conductivity is known to be a function of Earth's physiochemical state and temperature, and to be especially sensitive to the presence of fluids, melts and volatiles. Hence, electromagnetic methods offer a critical and independent constraint on our understanding of Earth's interior processes. Existing methods for parallelization of time-harmonic electromagnetic simulators, as applied to geophysics, have relied heavily on a combination of strategies: coarse-grained decompositions of the model domain; and/or, a high-order functional decomposition across spectral components, which in turn can be domain-decomposed themselves. Hence, in terms of scaling, both approaches are ultimately limited by the growing communication cost as the granularity of the forward problem increases. In this presentation we examine alternate parallelization strategies based on OpenMP shared-memory parallelization and CUDA-based GPU parallelization. As a test case, we use two different numerical simulation packages, each based on a staggered Cartesian grid: FDM3D (Weiss, 2006) which solves the curl-curl equation directly in terms of the scattered electric field (available under the LGPL at www.openem.org); and APHID, the A-Phi Decomposition based on mixed vector and scalar potentials, in which the curl-curl operator is replaced operationally by the vector Laplacian. We describe progress made in modifying the code to
A fast Poisson solver for unsteady incompressible Navier-Stokes equations on the half-staggered grid
NASA Technical Reports Server (NTRS)
Golub, G. H.; Huang, L. C.; Simon, H.; Tang, W. -P.
1995-01-01
In this paper, a fast Poisson solver for unsteady, incompressible Navier-Stokes equations with finite difference methods on the non-uniform, half-staggered grid is presented. To achieve this, new algorithms for diagonalizing a semi-definite pair are developed. Our fast solver can also be extended to the three dimensional case. The motivation and related issues in using this second kind of staggered grid are also discussed. Numerical testing has indicated the effectiveness of this algorithm.
Odd-even staggering of heavy cluster spontaneous emission rates
NASA Astrophysics Data System (ADS)
Poenaru, D. N.; Greiner, W.; Ivaşcu, M.; Mazilu, D.; Plonski, I. H.
1986-12-01
Experimentally observed enhanced14C and24Ne emission rates from even-even parents in comparison with that from even-odd or odd-even nuclei are explained in the framework of the analytical superasymmetric fission model, by taking various prescriptions for the zero point vibration energy of even-even, even-odd, odd-even and odd-odd emitters. Longer half-lives than previously computed are obtained by extrapolating the present prescriptions to emitted clusters heavier than24Ne.
Novel integrated CMOS pixel structures for vertex detectors
Kleinfelder, Stuart; Bieser, Fred; Chen, Yandong; Gareus, Robin; Matis, Howard S.; Oldenburg, Markus; Retiere, Fabrice; Ritter, Hans Georg; Wieman, Howard H.; Yamamoto, Eugene
2003-10-29
Novel CMOS active pixel structures for vertex detector applications have been designed and tested. The overriding goal of this work is to increase the signal to noise ratio of the sensors and readout circuits. A large-area native epitaxial silicon photogate was designed with the aim of increasing the charge collected per struck pixel and to reduce charge diffusion to neighboring pixels. The photogate then transfers the charge to a low capacitance readout node to maintain a high charge to voltage conversion gain. Two techniques for noise reduction are also presented. The first is a per-pixel kT/C noise reduction circuit that produces results similar to traditional correlated double sampling (CDS). It has the advantage of requiring only one read, as compared to two for CDS, and no external storage or subtraction is needed. The technique reduced input-referred temporal noise by a factor of 2.5, to 12.8 e{sup -}. Finally, a column-level active reset technique is explored that suppresses kT/C noise during pixel reset. In tests, noise was reduced by a factor of 7.6 times, to an estimated 5.1 e{sup -} input-referred noise. The technique also dramatically reduces fixed pattern (pedestal) noise, by up to a factor of 21 in our tests. The latter feature may possibly reduce pixel-by-pixel pedestal differences to levels low enough to permit sparse data scan without per-pixel offset corrections.
Capacitively coupled hybrid pixel assemblies for the CLIC vertex detector
NASA Astrophysics Data System (ADS)
Tehrani, N. Alipour; Arfaoui, S.; Benoit, M.; Dannheim, D.; Dette, K.; Hynds, D.; Kulis, S.; Perić, I.; Petrič, M.; Redford, S.; Sicking, E.; Valerio, P.
2016-07-01
The vertex detector at the proposed CLIC multi-TeV linear e+e- collider must have minimal material content and high spatial resolution, combined with accurate time-stamping to cope with the expected high rate of beam-induced backgrounds. One of the options being considered is the use of active sensors implemented in a commercial high-voltage CMOS process, capacitively coupled to hybrid pixel ASICs. A prototype of such an assembly, using two custom designed chips (CCPDv3 as active sensor glued to a CLICpix readout chip), has been characterised both in the lab and in beam tests at the CERN SPS using 120 GeV/c positively charged hadrons. Results of these characterisation studies are presented both for single and dual amplification stages in the active sensor, where efficiencies of greater than 99% have been achieved at -60 V substrate bias, with a single hit resolution of 6.1 μm . Pixel cross-coupling results are also presented, showing the sensitivity to placement precision and planarity of the glue layer.
Fast unmixing of multispectral optoacoustic data with vertex component analysis
NASA Astrophysics Data System (ADS)
Luís Deán-Ben, X.; Deliolanis, Nikolaos C.; Ntziachristos, Vasilis; Razansky, Daniel
2014-07-01
Multispectral optoacoustic tomography enhances the performance of single-wavelength imaging in terms of sensitivity and selectivity in the measurement of the biodistribution of specific chromophores, thus enabling functional and molecular imaging applications. Spectral unmixing algorithms are used to decompose multi-spectral optoacoustic data into a set of images representing distribution of each individual chromophoric component while the particular algorithm employed determines the sensitivity and speed of data visualization. Here we suggest using vertex component analysis (VCA), a method with demonstrated good performance in hyperspectral imaging, as a fast blind unmixing algorithm for multispectral optoacoustic tomography. The performance of the method is subsequently compared with a previously reported blind unmixing procedure in optoacoustic tomography based on a combination of principal component analysis (PCA) and independent component analysis (ICA). As in most practical cases the absorption spectrum of the imaged chromophores and contrast agents are known or can be determined using e.g. a spectrophotometer, we further investigate the so-called semi-blind approach, in which the a priori known spectral profiles are included in a modified version of the algorithm termed constrained VCA. The performance of this approach is also analysed in numerical simulations and experimental measurements. It has been determined that, while the standard version of the VCA algorithm can attain similar sensitivity to the PCA-ICA approach and have a robust and faster performance, using the a priori measured spectral information within the constrained VCA does not generally render improvements in detection sensitivity in experimental optoacoustic measurements.
CDF Run IIb Silicon Vertex Detector DAQ Upgrade
S. Behari et al.
2003-12-18
The CDF particle detector operates in the beamline of the Tevatron proton-antiproton collider at Fermilab, Batavia, IL. The Tevatron is expected to undergo luminosity upgrades (Run IIb) in the future, resulting in a higher number of interactions per beam crossing. To operate in this dense radiation environment, an upgrade of CDF's silicon vertex detector (SVX) subsystem and a corresponding upgrade of its VME-based DAQ system has been explored. Prototypes of all the Run IIb SVX DAQ components have been constructed, assembled into a test stand and operated successfully using an adapted version of CDF's network-capable DAQ software. In addition, a PCI-based DAQ system has been developed as a fast and inexpensive tool for silicon detector and DAQ component testing in the production phase. In this paper they present an overview of the Run IIb silicon DAQ upgrade, emphasizing the new features and improvements incorporated into the constituent VME boards, and discuss a PCI-based DAQ system developed to facilitate production tests.
From vertex detectors to inner trackers with CMOS pixel sensors
NASA Astrophysics Data System (ADS)
Besson, A.; Pérez, A. Pérez; Spiriti, E.; Baudot, J.; Claus, G.; Goffe, M.; Winter, M.
2017-02-01
The use of CMOS Pixel Sensors (CPS) for high resolution and low material vertex detectors has been validated with the 2014 and 2015 physics runs of the STAR-PXL detector at RHIC/BNL. This opens the door to the use of CPS for inner tracking devices, with 10-100 times larger sensitive area, which require therefore a sensor design privileging power saving, response uniformity and robustness. The 350 nm CMOS technology used for the STAR-PXL sensors was considered as too poorly suited to upcoming applications like the upgraded ALICE Inner Tracking System (ITS), which requires sensors with one order of magnitude improvement on readout speed and improved radiation tolerance. This triggered the exploration of a deeper sub-micron CMOS technology, Tower-Jazz 180 nm, for the design of a CPS well adapted for the new ALICE-ITS running conditions. This paper reports the R & D results for the conception of a CPS well adapted for the ALICE-ITS.
Spectral flow for an integrable staggered superspin chain
NASA Astrophysics Data System (ADS)
Frahm, Holger; Hobuß, Konstantin
2017-07-01
The flow of the low energy eigenstates of a U_q[sl(2\\vert 1)] superspin chain with alternating fundamental (3) and dual (\\bar{3} ) representations is studied as function of a twist angle determining the boundary conditions. The finite size spectrum is characterized in terms of scaling dimensions and quasi momenta representing the two families of commuting transfer matrices for the model which are even and odd under the interchange 3≤ftrightarrow \\bar{3} , respectively. Based on the extrapolation of our finite size data we find that under a variation of the boundary conditions from periodic to antiperiodic for the fermionic degrees of freedom levels from the continuous part of the spectrum flow into discrete levels and vice versa.
G-equivariant {phi}-coordinated quasi modules for quantum vertex algebras
Li, Haisheng
2013-05-15
This is a paper in a series to study quantum vertex algebras and their relations with various quantum algebras. In this paper, we introduce a notion of T-type quantum vertex algebra and a notion of G-equivariant {phi}-coordinated quasi module for a T-type quantum vertex algebra with an automorphism group G. We refine and extend several previous results and we obtain a commutator formula for G-equivariant {phi}-coordinated quasi modules. As an illustrating example, we study a special case of the deformed Virasoro algebra Vir{sub p,q} with q=-1, to which we associate a Clifford vertex superalgebra and its G-equivariant {phi}-coordinated quasi modules.
Quantifying array losses due to spacing and staggering in offshore wind farms (Invited)
NASA Astrophysics Data System (ADS)
Archer, C. L.; Mirzaeisefat, S.; Lee, S.; Xie, S.
2013-12-01
The layout of wind turbines can have an impact on the power production of a wind farm. Design variables that define the layout of wind turbines within a wind farm include: orientation of the rows with respect to the prevailing wind direction, size and shape of the wind farm, spacing between turbines, and alignment of the turbines (i.e., whether in-line or staggered with one another). There are no universal layout recommendations for offshore wind farms, partly because isolating the contribution of each individual design variable is impossible at existing offshore wind farms, where multiple effects overlap non-linearly on one another, and partly because analyzing the sensitivity to design variables requires sophisticated and computer-intensive numerical codes, such as large-eddy simulations (LES), that can simulate the small-scale turbulent features of turbine wakes. The National Renewable Energy Laboratory (NREL) developed the only publicly available and open-source LES code that is capable of resolving wind turbine blades as rotating actuator lines (not fixed disks), includes both neutral and unstable atmospheric conditions (stable case is currently under development), and does not rely on periodic boundary conditions. This code, named Simulator for Offshore/Onshore Wind Farm Applications (SOWFA), is based on OpenFOAM and has been used successfully in the past for turbulent wake simulations. Here we address the issue of quantifying two design variables: turbine spacing (both along and across the prevailing wind direction) and alignment (in-line or staggered for consecutive rows). SOWFA is used to simulate an existing offshore wind farm in Lillgrund (Sweden), consisting of 48 Siemens 2.3 MW turbines with spacing of 3.2D across and 4.3D along the prevailing wind direction and without staggering, where D is the turbine diameter (93 m). This spacing is exceptionally tight, to our knowledge the tightest of all modern wind farms. While keeping the area and the shape of
Quantifying array losses due to spacing and staggering in offshore wind farms (Invited)
NASA Astrophysics Data System (ADS)
Archer, C. L.; Mirzaeisefat, S.; Lee, S.; Xie, S.
2011-12-01
The layout of wind turbines can have an impact on the power production of a wind farm. Design variables that define the layout of wind turbines within a wind farm include: orientation of the rows with respect to the prevailing wind direction, size and shape of the wind farm, spacing between turbines, and alignment of the turbines (i.e., whether in-line or staggered with one another). There are no universal layout recommendations for offshore wind farms, partly because isolating the contribution of each individual design variable is impossible at existing offshore wind farms, where multiple effects overlap non-linearly on one another, and partly because analyzing the sensitivity to design variables requires sophisticated and computer-intensive numerical codes, such as large-eddy simulations (LES), that can simulate the small-scale turbulent features of turbine wakes. The National Renewable Energy Laboratory (NREL) developed the only publicly available and open-source LES code that is capable of resolving wind turbine blades as rotating actuator lines (not fixed disks), includes both neutral and unstable atmospheric conditions (stable case is currently under development), and does not rely on periodic boundary conditions. This code, named Simulator for Offshore/Onshore Wind Farm Applications (SOWFA), is based on OpenFOAM and has been used successfully in the past for turbulent wake simulations. Here we address the issue of quantifying two design variables: turbine spacing (both along and across the prevailing wind direction) and alignment (in-line or staggered for consecutive rows). SOWFA is used to simulate an existing offshore wind farm in Lillgrund (Sweden), consisting of 48 Siemens 2.3 MW turbines with spacing of 3.2D across and 4.3D along the prevailing wind direction and without staggering, where D is the turbine diameter (93 m). This spacing is exceptionally tight, to our knowledge the tightest of all modern wind farms. While keeping the area and the shape of
NASA Astrophysics Data System (ADS)
Xu, Min; He, Kang-Lin; Zhang, Zi-Ping; Wang, Yi-Fang; Bian, Jian-Ming; Cao, Guo-Fu; Cao, Xue-Xiang; Chen, Shen-Jian; Deng, Zi-Yan; Fu, Cheng-Dong; Gao, Yuan-Ning; Han, Lei; Han, Shao-Qing; He, Miao; Hu, Ji-Feng; Hu, Xiao-Wei; Huang, Bin; Huang, Xing-Tao; Jia, Lu-Kui; Ji, Xiao-Bin; Li, Hai-Bo; Li, Wei-Dong; Liang, Yu-Tie; Liu, Chun-Xiu; Liu, Huai-Min; Liu, Ying; Liu, Yong; Luo, Tao; Lü, Qi-Wen; Ma, Qiu-Mei; Ma, Xiang; Mao, Ya-Jun; Mao, Ze-Pu; Mo, Xiao-Hu; Ning, Fei-Peng; Ping, Rong-Gang; Qiu, Jin-Fa; Song, Wen-Bo; Sun, Sheng-Sen; Sun, Xiao-Dong; Sun, Yong-Zhao; Tian, Hao-Lai; Wang, Ji-Ke; Wang, Liang-Liang; Wen, Shuo-Pin; Wu, Ling-Hui; Wu, Zhi; Xie, Yu-Guang; Yan, Jie; Yan, Liang; Yao, Jian; Yuan, Chang-Zheng; Yuan, Ye; Zhang, Chang-Chun; Zhang, Jian-Yong; Zhang, Lei; Zhang, Xue-Yao; Zhang, Yao; Zheng, Yang-Heng; Zhu, Yong-Sheng; Zou, Jia-Heng
2009-06-01
This paper focuses mainly on the vertex reconstruction of resonance particles with a relatively long lifetime such as K0S, Λ, as well as on lifetime measurements using a 3-dimensional fit. The kinematic constraints between the production and decay vertices and the decay vertex fitting algorithm based on the least squares method are both presented. Reconstruction efficiencies including experimental resolutions are discussed. The results and systematic errors are calculated based on a Monte Carlo simulation.
Vertex evoked potentials in a rating-scale detection task - Relation to signal probability
NASA Technical Reports Server (NTRS)
Squires, K. C.; Squires, N. K.; Hillyard, S. A.
1975-01-01
Results of vertex-evoked potential studies conducted to determine how decision confidence level and decision probability interact to determine P3 amplitude for both signal-present and signal-absent decisions. They support the contention that the form of the vertex-evoked response is closely correlated with the subject's psychophysical response regarding the presence or absence of a threshold-level signal.
Big subsets with small boundaries in a graph with a vertex-transitive group of automorphisms
NASA Astrophysics Data System (ADS)
Seifter, N.; Trofimov, V. I.
2017-02-01
The theory of ends of finitely generated groups G and connected locally finite graphs Γ with vertex- transitive groups of automorphisms can be regarded as a theory of Boolean algebras of subsets of G or vertex set of Γ with finite boundaries (in the locally finite Cayley graph of G or in Γ respectively), considered modulo finite subsets. We develop a more general theory where infinite subsets with finite boundaries are replaced by certain `big' subsets with `small' boundaries.
NASA Astrophysics Data System (ADS)
Gornushkin, Yu. A.; Dmitrievsky, S. G.; Chukanov, A. V.
2015-01-01
The OPERA experiment is designed for the direct observation of the appearance of ντ from νμ → ντ oscillation in a νμ beam. A description of the procedure of neutrino interaction vertex localization (Brick Finding) by electronic detectors of a hybrid OPERA setup is presented. The procedure includes muon track and hadronic shower axis reconstruction and a determination of the target bricks with the highest probability to contain the vertex.
Hubble Space Telescope secondary mirror vertex radius/conic constant test
NASA Technical Reports Server (NTRS)
Parks, Robert
1991-01-01
The Hubble Space Telescope backup secondary mirror was tested to determine the vertex radius and conic constant. Three completely independent tests (to the same procedure) were performed. Similar measurements in the three tests were highly consistent. The values obtained for the vertex radius and conic constant were the nominal design values within the error bars associated with the tests. Visual examination of the interferometric data did not show any measurable zonal figure error in the secondary mirror.
Non-Abelian Ball-Chiu vertex for arbitrary Euclidean momenta
NASA Astrophysics Data System (ADS)
Aguilar, A. C.; Cardona, J. C.; Ferreira, M. N.; Papavassiliou, J.
2017-07-01
We determine the non-Abelian version of the four nontransverse form factors of the quark-gluon vertex, using exact expressions derived from the Slavnov-Taylor identity that this vertex satisfies. In addition to the quark and ghost propagators, a key ingredient of the present approach is the quark-ghost scattering kernel, which is computed within the one-loop dressed approximation. The vertex form factors obtained from this procedure are evaluated for arbitrary Euclidean momenta, and display features not captured by the well-known Ball-Chiu vertex, deduced from the Abelian (ghost-free) Ward identity. Particularly interesting in this analysis is the so-called soft-gluon limit, which, unlike other kinematic configurations considered, is especially sensitive to the approximations employed for the vertex entering in the quark-ghost scattering kernel, and may even be affected by a subtle numerical instability. As an elementary application of the results obtained, we evaluate and compare certain renormalization-point-independent combinations, which contribute to the interaction kernels appearing in the standard quark gap and Bethe-Salpeter equations. In doing so, even though all form factors of the quark-gluon vertex, and in particular the transverse ones which are unconstrained by our procedure, enter nontrivially in the aforementioned kernels, only the contribution of a single form factor, corresponding to the classical (tree-level) tensor, will be considered.
Constructing scalar-photon three point vertex in massless quenched scalar QED
NASA Astrophysics Data System (ADS)
Fernández-Rangel, L. Albino; Bashir, Adnan; Gutiérrez-Guerrero, L. X.; Concha-Sánchez, Y.
2016-03-01
Nonperturbative studies of Schwinger-Dyson equations require their infinite, coupled tower to be truncated in order to reduce them to a practically solvable set. In this connection, a physically acceptable Ansatz for the three point vertex is the most favorite choice. Scalar quantum electrodynamics (sQED) provides a simple and neat platform to address this problem. The most general form of the three point scalar-photon vertex can be expressed in terms of only two independent form factors, a longitudinal and a transverse one. Ball and Chiu have demonstrated that the longitudinal vertex is fixed by requiring the Ward-Fradkin-Green-Takahashi identity while the transverse vertex remains undetermined. In massless quenched sQED, we construct the transverse part of the nonperturbative scalar-photon vertex. This construction (i) ensures multiplicative renormalizability of the scalar propagator in keeping with the Landau-Khalatnikov-Fradkin transformations, (ii) has the same transformation properties as the bare vertex under charge conjugation, parity and time reversal, (iii) has no kinematic singularities and (iv) reproduces the one-loop asymptotic result in the weak coupling regime of the theory.
Retroreflector for GRACE follow-on: Vertex vs. point of minimal coupling.
Schütze, Daniel; Müller, Vitali; Stede, Gunnar; Sheard, Benjamin S; Heinzel, Gerhard; Danzmann, Karsten; Sutton, Andrew J; Shaddock, Daniel A
2014-04-21
The GRACE Follow-On mission will monitor fluctuations in Earth's geoid using, for the first time, a Laser Ranging Interferometer to measure intersatellite distance changes. We have investigated the coupling between spacecraft rotation and the intersatellite range measurement that is incurred due to manufacturing and assembly tolerances of the Triple Mirror Assembly (TMA), a precision retroreflector to ensure alignment between in- and outgoing laser beams. The three TMA mirror planes intersect in a virtual vertex to which satellite displacements are referenced. TMA manufacturing tolerances degrade this ideal vertex, however, a Point of Minimal Coupling (PMC) between spacecraft rotation and displacement exists. This paper presents the experimental location of the PMC under pitch and yaw rotations for a prototype TMA. Rotations are performed using a hexapod, while displacements are monitored with heterodyne laser interferometry to verify the PMC position. Additionally, the vertex of the three TMA mirror planes is measured using a Coordinate Measuring Machine and compared to the PMC position. In the pitch and yaw axes, the biggest deviation between TMA vertex and PMC was 50 ± 64 μm. Thus, within the measurement uncertainties, no difference between TMA vertex and PMC could be observed. This is a key piece of information for integration of the TMA into the spacecraft: It is sufficient to use the readily-available TMA vertex location to ensure minimal rotation-to-displacement coupling during the mission.
VERTEX: Manganese transport with CaCO 3
NASA Astrophysics Data System (ADS)
Martin, John H.; Knauer, George A.
1983-04-01
Manganese transport was studied off central California in August and September 1981 as part of the VERTEX (Vertica l Transport and Exchange) research program. Refractory, leachable, and dissolved Mn fractions associated with particles caught in traps set at 11 depths (50 to 2000 m) were analyzed. Through intentional and unintentional CaCO 3 dissolution 'experiments', it was learned that the weakly leachable Mn was originally in association with the carbonate phase. Adsorption on surfaces rather than absorption in CaCO 3 matrices was indicated by the finding that Mn was not released in proportion to the CaCo 3 dissolved, instead it appeared to keep readsorbing to the dissolving surface. Ultimately, Mn went into solution when the particulate CaCO 3 was essentially depleted, suggesting that sufficient sites for adsorption were no longer available. Manganese fluxes with CaCO 3 were low near the surface (0.1 mg cm -2 ky -1), but increased rapidly in the 50 to 200-m depth interval, and then became more or less constant (1.3 mg cm -2 ky -1 for the remainder of the water column (300 to 2000 m). Rate-of-change estimates indicate that Mn is rapidly scavenged in near-surface waters (-130 ng 1 -1 y -1) and slowly regenerated at depth (2.7 ng 1 -1 y -1) in our near-shore study area. Residence times for dissolved Mn were estimated at 1.2 y for surface waters and 17 y at depth. The implications of Mn transport with CaCO 3 in relation to open-ocean sediment excess Mn are discussed.
TECHNICAL DESIGN REPORT OF THE FORWARD SILICON VERTEX (FVTX)
PHENIX EXPERIMENT; OBRIEN,E.; PAK, R.; DREES, K.A.
2007-08-01
The main goal of the RHIC heavy ion program is the discovery of the novel ultra-hot high-density state of matter predicted by the fundamental theory of strong interactions and created in collisions of heavy nuclei, the Quark-Gluon Plasma (QGP). From measurements of the large elliptic flow of light mesons and baryons and their large suppression at high transverse momentum pT that have been made at RHIC, there is evidence that new degrees of freedom, characteristic of a deconfined QCD medium, drive the dynamics of nucleus-nucleus collisions. It has been recognized, however, that the potential of light quarks and gluons to characterize the properties of the QGP medium is limited and the next phase of the RHIC program calls for the precise determination of its density, temperature, opacity and viscosity using qualitatively new probes, such as heavy quarks. We propose the construction of two Forward Silicon Vertex Trackers (FVTX) for the PHENIX experiment that will directly identify and distinguish charm and beauty decays within the acceptance of the muon spectrometers. The FVTX will provide this essential coverage over a range of forward and backward rapidities (1.2 < |y| < 2.4)--a rapidity range coverage which not only brings significantly larger acceptance to PHENIX but which is critical for separating cold nuclear matter effects from QGP effects and is critical for measuring the proton spin contributions over a significant fraction of the kinematic range of interest. In addition, the FVTX will provide greatly reduced background and improved mass resolution for dimuon events, culminating in the first measurements of the {upsilon}{prime} and Drell-Yan at RHIC. These same heavy flavor and dimuon measurements in p+p collisions will allow us to place significant constraints on the gluon and sea quark contributions to the proton's spin and to make fundamentally new tests of the Sivers function universality.
2017-09-06
This view from NASA's Cassini spacecraft shows a wave structure in Saturn's rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn's rings are much more tightly wound. In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times. This is the only major density wave visible in Saturn's B ring. Most of the B ring is characterized by structures that dominate the areas where density waves might otherwise occur, but this innermost portion of the B ring is different. The radius from Saturn at which the wave originates (toward lower-right in this image) is 59,796 miles (96,233 kilometers) from the planet. At this location, ring particles orbit Saturn twice for every time the moon Janus orbits once, creating an orbital resonance. The wave propagates outward from the resonance (and away from Saturn), toward upper-left in this view. For reasons researchers do not entirely understand, damping of waves by larger ring structures is very weak at this location, so this wave is seen ringing for hundreds of bright wave crests, unlike density waves in Saturn's A ring. The image gives the illusion that the ring plane is tilted away from the camera toward upper-left, but this is not the case. Because of the mechanics of how this kind of wave propagates, the wavelength decreases with distance from the resonance. Thus, the upper-left of the image is just as close to the camera as the lower-right, while the wavelength of the density wave is simply shorter. This wave is remarkable because Janus, the moon that generates it, is in a strange orbital configuration. Janus and Epimetheus share practically the same orbit and trade places every four years. Every time one of those orbit swaps takes place, the ring at this location responds, spawning a new crest in the wave. The distance between any pair of crests corresponds to four years' worth of the wave propagating downstream from the resonance, which means the wave seen here encodes many decades' worth of the orbital history of Janus and Epimetheus. According to this interpretation, the part of the wave at the very upper-left of this image corresponds to the positions of Janus and Epimetheus around the time of the Voyager flybys in 1980 and 1981, which is the time at which Janus and Epimetheus were first proven to be two distinct objects (they were first observed in 1966). Epimetheus also generates waves at this location, but they are swamped by the waves from Janus, since Janus is the larger of the two moons. This image was taken on June 4, 2017, with the Cassini spacecraft narrow-angle camera. The image was acquired on the sunlit side of the rings from a distance of 47,000 miles (76,000 kilometers) away from the area pictured. The image scale is 1,730 feet (530 meters) per pixel. The phase angle, or sun-ring-spacecraft angle, is 90 degrees. https://photojournal.jpl.nasa.gov/catalog/PIA21627
EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters
Andreyev, Andriy; Sitek, Arkadiusz; Celler, Anna
2014-01-01
Purpose: The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy. Methods: Recently, the authors have proposed a DIPET technique that uses a combination of radiotracer A which is a pure positron emitter (such as 18F or 11C) and radiotracer B in which positron decay is accompanied by the emission of a high-energy (HE) prompt gamma (such as 38K or 60Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines-of-response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM-based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions. Results: The authors’ experiments performed using Monte-Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron-gamma DIPET method or staggered injections alone. Conclusions: The authors demonstrate that the authors’ new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves
Enhanced staggered magnetization probed by NMR in Zn-doped YBCO
NASA Astrophysics Data System (ADS)
Julien, Marc-Henri
2001-03-01
We present NMR measurements in Zn-doped YBCO. The electronic spin polarization of Cu sites is probed through 63Cu NMR spectra, and is found to grow rapidly on cooling, in agreement with previous 63Cu, 89Y and 17O NMR works [1]. This is attributed to staggered magnetic moments induced on many sites around the impurity, presumably including also the first neighbor sites. Hence, the notion of destruction of AF correlations by Zn is not valid, as also shown by the enhanced low temperature/low energy spectral weight at Q=(pi/a,pi/a), detected in inelastic neutron scattering [2] and NMR T1 measurements [3]. In Ref. [3], we have used the expression "enhancement of AF correlations", proposed in another context [4]. Strictly speaking, however, it is the staggered polarization, rather than the strength of AF correlations, which is enhanced with respect to the pure material: Zn only reveals the already-existing AF-correlated Cu2+ moments. Actually, this kind of magnetic response is expected for any kind of local disorder in CuO2 planes. The staggered magnetic moments with spatially distributed amplitude in CuO2 planes (AF-like patches) give rise to a Curie-like contribution in the bulk susceptibility. They may also have an important impact in transport or spectroscopic measurements. [1] R.E. Walstedt et al., PRB 48, 10646 (1993); A.V. Mahajan et al. PRL 72, 3100 (1994); J. Bobroff et al., Physica C 282-287, 139 (1997). [2] Y. Sidis et al., PRB 53, 6811 (1996); P. Bourges et al., Czech. J. Phys 46, 1155 (1996). [3] M.-H. Julien et al., PRL 84, 3422 (2000). [4] G.B. Martins, PRL 78, 3563 (1997).
In vitro efficacy of the successive or staggered use of eardrops.
Kalcioglu, M Tayyar; Ozturan, Orhan; Durmaz, Riza; Aktas, Elif
2006-05-01
Chronic suppurative otitis media is still a significant health problem. Several topical agents such as antibacterials, steroids and acid media eardrops are widely used alone or in combination to control active otorrhea and obtain a dry ear. Patients frequently ask if there is any benefit or loss in the effect of these due to their use in a successive or staggered manner. This question led us to design this in vitro study to investigate the effect of the acetic acid solution and dexamethasone sodium phosphate on the antimicrobial effects of some ototopical antibiotics during their successive or staggered usage. Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis and Escherichia coli were used for testing the antimicrobial activities of the selected antibiotic drops. Six microliters of acetic acid solution and dexamethasone sodium phosphate were used alone or together with 6 microl each of ciprofloxacin HCl, tobramycin and ofloxacin solution. Drops were placed on Whatman no. 1 paper disks with a diameter of 6 mm, and the disks were placed onto Mueller-Hinton agar plates on which bacteria had been swabbed over the entire surface. After overnight incubation of the plates at 35 degrees C, the diameters of the inhibition zones were recorded. There was no antibacterial effect in response to either acid solution or dexamethasone used alone. The inhibition zones of the antibiotics did not change with either steroid or acid media solution added onto the antibiotic disks alone or together. Acid solution or steroids should be preferred to use in combination with antibacterial otic drugs in in-vivo settings; no negative or positive effects were seen in in-vitro conditions. Therefore, prescribed eardrops can be used in a successive or staggered manner without any influence on the treatment results.
Blackburn, R; Osborn, D; Falcaro, M; Nazareth, I; Petersen, I
2017-01-01
Objectives To estimate the ‘real-world effectiveness of statins for primary prevention of cardiovascular disease (CVD) and for lipid modification in people with severe mental illnesses (SMI), including schizophrenia and bipolar disorder. Design Series of staggered cohorts. We estimated the effect of statin prescribing on CVD outcomes using a multivariable Poisson regression model or linear regression for cholesterol outcomes. Setting 587 general practice (GP) surgeries across the UK reporting data to The Health Improvement Network. Participants All permanently registered GP patients aged 40–84 years between 2002 and 2012 who had a diagnosis of SMI. Exclusion criteria were pre-existing CVD, statin-contraindicating conditions or a statin prescription within the 24 months prior to the study start. Exposure One or more statin prescriptions during a 24-month ‘baseline’ period (vs no statin prescription during the same period). Main outcome measures The primary outcome was combined first myocardial infarction and stroke. All-cause mortality and total cholesterol concentration were secondary outcomes. Results We identified 2944 statin users and 42 886 statin non-users across the staggered cohorts. Statin prescribing was not associated with significant reduction in CVD events (incident rate ratio 0.89; 95% CI 0.68 to 1.15) or all-cause mortality (0.89; 95% CI 0.78 to 1.02). Statin prescribing was, however, associated with statistically significant reductions in total cholesterol of 1.2 mmol/L (95% CI 1.1 to 1.3) for up to 2 years after adjusting for differences in baseline characteristics. On average, total cholesterol decreased from 6.3 to 4.6 in statin users and 5.4 to 5.3 mmol/L in non-users. Conclusions We found that statin prescribing to people with SMI in UK primary care was effective for lipid modification but not CVD events. The latter finding may reflect insufficient power to detect a smaller effect size than that observed in randomised
A staggered mesh finite difference scheme for the computation of hypersonic Euler flows
NASA Technical Reports Server (NTRS)
Sanders, Richard
1991-01-01
A shock capturing finite difference method for systems of hyperbolic conservation laws is presented which avoids the need to solve Riemann problems while being competitive in performance with other current methods. A staggered spatial mesh is employed, so that complicated nonlinear waves generated at cell interfaces are averaged over cell interiors at the next time level. The full method combines to form a conservative version of the modified method of characteristics. The advantages of the method are discussed, and numerical results are presented for the two-dimensional double ellipse problem.
A conservative staggered-grid Chebyshev multidomain method for compressible flows
Kopriva, D.A.; Kolias, J.H.
1996-04-01
The authors present a new multidomain spectral collocation method that uses a staggered grid for the solution of compressible flow problems. The solution unknowns are defined at the nodes of a Gauss quadrature rule. The fluxes are evaluated at the nodes of a Gauss-Lobatto rule. The method is conservative, free-stream preserving, and exponentially accurate. A significant advantage of the method is that subdomain corners are not included in the approximation, making solutions in complex geometries easier to compute. 41 refs., 23 figs., 1 tab.
PROPOSAL FOR A SILICON VERTEX TRACKER (VTX) FOR THE PHENIX EXPERIMENT.
AKIBA,Y.
2004-03-30
We propose the construction of a Silicon Vertex Tracker (VTX) for the PHENIX experiment at RHIC. The VTX will substantially enhance the physics capabilities of the PHENIX central arm spectrometers. Our prime motivation is to provide precision measurements of heavy-quark production (charm and beauty) in A+A, p(d)+A, and polarized p+p collisions. These are key measurements for the future RHIC program, both for the heavy ion program as it moves from the discovery phase towards detailed investigation of the properties of the dense nuclear medium created in heavy ion collisions, and for the exploration of the nucleon spin-structure functions. In addition, the VTX will also considerably improve other measurements with PHENIX. The main physics topics addressed by the VTX are: (1) Hot and dense strongly interacting matter--Potential enhancement of charm production; Open beauty production; Flavor dependence of jet quenching and QCD energy loss; Accurate charm reference for quarkonium; Thermal dilepton radiation; High p{sub T} phenomena with light flavors above 10-15 GeV/c in p{sub T}; and Upsilon spectroscopy in the e{sup +}e{sup -} decay channel. (2) Gluon spin structure of the nucleon--{Delta}G/G with charm; {Delta}G/G with beauty; and x dependence of {Delta}G/G with {gamma}-jet correlations. (3) Nucleon structure in nuclei--Gluon shadowing over broad x-range. With the present PHENIX detector, heavy-quark production has been measured indirectly through the observation of single electrons. These measurements are inherently limited in accuracy by systematic uncertainties resulting from the large electron background from Dalitz decays and photon conversions. In particular, the statistical nature of the analysis does not allow for a model-independent separation of the charm and beauty contributions. The VTX detector will provide vertex tracking with a resolution of <50 {micro}m over a large coverage both in rapidity (|{eta}| < 1.2) and in azimuthal angle ({Delta}{phi} {approx
NASA Astrophysics Data System (ADS)
Gómez-Rocha, M.; Hilger, T.; Krassnigg, A.
2016-04-01
We extend earlier investigations of heavy-light pseudoscalar mesons to the vector case, using a simple model in the context of the Dyson-Schwinger-Bethe-Salpeter approach. We investigate the effects of a dressed quark-gluon vertex in a systematic fashion and illustrate and attempt to quantify corrections beyond the phenomenologically very useful and successful rainbow-ladder truncation. In particular we investigate the dressed quark-photon vertex in such a setup and make a prediction for the experimentally as yet unknown mass of the Bc* , which we obtain at 6.334 GeV well in line with predictions from other approaches. Furthermore, we combine a comprehensive set of results from the theoretical literature. The theoretical average for the mass of the Bc* meson is 6.336 ±0.002 GeV .
Vercher-Martínez, Ana; Giner, Eugenio; Arango, Camila; Fuenmayor, F Javier
2015-02-01
In this work, a three-dimensional finite element model of the staggered distribution of the mineral within the mineralized collagen fibril has been developed to characterize the lamellar bone elastic behavior at the sub-micro length scale. Minerals have been assumed to be embedded in a collagen matrix, and different degrees of mineralization have been considered allowing the growth of platelet-shaped minerals both in the axial and the transverse directions of the fibril, through the variation of the lateral space between platelets. We provide numerical values and trends for all the elastic constants of the mineralized collagen fibril as a function of the volume fraction of mineral. In our results, we verify the high influence of the mineral overlapping on the mechanical response of the fibril and we highlight that the lateral distance between crystals is relevant to the mechanical behavior of the fibril and not only the mineral overlapping in the axial direction. Copyright © 2014 Elsevier Ltd. All rights reserved.
Graphical method for deriving an effective interaction with a new vertex function
Suzuki, K.; Okamoto, R.; Kumagai, H.; Fujii, S.
2011-02-15
Introducing a new vertex function, Z(E), of an energy variable E, we derive a new equation for the effective interaction. The equation is obtained by replacing the Q box in the Krenciglowa-Kuo (KK) method with Z(E). This new approach can be viewed as an extension of the KK method. We show that this equation can be solved both in iterative and noniterative ways. We observe that the iteration procedure with Z(E) brings about fast convergence compared to the usual KK method. It is shown that, as in the KK approach, the procedure of calculating the effective interaction can be reduced to determining the true eigenvalues of the original Hamiltonian H and they can be obtained as the positions of intersections of graphs generated from Z(E). We find that this graphical method yields always precise results and reproduces any of the true eigenvalues of H. The calculation in the present approach can be made regardless of overlaps with the model space and energy differences between unperturbed energies and the eigenvalues of H. We find also that Z(E) is a well-behaved function of E and has no singularity. These characteristics of the present approach ensure stability in actual calculations and would be helpful to resolve some difficulties due to the presence of poles in the Q box. Performing test calculations, we verify numerically theoretical predictions made in the present approach.
The beam test measurements of the Belle II vertex detector modules
NASA Astrophysics Data System (ADS)
Bilka, T.
2017-03-01
The Belle II experiment designed to study CP Violation and Beyond Standard model physics at the decays of B-mesons is quickly approaching its first physics run with the SuperKEKB accelerator (Tsukuba, Japan) already under commissioning. To operate in the unique conditions of the Belle II experiment, its vertex detector (VXD) is a six layers silicon detector with two innermost layers of DEPFET active pixel modules and four layers of double-sided strip modules. A section of it will become a commissioning detector for the first collisions of the next-generation high luminosity B-factory. The same setup, from cooling services, mechanical support or sensors and front-end electronics to DAQ, including the software and alignment framework, is tested under an electron beam provided by DESY facilities. We present the basic characteristics of the pixel and strip modules and the setup under test, including software and alignment framework—as close to the final system as possible.
Controllability and observability analysis for vertex domination centrality in directed networks
Wang, Bingbo; Gao, Lin; Gao, Yong; Deng, Yue; Wang, Yu
2014-01-01
Topological centrality is a significant measure for characterising the relative importance of a node in a complex network. For directed networks that model dynamic processes, however, it is of more practical importance to quantify a vertex's ability to dominate (control or observe) the state of other vertices. In this paper, based on the determination of controllable and observable subspaces under the global minimum-cost condition, we introduce a novel direction-specific index, domination centrality, to assess the intervention capabilities of vertices in a directed network. Statistical studies demonstrate that the domination centrality is, to a great extent, encoded by the underlying network's degree distribution and that most network positions through which one can intervene in a system are vertices with high domination centrality rather than network hubs. To analyse the interaction and functional dependence between vertices when they are used to dominate a network, we define the domination similarity and detect significant functional modules in glossary and metabolic networks through clustering analysis. The experimental results provide strong evidence that our indices are effective and practical in accurately depicting the structure of directed networks. PMID:24954137
Controllability and observability analysis for vertex domination centrality in directed networks
NASA Astrophysics Data System (ADS)
Wang, Bingbo; Gao, Lin; Gao, Yong; Deng, Yue; Wang, Yu
2014-06-01
Topological centrality is a significant measure for characterising the relative importance of a node in a complex network. For directed networks that model dynamic processes, however, it is of more practical importance to quantify a vertex's ability to dominate (control or observe) the state of other vertices. In this paper, based on the determination of controllable and observable subspaces under the global minimum-cost condition, we introduce a novel direction-specific index, domination centrality, to assess the intervention capabilities of vertices in a directed network. Statistical studies demonstrate that the domination centrality is, to a great extent, encoded by the underlying network's degree distribution and that most network positions through which one can intervene in a system are vertices with high domination centrality rather than network hubs. To analyse the interaction and functional dependence between vertices when they are used to dominate a network, we define the domination similarity and detect significant functional modules in glossary and metabolic networks through clustering analysis. The experimental results provide strong evidence that our indices are effective and practical in accurately depicting the structure of directed networks.
Design and performance of the SLD Vertex Detector, a 120 Mpixel tracking system
Agnew, G.D.; Cotton, R.; Damerell, C.J.S.
1992-03-01
This paper describes the design, construction, and initial operation of the SLD Vertex Detector, the first device to employ charge coupled devices (CCDs) on a large scale in a high energy physics experiment. The Vertex Detector comprises 480 CCDs, with a total of 120 Mpixels. Each pixel functions as an independent particle detecting element, providing space point measurements of charged particle tracks with a typical precision of 5 {mu}m in each co-ordinate. The CCDs are arranged in four concentric cylinders just outside the beam pipe which surrounds the e{sup +}e{sup {minus}} collision point of the SLAC Linear Collider (SLC). The Vertex Detector is a powerful tool for distinguishing secondary vertex tracks, produced by decay in flight of heavy flavour hadrons or tau leptons, from tracks produced at the primary event vertex. Because the colliding beam environment imposes severe constraints on the design of such a detector, a six year R&D programme was needed to develop solutions to a number of problems. The requirements include a low-mass structure (to minimise multiple scattering) both for mechanical support and to provide signal paths for the CCDS; operation at low temperature with a high degree of mechanical stability; and relatively high speed CCD readout, signal processing, and data sparsification. The lessons learned through the long R&D period should be useful for the construction of large arrays of CCDs or smart pixel devices in the future, in a number of areas of science and technology.
Localization of sleep spindles, k-complexes, and vertex waves with subdural electrodes in children.
Pinto, Anna L R; Fernández, Iván S; Peters, Jurriaan M; Manganaro, Sheryl; Singer, Jedediah M; Vendrame, Martina; Prabhu, Sanjay P; Loddenkemper, Tobias; Kothare, Sanjeev V
2014-08-01
To describe for the first time in children the localization of sleep spindles, K-complexes, and vertex waves using subdural electrodes. We enrolled children who underwent presurgical evaluation of refractory epilepsy with subdural grid electrodes. We analyzed electroencephalogram data from subdural electrodes and simultaneous recording with Cz scalp electrode. Sleep spindles, K-complexes, and vertex waves were identified and localized based on their morphology on the subdural electrodes. Sixteen patients (9 boys; age range, 3-18 years) were enrolled in the study. The inter-rater reliability on identification and localization of maximal amplitude was high with an intraclass correlation coefficient of 0.85 for vertex waves, 0.94 for sleep spindles, and 0.91 for K-complexes. Sleep spindles presented maximum amplitude around the perirolandic area with a field extending to the frontal regions. K-complexes presented maximum amplitude around the perirolandic area with a field extending to the frontal regions. Vertex waves presented maximum amplitude around the perirolandic areas. In our series of pediatric patients, sleep spindles, K-complexes, and vertex waves were localized around the perirolandic area.
Meson-baryon-baryon vertex function and the Ward-Takahashi identity
NASA Astrophysics Data System (ADS)
Wang, Siwen; Banerjee, Manoj K.
1996-12-01
Ohta proposed a solution for the well-known difficulty of satisfying the Ward-Takahashi identity for a photo-meson-baryon-baryon amplitude (γMBB) when a dressed meson-baryon-baryon (MBB) vertex function is present. He obtained a form for the γMBB amplitude which contained, in addition to the usual pole terms, longitudinal seagull terms which were determined entirely by the MBB vertex function. He arrived at his result by using a Lagrangian which yields the MBB vertex function at tree level. We show that such a Lagrangian can be neither Hermitian nor charge conjugation invariant. We have been able to reproduce Ohta's result for the γMBB amplitude using the Ward-Takahashi identity and no other assumption, dynamical or otherwise, and the most general form for the MBB and γMBB vertices. However, contrary to Ohta's finding, we find that the seagull terms are not robust. The seagull terms extracted from the γMBB vertex occur unchanged in tree graphs, such as in an exchange current amplitude. But the seagull terms which appear in a loop graph, as in the calculation of an electromagnetic form factor, are, in general, different. The whole procedure says nothing about the transverse part of the (γMBB) vertex and its contributions to the amplitudes in question.
Meson-baryon-baryon vertex function and the Ward-Takahashi identity
Wang, S.; Banerjee, M.K.
1996-12-01
Ohta proposed a solution for the well-known difficulty of satisfying the Ward-Takahashi identity for a photo-meson-baryon-baryon amplitude ({gamma}MBB) when a dressed meson-baryon-baryon (MBB) vertex function is present. He obtained a form for the {gamma}MBB amplitude which contained, in addition to the usual pole terms, longitudinal seagull terms which were determined entirely by the MBB vertex function. He arrived at his result by using a Lagrangian which yields the MBB vertex function at tree level. We show that such a Lagrangian can be neither Hermitian nor charge conjugation invariant. We have been able to reproduce Ohta{close_quote}s result for the {gamma}MBB amplitude using the Ward-Takahashi identity and no other assumption, dynamical or otherwise, and the most general form for the MBB and {gamma}MBB vertices. However, contrary to Ohta{close_quote}s finding, we find that the seagull terms are not robust. The seagull terms extracted from the {gamma}MBB vertex occur unchanged in tree graphs, such as in an exchange current amplitude. But the seagull terms which appear in a loop graph, as in the calculation of an electromagnetic form factor, are, in general, different. The whole procedure says nothing about the transverse part of the ({gamma}MBB) vertex and its contributions to the amplitudes in question. {copyright} {ital 1996 The American Physical Society.}
Minimum Vertex-type Sequence Indexing for Clusters on Square Lattice.
Liao, Longguang; Zhao, Yu-Jun; Cao, Zexian; Yang, Xiao-Bao
2017-03-24
An effective indexing scheme for clusters that enables fast structure comparison and congruence check is desperately desirable in the field of mathematics, artificial intelligence, materials science, etc. Here we introduce the concept of minimum vertex-type sequence for the indexing of clusters on square lattice, which contains a series of integers each labeling the vertex type of an atom. The minimum vertex-type sequence is orientation independent, and it builds a one-to-one correspondence with the cluster. By using minimum vertex-type sequence for structural comparison and congruence check, only one type of data is involved, and the largest amount of data to be compared is n pairs, n is the cluster size. In comparison with traditional coordinate-based methods and distance-matrix methods, the minimum vertex-type sequence indexing scheme has many other remarkable advantages. Furthermore, this indexing scheme can be easily generalized to clusters on other high-symmetry lattices. Our work can facilitate cluster indexing and searching in various situations, it may inspire the search of other practical indexing schemes for handling clusters of large sizes.
Staggered scheduling of sensor estimation and fusion for tracking over long-haul links
Liu, Qiang; Rao, Nageswara S. V.; Wang, Xin
2016-08-01
Networked sensing can be found in a multitude of real-world applications. Here, we focus on the communication-and computation-constrained long-haul sensor networks, where sensors are remotely deployed over a vast geographical area to perform certain tasks. Of special interest is a class of such networks where sensors take measurements of one or more dynamic targets and send their state estimates to a remote fusion center via long-haul satellite links. The severe loss and delay over such links can easily reduce the amount of sensor data received by the fusion center, thereby limiting the potential information fusion gain and resulting in suboptimal tracking performance. In this paper, starting with the temporal-domain staggered estimation for an individual sensor, we explore the impact of the so-called intra-state prediction and retrodiction on estimation errors. We then investigate the effect of such estimation scheduling across different sensors on the spatial-domain fusion performance, where the sensing time epochs across sensors are scheduled in an asynchronous and staggered manner. In particular, the impact of communication delay and loss as well as sensor bias on such scheduling is explored by means of numerical and simulation studies that demonstrate the validity of our analysis.
A staggered differential phase-shift keying modulation format for 100Gbit/s applications.
Shao, Yufeng; Wen, Shuangchun; Chen, Lin; Li, Ying; Xu, Huiwen
2008-08-18
We propose and demonstrate by numerical simulation a new phase modulation format, the staggered differential phase-shift keying (SDPSK), for 100 Gbit/s applications. Non-return-to-zero (NRZ) SDPSK signals was generated by using two phase modulators, and return-to-zero (RZ) SDPSK signals with 50% duty cycle was generated by cascading a dual-arm Mach-Zehnder modulator. The demodulation of 2 bit/symbol can be simply achieved on 1 bit rate through only one Mach-Zehnder delay interferometer and a balanced receiver. By comparing the transmission characteristics of the two staggered phase modulation formats with those of NRZ-DPSK, RZ-DPSK, NRZ-DQPSK, and RZ-DQPSK, respectively, we show that, the SDPSK signal has similar chromatic dispersion and polarization-mode-dispersion tolerance to the DPSK signal with same NRZ or RZ shape, while the SDPSK signal has stronger nonlinear tolerance than the DPSK or DQPSK signal. In addition, the SDPSK signal has the best transmission performance when each signal was transmitted over 106km optical SMF+DCF, and then launched into a third-order Gaussian optical bandpass filter placed with beyond 125GHz bandwidth.
Computational imaging from non-uniform degradation of staggered TDI thermal infrared imager.
Sun, Tao; Liu, Jian Guo; Shi, Yan; Chen, Wangli; Qin, Qianqing; Zhang, Zijian
2015-09-21
For the Time Delay Integration (TDI) staggered line-scanning thermal infrared imager, a Computational Imaging (CI) approach is developed to achieve higher spatial resolution images. After a thorough analysis of the causes of non-uniform image displacement and degradation for multi-channel staggered TDI arrays, the study aims to approach one-dimensional (1D) sub-pixel displacement estimation and superposition of images from time-division multiplexing scanning lines. Under the assumption that a thermal image is 2D piecewise C(2) smooth, a sparse-and-smooth deconvolution algorithm with L1-norm regularization terms combining the first and second order derivative operators is proposed to restore high frequency components and to suppress aliasing simultaneously. It is theoretically and experimentally demonstrated, with simulation and airborne thermal infrared images, that this is a state-of-the-art practical CI method to reconstruct clear images with higher frequency components from raw thermal images that are subject to instantaneous distortion and blurring.
Heat transfer characteristics of staggered wing-shaped tubes bundle at different angles of attack
NASA Astrophysics Data System (ADS)
Sayed Ahmed, Sayed Ahmed E.; Ibrahiem, Emad Z.; Mesalhy, Osama M.; Abdelatief, Mohamed A.
2014-08-01
An experimental and numerical study has been conducted to clarify heat transfer characteristics and effectiveness of a cross-flow heat exchanger employing staggered wing-shaped tubes at different angels of attack. The water-side Rew and the air-side Rea were at 5 × 102 and at from 1.8 × 103 to 9.7 × 103, respectively. The tubes arrangements were employed with various angles of attack θ1,2,3 from 0° to 330° at the considered Rea range. Correlation of Nu, St, as well as the heat transfer per unit pumping power (ɛ) in terms of Rea and design parameters for the studied bundle were presented. The temperature fields around the staggered wing-shaped tubes bundle were predicted by using commercial CFD FLUENT 6.3.26 software package. Results indicated that the heat transfer increased with the angle of attack in the range from 0° to 45°, while the opposite was true for angles of attack from 135° to 180°. The best thermal performance and hence the efficiency η of studied bundle occurred at the lowest Rea and/or zero angle of attack. Comparisons between the experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.
Test of {Delta}I = 2 staggering in the superdeformed bands of {sup 194}Hg
Kruecken, R.; Deleplanque, M.A.; Hackman, G.
1996-11-01
Superdeformed (SD) states in {sup 194}Hg were populated in {sup 150}Nd({sup 48}Ca,4n) using a 201 MeV {sup 48}Ca beam from the 88- inch cyclotron. A high statistics experiment was done to test for the previously reported evidence for a {Delta}I = 2 staggering in the three SD bands in {sup 194}Hg. The transition energies were determined with a precision of at least 60 eV for most transitions. From this improvement, we cannot confirm evidence for an extended regular {Delta}I = 2 staggering in any of the three SD bands of {sup 194}Hg. However, we observe deviations from a smooth reference in the SD bands 2 and 3 which differ from previous results. Oscillation patterns of the {gamma}-ray energies that can be induced by a simple band crossing or level shift are discussed. Even though such level shifts would explain the observed effects, other experimental signatures, such as a crossing band, are needed to fully understand the results of the present work; no such band was found.
Calculations of separated 3-D flows with a pressure-staggered Navier-Stokes equations solver
NASA Technical Reports Server (NTRS)
Kim, S.-W.
1991-01-01
A Navier-Stokes equations solver based on a pressure correction method with a pressure-staggered mesh and calculations of separated three-dimensional flows are presented. It is shown that the velocity pressure decoupling, which occurs when various pressure correction algorithms are used for pressure-staggered meshes, is caused by the ill-conditioned discrete pressure correction equation. The use of a partial differential equation for the incremental pressure eliminates the velocity pressure decoupling mechanism by itself and yields accurate numerical results. Example flows considered are a three-dimensional lid driven cavity flow and a laminar flow through a 90 degree bend square duct. For the lid driven cavity flow, the present numerical results compare more favorably with the measured data than those obtained using a formally third order accurate quadratic upwind interpolation scheme. For the curved duct flow, the present numerical method yields a grid independent solution with a very small number of grid points. The calculated velocity profiles are in good agreement with the measured data.
Unquenched determination of the kaon parameter B{sub K} from improved staggered fermions
Gamiz, Elvira; Collins, Sara; Davies, Christine T.H.; Lepage, G. Peter; Shigemitsu, Junko; Wingate, Matthew
2006-06-01
The use of improved staggered actions (HYP, Asqtad) has been proved to reduce the scaling corrections that affected previous calculations of B{sub K} with unimproved (standard) staggered fermions in the quenched approximation. This improved behavior allows us to perform a reliable calculation of B{sub K} including quark vacuum polarization effects, using the MILC configurations with n{sub f}=2+1 flavors of sea fermions. We perform such a calculation for a single lattice spacing, a=0.125 fm, and with kaons made up of degenerate quarks with m{sub s}/2. The valence strange quark mass m{sub s} is fixed to its physical value and we use two different values of the light sea quark masses. After a chiral extrapolation of the results to the physical value of the sea quark masses, we find B-circumflex{sub K}=0.83{+-}0.18, where the error is dominated by the uncertainty in the lattice to continuum matching at O({alpha}{sub s}{sup 2}). The matching will need to be improved to get the precision needed to make full use of the experimental data on {epsilon}{sub K} to constrain the unitarity triangle.
Interaction induced staggered spin-orbit order in two-dimensional electron gas
Das, Tanmoy
2012-06-05
Decoupling spin and charge transports in solids is among the many prerequisites for realizing spin electronics, spin caloritronics, and spin-Hall effect. Beyond the conventional method of generating and manipulating spin current via magnetic knob, recent advances have expanded the possibility to optical and electrical method which are controllable both internally and externally. Yet, due to the inevitable presence of charge excitations and electrical polarizibility in these methods, the separation between spin and charge degrees of freedom of electrons remains a challenge. Here we propose and formulate an interaction induced staggered spin-orbit order as a new emergent phase of matter. We show that when some form of inherent spin-splitting via Rashba-type spin-orbit coupling renders two helical Fermi surfaces to become significantly nested, a Fermi surface instability arises. To lift this degeneracy, a spontaneous symmetry breaking spin-orbit density wave develops, causing a surprisingly large quasiparticle gapping with chiral electronic states, with no active charge excitations. Since the staggered spin-orbit order is associated with a condensation energy, quantified by the gap value, destroying such spin-orbit interaction costs sufficiently large perturbation field or temperature or de-phasing time. BiAg2 surface state is shown to be a representative system for realizing such novel spin-orbit interaction with tunable and large strength, and the spin-splitting is decoupled from charge excitations.
NASA Astrophysics Data System (ADS)
Kaus, Boris; Popov, Anton; Püsök, Adina
2014-05-01
In order to solve high-resolution 3D problems in computational geodynamics it is crucial to use multigrid solvers in combination with parallel computers. A number of approaches are currently in use in the community, which can broadly be divided into coupled and decoupled approaches. In the decoupled approach, an algebraic or geometric multigrid method is used as a preconditioner for the velocity equations only while an iterative approach such as Schur complement reduction used to solve the outer velocity-pressure equations. In the coupled approach, on the other hand, a multigrid approach is applied to both the velocity and pressure equations. The coupled multigrid approaches are typically employed in combination with staggered finite difference discretizations, whereas the decoupled approach is the method of choice in many of the existing finite element codes. Yet, it is unclear whether there are differences in speed between the two approaches, and if so, how this depends on the initial guess. Here, we implemented both approaches in combination with a staggered finite difference discretization and test the robustness of the two approaches with respect to large jumps in viscosity contrast, as well as their computational efficiency as a function of the initial guess. Acknowledgements. Funding was provided by the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Grant agreement #258830. Numerical computations have been performed on JUQUEEN of the Jülich high-performance computing center.
Staggered scheduling of sensor estimation and fusion for tracking over long-haul links
Liu, Qiang; Rao, Nageswara S. V.; Wang, Xin
2016-08-01
Networked sensing can be found in a multitude of real-world applications. Here, we focus on the communication-and computation-constrained long-haul sensor networks, where sensors are remotely deployed over a vast geographical area to perform certain tasks. Of special interest is a class of such networks where sensors take measurements of one or more dynamic targets and send their state estimates to a remote fusion center via long-haul satellite links. The severe loss and delay over such links can easily reduce the amount of sensor data received by the fusion center, thereby limiting the potential information fusion gain and resulting in suboptimal tracking performance. In this paper, starting with the temporal-domain staggered estimation for an individual sensor, we explore the impact of the so-called intra-state prediction and retrodiction on estimation errors. We then investigate the effect of such estimation scheduling across different sensors on the spatial-domain fusion performance, where the sensing time epochs across sensors are scheduled in an asynchronous and staggered manner. In particular, the impact of communication delay and loss as well as sensor bias on such scheduling is explored by means of numerical and simulation studies that demonstrate the validity of our analysis.