Complex-time singularity and locality estimates for quantum lattice systems
Bouch, Gabriel
2015-12-15
We present and prove a well-known locality bound for the complex-time dynamics of a general class of one-dimensional quantum spin systems. Then we discuss how one might hope to extend this same procedure to higher dimensions using ideas related to the Eden growth process and lattice trees. Finally, we demonstrate with a specific family of lattice trees in the plane why this approach breaks down in dimensions greater than one and prove that there exist interactions for which the complex-time dynamics blows-up in finite imaginary time. .
Complex-time singularity and locality estimates for quantum lattice systems
NASA Astrophysics Data System (ADS)
Bouch, Gabriel
2015-12-01
We present and prove a well-known locality bound for the complex-time dynamics of a general class of one-dimensional quantum spin systems. Then we discuss how one might hope to extend this same procedure to higher dimensions using ideas related to the Eden growth process and lattice trees. Finally, we demonstrate with a specific family of lattice trees in the plane why this approach breaks down in dimensions greater than one and prove that there exist interactions for which the complex-time dynamics blows-up in finite imaginary time.
Localization of Waves in Merged Lattices.
Alagappan, G; Png, C E
2016-01-01
This article describes a new two-dimensional physical topology-merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two-dimensional scattering "beats" which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its' quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications. PMID:27535096
Localization of Waves in Merged Lattices
Alagappan, G.; Png, C. E.
2016-01-01
This article describes a new two–dimensional physical topology–merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two–dimensional scattering “beats” which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its’ quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications. PMID:27535096
Localization of Waves in Merged Lattices
NASA Astrophysics Data System (ADS)
Alagappan, G.; Png, C. E.
2016-08-01
This article describes a new two-dimensional physical topology-merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two-dimensional scattering “beats” which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its’ quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications.
Localization of Waves in Merged Lattices.
Alagappan, G; Png, C E
2016-08-18
This article describes a new two-dimensional physical topology-merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two-dimensional scattering "beats" which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its' quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications.
Localized structures in Kagome lattices
Saxena, Avadh B; Bishop, Alan R; Law, K J H; Kevrekidis, P G
2009-01-01
We investigate the existence and stability of gap vortices and multi-pole gap solitons in a Kagome lattice with a defocusing nonlinearity both in a discrete case and in a continuum one with periodic external modulation. In particular, predictions are made based on expansion around a simple and analytically tractable anti-continuum (zero coupling) limit. These predictions are then confirmed for a continuum model of an optically-induced Kagome lattice in a photorefractive crystal obtained by a continuous transformation of a honeycomb lattice.
NASA Astrophysics Data System (ADS)
Wang, Zhi-Gang; Suqing, Duan; Zhao, Xian-Geng
2006-04-01
The quasi-energy spectrum of two charged particles in a one-dimensional lattice system driven by an external field are theoretically studied with the help of numerical calculations. It is found that the quasi-energy spectrum splits into two regions. In the gourd-shaped region the Floquet states mainly contain the Wannier states |l,m> (l≠m), which describe the two particles occupy the different sites. The (avoid) crossing points in this region are corresponding to the dynamical localizations of the two particles which initially occupy on different sites when the distance between the initial sites is large. These conditions of dynamical localization are the same as that in single particle system. In the other region (electron electron or electron hole pair region), the Floquet states mainly contain the Wannier states |l,l>, which describe the two particles simultaneously occupy the lth site. The (avoid) crossing points in this region are corresponding to the dynamical localizations of the two particles happening which initially occupy on same site.
A measure of localization properties of one-dimensional single electron lattice systems
NASA Astrophysics Data System (ADS)
Gong, Longyan; Li, Wenjia; Zhao, Shengmei; Cheng, Weiwen
2016-01-01
We propose a novel quantity to measure the degree of localization properties of various types of one-dimension single electron states. The quantity includes information about the spatial variation of probability density of quantum states. Numerical results show that it can distinguish localized states from delocalized ones, so it can be used as a fruitful index to monitor the localization-delocalization transition. Comparing with existing measures, such as geometric average density of states, inverse participation ratio, and quantum information entropies, our proposed quantity has some advantages over them.
Local Scale Transformations on the Lattice with Tensor Network Renormalization.
Evenbly, G; Vidal, G
2016-01-29
Consider the partition function of a classical system in two spatial dimensions, or the Euclidean path integral of a quantum system in two space-time dimensions, both on a lattice. We show that the tensor network renormalization algorithm [G. Evenbly and G. Vidal Phys. Rev. Lett. 115, 180405 (2015)] can be used to implement local scale transformations on these objects, namely, a lattice version of conformal maps. Specifically, we explain how to implement the lattice equivalent of the logarithmic conformal map that transforms the Euclidean plane into a cylinder. As an application, and with the 2D critical Ising model as a concrete example, we use this map to build a lattice version of the scaling operators of the underlying conformal field theory, from which one can extract their scaling dimensions and operator product expansion coefficients.
Local Scale Transformations on the Lattice with Tensor Network Renormalization
NASA Astrophysics Data System (ADS)
Evenbly, G.; Vidal, G.
2016-01-01
Consider the partition function of a classical system in two spatial dimensions, or the Euclidean path integral of a quantum system in two space-time dimensions, both on a lattice. We show that the tensor network renormalization algorithm [G. Evenbly and G. Vidal Phys. Rev. Lett. 115, 180405 (2015)] can be used to implement local scale transformations on these objects, namely, a lattice version of conformal maps. Specifically, we explain how to implement the lattice equivalent of the logarithmic conformal map that transforms the Euclidean plane into a cylinder. As an application, and with the 2D critical Ising model as a concrete example, we use this map to build a lattice version of the scaling operators of the underlying conformal field theory, from which one can extract their scaling dimensions and operator product expansion coefficients.
Localization in momentum space of ultracold atoms in incommensurate lattices
Larcher, M.; Dalfovo, F.; Modugno, M.
2011-01-15
We characterize the disorder-induced localization in momentum space for ultracold atoms in one-dimensional incommensurate lattices, according to the dual Aubry-Andre model. For low disorder the system is localized in momentum space, and the momentum distribution exhibits time-periodic oscillations of the relative intensity of its components. The behavior of these oscillations is explained by means of a simple three-mode approximation. We predict their frequency and visibility by using typical parameters of feasible experiments. Above the transition the system diffuses in momentum space, and the oscillations vanish when averaged over different realizations, offering a clear signature of the transition.
Diffusion and transport in locally disordered driven lattices
NASA Astrophysics Data System (ADS)
Wulf, Thomas; Okupnik, Alexander; Schmelcher, Peter
2016-09-01
We study the effect of disorder on the particle density evolution in a classical Hamiltonian driven lattice setup. If the disorder is localized within a finite sub-domain of the lattice, the emergence of strong tails in the density distribution which even increases towards larger positions is shown, thus yielding a highly non-Gaussian particle density evolution. As the key underlying mechanism, we identify the conversion between different components of the unperturbed systems mixed phase space which is induced by the disorder. Based on the introduction of individual conversion rates between chaotic and regular components, a theoretical model is developed which correctly predicts the scaling of the particle density. The effect of disorder on the transport properties is studied where a significant enhancement of the transport for cases of localized disorder is shown, thereby contrasting strongly the merely weak modification of the transport for global disorder.
Nuclear magnetic resonance in Kondo lattice systems.
Curro, Nicholas J
2016-06-01
Nuclear magnetic resonance has emerged as a vital tool to explore the fundamental physics of Kondo lattice systems. Because nuclear spins experience two different hyperfine couplings to the itinerant conduction electrons and to the local f moments, the Knight shift can probe multiple types of spin correlations that are not accessible via other techniques. The Knight shift provides direct information about the onset of heavy electron coherence and the emergence of the heavy electron fluid.
Intrinsic Localized Modes in Optical Photonic Lattices and Arrays
NASA Astrophysics Data System (ADS)
Christodoulides, Demetrios
Discretizing light behavior requires optical elements that can confine optical energy at distinct sites. One possible scenario in implementing such arrangements is to store energy within low loss high Q-microcavities and then allow photon exchange between such components in time. This scheme requires high-contrast dielectric elements that became available with the advent of photonic crystal technologies. Another possible avenue where such light discretization can be directly observed and studied is that based on evanescently coupled waveguide arrays. As indicated in several studies, discrete systems open up whole new directions in terms of modifying light transport properties. One such example is that of discrete solitons. By nature, discrete solitons represent self-trapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of self-localized states has been successfully observed in both one- and two-dimensional nonlinear waveguide arrays. In recent years such photonic lattices have been implemented or induced in a variety of material systems, including those with cubic (Kerr), quadratic, photorefractive, and liquid-crystal nonlinearities. In all cases the underlying periodicity or discreteness can lead to new families of optical solitons that have no counterpart whatsoever in continuous systems. Interestingly, these results paved the way for observations in other physical systems obeying similar evolution equations like Bose-Einstein condensates. New developments in laser writing ultrashort femtosecond laser pulses, now allow the realization of all-optical switching networks in fully 3D environments using nonlinear discrete optics. Using this approach all-optical routing can be achieved using blocking operations. The spatio-temporal evolution of optical pulses in both normally and anomalously dispersive arrays can lead to novel schemes for mode
Anderson localization in optical lattices with speckle disorder
Sucu, Serpil; Aktas, Saban; Okan, S. Erol; Akdeniz, Zehra; Vignolo, Patrizia
2011-12-15
We study the localization properties of noninteracting waves propagating in a speckle-like potential superposed on a one-dimensional lattice. Using a combined decimation-renormalization procedure, we estimate the localization length for a tight-binding Hamiltonian where site energies are square-sinc-correlated random variables. By decreasing the width of the correlation function, the disorder patterns approach a {delta}-correlated disorder, and the localization length becomes almost energy independent in the strong disorder limit. We show that this regime can be reached for a size of the speckle grains on the order of (lower than) four lattice steps.
LocalMove: computing on-lattice fits for biopolymers
Ponty, Y.; Istrate, R.; Porcelli, E.; Clote, P.
2008-01-01
Given an input Protein Data Bank file (PDB) for a protein or RNA molecule, LocalMove is a web server that determines an on-lattice representation for the input biomolecule. The web server implements a Markov Chain Monte-Carlo algorithm with simulated annealing to compute an approximate fit for either the coarse-grain model or backbone model on either the cubic or face-centered cubic lattice. LocalMove returns a PDB file as output, as well as dynamic movie of 3D images of intermediate conformations during the computation. The LocalMove server is publicly available at http://bioinformatics.bc.edu/clotelab/localmove/. PMID:18556754
Local theorems in strengthened form for lattice random variables.
NASA Technical Reports Server (NTRS)
Mason, J. D.
1971-01-01
Investigation of some conditions which are sufficient for a sequence of independent integral-valued lattice random variables to satisfy a local theorem in strengthened form. A number of theorems giving the conditions under which the investigated sequence satisfies a local theorem in strengthened form are proven with the aid of lemmas derived by Kruglov (1968).
Dynamic localization of light in squeezed-like photonic lattices
NASA Astrophysics Data System (ADS)
Nezhad, M. Khazaei; Golshani, M.; Mahdavi, S. M.; Bahrampour, A. R.; Langari, A.
2016-05-01
We investigate the dynamic localization of light in the sinusoidal bent squeezed-like photonic lattices, a class of inhomogeneous semi-infinite waveguide arrays. Our findings show that, dynamic localization takes place for the normalized amplitude of sinusoidal profile (α) above a critical value αc. In this regime, for any normalized amplitude α >αc, there is a specific spatial period (ℓ) of waveguides, in which the dynamical oscillation, with the same spatial period occurs. Moreover, the specific spatial period is a decreasing function of the normalized amplitude α. Accordingly, the dynamical oscillation and self-imaging is realized, in spite of the existence of inhomogeneous coupling coefficients and semi-infinite nature of the squeezed-like photonic lattices. In addition, a comparison between the dynamic localization and Bloch oscillation in squeezed-like photonic lattices reveals that for the same values of α (>αc), the variation in the width and the mean center of the Bloch oscillation profile are less than the corresponding values of the dynamic localization. Also, we propose the experimental conditions to observation of dynamic localization in squeezed photonic lattices.
The Chroma Software System for Lattice QCD
Robert Edwards; Balint Joo
2004-06-01
We describe aspects of the Chroma software system for lattice QCD calculations. Chroma is an open source C++ based software system developed using the software infrastructure of the US SciDAC initiative. Chroma interfaces with output from the BAGEL assembly generator for optimized lattice fermion kernels on some architectures. It can be run on workstations, clusters and the QCDOC supercomputer.
Quasilocal charges in integrable lattice systems
NASA Astrophysics Data System (ADS)
Ilievski, Enej; Medenjak, Marko; Prosen, Tomaž; Zadnik, Lenart
2016-06-01
We review recent progress in understanding the notion of locality in integrable quantum lattice systems. The central concept concerns the so-called quasilocal conserved quantities, which go beyond the standard perception of locality. Two systematic procedures to rigorously construct families of quasilocal conserved operators based on quantum transfer matrices are outlined, specializing on anisotropic Heisenberg XXZ spin-1/2 chain. Quasilocal conserved operators stem from two distinct classes of representations of the auxiliary space algebra, comprised of unitary (compact) representations, which can be naturally linked to the fusion algebra and quasiparticle content of the model, and non-unitary (non-compact) representations giving rise to charges, manifestly orthogonal to the unitary ones. Various condensed matter applications in which quasilocal conservation laws play an essential role are presented, with special emphasis on their implications for anomalous transport properties (finite Drude weight) and relaxation to non-thermal steady states in the quantum quench scenario.
Local theorems for nonidentically distributed lattice random variables.
NASA Technical Reports Server (NTRS)
Mason, J. D.
1972-01-01
Derivation of local limit theorems for a sequence X sub n of independent integral-valued lattice random variables involving only a finite number of distinct nondegenerate distributions. Given appropriate sequences A sub n and B sub n of constants such that 1/B sub n (X sub 1 +
Local second-order boundary methods for lattice Boltzmann models
Ginzbourg, I.; d`Humieres, D.
1996-09-01
A new way to implement solid obstacles in lattice Boltzmann models is presented. The unknown populations at the boundary nodes are derived from the locally known populations with the help of a second-order Chapman-Enskog expansion and Dirichlet boundary conditions with a given momentum. Steady flows near a flat wall, arbitrarily inclined with respect to the lattice links, are then obtained with a third-order error. In particular, Couette and Poiseuille flows are exactly recovered without the Knudsen layers produced for inclined walls by the bounce back condition.
A lattice controller for telerobotic systems
NASA Technical Reports Server (NTRS)
Sliwa, Nancy Orlando; Soloway, Donald
1987-01-01
A model for a lattice control structure for telerobotic systems (Critter) has been developed and prototyped. The Critter hierarchical lattice structure, node potentiation, and weighted feedback are described, and the implementation of the Critter model on a VAX architecture is addressed with regard to node processes, lattice structure, node potentiation, and network activation. The implementation environment is considered and the Critter model attributes which are desirable in a telerobotic system are discussed. Future research directions on the use of this concept for telerobotic control are examined.
Quantum projectors and local operators in lattice integrable models
NASA Astrophysics Data System (ADS)
Oota, Takeshi
2004-01-01
In the framework of the quantum inverse scattering method, we consider a problem of constructing local operators for one-dimensional quantum integrable models, especially for the lattice versions of the nonlinear Schrödinger and sine-Gordon models. We show that a certain class of local operators can be constructed from the matrix elements of the monodromy matrix in a simple way. They are closely related to the quantum projectors and have nice commutation relations with half of the matrix elements of the elementary monodromy matrix. The form factors of these operators can be calculated by using the standard algebraic Bethe ansatz techniques.
Locally resonant band gaps in periodic beam lattices by tuning connectivity
NASA Astrophysics Data System (ADS)
Wang, Pai; Casadei, Filippo; Kang, Sung Hoon; Bertoldi, Katia
2015-01-01
Lattice structures have long fascinated physicists and engineers not only because of their outstanding functionalities, but also for their ability to control the propagation of elastic waves. While the study of the relation between the connectivity of these systems and their static properties has a long history that goes back to Maxwell, rules that connect the dynamic response to the network topology have not been established. Here, we demonstrate that by tuning the average connectivity of a beam network (z ¯), locally resonant band gaps can be generated in the structures without embedding additional resonating units. In particular, a critical threshold for z ¯ is identified, far from which the band gap size is purely dictated by the global lattice topology. By contrast, near this critical value, the detailed local geometry of the lattice also has strong effects. Moreover, in stark contrast to the static case, we find that the nature of the joints is irrelevant to the dynamic response of the lattices. Our results not only shed new light on the rich dynamic properties of periodic lattices, but also outline a new strategy to manipulate mechanical waves in elastic systems.
Optical spectrum and local lattice structure for ruby
NASA Astrophysics Data System (ADS)
Wang, H.; Kuang, X.-Y.; Mao, A.-J.; Huang, X.-F.
2007-01-01
By diagonalizing the 120×120 complete energy matrices for d3 ion in trigonal crystal field, which contains the electrostatic interaction, the trigonal field as well as the spin-orbit interaction, the unified calculation of the whole optical and EPR spectra for ruby are made. And matrix elements of the Zeeman energy with the magnetic field parallel or perpendicular to the trigonal axis are introduced into the complete energy matrices for obtaining the g factors of the energy levels. It is concluded that zero-field splitting and optical spectra as well as g factors are in good agreement with the experimental data and the distorted local lattice structure is determined firstly results from a stretching of the O2- ions along the C3 axis. The pressure-induced shifts of energy levels, g factors and local lattice structure are also discussed. In particular, all the calculations are carried out successfully within the framework of the crystal-field model which is consistent with the opinion of Macfarlane and Sturge that if all terms within the d3 configuration are included, one need not go outside conventional crystal-field theory.
NASA Astrophysics Data System (ADS)
Vettchinkina, V.; Kartsev, A.; Karlsson, D.; Verdozzi, C.
2013-03-01
We investigate the static and dynamical behavior of one-dimensional interacting fermions in disordered Hubbard chains contacted to semi-infinite leads. The chains are described via the repulsive Anderson-Hubbard Hamiltonian, using static and time-dependent lattice density-functional theory. The dynamical behavior of our quantum transport system is studied using an integration scheme available in the literature, which we modify via the recursive Lanczos method to increase its efficiency. To quantify the degree of localization due to disorder and interactions, we adapt the definition of the inverse participation ratio to obtain an indicator which is suitable for quantum transport geometries and can be obtained within density-functional theory. Lattice density-functional theories are reviewed and, for contacted chains, we analyze the merits and limits of the coherent-potential approximation in describing the spectral properties, with interactions included via lattice density-functional theory. Our approach appears to be able to capture complex features due to the competition between disorder and interactions. Specifically, we find a dynamical enhancement of delocalization in the presence of a finite bias and an increase of the steady-state current induced by interparticle interactions. This behavior is corroborated by results for the time-dependent densities and for the inverse participation ratio. Using short isolated chains with interaction and disorder, a brief comparative analysis between time-dependent density-functional theory and exact results is then given, followed by general concluding remarks.
Magnetizm Localization and Hole Localization in Fermionic Atoms Loaded on Optical Lattice
NASA Astrophysics Data System (ADS)
Okumura, Masahiko; Yamada, Susumu; Taniguchi, Nobuhiko; Machida, Masahiko
2009-03-01
In order to study an interplay of disorder, correlation, and spin imbalance on antiferromagnetism, we systematically explore the ground state of one-dimensional spin-imbalanced Fermionic atoms loaded on an optical lattice by using the density-matrix renormalization group method [1]. We find that disorders localize the antiferromagnetic spin density wave induced by imbalanced fermions and the increase of the disorder magnitude shrinks the areas of the localized antiferromagnetized regions. Moreover, the antiferromagnetism finally disappears above a large disorder. We also study hole doped cases [2]. Concentrating on the doped-hole density profile, we find in a large U/t regime that the clean system exhibits a simple fluid-like behavior whereas finite disorders create locally Mott regions which expand their area with increasing the disorder strength contrary to the conventional sense. References [1] M. Okumura, S. Yamada, N. Taniguchi, and M. Machida, arXiv:0810:3953. [2] M. Okumura, S. Yamada, N. Taniguchi, and M. Machida, Phys. Rev. Lett. 101 016407 (2008).
Transport and Anderson localization in disordered two-dimensional photonic lattices.
Schwartz, Tal; Bartal, Guy; Fishman, Shmuel; Segev, Mordechai
2007-03-01
One of the most interesting phenomena in solid-state physics is Anderson localization, which predicts that an electron may become immobile when placed in a disordered lattice. The origin of localization is interference between multiple scatterings of the electron by random defects in the potential, altering the eigenmodes from being extended (Bloch waves) to exponentially localized. As a result, the material is transformed from a conductor to an insulator. Anderson's work dates back to 1958, yet strong localization has never been observed in atomic crystals, because localization occurs only if the potential (the periodic lattice and the fluctuations superimposed on it) is time-independent. However, in atomic crystals important deviations from the Anderson model always occur, because of thermally excited phonons and electron-electron interactions. Realizing that Anderson localization is a wave phenomenon relying on interference, these concepts were extended to optics. Indeed, both weak and strong localization effects were experimentally demonstrated, traditionally by studying the transmission properties of randomly distributed optical scatterers (typically suspensions or powders of dielectric materials). However, in these studies the potential was fully random, rather than being 'frozen' fluctuations on a periodic potential, as the Anderson model assumes. Here we report the experimental observation of Anderson localization in a perturbed periodic potential: the transverse localization of light caused by random fluctuations on a two-dimensional photonic lattice. We demonstrate how ballistic transport becomes diffusive in the presence of disorder, and that crossover to Anderson localization occurs at a higher level of disorder. Finally, we study how nonlinearities affect Anderson localization. As Anderson localization is a universal phenomenon, the ideas presented here could also be implemented in other systems (for example, matter waves), thereby making it feasible
Multi-hadron systems in lattice QCD
Will Detmold
2009-07-01
Lattice QCD is currently entering the stage when it can usefully be applied to systems of multiple hadrons. I briefly review the status of recent calculations of scattering parameters in the two hadron sector and discuss recent calculations of systems composed of many mesons or baryons. In the mesonic case, the NPLQCD collaboration has continued its study of systems of up to twelve pions or kaons and have computed the effect of such a hadronic medium on the static quark potential. High statistics calculations on anisotropic lattices have allowed for precision extraction of the energies and scattering phase shifts of various two baryon systems and, for the first time, the energies of certain three baryon systems have been computed.
Longhi, Stefano; Dreisow, Felix; Heinrich, Matthias; Pertsch, Thomas; Tuennermann, Andreas; Nolte, Stefan; Szameit, Alexander
2010-11-15
Polychromatic dynamic localization in tight-binding lattices with long-range interaction is theoretically proposed and experimentally demonstrated in curved-waveguide photonic lattices. Efficient suppression of discrete diffraction over the whole white-light spectral region (450-750 nm) has been demonstrated in femtosecond-laser-written triangular-waveguide lattices with first- and second-order coupling.
Anderson localization in optical lattices with correlated disorder
NASA Astrophysics Data System (ADS)
Fratini, E.; Pilati, S.
2015-12-01
We study the Anderson localization of atomic gases exposed to simple-cubic optical lattices with a superimposed disordered speckle pattern. The two mobility edges in the first band and the corresponding critical filling factors are determined as a function of the disorder strength, ranging from vanishing disorder up to the critical disorder intensity where the two mobility edges merge and the whole band becomes localized. Our theoretical analysis is based both on continuous-space models that take into account the details of the spatial correlation of the speckle pattern, and also on a simplified tight-binding model with an uncorrelated distribution of the on-site energies. The mobility edges are computed via the analysis of the energy-level statistics, and we determine the universal value of the ratio between consecutive level spacings at the mobility edge. We analyze the role of the spatial correlation of the disorder, and we also discuss a qualitative comparison with available experimental data for interacting atomic Fermi gases obtained in the moderate interaction regime.
An off-lattice, self-learning kinetic Monte Carlo method using local environments
NASA Astrophysics Data System (ADS)
Konwar, Dhrubajit; Bhute, Vijesh J.; Chatterjee, Abhijit
2011-11-01
We present a method called local environment kinetic Monte Carlo (LE-KMC) method for efficiently performing off-lattice, self-learning kinetic Monte Carlo (KMC) simulations of activated processes in material systems. Like other off-lattice KMC schemes, new atomic processes can be found on-the-fly in LE-KMC. However, a unique feature of LE-KMC is that as long as the assumption that all processes and rates depend only on the local environment is satisfied, LE-KMC provides a general algorithm for (i) unambiguously describing a process in terms of its local atomic environments, (ii) storing new processes and environments in a catalog for later use with standard KMC, and (iii) updating the system based on the local information once a process has been selected for a KMC move. Search, classification, storage and retrieval steps needed while employing local environments and processes in the LE-KMC method are discussed. The advantages and computational cost of LE-KMC are discussed. We assess the performance of the LE-KMC algorithm by considering test systems involving diffusion in a submonolayer Ag and Ag-Cu alloy films on Ag(001) surface.
Exposing local symmetries in distorted driven lattices via time-averaged invariants
NASA Astrophysics Data System (ADS)
Wulf, T.; Morfonios, C. V.; Diakonos, F. K.; Schmelcher, P.
2016-05-01
Time-averaged two-point currents are derived and shown to be spatially invariant within domains of local translation or inversion symmetry for arbitrary time-periodic quantum systems in one dimension. These currents are shown to provide a valuable tool for detecting deformations of a spatial symmetry in static and driven lattices. In the static case the invariance of the two-point currents is related to the presence of time-reversal invariance and/or probability current conservation. The obtained insights into the wave functions are further exploited for a symmetry-based convergence check which is applicable for globally broken but locally retained potential symmetries.
On the Locality and Scaling of Overlap Fermions at Coarse Lattice Spacings
Terrence Draper; Nilmani Mathur; Jianbo Zhang; Andrei Alexandru; Ying Chen; Shao-Jing Dong; Ivan Horvath; Frank X. Lee; Keh-Fei Liu; Sonali Tamhankar
2006-11-07
The overlap fermion offers the considerable advantage of exact chiral symmetry on the lattice, but is numerically intensive. This can be made affordable while still providing large lattice volumes, by using coarse lattice spacing, given that good scaling and localization properties are established. Here, using overlap fermions on quenched Iwasaki gauge configurations, we demonstrate directly that, with appropriate choice of negative Wilson's mass, the overlap Dirac operator's range is comfortably small in lattice units for each of the lattice spacings 0.20 fm, 0.17 fm, and 0.13 fm (and scales to zero in physical units in the continuum limit). In particular, our direct results contradict recent speculation that an inverse lattice spacing of 1 GeV is too low to have satisfactory localization. Furthermore, hadronic masses (available on the two coarser lattices) scale very well.
Localization of two-component Bose-Einstein condensates in optical lattices.
Ostrovskaya, Elena A; Kivshar, Yuri S
2004-05-01
We study nonlinear localization of a two-component Bose-Einstein condensate (BEC) in a one-dimensional optical lattice. Our theory shows that spin-dependent optical lattices can be used to effectively manipulate the nonlinear interactions between the BEC components, and to observe composite localized states of a BEC in both bands and gaps of the matter-wave spectrum.
Nonlinear localized modes in dipolar Bose-Einstein condensates in two-dimensional optical lattices
NASA Astrophysics Data System (ADS)
Rojas-Rojas, Santiago; Naether, Uta; Delgado, Aldo; Vicencio, Rodrigo A.
2016-09-01
We analyze the existence and properties of discrete localized excitations in a Bose-Einstein condensate loaded into a periodic two-dimensional optical lattice, when a dipolar interaction between atoms is present. The dependence of the Number of Atoms (Norm) on the energy of solutions is studied, along with their stability. Two important features of the system are shown, namely, the absence of the Norm threshold required for localized solutions to exist in finite 2D systems, and the existence of regions in the parameter space where two fundamental solutions are simultaneously unstable. This feature enables mobility of localized solutions, which is an uncommon feature in 2D discrete nonlinear systems. With attractive dipolar interaction, a non-trivial behavior of the Norm dependence is obtained, which is well described by an analytical model.
Exact Relaxation in a Class of Nonequilibrium Quantum Lattice Systems
Cramer, M.; Eisert, J.; Dawson, C. M.; Osborne, T. J.
2008-01-25
A reasonable physical intuition in the study of interacting quantum systems says that, independent of the initial state, the system will tend to equilibrate. In this work we introduce an experimentally accessible setting where relaxation to a steady state is exact, namely, for the Bose-Hubbard model quenched from a Mott quantum phase to the free strong superfluid regime. We rigorously prove that the evolving state locally relaxes to a steady state with maximum entropy constrained by second moments--thus maximizing the entanglement. Remarkably, for this to be true, no time average is necessary. Our argument includes a central limit theorem and exploits the finite speed of information transfer. We also show that for all periodic initial configurations (charge density waves) the system relaxes locally, and identify experimentally accessible signatures in optical lattices as well as implications for the foundations of statistical mechanics.
Observation of localized flat-band states in Kagome photonic lattices.
Zong, Yuanyuan; Xia, Shiqiang; Tang, Liqin; Song, Daohong; Hu, Yi; Pei, Yumiao; Su, Jing; Li, Yigang; Chen, Zhigang
2016-04-18
We report the first experimental demonstration of localized flat-band states in optically induced Kagome photonic lattices. Such lattices exhibit a unique band structure with the lowest band being completely flat (diffractionless) in the tight-binding approximation. By taking the advantage of linear superposition of the flat-band eigenmodes of the Kagome lattices, we demonstrate a high-fidelity transmission of complex patterns in such two-dimensional pyrochlore-like photonic structures. Our numerical simulations find good agreement with experimental observations, upholding the belief that flat-band lattices can support distortion-free image transmission.
Archer, Charles Jens; Musselman, Roy Glenn; Peters, Amanda; Pinnow, Kurt Walter; Swartz, Brent Allen; Wallenfelt, Brian Paul
2010-03-16
A massively parallel computer system contains an inter-nodal communications network of node-to-node links. Each node implements a respective routing strategy for routing data through the network, the routing strategies not necessarily being the same in every node. The routing strategies implemented in the nodes are dynamically adjusted during application execution to shift network workload as required. Preferably, adjustment of routing policies in selective nodes is performed at synchronization points. The network may be dynamically monitored, and routing strategies adjusted according to detected network conditions.
Composite boson mapping for lattice boson systems.
Huerga, Daniel; Dukelsky, Jorge; Scuseria, Gustavo E
2013-07-26
We present a canonical mapping transforming physical boson operators into quadratic products of cluster composite bosons that preserves matrix elements of operators when a physical constraint is enforced. We map the 2D lattice Bose-Hubbard Hamiltonian into 2×2 composite bosons and solve it within a generalized Hartree-Bogoliubov approximation. The resulting Mott insulator-superfluid phase diagram reproduces well quantum Monte Carlo results. The Higgs boson behavior in the superfluid phase along the unit density line is unraveled and in remarkable agreement with experiments. Results for the properties of the ground and excited states are competitive with other state-of-the-art approaches, but at a fraction of their computational cost. The composite boson mapping here introduced can be readily applied to frustrated many-body systems where most methodologies face significant hurdles. PMID:23931383
Lattice Induced Resonances in One Dimensional Bosonic Systems
NASA Astrophysics Data System (ADS)
von Stecher, Javier; Gurarie, Victor; Radzihovsky, Leo; Rey, Ana Maria
2011-05-01
Feshbach resonances and optical lattices offer a unique opportunity for achieving new ways to control and explore novel many-body phenomena in strongly correlated atomic systems. To deal with such complex systems a natural prerequisite is a full understanding of the underlying two-body physics. Here, we investigate the lattice induced resonances produced when dimers formed with atoms in excited bands become resonant with the atoms in the lowest band. We first obtain accurate two-body solutions and demonstrate that the resonant effects depend strongly on the parity properties of the dimer. Then, we develop a novel two-channel effective lattice Hamiltonian with a parity dependent atom-dimer coupling that provides a starting point to analyze the many-body behavior of the resonant lattice system. We conclude that the lattice induced resonances significantly affect the behavior of the atoms in the lowest band and can be used to tune lattice systems to novel many-body regimes.
Transverse localization of light in nonlinear photonic lattices with dimensionality crossover
Jovic, Dragana M.; Belic, Milivoj R.; Denz, Cornelia
2011-10-15
In a numerical study, we demonstrate the dimensionality crossover in Anderson localization of light. We consider crossover from the two-dimensional (2D) to the one-dimensional (1D) lattice, optically induced in both linear and nonlinear dielectric media. The joint influence of nonlinearity and disorder on Anderson localization in such systems is discussed in some detail. We find that, in the linear regime, the localization is more pronounced in two dimensions than in one dimension. We also find that the localization in the intermediate cases of crossover is less pronounced than in both the pure 1D and 2D cases in the linear regime, whereas in the nonlinear regime this depends on the strength of the nonlinearity. There exist strongly nonlinear regimes in which 1D localization is more pronounced than the 2D localization, opposite to the case of the linear regime. We find that the dimensionality crossover is characterized by two different localization lengths, whose behavior is different along different transverse directions.
NASA Astrophysics Data System (ADS)
Charukhchyan, M. V.; Sedov, E. S.; Arakelian, S. M.; Alodjants, A. P.
2014-06-01
We consider the problem of formation of small-amplitude spatially localized oscillatory structures for atomic Bose-Einstein condensates confined in two- and three-dimensional optical lattices, respectively. Our approach is based on applying the regions with different signs of atomic effective masses where an atomic system exhibits effective hyperbolic dispersion within the first Brillouin zone. By using the kp method we have demonstrated mapping of the initial Gross-Pitaevskii equation on nonlinear Klein-Gordon and/or Ginzburg-Landau-Higgs equations, which is inherent in matter fields within ϕ4-field theories. Formation of breatherlike oscillating localized states—atomic oscillons—as well as kink-shaped states have been predicted in this case. Apart from classical field theories atomic field oscillons occurring in finite lattice structures possess a critical number of particles for their formation. The obtained results pave the way to simulating some analogues of fundamental cosmological processes occurring during our Universe's evolution and to modeling nonlinear hyperbolic metamaterials with condensed matter (atomic) systems.
Forcherio, Gregory T; Blake, Phillip; DeJarnette, Drew; Roper, D Keith
2014-07-28
Lattices of plasmonic nanorings with particular geometries exhibit singular, tunable resonance features in the infrared. This work examined effects of nanoring inner radius, wall thickness, and lattice constant on the spectral response of single nanorings and in Fano resonant square lattices, combining use of the discrete and coupled dipole approximations. Increasing nanoring inner radius red-shifted and broadened the localized surface plasmon resonance (LSPR), while wall thickness modulated the LSPR wavelength and decreased absorption relative to scattering. The square lattice constant was tuned to observe diffractively-coupled lattice resonances, which increased resonant extinction 4.3-fold over the single-ring LSPR through Fano resonance. Refractive index sensitivities of 760 and 1075 nm RIU(-1) were computed for the plasmon and lattice resonances of an optimized nanoring lattice. Sensitivity of an optimal nanoring lattice to a local change in dielectric, useful for sensing applications, was 4 to 5 times higher than for isolated nanorings or non-coupling arrays. This was attributable to the Fano line-shape in far-field diffractive coupling with near-field LSPR.
Observation of many-body localization of interacting fermions in a quasirandom optical lattice
NASA Astrophysics Data System (ADS)
Schreiber, Michael; Hodgman, Sean S.; Bordia, Pranjal; Lüschen, Henrik P.; Fischer, Mark H.; Vosk, Ronen; Altman, Ehud; Schneider, Ulrich; Bloch, Immanuel
2015-08-01
Many-body localization (MBL), the disorder-induced localization of interacting particles, signals a breakdown of conventional thermodynamics because MBL systems do not thermalize and show nonergodic time evolution. We experimentally observed this nonergodic evolution for interacting fermions in a one-dimensional quasirandom optical lattice and identified the MBL transition through the relaxation dynamics of an initially prepared charge density wave. For sufficiently weak disorder, the time evolution appears ergodic and thermalizing, erasing all initial ordering, whereas above a critical disorder strength, a substantial portion of the initial ordering persists. The critical disorder value shows a distinctive dependence on the interaction strength, which is in agreement with numerical simulations. Our experiment paves the way to further detailed studies of MBL, such as in noncorrelated disorder or higher dimensions.
Magnetic Nano-skyrmion Lattice Observed in a Si-Wafer-Based Multilayer System.
Schlenhoff, Anika; Lindner, Philipp; Friedlein, Johannes; Krause, Stefan; Wiesendanger, Roland; Weinl, Michael; Schreck, Matthias; Albrecht, Manfred
2015-06-23
Growth, electronic properties, and magnetic properties of an Fe monolayer (ML) on an Ir/YSZ/Si(111) multilayer system have been studied using spin-polarized scanning tunneling microscopy. Our experiments reveal a magnetic nano-skyrmion lattice, which is fully equivalent to the magnetic ground state that has previously been observed for the Fe ML on Ir(111) bulk single crystals. In addition, the experiments indicate that the interface-stabilized skyrmion lattice is robust against local atomic lattice distortions induced by multilayer preparation.
Roles of lattice cooling on local heating in metal-molecule-metal junctions
NASA Astrophysics Data System (ADS)
Tsutsui, Makusu; Taniguchi, Masateru; Yokota, Kazumichi; Kawai, Tomoji
2010-03-01
We report a quantitative assessment of the efficacy of lattice cooling on mitigating local heating in a current-carrying single molecule wire connected to gold nanoelectrodes by comparative analyses of high-field effective temperatures at different ambient temperatures. We find substantial local heating in benzenedithiol single molecule junctions raising the local temperatures by ˜320 K from the ambient to ˜400 K at 0.85 V. The intense self-heating are attributable to decreased thermal conductance at low temperatures that leads to deteriorated heat transfer at metal-molecule contacts, thereby manifesting a critical role of lattice cooling for alleviating metal-molecule-metal junction overheating.
Pinned modes in two-dimensional lossy lattices with local gain and nonlinearity.
Ding, Edwin; Tang, A Y S; Chow, K W; Malomed, Boris A
2014-10-28
We introduce a system with one or two amplified nonlinear sites ('hot spots', HSs) embedded into a two-dimensional linear lossy lattice. The system describes an array of evanescently coupled optical or plasmonic waveguides, with gain applied to selected HS cores. The subject of the analysis is discrete solitons pinned to the HSs. The shape of the localized modes is found in quasi-analytical and numerical forms, using a truncated lattice for the analytical consideration. Stability eigenvalues are computed numerically, and the results are supplemented by direct numerical simulations. In the case of self-focusing nonlinearity, the modes pinned to a single HS are stable and unstable when the nonlinearity includes the cubic loss and gain, respectively. If the nonlinearity is self-defocusing, the unsaturated cubic gain acting at the HS supports stable modes in a small parametric area, whereas weak cubic loss gives rise to a bistability of the discrete solitons. Symmetric and antisymmetric modes pinned to a symmetric set of two HSs are also considered.
Dynamic behavior of multirobot systems using lattice gas automata
NASA Astrophysics Data System (ADS)
Stantz, Keith M.; Cameron, Stewart M.; Robinett, Rush D., III; Trahan, Michael W.; Wagner, John S.
1999-07-01
Recent attention has been given to the deployment of an adaptable sensor array realized by multi-robotic systems (or swarms). Our group has been studying the collective, autonomous behavior of these such systems and their applications in the area of remote-sensing and emerging threats. To accomplish such tasks, an interdisciplinary research effort at Sandia National Laboratories are conducting tests in the fields of sensor technology, robotics, and multi- agents architectures. Our goal is to coordinate a constellation of point sensors using unmanned robotic vehicles (e.g., RATLERs, Robotic All-Terrain Lunar Exploration Rover- class vehicles) that optimizes spatial coverage and multivariate signal analysis. An overall design methodology evolves complex collective behaviors realized through local interaction (kinetic) physics and artificial intelligence. Learning objectives incorporate real-time operational responses to environmental changes. This paper focuses on our recent work understanding the dynamics of many-body systems according to the physics-based hydrodynamic model of lattice gas automata. Three design features are investigated. One, for single-speed robots, a hexagonal nearest-neighbor interaction topology is necessary to preserve standard hydrodynamic flow. Two, adaptability, defined by the swarm's rate of deformation, can be controlled through the hydrodynamic viscosity term, which, in turn, is defined by the local robotic interaction rules. Three, due to the inherent nonlinearity of the dynamical equations describing large ensembles, stability criteria ensuring convergence to equilibrium states is developed by scaling information flow rates relative to a swarm's hydrodynamic flow rate. An initial test case simulates a swarm of twenty-five robots maneuvering past an obstacle while following a moving target. A genetic algorithm optimizes applied nearest-neighbor forces in each of five spatial regions distributed over the simulation domain. Armed with
Local non-Calderbank-Shor-Steane quantum error-correcting code on a three-dimensional lattice
NASA Astrophysics Data System (ADS)
Kim, Isaac H.
2011-05-01
We present a family of non-Calderbank-Shor-Steane quantum error-correcting code consisting of geometrically local stabilizer generators on a 3D lattice. We study the Hamiltonian constructed from ferromagnetic interaction of overcomplete set of local stabilizer generators. The degenerate ground state of the system is characterized by a quantum error-correcting code whose number of encoded qubits are equal to the second Betti number of the manifold. These models (i) have solely local interactions; (ii) admit a strong-weak duality relation with an Ising model on a dual lattice; (iii) have topological order in the ground state, some of which survive at finite temperature; and (iv) behave as classical memory at finite temperature.
Controlling spin-dependent localization and directed transport in a bipartite lattice
NASA Astrophysics Data System (ADS)
Luo, Yunrong; Lu, Gengbiao; Kong, Chao; Hai, Wenhua
2016-04-01
We study coherent control of spin-dependent dynamical localization (DL) and directed transport (DT) of a spin-orbit-coupled single atom held in a driven optical bipartite lattice. Under the high-frequency limit and nearest-neighbor tight-binding approximation, we find a new decoupling mechanism between states with the same (different) spins, which leads to two sets of analytical solutions describing DL and DT with (without) spin flipping. The analytical results are numerically confirmed, and perfect agreements are found. Extending the research to a system of spin-orbit-coupled single atoms, the spin current and quantum information transport with controllable propagation speed and distance are investigated. The results can be experimentally tested in the current setups and may be useful in quantum information processing.
NASA Astrophysics Data System (ADS)
Ying, Guanwen; Kouzaev, Guennadi
2016-10-01
We present the eigenmodal analysis techniques enhanced towards calculations of optical and non-interacting Bose-Einstein condensate (BEC) modes formed by random potentials and localized by Anderson effect. The results are compared with the published measurements and verified additionally by the convergence criterion. In 2-D BECs captured in circular areas, the randomness shows edge localization of the high-order Tamm-modes. To avoid strong diffusive effect, which is typical for BECs trapped by speckle potentials, a 3-D-lattice potential with increased step magnitudes is proposed, and the BECs in these lattices are simulated and plotted.
Lee, Young Ki; Ahn, Kyung Hyun; Lee, Seung Jong
2014-12-01
The local shear stress of non-Brownian suspensions was investigated using the lattice Boltzmann method coupled with the smoothed profile method. Previous studies have only focused on the bulk rheology of complex fluids because the local rheology of complex fluids was not accessible due to technical limitations. In this study, the local shear stress of two-dimensional solid particle suspensions in Couette flow was investigated with the method of planes to correlate non-Newtonian fluid behavior with the structural evolution of concentrated particle suspensions. Shear thickening was successfully captured for highly concentrated suspensions at high particle Reynolds number, and both the local rheology and local structure of the suspensions were analyzed. It was also found that the linear correlation between the local particle stress and local particle volume fraction was dramatically reduced during shear thickening. These results clearly show how the change in local structure of suspensions influences the local and bulk rheology of the suspensions. PMID:25615103
NASA Astrophysics Data System (ADS)
Wang, Da-Wei; Liu, Ren-Bao; Zhu, Shi-Yao; Scully, Marlan O.
2015-01-01
We show that the timed Dicke states of a collection of three-level atoms can form a tight-binding lattice in momentum space. This lattice, coined the superradiance lattice (SL), can be constructed based on electromagnetically induced transparency (EIT). For a one-dimensional SL, we need the coupling field of the EIT system to be a standing wave. The detuning between the two components of the standing wave introduces an effective uniform force in momentum space. The quantum lattice dynamics, such as Bloch oscillations, Wannier-Stark ladders, Bloch band collapsing, and dynamic localization can be observed in the SL. The two-dimensional SL provides a flexible platform for Dirac physics in graphene. The SL can be extended to three and higher dimensions where no analogous real space lattices exist with new physics waiting to be explored.
Local configuration measures for categorical spatial data: binary regular lattices
NASA Astrophysics Data System (ADS)
Boots, Barry
2006-03-01
This paper examines the utility of a number of pattern measures for local exploratory analysis of binary spatial data. Based on a review of existing pattern measures in cartography, geography, image analysis, and landscape ecology, two fundamental classes of such measures, termed compositional and configurational, are identified. The paper focuses on configurational measures and it is suggested that as many as five such measures (join counts, patch numbers, patch sizes, patch proximity, and distribution of the classes relative to the focal cell of the window) are required to differentiate between all possible local categorical maps. This suggestion is explored by examining aspects of the statistical behaviour (probability distributions and correlations between extreme values of pairs of measures) of a set of 12 configurational measures. Their use is also demonstrated by means of an empirical example.
Cuevas, F.A.; Curilef, S.; Plastino, A.R.
2011-10-15
The spread of a wave-packet (or its deformation) is a very important topic in quantum mechanics. Understanding this phenomenon is relevant in connection with the study of diverse physical systems. In this paper we apply various 'spreading measures' to characterize the evolution of an initially localized wave-packet in a tight-binding lattice, with special emphasis on information-theoretical measures. We investigate the behavior of both the probability distribution associated with the wave packet and the concomitant probability current. Complexity measures based upon Renyi entropies appear to be particularly good descriptors of the details of the delocalization process. - Highlights: > Spread of highly localized wave-packet in the tight-binding lattice. > Entropic and information-theoretical characterization is used to understand the delocalization. > The behavior of both the probability distribution and the concomitant probability current is investigated. > Renyi entropies appear to be good descriptors of the details of the delocalization process.
Superfluid qubit systems with ring shaped optical lattices.
Amico, Luigi; Aghamalyan, Davit; Auksztol, Filip; Crepaz, Herbert; Dumke, Rainer; Kwek, Leong Chuan
2014-01-01
We study an experimentally feasible qubit system employing neutral atomic currents. Our system is based on bosonic cold atoms trapped in ring-shaped optical lattice potentials. The lattice makes the system strictly one dimensional and it provides the infrastructure to realize a tunable ring-ring interaction. Our implementation combines the low decoherence rates of neutral cold atoms systems, overcoming single site addressing, with the robustness of topologically protected solid state Josephson flux qubits. Characteristic fluctuations in the magnetic fields affecting Josephson junction based flux qubits are expected to be minimized employing neutral atoms as flux carriers. By breaking the Galilean invariance we demonstrate how atomic currents through the lattice provide an implementation of a qubit. This is realized either by artificially creating a phase slip in a single ring, or by tunnel coupling of two homogeneous ring lattices. The single qubit infrastructure is experimentally investigated with tailored optical potentials. Indeed, we have experimentally realized scaled ring-lattice potentials that could host, in principle, n ~ 10 of such ring-qubits, arranged in a stack configuration, along the laser beam propagation axis. An experimentally viable scheme of the two-ring-qubit is discussed, as well. Based on our analysis, we provide protocols to initialize, address, and read-out the qubit.
Schulte, T.; Drenkelforth, S.; Kruse, J.; Ertmer, W.; Arlt, J.; Sacha, K.; Zakrzewski, J.; Lewenstein, M.
2005-10-21
We investigate, both experimentally and theoretically, possible routes towards Anderson-like localization of Bose-Einstein condensates in disordered potentials. The dependence of this quantum interference effect on the nonlinear interactions and the shape of the disorder potential is investigated. Experiments with an optical lattice and a superimposed disordered potential reveal the lack of Anderson localization. A theoretical analysis shows that this absence is due to the large length scale of the disorder potential as well as its screening by the nonlinear interactions. Further analysis shows that incommensurable superlattices should allow for the observation of the crossover from the nonlinear screening regime to the Anderson localized case within realistic experimental parameters.
NASA Astrophysics Data System (ADS)
Hu, Hui; Wang, An-Bang; Yi, Su; Liu, Xia-Ji
2016-05-01
We theoretically investigate the behavior of a moving impurity immersed in a sea of fermionic atoms that are confined in a quasiperiodic (bichromatic) optical lattice within a standard variational approach. We consider both repulsive and attractive contact interactions for such a simple many-body localization problem of Fermi polarons. The variational approach enables us to access relatively large systems and therefore may be used to understand many-body localization in the thermodynamic limit. The energy and wave function of the polaron states are found to be strongly affected by the quasirandom lattice potential and their experimental measurements (i.e., via radio-frequency spectroscopy or quantum gas microscope) therefore provide a sensitive way to underpin the localization transition. We determine a phase diagram by calculating two critical quasirandom disorder strengths, which correspond to the onset of the localization of the ground-state polaron state and the many-body localization of all polaron states, respectively. Our predicted phase diagram could be straightforwardly examined in current cold-atom experiments.
Dynamical Localization in Molecular Systems.
NASA Astrophysics Data System (ADS)
Wang, Xidi
In the first four chapters of this thesis we concentrate on the Davydov model which describes the vibrational energy quanta of Amide I bonds (C=O bonds on the alpha -helix) coupled to the acoustic phonon modes of the alpha-helix backbone in the form of a Frohlich Hamiltonian. Following a brief introduction in chapter one, in chapter two we formulate the dynamics of vibrational quanta at finite temperature by using coherent state products. The fluctuation-dissipation relation is derived. At zero temperature, in the continuum limit, we recover the original results of Davydov. We also achieve good agreement with numerical simulations. In chapter three, the net contraction of the lattice is calculated exactly at any temperature, and its relation to the so -call "topological stability" of the Davydov soliton is discussed. In the second section of the chapter three we calculate the overtone spectra of crystalline acetanilide (according to some opinions ACN provides experimental evidence for the existence of Davydov solitons). Good agreement with experimental data has been obtained. In chapter four we study the self-trapped vibrational excitations by the Quantum Monte Carlo technique. For a single excitation, the temperature dependence of different physical observables is calculated. The quasi-particle which resembles the Davydov soliton has been found to be fairly narrow using the most commonly used data for the alpha -helix; at temperatures above a few Kelvin, the quasi-particle reaches its smallest limit (extends over three sites), which implies diffusive motion of the small polaron-like quasi-particle at high temperatures. For the multi-excitation case, bound pairs and clusters of excitations are found at low temperatures; they gradually dissociate when the temperature of the system is increased as calculated from the density-density correlation function. In the last chapter of this thesis, we study a more general model of dynamical local modes in molecular systems
NASA Astrophysics Data System (ADS)
Hérisson, Benjamin; Challamel, Noël; Picandet, Vincent; Perrot, Arnaud
2016-09-01
The static behavior of the Fermi-Pasta-Ulam (FPU) axial chain under distributed loading is examined. The FPU system examined in the paper is a nonlinear elastic lattice with linear and quadratic spring interaction. A dimensionless parameter controls the possible loss of convexity of the associated quadratic and cubic energy. Exact analytical solutions based on Hurwitz zeta functions are developed in presence of linear static loading. It is shown that this nonlinear lattice possesses scale effects and possible localization properties in the absence of energy convexity. A continuous approach is then developed to capture the main phenomena observed regarding the discrete axial problem. The associated continuum is built from a continualization procedure that is mainly based on the asymptotic expansion of the difference operators involved in the lattice problem. This associated continuum is an enriched gradient-based or nonlocal axial medium. A Taylor-based and a rational differential method are both considered in the continualization procedures to approximate the FPU lattice response. The Padé approximant used in the continualization procedure fits the response of the discrete system efficiently, even in the vicinity of the limit load when the non-convex FPU energy is examined. It is concluded that the FPU lattice system behaves as a nonlocal axial system in dynamic but also static loading.
Nonlinear nano-scale localized breather modes in a discrete weak ferromagnetic spin lattice
NASA Astrophysics Data System (ADS)
Kavitha, L.; Parasuraman, E.; Gopi, D.; Prabhu, A.; Vicencio, Rodrigo A.
2016-03-01
We investigate the propagation dynamics of highly localized discrete breather modes in a weak ferromagnetic spin lattice with on-site easy axis anisotropy due to crystal field effect. We derive the discrete nonlinear equation of motion by employing boson mappings and p-representation. We explore the onset of modulational instability both analytically in the framework of linear stability analysis and numerically by means of molecular dynamics (MD) simulations, and a perfect agreement was demonstrated. It is also explored that how the antisymmetric nature of the canted ferromagnetic lattice supports highly localized discrete breather (DBs) modes as shown in the stability/instability windows. The energy exchange between low amplitude discrete breathers favours the growth of higher amplitude DBs, resulting eventually in the formation of few long-lived high amplitude DBs.
Transport and localization in a topological phononic lattice with correlated disorder
NASA Astrophysics Data System (ADS)
Ong, Zhun-Yong; Lee, Ching Hua
2016-10-01
Recently proposed classical analogs of topological insulators in phononic lattices have the advantage of much more accessible experimental realization compared to conventional materials. Drawn to their potential practical structural applications, we investigate how disorder, which is generically nonnegligible in macroscopic realization, can attenuate the topologically protected edge (TPE) modes that constitute robust transmitting channels at zero disorder. We simulate the transmission of phonon modes in a quasi-one-dimensional classical lattice waveguide with mass disorder and show that the TPE mode transmission remains highly robust (Ξ ˜1 ) in the presence of uncorrelated disorder but diminishes when disorder is spatially correlated. This reduction in transmittance is attributed to the Anderson localization of states within the mass disorder domains. By contrast, non-TPE channels exhibit qualitatively different behavior, with spatial correlation in the mass disorder leading to significant transmittance reduction (enhancement) at low (high) frequencies. Our results demonstrate how TPE modes drastically modify the effect of spatial correlation on mode localization.
Nonlinear propagating localized modes in a 2D hexagonal crystal lattice
NASA Astrophysics Data System (ADS)
Bajars, Janis; Eilbeck, J. Chris; Leimkuhler, Benedict
2015-05-01
In this paper we consider a 2D hexagonal crystal lattice model first proposed by Marín, Eilbeck and Russell in 1998. We perform a detailed numerical study of nonlinear propagating localized modes, that is, propagating discrete breathers and kinks. The original model is extended to allow for arbitrary atomic interactions, and to allow atoms to travel out of the unit cell. A new on-site potential is considered with a periodic smooth function with hexagonal symmetry. We are able to confirm the existence of long-lived propagating discrete breathers. Our simulations show that, as they evolve, breathers appear to localize in frequency space, i.e. the energy moves from sidebands to a main frequency band. Our numerical findings shed light on the open question of whether exact moving breather solutions exist in 2D hexagonal layers in physical crystal lattices.
NASA Astrophysics Data System (ADS)
Biddle, J.; Priour, D. J., Jr.; Wang, B.; Das Sarma, S.
2011-02-01
We study the quantum localization phenomena of noninteracting particles in one-dimensional lattices based on tight-binding models with various forms of hopping terms beyond the nearest neighbor, which are generalizations of the famous Aubry-André and noninteracting Anderson models. For the case with deterministic disordered potential induced by a secondary incommensurate lattice (i.e., the Aubry-André model), we identify a class of self-dual models, for which the boundary between localized and extended eigenstates are determined analytically by employing a generalized Aubry-André transformation. We also numerically investigate the localization properties of nondual models with next-nearest-neighbor hopping, Gaussian, and power-law decay hopping terms. We find that even for these nondual models, the numerically obtained mobility edges can be well approximated by the analytically obtained condition for localization transition in the self-dual models, as long as the decay of the hopping rate with respect to distance is sufficiently fast. For the disordered potential with genuinely random character, we examine scenarios with next-nearest-neighbor hopping, exponential, Gaussian, and power-law decay hopping terms numerically. We find that the higher-order hopping terms can remove the symmetry in the localization length about the energy band center compared to the Anderson model. Furthermore, our results demonstrate that for the power-law decay case, there exists a critical exponent below which mobility edges can be found. Our theoretical results could, in principle, be directly tested in shallow atomic optical lattice systems enabling non-nearest-neighbor hopping.
NASA Astrophysics Data System (ADS)
Yao, Ying-Bo; Li, De-Jun; Tang, Bing
2015-10-01
We present an analytical study on intrinsic localized modes (ILMs) in the quantum β-Fermi-Pasta-Ulam lattice model with first- and second-nearest neighbor interactions by means of the semiclassical approach. We quantize the lattice model Hamiltonian by introducing vibron creation and annihilation operators, and retaining only number conserving terms. The coherent state representation is considered as the basic representation of the quantum lattice system. In order to obtain the ILM solutions, we adopt the multiple scales method combined with a quasidiscreteness approximation. It is found that, when the system parameters satisfy K2 > 4K2‧, at the Brillouin zone (BZ) boundary, a bright ILM occurs above the top of the harmonic wave frequency band. While for K2 < 4K2‧, our results indicate that at wave number kc a bright ILM occurs above the top of the harmonic wave frequency band and at the BZ boundary, the system support a dark intrinsic localized resonant mode.
Primo, C; Szendro, I G; Rodríguez, M A; Gutiérrez, J M
2007-03-01
Error growth in spatiotemporal chaotic systems is investigated by analyzing the interplay between temporal and spatial dynamics. The spatial correlation and localization of relative fluctuations grow and decay indicating two different regimes, before and after saturation by nonlinear effects. This general behavior is shown to hold both in simple coupled map lattices and in global weather models. This explains the increasing or decreasing trends previously observed in the exponential growth rate of these spatiotemporal systems.
Acoustic sniper localization system
NASA Astrophysics Data System (ADS)
Prado, Gervasio; Dhaliwal, Hardave; Martel, Philip O.
1997-02-01
Technologies for sniper localization have received increased attention in recent months as American forces have been deployed to various trouble spots around the world. Among the technologies considered for this task acoustics is a natural choice for various reasons. The acoustic signatures of gunshots are loud and distinctive, making them easy to detect even in high noise background environments. Acoustics provides a passive sensing technology with excellent range and non line of sight capabilities. Last but not least, an acoustic sniper location system can be built at a low cost with off the shelf components. Despite its many advantages, the performance of acoustic sensors can degrade under adverse propagation conditions. Localization accuracy, although good, is usually not accurate enough to pinpoint a sniper's location in some scenarios (for example which widow in a building or behind which tree in a grove). For these more demanding missions, the acoustic sensor can be used in conjunction with an infra red imaging system that detects the muzzle blast of the gun. The acoustic system can be used to cue the pointing system of the IR camera in the direction of the shot's source.
Kyker, R.
1995-07-25
Navigation systems have been vital to transportation ever since man took to the air and sea. Early navigation systems utilized the sextant to navigate by starlight as well as the magnetic needle compass. As electronics and communication technologies improved, inertial navigation systems were developed for use in ships and missile delivery. These systems consisted of electronic compasses, gyro-compasses, accelerometers, and various other sensors. Recently, systems such as LORAN and the Global Positioning System (GPS) have utilized the properties of radio wave propagation to triangulate position. The Local Positioning System (LPS), described in this paper, is an implementation of a limited inertial navigation system designed to be used on a bicycle. LPS displays a cyclist`s current position relative to a starting location. This information is displayed in Cartesian-like coordinates. To accomplish this, LPS relies upon two sensors, an electronic compass sensor and a distance sensor. The compass sensor provides directional information while the distance sensor provides the distance traveled. This information yields a distance vector for each point in time which when summed produces the cyclist`s current position. LPS is microprocessor controlled and is designed for a range of less than 90 miles.
Random attractor of non-autonomous stochastic Boussinesq lattice system
Zhao, Min Zhou, Shengfan
2015-09-15
In this paper, we first consider the existence of tempered random attractor for second-order non-autonomous stochastic lattice dynamical system of nonlinear Boussinesq equations effected by time-dependent coupled coefficients and deterministic forces and multiplicative white noise. Then, we establish the upper semicontinuity of random attractors as the intensity of noise approaches zero.
Analysis of local lattice strain around oxygen precipitates in silicon crystals using CBED technique
NASA Astrophysics Data System (ADS)
Yonemura, Mitsuharu; Sueoka, Koji; Kamei, Kazuhito
1998-06-01
Oxygen precipitates (SiO x) in Czochralski-grown silicon single crystals (CZ-Si) have been used for the `getter' sink for impurities introduced during the LSI wafer manufacturing process. In order to understand the `gettering' phenomena, lattice strain fields around the precipitates have been measured quantitatively using convergent beam electron diffraction (CBED). The local lattice strain can be measured from higher order Laue zone (HOLZ) patterns since the HOLZ pattern in the bright field disk is sensitive to the lattice displacement. As a result, a tetragonal distortion of silicon lattices was found in the vicinity of a platelet of an oxygen precipitate. That is, the strain due to the displacement of (001) Si planes is compressive along the direction normal to [001] Si and is tensile along the direction parallel to [001] Si. The normal strain is estimated to be about 0.3% near the flat plane of the platelet and 0.1% near the edge of the platelet whose edge length is about 500 nm. The results are discussed and compared to those from the finite element method (FEM) simulation.
Revealing ultralarge and localized elastic lattice strains in Nb nanowires embedded in NiTi matrix
Zang, Ketao; Mao, Shengcheng; Cai, Jixiang; Liu, Yinong; Li, Haixin; Hao, Shijie; Jiang, Daqiang; Cui, Lishan
2015-01-01
Freestanding nanowires have been found to exhibit ultra-large elastic strains (4 to 7%) and ultra-high strengths, but exploiting their intrinsic superior mechanical properties in bulk forms has proven to be difficult. A recent study has demonstrated that ultra-large elastic strains of ~6% can be achieved in Nb nanowires embedded in a NiTi matrix, on the principle of lattice strain matching. To verify this hypothesis, this study investigated the elastic deformation behavior of a Nb nanowire embedded in NiTi matrix by means of in situ transmission electron microscopic measurement during tensile deformation. The experimental work revealed that ultra-large local elastic lattice strains of up to 8% are induced in the Nb nanowire in regions adjacent to stress-induced martensite domains in the NiTi matrix, whilst other parts of the nanowires exhibit much reduced lattice strains when adjacent to the untransformed austenite in the NiTi matrix. These observations provide a direct evidence of the proposed mechanism of lattice strain matching, thus a novel approach to designing nanocomposites of superior mechanical properties. PMID:26625854
Ferroelectric phase transitions in multiferroic Ge1 -xMnxTe driven by local lattice distortions
NASA Astrophysics Data System (ADS)
Kriegner, Dominik; Furthmüller, Jürgen; Kirchschlager, Raimund; Endres, Jan; Horak, Lukas; Cejpek, Petr; Reichlova, Helena; Marti, Xavier; Primetzhofer, Daniel; Ney, Andreas; Bauer, Günther; Bechstedt, Friedhelm; Holy, Vaclav; Springholz, Gunther
2016-08-01
The evolution of local ferroelectric lattice distortions in multiferroic Ge1 -xMnxTe is studied by x-ray diffraction, x-ray absorption spectroscopy, and density functional theory. We show that the anion/cation displacements smoothly decrease with increasing Mn content, thereby reducing the ferroelectric transition from 700 to 100 K at x =0.5 , where the ferromagnetic Curie temperature reaches its maximum. First principles calculations explain this quenching by different local bond contributions of the Mn 3 d shell compared to the Ge 4 s shell in excellent quantitative agreement with the experiments.
Localized surface plasmon effects of two dimensional lattice of metal nanoislands
NASA Astrophysics Data System (ADS)
Oda, Yukari; Shimada, Ryoko; Japan Women's University Team
2015-03-01
Localized surface plasmon (LSP) of metal nanoparticles results from non-propagating excitation of their conduction electrons coupled to the electromagnetic field. LSP localizes the electric field and enhances light emission from fluorescent materials. In this study, a two dimensional (2D) lattice of silver (Ag) nanoislands was fabricated by nanosphere lithography (NSL) method utilizing self-assembled, close-packed hexagonal structures of polystyrene spheres as the etching mask. This 2D lattice was subjected to the electric field for investigating a role of the periodicity of metal islands in the LSP effect. 9,10-di(2-naphthyl) anthracene (ADN), a well-known blue-emitting material in the field of electroluminescence, was used for the study of the enhancement of emission due to the LSP effect. Hybrid thin films of poly(methyl methacrylate) containing ADN were prepared with spin-casting onto the 2D lattice of Ag nanoislands. Transmission and photoluminescence measurements were conducted for these hybrid thin films at room temperature. Detailed results will be presented on site.
Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures
NASA Astrophysics Data System (ADS)
Lotnyk, Andriy; Ross, Ulrich; Bernütz, Sabine; Thelander, Erik; Rauschenbach, Bernd
2016-05-01
Insights into the local atomic arrangements of layered Ge-Sb-Te compounds are of particular importance from a fundamental point of view and for data storage applications. In this view, a detailed knowledge of the atomic structure in such alloys is central to understanding the functional properties both in the more commonly utilized amorphous–crystalline transition and in recently proposed interfacial phase change memory based on the transition between two crystalline structures. Aberration-corrected scanning transmission electron microscopy allows direct imaging of local arrangement in the crystalline lattice with atomic resolution. However, due to the non-trivial influence of thermal diffuse scattering on the high-angle scattering signal, a detailed examination of the image contrast requires comparison with theoretical image simulations. This work reveals the local atomic structure of trigonal Ge-Sb-Te thin films by using a combination of direct imaging of the atomic columns and theoretical image simulation approaches. The results show that the thin films are prone to the formation of stacking disorder with individual building blocks of the Ge2Sb2Te5, Ge1Sb2Te4 and Ge3Sb2Te6 crystal structures intercalated within randomly oriented grains. The comparison with image simulations based on various theoretical models reveals intermixed cation layers with pronounced local lattice distortions, exceeding those reported in literature.
Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures
Lotnyk, Andriy; Ross, Ulrich; Bernütz, Sabine; Thelander, Erik; Rauschenbach, Bernd
2016-01-01
Insights into the local atomic arrangements of layered Ge-Sb-Te compounds are of particular importance from a fundamental point of view and for data storage applications. In this view, a detailed knowledge of the atomic structure in such alloys is central to understanding the functional properties both in the more commonly utilized amorphous–crystalline transition and in recently proposed interfacial phase change memory based on the transition between two crystalline structures. Aberration-corrected scanning transmission electron microscopy allows direct imaging of local arrangement in the crystalline lattice with atomic resolution. However, due to the non-trivial influence of thermal diffuse scattering on the high-angle scattering signal, a detailed examination of the image contrast requires comparison with theoretical image simulations. This work reveals the local atomic structure of trigonal Ge-Sb-Te thin films by using a combination of direct imaging of the atomic columns and theoretical image simulation approaches. The results show that the thin films are prone to the formation of stacking disorder with individual building blocks of the Ge2Sb2Te5, Ge1Sb2Te4 and Ge3Sb2Te6 crystal structures intercalated within randomly oriented grains. The comparison with image simulations based on various theoretical models reveals intermixed cation layers with pronounced local lattice distortions, exceeding those reported in literature. PMID:27220411
Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures.
Lotnyk, Andriy; Ross, Ulrich; Bernütz, Sabine; Thelander, Erik; Rauschenbach, Bernd
2016-05-25
Insights into the local atomic arrangements of layered Ge-Sb-Te compounds are of particular importance from a fundamental point of view and for data storage applications. In this view, a detailed knowledge of the atomic structure in such alloys is central to understanding the functional properties both in the more commonly utilized amorphous-crystalline transition and in recently proposed interfacial phase change memory based on the transition between two crystalline structures. Aberration-corrected scanning transmission electron microscopy allows direct imaging of local arrangement in the crystalline lattice with atomic resolution. However, due to the non-trivial influence of thermal diffuse scattering on the high-angle scattering signal, a detailed examination of the image contrast requires comparison with theoretical image simulations. This work reveals the local atomic structure of trigonal Ge-Sb-Te thin films by using a combination of direct imaging of the atomic columns and theoretical image simulation approaches. The results show that the thin films are prone to the formation of stacking disorder with individual building blocks of the Ge2Sb2Te5, Ge1Sb2Te4 and Ge3Sb2Te6 crystal structures intercalated within randomly oriented grains. The comparison with image simulations based on various theoretical models reveals intermixed cation layers with pronounced local lattice distortions, exceeding those reported in literature.
NASA Astrophysics Data System (ADS)
Nishino, Masamichi; Nakada, Taro; Enachescu, Cristian; Boukheddaden, Kamel; Miyashita, Seiji
2013-09-01
We study domain wall propagation in systems with long-range interactions caused by lattice distortion. When the local bistable states of the molecular unit have different sizes, e.g., high-spin and low-spin states in spin-crossover systems, the elastic distortion causes an effective long-range interaction. In switching processes between the ordered states in such systems, there exist two degrees of freedom for the domain wall, that is, one with respect to lattice structure and the other to a bistable spin (electronic) state. The interface width of the lattice domain wall is proportional to the system size, which reflects the macroscopic structure due to the long-range interaction, while the interface width of the spin state shows different characteristics depending on the relative time scales of dynamics of the spin state and the lattice. When the change of the spin state is relatively fast and the lattice relaxation is insufficient, the roughness exponent α is 1/2, which has been commonly found in growth models of short-range interaction systems in two dimensions. In contrast, when the lattice relaxes sufficiently, α of the spin interface is the same as that of the lattice interface, i.e., α=1. We analyze the pressure field of the systems and find that the equilibration of the field via the long-range interaction plays a key role in the mechanism of the crossover of α between 1/2 and 1.
Formal Developments for Lattice QCD with Applications to Hadronic Systems
NASA Astrophysics Data System (ADS)
Davoudi, Zohreh
In order to make reliable predictions with controlled uncertainties for a wide range of nuclear phenomena, a theoretical bottom-up approach, by which hadrons emerge from the underlying theory of strong interactions, quantum chromodynamics (QCD), is desired. The strongly interacting quarks and gluons at low energies are responsible for all the dynamics of nucleons and their clusters, the nuclei. The theoretical framework and the combination of analytical and numerical tools used to carry out a rigorous non-perturbative study of these systems from QCD is called lattice QCD. The result of a lattice QCD calculation corresponds to that of nature only in the limit when the volume of the spacetime is taken to infinity and the spacing between discretized points on the lattice is taken to zero. A better understanding of these discretization and volume effects, not only provides the connection to the infinite-volume continuum observables, but also leads to optimized calculations that can be performed with available computational resources. This thesis includes various formal developments in this direction, along with proposals for novel improvements, to be used in the upcoming LQCD studies of nuclear and hadronic systems. As the space(time) is discretized on a (hyper)cubic lattice in (most of) lattice QCD calculations, the lattice correlation functions are not fully rotationally invariant. This is known to lead to mixing between operators (those interpolating the states or inserting external currents) of higher dimensions with those of lower dimensions where the coefficients of latter diverge with powers of inverse lattice spacing, a, as the continuum limit is approached. This issue has long posed computational challenges in lattice spectroscopy of higher spin states, as well as in the lattice extractions of higher moments of hadron structure functions. We have shown, through analytical perturbative investigations of field theories, including QCD, on the lattice that a novel
Sato, M; Nakaguchi, T; Ishikawa, T; Shige, S; Soga, Y; Doi, Y; Sievers, A J
2015-10-01
It is well known that a moving intrinsic localized mode (ILM) in a nonlinear physical lattice looses energy because of the resonance between it and the underlying small amplitude plane wave spectrum. By exploring the Fourier transform (FT) properties of the nonlinear force of a running ILM in a driven and damped 1D nonlinear lattice, as described by a 2D wavenumber and frequency map, we quantify the magnitude of the resonance where the small amplitude normal mode dispersion curve and the FT amplitude components of the ILM intersect. We show that for a traveling ILM characterized by a specific frequency and wavenumber, either inside or outside the plane wave spectrum, and for situations where both onsite and intersite nonlinearity occur, either of the hard or soft type, the strength of this resonance depends on the specific mix of the two nonlinearities. Examples are presented demonstrating that by engineering this mix the resonance can be greatly reduced. The end result is a supertransmission channel for either a driven or undriven ILM in a nonintegrable, nonlinear yet physical lattice.
NASA Astrophysics Data System (ADS)
Sato, M.; Nakaguchi, T.; Ishikawa, T.; Shige, S.; Soga, Y.; Doi, Y.; Sievers, A. J.
2015-10-01
It is well known that a moving intrinsic localized mode (ILM) in a nonlinear physical lattice looses energy because of the resonance between it and the underlying small amplitude plane wave spectrum. By exploring the Fourier transform (FT) properties of the nonlinear force of a running ILM in a driven and damped 1D nonlinear lattice, as described by a 2D wavenumber and frequency map, we quantify the magnitude of the resonance where the small amplitude normal mode dispersion curve and the FT amplitude components of the ILM intersect. We show that for a traveling ILM characterized by a specific frequency and wavenumber, either inside or outside the plane wave spectrum, and for situations where both onsite and intersite nonlinearity occur, either of the hard or soft type, the strength of this resonance depends on the specific mix of the two nonlinearities. Examples are presented demonstrating that by engineering this mix the resonance can be greatly reduced. The end result is a supertransmission channel for either a driven or undriven ILM in a nonintegrable, nonlinear yet physical lattice.
Energy landscape paving with local search for global optimization of the BLN off-lattice model
NASA Astrophysics Data System (ADS)
Liu, Jingfa; Huang, Weibo; Liu, Wenjie; Song, Beibei; Sun, Yuanyuan; Chen, Mao
2014-02-01
The optimization problem for finding the global minimum energy structure is one of the main problems of protein structure prediction and is known to be an NP-hard problem in computational molecular biology. The low-energy conformational search problem in the hydrophobic-hydrophilic-neutral (BLN) off-lattice model is studied. We convert the problem into an unconstrained optimization problem by introducing the penalty function. By putting forward a new updating mechanism of the histogram function in the energy landscape paving (ELP) method and incorporating heuristic conformation update strategies into the ELP method, we obtain an improved ELP (IELP) method. Subsequently, by combining the IELP method with the local search (LS) based on the gradient descent method, we propose a hybrid algorithm, denoted by IELP-LS, for the conformational search of the off-lattice BLN model. Simulation results indicate that IELP-LS can find lower-energy states than other methods in the literature, showing that the proposed method is an effective tool for global optimization in the BLN off-lattice protein model.
Applications of lattice QCD techniques for condensed matter systems
NASA Astrophysics Data System (ADS)
Buividovich, P. V.; Ulybyshev, M. V.
2016-08-01
We review the application of lattice QCD techniques, most notably the Hybrid Monte Carlo (HMC) simulations, to first-principle study of tight-binding models of crystalline solids with strong inter-electron interactions. After providing a basic introduction into the HMC algorithm as applied to condensed matter systems, we review HMC simulations of graphene, which in the recent years have helped to understand the semimetal behavior of clean suspended graphene at the quantitative level. We also briefly summarize other novel physical results obtained in these simulations. Then we comment on the applicability of hybrid Monte Carlo to topological insulators and Dirac and Weyl semimetals and highlight some of the relevant open physical problems. Finally, we also touch upon the lattice strong-coupling expansion technique as applied to condensed matter systems.
Lattice QCD study of mixed systems of pions and kaons
William Detmold, Brian Smigielski
2011-07-01
The O(100) different ground state energies of N-pion and M-kaon systems for N+M <= 12 are studied in lattice QCD. These energies are then used to extract the various two- and three- body interactions that occur in these systems. These calculations are performed using one ensemble of 2+1 flavor anisotropic lattices with a spatial lattice spacing $a_s$ ~ 0.125 fm, an anisotropy factor $\\xi=a_s/a_t=3.5$, and a spatial volume $L^3\\sim (2.5\\ {\\rm fm})^3$. Particular attention is paid to additional thermal states present in the spectrum because of the finite temporal extent. The quark masses used correspond to pion and kaon masses of $m_\\pi$ ~ 383 MeV and $m_K$ ~ 537 MeV, respectively. The isospin and strangeness chemical potentials of these systems are found to be in the region where chiral perturbation theory and hadronic models predict a phase transition between a pion condensed phase and a kaon condensed phase.
Kasamatsu, Kenichi; Ichinose, Ikuo; Matsui, Tetsuo
2013-09-13
Recently, the possibility of quantum simulation of dynamical gauge fields was pointed out by using a system of cold atoms trapped on each link in an optical lattice. However, to implement exact local gauge invariance, fine-tuning the interaction parameters among atoms is necessary. In the present Letter, we study the effect of violation of the U(1) local gauge invariance by relaxing the fine-tuning of the parameters and showing that a wide variety of cold atoms is still a faithful quantum simulator for a U(1) gauge-Higgs model containing a Higgs field sitting on sites. The clarification of the dynamics of this gauge-Higgs model sheds some light upon various unsolved problems, including the inflation process of the early Universe. We study the phase structure of this model by Monte Carlo simulation and also discuss the atomic characteristics of the Higgs phase in each simulator.
Sedrakyan, T. A.; Kestner, J. P.; Das Sarma, S.
2011-11-15
We propose a realization of the one-dimensional random dimer model and certain N-leg generalizations using cold atoms in an optical lattice. We show that these models exhibit multiple delocalization energies that depend strongly on the symmetry properties of the corresponding Hamiltonian, and we provide analytical and numerical results for the localization length as a function of energy. We demonstrate that the N-leg systems possess similarities with their one-dimensional ancestors but are demonstrably distinct. The existence of critical delocalization energies leads to dips in the momentum distribution that serve as a clear signal of the localization-delocalization transition. These momentum distributions are different for models with different group symmetries and are identical for those with the same symmetry.
Optimum inhomogeneity of local lattice distortions in La2CuO4+y
Poccia, Nicola; Ricci, Alessandro; Campi, Gaetano; Fratini, Michela; Puri, Alessandro; Gioacchino, Daniele Di; Marcelli, Augusto; Reynolds, Michael; Burghammer, Manfred; Saini, Naurang Lal; Aeppli, Gabriel; Bianconi, Antonio
2012-01-01
Electronic functionalities in materials from silicon to transition metal oxides are, to a large extent, controlled by defects and their relative arrangement. Outstanding examples are the oxides of copper, where defect order is correlated with their high superconducting transition temperatures. The oxygen defect order can be highly inhomogeneous, even in optimal superconducting samples, which raises the question of the nature of the sample regions where the order does not exist but which nonetheless form the “glue” binding the ordered regions together. Here we use scanning X-ray microdiffraction (with a beam 300 nm in diameter) to show that for La2CuO4+y, the glue regions contain incommensurate modulated local lattice distortions, whose spatial extent is most pronounced for the best superconducting samples. For an underdoped single crystal with mobile oxygen interstitials in the spacer La2O2+y layers intercalated between the CuO2 layers, the incommensurate modulated local lattice distortions form droplets anticorrelated with the ordered oxygen interstitials, and whose spatial extent is most pronounced for the best superconducting samples. In this simplest of high temperature superconductors, there are therefore not one, but two networks of ordered defects which can be tuned to achieve optimal superconductivity. For a given stoichiometry, the highest transition temperature is obtained when both the ordered oxygen and lattice defects form fractal patterns, as opposed to appearing in isolated spots. We speculate that the relationship between material complexity and superconducting transition temperature Tc is actually underpinned by a fundamental relation between Tc and the distribution of ordered defect networks supported by the materials. PMID:22961255
Optimum inhomogeneity of local lattice distortions in La2CuO(4+y).
Poccia, Nicola; Ricci, Alessandro; Campi, Gaetano; Fratini, Michela; Puri, Alessandro; Di Gioacchino, Daniele; Marcelli, Augusto; Reynolds, Michael; Burghammer, Manfred; Saini, Naurang Lal; Aeppli, Gabriel; Bianconi, Antonio
2012-09-25
Electronic functionalities in materials from silicon to transition metal oxides are, to a large extent, controlled by defects and their relative arrangement. Outstanding examples are the oxides of copper, where defect order is correlated with their high superconducting transition temperatures. The oxygen defect order can be highly inhomogeneous, even in optimal superconducting samples, which raises the question of the nature of the sample regions where the order does not exist but which nonetheless form the "glue" binding the ordered regions together. Here we use scanning X-ray microdiffraction (with a beam 300 nm in diameter) to show that for La(2)CuO(4+y), the glue regions contain incommensurate modulated local lattice distortions, whose spatial extent is most pronounced for the best superconducting samples. For an underdoped single crystal with mobile oxygen interstitials in the spacer La(2)O(2+y) layers intercalated between the CuO(2) layers, the incommensurate modulated local lattice distortions form droplets anticorrelated with the ordered oxygen interstitials, and whose spatial extent is most pronounced for the best superconducting samples. In this simplest of high temperature superconductors, there are therefore not one, but two networks of ordered defects which can be tuned to achieve optimal superconductivity. For a given stoichiometry, the highest transition temperature is obtained when both the ordered oxygen and lattice defects form fractal patterns, as opposed to appearing in isolated spots. We speculate that the relationship between material complexity and superconducting transition temperature T(c) is actually underpinned by a fundamental relation between T(c) and the distribution of ordered defect networks supported by the materials. PMID:22961255
Method to study complex systems of mesons in lattice QCD
Detmold, William; Savage, Martin J.
2010-07-30
Correlation functions involving many hadrons allow finite density systems to be explored with Lattice QCD. Recently, systems with up to 12more » $$\\pi^+$$'s or $K^+$'s have been studied to determine the the $3$-$$\\pi^+$$ and $3$-$K^+$ interactions and the corresponding chemical potential has been determined as a function of density in each case. We derive recursion relations between correlation functions that allow us to extend this work to systems of arbitrary numbers of mesons and to systems containing arbitrary different types of mesons such as $$\\pi^+$$'s, $K^+$'s, $D^0$'s and $B^+$'s. These relations allow for the study of finite-density systems in arbitrary volumes, and the study of high-density systems. Systems comprised of up to N=12 m mesons can be explored with Lattice QCD calculations utilizing $m$ different sources for the quark propagators. As the recursion relations require only a small, N-independent, number of operations to derive the N+1 meson contractions from the N meson contractions, they are compuationally feasible.« less
Method to study complex systems of mesons in lattice QCD
Detmold, William; Savage, Martin J.
2010-07-30
Correlation functions involving many hadrons allow finite density systems to be explored with Lattice QCD. Recently, systems with up to 12 $\\pi^+$'s or $K^+$'s have been studied to determine the the $3$-$\\pi^+$ and $3$-$K^+$ interactions and the corresponding chemical potential has been determined as a function of density in each case. We derive recursion relations between correlation functions that allow us to extend this work to systems of arbitrary numbers of mesons and to systems containing arbitrary different types of mesons such as $\\pi^+$'s, $K^+$'s, $D^0$'s and $B^+$'s. These relations allow for the study of finite-density systems in arbitrary volumes, and the study of high-density systems. Systems comprised of up to N=12 m mesons can be explored with Lattice QCD calculations utilizing $m$ different sources for the quark propagators. As the recursion relations require only a small, N-independent, number of operations to derive the N+1 meson contractions from the N meson contractions, they are compuationally feasible.
Using superconducting qubit circuits to engineer exotic lattice systems
Tsomokos, Dimitris I.; Ashhab, Sahel; Nori, Franco
2010-11-15
We propose an architecture based on superconducting qubits and resonators for the implementation of a variety of exotic lattice systems, such as spin and Hubbard models in higher or fractal dimensions and higher-genus topologies. Spin systems are realized naturally using qubits, while superconducting resonators can be used for the realization of Bose-Hubbard models. Fundamental requirements for these designs, such as controllable interactions between arbitrary qubit pairs, have recently been implemented in the laboratory, rendering our proposals feasible with current technology.
Localization of a Bose-Einstein-condensate vortex in a bichromatic optical lattice
Adhikari, S. K.
2010-04-15
By numerical simulation of the time-dependent Gross-Pitaevskii equation we show that a weakly interacting or noninteracting Bose-Einstein condensate (BEC) vortex can be localized in a three-dimensional bichromatic quasiperiodic optical-lattice (OL) potential generated by the superposition of two standing-wave polarized laser beams with incommensurate wavelengths. We also study the localization of a (nonrotating) BEC in two and three dimensions by bichromatic OL potentials along orthogonal directions. This is a generalization of the localization of a BEC in a one-dimensional bichromatic OL as studied in a recent experiment [Roati et al., Nature 453, 895 (2008)]. We demonstrate the stability of the localized state by considering its time evolution in the form of a stable breathing oscillation in a slightly altered potential for a large period of time. Finally, we consider the localization of a BEC in a random one-dimensional potential in the form of several identical repulsive spikes arbitrarily distributed in space.
Cheng Yongshan; Adhikari, S. K.
2010-02-15
By direct numerical simulation of the time-dependent Gross-Pitaevskii equation using the split-step Fourier spectral method, we study different aspects of the localization of a cigar-shaped interacting binary (two-component) Bose-Einstein condensate (BEC) in a one-dimensional bichromatic quasiperiodic optical-lattice potential, as used in a recent experiment on the localization of a BEC [Roati et al., Nature 453, 895 (2008)]. We consider two types of localized states: (i) when both localized components have a maximum of density at the origin x=0, and (ii) when the first component has a maximum of density and the second a minimum of density at x=0. In the noninteracting case, the density profiles are symmetric around x=0. We numerically study the breakdown of this symmetry due to interspecies and intraspecies interactions acting on the two components. Where possible, we have compared the numerical results with a time-dependent variational analysis. We also demonstrate the stability of the localized symmetry-broken BEC states under small perturbation.
RENO-CC: A new system to fuel lattice design in boiling water reactors using neural networks
Ortiz, J. J.; Perusquia, R.; Hernandez, J. L.
2006-07-01
We show a new system to optimize fuel lattices in BWRs named RENO-CC. The system employs a multi state recurrent neural network (MSRNN) for optimizing a fuel lattice pin-by-pin {sup 235}U enrichment distribution. Local Power Peaking Factor (LPPF) and k-infinite (k{sub {infinity}}) are involved in the MSRNN energy function. Both parameters are calculated by the 2D HELIOS transport code for lattice burn-up. Through the iterative process the MSRNN decreases PPF value while k{sub {infinity}}, is kept in a rank of values, at the beginning of lattice life (BOL). The iterative process ends after 20 iterations. If PPF is not lower than limit, RENO-CC applies a fuzzy logic rule in order to recommend if the fuel lattice has an acceptable LPPF value and it might eventually be used in a fuel load. When a fuel lattice is obtained it can be used into a fuel assembly. And eventually, this fuel assembly would be used in the process of fuel load and control rod patterns optimization. So, a 3D core reactor calculation must decide if such a lattice design can fulfill the operation conditions into the reactor core. Preliminary results are shown in this paper. (authors)
NASA Astrophysics Data System (ADS)
Chien, Chihchun; Metcalf, Mekena; Lai, Chenyen
2016-05-01
Memory effects are observable in magnetization, rechargeable batteries, and many systems exhibiting history-dependent states. Quantum memory effects are observable, for instance, in atomic superfluids. A counter-intuitive question is whether quantum memory effects can exist in noninteracting systems. Here we present two examples of cold-atom systems demonstrating memory effects in noninteracting systems. The first example is a ring-shaped potential loaded with noninteracting fermions. An artificial vector potential drives a current and with a tunable dissipative background, the current lags behind the driving and exhibits hysteresis loops. The dissipative energy can be controlled by the coupling between the fermions and the background. In the second example, cold atoms loaded in a tunable optical lattice transformed from the triangular to the kagome geometry. The kagome lattice supports a flat-band consisting of degenerate localized states. Quantum memory effects are observable after a lattice transformation as the steady-state density depends on the rate of the transformation. The versatility of memory effects in cold-atom systems promises novel applications in atomtronics.
Lie algebraic similarity transformed Hamiltonians for lattice model systems
NASA Astrophysics Data System (ADS)
Wahlen-Strothman, Jacob M.; Jiménez-Hoyos, Carlos A.; Henderson, Thomas M.; Scuseria, Gustavo E.
2015-01-01
We present a class of Lie algebraic similarity transformations generated by exponentials of two-body on-site Hermitian operators whose Hausdorff series can be summed exactly without truncation. The correlators are defined over the entire lattice and include the Gutzwiller factor ni ↑ni ↓ , and two-site products of density (ni ↑+ni ↓) and spin (ni ↑-ni ↓) operators. The resulting non-Hermitian many-body Hamiltonian can be solved in a biorthogonal mean-field approach with polynomial computational cost. The proposed similarity transformation generates locally weighted orbital transformations of the reference determinant. Although the energy of the model is unbound, projective equations in the spirit of coupled cluster theory lead to well-defined solutions. The theory is tested on the one- and two-dimensional repulsive Hubbard model where it yields accurate results for small and medium sized interaction strengths.
Sharing lattice QCD data over a widely distributed file system
NASA Astrophysics Data System (ADS)
Amagasa, T.; Aoki, S.; Aoki, Y.; Aoyama, T.; Doi, T.; Fukumura, K.; Ishii, N.; Ishikawa, K.-I.; Jitsumoto, H.; Kamano, H.; Konno, Y.; Matsufuru, H.; Mikami, Y.; Miura, K.; Sato, M.; Takeda, S.; Tatebe, O.; Togawa, H.; Ukawa, A.; Ukita, N.; Watanabe, Y.; Yamazaki, T.; Yoshie, T.
2015-12-01
JLDG is a data-grid for the lattice QCD (LQCD) community in Japan. Several large research groups in Japan have been working on lattice QCD simulations using supercomputers distributed over distant sites. The JLDG provides such collaborations with an efficient method of data management and sharing. File servers installed on 9 sites are connected to the NII SINET VPN and are bound into a single file system with the GFarm. The file system looks the same from any sites, so that users can do analyses on a supercomputer on a site, using data generated and stored in the JLDG at a different site. We present a brief description of hardware and software of the JLDG, including a recently developed subsystem for cooperating with the HPCI shared storage, and report performance and statistics of the JLDG. As of April 2015, 15 research groups (61 users) store their daily research data of 4.7PB including replica and 68 million files in total. Number of publications for works which used the JLDG is 98. The large number of publications and recent rapid increase of disk usage convince us that the JLDG has grown up into a useful infrastructure for LQCD community in Japan.
Spatial Localization in Dissipative Systems
NASA Astrophysics Data System (ADS)
Knobloch, E.
2015-03-01
Spatial localization is a common feature of physical systems, occurring in both conservative and dissipative systems. This article reviews the theoretical foundations of our understanding of spatial localization in forced dissipative systems, from both a mathematical point of view and a physics perspective. It explains the origin of the large multiplicity of simultaneously stable spatially localized states present in a parameter region called the pinning region and its relation to the notion of homoclinic snaking. The localized states are described as bound states of fronts, and the notions of front pinning, self-pinning, and depinning are emphasized. Both one-dimensional and two-dimensional systems are discussed, and the reasons behind the differences in behavior between dissipative systems with conserved and nonconserved dynamics are explained. The insights gained are specific to forced dissipative systems and are illustrated here using examples drawn from fluid mechanics (convection and shear flows) and a simple model of crystallization.
Inhomogeneous Fermi and quantum spin systems on lattices
NASA Astrophysics Data System (ADS)
Bru, J.-B.; de Siqueira Pedra, W.
2012-12-01
We study the thermodynamic properties of a certain type of space-inhomogeneous Fermi and quantum spin systems on lattices. We are particularly interested in the case where the space scale of the inhomogeneities stays macroscopic, but very small as compared to the side-length of the box containing fermions or spins. The present study is however not restricted to "macroscopic inhomogeneities" and also includes the (periodic) microscopic and mesoscopic cases. We prove that - as in the homogeneous case - the pressure is, up to a minus sign, the conservative value of a two-person zero-sum game, named here thermodynamic game. Because of the absence of space symmetries in such inhomogeneous systems, it is not clear from the beginning what kind of object equilibrium states should be in the thermodynamic limit. However, we give rigorous statements on correlations functions for large boxes.
Sato, M; Imai, S; Fujita, N; Shi, W; Takao, Y; Sada, Y; Hubbard, B E; Ilic, B; Sievers, A J
2013-01-01
An intrinsic localized mode (ILM) represents a localized vibrational excitation in a nonlinear lattice. Such a mode will stay in resonance as the driver frequency is changed adiabatically until a bifurcation point is reached, at which point the ILM switches and disappears. The dynamics behind switching in such a many body system is examined here through experimental measurements and numerical simulations. Linear response spectra of a driven micromechanical array containing an ILM were measured in the frequency region between two fundamentally different kinds of bifurcation points that separate the large amplitude ILM state from the two low amplitude vibrational states. Just as a natural frequency can be associated with a driven harmonic oscillator, a similar natural frequency has been found for a driven ILM via the beat frequency between it and a weak, tunable probe. This finding has been confirmed using numerical simulations. The behavior of this nonlinear natural frequency plays important but different roles as the two bifurcation points are approached. At the upper transition its frequency coalesces with the driver and the resulting bifurcation is very similar to the saddle-node bifurcation of a single driven Duffing oscillator, which is treated in an Appendix. The lower transition occurs when the four-wave mixing partner of the natural frequency of the ILM intersects the topmost extended band mode of the same symmetry. The properties of linear local modes associated with the driven ILM are also identified experimentally for the first time and numerically but play no role in these transitions. PMID:23410417
NASA Astrophysics Data System (ADS)
Farzanehpour, Mehdi; Tokatly, Ilya; Nano-Bio Spectroscopy Group; ETSF Scientific Development Centre Team
2015-03-01
We present a rigorous formulation of the time-dependent density functional theory for interacting lattice electrons strongly coupled to cavity photons. We start with an example of one particle on a Hubbard dimer coupled to a single photonic mode, which is equivalent to the single mode spin-boson model or the quantum Rabi model. For this system we prove that the electron-photon wave function is a unique functional of the electronic density and the expectation value of the photonic coordinate, provided the initial state and the density satisfy a set of well defined conditions. Then we generalize the formalism to many interacting electrons on a lattice coupled to multiple photonic modes and prove the general mapping theorem. We also show that for a system evolving from the ground state of a lattice Hamiltonian any density with a continuous second time derivative is locally v-representable. Spanish Ministry of Economy and Competitiveness (Grant No. FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT578-13), COST Actions CM1204 (XLIC) and MP1306 (EUSpec).
Local lattice distortions and magnetic properties of CdCr2Se4-xSx
NASA Astrophysics Data System (ADS)
Behera, P. Suchismita; Bhobe, P. A.; Sathe, V. G.; Nigam, A. K.
2016-07-01
Interplay between structural disorder and magnetic interaction is investigated here for a multiferroic candidate material, CdCr2Se4. Ferromagnetic order in CdCr2Se4 sets in below TC ˜ 130 K as a result of competition between the direct Cr-Cr spin coupling and the near neighbour Cr-Se-Cr exchange interactions. Hence, a small change in the crystal structure is expected to drastically affect its magnetic order. In this report, local lattice distortions within the overall cubic symmetry were brought about by replacing a small percentage of Se by isovalent S. Detailed crystal structure study using EXAFS and Raman Spectroscopy reflects the presence of local distortions within the overall cubic symmetry. Contrary to the expectation, magnetic properties of the substituted compositions do not show any drastic changes. Though, a signature of spin-phonon coupling is present across the magnetic ordering temperature. No structural phase transition occurs within the investigated temperature range of 80-300 K.
More surprises in the general theory of lattice systems
NASA Astrophysics Data System (ADS)
Sokal, Alan D.
1982-09-01
I use Israel's methods to prove new theorems of “ubiquitous pathology” for classical and quantum lattice systems. The main result is the following: Let Φ be any interaction and ϱ be any translation-invariant equilibrium state for Φ (extremal or not). Then there exists a sequence {Φ k } of interactions converging to Φ, having extremal (or even unique) translation-invariant equilibrium states ϱ k , such that {ϱ k } converges to ϱ. In certain situations the perturbations Φ k -Φ can be chosen to lie in a cone of “antiferromagnetic pair interactions.” I discuss the connection with results of Daniëls and van Enter, and point out an application to the one-dimensional ferromagnetic Ising model with 1/ r 2 interaction (Thouless effect).
Characterization of nanoscale local lattice strains in silicon CMOS devices by TEM/CBED
NASA Astrophysics Data System (ADS)
Huang, Jiang
Strained-Si technology has become one of the leading approaches to further improve the performance of the metal-oxide-semiconductor field effect transistors (MOSFETs) as traditional device scaling faces its physical limitation. In particular, mechanical strain induced in the Si channel region is used to increase the carrier mobility and the transistor drive current. To be able to understand and engineer the local lattice strain incorporated in the nanoscale device region, a strain measurement technique with high spatial resolution and high sensitivity is essential. Currently, transmission electron microscope (TEM)/convergent beam electron diffraction (CBED) is the only method to measure local changes in lattice parameters due to strain in advanced CMOS devices, because this technique provides nanometer spatial resolution and strain sensitivity on the order of 10-4. In this study, a novel experimental methodology is developed to measure the strain effectively and efficiently. Site-specific TEM samples are prepared by focused ion beam (FIB) with controlled thickness. Zone axes such as <230>, <340>, <560> and <910> are evaluated for obtaining CBED patterns. The specimen-tilt projection and dynamical effects related to the zone axis are discussed. CBED pattern simulation and matching procedures are explained to extract the strain tensors. The accuracy of the strain measurement depends on the clarity of the CBED pattern, which can be improved by using an energy-filter or sample cooling stage. The direct strain measurements are performed in sub-100 nm CMOS devices with either structure-induced or process-induced strains. It is found that the compressive strains are induced when the shallow trench structure (STI) is filled with isolation films. The compressive strains on the order of 10 -3 are observed under the gate region in a Si <110> PMOS transistor with a 37 nm gate length. One-dimensional quantitative strain-mapping is demonstrated using the nanometer probe. The
Observation of localized flat-band modes in a quasi-one-dimensional photonic rhombic lattice.
Mukherjee, Sebabrata; Thomson, Robert R
2015-12-01
We experimentally demonstrate the photonic realization of a dispersionless flat band in a quasi-one-dimensional photonic lattice fabricated by ultrafast laser inscription. In the nearest neighbor tight binding approximation, the lattice supports two dispersive and one nondispersive (flat) band. We experimentally excite superpositions of flat-band eigenmodes at the input of the photonic lattice and show the diffractionless propagation of the input states due to their infinite effective mass. In the future, the use of photonic rhombic lattices, together with the successful implementation of a synthetic gauge field, will enable the observation of Aharonov-Bohm photonic caging.
Lattice Statistical Models for the Nematic Transitions in Liquid-Crystalline Systems
NASA Astrophysics Data System (ADS)
Nascimento, E. S.; Vieira, A. P.; Salinas, S. R.
2016-08-01
We investigate the connections between some simple Maier-Saupe lattice models, with a discrete choice of orientations of the microscopic directors, and a recent proposal of a two-tensor formalism to describe the phase diagrams of nematic liquid-crystalline systems. This two-tensor proposal is used to formulate the statistical problem in terms of fully connected lattice Hamiltonians, with the local nematic directors restricted to the Cartesian axes. Depending on the choice of interaction parameters, we regain all of the main features of the original mean-field two-tensor calculations. With a standard choice of parameters, we obtain the well-known sequence of isotropic, uniaxial, and biaxial nematic structures, with a Landau multicritical point. With another suitably chosen set of parameters, we obtain two tricritical points, according to some recent predictions of the two-tensor calculations. The simple statistical lattice models are quite easy to work with, for all values of parameters, and the present calculations can be carried out beyond the mean-field level.
Spontaneous Charge Carrier Localization in Extended One-Dimensional Systems
NASA Astrophysics Data System (ADS)
Vlček, Vojtěch; Eisenberg, Helen R.; Steinle-Neumann, Gerd; Neuhauser, Daniel; Rabani, Eran; Baer, Roi
2016-05-01
Charge carrier localization in extended atomic systems has been described previously as being driven by disorder, point defects, or distortions of the ionic lattice. Here we show for the first time by means of first-principles computations that charge carriers can spontaneously localize due to a purely electronic effect in otherwise perfectly ordered structures. Optimally tuned range-separated density functional theory and many-body perturbation calculations within the G W approximation reveal that in trans-polyacetylene and polythiophene the hole density localizes on a length scale of several nanometers. This is due to exchange-induced translational symmetry breaking of the charge density. Ionization potentials, optical absorption peaks, excitonic binding energies, and the optimally tuned range parameter itself all become independent of polymer length as it exceeds the critical localization length. Moreover, we find that lattice disorder and the formation of a polaron result from the charge localization in contrast to the traditional view that lattice distortions precede charge localization. Our results can explain experimental findings that polarons in conjugated polymers form instantaneously after exposure to ultrafast light pulses.
Dynamics of a lattice gas system of three species
NASA Astrophysics Data System (ADS)
Wang, Yuanshi; Wu, Hong; Liang, Junhao
2016-10-01
This paper considers a mutualism system of three species in which each species provides resource for the next one in a one-directional loop, while there exists spatial competition among them. The system is characterized by a lattice gas model and the cases of obligate mutualisms, obligate-facultative mutualisms and facultative mutualisms are considered. Using dynamical systems theory, it is shown that (i) the mutualisms can lead to coexistence of species; (ii) A weak mutualism or an extremely strong mutualism will result in extinction of species, while even the superior facultative species will be driven into extinction by its over-strong mutualism on the next one; (iii) Initial population density plays a role in the coexistence of species. It is also shown that when there exists weak mutualism, an obligate species can survive by providing more benefit to the next one, and the inferior facultative species will not be driven into extinction if it can strengthen its mutualism on the next species. Moreover, Hopf bifurcation, saddle-node bifurcation and bifurcation of heteroclinic cycles are shown in the system. Projection method is extended to exhibit bistability in the three-dimensional model: when saddle-node bifurcation occurs, stable manifold of the saddle-node point divides intR+3 into two basins of attraction of two equilibria. Furthermore, Lyapunov method is applied to exhibit unstability of heteroclinic cycles. Numerical simulations confirm and extend our results.
NASA Astrophysics Data System (ADS)
Toda, Akio; Ikarashi, Nobuyuki; Ono, Haruhiko
2000-03-01
We examined the lattice strain distribution around local oxidation of silicon (LOCOS) in a semiconductor device by using highly accurate (1.8×10 -4 standard deviation) convergent-beam electron diffraction (CBED) at a nanometer-scale spatial resolution (10 nm in diameter). The nanometer-scale measurement was done by reducing the elastic relaxation using a thick (about 600 nm) sample and by removing the inelastically scattered electrons by means of an electron energy filter. A highly accurate measurement was achieved through the analysis of higher-order Laue zone (HOLZ) patterns using the least-squares fitting of HOLZ line intersection distances between the observations and calculations. Our examination showed that the LOCOS structure gave singularities in strain distributions at the field edge. That is, compressive strain exists in both the vertical and horizontal directions of the substrate, and the shear strain increased there. Most notably, two-dimensional measurements revealed that the singularity of the normal strain in the horizontal direction of the substrate generated at the field edge propagated into the substrate.
NASA Astrophysics Data System (ADS)
Ginzburg, Irina; Roux, Laetitia; Silva, Goncalo
2015-10-01
This work demonstrates that in advection-diffusion Lattice Boltzmann schemes, the local mass-conserving boundary rules, such as bounce-back and local specular reflection, may modify the transport coefficients predicted by the Chapman-Enskog expansion when they enforce to zero not only the normal, but also the tangential boundary flux. In order to accommodate it to the bulk solution, the system develops a Knudsen-layer correction to the non-equilibrium part of the population solution. Two principal secondary effects-(i) decrease in the diffusion coefficient, and (ii) retardation of the average advection velocity, obtained in a closed analytical form, are proportional, respectively, to freely assigned diagonal weights for equilibrium mass and velocity terms. In addition, due to their transverse velocity gradients, the boundary layers affect the longitudinal diffusion coefficient similarly to Taylor dispersion, as they grow as the square of the Péclet number. These numerical artifacts can be eliminated or reduced by a proper space distribution of the free-tunable collision eigenvalue in two-relaxation-time schemes.
NASA Astrophysics Data System (ADS)
Saubanère, Matthieu; Lepetit, Marie Bernadette; Pastor, G. M.
2016-07-01
The interaction energy W [γ ] of the Hubbard model is regarded as a functional of the single-particle density matrix γ in the framework of lattice density-functional theory. The local character of the Hubbard interaction is exploited to express W as a sum of local contributions ωi[γ ] , for which a simple semilocal scaling approximation is proposed. The method is applied to the ionic Hubbard model on one- and two-dimensional lattices with homogeneous and inhomogeneous Coulomb repulsions. Results are given for the kinetic and Coulomb energies, interatomic charge transfers, local magnetic moments, and charge gaps. Goals and limitations of the functional are discussed by comparison with exact results.
Lattice Boltzmann models for the grain growth in polycrystalline systems
NASA Astrophysics Data System (ADS)
Zheng, Yonggang; Chen, Cen; Ye, Hongfei; Zhang, Hongwu
2016-08-01
In the present work, lattice Boltzmann models are proposed for the computer simulation of normal grain growth in two-dimensional systems with/without immobile dispersed second-phase particles and involving the temperature gradient effect. These models are demonstrated theoretically to be equivalent to the phase field models based on the multiscale expansion. Simulation results of several representative examples show that the proposed models can effectively and accurately simulate the grain growth in various single- and two-phase systems. It is found that the grain growth in single-phase polycrystalline materials follows the power-law kinetics and the immobile second-phase particles can inhibit the grain growth in two-phase systems. It is further demonstrated that the grain growth can be tuned by the second-phase particles and the introduction of temperature gradient is also an effective way for the fabrication of polycrystalline materials with grained gradient microstructures. The proposed models are useful for the numerical design of the microstructure of materials and provide effective tools to guide the experiments. Moreover, these models can be easily extended to simulate two- and three-dimensional grain growth with considering the mobile second-phase particles, transient heat transfer, melt convection, etc.
Lattice-induced resonances in one-dimensional bosonic systems.
von Stecher, Javier; Gurarie, Victor; Radzihovsky, Leo; Rey, Ana Maria
2011-06-10
We study the resonant effects produced when a Feshbach dimer crosses a scattering continuum band of atoms in an optical lattice. We numerically obtain the exact spectrum of two particles in a one-dimensional lattice and develop an effective atom-dimer Hamiltonian that accurately captures resonant effects. The lattice-induced resonances lead to the formation of bound states simultaneously above and below the scattering continuum and significantly modify the curvature of the dimer dispersion relation. The nature of the atom-dimer coupling depends strongly on the parity of the dimer state leading to a novel coupling in the case of negative parity dimers. PMID:21770514
Lattice-Induced Resonances in One-Dimensional Bosonic Systems
NASA Astrophysics Data System (ADS)
von Stecher, Javier; Gurarie, Victor; Radzihovsky, Leo; Rey, Ana Maria
2011-06-01
We study the resonant effects produced when a Feshbach dimer crosses a scattering continuum band of atoms in an optical lattice. We numerically obtain the exact spectrum of two particles in a one-dimensional lattice and develop an effective atom-dimer Hamiltonian that accurately captures resonant effects. The lattice-induced resonances lead to the formation of bound states simultaneously above and below the scattering continuum and significantly modify the curvature of the dimer dispersion relation. The nature of the atom-dimer coupling depends strongly on the parity of the dimer state leading to a novel coupling in the case of negative parity dimers.
Population dynamics of intraguild predation in a lattice gas system.
Wang, Yuanshi; Wu, Hong
2015-01-01
In the system of intraguild predation (IGP) we are concerned with, species that are in a predator-prey relationship, also compete for shared resources (space or food). While several models have been established to characterize IGP, mechanisms by which IG prey and IG predator can coexist in IGP systems with spatial competition, have not been shown. This paper considers an IGP model, which is derived from reactions on lattice and has a form similar to that of Lotka-Volterra equations. Dynamics of the model demonstrate properties of IGP and mechanisms by which the IGP leads to coexistence of species and occurrence of alternative states. Intermediate predation is shown to lead to persistence of the predator, while extremely big predation can lead to extinction of one/both species and extremely small predation can lead to extinction of the predator. Numerical computations confirm and extend our results. While empirical observations typically exhibit coexistence of IG predator and IG prey, theoretical analysis in this work demonstrates exact conditions under which this coexistence can occur.
Population dynamics of intraguild predation in a lattice gas system.
Wang, Yuanshi; Wu, Hong
2015-01-01
In the system of intraguild predation (IGP) we are concerned with, species that are in a predator-prey relationship, also compete for shared resources (space or food). While several models have been established to characterize IGP, mechanisms by which IG prey and IG predator can coexist in IGP systems with spatial competition, have not been shown. This paper considers an IGP model, which is derived from reactions on lattice and has a form similar to that of Lotka-Volterra equations. Dynamics of the model demonstrate properties of IGP and mechanisms by which the IGP leads to coexistence of species and occurrence of alternative states. Intermediate predation is shown to lead to persistence of the predator, while extremely big predation can lead to extinction of one/both species and extremely small predation can lead to extinction of the predator. Numerical computations confirm and extend our results. While empirical observations typically exhibit coexistence of IG predator and IG prey, theoretical analysis in this work demonstrates exact conditions under which this coexistence can occur. PMID:25447811
Observation of a Localized Flat-Band State in a Photonic Lieb Lattice.
Mukherjee, Sebabrata; Spracklen, Alexander; Choudhury, Debaditya; Goldman, Nathan; Öhberg, Patrik; Andersson, Erika; Thomson, Robert R
2015-06-19
We demonstrate the first experimental realization of a dispersionless state, in a photonic Lieb lattice formed by an array of optical waveguides. This engineered lattice supports three energy bands, including a perfectly flat middle band with an infinite effective mass. We analyze, both experimentally and theoretically, the evolution of well-prepared flat-band states, and show their remarkable robustness, even in the presence of disorder. The realization of flat-band states in photonic lattices opens an exciting door towards quantum simulation of flat-band models in a highly controllable environment.
The Repulsive Lattice Gas, the Independent-Set Polynomial, and the Lovász Local Lemma
NASA Astrophysics Data System (ADS)
Scott, Alexander D.; Sokal, Alan D.
2005-03-01
We elucidate the close connection between the repulsive lattice gas in equilibrium statistical mechanics and the Lovász local lemma in probabilistic combinatorics. We show that the conclusion of the Lovász local lemma holds for dependency graph G and probabilities { p x } if and only if the independent-set polynomial for G is nonvanishing in the polydisc of radii { p x }. Furthermore, we show that the usual proof of the Lovász local lemma - which provides a sufficient condition for this to occur - corresponds to a simple inductive argument for the nonvanishing of the independent-set polynomial in a polydisc, which was discovered implicitly by Shearer(98) and explicitly by Dobrushin.(37,38) We also present some refinements and extensions of both arguments, including a generalization of the Lovász local lemma that allows for ``soft'' dependencies. In addition, we prove some general properties of the partition function of a repulsive lattice gas, most of which are consequences of the alternating-sign property for the Mayer coefficients. We conclude with a brief discussion of the repulsive lattice gas on countably infinite graphs.
Design of a lattice-based faceted classification system
NASA Technical Reports Server (NTRS)
Eichmann, David A.; Atkins, John
1992-01-01
We describe a software reuse architecture supporting component retrieval by facet classes. The facets are organized into a lattice of facet sets and facet n-tuples. The query mechanism supports precise retrieval and flexible browsing.
Phase separation in thermal systems: a lattice Boltzmann study and morphological characterization.
Gan, Yanbiao; Xu, Aiguo; Zhang, Guangcai; Li, Yingjun; Li, Hua
2011-10-01
We investigate thermal and isothermal symmetric liquid-vapor separations via a fast Fourier transform thermal lattice Boltzmann (FFT-TLB) model. Structure factor, domain size, and Minkowski functionals are employed to characterize the density and velocity fields, as well as to understand the configurations and the kinetic processes. Compared with the isothermal phase separation, the freedom in temperature prolongs the spinodal decomposition (SD) stage and induces different rheological and morphological behaviors in the thermal system. After the transient procedure, both the thermal and isothermal separations show power-law scalings in domain growth, while the exponent for thermal system is lower than that for isothermal system. With respect to the density field, the isothermal system presents more likely bicontinuous configurations with narrower interfaces, while the thermal system presents more likely configurations with scattered bubbles. Heat creation, conduction, and lower interfacial stresses are the main reasons for the differences in thermal system. Different from the isothermal case, the release of latent heat causes the changing of local temperature, which results in new local mechanical balance. When the Prandtl number becomes smaller, the system approaches thermodynamical equilibrium much more quickly. The increasing of mean temperature makes the interfacial stress lower in the following way: σ=σ(0)[(T(c)-T)/(T(c)-T(0))](3/2), where T(c) is the critical temperature and σ(0) is the interfacial stress at a reference temperature T(0), which is the main reason for the prolonged SD stage and the lower growth exponent in the thermal case. Besides thermodynamics, we probe how the local viscosities influence the morphology of the phase separating system. We find that, for both the isothermal and thermal cases, the growth exponents and local flow velocities are inversely proportional to the corresponding viscosities. Compared with the isothermal case, the
Thermalization and Canonical Typicality in Translation-Invariant Quantum Lattice Systems
NASA Astrophysics Data System (ADS)
Müller, Markus P.; Adlam, Emily; Masanes, Lluís; Wiebe, Nathan
2015-12-01
It has previously been suggested that small subsystems of closed quantum systems thermalize under some assumptions; however, this has been rigorously shown so far only for systems with very weak interaction between subsystems. In this work, we give rigorous analytic results on thermalization for translation-invariant quantum lattice systems with finite-range interaction of arbitrary strength, in all cases where there is a unique equilibrium state at the corresponding temperature. We clarify the physical picture by showing that subsystems relax towards the reduction of the global Gibbs state, not the local Gibbs state, if the initial state has close to maximal population entropy and certain non-degeneracy conditions on the spectrumare satisfied.Moreover,we showthat almost all pure states with support on a small energy window are locally thermal in the sense of canonical typicality. We derive our results from a statement on equivalence of ensembles, generalizing earlier results by Lima, and give numerical and analytic finite size bounds, relating the Ising model to the finite de Finetti theorem. Furthermore, we prove that global energy eigenstates are locally close to diagonal in the local energy eigenbasis, which constitutes a part of the eigenstate thermalization hypothesis that is valid regardless of the integrability of the model.
Lattice hydrodynamic model based traffic control: A transportation cyber-physical system approach
NASA Astrophysics Data System (ADS)
Liu, Hui; Sun, Dihua; Liu, Weining
2016-11-01
Lattice hydrodynamic model is a typical continuum traffic flow model, which describes the jamming transition of traffic flow properly. Previous studies in lattice hydrodynamic model have shown that the use of control method has the potential to improve traffic conditions. In this paper, a new control method is applied in lattice hydrodynamic model from a transportation cyber-physical system approach, in which only one lattice site needs to be controlled in this control scheme. The simulation verifies the feasibility and validity of this method, which can ensure the efficient and smooth operation of the traffic flow.
NASA Technical Reports Server (NTRS)
Baskaran, G.
1989-01-01
Using a nonmean-field approach the triangular-lattice S = 1/2 Heisenberg antiferromagnet with nearest- and next-nearest-neighbor couplings is shown undergo an Ising-type phase transition into a chiral-symmetry-broken phase (Kalmeyer-Laughlin-like state) at small T. Removal of next-nearest-neighbor coupling introduces a local Z2 symmetry, thereby suppressing any finite-T chiral order.
Fundamental cycle of a periodic box ball system and solvable lattice models
NASA Astrophysics Data System (ADS)
Mada, Jun; Idzumi, Makoto; Tokihiro, Tetsuji
2006-05-01
We investigate the fundamental cycle of a periodic box-ball system (PBBS) from a relation between the PBBS and a solvable lattice model. We show that the fundamental cycle of the PBBS is obtained from eigenvalues of the transfer matrix of the solvable lattice model.
Coarse-grained Simulations of Chemical Oscillation in Lattice Brusselator System
NASA Astrophysics Data System (ADS)
Rao, Ting; Zhang, Zhen; Hou, Zhong-huai; Xin, Hou-wen
2011-08-01
The oscillation behavior of a two-dimension lattice-gas Brusselator model was investigated. We have adopted a coarse-grained kinetic Monte Carlo (CG-KMC) procedure, where m×m microscopic lattice sites are grouped together to form a CG cell, upon which CG processes take place with well-defined CG rates. Such a CG approach almost fails if the CG rates are obtained by a simple local mean field (s-LMF) approximation, due to the ignorance of correlation among adjcent cells resulting from the trimolecular reaction in this nonlinear system. By proper incorporating such boundary effects, thus introduce the so-called b-LMF CG approach. Extensive numerical simulations demonstrate that the b-LMF method can reproduce the oscillation behavior of the system quite well, given that the diffusion constant is not too small. In addition, the deviation from the KMC results reaches a nearly zero minimum level at an intermediate cell size, which lies in between the effective diffusion length and the minimal size required to sustain a well-defined temporal oscillation.
Local lattice distortions vs. structural phase transition in NdFeAsO1-xFx
NASA Astrophysics Data System (ADS)
Calamiotou, M.; Lampakis, D.; Zhigadlo, N. D.; Katrych, S.; Karpinski, J.; Fitch, A.; Tsiaklagkanos, P.; Liarokapis, E.
2016-08-01
The lattice properties at low temperatures of two samples of NdFeAsO1-xFx (x = 0.05 and 0.25) have been examined in order to investigate possible structural phase transition that may occur in the optimally doped superconducting sample with respect to the non-superconducting low-F concentration compound. In order to detect small modifications in the ion displacements with temperature micro-Raman and high resolution synchrotron powder diffraction measurements were carried out. No increase of the width of the (2 2 0) or (3 2 2) tetragonal diffraction peaks and microstrains could be found in the superconducting sample from synchrotron XRD measurements. On the other hand, the atomic displacement parameters deviate from the expected behavior, in agreement with modifications in the phonon width, as obtained by Raman scattering. These deviations occur around 150 K for both F dopings, with distinct differences among the two compounds, i.e., they decrease at low doping and increase for the superconducting sample. The data do not support a hidden phase transition to an orthorhombic phase in the superconducting compound, but point to an isostructural lattice deformation. Based on the absence of magnetic effects in this temperature range for the superconducting sample, we attribute the observed lattice anomalies to the formation of local lattice distortions that, being screened by the carriers, can only acquire long-range coherence by means of a structural phase transition at low doping levels.
Agarwala, R.; Batzoglou, S.; Dancik, V.
1997-06-01
We consider the problem of determining the three-dimensional folding of a protein given its one-dimensional amino acid sequence. We use the HP model for protein folding proposed by Dill, which models protein as a chain of amino acid residues that are either hydrophobic or polar, and hydrophobic interactions are the dominant initial driving force for the protein folding. Hart and Istrail gave approximation algorithms for folding proteins on the cubic lattice under HP model. In this paper, we examine the choice of a lattice by considering its algorithmic and geometric implications and argue that triangular lattice is a more reasonable choice. We present a set of folding rules for a triangular lattice and analyze the approximation ratio which they achieve. In addition, we introduce a generalization of the HP model to account for residues having different levels of hydrophobicity. After describing the biological foundation for this generalization, we show that in the new model we are able to achieve similar constant factor approximation guarantees on the triangular lattice as were achieved in the standard HP model. While the structures derived from our folding rules are probably still far from biological reality, we hope that having a set of folding rules with different properties will yield more interesting folds when combined.
NASA Astrophysics Data System (ADS)
Zhao, Hai-qiong; Zhu, Zuo-nong
2011-02-01
This paper aims to find new explicit solutions including multisoliton, multipositon, multinegaton, and multiperiodic for a coupled Volterra lattice system. This coupled lattice system is an integrable discrete version of the coupled Korteweg-deVries (KdV) equation which has many physical applications. The dynamical properties of these new solutions are discussed in detail. We also prove that the theory of the coupled Volterra lattice system including the Lax pair, the Darboux transformation, and explicit solutions yield the corresponding theory of the coupled KdV equation in the continuous limit.
Agarwala, R.; Batzoglou, S.; Dancik, V.
1997-12-01
A long standing problem in molecular biology is to determine the three-dimensional structure of a protein, given its amino acid sequence. A variety of simplifying models have been proposed abstracting only the {open_quotes}essential physical properties{close_quotes} of real proteins. In these models, the three dimensional space is often represented by a lattice. Residues which are adjacent in the primary sequence (i.e. covalently linked) must be placed at adjacent points in the lattice. A conformation of a protein is simply a self-avoiding walk along the lattice. The protein folding problem STRING-FOLD is that of finding a conformation of the protein sequence on the lattice such that the overall energy is minimized, for some reasonable definition of energy. This formulation leaves open the choices of a lattice and an energy function. Once these choices are made, one may then address the algorithmic complexity of optimizing the energy function for the lattice. For a variety of such simple models, this minimization problem is in fact NP-hard. In this paper, we consider the Hydrophobic-Polar (HP) Model introduced by Dill. The HP model abstracts the problem by grouping the 20 amino acids into two classes: hydrophobic (or non-polar) residues and hydrophilic (or polar) residues. For concreteness, we will take our input to be a string from (H,P){sup +}, where P represents polar residues, and H represents hydrophobic residues. Dill et.al. survey the literature analyzing this model. 8 refs., 2 figs., 1 tab.
Advanced information processing system: Local system services
NASA Technical Reports Server (NTRS)
Burkhardt, Laura; Alger, Linda; Whittredge, Roy; Stasiowski, Peter
1989-01-01
The Advanced Information Processing System (AIPS) is a multi-computer architecture composed of hardware and software building blocks that can be configured to meet a broad range of application requirements. The hardware building blocks are fault-tolerant, general-purpose computers, fault-and damage-tolerant networks (both computer and input/output), and interfaces between the networks and the computers. The software building blocks are the major software functions: local system services, input/output, system services, inter-computer system services, and the system manager. The foundation of the local system services is an operating system with the functions required for a traditional real-time multi-tasking computer, such as task scheduling, inter-task communication, memory management, interrupt handling, and time maintenance. Resting on this foundation are the redundancy management functions necessary in a redundant computer and the status reporting functions required for an operator interface. The functional requirements, functional design and detailed specifications for all the local system services are documented.
Local public health system partnerships.
Zahner, Susan J.
2005-01-01
OBJECTIVES: Interorganizational collaboration aimed at community health improvement is an expectation of local public health systems. This study assessed the extent to which such collaboration occurred within one state (Wisconsin), described the characteristics of existing partnerships, and identified factors associated with partnership effectiveness. METHODS: In Stage 1, local health department (LHD) directors in Wisconsin were surveyed (93% response rate). In Stage 2, LHDs completed self-administered mailed surveys for each partnership identified in Stage 1 (85% response rate). Two-level hierarchical logit regression methods were used to model relationships between partnership and LHD variables and partnership outcomes. Data from 924 partnerships associated with 74 LHDs were included in the analysis. RESULTS: Partnerships most frequently addressed tobacco prevention and control, maternal and child health, emergency planning, community assessment and planning, and immunizations. Partnering was most frequent with other government agencies, hospitals, medical practices or clinics, community-based organizations, and schools. Partnership effectiveness was predicted by having a budget, having more partners contributing financially, having a broader array of organizations involved, and having been in existence for a longer period of time. A government mandate to start the partnership was inversely related to successful outcomes. Characteristics of LHDs did not predict partnership effectiveness. CONCLUSIONS: Financial support, having a broader array of partners, and allowing sufficient time for partnerships to succeed contribute to partnership effectiveness. Further study-using objective outcome measures-is needed to examine the effects of organizational and community characteristics on the effectiveness of local public health system partnerships. PMID:15736335
Spatiotemporal dynamics of a digital phase-locked loop based coupled map lattice system
Banerjee, Tanmoy Paul, Bishwajit; Sarkar, B. C.
2014-03-15
We explore the spatiotemporal dynamics of a coupled map lattice (CML) system, which is realized with a one dimensional array of locally coupled digital phase-locked loops (DPLLs). DPLL is a nonlinear feedback-controlled system widely used as an important building block of electronic communication systems. We derive the phase-error equation of the spatially extended system of coupled DPLLs, which resembles a form of the equation of a CML system. We carry out stability analysis for the synchronized homogeneous solutions using the circulant matrix formalism. It is shown through extensive numerical simulations that with the variation of nonlinearity parameter and coupling strength the system shows transitions among several generic features of spatiotemporal dynamics, viz., synchronized fixed point solution, frozen random pattern, pattern selection, spatiotemporal intermittency, and fully developed spatiotemporal chaos. We quantify the spatiotemporal dynamics using quantitative measures like average quadratic deviation and spatial correlation function. We emphasize that instead of using an idealized model of CML, which is usually employed to observe the spatiotemporal behaviors, we consider a real world physical system and establish the existence of spatiotemporal chaos and other patterns in this system. We also discuss the importance of the present study in engineering application like removal of clock-skew in parallel processors.
Spatiotemporal dynamics of a digital phase-locked loop based coupled map lattice system
NASA Astrophysics Data System (ADS)
Banerjee, Tanmoy; Paul, Bishwajit; Sarkar, B. C.
2014-03-01
We explore the spatiotemporal dynamics of a coupled map lattice (CML) system, which is realized with a one dimensional array of locally coupled digital phase-locked loops (DPLLs). DPLL is a nonlinear feedback-controlled system widely used as an important building block of electronic communication systems. We derive the phase-error equation of the spatially extended system of coupled DPLLs, which resembles a form of the equation of a CML system. We carry out stability analysis for the synchronized homogeneous solutions using the circulant matrix formalism. It is shown through extensive numerical simulations that with the variation of nonlinearity parameter and coupling strength the system shows transitions among several generic features of spatiotemporal dynamics, viz., synchronized fixed point solution, frozen random pattern, pattern selection, spatiotemporal intermittency, and fully developed spatiotemporal chaos. We quantify the spatiotemporal dynamics using quantitative measures like average quadratic deviation and spatial correlation function. We emphasize that instead of using an idealized model of CML, which is usually employed to observe the spatiotemporal behaviors, we consider a real world physical system and establish the existence of spatiotemporal chaos and other patterns in this system. We also discuss the importance of the present study in engineering application like removal of clock-skew in parallel processors.
Some properties of correlations of quantum lattice systems in thermal equilibrium
Fröhlich, Jürg; Ueltschi, Daniel
2015-05-15
Simple proofs of uniqueness of the thermodynamic limit of KMS states and of the decay of equilibrium correlations are presented for a large class of quantum lattice systems at high temperatures. New quantum correlation inequalities for general Heisenberg models are described. Finally, a simplified derivation of a general result on power-law decay of correlations in 2D quantum lattice systems with continuous symmetries is given, extending results of McBryan and Spencer for the 2D classical XY model.
Local optimization of energy systems
Lozano, M.A.; Valero, A.; Serra, L.
1996-12-31
Many thermal systems are very complex due to the number of components and/or its strong interdependence. This complexity makes difficult the optimization of the system design and operation. The theory of Exergetic Cost is based on concepts such as resources, structure, efficiency and purpose (belonging to any theory of production) and on the Second Law. This paper will show how it is possible to obtain from the theory of exergetic cost the marginal costs (Lagrange multipliers) of local resources being consumed by a component. This paper also shows the advantage of the proposed Theory of Perturbations when describing the complexity of structural interactions in a straightforward way. This theory allows to formulate simple procedures for local optimization of components in a plant. Finally, strategies for optimization of complex systems are shown. They are based in the sequential optimization from component to component. This clear and efficient method comes form the fact that the authors have now an operative application of the Thermoeconomic Isolation Principle. This is applied here to thermal power plants.
Dynamics of exciton-polaritons in discrete lattices under incoherent localized pumping
NASA Astrophysics Data System (ADS)
Yulin, A. V.; Chestnov, I. Yu.; Ma, X.; Schumacher, S.; Peschel, U.; Egorov, O. A.
2016-08-01
The paper deals with the spontaneous coherence building up between exciton-polaritons trapped in an array of deep potential wells in the presence of an incoherent pump. A theoretical approach based on a standard tight-binding mean-field approximation is used to reduce the continuous periodic problem to a discrete model. The typical dynamics of the nonlinear exciton-polariton system for the cases of spatially uniform and for localized pumps are discussed. Special attention is paid to the "staggered" coherent steady states with π jumps in the phases between neighboring sites and to "uniform" states with a smooth phase distribution. It is shown that, apart from the states with a single frequency, mixed states with spectra with several harmonics can form in the system. The selection mechanism that controls the type of steady state growing from a weak noise is studied. It is found that in the case of localized pumps the decaying tails of the solutions play a crucial role in the dynamics of the polaritons. The applicability of the obtained theoretical results for a qualitative explanation of the complex phenomena observed in recent experiments is discussed.
Lattice physics capabilities of the SCALE code system using TRITON
DeHart, M. D.
2006-07-01
This paper describes ongoing calculations used to validate the TRITON depletion module in SCALE for light water reactor (LWR) fuel lattices. TRITON has been developed to provide improved resolution for lattice physics mixed-oxide fuel assemblies as programs to burn such fuel in the United States begin to come online. Results are provided for coupled TRITON/PARCS analyses of an LWR core in which TRITON was employed for generation of appropriately weighted few-group nodal cross-sectional sets for use in core-level calculations using PARCS. Additional results are provided for code-to-code comparisons for TRITON and a suite of other depletion packages in the modeling of a conceptual next-generation boiling water reactor fuel assembly design. Results indicate that the set of SCALE functional modules used within TRITON provide an accurate means for lattice physics calculations. Because the transport solution within TRITON provides a generalized-geometry capability, this capability is extensible to a wide variety of non-traditional and advanced fuel assembly designs. (authors)
Monte Carlo simulations of lattice models for single polymer systems
Hsu, Hsiao-Ping
2014-10-28
Single linear polymer chains in dilute solutions under good solvent conditions are studied by Monte Carlo simulations with the pruned-enriched Rosenbluth method up to the chain length N∼O(10{sup 4}). Based on the standard simple cubic lattice model (SCLM) with fixed bond length and the bond fluctuation model (BFM) with bond lengths in a range between 2 and √(10), we investigate the conformations of polymer chains described by self-avoiding walks on the simple cubic lattice, and by random walks and non-reversible random walks in the absence of excluded volume interactions. In addition to flexible chains, we also extend our study to semiflexible chains for different stiffness controlled by a bending potential. The persistence lengths of chains extracted from the orientational correlations are estimated for all cases. We show that chains based on the BFM are more flexible than those based on the SCLM for a fixed bending energy. The microscopic differences between these two lattice models are discussed and the theoretical predictions of scaling laws given in the literature are checked and verified. Our simulations clarify that a different mapping ratio between the coarse-grained models and the atomistically realistic description of polymers is required in a coarse-graining approach due to the different crossovers to the asymptotic behavior.
Elton, A.B.H.
1990-09-24
A numerical theory for the massively parallel lattice gas and lattice Boltzmann methods for computing solutions to nonlinear advective-diffusive systems is introduced. The convergence theory is based on consistency and stability arguments that are supported by the discrete Chapman-Enskog expansion (for consistency) and conditions of monotonicity (in establishing stability). The theory is applied to four lattice methods: Two of the methods are for some two-dimensional nonlinear diffusion equations. One of the methods is for the one-dimensional lattice method for the one-dimensional viscous Burgers equation. And one of the methods is for a two-dimensional nonlinear advection-diffusion equation. Convergence is formally proven in the L{sub 1}-norm for the first three methods, revealing that they are second-order, conservative, conditionally monotone finite difference methods. Computational results which support the theory for lattice methods are presented. In addition, a domain decomposition strategy using mesh refinement techniques is presented for lattice gas and lattice Boltzmann methods. The strategy allows concentration of computational resources on regions of high activity. Computational evidence is reported for the strategy applied to the lattice gas method for the one-dimensional viscous Burgers equation. 72 refs., 19 figs., 28 tabs.
Spontaneous charge carrier localization in extended one-dimensional systems
NASA Astrophysics Data System (ADS)
Vlček, Vojtěch; Eisenberg, Helen; Steinle-Neumann, Gerd; Baer, Roi
Charge carrier localization in extended atomic systems can be driven by disorder, point defects or distortions of the ionic lattice. Herein we give first-principles theoretical computational evidence that it can also appear as a purely electronic effect in otherwise perfectly ordered periodic structures and we show that electronic eigenstates can spontaneously localize upon excitation. Optimally-tuned range separated density functional calculations reveal that in trans-polyacetylene and polythiophene the hole density localizes on a length scale of several nanometers. This is due to exchange induced translational symmetry breaking of the charge density. Ionization potentials, optical absorption peaks, excitonic binding energies and the optimally-tuned range parameter itself all become independent of polymer length when it exceeds the critical localization length scale. These first-principles findings show, for the first time, that charge localization is not caused by lattice distortion but rather it is their cause, changing the physical models of polaron formation and dynamics, helping to explain experimental findings that polarons in conjugated polymers form instantaneously after exposure to ultrafast light pulses. Secondary affiliation: Bayerisches Geoinstitut, Universität Bayreuth, Germany.
Dynamical Behavior of Multi-Robot Systems Using Lattice Gas Automata
Cameron, S.M.; Robinett, R.; Stantz, K.M.; Trahan, M.W.; Wagner, J.S.
1999-03-11
Recent attention has been given to the deployment of an adaptable sensor array realized by multi-robotic systems. Our group has been studying the collective behavior of autonomous, multi-agent systems and their applications in the area of remote-sensing and emerging threats. To accomplish such tasks, an interdisciplinary research effort at Sandia National Laboratories are conducting tests in the fields of sensor technology, robotics, and multi-robotic and multi-agents architectures. Our goal is to coordinate a constellation of point sensors that optimizes spatial coverage and multivariate signal analysis using unmanned robotic vehicles (e.g., RATLERs, Robotic All-ten-sin Lunar Exploration Rover-class vehicles). Overall design methodology is to evolve complex collective behaviors realized through simple interaction (kinetic) physics and artificial intelligence to enable real-time operational responses to emerging threats. This paper focuses on our recent work understanding the dynamics of many-body systems using the physics-based hydrodynamic model of lattice gas automata. Three design features are investigated. One, for single-speed robots, a hexagonal nearest-neighbor interaction topology is necessary to preserve standard hydrodynamic flow. Two, adaptability, defined by the swarm's deformation rate, can be controlled through the hydrodynamic viscosity term, which, in turn, is defined by the local robotic interaction rules. Three, due to the inherent non-linearity of the dynamical equations describing large ensembles, development of stability criteria ensuring convergence to equilibrium states is developed by scaling information flow rates relative to a swarm's hydrodynamic flow rate. An initial test case simulates a swarm of twenty-five robots that maneuvers past an obstacle while following a moving target. A genetic algorithm optimizes applied nearest-neighbor forces in each of five spatial regions distributed over the simulation domain. Armed with knowledge, the
Identifying Local and Quasilocal Conserved Quantities in Integrable Systems
NASA Astrophysics Data System (ADS)
Mierzejewski, Marcin; Prelovšek, Peter; Prosen, Tomaž
2015-04-01
We outline a procedure for counting and identifying a complete set of local and quasilocal conserved operators in integrable lattice systems. The method yields a systematic generation of all independent, conserved quasilocal operators related to the time average of local operators with a support on up to M consecutive sites. As an example, we study the anisotropic Heisenberg spin-1 /2 chain and show that the number of independent conserved operators grows linearly with M . In addition to the known local operators, there exist novel quasilocal conserved quantities in all the parity sectors. The existence of quasilocal conserved operators is shown also for the isotropic Heisenberg model. Implications for the anomalous relaxation of quenched systems are discussed as well.
Lattice gas automata for flow and transport in geochemical systems
Janecky, D.R.; Chen, S.; Dawson, S.; Eggert, K.C.; Travis, B.J.
1992-05-01
Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because hydrodynamic transport, solute diffusion and mineral surface processes are all treated explicitly. The simplicity and flexibility of the approach provides the ability to study the interrelationship between fluid flow and chemical reactions in porous materials, at a level of complexity that has not previously been computationally possible.
Lattice gas automata for flow and transport in geochemical systems
Janecky, D.R.; Chen, S.; Dawson, S.; Eggert, K.C.; Travis, B.J.
1992-01-01
Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because hydrodynamic transport, solute diffusion and mineral surface processes are all treated explicitly. The simplicity and flexibility of the approach provides the ability to study the interrelationship between fluid flow and chemical reactions in porous materials, at a level of complexity that has not previously been computationally possible.
NASA Astrophysics Data System (ADS)
Barbiero, L.; Malomed, B. A.; Salasnich, L.
2016-05-01
We study the dynamics of quantum bosonic waves in a one-dimensional tilted optical lattice. An effective spatially localized nonlinear two-body potential barrier is set at the center of the lattice. This version of the Bose-Hubbard model can be realized in atomic Bose-Einstein condensates, with the help of localized optical Feshbach resonance, controlled by a focused laser beam, and in quantum optics, using an arrayed waveguide with selectively doped guiding cores. Our numerical analysis demonstrates that the central barrier induces anomalous quantum reflection of incident wave packets, which acts solely on bosonic components with multiple onsite occupancies, while single-occupancy components pass the barrier, allowing one to distill them in the interaction zone. As a consequence, in this region one finds a hard-core-like state, in which the multiple occupancy is forbidden. Our results demonstrate that this regime can be attained dynamically, using relatively weak interactions, irrespective of their sign. Physical parameters necessary for the experimental implementation of the setting in ultracold atomic gases are estimated.
NASA Astrophysics Data System (ADS)
Barbiero, L.; Malomed, B. A.; Salasnich, L.
2016-05-01
We study the dynamics of quantum bosonic waves in a one-dimensional tilted optical lattice. An effective spatially localized nonlinear two-body potential barrier is set at the center of the lattice. This version of the Bose–Hubbard model can be realized in atomic Bose–Einstein condensates, with the help of localized optical Feshbach resonance, controlled by a focused laser beam, and in quantum optics, using an arrayed waveguide with selectively doped guiding cores. Our numerical analysis demonstrates that the central barrier induces anomalous quantum reflection of incident wave packets, which acts solely on bosonic components with multiple onsite occupancies, while single-occupancy components pass the barrier, allowing one to distill them in the interaction zone. As a consequence, in this region one finds a hard-core-like state, in which the multiple occupancy is forbidden. Our results demonstrate that this regime can be attained dynamically, using relatively weak interactions, irrespective of their sign. Physical parameters necessary for the experimental implementation of the setting in ultracold atomic gases are estimated.
Absence of localization in a class of topological systems
NASA Astrophysics Data System (ADS)
Castro, Eduardo V.; de Gail, Raphael; López-Sancho, M. Pilar; Vozmediano, María A. H.
2016-06-01
Topological matter is a trending topic in condensed matter: From a fundamental point of view, it has introduced new phenomena and tools and, for technological applications, it holds the promise of basic stable quantum computing. Similarly, the physics of localization by disorder, an old paradigm of obvious technological importance in the field, continues to reveal surprises when new properties of matter appear. This work deals with the localization behavior of electronic systems based on partite lattices, with special attention to the role of topology. We find an unexpected result from the point of view of localization properties: A robust topological metallic state characterized by a nonquantized Hall conductivity arises from strong disorder in topological systems based on bipartite lattices. The key issue is the nature of the disorder realization: selective disorder in only one sublattice. The generality of the result is based on the partite nature of most recent two-dimensional materials such as graphene or transition-metal dichalcogenides, and the possibility of the physical realization of the particular disorder demonstrated in Ugeda et al. [M. M. Ugeda et al., Phys. Rev. Lett. 104, 096804 (2010), 10.1103/PhysRevLett.104.096804] and Zhao et al. [L. Zhao et al., Science 333, 999 (2011), 10.1126/science.1208759].
Solitons in PT-symmetric nonlinear lattices
Abdullaev, Fatkhulla Kh.; Konotop, Vladimir V.; Zezyulin, Dmitry A.; Kartashov, Yaroslav V.
2011-04-15
The existence of localized modes supported by the PT-symmetric nonlinear lattices is reported. The system considered reveals unusual properties: unlike other typical dissipative systems, it possesses families (branches) of solutions, which can be parametrized by the propagation constant; relatively narrow localized modes appear to be stable, even when the conservative nonlinear lattice potential is absent; and finally, the system supports stable multipole solutions.
Effects of lattice disorder in the UCu5-xPdx system
NASA Astrophysics Data System (ADS)
Bauer, E. D.; Booth, C. H.; Kwei, G. H.; Chau, R.; Maple, M. B.
2002-06-01
The UCu5-xPdx system exhibits non-Fermi liquid (NFL) behavior in thermodynamic and transport properties at low temperatures for Pd concentrations 0.9<~x<~1.5. The local structure around the U, Cu, and Pd atoms has been measured for 0<=x<=1.5 using the x-ray absorption fine structure technique in order to quantify the effects of lattice disorder on the NFL properties. A model which allows a percentage of the Pd atoms to occupy nominal Cu (16e) sites s was used to fit the Pd and Cu K edge and U LIII edge data. Pd/Cu site interchange was found to occur in all samples (x≠0), reaching a minimum value of s~0.17 at x=0.7 and increasing monotonically to s~=0.4 at x=1.5. These data also determine an upper limit on the static disorder of the nearest-neighbor U-Cu pairs. A single-ion Kondo disorder model with a lattice-disorder origin of the distribution of f/conduction electron hybridization strengths within a tight-binding approach is used to calculate magnetic susceptibility. The results indicate that the measured U-Cu static disorder is not sufficient to explain the NFL behavior of the magnetic susceptibility within this variant of the Kondo disorder model, suggesting either that other sources of Kondo disorder exist or that the Kondo disorder model is not applicable to UCu5-xPdx.
An Integrated Support and Alignment System for Large ILC Lattice Elements
Viola, Robert
2013-05-15
The manipulators used to support and position lattice elements are critical components of all particle accelerators. The increased use of large superconducting magnets and accelerator modules places even greater demands on these manipulators. However, the performance of these support systems has not kept pace with the advances made in other areas of accelerator technology. This results in accelerators that are difficult to align and may not be capable of achieving target luminosities. An innovative new type of positioning mechanism tailored to the requirements of the International Linear Collider is proposed. The Tri-Sphere System provides secure support for large lattice elements and precision adjustment in six degrees of freedom. Integrated target sockets allow the support system to be rapidly pre-aligned. The system's kinematic design passively guides lattice elements into their correct location during installation. A complimentary Portable Actuation Unit provides the advantages of automated adjustment and allows these adjustments to be completely decoupled from surveying.
Effect of quantum-lattice fluctuations in one-dimensional fluctuating-valence systems
NASA Astrophysics Data System (ADS)
Zheng, H.; Avignon, M.
1994-04-01
We have developed a variational approach to treat the nonadiabaticity, that is, the quantum-lattice fluctuations, of the electron-phonon interactions in the one-dimensional half-filled spinless Anderson lattice model including Coulomb interaction between both types of electrons. The nonadiabaticity due to finite phonon frequency is treated through a variational polaronic-type wave function, in which two variational parameters δ and τ2 are used to take into account the dynamical distortion and the squeezing effect of phonon modes. We have found that the quantum-lattice fluctuations gradually smoothes the valence transitions when the polaronic level ɛf-v changes. We have shown that conditions somewhat different from those of Hewson and Newns should be satisfied for the occurrence of a significant reduction of the effective hybridization. The effect of the Coulomb repulsion U is to suppress the quantum-lattice fluctuations, that is, to suppress the reduction of the fluctuating-valence frequency and the relaxation shift. We have also discussed the valence-density-wave ordering in the symmetric case. Our results show that the quantum-lattice fluctuations disfavor the ordering and the lattice dimerization parameter decreases with increasing phonon frequency. We have pointed out the possibility of an order-disorder transition in such systems.
Properties of localization in silicon-based lattice periodicity breaking photonic crystal waveguides
Wu, Yuquan; Wang, Xiaofei; Wang, Yufang; Zhang, Guoquan; Fan, Wande; Cao, Xuewei; Wu, Yuanbin
2013-11-15
The light localization effects in silicon photonic crystal cavities at different disorder degrees have been studied using the finite difference time domain (FDTD) method in this paper. Numerical results showed that localization occurs and enhancement can be gained in the region of the cavity under certain conditions. The stabilities of the localization effects due to the structural perturbations have been investigated too. Detailed studies showed that when the degree of structural disorder is small(about 10%), the localization effects are stable, the maximum enhancement factor can reach 16.5 for incident wavelength of 785 nm and 23 for 850 nm in the cavity, with the degree of disorder about 8%. The equivalent diameter of the localized spot is almost constant at different disorder degrees, approximating to λ/7, which turned out to be independent on the structural perturbation.
Phase diagrams of adsorption systems and calibration functions in the lattice-gas model.
Tovbin, Yuriy K; Rabinovich, Alexander B
2004-07-01
Using the calibration function is suggested to increase the accuracy of approximate equations in the lattice-gas model at calculating various concentration dependences of equilibrium characteristics for nonideal adsorption systems in the vicinity of the critical point. This function should provide a shift of the approximate result to the exact one, when the lattice-gas model equations are used in the quality of the interpolation tool between the exact solutions. A comparison of approximate equations with Onsager's exact solution preferrably allows a use of the quasi-chemical approximation as the interpolation procedure and the exact information on the critical point. The modified lattice-gas model takes into account next the molecular properties of the Lennard-Jones fluid: the long-range potential of adsorbate-adsorbate, an excluded volume of the adsorption site, and a contribution of the triple interactions, as well as a softness of the lattice structure. The modified lattice-gas model with the calibration function is used for the phase diagram descriptions for argon adsorption on the homogeneous (111) CdCl2 face (two-dimensional systems) and for methane adsorption in carbon slitlike pores (three-dimensional system) as well as the other equilibrium characteristics of mentioned systems.
Interaction-induced localization of mobile impurities in ultracold systems
Li, Jian; An, Jin; Ting, C. S.
2013-01-01
The impurities, introduced intentionally or accidentally into certain materials, can significantly modify their characteristics or reveal their intrinsic physical properties, and thus play an important role in solid-state physics. Different from those static impurities in a solid, the impurities realized in cold atomic systems are naturally mobile. Here we propose an effective theory for treating some unique behaviors exhibited by ultracold mobile impurities. Our theory reveals the interaction-induced transition between the extended and localized impurity states, and also explains the essential features obtained from several previous models in a unified way. Based on our theory, we predict many intriguing phenomena in ultracold systems associated with the extended and localized impurities, including the formation of the impurity-molecules and impurity-lattices. We hope this investigation can open up a new avenue for the future studies on ultracold mobile impurities. PMID:24192986
Interaction-induced localization of mobile impurities in ultracold systems
NASA Astrophysics Data System (ADS)
Li, Jian; An, Jin; Ting, C. S.
2013-11-01
The impurities, introduced intentionally or accidentally into certain materials, can significantly modify their characteristics or reveal their intrinsic physical properties, and thus play an important role in solid-state physics. Different from those static impurities in a solid, the impurities realized in cold atomic systems are naturally mobile. Here we propose an effective theory for treating some unique behaviors exhibited by ultracold mobile impurities. Our theory reveals the interaction-induced transition between the extended and localized impurity states, and also explains the essential features obtained from several previous models in a unified way. Based on our theory, we predict many intriguing phenomena in ultracold systems associated with the extended and localized impurities, including the formation of the impurity-molecules and impurity-lattices. We hope this investigation can open up a new avenue for the future studies on ultracold mobile impurities.
Characteristics of lattice and magnet system of TARN II
Noda, A.; Hattori, Y.; Itano, A.; Kanazawa, M.; Katayama, T.; Kodaira, M.; Mutou, M.; Sasaki, S.; Takahashi, N.; Takanaka, M.
1985-10-01
TARN II is a ring which is designed to be operated both as a synchrotron and a cooler ring for ions. Its mean radius is about 12.4 m and is to be able to accelerate protons up to 1300 MeV and ions with charge to mass ratio of 1/2 up to 450 MeV/u. The ring consists of 24 dipole and 18 quadrupole magnets, which compose the lattice with sixfold symmetry for synchrotron acceleration (Synchrotron Mode) and another one with threefold symmetry to realize doubly achromatic sections for beam cooling (Cooler Ring Mode). These modes can be transferred between each other keeping the operating point at the position of (..nu.. /SUB H/ , ..nu.. /SUB V/ ) about (1.75, 1.25). The acceptance for beam cooling experiment at TARN II is expected to be improved from 70..pi.. to 400..pi.. mm . mrad by application of pre-cooling of horizontal betatron amplitude by stochastic method with Synchrotron Mode before moving the Cooler Ring Mode. Main magnets of the ring with AC characteristics have already been fabricated. Dipole magnets with H-type are found to have realized required good field region of + or - 100 mm from the result of static field measurement.
The existence of traveling wave solutions for a bistable three-component lattice dynamical system
NASA Astrophysics Data System (ADS)
Guo, Jong-Shenq; Wu, Chin-Chin
2016-01-01
We study the traveling wave solutions for a three-component lattice dynamical system. This problem arises in the modeling of three species competing two food resources in an environment with migration in which the habitat is one-dimensional and is divided into countable niches. We are concerned with the case when two species have different preferences of food and the third species has both preferences of food. To understand which species win the competition under the bistable condition, the existence of a traveling wave solution for this lattice dynamical system is proven.
NASA Astrophysics Data System (ADS)
Li, Chao-Ying; Liu, Shi-Fei; Fu, Jin-Xian
2016-03-01
The electron paramagnetic resonance (EPR) parameters [i.e. g factors gi (i=x, y, z) and hyperfine structure constants Ai] and the local lattice structure for the Cu2+ centre in Tl2Zn(SO4)2·6H2O (TZSH) crystal were theoretically investigated by utilising the perturbation formulae of these parameters for a 3d9 ion under rhombically elongated octahedra. In the calculations, the admixture of d orbitals in the ground state and the ligand orbital and spin-orbit coupling interactions are taken into account based on the cluster approach. The theoretical EPR parameters show good agreement with the observed values, and the Cu2+-H2O bond lengths are obtained as follows: Rx≈1.98 Å, Ry≈2.09 Å, Rz≈2.32 Å. The results are discussed.
Local gap threshold for frustration-free spin systems
NASA Astrophysics Data System (ADS)
Gosset, David; Mozgunov, Evgeny
2016-09-01
We improve Knabe's spectral gap bound for frustration-free translation-invariant local Hamiltonians in 1D. The bound is based on a relationship between global and local gaps. The global gap is the spectral gap of a size-m chain with periodic boundary conditions, while the local gap is that of a subchain of size n < m with open boundary conditions. Knabe proved that if the local gap is larger than the threshold value 1/(n - 1) for some n > 2, then the global gap is lower bounded by a positive constant in the thermodynamic limit m → ∞. Here we improve the threshold to 6/n (n +1 ) , which is better (smaller) for all n > 3 and which is asymptotically optimal. As a corollary we establish a surprising fact about 1D translation-invariant frustration-free systems that are gapless in the thermodynamic limit: for any such system the spectral gap of a size-n chain with open boundary conditions is upper bounded as O(n-2). This contrasts with gapless frustrated systems where the gap can be Θ(n-1). It also limits the extent to which the area law is violated in these frustration-free systems, since it implies that the half-chain entanglement entropy is O (1 /√{ɛ }) as a function of spectral gap ɛ. We extend our results to frustration-free systems on a 2D square lattice.
Semiclassical solitons in strongly correlated systems of ultracold bosonic atoms in optical lattices
Demler, Eugene; Maltsev, Andrei
2011-07-15
Highlights: > Dynamics of their formation in strongly correlated systems of ultracold bosonic atoms in optical lattices. > Regime of very strong interactions between atoms, the so-called hard core bosons regime. > Character of soliton excitations is dramatically different from the usual Gross-Pitaevskii regime. - Abstract: We investigate theoretically soliton excitations and dynamics of their formation in strongly correlated systems of ultracold bosonic atoms in two and three dimensional optical lattices. We derive equations of nonlinear hydrodynamics in the regime of strong interactions and incommensurate fillings, when atoms can be treated as hard core bosons. When parameters change in one direction only we obtain Korteweg-de Vries type equation away from half-filling and modified KdV equation at half-filling. We apply this general analysis to a problem of the decay of the density step. We consider stability of one dimensional solutions to transverse fluctuations. Our results are also relevant for understanding nonequilibrium dynamics of lattice spin models.
The massive schwinger model on the lattice studied via a local hamiltonian Monte Carlo method
NASA Astrophysics Data System (ADS)
Schiller, A.; Ranft, J.
1983-10-01
A local hamiltonian Monte Carlo method is used to study the massive Schwinger model. A non-vanishing quark condensate is found and the dependence of the condensate and the string tension on the background field is calculated. These results reproduce well the expected continuum results. We study also the first order phase transition which separates the weak and strong coupling regimes and find evidence for the behaviour conjectured by Coleman.
Adaptive identification and control of structural dynamics systems using recursive lattice filters
NASA Technical Reports Server (NTRS)
Sundararajan, N.; Montgomery, R. C.; Williams, J. P.
1985-01-01
A new approach for adaptive identification and control of structural dynamic systems by using least squares lattice filters thar are widely used in the signal processing area is presented. Testing procedures for interfacing the lattice filter identification methods and modal control method for stable closed loop adaptive control are presented. The methods are illustrated for a free-free beam and for a complex flexible grid, with the basic control objective being vibration suppression. The approach is validated by using both simulations and experimental facilities available at the Langley Research Center.
Color fields computed in SU(3) lattice QCD for the static tetraquark system
NASA Astrophysics Data System (ADS)
Cardoso, Nuno; Cardoso, Marco; Bicudo, Pedro
2011-09-01
The color fields created by the static tetraquark system are computed in quenched SU(3) lattice QCD, in a 243×48 lattice at β=6.2 corresponding to a lattice spacing a=0.07261(85)fm. We find that the tetraquark color fields are well described by a double-Y, or butterfly, shaped flux tube. The two flux-tube junction points are compatible with Fermat points minimizing the total flux-tube length. We also compare the diquark-diantiquark central flux-tube profile in the tetraquark with the quark-antiquark fundamental flux-tube profile in the meson, and they match, thus showing that the tetraquark flux tubes are composed of fundamental flux tubes.
Color fields of the static pentaquark system computed in SU(3) lattice QCD
NASA Astrophysics Data System (ADS)
Cardoso, Nuno; Bicudo, Pedro
2013-02-01
We compute the color fields of SU(3) lattice QCD created by static pentaquark systems, in a 243×48 lattice at β=6.2 corresponding to a lattice spacing a=0.07261(85)fm. We find that the pentaquark color fields are well described by a multi-Y-type shaped flux tube. The flux tube junction points are compatible with Fermat-Steiner points minimizing the total flux tube length. We also compare the pentaquark flux tube profile with the diquark-diantiquark central flux tube profile in the tetraquark and the quark-antiquark fundamental flux tube profile in the meson, and they match, thus showing that the pentaquark flux tubes are composed of fundamental flux tubes.
Fully-Lagrangian and Lattice-Boltzmann Methods for Solving Systems of Conservation Equations
NASA Astrophysics Data System (ADS)
Ancona, M. G.
1994-11-01
A class of "fully-Lagrangian" methods for solving systems of conservation equations is defined. The key step in formulating these methods is the definition of a new set of field variables for which Lagrangian discretization is trivial. Recently popular lattice-Boltzmann simulation schemes for solving such systems are shown to be a useful sub-class of these fully-Lagrangian methods in which (a) the conservation laws are satisfied at each grid point, (b) the Lagrangian variables are expanded perturbatively, and (c) discretization error is used to represent physics. Such schemes are typically derived using methods of kinetic theory. Our numerical analysis approach shows that the conventional physical derivation, while certainly valid and fruitful, is not essential, that it often confuses physics and numerics and that it can be unnecessarily constraining. For example, we show that lattice-Boltzmann-like methods can be non-perturbative and can be made higher-order, implicit and/or with non-uniform grids. Furthermore, our approach provides new perspective on the relationship between lattice-Boltzmann methods and finite-difference techniques. Among other things, we show that the lattice-Boltzmann schemes are only conditionally consistent and in some cases are identical to the well-known Dufort-Frankel method. Through this connection, the lattice-Boltzmann method provides a rational basis for understanding Dufort-Frankel and gives a pathway for its generalization. At the same time, that Dufort Frankel is no longer much used suggests that the lattice-Boltzmann approach might also share this fate.
System Identification of a Vortex Lattice Aerodynamic Model
NASA Technical Reports Server (NTRS)
Juang, Jer-Nan; Kholodar, Denis; Dowell, Earl H.
2001-01-01
The state-space presentation of an aerodynamic vortex model is considered from a classical and system identification perspective. Using an aerodynamic vortex model as a numerical simulator of a wing tunnel experiment, both full state and limited state data or measurements are considered. Two possible approaches for system identification are presented and modal controllability and observability are also considered. The theory then is applied to the system identification of a flow over an aerodynamic delta wing and typical results are presented.
NASA Astrophysics Data System (ADS)
Papp, E.; Micu, C.; Aur, L.
2008-12-01
In this paper we deal with the derivation of dynamic localization conditions for electrons on the one-dimensional (1D) lattice under the influence of ac electric and magnetic fields of the same frequency. We resort, for convenience, to a tight-binding single-band Hamiltonian. Our emphasis is on a more fundamental theoretical understanding by investigating interplays between such fields and the nearest-neighbor hopping interactions characterizing the Hamiltonian. In general, such conditions get expressed in terms of infinite sums of binary products of Bessel functions of the first kind. These sums are hardly tractable, but we found that selecting in a suitable manner the phases of time-dependent modulations leads to controllable frequency-mixing effects providing appreciable simplifications. Such mixings concern competitions between the number of flux quanta and the quotients of field amplitudes and field frequencies. More exactly, tuning one of the mixed frequencies to zero opens the way to establishing the simplified dynamic localization conditions. By resorting again to the zeros of the Bessel function of zeroth order. This results in quickly tractable relationships between the amplitudes of electric and magnetic fields, the field frequency, and the zeros referred to just above. Pure field limits and superpositions between uniform electric and time-dependent magnetic fields are also discussed. Comments concerning the role of disorder and of the Coulomb interaction are also made.
NASA Astrophysics Data System (ADS)
Xu, Cenke
Several examples of quantum spin systems and pseudo spin systems have been studied, and unconventional states of matters and phase transitions have been realized in all these systems under consideration. In the p +/- ip superconductor Josephson lattice and the p--band cold atomic system trapped in optical lattices, novel phases which behave similarly to 1+1 dimensional systems are realized, despite the fact that the real physical systems are in two or three dimensional spaces. For instance, by employing a spin-wave analysis together with a new duality transformation, we establish the existence and stability of a novel gapless "critical phase", which we refer to as a "bond algebraic liquid". This novel critical phase is analogous to the 1+1 dimensional algebraic boson liquid phase. The reason for the novel physics is that there is a quasilocal gauge symmetry in the effective low energy Hamiltonian. In a spin-1 system on the kagome lattice, and a hard-core boson system on the honeycomb lattice, the low energy physics is controlled by two components of compact U(1) gauge symmetries that emerge at low energy. Making use of the confinement nature of the 2+1 dimensional compact gauge theories and the powerful duality between gauge theories and height field theories, the crystalline phase diagrams are studied for both systems, and the transitions to other phases are also considered. These phase diagrams might be accessible in strongly correlated materials, or atomic systems in optical lattices. A novel quantum ground state of matter is realized in a bosonic model on three dimensional fcc lattice with emergent low energy excitations. The novel phase obtained is a stable gapless boson liquid phase, with algebraic boson density correlations. The stability of this phase is protected against the instanton effect and superfluidity by self-duality and large gauge symmetries on both sides of the duality. The gapless collective excitations of this phase closely resemble the
Design and construction of a fast imaging system for detection and analysis of optical lattices
NASA Astrophysics Data System (ADS)
Gillette, Matthew C.
A home built system for imaging optical lattices is presented. Our imaging system uses a repurposed astronomy camera--the complete system costs less than 5,000 while rivaling the performance of a commercially available system which costs 40-50k. The camera must have an extremely low dark current, high quantum efficiency, as well as the ability to take precisely timed millisecond exposures. Using LabVIEW a sequence of precise electronic pulses is created to control the laser beams in order to load the lattice structure with cold atoms. When running a LabVIEW VI at millisecond timescales Windows introduces inaccuracies in pulse timing. A master slave computer setup, called a real time target (RTT) is created in order to keep accuracy to the microsecond level.
Design and Implementation of a Fast Imaging System for Detection of Optical Lattices
NASA Astrophysics Data System (ADS)
Gillette, Matthew; Hachtel, Andrew; Clements, Ethan; Zhong, Shan; Ducay, Ray; Bali, Samir
2014-05-01
A home built system for imaging optical lattices is presented. Our imaging system uses a repurposed astronomy camera- the complete system costs less than 5000 while rivaling the performance of a commercially available system which costs 40-50000. The camera must have an extremely low dark current, high quantum efficiency, as well as the ability to take precisely timed millisecond exposures. Using LabVIEW a sequence of precise electronic pulses is created to control the laser beams in order to load the lattice structure with cold atoms. When running a LabVIEW VI at millisecond timescales Windows introduces inaccuracies in pulse timing. A master slave computer setup, called a real time target (RTT) is created in order to increase this accuracy to the microsecond level. We gratefully acknowledge support from the Petroleum Research Fund and Miami University. We acknowledge invaluable help from the Miami University Instrumentation Lab.
Controlling chaos in the Bose-Einstein condensate system of a double lattice
Wang Zhixia Ni Zhengguo; Cong Fuzhong; Liu Xueshen; Chen Lei
2011-02-15
We study the chaotic dynamics in the Bose-Einstein condensate (BEC) system of a double lattice. Chaotic space-time evolution is investigated for the particle number density in a BEC. By changing of the s-wave scattering length with a Feshbach resonance, the chaotic behavior can be well controlled to enter into periodicity. Numerical calculation shows that there is periodic orbit according to the s-wave scattering length only if the maximal Lyapunov exponent of the system is negative.
Non-autonomous lattice systems with switching effects and delayed recovery
NASA Astrophysics Data System (ADS)
Han, Xiaoying; Kloeden, Peter E.
2016-09-01
The long term behavior of a type of non-autonomous lattice dynamical systems is investigated, where these have a diffusive nearest neighborhood interaction and discontinuous reaction terms with recoverable delays. This problem is of both biological and mathematical interests, due to its application in systems of excitable cells as well as general biological systems involving delayed recovery. The problem is formulated as an evolution inclusion with delays and the existence of weak and strong solutions is established. It is then shown that the solutions generate a set-valued non-autonomous dynamical system and that this non-autonomous dynamical system possesses a non-autonomous global pullback attractor.
[Development of local health systems in Uruguay].
Noceti, M C; Gherardi, A; Ríos, A M; Ríos, F
1990-01-01
This article summarizes Uruguay's experience in local health systems development and the elements that have contributed to awareness and dissemination of this concept. In 1988 the Ministry of Public Health assumed responsibility as one of the entities charged with strengthening the country's local health systems. A technical group was created to act at the central level. It has proposed and promoted changes directed toward the deconcentration of resource utilization in accordance with a set of general guidelines and, at the local level, has acted as a catalyst in the understanding of health services delivery management as a systemic concept.
On locally and nonlocally related potential systems
NASA Astrophysics Data System (ADS)
Cheviakov, Alexei F.; Bluman, George W.
2010-07-01
For any partial differential equation (PDE) system, a local conservation law yields potential equations in terms of some potential variable, which normally is a nonlocal variable. The current paper examines situations when such a potential variable is a local variable, i.e., is a function of the independent and dependent variables of a given PDE system, and their derivatives. In the case of two independent variables, a simple necessary and sufficient condition is presented for the locality of such a potential variable, and this is illustrated by several examples. As a particular example, two-dimensional reductions of equilibrium equations for fluid and plasma dynamics are considered. It is shown that such reductions with respect to helical, axial, and translational symmetries have conservation laws which yield local potential variables. This leads to showing that the well-known Johnson-Frieman-Kruskal-Oberman (JFKO) and Bragg-Hawthorne (Grad-Shafranov) equations are locally related to the corresponding helically and axially symmetric PDE systems of fluid/plasma dynamics. For the axially symmetric case, local symmetry classifications and arising invariant solutions are compared for the original PDE system and the Bragg-Hawthorne (potential) equation. The potential equation is shown to have additional symmetries, denoted as restricted symmetries. Restricted symmetries leave invariant a family of solutions of a given PDE system but not the whole solution manifold, and hence are not symmetries of the given PDE system. Corresponding reductions are shown to yield solutions, which are not obtained as invariant solutions from local symmetry reduction.
Zhu Jiang; Dong Guangjiong; Zhang Weiping; Shneider, Mikhail N.
2011-05-27
We study a recent experiment [K. Li et al., Phys. Rev. Lett. 101, 250401 (2008)] on diffracting a Bose-Einstein condensate by two counterpropagating optical fields. Including the local-field effect, we explain the asymmetric momentum distribution and self-imaging of the Bose-Einstein condensate self-consistently. Moreover, we find that the two counterpropagating optical fields could not produce a perfect optical lattice, which is actually deformed by the local-field effect. Our work implies that the local-field effect could be essential for getting a better quantitative analysis of other optical lattice experiments. In particular, the intensity imbalance of the two optical fields could act as a new means to tailor both cold atom dynamics and light propagation.
Universal threshold for the dynamical behavior of lattice systems with long-range interactions.
Bachelard, Romain; Kastner, Michael
2013-04-26
Dynamical properties of lattice systems with long-range pair interactions, decaying like 1/r(α) with the distance r, are investigated, in particular the time scales governing the relaxation to equilibrium. Upon varying the interaction range α, we find evidence for the existence of a threshold at α=d/2, dependent on the spatial dimension d, at which the relaxation behavior changes qualitatively and the corresponding scaling exponents switch to a different regime. Based on analytical as well as numerical observations in systems of vastly differing nature, ranging from quantum to classical, from ferromagnetic to antiferromagnetic, and including a variety of lattice structures, we conjecture this threshold and some of its characteristic properties to be universal.
Harnessing intrinsic localized modes to identify impurities in nonlinear periodic systems
NASA Astrophysics Data System (ADS)
Thota, M.; Harne, R. L.; Wang, K. W.
2015-02-01
Intrinsic localized modes (ILMs) are concentrations of vibrational energy in periodic systems/lattices due to the combined influences of nonlinearity and discreteness. Moreover, ILMs can move within the system and may strongly interact with an impurity, such as a stiffness change, mass variation, etc. Numerous scientific fields have uncovered examples and evidence of ILMs, motivating a multidisciplinary pursuit to rigorously understand the underlying principles. In spite of the diverse technical studies, a characterization of ILM interaction behaviors with multiple impurities in dissipative lattices remains outstanding. The insights on such behaviors may be broadly useful when dynamic measurements are the only accessible features of the periodic system. For instance, one may guide an ILM within the lattice using a deliberately applied and steered impurity and harness the observed interaction behaviors with a second, static (immovable) impurity/defect to identify how the underlying lattice is different at the second, defected site, whether or not one knew the position of the defect a priori. In this spirit, this research studies, analyzes, and characterizes the interaction types amongst an ILM and multiple impurities, and devises a method to identify a static defect impurity using quantitatively and qualitatively distinct interaction phenomena. The method is found to be robust to moderate levels of lattice stiffness heterogeneity and is applicable to monitor various property changes that represent impurities. Finally, experimental studies verify that ILMs interact with multiple impurities in unique ways such that defect features may be effectively identified.
Quantum localization in open chaotic systems.
Ryu, Jung-Wan; Hur, G; Kim, Sang Wook
2008-09-01
We study a quasibound state of a delta -kicked rotor with absorbing boundaries focusing on the nature of the dynamical localization in open quantum systems. The localization lengths xi of lossy quasibound states located near the absorbing boundaries decrease as they approach the boundary while the corresponding decay rates Gamma are dramatically enhanced. We find the relation xi approximately Gamma(-1/2) and explain it based upon the finite time diffusion, which can also be applied to a random unitary operator model. We conjecture that this idea is valid for the system exhibiting both the diffusion in classical dynamics and the exponential localization in quantum mechanics.
Many-body localization in dipolar systems.
Yao, N Y; Laumann, C R; Gopalakrishnan, S; Knap, M; Müller, M; Demler, E A; Lukin, M D
2014-12-12
Systems of strongly interacting dipoles offer an attractive platform to study many-body localized phases, owing to their long coherence times and strong interactions. We explore conditions under which such localized phases persist in the presence of power-law interactions and supplement our analytic treatment with numerical evidence of localized states in one dimension. We propose and analyze several experimental systems that can be used to observe and probe such states, including ultracold polar molecules and solid-state magnetic spin impurities. PMID:25541771
Pȩkalski, J.; Ciach, A.; Almarza, N. G.
2015-01-07
The impact of confinement on self-assembly of particles interacting with short-range attraction and long-range repulsion potential is studied for thermodynamic states corresponding to local ordering of clusters or layers in the bulk. Exact and asymptotic expressions for the local density and for the effective potential between the confining surfaces are obtained for a one-dimensional lattice model introduced by J. Pȩkalski et al. [J. Chem. Phys. 138, 144903 (2013)]. The simple asymptotic formulas are shown to be in good quantitative agreement with exact results for slits containing at least 5 layers. We observe that the incommensurability of the system size and the average distance between the clusters or layers in the bulk leads to structural deformations that are different for different values of the chemical potential μ. The change of the type of defects is reflected in the dependence of density on μ that has a shape characteristic for phase transitions. Our results may help to avoid misinterpretation of the change of the type of defects as a phase transition in simulations of inhomogeneous systems. Finally, we show that a system confined by soft elastic walls may exhibit bistability such that two system sizes that differ approximately by the average distance between the clusters or layers are almost equally probable. This may happen when the equilibrium separation between the soft boundaries of an empty slit corresponds to the largest stress in the confined self-assembling system.
[Human resources for local health systems].
Linger, C
1989-01-01
The economic and social crises affecting Latin America have had a profound social and political effect on its structures. This paper analyzes this impact from 2 perspectives: 1) the impact on the apparatus of the state, in particular on its health infra-structures; and 2) the direction of the democratic process in the continent and the participatory processes of civil societies. The institutionalization of the Local Health Systems (SILOS) is an effort to analyze the problem from within the health sector and propose solutions. This paper discusses the issues of human resource development in health systems; training in human resource development and human resource development in local health care systems. There are 3 strategies used to change health systems: 1) The judicial-political system: The state's apparatus 2) The political-administrative system: the national health care system; and 3) the political-operative system: local health care systems. To assure implementation of SILOS there are 4 steps to be followed: 1) create political conditions that allow the transformation and development of local health systems; 2) development of high-level institutional and political initiatives to develop health care networks; 3) offer key players institutional space and social action to develop the SILOS process; 4) rapidly develop SILOS in regions to assure its integration with other development efforts. The labor force in the health sector and organized communities play critical roles in proposing and institutionalizing health programs.
[Human resources for local health systems].
Linger, C
1989-01-01
The economic and social crises affecting Latin America have had a profound social and political effect on its structures. This paper analyzes this impact from 2 perspectives: 1) the impact on the apparatus of the state, in particular on its health infra-structures; and 2) the direction of the democratic process in the continent and the participatory processes of civil societies. The institutionalization of the Local Health Systems (SILOS) is an effort to analyze the problem from within the health sector and propose solutions. This paper discusses the issues of human resource development in health systems; training in human resource development and human resource development in local health care systems. There are 3 strategies used to change health systems: 1) The judicial-political system: The state's apparatus 2) The political-administrative system: the national health care system; and 3) the political-operative system: local health care systems. To assure implementation of SILOS there are 4 steps to be followed: 1) create political conditions that allow the transformation and development of local health systems; 2) development of high-level institutional and political initiatives to develop health care networks; 3) offer key players institutional space and social action to develop the SILOS process; 4) rapidly develop SILOS in regions to assure its integration with other development efforts. The labor force in the health sector and organized communities play critical roles in proposing and institutionalizing health programs. PMID:2766984
NASA Astrophysics Data System (ADS)
Singh, Kevin; Geiger, Zachary; Senaratne, Ruwan; Rajagopal, Shankari; Fujiwara, Kurt; Weld, David; Weld Group Team
2015-05-01
Quasiperiodicity is intimately involved in quantum phenomena from localization to the quantum Hall effect. Recent experimental investigation of quasiperiodic quantum effects in photonic and electronic systems have revealed intriguing connections to topological phenomena. However, such experiments have been limited by the absence of techniques for creating tunable quasiperiodic structures. We propose a new type of quasiperiodic optical lattice, constructed by intersecting a Gaussian beam with a 2D square lattice at an angle with an irrational tangent. The resulting potential, a generalization of the Fibonacci lattice, is a physical realization of the mathematical ``cut-and-project'' construction which underlies all quasiperiodic structures. Calculation of the energies and wavefunctions of atoms loaded into the proposed quasiperiodic lattice demonstrate a fractal energy spectrum and the existence of edge states. We acknowledge support from the ONR (award N00014-14-1-0805), the ARO and the PECASE program (award W911NF-14-1-0154), the AFOSR (award FA9550-12-1-0305), and the Alfred P. Sloan foundation (grant BR2013-110).
Rossby vortex simulation on a paraboloidal coordinate system using the lattice Boltzmann method
NASA Astrophysics Data System (ADS)
Yu, Huidan; Zhao, Kaihua
2001-11-01
In this paper, we apply our compressible lattice Boltzmann model to a rotating parabolic coordinate system to simulate Rossby vortices emerging in a layer of shallow water flowing zonally in a rotating paraboloidal vessel. By introducing a scaling factor, nonuniform curvilinear mesh can be mapped to a flat uniform mesh and then normal lattice Boltzmann method works. Since the mass per unit area on the two-dimensional (2D) surface varies with the thickness of the water layer, the 2D flow seems to be ``compressible'' and our compressible model is applied. Simulation solutions meet with the experimental observations qualitatively. Based on this research, quantitative solutions and many natural phenomena simulations in planetary atmospheres, oceans, and magnetized plasma, such as the famous Jovian Giant Red Spot, the Galactic Spiral-vortex, the Gulf Stream, and the Kuroshio Current, etc., can be expected.
Rossby vortex simulation on a paraboloidal coordinate system using the lattice Boltzmann method.
Yu, H; Zhao, K
2001-11-01
In this paper, we apply our compressible lattice Boltzmann model to a rotating parabolic coordinate system to simulate Rossby vortices emerging in a layer of shallow water flowing zonally in a rotating paraboloidal vessel. By introducing a scaling factor, nonuniform curvilinear mesh can be mapped to a flat uniform mesh and then normal lattice Boltzmann method works. Since the mass per unit area on the two-dimensional (2D) surface varies with the thickness of the water layer, the 2D flow seems to be "compressible" and our compressible model is applied. Simulation solutions meet with the experimental observations qualitatively. Based on this research, quantitative solutions and many natural phenomena simulations in planetary atmospheres, oceans, and magnetized plasma, such as the famous Jovian Giant Red Spot, the Galactic Spiral-vortex, the Gulf Stream, and the Kuroshio Current, etc., can be expected. PMID:11736137
Volatility Behaviors of Financial Time Series by Percolation System on Sierpinski Carpet Lattice
NASA Astrophysics Data System (ADS)
Pei, Anqi; Wang, Jun
2015-01-01
The financial time series is simulated and investigated by the percolation system on the Sierpinski carpet lattice, where percolation is usually employed to describe the behavior of connected clusters in a random graph, and the Sierpinski carpet lattice is a graph which corresponds the fractal — Sierpinski carpet. To study the fluctuation behavior of returns for the financial model and the Shanghai Composite Index, we establish a daily volatility measure — multifractal volatility (MFV) measure to obtain MFV series, which have long-range cross-correlations with squared daily return series. The autoregressive fractionally integrated moving average (ARFIMA) model is used to analyze the MFV series, which performs better when compared to other volatility series. By a comparative study of the multifractality and volatility analysis of the data, the simulation data of the proposed model exhibits very similar behaviors to those of the real stock index, which indicates somewhat rationality of the model to the market application.
NASA Astrophysics Data System (ADS)
Shi, Chenyang
Structure and dynamics lie at the heart of the materials science. A detailed knowledge of both subjects would be foundational in understanding the materials' properties and predicting their potential applications. However, the task becomes increasingly dicult as the particle size is reduced to the nanometer scale. For nanostructured materials their laboratory x-ray scattering patterns are overlapped and broadened, making structure determination impossible. Atomic pair distribution function technique based on either synchrotron x-ray or neutron scattering data is known as the tool of choice for probing local structures. However, to solve the "structure problem" in low-dimensional materials with PDF is still challenging. For example for 2D materials of interest in this thesis the crystallographic modeling approach often yields unphysical thermal factors along stacking direction where new chemical intuitions about their actual structures and new modeling methodology/program are needed. Beyond this, lattice dynamical investigations on nanosized particles are extremely dicult. Laboratory tools such as Raman and infra-red only probe phonons at Brillouin zone center. Although in literature there are a great number of theoretical studies of their vibrational properties based on either empirical force elds or density functional theory, various approximations made in theories make the theoretical predictions less reliable. Also, there lacks the direct experiment result to validate the theory against. In this thesis, we studied the structure and dynamics of a wide variety of technologically relevant low-dimensional materials through synchrotron based x-ray PDF and high energy resolution inelastic x-ray scattering (HERIX) techniques. By collecting PDF data and employing advanced modeling program such as DiPy-CMI, we successfully determined the atomic structures of (i) emerging Ti3C2, Nb4C3 MXenes (transition metal carbides and/or nitrides) that are promising for energy storage
Optical lattices of excitons in InGaN/GaN quantum well systems
Chaldyshev, V. V. Bolshakov, A. S. Zavarin, E. E.; Sakharov, A. V.; Lundin, V. V.; Tsatsulnikov, A. F.; Yagovkina, M. A.
2015-01-15
Optical lattices of excitons in periodic systems of InGaN quantum wells with GaN barriers are designed, implemented, and investigated. Due to the collective interaction of quasi-two-dimensional excitons with light and a fairly high binding energy of excitons in GaN, optical Bragg reflection at room temperature is significantly enhanced. To increase the resonance optical response of the system, new structures with two quantum wells in a periodic supercell are designed and implemented. Resonance reflection of 40% at room temperatures for structures with 60 periods is demonstrated.
Charge ordering, charge fluctuations and lattice effects in strongly correlated electron systems
NASA Astrophysics Data System (ADS)
Goto, Terutaka; Lüthi, Bruno
2003-02-01
Charge fluctuation and charge-ordering phenomena in compounds based on the 3d electrons of transition-metal ions and 4f electrons of rare-earth ions are reviewed with particular emphasis on the mutual coupling of charge and lattice degrees of freedom. For the description of charge ordering in inhomogeneously mixed-valence compounds of localized 3d or 4f-electron systems, we employ Landau's phenomenological theory for second-order phase transitions. By use of the group-theoretical method, the charge fluctuation mode corresponding to the active representation for the second-order transition is determined. The localization of 3d and 4f electrons makes the valence for the specific ions an integer number of charge units e in the ordered phases at low temperatures. The elastic soft mode observed by the ultrasonic method is often a useful indication for the charge fluctuation mode that is frozen below the charge-ordering point TC. The transverse c44 mode exhibiting a considerable softening in the rare-earth compound Yb4As3 couples to the Γ5 triplet of the charge fluctuation mode, giving rise to a linear chain of magnetic Yb3+ ions along [111] below TC = 292 K. Magnetite Fe3O4 and the substitution system Fe3-xZnxO4 exhibit softening of the c44 mode that couples to the charge fluctuation mode, which freezes below the Verwey transition temperature TV = 124 K. The soft c66 mode of the transition-metal compound NaV2O5 gives evidence for a zigzag structure of V4+ ions in the a-b plane below TC = 34 K and is the precursor for the orthorhombic-monoclinic phase transition. The charge glass compounds of Sm3X4 (X = Se or Te) show ultrasonic dispersion due to thermal hopping of 4f electrons between Sm2+ and Sm3+ ions. The ln T decrease in elastic constants of Sm3X4 is described in terms of a two-level system of the 4f-electron tunnelling in the random potential. The characteristic ultrasonic dispersion for the copper oxide compound Sr12Ca2Cu24O41 is also presented. The elastic
Dynamics of a Many-Body-Localized System Coupled to a Bath.
Fischer, Mark H; Maksymenko, Mykola; Altman, Ehud
2016-04-22
Coupling a many-body-localized system to a dissipative bath necessarily leads to delocalization. Here, we investigate the nature of the ensuing relaxation dynamics and the information it holds on the many-body-localized state. We formulate the relevant Lindblad equation in terms of the local integrals of motion of the underlying localized Hamiltonian. This allows us to map the quantum evolution deep in the localized state to tractable classical rate equations. We consider two different types of dissipation relevant to systems of ultracold atoms: dephasing due to inelastic scattering on the lattice lasers and particle loss. Our approach allows us to characterize their different effects in the limiting cases of weak and strong interactions. PMID:27152775
Dynamics of a Many-Body-Localized System Coupled to a Bath
NASA Astrophysics Data System (ADS)
Fischer, Mark; Maksymenko, Mykola; Altman, Ehud
Coupling a many-body localized system to a dissipative bath necessarily leads to delocalization. Here we investigate the nature of the ensuing relaxation dynamics and the information it holds on the many-body localized state. To solve for the time evolution, we formulate the relevant Lindblad equation in terms of the local integrals of motion of the underlying localized Hamiltonian. This allows to map the quantum evolution deep in the localized state to tractable classical rate equations. We consider two different types of dissipation relevant to systems of ultra-cold atoms: particle loss and dephasing due to inelastic scattering on the lattice lasers. Only the first mechanism shows a pronounced effect of interactions on the relaxation of observables.
Dynamics of a Many-Body-Localized System Coupled to a Bath
NASA Astrophysics Data System (ADS)
Fischer, Mark H.; Maksymenko, Mykola; Altman, Ehud
2016-04-01
Coupling a many-body-localized system to a dissipative bath necessarily leads to delocalization. Here, we investigate the nature of the ensuing relaxation dynamics and the information it holds on the many-body-localized state. We formulate the relevant Lindblad equation in terms of the local integrals of motion of the underlying localized Hamiltonian. This allows us to map the quantum evolution deep in the localized state to tractable classical rate equations. We consider two different types of dissipation relevant to systems of ultracold atoms: dephasing due to inelastic scattering on the lattice lasers and particle loss. Our approach allows us to characterize their different effects in the limiting cases of weak and strong interactions.
Berg, J. S.
2015-05-03
I describe a generic formulation for the evolution of emittances and lattice functions under arbitrary, possibly non-Hamiltonian, linear equations of motion. The average effect of stochastic processes, which would include ionization interactions and synchrotron radiation, is also included. I first compute the evolution of the covariance matrix, then the evolution of emittances and lattice functions from that. I examine the particular case of a cylindrically symmetric system, which is of particular interest for ionization cooling.
Modeling Parallel System Workloads with Temporal Locality
NASA Astrophysics Data System (ADS)
Minh, Tran Ngoc; Wolters, Lex
In parallel systems, similar jobs tend to arrive within bursty periods. This fact leads to the existence of the locality phenomenon, a persistent similarity between nearby jobs, in real parallel computer workloads. This important phenomenon deserves to be taken into account and used as a characteristic of any workload model. Regrettably, this property has received little if any attention of researchers and synthetic workloads used for performance evaluation to date often do not have locality. With respect to this research trend, Feitelson has suggested a general repetition approach to model locality in synthetic workloads [6]. Using this approach, Li et al. recently introduced a new method for modeling temporal locality in workload attributes such as run time and memory [14]. However, with the assumption that each job in the synthetic workload requires a single processor, the parallelism has not been taken into account in their study. In this paper, we propose a new model for parallel computer workloads based on their result. In our research, we firstly improve their model to control locality of a run time process better and then model the parallelism. The key idea for modeling the parallelism is to control the cross-correlation between the run time and the number of processors. Experimental results show that not only the cross-correlation is controlled well by our model, but also the marginal distribution can be fitted nicely. Furthermore, the locality feature is also obtained in our model.
Localized hyperthermia in the central nervous system
Lyons, B.E. Jr.
1986-01-01
A new localized treatment modality for malignant brain tumors is hyperthermia. Primary brain tumors are ideally suited to localized therapies because they are initially found in a single area of the brain and local recurrence is the general rule, despite aggressive multimodality treatment. The potential of hyperthermia is based on the rationale that these tumors contain a heterogeneous anaplastic cell population. In contrast to radiation and chemotherapy, hyperthermia is equally effective against both hypoxic and oxygenated cells. Moreover, higher temperatures result in tissues that have an inability to cool themselves through perfusion. The feasibility of localized heating in normal and malignant brain tissue was investigated using external ultrasound and microwave applicators and an interstitial microwave antenna array. The ability to generate uniform temperature distributions using these systems was tested in thermal dosimetry studies. Lesion threshold studies were performed to define the acute and chronic histopathological effects of localized hyperthermia in normal brain tissue. Results demonstrated that these techniques can effectively heat clinically relevant volumes of brain tissue to therapeutic temperatures in an extremely controlled and precise manner. Thresholds for cytological damage have been defined over a range of time/temperature parameters. Various physical and physiological factors within the central nervous system as they relate to temperature exposure have also been defined. These feasibility and toxicity studies have led to the initiation of Phase I clinical trials of hyperthermia in combination with radiation therapy at several institutions.
High Statistics Analysis using Anisotropic Clover Lattices: (II) Three-Baryon Systems
Beane, S; Detmold, W; Luu, T; Orginos, K; Parreno, A; Savage, M; Torok, A; Walker-Loud, A
2009-05-05
We present the results of an exploratory Lattice QCD calculation of three-baryon systems through a high-statistics study of one ensemble of anisotropic clover gauge-field configurations with a pion mass of m{sub {pi}} {approx} 390 MeV. Because of the computational cost of the necessary contractions, we focus on correlation functions generated by interpolating-operators with the quantum numbers of the {Xi}{sup 0}{Xi}{sup 0}n system, one of the least demanding three baryon systems in terms of the number of contractions. We find that the ground state of this system has an energy of E{sub {Xi}{sup 0}{Xi}{sup 0}n} = 3877.9 {+-} 6.9 {+-} 9.2 {+-} 3.3 MeV corresponding to an energy-shift due to interactions of {delta}E{sub {Xi}{sup 0}{Xi}{sup 0}n} = E{sub {Xi}{sup 0}{Xi}{sup 0}n} - 2M{sub {Xi}{sup 0}} - M{sub n} = 4.6 {+-} 5.0 {+-} 7.9 {+-} 4.2 MeV. There are a significant number of time-slices in the three-baryon correlation function for which the signal-to-noise ratio is only slowly degrading with time. This is in contrast to the exponential degradation of the signal-to-noise ratio that is observed at larger times, and is due to the suppressed overlap of the source and sink interpolating-operators that are associated with the variance of the three-baryon correlation function onto the lightest eigenstates in the lattice volume (mesonic systems). As one of the motivations for this area of exploration is the calculation of the structure and reactions of light nuclei, we also present initial results for a system with the quantum numbers of the triton (pnn). This present work establishes a path to multi-baryon systems, and shows that Lattice QCD calculations of the properties and interactions of systems containing four and five baryons are now within sight.
High Statistics Analysis using Anisotropic Clover Lattices: (II) Three-Baryon Systems
Andre Walker-Loud, Will Detmold, William Detmold, Aaron Torok, Konstantinos Orginos, Silas Beane, Tom Luu, Martin Savage, Assumpta Parreno
2009-10-01
We present the results of an exploratory Lattice QCD calculation of three-baryon systems through a high-statistics study of one ensemble of anisotropic clover gauge-field configurations with a pion mass of m_\\pi ~ 390 MeV. Because of the computational cost of the necessary contractions, we focus on correlation functions generated by interpolating-operators with the quantum numbers of the $\\Xi^0\\Xi^0 n$ system, one of the least demanding three baryon systems in terms of the number of contractions. We find that the ground state of this system has an energy of E_{\\Xi^0\\Xi^0n}= 3877.9\\pm 6.9\\pm 9.2\\pm3.3 MeV corresponding to an energy-shift due to interactions of \\delta E_{\\Xi^0\\Xi^0n}=E_{\\Xi^0\\Xi^0n}-2M_{\\Xi^0} -M_n=4.6\\pm 5.0\\pm 7.9\\pm 4.2 MeV. There are a significant number of time-slices in the three-baryon correlation function for which the signal-to-noise ratio is only slowly degrading with time. This is in contrast to the exponential degradation of the signal-to-noise ratio that is observed at larger times, and is due to the suppressed overlap of the source and sink interpolating-operators that are associated with the variance of the three-baryon correlation function onto the lightest eigenstates in the lattice volume (mesonic systems). As one of the motivations for this area of exploration is the calculation of the structure and reactions of light nuclei, we also present initial results for a system with the quantum numbers of the triton (pnn). This present work establishes a path to multi-baryon systems, and shows that Lattice QCD calculations of the properties and interactions of systems containing four and five baryons are now within sight.
High statistics analysis using anisotropic clover lattices. II. Three-baryon systems
Beane, Silas R.; Torok, Aaron; Detmold, William; Orginos, Kostas; Luu, Thomas C.; Parreno, Assumpta; Savage, Martin J.; Walker-Loud, Andre
2009-10-01
We present the results of an exploratory lattice QCD calculation of three-baryon systems through a high statistics study of one ensemble of anisotropic clover gauge-field configurations with a pion mass of m{sub {pi}}{approx}390 MeV. Because of the computational cost of the necessary contractions, we focus on correlation functions generated by interpolating operators with the quantum numbers of the {xi}{sup 0}{xi}{sup 0}n system, one of the least demanding three-baryon systems in terms of the number of contractions. We find that the ground state of this system has an energy of E{sub {xi}{sup 0}}{sub {xi}{sup 0}}{sub n}=3877.9{+-}6.9{+-}9.2{+-}3.3 MeV corresponding to an energy shift due to interactions of {delta}E{sub {xi}{sup 0}}{sub {xi}{sup 0}}{sub n}=E{sub {xi}{sup 0}}{sub {xi}{sup 0}}{sub n}-2M{sub {xi}{sup 0}}-M{sub n}=4.6{+-}5.0{+-}7.9{+-}4.2 MeV. There are a significant number of time slices in the three-baryon correlation function for which the signal-to-noise ratio is only slowly degrading with time. This is in contrast to the exponential degradation of the signal-to-noise ratio that is observed at larger times, and is due to the suppressed overlap of the source and sink interpolating operators that are associated with the variance of the three-baryon correlation function onto the lightest eigenstates in the lattice volume (mesonic systems). As one of the motivations for this area of exploration is the calculation of the structure and reactions of light nuclei, we also present initial results for a system with the quantum numbers of the triton (pnn). This present work establishes a path to multibaryon systems, and shows that lattice QCD calculations of the properties and interactions of systems containing four and five baryons are now within sight.
NASA Astrophysics Data System (ADS)
Pingen, Georg
The objective of this work is the development of a formal design approach for fluidic systems, providing conceptually novel design layouts with the provision of only boundary conditions and some basic parameters. The lattice Boltzmann method (LBM) is chosen as a flow model due to its simplicity, inherent use of immersed boundary methods, parallelizability, and general flexibility. Immersed Boundary Methods in the form of a Brinkmann penalization are used to continuously vary the flow from fluid to solid, leading to a material distribution based boundary representation. An analytical adjoint sensitivity analysis is derived for the lattice Boltzmann method, enabling the combination of the lattice Boltzmann method with optimization techniques. This results in the first application of design optimization with the lattice Boltzmann method. In particular, the first LBM topology optimization framework for 2D and 3D problems is developed and validated with numerical design optimization problems for drag and pressure drop minimization. To improve the parallel scalability of the LBM sensitivity analysis and permit the solution of large 2D and 3D problems, iterative solvers are studied and a parallel GMRES Schur Complement method is applied to the solution of the linear adjoint problem in the LBM sensitivity analysis. This leads to improved parallel scalability through reduced memory use and algorithmic speedup. The potential of the developed design approach for fluidic systems is illustrated with the optimization of a 3D dual-objective fixed-geometry valve. The use of a parametric level-set method coupled with the LBM material distribution based topology optimization framework is shown to provide further versatility for design applications. Finally, the use of a penalty formulation of the fluid volume constraint permits the topology optimization of flows at moderate Reynolds numbers for a steady-state pipe bend application. Concluding, this work has led to the development of
Strong local passivity in finite quantum systems.
Frey, Michael; Funo, Ken; Hotta, Masahiro
2014-07-01
Passive states of quantum systems are states from which no system energy can be extracted by any cyclic (unitary) process. Gibbs states of all temperatures are passive. Strong local (SL) passive states are defined to allow any general quantum operation, but the operation is required to be local, being applied only to a specific subsystem. Any mixture of eigenstates in a system-dependent neighborhood of a nondegenerate entangled ground state is found to be SL passive. In particular, Gibbs states are SL passive with respect to a subsystem only at or below a critical system-dependent temperature. SL passivity is associated in many-body systems with the presence of ground state entanglement in a way suggestive of collective quantum phenomena such as quantum phase transitions, superconductivity, and the quantum Hall effect. The presence of SL passivity is detailed for some simple spin systems where it is found that SL passivity is neither confined to systems of only a few particles nor limited to the near vicinity of the ground state.
Gillespie, Dirk
2013-10-01
An algorithm to approximately calculate the partition function (and subsequently ensemble averages) and density of states of lattice spin systems through non-Monte-Carlo random sampling is developed. This algorithm (called the sampling-the-mean algorithm) can be applied to models where the up or down spins at lattice nodes interact to change the spin states of other lattice nodes, especially non-Ising-like models with long-range interactions such as the biological model considered here. Because it is based on the Central Limit Theorem of probability, the sampling-the-mean algorithm also gives estimates of the error in the partition function, ensemble averages, and density of states. Easily implemented parallelization strategies and error minimizing sampling strategies are discussed. The sampling-the-mean method works especially well for relatively small systems, systems with a density of energy states that contains sharp spikes or oscillations, or systems with little a priori knowledge of the density of states.
NASA Astrophysics Data System (ADS)
Halliday, I.; Lishchuk, S. V.; Spencer, T. J.; Pontrelli, G.; Evans, P. C.
2016-08-01
We present a method for applying a class of velocity-dependent forces within a multicomponent lattice Boltzmann equation simulation that is designed to recover continuum regime incompressible hydrodynamics. This method is applied to the problem, in two dimensions, of constraining to uniformity the tangential velocity of a vesicle membrane implemented within a recent multicomponent lattice Boltzmann simulation method, which avoids the use of Lagrangian boundary tracers. The constraint of uniform tangential velocity is carried by an additional contribution to an immersed boundary force, which we derive here from physical arguments. The result of this enhanced immersed boundary force is to apply a physically appropriate boundary condition at the interface between separated lattice fluids, defined as that region over which the phase-field varies most rapidly. Data from this enhanced vesicle boundary method are in agreement with other data obtained using related methods [e.g., T. Krüger, S. Frijters, F. Günther, B. Kaoui, and J. Harting, Eur. Phys. J. 222, 177 (2013), 10.1140/epjst/e2013-01834-y] and underscore the importance of a correct vesicle membrane condition.
Halliday, I; Lishchuk, S V; Spencer, T J; Pontrelli, G; Evans, P C
2016-08-01
We present a method for applying a class of velocity-dependent forces within a multicomponent lattice Boltzmann equation simulation that is designed to recover continuum regime incompressible hydrodynamics. This method is applied to the problem, in two dimensions, of constraining to uniformity the tangential velocity of a vesicle membrane implemented within a recent multicomponent lattice Boltzmann simulation method, which avoids the use of Lagrangian boundary tracers. The constraint of uniform tangential velocity is carried by an additional contribution to an immersed boundary force, which we derive here from physical arguments. The result of this enhanced immersed boundary force is to apply a physically appropriate boundary condition at the interface between separated lattice fluids, defined as that region over which the phase-field varies most rapidly. Data from this enhanced vesicle boundary method are in agreement with other data obtained using related methods [e.g., T. Krüger, S. Frijters, F. Günther, B. Kaoui, and J. Harting, Eur. Phys. J. 222, 177 (2013)10.1140/epjst/e2013-01834-y] and underscore the importance of a correct vesicle membrane condition. PMID:27627411
Local spacetime effects on gyroscope systems
NASA Astrophysics Data System (ADS)
Wohlfarth, Mattias N. R.; Pfeifer, Christian
2013-01-01
We give a precise theoretical description of initially aligned sets of orthogonal gyroscopes which are transported along different paths from some initial point to the same final point in spacetime. These gyroscope systems can be used to synchronize separated observers’ spatial frames by free fall along timelike geodesics. We find that initially aligned gyroscope systems, or spatial frames, lose their synchronization due to the curvature of spacetime and their relative motion. On the basis of our results we propose a simple experiment that enables observers to determine locally whether their spacetime is described by a rotating Kerr or a nonrotating Schwarzschild metric.
A quantum many-body spin system in an optical lattice clock.
Martin, M J; Bishof, M; Swallows, M D; Zhang, X; Benko, C; von-Stecher, J; Gorshkov, A V; Rey, A M; Ye, Jun
2013-08-01
Strongly interacting quantum many-body systems arise in many areas of physics, but their complexity generally precludes exact solutions to their dynamics. We explored a strongly interacting two-level system formed by the clock states in (87)Sr as a laboratory for the study of quantum many-body effects. Our collective spin measurements reveal signatures of the development of many-body correlations during the dynamical evolution. We derived a many-body Hamiltonian that describes the experimental observation of atomic spin coherence decay, density-dependent frequency shifts, severely distorted lineshapes, and correlated spin noise. These investigations open the door to further explorations of quantum many-body effects and entanglement through use of highly coherent and precisely controlled optical lattice clocks. PMID:23929976
Lattice dynamics and elastic properties of the 4f electron system: CeN
NASA Astrophysics Data System (ADS)
Kanchana, V.; Vaitheeswaran, G.; Zhang, Xinxin; Ma, Yanming; Svane, A.; Eriksson, O.
2011-11-01
The electronic structure, structural stability, and lattice dynamics of cerium mononitride are investigated using ab initio density-functional methods involving an effective potential derived from the generalized gradient approximation and without special treatment for the 4f states. The 4f states are hence allowed to hop from site to site, without an on-site Hubbard U, and contribute to the bonding, in a picture often referred to as itinerant. It is argued that this picture is appropriate for CeN at low temperatures, while the anomalous thermal expansion observed at elevated temperatures indicates entropy-driven localization of the Ce f electrons, similar to the behavior of elemental cerium. The elastic constants are predicted from the total energy variation of strained crystals and are found to be large, typical for nitrides. The phonon dispersions are calculated showing no soft modes, and the Grüneisen parameter behaves smoothly. The electronic structure is also calculated using the quasiparticle self-consistent GW approximation (where G denotes the Green's function and W denotes the screened interaction). The Fermi surface of CeN is dominated by large egg-shaped electron sheets centered on the X points, which stem from the p-f mixing around the X point. In contrast, assuming localized f electrons leads to a semimetallic picture with small band overlaps around X.
Incoherent control of locally controllable quantum systems
Dong Daoyi; Zhang Chenbin; Rabitz, Herschel; Pechen, Alexander; Tarn, T.-J.
2008-10-21
An incoherent control scheme for state control of locally controllable quantum systems is proposed. This scheme includes three steps: (1) amplitude amplification of the initial state by a suitable unitary transformation, (2) projective measurement of the amplified state, and (3) final optimization by a unitary controlled transformation. The first step increases the amplitudes of some desired eigenstates and the corresponding probability of observing these eigenstates, the second step projects, with high probability, the amplified state into a desired eigenstate, and the last step steers this eigenstate into the target state. Within this scheme, two control algorithms are presented for two classes of quantum systems. As an example, the incoherent control scheme is applied to the control of a hydrogen atom by an external field. The results support the suggestion that projective measurements can serve as an effective control and local controllability information can be used to design control laws for quantum systems. Thus, this scheme establishes a subtle connection between control design and controllability analysis of quantum systems and provides an effective engineering approach in controlling quantum systems with partial controllability information.
14 CFR 171.263 - Localizer automatic monitor system.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Localizer automatic monitor system. 171.263... System (ISMLS) § 171.263 Localizer automatic monitor system. (a) The ISMLS localizer equipment must provide an automatic monitor system that transmits a warning to designated local and remote control...
The Fermilab lattice supercomputer project
NASA Astrophysics Data System (ADS)
Fischler, Mark; Atac, R.; Cook, A.; Deppe, J.; Gaines, I.; Husby, D.; Nash, T.; Pham, T.; Zmuda, T.; Hockney, George; Eichten, E.; Mackenzie, P.; Thacker, H. B.; Toussaint, D.
1989-06-01
The ACPMAPS system is a highly cost effective, local memory MIMD computer targeted at algorithm development and production running for gauge theory on the lattice. The machine consists of a compound hypercube of crates, each of which is a full crossbar switch containing several processors. The processing nodes are single board array processors based on the Weitek XL chip set, each with a peak power of 20 MFLOPS and supported by 8MBytes of data memory. The system currently being assembled has a peak power of 5 GFLOPS, delivering performance at approximately $250/MFLOP. The system is programmable in C and Fortran. An underpinning of software routines (CANOPY) provides an easy and natural way of coding lattice problems, such that the details of parallelism, and communication and system architecture are transparent to the user. CANOPY can easily be ported to any single CPU or MIMD system which supports C, and allows the coding of typical applications with very little effort.
Localized chaotic patterns in weakly dissipative systems
NASA Astrophysics Data System (ADS)
Urzagasti, D.; Laroze, D.; Pleiner, H.
2014-01-01
A generalized parametrically driven damped nonlinear Schrödinger equation is used to describe, close to the resonance, the dynamics of weakly dissipative systems, like a harmonically coupled pendula chain or an easy-plane magnetic wire. The combined effects of parametric forcing, spatial coupling, and dissipation allows for the existence of stable non-trivial uniform states as well as homogeneous pattern states. The latter can be regular or chaotic. A new family of localized states that connect asymptotically a non-trivial uniform state with a spatio-temporal chaotic pattern is numerically found. We discuss the parameter range, where these localized structures exist. This article is dedicated to Prof. Helmut R. Brand on the occasion of his 60th birthday.
Solitary waves on tensegrity lattices
NASA Astrophysics Data System (ADS)
Fraternali, F.; Senatore, L.; Daraio, C.
2012-06-01
We study the dynamics of lattices formed by masses connected through tensegrity prisms. By employing analytic and numerical arguments, we show that such structures support two limit dynamic regimes controlled by the prisms' properties: (i) in the low-energy (sonic) regime the system supports the formation and propagation of solitary waves which exhibit sech2 shape and (ii) in the high-energy (ultrasonic) regime the system supports atomic-scale localization. Such peculiar features found in periodic arrays of tensegrity structures suggest their use for the creation of new composite materials (here called "tensegrity materials") of potential interest for applications in impact absorption, energy localization and in new acoustic devices.
Smile (System/Machine-Independent Local Environment)
Fletcher, J.G.
1988-04-01
This document defines the characteristics of Smile, a System/machine-independent local environment. This environment consists primarily of a number of primitives (types, macros, procedure calls, and variables) that a program may use; these primitives provide facilities, such as memory allocation, timing, tasking and synchronization beyond those typically provided by a programming language. The intent is that a program will be portable from system to system and from machine to machine if it relies only on the portable aspects of its programming language and on the Smile primitives. For this to be so, Smile itself must be implemented on each system and machine, most likely using non-portable constructions; that is, while the environment provided by Smile is intended to be portable, the implementation of Smile is not necessarily so. In order to make the implementation of Smile as easy as possible and thereby expedite the porting of programs to a new system or a new machine, Smile has been defined to provide a minimal portable environment; that is, simple primitives are defined, out of which more complex facilities may be constructed using portable procedures. The implementation of Smile can be as any of the following: the underlying software environment for the operating system of an otherwise {open_quotes}bare{close_quotes} machine, a {open_quotes}guest{close_quotes} system environment built upon a preexisting operating system, an environment within a {open_quotes}user{close_quotes} process run by an operating system, or a single environment for an entire machine, encompassing both system and {open_quotes}user{close_quotes} processes. In the first three of these cases the tasks provided by Smile are {open_quotes}lightweight processes{close_quotes} multiplexed within preexisting processes or the system, while in the last case they also include the system processes themselves.
Exponential orthogonality catastrophe in single-particle and many-body localized systems
NASA Astrophysics Data System (ADS)
Deng, Dong-Ling; Pixley, J. H.; Li, Xiaopeng; Das Sarma, S.
2015-12-01
We investigate the statistical orthogonality catastrophe (STOC) in single-particle and many-body localized systems by studying the response of the many-body ground state to a local quench. Using scaling arguments and exact numerical calculations, we establish that the STOC gives rise to a wave function overlap between the pre- and postquench ground states that has an exponential decay with the system size, in sharp contrast to the well-known power law Anderson orthogonality catastrophe in metallic systems. This exponential decay arises from a statistical charge transfer process where a particle can be effectively "transported" to an arbitrary lattice site. In a many-body localized phase, this nonlocal transport and the associated exponential STOC phenomenon persist in the presence of interactions. We study the possible experimental consequences of the exponential STOC on the Loschmidt echo and spectral function, establishing that this phenomenon might be observable in cold atomic experiments through Ramsey interference and radio-frequency spectroscopy.
GIDL: Generalized Interference Detection and Localization System
NASA Astrophysics Data System (ADS)
Gromov, Konstantin Gennadievich
The Local Area Augmentation System (LAAS) and the Wide Area Augmentation System (WAAS) are being developed by the U.S. Federal Aviation Administration (FAA) to provide satellite navigation performance compliant with the stringent requirements for aircraft precision approach and landing. A primary design goal of both systems is to insure that signal-in-space failures are detected by ground facilities and to exclude the affected measurements before differential corrections are broadcast to users. One such failure is unintentional interference or intentional jamming in the GPS frequency band. To protect integrity, LAAS and WAAS ground facilities must quickly detect the presence of any hazardous interference falling within the restricted band used by GPS. To protect availability, ground personnel must be able to quickly locate and deactivate the interference source. In order to serve this purpose, the prototype Generalized Interference Detection and Localization System (GIDL) has been developed. This prototype includes four antennae and RF sections slaved to a common clock to allow detection and determination of a three-dimensional interference location. Measurements of differential signal propagation delays across the multiple baselines between the GIDL antennae are combined to estimate the location of the undesired interference transmitter. The GIDL system can be implemented in parallel with a three- or four-receiver LAAS ground facility (sharing components with the LAAS reference receivers and processors) or as a separate installation to support nearby LAAS and WAAS sites. This dissertation describes the GIDL theory and GIDL receiver design and derives theoretical predictions of the ability of the GIDL to accurately locate interference sources. The GIDL System has been successfully demonstrated to the Federal Aviation Administration (FAA).
Collective Behaviors in Spatially Extended Systems with Local Interactions and Synchronous Updating
NASA Astrophysics Data System (ADS)
ChatÉ, H.; Manneville, P.
1992-01-01
Assessing the extent to which dynamical systems with many degrees of freedom can be described within a thermodynamics formalism is a problem that currently attracts much attention. In this context, synchronously updated regular lattices of identical, chaotic elements with local interactions are promising models for which statistical mechanics may be hoped to provide some insights. This article presents a large class of cellular automata rules and coupled map lattices of the above type in space dimensions d = 2 to 6.Such simple models can be approached by a mean-field approximation which usually reduces the dynamics to that of a map governing the evolution of some extensive density. While this approximation is exact in the d = infty limit, where macroscopic variables must display the time-dependent behavior of the mean-field map, basic intuition from equilibrium statistical mechanics rules out any such behavior in a low-dimensional systems, since it would involve the collective motion of locally disordered elements.The models studied are chosen to be as close as possible to mean-field conditions, i.e., rather high space dimension, large connectivity, and equal-weight coupling between sites. While the mean-field evolution is never observed, a new type of non-trivial collective behavior is found, at odds with the predictions of equilibrium statistical mechanics. Both in the cellular automata models and in the coupled map lattices, macroscopic variables frequently display a non-transient, time-dependent, low-dimensional dynamics emerging out of local disorder. Striking examples are period 3 cycles in two-state cellular automata and a Hopf bifurcation for a d = 5 lattice of coupled logistic maps. An extensive account of the phenomenology is given, including a catalog of behaviors, classification tables for the celular automata rules, and bifurcation diagrams for the coupled map lattices.The observed underlying dynamics is accompanied by an intrinsic quasi-Gaussian noise
Honeycomb optical lattices with harmonic confinement
Block, J. Kusk; Nygaard, N.
2010-05-15
We consider the fate of the Dirac points in the spectrum of a honeycomb optical lattice in the presence of a harmonic confining potential. By numerically solving the tight binding model, we calculate the density of states and find that the energy dependence can be understood from analytical arguments. In addition, we show that the density of states of the harmonically trapped lattice system can be understood by application of a local density approximation based on the density of states in the homogeneous lattice. The Dirac points are found to survive locally in the trap as evidenced by the local density of states. Furthermore, they give rise to a distinct spatial profile of a noninteracting Fermi gas.
Pediatric scleroderma: systemic or localized forms.
Torok, Kathryn S
2012-04-01
Pediatric scleroderma includes 2 major groups of clinical entities, systemic sclerosis (SSc) and localized scleroderma (LS). Although both share a common pathophysiology, their clinical manifestations differ. LS is typically confined to the skin and underlying subcutis, with up to a quarter of patients showing extracutaneous disease manifestations such as arthritis and uveitis. Vascular, cutaneous, gastrointestinal, pulmonary, and musculoskeletal involvement are most commonly seen in children with SSc. Treatment of both forms targets the active inflammatory stage and halts disease progression; however, progress needs to be made toward the development of more effective antifibrotic therapy to help reverse disease damage.
Imaging Photon Lattice States by Scanning Defect Microscopy
NASA Astrophysics Data System (ADS)
Underwood, D. L.; Shanks, W. E.; Li, Andy C. Y.; Ateshian, Lamia; Koch, Jens; Houck, A. A.
2016-04-01
Microwave photons inside lattices of coupled resonators and superconducting qubits can exhibit surprising matterlike behavior. Realizing such open-system quantum simulators presents an experimental challenge and requires new tools and measurement techniques. Here, we introduce scanning defect microscopy as one such tool and illustrate its use in mapping the normal-mode structure of microwave photons inside a 49-site kagome lattice of coplanar waveguide resonators. Scanning is accomplished by moving a probe equipped with a sapphire tip across the lattice. This locally perturbs resonator frequencies and induces shifts of the lattice resonance frequencies, which we determine by measuring the transmission spectrum. From the magnitude of mode shifts, we can reconstruct photon field amplitudes at each lattice site and thus create spatial images of the photon-lattice normal modes.
Charged local defects in extended systems
NASA Astrophysics Data System (ADS)
Schultz, Peter A.
2000-03-01
The conventional approach to treating charged defects in extended systems in first principles calculations is via the supercell approximation using a neutralizing jellium background charge. I explicitly demonstrate shortcomings of this standard appoach and show that the resulting errors in the electrostatic potential energy surface are comparable to band gaps energies, for supercell sizes typically used in defect calculations. I present an alternate scheme, generalized from the local moment counter-charge method [P.A. Schultz, Phys. Rev. B 60, 1551 (1999)], that gives the correct electrostatic potential in the vicinity of a defect, via a mixed boundary condition approach. As examples, I present results of first principles calculations for charged defects in extended systems.
Lunar rovers and local positioning system
NASA Technical Reports Server (NTRS)
Avery, James; Su, Renjeng
1991-01-01
Telerobotic rovers equipped with adequate actuators and sensors are clearly necessary for extraterrestrial construction. They will be employed as substitutes for humans, to perform jobs like surveying, sensing, signaling, manipulating, and the handling of small materials. Important design criteria for these rovers include versatility and robustness. They must be easily programmed and reprogrammed to perform a wide variety of different functions, and they must be robust so that construction work will not be jeopardized by parts failures. The key qualities and functions necessary for these rovers to achieve the required versatility and robustness are modularity, redundancy, and coordination. Three robotic rovers are being built by CSC as a test bed to implement the concepts of modularity and coordination. The specific goal of the design and construction of these robots is to demonstrate the software modularity and multirobot control algorithms required for the physical manipulation of constructible elements. Each rover consists of a transporter platform, bus manager, simple manipulator, and positioning receivers. These robots will be controlled from a central control console via a radio-frequency local area network (LAN). To date, one prototype transporter platform frame was built with batteries, motors, a prototype single-motor controller, and two prototype internal LAN boards. Software modules were developed in C language for monitor functions, i/o, and parallel port usage in each computer board. Also completed are the fabrication of half of the required number of computer boards, the procurement of 19.2 Kbaud RF modems for inter-robot communications, and the simulation of processing requirements for positioning receivers. In addition to the robotic platform, the fabrication of a local positioning system based on infrared signals is nearly completed. This positioning system will make the rovers into a moving reference system capable of performing site surveys. In
Lunar rovers and local positioning system
NASA Astrophysics Data System (ADS)
Avery, James; Su, Renjeng
1991-11-01
Telerobotic rovers equipped with adequate actuators and sensors are clearly necessary for extraterrestrial construction. They will be employed as substitutes for humans, to perform jobs like surveying, sensing, signaling, manipulating, and the handling of small materials. Important design criteria for these rovers include versatility and robustness. They must be easily programmed and reprogrammed to perform a wide variety of different functions, and they must be robust so that construction work will not be jeopardized by parts failures. The key qualities and functions necessary for these rovers to achieve the required versatility and robustness are modularity, redundancy, and coordination. Three robotic rovers are being built by CSC as a test bed to implement the concepts of modularity and coordination. The specific goal of the design and construction of these robots is to demonstrate the software modularity and multirobot control algorithms required for the physical manipulation of constructible elements. Each rover consists of a transporter platform, bus manager, simple manipulator, and positioning receivers. These robots will be controlled from a central control console via a radio-frequency local area network (LAN). To date, one prototype transporter platform frame was built with batteries, motors, a prototype single-motor controller, and two prototype internal LAN boards. Software modules were developed in C language for monitor functions, i/o, and parallel port usage in each computer board. Also completed are the fabrication of half of the required number of computer boards, the procurement of 19.2 Kbaud RF modems for inter-robot communications, and the simulation of processing requirements for positioning receivers. In addition to the robotic platform, the fabrication of a local positioning system based on infrared signals is nearly completed. This positioning system will make the rovers into a moving reference system capable of performing site surveys. In
Engineering novel optical lattices.
Windpassinger, Patrick; Sengstock, Klaus
2013-08-01
Optical lattices have developed into a widely used and highly recognized tool to study many-body quantum physics with special relevance for solid state type systems. One of the most prominent reasons for this success is the high degree of tunability in the experimental setups. While at the beginning quasi-static, cubic geometries were mainly explored, the focus of the field has now shifted toward new lattice topologies and the dynamical control of lattice structures. In this review we intend to give an overview of the progress recently achieved in this field on the experimental side. In addition, we discuss theoretical proposals exploiting specifically these novel lattice geometries. PMID:23828639
Democracy and Governance in the Local School System
ERIC Educational Resources Information Center
Hatcher, Richard
2012-01-01
The Labour government showed no interest in extending local democracy in the school system, in spite of a policy rhetoric of local democratic renewal. The Conservative-Liberal Democrat coalition government's localism agenda promotes the autonomy of schools from local authorities without proposing alternative forms of local democracy in the school…
Development of a Prototype Lattice Boltzmann Code for CFD of Fusion Systems.
Pattison, Martin J; Premnath, Kannan N; Banerjee, Sanjoy; Dwivedi, Vinay
2007-02-26
Designs of proposed fusion reactors, such as the ITER project, typically involve the use of liquid metals as coolants in components such as heat exchangers, which are generally subjected to strong magnetic fields. These fields induce electric currents in the fluids, resulting in magnetohydrodynamic (MHD) forces which have important effects on the flow. The objective of this SBIR project was to develop computational techniques based on recently developed lattice Boltzmann techniques for the simulation of these MHD flows and implement them in a computational fluid dynamics (CFD) code for the study of fluid flow systems encountered in fusion engineering. The code developed during this project, solves the lattice Boltzmann equation, which is a kinetic equation whose behaviour represents fluid motion. This is in contrast to most CFD codes which are based on finite difference/finite volume based solvers. The lattice Boltzmann method (LBM) is a relatively new approach which has a number of advantages compared with more conventional methods such as the SIMPLE or projection method algorithms that involve direct solution of the Navier-Stokes equations. These are that the LBM is very well suited to parallel processing, with almost linear scaling even for very large numbers of processors. Unlike other methods, the LBM does not require solution of a Poisson pressure equation leading to a relatively fast execution time. A particularly attractive property of the LBM is that it can handle flows in complex geometries very easily. It can use simple rectangular grids throughout the computational domain -- generation of a body-fitted grid is not required. A recent advance in the LBM is the introduction of the multiple relaxation time (MRT) model; the implementation of this model greatly enhanced the numerical stability when used in lieu of the single relaxation time model, with only a small increase in computer time. Parallel processing was implemented using MPI and demonstrated the
Model reduction of systems with localized nonlinearities.
Segalman, Daniel Joseph
2006-03-01
An LDRD funded approach to development of reduced order models for systems with local nonlinearities is presented. This method is particularly useful for problems of structural dynamics, but has potential application in other fields. The key elements of this approach are (1) employment of eigen modes of a reference linear system, (2) incorporation of basis functions with an appropriate discontinuity at the location of the nonlinearity. Galerkin solution using the above combination of basis functions appears to capture the dynamics of the system with a small basis set. For problems involving small amplitude dynamics, the addition of discontinuous (joint) modes appears to capture the nonlinear mechanics correctly while preserving the modal form of the predictions. For problems involving large amplitude dynamics of realistic joint models (macro-slip), the use of appropriate joint modes along with sufficient basis eigen modes to capture the frequencies of the system greatly enhances convergence, though the modal nature the result is lost. Also observed is that when joint modes are used in conjunction with a small number of elastic eigen modes in problems of macro-slip of realistic joint models, the resulting predictions are very similar to those of the full solution when seen through a low pass filter. This has significance both in terms of greatly reducing the number of degrees of freedom of the problem and in terms of facilitating the use of much larger time steps.
Local chemical potentials and pressures in heterogeneous systems: Adsorptive, absorptive, interfaces
NASA Astrophysics Data System (ADS)
Tovbin, Yu. K.
2016-07-01
Equations self-consistently describing chemical and mechanical equilibria in heterogeneous systems are derived. The equations are based on the lattice gas model using discrete distributions of molecules in space (on a scale comparable to molecular size) and continuum distributions of molecules (at short distances inside the cells) during their translational and vibrational motions. It is shown that the theory provides a unified description of the equilibrium distributions of molecules in three aggregate states and at their interfaces. Potential functions of intermolecular interactions (such as Mie pair potentials) in several coordination spheres that determine the compressibility of the lattice structure are considered. For simplicity, it is assumed that differences between the sizes of mixture components are small. Expressions for the local components of the pressure tensor inside multicomponent solid phases and heterogeneous systems (adsorptive, absorptive, and interfaces) are obtained. It is established that they can be used to calculate the lattice parameters of deforming phases and the thermodynamic characteristics of interfaces, including surface tension. The tensor nature of the chemical potential in heterogeneous systems is discussed.
Shavykin, Oleg V; Neelov, Igor M; Darinskii, Anatolii A
2016-09-21
The effect of excluded volume (EV) interactions on the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers has been studied by using Brownian dynamics simulations. The study was motivated by the theory developed by Markelov et al., [J. Chem. Phys., 2014, 140, 244904] for a Gaussian dendrimer model without EV interactions. The theory connects the experimentally observed dependence of the spin-lattice relaxation rate 1/T(1)H on the location of NMR active groups with the restricted flexibility (semiflexibility) of dendrimers. Semiflexibility was introduced through the correlations between the orientations of different segments. However, these correlations exist even in flexible dendrimer models with EV interactions. We have simulated coarse-grained flexible and semiflexible dendrimer models with and without EV interactions. Every dendrimer segment consisted of two rigid bonds. Semiflexibility was introduced through a potential which restricts the fluctuations of angles between neighboring bonds but does not change orientational correlations in the EV model as compared to the flexible case. The frequency dependence of the reduced 1/T(1)H(ωH) for segments and bonds belonging to different dendrimer shells was calculated. It was shown that the main effect of EV interactions consists of a much stronger contribution of the overall dendrimer rotation to the dynamics of dendrimer segments as compared to phantom models. After the exclusion of this contribution the manifestation of internal dynamics in spin-lattice NMR relaxation appears to be practically insensitive to EV interactions. For the flexible models, the position ωmax of the peak of the modified 1/T(1)H(ωH) does not depend on the shell number. For semiflexible models, the maximum of 1/T(1)H(ωH) for internal segments or bonds shifts to lower frequencies as compared to outer ones. The dependence of ωmax on the number of dendrimer shells appears to be universal for segments and
Quasi-Monte Carlo methods for lattice systems: A first look
NASA Astrophysics Data System (ADS)
Jansen, K.; Leovey, H.; Ammon, A.; Griewank, A.; Müller-Preussker, M.
2014-03-01
We investigate the applicability of quasi-Monte Carlo methods to Euclidean lattice systems for quantum mechanics in order to improve the asymptotic error behavior of observables for such theories. In most cases the error of an observable calculated by averaging over random observations generated from an ordinary Markov chain Monte Carlo simulation behaves like N, where N is the number of observations. By means of quasi-Monte Carlo methods it is possible to improve this behavior for certain problems to N-1, or even further if the problems are regular enough. We adapted and applied this approach to simple systems like the quantum harmonic and anharmonic oscillator and verified an improved error scaling. Catalogue identifier: AERJ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AERJ_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public Licence version 3 No. of lines in distributed program, including test data, etc.: 67759 No. of bytes in distributed program, including test data, etc.: 2165365 Distribution format: tar.gz Programming language: C and C++. Computer: PC. Operating system: Tested on GNU/Linux, should be portable to other operating systems with minimal efforts. Has the code been vectorized or parallelized?: No RAM: The memory usage directly scales with the number of samples and dimensions: Bytes used = “number of samples” × “number of dimensions” × 8 Bytes (double precision). Classification: 4.13, 11.5, 23. External routines: FFTW 3 library (http://www.fftw.org) Nature of problem: Certain physical models formulated as a quantum field theory through the Feynman path integral, such as quantum chromodynamics, require a non-perturbative treatment of the path integral. The only known approach that achieves this is the lattice regularization. In this formulation the path integral is discretized to a finite, but very high dimensional integral. So far only Monte
Effects of lattice disorder in the UCu(5-x)Pd(x) system
Bauer, E.D.; Booth, C.H.; Kwei, G.H.; Chau, R.; Maple, M.B.
2002-02-19
The UCu5-x Pdx system exhibits non-Fermi liquid (NFL) behavior in thermodynamic and transport properties at low temperatures for Pd concentrations 0.9 less than or approximately x less than or approximately 1.5. The local structure around the U, Cu, and Pd atoms has been measured for
Tseng, Ching-Li; Chen, Jung-Chih; Wu, Yu-Chun; Fang, Hsu-Wei; Lin, Feng-Huei; Tang, Tzu-Piao
2015-10-01
Developing an effective vehicle for cancer treatment, hydroxyapatite nanoparticles were fabricated for drug delivery. When 5-Fluorouracil, a major chemoagent, is combined with hydroxyapatite nanocarriers by interclay insertion, the modified hydroxyapatite nanoparticles have superior lysosomal degradation profiles, which could be leveraged as controlled drug release. The decomposition of the hydroxyapatite nanocarriers facilitates the release of 5-Fluorouracil into the cytoplasm causing cell death. Hydroxyapatite nanoparticles with/without 5-Fluorouracil were synthesized and analyzed in this study. Their crystallization properties and chemical composition were examined by X-ray diffraction and Fourier transforms infrared spectroscopy. The 5-Fluorouracil release rate was determined by UV spectroscopy. The biocompatibility of hydroxyapatite-5-Fluorouracil extraction solution was assessed using 3T3 cells via a WST-8 assay. The effect of hydroxyapatite-5-Fluorouracil particles which directly work on the human lung adenocarcinoma (A549) cells was evaluated by a lactate dehydrogenase assay via contact cultivation. A 5-Fluorouracil-absorbed hydroxyapatite particles were also tested. Overall, hydroxyapatite-5-Fluorouracils were prepared using a co-precipitation method wherein 5-Fluorouracil was intercalated in the hydroxyapatite lattice as determined by X-ray diffraction. Energy dispersive scanning examination showed the 5-Fluorouracil content was higher in hydroxyapatite-5-Fluorouracil than in a prepared absorption formulation. With 5-Fluorouracil insertion in the lattice, the widths of the a and c axial constants of the hydroxyapatite crystal increased. The extraction solution of hydroxyapatite-5-Fluorouracil was nontoxic to 3T3 cells, in which 5-Fluorouracil was not released in a neutral phosphate buffer solution. In contrast, at a lower pH value (2.5), 5-Fluorouracil was released by the acidic decomposition of hydroxyapatite. Finally, the results of the lactate
Charm quark system at the physical point of 2+1 flavor lattice QCD
Namekawa, Y.; Ukita, N.; Aoki, S.; Ishizuka, N.; Taniguchi, Y.; Ukawa, A.; Yoshie, T.; Ishikawa, K.-I.; Okawa, M.; Izubuchi, T.; Kanaya, K.; Kuramashi, Y.
2011-10-01
We investigate the charm quark system using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on 32{sup 3}x64 lattice. The dynamical up, down, and strange quark masses are set to the physical values by using the technique of reweighting to shift the quark-hopping parameters from the values employed in the configuration generation. At the physical point, the lattice spacing equals a{sup -1}=2.194(10) GeV and the spatial extent L=2.88(1) fm. The charm quark mass is determined by the spin-averaged mass of the 1S charmonium state, from which we obtain m{sub charm}{sup MS}({mu}=m{sub charm}{sup MS})=1.260(1)(6)(35) GeV, where the errors are due to our statistics, scale determination and renormalization factor. An additional systematic error from the heavy quark is of order {alpha}{sub s}{sup 2}f(m{sub Q}a)(a{Lambda}{sub QCD}), f(m{sub Q}a)(a{Lambda}{sub QCD}){sup 2}, which are estimated to be a percent level if the factor f(m{sub Q}a) analytic in m{sub Q}a is of order unity. Our results for the charmed and charmed-strange meson decay constants are f{sub D}=226(6)(1)(5) MeV, f{sub D{sub s}}=257(2)(1)(5) MeV, again up to the heavy quark errors of order {alpha}{sub s}{sup 2}f(m{sub Q}a)(a{Lambda}{sub QCD}), f(m{sub Q}a)(a{Lambda}{sub QCD}){sup 2}. Combined with the CLEO values for the leptonic decay widths, these values yield |V{sub cd}|=0.205(6)(1)(5)(9), |V{sub cs}|=1.00(1)(1)(3)(3), where the last error is because of the experimental uncertainty of the decay widths.
Charm quark system at the physical point of 2+1 flavor lattice QCD
Izubuchi T.; Namekawa, Y.; Aoki, S.; Ishikawa, K.; Ishizuka, N.; Kanaya, K.; Kuramashi, Y.; Okawa, M.; Taniguchi, Y.; Ukawa, A.; Ukita, N.: Yoshie, T.
2011-04-24
We investigate the charm quark system using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on 32{sup 3} x 64 lattice. The dynamical up, down, and strange quark masses are set to the physical values by using the technique of reweighting to shift the quark-hopping parameters from the values employed in the configuration generation. At the physical point, the lattice spacing equals a{sup -1} = 2.194(10) GeV and the spatial extent L = 2.88(1) fm. The charm quark mass is determined by the spin-averaged mass of the 1S charmonium state, from which we obtain m{sub charm}{sup M{bar S}} ({mu} = m{sub charm}{sup M{bar S}}) = 1.260(1)(6)(35) GeV, where the errors are due to our statistics, scale determination and renormalization factor. An additional systematic error from the heavy quark is of order {alpha}{sub s}{sup 2}f(m{sub Q}a)(a{Lambda}{sub QCD}), f(m{sub Q}a)(a{Lambda}{sub QCD}){sup 2}, which are estimated to be a percent level if the factor f(m{sub Q}a) analytic in m{sub Q}a is of order unity. Our results for the charmed and charmed-strange meson decay constants are f{sub D} = 226(6)(1)(5) MeV, f{sub D}{sub s} = 257(2)(1)(5) MeV, again up to the heavy quark errors of order {alpha}{sub s}{sup 2}f(m{sub Q}a)(a{Lambda}{sub QCD}), f(m{sub Q}a)(a{Lambda}{sub QCD}){sup 2}. Combined with the CLEO values for the leptonic decay widths, these values yield |V{sub cd}| = 0.205(6)(1)(5)(9), |V{sub cs}| = 1.00(1)(1)(3)(3), where the last error is because of the experimental uncertainty of the decay widths.
Scalar-quark systems and chimera hadrons in SU(3){sub c} lattice QCD
Iida, H.; Takahashi, T. T.; Suganuma, H.
2007-06-01
In terms of mass generation in the strong interaction without chiral symmetry breaking, we perform the first study for light scalar-quarks {phi} (colored scalar particles with 3{sub c} or idealized diquarks) and their color-singlet hadronic states using quenched SU(3){sub c} lattice QCD with {beta}=5.70 (i.e., a{approx_equal}0.18 fm) and lattice size 16{sup 3}x32. We investigate ''scalar-quark mesons'' {phi}{sup {dagger}}{phi} and ''scalar-quark baryons'' {phi}{phi}{phi} as the bound states of scalar-quarks {phi}. We also investigate the color-singlet bound states of scalar-quarks {phi} and quarks {psi}, i.e., {phi}{sup {dagger}}{psi}, {psi}{psi}{phi}, and {phi}{phi}{psi}, which we name ''chimera hadrons.'' All the new-type hadrons including {phi} are found to have a large mass even for zero bare scalar-quark mass m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV. We find a ''constituent scalar-quark/quark picture'' for both scalar-quark hadrons and chimera hadrons. Namely, the mass of the new-type hadron composed of m {phi}'s and n {psi}'s, M{sub m{phi}}{sub +n{psi}}, approximately satisfies M{sub m{phi}}{sub +n{psi}}{approx_equal}mM{sub {phi}}+nM{sub {psi}}, where M{sub {phi}} and M{sub {psi}} are the constituent scalar-quark and quark masses, respectively. We estimate the constituent scalar-quark mass M{sub {phi}} for m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV as M{sub {phi}}{approx_equal}1.5-1.6 GeV, which is much larger than the constituent quark mass M{sub {psi}}{approx_equal}400 MeV in the chiral limit. Thus, scalar quarks acquire a large mass due to large quantum corrections by gluons in the systems including scalar quarks. Together with other evidences of mass generation of glueballs and charmonia, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluon effects. In addition, the large mass generation of pointlike colored scalar particles indicates that plausible diquarks used in effective hadron models cannot
Carter, Jonathan; Oliker, Leonid
2006-01-09
The last decade has witnessed a rapid proliferation of superscalarcache-based microprocessors to build high-end computing (HEC) platforms, primarily because of their generality, scalability, and cost effectiveness. However, the growing gap between sustained and peak performance for full-scale scientific applications on such platforms has become major concern in high performance computing. The latest generation of custom-built parallel vector systems have the potential to address this concern for numerical algorithms with sufficient regularity in their computational structure. In this work, we explore two and three dimensional implementations of a lattice-Boltzmann magnetohydrodynamics (MHD) physics application, on some of today's most powerful supercomputing platforms. Results compare performance between the vector-based Cray X1, Earth Simulator, and newly-released NEC SX-8, with the commodity-based superscalar platforms of the IBM Power3, IntelItanium2, and AMD Opteron. Overall results show that the SX-8 attains unprecedented aggregate performance across our evaluated applications.
Quadruple-junction lattice coherency and phase separation in a binary-phase system
Chung, Sung-Yoon; Choi, Si-Young; Kim, Jin-Gyu; Kim, Young-Min
2015-01-01
If each phase has an identical crystal structure and small misfit in the lattice parameters in a binary-phase crystalline system, coherent phase boundaries usually form during separation. Although there have been numerous studies on the effect of coherency elastic energy, no attempt has been made to demonstrate how the phase-separation behaviour varies when multiple interfaces meet at a junction. Here we show that a comprehensively different phase-separation morphology is induced, to release the high coherency strain confined to quadruple junctions. High-temperature in-situ transmission electron microscopy reveals that phase boundaries with a new crystallographic orientation emerge over twinned crystals to provide strain relaxation at quadruple junctions. The high coherency strain and the formation of different phase boundaries can be understood in terms of the force equilibrium between interface tensions at a junction point. Visualizing the quadruple points at atomic resolution, our observations emphasize the impact of multiple junctions on the morphology evolution during phase separation. PMID:26346223
Lattice Boltzmann kinetic modeling and simulation of thermal liquid-vapor system
NASA Astrophysics Data System (ADS)
Gan, Yanbiao; Xu, Aiguo; Zhang, Guangcai; Wang, Junqi; Yu, Xijun; Yang, Yang
2014-04-01
We present a highly efficient lattice Boltzmann (LB) kinetic model for thermal liquid-vapor system. Three key components are as below: (i) a discrete velocity model (DVM) by Kataoka et al. [Phys. Rev. E69, 035701(R) (2004)]; (ii) a forcing term Ii aiming to describe the interfacial stress and recover the van der Waals (VDW) equation of state (EOS) by Gonnella et al. [Phys. Rev. E76, 036703 (2007)] and (iii) a Windowed Fast Fourier Transform (WFFT) scheme and its inverse by our group [Phys. Rev. E84, 046715 (2011)] for solving the spatial derivatives, together with a second-order Runge-Kutta (RK) finite difference scheme for solving the temporal derivative in the LB equation. The model is verified and validated by well-known benchmark tests. The results recovered from the present model are well consistent with previous ones [Phys. Rev. E84, 046715 (2011)] or theoretical analysis. The usage of less discrete velocities, high-order RK algorithm and WFFT scheme with 16th-order in precision makes the model more efficient by about 10 times and more accurate than the original one.
Quadruple-junction lattice coherency and phase separation in a binary-phase system
NASA Astrophysics Data System (ADS)
Chung, Sung-Yoon; Choi, Si-Young; Kim, Jin-Gyu; Kim, Young-Min
2015-09-01
If each phase has an identical crystal structure and small misfit in the lattice parameters in a binary-phase crystalline system, coherent phase boundaries usually form during separation. Although there have been numerous studies on the effect of coherency elastic energy, no attempt has been made to demonstrate how the phase-separation behaviour varies when multiple interfaces meet at a junction. Here we show that a comprehensively different phase-separation morphology is induced, to release the high coherency strain confined to quadruple junctions. High-temperature in-situ transmission electron microscopy reveals that phase boundaries with a new crystallographic orientation emerge over twinned crystals to provide strain relaxation at quadruple junctions. The high coherency strain and the formation of different phase boundaries can be understood in terms of the force equilibrium between interface tensions at a junction point. Visualizing the quadruple points at atomic resolution, our observations emphasize the impact of multiple junctions on the morphology evolution during phase separation.
Two nucleon systems at mπ~450MeV from lattice QCD
Orginos, Kostas; Parreño, Assumpta; Savage, Martin J.; Beane, Silas R.; Chang, Emmanuel; Detmold, William
2015-12-23
Nucleon-nucleon systems are studied with lattice quantum chromodynamics at a pion mass ofmore » $$m_\\pi\\sim 450~{\\rm MeV}$$ in three spatial volumes using $n_f=2+1$ flavors of light quarks. At the quark masses employed in this work, the deuteron binding energy is calculated to be $$B_d = 14.4^{+3.2}_{-2.6} ~{\\rm MeV}$$, while the dineutron is bound by $$B_{nn} = 12.5^{+3.0}_{-5.0}~{\\rm MeV}$$. Over the range of energies that are studied, the S-wave scattering phase shifts calculated in the 1S0 and 3S1-3D1 channels are found to be similar to those in nature, and indicate repulsive short-range components of the interactions, consistent with phenomenological nucleon-nucleon interactions. In both channels, the phase shifts are determined at three energies that lie within the radius of convergence of the effective range expansion, allowing for constraints to be placed on the inverse scattering lengths and effective ranges. Thus, the extracted phase shifts allow for matching to nuclear effective field theories, from which low energy counterterms are extracted and issues of convergence are investigated. As part of the analysis, a detailed investigation of the single hadron sector is performed, enabling a precise determination of the violation of the Gell-Mann–Okubo mass relation.« less
Laterally closed lattice homomorphisms
NASA Astrophysics Data System (ADS)
Toumi, Mohamed Ali; Toumi, Nedra
2006-12-01
Let A and B be two Archimedean vector lattices and let be a lattice homomorphism. We call that T is laterally closed if T(D) is a maximal orthogonal system in the band generated by T(A) in B, for each maximal orthogonal system D of A. In this paper we prove that any laterally closed lattice homomorphism T of an Archimedean vector lattice A with universal completion Au into a universally complete vector lattice B can be extended to a lattice homomorphism of Au into B, which is an improvement of a result of M. Duhoux and M. Meyer [M. Duhoux and M. Meyer, Extended orthomorphisms and lateral completion of Archimedean Riesz spaces, Ann. Soc. Sci. Bruxelles 98 (1984) 3-18], who established it for the order continuous lattice homomorphism case. Moreover, if in addition Au and B are with point separating order duals (Au)' and B' respectively, then the laterally closedness property becomes a necessary and sufficient condition for any lattice homomorphism to have a similar extension to the whole Au. As an application, we give a new representation theorem for laterally closed d-algebras from which we infer the existence of d-algebra multiplications on the universal completions of d-algebras.
Local rollback for fault-tolerance in parallel computing systems
Blumrich, Matthias A.; Chen, Dong; Gara, Alan; Giampapa, Mark E.; Heidelberger, Philip; Ohmacht, Martin; Steinmacher-Burow, Burkhard; Sugavanam, Krishnan
2012-01-24
A control logic device performs a local rollback in a parallel super computing system. The super computing system includes at least one cache memory device. The control logic device determines a local rollback interval. The control logic device runs at least one instruction in the local rollback interval. The control logic device evaluates whether an unrecoverable condition occurs while running the at least one instruction during the local rollback interval. The control logic device checks whether an error occurs during the local rollback. The control logic device restarts the local rollback interval if the error occurs and the unrecoverable condition does not occur during the local rollback interval.
Non-locality Sudden Death in Tripartite Systems
Jaeger, Gregg; Ann, Kevin
2009-03-10
Bell non-locality sudden death is the disappearance of non-local properties in finite times under local phase noise, which decoheres states only in the infinite-time limit. We consider the relationship between decoherence, disentanglement, and Bell non-locality sudden death in bipartite and tripartite systems in specific large classes of state preparation.
Basic Mars Navigation System For Local Areas
NASA Astrophysics Data System (ADS)
Petitfils, E.-A.; Boche-Sauvan, L.; Foing, B. H.; Monaghan, E.; Crews, Eurogeomars
2009-04-01
Introduction: This project has been first set up as a basic solution in navigation during EVA (extra-vehicular activities) in the Mars Society Desert Research Station in the desert of Utah. The main idea is to keep the system as simple as possible so that it can be easily adaptable and portable. The purpose of such a device is to tell the astronauts in EVA where they roughly are and then letting them reaching different points in avoiding any risky way. Thus the precision needed has not to be really high: even if it is about 50m, every astronaut can then look on a map and be able to design a way to another point. This navigation system will improve the safety of the EVA as it is an added reliable orientating tool. Concept: To look at a simple way to localize oneself, one should have a look at what has been done by mankind on Earth. Today, everyone can think of the GPS because it's simple and very reliable. However the infrastructure for such a system is huge and will not be for sure available during the first missions. We can think of course of a basic GPS using the satellites being in orbit but this approach is not yet as simple as we would like. If we want to keep the sky in sight, we can use the stars and the moons of Mars. Yet this would be a good solution and we can even have a star tracker that would give a good position according to the time of the picture. This solution has to be kept in mind but a star tracker is quite big for an astronaut without any rover nearby and using the sky may not be as precise as one should expect. Another useful tool is the compass. It has been used for centuries by sailors but on Mars, without a good magnetic field for this purpose. But sailors also use lighthouses and some placemarks on the land to localize themselves. This is done with a compass, measuring the angle between a placemark and the magnetic North. With two angles, we can then have the position of the boat. The idea here is the same: measuring the angles between
NASA Astrophysics Data System (ADS)
Zhang, Jun; Jiang, Ying
2016-09-01
By treating the hopping parameter as a perturbation, with the help of cumulant expansion and the re-summing technique, the one-particle Green’s function of a spin-1 Bose system in a honeycomb optical lattice is calculated analytically. By the use of the re-summed Green’s function, the quantum phase diagrams of the system in ferromagnetic cases as well as in antiferromagnetic cases are determined. It is found that in antiferromagnetic cases the Mott insulating states with even filling factor are more robust against the hopping parameter than that with odd filling factor, in agreement with results via other different approaches. Moreover, in order to illustrate the effectiveness of the re-summed Green’s function method in calculating time-of-flight pictures, the momentum distribution function of a honeycomb lattice spin-1 Bose system in the antiferromagnetic case is also calculated analytically and the corresponding time-of-flight absorption pictures are plotted.
Optimal Jammer Placement in Wireless Localization Systems
NASA Astrophysics Data System (ADS)
Gezici, Sinan; Bayram, Suat; Kurt, Mehmet Necip; Gholami, Mohammad Reza
2016-09-01
In this study, the optimal jammer placement problem is proposed and analyzed for wireless localization systems. In particular, the optimal location of a jammer node is obtained by maximizing the minimum of the Cramer-Rao lower bounds (CRLBs) for a number of target nodes under location related constraints for the jammer node. For scenarios with more than two target nodes, theoretical results are derived to specify conditions under which the jammer node is located as close to a certain target node as possible, or the optimal location of the jammer node is determined by two of the target nodes. Also, explicit expressions are provided for the optimal location of the jammer node in the presence of two target nodes. In addition, in the absence of distance constraints for the jammer node, it is proved, for scenarios with more than two target nodes, that the optimal jammer location lies on the convex hull formed by the locations of the target nodes and is determined by two or three of the target nodes, which have equalized CRLBs. Numerical examples are presented to provide illustrations of the theoretical results in different scenarios.
Quantum nonergodicity and fermion localization in a system with a single-particle mobility edge
NASA Astrophysics Data System (ADS)
Li, Xiaopeng; Pixley, J. H.; Deng, Dong-Ling; Ganeshan, Sriram; Das Sarma, S.
2016-05-01
We study the many-body localization aspects of single-particle mobility edges in fermionic systems. We investigate incommensurate lattices and random disorder Anderson models. Many-body localization and quantum nonergodic properties are studied by comparing entanglement and thermal entropy, and by calculating the scaling of subsystem particle-number fluctuations, respectively. We establish a nonergodic extended phase as a generic intermediate phase (between purely ergodic extended and nonergodic localized phases) for the many-body localization transition of noninteracting fermions where the entanglement entropy manifests a volume law (hence, "extended"), but there are large fluctuations in the subsystem particle numbers (hence, "nonergodic"). Based on the numerical results, we expect such an intermediate phase scenario may continue to hold even for the many-body localization in the presence of interactions as well. We find for many-body fermionic states in noninteracting one-dimensional Aubry-André and three-dimensional Anderson models that the entanglement entropy density and the normalized particle-number fluctuation have discontinuous jumps at the localization transition where the entanglement entropy is subthermal but obeys the "volume law." In the vicinity of the localization transition, we find that both the entanglement entropy and the particle-number fluctuations obey a single parameter scaling based on the diverging localization length. We argue using numerical and theoretical results that such a critical scaling behavior should persist for the interacting many-body localization problem with important observable consequences. Our work provides persuasive evidence in favor of there being two transitions in many-body systems with single-particle mobility edges, the first one indicating a transition from the purely localized nonergodic many-body localized phase to a nonergodic extended many-body metallic phase, and the second one being a transition
Quantization of systems with temporally varying discretization. II. Local evolution moves
Höhn, Philipp A.
2014-10-15
Several quantum gravity approaches and field theory on an evolving lattice involve a discretization changing dynamics generated by evolution moves. Local evolution moves in variational discrete systems (1) are a generalization of the Pachner evolution moves of simplicial gravity models, (2) update only a small subset of the dynamical data, (3) change the number of kinematical and physical degrees of freedom, and (4) generate a dynamical (or canonical) coarse graining or refining of the underlying discretization. To systematically explore such local moves and their implications in the quantum theory, this article suitably expands the quantum formalism for global evolution moves, constructed in Paper I [P. A. Höhn, “Quantization of systems with temporally varying discretization. I. Evolving Hilbert spaces,” J. Math. Phys. 55, 083508 (2014); e-print http://arxiv.org/abs/arXiv:1401.6062 [gr-qc
Correlation versus commensurability effects for finite bosonic systems in one-dimensional lattices
Brouzos, Ioannis; Schmelcher, Peter; Zoellner, Sascha
2010-05-15
We investigate few-boson systems in finite one-dimensional multiwell traps covering the full interaction crossover from uncorrelated to fermionized particles. Our treatment of the ground-state properties is based on the numerically exact multiconfigurational time-dependent Hartree method. For commensurate filling, we trace the fingerprints of localization as the interaction strength increases, in several observables like reduced-density matrices, fluctuations, and momentum distribution. For a filling factor larger than 1 we observe on-site repulsion effects in the densities and fragmentation of particles beyond the validity of the Bose-Hubbard model upon approaching the Tonks-Girardeau limit. The presence of an incommensurate fraction of particles induces incomplete localization and spatial modulations of the density profiles, taking into account the finite size of the system.
Topological phases: An expedition off lattice
Freedman, Michael H.; Gamper, Lukas; Gils, Charlotte; Isakov, Sergei V.; Trebst, Simon; Troyer, Matthias
2011-08-15
Highlights: > Models of topological phases where the lattice topology is a dynamical variable. > We discuss off-lattice hazards that destroy topological protection. > The Cheeger constant yields upper bound to the energy of excited states. > Baby universes meet condensed matter physics. > We study the graph Laplacian of loop gases and string nets on fluctuating lattices. - Abstract: Motivated by the goal to give the simplest possible microscopic foundation for a broad class of topological phases, we study quantum mechanical lattice models where the topology of the lattice is one of the dynamical variables. However, a fluctuating geometry can remove the separation between the system size and the range of local interactions, which is important for topological protection and ultimately the stability of a topological phase. In particular, it can open the door to a pathology, which has been studied in the context of quantum gravity and goes by the name of 'baby universe', here we discuss three distinct approaches to suppressing these pathological fluctuations. We complement this discussion by applying Cheeger's theory relating the geometry of manifolds to their vibrational modes to study the spectra of Hamiltonians. In particular, we present a detailed study of the statistical properties of loop gas and string net models on fluctuating lattices, both analytically and numerically.
Bornyakov, V.G.
2005-06-01
Possibilities that are provided by a lattice regularization of QCD for studying nonperturbative properties of QCD are discussed. A review of some recent results obtained from computer calculations in lattice QCD is given. In particular, the results for the QCD vacuum structure, the hadron mass spectrum, and the strong coupling constant are considered.
Shavykin, Oleg V; Neelov, Igor M; Darinskii, Anatolii A
2016-09-21
The effect of excluded volume (EV) interactions on the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers has been studied by using Brownian dynamics simulations. The study was motivated by the theory developed by Markelov et al., [J. Chem. Phys., 2014, 140, 244904] for a Gaussian dendrimer model without EV interactions. The theory connects the experimentally observed dependence of the spin-lattice relaxation rate 1/T(1)H on the location of NMR active groups with the restricted flexibility (semiflexibility) of dendrimers. Semiflexibility was introduced through the correlations between the orientations of different segments. However, these correlations exist even in flexible dendrimer models with EV interactions. We have simulated coarse-grained flexible and semiflexible dendrimer models with and without EV interactions. Every dendrimer segment consisted of two rigid bonds. Semiflexibility was introduced through a potential which restricts the fluctuations of angles between neighboring bonds but does not change orientational correlations in the EV model as compared to the flexible case. The frequency dependence of the reduced 1/T(1)H(ωH) for segments and bonds belonging to different dendrimer shells was calculated. It was shown that the main effect of EV interactions consists of a much stronger contribution of the overall dendrimer rotation to the dynamics of dendrimer segments as compared to phantom models. After the exclusion of this contribution the manifestation of internal dynamics in spin-lattice NMR relaxation appears to be practically insensitive to EV interactions. For the flexible models, the position ωmax of the peak of the modified 1/T(1)H(ωH) does not depend on the shell number. For semiflexible models, the maximum of 1/T(1)H(ωH) for internal segments or bonds shifts to lower frequencies as compared to outer ones. The dependence of ωmax on the number of dendrimer shells appears to be universal for segments and
Sato, M; Imai, S; Fujita, N; Nishimura, S; Takao, Y; Sada, Y; Hubbard, B E; Ilic, B; Sievers, A J
2011-12-01
Linear response spectra of a driven intrinsic localized mode in a micromechanical array are measured as it approaches two fundamentally different kinds of bifurcation points. A linear phase mode associated with this autoresonant state softens in frequency and its amplitude grows as the upper frequency bifurcation point is approached, similar to the soft-mode kinetic transition for a single driven Duffing resonator. A lower frequency bifurcation point occurs when the four-wave-mixing partner of this same phase mode intercepts the top of the extended wave branch, initiating a second kinetic transition process. PMID:22182091
Discrete breathers in hexagonal dusty plasma lattices.
Koukouloyannis, V; Kourakis, I
2009-08-01
The occurrence of single-site or multisite localized vibrational modes, also called discrete breathers, in two-dimensional hexagonal dusty plasma lattices is investigated. The system is described by a Klein-Gordon hexagonal lattice characterized by a negative coupling parameter epsilon in account of its inverse dispersive behavior. A theoretical analysis is performed in order to establish the possibility of existence of single as well as three-site discrete breathers in such systems. The study is complemented by a numerical investigation based on experimentally provided potential forms. This investigation shows that a dusty plasma lattice can support single-site discrete breathers, while three-site in phase breathers could exist if specific conditions, about the intergrain interaction strength, would hold. On the other hand, out of phase and vortex three-site breathers cannot be supported since they are highly unstable.
Discrete breathers in hexagonal dusty plasma lattices
Koukouloyannis, V.; Kourakis, I.
2009-08-15
The occurrence of single-site or multisite localized vibrational modes, also called discrete breathers, in two-dimensional hexagonal dusty plasma lattices is investigated. The system is described by a Klein-Gordon hexagonal lattice characterized by a negative coupling parameter epsilon in account of its inverse dispersive behavior. A theoretical analysis is performed in order to establish the possibility of existence of single as well as three-site discrete breathers in such systems. The study is complemented by a numerical investigation based on experimentally provided potential forms. This investigation shows that a dusty plasma lattice can support single-site discrete breathers, while three-site in phase breathers could exist if specific conditions, about the intergrain interaction strength, would hold. On the other hand, out of phase and vortex three-site breathers cannot be supported since they are highly unstable.
Basic Mars Navigation System For Local Areas
NASA Astrophysics Data System (ADS)
Petitfils, E.-A.; Boche-Sauvan, L.; Foing, B. H.; Monaghan, E.; Crews, Eurogeomars
2009-04-01
Introduction: This project has been first set up as a basic solution in navigation during EVA (extra-vehicular activities) in the Mars Society Desert Research Station in the desert of Utah. The main idea is to keep the system as simple as possible so that it can be easily adaptable and portable. The purpose of such a device is to tell the astronauts in EVA where they roughly are and then letting them reaching different points in avoiding any risky way. Thus the precision needed has not to be really high: even if it is about 50m, every astronaut can then look on a map and be able to design a way to another point. This navigation system will improve the safety of the EVA as it is an added reliable orientating tool. Concept: To look at a simple way to localize oneself, one should have a look at what has been done by mankind on Earth. Today, everyone can think of the GPS because it's simple and very reliable. However the infrastructure for such a system is huge and will not be for sure available during the first missions. We can think of course of a basic GPS using the satellites being in orbit but this approach is not yet as simple as we would like. If we want to keep the sky in sight, we can use the stars and the moons of Mars. Yet this would be a good solution and we can even have a star tracker that would give a good position according to the time of the picture. This solution has to be kept in mind but a star tracker is quite big for an astronaut without any rover nearby and using the sky may not be as precise as one should expect. Another useful tool is the compass. It has been used for centuries by sailors but on Mars, without a good magnetic field for this purpose. But sailors also use lighthouses and some placemarks on the land to localize themselves. This is done with a compass, measuring the angle between a placemark and the magnetic North. With two angles, we can then have the position of the boat. The idea here is the same: measuring the angles between
Pair-Supersolid Phase in a Bilayer System of Dipolar Lattice Bosons
Trefzger, C.; Menotti, C.; Lewenstein, M.
2009-07-17
The competition between tunneling and interactions in bosonic lattice models generates a whole variety of different quantum phases. While, in the presence of a single species interacting via on site interaction, the phase diagram presents only superfluid or Mott insulating phases, for long-range interactions or multiple species, exotic phases such as supersolid or pair-superfluid appear. In this Letter, we show for the first time that the coexistence of effective multiple species and long-range interactions leads to the formation of a novel pair-supersolid phase, namely, a supersolid of composites. We propose a possible implementation with dipolar bosons in a bilayer two-dimensional optical lattice.
NonSymmorphic Symmetry Protected Topological Order in Many-body Localized Systems
NASA Astrophysics Data System (ADS)
Ashraf, Khalid
Many-body localized systems have many interesting physical properties such as localization protected quantum order, symmetry protected topological order, area law in entanglement spectrum etc.. Specifically, it has been shown that closed quantum system in 1D i.e. p-wave superconducting wires host localization protected topological order. In this work, we explore the interplay between non-symmorphic symmetry which protects topological order and localization due to disorder. Using a Bogoliubov-de Gennes (BdG) description of p-wave superconductors, we study the topological edge states on a 2D non-symmorphic crystal. We show that a localization protected topological order can exist at high energy in a 2D non-symmorphic crystal. The system goes between topologically trivial and non-trivial phases based on the degree of disorder and shift between the adjacent atoms in the bipartite lattice. We further explore the nature of this phase transition by calculating the entanglement spectrum of the two phases. Finally, the effect of dimensionality on the realization of these phases are discussed.
β-Cu2V2O7 : A spin- (1)/(2) honeycomb lattice system
NASA Astrophysics Data System (ADS)
Tsirlin, Alexander A.; Janson, Oleg; Rosner, Helge
2010-10-01
We report on band-structure calculations and a microscopic model of the low-dimensional magnet β-Cu2V2O7 . Magnetic properties of this compound can be described by a spin- (1)/(2) anisotropic honeycomb lattice model with the averaged coupling J¯1=60-66K . The low symmetry of the crystal structure leads to two inequivalent couplings J1 and J1' but this weak spatial anisotropy does not affect the essential physics of the honeycomb spin lattice. The structural realization of the honeycomb lattice is highly nontrivial: the leading interactions J1 and J1' run via double bridges of VO4 tetrahedra between spatially separated Cu atoms while the interactions between structural nearest neighbors are negligible. The non-negligible interplane coupling J⊥≃15K gives rise to the long-range magnetic ordering at TN≃26K . Our model simulations improve the fit of the magnetic susceptibility data, compared to the previously assumed spin-chain models. Additionally, the simulated ordering temperature of 27 K is in remarkable agreement with the experiment. Our study evaluates β-Cu2V2O7 as the best available experimental realization of the spin- (1)/(2) Heisenberg model on the honeycomb lattice. We also provide an instructive comparison of different band-structure codes and computational approaches to the evaluation of exchange couplings in magnetic insulators.
Geometric Frustration of Colloidal Dimers on a Honeycomb Magnetic Lattice
NASA Astrophysics Data System (ADS)
Tierno, Pietro
2016-01-01
We study the phase behavior and the collective dynamics of interacting paramagnetic colloids assembled above a honeycomb lattice of triangular shaped magnetic minima. A frustrated colloidal molecular crystal is realized when filling these potential minima with exactly two particles per pinning site. External in-plane rotating fields are used to anneal the system into different phases, including long range ordered stripes, random fully packed loops, labyrinth and disordered states. At a higher amplitude of the annealing field, the dimer lattice displays a two-step melting transition where the initially immobile dimers perform first localized rotations and later break up by exchanging particles across consecutive lattice minima.
NASA Astrophysics Data System (ADS)
Hackmann, Andreas; Ailion, David C.; Ganesan, Krishnamurthy; Laicher, Gernot; Goodrich, K. Craig; Cutillo, Antonio G.
1996-02-01
The water-biopolymer cross-relaxation model, proposed by H. E. Rorschach and C. F. Hazlewood (RH) [J. Magn. Reson.70,79 (1986)], explains the Larmor frequency dependence ofT1in many biological systems. However, the RH theory fails at low Larmor frequencies. In this paper, a more general version of the RH theory has been developed. This theory is valid at all frequencies. Use of the new expression for the spin-lattice relaxation rate (1/T1), earlier published experimental data in H2O/D2O bovine serum albumin, which had been measured over a wide frequency range (10 kHz to 100 MHz), were fitted over the entire frequency range. The agreement between theory and the experimental data is excellent. Theoretical expressions for the rotating-frame spin-lattice relaxation rate (1/T1ρ) were also obtained.
Akhlaghi, Maryam; Steiner, Tobias; Meka, Sai Ramudu; Mittemeijer, Eric Jan
2016-01-01
Elastic accommodation of precipitation-induced or thermally induced misfit leads to lattice-parameter changes in crystalline multi-phase systems. Formulae for calculation of such misfit-induced lattice-parameter changes are presented for the aggregate (matrix + second-phase particles) and for the individual matrix and second phase, recognizing the occurrence of either coherent or incoherent diffraction by the matrix and second-phase particles. An overview and an (re)interpretation on the above basis is presented of published lattice-parameter data, obtained by X-ray diffraction analyses of aggregates of matrix plus second-phase particles. Examples for three types of systems consisting of a matrix with misfitting second-phase particles are dealt with, which differ in the origin of the misfit (precipitation or thermally induced) and in the type of diffraction (coherent or incoherent diffraction of matrix plus second-phase particles). The experimental data are shown to be in good to very good agreement with predictions according to the current treatment. PMID:26937236
NASA Astrophysics Data System (ADS)
You, Yi-Zhuang; Qi, Xiao-Liang; Xu, Cenke
We introduce the spectrum bifurcation renormalization group (SBRG) as a generalization of the real-space renormalization group for the many-body localized (MBL) system without truncating the Hilbert space. Starting from a disordered many-body Hamiltonian in the full MBL phase, the SBRG flows to the MBL fixed-point Hamiltonian, and generates the local conserved quantities and the matrix product state representations for all eigenstates. The method is applicable to both spin and fermion models with arbitrary interaction strength on any lattice in all dimensions, as long as the models are in the MBL phase. In particular, we focus on the 1 d interacting Majorana chain with strong disorder, and map out its phase diagram using the entanglement entropy. The SBRG flow also generates an entanglement holographic mapping, which duals the MBL state to a fragmented holographic space decorated with small blackholes.
Castle, Toen; Sussman, Daniel M.; Tanis, Michael; Kamien, Randall D.
2016-01-01
Kirigami uses bending, folding, cutting, and pasting to create complex three-dimensional (3D) structures from a flat sheet. In the case of lattice kirigami, this cutting and rejoining introduces defects into an underlying 2D lattice in the form of points of nonzero Gaussian curvature. A set of simple rules was previously used to generate a wide variety of stepped structures; we now pare back these rules to their minimum. This allows us to describe a set of techniques that unify a wide variety of cut-and-paste actions under the rubric of lattice kirigami, including adding new material and rejoining material across arbitrary cuts in the sheet. We also explore the use of more complex lattices and the different structures that consequently arise. Regardless of the choice of lattice, creating complex structures may require multiple overlapping kirigami cuts, where subsequent cuts are not performed on a locally flat lattice. Our additive kirigami method describes such cuts, providing a simple methodology and a set of techniques to build a huge variety of complex 3D shapes. PMID:27679822
Castle, Toen; Sussman, Daniel M.; Tanis, Michael; Kamien, Randall D.
2016-01-01
Kirigami uses bending, folding, cutting, and pasting to create complex three-dimensional (3D) structures from a flat sheet. In the case of lattice kirigami, this cutting and rejoining introduces defects into an underlying 2D lattice in the form of points of nonzero Gaussian curvature. A set of simple rules was previously used to generate a wide variety of stepped structures; we now pare back these rules to their minimum. This allows us to describe a set of techniques that unify a wide variety of cut-and-paste actions under the rubric of lattice kirigami, including adding new material and rejoining material across arbitrary cuts in the sheet. We also explore the use of more complex lattices and the different structures that consequently arise. Regardless of the choice of lattice, creating complex structures may require multiple overlapping kirigami cuts, where subsequent cuts are not performed on a locally flat lattice. Our additive kirigami method describes such cuts, providing a simple methodology and a set of techniques to build a huge variety of complex 3D shapes.
PT-symmetric phase in kagome-based photonic lattices.
Chern, Gia-Wei; Saxena, Avadh
2015-12-15
The kagome lattice is a two-dimensional network of corner-sharing triangles and is often associated with geometrical frustration. In particular, the frustrated coupling between waveguide modes in a kagome array leads to a dispersionless flat band consisting of spatially localized modes. Here we propose a complex photonic lattice by placing PT-symmetric dimers at the kagome lattice points. Each dimer corresponds to a pair of strongly coupled waveguides. With balanced arrangement of gain and loss on individual dimers, the system exhibits a PT-symmetric phase for finite gain/loss parameter up to a critical value. The beam evolution in this complex kagome waveguide array exhibits a novel oscillatory rotation of optical power along the propagation distance. Long-lived local chiral structures originating from the nearly flat bands of the kagome structure are observed when the lattice is subject to a narrow beam excitation.
System and method for object localization
NASA Technical Reports Server (NTRS)
Kelly, Alonzo J. (Inventor); Zhong, Yu (Inventor)
2005-01-01
A computer-assisted method for localizing a rack, including sensing an image of the rack, detecting line segments in the sensed image, recognizing a candidate arrangement of line segments in the sensed image indicative of a predetermined feature of the rack, generating a matrix of correspondence between the candidate arrangement of line segments and an expected position and orientation of the predetermined feature of the rack, and estimating a position and orientation of the rack based on the matrix of correspondence.
Exponential Orthogonality Catastrophe in Single-Particle and Many-Body Localized Systems
NASA Astrophysics Data System (ADS)
Deng, Dong-Ling; Pixley, J. H.; Li, Xiaopeng
We investigate the statistical orthogonality catastrophe (StOC) in single-particle and many-body localized systems by studying the response of the many-body ground state to a local quench. Using scaling arguments and exact numerical calculations, we establish that the StOC gives rise to a wave function overlap between the pre- and post-quench ground states that has an exponential decay with the system size, in sharp contrast to the well-known power law Anderson orthogonality catastrophe in metallic systems. This exponential decay arises from a statistical charge transfer process where a particle can be effectively ``transported'' to an arbitrary lattice site. We show that in a many-body localized phase, this non-local transport and the associated exponential StOC phenomenon persist in the presence of interactions. We study the possible experimental consequences of the exponential StOC on the Loschmidt echo and spectral function, establishing that this phenomenon might be observable in cold atomic experiments through Ramsey interference and radio-frequency spectroscopy. We thank S.-T. Wang, Z.-X. Gong, Y.-L. Wu, J. D. Sau, and Z. Ovadyahu for discussions. This work is supported by LPS-MPO-CMTC, JQI-NSF-PFC, and ARO-Atomtronics-MURI. The authors acknowledge the University of Maryland supercomputing resources.
Kanazawa, Takuya
2009-08-15
We extend the inequality of Tomboulis and Yaffe in SU(2) lattice gauge theory (LGT) to SU(N) LGT and to general classical spin systems, by use of reflection positivity. Basically the inequalities guarantee that a system in a box that is sufficiently insensitive to boundary conditions has a non-zero mass gap. We explicitly illustrate the theorem in some solvable models. Strong-coupling expansion is then utilized to discuss some aspects of the theorem. Finally, a conjecture for exact expression to the off-axis mass gap of the triangular Ising model is presented. The validity of the conjecture is tested in multiple ways.
The effect of local dipole moments on the structure and lattice dynamics of K0.98Li0.02TaO3
Wen, Jinsheng; Xu, G; Stock, C.; Gehring, P. M.; Zhong, Zhaopeng; Boatner, Lynn A; Venturini, E. L.; Samara, G. A.
2008-01-01
We present high energy x-ray (67 keV) and neutron scattering measurements on a single crystal of K1−xLixTaO3 for which the Li content (x = 0.02) is less than xc = 0.022, the critical value below which no structural phase transitions have been reported in zero field. While the crystal lattice does remain cubic down to T = 10K under both zero-field and field-cooled (E 4 kV/cm) conditions, indications of crystal symmetry lowering are seen at TC = 63K where the Bragg peak intensity changes significantly. A strong and frequencydependent dielectric permittivity is observed at ambient pressure, a defining characteristic of relaxors. However an extensive search for static polar nanoregions, which is also widely associated with relaxor materials, detected no evidence of elastic neutron diffuse scattering between 300 K and 10 K. Neutron inelastic scattering methods were used to characterize the transverse acoustic and optic phonons (TA1 and TO1 modes) near the (200) and (002) Bragg peaks. The zone center TO1 mode softens monotonically with cooling but never reaches zero energy in either zero field or in external electric fields of up to 4 kV/cm. These results are consistent with the behavior expected for a dipolar glass in which the local polar moments are frozen and exhibit no long-range order at low temperatures.
Quantum Impurities develop Fractional Local Moments in Spin-Orbit Coupled Systems
NASA Astrophysics Data System (ADS)
Agarwala, Adhip; Shenoy, Vijay B.
Systems with spin-orbit coupling have the potential to realize exotic quantum states which are interesting both from fundamental and technological perspectives. We investigate the new physics that arises when a correlated spin-1/2 quantum impurity hybridizes with a spin-orbit coupled Fermi system. The intriguing aspect uncovered is that, in contrast to unit local moment in conventional systems, the impurity here develops a fractional local moment of 2/3. The concomitant Kondo effect has a high Kondo temperature (TK). Our theory explains these novel features including the origins of the fractional local moment and provides a recipe to use spin-orbit coupling(λ) to enhance Kondo temperature (TK ~λ 4 / 3). These results will be useful in shedding light on a range of experiments, including those of magnetic impurities at oxide interfaces. Our predictions can also be directly tested in cold-atom systems where the spin-orbit coupling can be engendered via a uniform synthetic non-Abelian gauge field. In addition, this work opens up new directions of research in spin-orbit coupled Kondo lattice systems. Reference: arXiv:1509.07328 Work supported by CSIR, DST and DAE.
Chen, D; Ma, X L
2013-11-07
Dislocations in a crystal are usually classified into several independent slip systems. Motion of a partial dislocation in monometallic crystals may remove or create stacking fault characterized with a partial of a lattice translation vector. However, it is recently known that motion of partial dislocations in complex structure, such as that inside an intermetallic Al2Cu compound, lead to a local composition deviation from its stoichiometric ratio and the resultant structure collapse. Here we report such a local decomposition behaviors are strongly dependent on slip system of dislocations. Under applied external stress, we have studied dislocation motion behaviors in the three independent slip systems of [001](110), [100]() and [110]() within tetragonal Al2Cu crystal by using molecular dynamics method. We found dislocation motions in all these slip systems result in local decomposition but their physical details differ significantly.
Automated Bilingual Circulation System Using PC Local Area Networks.
ERIC Educational Resources Information Center
Iskanderani, A. I.; Anwar, M. A.
1992-01-01
Describes a local automated bilingual circulation system using personal computers in a local area network that was developed at King Abdulaziz University (Saudi Arabia) for Arabic and English materials. Topics addressed include the system structure, hardware, major features, storage requirements, and costs. (nine references) (LRW)
State-Local Revenue Systems and Educational Finance.
ERIC Educational Resources Information Center
Myers, Will S.; And Others
This study analyzes the self-help capabilities of the States to equip themselves with a highly productive State-local revenue system that could underwrite a major share of school costs. The present state-local revenue system is said to be impaired in its productivity and equity by: (1) the regressive impact of property, general sales, and…
NASA Astrophysics Data System (ADS)
Weidner, Carrie; Yu, Hoon; Anderson, Dana
2016-05-01
In this work, we report on progress towards performing interferometry using atoms trapped in an optical lattice. That is, we start with atoms in the ground state of an optical lattice potential V(x) =V0cos [ 2 kx + ϕ(t) ] , and by a prescribed phase function ϕ(t) , transform from one atomic wavefunction to another. In this way, we implement the standard interferometric sequence of beam splitting, propagation, reflection, reverse propagation, and recombination. Through the use of optimal control techniques, we have computationally demonstrated a scalable accelerometer that provides information on the sign of the applied acceleration. Extension of this idea to a two-dimensional shaken-lattice-based gyroscope is discussed. In addition, we report on the experimental implementation of the shaken lattice system.
NASA Astrophysics Data System (ADS)
Yan, Weigen; Zhang, Zuhe
2009-04-01
The energy of a simple graph G arising in chemical physics, denoted by E(G), is defined as the sum of the absolute values of eigenvalues of G. As the dimer problem and spanning trees problem in statistical physics, in this paper we propose the energy per vertex problem for lattice systems. In general for a type of lattice in statistical physics, to compute the entropy constant with toroidal, cylindrical, Mobius-band, Klein-bottle, and free boundary conditions are different tasks with different hardness and may have different solutions. We show that the energy per vertex of plane lattices is independent of the toroidal, cylindrical, Mobius-band, Klein-bottle, and free boundary conditions. In particular, the asymptotic formulae of energies of the triangular, 33.42, and hexagonal lattices with toroidal, cylindrical, Mobius-band, Klein-bottle, and free boundary conditions are obtained explicitly.
Locally indistinguishable orthogonal product bases in arbitrary bipartite quantum system
NASA Astrophysics Data System (ADS)
Xu, Guang-Bao; Yang, Ying-Hui; Wen, Qiao-Yan; Qin, Su-Juan; Gao, Fei
2016-08-01
As we know, unextendible product basis (UPB) is an incomplete basis whose members cannot be perfectly distinguished by local operations and classical communication. However, very little is known about those incomplete and locally indistinguishable product bases that are not UPBs. In this paper, we first construct a series of orthogonal product bases that are completable but not locally distinguishable in a general m ⊗ n (m ≥ 3 and n ≥ 3) quantum system. In particular, we give so far the smallest number of locally indistinguishable states of a completable orthogonal product basis in arbitrary quantum systems. Furthermore, we construct a series of small and locally indistinguishable orthogonal product bases in m ⊗ n (m ≥ 3 and n ≥ 3). All the results lead to a better understanding of the structures of locally indistinguishable product bases in arbitrary bipartite quantum system.
Locally indistinguishable orthogonal product bases in arbitrary bipartite quantum system
Xu, Guang-Bao; Yang, Ying-Hui; Wen, Qiao-Yan; Qin, Su-Juan; Gao, Fei
2016-01-01
As we know, unextendible product basis (UPB) is an incomplete basis whose members cannot be perfectly distinguished by local operations and classical communication. However, very little is known about those incomplete and locally indistinguishable product bases that are not UPBs. In this paper, we first construct a series of orthogonal product bases that are completable but not locally distinguishable in a general m ⊗ n (m ≥ 3 and n ≥ 3) quantum system. In particular, we give so far the smallest number of locally indistinguishable states of a completable orthogonal product basis in arbitrary quantum systems. Furthermore, we construct a series of small and locally indistinguishable orthogonal product bases in m ⊗ n (m ≥ 3 and n ≥ 3). All the results lead to a better understanding of the structures of locally indistinguishable product bases in arbitrary bipartite quantum system. PMID:27503634
Locally indistinguishable orthogonal product bases in arbitrary bipartite quantum system.
Xu, Guang-Bao; Yang, Ying-Hui; Wen, Qiao-Yan; Qin, Su-Juan; Gao, Fei
2016-01-01
As we know, unextendible product basis (UPB) is an incomplete basis whose members cannot be perfectly distinguished by local operations and classical communication. However, very little is known about those incomplete and locally indistinguishable product bases that are not UPBs. In this paper, we first construct a series of orthogonal product bases that are completable but not locally distinguishable in a general m ⊗ n (m ≥ 3 and n ≥ 3) quantum system. In particular, we give so far the smallest number of locally indistinguishable states of a completable orthogonal product basis in arbitrary quantum systems. Furthermore, we construct a series of small and locally indistinguishable orthogonal product bases in m ⊗ n (m ≥ 3 and n ≥ 3). All the results lead to a better understanding of the structures of locally indistinguishable product bases in arbitrary bipartite quantum system. PMID:27503634
Partial lattice participation in the spin-lattice relaxation of potassium chromium alum
NASA Astrophysics Data System (ADS)
Overweg, J. A.; Flokstra, J.; ter Brake, H. J. M.; Gerritsma, G. J.
1981-08-01
We developed a SQUID-based frequency sweeping system for a.c. susceptibility measurements. Using this instrument we found that in Potassium Chromium Alum only a part of the lattice system is involved in the spin-lattice relaxation process. This partial lattice participation amounts 60-75% of the total lattice specific heat.
Fractal properties of the lattice Lotka-Volterra model.
Tsekouras, G A; Provata, A
2002-01-01
The lattice Lotka-Volterra (LLV) model is studied using mean-field analysis and Monte Carlo simulations. While the mean-field phase portrait consists of a center surrounded by an infinity of closed trajectories, when the process is restricted to a two-dimensional (2D) square lattice, local inhomogeneities/fluctuations appear. Spontaneous local clustering is observed on lattice and homogeneous initial distributions turn into clustered structures. Reactions take place only at the interfaces between different species and the borders adopt locally fractal structure. Intercluster surface reactions are responsible for the formation of local fluctuations of the species concentrations. The box-counting fractal dimension of the LLV dynamics on a 2D support is found to depend on the reaction constants while the upper bound of fractality determines the size of the local oscillators. Lacunarity analysis is used to determine the degree of clustering of homologous species. Besides the spontaneous clustering that takes place on a regular 2D lattice, the effects of fractal supports on the dynamics of the LLV are studied. For supports of dimensionality D(s)<2 the lattice can, for certain domains of the reaction constants, adopt a poisoned state where only one of the species survives. By appropriately selecting the fractal dimension of the substrate, it is possible to direct the system into a poisoned or oscillatory steady state at will.
Localization and glassy dynamics of many-body quantum systems.
Carleo, Giuseppe; Becca, Federico; Schiró, Marco; Fabrizio, Michele
2012-01-01
When classical systems fail to explore their entire configurational space, intriguing macroscopic phenomena like aging and glass formation may emerge. Also closed quanto-mechanical systems may stop wandering freely around the whole Hilbert space, even if they are initially prepared into a macroscopically large combination of eigenstates. Here, we report numerical evidences that the dynamics of strongly interacting lattice bosons driven sufficiently far from equilibrium can be trapped into extremely long-lived inhomogeneous metastable states. The slowing down of incoherent density excitations above a threshold energy, much reminiscent of a dynamical arrest on the verge of a glass transition, is identified as the key feature of this phenomenon. We argue that the resulting long-lived inhomogeneities are responsible for the lack of thermalization observed in large systems. Such a rich phenomenology could be experimentally uncovered upon probing the out-of-equilibrium dynamics of conveniently prepared quantum states of trapped cold atoms which we hereby suggest.
Ultracold Quantum Gases in Hexagonal Optical Lattices
NASA Astrophysics Data System (ADS)
Sengstock, Klaus
2010-03-01
Hexagonal structures occur in a vast variety of systems, ranging from honeycombs of bees in life sciences to carbon nanotubes in material sciences. The latter, in particular its unfolded two-dimensional layer -- Graphene -- has rapidly grown to one of the most discussed topics in condensed-matter physics. Not only does it show proximity to various carbon-based materials but also exceptional properties owing to its unusual energy spectrum. In quantum optics, ultracold quantum gases confined in periodic light fields have shown to be very general and versatile instruments to mimic solid state systems. However, so far nearly all experiments were performed in cubic lattice geometries only. Here we report on the first experimental realization of ultracold quantum gases in a state-dependent, two-dimensional, Graphene-like optical lattice with hexagonal symmetry. The lattice is realized via a spin-dependent optical lattice structure with alternating σ^+ and σ^- -sites and thus constitutes a so called `magnetic'-lattice with `antiferromagnetic'-structure. Atoms with different spin orientation can be loaded to specific lattice sites or -- depending on the parameters -- to the whole lattice. As a consequence e.g. superpositions of a superfluid spin component with a different spin component in the Mott-insulating phase can be realized as well as spin-dependent transport properties, disorder etc. After preparing an antiferromagnetically ordered state we e.g. measure sustainable changes of the transport properties of the atoms. This manifests in a significant reduction of the tunneling as compared to a single-component system. We attribute this observation to a partial tunneling blockade for one spin component induced by population in another spin component localized at alternating lattice sites. Within a Gutzwiller-Ansatz we calculate the phase diagrams for the mixed spin-states and find very good agreement with our experimental results. Moreover, by state-resolved recording
NASA Astrophysics Data System (ADS)
Roberts, Daniel A.; Stanford, Douglas; Susskind, Leonard
2015-03-01
We study products of precursors of spatially local operators, , where W x ( t) = e - iHt W x e iHt . Using chaotic spin-chain numerics and gauge/gravity duality, we show that a single precursor fills a spatial region that grows linearly in t. In a lattice system, products of such operators can be represented using tensor networks. In gauge/gravity duality, they are related to Einstein-Rosen bridges supported by localized shock waves. We find a geometrical correspondence between these two descriptions, generalizing earlier work in the spatially homogeneous case.
Local Positioning Systems in (Game) Sports
Leser, Roland; Baca, Arnold; Ogris, Georg
2011-01-01
Position data of players and athletes are widely used in sports performance analysis for measuring the amounts of physical activities as well as for tactical assessments in game sports. However, positioning sensing systems are applied in sports as tools to gain objective information of sports behavior rather than as components of intelligent spaces (IS). The paper outlines the idea of IS for the sports context with special focus to game sports and how intelligent sports feedback systems can benefit from IS. Henceforth, the most common location sensing techniques used in sports and their practical application are reviewed, as location is among the most important enabling techniques for IS. Furthermore, the article exemplifies the idea of IS in sports on two applications. PMID:22163725
Multi-meson systems in lattice QCD / Many-body QCD
Detmold, William
2013-08-31
Nuclear physics entails the study of the properties and interactions of hadrons, such as the proton and neutron, and atomic nuclei and it is central to our understanding of our world at the smallest scales. The underlying basis for nuclear physics is provided by the Standard Model of particle physics which describes how matter interacts through the strong, electromagnetic and weak (electroweak) forces. This theory was developed in the 1970s and provides an extremely successful description of our world at the most fundamental level to which it has been probed. The Standard Model has been, and continues to be, subject to stringent tests at particle accelerators around the world, so far passing without blemish. However, at the relatively low energies that are relevant for nuclear physics, calculations involving the strong interaction, governed by the equations of Quantum Chromodynamics (QCD), are enormously challenging, and to date, the only systematic way to perform them is numerically, using a framework known as lattice QCD (LQCD). In this approach, one discretizes space-time and numerically solves the equations of QCD on a space-time lattice; for realistic calculations, this requires highly optimized algorithms and cutting-edge high performance computing (HPC) resources. Progress over the project period is discussed in detail in the following subsections
Local temperature of out-of-equilibrium quantum electron systems
NASA Astrophysics Data System (ADS)
Meair, J.; Bergfield, J. P.; Stafford, C. A.; Jacquod, Ph.
2014-07-01
We show how the local temperature of out-of-equilibrium, quantum electron systems can be consistently defined with the help of an external voltage and temperature probe. We determine sufficient conditions under which the temperature measured by the probe (i) is independent of details of the system-probe coupling, (ii) is equal to the temperature obtained from an independent current-noise measurement, (iii) satisfies the transitivity condition expressed by the zeroth law of thermodynamics, and (iv) is consistent with Carnot's theorem. This local temperature therefore characterizes the system in the common sense of equilibrium thermodynamics, but remains well defined even in out-of-equilibrium situations with no local equilibrium.
The Struggle for Democracy in the Local School System
ERIC Educational Resources Information Center
Hatcher, Richard
2011-01-01
The Coalition Government, building on the foundations laid by its Labour predecessor, aims to dismantle the local authority system and with it what remains of the accountability of schools to local elected government. In this article, a response to Stewart Ranson's in a recent issue of "FORUM," the author examines his claims for the emergence of…
Think Locally: A Prudent Approach to Electronic Resource Management Systems
ERIC Educational Resources Information Center
Gustafson-Sundell, Nat
2011-01-01
A few articles have drawn some amount of attention specifically to the local causes of the success or failure of electronic resource management system (ERMS) implementations. In fact, it seems clear that local conditions will largely determine whether any given ERMS implementation will succeed or fail. This statement might seem obvious, but the…
NASA Astrophysics Data System (ADS)
Masrour, R.; Jabar, A.
2016-07-01
Mixed-spin-1 and spin-3/2 Ising model on the decorated triangular lattice is studied by the use of Monte Carlo simulation. Within this approach, the results for the ground-state of the antiferromagnetic and ferromagnetic of decorated triangular lattice are obtained. The reduced transition temperature of each sublattice are obtained. The reduced temperature of compensation is also obtained. The thermal total ratio of magnetic susceptibilities of sublattices is given. The effect of crystal field and exchange interactions on the magnetization of the system are detailed. The magnetic hysteresis cycles are found for different values of exchanges interactions between the same lattice and the two sublattices different, for different crystal filed and temperatures. In addition, very weak exchange interactions and for a higher temperatures and a higher crystal filed values the decorated triangular lattice has been exhibited the superparamagnetic behavior.
NASA Astrophysics Data System (ADS)
Amaya-Ventura, Gilberto; Rodríguez-Romo, Suemi
2011-09-01
This paper deals with the computational simulation of the reaction-diffusion-advection phenomena emerging in Rayleigh-Bénard (RB) and Poiseuille-Bénard reactive convection systems. We use the Boussinesq's approximation for buoyancy forces and the Lattice Boltzmann method (LBM). The first kinetic mesoscopic model proposed here is based on the discrete Boltzmann equation needed to solve the momentum balance coupled with buoyancy forces. Then, a second lattice Boltzmann algorithm is applied to solve the reaction-diffusion-advection equation to calculate the evolution of the chemical species concentration. We use a reactive system composed by nitrous oxide (so call laughing gas) in air as an example; its spatio-temporal decomposition is calculated. Two cases are considered, a rectangular enclosed cavity and an open channel. The simulations are performed at low Reynolds numbers and in a steady state between the first and second thermo-hydrodynamic instabilities. The results presented here, for the thermo-hydrodynamic behavior, are in good agreement with experimental data; while our| chemical kinetics simulation yields expected results. Some applications of our approach are related to chemical reactors and atmospheric phenomena, among others.
Lattice crossover and phase transitions in NdAlO3-GdAlO3 system
NASA Astrophysics Data System (ADS)
Vasylechko, L.; Shmanko, H.; Ohon, N.; Prots, Yu.; Hoffmann, S.; Ubizskii, S.
2013-02-01
Phase and structural behaviour in the (1-x)NdAlO3-xGdAlO3 system in a whole concentration range has been studied by means of in situ high-resolution X-ray synchrotron powder diffraction technique and differential thermal analysis. Two kinds of solid solutions Nd1-xGdxAlO3 have been found at room temperature: one with rhombohedral (x<0.15) and one with orthorhombic (x≥0.20) symmetry. A morphotropic phase transition occurs at x≈0.15, where the co-existence of both phases was observed. Peculiarity of the orthorhombic solid solution is the lattice parameter crossover at the compositions with x=0.33, 0.49 and 0.62. First-order structural transition Pbnm↔R3¯с has been detected both from in situ powder diffraction and thermal analysis data. Continuous phase transformation R3¯с↔Pm3¯m above 2140 K has been predicted for Nd-rich sample Nd0.85Gd0.15AlO3 from the extrapolation of high-temperature behaviour of the lattice parameter ratio of the rhombohedral phase. Based on the experimental data, the phase diagram of the pseudo-binary system NdAlO3-GdAlO3 has been constructed.
Lattice-induced nonadiabatic frequency shifts in optical lattice clocks
Beloy, K.
2010-09-15
We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.
Many-body energy localization transition in periodically driven systems
D’Alessio, Luca; Polkovnikov, Anatoli
2013-06-15
According to the second law of thermodynamics the total entropy of a system is increased during almost any dynamical process. The positivity of the specific heat implies that the entropy increase is associated with heating. This is generally true both at the single particle level, like in the Fermi acceleration mechanism of charged particles reflected by magnetic mirrors, and for complex systems in everyday devices. Notable exceptions are known in noninteracting systems of particles moving in periodic potentials. Here the phenomenon of dynamical localization can prevent heating beyond certain threshold. The dynamical localization is known to occur both at classical (Fermi–Ulam model) and at quantum levels (kicked rotor). However, it was believed that driven ergodic systems will always heat without bound. Here, on the contrary, we report strong evidence of dynamical localization transition in both classical and quantum periodically driven ergodic systems in the thermodynamic limit. This phenomenon is reminiscent of many-body localization in energy space. -- Highlights: •A dynamical localization transition in periodically driven ergodic systems is found. •This phenomenon is reminiscent of many-body localization in energy space. •Our results are valid for classical and quantum systems in the thermodynamic limit. •At critical frequency, the short time expansion for the evolution operator breaks down. •The transition is associated to a divergent time scale.
Decay of density waves in coupled one-dimensional many-body-localized systems
NASA Astrophysics Data System (ADS)
Prelovšek, Peter
2016-10-01
This work analyzes the behavior of coupled disordered one-dimensional systems as modelled by identical fermionic Hubbard chains with the on-site potential disorder and coupling emerging through the interchain hopping t'. The study is motivated by the experiment on fermionic cold atoms on a disordered lattice, where a decay rate of the quenched density wave was measured. We present a derivation of the decay rate Γ within perturbation theory and show that, even at large disorder along the chains, the interaction leads to finite Γ >0 , the mechanism being the interaction-induced coupling of in-chain localized and interchain extended single-fermion states. Explicit expressions for Γ are presented for a weak interaction U
Periodically driven ergodic and many-body localized quantum systems
Ponte, Pedro; Chandran, Anushya; Papić, Z.; Abanin, Dmitry A.
2015-02-15
We study dynamics of isolated quantum many-body systems whose Hamiltonian is switched between two different operators periodically in time. The eigenvalue problem of the associated Floquet operator maps onto an effective hopping problem. Using the effective model, we establish conditions on the spectral properties of the two Hamiltonians for the system to localize in energy space. We find that ergodic systems always delocalize in energy space and heat up to infinite temperature, for both local and global driving. In contrast, many-body localized systems with quenched disorder remain localized at finite energy. We support our conclusions by numerical simulations of disordered spin chains. We argue that our results hold for general driving protocols, and discuss their experimental implications.
NASA Astrophysics Data System (ADS)
Xia, J. W.; Yuan, Y. J.; Song, M. T.; Zhang, W. Z.; Yang, X. D.; He, Y.; Mao, L. Z.; Xia, G. X.; Yang, J. C.; Wu, J. X.; Liu, W.
2001-12-01
CSR, a new Cooler-Storage-Ring project, is the post-acceleration system of the Heavy Ion Research Facility in Lanzhou (HIRFL). It consists of a main ring (CSRm) and an experimental ring (CSRe). From the HIRFL cyclotron system the heavy ions will be accumulated, cooled and accelerated in the CSRm, then extracted fast and injected into the CSRe for many internal-target experiments with electron cooling. The experimental ring (CSRe) will be operated with three lattice modes for different experiments. The details of the lattice for the two rings will be described in this paper.
Systemic side effects of locally used oxymetazoline
Dokuyucu, Recep; Gokce, Hasan; Sahan, Mustafa; Sefil, Fatih; Tas, Zeynel Abidin; Tutuk, Okan; Ozturk, Atakan; Tumer, Cemil; Cevik, Cengiz
2015-01-01
Objectives: The object of the study is to experimentally investigate the possible systemic side effects of Oxymetazoline including its nasal spray which has been in use for a long time both by the physicians and patients. There is no study in the literature to address the damages of oxymetazoline on the end organ. Materials and methods: The study conducted on 2 groups of rat. Group 1 (n = 8): Control; and Group 2 (n = 8): Oxymetazoline. During 4 week, the control group was applied with 2 drops of saline water on each nasal cavity 3 times a day and the other group was applied with 2 drops of oxymetazoline HCl 3 times a day. At the end of experiment, samples from mandible, parotid and tails of the rats were taken in 10% formalin for histopathological investigations. Results: In histopathological experiments, when compared with the control group, the oxymetazoline group showed significant increase in many of the histopathological parameters (ischemic changes: P = 0.0001; congestion: P = 0.0006; arterial thrombosis: P = Ns; PNL accumulations: P = 0.001; necrosis: P = 0.0001; and ulceration: P = 0.014). The results of histopathologic tests on the samples taken from mandible and parotid gland, in comparison with the control group, showed no significant increase (focal inflammation: P = Ns; and lymphocyte aggregation: P = Ns). Conclusion: Due to the damage that the long-term use of nasal spray including oxymetazoline, it may cause injury on the end organ, which we revealed in our histopathological experiments. We believe that it’s essential for the physicians to provide information on the side effects of the medicine to their patients who use for a long term. PMID:25932218
A theoretical study of a carbon lattice system for lithium intercalated carbon anodes
Scanlon, L.G.; Storch, D.M.; Newton, J.H.; Sandi, G.
1997-09-01
A theoretical study was performed using computational chemistry to describe the intermolecular forces between graphite layers as well as spacing and conformation. It was found that electron correlation and a diffuse basis set were important for this calculation. In addition, the high reactivity of edge sites in lithium intercalated carbon anodes was also investigated. In this case, the reactive sites appear to strongly correlate with the relative distribution of the total atomic spin densities as well as total atomic charges. The spacing of graphite layers and lithium ion separation within an {open_quotes}approximated{close_quotes} lithium intercalated carbon anode was also investigated. The spacing of the carbon layers used in this investigation agrees most closely for that found in disordered carbon lattices.
Lattice Boltzmann simulations of incompressible liquid-gas systems on partial wetting surfaces.
Shih, Ching-Hsiang; Wu, Cheng-Long; Chang, Li-Chen; Lin, Chao-An
2011-06-28
A three-dimensional Lattice Boltzmann two-phase model capable of dealing with large liquid and gas density ratios and with a partial wetting surface is introduced. This is based on a high density ratio model combined with a partial wetting boundary method. The predicted three-dimensional droplets at different partial wetting conditions at equilibrium are in good agreement with analytical solutions. Despite the large density ratio, the spurious velocity around the interface is not substantial, and is rather insensitive to the examined liquid and gas density and viscosity ratios. The influence of the gravitational force on the droplet shape is also examined through the variations of the Bond number, where the droplet shape migrates from spherical to flattened interface in tandem with the increase of the Bond number. The predicted interfaces under constant Bond number are also validated against measurements with good agreements.
Multi-Pion Systems in Lattice QCD and the Three-Pion Interaction
Silas Beane; William Detmold; Thomas Luu; Konstantinos Orginos; Assumpta Parreno; Martin Savage; Aaron Torok
2007-10-04
The ground-state energies of 2, 3, 4 and 5 Π+’s in a spatial-volume V ~ (2.5 fm)3 are computed with lattice QCD. By eliminating the leading contribution from three- Π+ interactions, particular combinations of these n- Π+ ground-state energies provide precise extractions of the Π+ Π+ scattering length that are in agreement with that obtained from calculations involving only two Π+’s. The three- Π+ interaction can be isolated by forming other combinations of the n- Π+ ground-state energies, and we find a result that is consistent with a repulsive three-Π+ interaction for mΠ ≲ 350 MeV.
Multipion Systems in Lattice QCD and the Three-Pion Interaction
Beane, Silas R.; Torok, Aaron; Detmold, William; Savage, Martin J.; Luu, Thomas C.; Orginos, Kostas
2008-02-29
The ground-state energies of 2, 3, 4, and 5 {pi}{sup +}'s in a spatial volume V{approx}(2.5 fm){sup 3} are computed with lattice QCD. By eliminating the leading contribution from three-{pi}{sup +} interactions, particular combinations of these n-{pi}{sup +} ground-state energies provide precise extractions of the {pi}{sup +}{pi}{sup +} scattering length in agreement with that obtained from calculations involving only two {pi}{sup +}'s. The three-{pi}{sup +} interaction can be isolated by forming other combinations of the n-{pi}{sup +} ground-state energies. We find a result that is consistent with a repulsive three-{pi}{sup +} interaction for m{sub {pi}} < or approx. 352 MeV.
Tier 3 batch system data locality via managed caches
NASA Astrophysics Data System (ADS)
Fischer, Max; Giffels, Manuel; Jung, Christopher; Kühn, Eileen; Quast, Günter
2015-05-01
Modern data processing increasingly relies on data locality for performance and scalability, whereas the common HEP approaches aim for uniform resource pools with minimal locality, recently even across site boundaries. To combine advantages of both, the High- Performance Data Analysis (HPDA) Tier 3 concept opportunistically establishes data locality via coordinated caches. In accordance with HEP Tier 3 activities, the design incorporates two major assumptions: First, only a fraction of data is accessed regularly and thus the deciding factor for overall throughput. Second, data access may fallback to non-local, making permanent local data availability an inefficient resource usage strategy. Based on this, the HPDA design generically extends available storage hierarchies into the batch system. Using the batch system itself for scheduling file locality, an array of independent caches on the worker nodes is dynamically populated with high-profile data. Cache state information is exposed to the batch system both for managing caches and scheduling jobs. As a result, users directly work with a regular, adequately sized storage system. However, their automated batch processes are presented with local replications of data whenever possible.
Pseudo-gap phase and duality in a holographic fermionic system with dipole coupling on Q-lattice
NASA Astrophysics Data System (ADS)
Ling, Yi; Liu, Peng; Niu, Chao; Wu, Jian-Pin
2016-04-01
We classify the different phases by the “pole-zero mechanism” for a holographic fermionic system which contains a dipole coupling with strength p on a Q-lattice background. A complete phase structure in p space can be depicted in terms of Fermi liquid, non-Fermi liquid, Mott phase and pseudo-gap phase. In particular, we find that in general the region of the pseudo-gap phase in p space is suppressed when the Q-lattice background is dual to a deep insulating phase, while for an anisotropic background, we have an anisotropic region for the pseudo-gap phase in p space as well. In addition, we find that the duality between zeros and poles always exists regardless of whether or not the model is isotropic. Supported by National Natural Science Foundation of China (11275208, 11305018, 11178002), Jiangxi Young Scientists (JingGangStar) Progran and 555 Talent Project of Jiangxi Province, Liaoning Excellent Talents in University (LJQ2014123)
NASA Astrophysics Data System (ADS)
Gadzuk, J. W.
1998-09-01
The phenomenon of breathing mode excitation or bound-state wavepacket squeezing and spreading driven by a time-dependent oscillator frequency (due to either a transient force constant or mass) is considered here. An easily implemented theory of stimulated wavepacket dynamics for near-harmonic systems is presented which describes a variety of generic time dependences such as single sudden excitation, double switching (excitation/time delay/de-excitation) and decaying initially excited states which characterize many processes in spectroscopy, pump-probe control in intramolecular dynamics, and femtochemistry. The model is used as the theoretical basis for understanding such diverse phenomena as quantum excitation due to temporary neutron capture, stimulated bond-breaking resulting in delocalization, desorption, or dissociation, and breathing mode excitation of ultracold atoms trapped in optical lattices. Whilst the first two examples are speculative, results for transient wavepacket dynamics of the occupied excited optical lattice are in accord with recent experimental observations reported by the NIST Laser Cooling Group. Emphasis on the inherent theoretical simplicity and the multidisciplinary aspects of near-harmonic breathing mode excitation, as exemplified by the specific realizations considered here, has been a major intent of this topical review.
Zhang, Xue-Feng; Eggert, Sebastian
2013-10-01
We consider the extended hard-core Bose-Hubbard model on a kagome lattice with boundary conditions on two edges. We find that the sharp edges lift the degeneracy and freeze the system into a striped order at 1/3 and 2/3 filling for zero hopping. At small hopping strengths, holes spontaneously appear and separate into fractional charges which move to the edges of the system. This leads to a novel edge liquid phase, which is characterized by fractional charges near the edges and a finite edge compressibility but no superfluid density. The compressibility is due to excitations on the edge which display a chiral symmetry breaking that is reminiscent of the quantum Hall effect and topological insulators. Large scale Monte Carlo simulations confirm the analytical considerations.
NASA Astrophysics Data System (ADS)
Zhang, Xue-Feng; Eggert, Sebastian
2013-10-01
We consider the extended hard-core Bose-Hubbard model on a kagome lattice with boundary conditions on two edges. We find that the sharp edges lift the degeneracy and freeze the system into a striped order at 1/3 and 2/3 filling for zero hopping. At small hopping strengths, holes spontaneously appear and separate into fractional charges which move to the edges of the system. This leads to a novel edge liquid phase, which is characterized by fractional charges near the edges and a finite edge compressibility but no superfluid density. The compressibility is due to excitations on the edge which display a chiral symmetry breaking that is reminiscent of the quantum Hall effect and topological insulators. Large scale Monte Carlo simulations confirm the analytical considerations.
Local temperature of an interacting quantum system far from equilibrium
NASA Astrophysics Data System (ADS)
Stafford, Charles
2015-03-01
A theory of local temperature measurement of an interacting quantum electron system far from equilibrium via a floating thermoelectric probe is developed. A number of relations are derived relating the probe temperature (and chemical potential) to the local properties of the nonequilibrium system, including a fluctuation-dissipation relation. It is shown that the measured local electron temperature of a steady-state system arbitrarily far from equilibrium is consistent with the zeroth, first, second, and third laws of thermodynamics, provided the probe-system coupling is weak and broad band (ideal temperature measurement). For general probe-system couplings, there are corrections to the zeroth and first laws that are higher-order in the Sommerfeld expansion. The corrections to the zeroth and first laws are related, and can be interpreted in terms of the error of a non-ideal temperature measurement. This work was supported by the Department of Energy, Basic Energy Sciences Grant No. DE-SC0006699.
Mandal, R.; Barman, S.; Saha, S.; Barman, A.; Otani, Y.
2015-08-07
Ferromagnetic antidot lattices are important systems for magnetic data storage and magnonic devices, and understanding their magnetization dynamics by varying their structural parameters is an important problems in magnetism. Here, we investigate the variation in spin wave spectrum in two-dimensional nanoscale Ni{sub 80}Fe{sub 20} antidot lattices with lattice symmetry. By varying the bias magnetic field values in a broadband ferromagnetic resonance spectrometer, we observed a stark variation in the spin wave spectrum with the variation of lattice symmetry. The simulated mode profiles showed further difference in the spatial nature of the modes between different lattices. While for square and rectangular lattices extended modes are observed in addition to standing spin wave modes, all modes in the hexagonal, honeycomb, and octagonal lattices are either localized or standing waves. In addition, the honeycomb and octagonal lattices showed two different types of modes confined within the honeycomb (octagonal) units and between two such consecutive units. Simulated internal magnetic fields confirm the origin of such a wide variation in the frequency and spatial nature of the spin wave modes. The tunability of spin waves with the variation of lattice symmetry is important for the design of future magnetic data storage and magnonic devices.
A Tagless Indoor Localization System Based on Capacitive Sensing Technology.
Ramezani Akhmareh, Alireza; Lazarescu, Mihai Teodor; Bin Tariq, Osama; Lavagno, Luciano
2016-01-01
Accurate indoor person localization is essential for several services, such as assisted living. We introduce a tagless indoor person localization system based on capacitive sensing and localization algorithms that can determine the location with less than 0.2 m average error in a 3 m × 3 m room and has recall and precision better than 70%. We also discuss the effects of various noise types on the measurements and ways to reduce them using filters suitable for on-sensor implementation to lower communication energy consumption. We also compare the performance of several standard localization algorithms in terms of localization error, recall, precision, and accuracy of detection of the movement trajectory. PMID:27618049
A Tagless Indoor Localization System Based on Capacitive Sensing Technology
Ramezani Akhmareh, Alireza; Lazarescu, Mihai Teodor; Bin Tariq, Osama; Lavagno, Luciano
2016-01-01
Accurate indoor person localization is essential for several services, such as assisted living. We introduce a tagless indoor person localization system based on capacitive sensing and localization algorithms that can determine the location with less than 0.2 m average error in a 3 m × 3 m room and has recall and precision better than 70%. We also discuss the effects of various noise types on the measurements and ways to reduce them using filters suitable for on-sensor implementation to lower communication energy consumption. We also compare the performance of several standard localization algorithms in terms of localization error, recall, precision, and accuracy of detection of the movement trajectory. PMID:27618049
Local Dynamic Reactive Power for Correction of System Voltage Problems
Kueck, John D; Rizy, D Tom; Li, Fangxing; Xu, Yan; Li, Huijuan; Adhikari, Sarina; Irminger, Philip
2008-12-01
Distribution systems are experiencing outages due to a phenomenon known as local voltage collapse. Local voltage collapse is occurring in part because modern air conditioner compressor motors are much more susceptible to stalling during a voltage dip than older motors. These motors can stall in less than 3 cycles (.05s) when a fault, such as on the sub-transmission system, causes voltage to sag to 70 to 60%. The reasons for this susceptibility are discussed in the report. During the local voltage collapse, voltages are depressed for a period of perhaps one or two minutes. There is a concern that these local events are interacting together over larger areas and may present a challenge to system reliability. An effective method of preventing local voltage collapse is the use of voltage regulation from Distributed Energy Resources (DER) that can supply or absorb reactive power. DER, when properly controlled, can provide a rapid correction to voltage dips and prevent motor stall. This report discusses the phenomenon and causes of local voltage collapse as well as the control methodology we have developed to counter voltage sag. The problem is growing because of the use of low inertia, high efficiency air conditioner (A/C) compressor motors and because the use of electric A/C is growing in use and becoming a larger percentage of system load. A method for local dynamic voltage regulation is discussed which uses reactive power injection or absorption from local DER. This method is independent, rapid, and will not interfere with conventional utility system voltage control. The results of simulations of this method are provided. The method has also been tested at the ORNL s Distributed Energy Communications and Control (DECC) Laboratory using our research inverter and synchronous condenser. These systems at the DECC Lab are interconnected to an actual distribution system, the ORNL distribution system, which is fed from TVA s 161kV sub-transmission backbone. The test results
Lattice-Boltzmann modeling of micromodel experiments representing a CO2-brine system
Porter, Mark L; Kang, Qinjun; Tarimala, Sowmitri; Abdel - Fattah, Amr I; Backhaus, Scott; Carey, James W
2010-12-21
Successful sequestration of CO{sub 2} into deep saline aquifers presents an enormous challenge that requires fundamental understanding of reactive-multi phase flow and transport across many temporal and spatial scales. Of critical importance is accurately predicting the efficiency of CO{sub 2} trapping mechanisms. At the pore scale (e.g., microns to millimeters) the interfacial area between CO{sub 2} and brine, as well as CO{sub 2} and the solid phase, directly influences the amount of CO{sub 2} trapped due to capillary forces, dissolution and mineral precipitation. In this work, we model immiscible displacement micromodel experiments using the lattice-Boltzmann (LB) method. We focus on quantifying interfacial area as a function of capillary numbers and viscosity ratios typically encountered in CO{sub 2} sequestration operations. We show that the LB model adequately predicts the steady-state experimental flow patterns and interfacial area measurements. Based on the steady-state agreement, we use the LB model to investigate interfacial dynamics (e.g., fluid-fluid interfacial velocity and the rate of production of fluid-fluid interfacial area). In addition, we quantify the amount of interfacial area and the interfacial dynamics associated with the capillary trapped nonwetting phase. This is expected to be important for predicting the amount of nonwetting phase subsequently trapped due to dissolution and mineral precipitation.
[Local health systems. Moral rationality of community decisions].
Tealdi, J C
1990-01-01
The author examines the points of convergence between local health systems and bioethics in three basic areas: structural or institutional, methodological or justificatory, and regulatory or normative. Comparisons are drawn between the decentralization of the health system posed by local health systems and deconcentration of the power vested in multidisciplinary ethics committees; the strategy of social participation and the movement in the United States of community decision-making in the area of health; and the basic concepts of primary health care and the principle of justice. The theories of Pellegrino and Thomasma on the philosophic bases for medical practice provide the framework of this comparative analysis. The article concludes with a call for a local health systems-bioethical nexus in which this discipline can provide the basis for infusing an ethical component into participatory planning and community decision-making.
IRVING: Interfacing Dissimilar Systems at the Local Level.
ERIC Educational Resources Information Center
Luce, Richard E.
1984-01-01
The IRVING Library Network provides state-of-the-art design, using a distributed packet switched network which implements parts of the Open System Interconnection Reference Model as defined by International Standards Organization. It provides gateway to other networks without disturbing local host systems and creates network language. Glossary and…
Mathematically Designing a Local Interaction Algorithm for Decentralized Network Systems
NASA Astrophysics Data System (ADS)
Kubo, Takeshi; Hasegawa, Teruyuki; Hasegawa, Toru
In the near future, decentralized network systems consisting of a huge number of sensor nodes are expected to play an important role. In such a network, each node should control itself by means of a local interaction algorithm. Although such local interaction algorithms improve system reliability, how to design a local interaction algorithm has become an issue. In this paper, we describe a local interaction algorithm in a partial differential equation (or PDE) and propose a new design method whereby a PDE is derived from the solution we desire. The solution is considered as a pattern of nodes' control values over the network each of which is used to control the node's behavior. As a result, nodes collectively provide network functions such as clustering, collision and congestion avoidance. In this paper, we focus on a periodic pattern comprising sinusoidal waves and derive the PDE whose solution exhibits such a pattern by exploiting the Fourier method.
Integrals of motion for one-dimensional Anderson localized systems
NASA Astrophysics Data System (ADS)
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; Shastry, B. Sriram
2016-03-01
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. We answer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precise sense, motivate our construction. We note that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order. We show that despite the infinite range hopping, all states but one are localized. We also study the conservation laws for the disorder free Aubry-Andre model, where the states are either localized or extended, depending on the strength of a coupling constant. We formulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry-Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Finally, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.
An emergency response and local weather forecasting software system
Tremback, C.J.; Lyons, W.A.; Thorson, W.P.; Walko, R.L.
1994-12-31
Recent advances in computer technology have now placed supercomputer power on the desktop for a small fraction of the price. Many traditional supercomputer applications have benefited greatly in the move from the realm of the supercomputer center to more direct local control of the end user. Two of the atmospheric applications that have and will continue to benefit greatly from these advances in computer technology is in the arenas of local weather forecasting and emergency response systems.
Probing the Nuclear Spin-Lattice Relaxation Time at the Nanoscale
NASA Astrophysics Data System (ADS)
Wagenaar, J. J. T.; den Haan, A. M. J.; de Voogd, J. M.; Bossoni, L.; de Jong, T. A.; de Wit, M.; Bastiaans, K. M.; Thoen, D. J.; Endo, A.; Klapwijk, T. M.; Zaanen, J.; Oosterkamp, T. H.
2016-07-01
Nuclear spin-lattice relaxation times are measured on copper using magnetic-resonance force microscopy performed at temperatures down to 42 mK. The low temperature is verified by comparison with the Korringa relation. Measuring spin-lattice relaxation times locally at very low temperatures opens up the possibility to measure the magnetic properties of inhomogeneous electron systems realized in oxide interfaces, topological insulators, and other strongly correlated electron systems such as high-Tc superconductors.
Quantum simulations of lattice gauge theories using ultracold atoms in optical lattices
NASA Astrophysics Data System (ADS)
Zohar, Erez; Cirac, J. Ignacio; Reznik, Benni
2016-01-01
Can high-energy physics be simulated by low-energy, non-relativistic, many-body systems such as ultracold atoms? Such ultracold atomic systems lack the type of symmetries and dynamical properties of high energy physics models: in particular, they manifest neither local gauge invariance nor Lorentz invariance, which are crucial properties of the quantum field theories which are the building blocks of the standard model of elementary particles. However, it turns out, surprisingly, that there are ways to configure an atomic system to manifest both local gauge invariance and Lorentz invariance. In particular, local gauge invariance can arise either as an effective low-energy symmetry, or as an exact symmetry, following from the conservation laws in atomic interactions. Hence, one could hope that such quantum simulators may lead to a new type of (table-top) experiments which will be used to study various QCD (quantum chromodynamics) phenomena, such as the confinement of dynamical quarks, phase transitions and other effects, which are inaccessible using the currently known computational methods. In this report, we review the Hamiltonian formulation of lattice gauge theories, and then describe our recent progress in constructing the quantum simulation of Abelian and non-Abelian lattice gauge theories in 1 + 1 and 2 + 1 dimensions using ultracold atoms in optical lattices.
Quantum simulations of lattice gauge theories using ultracold atoms in optical lattices.
Zohar, Erez; Cirac, J Ignacio; Reznik, Benni
2016-01-01
Can high-energy physics be simulated by low-energy, non-relativistic, many-body systems such as ultracold atoms? Such ultracold atomic systems lack the type of symmetries and dynamical properties of high energy physics models: in particular, they manifest neither local gauge invariance nor Lorentz invariance, which are crucial properties of the quantum field theories which are the building blocks of the standard model of elementary particles. However, it turns out, surprisingly, that there are ways to configure an atomic system to manifest both local gauge invariance and Lorentz invariance. In particular, local gauge invariance can arise either as an effective low-energy symmetry, or as an exact symmetry, following from the conservation laws in atomic interactions. Hence, one could hope that such quantum simulators may lead to a new type of (table-top) experiments which will be used to study various QCD (quantum chromodynamics) phenomena, such as the confinement of dynamical quarks, phase transitions and other effects, which are inaccessible using the currently known computational methods. In this report, we review the Hamiltonian formulation of lattice gauge theories, and then describe our recent progress in constructing the quantum simulation of Abelian and non-Abelian lattice gauge theories in 1 + 1 and 2 + 1 dimensions using ultracold atoms in optical lattices. PMID:26684222
Local temperature of an interacting quantum system far from equilibrium
NASA Astrophysics Data System (ADS)
Stafford, Charles A.
2016-06-01
A theory of local temperature measurement of an interacting quantum electron system far from equilibrium via a floating thermoelectric probe is developed. It is shown that the local temperature so defined is consistent with the zeroth, first, second, and third laws of thermodynamics, provided the probe-system coupling is weak and broadband. For non-broadband probes, the local temperature obeys the Clausius form of the second law and the third law exactly, but there are corrections to the zeroth and first laws that are higher order in the Sommerfeld expansion. The corrections to the zeroth and first laws are related, and can be interpreted in terms of the error of a nonideal temperature measurement. These results also hold for systems at negative absolute temperature.
Fault Location Methods for Ungrounded Distribution Systems Using Local Measurements
NASA Astrophysics Data System (ADS)
Xiu, Wanjing; Liao, Yuan
2013-08-01
This article presents novel fault location algorithms for ungrounded distribution systems. The proposed methods are capable of locating faults by using obtained voltage and current measurements at the local substation. Two types of fault location algorithms, using line to neutral and line to line measurements, are presented. The network structure and parameters are assumed to be known. The network structure needs to be updated based on information obtained from utility telemetry system. With the help of bus impedance matrix, local voltage changes due to the fault can be expressed as a function of fault currents. Since the bus impedance matrix contains information about fault location, superimposed voltages at local substation can be expressed as a function of fault location, through which fault location can be solved. Simulation studies have been carried out based on a sample distribution power system. From the evaluation study, it is evinced that very accurate fault location estimates are obtained from both types of methods.
The integrated local flood warning system: A look at the flood response system
Neal, D.M.; Lee, R.
1988-01-01
Local Flood Warning Systems are instituted and maintained at a local level. They consist of two parts: (1) the flood forecast system, and (2) the flood response system. The flood forecast system is primarily built around the technology used to predict flooding. In this paper, we stress two points about local flood warning systems. First, the system must be integrated. Specifically, collecting data, transmitting data, forecasting the flood, informing local officials, warning local residents, and taking protective action (including evacuation of residents) must all occur in an integrated fashion if the whole system is to succeed. Second, we outline some important organizational characteristics that should be improved when developing a local flood response system. Key organizational characteristics include experience, networks, communications, decision making, everyday disaster task overlap. By focusing upon experience (including learning from the past flood or disaster experience or participating in drills and exercises) and by improving preparedness can be inexpensively improved. 6 refs.,
New Delivery Systems for Local Anaesthetics—Part 2
Shipton, Edward A.
2012-01-01
Part 2 of this paper deals with the techniques for drug delivery of topical and injectable local anaesthetics. The various routes of local anaesthetic delivery (epidural, peripheral, wound catheters, intra-nasal, intra-vesical, intra-articular, intra-osseous) are explored. To enhance transdermal local anaesthetic permeation, additional methods to the use of an eutectic mixture of local anaesthetics and the use of controlled heat can be used. These methods include iontophoresis, electroporation, sonophoresis, and magnetophoresis. The potential clinical uses of topical local anaesthetics are elucidated. Iontophoresis, the active transportation of a drug into the skin using a constant low-voltage direct current is discussed. It is desirable to prolong local anaesthetic blockade by extending its sensory component only. The optimal release and safety of the encapsulated local anaesthetic agents still need to be determined. The use of different delivery systems should provide the clinician with both an extended range and choice in the degree of prolongation of action of each agent. PMID:22190921
Cortical systems for local and global integration in discourse comprehension.
Egidi, Giovanna; Caramazza, Alfonso
2013-05-01
To understand language, we integrate what we hear or read with prior context. This research investigates the neural systems underlying this integration process, in particular the integration of incoming linguistic information with local, proximal context and with global, distal context. The experiments used stories whose endings were locally consistent or locally inconsistent. In addition, the stories' global context was either relevant or irrelevant for the integration of the endings. In Experiment 1, reading latencies showed that the perceived consistency of an ending depended on its fit with the local context, but the availability of a relevant global context attenuated this effect. Experiment 2 used BOLD fMRI to study whether different neural systems are sensitive to the local consistency of the endings and the relevance of the global context. A first analysis evaluated BOLD responses during the comprehension of story endings. It identified three networks: one sensitive to consistency with local context, one sensitive to the relevance of the global context, and one sensitive to both factors. These findings suggest that some regions respond to the holistic relation of local and global contexts while others track only the global or the local contexts. A second analysis examined correlations between BOLD activity during listening of the story endings and subsequent memory for those endings. It revealed two distinct networks: Positive correlations in areas usually involved in semantic processing and memory for language, and negative correlations in sensory, motor, and visual areas, indicating that weaker activity in the latter regions is conducive to better memory for linguistic content. More widespread memory correlates were found when global context was relevant for understanding a story ending. We conclude that integration at the discourse level involves the cooperation of different networks each sensitive to separate aspects of the task, and that integration is
Elimination of spurious lattice fermion solutions and noncompact lattice QCD
Lee, T.D.
1997-09-22
It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2{sup D} degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l {ne} 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in {rvec {gamma}}, and herein lies one of the essential differences.
Spiral wave chimeras in locally coupled oscillator systems.
Li, Bing-Wei; Dierckx, Hans
2016-02-01
The recently discovered chimera state involves the coexistence of synchronized and desynchronized states for a group of identical oscillators. In this work, we show the existence of (inwardly) rotating spiral wave chimeras in the three-component reaction-diffusion systems where each element is locally coupled by diffusion. A transition from spiral waves with the smooth core to spiral wave chimeras is found as we change the local dynamics of the system or as we gradually increase the diffusion coefficient of the activator. Our findings on the spiral wave chimera in the reaction-diffusion systems suggest that spiral chimera states may be found in chemical and biological systems that can be modeled by a large population of oscillators indirectly coupled via a diffusive environment. PMID:26986275
Spiral wave chimeras in locally coupled oscillator systems
NASA Astrophysics Data System (ADS)
Li, Bing-Wei; Dierckx, Hans
2016-02-01
The recently discovered chimera state involves the coexistence of synchronized and desynchronized states for a group of identical oscillators. In this work, we show the existence of (inwardly) rotating spiral wave chimeras in the three-component reaction-diffusion systems where each element is locally coupled by diffusion. A transition from spiral waves with the smooth core to spiral wave chimeras is found as we change the local dynamics of the system or as we gradually increase the diffusion coefficient of the activator. Our findings on the spiral wave chimera in the reaction-diffusion systems suggest that spiral chimera states may be found in chemical and biological systems that can be modeled by a large population of oscillators indirectly coupled via a diffusive environment.
Global and Local Sensitivity Analysis Methods for a Physical System
ERIC Educational Resources Information Center
Morio, Jerome
2011-01-01
Sensitivity analysis is the study of how the different input variations of a mathematical model influence the variability of its output. In this paper, we review the principle of global and local sensitivity analyses of a complex black-box system. A simulated case of application is given at the end of this paper to compare both approaches.…
Students Investigate Local Communities with Geographic Information Systems (GIS).
ERIC Educational Resources Information Center
Carlstrom, Dick; Quinlan, Laurie A.
1997-01-01
Describes the use of Geographic Information Systems (GIS) in elementary and secondary school classrooms to analyze neighborhoods, cities, and regions. Discusses GIS software, databases, graphing data, and spatial analysis, and includes an example of a project for secondary school students investigating the local economy for summer jobs. (LRW)
Instantaneous Spreading Versus Space Localization for Nonrelativistic Quantum Systems
NASA Astrophysics Data System (ADS)
Coutinho, F. A. B.; Wreszinski, W. F.
2016-08-01
A theorem of Hegerfeldt (Kielanowski et al. 1998) establishes, for a class of quantum systems, a dichotomy between those which are permanently localized in a bounded region of space, and those exhibiting instantaneous spreading. We analyze in some detail the physical inconsistencies which follow from both of these options, and formulate which, in our view, are the basic open problems.
Efficient solution procedures for systems with local non-linearities
NASA Astrophysics Data System (ADS)
Ibrahimbegovic, Adnan; Wilson, Edward L.
1992-06-01
This paper presents several methods for enhancing computational efficiency in both static and dynamic analysis of structural systems with localized nonlinear behavior. A significant reduction of computational effort with respect to brute-force nonlinear analysis is achieved in all cases at the insignificant (or no) loss of accuracy. The presented methodologies are easily incorporated into a standard computer program for linear analysis.
Omnidirectional beacon-localization using a catadioptric system.
Shen, Thomas C; Drost, Robert J; Sadler, Brian M; Rzasa, John R; Davis, Christopher C
2016-04-01
We present a catadioptric beacon localization system that can provide mobile network nodes with omnidirectional situational awareness of neighboring nodes. In this system, a receiver composed of a hyperboloidal mirror and camera is used to estimate the azimuth, elevation, and range of an LED beacon. We provide a general framework for understanding the propagation of error in the angle-of-arrival estimation and then present an experimental realization of such a system. The situational awareness provided by the proposed system can enable the alignment of communication nodes in an optical wireless network, which may be particularly useful in addressing RF-denied environments. PMID:27136988
Omnidirectional beacon-localization using a catadioptric system.
Shen, Thomas C; Drost, Robert J; Sadler, Brian M; Rzasa, John R; Davis, Christopher C
2016-04-01
We present a catadioptric beacon localization system that can provide mobile network nodes with omnidirectional situational awareness of neighboring nodes. In this system, a receiver composed of a hyperboloidal mirror and camera is used to estimate the azimuth, elevation, and range of an LED beacon. We provide a general framework for understanding the propagation of error in the angle-of-arrival estimation and then present an experimental realization of such a system. The situational awareness provided by the proposed system can enable the alignment of communication nodes in an optical wireless network, which may be particularly useful in addressing RF-denied environments.
Intruder localization and identification in fiber optic systems
NASA Astrophysics Data System (ADS)
Zyczkowski, M.
2008-10-01
The ultimate goal in all fiber optic systems is to extract information about the mechanical perturbations. For example, this information may be the frequency dependent index of perturbation. For security systems we desire to detect and differentiate between different intruders based on the mechanical response. This article shows experimental investigation of ideal intruder classifier. We considered demodulation, denoising, deconvolution and normalisation. We present additionally possible configuration of fiber optic sensor to localizing perturbation place.
Electromagnetic scattering in two-dimensional dissipative systems without localization
NASA Astrophysics Data System (ADS)
Spieker, H.; Nimtz, G.
1996-10-01
Two-dimensional microwave propagation is experimentally studied in strongly scattering and absorbing random media. The results are compared with adapted theories of Genack, Ferrari, and Kaveh, as well as with classical diffusion theory. The diffusion constants and propagation velocities are determined. Most metallic or semiconductor system's localization effects, if they exist, are so weak that a classical description of the system is appropriate within measuring resolution.
Universal Dynamics and Renormalization in Many-Body-Localized Systems
NASA Astrophysics Data System (ADS)
Altman, Ehud; Vosk, Ronen
2015-03-01
We survey the recent progress made in understanding nonequilibrium dynamics in closed random systems. The emphasis is on the important role played by concepts from quantum information theory and on the application of systematic renormalization group methods to capture universal aspects of the dynamics. Finally, we outline some outstanding open questions, which include the description of the many-body-localization phase transition and the identification of physical systems that allow systematic experimental study of these phenomena.
Anomalies, gauge field topology, and the lattice
Creutz, Michael
2011-04-15
Motivated by the connection between gauge field topology and the axial anomaly in fermion currents, I suggest that the fourth power of the naive Dirac operator can provide a natural method to define a local lattice measure of topological charge. For smooth gauge fields this reduces to the usual topological density. For typical gauge field configurations in a numerical simulation, however, quantum fluctuations dominate, and the sum of this density over the system does not generally give an integer winding. On cooling with respect to the Wilson gauge action, instanton like structures do emerge. As cooling proceeds, these objects tend shrink and finally 'fall through the lattice.' Modifying the action can block the shrinking at the expense of a loss of reflection positivity. The cooling procedure is highly sensitive to the details of the initial steps, suggesting that quantum fluctuations induce a small but fundamental ambiguity in the definition of topological susceptibility.
Integrals of motion for one-dimensional Anderson localized systems
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; Shastry, B. Sriram
2016-03-02
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. Weanswer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precisemore » sense, motivate our construction.Wenote that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order.Weshow that despite the infinite range hopping, all states but one are localized.Wealso study the conservation laws for the disorder free Aubry–Andre model, where the states are either localized or extended, depending on the strength of a coupling constant.Weformulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry–Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Lastly, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.« less
NASA Astrophysics Data System (ADS)
Schaich, David
2016-03-01
Lattice field theory provides a non-perturbative regularization of strongly interacting systems, which has proven crucial to the study of quantum chromodynamics among many other theories. Supersymmetry plays prominent roles in the study of physics beyond the standard model, both as an ingredient in model building and as a tool to improve our understanding of quantum field theory. Attempts to apply lattice techniques to supersymmetric field theories have a long history, but until recently these efforts have generally encountered insurmountable difficulties related to the interplay of supersymmetry with the lattice discretization of spacetime. In recent years these difficulties have been overcome for a class of theories that includes the particularly interesting case of maximally supersymmetric Yang-Mills (N = 4 SYM) in four dimensions, which is a cornerstone of AdS/CFT duality. In combination with computational advances this progress enables practical numerical investigations of N = 4 SYM on the lattice, which can address questions that are difficult or impossible to handle through perturbation theory, AdS/CFT duality, or the conformal bootstrap program. I will briefly review some of the new ideas underlying this recent progress, and present some results from ongoing large-scale numerical calculations, including comparisons with analytic predictions.
Universal Sign Control of Coupling in Tight-Binding Lattices
NASA Astrophysics Data System (ADS)
Keil, Robert; Poli, Charles; Heinrich, Matthias; Arkinstall, Jake; Weihs, Gregor; Schomerus, Henning; Szameit, Alexander
2016-05-01
We present a method of locally inverting the sign of the coupling term in tight-binding systems, by means of inserting a judiciously designed ancillary site and eigenmode matching of the resulting vertex triplet. Our technique can be universally applied to all lattice configurations, as long as the individual sites can be detuned. We experimentally verify this method in laser-written photonic lattices and confirm both the magnitude and the sign of the coupling by interferometric measurements. Based on these findings, we demonstrate how such universal sign-flipped coupling links can be embedded into extended lattice structures to impose a Z2-gauge transformation. This opens a new avenue for investigations on topological effects arising from magnetic fields with aperiodic flux patterns or in disordered systems.
Dynamics of Localized Structures in Systems with Broken Parity Symmetry
NASA Astrophysics Data System (ADS)
Javaloyes, J.; Camelin, P.; Marconi, M.; Giudici, M.
2016-04-01
A great variety of nonlinear dissipative systems are known to host structures having a correlation range much shorter than the size of the system. The dynamics of these localized structures (LSs) has been investigated so far in situations featuring parity symmetry. In this Letter we extend this analysis to systems lacking this property. We show that the LS drifting speed in a parameter varying landscape is not simply proportional to the parameter gradient, as found in parity preserving situations. The symmetry breaking implies a new contribution to the velocity field which is a function of the parameter value, thus leading to a new paradigm for LSs manipulation. We illustrate this general concept by studying the trajectories of the LSs found in a passively mode-locked laser operated in the localization regime. Moreover, the lack of parity affects significantly LSs interactions which are governed by asymmetrical repulsive forces.
Localized Multi-Reference Approach for Mixed-Valence Systems
NASA Astrophysics Data System (ADS)
Helal, W.; Evangelisti, S.; Leininger, T.; Maynau, D.
2008-09-01
The electronic structure and some important intra-molecular charge transfer parameters were investigated at CAS-SCF, MRCI, CAS+S and multi-reference localization levels of theory for purely organic mixed-valence molecules. In particular, a spiro cation has been taken as a model system. The potential energy surfaces of the ground and the lower three excited electronic states have been computed within a two-state model, at CAS-SCF using TZP basis for the spiro cation, and an adiabatic double-well potential has been obtained for the ground electronic state. Our analysis of the geometry through the reaction coordinate indicate that the spiro cation is a valence trapped bistable system. The effect of non-dynamical correlation, using a localized orbital approach, was found to be crucial for a quantitative description of the electronic structure and some important electron transfer parameters of these organic mixed-valence systems.
Spin-Lattice Order in One-Dimensional Conductors: Beyond the RKKY Effect.
Schecter, Michael; Rudner, Mark S; Flensberg, Karsten
2015-06-19
We investigate magnetic order in a lattice of classical spins coupled to an isotropic gas of one-dimensional conduction electrons via local exchange interactions. The frequently discussed Ruderman-Kittel-Kasuya-Yosida effective exchange model for this system predicts that spiral order is always preferred. Here we consider the problem nonperturbatively, and find that such order vanishes above a critical value of the exchange coupling that depends strongly on the lattice spacing. The critical coupling tends to zero as the lattice spacing becomes commensurate with the Fermi wave vector, signaling the breakdown of the perturbative Ruderman-Kittel-Kasuya-Yosida picture, and spiral order, even at weak coupling. We provide the exact phase diagram for arbitrary exchange coupling and lattice spacing, and discuss its stability. Our results shed new light on the problem of utilizing a spiral spin-lattice state to drive a one-dimensional superconductor into a topological phase.
Spin-Lattice Order in One-Dimensional Conductors: Beyond the RKKY Effect.
Schecter, Michael; Rudner, Mark S; Flensberg, Karsten
2015-06-19
We investigate magnetic order in a lattice of classical spins coupled to an isotropic gas of one-dimensional conduction electrons via local exchange interactions. The frequently discussed Ruderman-Kittel-Kasuya-Yosida effective exchange model for this system predicts that spiral order is always preferred. Here we consider the problem nonperturbatively, and find that such order vanishes above a critical value of the exchange coupling that depends strongly on the lattice spacing. The critical coupling tends to zero as the lattice spacing becomes commensurate with the Fermi wave vector, signaling the breakdown of the perturbative Ruderman-Kittel-Kasuya-Yosida picture, and spiral order, even at weak coupling. We provide the exact phase diagram for arbitrary exchange coupling and lattice spacing, and discuss its stability. Our results shed new light on the problem of utilizing a spiral spin-lattice state to drive a one-dimensional superconductor into a topological phase. PMID:26197005
Spin-Lattice Order in One-Dimensional Conductors: Beyond the RKKY Effect
NASA Astrophysics Data System (ADS)
Schecter, Michael; Rudner, Mark S.; Flensberg, Karsten
2015-06-01
We investigate magnetic order in a lattice of classical spins coupled to an isotropic gas of one-dimensional conduction electrons via local exchange interactions. The frequently discussed Ruderman-Kittel-Kasuya-Yosida effective exchange model for this system predicts that spiral order is always preferred. Here we consider the problem nonperturbatively, and find that such order vanishes above a critical value of the exchange coupling that depends strongly on the lattice spacing. The critical coupling tends to zero as the lattice spacing becomes commensurate with the Fermi wave vector, signaling the breakdown of the perturbative Ruderman-Kittel-Kasuya-Yosida picture, and spiral order, even at weak coupling. We provide the exact phase diagram for arbitrary exchange coupling and lattice spacing, and discuss its stability. Our results shed new light on the problem of utilizing a spiral spin-lattice state to drive a one-dimensional superconductor into a topological phase.
Finite Temperature Properties of Three-Component Fermion Systems in Optical Lattice
NASA Astrophysics Data System (ADS)
Yanatori, Hiromasa; Koga, Akihisa
2016-01-01
We investigate finite temperature properties in the half-filled three-component (colors) fermion systems. It is clarified that a color density-wave (CDW) state is more stable than a color-selective "antiferromagnetic" (CSAF) state against thermal fluctuations. The reentrant behavior in the phase boundary for the CSAF state is found. We also address the maximum critical temperature of the translational symmetry breaking states in the multicomponent fermionic systems.
Vibration localization in dual-span axially moving elastic systems
NASA Astrophysics Data System (ADS)
Aljawi, Abdulghaffar Azhari Nawawi
To date, vibration localization in the large class of systems modeled by multispan axially moving materials has not been examined. These systems are common in many engineering applications, such as band saw blades, power transmission, belts and chains, and magnetic and paper tapes. An investigation of the vibration localization phenomenon in two-span, axially moving beams is presented. The effects of tension disorder, interspan coupling, and transport speed on the confinement of the natural modes of free vibration are studied. The equations governing the transverse vibration of the two-span, axially moving beam are derived through Hamilton's principle and solution methods are developed. Numerical results demonstrate that normal mode localization indeed occurs for both stationary and translating disordered two-span beams, especially for small interspan coupling. The occurrence of localization is characterized by a peak deflection much greater in one span than in the other. In the stationary disordered case, localization becomes more pronounced as interspan coupling decreases, i.e., as the span axial tension increases. For an axially translating beam with identical spans, the two loci in each pair of natural frequencies may exhibit a single or double crossing (depending on the value of tension) when plotted against the axial transport speed. These crossings become veerings when the beam is disordered, and localization is strongest at those speeds where the eigenvalue veerings occur. A perturbation approach, which provides additional insights into the sensitivity of the system to disorder, is also utilized. Analytical expressions are obtained in the limiting cases of weak and strong interspan coupling. Findings show that the sensitivity of the system to disorder primarily depends upon disorder and interspan coupling strengths. Finally, an investigation of the localization phenomenon is performed for a more complete model of a band/wheel system. The effects of tension
Natural evolution, disease, and localization in the immune system
NASA Astrophysics Data System (ADS)
Deem, Michael
2004-03-01
Adaptive vertebrate immune system is a wonder of modern evolution. Under most circumstances, the dynamics of the immune system is well-matched to the dynamics of pathogen growth during a typical infection. Some pathogens, however, have evolved escape mechanisms that interact in subtle ways with the immune system dynamics. In addition, negative interactions the immune system, which has evolved over 400 000 000 years, and vaccination,which has been practiced for only 200 years, are possible. For example,vaccination against the flu can actually increase susceptibility to the flu in the next year. As another example, vaccination against one of the four strains of dengue fever typically increases susceptibility against the other three strains. Immunodominance also arises in the immune system control of nascent tumors--the immune system recognizes only a small subset of the tumor specific antigens, and the rest are free to grow and cause tumor growth. In this talk, I present a physical theory of original antigenic sin and immunodominance. How localization in the immune system leads to the observed phenomena is discussed. 1) M. W. Deem and H. Y. Lee, ``Sequence Space Localization in the Immune System Response to Vaccination and Disease,'' Phys. Rev. Lett. 91 (2003) 068101
An active UHF RFID localization system for fawn saving
NASA Astrophysics Data System (ADS)
Eberhardt, M.; Lehner, M.; Ascher, A.; Allwang, M.; Biebl, E. M.
2015-11-01
We present a localization concept for active UHF RFID transponders which enables mowing machine drivers to detect and localize marked fawns. The whole system design and experimental results with transponders located near the ground in random orientations in a meadow area are shown. The communication flow between reader and transponders is realized as a dynamic master-slave concept. Multiple marked fawns will be localized by processing detected transponders sequentially. With an eight-channel-receiver with integrated calibration method one can estimate the direction-of-arrival by measuring the phases of the transponder signals up to a range of 50 m in all directions. For further troubleshooting array manifolds have been measured. An additional hand-held receiver with a two-channel receiver allows a guided approaching search without endangering the fawn by the mowing machine.
Kondo lattice mixed valence behavior in the Ce(SnxPb1 - x)3 system
NASA Astrophysics Data System (ADS)
Teter, J.; Freitag, R.; Maury*, A.; Crow, J. E.; Mihalisin, T.
1982-11-01
Measurements of the electrical resistivity versus x and temperature T, for 1.5≤T≤300 K for the fcc system Ce(SnxPb1-x)3 are reported. CeSn3 has been shown to be a strongly mixed valent system with an average occupation number of the Ce 4f level nf of ˜0.4 at low temperatures. The electrical resistivity for Ce(SnxPb1-x)3 is compared to that obtained for other Ce based mixed valent-trivalent systems and to the predictions of the Newns and Hewson theory. These comparisons suggest that Ce(SnxPb1-x)3 is mixed valent for x≳0.5 and the scaling of the resistivity supports the previous result that CeSn3 is strong mixed valent with nf≂0.4.
Assessing youth policies. A system of indicators for local government.
Planas, Anna; Soler, Pere; Vilà, Montserrat
2014-08-01
In the current European climate of economic, financial and political crisis and the questioning of the welfare state, assessing public policies assume a primary and strategic relevance in clarifying the results and contributions of policy actions. In this article, we aim to present the current situation in relation to youth policy assessment so as to formulate a system of assessment indicators in the sphere of Spanish local government youth policy. A review is conducted of some of the principal contributions in the field of constructing indicators for evaluating youth policies. We have found that most of these evaluation tools exist on a national or state level and that there is a dearth of local or municipal tools. The article concludes with a concrete proposal for an assessment tool: the SIAPJove (Sistema d'Indicadors d'Avaluació per a les Polítiques Municipals de Joventut or System of Assessment Indicators for Local Government Youth Policies) (web page: http://siapjove.udg.edu/). It provides both quantitative and qualitative indicators for local youth policy managers to obtain assessment reports with relative ease in 12 possible areas for assessment within youth policy. PMID:24681521
Assessing youth policies. A system of indicators for local government.
Planas, Anna; Soler, Pere; Vilà, Montserrat
2014-08-01
In the current European climate of economic, financial and political crisis and the questioning of the welfare state, assessing public policies assume a primary and strategic relevance in clarifying the results and contributions of policy actions. In this article, we aim to present the current situation in relation to youth policy assessment so as to formulate a system of assessment indicators in the sphere of Spanish local government youth policy. A review is conducted of some of the principal contributions in the field of constructing indicators for evaluating youth policies. We have found that most of these evaluation tools exist on a national or state level and that there is a dearth of local or municipal tools. The article concludes with a concrete proposal for an assessment tool: the SIAPJove (Sistema d'Indicadors d'Avaluació per a les Polítiques Municipals de Joventut or System of Assessment Indicators for Local Government Youth Policies) (web page: http://siapjove.udg.edu/). It provides both quantitative and qualitative indicators for local youth policy managers to obtain assessment reports with relative ease in 12 possible areas for assessment within youth policy.
Vasodilator factors in the systemic and local adaptations to pregnancy
Valdes, Gloria; Kaufmann, Peter; Corthorn, Jenny; Erices, Rafaela; Brosnihan, K Bridget; Joyner-Grantham, JaNae
2009-01-01
We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1–7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the
Reliability analysis of interdependent lattices
NASA Astrophysics Data System (ADS)
Limiao, Zhang; Daqing, Li; Pengju, Qin; Bowen, Fu; Yinan, Jiang; Zio, Enrico; Rui, Kang
2016-06-01
Network reliability analysis has drawn much attention recently due to the risks of catastrophic damage in networked infrastructures. These infrastructures are dependent on each other as a result of various interactions. However, most of the reliability analyses of these interdependent networks do not consider spatial constraints, which are found important for robustness of infrastructures including power grid and transport systems. Here we study the reliability properties of interdependent lattices with different ranges of spatial constraints. Our study shows that interdependent lattices with strong spatial constraints are more resilient than interdependent Erdös-Rényi networks. There exists an intermediate range of spatial constraints, at which the interdependent lattices have minimal resilience.
High-Fidelity Lattice Physics Capabilities of the SCALE Code System Using TRITON
DeHart, Mark D
2007-01-01
Increasing complexity in reactor designs suggests a need to reexamine of methods applied in spent-fuel characterization. The ability to accurately predict the nuclide composition of depleted reactor fuel is important in a wide variety of applications. These applications include, but are not limited to, the design, licensing, and operation of commercial/research reactors and spent-fuel transport/storage systems. New complex design projects such as space reactors and Generation IV power reactors also require calculational methods that provide accurate prediction of the isotopic inventory. New high-fidelity physics methods will be required to better understand the physics associated with both evolutionary and revolutionary reactor concepts as they depart from traditional and well-understood light-water reactor designs. The TRITON sequence of the SCALE code system provides a powerful, robust, and rigorous approach for reactor physics analysis. This paper provides a detailed description of TRITON in terms of its key components used in reactor calculations.
Speeding up local correlation methods: System-inherent domains
NASA Astrophysics Data System (ADS)
Kats, Daniel
2016-07-01
A new approach to determine local virtual space in correlated calculations is presented. It restricts the virtual space in a pair-specific manner on the basis of a preceding approximate calculation adapting automatically to the locality of the studied problem. The resulting pair system-inherent domains are considerably smaller than the starting domains, without significant loss in the accuracy. Utilization of such domains speeds up integral transformations and evaluations of the residual and reduces memory requirements. The system-inherent domains are especially suitable in cases which require high accuracy, e.g., in generation of pair-natural orbitals, or for which standard domains are problematic, e.g., excited-state calculations.
Theory of many-body localization in periodically driven systems
NASA Astrophysics Data System (ADS)
Abanin, Dmitry A.; De Roeck, Wojciech; Huveneers, François
2016-09-01
We present a theory of periodically driven, many-body localized (MBL) systems. We argue that MBL persists under periodic driving at high enough driving frequency: The Floquet operator (evolution operator over one driving period) can be represented as an exponential of an effective time-independent Hamiltonian, which is a sum of quasi-local terms and is itself fully MBL. We derive this result by constructing a sequence of canonical transformations to remove the time-dependence from the original Hamiltonian. When the driving evolves smoothly in time, the theory can be sharpened by estimating the probability of adiabatic Landau-Zener transitions at many-body level crossings. In all cases, we argue that there is delocalization at sufficiently low frequency. We propose a phase diagram of driven MBL systems.
Many-body localization in periodically driven systems.
Ponte, Pedro; Papić, Z; Huveneers, François; Abanin, Dmitry A
2015-04-10
We consider disordered many-body systems with periodic time-dependent Hamiltonians in one spatial dimension. By studying the properties of the Floquet eigenstates, we identify two distinct phases: (i) a many-body localized (MBL) phase, in which almost all eigenstates have area-law entanglement entropy, and the eigenstate thermalization hypothesis (ETH) is violated, and (ii) a delocalized phase, in which eigenstates have volume-law entanglement and obey the ETH. The MBL phase exhibits logarithmic in time growth of entanglement entropy when the system is initially prepared in a product state, which distinguishes it from the delocalized phase. We propose an effective model of the MBL phase in terms of an extensive number of emergent local integrals of motion, which naturally explains the spectral and dynamical properties of this phase. Numerical data, obtained by exact diagonalization and time-evolving block decimation methods, suggest a direct transition between the two phases. PMID:25910094
Speeding up local correlation methods: System-inherent domains.
Kats, Daniel
2016-07-01
A new approach to determine local virtual space in correlated calculations is presented. It restricts the virtual space in a pair-specific manner on the basis of a preceding approximate calculation adapting automatically to the locality of the studied problem. The resulting pair system-inherent domains are considerably smaller than the starting domains, without significant loss in the accuracy. Utilization of such domains speeds up integral transformations and evaluations of the residual and reduces memory requirements. The system-inherent domains are especially suitable in cases which require high accuracy, e.g., in generation of pair-natural orbitals, or for which standard domains are problematic, e.g., excited-state calculations. PMID:27394095
NASA Astrophysics Data System (ADS)
Joshi, Nalini; Nakazono, Nobutaka; Shi, Yang
2015-09-01
We introduce the concept of ω-lattice, constructed from τ functions of Painlevé systems, on which quad-equations of ABS (Adler-Bobenko-Suris) type appear. In particular, we consider the A5 ( 1 ) - and A6 ( 1 ) -surface q-Painlevé systems corresponding affine Weyl group symmetries are of (A2 + A1)(1)- and (A1 + A1)(1)-types, respectively.
Le Hur, Karyn Maurice Rice, T.
2009-07-15
Since the discovery of high-temperature superconductivity in 1986 by Bednorz and Mueller, great efforts have been devoted to finding out how and why it works. From the d-wave symmetry of the order parameter, the importance of antiferromagnetic fluctuations, and the presence of a mysterious pseudogap phase close to the Mott state, one can conclude that high-T{sub c} superconductors are clearly distinguishable from the well-understood BCS superconductors. The d-wave superconducting state can be understood through a Gutzwiller-type projected BCS wavefunction. In this review article, we revisit the Hubbard model at half-filling and focus on the emergence of exotic superconductivity with d-wave symmetry in the vicinity of the Mott state, starting from ladder systems and then studying the dimensional crossovers to higher dimensions. This allows to confirm that short-range antiferromagnetic fluctuations can mediate superconductivity with d-wave symmetry. Ladders are also nice prototype systems allowing to demonstrate the truncation of the Fermi surface and the emergence of a Resonating Valence Bond (RVB) state with preformed pairs in the vicinity of the Mott state. In two dimensions, a similar scenario emerges from renormalization group arguments. We also discuss theoretical predictions for the d-wave superconducting phase as well as the pseudogap phase, and address the crossover to the overdoped regime. Finally, cold atomic systems with tunable parameters also provide a complementary insight into this outstanding problem.
A novel wireless local positioning system for airport (indoor) security
NASA Astrophysics Data System (ADS)
Zekavat, Seyed A.; Tong, Hui; Tan, Jindong
2004-09-01
A novel wireless local positioning system (WLPS) for airport (or indoor) security is introduced. This system is used by airport (indoor) security guards to locate all of, or a group of airport employees or passengers within the airport area. WLPS consists of two main parts: (1) a base station that is carried by security personnel; hence, introducing dynamic base station (DBS), and (2) a transponder (TRX) that is mounted on all people (including security personnel) present at the airport; thus, introducing them as active targets. In this paper, we (a) draw a futuristic view of the airport security systems, and the flow of information at the airports, (b) investigate the techniques of extending WLPS coverage area beyond the line-of-sight (LoS), and (c) study the performance of this system via standard transceivers, and direct sequence code division multiple access (DS-CDMA) systems with and without antenna arrays and conventional beamforming (BF).
Local composition in solvent + polymer or biopolymer systems.
Shulgin, Ivan L; Ruckenstein, Eli
2008-03-13
The focus of this paper is on the application of the Kirkwood-Buff (KB) fluctuation theory to the analysis of the local composition in systems composed of a low molecular weight solvent and a high molecular weight polymer or protein. A key quantity in the calculation of the local composition is the excess (or deficit) of any species i around a central molecule j in a binary mixture. A new expression derived by the authors (J. Phys. Chem. B 2006, 110, 12707) for the excess (deficit) is used in the present paper. First, the literature regarding the local composition in such systems is reviewed. It is shown that the frequently used Zimm cluster integral provides incorrect results because it is based on an incorrect expression for the excess (or deficit). In the present paper, our new expression is applied to solvent + macromolecule systems to predict the local composition around both a solvent and a macromolecule central molecule. Five systems (toluene + polystyrene, water + collagen, water + serum albumin, water + hydroxypropyl cellulose, and water + Pluronic P105) were selected for this purpose. The results revealed that for water + collagen and water + serum albumin mixtures, the solvent was in deficit around a central solvent molecule and that for the other three mixtures, the opposite was true. In contrast, the solvent was always in excess around the macromolecule for all mixtures investigated. In the dilute range of the solvent, the excesses are due mainly to the different solvent and macromolecule sizes. However, in the dilute range of the macromolecule, the intermolecular interactions between solvent and macromolecule are mainly responsible for the excess. The obtained results shed some light on protein hydration.
NASA Astrophysics Data System (ADS)
Roy Chowdhury, Soumi; Chaudhury, Ranjan
2015-05-01
Cooper's original one pair problem in continuum is revisited here corresponding to a lattice of tight binding nature, with an aim to investigate superconductivity in low dimensional systems. An electronic type of boson mediated attraction in a passive Fermi sea-like background is considered for the pairing mechanism with the non-trivial energy dependence of the electronic density of states taken into account in the calculation in a rigorous way. Some of the very important electronic and optical properties in the normal phase of quasi one dimensional organic superconductors are used for the development of the formalism and calculations. The results of our calculations show that a realistic fermionic pair formation is indeed possible with some constraints, without any necessity at all of invoking Luttinger-Tomonaga liquid (LTL) theory. Similarities emerge in the physical properties of the electron pair formed from Cooper's treatment corresponding to continuum and ours, excepting the striking difference appearing in the form of occurrences of a maximum allowed band filling for pairing and of an upper bound of the pairing energy found in our approach.
Scanu, Lauriane F; Gubbins, Keith E; Hall, Carol K
2004-01-20
Lattice Monte Carlo simulations are used to study the effect of nonionic surfactant concentration and CO2 density on the micellization and phase equilibria of supercritical CO2/surfactant systems. The interaction parameter for carbon dioxide is obtained by matching the critical temperature of the model fluid with the experimental critical temperature. Various properties such as the critical micelle concentration and the size, shape, and structure ofmicelles are calculated, and the phase diagram in the surfactant concentration-CO2 density space is constructed. On increasing the CO2 density, we find an increase in the critical micelle concentration and a decrease in the micellar size; this is consistent with existing experimental results. The variation of the micellar shape and structure with CO2 density shows that the micelles are spherical and that the extension of the micellar core increases with increasing micellar size, while the extension of the micellar corona increases with increasing CO2 density. The predicted phase diagram is in qualitative agreement with experimental phase diagrams for nonionic surfactants in carbon dioxide.
Long-range order instead of phase separation in large lattice-mismatch isovalent AX-BX systems
Zhang, Xiuwen; Trimarchi, Giancarlo; d'Avezac, Mayeul; Zunger, Alex
2009-12-15
Large atomic size mismatch between compounds discourages their binding into a common lattice because of the ensuing cost in strain energy. This central paradigm in the theory of isovalent alloys long used to disqualify alloys with highly mismatched components from technological use is clearly broken by the occurrence of stable spontaneous long-range order in mixtures of alkali halides with as much as 40% size mismatch (e.g., LiF-CsF). Our theoretical analysis of these failures uncovered a different design principle for stable alloys: very large atomic size mismatch can lead to spontaneous ordering if the large (small) components have the ability to raise (lower) their coordination number (CN) within the mixed phase. This heuristic design principle has led us to explore via first-principles structure search a few very largely mismatched binary systems whose components have a propensity for CN disproportionation. We find ordered structures for BeO-BaO (37% size mismatch) and BeO-SrO (30%), and ordering in LiCl-KCl (20%), whereas BN-InN (33%) is found to lower its positive formation enthalpy by ~60% when CN disproportionation is allowed. This new design principle could be used to explore phases unsuspected to order by the common paradigm of strain instability.
NASA Astrophysics Data System (ADS)
Datta, Nilanjana; Pautrat, Yan; Rouzé, Cambyse
2016-06-01
Quantum Stein's lemma is a cornerstone of quantum statistics and concerns the problem of correctly identifying a quantum state, given the knowledge that it is one of two specific states (ρ or σ). It was originally derived in the asymptotic i.i.d. setting, in which arbitrarily many (say, n) identical copies of the state (ρ⊗n or σ⊗n) are considered to be available. In this setting, the lemma states that, for any given upper bound on the probability αn of erroneously inferring the state to be σ, the probability βn of erroneously inferring the state to be ρ decays exponentially in n, with the rate of decay converging to the relative entropy of the two states. The second order asymptotics for quantum hypothesis testing, which establishes the speed of convergence of this rate of decay to its limiting value, was derived in the i.i.d. setting independently by Tomamichel and Hayashi, and Li. We extend this result to settings beyond i.i.d. Examples of these include Gibbs states of quantum spin systems (with finite-range, translation-invariant interactions) at high temperatures, and quasi-free states of fermionic lattice gases.
Assessment of optical localizer accuracy for computer aided surgery systems.
Elfring, Robert; de la Fuente, Matías; Radermacher, Klaus
2010-01-01
The technology for localization of surgical tools with respect to the patient's reference coordinate system in three to six degrees of freedom is one of the key components in computer aided surgery. Several tracking methods are available, of which optical tracking is the most widespread in clinical use. Optical tracking technology has proven to be a reliable method for intra-operative position and orientation acquisition in many clinical applications; however, the accuracy of such localizers is still a topic of discussion. In this paper, the accuracy of three optical localizer systems, the NDI Polaris P4, the NDI Polaris Spectra (in active and passive mode) and the Stryker Navigation System II camera, is assessed and compared critically. Static tests revealed that only the Polaris P4 shows significant warm-up behavior, with a significant shift of accuracy being observed within 42 minutes of being switched on. Furthermore, the intrinsic localizer accuracy was determined for single markers as well as for tools using a volumetric measurement protocol on a coordinate measurement machine. To determine the relative distance error within the measurement volume, the Length Measurement Error (LME) was determined at 35 test lengths. As accuracy depends strongly on the marker configuration employed, the error to be expected in typical clinical setups was estimated in a simulation for different tool configurations. The two active localizer systems, the Stryker Navigation System II camera and the Polaris Spectra (active mode), showed the best results, with trueness values (mean +/- standard deviation) of 0.058 +/- 0.033 mm and 0.089 +/- 0.061 mm, respectively. The Polaris Spectra (passive mode) showed a trueness of 0.170 +/- 0.090 mm, and the Polaris P4 showed the lowest trueness at 0.272 +/- 0.394 mm with a higher number of outliers than for the other cameras. The simulation of the different tool configurations in a typical clinical setup revealed that the tracking error can
GMUGLE: A goal lattice constructor
NASA Astrophysics Data System (ADS)
Hintz, Kenneth J.
2001-08-01
Goal lattices are a method for ordering the goals of a system and associating with each goal the value of performing that goal in terms of how much it contributes to the accomplishment of the topmost goal of a system. This paper presents a progress report on the development of a web-based implementation of the George Mason University Goal Lattice Engine (GMUGLE). GMUGLE allows a user to interactively create goal lattices, add/delete goals, and specify their ordering relations through a web-based interface. The database portion automatically computes the GLB and LUB of pairs of goals which have been entered to form them into a lattice. Yet to be implemented is the code to input goal values, automatically apportion the values among included goals, and accrue value among the included goals.
Time-Localization of Forced Oscillations in Power Systems
Follum, James D.; Pierre, John W.
2015-07-26
In power systems forced oscillations occur, and identification of these oscillations is important for the proper operation of the system. Two of the parameters of interest in analyzing and addressing forced oscillations are the starting and ending points. To obtain estimates of these parameters, this paper proposes a time-localization algorithm based on the geometric analysis of the sample cross-correlation between the measured data and a complex sinusoid at the frequency of the forced oscillation. Results from simulated and measured synchrophasor data demonstrate the algorithm's ability to accurately estimate the starting and ending points of forced oscillations.
A local area computer network expert system framework
NASA Technical Reports Server (NTRS)
Dominy, Robert
1987-01-01
Over the past years an expert system called LANES designed to detect and isolate faults in the Goddard-wide Hybrid Local Area Computer Network (LACN) was developed. As a result, the need for developing a more generic LACN fault isolation expert system has become apparent. An object oriented approach was explored to create a set of generic classes, objects, rules, and methods that would be necessary to meet this need. The object classes provide a convenient mechanism for separating high level information from low level network specific information. This approach yeilds a framework which can be applied to different network configurations and be easily expanded to meet new needs.
Inverse source localization for EEG using system identification approach
NASA Astrophysics Data System (ADS)
Xanthopoulos, Petros; Yatsenko, Vitaliy; Kammerdiner, Alla; Pardalos, Panos M.
2007-11-01
The reconstruction of the brain current sources from scalp electric recordings (Electroen-cephalogram) also known as the inverse source localization problem is a highly underdetermined problem in the field of computational neuroscience, and this problem still remains open . In this chapter we propose an alternative formulation for the inverse electroencephalography (EEG) problem based on optimization theory. For simulation purposes, a three shell realistic head model based on an averaged magnetic resonance imaging (MRI) segmentation and Boundary Element method (BEM) is constructed. System identification methodology is employed in order to determine the parameters of the system. In the last stage the inverse problem is solved using the computed forward model.
System and method for bullet tracking and shooter localization
Roberts, Randy S.; Breitfeller, Eric F.
2011-06-21
A system and method of processing infrared imagery to determine projectile trajectories and the locations of shooters with a high degree of accuracy. The method includes image processing infrared image data to reduce noise and identify streak-shaped image features, using a Kalman filter to estimate optimal projectile trajectories, updating the Kalman filter with new image data, determining projectile source locations by solving a combinatorial least-squares solution for all optimal projectile trajectories, and displaying all of the projectile source locations. Such a shooter-localization system is of great interest for military and law enforcement applications to determine sniper locations, especially in urban combat scenarios.
Derivation of the Leroux System as the Hydrodynamic Limit of a Two-Component Lattice Gas
NASA Astrophysics Data System (ADS)
Fritz, József; Tóth, Bálint
The long time behavior of a couple of interacting asymmetric exclusion processes of opposite velocities is investigated in one space dimension. We do not allow two particles at the same site, and a collision effect (exchange) takes place when particles of opposite velocities meet at neighboring sites. There are two conserved quantities, and the model admits hyperbolic (Euler) scaling; the hydrodynamic limit results in the classical Leroux system of conservation laws, even beyond the appearance of shocks. Actually, we prove convergence to the set of entropy solutions, the question of uniqueness is left open. To control rapid oscillations of Lax entropies via logarithmic Sobolev inequality estimates, the symmetric part of the process is speeded up in a suitable way, thus a slowly vanishing viscosity is obtained at the macroscopic level. Following [4, 5], the stochastic version of Tartar-Murat theory of compensated compactness is extended to two-component stochastic models.
Kenneth Wilson and Lattice QCD
NASA Astrophysics Data System (ADS)
Ukawa, Akira
2015-09-01
We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward better understanding of physics, better algorithms, and more powerful supercomputers have produced major breakthroughs in our understanding of the strong interactions. We review the salient results of this effort in understanding the hadron spectrum, the Cabibbo-Kobayashi-Maskawa matrix elements and CP violation, and quark-gluon plasma at high temperatures. We conclude with a brief summary and a future perspective.
Coexistence of Mott and superfluid domains of bosons confined in optical lattice
NASA Astrophysics Data System (ADS)
Khanore, Mukesh; Dey, Bishwajyoti
2015-06-01
We investigate ground state properties of the attractive Bose-gas confined on square optical lattice and superimposed wine-bottle-bottom or Mexican hat trap potential. The system is modeled by two-dimensional Bose-Hubbard model with attractive interactions and inhomogeneous lattice potential. We calculate the energy spectrum, the on-site number fluctuation, local density and local compressibility using numerical exact diagonalization method for incommensurate lattice filling. The trap potential has several degenerate minimum sites distributed along a ring at the wine-bottle-bottom. It is shown that beyond a certain value of the attractive interaction strength there is phase coherent condensate on these degenerate sites with finite value of the on-site number fluctuation and local compressibility giving rise to localized superfluidity or superfluidity on a ring. For the same value of the interaction strength the non-degenerate sites produces Mott region.
Transport of a lattice gas under continuous measurement
NASA Astrophysics Data System (ADS)
Cheung, Hil F. H.; Patil, Yogesh Sharad; Madjarov, Ivaylo S.; Chen, Huiyao Y.; Vengalattore, Mukund
2016-05-01
The act of measurement has a profound consequence on a quantum system. While this backaction has hitherto been discussed as a limitation to the precision of measurements, it is increasingly being appreciated that measurement backaction is a powerful means of quantum control. We have previously demonstrated that backaction from position measurement can modify the coherent tunneling rate of a lattice gas through the Quantum Zeno effect. By suitably designing measurement landscapes we can control the transport properties of the lattice gas. We describe a quantitative study of lattice gas dynamics under continuous quantum measurement in the context of a quantum to classical transition where the atom dynamics goes from a quantum walk at low measurement strengths to classical diffusion at high measurement strengths. We further discuss the prospect of using disorder measurement landscapes to realize a new form of Anderson localization. This work is supported by the ARO MURI on non-equilibrium dynamics.
Mello Koch, Robert de; Mashile, Grant; Park, Nicholas
2010-05-15
In this article the anomalous dimension of a class of operators with a bare dimension of O(N) is studied. The operators considered are dual to excited states of a two giant graviton system. In the Yang-Mills theory they are described by restricted Schur polynomials, labeled with Young diagrams that have at most two columns. In a certain limit the dilatation operator looks like a lattice version of a second derivative, with the lattice emerging from the Young diagram itself.
Spin-Lattice-Coupled Order in Heisenberg Antiferromagnets on the Pyrochlore Lattice.
Aoyama, Kazushi; Kawamura, Hikaru
2016-06-24
Effects of local lattice distortions on the spin ordering are investigated for the antiferromagnetic classical Heisenberg model on the pyrochlore lattice. It is found by Monte Carlo simulations that the spin-lattice coupling (SLC) originating from site phonons induces a first-order transition into two different types of collinear magnetic ordered states. The state realized at the stronger SLC is cubic symmetric characterized by the magnetic (1/2,1/2,1/2) Bragg peaks, while that at the weaker SLC is tetragonal symmetric characterized by the (1,1,0) ones, each accompanied by the commensurate local lattice distortions. Experimental implications to chromium spinels are discussed. PMID:27391746
Spin-Lattice-Coupled Order in Heisenberg Antiferromagnets on the Pyrochlore Lattice
NASA Astrophysics Data System (ADS)
Aoyama, Kazushi; Kawamura, Hikaru
2016-06-01
Effects of local lattice distortions on the spin ordering are investigated for the antiferromagnetic classical Heisenberg model on the pyrochlore lattice. It is found by Monte Carlo simulations that the spin-lattice coupling (SLC) originating from site phonons induces a first-order transition into two different types of collinear magnetic ordered states. The state realized at the stronger SLC is cubic symmetric characterized by the magnetic (1/2 ,1/2 ,1/2 ) Bragg peaks, while that at the weaker SLC is tetragonal symmetric characterized by the (1,1,0) ones, each accompanied by the commensurate local lattice distortions. Experimental implications to chromium spinels are discussed.
Recognition of bacterial plant pathogens: local, systemic and transgenerational immunity.
Henry, Elizabeth; Yadeta, Koste A; Coaker, Gitta
2013-09-01
Bacterial pathogens can cause multiple plant diseases and plants rely on their innate immune system to recognize and actively respond to these microbes. The plant innate immune system comprises extracellular pattern recognition receptors that recognize conserved microbial patterns and intracellular nucleotide binding leucine-rich repeat (NLR) proteins that recognize specific bacterial effectors delivered into host cells. Plants lack the adaptive immune branch present in animals, but still afford flexibility to pathogen attack through systemic and transgenerational resistance. Here, we focus on current research in plant immune responses against bacterial pathogens. Recent studies shed light onto the activation and inactivation of pattern recognition receptors and systemic acquired resistance. New research has also uncovered additional layers of complexity surrounding NLR immune receptor activation, cooperation and sub-cellular localizations. Taken together, these recent advances bring us closer to understanding the web of molecular interactions responsible for coordinating defense responses and ultimately resistance.
Lattice time-dependent correlated two-electron system approach to scattering problems
NASA Astrophysics Data System (ADS)
Odero, Dan Onyango
2000-09-01
This thesis presents a time-dependent approach for the solution of the quantum mechanical three-body problem. The solution presented here is exact in that the approximations are numerical. All the Coulomb interactions between the three particles are taken into account with no approximations. In the time-dependent approach, the quantum mechanical wave functions for the system are obtained at successive times. One of the possible three-body problems is electron-hydrogen scattering. For this case, time- dependent probabilities for exciting the hydrogen atom may be obtained by projecting the states of the target atom onto the time-dependent correlated two-electron wave function. Measurable cross sections for electron impact excitation are obtained at the point where the probabilities are no longer changing with time. The accuracy of this approach is found to be dependent on the total angular momentum. In the lowest total angular momentum, L = 0 case, the angular momentum coupling terms do not contribute and the results compare favorably with those obtained from other methods. However, with increasing total angular momentum, there are numerical instabilities that are associated with the coupling terms. It is found that there is an angular range for the stability of the coupling terms for each total angular momentum. This range greatly reduces with increasing total angular momentum.
A review of localization systems for robotic endoscopic capsules.
Than, Trung Duc; Alici, Gursel; Zhou, Hao; Li, Weihua
2012-09-01
Obscure gastrointestinal (GI) bleeding, Crohn disease, Celiac disease, small bower tumors, and other disorders that occur in the GI tract have always been challenging to be diagnosed and treated due to the inevitable difficulty in accessing such a complex environment within the human body. With the invention of wireless capsule endoscope, the next generation of the traditional cabled endoscope, not only a dream has come true for the patients who have experienced a great discomfort and unpleasantness caused by the conventional endoscopic method, but also a new research field has been opened to develop a complete miniature robotic device that is swallowable and has full functions of diagnosis and treatment of the GI diseases. However, such an ideal device needs to be equipped with a highly accurate localization system to be able to exactly determine the location of lesions in the GI tract and provide essential feedback to an actuation mechanism controlling the device's movement. This paper presents a comprehensive overview of the localization systems for robotic endoscopic capsules, for which the motivation, challenges, and possible solutions of the proposed localization methods are also discussed. PMID:22736628
ERIC Educational Resources Information Center
Schwartz, Stanley F.
This publication introduces electronic document imaging systems and provides guidance for local governments in New York in deciding whether such systems should be adopted for their own records and information management purposes. It advises local governments on how to develop plans for using such technology by discussing its advantages and…
Simultaneous localization and mapping with consideration of robot system dynamics
NASA Astrophysics Data System (ADS)
Jaai, R.; Chopra, N.; Balachandran, B.; Karki, H.
2012-04-01
In the simultaneous localization and mapping (SLAM) problem, it is required for a robotic system to acquire the map of its environment while simultaneously localizing itself relative to this evolving map. In order to solve the SLAM problem, given observations of the environment and control inputs, the joint posterior probability of the robot pose and the map are estimated by using recursive filters such as the extended Kalman filter (EKF) and the particle filter. The implementation of these filters requires a motion model to describe the evolution of the robot pose with control inputs, and additionally, an observation model to describe the relations between the robot pose and measurements of the environment. In general, the motion model is derived from the kinematics of the robotic system, without taking the system dynamics into account. In this article, the authors investigate the performance and efficacy of standard SLAM algorithms when the dynamics of the robotic system is taken into account in the motion model and provide experimental results to complement the simulation findings.
Neural networks for local structure detection in polymorphic systems.
Geiger, Philipp; Dellago, Christoph
2013-10-28
The accurate identification and classification of local ordered and disordered structures is an important task in atomistic computer simulations. Here, we demonstrate that properly trained artificial neural networks can be used for this purpose. Based on a neural network approach recently developed for the calculation of energies and forces, the proposed method recognizes local atomic arrangements from a set of symmetry functions that characterize the environment around a given atom. The algorithm is simple and flexible and it does not rely on the definition of a reference frame. Using the Lennard-Jones system as well as liquid water and ice as illustrative examples, we show that the neural networks developed here detect amorphous and crystalline structures with high accuracy even in the case of complex atomic arrangements, for which conventional structure detection approaches are unreliable.
Localization in chaotic systems with a single-channel opening.
Lippolis, Domenico; Ryu, Jung-Wan; Kim, Sang Wook
2015-07-01
We introduce a single-channel opening in a random Hamiltonian and a quantized chaotic map: localization on the opening occurs as a sensible deviation of the wave-function statistics from the predictions of random matrix theory, even in the semiclassical limit. Increasing the coupling to the open channel in the quantum model, we observe a similar picture to resonance trapping, made of a few fast-decaying states, whose left (right) eigenfunctions are entirely localized on the (preimage of the) opening, and plentiful long-lived states, whose probability density is instead suppressed at the opening. For the latter, we derive and test a linear relation between the wave-function intensities and the decay rates, similar to the Breit-Wigner law. We then analyze the statistics of the eigenfunctions of the corresponding (discretized) classical propagator, finding a similar behavior to the quantum system only in the weak-coupling regime.
Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms.
Williams, R A; Pillet, J D; Al-Assam, S; Fletcher, B; Shotter, M; Foot, C J
2008-10-13
We demonstrate a novel experimental arrangement which can rotate a 2D optical lattice at frequencies up to several kilohertz. Ultracold atoms in such a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, allowing investigation of phenomena such as the fractional quantum Hall effect. Our arrangement also allows the periodicity of a 2D optical lattice to be varied dynamically, producing a 2D accordion lattice.
The Origin of the Local System of Gas and Stars
NASA Astrophysics Data System (ADS)
Olano, C. A.
2001-01-01
We present a model for the local system of gas and stars that we associate essentially with Gould's Belt, the Sirius supercluster, and the Local arm. We consider that these subsystems were formed in different epochs within a supercloud that was initially moving almost ballistically in the Galactic field until an encounter with a major spiral arm started a braking process. The stars of older generations, i.e., the Sirius supercluster, tended to conserve the kinematics of the prebraking phase of the supercloud, while the remaining gas and the early star complexes reflect the recent kinematics, resulting from the braking process. We have calculated back in time the epicyclic orbits of the Sirius supercluster, as well as of the postulated supercloud, starting from adequate initial conditions and taking into account the action of a friction force on the gas. From the condition that the Sirius supercluster and the postulated supercloud shared the same orbits before the separation of gas and stars because of the braking forces, we have determined the free parameters of the model. The main evidence supporting our hypothesis is that the supercloud's track derived from the model coincides with a large ``tunnel'' in the distribution of the local interstellar matter, toward l~240°. We conclude that a supercloud of ~2×107 Msolar and a radius of ~400 pc was the common precursor of the Sirius supercluster, Gould's Belt, and the Local arm. The Sirius supercluster was born ~500 Myr ago in the supercloud, rotating in the Galactic sense and coexisting with the supercloud ever since. We show that the theoretical velocity distribution of the Sirius supercluster derived from the model is consistent with the observed vertex deviation and velocity dispersions of the Sirius supercluster. The supercloud entered into a major spiral arm 100 Myr ago. The interaction with the Galactic shock and the subsequent gas streaming generated a process of braking and compression of the gas in the
Manipulation and control of a bichromatic lattice
NASA Astrophysics Data System (ADS)
Thomas, Claire; Barter, Thomas; Daiss, Severin; Leung, Zephy; Stamper-Kurn, Dan
2015-05-01
Recent experiments with ultracold atoms in optical lattices have had great success emulating the simple models of condensed matter systems. These experiments are typically performed with a single site per unit cell. We realize a lattice with up to four sites per unit cell by overlaying an attractive triangular lattice with a repulsive one at twice the wavelength. The relative displacement of the two lattices determines the particular structure. One available configuration is the kagome lattice, which has a flat energy band. In the flat band all kinetic energy states are degenerate, so we have the opportunity to explore a regime where interactions dominate. This bichromatic lattice requires careful stabilization, but offers an opportunity to manipulate the unit cell and band structure by perturbing the lattices relative to one another. I will discuss recent progress.
Local temperatures and voltages in quantum systems far from equilibrium
NASA Astrophysics Data System (ADS)
Shastry, Abhay; Stafford, Charles; Department of Physics Collaboration
We show that the local measurement of temperature and voltage for a quantum system in steady state, arbitrarily far from equilibrium, with arbitrary interactions within the system, is unique when it exists. This is interpreted as a consequence of the second law of thermodynamics. We further derive a necessary and sufficient condition for the existence of a solution. In this regard, we find that a solution occurs whenever there is no net population inversion. However, when there is a net population inversion, we may characterize the system with a (unique) negative temperature. These results provide a firm mathematical foundation for our measurement protocol, and sound meaning to such measurements in the thermodynamic sense. Research supported by the US Department of Energy, grant DE-SC 0006699.
Rainfall Hazards Prevention based on a Local Model Forecasting System
NASA Astrophysics Data System (ADS)
Buendia, F.; Ojeda, B.; Buendia Moya, G.; Tarquis, A. M.; Andina, D.
2009-04-01
Rainfall is one of the most important events of human life and society. Some rainfall phenomena like floods or hailstone are a threat to the agriculture, business and even life. However in the meteorological observatories there are methods to detect and alarm about this kind of events, nowadays the prediction techniques based on synoptic measurements need to be improved to achieve medium term feasible forecasts. Any deviation in the measurements or in the model description makes the forecast to diverge in time from the real atmosphere evolution. In this paper the advances in a local rainfall forecasting system based on time series estimation with General Regression Neural Networks are presented. The system is introduced, explaining the measurements, methodology and the current state of the development. The aim of the work is to provide a complementary criteria to the current forecast systems, based on the daily atmosphere observation and tracking over a certain place.
Tehler, Ulrika; Fagerberg, Jonas H; Svensson, Richard; Larhed, Mats; Artursson, Per; Bergström, Christel A S
2013-03-28
Esterification was used to simultaneously increase solubility and permeability of ciprofloxacin, a biopharmaceutics classification system (BCS) class 4 drug (low solubility/low permeability) with solid-state limited solubility. Molecular flexibility was increased to disturb the crystal lattice, lower the melting point, and thereby improve the solubility, whereas lipophilicity was increased to enhance the intestinal permeability. These structural changes resulted in BCS class 1 analogues (high solubility/high permeability) emphasizing that simple medicinal chemistry may improve both these properties.
Localization Transport in Granular and Nanoporous Carbon Systems.
NASA Astrophysics Data System (ADS)
Fung, Alex Weng Pui
variable-range hopping mechanism cannot be totally disregarded in the understanding of the low-temperature conduction process in some granular metals having a similar morphology. In the transport study of the heat-treated activated carbon fibers, the surprising observation of a negative magnetoresistance at room temperature has also provided some insight into the weak localization phenomenon in the percolation limit. In particular, the effects of anomalous diffusion in a percolating system is now included in the calculations of the weak-localization corrections to the conductivity and magnetoresistance, yielding a new temperature dependence of the dephasing distance. These localization phenomena in the nanoporous carbon structures studied here are mostly understandable in terms of the existing theories for disordered systems, but their detailed interpretations often indicate problems and shortcomings in some of these theories, at times because the physical properties of the nanoporous carbon materials studied here are unique among disordered materials. Hence, nanoporous carbons belong to a distinct class of disordered systems in their own rights. In the field of transport in disordered systems, porous media also seem to have been an oversight of the general research community, although theoretical percolation studies have often touched upon systems with similar morphologies. This thesis presents a study of the transport behavior in nanoporous carbons over the full spectrum of disorder, controlled by heat treatment, starting from the strong localization regime, then crossing the metal-insulator transition, and finally to the weak localization limit. In each regime of disorder, the existing theories are either adapted, and when necessary, extended to explain the observed transport behavior in these fascinating materials. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-1690.).
Engineered nonlinear lattices.
Clausen, C B; Christiansen, P L; Torner, L; Gaididei, Y B
1999-11-01
We show that with the quasi-phase-matching technique it is possible to fabricate stripes of nonlinearity that trap and guide light like waveguides. We investigate an array of such stripes and find that when the stripes are sufficiently narrow, the beam dynamics is governed by a quadratic nonlinear discrete equation. The proposed structure therefore provides an experimental setting for exploring discrete effects in a controlled manner. In particular, we show propagation of breathers that are eventually trapped by discreteness. When the stripes are wide the beams evolve in a structure we term a quasilattice, which interpolates between a lattice system and a continuous system. PMID:11970457
Intraband discrete breathers in disordered nonlinear systems. II. Localization
NASA Astrophysics Data System (ADS)
Kopidakis, G.; Aubry, S.
2000-05-01
We find spatially localized, time-periodic solutions (discrete breathers or DBs) in disordered nonlinear systems with frequency inside the linear phonon spectrum under conditions that strictly prohibit their existence in their periodic counterparts. For that purpose, we develop a new in situ method for the accurate calculation of these solutions which does not make use of any continuation from an anticontinuous limit. Using this method, we demonstrate that intraband localized modes (intraband discrete breathers or IDBs) at a given site with frequencies inside the discrete linear spectrum do exist, provided these frequencies do not belong to forbidden resonance gaps. Since there is a dense set of resonant frequencies, we illustrate numerically, in agreement with a theorem by Albanese and Fröhlich, that the localized DBs exist provided that their frequencies belong to fat Cantor sets (i.e., with finite measure). Such a set contains as accumulation points the linear frequency of the normal mode at the occupied site. We check that many of these solutions are linearly stable and conjecture that their frequency belongs to another smaller fat Cantor set. Our numerical methods provide a much wider set of exact solutions which are multisite breathers and suggest conjectures extending the existing theorems. The physical implications of the existence of IDBs and possible applications for glasses and the persistent spectral hole burning are discussed.
Skin vasodilator response to local heating in multiple system atrophy.
Yamanaka, Yoshitaka; Asahina, Masato; Mathias, Christopher J; Akaogi, Yuichi; Koyama, Yu; Hattori, Takamichi
2007-12-01
Local heating of nonglabrous skin increases skin blood flow (SkBF) in two phases. The initial peak (P1) is mediated by a sensory-axon reflex and the plateau phase (P2) by local production of substances such as nitric oxide. We evaluated the SkBF response to local heating in 15 multiple system atrophy (MSA) patients with autonomic failure and 12 age-matched healthy controls. The mean ratio of SkBF at P1 to that at baseline (SkBF(P1)/SkBF(base) ratio) in MSA was significantly lower than that in controls (P < 0.01). The mean ratio of SkBF at P2 seemed to be slightly reduced in the MSA patients, compared with controls, although there was no significant difference. The P1 phase is thought to be mediated by a sensory-axon reflex modulated by sympathetic nerve activity. These findings are indicative of the skin sympathetic vasomotor dysfunction in MSA.
Sobolewski, Bogusław; Doman, Paweł; Oszukowski, Przemysław; Woźniak, Piotr
2015-01-01
Gynaecologists often use local anaesthetics in their medical practice. Some concomitant diseases during the menopausal period may cause problems during the qualification of postmenopausal women for general anaesthesia in gynaecological surgery. Many authors suggest the application of local analgesia for particular kinds of gynaecological surgery procedures performed on postmenopausal women, taking into consideration health determinants. While applying local anaesthetics, the possibility of their overdose has to be taken into account. Generalised toxic symptoms which appeared after the local anaesthesia are rare, but potentially are lethal complications. Toxic symptoms after local anaesthetic administration are manifested after accidental administration of a medicine into a blood vessel, when extravascular administration of a large volume of a local anaesthetic is absorbed into a bloodstream or with the reproducible doses of local anaesthetics which are administered when metabolism does not work sufficiently and cannot eliminate these substances. Clinical overdose of local anaesthetics is manifested by disorders in two systems. Firstly, the pathological symptoms come from the central nervous system (CNS). In the second phase, the pathological symptoms will additionally appear in the cardiovascular system. The aim of the present thesis is to remind clinical manifestations of the local anaesthetic overdose and suggest the management of patients with the aforementioned symptoms, especially in the case of intravenous lipid emulsions which have the status of an antidote in life-threatening conditions caused by cardiotoxic effects of local anaesthetics. PMID:26327891
Local markets and systems: hospital consolidations in metropolitan areas.
Luke, R D; Ozcan, Y A; Olden, P C
1995-01-01
OBJECTIVE. This study examines the formation of local hospital systems (LHSs) in urban markets by the end of 1992. We argue that a primary reason why hospitals join LHSs is to achieve improved positions of market power relative to threatening rivals. DATA SOURCES/DATA COLLECTION. The study draws from a unique database of LHSs located in and around metropolitan statistical areas (MSAs). Data were obtained from the 1991 AHA Annual Hospital Survey, updated to the year 1992 using information obtained from multiple sources (telephone contacts of systems, systems lists of hospitals, published changes in ownership, etc.). Other measures were obtained from a variety of sources, principally the 1989 Area Resources File. STUDY DESIGN. The study presents cross-sectional analyses of rival threats and other factors bearing on LHS formation. Three characteristics of LHS formation are examined: LHS penetration of urban areas, LHS size, and number of LHS members located just outside the urban boundaries. LHS penetration is analyzed across urban markets, and LHS size and rural partners are examined across the LHSs. PRINCIPAL FINDINGS. Major hypothesized findings are: (1) with the exception of the number of rural partners, all dependent variables are positively associated with the number of hospitals in the markets; the rural partner measure is negatively associated with the number of hospitals; (2) the number of doctors per capita is positively associated with all but the rural penetration measure; and (3) the percentage of the population in HMOs is positively associated with local cluster penetration and negatively associated with rural system partners. Other findings: (1) average income in the markets is negatively associated with all but the rural penetration measure; (2) LHS size and rural partners are both positively associated with nonprofit system ownership; and (3) they are also both negatively associated with the degree to which their multihospital systems are
Mott Insulating Ground State on a Triangular Surface Lattice
Weitering, H.; Shi, X.; Weitering, H.; Johnson, P.; Chen, J.; DiNardo, N.; DiNardo, N.; Kempa, K.
1997-02-01
Momentum-resolved direct and inverse photoemission spectra of the K/Si(111)-({radical}(3){times}{radical}(3))R30{degree}-B interface reveals the presence of strongly localized surface states. The K overlayer remains nonmetallic up to the saturation coverage. This system most likely presents the first experimental realization of a frustrated spin 1/2 Heisenberg antiferromagnet on a two-dimensional triangular lattice. {copyright} {ital 1997} {ital The American Physical Society}
Central nervous system effects of local anaesthetic agents.
Englesson, S; Matousek, M
1975-02-01
A review is given of an experimental study on cats where the influence of acid-base changes on central nervous system toxicity of local anaesthetic agents was studied. The conclusion of this study was that a respiratory acidosis increased the central nervous system toxicity of local anaesthetics and that the underlying metabolic conditions modified this increase. Thus a respiratory acidosis increased this toxicity more if it was based on a metabolic acidosis than on a metabolic alkalosis (Englesson, 1974; Englesson and Grevsten, 1974). An extended analysis is presented where automatic frequency analysis was performed on the e.e.g. recordings performed during the i.v. infusion of lignocaine, bupivacaine, L 134, HS 37 and its optical isomers. The preliminary results show that the electrical changes appearing in the e.e.g. from the start of the i.v. infusion until seizure activity were the same if this time interval was as short as 1 min or as long as 8 min. It also revealed remarkable individual differences between agents, for instance lignocaine displaying marked electrical changes already in the first third of this time period where bupivacaine showed no changes until shortly before seizures. PMID:238556
[Participation of dental auxiliary personnel in local health systems].
Frazão, P; Castellanos, R A
1999-02-01
Though numerous local health systems (sistemas locales de salud, or SILOS) in Brazil employ dental assistants, there is little information on the contributions these workers make to oral health programs. The purpose of this study was to examine the role of such workers in 10 SILOS in five municipalities in the state of São Paulo. Of the 325 dental assistants and dental hygienists employed in those systems, 245 (75.4%) answered a questionnaire that had been prepared. The results showed variations in the degree to which dental assistants participated in oral health promotion activities in the SILOS studied. In some SILOS, these workers devoted more time to dental health promotion activities than to helping perform dental tasks with individual patients. The most frequent oral health promotion activities were fluoride rinses, plaque detection followed by supervised brushing, and educational activities at basic health units and schools. In all cases, dental assistants working in the SILOS played a significant role in helping transform the practice of dentistry within the sphere of public health.
Transport in nanoscale systems: hydrodynamics, turbulence, and local electron heating
NASA Astrophysics Data System (ADS)
di Ventra, Massimiliano
2007-03-01
Transport in nanoscale systems is usually described as an open-boundary scattering problem. This picture, however, says nothing about the dynamical onset of steady states, their microscopic nature, or their dependence on initial conditions [1]. In order to address these issues, I will first describe the dynamical many-particle state via an effective quantum hydrodynamic theory [2]. This approach allows us to predict a series of novel phenomena like turbulence of the electron liquid [2], local electron heating in nanostructures [3], and the effect of electron viscosity on resistance [4]. I will provide both analytical results and numerical examples of first-principles electron dynamics in nanostructures using the above approach. I will also discuss possible experimental tests of our predictions. Work supported in part by NSF and DOE. [1] N. Bushong, N. Sai and M. Di Ventra, ``Approach to steady-state transport in nanoscale systems'' Nano Letters, 5 2569 (2005); M. Di Ventra and T.N. Todorov, ``Transport in nanoscale systems: the microcanonical versus grand-canonical picture,'' J. Phys. Cond. Matt. 16, 8025 (2004). [2] R. D'Agosta and M. Di Ventra, ``Hydrodynamic approach to transport and turbulence in nanoscale conductors,'' cond-mat/05123326; J. Phys. Cond. Matt., in press. [3] R. D'Agosta, N. Sai and M. Di Ventra, ``Local electron heating in nanoscale conductors,'' cond-mat/0605312; Nano Letters, in press. [4] N. Sai, M. Zwolak, G. Vignale and M. Di Ventra, ``Dynamical corrections to the DFT-LDA electron conductance in nanoscale systems,'' Phys. Rev. Lett. 94, 186810 (2005).
Fluoroscopic image-guided intervention system for transbronchial localization
NASA Astrophysics Data System (ADS)
Rai, Lav; Keast, Thomas M.; Wibowo, Henky; Yu, Kun-Chang; Draper, Jeffrey W.; Gibbs, Jason D.
2012-02-01
Reliable transbronchial access of peripheral lung lesions is desirable for the diagnosis and potential treatment of lung cancer. This procedure can be difficult, however, because accessory devices (e.g., needle or forceps) cannot be reliably localized while deployed. We present a fluoroscopic image-guided intervention (IGI) system for tracking such bronchoscopic accessories. Fluoroscopy, an imaging technology currently utilized by many bronchoscopists, has a fundamental shortcoming - many lung lesions are invisible in its images. Our IGI system aligns a digitally reconstructed radiograph (DRR) defined from a pre-operative computed tomography (CT) scan with live fluoroscopic images. Radiopaque accessory devices are readily apparent in fluoroscopic video, while lesions lacking a fluoroscopic signature but identifiable in the CT scan are superimposed in the scene. The IGI system processing steps consist of: (1) calibrating the fluoroscopic imaging system; (2) registering the CT anatomy with its depiction in the fluoroscopic scene; (3) optical tracking to continually update the DRR and target positions as the fluoroscope is moved about the patient. The end result is a continuous correlation of the DRR and projected targets with the anatomy depicted in the live fluoroscopic video feed. Because both targets and bronchoscopic devices are readily apparent in arbitrary fluoroscopic orientations, multiplane guidance is straightforward. The system tracks in real-time with no computational lag. We have measured a mean projected tracking accuracy of 1.0 mm in a phantom and present results from an in vivo animal study.
Lattice constant grading in the Al.sub.y Ga.sub.1-y As.sub.1-x Sb.sub.x alloy system
Moon, Ronald L.
1980-01-01
Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5 .mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photolvoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of growing layer.
Lattice constant grading in the Al.sub.y Ca.sub.1-y As.sub.1-x Sb.sub.x alloy system
Moon, Ronald L.
1981-01-01
Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5.mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photovoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of the growing layer.
Experimental evidence for lattice effects in high temperature superconductors
Billinge, S.J.L.; Kwei, G.H.; Thompson, J.D.
1994-01-18
We present an overview of the experimental evidence for a role of the lattice in the mechanism of high temperature superconductivity. It appears unlikely that a solely conventional electron-phonon interaction produces the pairing. However, there is ample evidence of strong electron and spin to lattice coupling and observations of a response of the lattice to the electronic state. We draw attention to the importance of the local structure in discussions of lattice effects in high-{Tc} superconductivity.
Localization precision of the superconducting imaging-surface MEG system
Kraus, Robert H., Jr.; Matlachov, A. N.; Espy, M. A.; Maharajh, K.; Volegov, P.
2001-01-01
A unique whole-head Magnetoencephalography (MEG) system incorporating a superconducting imaging surface (SIS) has been designed and built at Los Alamos with the goal of dramatically improving source localization accuracy while mitigating limitations of current systems (e.g. low signal-to-noise, cost, bulk). Magnetoencephalography (MEG) measures the weak magnetic fields emanating from the brain as a direct consequence of the neuronal currents resulting from brain function[1]. The extraordinarily weak magnetic fields are measured by an array of SQUID (Superconducting QUantum Interference Device) sensors. The position and vector characteristics of these neuronal sources can be estimated from the inverse solution of the field distribution at the surface of the head. In addition, MEG temporal resolution is unsurpassed by any other method currently used for brain imaging. Although MEG source reconstruction is limited by solutions of the electromagnetic inverse problem, constraints used for source localization produce reliable results. The Los Alamos SIS-MEG system[2] is based on the principal that fields from nearby sources measured by a SQUID sensor array while the SIS shields the sensor array from distant noise fields. In general, Meissner currents flow in the surface of superconductors, preventing any significant penetration of magnetic fields. A hemispherical SIS with a brim, or helmet, surrounds the SQUID sensor array largely sheilding the SQUIDs from sources outside the helmet while measuring fields from nearby sources within the helmet. We have implemented a finite element model (FEM) description of the SIS using the exact as-built geometry to accurately describe how the SIS impacts the forward physics of source models. The FEM is used to calculate the distribution of Meissner currents in the complicated surface geometry of the SIS such that B{perpendicular} = 0 at the surface. This model of the forward physics is described elsewhere in these proceedings [3]. In
Polarization response of RHIC electron lens lattices
NASA Astrophysics Data System (ADS)
Ranjbar, V. H.; Méot, F.; Bai, M.; Abell, D. T.; Meiser, D.
2016-10-01
Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. In particular we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. These results are benchmarked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. Finally we consider the effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.
Design of laser monitoring and sound localization system
NASA Astrophysics Data System (ADS)
Liu, Yu-long; Xu, Xi-ping; Dai, Yu-ming; Qiao, Yang
2013-08-01
In this paper, a novel design of laser monitoring and sound localization system is proposed. It utilizes laser to monitor and locate the position of the indoor conversation. In China most of the laser monitors no matter used in labor in an instrument uses photodiode or phototransistor as a detector at present. At the laser receivers of those facilities, light beams are adjusted to ensure that only part of the window in photodiodes or phototransistors received the beams. The reflection would deviate from its original path because of the vibration of the detected window, which would cause the changing of imaging spots in photodiode or phototransistor. However, such method is limited not only because it could bring in much stray light in receivers but also merely single output of photocurrent could be obtained. Therefore a new method based on quadrant detector is proposed. It utilizes the relation of the optical integral among quadrants to locate the position of imaging spots. This method could eliminate background disturbance and acquired two-dimensional spots vibrating data pacifically. The principle of this whole system could be described as follows. Collimated laser beams are reflected from vibrate-window caused by the vibration of sound source. Therefore reflected beams are modulated by vibration source. Such optical signals are collected by quadrant detectors and then are processed by photoelectric converters and corresponding circuits. Speech signals are eventually reconstructed. In addition, sound source localization is implemented by the means of detecting three different reflected light sources simultaneously. Indoor mathematical models based on the principle of Time Difference Of Arrival (TDOA) are established to calculate the twodimensional coordinate of sound source. Experiments showed that this system is able to monitor the indoor sound source beyond 15 meters with a high quality of speech reconstruction and to locate the sound source position accurately.
Local arterial wall drug delivery using balloon catheter system.
Tesfamariam, Belay
2016-09-28
Balloon-based drug delivery systems allow localized application of drugs to a vascular segment to reduce neointimal hyperplasia and restenosis. Drugs are coated onto balloons using excipients as drug carriers to facilitate adherence and release of drug during balloon inflation. Drug-coated balloon delivery system is characterized by a rapid drug transfer that achieves high drug concentration along the vessel wall surface, intended to correspond to the balloon dilation-induced vascular injury and healing processes. The balloon catheter system allows homogenous drug delivery to the vessel wall, such that the drug release per unit surface area is kept constant along balloons of different lengths. Optimization of the balloon coating matrix is essential for efficient drug transfer and tissue retention until the artery remodels to a normal set point. Challenges in the development of balloon-based drug delivery to the arterial wall include finding suitable excipients for drug formulation to enable drug release to a targeted lesion site effectively, maintain coating integrity during transit, prolong tissue retention and reduce particulate generation. This review highlights various factors involved in the successful design of balloon-based delivery systems, including drug release kinetics, matrix coating transfer, transmural drug partitioning, dissolution rate and release of unbound active drug. PMID:27473765
Supersymmetry protected topological phases of isostatic lattices and kagome antiferromagnets
NASA Astrophysics Data System (ADS)
Lawler, Michael J.
2016-10-01
I generalize the theory of phonon topological band structures of isostatic lattices to frustrated antiferromagnets. I achieve this with a discovery of a many-body supersymmetry (SUSY) in the phonon problem of balls and springs and its connection to local constraints satisfied by ground states. The Witten index of the SUSY model demands the Maxwell-Calladine index of mechanical structures. "Spontaneous supersymmetry breaking" is identified as the need to gap all modes in the bulk to create the topological isostatic lattice state. Since ground states of magnetic systems also satisfy local constraint conditions (such as the vanishing of the total spin on a triangle), I identify a similar SUSY structure for many common models of antiferromagnets including the square, triangluar, kagome, pyrochlore nearest-neighbor antiferromagnets, and the J2=J1/2 square-lattice antiferromagnet. Remarkably, the kagome family of antiferromagnets is the analog of topological isostatic lattices among this collection of models. Thus, a solid-state realization of the theory of phonon topological band structure may be found in frustrated magnetic materials.
Availability of Locally Synthesized and Systemic Antibodies in the Intestine
Fubara, Ernest S.; Freter, Rolf
1972-01-01
The present studies are concerned with the parameters which control the appearance of locally synthesized or serum-derived antibodies in the intestine. The data show that intestinal antibody may be found in rabbits as well as in conventional or germfree mice after active immunization with Vibrio cholerae. However, a large fraction of the intestinal antibody in rabbits and conventional mice originated from the serum as indicated by (i) analysis of correlation between serum and intestinal antibody titers, and (ii) the occurrence of intestinal antibody after parenteral administration of antiserum. In contrast, only locally synthesized 11S immunoglobulin A antibody was detected in the intestine of actively immunized germfree mice. No intestinal antibody was demonstrable in germfree mice after parenteral injection of V. cholerae antiserum. With respect to the appearance of serum antibody in the intestine, the response of conventionalized (ex-germfree) mice was intermediate between that of rabbits or conventional mice and germfree mice. The availability of serum-derived coproantibody in germfree and conventional mice was related to the rates of intestinal degradation of serum antibody. When enzymes were removed by prior washing of intestinal segments, serum antibodies entered the intestine of germfree or conventional mice at similar rates. Rates of entry of serum antibodies into the lumen were comparable at different levels of the small intestine. The presence of a normal enteric flora appeared to protect intestinal antibody from degradation by lowering the concentration or activity of intestinal enzymes. The results are discussed in relation to the question of whether antibacterial immunity to cholera involves local or systemic mechanisms. Images PMID:4638499
Localization/mapping motion control system for a mobile robot
NASA Astrophysics Data System (ADS)
Yang-Syu, Jr.; Su, Chiun-Shiang; Yang, Chan-Yun
2011-12-01
The objective of this paper is to design a mobile robot with automatic motion behaviors and obstacle avoidance functions. The robot is also able to make the SLAM (Simultaneous Localization And Mapping) at an unknown environment. The robot position is calculated by the developed software program from the motor encoders. An obstacle avoidance controller is developed by the fuzzy theory. A LRF(laser ranger finder) is installed on the robot. The sensing data of this LRF are applied to calculate the environmental information for the obstacle avoidance controller. Then, the ICP (Iterative Closest Point) algorithm is applied to compare the position error of the environmental data in order to obtain the estimated position of the LRF. Finally, these estimated position data are used to calculate the final SLAM of this mobile robot. Both the simulation and experimental results show that this developed robot system work very well.
NASA Astrophysics Data System (ADS)
Fan, W. J.; Bose, Sumanta; Zhang, D. H.
2016-09-01
Dilute nitride bismide GaNBiAs is a potential semiconductor alloy for near- and mid-infrared applications, particularly in 1.55 μm optical communication systems. Incorporating dilute amounts of bismuth (Bi) into GaAs reduces the effective bandgap rapidly, while significantly increasing the spin-orbit-splitting energy. Additional incorporation of dilute amounts of nitrogen (N) helps to attain lattice matching with GaAs, while providing a route for flexible bandgap tuning. Here we present a study of the electronic bandstructure and optical gain of the lattice matched GaNxBiy As1 -x -y /GaAs quaternary alloy quantum well (QW) based on the 16-band k .p model. We have taken into consideration the interactions between the N and Bi impurity states with the host material based on the band anticrossing and valence band anticrossing model. The optical gain calculation is based on the density matrix theory. We have considered different lattice matched GaNBiAs QW cases and studied their energy dispersion curves, optical gain spectrum, maximum optical gain, and differential gain and compared their performances based on these factors. The thickness and composition of these QWs were varied in order to keep the emission peak fixed at 1.55 μm. The well thickness has an effect on the spectral width of the gain curves. On the other hand, a variation in the injection carrier density has different effects on the maximum gain and differential gain of QWs of varying thicknesses. Among the cases studied, we found that the 6.3 nm thick GaN3 Bi5.17 As91.83 lattice matched QW was most suited for 1.55 μm (0.8 eV) GaAs-based photonic applications.
Chiral bosonic phases on the Haldane honeycomb lattice
NASA Astrophysics Data System (ADS)
Vasić, Ivana; Petrescu, Alexandru; Le Hur, Karyn; Hofstetter, Walter
2015-03-01
Recent experiments in ultracold atoms and photonic analogs have reported the implementation of artificial gauge fields in lattice systems, facilitating the realization of topological phases. Motivated by such advances, we investigate the Haldane honeycomb lattice tight-binding model, for bosons with local interactions at the average filling of one boson per site. We analyze the ground-state phase diagram and uncover three distinct phases: a uniform superfluid (SF), a chiral superfluid (CSF), and a plaquette Mott insulator with local current loops (PMI). Nearest-neighbor and next-nearest-neighbor currents distinguish CSF from SF, and the phase transition between them is first order. We apply bosonic dynamical mean-field theory and exact diagonalization to obtain the phase diagram, complementing numerics with calculations of excitation spectra in strong and weak coupling perturbation theory. The characteristic density fluctuations, current correlation functions, and excitation spectra are measurable in ultracold atom experiments.
Local Melatoninergic System as the Protector of Skin Integrity
Slominski, Andrzej T.; Kleszczyński, Konrad; Semak, Igor; Janjetovic, Zorica; Żmijewski, Michał A.; Kim, Tae-Kang; Slominski, Radomir M.; Reiter, Russel J.; Fischer, Tobias W.
2014-01-01
The human skin is not only a target for the protective actions of melatonin, but also a site of melatonin synthesis and metabolism, suggesting an important role for a local melatoninergic system in protection against ultraviolet radiation (UVR) induced damages. While melatonin exerts many effects on cell physiology and tissue homeostasis via membrane bound melatonin receptors, the strong protective effects of melatonin against the UVR-induced skin damage including DNA repair/protection seen at its high (pharmocological) concentrations indicate that these are mainly mediated through receptor-independent mechanisms or perhaps through activation of putative melatonin nuclear receptors. The destructive effects of the UVR are significantly counteracted or modulated by melatonin in the context of a complex intracutaneous melatoninergic anti-oxidative system with UVR-enhanced or UVR-independent melatonin metabolites. Therefore, endogenous intracutaneous melatonin production, together with topically-applied exogenous melatonin or metabolites would be expected to represent one of the most potent anti-oxidative defense systems against the UV-induced damage to the skin. In summary, we propose that melatonin can be exploited therapeutically as a protective agent or as a survival factor with anti-genotoxic properties or as a “guardian” of the genome and cellular integrity with clinical applications in UVR-induced pathology that includes carcinogenesis and skin aging. PMID:25272227
Local and global navigational coordinate systems in desert ants.
Collett, Matthew; Collett, Thomas S
2009-04-01
While foraging, the desert ant Cataglyphis fortis keeps track of its position with respect to its nest through a process of path integration (PI). Once it finds food, it can then follow a direct home vector to its nest. Furthermore, it remembers the coordinates of a food site, and uses these coordinates to return to the site. Previous studies suggest, however, that it does not associate any coordinates remembered from previous trips with familiar views such that it can produce a home vector when displaced to a familiar site. We ask here whether a desert ant uses any association between PI coordinates and familiar views to ensure consistent PI coordinates as it travels along a habitual route. We describe an experiment in which we manipulated the PI coordinates an ant has when reaching a distinctive point along a habitual route on the way to a feeder. The subsequent home vectors of the manipulated ants, when displaced from the food-site to a test ground, show that also when a route memory is evoked at a significant point on the way to a food site, C. fortis does not reset its PI coordinates to those it normally has at that point. We use this result to argue that local vector memories, which encode the metric properties of a segment of a habitual route, must be encoded in a route-based coordinate system that is separate from the nest-based global coordinates. We propose a model for PI-based guidance that can account for several puzzling observations, and that naturally produces the route-based coordinate system required for learning and following local vectors.
NASA Astrophysics Data System (ADS)
Kuramashi, Yoshinobu
2007-12-01
Preface -- Fixed point actions, symmetries and symmetry transformations on the lattice / P. Hasenfratz -- Algorithms for dynamical fennions / A. D. Kennedy -- Applications of chiral perturbation theory to lattice QCD / Stephen R. Sharpe -- Lattice QCD with a chiral twist / S. Sint -- Non-perturbative QCD: renormalization, O(A) - Improvement and matching to Heavy Quark effective theory / Rainer Sommer.
NASA Astrophysics Data System (ADS)
Golubeva, Anna; Sotnikov, Andrii; Hofstetter, Walter
2015-10-01
We study the effects of anisotropic hopping amplitudes on quantum phases of ultracold fermions in optical lattices described by the repulsive Fermi-Hubbard model. In particular, using dynamical mean-field theory (DMFT) we investigate the dimensional crossover between the isotropic square and the isotropic cubic lattice. We analyze the phase transition from the antiferromagnetic to the paramagnetic state and observe a significant change in the critical temperature: depending on the interaction strength, the anisotropy can lead to both a suppression or increase. We also investigate the localization properties of the system, such as the compressibility and double occupancy. Using the local-density approximation in combination with DMFT we conclude that density profiles can be used to detect the mentioned anisotropy-driven transitions.
The role of the vestibular system in manual target localization
NASA Technical Reports Server (NTRS)
Barry, Susan R.; Mueller, S. Alyssa
1995-01-01
Astronauts experience perceptual and sensory-motor disturbances during spaceflight and immediately after return to the 1-g environment of Earth. During spaceflight, sensory information from the eyes, limbs and vestibular organs is reinterpreted by the central nervous system so that astronauts can produce appropriate body movements in microgravity. Alterations in sensory-motor function may affect eye-head-hand coordination and, thus, the crewmember's ability to manually locate objects in extrapersonal space. Previous reports have demonstrated that crewmembers have difficulty in estimating joint and limb position and in pointing to memorized target positions on orbit and immediately postflight. One set of internal cues that may assist in the manual localization of objects is information from the vestibular system. This system contributes to our sense of the body's position in space by providing information on head position and movement and the orientation of the body with respect to gravity. Research on the vestibular system has concentrated on its role in oculo-motor control. Little is known about the role that vestibular information plays in manual motor control, such as reaching and pointing movements. Since central interpretation of vestibular information is altered in microgravity, it is important to determine its role in this process. This summer, we determined the importance of vestibular information in a subject's ability to point accurately toward a target in extrapersonal space. Subjects were passively rotated across the earth-vertical axis and then asked to point back to a previously-seen target. In the first paradigm, the subjects used both visual and vestibular cues for the pointing response, while, in the second paradigm, subjects used only vestibular information. Subjects were able to point with 85 percent accuracy to a target using vestibular information alone. We infer from this result that vestibular input plays a role in the spatial programming of
Fractionalized topological defects in optical lattices
NASA Astrophysics Data System (ADS)
Zhang, Xing-Hai; Fan, Wen-Jun; Shi, Jin-Wei; Kou, Su-Peng
2015-10-01
Topological objects are interesting topics in various fields of physics ranging from condensed matter physics to the grand unified and superstring theories. Among those, ultracold atoms provide a playground to study the complex topological objects. In this paper we present a proposal to realize an optical lattice with stable fractionalized topological objects. In particular, we generate the fractionalized topological fluxes and fractionalized skyrmions on two-dimensional optical lattices and fractionalized monopoles on three-dimensional optical lattices. These results offer a new approach to study the quantum many-body systems on optical lattices of ultracold quantum gases with controllable topological defects, including dislocations, topological fluxes and monopoles.
Locality of Gravitational Systems from Entanglement of Conformal Field Theories.
Lin, Jennifer; Marcolli, Matilde; Ooguri, Hirosi; Stoica, Bogdan
2015-06-01
The Ryu-Takayanagi formula relates the entanglement entropy in a conformal field theory to the area of a minimal surface in its holographic dual. We show that this relation can be inverted for any state in the conformal field theory to compute the bulk stress-energy tensor near the boundary of the bulk spacetime, reconstructing the local data in the bulk from the entanglement on the boundary. We also show that positivity, monotonicity, and convexity of the relative entropy for small spherical domains between the reduced density matrices of any state and of the ground state of the conformal field theory are guaranteed by positivity conditions on the bulk matter energy density. As positivity and monotonicity of the relative entropy are general properties of quantum systems, this can be interpreted as a derivation of bulk energy conditions in any holographic system for which the Ryu-Takayanagi prescription applies. We discuss an information theoretical interpretation of the convexity in terms of the Fisher metric.
Traveling waves and their tails in locally resonant granular systems
Xu, H.; Kevrekidis, P. G.; Stefanov, A.
2015-04-22
In the present study, we revisit the theme of wave propagation in locally resonant granular crystal systems, also referred to as mass-in-mass systems. We use three distinct approaches to identify relevant traveling waves. In addition, the first consists of a direct solution of the traveling wave problem. The second one consists of the solution of the Fourier tranformed variant of the problem, or, more precisely, of its convolution reformulation (upon an inverse Fourier transform) in real space. Finally, our third approach will restrict considerations to a finite domain, utilizing the notion of Fourier series for important technical reasons, namely themore » avoidance of resonances, which will be discussed in detail. All three approaches can be utilized in either the displacement or the strain formulation. Typical resulting computations in finite domains result in the solitary waves bearing symmetric non-vanishing tails at both ends of the computational domain. Importantly, however, a countably infinite set of anti-resonance conditions is identified for which solutions with genuinely rapidly decaying tails arise.« less
Traveling waves and their tails in locally resonant granular systems
Xu, H.; Kevrekidis, P. G.; Stefanov, A.
2015-04-22
In the present study, we revisit the theme of wave propagation in locally resonant granular crystal systems, also referred to as mass-in-mass systems. We use three distinct approaches to identify relevant traveling waves. In addition, the first consists of a direct solution of the traveling wave problem. The second one consists of the solution of the Fourier tranformed variant of the problem, or, more precisely, of its convolution reformulation (upon an inverse Fourier transform) in real space. Finally, our third approach will restrict considerations to a finite domain, utilizing the notion of Fourier series for important technical reasons, namely the avoidance of resonances, which will be discussed in detail. All three approaches can be utilized in either the displacement or the strain formulation. Typical resulting computations in finite domains result in the solitary waves bearing symmetric non-vanishing tails at both ends of the computational domain. Importantly, however, a countably infinite set of anti-resonance conditions is identified for which solutions with genuinely rapidly decaying tails arise.
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2011-10-12
... AFFAIRS Proposed Information Collection (Locality Pay System for Nurses and Other Health Care Personnel...: Locality Pay System for Nurses and Other Health Care Personnel, VA Form 10-0132. OMB Control Number: 2900... determine locality pay system for certain health care personnel. VA medical facility Directors will use...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-12-19
... AFFAIRS Agency Information Collection (Locality Pay System for Nurses and Other Health Care Personnel... INFORMATION: Title: Locality Pay System for Nurses and Other Health Care Personnel. OMB Control Number: 2900... determine locality pay system for certain health care personnel. VA medical facility Directors will use...
Interactive intraoperative localization using an infrared-based system.
Zamorano, L J; Nolte, L; Kadi, A M; Jiang, Z
1993-10-01
We discuss new methods of localizing and treating brain lesions for both the conventional method of a base-ring fixed to the patient's skull (referred to as frame-based procedures) and the new method of frameless procedures (no base ring). Frame-based procedures are used for finding a precise instrument position during neurosurgical procedures, such as stereotactic biopsy of deep-seated lesions, placing electrodes for functional stereotaxis or catheters with radioactive seeds for brachytherapy, or even the placement of a stereotactic retractor or endoscope for removal or internal decompression of lesions. In such procedures, the intraoperative image localization of instruments becomes useful as it tracks instruments as they travel through the preplanned trajectory. Additional intraoperative digitization of surgical instruments, e.g., bipolar suction, biopsy forceps, microscope, ultrasound probe, etc, can be achieved during the stereotactic resection of eloquent areas or deep intracranial lesions by adding an infrared-based system. Frameless procedures broaden the range of surgical approaches, image guidance planning, and operative procedures, since no ring is attached to the patient's head which might interfere with the surgical approach, and offers logistic advantages in scheduling diagnostic studies. Frameless diagnostic studies employ anatomical markers and/or surface matching techniques for data registration in the computer software surgical preplanning program. This simplifies scheduling of the procedures since the image study does not need to be acquired the same day as surgery. Frameless diagnostic studies allow for the use of more than one type of imaging data for planning and optimization of surgical procedures, and greatly improve patient tolerance and comfort during these procedures and during surgery, as compared with frame-based procedures.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7905601
Jung, Hosung; Yoon, Byung C.; Holt, Christine E.
2013-01-01
mRNAs can be targeted to specific neuronal subcellular domains, which enables rapid changes in the local proteome through local translation. This mRNA-based mechanism links extrinsic signals to spatially restricted cellular responses and can mediate stimulus-driven adaptive responses such as dendritic plasticity. Local mRNA translation also occurs in growing axons where it can mediate directional responses to guidance signals. Recent profiling studies have revealed that both growing and mature axons possess surprisingly complex and dynamic transcriptomes, thereby suggesting that axonal mRNA localization is highly regulated and has a role in a broad range of processes, a view that is increasingly being supported by new experimental evidence. Here, we review current knowledge on the roles and regulatory mechanisms of axonal mRNA translation and discuss emerging links to axon guidance, survival, regeneration and neurological disorders. PMID:22498899
NASA Astrophysics Data System (ADS)
Jiang, Shenghan; Mesaros, Andrej; Ran, Ying
2014-07-01
Recently, two interesting candidate quantum phases—the chiral spin-density wave state featuring anomalous quantum Hall effect and the d+id superconductor—were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping. Using a combination of exact diagonalization, density matrix renormalization group, the variational Monte Carlo method, and quantum field theories, we study the quantum phase diagrams of both the Hubbard model and the t-J model on the honeycomb lattice at 1/4 doping. The main advantage of our approach is the use of symmetry quantum numbers of ground-state wave functions on finite-size systems (up to 32 sites) to sharply distinguish different quantum phases. Our results show that for 1≲U/t<40 in the Hubbard model and for 0.1
local alternative sources for cogeneration combined heat and power system
NASA Astrophysics Data System (ADS)
Agll, Abdulhakim Amer
Global demand for energy continues to grow while countries around the globe race to reduce their reliance on fossil fuels and greenhouse gas emissions by implementing policy measures and advancing technology. Sustainability has become an important issue in transportation and infrastructure development projects. While several agencies are trying to incorporate a range of sustainability measures in their goals and missions, only a few planning agencies have been able to implement these policies and they are far from perfect. The low rate of success in implementing sustainable policies is primarily due to incomplete understanding of the system and the interaction between various elements of the system. The conventional planning efforts focuses mainly on performance measures pertaining to the system and its impact on the environment but seldom on the social and economic impacts. The objective of this study is to use clean and alternative energy can be produced from many sources, and even use existing materials for energy generation. One such pathway is using wastewater, animal and organic waste, or landfills to create biogas for energy production. There are three tasks for this study. In topic one evaluated the energy saving that produced from combined hydrogen, heat, and power and mitigate greenhouse gas emissions by using local sustainable energy at the Missouri S&T campus to reduce energy consumption and fossil fuel usage. Second topic aimed to estimate energy recovery and power generation from alternative energy source by using Rankin steam cycle from municipal solid waste at Benghazi-Libya. And the last task is in progress. The results for topics one and two have been presented.
Vladimirov, Igor; Jak, Eugene
2007-04-28
We study an interacting particle system on the simple cubic lattice satisfying the nearest neighbor exclusion (NNE) which forbids any two nearest sites to be simultaneously occupied. Under the constraint, we develop an edge-to-site reduction of the Bethe-Peierls entropy approximation of the cluster variation method. The resulting NNE-corrected Bragg-Williams approximation is applied to statistical mechanical modeling of a liquid silicate formed by silica and a univalent network modifier, for which we derive the molar Gibbs energy of mixing and enthalpy of mixing and compare the predictions with available thermodynamic data.
Matter-wave propagation in optical lattices: geometrical and flat-band effects
NASA Astrophysics Data System (ADS)
Metcalf, Mekena; Chern, Gia-Wei; Di Ventra, Massimiliano; Chien, Chih-Chun
2016-04-01
The geometry of optical lattices can be engineered, allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question feasible to atomic systems is related to the speed of matter-wave propagation as a function of the lattice geometry. To address this issue, we investigated, theoretically, the quantum transport of noninteracting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, and the cross-linked square lattice has an even faster propagation velocity. The increase results from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity due to its localized atoms. Possible realizations of those dynamical phenomena are discussed.
NASA Astrophysics Data System (ADS)
Berrabah, Sid Ahmed; Sahli, Hichem; Baudoin, Yvan
2011-12-01
This paper introduces an approach combining visual-based simultaneous localization and mapping (V-SLAM) and global positioning system (GPS) correction for accurate multi-sensor localization of an outdoor mobile robot in geo-referenced maps. The proposed framework combines two extended Kalman filters (EKF); the first one, referred to as the integration filter, is dedicated to the improvement of the GPS localization based on data from an inertial navigation system and wheels' encoders. The second EKF implements the V-SLAM process. The linear and angular velocities in the dynamic model of the V-SLAM EKF filter are given by the GPS/INS/Encoders integration filter. On the other hand, the output of the V-SLAM EKF filter is used to update the dynamics estimation in the integration filter and therefore the geo-referenced localization. This solution increases the accuracy and the robustness of the positioning during GPS outage and allows SLAM in less featured environments.
Different lattice geometries with a synthetic dimension
NASA Astrophysics Data System (ADS)
Suszalski, Dominik; Zakrzewski, Jakub
2016-09-01
The possibility of creating different geometries with the help of an extra synthetic dimension in optical lattices is studied. The additional linear potential together with Raman-assisted tunnelings are used to engineer well-controlled tunnelings between available states. The great flexibility of the system allows us to obtain different geometries of synthetic lattices with the possibility for adding synthetic gauge fields.
Vibration of prestressed periodic lattice structures
NASA Technical Reports Server (NTRS)
Anderson, M. S.
1981-01-01
Equations are developed for vibration of general lattice structures that have repetitive geometry. The method of solution is an extension of a previous paper for buckling of similar structures. The theory is based on representing each member of the structure with the exact dynamic stiffness matrix and taking advantage of the repetitive geometry to obtain an eigenvalue problem involving the degrees-of-freedom at a single node in the lattice. Results are given for shell-and beam-like lattice structures and for rings stiffened with tension cables and a central mast. The variation of frequency with external loading and the effect of local member vibration on overall modes is shown.
Bound states in two-dimensional spin systems near the Ising limit: A quantum finite-lattice study
Dusuel, Sebastien; Kamfor, Michael; Schmidt, Kai Phillip; Thomale, Ronny; Vidal, Julien
2010-02-01
We analyze the properties of low-energy bound states in the transverse-field Ising model and in the XXZ model on the square lattice. To this end, we develop an optimized implementation of perturbative continuous unitary transformations. The Ising model is studied in the small-field limit which is found to be a special case of the toric code model in a magnetic field. To analyze the XXZ model, we perform a perturbative expansion about the Ising limit in order to discuss the fate of the elementary magnon excitations when approaching the Heisenberg point.
14 CFR 171.263 - Localizer automatic monitor system.
Code of Federal Regulations, 2014 CFR
2014-01-01
... (CONTINUED) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES Interim Standard Microwave Landing... prescribed in paragraph (a) of this section, including periods of zero radiation, localizer signal...
14 CFR 171.263 - Localizer automatic monitor system.
Code of Federal Regulations, 2013 CFR
2013-01-01
... (CONTINUED) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES Interim Standard Microwave Landing... prescribed in paragraph (a) of this section, including periods of zero radiation, localizer signal...
14 CFR 171.263 - Localizer automatic monitor system.
Code of Federal Regulations, 2012 CFR
2012-01-01
... (CONTINUED) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES Interim Standard Microwave Landing... prescribed in paragraph (a) of this section, including periods of zero radiation, localizer signal...
14 CFR 171.263 - Localizer automatic monitor system.
Code of Federal Regulations, 2011 CFR
2011-01-01
... (CONTINUED) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES Interim Standard Microwave Landing... prescribed in paragraph (a) of this section, including periods of zero radiation, localizer signal...
Building the RHIC tracking lattice model
Luo, Y.; Fischer, W.; Tepikian, S.
2010-01-27
In this note we outline the procedure to build a realistic lattice model for the RHIC beam-beam tracking simulation. We will install multipole field errors in the arc main dipoles, arc main quadrupols and interaction region magnets (DX, D0, and triplets) and introduce a residual closed orbit, tune ripples, and physical apertures in the tracking lattice model. Nonlinearities such as local IR multipoles, second order chromaticies and third order resonance driving terms are also corrected before tracking.
Atom optics simulator of lattice transport phenomena
NASA Astrophysics Data System (ADS)
An, Fangzhao; Meier, Eric; Gadway, Bryce
2016-05-01
We report on a novel scheme for studying lattice transport phenomena, based on the controlled momentum-space dynamics of ultracold atomic matter waves. In the effective tight binding models that can be simulated, we demonstrate that this technique allows for a local and time-dependent control over all system parameters, and additionally allows for single-site resolved detection of atomic populations. We demonstrate full control over site-to-site off-diagonal tunneling elements (amplitude and phase) and diagonal site-energies, through the observation of continuous time quantum walks, Bloch oscillations, and negative tunneling. These capabilities open up new prospects in the experimental study of disordered and topological systems.
Nonlinear and locally optimal controllers design for input affine locally controllable systems
NASA Astrophysics Data System (ADS)
Sahnoun, Mariem; Andrieu, Vincent; Nadri, Madiha
2012-02-01
Given a global nonlinear state feedback which globally stabilises an equilibrium, the aim of this article is to modify the local behaviour of the trajectories in order to get local optimality with respect to a given quadratic cost. A sufficient condition is given in terms of Linear Matrix Inequalities (LMIs) to design a locally optimal and globally stabilising control law. This approach is illustrated on an academic inverted pendulum model in order to stabilise its upper equilibrium point. An extension of the main result is then given to address the problematic cases. Moreover, the cases in which the previous LMI condition failed to be satisfied is addressed and a new sufficient condition is then given (which is not anymore linear).
Pediatric Scleroderma –Systemic and Localized Forms
Torok, Kathryn S.
2012-01-01
Synopsis statement Pediatric scleroderma includes two major groups of clinical entities, systemic sclerosis (SSc) and localized scleroderma (LS). Although both share a common pathophysiology, with an initial inflammatory phase associated with endothelial activation, and a later fibrotic phase evidenced by collagenization of tissue and appreciable skin thickness, their clinical manifestations differ. LS is typically confined to the skin and underlying subcutis, and though not fatal like SSc, up to a quarter of the patients may have extracutaneous disease manifestations, such as arthritis and uveitis. While any organ may be affected in SSc, vascular (Raynaud’s phenomenon), cutaneous (skin thickening), GI, pulmonary and musculoskeletal involvement are most commonly seen in children. Auto-antibody profiles in childhood onset SSc can assist in predicting internal organ involvement. Treatment for both forms of scleroderma targets the active inflammatory stage and halts disease progression; however, progress still needs to be made towards the development of a more effective anti-fibrotic therapy to help reverse disease damage. PMID:22560576
State analysis of nonlinear systems using local canonical variate analysis
Hunter, N.F.
1997-01-01
There are many instances in which time series measurements are used to derive an empirical model of a dynamical system. State space reconstruction from time series measurement has applications in many scientific and engineering disciplines including structural engineering, biology, chemistry, climatology, control theory, and physics. Prediction of future time series values from empirical models was attempted as early as 1927 by Yule, who applied linear prediction methods to the sunspot values. More recently, efforts in this area have centered on two related aspects of time series analysis, namely prediction and modeling. In prediction future time series values are estimated from past values, in modeling, fundamental characteristics of the state model underlying the measurements are estimated, such as dimension and eigenvalues. In either approach a measured time series, [{bold y}(t{sub i})], i= 1,... N is assumed to derive from the action of a smooth dynamical system, s(t+{bold {tau}})=a(s(t)), where the bold notation indicates the (potentially ) multivariate nature of the time series. The time series is assumed to derive from the state evolution via a measurement function c. {bold y}(t)=c(s(t)) In general the states s(t), the state evolution function a and the measurement function c are In unknown, and must be inferred from the time series measurements. We approach this problem from the standpoint of time series analysis. We review the principles of state space reconstruction. The specific model formulation used in the local canonical variate analysis algorithm and a detailed description of the state space reconstruction algorithm are included. The application of the algorithm to a single-degree-of- freedom Duffing-like Oscillator and the difficulties involved in reconstruction of an unmeasured degree of freedom in a four degree of freedom nonlinear oscillator are presented. The advantages and current limitations of state space reconstruction are summarized.
Spontaneous formation of kagome network and Dirac half-semimetal on a triangular lattice
NASA Astrophysics Data System (ADS)
Akagi, Yutaka; Motome, Yukitoshi
2015-04-01
In spin-charge coupled systems, geometrical frustration of underlying lattice structures can give rise to nontrivial magnetic orders and electronic states. Here we explore such a possibility in the Kondo lattice model with classical localized spins on a triangular lattice by using a variational calculation and simulated annealing. We find that the system exhibits a four-sublattice collinear ferrimagnetic phase at 5/8 filling for a large Hund's-rule coupling. In this state, the system spontaneously differentiates into the up-spin kagome network and the isolated down-spin sites, which we call the kagome network formation. In the kagome network state, the system becomes Dirac half-semimetallic: The electronic structure shows a massless Dirac node at the Fermi level, and the Dirac electrons are almost fully spin polarized due to the large Hund's-rule coupling. We also study the effect of off-site Coulomb repulsion in the kagome network phase where the system is effectively regarded as a 1/3-filling spinless fermion system on the kagome lattice. We find that, at the level of the mean-field approximation, a √{3 }×√{3 } -type charge order occurs in the kagome network state, implying the possibility of fractional charge excitations in this triangular lattice system. Moreover, we demonstrate that the kagome network formation with fully polarized Dirac electrons are controllable by an external magnetic field.
On Some Periodic Toda Lattices
Kac, M.; Van Moerbeke, Pierre
1975-01-01
A discrete version of Floquet's theory is developed and applied to a system of non-linear differential equations related to the periodic Toda lattice. A special solution previously found by Toda is thus seen to fit into the formalism of inverse scattering problems. PMID:16592244
LOCALIZED MECHANICS OF DENTIN SELF-ETCHING ADHESIVE SYSTEM
Anchieta, Rodolfo Bruniera; Rocha, Eduardo Passos; Ko, Ching-Chang; Sundfeld, Renato Herman; Martin, Manoel; Archangelo, Carlos Marcelo
2007-01-01
The bond strength of composite resins (CRs) to dentin is influenced by the interfacial microstructure of the hybrid layer (HL) and the resin tags (TAG). The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 μm), two TAG lengths (13 or 17 μm) and two loading conditions (perpendicular and oblique-25o) were investigated by the finite element (FE) analysis. Five two-dimensional FE models (M) of a dentin specimen restored with CR (38 x 64 μm) were constructed: Ml - no HL and no TAG; M2 - 3 μm of HL and 13 μm of TAG; M3 - 3 μm of HL and 17 μm of TAG; M4 - 6 μm of HL and 13 μm of TAG; and M5 - 6 μm of HL and 17 μm of TAG. Two distributed loadings (L) (20N) were applied on CR surface: L1 - perpendicular, and L2 - oblique (25°). Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys®, Houston, PA, USA) software was used to calculate the stress fields. The peak of von Mises (σvM) and maximum principal stress (σmax) was higher in L2 than in L1. Microstructures (HL and TAG) had no effect on local stresses for L1. Decreasing HL decreased σvM and σmax in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the σvM and σmax than TAG length. The peritubular dentin and its adjacent structures showed the highest σvM and σmax, mainly in the oblique loading. PMID:19089152
NASA Astrophysics Data System (ADS)
Itin, A. P.; Katsnelson, M. I.
2015-08-01
We consider 1D lattices described by Hubbard or Bose-Hubbard models, in the presence of periodic high-frequency perturbations, such as uniform ac force or modulation of hopping coefficients. Effective Hamiltonians for interacting particles are derived using an averaging method resembling classical canonical perturbation theory. As is known, a high-frequency force may renormalize hopping coefficients, causing interesting phenomena such as coherent destruction of tunneling and creation of artificial gauge fields. We find explicitly additional corrections to the effective Hamiltonians due to interactions, corresponding to nontrivial processes such as single-particle density-dependent tunneling, correlated pair hoppings, nearest neighbor interactions, etc. Some of these processes arise also in multiband lattice models, and are capable of giving rise to a rich variety of quantum phases. The apparent contradiction with other methods, e.g., Floquet-Magnus expansion, is explained. The results may be useful for designing effective Hamiltonian models in experiments with ultracold atoms, as well as in the field of ultrafast nonequilibrium magnetism. An example of manipulating exchange interaction in a Mott-Hubbard insulator is considered, where our corrections play an essential role.
Metal-oxide-semiconductor field effect nanostructure spin lattice devices
NASA Astrophysics Data System (ADS)
Yang, Jun
This dissertation explored and developed technologies for silicon based spin lattice devices. Spin lattices are artificial electron spin systems with a periodic structure having one to a few electrons at each site. They are expected to have various magnetic and even superconducting properties when structured at an optimal scale with a specific number i of electrons. Silicon turns out to be a very good material choice in realizing spin lattices. A metal-oxide-semiconductor field-effect nanostructure (MOSFENS) device, which is closely related to a MOS transistor but with a nanostructured oxide-semiconductor interface, can define the spin lattices potential at the interface and alter the occupation i with the gate electrode potential to change the magnetic phase. The MOSFENS spin lattices engineering challenge addressed in this work has come from the practical difficulty of process integration in modifying a transistor fabrication process to accommodate the interface patterning requirements. Two distinct design choices for the fabrication sequences that create the nanostructure have been examined. Patterning the silicon surface before the MOS gate stack layers gives a "nanostructure first" process, and patterning the interface after forming the gate stack gives a "nanostructure last process." Both processes take advantage of a nano-LOCOS (nano-local oxidation of silicon) invention developed in this work. The nano-LOCOS process plays a central role in defining a clean, sharp confining potential for the spin lattice electrons. The MOSFENS process required a basic transistor fabrication process that can accommodate the nanostructures. The process developed for this purpose has a gate stack with a 15 nm polysilicon gate electrode and a 3 nm thermal gate oxide on a p-type silicon substrate. The measured threshold voltage is 0.25 V. Device processes were examined for either isolating the devices with windows in the field oxide or with mesas defined by the etched trenches
Silicon network structure and 29Si spin-lattice relaxation in amorphous hydrogenated silicon
NASA Astrophysics Data System (ADS)
Cheung, Man Ken; Petrich, Mark A.
1992-04-01
We report a NMR study of amorphous hydrogenated silicon (a-Si:H) that measures the 29Si spin-lattice relaxation time T1. Measurements of 29Si T1 are useful in learning about the silicon network structure and the localized states within the mobility gap. Coupling to paramagnetic dangling bonds is the predominant 29Si spin-lattice relaxation mechanism in a-Si:H. Spin flipping of paramagnetic electrons, caused by coupling to the lattice, produces fluctuating local fields that stimulate nuclear spin-lattice relaxation. By comparing our experimental results with existing theory, we find that dangling bonds are randomly distributed in device-quality materials but are inhomogeneously distributed in non-device-quality materials. We also find that there are two simultaneously occurring dangling-bond spin-lattice relaxation mechanisms: one through the spin-orbit coupling modulated by thermal excitation of ``two-level systems,'' and the other through hopping conduction between localized states near the Fermi level. Simple chemical-shift measurements are also helpful in characterizing a-Si:H. We find that the 29Si resonance shifts upfield with increasing microstructure in the material.
40 CFR 35.936-2 - Grantee procurement systems; State or local law.
Code of Federal Regulations, 2013 CFR
2013-07-01
...-Clean Water Act § 35.936-2 Grantee procurement systems; State or local law. (a) Grantee procurement... local law. 35.936-2 Section 35.936-2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GRANTS... of State, territorial, or local laws and ordinances to the extent that these systems and...
40 CFR 35.936-2 - Grantee procurement systems; State or local law.
Code of Federal Regulations, 2011 CFR
2011-07-01
...-Clean Water Act § 35.936-2 Grantee procurement systems; State or local law. (a) Grantee procurement... local law. 35.936-2 Section 35.936-2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GRANTS... of State, territorial, or local laws and ordinances to the extent that these systems and...
40 CFR 35.936-2 - Grantee procurement systems; State or local law.
Code of Federal Regulations, 2010 CFR
2010-07-01
...-Clean Water Act § 35.936-2 Grantee procurement systems; State or local law. (a) Grantee procurement... local law. 35.936-2 Section 35.936-2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GRANTS... of State, territorial, or local laws and ordinances to the extent that these systems and...
An autonomous surveillance system for blind sources localization and separation
NASA Astrophysics Data System (ADS)
Wu, Sean; Kulkarni, Raghavendra; Duraiswamy, Srikanth
2013-05-01
This paper aims at developing a new technology that will enable one to conduct an autonomous and silent surveillance to monitor sound sources stationary or moving in 3D space and a blind separation of target acoustic signals. The underlying principle of this technology is a hybrid approach that uses: 1) passive sonic detection and ranging method that consists of iterative triangulation and redundant checking to locate the Cartesian coordinates of arbitrary sound sources in 3D space, 2) advanced signal processing to sanitizing the measured data and enhance signal to noise ratio, and 3) short-time source localization and separation to extract the target acoustic signals from the directly measured mixed ones. A prototype based on this technology has been developed and its hardware includes six B and K 1/4-in condenser microphones, Type 4935, two 4-channel data acquisition units, Type NI-9234, with a maximum sampling rate of 51.2kS/s per channel, one NI-cDAQ 9174 chassis, a thermometer to measure the air temperature, a camera to view the relative positions of located sources, and a laptop to control data acquisition and post processing. Test results for locating arbitrary sound sources emitting continuous, random, impulsive, and transient signals, and blind separation of signals in various non-ideal environments is presented. This system is invisible to any anti-surveillance device since it uses the acoustic signal emitted by a target source. It can be mounted on a robot or an unmanned vehicle to perform various covert operations, including intelligence gathering in an open or a confined field, or to carry out the rescue mission to search people trapped inside ruins or buried under wreckages.
On Traveling Waves in Lattices: The Case of Riccati Lattices
NASA Astrophysics Data System (ADS)
Dimitrova, Zlatinka
2012-09-01
The method of simplest equation is applied for analysis of a class of lattices described by differential-difference equations that admit traveling-wave solutions constructed on the basis of the solution of the Riccati equation. We denote such lattices as Riccati lattices. We search for Riccati lattices within two classes of lattices: generalized Lotka-Volterra lattices and generalized Holling lattices. We show that from the class of generalized Lotka-Volterra lattices only the Wadati lattice belongs to the class of Riccati lattices. Opposite to this many lattices from the Holling class are Riccati lattices. We construct exact traveling wave solutions on the basis of the solution of Riccati equation for three members of the class of generalized Holling lattices.
NASA Astrophysics Data System (ADS)
Ding, Hanqin; Zhang, Jun
2016-05-01
Motivated by recent experimental realization of the tunability of many-body interactions in ultracold fermionic gases trapped in optical lattices, we investigate analytically effects of nearest-neighboring diagonal three-body (T) and four-body (F) couplings on the one-dimensional conventional extended Hubbard model with on-site (U) and inter-site (V) interactions. Applying the bosonization and renormalization-group techniques, we present quantum phase diagrams at half filling and in the weak-coupling regime. The result shows that, whether the three-body or four-body effective attraction may give rise to superconducting phases in the region for repulsive U and V. Besides, the four-body coupling can lead to a bond-spin-density-wave phase for F > 0 and a bond-charge-density-wave phase for F < 0.
NASA Astrophysics Data System (ADS)
Armstrong, N. M. R.; Mortimer, K. D.; Kong, T.; Bud'ko, S. L.; Canfield, P. C.; Basov, D. N.; Timusk, T.
2016-04-01
Icosahedral quasicrystals are characterised by the absence of a distinct Drude peak in their low-frequency optical conductivity and the same is true of their crystalline approximants. We have measured the optical conductivity of i-GdCd?, an icosahedral quasicrystal, and two approximants, GdCd? and YCd?. We find that there is a significant difference in the optical properties of these compounds. The approximants have a zero frequency peak, characteristic of a metal, whereas the quasicrystal has a striking minimum. This is the first example where the transport properties of a quasicrystal and its approximant differ in such a fundamental way. Using a generalised Drude model introduced by Mayou, we find that our data are well described by this model. It implies that the quantum diffusion of electron wave packets through the periodic and quasiperiodic lattices is responsible for these dramatic differences: in the approximants, the transport is superdiffusive, whereas the quasicrystals show subdiffusive motion of the electrons.
A local particle filter for high dimensional geophysical systems
NASA Astrophysics Data System (ADS)
Penny, S. G.; Miyoshi, T.
2015-12-01
A local particle filter (LPF) is introduced that outperforms traditional ensemble Kalman filters in highly nonlinear/non-Gaussian scenarios, both in accuracy and computational cost. The standard Sampling Importance Resampling (SIR) particle filter is augmented with an observation-space localization approach, for which an independent analysis is computed locally at each gridpoint. The deterministic resampling approach of Kitagawa is adapted for application locally and combined with interpolation of the analysis weights to smooth the transition between neighboring points. Gaussian noise is applied with magnitude equal to the local analysis spread to prevent particle degeneracy while maintaining the estimate of the growing dynamical instabilities. The approach is validated against the Local Ensemble Transform Kalman Filter (LETKF) using the 40-variable Lorenz-96 model. The results show that: (1) the accuracy of LPF surpasses LETKF as the forecast length increases (thus increasing the degree of nonlinearity), (2) the cost of LPF is significantly lower than LETKF as the ensemble size increases, and (3) LPF prevents filter divergence experienced by LETKF in cases with non-Gaussian observation error distributions.
Geometric local invariants and pure three-qubit states
Williamson, Mark S.; Ericsson, Marie; Johansson, Markus; Sjoeqvist, Erik; Sudbery, Anthony; Vedral, Vlatko; Wootters, William K.
2011-06-15
We explore a geometric approach to generating local SU(2) and SL(2,C) invariants for a collection of qubits inspired by lattice gauge theory. Each local invariant or ''gauge'' invariant is associated with a distinct closed path (or plaquette) joining some or all of the qubits. In lattice gauge theory, the lattice points are the discrete space-time points, the transformations between the points of the lattice are defined by parallel transporters, and the gauge invariant observable associated with a particular closed path is given by the Wilson loop. In our approach the points of the lattice are qubits, the link transformations between the qubits are defined by the correlations between them, and the gauge invariant observable, the local invariants associated with a particular closed path, are also given by a Wilson looplike construction. The link transformations share many of the properties of parallel transporters, although they are not undone when one retraces one's steps through the lattice. This feature is used to generate many of the invariants. We consider a pure three-qubit state as a test case and find we can generate a complete set of algebraically independent local invariants in this way; however, the framework given here is applicable to generating local unitary invariants for mixed states composed of any number of d-level quantum systems. We give an operational interpretation of these invariants in terms of observables.
Breathers in strongly anharmonic lattices.
Rosenau, Philip; Pikovsky, Arkady
2014-02-01
We present and study a family of finite amplitude breathers on a genuinely anharmonic Klein-Gordon lattice embedded in a nonlinear site potential. The direct numerical simulations are supported by a quasilinear Schrodinger equation (QLS) derived by averaging out the fast oscillations assuming small, albeit finite, amplitude vibrations. The genuinely anharmonic interlattice forces induce breathers which are strongly localized with tails evanescing at a doubly exponential rate and are either close to a continuum, with discrete effects being suppressed, or close to an anticontinuum state, with discrete effects being enhanced. Whereas the D-QLS breathers appear to be always stable, in general there is a stability threshold which improves with spareness of the lattice.
Cold atoms in a rotating optical lattice
NASA Astrophysics Data System (ADS)
Foot, Christopher J.
2009-05-01
We have demonstrated a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz. Our arrangement also allows the periodicity of the optical lattice to be varied dynamically, producing a 2D ``accordion lattice'' [1]. The angles of the laser beams are controlled by acousto-optic deflectors and this allows smooth changes with little heating of the trapped cold (rubidium) atoms. We have loaded a BEC into lattices with periodicities ranging from 1.8μm to 18μm, observing the collapse and revival of the diffraction orders of the condensate over a large range of lattice parameters as recently reported by a group in NIST [2]. We have also imaged atoms in situ in a 2D lattice over a range of lattice periodicities. Ultracold atoms in a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, i.e. the Hamiltonian of the atoms in the rotating frame resembles that of a charged particle in a strong magnetic field. In the future, we plan to use this to investigate a range of phenomena such as the analogue of the fractional quantum Hall effect. [4pt] [1] R. A. Williams, J. D. Pillet, S. Al-Assam, B. Fletcher, M. Shotter, and C. J. Foot, ``Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms,'' Opt. Express 16, 16977-16983 (2008) [0pt] [2] J. H. Huckans, I. B. Spielman, B. Laburthe Tolra, W. D. Phillips, and J. V. Porto, Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice, arXiv:0901.1386v1
Some Poisson structures and Lax equations associated with the Toeplitz lattice and the Schur lattice
NASA Astrophysics Data System (ADS)
Lemarie, Caroline
2016-01-01
The Toeplitz lattice is a Hamiltonian system whose Poisson structure is known. In this paper, we unveil the origins of this Poisson structure and derive from it the associated Lax equations for this lattice. We first construct a Poisson subvariety H n of GL n (C), which we view as a real or complex Poisson-Lie group whose Poisson structure comes from a quadratic R-bracket on gl n (C) for a fixed R-matrix. The existence of Hamiltonians, associated to the Toeplitz lattice for the Poisson structure on H n , combined with the properties of the quadratic R-bracket allow us to give explicit formulas for the Lax equation. Then we derive from it the integrability in the sense of Liouville of the Toeplitz lattice. When we view the lattice as being defined over R, we can construct a Poisson subvariety H n τ of U n which is itself a Poisson-Dirac subvariety of GL n R (C). We then construct a Hamiltonian for the Poisson structure induced on H n τ , corresponding to another system which derives from the Toeplitz lattice the modified Schur lattice. Thanks to the properties of Poisson-Dirac subvarieties, we give an explicit Lax equation for the new system and derive from it a Lax equation for the Schur lattice. We also deduce the integrability in the sense of Liouville of the modified Schur lattice.
Local Public Health Systems and the Incidence of Sexually Transmitted Diseases
Chen, Jie; Owusu-Edusei, Kwame; Suh, Allen; Bekemeier, Betty
2012-01-01
Objectives. We examined the associations of local public health system organization and local health department resources with county-level sexually transmitted disease (STD) incidence rates in large US health jurisdictions. Methods. We linked annual county STD incidence data (2005–2008) to local health department director responses (n = 211) to the 2006 wave of the National Longitudinal Study of Local Public Health Systems, the 2005 national Local Health Department Profile Survey, and the Area Resource File. We used nested mixed effects regression models to assess the relative contribution of local public health system organization, local health department financial and resource factors, and sociodemographic factors known to be associated with STD incidence to county-level (n = 307) STD incidence. Results. Jurisdictions with local governing boards had significantly lower county-level STD incidence. Local public health systems with comprehensive services where local health departments shoulder much of the effort had higher county-level STD rates than did conventional systems. Conclusions. More integration of system partners in local public health system activities, through governance and interorganizational arrangements, may reduce the incidence and burden of STDs. PMID:22813090
Prototype Local Data Integration System and Central Florida Data Deficiency
NASA Technical Reports Server (NTRS)
Manobianco, John; Case, Jonathan
1998-01-01
This report describes the Applied Meteorology Unit's (AMU) task on the Local Data Integration System (LDIS) and central Florida data deficiency. The objectives of the task are to identify all existing meteorological data sources within 250 km of the Kennedy Space Center (KSC) and the Eastern Range at Cape Canaveral Air Station (CCAS), identify and configure an appropriate LDIS to integrate these data, and implement a working prototype to be used for limited case studies and data non-incorporation (DNI) experiments. The ultimate goal for running LDIS is to generate products that may enhance weather nowcasts and short-range (less than 6 h) forecasts issued in support of the 45th Weather Squadron (45 WS), Spaceflight Meteorology Group (SMG), and the Melbourne National Weather Service (NWS MLB) operational requirements. The LDIS has the potential to provide added value for nowcasts and short term forecasts for two reasons. First, it incorporates all data operationally available in east central Florida. Second, it is run at finer spatial and temporal resolutions than current national-scale operational models. In combination with a suitable visualization tool, LDIS may provide users with a more complete and comprehensive understanding of evolving fine-scale weather features than could be developed by individually examining the disparate data sets over the same area and time. The utility of LDIS depends largely on the reliability and availability of observational data. Therefore, it is important to document all existing meteorological data sources around central Florida that can be incorporated by it. Several factors contribute to the data density and coverage over east central Florida including the level in the atmosphere, distance from KSC/CCAS, time, and prevailing weather. The central Florida mesonet consists of existing surface meteorological and hydrological data available from the Tampa NWS and data servers at Miami and Jacksonville. However the utility of these
Quantum transport in d-dimensional lattices
Manzano, Daniel; Chuang, Chern; Cao, Jianshu
2016-04-28
We show that both fermionic and bosonic uniform d-dimensional lattices can be reduced to a set of independent one-dimensional chains. This reduction leads to the expression for ballistic energy fluxes in uniform fermionic and bosonic lattices. By the use of the Jordan–Wigner transformation we can extend our analysis to spin lattices, proving the coexistence of both ballistic and non-ballistic subspaces in any dimension and for any system size. Lastly, we then relate the nature of transport to the number of excitations in the homogeneous spin lattice, indicating that a single excitation always propagates ballistically and that the non-ballistic behaviour ofmore » uniform spin lattices is a consequence of the interaction between different excitations.« less
Lattice Boltzmann modeling of phonon transport
NASA Astrophysics Data System (ADS)
Guo, Yangyu; Wang, Moran
2016-06-01
A novel lattice Boltzmann scheme is proposed for phonon transport based on the phonon Boltzmann equation. Through the Chapman-Enskog expansion, the phonon lattice Boltzmann equation under the gray relaxation time approximation recovers the classical Fourier's law in the diffusive limit. The numerical parameters in the lattice Boltzmann model are therefore rigorously correlated to the bulk material properties. The new scheme does not only eliminate the fictitious phonon speed in the diagonal direction of a square lattice system in the previous lattice Boltzmann models, but also displays very robust performances in predicting both temperature and heat flux distributions consistent with analytical solutions for diverse numerical cases, including steady-state and transient, macroscale and microscale, one-dimensional and multi-dimensional phonon heat transport. This method may provide a powerful numerical tool for deep studies of nonlinear and nonlocal heat transports in nanosystems.
Quantum transport in d-dimensional lattices
NASA Astrophysics Data System (ADS)
Manzano, Daniel; Chuang, Chern; Cao, Jianshu
2016-04-01
We show that both fermionic and bosonic uniform d-dimensional lattices can be reduced to a set of independent one-dimensional chains. This reduction leads to the expression for ballistic energy fluxes in uniform fermionic and bosonic lattices. By the use of the Jordan–Wigner transformation we can extend our analysis to spin lattices, proving the coexistence of both ballistic and non-ballistic subspaces in any dimension and for any system size. We then relate the nature of transport to the number of excitations in the homogeneous spin lattice, indicating that a single excitation always propagates ballistically and that the non-ballistic behaviour of uniform spin lattices is a consequence of the interaction between different excitations.
Nonextensivity of the cyclic lattice Lotka-Volterra model.
Tsekouras, G A; Provata, A; Tsallis, C
2004-01-01
We numerically show that the lattice Lotka-Volterra model, when realized on a square lattice support, gives rise to a finite production, per unit time, of the nonextensive entropy S(q)=(1- summation operator (i)p(q)(i))/(q-1) (S(1)=- summation operator (i)p(i) ln p(i)). This finiteness only occurs for q=0.5 for the d=2 growth mode (growing droplet), and for q=0 for the d=1 one (growing stripe). This strong evidence of nonextensivity is consistent with the spontaneous emergence of local domains of identical particles with fractal boundaries and competing interactions. Such direct evidence is, to our knowledge, exhibited for the first time for a many-body system which, at the mean field level, is conservative.
Entanglement and localization transitions in eigenstates of interacting chaotic systems.
Lakshminarayan, Arul; Srivastava, Shashi C L; Ketzmerick, Roland; Bäcker, Arnd; Tomsovic, Steven
2016-07-01
The entanglement and localization in eigenstates of strongly chaotic subsystems are studied as a function of their interaction strength. Excellent measures for this purpose are the von Neumann entropy, Havrda-Charvát-Tsallis entropies, and the averaged inverse participation ratio. All the entropies are shown to follow a remarkably simple exponential form, which describes a universal and rapid transition to nearly maximal entanglement for increasing interaction strength. An unexpectedly exact relationship between the subsystem averaged inverse participation ratio and purity is derived that prescribes the transition in the localization as well. PMID:27575066
Localized modulated wave solutions in diffusive glucose-insulin systems
NASA Astrophysics Data System (ADS)
Mvogo, Alain; Tambue, Antoine; Ben-Bolie, Germain H.; Kofané, Timoléon C.
2016-06-01
We investigate intercellular insulin dynamics in an array of diffusively coupled pancreatic islet β-cells. The cells are connected via gap junction coupling, where nearest neighbor interactions are included. Through the multiple scale expansion in the semi-discrete approximation, we show that the insulin dynamics can be governed by the complex Ginzburg-Landau equation. The localized solutions of this equation are reported. The results suggest from the biophysical point of view that the insulin propagates in pancreatic islet β-cells using both temporal and spatial dimensions in the form of localized modulated waves.
Random sequential adsorption on imprecise lattice.
Privman, Vladimir; Yan, Han
2016-06-28
We report a surprising result, established by numerical simulations and analytical arguments for a one-dimensional lattice model of random sequential adsorption, that even an arbitrarily small imprecision in the lattice-site localization changes the convergence to jamming from fast, exponential, to slow, power-law, with, for some parameter values, a discontinuous jump in the jamming coverage value. This finding has implications for irreversible deposition on patterned substrates with pre-made landing sites for particle attachment. We also consider a general problem of the particle (depositing object) size not an exact multiple of the lattice spacing, and the lattice sites themselves imprecise, broadened into allowed-deposition intervals. Regions of exponential vs. power-law convergence to jamming are identified, and certain conclusions regarding the jamming coverage are argued for analytically and confirmed numerically. PMID:27369530
Random sequential adsorption on imprecise lattice
NASA Astrophysics Data System (ADS)
Privman, Vladimir; Yan, Han
2016-06-01
We report a surprising result, established by numerical simulations and analytical arguments for a one-dimensional lattice model of random sequential adsorption, that even an arbitrarily small imprecision in the lattice-site localization changes the convergence to jamming from fast, exponential, to slow, power-law, with, for some parameter values, a discontinuous jump in the jamming coverage value. This finding has implications for irreversible deposition on patterned substrates with pre-made landing sites for particle attachment. We also consider a general problem of the particle (depositing object) size not an exact multiple of the lattice spacing, and the lattice sites themselves imprecise, broadened into allowed-deposition intervals. Regions of exponential vs. power-law convergence to jamming are identified, and certain conclusions regarding the jamming coverage are argued for analytically and confirmed numerically.
Local effects of structure formation and control in self-organizing systems. II
Chugaev, V.I.
1995-09-01
This theoretical problem focuses on stability, controllability, and adaptation methods in nonlinear distributed dissipative systems subject to external local changes of diffusion coefficients. The control directly affect the main equations describing the controlled system, and it is applied in the form of a local change in the field of diffusion coefficients of the reactive system at the control point.
NASA Astrophysics Data System (ADS)
Bergner, Georg; Catterall, Simon
2016-08-01
We discuss the motivations, difficulties and progress in the study of supersymmetric lattice gauge theories focusing in particular on 𝒩 = 1 and 𝒩 = 4 super-Yang-Mills in four dimensions. Brief reviews of the corresponding lattice formalisms are given and current results are presented and discussed. We conclude with a summary of the main aspects of current work and prospects for the future.
Dynamics of Hubbard-Band Quasiparticles in Disordered Optical Lattices
NASA Astrophysics Data System (ADS)
Scarola, Vito; Demarco, Brian
Recent experiments use transport of degenerate Fermi gases in optical lattices (Kondov et al. Phys. Rev. Lett. 114, 083002 (2015) to probe the interplay of disorder and strong interactions. These experiments find evidence for an intriguing insulating phase where quantum diffusion is completely suppressed by strong disorder. Quantitative interpretation of these experiments remains an open problem that requires inclusion of non-zero entropy, strong interaction, and trapping in an Anderson-Hubbard model. We construct a theory of dynamics of Hubbard-band quasiparticles tailored to trapped optical lattice experiments. We compare the theory directly with center-of-mass transport experiments of Kondov et al. with no fitting parameters. The close agreement between theory and experiments shows that the suppression of transport is only partly due to finite entropy effects. We argue that the complete suppression of transport is consistent with short-time, finite size precursors of Anderson localization of Hubbard-band quasiparticles. The combination of our theoretical framework and optical lattice experiments offers an important platform for studying localization in isolated many-body quantum systems. V.W.S. acknowledges support from AFOSR under Grant FA9550-11-1-0313.
Cutaneous localization of Ga-67 in systemic sarcoidosis
Rohatgi, P.K.
1981-03-01
/sup 67/Ga scans have been used in patients with sarcoidosis to assess noninvasively the intensity of alveolitis and to detect areas of extrathoracic involvement. To the author's knowledge, this is the first report of the localization of gallium in cutaneous lesions of a patient with sarcoidosis.
Collective Leadership of Local School Systems: Power, Autonomy and Ethics
ERIC Educational Resources Information Center
Lumby, Jacky
2009-01-01
The rhetoric of "partnership" is ubiquitous in UK policy at national, regional, local and organizational levels. Self-styled partnership activity is espoused by most schools in England and Wales. This article considers the implications of the growth of partnership for conceptualizing leadership. It draws on evidence of interviews with young…
Financial Accounting for Local and State School Systems, 1990.
ERIC Educational Resources Information Center
Fowler, William J., Jr.
The purpose of this guidebook is to reflect the changes that have occurred since 1973 in governmental accounting and education finance. This document serves as a vehicle for program cost accounting at the local and intermediate levels. Although not required by federal law, the National Center for Education Statistics (NCES) encourages state and…
A Guide to Federal Assistance Programs for Local School Systems.
ERIC Educational Resources Information Center
Fairley, Richard L.; Krumbein, Gerald
This manual is written to provide an overview of the Federal programs which are available at the local level and to aid school administrators in locating particular Federal programs that will fulfill specific educational needs. The guide is designed for use as a tool in planning and programing a comprehensive educational program, rather than as a…
Heat transport through lattices of quantum harmonic oscillators in arbitrary dimensions.
Asadian, A; Manzano, D; Tiersch, M; Briegel, H J
2013-01-01
In d-dimensional lattices of coupled quantum harmonic oscillators, we analyze the heat current caused by two thermal baths of different temperatures, which are coupled to opposite ends of the lattice, with a focus on the validity of Fourier's law of heat conduction. We provide analytical solutions of the heat current through the quantum system in the nonequilibrium steady state using the rotating-wave approximation and bath interactions described by a master equation of Lindblad form. The influence of local dephasing in the transition of ballistic to diffusive transport is investigated.
Local Authorities and the School System: The New Authority-Wide Partnerships
ERIC Educational Resources Information Center
Hatcher, Richard
2014-01-01
Coalition government policies have put into question the role of local authorities in a "self-improving school system". In a number of local authorities new authority-wide partnership bodies are being set up involving all local schools, including academies, and controlled by headteachers. This article begins with an analysis of the new…
40 CFR 35.936-2 - Grantee procurement systems; State or local law.
Code of Federal Regulations, 2014 CFR
2014-07-01
...-Clean Water Act § 35.936-2 Grantee procurement systems; State or local law. (a) Grantee procurement... local law. 35.936-2 Section 35.936-2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GRANTS... do not conflict with the minimum requirements of this subchapter. (b) State or local law....
40 CFR 35.936-2 - Grantee procurement systems; State or local law.
Code of Federal Regulations, 2012 CFR
2012-07-01
...-Clean Water Act § 35.936-2 Grantee procurement systems; State or local law. (a) Grantee procurement... local law. 35.936-2 Section 35.936-2 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY GRANTS... do not conflict with the minimum requirements of this subchapter. (b) State or local law....
BERG,J.S.; RUGGIERO, A.; MACHIDA, S.; KOSCIELNIAK, S.
2007-06-25
EMMA is a 10 to 20 MeV electron ring designed to test our understanding of beam dynamics in a relativistic linear non-scaling fixed field alternating gradient accelerator (FFAG). This paper describes the design of the EMMA lattice. We begin with a summary of the experimental goals that impact the lattice design, and then outline what motivated the choice for the basic lattice parameters, such as the type of cells, the number of cells, and the RF frequency. We next list the different configurations that we wish to operate the machine in so as to accomplish our experimental goals. Finally, we enumerate the detailed lattice parameters, showing how these parameters result from the various lattice configurations.
Towards the reliable calculation of residence time for off-lattice kinetic Monte Carlo simulations
NASA Astrophysics Data System (ADS)
Alexander, Kathleen C.; Schuh, Christopher A.
2016-08-01
Kinetic Monte Carlo (KMC) methods have the potential to extend the accessible timescales of off-lattice atomistic simulations beyond the limits of molecular dynamics by making use of transition state theory and parallelization. However, it is a challenge to identify a complete catalog of events accessible to an off-lattice system in order to accurately calculate the residence time for KMC. Here we describe possible approaches to some of the key steps needed to address this problem. These include methods to compare and distinguish individual kinetic events, to deterministically search an energy landscape, and to define local atomic environments. When applied to the ground state ∑5(2 1 0) grain boundary in copper, these methods achieve a converged residence time, accounting for the full set of kinetically relevant events for this off-lattice system, with calculable uncertainty.
NASA Astrophysics Data System (ADS)
Takei, Yasuko; Shimizu, Ichiko
2003-10-01
Dihedral angles of binary eutectic systems, such as silicate+melt systems, silicate+H 2O systems, binary alloys, and binary organic systems, tend to decrease with increasing concentration of the solid component in the liquid phase. This empirical law is useful to estimate dihedral angles in the Earth's interior from phase diagrams of solid-liquid systems. In this paper, we investigate the mechanism underlying this empirical law. By employing a lattice-like model in which the liquid phase is treated as a regular solution, we clarify the liquid composition, temperature, and pressure effects on the solid-liquid interfacial tension. It is shown that the non-ideality in chemical bonding causes a strong compositional dependence of the solid-liquid interfacial tension; due to the non-ideality in chemical bonding, the solid surface preferentially adsorbs the solid component, which results in the decrease of the interfacial tension with increasing concentration of this component in the bulk liquid phase. With this effect, the significant decrease of the dihedral angle with T observed in the SiO 2-H 2O system near the monotectic temperature, and the decrease with P observed in the forsterite-H 2O system, can be explained semi-quantitatively.
State diagrams for harmonically trapped bosons in optical lattices
Rigol, Marcos; Batrouni, George G.; Rousseau, Valery G.; Scalettar, Richard T.
2009-05-15
We use quantum Monte Carlo simulations to obtain zero-temperature state diagrams for strongly correlated lattice bosons in one and two dimensions under the influence of a harmonic confining potential. Since harmonic traps generate a coexistence of superfluid and Mott insulating domains, we use local quantities such as the quantum fluctuations of the density and a local compressibility to identify the phases present in the inhomogeneous density profiles. We emphasize the use of the 'characteristic density' to produce a state diagram that is relevant to experimental optical lattice systems, regardless of the number of bosons or trap curvature and of the validity of the local-density approximation. We show that the critical value of U/t at which Mott insulating domains appear in the trap depends on the filling in the system, and it is in general greater than the value in the homogeneous system. Recent experimental results by Spielman et al. [Phys. Rev. Lett. 100, 120402 (2008)] are analyzed in the context of our two-dimensional state diagram, and shown to exhibit a value for the critical point in good agreement with simulations. We also study the effects of finite, but low (T{<=}t/2), temperatures. We find that in two dimensions they have little influence on our zero-temperature results, while their effect is more pronounced in one dimension.
Developing a system for blind acoustic source localization and separation
NASA Astrophysics Data System (ADS)
Kulkarni, Raghavendra
This dissertation presents innovate methodologies for locating, extracting, and separating multiple incoherent sound sources in three-dimensional (3D) space; and applications of the time reversal (TR) algorithm to pinpoint the hyper active neural activities inside the brain auditory structure that are correlated to the tinnitus pathology. Specifically, an acoustic modeling based method is developed for locating arbitrary and incoherent sound sources in 3D space in real time by using a minimal number of microphones, and the Point Source Separation (PSS) method is developed for extracting target signals from directly measured mixed signals. Combining these two approaches leads to a novel technology known as Blind Sources Localization and Separation (BSLS) that enables one to locate multiple incoherent sound signals in 3D space and separate original individual sources simultaneously, based on the directly measured mixed signals. These technologies have been validated through numerical simulations and experiments conducted in various non-ideal environments where there are non-negligible, unspecified sound reflections and reverberation as well as interferences from random background noise. Another innovation presented in this dissertation is concerned with applications of the TR algorithm to pinpoint the exact locations of hyper-active neurons in the brain auditory structure that are directly correlated to the tinnitus perception. Benchmark tests conducted on normal rats have confirmed the localization results provided by the TR algorithm. Results demonstrate that the spatial resolution of this source localization can be as high as the micrometer level. This high precision localization may lead to a paradigm shift in tinnitus diagnosis, which may in turn produce a more cost-effective treatment for tinnitus than any of the existing ones.
Reinforcement active learning in the vibrissae system: optimal object localization.
Gordon, Goren; Dorfman, Nimrod; Ahissar, Ehud
2013-01-01
Rats move their whiskers to acquire information about their environment. It has been observed that they palpate novel objects and objects they are required to localize in space. We analyze whisker-based object localization using two complementary paradigms, namely, active learning and intrinsic-reward reinforcement learning. Active learning algorithms select the next training samples according to the hypothesized solution in order to better discriminate between correct and incorrect labels. Intrinsic-reward reinforcement learning uses prediction errors as the reward to an actor-critic design, such that behavior converges to the one that optimizes the learning process. We show that in the context of object localization, the two paradigms result in palpation whisking as their respective optimal solution. These results suggest that rats may employ principles of active learning and/or intrinsic reward in tactile exploration and can guide future research to seek the underlying neuronal mechanisms that implement them. Furthermore, these paradigms are easily transferable to biomimetic whisker-based artificial sensors and can improve the active exploration of their environment. PMID:22789551
Reinforcement active learning in the vibrissae system: optimal object localization.
Gordon, Goren; Dorfman, Nimrod; Ahissar, Ehud
2013-01-01
Rats move their whiskers to acquire information about their environment. It has been observed that they palpate novel objects and objects they are required to localize in space. We analyze whisker-based object localization using two complementary paradigms, namely, active learning and intrinsic-reward reinforcement learning. Active learning algorithms select the next training samples according to the hypothesized solution in order to better discriminate between correct and incorrect labels. Intrinsic-reward reinforcement learning uses prediction errors as the reward to an actor-critic design, such that behavior converges to the one that optimizes the learning process. We show that in the context of object localization, the two paradigms result in palpation whisking as their respective optimal solution. These results suggest that rats may employ principles of active learning and/or intrinsic reward in tactile exploration and can guide future research to seek the underlying neuronal mechanisms that implement them. Furthermore, these paradigms are easily transferable to biomimetic whisker-based artificial sensors and can improve the active exploration of their environment.
[Systemic therapy and hyperthermia for locally advanced soft tissue sarcoma].
Lindner, L H; Angele, M; Dürr, H R; Rauch, J; Bruns, C
2014-05-01
Patients with high-risk soft tissue sarcomas (FNCLCC grades 2-3, > 5 cm and deep lying) are at a high risk of local recurrence or distant metastases despite optimal surgical tumor resection. Therefore, multimodal treatment should be considered for this difficult to treat patient group. Besides surgery, radiation therapy and chemotherapy, hyperthermia has become a valid, complementary treatment option within multimodal treatment concepts. Hyperthermia in this context means the selective heating of the tumor region to temperatures of 40-43 °C for 60 min by microwave radiation in addition to simultaneous chemotherapy or radiation therapy. A randomized phase III study demonstrated that the addition of hyperthermia to neoadjuvant chemotherapy improved tumor response and was associated with a minimal risk of early disease progression as compared to chemotherapy alone. The addition of hyperthermia to a multimodal treatment regimen for high-risk soft tissue sarcoma consisting of surgery, radiation therapy and chemotherapy, either in the neoadjuvant or adjuvant setting after incomplete or marginal tumor resection, significantly improved local progression-free and disease-free survival. Based on these results and due to the generally good tolerability of hyperthermia, this treatment method in combination with chemotherapy should be considered as a standard treatment option within multimodal treatment approaches for locally advanced high-risk soft tissue sarcoma.
Finite-temperature mechanical instability in disordered lattices.
Zhang, Leyou; Mao, Xiaoming
2016-02-01
Mechanical instability takes different forms in various ordered and disordered systems and little is known about how thermal fluctuations affect different classes of mechanical instabilities. We develop an analytic theory involving renormalization of rigidity and coherent potential approximation that can be used to understand finite-temperature mechanical stabilities in various disordered systems. We use this theory to study two disordered lattices: a randomly diluted triangular lattice and a randomly braced square lattice. These two lattices belong to two different universality classes as they approach mechanical instability at T=0. We show that thermal fluctuations stabilize both lattices. In particular, the triangular lattice displays a critical regime in which the shear modulus scales as G∼T(1/2), whereas the square lattice shows G∼T(2/3). We discuss generic scaling laws for finite-T mechanical instabilities and relate them to experimental systems. PMID:26986291
Sun, Wen-Bin; Yan, Bing; Jia, Li-Hui; Wang, Bing-Wu; Yang, Qian; Cheng, Xin; Li, Hong-Feng; Chen, Peng; Wang, Zhe-Ming; Gao, Song
2016-06-01
Two dinuclear dysprosium complexes with the Dy(iii) ions bridged by the neutral bipyrimidine (BPYM) ligand were synthesized and magnetically characterized. They crystallized in a monoclinic and triclinic crystal system, respectively, with almost the same structural core, only differing in the lattice solvent molecules. Alternating current (ac) susceptibility measurements revealed that they exhibit significant slow relaxation of magnetization until 25 K in the absence of a dc field. The single and double relaxation processes were assigned to one and two types of Dy(iii) environments in the two dimmers, respectively, with barriers of 266 and 345 K under zero field conditions. The magnetic hysteresis loops of 1 and 2 were both observed up to 2.5 K. PMID:27143486
Sun, Wen-Bin; Yan, Bing; Jia, Li-Hui; Wang, Bing-Wu; Yang, Qian; Cheng, Xin; Li, Hong-Feng; Chen, Peng; Wang, Zhe-Ming; Gao, Song
2016-06-01
Two dinuclear dysprosium complexes with the Dy(iii) ions bridged by the neutral bipyrimidine (BPYM) ligand were synthesized and magnetically characterized. They crystallized in a monoclinic and triclinic crystal system, respectively, with almost the same structural core, only differing in the lattice solvent molecules. Alternating current (ac) susceptibility measurements revealed that they exhibit significant slow relaxation of magnetization until 25 K in the absence of a dc field. The single and double relaxation processes were assigned to one and two types of Dy(iii) environments in the two dimmers, respectively, with barriers of 266 and 345 K under zero field conditions. The magnetic hysteresis loops of 1 and 2 were both observed up to 2.5 K.
A transportable optical lattice clock
NASA Astrophysics Data System (ADS)
Vogt, Stefan; Häfner, Sebastian; Grotti, Jacopo; Koller, Silvio; Al-Masoudi, Ali; Sterr, Uwe; Lisdat, Christian
2016-06-01
We present the experimental setup and first results of PTB's transportable 87Sr clock. It consists of a physics package, several compact laser breadboards, and a transportable high finesse cavity for the clock laser. A comparison of the transportable system with our stationary optical lattice clock yields an instability of 2.2 x 10-15 √s/τ for the transportable clock. The current fractional uncertainty of 1 × 10-15 is still limited by the not yet fully evaluated light shift from the free running optical lattice laser operated near the magic wavelength. We are currently improving our transportable system to reach an uncertainty at or below the 10-17 level, which will finaly be limited by the uncertainty in blackbody radiation shift correction.
Matter-wave propagation in optical lattices: geometrical and flat-band effects
Metcalf, Mekena; Chern, Gia-Wei; Di Ventra, Massimiliano; Chien, Chih-Chun
2016-03-17
Here we report that the geometry of optical lattices can be engineered allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question feasible to atomic systems is related to the speed of propagation of matter-waves as a function of the lattice geometry. To address this issue, we have investigated theoretically the quantum transport of non-interacting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, and the cross-linked square latticemore » has an even faster propagation velocity. The increase results from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity due to its localized atoms. Lastly, we discuss possible realizations of those dynamical phenomena.« less