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1

Can Gravity Probe B usefully constrain torsion gravity theories?  

SciTech Connect

In most theories of gravity involving torsion, the source for torsion is the intrinsic spin of matter. Since the spins of fermions are normally randomly oriented in macroscopic bodies, the amount of torsion generated by macroscopic bodies is normally negligible. However, in a recent paper, Mao et al. (arXiv:gr-qc/0608121) point out that there is a class of theories, including the Hayashi-Shirafuji (1979) theory, in which the angular momentum of macroscopic spinning bodies generates a significant amount of torsion. They further argue that, by the principle of action equals reaction, one would expect the angular momentum of test bodies to couple to a background torsion field, and therefore the precession of the Gravity Probe B gyroscopes should be affected in these theories by the torsion generated by the Earth. We show that in fact the principle of action equals reaction does not apply to these theories, essentially because the torsion is not an independent dynamical degree of freedom. We examine in detail a generalization of the Hayashi-Shirafuji theory suggested by Mao et al. called Einstein-Hayashi-Shirafuji theory. There are a variety of different versions of this theory, depending on the precise form of the coupling to matter chosen for the torsion. We show that, for any coupling to matter that is compatible with the spin transport equation postulated by Mao et al., the theory has either ghosts or an ill-posed initial-value formulation. These theoretical problems can be avoided by specializing the parameters of the theory and in addition choosing the standard minimal coupling to matter of the torsion tensor. This yields a consistent theory, but one in which the action equals reaction principle is violated, and in which the angular momentum of the gyroscopes does not couple to the Earth's torsion field. Thus, the Einstein-Hayashi-Shirafuji theory does not predict a detectable torsion signal for Gravity Probe B. There may be other torsion theories which do.

Flanagan, Eanna E.; Rosenthal, Eran [Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, 14853 (United States)

2007-06-15

2

Reidemeister torsion in knot theory  

Microsoft Academic Search

CONTENTS Introduction § 0. Preliminary material § 1. Milnor torsion and the Alexander polynomial § 2. Proof of Theorems 1.1.1, 1.1.2, and 1.1.3 § 3. Refined torsion and the refined Alexander function § 4. The Conway link function § 5. The torsion omega and the polynomial delta § 6. Proof of Theorem 5.1.1 Appendix. Duality theorems for torsions References

V. G. Turaev

1986-01-01

3

Reidemeister torsion in knot theory  

NASA Astrophysics Data System (ADS)

CONTENTS Introduction § 0. Preliminary material § 1. Milnor torsion and the Alexander polynomial § 2. Proof of Theorems 1.1.1, 1.1.2, and 1.1.3 § 3. Refined torsion and the refined Alexander function § 4. The Conway link function § 5. The torsion ? and the polynomial ? § 6. Proof of Theorem 5.1.1 Appendix. Duality theorems for torsions References

Turaev, V. G.

1986-02-01

4

Reidemeister torsion in knot theory  

Microsoft Academic Search

CONTENTS Introduction § 0. Preliminary material § 1. Milnor torsion and the Alexander polynomial § 2. Proof of Theorems 1.1.1, 1.1.2, and 1.1.3 § 3. Refined torsion and the refined Alexander function § 4. The Conway link function § 5. The torsion ? and the polynomial ? § 6. Proof of Theorem 5.1.1 Appendix. Duality theorems for torsions References

V G Turaev

1986-01-01

5

New constraints in dynamical torsion theory  

SciTech Connect

The most general Lagrangian for dynamical torsion theory quadratic in curvature and torsion is considered. The authors impose two simple and physically reasonable constraints on the solution of the equations of motion (i) there must be solutions with zero curvature and nontrivial torsion and (ii) there must be solutions with torsion and non covariantly constant curvature. The constraints reduce the number of independent coupling constants from ten to five. The resulting theory contains Einstein's general relativity and Weitzenboeck's absolute parallelism theory as the two sectors. 32 refs.

Katanaev, M.O. (Steklov Mathematical Inst., Moscow (Russian Federation))

1993-04-01

6

35. VERTICAL AND TORSIONAL MOTION FROM EAST TOWER SHOWING ANGULAR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

35. VERTICAL AND TORSIONAL MOTION FROM EAST TOWER SHOWING ANGULAR DISTORTION APPROACHING 45 DEGREES WITH LAMP POSTS APPEARING TO BE AT EIGHT ANGLES, 7 NOVEMBER 1940, FROM 16MN FILM SHOT BY PROFESSOR F.B. FARQUHARSON, UNIVERSITY OF WASHINGTON. (LABORATORY STUDIES ON THE TACOMA NARROWS BRIDGE, AT UNIVERSITY OF WASHINGTON SEATTLE: UNIVERSITY OF WASHINGTON, DEPARTMENT OF CIVIL ENGINEERING, 1941) - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA

7

Quantum theory of angular momentum  

SciTech Connect

Containing basic definitions and theorems as well as relations, tables of formulas and numerical tables which are essential for applications to many physical problems, the book is useful for specialists in nuclear and particle physics, atomic and molecular spectroscopy, plasma physics, collision and reaction theory, quantum chemistry, etc. The authors write many formulas in different coordinate systems. Each chapter opens with a list of its contents. New results relating to different aspects of the angular momentum theory are included. This book gathers together many useful formulas besides those related to angular momentum, and compares different notations used by previous authors.

Varshalovich, D.A.; Moskalev, A.N.; Khersonskii, V.K.

1987-01-01

8

Linearized Torsion Waves in a Tensor-Tensor Theory of Gravity  

Microsoft Academic Search

We investigate a linearized tensor-tensor theory of gravity with torsion and a perturbed torsion wave solution is discovered in background Minkowski spacetime with zero torsion. Furthermore, gauge transformations of any perturbed tensor field are derived in general background non-Riemannian geometries. By calculating autoparallel deviations, both longitudinal and transverse polarizations of the torsion wave are discovered.

Chih-Hung Wang

2007-01-01

9

Metric theory of gravity with torsion in an extra dimension  

NASA Astrophysics Data System (ADS)

We consider a theory of gravity with a hidden extra dimension and metric-dependent torsion. A set of physically motivated constraints are imposed on the geometry so that the torsion stays confined to the extra dimension and the extra dimension stays hidden at the level of four-dimensional geodesic motion. At the kinematic level, the theory maps onto general relativity, but the dynamical field equations that follow from the action principle deviate markedly from the standard Einstein equations. We study static spherically symmetric vacuum solutions and homogeneous-isotropic cosmological solutions that emerge from the field equations. In both cases, we find solutions of significant physical interest. Most notably, we find positive mass solutions with naked singularity that match the well-known Schwarzschild solution at large distances but lack an event horizon. In the cosmological context, we find an oscillatory scenario, in contrast to the inevitable singular big bang of the standard cosmology.

Shankar, Karthik H.; Balaraman, Anand; Wali, Kameshwar C.

2012-07-01

10

Nonlocal Potentials and Complex Angular Momentum Theory  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to establish meromorphy properties of the partial scattering amplitude T(lambda,k) associated with physically relevant classes N_{w,alpha}^gamma of nonlocal potentials in corresponding domains D_{gamma,alpha}^delta of the space C^2 of the complex angular momentum lambda and of the complex momentum k (namely, the square root of the energy). The general expression of T as a quotient Theta(lambda,k)/sigma(lambda,k) of two holomorphic functions in D_{gamma,alpha}^delta is obtained by using the Fredholm-Smithies theory for complex k, at first for lambda=l integer, and in a second step for lambda complex (Real(lambda)>-1/2). Finally, we justify the "Watson resummation" of the partial wave amplitudes in an angular sector of the lambda-plane in terms of the various components of the polar manifold of T with equation sigma(lambda,k)=0. While integrating the basic Regge notion of interpolation of resonances in the upper half-plane of lambda, this unified representation of the singularities of T also provides an attractive possible description of antiresonances in the lower half-plane of lambda. Such a possibility, which is forbidden in the usual theory of local potentials, represents an enriching alternative to the standard Breit-Wigner hard-sphere picture of antiresonances.

Bros, Jacques; de Micheli, Enrico; Viano, Giovanni Alberto

2010-07-01

11

Constraining torsion with Gravity Probe B  

SciTech Connect

It is well-entrenched folklore that all torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally, and consider nonstandard torsion theories in which torsion can be generated by macroscopic rotating objects. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope would be expected to feel torsion. An experiment with a gyroscope (without nuclear spin) such as Gravity Probe B (GPB) can test theories where this is the case. Using symmetry arguments, we show that to lowest order, any torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the parametrized post-Newtonian formalism and provide a concrete framework for further testing Einstein's general theory of relativity (GR). We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B is an ideal experiment for further constraining nonstandard torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters.

Mao Yi; Guth, Alan H.; Cabi, Serkan [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Tegmark, Max [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); MIT Kavli Institute for Astrophysics and Space Research, Cambridge, Massachusetts 02139 (United States)

2007-11-15

12

THEORIES FOR ANGULAR DISTRIBUTIONS IN LOW ENERGY NUCLEAR REACTIONS  

Microsoft Academic Search

A series of six lectures presented at the Lawrence Radiation Laboratory ; on angular distributions in nuclear reactions are given. Topics covered include ; a survey of reaction mechanisms, Born approximation for direct interaction ; theory, semiclassical approximation for direct interaction, distorted wave ; analysis and direct surface interactions, the general theory of angular ; correlation, and interpretation of inelastic

S. A. Moszkowski; J. Benveniste; E. H. eds. Schwarcz

1962-01-01

13

Bianchi Identities and the Automatic Conservation of Energy-Momentum and Angular Momentum in General-Relativistic Field Theories  

NASA Astrophysics Data System (ADS)

Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if the conservation laws for the material currents are reduced to the contracted Bianchi identities. The authors first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, they determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model.

Hehl, Friedrich W.; Dermott McCrea, J.

14

de Sitter spacetimes with torsion in the model of de Sitter gauge theory of gravity  

SciTech Connect

In the model of the de Sitter gauge theory of gravity, the empty homogenous and isotropic spacetimes with constant curvature scalar and nonvanishing homogenous and isotropic torsion must have de Sitter metrics. The static de Sitter spacetime with static, O(3)-symmetric, vector torsion is the only spherically symmetric, vacuum solution with the metric of the form g{sub {mu}}{sub {nu}}=diag(A{sup 2}(r),-B{sup 2}(r),-r{sup 2},-r{sup 2}sin{sup 2}{theta}). The expressions of the torsion for different de Sitter spacetimes are presented. They are different from one to another. The properties of different de Sitter spacetimes with torsion are also studied.

Huang Chaoguang [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing 100049 (China); Ma Mengsen [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing 100049 (China); Graduate School of Chinese Academy of Sciences, Beijing, 100049 (China)

2009-10-15

15

Equations of motion in gravity theories with nonminimal coupling: A loophole to detect torsion macroscopically?  

NASA Astrophysics Data System (ADS)

We derive multipolar equations of motion for gravitational theories with general nonminimal coupling in spacetimes admitting torsion. Our very general findings allow for the systematic testing of whole classes of theories by means of extended test bodies. One peculiar feature of certain subclasses of nonminimal theories turns out to be their sensitivity to post-Riemannian spacetime structures even in experiments without microstructured test matter.

Puetzfeld, Dirk; Obukhov, Yuri N.

2013-09-01

16

Renormalization of a quantum field theory model in a curved space-time with torsion  

SciTech Connect

The authors consider a quantum field theory model that contains interacting non-Abelian gauge fields, scalar fields, and spinor fields in a curved space-time with torsion. The one-loop counterterms are found. It is shown that the multiplicative renormalization condition requires a nonminimal coupling of the matter with the gravitational field.

Bukhbinder, I.L.; Shapiro, I.L.

1986-02-01

17

Bianchi identities and the automatic conservation of energy-momentum and angular momentum in general-relativistic field theories  

NASA Astrophysics Data System (ADS)

Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if, via the field equations, the conservation laws for the material currents are reduced to the contracted Bianchi identities. We first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, we determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model. The Poincaré gauge theory of gravity, like gauge theories of internal groups, has no automatic conservation in the sense defined above. This does not lead to any difficulties in principle. Analogies to 3-dimensional continuum mechanics are stressed throughout the article.

Hehl, Friedrich W.; McCrea, J. Dermott

1986-03-01

18

Angular momentum theory applied to interactions in solids  

NASA Astrophysics Data System (ADS)

Concepts of group theory applied to the spectra of impurity ions in crystals are discussed. Beginning with the simple hydrogen atom, spectroscopic notation and angular momentum operators are discussed. This is followed by a general discussion of angular momentum theory including Clebsch Gordon coefficients, the Wigner Eckart theorem, unit spherical tensors, and Racah coefficients. The extension of these techniques to the electronic configuration, (nl to the Nth power), for N equivalent electrons is discussed. The theory of point groups as applied to ions in solids is introduced, along with the use of the International Tables of Crystallography and character tables. The phenomenological theory of crystal fields is discussed in some detail along with the so-called free ion parameters characterizing the Coulomb interaction, the spin-orbit interaction, and the interconfiguration interaction. The use of tables of 3-j and 6-j symbols in the calculation of the matrix elements of the various interactions is presented, along with other tables and aids in the computation of the energy levels. The point ion model of crystal-field interaction is discussed with particular emphasis on the work done at the Harry Diamond Laboratories (HDL) on its development. The earlier work at HDL was applied to triply ionized rare earth ions (l to the Nth power electronic configuration), and the preliminary extensions presently being undertaken at HDL are applied to the transit.

Morrison, Clyde A.

1987-02-01

19

Gyrokinetic theory and simulation of angular momentum transport  

SciTech Connect

A gyrokinetic theory of turbulent toroidal angular momentum transport as well as modifications to neoclassical poloidal rotation from turbulence is formulated starting from the fundamental six-dimensional kinetic equation. The gyro-Bohm scaled transport is evaluated from toroidal delta-f gyrokinetic simulations using the GYRO code [Candy and Waltz, J. Comput. Phys. 186, 545 (2003)]. The simulations recover two pinch mechanisms in the radial transport of toroidal angular momentum: The slab geometry ExB shear pinch [Dominguez and Staebler, Phys. Fluids B 5, 387 (1993)] and the toroidal geometry 'Coriolis' pinch [Peeters, Angioni, and Strintzi, Phys. Rev. Lett. 98, 265003 (2007)]. The pinches allow the steady state null stress (or angular momentum transport flow) condition required to understand intrinsic (or spontaneous) toroidal rotation in heated tokamak without an internal source of torque [Staebler, Kinsey, and Waltz, Bull. Am. Phys. Soc. 46, 221 (2001)]. A predicted turbulent shift in the neoclassical poloidal rotation [Staebler, Phys. Plasmas 11, 1064 (2004)] appears to be small at the finite relative gyroradius (rho-star) of current experiments.

Waltz, R. E.; Staebler, G. M.; Candy, J.; Hinton, F. L. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

2007-12-15

20

Gyrokinetic theory and simulation of angular momentum transport  

NASA Astrophysics Data System (ADS)

A gyrokinetic theory of turbulent toroidal angular momentum transport as well as modifications to neoclassical poloidal rotation from turbulence is formulated starting from the fundamental six-dimensional kinetic equation. The gyro-Bohm scaled transport is evaluated from toroidal delta-f gyrokinetic simulations using the GYRO code [Candy and Waltz, J. Comput. Phys. 186, 545 (2003)]. The simulations recover two pinch mechanisms in the radial transport of toroidal angular momentum: The slab geometry E×B shear pinch [Dominguez and Staebler, Phys. Fluids B 5, 387 (1993)] and the toroidal geometry ``Coriolis'' pinch [Peeters, Angioni, and Strintzi, Phys. Rev. Lett. 98, 265003 (2007)]. The pinches allow the steady state null stress (or angular momentum transport flow) condition required to understand intrinsic (or spontaneous) toroidal rotation in heated tokamak without an internal source of torque [Staebler, Kinsey, and Waltz, Bull. Am. Phys. Soc. 46, 221 (2001)]. A predicted turbulent shift in the neoclassical poloidal rotation [Staebler, Phys. Plasmas 11, 1064 (2004)] appears to be small at the finite relative gyroradius (rho-star) of current experiments.

Waltz, R. E.; Staebler, G. M.; Candy, J.; Hinton, F. L.

2007-12-01

21

Note: Determination of torsional spring constant of atomic force microscopy cantilevers: Combining normal spring constant and classical beam theory  

NASA Astrophysics Data System (ADS)

A technique has been developed for the calculation of torsional spring constants for AFM cantilevers based on the combination of the normal spring constant and plate/beam theory. It is easy to apply and allow the determination of torsional constants for stiff cantilevers where the thermal power spectrum is difficult to obtain due to the high resonance frequency and low signal/noise ratio. The applicability is shown to be general and this simple approach can thus be used to obtain torsional constants for any beam shaped cantilever.

Álvarez-Asencio, R.; Thormann, E.; Rutland, M. W.

2013-09-01

22

Lagrangian theory of the motion of spinning particles in torsion gravitational theories  

Microsoft Academic Search

The (second-order differential) equations of motion of spinning test particles (tops) are derived from a variational principle in a given gravitational background defined by a Riemannian metric and a torsion tensor. The mass and (magnitude of) the spin of the top are conserved. There exists a Regge trajectory linking the mass and the spin of the top. Constants of the

Sergio Hojman

1978-01-01

23

Angular-momentum-dependent orbital-free density functional theory.  

PubMed

Orbital-free (OF) density functional theory (DFT) directly solves for the electron density rather than the wave function of many electron systems, greatly simplifying and enabling large scale first principles simulations. However, the required approximate noninteracting kinetic energy density functionals and local electron-ion pseudopotentials severely restrict the general applicability of conventional OFDFT. Here, we present a new generation of OFDFT called angular-momentum-dependent (AMD)-OFDFT to harness the accuracy of Kohn-Sham DFT and the simplicity of OFDFT. The angular momenta of electrons are explicitly introduced within atom-centered spheres so that the important ionic core region can be accurately described. In addition to conventional OF total energy functionals, we introduce a crucial nonlocal energy term with a set of AMD energies to correct errors due to the kinetic energy density functional and the local pseudopotential. We find that our AMD-OFDFT formalism offers substantial improvements over conventional OFDFT, as we show for various properties of the transition metal titanium. PMID:23971595

Ke, Youqi; Libisch, Florian; Xia, Junchao; Wang, Lin-Wang; Carter, Emily A

2013-08-09

24

Angular-Momentum-Dependent Orbital-Free Density Functional Theory  

NASA Astrophysics Data System (ADS)

Orbital-free (OF) density functional theory (DFT) directly solves for the electron density rather than the wave function of many electron systems, greatly simplifying and enabling large scale first principles simulations. However, the required approximate noninteracting kinetic energy density functionals and local electron-ion pseudopotentials severely restrict the general applicability of conventional OFDFT. Here, we present a new generation of OFDFT called angular-momentum-dependent (AMD)-OFDFT to harness the accuracy of Kohn-Sham DFT and the simplicity of OFDFT. The angular momenta of electrons are explicitly introduced within atom-centered spheres so that the important ionic core region can be accurately described. In addition to conventional OF total energy functionals, we introduce a crucial nonlocal energy term with a set of AMD energies to correct errors due to the kinetic energy density functional and the local pseudopotential. We find that our AMD-OFDFT formalism offers substantial improvements over conventional OFDFT, as we show for various properties of the transition metal titanium.

Ke, Youqi; Libisch, Florian; Xia, Junchao; Wang, Lin-Wang; Carter, Emily A.

2013-08-01

25

Singularity in the Laboratory Frame Angular Distribution Derived in Two-Body Scattering Theory  

ERIC Educational Resources Information Center

|The laboratory (lab) frame angular distribution derived in two-body scattering theory exhibits a singularity at the maximum lab scattering angle. The singularity appears in the kinematic factor that transforms the centre of momentum (cm) angular distribution to the lab angular distribution. We show that it is caused in the transformation by the…

Dick, Frank; Norbury, John W.

2009-01-01

26

Semiclassical complex angular momentum theory and Pade reconstruction for resonances, rainbows, and reaction thresholds  

SciTech Connect

A semiclassical complex angular momentum theory, used to analyze atom-diatom reactive angular distributions, is applied to several well-known potential (one-particle) problems. Examples include resonance scattering, rainbow scattering, and the Eckart threshold model. Pade reconstruction of the corresponding matrix elements from the values at physical (integral) angular momenta and properties of the Pade approximants are discussed in detail.

Sokolovski, D. [School of Mathematics and Physics, Queen's University of Belfast, Belfast, BT7 1NN (United Kingdom); Msezane, A.Z. [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta, Georgia 30314 (United States)

2004-09-01

27

D Quantum Gravity with Torsion, Dilaton Theory and Black Hole Formation  

NASA Astrophysics Data System (ADS)

The main motivation to study general dilaton theories comes from spherically reduced gravity (SRG) 1 or string theory 2,3, although the dilaton black hole has a null-complete singularity 4. Previous studies of general dilaton theories 5 in the conformal gauge only could treat quantum theory in a semiclassical way 6 through the addition of the Polyakov action 7. For the example of a 2d model with torsion 8,9 the crucial advantages of a physical gauge 10 like the light cone gauge for the Cartan variables 11,12 were realised which, for that model, even allowed an exact path integral 13 and exact Dirac quantization 14. Because the light cone gauge for Cartan variables implies Eddington-Finkelstein gauge for the metric the global features of all 2d theories could be analysed in great detail 15. Motivated by the Hamiltonian analysis 16 and an analogous formulation in string theory 17 the importance of a first order formulation 18 was realized because of its local and global equivalence to the usual formulation as a dilaton theory 14,19. Even in the presence of matter 20 an absolute conservation law, generalizing the notion of the ADM-mass 21 to an energy flux relation 22 and a related novel type of Noether symmetry 23 were found. The concept of the "Poisson-Sigma-Model" 24 emerged in this context which now also finds an application in string theory 25 and can be used to create all possible 2d supergravity theories 26,27. The main power of the first order formulation was noticed in connection with the path integral formulation of 2d gravity where matter can be included by systematic loop-wise expansion 19. Based upon the formalism of extended Hamilton theory 28 with contributions to the constraints also including fermions 29 it was shown recently 30 that as one of the results of 2d quantum gravity a "virtual black hole" appears in the scattering of scalars. Planned applications include reduced generalized Einstein theories 31.

Kummer, W.

2002-12-01

28

Parallel spinors and connections with skew-symmetric torsion in string theory  

Microsoft Academic Search

We describe all almost contact metric, almost hermitian and $G_2$-structures admitting a connection with totally skew-symmetric torsion tensor, and prove that there exists at most one such connection. We investigate its torsion form, its Ricci tensor, the Dirac operator and the $\\\

Thomas Friedrich; Stefan Ivanov

2001-01-01

29

Angular correlation between photoelectrons and Auger electrons within scattering theory  

SciTech Connect

In this paper we present a single-particle scattering approach for the angular correlation between a photoelectron and the subsequent Auger electron from atomic targets. This method is proposed as an alternative approach with respect to the usual density matrix formalism, since it is more convenient for extension to the solid state case. Such an extension is required by the great progress made in the field of coincidence spectroscopy in condensed matter systems. We derived a tensor expression for the cross section and an equivalent expression in terms of convenient angular functions has been treated for the case of linearly polarized light. Numerical calculations are performed for the L{sub 3}M{sub 2,3}M{sub 2,3} transition in argon, in the single configuration Dirac-Fock scheme. Results are compared with experimental data for different final angular momentum states of the doubly charged ion and for different kinematical conditions.

Da Pieve, F.; Stefani, G. [Physics Department, University Roma Tre and CNISM, via della Vasca Navale 84, I-00146 Rome (Italy); Di Matteo, S.; Natoli, C. R. [INFN Laboratori Nazionali di Frascati, via Enrico Fermi 40, I-00044 Frascati (Italy); Sebilleau, D. [Equipe de Physique des Surfaces et des Interfaces, Laboratoire de Physique des Atomes, Lasers, Molecules et Surfaces, UMR CNRS-Universite 6627, Universite de Rennes 1, 35042 Rennes Cedex (France); Gunnella, R. [Physics Department, University of Camerino, Via Madonna delle Carceri, I-62032 Camerino (Italy)

2007-05-15

30

Spin and orbital angular momentum propagation in anisotropic media: theory  

NASA Astrophysics Data System (ADS)

This paper is devoted to a study of the propagation of light beams carrying orbital angular momentum in optically anisotropic media. We first review some properties of homogeneous anisotropic media, and describe how the paraxial formalism is modified in order to proceed with a new approach dealing with the general setting of paraxial propagation along uniaxial inhomogeneous media. This approach is suitable for describing space-variant optical-axis phase plates.

Picón, Antonio; Benseny, Albert; Mompart, Jordi; Calvo, Gabriel F.

2011-06-01

31

Angular Pseudomomentum Theory for the Generalized Nonlinear Schrodinger Equation in Discrete Rotational Symmetry Media  

Microsoft Academic Search

We develop a complete mathematical theory for the symmetrical solutions of the generalized nonlinear Schrodinger equation based on the new concept of angular pseudomomentum. We consider the symmetric solitons of a generalized nonlinear Schrodinger equation with a nonlinearity depending on the modulus of the eld. We provide a rigorous proof of a set of mathematical results justifying that these solitons

M.-A. Garc; A. Ferrando; M. Zacar; J. Vijande; L. D. Carr

32

Performance test and improvement of piezoelectric torsional actuators  

Microsoft Academic Search

This paper presents the design, test and improvement of a newly developed piezoelectric torsional actuator which generates large angular displacement using piezoceramics and a torsion bar. Because the proposed piezoelectric torsional actuator can generate torsional displacement, directly invoking the shear mode of the piezoelectric material, no complicated additional mechanism is needed. The electrodes are formed from a cylindrical piezoceramic poled

Jaehwan Kim; Byungwoo Kang

2001-01-01

33

On Poincaré gauge theory of gravity, its equations of motion, and Gravity Probe B  

NASA Astrophysics Data System (ADS)

We discuss the structure of the Poincaré gauge theory of gravity (PG) that can be considered as the standard theory of gravity with torsion. We reconfirm that torsion, in the context of PG, couples only to the elementary particle spin and under no circumstances to the orbital angular momentum of test particles. We conclude that, unfortunately, the investigations of Mao et al. (2007) and March et al. (2011)—who claimed a coupling of torsion to orbital angular momentum, in particular in the context of the Gravity Probe B (GPB) experiment—do not yield any information on torsion.

Hehl, Friedrich W.; Obukhov, Yuri N.; Puetzfeld, Dirk

2013-10-01

34

CIRCLE-VALUED MORSE THEORY, REIDEMEISTER TORSION, AND SEIBERG–WITTEN INVARIANTS OF 3-MANIFOLDS  

Microsoft Academic Search

Let X be a closed oriented Riemannian manifold with ?(X)=0 and b1(X)>0, and let ?:X?S1 be a circle-valued Morse function. Under some mild assumptions on ?, we prove a formula relating1.the number of closed orbits of the gradient flow of ? in different homology classes;2.the torsion of the Novikov complex, which counts gradient flow lines between critical points of ?;

Michael Hutchings; Yi-Jen Lee

1999-01-01

35

Spin and Orbital Angular Momentum in Gauge Theories: Nucleon Spin Structure and Multipole Radiation Revisited  

SciTech Connect

We address and solve the long-standing gauge-invariance problem of the nucleon spin structure. Explicitly gauge-invariant spin and orbital angular momentum operators of quarks and gluons are obtained. This was previously thought to be an impossible task and opens a more promising avenue towards the understanding of the nucleon spin. Our research also justifies the traditional use of the canonical, gauge-dependent angular momentum operators of photons and electrons in the multipole-radiation analysis and labeling of atomic states and sheds much light on the related energy-momentum problem in gauge theories, especially in connection with the nucleon momentum.

Chen Xiangsong [Department of Physics, Sichuan University, Chengdu 610064 (China); Department of Physics, Nanjing University, CPNPC, Nanjing 210093 (China); Lue Xiaofu [Department of Physics, Sichuan University, Chengdu 610064 (China); Sun Weimin; Wang Fan [Department of Physics, Nanjing University, CPNPC, Nanjing 210093 (China); Goldman, T. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2008-06-13

36

Propagating torsion in the Einstein frame  

SciTech Connect

The Einstein-Cartan-Saa theory of torsion modifies the spacetime volume element so that it is compatible with the connection. The condition of connection compatibility gives constraints on torsion, which are also necessary for the consistence of torsion, minimal coupling, and electromagnetic gauge invariance. To solve the problem of positivity of energy associated with the torsionic scalar, we reformulate this theory in the Einstein conformal frame. In the presence of the electromagnetic field, we obtain the Hojman-Rosenbaum-Ryan-Shepley theory of propagating torsion with a different factor in the torsionic kinetic term.

Poplawski, Nikodem J. [Department of Physics, Indiana University, 727 East Third Street, Bloomington, Indiana 47405 (United States)

2006-11-15

37

Torsional and Bending Vibration Measurement on Rotors Using Laser Technology  

NASA Astrophysics Data System (ADS)

Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) was developed for non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. This paper describes comprehensive theory to account for the sensitivity of the LTV's measurements to shaft motion in all degrees of freedom. The optical geometry of the LTV offers inherent immunity to translational motion of the target shaft, either axial or radial. However, its measurements are sensitive to angular lateral vibration of the shaft. The significance of this sensitivity is compared with the instrument noise floor and typical torsional and lateral vibration levels. Optimum alignments of the instrument are then specified to ensure effective immunity to all lateral motion in typical applications. To overcome this problem more reliably, a new technique is proposed permitting unambiguous measurement of pure torsional vibration in situations where use of a single LTV demonstrates unacceptable sensitivity to angular lateral vibrations. Practical application of this technology is demonstrated with torsional vibration measurements from a diesel engine crankshaft. Simultaneously, previously unattained measurements of shaft bending vibration measurements are made. The first bending mode of the crankshaft was identified and its vibration amplitude and damping estimated. This application of laser vibrometry for non-contact measurements of shaft vibration represents a further step forward in the use of this technology for machinery diagnostics.

Miles, T. J.; Lucas, M.; Halliwell, N. A.; Rothberg, S. J.

1999-09-01

38

Complex Angular Momentum Diagonalization of the Bethe-Salpeter Structure in General Quantum Field Theory  

Microsoft Academic Search

The Complex Angular Momentum (CAM) representation of (scalar) fourpoint functions has been previously established starting from the general principles of local relativistic Quantum Field Theory (QFT). Here, we carry out the diagonalization of the general t-channel Bethe-Salpeter (BS) structure of four-point functions in the corresponding CAM variable 5t, for all negative values of the squared-energy variable t. This diagonalization is

J. Bros; G. A. Viano

2003-01-01

39

Siegert pseudostate formulation of scattering theory: Nonzero angular momenta in the one-channel case  

NASA Astrophysics Data System (ADS)

The Siegert pseudostate (SPS) formulation of scattering theory, originally developed by Tolstikhin, Ostrovsky, and Nakamura [Phys. Rev. A, 58, 2077 (1998)] for s -wave scattering in a spherically symmetric finite-range potential, is generalized to nonzero angular momenta. The orthogonality and completeness properties of SPSs are established and SPS expansions for the outgoing-wave Green’s function, physical states, and scattering matrix are obtained. The present formulation completes the theory of SPSs in the one-channel case, making its application to three-dimensional problems possible. The results are illustrated by calculations for several model potentials.

Batishchev, Pavel A.; Tolstikhin, Oleg I.

2007-06-01

40

Generalized extended Navier-Stokes theory: Correlations in molecular fluids with intrinsic angular momentum  

NASA Astrophysics Data System (ADS)

The extended Navier-Stokes theory accounts for the coupling between the translational and rotational molecular degrees of freedom. In this paper, we generalize this theory to non-zero frequencies and wavevectors, which enables a new study of spatio-temporal correlation phenomena present in molecular fluids. To discuss these phenomena in detail, molecular dynamics simulations of molecular chlorine are performed for three different state points. In general, the theory captures the behavior for small wavevector and frequencies as expected. For example, in the hydrodynamic regime and for molecular fluids with small moment of inertia like chlorine, the theory predicts that the longitudinal and transverse intrinsic angular velocity correlation functions are almost identical, which is also seen in the molecular dynamics simulations. However, the theory fails at large wavevector and frequencies. To account for the correlations at these scales, we derive a phenomenological expression for the frequency dependent rotational viscosity and wavevector and frequency dependent longitudinal spin viscosity. From this we observe a significant coupling enhancement between the molecular angular velocity and translational velocity for large frequencies in the gas phase; this is not observed for the supercritical fluid and liquid state points.

Hansen, J. S.; Daivis, Peter J.; Dyre, Jeppe C.; Todd, B. D.; Bruus, Henrik

2013-01-01

41

Optical surface measurement using phase retrieval hybrid algorithm based on diffraction angular spectrum theory  

NASA Astrophysics Data System (ADS)

In order to test the high dynamic range error beyond one wavelength after the rough polish process, we design a phase retrieval hybrid algorithm based on diffraction angular spectrum theory. Phase retrieval is a wave front sensing method that uses the intensity distribution to reconstruct the phase distribution of optical field. Phase retrieval is established on the model of diffractive propagation and approach the real intensity distribution gradually. In this paper, we introduce the basic principle and challenges of optical surface measurement using phase retrieval, then discuss the major parts of phase retrieval: diffractive propagation and hybrid algorithm. The angular spectrum theory describes the diffractive propagation in the frequency domain instead of spatial domain, which simplifies the computation greatly. Through the theoretical analysis, the angular spectrum in discrete form is more effective when the high frequency part values less and the diffractive distance isn't far. The phase retrieval hybrid algorithm derives from modified GS algorithm and conjugate gradient method, aiming to solve the problem of phase wrapping caused by the high dynamic range error. In the algorithm, phase distribution is described by Zernike polynomials and the coefficients of Zernike polynomials are optimized by the hybrid algorithm. Simulation results show that the retrieved phase distribution and real phase distribution are quite contiguous for the high dynamic range error beyond ?.

Feng, Liang; Zeng, Zhi-ge; Wu, Yong-qian

2013-08-01

42

Mean-field theory for spin ladders using angular-momentum coupled bases  

SciTech Connect

We study properties of two-leg Heisenberg spin ladders in a mean-field approximation using a variety of angular-momentum-coupled bases. The mean-field theory proposed by Gopalan, Rice, and Sigrist, which uses a rung basis, assumes that the mean-field ground state consists of a condensate of spin singlets along the rungs of the ladder. We generalize this approach to larger angular-momentum-coupled bases that incorporate{emdash}by their mere definition{emdash}a substantial fraction of the important short-range structure of these materials. In these bases the mean-field ground state remains a condensate of spin singlet{emdash}but now with each involving a larger fraction of the spins in the ladder. As expected, the {open_quotes}purity{close_quotes} of the ground state, as judged by the condensate fraction, increases with the size of the elementary block defining the basis. Moreover, the coupling to quasiparticle excitations becomes weaker as the size of the elementary block increases. Thus, the weak-coupling limit of the theory becomes an accurate representation of the underlying mean-field dynamics. We illustrate the method by computing static and dynamic properties of two-leg ladders in the various angular-momentum-coupled bases. {copyright} {ital 1999} {ital The American Physical Society}

Piekarewicz, J. [Department of Physics and Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306 (United States); Shepard, J.R. [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)

1999-10-01

43

Time-dependent theory of angular correlations in sequential double ionization.  

PubMed

In this work, we emphasize the importance of the bound-state dynamics to the two-electron ejection in double ionization processes. The conclusions of the present study are pertinent to all excitation or decay processes that proceed via well-defined intermediate states. A general strong-field time-dependent density matrix theory is established and applied to the case of neon, allowing us to analyze the role of the ionizing field in the interpretation of reported angular patterns [M. Kurka et al., J. Phys. B 42, 141002 (2009); A.?S. Kheifets, J. Phys. B 42, 134016 (2009)] and in the dynamic ionic alignment. The present analysis reveals that short-pulse coherent excitation of the neon ionic doublet ^{2}P_{1/2,3/2} leads to quantum beats in the two-electron angular correlation patterns. PMID:24033028

Nikolopoulos, L A A

2013-08-26

44

Time-Dependent Theory of Angular Correlations in Sequential Double Ionization  

NASA Astrophysics Data System (ADS)

In this work, we emphasize the importance of the bound-state dynamics to the two-electron ejection in double ionization processes. The conclusions of the present study are pertinent to all excitation or decay processes that proceed via well-defined intermediate states. A general strong-field time-dependent density matrix theory is established and applied to the case of neon, allowing us to analyze the role of the ionizing field in the interpretation of reported angular patterns [M. Kurka et al., J. Phys. B 42, 141002 (2009); A. S. Kheifets, J. Phys. B 42, 134016 (2009)] and in the dynamic ionic alignment. The present analysis reveals that short-pulse coherent excitation of the neon ionic doublet P1/2,3/22 leads to quantum beats in the two-electron angular correlation patterns.

Nikolopoulos, L. A. A.

2013-08-01

45

Graphical approach to the U(n) Racah-Wigner theory of angular momentum  

NASA Astrophysics Data System (ADS)

We demonstrate the use of angular momentum graphs, based on those of Yutsis, Levinson, and Vanagas [Mathematical 1 Apparatus of the Theory of Angular Momentum (Israel Program for Scientific Translation, Jerusalem, 1962)], adapted for the unitary group approach to the theory of many-particle systems. Using a variant of the standard Gel'fand state labels, we show that graphical representations of generator matrix elements in U(n) parallel the SU(2) vector-coupling approaches of Drake and Schlesinger [Phys. Rev. A 15, 1990 (1977)] and Paldus and Boyle [Phys. Scr. 21, 295 (1980)]. The graphs are constructed using the U(n) Clebsch-Gordan coefficients. Fundamental subgraphs, such as occur in the evaluation of operator matrix elements, are expressed in terms of U(n) Racah coefficients and generalized 3n-j coefficients. The results are anticipated to be of interest to high-energy physicists and to others concerned with systems of particles involving spin higher than (1/2.

Kent, R. D.; Schlesinger, M.

1989-07-01

46

Beyond the Chemiosmotic Theory: Analysis of Key Fundamental Aspects of Energy Coupling in Oxidative Phosphorylation in the Light of a Torsional Mechanism of Energy Transduction and ATP Synthesis—Invited Review Part 2  

Microsoft Academic Search

The core of this second article shows how logical errors and inconsistencies in previous theories of energy coupling in oxidative\\u000a phosphorylation are overcome by use of a torsional mechanism and the unified theory of ATP synthesis\\/hydrolysis. The torsional\\u000a mechanism is shown to satisfy the pioneering and verified features of previous mechanisms. A considerable amount of data is\\u000a identified that is

Sunil Nath

2010-01-01

47

[Gallbladder torsion].  

PubMed

We report two cases of gallbladder torsion, which were diagnosed intraoperatively. This rare condition should be suspected in elderly women with acute abdominal pain of unknown origin. The treatment is cholecystectomy. Promptly treated, the prognosis is good. PMID:12043407

Tuckus, Grazvydas; Kåg, Lise

2002-05-13

48

Interplay between theory and experiment for fission-fragment angular distributions from nuclei near the limits of stability  

Microsoft Academic Search

We examine the application of transition-state theory for fission-fragment angular distributions to composite nuclei near the limits of stability. The possible roles of saddle-point and scission-point configurations are explored. For many heavy-ion reactions that involve large angular momenta, the observed anisotropies are between the predictions of the saddle-point and scisson--point models. Empirical correlations are shown between the effective moments of

R. Freifelder; M. Prakash; John M. Alexander

1986-01-01

49

Quaternions, Torsion and the Physical Vacuum: Theories of M. Sachs and G. Shipov Compared  

NASA Astrophysics Data System (ADS)

Of several developments of unified field theories in the spirit of Einstein's original objective of a fully geometric description of all classical fields as well as quantum mechanics, two are particularly noteworthy. The works of Mendel Sachs and Gennady Shipov stand apart as major life works comprising tens of papers, several monographs and decades of effort. Direct comparison of these theories is hampered however by differences in notation and conceptual view-point. Despite these differences, there are many parallels between the fundamental mathematical structures appearing in each. In this paper we discuss the main tenets of the two approaches and demonstrate that they both give rise to a factorization of the invariant interval of general relativity.

Cyganski, David; Page, William S.

50

Some Remarks about Duality, Analytic Torsion and Gaussian Integration in Antisymmetric Field Theories  

Microsoft Academic Search

From a path integral point of view (e.g. \\\\cite{Q98}) physicists have shown\\u000ahow {\\\\it duality} in antisymmetric quantum field theories on a closed\\u000aspace-time manifold $M$ relies in a fundamental way on Fourier Transformations\\u000aof formal infinite-dimensional volume measures. We first review these facts\\u000afrom a measure theoretical point of view, setting the importance of the Hodge\\u000adecomposition theorem in

Alexander Cardona; Blaise Pascal

2000-01-01

51

Theoretical analysis of coupled torsional, warping and distortional waves in a straight thin-walled box beam by higher-order beam theory  

NASA Astrophysics Data System (ADS)

When a thin-walled box beam is subjected to a dynamic torsional load, warping and distortional deformations of its cross section are coupled with torsional deformation. Due to the coupling, the wave propagation along the beam axis becomes considerably complicated. However, there appears no in-depth investigation on dispersion phenomena. It is difficult to see the intriguing interconnection of branches of the dispersion curves by means of numerical solutions of three-dimensional elastodynamic equations. Thus, we aim to analytically investigate the dispersion relation and wave reflection phenomena by using a one-dimensional higher-order beam theory that is capable of representing the three aforementioned deformations. Through this study, the interconnections of real, imaginary and complex branches of the dispersion relation for low frequencies are revealed and reflection and transmission phenomena occurring at a joint of two beams of different cross-sectional dimensions are also investigated.

Jang, Gang Won; Kim, Yoon Young

2011-06-01

52

Spin matrices for gravitons and the Humblet decomposition of the angular momentum of gravitational radiation in the linearized theory  

SciTech Connect

The authors develop spin matrices for a classical gravitational field in the linearized theory which satisfy angular-momentum commutation relations and are appropriate for a spin angular momentum of two. The same spin matrices come out of a decomposition of the angular momentum density of the linearized gravitational field into orbital and spin parts, similar to that carried out by Humblet for the electromagnetic field. To achieve this decomposition, they use the momentum density for the gravitational field obtained from the Landau-Lifshitz pseudo-tensor in the weak gravity limit. They not a formal connection between the spin angular momenta of gravitational and electromagnetic fields using the Kaluza-Klein idea.

Crichton, J.H.; Medina, T.J. (Seattle Pacific Univ., WA (USA))

1990-01-01

53

Analysis and simulation of diffractive imaging field in thick film photoresist by using angular spectrum theory  

NASA Astrophysics Data System (ADS)

The thick film photoresist lithography is a much more complicated process compared to the thin film photoresist lithography. In this paper, we have developed a new model for lithography of thick film photoresist by using the angular spectrum theory. The thick film photoresist is divided into many homogeneous layers, and the diffractive optical imaging distribution in photoresist is regarded as superposition of different spectrum plane waves. Propagation of each plane wave is determined by the optical transfer function, and the propagation direction, amplitude and phase are dominated by reflection and transmission between each interface of the sub-layers. The fast Fourier transform (FFT) has been converted into a convolution calculation to keep the computation accurate and reduce computation cost. Numerical calculation results show that optical intensity in cross-sect of thick film resist is strongly affected by reflection, transmission on interface and variation of dielectric permittivity along direction of depth, and therefore these factors should be considered while analyzing diffractive imaging field in thick film photoresist.

Xionggui, Tang; Fuhua, Gao; Yongkang, Guo; Jinglei, Du; Shijie, Liu; Feng, Gao

2005-01-01

54

The angular momentum content of dwarf galaxies: new challenges for the theory of galaxy formation  

NASA Astrophysics Data System (ADS)

We compute the specific angular momentum distributions for a sample of low-mass disc galaxies observed by Swaters. We compare these distributions to those of dark matter haloes obtained by Bullock et al. from high-resolution N-body simulations of structure formation in a ?CDM universe. We find that although the disc mass fractions are significantly smaller than the universal baryon fraction, the total specific angular momenta of the discs are in good agreement with those of dark matter haloes. This suggests that discs form out of only a small fraction of the available baryons, but yet manage to draw most of the available angular momentum. In addition we find that the angular momentum distributions of discs are clearly distinct from those of the dark matter; discs lack predominantly both low and high specific angular momenta. Understanding these findings in terms of a coherent picture for disc formation is challenging. Cooling, feedback and stripping, which are the main mechanisms to explain the small disc mass fractions found, seem unable to simultaneously explain the angular momentum distributions of the discs. In fact, it seems that the baryons that make up the discs must have been born out of angular momentum distributions that are clearly distinct from those of ?CDM haloes. However, the dark and baryonic mass components experience the same tidal forces, and it is therefore expected that they should have similar angular momentum distributions. Therefore, understanding the angular momentum content of disc galaxies remains an important challenge for our picture of galaxy formation.

van den Bosch, Frank C.; Burkert, Andreas; Swaters, Rob A.

2001-09-01

55

Torsional vibration isolator and method  

SciTech Connect

This patent describes a multicylinder internal combustion engine having a rotatable crankshaft and a rotatable flywheel which together define an inertial system rotating about a predetermined axis of rotation. An improvement is described here which facilitates avoiding destructive effects on the crankshaft of stress induced by torsional vibration. The method comprises an elastomeric annulus coupling means operatively interposed between the crankshaft and flywheel for coupling the crankshaft and flywheel together for rotation of the flywheel with the crankshaft. The coupling means has a torsional spring rate of less than 20,000 in lb/radian effective to permit substantial angular displacement between the flywheel and the crankshaft for isolating the rotating inertia of the flywheel from the rotating inertia of the crankshaft after engine startup. The coupling means avoids dampening while preventing torsional vibration from being transferred between the flywheel and the crankshaft.

Allen, C.A.; Durrett, V.D.

1986-10-21

56

Performance test and improvement of piezoelectric torsional actuators  

NASA Astrophysics Data System (ADS)

This paper presents the design, test and improvement of a newly developed piezoelectric torsional actuator which generates large angular displacement using piezoceramics and a torsion bar. Because the proposed piezoelectric torsional actuator can generate torsional displacement, directly invoking the shear mode of the piezoelectric material, no complicated additional mechanism is needed. The electrodes are formed from a cylindrical piezoceramic poled along the axial direction and divided into six segments that are arranged radially and bonded to each other in opposite poling directions with conductive adhesive. The key to designing such an actuator is to match the torsional resonant frequency of the actuator with the excitation frequency. Finite element analysis for the piezoelectric actuator is performed to find the torsional resonant mode; an experimental investigation in terms of electrical impedance and torsional displacement measurement was conducted to verify the mode. As a result a maximum angular displacement of 0.18° was measured. To magnify the torsional displacement, a torsion bar was attached on top of the actuator. Thus, the torsional displacement was magnified by a factor of three. A resonance decrease due to the added mass of the torsion bar was observed and a theoretical investigation was performed using a two degrees of freedom lumped model.

Kim, Jaehwan; Kang, Byungwoo

2001-08-01

57

Angular effects on upper critical field in LiFeAs using two-band Ginzburg-Landau theory  

NASA Astrophysics Data System (ADS)

The influence of angular effects on the upper critical field is studied by using generalized two-band Ginzburg-Landau (GL) theory. It is shown that such a model is in better agreement with known experimental data for the new superconductor LiFeAs. The deviation from single-band GL theory is maximum at temperatures close to Tc. Different anisotropy of different bands leads to an increase of the anisotropy parameter of the upper critical field ?(T) with increase of temperature.

Askerzade, I. N.; Tagiyeva (Askerbeyli, R. T.

2012-09-01

58

An experimental study torsional fretting behaviors of LZ50 steel  

Microsoft Academic Search

Four simple fretting modes are defined according to relative motion: tangential, radial, rotational, and torsional fretting. This paper presents a new test rig that was developed from a low-speed reciprocating rotary system to show torsional fretting wear under ball-on-flat contact. Torsional fretting behavior was investigated for LZ50 steel flats against AISI52100 steel balls under various angular displacement amplitudes and normal

Zhen-bing Cai; Min-hao Zhu; Zhong-rong Zhou

2010-01-01

59

Transverse coincidence structures in spontaneous parametric down-conversion with orbital angular momentum: Theory  

SciTech Connect

Coincidence structures in the transverse plane of type-II spontaneous parametric down-conversion carrying orbital angular momentum are obtained. Azimuthal symmetry breaking around the pump beam direction reveals itself on these quantum images. Analytical expressions for the amplitude probability of the down-conversion process are shown including the nonlinear polarizability components.

Barbosa, Geraldo A. [Department of Electrical Engineering and Computer Science, Center for Photonic Communication and Computing, Northwestern University, 2145 North Sheridan Road, Evanston, Illinois 60208-3118 (United States)

2007-09-15

60

Torsional Waves in Composite Rods.  

National Technical Information Service (NTIS)

The propagation of torsional waves in composite, infinitely long, traction-free, circular, cylindrical rods is investigated on the basis of the three-dimensional linear theory of elasticity. The composite rods consist of an internal circular rod made of o...

A. E. Armenakas

1965-01-01

61

Angular Acceleration  

NSDL National Science Digital Library

The simulation of a rotating wheel below shows the relationship between angular position, angular velocity, and angular acceleration. Graphs of angular position and angular velocity as a function of time are shown.

Christian, Wolfgang; Belloni, Mario

2008-02-19

62

Two-dimensional resonances in Coulomb few body system and theory of electron energy and angular distribution  

SciTech Connect

The two-dimensional resonances in the problem of two Coulomb centers are discussed. The ab initio calculation of electron energy and angular distributions of saddle-point and S-promotion electrons for ionization in proton-hydrogen atom collisions are presented. The calculation is based on an outgoing wave Sturmian expansion in the frequency domain. It goes beyond the usual Born-Oppenheimer separation of electron and nuclei motions and displays the ``{upsilon}/2`` peak and the continuum cusp, missing in previous theories.

Ovchinnikov, S.Y. [Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy; Macek, J.H. [Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy]|[Oak Ridge National Lab., TN (United States)

1994-12-31

63

Trapped torsional vibrations in elastic plates  

NASA Astrophysics Data System (ADS)

We report observation and analysis of trapped torsional vibrations in elastic plates. Each trapping element consists of a circular mesa machined in cast aluminum plate, with an electromagnetic acoustic transducer used to generate oscillatory surface traction. Suitably applied traction induced torsional vibrations trapped in the mesa. The resonant frequencies, relative displacements and Q-values were measured, and an approximate theory was developed to analyze the trapping effect with good agreement between measurements and theory. It was found that these trapped torsional modes have Q-values exceeding 100 000 with pure in-plane motion, which is of practical importance for acoustic sensor applications.

Knowles, T.; Kang, M. K.; Huang, R.

2005-11-01

64

Torsional Magnetic Oscillations in Type I X-Ray Bursts  

NASA Astrophysics Data System (ADS)

Thermonuclear burning on the surface of a neutron star causes the expansion of a thin outer layer of the star, ?R(t). The layer rotates slower than the star due to angular momentum conservation. The shear between the star and the layer acts to twist the star's dipole magnetic field, giving at first a trailing spiral field. The twist of the field acts in turn to ``torque up'' the layer, increasing its specific angular momentum. As the layer cools and contracts, its excess specific angular momentum causes it to rotate faster than the star, which gives a leading spiral magnetic field. The process repeats, giving rise to torsional oscillations. We derive equations for the angular velocity and magnetic field of the layer, taking into account the diffusivity and viscosity that are probably due to turbulence. The magnetic field causes a nonuniformity of the star's photosphere (at the top of the heated layer), and this gives rise to the observed X-ray oscillations. The fact that the layer periodically rotates faster than the star means that the X-ray oscillation frequency may ``overshoot'' the star's rotation frequency. Comparison of the theory is made with observations of Chakrabarty et al. of an X-ray burst of SAX J1808.4-3658.

Lovelace, R. V. E.; Kulkarni, A. K.; Romanova, M. M.

2007-02-01

65

Torsion Corrections in Brane World Gravity  

NASA Astrophysics Data System (ADS)

In the frame of brane world theory the effects of torsion fields are examined. Considering a five dimensional Non-Riemannian bulk with a noncompact extra dimension, we derive the modified Einstein field equations in a four dimensional (3-brane) arbitrary manifold embedded in this bulk. The necessary matching conditions are investigated assuming that the torsion in the bulk is continuous. In this context the extrinsic curvature is connected to the matter content restricted to the brane and the torsion components of the bulk. As a final result we observe that the corrections - due to torsion fields - in the modified field equations depend crucially on the embedding that is taken. Therefore, by considering a simple embedding, we develop a cosmological model that describes a flat FLRW embedded in a 5-dimensional de Sitter (or Anti de Sitter) spacetime, where a 5-dimensional cosmological constant emerges from the torsion components of the bulk.

Maier, R.

2011-06-01

66

Effects of High Angular Momentum on the Unimolecular Dissociation of CD2CD2OH: Theory and Comparisons with Experiment.  

PubMed

This paper explores the dynamics of a highly rotationally and vibrationally excited radical, CD2CD2OH. The radical is produced from the 193 nm photodissociation of 2-bromoethanol-d4, so it is imparted with high angular momentum and high vibrational energy and subsequently dissociates to several product channels. This paper focuses on characterizing its angular momentum and modeling its effect on the product channels, including the HOD + vinyl-d3 product channel resulting from a frustrated dissociation of the radical originally en route to OH + ethene-d4 that instead results in D atom abstraction. Our impulsive model of the initial photodissociation shows that, for some cases, upward of 200 au of angular momentum is imparted, which greatly affects the dynamics of the competing product channels. Using a permutationally invariant potential energy surface and quasiclassical trajectories, we simulated the dissociation dynamics of CD2CD2OH and compared these results to those of Kamarchik et al. (J. Phys. Chem. Lett. 2010, 1, 3058-3065), who studied the dynamics of CH2CH2OH with zero angular momentum. We found that the recoil translational energy distribution for radicals that dissociated to OH + C2D4 matched experiment closely only when high angular momentum of the initial radical was explicitly included in the trajectory calculations. Similarly, the rate constant for dissociation changes when rotational energy was added to the vibrational energy in the initial conditions. Lastly, we applied the sketch-map dimensionality reduction technique to analyze mechanistic information leading to the vinyl + water product channel. Projecting the ab initio intrinsic reaction coordinates onto the lower dimensional space identified with sketch map offers new insight into the dynamics when one looks at the simulated trajectories in the lower dimensional space. Further analysis shows that the transition path resembles a frustrated dissociation of the OH + ethene radical adduct, followed instead by branching to vinyl + water when the leaving OH group encounters a nearby D atom on the ethene moiety. This characterization is in accord with the one made previously. We show that the transition path bifurcation between the two similar channels occurs at carbon-oxygen distances and oxygen-abstracted deuterium distances of 2-2.5 Å controlled by the C-O-D bond angle with large angles preferentially branching to the water plus vinyl product state. The experimental branching ratios were not reproduced by theory, however, due partly to the insufficient quality of the fitted potential surface. We also have evidence of a minor product channel, HD + vinoxy-d3, from our molecular dynamics simulations that allows us to assign the HD signal in prior experimental work. PMID:24124756

McKown, Benjamin G; Ceriotti, Michele; Womack, Caroline C; Kamarchik, Eugene; Butler, Laurie J; Bowman, Joel M

2013-10-14

67

Variable Stiffness Torsion Springs.  

National Technical Information Service (NTIS)

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs emp...

D. C. Alhorn M. E. Polites

1994-01-01

68

Study on torsional fretting behavior of UHMWPE  

NASA Astrophysics Data System (ADS)

Torsional fretting tests of UHMWPE against titanium alloy ball (TC4) had been carried out. A frictional torque-angular displacement ( T- ?) curve was used to analyze the kinetics behaviors of torsional fretting mode. The wear morphology and damage mechanisms of UHMWPE were studied based on examinations by scanning electron microscopy (SEM). It is found that the contact stiffness and friction-dissipated energy initially rise and then gradually reach a steady state. The worn surface is characterized by adhesion in the centre zone, while in the outer annulus, ripples, ploughs and delamination appeared. In addition, a transfer film is found on the surface of titanium alloy ball.

Yu, Jia; Cai, Zhenbing; Zhu, Minhao; Qu, Shuxin; Zhou, Zhongrong

2008-11-01

69

Torsion and entropy driven denaturation of DNA  

NASA Astrophysics Data System (ADS)

A unified theory of the denaturation transition having torsion energy as the control parameter has been formulated here in the framework of the mapping of a DNA molecule onto a Heisenberg spin system. The torsion energy incorporates the torque, tension and temperature, the latter being associated with the twist angle. The denaturation transition can be mapped onto the quantum phase transition induced by a quench when the temperature effect is incorporated in the quench time and torsion takes the role of the external field. The denaturation transition occurs when the entanglement entropy of the spin system vanishes.

Roy, Subhamoy Singha; Bandyopadhyay, Pratul

2013-11-01

70

New torsional actuator based on shear piezoelectric response  

NASA Astrophysics Data System (ADS)

A torsional actuator generating angular displacement from the piezoelectric shear strain was developed. The actuator is a tube consisting of an even number of the segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuator: (1) prove the proposed concept of the torsional actuator, (2) show that the actuator functions well under the torque load, and (3) demonstrate that is has superior characteristics compared to previously reported designs of torsional actuators. In addition, one of the obvious advantages of the present design of the actuator is its simplicity: the piezoelectric shear strain is transformed directly into the angular displacement, whereas in the previously reported actuators, the conversion mechanism into the torsional motion was rather complicated which thus required a sophisticated design of the whole system.

Glazounov, Alexandre E.; Zhang, Qiming; Kim, Chulho

1998-07-01

71

Angular dependence of ultrasonic wave propagation in a stressed, orthorhombic continuum: Theory and application to the measurement of stress and texture  

Microsoft Academic Search

A theory for ultrasonic wave propagation in a symmetry plane of a biaxially stressed, orthorhombic continuum is presented. Since many of the material parameters which appear in the analysis are unknown, in particular the third-order elastic constants of polycrystalline metals, emphasis is placed on the angular dependence of the velocities. An expansion to first order in stress-induced anisotropy and to

R. Bruce Thompson; S. S. Lee; J. F. Smith

1986-01-01

72

Torsion cosmology and the accelerating universe  

SciTech Connect

Investigations of the dynamic modes of the Poincare gauge theory of gravity found only two good propagating torsion modes; they are effectively a scalar and a pseudoscalar. Cosmology affords a natural situation where one might see observational effects of these modes. Here, we consider only the 'scalar torsion' mode. This mode has certain distinctive and interesting qualities. In particular, this type of torsion does not interact directly with any known matter, and it allows a critical nonzero value for the affine scalar curvature. Via numerical evolution of the coupled nonlinear equations we show that this mode can contribute an oscillating aspect to the expansion rate of the Universe. From the examination of specific cases of the parameters and initial conditions we show that for suitable ranges of the parameters the dynamic 'scalar torsion' model can display features similar to those of the presently observed accelerating universe.

Shie, K.-F. [Department of Physics, National Central University, Chungli 320, Taiwan (China); Nester, James M. [Department of Physics, National Central University, Chungli 320, Taiwan (China); Graduate Institute of Astronomy, National Central University, Chungli 320, Taiwan (China); Center for Mathematics and Theoretical Physics, National Central University, Chungli 320, Taiwan (China); Yo, H.-J. [Department of Physics, National Cheng-Kung University, Tainan 701, Taiwan (China)

2008-07-15

73

Uterine torsion in mares.  

PubMed

Uterine torsion typically occurs during mid to late gestation and is estimated to cause 5% to 10% of all equine obstetric emergencies. Clinical signs include abdominal pain that may be mistaken for gastrointestinal distress, parturition, or abortion. Uterine torsion is an emergency for the mare and fetus, and early recognition and intervention are essential to optimizing the chance of survival. This article reviews the etiology, diagnosis, treatment, and prognosis of uterine torsion in mares. PMID:23532880

Yorke, Elizabeth H; Caldwell, Fred J; Johnson, Aime K

2012-12-01

74

A comparison of two theories of perceived distance on the ground plane: The angular expansion hypothesis and the intrinsic bias hypothesis  

PubMed Central

Two theories of distance perception—ie, the angular expansion hypothesis (Durgin and Li, 2011 Attention, Perception, & Psychophysics 73 1856–1870) and the intrinsic bias hypothesis (Ooi et al, 2006, Perception 35 605–624)—are compared. Both theories attribute exocentric distance foreshortening to an exaggeration in perceived slant, but their fundamental geometrical assumptions are very different. The intrinsic bias hypothesis assumes a constant bias in perceived geographical slant of the ground plane and predicts both perceived egocentric and exocentric distances are increasingly compressed. In contrast, the angular expansion hypothesis assumes exaggerations in perceived gaze angle and perceived optical slant. Because the bias functions of the two angular variables are different, it allows the angular expansion hypothesis to distinguish two types of distance foreshortening—the linear compression in perceived egocentric distance and the nonlinear compression in perceived exocentric distance. While the intrinsic bias is proposed only for explaining distance biases, the angular expansion hypothesis provides accounts for a broader range of spatial biases.

Li, Zhi; Durgin, Frank H

2012-01-01

75

Nuclear spin selective laser control of rotational and torsional dynamics.  

PubMed

We explore the possibility of controlling rotational-torsional dynamics of non-rigid molecules with strong, non-resonant laser pulses and demonstrate that transient, laser-induced torsional alignment depends on the nuclear spin of the molecule. Consequently, nuclear spin isomers can be manipulated selectively by a sequence of time-delayed laser pulses. We show that two pulses with different polarization directions can induce either overall rotation or internal torsion, depending on the nuclear spin. Nuclear spin selective control of the angular momentum distribution may open new ways to separate and explore nuclear spin isomers of polyatomic molecules. PMID:22380044

Floss, J; Grohmann, T; Leibscher, M; Seideman, T

2012-02-28

76

Anti-skid control system with torsion torque correction  

US Patent & Trademark Office Database

A anti-skid control system detects a torsion torque applied to each of the wheels of a vehicle, and controls a braking force on the basis of a corrected acceleration as a wheel acceleration is corrected by the detected torsion torque. The corrected acceleration Gc can approximately be expressed by Gc=(Kr/Iw)(.mu..multidot.W.multidot.r-Tb), where Iw, inertia moment of the wheel .omega., angular velocity of the wheel (the turning direction of the wheel when it advances is positive); Tt, torsion torque; .mu., friction coefficient of the road surface; W, load on the wheel; r, radius of the wheel; Tb, brake torque; Kr, constant.

1997-08-12

77

Perturbation theory for spin ladders using angular-momentum coupled bases  

SciTech Connect

We compute bulk properties of Heisenberg spin-1/2 ladders using Rayleigh-Schr{umlt o}dinger perturbation theory in the rung and plaquette bases. We formulate a method to extract high-order perturbative coefficients in the bulk limit from solutions for relatively small finite clusters. For example, a perturbative calculation for an isotropic 2{times}12 ladder yields an eleventh-order estimate of the ground-state energy per site that is within 0.02{percent} of the density-matrix-renormalization-group value. Moreover, the method also enables a reliable estimate of the radius of convergence of the perturbative expansion. We find that for the rung basis the radius of convergence is {lambda}{sub c}{approx_equal}0.8, with {lambda} defining the ratio between the coupling along the chain relative to the coupling across the chain. In contrast, for the plaquette basis we estimate a radius of convergence of {lambda}{sub c}{approx_equal}1.25. Thus, we conclude that the plaquette basis offers the best currently available perturbative approach which can provide a reliable treatment of the physically interesting case of isotropic ({lambda}=1) spin ladders. We illustrate our methods by computing perturbative coefficients for the ground-state energy per site, the gap, and the one-magnon dispersion relation. {copyright} {ital 1998} {ital The American Physical Society}

Piekarewicz, J. [Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306 (United States); Shepard, J.R. [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)

1998-10-01

78

Can Torsion BE Treated as Just another Tensor Field?  

NASA Astrophysics Data System (ADS)

Many alternative gravity theories use an independent connection which leads to torsion in addition to curvature. Some have argued that there is no physical need to use such connections, that one can always use the Levi-Civita connection and just treat torsion as another tensor field. We explore this issue here in the context of the Poincaré Gauge theory of gravity, which is usually formulated in terms of an affine connection for a Riemann-Cartan geometry (torsion and curvature). We compare the equations obtained by taking as the independent dynamical variables: (i) the orthonormal coframe and the connection and (ii) the orthonormal coframe and the torsion (contortion), and we also consider the coupling to a source. From this analysis we conclude that, at least for this class of theories, torsion should not be considered as just another tensor field.

Nester, James M.; Wang, Chih-Hung

79

Kinematics of the Torsion of space-time  

SciTech Connect

On a macroscopic level we take general relativity as the appropriate theory of space-time and gravity. We will argue that, on a more microscopic level, in the Compton wavelength regime of elementary particles, there are good reasons for suspecting the presence of a torsion of space-time. A corresponding gauge-theoretical formalism related to the Poincare group is reviewed, and the kinematical consequences of the presence of a torsion are worked out. In particular we dicuss the operational meaning and the measurability of torsion. The dynamics of torsion is left for a forthcoming article.

Hehl, F.W.

1985-04-01

80

Testicular torsion: a review.  

PubMed

Torsion of the testis, also referred to as torsion of the spermatic cord, is a subject of debate among physicians and surgeons. Testicular torsion is an acute vascular event causing the rotation of the vascular pedicle of the testis, thereby impeding the blood flow to the testis and the scrotal contents. It could be either within or outside the tunica vaginalis. Testicular torsion causes immediate circulatory changes and long-term sequelae such as testicular function and fertility. It is considered a surgical emergency, as a delay causes irreversible testicular damage. The diagnosis and treatment of testicular torsion are discussed in this review, which also illustrates an algorithm and a scoring system for the diagnosis and management of this condition based on current literature. PMID:17043561

Pentyala, S; Lee, J; Yalamanchili, P; Vitkun, S; Khan, S A

2001-01-01

81

Torsional actuator motor using solid freeform fabricated PZT ceramics  

NASA Astrophysics Data System (ADS)

A torsional actuator has been developed at NRL utilizing the high piezoelectric shear coefficient, d15. This torsional actuator uses an even number of alternately poled segments of electroactive PZT. Under an applied electric field, the torsional actuator produces large angular displacement and a high torque. The solid freeform fabrication technique of the laminated object manufacturing (LOM) is used for rapid prototyping of torsional actuator with potential cost and time saving. First step to demonstrate the feasibility of the LOM technique for the torsional actuator device fabrication is to make near net shape segments. We report a prototype PZT torsional actuator using LOM prepared PZT-5A segments. Fabrication processes and test results are described. The torsional actuator PZT-5A tube has dimensions of 13 cm long, 2.54 cm OD and 1.9 cm ID. Although the piezoelectric strain is small, it may be converted into large displacement via accumulation of the small single cycle displacements over many cycles using AC driving voltage such as with a rotary 'inchworm' actuator or an ultrasonic rotary motor. A working prototype of a full-cycle motor driven by the piezoelectric torsional actuator has been achieved. The rotational speed is 1,200 rpm under 200 V/cm field at the resonant frequency of 4.5 kHz.

Kim, Chulho; Wu, Carl C. M.; Bender, Barry

2004-07-01

82

Piezoelectric actuator generating torsional displacement from piezoelectric d15 shear response  

Microsoft Academic Search

A torsional actuator generating angular displacement from piezoelectric shear strain was developed. The actuator is a tube consisting of an even number of segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuator: (i) prove the proposed concept of the torsional

A. E. Glazounov; Q. M. Zhang; C. Kim

1998-01-01

83

[Tibial torsion deformities].  

PubMed

Tibial torsion defects are usually not clinically evident and, hence, are often overlooked. Clinical examination and CT scan have proved to be the best ways of measuring static tibial torsion, whereas dynamic measurements are usually performed in the clinic and the "gait laboratory." Only few studies have determined there to be a connection between a torsion defect in the lower leg and expected pathological conditions of the knee and ankle joints. However, patellofemoral instability, Osgood-Schlatter disease, osteochondrosis dissecans are increasingly being found in cases of increased external tibial torsion and arthrosis in reduced torsion. Although spontaneous correction may occur in certain cases, in others the only way to correct the condition is by employing physiologic torsion. Conservative treatment methods such as bandages or orthosis have been shown to not have any effect on torsion; thus, surgical treatment is the only successful way to correct a pathologic angle of rotation of the tibia. For this, supramalleolar osteotomy with fixation using Kirscher wires and plaster or an external fixator are the most common treatments. PMID:11092002

Lampert, C; Thomann, B; Brunner, R

2000-09-01

84

Torsion cosmological dynamics  

SciTech Connect

In this paper, the dynamical attractor and heteroclinic orbit have been employed to make the late-time behaviors of the model insensitive to the initial condition and thus alleviate the fine-tuning problem in the torsion cosmology. The late-time de Sitter attractor indicates that torsion cosmology is an elegant scheme and the scalar torsion mode is an interesting geometric quantity for physics. The numerical solutions obtained by Nester et al. are not periodic solutions but are quasiperiodic solutions near the focus for the coupled nonlinear equations.

Li Xinzhou; Sun Changbo; Xi Ping [Shanghai United Center for Astrophysics (SUCA), Shanghai Normal University, 100 Guilin Road, Shanghai 200234 (China)

2009-01-15

85

Flexural-Torsional Buckling of Arches.  

National Technical Information Service (NTIS)

A flexural-torsional buckling theory for circular arches of doubly symmetric cross-section is developed. Nonlinear expressions for the axial and shear strains are derived and these are substituted into the second variation of the total potential to obtain...

J. P. Papangelis N. S. Trahair

1985-01-01

86

Complex elasticoplastic torsion of cylindrical shafts  

Microsoft Academic Search

The present article discusses axisymmetric problems involving the torsion of variable or constant diameter, with complex static and mixed boundary conditions. In the general case, it is assumed that the material of the shaft is isotropic, and that it is subject to the deformation theory of plasticity, with an arbitrary degree of hardening, during the active loading process. The investigated

Yu. V. Nemirovskii; É. É. Saks

1973-01-01

87

[Adnexal torsion: three cases].  

PubMed

Adnexal torsion is a gynecological emergency caused by the torsion of the ovary over its pedicle producing lymphatic and venous stasis, later it develops into ischemia and necrosis, when is not treated. Until recently, the treatment for adnexal torsion has been adnexectomy. This paper report three cases treated successfully with conservative treatment. It is essential to establish a protocol for adnexal torsion management where radical treatments are abandoned and conservative surgeries, such as detorsion and plication, are performed. We suggest as a first choice management adnexal detorsion, in case malignity is suspected to have intraoperative pathologic analysis, and based on the results to decide to preserve the adnexal or remove it for definitive cure. PMID:23819427

Sánez, Henry Aristóteles Mateo; Taboada-Pérez, Grecia Carolina; Hernández-Arroyo, Lysandra; Mateo-Madrigal, Melissa; Mateo-Madrigal, Victoria

2013-05-01

88

Torsion pendulum revisited  

NASA Astrophysics Data System (ADS)

We present an analysis of the motion of a simple torsion pendulum and we describe how, with straightforward extensions to the usual basic dynamical model, we succeed in explaining some unexpected features we found in our data, like the modulation of the torsion mode at a higher frequency and the frequency splitting of the swinging motion. Comparison with observed values yields estimates for the misalignment angles and other parameters of the model.

Bassan, Massimo; De Marchi, Fabrizio; Marconi, Lorenzo; Pucacco, Giuseppe; Stanga, Ruggero; Visco, Massimo

2013-10-01

89

New torsional actuator based on shear piezoelectric response  

Microsoft Academic Search

A torsional actuator generating angular displacement from the piezoelectric shear strain was developed. The actuator is a tube consisting of an even number of the segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuator: (1) prove the proposed concept of

Alexandre E. Glazounov; Qiming Zhang; Chulho Kim

1998-01-01

90

Torsional actuator based on mechanically amplified shear piezoelectric response  

Microsoft Academic Search

A torsional actuator, based on the concept of mechanical amplification of piezoelectric shear strain and capable of generating large angular displacement, was proposed and studied experimentally. The actuator is a tube consisting of an even number of the segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The

A. E Glazounov; Q. M Zhang; C Kim

2000-01-01

91

Angular and Linear Velocity Estimation for a Re-Entry Vehicle Using Six Distributed Accelerometers: Theory, Simulation and Feasibility  

SciTech Connect

This report describes a feasibility study. We are interested in calculating the angular and linear velocities of a re-entry vehicle using six acceleration signals from a distributed accelerometer inertial measurement unit (DAIMU). Earlier work showed that angular and linear velocity calculation using classic nonlinear ordinary differential equation (ODE) solvers is not practically feasible, due to mathematical and numerical difficulties. This report demonstrates the theoretical feasibility of using model-based nonlinear state estimation techniques to obtain the angular and linear velocities in this problem. Practical numerical and calibration issues require additional work to resolve. We show that the six accelerometers in the DAIMU are not sufficient to provide observability, so additional measurements of the system states are required (e.g. from a Global Positioning System (GPS) unit). Given the constraint that our system cannot use GPS, we propose using the existing on-board 3-axis magnetometer to measure angular velocity. We further show that the six nonlinear ODE's for the vehicle kinematics can be decoupled into three ODE's in the angular velocity and three ODE's in the linear velocity. This allows us to formulate a three-state Gauss-Markov system model for the angular velocities, using the magnetometer signals in the measurement model. This re-formulated model is observable, allowing us to build an Extended Kalman Filter (EKF) for estimating the angular velocities. Given the angular velocity estimates from the EKF, the three ODE's for the linear velocity become algebraic, and the linear velocity can be calculated by numerical integration. Thus, we do not need direct measurements of the linear velocity to provide observability, and the technique is mathematically feasible. Using a simulation example, we show that the estimator adds value over the numerical ODE solver in the presence of measurement noise. Calculating the velocities in the presence of significant measurement noise is not feasible with a classic ODE solver. The EKF is able to deal effectively with the noise and provide useful angular velocity estimates. The linear velocity estimates for this simulation show numerical difficulties associated with the nonlinear ODE's and the quadrature operation. Future work will focus on dealing with practical numerical issues and the issue of calibrating the DAIMU to deal with uncertainties in the accelerometer positions and locations.

Clark, G

2003-04-28

92

Angular distribution of Auger electrons from fixed-in-space and rotating C 1s-->2pi photoexcited CO: theory.  

PubMed

The one-center approach for molecular Auger decay is applied to predict the angular distribution of Auger electrons from rotating and fixed-in-space molecules. For that purpose, phase shifts between the Auger decay amplitudes have been incorporated in the atomic model. The approach is applied to the resonant Auger decay of the photoexcited C 1s-->2pi resonance in carbon monoxide. It is discussed how the symmetry of the final ionic state is related to features in the angular distributions and a parametrization for the molecular frame Auger electron angular distribution is suggested. The angular distribution of Auger electrons after partial orientation of the molecule by the sigma-->pi-excitation process is also calculated and compared to available experimental and theoretical data. The results of the one-center approach are at least of the same quality as the available theoretical data even though the latter stem from a much more sophisticated method. As the one-center approximation can be applied with low computational demand even to extended systems, the present approach opens a way to describe the angular distribution of Auger electrons in a wide variety of applications. PMID:19140614

Fink, R F; Piancastelli, M N; Grum-Grzhimailo, A N; Ueda, K

2009-01-01

93

Angular momentum of synchrotron radiation  

NASA Astrophysics Data System (ADS)

Exact methods of the theory of relativistic radiation of an arbitrarily moving charge provide the basis for the theory of radiation of the angular momentum of an electromagnetic field stated here. As an application, properties of orbital and spin angular momenta of synchrotron radiation are considered.

Bordovitsyn, V. A.; Konstantinova, O. A.; Nemchenko, E. A.

2012-06-01

94

Brane world black holes in teleparallel theory equivalent to general relativity and their Killing vectors, energy, momentum and angular momentum  

NASA Astrophysics Data System (ADS)

The energy-momentum tensor, which is coordinate-independent, is used to calculate energy, momentum and angular momentum of two different tetrad fields. Although, the two tetrad fields reproduce the same space-time their energies are different. Therefore, a regularized expression of the gravitational energy-momentum tensor of the teleparallel equivalent of general relativity (TEGR), is used to make the energies of the two tetrad fields equal. The definition of the gravitational energy-momentum is used to investigate the energy within the external event horizon. The components of angular momentum associated with these space-times are calculated. In spite of using a static space-time, we get a non-zero component of angular momentum! Therefore, we derive the Killing vectors associated with these space-times using the definition of the Lie derivative of a second rank tensor in the framework of the TEGR to make the picture more clear.

Nashed, Gamal G. L.

2010-02-01

95

Nanomechanical torsional resonators for frequency-shift infrared thermal sensing.  

PubMed

We investigate use of nanomechanical torsional resonators for frequency-shift-based infrared (IR) thermal sensing. Nanoscale torsion rods, ~1 ?m long and 50-100 nm in diameter, provide both extraordinary thermal isolation and excellent angular displacement and torque sensitivities, of order ~10(-7) rad·Hz(-1/2) and ~10(-22) (N·m) Hz(-1/2), respectively. Furthermore, these nanorods act as linear torsional springs, yielding a maximum angular displacement of 3.6° and a dynamic range of over 100 dB; this exceeds the performance of flexural modes by as much as 5 orders of magnitude. These attributes lead to superior noise performance for torsional-mode sensing. We demonstrate the operational principles of torsional-mode IR detection, attaining an uncooled noise equivalent temperature difference (NETD) of 390 mK. By modeling the fundamental noise processes, we project that further reduction of device size can significantly improve thermal responsivity; a room-temperature NETD below 10 mK appears feasible. PMID:23458733

Zhang, X C; Myers, E B; Sader, J E; Roukes, M L

2013-03-07

96

Torsional tibia vara.  

PubMed

Infantile tibial torsion and tibia vara are common childhood deformities with controversial methods of measurement and treatment. The authors believe that the two deformities are different manifestations of the same entity for which the term "torsional tibia vara" is adopted. A practical method of measurement and a decisive method of conservative treatment are presented for this disorder. The concept as well as the methods of measurement and treatment have been successfully practiced by the senior author (H.Z.) for the past 20 years. PMID:1308881

Zahiri, H; Shariatmadari, F; Sadighi, S

1992-01-01

97

Torsion and the Electromagnetic Field  

Microsoft Academic Search

In the framework of the teleparallel equivalent of general relativity, we study the dynamics of a gravitationally coupled electromagnetic field. It is shown that the electromagnetic field is able not only to couple to torsion, but also, through its energy-momentum tensor, produce torsion. Furthermore, it is shown that the coupling of the electromagnetic field with torsion preserves the local gauge

V. C. de Andrade; J. G. Pereira

1999-01-01

98

Beyond the chemiosmotic theory: analysis of key fundamental aspects of energy coupling in oxidative phosphorylation in the light of a torsional mechanism of energy transduction and ATP synthesis--invited review part 1.  

PubMed

In Part 1 of this invited article, we consider the fundamental aspects of energy coupling in oxidative phosphorylation. The central concepts of the chemiosmotic theory are re-examined and the major problems with its experimental verification are analyzed and reassessed from first principles. Several of its assumptions and interpretations (with regard, for instance, to consideration of the membrane as an inert barrier, the occurrence of energy transduction at thermodynamic equilibrium, the completely delocalized nature of the protonmotive force, and the notion of indirect coupling) are shown to be questionable. Important biological implications of this analysis for molecular mechanisms of biological energy transduction are enumerated. A fresh molecular mechanism of the uncoupling of oxidative phosphorylation by classical weak acid anion uncouplers and an adequate explanation for the existence of uncoupler-resistant mutants (which until now has remained a mystery) has been proposed based on novel insights arising from a new torsional mechanism of energy transduction and ATP synthesis. PMID:20490637

Nath, Sunil

2010-05-20

99

Depth-selective 57Fe conversion-electron Mössbauer spectroscopy. I. Theory-improved accuracy, angular effects  

Microsoft Academic Search

The simultaneous energy loss and angular distribution of 7.3- and 13.6-keV internal conversion electrons as a function of their starting depth in a plane iron sample has been determined by Monte Carlo simulation of ~=6×106 electron histories. The calculation is based on a corrected, screened Rutherford elastic cross section combined with a simple generalized-oscillator-strength-density model for the inelastic interaction. As

D. Liljequist; M. Ismail

1985-01-01

100

Torsional anharmonicity in the conformational thermodynamics of flexible molecules  

NASA Astrophysics Data System (ADS)

We present an algorithm for calculating the conformational thermodynamics of large, flexible molecules that combines ab initio electronic structure theory calculations with a torsional path integral Monte Carlo (TPIMC) simulation. The new algorithm overcomes the previous limitations of the TPIMC method by including the thermodynamic contributions of non-torsional vibrational modes and by affordably incorporating the ab initio calculation of conformer electronic energies, and it improves the conventional ab initio treatment of conformational thermodynamics by accounting for the anharmonicity of the torsional modes. Using previously published ab initio results and new TPIMC calculations, we apply the algorithm to the conformers of the adrenaline molecule.

Miller, Thomas F., III; Clary, David C.

101

Torsional Measurements on Skin  

Microsoft Academic Search

Synopsis--An apparatus is described for measuring the STIFFNESS and ELASTICITY of thin strips of SKIN. Physical properties of skin in TORSION show decreases in sliffness with increased humidity of the ambient environment. The elasticity of the strips under- went a minimum between 50-80% relative humidity. Extraction of naturally occurring humectant was demonstrated to increase the physical stiffness of CALIUS and

KARL LADEN; ROBERT MORROW

102

Idiopathic torsion dystonia  

Microsoft Academic Search

Idiopathic torsion dystonia (ITD) is characterized by involuntary, repetitive, sustained muscle contractions or postures involving one or more sites of the body. Symptoms typically develop first in an arm or leg in middle to late childhood and progress in approximately 30% of patients to other body regions (generalized dystonia) within about five years. Distribution and severity of symptoms vary widely

Thomas Gasser

2004-01-01

103

Torsion-vibration coupling in methanol: The adiabatic approximation and intramolecular vibrational redistribution scaling  

NASA Astrophysics Data System (ADS)

The four-dimensional model Hamiltonian of Wang and Perry [J. Chem. Phys. 109, 10795 (1998)] is used to compare the approximate adiabatic separation of the torsion and CH stretches in methanol to an exact solution of the same Hamiltonian. The adiabatic approximation accounts for the pattern of the energy levels in the lowest torsional states, including the inverted tunneling splittings, but does not account for the pattern of systematic two- and four-fold near degeneracies at high torsional excitation. In the adiabatic basis, the nonadiabatic couplings mix the torsional and vibrational degrees of freedom and hence are a source for intramolecular vibrational redistribution (IVR). These IVR matrix elements are found to decrease by only a factor of 2 or 3 with each higher coupling order, in agreement with the results of Pearman and Gruebele [Z. Phys. Chem. Munich 214, 1439 (2000)]. This gentle scaling behavior, which contrasts with a steeper falloff with coupling order in more rigid molecules, points to a more important role for direct high-order couplings in torsional molecules. In this model, the scaling behavior derives from a single coupling term that is low order in the torsional angular momentum in combination with one-dimensional torsional functions that include contributions from many torsional angular momenta.

Clasp, Trocia N.; Perry, David S.

2006-09-01

104

Torsion as a source of expansion in a Bianchi type-I universe in the self-consistent Einstein-Cartan theory of a perfect fluid with spin density  

SciTech Connect

We show that a generalized (or ''power law'') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley. This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.

Bradas, J.C.; Fennelly, A.J.; Smalley, L.L.

1987-04-15

105

Constraining spacetime torsion with the Moon and Mercury  

SciTech Connect

We report a search for new gravitational physics phenomena based on Riemann-Cartan theory of general relativity including spacetime torsion. Starting from the parametrized torsion framework of Mao, Tegmark, Guth, and Cabi, we analyze the motion of test bodies in the presence of torsion, and, in particular, we compute the corrections to the perihelion advance and to the orbital geodetic precession of a satellite. We consider the motion of a test body in a spherically symmetric field, and the motion of a satellite in the gravitational field of the Sun and the Earth. We describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general differ from geodesics when torsion is present. We derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of celestial mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter of the satellite. The computed secular variations show how the corrections to the perihelion advance and to the orbital de Sitter effect depend on the torsion parameters. All computations are performed under the assumptions of weak field and slow motion. To test our predictions, we use the measurements of the Moon's geodetic precession from lunar laser ranging data, and the measurements of Mercury's perihelion advance from planetary radar ranging data. These measurements are then used to constrain suitable linear combinations of the torsion parameters.

March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone [Istituto per le Applicazioni del Calcolo, CNR, Via dei Taurini 19, 00185 Roma, Italy, and INFN - Laboratori Nazionali di Frascati (LNF), via E. Fermi 40 Frascati, 00044 Roma (Italy); Dipartimento di Matematica, Universita di Roma ''Tor Vergata'', via della Ricerca Scientifica 1, 00133 Roma, Italy, and INFN - Laboratori Nazionali di Frascati (LNF), via E. Fermi 40 Frascati, 00044 Roma (Italy); Dipartimento di Matematica, Universita di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Roma, Italy, and INFN - Laboratori Nazionali di Frascati (LNF), via E. Fermi 40 Frascati, 00044 Roma (Italy); INFN - Laboratori Nazionali di Frascati (LNF), via E. Fermi 40 Frascati, 00044 Roma (Italy)

2011-05-15

106

Primordial magnetic fields and dynamos from parity violated torsion  

NASA Astrophysics Data System (ADS)

It is well known that torsion induced magnetic fields may seed galactic dynamos, but the price one pays for that is the conformal and gauge invariance breaks and a tiny photon mass. More recently I have shown [L.C. Garcia de Andrade, Phys. Lett. B 468 (2011) 28] that magnetic fields decay in a gauge invariant non-minimal coupling theory of torsion is slow down, which would allow for dynamo action to take place. In this Letter, by adding a parity violation term of the type R? to the non-coupling term, a magnetic dynamo equation is obtained. From dynamo equation it is shown that torsion terms only appear in the dynamo equation when diffusion in the cosmic plasma is present. Torsion breaks the homogeneity of the magnetic field in the universe. Since Zeldovich anti-dynamo theorem assumes that the spacetime should be totally flat, torsion is responsible for violation of anti-dynamo theorem in 2D spatial dimensions. Contrary to previous results torsion induced primordial magnetic fields cannot seed galactic dynamos since from torsion and diffusion coefficient the decaying time of the magnetic field is 106yrs, which is much shorter than the galaxy age.

Garcia de Andrade, L. C.

2012-05-01

107

Triorchidism with Torsion  

PubMed Central

Polyorchidism is a rare anomaly; triorchidism is the commonest type and is frequently associated with cryptorchidism, inguinal hernia, and testicular torsion. It is also reported as an increased risk of testicular malignancy. We report a case of 72-year-old man with left supernumerary testes in the left hemiscrotum. He presented with pain in his left hemiscrotum of short duration. Physical examination revealed tender hemiscrotum. Both ultrasound and MRI examinations revealed polyorchidism. One of the testes in the left hemiscrotum revealed features of torsion and hemorrhagic necrosis. Polyorchidism is a rare entity. In most cases, sonography alone is diagnostic of polyorchidism. Magnetic resonance imaging may provide additional information in complicated cases of polyorchidism.

Kumar, K; Das, D; Shivaraj

2012-01-01

108

Transcription under torsion.  

PubMed

In cells, RNA polymerase (RNAP) must transcribe supercoiled DNA, whose torsional state is constantly changing, but how RNAP deals with DNA supercoiling remains elusive. We report direct measurements of individual Escherichia coli RNAPs as they transcribed supercoiled DNA. We found that a resisting torque slowed RNAP and increased its pause frequency and duration. RNAP was able to generate 11 ± 4 piconewton-nanometers (mean ± standard deviation) of torque before stalling, an amount sufficient to melt DNA of arbitrary sequence and establish RNAP as a more potent torsional motor than previously known. A stalled RNAP was able to resume transcription upon torque relaxation, and transcribing RNAP was resilient to transient torque fluctuations. These results provide a quantitative framework for understanding how dynamic modification of DNA supercoiling regulates transcription. PMID:23812716

Ma, Jie; Bai, Lu; Wang, Michelle D

2013-06-28

109

Femtosecond torsional relaxation  

NASA Astrophysics Data System (ADS)

Molecular conformational reorganization following photon absorption is a fundamental process driving reactions such as the cis-trans isomerization at the heart of the primary step of vision and can be exploited for switching in artificial systems using photochromics. In general, conformational change occurs on a timescale defined by the energy of the main vibrational mode and the rate of energy dissipation. Typically, for a conformational change such as a twist around the backbone of a conjugated molecule, this occurs on the tens of picoseconds timescale. However, here we demonstrate experimentally that in certain circumstances the molecule, in this case an oligofluorene, can change conformation over two orders of magnitude faster (that is sub-100fs) in a manner analogous to inertial solvent reorganization demonstrated in the 1990s. Theoretical simulations demonstrate that non-adiabatic transitions during internal conversion can efficiently convert electronic potential energy into torsional kinetic energy, providing the `kick' that prompts sub-100fs torsional reorganization.

Clark, J.; Nelson, T.; Tretiak, S.; Cirmi, G.; Lanzani, G.

2012-03-01

110

Torsional oscillations of sunspots  

Microsoft Academic Search

The torsional oscillations of four single sunspots are investigated on the basis of the observations of the longitudinal magnetic fields and the velocity fields in the photospheric line Fe I lambda 525.3 nm. We reconstructed all three components of the magnetic field and velocity field from their line-of-sight components. The period of the oscillations is from 3.4 to 7.7 days.

S. Gopasyuk

2004-01-01

111

Performance of an angular flange aeroelastic wind energy converter  

SciTech Connect

ALL conventional wind turbines operate on the principles of turbomachinaries, with wind being made to flow over a set of rotating vanes. Recently, a new concept for wind energy conversion based on aeroelastic instability was introduced. It is well known that couplings between the vibration of an elastic structure and fluid stream may lead to aeroelastic instability. Energy then is transferred from the airstream into the elastic structure, which results in a destructive monotonic increase of the vibration amplitude of the structure. The failure of the Tacoma Narrows Bridge is one of the well-known examples of such a disaster. The use of an aeroelastic instability (or flutter) mechanism for constructing a wind energy converter was suggested. The theory for a torsional wind energy converter and the results of some model tests were also presented. Recently, some studies on similar types of wind energy converters using oscillating airfoils were reported. In the present study an angular flange H-section model of a torsional aeroelastic wind energy converter is constructed, and its performances under various conditions are investigated. The effects of the variations of the flange angle and the flange width on the performance of the model are studied. The weight of the pendulum is also varied, and its effects on the power coefficient of the model are investigated. It is observed that the efficiency of energy conversion decreases with an increase in wind speed. A method for possible improvement of the theoretical prediction is suggested and discussed.

Ahmadi, G.

1983-05-01

112

Nanoscale Torsional Optomechanics  

NASA Astrophysics Data System (ADS)

Torsional resonators, which can be designed to measure torques with high sensitivity, have been an effective tool to study magnetism, gravity, and various material and optical properties. Taking advantage of improved micro-fabrication techniques, these torque sensors are now pushing the limit in terms of size - scaling all the way down to the nanoscale regime - and therefore must be equipped with sensitive mechanical transduction schemes. Here we present a method for measuring torques as little as 4 x10^20 Nm, using optomechanics. Recently optomechanics has been revealed as a reliable method for mechanical transduction, with higher sensitivity than previously possible. This sensitivity of the optomechanical system comes from the evanescent coupling between a high quality factor optical resonator and the mechanical device, and is fully integratable on a chip using the silicon-on-insulator platform. We present our first generation torsional optomechanics, using a dimpled optical fiber system for measurement, with a calibrated sensitivity down to 7 fm/?Hz. This torsional optomechanical platform will now serve as a basis for further experiments to explore new physics and technology, in particular quantum resonators at low temperatures.

Kim, Paul H.; Doolin, Callum; Hauer, Bradley D.; MacDonald, Allison J. R.; Freeman, Mark R.; Barclay, Paul E.; Davis, John P.

2013-03-01

113

The effect to bending fatigue strength of 65 mn under torsion strain-hardening  

NASA Astrophysics Data System (ADS)

Bending Fatigue experiments for 65Mn are carried out to study the effects of torsion strain-hardening. Firstly bending fatigue specimens are pre-twisted for torsion strain-hardening by using torsion testing machine. And specimens are divided as 8 groups and each group has 8 specimens. A series of plastic shear strains are applied to each group. Then bending fatigue experiments are carried on to estimate torsion fatigue strength by fatigue bending machine. Finally micrograms of fatigue damage are taken by stereo microscope. The test results showed that torsion strain-hardening has a certain effects that when torsion plastic strain is small, bending fatigue strength is increased. Oppositely, when torsion plastic strain is large, bending fatigue strength are all decreased in a large rate compared with specimens without torsion strain-hardening. Comparing different test results and corresponding paragraphs obtained from stereo microscope, a reasonable explanation can be deduced by using metal micromechanics theory and crystal lattice dislocation theory. A possible reason is that when torsion plastic strain is small, there will be more dislocation in crystal lattice, which can raise the fatigue strength. And when torsion plastic strain is large, dislocations are piled up in some position which can bring flaws under loads, which reduce the fatigue strength of specimen.

Zou, Guangping; Xue, Qichao; Li, Wei

2009-12-01

114

Optimal Estimation of Angular Misalignment.  

National Technical Information Service (NTIS)

This work considers the application of optimal estimation theory to the general problem of coordinate frame angular misalignment estimation. Two cases of interest are considered in the theoretical investigations and simulations presented.

J. C. Ryles

1973-01-01

115

Torsional surface waves in a gradient-elastic half-space  

Microsoft Academic Search

The present work deals with torsional wave propagation in a linear gradient-elastic half-space. More specifically, we prove that torsional surface waves (i.e. waves with amplitudes exponentially decaying with distance from the free surface) do exist in a homogeneous gradient-elastic half-space. This finding is in contrast with the well-known result of the classical theory of linear elasticity that torsional surface waves

H. G. Georgiadis; I. Vardoulakis; G. Lykotrafitis

2000-01-01

116

Randall-Sundrum scenario with bulk dilaton and torsion  

NASA Astrophysics Data System (ADS)

We consider a string-inspired torsion-dilaton-gravity action in a Randall-Sundrum braneworld scenario and show that, in an effective four-dimensional theory on the visible brane, the rank-2 antisymmetric Kalb-Ramond field (source of torsion) is exponentially suppressed. The result is similar to our earlier result in [B. Mukhopadhyaya, S. Sen, and S. SenGupta, Phys. Rev. Lett. 89, 121101 (2002); Phys. Rev. Lett. 89, 259902(E) (2002)], where no dilaton was present in the bulk. This offers an explanation of the apparent invisibility of torsion in our space-time. However, in this case the trilinear couplings ˜TeV-1 between the dilaton and torsion may lead to new signals in TeV-scale experiments, bearing the stamp of extra warped dimensions.

Mukhopadhyaya, Biswarup; Sen, Somasri; Sengupta, Soumitra

2009-06-01

117

Torsion and the Electromagnetic Field  

Microsoft Academic Search

In the framework of the teleparallel equivalent of general relativity, we\\u000astudy the dynamics of a gravitationally coupled electromagnetic field. It is\\u000ashown that the electromagnetic field is able not only to couple to torsion, but\\u000aalso, through its energy-momentum tensor, to produce torsion. Furthermore, it\\u000ais shown that the coupling of the electromagnetic field with torsion preserves\\u000athe local

V. C. de Andrade; J. G. Pereira

1997-01-01

118

Regular and anomalous torsional splitting patterns: a trend in ethane-like molecules and general perspectives  

NASA Astrophysics Data System (ADS)

It is shown that torsional Coriolis coupling can alter the torsional splittings in molecules with hindered internal rotation. Splitting patterns that would occur in the absence of any vibrational contribution to the torsional angular momentum, with reference to a molecular axis system (IAM), are called regular. It is shown that different sets of vibrational coordinates, corresponding to vibrational states with different splitting patterns, can be defined for modes normal to the internal rotation axis. The forms of normal coordinates appropriate to basis vibrational states with regular and inverted splitting patterns are identified. It is found that in normal coordinates appropriate to vibrational states with regular torsional splitting patterns, the relative orientation of the displacements of pairs of atoms belonging to different molecular moieties is independent of the internal rotation angle, and relative displacements normal to the internal rotation axis can be cis or trans at any conformation. On the contrary, in normal coordinates appropriate to vibrational states with inverted torsional splitting patterns the relative orientation of such displacements changes by ?(cis-trans interchange) upon half the internal rotation converting two neighbor equivalent conformations (as in a staggered-eclipsed conformational conversion). The formation of the actual torsional splitting patterns in degenerate vibrational states of CH3CH3-type molecules depends on the joint effect of torsional Coriolis and head-tail coupling. The torsional Coriolis operator can tune pairs of levels to resonance for the action of typical head-tail coupling operators (torsion-dependent vibrational operators), depending on the values of the torsional Coriolis coefficients, generating vibrational states with either regular or inverted torsional splitting patterns and affecting the splitting magnitude. It is shown that operators with a sin3?-type torsional dependence favor the formation of inverted splitting patterns. In less symmetric molecules torsional Coriolis coupling affects the torsional splitting patterns by the same mechanism as in CH3CH3-type molecules, but the torsion-dependent operators are different and their action is expected to be less effective. Typical anomalous perpendicular splitting patterns can be predicted for non-degenerate modes localized in a single molecular moiety, normal or with a component normal to the internal rotation axis, having fixed orientation in that moiety (as the C=O or C-H stretchings of acetaldehyde). Adopting a barrier-hindered torsional basis, where the lower torsional levels can be seen as vibrational states with quantum numbers v? exhibiting tunneling splitting, one finds that all operators generating matrix elements with ?v?=+/-1, or in general odd, work toward the formation of inverted splitting patterns, generating anomalous patterns.

Lattanzi, F.; di Lauro, C.

2004-01-01

119

Torsion effects in braneworld scenarios  

SciTech Connect

We present gravitational aspects of braneworld models endowed with torsion terms both in the bulk and on the brane. In order to investigate a conceivable and measurable gravitational effect, arising genuinely from bulk torsion terms, we analyze the variation in the black hole area by the presence of torsion. Furthermore, we extend the well-known results about consistency conditions in a framework that incorporates brane torsion terms. It is shown, in a rough estimate, that the resulting effects are generally suppressed by the internal space volume. This formalism provides manageable models and their possible ramifications into some aspects of gravity in this context, and cognizable corrections and physical effects as well.

Hoff da Silva, J. M.; Rocha, R. da [Centro de Matematica, Computacao e Cognicao, Universidade Federal do ABC, 09210-170, Santo Andre, SP (Brazil)

2010-01-15

120

Superplasticity of a microcrystalline aluminum-lithium alloy under torsion  

Microsoft Academic Search

The deformation of an aluminum-lithium alloy under torsion in the temperature range 523–673 K at angular velocities of 0.322\\u000a and 0.0322 rad\\/s is studied. The shear strain ? prior to failure is found to increase with decreasing strain rate, and its\\u000a temperature dependence has a maximum at 553 K (??30). The initial loading-induced jump in the dependence of the torque

V. V. Shpeizman; M. M. Myshlyaev; M. M. Kamalov; M. M. Myshlyaeva

2003-01-01

121

Piezoelectric actuator generating torsional displacement from piezoelectric d15 shear response  

NASA Astrophysics Data System (ADS)

A torsional actuator generating angular displacement from piezoelectric shear strain was developed. The actuator is a tube consisting of an even number of segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuator: (i) prove the proposed concept of the torsional actuator, (ii) show that the actuator functions well under the torque load, and (iii) demonstrate that it has superior characteristics compared to previously reported designs of torsional actuators.

Glazounov, A. E.; Zhang, Q. M.; Kim, C.

1998-05-01

122

Transverse angular momentum of photons  

SciTech Connect

We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasiparaxial photon beams in vacuum and reproduces the known results for classical beams when applied to coherent states of the field. Both the Poynting vector, alias the linear momentum, and the angular-momentum quantum operators of a light beam are calculated including contributions from first-order transverse derivatives. This permits a correct description of the energy flow in the beam and the natural emergence of both the spin and the angular momentum of the photons. We show that for collimated beams of light, orbital angular-momentum operators do not satisfy the standard commutation rules. Finally, we discuss the application of our theory to some concrete cases.

Aiello, Andrea [Max Planck Institute for the Science of Light, Guenter-Scharowsky-Strasse 1/Bau 24, D-91058 Erlangen (Germany); Marquardt, Christoph; Leuchs, Gerd [Max Planck Institute for the Science of Light, Guenter-Scharowsky-Strasse 1/Bau 24, D-91058 Erlangen (Germany); Institute for Optics, Information and Photonics, University Erlangen-Nuernberg, Staudtstrasse 7/B2, D-91058 Erlangen (Germany)

2010-05-15

123

Torsion, superconductivity, and massive electrodynamics  

SciTech Connect

A model for superconductor, based on massive electrodynamics in spaces with torsion is given. The generalized London equations for Cartan spaces are presented. From the London equations we show that it is possible to obtain an expression for the magnetic permeability constant in vacuum in terms of the time component of the torsion vector. 14 refs.

de Andrade, L.C. [Departamento de Fisica, Rio de Janerio (Brazil)

1992-07-01

124

Reduced Systolic Torsion in Chronic \\  

Microsoft Academic Search

Background—Global left ventricular (LV) torsion declines with chronic ischemic mitral regurgitation (MR), which may accelerate the LV remodeling spiral toward global cardiomyopathy; however, it has not been definitively established whether this torsional decline is attributable to the infarct, the MR, or their combined effect. We tested the hypothesis that chronic \\

Daniel B. Ennis; Tom C. Nguyen; Akinobu Itoh; Wolfgang Bothe; David H. Liang; Neil B. Ingels; D. Craig Miller

2010-01-01

125

Big bounce from spin and torsion  

NASA Astrophysics Data System (ADS)

The Einstein-Cartan-Sciama-Kibble theory of gravity naturally extends general relativity to account for the intrinsic spin of matter. Spacetime torsion, generated by spin of Dirac fields, induces gravitational repulsion in fermionic matter at extremely high densities and prevents the formation of singularities. Accordingly, the big bang is replaced by a bounce that occurred when the energy density {? ? gT^4} was on the order of {n^2/m_Pl^2} (in natural units), where {n ? gT^3} is the fermion number density and g is the number of thermal degrees of freedom. If the early Universe contained only the known standard-model particles ( g ? 100), then the energy density at the big bounce was about 15 times larger than the Planck energy. The minimum scale factor of the Universe (at the bounce) was about 1032 times smaller than its present value, giving ? 50 ?m. If more fermions existed in the early Universe, then the spin-torsion coupling causes a bounce at a lower energy and larger scale factor. Recent observations of high-energy photons from gamma-ray bursts indicate that spacetime may behave classically even at scales below the Planck length, supporting the classical spin-torsion mechanism of the big bounce. Such a classical bounce prevents the matter in the contracting Universe from reaching the conditions at which a quantum bounce could possibly occur.

Pop?awski, Nikodem J.

2012-04-01

126

A random matrix\\/transition state theory for the probability distribution of state-specific unimolecular decay rates: Generalization to include total angular momentum conservation and other dynamical symmetries  

Microsoft Academic Search

A previously developed random matrix\\/transition state theory (RM\\/TST) model for the probability distribution of state-specific unimolecular decay rates has been generalized to incorporate total angular momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall

Rigoberto Hernandez; William H. Miller; C. Bradley Moore; William F. Polik

1993-01-01

127

Torsional oscillations of sunspots  

NASA Astrophysics Data System (ADS)

The torsional oscillations of four single sunspots are investigated on the basis of the observations of the longitudinal magnetic fields and the velocity fields in the photospheric line Fe I ? 525.3 nm. We reconstructed all three components of the magnetic field and velocity field from their line-of-sight components. The period of the oscillations is from 3.4 to 7.7 days. The phase of the azimuthal component of the velocity is ahead of the phases of all three components of the magnetic field. If the density of plasma in the penumbra 10-4 kg/m3, as the magnetic energy of oscillations exceeds their kinetic energy by a factor of 10 to 100. Our results indicate that those oscillations are not free oscillations.

Gopasyuk, S.

2004-10-01

128

Torsional nystagmus during vertical pursuit.  

PubMed

We examined three patients with cavernous angioma within the middle cerebellar peduncle. Each patient had an unusual ocular motor finding: the appearance of a strong torsional nystagmus during vertical pursuit. The uncalled-for torsion changed direction when vertical pursuit changed direction. In one patient, we recorded eye movements with the magnetic field technique using a combined direction and torsion eye coil. The slow-phase velocity of the inappropriate torsional nystagmus was linearly related to the slow-phase velocity of vertical smooth pursuit, and changed direction when vertical pursuit changed direction. This torsional nystagmus also appeared during fixation suppression of the vertical vestibulo-ocular reflex (VOR), but was minimal during vertical head rotation when fixing a stationary target in the light. We suggest that inappropriately directed eye movements during pursuit might be another ocular motor sign of cerebellar dysfunction. Furthermore, we speculate that the signals used for vertical smooth pursuit are, at some stage, encoded in a semicircular canal VOR coordinate framework. To illustrate, for the vertical semicircular canals, vertical and torsional motion are combined on the same cells, with the anterior semicircular canals mediating upward movements and the posterior semicircular canals mediating downward movements. For the right labyrinth, however, both vertical semicircular canals produce clockwise slow phases (ipsilateral eye intorts, contralateral eye extorts). The opposite is true for the vertical semicircular canals in the left labyrinth; counterclockwise slow phases are produced. Hence, to generate a pure vertical VOR, the anterior or posterior semicircular canals on both sides of the head must be excited so that opposite-directed torsional components cancel. Thus, if pursuit were organized in a way similar to the VOR, pure vertical pursuit would require that oppositely-directed torsional components cancel in normals. If this did not happen, a residual torsional nystagmus could appear during attempted vertical pursuit. PMID:8797162

FitzGibbon, E J; Calvert, P C; Dieterich, M; Brandt, T; Zee, D S

1996-06-01

129

Redesign of a Torsion Bar Testing Machine  

Microsoft Academic Search

Many types of vehicles utilize torsion bar suspensions. In particular, many types of racecars use torsion bar suspension systems because they are durable, compact, easy to remove, and easy to replace. In order to more effectively test torsion bar suspensions, a torsion bar rating machine was redesigned using 3D solid modeling, finite element analysis, and computer programming software. Some distinct

Amanda J. Meiser; David Lawrence; Brian Maher

2011-01-01

130

Domain walls and torsion potentials  

Microsoft Academic Search

A Lagrangian for flat domain walls in spaces with Cartan torsion and\\u000aelectromagnetic fields is proposed.The Lagrangian is very similar to a recently\\u000aproposed Lagrangian for domain walls in a Chern-Simons electrodynamics in 2+1\\u000adimensions.We show that in the first approximation of the torsion scalar\\u000apotential the field equations are reduced to a Klein-Gordon type field equation\\u000afor the torsion

L. C. Garcia de Andrade

1998-01-01

131

Global Aspects of Symmetries in Sigma Models with Torsion  

Microsoft Academic Search

It is shown that non-trivial topological sectors can prevent the quantum mechanical implementation of the symmetries of the classical field equations of sigma models with torsion. The associated anomaly is computed, and it is shown that it depends on the homotopy class of the topological sector of the theory and the group action on the sigma model manifold that generates

G. Papadopoulos

1994-01-01

132

The Torsion of Thick-Walled Box-Beams.  

National Technical Information Service (NTIS)

The present methods of calculation of restrained torsion in box-beams are applicable to thin-walled cross-sections and provide rather inaccurate results for thick-walled box-beams of actual structures. In this investigation, there are presented two theori...

V. Penttala

1978-01-01

133

Fermi Liquid in a Torsional Oscillator  

NASA Astrophysics Data System (ADS)

We study the transverse acoustic impedance of normal Fermi liquid inside a torsionally oscillating cylindrical container. We use Landau's Fermi liquid theory, and our approach is applicable to both normal 3He and mixtures of 3He in superfluid 4He. The fluid causes dissipation and a change of the resonant frequency of the oscillator. Usually, a liquid medium increases the moment of inertia of the oscillator, but we show that for a suitable choice of container radius and driving frequency, the Fermi liquid can actually decrease the inertia and increase the resonant frequency. Results of numerical calculations for all values of mean free path l are shown and comparison is made to both hydrodynamic theory and simple kinetic theory in the ballistic limit.

Virtanen, T. H.; Thuneberg, E. V.

2012-12-01

134

Coupling phenomenon of torsional modes  

SciTech Connect

The coupling phenomenon of the torsional modes of a steam turbine-generator (T-G) set is investigated. The impacts of: (1) generator load, (2) series capacitor compensation level, (3) power system stabilizer (PSS) and (4) auxiliary controllers of an static VAr compensator (SVC) on the torsional coupling phenomenon, are investigated. The system eigen structure is used to develop an analytical formulation to detect the coupling phenomenon and determine its strength. The analytical results are verified by detailed digital computer simulation studies, using the BPA's Electromagnetic Transients Program (EMTP). The studies indicate that depending on the network configuration and parameters, two or more of the torsional modes of a T-G set can be coupled. The coupling level can be significantly affected by the controller parameters and feedback signals of the torsional countermeasure devices.

Iravani, M.R.

1989-08-01

135

A Meter Stick Torsion Oscillator  

Microsoft Academic Search

This paper discusses a simple experiment in which torsion oscillations are set up in a pivoted meter stick that is balanced by a weight on one side of the axis of rotation and a stretched spring on the other side. By varying the torques applied to the mass-meter-stick-spring system, a non-conventional torsion oscillator can be studied and an expression for

Ken Taylor; Chris Atieno; Shannon O'Brien; Ben Stewart

2008-01-01

136

Nonsingular, big-bounce cosmology from spinor-torsion coupling  

NASA Astrophysics Data System (ADS)

The Einstein-Cartan-Sciama-Kibble theory of gravity removes the constraint of general relativity that the affine connection be symmetric by regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between the torsion tensor and Dirac spinors generates a spin-spin interaction which is significant in fermionic matter at extremely high densities. We show that such an interaction averts the unphysical big-bang singularity, replacing it with a cusp-like bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic.

Pop?awski, Nikodem

2012-05-01

137

Plastic Behavior and Fracture of Aluminum and Copper in Torsion Tests  

SciTech Connect

Present work investigates the plastic behavior, work hardening and the beginning of plastic instabilities, of cylindrical specimens deformed by high speed cold plastic torsion tests and at low speed tensile test. The tests were carried out in a laboratory torsion test equipment and an universal tensile test machine. The tensile tests were performed at room temperature in an universal testing machine at low strain rate of 0.034/s. Experimental torsion tests were carried out at constant angular speed that imposed a constant shear strain rate to the specimen. In the tests, the rotation speed were set to 62 rpm and 200 rpm which imposed high strain rates of about 2/s and 6.5/s respectively. The torsion tests performed at room temperature on annealed commercial pure copper and aluminum. Two types of torsion specimen for aluminum were used: solid and tubular. The solid aluminum specimen curves presented various points of maximum torque. The tubular copper specimens showed two points of maximum. Shear bands or shear strain localization at specimen were possibly the mechanism of maximum torque points formation. The work hardening coefficient n and the strain rate sensitivity parameter m were evaluated from the equivalent stress versus strain curve from tensile and torsion tests. The n-value remained constant whereas the m-value increased ten folds for aluminum specimens: from tensile test m= 0.027 and torsion test m= 0.27. However, the hardening curves were sigmoidal.

Bressan, Jose Divo [Department of Mechanical Engineering - UDESC Joinville - 89.223-100 Joinville - SC (Brazil)

2007-04-07

138

On the unsteady non-Newtonian rotating flow induced by torsional oscillations of a disk  

Microsoft Academic Search

The unsteady boundary layer flow generated in an incompressible, homogeneous elastico-viscous fluid bounded by an infinite rigid disk is investigated when the whole system is in a state of solid body rotation with uniform angular velocity and at some instant of time, the disk executes small amplitude torsional oscillations with a given frequency. The analysis is carried out to determine

L. Debnath; U. Basu

1975-01-01

139

Torsional carbon nanotube artificial muscles.  

PubMed

Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated. PMID:21998253

Foroughi, Javad; Spinks, Geoffrey M; Wallace, Gordon G; Oh, Jiyoung; Kozlov, Mikhail E; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D W; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H

2011-10-13

140

Detecting torsion from massive electrodynamics  

SciTech Connect

A new method of detecting torsion in the case of massive electrodynamics is proposed. The method is based on the study of spectral lines of hydrogen-like atoms placed in a torsion field, where the interaction energy between the torsion vector field Q and an electric dipole is given by [epsilon] [approximately] p [center dot] Q. All the methods designed so far have been based on spinning test particles interacting with magnetic fields in which the energy splitting is given by [epsilon] [approximately] S [center dot] B on a Stern-Gerlach type experiment. The authors arrive at an energy splitting of order of [epsilon] [approximately] 10[sup [minus]21]erg[approximately]10[sup [minus]9]eV, which is within the frequency band of radio waves. 15 refs.

Garcia de Andrade, L.C.; Lopes, M. (Instituto de Fisica, Rio de Janeiro (Brazil))

1993-11-01

141

Design Proposals for Torsional Buckling of Stiffeners.  

National Technical Information Service (NTIS)

The ability to predict torsional instability in the early stages of design can have important consequences on the design of both conventional and high performance ships. This thesis develops fast approximate methods of torsional buckling analysis for part...

S. L. Coulter

1984-01-01

142

Association of cold weather with testicular torsion.  

PubMed Central

A retrospective study of 46 patients who presented with proved testicular torsion over five years at two Dublin hospitals showed that in 40 cases torsion had occurred when the temperature was under 2 degrees C; the incidence of torsion was higher during the cold months of the year. Both of these findings were statistically significant. These and other results suggest that the ambient temperature may have some role in the incidence and aetiology of testicular torsion.

Shukla, R B; Kelly, D G; Daly, L; Guiney, E J

1982-01-01

143

A Geometrical Theory of Spin Motion  

NASA Astrophysics Data System (ADS)

A discussion of the fundamental interrelation of geometry and physical laws with Lie groups leads to a reformulation and heuristic modification of the principle of inertia and the principle of equivalence, which is based on the simple de Sitter group instead of the Poincaré group. The resulting law of motion allows a unified formulation for structureless and spinning test particles. A metrical theory of gravitation is constructed with the modified principle, which is structured after the geometry of the manifold of the de Sitter group. The theory is equivalent to a particular Kaluza-Klein theory in ten dimensions with the Lorentz group as gauge group. A restricted version of this theory excludes torsion. It is shown by a reformulation of the energy momentum complex that this version is equivalent to general relativity with a cosmologic term quadratic in the curvature tensor and in which the existence of spinning particle fields is inherent from first principles. The equations of the general theory with torsion are presented and it is shown in a special case how the boundary conditions for the torsion degree of freedom have to be chosen such as to treat orbital and spin angular momenta on an equal footing. The possibility of verification of the resulting anomalous spin-spin interaction is mentioned and a model imposed by the group topology of SO(3,2) is outlined in which the unexplained discrepancy between the magnitude of the discrete valued coupling constants and the gravitational constant in Kaluza-Klein theories is resolved by the identification of identical fermions as one orbit. The mathematical structure can be adapted to larger groups to include other degrees of freedom.

Halpern, Leopold

1984-09-01

144

PROPOSAL OF THE DYNAMIC ANALYSIS TECHNIQUE CONSIDERING INTERACTION BETWEEN BENDING AND TORSION AND NONLINEAR TORSION  

NASA Astrophysics Data System (ADS)

When the structures, for example arch bridges are subjected bending moments and torsional moments, the strength and rigidity of the members decline compared to those of pure bending or torsion load condition. However, any analysis soft don't consider interrelation between bending and torsion ,and effects of torsional moments have not been considered severely in seismic design. In this study, the authors proposed analysis technique considering interaction between bending and torsion to estimate torsional moments severely, and formulized the analysis tools for this technique. These are interaction curve, skeleton for combined load, hysteresis for torsion. Moreover, the authors analyzed a RC arch bridge using this method, and inspected the validity of comparing the results obtained equivalent linear analysis about torsion and nonlinear torsional analysis not considering the interaction between bending and torsion.

Otsuka, Hisanori; Hattori, Masahiro

145

Non-linear torsional vibration characteristics of an internal combustion engine crankshaft assembly  

NASA Astrophysics Data System (ADS)

Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines. The linear lumped mass method, which has been universally applied to the dynamic modeling of engine crankshaft assembly, reveals obvious simulation errors. The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness. In this paper, a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method. The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments. The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method. The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method. The simulation results are compared with a lumped mass model and a detailed model using the system matrix method. Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration, and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor. The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia. This research project is aimed at improving nonlinear dynamics theory, and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.

Huang, Ying; Yang, Shouping; Zhang, Fujun; Zhao, Changlu; Ling, Qiang; Wang, Haiyan

2012-07-01

146

The genesis of torsional drillstring vibrations  

Microsoft Academic Search

Inherent drilling characteristics of polycrystalline diamond compact (PDC) bits alone can be sufficient to excite severe torsional drillstring vibrations. The work presented in this paper augments previous findings that torsional vibrations can result from the drilling characteristics of the bit itself. Laboratory and field torsional measurements are compared with model results to show that the observed vibrations can be explained

J. F. Brett

1992-01-01

147

Torsion of the spermatic cord after orchiopexy  

Microsoft Academic Search

The cases of spermatic cord torsion reported here show that this condition may occur even some time after fixation. Three men, aged 22, 30 and 35 years, visited the urologist with complaints of an acute scrotum following earlier orchiopexy for spermatic cord torsion. Different techniques are employed to fixate the testicles after spermatic cord torsion. These cases confirm that Jaboulay's

A. M. A. de Vylder; A. J. Breeuwsma; M. F. van Driel; E. Fonteyne; J. M. Nijman

2006-01-01

148

Theory of twisting and bending of chain macromolecules; analysis of the fluorescence depolarization of DNA  

NASA Astrophysics Data System (ADS)

An elastic model of semiflexible chain macromolecules is developed in order to treat internal rotatory Brownian motion in the DNA helix. Dynamical equations for torsion and bending of the chain are generated, using results from classical elasticity and hydrodynamic theories. The rotational diffusion equation in normal coordinates is derived, and the initial-boundary value problem solved for the conditions of a nanosecond fluorescence depolarization experiment. The resulting time distribution function of the angular orientation of a fluorescent probe, embedded in a chain at thermal equilibrium, is used to compute the emission anisotropy. The predicted decay law is unusual, with exponentials in ~t due to twisting and in ~t1/4 due to bending. Comparison with published data for ethidium-DNA complex reveals that the decay of the anisotropy arises primarily from twisting of the DNA helix, with a small contribution from bending. By fitting theory and experiment, the torsional rigidity C of DNA may be obtained.

Barkley, Mary D.; Zimm, Bruno H.

1979-03-01

149

Torsional wave dispersion in a finitely pre-strained hollow sandwich circular cylinder  

NASA Astrophysics Data System (ADS)

This paper studies torsional wave dispersion in a three-layered (sandwich) hollow cylinder with finite initial strains. The investigations are carried out within the scope of the piecewise homogeneous body model with the use of the three-dimensional linearized theory of elastic waves in initially stressed bodies. The mechanical relations of the materials of the cylinders are described through their harmonic potential. The analytical expression is obtained for the low wavenumber limit values of the torsional wave propagation velocity. The numerical results on the influence of the initial stretching or compression of the cylinders along the torsional wave propagation direction are presented and discussed.

Akbarov, S. D.; Kepceler, T.; Mert Egilmez, M.

2011-08-01

150

Torsional Wave Propagation in a Pre-Strained Hollow Three-Layered Circular Cylinder  

NASA Astrophysics Data System (ADS)

This paper studies torsional wave dispersion in a pre-strained three-layered (sandwich) hollow cylinder made from high elastic materials the mechanical relations of which are described through the harmonic potential. The investigations are carried out within the scope of the piecewise homogeneous body model with the use of the three-dimensional linearized theory of elastic waves in initially stressed bodies. The analytical expression is obtained for the low wave number limit values of the torsional wave propagation velocity. The numerical results on the influence of the initial strains of the cylinders along the torsional wave propagation direction are presented and discussed.

Akbarov, S. D.; Kepceler, T.; Egilmez, M. Mert

151

Conjoint bending torsion fatigue — fractography  

Microsoft Academic Search

The fractography of conjoint bending torsion fatigue (CBTF) has been reported in this paper for a superalloy (Nimonic 75A) material used in gas turbine engines. The fracture surface features were characteristic of bending fatigue (BF), a distinct area of CBTF, and a region between the BF and CBTF, overloading (OL). Striations were documented in the two former regions, whereas ductile

Tarun Goswami

2002-01-01

152

Medicolegal aspects of testicular torsion  

Microsoft Academic Search

Objectives. Testicular torsion is an active area of medical malpractice litigation because of the diagnostic uncertainty, delays in diagnosis and treatment, diagnostic errors, and resultant testicular loss. We reviewed this topic to determine the nature of patient claims and their clinical and legal outcomes.Methods. All closed case files of a large medical malpractice insurance company based in New Jersey involving

James R Matteson; Jeffrey A Stock; Moneer K Hanna; Theresa V Arnold; Harris M Nagler

2001-01-01

153

Simultaneous normal and torsional force measurement by cantilever surface contour analysis  

NASA Astrophysics Data System (ADS)

This study presents an alternative to the current Hooke's law-based force relation between rectangular cantilever deflection and applied force. In the new approach, a transduction constant is presented that (1) includes no cross-talk between torsion and normal force components, (2) is independent of the load application point, and (3) does not depend on the cantilever beam length. Rather than measuring the cantilever deformation at a single point (such as the tip location), it is measured at multiple adjacent points using scanning white light interferometry to provide a three-dimensional description of the cantilever deformation during loading. This measurement, processed by a force relation based on a superposition of deflections derived from Euler-Bernoulli bending theory and St Venant's torsion theory, provides the vertical, axial, and torsional force components simultaneously. Experimental results are compared to force predictions for the vertical and torsional components using macro-scale cantilevers under mass loading. An uncertainty analysis is also provided.

Kumanchik, Lee; Schmitz, Tony; Pratt, Jon

2011-05-01

154

Isolated tubal torsion in pregnancy.  

PubMed

Adnexal torsion is an uncommon cause of acute abdomen in pregnancy and isolated fallopian tube twisting accounts for a very small number of these cases. These conditions, either in pregnancy or in non-gestational circumstances, are known to be due to both genital and non-genital causes and, in most cases, predisposing factors can be identified. We reviewed the literature and retrieved only 19 cases of isolated fallopian tube torsion in pregnancy treated surgically from 1936 to today, including one recently published case from our experience. The clinical presentation was lower quadrant abdominal pain in all cases. The right side was involved in 90% of the cases. Tenderness was usually present but peritoneal irritation with guarding or rebound was exceptional. Symptoms were nausea and vomiting, scanty vaginal bleeding and dysuria. Signs suggestive of necrosis such as leucocytosis, increased CRP and mild hyperpyrexia were uncommon. Preoperative ultrasound evaluation was performed in eight patients and in all cases an adnexal cyst was detected on the ipsilateral side of the abdominal pain. The case we recently published was carefully investigated preoperatively by Doppler flow ultrasound techniques which allowed for a precise differential diagnosis with total adnexal torsion. This aspect has never been previously considered. The surgical approach showed acute isolated fallopian tube torsion in all the cases and a predisposing factor was identified in 75% of the patients. Foetal and maternal outcome were always excellent. In cases of acute abdomen in pregnancy, with detailed Doppler flow ultrasound evidence of normal ovaries and of a pelvic cyst, an isolated tubal-paratubal cyst torsion should be considered and appropriate ovary-sparing surgical treatment foreseen. PMID:19493607

Origoni, Massimo; Cavoretto, Paolo; Conti, Enrico; Ferrari, Augusto

2009-06-02

155

Neutron star in the presence of a torsion-dilaton field  

NASA Astrophysics Data System (ADS)

We develop the general theory of stars in Saa's model of gravity with propagating torsion and study the basic stationary state of a neutron star. Our numerical results show that the torsion force decreases the role of the gravity in the star configuration, leading to significant changes in the neutron star masses depending on the equation of state of star matter. The inconsistency of Saa's model with Roll - Krotkov - Dicke and Braginsky - Panov experiments is discussed.

Boyadjiev, T.; Fiziev, P.; Yazadjiev, S.

1999-07-01

156

Torsional Vibration Control and Cosserat Dynamics of a Drill-Rig Assembly  

Microsoft Academic Search

Aspects of drill-string vibrations in the context of a recently developed integrated model of a drill-rig assembly based on the Cosserat theory of rods are discussed. Computer simulations are used to compare existing rotary feedback strategies currently in use to optimise drilling performance where torsional slip-stick vibrations are a hazard. Guided by the wave nature of axial and torsional vibrations

Robin W. Tucker; Charles Wang

2003-01-01

157

A Kinetic Theory for Nonanalog Monte Carlo Particle Transport Algorithms: Exponential Transform with Angular Biasing in Planar-Geometry Anisotropically Scattering Media  

Microsoft Academic Search

We show that Monte Carlo simulations of neutral particle transport in planar-geometry anisotropically scattering media, using the exponential transform with angular biasing as a variance reduction device, are governed by a new “Boltzmann Monte Carlo” (BMC) equation, which includes particle weight as an extra independent variable. The weight moments of the solution of the BMC equation determine the moments of

Taro Ueki; Edward W Larsen

1998-01-01

158

Area-angular momentum-charge inequality for stable marginally outer trapped surfaces in 4D Einstein-Maxwell-dilaton theory  

NASA Astrophysics Data System (ADS)

We derive inequalities between the area, the angular momentum, and the charges for axisymmetric closed outermost stably marginally outer trapped surfaces, embedded in dynamical and, in general, nonaxisymmetric spacetimes satisfying the Einstein-Maxwell-dilaton-matter equations. In proving the inequalities, we assume that the dilaton potential is non-negative and that the matter energy-momentum tensor satisfies the dominant energy condition.

Yazadjiev, Stoytcho

2013-01-01

159

Dispersion of torsional waves in initially stressed multilayered circular cylinders  

Microsoft Academic Search

Within the framework of a piecewise homogeneous body model, with the use of the three-dimensional linearized theory of elastic\\u000a waves in initially stressed bodies, the propagation of torsional waves in prestressed multilayered circular cylinders is investigated.\\u000a The elasticity relations for cylinder components are given through the Murnaghan potential. The influence of variations in\\u000a the geometric and mechanical parameters of the

A. Cilli; A. Ozturk

2010-01-01

160

Electron Conductance of Thiophene Dimers with Different Torsional Angles  

Microsoft Academic Search

We study the electron conductance of thiophene dimers though metal-molecule-metal systems using the first principles method, which is based on the density functional theory (DFT) with norm conserving nonlocal pseudopotentials and nonequilibrium Green's function (NEGF) to calculate the charge distribution for open metal-molecule-metal systems. The structure and chemical properties of different thiophene dimers are investigated by changing the inter-ring torsional

Ping Bai; Erping Li; Peter. A. Collier; Wee-Shong Chin; Kian-Ping Loh

2006-01-01

161

Inverting the angular correlation function  

NASA Astrophysics Data System (ADS)

The two point angular correlation function is an excellent measure of structure in the Universe. To extract from it the three-dimensional power spectrum, one must invert Limber's equation. Here we perform this inversion using a Bayesian prior constraining the smoothness of the power spectrum. Among other virtues, this technique allows for the possibility that the estimates of the angular correlation function are correlated from bin to bin. The outputs of this technique are estimators for the binned power spectrum and a full covariance matrix. Angular correlations mix small and large scales but after the inversion, small-scale data can be trivially eliminated, thereby allowing for realistic constraints on theories of large-scale structure. We analyse the automated plate measurement (APM) catalogue as an example, comparing our results with previous results. As a by-product of these tests, we find - in rough agreement with previous work - that APM places stringent constraints on cold dark matter inspired models, with the shape parameter constrained to be 0.25+/-0.04 (using data with wavenumber k<=0.1hMpc-1). This range of allowed values uses the full power spectrum covariance matrix, but assumes negligible covariance in the off-diagonal angular correlation error matrix, which is estimated with a large angular resolution of 0.5 deg (in the range 0.5 deg and 20 deg).

Dodelson, Scott; Gaztañaga, Enrique

2000-03-01

162

Torsion of the gravid uterus  

PubMed Central

A case is reported of a 180° levorotation of the gravid uterus with successful outcome for mother and child. Delivery was by cesarean section. Only 108 cases of rotation of the gravid uterus have been reported in the world's literature. A uterine tumour was associated in almost one third of cases. The condition usually presents as an acute abdomen. Complications include uterine rupture and pulmonary embolism. Treatment is by laparotomy and de-torsion, with cesarean section if at term or near term.

Piot, Didier; Gluck, Manuel; Oxorn, Harry

1973-01-01

163

Torsional oscillations of sunspot umbra  

Microsoft Academic Search

Torsional oscillations of six single sunspot umbrae are investigated from observations of the longitudinal magnetic field and velocity field in the photospheric line Fe I lambda 525.3 nm. All three components of the magnetic field and velocity field are reconstructed from their line-of-sight components. The periods of the umbra oscillations correspond to 2.2--7.1 days. The initial phases of the oscillations

O. S. Gopasyuk

2005-01-01

164

Computing Torsion Points on Curves  

Microsoft Academic Search

Let $X$ be a curve of genus $g \\\\ge 2$ over a field $k$ of characteristic zero. Let $X\\\\box0 A$ be an Albanese map\\u000aassociated to a point $P_0$ on $X$. The Manin--Mumford conjecture, first proved by Raynaud, asserts that the set $T$ of points in $X(\\\\kbar)$ mapping to torsion points on $A$ is finite. Using a $p$-adic approach, we

Bjorn Poonen

2001-01-01

165

a Torsional Model of Leptons  

NASA Astrophysics Data System (ADS)

Quite recently it was shown that torsion induces interactions among leptons that are identical to the weak interactions of leptons of the Weinberg Standard Model, if it is in terms of leptonic bound states that the bosonic sector is built; here we obtain the partially conserved axial currents showing that they are the same of the Standard Model, if the composite mediators have specific mass relationships: we show that their masses are indeed the measured ones, if reasonable approximations are taken.

Fabbri, Luca

2012-11-01

166

Isolated tubal torsion in pregnancy  

Microsoft Academic Search

Adnexal torsion is an uncommon cause of acute abdomen in pregnancy and isolated fallopian tube twisting accounts for a very small number of these cases. These conditions, either in pregnancy or in non-gestational circumstances, are known to be due to both genital and non-genital causes and, in most cases, predisposing factors can be identified.We reviewed the literature and retrieved only

Massimo Origoni; Paolo Cavoretto; Enrico Conti; Augusto Ferrari

2009-01-01

167

Torsion and gauge-invariant massive electrodynamics  

SciTech Connect

The authors study electrodynamics in Einstein-Cartan space-time, that is, in space-time with torsion, and show an analogy with the Chern-Simons gauge-invariant massive electrodynamics. In their case, however, there is no arbitrary parameter, the torsion Q playing the role of the Chern-Simons parameter k. This leads to bounds on the photon mass, charge, and torsion coupling.

Sabbata, V. de (Univ. of Ferrara, Sezione di Ferrara (Italy)); Sivaram, C. (Institute of Astrophysics, Bangalore (India)); Andrade, L.G. de (Instituto de Fisica, Rio de Janeiro (Brazil))

1993-09-01

168

Torsion of the spermatic cord after orchiopexy.  

PubMed

The cases of spermatic cord torsion reported here show that this condition may occur even some time after fixation. Three men, aged 22, 30 and 35 years, visited the urologist with complaints of an acute scrotum following earlier orchiopexy for spermatic cord torsion. Different techniques are employed to fixate the testicles after spermatic cord torsion. These cases confirm that Jaboulay's bottleneck procedure is the method of choice for bilateral fixation in patients presenting with this condition. PMID:18947666

de Vylder, A M A; Breeuwsma, A J; van Driel, M F; Fonteyne, E; Nijman, J M

2005-11-23

169

Torsional oscillator for high magnetic field experiments  

Microsoft Academic Search

A new type of torsional oscillator for experiments in the high magnetic field of 12 Tesla is reported. A beryllium copper alloy (BeCu25) was chosen as a torsion rod for its reliable mechanical properties. Two non-metallic materials were tested for a torsion head except a small amount of silver paste for the electrode. For a quartz glass head, liquid3He was

Hikota Akimoto; Tetsuji Okuda; Hidehiko Ishimoto

1995-01-01

170

Angular Momentum Experiment  

NSDL National Science Digital Library

After using the historical development of concepts of conserved motion to develop introductory understanding, students are directed to a series of activities to gain a better understanding of momentum, conservation of momenta, angular momentum, and conservation of angular momenta.

Trapp, David

171

Optical Angular Motion Sensor.  

National Technical Information Service (NTIS)

The Optical Angular Motion Sensor (OAMS) Program, Phase I, consisted of the design, fabrication, test and analysis of a Triaxial Angular Motion Sensor. A brassboard system was fabricated and assembled. It included a transmitter, a receiver assembly and an...

H. T. Braswell J. W. Fontenot L. L. Hartley B. F. Heinrich W. E. Miller

1975-01-01

172

The genesis of torsional drillstring vibrations  

SciTech Connect

Inherent drilling characteristics of polycrystalline diamond compact (PDC) bits alone can be sufficient to excite severe torsional drillstring vibrations. The work presented in this paper augments previous findings that torsional vibrations can result from the drilling characteristics of the bit itself. Laboratory and field torsional measurements are compared with model results to show that the observed vibrations can be explained by a reduction in PDC bit torque as rotary speed increases. These torsional vibrations are important because they can cause drillpipe fatigue and may be severe enough to damage the bit. The model also is used to pinpoint possible solutions to the problem.

Brett, J. (Oil and Gas Consultants International Inc., Tulsa, OK (US))

1992-09-01

173

On the unsteady non-Newtonian rotating flow induced by torsional oscillations of a disk  

Microsoft Academic Search

Summary  The unsteady boundary-layer flow generated in an incompressible, homogeneous elastico-viscous fluid bounded by an infinite\\u000a rigid disk is investigated when the whole system is in a state of solid-body rotation with uniform angular velocity and, at\\u000a some instant of time, the disk executes small-amplitude torsional oscillations with a given frequency. The analysis is carried\\u000a out to determine various qualitative and

L. Debnath; U. Basu

1975-01-01

174

Experimental identification of viscoelastic properties of rubber compounds by means of torsional rheometry  

Microsoft Academic Search

Rheological models are used for the description of viscoelastic properties. Such investigations are mostly based on experiments\\u000a with a torsional rheometer, i.e. a Rubber Process Analyzer. The results of such experiments are storage and loss modulus,\\u000a which depend on the applied angular frequency. The investigations were performed with rubber compounds used in industry, with\\u000a different crystallization degrees of the used

Herbert W. Müllner; Andreas Jäger; Elisabeth G. Aigner; Josef Eberhardsteiner

2008-01-01

175

Gauge invariant coupling of fields to torsion: A string inspired model  

SciTech Connect

In a consistent heterotic string theory, the Kalb-Ramond field, which is the source of space-time torsion, is augmented by Yang-Mills and gravitational Chern-Simons terms. When compactified to 4 dimensions and in the field theory limit, such additional terms give rise to interactions with interesting astrophysical predictions like rotation of plane of polarization for electromagnetic and gravitational waves. On the other hand, if one is also interested in coupling 2- or 3-form (Abelian or non-Abelian) gauge fields to torsion, one needs another class of interaction. In this paper, we shall study this interaction and offer some astrophysical and cosmological predictions. We explicitly calculate the Coleman-Weinberg potential for this theory. We also comment on the possibility of such terms in loop quantum gravity where, if the Barbero-Immirzi parameter is promoted to a field, acts as a source for torsion.

Bhattacharjee, Srijit; Chatterjee, Ayan [Theory Group, Saha Institute of Nuclear Physics, Kolkata 700064 (India); The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai-600113 (India)

2011-05-15

176

Gauge invariant coupling of fields to torsion: A string inspired model  

NASA Astrophysics Data System (ADS)

In a consistent heterotic string theory, the Kalb-Ramond field, which is the source of space-time torsion, is augmented by Yang-Mills and gravitational Chern-Simons terms. When compactified to 4 dimensions and in the field theory limit, such additional terms give rise to interactions with interesting astrophysical predictions like rotation of plane of polarization for electromagnetic and gravitational waves. On the other hand, if one is also interested in coupling 2- or 3-form (Abelian or non-Abelian) gauge fields to torsion, one needs another class of interaction. In this paper, we shall study this interaction and offer some astrophysical and cosmological predictions. We explicitly calculate the Coleman-Weinberg potential for this theory. We also comment on the possibility of such terms in loop quantum gravity where, if the Barbero-Immirzi parameter is promoted to a field, acts as a source for torsion.

Bhattacharjee, Srijit; Chatterjee, Ayan

2011-05-01

177

Cosmology with torsion: An alternative to cosmic inflation  

NASA Astrophysics Data System (ADS)

We propose a simple scenario which explains why our Universe appears spatially flat, homogeneous and isotropic. We use the Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity which naturally extends general relativity to include the spin of matter. The torsion of spacetime generates gravitational repulsion in the early Universe filled with quarks and leptons, preventing the cosmological singularity: the Universe expands from a state of minimum but finite radius. We show that the dynamics of the closed Universe immediately after this state naturally solves the flatness and horizon problems in cosmology because of an extremely small and negative torsion density parameter, ??-10-69. Thus the ECKS gravity provides a compelling alternative to speculative mechanisms of standard cosmic inflation. This scenario also suggests that the contraction of our Universe preceding the bounce at the minimum radius may correspond to the dynamics of matter inside a collapsing black hole existing in another universe, which could explain the origin of the Big Bang.

Pop?awski, Nikodem J.

2010-11-01

178

Dirac fields in f(R)-gravity with torsion  

NASA Astrophysics Data System (ADS)

We study f(R)-gravity with torsion in the presence of Dirac massive fields. Using the Bianchi identities, we formulate the conservation laws of the theory and we check the consistency with the matter field equations. Further, we decompose the field equations in torsionless and torsional terms: we show that the nonlinearity of the gravitational Lagrangian reduces to the presence of a scalar field that depends on the spinor field; this additional scalar field gives rise to an effective stress-energy tensor and plays the role of a scale factor modifying the normalization of Dirac fields. Problems for fermions regarding the positivity of energy and the particle-antiparticle duality are discussed.

Fabbri, Luca; Vignolo, Stefano

2011-06-01

179

Linear sigma models with torsion  

NASA Astrophysics Data System (ADS)

Gauged linear sigma models with (0, 2) supersymmetry allow a larger choice of couplings than models with (2, 2) supersymmetry. We use this freedom to find a fully linear construction of torsional heterotic compactifications, including models with branes. As a non-compact example, we describe a family of metrics which correspond to deformations of the heterotic conifold by turning on H-flux. We then describe compact models which are gauge-invariant only at the quantum level. Our construction gives a generalization of symplectic reduction. The resulting spaces are non-Kähler analogues of familiar toric spaces like complex projective space. Perturbatively conformal models can be constructed by considering intersections.

Quigley, Callum; Sethi, Savdeep

2011-11-01

180

Torsional device for remote control steering system  

NASA Astrophysics Data System (ADS)

A steering simulation device provides torsional resistance and a 'center return' function to a remote control steering mechanism experiencing bidirectional (clockwise or counterclockwise) rotational movement. A compact design is provided by utilizing a series of rotationally elastic couplings that permit an adjustable turning resistance, (torsional resistance), an adjustable, bidirectional rotary range (clockwise or counter-clockwise), and a self-centering capability.

Koyamatsu, Anthony H.; Ono, Owen T.; Hahn, Warren L.

1993-12-01

181

Analytic torsion and holomorphic determinant bundles  

Microsoft Academic Search

In this paper, we derive the main properties of Kähler fibrations. We introduce the associated Levi-Civita superconnection to construct analytic torsion forms for holomorphic direct images. These forms generalize in any degree the analytic torsion of Ray and Singer. In the case of acyclic complexes of holomorphic Hermitian vector bundles, such forms are calculated by means of Bott-Chern classes.

Jean-Michel Bismut; Henri Gillet; Christophe Soulé

1988-01-01

182

Study on Torsional Stiffness of Engine Crankshaft  

Microsoft Academic Search

Many empirical formulae are used to calculate torsional stiffness of Engine Crank, but discrepancy exists between these calculation results. In this paper, in order to obtain a more precise result, the modified Ker Wilson formula and Carter formula were employed to calculate torsional stiffness of engine crankthrow in the case of different thickness and width of both sides of crankthrows.

Zhao Guangming; Jiang Zhengfeng

2009-01-01

183

Measurement and analysis of angular velocity variations of twelve-cylinder diesel engine crankshaft  

Microsoft Academic Search

This paper presents the procedures for measuring and analyzing the angular velocity variation of twelve-cylinder diesel engine crankshaft on its free end and on the power-output end. In addition, the paper deals with important aspects of the measurement of crankshaft torsional oscillations. The method is based on digital encoders placed at two distances, and one of them is a sensor

Z. M. Bulatovic; M. S. Stavljanin; M. V. Tomic; D. M. Knezevic; S. Lj. Biocanin

2011-01-01

184

Torsion of the gallbladder: a systematic review  

PubMed Central

Background Gallbladder torsion is a rare disease, predominantly affecting elderly women. It is an important differential in the acute surgical abdomen. Methods A total of 324 published case reports of torsion of the gallbladder were reviewed. Features in diagnostic imaging suggestive of torsion were reviewed and summarized. Results Gallbladder torsion is primarily a disease of elderly people; the median age at presentation is 77 years. It is more common amongst women, occurring at a female : male ratio of 4 : 1, although not in childhood, when it occurs at a male : female ratio of 2.5 : 1. Conclusions Improved imaging techniques within the last 20 years have enabled the preoperative diagnosis of one quarter of patients with gallbladder torsion. With prompt surgical intervention, the condition has an excellent prognosis.

Reilly, Daniel J; Kalogeropoulos, George; Thiruchelvam, Dhan

2012-01-01

185

Variation of the resonance width of HOCl(6{nu}{sub OH}) with total angular momentum: Comparison between {ital ab initio} theory and experiment  

SciTech Connect

Complex L{sup 2} calculations of the variation of (very narrow) resonance widths of the 6{nu}{sub OH} state of HOCl with total angular momentum are reported, using a recently developed, accurate {ital ab initio} potential energy surface [S. Skokov, J. M. Bowman, and K. A. Peterson, J. Chem. Phys. {bold 109}, 2662 (1998)]. The calculations are carried out within the adiabatic rotation approximation for the overall rotation and a truncation/recoupling method for the vibrational states. Comparisons with recent double-resonance experiments of the Rizzo and Sinha groups are made. The variation of resonance width with {ital J} for {ital K}=0 is shown to be due to rotation-induced coupling of the 6{nu}{sub OH} state with a dense set of states with large excitation in the dissociative coordinate. {copyright} {ital 1999 American Institute of Physics.}

Skokov, S.; Bowman, J.M. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)

1999-05-01

186

Flexural and torsional stiffness in multi-jointed biological beams.  

PubMed

Flexibility, the ability to deform in response to loads, is a common property of biological beams. This paper investigates the mechanical behavior of multi-jointed beams, which are characterized by a linear series of morphologically similar joints. Flexural stiffness and torsional stiffness were measured in two structurally distinct beams, crinoid arms (Echinodermata, Comatulida) and crustacean antennae (Arthropoda, Decapoda). Morphological data from these beams were used to determine the relative contributions of beam diameter and joint density (number of joints per millimeter of beam length) to the flexural and torsional stiffness of these two structures. As predicted by beam theory, beam diameter influenced stiffness in both crinoid arms and crustacean antennae. In crinoid arms, increases in joint density were associated with decreases in stiffness, but joint density had no significant influence on stiffness in crustacean antennae. In both crinoid arms and crustacean antennae, the magnitudes of flexural and torsional stiffness, as well as the ratio of these two variables, were similar to previously reported values for non-jointed biological beams. These results suggest that the structural design of a biological beam is not a limiting factor determining its mechanical properties. PMID:11249208

Etnier, S A

2001-02-01

187

Torsional directed walks, entropic elasticity, and DNA twist stiffness  

PubMed Central

DNA and other biopolymers differ from classical polymers because of their torsional stiffness. This property changes the statistical character of their conformations under tension from a classical random walk to a problem we call the “torsional directed walk.” Motivated by a recent experiment on single lambda-DNA molecules [Strick, T.?R., Allemand, J.-F., Bensimon, D., Bensimon, A. & Croquette, V. (1996) Science 271, 1835–1837], we formulate the torsional directed walk problem and solve it analytically in the appropriate force regime. Our technique affords a direct physical determination of the microscopic twist stiffness C and twist-stretch coupling D relevant for DNA functionality. The theory quantitatively fits existing experimental data for relative extension as a function of overtwist over a wide range of applied force; fitting to the experimental data yields the numerical values C = 120 nm and D = 50 nm. Future experiments will refine these values. We also predict that the phenomenon of reduction of effective twist stiffness by bend fluctuations should be testable in future single-molecule experiments, and we give its analytic form.

Moroz, J. David; Nelson, Philip

1997-01-01

188

Neoclassical Angular Momentum Flux Revisited  

NASA Astrophysics Data System (ADS)

The toroidal angular momentum flux in neoclassical transport theory of small rotations depends on the second order (in ion poloidal gyroradius over plasma scale length) ion distribution function. Owing to the complexity of the calculation, the result obtained a long time ago for circular cross-section tokamak plasmas in the banana regime [M.N. Rosenbluth, et al., Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1971), Vol. 1, p. 495] has never been reproduced. Using a representation of the angular momentum flux based on the solution of an adjoint equation to the usual linearized drift kinetic equation, and performing systematically a large-aspect-ratio expansion, we have obtained the flux for flux surfaces of arbitrary shape. We have found the same analytic form for the temperature gradient driven part of the flux, but the overall numerical multiplier is different and has the opposite sign. Implications for rotations in discharges with no apparent momentum input will be discussed.

Wong, S. K.; Chan, V. S.

2004-11-01

189

Torsional oscillations of sunspot umbra  

NASA Astrophysics Data System (ADS)

Torsional oscillations of six single sunspot umbrae are investigated from observations of the longitudinal magnetic field and velocity field in the photospheric line Fe I ? 525.3 nm. All three components of the magnetic field and velocity field are reconstructed from their line-of-sight components. The periods of the umbra oscillations correspond to 2.2--7.1 days. The initial phases of the oscillations are distributed over the interval from 0 to 2?. The azimuthal velocity calculated from the velocity field is much more than the azimuthal velocity measured from photoheliograms. The azimuthal velocity oscillation phase is ahead of the phases of all other component oscillations of both vectors. The period of oscillations increases with latitude of a sunspot. The magnetic energy of oscillations exceeds their kinetic energy by a factor up to 1000 (when the plasma density is 10-4 kg/m3).

Gopasyuk, O. S.

2005-06-01

190

Piezoelectric d15 shear-response-based torsion actuation mechanism: An exact 3D Saint-Venant type solution  

Microsoft Academic Search

This paper is concerned with the detailed analysis of the behavior of a piezoceramic bi-morph torsion actuator using the d15-effect. The bi-morph actuator is made of two oppositely polarized adjacent piezoceramic prismatic beams. The mathematical analysis is based on the Saint-Venant torsion theory; a formulation of the electromechanically coupled problem in terms of a stress function and of the electric

Michael Krommer; Pelin Berik; Yury Vetyukov; Ayech Benjeddou

2012-01-01

191

Nonseparable transition state theory for nonzero total angular momentum: Implications for {ital J} shifting and application to the OH+H{sub 2} reaction  

SciTech Connect

We report vibration/rotation energies of the OHH{sub 2} transition state using the code {open_quotes}Multimode,{close_quotes} for total angular momentum J=0, 1, and 4. Rotation is treated in the adiabatic rotation approximation for J=1 and 4, as well as exactly, i.e., including Coriolis coupling, for J=1. State-dependent rotation constants are obtained using the adiabatic rotation energies from the J=0 and 1 calculations and shown to predict accurately the adiabatic rotation rovibrational energies for J=4. These rotation constants are used in new {ital J}-shifting calculations of the thermal rate constant for the reaction OH+H{sub 2}{r_arrow}H{sub 2}O+H using results from a previous accurate calculation of the rate constant for J=0 [U. Manthe, T. Seideman, and W. H. Miller, J. Chem. Phys. {bold 99}, 10078 (1993); {bold 101}, 4759 (1994)]. Comparisons with previous {ital J}-shifting and recent centrifugal sudden calculations of the rate constant [D. H. Zhang, J. C. Light, and S-Y. Lee, J. Chem. Phys. {bold 109}, 79 (1998)] of this reaction are presented. A modification of the previous centrifugal sudden rate constant is made and shown to yield results that are in good agreement with the new {ital J}-shifting calculations. Finally, an assessment of Coriolis coupling is made. {copyright} {ital 1999 American Institute of Physics.}

Bowman, J.M.; Shnider, H.M. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)

1999-03-01

192

TORSIONAL EFFECTS AND REGULARITY CONDITIONS IN RC BUILDINGS  

Microsoft Academic Search

SUMMARY Earthquake damages at the perimeter of buildings are often the result of excessive deformations caused by torsion during the earthquake. Large torsional responses can be expected if the buildings have large eccentricity and low torsional stiffness. Modern codes, including Eurocode 8, recognise the importance of the torsional stiffness on the seismic response and include such information in its static

Edoardo COSENZA; Gaetano MANFREDI; Roberto REALFONZO

193

Modification of gravity due to torsion  

SciTech Connect

Modifications of general relativity have been considered as one of the possible ways of addressing some of the outstanding problems related to the large scale gravitational physics. In this contribution we review some of the recent results which are due to the inclusion of dynamical torsion. More specifically we shall discuss the propagation of massive spin-2 particles in flat and curved space times. We shall show that, contrary to what is generally believed, spinning matter is not the sole source of torsion field. A symmetric energy momentum tensor can also couple to torsion degrees of freedom. The massive and massless spin-2 particles mix giving rise to an infrared modification of gravity.

Nair, V. P. [Physics Department, City College of the CUNY, New York, NY 10031 (United States); Nikiforova, V. [Physics Department, Mascow State University Moscow (Russian Federation); Randjbar-Daemi, S. [The Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Rubakov, V. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow (Russian Federation)

2010-01-01

194

Angular Acceleration without Torque?  

ERIC Educational Resources Information Center

|Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.|

Kaufman, Richard D.

2012-01-01

195

Residual torsional strength after impact of CFRP tubes  

Microsoft Academic Search

This paper investigates the residual torsional strength of cylindrical T300-carbon\\/epoxy tubular specimens damaged by low-velocity impacts. A total of 24 specimens were subjected to a 7J transverse impact under various torsional preloads. First, the torsional strength of four different lamination sequences is studied. Later it is compared with the residual torsional strength (RTS) of tubes impacted under different torsional preloads.

G. Minak; S. Abrate; D. Ghelli; R. Panciroli; A. Zucchelli

2010-01-01

196

Output Feedback Sliding Mode Control for Bending and Torsional Vibration Control of 6-story Flexible Structure  

Microsoft Academic Search

We discuss bending and torsional vibration control of a 6-story flexible structure. In the case in which the vibration control of high-rise buildings is considered, it is necessary to design a controller which shows good control performances, and which is simply designed so that personnel expenses are reduced. To this end, we have applied a sliding mode control theory, which

Kosuke Iwamoto; Yuji Koike; Kenzo Nonami; Koji Tanida; Itaru Iwasaki

2002-01-01

197

Torsional wave dispersion in a finitely pre-strained hollow sandwich circular cylinder  

Microsoft Academic Search

This paper studies torsional wave dispersion in a three-layered (sandwich) hollow cylinder with finite initial strains. The investigations are carried out within the scope of the piecewise homogeneous body model with the use of the three-dimensional linearized theory of elastic waves in initially stressed bodies. The mechanical relations of the materials of the cylinders are described through their harmonic potential.

S. D. Akbarov; T. Kepceler; M. Mert Egilmez

2011-01-01

198

Dispersion of Torsional Waves in the Compound Circular Cylinder with Initial Stresses  

Microsoft Academic Search

Within the framework of the piecewise homogeneous body model with the use of the three-dimensional linearized theory of elastic waves in initially stressed body the torsional wave propagation in the pre-stressed compound circular cylinder is investigated. It is assumed that the elasticity relations of the materials of the components of the cylinders are given through the Murnaghan potential.

Ayhan Ozturk; Surkay D. Akbarov

2007-01-01

199

Maximum principles and bounds on stress concentration factors in the torsion of grooved shafts of revolution  

Microsoft Academic Search

This paper provides an analytical approach for obtaining bounds for stress concentration factors in the theory of axisymmetric torsion of circumferentially grooved shafts of revolution. The analysis is based on application of maximum principles for linear second-order elliptic partial differential equations. The particular case of a straight shaft with a semi-circular groove is considered in detail. Explicit estimates are obtained

Cornelius O. Horgan

1982-01-01

200

Anisotropic angular distribution of sputtered atoms  

NASA Astrophysics Data System (ADS)

The sputtering yield angular distributions have been calculated on the basis of the ion energy dependence of total sputtering yields for Ni and Mo targets bombarded by low-energy Hg+ ions. The calculated curves show excellent agreement with the corresponding Wehner's experimental results of sputtering yield angular distributions. This fact clearly demonstrates the intrinsic relation between the ion energy dependence of total sputtering yields and the sputtering yield angular distribution. This intrinsic relation had been ignored in Yamamura's papers [Yamamura, Y. (1982). Theory of sputtering and comparison to experimental data, Nucl. Instr. and Meth. , 194 , 515-522; Yamamura, Y. (1981). Contribution of anisotropic velocity distribution of recoil atoms to sputtering yields and angular distributions of sputtered atoms, Rad. Eff. , 55 , 49-55.] due to some obvious mistakes.

Zhang, Z. L.; Zhang, L.

2004-05-01

201

Immirzi parameter, torsion, and discrete symmetries  

SciTech Connect

We point out that the new interaction of spinning particles with the torsion tensor, discussed recently, is odd under charge conjugation and time reversal. This explains rather unexpected symmetry properties of the induced effective 4-fermion interaction.

Khriplovich, I.B.; Pomeransky, A.A. [Budker Institute of Nuclear Physics, 630090, Novosibirsk (Russian Federation); Novosibirsk University, 630090, Novosibirsk (Russian Federation)

2006-05-15

202

Computational Investigation of Subsonic Torsional Airfoil Flutter.  

National Technical Information Service (NTIS)

In this thesis single-degree-of-freedom torsional airfoil flutter is investigated using an incompressible potential flow code, a compressible inviscid Euler code and a compressible viscous Navier-Stokes code. It is found that the classical linearized inco...

C. Kakkavas

1998-01-01

203

Methamphetamine use can mimic testicular torsion.  

PubMed

We report the case of a patient presenting with the classic clinical appearance of testicular torsion. Ultrasound showed testicular ischemia supporting the clinical diagnosis, but the lack of visualization of spermatic cord torsion was of concern. An attempt of clinical detorsion was considered unsuccessful and the patient was explored. No torsion was found. On postoperative review of the patient's medical history, we found methamphetamine use, with a positive urine test at the time of his emergent consultation for the scrotal pain episode. The use of amphetamines has been previously reported as the cause of ischemia of multiple organs, but we could not find previous reports of involvement of the testis mimicking torsion. PMID:23606543

Doherty, Michael H; Gerscovich, Eugenio O; Corwin, Michael T; Wilkendorf, Stephen R

2013-04-22

204

Acute gallbladder torsion: an unexpected intraoperative finding.  

PubMed

Gallbladder torsion is an uncommon clinical entity and a difficult condition to diagnose preoperatively. Since its first description in 1898 by Wendel there have been over 500 documented cases in the literature. It is known to occur when there is rotation of the gallbladder along the axis of the cystic duct and vascular pedicle. Except for isolated cases reported in childhood, this disease is more frequently encountered in the elderly with 85% of the cases reported between the ages of 60 and 80 years. There is a female preponderance with a female to male ratio of 3:1. Gallbladder torsion typically presents as an acute abdomen requiring emergency surgery but preoperative diagnosis of gallbladder torsion is difficult and most cases are found as a surprise at surgery.We report a case of acute gallbladder torsion in an elderly lady and review the clinical aspect of the disease. PMID:18294374

Janakan, Gnananandan; Ayantunde, Abraham A; Hoque, Happy

2008-02-22

205

Acute gallbladder torsion: an unexpected intraoperative finding  

PubMed Central

Gallbladder torsion is an uncommon clinical entity and a difficult condition to diagnose preoperatively. Since its first description in 1898 by Wendel there have been over 500 documented cases in the literature. It is known to occur when there is rotation of the gallbladder along the axis of the cystic duct and vascular pedicle. Except for isolated cases reported in childhood, this disease is more frequently encountered in the elderly with 85% of the cases reported between the ages of 60 and 80 years. There is a female preponderance with a female to male ratio of 3:1. Gallbladder torsion typically presents as an acute abdomen requiring emergency surgery but preoperative diagnosis of gallbladder torsion is difficult and most cases are found as a surprise at surgery. We report a case of acute gallbladder torsion in an elderly lady and review the clinical aspect of the disease.

Janakan, Gnananandan; Ayantunde, Abraham A; Hoque, Happy

2008-01-01

206

Holographically observed torsion in a cylindrical shaft.  

PubMed

Using holographic interferometry, the rotation of a rigid cylinder and the torsion of a flexible shaft (RTV silastic rubber) have been observed. The experimentally generated fringe patterns are compared with computed ones and good agreement is obtained. PMID:20094202

Wilson, A D

1970-09-01

207

Angular Distributions of Gamma Rays in Terms of Phase-Defined Reduced Matrix Elements  

Microsoft Academic Search

The theory of angular distributions of gamma rays is developed systematically, aiming at a phase consistent derivation of angular distribution formulas for gamma rays emitted in the decay of an aligned initial state. The development starts from first principles, that is, the angular distribution formulas are derived directly from perturbation theory and all quantities introduced are carefully and explicitly defined.

H. J. Rose; D. M. Brink

1967-01-01

208

Postural laterality in torticollis and torsion dystonia.  

PubMed Central

Tests of postural rotational laterality were carried out in 63 patients suffering from torticollis (53) or torsion dystonia with torticollis (10) and in 33 normal subjects. There was a correlation between the predominant direction of postural functions and the direction of the rotatory component of torticollis. Torticollis and torsion dystonia may be due to the release of a postural rotational laterality in pre-disposed subjects and not to a presumed asymmetric lesion of the brain-stem. Images

Stejskal, L; Tomanek, Z

1981-01-01

209

Testicular torsion: Evaluation of contralateral testicular histology  

Microsoft Academic Search

Infertility may occur in patients with unilateral testicular torsion whose contralateral testis is intact. Depending on this\\u000a observation, the physicians have begun to examine the contralateral testis.\\u000a \\u000a In the present prospective study we aimed to examine the histopathologic alterations occurring in the contralateral testicle\\u000a with time. Sixty adult male albino rats were included in the programme, and following experimental torsion

A. Ko?ar; K. Sarica; B. Küpeli; G. Alçi?ir; O. Süzer; S. Küpeli

1997-01-01

210

Contact metric manifolds with ? -parallel torsion tensor  

Microsoft Academic Search

We show that a non-Sasakian contact metric manifold with ?-parallel torsion tensor and sectional curvatures of plane sections containing the Reeb vector field different from 1 at some\\u000a point, is a (k, ?)-contact manifold. In particular for the standard contact metric structure of the tangent sphere bundle the torsion tensor\\u000a is ?-parallel if and only if M is of constant curvature, in

Amalendu Ghosh; Ramesh Sharma; Jong Taek Cho

2008-01-01

211

Torsion and geometrostasis in covariant superstrings  

SciTech Connect

The covariant action for freely propagating heterotic superstrings consists of a metric and a torsion term with a special relative strength. It is shown that the strength for which torsion flattens the underlying 10-dimensional superspace geometry is precisely that which yields free oscillators on the light cone. This is in complete analogy with the geometrostasis of two-dimensional sigma-models with Wess-Zumino interactions. 13 refs.

Zachos, C.

1985-01-01

212

Coupled modes of the torsion pendulum  

NASA Astrophysics Data System (ADS)

The coupling of the swing modes of a torsion pendulum to the torsional mode has been solved analytically. Our solution provides a clear explanation of why a magnetic damper is effective in suppressing unwanted modes in most gravitational experiments. The analytic solution also shows that the amplitude of the mode coupling is greatest at the lowest frequencies. This explains why mode coupling at the lowest frequency is all that is observed in the experiments reported here.

Fan, Xiang-Dong; Liu, Qi; Liu, Lin-Xia; Milyukov, Vadim; Luo, Jun

2008-01-01

213

Angular and interstitial pregnancy.  

PubMed

Two cases of interstitial and one of angular pregnancy have been presented. Angular pregnancy occurs in the angle of the uterine cavity, while interstitial pregnancy is a true ectopic pregnancy. The outcome may therefore be different: the first may develop or abort into the cavity, while the second will almost always rupture. Because of the rich vascularization of this area, hemorrhage is usually profuse and may be catastrophic. Preoperative diagnosis is rare, but the triad of bleeding in pregnancy, no fetal remnants on dialation and curettage and an asymmetric uterus suggest angular or interstitial pregnancy. More liberal use of laparoscopy may increase the number of cases diagnosed before severe bleeding occurs. PMID:844965

Lancet, M; Bin-Nun, I; Kessler, I

1977-02-01

214

Nondipolar photoelectron angular distributions  

SciTech Connect

The deviations of photoelectron angular distributions from the simple, highly symmetric shapes predicted within the electric-dipole approximation are investigated. The admixture of an electric-quadrupole component in the photon-atom interaction causes an asymmetry in the angular distribution with respect to the direction of photon propagation. The reported measurement of the angular distributions of argon {ital 1s}, krypton {ital 2s}, and krypton {ital 2p} photoemission within 2-3 keV above their respective thresholds reveal pronounced asymmetries which are present even at low electron kinetic energies. The measured asymmetry parameters are in good agreement with recent predictions from nonrelativistic calculations.

Kraessig, B.; Jung, M.; Gemmell, D.S.; Kanter, E.P.; LeBrun, T.; Southworth, S.H.; Young, L.

1996-12-31

215

NMR structure calculation methods for large proteins Application of torsion angle dynamics and distance geometry\\/ simulated annealing to the 269-residue protein serine protease PB92  

Microsoft Academic Search

Molecular dynamics in torsion angle space together with the well established combination of metric matrix distance geometry and simulated annealing in Cartesian space have been applied to the solution structure determination of serine protease PB92, a 269-residue monomeric protein from Bacillus alcalophilus. The input data set comprised distance restraints and a combination of distance and angular restraints derived from NMR

Yasmin Karimi-Nejad; GREGORY L. WARREN; DICK SCHIPPER; AXEL T. BRÜNGER; ROLF BOELENS

1998-01-01

216

Cross-shaped torsional spring  

DOEpatents

The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section. 30 figs.

Williamson, M.M.; Pratt, G.A.

1999-06-08

217

Cross-shaped torsional spring  

DOEpatents

The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section.

Williamson, Matthew M. (Boston, MA); Pratt, Gill A. (Lexington, MA)

1999-06-08

218

Accurate torsional potentials for monohalo and fluorohalo keto-enolate compounds  

NASA Astrophysics Data System (ADS)

Accurate torsional potentials upon two rotatable carbon-carbon bonds for monohalo and fluorohalo keto-enolate compounds were constructed using CCSD(T)/CBS level of theory. Stable conformers of monohalo and fluorohalo keto-enolates can be determined from the steric repulsion between moieties around these carbon-carbon bonds. The repulsion between fluorine and halogen atoms is the strongest and stronger than that between oxygen and halogen, followed by that between oxygen and oxygen. The maximum of the torsional potentials corresponds to the conformation where both or one of the two rotatable bonds align perpendicular to the molecular plane, suggesting the strong double bond character between these two carbon-carbon bonds. Thus, the ?-bond conjugation and steric repulsion control the torsional potentials of monohalo and fluorohalo keto-enolate compounds.

Vongachariya, Arthit; Tantiwattanakul, Sutheera; Parasuk, Vudhichai

219

Analytical procedure for modelling recursively and wire by wire stranded ropes subjected to traction and torsion loads  

Microsoft Academic Search

The aim of this article is to introduce a new theoretical procedure for modelling wire ropes subjected simultaneously to tensile and torsional loads. The procedure is based upon the beam assumption and takes account wire by wire of the double helical wires on the basis of general thin rod theory developed by [Love, A., 1944. Mathematical Theory of Elasticity. Dover

H. Usabiaga; J. M. Pagalday

2008-01-01

220

Magnetostrictive Angular Positioning Motor.  

National Technical Information Service (NTIS)

This patent application discloses a device in which a plurality of axially elongated drive modules are interconnected at their opposite ends in a polygonal arrangement to angularly spaced locations on an outer annular ring to establish compressive stress ...

A. E. Clark J. P. Teter

1990-01-01

221

Seismic Angular Motion Sensor.  

National Technical Information Service (NTIS)

The design, fabrication and evaluation of a fused silica, balanced rotor, angular motion sensor which is insensitive to linear accelerations is described. A mathematical model was developed which defines the physical parameters that could be controlled du...

S. Okubo

1973-01-01

222

Optical Angular Motion Sensor.  

National Technical Information Service (NTIS)

The Optical Angular Motion Sensor (OAMS) Program, Phase II, consisted of the fabrication and testing of a prototype model to demonstrate compilance with OAMS performance requirements. The qualification model consisted of a transmitter, a receiver, and an ...

H. T. Braswell S. A. Chin Bing J. W. Fontenot W. E. Miller N. J. Ockman

1977-01-01

223

Comparisons Between Integral Equation Theory and Molecular Dynamics Simulations for Atomistic Models of Polyethylene Liquids  

SciTech Connect

Molecular dynamics (MD) simulations were performed on dense liquids of polyethylene chains of 24 and 66 united atom CH{sub 2} units. A series of models was studied ranging in atomistic detail from coarse-grained, freely-jointed, tangent site chains to realistic, overlapping site models subjected to bond angle restrictions and torsional potentials. These same models were also treated with the self-consistent, polymer reference interaction site model (PRISM) theory. The intramolecular and total structure factors, as well as, the intermolecular radial distribution functions g(r) and direct correlation functions C(r) were obtained from theory and simulation. Angular correlation functions were also simulation obtained from the MD simulations. Comparisons between theory and reveal that PRISM theory works well for computing the intermolecular structure of coarse-grained chain models, but systematically underpredicts the extent of intermolecular packing as more atomistic details are introduced into the model. A consequence of g(r) having insufficient structure is that the theory yields an isothermal compressibility that progressively becomes larger, relative to the simulations, as overlapping the PRISM sites and angular restrictions are introduced into the model. We found that theory could be considerably improved by adding a tail function to C(r) beyond the effective hard core diameter. The range of this tail function was determined by requiring the theory to yield the correct compressibility.

Curro, John G.; Webb III, Edmund B.; Grest, Gary S.; Weinhold, Jeffrey D.; Putz, Mathias; McCoy, John D.

1999-07-21

224

Chapter 8. Efficiency of Angular Momentum Transfer by Shear Instability  

Microsoft Academic Search

In order to calculate the rate of angular momentum transfer by the shear instability, we use perturbation theory. We obtain the lowest order of the flux of the angular momentum, solving the linear order as well as the second order perturbation equations. The differentially rotating cylinder with isentropic and polytropic equation of state is investigated for the sake of simplicity.

S. M. Miyama; Minoru Sekiya

1988-01-01

225

Mechanical behavior of twinned SiC nanowires under combined tension-torsion and compression-torsion strain  

NASA Astrophysics Data System (ADS)

The mechanical behavior of twinned silicon carbide (SiC) nanowires under combined tension-torsion and compression-torsion is investigated using molecular dynamics simulations with an empirical potential. The simulation results show that both the tensile failure stress and buckling stress decrease under combined tension-torsional and combined compression-torsional strain, and they decrease with increasing torsional rate under combined loading. The torsion rate has no effect on the elastic properties of the twinned SiC nanowires. The collapse of the twinned nanowires takes place in a twin stacking fault of the nanowires.

Li, Zhijie; Wang, Shenjie; Wang, Zhiguo; Zu, Xiaotao; Gao, Fei; Weber, William J.

2010-07-01

226

Ideal linear-chain polymers with fixed angular momentum.  

PubMed

The statistical mechanics of a linear noninteracting polymer chain with a large number of monomers is considered with fixed angular momentum. The radius of gyration for a linear polymer is derived exactly by functional integration. This result is then compared to simulations done with a large number of noninteracting rigid links at fixed angular momentum. The simulation agrees with the theory up to finite-size corrections. The simulations are also used to investigate the anisotropic nature of a spinning polymer. We find universal scaling of the polymer size along the direction of the angular momentum, as a function of rescaled angular momentum. PMID:21867202

Brunner, Matthew; Deutsch, J M

2011-07-15

227

Torsional oscillator for high magnetic field experiments  

NASA Astrophysics Data System (ADS)

A new type of torsional oscillator for experiments in the high magnetic field of 12 Tesla is reported. A beryllium copper alloy (BeCu25) was chosen as a torsion rod for its reliable mechanical properties. Two non-metallic materials were tested for a torsion head except a small amount of silver paste for the electrode. For a quartz glass head, liquid3He was successfully cooled down below 0.5 mK at 12 Tesla. The quality factor was 2 × 104 even at the highest field. On the other hand, a Stycast 1266 head in a field of 12 Tesla caused a large temperature difference between the liquid in the head and in the open space, in spite of a comparable quality factor with the quartz head.

Akimoto, Hikota; Okuda, Tetsuji; Ishimoto, Hidehiko

1995-11-01

228

A new method for torsional critical speed calculation of practical industrial rotors  

NASA Astrophysics Data System (ADS)

A new approach to calculating the torsional critical speed of rotors is presented. The governing equations for these speeds and the method of solutions differ from existing methods such as Holzer's, and the theory and numerical algorithm are straight forward, without any change in the field variables. The rotor studied has a distributed mass and rigid disks, and consists of many shaft segments of different diameters. The exact solution for undamped torsional motion of a uniform shaft segment is applied to a practical rotor-bearing system to generate the simultaneous governing equations for the torsional critical speeds. Within the framework of the theory, the set of governing equations is completely analytical and explicit, and it does not include any approximations, such as discretization of shaft mass and polynomial approximations. A computer program for the torsional critical speeds and the related mode shapes is developed by introducing a simple recurring numerical algorithm for a 3 by 4 submatrix in calculating the determinant generated by the simultaneous equations. The numerical algorithm essentially eliminates the necessity of constructing a huge matrix. The effectiveness of the new method is demonstrated in analyses of three rotors.

Jun, Oh-Sung; Kim, Paul Y.

1993-07-01

229

Cryptorchid testicular tumour presenting with torsion.  

PubMed

An undescended, cryptorchid testis is predisposed to 3 to 40 times risk of malignancy. Torsion of a cryptorchid testis is more difficult to diagnose than a normally placed testis. We present a case of a 25-year-old man with acute abdomen due to the torsion of an intra-abdominal testis. Subsequent histopathology of the testis revealed seminoma, making this single testis the seat for triple pathology. Orchidectomy was done followed by radiotherapy. A follow-up of upto nine months showed no recurrence or metastases. PMID:12685961

Memon, Abdul Sattar; Siddiqui, Faisal Ghani

2003-02-01

230

Primary omental torsion: A case report  

PubMed Central

A patient presented with an acute abdomen at the Emergency Department. The patient, a 69-year-old man, was admitted and underwent surgery with a provisional diagnosis of acute appendicitis. During surgery, omental torsion was diagnosed and the involved omentum was removed. The patient had no previous surgical history. Omental torsion is a rare cause of acute abdomen in children and adults who may present with various signs and symptoms; a preoperative diagnosis may therefore be difficult and can usually only be established during surgery.

Scabini, Stefano; Rimini, Edoardo; Massobrio, Andrea; Romairone, Emanuele; Linari, Chiara; Scordamaglia, Renato; Marini, Luisito De; Ferrando, Valter

2011-01-01

231

Acute torsion of a wandering spleen.  

PubMed

The 'wandering spleen' is a rare condition due to extreme laxity or absence of ligaments that fix the organ in its normal anatomical position within the left upper quadrant. Without early surgical intervention, wandering spleen can lead to torsion and subsequent splenic infarction or rupture. Clinical suspicion plus urgent investigation and intervention are important, so as to salvage the spleen and prevent complications. We present a case of torsion of a wandering spleen in a 21-year-old young woman, who presented with a painful pelvic mass. We also reviewed the literature on this entity. PMID:22477742

Lam, Y; Yuen, Kenny K Y; Chong, L C

2012-04-01

232

Clinical variants of idiopathic torsion dystonia.  

PubMed Central

Some patients with dystonic movements and postures not known to be caused by environmental or degenerative disorders can be segregated from classical-appearing idiopathic torsion dystonia on the basis of distinctive clinical and pharmacologic features. Many of them should be considered within the family of dystonia, as clinical variants of idiopathic torsion dystonia, while others are better classified as being part of other families of dyskinesias. In the former group are paradoxical dystonia, myoclonic dystonia, diurnal dystonia, and dopa-responsive dystonia. The latter group consists of dystonic tics and the various entities comprising paroxysmal dystonia, namely kinesigenic, nonkinesigenic and hypnogenic dystonia.

Fahn, S

1989-01-01

233

Clinical variants of idiopathic torsion dystonia.  

PubMed

Some patients with dystonic movements and postures not known to be caused by environmental or degenerative disorders can be segregated from classical-appearing idiopathic torsion dystonia on the basis of distinctive clinical and pharmacologic features. Many of them should be considered within the family of dystonia, as clinical variants of idiopathic torsion dystonia, while others are better classified as being part of other families of dyskinesias. In the former group are paradoxical dystonia, myoclonic dystonia, diurnal dystonia, and dopa-responsive dystonia. The latter group consists of dystonic tics and the various entities comprising paroxysmal dystonia, namely kinesigenic, nonkinesigenic and hypnogenic dystonia. PMID:2666583

Fahn, S

1989-06-01

234

Mag Lab U: Interactive Tutorials - Torsion Balance  

NSDL National Science Digital Library

This interactive Java tutorial allows users to play with a replica of the historic torsion balance used by Coulomb in his 18th-century experiments to measure the electrostatic force between charges. By carefully recording the measurements he obtained with his torsion balance, Coulomb was able to establish the law that bears his name. Coloumb's law states that the attraction or repulsion force between two electrical charges is proportional to their product and inversely proportional to the square of their distance apart. Mag Lab U is part of a large collection of web-based educational materials for K-20, developed by the National High Magnetic Field Laboratory at Florida State University.

2010-05-25

235

Primary omental torsion: A case report.  

PubMed

A patient presented with an acute abdomen at the Emergency Department. The patient, a 69-year-old man, was admitted and underwent surgery with a provisional diagnosis of acute appendicitis. During surgery, omental torsion was diagnosed and the involved omentum was removed. The patient had no previous surgical history. Omental torsion is a rare cause of acute abdomen in children and adults who may present with various signs and symptoms; a preoperative diagnosis may therefore be difficult and can usually only be established during surgery. PMID:22110847

Scabini, Stefano; Rimini, Edoardo; Massobrio, Andrea; Romairone, Emanuele; Linari, Chiara; Scordamaglia, Renato; Marini, Luisito De; Ferrando, Valter

2011-10-27

236

Structural Properties and Torsional Dynamics of Peroxides and Persulfides  

NASA Astrophysics Data System (ADS)

For the study of molecules containing O—O and S—S bonds, an analysis on the effect of level of theory and basis sets on electronic properties and geometrical parameters for H2O2 and H2S2 was done. Substitutions of one or both hydrogens in these molecules either by halogen atoms or alkyl groups were investigated for properties like geometries, dipole moments, cis and trans barriers. Attention has also been dedicated to the study of energy levels in the very anharmonic torsional potentials, obtaining their distributions as a function of temperature and partition functions for the torsional motion, of relevance for the isomerization rate leading to exchange between chiral enantiomers. Estimated rates both for underbarrier tunnelling and overbarrier transitions are consistently smaller for the S—S cases with respect to the corresponding O—O ones, due to the generally higher barriers. Regarding intermolecular interactions, of specific importance for collisional chirality exchange, an exploration was done for both H2O2- and H2S2-rare gases systems, extending the joint experimental and theoretical approach already tackled in this laboratory for interactions of H2O and H2S with the rare gases.

Maciel, Glauciete S.; Bitencourt, Ana Carla P.; Ragni, Mirco; Grossi, Gaia; Aquilanti, Vincenzo

237

Tussive syncope in a pug with lung-lobe torsion  

PubMed Central

The most common presenting clinical signs of lung-lobe torsion include dyspnea, tachypnea, lethargy, and anorexia. Tussive syncope secondary to lung-lobe torsion has not been documented. This article describes the presentation, diagnosis, management, and outcome of a pug with tussive syncope secondary to lung-lobe torsion.

Davies, John A.; Snead, Elisabeth C.R.; Pharr, John W.

2011-01-01

238

Dynamic torsion of a two-layer viscoelastic beam  

Microsoft Academic Search

The complex dynamic shear modulus of soft polymeric materials may be determined in principle at low and audio frequencies from torsion pendulum and torsional resonance experiments on metal strips coated with the polymer. In order to determine the polymer shear properties from such experiments, it is necessary to know the torsional rigidity of the two-layer compound beam. This is calculated

A. F. Johnson; A. Woolf

1976-01-01

239

PWM inverters producing torsional components in AC motors  

Microsoft Academic Search

Voltage source adjustable frequency drives produce voltage spectra capable of exciting torsional components within the bandwidth of a loadpsilas criticals. If not damped, a motorpsilas torsional spectrum may excite the mechanicalpsilas resonant frequencies destroying fan blades or fail couplings and shafts. This paper reports on an oil refinerypsilas induced draft fanpsilas coupling and drive motorpsilas shaft failures. Field torsional data,

Russel J. Kerkman; Jeff Theisen; Kirti Shah

2008-01-01

240

Angular momentum conservation demonstration  

NSDL National Science Digital Library

A short article describing the fabrication and operation of a simple angular momentum conservation demonstration. The demonstration is based on a Lazy Susan, and cylindrical brass weights tied with a nylon string. The string can be pulled or released changing the radius or rotation of the weights.

Berg, Richard E.; Anders, Robert E.

2010-12-23

241

Comb Actuated resonant torsional scanner for microdisplays  

Microsoft Academic Search

A comb-actuated 1D torsional MEMS scanner is developed for high resolution projection display systems using mechanical coupling principle. 64deg TOSA (total optical scan angle) is achieved at 22.1 kHz with 170 V peak-to-peak excitation voltages.

Aslihan Arslan; Sven Holmstrom; S. Kutal Gokce; Hakan Urey

2009-01-01

242

Damping Torsional Interharmonic Effects of Large Drives  

Microsoft Academic Search

Current source thyristor converters are the most widespread technology for large drives, and today still a suitable choice for supplying high-power variable speed drives because of excellent reliability records. The integer and noninteger harmonics generated by line-commutated converters cause pulsating torque harmonics on the motor and on the grid side of the converter. Intersections of harmonic excitation frequencies with torsional

Simon Schramm; Christof Sihler; Joseph Song-Manguelle; Paola Rotondo

2010-01-01

243

Flexural-Torsional Buckling Tests on Arches.  

National Technical Information Service (NTIS)

Flexural-torsional buckling tests on circular aluminum arches of doubly-symmetric I-section are described. The arches were fabricated by bending straight specimens to the required radius of curvature in a rolling machine. Calculations of the resulting res...

J. P. Papangelis N. S. Trahair

1986-01-01

244

Stress Analysis of Model Device for Torsion  

Microsoft Academic Search

On the example of stress analysis of model device for torsion, during the work, justification of Finite Element Method (FEM) application was shown by use of CAD\\/CAM\\/CAE software system CATIA V5 in the case when it is impossible to make a prototype in order to do its experimental testing. First, stress analysis of real model device was done by experimental

Adil Muminovi'c; Isad Šari'c; Nedžad Rep?i'c

2007-01-01

245

Acute ovarian torsion and primary hypothyroidism.  

PubMed

A 12-year-old girl presented with acute abdominal pain due to an acute ovarian torsion. She required an oophorectomy. Clinical and laboratory assessment confirmed severe primary hypothyroidism. In this report, we review this rare complication of untreated primary hypothyroidism and the physiologic mechanisms proposed to explain this phenomenon. PMID:23753092

Nandi-Munshi, Debika; Tridgell, Angela; Taplin, Craig E

2013-06-10

246

Effective torsional properties of carbon nanotubes  

Microsoft Academic Search

In this paper, a dynamic continuum modeling method is proposed to evaluate effective torsional structural properties of single-walled carbon nanotubes without any need to assume their fictitious wall thickness. The dynamic continuum modeling method has been developed based on the energy equivalence principle as well as on the molecular mechanics. The proposed dynamic continuum modeling method is applied to armchair

Usik Lee; Changho Lee; Jaesang Lee

2007-01-01

247

Adhesive torsional creep\\/failure study  

Microsoft Academic Search

The test method and results of the creep\\/failure behavior of three adhesive formulations with a torsional load applied are described. The load of a predetermined value was applied to the sample via a torque wrench\\/holding frame apparatus and was held until the sample failed. The adhesive formulations were tested after cure in two modes (ambient and elevated temperature) and at

1977-01-01

248

Inheritance of idiopathic torsion dystonia among Jews  

Microsoft Academic Search

Idiopathic torsion dystonia (ITD) has long been considered to be genetically determined, but the pattern of inheritance has been unclear. It has been suggested that inheritance may differ in Jews and non-Jews. In the present study, data gathered in a nationwide survey of ITD in Israel were analysed. Between 1969 and 1980, 47 patients were collected, of whom 40 were

N Zilber; A D Korczyn; E Kahana; K Fried; M Alter

1984-01-01

249

On the angular distributions in molecular photoionization beyond the dipole approximation  

Microsoft Academic Search

The theory of angular distributions and angular correlations of photoelectrons and recoil ions in molecular photoionization is reformulated in terms of the density matrix and statistical tensor formalism, which incorporates a full multipole expansion of the radiation field. The dynamical parameters of the angular distributions are expressed in terms of the multipole photoionization amplitudes. Photoionization of linear molecules is analysed

A N Grum-Grzhimailo

2003-01-01

250

Regional assessment of left ventricular torsion by CMR tagging  

PubMed Central

Purpose To introduce a standardized method for calculation of left ventricular torsion by CMR tagging and to determine the accuracy of torsion analysis in regions using an analytical model. Methods Torsion between base and apex, base and mid, and mid and apex levels was calculated using CSPAMM tagging and Harmonic Phase tracking. The accuracy of torsion analysis on a regional basis (circumferential segments and transmural layers) was analyzed using an analytical model of a deforming cylinder with a displaced axis of rotation (AoR). Regional peak torsion values from twelve healthy volunteers calculated by the described method were compared to literature. Results The deviation from the analytical torsion per % AoR-displacement (of the radius) was 0.90 ± 0.44% for the circumferential segments and only 0.05% for the transmural layers. In the subjects, circumferentially, anterolateral torsion was larger than inferior (12.4 ± 3.9° vs. 5.0 ± 3.3°, N.S.). Transmurally, endocardial torsion was smaller than epicardial (7.5 ± 1.3° vs. 8.0 ± 1.5°, p < 0.001). Conclusion Variability in the position of the AoR causes a large variability in torsion in circumferential segments. This effect was negligible for global torsion, and torsion calculated in transmural layers. Results were documented for the healthy human heart and are in agreement with data from literature.

Russel, Iris K; Gotte, Marco J; Kuijer, Joost P; Marcus, J Tim

2008-01-01

251

Space-Time Torsion Contribution to Quantum Interference Phases  

NASA Astrophysics Data System (ADS)

The field of neutron interferometry achieved one of its most significant successes with the detection of the influence of gravity in the quantum mechanical phase of a thermal neutron beam. From the latest experimental readouts in this context an intriguing discrepancy has been elicited. Indeed, theory and experiment dissent by one per cent, and though this fact could be a consequence of the mounting of the experimental device, it might also embody a difference between the way in which gravity behaves in classical and quantum mechanics. In this work the effects, upon the interference pattern, of space-time torsion will be analyzed heeding its coupling with the spin of the neutron beam. It will be proved that, even with this contribution, there is enough leeway for a further discussion of the validity of the equivalence principle in nonrelativistic quantum mechanics.

Camacho, A.; Macías, A.

2006-08-01

252

Angular Momentum Diagrams  

NASA Astrophysics Data System (ADS)

Starting from the simplest possible building blocks--a ket, a bra, a time-reversed ket, and a time-reversed bra--a diagrammatic formalism is developed for angular momentum coupling problems. The formalism comprises Clebsch-Gordan coefficients as well as 3jm-symbols. The idea of constructing invariants (internal lines) by contracting contragredient pairs of quantities is emphasized throughout. The Clebsch-Gordan series, and its extension to the coupling of more than two angular momenta, is introduced algebraically and diagrammatically. Recoupling between bases obtained in different coupling schemes is introduced and the connection between recoupling coefficients and irreducible 3nj-symbols is derived diagrammatically. The well-known diagrammatic rules due to Jucys and co-workers are derived by group theoretical means and simple rules for their practical exploitation are presented.

Wormer, Paul E. S.; Paldus, Josef

253

Attosecond angular streaking  

Microsoft Academic Search

Ultrashort measurement-time resolution is traditionally obtained in pump–probe experiments, for which two ultrashort light pulses are required; the time resolution is then determined by the pulse duration. But although pulses of subfemtosecond duration are available, so far the energy of these pulses is too low to fully implement the traditional pump–probe technique. Here, we demonstrate ‘attosecond angular streaking’, an alternative

Mathias Smolarski; Philip Schlup; Jens Biegert; André Staudte; Markus Schöffler; Harm G. Muller; Reinhard Dörner; Ursula Keller; Petrissa Eckle

2008-01-01

254

Ab InitioPotential Energy Surface and Internal Torsional-Wagging States of Hydroxylamine  

NASA Astrophysics Data System (ADS)

The two-dimensional potential energy surface describing the interaction of the large-amplitude torsional and wagging motions in hydroxylamine has been determined fromab initiocalculations. This surface has been sampled by a large set of grid points from a two-dimensional configuration space spanned by the torsional and wagging coordinates. At each grid point, the geometry optimization has been performed using the second-order Møller-Plesset perturbation theory with the basis set 6-311 + G(2d,p). At the optimized geometry, the single-point calculation of the electronic energy has been carried out using a larger basis set 6-311 + G(3df, 2p). This method was verified to yield the results comparable to those obtained by a direct optimization of the geometry with the basis set 6-311 + G(3df, 2p) which had been used by A. Chung-Phillips and K. A. Jebber (1995.J. Chem. Phys.102,7080-7087) to calculate the energies of only three points in the potential energy surface of hydroxylamine. Thetransandcislocal minima have been found on the determined potential energy surface. The localization features of the torsional-wagging states have been studied by solving the two-dimensional Schrödinger equation for the coupled torsional and wagging motions.

Makarewicz, Jan; Kr?glewski, Marek; Senent, Maria Luisa

1997-11-01

255

Approximate Torsional Analysis of Multi-layered Tubes with Non-circular Cross-Sections  

NASA Astrophysics Data System (ADS)

In this paper an approximate formulation for torsional analysis of tubes with multi-layered non-circular cross-sections is presented. A previously presented method based on Bredt's theory is extended to achieve these formulas. Layers are assumed to be isotropic and may possess different thicknesses and material properties. The obtained formulas for shear stress and angle of twist are applicable to thin to moderately thick closed cross-sections. It is shown that depending on the properties of the layers, maximum shear stress does not necessarily happen on the outer boundary. Furthermore, the effect of different cross-sectional shapes on torsional response is studied. Using the presented method, one can achieve desirable shear stresses and angles of twist for a polygonal multi-layered tube with a proper choice of bluntness. The method can be extended for torsion problem of FGM tubes as well. The presented formulas for torsion problem are relatively accurate and suitable to be implemented in optimization programs.

Gholami Bazehhour, Benyamin; Rezaeepazhand, Jalil

2011-12-01

256

Transforming between discrete and continuous angle distribution models: application to protein ?? torsions.  

PubMed

Two commonly employed angular-mobility models for describing amino-acid side-chain ?(1) torsion conformation, the staggered-rotamer jump and the normal probability density, are discussed and performance differences in applications to scalar-coupling data interpretation highlighted. Both models differ in their distinct statistical concepts, representing discrete and continuous angle distributions, respectively. Circular statistics, introduced for describing torsion-angle distributions by using a universal circular order parameter central to all models, suggest another distribution of the continuous class, here referred to as the elliptic model. Characteristic of the elliptic model is that order parameter and circular variance form complementary moduli. Transformations between the parameter sets that describe the probability density functions underlying the different models are provided. Numerical aspects of parameter optimization are considered. The issues are typified by using a set of ?(1) related (3) J coupling constants available for FK506-binding protein. The discrete staggered-rotamer model is found generally to produce lower order parameters, implying elevated rotatory variability in the amino-acid side chains, whereas continuous models tend to give higher order parameters that suggest comparatively less variation in angle conformations. The differences perceived regarding angular mobility are attributed to conceptually different features inherent to the models. PMID:22847493

Schmidt, Jürgen M

2012-07-31

257

A Novel Angular Acceleration Sensor Based on the Electromagnetic Induction Principle and Investigation of Its Calibration Tests  

PubMed Central

An angular acceleration sensor can be used for the dynamic analysis of human and joint motions. In this paper, an angular acceleration sensor with novel structure based on the principle of electromagnetic induction is designed. The method involves the construction of a constant magnetic field by the excitation windings of sensor, and the cup-shaped rotor that cut the magnetic field. The output windings of the sensor generate an electromotive force, which is directly proportional to the angular acceleration through the electromagnetic coupling when the rotor has rotational angular acceleration. The mechanical structure and the magnetic working circuit of the sensor are described. The output properties and the mathematical model including the transfer function and state-space model of the sensor are established. The asymptotical stability of the sensor when it is working is verified by the Lyapunov Theorem. An angular acceleration calibration device based on the torsional pendulum principle is designed. The method involves the coaxial connection of the angular acceleration sensor, torsion pendulum and a high-precision angle sensor, and then an initial external force is applied to the torsion pendulum to produce a periodic damping angle oscillation. The angular acceleration sensor and the angle sensor will generate two corresponding electrical signals. The sensitivity coefficient of the angular acceleration sensor can be obtained after processing these two-channel signals. The experiment results show that the sensitivity coefficient of the sensor is about 17.29 mv/Krad·s2. Finally, the errors existing in the practical applications of the sensor are discussed and the corresponding improvement measures are proposed to provide effective technical support for the practical promotion of the novel sensor.

Zhao, Hao; Feng, Hao

2013-01-01

258

Global Alfven torsional vibrations of neutron star in its own magnetic field of Ferraro's form  

Microsoft Academic Search

The Lorentz-force-driven global torsional nodeless vibrations of the neutron star model with Ferraro's form of axisymmetric nonhomogeneous poloidal in- ternal and dipolar external magnetic field are investigated. Using the energy variational method of magneto-solid-mechanical theory of a perfectly conducting elastic medium threaded by magnetic field, the one-parametric spectral formula for the frequency of this toroidal Alfven vibrational mode is obtained

S. I. Bastrukov; H.-K. Chang; I. V. Molodtsova; E.-H. Wu; G.-T. Chen; S.-H. Lan

259

Propagation of torsional waves in a prestretched compound hollow circular cylinder  

Microsoft Academic Search

The propagation of torsional waves in a prestressed compound (bi-layered) hollow circular cylinder is in vestigated within\\u000a the frame work of a piecewise homogeneous body model, with the use of a three-dimensional linerized theory of elastic waves\\u000a in initially stressed bodies. The elasticity relations for components of the compound cylinder are obtained from the Murnaghan\\u000a potential. Numerical investigations are performed

A. Ozturk; S. D. Akbarov

2008-01-01

260

External and internal coupling effects of rotor's bending and torsional vibrations under unbalances  

Microsoft Academic Search

External and internal bending–torsion coupling effects of a rotor system with comprehensive unbalances are studied by analytical analysis and numerical simulations. Based on Lagrangian approach, a full-degree-of-freedom dynamic model of a Jeffcott rotor is developed. The harmonic balance method and the Floquet theory are combined to analyze the stability of the system equations. Numerical simulations are conducted to observe the

Zhenwei Yuan; Fulei Chu; Yanli Lin

2007-01-01

261

Investigations of magnetic hysteresis of barium ferrite using the torsion pendulum method  

SciTech Connect

The magnetic stiffness is measured by the torsion pendulum method as a function of the applied field. Measurements are performed on random assemblies of chemically coprecipitated barium ferrite powders. The magnetic stiffness for both minor and major loops of the hysteresis cycle is measured and compared with calculated curves based on the model of coherent rotation. The discrepancies between theory and experiment are partly due to the effect of magnetic interaction.

Richter, H.J.; Hempel, K.A.

1988-11-15

262

Torsional wave dispersion relations in a pre-stressed bi-material compounded cylinder with an imperfect interface  

Microsoft Academic Search

This paper studies the influence of the imperfectness of the contact condition on the torsional wave propagation in the initially stressed (stretched) bi-material compounded circular cylinder. The investigation is carried out within the scope of the piecewise homogeneous body model with the use of the Three-dimensional Linearized Theory of Elastic Waves in Initially Stresses Bodies. The mathematical formulation of the

Tamer Kepceler

2010-01-01

263

Torsional wave propagation in a pre-stressed circular cylinder embedded in a pre-stressed elastic medium  

Microsoft Academic Search

Within the framework of the piecewise homogeneous body model with utilization of the three-dimensional linearized theory of elastic waves in initially stressed bodies, the mathematical modeling of the torsional wave propagation in the initially stressed infinite body containing an initially stressed circular solid cylinder (case 1) and circular hollow cylinder (case 2) are proposed. In these cases, it has been

A. Ozturk; S. D. Akbarov

2009-01-01

264

Ab Initio Modeling of Glycosyl Torsions and Anomeric Effects in a Model Carbohydrate: 2-Ethoxy Tetrahydropyran  

PubMed Central

A range of ab initio calculations were carried out on the axial and equatorial anomers of the model carbohydrate 2-ethoxy tetrahydropyran to evaluate the level of theory required to accurately evaluate the glycosyl dihedral angle and the anomeric ratio. Vacuum CCSD(T)/CBS extrapolations at the global minimum yield ?E = Eequatorial ? Eaxial = 1.42 kcal/mol. When corrected for solvent (by the IEFPCM model), zero-point vibrations and entropy, ?G298 = 0.49 kcal/mol, in excellent agreement with the experimental value of 0.47 ± 0.3 kcal/mol. A new additivity scheme, the layered composite method (LCM), yields ?E to within 0.1 kcal/mol of the CCSD(T)/CBS result at a fraction of the computer requirements. Anomeric ratios and one-dimensional torsional surfaces generated by LCM and the even more efficient MP2/cc-pVTZ level of theory are in excellent agreement, indicating that the latter is suitable for force-field parameterization of carbohydrates. Hartree-Fock and density functional theory differ from CCSD(T)/CBS for ?E by ?1 kcal/mol; they show similar deviations in torsional surfaces evaluated from LCM. A comparison of vacuum and solvent-corrected one- and two-dimensional torsional surfaces indicates the equatorial form of 2-ethoxy tetrahydropyran is more sensitive to solvent than the axial.

Woodcock, H. Lee; Moran, Damian; Pastor, Richard W.; MacKerell, Alexander D.; Brooks, Bernard R.

2007-01-01

265

DNA loop statistics and torsional modulus  

NASA Astrophysics Data System (ADS)

The modelling of DNA mechanics under external constraints is discussed. Two analytical models are widely known, but disagree, for instance, on the value of the torsional modulus. The origin of this embarassing situation is located in the concept of writhe. This letter presents a unified model for DNA establishing a relation between the different approaches. I show that the writhe created by the loops of DNA is at the origin of the discrepancy. To take this into account, I propose a new treatment of loop statistics based on numerical simulations using the most general formula for the writhe, and on analytic calculations with only one fit parameter. One can then compute the value of the torsional modulus of DNA without the need of any cut-off.

Rossetto, V.

2005-01-01

266

Torsional behavior of shape memory alloys  

NASA Astrophysics Data System (ADS)

This study investigates the properties of TiNi and TiNi-Cu (K- alloy) Shape Memory Alloys and their behavior in torsion (uniaxial) and combined tension-torsion (biaxial). Test results include torque versus angle curves and recovery torque versus pretwist for both uniaxial and biaxial loading. Preliminary results for low cycle fatigue are also presented. The wall thickness of the torque tube influences all of these curves considerably due to the gradation of stresses and strains through the thickness. All test data presented in this paper is for moderate torques where maximum shear strains are below 3.5% and as such represent an actuator capable of long fatigue life, based on previous experimental data for wire systems. A theoretical model for recovery torque is also described.

Keefe, Andrew C.; Carman, Gregory P.; Jardine, A. Peter

1998-07-01

267

Interfacing a torsion pendulum with a microcomputer  

SciTech Connect

Shear modulus testing is performed on the torsion pendulum at the General Electric Neutron Devices Department (GEND) as a means of gauging the state of cure for a polymer system. However, collection and reduction of the data to obtain the elastic modulus necessitated extensive operator involved measurements and calculations, which were subject to errors. To improve the reliability of the test, an analog-to-digital interface was designed and built to connect the torsion pendulum with a minicomputer. After the necessary programming was prepared, the system was tested and found to be an improvement over the old procedure in both quality and time of operation. An analysis of the data indicated that the computer generated modulus data were equivalent to the hand method data, but potential operator errors in frequency measurements and calculations were eliminated. The interfacing of the pendulum with the computer resulted in an overall time savings of 52 percent.

Bush, J.A.; Newby, J.W.

1983-02-24

268

UBIQUITOUS TORSIONAL MOTIONS IN TYPE II SPICULES  

SciTech Connect

Spicules are long, thin, highly dynamic features that jut out ubiquitously from the solar limb. They dominate the interface between the chromosphere and corona and may provide significant mass and energy to the corona. We use high-quality observations with the Swedish 1 m Solar Telescope to establish that so-called type II spicules are characterized by the simultaneous action of three different types of motion: (1) field-aligned flows of order 50-100 km s{sup -1}, (2) swaying motions of order 15-20 km s{sup -1}, and (3) torsional motions of order 25-30 km s{sup -1}. The first two modes have been studied in detail before, but not the torsional motions. Our analysis of many near-limb and off-limb spectra and narrowband images using multiple spectral lines yields strong evidence that most, if not all, type II spicules undergo large torsional modulation and that these motions, like spicule swaying, represent Alfvenic waves propagating outward at several hundred km s{sup -1}. The combined action of the different motions explains the similar morphology of spicule bushes in the outer red and blue wings of chromospheric lines, and needs to be taken into account when interpreting Doppler motions to derive estimates for field-aligned flows in spicules and determining the Alfvenic wave energy in the solar atmosphere. Our results also suggest that large torsional motion is an ingredient in the production of type II spicules and that spicules play an important role in the transport of helicity through the solar atmosphere.

De Pontieu, B.; Hansteen, V. H. [Lockheed Martin Solar and Astrophysics Laboratory, Org. A021S, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States); Carlsson, M.; Rouppe van der Voort, L. H. M.; Rutten, R. J. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, N-0315 Oslo (Norway); Watanabe, H., E-mail: bdp@lmsal.com [Unit of Synergetic Studies for Space, Kyoto University, 17 Kitakazan Ohmine-cho, Yamashina, Kyoto 607-8471 (Japan)

2012-06-10

269

Fluid driven torsional dipole seismic source  

DOEpatents

A compressible fluid powered oscillating downhole seismic source device capable of periodically generating uncontaminated horizontally-propagated, shear waves is provides. A compressible fluid generated oscillation is created within the device which imparts an oscillation to a housing when the device is installed in a housing such as the cylinder of an existing downhole tool, thereby a torsional seismic source is established. Horizontal waves are transferred to the surrounding bore hole medium through downhole clamping. 4 figs.

Hardee, H.C.

1990-08-08

270

Fluid driven torsional dipole seismic source  

DOEpatents

A compressible fluid powered oscillating downhole seismic source device capable of periodically generating uncontaminated horizontally-propagated, shear waves is provided. A compressible fluid generated oscillation is created within the device which imparts an oscillation to a housing when the device is installed in a housing such as the cylinder off an existing downhole tool, thereby a torsional seismic source is established. Horizontal waves are transferred to the surrounding bore hole medium through downhole clamping.

Hardee, Harry C. (Albuquerque, NM)

1991-01-01

271

Evaluation of Torsional Provisions in Seismic Codes  

Microsoft Academic Search

The effects of plan asymmetry on the earthquake response of code-designed, one-story systems are identified with the objective of evaluating how well these effects are represented by torsional provisions in building codes. The earthquake-induced deformations and ductility demands on resisting elements of asymmetric-plan systems, designed according to several different codes, are compared with their values if the system plan were

Anil K. Chopra; Rakesh K. Goel

1991-01-01

272

Torsional vibration suppression of ship elevator  

Microsoft Academic Search

Torsional vibration is one of the major problems of the Yangtze-Gorges ship elevator. The cause of the vibration and its suppression method are approached in this paper. To simplify the analysis, a 2 motor-1 shaft (2M-1S) system instead of real 4 motor-4 shaft (4M-4S) system is investigated first and the analysis results are verified by simulation and experiments. Then the

Qi Jiang; Bingyuan Wang; Xiaoliang Ma

2000-01-01

273

Cecocolic Torsion: Classification, Pathogenesis, and Treatment  

PubMed Central

Cecocolic torsion is a class of right colon obstruction. Under this heading, the known and the recently identified variants are unified under 1 classification. An algorithm is utilized to trace the pathogenesis of these variants. Recent data, prevailing definitions, and controversies are discussed and resolved. The significance of specific membranes and the blood supply is clarified. New symptoms, clinical and x-ray diagnoses are elucidated. The recommended treatments are outlined.

2005-01-01

274

Early onset torsion dystonia (Oppenheim's dystonia)  

Microsoft Academic Search

Early onset torsion dystonia (EOTD) is a rare movement disorder characterized by involuntary, repetitive, sustained muscle contractions or postures involving one or more sites of the body. A US study estimated the prevalence at approximately 1 in 30,000. The estimated prevalence in the general population of Europe seems to be lower, ranging from 1 in 330,000 to 1 in 200,000,

Christoph Kamm

2006-01-01

275

Analytic Model for the Rototranslational Torsion Pendulum  

NASA Astrophysics Data System (ADS)

We develop an analytic model to describe the motion of the RotoTranslational Torsion Pendulum PETER in a wide range of frequencies (from 1mHz up to 10-15Hz). We also try to explain some unexpected features we found in the data with only 1 soft degree of freedom and we estimate values for the misalignment angles and other parameters of the model.

De Marchi, F.; Bassan, M.; Pucacco, G.; Marconi, L.; Stanga, R.; Visco, M.

2013-01-01

276

Angular distributions in multifragmentation  

SciTech Connect

Angular distributions are reported for {sup 37}Ar and {sup 127}Xe from 381-GeV {sup 28}Si+Au interactions and for products between {sup 24}Na and {sup 149}Gd from 28-GeV {sup 1}H+Au. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.

Stoenner, R.W.; Klobuchar, R.L.; Haustein, P.E.; Virtes, G.J.; Cumming, J.B.; Loveland, W. [Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)

2006-04-15

277

Angularly selective mesoscopic tomography.  

PubMed

We report three-dimensional tomographic reconstruction of optical parameters for the mesoscopic light-scattering regime from experimentally obtained datasets by employing angularly selective data acquisition. The approach is based on the assumption that the transport coefficient of a scattering medium differs by an order of magnitude for weakly and highly scattering regions. Datasets were obtained by imaging a weakly scattering phantom, which embeds a highly scattering cylinder of two to three photons' mean path length in diameter containing light-absorbing inclusions. Reconstruction results are presented and discussed. PMID:22181452

Soloviev, Vadim Y; Bassi, Andrea; Fieramonti, Luca; Valentini, Gianluca; D'Andrea, Cosimo; Arridge, Simon R

2011-11-22

278

Enhanced angular current intensity from Schottky emitters.  

PubMed

Even though the Schottky emitter is a high-brightness source of choice for electron beam systems, its angular current intensity is substantially lower than that of thermionic cathodes, rendering the emitter impractical for applications that require high beam current. In this study, two strategies were attempted to enhance its angular intensity, and their experimental results are reported. The first scheme is to employ a higher extraction field for increasing the brightness. However, the tip shape transformation was found to induce undesirably elevated emission from the facet edges at high fields. The second scheme exploits the fact that the angular intensity is proportional to the square of the electron gun focal length [Fujita, S. & Shimoyama, H. (2005) Theory of cathode trajectory characterization by canonical mapping transformation. J. Electron Microsc. 54, 331-343], which can be increased by scaling-up the emitter tip radius. A high angular current intensity (J(Omega) approximately 1.5 mA sr(-1)) was obtained from a scaled-up emitter. Preliminary performance tests were conducted on an electron probe-forming column by substituting the new emitter for the original tungsten filament gun. The beam current up to a few microamperes was achieved with submicron spatial resolution. PMID:20701659

Fujita, S; Wells, T R C; Ushio, W; Sato, H; El-Gomati, M M

2010-09-01

279

Triply coupled bending-torsion vibration of Timoshenko and Euler-Bernoulli shaft beams with arbitrarily oriented open crack  

NASA Astrophysics Data System (ADS)

The paper presents the full formulation for a crack model for analyzing the triply coupled free vibration of both Timoshenko (short) and Euler-Bernoulli (long) shaft beams based on compliance approach in the presence of a planar open edge crack in an arbitrary angular orientation with a reference direction. The compliance coefficients to account for the local flexibility due to the crack for both the beams have been obtained through the concept of strain energy release rate and crack tip stress field given in terms of the stress intensity factors. The type of disturbance in stress-strain field that a continuous cracked beam theory can accommodate is not within the scope of the model. The compliance matrices for the Timoshenko (short) and Euler-Bernoulli (long) beams, respectively, are of size 6×6 and 3×3, and they consist of only 9 and 4 nonzero coefficients. The variation of the coefficients with crack orientation is presented. Equations governing the free transverse and torsion vibrations are derived and solved in both the cases. The formulation has been checked by comparing the theoretical frequencies with the finite element results for a few crack orientations, locations and depths. The agreement is good. It is shown further that, when such cases are analysed for studying the transverse vibration only in one plane by invoking a single rotational spring at the crack location, the approach leads to an erroneous variation of the frequencies with the crack orientations. The data presented here will be useful to solve both forward and inverse problems.

Naik, Sachin S.; Maiti, Surjya K.

2009-07-01

280

Factorized, Resummed and Gapped Angularity Distributions in SCET  

NASA Astrophysics Data System (ADS)

Angularities ?a are a class of event shapes varying in their sensitivity to the substructure of jets in the final state, controlled by a continuous parameter a. Using the framework of soft-collinear effective theory (SCET), we factorize and calculate e+e- angularity distributions for all a<1, including perturbative resummation to next-to-leading logarithmic accuracy and the incorporation of a universal model for the nonperturbative soft function.

Lee, Christopher; Hornig, Andrew; Ovanesyan, Grigory

2009-12-01

281

Analytical scheme calculations of angular momentum coupling and recoupling coefficients  

NASA Astrophysics Data System (ADS)

We investigate the Scheme programming language opportunities to analytically calculate the Clebsch-Gordan coefficients, Wigner 6j and 9j symbols, and general recoupling coefficients that are used in the quantum theory of angular momentum. The considered coefficients are calculated by a direct evaluation of the sum formulas. The calculation results for large values of quantum angular momenta were compared with analogous calculations with FORTRAN and Java programming languages.

Deveikis, A.; Kuznecovas, A.

2007-03-01

282

Factorized, Resummed and Gapped Angularity Distributions in SCET  

SciTech Connect

Angularities {tau}{sub a} are a class of event shapes varying in their sensitivity to the substructure of jets in the final state, controlled by a continuous parameter a. Using the framework of soft-collinear effective theory (SCET), we factorize and calculate e{sup +}e{sup -} angularity distributions for all a<1, including perturbative resummation to next-to-leading logarithmic accuracy and the incorporation of a universal model for the nonperturbative soft function.

Lee, Christopher; Hornig, Andrew; Ovanesyan, Grigory [Berkeley Center for Theoretical Physics, University of California (United States) and Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2009-12-17

283

Statistical prescission point model of fission fragment angular distributions  

NASA Astrophysics Data System (ADS)

In light of recent developments in fission studies such as slow saddle to scission motion and spin equilibration near the scission point, the theory of fission fragment angular distribution is examined and a new statistical prescission point model is developed. The conditional equilibrium of the collective angular bearing modes at the prescission point, which is guided mainly by their relaxation times and population probabilities, is taken into account in the present model. The present model gives a consistent description of the fragment angular and spin distributions for a wide variety of heavy and light ion induced fission reactions.

John, Bency; Kataria, S. K.

1998-03-01

284

Cyclic high-pressure torsion of nickel and Armco iron  

Microsoft Academic Search

Cyclic high-pressure torsion, a modified version of high-pressure torsion, is applied to Armco iron and nickel. The results in terms of microstructure and flow stress are compared to samples deformed by conventional high-pressure torsion. For both processes and both materials, a saturation in the decrease of the structure size and the increase in the flow stress is observed. The minimum

F. Wetscher; R. Pippan

2006-01-01

285

Missed Spermatic Cord Torsion in an Old Man  

PubMed Central

The fate of testicular salvage in spermatic cord torsion depends on the duration of ischemia and the degree of torsion. Even though spermatic cord torsion (SCT) can occur at any age, it is rarely reported in older patients. If the physician does not pay close attention to this unusual situation, the lack of suspicion for SCT may result in a missed or delayed diagnosis. We report a very uncommon case of missed SCT occurring in a 63-year-old man.

Seo, Yu Mi; Myung, Na-Hye

2013-01-01

286

Compensation of torsional vibrations in rods by piezoelectric actuation  

Microsoft Academic Search

In this paper, the piezoelectric compensation of torsional vibrations in rods caused by external excitations is studied. As\\u000a an illustrative example, a laminated rod containing piezoelectric shear actuators is assumed to be fixed at the one end, and\\u000a the other end is subjected to a torsional couple; additionally, a distributed torsional couple per unit length is acting.\\u000a In such a

Christian Zehetner

2009-01-01

287

Ultrasonic rotary motor using a longitudinal-torsional vibration converter  

Microsoft Academic Search

The characteristics of ultrasonic rotary motors using a converter from longitudinal to torsional vibration are studied. To obtain a rotary motor with large torque, ultrasonic motors using some types of slitted longitudinal-torsional converters are proposed. The longitudinal-torsion vibration converter consists of cylinders with a diagonally slitted vibration-converting part. Ultrasonic motors consist of such a converter with a driving part at

J. Tsujino; M. Takeuchi; H. Koshisako

1992-01-01

288

Time-dependent photoelectron angular distributions  

NASA Astrophysics Data System (ADS)

I show that the angular distribution of electrons photoionized from gas phase targets by short light pulses is time-dependent, when the orbital momentum composition of the photocurrent changes with excitation energy so evolves with the time of detection. A theory of time- dependent photoionization is outlined and general formulas of time-dependent photoelectron flux and angular distribution are given. Two general propagator methods suitable to describe the time-dependent photoionization and scattering processes are developed. The photoionization process is viewed as a local excitation followed by a half scattering. The local excitation process is solved theoretically in a small region around the target core. This approach has been generalized to describe the evolution of a wavepacket in an unbound system. An asymptotic propagator theorem is discovered and used to derive analytic expressions for asymptotic propagators. The origin of the time dependence is explored by parameterizing the time delay and orbital momentum coupling in a two channel model. K-shell photoionization of N2 and CO are calculated with this time- dependent photoionization theory, implemented using a multiple scattering model. Numerical results demonstrate that the time dependence of photoelectron angular distributions is a realistic effect.

Wang, Xiangyang

1999-09-01

289

Measurement and analysis of angular velocity variations of twelve-cylinder diesel engine crankshaft  

NASA Astrophysics Data System (ADS)

This paper presents the procedures for measuring and analyzing the angular velocity variation of twelve-cylinder diesel engine crankshaft on its free end and on the power-output end. In addition, the paper deals with important aspects of the measurement of crankshaft torsional oscillations. The method is based on digital encoders placed at two distances, and one of them is a sensor not inserted directly on the shaft, i.e. a non-contact method with a toothed disc is used. The principle based on toothed disc is also used to measure the actual camshaft angular velocity of in-line compact high-pressure pump the engine is equipped with, and this paper aims to demonstrate the possibility of measuring the actual angular velocity of any rotating shaft in the engine, on which it is physically possible to mount a toothed disc. The method was created completely independently during long-range development and research tests of V46 family engines. This method is specific for its particular adaptability for use on larger engines with extensive vibrations and torsional oscillations. The main purpose of this paper is a practical contribution to all the more interesting research of the use of engine crankshaft angular velocity as a diagnostic tool for identifying the engine irregular running.

Bulatovi?, Ž. M.; Štavljanin, M. S.; Tomi?, M. V.; Kneževi?, D. M.; Bio?anin, S. Lj.

2011-11-01

290

Size-dependent pull-in instability of torsional nano-actuator  

NASA Astrophysics Data System (ADS)

It is well established that the mechanical behavior of ultra-small elements is size-dependent. In this paper, strain gradient continuum theory is applied for modeling the size-dependent pull-in instability of torsional nano-actuator. An actuator with a general hexagonal shape main plate is considered. The governing equation of the actuator is derived taking the effect of electrostatic and Casimir forces into account. Variation of the tilt angle as a function of the applied voltage is calculated. Moreover, the pull-in voltage and pull-in angle of the actuator are determined. Results show that when the thickness of the torsional beam is comparable with the intrinsic material length scales, size effect can substantially increase the instability voltage and angle of the rotational actuator. Moreover, the effect of the Casimir force on the size-dependent pull-in instability of the torsional actuator is discussed. Interestingly, the proposed model is able to predict the experimental results more accurately than the previous classic models and reduce the gap between previous theories and experimental measurements.

Tadi Beni, Y.; Abadyan, M.

2013-11-01

291

Liquid state torsional dynamics of butane: The Kramers rate and the torsion angle correlation times  

NASA Astrophysics Data System (ADS)

The diffusion equation for hindered internal rotation of a butane molecule in the liquid state is solved for the Kramers-like rate for trans-gauche isomerization and the torsion angle correlation times. High accuracy solutions obtained by numerical quadrature and approximate asymptotic results are compared with previous molecular dynamics calculations of butane in several thermodynamic states.

Knauss, D. C.; Evans, G. T.

1980-10-01

292

Comparisons between integral equation theory and molecular dynamics simulations for realistic models of polyethylene liquids  

SciTech Connect

Molecular dynamics (MD) simulations were performed on dense liquids of polyethylene chains of 24 and 66 united atom CH{sub 2} units. A series of models was studied ranging in atomistic detail from coarse-grained, freely-jointed, tangent site chains to realistic, overlapping site models subjected to bond angle restrictions and torsional potentials. These same models were also treated with the self-consistent, polymer reference interaction site model (PRISM) theory. The intramolecular and total structure factors, as well as, the intermolecular radial distribution functions g(r) and direct correlation functions C(r) were obtained from theory and simulation. Angular correlation functions were also obtained from the MD simulations. Comparisons between theory and simulation reveal that PRISM theory works well for computing the intermolecular structure of coarse-grained chain models, but systematically underpredicts the extent of intermolecular packing, and overpredicts the compressibility, as more realistic details are introduced into the model. We found that the PRISM theory could be considerably improved by adding a tail function to C(r) beyond the effective hard core diameter. The range of this tail function was determined by requiring the theory to yield the correct compressibility. The intermolecular radial distribution functions from this modified PRISM theory were in excellent agreement with g(r){close_quote}s obtained from the simulations. {copyright} {ital 1999 American Institute of Physics.}

Curro, J.G.; Webb, E.B. III,; Grest, G.S.; Weinhold, J.D. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Puetz, M. [Center for Microengineered Materials, University of New Mexico, Albuquerque, New Mexico 87106 (United States); McCoy, J.D. [Department of Materials and Metallurgical Engineering, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87185 (United States)

1999-11-01

293

Carbon nanotube fibers as torsion sensors  

NASA Astrophysics Data System (ADS)

Carbon nanotube fibers possess the ability to respond electrically to tensile loading. This research explores their electrical response to torsional loading; results demonstrate that applied twist compacts the fiber, resulting in increased electrical contact between carbon nanotubes. Shear strains in excess of 24% do not result in permanent changes in electrical resistance along uninfused fibers, while irreversible changes in electrical resistance arise from applied shear strains of 12.9% in epoxy infused fibers. Bulk shear modulus is approximated to be 0.40 +/- 0.02 GPa for unreinforced and 2.79 +/- 0.64 GPa for infused fibers.

Wu, A. S.; Nie, X.; Hudspeth, M. C.; Chen, W. W.; Chou, T.-W.; Lashmore, D. S.; Schauer, M. W.; Towle, E.; Rioux, J.

2012-05-01

294

High temperature tension-torsion testing machine  

NASA Astrophysics Data System (ADS)

This paper describes an improved tension-torsion testing machine operating at high temperature (1000 C). On the basis of studies of materials characterization and fatigue damage under multiaxial loading, experimental procedures have been developed with new means of extensometer measurement and medium frequency induction heating. The first set of experimental data using these procedures is given for various materials, such as AISI316 steel at 600 C and INCO718 alloy at 650 and 550 C. The tests are used to investigate multiaxiality effects under proportional and nonproportonal, in- and out-of-phase strain and stress paths.

Policella, H.; Pacou, D.

295

Stable Operating Regions of Torsional Interaction Phenomenon in Synchronous Generators  

Microsoft Academic Search

This paper shows that the unstable torsional interaction phenomenon, which had been the cause of shaft failures, is restricted only to the condition when the network resonance frequency and the interacting torsional resonance frequency are both subsynhronous. The interactions, in which this condition is not fulfilled, are positively damped and therefore, safe. The paper also presents physical and analytical insights

Boon-Teck Ooi; Geza Joos

1987-01-01

296

Axial torsion of Meckel's diverticulum presenting as a pelvic mass  

Microsoft Academic Search

.   Meckel's diverticulum is the most common congenital gastrointestinal anomaly. Axial torsion of the diverticulum is rare and\\u000a may produce nonspecific abdominal signs and symptoms. We describe a case of torsion of a Meckel's diverticulum that was noted\\u000a as a pelvic mass on CT images.

S. L. Farris; S. K. Fernbach

2001-01-01

297

Axial torsion of Meckel's diverticulum presenting as a pelvic mass.  

PubMed

Meckel's diverticulum is the most common congenital gastrointestinal anomaly. Axial torsion of the diverticulum is rare and may produce nonspecific abdominal signs and symptoms. We describe a case of torsion of a Meckel's diverticulum that was noted as a pelvic mass on CT images. PMID:11727027

Farris, S L; Fernbach, S K

2001-12-01

298

Torsional Vibration Assessment Using Induction Machine Electromagnetic Torque Estimation  

Microsoft Academic Search

Mechanical anomalies such as load troubles, great torque dynamic variations, and torsional oscillations result in the shaft fatigue of electrical machine and other mechanical parts such as bearings and gearboxes. Particularly, the torsional vibration may attain a significant level at resonant frequencies which damage or cause additional lifetime consumption of mechanical parts. In this way, this paper proposes a noninvasive

Shahin Hedayati Kia; Humberto Henao; GÉrard-AndrÉ Capolino

2010-01-01

299

TALI: Protein Structure Alignment Using Backbone Torsion Angles  

Microsoft Academic Search

This article introduces a novel protein structure alignment method (named TALI) based on protein backbone torsion angle instead of the more traditional distance matrix. Representing protein structure by a serial backbone torsion angles (?, ?), protein structure have a simple mapping relationship to protein sequence. Thus, TALI can naturally incorporate sequence information and sequence analysis method into structure comparison. Here

Xijiang Miao; Michael Bryson; Homayoun Valafar

2006-01-01

300

Torsional Behavior of Reinforced Concrete Beams Strengthened with FRP Composites  

Microsoft Academic Search

Fiber Reinforced Polymer (FRP) as an external reinforcement is used extensively to address the strength requirements related to flexure and shear in structural systems. But the strengthening of members subjected to torsion is yet to be explored. In this paper, the behavior and performance of reinforced concrete members strengthened with externally bonded Glass FRP (GFRP) sheets subjected to pure torsion

Saravanan Panchacharam; Abdeldjelil Belarbi

301

Laboratory Tests of Gravitational Physics Using a Cryogenic Torsion Pendulum  

Microsoft Academic Search

Progress and plans are reported for a program of gravitational physics experiments using cryogenic torsion pendula undergoing large amplitude torsional oscillation. The program includes a UC Irvine project to measure the gravitational constant G and joint UC Irvine-U. Washington projects to test the gravitational inverse square law at a range of about 10 cm and to test the weak equivalence

E. C. Berg; M. K. Bantel; W. D. Cross; T. Inoue; R. D. Newman; J. H. Steffen; M. W. Moore; P. E. Boynton

2005-01-01

302

ADVANCED TORSIONAL STUDY METHOD AND COUPLING SELECTION FOR RECIPROCATING MACHINES  

Microsoft Academic Search

Trains including reciprocating machines are subject to the most varied and often most severe torsional disturbances in comparison to other machinery classes. If crankshaft or rotating component failures occur as a result of shaft torsional oscillations, the consequences can be catastrophic. In this paper a new comprehensive model and solution method using analytical formulations are developed to study both steady

Amin ALMASI

303

Modal analysis techniques for torsional vibration of diesel crankshafts  

Microsoft Academic Search

Torsional vibration in diesel engines, creates a potentially dangerous condition in that there may be no visible or audible indication of its existence, but catastrophic shaft fatigue failure can result. Classical methodology for torsional vibration analysis is cumbersome to employ and provides limited useful information. A methodology is presented which allows a quick and complete analysis of vibratory stress in

P. J. Carrato; C. C. Fu

1986-01-01

304

Friction and shear fracture of an adhesive contact under torsion  

Microsoft Academic Search

The shear failure or stiction of an adhesive contact between a poly(dimethylsiloxane) (PDMS) rubber and a glass lens has been investigated using a torsional contact configuration. As compared to linear sliding, torsion presents the advantage of inducing a shear failure under a pure mode III condition, while preserving the cylindrical symmetry of the contact. The surface of the transparent PDMS

Antoine Chateauminois; Christian Fretigny; Ludovic Olanier

2010-01-01

305

A Stress Analysis of Butt Adhesive Joints Under Torsional Loads  

Microsoft Academic Search

The stress distribution and the displacement are examined when a butt adhesive joint, in which two dissimilar tubular shafts are joined, is subjected to a torsional load. In the analyses, general representations of the stresses and the displacements are given as a torsion problem when two dissimilar tubular shafts are band-adhesively bonded. Next, in the case of shafts with the

Toshiyuki Sawa; Yuichi Nakano; Katsuhiro Temma

1987-01-01

306

Pentoxifylline improves blood flow to both testes in testicular torsion  

Microsoft Academic Search

Objectives: Electromagnetic and radioisotopic studies have shown thatunilateral testicular torsion causes a decrease in contralateral testicularblood flow. Pentoxifylline improves microvascular blood flow in conditionsof vascular insufficiency. An experimental study was designed to evaluatethe effects of pentoxifylline (Ptx) on blood flow to both testes duringunilateral testicular torsion and detorsion.Materials and methods: Thirty-six adult male albino Wistar rats wererandomly divided into six

Ça?r? Sava?; Hüseyin Dindar; Tülin Aras; Selçuk Yücesan

2002-01-01

307

Response of Robust Torsion Balances to Teleseismic Events  

Microsoft Academic Search

We have built a prototype of a robust rotational seismometer [1] based on the concept that torsion balances act as good filters to rotational seismic oscillations at frequencies above their natural frequency of torsional oscillations. We have operated it in spatial and temporal coincidence with a translational seismometer and have recorded several teleseismic events. This has allowed us to calibrate

T. G. Madziwa-Nussinov; R. Cowsik; K. Wagoner; D. A. Wiens; M. E. Wysession

2009-01-01

308

Ultrasonic Welding of Plastic Pipes Using Torsional Vibration  

Microsoft Academic Search

In recent years, the application of ultrasonic welding to plastics has become common. In this paper a method for ultrasonic welding of plastic pipes using torsional vibrations is reported. In this method torsional vibrations are applied to the welding pipe from the circumferential direction with horns placed near the welding surface. Static pressure is independently applied from the vibrations to

Nobuyoshi Masuzawa; Kiichi Hori; Masao Ide

1998-01-01

309

Fission-fragment angular distributions  

Microsoft Academic Search

The universally used ''exact'' formula for fission-fragment angular distributions is shown to be valid only under restrictive assumptions. The more general expression, which depends crucially on the final fragment spin distributions, predicts dramatically more anisotropic angular distributions for fission from nuclei at high spin. Recent ''anomalous'' results are analyzed.

P. Bond

1984-01-01

310

Angular Momenta of the Planets.  

National Technical Information Service (NTIS)

The angular momentum densities of planet-satellite systems (including the asteroids but excepting Venus, Mercury, Mars, and Neptune), viewed as a rest in their solar orbits, exhibit a regularity expressed by A=k(M to the 2/3 power, where A is the angular ...

F. F. Fish

1967-01-01

311

Feynman's angular momentum paradox revisited  

NASA Astrophysics Data System (ADS)

We reexamine Feynman's angular momentum paradox, in which a cylinder of charge around a current carrying solenoid is set in rotational motion when the current is turned off (due to the induced electric field caused by the change in magnetic flux), apparently violating conservation of angular momentum. The standard explanation of the resolution of this paradox is that, when the electric current in the solenoid is on, the combination of the magnetic field from the current and the electric field from the charges results in non-zero angular momentum which is stored in the electromagnetic fields in the vicinity of the solenoid. This angular momentum is transferred to the charged cylinder when the current is turned off. However, we show that for certain geometries of the solenoid and position of the charges, the angular momentum in the vicinity of the solenoid is in fact zero even when the solenoid carries electric current and hence magnetic field is present in the vicinity of the solenoid. We show that angular momentum is in fact still conserved, because the electromagnetic fields which radiate outwards from the solenoid after the current is turned off carry angular momentum which is opposite to the direction of the angular momentum imparted to the charge on the cylinder.

Hu, Ben Yu-Kuang; Loeber, Brian

2012-04-01

312

Intrinsic Angular Momentum of Light.  

ERIC Educational Resources Information Center

Derives a familiar torque-angular momentum theorem for the electromagnetic field, and includes the intrinsic torques exerted by the fields on the polarized medium. This inclusion leads to the expressions for the intrinsic angular momentum carried by the radiation traveling through a charge-free medium. (Author/MA)

Santarelli, Vincent

1979-01-01

313

Infrared modified gravity with dynamical torsion  

SciTech Connect

We continue the recent study of the possibility of constructing a consistent infrared modification of gravity by treating the vierbein and connection as independent dynamical fields. We present the generalized Fierz-Pauli equation that governs the propagation of a massive spin-2 mode in a model of this sort in the backgrounds of arbitrary torsionless Einstein manifolds. We show explicitly that the number of propagating degrees of freedom in these backgrounds remains the same as in flat space-time. This generalizes the recent result that the Boulware-Deser phenomenon does not occur in de Sitter and anti-de Sitter backgrounds. We find that, at least for weakly curved backgrounds, there are no ghosts in the model. We also discuss the interaction of sources in flat background. It is generally believed that the spinning matter is the only source of torsion. Our flat space study shows that this is not the case. We demonstrate that an ordinary conserved symmetric energy-momentum tensor can also generate torsion fields and thus excite massive spin-2 degrees of freedom.

Nikiforova, V. [Physics Department, Moscow State University, Moscow, 119899 (Russian Federation); Institute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary Prospect, 7a, Moscow, 117312 (Russian Federation); Randjbar-Daemi, S. [Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, I-34014, Trieste (Italy); Rubakov, V. [Institute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary Prospect, 7a, Moscow, 117312 (Russian Federation)

2009-12-15

314

Curvature and torsion in growing actin networks  

NASA Astrophysics Data System (ADS)

Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque.

Shaevitz, Joshua W.; Fletcher, Daniel A.

2008-06-01

315

Optical measurement of DNA torsional modulus under various stretching forces  

NASA Astrophysics Data System (ADS)

Optical measurement of DNA torsional modulus under various stretching forces Jaehyuck Choi[1], Kai Zhao[2] Y.-H. Lo[1] [1] Department of Electrical and Computer Engineering, [2] Department of Physics University of California at San Diego, La Jolla, California 92093-0407 We have measured the torsional spring modulus of a double stranded-DNA by applying an external torque around the axis of a vertically stretched DNA molecule. We observed that the torsional modulus of the DNA increases with stretching force. This result supports the hypothesis that an applied stretching force may raise the intrinsic torsional modulus of ds-DNA via elastic coupling between twisting and stretching. This further verifies that the torsional modulus value (C = 46.5 +/- 10 pN nm2) of a ds-DNA investigated under Brownian torque (no external force and torque) could be the pure intrinsic value without contribution from other effects such as stretching, bending, or buckling of DNA chains.

Choi, Jaehyuck

2005-03-01

316

A parity-violating U[sub 4]-gravitation theory  

SciTech Connect

The general structure of a metric-torsion theory of gravitation allows a parity-violating contribution to the complete action which is linear in the curvature tensor and vanishes identically in the absence of torsion. The resulting action involves, apart from the constant [tilde K][sub E] = 8[pi]/c[sup 4], a coupling (B) which governs the strength of the parity interaction mediated by torsion. In this model the Brans-Dicke scalar field generates the torsion field, even though it has zero spin. The interesting consequence of the theory is that its results for the solar-system differ very little from those obtained from Brans-Dicke (BD) theory. Therefore the theory is indistinguishable from BD theory in solar-system experiments. 5 refs.

Jha, R. (Indian Inst. of Science, Bangalore (India))

1993-03-01

317

PREDICTED EFFECTS OF LOCAL CONFORMATIONAL COUPLING AND EXTERNAL RESTRAINTS ON THE TORSIONAL PROPERTIES OF SINGLE DNA MOLECULES*  

PubMed Central

A newly developed, coarse-grained treatment of the low-frequency normal modes of DNA has been adapted to study the torsional properties of fully extended, double-helical molecules. Each base pair is approximated in this scheme as a rigid body, and molecular structure is described in terms of the relative position and orientation of successive base pairs. The torsional modulus C is computed from the lowest-frequency normal twisting mode using expressions valid for a homogeneous, naturally straight elastic rod. Fluctuations of local dimeric structure, including the coupled variation of conformational parameters, are based on the observed arrangements of neighboring base pairs in high-resolution structures. Chain ends are restrained by an elastic energy term. The calculations show how the end-to-end constraints placed on a naturally straight DNA molecule, in combination with the natural conformational features of the double helix, can account for the substantially larger torsional moduli determined with state-of-the-art, single-molecule experiments compared to values extracted from solution measurements and/or incorporated into theories to account for the force-extension properties of single molecules. The computed normal-mode frequencies and torsional moduli increase substantially if base pairs are inclined with respect to the double-helical axis and the deformations of selected conformational variables follow known interdependent patterns. The changes are greatest if the fluctuations in dimeric twisting are coupled with parameters that directly alter the end-to-end displacement. Imposed restraints that mimic the end-to-end conditions of single-molecule experiments then impede the twisting of base pairs and increase the torsional modulus. The natural inclination of base pairs concomitantly softens the Young’s modulus, i.e., ease of duplex stretching. The analysis of naturally curved DNA points to a drop in the torsional modulus upon imposed extension of the double-helical molecule.

MATSUMOTO, ATSUSHI; OLSON, WILMA K.

2008-01-01

318

PREDICTED EFFECTS OF LOCAL CONFORMATIONAL COUPLING AND EXTERNAL RESTRAINTS ON THE TORSIONAL PROPERTIES OF SINGLE DNA MOLECULES.  

PubMed

A newly developed, coarse-grained treatment of the low-frequency normal modes of DNA has been adapted to study the torsional properties of fully extended, double-helical molecules. Each base pair is approximated in this scheme as a rigid body, and molecular structure is described in terms of the relative position and orientation of successive base pairs. The torsional modulus C is computed from the lowest-frequency normal twisting mode using expressions valid for a homogeneous, naturally straight elastic rod. Fluctuations of local dimeric structure, including the coupled variation of conformational parameters, are based on the observed arrangements of neighboring base pairs in high-resolution structures. Chain ends are restrained by an elastic energy term. The calculations show how the end-to-end constraints placed on a naturally straight DNA molecule, in combination with the natural conformational features of the double helix, can account for the substantially larger torsional moduli determined with state-of-the-art, single-molecule experiments compared to values extracted from solution measurements and/or incorporated into theories to account for the force-extension properties of single molecules. The computed normal-mode frequencies and torsional moduli increase substantially if base pairs are inclined with respect to the double-helical axis and the deformations of selected conformational variables follow known interdependent patterns. The changes are greatest if the fluctuations in dimeric twisting are coupled with parameters that directly alter the end-to-end displacement. Imposed restraints that mimic the end-to-end conditions of single-molecule experiments then impede the twisting of base pairs and increase the torsional modulus. The natural inclination of base pairs concomitantly softens the Young's modulus, i.e., ease of duplex stretching. The analysis of naturally curved DNA points to a drop in the torsional modulus upon imposed extension of the double-helical molecule. PMID:19081755

Matsumoto, Atsushi; Olson, Wilma K

2006-01-01

319

Torsional ARC Effectively Expands the Visual Field in Hemianopia  

PubMed Central

Purpose Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonios anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demonstrating a field expansion consistent with torsion we documented torsional strabismus and torsional HARC. Methods Monocular visual fields under binocular fixation conditions were plotted using a custom dichoptic visual field perimeter (DVF). The DVF was also modified to measure perceived visual directions under dissociated and associated conditions across the central 50° diameter field. The field expansion and retinal correspondence of a subject with torsional strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared to that of another exotropic subject with acquired homonymous hemianopia without torsion and to a control subject with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry. Results Torsional ARC documented in the subject with congenital homonymous hemianopia provided a functional binocular field expansion up to 18°. Normal retinal correspondence was mapped for the full 50° visual field in the control subject and for the seeing field of the acquired homonymous hemianopia subject, limiting the functional field expansion benefit. Conclusions Torsional strabismus with ARC, when occurring with homonymous hemianopia provides useful field expansion in the lower and upper fields. Dichoptic perimetry permits documentation of ocular alignment (lateral, vertical and torsional) and perceived visual direction under binocular and monocular viewing conditions. Evaluating patients with congenital or early strabismus for HARC is useful when considering surgical correction, particularly in the presence of congenital homonymous hemianopia.

Satgunam, PremNandhini; Peli, Eli

2012-01-01

320

Relaxation of rotational angular momentum of polar diatomic molecules in simple liquids  

SciTech Connect

The relaxation processes of rotational angular momentum of polar diatomic molecules diluted in simple liquids are analyzed by applying a non-Markovian relaxation theory to the study of the binary time autocorrelation function of the angular momentum. This non-Markovian theory was previously applied to the study of the infrared and Raman spectroscopy, and also to the analysis of the rotational energy relaxation processes. We have obtained non-Markovian evolution equations for the two-time j-level angular momentum correlation components involved in the angular momentum correlation function. In these equations, the time-dependent angular momentum transfer rates and the pure orientational angular transfer rates are given in terms of the binary time autocorrelation function of the diatomic-solvent anisotropic interaction. The non-Markovian evolution equations converge to Markovian ones in the long time limit, reaching the angular momentum transfer rates in the usual time-independent form. Alternative time scales for the angular relaxation processes, relative to the individual rotational processes as well as to the global decay correlations, are introduced and analyzed. The theory is applied to the study of the angular momentum relaxation processes of HCl diluted in liquid SF{sub 6}, a system for which rotational energy relaxation and infrared and Raman spectroscopy was previously analyzed in the scope of the same theory.

Padilla, A.; Perez, J. [Departamento de Fisica Fundamental y Experimental, Electronica y Sistemas, Universidad de La Laguna, 38204 Tenerife (Spain)

2007-03-15

321

Microwavea-Dipole Transitions of CH2DOH and CHD2OH in Excited Torsional States  

NASA Astrophysics Data System (ADS)

Previously identified, measured, and rotationally assigned but unpublishedJ= 0-1 and 1-2 microwavea-dipole lines for excited states of the torsion for CH2DOH and CHD2OH are given torsional assignments for the first four excited states. The troublesome assignments were for theK-1= 0 lines of theo2state of CH2DOH and thee2state of CHD2OH, where a resonance is found for theJ0Jlevels. The assignment for these states was facilitated by combination differences with theb- orc-dipole intratorsional state transitions, relative intensities, and FIR combination differences for thee2ande3states of CH2DOH. A few newb- andc-dipole assignments are reported foro2of CH2DOH ande2of CHD2OH. Transitions for these two states have been analyzed to estimate the strength of the resonant interaction and energy difference for the levels involved and to estimate how well the theory is predicting theK-1-dependent torsional energy levels. The empirically determined ?Band ?Cfrom nonrigidity for each species for the four excited states should prove helpful for future calculations of vibration-internal rotation-overall rotation interactions in these molecules.

Quade, C. Richard; Liu, Mujian; Mukhopadhyay, Indranath; Su, Chun Fu

1998-12-01

322

Chirality and angular momentum in optical radiation  

NASA Astrophysics Data System (ADS)

This paper develops, in precise quantum electrodynamic terms, photonic attributes of the “optical chirality density,” one of several measures long known to be conserved quantities for a vacuum electromagnetic field. The analysis lends insights into some recent interpretations of chiroptical experiments, in which this measure, and an associated chirality flux, have been treated as representing physically distinctive “superchiral” phenomena. In the fully quantized formalism the chirality density is promoted to operator status, whose exploration with reference to an arbitrary polarization basis reveals relationships to optical angular momentum and helicity operators. Analyzing multimode beams with complex wave-front structures, notably Laguerre-Gaussian modes, affords a deeper understanding of the interplay between optical chirality and optical angular momentum. By developing theory with due cognizance of the photonic character of light, it emerges that only the spin-angular momentum of light is engaged in such observations. Furthermore, it is shown that these prominent measures of the helicity of chiral electromagnetic radiation have a common basis in differences between the populations of optical modes associated with angular momenta of opposite sign. Using a calculation of the rate of circular dichroism as an example, with coherent states to model the electromagnetic field, it is discovered that two terms contribute to the differential effect. The primary contribution relates to the difference in left- and right-handed photon populations; the only other contribution, which displays a sinusoidal distance dependence corresponding to the claim of nodal enhancements, is connected with the quantum photon number-phase uncertainty relation. From the full analysis, it appears that the term “superchiral” can be considered redundant.

Coles, Matt M.; Andrews, David L.

2012-06-01

323

Quantitative analysis of extension-torsion coupling of actin filaments.  

PubMed

Actin filaments have a double-helix structure consisting of globular actin molecules. In many mechanical cellular activities, such as cell movement, division, and shape control, modulation of the extensional and torsional dynamics of the filament has been linked to regulatory actin-binding protein functions. Therefore, it is important to quantitatively evaluate extension-torsion coupling of filament to better understand the actin filament dynamics. In the present study, the extension-torsion coupling was investigated using molecular dynamics simulations. We constructed a model for the actin filament consisting of 14 actin subunits in an ionic solvent as a minimal functional unit, and analyzed longitudinal and twisting Brownian motions of the filament. We then derived the expected value of energy associated with extension and torsion at equilibrium, and evaluated the extension-torsion stiffness of the filament from the thermal fluctuations obtained from the MD simulations. The results demonstrated that as the analyzed sampling-window duration was increased, the extension-torsion coupling stiffness evaluated on a nanosecond scale tended to converge to a value of 7.6×10(-11) N. The results obtained from this study will contribute to the understanding of biomechanical events, under mechanical tension and torque, involving extension-torsion coupling of filaments. PMID:22366037

Matsushita, Shinji; Inoue, Yasuhiro; Adachi, Taiji

2012-02-15

324

Torsional Stress and Local Denaturation in Supercoiled DNA  

NASA Astrophysics Data System (ADS)

It is shown that local denaturation can be a natural consequence of supercoiling, even in environments where base pairing of linear DNA is energetically favored. Any change in the molecular total twist from its unstressed value is partitioned between local denaturation and smooth twisting in both the native and coil regions so as to minimize the total conformational free energy involved. Threshold degrees of torsional deformation are found for the existence of stable, locally melted conformations. As these thresholds are surpassed, the number of denatured bases increase smoothly from zero. Existing experimental evidence regarding denaturation in supercoiled DNA is in good agreement with the predictions of this theory. In addition, from existing data one can estimate the partitioning of superhelicity between twisting and writhing. Possible consequences of stress-induced strand separation on the accessibility of the DNA to enzyme attack are discussed. Control of local melting by DNA topoisomerases and DNA gyrases could regulate diverse events involved in transcription, replication, recombination, and repair.

Benham, Craig J.

1979-08-01

325

The Quadratic Spinor Lagrangian, Axial Torsion Current and Generalizations  

NASA Astrophysics Data System (ADS)

We show that the Einstein-Hilbert, the Einstein-Palatini, and the Holst actions can be derived from the Quadratic Spinor Lagrangian (QSL), when the three classes of Dirac spinor fields, under Lounesto spinor field classification, are considered. To each one of these classes, there corresponds an unique kind of action for a covariant gravity theory. In other words, it is shown to exist a one-to-one correspondence between the three classes of non-equivalent solutions of the Dirac equation, and Einstein-Hilbert, Einstein-Palatini, and Holst actions. Furthermore, it arises naturally, from Lounesto spinor field classification, that any other class of spinor field — Weyl, Majorana, flagpole, or flag-dipole spinor fields — yields a trivial (zero) QSL, up to a boundary term. To investigate this boundary term, we do not impose any constraint on the Dirac spinor field, and consequently we obtain new terms in the boundary component of the QSL. In the particular case of a teleparallel connection, an axial torsion one-form current density is obtained. New terms are also obtained in the corresponding Hamiltonian formalism. We then discuss how these new terms could shed new light on more general investigations.

Da Rocha, R.; Pereira, J. G.

326

Mutations in GNAL cause primary torsion dystonia  

PubMed Central

Dystonia is a movement disorder characterized by repetitive twisting muscle contractions and postures1,2. Its molecular pathophysiology is poorly understood, in part due to limited knowledge of the genetic basis of the disorder. Only three genes for primary torsion dystonia (PTD), TOR1A (DYT1)3, THAP1 (DYT6)4, and CIZ15 have been identified. Using exome sequencing in two PTD families we identified a novel causative gene, GNAL, with a nonsense p.S293X mutation resulting in premature stop codon in one family and a missense p.V137M mutation in the other. Screening of GNAL in 39 PTD families, revealed six additional novel mutations in this gene. Impaired function of several of the mutations was shown by bioluminescence resonance energy transfer (BRET) assays.

Fuchs, Tania; Saunders-Pullman, Rachel; Masuho, Ikuo; Luciano, Marta San; Raymond, Deborah; Factor, Stewart; Lang, Anthony E.; Liang, Tsao-Wei; Trosch, Richard M.; White, Sierra; Ainehsazan, Edmond; Herve, Denis; Sharma, Nutan; Ehrlich, Michelle E.; Martemyanov, Kirill A.; Bressman, Susan B.; Ozelius, Laurie J.

2012-01-01

327

Mutations in GNAL cause primary torsion dystonia.  

PubMed

Dystonia is a movement disorder characterized by repetitive twisting muscle contractions and postures. Its molecular pathophysiology is poorly understood, in part owing to limited knowledge of the genetic basis of the disorder. Only three genes for primary torsion dystonia (PTD), TOR1A (DYT1), THAP1 (DYT6) and CIZ1 (ref. 5), have been identified. Using exome sequencing in two families with PTD, we identified a new causative gene, GNAL, with a nonsense mutation encoding p.Ser293* resulting in a premature stop codon in one family and a missense mutation encoding p.Val137Met in the other. Screening of GNAL in 39 families with PTD identified 6 additional new mutations in this gene. Impaired function of several of the mutants was shown by bioluminescence resonance energy transfer (BRET) assays. PMID:23222958

Fuchs, Tania; Saunders-Pullman, Rachel; Masuho, Ikuo; Luciano, Marta San; Raymond, Deborah; Factor, Stewart; Lang, Anthony E; Liang, Tsao-Wei; Trosch, Richard M; White, Sierra; Ainehsazan, Edmond; Hervé, Denis; Sharma, Nutan; Ehrlich, Michelle E; Martemyanov, Kirill A; Bressman, Susan B; Ozelius, Laurie J

2012-12-09

328

Plant-based torsional actuator with memory  

NASA Astrophysics Data System (ADS)

A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg-1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-activated, shape memory twist effect. Over 70% of the twist in a wetted bundle can be locked-in by drying under constraint and then released by rewetting the bundle. Our results indicate that hemicelluloses dominate the shape fixity mechanism and lignin is primarily responsible for remembering the bundle’s original form. The bundles demonstrate proof of a high specific torque actuator with large angles of rotation and shape memory twist capabilities that can be used in microactuators, sensors, and energy harvesters.

Plaza, Nayomi; Zelinka, Samuel L.; Stone, Don S.; Jakes, Joseph E.

2013-07-01

329

Is angular impulse always equal to the change of angular momentum in collisions between rigid bodies?  

Microsoft Academic Search

The relationships between angular impulse and angular momentum have been derived in the particular case of collisions between rigid bodies. It is shown that the change in absolute angular momentum about an arbitrary reference point is always equal to the angular impulse. However, the change in relative angular momentum is equal to the angular impulse only when it is calculated

M. A. Illarramendi; T. del Río Gaztelurrutia; L. M. Villar

1997-01-01

330

Development of torsion loading facility used for evaluating shear performance of polymeric composite implant rods  

Microsoft Academic Search

A torsion loading facility, which integrates a specially-devised torsion tester with an Instron universal testing machine, was developed to evaluate shear performance and failure behavior of implant rods comprised of a variety of materials. The experimental technique and some key instruments employed during the torsion test are described in detail. With this newly-developed facility, torsion fracture test for seven kinds

Kh. G Schmitt-Thomas; Zhen-Guo Yang; T Hiermer

1998-01-01

331

Inelastic buckling and strengths of steel I-section arches with central torsional restraints  

Microsoft Academic Search

The elastic flexural–torsional buckling behaviour of arches with a central elastic torsional restraint has been reported elsewhere by the authors, and it was found that a central elastic torsional restraint restricts the buckling shape of an elastic arch and increases its elastic buckling resistance. However, both the inelastic buckling and strength of arches with a central elastic torsional restraint have

Y. L. Pi; M. A. Bradford

2003-01-01

332

Plasmons with orbital angular momentum  

SciTech Connect

Electron plasma waves carrying orbital angular momentum are investigated in an unmagnetized collisionless plasma composed of inertial electrons and static ions. For this purpose, the usual plasmon dispersion relation is employed to derive an approximate paraxial equation. The latter is analyzed with a Gaussian beam solution. For a finite angular momentum associated with the plasmon, Laguerre-Gaussian (LG) solutions are employed for solving the electrostatic potential problem which gives approximate solution and is valid for plasmon beams in the paraxial approximation. The LG potential determines the electric field components and energy flux of plasmons with finite angular momentum. Numerical illustrations show that the radial and angular mode numbers strongly modify the profiles of the LG potential.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Ali, S. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); National Centre for Physics, Shahdra Valley Road, Islamabad 44000 (Pakistan); Thide, B. [Swedish Institute of Space Physics, Angstroem Laboratory, P.O. Box 537, SE-751 21 Uppsala (Sweden)

2009-11-15

333

Influence of Electric and Magnetic Fields on Angular Correlations  

Microsoft Academic Search

The theory of the influence on angular correlations of perturbing interactions in the intermediate state is reformulated to allow the description of the effects of time-dependent as well as of static perturbations. For static interactions of the nuclear electric quadrupole moment with crystalline fields of axial symmetry in polycrystalline sources, attenuation factors are calculated for the coefficients of the various

A. Abragam; R. V. Pound

1953-01-01

334

Automated angular momentum recoupling algebra  

SciTech Connect

We describe a code, RACAH, for algebraic solution of angular momentum recoupling problems. The general problem is to find an optimal path from one binary tree (representing the angular momentum coupling scheme for the reduced matrix element) to another (representing the sub-integrals and spin sums to be done). RACAH is implemented on a MS-DOS microcomputer, using the SCHEME dialect of LISP. 6 refs.

Williams, H.T. (Washington and Lee Univ., Lexington, VA (USA). Dept. of Physics); Silbar, R.R. (Los Alamos National Lab., NM (USA))

1990-01-01

335

Four-fermion interaction from torsion as dark energy  

NASA Astrophysics Data System (ADS)

The observed small, positive cosmological constant may originate from a four-fermion interaction generated by the spin-torsion coupling in the Einstein-Cartan-Sciama-Kibble gravity if the fermions are condensing. In particular, such a condensation occurs for quark fields during the quark-gluon/hadron phase transition in the early Universe. We study how the torsion-induced four-fermion interaction is affected by adding two terms to the Dirac Lagrangian density: the parity-violating pseudoscalar density dual to the curvature tensor and a spinor-bilinear scalar density which measures the nonminimal coupling of fermions to torsion.

Pop?awski, Nikodem J.

2012-02-01

336

Effect of tensile and torsion on GMI in amorphous wire  

Microsoft Academic Search

GMI effect, ?Z\\/Z = [Z(H) ? Z(Hmax)]\\/Z(Hmax) has been measured in (Fe0.94Co0.06)72.5B15Si12.5 wire under tensile, ?ten, and torsional, ?tor, stresses. Generally ?Z\\/Z(H) dependence has a non-monotonic shape with a maximum at certain axial magnetic field, Hm. Both tension and torsion modify ?Z\\/Z(H) dependence. Application of tension results in an increase of Hm with ?ten. Torsional stress dependence of GMI effect

J. M. Blanco; A. Zhukov; J. Gonzalez

1999-01-01

337

Discussion on massive gravitons and propagating torsion in arbitrary dimensions  

SciTech Connect

In this paper, we reassess a particular R{sup 2}-type gravity action in D dimensions, recently studied by Nakasone and Oda, now taking torsion effects into account. Considering that the vielbein and the spin connection carry independent propagating degrees of freedom, we conclude that ghosts and tachyons are absent only if torsion is nonpropagating, and we also conclude that there is no room for massive gravitons. To include these excitations, we understand how to enlarge Nakasone-Oda's model by means of explicit torsion terms in the action and we discuss the unitarity of the enlarged model for arbitrary dimensions.

Hernaski, C. A.; Vargas-Paredes, A. A.; Helayeel-Neto, J. A. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, Urca, Rio de Janeiro, CEP 22290-180 (Brazil)

2009-12-15

338

Coupling and degenerating modes in longitudinal-torsional step horns.  

PubMed

Longitudinal-torsional vibration is used and proposed for a variety of ultrasonic applications including motors, welding, and rock-cutting. To obtain this behavior in an ultrasonic step horn one can either, (i) couple the longitudinal and torsional modes of the horn by incorporating a ring of diagonal slits in the thick base section or, (ii) place helical flutes in the thin stem section to degenerate the longitudinal mode into a modified behavior with a longitudinal-torsional motion. This paper compares the efficacy of these two design approaches using both numerical and experimental techniques. PMID:22770885

Harkness, Patrick; Lucas, Margaret; Cardoni, Andrea

2012-05-30

339

Cecal torsion in rodents associated with chronic administration of clinafloxacin.  

PubMed

The chronic toxicity of clinafloxacin, a fluoroquinolone antibacterial agent, was evaluated in multiple strains of mice and rats. In 5 separate studies, mice and rats that were orally administered up to 1,000 mg/kg of clinafloxacin from 9 to 104 weeks developed dose-related cecal dilatation and deaths that were attributable to cecal torsion. Cecal rupture was observed in association with torsion. Although cecal dilatation is commonly observed in rodents given antibacterials such as fluoroquinolones, cecal torsion has not been a reported sequelae to dilatation. PMID:11026598

Courtney, C L

340

Angular resolved soft X-ray scattering from optical surfaces  

Microsoft Academic Search

We present angular resolved scattering (ARS) distributions of various glass mirrors and of SiC mirrors at glancing incidence. The measurements have been performed at the XUV reflectometer station at the DORIS2 storage ring (HASYLAB) between 25 and 1.2 nm wavelength. The data are compared with different scattering theories by using least squares fitting procedures. Of all the available theories the

H.-G. Birken; C. Kunz; R. Wolf

1990-01-01

341

Beyond Einstein-Cartan gravity: quadratic torsion and curvature invariants with even and odd parity including all boundary terms  

NASA Astrophysics Data System (ADS)

Recently, gravitational gauge theories with torsion have been discussed by an increasing number of authors from a classical as well as from a quantum field theoretical point of view. The Einstein-Cartan(-Sciama-Kibble) Lagrangian has been enriched by the parity odd pseudoscalar curvature (Hojman, Mukku and Sayed) and by torsion square and curvature square pieces, likewise of even and odd parity. (i) We show that the inverse of the so-called Barbero-Immirzi parameter multiplying the pseudoscalar curvature, because of the topological Nieh-Yan form, can be appropriately discussed if torsion square pieces are included. (ii) The quadratic gauge Lagrangian with both parities, proposed by Obukhov et al and Baekler et al, emerges also in the framework of Diakonov et al. We establish the exact relations between both approaches by applying the topological Euler and Pontryagin forms in a Riemann-Cartan space expressed for the first time in terms of irreducible pieces of the curvature tensor. (iii) In a Riemann-Cartan spacetime, that is, in a spacetime with torsion, parity-violating terms can be brought into the gravitational Lagrangian in a straightforward and natural way. Accordingly, Riemann-Cartan spacetime is a natural habitat for chiral fermionic matter fields.

Baekler, Peter; Hehl, Friedrich W.

2011-11-01

342

The equilibrium statistical mechanics of the helix-coil transition in torsionally stressed DNA  

NASA Astrophysics Data System (ADS)

A theory of helix-coil transitions in torsionally stressed heteropolymeric DNA is developed. Specifically, the polymer is constrained to have a fixed value of total twist in all accessible states, which may differ from its unstressed total twist. This imposed deformation is partitioned between twisting of the helical portions and melting with subsequent twisting in the coil regions. Quadratic free energy densities are associated to torsion in both types of regions. In this theory two parameters influence helix stability-temperature and the magnitude of the imposed twist. Consequently the predicted transition behavior is considerably more intricate than that arising from thermal transitions in unconstrained molecules. In particular, sufficient untwisting can significantly destabilize the helix, even at low temperatures. In this case melting occurs predominantly in AT-rich regions, is complicated. For example, if the imposed twist is altered to decrease helix stability at fixed temperature, the probability of melting of a given monomer unit need not increase monotonically. The predictions of this theory compare favorably with a previous thermodynamic analysis of the same problem.

Benham, Craig J.

1980-03-01

343

The influence of Murnaghan constants on the propagation of a torsional wave in pre-stretched compound circular cylinders  

Microsoft Academic Search

The propagation of torsional waves in prestressed compound circular cylinders is investigated modeling them by a piecewise-homogeneous\\u000a body and using the three-dimensional linearized theory of elastic waves in prestressed body. It is assumed that the elastic\\u000a relations for the components of the cylinders include the Murnaghan potential. The numerical investigations are performed\\u000a for bronze (Br) or brass (Pr) (for the

S. D. Akbarov; A. Ozturk

2010-01-01

344

Multiphoton ionisation of atomic hydrogen and the angular distribution of photoelectrons (Short Note)  

NASA Astrophysics Data System (ADS)

The angular distribution of electrons resulting from off-resonant ionisation of atomic hydrogen has been measured recently [1]. Here we report calculations of these angular distributions using the method of implicit summation [2] to calculate the n-photon absorption probabilities in the nth order of perturbation theory.

Kracke, G.; Marxer, H.; Broad, J. T.; Briggs, J. S.

1988-03-01

345

NMR structure calculation methods for large proteins Application of torsion angle dynamics and distance geometry/ simulated annealing to the 269-residue protein serine protease PB92  

NASA Astrophysics Data System (ADS)

Molecular dynamics in torsion angle space together with the well established combination of metric matrix distance geometry and simulated annealing in Cartesian space have been applied to the solution structure determination of serine protease PB92, a 269-residue monomeric protein from Bacillus alcalophilus. The input data set comprised distance restraints and a combination of distance and angular restraints derived from NMR data. A number of different modifications of the two calculation strategies were studied with respect to their convergence behaviour. The resulting structural ensembles were evaluated according to several criteria for protein structure quality. Improved protocols for both methods have been developed from these analyses. A comparison of the structures obtained with these protocols demonstrates the superior convergence behaviour of the torsion angle dynamics method. Although both methods are able to fold up the protein correctly, the torsion angle dynamics protocol scores slightly better with respect to measures of structural quality, especially when dihedral angle restraints are available. Torsion angle molecular dynamics presents a simple and robust method for the NMR structure calculations of large proteins.

Karimi-Nejad, Yasmin

1998-12-01

346

Ocular Torsion in the Weightlessness of Parabolic Flight (Abstract Only),  

National Technical Information Service (NTIS)

Preliminary findings of torsional eyeball displacements (rotational displacements about the optic axis) in parabolic flight that were reported in Spacebound '87 have been confirmed. The more recent experiments have used photographs of both eyes, instead o...

K. E. Money N. M. Kirienko W. H. Johnson D. G. D. Watt C. H. Markham

1988-01-01

347

Time-resolved observation of molecular torsional dynamics  

NASA Astrophysics Data System (ADS)

We recently presented the first efforts made to extend the methods of alignment to manipulating and observing the torsion in a molecule [1,2]. Experimental and theoretical results obtained through the joint effort of four Aarhus groups from experimental strong-field laser physics, theoretical physics, theoretical quantum chemistry, and organic synthetic chemistry, demonstrated that strong-field laser physics methods and time-resolved measurements are not limited to small linear molecules, but can actually be useful for studying exciting fundamental phenomena in larger complex systems. Lately, we have explored the torsional dynamics on long time scales (ps). These studies revealed the decay of the torsional oscillation in time. Theoretical efforts are made to explore how energy dissipates from the torsional degree of freedom into overall rotation of the molecule. [4pt] [1] C. B. Madsen et al., Phys. Rev. Lett. 102, 073007 (2009).[2] C. B. Madsen et al., J. Chem. Phys. 130, 234310 (2009).

Madsen, C. B.; Hansen, J. L.; Madsen, L. B.; Stapelfeldt, H.

2011-06-01

348

Lung torsion after tracheoesophageal fistula repair in an infant.  

PubMed

Lung torsion is a very rare event that has been reported in only 9 cases in the pediatric literature but has not yet been reported in Korean infants. We present a case of lung torsion after tracheoesophageal fistula repair in an infant. Bloody secretion from the endotracheal tube and chest radiographs and computed tomographic scan results indicated lung torsion. Emergency exploration indicated 180° torsion of the right upper lobe (RUL) and right middle lobe (RML). After detorsion of both lobes, some improvement in the RUL color was observed, but the color change in the RML could not be determined. Although viability of the RML could not be proven, pexy was performed for both the lobes. Despite reoperation, clinical signs and symptoms did not improve. The bronchoscopy revealed a patent airway in the RUL but not in the RML. Finally, the RML was surgically removed. The patient was discharged on the 42nd day after birth. PMID:23646058

Yang, Eun Mi; Song, Eun Song; In Jang, Hae; Jeong, In Seok; Choi, Young Youn

2013-04-22

349

Lung torsion after tracheoesophageal fistula repair in an infant  

PubMed Central

Lung torsion is a very rare event that has been reported in only 9 cases in the pediatric literature but has not yet been reported in Korean infants. We present a case of lung torsion after tracheoesophageal fistula repair in an infant. Bloody secretion from the endotracheal tube and chest radiographs and computed tomographic scan results indicated lung torsion. Emergency exploration indicated 180° torsion of the right upper lobe (RUL) and right middle lobe (RML). After detorsion of both lobes, some improvement in the RUL color was observed, but the color change in the RML could not be determined. Although viability of the RML could not be proven, pexy was performed for both the lobes. Despite reoperation, clinical signs and symptoms did not improve. The bronchoscopy revealed a patent airway in the RUL but not in the RML. Finally, the RML was surgically removed. The patient was discharged on the 42nd day after birth.

Yang, Eun Mi; Song, Eun Song; in Jang, Hae; Jeong, In Seok

2013-01-01

350

Torsional vibration suppression of drive system based on DMC method  

Microsoft Academic Search

In this paper, a novel torsional vibration predictive control design based on DMC (dynamic matrix control) is proposed for drive system. The state equation of two-mass drive system is established based on model matching. A PI-DMC controller for suppressing torsional vibration of drive system was designed by PI controller with dynamic matrix control. The random disturbance is avoided by inner-controller,

Peiming Shi; Bin Liu; Dongxiao Hou

2008-01-01

351

G2-structures with torsion from half-integrable nilmanifolds  

NASA Astrophysics Data System (ADS)

The equations for a G2-structure with torsion on a product M=N×S are studied in relation to the induced SU(3)-structure on N. All solutions are found in the case when the Lee-form of the G2-structure is non-zero and N is a six-dimensional nilmanifold with half-integrable SU(3)-structure. Special properties of the torsion of these solutions are discussed.

Chiossi, Simon G.; Swann, Andrew

2005-07-01

352

Considerations on the Spörer-diagram - torsional wave relationship  

NASA Astrophysics Data System (ADS)

Studies on the earlier reported spatial correlations between magnetic field distributions and the torsional wave have been substantially extended to the period 1975-2009. The investigations are based on Debrecen sunspot data and magnetic field data of Mount Wilson. The recently available data and distributions seem to support the idea that the torsional wave may be caused by flows around the toruses which result in Coriolis-deviations forward and backward, establishing the prograde and retrograde belts.

Muraközy, J.; Ludmány, A.

353

Ultrasonic Welding of Plastic Pipes Using Torsional Vibration  

NASA Astrophysics Data System (ADS)

In recent years, the application of ultrasonic welding to plastics has become common. In this paper a method for ultrasonic welding of plastic pipes using torsional vibrations is reported. In this method torsional vibrations are applied to the welding pipe from the circumferential direction with horns placed near the welding surface. Static pressure is independently applied from the vibrations to the welding surface. It was observed that acrylic resin pipes could be effectively welded by the proposed method.

Masuzawa, Nobuyoshi; Hori, Kiichi; Ide, Masao

1998-05-01

354

On the Effective Control of Torsional Vibrations in Drilling Systems  

Microsoft Academic Search

This paper analyses a control mechanism designed to significantly ameliorate the sustained excitation of torsional relaxation oscillations (slip–stick) due to frictional torques generated by an active bit during drilling operations with an extended drill-string. The proposed mechanism of torsional rectification is compared with existing soft-torque devices in a series of mathematical models. Both analytic and numerical simulations indicate that many

R. W. Tucker; C. Wang

1999-01-01

355

A new hybrid longitudinal-torsional magnetostrictive ultrasonic transducer  

NASA Astrophysics Data System (ADS)

In this paper, a novel hybrid longitudinal-torsional magnetostrictive ultrasonic transducer (HL-TMUT) is introduced. The transducer is composed of a magnetostrictive exponential horn and a stainless steel tail mass. In this transducer a spiral magnetic field made up of longitudinal and circumferential magnetic fields is applied to the magnetostrictive horn. As a result, the magnetostrictive horn oscillates simultaneously both longitudinally and torsionally in accordance with the Joule and Wiedemann effects. The magnetostrictive exponential horn is designed in such a manner that it has the same longitudinal and torsional resonant frequency. It is made up of ‘2V Permendur’, which has isotropic magnetic properties. The differential equations of the torsional and longitudinal vibration of the horn are derived, and a HL-TMUT is designed with a resonant frequency of 20?573 Hz. The natural frequency and mode shapes of the transducer are considered theoretically and numerically. The experimental results show that this transducer resonates torsionally and longitudinally with frequencies of 20?610 Hz and 20?830 Hz respectively. The maximum torsional displacement is 1.5 mrad m-1 and the maximum longitudinal displacement is 0.6 ?m. These are promising features for industrial applications.

Karafi, Mohammad Reza; Hojjat, Yousef; Sassani, Farrokh

2013-06-01

356

Torsional eye movements during psychophysical testing with rotating patterns.  

PubMed

Torsional eye movements were measured while subjects viewed a large, high contrast windmill pattern rotating at 53 degrees /s or a small (5 degrees diameter) dot pattern rotating at 115 degrees /s. Both stimuli generated rotational eye movements consisting of torsional optokinetic nystagmus (tOKN) superimposed on a slow torsional drift in the direction of pattern rotation. With the wide-field windmill stimulus, torsional drifts of up to 7 degrees over 20 s were found. The dot pattern produced drifts of up to 2 degrees over 5-20 s. In both cases, the slow-phase speeds during tOKN were low (0.5-1 degrees /s). We conclude that reductions in slip speed are minimal with rotating stimuli, so torsional eye speeds will have a minimal effect on investigations of rotational motion aftereffect strength and perceived speed. While the slow-phase tOKN gain is low, the slow drift in torsional eye position will have significant effects on psychophysical results when the tests rely on keeping selected regions of the stimulus confined to specific areas of the retina, as is the case for phantom or remote motion aftereffects. PMID:15551078

Ibbotson, M R; Price, N S C; Das, V E; Hietanen, M A; Mustari, M J

2004-11-16

357

Geometry and torsional energies of a C-C-protonated n-alkane  

NASA Astrophysics Data System (ADS)

The geometry and relative energies of torsional conformers of centrally protonated C4H11+ were studied with ab initio methods, to (a) obtain the most accurate geometry of the three-center-two-electron CHC bond to date, (b) evaluate the performance of lower levels of approximation upon this challenging structure, and (c) gain an understanding of the torsional dynamics of C4H11+. Twenty-nine combined levels of theory were used to optimize the geometry of the C2-symmetry minimum for trans-C4H11+, and the most accurate one [CCSD(T)/cc-pVTZ] gave the following CHC bond geometry: ?CHC=122.4°, RCC=2.177 Å, RCH=1.2424 Å. Molecular-orbital-based methods generally perform better than density functional methods for describing the three-center-two-electron bond. A smaller subset of levels of theory was used to optimize other torsional conformers of centrally protonated C4H11+, varying the CCCC dihedral (trans, gauche, cis) and the dihedral for the bridging proton (various eclipsed and staggered positions). The results show that all conformers lie within a 4 kJ mol-1 range, with the lowest-energy conformer being either trans or gauche with a staggered dihedral for the bridging proton. The effect of core-valence correlation was also investigated. Finally, the potential energy surface as a function of the CCCC and bridging-proton dihedral angles was qualitatively estimated and drawn, based on our computed data, to aid in understanding the fluxional character of C4H11+.

Li, Qingbin; Hunter, Ken C.; Seitz, Christa; East, Allan L. L.

2003-10-01

358

Torsional texturing of superconducting oxide composite articles  

DOEpatents

A method of texturing a multifilamentary article having filaments comprising a desired oxide superconductor or its precursors by torsionally deforming the article is provided. The texturing is induced by applying a torsional strain which is at least about 0.3 and preferably at least about 0.6 at the surface of the article, but less than the strain which would cause failure of the composite. High performance multifilamentary superconducting composite articles having a plurality of low aspect ratio, twisted filaments with substantially uniform twist pitches in the range of about 1.00 inch to 0.01 inch (25 to 0.25 mm), each comprising a textured desired superconducting oxide material, may be obtained using this texturing method. If tighter twist pitches are desired, the article may be heat treated or annealed and the strain repeated as many times as necessary to obtain the desired twist pitch. It is preferred that the total strain applied per step should be sufficient to provide a twist pitch tighter than 5 times the diameter of the article, and twist pitches in the range of 1 to 5 times the diameter of the article are most preferred. The process may be used to make a high performance multifilamentary superconducting article, having a plurality of twisted filaments, wherein the degree of texturing varies substantially in proportion to the radial distance from the center of the article cross-section, and is substantially radially homogeneous at any given cross-section of the article. Round wires and other low aspect ratio multifilamentary articles are preferred forms. The invention is not dependent on the melting characteristics of the desired superconducting oxide. Desired oxide superconductors or precursors with micaceous or semi-micaceous structures are preferred. When used in connection with desired superconducting oxides which melt irreversibly, it provides multifilamentary articles that exhibit high DC performance characteristics and AC performance markedly superior to any currently available for these materials. In a preferred embodiment, the desired superconducting oxide material is BSCCO 2223.

Christopherson, Craig John (Grafton, MA); Riley, Jr., Gilbert N. (Marlborough, MA); Scudiere, John (Bolton, MA)

2002-01-01

359

Spatially resolved Fourier holographic light scattering angular spectroscopy  

NASA Astrophysics Data System (ADS)

We show for what is the first time to our knowledge that digital Fourier holography can be used to record spatially resolved angular light scattering spectra from microscopically structured samples. This is achieved in one or a few digital image captures over large millimeter-scale fields of view. Such spectra are a sensitive measure of microscopic morphology, with wide applications in biological and medical imaging. We demonstrate good agreement between results of experiment and Mie theory for the angular scattering spectra of microspheres in water extracted from local regions within reconstructed 2×1 millimeter image sets.

Alexandrov, Sergey A.; Hillman, Timothy R.; Sampson, David D.

2005-12-01

360

Kinetic description of electron plasma waves with orbital angular momentum  

SciTech Connect

We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2012-11-15

361

Theory, Theory  

NSDL National Science Digital Library

This lesson includes a theory-evaluation activity. A set of five scenarios (theories for how diverse life came into existence on Earth) is divided evenly throughout the class, so each student is asked to evaluate one theory. Students then come together in groups of five, so that all theories are represented in each group, where they are compared and evaluated. Each group reports to the entire class for further discussion and clarifications.

Kimmel, Michael

2007-12-12

362

Interferometric measurement of angular motion  

NASA Astrophysics Data System (ADS)

This paper describes the design and realization of a homodyne polarization interferometer for measuring angular motion. The optical layout incorporates carefully designed cat's eye retroreflectors that maximize the measurable range of angular motion and facilitate initial alignment. The retroreflectors are optimized and numerically characterized in terms of defocus and spherical aberrations using Zemax software for optical design. The linearity of the measurement is then calculated in terms of the aberrations. The actual physical interferometer is realized as a compact device with optical components from stock and without relying on adjustable holders. Evaluation of its performance using a commercial autocollimator confirmed a reproducibility within 0.1%, a non-linearity of less than 1 ppm with respect to the autocollimator, an upper limit to its sensitivity of about 5 × 10-11 rad/Hz from audioband down to 100 mHz and an angular measurement range of more than +/-1°.

Peña Arellano, Fabián Erasmo; Panjwani, Hasnain; Carbone, Ludovico; Speake, Clive C.

2013-04-01

363

Interferometric measurement of angular motion.  

PubMed

This paper describes the design and realization of a homodyne polarization interferometer for measuring angular motion. The optical layout incorporates carefully designed cat's eye retroreflectors that maximize the measurable range of angular motion and facilitate initial alignment. The retroreflectors are optimized and numerically characterized in terms of defocus and spherical aberrations using Zemax software for optical design. The linearity of the measurement is then calculated in terms of the aberrations. The actual physical interferometer is realized as a compact device with optical components from stock and without relying on adjustable holders. Evaluation of its performance using a commercial autocollimator confirmed a reproducibility within 0.1%, a non-linearity of less than 1 ppm with respect to the autocollimator, an upper limit to its sensitivity of about 5 × 10(-11) rad/Hz from audioband down to 100 mHz and an angular measurement range of more than ±1°. PMID:23635175

Peña Arellano, Fabián Erasmo; Panjwani, Hasnain; Carbone, Ludovico; Speake, Clive C

2013-04-01

364

Nonlinear torsional vibrations of rigid bodies  

NASA Astrophysics Data System (ADS)

Nonlinear dynamical models of a rigid body working under oscillatory conditions with damping, and fastened at a fixed point, e g., centre of mass, are discussed. Special stress is laid on isotropic models, invariant under so-called hyperrotations, i.e. rotations of the rotation vector. For the damping-free (purely oscillatory) case completely degenerate potentials are determined, and general solutions of equations of motion are discussed. These results can be helpful in designing instruments sensitive to inertial forces and their moments, e.g., sensors of angular acceleration in automatic control systems and navigation.

Slawianowski, J. J.

365

Angular momentum transport in complex fluids  

NASA Astrophysics Data System (ADS)

When dyes are dissolved in nematic liquid crystals, the light intensity required for the optical Freedericksz transition can be dramatically decreased. This is due to the torque exerted by the dye on the liquid crystal. The dye molecules absorb light energy and rotate; torque balance is mediated by angular momentum transport from the cell walls via shear flow generated by the rotation [1]. We present a model which accounts for the transport of angular momentum caused by singular vortices present in these complex fluids. The singular vortices generate flow, and are transported by the flow which they generate. For simple fluids, the distribution of vorticity satisfies the biharmonic equation in the Stokes limit, which can be solved analytically. In the case of the non-Newtonian fluids, such as liquid crystals, Leslie-Ericksen continuum theory is used to describe the interactions between the rod-like molecules. [1] P. Palffy-Muhoray, T. Kosa and Weinan E, ``Brownian Motors in the Photoalignment of Liquid Crystals'', Appl. Phys. A 75, 293-300 (2002).

Zheng, Xiaoyu; Palffy-Muhoray, Peter; Shelley, Michael

2008-03-01

366

On quantum gauge theories in two dimensions  

Microsoft Academic Search

Two dimensional quantum Yang-Mills theory is studied from three points of view: (i) by standard physical methods; (ii) by relating it to the largek limit of three dimensional Chern-Simons theory and two dimensional conformal field theory; (iii) by relating its weak coupling limit to the theory of Reidemeister-Ray-Singer torsion. The results obtained from the three points of view agree and

Edward Witten

1991-01-01

367

Calculating limits for torsion and tensile loads on drill pipe  

SciTech Connect

Drill pipe used for drilling horizontal and extended reach holes experiences much higher torsional and tensile loads than normally seen while drilling vertical holes. This is particularly true for rigs with top drives vs. rigs with rotary tables. When pipe is rotated while pulling out of the hole, which is commonly done on top drive rigs, the drill pipe can experience high tensile and torsional loading simultaneously. These conditions increase the probability of overload on tool joints and require that the drill pipe and tool joint selection process include consideration of combined loading. Calculating the required drill pipe strength for vertical holes is straightforward and spelled out in Section 5 of API RP7G. In vertical hole applications, pipe is almost always selected for its tensile capacity and the torsional strength of the pipe generally does not require special consideration. In Section 4 of API Sec 7, API recommends that the tool joints have a torsional strength of 80% of the pipe`s torsional strength; this is usually adequate. The torsional strength and tensile strength of commonly used drill pipe and tool joint combinations are tabulated in Tables 2 through 10 of API RP7G. Appendix A.8.3 in API RP7G shows a method for plotting a graphical representation of the combined torsional and tensile operational limits of tool joints. How to calculate the limits of the drill pipe tube is shown in Appendix A.9.2. This paper defines terms and limits, and discusses building and using a diagram to determine safe loads.

Bailey, E.I. [Stress Engineering Service Inc., Houston, TX (United States); Smith, J.E. [Grant Prideco, Houston, TX (United States)

1998-02-01

368

The Extremely Flat Torsional Potential Energy Surface of Oxalyl Chloride  

SciTech Connect

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The conformational behavior of oxalyl chloride has been investigated using ab initio Hartree–Fock (HF) and second-order Møller–Plesset (MP2) perturbation theories, and the coupled-cluster singles and doubles method appended with a perturbative inclusion of connected triple excitations [CCSD(T)]. Correlation consistent polarized valence quadruple-z (cc-pVQZ) and quintuple-z (cc-pV5Z) basis sets were used in this research. At the cc-pVQZ and cc-pV5Z HF levels, there is no stationary point corresponding to a stable gauche conformer. On the other hand, at the cc-pVQZ and cc-pV5Z MP2 levels and with the cc-pVQZ CCSD(T) method, the gauche conformer of oxalyl chloride was found at O=C-C=O dihedral angles of 81.9°, 79.4°, and 83.4°, respectively. At the cc-pV5Z MP2 level, the energy barrier from trans to gauche was predicted to be 0.74 kcal mol?1 and that from gauche to trans to be 0.09 kcal mol?1. Thus, the potential-energy surface along the OvC-CvO torsional mode is exceedingly flat. The existence of the gauche conformation is mainly due to the minimization of steric repulsion.

Kim, Sunghwang; Wheeler, Steven E.; DeYonker, Nathan John; Schaefer, Henry F.

2005-06-21

369

Angular correlation in ^134Pr  

NASA Astrophysics Data System (ADS)

A background subtraction method for ?-ray spectroscopic measurements with large multidetector HpGe arrays has been applied to data from the GS2K009 experiment in which the ^116Cd(^23Na,5n) reaction was employed to study ^134Pr. The method takes advantage of recently developed BLUE data storage which allows for event retrieval in their native fold. The background spectrum is constructed based on the parameters evaluated from one-dimensional spectra only; the method, therefore, is complementary to other methods applied so far which are optimized for multidimensional, symmetrized histograms. When the background subtracted spectra projected on the Gammasphere rings are summed together, the applied algorithm compare well to that in the RADWARE data analysis package. Double gated spectra projected on Gammasphere rings were analyzed for angular correlations and Doppler Shift Attenuation studies. The method allows investigation of triple-? correlations which can be used to enhance angular asymmetry. It can also be apply to DCO or angular distributions studies from doubly gated spectra if appropriate angular conditions are set for the gating ?-rays. The resulting spin/parity assignments in ^134Pr will be presented.

Starosta, Krzysztof

2004-10-01

370

Olympic Wrestling and Angular Momentum.  

ERIC Educational Resources Information Center

Reported is the use of a wrestling photograph in a noncalculus introductory physics course. The photograph presents a maneuver that could serve as an example for a discussion on equilibrium, forces, torque, and angular motion. Provided are some qualitative thoughts as well as quantitative calculations. (YP)

Carle, Mark

1988-01-01

371

Orbital-angular-momentum entanglement in turbulence  

NASA Astrophysics Data System (ADS)

The turbulence-induced decay of orbital-angular-momentum (OAM) entanglement between two photons is investigated numerically and experimentally. To compare our results with previous work, we simulate the turbulent atmosphere with a single phase screen based on the Kolmogorov theory of turbulence. We consider two different scenarios: in the first only one of the two photons propagates through turbulence, and in the second both photons propagate through uncorrelated turbulence. Comparing the entanglement evolution for different OAM values, we found the entanglement to be more robust in turbulence for higher OAM values. We derive an empirical formula for the distance scale at which entanglement decays in terms of the scale parameters and the OAM value.

Hamadou Ibrahim, A.; Roux, Filippus S.; McLaren, Melanie; Konrad, Thomas; Forbes, Andrew

2013-07-01

372

Gas-Phase Detection of HSOH: Synthesis by Flash Vacuum Pyrolysis of Di-tert-butyl Sulfoxide and Rotational-Torsional Spectrum  

NASA Astrophysics Data System (ADS)

Gas-phase oxadisulfane (HSOH), the missing link between the well-known molecules hydrogen peroxide (HOOH) and disulfane (HSSH), was synthesized by flash vacuum pyrolysis of di-tert-butyl sulfoxide. Using mass spectrometry, the pyrolysis conditions have been optimized towards formation of HSOH. Microwave spectroscopic investigation of the pyrolysis products allowed - assisted by high-level quantum-chemical calculations - the first measurement of the rotational-torsional spectrum of HSOH. In total, we have measured approximately 600 lines of the rotational-torsional spectrum in the frequency range from 64 GHz to 1.9 THz and assigned some 470 of these to the rotational-torsional spectrum of HSOH in its ground torsional state. Some 120 out of the 600 lines arise from the isotopomer H34SOH. The HSOH molecule displays strong c-type and somewhat weaker b-type transitions, indicating a nonplanar skew chain structure, similar to the analogous molecules HOOH and HSSH. The rotational constants (MHz) of the main isotopomer (A=202 069, B=15 282, C=14 840), determined by applying a least-squares analysis to the presently available data set, are in excellent agreement with those predicted by quantum-chemical calculations (A=202 136, B=15 279, C=14 840). Our theoretical treatment also derived the following barrier heights against internal rotation in HSOH (when in the cis and trans configurations) to be Vcis=2216 cm-1 and Vtrans=1579 cm-1. The internal rotational motion results in detectable torsional splittings that are dependent on the angular momentum quantum numbers J and Ka.

Winnewisser, G.; Lewen, F.; Thorwirth, S.; Behnke, M.; Hahn, J.; Gauss, J.; Herbst, E.

2003-11-01

373

Flutter Suppression of Composite Plate Wings Based on the Measurement and Control of Torsional Vibration Mode (The Second Report)  

NASA Astrophysics Data System (ADS)

The present paper treats the flutter suppression of composite plate wings with segmented piezoelectric sensors and actuators. In the second report of this paper, validity of the flutter suppression based on the optimal placement of sensors and actuators is examined for composite plate wings. Modal sensor for measurement of the modal displacement of the first torsional vibration mode is designed by the optimal placement of PVDF sensors based on the minimization criterion of observation spillover. Actuation system to generate the modal force for the first torsional vibration mode is designed by the optimal placement of PZT actuators based on the minimization criterion of control spillover. Aeroelastic analysis of composite plates is based on the finite element method and the subsonic unsteady lifting surface theory. The minimum state method is applied to approximate the unsteady aerodynamic forces as the transfer functions of the Laplace variables. The effectiveness of optimal placement of sensors and actuators in the flutter suppression is clarified through the numerical examples.

Kameyama, Masaki

374

Early onset torsion dystonia (Oppenheim's dystonia)  

PubMed Central

Early onset torsion dystonia (EOTD) is a rare movement disorder characterized by involuntary, repetitive, sustained muscle contractions or postures involving one or more sites of the body. A US study estimated the prevalence at approximately 1 in 30,000. The estimated prevalence in the general population of Europe seems to be lower, ranging from 1 in 330,000 to 1 in 200,000, although precise numbers are currently not available. The estimated prevalence in the Ashkenazi Jewish population is approximately five to ten times higher, due to a founder mutation. Symptoms of EOTD typically develop first in an arm or leg in middle to late childhood and progress in approximately 30% of patients to other body regions (generalized dystonia) within about five years. Distribution and severity of symptoms vary widely between affected individuals. The majority of cases from various ethnic groups are caused by an autosomal dominantly inherited deletion of 3 bp (GAG) in the DYT1 gene on chromosome 9q34. This gene encodes a protein named torsinA, which is presumed to act as a chaperone protein associated with the endoplasmic reticulum and the nuclear envelope. It may interact with the dopamine transporter and participate in intracellular trafficking, although its precise function within the cell remains to be determined. Molecular genetic diagnostic and genetic counseling is recommended for individuals with age of onset below 26 years, and may also be considered in those with onset after 26 years having a relative with typical early onset dystonia. Treatment options include botulinum toxin injections for focal symptoms, pharmacological therapy such as anticholinergics (most commonly trihexiphenydil) for generalized dystonia and surgical approaches such as deep brain stimulation of the internal globus pallidus or intrathecal baclofen application in severe cases. All patients have normal cognitive function, and despite a high rate of generalization of dystonia, 75% of those patients are able to maintain ambulation and independence, and therefore a comparatively good quality of life, with modern treatment modalities.

Kamm, Christoph

2006-01-01

375

Numerical modeling of pendulum dampers in torsional systems  

SciTech Connect

Centrifugal pendulum-design dampers are utilized in torsional systems to reduce the vibration amplitude at certain objectionable torsional speeds. The damper is tuned by proper design of its mass, dimensions, and position on a carrier disk, which is rigidly attached to the torsional system. The effects of the pendulum damper on the response of the torsional system may be included by modifying the structural model to include a separate damper element representing each order of the pendulum damper. The stiffness and mass matrices for a damper element are dependent upon the order of vibration being dampened, the mass, and the geometry of the damper. A general form of the mass and stiffness equations for a simple centrifugal pendulum damper are derived from first principles using Lagrange's equations of motion. The analysis of torsional systems with pendulum dampers utilizing the mass and stiffness properties developed is included in the program SHAMS. SHAMS calculates the steady-state response of a system of springs and masses to harmonic loads using modal superposition. The response of a crankshaft system with and without the pendulum dampers are included as a case study.

Johnston, P.R.; Shusto, L.M.

1986-01-01

376

Elevated temperature axial and torsional fatigue behavior of Haynes 188  

NASA Astrophysics Data System (ADS)

The results of high-temperature axial and torsional low-cycle fatigue experiments performed on Haynes 188, a wrought cobalt-base superalloy, are reported. Fatigue tests were performed at 760 C in air on thin-walled tubular specimens at various ranges under strain control. Data are also presented for coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. The data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME boiler and pressure vessel code), Manson-Halford, Modified Multiaxiality Factor (proposed here), Modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The Modified Multiaxiality Factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

Bonacuse, Peter J.; Kalluri, Sreeramesh

1992-06-01

377

Plate tectonics conserves angular momentum  

NASA Astrophysics Data System (ADS)

A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4 E+27 kgm2s-1). Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates). Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth). The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant velocity on the crests of convection cells driven by rising heat. These results imply that spreading centers are primarily passive reactive features, and fracture zones (and wedge-shaped sites of seafloor spreading) are adjustment zones that accommodate strains in the lithosphere. Further, the interlocked pattern of the Australian and Pacific plates the past 42 Million years (with their absolute plate motions near 90° to each other) is taken as strong evidence that large thermally driven "roller" convection cells previously inferred as the driving mechanism in earlier interpretations of continental drift and plate tectonics, have not been active in the Earth's mantle the past 42 Million years, if ever. This report also presents estimates of the changes in location and magnitude of the Earth's axis of total plate tectonic angular momentum for the past 62 million years.

Bowin, C.

2009-03-01

378

Torsion, AN Alternative to the Cosmological Constant?  

NASA Astrophysics Data System (ADS)

We confront Einstein-Cartan's theory with the Hubble diagram and obtain a negative answer to the question in the title. Contrary findings in the literature seem to stem from an error in the field equations.

Schücker, Thomas; Tilquin, André

2012-12-01

379

Higher torsional mode suppression in a pipe for enhancing the first torsional mode by using magnetostrictive patch transducers.  

PubMed

Small-sized defects in pipes can be better detected if the first nondispersive torsional mode is used in a higher frequency range. However, dispersive higher torsional modes accompany the first mode if the actuation frequency is above the first cutoff frequency, thereby making the detection difficult. This study proposes a new technique that is particularly useful for guided torsional waves in a pipe; it enhances the desired first nondispersive mode and suppresses the undesired second mode. The technique uses two transmitting transducers separated by an optimized distance and actuated with an optimized delay time. Unlike previous methods, such as a method tuning the delay time for desired mode enhancement and tuning the distance for undesired mode suppression, the proposed approach determines both the distance and delay time mainly to suppress the undesired second mode. With the selected values, the desired first mode is substantially enhanced. This phenomenon is unique in torsional waves, not longitudinal waves, for which delay time and distance controlling methods have been developed. After wave simulations were carried out to show why the proposed method is more effective for the case of torsional waves, several experiments using magnetostrictive transducers were performed to demonstrate the effectiveness of the proposed method. PMID:23475921

Kim, Hoe Woong; Kwon, Young Eui; Lee, Joo Kyung; Kim, Yoon Young

2013-03-01

380

Torsional response of inhomogeneous and multilayered composite beams  

NASA Astrophysics Data System (ADS)

The elastic response of inhomogeneous orthotropic beams with general cross-section and subject to uniform torsion is investigated. The problem is formulated both in terms of the warping and of the Prandtl stress function. Moreover, the exact solution for rectangular orthotropic beams constituted by any number of layers is derived, making use of a series form which is unaffected by unstable behaviors. Several examples are presented, showing that approximate solutions based on simplified kinematical models can yield very poor estimates of the torsional rigidity. Finally, it is shown that the plating of homogeneous beams by means of thin carbon or glass fiber-reinforced laminae can be used to make the torsional rigidity 8-10 times as much.

Savoia, Marco; Tullini, Nerio

381

Ab Initio Torsion-Wag Surface for the Ethyl Radical  

NASA Astrophysics Data System (ADS)

The torsion-wag potential of the ethyl radical has a 6-fold barrier to internal rotation and the minimum energy path involves deviations of the CH2 wag angle of 6 to 11 degrees on either side of planar. Partially optimized 2-dimensional surfaces were calculated at the B3LYP, MP2, and CCSD(T) levels with 6-311++G(d,p) and 6-311++G(3df, 2p) basis sets and they were fit to a function containing a polynomial in the wag angle ? and trigonometric functions of the torsional angle ?. Comparison is made with the corresponding surfaces for CH3NH2 and CH3OH2^+. Unlike CH3CH2^, both have a substantial barrier to inversion. The dominant torsion-wag coupling term in all three cases has the form ?cos3?.

Bhatta, Ram S.; Perry, David S.

2009-03-01

382

Liver lobe torsion and liver abscess in a dog.  

PubMed

A 4-year-old Rhodesian Ridgeback had acute onset of vomiting, lethargy, and discolored urine. Physical examination revealed lethargy, pyrexia, weak femoral pulses, cardiac arrhythmia, distended abdomen, and signs of pain on abdominal palpation. Abdominal radiography and ultrasonography revealed a gas-containing lesion in the cranial portion of the abdomen. Preoperative care included administration of fluids, antibiotics, and antiarrhythmic medication. Exploratory laparotomy revealed hemobilia and a 360 degrees clockwise torsion of the papillary process of the caudate lobe of the liver. Clinical signs resolved completely after liver lobectomy, and the dog was alive 2 years after surgery. Torsion of a liver lobe is rare in dogs. Necrosis of the involved liver lobe can result in acute weakness, shock, and death. Hemodynamic stabilization, antibiotic treatment, and surgical intervention have been successful in treating this condition. Liver lobe torsion should be considered on the differential diagnoses list of acute abdominal pain. PMID:9524639

Downs, M O; Miller, M A; Cross, A R; Selcer, B A; Abdy, M J; Watson, E

1998-03-01

383

Splenic Torsion Requiring Splenectomy Six Years Following Laparoscopic Nissen Fundoplication  

PubMed Central

Background: Laparoscopic Nissen fundoplication has become a mainstay in the surgical treatment of gastroesophageal reflux disease, as it has proved to be a durable, well-tolerated procedure. Despite the safety and efficacy associated with this procedure, surgeons performing this advanced laparoscopic surgery should be well versed in the potential intraoperative and postoperative complications. Methods: A case is presented of a rare complication of splenic torsion following laparoscopic Nissen fundoplication. Diagnostic evaluations and intraoperative findings are discussed. Results: We present an otherwise healthy 41-year-old woman who underwent a laparoscopic Nissen fundoplication 6 years earlier at another medical center and presented with worsening chronic left upper quadrant abdominal pain. She was diagnosed with torsion of the splenic vascular pedicle, resulting in heterogenicity of perfusion with associated hematoma requiring open splenectomy. Conclusion: Surgeons should be aware of splenic torsion as a potential, albeit rare, complication related to laparoscopic Nissen fundoplication.

Le, Khoi; Griner, Devan; Tackett, Darryl

2012-01-01

384

A novel low-profile shape memory alloy torsional actuator  

NASA Astrophysics Data System (ADS)

This paper presents low-profile torsional actuators applicable for mesoscale and microscale robots. The primary actuator material is thermally activated Ni-Ti shape memory alloy (SMA), which exhibits remarkably high torque density. Despite the advantages of SMAs for actuator applications—high strain, silent operation, and mechanical simplicity—the response time and energy efficiency limit overall performance. As an alternative to SMA wires, thin SMA sheets are used to fabricate effective yet compact torsional actuators. Also, instead of using conventional Joule heating, an external Ni-Cr heating element is utilized to focus heat on the regions of highest required strain. Various design parameters and fabrication variants are described and experimentally explored in actuator prototypes. Controlled current profiles and discrete heating produces a 20% faster response time with 40% less power consumption as compared to Joule heating in a low-profile (sub-millimeter) torsional actuator capable of 180° motion.

Paik, Jamie K.; Hawkes, Elliot; Wood, Robert J.

2010-12-01

385

The Inversion-Torsion Potential Function for Hydrazine  

NASA Astrophysics Data System (ADS)

The torsion-inversion potential surface for hydrazine has been determined from the rovibrational data using a new rotation-torsion-inversion Hamiltonian. All elements of the inverse moment of inertia tensor have been expanded into mixed Fourier series of large amplitude coordinates. That gives two major advantages: (i) no numerical integration is necessary at any step of calculation, and (ii) the three-dimensional integrals have been replaced by the products of one-dimensional integrals. It has been proven that the inversion-torsion coupling in hydrazine is negligible and the inversion-inversion coupling is very strong. The barrier to inversion of 2072 cm-1is slightly higher than that in ammonia and the barrier to internal rotation of 934 cm-1is relatively high but lower than that determined previously from one-dimensional models.

Lodyga, Wieslaw; Kr?glewski, Marek; Makarewicz, Jan

1997-06-01

386

FREQUENCY FILTERING OF TORSIONAL ALFVEN WAVES BY CHROMOSPHERIC MAGNETIC FIELD  

SciTech Connect

In this Letter, we demonstrate how the observation of broadband frequency propagating torsional Alfven waves in chromospheric magnetic flux tubes can provide valuable insight into their magnetic field structure. By implementing a full nonlinear three-dimensional magnetohydrodynamic numerical simulation with a realistic vortex driver, we demonstrate how the plasma structure of chromospheric magnetic flux tubes can act as a spatially dependent frequency filter for torsional Alfven waves. Importantly, for solar magnetoseismology applications, this frequency filtering is found to be strongly dependent on magnetic field structure. With reference to an observational case study of propagating torsional Alfven waves using spectroscopic data from the Swedish Solar Telescope, we demonstrate how the observed two-dimensional spatial distribution of maximum power Fourier frequency shows a strong correlation with our forward model. This opens the possibility of beginning an era of chromospheric magnetoseismology, to complement the more traditional methods of mapping the magnetic field structure of the solar chromosphere.

Fedun, V.; Erdelyi, R. [School of Mathematics and Statistics, University of Sheffield, Hounsfield Road, Hicks Building, Sheffield S3 7RH (United Kingdom); Verth, G. [School of Computing, Engineering and Information Sciences, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom); Jess, D. B. [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University, Belfast University Road, Belfast BT7 1NN (United Kingdom)

2011-10-20

387

Increased external tibial torsion in Osgood-Schlatter disease.  

PubMed

We studied the relationship between Osgood-Schlatter disease and torsional abnormalities of the lower limb in 21 boys with this condition and 20 age- and sex-matched controls. 3 groups of knees (20 control knees, 21 symptomatic and 21 asymptomatic or less symptomatic knees) were subjected to clinical, radiographic and CT evaluation. We found no statistically significant differences between patients and controls, as regards femoral anteversion, patellar congruence angle, patellar tilt angle and anterior tibial tuberosity-trochlear groove distance, but the condylomalleolar angle and tibial torsion angle were greater in patients. We found no differences between symptomatic and asymptomatic or less symptomatic knees in any of the parameters. All the symptomatic knees were on the side preferentially involved in jumping and sprinting. This increase in external tibial torsion may play a role as a predisposing mechanical factor in the onset of Osgood-Schlatter disease in male athletes. PMID:14521294

Gigante, Antonio; Bevilacqua, Claudia; Bonetti, Massimo G; Greco, Francesco

2003-08-01

388

The Inversion-Torsion Potential Function for Hydrazine  

PubMed

The torsion-inversion potential surface for hydrazine has been determined from the rovibrational data using a new rotation-torsion-inversion Hamiltonian. All elements of the inverse moment of inertia tensor have been expanded into mixed Fourier series of large amplitude coordinates. That gives two major advantages: (i) no numerical integration is necessary at any step of calculation, and (ii) the three-dimensional integrals have been replaced by the products of one-dimensional integrals. It has been proven that the inversion-torsion coupling in hydrazine is negligible and the inversion-inversion coupling is very strong. The barrier to inversion of 2072 cm-1 is slightly higher than that in ammonia and the barrier to internal rotation of 934 cm-1 is relatively high but lower than that determined previously from one-dimensional models. PMID:9252307

Lodyga; Kreglewski; Makarewicz

1997-06-01

389

``Quasi-complete'' mechanical model for a double torsion pendulum  

NASA Astrophysics Data System (ADS)

We present a dynamical model for the double torsion pendulum nicknamed “PETER,” where one torsion pendulum hangs in cascade, but off axis, from the other. The dynamics of interest in these devices lies around the torsional resonance, that is at very low frequencies (mHz). However, we find that, in order to properly describe the forced motion of the pendulums, also other modes must be considered, namely swinging and bouncing oscillations of the two suspended masses, that resonate at higher frequencies (Hz). Although the system has obviously 6+6 degrees of freedom, we find that 8 are sufficient for an accurate description of the observed motion. This model produces reliable estimates of the response to generic external disturbances and actuating forces or torques. In particular, we compute the effect of seismic floor motion (“tilt” noise) on the low frequency part of the signal spectra and show that it properly accounts for most of the measured low frequency noise.

De Marchi, Fabrizio; Pucacco, Giuseppe; Bassan, Massimo; De Rosa, Rosario; Di Fiore, Luciano; Garufi, Fabio; Grado, Aniello; Marconi, Lorenzo; Stanga, Ruggero; Stolzi, Francesco; Visco, Massimo

2013-06-01

390

Response of Oversized Epoxy Strand Models to Axial, Torsional and Bending Loads.  

National Technical Information Service (NTIS)

Axial, torsional and bending loadings have been applied to the models. Strains, stresses and displacements have been determined using mechanical and electrical strain gages, dial gages and brittle coatings. In the case of axial and torsional loadings, the...

A. J. Durelli S. Machida

1972-01-01

391

Constraint of a general effective potential in vector torsion coupled conformally induced gravity  

NASA Astrophysics Data System (ADS)

It is found that the deviation of an effective potential from the quartic form is related to the metric and vector torsion dependences of the effective potential in the vector torsion coupled conformally induced gravity.

Kim, Jewan; Park, C. J.; Yoon, Yongsung

1995-04-01

392

Torsional analysis of 1 MW gearbox and shaft system in the Avedoere wind turbine.  

National Technical Information Service (NTIS)

In order to predict undesired high gear noise emission from the Avedoere wind turbine due to critical torsional resonances in the shaft system, the torsional natural frequencies and corresponding mode shapes have been calculated. The analysis has involved...

A. Crone

1993-01-01

393

Torsional Buckling of I Beam and Flat Bar Stiffeners under Combined Lateral and Axial Loading.  

National Technical Information Service (NTIS)

The prediction of torsional buckling of stiffeners is a necessary design skill in the planning of any framed structure or vehicle. The likelihood of torsional failure is increased when the stiffener is simultaneously loaded from perpendicular directions, ...

G. E. Klein

1985-01-01

394

Fiber ring laser incorporating a pair of rotary long-period fiber gratings for torsion measurement  

NASA Astrophysics Data System (ADS)

We demonstrate a fiber ring laser for high-resolution torsion measurement, where the laser cavity consists of a Mach-Zehnder interferometer (MZI) formed with a pair of long-period fiber gratings written in a twisted single-mode fiber (SMF) by a CO2 laser. The emitting wavelength of the laser provides a measure of the rate of the torsion applied to the grating pair, while the direction of the wavelength shift indicates the sense direction of the applied torsion. The narrow linewidth and the large side-mode suppression ratio of the laser can provide a much more precise measurement of torsion, compared with passive fiber-optic torsion sensors. The torsion sensitivity achieved is 0.084 nm/(rad/m) in the torsion range +/-100 rad/m, which corresponds to a torsion resolution of 0.12 rad/m, assuming a wavelength resolution of 10 pm for a typical optical spectrum analyzer.

Shi, Leilei; Zhu, Tao; Chen, Fangyuan; Chiang, Kinseng; Rao, Yunjiang

2012-01-01

395

Phonons with orbital angular momentum  

NASA Astrophysics Data System (ADS)

Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.

Ayub, M. K.; Ali, S.; Mendonca, J. T.

2011-10-01

396

Phonons with orbital angular momentum  

SciTech Connect

Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.

Ayub, M. K. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2011-10-15

397

Two-way behavior of a Nitinol torsion bar  

NASA Astrophysics Data System (ADS)

In this paper, the experimental study of a NiTi shape memory alloy bar with nominal diameter of 6.5 mm is presented. First, some torsion experiments, including torsion cycling at constant temperature and thermal cycling under constant torque, were carried out. In these test, the torque was applied in both positive and negative directions. Two-way memory behavior and some unique phenomena, such as kink and easy-training, were found and hence, a series of uniaxial tension test was performed in order to understand the observations. After presenting the experimental work, the reason behind these phenomena is discussed.

Huang, Wei Min

1999-07-01

398

Analytic torsion of all vector bundles over an elliptic curve  

NASA Astrophysics Data System (ADS)

The spectrum of the Hodge-Laplace operator of all holomorphic vector bundles (with parallel curvature metrics) over a flat elliptic curve is shown to be the union of the spectra of some infinite set of (explicit) finite rank matrices. The analytic torsion is then deduced by direct computation. Another evaluation of the analytic torsion is then performed using Bismut, Gillet, and Soulé's comparison formula for short exact sequences of vector bundles. This is a test for this method which could be useful when direct calculation is hopeless.

Berthomieu, A.

2001-09-01

399

The torsional fatigue properties of titanium-alloy spring wire  

Microsoft Academic Search

The absence of any torsional fatigue-test data on currently used titanium-alloy spring wire along with inconsistent fatigue-test data derived from earlier test programs prompted this investigation. The torsional fatigue testing was performed on straight lengths of 13V–11Cr–3Al titanium-alloy spring wire in diameters of 0.148 in. (0.376 cm), 0.225 in. (0.572 cm) and 0.374 in. (0.950 cm) considered as representative. A

E. L. Hayman; D. W. Greenwood; B. G. Martin

1977-01-01

400

[Splenic torsion as cause of acute abdomen in children].  

PubMed

A six-year-old boy was admitted with symptoms consistent with acute appendicitis. Immediately before placement of the first trocar, a large abdominal mass was observed which on imaging was identified as a torsioned spleen. Due to suboptimal reperfusion and risk of reperfusion-mediated morbidity a splenectomy was performed. The recovery was uneventful. The child had a twin brother who on a routine ultrasound examination was found to have a normally positioned spleen. Challenges in diagnosis and treatment of children with splenic torsion is discussed. PMID:23608013

Helvind, Neel Maria; Gögenur, Ismail; Stadeager, Morten

2013-02-25

401

O the Effective Control of Torsional Vibrations in Drilling Systems  

NASA Astrophysics Data System (ADS)

This paper analyses a control mechanism designed to significantly ameliorate the sustained excitation of torsional relaxation oscillations (slip-stick) due to frictional torques generated by an active bit during drilling operations with an extended drill-string. The proposed mechanism of torsional rectification is compared with existing soft-torque devices in a series of mathematical models. Both analytic and numerical simulations indicate that many of the volatilities suffered by existing soft-torque feedback approaches used to combat slip-stick can be eliminated by the alternative proposed here.

Tucker, R. W.; Wang, C.

1999-07-01

402

Small torsional piezoelectric fiber actuators with helical electrodes  

NASA Astrophysics Data System (ADS)

Small piezoelectric fibers wound with helical electrodes on their outer surface will produce torsional displacement. A piece of piezoelectric tube with an outer diameter of 1 mm, a wall thickness of 0.1 mm, and an effective axial length of 40 mm was used as a prototype actuator's body, while two pieces of copper wires of 40 ?m diameter were used as the electrodes. After poled with 2 kV/mm electric field strength, the prototype actuator produces 1.7° torsional angle when it was driven from -500 to 500 V. A resonant frequency as high as 10 kHz was observed on this actuator.

Pan, C. L.; Feng, Z. H.; Ma, Y. T.; Liu, Y. B.

2008-01-01

403

Fermion condensate from torsion in the reheating era after inflation  

NASA Astrophysics Data System (ADS)

The inclusion of Dirac fermions in Einstein-Cartan gravity leads to a four-fermion interaction mediated by nonpropagating torsion, which can allow for the formation of a Bardeen-Cooper-Schrieffer condensate. By considering a simplified model in 2+1 spacetime dimensions, we show that even without an excess of fermions over antifermions, the nonthermal distribution arising from preheating after inflation can give rise to a fermion condensate generated by torsion. We derive the effective Lagrangian for the spacetime-dependent pair field describing the condensate in the extreme cases of nonrelativistic and massless fermions, and show that it satisfies the Gross-Pitaevski equation for a gapless, propagating mode.

Weller, Joel M.

2013-10-01

404

The angular momentum of the Oort cloud  

Microsoft Academic Search

An evaluation is made of the work of Marochnik et al. (1988), which estimated that the angular momentum of the Oort cloud is 2-3 orders of magnitude greater than the planetary system's total angular momentum. It is noted that most of the angular momentum in the currently observed Oort cloud is the result of the effects of external perturbers over

P Weissman

1991-01-01

405

Angular Momentum Decomposition for an Electron  

SciTech Connect

We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.

Burkardt, Matthias; BC, Hikmat

2009-01-01

406

Torsional Splittings in the Band nu9 + nu4 - nu4 of Ethane.  

PubMed

Torsional splittings of the C2H6 hot band nu9 + nu4 - nu4 have been determined based on measurements taken with the Kitt Peak National Observatory Fourier transform spectrometer with .0025 cm-1 resolution. The measured splittings range from -.2347 cm-1 (the sign is relative to that of the observed splitting in the nu9 band of C2H6) to .0682 cm-1, with a standard deviation of the observed splittings of .0251 cm-1. The splittings can be explained as a result of xy Coriolis interaction of nu9 + nu4 with the excited torsional states taunu4, with the major effect arising from the "forbidden" interaction with the nearly degenerate state 5nu4final sigma = 2. The rms error of the predicted splittings is .00422 cm-1, if parameters determined from theory and previous work are used, and is .00217 cm-1, if small refinements to the parameters are made based on the measured splittings themselves. Copyright 1998 Academic Press. PMID:9770395

Susskind; Iredell; Blass; Reuter; Halsey; Jennings

1998-11-01

407

Alkyl peroxides: Effect of substituent groups on the torsional mode around the O?O bond  

NASA Astrophysics Data System (ADS)

We present here a systematic study by quantum mechanical methods of structural and energetic properties for a series of substitutions by alkyl groups of the hydrogens in hydrogen peroxide. The emphasis is on the torsion around the peroxidic bond, which leads to the chirality changing stereomutation. The dihedral angle dependence of the geometrical features and of the dipole moment is discussed with reference to previous experimental and theoretical information, and with respect to the preceding paper on hydrogen peroxide (Maciel et al., Chem Phys Lett, 2006, 432, 383). This information is of interest for chiral separation experiments as well as in view of a possible dynamical mechanism for chirality exchange by molecular collisions. The cis and trans barriers appear to vary remarkably upon substitution by alkyl groups (methyl, ethyl, n- and iso-propyl, sec- and tert-butyl hydroperoxides), the most important property being their geometrical dimensions. As the latter increase, tendency for the equilibrium configuration towards the trans structure increases, so that the trans barrier becomes negligible for dimethyl and diethyl peroxides and for n- and iso-butyl hydroperoxides, giving essentially achiral molecules. For the chiral ones (HOOH, CH3OOH, and C2H5OOH) torsional level energies and eigenfunctions are calculated and their distribution as a function of temperature determined. Their use is exemplified by a calculation of the dipole moment of hydrogen peroxide at room temperature, reconciling previous disagreement between theory and experiment.0

Maciel, Glauciete S.; Bitencourt, Ana Carla P.; Ragni, Mirco; Aquilanti, Vincenzo

408

Anomalous Response of 4He Confined in Nanoporous Media to Torsional Oscillation  

NASA Astrophysics Data System (ADS)

The existence of "Non-Classical Rotational Inertia (NCRI)" in solid 4He below 0.2 K has been controversial and interpreted by a number of different theories. We report on torsional oscillator measurements for 4He in a nanoporous Gelsil glass, which has a network of nanopores with 3.5 nm in diameter. In addition to the usual "low- T NCRI" with an onset temperature 0.15 K, we find a larger decrease in rotational moment of inertia in a broad range of temperature from 0.2 to 1.9 K. This "high- T inertial anomaly" is accompanied with multiple dissipation peaks, but has no dependence on torsional oscillation velocity unlike the low- T NCRI. Since the high- T anomaly is observed also in confined liquid states, it originates in amorphous solid 4He layer near the pore wall. Our result shows that different types of supersolid—like phenomena, i.e. inertial anomalies, can coexist in a single 4He sample, even with genuine superfluidity of liquid 4He.

Yoshimura, Hitomi; Higashino, Rama; Shibayama, Yoshiyuki; Shirahama, Keiya

2012-11-01

409

Influence of Humeral Torsion on Interpretation of Posterior Shoulder Tightness Measures in Overhead Athletes  

Microsoft Academic Search

Results: The dominant limb of the baseball players demonstrated greater humeral torsion, and less internal rotation and total rotation range of motion, compared with control participants and the non- dominant limb in both groups. Once corrected for torsion, no group or limb differences in internal rotation were present. Statistically significant relationships existed between the amount of humeral torsion and measures

Joseph B. Myers; Sakiko Oyama; Benjamin M. Goerger; Terri Jo Rucinski; J. Troy Blackburn; R. Alexander Creighton

2009-01-01

410

Behaviour and strengthening of RC T-girders in torsion and shear  

Microsoft Academic Search

Failure of a structural element under shear and torsion is brittle in nature and should be avoided as it compromises the ductile behaviour of the structure. Under various cases of loading and geometric configuration, concrete structural members are subjected to significant torsion accompanied by either bending, or shear and bending. A limited number of studies were conducted to study torsion

Ahmed Farouk Mohamed Hassan Deifalla

2007-01-01

411

On using the torsional balance rheometer to measure normal stresses in lubricating greases  

Microsoft Academic Search

Summary A new instrument, a Torsional Balance rheometer, has been used to measure shear and normal stress functions of lubricating greases. The new rheometer is based on torsional flow between parallel plates, but differs from conventional torsional flow instruments in that the plate separation is not held constant but allowed to adjust until the normal force is balanced by the

D. M. Binding; J. F. Hutton; K. Walters

1976-01-01

412

Controlling the secondary-structure-forming tendencies of proteins by a backbone torsion-energy term  

Microsoft Academic Search

We examined a new backbone torsion-energy term proposed by us in the force field for protein systems. This torsion-energy term is represented by a double Fourier series in two variables, namely the backbone dihedral angles ? and ?. It gives a natural representation of the torsion energy in the Ramachandran space in the sense that any two-dimensional energy surface periodic

Yoshitake Sakae; Yuko Okamoto

2010-01-01

413

Angular Synchronization by Eigenvectors and Semidefinite Programming.  

PubMed

The angular synchronization problem is to obtain an accurate estimation (up to a constant additive phase) for a set of unknown angles ?(1), …, ?(n) from m noisy measurements of their offsets ?(i) - ?(j) mod 2?. Of particular interest is angle recovery in the presence of many outlier measurements that are uniformly distributed in [0, 2?) and carry no information on the true offsets. We introduce an efficient recovery algorithm for the unknown angles from the top eigenvector of a specially designed Hermitian matrix. The eigenvector method is extremely stable and succeeds even when the number of outliers is exceedingly large. For example, we successfully estimate n = 400 angles from a full set of m=(4002) offset measurements of which 90% are outliers in less than a second on a commercial laptop. The performance of the method is analyzed using random matrix theory and information theory. We discuss the relation of the synchronization problem to the combinatorial optimization problem Max-2-Lin mod L and present a semidefinite relaxation for angle recovery, drawing similarities with the Goemans-Williamson algorithm for finding the maximum cut in a weighted graph. We present extensions of the eigenvector method to other synchronization problems that involve different group structures and their applications, such as the time synchronization problem in distributed networks and the surface reconstruction problems in computer vision and optics. PMID:21179593

Singer, A

2011-01-30

414

Angular Synchronization by Eigenvectors and Semidefinite Programming  

PubMed Central

The angular synchronization problem is to obtain an accurate estimation (up to a constant additive phase) for a set of unknown angles ?1, …, ?n from m noisy measurements of their offsets ?i ? ?j mod 2?. Of particular interest is angle recovery in the presence of many outlier measurements that are uniformly distributed in [0, 2?) and carry no information on the true offsets. We introduce an efficient recovery algorithm for the unknown angles from the top eigenvector of a specially designed Hermitian matrix. The eigenvector method is extremely stable and succeeds even when the number of outliers is exceedingly large. For example, we successfully estimate n = 400 angles from a full set of m=(4002) offset measurements of which 90% are outliers in less than a second on a commercial laptop. The performance of the method is analyzed using random matrix theory and information theory. We discuss the relation of the synchronization problem to the combinatorial optimization problem Max-2-Lin mod L and present a semidefinite relaxation for angle recovery, drawing similarities with the Goemans-Williamson algorithm for finding the maximum cut in a weighted graph. We present extensions of the eigenvector method to other synchronization problems that involve different group structures and their applications, such as the time synchronization problem in distributed networks and the surface reconstruction problems in computer vision and optics.

Singer, A.

2010-01-01

415

Spin chains and string theory  

Microsoft Academic Search

Recently, an impressive agreement was found between anomalous dimen- sions of certain operators in N = 4 SYM and rotating strings with two angular mo- menta in the bulk of AdS5 × S5. A one-loop field theory computation, which involves solving a Heisenberg chain by means of the Bethe ansatz agrees with the large angular momentum limit of a rotating

Martin Kruczenski

416

Two-dimensional angular filter array for angular domain imaging with 3D printed angular filters  

NASA Astrophysics Data System (ADS)

Angular Domain Imaging (ADI) is a technique that is capable of generating two dimensional shadowgrams of attenuating targets embedded in a scattering medium. In ADI, an angular filter array (AFA) is positioned between the sample and the detector to distinguish between quasi-ballistic photons and scattered photons. An AFA is a series of micro-channels with a high aspect ratio. Previous AFAs from our group were constructed by micro-machining the micro-channels into a silicon wafer, limiting the imaging area to a one dimensional line. Two dimensional images were acquired via scanning. The objective of this work was to extend the AFA design to two dimensions to allow for two dimensional imaging with minimal scanning. The second objective of this work was to perform an initial characterization of the imaging capabilities of the 2D AFA. Our approach was to use rapid 3D prototyping techniques to generate an array of micro-channels. The imaging capabilities were then evaluated by imaging a 0.9 mm graphite rod submerged in a scattering media. Contrast was observed to improve when a second angular filter array was placed in front of the sample to mask the incoming light.

Ng, Eldon; Carson, Jeffrey J. L.

2013-02-01

417

Texture Development During Equal Channel Angular Forging of BCC Metals  

SciTech Connect

Equal channel angular forging (ECAF) has been proposed as a severe plastic deformation technique for processing metals, alloys, and composites [e.g. Segal, 1995] (Fig. 1). The technique offers two capabilities of practical interest: a high degree of strain can be introduced with no change in the cross-sectional dimensions of the work-piece, hence, even greater strains can be introduced by re-inserting the work-piece for further deformation during subsequent passes through the ECAF die. Additionally, the deformation is accomplished by simple shear (like torsion of a short tube) on a plane whose orientation, with respect to prior deformations, can be controlled by varying the processing route. There is a nomenclature that has developed in the literature for the typical processing routes: A: no rotations; B{sub A}: 90 degrees CW (clockwise), 90 degrees CCW (counterclockwise), 9O degrees CW, 90 degrees CCW...; Bc: 90 degrees CW, 90 degrees CW, 90 degrees CW...; and C: 180 degrees, 18 0 degrees.... The impact of processing route on the subsequent microstructure [Ferasse, Segal, Hartwig and Goforth, 1997; Iwahashi, Horita, Nemoto and Langdon, 1996] and texture [Gibbs, Hartwig, Cornwell, Goforth and Payzant, 1998] has been the subject of numerous experimental studies.

Agnew, S.R.

1999-08-08

418

On the Ricci tensor in the common sector of type II string theory  

NASA Astrophysics Data System (ADS)

Let ? be a metric connection with totally skew-symmetric torsion T on a Riemannian manifold. Given a spinor field ? and a dilaton function ?, the basic equations in the common sector of type II string theory are \\fl \

Agricola, I.; Friedrich, T.; Nagy, P.-A.; Puhle, C.

2005-07-01

419

Connection dynamics of a gauge theory of gravity coupled with matter  

NASA Astrophysics Data System (ADS)

We study the coupling of the gravitational action, which is a linear combination of the Hilbert–Palatini term and the quadratic torsion term, to the action of Dirac fermions. The system possesses local Poincare invariance and hence belongs to Poincare gauge theory (PGT) with matter. The complete Hamiltonian analysis of the theory is carried out without gauge fixing but under certain ansatz on the coupling parameters, which leads to a consistent connection dynamics with second-class constraints and torsion. After performing a partial gauge fixing, all second-class constraints can be solved, and a SU(2)-connection dynamical formalism of the theory can be obtained. Hence, the techniques of loop quantum gravity (LQG) can be employed to quantize this PGT with non-zero torsion. Moreover, the Barbero–Immirzi parameter in LQG acquires its physical meaning as the coupling parameter between the Hilbert–Palatini term and the quadratic torsion term in this gauge theory of gravity.

Yang, Jian; Banerjee, Kinjal; Ma, Yongge

2013-10-01

420

A case of splenic torsion with progressive anemia and thrombocytopenia  

PubMed Central

A 4-year-old male, castrated Saint Bernard was evaluated for acute onset of lethargy and collapse. Moderately severe anemia and splenomegaly were noted. Immune mediated hemolytic anemia was initially suspected. Abdominal ultrasound demonstrated an absence of splenic blood flow. Splenic torsion was confirmed on exploratory laparotomy and a splenectomy was performed.

Schnier, Lisa M.

2010-01-01

421

DYT1 mutation in French families with idiopathic torsion dystonia  

Microsoft Academic Search

Summary A GAG deletion at position 946 in DYT1, one of the genes responsible for autosomal dominant idiopathic torsion dystonia (ITD), has recently been identified. We tested 24 families and six isolated cases with ITD and found 14 individuals from six French families who carried this mutation, indicating that 20% of the affected families carried the DYT1 mutation. Age at

A.-S. Lebre; A. Durr; P. Jedynak; G. Ponsot; M. Vidailhet; Y. Agid; A. Brice

1999-01-01

422

34. VERTICAL AND TORSIONAL MOTION VIEWED FROM EAST TOWER, 7 ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

34. VERTICAL AND TORSIONAL MOTION VIEWED FROM EAST TOWER, 7 NOVEMBER 1940, FROM 16MN FILM SHOT BY PROFESSOR F.B. FARQUHARSON, UNIVERSITY OF WASHINGTON. (LABORATORY STUDIES ON THE TACOMA NARROWS BRIDGE, AT UNIVERSITY OF WASHINGTON (SEATTLE: UNIVERSITY OF WASHINGTON, DEPARTMENT OF CIVIL ENGINEERING, 1941) - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA

423

Torsional Oscillations and Waves Projected on the Wall  

ERIC Educational Resources Information Center

|The article "Torsional Oscillations with Lorentz Force" by Paul Gluck provides a glimpse into the major world of ancient physics demonstrations in the late 19th and first half of the 20th centuries. The apparatus that was described and similar pieces of apparatus are the basis for many memorable but long forgotten educational demonstrations. The…

Bartlett, Albert A.

2008-01-01

424

Relationship Between the Photoelectron Spectra and Torsional Barriers of Aminophosphines.  

National Technical Information Service (NTIS)

The trends in the nitrogen and phosphorus lone-pair ionization potentials of Me2NP(CF3)2, Me2NP(Cl)CF3, and Me2NPCl2 suggest that the P-N torsional barriers in aminophosphines arise predominantly from steric and lone pair-lone pair repulsion effects. (Aut...

A. H. Cowley M. J. S. Dewar J. W. Gilje D. W. Goodman J. R. Schweiger

1973-01-01

425

Quaternionic Torsion Geometry, Superconformal Symmetry and T-duality  

NASA Astrophysics Data System (ADS)

HyperKähler metrics with torsion (HKT metrics) are constructed via superconformal symmetry. It is shown how T-duality interpreted as a twist construction for circle actions provides a number of compact simply-connected examples. Further applications of the twist construction are discussed to obtain compact simply-connected HKT manifolds with few symmetries and to construct all HKT nilmanifolds.

Swann, Andrew

2009-02-01

426

Curvature and torsion estimators based on parametric curve fitting  

Microsoft Academic Search

Many applications of geometry processing and computer vision rely on geometric properties of curves, particularly their curvature. Several methods have already been proposed to estimate the curvature of a planar curve, most of them for curves in digital spaces. This work proposes a new scheme for estimating curvature and torsion of planar and spatial curves, based on weighted least-squares fitting

Thomas Lewiner; João D. Gomes Jr.; Hélio Lopes; Marcos Craizer

2005-01-01

427

Conservative management of accessory spleen torsion in children.  

PubMed

Accessory spleen torsion is very rare condition especially in children. The aim of this study is to report the conservative treatment option. In April 2009 we observed a 10-year-old child affected by hereditary spherocytosis who reported acute abdominal pain without fever or vomiting. At hospitalization all blood tests were within normal value. Abdominal ultrasounds showed an increase in spleen volume and a solid round-shaped hypoechogenic formation with hyperechogenic areas in the lower pole without vascolarisation on color-Doppler scan. These findings suggested torsion of the accessory spleen. We opted for a conservative approach: analgesics on demand and antibiotics. After a week symptoms resolved spontaneously and patient was discharged in good health conditions. Follow-up ultrasound scans were performed at one week, three-six months and one year after hospitalization and showed a progressive reduction of the dimensions of the solid round-shaped formation. Accessory spleen torsion needs to be added to the differential diagnosis of cases of acute abdomen in children. Ultrasounds with eco-color-Doppler scans seem to be the best option for the diagnosis of such condition in the pediatric age since other diagnostic methods are more invasive and require sedation of patients. Once accessory spleen torsion is correctly diagnosed it is possible to opt for its conservative treatment. PMID:24051978

Scirè, G; Zampieri, N; El-Dalati, G; Camoglio, F S

2013-08-01

428

Torsion of an epiploic appendix pretending as acute appendicitis.  

PubMed

Torsion of an epiploic appendix is a rare surgical entity. Its unusual symptomatology, wide variation in physical findings and the absence of helpful laboratory and radiological studies makes it very difficult to diagnose pre-operatively. This is a report of this rare entity found in a patient upon diagnostic laparoscopy performed for suspected acute appendicitis. PMID:22043343

Malik, Kamran Ahmad

2010-07-01

429

An Uncommon Twist: Isolated Fallopian Tube Torsion in an Adolescent  

PubMed Central

We report a 13-year-old girl with bilateral paratubal cysts and left isolated fallopian tube torsion (IFTT). Paratubal cysts are uncommon in children, and IFTT is a rare complication. Awareness of this entity and prompt surgical intervention could potentially salvage the fallopian tube preserving fertility.

Kisku, Sundeep; Thomas, Reju Joseph

2013-01-01

430

Coupled horizontal and torsional vibrations of a flexible barge  

Microsoft Academic Search

Differential equations of coupled flexural and torsional vibrations of a prismatic beam are derived. The equations are solved analytically by the direct integration and the Ritz method. In the former case, the frequency equation is reduced to a polynomial of the third order. In the latter case, beam response is assumed in the form of series of natural modes of

I. Senjanovi?; I. ?atipovi?; S. Tomaševi?

2008-01-01

431

Torsional springs for two-dimensional dynamic unstructured fluid meshes  

Microsoft Academic Search

Dynamic fluid grids are commonly used for the solution of flow problems with moving boundaries. They are often represented by a network of fictitious lineal springs that can become unreliable when the fluid mesh undergoes large displacements and\\/or deformations. In this paper, we propose to control the arbitrary motion of two-dimensional dynamic unstructured fluid grids with additional torsional springs. We

C. Farhat; C. Degand; B. Koobus; M. Lesmoinne

1998-01-01

432

Determining the Gravitational Constant Using a Cryogenic Torsion Pendulum  

Microsoft Academic Search

We report progress in measurements of G using a cryogenic torsion pendulum in the 'dynamic' (time-of-swing) mode. We have collected about 550 hours of data which should yield a G measurement with statistical uncertainty less than 20 ppm.

M. K. Bantel; R. D. Newman

2002-01-01

433

Torsion pendulum testing of the LISA Pathfinder Gravitational Reference Sensor  

Microsoft Academic Search

We present results of testing of the LISA pathfinder gravitational reference sensor (GRS) using the torsion pendulum facitlity at the University of Trento. We investigate the surface force disturbances arising from of the GRS and the sensor stiffness, or coupling between the sensor and test mass motion. We also investigate specific sources of noise, including DC bias variations in the

Peter Wass; Stefano Vitale; Bill Weber; Rita Dolesi; Giacomo Ciani; David Tombolato; Antonella Cavalleri; Daniele Nicolodi; Mauro Hueller

2008-01-01

434

Torsion wave diffraction by an absolutely rigid body  

Microsoft Academic Search

An approximate method is proposed in this paper for the solution of axisymmetric stationary torsion wave scattering problems by absolutely rigid mobile and fixed inclusions of different shape imbedded in an elastic space. The method is based on applying solutions with a singularity of the type of a center of rotation which are distributed over a segment of the axis

V. A. Starikov

1984-01-01

435

New Approaches to Data Acquisitions in a Torsion Pendulum Experiment  

ERIC Educational Resources Information Center

In this paper, two simple non-contact and cost-effective methods to acquire data in the student laboratory are applied to investigate the motion of a torsion pendulum. The first method is based on a Hall sensor, while the second makes use of an optical mouse.

Jiang, Daya; Xiao, Jinghua; Li, Haihong; Dai, Qionglin

2007-01-01

436

Non-contact torsion sensor using fibre Bragg gratings  

Microsoft Academic Search

Non-contact measurement of torsion on a rotating shaft was done with fibre Bragg gratings and involved the use of graded index lenses for transmitting optical information between the light source and the gratings, and back to a spectrum analyser. Special Böhler steel with high yield strength was used for the shaft. For the experimental measurements, one end of the shaft

Ludi Kruger; Pieter L Swart; Anatoli A Chtcherbakov; A J van Wyk

2004-01-01

437

Geometry of Hyper-Kaehler connection with torsion.  

National Technical Information Service (NTIS)

The internal space of a N=4 supersymmetric model with Wess-Zumino term has a connection with totally skew-symmetric torsion and holonomy in Sp(n). We study the mathematical background of this type of connection. In particular, we relate it to classical He...

G. Grantcharov Y. S. Poon

1999-01-01

438

Nonlinear dynamic strand model with coupled tension and torsion  

Microsoft Academic Search

We simulate the nonlinear dynamic responses in Kirchhoff rod by including the important effects due to inertia and kinematic coupling of tension and torsion. We begin by reviewing a dynamic rod model of a strand (length of cable or DNA) in the form of a 12th order partial differential equation system. Numerical solutions reveal the effects of dynamics on clamped

Sachin Goyal; Noel C. Perkins

2007-01-01

439

Predicting Creep Behavior of Wood Adhesives by Torsional Braid Analysis  

Microsoft Academic Search

Rheological changes in four cured wood adhesives exposed to temperature and humidity conditions were determined using torsional braid analysis. The adhesives ranged from thermosetting to thermoplastic types. Creep extension in shear also was measured for wood laminates bonded with these adhesives and exposed to conditions of 27°C\\/90% RH and 60°C\\/60% RH. A positive trend was found between creep extension and

Paul R. Steiner

1984-01-01

440

Simulation of the behaviour of FCC polycrystals during reversed torsion  

Microsoft Academic Search

Taylor-type polycrystal plasticity models with various single slip hardening laws are evaluated by studying the large strain behaviour of FCC polycrystals during reversed torsion. The hardening laws considered include the model of Asaro and Needleman (“Texture Development and Strain Hardening in Rate Dependent Polycrystals,” Acta Metall. (1985), 34, 1553) as well as a power-law and an exponential version of that,

P. D. Wu; K. W. Neale; E. Van der Giessen

1996-01-01

441

Numerical verification of solutions for elasto-plastic torsion problems  

Microsoft Academic Search

In this paper, we consider a numerical technique which enables us to verify the existence of solutions for the elasto-plastic torsion problems governed by the variational inequality. Based upon the finite element approximations and the explicit a priori error estimates for a simple problem, we present an effective verification procedure that through numerical computation generates a set which includes the

S. H. Lee; Cheon Seoung Ryoo

2000-01-01

442

Variational Inequalities and the Elastic-Plastic Torsion Problem  

Microsoft Academic Search

We show that, under suitable conditions, the variational inequality that expresses the elastic-plastic torsion problem is equivalent to a variational inequality on a convex set which depends on d(x)=d(x, ?O). Such an equivalence allows us to find the related Lagrange multipliers and to exhibit a computational procedure based on the subgradient method.

G. Idone; A. Maugeri; C. Vitanza

2003-01-01

443

Transverse and torsional modes of vibration of American organ reeds  

Microsoft Academic Search

A reed from an American reed organ consists of a brass tongue riveted to a frame with an opening just large enough for the reed to pass through during the course of its oscillation. To a first approximation, the reed tongue can be modeled as a cantilever beam of uniform cross section, and the mode frequencies of transverse and torsional

Blake M. Dirksen; James P. Cottingham

2002-01-01

444

Design and simulation of microspectrometer based on torsional MEMS grating  

NASA Astrophysics Data System (ADS)

Micro-opto-electro-mechanical systems (MOEMS) has prominent advantages over conventional optical devices, such as smaller, lighter, more stable, lower cost and power consumption. It has been widely applied in the last few years. This paper presents a micro spectrometer based on torsional MEMS grating with micromachining process. As a diffractive component in the micro spectrometer, the torsional MEMS grating is actuated by electrostatic force to scan the spectrum. In contrast to common linear detector arrays with stationary diffraction grating and non-fixed grating rotated by stepper motor to scan spectrum used in most micro spectrometer, MEMS-based spectrometer is dynamically controllable, and has no mechanical moving parts with small size. ZEMAX is used for design, optimization, and simulation analysis of the micro spectrometer with multi-configurations in the cross Czerny-Turner optical system. The results indicate that torsional MEMS grating operates at a torsion angle of +/-3 degree, the spectrometer can scan spectral range of 800-1600nm in NIR (near infrared), spectral resolution is around 10 nm, and the whole spectrometer has a volume of 80mm×55mm×30mm. The study provides an initial theoretical foundation for the further development and design.

Yan, Bin; Yuan, Weizheng; Sun, Ruikang; Qiao, Dayong; Yu, Yiting; Li, Taiping

2010-05-01

445

Compressive and torsional behaviour of Kevlar 49 fibre  

Microsoft Academic Search

The mechanical anisotropy of an aromatic polyamide fibre, Kevlar 49, was studied in tension, compression and torsion. A new technique involved applying small and defined compressive strains to filaments by bonding them to one side of a beam which is subsequently bent to compress the fibres. Using scanning electron and optical microscopy, fibres were shown to form regularly-spaced helical kink

S. J. Deteresa; S. R. Allen; R. J. Farris; R. S. Porter

1984-01-01

446

3D numerical simulations of a torsional Alfven waves  

NASA Astrophysics Data System (ADS)

Recent high-resolution ground-based observations provide clear evidence for the existence of os-cillations driven by magnetic twist in flux tubes. These torsional oscillations are associated with Alfven waves. It is of particular interest to study the excitation and propagation of torsional Alfven waves into the upper, magnetised atmosphere because they can channel photospheric energy into the corona. Here we examine numerically the direct propagation of such torsional waves, driven at the foot-point of a solar magnetic flux tube, into a three-dimensional magnetised atmosphere rep-resenting the soar atmosphere between the photosphere and low corona. The simulations are based on fully compressible ideal magneto-hydrodynamical modelling. The model solar atmo-sphere is constructed based on realistic temperature and density stratification derived from VAL IIIF, and is most suitable perhaps for a bright network element or magnetic pore. We discuss how torsional phosphoric motion can excite Alfven and other types of MHD waves that reach the upper parts of the solar atmosphere. We also discuss the energetic implications as far as heating is concerned. Finally, we briefly discuss the observational signatures of these waves.

Fedun, Viktor; von Fay-Siebenburgen (Erdélyi), Robert

447

Matrix Properties Controlling Torsional Fatigue Life of Fiber Reinforced Composites.  

National Technical Information Service (NTIS)

The fatigue life of torsionally stressed N.O.L. rings can be correlated with basic properties of the matrix. In a constant maximum deformation mode, fatigue life correlates, in a nonlinear fashion, with the ultimate strain of the matrix. Performance is al...

R. E. Lavengood R. M. Anderson

1969-01-01

448

Free torsional vibration characteristics of compound planetary gear sets  

Microsoft Academic Search

A family of torsional dynamic models of compound gear sets is developed to predict the free vibration characteristics under different kinematic configurations resulting in different speed ratios. The compound gear sets considered consist of two planes of single- or double-planet gear sets connected by a straight long planet. All of the planets are mounted on a single carrier. The system

Ahmet Kahraman

2001-01-01

449

Coupled flexural and torsional vibrations of ship-like girders  

Microsoft Academic Search

The paper is related to investigation of coupled horizontal flexural and torsional vibrations of container vessels. Differential equations of coupled vibrations of a prismatic beam with open cross-section are derived. The equations are solved analytically by direct integration and by variational method. In the former case, the frequency equation is reduced to a polynomial of the fourth order. In the

I. Senjanovi?; I. ?atipovi?; S. Tomaševi?

2007-01-01

450

An abnormal mode of torsion pendulum and its suppression  

NASA Astrophysics Data System (ADS)

The numerical solution of non-linear equations shows that the abnormal mode observed in our torsion pendulum experiments is an intrinsic mode of the pendulum. Further analysis shows that the amplitude of abnormal mode increasing with of swing modes can be suppressed with a magnetic damper effectively.

Tu, Ying; Zhao, Liang; Liu, Qi; Ye, Hong-Ling; Luo, Jun

2004-11-01

451

Determining the Gravitational Constant Using a Cryogenic Torsion Pendulum  

NASA Astrophysics Data System (ADS)

We report progress in measurements of G using a cryogenic torsion pendulum in the 'dynamic' (time-of-swing) mode. We have collected about 550 hours of data which should yield a G measurement with statistical uncertainty less than 20 ppm.

Bantel, M. K.; Newman, R. D.

2002-12-01

452

Plate tectonics conserves angular momentum  

NASA Astrophysics Data System (ADS)

A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4+27 kg m2 s-1). Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates). Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies revealed by geoid anomalies of the degree 4-10 packet of the Earth's spherical harmonic coefficients. These linear positive geoid anomalies underlie plate subduction zones and are presumed due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth). The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant velocity on the crests of convection cells driven by rising heat. The magnitude of these sinking mass anomalies is inferred also to be sufficient to overcome basal plate and transform fault frictions. These results imply that spreading centers are primarily passive reactive features, and fracture zones (and wedge-shaped sites of seafloor spreading) are adjustment zones that accommodate strains in the lithosphere. Further, the interlocked pattern of the Australian and Pacific plates the past 42 Million years (with their absolute plate motions near 90° to each other) is taken as strong evidence that large thermally driven "roller" convection cells previously inferred as the driving mechanism in earlier interpretations of continental drift and plate tectonics, have not been active in the Earth's mantle the past 42 Million years, if ever. This report also presents estimates of the changes in location and magnitude of the Earth's axis of total plate tectonic angular momentum for the past 62 million years.

Bowin, C.

2010-03-01

453

New Aspects of Angular Momentum Quantization in Curved Geometries  

NASA Astrophysics Data System (ADS)

Curvature in velocity space affects angular momentum through the Thomas precession, observable through quantum effects. When position space is curved too, a similar angular momentum effect arises, with an even smaller curvature parameter. In a phase space view of dynamics and group theory the two effects appear through a direct product of two Lorentz groups, one centered on Lorentz boosts and the other on translations in a hyperbolic position space. The usual tensor representation must now be extended to 8x8 matrices arising from position and velocity submatrices. The rotation subgroup becomes a direct product group R( 3 )vel R( 3 )pos . Its matrices recouple into a total angular momentum of standard form and a new contra-angular momentum Q represented by 6x6 matrices whose Lie algebra and quantization properties have been derived (Smith, F. T., Ann. Fond. L. de Broglie, 30, 179 (2010)). It has quantum numbers q,mq whose connections with elementary particles are as yet undetermined. Transitions will be highly forbidden except in regions of high gravitational curvature or high relative velocity.

Smith, Felix T.

2011-04-01

454

Oxidative and antioxidative defense system in testicular torsion/detorsion  

PubMed Central

Aim: The present study was aimed to assess the early effects of ischemia/reperfusion injury on the oxidants and anti-oxidant defense status in rat testicular tissue by measuring MDA, glucose-6-phosphte dehydrogenase activity and reduced glutathione levels in a designated time frame sequel to reperfusion. Animals were divided randomly into six groups (12 animals per group) in the following order: Group I: Sham-operated control group (Cso) without the application of the torsion. Group 2: Torsion-induced ischemia group (T30 m): Ischemia was induced through the torsion of spermatic cord for a period of 30 min. Group 3: One hour reperfusion group after detorsion (T30 mR1 h). Group 4: Twenty-four hour reperfusion group after detorsion (T30 mR24 h). Group 5: Forty-eight hours reperfusion group after detorsion (T30mR48h). Group 6: One week reperfusion group after detorsion (T30mR1wk). Results and Discussion: The oxidant-antioxidant system of the testicular tissue is altered during torsion as well as detorsion which results in the altered activities involved in the key enzyme of hexose monophosphate shunt pathway, glucose 6 phosphate dehydrogenase activity along with a reduction of glutathione (G.SH) content. The increase in G6PDH activity during torsion and followed by an increase in detorsion indicates the tissue's response to counter the oxidant stress caused by reduced blood supply. Continued exposure to such oxidant stressed physiological state of a tissue may lead to decreased capacity of the tissue to perform its physiological function such as testicular steroidogenesis and spermiogenesis shown in the present study.

Elshaari, F. A.; Elfagih, R. I.; Sheriff, D S; Barassi, I. F.

2011-01-01

455

Torsional ultrasound modality for hard nucleus phacoemulsification cataract extraction  

PubMed Central

Aim: To evaluate the efficacy and safety of phacoemulsification using torsional modality with different parameter settings for hard nucleus cataract extraction. Design: A prospective, randomised clinical study. Methods: A clinical practice study conducted at the Cataract Service, Zhongshan Ophthalmic Center, Sun-Yat-Sen University, and Guangzhou. One eye each from 198 consecutive patients with cataract density grade IV according to the Emery–Little system classification system, requiring phacoemulsification and intraocular lens implantation, was included. Eyes were randomly assigned to the Linear Torsional combined with Ultrasound power group (Linear Tor+US group, n?=?66), 100% Fixed Torsional group (Fixed Tor group, n?=?65) and conventional Ultrasound burst group (US group, n?=?67). All surgeries were performed by a single experienced surgeon and outcomes evaluated by another surgeon masked to treatment. Intraoperative parameters were Ultrasound Time (UST), Cumulative Dissipated Energy (CDE) and surgical complications. Patients were examined on post-op days 1, 7 and 30. Postoperative outcomes were final best corrected visual acuity (BCVA), average central and incisional corneal thickness and central endothelial cell counts. Results: The mean UST was lower in the Fixed Tor group than in the US group and in the Lin US+Tor group (p?0.0001). The mean CDE was lower in the Lin Tor+US group and in the Fixed Tor group than in the US group (p?0.0001). Comparing with the two Tor group, the US group had a lower average BCVA on post-op 1, 7 (p?0.0001) and 30 (p>0.01), greater average central corneal and incisional thickness on days 1, 7 (p?0.0001) and 30 (p>0.01), and higher average corneal endothelial cell losses on day 7 and 30 days (p?0.0001). Conclusions: Torsional combined with ultrasound power or high fixed torsional amplitude can yield more effective hard nucleus phacoemulsification than conventional ultrasound modality.

Zeng, M; Liu, X; Liu, Y; Xia, Y; Luo, L; Yuan, Z; Zeng, Y; Liu, Y

2008-01-01

456

An Ap-Structure with Finslerian Flavor II:. Torsion, Curvature and Other Objects  

NASA Astrophysics Data System (ADS)

An absolute parallelism (AP-) space having Finslerian properties is called FAP-space. This FAP-structure is wider than both conventional AP and Finsler structures. In the present work, more geometric objects as curvature and torsion tensors are derived in the context of this structure. Also second order tensors, usually needed for physical applications, are derived and studied. Furthermore, the anti-curvature and the W-tensor are defined for the FAP-structure. Relations between Riemannian, AP, Finsler and FAP structures are given. These relations facilitate comparison between results of applications carried out in the framework of these structures. We hope that the use of the FAP-structure, in applications may throw some light on some of the problems facing geometric field theories.

Wanas, M. I.; Kamal, Mona M.

457

Atomic and molecular alignment from photoelectron angular distributions in (n+1) resonantly enhanced multiphoton ionization  

SciTech Connect

Two distinct (n+1) REMPI techniques for obtaining the alignment of gas phase atoms and molecules from photoelectron angular distributions are presented. In both methods, the alignment is extracted from the angular distributions independently of the photoionization dynamics. The first method, which takes advantage of circular dichroism in the angular distributions (CDAD) has already been established experimentally as a useful probe of state alignment. The theory outlined in previous work is expanded here. The second method involves photoionization with light linearly polarized along the photoelectron collection direction and is presented here for the first time.

Dubs, R.L.; McKoy, V.; Dixit, S.N.

1988-01-15

458

Atomic and molecular alignment from photoelectron angular distributions in (n+1) resonantly enhanced multiphoton ionization  

SciTech Connect

Two distinct (n + 1) REMPI techniques for obtaining the alignment of gas-phase atom molecules from photoelectron angular distributions are presented. In both methods, the alignment is extracted from the angular distributions independently of the photoionization dynamics. The first method, which takes advantage of circular dichroism in the angular distributions (CDAD) has already been established experimentally as a useful probe of state alignment. The theory outlined in previous work is expanded here. The second method involves photoionization with light linearly polarized along the photoelectron collection direction and is presented here for the first time.

Dubs, R.L.; McKoy, V.; Dixit, S.N.

1988-01-15

459

Inter-Ring and Hexyl Chain Torsional Potentials in Poly (3-HEXYLTHIOPHENE) Oligomers: Scaling with the Length of the Conjugted Polymer Backbone  

NASA Astrophysics Data System (ADS)

Density functional theory calculations are presented for the equilibrium structures and torsional potentials for isolated Poly (3-Hexylthiophene) (P3HT) oligomers up to 12 monomer units (up to 302 atoms). Calculations were performed at B3LYP/6-31++G(d,p) treating both the backbone of thiophene rings and the hexyl chains explicitly. One-dimensional inter-ring torsional potentials were calculated by rotating backbone around the central inter-ring bond and hexyl torsional potentials were calculated rotating n-hexyl group adjacent to the central inter-ring bond for each oligomer. The torsional and electronic properties change significantly for oligomers with 2 to 8 units but reach asymptotic values for a 10 unit P3HT chain, thereby suggesting the 10 unit long oligomer as a molecular model for the extended polymer. For P3HT oligomers having 10 or more units, all the rings and the hexyl groups are approximately coplanar except for one hexyl group at head end. The principal interaction that promotes the coplanarity of the hexyl groups is the attraction of the proximal methylene hydrogens to the sulfur on the adjacent thiophene ring. The cis conformation of the backbone is about 2kT higher than the trans minimum at room temperature. The gauche conformation of the hexyl group is within about half kT of the planar minimum. Therefore conformational polymorphisms of both types will likely be significant in the heterogeneous environment of photovoltaic devices.

Bhatta, Ram S.; Perry, David S.; Yimer, Yeneneh; Tsige, Mesfin

2011-06-01

460

On Inflation and Torsion in Cosmology  

NASA Astrophysics Data System (ADS)

In a recent letter by H. Davoudiasl, R. Kitano, T. Li and H. Murayama ``The new Minimal Standard Model'' (NMSM) was constructed which incorporates new physics beyond the Minimal Standard Model (MSM) of particle physics. The authors follow the principle of minimal particle content and therefore adopt the viewpoint of particle physicists. It is shown that a generalisation of the geometric structure of spacetime can also be used to explain physics beyond the MSM. It is explicitly shown that for example inflation, i.e. an exponentially expanding universe, can easily be explained within the framework of Einstein--Cartan theory.

Boehmer, C. G.

2005-10-01

461

Geometric approach to dislocation and disclination theory  

SciTech Connect

Cartan structure equations are used to create a four-dimensional geometric description of dislocations in continuum theory. It is shown that the dislocation distribution is determined by the torsion tensor, while the disclination distribution is determined by the curvature tensor. An analogy to electrodynamics is offered.

Nesterov, A.I.; Ovchinnikov, S.G.

1988-05-01

462

Model-based diagnosis of large diesel engines based on angular speed variations of the crankshaft  

NASA Astrophysics Data System (ADS)

This work aims at monitoring large diesel engines by analyzing the crankshaft angular speed variations. It focuses on a powerful 20-cylinder diesel engine with crankshaft natural frequencies within the operating speed range. First, the angular speed variations are modeled at the crankshaft free end. This includes modeling both the crankshaft dynamical behavior and the excitation torques. As the engine is very large, the first crankshaft torsional modes are in the low frequency range. A model with the assumption of a flexible crankshaft is required. The excitation torques depend on the in-cylinder pressure curve. The latter is modeled with a phenomenological model. Mechanical and combustion parameters of the model are optimized with the help of actual data. Then, an automated diagnosis based on an artificially intelligent system is proposed. Neural networks are used for pattern recognition of the angular speed waveforms in normal and faulty conditions. Reference patterns required in the training phase are computed with the model, calibrated using a small number of actual measurements. Promising results are obtained. An experimental fuel leakage fault is successfully diagnosed, including detection and localization of the faulty cylinder, as well as the approximation of the fault severity.

Desbazeille, M.; Randall, R. B.; Guillet, F.; El Badaoui, M.; Hoisnard, C.

2010-07-01

463

Angular Power Spectrum in Modular Invariant Inflation Model  

SciTech Connect

A scalar potential of inflation is proposed and the angular power spectra of the adiabatic density perturbations are computed. The potential consists of three scalar fields, S, Y and T, together with two free parameters. By fitting the parameters to cosmological data at the fixed point T = 1, we find that the potential behaves like the single-field potential of S, which slowly rolls down. We further show that the inflation predictions corresponding to this potential provide a good fit to the recent three-year WMAP data, e.g. the spectral index n{sub s} = 0.951.The TT and TE angular power spectra obtained from our model almost completely coincide with the corresponding results obtained from the {lambda}CDM model. We conclude that our model is considered to be an adequate theory of inflation that explains the present data.

Hayashi, Mitsuo J.; Okame, Y.; Takagi, K.; Watanabe, T. [Department of Physics, Tokai University, 1117 Kitakaname, Hiratsuka, 259-1292 (Japan); Hirai, S.; Takami, T. [Department of Digital Games, Osaka Electro-Communication University, 1130-70 Kiyotaki, Shijonawate, Osaka, 575-0063 (Japan)

2008-05-29

464

Semiclassical model for attosecond angular streaking.  

PubMed

Attosecond angular streaking is a new technique to achieve unsurpassed time accuracy of only a few attoseconds. Recently this has been successfully used to set an upper limit on the electron tunneling delay time in strong laser field ionization. The measurement technique can be modeled with either the time-dependent Schrödinger equation (TDSE) or a more simple semiclassical approach that describes the process in two steps in analogy to the three-step model in high harmonic generation (HHG): step one is the tunnel ionization and step two is the classical motion in the strong laser field. Here we describe in detail a semiclassical model which is based on the ADK theory for the tunneling step, with subsequent classical propagation of the electron in the laser field. We take into account different ellipticities of the laser field and a possible wavelength-dependent ellipticity that is typically observed for pulses in the two-optical-cycle regime. This semiclassical model shows excellent agreement with the experimental result. PMID:20721150

Smolarski, M; Eckle, P; Keller, U; Dörner, R

2010-08-16

465

Modular Approach to Physics: Angular Velocity  

NSDL National Science Digital Library

This web page contains an interactive simulation for introductory physics students describing different types of motion in term of angular coordinates. It consists of a moving car, a graph of angular velocity vs. time, and real-time values for areal and angular velocity. The path of the car can be a straight line, a circle, or a parabola with the angular motion given relative to a fixed point. This item is part of a larger collection of physics simulations sponsored by the MAP project (Modular Approach to Physics).

Austin, David; Martin, Brian

2008-08-03

466

Vacuum static compactified wormholes in eight-dimensional Lovelock theory  

SciTech Connect

In this paper, new exact solutions in eight-dimensional Lovelock theory will be presented. These solutions are the vacuum static wormhole, the black hole, and generalized Bertotti-Robinson space-times with nontrivial torsion. All of the solutions have a cross product structure of the type M{sub 5}x{sigma}{sub 3}, where M{sub 5} is a five-dimensional manifold and {sigma}{sub 3} a compact constant curvature manifold. The wormhole is the first example of a smooth vacuum static Lovelock wormhole which is neither Chern-Simons nor Born-Infeld. It will be also discussed how the presence of torsion affects the 'navigableness' of the wormhole for scalar and spinning particles. It will be shown that the wormhole with torsion may act as 'geometrical filter': A very large torsion may 'increase the traversability' for scalars while acting as a 'polarizator' on spinning particles. This may have interesting phenomenological consequences.

Canfora, Fabrizio [Centro de Estudios Cientificos (CECS), Valdivia (Chile); Giacomini, Alex [Instituto de Fisica, Facultad de Ciencias, Universidad Austral de Chile, Valdivia (Chile); Centro de Estudios Cientificos (CECS), Valdivia (Chile)

2008-10-15

467

Torsion and free vibration characteristics of turbogenerator end windings  

NASA Astrophysics Data System (ADS)

Stator end windings of large turbogenerators are subjected to static and harmonic forces due to electromagnetic interaction of the electric currents in them. In this paper the free vibration characteristics of these end winding coils are analyzed by using a transfer matrix approach, with account taken of the flexural and torsional rigidities of the composite coil section. An analytical method in which Prandtl's stress function and Roth's double infinite series are used is developed for determining the effective torsional rigidity of the composite rectangular sections with jump non-homogeneity along the principal directions of the section. The necessary equations for the space curve representing the end winding coils are developed. The natural frequencies of a single coil have been experimentally determined by an impact hammer test. The theoretical and experimental values are in good agreement.

Narayanan, S.; Krishna Dutt, R. V. S.; Pramanik, A.; Bhave, S. K.

1992-01-01

468

MAGNETOSEISMOLOGY: EIGENMODES OF TORSIONAL ALFVEN WAVES IN STRATIFIED SOLAR WAVEGUIDES  

SciTech Connect

There have recently been significant claims of Alfven wave observation in the solar chromosphere and corona. We investigate how the radial and longitudinal plasma structuring affects the observational properties of torsional Alfven waves in magnetic flux tubes for the purposes of solar magnetoseismology. The governing magnetohydrodynamic equations of these waves in axisymmetric flux tubes of arbitrary radial and axial plasma structuring are derived and we study their observable properties for various equilibria in both thin and finite-width magnetic flux tubes. For thin flux tubes, it is demonstrated that observation of the eigenmodes of torsional Alfven waves can provide temperature diagnostics of both the internal and surrounding plasma. In the finite-width flux tube regime, it is shown that these waves are the ideal magnetoseismological tool for probing radial plasma inhomogeneity in solar waveguides.

Verth, G.; Goossens, M. [Centrum voor Plasma Astrofysica, KU Leuven, Celestijnenlaan 200B, 3001 Heverlee (Belgium); Erdelyi, R., E-mail: Gary.Verth@wis.kuleuven.b, E-mail: Marcel.Goossens@wis.kuleuven.b, E-mail: robertus@sheffield.ac.u [Solar Physics and Space Plasma Research Centre (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

2010-05-10

469

Quartz crystal microbalance based on torsional piezoelectric resonators  

SciTech Connect

A quartz crystal microbalance (QCM) is described, which is based on a torsional resonator, rather than a conventional thickness-shear resonator. Typical applications are measurements of film thickness in the coating industry and monitoring of biofouling. The torsional QCM is about a factor of 100 less sensitive than the conventional QCM. On the other hand, it can probe film thicknesses in the range of hundreds of microns, which is impossible with the conventional QCM due to viscoelastic artifacts. Data acquisition and data analysis proceed in analogy to the conventional QCM. An indicator of the material's softness can be extracted from the bandwidth of the resonance. Within the small-load approximation, the frequency shift is independent of whether the sample is applied to the face or to the side of the cylinder. Details of the geometry matter if the viscoelastic properties of the sample are of interest.

Buecking, W.; Du, B.; Turshatov, A.; Koenig, A. M.; Reviakine, I.; Bode, B.; Johannsmann, D. [Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Strasse 4, D-38678 Clausthal-Zellerfeld (Germany); Flucon Fluid Control GmbH, Burgstaetter Strasse 6, D-38678 Clausthal-Zellerfeld (Germany); Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Strasse 4, D-38678 Clausthal-Zellerfeld (Germany)

2007-07-15

470

Quartz crystal microbalance based on torsional piezoelectric resonators  

NASA Astrophysics Data System (ADS)

A quartz crystal microbalance (QCM) is described, which is based on a torsional resonator, rather than a conventional thickness-shear resonator. Typical applications are measurements of film thickness in the coating industry and monitoring of biofouling. The torsional QCM is about a factor of 100 less sensitive than the conventional QCM. On the other hand, it can probe film thicknesses in the range of hundreds of microns, which is impossible with the conventional QCM due to viscoelastic artifacts. Data acquisition and data analysis proceed in analogy to the conventional QCM. An indicator of the material's softness can be extracted from the bandwidth of the resonance. Within the small-load approximation, the frequency shift is independent of whether the sample is applied to the face or to the side of the cylinder. Details of the geometry matter if the viscoelastic properties of the sample are of interest.

Bücking, W.; Du, B.; Turshatov, A.; König, A. M.; Reviakine, I.; Bode, B.; Johannsmann, D.

2007-07-01

471

Photonic crystal split-beam nanocavities for torsional optomechanics  

NASA Astrophysics Data System (ADS)

A novel type of photonic crystal nanocavity nanocavity tailored to sensitively measure torques is theoretically investigated. Suspended low-mass elements (< pg) in the nanomechanical resonator are sensitive to environmental stimuli, such as a magnetic field from external sources or from embedded nanomagnetic systems. The torsional mechanical motion of these elements directly influences the optical field concentrated inside the optical nanocavity, resulting in a strong cavity optomechanical coupling rate up to 90 GHz/nm. The actuation of the mechanical resonator is readout with high sensitivity using evanescent coupling between the photonic crystal nanocavity and an optical fiber taper. A sub-100nm physical air gap in the middle of the nanobeam cavity allows torsional mechanical degrees of freedom as well as strong optical field confinement in a small mode volume. Numerical simulations show that high-Q ~ 106 optical cavities with a gap are possible. Potential applications incorporating these devices include sensitive magnetometry and probing the quantum properties of nanomagnetic systems.

Wu, Marcelo; Hryciw, Aaron C.; Khanaliloo, Behzad; Healey, Chris; Freeman, Mark R.; Davis, John P.; Barclay, Paul E.

2013-03-01

472

Dark energy fifth forces in torsion pendulum experiments  

NASA Astrophysics Data System (ADS)

The chameleon scalar field is a matter-coupled dark energy candidate whose nonlinear self-interaction partially screens its fifth force at laboratory scales. Nevertheless, small-scale experiments such as the torsion pendulum can provide powerful constraints on chameleon models. Here we develop a simple approximation for computing chameleon fifth forces in torsion pendulum experiments such as Eöt-Wash. We show that our approximation agrees well with published constraints on the quartic chameleon, and we use it to extend these constraints to a much wider range of models. Finally, we forecast the constraints which will result from the next-generation Eöt-Wash experiment, and show that this experiment will exclude a wide range of quantum-stable models.

Upadhye, Amol

2012-11-01

473

Resistance to torsional forces of various post and core designs.  

PubMed

This in vitro study investigated the resistance of various post and core designs to torsional forces. Cast gold, parallel-sided, serrated post and cores were cemented in extracted teeth. The test groups were made up of the following designs: controls without an antirotational feature, keyway form, coronal flare form, auxiliary pin form, a cervical collar form, and included a tapered post group. The specimens were mounted on an Instron Universal testing machine and a torsional force was applied to the core using a lever arm until failure. All the antirotational features tested elevated resistance to torque. Failure occurred through fracture of the tooth, the cement, or an optional auxiliary pin. The cervical collar was the most favorable design, embracing resistance and reducing tooth fractures. PMID:1800728

Hemmings, K W; King, P A; Setchell, D J

1991-09-01

474

Acute gallbladder torsion - a continued pre-operative diagnostic dilemma  

Microsoft Academic Search

Acute gallbladder volvulus continues to remain a relatively uncommon process, manifesting itself usually during exploration\\u000a for an acute surgical abdomen with a presumptive diagnosis of acute cholecystitis. The pathophysiology is that of mechanical\\u000a organo-axial torsion along the gallbladder's longitudinal axis involving the cystic duct and cystic artery, and with a pre-requisite\\u000a of local mesenteric redundancy. The demographic tendency is septua-

Nicolas J Mouawad; Brianne Crofts; Rachel Streu; Randal Desrochers; Beth C Kimball

2011-01-01

475

Electromechanical Behavior of Carbon Nanotube Turfs Under Torsion  

Microsoft Academic Search

This paper describes the electromechanical behavior of carbon nanotube (CNT) turfs when a torque is applied. High aspect ratio (~3.83) cylindrical CNT turfs were grown by a three-zone temperature chemical vapor deposition (TZT-CVD). A distinctive apparatus is developed to apply a torque on the CNT turf and measure the torsional angle simultaneously. Electrical resistance of CNT turf can be recorded

Tsung-Cho Wu; Shuo-Hung Chang

2010-01-01

476

On Large-Strain Inelastic Torsion of Glassy Polymers  

Microsoft Academic Search

Abstrzet--Large-strain elastic-viscoplastic torsion of circular tubes and solid bars of glassy polymers is investigated under fixed-end as well as free-end conditions. The analysis employs a large inelastic deformation model for glassy polymers that incorporates a recently proposed constitutive law for the so-called orientational hardening, which is identified to play a key role in the description of the deformation-induced anisotropy in

P. D. Wu; E. van der Giessen

1993-01-01

477

Torsional oscillations of umbra and penumbra of sunspots  

Microsoft Academic Search

Torsional oscillations of seven single spots are studied based on the observations of the longitudinal magnetic field and\\u000a the field of radial velocities in the photospheric Fe I ? 525.3 nm line. The periods of umbra and penumbra oscillations are\\u000a 2.2–7.1 and 3.3–7.7 days, respectively. The spots at a greater solar latitude are characterized by a longer period of oscillations

O. S. Gopasyuk

2010-01-01