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1

Conjugate gradient type methods for linear systems with complex symmetric coefficient matrices  

NASA Technical Reports Server (NTRS)

We consider conjugate gradient type methods for the solution of large sparse linear system Ax equals b with complex symmetric coefficient matrices A equals A(T). Such linear systems arise in important applications, such as the numerical solution of the complex Helmholtz equation. Furthermore, most complex non-Hermitian linear systems which occur in practice are actually complex symmetric. We investigate conjugate gradient type iterations which are based on a variant of the nonsymmetric Lanczos algorithm for complex symmetric matrices. We propose a new approach with iterates defined by a quasi-minimal residual property. The resulting algorithm presents several advantages over the standard biconjugate gradient method. We also include some remarks on the obvious approach to general complex linear systems by solving equivalent real linear systems for the real and imaginary parts of x. Finally, numerical experiments for linear systems arising from the complex Helmholtz equation are reported.

Freund, Roland

1989-01-01

2

Linearization Method and Linear Complexity  

NASA Astrophysics Data System (ADS)

We focus on the relationship between the linearization method and linear complexity and show that the linearization method is another effective technique for calculating linear complexity. We analyze its effectiveness by comparing with the logic circuit method. We compare the relevant conditions and necessary computational cost with those of the Berlekamp-Massey algorithm and the Games-Chan algorithm. The significant property of a linearization method is that it needs no output sequence from a pseudo-random number generator (PRNG) because it calculates linear complexity using the algebraic expression of its algorithm. When a PRNG has n [bit] stages (registers or internal states), the necessary computational cost is smaller than O(2n). On the other hand, the Berlekamp-Massey algorithm needs O(N2) where N(?2n) denotes period. Since existing methods calculate using the output sequence, an initial value of PRNG influences a resultant value of linear complexity. Therefore, a linear complexity is generally given as an estimate value. On the other hand, a linearization method calculates from an algorithm of PRNG, it can determine the lower bound of linear complexity.

Tanaka, Hidema

3

Complex symmetric matrices with strongly stable iterates  

NASA Technical Reports Server (NTRS)

Complex-valued symmetric matrices are studied. A simple expression for the spectral norm of such matrices is obtained, by utilizing a unitarily congruent invariant form. A sharp criterion is provided for identifying those symmetric matrices whose spectral norm is not exceeding one: such strongly stable matrices are usually sought in connection with convergent difference approximations to partial differential equations. As an example, the derived criterion is applied to conclude the strong stability of a Lax-Wendroff scheme.

Tadmor, E.

1985-01-01

4

Soliton dynamics in symmetric and non-symmetric complex potentials  

NASA Astrophysics Data System (ADS)

Soliton propagation dynamics under the presence of a complex potential are investigated. A large variety of qualitatively different potentials, including periodic, semi-infinite periodic and localized potentials, is considered. Cases of both symmetric and non-symmetric potentials are studied in terms of their effect on soliton dynamics. The rich set of dynamical features of soliton propagation includes dynamical trapping, periodic and non-periodic soliton mass variation and non-reciprocal scattering dynamics. These features are systematically investigated with the utilization of an effective particle phase space approach which is shown in remarkable agreement with direct numerical simulations. The generality of the results enables the consideration of potential applications where the inhomogeneity of the gain and loss is appropriately engineered in order to provide desirable soliton dynamics.

Kominis, Yannis

2015-01-01

5

Experimental scheme for unambiguous discrimination of linearly independent symmetric states  

SciTech Connect

We propose an experimental setup for discriminating four linearly independent nonorthogonal symmetric quantum states. The setup is based on linear optics only and can be configured to implement both optimal unambiguous state discrimination [Chefles and Barnett, Phys. Lett. A 250, 223 (1998)] and minimum error discrimination. In both cases, the setup is characterized by an optimal success probability. The experimental setup can be generalized to the case of discrimination among N linearly nonorthogonal symmetric quantum states. We also study the discrimination between two incoherent superpositions of symmetric states. In this case, the setup also achieves an optimal success probability in the case of unambiguous discrimination as well as minimum error discrimination.

Jimenez, O.; Burgos-Inostroza, E.; Delgado, A.; Saavedra, C. [Center for Quantum Optics and Quantum Information, Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Sanchez-Lozano, X. [Center for Quantum Optics and Quantum Information, Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Instituto de Fisica, Universidad de Guanajuato, P. O. Box E-143, 37150, Leon Guanajuato (Mexico)

2007-12-15

6

Complex PT-symmetric nonlinear Schrödinger equation and Burgers equation.  

PubMed

The complex -symmetric nonlinear wave models have drawn much attention in recent years since the complex -symmetric extensions of the Korteweg-de Vries (KdV) equation were presented in 2007. In this review, we focus on the study of the complex -symmetric nonlinear Schrödinger equation and Burgers equation. First of all, we briefly introduce the basic property of complex symmetry. We then report on exact solutions of one- and two-dimensional nonlinear Schrödinger equations (known as the Gross-Pitaevskii equation in Bose-Einstein condensates) with several complex -symmetric potentials. Finally, some complex -symmetric extension principles are used to generate some complex -symmetric nonlinear wave equations starting from both -symmetric (e.g. the KdV equation) and non- -symmetric (e.g. the Burgers equation) nonlinear wave equations. In particular, we discuss exact solutions of some representative ones of the complex -symmetric Burgers equation in detail. PMID:23509385

Yan, Zhenya

2013-04-28

7

Linear transformations on symmetric matrices II  

Microsoft Academic Search

Let Tbe a linear mapping on the space of n× nsymmetric matrices over a field Fof characteristic not equal to two. We obtain the structure of Tfor the following cases:(i) Tpreserves matrices of rank less than three; (ii) Tpreserves nonzero matrices of rank less than K + 1 where Kis a fixed positive integer less than nand Fis algebraically closed;

G. H. Chan; M. H. Lim

1992-01-01

8

Invisibility in {PT}-symmetric complex crystals  

NASA Astrophysics Data System (ADS)

Bragg scattering in sinusoidal {PT}-symmetric complex crystals of finite thickness is theoretically investigated by the derivation of exact analytical expressions for reflection and transmission coefficients in terms of modified Bessel functions of first kind. The analytical results indicate that unidirectional invisibility, recently predicted for such crystals by coupled-mode theory (Z Lin et al 2011 Phys. Rev. Lett. http://dx.doi.org/10.1103/PhysRevLett.106.213901), breaks down for crystals containing a large number of unit cells. In particular, for a given modulation depth in a shallow sinusoidal potential, three regimes are encountered as the crystal thickness is increased. At short lengths the crystal is reflectionless and invisible when probed from one side (unidirectional invisibility), whereas at intermediate lengths the crystal remains reflectionless but not invisible; for longer crystals both unidirectional reflectionless and invisibility properties are broken.

Longhi, Stefano

2011-12-01

9

Minimal Residual Methods for Complex Symmetric, Skew Symmetric ...  

E-print Network

Apr 26, 2013 ... lems, which could arise in Helmholtz equations, linear systems that involve Hankel matrices, or applications ...... preconditioners like diagonal preconditioning and incomplete Cholesky factorization .... function pinv. For TSVD ...

Sou-Cheng (Terrya) Choi

2013-04-26

10

Linear programming using symmetric triangular intuitionistic fuzzy numbers  

NASA Astrophysics Data System (ADS)

This paper introduces Symmetric Triangular Intuitionistic Fuzzy Numbers (STriFNs) and also proposes a new type of intuitionistic fuzzy arithmetic operations on STriIFNs. A special ranking function for ordering STriIFNs has been introduced. A solution methodology for Intuitionistic Fuzzy Linear Programming Problems (IFLPPs) with STriIFNs as parameters has been proposed by using Intuitionistic Fuzzy Simplex Method and the arithmetic operations on STriIFNs. Finally, an illustrative numerical example is presented to demonstrate the proposed approach.

Parvathi, R.; Malathi, C.

2012-09-01

11

Symmetrical directional dual-tree complex wavelet packet transform.  

PubMed

In this study, a symmetrical directional complex discrete wavelet packet transform, which can be applied directly to the quadrature format signals and has the ability of mapping directional information during decomposition stage, is proposed. With the proposed symmetrical directional complex wavelet packet transform, traditional symmetrical phasing filter technique, which is used for quadrature signal to directional signal conversion, is eliminated and the computational complexity of whole process is reduced. The performance of proposed method is examined in detail using real quadrature embolic signals. PMID:25570085

Serbes, Gorkem; Gulcur, Halil Ozcan; Aydin, Nizamettin

2014-08-01

12

Trigonometry of 'complex Hermitian'-type homogeneous symmetric spaces  

Microsoft Academic Search

This paper contains a thorough study of the trigonometry of the homogeneous symmetric spaces in the Cayley-Klein-Dickson family of spaces of 'complex Hermitian' type and rank-one. The complex Hermitian elliptic CP^N and hyperbolic CH^N spaces, their analogues with indefinite Hermitian metric and some non-compact symmetric spaces associated to SL(N+1,R) are the generic members in this family. The method encapsulates trigonometry

Ramón Ortega; Mariano Santander

2002-01-01

13

Norm estimates of complex symmetric operators applied to quantum systems  

E-print Network

This paper communicates recent results in theory of complex symmetric operators and shows, through two non-trivial examples, their potential usefulness in the study of Schr\\"odinger operators. In particular, we propose a formula for computing the norm of a compact complex symmetric operator. This observation is applied to two concrete problems related to quantum mechanical systems. First, we give sharp estimates on the exponential decay of the resolvent and the single-particle density matrix for Schr\\"odinger operators with spectral gaps. Second, we provide new ways of evaluating the resolvent norm for Schr\\"odinger operators appearing in the complex scaling theory of resonances.

Emil Prodan; Stephan R. Garcia; Mihai Putinar

2005-10-24

14

Evolution of linear perturbations in spherically symmetric dust spacetimes  

NASA Astrophysics Data System (ADS)

We present results from a numerical code implementing a new method to solve the master equations describing the evolution of linear perturbations in a spherically symmetric but inhomogeneous background. This method can be used to simulate several configurations of physical interest, such as relativistic corrections to structure formation, the lensing of gravitational waves (GWs) and the evolution of perturbations in a cosmological void model. This paper focuses on the latter problem, i.e. structure formation in a Hubble scale void in the linear regime. This is considerably more complicated than linear perturbations of a homogeneous and isotropic background because the inhomogeneous background leads to coupling between density perturbations and rotational modes of the spacetime geometry, as well as GWs. Previous analyses of this problem ignored this coupling in the hope that the approximation does not affect the overall dynamics of structure formation in such models. We show that for a giga-parsec void, the evolution of the density contrast is well approximated by the previously studied decoupled evolution only for very large-scale modes. However, the evolution of the gravitational potentials within the void is inaccurate at more than the 10% level, and is even worse on small scales.

February, S.; Larena, J.; Clarkson, C.; Pollney, D.

2014-09-01

15

Trigonometry of 'complex Hermitian' type homogeneous symmetric spaces  

E-print Network

This paper contains a thorough study of the trigonometry of the homogeneous symmetric spaces in the Cayley-Klein-Dickson family of spaces of 'complex Hermitian' type and rank-one. The complex Hermitian elliptic CP^N and hyperbolic CH^N spaces, their analogues with indefinite Hermitian metric and some non-compact symmetric spaces associated to SL(N+1,R) are the generic members in this family. The method encapsulates trigonometry for this whole family of spaces into a single "basic trigonometric group equation", and has 'universality' and '(self)-duality' as its distinctive traits. All previously known results on the trigonometry of CP^N and CH^N follow as particular cases of our general equations. The physical Quantum Space of States of any quantum system belongs, as the complex Hermitian space member, to this parametrised family; hence its trigonometry appears as a rather particular case of the equations we obtain.

Ramon Ortega; Mariano Santander

2001-12-14

16

A study of PT-symmetric Non-linear Schroedinger Equation  

E-print Network

Systems governed by the Non-linear Schroedinger Equation (NLSE) with various external PT-symmetric potentials are considered. Exact solutions have been obtained for the same through the method of ansatz, some of them being solitonic in nature. It is found that only the unbroken PT-symmetric phase is realized in these systems, characterized by real energies.

K. Nireekshan Reddy; Subhrajit Modak; Kumar Abhinav; Prasanta K. Panigrahi

2014-02-24

17

Bounds for axially symmetric linear perturbations for the extreme Kerr black hole  

E-print Network

We obtain remarkably simple integral bounds for axially symmetric linear perturbations for the extreme Kerr black hole in terms of conserved energies. From these estimates we deduce pointwise bounds for the perturbations outside the horizon.

Sergio Dain; Ivan Gentile de Austria

2015-01-15

18

Bounds for axially symmetric linear perturbations for the extreme Kerr black hole  

E-print Network

We obtain remarkably simple integral bounds for axially symmetric linear perturbations for the extreme Kerr black hole in terms of conserved energies. From these estimates we deduce pointwise bounds for the perturbations outside the horizon.

Dain, Sergio

2015-01-01

19

Transparency of PT-symmetric complex potentials for coherent injection  

E-print Network

It is known that when two identical waves are injected from left and right on a complex PT-symmetric scattering potential the two-port s-matrix can have uni-modular eigenvalues. If this happens for all energies, there occurs a perfect emission of waves at both ends. We call this phenomenon transparency. Using the versatile PT-Symmetric complex Scarf II potential, we demonstrate analytically that the transparency occurs when the potential has real discrete spectrum i.e., when PT-symmetry is exact(unbroken). Next, we find that exactness of PT-symmetry is only sufficient but not necessary for the transparency. Two other PT-symmetric domains of Scarf II reveal transparency without the PT-symmetry being exact. In these two cases there exist only scattering states. In one case the real part of the potential is a well devoid of real discrete spectrum and in the other real part is a barrier. Other numerically solved models also support our findings.

Zafar Ahmed; Joseph Amal Nathan

2014-10-21

20

Scattering of linear and nonlinear waves in a waveguide array with a PT-symmetric defect  

SciTech Connect

We study the scattering of linear and nonlinear waves in a long waveguide array with a parity-time (PT)-symmetric defect created by two waveguides with balanced gain and loss. We present exact solutions for the scattering of linear waves on such a defect, and then demonstrate numerically that the linear theory can describe, with a good accuracy, the soliton scattering in the case of weak nonlinearity. We reveal that the reflected and transmitted linear and nonlinear waves can be amplified substantially after interaction with the PT-symmetric defect thus allowing an active control of the wave scattering in the array.

Dmitriev, Sergey V.; Suchkov, Sergey V. [Institute for Metals Superplasticity Problems, Russian Academy of Science, Ufa RU-450001 (Russian Federation); Sukhorukov, Andrey A.; Kivshar, Yuri S. [Nonlinear Physics Centre, Research School of Physics and Engineering,Australian National University, Canberra, ACT 0200 (Australia)

2011-07-15

21

Algorithm 937: MINRES-QLP for Symmetric and Hermitian Linear Equations and Least-Squares Problems.  

PubMed

We describe algorithm MINRES-QLP and its FORTRAN 90 implementation for solving symmetric or Hermitian linear systems or least-squares problems. If the system is singular, MINRES-QLP computes the unique minimum-length solution (also known as the pseudoinverse solution), which generally eludes MINRES. In all cases, it overcomes a potential instability in the original MINRES algorithm. A positive-definite pre-conditioner may be supplied. Our FORTRAN 90 implementation illustrates a design pattern that allows users to make problem data known to the solver but hidden and secure from other program units. In particular, we circumvent the need for reverse communication. Example test programs input and solve real or complex problems specified in Matrix Market format. While we focus here on a FORTRAN 90 implementation, we also provide and maintain MATLAB versions of MINRES and MINRES-QLP. PMID:25328255

Choi, Sou-Cheng T; Saunders, Michael A

2014-02-01

22

Algorithm 937: MINRES-QLP for Symmetric and Hermitian Linear Equations and Least-Squares Problems  

PubMed Central

We describe algorithm MINRES-QLP and its FORTRAN 90 implementation for solving symmetric or Hermitian linear systems or least-squares problems. If the system is singular, MINRES-QLP computes the unique minimum-length solution (also known as the pseudoinverse solution), which generally eludes MINRES. In all cases, it overcomes a potential instability in the original MINRES algorithm. A positive-definite pre-conditioner may be supplied. Our FORTRAN 90 implementation illustrates a design pattern that allows users to make problem data known to the solver but hidden and secure from other program units. In particular, we circumvent the need for reverse communication. Example test programs input and solve real or complex problems specified in Matrix Market format. While we focus here on a FORTRAN 90 implementation, we also provide and maintain MATLAB versions of MINRES and MINRES-QLP. PMID:25328255

Choi, Sou-Cheng T.; Saunders, Michael A.

2014-01-01

23

Solitons supported by complex PT-symmetric Gaussian potentials  

SciTech Connect

The existence and stability of fundamental, dipole, and tripole solitons in Kerr nonlinear media with parity-time-symmetric Gaussian complex potentials are reported. Fundamental solitons are stable not only in deep potentials but also in shallow potentials. Dipole and tripole solitons are stable only in deep potentials, and tripole solitons are stable in deeper potentials than for dipole solitons. The stable regions of solitons increase with increasing potential depth. The power of solitons increases with increasing propagation constant or decreasing modulation depth of the potentials.

Hu Sumei [Laboratory of Photonic Information Technology, South China Normal University, Guangzhou 510631 (China); Department of Physics, Guangdong University of Petrochemical Technology, Maoming 525000 (China); Ma Xuekai; Lu Daquan; Yang Zhenjun; Zheng Yizhou; Hu Wei [Laboratory of Photonic Information Technology, South China Normal University, Guangzhou 510631 (China)

2011-10-15

24

IMPROVED SEED METHODS FOR SYMMETRIC POSITIVE DEFINITE LINEAR EQUATIONS WITH MULTIPLE RIGHT-HAND  

E-print Network

IMPROVED SEED METHODS FOR SYMMETRIC POSITIVE DEFINITE LINEAR EQUATIONS WITH MULTIPLE RIGHT-HAND positive definite systems of linear equations with multiple right-hand sides. The seed conjugate gradient method solves one right-hand side with the conjugate gradient method and simultaneously projects over

Morgan, Ron

25

Talbot self-imaging in PT-symmetric complex crystals  

NASA Astrophysics Data System (ADS)

The Talbot effect, i.e., the self-imaging property of a periodic wave in near-field diffraction, is a remarkable interference phenomenon in paraxial systems with continuous translational invariance. In crystals, i.e., systems with discrete translational invariance, self-imaging has been regarded so far as a rare effect, restricted to special sets of initial field distributions. Here it is shown that in a class of gapless PT-symmetric complex crystals at the symmetry-breaking threshold Talbot revivals can arise for almost any initial periodic wave distribution which is commensurate with the lattice period. A possible experimental realization of commensurate Talbot self-imaging for light pulses in complex "temporal" crystals, realized in an optical dispersive fiber loop with amplitude and phase modulators, is briefly discussed.

Longhi, Stefano

2014-10-01

26

A new Krylov-subspace method for symmetric indefinite linear systems  

SciTech Connect

Many important applications involve the solution of large linear systems with symmetric, but indefinite coefficient matrices. For example, such systems arise in incompressible flow computations and as subproblems in optimization algorithms for linear and nonlinear programs. Existing Krylov-subspace iterations for symmetric indefinite systems, such as SYMMLQ and MINRES, require the use of symmetric positive definite preconditioners, which is a rather unnatural restriction when the matrix itself is highly indefinite with both many positive and many negative eigenvalues. In this note, the authors describe a new Krylov-subspace iteration for solving symmetric indefinite linear systems that can be combined with arbitrary symmetric preconditioners. The algorithm can be interpreted as a special case of the quasi-minimal residual method for general non-Hermitian linear systems, and like the latter, it produces iterates defined by a quasi-minimal residual property. The proposed method has the same work and storage requirements per iteration as SYMMLQ or MINRES, however, it usually converges in considerably fewer iterations. Results of numerical experiments are reported.

Freund, R.W. [AT and T Bell Labs., Murray Hill, NJ (United States); Nachtigal, N.M. [Oak Ridge National Lab., TN (United States). Mathematical Sciences Section

1994-10-01

27

Spherically symmetric analysis on open FLRW solution in non-linear massive gravity  

SciTech Connect

We study non-linear massive gravity in the spherically symmetric context. Our main motivation is to investigate the effect of helicity-0 mode which remains elusive after analysis of cosmological perturbation around an open Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. The non-linear form of the effective energy-momentum tensor stemming from the mass term is derived for the spherically symmetric case. Only in the special case where the area of the two sphere is not deviated away from the FLRW universe, the effective energy momentum tensor becomes completely the same as that of cosmological constant. This opens a window for discriminating the non-linear massive gravity from general relativity (GR). Indeed, by further solving these spherically symmetric gravitational equations of motion in vacuum to the linear order, we obtain a solution which has an arbitrary time-dependent parameter. In GR, this parameter is a constant and corresponds to the mass of a star. Our result means that Birkhoff's theorem no longer holds in the non-linear massive gravity and suggests that energy can probably be emitted superluminously (with infinite speed) on the self-accelerating background by the helicity-0 mode, which could be a potential plague of this theory.

Chiang, Chien-I; Izumi, Keisuke; Chen, Pisin, E-mail: chienichiang@berkeley.edu, E-mail: izumi@phys.ntu.edu.tw, E-mail: chen@slac.stanford.edu [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei 10617, Taiwan (China)

2012-12-01

28

The complexity of propositional linear temporal logics  

Microsoft Academic Search

The complexity of satisfiability and determination of truth in a particular finite structure are considered for different propositional linear temporal logics. It is shown that these problems are NP-complete for the logic with F and are PSPACE-complete for the logics with F, X, with U, with U, S, X operators and for the extended logic with regular operators given by

A. Prasad Sistla; Edmund M. Clarke

1985-01-01

29

Scattering of solitons by complex ???????? symmetric Gaussian potentials.  

PubMed

Scattering of bright soliton by -symmetric potential well and barrier is investigated numerically. The numerical results show that increasing strength of real part of -symmetric potential can cause repeated reflection, transmission, and trapping regions due to energy exchange between the kinetic energy of incoming soliton and the internal modes of the potential structure. In addition, the width of the scattering windows increases with increase of the imaginary part of the -symmetric potential. The results obtained can be exploited in the development of interferometry as well as for diodes devices in information technology. PMID:25321582

Al-Marzoug, S M

2014-09-01

30

Generation of Symmetric Dicke States of Remote Qubits with Linear Optics  

SciTech Connect

We propose a method for generating all symmetric Dicke states, either in the long-lived internal levels of N massive particles or in the polarization degrees of freedom of photonic qubits, using linear optical tools only. By means of a suitable multiphoton detection technique, erasing Welcher-Weg information, our proposed scheme allows the generation and measurement of an important class of entangled multiqubit states.

Thiel, C.; Zanthier, J. von [Institut fuer Optik, Information und Photonik, Max-Planck Forschungsgruppe, Universitaet Erlangen-Nuernberg, 91058 Erlangen (Germany); Bastin, T. [Institut de Physique Nucleaire, Atomique et de Spectroscopie, Universite de Liege, 4000 Liege (Belgium); Solano, E. [Physics Department, ASC, and CeNS, Ludwig-Maximilians-Universitaet, Theresienstrasse 37, 80333 Munich (Germany); Seccion Fisica, Departamento de Ciencias, Pontificia Universidad Catolica del Peru, Apartado Postal 1761, Lima (Peru); Agarwal, G. S. [Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078-3072 (United States)

2007-11-09

31

A JACOBIDAVIDSON METHOD FOR SOLVING COMPLEX SYMMETRIC EIGENVALUE PROBLEMS  

E-print Network

walls. This approach leads to a generalized real symmetric eigenvalue problem [2]. However, in cases where the damping of higher modes is more important than the high efficiency of a cavity, and for cavities with ferrite inserts for tuning purposes, the currents produced in the walls or in the ferrite

Hochstenbach, Michiel

32

Real discrete spectrum in the complex non-PT-symmetric Scarf II potential  

E-print Network

Hitherto, it is well known that complex PT-symmetric Scarf II has real discrete spectrum in the parametric domain of unbroken PT-symmetry. We reveal new interesting complex, non-PT-symmetric parametric domains of this versatile potential, $V(x)$, where the spectrum is again discrete and real. Showing that the Hamiltonian, $p^2/2m+V(x)$, in the new cases is pseudo-Hermitian could be challenging, if possible.

Zafar Ahmed; Joseph Amal Nathan

2015-01-20

33

The Real Anatomy of Complex Linear Superfields  

E-print Network

Recent work on classicication of off-shell representations of N-extended worldline supersymmetry without central charges has uncovered an unexpectedly vast number--trillions of even just (chromo)topology types--of so called adinkraic supermultiplets. Herein, we show by explicit analysis that a long-known but rarely used representation, the complex linear supermultiplet, is not adinkraic, cannot be decomposed locally, but may be reduced by means of a Wess-Zumino type gauge. This then indicates that the already unexpectedly vast number of adinkraic off-shell supersymmetry representations is but the proverbial tip of the iceberg.

S. J. Gates Jr; J. Hallett; T. Hubsch; K. Stiffler

2012-02-20

34

The Real Anatomy of Complex Linear Superfields  

E-print Network

Recent work on classicication of off-shell representations of N-extended worldline supersymmetry without central charges has uncovered an unexpectedly vast number--trillions of even just (chromo)topology types--of so called adinkraic supermultiplets. Herein, we show by explicit analysis that a long-known but rarely used representation, the complex linear supermultiplet, is not adinkraic, cannot be decomposed locally, but may be reduced by means of a Wess-Zumino type gauge. This then indicates that the already unexpectedly vast number of adinkraic off-shell supersymmetry representations is but the proverbial tip of the iceberg.

Gates, S J; Hubsch, T; Stiffler, K

2012-01-01

35

Future global non-linear stability of surface symmetric solutions of the Einstein-Vlasov system with a cosmological constant  

E-print Network

We show future global non-linear stability of surface symmetric solutions of the Einstein-Vlasov system with a positive cosmological constant. Estimates of higher derivatives of the metric and the matter terms are obtained using an inductive argument. In a recent research monograph Ringstr\\"{o}m shows future non-linear stability of (not necessarily symmetric) solutions of the Einstein-Vlasov system with a non-linear scalar field if certain local estimates on the geometry and the matter terms are fulfilled. We show that these assumptions are satisfied at late times for the case under consideration here which together with Cauchy stability leads to our main conclusion.

Ernesto Nungesser

2014-02-27

36

Krylov subspace methods for complex non-Hermitian linear systems. Thesis  

NASA Technical Reports Server (NTRS)

We consider Krylov subspace methods for the solution of large sparse linear systems Ax = b with complex non-Hermitian coefficient matrices. Such linear systems arise in important applications, such as inverse scattering, numerical solution of time-dependent Schrodinger equations, underwater acoustics, eddy current computations, numerical computations in quantum chromodynamics, and numerical conformal mapping. Typically, the resulting coefficient matrices A exhibit special structures, such as complex symmetry, or they are shifted Hermitian matrices. In this paper, we first describe a Krylov subspace approach with iterates defined by a quasi-minimal residual property, the QMR method, for solving general complex non-Hermitian linear systems. Then, we study special Krylov subspace methods designed for the two families of complex symmetric respectively shifted Hermitian linear systems. We also include some results concerning the obvious approach to general complex linear systems by solving equivalent real linear systems for the real and imaginary parts of x. Finally, numerical experiments for linear systems arising from the complex Helmholtz equation are reported.

Freund, Roland W.

1991-01-01

37

Conformal geometry of symmetric spaces and generalized linear-fractional maps of Krein-Shmul'yan  

SciTech Connect

The matrix balls B{sub p,q} consisting of pxq-matrices of norm <1 over C are considered. These balls are one possible realization of the symmetric spaces B{sub p,q}=U(p,q)/U(p)xU(q). Generalized linear-fractional maps are maps B{sub p,q}{yields}B{sub r,s} of the form Z{yields}K+LZ(1-NZ){sup -1} (they are in general neither injective nor surjective). Characterizations of generalized linear-fractional maps in the spirit of the 'fundamental theorem of projective geometry' are obtained: for a certain family of submanifolds of B{sub p,q} ('quasilines') it is shown that maps taking quasilines to quasilines are generalized linear-fractional. In addition, for the standard field of cones on B{sub p,q} (described by the inequality rkdZ{<=}1) it is shown that maps taking cones to cones are generalized linear-fractional.

Neretin, Yu A [Moscow State Institute of Electronics and Mathematics (Technical University), Moscow (Russian Federation)

1999-02-28

38

An efficient EM-ICP algorithm for symmetric consistent non-linear registration of point sets.  

PubMed

In this paper, we present a new algorithm for non-linear registration of point sets. We estimate both forward and backward deformations fields best superposing the two point sets of interest and we make sure that they are consistent with each other by designing a symmetric cost function where they are coupled. Regularisation terms are included in this cost function to enforce deformation smoothness. Then we present a two-step iterative algorithm to optimise this cost function, where the two fields and the fuzzy matches between the two sets are estimated in turn. Building regularisers using the RKHS theory allows to obtain fast and efficient closed-form solutions for the optimal fields. The resulting algorithm is efficient and can deal with large point sets. PMID:20879364

Combès, Benoit; Prima, Sylvain

2010-01-01

39

Improved Seed Methods for Symmetric Positive Definite Linear Equations with Multiple Right-hand Sides  

E-print Network

We consider symmetric positive definite systems of linear equations with multiple right-hand sides. The seed conjugate gradient method solves one right-hand side with the conjugate gradient method and simultaneously projects over the Krylov subspace thus developed for the other right-hand sides. Then the next system is solved and used to seed the remaining ones. Rounding error in the conjugate gradient method limits how much the seeding can improve convergence. We propose three changes to the seed conjugate gradient method: only the first right-hand side is used for seeding, this system is solved past convergence, and the roundoff error is controlled with some reorthogonalization. We will show that results are actually better with only one seeding, even in the case of related right-hand sides. Controlling rounding error gives the potential for rapid convergence for the second and subsequent right-hand sides.

Abdou M. Abdel-Rehim; Ronald B. Morgan; Walter Wilcox

2008-10-02

40

Symmetrized complex amplitudes for He double photoionization from the time-dependent close coupling and exterior complex scaling methods  

SciTech Connect

Symmetrized complex amplitudes for the double photoionization of helium are computed by the time-dependent close-coupling and exterior complex scaling methods, and it is demonstrated that both methods are capable of the direct calculation of these amplitudes. The results are found to be in excellent agreement with each other and in very good agreement with results of other ab initio methods and experiment.

Horner, D.A.; Colgan, J.; Martin, F.; McCurdy, C.W.; Pindzola, M.S.; Rescigno, T.N.

2004-06-01

41

Symmetrical modified dual tree complex wavelet transform for processing quadrature Doppler ultrasound signals.  

PubMed

Dual-tree complex wavelet transform (DTCWT), which is a shift invariant transform with limited redundancy, is an improved version of discrete wavelet transform. Complex quadrature signals are dual channel signals obtained from the systems employing quadrature demodulation. An example of such signals is quadrature Doppler signal obtained from blood flow analysis systems. Prior to processing Doppler signals using the DTCWT, directional flow signals must be obtained and then two separate DTCWT applied, increasing the computational complexity. In this study, in order to decrease computational complexity, a symmetrical modified DTCWT algorithm is proposed (SMDTCWT). A comparison between the new transform and the symmetrical phasing-filter technique is presented. Additionally denoising performance of SMDTCWT is compared with the DWT and the DTCWT using simulated signals. The results show that the proposed method gives the same output as the symmetrical phasing-filter method, the computational complexity for processing quadrature signals using DTCWT is greatly reduced and finally the SMDTCWT based denoising outperforms conventional DWT with same computational complexity. PMID:22255416

Serbes, G; Aydin, N

2011-01-01

42

A numerical evaluation of sparse direct solvers for the solution of large sparse symmetric linear systems of equations  

Microsoft Academic Search

In recent years a number of solvers for the direct solution of large sparse, symmetric linear systems of equations have been developed. These include solvers that are designed for the solution of positive-denite systems as well as those that are principally intended for solving indenite problems. The available choice can make it dicult for users to know which solver is

Nicholas I. M. Gould; Jennifer A. Scott; Yifan Hu

2007-01-01

43

On the complexity of quantified linear systems Salvatore Ruggieria,  

E-print Network

On the complexity of quantified linear systems Salvatore Ruggieria, , Pavlos Eirinakisb,1 , K fragment of the first- order theory of linear arithmetic. Quantified propositional formulas of linear inequalities with (k - 1) quantifier alternations are log-space complete in P k or P k depending on the initial

Ruggieri, Salvatore

44

Novel supramolecular assembly of symmetrical mixed-metal-ligand complexes of dioxouranium(VI).  

PubMed

Some binary and ternary novel complexes of dioxouranium(VI) with 8-hydroxy-7-quinolinecarboxaldehyde (OXH) have been prepared and characterized by elemental analyses, magnetic susceptibility measurements and spectral studies. Coordination effects on the vibrational spectra of the ligands have been investigated. The amine exchange reactions of coordinated Schiff bases in these complexes have been also studied, which reveal symmetrical tetradentate Schiff base complexes. Metal exchange reaction of dioxouranium(VI) complexes was obtained when reacted with tetradentate Schiff base complexes of Cu(II) with ZrCl(4)/UO(2)(CH(3)COO)(2) giving heterobinuclear complexes. Magnetic, electronic and IR spectral data suggest the configurations of distorted square planar ligand field copper(II) complexes. The ligands behave as bi-(O,O) and tetradentate (N(2),O(2)) donors. El-Sonbati equation has been used to evaluate the symmetric stretching frequency from which the F(U-O) and F(UO,UO)(-) were calculated. The bond distances of these complexes were also investigated. PMID:16843709

Mubarak, Ahmed T

2006-12-01

45

Linear stability of spherically symmetric and wormhole solutions supported by the sine-Gordon ghost scalar field  

SciTech Connect

In this paper we investigate wormhole and spherically symmetric solutions in four-dimensional gravity plus a matter source consisting of a ghost scalar field with a sine-Gordon potential. For the wormhole solutions we also include the possibility of electric and/or magnetic charges. For both types of solutions we perform a linear stability analysis and show that the wormhole solutions are stable and that when one turns on the electric and/or magnetic field the solution remains stable. The linear stability analysis of the spherically symmetric solutions indicates that they can be stable or unstable depending on one of the parameters of the system. This result for the spherically symmetric solution is nontrivial since a previous investigation of four-dimensional gravity plus a ghost scalar field with a {lambda}{phi}{sup 4} interaction found only unstable spherically symmetric solutions. Both the wormhole and spherically symmetric solutions presented here asymptotically go to anti-de Sitter space-time.

Dzhunushaliev, Vladimir [Institute for Basic Research, Eurasian National University, Astana, 010008 (Kazakhstan); Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Institut fuer Physik, Universitaet Oldenburg, Postfach 2503 D-26111 Oldenburg (Germany); Folomeev, Vladimir [Institute of Physicotechnical Problems and Material Science of the NAS of the Kyrgyz Republic, 265 a, Chui Street, Bishkek, 720071 (Kyrgyzstan); Institut fuer Physik, Universitaet Oldenburg, Postfach 2503 D-26111 Oldenburg (Germany); Singleton, Douglas [Physics Department, CSU Fresno, Fresno, California 93740-8031 (United States); Myrzakulov, Ratbay [Eurasian International Center for Theoretical Physics and Department of General and Theoretical Physics, Eurasian National University, Astana, 010008 (Kazakhstan)

2010-08-15

46

A Shared and Programmable Maximum-Confident Discrimination among Linearly Dependent Symmetric Qubit States  

NASA Astrophysics Data System (ADS)

We show how a shared and programmable maximum-confidence discrimination (SPMCD) can be implemented by two remote parters Alice and Bob. Here Bob is given a qubit prepared in one of N linearly dependent symmetric equiprobable states. Alice has the knowledge of Bob's signal states, but Bob has not. We build a quantum network that would be able to perform various desired maximum-confidence discrimination among Bob's measured (data) states depending on Alice's auxiliary (program) state. The SPMCD can be thought of as a two-step process, in which a two-outcome shared and programmable probability operator measure (POM) performed on data qubit B is firstly implemented by Alice and Bob followed by a N-outcome local POM on B implemented by Bob. We explicitly construct the required POMs. The fact that the nonlocal data-program conditional evolution, which induces the shared and programmable POM, can be realized deterministically using only two partially entangled qubit pairs is notable. The successful probability of implementing this SPMCD is optimal only for one program setting. However, for a relatively large set of program settings it can be very close to the optimal value in an ordinary, local, maximum-confidence discrimination. This protocol is feasible for current experimental technology.

Chen, LiBing; Lu, Hong

2014-11-01

47

Deflated and restarted symmetric Lanczos methods for eigenvalues and linear equations with multiple right-hand sides  

E-print Network

A deflated restarted Lanczos algorithm is given for both solving symmetric linear equations and computing eigenvalues and eigenvectors. The restarting limits the storage so that finding eigenvectors is practical. Meanwhile, the deflating from the presence of the eigenvectors allows the linear equations to generally have good convergence in spite of the restarting. Some reorthogonalization is necessary to control roundoff error, and several approaches are discussed. The eigenvectors generated while solving the linear equations can be used to help solve systems with multiple right-hand sides. Experiments are given with large matrices from quantum chromodynamics that have many right-hand sides.

Abdou M. Abdel-Rehim; Ronald B. Morgan; Dywayne A. Nicely; Walter Wilcox

2008-06-20

48

From scattering theory to complex wave dynamics in non-Hermitian PT-symmetric resonators.  

PubMed

I review how methods from mesoscopic physics can be applied to describe the multiple wave scattering and complex wave dynamics in non-Hermitian PT-symmetric resonators, where an absorbing region is coupled symmetrically to an amplifying region. Scattering theory serves as a convenient tool to classify the symmetries beyond the single-channel case and leads to effective descriptions that can be formulated in the energy domain (via Hamiltonians) and in the time domain (via time evolution operators). These models can then be used to identify the mesoscopic time and energy scales that govern the spectral transition from real to complex eigenvalues. The possible presence of magneto-optical effects (a finite vector potential) in multi-channel systems leads to a variant (termed PTT' symmetry) that imposes the same spectral constraints as PT symmetry. I also provide multi-channel versions of generalized flux-conservation laws. PMID:23509389

Schomerus, Henning

2013-04-28

49

A symmetrical tetramer for S. aureus pyruvate carboxylase in complex with coenzyme A  

PubMed Central

Pyruvate carboxylase (PC) is a conserved metabolic enzyme with important cellular functions. We report here crystallographic and cryoEM studies of S. aureus PC (SaPC) in complex with acetyl-CoA, an allosteric activator, as well as mutagenesis, biochemical and structural studies of the biotin binding site of its carboxyltransferase (CT) domain. The disease-causing A610T mutation abolishes catalytic activity by blocking biotin binding to the CT active site, and Thr908 may play a catalytic role in the CT reaction. The crystal structure of SaPC in complex with CoA reveals a symmetrical tetramer, with one CoA molecule bound to each monomer, and cryoEM studies confirm the symmetrical nature of the tetramer. These observations are in sharp contrast to the highly asymmetrical tetramer of R. etli PC in complex with ethyl-CoA. Our structural information suggests that acetyl-CoA promotes a conformation for the dimer of the biotin carboxylase domain of PC that may be catalytically more competent. PMID:19523900

Yu, Linda P. C.; Xiang, Song; Lasso, Gorka; Gil, David; Valle, Mikel; Tong, Liang

2009-01-01

50

Almost Linear Complexity Methods for Delay-Doppler Channel Estimation  

E-print Network

Almost Linear Complexity Methods for Delay-Doppler Channel Estimation Alexander Fish and Shamgar an analog waveform SA L2 (R) with bandwidth W and a carrier frequency fc W. Transmitting SA, the receiver obtains the analog waveform RA L2 (R). We make the sparsity assumption on the number of paths

Fish, Alexander

51

Trans ruthenium(II) complexes with NH-bridged tetradentate symmetric and asymmetric polypyridyl ligands.  

PubMed

NH-Bridged tetradentate ligands were synthesized to achieve stable trans Ru(II) bis(polypyridyl) complexes. The polypyridyl part of the ligand was either symmetric, as in N,N-bis(1,10-phenanthroline-2-yl)amine (phen-NH-phen), or asymmetric, as in N-(1,10-phenanthroline-2-yl)-N-(6-yl-dipyridyl[2,3-a:2',3'-c]phenazine)amine (dppz-NH-phen). Protonation of phen-NH-phen with trifluoroacetic acid and the subsequent reaction with RuCl3 yield trans-[Ru(phen-NH-phen)Cl2]. The chloro ligands in this compound can easily be replaced by stronger ligands, such as CH3CN and DMSO. In this way, complexes trans-[Ru(phen-NH-phen)(CH3CN)(DMSO)](PF6)2 (1), trans-[Ru(phen-NH-phen)(DMSO)2](PF6)2 (2), and trans-[Ru(phen-NH-phen)(CH3CN)2](PF6)2 (3) were obtained. X-ray structures were determined for 1 and 3. Following a procedure similar to that used with phen-NH-phen, the complex trans-[Ru(dppz-NH-phen)(CH3CN)2](PF6)2 (4) was obtained. To our knowledge, this is the first reported trans ruthenium(II) bis(polypyridyl) complex with two different polypyridyl ligands in the equatorial plane. PMID:12425616

Concepción, Javier; Just, Oliver; Leiva, Ana María; Loeb, Barbara; Rees, William S

2002-11-18

52

Solving complex-valued linear systems via equivalent real formulations  

SciTech Connect

Most algorithms used in preconditioned iterative methods are generally applicable to complex valued linear systems, with real valued linear systems simply being a special case. However, most iterative solver packages available today focus exclusively on real valued systems, or deal with complex valued systems as an afterthought. One obvious approach to addressing this problem is to recast the complex problem into one of a several equivalent real forms and then use a real valued solver to solve the related system. However, well-known theoretical results showing unfavorable spectral properties for the equivalent real forms have diminished enthusiasm for this approach. At the same time, experience has shown that there are situations where using an equivalent real form can be very effective. In this paper, the authors explore this approach, giving both theoretical and experimental evidence that an equivalent real form can be useful for a number of practical situations. Furthermore, they show that by making good use of some of the advance features of modem solver packages, they can easily generate equivalent real form preconditioners that are computationally efficient and mathematically identical to their complex counterparts. Using their techniques, they are able to solve very ill-conditioned complex valued linear systems for a variety of large scale applications. However, more importantly, they shed more light on the effectiveness of equivalent real forms and more clearly delineate how and when they should be used.

DAY,DAVID M.; HEROUX,MICHAEL A.

2000-05-22

53

Reducing the complexity of perturbation based nonlinearity pre-compensation using symmetric EDC and pulse shaping.  

PubMed

Perturbation based nonlinearity pre-compensation has been performed for a 128 Gbit/s single-carrier dual-polarization 16-ary quadrature-amplitude-modulation (DP 16-QAM) signal. Without any performance degradation, a complexity reduction factor of 6.8 has been demonstrated for a transmission distance of 3600 km by combining symmetric electronic dispersion compensation and root-raised-cosine pulse shaping with a roll-off factor of 0.1. Transmission over 4200 km of standard single-mode fiber with EDFA amplification was achieved for the 128 Gbit/s DP 16-QAM signals with a forward error correction (FEC) threshold of 2 × 10(-2). PMID:24515126

Gao, Ying; Cartledge, John C; Karar, Abdullah S; Yam, Scott S-H; O'Sullivan, Maurice; Laperle, Charles; Borowiec, Andrzej; Roberts, Kim

2014-01-27

54

Synchronization of fractional-order linear complex networks.  

PubMed

In this paper, we concentrate on the synchronization problem of fractional-order complex networks with general linear dynamics under connected topology. By introducing a pseudo-state transformation, the problem is converted into an equivalent simultaneous stabilization problem of independent subsystems, which is characterized by nonzero eigenvalues of the Laplacian matrix. Then, sufficient conditions in terms of linear matrix inequalities (LMIs) for synchronization are established, which can be easily solved by efficient convex optimization algorithms. Finally, three examples are provided to illustrate the effectiveness of the proposed method. PMID:25467542

Wang, Junwei; Zeng, Caibin

2014-11-25

55

Symmetric Orthogonal Complex-Valued Filter Bank Design by Semidefinite Programming  

Microsoft Academic Search

A new design method for complex-valued two-channel FIR filter banks with both orthogonality and symmetry properties is developed. Based on a novel linear matrix inequality (LMI) characterization of trigonometric curves, the optimal design of the perfect reconstruction filter bank is reformulated as a semi-definite programme. The dimension of the resulting semi-definite programme is further reduced by exploiting the strong convex

H. H. Kha; H. D. Tuan; B. Vo; T. Q. Nguyen

2006-01-01

56

Symmetric Orthogonal Complex-Valued Filter Bank Design by Semidefinite Programming  

Microsoft Academic Search

Abstract—A new design method for complex-valued two- channel finite impulse response (FIR) filter banks with both orthogonality and symmetry properties is developed. Based on a novel linear matrix inequality (LMI) characterization of trigono- metric curves, the optimal design of perfect-reconstruction filter banks is cast into a semidefinite programming (SDP) problem. The dimension of the resulting SDP problem is further reduced

Ha Hoang Kha; Hoang Duong Tuan; Ba-ngu Vo; Truong Q. Nguyen

2007-01-01

57

Malachite green mediates homodimerization of antibody VL domains to form a fluorescent ternary complex with singular symmetric interfaces  

PubMed Central

We report that a symmetric small molecule ligand mediates the assembly of antibody light chain variable domains (VLs) into a correspondent symmetric ternary complex with novel interfaces. The L5* Fluorogen Activating Protein (FAP) is a VL domain that binds malachite green dye (MG) to activate intense fluorescence. Crystallography of liganded L5* reveals a 2:1 protein:ligand complex with inclusive C2 symmetry, where MG is almost entirely encapsulated between an antiparallel arrangement of the two VL domains. Unliganded L5* VL domains crystallize as a similar antiparallel VL/VL homodimer. The complementarity determining regions (CDRs) are spatially oriented to form novel VL/VL and VL/ligand interfaces that tightly constrain a propeller conformer of MG. Binding equilibrium analysis suggests highly cooperative assembly to form a very stable VL/MG/VL complex, such that MG behaves as a strong chemical inducer of dimerization. Fusion of two VL domains into a single protein tightens MG binding over 1,000-fold to low picomolar affinity without altering the large binding enthalpy, suggesting that bonding interactions with ligand and restriction of domain movements make independent contributions to binding. Fluorescence activation of a symmetrical fluorogen provides a selection mechanism for the isolation and directed evolution of ternary complexes where unnatural symmetric binding interfaces are favored over canonical antibody interfaces. As exemplified by L5*, these self-reporting complexes may be useful as modulators of protein association or as high affinity protein tags and capture reagents. PMID:23978698

Szent-Gyorgyi, Chris; Stanfield, Robyn L.; Andreko, Susan; Dempsey, Alison; Ahmed, Mushtaq; Capek, Sara; Waggoner, Alan; Wilson, Ian A.; Bruchez, Marcel P.

2013-01-01

58

Malachite green mediates homodimerization of antibody VL domains to form a fluorescent ternary complex with singular symmetric interfaces.  

PubMed

We report that a symmetric small-molecule ligand mediates the assembly of antibody light chain variable domains (VLs) into a correspondent symmetric ternary complex with novel interfaces. The L5* fluorogen activating protein is a VL domain that binds malachite green (MG) dye to activate intense fluorescence. Crystallography of liganded L5* reveals a 2:1 protein:ligand complex with inclusive C2 symmetry, where MG is almost entirely encapsulated between an antiparallel arrangement of the two VL domains. Unliganded L5* VL domains crystallize as a similar antiparallel VL/VL homodimer. The complementarity-determining regions are spatially oriented to form novel VL/VL and VL/ligand interfaces that tightly constrain a propeller conformer of MG. Binding equilibrium analysis suggests highly cooperative assembly to form a very stable VL/MG/VL complex, such that MG behaves as a strong chemical inducer of dimerization. Fusion of two VL domains into a single protein tightens MG binding over 1000-fold to low picomolar affinity without altering the large binding enthalpy, suggesting that bonding interactions with ligand and restriction of domain movements make independent contributions to binding. Fluorescence activation of a symmetrical fluorogen provides a selection mechanism for the isolation and directed evolution of ternary complexes where unnatural symmetric binding interfaces are favored over canonical antibody interfaces. As exemplified by L5*, these self-reporting complexes may be useful as modulators of protein association or as high-affinity protein tags and capture reagents. PMID:23978698

Szent-Gyorgyi, Chris; Stanfield, Robyn L; Andreko, Susan; Dempsey, Alison; Ahmed, Mushtaq; Capek, Sarah; Waggoner, Alan S; Wilson, Ian A; Bruchez, Marcel P

2013-11-15

59

Near consensus complex linear and nonlinear social networks  

NASA Astrophysics Data System (ADS)

Some of the nodes of complex social networks may support for a given proposal, while the rest of the nodes may be against the given proposal. Even though all the nodes support for or are against the given proposal, the decision certitudes of individual nodes may be different. In this case, the steady state values of the decision certitudes of the majority of the nodes are either higher than or lower than a threshold value. Deriving the near consensus property is a key to the analysis of the behaviors of complex social networks. So far, no result on the behaviors of the complex social networks satisfying the near consensus property has been reported. Hence, it is useful to extend the definition of the exact consensus property to that of a near consensus property and investigate the behaviors of the complex social networks satisfying the near consensus property. This paper extends the definition of exact consensus complex social networks to that of near consensus complex social networks. For complex linear social networks, this paper investigates the relationships among the vectors representing the steady state values of the decision certitudes of the nodes, the influence weight matrix and the set of vectors representing the initial state values of the decision certitudes of the nodes under a given near consensus specification. The above analysis is based on the Eigen theory. For complex nonlinear social networks with certain types of nonlinearities, the relationship between the influence weight matrix and the vectors representing the steady state values of the decision certitudes of the nodes is studied. When a complex nonlinear social network does not achieve the exact consensus property, the optimal near consensus condition that the complex social network can achieve is derived. This problem is formulated as an optimization problem. The total number of nodes that the decision certitudes of the nodes are either higher than or lower than a threshold value is maximized subject to the corresponding near consensus specification. The optimization problem is a nonsmooth optimization problem. The nonsmooth constraints are first approximated by smooth constraints. Then, the approximated optimization problem is solved via a conventional smooth optimization approach. Computer numerical simulation results as well as the comparisons of the behaviors of complex nonlinear social networks to those of the complex linear social networks are presented. The obtained results demonstrate that some complex social networks can satisfy the near consensus property but not the exact consensus property. Also, the conditions for the near consensus property are dependent on the types of nonlinearities, the influence weight matrix and the vectors representing the initial state values of the decision certitudes of the nodes.

Ling, Bingo Wing-Kuen; Ho, Charlotte Yuk-Fan; Wang, Lidong; Teo, Kok-Lay; Tse, Chi K.; Dai, Qingyun

2014-05-01

60

Extending the eigCG algorithm to non-symmetric linear systems with multiple right-hand sides  

SciTech Connect

For Hermitian positive definite linear systems and eigenvalue problems, the eigCG algorithm is a memory efficient algorithm that solves the linear system and simultaneously computes some of its eigenvalues. The algorithm is based on the Conjugate-Gradient (CG) algorithm, however, it uses only a window of the vectors generated by the CG algorithm to compute approximate eigenvalues. The number and accuracy of the eigenvectors can be increased by solving more right-hand sides. For Hermitian systems with multiple right-hand sides, the computed eigenvectors can be used to speed up the solution of subsequent systems. The algorithm was tested on Lattice QCD problems by solving the normal equations and was shown to give large speed up factors and to remove the critical slowing down as we approach light quark masses. Here, an extension to the non-symmetric case based on the two-sided Lanczos algorithm is given. The new algorithm is tested on Lattice QCD problems and is shown to give promising results. We also study the removal of the critical slowing down and compare results with those of the eigCG algorithm. We also discuss the case when the system is gamma5-Hermitian.

Abdou Abdel-Rehim, Kostas Orginos, Andreas Stathopoulos

2009-11-01

61

Extending the eigCG algorithm to non-symmetric linear systems with multiple right-hand sides  

E-print Network

For Hermitian positive definite linear systems and eigenvalue problems, the eigCG algorithm is a memory efficient algorithm that solves the linear system and simultaneously computes some of its eigenvalues. The algorithm is based on the Conjugate-Gradient (CG) algorithm, however, it uses only a window of the vectors generated by the CG algorithm to compute approximate eigenvalues. The number and accuracy of the eigenvectors can be increased by solving more right-hand sides. For Hermitian systems with multiple right-hand sides, the computed eigenvectors can be used to speed up the solution of subsequent systems. The algorithm was tested on Lattice QCD problems by solving the normal equations and was shown to give large speed up factors and to remove the critical slowing down as we approach light quark masses. Here, an extension to the non-symmetric case based on the two-sided Lanczos algorithm is given. The new algorithm is tested on Lattice QCD problems and is shown to give promising results. We also study the removal of the critical slowing down and compare results with those of the eigCG algorithm. We also discuss the case when the system is gamma5-Hermitian.

Abdou Abdel-Rehim; Kostas Orginos; Andreas Stathopoulos

2009-11-12

62

Relaxation modulus—complex modulus interconversion for linear viscoelastic materials  

NASA Astrophysics Data System (ADS)

This paper is aimed at exploring the interconversion path between the relaxation modulus E( t) and the corresponding complex modulus E ?( ?) for linear viscoelastic solid materials. In contrast to other approximate methods, the fast Fourier transform (FFT) algorithm is directly applied on the time-dependent part of the viscoelastic response R( t). Firstly, the method foundations are presented. Then, a theoretical example is performed by means of a generalized Maxwell model, where the influence of sampling conditions and eventual experimental error and data dispersion is analyzed. Finally, an application example using experimental data is carried out to assess the method. As a result, the proposed procedure allows obtaining the complex modulus by means of relaxation tests, and vice versa.

García-Barruetabeña, Jon; Cortés, Fernando; Abete, José Manuel; Fernández, Pelayo; Lamela, María Jesús; Fernández-Canteli, Alfonso

2013-08-01

63

Trajectories of probe spheres in generalized linear viscoelastic complex fluids.  

PubMed

We have developed a fast simulation that generates a random walk of an isolated probe sphere in a generalized linear viscoelastic complex fluid over a highly extended dynamic range. We introduce a coupled harmonically bound Brownian particle (c-HBBP) model, in which the relaxation modes of the viscoelastic medium are treated as harmonic wells. These wells are coupled to the probe sphere and perform Brownian motion in bound harmonic potentials corresponding to the next-longer relaxation mode, according to the relaxation spectrum of the viscoelastic material. We implement this c-HBBP model by generating variable temporal step sizes that have a uniform distribution in logarithmic time. We create and analyze trajectories for several different viscoelastic complex fluids: a polymer system at its gel point, a dense emulsion system, a blend of two monodisperse polystyrene polymers for which the relaxation spectrum has been measured, and a model anisotropic soft system that shows dense emulsion-like and gel-point behaviors along two orthogonal directions. Except for unusual viscoelastic materials, such as the polymer system at its gel point, the generated trajectories are neither self-similar nor self-affine. The resulting mean square displacements predicted by the c-HBBP model are consistent with the single-particle generalized Stokes-Einstein relation of linear passive microrheology. PMID:25259775

Khan, Manas; Mason, Thomas G

2014-12-01

64

On the linear complexity of Sidel'nikov Sequences over Fd  

E-print Network

. Alternatively, the linear complexity of a periodic sequence with terms in Fd is the length of the shortestOn the linear complexity of Sidel'nikov Sequences over Fd Nina Brandst¨atter1 and Wilfried Meidl2 1 Istanbul, Turkey wmeidl@sabanciuniv.edu Abstract. We study the linear complexity of sequences over

Yanikoglu, Berrin

65

Catalytic performance of symmetrical and unsymmetrical sulfur-containing pincer complexes: synthesis and tandem catalytic activity of the first PCS-pincer palladium complex.  

PubMed

The synthesis and catalytic applications of a new aryl-based unsymmetrical PCS-pincer complex are reported. Preparation of the robust air- and moisture-stable PCS-pincer palladium complex 5[X] started from the symmetrical alpha,alpha'-dibromo-meta-xylene and involved the selective substitution of one bromide by PPh(2)(BH(3)), followed by substitution of the second bromide by SPh and subsequent introduction of the palladium. The new PCS complexes (5[X]) were employed as catalysts in two important organic transformations. Firstly, complex 5[Cl] displays high catalytic activity in aldol reactions but enters the catalytic cycle as a precatalyst. Secondly, complex 5[BF(4)] displays tandem catalytic activity in the coupling of allyl chlorides with aldehydes and imines in the presence of hexamethylditin. In these tandem catalytic reactions the first process is the conversion of allyl chlorides into trimethylallyltin (and trimethyltin chloride) with Sn(2)Me(6), which is followed by catalytic allylation of aldehyde and sulfonimine substrates. In addition, we present a new catalytic process for the one-pot allylation of 4-nitrobenzaldehyde with vinyloxirane. The catalytic performance of the novel PCS-pincer palladium complex was compared to those of its symmetrical PCP- and SCS-pincer complex analogues. It was concluded that the unsymmetrical PCS complex advantageously unifies the attractive catalytic features of the corresponding symmetrical pincer complexes including both (pi-) electron-withdrawing (such as phosphorus) or (sigma-) electron-donating (such as sulfur and nitrogen) heteroatoms. Thus, in the aldol reaction the PCS-pincer palladium complex 5[X] provides a high turnover frequency, while in the tandem process both reactions are catalysed with sufficiently high activity. PMID:18432627

Gagliardo, Marcella; Selander, Nicklas; Mehendale, Nilesh C; van Koten, Gerard; Klein Gebbink, Robertus J M; Szabó, Kálmán J

2008-01-01

66

On the experimental verification of quantum complexity in linear optics  

NASA Astrophysics Data System (ADS)

Quantum computers promise to solve certain problems that are forever intractable to classical computers. The first of these devices are likely to tackle bespoke problems suited to their own particular physical capabilities. Sampling the probability distribution from many bosons interfering quantum-mechanically is conjectured to be intractable to a classical computer but solvable with photons in linear optics. However, the complexity of this type of problem means its solution is mathematically unverifiable, so the task of establishing successful operation becomes one of gathering sufficiently convincing circumstantial or experimental evidence. Here, we develop scalable methods to experimentally establish correct operation for this class of computation, which we implement for three, four and five photons in integrated optical circuits, on Hilbert spaces of up to 50,000 dimensions. Our broad approach is practical for all quantum computational architectures where formal verification methods for quantum algorithms are either intractable or unknown.

Carolan, Jacques; Meinecke, Jasmin D. A.; Shadbolt, Peter J.; Russell, Nicholas J.; Ismail, Nur; Wörhoff, Kerstin; Rudolph, Terry; Thompson, Mark G.; O'Brien, Jeremy L.; Matthews, Jonathan C. F.; Laing, Anthony

2014-08-01

67

Complex Dynamics of Compound Vesicles in Linear Flow  

NASA Astrophysics Data System (ADS)

We report first experimental observations of dynamics of compound vesicles in linear flow realized in a microfluidic four-roll mill. We show that while a compound vesicle undergoes the same main tank-treading, trembling (TR), and tumbling regimes, its dynamics are far richer and more complex than that of unilamellar vesicles. A new swinging motion of the inner vesicle is found in TR in accord with simulations. The inner and outer vesicles can exist simultaneously in different dynamical regimes and can undergo either synchronized or unsynchronized motions depending on the filling factor. A compound vesicle can be used as a physical model to study white blood cell dynamics in flow similar to a unilamellar vesicle used successfully to model anucleate cells.

Levant, Michael; Steinberg, Victor

2014-04-01

68

Spreading of infectious diseases on complex networks with non-symmetric transmission probabilities  

E-print Network

We model the spread of a SIS infection on Small World and random networks using weighted graphs. The entry $w_{ij}$ in the weight matrix W holds information about the transmission probability along the edge joining node $v_i$ and node $v_j$. We use the analogy between the spread of a disease on a network and a random walk performed on this network to derive a master equation describing the dynamics of the process. We find conditions under which an epidemic does not break out and investigate numerically the effect of a non-symmetric weight distribution of the initially infected individual on the dynamics of the disease spread.

Britta Daudert; Bai-Lian Li

2006-11-23

69

Conventional quantum phase transition driven by a complex parameter in a non-Hermitian PT-symmetric Ising model  

NASA Astrophysics Data System (ADS)

A conventional quantum phase transition (QPT) can be accessed by varying a real parameter at absolute zero temperature. Motivated by the discovery of the pseudo-Hermiticity of non-Hermitian systems, we explore the QPT in the non-Hermitian PT-symmetric Ising model, which is driven by a staggered complex transverse field. Exact solution shows that the Laplacian of the ground-state energy density, with respect to real and imaginary components of the transverse field, diverges on the boundary in the complex plane. The phase diagram indicates that the imaginary transverse field has the effect of shrinking the paramagnetic phase. In addition, we also investigate the connection between the geometric phase and the QPT.

Li, C.; Zhang, G.; Zhang, X. Z.; Song, Z.

2014-07-01

70

Design, Activity, and 2.8 overset{circ}{A} Crystal Structure of a C_2 Symmetric Inhibitor Complexed to HIV-1 Protease  

NASA Astrophysics Data System (ADS)

A two-fold (C_2) symmetric inhibitor of the protease of human immunodeficiency virus type-1 (HIV-1) has been designed on the basis of the three-dimensional symmetry of the enzyme active site. The symmetric molecule inhibited both protease activity and acute HIV-1 infection in vitro, was at least 10,000-fold more potent against HIV-1 protease than against related enzymes, and appeared to be stable to degradative enzymes. The 2.8 angstrom crystal structure of the inhibitor-enzyme complex demonstrated that the inhibitor binds to the enzyme in a highly symmetric fashion.

Erickson, John; Neidhart, David J.; Vandrie, John; Kempf, Dale J.; Wang, Xiu Chun; Norbeck, Daniel W.; Plattner, Jacob J.; Rittenhouse, Judith W.; Turon, Mary; Wideburg, Norman; Kohlbrenner, William E.; Simmer, Robert; Helfrich, Rosalind; Paul, Deborah A.; Knigge, Mark

1990-08-01

71

Complex Non-Linear Modal Analysis for Mechanical Systems: Application to Turbomachinery Bladings With Friction  

E-print Network

Complex Non-Linear Modal Analysis for Mechanical Systems: Application to Turbomachinery Bladings.laxalde@ec-lyon.fr, fabrice.thouverez@ec-lyon.fr Abstract A method for modal analysis of non-linear and non to numerical methods for non-linear modal analysis would probably help reducing this gap between academic

Paris-Sud XI, Université de

72

On the Solutions of Some Linear Complex Quaternionic Equations  

PubMed Central

Some complex quaternionic equations in the type AX ? XB = C are investigated. For convenience, these equations were called generalized Sylvester-quaternion equations, which include the Sylvester equation as special cases. By the real matrix representations of complex quaternions, the necessary and sufficient conditions for the solvability and the general expressions of the solutions are obtained. PMID:25101318

?pek, Ahmet

2014-01-01

73

On the solutions of some linear complex quaternionic equations.  

PubMed

Some complex quaternionic equations in the type AX - XB = C are investigated. For convenience, these equations were called generalized Sylvester-quaternion equations, which include the Sylvester equation as special cases. By the real matrix representations of complex quaternions, the necessary and sufficient conditions for the solvability and the general expressions of the solutions are obtained. PMID:25101318

Bolat, Cennet; ?pek, Ahmet

2014-01-01

74

Randomized Communication Complexity for Linear Algebra Problems over Finite Fields  

E-print Network

to decide if the rank of a matrix is k, and proved an (k2 ) lower bound for randomized one-way protocols and Chengu Wang2 1 Institute of Computing Technology, Chinese Academy of Sciences, Beijing, China sunxiaoming in the communication complexity model. We prove that the randomized/quantum communication complexity of the singularity

Tang, Pingzhong

75

Randomized Communication Complexity for Linear Algebra Problems over Finite Fields  

E-print Network

if the rank of a matrix is k, and proved an (k2 ) lower bound for randomized one-way protocols and Chengu Wang2 1 Institute of Computing Technology, Chinese Academy of Sciences Beijing, China sunxiaoming in the communication complexity model. We prove that the randomized/quantum communication complexity of the singularity

Boyer, Edmond

76

Evaluation of out-of-core computer programs for the solution of symmetric banded linear equations. [simultaneous equations  

NASA Technical Reports Server (NTRS)

FORTRAN coded out-of-core equation solvers that solve using direct methods symmetric banded systems of simultaneous algebraic equations. Banded, frontal and column (skyline) solvers were studied as well as solvers that can partition the working area and thus could fit into any available core. Comparison timings are presented for several typical two dimensional and three dimensional continuum type grids of elements with and without midside nodes. Extensive conclusions are also given.

Dunham, R. S.

1976-01-01

77

Mechanism underlying I?B kinase activation mediated by the linear ubiquitin chain assembly complex.  

PubMed

The linear ubiquitin chain assembly complex (LUBAC) ligase, consisting of HOIL-1L, HOIP, and SHARPIN, specifically generates linear polyubiquitin chains. LUBAC-mediated linear polyubiquitination has been implicated in NF-?B activation. NEMO, a component of the I?B kinase (IKK) complex, is a substrate of LUBAC, but the precise molecular mechanism underlying linear chain-mediated NF-?B activation has not been fully elucidated. Here, we demonstrate that linearly polyubiquitinated NEMO activates IKK more potently than unanchored linear chains. In mutational analyses based on the crystal structure of the complex between the HOIP NZF1 and NEMO CC2-LZ domains, which are involved in the HOIP-NEMO interaction, NEMO mutations that impaired linear ubiquitin recognition activity and prevented recognition by LUBAC synergistically suppressed signal-induced NF-?B activation. HOIP NZF1 bound to NEMO and ubiquitin simultaneously, and HOIP NZF1 mutants defective in interaction with either NEMO or ubiquitin could not restore signal-induced NF-?B activation. Furthermore, linear chain-mediated activation of IKK2 involved homotypic interaction of the IKK2 kinase domain. Collectively, these results demonstrate that linear polyubiquitination of NEMO plays crucial roles in IKK activation and that this modification involves the HOIP NZF1 domain and recognition of NEMO-conjugated linear ubiquitin chains by NEMO on another IKK complex. PMID:24469399

Fujita, Hiroaki; Rahighi, Simin; Akita, Mariko; Kato, Ryuichi; Sasaki, Yoshiteru; Wakatsuki, Soichi; Iwai, Kazuhiro

2014-04-01

78

Mechanism Underlying I?B Kinase Activation Mediated by the Linear Ubiquitin Chain Assembly Complex  

PubMed Central

The linear ubiquitin chain assembly complex (LUBAC) ligase, consisting of HOIL-1L, HOIP, and SHARPIN, specifically generates linear polyubiquitin chains. LUBAC-mediated linear polyubiquitination has been implicated in NF-?B activation. NEMO, a component of the I?B kinase (IKK) complex, is a substrate of LUBAC, but the precise molecular mechanism underlying linear chain-mediated NF-?B activation has not been fully elucidated. Here, we demonstrate that linearly polyubiquitinated NEMO activates IKK more potently than unanchored linear chains. In mutational analyses based on the crystal structure of the complex between the HOIP NZF1 and NEMO CC2-LZ domains, which are involved in the HOIP-NEMO interaction, NEMO mutations that impaired linear ubiquitin recognition activity and prevented recognition by LUBAC synergistically suppressed signal-induced NF-?B activation. HOIP NZF1 bound to NEMO and ubiquitin simultaneously, and HOIP NZF1 mutants defective in interaction with either NEMO or ubiquitin could not restore signal-induced NF-?B activation. Furthermore, linear chain-mediated activation of IKK2 involved homotypic interaction of the IKK2 kinase domain. Collectively, these results demonstrate that linear polyubiquitination of NEMO plays crucial roles in IKK activation and that this modification involves the HOIP NZF1 domain and recognition of NEMO-conjugated linear ubiquitin chains by NEMO on another IKK complex. PMID:24469399

Fujita, Hiroaki; Akita, Mariko; Kato, Ryuichi; Sasaki, Yoshiteru; Wakatsuki, Soichi

2014-01-01

79

Assembly of symmetrical and unsymmetrical platinum(II) rollover complexes with bidentate phosphine ligands.  

PubMed

The reaction of the cyclometalated rollover complex [Pt(bpy-H)(Me)(DMSO)] (bpy-H = cyclometalated 2,2'-bipyridine) with two diphosphines, dppm (1,1-bis(diphenylphosphino)methane) and dppe (1,2-bis(diphenylphosphino)ethane), was investigated. According to the reaction conditions, dppm behaves as a monodentate, bridging or chelated ligand, whereas dppe gave only chelated species. Some aspects of the reactivity of the isolated species were studied, including protonation with [H3O·18-crown-6][BF4] and coordination reactions of mononuclear complexes, obtaining, inter alia, rare examples of unsymmetrical organometallic species with bridging dppm. PMID:25162179

Maidich, Luca; Zuri, Giuseppina; Stoccoro, Sergio; Cinellu, Maria Agostina; Zucca, Antonio

2014-10-21

80

The linear and nonlinear rheology of multiscale complex fluids  

E-print Network

The microstructures of many complex fluids are typically characterized by a broad distribution of internal length scales. Examples of such multiscale materials include physically and chemically cross-linked gels, emulsions, ...

Jaishankar, Aditya

2014-01-01

81

Radical localization in a series of symmetric Ni(II) complexes with oxidized salen ligands.  

PubMed

Square-planar nickel(II) complexes of salen ligands, N,N'-bis(3-tert-butyl-(5R)-salicylidene)-1,2-cyclohexanediamine), in which R=tert-butyl (1), OMe (2), and NMe(2) (3), were prepared and the electronic structure of the one-electron-oxidized species [1-3](+·) was investigated in solution. Cyclic voltammograms of [1-3] showed two quasi-reversible redox waves that were assigned to the oxidation of the phenolate moieties to phenoxyl radicals. From the difference between the first and second redox potentials, the trend of electronic delocalization 1(+·) >2(+·) >3(+·) was obtained. The cations [1-3](+·) exhibited isotropic g tensors of 2.045, 2.023, and 2.005, respectively, reflecting a lower metal character of the singly occupied molecular orbital (SOMO) for systems that involve strongly electron-donating substituents. Pulsed-EPR spectroscopy showed a single population of equivalent imino nitrogen atoms for 1(+·), whereas two distinct populations were observed for 2(+·). The resonance Raman spectra of 2(+·) and 3(+·) displayed the ?(8a) band of the phenoxyl radicals at 1612 cm(-1), as well as the ?(8a) bands of the phenolates. In contrast, the Raman spectrum of 1(+·) exhibited the ?(8a) band at 1602 cm(-1), without any evidence of the phenolate peak. Previous work showed an intense near-infrared (NIR) electronic transition for 1(+·) (??(1/2) =660 cm(-1), ?=21,700 M(-1) cm(-1)), indicating that the electron hole is fully delocalized over the ligand. The broader and moderately intense NIR transition of 2(+·) (??(1/2) =1250 cm(-1) , ?=12,800 M(-1) cm(-1)) suggests a certain degree of ligand-radical localization, whereas the very broad NIR transition of 3(+·) (??(1/2) =8630 cm(-1), ?=2550 M(-1) cm(-1)) indicates significant localization of the ligand radical on a single ring. Therefore, 1(+·) is a Class III mixed-valence complex, 2(+·) is Class II/III borderline complex, and 3(+·) is a Class II complex according to the Robin-Day classification method. By employing the Coulomb-attenuated method (CAM-B3LYP) we were able to predict the electron-hole localization and NIR transitions in the series, and show that the energy match between the redox-active ligand and the metal d orbitals is crucial for delocalization of the radical SOMO. PMID:22997000

Chiang, Linus; Kochem, Amélie; Jarjayes, Olivier; Dunn, Tim J; Vezin, Hervé; Sakaguchi, Miyuki; Ogura, Takashi; Orio, Maylis; Shimazaki, Yuichi; Thomas, Fabrice; Storr, Tim

2012-10-29

82

Mixed-valence state of symmetric diruthenium complexes: synthesis, characterization, and electron transfer investigation.  

PubMed

Complexes of the type {[(pyS)Ru(NH(3))(4)](2)-?-L}(n), where pyS = 4-mercaptopyridine, L = 4,4'-dithiodipyridine (pySSpy), pyrazine (pz) and 1,4-dicyanobenzene (DCB), and n = +4 and +5 for fully reduced and mixed-valence complexes, respectively, were synthesized and characterized. Electrochemical data showed that there is electron communication between the metal centers with comproportionation constants of 33.2, 1.30 × 10(8) and 5.56 × 10(5) for L = pySSpy, pz and DCB, respectively. It was also observed that the electronic coupling between the metal centers is affected by the ?-back-bonding interaction toward the pyS ligand. Raman spectroscopy showed a dependence of the intensity of the vibrational modes on the exciting radiations giving support to the assignments of the electronic transitions. The degree of electron communication between the metal centers through the bridging ligands suggests that these systems can be molecular wire materials. PMID:23086129

Pinheiro, Solange de Oliveira; Paulo, Tércio de F; de Abreu, Dieric dos S; Longhinotti, Elisane; Silva, Claudio H B; Andrade, Gustavo F S; Temperini, Márcia L A; Diógenes, Izaura Cirino Nogueira

2012-12-28

83

Non-linear change in organizations: organization change management informed by complexity theory  

Microsoft Academic Search

Organizational change processes are often modeled on a linear understanding of change in which the process is composed of individual succeeding steps. In this paper, an organization change process in a Swedish telecommunication company, TelCo., is studied from the perspective of non-linearity. Complexity theory is used in the paper as a loosely coupled framework of theories and perspectives that do

Alexander Styhre

2002-01-01

84

Complex response of a food-web module to symmetric and asymmetric migration between several patches.  

PubMed

We investigate the stability of a diamond food-web module on two patches coupled by migration in terms of robustness, which is the proportion of surviving species in the system. The parameters are chosen such that the dynamics on an isolated patch have a periodic attractor with all four species present as well as an attractor where the prey that is preferred by the top predator dies out. The migration rate and the migration bias between the two patches are varied, resulting in a surprisingly complex relation between migration rate and robustness. In particular, while the degree of synchronization usually increases with increasing migration rate, robustness can increase as well as decrease. We find that the main results also hold when the number of patches is larger. Different types of connectivity patterns between patches can lead to different extent of migration bias if the migration rate out of each patch is the same. PMID:24641820

Ristl, Konstantin; Plitzko, Sebastian J; Drossel, Barbara

2014-08-01

85

Characterization of a potentially axially symmetric europium(III) complex of a tetraacetate,tetraaza, macrocyclic ligand by luminescence excitation, emission and lifetime spectroscopy  

NASA Astrophysics Data System (ADS)

The Eu(III) complex of the octadentate macrocyclic ligand, 1,4,7,10-tetraazacyclododecane-N,N',N'',N''' -tetraacetate, DOTA, has been examined by luminescence excitation, emission, and lifetime spectroscopy using pulsed dye laser techniques. The results confirm the expected axially symmetric nature of the major component in solution and reveal that 1.2 ± 0.4 water molecules arc coordinatcd to the Eu(III) ion in the complex.

Albin, Michael; de, William; Horrocks, W., Jr.; Liotta, Frank J.

1982-01-01

86

Complexity and Fragility in Stability for Linear Systems Aaron D. Ames and John C. Doyle  

E-print Network

Complexity and Fragility in Stability for Linear Systems Aaron D. Ames and John C. Doyle Abstract-- This paper presents a formal axiomization of the notion that (proof) complexity implies (property) fragility and unforseen circumstances. It is, moreover, often the case that the lack of robustness, or fragility

Ames, Aaron

87

PT-Symmetric Quantum Theory Defined in a Krein Space  

E-print Network

We provide a mathematical framework for PT-symmetric quantum theory, which is applicable irrespective of whether a system is defined on R or a complex contour, whether PT symmetry is unbroken, and so on. The linear space in which PT-symmetric quantum theory is naturally defined is a Krein space constructed by introducing an indefinite metric into a Hilbert space composed of square integrable complex functions in a complex contour. We show that in this Krein space every PT-symmetric operator is P-Hermitian if and only if it has transposition symmetry as well, from which the characteristic properties of the PT-symmetric Hamiltonians found in the literature follow. Some possible ways to construct physical theories are discussed within the restriction to the class K(H).

Toshiaki Tanaka

2006-05-17

88

Symmetrized photoinitiated electron flow within the [myoglobin:cytochrome b?] complex on singlet and triplet time scales: energetics vs dynamics.  

PubMed

We report here that photoinitiated electron flow involving a metal-substituted (M = Mg, Zn) myoglobin (Mb) and its physiological partner protein, cytochrome b5 (cyt b5) can be "symmetrized": the [Mb:cyt b5] complex stabilized by three D/E ? K mutations on Mb (D44K/D60K/E85K, denoted MMb) exhibits both oxidative and reductive ET quenching of both the singlet and triplet photoexcited MMb states, the direction of flow being determined by the oxidation state of the cyt b5 partner. The first-excited singlet state of MMb ((1)MMb) undergoes ns-time scale reductive ET quenching by Fe(2+)cyt b5 as well as ns-time scale oxidative ET quenching by Fe(3+)cyt b5, both processes involving an ensemble of structures that do not interconvert on this time scale. Despite a large disparity in driving force favoring photooxidation of (1)MMb relative to photoreduction (?(-?G(0)) ? 0.4 eV, M = Mg; ? 0.2 eV, M = Zn), for each M the average rate constants for the two reactions are the same within error, (1)k(f) > 10(8) s(-1). This surprising observation is explained by considering the driving-force dependence of the Franck-Condon factor in the Marcus equation. The triplet state of the myoglobin ((3)MMb) created by intersystem crossing from (1)MMb likewise undergoes reductive ET quenching by Fe(2+)cyt b5 as well as oxidative ET quenching by Fe(3+)cyt b5. As with singlet ET, the rate constants for oxidative ET quenching and reductive ET quenching on the triplet time scale are the same within error, (3)k(f) ? 10(5) s(-1), but here the equivalence is attributable to gating by intracomplex conversion among a conformational ensemble. PMID:25133915

Co, Nadia Petlakh; Young, Ryan M; Smeigh, Amanda L; Wasielewski, Michael R; Hoffman, Brian M

2014-09-10

89

An analytical model to determine equilibrium quantities of azimuthally symmetric and mismatched charged particle beams under linear focusing  

SciTech Connect

The model developed here analytically allows to obtain equilibrium quantities of interest from high-intensity charged particle beams such as the emittance, beam envelope, and the number of beam halo particles. The results obtained in this work have been particularized to the case of initially homogeneous beams, with azimuthal symmetry, and focused by a constant magnetic field while confined in a linear channel. For validation, full self-consistent N-particle beam simulations have been carried out and its results compared with the predictions supplied by the developed hybrid numerical-analytical model. The agreement has been reasonable. Also, the model revealed to be useful to understand the basic physical aspects of the problem.

Nunes, R. P.; Pakter, R.; Rizzato, F. B. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, Caixa Postal 15051, CEP 91501-970, Porto Alegre, Rio Grande do Sul (Brazil)

2008-07-01

90

Almost Linear Complexity Methods for Delay-Doppler Channel Alexander Fish and Shamgar Gurevich  

E-print Network

1 Almost Linear Complexity Methods for Delay-Doppler Channel Estimation Alexander Fish and Shamgar that a transmitter uses a sequence S H to generate an analog waveform SA L2 (R) with bandwidth W and a carrier frequency fc W. Transmitting SA, the receiver obtains the analog waveform RA L2 (R). We make the sparsity

Sydney, University of

91

Symmetric GroEL:GroES2 complexes are the protein-folding functional form of the chaperonin nanomachine  

PubMed Central

Using calibrated FRET, we show that the simultaneous occupancy of both rings of GroEL by ATP and GroES occurs, leading to the rapid formation of symmetric GroEL:GroES2 “football” particles regardless of the presence or absence of substrate protein (SP). In the absence of SP, these symmetric particles revert to asymmetric GroEL:GroES1 “bullet” particles. The breakage of GroES symmetry requires the stochastic hydrolysis of ATP and the breakage of nucleotide symmetry. These asymmetric particles are both persistent and dynamic; they turnover via the asymmetric cycle. When challenged with SP, however, they revert to symmetric particles within a second. In the presence of SP, the symmetric particles are also persistent and dynamic. They turn over via the symmetric cycle. Under these conditions, the stochastic hydrolysis of ATP and the breakage of nucleotide symmetry also occur within the ensemble of particles. However, on account of SP-catalyzed ADP/ATP exchange, GroES symmetry is rapidly restored. The residence time of both GroES and SP on functional GroEL is reduced to ?1 s, enabling many more iterations than was previously believed possible, consistent with the iterative annealing mechanism. This result is inconsistent with currently accepted models. Using a foldable SP, we show that as the SP folds to the native state and the population of unfolded SP declines, the population of symmetric particles reverts to asymmetric particles in parallel, a result that is consistent with the former being the folding functional form. PMID:24167279

Yang, Dong; Ye, Xiang; Lorimer, George H.

2013-01-01

92

Infrared diode laser spectroscopy of O2—N2O van der Waals complex in the ?1 symmetric stretch region of N2O  

NASA Astrophysics Data System (ADS)

The rovibrational spectrum of O2—N2O van der Waals complex is measured in the ?1 symmetric stretch region of N2O monomer using a tunable diode laser spectrometer. The complex is generated by a slit-pulsed supersonic expansion with gas mixtures of O2, N2O, and He. Both a- and b-type transitions are observed. The effective Hamiltonian for an open-shell complex consisting of a diatomic molecule in a 3? electronic state and a closed-shell partner is used to analyze the observed spectrum. Molecular constants in the vibrationally excited state are determined accurately. The band-origin of the spectrum is determined to be 1284.7504(25) cm?1, red-shifted from that of the N2O monomer by ~ 0.1529 cm?1.

Li, Song; Zheng, Rui; Duan, Chuan-Xi

2014-12-01

93

Bayesian Model Selection in Complex Linear Systems, as Illustrated in Genetic Association Studies  

PubMed Central

Summary Motivated by examples from genetic association studies, this paper considers the model selection problem in a general complex linear model system and in a Bayesian framework. We discuss formulating model selection problems and incorporating context-dependent a priori information through different levels of prior specifications. We also derive analytic Bayes factors and their approximations to facilitate model selection and discuss their theoretical and computational properties. We demonstrate our Bayesian approach based on an implemented Markov Chain Monte Carlo (MCMC) algorithm in simulations and a real data application of mapping tissue-specific eQTLs. Our novel results on Bayes factors provide a general framework to perform efficient model comparisons in complex linear model systems. PMID:24350677

Wen, Xiaoquan

2013-01-01

94

A short Note on Linear Autarkies, q-Horn Formulas and the Complexity Index  

Microsoft Academic Search

It is shown that the tractable class of CNF formulas solvable by Linear Autarkies properlycontains the class of q-Horn formulas and that it is incomparable with SLUR.Keywords: Satisfiability, Autarkies, Horn, Complexity.1991 Mathematics Subject Classification. Primary 68Q15, 03B05, 68T15; Secondary90C09.1 IntroductionThe reader is supposed to be familiar with the basic terminology and facts regarding theSatisfiability Problem (see [7] for a survey).Some

H. Van Maaren

1999-01-01

95

Adequacy of approximations to distributions of test statistics in complex mixed linear models  

Microsoft Academic Search

A recent study of lady beetle antennae was a small sample repeated measures design involving a complex covariance structure.\\u000a Distributions of test statistics based on mixed models fitted to such data are unknown, but two recently developed methods\\u000a for approximating the distributions of test statistics in mixed linear models have been included as options in the latest\\u000a release of the

G. Bruce Schaalje; Justin B. McBride; Gilbert W. Fellingham

2002-01-01

96

The linear ubiquitin assembly complex (LUBAC) is essential for NLRP3 inflammasome activation  

PubMed Central

Linear ubiquitination is a newly discovered posttranslational modification that is currently restricted to a small number of known protein substrates. The linear ubiquitination assembly complex (LUBAC), consisting of HOIL-1L, HOIP, and Sharpin, has been reported to activate NF-?B–mediated transcription in response to receptor signaling by ligating linear ubiquitin chains to Nemo and Rip1. Despite recent advances, the detailed roles of LUBAC in immune cells remain elusive. We demonstrate a novel HOIL-1L function as an essential regulator of the activation of the NLRP3/ASC inflammasome in primary bone marrow–derived macrophages (BMDMs) independently of NF-?B activation. Mechanistically, HOIL-1L is required for assembly of the NLRP3/ASC inflammasome and the linear ubiquitination of ASC, which we identify as a novel LUBAC substrate. Consequently, we find that HOIL-1L?/? mice have reduced IL-1? secretion in response to in vivo NLRP3 stimulation and survive lethal challenge with LPS. Together, these data demonstrate that linear ubiquitination is required for NLRP3 inflammasome activation, defining the molecular events of NLRP3 inflammasome activation and expanding the role of LUBAC as an innate immune regulator. Furthermore, our observation is clinically relevant because patients lacking HOIL-1L expression suffer from pyogenic bacterial immunodeficiency, providing a potential new therapeutic target for enhancing inflammation in immunodeficient patients. PMID:24958845

Rodgers, Mary A.; Bowman, James W.; Fujita, Hiroaki; Orazio, Nicole; Shi, Mude; Liang, Qiming; Amatya, Rina; Kelly, Thomas J.; Iwai, Kazuhiro; Ting, Jenny

2014-01-01

97

Metal-metal interactions in linear tri-, penta-, hepta-, and nona-nuclear ruthenium string complexes.  

PubMed

Density functional theory (DFT) methodology was used to examine the structural properties of linear metal string complexes: [Ru(3)(dpa)(4)X(2)] (X = Cl(-), CN(-), NCS(-), dpa = dipyridylamine(-)), [Ru(5)(tpda)(4)Cl(2)], and hypothetical, not yet synthesized complexes [Ru(7)(tpta)(4)Cl(2)] and [Ru(9)(ppta)(4)Cl(2)] (tpda = tri-?-pyridyldiamine(2-), tpta = tetra-?-pyridyltriamine(3-), ppta = penta-?-pyridyltetraamine(4-)). Our specific focus was on the two longest structures and on comparison of the string complexes and unsupported ruthenium backboned chain complexes, which have weaker ruthenium-ruthenium interactions. The electronic structures were studied with the aid of visualized frontier molecular orbitals, and Bader's quantum theory of atoms in molecules (QTAIM) was used to study the interactions between ruthenium atoms. The electron density was found to be highest and distributed most evenly between the ruthenium atoms in the hypothetical [Ru(7)(tpta)(4)Cl(2)] and [Ru(9)(ppta)(4)Cl(2)] string complexes. PMID:21870194

Niskanen, Mika; Hirva, Pipsa; Haukka, Matti

2012-05-01

98

IFN-? or IFN-? ameliorates chronic proliferative dermatitis by inducing expression of linear ubiquitin chain assembly complex.  

PubMed

The linear ubiquitin chain assembly complex (LUBAC) ubiquitin ligase complex, composed of HOIL-1L-interacting protein (HOIP), heme-oxidized IRP2 ubiquitin ligase-1L (HOIL-1L), and SHANK-associated RH domain protein, specifically generates linear polyubiquitin chains and is involved in NF-?B activation. Lack of SHANK-associated RH domain protein, which drastically reduces the amount of HOIP and HOIL-1L, causes chronic proliferative dermatitis (cpdm) in mice. Impaired NF-?B activation and augmented apoptosis have been implicated in the pathogenesis of cpdm in mice. In this study, we found that IFN-? increased the amount of LUBAC by inducing HOIP and HOIL-1L mRNA transcription and enhanced the signal-induced NF-?B activation in embryonic fibroblasts, keratinocytes, and bone marrow-derived macrophages from wild-type and/or cpdm mice; however, IFN-? failed to augment NF-?B activation in mouse embryonic fibroblasts lacking linear polyubiquitination activity of LUBAC. Moreover, s.c. injection of IFN-? for 3 wk into the skin of cpdm mice increased the amount of HOIP, suppressed apoptosis, and ameliorated the dermatitis. Inhibition of keratinocyte apoptosis by IFN-? injection suppressed neutrophil, macrophage, and mast cell infiltration and the amount of TNF-? in the skin of cpdm mice. Similarly, IFN-? also enhanced the amount of HOIP as well as NF-?B activation, inhibited apoptosis, and ameliorated cpdm dermatitis. These results indicate that the IFNs enhance NF-?B activation and ameliorate cpdm dermatitis by augmenting expression of HOIP and HOIL-1L and linear polyubiquitination activity of LUBAC. PMID:24634492

Tamiya, Hironari; Terao, Mika; Takiuchi, Tsuyoshi; Nakahara, Masaki; Sasaki, Yoshiteru; Katayama, Ichiro; Yoshikawa, Hideki; Iwai, Kazuhiro

2014-04-15

99

Symmetric textures  

SciTech Connect

The Wolfenstein parametrization is extended to the quark masses in the deep ultraviolet, and an algorithm to derive symmetric textures which are compatible with existing data is developed. It is found that there are only five such textures.

Ramond, P. (Florida Univ., Gainesville, FL (United States). Dept. of Physics)

1993-01-01

100

Symmetric textures  

SciTech Connect

The Wolfenstein parametrization is extended to the quark masses in the deep ultraviolet, and an algorithm to derive symmetric textures which are compatible with existing data is developed. It is found that there are only five such textures.

Ramond, P. [Florida Univ., Gainesville, FL (United States). Dept. of Physics

1993-04-01

101

Symmetrical P4 cleavage at cobalt half sandwich complexes [(?5-C5H5)Co(L)] (L = CO, NHC)--a computational case study on the mechanism of symmetrical P4 degradation to P2 ligands.  

PubMed

A full theoretical mechanistic investigation on the symmetrical cleavage of P4 at the active complex fragments [(?(5)-C5H5)Co(L)] (L = CO, (i)Pr2Im; (i)Pr2Im = 1,3-di-iso-propylimidazolin-2-ylidene), which results in the formation of the complex [{(?(5)-C5H5)Co}2(?,?(2:2)-P2)2] 9, is presented. The overall reaction mechanism is a complex, multistep process. Rate-determining steps of the reaction sequence are two consecutive dissociations of the co-ligands L, which induce the decisive structural rearrangements of the P4 unit. The choice of the co-ligand L ( = CO, (i)Pr2Im) influences the kinetic barrier as well as the energy balance of the overall reaction path significantly. The calculations further reveal a strong influence of the entropic effect on the overall reaction. As a consequence, the energy balance of the overall formation of 9 starting from [(?(5)-C5H5)Co(CO)] precursors is almost thermoneutral and has to overcome high kinetic barriers, whereas the reaction starting from [(?(5)-C5H5)Co((i)Pr2Im)] precursors is exothermic, featuring lower transition barriers with stabilized intermediates. From the direct comparison of both reaction coordinates it seems that the entropic effect of the co-ligands is even stronger than their electronic influence, as for both investigated systems the reactions' energy profiles are almost identical up to intermediate [{(?(5)-C5H5)Co(L)}2(?,?(2:2)-P4)] 5 (L = CO, (i)Pr2Im). After the formation of 5, the first CO dissociation step renders the reaction endothermic for L = CO, whereas in the case of (i)Pr2Im dissociation the reaction progresses exothermically. Energy decomposition analysis and fragment analysis provide a picture of the bonding mechanisms between the metal complex fragments and P4 in the case of the most significant intermediates and the final product. PMID:23515870

Zarzycki, Bartosz; Bickelhaupt, F Matthias; Radius, Udo

2013-05-28

102

Essential Role of the Linear Ubiquitin Chain Assembly Complex in Lymphoma Revealed by Rare Germline Polymorphisms  

PubMed Central

Constitutive activation of NF-?B is a hallmark of the activated B cell-like (ABC) subtype of diffuse large B cell lymphoma (DLBCL), owing to upstream signals from the B cell receptor (BCR) and MyD88 pathways. The linear polyubiquitin chain assembly complex (LUBAC) attaches linear polyubiquitin chains to I?B kinase ?, a necessary event in some pathways that engage NF-?B. Two germ line polymorphisms affecting the LUBAC subunit RNF31 are rare among healthy individuals (~1%) but enriched in ABC DLBCL (7.8%). These polymorphisms alter RNF31 ? helices that mediate binding to the LUBAC subunit RBCK1, thereby increasing RNF31-RBCK1 association, LUBAC enzymatic activity, and NF-?B engagement. In the BCR pathway, LUBAC associates with the CARD11/MALT1/BCL10 adapter complex and is required for ABC DLBCL viability. A stapled RNF31 ?-helical peptide based on the ABC DLBCL-associated Q622L polymorphism inhibited RFN31-RBCK1 binding, decreased NF-?B and killed ABC DLBCL cells, credentialing this protein-protein interface as a therapeutic target. PMID:24491438

Yang, Yibin; Schmitz, Roland; Mitala, Joseph; Whiting, Amanda; Xiao, Wenming; Ceribelli, Michele; Wright, George W.; Zhao, Hong; Yang, Yandan; Xu, Weihong; Rosenwald, Andreas; Ott, German; Gascoyne, Randy D.; Connors, Joseph M.; Rimsza, Lisa M.; Campo, Elias; Jaffe, Elaine S.; Delabie, Jan; Smeland, Erlend B.; Braziel, Rita M.; Tubbs, Raymond R.; Cook, James. R.; Weisenburger, Dennis D.; Chan, Wing C.; Wiestner, Adrian; Kruhlak, Michael J.; Iwai, Kazuhiro; Bernal, Federico; Staudt, Louis M.

2014-01-01

103

Ab initio anharmonic vibrational frequency predictions for linear proton-bound complexes OC-H(+)-CO and N(2)-H(+)-N(2).  

PubMed

Ab initio anharmonic transition frequencies are calculated for strongly coupled (i) asymmetric and (ii) symmetric proton stretching modes in the X-H(+)-X linear ionic hydrogen bonded complexes for OCHCO(+) and N(2)HN(2)(+). The optimized potential surface is calculated in these two coordinates for each molecular ion at CCSD(T)/aug-cc-pVnZ (n = 2-4) levels and extrapolated to the complete-basis-set limit (CBS). Slices through both 2D surfaces reveal a relatively soft potential in the asymmetric proton stretching coordinate at near equilibrium geometries, which rapidly becomes a double minimum potential with increasing symmetric proton acceptor center of mass separation. Eigenvalues are obtained by solution of the 2D Schrödinger equation with potential/kinetic energy coupling explicity taken into account, converged in a distributed Gaussian basis set as a function of grid density. The asymmetric proton stretch fundamental frequency for N(2)HN(2)(+) is predicted at 848 cm(-1), with strong negative anharmonicity in the progression characteristic of a shallow "particle in a box" potential. The corresponding proton stretch fundamental for OCHCO(+) is anomalously low at 386 cm(-1), but with a strong alternation in the vibrational spacing due to the presence of a shallow D(infinityh) transition state barrier (Delta = 398 cm(-1)) between the two equivalent minimum geometries. Calculation of a 2D dipole moment surface and transition matrix elements reveals surprisingly strong combination and difference bands with appreciable intensity throughout the 300-1500 cm(-1) region. Corrected for zero point (DeltaZPE) and thermal vibrational excitation (DeltaE(vib)) at 300 K, the single and double dissociation energies in these complexes are in excellent agreement with thermochemical gas phase ion data. PMID:20589281

Terrill, Kasia; Nesbitt, David J

2010-08-01

104

Structures of KcsA in complex with symmetrical quaternary ammonium compounds reveal a hydrophobic binding site.  

PubMed

Potassium channels allow for the passive movement of potassium ions across the cell membrane and are instrumental in controlling the membrane potential in all cell types. Quaternary ammonium (QA) compounds block potassium channels and have long been used to study the functional and structural properties of these channels. Here we describe the interaction between three symmetrical hydrophobic QAs and the prokaryotic potassium channel KcsA. The structures demonstrate the presence of a hydrophobic pocket between the inner helices of KcsA and provide insight into the binding site and blocking mechanism of hydrophobic QAs. The structures also reveal a structurally hidden pathway between the central cavity and the outside membrane environment reminiscent of the lateral fenestration observed in sodium channels that can be accessed through small conformational changes in the pore wall. We propose that the hydrophobic binding pocket stabilizes the alkyl chains of long-chain QA molecules and may play a key role in hydrophobic drug binding in general. PMID:25093676

Lenaeus, Michael J; Burdette, Dylan; Wagner, Tobias; Focia, Pamela J; Gross, Adrian

2014-08-19

105

One of the most interesting types of propagation-invariant vectorial beams is the linearly polarized axially symmetric beam (L Light manipulation by use of micro & nanostructures  

E-print Network

measurement [4], spatial-polarization state scrambling for image encryption, vectorial vortex mode polarized axially symmetric beam (L Light manipulation by use of micro & nanostructures Avi Niv, Gabriel-variant polarization manipulation for obtaining vectorial beams. In general, vectorial beams are defined as beams

Rimon, Elon

106

Linear assembly of a porphyrin-C60 complex confined in vertical nanocylinders of amphiphilic block copolymer films.  

PubMed

Linear assemblies of a 1?:?1 porphyrin-fullerene C60 complex were formed in vertical cylindrical polyether nanodomains of amphiphilic block copolymer films by a simple spin coating-annealing method. The nanocylinder structures were retained even with high contents of the complex in the polymer films. PMID:25512950

Kamimura, Takuya; Komura, Motonori; Komiyama, Hideaki; Iyoda, Tomokazu; Tani, Fumito

2015-01-15

107

Interactions of an asymmetric amine with a non-C2 symmetric Cu-salen complex: an EPR/ENDOR and HYSCORE investigation.  

PubMed

Single enantiomers of R-/S-methylbenzylamine (MBA) were found to selectively form adducts with the chiral non-C(2) symmetric Cu-salen complex N-(3,5-di-tert-butylsalicylidene)-N'-(salicylidene)-cyclohexane-1,2-diamine copper(II), hereafter labelled [Cu(3)]. The g/A spin Hamiltonian parameters of this Cu(II) complex showed a decrease in symmetry from axial to rhombic upon formation of the [Cu(3)] + MBA adducts. The selectivity in enantiomeric discrimination was found to be only 59 ± 5% in favour of the heterochiral R,R'-[Cu(3)] + S-MBA and S,S'-[Cu(3)] + R-MBA adducts. This was directly evidenced by W-band EPR spectroscopy. The observed low selectivity for enantiomer discrimination is primarily attributed to the loss of the bulky tert-butyl groups from the 3,5 positions of [Cu(3)] compared to the parent N,N'-bis(3,5-di-tert-butylsalicylidene)-cyclohexane-1,2-diamine copper(II) ligand (labelled [Cu(1)]). The structure of the [Cu(3)] complex in the presence and absence of coordinating amine was further investigated by analysis of the ligand hyperfine interactions, as revealed through Q-band CW-ENDOR, X-band Davies ENDOR and HYSCORE. (1)H couplings from the -NH(2) group of the amine, observed by ENDOR and HYSCORE, provided direct evidence of amine coordination. PMID:21993696

Caretti, Ignacio; Carter, Emma; Fallis, Ian A; Murphy, Damien M; Van Doorslaer, Sabine

2011-12-01

108

Waste management under multiple complexities: Inexact piecewise-linearization-based fuzzy flexible programming  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Inexact piecewise-linearization-based fuzzy flexible programming is proposed. Black-Right-Pointing-Pointer It's the first application to waste management under multiple complexities. Black-Right-Pointing-Pointer It tackles nonlinear economies-of-scale effects in interval-parameter constraints. Black-Right-Pointing-Pointer It estimates costs more accurately than the linear-regression-based model. Black-Right-Pointing-Pointer Uncertainties are decreased and more satisfactory interval solutions are obtained. - Abstract: To tackle nonlinear economies-of-scale (EOS) effects in interval-parameter constraints for a representative waste management problem, an inexact piecewise-linearization-based fuzzy flexible programming (IPFP) model is developed. In IPFP, interval parameters for waste amounts and transportation/operation costs can be quantified; aspiration levels for net system costs, as well as tolerance intervals for both capacities of waste treatment facilities and waste generation rates can be reflected; and the nonlinear EOS effects transformed from objective function to constraints can be approximated. An interactive algorithm is proposed for solving the IPFP model, which in nature is an interval-parameter mixed-integer quadratically constrained programming model. To demonstrate the IPFP's advantages, two alternative models are developed to compare their performances. One is a conventional linear-regression-based inexact fuzzy programming model (IPFP2) and the other is an IPFP model with all right-hand-sides of fussy constraints being the corresponding interval numbers (IPFP3). The comparison results between IPFP and IPFP2 indicate that the optimized waste amounts would have the similar patterns in both models. However, when dealing with EOS effects in constraints, the IPFP2 may underestimate the net system costs while the IPFP can estimate the costs more accurately. The comparison results between IPFP and IPFP3 indicate that their solutions would be significantly different. The decreased system uncertainties in IPFP's solutions demonstrate its effectiveness for providing more satisfactory interval solutions than IPFP3. Following its first application to waste management, the IPFP can be potentially applied to other environmental problems under multiple complexities.

Sun Wei [Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan, S4S 0A2 (Canada); Huang, Guo H., E-mail: huang@iseis.org [Institute for Energy, Environment and Sustainability Research, UR-NCEPU, North China Electric Power University, Beijing 102206 (China); Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, Saskatchewan, S4S 0A2 (Canada); Lv Ying; Li Gongchen [Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan, S4S 0A2 (Canada)

2012-06-15

109

Detecting internally symmetric protein structures  

PubMed Central

Background Many functional proteins have a symmetric structure. Most of these are multimeric complexes, which are made of non-symmetric monomers arranged in a symmetric manner. However, there are also a large number of proteins that have a symmetric structure in the monomeric state. These internally symmetric proteins are interesting objects from the point of view of their folding, function, and evolution. Most algorithms that detect the internally symmetric proteins depend on finding repeating units of similar structure and do not use the symmetry information. Results We describe a new method, called SymD, for detecting symmetric protein structures. The SymD procedure works by comparing the structure to its own copy after the copy is circularly permuted by all possible number of residues. The procedure is relatively insensitive to symmetry-breaking insertions and deletions and amplifies positive signals from symmetry. It finds 70% to 80% of the TIM barrel fold domains in the ASTRAL 40 domain database and 100% of the beta-propellers as symmetric. More globally, 10% to 15% of the proteins in the ASTRAL 40 domain database may be considered symmetric according to this procedure depending on the precise cutoff value used to measure the degree of perfection of the symmetry. Symmetrical proteins occur in all structural classes and can have a closed, circular structure, a cylindrical barrel-like structure, or an open, helical structure. Conclusions SymD is a sensitive procedure for detecting internally symmetric protein structures. Using this procedure, we estimate that 10% to 15% of the known protein domains may be considered symmetric. We also report an initial, overall view of the types of symmetries and symmetric folds that occur in the protein domain structure universe. PMID:20525292

2010-01-01

110

Preparation, linear and NLO properties of DNA-CTMA-SBE complexes  

NASA Astrophysics Data System (ADS)

Synthesis of deoxyribonucleic acid (DNA) - was cetyltrimethylammonium (CTMA) - sea buckthorn extract (SBE) at different concentrations is decribed. The complexes were processed into good optical quality thin films by spin coating on different substrates such as: glass, silica and ITO covered glass substrates. SBE contains many bioactive substances that can be used in the treatment of several diseases, such as cardiovascular disease, cancer, and acute mountain sickness. The obtained thin films were characterized for their spectroscopic, fluorescent, linear and nonlinear optical properties as function of SBE concentration. The third-order nonlinear optical (NLO) properties of thin films were determined by the optical third-harmonic generation technique at 1 064.2 nm fundamental wavelength.

Manea, Ana-Maria; Rau, Ileana; Kajzar, Francois; Meghea, Aurelia

2013-10-01

111

Simple scheme for universal linear-optics quantum computing with constant experimental complexity using fiber loops  

NASA Astrophysics Data System (ADS)

Recently, Motes, Gilchrist, Dowling, and Rohde [Phys. Rev. Lett. 113, 120501 (2014)., 10.1103/PhysRevLett.113.120501] presented a scheme for photonic boson sampling using a fiber-loop architecture. Here we show that the same architecture can be modified to implement full, universal linear-optics quantum computing, in various incarnations. The scheme employs two embedded fiber loops, a single push-button photon source, three dynamically controlled beamsplitters, and a single time-resolved photodetector. The architecture has only a single point of interference, and thus may be significantly easier to align than other schemes. The experimental complexity of the scheme is constant, irrespective of the size of the computation, limited only by fiber lengths and their respective loss rates.

Rohde, Peter P.

2015-01-01

112

Linear-algebraic bath transformation for simulating complex open quantum systems  

NASA Astrophysics Data System (ADS)

In studying open quantum systems, the environment is often approximated as a collection of non-interacting harmonic oscillators, a configuration also known as the star-bath model. It is also well known that the star-bath can be transformed into a nearest-neighbor interacting chain of oscillators. The chain-bath model has been widely used in renormalization group approaches. The transformation can be obtained by recursion relations or orthogonal polynomials. Based on a simple linear algebraic approach, we propose a bath partition strategy to reduce the system-bath coupling strength. As a result, the non-interacting star-bath is transformed into a set of weakly coupled multiple parallel chains. The transformed bath model allows complex problems to be practically implemented on quantum simulators, and it can also be employed in various numerical simulations of open quantum dynamics.

Huh, Joonsuk; Mostame, Sarah; Fujita, Takatoshi; Yung, Man-Hong; Aspuru-Guzik, Alán

2014-12-01

113

Information and linearity of time-domain complex demodulated amplitude and phase data in shallow water.  

PubMed

Wave-theoretic ocean acoustic propagation modeling is used to derive the sensitivity of pressure, and complex demodulated amplitude and phase, at a receiver to the sound speed of the medium using the Born-Fre?chet derivative. Although the procedure can be applied for pressure as a function of frequency instead of time, the time domain has advantages in practical problems, as linearity and signal-to-noise are more easily assigned in the time domain. The linearity and information content of these sensitivity kernels is explored for an example of a 3-4 kHz broadband pulse transmission in a 1 km shallow water Pekeris waveguide. Full-wave observations (pressure as a function of time) are seen to be too nonlinear for use in most practical cases, whereas envelope and phase data have a wider range of validity and provide complementary information. These results are used in simulated inversions with a more realistic sound speed profile, comparing the performance of amplitude and phase observations. PMID:21895067

Sarkar, Jit; Cornuelle, Bruce D; Kuperman, W A

2011-09-01

114

Synthesis and characterization of a series of transition metal complexes with a new symmetrical polyoxaaza macroacyclic Schiff base ligand: X-ray crystal structure of cobalt(II) and nickel(II) complexes and their antibacterial properties  

NASA Astrophysics Data System (ADS)

A new symmetrical [N4O2] hexadentate Schiff base ligand, (E)-N-(pyridin-2-ylmethylene)-2-(3-(2-((E)-pyridin-2-lmethyleneamino)phenoxy)naphthalen-2-yloxy)benzenamine, abbreviated to L, and its complexes of Ni(II), Cu(II), Zn(II), Co(II), Cd(II) and Mn(II) have been synthesized in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV-Vis, NMR and molar conductivity. The crystal structures of two complexes, [NiL(ONO2)2]·2H2O and [CoLCl2]CH3OH·0.5H2O, have been determined by a single crystal X-ray diffraction study. In these complexes, the ligand is coordinated in a neutral form via pyridine and azomethine nitrogen atoms. The metal ions complete their six coordination with two coordinated nitrate or chloride ions, forming a distorted octahedral geometry. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Enterococcus faecalis, Bacillus cereus and Staphylococcus epid and also against the three Gram-negative bacteria: Citrobacter freundii, Enterobacter aerogenes and Salmonella typhi. The activity data show that the complexes are more potent antibacterials than the parent Schiff base.

Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Chalabian, Firoozeh; Valencia, Laura

2013-01-01

115

A new ion mobility-linear ion trap instrument for complex mixture analysis.  

PubMed

A new instrument that couples a low-pressure drift tube with a linear ion trap mass spectrometer is demonstrated for complex mixture analysis. The combination of the low-pressure separation with the ion trapping capabilities provides several benefits for complex mixture analysis. These include high sensitivity, unique ion fragmentation capabilities, and high reproducibility. Even though the gas-phase separation and the mass measurement steps are each conducted in an ion filtering mode, detection limits for mobility-selected peptide ions are in the tens of attomole range. In addition to ion separation, the low-pressure drift tube can be used as an ion fragmentation cell yielding mobility-resolved fragment ions that can be subsequently analyzed by multistage tandem mass spectrometry (MS(n)) methods in the ion trap. Because of the ion trap configuration, these methods can be comprised of any number (limited by ion signal) of collision-induced dissociation (CID) and electron transfer dissociation (ETD) processes. The high reproducibility of the gas-phase separation allows for comparison of two-dimensional ion mobility spectrometry (IMS)-MS data sets in a pixel-by-pixel fashion without the need for data set alignment. These advantages are presented in model analyses representing mixtures encountered in proteomics and metabolomics experiments. PMID:25068446

Donohoe, Gregory C; Maleki, Hossein; Arndt, James R; Khakinejad, Mahdiar; Yi, Jinghai; McBride, Carroll; Nurkiewicz, Timothy R; Valentine, Stephen J

2014-08-19

116

Crystallization and structure determination of a symmetrical 'football' complex of the mammalian mitochondrial Hsp60-Hsp10 chaperonins.  

PubMed

The mitochondrial Hsp60-Hsp10 complex assists the folding of various proteins impelled by ATP hydrolysis, similar to the bacterial chaperonins GroEL and GroES. The near-atomic structural details of the mitochondrial chaperonins are not known, despite the fact that almost two decades have passed since the structures of the bacterial chaperonins became available. Here, the crystallization procedure, diffraction experiments and structure determination by molecular replacement of the mammalian mitochondrial chaperonin HSP60 (E321K mutant) and its co-chaperonin Hsp10 are reported. PMID:24419632

Nisemblat, Shahar; Parnas, Avital; Yaniv, Oren; Azem, Abdussalam; Frolow, Felix

2014-01-01

117

Investigation on the linear and nonlinear optical properties of a metal organic complex—Bis thiourea zinc acetate single crystal  

NASA Astrophysics Data System (ADS)

The third order nonlinear optical properties of bis thiourea zinc acetate single crystal were measured using He-Ne laser (?=632.8nm) by employing the Z-scan technique. The magnitude of nonlinear refractive index and nonlinear absorption coefficient were found to be -2.11×10-8cm2/W and -1.201×10-3cm/W respectively. The linear refractive index of the complex was measured by the Brewster angle method and was found to be 1.483. The third order non-linear optical susceptibility ?(3) was found to be in the order of 10-6esu. The negative non-linear absorption coefficient shows the defocusing nature of the complex which is an essential property required for the application in optical limiting application. The second harmonic generation efficiency of the complex was studied using the Powder Kurtz method and was found to be 1.5 times greater than that of KDP.

Pabitha, G.; Dhanasekaran, R.

2013-09-01

118

Turning symmetric an asymmetric hydrogen bond with the inclusion of nuclear quantum effects: The case of the [CN...H...NC]- complex  

NASA Astrophysics Data System (ADS)

Nuclear quantum effects (NQE) on the geometry, energy, and electronic structure of the [{CN}\\cdot {L} \\cdot {NC}]- complex (L = H, D, T) are investigated with the recently developed APMO/MP2 code. This code implements the nuclear molecular orbital approach (NMO) at the Hartree-Fock (HF) and MP2 levels of theory for electrons and quantum nuclei. In a first study, we examined the H/D/T isotope effects on the geometry and electronic structure of the CNH molecule at NMO/HF and NMO/MP2 levels of theory. We found that when increasing the hydrogen nuclear mass there is a reduction of the R_{{N-H}} bond distance and an increase of the electronic population on the hydrogen atom. Our calculated bond distances are in good agreement with experimental and other theoretical results. In a second investigation, we explored the hydrogen NQE on the geometry of [CNHNC] ^- complex at the NMO/HF and NMO/MP2 levels of theory. We discovered that while a NMO/HF calculation presented an asymmetric hydrogen bond, the NMO/MP2 calculation revealed a symmetric H-bond. We also examined the H/D/T isotope effects on the geometry and stabilization energy of the [CNHNC] ^- complex. We noted that gradual increases in hydrogen mass led to reductions of the R_{{NN}} distance and destabilization of the hydrogen bond (H-bond). A discussion of these results is given in terms of the hydrogen nuclear delocalization effects on the electronic structure and energy components. To the best of our knowledge, this is the first ab initio NMO study that reveals the importance of including nuclear quantum effects in conventional electronic structure calculations for an enhanced description of strong-low-barrier H-bonded systems.

Moreno, Diego V.; González, Sergio A.; Reyes, Andrés

2011-01-01

119

Symmetric Cryptography Asymmetric Cryptography  

E-print Network

Outline Symmetric Cryptography Asymmetric Cryptography Key Management Network Security Cryptography Symmetric Cryptography Asymmetric Cryptography Key Management Network Security 1 Symmetric Cryptography Symmetric Cryptography Overview Block Cipher Modes Multiple Encryption Hash Functions Message Authentication

Ramkumar, Mahalingam

120

Synthesis, structure, and magnetic and electrochemical properties of quasi-linear and linear iron(I), cobalt(I), and nickel(I) amido complexes.  

PubMed

Three potassium crown ether salts, [K(Et2O)2(18-crown-6)][Fe{N(SiMe3)Dipp}2] (1a; Dipp = C6H3-2,6-Pr(i)2), [K(18-crown-6)][Fe{N(SiMe3)Dipp}2]·0.5PhMe (1b), and [K(18-crown-6)][M{N(SiMe3)Dipp}2] (M = Co, 2; M = Ni, 3), of the two-coordinate linear or near-linear bis-amido monoanions [M{N(SiMe3)Dipp}2](-) (M = Fe, Co, Ni) were synthesized by one-electron reduction of the neutral precursors M{N(SiMe3)Dipp}2 with KC8 in the presence of 18-crown-6. They were characterized by X-ray crystallography, UV-vis spectroscopy, cyclic voltammetry, and magnetic measurements. The anions feature lengthened M-N bonds in comparison with their neutral precursors, with slightly bent coordination (N-Fe-N = ca. 172°) for the iron(I) complex, but linear coordination for the cobalt(I) and nickel(I) complexes. Fits of the temperature dependence of ?MT of 1 and 2 reveal that the iron(I) and cobalt(I) complexes have large negative D zero-field splittings and a substantial orbital contribution to their magnetic moments with L = 2, whereas the nickel(I) complex has at most a small orbital contribution to its magnetic moment. The magnetic results have been used to propose an ordering of the 3d orbitals in each of the complexes. PMID:25119436

Lin, Chun-Yi; Fettinger, James C; Grandjean, Fernande; Long, Gary J; Power, Philip P

2014-09-01

121

Dual emission and excited-state mixed-valence in a quasi-symmetric dinuclear ru-ru complex.  

PubMed

The synthesis and characterization of the new dinuclear dipeptide [(EtOOC-tpy)Ru(tpy-NHCO-tpy)Ru(tpy-NHCOCH3)](4+) 3(4+) of the bis(terpyridine)ruthenium amino acid [(HOOC-tpy)Ru(tpy-NH2)](2+) 1(2+) are described, and the properties of the dipeptide are compared to those of the mononuclear complex [(EtOOC-tpy)Ru(tpy-NHCOCH3)](2+) 4(2+) carrying the same functional groups. 3(4+) is designed to serve a high electronic similarity of the two ruthenium sites despite the intrinsic asymmetry arising from the amide bridge. This is confirmed via UV-vis absorption and NMR spectroscopy as well as cyclic voltammetry. 4(2+) and 3(4+) are emissive at room temperature, as expected. Moreover, 3(4+) exhibits dual emission from two different triplet states with different energies and lifetimes at room temperature. This is ascribed to the presence of a unique thermal equilibrium between coexisting [Ru(II)(tpy-NHCO-tpy(·-))Ru(III)] and [Ru(III)(tpy-NHCO-tpy(·-))Ru(II)] states leading to an unprecedented excited-state Ru(II)Ru(III) mixed-valent system via the radical anion bridge tpy-NHCO-tpy(·-). The mixed-valent cation 3(5+), on the other hand, shows no measurable interaction of the Ru(II)Ru(III) centers via the neutral bridge tpy-NHCO-tpy (Robin-Day class I). Reduction of 3(4+) to the radical cation 3(3+) by decamethylcobaltocene is bridge-centered as evidenced by rapid-freeze electron paramagnetic resonance spectroscopy. Interestingly, all attempts to observe 3(3+) via NMR and UV-vis absorption spectroscopy only led to the detection of the diamagnetic complex 3-H(3+) in which the bridging amide is deprotonated. Hence 3-H(3+) (and 4-H(+)) appear to reduce protons to dihydrogen. The ease of single and double deprotonation of 4(2+) and 3(4+) to 4-H(+), 3-H(3+), and 3-2H(2+) was demonstrated using a strong base and was studied using NMR and UV-vis absorption spectroscopies. The equilibrating excited triplet states of 3(4+) are reductively quenched by N,N-dimethylaniline assisted by hydrogen bonding to the bridging amide. PMID:25412276

Kreitner, Christoph; Grabolle, Markus; Resch-Genger, Ute; Heinze, Katja

2014-12-15

122

Waste management under multiple complexities: inexact piecewise-linearization-based fuzzy flexible programming.  

PubMed

To tackle nonlinear economies-of-scale (EOS) effects in interval-parameter constraints for a representative waste management problem, an inexact piecewise-linearization-based fuzzy flexible programming (IPFP) model is developed. In IPFP, interval parameters for waste amounts and transportation/operation costs can be quantified; aspiration levels for net system costs, as well as tolerance intervals for both capacities of waste treatment facilities and waste generation rates can be reflected; and the nonlinear EOS effects transformed from objective function to constraints can be approximated. An interactive algorithm is proposed for solving the IPFP model, which in nature is an interval-parameter mixed-integer quadratically constrained programming model. To demonstrate the IPFP's advantages, two alternative models are developed to compare their performances. One is a conventional linear-regression-based inexact fuzzy programming model (IPFP2) and the other is an IPFP model with all right-hand-sides of fussy constraints being the corresponding interval numbers (IPFP3). The comparison results between IPFP and IPFP2 indicate that the optimized waste amounts would have the similar patterns in both models. However, when dealing with EOS effects in constraints, the IPFP2 may underestimate the net system costs while the IPFP can estimate the costs more accurately. The comparison results between IPFP and IPFP3 indicate that their solutions would be significantly different. The decreased system uncertainties in IPFP's solutions demonstrate its effectiveness for providing more satisfactory interval solutions than IPFP3. Following its first application to waste management, the IPFP can be potentially applied to other environmental problems under multiple complexities. PMID:22370050

Sun, Wei; Huang, Guo H; Lv, Ying; Li, Gongchen

2012-06-01

123

T-Matrix Modeling of Linear Depolarization by Morphologically Complex Soot and Soot-Containing Aerosols  

NASA Technical Reports Server (NTRS)

We use state-of-the-art public-domain Fortran codes based on the T-matrix method to calculate orientation and ensemble averaged scattering matrix elements for a variety of morphologically complex black carbon (BC) and BC-containing aerosol particles, with a special emphasis on the linear depolarization ratio (LDR). We explain theoretically the quasi-Rayleigh LDR peak at side-scattering angles typical of low-density soot fractals and conclude that the measurement of this feature enables one to evaluate the compactness state of BC clusters and trace the evolution of low-density fluffy fractals into densely packed aggregates. We show that small backscattering LDRs measured with groundbased, airborne, and spaceborne lidars for fresh smoke generally agree with the values predicted theoretically for fluffy BC fractals and densely packed near-spheroidal BC aggregates. To reproduce higher lidar LDRs observed for aged smoke, one needs alternative particle models such as shape mixtures of BC spheroids or cylinders.

Mishchenko, Michael I.; Liu, Li; Mackowski, Daniel W.

2013-01-01

124

T-matrix modeling of linear depolarization by morphologically complex soot and soot-containing aerosols  

NASA Astrophysics Data System (ADS)

We use state-of-the-art public-domain Fortran codes based on the T-matrix method to calculate orientation and ensemble averaged scattering matrix elements for a variety of morphologically complex black carbon (BC) and BC-containing aerosol particles, with a special emphasis on the linear depolarization ratio (LDR). We explain theoretically the quasi-Rayleigh LDR peak at side-scattering angles typical of low-density soot fractals and conclude that the measurement of this feature enables one to evaluate the compactness state of BC clusters and trace the evolution of low-density fluffy fractals into densely packed aggregates. We show that small backscattering LDRs measured with ground-based, airborne, and spaceborne lidars for fresh smoke generally agree with the values predicted theoretically for fluffy BC fractals and densely packed near-spheroidal BC aggregates. To reproduce higher lidar LDRs observed for aged smoke, one needs alternative particle models such as shape mixtures of BC spheroids or cylinders.

Mishchenko, Michael I.; Liu, Li; Mackowski, Daniel W.

2013-07-01

125

Mechanistic investigation of the cleavage of phosphodiester catalyzed by a symmetrical oxyimine-based macrocyclic dinuclear zinc complex: a DFT study.  

PubMed

Density functional theory (DFT) was utilized to investigate the hydrolysis reaction mechanisms of phosphodiester BNPP (BNPP = bis(4-nitrophenyl)phosphate) catalyzed by a symmetrical oxyimine-based macrocyclic dinuclear zinc(ii) complex. We examined the nature of the nucleophilic reagent and the active form of the catalyst. The coordination and binding models of the catalyst-substrate complex were explored and we investigated two catalyst configurations (a ridge configuration and a plane configuration), four basic catalyst-substrate binding models (a mono-point-binding model, a dual-point-binding model, an OH-bridging model and a mono-center-dual-binding model) and two alternate roles for the metal-coordinated hydroxide ion (whether it acts as a nucleophile or as a general base to facilitate the deprotonation of a solvent molecule). The one-point-binding mode was found to be preferred to construct a starting reactant. Nine plausible reaction mechanisms were proposed and investigated. Mechanism 1, a stepwise SN2-type addition-substitution reaction involving a para-position nucleophilic attack and the configuration inversion of the phosphate, was found to be the most favorable pathway. All of the proposed pathways are derived from alternate mechanisms such as a ping-pong mechanism and an AP mechanism. The ping-pong mechanism in combination with the role of the metal-coordinated hydroxide ion acting as a nucleophile was found to be more competitive than the other mechanisms examined. Results reported in this paper are consistent with, and can be utilized to systematically interpret, the experimental observations in the literature. PMID:25141046

Zhang, Xuepeng; Zheng, Xiaowei; Phillips, David Lee; Zhao, Cunyuan

2014-11-21

126

Hybrid organic/inorganic complexes based on electroactive tetrathiafulvalene-functionalized diphosphanes tethered to C(3)-symmetrized Mo(3)Q(4) (Q = S, Se) clusters.  

PubMed

A two-step procedure for the preparation of hybrid complexes based on electroactive tetrathiafulvalene (TTF)- functionalized o-P(2) diphosphanes (o-P(2) = 3,4-dimethyl-3,4-bis(diphenylphosphino)tetrathiafulvalene) and inorganic C(3)-symmetrized Mo(3)Q(4) (Q = S, Se) clusters, namely, [Mo(3)S(4)Cl(3)(o-P(2))(3)]PF(6) ([1]PF(6)) and [Mo(3)Se(4)Cl(3)(o-P(2))(3)]PF(6) ([2]PF(6)), is reported. Their molecular and electronic structures are also described on the basis of X-ray diffraction experiments and density functional theory (DFT) calculations aimed at understanding the interactions established between both the organic and the inorganic parts. Cyclic voltammograms of compounds [1]PF(6) and [2]PF(6) display reduction features associated to the Mo(3)Q(4) core and oxidation characteristics due to the TTF skeleton. The oxidation chemistry of [1]PF(6) and [2]PF(6) in solution is also investigated by means of in situ electrospray ionization (ESI) mass spectrometry, UV-vis, and, electron paramagnetic resonance (EPR) measurements. Upon addition of increasing amounts of NOPF(6) (less than 3 equiv), the sequential formation of 1(n+) (n = 1-4) species was observed whereas addition of a 3-fold excess of NOPF(6) allows to access the three-electron oxidized [Mo(3)S(4)Cl(3)(o-P(2))(3)](4+) (1(4+)) and [Mo(3)Se(4)Cl(3)(o-P(2))(3)](4+) (2(4+)) cations. These 1(4+) and 2(4+) cations represent still rare examples of complexes with oxidized TTF-ligands that are remarkably stable either toward diphosphane dissociation or phosphane oxidation. Polycrystalline samples of compound [1](PF(6))(4) were obtained by oxidation of compound [1]PF(6) using NOPF(6) which were analyzed by solid state absorption, UV-vis, and Raman spectroscopies. PMID:20085305

Avarvari, Narcis; Kiracki, Kaplan; Llusar, Rosa; Polo, Victor; Sorribes, Ivan; Vicent, Cristian

2010-02-15

127

EVALUATING PREDICTIVE ERRORS OF A COMPLEX ENVIRONMENTAL MODEL USING A GENERAL LINEAR MODEL AND LEAST SQUARE MEANS  

EPA Science Inventory

A General Linear Model (GLM) was used to evaluate the deviation of predicted values from expected values for a complex environmental model. For this demonstration, we used the default level interface of the Regional Mercury Cycling Model (R-MCM) to simulate epilimnetic total mer...

128

[Liquid-crystalline dispersions formed by complexes of linear double-stranded DNA molecules with dendrimers].  

PubMed

The formation of liquid-crystalline dispersions as a result of interaction of linear, double-stranded DNA molecules with poly(propyleneimine) dendrimers in water-salt solutions was studied. It was shown, that this process does not depend on the ionic strength of solution and molecular structure of dendrimer. By means of the atomic force microscopy, it was established, that in the case of the dendrimer molecules of the 4th generation (G4), the mean size of particles of (DNA-dendrimer G4) liquid-crystalline dispersion is equal to 300-400 nm. The "boundary" conditions (ionic strength of solutionand molecular mass of dendrimer) of formation of optically active (cholesteric) and optically inactive of the (DNA-dendrimer) dispersions were determined using circular dichroism spectroscopy. The interaction of dendrimers of 1st, 2nd, 3rd and 5th generations with DNA molecules results in the obtaining of the optically inactive dispersions. Dendrimer molecules of 4th generation induce the formation of two types dispersions: in solutions of high ionic strength (micro > 0.4) they induce the formation of cholesteric liquid-crystalline dispersions, and in solutions of low or intermediate ionic strength (micro < 0.4) they can form the optically inactive one. The "molecular crowding" affects both the efficiency of binding of dendrimer molecules of 4th generation to DNA, and the mode of spatial packing of (DNA-dendrimer G4) complexes in particles of liquid-crystalline dispersion. The possible reasons capable of explaining the structural polymorphism of (DNA-dendrimer) liquid-crystalline dispersions are discussed. PMID:19548535

Skuridin, S G; Popenko, V I; Dubinskaia, V A; Bykov, V A; Evdokimov, Iu M

2009-01-01

129

RNA polymerase II ternary complexes may become arrested after transcribing to within 10 bases of the end of linear templates.  

PubMed

In the presence of elongation factor SII, arrested RNA polymerase II ternary complexes cleave 7-17 nucleotides from the 3'-ends of their nascent RNAs. It has been shown that transcription of linear templates generates apparent run-off RNAs, which are nevertheless truncated upon incubation with SII. By using high resolution gels, we demonstrate that transcription of blunt or 3'-overhung templates with RNA polymerase II generates two populations of ternary complexes. The first class pauses 5-10 bases prior to the end of the template strand. These complexes respond to SII by cleaving approximately 9-17 nucleotide RNAs from their 3'-ends and therefore may be termed arrested. A second class of complexes, which fail to respond to SII, transcribe to within 3 bases of the end of the template strand. These complexes appear to have run off the template since they have released their nascent RNAs. Run-off transcription occurs on all types of templates, but it is the predominant reaction on DNAs with 5'-overhung ends. Thus, RNA polymerase II ternary complexes that retain 5-10 bases of contact with the template strand down-stream of the catalytic site become arrested. Further reduction of downstream template contacts can lead to termination. We also show that the addition of Sarkosyl to the elongation reactions significantly changes the pattern of transcriptional arrest near the end of linear templates. PMID:7836462

Izban, M G; Samkurashvili, I; Luse, D S

1995-02-01

130

Differential Dynamic Engagement within 24 SH3 Domain: Peptide Complexes Revealed by Co-Linear Chemical Shift Perturbation Analysis  

PubMed Central

There is increasing evidence for the functional importance of multiple dynamically populated states within single proteins. However, peptide binding by protein-protein interaction domains, such as the SH3 domain, has generally been considered to involve the full engagement of peptide to the binding surface with minimal dynamics and simple methods to determine dynamics at the binding surface for multiple related complexes have not been described. We have used NMR spectroscopy combined with isothermal titration calorimetry to comprehensively examine the extent of engagement to the yeast Abp1p SH3 domain for 24 different peptides. Over one quarter of the domain residues display co-linear chemical shift perturbation (CCSP) behavior, in which the position of a given chemical shift in a complex is co-linear with the same chemical shift in the other complexes, providing evidence that each complex exists as a unique dynamic rapidly inter-converting ensemble. The extent the specificity determining sub-surface of AbpSH3 is engaged as judged by CCSP analysis correlates with structural and thermodynamic measurements as well as with functional data, revealing the basis for significant structural and functional diversity amongst the related complexes. Thus, CCSP analysis can distinguish peptide complexes that may appear identical in terms of general structure and percent peptide occupancy but have significant local binding differences across the interface, affecting their ability to transmit conformational change across the domain and resulting in functional differences. PMID:23251481

Stollar, Elliott J.; Lin, Hong; Davidson, Alan R.; Forman-Kay, Julie D.

2012-01-01

131

Two C3 -symmetric Dy3III complexes with triple di-?-methoxo-?-phenoxo bridges, magnetic ground state, and single-molecule magnetic behavior.  

PubMed

Two series of isostructural C(3)-symmetric Ln(3) complexes Ln(3)?[BPh(4)] and Ln(3)?0.33[Ln(NO(3))(6)] (in which Ln(III) =Gd and Dy) have been prepared from an amino-bis(phenol) ligand. X-ray studies reveal that Ln(III) ions are connected by one ?(2)-phenoxo and two ?(3)-methoxo bridges, thus leading to a hexagonal bipyramidal Ln(3)O(5) bridging core in which Ln(III) ions exhibit a biaugmented trigonal-prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self-consistent field (CASSCF) calculations indicate that the magnetic coupling between the Dy(III) ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest Dy-O distance, the local magnetic moments are oriented almost perpendicular to the Dy(3) plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the Dy(III) ions are separated by approximately 150 and 177?cm(-1), for Dy(3)?[BPh(4)] and Dy(3)?0.33[Dy(NO(3))(6)], respectively. As expected for these large energy gaps, Dy(3)?[BPh(4)] and Dy(3)?0.33[Dy(NO(3)(6)] exhibit, under zero direct-current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied Hdc field of 1000?Oe, Dy(3)?[BPh(4)] exhibits two thermally activated processes with U(eff) values of 34.7 and 19.5?cm(-1), whereas Dy(3)?0.33[Dy(NO(3))(6)] shows only one activated process with Ueff =19.5?cm(-1). PMID:24890335

Hänninen, Mikko M; Mota, Antonio J; Aravena, Daniel; Ruiz, Eliseo; Sillanpää, Reijo; Camón, Agustín; Evangelisti, Marco; Colacio, Enrique

2014-07-01

132

A strain-energy-based non-linear failure criterion: comparison of numerical predictions and experimental observations for symmetric composite laminates  

Microsoft Academic Search

A strain-energy-based model to predict non-linear stress\\/strain response, failure onset and progression in composite laminates was presented by Wolfe and Butalia (Compos. Sci. Technol. 1998, 58, 1107). This paper focuses on some of the critical issues relating to the development of that model. Several of the assumptions made in the model are relaxed or modified. A variety of unidirectional and

Tarunjit S. Butalia; William E. Wolfe

2002-01-01

133

Simply Symmetric  

ERIC Educational Resources Information Center

Symmetry is found in the visual arts, architecture and design of artefacts since the earliest time. Many natural objects, both organic and inorganic, display symmetry: from microscopic crystals and sub-atomic particles to macro-cosmic galaxies. Today it features strongly in higher mathematics such as Linear and Abstract Algebra, Projective and…

de Villiers, Michael

2011-01-01

134

The optical properties of two-dimensional Scarff parity-time symmetric potentials  

NASA Astrophysics Data System (ADS)

We investigate the optical properties with two-dimensional (2D) Scarff parity-time (PT) symmetric potentials, including linear case, and self-focusing and self-defocussing nonlinear cases. For linear case, the PT-breaking points, the eigenvalues and eigenfunction for different modulated depths of 2D Scarff PT symmetry complex potential are obtained numerically. The PT-breaking points increase linearly with increasing the real part of the modulated depths of PT potential. Below the PT-breaking points, the eigenvalues of linear modes are real, however, eigenvalues of linear modes are complex above the PT-breaking points. For nonlinear cases, the existence of fundamental and multipole solitons is studied in self-focusing and self-defocussing media. The eigenvalue for linear case is equal to the critical propagation constant bc of soliton existing.

Hu, Sumei; Chen, Haibo

2014-08-01

135

Symmetric cones Jordan algebras  

E-print Network

Symmetric cones Jordan algebras The partial differential equation A partial differential equation;Symmetric cones Jordan algebras The partial differential equation Outline 1 Symmetric cones Geometric characterization Algebraic characterization 2 Jordan algebras Exponential and logarithm Trace forms and determinant

Hildebrand, Roland

136

Normalized linear variance decay dimension density and its application of dynamical complexity detection in physiological (fMRI) time series  

NASA Astrophysics Data System (ADS)

The upper and lower bounds of the linear variance decay (LVD) dimension density are analytically deduced using multivariate series with uncorrelated and perfectly correlated component series. Then, the normalized LVD dimension density ( ?) is introduced. In order to measure the complexity of a scalar series with ?, a pseudo-multivariate series was constructed from the scalar time series using time-delay embedding. Thus, ? is used to characterize the complexity of the pseudo-multivariate series. The results from the model systems and fMRI data of anxiety subjects reveal that this method can be used to analyze short and noisy time series.

Xie, Xiaoping; Zhao, Xiaohu; Fang, Youtong; Cao, Zhitong; He, Guoguang

2011-04-01

137

Probabilistic cloning of three symmetric states  

SciTech Connect

We study the probabilistic cloning of three symmetric states. These states are defined by a single complex quantity, the inner product among them. We show that three different probabilistic cloning machines are necessary to optimally clone all possible families of three symmetric states. We also show that the optimal cloning probability of generating M copies out of one original can be cast as the quotient between the success probability of unambiguously discriminating one and M copies of symmetric states.

Jimenez, O. [Center for Optics and Photonics, Departamento de Fisica, Universidad de Concepcion, Casilla 4016, Concepcion (Chile); Departamento de Fisica, Facultad de Ciencias Basicas, Universidad de Antofagasta, Casilla 170, Antofagasta (Chile); Bergou, J. [Department of Physics, Hunter College, City University of New York, 695 Park Avenue, New York, New York 10021 (United States); Delgado, A. [Center for Optics and Photonics, Departamento de Fisica, Universidad de Concepcion, Casilla 4016, Concepcion (Chile); Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

2010-12-15

138

Transmission of linear regression patterns between time series: From relationship in time series to complex networks  

NASA Astrophysics Data System (ADS)

The linear regression parameters between two time series can be different under different lengths of observation period. If we study the whole period by the sliding window of a short period, the change of the linear regression parameters is a process of dynamic transmission over time. We tackle fundamental research that presents a simple and efficient computational scheme: a linear regression patterns transmission algorithm, which transforms linear regression patterns into directed and weighted networks. The linear regression patterns (nodes) are defined by the combination of intervals of the linear regression parameters and the results of the significance testing under different sizes of the sliding window. The transmissions between adjacent patterns are defined as edges, and the weights of the edges are the frequency of the transmissions. The major patterns, the distance, and the medium in the process of the transmission can be captured. The statistical results of weighted out-degree and betweenness centrality are mapped on timelines, which shows the features of the distribution of the results. Many measurements in different areas that involve two related time series variables could take advantage of this algorithm to characterize the dynamic relationships between the time series from a new perspective.

Gao, Xiangyun; An, Haizhong; Fang, Wei; Huang, Xuan; Li, Huajiao; Zhong, Weiqiong; Ding, Yinghui

2014-07-01

139

Lipophilic platinum complexes entrapped in liposomes: improved stability and preserved antitumor activity with complexes containing linear alkyl carboxylato leaving groups  

Microsoft Academic Search

Lipophilic diaminocyclohexane (DACH) platinum complexes have shown significant promise in preclinical studies. One of these compounds, cis-bis-neodecanoato- trans-R,R-1,2-diaminocyclohexaneplatinum(II) (NDDP), which contains two branched leaving groups of 10 carbons, showed a favorable toxicity profile in a liposomal formulation in early clinical trials. However, like many other DACH platinum compounds with branched leaving groups, it is unstable within the liposomes, thus preventing

Roman Perez-Soler; Insook Han; Salaam Al-Baker; Abdul R. Khokhar

1994-01-01

140

Haptic rendering of complex deformations through handle-space force linearization  

Microsoft Academic Search

The force-update-rate requirements of transparent rendering of vir- tual environments are in conflict with the computational cost re- quired for computing complex interactions between deforming ob- jects. In this paper we introduce a novel method for satisfying high force update rates with deformable objects, yet retaining the visual quality of complex deformations and interactions. The objects that are haptically manipulated

Carlos Garre; Miguel A. Otaduy

2009-01-01

141

Linear Motif-Mediated Interactions Have Contributed to the Evolution of Modularity in Complex Protein Interaction Networks  

PubMed Central

The modular architecture of protein-protein interaction (PPI) networks is evident in diverse species with a wide range of complexity. However, the molecular components that lead to the evolution of modularity in PPI networks have not been clearly identified. Here, we show that weak domain-linear motif interactions (DLIs) are more likely to connect different biological modules than strong domain-domain interactions (DDIs). This molecular division of labor is essential for the evolution of modularity in the complex PPI networks of diverse eukaryotic species. In particular, DLIs may compensate for the reduction in module boundaries that originate from increased connections between different modules in complex PPI networks. In addition, we show that the identification of biological modules can be greatly improved by including molecular characteristics of protein interactions. Our findings suggest that transient interactions have played a unique role in shaping the architecture and modularity of biological networks over the course of evolution. PMID:25299147

Kim, Inhae; Lee, Heetak; Han, Seong Kyu; Kim, Sanguk

2014-01-01

142

Two dimensional symmetric correlation functions of the ? operator and two dimensional Fourier transforms: considering the line coupling for P and R lines of linear molecules.  

PubMed

The refinement of the Robert-Bonamy (RB) formalism by considering the line coupling for isotropic Raman Q lines of linear molecules developed in our previous study [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] has been extended to infrared P and R lines. In these calculations, the main task is to derive diagonal and off-diagonal matrix elements of the Liouville operator iS1 - S2 introduced in the formalism. When one considers the line coupling for isotropic Raman Q lines where their initial and final rotational quantum numbers are identical, the derivations of off-diagonal elements do not require extra correlation functions of the ? operator and their Fourier transforms except for those used in deriving diagonal elements. In contrast, the derivations for infrared P and R lines become more difficult because they require a lot of new correlation functions and their Fourier transforms. By introducing two dimensional correlation functions labeled by two tensor ranks and making variable changes to become even functions, the derivations only require the latters' two dimensional Fourier transforms evaluated at two modulation frequencies characterizing the averaged energy gap and the frequency detuning between the two coupled transitions. With the coordinate representation, it is easy to accurately derive these two dimensional correlation functions. Meanwhile, by using the sampling theory one is able to effectively evaluate their two dimensional Fourier transforms. Thus, the obstacles in considering the line coupling for P and R lines have been overcome. Numerical calculations have been carried out for the half-widths of both the isotropic Raman Q lines and the infrared P and R lines of C2H2 broadened by N2. In comparison with values derived from the RB formalism, new calculated values are significantly reduced and become closer to measurements. PMID:24628166

Ma, Q; Boulet, C; Tipping, R H

2014-03-14

143

Two dimensional symmetric correlation functions of the S-circumflex operator and two dimensional Fourier transforms: Considering the line coupling for P and R lines of linear molecules  

SciTech Connect

The refinement of the Robert-Bonamy (RB) formalism by considering the line coupling for isotropic Raman Q lines of linear molecules developed in our previous study [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] has been extended to infrared P and R lines. In these calculations, the main task is to derive diagonal and off-diagonal matrix elements of the Liouville operator iS{sub 1} ? S{sub 2} introduced in the formalism. When one considers the line coupling for isotropic Raman Q lines where their initial and final rotational quantum numbers are identical, the derivations of off-diagonal elements do not require extra correlation functions of the S-circumflex operator and their Fourier transforms except for those used in deriving diagonal elements. In contrast, the derivations for infrared P and R lines become more difficult because they require a lot of new correlation functions and their Fourier transforms. By introducing two dimensional correlation functions labeled by two tensor ranks and making variable changes to become even functions, the derivations only require the latters’ two dimensional Fourier transforms evaluated at two modulation frequencies characterizing the averaged energy gap and the frequency detuning between the two coupled transitions. With the coordinate representation, it is easy to accurately derive these two dimensional correlation functions. Meanwhile, by using the sampling theory one is able to effectively evaluate their two dimensional Fourier transforms. Thus, the obstacles in considering the line coupling for P and R lines have been overcome. Numerical calculations have been carried out for the half-widths of both the isotropic Raman Q lines and the infrared P and R lines of C{sub 2}H{sub 2} broadened by N{sub 2}. In comparison with values derived from the RB formalism, new calculated values are significantly reduced and become closer to measurements.

Ma, Q. [NASA/Goddard Institute for Space Studies and Department of Applied Physics and Applied Mathematics, Columbia University, 2880 Broadway, New York, New York 10025 (United States)] [NASA/Goddard Institute for Space Studies and Department of Applied Physics and Applied Mathematics, Columbia University, 2880 Broadway, New York, New York 10025 (United States); Boulet, C. [Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS (UMR8214) et Université Paris-Sud Bât 350, Campus d'Orsay F-91405 (France)] [Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS (UMR8214) et Université Paris-Sud Bât 350, Campus d'Orsay F-91405 (France); Tipping, R. H. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487-0324 (United States)] [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487-0324 (United States)

2014-03-14

144

Scaled Langevin equation for complex systems: New linear scaling relation for weight factor  

Microsoft Academic Search

A set of scaled Langevin equations is proposed to study a long time tail of correlation functions for two model systems (Type I and Type II). Each system is composed of elements which are grouped into clusters according to dynamical activations for external forces. The clusters in Type I are characterized by linear scaling rules in repetitive operations, whereas the

S. Fujita; S. S. Lee; J. Koyama

1997-01-01

145

Complex-grid spectral algorithms for inviscid linear instability of boundary-layer flows  

Microsoft Academic Search

We present a suite of algorithms designed to obtain accurate numerical solutions of the generalised eigenvalue problem governing inviscid linear instability of boundary-layer type of flow in both the incompressible and compressible regimes on planar and axisymmetric curved geometries. The large gradient problems which occur in the governing equations at critical layers are treated by diverting the integration path into

V. Theofilis; A. Karabis; S. J. Shaw

2003-01-01

146

Navigation Tools for Text Embedded within Complex-Shaped Area Features and Meandering Linear Features  

Microsoft Academic Search

By presenting textual information within the space of corresponding images, the con- cept of DUAL-USE OF IMAGE SPACE (DUIS) eases the mental integration of textual and pictorial information. This paper applies the DUIS approach which was initially developed for area features to linear features. Moreover, we enhance the DUIS approach with new tools to navigate within embedded texts: The sidebar,

Wallace Chigona; Knut Hartmann; Axel Berndt; Sebastian Mirschel; Thomas Strothotte

2003-01-01

147

Multipeaked gap solitons in PT-symmetric optical lattices.  

PubMed

We report the existence and stability properties of multipeaked solitons in a defocusing Kerr medium with an imprinted complex optical lattice featuring a parity-time (PT) symmetry. Various families of soliton solutions with a different number of peaks are found in the first finite gap of the lattice. Linear stability analysis corroborated by direct propagation simulations reveals that multipeaked gap solitons can propagate stably in a wide range, provided that their propagation constant exceeds a critical value. Our findings demonstrate, for the first time, the existence of stable multipeaked gap solitons in a PT-symmetric lattice. PMID:23114357

Li, Chunyan; Huang, Changming; Liu, Haidong; Dong, Liangwei

2012-11-01

148

Crystal structure of a symmetric football-shaped GroEL:GroES2-ATP14 complex determined at 3.8Å reveals rearrangement between two GroEL rings.  

PubMed

The chaperonin GroEL is an essential chaperone that assists in protein folding with the aid of GroES and ATP. GroEL forms a double-ring structure, and both rings can bind GroES in the presence of ATP. Recent progress on the GroEL mechanism has revealed the importance of a symmetric 1:2 GroEL:GroES2 complex (the "football"-shaped complex) as a critical intermediate during the functional GroEL cycle. We determined the crystal structure of the football GroEL:GroES2-ATP14 complex from Escherichia coli at 3.8Å, using a GroEL mutant that is extremely defective in ATP hydrolysis. The overall structure of the football complex resembled the GroES-bound GroEL ring of the asymmetric 1:1 GroEL:GroES complex (the "bullet" complex). However, the two GroES-bound GroEL rings form a modified interface by an ~7° rotation about the 7-fold axis. As a result, the inter-ring contacts between the two GroEL rings in the football complex differed from those in the bullet complex. The differences provide a structural basis for the apparently impaired inter-ring negative cooperativity observed in several biochemical analyses. PMID:25174333

Koike-Takeshita, Ayumi; Arakawa, Takatoshi; Taguchi, Hideki; Shimamura, Tatsuro

2014-10-23

149

Structure of an Antibody in Complex with Its Mucin Domain Linear Epitope That Is Protective against Ebola Virus  

PubMed Central

Antibody 14G7 is protective against lethal Ebola virus challenge and recognizes a distinct linear epitope in the prominent mucin-like domain of the Ebola virus glycoprotein GP. The structure of 14G7 in complex with its linear peptide epitope has now been determined to 2.8 Å. The structure shows that this GP sequence forms a tandem ?-hairpin structure that binds deeply into a cleft in the antibody-combining site. A key threonine at the apex of one turn is critical for antibody interaction and is conserved among all Ebola viruses. This work provides further insight into the mechanism of protection by antibodies that target the protruding, highly accessible mucin-like domain of Ebola virus and the structural framework for understanding and characterizing candidate immunotherapeutics. PMID:22171276

Olal, Daniel; Kuehne, Ana I.; Bale, Shridhar; Halfmann, Peter; Hashiguchi, Takao; Fusco, Marnie L.; Lee, Jeffrey E.; King, Liam B.; Kawaoka, Yoshihiro; Dye, John M.

2012-01-01

150

Integrated energy system for industrial complexes. Part I: A linear programming approach  

Microsoft Academic Search

A personal-computer based model of an Integrated Energy System for Industrial Estates (IESIE) has been developed as a pre-feasibility tool: it addresses the total energy concept by combining a set of CHP plant(s), boilers, vapor-compression and absorption chillers, national grid and utility transportation system. The core of the general model is the linear programming (LP) model which takes into account

Brahmanand Mohanty; Haribandhu Panda

1993-01-01

151

Copper(II) complexes of asymmetrical and symmetrical acyclic pentadentate (N 5 ) mono-Schiff-base ligands. The X-ray structure of [Cu(ppe-py)](ClO 4 ) 2  

Microsoft Academic Search

In the presence of copper(II) ion, two asymmetrical tripodal tetraamine ligands N{(CH2)3NH2}{(CH2)2NH2}2 (pee), N{(CH2)3NH2}2{(CH2)2NH2} (ppe) and one symmetrical ligand, N{(CH2)3NH2}3 (tpt), were condensed with 2-acetylpyridine. In EtOH–H2O solutions the reaction stops after the first condensation stage, and complexes of acyclic pentadentate(N5) mono-Schiff-base ligands were obtained. With asymmetrical tetraamines there are two possible condensation sites: the primary amine of the propylene,

Hassan Keypour; Sadegh Salehzadeh; Robin G. Pritchard; Richard V. Parish

2002-01-01

152

Linear copper 'chain' complexes with bulky tritopic hydrazone ligands--structural and magnetic studies.  

PubMed

Tritopic 2,6-picolyl-bis-hydrazone ligands with bulky terminal groups derived from phenyl-pyridyl ketone do not form the expected [3 x 3] grids on reaction with copper(II), but instead form Cu8 'pinwheels', and in the present case linear trinuclear, pentanuclear and chain structures also. Direct bridging between copper ions occurs through micro2-N-N diazine groups, and longer O-C-N hydrazone connections, leading to moderately strong antiferromagnetic exchange between adjacent metal centres. Structural and magnetic properties are discussed in the context of specific orthogonal and non-orthogonal bridges, which can be distinguished and quantified. PMID:17702175

Tandon, Santokh S; Dawe, Louise N; Milway, Victoria A; Collins, Julie L; Thompson, Laurence K

2007-05-21

153

Light propagation in periodically modulated complex waveguides  

E-print Network

Light propagation in optical waveguides with periodically modulated index of refraction and alternating gain and loss are investigated for linear and nonlinear systems. Based on a multiscale perturbation analysis, it is shown that for many non-parity-time ($\\mathcal{PT}$) symmetric waveguides, their linear spectrum is partially complex, thus light exponentially grows or decays upon propagation, and this growth or delay is not altered by nonlinearity. However, several classes of non-$\\mathcal{PT}$-symmetric waveguides are also identified to possess all-real linear spectrum. In the nonlinear regime longitudinally periodic and transversely quasi-localized modes are found for $\\mathcal{PT}$-symmetric waveguides both above and below phase transition. These nonlinear modes are stable under evolution and can develop from initially weak initial conditions.

Nixon, Sean

2014-01-01

154

Strongly degenerate homogeneous pseudo-Kähler structures of linear type and complex plane waves  

NASA Astrophysics Data System (ADS)

We study the class K2+K4 of homogeneous pseudo-Kähler structures in the strongly degenerate case. The local form and the holonomy of a pseudo-Kähler manifold admitting such a structure are obtained, leading to a possible complex generalization of homogeneous plane waves. The same question is tackled in the case of pseudo-hyper-Kähler and pseudo-quaternion Kähler manifolds.

Castrillón López, M.; Luján, I.

2013-11-01

155

Controlled loading of cryoprotectants (CPAs) to oocyte with linear and complex CPA profiles on a microfluidic platform.  

PubMed

Oocyte cryopreservation has become an essential tool in the treatment of infertility by preserving oocytes for women undergoing chemotherapy. However, despite recent advances, pregnancy rates from all cryopreserved oocytes remain low. The inevitable use of the cryoprotectants (CPAs) during preservation affects the viability of the preserved oocytes and pregnancy rates either through CPA toxicity or osmotic injury. Current protocols attempt to reduce CPA toxicity by minimizing CPA concentrations, or by minimizing the volume changes via the step-wise addition of CPAs to the cells. Although the step-wise addition decreases osmotic shock to oocytes, it unfortunately increases toxic injuries due to the long exposure times to CPAs. To address limitations of current protocols and to rationally design protocols that minimize the exposure to CPAs, we developed a microfluidic device for the quantitative measurements of oocyte volume during various CPA loading protocols. We spatially secured a single oocyte on the microfluidic device, created precisely controlled continuous CPA profiles (step-wise, linear and complex) for the addition of CPAs to the oocyte and measured the oocyte volumetric response to each profile. With both linear and complex profiles, we were able to load 1.5 M propanediol to oocytes in less than 15 min and with a volumetric change of less than 10%. Thus, we believe this single oocyte analysis technology will eventually help future advances in assisted reproductive technologies and fertility preservation. PMID:21887438

Heo, Yun Seok; Lee, Ho-Joon; Hassell, Bryan A; Irimia, Daniel; Toth, Thomas L; Elmoazzen, Heidi; Toner, Mehmet

2011-10-21

156

Optimal symmetric flight studies  

NASA Technical Reports Server (NTRS)

Several topics in optimal symmetric flight of airbreathing vehicles are examined. In one study, an approximation scheme designed for onboard real-time energy management of climb-dash is developed and calculations for a high-performance aircraft presented. In another, a vehicle model intermediate in complexity between energy and point-mass models is explored and some quirks in optimal flight characteristics peculiar to the model uncovered. In yet another study, energy-modelling procedures are re-examined with a view to stretching the range of validity of zeroth-order approximation by special choice of state variables. In a final study, time-fuel tradeoffs in cruise-dash are examined for the consequences of nonconvexities appearing in the classical steady cruise-dash model. Two appendices provide retrospective looks at two early publications on energy modelling and related optimal control theory.

Weston, A. R.; Menon, P. K. A.; Bilimoria, K. D.; Cliff, E. M.; Kelley, H. J.

1985-01-01

157

Symmetric Cryptography Asymmetric Cryptography  

E-print Network

Outline Trust Symmetric Cryptography Asymmetric Cryptography Key Management Network Security Cryptography - A Review Mahalingam Ramkumar Mississippi State University, MS September 22, 2006 Ramkumar Review #12;Outline Trust Symmetric Cryptography Asymmetric Cryptography Key Management Network Security 1

Ramkumar, Mahalingam

158

Solution NMR characterization of an unusual distal H-bond network in the active site of the cyanide-inhibited, human heme oxygenase complex of the symmetric substrate, 2,4-dimethyldeuterohemin.  

PubMed

The presence of variable static hemin orientational disorder about the alpha-gamma-meso axis in the substrate complexes of mammalian heme oxygenase, together with the incomplete averaging of a second, dynamic disorder, for each hemin orientation, has led to NMR spectra with severe spectral overlap and loss of key two-dimensional correlations that seriously interfere with structural characterization in solution. We demonstrate that the symmetric substrate, 2,4-dimethyldeuterohemin, yields a single solution species for which the dynamic disorder is sufficiently rapid to allow effective and informative (1)H NMR structural characterization. A much more extensive, effective, and definitive NMR characterization of the cyanide-inhibited, symmetric heme complex of human heme oxygenase shows that the active site structure, with some minor differences, is essentially the same as that for the native protohemin in solution and crystal. A unique distal network that involves particularly strong hydrogen bonds, as well as inter-aromatic contacts, is described that is proposed to stabilize the position of the catalytically critical distal helix Asp-140 carboxylate (Liu, Y., Koenigs Lightning, L., Huang, H., Moënne-Loccoz, P., Schuller, D. J., Poulos, T. L., Loehr, T. M., and Ortiz de Montellano, P. R. (2000) J. Biol. Chem. 275, 34501-34507). The potential role of this network in placing a water molecule to stabilize the hydroperoxy species and as a template for the condensation of the distal helix upon substrate binding are discussed. PMID:12070167

Li, Yiming; Syvitski, Ray T; Auclair, Karine; Wilks, Angela; Ortiz De Montellano, Paul R; La Mar, Gerd N

2002-09-01

159

Linear free energy relationships for metal-ligand complexation: Bidentate binding to negatively-charged oxygen donor atoms  

NASA Astrophysics Data System (ADS)

Stability constants for metal complexation to bidentate ligands containing negatively-charged oxygen donor atoms can be estimated from the following linear free energy relationship (LFER): log KML = ?OO( ?O log KHL,1 + ?O log KHL,2) where KML is the metal-ligand stability constant for a 1:1 complex, KHL,1 and KHL,2 are the proton-ligand stability constants (the ligand p Ka values), and ?O is the Irving-Rossotti slope. The parameter ?OO is metal specific and has slightly different values for five and six membered chelate rings. LFERs are presented for 21 different metal ions and are accurate to within approximately 0.30 log units in predictions of log KML values. Ligands selected for use in LFER development include dicarboxylic acids, carboxyphenols, and ortho-diphenols. For ortho-hydroxybenzaldehydes, ?-hydroxycarboxylic acids, and ?-ketocarboxylic acids, a modification of the LFER where log KHL,2 is set equal to zero is required. The chemical interpretation of ?OO is that it accounts for the extra stability afforded to metal complexes by the chelate effect. Cu-NOM binding constants calculated from the bidentate LFERs are similar in magnitude to those used in WHAM 6. This LFER can be used to make log KML predictions for small organic molecules. Since natural organic matter (NOM) contains many of the same functional groups (i.e. carboxylic acids, phenols, alcohols), the LFER log KML predictions shed light on the range of appropriate values for use in modeling metal partitioning in natural systems.

Carbonaro, Richard F.; Atalay, Yasemin B.; Di Toro, Dominic M.

2011-05-01

160

Localization of c-di-GMP-binding protein with the linear terminal complexes of Acetobacter xylinum.  

PubMed

Specific labeling of a single row of cellulose-synthesizing complexes (terminal complexes, TC subunits, TCs, or TC arrays) in Acetobacter xylinum by antibodies raised against a 93-kDa protein (the cyclic dignanylic acid-binding protein) has been demonstrated by using the sodium dodecyl sulfate (SDS)-freeze-fracture labeling (FRL) technique. The antibodies to the 93-kDa protein specifically recognized the TC subunits on the protoplasmic fracture (PF) face of the outer membrane in A. xylinum; however, nonlabeled TCs were also observed. Two types of TC subunits (particles or pits) are observed on the PF face of the outer membrane: (i) immunogold-labeled TCs showing a line of depressions (pits) with an indistinct particle array and (ii) nonlabeled TC subunits with a distinct single row of particle arrays. The evidence indicates that the labeling patterns differ with respect to the presence or absence of certain TC subunits remaining attached to the replica after SDS treatment. This suggests the presence of at least two TC components, one in the outer membrane and the other in the cytoplasmic membrane. If the TC component in the outer membrane is preferentially fractured and remains attached to the ectoplasmic fracture face (or outer leaflet) of the outer membrane, subsequent replica formation reveals a pit or depression with positive antibody labeling on the PF face of the outer membrane. If the TC component in the outer membrane remains with the PF face (or inner leaflet) of the outer membrane, the innermost TC component is removed during SDS treatment and labeling does not occur. SDS-FRL of TCs in A. xylinum has enabled us to provide the first topological molecular analysis of component proteins in a cellulose-synthesizing TC structure in a prokaryotic organism. PMID:11544230

Kimura, S; Chen, H P; Saxena, I M; Brown, R M; Itoh, T

2001-10-01

161

A HLL-Rankine-Hugoniot Riemann solver for complex non-linear hyperbolic problems  

NASA Astrophysics Data System (ADS)

We present a new HLL-type approximate Riemann solver that aims at capturing any isolated discontinuity without necessitating extensive characteristic analysis of governing partial differential equations. This property is especially attractive for complex hyperbolic systems with more than two equations. Following Linde's (2002) approach [6], we introduce a generic middle wave into the classical two-state HLL solver. The property of this third wave is typified by the way of a "strength indicator" that is derived from polynomial considerations. The polynomial that constitutes the basis of the procedure is made non-oscillatory by an adapted fourth-order WENO algorithm (CWENO4). This algorithm makes it possible to derive an expression for the strength indicator. According to the size of this latter parameter, the resulting solver (HLL-RH), either computes the multi-dimensional Rankine-Hugoniot equations if an isolated discontinuity appears in the Riemann fan, or asymptotically tends towards the two-state HLL solver if the solution is locally smooth. The asymptotic version of the HLL-RH solver is demonstrated to be positively conservative and entropy satisfying in its first-order multi-dimensional form provided that a relevant and not too restrictive CFL condition is considered; specific limitations of the conservative increments of the numerical solution and a suited entropy condition enable to maintain these properties in its high-order version. With a monotonicity-preserving algorithm for the time integration, the numerical method so generated, is third order in time and fourth-order accurate in space for the smooth part of the solution; moreover, the scheme is stable and accurate when capturing a shock wave, whatever the complexity of the underlying differential system. Extensive numerical tests for the one- and two-dimensional Euler equation of gas dynamics and comparisons with classical Godunov-type methods help to point out the potentialities and insufficiencies of the method.

Guy, Capdeville

2013-10-01

162

The two band model for halogen-bridged transition metal linear chain complexes  

SciTech Connect

Halogen-bridged transition-metal complexes have been of interest to chemists for many decades as dyes and strongly dichroic materials. However they have only recently begun to receive detailed consideration in the physics community. Their potential important arises because of: the increasing appreciation of strong, competing electron-electron and electron-phonon interactions in low-dimensional materials and the consequent need to expand many-body techniques. The MX materials offer a rapidly expanding, near single-crystal, class of quasi-1-D systems which can be ''tuned'' (by chemistry, pressure, doping, etc.) between various ground state extremes: from strong charge-disproportionation and large lattice distortion to weak charge-density-wave and small lattice distortion, to magnetic and undistorted; the opportunity to probe doping- and photo-induced local defect states (polarons, bipolarons, kinks, excitons) and their interactions in controlled environments and the same large range of ground states; and, the similarities between models and theoretical issues in these materials and the recently discovered oxide superconductors. The MX materials are also closely connected conceptually with mixed-stack charge-transfer salts. The MX class, then, is important in its own right, but also as a template for concepts and electronic structure techniques in strongly interacting (both electron-electron (e-e) and electron-phonon (e-p)), low dimensional electronic materials. This paper discusses the two band model for the isolated MX chains. 14 refs., 6 figs.

Bishop, A.R.; Gammel, J.T.; Loh, E.Y. Jr.; Phillpot, S.R.; Weber-Milbrodt, S.M.

1988-01-01

163

A simple scheme for universal linear optics quantum computing with constant experimental complexity using fiber-loops  

E-print Network

Recently, Motes, Gilchrist, Dowling & Rohde [Phys. Rev. Lett. 113, 120501 (2014)] presented a scheme for photonic boson-sampling using a fiber-loop architecture. Here we show that the same architecture can be modified to implement full, universal linear optics quantum computing, in various incarnations. The scheme employs two embedded fiber-loops, a single push-button photon source, three dynamically controlled beamsplitters, and a single time-resolved photo-detector. The architecture has only a single point of interference, and thus may be significantly easier to align than other schemes. The experimental complexity of the scheme is constant, irrespective of the size of the computation, limited only by fiber lengths and their respective loss rates.

Peter P. Rohde

2014-10-02

164

Energy of gravitational radiation in plane-symmetric space-times  

E-print Network

Gravitational radiation in plane-symmetric space-times can be encoded in a complex potential, satisfying a non-linear wave equation. An effective energy tensor for the radiation is given, taking a scalar-field form in terms of the potential, entering the field equations in the same way as the matter energy tensor. It reduces to the Isaacson energy tensor in the linearized, high-frequency approximation. An energy conservation equation is derived for a quasi-local energy, essentially the Hawking energy. A transverse pressure exerted by interacting low-frequency gravitational radiation is predicted.

Sean A. Hayward

2008-05-19

165

Synthesis, spectroscopic, antimicrobial, DNA binding and cleavage studies of some metal complexes involving symmetrical bidentate N, N donor Schiff base ligand.  

PubMed

The Schiff base ligand, N,N'-bis-(4-isopropylbenzaldimine)-1,2-diaminoethane (L), obtained by the condensation of 4-isopropylbenzaldehyde and 1,2-diaminoethane, has been used to synthesize the complexes of the type [ML(2)X(2)] [M = Co(II), Ni(II) and Zn(II); X = Cl and OAc]. The newly synthesized ligand (L) and its complexes have been characterized on the basis of elemental analyses, mass, (1)H and (13)C-NMR, molar conductance, IR, UV-vis, magnetic moment, CV and thermal analyses, powder XRD and SEM. IR spectral data show that the ligand is coordinated to the metal ions in a bidentate manner. The geometrical structures of these complexes are found to be octahedral. Interestingly, reaction with Cu(II) ion with this ligand undergoes hydrolytic cleavage to form ethylenediamine copper(II) complex and the corresponding aldehyde. The antimicrobial results indicate that the chloro complexes exhibit more activity than the acetato complexes. The complexes bind to CT-DNA by intercalation modes. Novel chloroform soluble ZnL(2)Cl(2) complex exhibits tremendous antimicrobial, DNA binding and cleaving properties. PMID:21855399

Arish, D; Nair, M Sivasankaran

2011-11-01

166

Linear Free Energy Relationships for Metal-Ligand Complexation: Bidentate Binding to Negatively-Charged Oxygen Donor Atoms  

PubMed Central

Stability constants for metal complexation to bidentate ligands containing negatively-charged oxygen donor atoms can be estimated from the following linear free energy relationship (LFER): log KML = ?OO(?O log KHL,1 + ?O log KHL,2) where KML is the metal-ligand stability constant for a 1:1 complex, KHL,1 and KHL,2 are the proton-ligand stability constants (the ligand pKa values), and ?O is the Irving-Rossotti slope. The parameter ?OO is metal specific and has slightly different values for 5 and 6 membered chelate rings. LFERs are presented for 21 different metal ions and are accurate to within approximately 0.30 log units in predictions of log KML values. Ligands selected for use in LFER development include dicarboxylic acids, carboxyphenols, and ortho-diphenols. For ortho-hydroxybenzaldehydes, ?-hydroxycarboxylic acids, and ?-ketocarboxylic acids, a modification of the LFER where log KHL,2 is set equal to zero is required. The chemical interpretation of ?OO is that it accounts for the extra stability afforded to metal complexes by the chelate effect. Cu-NOM binding constants calculated from the bidentate LFERs are similar in magnitude to those used in WHAM 6. This LFER can be used to make log KML predictions for small organic molecules. Since natural organic matter (NOM) contains many of the same functional groups (i.e. carboxylic acids, phenols, alcohols), the LFER log KML predictions shed light on the range of appropriate values for use in modeling metal partitioning in natural systems. PMID:21833149

Carbonaro, Richard F.; Atalay, Yasemin B.; Di Toro, Dominic M.

2011-01-01

167

Isospecific polymerization of 1-hexene by C1-symmetric half-metallocene dimethyl complexes of group 4 metals with bidentate N-substituted iminomethylpyrrolyl ligands.  

PubMed

Non-bridged half-metallocene dimethyl complexes of group 4 metals 2a-4a with an N-4-methoxyphenyl(iminomethyl)pyrrolyl ligand 1a were synthesized and characterized by NMR spectroscopy and X-ray analysis. Upon activation with [Ph3C][B(C6F5)4], these complexes became active catalysts for the polymerization of 1-hexene. A series of hafnium complexes with various N-substituents on the imine group of ligands 1b-1g were also prepared and applied as catalysts for 1-hexene polymerization. The activation parameters for the exchange process between the two methyl groups bound to the metal for Cp*MMe2(R-pyr) complexes were estimated by NMR shape analysis at various temperatures. The findings indicated that the transition state of the ligand flipping process might be associated with the isoselectivity of the polymerization reaction. PMID:23235804

Yasumoto, Takahiro; Yamamoto, Keishi; Tsurugi, Hayato; Mashima, Kazushi

2013-07-01

168

Enantioselective Synthesis of Homoallylic Amines through Reactions of (Pinacolato)allylborons with Aryl-, Heteroaryl-, Alkyl- or Alkene-Substituted Aldimines Catalyzed by Chiral C1-Symmetric NHC–Cu Complexes  

PubMed Central

A catalytic method for enantioselective synthesis of homoallylamides through Cu-catalyzed reactions of stable and easily accessible (pinacolato)allylborons with aryl-, heteroaryl-,alkyl- or alkenyl-substituted N-phosphinoylimines is disclosed. Transformations are promoted by 1–5 mol % of readily accessible NHC–Cu complexes, derived from C1-symmetric imidazolinium salts, which can be prepared in multi-gram quantities in four steps from commercially available materials. Allyl additions deliver the desired products in up to quantitative yield and 98.5:1.5 enantiomeric ratio and are amenable to gram-scale operations. A mechanistic model accounting for the observed selectivity levels and trends is proposed. PMID:21341657

Vieira, Erika M.; Snapper, Marc L.; Hoveyda, Amir H.

2011-01-01

169

The first example of a centro-symmetrical bis(imido)-bridged dinuclear cobalt(III) complex: synthesis via oxidative dehydrogenation and phenoxazinone synthase activity.  

PubMed

A bis(imido)-bridged dinuclear cobalt(III) complex, [Co2(amp)2(?-imp)2Cl2]Cl2·2H2O () [amp = 2-aminomethylpyridine; imp = 2-iminomethylpyridine anion], was synthesized by the reaction of cobalt(II) chloride with 2-aminomethylpyridine in the presence of alkaline hydrogen peroxide at room temperature. X-ray crystallography reveals that both the metal centres in the molecule are related to each other through an inversion centre, and the geometry of each of the Co(III) ions is a distorted octahedral structure having a CoN5Cl coordination environment. The most important feature of the structure is the modification of half of the coordinated amines by the oxidative dehydrogenation process which involves double bridging in the complex cation. To the best of our knowledge, this is the first example of a bis(imido)-bridged dinuclear cobalt(III) complex derived from metal-assisted oxidative dehydrogenation of the coordinated primary amine ligand. Complex was found to be an excellent functional model for the phenoxazinone synthase, catalyzing the oxidative coupling of 2-aminophenol to the corresponding 2-aminophenoxazinone chromophore in dioxygen saturated methanol. The detailed kinetic investigations reveal that the phenoxazinone chromophore is produced via a potential complex-substrate intermediate. PMID:23396321

Panja, Anangamohan; Guionneau, Philippe

2013-04-14

170

The optical solitons in the Scarff parity-time symmetric potentials  

NASA Astrophysics Data System (ADS)

We investigate the existence and stability of solitons in parity-time (PT) symmetric Scarff complex potentials, including linear case, and self-focusing and self-defocusing nonlinear cases. For linear case, the PT-breaking points, the eigenvalues and eigenfunction for different modulated depths of PT symmetry Scarff complex potential are obtained numerically. For nonlinear cases, the existence and stability of fundamental and multipole solitons are studied in self-focusing and self-defocusing media. For a fixed modulated depth, the eigenvalue for fundamental or multipole linear modes is equal to the critical propagation constant bc of fundamental and multipole solitons existence. Fundamental solitons are stable in the self-defocusing nonlinear media and low power region for the self-focusing nonlinear case. Multipole solitons are stable with the propagation constants close to bc both for self-focusing and self-defocusing nonlinearities.

Chen, Haibo; Hu, Sumei; Qi, Lingmin

2014-11-01

171

Control of linear modes in cylindrical resistive magnetohydrodynamics with a resistive wall, plasma rotation, and complex gain  

NASA Astrophysics Data System (ADS)

Feedback stabilization of magnetohydrodynamic (MHD) modes in a tokamak is studied in a cylindrical model with a resistive wall, plasma resistivity, viscosity, and toroidal rotation. The control is based on a linear combination of the normal and tangential components of the magnetic field just inside the resistive wall. The feedback includes complex gain, for both the normal and for the tangential components, and it is known that the imaginary part of the feedback for the former is equivalent to plasma rotation [J. M. Finn and L. Chacon, Phys. Plasmas 11, 1866 (2004)]. The work includes (1) analysis with a reduced resistive MHD model for a tokamak with finite ? and with stepfunction current density and pressure profiles, and (2) computations with a full compressible visco-resistive MHD model with smooth decreasing profiles of current density and pressure. The equilibria are stable for ? = 0 and the marginal stability values ?rp,rw < ?rp,iw < ?ip,rw < ?ip,iw (resistive plasma, resistive wall; resistive plasma, ideal wall; ideal plasma, resistive wall; and ideal plasma, ideal wall) are computed for both models. The main results are: (a) imaginary gain with normal sensors or plasma rotation stabilizes below ?rp,iw because rotation suppresses the diffusion of flux from the plasma out through the wall and, more surprisingly, (b) rotation or imaginary gain with normal sensors destabilizes above ?rp,iw because it prevents the feedback flux from entering the plasma through the resistive wall to form a virtual wall. A method of using complex gain Gi to optimize in the presence of rotation in this regime with ? > ?rp,iw is presented. The effect of imaginary gain with tangential sensors is more complicated but essentially destabilizes above and below ?rp,iw.

Brennan, D. P.; Finn, J. M.

2014-10-01

172

Control of linear modes in cylindrical resistive magnetohydrodynamics with a resistive wall, plasma rotation, and complex gain  

SciTech Connect

Feedback stabilization of magnetohydrodynamic (MHD) modes in a tokamak is studied in a cylindrical model with a resistive wall, plasma resistivity, viscosity, and toroidal rotation. The control is based on a linear combination of the normal and tangential components of the magnetic field just inside the resistive wall. The feedback includes complex gain, for both the normal and for the tangential components, and it is known that the imaginary part of the feedback for the former is equivalent to plasma rotation [J. M. Finn and L. Chacon, Phys. Plasmas 11, 1866 (2004)]. The work includes (1) analysis with a reduced resistive MHD model for a tokamak with finite ? and with stepfunction current density and pressure profiles, and (2) computations with a full compressible visco-resistive MHD model with smooth decreasing profiles of current density and pressure. The equilibria are stable for ??=?0 and the marginal stability values ?{sub rp,rw}?complex gain G{sub i} to optimize in the presence of rotation in this regime with ??>??{sub rp,iw} is presented. The effect of imaginary gain with tangential sensors is more complicated but essentially destabilizes above and below ?{sub rp,iw}.

Brennan, D. P. [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Finn, J. M. [Applied Mathematics and Plasma Physics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-10-15

173

Spherically symmetric spacetimes in massive gravity  

Microsoft Academic Search

We explore spherically symmetric stationary solutions, generated by ``stars'' with regular interiors, in purely massive gravity. We reexamine the claim that the resummation of nonlinear effects can cure, in a domain near the source, the discontinuity exhibited by the linearized theory as the mass m of the graviton tends to zero. First, we find analytical difficulties with this claim, which

Thibault Damour; Ian I. Kogan; Antonios Papazoglou

2003-01-01

174

Passivity indices for symmetrically interconnected distributed systems  

Microsoft Academic Search

In this paper, the passivity indices for both lin- ear and nonlinear multi-agent systems with feedforward and feedback interconnections are derived. For linear systems, the passivity indices are explicitly characterized, while the passivity indices in the nonlinear case are characterized by a set of matrix inequalities. We also focus on symmetric interconnections and specialize the passivity indices results to this

Po Wu; Panos J. Antsaklis

2011-01-01

175

Liquid Crystal Polarizers with Axially Symmetrical Properties  

Microsoft Academic Search

Liquid crystal polarizers are prepared by using a common linear polarizer, a nematic liquid crystal and PVA-coated glass substrates. The surface of one substrate is treated for unidirectional molecular orientation and the other substrate is treated for concentrically circular molecular orientation. The liquid crystal cell has axially symmetrical polarization properties, that is, a concentrically circular or radial polarization can be

Rumiko Yamaguchi; Toshiaki Nose; Susumu Sato

1989-01-01

176

Explicit symmetric multistep methods for first-order differential equations  

Microsoft Academic Search

We show the comprehensive evaluations of symmetric linear multistep methods for first-order ordinary differential equations (ODEs). First, paying attention to the maximum value of stable stepsize and the error constants, we investigate widely. Because the symmetric formulas contain multiple free parameters in each order, the property of formula is greatly different depending on the values of free parameters. Thus, changing

Tadato Yamamoto; Toshio Fukushima

2003-01-01

177

Synthesis, characterization and electrochemical behaviour of cobalt(II) and cobalt(III):O 2- complexes, respectively, with linear and tripodal tetradentate ligands derived from Schiff bases  

NASA Astrophysics Data System (ADS)

New octahedral cobalt complexes with linear and tripodal tetradentate ligands derived from Schiff bases have been synthesized and characterized using elemental analysis, molar conductance, IR spectra, magnetic measurements, electronic and ESR spectra. The experimental results support the binding of linear ligands with two N and two O donor sites to cobalt ion. They show a square planar geometry and tripodal ligands coordinated to the metal ion by only one nitrogen atom, giving an arrangement of NO 3 donor groups, the other axial sites being occupied by the molecular oxygen and/or the aquo molecules. From the results of cyclic voltammetry it is shown that chelate structure and ligand geometry and electron donating effect of the ligand substituents are among the factors influencing the redox potentials of the complexes. Linear ligands lead to high-spin cobalt(II) complexes. They do not interact with dioxygen and stabilize the Co(II) state counter to their related Schiff-base complexes. The low-spin complexes with tripodal ligands are O 2 adducts and the configuration in these complexes is best formulated as [Co IIIO 2-].

Djebbar-Sid, S.; Benali-Baitich, O.; Deloume, J. P.

2001-07-01

178

The pneumococcal MgaSpn virulence transcriptional regulator generates multimeric complexes on linear double-stranded DNA  

PubMed Central

The MgaSpn transcriptional regulator contributes to the virulence of Streptococcus pneumoniae. It is thought to be a member of the Mga/AtxA family of global regulators. MgaSpn was shown to activate in vivo the P1623B promoter, which is divergent from the promoter (Pmga) of its own gene. This activation required a 70-bp region (PB activation region) located between both promoters. In this work, we purified an untagged form of the MgaSpn protein, which formed dimers in solution. By gel retardation and footprinting assays, we analysed the binding of MgaSpn to linear double-stranded DNAs. MgaSpn interacted with the PB activation region when it was placed at internal position on the DNA. However, when it was positioned at one DNA end, MgaSpn recognized preferentially the Pmga promoter placed at internal position. In both cases, and on binding to the primary site, MgaSpn spread along the adjacent DNA regions generating multimeric protein–DNA complexes. When both MgaSpn-binding sites were located at internal positions on longer DNAs, electron microscopy experiments demonstrated that the PB activation region was the preferred target. DNA molecules totally or partially covered by MgaSpn were also visualized. Our results suggest that MgaSpn might recognize particular DNA conformations to achieve DNA-binding specificity. PMID:23723245

Solano-Collado, Virtu; Lurz, Rudi; Espinosa, Manuel; Bravo, Alicia

2013-01-01

179

An application of the complex general linear model to analysis of fMRI single subjects multiple stimuli input data  

NASA Astrophysics Data System (ADS)

The general linear model (GLM) has been extensively applied to fMRI data in the time domain. However, traditionally time series data can be analyzed in the Fourier domain where the assumptions made as to the noise in the signal can be less restrictive and statistical tests are mathematically more rigorous. A complex form of the GLM in the Fourier domain has been applied to the analysis of fMRI (BOLD) data. This methodology has a number of advantages over temporal methods: 1. Noise in the fMRI data is modeled more generally and closer to that actually seen in the data. 2. Any input function is allowed regardless of the timing. 3. Non-parametric estimation of the transfer functions at each voxel are possible. 4. Rigorous statistical inference of single subjects is possible. This is demonstrated in the analysis of an experimental design with random exponentially distributed stimulus inputs (a two way ANOVA design with input stimuli images of alcohol, non-alcohol beverage and positive or negative images) sampled at 400 milliseconds. This methodology applied to a pair of subjects showed precise and interesting results (e.g. alcoholic beverage images attenuate the response of negative images in an alcoholic as compared to a control subject).

Rio, Daniel; Rawlings, Robert; Woltz, Lawrence; Gilman, Jodi; Hommer, Daniel

2009-02-01

180

Synthesis and crystal structure determination of some asymmetrical and symmetrical CR-type macrocyclic Schiff base complexes, with a single pendant coordinating 2-aminoethyl arm.  

PubMed

A novel, totally asymmetrical tripodal 2,3',4"-tetraamine ligand, N((CH2)2NH2)((CH2)3NH2)((CH2)4NH2), epb, has been synthesized. In the presence of copper(II) and nickel(II) ions it condenses with 2,6-diacetylpyridine in 1:1 ethanol-water solution, producing some new CR-type complexes with a pendant primary amino group. The X-ray crystal structure of the resulting copper(II) complex, [Cu(3,4(2)-CR)](PF6)2 (1), and two other related complexes, [Cu(2,4(2)-CR)](ClO4)2 (2) and [Cu(3,3(2)-CR)](ClO4)2 (3), are reported. Crystal data: complex 1, monoclinic, P2(1)/n, a = 8.366(3) A, b = 15.549(3) A, c = 20.283(2) A, beta = 98.73(2) degrees, V = 2607.8(11) A3, Z = 4, R1 = 0.0621, wR2 = 0.1615; complex 2, monoclinic, P2(1)/c, a = 7.981(10) A, b = 18.882(3) A, c = 15.185(3) A, beta = 96.40(2) degrees, V = 2275.7(6) A3, Z = 4, R1 = 0.0773, wR2 = 0.1635; complex 3, monoclinic, P2(1)/n, a = 7.8764(10) A, b = 15.361(2) A, c = 19.370(2) A, beta = 100.330(10) degrees, V = 2305.7(5) A3, Z = 4, R1 = 0.0537, wR2 = 0.1397. In all of these, copper atoms are bonded to four nitrogens of a macrocyclic ring and a nitrogen of the pendant arm. The arrangements are slightly distorted square-pyramidal in which the primary amino groups occupy apical positions and have the longest Cu-N distances. For all isomers, copper(II) ions are somewhat above the plane of the imino-pyridine system of the macrocylic ring in the direction of the pendant coordinated primary amino group. PMID:11153507

Keypour, H; Salehzadeh, S; Pritchard, R G; Parish, R V

2000-12-11

181

PT-Symmetric Quantum Field Theory  

SciTech Connect

In 1998 it was discovered that the requirement that a Hamiltonian be Dirac Hermitian (H = H{sup {dagger}}) can be weakened and generalized to the requirement that a Hamiltonian be PT symmetric ([H,PT] = 0); that is, invariant under combined space reflection and time reversal. Weakening the constraint of Hermiticity allows one to consider new kinds of physically acceptable Hamiltonians and, in effect, it amounts to extending quantum mechanics from the real (Hermitian) domain into the complex domain. Much work has been done on the analysis of various PT-symmetric quantum-mechanical models. However, only very little analysis has been done on PT-symmetric quantum-field-theoretic models. Here, we describe some of what has been done in the context of PT-symmetric quantum field theory and describe some possible fundamental applications.

Bender, Carl M. [Physics Department, Washington University, St. Louis, MO 63130 (United States)

2011-09-22

182

SPECTRAL ANALYSIS OF INEXACT CONSTRAINT PRECONDITIONING FOR SYMMETRIC SADDLE POINT  

E-print Network

SESANA AND VALERIA SIMONCINI Abstract. Large symmetric linear systems in saddle point form arise in many Bologna, Piazza di Porta S. Donato, 5, 40127 Bologna, Italy (valeria.simoncini@unibo.it). 1 #12;2 D

Simoncini, Valeria

183

SPECTRAL ANALYSIS OF INEXACT CONSTRAINT PRECONDITIONING FOR SYMMETRIC SADDLE POINT  

E-print Network

SESANA AND VALERIA SIMONCINI Abstract. Large symmetric linear systems in saddle point form arise in many di Porta S. Donato, 5, 40127 Bologna, Italy (valeria.simoncini@unibo.it). 1 #12;2 D. Sesana and V

Simoncini, Valeria

184

An adaptive neural network-fuzzy linear regression approach for improved car ownership estimation and forecasting in complex and uncertain environments: the case of Iran  

Microsoft Academic Search

This paper applies a novel adaptive approach consisting of Artificial Neural Network (ANN) and Fuzzy Linear Regression (FLR) to improve car ownership forecasting in complex, ambiguous, and uncertain environments. This integrated approach is applied to forecast car ownership in Iran from 1930 to 2007. In this study, the level of car ownership is viewed as the result of demographic, politico-social,

A. Azadeh; N. Neshat; K. Rafiee; A. M. Zohrevand

2012-01-01

185

The Fc segment of IgE influences the kinetics of dissociation of a symmetrical bivalent ligand from cyclic dimeric complexes  

SciTech Connect

As part of a systematic effort to determine the features of immunoglobulin E-receptor (IgE-Fc{epsilon}RI) aggregation that are critical for cellular activation, we used fluorescence to examine the dissociation of a soluble bivalent ligand, N,N{prime}-bis[[{epsilon}-[(2,4-dinitrophenyl)amino]caproyl]-L-tyrosyl]-L-cystine ((DCT){sub 2{minus}}cys), from soluble bivalent IgE and its bivalent F(ab{prime}){sub 2} and monovalent Fab{prime} fragments. Cross-linking of Fab{prime} fragments by (DCT){sub 2}-cys is limited to linear dimers, and we find that (DCT){sub 2}-cys dissociation from Fab{prime} occurs with a single kinetic coefficient [(4.2 {plus_minus} 0.6) {times} 10{sup {minus}3}s{sup {minus}1}] that corresponds to the lower of the two kinetic coefficients observed with the bivalent IgE[(4.7 {plus_minus} 0.7) {times} 10{sup {minus}2} s{sup {minus}1} and (4.4 {plus_minus} 0.3) {times} 10{sup {minus}3} s{sup {minus}1}]. Similarly, the lower value is obtained for dissociation of (DCT){sub 2}-cys that is monovalently bound to IgE after incubation with a large excess of the ligand. (DCT){sub 2}-cys can bind to bivalent F(ab{prime}){sub 2} fragments and form a variety of linear and cyclic aggregates, similarly to IgE, but, unlike IgE, we find that dissociation occurs with a single kinetic coefficient similar to that observed for Fab{prime}. We find that IgE and its (Fab{prime}){sub 2} fragments form highly stable cyclic dimer rings with two (DCT){sub 2}-cys. We demonstrate that the kinetic coefficients are independent of enhanced fluorescence quenching observed for bound sites in cyclic dimers. 29 refs., 6 figs., 2 tabs.

Subramanian, K.; Holowka, D.; Baird, B. [Cornell Univ., Ithaca, NY (United States)] [Cornell Univ., Ithaca, NY (United States); Goldstein, B. [Los Alamos National Lab., Los Alamos, NM (United States)] [Los Alamos National Lab., Los Alamos, NM (United States)

1996-04-30

186

NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS Numer. Linear Algebra Appl. (2012)  

E-print Network

NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS Numer. Linear Algebra Appl. (2012) Published online for linear systems in the case of a standard quadratic optimization problem with symmetric positive definite- erates convergence of the alternating least squares (ALS) optimization method for the canonical tensor

De Sterck, Hans

187

A Concrete Security Treatment of Symmetric Encryption  

Microsoft Academic Search

We study notions and schemes for symmetric (ie. private key) encryption in a concrete security framework. We give four different notions of security against chosen plaintext attack and analyze the concrete complexity of reductions among them, providing both upper and lower bounds, and obtaining tight relations. In this way we classify notions (even though polynomially reducible to each other) as

Mihir Bellare; Anand Desai; E. Jokipii; Phillip Rogaway

1997-01-01

188

Resonances for Symmetric Two-Barrier Potentials  

ERIC Educational Resources Information Center

We describe a method for the accurate calculation of bound-state and resonance energies for one-dimensional potentials. We calculate the shape resonances for symmetric two-barrier potentials and compare them with those coming from the Siegert approximation, the complex scaling method and the box-stabilization method. A comparison of the…

Fernandez, Francisco M.

2011-01-01

189

A novel malformation complex of bilateral and symmetric preaxial radial ray-thumb aplasia and lower limb defects with minimal facial dysmorphic features: a case report and literature review  

PubMed Central

Introduction Radial hemimelia is a congenital abnormality characterised by the partial or complete absence of the radius. The longitudinal hemimelia indicates the absence of one or more bones along the preaxial (medial) or postaxial (lateral) side of the limb. Preaxial limb defects occurred more frequently with a combination of microtia, esophageal atresia, anorectal atresia, heart defects, unilateral kidney dysgenesis, and some axial skeletal defects. Postaxial acrofacial dysostoses are characterised by distinctive facies and postaxial limb deficiencies, involving the 5th finger, metacarpal/ulnar/fibular/and metatarsal. Case presentation The patient, an 8-year-old-boy with minimal craniofacial dysmorphic features but with profound upper limb defects of bilateral and symmetrical absence of the radius and the thumbs respectively. In addition, there was a unilateral tibio-fibular hypoplasia (hemimelia) associated with hypoplasia of the terminal phalanges and malsegmentation of the upper thoracic vertebrae, causing effectively the development of thoracic kyphosis. Conclusion In the typical form of the preaxial acrofacial dysostosis, there are aberrations in the development of the first and second branchial arches and limb buds. The craniofacial dysmorphic features are characteristic such as micrognathia, zygomatic hypoplasia, cleft palate, and preaxial limb defects. Nager and de Reynier in 1948, who used the term acrofacial dysostosis (AFD) to distinguish the condition from mandibulofacial dysostosis. Neither the facial features nor the limb defects in our present patient appear to be absolutely typical with the previously reported cases of AFD. Our patient expands the phenotype of syndromic preaxial limb malformation complex. He might represent a new syndromic entity of mild naso-maxillary malformation in connection with axial and extra-axial malformation complex. PMID:18950501

Al Kaissi, Ali; Klaushofer, Klaus; Krebs, Alexander; Grill, Franz

2008-01-01

190

Symmetric and irregular aromatic silicon nanoclusters  

NASA Astrophysics Data System (ADS)

Based on first-principles calculations, we predict the existence of two classes of aromatic hydrogenated silicon nanoclusters. Despite their completely different structure, they both exhibit quite comparable physical and chemical properties due to the common presence of overcoordinated silicon atoms inducing extensive electron delocalization. Due to a complex interplay between strain relaxation and aromatic stabilization, apparently ill-defined nanoclusters might sometimes turn out to be more stable than their symmetric counterparts. Both symmetric and irregular aromatic silicon nanoclusters are extremely stable at ambient conditions and might readily find applications in future nano-technological devices.

Vach, Holger

2014-10-01

191

A Minimally Symmetric Higgs Boson  

E-print Network

Models addressing the naturalness of a light Higgs boson typically employ symmetries, either bosonic or fermionic, to stabilize the Higgs mass. We consider a setup with the minimal amount of symmetries: four shift symmetries acting on the four components of the Higgs doublet, subject to the constraints of linearly realized SU(2)xU(1) electroweak symmetry. Up to terms that explicitly violate the shift symmetries, the effective lagrangian can be derived, irrespective of the spontaneously broken group G in the ultraviolet, and is universal in all models where the Higgs arises as a pseudo-Nambu-Goldstone boson (PNGB). Very high energy scatterings of vector bosons could provide smoking gun signals of a minimally symmetric Higgs boson.

Ian Low

2014-12-05

192

Elucidation of structure-function relationships in photosynthetic light-harvesting antenna complexes by non-linear polarization spectroscopy in the frequency domain (NLPF).  

PubMed

Photosynthetically active pigments are usually organized into pigment-protein complexes. These include light-harvesting antenna complexes (LHCs) and reaction centers. Site energies of the bound pigments are determined by interactions with their environment, i.e., by pigment-protein as well as pigment-pigment interactions. Thus, resolution of spectral substructures of the pigment-protein complexes may provide valuable insight into structure-function relationships. By means of conventional (linear) and time-resolved spectroscopic techniques, however, it is often difficult to resolve the spectral substructures of complex pigment-protein assemblies. Nonlinear polarization spectroscopy in the frequency domain (NLPF) is shown to be a valuable technique in this regard. Based on initial experimental work with purple bacterial antenna complexes as well as model systems NLPF has been extended to analyse the substructure(s) of very complex spectra, including analyses of interactions between chlorophylls and "optically dark" states of carotenoids in LHCs. The paper reviews previous work and outlines perspectives regarding the application of NLPF spectroscopy to disentangle structure-function relationships in pigment-protein complexes. PMID:21316796

Lokstein, Heiko; Krikunova, Maria; Teuchner, Klaus; Voigt, Bernd

2011-08-15

193

Cadmium(II) complexes of fully condensed Schiff-base ligands derived from two different symmetrical and asymmetrical tripodal tetraamines and 2-acetylpyridine; the novel observations for heptadentate mono-capped trigonal antiprismatic Schiff-base complexes  

Microsoft Academic Search

In the presence of cadmium(II), 2-acetylpyridine condenses with tris(3-aminopropyl)amine, tpt, and bis(3-aminopropyl)(2-aminoethyl)amine, ppe, in absolute methanol to produce two fully condensed potentially heptadentate Schiff-base complexes, [Cd(py3tpt)](ClO4)2 and [Cd(py3ppe)](ClO4)2. X-ray structure analysis of the former complex shows mono-capped distorted trigonal antiprism geometry wherein the Cd?unique nitrogen distance is 2.486 Å. In comparison with the weighted mean of other Cd?N distances, 2.425

Hassan Keypour; Sadegh Salehzadeh; Robin G. Pritchard; R. V. Parish

2000-01-01

194

Integrability of PT-symmetric dimers  

NASA Astrophysics Data System (ADS)

The coupled discrete linear and Kerr nonlinear Schrödinger equations with gain and loss describing transport on dimers with parity-time (PT)-symmetric potentials are considered. The model is relevant among others to experiments in optical couplers and proposals on Bose-Einstein condensates in PT-symmetric double-well potentials. It is known that the models are integrable. Here, the integrability is exploited further to construct the phase portraits of the system. A pendulum equation with a linear potential and a constant force for the phase difference between the fields is obtained, which explains the presence of unbounded solutions above a critical threshold parameter. The behavior of all solutions of the system, including changes in the topological structure of the phase plane, is then discussed.

Pickton, J.; Susanto, H.

2013-12-01

195

The Symmetric Teleparallel Gravity  

E-print Network

We study symmetric teleparallel (STP) gravity model, in which only spacetime non-metricity is nonzero. First we obtain STP equivalent Einstein-Hilbert Lagrangian and give an approach for a generic solution in terms of only metric tensor. Then we obtain a spherically symmetric static solution to the Einstein's equation in STP space-time and discuss the singularities. Finally, we study a model given by a Lagrangian 4-form quadratic in non-metricity. Thus, we seek Schwarzschild-type solutions because of its observational success and obtain some sets of solutions. Finally, we discuss physical relevance of the solutions.

M. Adak

2006-11-14

196

Braids, shuffles and symmetrizers  

NASA Astrophysics Data System (ADS)

Multiplicative analogues of the shuffle elements of the braid group rings are introduced; in local representations they give rise to certain graded associative algebras (b-shuffle algebras). For the Hecke and BMW algebras, the (anti)-symmetrizers have simple expressions in terms of the multiplicative shuffles. The (anti)-symmetrizers can be expressed in terms of the highest multiplicative 1-shuffles (for the Hecke and BMW algebras) and in terms of the highest additive 1-shuffles (for the Hecke algebras). The spectra and multiplicities of eigenvalues of the operators of the multiplication by the multiplicative and additive 1-shuffles are examined. Dedicated to the memory of Aleosha Zamolodchikov.

Isaev, A. P.; Ogievetsky, O. V.

2009-07-01

197

Symmetric Cryptography in Javascript  

Microsoft Academic Search

We take a systematic approach to developing a symmetric cryptography library in Javascript. We study various strategies for optimizing the code for the Javascript interpreter, and observe that traditional crypto optimization techniques do not apply when implemented in Javascript. We propose a number of optimizations that reduce both running time and code size. Our optimized library is about four times

Emily Stark; Michael Hamburg; Dan Boneh

2009-01-01

198

PT-symmetric kinks  

SciTech Connect

Some kinks for non-Hermitian quantum field theories in 1+1 dimensions are constructed. A class of models where the soliton energies are stable and real are found. Although these kinks are not Hermitian, they are symmetric under PT transformations.

Souza Dutra, A. de [Abdus Salam ICTP, Strada Costiera 11, Trieste, I-34100 (Italy) and UNESP-Campus de Guaratingueta-DFQ, Departmento de Fisica e Quimica, 12516-410 Guaratingueta SP (Brazil); Santos, V. G. C. S. dos; Amaro de Faria, A. C. Jr. [UNESP-Campus de Guaratingueta-DFQ, Departmento de Fisica e Quimica, 12516-410 Guaratingueta SP (Brazil)

2007-06-15

199

Synthesis, structure, catalytic and calculated non-linear optical properties of cis- and trans-, mer-chlorobis(triphenyl phosphine/triphenyl arsine)-dipicolinato ruthenium III complexes  

NASA Astrophysics Data System (ADS)

The new mononuclear Ru III complexes cis-, mer-[Ru( k3-dipic)(EPh 3) 2Cl]·2H 2O (E = P ( 1), As ( 2)), (L = 2,6-pyridyldicarboxylate; dipic) have been synthesized and characterized. The X-ray crystal structure of 1 reveals that the coordination geometry around the Ru III center is distorted octahedral in which three sites are occupied by tridentate dipic ligand and remaining three sites are occupied by two mutually cis triphenyl phosphine ligands and one chloride ions. In chloroform solvent, cis-, mer-[Ru( k3-dipic)(EPh 3) 2Cl]·2H 2O (E = P ( 1), As ( 2)) complexes undergoes thermal rearrangement to more stable trans-, mer-[Ru( k3-dipic)(EPh 3) 2Cl] (E = P( 3), As( 4)) complexes. Complexes 1 and 2 show rhombic EPR spectral features, while complex 3 and 4 show tetragonal distortion. The new Ru III complexes 1 and 2 display both Ru III-Ru II reduction and Ru III-Ru IV oxidation processes. These geometric isomers exhibit textbook differences both in spectroscopic as well as structural properties in the solid state. The new complexes 1 and 2 were found to catalyze the oxidation of alcohols to carbonyl derivatives using N-methyl morpholine- N-oxide as co-oxidant. The first static hyperpolarizability ( ?) for all of the complexes have been investigated by density functional theory (DFT) which suggests ? value increases from trans to cis form. Also, the solvent-induced effects on the non-linear optical properties (NLO) were studied by using self-consistent reaction field (SCRF) method. As the solvent polarity increases, the ? value increases monotonically. The electronic absorption bands of 1 have been assigned by time dependent density functional theory (TD-DFT).

Trivedi, Manoj; Nagarajan, R.; Kumar, Abhinav; Singh, Narendra K.; Rath, Nigam P.

2011-05-01

200

A free-knot spline modeling framework for piecewise linear logistic regression in complex samples with body mass index and mortality as an example  

PubMed Central

This paper details the design, evaluation, and implementation of a framework for detecting and modeling nonlinearity between a binary outcome and a continuous predictor variable adjusted for covariates in complex samples. The framework provides familiar-looking parameterizations of output in terms of linear slope coefficients and odds ratios. Estimation methods focus on maximum likelihood optimization of piecewise linear free-knot splines formulated as B-splines. Correctly specifying the optimal number and positions of the knots improves the model, but is marked by computational intensity and numerical instability. Our inference methods utilize both parametric and nonparametric bootstrapping. Unlike other nonlinear modeling packages, this framework is designed to incorporate multistage survey sample designs common to nationally representative datasets. We illustrate the approach and evaluate its performance in specifying the correct number of knots under various conditions with an example using body mass index (BMI; kg/m2) and the complex multi-stage sampling design from the Third National Health and Nutrition Examination Survey to simulate binary mortality outcomes data having realistic nonlinear sample-weighted risk associations with BMI. BMI and mortality data provide a particularly apt example and area of application since BMI is commonly recorded in large health surveys with complex designs, often categorized for modeling, and nonlinearly related to mortality. When complex sample design considerations were ignored, our method was generally similar to or more accurate than two common model selection procedures, Schwarz’s Bayesian Information Criterion (BIC) and Akaike’s Information Criterion (AIC), in terms of correctly selecting the correct number of knots. Our approach provided accurate knot selections when complex sampling weights were incorporated, while AIC and BIC were not effective under these conditions. PMID:25610831

Keith, Scott W.; Allison, David B.

2014-01-01

201

Bcl2 inhibits recruitment of Mre11 complex to DNA double-strand breaks in response to high-linear energy transfer radiation.  

PubMed

High-linear energy transfer ionizing radiation, derived from high charge (Z) and energy (E) (HZE) particles, induces clustered/complex DNA double-strand breaks (DSBs) that include small DNA fragments, which are not repaired by the non-homologous end-joining (NHEJ) pathway. The homologous recombination (HR) DNA repair pathway plays a major role in repairing DSBs induced by HZE particles. The Mre11 complex (Mre11/Rad50/NBS1)-mediated resection of DSB ends is a required step in preparing for DSB repair via the HR DNA repair pathway. Here we found that expression of Bcl2 results in decreased HR activity and retards the repair of DSBs induced by HZE particles (i.e. (56)iron and (28)silicon) by inhibiting Mre11 complex activity. Exposure of cells to (56)iron or (28)silicon promotes Bcl2 to interact with Mre11 via the BH1 and BH4 domains. Purified Bcl2 protein directly suppresses Mre11 complex-mediated DNA resection in vitro. Expression of Bcl2 reduces the ability of Mre11 to bind DNA following exposure of cells to HZE particles. Our findings suggest that, after cellular exposure to HZE particles, Bcl2 may inhibit Mre11 complex-mediated DNA resection leading to suppression of the HR-mediated DSB repair in surviving cells, which may potentially contribute to tumor development. PMID:25567982

Xie, Maohua; Park, Dongkyoo; You, Shuo; Li, Rui; Owonikoko, Taofeek K; Wang, Ya; Doetsch, Paul W; Deng, Xingming

2015-01-30

202

Symmetrical reconfiguration of tensegrity structures  

Microsoft Academic Search

In this article we first present a mathematical model which describes the nonlinear dynamics of tensegrity structures. For certain tensegrity structures a particular class of motions, coined symmetrical motions, is defined. The corresponding equations of motion are derived and the conditions under which symmetrical motions occur are established. Reconfiguration procedures through symmetrical motions are proposed and examples are given.

Cornel Sultan; Martin Corless; Robert E. Skelton

2002-01-01

203

Self-assembly behavior of a linear-star supramolecular amphiphile based on host-guest complexation.  

PubMed

A star polymer, ?-cyclodextrin-poly(l-lactide) (?-CD-PLLA), and a linear polymer, azobenzene-poly(ethylene glycol) (Azo-PEG), could self-assemble into a supramolecular amphiphilic copolymer (?-CD-PLLA@Azo-PEG) based on the host-guest interaction between ?-CD and azobenzene moieties. This linear-star supramolecular amphiphilic copolymer further self-assembled into a variety of morphologies, including sphere-like micelle, carambola-like micelle, naan-like micelle, shuttle-like lamellae, tube-like fiber, and random curled-up lamellae, by tuning the length of hydrophilic or hydrophobic chains. The variation of morphology was closely related to the topological structure and block ratio of the supramolecular amphiphiles. These self-assembly structures could disassemble upon an ultraviolet (UV) light irradiation. PMID:25310380

Wang, Juan; Wang, Xing; Yang, Fei; Shen, Hong; You, Yezi; Wu, Decheng

2014-11-01

204

Symmetric modular torsatron  

DOEpatents

A fusion reactor device is provided in which the magnetic fields for plasma confinement in a toroidal configuration is produced by a plurality of symmetrical modular coils arranged to form a symmetric modular torsatron referred to as a symmotron. Each of the identical modular coils is helically deformed and comprise one field period of the torsatron. Helical segments of each coil are connected by means of toroidally directed windbacks which may also provide part of the vertical field required for positioning the plasma. The stray fields of the windback segments may be compensated by toroidal coils. A variety of magnetic confinement flux surface configurations may be produced by proper modulation of the winding pitch of the helical segments of the coils, as in a conventional torsatron, winding the helix on a noncircular cross section and varying the poloidal and radial location of the windbacks and the compensating toroidal ring coils.

Rome, J.A.; Harris, J.H.

1984-01-01

205

Symmetric iterative interpolation processes  

Microsoft Academic Search

Using a baseb and an even number of knots, we define a symmetric iterative interpolation process. The main properties of this process come from an associated functionF. The basic functional equation forF is thatF(t\\/b)=snF(n\\/b)F(t-n). We prove thatF is a continuous positive definite function. We find almost precisely in which Lipschitz classes derivatives ofF belong. If a functiony is defined only

Gilles Deslauriers; Serge Dubuc

1989-01-01

206

PT-symmetric Sturmians  

E-print Network

Sturmian bound states emerging at a fixed energy and numbered by a complete set of real eigencouplings are considered. For Sturm-Schroedinger equations which are manifestly non-Hermitian we outline the way along which the correct probabilistic interpretation of the system can constructively be re-established via a new formula for the metric. PT-symmetrized Coulomb potential is chosen for illustration purposes.

Miloslav Znojil

2008-04-24

207

Synthesis, structure, and magnetic characterization of a C3-symmetric Mn(III)3Cr(III) assembly: molecular recognition between a trinuclear Mn(III) triplesalen complex and a fac-triscyano Cr(III) complex.  

PubMed

The reaction of the tris(tetradentate) triplesalen ligand H(6)talen(t-Bu(2)), which provides three salen-like coordination environments bridged in a meta-phenylene arrangement by a phloroglucinol backbone, with Mn(II) salts under aerobic conditions, affords, in situ, the trinuclear Mn(III) triplesalen complex [(talen(t-Bu(2))){Mn(III)(solv)(n)}(3)](3+). This species then reacts with [(Me(3)tacn)Cr(CN)(3)] to form the tetranuclear complex [{(talen(t-Bu(2)))Mn(III)(3)}{(Me(3)tacn)Cr(CN)(3)}](3+) ([Mn(III)(3)Cr(III)](3+)). The regular ligand folding observed in the trinuclear triplesalen complex preorganizes the three metal ions for the reaction with three facially coordinated nitrogen atoms of [(Me(3)tacn)Cr(CN)(3)]. [{(talen(t-Bu(2)))(Mn(III)(MeOH))(3)}{(Me(3)tacn)Cr(CN)(3)}](ClO(4))(3) (1) was characterized by infrared spectroscopy, elemental analysis, mass spectrometry, electron absorption spectroscopy, and magnetic measurements. The molecular structure was established for the acetate-substituted derivative [{(talen(t-Bu(2)))(Mn(III)(MeOH))(2)(Mn(III)(OAc))}{(Me(3)tacn)Cr(CN)(3)}](ClO(4))(2) (2) by single-crystal X-ray diffraction. Variable-temperature-variable-field and mu(eff) versus T magnetic data have been analyzed in detail by full-matrix diagonalization of the appropriate spin-Hamiltonian, consisting of isotropic exchange, zero-field splitting, and Zeeman interaction components. Satisfactory reproduction of the experimental data has been obtained for the parameters J(Mn-Cr) = -0.12 +/- 0.04 cm(-1), J(Mn-Mn) = -0.70 +/- 0.03 cm(-1), and D(Mn) = -3.0 +/- 0.4 cm(-1). These generate a triply degenerate pseudo S(t) = 7/2 spin manifold, which cannot be appropriately described by a giant spin model and which exhibits a weak easy-axis magnetic anisotropy. This is corroborated by the onset of a frequency-dependent chi'' signal at low temperatures, demonstrating a slow relaxation of the magnetization indicative of 1 being a single-molecule magnet. Comparing the properties to those of the heptanuclear analogue [{(talen(t-Bu(2)))Mn(III)(3)}(2){Cr(III)(CN)(6)}](3+) ([Mn(III)(6)Cr(III)](3+)) formed by the reaction of 2 equiv of [(talen(t-Bu(2))){Mn(III)(solv)(n)}(3)](3+) with 1 equiv of [Cr(CN)(6)](3-) [Glaser, T.; Heidemeier, M.; Weyhermüller, T.; Hoffmann, R.-D.; Rupp, H.; Müller, P. Angew. Chem. Int. Ed., 2006, 45, 6033-6037] demonstrates a lower driving force for formation, a strongly reduced J(Mn-Cr) exchange, a slightly reduced J(Mn-Mn) exchange, and a significantly longer Mn-N(N[triple bond]C) bond length in [Mn(III)(3)Cr(III)](3+). Taking into account magneto-structural correlations establishes a supramolecular interaction between the two [(talen(t-Bu(2)))Mn(III)(3)](3+) subunits in [Mn(III)(6)Cr(III)](3+) responsible for the structural distortion and the short Mn-N(N[triple bond]C) distance which results in a strong J(Mn-Cr) exchange and thus [Mn(III)(6)Cr(III)](3+) being a single-molecule magnet with a relatively high effective anisotropy barrier of 25.4 K. PMID:19803531

Freiherr von Richthofen, Carl-Georg; Stammler, Anja; Bögge, Hartmut; DeGroot, Marty W; Long, Jeffrey R; Glaser, Thorsten

2009-11-01

208

The new WAsP flow model: a fast, linearized Mixed Spectral-Integration model applicable to complex terrain  

E-print Network

. There is interest in placing wind turbines in hilly and mountainous areas, due to the potentially high speed commercial PC-based tool to estimate wind resources at a potential wind turbine site, given a set of wind challenge for the wind energy industry is the prediction of the wind resource in complex terrain

209

DNA complex lesions induced by protons and alpha-particles: track structure characteristics determining linear energy transfer and particle type dependence.  

PubMed

The yield of DNA double-strand breaks (dsb) and DNA complex lesions induced by protons and alpha-particles of various energies was simulated using a Monte Carlo track structure code (MOCA15) and a simple model of the DNA molecule. DNA breaks of different complexity were analysed. The linear energy transfer (LET) and particle-type dependence of lesions of higher complexity seems to confirm the importance of clustered damage in DNA as a relevant step leading to biological endpoints such as cell inactivation. The detailed structure of proton and alpha-particle tracks was analysed to identify the main characteristics possibly responsible for such a dependence. The role of the primary ion and of its secondary electrons in inducing dsb and complex lesions is described, showing that the relative contribution of secondary electron tracks alone in inducing clustered lesions is almost negligible at high LET, but tends to dominate below = 10 keV/micron. This is consistent with the observed similar effectiveness of low-LET fast particle radiation and sparsely ionizing radiation such as x-rays. The dependence on LET and particle type is mainly due to energy deposition events of the primary ion together with short range electrons surrounding the ion track; the yield of complex lesions due to secondary electron tracks alone is substantially LET independent. The radial distributions of the energy contributing to the induction of complex lesions were analyzed and compared with the radial distributions of energy deposition of the full tracks. The results suggest that the stochastic behaviour (i.e. cluster properties) of the energy deposition pattern within a radius of a few nanometers around the ion track plays a relevant role in determining the biological radiation effectiveness. PMID:9271797

Ottolenghi, A; Merzagora, M; Paretzke, H G

1997-06-01

210

A Full-Diversity Space-Time-Frequency Coded MIMO-OFDM System with Linear Decoding Complexity  

Microsoft Academic Search

Early research on space-time-frequency (STF) codes are aimed at achieving maximum frequency and spatial diversity only. Over a space-time-frequency selective fading channel, there is a possibility of achieving better performance if coding across spatial, temporal, and spectra dimensions is designed properly. To date, only two STF codes were proposed to achieve full diversity. The decoding complexity, however, of these codes

Chao-Cheng Tu

2006-01-01

211

Complexity reduction through a Schur-based decomposition for reachability analysis of linear time-invariant systems  

Microsoft Academic Search

This article presents a method for complexity reduction in reachability analysis and safety-preserving controller synthesis via Schur-based decomposition. The decomposition results in either decoupled or weakly-coupled (lower dimensional) subsystems. Reachable sets, computed independently for each subsystem, are back-projected and intersected to yield an overapproximation of the actual reachable set. Moreover, applying this technique to a class of unstable LTI systems,

Shahab Kaynama; Meeko Oishi

2011-01-01

212

Linear coding of complex sound spectra by discharge rate in neurons of the medial nucleus of the trapezoid body (MNTB) and its inputs  

PubMed Central

The interaural level difference (ILD) cue to sound location is first encoded in the lateral superior olive (LSO). ILD sensitivity results because the LSO receives excitatory input from the ipsilateral cochlear nucleus and inhibitory input indirectly from the contralateral cochlear nucleus via glycinergic neurons of the ipsilateral medial nucleus of the trapezoid body (MNTB). It is hypothesized that in order for LSO neurons to encode ILDs, the sound spectra at both ears must be accurately encoded via spike rate by their afferents. This spectral-coding hypothesis has not been directly tested in MNTB, likely because MNTB neurons have been mostly described and studied recently in regards to their abilities to encode temporal aspects of sounds, not spectral. Here, we test the hypothesis that MNTB neurons and their inputs from the cochlear nucleus and auditory nerve code sound spectra via discharge rate. The Random Spectral Shape (RSS) method was used to estimate how the levels of 100-ms duration spectrally stationary stimuli were weighted, both linearly and non-linearly, across a wide band of frequencies. In general, MNTB neurons, and their globular bushy cell inputs, were found to be well-modeled by a linear weighting of spectra demonstrating that the pathways through the MNTB can accurately encode sound spectra including those resulting from the acoustical cues to sound location provided by head-related directional transfer functions (DTFs). Together with the anatomical and biophysical specializations for timing in the MNTB-LSO complex, these mechanisms may allow ILDs to be computed for complex stimuli with rapid spectrotemporally-modulated envelopes such as speech and animal vocalizations and moving sound sources. PMID:25565971

Koka, Kanthaiah; Tollin, Daniel J.

2014-01-01

213

Temporal linear mode complexity as a surrogate measure of the effect of remifentanil on the central nervous system in healthy volunteers  

PubMed Central

AIMS Previously, electroencephalographic approximate entropy (ApEn) effectively described both depression of central nervous system (CNS) activity and rebound during and after remifentanil infusion. ApEn is heavily dependent on the record length. Linear mode complexity, which is algorithmatically independent of the record length, was investigated to characterize the effect of remifentanil on the CNS using the combined effect and tolerance, feedback and sigmoid Emax models. METHODS The remifentanil blood concentrations and electroencephalographic data obtained in our previous study were used. With the recording of the electroencephalogram, remifentanil was infused at a rate of 1, 2, 3, 4, 5, 6, 7 or 8 µg kg?1 min?1 for 15–20 min. The areas below (AUCeffect) or above (AACrebound) the effect vs. time curve of temporal linear mode complexity (TLMC) and ApEn were calculated to quantitate the decrease of the CNS activity and rebound. The coefficients of variation (CV) of median baseline (E0), maximal (Emax), and individual median E0 minus Emaxvalues of TLMC were compared with those of ApEn. The concentration–TLMC relationship was characterized by population analysis using non-linear mixed effects modelling. RESULTS Median AUCeffectand AACreboundwere 1016 and 5.3 (TLMC), 787 and 4.5 (ApEn). The CVs of individual median E0 minus Emax were 35.6, 32.5% (TLMC, ApEn). The combined effect and tolerance model demonstrated the lowest Akaike information criteria value and the highest positive predictive value of rebound in tolerance. CONCLUSIONS The combined effect and tolerance model effectively characterized the time course of TLMC as a surrogate measure of the effect of remifentanil on the CNS. PMID:21223358

Choi, Byung-Moon; Shin, Da-Huin; Noh, Moon-Ho; Kim, Young-Hac; Jeong, Yong-Bo; Lee, Soo-Han; Lee, Eun-Kyung; Noh, Gyu-Jeong

2011-01-01

214

Complex degree of mutual anisotropy of linear birefringence and optical activity of biological tissues in diagnostics of prostate cancer  

NASA Astrophysics Data System (ADS)

We present theoretical fundamentals of polarization and correlation analysis of the optical anisotropy of biological tissues. Results of measurements of coordinate distributions of the complex degree of mutual anisotropy (CDMA) that are formed by birefringent structures of the prostate tissue with benign and malignant changes are compared. Magnitudes and ranges of variation of statistical (the firstto fourth-order distribution moments) and correlation (excess of autocorrelation functions) parameters of the coordinate CDMA distributions of histological sections of the prostate postoperative bioptic material are studied. Objective criteria of the diagnostics of the appearance of pathology and of the differentiation of the degree of its severity are determined.

Ushenko, V. A.; Gorsky, M. P.

2013-08-01

215

Comparing movement preparation of unimanual, bimanual symmetric, and bimanual asymmetric movements.  

PubMed

The goal of this study was to determine the process or processes most likely to be involved in reaction-time costs for spatially cued bimanual reaching. We used reaction time to measure the cost of bimanual symmetric movements compared to unimanual movements (a bimanual symmetric cost) and the cost for bimanual asymmetric movements compared to symmetric movements (a bimanual asymmetric cost). The results showed that reaction times were comparable for all types of movements in simple reaction time; that is, there was neither a bimanual symmetric cost nor an asymmetric cost. Therefore, unimanual, bimanual symmetric, and bimanual asymmetric movements have comparable complexity during response initiation. In choice conditions, there was no bimanual symmetric cost but there was a bimanual asymmetric cost, indicating that the preparation of asymmetric movements is more complex than symmetric movements. This asymmetric cost is likely the result of interference during response programming. PMID:24381087

Blinch, Jarrod; Cameron, Brendan D; Cressman, Erin K; Franks, Ian M; Carpenter, Mark G; Chua, Romeo

2014-03-01

216

An unprecedented "linear-bent" isomerism in tri-nuclear Cu2(II)Zn(II) complexes with a salen type di-Schiff base ligand.  

PubMed

Two new trinuclear hetero-metallic copper(II)-zinc(II) complexes [(CuL)(2)Zn(N(3))(2)] (1A and 1B) have been synthesized using [CuL] as a so-called "metalloligand" (where H(2)L = N,N'-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Complexes 1A and 1B have the same molecular formula but crystallize in different crystal systems (triclinic for 1A and monoclinic for 1B) with space group P1 for 1A and P2(1)/c for 1B. 1A is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligand" [CuL] are coordinated to a central Zn(II) through double phenoxido bridges. The Zn(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal azide ions. In complex 1B, in addition to the double phenoxido bridge, the two terminal Cu(II) ions are linked to the central Zn(II) via a ?(-l,l) azido bridge giving rise to a square pyramidal environment around the Cu(II) ions and consequently the structure becomes linear. These two species can be considered as "linear-bent" isomers. EPR spectra and ESI mass spectra show that the two isomers are identical in solution. The DFT calculation reveals that the energy of 1A is 7.06 kcal mol(-1) higher than that of 1B. The existence of both isomers in the solid state suggests that crystal packing interactions in are more efficient and probably compensate for the difference in energy. PMID:22858718

Das, Lakshmi Kanta; Park, Sung-Woo; Cho, Seung Joo; Ghosh, Ashutosh

2012-08-28

217

Dynamical behavior of a class of vibratory systems with symmetrical rigid stops near the point of codimension two bifurcation  

NASA Astrophysics Data System (ADS)

A multi-degree-of-freedom vibratory system having symmetrically placed rigid stops is considered. The system consists of linear components, but the maximum displacement of one of the masses is limited to a threshold value by the symmetrical rigid stops. Repeated impacts usually occur in the vibratory system due to the rigid amplitude constraints. Such models play an important role in the studies of mechanical systems with clearances or gaps. Local codimension two bifurcation of maps, involving a real eigenvalue and a complex conjugate pair escaping the unit circle simultaneously, is analyzed by using the center manifold theorem technique and normal form method for maps. Symmetrical double-impact periodic motion and Poincaré map of the system are derived analytically. A center manifold theorem technique is applied to reduce the Poincaré map to a three-dimensional one, and the normal form map associated with the codimension two bifurcation is obtained. Local behaviors of the vibratory systems with symmetrical rigid stops, near the points of codimension two bifurcations, are reported by the presentation of results for a two-degree-of-freedom vibratory system with symmetrical stops. The existence and stability of symmetrical double-impact periodic motion are analyzed explicitly. Also, local bifurcations at the points of change in stability, are analyzed. Near the point of codimension two bifurcation, there exists not only Hopf bifurcation of period-one double-impact motion, but also pitchfork bifurcation of the motion. Pitchfork bifurcation of period-one double-impact symmetrical motion results in the period-one double-impact unsymmetrical motion. The unsymmetrical double-impact motion is of two antisymmetrical forms due to different initial conditions and symmetrical stops. With change of the forcing frequency, the unsymmetrical double-impact periodic motion will undergo Hopf bifurcation. Moreover the period-one double-impact symmetrical motion will undergo Hopf bifurcation directly as the forcing frequency is changed in the contrary direction. The routes of quasi-periodic impact motions to chaos are observed by results from simulation.

Luo, G. W.; Zhang, Y. L.; Zhang, J. G.

2006-10-01

218

Møller energy of the nonstatic spherically symmetric metrics  

E-print Network

The energy distribution in the most general nonstatic spherically symmetric space-time is obtained using M{\\o}ller's energy-momentum complex. This result is compared with the energy expression obtained by using the energy-momentum complex of Einstein. Some examples of energy distributions in different prescriptions are discussed.

S. S. Xulu

2000-10-19

219

Reversible Switching between Nonquenched and Quenched States in Nanoscale Linear Arrays of Plant Light-Harvesting Antenna Complexes  

PubMed Central

A simple and robust nanolithographic method that allows sub-100 nm chemical patterning on a range of oxide surfaces was developed in order to fabricate nanoarrays of plant light-harvesting LHCII complexes. The site-specific immobilization and the preserved functionality of the LHCII complexes were confirmed by fluorescence emission spectroscopy. Nanopatterned LHCII trimers could be reversibly switched between fluorescent and quenched states by controlling the detergent concentration in the imaging buffer. A 3-fold quenching of the average fluorescence intensity was accompanied by a decrease in the average (amplitude-weighted) fluorescence lifetime from approximately 2.24 ns to approximately 0.4 ns, attributed to the intrinsic ability of LHCII to switch between fluorescent and quenched states upon changes in its conformational state. The nanopatterning methodology was extended by immobilizing a second protein, the enhanced green fluorescent protein (EGFP), onto LHCII-free areas of the chemically patterned surfaces. This very simple surface chemistry, which allows simultaneous selective immobilization and therefore sorting of the two types of protein molecules on the surface, is a key underpinning step toward the integration of LHCII into switchable biohybrid antenna constructs. PMID:24988144

2014-01-01

220

Linear {NiII-LnIII-NiII} complexes containing twisted planar Ni(?-phenolate)2 Ln fragments: synthesis, structure, and magnetothermal properties.  

PubMed

Sequential reaction of a multisite LH(4) ligand {2-[2-hydroxy-3-(hydroxymethyl)-5-methylbenzylideneamino]-2-methylpropane-1,3-diol} with appropriate lanthanide salts followed by the addition of Ni(NO(3))(2)?6?H(2)O in a 4:1:2 stoichiometric ratio in the presence of triethylamine afforded four heterobimetallic trinuclear complexes [Ni(2)Gd(LH(3))(4)]?3NO(3)?3?MeOH?H(2)O?CH(3)CN (1), [Ni(2)Tb(LH(3))(4)]?(3?)NO(3)?3?MeOH?CH(3)CN (2), [Ni(2)Dy(LH(3))(4)]?3?NO(3)?3?MeOH?H(2)O?CH(3)CN (3), and [Ni(2)Ho(LH(3))(4)]?3?NO(3)?3?MeOH?H(2)O?CH(3)CN (4). Complexes 1-4 possess linear trimetallic cores with a central lanthanide ion. Magnetic studies revealed a predominant ferromagnetic interaction between the Ni and Ln centers. Alternating current susceptibility measurements of complex 3 showed a small frequency dependence of the out-of-phase signal, ?''(M), under zero direct current field, but without achieving a net maximum above 2?K. Magnetic studies on 1 revealed that it has a significant magnetocaloric effect. PMID:24817615

Das, Sourav; Dey, Atanu; Kundu, Subrata; Biswas, Sourav; Mota, A J; Colacio, Enrique; Chandrasekhar, Vadapalli

2014-07-01

221

Forecasting transitions in systems with high-dimensional stochastic complex dynamics: a linear stability analysis of the tangled nature model.  

PubMed

We propose a new procedure to monitor and forecast the onset of transitions in high-dimensional complex systems. We describe our procedure by an application to the tangled nature model of evolutionary ecology. The quasistable configurations of the full stochastic dynamics are taken as input for a stability analysis by means of the deterministic mean-field equations. Numerical analysis of the high-dimensional stability matrix allows us to identify unstable directions associated with eigenvalues with a positive real part. The overlap of the instantaneous configuration vector of the full stochastic system with the eigenvectors of the unstable directions of the deterministic mean-field approximation is found to be a good early warning of the transitions occurring intermittently. PMID:25615342

Cairoli, Andrea; Piovani, Duccio; Jensen, Henrik Jeldtoft

2014-12-31

222

Forecasting Transitions in Systems with High-Dimensional Stochastic Complex Dynamics: A Linear Stability Analysis of the Tangled Nature Model  

NASA Astrophysics Data System (ADS)

We propose a new procedure to monitor and forecast the onset of transitions in high-dimensional complex systems. We describe our procedure by an application to the tangled nature model of evolutionary ecology. The quasistable configurations of the full stochastic dynamics are taken as input for a stability analysis by means of the deterministic mean-field equations. Numerical analysis of the high-dimensional stability matrix allows us to identify unstable directions associated with eigenvalues with a positive real part. The overlap of the instantaneous configuration vector of the full stochastic system with the eigenvectors of the unstable directions of the deterministic mean-field approximation is found to be a good early warning of the transitions occurring intermittently.

Cairoli, Andrea; Piovani, Duccio; Jensen, Henrik Jeldtoft

2014-12-01

223

Symmetry breaking in linearly coupled Korteweg-de Vries systems.  

PubMed

We consider solitons in a system of linearly coupled Korteweg-de Vries (KdV) equations, which model two-layer settings in various physical media. We demonstrate that traveling symmetric solitons with identical components are stable at velocities lower than a certain threshold value. Above the threshold, which is found exactly, the symmetric modes are unstable against spontaneous symmetry breaking, which gives rise to stable asymmetric solitons. The shape of the asymmetric solitons is found by means of a variational approximation and in the numerical form. Simulations of the evolution of an unstable symmetric soliton sometimes produce its breakup into two different asymmetric modes. Collisions between moving stable solitons, symmetric and asymmetric ones, are studied numerically, featuring noteworthy features. In particular, collisions between asymmetric solitons with identical polarities are always elastic, while in the case of opposite polarities the collision leads to a switch of the polarities of both solitons. Three-soliton collisions are studied too, featuring quite complex interaction scenarios. PMID:23020484

Espinosa-Cerón, A; Malomed, B A; Fujioka, J; Rodríguez, R F

2012-09-01

224

On the complex non-linear interaction between bacteria and redox dynamics in sediments and its effects on water quality  

NASA Astrophysics Data System (ADS)

Despite the fact that the prognoses on the availability of resources related to different climate scenarios have been already formulated, the complex hydrological and biogeochemical reactions taking place in different compartments in natural environmental media are poorly understood, especially regarding the interactions between water bodies, and the reactions taking place at soil-water interfaces. Amongst them, the inter-relationship between hydrology, chemistry and biology has important implications in natural (rivers, lakes) and man-made water facilities (lagoons, artificial recharge pounds, reservoirs, slow infiltration systems, etc). The consequences involve environment, economic, social and health-risk aspects. At the current stage, only limited explanations are available to understand the implications of these relationships on ecosystem services, water quality and water quantity. Therefore, there is an urgent need to seek a full understanding of these physical-biogeochemical processes in water-bodies, sediments and biota and its implications in ecological and health risk. We present a soil column experiment and a mathematical model which aim to study the mutual interplay between water and bacteria activity in porous media, the corresponding dynamics and the feedback on nutrient cycling by using a multidisciplinary approach.

Sanchez-Vila, X.; Rubol, S.; Fernandez-Garcia, D.

2011-12-01

225

Numerical Simulations of PT-Symmetric Quantum Field Theories  

E-print Network

Many non-Hermitian but PT-symmetric theories are known to have a real positive spectrum. Since the action is complex for there theories, Monte Carlo methods do not apply. In this paper the first field-theoretic method for numerical simulations of PT-symmetric Hamiltonians is presented. The method is the complex Langevin equation, which has been used previously to study complex Hamiltonians in statistical physics and in Minkowski space. We compute the equal-time one-point and two-point Green's functions in zero and one dimension, where comparisons to known results can be made. The method should also be applicable in four-dimensional space-time. Our approach may also give insight into how to formulate a probabilistic interpretation of PT-symmetric theories.

Claude Bernard; Van M. Savage

2001-06-15

226

Principal Geodesic Analysis on Symmetric Spaces: Statistics of Diffusion Tensors  

Microsoft Academic Search

Diffusion tensor magnetic resonance imaging (DT-MRI) is emerging as an important tool in medical image analysis of the brain. However, relatively little work has been done on producing statistics of diffusion tensors. A main dif- ficulty is that the space of diffusion tensors, i.e., the space of symmetric, positive- definite matrices, does not form a vector space. Therefore, standard linear

P. Thomas Fletcher; Sarang C. Joshi

2004-01-01

227

Pyramid diffraction in parity-time-symmetric optical lattices  

E-print Network

Pyramid diffraction in parity-time-symmetric optical lattices Sean Nixon and Jianke Yang diffraction pattern is demonstrated in both the linear and nonlinear regimes. Blow-up is also possible oscillation, unidirectional propagation, distinct pattern of diffraction, formation of solitons and breath

Yang, Jianke

228

Controller Failure Time Analysis for Symmetric H Control Systems Guisheng ZHAI  

E-print Network

Controller Failure Time Analysis for Symmetric H Control Systems Guisheng ZHAI Department of Opto a controller failure time analysis problem for a class of symmetric linear time-invariant (LTI) systems properties for the entire system. Our objective is to find conditions concerning controller failure time

Antsaklis, Panos

229

On the Stability of Spherically Symmetric Configurations in Newtonian Limit of Jordan, Brans-Dicke Theory  

E-print Network

We discuss stability of spherically symmetric static solutions in Newtonian limit of Jordan, Brans-Dicke field equations. The behavior of the stable equilibrium solutions for the spherically symmetric configurations considered here, it emerges that the more compact a model is, the more stable it is. Moreover, linear stability analysis shows the existence of stable configurations for any polytropic index.

S. Kozyrev

2003-04-08

230

ccsd00003900, ON SYMMETRIC SENSITIVITY  

E-print Network

ccsd­00003900, version 1 ­ 14 Jan 2005 ON SYMMETRIC SENSITIVITY Benoît CADRE and Pierre JACOB UMR, 34095 Montpellier cedex 5, FRANCE Abstract We de#28;ne the concept of symmetric sensitivity with respect sensitive map may diverge from a positive quantity independent of the initial points. We study

231

Computational design of a self-assembling symmetrical ?-propeller protein.  

PubMed

The modular structure of many protein families, such as ?-propeller proteins, strongly implies that duplication played an important role in their evolution, leading to highly symmetrical intermediate forms. Previous attempts to create perfectly symmetrical propeller proteins have failed, however. We have therefore developed a new and rapid computational approach to design such proteins. As a test case, we have created a sixfold symmetrical ?-propeller protein and experimentally validated the structure using X-ray crystallography. Each blade consists of 42 residues. Proteins carrying 2-10 identical blades were also expressed and purified. Two or three tandem blades assemble to recreate the highly stable sixfold symmetrical architecture, consistent with the duplication and fusion theory. The other proteins produce different monodisperse complexes, up to 42 blades (180 kDa) in size, which self-assemble according to simple symmetry rules. Our procedure is suitable for creating nano-building blocks from different protein templates of desired symmetry. PMID:25288768

Voet, Arnout R D; Noguchi, Hiroki; Addy, Christine; Simoncini, David; Terada, Daiki; Unzai, Satoru; Park, Sam-Yong; Zhang, Kam Y J; Tame, Jeremy R H

2014-10-21

232

Nonlinear localized modes in PT-symmetric optical media with competing gain and loss  

SciTech Connect

The existence and stability of the nonlinear spatial localized modes are investigated in parity-time symmetric optical media characterized by a generic complex hyperbolic refractive index distribution with competing gain and loss profile. The exact analytical expression of the localized modes are found for all values of the competing parameter and in the presence of both the self-focusing and self-defocusing Kerr nonlinearity. The effects of competing gain/loss profile on the stability structure of these localized modes are discussed with the help of linear stability analysis followed by the direct numerical simulation of the governing equation. The spatial localized modes in two-dimensional geometry as well as the transverse power-flow density associated with these localized modes are also examined. -- Highlights: • Existence of localized modes is investigated in PT-symmetric complex potentials. • Exact analytical expression of the localized modes is obtained. • Effect of gain/loss profile on the stability of these localized modes is discussed. • Localized modes in 2D and associated transverse power-flow density are also examined.

Midya, Bikashkali, E-mail: bikash.midya@gmail.com [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108 (India)] [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108 (India); Roychoudhury, Rajkumar, E-mail: rroychoudhury123@gmail.com [Advanced Center for Nonlinear and Complex Phenomena, Kolkata 700075 (India)] [Advanced Center for Nonlinear and Complex Phenomena, Kolkata 700075 (India)

2014-02-15

233

On Pauli’s principles of “Zweiteilung und symmetrie verminderung” in Higgs physics and non-linear dynamics  

Microsoft Academic Search

Pauli’s principle of bi-division and symmetry reduction “Zweiteilung und symmetrie verminderung” is generalized to cover maximally symmetric spaces specified by Killing’s vector fields and its successive symmetry breaking to yield the particles of the standard model of high energy physics.An analogous picture borrowed from non-linear dynamics and complexity theory will be used to illustrate the conceptual aspect of the procedure

M. S. El Naschie

2005-01-01

234

Linear independence over tropical semirings and beyond  

E-print Network

We investigate different notions of linear independence and of matrix rank that are relevant for max-plus or tropical semirings. The factor rank and tropical rank have already received attention, we compare them with the ranks defined in terms of signed tropical determinants or arising from a notion of linear independence introduced by Gondran and Minoux. To do this, we revisit the symmetrization of the max-plus algebra, establishing properties of linear spaces, linear systems, and matrices over the symmetrized max-plus algebra. In parallel we develop some general technique to prove combinatorial and polynomial identities for matrices over semirings that we illustrate by a number of examples.

Akian, Marianne; Guterman, Alexander

2008-01-01

235

Time-dependent and coupled-perturbed DFT and HF investigations on the absorption spectrum and non-linear optical properties of push–pull M(II)–porphyrin complexes (M = Zn, Cu, Ni)  

Microsoft Academic Search

We report time-dependent (TD) and coupled-perturbed (CP) DFT\\/HF investigations, on the linear and non-linear optical properties of M(II)-complexes of [5-[(4?-dimethylaminophenyl)-ethynyl]-15-[(4?-nitrophenyl)ethynyl]-10,20-diphenylporphyrin], with M=Zn, Cu, Ni. The TD-DFT absorption spectrum is in good agreement with the experimental one, allowing us to identify the transitions mainly responsible of the NLO response. CP-DFT\\/CP-HF calculations provide similar hyperpolarizability values for the three complexes, suggesting an

Filippo De Angelis; Simona Fantacci; Antonio Sgamellotti; Maddalena Pizzotti; Francesca Tessore; Alessio Orbelli Biroli

2007-01-01

236

APPROXIMATING SYMMETRIC POSITIVE SEMIDEFINITE TENSORS OF EVEN ORDER*  

PubMed Central

Tensors of various orders can be used for modeling physical quantities such as strain and diffusion as well as curvature and other quantities of geometric origin. Depending on the physical properties of the modeled quantity, the estimated tensors are often required to satisfy the positivity constraint, which can be satisfied only with tensors of even order. Although the space P02m of 2mth-order symmetric positive semi-definite tensors is known to be a convex cone, enforcing positivity constraint directly on P02m is usually not straightforward computationally because there is no known analytic description of P02m for m > 1. In this paper, we propose a novel approach for enforcing the positivity constraint on even-order tensors by approximating the cone P02m for the cases 0 < m < 3, and presenting an explicit characterization of the approximation ?2m ? ?2m for m ? 1, using the subset ?2m?P02m of semi-definite tensors that can be written as a sum of squares of tensors of order m. Furthermore, we show that this approximation leads to a non-negative linear least-squares (NNLS) optimization problem with the complexity that equals the number of generators in ?2m. Finally, we experimentally validate the proposed approach and we present an application for computing 2mth-order diffusion tensors from Diffusion Weighted Magnetic Resonance Images. PMID:23285313

BARMPOUTIS, ANGELOS; JEFFREY, HO; VEMURI, BABA C.

2012-01-01

237

A new conformal duality of spherically symmetric space-times  

E-print Network

A contribution linear in r to the gravitational potential can be created by a suitable conformal duality transformation: the conformal factor is 1/(1+r)^2 and r will be replaced by r/(1+r), where r is the Schwarzschild radial coordinate. Thus, every spherically symmetric solution of conformal Weyl gravity is conformally related to an Einstein space. This result finally resolves a long controversy about this topic. As a byproduct, we present an example of a spherically symmetric Einstein space which is a limit of a sequence of Schwarzschild-de Sitter space-times but which fails to be expressable in Schwarzschild coordinates. This example also resolves a long controversy.

H. -J. Schmidt

1999-05-28

238

PT-symmetric lattices with spatially extended gain/loss are generically unstable  

E-print Network

We illustrate, through a series of prototypical examples, that linear parity-time (PT) symmetric lattices with extended gain/loss profiles are generically unstable, for any non-zero value of the gain/loss coefficient. Our examples include a parabolic real potential with a linear imaginary part and the cases of no real and constant or linear imaginary potentials. On the other hand, this instability can be avoided and the spectrum can be real for localized or compact PT-symmetric potentials. The linear lattices are analyzed through discrete Fourier transform techniques complemented by numerical computations.

D. E. Pelinovsky; P. G. Kevrekidis; D. J. Frantzeskakis

2012-11-25

239

Synthesis, characterization of N,N?-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine with M(II)(M = Ni, Zn and Fe) Schiff-base complexes and their non-linear optical studies by z-scan technique  

NASA Astrophysics Data System (ADS)

Schiff-base complexes of N, N'-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine ligand with metal M (M = Ni(II), Zn(II) and Fe(II)) have been synthesized and characterized by their UV, FT-IR, NMR, elemental analysis and magnetic susceptibility measurements. Non-linear optical measurements carried out using nanosecond laser pulses at 532 nm show that these complexes can be used for optical limiting applications.

Sampath Kumar, H. C.; Ramachandra Bhat, B.; Rudresha, B. J.; Ravindra, R.; Philip, Reji

2010-07-01

240

Synthesis, characterization of N, N?-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine with M(II)(M = Ni, Zn and Fe) Schiff-base complexes and their non-linear optical studies by z-scan technique  

Microsoft Academic Search

Schiff-base complexes of N,N?-bis(2-hydroxynaphthalidene)phenylene-1,2-diamine ligand with metal M (M=Ni(II), Zn(II) and Fe(II)) have been synthesized and characterized by their UV, FT-IR, NMR, elemental analysis and magnetic susceptibility measurements. Non-linear optical measurements carried out using nanosecond laser pulses at 532nm show that these complexes can be used for optical limiting applications.

H. C. Sampath Kumar; B. Ramachandra Bhat; B. J. Rudresha; R. Ravindra; Reji Philip

2010-01-01

241

Linear electric field mass spectrometry  

DOEpatents

A mass spectrometer and methods for mass spectrometry are described. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field. 8 figs.

McComas, D.J.; Nordholt, J.E.

1992-12-01

242

The linear-ordered collagen scaffold-BDNF complex significantly promotes functional recovery after completely transected spinal cord injury in canine.  

PubMed

Spinal cord injury (SCI) is still a worldwide clinical challenge for which there is no viable therapeutic method. We focused on developing combinatorial methods targeting the complex pathological process of SCI. In this study, we implanted linear-ordered collagen scaffold (LOCS) fibers with collagen binding brain-derived neurotrophic factor (BDNF) by tagging a collagen-binding domain (CBD) (LOCS + CBD-BDNF) in completely transected canine SCI with multisystem rehabilitation to validate its potential therapeutic effect through a long-term (38 weeks) observation. We found that LOCS + CBD-BDNF implants strikingly promoted locomotion and functional sensory recovery, with some dogs standing unassisted and transiently moving. Further histological analysis showed that administration of LOCS + CBD-BDNF reduced lesion volume, decreased collagen deposits, promoted axon regeneration and improved myelination, leading to functional recovery. Collectively, LOCS + CBD-BDNF showed striking therapeutic effect on completely transected canine SCI model and it is the first time to report such breakthrough in the war with SCI. Undoubtedly, it is a potentially promising therapeutic method for SCI paralysis or other movement disorders caused by neurological diseases in the future. PMID:25522968

Han, Sufang; Wang, Bin; Jin, Wei; Xiao, Zhifeng; Li, Xing; Ding, Wenyong; Kapur, Meghan; Chen, Bing; Yuan, Baoyu; Zhu, Tiansheng; Wang, Handong; Wang, Jing; Dong, Qun; Liang, Weibang; Dai, Jianwu

2015-02-01

243

Partially PT symmetric optical potentials with all-real spectra and  

E-print Network

Partially PT symmetric optical potentials with all-real spectra and soliton families complex optical potentials with partial parity-time (PT ) symmetry are proposed. The usual PT symmetry spatial directions. However, we show that if the potential is only partially PT symmetric, i

Yang, Jianke

244

Jack-Laurent symmetric functions for special values of parameters  

E-print Network

We consider the Jack--Laurent symmetric functions for special values of parameters p_0=n+k^{-1}m, where k is not rational and m and n are natural numbers. In general, the coefficients of such functions may have poles at these values of p_0. The action of the corresponding algebra of quantum Calogero-Moser integrals D(k,p_0) on the space of Laurent symmetric functions defines the decomposition into generalised eigenspaces. We construct a basis in each generalised eigenspace as certain linear combinations of the Jack--Laurent symmetric functions, which are regular at p_0=n+k^{-1}m, and describe the action of D(k,p_0) in these eigenspaces.

A. N. Sergeev; A. P. Veselov

2014-12-29

245

Transformations between symmetric sets of quantum states  

E-print Network

We investigate probabilistic transformations of quantum states from a `source' set to a `target' set of states. Such transforms have many applications. They can be used for tasks which include state-dependent cloning or quantum state discrimination, and as interfaces between systems whose information encodings are not related by a unitary transform, such as continuous-variable systems and finite-dimensional systems. In a probabilistic transform, information may be lost or leaked, and we explain the concepts of leak and redundancy. Following this, we show how the analysis of probabilistic transforms significantly simplifies for symmetric source and target sets of states. In particular, we give a simple linear program which solves the task of finding optimal transforms, and a method of characterizing the introduced leak and redundancy in information-theoretic terms. Using the developed techniques, we analyse a class of transforms which convert coherent states with information encoded in their relative phase to symmetric qubit states. Each of these sets of states on their own appears in many well studied quantum information protocols. Finally, we suggest an asymptotic realization based on quantum scissors.

Vedran Dunjko; Erika Andersson

2012-06-22

246

Symmetrizers and antisymmetrizers for the BMW algebra  

E-print Network

Let $n\\in\\mathds{N}$ and $B_n(r,q)$ be the generic Birman-Murakami-Wenzl algebra with respect to indeterminants $r$ and $q$. It is known that $B_n(r,q)$ has two distinct linear representations generated by two central elements of $B_n(r,q)$ called the symmetrizer and antisymmetrizer of $B_n(r,q)$. These generate for $n\\geq 3$ the only one dimensional one sided ideals of $B_n(r,q)$ and generalize the corresponding notion for Hecke algebras of type $A$. In this paper the coefficients of these elements with respect to the graphical basis of $B_n(r,q)$ are determined explicitly.

Dipper, Richard; Stoll, Friederike

2011-01-01

247

Can PT-Symmetric Quantum Mechanics be a Viable Alternative Quantum Theory?  

E-print Network

Update: A time-independent $n\\times n$ PT-symmetric (and symmetric) Hamiltonian is diagonalizable since it has all distinct real eigenvalues and the resulting diagonal matrix is a real symmetric matrix. The diagonalization results an isometry so there shouldn't be any issue with unitarity and unfortunately this very elementary mathematical fact somehow did not draw the authors' attention. However, PT-symmetric quantum mechanics is not out of trouble. For time-dependent PT-symmetric (and symmetric) Hamiltonians (even $2\\times 2$ ones) the authors observed that there is a violation of unitarity. Moreover, the first named author showed in his recent article arXiv:1312.7738 that PT-symmetric quantum mechanics is indeed a certain kind of Hermitian quantum mechanics and that in order for time-evolution to be unitary with respect to $J$-inner product (one that gives rise to a Hilbert space structure on the space of state functions), the potential energy operator $V(x)$ must be real. This means that those complex PT-symmetric Hamiltonians that have been studied by physicists are unfortunately unphysical. The first named author discussed in a subsequent article arXiv:1401.5149 that while finite-state PT-symmetric quantum mechanics with time-independent Hamiltonians is not physically any different from Hermitian quantum mechanics, PT-symmetric quantum mechanics exhibits a distinctive symmetry from that of Hermitian quantum mechanics.

Sungwook Lee; Lawrence R. Mead

2014-05-18

248

Symmetric and antisymmetric nonlinear modes supported by dual local gain in lossy lattices  

NASA Astrophysics Data System (ADS)

We introduce a discrete lossy system, into which a double "hot spot" (HS) is inserted, i.e., two mutually symmetric sites carrying linear gain and cubic nonlinearity. The system can be implemented as an array of optical or plasmonic waveguides, with a pair of amplified nonlinear cores embedded into it. We focus on the case of self-defocusing nonlinearity and cubic losses acting at the HSs. Symmetric localized modes pinned to the double HS are constructed in an implicit analytical form, which is done separately for the cases of odd and even numbers of intermediate sites between the HSs. In the former case, some stationary solutions feature a W-like shape, with a low peak at the central site, added to tall peaks at the positions of the embedded HSs. The special case of two adjacent HSs is considered too. Stability of the solution families against small perturbations is investigated in a numerical form, which reveals stable and unstable subfamilies. The instability generated by an isolated positive eigenvalue leads to a spontaneous transformation into a co-existing stable antisymmetric mode, while a pair of complex-conjugate eigenvalues gives rise to persistent breathers. This article is a contribution to the volume dedicated to Professor Helmut Brand on the occasion of his 60th birhday.

Chow, K. W.; Ding, Edwin; Malomed, B. A.; Tang, A. Y. S.

2014-01-01

249

Dynamical conservation laws in supersymmetric theories of symmetric-space valued fields  

NASA Astrophysics Data System (ADS)

We define supersymmetric extensions of non-linear ?-models with fields taking values in riemannian symmetric spaces, and develop the associated classical theory of dynamical symmetry. A central role is played by a pair of dual spinorial superfields, in close analogy with the structure of dual currents identified in the purely bosonic case by Eichenherr and Forger. When the field variations vanish sufficiently rapidly at spatial infinity, there are infinitely many conserved non-local charges (non fermionic) over and above anything implied directly by translation, Lorentz, conformal, supersymmetry or isospin invariance. The charges in general conform to the pattern conjectured by Curtright and Zachos. Each of these charges is invariant under simple supersymmetry. When the underlying symmetric space is a complex manifold, the invariance group of such a model enlarges to include chiral and O(2) supersymmetry transformations; the non-local charges are also unchanged by these. The relations between this dynamical symmetry and instantons (when they exist), and a limit in which these models become purely fermionic while retaining their dynamical symmetry, are also described. The ordinary and chiral Gross-Neveu models are examples of this limit.

Schonfeld, Jonathan F.

1980-06-01

250

PT-symmetric knotting of coordinates: a new, topological mechanism of quantum confinement  

E-print Network

We construct an exactly solvable PT-symmetric example of Sturmian bound states which exist in the absence of any confining potential. Their origin is purely topological -- these states live on certain nontrivial contours of complex coordinates.

Miloslav Znojil

2008-01-03

251

The generalized sidelobe canceller based on quaternion widely linear processing.  

PubMed

We investigate the problem of quaternion beamforming based on widely linear processing. First, a quaternion model of linear symmetric array with two-component electromagnetic (EM) vector sensors is presented. Based on array's quaternion model, we propose the general expression of a quaternion semiwidely linear (QSWL) beamformer. Unlike the complex widely linear beamformer, the QSWL beamformer is based on the simultaneous operation on the quaternion vector, which is composed of two jointly proper complex vectors, and its involution counterpart. Second, we propose a useful implementation of QSWL beamformer, that is, QSWL generalized sidelobe canceller (GSC), and derive the simple expressions of the weight vectors. The QSWL GSC consists of two-stage beamformers. By designing the weight vectors of two-stage beamformers, the interference is completely canceled in the output of QSWL GSC and the desired signal is not distorted. We derive the array's gain expression and analyze the performance of the QSWL GSC in the presence of one type of interference. The advantage of QSWL GSC is that the main beam can always point to the desired signal's direction and the robustness to DOA mismatch is improved. Finally, simulations are used to verify the performance of the proposed QSWL GSC. PMID:24955425

Tao, Jian-wu; Chang, Wen-xiu

2014-01-01

252

Universal symmetric cloning: No-signalling and nonlinear quantum mechanics  

E-print Network

We present a pseudo-spin representation for universal symmetric 1-to-M cloning of qubits, including both linear and nonlinear evolutions. We derive a set of equations to be satisfied by the cloning transformation under the no-signalling condition, and find an expression for the fidelity. We further introduce the linearity constraint, and obtain the unique universal symmetric quantum cloning machine for "an arbitrary" fidelity. No-signalling condition alone leads to fidelities higher than those of the quantum machines, and the maximum value converges to 3/4 rather than the optimal quantum limit of 2/3. We introduce the "prime cloners" whose fidelities have multiplicative property and show that the infinite copy limit of the prime cloners is 1/2.

Gedik, Z

2012-01-01

253

Canonical distributions on Riemannian homogeneous k-symmetric spaces  

NASA Astrophysics Data System (ADS)

It is known that distributions generated by almost product structures are applicable, in particular, to some problems in the theory of Monge-Ampère equations. In this paper, we characterize canonical distributions defined by canonical almost product structures on Riemannian homogeneous k-symmetric spaces in the sense of types AF (anti-foliation), F (foliation), TGF (totally geodesic foliation). Algebraic criteria for all these types on k-symmetric spaces of orders k = 4 , 5 , 6 were obtained. Note that canonical distributions on homogeneous k-symmetric spaces are closely related to special canonical almost complex structures and f-structures, which were recently applied by I. Khemar to studying elliptic integrable systems.

Balashchenko, Vitaly V.

2015-01-01

254

Optical bistability in nonlinear periodical structures with PT -symmetric potential  

NASA Astrophysics Data System (ADS)

The interaction between forward and backward waves in a periodical structure with PT -symmetric potential is investigated. The results demonstrate that the PT -term can change the bandgap of the periodical structure and affect the effective feedback mechanism. The linear solution, reflectivity, dispersion relation, and a generalized analytical solution of this periodical structure are obtained. The influences of the PT -term and detunings on the characteristic of bistability (or multistability) are also discussed.

Liu, Jibing; Xie, Xiao-Tao; Shan, Chuan-Jia; Liu, Tang-Kun; Lee, Ray-Kuang; Wu, Ying

2015-01-01

255

Pyramid diffraction in parity-time-symmetric optical lattices  

E-print Network

Nonlinear dynamics of wave packets in two-dimensional parity-time-symmetric optical lattices near the phase-transition point are analytically studied. A novel fourth-order equation is derived for the envelope of these wave packets. A pyramid diffraction pattern is demonstrated in both the linear and nonlinear regimes. Blow-up is also possible in the nonlinear regime for both focusing and defocusing nonlinearities.

Nixon, Sean

2013-01-01

256

Nuclear physics with spherically symmetric supernova models  

E-print Network

Few years ago, Boltzmann neutrino transport led to a new and reliable generation of spherically symmetric models of stellar core collapse and postbounce evolution. After the failure to prove the principles of the supernova explosion mechanism, these sophisticated models continue to illuminate the close interaction between high-density matter under extreme conditions and the transport of leptons and energy in general relativistically curved space-time. We emphasize that very different input physics is likely to be relevant for the different evolutionary phases, e.g. nuclear structure for weak rates in collapse, the equation of state of bulk nuclear matter during bounce, multidimensional plasma dynamics in the postbounce evolution, and neutrino cross sections in the explosive nucleosynthesis. We illustrate the complexity of the dynamics using preliminary 3D MHD high-resolution simulations based on parameterized deleptonization. With established spherically symmetric models we show that typical features of the different phases are reflected in the predicted neutrino signal and that a consistent neutrino flux leads to electron fractions larger than 0.5 in neutrino-driven supernova ejecta.

M. Liebendoerfer; T. Fischer; C. Fröhlich; F. -K. Thielemann; S. Whitehouse

2007-08-31

257

PT-symmetrically deformed shock waves  

E-print Network

We investigate for a large class of nonlinear wave equations, which allow for shock wave formations, how these solutions behave when they are PT-symmetrically deformed. For real solutions we find that they are transformed into peaked solutions with a discontinuity in the first derivative instead. The systems we investigate include the PT-symmetrically deformed inviscid Burgers equation recently studied by Bender and Feinberg, for which we show that it does not develop any shocks, but peaks instead. In this case we exploit the rare fact that the PT-deformation can be provided by an explicit map found by Curtright and Fairlie together with the property that the undeformed equation can be solved by the method of characteristics. We generalise the map and observe this type of behaviour for all integer values of the deformation parameter epsilon. The peaks are formed as a result of mapping the multi-valued self-avoiding shock profile to a multi-valued self-crossing function by means of the PT-deformation. For some deformation parameters we also investigate the deformation of complex solutions and demonstrate that in this case the deformation mechanism leads to discontinuties.

Andrea Cavaglia; Andreas Fring

2012-01-27

258

Secure Symmetrical Multilevel Diversity Coding  

E-print Network

Secure symmetrical multilevel diversity coding (S-SMDC) is a source coding problem, where a total of L - N discrete memoryless sources (S1,...,S_L-N) are to be encoded by a total of L encoders. This thesis considers a natural generalization of SMDC...

Li, Shuo

2012-07-16

259

Spherically symmetric spacetimes in massive gravity  

E-print Network

We explore spherically symmetric stationary solutions, generated by ``stars'' with regular interiors, in purely massive gravity. We reexamine the claim that the resummation of non-linear effects can cure, in a domain near the source, the discontinuity exhibited by the linearized theory as the mass m of the graviton tends to zero. First, we find analytical difficulties with this claim, which appears not to be robust under slight changes in the form of the mass term. Second, by numerically exploring the inward continuation of the class of asymptotically flat solutions, we find that, when m is ``small'', they all end up in a singularity at a finite radius, well outside the source, instead of joining some conjectured ``continuous'' solution near the source. We reopen, however, the possibility of reconciling massive gravity with phenomenology by exhibiting a special class of solutions, with ``spontaneous symmetry breaking'' features, which are close, near the source, to general relativistic solutions and asymptote, for large radii, a de Sitter solution of curvature ~m^2.

Thibault Damour; Ian I. Kogan; Antonios Papazoglou

2002-12-13

260

Skyrmions and vector mesons: a symmetric approach  

SciTech Connect

We propose an extension of the effective, low-energy chiral Lagrangian known as the Skyrme model, to one formulated by a non-linear sigma model generalized to include vector mesons in a symmetric way. The model is based on chiral SU(6) x SU(6) symmetry spontaneously broken to static SU(6). The rho and other vector mesons are dormant Goldstone bosons since they are in the same SU(6) multiplet as the pion and other pseudoscalars. Hence the manifold of our generalized non-linear sigma model is the coset space (SU(6) x SU(6))/Su(6). Relativistic effects, via a spin-dependent mass term, break the static SU(6) and give the vectors a mass. The model can then be fully relativistic and covariant. The lowest-lying Skyrmion in this model is the whole baryonic 56-plet, which splits into the octet and decuplet in the presence of relativistic SU(6)-breaking. Due to the built-in SU(6) and the presence of vector mesons, the model is expected to have better phenomenological results, as well as providing a conceptually more unified picture of mesons and baryons. 29 references.

Caldi, D.G.

1984-01-01

261

PT-symmetric phonon laser.  

PubMed

By exploiting recent developments associated with coupled microcavities, we introduce the concept of the PT-symmetric phonon laser with balanced gain and loss. This is accomplished by introducing gain to one of the microcavities such that it balances the passive loss of the other. In the vicinity of the gain-loss balance, a strong nonlinear relation emerges between the intracavity-photon intensity and the input power. This then leads to a giant enhancement of both optical pressure and mechanical gain, resulting in a highly efficient phonon-lasing action. These results provide a promising approach for manipulating optomechanical systems through PT-symmetric concepts. Potential applications range from enhancing mechanical cooling to designing phonon-laser amplifiers. PMID:25126921

Jing, Hui; Özdemir, S K; Lü, Xin-You; Zhang, Jing; Yang, Lan; Nori, Franco

2014-08-01

262

General PT-Symmetric Matrices  

E-print Network

Three ways of constructing a non-Hermitian matrix with possible all real eigenvalues are discussed. They are PT symmetry, pseudo-Hermiticity, and generalized PT symmetry. Parameter counting is provided for each class. All three classes of matrices have more real parameters than a Hermitian matrix with the same dimension. The generalized PT-symmetric matrices are most general among the three. All self-adjoint matrices process a generalized PT symmetry. For a given matrix, it can be both PT-symmetric and P'-pseudo-Hermitian with respect to some P' operators. The relation between corresponding P and P' operators is established. The Jordan block structures of each class are discussed. Explicit examples in 2x2 are shown.

Jia-wen Deng; Uwe Guenther; Qing-hai Wang

2012-12-09

263

Inflation in a Symmetric Vacuum  

E-print Network

If in a finite universe, the tree-level vacuum is a symmetric superposition of coherent states, in each of which the inflaton field assumes a different, energy-minimizing mean value (vev), then the resulting energy is positive and decreases exponentially as the volume of the universe increases. This effect can drive inflation when that volume is small and explain part of dark energy when it is big, but the effect is exceedingly tiny except at very early times.

Kevin Cahill

2007-05-23

264

On the stability of spherically symmetric and wormhole solutions supported by the sine-Gordon ghost scalar field  

E-print Network

In this paper we investigate wormhole and spherically symmetric solutions in 4D gravity plus a matter source consisting of a ghost scalar field with a sine-Gordon potential. For the wormhole solutions we also include the possibility of electric and/or magnetic charges. For both types of solutions we perform a linear stability analysis and show that the wormhole solutions are stable and that when one turns on the electric and/or magnetic field the solution remains stable. The linear stability analysis of the spherically symmetric solutions indicates that they can be stable or unstable depending on one of the parameters of the system. This result for the spherically symmetric solution is nontrivial since a previous investigation of 4D gravity plus a ghost scalar field with a $\\lambda \\phi ^4$ interaction found only unstable spherically symmetric solutions. Both the wormhole and spherically symmetric solutions presented here asymptotically go to anti-de-Sitter space-time.

Vladimir Dzhunushaliev; Vladimir Folomeev; Ratbay Myrzakulov; Douglas Singleton

2010-06-08

265

Dust Static Spherically Symmetric Solution in $f(R)$ Gravity  

E-print Network

In this paper, we take dust matter and investigate static spherically symmetric solution of the field equations in metric f(R) gravity. The solution is found with constant Ricci scalar curvature and its energy distribution is evaluated by using Landau-Lifshitz energy-momentum complex. We also discuss the stability condition and constant scalar curvature condition for some specific popular choices of f(R) models in addition to their energy distribution.

Muhammad Sharif; Hafiza Rizwana Kausar

2011-02-21

266

Discrete PT-symmetric square-well oscillators  

E-print Network

Exact solvability of the discretized N-point version of the PT-symmetric square-well model is pointed out. Its wave functions are found proportional to the classical Tshebyshev polynomials of a complex argument. At all N a compact secular equation is derived giving the real spectrum of energies at any non-Hermiticity strength Z below its finite and weakly N-dependent critical value. In the limit of vanishing Z the model degenerates to a Hermitian Hueckel Hamiltonian.

Miloslav Znojil

2005-11-11

267

A polypeptide "building block" for the ?-trefoil fold identified by "top-down symmetric deconstruction".  

PubMed

Fibroblast growth factor-1, a member of the 3-fold symmetric ?-trefoil fold, was subjected to a series of symmetric constraint mutations in a process termed "top-down symmetric deconstruction." The mutations enforced a cumulative exact 3-fold symmetry upon symmetrically equivalent positions within the protein and were combined with a stability screen. This process culminated in a ?-trefoil protein with exact 3-fold primary-structure symmetry that exhibited excellent folding and stability properties. Subsequent fragmentation of the repeating primary-structure motif yielded a 42-residue polypeptide capable of spontaneous assembly as a homotrimer, producing a thermostable ?-trefoil architecture. The results show that despite pronounced reduction in sequence complexity, pure symmetry in the design of a foldable, thermostable ?-trefoil fold is possible. The top-down symmetric deconstruction approach provides a novel alternative means to successfully identify a useful polypeptide "building block" for subsequent "bottom-up" de novo design of target protein architecture. PMID:21315087

Lee, Jihun; Blaber, Sachiko I; Dubey, Vikash K; Blaber, Michael

2011-04-15

268

Symmetry breaking of solitons in one-dimensional parity-time-symmetric optical potentials.  

PubMed

Symmetry breaking of solitons in a class of one-dimensional parity-time (PT) symmetric complex potentials with cubic nonlinearity is reported. In generic PT-symmetric potentials, such symmetry breaking is forbidden. However, in a special class of PT-symmetric potentials V(x)=g(2)(x)+?g(x)+ig'(x), where g(x) is a real and even function and ? a real constant, symmetry breaking of solitons can occur. That is, a branch of non-PT-symmetric solitons can bifurcate out from the base branch of PT-symmetric solitons when the base branch's power reaches a certain threshold. At the bifurcation point, the base branch changes stability, and the bifurcated branch can be stable. PMID:25360924

Yang, Jianke

2014-10-01

269

Design of a vertical ultra-precision linear axis modular driven by dual linear motors  

NASA Astrophysics Data System (ADS)

Non-rotational symmetric surface machining requires at least three numerically controlled axes, so there exists a desperately need of an ultra-precision vertical linear axis for ultra-precision machine tools. Based on the above consideration, a vertical ultra-precision linear axis has been developed to satisfy the need for non-rotational symmetric surface ultra-precision machining. The paper discusses the design challenges of the vertical ultra-precision linear axis and presents the mechanical structure designed with dual linear motor drive. A guide component and a gravity compensation mechanism have been designed. Finite element models for the vertical ultra-precision were established to evaluate the dynamic performance of the vertical ultra-precision linear axis. Analysis results show that the configuration of the vertical ultra-precision linear axis is reasonable with good dynamic performance.

Qi, Enbing; Fang, Zhenyong; Sun, Tao; Wang, Bo

2014-08-01

270

Modeling Symmetric Macromolecular Structures in Rosetta3  

PubMed Central

Symmetric protein assemblies play important roles in many biochemical processes. However, the large size of such systems is challenging for traditional structure modeling methods. This paper describes the implementation of a general framework for modeling arbitrary symmetric systems in Rosetta3. We describe the various types of symmetries relevant to the study of protein structure that may be modeled using Rosetta's symmetric framework. We then describe how this symmetric framework is efficiently implemented within Rosetta, which restricts the conformational search space by sampling only symmetric degrees of freedom, and explicitly simulates only a subset of the interacting monomers. Finally, we describe structure prediction and design applications that utilize the Rosetta3 symmetric modeling capabilities, and provide a guide to running simulations on symmetric systems. PMID:21731614

DiMaio, Frank; Leaver-Fay, Andrew; Bradley, Phil; Baker, David; André, Ingemar

2011-01-01

271

Linear Accelerators  

SciTech Connect

In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

Sidorin, Anatoly [Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna (Russian Federation)

2010-01-05

272

Mueller matrix decomposition for extraction of individual polarization parameters from complex turbid media exhibiting multiple scattering, optical activity, and linear birefringence  

Microsoft Academic Search

Linear birefringence and optical activity are two common optical polarization effects present in biological tissue, and determi- nation of these properties has useful biomedical applications. How- ever, measurement and unique interpretation of these parameters in tissue is hindered by strong multiple scattering effects and by the fact that these and other polarization effects are often present simulta- neously. We have

Nirmalya Ghosh; Michael F. G. Wood; I. Alex Vitkin

2008-01-01

273

The first near-linear bis(amide) f-block complex: a blueprint for a high temperature single molecule magnet.  

PubMed

We report the first near-linear bis(amide) 4f-block compound and show that this novel structure, if implemented with dysprosium(iii), would have unprecedented single molecule magnet (SMM) properties with an energy barrier, Ueff, for reorientation of magnetization of 1800 cm(-1). PMID:25384179

Chilton, Nicholas F; Goodwin, Conrad A P; Mills, David P; Winpenny, Richard E P

2015-01-01

274

Magnetic linear dichroism in S4 symmetry: Experimental evidence for complex coefficients in wavefunctions for Nd3+ in SrMoO4  

Microsoft Academic Search

A detailed calculation of magnetic linear dichroism (MLD) is performed in the case of S4 symmetry for ions with an odd number of active electrons, using perturbation theory. First it is shown that MLD anisotropy provides reliable assignments of the symmetry of the excited states. Then, in case of sinusoidal variation of the MLD amplitude, it is demonstrated that the

N. Moreau; A. C. Boccara

1976-01-01

275

Critical binding and electron scattering by symmetric-top polar molecules  

NASA Astrophysics Data System (ADS)

Quantum treatments of electron interactions with polar symmetric-top rotor molecules show features not present in the treatment of the linear-polar-rotor model. For symmetric tops possessing non-zero angular momentum about the symmetry axis, a new critical dipole can be defined that guarantees an infinite set of dipole-bound states independent of the values of the components of the inertial tensor. Additionally, for this same class, the scattering cross section diverges for all nonzero values of dipole moments and inertial moments, similar to solutions for the fixed linear dipole. Additional predictions are presented for electron affinities and rotational resonances of these systems.

Garrett, W. R.

2014-10-01

276

PT and non-PT-Symmetric Solutions of the Schrodinger Equation for the Generalized Woods-Saxon Potential  

E-print Network

We investigate complex PT and non-PT-symmetric forms of the generalized Woods- Saxon potential. We also look for exact solutions of the Schrodinger equation for the PT and/or non-PT-symmetric potentials of the kind mentioned above. Nikiforov-Uvarov method is used to obtain their energy eigenvalues and associated eigenfunctions.

Cuneyt Berkdemir; Ayse Berkdemir; Ramazan Sever

2006-03-01

277

Vibration reduction of beams under successive traveling loads by means of linear and nonlinear dynamic absorbers  

NASA Astrophysics Data System (ADS)

The goal of the present work is to assess the performances of dynamic vibration absorbers (DVA) in suppressing the vibrations of a simply supported beam subjected to an infinite sequence of regularly spaced concentrated moving loads. In particular, several types of DVA are considered: linear, cubic, higher odd-order monomials and piecewise linear stiffness; linear, cubic and linear-quadratic viscous damping. The purpose is to clarify if nonlinear DVAs show improvements with respect to the classical linear devices. The dynamic scenario is deeply investigated in a wide range of operating conditions, spanning the parameter space of the DVA (damping, stiffness). Nonlinear stiffness can lead to complex dynamics such as quasi-periodic, chaotic and sub-harmonic responses; moreover, acting on the stiffness nonlinearity no improvement is found with respect to the linear DVA. A nonlinear non-symmetric dissipation in the DVA leads to a great reduction of the beam response, the reduction is larger with respect to the linear DVA.

Samani, Farhad S.; Pellicano, Francesco

2012-05-01

278

Mueller matrix decomposition for extraction of individual polarization parameters from complex turbid media exhibiting multiple scattering, optical activity, and linear birefringence.  

PubMed

Linear birefringence and optical activity are two common optical polarization effects present in biological tissue, and determination of these properties has useful biomedical applications. However, measurement and unique interpretation of these parameters in tissue is hindered by strong multiple scattering effects and by the fact that these and other polarization effects are often present simultaneously. We have investigated the efficacy of a Mueller matrix decomposition methodology to extract the individual intrinsic polarimetry characteristics (linear retardance delta and optical rotation psi, in particular) from a multiply scattering medium exhibiting simultaneous linear birefringence and optical activity. In the experimental studies, a photoelastic modulation polarimeter was used to record Mueller matrices from polyacrylamide phantoms having strain-induced birefringence, sucrose-induced optical activity, and polystyrene microspheres-induced scattering. Decomposition of the Mueller matrices recorded in the forward detection geometry from these phantoms with controlled polarization properties yielded reasonable estimates for delta and psi parameters. The confounding effects of scattering, the propagation path of multiple scattered photons, and detection geometry on the estimated values for delta and psi were further investigated using polarization-sensitive Monte Carlo simulations. The results show that in the forward detection geometry, the effects of scattering induced linear retardance and diattenuation are weak, and the decomposition of the Mueller matrix can retrieve the intrinsic values for delta and psi with reasonable accuracy. The ability of this approach to extract the individual intrinsic polarimetry characteristics should prove valuable in diagnostic photomedicine, for example, in quantifying the small optical rotations due to the presence of glucose in tissue and for monitoring changes in tissue birefringence as a signature of tissue abnormality. PMID:19021363

Ghosh, Nirmalya; Wood, Michael F G; Vitkin, I Alex

2008-01-01

279

A Mn(III)-superoxo complex of a zwitterionic calix[4]arene with an unprecedented linear end-on Mn(III)-O2 arrangement and good catalytic performance for alkene epoxidation.  

PubMed

Reactions of [H(4)L][PF(6)](4) with 4 equiv. of Mn(OAc)(2)·4H(2)O in the presence of air gave rise to a mononuclear Mn(III)-superoxo complex [Mn(III)L(O(2))(H(2)O)](PF(6))(2), which contains a bowl-shaped cationic structure with a D(4d) symmetry. It has an unprecedented linear end-on Mn(III)-O(2) unit and exhibited good efficiency and selectivity in the catalytic oxidation of alkenes with O(2) plus isobutyraldehyde under mild conditions. PMID:21892451

Liu, Lei-Lei; Li, Hong-Xi; Wan, Li-Min; Ren, Zhi-Gang; Wang, Hui-Fang; Lang, Jian-Ping

2011-10-21

280

Stabilization and rovibronic spectra of the T-shaped and linear ground-state conformers of a weakly bound rare-gas-homonuclear dihalogen complex: He ⋯Br2  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence spectra of Br2 entrained in a He supersonic expansion have been recorded in the Br2B-X, 8-0, 12-0, and 21-0 spectral regions at varying downstream distances, and thus different temperature regimes. Features associated with transitions of the T-shaped and linear He ⋯Br2(X,??=0) complexes are identified. The changes in the relative intensities of the T-shaped and linear features with cooling in the expansion indicate that the linear conformer is energetically more stable than the T-shaped conformer. A He +Br2(X,??=0) ab initio potential-energy surface, computed at the coupled cluster level of theory with a large, flexible basis set, is used to calculate the binding energies of the two conformers, 15.8 and 16.5 cm-1 for the T-shaped and linear complexes, respectively. This potential and an excited-state potential [M. P. de Lara-Castells, A. A. Buchachenko, G. Delgado-Barrio, and P. Villareal, J. Chem. Phys. 120, 2182 (2004)] are used to calculate the excitation spectra of He ⋯Br279(X,??=0) in the Br2B-X, 12-0 region. The calculated spectra are used to make spectral assignments and to determine the energies of the excited-state intermolecular vibrational levels accessed in the observed transitions. Temperature-dependent laser-induced fluorescence spectra and a simple thermodynamic model [D. S. Boucher, J. P. Darr, M. D. Bradke, R. A. Loomis, and A. B. McCoy, Phys. Chem. Chem. Phys. 6, 5275 (2004)] are used to estimate that the linear conformer is 0.4(2)cm-1 more strongly bound than the T-shaped conformer. Two-laser action spectroscopy experiments reveal that the binding energy of the linear He ⋯Br279(X,??=0) conformer is 17.0(8)cm-1, and that of the T-shaped He ⋯Br279(X,??=0) conformer is then 16.6(8)cm-1, in good agreement with the calculated values.

Boucher, David S.; Strasfeld, David B.; Loomis, Richard A.; Herbert, John M.; Ray, Sara E.; McCoy, Anne B.

2005-09-01

281

A Hopf laboratory for symmetric functions  

E-print Network

An analysis of symmetric function theory is given from the perspective of the underlying Hopf and bi-algebraic structures. These are presented explicitly in terms of standard symmetric function operations. Particular attention is focussed on Laplace pairing, Sweedler cohomology for 1- and 2-cochains, and twisted products (Rota cliffordizations) induced by branching operators in the symmetric function context. The latter are shown to include the algebras of symmetric functions of orthogonal and symplectic type. A commentary on related issues in the combinatorial approach to quantum field theory is given.

Bertfried Fauser; P. D. Jarvis

2003-08-29

282

Non-Symmetric Finite Networks: The Two-Point Resistance  

NASA Astrophysics Data System (ADS)

An explicit formula for the resistance between two nodes in a network described by non-symmetric Laplacian matrix L is obtained. This is of great advantage eg in electronic circuit fault analysis, where non-linear systems have to be solved repeatedly. Analysis time can be greatly reduced by utilization of the obtained formula. The presented approach is based on the "mutual orthogonality" of the full system of left and right-hand eigenvectors of a diagonalizable matrix L. Simple examples are given to demonstrate the accuracy of this approach to circuit networks

?er?anová, Viera; Brenku?, Juraj; Stopjaková, Viera

2014-09-01

283

Geometrodynamics in a spherically symmetric, static crossflow of null dust  

E-print Network

The spherically symmetric, static spacetime generated by a crossflow of non-interacting radiation streams, treated in the geometrical optics limit (null dust) is equivalent to an anisotropic fluid forming a radiation atmosphere of a star. This reference fluid provides a preferred / internal time, which is employed as a canonical coordinate. Among the advantages we encounter a new Hamiltonian constraint, which becomes linear in the momentum conjugate to the internal time (therefore yielding a functional Schr\\"{o}dinger equation after quantization), and a strongly commuting algebra of the new constraints.

Zsolt Horváth; Zoltán Kovács; László Á. Gergely

2006-10-12

284

Entropic gravity versus gravitational pseudotensors in static spherically symmetric spacetimes  

E-print Network

We present some well-known energy-momentum complexes and evaluate the gravitational energy associated with static spherically symmetric spacetimes. In fact, the energy distribution of the aforementioned gravitational background that is contained in a two-sphere of radius $r$ shows that a test particle situated at a finite distance $r$ experiences the gravitational field of the effective gravitational mass. In addition, we apply Verlinde's entropic gravity to find the emergent gravitational energy on static spherically symmetric screens. In this setup, we find that the energy distribution in the prescription of M{\\o}ller is similar to the energy derived from the emergent gravity, while other prescriptions give the different results. This result may confirm the argument of Lessner who argues that M{\\o}ller's definition of energy is a powerful concept of energy in General Relativity.

S. Hamid Mehdipour

2014-04-15

285

Strong photon antibunching of symmetric and antisymmetric modes in weakly nonlinear photonic molecules  

NASA Astrophysics Data System (ADS)

We study the photon statistics of symmetric and antisymmetric modes in a photonic molecule consisting of two linearly coupled nonlinear cavity modes. Our calculations show that strong photon antibunching of both symmetric and antisymmetric modes can be obtained even when the nonlinearity in the photonic molecule is weak. The strong antibunching effect results from the destructive interference between different paths for two-photon excitation. Moreover, we find that the optimal frequency detunings for strong photon antibunching in the symmetric and antisymmetric modes are linearly dependent on the coupling strength between the cavity modes in the photonic molecule. This implies that the photonic molecules can be used to generate tunable single-photon sources by tuning the values of the coupling strength between the cavity modes with weak nonlinearity.

Xu, Xun-Wei; Li, Yong

2014-09-01

286

Nonlinearly-PT-symmetric systems: spontaneous symmetry breaking and transmission resonances  

E-print Network

We introduce a class of PT-symmetric systems which include mutually matched nonlinear loss and gain (inother words, a class of PT-invariant Hamiltonians in which both the harmonic and anharmonic parts are non-Hermitian). For a basic system in the form of a dimer, symmetric and asymmetric eigenstates, including multistable ones, are found analytically. We demonstrate that, if coupled to a linear chain, such a nonlinear PT-symmetric dimer generates new types of nonlinear resonances, with the completely suppressed or greatly amplified transmission, as well as a regime similar to the electromagnetically-induced transparency (EIT). The implementation of the systems is possible in various media admitting controllable linear and nonlinear amplification of waves.

Andrey E. Miroshnichenko; Boris A. Malomed; Yuri S. Kivshar

2011-04-05

287

Fully physical time-dependent compact thermal modelling of complex non linear 3-dimensional systems for device and circuit level electro-thermal CAD  

Microsoft Academic Search

An fully analytical spectral domain decomposition approach to solution of the nonlinear time-dependent heat diffusion equation in complex volumes is introduced. Its application to device\\/circuit level electro-thermal simulation on CAD timescales is illustrated. The full treatment in coupled electro-thermal CAD of thermal nonlinearity due to temperature dependent diffusivity is described. Thermal solutions are presented in the form of thermal impedance

W. Battyxf; C. E. Christoffersen; S. David; A. J. Panks; R. G. Johnson; C. M. Snowden; M. B. Steer

2001-01-01

288

Maximum-confidence discrimination among symmetric qudit states  

SciTech Connect

We study the maximum-confidence (MC) measurement strategy for discriminating among nonorthogonal symmetric qudit states. Restricting to linearly dependent and equally likely pure states, we find the optimal positive operator valued measure (POVM) that maximizes our confidence in identifying each state in the set and minimizes the probability of obtaining inconclusive results. The physical realization of this POVM is completely determined and it is shown that after an inconclusive outcome, the input states may be mapped into a new set of equiprobable symmetric states, restricted, however, to a subspace of the original qudit Hilbert space. By applying the MC measurement again onto this new set, we can still gain some information about the input states, although with less confidence than before. This leads us to introduce the concept of sequential maximum-confidence (SMC) measurements, where the optimized MC strategy is iterated in as many stages as allowed by the input set, until no further information can be extracted from an inconclusive result. Within each stage of this measurement our confidence in identifying the input states is the highest possible, although it decreases from one stage to the next. In addition, the more stages we accomplish within the maximum allowed, the higher will be the probability of correct identification. We will discuss an explicit example of the optimal SMC measurement applied in the discrimination among four symmetric qutrit states and propose an optical network to implement it.

Jimenez, O. [Departamento de Fisica, Facultad de Ciencias Basicas, Universidad de Antofagasta, Casilla 170, Antofagasta (Chile); Center for Optics and Photonics, Universidad de Concepcion, Casilla 4016, Concepcion (Chile); Solis-Prosser, M. A.; Delgado, A.; Neves, L. [Center for Optics and Photonics, Universidad de Concepcion, Casilla 4016, Concepcion (Chile); MSI-Nucleus on Advanced Optics, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

2011-12-15

289

Generalised KdV and MKdV equations associated with symmetric spaces  

Microsoft Academic Search

The authors extend previous results on the linear spectral problem introduced by Fordy and Kulish (1983). The odd-order isospectral flows admit both a KdV and MKdV type reduction. The non-linear terms are related to the curvature tensor of the corresponding Hermitian symmetric space. Their KdV equations are themselves reductions of known matrix KdV equations. They discuss the conserved densities and

C. Athorne; A. P. Fordy

1987-01-01

290

New approaches to the linear propagation of acoustic fields.  

PubMed

New algorithms are described that provide insight into linear field propagation and offer significant reductions in computational complexity. The developments presented here include the usage of a recently developed discrete Hankel transform to implement two single step, planar propagation algorithms for baffled, radially symmetric, acoustic pressure or velocity fields; an update on the single step approaches that reduce computational complexity through geometrically determined spatial frequency limitations; and algorithms for extending to multistep propagation. Two equivalent means of introducing arbitrary medium attenuation into the above schemes are presented. Finally, a planar boundary crossing algorithm that accounts for refraction and reflection (but not multiple reflections) is added to one of the multistep propagating algorithms. The resulting algorithm is then used to examine the differences between the corresponding fields of a focused piston source operating in water and in a layered fat/liver (biomedical imaging) medium. The results yield computationally efficient algorithms that can be used for linear propagation of focused or unfocused beams in attenuating, multilayer media, and also provide the basis for a novel nonlinear propagation algorithm. PMID:1880299

Christopher, P T; Parker, K J

1991-07-01

291

A highly symmetrical capacitive micro-accelerometer with single degree-of-freedom response  

Microsoft Academic Search

A high-performance acceleration sensor concept is presented, which combines multiple wafer bonding and differential capacitance measurement into a fully symmetrical design. The main device characteristics are an exclusive response to a translational acceleration component in a single axis, a maximized sensitivity for a given chip area and a substantially improved linearity by suppression of error sources as fringing fields, stray

E. Peeters; S. Vergote; B. Puers; W. Sansen

1992-01-01

292

On the Application of Symmetric Dirichlet Distributions and their Mixtures to Contingency Tables  

Microsoft Academic Search

Bayes factors against various hypotheses of independence are proposed for contingency tables and for multidimensional contingency tables. The priors assumed for the nonnull hypothesis are linear combinations of symmetric Dirichlet distributions as in some work of 1965 and later. The results can be used also for probability estimation. The evidence concerning independence, provided by the marginal totals alone, is evaluated,

I. J. Good

1976-01-01

293

Symmetric Log-Domain Diffeomorphic Registration: A Demons-based Approach  

E-print Network

Symmetric Log-Domain Diffeomorphic Registration: A Demons-based Approach Tom Vercauteren1 , Xavier's demons algorithm to provide a fast non-linear registration algorithm. First results show that our algorithm outperforms both the demons algorithm and the recently proposed diffeomorphic demons algo- rithm

Paris-Sud XI, Université de

294

The Caenorhabditis elegans septin complex is nonpolar  

PubMed Central

Septins are conserved GTPases that form heteromultimeric complexes and assemble into filaments that play a critical role in cell division and polarity. Results from budding and fission yeast indicate that septin complexes form around a tetrameric core. However, the molecular structure of the core and its influence on the polarity of septin complexes and filaments is poorly defined. The septin complex of the nematode Caenorhabditis elegans is formed entirely by the core septins UNC-59 and UNC-61. We show that UNC-59 and UNC-61 form a dimer of coiled-coil-mediated heterodimers. By electron microscopy, this heterotetramer appears as a linear arrangement of four densities representing the four septin subunits. Fusion of GFP to the N termini of UNC-59 and UNC-61 and subsequent electron microscopic visualization suggests that the sequence of septin subunits is UNC-59/UNC-61/UNC-61/UNC-59. Visualization of GFP extensions fused to the extremity of the C-terminal coiled coils indicates that these extend laterally from the heterotetrameric core. Together, our study establishes that the septin core complex is symmetric, and suggests that septins form nonpolar filaments. PMID:17599066

John, Corinne M; Hite, Richard K; Weirich, Christine S; Fitzgerald, Daniel J; Jawhari, Hatim; Faty, Mahamadou; Schläpfer, Dominik; Kroschewski, Ruth; Winkler, Fritz K; Walz, Tom; Barral, Yves; Steinmetz, Michel O

2007-01-01

295

Radiative Corrections in Symmetrized Classical Electrodynamics  

Microsoft Academic Search

The physics of radiation reaction for a point charge is discussed within the context of classical electrodynamics. The fundamental equations of classical electrodynamics are first symmetrized to include magnetic charges: a double 4-potential formalism is introduced, in terms of which the field tensor and its dual are employed to symmetrize Maxwell's equations and the Lorentz force equation in covariant form.

J. R. van Meter; A. L. Troha; D. J. Gibson; A. K. Kerman; P. Chen; F. V. Hartemann

2002-01-01

296

Radiative corrections in symmetrized classical electrodynamics  

Microsoft Academic Search

The physics of radiation reaction for a point charge is discussed within the context of classical electrodynamics. The fundamental equations of classical electrodynamics are first symmetrized to include magnetic charges: a double four-potential formalism is introduced, in terms of which the field tensor and its dual are employed to symmetrize Maxwell's equations and the Lorentz force equation in covariant form.

J. R. van Meter; A. K. Kerman; P. Chen; F. V. Hartemann

2000-01-01

297

Integrability and Huygens' principle on symmetric spaces  

Microsoft Academic Search

The explicit formulas for fundamental solutions of the modified wave equations on certain symmetric spaces are found. These symmetric spaces have the following characteristic property: all multiplicities of their restricted roots are even. As a corollary in the odd-dimensional case one has that the Huygens' principle in Hadamard's sense for these equations is fulfilled. We consider also the heat and

Oleg A. Chalykh; Alexander P. Veselov

1996-01-01

298

Magnetoresistance of symmetric spin valve structures  

Microsoft Academic Search

A spin valve configuration is presented in which an unpinned ferromagnetic film is separated from exchange-pinned ferromagnetic films on either side by two nonmagnetic spacers, thereby creating a symmetric spin valve structure. The symmetric spin valve is shown to increase the magnetoresistance by 50% over the values of individual spin valves. The increase is attributed to a reduction of spin-independent

T. C. Anthony; J. A. Brug; Shufeng Zhang

1994-01-01

299

Detecting Symmetry and Symmetric Constellations of Features  

Microsoft Academic Search

A novel and efficient method is presented for grouping feature points on the basis of their underlying symmetry and characterising the symmetries present in an image. We show how symmetric pairs of features can be efficiently detected, how the symmetry bonding each pair is extracted and evaluated, and how these can be grouped into symmetric constellations that specify the domi-

Gareth Loyand; Jan-olof Eklundh

2006-01-01

300

Anion dependent self-assembly of a linear hexanuclear Yb(III) salen complex with enhanced near-infrared (NIR) luminescence properties.  

PubMed

Reactions of H2salen (H2L, N,N'-ethylene bis(salicylideneimine)) with Yb(CF3SO3)3, Yb(OAc)34H2O and Yb(NO3)36H2O in MeOH–EtOH under reflux gave NIR luminescent complexes [Yb6L9(H2L)2] (1), [Yb3L3(HL)(OH)2] (2) and [Yb2L2(H2L)2(NO3)(MeOH)2]NO3 (3), respectively. PMID:24019025

Yang, Xiaoping; Oye, Michael M; Jones, Richard A; Huang, Shaoming

2013-10-25

301

IR linear dichroic study of high-symmetry molecules dissolved in a liquid crystal solvent. II. Metal hexacarbonyl complexes M(CO) 6 (M = Mo, Cr)  

NASA Astrophysics Data System (ADS)

The presence of weak specific solvent—solute interactions is proved by studying the splitting of the ? 3(F 1u) band of M(CO) 6 (M = Mo, Cr) in some isotropic electron donor solvents. A similar spectral effect is observed in the smectic, nematic and isotropic phases of the liquid crystal ZLI 1167 (Merck) and is explained by similar interactions. The complex (bisignate) shape of the IR-LD spectra of M(CO) 6 in the anisotropic solvent is considered to be a manifestation of the same solvent effect.

Rogojerov, Marin I.; Arnaudov, Michail G.

1994-05-01

302

Clay content analysis across landscape by means of linear and non-linear empirical models  

NASA Astrophysics Data System (ADS)

In soil science literature there exist many applications that deals with the spatial prediction of soil features by means of a set of statistical techniques. In this work the amount of clay content at level of soil horizon was put in a spatial framework and analyzed using four alternative models for describing its variability in a geopedological complex landscape such as Telese valley (Campania, South Italy) study area. Three statistical models were involved, that is (i) the multiple linear regression (MLR), (ii) the multicollocated ordinary cokriging (MOCOK), and (iii) a two-layers FFBP (FeedForward Back-Propagation) neural network with topology 6 : 1 (ANN). Apart from these technologies (neurocomputing, and multivariate regression and geostatistics) a polygonal soil map (UDP) was also used for the sake of comparing complex and sometimes cumbersome models with the standard approach of representing the soil spatial distribution. Clay data was splitted in calibration/validation subsets in order to unbiasedly compare the four models (in order of complexity UDP, MLR, MOCOK, ANN). Comparison was based on multi-criteria assessment using six measures of performance: RMSE (root mean square error), MBE (mean bias error), Pearson's correlation (r), an efficiency index (eff), SMAPE (symmetrical mean absolute percent error), and Wilmott's agreement index (D). Generally all indicators seem to demonstrate that the more complex (from UDP to ANN) the models the better their performance in representing the spatial variability of some pedological parameters. Despite such statement much endeavour should be spent in model comparison by considering also the cost/profit trade off incorporating a cost function.

Langella, G.; Minieri, L.; Terribile, F.

2009-04-01

303

Permutation inference for the general linear model.  

PubMed

Permutation methods can provide exact control of false positives and allow the use of non-standard statistics, making only weak assumptions about the data. With the availability of fast and inexpensive computing, their main limitation would be some lack of flexibility to work with arbitrary experimental designs. In this paper we report on results on approximate permutation methods that are more flexible with respect to the experimental design and nuisance variables, and conduct detailed simulations to identify the best method for settings that are typical for imaging research scenarios. We present a generic framework for permutation inference for complex general linear models (GLMS) when the errors are exchangeable and/or have a symmetric distribution, and show that, even in the presence of nuisance effects, these permutation inferences are powerful while providing excellent control of false positives in a wide range of common and relevant imaging research scenarios. We also demonstrate how the inference on GLM parameters, originally intended for independent data, can be used in certain special but useful cases in which independence is violated. Detailed examples of common neuroimaging applications are provided, as well as a complete algorithm - the "randomise" algorithm - for permutation inference with the GLM. PMID:24530839

Winkler, Anderson M; Ridgway, Gerard R; Webster, Matthew A; Smith, Stephen M; Nichols, Thomas E

2014-05-15

304

Application of non-linear angle synchronous spectrofluorimetry to the determination of complex mixtures of drugs in urine: A comparative study  

NASA Astrophysics Data System (ADS)

Synchronous fluorescence spectroscopy (SFS) is a rapid, sensitive and non-destructive method suitable for the analysis of multifluorophoric mixtures. In this study non linear variable angle synchronous spectrofluorimetry was applied to the determination of three fluoroquinololes in urine. Although this technique provides very good results, total resolution of multicomponent mixtures is not always achieved when the spectral profiles strongly overlap. Partial least-squares regression (PLS-1) was utilized to a develop calibration model that related synchronous fluorescence spectra to the analytical concentration of fluoroquinolones in the presence of urine. The same multicomponent mixture was determined using excitation emission matrix fluorescence (EEMF) along with N-way partial least squares regression (N-PLS and U-PLS). The determination was carried out in micellar medium 0.01 M with a pH of 4.8 provided by 0.2 M sodium acetate/acetic acid buffer. A central composite design was selected to obtain a calibration matrix of 25 standards plus a blank sample. The proposed methods were validated by application to a test set of synthetic samples. The results show that SFS with PLS-1 is a better method compared to EEMF with N-PLS or U-PLS because of the low RMSEP values of the former.

Murillo Pulgarín, J. A.; Alañón Molina, A.; Boras, N.

2012-12-01

305

Development of the complex general linear model in the Fourier domain: application to fMRI multiple input-output evoked responses for single subjects.  

PubMed

A linear time-invariant model based on statistical time series analysis in the Fourier domain for single subjects is further developed and applied to functional MRI (fMRI) blood-oxygen level-dependent (BOLD) multivariate data. This methodology was originally developed to analyze multiple stimulus input evoked response BOLD data. However, to analyze clinical data generated using a repeated measures experimental design, the model has been extended to handle multivariate time series data and demonstrated on control and alcoholic subjects taken from data previously analyzed in the temporal domain. Analysis of BOLD data is typically carried out in the time domain where the data has a high temporal correlation. These analyses generally employ parametric models of the hemodynamic response function (HRF) where prewhitening of the data is attempted using autoregressive (AR) models for the noise. However, this data can be analyzed in the Fourier domain. Here, assumptions made on the noise structure are less restrictive, and hypothesis tests can be constructed based on voxel-specific nonparametric estimates of the hemodynamic transfer function (HRF in the Fourier domain). This is especially important for experimental designs involving multiple states (either stimulus or drug induced) that may alter the form of the response function. PMID:23840281

Rio, Daniel E; Rawlings, Robert R; Woltz, Lawrence A; Gilman, Jodi; Hommer, Daniel W

2013-01-01

306

Towards an exact theory of linear absorbance and circular dichroism of pigment-protein complexes: Importance of non-secular contributions.  

PubMed

A challenge for the theory of optical spectra of pigment-protein complexes is the equal strength of the pigment-pigment and the pigment-protein couplings. Treating both on an equal footing so far can only be managed by numerically costly approaches. Here, we exploit recent results on a normal mode analysis derived spectral density that revealed the dominance of the diagonal matrix elements of the exciton-vibrational coupling in the exciton state representation. We use a cumulant expansion technique that treats the diagonal parts exactly, includes an infinite summation of the off-diagonal parts in secular and Markov approximations, and provides a systematic perturbative way to include non-secular and non-Markov corrections. The theory is applied to a model dimer and to chlorophyll (Chl) a and Chl b homodimers of the reconstituted water-soluble chlorophyll-binding protein (WSCP) from cauliflower. The model calculations reveal that the non-secular/non-Markov effects redistribute oscillator strength from the strong to the weak exciton transition in absorbance and they diminish the rotational strength of the exciton transitions in circular dichroism. The magnitude of these corrections is in a few percent range of the overall signal, providing a quantitative explanation of the success of time-local convolution-less density matrix theory applied earlier. A close examination of the optical spectra of Chl a and Chl b homodimers in WSCP suggests that the opening angle between Qy transition dipole moments in Chl b homodimers is larger by about 9(?) than for Chl a homodimers for which a crystal structure of a related WSCP complex exists. It remains to be investigated whether this change is due to a different mutual geometry of the pigments or due to the different electronic structures of Chl a and Chl b. PMID:25612686

Dinh, Thanh-Chung; Renger, Thomas

2015-01-21

307

Towards an exact theory of linear absorbance and circular dichroism of pigment-protein complexes: Importance of non-secular contributions  

NASA Astrophysics Data System (ADS)

A challenge for the theory of optical spectra of pigment-protein complexes is the equal strength of the pigment-pigment and the pigment-protein couplings. Treating both on an equal footing so far can only be managed by numerically costly approaches. Here, we exploit recent results on a normal mode analysis derived spectral density that revealed the dominance of the diagonal matrix elements of the exciton-vibrational coupling in the exciton state representation. We use a cumulant expansion technique that treats the diagonal parts exactly, includes an infinite summation of the off-diagonal parts in secular and Markov approximations, and provides a systematic perturbative way to include non-secular and non-Markov corrections. The theory is applied to a model dimer and to chlorophyll (Chl) a and Chl b homodimers of the reconstituted water-soluble chlorophyll-binding protein (WSCP) from cauliflower. The model calculations reveal that the non-secular/non-Markov effects redistribute oscillator strength from the strong to the weak exciton transition in absorbance and they diminish the rotational strength of the exciton transitions in circular dichroism. The magnitude of these corrections is in a few percent range of the overall signal, providing a quantitative explanation of the success of time-local convolution-less density matrix theory applied earlier. A close examination of the optical spectra of Chl a and Chl b homodimers in WSCP suggests that the opening angle between Qy transition dipole moments in Chl b homodimers is larger by about 9? than for Chl a homodimers for which a crystal structure of a related WSCP complex exists. It remains to be investigated whether this change is due to a different mutual geometry of the pigments or due to the different electronic structures of Chl a and Chl b.

Dinh, Thanh-Chung; Renger, Thomas

2015-01-01

308

The structure of symmetric attractors  

NASA Astrophysics Data System (ADS)

We consider discrete equivariant dynamical systems and obtain results about the structure of attractors for such systems. We show, for example, that the symmetry of an attractor cannot, in general, be an arbitrary subgroup of the group of symmetries. In addition, there are group-theoretic restrictions on the symmetry of connected components of a symmetric attractor. The symmetry of attractors has implications for a new type of pattern formation mechanism by which patterns appear in the time-average of a chaotic dynamical system. Our methods are topological in nature and exploit connectedness properties of the ambient space. In particular, we prove a general lemma about connected components of the complement of preimage sets and how they are permuted by the mapping. These methods do not themselves depend on equivariance. For example, we use them to prove that the presence of periodic points in the dynamics limits the number of connected components of an attractor, and, for one-dimensional mappings, to prove results on sensitive dependence and the density of periodic points.

Melbourne, Ian; Dellnitz, Michael; Golubitsky, Martin

1993-03-01

309

Baryon symmetric big bang cosmology  

NASA Technical Reports Server (NTRS)

Both the quantum theory and Einsteins theory of special relativity lead to the supposition that matter and antimatter were produced in equal quantities during the big bang. It is noted that local matter/antimatter asymmetries may be reconciled with universal symmetry by assuming (1) a slight imbalance of matter over antimatter in the early universe, annihilation, and a subsequent remainder of matter; (2) localized regions of excess for one or the other type of matter as an initial condition; and (3) an extremely dense, high temperature state with zero net baryon number; i.e., matter/antimatter symmetry. Attention is given to the third assumption, which is the simplest and the most in keeping with current knowledge of the cosmos, especially as pertains the universality of 3 K background radiation. Mechanisms of galaxy formation are discussed, whereby matter and antimatter might have collided and annihilated each other, or have coexisted (and continue to coexist) at vast distances. It is pointed out that baryon symmetric big bang cosmology could probably be proved if an antinucleus could be detected in cosmic radiation.

Stecker, F. W.

1978-01-01

310

The cost of linearization  

NASA Astrophysics Data System (ADS)

Information processing in the brain is metabolically expensive and energy usage by the different components of the nervous system is not well understood. In a continuing effort to explore the costs and constraints of information processing at the single neuron level, dendritic processes are being studied. More specifically, the role of various ion channel conductances is explored in terms of integrating dendritic excitatory synaptic input. Biophysical simulations of dendritic behavior show that the complexity of voltage-dependent, non-linear dendritic conductances can produce simplicity in the form of linear synaptic integration. Over increasing levels of synaptic activity, it is shown that two types of voltage-dependent conductances produce linearization over a limited range. This range is determined by the parameters defining the ion channel and the 'passive' properties of the dendrite. A persistent sodium and a transient A-type potassium channel were considered at steady-state transmembrane potentials in the vicinity of and hyperpolarized to the threshold for action potential initiation. The persistent sodium is seen to amplify and linearize the synaptic input over a short range of low synaptic activity. In contrast, the A-type potassium channel has a broader linearization range but tends to operate at higher levels of synaptic bombardment. Given equivalent 'passive' dendritic properties, the persistent sodium is found to be less costly than the A-type potassium in linearizing synaptic input.

Morel, Danielle; Levy, William B.

2006-03-01

311

A Symmetrical Interpretation of the Klein-Gordon Equation  

NASA Astrophysics Data System (ADS)

This paper presents a new Symmetrical Interpretation (SI) of relativistic quantum mechanics which postulates: quantum mechanics is a theory about complete experiments, not particles; a complete experiment is maximally described by a complex transition amplitude density; and this transition amplitude density never collapses. This SI is compared to the Copenhagen Interpretation (CI) for the analysis of Einstein's bubble experiment. This SI makes several experimentally testable predictions that differ from the CI, solves one part of the measurement problem, resolves some inconsistencies of the CI, and gives intuitive explanations of some previously mysterious quantum effects.

Heaney, Michael B.

2013-06-01

312

The Topology of Three-Dimensional Symmetric Tensor Fields  

NASA Technical Reports Server (NTRS)

We study the topology of 3-D symmetric tensor fields. The goal is to represent their complex structure by a simple set of carefully chosen points and lines analogous to vector field topology. The basic constituents of tensor topology are the degenerate points, or points where eigenvalues are equal to each other. First, we introduce a new method for locating 3-D degenerate points. We then extract the topological skeletons of the eigenvector fields and use them for a compact, comprehensive description of the tensor field. Finally, we demonstrate the use of tensor field topology for the interpretation of the two-force Boussinesq problem.

Lavin, Yingmei; Levy, Yuval; Hesselink, Lambertus

1994-01-01

313

Photophysics and non-linear absorption of Au(I) and Pt(II) acetylide complexes of a thienyl-carbazole chromophore.  

PubMed

In order to understand the photophysics and non-linear optical properties of carbazole containing ?-conjugated oligomers of the type ET-Cbz-TE (E = ethynylene, T = 2,5-thienylene, Cbz = 3,6-carbazole), a detailed investigation was carried out on a series of oligomers that feature Au(i) or Pt(ii) acetylide "end groups", as well as a Pt(ii)-acetylide linked polymer (CBZ-Au-1 and CBZ-Pt-1, CBZ-Poly-Pt). These organometallic chromophores were characterized by UV-visible absorption and variable temperature photoluminescence spectroscopy, nanosecond transient absorption spectroscopy, open aperture nanosecond z-scan and two photon absorption (2PA) spectroscopy. The Au(i) and Pt(ii) oligomers and polymer exhibit weak fluorescence in fluid solution at room temperature. Efficient phosphorescence is observed from the Pt(ii) systems below 150 K in a solvent glass; however, the Au(i) oligomer exhibits only weak phosphorescence at 77 K. Taken together, the emission results indicate that the intersystem crossing efficiency for the Pt(ii) chromophores is greater than for the Au(i) oligomer. Nonetheless, nanosecond transient absorption indicates that direct excitation affords moderately long-lived triplet states for all of the chromophores. Open aperture z-scan measurement shows effective optical attenuation can be achieved by using these materials. The 2PA cross section in the degenerate S0?S1 transition region was in the range 10-100 GM, and increased monotonically toward shorter wavelengths, reaching 800-1000 GM at 550 nm. PMID:25222112

Goswami, Subhadip; Wicks, Geoffrey; Rebane, Aleksander; Schanze, Kirk S

2014-12-21

314

Complexity and Relations  

ERIC Educational Resources Information Center

A central feature of complexity is that it is based on non-linear, recursive relations. However, in most current accounts of complexity such relations, while non-linear, are based on the reductive relations of a Newtonian onto-epistemological framework. This means that the systems that are emergent from the workings of such relations are a…

Lancaster, Jeanette Elizabeth

2013-01-01

315

Discussion: Time-Symmetric Quantum Counterfactuals  

E-print Network

There is a trend to consider counterfactuals as invariably time-asymmetric. Recently, this trend manifested itself in the controversy about validity of counterfactual application of a time-symmetric quantum probability rule. Kastner (2003) analyzed this controversy and concluded that there are time-symmetric quantum counterfactuals which are consistent, but they turn out to be trivial. I correct Kastner's misquotation of my defense of time-symmetric quantum counterfactuals and explain their non-trivial aspects, thus contesting the claim that counterfactuals have to be time-asymmetric.

Lev Vaidman

2014-01-24

316

Multiqubit symmetric states with high geometric entanglement  

SciTech Connect

We propose a detailed study of the geometric entanglement properties of pure symmetric N-qubit states, focusing more particularly on the identification of symmetric states with a high geometric entanglement and how their entanglement behaves asymptotically for large N. We show that much higher geometric entanglement with improved asymptotical behavior can be obtained in comparison with the highly entangled balanced Dicke states studied previously. We also derive an upper bound for the geometric measure of entanglement of symmetric states. The connection with the quantumness of a state is discussed.

Martin, J.; Bastin, T. [Institut de Physique Nucleaire, Atomique et de Spectroscopie, Universite de Liege, B-4000 Liege (Belgium); Giraud, O. [Universite de Toulouse, UPS, Laboratoire de Physique Theorique (IRSAMC), F-31062 Toulouse (France); CNRS, LPT (IRSAMC), F-31062 Toulouse (France); Universite Paris-Sud, LPTMS, UMR8626, Ba circumflex t. 100, Universite Paris-Sud, F-91405 Orsay (France); CNRS, LPTMS, UMR8626, Ba circumflex t. 100, Universite Paris-Sud, F-91405 Orsay (France); Braun, P. A. [Fachbereich Physik, Universitaet Duisburg-Essen, D-47048 Duisburg (Germany); Institute of Physics, Saint-Petersburg University, 198504 Saint-Petersburg (Russian Federation); Braun, D. [Universite de Toulouse, UPS, Laboratoire de Physique Theorique (IRSAMC), F-31062 Toulouse (France); CNRS, LPT (IRSAMC), F-31062 Toulouse (France)

2010-06-15

317

Linear Inequalities  

NSDL National Science Digital Library

Upon completing this lesson, student should be able to use the addition, subtraction, multiplication, and division properties of inequalities to solve linear inequalities; write the answer to an inequality using interval notation; and draw a graph to give a visual answer to an inequality problem. The lesson begins with explanations of inequality signs and interval notation and then moves on to demonstrate addition/subtraction and multiplication/division properties in inequalities. The site demonstrates a strategy for solving linear inequalities and presents three problems for students to practice what they have learned. There is also a link to a previous tutorial which covers solving linear equations of one variable for students who need the review.

Seward, Kim; Puckett, Jennifer

2008-01-01

318

Spatial-frequency Fourier polarimetry of the complex degree of mutual anisotropy of linear and circular birefringence in the diagnostics of oncological changes in morphological structure of biological tissues  

NASA Astrophysics Data System (ADS)

Theory of polarisation-correlation analysis of laser images of histological sections of biopsy material from cervix tissue based on spatial frequency selection of linear and circular birefringence mechanisms is formulated. Comparative results of measuring the coordinate distributions of the complex degree of mutual anisotropy (CDMA), produced by fibrillar networks formed by myosin and collagen fibres of cervix tissue in different pathological conditions, namely, pre-cancer (dysplasia) and cancer (adenocarcinoma), are presented. The values and variation ranges of statistical (moments of the first — fourth order), correlation (excess-autocorrelation functions), and fractal (slopes of approximating curves and dispersion of extrema of logarithmic dependences of power spectra) parameters of the CDMA coordinate distributions are studied. Objective criteria for pathology diagnostics and differentiation of its severity degree are determined.

Ushenko, Yu A.; Gorskii, M. P.; Dubolazov, A. V.; Motrich, A. V.; Ushenko, V. A.; Sidor, M. I.

2012-08-01

319

Spatial-frequency Fourier polarimetry of the complex degree of mutual anisotropy of linear and circular birefringence in the diagnostics of oncological changes in morphological structure of biological tissues  

SciTech Connect

Theory of polarisation-correlation analysis of laser images of histological sections of biopsy material from cervix tissue based on spatial frequency selection of linear and circular birefringence mechanisms is formulated. Comparative results of measuring the coordinate distributions of the complex degree of mutual anisotropy (CDMA), produced by fibrillar networks formed by myosin and collagen fibres of cervix tissue in different pathological conditions, namely, pre-cancer (dysplasia) and cancer (adenocarcinoma), are presented. The values and variation ranges of statistical (moments of the first - fourth order), correlation (excess-autocorrelation functions), and fractal (slopes of approximating curves and dispersion of extrema of logarithmic dependences of power spectra) parameters of the CDMA coordinate distributions are studied. Objective criteria for pathology diagnostics and differentiation of its severity degree are determined. (image processing)

Ushenko, Yu A; Gorskii, M P; Dubolazov, A V; Motrich, A V; Ushenko, V A; Sidor, M I [Yuriy Fedkovych Chernivtsi National University, Chernivtsi (Ukraine)

2012-08-31

320

Linear Algebra  

NSDL National Science Digital Library

A mathematics professor from Saint Michael's College is the author of this free online textbook about linear algebra. Being just shy of 450 pages, the book is very comprehensive and of high quality. It gives an excellent introduction into topics such as vector spaces, linear systems, and determinants, and the author is quite good at defining a consistent notation throughout the book. Each chapter has several examples that demonstrate the concepts, concluding with exercises to be solved by the reader. Solutions to the exercises are given in a separate file. [CL

Hefferon, Jim.

321

On the local form of static plane symmetric space-times in the presence of matter  

E-print Network

For any configuration of a static plane-symmetric distribution of matter along space-time, there are coordinates where the metric can be put explicitly as a functional of the energy density and pressures. It satisfies Einstein equations as far as we require the conservation of the energy-momentum tensor, which is the single ODE for self-gravitating hydrostatic equilibrium. As a direct application, a general solution is given when the pressures are linearly related to the energy density, recovering, as special cases, most of known solutions of static plane-symmetric Einstein equations.

Gomes, Leandro G

2015-01-01

322

Dynamics of intense particle beam in axial-symmetric magnetic field  

NASA Astrophysics Data System (ADS)

Axial-symmetric magnetic field is often used in focusing of particle beams. Most existing ion Low Energy Beam Transport lines are based on solenoid focusing. Modern accelerator projects utilize superconducting solenoids in combination with superconducting accelerating cavities for acceleration of high-intensity particle beams. Present article discusses conditions for matched beam in axial-symmetric magnetic field. Analysis allows us to minimize power consumption of solenoids and beam emittance growth due to nonlinear space charge, lens aberrations, and maximize acceptance of the channel. Expressions for maximum beam current in focusing structure, beam emittance growth due to spherical aberrations and non-linear space charge forces are derived.

Batygin, Yuri K.

2015-02-01

323

Self-Gravitating Spherically Symmetric Solutions in Scalar-Torsion Theories  

E-print Network

We studied spherically symmetric solutions in scalar-torsion gravity theories in which a scalar field is coupled to torsion with a derivative coupling. We obtained the general field equations from which we extracted a decoupled master equation, the solution of which leads to the specification of all other unknown functions. We first obtained an exact solution which represents a new wormhole-like solution dressed with a regular scalar field. Then, we found large distance linearized spherically symmetric solutions in which the space asymptotically is AdS.

Kofinas, Georgios; Saridakis, Emmanuel N

2015-01-01

324

PT-symmetric quantum mechanics  

Microsoft Academic Search

This paper proposes to broaden the canonical formulation of quantum mechanics. Ordinarily, one imposes the condition H†=H on the Hamiltonian, where † represents the mathematical operation of complex conjugation and matrix transposition. This conventional Hermiticity condition is sufficient to ensure that the Hamiltonian H has a real spectrum. However, replacing this mathematical condition by the weaker and more physical requirement

Carl M. Bender; Stefan Boettcher; Peter N. Meisinger

1999-01-01

325

General theory for multiple input-output perturbations in complex molecular systems. 1. Linear QSPR electronegativity models in physical, organic, and medicinal chemistry.  

PubMed

In general perturbation methods starts with a known exact solution of a problem and add "small" variation terms in order to approach to a solution for a related problem without known exact solution. Perturbation theory has been widely used in almost all areas of science. Bhor's quantum model, Heisenberg's matrix mechanincs, Feyman diagrams, and Poincare's chaos model or "butterfly effect" in complex systems are examples of perturbation theories. On the other hand, the study of Quantitative Structure-Property Relationships (QSPR) in molecular complex systems is an ideal area for the application of perturbation theory. There are several problems with exact experimental solutions (new chemical reactions, physicochemical properties, drug activity and distribution, metabolic networks, etc.) in public databases like CHEMBL. However, in all these cases, we have an even larger list of related problems without known solutions. We need to know the change in all these properties after a perturbation of initial boundary conditions. It means, when we test large sets of similar, but different, compounds and/or chemical reactions under the slightly different conditions (temperature, time, solvents, enzymes, assays, protein targets, tissues, partition systems, organisms, etc.). However, to the best of our knowledge, there is no QSPR general-purpose perturbation theory to solve this problem. In this work, firstly we review general aspects and applications of both perturbation theory and QSPR models. Secondly, we formulate a general-purpose perturbation theory for multiple-boundary QSPR problems. Last, we develop three new QSPR-Perturbation theory models. The first model classify correctly >100,000 pairs of intra-molecular carbolithiations with 75-95% of Accuracy (Ac), Sensitivity (Sn), and Specificity (Sp). The model predicts probabilities of variations in the yield and enantiomeric excess of reactions due to at least one perturbation in boundary conditions (solvent, temperature, temperature of addition, or time of reaction). The model also account for changes in chemical structure (connectivity structure and/or chirality paterns in substrate, product, electrophile agent, organolithium, and ligand of the asymmetric catalyst). The second model classifies more than 150,000 cases with 85-100% of Ac, Sn, and Sp. The data contains experimental shifts in up to 18 different pharmacological parameters determined in >3000 assays of ADMET (Absorption, Distribution, Metabolism, Elimination, and Toxicity) properties and/or interactions between 31723 drugs and 100 targets (metabolizing enzymes, drug transporters, or organisms). The third model classifies more than 260,000 cases of perturbations in the self-aggregation of drugs and surfactants to form micelles with Ac, Sn, and Sp of 94-95%. The model predicts changes in 8 physicochemical and/or thermodynamics output parameters (critic micelle concentration, aggregation number, degree of ionization, surface area, enthalpy, free energy, entropy, heat capacity) of self-aggregation due to perturbations. The perturbations refers to changes in initial temperature, solvent, salt, salt concentration, solvent, and/or structure of the anion or cation of more than 150 different drugs and surfactants. QSPR-Perturbation Theory models may be useful for multi-objective optimization of organic synthesis, physicochemical properties, biological activity, metabolism, and distribution profiles towards the design of new drugs, surfactants, asymmetric ligands for catalysts, and other materials. PMID:23889050

González-Díaz, Humberto; Arrasate, Sonia; Gómez-SanJuan, Asier; Sotomayor, Nuria; Lete, Esther; Besada-Porto, Lina; Ruso, Juan M

2013-01-01

326

Characterization of Randomly Time-Variant Linear Channels  

Microsoft Academic Search

This paper is concerned with various aspects of the characterization of randomly time-variant linear channels. At the outset it is demonstrated that time-varying linear channels (or filters) may be characterized in an interesting symmetrical manner in time and frequency variables by arranging system functions in (timefrequency) dual pairs. Following this a statistical characterization of randomly time-variant linear channels is carried

P. Bello

1963-01-01

327

Analytical integrations for two-dimensional elastic analysis by the symmetric Galerkin boundary element method  

NASA Astrophysics Data System (ADS)

In the context of linear elasticity, this paper presents a way to perform hypersingular integrals arising from the symmetric Galerkin Boundary Element Method (BEM). In contrast to the existing integration techniques, the one here proposed does not need any regularization or limit processes: in fact it works directly on the final form of the hypersingular double integrals without any previous manipulation. The present method is applied to 2D linear elastic problems, using straight elements with continuous piecewise-linear displacements and piecewise-constant tractions. Numerical tests are presented for the validation of the obtained analytic results.

Carini, A.; Diligenti, M.; Maranesi, P.; Zanella, M.

328

Bregman sided and symmetrized centroids Frank Nielsen  

E-print Network

Bregman sided and symmetrized centroids Frank Nielsen ´Ecole Polytechnique Sony Computer Science Laboratories France nielsen@lix.polytechnique.fr Richard Nock CEREGMIA University of Antilles-Guyane France

Nielsen, Frank

329

Cylindrically Symmetric Systems in Gauge Theory Gravity  

E-print Network

their financial support and personal assistance. i #12;Contents 1 Introduction 1 1.1 Geometric Algebra symmetric systems. This approach, based on the mathematics of geometric algebra, deals with gauge fields

Cambridge, University of

330

Spherically symmetric brane spacetime with bulk gravity  

NASA Astrophysics Data System (ADS)

Introducing term in the five-dimensional bulk action we derive effective Einstein's equation on the brane using Gauss-Codazzi equation. This effective equation is then solved for different conditions on dark radiation and dark pressure to obtain various spherically symmetric solutions. Some of these static spherically symmetric solutions correspond to black hole solutions, with parameters induced from the bulk. Specially, the dark pressure and dark radiation terms (electric part of Weyl curvature) affect the brane spherically symmetric solutions significantly. We have solved for one parameter group of conformal motions where the dark radiation and dark pressure terms are exactly obtained exploiting the corresponding Lie symmetry. Various thermodynamic features of these spherically symmetric space-times are studied, showing existence of second order phase transition. This phenomenon has its origin in the higher curvature term with gravity in the bulk.

Chakraborty, Sumanta; SenGupta, Soumitra

2015-01-01

331

Compact antenna has symmetrical radiation pattern  

NASA Technical Reports Server (NTRS)

Compact quadrifilar-helix antenna has exceptionally uniform and axially symmetric radiation pattern. It resists shock and vibration and gives excellent radiation characteristics which make it potentially useful for mobile citizenband radios and other terrestrial communications sytems.

Kuhlman, E. A.; Mckee, E. D.

1979-01-01

332

A Survey of Spherically Symmetric Spacetimes  

E-print Network

We survey many of the important properties of spherically symmetric spacetimes as follows. We present several different ways of describing a spherically symmetric spacetime and the resulting metrics. We then focus our discussion on an especially useful form of the metric of a spherically symmetric spacetime in polar-areal coordinates and its properties. In particular, we show how the metric component functions chosen are extremely compatible with notions in Newtonian mechanics. We also show the monotonicity of the Hawking mass in these coordinates. As an example, we discuss how these coordinates and the metric can be used to solve the spherically symmetric Einstein-Klein-Gordon equations. We conclude with a brief mention of some applications of these properties.

Alan R. Parry

2014-09-20

333

Dual PT-Symmetric Quantum Field Theories  

E-print Network

Some quantum field theories described by non-Hermitian Hamiltonians are investigated. It is shown that for the case of a free fermion field theory with a $\\gamma_5$ mass term the Hamiltonian is $\\cal PT$-symmetric. Depending on the mass parameter this symmetry may be either broken or unbroken. When the $\\cal PT$ symmetry is unbroken, the spectrum of the quantum field theory is real. For the $\\cal PT$-symmetric version of the massive Thirring model in two-dimensional space-time, which is dual to the $\\cal PT$-symmetric scalar Sine-Gordon model, an exact construction of the $\\cal C$ operator is given. It is shown that the $\\cal PT$-symmetric massive Thirring and Sine-Gordon models are equivalent to the conventional Hermitian massive Thirring and Sine-Gordon models with appropriately shifted masses.

Carl M. Bender; H. F. Jones; R. J. Rivers

2005-08-15

334

Laws of Trigonometry in Symmetric Spaces  

E-print Network

This paper consists of two parts. In the first part, we reformulate the work of E. Leuzinger on trigonometry in noncompact symmetric spaces. In the second part, we outline an alternative method using invariants of the isotropy group representation. Appropriately formulated, these methods apply to both compact and noncompact symmetric spaces. This work is contained in the Ph.D. dissertation of H.-L. Huynh.

Helmer Aslaksen; Hsueh-Ling Huynh

1994-01-01

335

On Radially Symmetric Solutions to Conservation Laws  

Microsoft Academic Search

\\u000a Radially symmetric solutions to multi-dimensional systems of conservations laws are important in applications and computations,\\u000a as well as in the general theory of conservative systems. Notwithstanding their one-dimensional nature they are poorly understood.\\u000a In particular this is true for the Euler equations in gas-dynamics. After a short review of symmetric solutions to the Euler\\u000a system, we introduce a scalar model

Helge Kristian Jenssen

336

Informational approach to the quantum symmetrization postulate  

NASA Astrophysics Data System (ADS)

A remarkable feature of quantum theory is that particles with identical intrinsic properties must be treated as indistinguishable if the theory is to give valid predictions in all cases. In the quantum formalism, indistinguishability is expressed via the symmetrization postulate (Dirac P 1926 Proc. R. Soc. A 112 661, Heisenberg W 1926 Z. Phys. 38 411), which restricts a system of identical particles to the set of symmetric states (‘bosons’) or the set of antisymmetric states (‘fermions’). However, the physical basis and range of validity of the symmetrization postulate has not been established. A well-known topological derivation of the postulate implies that its validity depends on the dimensionality of the space in which the particles move (Laidlaw M and DeWitt C 1971 Phys. Rev. D 3 1375–8, Leinaas J M and Myrheim J 1977 Il Nuovo Cimento B 37 1–23). Here we show that the symmetrization postulate can be derived by strictly adhering to the informational requirement that particles which cannot be experimentally distinguished from one another are not labelled. Our key novel postulate is the operational indistinguishability postulate, which posits that the amplitude of a process involving several indistinguishable particles is determined by the amplitudes of all possible transitions of these particles when treated as distinguishable. The symmetrization postulate follows by requiring consistency with the rest of the quantum formalism. The derivation implies that the symmetrization postulate admits no natural variants. In particular, the possibility that identical particles generically exhibit anyonic behavior in two dimensions is excluded.

Goyal, Philip

2015-01-01

337

Complex Trajectories of a Simple Pendulum  

E-print Network

The motion of a classical pendulum in a gravitational field of strength g is explored. The complex trajectories as well as the real ones are determined. If g is taken to be imaginary, the Hamiltonian that describes the pendulum becomes PT-symmetric. The classical motion for this PT-symmetric Hamiltonian is examined in detail. The complex motion of this pendulum in the presence of an external periodic forcing term is also studied.

Carl M. Bender; Darryl D. Holm; Daniel W. Hook

2006-09-25

338

Linear Models  

NSDL National Science Digital Library

This site uses linear models to demonstrate the change in bird populations on a barren island over time, supply and demand, and the natural cleaning of a polluted lake by fresh water over time. The problems are laid out and turned into both graphic and equation form in order to understand the rate of change happening in each scenario. There are also links to previously covered materials that can help student review material from past math lessons.

Frank Wattenberg

1997-01-01

339

PT-Symmetric dimer in a generalized model of coupled nonlinear oscillators  

E-print Network

In the present work, we explore the case of a general PT-symmetric dimer in the context of two both linearly and nonlinearly coupled cubic oscillators. To obtain an analytical handle on the system, we first explore the rotating wave approximation converting it into a discrete nonlinear Schr\\"odinger type dimer. In the latter context, the stationary solutions and their stability are identified numerically but also wherever possible analytically. Solutions stemming from both symmetric and anti-symmetric special limits are identified. A number of special cases are explored regarding the ratio of coefficients of nonlinearity between oscillators over the intrinsic one of each oscillator. Finally, the considerations are extended to the original oscillator model, where periodic orbits and their stability are obtained. When the solutions are found to be unstable their dynamics is monitored by means of direct numerical simulations.

J. Cuevas-Maraver; A. Khare; P. G. Kevrekidis; H. Xu; A. Saxena

2014-09-25

340

Symmetric Galerkin boundary formulations employing curved elements  

NASA Technical Reports Server (NTRS)

Accounts of the symmetric Galerkin approach to boundary element analysis (BEA) have recently been published. This paper attempts to add to the understanding of this method by addressing a series of fundamental issues associated with its potential computational efficiency. A new symmetric Galerkin theoretical formulation for both the (harmonic) heat conduction and the (biharmonic) elasticity problem that employs regularized singular and hypersingular boundary integral equations (BIEs) is presented. The novel use of regularized BIEs in the Galerkin context is shown to allow straightforward incorporation of curved, isoparametric elements. A symmetric reusable intrinsic sample point (RISP) numerical integration algorithm is shown to produce a Galerkin (i.e., double) integration strategy that is competitive with its counterpart (i.e., singular) integration procedure in the collocation BEA approach when the time saved in the symmetric equation solution phase is also taken into account. This new formulation is shown to be capable of employing hypersingular BIEs while obviating the requirement of C 1 continuity, a fact that allows the employment of the popular continuous element technology. The behavior of the symmetric Galerkin BEA method with regard to both direct and iterative equation solution operations is also addressed. A series of example problems are presented to quantify the performance of this symmetric approach, relative to the more conventional unsymmetric BEA, in terms of both accuracy and efficiency. It is concluded that appropriate implementations of the symmetric Galerkin approach to BEA indeed have the potential to be competitive with, if not superior to, collocation-based BEA, for large-scale problems.

Kane, J. H.; Balakrishna, C.

1993-01-01

341

Linear stability analysis of dynamical quadratic gravity  

NASA Astrophysics Data System (ADS)

We study the linear stability of dynamical, quadratic gravity, focusing on two particular subclasses (the even-parity sector, exemplified by Einstein-Dilaton-Gauss-Bonnet gravity, and the odd-parity sector, exemplified by dynamical Chern-Simons modified gravity) in the high-frequency, geometric optics approximation. This analysis is carried out by studying gravitational and scalar modes propagating on spherically symmetric and axially symmetric, vacuum solutions of the theory and finding the associated dispersion relations. These relations are solved in two separate cases (the scalar regime and the gravitational wave regime, defined by requiring the ratio of the amplitude of the perturbations to be much greater or smaller than unity) and found in both cases to not lead to exponential growth of the propagating modes, suggesting linearly stability. The modes are found to propagate at subluminal and superluminal speeds, depending on the propagating modes' direction relative to the background geometry, just as in dynamical Chern-Simons gravity.

Ayzenberg, Dimitry; Yagi, Kent; Yunes, Nicolás

2014-02-01

342

A Dirac Particle in a Complex Potential  

E-print Network

It has been observed that a quantum mechanical theory need not to be Hermitian to have a real spectrum. In this paper we obtain the eigenvalues of a Dirac charged particle in a complex static and spherically symmetric potential. Furthermore, we study the Complex Morse and complex Coulomb potentials.

Khaled Saaidi

2003-09-15

343

Central Limit Theorems for Linear Statistics of Heavy Tailed Random Matrices  

E-print Network

We show central limit theorems (CLT) for the linear statistics of symmetric matrices with independent heavy tailed entries, including entries in the domain of attraction of ?-stable laws and entries with moments exploding ...

Benaych-Georges, Florent

344

Impact of semi-annihilation of Bbb Z3 symmetric dark matter with radiative neutrino masses  

NASA Astrophysics Data System (ADS)

We investigate a Bbb Z3 symmetric model with two-loop radiative neutrino masses. Dark matter in the model is either a Dirac fermion or a complex scalar as a result of an unbroken Bbb Z3 symmetry. In addition to standard annihilation processes, semi-annihilation of the dark matter contributes to the relic density. We study the effect of the semi-annihilation in the model and find that those contributions are important to obtain the observed relic density. The experimental signatures in dark matter searches are also discussed, where some of them are expected to be different from the signatures of dark matter in Bbb Z2 symmetric models.

Aoki, Mayumi; Toma, Takashi

2014-09-01

345

Finite element Calculations of PT-Symmetric Bose-Einstein Condensates  

NASA Astrophysics Data System (ADS)

PT-symmetric systems have been intensively studied in optical waveguides, where the PT symmetry is achieved by pumping and absorption processes. In such systems the PT symmetry leads to a wide range of effects promising technical and scientific applications. By analogy, balanced gain and loss of particles in Bose-Einstein condensates (BEC) can be described by introducing a PT-symmetric imaginary potential into the Gross-Pitaevskii equation (GPE). This equation can be solved numerically by various methods including the finite element approach. We apply this method to the GPE with arbitrary complex potentials and explicitly solve a double-well potential with shifted barriers.

Haag, Daniel; Dast, Dennis; Cartarius, Holger; Wunner, Günter

2015-01-01

346

PT Symmetric, Hermitian and P-Self-Adjoint Operators Related to Potentials in PT Quantum Mechanics  

E-print Network

In the recent years a generalization $H=p^2 +x^2(ix)^\\epsilon$ of the harmonic oscillator using a complex deformation was investigated, where \\epsilon\\ is a real parameter. Here, we will consider the most simple case: \\epsilon even and x real. We will give a complete characterization of three different classes of operators associated with the differential expression H: The class of all self-adjoint (Hermitian) operators, the class of all PT symmetric operators and the class of all P-self-adjoint operators. Surprisingly, some of the PT symmetric operators associated to this expression have no resolvent set.

Tomas Azizov; Carsten Trunk

2011-09-15

347

Symmetric multi-component diffusion modeling for Magnum PSI  

NASA Astrophysics Data System (ADS)

Magnum PSI is a linear plasma generator for studying plasma surface interaction in conditions as expected in the ITER divertor. In Magnum PSI, the diffusive fluxes do not follow the simple Fick law for diffusion, due to coupling of the fluxes between species and directions, and ambipolar and magnetic fields. Instead they are described by the Stefan-Maxwell equations. In our contribution, we will address the numerical issues associated with solving the Stefan-Maxwell equations and the resulting set of continuity equations for the species. In particular, we will present a symmetric approach where all species are treated as independent unknowns and no species are singled out in order to account for mass and charge conservation. Modeling results of Magnum PSI using this approach will be presented.

Peerenboom, Kim; van Dijk, Jan; Goedheer, Wim; van der Mullen, Joost

2011-11-01

348

Two loop QCD vertices at the symmetric point  

SciTech Connect

We compute the triple gluon, quark-gluon and ghost-gluon vertices of QCD at the symmetric subtraction point at two loops in the MS scheme. In addition we renormalize each of the three vertices in their respective momentum subtraction schemes, MOMggg, MOMq and MOMh. The conversion functions of all the wave functions, coupling constant and gauge parameter renormalization constants of each of the schemes relative to MS are determined analytically. These are then used to derive the three loop anomalous dimensions of the gluon, quark, Faddeev-Popov ghost and gauge parameter as well as the {beta} function in an arbitrary linear covariant gauge for each MOM scheme. There is good agreement of the latter with earlier Landau gauge numerical estimates of Chetyrkin and Seidensticker.

Gracey, J. A. [Theoretical Physics Division, Department of Mathematical Sciences, University of Liverpool, P.O. Box 147, Liverpool, L69 3BX (United Kingdom)

2011-10-15

349

Spherically symmetric cosmological spacetimes with dust and radiation — numerical implementation  

SciTech Connect

We present new numerical cosmological solutions of the Einstein Field Equations. The spacetime is spherically symmetric with a source of dust and radiation approximated as a perfect fluid. The dust and radiation are necessarily non-comoving due to the inhomogeneity of the spacetime. Such a model can be used to investigate non-linear general relativistic effects present during decoupling or big-bang nucleosynthesis, as well as for investigating void models of dark energy with isocurvature degrees of freedom. We describe the full evolution of the spacetime as well as the redshift and luminosity distance for a central observer. After demonstrating accuracy of the code, we consider a few example models, and demonstrate the sensitivity of the late time model to the degree of inhomogeneity of the initial radiation contrast.

Lim, Woei Chet [Department of Mathematics, University of Waikato, Private Bag 3105, Hamilton 3240 (New Zealand); Regis, Marco [Dipartimento di Fisica, Università di Torino and INFN, Torino (Italy); Clarkson, Chris, E-mail: wclim@waikato.ac.nz, E-mail: regis@to.infn.it, E-mail: chris.clarkson@gmail.com [Astrophysics, Cosmology and Gravity Centre, and Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa)

2013-10-01

350

Cervical Symmetric Dumbbell Ganglioneuromas Causing Severe Paresis  

PubMed Central

We report an extremely rare case with bilateral and symmetric dumbbell ganglioneuromas of the cervical spine in an elderly patient. A 72-year-old man came by ambulance to our hospital due to progressive incomplete paraplegia. Magnetic resonance imaging demonstrated bilateral symmetric dumbbell tumors at the C1/2 level. We performed total resection of the intracanalar tumor, aiming at complete decompression of the spinal cord, and partial and subtotal resection of foraminal outside portions. Histopathological examination of the surgical specimen indicated the tumor cells to be spindle cells with the presence of ganglion cells and no cellular pleomorphism, suggesting a diagnosis of ganglioneuroma. Although the surgery was not curative, the postoperative course was uneventful and provided a satisfactory outcome. This is the fourth known case of cervical ganglioneuromas of the bilateral symmetric dumbbell type. PMID:24596609

Miyamoto, Kei; Hirose, Yoshinobu; Kito, Yusuke; Fushimi, Kazunari; Shimizu, Katsuji

2014-01-01

351

Systems of coupled PT-symmetric oscillators  

E-print Network

The Hamiltonian for a PT-symmetric chain of coupled oscillators is constructed. It is shown that if the loss-gain parameter $\\gamma$ is uniform for all oscillators, then as the number of oscillators increases, the region of unbroken PT-symmetry disappears entirely. However, if $\\gamma$ is localized in the sense that it decreases for more distant oscillators, then the unbroken-PT-symmetric region persists even as the number of oscillators approaches infinity. In the continuum limit the oscillator system is described by a PT-symmetric pair of wave equations, and a localized loss-gain impurity leads to a pseudo-bound state. It is also shown that a planar configuration of coupled oscillators can have multiple disconnected regions of unbroken PT symmetry.

Carl M. Bender; Mariagiovanna Gianfreda; S. P. Klevansky

2014-06-23

352

The quantum capacity with symmetric side channels  

E-print Network

We present an upper bound for the quantum channel capacity that is both additive and convex. Our bound can be interpreted as the capacity of a channel for high-fidelity quantum communication when assisted by a family of channels that have no capacity on their own. This family of assistance channels, which we call symmetric side channels, consists of all channels mapping symmetrically to their output and environment. The bound seems to be quite tight, and for degradable quantum channels it coincides with the unassisted channel capacity. Using this symmetric side channel capacity, we find new upper bounds on the capacity of the depolarizing channel. We also briefly indicate an analogous notion for distilling entanglement using the same class of (one-way) channels, yielding one of the few entanglement measures that is monotonic under local operations with one-way classical communication (1-LOCC), but not under the more general class of local operations with classical communication (LOCC).

Graeme Smith; John A. Smolin; Andreas Winter

2006-07-05

353

-symmetric nonlinear metamaterials and zero-dimensional systems  

NASA Astrophysics Data System (ADS)

A one dimensional, parity-time ()-symmetric magnetic metamaterial comprising split-ring resonators having both gain and loss is investigated. In the linear regime, the transition from the exact to the broken -phase is determined through the calculation of the eigenfrequency spectrum for two different configurations; the one with equidistant split-rings and the other with the split-rings forming a binary pattern ( dimer chain). The latter system features a two-band, gapped spectrum with its shape determined by the gain/loss coefficient as well as the interelement coupling. In the presence of nonlinearity, the dimer chain configuration with balanced gain and loss supports nonlinear localized modes in the form of a novel type of discrete breathers below the lower branch of the linear spectrum. These breathers that can be excited from a weak applied magnetic field by frequency chirping, can be subsequently driven solely by the gain for very long times. The effect of a small imbalance between gain and loss is also considered. Fundamental gain-driven breathers occupy both sites of a dimer, while their energy is almost equally partitioned between the two split-rings, the one with gain and the other with loss. We also introduce a model equation for the investigation of classical symmetry in zero dimensions, realized by a simple harmonic oscillator with matched time-dependent gain and loss that exhibits a transition from oscillatory to diverging motion. This behavior is similar to a transition from the exact to the broken phase in higher-dimensional -symmetric systems. A stability condition relating the parameters of the problem is obtained in the case of a piece-wise constant gain/loss function that allows the construction of a phase diagram with alternating stable and unstable regions.

Tsironis, G. P.; Lazarides, N.

2014-05-01

354

Linear baroclinic instability in the Martian atmosphere  

NASA Astrophysics Data System (ADS)

A spherical quasi-geostrophic model is used in an examination of linear baroclinic instability in such zonal-mean flows as those of the Martian atmosphere in winter, under both relatively nondusty and very dusty conditions. These zonal flows, which possess both vertical and meridional shear, are characterized by baroclinically unstable modes whose growth rates and phase speeds are generally consistent with available observations. The structures of the spherical modes are similar to those obtained for terrestrial zonal flows, if similar zonal wavelengths are compared. Zonally symmetric topography, like that of Mars' northern hemisphere, reduces linear growth rates without changing the most unstable scale. It also increases phase speeds.

Barnes, J. R.

1984-05-01

355

Mutual Private Set Intersection with Linear Complexity  

E-print Network

151-747, Korea {msunkim,htsm1138,jhcheon}@snu.ac.kr Abstract. A private set intersection (PSI the client can obtain the intersection, the mutual PSI protocol en- ables all players to get the desired result. In this work, we construct a mutual PSI protocol that is significantly more efficient than

356

Influence of initial conditions in symmetric games  

NASA Astrophysics Data System (ADS)

It is known that quantum game is characterized by the payoff matrix as well as initial states of the quantum objects used as carriers of information in a game. Further, the initial conditions of the quantum states influence the strategies adopted by the quantum players. In this paper, we identify the necessary condition on the initial states of quantum objects for converting symmetric games into potential games, in which the players acquire the same payoff matrix. The necessary condition to preserve the symmetric type and potential type of the game is found to be the same. The present work emphasizes the influence of the initial states in the quantization of games.

Balakrishnan, S.

2014-12-01

357

Observational tests of Baryon symmetric cosmology  

NASA Technical Reports Server (NTRS)

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of pi(0)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the amma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurement of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed.

Stecker, F. W.

1982-01-01

358

Multipartite maximally entangled states in symmetric scenarios  

NASA Astrophysics Data System (ADS)

We consider the class of (N+1)-partite states suitable for protocols where there is a powerful party, the authority, and the other N parties play the same role, namely, the state of their system lies in the symmetric Hilbert space. We show that, within this scenario, there is a “maximally entangled state” that can be transform by a local operations and classical communication protocol into any other state. In addition, we show how to use the protocol efficiently, including the construction of the state, and discuss security issues for possible applications to cryptographic protocols. As an immediate consequence we recover a sequential protocol that implements the 1-to-N symmetric cloning.

González-Guillén, Carlos E.

2012-08-01

359

All-optical symmetric ternary logic gate  

NASA Astrophysics Data System (ADS)

Symmetric ternary number (radix=3) has three logical states (1¯, 0, 1). It is very much useful in carry free arithmetical operation. Beside this, the logical operation using this type of number system is also effective in high speed computation and communication in multi-valued logic. In this literature all-optical circuits for three basic symmetrical ternary logical operations (inversion, MIN and MAX) are proposed and described. Numerical simulation verifies the theoretical model. In this present scheme the different ternary logical states are represented by different polarized state of light. Terahertz optical asymmetric demultiplexer (TOAD) based interferometric switch has been used categorically in this manuscript.

Chattopadhyay, Tanay

2010-09-01

360

Observational tests of Baryon symmetric cosmology  

SciTech Connect

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of pi(0)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the gamma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurement of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed.

Stecker, F.W.

1982-09-01

361

Design and analysis on micro-worktable using novel symmetric flexure hinge based on micro-assembly  

NASA Astrophysics Data System (ADS)

Micro-worktable is an important part of a micro-assembly system, and it implements the translation along X- and Y- axes and the rotation along X-, Y- and Z-axes of the assembly system. In order to amplify the micro-worktable displacement output and improve the micro-positioning accuracy, a novel 3-DOF organ-drive-inspecting micro-positioning worktable was designed and analyzed using modified double-parallelogram symmetrical structure flexure hinge and piezoelectric-actuators. For the symmetric mechanism effectively eliminated the coupling deflection angle and limited the vertical direction motion, the modified double-parallelogram flexure hinge increased the output displacement of X, Y and Z axes. Finite element model of the micro-worktable was established in ANSYS to make its static performances simulation by finite elements method (FEM). Simulation results showed that stiffness and accuracy of the modified double-parallelogram flexure hinge mechanism are higher than general double-parallelogram flexure hinge mechanism, and output displacement linearity is better than single-parallelogram flexure hinge mechanism. Flexure hinge mechanism and piezoelectric-actuator self-features reduce the system complexity, coupling displacement error, and also assure the stable accuracy, high resolution, and high frequent-response of the micro-positioning worktable. Finally, static performance was tested and analyzed through experiments. In experiments, the piezoelectric-power provided voltage to drive the micro-positioning worktable along X, Y and Z axes, and an electric inductance micrometer dial was used to measure the output displacement. Experimental results show that the resolution is 0.04?m for displacement in X, Y, and Z axes, and the maximum stroke length reaches 6?m. The design meets with the requirement of the micro-assembly system.

Duan, Ruiling; Li, Yuhe; Li, Qingxiang; Gong, Juan

2005-12-01

362

Dissipative analysis and control for discrete-time state-space symmetric systems  

Microsoft Academic Search

In this paper, the problem of dissipativity analysis and output feedback control synthesis for discrete linear time-invariant systems with state-space symmetry is investigated. Firstly, an explicit expression of H? norm for discrete-time symmetric system is given under the mixed H? and positive real performance criterion, and this is a particular case of dissipative systems. Subsequently, we consider the control synthesis

Wang Shuping; Zhang Guoshan; Liu Wanquan

2010-01-01

363

CCM3 as applied to an idealized all land zonally symmetric planet, Terra Blanda 3  

E-print Network

response curve of simulations of the step function increase of the solar constan on a dry Terra Blanda (North et al., 1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 28 Ensemble of the normalized response curve of simulations of the step... the original NCAR Community Climate Model 3 with modified boundary conditions and solar forcings. Terra Blanda 3 is a simulation of an all land, north-south symmetrical planet, which stays on the equinox throughout the run, and has no non-linearity associated...

Mahajan, Salil

2005-02-17

364

Symmetric instability in two-layer rotating shallow water model and its nonlinear evolution  

Microsoft Academic Search

We study symmetric instability in 2-layer rotating shallow water model. We consider a barotropic localized jet on the f-plane and on the equatorial-beta plane, and use the collocation method to obtain the structure of linearly unstable modes. We then simulate the nonlinear evolution of the flow disturbed by thus obtained most unstable mode, with the help of a high-resolution finite-volume

F. Bouchut; E. Scherer; V. Zeitlin

2009-01-01

365

GENERALIZATIONS OF DAVIDSON’S METHOD FOR COMPUTING EIGENVALUES OF SPARSE SYMMETRIC MATRICES*  

E-print Network

Abstract. This paper analyzes Davidson’s method for computing a few eigenpairs of large sparse symmetric matrices. An explanation is given for why Davidson’s method often performs well but occasionally performs very badly. Davidson’s method is then generalized to a method which offers a powerful way of applying preconditioning techniques developed for solving systems of linear equations to solving eigenvalue problems. Key words, eigenvalues, eigenvectors, sparse matrices AMS(MOS) subject classifications. 65, 15

Ronald B. Morganf; David; S. Scott

366

Axially symmetric spacetimes: numerical and analytical perspectives  

E-print Network

Some new aspects of axially symmetric spacetimes are discussed. These results open the door for future interplay between analytical and numerical studies. The new developments are based on the role of the total mass in axial symmetry. Finally, a list of relevant open problems is presented. These problems can be hopefully solved with an interaction between numerical and analytical insights.

Sergio Dain

2011-06-15

367

Laws of Trigonometry in Symmetric Spaces  

Microsoft Academic Search

This paper consists of two parts. In the flrst part, we reformulate the work of E. Leuzinger on trigonometry in noncompact symmetric spaces. In the second part, we outline an alternative method using invariants of the isotropy group representation. Appropriately formulated, these methods apply to both compact and noncompact sym- metric spaces. This work is contained in the Ph.D. dissertation

Helmer Aslaksen; Hsueh-Ling Huynh

368

SEARCHABLE SYMMETRIC ENCRYPTION: REVIEW AND EVALUATION  

Microsoft Academic Search

Searchable Symmetric Encryption (SSE) allows a user to search over their encrypted data on a third party storage provider privately. There are several existing SSE schemes have been proposed to achieve this goal. This paper concerns with three currentSSE schemes, which are the Practical Techniques for Searches in Encrypted Data (PTSED), the Secure Index(SI), and the Fuzzy Keyword Search over

YAP JOE EARN; RAED ALSAQOUR; MAHA ABDELHAQ; TARIQ ABDULLAH

2011-01-01

369

Dissociative recombination of highly symmetric polyatomic ions.  

PubMed

A general first-principles theory of dissociative recombination is developed for highly symmetric molecular ions and applied to H(3)O(+) and CH(3)(+), which play an important role in astrophysical, combustion, and laboratory plasma environments. The theoretical cross sections obtained for the dissociative recombination of the two ions are in good agreement with existing experimental data from storage ring experiments. PMID:22324682

Douguet, Nicolas; Orel, Ann E; Greene, Chris H; Kokoouline, Viatcheslav

2012-01-13

370

HARMONIC TWOSPHERES IN COMPACT SYMMETRIC SPACES, REVISITED  

E-print Network

HARMONIC TWO­SPHERES IN COMPACT SYMMETRIC SPACES, REVISITED F. E. Burstall and M. A. Guest Introduction The purpose of this article is to give a new description of harmonic maps from the two­sphere S 2 of such harmonic maps occur when G=K = S n or CP n . In 1967, E. Calabi gave a construction of all harmonic maps

Bath, University of

371

HARMONIC MORPHISMS, HERMITIAN STRUCTURES AND SYMMETRIC SPACES  

E-print Network

HARMONIC MORPHISMS, HERMITIAN STRUCTURES AND SYMMETRIC SPACES In this text we refer to the following papers by capital letters as indicated. [A] M. Svensson, On holomorphic harmonic morphisms, Manuscripta Math. 107 (2002), 1­13. [B] M. Svensson, Harmonic morphisms from even-dimensional hyper- bolic

Gudmundsson, Sigmundur

372

Miniaturized symmetrization optics for junction laser  

NASA Technical Reports Server (NTRS)

Miniaturized optics comprising transverse and lateral cylindrical lenses composed of millimeter-sized rods with diameters, indices-of-refraction and spacing such that substantially all the light emitted as an asymmetrical beam from the emitting junction of the laser is collected and translated to a symmetrical beam.

Hammer, Jacob M. (Inventor); Kaiser, Charlie J. (Inventor); Neil, Clyde C. (Inventor)

1982-01-01

373

Symmetric Representation Rings are lambda-Rings.  

E-print Network

The representation ring of an affine algebraic group scheme can be endowed with the structure of a (special) lambda-ring. We show that the same is true for the ring of symmetric representations, i.e. for the Grothendieck-Witt ring of the representation category, for any affine algebraic group scheme over a field of characteristic not two.

Marcus Zibrowius

374

Amplituhedron cells and Stanley symmetric functions  

E-print Network

The amplituhedron was recently introduced in the study of scattering amplitudes in $N=4$ super Yang-Mills. We compute the cohomology class of a tree amplituhedron subvariety of the Grassmannian to be the truncation of an affine Stanley symmetric function.

Thomas Lam

2014-09-19

375

Reciprocal Symmetric and Origin of Quantum Statistics  

E-print Network

Boltzmann's differential equation is replaced by the corresponding reciprocal symmetric finite difference equation. Finite difference translates discreteness of energy. Boltzmann's function, then, splits into two reciprocally related functions. One of them gives Planck's radiation relation and the other one gives the corresponding Fermi-Dirac relation.

Mushfiq Ahmad

2007-03-21

376

SYMMETRIC IMPRIMITIVITY THEOREMS FOR GRAPH C  

E-print Network

SYMMETRIC IMPRIMITIVITY THEOREMS FOR GRAPH C -ALGEBRAS DAVID PASK AND IAIN RAEBURN The C -algebra C of the Kumjian-Pask theorem in [10] and [9] rely on a result of Gross and Tucker which realises free actions the University of Newcastle. 1 #12;2 DAVID PASK AND IAIN RAEBURN the theorem for full crossed products. This time

Pask, David

377

Bruhat Order in Full Symmetric Toda System  

NASA Astrophysics Data System (ADS)

In this paper we discuss some geometrical and topological properties of the full symmetric Toda system. We show by a direct inspection that the phase transition diagram for the full symmetric Toda system in dimensions n = 3, 4 coincides with the Hasse diagram of the Bruhat order of symmetric groups S 3 and S 4. The method we use is based on the existence of a vast collection of invariant subvarieties of the Toda flow in orthogonal groups. We show how one can extend it to the case of general n. The resulting theorem identifies the set of singular points of dim = n Toda flow with the elements of the permutation group S n , so that points will be connected by a trajectory, if and only if the corresponding elements are Bruhat comparable. We also show that the dimension of the submanifolds, spanned by the trajectories connecting two singular points, is equal to the length of the corresponding segment in the Hasse diagram. This is equivalent to the fact that the full symmetric Toda system is in fact a Morse-Smale system.

Chernyakov, Yu. B.; Sharygin, G. I.; Sorin, A. S.

2014-08-01

378

Analysis of non-symmetrical flapping airfoils  

Microsoft Academic Search

Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables

W. B. Tay; K. B. Lim

2009-01-01

379

Analysis of Non-symmetrical Flapping Airfoils  

Microsoft Academic Search

Simulations have been done to assess the performance of different types of non-symmetrical airfoils on lift, thrust and propulsive efficiency under different flapping configurations at a Reynolds number of 10,000. The variables studied include the Stroudal number, reduced frequency, pitch angle and phase angle difference. In order to analyze the variables more efficiently, the Design of Experiments using the response

Wee Beng Tay; Kah Bin Lim

2007-01-01

380

Highly Symmetric 3-refinement Bi-frames  

E-print Network

Highly Symmetric 3-refinement Bi-frames for Surface Multiresolution Processing Qingtang Jiang: Qingtang Jiang, e-mail: jiangqumsl.edu, phone: 1-314-516-6358, fax: 1-314-516-5400. The authors are with the Department of Mathematics and Computer Science, University of Missouri­St. Louis, St. Louis, MO 63121, USA. 1

Jiang, Qingtang

381

Highly Symmetric 3-refinement Bi-frames  

E-print Network

Highly Symmetric 3-refinement Bi-frames for Surface Multiresolution Processing Qingtang Jiang Corresponding author: Qingtang Jiang, e-mail: jiangq@umsl.edu, phone: 1-314-516-6358, fax: 1-314-516-5400. The authors are with the Department of Mathematics and Computer Science, University of Missouri­St. Louis, St

Jiang, Qingtang

382

HOMOGENEOUS EINSTEINWEYL STRUCTURES ON SYMMETRIC SPACES  

E-print Network

HOMOGENEOUS EINSTEIN­WEYL STRUCTURES ON SYMMETRIC SPACES MEGAN M. KERR Abstract. In this paper we must be constant, thus Einstein manifolds are spaces of constant Ricci curvature. In conformal geometry is Date: August 18, 1997. 1 #12;2 MEGAN M. KERR the Gauduchon metric. Hence we will assume from now

Kerr, Megan M.

383

Symmetric protein architecture in protein design: top-down symmetric deconstruction.  

PubMed

Top-down symmetric deconstruction (TDSD) is a joint experimental and computational approach to generate a highly stable, functionally benign protein scaffold for intended application in subsequent functional design studies. By focusing on symmetric protein folds, TDSD can leverage the dramatic reduction in sequence space achieved by applying a primary structure symmetric constraint to the design process. Fundamentally, TDSD is an iterative symmetrization process, in which the goal is to maintain or improve properties of thermodynamic stability and folding cooperativity inherent to a starting sequence (the "proxy"). As such, TDSD does not attempt to solve the inverse protein folding problem directly, which is computationally intractable. The present chapter will take the reader through all of the primary steps of TDSD-selecting a proxy, identifying potential mutations, establishing a stability/folding cooperativity screen-relying heavily on a successful TDSD solution for the common ?-trefoil fold. PMID:25213415

Longo, Liam M; Blaber, Michael

2014-01-01

384

Space Complexity Algorithms & Complexity  

E-print Network

Space Complexity Algorithms & Complexity Space Complexity Nicolas Stroppa Patrik Lambert - plambert@computing.dcu.ie CA313@Dublin City University. 2008-2009. December 4, 2008 #12;Space Complexity Hierarchy of problems #12;Space Complexity NP-intermediate Languages If P = NP, then are there languages which neither in P

Way, Andy

385

Macromolecular symmetric assembly prediction using swarm intelligence dynamic modeling.  

PubMed

Proteins often assemble in multimeric complexes to perform a specific biologic function. However, trapping these high-order conformations is difficult experimentally. Therefore, predicting how proteins assemble using in silico techniques can be of great help. The size of the associated conformational space and the fact that proteins are intrinsically flexible structures make this optimization problem extremely challenging. Nonetheless, known experimental spatial restraints can guide the search process, contributing to model biologically relevant states. We present here a swarm intelligence optimization protocol able to predict the arrangement of protein symmetric assemblies by exploiting a limited amount of experimental restraints and steric interactions. Importantly, within this scheme the native flexibility of each protein subunit is taken into account as extracted from molecular dynamics (MD) simulations. We show that this is a key ingredient for the prediction of biologically functional assemblies when, upon oligomerization, subunits explore activated states undergoing significant conformational changes. PMID:23810695

Degiacomi, Matteo T; Dal Peraro, Matteo

2013-07-01

386

Waterbomb base: a symmetric single-vertex bistable origami mechanism  

NASA Astrophysics Data System (ADS)

The origami waterbomb base is a single-vertex bistable origami mechanism that has unique properties which may prove useful in a variety of applications. It also shows promise as a test bed for smart materials and actuation because of its straightforward geometry and multiple phases of motion, ranging from simple to more complex. This study develops a quantitative understanding of the symmetric waterbomb base's kinetic behavior. This is done by completing kinematic and potential energy analyses to understand and predict bistable behavior. A physical prototype is constructed and tested to validate the results of the analyses. Finite element and virtual work analyses based on the prototype are used to explore the locations of the stable equilibrium positions and the force-deflection response. The model results are verified through comparisons to measurements on a physical prototype. The resulting models describe waterbomb base behavior and provide an engineering tool for application development.

Hanna, Brandon H.; Lund, Jason M.; Lang, Robert J.; Magleby, Spencer P.; Howell, Larry L.

2014-09-01

387

Tunneling control using classical non-linear oscillator  

SciTech Connect

A quantum particle is placed in symmetric double well potential which is coupled to a classical non-linear oscillator via a coupling function. With different spatial symmetry of the coupling and under various controlling fashions, the tunneling of the quantum particle can be enhanced or suppressed, or totally destroyed.

Kar, Susmita [Department of Physical Chemistry, Indian Association for the Cultivation of Science, Kolkata -700032 (India); Bhattacharyya, S. P., E-mail: pcspb@chem.iitb.ac.in [Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai- 400076 (India)

2014-04-24

388

Conformally Symmetric Circle Packings: A Generalization of Doyle's Spirals  

E-print Network

Conformally Symmetric Circle Packings: A Generalization of Doyle's Spirals Alexander I. Bobenko and Tim Hoffmann CONTENTS 1. Introduction 2. Geometry of Circle Flowers and Conformally Symmetric Circle Packings 3. Analytic Description of Conformally Symmetric Circle Packings 4. Doyle Spirals 5. Airy

Bobenko, Alexander I.

389

Non-linear Spectroscopy  

NSDL National Science Digital Library

First, the Wright research group at the University of Wisconsin-Madison presents its research using "narrow frequency distribution of tunable laser sources to gain spectral selectivity in an analytical measurement" (1). Along with a summary of its research and techniques, this website offers a great introduction to the fundamentals of non-linear spectroscopy. The second site describes the Ernest Orlando Lawrence Berkeley National Laboratory's success in observing non-linear spectra from chiral molecules (2). With the help of a pictorial poster, users can understand the complex issues of chiral vibrations and spectra. Next, the Sasada lab at Keio University summarizes its research interests in optical communications (3 ). Visitors can find diagrams illustrating absolute frequency difference measurements and the techniques used in the work. The fourth website describes the Regional Laser and Biomedical Technology Laboratories (RLBL) of the University of Pennsylvania's applications of laser spectroscopy in the biochemical, biophysical, and biomedical fields (4 ). Researchers can find out about using the laboratory's facilities, its technological developments, educational opportunities, and much more. Next, the University of Durham describes its examination of spectroscopy of Rubidium vapor (5). Users can learn about its conclusions that "the standard designation of 'saturation spectroscopy' is a misnomer in multilevel systems where hyperfine pumping can occur." At the sixth site, the Laboratories for Biophysical Dynamics' Nano-Biophotonics group addresses its applications of nanotechnology and non-linear spectroscopy to the biology field (6). Visitors can find synopses of its four main research projects and a list of publications. Lastly, the European Laboratory for Non Linear Spectroscopy (LENS) offers an introduction to its goal "to provide advanced laser and spectroscopic facilities for researchers from European countries and to promote and facilitate the exchange of ideas, scientific techniques, and technical skills" (7). Individuals can fine descriptions of past and upcoming events and seminars, lists of publication, and training and job opportunities.

390

Symmetrical peripheral gangrene following snake bite.  

PubMed

SPG (Symmetrical peripheral gangrene) is defined as symmetrical distal ischemic damage at two or more sites in the absence of large vessels obstruction. It has been ascribed to a number of infectious and non infectious conditions including connective tissue, cardiovascular, neoplastic and iatrogenic causes. We report a unique case of SPG in a 35-year-old Indian female who developed spontaneous gangrene of the distal phalanges of the right and left index, middle, ring and little fingers and the distal phalanges of all toes of the right and left foot following a snake bite. There have been very few cases of peripheral gangrene and acute renal failure associated with snake bite in literature. PMID:25386476

Shastri, Minal; Parikh, Mital; Patel, Dwijal; Chudasma, Ketan; Patell, Rushad

2014-09-01

391

Symmetrical Peripheral Gangrene Following Snake Bite  

PubMed Central

SPG (Symmetrical peripheral gangrene) is defined as symmetrical distal ischemic damage at two or more sites in the absence of large vessels obstruction. It has been ascribed to a number of infectious and non infectious conditions including connective tissue, cardiovascular, neoplastic and iatrogenic causes. We report a unique case of SPG in a 35-year-old Indian female who developed spontaneous gangrene of the distal phalanges of the right and left index, middle, ring and little fingers and the distal phalanges of all toes of the right and left foot following a snake bite. There have been very few cases of peripheral gangrene and acute renal failure associated with snake bite in literature. PMID:25386476

Shastri, Minal; Parikh, Mital; Patel, Dwijal; Chudasma, Ketan

2014-01-01

392

PT-symmetric representations of fermionic algebras  

SciTech Connect

A recent paper by Jones-Smith and Mathur, Phys. Rev. A 82, 042101 (2010) extends PT-symmetric quantum mechanics from bosonic systems (systems for which T{sup 2}=1) to fermionic systems (systems for which T{sup 2}=-1). The current paper shows how the formalism developed by Jones-Smith and Mathur can be used to construct PT-symmetric matrix representations for operator algebras of the form {eta}{sup 2}=0, {eta}{sup 2}=0, {eta}{eta}+{eta}{eta}={alpha}1, where {eta}={eta}{sup PT}=PT{eta}T{sup -1}P{sup -1}. It is easy to construct matrix representations for the Grassmann algebra ({alpha}=0). However, one can only construct matrix representations for the fermionic operator algebra ({alpha}{ne}0) if {alpha}=-1; a matrix representation does not exist for the conventional value {alpha}=1.

Bender, Carl M. [Physics Department, Washington University, St. Louis, Missouri 63130 (United States); Klevansky, S. P. [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany)

2011-08-15

393

Binary switching in a ‘symmetric' potential landscape  

PubMed Central

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a ‘symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a ‘symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature. PMID:24154561

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

394

Observational tests of baryon symmetric cosmology  

NASA Technical Reports Server (NTRS)

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of Pi(O)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the gamma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurements of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed. Previously announced in STAR as N83-10996

Stecker, F. W.

1983-01-01

395

PT-Symmetric Representations of Fermionic Algebras  

E-print Network

A recent paper by Jones-Smith and Mathur extends PT-symmetric quantum mechanics from bosonic systems (systems for which $T^2=1$) to fermionic systems (systems for which $T^2=-1$). The current paper shows how the formalism developed by Jones-Smith and Mathur can be used to construct PT-symmetric matrix representations for operator algebras of the form $\\eta^2=0$, $\\bar{\\eta}^2=0$, $\\eta\\bar{\\eta}+\\bar {\\eta} =\\alpha 1$, where $\\bar{eta}=\\eta^{PT} =PT \\eta T^{-1}P^{-1}$. It is easy to construct matrix representations for the Grassmann algebra ($\\alpha=0$). However, one can only construct matrix representations for the fermionic operator algebra ($\\alpha\

Carl M. Bender; S. P. Klevansky

2011-04-21

396

Stabilization of Quantum Computations by Symmetrization  

Microsoft Academic Search

We propose a method for the stabilization of quantum computations (including quan- tum state storage). The method is based on the operation of projection intoSYM, the symmetric subspace of the full state space of R redundant copies of the computer. We describe an ecient algorithm and quantum network eectingSYM{projection and discuss the stabilizing eect of the proposed method in the

Adriano Barenco; Andre? Berthiaume; David Deutsch; Artur Ekert; Richard Jozsa; Chiara Macchiavello

1997-01-01

397

Solitons in PT-symmetric nonlinear lattices  

SciTech Connect

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.

Abdullaev, Fatkhulla Kh.; Konotop, Vladimir V.; Zezyulin, Dmitry A. [Centro de Fisica Teorica e Computacional, Faculdade de Ciencias, Universidade de Lisboa, Avenida Professor Gama Pinto 2, P-1649-003 Lisboa (Portugal); Kartashov, Yaroslav V. [ICFO-Institut de Ciencies Fotoniques, and Universitat Politecnica de Catalunya, Mediterranean Technology Park, E-08860 Castelldefels, Barcelona (Spain)

2011-04-15

398

Axially symmetric solutions in electroweak theory  

SciTech Connect

We present the general ansatz, the energy density, and the Chern-Simons charge for static axially symmetric configurations in the bosonic sector of the electroweak theory. Containing the sphaleron, the multisphalerons, and the sphaleron-antisphaleron pair at finite mixing angle, the ansatz further allows the construction of the sphaleron and multisphaleron barriers and of the bisphalerons at finite mixing angle. We conjecture that further solutions exist.

Brihaye, Y. (Faculte des Sciences, Universite de Mons-Hainaut, B-7000 Mons (Belgium)); Kunz, J. (Fachbereich Physik, Universitaet Oldenburg, Postfach 2503, D-2611 Oldenburg (Germany) Instituut voor Theoretische Fysica, Rijksuniversiteit te Utrecht, NL-3508 TA Utrecht (Netherlands))

1994-09-15

399

Analysis of non-symmetrical flapping airfoils  

Microsoft Academic Search

Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils\\u000a under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and\\u000a phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology\\u000a is applied. Results show that both the variables

W. B. Tay; K. B. Lim

2009-01-01

400

PT symmetric Aubry-Andre model  

NASA Astrophysics Data System (ADS)

PT symmetric Aubry-Andre model describes an array of N coupled optical waveguides with position-dependent gain and loss. We show that the reality of the spectrum depends sensitively on the degree of quasi-periodicity for small number of lattice sites. We obtain the Hofstadter butterfly spectrum and discuss the existence of the phase transition from extended to localized states. We show that rapidly changing periodical gain/loss materials almost conserve the total intensity.

Yuce, C.

2014-06-01

401

PT Symmetric Aubry-Andre Model  

E-print Network

PT symmetric Aubry-Andre model describes an array of N coupled optical waveguides with position dependent gain and loss. We show that the reality of the spectrum depends sensitively on the degree of disorder for small number of lattice sites. We obtain the Hofstadter Butterfly spectrum and discuss the existence of the phase transition from extended to localized states. We show that rapidly changing periodical gain/loss materials almost conserves the total intensity.

C. Yuce

2014-02-12

402

Ballistic aggregation in symmetric and nonsymmetric flows  

Microsoft Academic Search

We consider explicit solutions to the problem of ballistic aggregation of dustlike matter whose particles stick together absolutely inelastically upon collisions---a description of the formation of a large-scale structure in cosmology in terms of the adhesion model, which is a generalization of the Zel'dovich approximation. The two previously suggested different representations of the solutions for a plane-symmetric 1D flow are

A. A. Andrievsky; S. N. Gurbatov; A. N. Sobolevsky

2007-01-01

403

Linear Thermodynamics of Rodlike DNA Filtration  

E-print Network

Linear thermodynamics transportation theory is employed to study filtration of rodlike DNA molecules. Using the repeated nanoarray consisting of alternate deep and shallow regions, it is demonstrated that the complex ...

Li, Zirui

404

Spherically symmetric thick branes cosmological evolution  

NASA Astrophysics Data System (ADS)

Spherically symmetric time-dependent solutions for the 5D system of a scalar field canonically coupled to gravity are obtained and identified as an extension of recent results obtained by Ahmed et al. (JHEP 1404:061. arXiv:1312.3576 [hep-th], 2014). The corresponding cosmology of models with regularized branes generated by such a 5D scalar field scenario is also investigated. It has been shown that the anisotropic evolution of the warp factor and consequently the Hubble like parameter are both driven by the radial coordinate on the brane, which leads to an emergent thick brane-world scenario with spherically symmetric time dependent warp factor. Meanwhile, the separability of variables depending on fifth dimension, , which is exhibited by the equations of motion, allows one to recover the extra dimensional profiles obtained in Ahmed et al. (2014), namely the extra dimensional part of the scale (warp) factor and the scalar field dependence on . Therefore, our results are mainly concerned with the time dependence of a spherically symmetric warp factor. Besides evincing possibilities for obtaining asymmetric stable brane-world scenarios, the extra dimensional profiles here obtained can also be reduced to those ones investigated in Ahmed et al. (2014).

Bernardini, A. E.; Cavalcanti, R. T.; da Rocha, Roldão

2015-01-01

405

PT-Symmetric Matrix Quantum Mechanics  

E-print Network

Recently developed methods for PT-symmetric models are applied to quantum-mechanical matrix models. We consider in detail the case of potentials of the form $V=-(g/N^{p/2-1})Tr(iM)^{p}$ and show how the calculation of all singlet wave functions can be reduced to solving a one-dimensional PT-symmetric model. The large-N limit of this class of models exists, and properties of the lowest-lying singlet state can be computed using WKB. For $p=3,4$, the energy of this state for small values of $N$ appears to show rapid convergence to the large-N limit. For the special case of $p=4$, we extend recent work on the $-gx^{4}$ potential to the matrix model: we show that the PT-symmetric matrix model is equivalent to a hermitian matrix model with a potential proportional to $+(4g/N)Tr\\Pi^{4}$. However, this hermitian equivalent model includes an anomaly term $\\hbar\\sqrt{2g/N}Tr\\Pi$. In the large-N limit, the anomaly term does not contribute at leading order to the properties of singlet states.

Peter N. Meisinger; Michael C. Ogilvie

2007-01-23

406

Experimental analysis of two measurement techniques to characterize photodiode linearity  

E-print Network

As photodiodes become more linear, accurately characterizing their linearity becomes very challenging. We compare the IMD3 results from a standard two tone measurement to those from a more complex three tone measurement ...

Klamkin, Jonathan

407

Robustness of linear quadratic state feedback designs in the presence of system uncertainty. [application to Augmentor Wing Jet STOL Research Aircraft flare control autopilot design  

NASA Technical Reports Server (NTRS)

The paper deals with the problem of expressing the robustness (stability) property of a linear quadratic state feedback (LQSF) design quantitatively in terms of bounds on the perturbations (modeling errors or parameter variations) in the system matrices so that the closed-loop system remains stable. Nonlinear time-varying and linear time-invariant perturbations are considered. The only computation required in obtaining a measure of the robustness of an LQSF design is to determine the eigenvalues of two symmetric matrices determined when solving the algebraic Riccati equation corresponding to the LQSF design problem. Results are applied to a complex dynamic system consisting of the flare control of a STOL aircraft. The design of the flare control is formulated as an LQSF tracking problem.

Patel, R. V.; Toda, M.; Sridhar, B.

1977-01-01

408

The Energy Distribution in a Static Spherically Symmetric Nonsingular Black Hole Space-Time  

E-print Network

We calculate the energy distribution in a static spherically symmetric nonsingular black hole space-time by using the Tolman's energy-momentum complex. All the calculations are performed in quasi-Cartesian coordinates. The energy distribution is positive everywhere and be equal to zero at origin. We get the same result as obtained by Y-Ching Yang by using the Einstein's and Weinberg's prescriptions.

I. Radinschi

2000-08-14

409

Energy-momentum distribution of a general plane symmetric spacetime in metric f(R) gravity  

E-print Network

In this paper, the exact vacuum solution of a general plane symmetric spacetime is investigated in metric f(R) gravity with the assumption of constant Ricci scalar. For this solution, we have studied the generalized Landau-Lifshitz energy-momentum complex in this theory to determine the energy distribution expressions for some specific f(R) models. Also, we show that these models satisfy the constant curvature condition.

Morteza Yavari

2014-06-13

410

Sparse Fisher's linear discriminant analysis  

NASA Astrophysics Data System (ADS)

Fisher's linear discriminant analysis (LDA) is traditionally used in statistics and pattern recognition to linearlyproject high-dimensional observations from two or more classes onto a low-dimensional feature space before classification. The computational complexity of the linear feature extraction method increases linearly with dimensionality of the observation samples. For high-dimensional signals, high computational cost can render the method unsuitable for implementation in real time. In this paper, we propose sparse Fisher's linear discriminant analysis, which allows one to search for lowdimensional subspaces, spanned by sparse discriminant vectors, in the high-dimensional space of observation samples from two classes. The sparsity constraints on the space of potential discriminant feature vectors are enforced using the sparse matrix transform (SMT) framework, proposed recently for regularized covariance estimation. Classical Fisher's LDA is a special case of sparse Fisher's LDA when the sparsity constraints on the feature vectors in the estimation algorithm are fully relaxed. The number of non-zero components in a discriminant direction estimated using our proposed discriminant analysis technique is tunable; this feature can be used to control the compromise between computational complexity and accuracy of the eventual classification algorithm. The experimental results discussed in the manuscript demonstrate the effectiveness of the new method for low-complexity data-classification applications.

Siddiqui, Hasib; Hwang, Hau

2011-03-01

411

Robust Linear and Support Vector Regression  

Microsoft Academic Search

ÐThe robust Huber M-estimator, a differentiable cost function that is quadratic for small errors and linear otherwise, is modeled exactly, in the original primal space of the problem, by an easily solvable simple convex quadratic program for both linear and nonlinear support vector estimators. Previous models were significantly more complex or formulated in the dual space and most involved specialized

Olvi L. Mangasarian; David R. Musicant

2000-01-01

412

Complex roots in the inhour equation of coupled reactors  

E-print Network

in this area should be concentrated on extending the discussion to non-symmetric cases and on calculating the coefficients nf the exponential time response terms corresponding to the complex recta. Purthermore, one should attempt to include the small influ...

Yeh, Elizabeth Ching

2012-06-07

413

Gap solitons in PT-symmetric optical lattices with higher-order diffraction.  

PubMed

The existence and stability of gap solitons are investigated in the semi-infinite gap of a parity-time (PT)-symmetric periodic potential (optical lattice) with a higher-order diffraction. The Bloch bands and band gaps of this PT-symmetric optical lattice depend crucially on the coupling constant of the fourth-order diffraction, whereas the phase transition point of this PT optical lattice remains unchangeable. The fourth-order diffraction plays a significant role in destabilizing the propagation of dipole solitons. Specifically, when the fourth-order diffraction coupling constant increases, the stable region of the dipole solitons shrinks as new regions of instability appear. However, fundamental solitons are found to be always linearly stable with arbitrary positive value of the coupling constant. We also investigate nonlinear evolution of the PT solitons under perturbation. PMID:25606878

Ge, Lijuan; Shen, Ming; Ma, Chunlan; Zang, Taocheng; Dai, Lu

2014-12-01

414

Relative equilibria in the unrestricted problem of a sphere and symmetric rigid body  

NASA Astrophysics Data System (ADS)

We consider the unrestricted problem of two mutually attracting rigid bodies, a uniform sphere (or a point mass) and an axially symmetric body. We present a global, geometric approach for finding all relative equilibria (stationary solutions) in this model, which was already studied by Kinoshita. We extend and generalize his results, showing that the equilibria solutions may be found by solving at most two non-linear, algebraic equations, assuming that the potential function of the symmetric rigid body is known explicitly. We demonstrate that there are three classes of the relative equilibria, which we call cylindrical, inclined coplanar and conic precessions, respectively. Moreover, we also show that in the case of conic precession, although the relative orbit is circular, the point mass and the mass centre of the body move in different parallel planes. This solution has not been known yet in the literature.

Vereshchagin, Mikhail; Maciejewski, Andrzej J.; Go?dziewski, Krzysztof

2010-04-01

415

Exact quantization of a PT-symmetric (reversible) Liénard-type nonlinear oscillator  

NASA Astrophysics Data System (ADS)

We carry out an exact quantization of a PT-symmetric (reversible) Liénard-type one-dimensional nonlinear oscillator both semiclassically and quantum mechanically. The associated time-independent classical Hamiltonian is of nonstandard type and is invariant under a combined coordinate reflection and time reversal transformation. We use the von Roos symmetric ordering procedure to write down the appropriate quantum Hamiltonian. While the quantum problem cannot be tackled in coordinate space, we show how the problem can be successfully solved in momentum space by solving the underlying Schrödinger equation therein. We explicitly obtain the eigenvalues and eigenfunctions (in momentum space) and deduce the remarkable result that the spectrum agrees exactly with that of the linear harmonic oscillator, which is also confirmed by a semiclassical modified Bohr-Sommerfeld quantization rule, while the eigenfunctions are completely different.

Chithiika Ruby, V.; Senthilvelan, M.; Lakshmanan, M.

2012-09-01

416

Cutting Force Predication Based on Integration of Symmetric Fuzzy Number and Finite Element Method  

PubMed Central

In the process of turning, pointing at the uncertain phenomenon of cutting which is caused by the disturbance of random factors, for determining the uncertain scope of cutting force, the integrated symmetric fuzzy number and the finite element method (FEM) are used in the prediction of cutting force. The method used symmetric fuzzy number to establish fuzzy function between cutting force and three factors and obtained the uncertain interval of cutting force by linear programming. At the same time, the change curve of cutting force with time was directly simulated by using thermal-mechanical coupling FEM; also the nonuniform stress field and temperature distribution of workpiece, tool, and chip under the action of thermal-mechanical coupling were simulated. The experimental result shows that the method is effective for the uncertain prediction of cutting force. PMID:24790556

Wang, Zhanli; Hu, Yanjuan; Wang, Yao; Dong, Chao; Pang, Zaixiang

2014-01-01

417

Symmetric RBF classifier for nonlinear detection in multiple-antenna-aided systems.  

PubMed

In this paper, we propose a powerful symmetric radial basis function (RBF) classifier for nonlinear detection in the so-called "overloaded" multiple-antenna-aided communication systems. By exploiting the inherent symmetry property of the optimal Bayesian detector, the proposed symmetric RBF classifier is capable of approaching the optimal classification performance using noisy training data. The classifier construction process is robust to the choice of the RBF width and is computationally efficient. The proposed solution is capable of providing a signal-to-noise ratio (SNR) gain in excess of 8 dB against the powerful linear minimum bit error rate (BER) benchmark, when supporting four users with the aid of two receive antennas or seven users with four receive antenna elements. PMID:18467204

Chen, Sheng; Wolfgang, Andreas; Harris, Chris J; Hanzo, Lajos

2008-05-01

418

Adaptive nonlinear least bit error-rate detection for symmetrical RBF beamforming.  

PubMed

A powerful symmetrical radial basis function (RBF) aided detector is proposed for nonlinear detection in so-called rank-deficient multiple-antenna assisted beamforming systems. By exploiting the inherent symmetry of the optimal Bayesian detection solution, the proposed RBF detector becomes capable of approaching the optimal Bayesian detection performance using channel-impaired training data. A novel nonlinear least bit error algorithm is derived for adaptive training of the symmetrical RBF detector based on a stochastic approximation to the Parzen window estimation of the detector output's probability density function. The proposed adaptive solution is capable of providing a signal-to-noise ratio gain in excess of 8 dB against the theoretical linear minimum bit error rate benchmark, when supporting four users with the aid of two receive antennas or seven users employing four receive antenna elements. PMID:18207699

Chen, S; Wolfgang, A; Harris, C J; Hanzo, L

2008-01-01

419

Error reduction in retrievals of atmospheric species from symmetrically measured lidar sounding absorption spectra.  

PubMed

We report new methods for retrieving atmospheric constituents from symmetrically-measured lidar-sounding absorption spectra. The forward model accounts for laser line-center frequency noise and broadened line-shape, and is essentially linearized by linking estimated optical-depths to the mixing ratios. Errors from the spectral distortion and laser frequency drift are substantially reduced by averaging optical-depths at each pair of symmetric wavelength channels. Retrieval errors from measurement noise and model bias are analyzed parametrically and numerically for multiple atmospheric layers, to provide deeper insight. Errors from surface height and reflectance variations are reduced to tolerable levels by "averaging before log" with pulse-by-pulse ranging knowledge incorporated. PMID:25401639

Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

2014-10-20

420

Cutting force predication based on integration of symmetric fuzzy number and finite element method.  

PubMed

In the process of turning, pointing at the uncertain phenomenon of cutting which is caused by the disturbance of random factors, for determining the uncertain scope of cutting force, the integrated symmetric fuzzy number and the finite element method (FEM) are used in the prediction of cutting force. The method used symmetric fuzzy number to establish fuzzy function between cutting force and three factors and obtained the uncertain interval of cutting force by linear programming. At the same time, the change curve of cutting force with time was directly simulated by using thermal-mechanical coupling FEM; also the nonuniform stress field and temperature distribution of workpiece, tool, and chip under the action of thermal-mechanical coupling were simulated. The experimental result shows that the method is effective for the uncertain prediction of cutting force. PMID:24790556

Wang, Zhanli; Hu, Yanjuan; Wang, Yao; Dong, Chao; Pang, Zaixiang

2014-01-01

421

Replication of Avocado Sunblotc Viroid: Evidence for a Symmetric Pathway with Two Rolling Circles and Hammerhead Ribozyme Processing  

Microsoft Academic Search

The structure of a series of RNAs extracted from avocado infected by the 247-nt avocado sunblotch viroid (ASBVd) was investigated. The identification of multistranded complexes containing circular ASBVd RNAs of (+) and (-) polarity suggests that replication of ASBVd proceeds through a symmetric pathway with two rolling circles where these two circular RNAs are the templates. This is in contrast

Jose A. Daros; Jose F. Marcos; Carmen Hernandez; Ricardo Flores

1994-01-01

422

Energy distribution of the Einstein-Klein-Gordon system for a static spherically symmetric spacetime in (2+1)-dimensions  

E-print Network

We use Moeller's energy-momentum complex in order to explicitly compute the energy and momentum density distributions for an exact solution of Einstein's field equations with a negative cosmological constant minimally coupled to a static massless scalar field in a static, spherically symmetric background in (2+1)-dimensions.

I. Radinschi; Th. Grammenos

2005-08-01

423

Characterization of noninnocent metal complexes using solid-state NMR spectroscopy: o-dioxolene vanadium complexes.  

PubMed

(51)V solid-state NMR (SSNMR) studies of a series of noninnocent vanadium(V) catechol complexes have been conducted to evaluate the possibility that (51)V NMR observables, quadrupolar and chemical shift anisotropies, and electronic structures of such compounds can be used to characterize these compounds. The vanadium(V) catechol complexes described in these studies have relatively small quadrupolar coupling constants, which cover a surprisingly small range from 3.4 to 4.2 MHz. On the other hand, isotropic (51)V NMR chemical shifts cover a wide range from -200 to 400 ppm in solution and from -219 to 530 ppm in the solid state. A linear correlation of (51)V NMR isotropic solution and solid-state chemical shifts of complexes containing noninnocent ligands is observed. These experimental results provide the information needed for the application of (51)V SSNMR spectroscopy in characterizing the electronic properties of a wide variety of vanadium-containing systems and, in particular, those containing noninnocent ligands and that have chemical shifts outside the populated range of -300 to -700 ppm. The studies presented in this report demonstrate that the small quadrupolar couplings covering a narrow range of values reflect the symmetric electronic charge distribution, which is also similar across these complexes. These quadrupolar interaction parameters alone are not sufficient to capture the rich electronic structure of these complexes. In contrast, the chemical shift anisotropy tensor elements accessible from (51)V SSNMR experiments are a highly sensitive probe of subtle differences in electronic distribution and orbital occupancy in these compounds. Quantum chemical (density functional theory) calculations of NMR parameters for [VO(hshed)(Cat)] yield a (51)V chemical shift anisotropy tensor in reasonable agreement with the experimental results, but surprisingly the calculated quadrupolar coupling constant is significantly greater than the experimental value. The studies demonstrate that substitution of the catechol ligand with electron-donating groups results in an increase in the HOMO-LUMO gap and can be directly followed by an upfield shift for the vanadium catechol complex. In contrast, substitution of the catechol ligand with electron-withdrawing groups results in a decrease in the HOMO-LUMO gap and can directly be followed by a downfield shift for the complex. The vanadium catechol complexes were used in this work because (51)V is a half-integer quadrupolar nucleus whose NMR observables are highly sensitive to the local environment. However, the results are general and could be extended to other redox-active complexes that exhibit coordination chemistry similar to that of the vanadium catechol complexes. PMID:21842875

Chatterjee, Pabitra B; Goncharov-Zapata, Olga; Quinn, Laurence L; Hou, Guangjin; Hamaed, Hiyam; Schurko, Robert W; Polenova, Tatyana; Crans, Debbie C

2011-10-17

424

Symmetrical and anti-symmetrical coherent perfect absorption for acoustic waves  

SciTech Connect

We investigate tunable acoustic absorption enabled by the coherent control of input waves. It relies on coherent perfect absorption originally proposed in optics. By designing appropriate acoustic metamaterial structures with resonating effective bulk modulus or density, we show that complete absorption of incident waves impinging on the metamaterial can be achieved for either symmetrical or anti-symmetrical inputs in the forward and backward directions. By adjusting the relative phase between the two incident beams, absorption can be tuned effectively from unity to zero, making coherent control useful in applications like acoustic modulators, noise controllers, transducers, and switches.

Wei, Pengjiang; Croënne, Charles; Tak Chu, Sai [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Li, Jensen, E-mail: j.li@bham.ac.uk [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom)

2014-03-24

425

Various scattering properties of a new PT-symmetric non-Hermitian potential  

SciTech Connect

We complexify a 1-d potential V(x)=V{sub 0}cosh{sup 2}?(tanh[(x??d)/d]+tanh(?)){sup 2} which exhibits bound, reflecting and free states to study various properties of a non-Hermitian system. This potential turns out a PT-symmetric non-Hermitian potential when one of the parameters (?,d) becomes imaginary. For the case of ??i?, we have an entire real bound state spectrum. Explicit scattering states are constructed to show reciprocity at certain discrete values of energy even though the potential is not parity symmetric. Coexistence of deep energy minima of transmissivity with the multiple spectral singularities (MSS) is observed. We further show that this potential becomes invisible from the left (or right) at certain discrete energies. The penetrating states in the other case (d?id) are always reciprocal even though it is PT-invariant and no spectral singularity (SS) is present in this case. The presence of MSS and reflectionlessness is also discussed for the free states in the later case. -- Highlights: •Existence of multiple spectral singularities (MSS) in PT-symmetric non-Hermitian system is shown. •Reciprocity is restored at discrete positive energies even for parity non-invariant complex system. •Co-existence of MSS with deep energy minima of transitivity is obtained. •Possibilities of both unidirectional and bidirectional invisibility are explored for a non-Hermitian system. •Penetrating states are shown to be reciprocal for all energies for PT-symmetric system.

Ghatak, Ananya, E-mail: gananya04@gmail.com [Department of Physics, Banaras Hindu University, Varanasi-221005 (India)] [Department of Physics, Banaras Hindu University, Varanasi-221005 (India); Mandal, Raka Dona Ray, E-mail: rakad.ray@gmail.com [Department of Physics, Rajghat Besant School, Varanasi-221001 (India); Mandal, Bhabani Prasad, E-mail: bhabani.mandal@gmail.com [Department of Physics, Banaras Hindu University, Varanasi-221005 (India)

2013-09-15

426

Supersymmetric Model of a Bose-Einstein Condensate in a 𝓟𝓣-Symmetric Double-delta Trap  

NASA Astrophysics Data System (ADS)

The most important properties of a Bose-Einstein condensate subject to balanced gain and loss can be modelled by a Gross-Pitaevskii equation with an external 𝓟𝓣-symmetric double-delta potential. We study its linear variant with a supersymmetric extension. It is shown that both in the 𝓟𝓣-symmetric as well as in the 𝓟𝓣-broken phase arbitrary stationary states can be removed in a supersymmetric partner potential without changing the energy eigenvalues of the other state. The characteristic structure of the singular delta potential in the supersymmetry formalism is discussed, and the applicability of the formalism to the nonlinear Gross-Pitaevskii equation is analysed. In the latter case the formalism could be used to remove 𝓟𝓣-broken states introducing an instability to the stationary 𝓟𝓣-symmetric states.

Abt, Nikolas; Cartarius, Holger; Wunner, Günter

2015-01-01

427

Three-Dimensional Structures of the Spatiotemporal Nonlinear Schrödinger Equation with Power-Law Nonlinearity in PT-Symmetric Potentials  

PubMed Central

The spatiotemporal nonlinear Schrödinger equation with power-law nonlinearity in -symmetric potentials is investigated, and two families of analytical three-dimensional spatiotemporal structure solutions are obtained. The stability of these solutions is tested by the linear stability analysis and the direct numerical simulation. Results indicate that solutions are stable below some thresholds for the imaginary part of -symmetric potentials in the self-focusing medium, while they are always unstable for all parameters in the self-defocusing medium. Moreover, some dynamical properties of these solutions are discussed, such as the phase switch, power and transverse power-flow density. The span of phase switch gradually enlarges with the decrease of the competing parameter k in -symmetric potentials. The power and power-flow density are all positive, which implies that the power flow and exchange from the gain toward the loss domains in the cell. PMID:24983624

Dai, Chao-Qing; Wang, Yan

2014-01-01

428

Linear or Nonlinear? Automatic Structure Discovery for Partially Linear Models  

PubMed Central

Partially linear models provide a useful class of tools for modeling complex data by naturally incorporating a combination of linear and nonlinear effects within one framework. One key question in partially linear models is the choice of model structure, that is, how to decide which covariates are linear and which are nonlinear. This is a fundamental, yet largely unsolved problem for partially linear models. In practice, one often assumes that the model structure is given or known and then makes estimation and inference based on that structure. Alternatively, there are two methods in common use for tackling the problem: hypotheses testing and visual screening based on the marginal fits. Both methods are quite useful in practice but have their drawbacks. First, it is difficult to construct a powerful procedure for testing multiple hypotheses of linear against nonlinear fits. Second, the screening procedure based on the scatterplots of individual covariate fits may provide an educated guess on the regression function form, but the procedure is ad hoc and lacks theoretical justifications. In this article, we propose a new approach to structure selection for partially linear models, called the LAND (Linear And Nonlinear Discoverer). The procedure is developed in an elegant mathematical framework and possesses desired theoretical and computational properties. Under certain regularity conditions, we show that the LAND estimator is able to identify the underlying true model structure correctly and at the same time estimate the multivariate regression function consistently. The convergence rate of the new estimator is established as well. We further propose an iterative algorithm to implement the procedure and illustrate its performance by simulated and real examples. Supplementary materials for this article are available online. PMID:22121305

Zhang, Hao Helen; Cheng, Guang; Liu, Yufeng

2011-01-01

429

PT-Symmetric Extension of the Korteweg-de Vries Equation  

E-print Network

The Korteweg-de Vries equation u_t+uu_x+u_{xxx}=0 is PT symmetric (invariant under space-time reflection). Therefore, it can be generalized and extended into the complex domain in such a way as to preserve the PT symmetry. The result is the family of complex nonlinear wave equations u_t-iu(i u_x)^epsilon+u_{xxx}=0, where epsilon is real. The features of these equations are discussed. Special attention is given to the epsilon=3 equation, for which conservation laws are derived and solitary waves are investigated.

Carl M. Bender; Dorje C. Brody; Junhua Chen; Elisabetta Furlan

2006-10-02

430

Scattering in PT-symmetric quantum mechanics  

SciTech Connect

A general formalism is worked out for the description of one-dimensional scattering in non-hermitian quantum mechanics and constraints on transmission and reflection coefficients are derived in the cases of P, T or PT invariance of the Hamiltonian. Applications to some solvable PT-symmetric potentials are shown in detail. Our main original results concern the association of reflectionless potentials with asymptotic exact PT symmetry and the peculiarities of separable kernels of non-local potentials in connection with Hermiticity, T invariance and PT invariance.

Cannata, Francesco [Istituto Nazionale di Fisica Nucleare, Sezione di Bologna and Dipartimento di Fisica dell' Universita, Via Irnerio 46, I 40126 Bologna (Italy)]. E-mail: Francesco.Cannata@bo.infn.it; Dedonder, Jean-Pierre [GMPIB Universite Paris 7 - Denis-Diderot, 2 Place Jussieu, F-75251, Paris Cedex 05 (France)]. E-mail: dedonder@paris7.jussieu.fr; Ventura, Alberto [Ente Nuove Tecnologie, Energia e Ambiente, Bologna and Istituto Nazionale di Fisica Nucleare, Sezione di Bologna (Italy)]. E-mail: Alberto.Ventura@bologna.enea.it

2007-02-15

431

Matter Collineations of Plane Symmetric Spacetimes  

E-print Network

This paper is devoted to the study of matter collineations of plane symmetric spacetimes (for a particular class of spacetimes) when the energy-momentum tensor is non-degenerate. There exists many interesting cases where we obtain proper matter collineations. The matter collineations in these cases are {\\it four}, \\emph{five}, {\\it six}, \\emph{seven} and {\\it ten} with some constraints on the energy-momentum tensor. We have solved some of these constraints to obtain solutions of the Einstein field equations.

M. Sharif; Nousheen Ilyas

2008-09-09

432

Quantum asymmetric cryptography with symmetric keys  

E-print Network

Based on quantum encryption, we present a new idea for quantum public-key cryptography (QPKC) and construct a whole theoretical framework of a QPKC system. We show that the quantum-mechanical nature renders it feasible and reasonable to use symmetric keys in such a scheme, which is quite different from that in conventional public-key cryptography. The security of our scheme is analyzed and some features are discussed. Furthermore, the state-estimation attack to a prior QPKC scheme is demonstrated.

Fei Gao; Qiao-Yan Wen; Su-Juan Qin; Fu-Chen Zhu

2008-10-16

433

Quantum exchange interaction of spherically symmetric plasmoids  

E-print Network

We study nano-sized spherically symmetric plasma structures which are radial nonlinear oscillations of electrons in plasma. The effective interaction of these plasmoids via quantum exchange forces between ions is described. We calculate the energy of this interaction for the realistic case of an atmospheric plasma. The conditions when the exchange interaction is attractive are examined and it is shown that separate plasmoids can form a single object. The application of our results to the theoretical description of stable atmospheric plasma structures is considered.

Dvornikov, Maxim

2011-01-01

434

Expanding symmetric multiprocessor capability through gang scheduling  

SciTech Connect

Symmetric Multiprocessor (SMP) systems normally provide both space- sharing and time-sharing to insure high system utilization and good responsiveness. However the prevailing lack of concurrent scheduling for parallel programs precludes SMP use in addressing many large-scale problems. Tightly synchronized communications are impractical and normal time-sharing reduces the benefit of cache memory. Evidence gathered at Lawrence Livermore National Laboratory (LLNL) indicates that gang scheduling can increase the capability of SMP systems and parallel program performance without adverse impact upon system utilization or responsiveness.

Jette, M.A.

1998-03-01

435

Geometrodynamics of spherically symmetric Lovelock gravity  

E-print Network

We derive the Hamiltonian for spherically symmetric Lovelock gravity using the geometrodynamics approach pioneered by Kucha\\v{r} in the context of four-dimensional general relativity. When written in terms of the areal radius, the generalized Misner-Sharp mass and their conjugate momenta, the generic Lovelock action and Hamiltonian take on precisely the same simple forms as in general relativity. This result supports the interpretation of Lovelock gravity as the natural higher-dimensional extension of general relativity. It also provides an important first step towards the study of the quantum mechanics, Hamiltonian thermodynamics and formation of generic Lovelock black holes.

Gabor Kunstatter; Tim Taves; Hideki Maeda

2012-03-24

436

Ballistic aggregation in symmetric and nonsymmetric flows  

SciTech Connect

We consider explicit solutions to the problem of ballistic aggregation of dustlike matter whose particles stick together absolutely inelastically upon collisions-a description of the formation of a large-scale structure in cosmology in terms of the adhesion model, which is a generalization of the Zel'dovich approximation. The two previously suggested different representations of the solutions for a plane-symmetric 1D flow are shown to be equivalent. Explicit representations of the solutions in cylindrical and spherical symmetries are constructed. We provide explicit examples showing that the two representations under consideration cannot be generalized to a multidimensional nonsymmetric flow.

Andrievsky, A. A. [Lomonosov Moscow State University (Russian Federation); Gurbatov, S. N. [Lobachevsky Nizhny Novgorod State University (Russian Federation); Sobolevsky, A. N. [Lomonosov Moscow State University (Russian Federation)], E-mail: sobolevski@phys.msu.ru

2007-06-15

437

PT-symmetric quantum state discrimination  

E-print Network

Suppose that a system is known to be in one of two quantum states, $|\\psi_1 > $ or $|\\psi_2 >$. If these states are not orthogonal, then in conventional quantum mechanics it is impossible with one measurement to determine with certainty which state the system is in. However, because a non-Hermitian PT-symmetric Hamiltonian determines the inner product that is appropriate for the Hilbert space of physical states, it is always possible to choose this inner product so that the two states $|\\psi_1 > $ and $|\\psi_2 > $ are orthogonal. Thus, quantum state discrimination can, in principle, be achieved with a single measurement.

Carl M. Bender; Dorje C. Brody; Joao Caldeira; Bernard K. Meister

2010-11-08

438

Microfabricated linear Paul-Straubel ion trap  

DOEpatents

An array of microfabricated linear Paul-Straubel ion traps can be used for mass spectrometric applications. Each ion trap comprises two parallel inner RF electrodes and two parallel outer DC control electrodes symmetric about a central trap axis and suspended over an opening in a substrate. Neighboring ion traps in the array can share a common outer DC control electrode. The ions confined transversely by an RF quadrupole electric field potential well on the ion trap axis. The array can trap a wide array of ions.

Mangan, Michael A. (Albuquerque, NM); Blain, Matthew G. (Albuquerque, NM); Tigges, Chris P. (Albuquerque, NM); Linker, Kevin L. (Albuquerque, NM)

2011-04-19

439

Analysis of New Step-up and Step-down Direct Symmetric 18-pulse Topologies for Aircraft Autotransformer-Rectifier Units  

Microsoft Academic Search

Among possible 18-pulse autotransformer-rectifier-unit (ATRU) topologies, direct symmetric circuit (DS-ATRU) demonstrates relatively low complexity, it is insensitive to impedance mismatch and distortions of input voltage and has low common mode voltage. This paper proposes new step-up and step-down direct symmetric 18-pulse ATRU topologies for aircraft application. Serious study of proposed topologies was performed. The authors analyzed the kVA ratings, effects

Alexander Uan-Zo-li; Rolando P. Burgos; F. Lacauz; Arman Roshan; Fred Wang; Dushan Boroyevich

2005-01-01

440

Complexity and shock wave geometries  

NASA Astrophysics Data System (ADS)

In this paper we refine a conjecture relating the time-dependent size of an Einstein-Rosen bridge (ERB) to the computational complexity of the dual quantum state. Our refinement states that the complexity is proportional to the spatial volume of the ERB. More precisely, up to an ambiguous numerical coefficient, we propose that the complexity is the regularized volume of the largest codimension one surface crossing the bridge, divided by GNlAdS . We test this conjecture against a wide variety of spherically symmetric shock wave geometries in different dimensions. We find detailed agreement.

Stanford, Douglas; Susskind, Leonard

2014-12-01

441

Not so Complex: Iteration in the Complex Plane  

ERIC Educational Resources Information Center

The simple process of iteration can produce complex and beautiful figures. In this article, Robin O'Dell presents a set of tasks requiring students to use the geometric interpretation of complex number multiplication to construct linear iteration rules. When the outputs are plotted in the complex plane, the graphs trace pleasing designs…

O'Dell, Robin S.

2014-01-01

442

Nonlinear coupling of tearing fluctuations in the Madison Symmetric Torus  

SciTech Connect

Three-wave, nonlinear, tearing mode coupling has been measured in the Madison Symmetric Torus (MST) reversed-field pinch (RFP) [Fusion Technol. 19, 131 (1991)] using bispectral analysis of edge magnetic fluctuations resolved in ``k-space. The strength of nonlinear three-wave interactions satisfying the sum rules m{sub 1} + m{sub 2} = m{sub 3} and n{sub 1} + n{sub 2} = n{sub 3} is measured by the bicoherency. In the RFP, m=l, n{approximately}2R/a (6 for MST) internally resonant modes are linearly unstable and grow to large amplitude. Large values of bicoherency occur for two m=l modes coupled to an m=2 mode and the coupling of intermediate toroidal modes, e.g., n=6 and 7 coupled to n=13. These experimental bispectral features agree with predicted bispectral features derived from MHD computation. However, in the experiment, enhanced coupling occurs in the ``crash`` phase of a sawtooth oscillation concomitant with a broadened mode spectrum suggesting the onset of a nonlinear cascade.

Sarff, J.S.; Almagri, A.F.; Cekic, M.; Den Hartog, D.J.; Fiksel, G.; Hokin, S.A.; Ji, H.; Prager, S.C.; Shen, W.; Stoneking, M.R. [Wisconsin Univ., Madison, WI (United States); Assadi, S. [Fermi National Accelerator Lab., Batavia, IL (United States); Sidikman, K.L. [Oak Ridge National Lab., TN (United States)

1992-11-01

443

Nonlinear coupling of tearing fluctuations in the Madison Symmetric Torus  

SciTech Connect

Three-wave, nonlinear, tearing mode coupling has been measured in the Madison Symmetric Torus (MST) reversed-field pinch (RFP) [Fusion Technol. 19, 131 (1991)] using bispectral analysis of edge magnetic fluctuations resolved in k-space. The strength of nonlinear three-wave interactions satisfying the sum rules m[sub 1] + m[sub 2] = m[sub 3] and n[sub 1] + n[sub 2] = n[sub 3] is measured by the bicoherency. In the RFP, m=l, n[approximately]2R/a (6 for MST) internally resonant modes are linearly unstable and grow to large amplitude. Large values of bicoherency occur for two m=l modes coupled to an m=2 mode and the coupling of intermediate toroidal modes, e.g., n=6 and 7 coupled to n=13. These experimental bispectral features agree with predicted bispectral features derived from MHD computation. However, in the experiment, enhanced coupling occurs in the crash'' phase of a sawtooth oscillation concomitant with a broadened mode spectrum suggesting the onset of a nonlinear cascade.

Sarff, J.S.; Almagri, A.F.; Cekic, M.; Den Hartog, D.J.; Fiksel, G.; Hokin, S.A.; Ji, H.; Prager, S.C.; Shen, W.; Stoneking, M.R. (Wisconsin Univ., Madison, WI (United States)); Assadi, S. (Fermi National Accelerator Lab., Batavia, IL (United States)); Sidikman, K.L. (Oak Ridge National Lab., TN (United States))

1992-11-01

444

Circularly symmetric distributed feedback semiconductor laser: An analysis  

SciTech Connect

We analyze the near-threshold behavior of a circularly symmetric distributed feedback laser by developing a coupled-mode theory analysis for all azimuthal modes. We show that the equations that describe the low-order azimuthal modes are, to a very good approximation, the same as those for the one-dimensional (linear) distributed feedback laser. We examine the behavior of higher-order azimuthal modes by numerically solving the exact coupled-mode equations. We find that while a significant amount of mode discrimination exists among radial (longitudinal) modes, as in the one-dimensional distributed feedback laser, there is a much smaller degree of discrimination among azimuthal modes, indicating probability of multimode operation. Despite the multimode behavior, we find that the frequency bandwidth associated with modes that do lase ought to be smaller than the spacing between Fabry-Perot modes of a typical semiconductor laser. This laser is an excellent candidate for a surface-emitting laser---it should have a superb quality output beam and is well-suited for array operation.

Erdogan, T.; Hall, D.G. (The Institute of Optics, University of Rochester, Rochester, New York 14627 (USA))

1990-08-15

445

Circularly symmetric distributed feedback semiconductor laser: An analysis  

SciTech Connect

We analyze the near-threshold behavior of a circularly symmetric distributed feedback laser by developing a coupled-mode theory analysis for all azimuthal modes. We show that the equations that describes the low-order azimuthal modes are, to a very good approximation, the same as those for the one-dimensional (linear) distributed feedback laser. We examine the behavior of higher-order azimuthal modes by numerically solving the exact coupled-mode equations. We find that while a significant amount of mode discrimination exists among radial (longitudinal) modes, as in the one-dimensional distributed feedback laser, there is a much smaller degree of discrimination among azimuthal modes, indicating probability of multimode operation. Despite the multimode behavior, we find the frequency bandwidth associated with modes that do lase ought to be smaller than the spacing between Fabry-Perot modes of a typical semiconductor laser. This laser is an excellent candidate for a surface-emitting laser-it should have a superb quality output beam and is well-suited for array operation.

Erdogan, T.; Hall, D.G.

1990-08-15

446

Analysis of non-symmetrical flapping airfoils  

NASA Astrophysics Data System (ADS)

Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. By using non-symmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.61, respectively. The lift production is highly dependent on the airfoil’s shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interactions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better ornithopter’s wing.

Tay, W. B.; Lim, K. B.

2009-08-01

447

Spectral singularities and Bragg scattering in complex crystals  

SciTech Connect

Spectral singularities that spoil the completeness of Bloch-Floquet states may occur in non-Hermitian Hamiltonians with complex periodic potentials. Here an equivalence is established between spectral singularities in complex crystals and secularities that arise in Bragg diffraction patterns. Signatures of spectral singularities in a scattering process with wave packets are elucidated for a PT-symmetric complex crystal.

Longhi, S. [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)

2010-02-15

448

Second order symmetric duality for nonlinear minimax mixed integer programs  

Microsoft Academic Search

Wolfe type second order minimax mixed integer dual programs are formulated and a symmetric duality theorem is e established under separability and bonvexity\\/boncavity of the kernel function K(x, y). Mond-Weir type symmetric duality is also discussed under weaker bonvexity assumptions. Moreover, self-duality theorems for these pairs are obtained assuming K(x, y) to be skew symmetric.

T. R. Gulati; Izhar Ahmad

1997-01-01

449

Operational multipartite entanglement classes for symmetric photonic qubit states  

SciTech Connect

We present experimental schemes that allow us to study the entanglement classes of all symmetric states in multiqubit photonic systems. We compare the efficiency of the proposed schemes and highlight the relation between the entanglement properties of symmetric Dicke states and a recently proposed entanglement scheme for atoms. In analogy to the latter, we obtain a one-to-one correspondence between well-defined sets of experimental parameters and multiqubit entanglement classes inside the symmetric subspace of the photonic system.

Kiesel, N.; Wieczorek, W.; Weinfurter, H. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet, D-80797 Garching (Germany); Krins, S.; Bastin, T. [Institut de Physique Nucleaire, Atomique et de Spectroscopie, Universite de Liege, 4000 Liege (Belgium); Solano, E. [Departamento de Quimica Fisica, Universidad del Pais Vasco/Euskal Herriko Unibertsitatea, Apdo. 644, 48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science, Alameda Urquijo 36, 48011 Bilbao (Spain)

2010-03-15

450

From PT-symmetric quantum mechanics to conformal field theory  

E-print Network

One of the simplest examples of a PT-symmetric quantum system is the scaling Yang-Lee model, a quantum field theory with cubic interaction and purely imaginary coupling. We give a historical review of some facts about this model in d PT-symmetric quantum mechanics. We also discuss some more general results on PT-symmetric quantum mechanics and the ODE/IM correspondence, and mention applications to magnetic systems and cold atom physics.

Patrick Dorey; Clare Dunning; Roberto Tateo

2009-06-05

451

Linear Back-Drive Differentials  

NASA Technical Reports Server (NTRS)

Linear back-drive differentials have been proposed as alternatives to conventional gear differentials for applications in which there is only limited rotational motion (e.g., oscillation). The finite nature of the rotation makes it possible to optimize a linear back-drive differential in ways that would not be possible for gear differentials or other differentials that are required to be capable of unlimited rotation. As a result, relative to gear differentials, linear back-drive differentials could be more compact and less massive, could contain fewer complex parts, and could be less sensitive to variations in the viscosities of lubricants. Linear back-drive differentials would operate according to established principles of power ball screws and linear-motion drives, but would utilize these principles in an innovative way. One major characteristic of such mechanisms that would be exploited in linear back-drive differentials is the possibility of designing them to drive or back-drive with similar efficiency and energy input: in other words, such a mechanism can be designed so that a rotating screw can drive a nut linearly or the linear motion of the nut can cause the screw to rotate. A linear back-drive differential (see figure) would include two collinear shafts connected to two parts that are intended to engage in limited opposing rotations. The linear back-drive differential would also include a nut that would be free to translate along its axis but not to rotate. The inner surface of the nut would be right-hand threaded at one end and left-hand threaded at the opposite end to engage corresponding right- and left-handed threads on the shafts. A rotation and torque introduced into the system via one shaft would drive the nut in linear motion. The nut, in turn, would back-drive the other shaft, creating a reaction torque. Balls would reduce friction, making it possible for the shaft/nut coupling on each side to operate with 90 percent efficiency.

Waydo, Peter

2003-01-01

452

Concrete Representation and Separability Criteria for Symmetric Quantum State  

NASA Astrophysics Data System (ADS)

Using the typical generators of the special unitary groups S U(2), the concrete representation of symmetric quantum state is established, then the relations satisfied by those coefficients in the representation are presented. Based on the representation of density matrix, the PPT criterion and CCNR criterion are proved to be equivalent on judging the separability of symmetric quantum states. Moreover, it is showed that the matrix ? ? of symmetric quantum state only has five efficient entries, thus the calculation of ?? ? ? is simplified. Finally, the quantitative expressions of real symmetric quantum state under the ?? ? ? separability criterion are obtained.

Li, Chang'e.; Tao, Yuanhong; Zhang, Jun; Li, Linsong; Nan, Hua

2014-09-01

453

PT-symmetric Models with O(N) Symmetry  

E-print Network

We construct PT-symmetric quantum mechanical models with an O(N)-symmetric interaction term of the form $-g(\\vec{x}^{2})^{2}/N$. Using functional integral methods, we find the equivalent Hermitian model, which has several unusual features. The effective potential obtained in the large-N limit of the Hermitian form is shown to be identical to the form obtained from the original PT-symmetric model using familiar constraint field methods. The analogous constraint field prescription in four dimensions suggests that $-g(\\vec{\\phi}^{2})^{2}/N$ PT-symmetric scalar field theories are asymptotically free.

Peter N. Meisinger; Michael C. Ogilvie

2007-07-11

454

A linear quadratic regulator approach to the stabilization of uncertain linear systems  

NASA Technical Reports Server (NTRS)

This paper presents a linear quadratic regulator approach to the stabilization of uncertain linear systems. The uncertain systems under consideration are described by state equations with the presence of time-varying unknown-but-bounded uncertainty matrices. The method is based on linear quadratic regulator (LQR) theory and Liapunov stability theory. The robust stabilizing control law for a given uncertain system can be easily constructed from the symmetric positive-definite solution of the associated augmented Riccati equation. The proposed approach can be applied to matched and/or mismatched systems with uncertainty matrices in which only their matrix norms are bounded by some prescribed values and/or their entries are bounded by some prescribed constraint sets. Several numerical examples are presented to illustrate the results.

Shieh, L. S.; Sunkel, J. W.; Wang, Y. J.

1990-01-01

455

The inequality between mass and angular momentum for axially symmetric black holes  

E-print Network

In this essay I first discuss the physical relevance of the inequality $m\\geq \\sqrt{|J|}$ for axially symmetric (non-stationary) black holes, where m is the mass and J the angular momentum of the spacetime. Then, I present a proof of this inequality for the case of one spinning black hole. The proof involves a remarkable characterization of the extreme Kerr black hole as an absolute minimum of the total mass. Finally, I conjecture on the physical implications of this characterization for the non linear stability problem for black holes.

Sergio Dain

2007-07-20

456

Local obstructions to projective surfaces admitting skew-symmetric Ricci tensor  

NASA Astrophysics Data System (ADS)

The equation determining whether a projective structure admits a connection in its given projective class that has skew-symmetric Ricci tensor is an overdetermined system of semi-linear partial differential equations which we call the projective Einstein-Weyl (pEW) equation. In 2-dimensions, we give local obstructions for projective surfaces to admit such a connection in its projective class. The obstructions are the resultants of polynomial equations that have to be satisfied for there to admit any pEW solution.

Randall, Matthew

2014-02-01

457

Rotational excitation of symmetric top molecules by collisions with atoms. II - Infinite order sudden approximation  

NASA Technical Reports Server (NTRS)

The infinite order sudden (IOS) approximation is extended to rotational excitation of symmetric tops by collisions with atoms. After development of a formalism for 'primitive' or 'one-ended' tops, proper parity-adapted linear combinations describing real rotors are considered and modifications needed for asymmetric rigid rotors are noted. The generalized spectroscopic relaxation cross sections are discussed. IOS calculations for NH3-He and H2CO-He are performed and compared with more accurate calculations, and the IOS approximation is found to provide a reasonably accurate description.

Green, S.

1979-01-01

458

Elementary symmetric functions of two solvents of a quadratic matrix equation  

E-print Network

Quadratic matrix equations occur in a variety of applications. In this paper we introduce new permutationally invariant functions of two solvents of the n quadratic matrix equation X^2- L1X - L0 = 0, playing the role of the two elementary symmetric functions of the two roots of a quadratic scalar equation. Our results rely on the connection existing between the QME and the theory of linear second order difference equations with noncommutative coefficients. An application of our results to a simple physical problem is briefly discussed.

M. A. Jivulescu; A. Napoli; A. Messina

2008-04-18

459

Polymer-coated symmetrical metal-cladding waveguide for chemical vapor detection with high sensitivity  

NASA Astrophysics Data System (ADS)

An optical platform for sensitive detection of chemical vapor based on a polymer-coated symmetrical metal-cladding waveguide is proposed. The diffusion of chemical vapor usually leads to a combinational effect in the polymer layer, i.e., swelling and refractive index change. Owing to the high sensitivity of ultrahigh-order modes, the vapor-induced effect will give rise to a dramatic variation of the reflected light intensity. For proof-of-concept, a good linearity and a low detection limit of toluene and benzene are experimentally demonstrated with an amorphous Teflon AF polymer layer.

Xiao, PingPing; Deng, ManLan

2012-11-01

460

Fast axis servo for the fast and precise machining of non-rotational symmetric optics  

NASA Astrophysics Data System (ADS)

A new long range tool servo-fast axis servo is developed, which is used for fabricating the non-rotational symmetric optics surface with millimeters' sag. The mechanism design, motion modeling and development of FAS device were studied. The FAS consists of a linear motor, aerostatic bearings, high-resolution encoder and a motion controller. A control strategy consists of a proportional, integral and derivative (PID) feedback controller and velocity/acceleration feedforward controller is implemented to accommodate the system control performance. Experimental tests have been carried out to verify the performance of the FAS system.

Tian, Fujing; Yin, Ziqiang; Li, Shengyi

2014-08-01

461

Symmetric instability in the Gulf Stream  

NASA Astrophysics Data System (ADS)

Analyses of wintertime surveys of the Gulf Stream (GS) conducted as part of the CLIvar MOde water Dynamic Experiment (CLIMODE) reveal that water with negative potential vorticity (PV) is commonly found within the surface boundary layer (SBL) of the current. The lowest values of PV are found within the North Wall of the GS on the isopycnal layer occupied by Eighteen Degree Water, suggesting that processes within the GS may contribute to the formation of this low-PV water mass. In spite of large heat loss, the generation of negative PV was primarily attributable to cross-front advection of dense water over light by Ekman flow driven by winds with a down-front component. Beneath a critical depth, the SBL was stably stratified yet the PV remained negative due to the strong baroclinicity of the current, suggesting that the flow was symmetrically unstable. A large eddy simulation configured with forcing and flow parameters based on the observations confirms that the observed structure of the SBL is consistent with the dynamics of symmetric instability (SI) forced by wind and surface cooling. The simulation shows that both strong turbulence and vertical gradients in density, momentum, and tracers coexist in the SBL of symmetrically unstable fronts. SI is a shear instability that draws its energy from geostrophic flows. A parameterization for the rate of kinetic energy (KE) extraction by SI applied to the observations suggests that SI could result in a net dissipation of 33 mW m-2 and 1 mW m-2 for surveys with strong and weak fronts, respectively. The surveys also showed signs of baroclinic instability (BCI) in the SBL, namely thermally direct vertical circulations that advect biomass and PV. The vertical circulation was inferred using the omega equation and used to estimate the rate of release of available potential energy (APE) by BCI. The rate of APE release was found to be comparable in magnitude to the net dissipation associated with SI. This result points to an energy pathway where the GS's reservoir of APE is drained by BCI, converted to KE, and then dissipated by SI and its secondary instabilities. Similar dynamics are likely to be found at other strong fronts forced by winds and/or cooling and could play an important role in the energy balance of the ocean circulation.

Thomas, Leif N.; Taylor, John R.; Ferrari, Raffaele; Joyce, Terrence M.

2013-07-01

462

Origin of maximal symmetry breaking in even PT-symmetric lattices  

SciTech Connect

By investigating a parity- and time-reversal- (PT-) symmetric, N-site lattice with impurities {+-}i{gamma} and hopping amplitudes t{sub 0} (t{sub b}) for regions outside (between) the impurity locations, we probe the interimpurity-distance dependence of the critical impurity strength and the origin of maximal PT-symmetry breaking that occurs when the impurities are nearest neighbors. Through a simple and exact derivation, we prove that the critical impurity strength is equal to the hopping amplitude between the impurities, {gamma}{sub c}=t{sub b}, and the simultaneous emergence of N complex eigenvalues is a robust feature of any PT-symmetric hopping profile. Our results show that the threshold strength {gamma}{sub c} can be widely tuned by a small change in the global profile of the lattice and thus have experimental implications.

Joglekar, Yogesh N.; Barnett, Jacob L. [Department of Physics, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, Indiana 46202 (United States)

2011-08-15

463

PT-symmetric coupler with a coupling defect: soliton interaction with exceptional point.  

PubMed

We study the interaction of a soliton in a parity-time (PT) symmetric coupler which has local perturbation of the coupling constant. This defect does not change the PT-symmetry of the system, but locally can achieve the exceptional point. We found that the symmetric solitons after interaction with the defect either transform into breathers or blow up. The dynamics of antisymmetric solitons are more complex, showing domains of successive broadening of the beam and of the beam splitting in two outward propagating solitons, in addition to the single breather generation and blowup. All the effects are preserved when the coupling strength in the center of the defect deviates from the exceptional point. If the coupling is strong enough, the only observable outcome of the soliton-defect interaction is the generation of the breather. PMID:24978491

Bludov, Yuli V; Hang, Chao; Huang, Guoxiang; Konotop, Vladimir V

2014-06-15

464

Generalized unitarity and reciprocity relations for PT-symmetric scattering potentials  

NASA Astrophysics Data System (ADS)

We derive certain identities satisfied by the left/right-reflection and transmission amplitudes, {{R}l/r}(k) and T(k), of general PT-symmetric scattering potentials. We use these identities to give a general proof of the relations, |T(-k)|=|T(k)| and |{{R}r}(-k)|=|{{R}l}(k)|, conjectured in Ahmed (2012 J. Phys. A: Math. Theor. 45 032004), and the generalized unitarity relation: {{R}l/r}(k){{R}l/r}(-k)+|T(k){{|}2}=1, and show that it is a common property of both real and complex PT-symmetric potentials. The same holds for T(-k)=T{{(k)}*} and |{{R}r}(-k)|=|{{R}l}(k)|.

Mostafazadeh, Ali

2014-12-01

465

Symmetric exchange of multi-protein building blocks between stationary focal adhesions and the cytosol  

PubMed Central

How can the integrin adhesome get self-assembled locally, rapidly, and correctly as diverse cell-matrix adhesion sites? Here, we investigate this question by exploring the cytosolic state of integrin-adhesome components and their dynamic exchange between adhesion sites and cytosol. Using fluorescence cross-correlation spectroscopy (FCCS) and fluorescence recovery after photobleaching (FRAP) we found that the integrin adhesome is extensively pre-assembled already in the cytosol as multi-protein building blocks for adhesion sites. Stationary focal adhesions release symmetrically the same types of protein complexes that they recruit, thereby keeping the cytosolic pool of building blocks spatiotemporally uniform. We conclude a model in which multi-protein building blocks enable rapid and modular self-assembly of adhesion sites and symmetric exchange of these building blocks preserves their specifications and thus the assembly logic of the system. DOI: http://dx.doi.org/10.7554/eLife.02257.001 PMID:24894463

Hoffmann, Jan-Erik; Fermin, Yessica; Stricker, Ruth LO; Ickstadt, Katja; Zamir, Eli

2014-01-01

466

Solution for Static, Spherically Symmetric Lovelock Gravity Coupled with Yang-Mills Hierarchy  

E-print Network

The hierarchies of both Lovelock gravity and power-Yang-Mills field are combined through gravity in a single theory. In static, spherically symmetric ansatz exact particular integrals are obtained in all higher dimensions. The advantage of such hierarchies is the possibility of choosing coefficients, which are arbitrary otherwise, to cast solutions into tractable forms. To our knowledge the solutions constitute the most general spherically symmetric metrics that incorporate complexities both of Lovelock and Yang-Mills hierarchies within the common context. A large portion of our general class of solutions concern and addresses to black holes for which specific examples are given. Thermodynamical behaviors of the system is briefly discussed in particular dimensions.

S. Habib Mazharimousavi; M. Halilsoy

2010-09-15

467

Symmetry matters: photodissociation dynamics of symmetrically versus asymmetrically substituted phenols.  

PubMed

We report a combined experimental (H (Rydberg) atom photofragment translational spectroscopy) and theoretical (ab initio electronic structure and vibronic coupling calculations) study of the effects of symmetry on the photodissociation dynamics of phenols. Ultraviolet photoexcitation to the bound S1((1)??*) state of many phenols leads to some O-H bond fission by tunneling through the barrier under the conical intersection (CI) between the S1 and dissociative S2((1)??*) potential energy surfaces in the R(O-H) stretch coordinate. Careful analysis of the total kinetic energy release spectra of the resulting products shows that the radicals formed following S1 ? S0 excitation of phenol and symmetrically substituted phenols like 4-fluorophenol all carry an odd number of quanta in vibrational mode ?(16a), whereas those deriving from asymmetrically substituted systems like 3-fluorophenol or 4-methoxyphenol do not. This contrasting behavior can be traced back to symmetry. Symmetrically substituted phenols exist in two equivalent rotamers, which interconvert by tunneling through the barrier to OH torsional motion. Their states are thus best considered in the non-rigid G4 molecular symmetry group, wherein radiationless transfer from the S1 to S2 state requires a coupling mode of a2 symmetry. Of the three a2 symmetry parent modes, the out-of-plane ring puckering mode ?(16a) shows much the largest interstate coupling constant in the vicinity of the S1/S2 CI. The nuclear motions associated with ?(16a) are orthogonal to the dissociation coordinate, and are thus retained in the radical products. Introducing asymmetry (even a non-linear substituent in the 4-position) lifts the degeneracy of the rotamers, and lowers the molecular symmetry to Cs. Many more parent motions satisfy the reduced (a'') symmetry requirement to enable S1/S2 coupling, the most effective of which is OH torsion. This motion 'disappears' on O-H bond fission; symmetry thus imposes no restriction to forming radical products with vibrational quantum number v = 0. The present work yields values for the O-H bond strengths in 3-FPhOH and 4-MeOPhOH, and recommends modest revisions to the previously reported O-H bond strengths in other asymmetrically substituted phenols like 3- and 2-methylphenol and 4-hydroxyindole. PMID:24201655