Can torsion play a role in angular momentum conservation law?
Yishi Duan; Ying Jiang
1998-11-24
In Einstein-Cartan theory, by the use of the general Noether theorem, the general covariant angular-momentum conservation law is obtained with the respect to the local Lorentz transformations. The corresponding conservative Noether current is interpreted as the angular momentum tensor of the gravity-matter system including the spin density. It is pointed out that, assuming the tetrad transformation given by eq. (15), torsion tensor can not play a role in the conservation law of angular momentum.
Universality Principle for Orbital Angular Momentum and Spin in Gravity with Torsion
H. Kleinert
1998-07-11
We argue that compatibility with elementary particle physics requires gravitational theories with torsion to be unable to distinguish between orbital angular momentum and spin. An important consequence of this principle is that spinless particles must move along autoparallel trajectories, not along geodesics.
Universality Principle for Orbital Angular Momentum and Spin in Gravity with Torsion
H. Kleinert
2000-01-01
We argue that compatibility with elementary particle physics requires gravitational theories with torsion to be unable to distinguish between orbital angular momentum and spin. An important consequence of this principle is that spinless particles must move along autoparallel trajectories, not along geodesics.
35. VERTICAL AND TORSIONAL MOTION FROM EAST TOWER SHOWING ANGULAR ...
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
Studies of torsional properties of DNA and nucleosomes using angular optical trapping
NASA Astrophysics Data System (ADS)
Sheinin, Maxim Y.
DNA in vivo is subjected to torsional stress due to the action of molecular motors and other DNA-binding proteins. Several decades of research have uncovered the fascinating diversity of DNA transformations under torsion and the important role they play in the regulation of vital cellular processes such as transcription and replication. Recent studies have also suggested that torsion can influence the structure and stability of nucleosomes---basic building blocks of the eukaryotic genome. However, our understanding of the impact of torsion is far from being complete due to significant experimental challenges. In this work we have used a powerful single-molecule experimental technique, angular optical trapping, to address several long-standing issues in the field of DNA and nucleosome mechanics. First, we utilized the high resolution and direct torque measuring capability of the angular optical trapping to precisely measure DNA twist-stretch coupling. Second, we characterized DNA melting under tension and torsion. We found that torsionally underwound DNA forms a left-handed structure, significantly more flexible compared to the regular B-DNA. Finally, we performed the first comprehensive investigation of the single nucleosome behavior under torque and force. Importantly, we discovered that positive torque causes significant dimer loss, which can have implications for transcription through chromatin.
Quan, Li-Di; Xue, Chao; Shao, Cheng-Gang; Yang, Shan-Qing; Tu, Liang-Cheng; Wang, Yong-Ji; Luo, Jun
2014-01-01
The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to [Formula: see text] at the signal frequency of 2?mHz, which contributes a [Formula: see text] uncertainty to the G value. PMID:24517789
M-theory moduli spaces and torsion-free structures
Graña, Mariana
2014-01-01
Motivated by the description of $\\mathcal{N}=1$ M-theory compactifications to four-dimensions given by Exceptional Generalized Geometry, we propose a way to geometrize the M-theory fluxes by appropriately relating the compactification space to a higher-dimensional manifold equipped with a torsion-free structure. As a non-trivial example of this proposal, we construct a bijection from the set of $Spin(7)$-structures on an eight-dimensional $S^{1}$-bundle to the set of $G_{2}$-structures on the base space, fully characterizing the $G_{2}$-torsion clases when the total space is equipped with a torsion-free $Spin(7)$-structure. Finally, we elaborate on how the higher-dimensional manifold and its moduli space of torsion-free structures can be used to obtain information about the moduli space of M-theory compactifications.
Universality Principle for Orbital Angular Momentum and Spin in Gravity with Torsion
H. Kleinert; Physik Freie
1998-01-01
We argue that compatibility with elementary particle physics requires\\u000agravitational theories with torsion to be unable to distinguish between orbital\\u000aangular momentum and spin. An important consequence of this principle is that\\u000aspinless particles must move along autoparallel trajectories, not along\\u000ageodesics.
NASA Astrophysics Data System (ADS)
Quan, Li-Di; Xue, Chao; Shao, Cheng-Gang; Yang, Shan-Qing; Tu, Liang-Cheng; Wang, Yong-Ji; Luo, Jun
2014-01-01
The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to 7.3× 10^{-7}rad/ sqrt{Hz} at the signal frequency of 2 mHz, which contributes a 0.4 textrm {ppm} uncertainty to the G value.
Quan, Li-Di [MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China) [MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); School of Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Xue, Chao; Shao, Cheng-Gang; Yang, Shan-Qing; Tu, Liang-Cheng; Luo, Jun, E-mail: junluo@mail.hust.edu.cn [MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)] [MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Wang, Yong-Ji [School of Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)] [School of Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)
2014-01-15
The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to 7.3×10{sup ?7} rad /?( Hz ) at the signal frequency of 2?mHz, which contributes a 0.4 ppm uncertainty to the G value.
Linearized Torsion Waves in a Tensor-Tensor Theory of Gravity
Chih-Hung Wang
2007-12-12
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.
Plane torsion waves in quadratic gravitational theories
O. V. Babourova; B. N. Frolov; E. A. Klimova
1998-05-03
The definition of the Riemann-Cartan space of the plane wave type is given. The condition under which the torsion plane waves exist is found. It is expressed in the form of the restriction imposed on the coupling constants of the 10-parametric quadratic gravitational Lagrangian. In the mathematical appendix the formula for commutator of the variation operator and Hodge operator is proved. This formula is applied for the variational procedure when the gravitational field equations are obtained in terms of the exterior differential forms.
Torsion waves in metric{ane eld theory Alastair D Kingy and Dmitri Vassilievz
King, Alastair
Torsion waves in metric{aÃ?ne #12;eld theory Alastair D Kingy and Dmitri Vassilievz Department which are stationary points. These spacetimes are waves of torsion in Minkowski space. We then #12;nd symbolically as @SYM =@g = 0 ; (2) #12; Torsion waves in metric{aÃ?ne #12;eld theory 2 @SYM =@ = 0 : (3
The Torsion Theory Cogenerated by M-Small Modules
Y. Talebi; N. Vanaja
2002-01-01
Let M and N be R-modules. We definewhere S denotes the class of all M-small modules. We call N an M-cosingular (non-M-cosingular) module if ZM(N) = 0 (ZM(N) = N). We study the properties of M-cosingular and non-M-cosingular modules in ?[M] We consider the torsion theory cogenerated by M-small modules and show that it is cohereditary when every injective module
Dynamical features of scalar-torsion theories
NASA Astrophysics Data System (ADS)
Skugoreva, Maria A.; Saridakis, Emmanuel N.; Toporensky, Alexey V.
2015-02-01
We investigate the cosmological dynamics in teleparallel gravity with nonminimal coupling. We analytically extract several asymptotic solutions, and we numerically study the exact phase-space behavior. Comparing the obtained results with the corresponding behavior of nonminimal scalar-curvature theory, we find significant differences, such as the rare stability and the frequent presence of oscillatory behavior.
Thermal Properties of SiCp/Al Composites Consolidated by Equal Channel Angular Pressing and Torsion
NASA Astrophysics Data System (ADS)
Qian, Chen-hao; Li, Ping; Xue, Ke-min
2015-02-01
Powder mixture of pure Al and oxidized SiC was consolidated into SiCp/Al composites by equal channel angular pressing and torsion (ECAP-T). The influences of several parameters on the thermal expansions, the thermal conductivities, and the recrystallization temperatures of the as-consolidated composites were studied. These parameters are the number of ECAP-T passes (1, 2, and 4), the content of SiC (10, 20, and 40 wt.%), and the fabrication temperature (150, 250, and 350 °C). The results show that increasing the number of ECAP-T passes has a positive effect on depressing the coefficient of thermal expansion (CTE) of the composite within a certain temperature range, since the total variation amplitude of the CTE is enlarged. The CTE can also be decreased by increasing the content of SiC. The number of ECAP-T passes and the contents of SiC in the composites are both positively related with the thermal conductivity of the composites. No direct relationship between the fabrication temperature and the thermal properties was detected. However, the composite fabricated at too low temperature (150 °C) can not obtain full densification, leading to the appearance of low CTE and thermal conductivity. Finally, when the number of ECAP-T passes is elevated from 2 to 4, the recrystallization temperature of the composite has an obvious declination.
Constraining torsion with Gravity Probe B
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
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.
Torsion waves in metric-affine field theory
Alastair D. King; Dmitri Vassiliev
2000-12-13
The approach of metric-affine field theory is to define spacetime as a real oriented 4-manifold equipped with a metric and an affine connection. The 10 independent components of the metric tensor and the 64 connection coefficients are the unknowns of the theory. We write the Yang-Mills action for the affine connection and vary it both with respect to the metric and the connection. We find a family of spacetimes which are stationary points. These spacetimes are waves of torsion in Minkowski space. We then find a special subfamily of spacetimes with zero Ricci curvature; the latter condition is the Einstein equation describing the absence of sources of gravitation. A detailed examination of this special subfamily suggests the possibility of using it to model the neutrino. Our model naturally contains only two distinct types of particles which may be identified with left-handed neutrinos and right-handed antineutrinos.
Elie Cartan's torsion in geometry and in field theory, an essay
Friedrich W. Hehl; Yuri N. Obukhov
2007-11-09
We review the application of torsion in field theory. First we show how the notion of torsion emerges in differential geometry. In the context of a Cartan circuit, torsion is related to translations similar as curvature to rotations. Cartan's investigations started by analyzing Einsteins general relativity theory and by taking recourse to the theory of Cosserat continua. In these continua, the points of which carry independent translational and rotational degrees of freedom, there occur, besides ordinary (force) stresses, additionally spin moment stresses. In a 3-dimensional continuized crystal with dislocation lines, a linear connection can be introduced that takes the crystal lattice structure as a basis for parallelism. Such a continuum has similar properties as a Cosserat continuum, and the dislocation density is equal to the torsion of this connection. Subsequently, these ideas are applied to 4-dimensional spacetime. A translational gauge theory of gravity is displayed (in a Weitzenboeck or teleparallel spacetime) as well as the viable Einstein-Cartan theory (in a Riemann-Cartan spacetime). In both theories, the notion of torsion is contained in an essential way. Cartan's spiral staircase is described as a 3-dimensional Euclidean model for a space with torsion, and eventually some controversial points are discussed regarding the meaning of torsion.
Comparison of dynamic torsion theories for beams of elliptical cross-section
NASA Astrophysics Data System (ADS)
Stephen, N. G.
1985-05-01
A comparison between several dynamic torsion theories for beams of non-circular cross-section and their predicted torsional wave first branch dispersion characteristics is made with some recently published "exact" data for elliptical cross-section beams of various eccentricities. Closest agreement, in particular for short wavelengths, is provided by two theories, both of which allow in-plane distortion of the section; however, a simpler theory adjusted to predict phase velocity asymptotic to Rayleigh surface wave velocity at short wavelengths gives closest overall agreement and appears preferable for torsional wave propagation and standing wave frequency analysis.
Comparison of dynamic torsion theories for beams of elliptical cross-section
N. G. Stephen
1985-01-01
A comparison between several dynamic torsion theories for beams of non-circular cross-section and their predicted torsional wave first branch dispersion characteristics is made with some recently published ``exact'' data for elliptical cross-section beams of various eccentricities. Closest agreement, in particular for short wavelengths, is provided by two theories, both of which allow in-plane distortion of the section; however, a simpler
M. R. Shammamy; O. M. Sidebottom
1967-01-01
Incremental and total-strain theories have been presented in the literature for hollow and solid circular torsion-tension members. The differential equations obtained for the incremental theory have been solved only for the conditions that the torsion-tension member is made of a nonstrain-hardening material and is subjected to restricted deformation histories. Computer programs were written to obtain numerical incremental solutions for hollow
Parallel spinors and connections with skewsymmetric torsion in string theory \\Lambda
Friedrich, Thomas
Parallel spinors and connections with skewÂsymmetric torsion in string theory \\Lambda Thomas is of importance in string theory, since they are associated with some string solitons (BPS solitons) [42Â plications in the exploration of perturbative and nonÂperturbative properties of string theory. An important
Space-Time Torsion and the Rotation of Galaxies
M. L. Fil'chenkov
1999-02-08
Torsion effects, including a spin precession in the torsion field, are considered. Some properties of neutrinos in cosmology are discussed. In the framework of Trautman's cosmological model with torsion estimated is a specific angular momentum of initial perturbations which proved to be of the order of the observable specific rotational moment for spiral galaxies. The results obtained are compared with those from the theories of potential and vortical perturbations in which rotation of galaxies is predicted.
Galois Theory, discriminants and torsion subgroups of elliptic curves
Garcia-Selfa, Irene; Tornero, Jose M
2008-01-01
We find a tight relationship between the torsion subgroup of an elliptic curve and a Galois group naturally arising from the curve. This relation is shown using some characterizations for the squareness of the discriminant of the elliptic curve. The proof of these facts involves quite different techniques, e.g. Tate normal form, Chabauty's method for hyperelliptic curves, Riemann--Hurwitz formulae, generalized Fermat equations and some previous work of us.
Brans-Dicke theory of gravity with torsion: A possible solution of the $?$-problem
Yu-Huei Wu; Chih-Hung Wang
2012-11-15
We study the Brans-Dicke theory of gravity in Riemann-Cartan space-times, and obtain general torsion solutions, which are completely determined by Brans-Dicke scalar field $\\Phi$, in the false vacuum energy dominated epoch. The substitution of the torsion solutions back to our action gives the original Brans-Dicke action with $\\Phi$-dependent Brans-Dicke parameter $\\omega(\\Phi)$. The evolution of $\\omega(\\Phi)$ during the inflation is studied and it is found that $\\omega$ approaches to infinity at the end of inflation. This may solve the $\\omega$-problem in the extended inflation model.
Self-Gravitating Spherically Symmetric Solutions in Scalar-Torsion Theories
Kofinas, Georgios; Saridakis, Emmanuel N
2015-01-01
We studied spherically symmetric solutions in scalar-torsion gravity theories in which a scalar field is coupled to torsion with a derivative coupling. We obtained the general field equations from which we extracted a decoupled master equation, the solution of which leads to the specification of all other unknown functions. We first obtained an exact solution which represents a new wormhole-like solution dressed with a regular scalar field. Then, we found large distance linearized spherically symmetric solutions in which the space asymptotically is AdS.
Cosmological perturbations in the metric-affine theory with a pseudoscalar torsion function
Jianbo Lu; G. Y. Chee
2014-06-27
A cosmological model in the metric-affine theory with a pseudoscalar torsion function is studied. The cosmological equations in this model are different from the Friedmann equations in the standard cosmology. It provides a different description of the cosmic acceleration from the $\\Lambda $CDM model. And the cosmological constant problem can be explained in a different manner. The origin of the cosmic acceleration in this metric-affine theory with a pseudoscalar torsion function can be interpreted by the exist of the curvature-torsion dark energy component caused by the energy and pressure of the matter. In this "curvature-torsion dark energy" scenario, the fact of the dimensionless matter density $\\Omega _m-1$). Perturbation theory and structure growth are the important aspects in cosmological studies, since they can relate to several cosmic observations. Also, in order to compare our model with the popular $\\Lambda $CDM model, we investigate its cosmological perturbations. The equations for linear perturbations of the metric and for density contrast growth are derived. And the analytic solutions of these equations are obtained. The gravitational potential and the growth of the baryon matter density perturbation in our model can be reduced to the ones in $\\Lambda $CDM as a special case.
Chern-Simons modified gravity as a torsion theory and its interaction with fermions
NASA Astrophysics Data System (ADS)
Alexander, Stephon; Yunes, Nicolás
2008-06-01
We study the tetrad formulation of Chern-Simons (CS) modified gravity, which adds a Pontryagin term to the Einstein-Hilbert action with a spacetime-dependent coupling field. We first verify that CS modified gravity leads to a theory with torsion, where this tensor is given by an antisymmetric product of the Riemann tensor and derivatives of the CS coupling. We then calculate the torsion in the far field of a weakly gravitating source within the parameterized post-Newtonian formalism, and specialize the result to Earth. We find that CS torsion vanishes only if the coupling vanishes, thus generically leading to a modification of gyroscopic precession, irrespective of the coupling choice. Perhaps most interestingly, we couple fermions to CS modified gravity via the standard Dirac action and find that these further correct the torsion tensor. Such a correction leads to two new results: (i) a generic enhancement of CS modified gravity by the Dirac equation and axial fermion currents; (ii) a new two-fermion interaction, mediated by an axial current and the CS correction. We conclude with a discussion of the consequences of these results in particle detectors and realistic astrophysical systems.
On Torsion-free Vacuum Solutions of the Model of de Sitter Gauge Theory of Gravity (II)
Chao-Guang Huang; Meng-Sen Ma
2009-06-15
It is shown that all torsion-free vacuum solutions of the model of dS gauge theory of gravity are the vacuum solutions of Einstein field equations with the same positive cosmological constant. Furthermore, for the gravitational theories with more general quadratic gravitational Lagrangian ($F^2+T^2$), the torsion-free vacuum solutions are also the vacuum solutions of Einstein field equations.
Torsion waves in metric-affine field theory
Alastair D. King; Dmitri Vassiliev
2001-01-01
The approach of metric-affine field theory is to define spacetime as a real oriented 4-manifold equipped with a metric and an affine connection. The 10 independent components of the metric tensor and the 64 connection coefficients are the unknowns of the theory. We write the Yang-Mills action for the affine connection and vary it both with respect to the metric
Atomic and Molecular Quantum Theory Course Number: C561 18 Theory of Angular Momentum
Iyengar, Srinivasan S.
Atomic and Molecular Quantum Theory Course Number: C561 18 Theory of Angular Momentum 1. Why do we Quantum Theory Course Number: C561 5. What if we consider the simplest molecular system: the hy- drogen (instructor) #12;Atomic and Molecular Quantum Theory Course Number: C561 11. This is the approach we will use
Neil Russell
2008-03-14
In this proceedings, similarities between the structure of theories with Lorentz violation and theories with constant torsion in flat spacetime are exploited to place bounds on torsion components. An example is given showing the analysis leading to bounds on the axial-vector and mixed-symmetry components of torsion, based on a dual-maser experiment.
NASA Astrophysics Data System (ADS)
Beenken, Wichard J. D.
2008-06-01
The optimized geometries of bithiophene in the electronic ground and excited state have been calculated by time-dependent density functional theory using the hybrid functional B3-LYP. The dependence of the singlet excitation energies and transition dipoles on the torsion between the two thienyl groups has been determined and compared with the torsional potential curve previously found for biphenyl. Based on these data the torsional progressions in absorption and emission have been computed quantum-mechanically in order to show their contribution to the inhomogeneous broadening in the respective spectra of bithiophene.
Gyrokinetic theory and simulation of angular momentum transport
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
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.
Gyrokinetic theory and simulation of angular momentum transport
NASA Astrophysics Data System (ADS)
Waltz, R. E.; Staebler, G. M.; Candy, J.; Hinton, F. L.
2007-12-01
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.
X. S. Chen; X. F. Lü; W. M. Sun; F. Wang; T. Goldman
2007-09-23
This two-paper series addresses and fixes the long-standing gauge invariance problem of angular momentum in gauge theories. This QED part reveals: 1) The spin and orbital angular momenta of electrons and photons can all be consistently defined gauge invariantly. 2) These gauge-invariant quantities can be conveniently computed via the canonical, gauge-dependent operators (e.g, $\\psi ^\\dagger \\vec x \\times\\frac 1i \\vec \
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
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.
The nonlinear bending-torsion theory for curved rods as Gamma-limit of three-dimensional elasticity
Lucia Scardia
2008-03-06
The problem of the rigorous derivation of one-dimensional models for nonlinearly elastic curved beams is studied in a variational setting. Considering different scalings of the three-dimensional energy and passing to the limit as the diameter of the beam goes to zero, a nonlinear model for strings and a bending-torsion theory for rods are deduced.
Parallel spinors and connections with skew-symmetric torsion in string theory
Thomas Friedrich; Stefan Ivanov
2001-01-01
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 $\\\
An elastoplastic theory of dislocations as a physical field theory with torsion
Markus Lazar
2002-01-01
We consider a static theory of dislocations with moment stress in an anisotropic or isotropic elastoplastic material as a T(3) gauge theory. We obtain Yang-Mills-type field equations which express the force and the moment equilibrium. Additionally, we discuss several constitutive laws between the dislocation density and the moment stress. For a straight screw dislocation, we find the stress field which
Jain, Paresh; Chhabra, Sheri; Parikh, Ketan; Vaidya, Amrish
2008-01-01
Omental torsion is a rare cause of acute abdominal pain, and clinically mimics acute appendicitis. A 11-year-old boy presented with symptoms and signs suggestive of appendicitis. A computed tomography of abdomen revealed findings suggestive of omental torsion. Diagnostic laparoscopy confirmed the diagnosis of torsion of a segment of the greater omentum. PMID:20011502
Torsion Cosmology of Poincaré gauge theory and the constraints of its parameters via SNeIa data
Xi-Chen Ao; Xin-Zhou Li
2011-11-10
Poincar\\`e gauge theory (PGT) is an alternative gravity theory, which attempts to bring the gravity into the gauge-theoretic frame, where the Lagrangian is quadratic in torsion and curvature. Recently, the cosmological models with torsion based on this theory have drawn many attentions, which try to explain the cosmic acceleration in a new way. Among these PGT cosmological models, the one with only even parity dynamical modes -- SNY model, for its realistic meaning, is very attractive. In this paper, we first analyze the past-time cosmic evolution of SNY model analytically. And based on these results we fit this model to the most comprehensive SNeIa data (Union 2) and thus find the best-fit values of model parameters and initial conditions, whose related $\\chi^{2}$ value is consistent with the one from $\\Lambda$CMD at the 1$\\sigma$ level. Also by the $\\chi^{2}$ estimate, we provide certain constraints on these parameters. Using these best-fit values for the Union 2 SNeIa dataset, we are able to predict the evolution of our real universe over the late time. From this prediction, we know the fate of our universe that it would expand forever, slowly asymptotically to a halt, which is in accordance with the earlier works.
Torsional and Bending Vibration Measurement on Rotors Using Laser Technology
NASA Astrophysics Data System (ADS)
MILES, T. J.; LUCAS, M.; HALLIWELL, N. A.; ROTHBERG, S. J.
1999-09-01
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.
Torsion as electromagnetism and spin
Nikodem J. Poplawski
2010-07-10
We show that it is possible to formulate the classical Einstein-Maxwell-Dirac theory of spinors interacting with the gravitational and electromagnetic fields as the Einstein-Cartan-Kibble-Sciama theory with the Ricci scalar of the traceless torsion, describing gravity, and the torsion trace acting as the electromagnetic potential.
Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M., E-mail: rrr@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States)
2013-06-10
The nature of angular momentum transport in the boundary layers of accretion disks has been one of the central and long-standing issues of accretion disk theory. In this work we demonstrate that acoustic waves excited by supersonic shear in the boundary layer serve as an efficient mechanism of mass, momentum, and energy transport at the interface between the disk and the accreting object. We develop the theory of angular momentum transport by acoustic modes in the boundary layer, and support our findings with three-dimensional hydrodynamical simulations, using an isothermal equation of state. Our first major result is the identification of three types of global modes in the boundary layer. We derive dispersion relations for each of these modes that accurately capture the pattern speeds observed in simulations to within a few percent. Second, we show that angular momentum transport in the boundary layer is intrinsically nonlocal, and is driven by radiation of angular momentum away from the boundary layer into both the star and the disk. The picture of angular momentum transport in the boundary layer by waves that can travel large distances before dissipating and redistributing angular momentum and energy to the disk and star is incompatible with the conventional notion of local transport by turbulent stresses. Our results have important implications for semianalytical models that describe the spectral emission from boundary layers.
A Bound for the Torsion in the K-Theory of Algebraic Integers
Christophe Soule
2003-01-01
Let m be an integer bigger than one, A a ring of algebraic integers, F its fraction field, and Km(A) the m-th Quillen K-group of A. We give a (huge) explicit bound for the order of the torsion subgroup of Km(A) (up to small primes), in terms of m, the degree of F over Q, and its absolute discriminant.
Generalization of Equivalent Crystal Theory to Include Angular Dependence
NASA Technical Reports Server (NTRS)
Ferrante, John; Zypman, Fredy R.
2004-01-01
In the original Equivalent Crystal Theory, each atomic site in the real crystal is assigned an equivalent lattice constant, in general different from the ground state one. This parameter corresponds to a local compression or expansion of the lattice. The basic method considers these volumetric transformations and, in addition, introduces the possibility that the reference lattice is anisotropically distorted. These distortions however, were introduced ad-hoc. In this work, we generalize the original Equivalent Crystal Theory by systematically introducing site-dependent directional distortions of the lattice, whose corresponding distortions account for the dependence of the energy on anisotropic local density variations. This is done in the spirit of the original framework, but including a gradient term in the density. This approach is introduced to correct a deficiency in the original Equivalent Crystal Theory and other semiempirical methods in quantitatively obtaining the correct ratios of the surface energies of low index planes of cubic metals (100), (110), and (111). We develop here the basic framework, and apply it to the calculation of Fe (110) and Fe (111) surface energy formation. The results, compared with first principles calculations, show an improvement over previous semiempirical approaches.
Unexpectedly low angular extent of journal bearing pressures: experiment and theory
NASA Astrophysics Data System (ADS)
Sharma, Nikhil; Vimal, T.; Chatterjee, Anindya
2014-03-01
Journal bearings have been studied for a long time. Pressure solutions for the same, as presented in textbooks, typically have angular extents exceeding 150°. Here, for a bearing with a relatively larger clearance ratio (0.01 as opposed to, say, 0.001), our experiments show an angular extent of about 50° only. Such small angular extents cannot be predicted, even approximately, by the existing simple theories for journal bearing pressures. However, such theories are based on assumptions whereby only the relative speed between bearing and journal surfaces enters the governing equations. We discuss how these same assumptions motivate some new combinations of boundary conditions that allow reasonably simple numerical treatment. In this paper, the resulting families of possible solutions are computed semi-numerically using a Fourier series expansion in one direction and finite differences and numerical continuation in the other. We find that one such solution family contains small-extent solutions similar to those observed experimentally.
Zhou, Yun, E-mail: zhou.yun.x@gmail.com; Pollak, Eli, E-mail: eli.pollak@weizmann.ac.il [Chemical Physics Department, Weizmann Institute of Science, 76100 Rehovot (Israel)] [Chemical Physics Department, Weizmann Institute of Science, 76100 Rehovot (Israel); Miret-Artés, Salvador, E-mail: s.miret@iff.csic.es [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain)] [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain)
2014-01-14
A second order classical perturbation theory is developed and applied to elastic atom corrugated surface scattering. The resulting theory accounts for experimentally observed asymmetry in the final angular distributions. These include qualitative features, such as reduction of the asymmetry in the intensity of the rainbow peaks with increased incidence energy as well as the asymmetry in the location of the rainbow peaks with respect to the specular scattering angle. The theory is especially applicable to “soft” corrugated potentials. Expressions for the angular distribution are derived for the exponential repulsive and Morse potential models. The theory is implemented numerically to a simplified model of the scattering of an Ar atom from a LiF(100) surface.
NASA Astrophysics Data System (ADS)
Zhou, Yun; Pollak, Eli; Miret-Artés, Salvador
2014-01-01
A second order classical perturbation theory is developed and applied to elastic atom corrugated surface scattering. The resulting theory accounts for experimentally observed asymmetry in the final angular distributions. These include qualitative features, such as reduction of the asymmetry in the intensity of the rainbow peaks with increased incidence energy as well as the asymmetry in the location of the rainbow peaks with respect to the specular scattering angle. The theory is especially applicable to "soft" corrugated potentials. Expressions for the angular distribution are derived for the exponential repulsive and Morse potential models. The theory is implemented numerically to a simplified model of the scattering of an Ar atom from a LiF(100) surface.
Torsion and buckling of open sections
NASA Technical Reports Server (NTRS)
Wagner, H; Pretschner, W
1936-01-01
Following an abstract of the well-known theory of torsion in compression, the writers give directions for the practical calculation of the values of C(sub BT) (resistance to flexure and torsion) and i(sub SP(exp 2)), which determine the torsion. The second part treats the experiments in support of the theory of torsion of plain and flanged angle sections.
Dangerous angular Kaluza-Klein/glueball relics in string theory cosmology
Dufaux, J. F. [Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); CITA, University of Toronto, 60 St. George st., Toronto, ON M5S 3H8 (Canada); Kofman, L. [CITA, University of Toronto, 60 St. George st., Toronto, ON M5S 3H8 (Canada); Peloso, M. [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
2008-07-15
The presence of Kaluza-Klein (KK) particles in the universe is a potential manifestation of string theory cosmology. In general, they can be present in the high temperature bath of the early universe. In particular examples, string theory inflation often ends with brane-antibrane annihilation followed by the energy cascading through massive closed string loops to KK modes which then decay into lighter standard model particles. However, massive KK modes in the early universe may become dangerous cosmological relics if the inner manifold contains warped throat(s) with approximate isometries. In the complimentary picture, in the AdS/CFT dual gauge theory with extra isometries, massive glueballs of various spins become the dangerous cosmological relics. The decay of these angular KK modes/glueballs, located around the tip of the throat, is caused by isometry breaking which results from gluing the throat to the compact Calabi-Yau (CY) manifold. We address the problem of these angular KK particles/glueballs, studying their interactions and decay channels, from the theory side, and the resulting cosmological constraints on the warped compactification parameters, from the phenomenology side. The abundance and decay time of the long-lived nonrelativistic angular KK modes depend strongly on the parameters of the warped geometry, so that observational constraints rule out a significant fraction of the parameter space. In particular, the coupling of the angular KK particles can be weaker than gravitational.
Crystal Field Theory and the Angular Overlap Model Applied to Hydrides of Main Group Elements.
ERIC Educational Resources Information Center
Moore, E. A.
1990-01-01
Described is how crystal field theory and the angular overlap model can be applied to very simple molecules which can then be used to introduce such concepts as bonding orbitals, MO diagrams, and Walsh diagrams. The main-group compounds are used as examples and a switch to the transition metal complexes. (KR)
Xiang-Song Chen; Xiao-Fu Lü; Wei-Min Sun; Fan Wang; T. Goldman
2008-06-19
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.
NSDL National Science Digital Library
Powell, Adam C., IV
2003-11-14
Solve the cylindrical Navier-Stokes equations for polymer flow in a torsional viscometer; calculate polymer viscosity from torque; qualitatively evaluate non-Newtonian nature of flow from a second torque data point.
NÃ¶ckelm, Jens
Degenerate Perturbation Theory Describing the Mixing of Orbital Angular Momentum Modes in Fabry orbital angular momentum (OAM) and polarization, but identical transverse order N, will become observably in three-dimensional optical systems have in recent years received attention under the aspect of orbital
Xiangdong Ji
2008-10-27
The individual parts of the total angular momentum operator in interacting theories cannot satisfy the canonical angular momentum commutation rule, including those proposed in the above paper. Furthermore, the operators in the new proposal a) are non-local in general gauge, b) do not have proper Lorentz transformation properties, and c) do not have any known physical measurements.
NASA Astrophysics Data System (ADS)
Feng, Liang; Zeng, Zhi-ge; Wu, Yong-qian
2013-08-01
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 ?.
Nonlinear Hysteretic Torsional Waves
Cabaret, J; Theocharis, G; Andreev, V; Gusev, V E; Tournat, V
2015-01-01
We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities, and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other type of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short term memory as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control de...
Nonlinear Hysteretic Torsional Waves
J. Cabaret; P. Béquin; G. Theocharis; V. Andreev; V. E. Gusev; V. Tournat
2015-01-09
We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities, and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other type of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short term memory as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.
Symmetry broken and restored coupled-cluster theory I. Rotational symmetry and angular momentum
T. Duguet
2014-11-03
We extend coupled-cluster theory performed on top of a Slater determinant breaking rotational symmetry to allow for the exact restoration of the angular momentum at any truncation order. The main objective relates to the description of near-degenerate finite quantum systems with an open-shell character. As such, the newly developed many-body formalism offers a wealth of potential applications and further extensions dedicated to the ab initio description of, e.g., doubly open-shell atomic nuclei and molecule dissociation. The formalism, which encompasses both single-reference coupled cluster theory and projected Hartree-Fock theory as particular cases, permits the computation of usual sets of connected diagrams while consistently incorporating static correlations through the highly non-perturbative restoration of rotational symmetry. Interestingly, the yrast spectroscopy of the system, i.e. the lowest energy associated with each angular momentum, is accessed within a single calculation. A key difficulty presently overcome relates to the necessity to handle generalized energy {\\it and} norm kernels for which naturally terminating coupled-cluster expansions could be eventually obtained. The present work focuses on $SU(2)$ but can be extended to any (locally) compact Lie group and to discrete groups, such as most point groups. In particular, the formalism will be soon generalized to $U(1)$ symmetry associated with particle number conservation. This is relevant to Bogoliubov coupled cluster theory that was recently formulated and applied to singly open-shell nuclei.
NASA Technical Reports Server (NTRS)
Hanson, Donald B.; Parzych, David J.
1993-01-01
This report presents the derivation of a frequency domain theory and working equations for radiation of propeller harmonic noise in the presence of angular inflow. In applying the acoustic analogy, integration over the tangential coordinate of the source region is performed numerically, permitting the equations to be solved without approximation for any degree of angular inflow. Inflow angle is specified in terms of yaw, pitch, and roll angles of the aircraft. Since these can be arbitrarily large, the analysis applies with equal accuracy to propellers and helicopter rotors. For thickness and loading, the derivation is given in complete detail with working equations for near and far field. However, the quadrupole derivation has been carried only far enough to show feasibility of the numerical approach. Explicit formulas are presented for computation of source elements, evaluation of Green's functions, and location of observer points in various visual and retarded coordinate systems. The resulting computer program, called WOBBLE has been written in FORTRAN and follows the notation of this report very closely. The new theory is explored to establish the effects of varying inflow angle on axial and circumferential directivity. Also, parametric studies were performed to evaluate various phenomena outside the capabilities of earlier theories, such as an unsteady thickness effect. Validity of the theory was established by comparison with test data from conventional propellers and Prop Fans in flight and in wind tunnels under a variety of operating conditions and inflow angles.
Symmetry broken and restored coupled-cluster theory: I. Rotational symmetry and angular momentum
NASA Astrophysics Data System (ADS)
Duguet, T.
2015-02-01
We extend coupled-cluster (CC) theory performed on top of a Slater determinant breaking rotational symmetry to allow for the exact restoration of the angular momentum at any truncation order. The main objective relates to the description of near-degenerate finite quantum systems with an open-shell character. As such, the newly developed many-body formalism offers a wealth of potential applications and further extensions dedicated to the ab initio description of, e.g., doubly open-shell atomic nuclei and molecule dissociation. The formalism, which encompasses both single-reference CC theory and projected Hartree–Fock theory as particular cases, permits the computation of usual sets of connected diagrams while consistently incorporating static correlations through the highly non-perturbative restoration of rotational symmetry. Interestingly, the yrast spectroscopy of the system, i.e. the lowest energy associated with each angular momentum, is accessed within a single calculation. A key difficulty presently overcome relates to the necessity to handle generalized energy and norm kernels for which naturally terminating CC expansions could be eventually obtained. The present work focuses on SU(2) but can be extended to any (locally) compact Lie group and to discrete groups, such as most point groups. In particular, the formalism will be soon generalized to U(1) symmetry associated with particle number conservation. This is relevant to Bogoliubov CC theory that was recently applied to singly open-shell nuclei.
Time-dependent theory of angular correlations in sequential double ionization.
Nikolopoulos, L A A
2013-08-30
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 2P(1/2,3/2) leads to quantum beats in the two-electron angular correlation patterns. PMID:24033028
Angular Momentum Evolution of Young Low-Mass Stars and Brown Dwarfs: Observations and Theory
NASA Astrophysics Data System (ADS)
Bouvier, J.; Matt, S. P.; Mohanty, S.; Scholz, A.; Stassun, K. G.; Zanni, C.
This chapter aims at providing the most complete review of both the emerging concepts and the latest observational results regarding the angular momentum evolution of young low-mass stars and brown dwarfs. In the time since Protostars and Planets V (Reipurth et al., 2007) (PPV), there have been major developments in the availability of rotation-period measurements at multiple ages and in different star-forming environments that are essential for testing theory. In parallel, substantial theoretical developments have been carried out in the last few years, including the physics of the star-disk interaction, numerical simulations of stellar winds, and the investigation of angular momentum transport processes in stellar interiors. This chapter reviews both the recent observational and theoretical advances that prompted the development of renewed angular momentum evolution models for cool stars and brown dwarfs. While the main observational trends of the rotational history of low-mass objects seem to be accounted for by these new models, a number of critical open issues remain that are outlined in this review.
R., Arora
2014-01-01
Torsion of greater omentum is one of the rare causes of acute abdominal pain. It can be primary or secondary. Primary Omental Torsion (POT) occurs because a mobile, thicken segment of omentum rotates around a proximal fixed point in the absence of any associated or secondary intra-abdominal pathology. Secondary omental torsion is associated with a number of pre-existing conditions most common among them is inguinal hernia, other causes include tumours, cysts, internal or external herniation, foci of intra-abdominal inflammation and postsurgical wound or scarring. Torsion of omentum causes twisting of omentum along its long axis resulting in impaired blood supply. This rare condition is more predominant in middle-aged males. It clinically mimics acute appendicitis. It should be kept in mind as a differential diagnosis for acute abdomen. Laparoscopy can aid in diagnosis and management but explorative laparotomy is the definitive and therapeutic procedure of choice. However the condition is not life threatening as omentectomy reduces the inflammation and focus of adhesions within the abdomen. PMID:25121029
Arc Hyperbolic sine creep theory applied to torsion-tension member of circular cross section
S. Dharmarajan; O. M. Sidebottom
1963-01-01
A multiaxial creep theory is presented in this paper which will predict the total deformations of a load-carrying member at any specified time after load. Load-deformation relations are derived based on the assumption that the isochronous stress-strain diagram of the material can be represented by an arc hyperbolic sine function [see, eq (2)]. A closed solution was obtained for the
Inverse torsional eigenvalue problems
Willis, C.
1983-06-01
We undertake a numerical and theoretical investigation of the inverse problem for the reconstruction of the density rho and S-wave velocity ..beta.. of the Earth from its torsional oscillations. We assume a spherically symmetric, non-rotating Earth which consists of a perfect elastic, isotropic material and transform the differential equation governing the torsional oscillations to a Sturm-Liouville problem. We present a numerical method for determining rho and ..beta.. in the upper mantle when rho and ..beta.. are smooth functions of radius. The method, based on the Rayleigh-Ritz method, solves iteratively for the coefficients of a generalized Fourier series for the potential. We reconstruct several earth models to 2% accuracy. However, the method is sensitive to error in the data. This is not true of the inversion for the density alone and suggests that the simultaneous inversion for the density and velocity from free oscillation data may be unstable. The smoothness assumption is a serious limitation of our numerical method, since most earth models have a discontinuity at the crust and many have gradients with discontinuities in the upper mantle. We study the associated discontinuous Sturm-Liouville problem and prove that if the eigenfunctions have two discontinuities and if the potential is known in half the interval then the potential in the whole interval is uniquely determined from one spectrum. We apply this theorem to the discontinuous earth model to prove that given rho in the lower mantle and ..beta.. in the mantle and crust, then the torsional spectra of one angular order uniquely determine rho in the upper mantle. In addition, if ..beta.. is known only in the lower mantle, then two torsional spectra uniquely determine both rho and ..beta.. in the upper mantle.
Bigoni, D.; Dal Corso, F.; Misseroni, D.; Bosi, F.
2014-01-01
One edge of an elastic rod is inserted into a friction-less and fitting socket head, whereas the other edge is subjected to a torque, generating a uniform twisting moment. It is theoretically shown and experimentally proved that, although perfectly smooth, the constraint realizes an expulsive axial force on the elastic rod, which amount is independent of the shape of the socket head. The axial force explains why screwdrivers at high torque have the tendency to disengage from screw heads and demonstrates torsional locomotion along a perfectly smooth channel. This new type of locomotion finds direct evidence in the realization of a ‘torsional gun’, capable of transforming torque into propulsive force. PMID:25383038
NASA Astrophysics Data System (ADS)
Brunner, Ilka; Carqueville, Nils; Plencner, Daniel
2015-02-01
Orbifolding two-dimensional quantum field theories by a symmetry group can involve a choice of discrete torsion. We apply the general formalism of `orbifolding defects' to study and elucidate discrete torsion for topological field theories. In the case of Landau-Ginzburg models only the bulk sector had been studied previously, and we re-derive all known results. We also introduce the notion of `projective matrix factorisations', show how they naturally describe boundary and defect sectors, and we further illustrate the efficiency of the defect-based approach by explicitly computing RR charges. Roughly half of our results are not restricted to Landau-Ginzburg models but hold more generally, for any topological field theory. In particular we prove that for a pivotal bicategory, any two objects of its orbifold completion that have the same base are orbifold equivalent. Equivalently, from any orbifold theory (including those based on nonabelian groups) the original unorbifolded theory can be obtained by orbifolding via the `quantum symmetry defect'.
Louis C. Vaz; John M. Alexander
1983-01-01
Fission angular distributions have been studied for years and have been treated as classic examples of trasitions-state theory. Early work involving composite nuclei of relatively low excitation energy E* (<~35 MeV) and spin I (<~25h) gave support to theory and delimited interesting properties of the transitions-state nuclei. More recent research on fusion fission and sequential fission after deeply inelastic reactions
The Relationship Between Dragonfly Wing Structure and Torsional Deformation
Shigeru Sunada; Lijiang Zeng; Keiji Kawachi
1998-01-01
The effect of wing corrugation on torsional deformation was investigated for dragonfly wings. Wing corrugation dramatically increases the warping rigidity, without significantly increasing the torsional rigidity. This behavior implies that the warping moment, which is proportional to the warping rigidity, has a larger resistance against the external moment than does the torsional moment by Saint-Venant's theory, which is proportional to
Bellows joint absorbs torsional deflections in duct system
NASA Technical Reports Server (NTRS)
Daniels, C. M.
1966-01-01
Long, thin-walled bellows compressed into a short length absorbs the same amount of torsional deflection as the same tube in full length condition and saves in cost, complexity and space. This bellows has lower torsional spring rate to absorb the bulk of the duct assembly tortional deflections, leaving the other bellows free to absorb axial and angular deflections.
Chao, Y. A. [Apartment 101, Building 2, 788 Hong Xu Road, Shanghai 201103 (China); Yamamoto, A. [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)
2012-07-01
The current SP{sub n} theory formulation, via either the asymptotic method or the variational method, does not provide an explicit and calculable representation for the corresponding angular flux solution. It is therefore not possible to reconstruct from the SP{sub n} solution the corresponding angular flux solution, or to extract from a reference transport solution the corresponding SP{sub n} solution. This makes it impossible to calculate the necessary surface discontinuity factors to force consistency between the SP{sub n} solution and the higher level transport solution. Without discontinuity factors, the superiority of SP{sub n} over diffusion could be significantly degraded in practical applications. In this paper we present a different SP{sub n} formulation that provides the explicit angular flux solution such that the physical picture for the SP{sub n} approximation is transparent and the SP{sub n} discontinuity factors can be calculated. (authors)
Torsional Elastic Waves in Double Wall Tube
Katanaev, M O
2015-01-01
We describe the double wall tube with cylindrical dislocation in the framework of the geometric theory of defects. The induced metric is found. The dispersion relation is obtained for the propagation of torsional elastic waves in the double wall tube.
A cryogenic torsion pendulum: progress report
M. K. Bantel; R. D. Newman
2000-01-01
A cryogenic torsion pendulum for gravitational experiments is being refined at its remote operation site near Richland, Washington. Features of the apparatus include: four stages of temperature control, an angular readout of the pendulum about three orthogonal axes and a remote operation capability. Currently, we are testing the apparatus with a nominally symmetric pendulum suspended from a 25 µm diameter
Spin and orbital angular momentum in gauge theories (II): QCD and nucleon spin structure
X. S. Chen; X. F. Lü; W. M. Sun; F. Wang; T. Goldman
2007-09-09
Parallel to the construction of gauge invariant spin and orbital angular momentum for QED in paper (I) of this series, we present here an analogous but non-trivial solution for QCD. 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 structure.
Variable stiffness torsion springs
NASA Technical Reports Server (NTRS)
Alhorn, Dean C. (inventor); Polites, Michael E. (inventor)
1995-01-01
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 employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.
Variable stiffness torsion springs
NASA Technical Reports Server (NTRS)
Alhorn, Dean C. (inventor); Polites, Michael E. (inventor)
1994-01-01
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 employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.
Equal-channel-angular processing (ECAP) of materials: Experiment and theory
NASA Astrophysics Data System (ADS)
Stoica, Grigoreta Mihaela
Equal Channel-Angular Processing (ECAP), as a severe plastic deformation of metals and composites, is analyzed both theoretically---to describe the ECAP macromechanics---and experimentally---to obtain ultrafine-grained materials with new thermo-mechanical properties---with a focus on hexagonal-closed-packed (HCP) structures such as Mg alloys. Due to their obvious similarity to ECAP, the slip-line - field theories developed for orthogonal cutting are applied to the ECAP deformation for predicting the shear-strain spatial heterogeneities. A theoretical model for predicting the plastic-deformation zone in an ECAP-ed billet with a free surface is provided, and is validated experimentally. A shear-strain-mapping procedure was developed by decomposing the large deformation process into fine steps, and, by analyzing the partially-deformed billets, the strain maps captured the spatio-temporal evolutions of the ECAP-induced plastic shear strains. This approach was later generalized for studying the local behavior of different material parameters, such as textures (texture mapping). The mechanical testing of the as-received and ECAP-deformed Mg-alloys (ZK60 and AZ31) was performed in monotonic and cyclic tests, for three loading orientations. The ECAP-ed samples demonstrate: (a) a good grain refinement from 50--70 mum down to 2.5--7 mum), (b) a superplastic ZK60 alloy, with an elongation to failure of 371% at 3500C and the strain rate of 10-2 s-1, and (c) a longer fatigue life for the AZ31 alloy, relative to the as-received material. The starting and ECAP-deformed materials were characterized by optical microscopy, X-ray diffraction using both soft and hard X-rays, and neutron diffraction. The grain sizes, the textures, the coherent-domain sizes, the elastic microstrains, and the dislocation densities were determined for the samples deformed by rolling, extrusion, and ECAP. The synchrotron radiation measurements allowed monitoring the lattice rotation induced by the ECAP deformation in Mg alloys. The grain-orientation dependent deformation is studied relative to the deformation history, and its influence on the mechanical behavior is analyzed relative to the twinning contribution. The results of the present work constitute a valuable benchmark for the understanding and modeling of the deformation mechanisms, such as the dislocations slip, twinning, recovery, or recrystallization in HCP structures.
Variable stiffness torsion springs
Dean C. Alhorn; Michael E. Polites
1995-01-01
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 employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their
Variable stiffness torsion springs
Dean C. Alhorn; Michael E. Polites
1994-01-01
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 employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their
Geraldo A. Barbosa
2007-06-06
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.
A bulk micromachined silicon angular rate sensor
Heikki Kuisma; Tapani Ryhanen; Juha Lahdenpera; Eero Punkka; S. Ruotsalainen; T. Sillanpaa; H. Seppa
1997-01-01
We describe an angular rate sensor based on bulk micro-machining of silicon. A silicon beam suspended on two sets of torsion springs has two orthogonal degrees of freedom for angular motion. The Coriolis force induced by external rotation modulates the coupling between the two modes which is then converted to a voltage output by an electro mechanical system operating at
First-principles computational studies of the torsional potential energy surface of the sec-butyl
Wang, Yan Alexander
to investigate the torsional potential energy surface (PES) of the sec- butyl radical. All the wave function words: sec-butyl, torsional potential energy surface, density functional theory, wave function theoryFirst-principles computational studies of the torsional potential energy surface of the sec
Analysis of the HOOO torsional potential
NASA Astrophysics Data System (ADS)
Beames, Joseph M.; Lester, Marsha I.; Murray, Craig; Varner, Mychel E.; Stanton, John F.
2011-01-01
Torsional levels of cis and trans HOOO and DOOO, observed previously via infrared action spectroscopy [E. L. Derro, T. D. Sechler, C. Murray, and M. I. Lester, J. Chem. Phys. 128, 244313 (2008), 10.1063/1.2945872], have been used in conjunction with ab initio theory to obtain a torsional potential energy surface for the hydrotrioxy radical. High level electronic structure calculations based on the equation-of-motion coupled-cluster method for ionized states (EOMIP-CCSD) are utilized to produce a torsional potential. Eigenvalues of the potential are computed by diagonalizing the torsional Hamiltonian in a free-rotor basis. Uniform scaling of the theoretical potential by a factor of 1.35 yields vibrational frequencies in good agreement with the experiment, and allows prediction of the barrier height to isomerization of ˜340 cm-1 and relative stability of trans-HOOO with respect to cis-HOOO of ˜70 cm-1. Examination of the optimized nuclear coordinates with respect to the torsional angle, suggests that the central O-O bond length is strongly coupled to the torsion and is important in determining the relative stabilities of the two conformers. The scaled potential is then used to determine the torsional contribution to the partition function for atmospheric modeling of HOOO.
Multimodality imaging in adnexal torsion.
Patil, Aruna R; Nandikoor, Shrivalli; Rao, Anuradha; M Janardan, Govindarajan; Kheda, AmithaVikrama; Hari, Mahesh; Basappa, Sharana
2015-02-01
Adnexal torsions are one among the causes of acute pelvic pain in females. Commonly occurring adnexal torsions are ovarian either involving the normal ovary with functional cysts or an associated mass. Fallopian tube torsions, torsions involving paraovarian, fimbrial cysts and subserosal fibroids are rare. Here we discuss the multimodality imaging approach for the diagnosis of adnexal torsion, its limitations and mimics. PMID:25528961
Rotating black holes with equal-magnitude angular momenta in d=5 Einstein-Gauss-Bonnet theory
Yves Brihaye; Burkhard Kleihaus; Jutta Kunz; Eugen Radu
2010-10-05
We construct rotating black hole solutions in Einstein-Gauss-Bonnet theory in five spacetime dimensions. These black holes are asymptotically flat, and possess a regular horizon of spherical topology and two equal-magnitude angular momenta associated with two distinct planes of rotation. The action and global charges of the solutions are obtained by using the quasilocal formalism with boundary counterterms generalized for the case of Einstein-Gauss-Bonnet theory. We discuss the general properties of these black holes and study their dependence on the Gauss-Bonnet coupling constant $\\alpha$. We argue that most of the properties of the configurations are not affected by the higher derivative terms. For fixed $\\alpha$ the set of black hole solutions terminates at an extremal black hole with a regular horizon, where the Hawking temperature vanishes and the angular momenta attain their extremal values. The domain of existence of regular black hole solutions is studied. The near horizon geometry of the extremal solutions is determined by employing the entropy function formalism.
The singularity problem for space-times with torsion
Esposito, G
1990-01-01
The problem of a rigorous theory of singularities in space-times with torsion is addressed. We define geodesics as curves whose tangent vector moves by parallel transport. This is different from what other authors have done, because their definition of geodesics only involves the Christoffel connection, though studying theories with torsion. We propose a preliminary definition of singularities which is based on timelike or null geodesic incompleteness, even though for theories with torsion the paths of particles are not geodesics. The study of the geodesic equation for cosmological models with torsion shows that the definition has a physical relevance. It can also be motivated, as done in the literature, remarking that the causal structure of a space-time with torsion does not get changed with respect to general relativity. We then prove how to extend Hawking's singularity theorem without causality assumptions to the space-time of the ECSK theory. This is achieved studying the generalized Raychaudhuri equatio...
Derivation of Einstein-Cartan theory from general relativity
R. J. Petti
2015-04-15
General relativity cannot describe exchange of classical intrinsic angular momentum and orbital angular momentum. Einstein Cartan theory fixes this problem in the least invasive way. In 1986 the author published a derivation of Einstein Cartan theory from general relativity, with no additional assumptions or parameters. The derivation begins with a sequence of arrays of general relativistic solutions that converge to a continuum of matter in which densities of mass, momentum, angular momentum and charge are constants. Starting without torsion, Poincare symmetry, classical or quantum spin or spinors, the continuum limit process derives torsion and its relation to spin. This paper adds more and simpler explanations, more details of the computation of holonomy, refinement of the continuum limit process, discussion of limitations of the derivation, a computer algebra validation of the computations, and discussion of some areas of gravitational research where Einstein Cartan theory is relevant.
Membranes from monopole operators in ABJM theory: Large angular momentum and M-theoretic AdS4/CFT3
NASA Astrophysics Data System (ADS)
Kovacs, Stefano; Sato, Yuki; Shimada, Hidehiko
2014-09-01
We study the duality between M-theory in AdS_4 × S^7/{Z}_k and the ABJM {N}=6 Chern-Simons-matter theory with gauge group U(N) × {U}(N) and level k, taking N large and k of order 1. In this M-theoretic regime the lack of an explicit formulation of M-theory in AdS_4 × S^7/{Z}_k makes the gravity side difficult, while the CFT is strongly coupled and the planar approximation is not applicable. We focus on states on the gravity side with large angular momentum J? 1 associated with a single plane of rotation in S^7 and identify their dual operators in the CFT. We show that natural approximation schemes arise on both sides thanks to the presence of the small parameter 1/J. On the AdS side, we use the matrix model of M-theory on the maximally supersymmetric pp-wave background with matrices of size J/k. A perturbative treatment of this matrix model provides a good approximation to M-theory in AdS_4 × S^7/{Z}_k when N^{1/3}? J? N^{1/2}. On the CFT side, we study the theory on S^2× {R} with magnetic flux J/k. A Born-Oppenheimer-type expansion arises naturally for large J in spite of the theory being strongly coupled. The energy spectra on the two sides agree at leading order. This provides a non-trivial test of the AdS_4/CFT_3 correspondence including near-BPS observables associated with membrane degrees of freedom, thus verifying the duality beyond the previously studied sectors corresponding to either BPS observables or the type IIA string regime.
Torsional waves propagation in an initially stressed dissipative cylinder
M. M. Selim
2009-01-01
The present paper has been framed to show the effect of damping on the propagation of torsional waves in an initially stressed, dissipative, incompressible cylinder of infinite length. A governing equation has been formulated on Biot's incremental deformation theory. The velocities of torsional waves are obtained as complex ones, in which real part gives the phase velocity of propagation and
NASA Astrophysics Data System (ADS)
Vaz, Louis C.; Alexander, John M.
1983-07-01
Fission angular distributions have been studied for years and have been treated as classic examples of trasitions-state theory. Early work involving composite nuclei of relatively low excitation energy E ? (?35 MeV) and spin I (?25?) gave support to theory and delimited interesting properties of the transitions-state nuclei. More recent research on fusion fission and sequential fission after deeply inelastic reactions involves composite nuclei of much higher energies (?200 MeV) and spins (?100?). Extension of the basic ideas developed for low-spin nuclei requires detailed consideration of the role of these high spins and, in particular, the “spin window” for fussion. We have made empirical correlations of cross sections for evaporation residues and fission in order to get a description of this spin window. A systematic reanalysis has been made for fusion fission induced by H, He and heavier ions. Empirical correlations of K 20 (K 20 = {IeffT }/{h?2}) are presented along with comparisons of Ieff to moments of inertia for saddle-point nuclei from the rotating liquid drop model. This model gives an excellent guide for the intermidiate spin zone (30? I ?65), while strong shell and/or pairing effects are evident for excitations less than ?35 MeV. Observations of strong anisotropies for very high-spin systems signal the demise of certain approximation commonly made in the theory, and suggestions are made toward this end.
Xin-zhou Li; Chang-bo Sun; Ping Xi
2009-03-18
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 quasi-periodic solutions near the focus for the coupled nonlinear equations.
Meana-Pañeda, Rubén; Fernández-Ramos, Antonio, E-mail: qf.ramos@usc.es [Department of Physical Chemistry and Center for Research in Biological Chemistry and Molecular Materials, University of Santiago de Compostela, 15706 Santiago de Compostela (Spain)] [Department of Physical Chemistry and Center for Research in Biological Chemistry and Molecular Materials, University of Santiago de Compostela, 15706 Santiago de Compostela (Spain)
2014-05-07
This work reports a detailed theoretical study of the hydrogen abstraction reactions from ethanol by atomic hydrogen. The calculated thermal rate constants take into account torsional anharmonicity and conformational flexibility, in addition to the variational and tunneling effects. Specifically, the kinetics calculations were performed by using multi-path canonical variational transition state theory with least-action path tunneling corrections, to which we have added the two-dimensional non-separable method to take into account torsional anharmonicity. The multi-path thermal rate constant is expressed as a sum over conformational reaction channels. Each of these channels includes all the transition states that can be reached by internal rotations. The results show that, in the interval of temperatures between 250 and 2500 K, the account for multiple paths leads to higher thermal rate constants with respect to the single path approach, mainly at low and at high temperatures. In addition, torsional anharmonicity enhances the slope of the Arrhenius plot in this range of temperatures. Finally, we show that the incorporation of tunneling into the hydrogen abstraction reactions substantially changes the contribution of each of the transition states to the conformational reaction channel.
Bassan, Massimo; Marconi, Lorenzo; Pucacco, Giuseppe; Stanga, Ruggero; Visco, Massimo
2013-01-01
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.
Massimo Bassan; Fabrizio De Marchi; Lorenzo Marconi; Giuseppe Pucacco; Ruggero Stanga; Massimo Visco
2013-05-30
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.
The dynamics and excitation of torsional waves in geodynamo simulations
Teed, Robert J; Tobias, Steven M
2013-01-01
The predominant force balance in rapidly rotating planetary cores is between Coriolis, pressure, buoyancy and Lorentz forces. This magnetostrophic balance leads to a Taylor state where the spatially averaged azimuthal Lorentz force is compelled to vanish on cylinders aligned with the rotation axis. Any deviation from this state leads to a torsional oscillation, signatures of which have been observed in the Earth's secular variation and are thought to influence length of day variations via angular momentum conservation. In order to investigate the dynamics of torsional oscillations, we perform several three-dimensional dynamo simulations in a spherical shell. We find torsional oscillations, identified by their propagation at the correct Alfv\\'{e}n speed, in many of our simulations. We find that the frequency, location and direction of propagation of the waves are influenced by the choice of parameters. Torsional waves are observed within the tangent cylinder and also have the ability to pass through it. Severa...
Li, Zhi; Durgin, Frank H
2012-01-01
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. PMID:22792434
Li, Zhi; Durgin, Frank H
2012-01-01
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. PMID:22792434
Two-step spacetime deformation induced dynamical torsion
G Ter-Kazarian
2011-02-12
We extend the geometrical ideas of the spacetime deformations to study the physical foundation of the post-Riemannian geometry. To this aim, we construct the theory of 'two-step spacetime deformation' as a guiding principle. We address the theory of teleparallel gravity and construct a consistent Einstein-Cartan (EC) theory with the 'dynamical torsion'. We show that the equations of the standard EC theory, in which the equation defining torsion is the algebraic type and, in fact, no propagation of torsion is allowed, can be equivalently replaced by the set of 'modified EC equations' in which the torsion, in general, is dynamical. The special physical constraint imposed upon the spacetime deformations yields the short-range propagating spin-spin interaction.
Derivation of Einstein-Cartan theory from general relativity
R. J. Petti
2015-03-30
General relativity cannot describe exchange of classical intrinsic angular momentum and orbital angular momentum. Einstein Cartan theory fixes this problem in the least invasive way. In 1986 the author published a derivation of Einstein Cartan theory from general relativity, with no additional assumptions or parameters. Starting without torsion, Poincare symmetry, classical or quantum spin or spinors, it derives torsion and its relation to spin from a continuum limit of general relativistic solutions. This paper adds more and simpler explanations, more details of the computation of holonomy, refinement of the continuum limit process, discussion of limitations of the derivation, a computer algebra validation of the computations, and discussion of some areas of gravitational research where Einstein Cartan theory is relevant.
NASA Technical Reports Server (NTRS)
Mattson, D. L.
1975-01-01
The effect of prolonged angular acceleration on choice reaction time to an accelerating visual stimulus was investigated, with 10 commercial airline pilots serving as subjects. The pattern of reaction times during and following acceleration was compared with the pattern of velocity estimates reported during identical trials. Both reaction times and velocity estimates increased at the onset of acceleration, declined prior to the termination of acceleration, and showed an aftereffect. These results are inconsistent with the torsion-pendulum theory of semicircular canal function and suggest that the vestibular adaptation is of central origin.
Precision Tilt Measurement for Torsion
Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group
torques #12;Torsion Balances: An Introduction Test fundamental physics at macroscopic scale We get much a torsion balance Composition dipole test mass for equivalence principle (to test universality of freefallPrecision Tilt Measurement for Torsion Balance Experiments Scott Yantek California Institute
NASA Astrophysics Data System (ADS)
Meibom, S.; Barnes, S. A.; Covey, K.; Jeffries, R. D.; Matt, S.; Morin, J.; Palacios, A.; Reiners, A.; Sicilia-Aguilar, A.; Irwin, J.
2013-02-01
The coexistence of fast and slowly rotating cool stars in ZAMS clusters - forming distinct sequences in the color vs. rotation period plane - is providing clues to differences in their pre main-sequence angular momentum evolution. This Cool Stars 17 splinter was dedicated to a discussion of new observational and theoretical results that may help discriminate between proposed mechanisms for early angular momentum regulation and help us explain the observed ZAMS dichotomy.
NASA Technical Reports Server (NTRS)
Ihrke, Chris A. (Inventor); Parsons, Adam H. (Inventor); Mehling, Joshua S. (Inventor); Griffith, Bryan Kristian (Inventor)
2012-01-01
A torsion spring comprises an inner mounting segment. An outer mounting segment is located concentrically around the inner mounting segment. A plurality of splines extends from the inner mounting segment to the outer mounting segment. At least a portion of each spline extends generally annularly around the inner mounting segment.
Metric-Torsional Conformal Gravity
Luca Fabbri
2014-04-10
When in general geometric backgrounds the metric is accompanied by torsion, the metric conformal properties should correspondingly be followed by analogous torsional conformal properties; however a combined metric torsional conformal structure has never been found which provides a curvature that is both containing metric-torsional degree of freedom and conformally invariant: in this paper we construct such a metric-torsional conformal curvature. We proceed by building the most general action, then deriving the most general system of field equations; we check their consistency by showing that both conservation laws and trace condition are verified. Final considerations and comments are outlined.
Tarim, Ebru; Ulusan, Serife; Kilicdag, Esra; Yildirim, Tulin; Bagis, Tayfun; Kuscu, Esra
2004-10-01
Angular pregnancy, a type of cornual pregnancy, is a rare obstetric complication that can be life-threatening. In this situation, the embryo is implanted in the lateral angle of the uterine cavity, medial to the uterotubal junction and round ligament. Angular pregnancy must be distinguished from interstitial pregnancy, in which the embryo is implanted lateral to the round ligament. The report presented here describes a case of angular pregnancy that was diagnosed by endovaginal ultrasonography and magnetic resonance imaging. Laparoscopy can be useful for guiding dilatation and curettage in angular pregnancies, and may circumvent the need for invasive surgery or hysterectomy. PMID:15327452
Torsional-flexural waves in thin-walled open beams
P. Muller
1983-01-01
A one-dimensional theory is developed for coupled torsional-flexural waves in thin-walled elastic beams of arbitrary open cross-section. Complex kinematical effects are fully taken into account with an emphasis on consistency. Exact equations of motion are obtained in terms of generalized stresses and generalized displacements defined by an averaging procedure. Constitutive relations accounting for flexural-torsional couplings are proposed. They include and
Torsional fatigue of aramid fibers
Kawabata, S. [Kyoto Univ. (Japan). Dept. of Polymer Chemistry; Sera, M.
1993-12-31
An experimental investigation on the shear fatigue process of aramid fibers is presented. Repeated cycles of the torsional deformation are applied on the aramid single fiber and the reduction of the shear modulus of the fiber with an increasing number of the cycles is observed for different strain amplitudes. It has been found that the reduction process of the shear modulus with an increasing number of the repeated cycles depends on the strain amplitude and the effect of the number of cycles is equivalent to that of the strain amplitude on the modulus reduction and they may be superposed like the time-temperature equivalence superposition observed in the viscoelasticity of amorphous polymeric solids. From this relation, the life prediction for the long term use of aramid fibers becomes possible by using this superimposed relation. A simple rate process theory is applied to interpret this fatigue process and to derive the equation for predicting the life cycle number of the loading.
Clark, G
2003-04-28
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.
Constraining spacetime torsion with the Moon and Mercury
Riccardo March; Giovanni Bellettini; Roberto Tauraso; Simone Dell'Agnello
2011-03-28
We report a search for new gravitational physics phenomena based on Einstein-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 describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general may differ from geodesics when torsion is present. We derive the equations of motion of a test body in a spherically symmetric field, and the equations of motion of a satellite in the gravitational field of the Sun and the Earth. 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 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.
NASA Technical Reports Server (NTRS)
Devries, P. L.; George, T. F.
1978-01-01
The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.
Torsional Ratcheting Actuating System
BARNES,STEPHEN MATTHEW; MILLER,SAMUEL L.; RODGERS,M. STEVEN; BITSIE,FERNANDO
2000-01-24
A new type of surface micromachined ratcheting actuation system has been developed at the Microelectronics Development Laboratory at Sandia National Laboratories. The actuator uses a torsional electrostatic comb drive that is coupled to an external ring gear through a ratcheting scheme. The actuator can be operated with a single square wave, has minimal rubbing surfaces, maximizes comb finger density, and can be used for open-loop position control. The prototypes function as intended with a minimum demonstrated operating voltage of 18V. The equations of motion are developed for the torsional electrostatic comb drive. The resonant frequency, voltage vs. displacement and force delivery characteristics are predicted and compared with the fabricated device's performance.
Torsion as a dynamic degree of freedom of quantum gravity
Sang-Woo Kim; D. G. Pak
2008-03-05
The gauge approach to gravity based on the local Lorentz group with a general independent affine connection A_{\\mu cd} is developed. We consider SO(1,3) gauge theory with a Lagrangian quadratic in curvature as a simple model of quantum gravity. The torsion is proposed to represent a dynamic degree of freedom of quantum gravity at scales above the Planckian energy. The Einstein-Hilbert theory is induced as an effective theory due to quantum corrections of torsion via generating a stable gravito-magnetic condensate. We conjecture that torsion possesses an intrinsic quantum nature and can be confined. A minimal Abelian projection for the Lorentz gauge model has been constructed, and an effective theory of the cosmic knot at the Planckian scale is proposed.
Torsional surface waves in a gradient-elastic half-space
H. G. Georgiadis; I. Vardoulakis; G. Lykotrafitis
2000-01-01
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
Development of Torsional and Linear Piezoelectrically Driven Motors
NASA Technical Reports Server (NTRS)
Duong, Khanh; Newton, David; Garcia, Ephrahim
1996-01-01
The development of rotary and linear inchworm-motors using piezoelectric actuators is presented. The motors' design has the advantage of a macro and micro stepper motor with high load and speed. The torsional design is capable of fast angular positioning with micro level accuracy. Additionally, the rotary motor, as designed, can be used as a clutch/brake mechanism. Constructed prototype motors of both types along with their characteristics are presented. The torsional motor consists of a torsional section that provides angular displacement and torque, and two alternating clamping sections which provide the holding force. The motor relies on the principal piezoelectric coupling coefficient (d33) with no torsional elements, increasing its torque capability. The linear motor consists of a longitudinal vibrator that provides displacement and load, and two alternating clamping sections which provide the holding force. This design eliminates bending moment, tension and shear applied to the actuator elements, increase its load capability and life. Innovative flexure designs have been introduced for both motor types. Critical issues that affect the design and performance of the motors are explored and discussed. Experiments are performed demonstrating the motor prototypes based on the aforementioned design considerations.
Torsional nystagmus in hypothalamic hamartoma.
Shaikh, Aasef G
2013-12-01
Torsional nystagmus was noted in a patient with hypothalamic hamartoma. Magnetic resonance imaging revealed an exophytic hypothalamic mass extending into the pre-pontine cistern and abutting ventral mesencephalon. The quickphase of the torsional nystagmus was directed towards the left side, ipsilateral to the side of compression by the hamartoma. Ipsi-lesionally directed pure torsional nystagmus in this case is attributed to the compressive lesion of ocular motor structures responsible for the neural integration of torsional and vertical eye movements, the interstitial nucleus of Cajal. [Published with video sequences]. PMID:24169305
ORIGINAL ARTICLE Torsional Anomalous Retinal Correspondence
Peli, Eli
anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional documented torsional strabismus and torsional HARC. Methods. Monocular visual fields under binocular fixation strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared
ERIC Educational Resources Information Center
Parker, G. W.
1978-01-01
Discusses, classically and quantum mechanically, the angular momentum induced in the bound motion of an electron by an external magnetic field. Calculates the current density and its magnetic moment, and then uses two methods to solve the first-order perturbation theory equation for the required eigenfunction. (Author/GA)
Neutral-meson oscillations with torsion
Nikodem J. Poplawski
2011-04-30
We propose a simple mechanism that may explain the observed particle-antiparticle asymmetry in the Universe. In the Einstein-Cartan-Sciama-Kibble theory of gravity, the intrinsic spin of matter generates spacetime torsion. Classical Dirac fields in the presence of torsion obey the nonlinear Hehl-Datta equation which is asymmetric under a charge-conjugation transformation. Accordingly, at extremely high densities that existed in the very early Universe, fermions have higher effective masses than antifermions. As a result, a meson composed of a light quark and a heavy antiquark has a lower effective mass than its antiparticle. Neutral-meson oscillations in thermal equilibrium therefore favor the production of light quarks and heavy antiquarks, which may be related to baryogenesis.
Neutral-meson oscillations with torsion
Poplawski, Nikodem J
2011-01-01
We propose a simple mechanism that may explain the observed particle-antiparticle asymmetry in the Universe. In the Einstein-Cartan-Sciama-Kibble theory of gravity, the intrinsic spin of matter generates spacetime torsion. Classical Dirac fields in the presence of torsion obey the nonlinear Hehl-Datta equation which is asymmetric under a charge-conjugation transformation. Accordingly, at extremely high densities that existed in the very early Universe, fermions have higher effective masses than antifermions. As a result, a meson composed of a light quark and a heavy antiquark has a lower effective mass than its antiparticle. Neutral-meson oscillations in thermal equilibrium therefore favor the production of light quarks and heavy antiquarks, which may be related to baryogenesis.
Orbital angular momentum in phase space
I. Rigas; L. L. Sanchez-Soto; A. B. Klimov; J. Rehacek; Z. Hradil
2010-11-29
A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.
NASA Technical Reports Server (NTRS)
Bradas, James C.; Fennelly, Alphonsus J.; Smalley, Larry L.
1987-01-01
It is shown 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 (1982, 1983). 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.
Testicular torsion: A surgical emergency
Prater, J.M.; Overdorf, B.S. (Surgical Residency Program at Yale University, New Haven, CT (USA))
1991-09-01
Testicular torsion is caused by twisting of the spermatic cord, which results in compromised testicular blood flow. The degree of ischemic injury is determined by the severity of arterial compression and the interval between the onset of symptoms and surgical intervention. Torsion usually occurs at puberty, and an anatomic defect known as bell-clapper deformity is usually present. Typical symptoms include acute scrotal pain with associated nausea and vomiting. Up to one-half of patients report previous similar episodes. On examination, the testis is high-riding, tender, swollen and firm. Testicular scan or Doppler ultrasound examination can be helpful in distinguishing torsion from acute epididymitis. Prompt surgical treatment is indicated to reduce the torsion, and bilateral orchiopexy is performed to prevent recurrence. Exocrine function, as determined by semen analysis, is often abnormal after unilateral torsion. 25 references.
A Study on the Torsional Wave of Fiber-reinforced Composite Materials
L. Bao; H. Yuan; M. Sakurai; M. Nakazawa; K. Kemmochi
2006-01-01
The impact characteristics of FRP are important for structures and other applications. In this article, a CFRP pole is used to study the effect of fiber orientation on the torsional strain wave rate. A method of forecasting torsional strain wave characteristic is subsequently suggested. An experiment is conducted to verify the theory and the calculation method. Good agreement is obtained
NASA Technical Reports Server (NTRS)
Stang, Ambrose H; Ramberg, Walter; Back, Goldie
1937-01-01
This report presents the results of tests of 63 chromium-molybdenum steel tubes and 102 17st aluminum-alloy tubes of various sizes and lengths made to study the dependence of the torsional strength on both the dimensions of the tube and the physical properties of the tube material. Three types of failure are found to be important for sizes of tubes frequently used in aircraft construction: (1) failure by plastic shear, in which the tube material reached its yield strength before the critical torque was reached; (2) failure by elastic two-lobe buckling, which depended only on the elastic properties of the tube material and the dimensions of the tube; and (3) failure by a combination of (1) and (2) that is, by buckling taking place after some yielding of the tube material.
Torsional oscillations in dynamo simulations
NASA Astrophysics Data System (ADS)
Wicht, Johannes; Christensen, Ulrich R.
2010-06-01
Cylinders aligned with the planetary rotation axis have a special significance in the dynamics of planetary dynamo regions. The azimuthal Lorentz forces on these geostrophic cylinders is expected to cancel to a large degree, establishing the so-called Taylor state. Deviations from this state take the form of torsional oscillations (TOs) that are supposed to represent important fast flow variations. These oscillations have reportedly been identified in the secular variation signal from the top of Earth's core. We have performed several dynamo simulations at different parameters to check whether Taylor state and TOs can also be identified in a numerical model. Taylor states are approached when viscous effects are small at Ekman numbers of E = 3 × 10-5 or below and Reynolds stresses are kept low by choosing moderate Rayleigh numbers. One-dimensional magnetic Alfvén waves that travel towards the boundaries then become prominent in the motion of the geostrophic cylinders. These waves obey the TO theory but are also damped and modified by other effects. For example, fast variations of likely convective origin remain important in all our simulations. Reynolds stresses may play a more sizable role for the dynamics in Earth's dynamo region than commonly assumed. They may also contribute to the motions of geostrophic cylinders and severely reduce the significance of TOs for the fast core dynamics. The amplitude of TOs amounts to not more than a few percent of the total flow amplitude in the simulations, which renders these motions insignificant for the long-term dynamo process.
A minimal model of Lorentz gauge gravity with dynamical torsion
Y. M. Cho; D. G. Pak; B. S. Park
2010-06-23
A new Lorentz gauge gravity model with R^2-type Lagrangian is proposed. In the absence of classical torsion the model admits a topological phase with an arbitrary metric. We analyze the equations of motion in constant curvature space-time background using the Lagrange formalism and demonstrate that the model possesses a minimal set of dynamic degrees of freedom for the torsion. Surprisingly, the number of torsion dynamic degrees of freedom equals the number of physical degrees of freedom for the metric tensor. An interesting feature of the model is that the spin two mode of torsion becomes dynamical essentially due to the non-linear structure of the theory. We perform covariant one-loop quantization of the model for a special case of constant curvature space-time background. We treat the contortion as a quantum field variable whereas the metric tensor is kept as a classical object. We discuss a possible mechanism of an emergent Einstein gravity as a part of the effective theory induced due to quantum dynamics of torsion.
Transverse angular momentum of photons
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
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.
Kantowski-Sachs cosmological solution with torsion
NASA Astrophysics Data System (ADS)
Lorenz, D.
1982-09-01
An exact stiff matter solution with torsion of the Kantowski-Sachs models to the Einstein-Cartan theory of gravitation (ECT) in the presence of a magnetic field is constructed. The models are found to be geodesically incomplete both to the past and the future. Comparisons with the situation where no magnetic field exists shows that the field acts as a tension along its own direction. The ratio of the energy density of the field to the energy density of matter approaches zero at both singularities in the magnetic ECT model.
Constraining spacetime torsion with LAGEOS
Riccardo March; Giovanni Bellettini; Roberto Tauraso; Simone Dell'Agnello
2011-07-12
We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We derive the equations of motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB) complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters.
NASA Astrophysics Data System (ADS)
Cavinato, M.; Marangoni, M.; Saruis, A. M.
1984-06-01
The (?, p), (?, n) and inverse capture reactions in 12C, 16O and 40Ca below pion threshold have been analysed in the frame of a self-consistent RPA theory with a Skyrme force (Sk3). E1 and E2 transitions in LWA are present in the calculation. Thereby, EC linked by gauge invariance to the effective interaction are included in the predicted cross sections. Through an overall comparison with the available experimental data, we attain, in the present context, a good fit of data up to 80 MeV. The observed symmetric behaviour of (?, p) and (?, n) angular distributions is well reproduced. The rôle of nuclear correlations on the action of EC by gauge invariance is discussed.
A torsional wave model for solar radio pulsations
K. F. Tapping
1983-01-01
One of the widely accepted models for solar radio pulsations invokes radial oscillations of a magnetic flux tube. Due to acoustic, radiative damping, this theory does not easily explain the long length of the pulse trains, the large modulation depths or the great stability of the pulse repetition rate often observed. Torsional waves efficiently modulate synchrotron emission, and since they
Web flexibility and I-beam torsional oscillation
NASA Astrophysics Data System (ADS)
Stephen, N. G.; Wang, P. J.
1986-08-01
Two recent theories on torsional oscillation of general doubly-symmetric non-circular cross-section beams incorporate a second order effect, that of in-plane shear deformation involving a change in cross-sectional shape, and are found to give excellent agreement with exact results for an elliptical section rod. For "technical" torsional oscillation theories of I-section beams this in-plane shear has previously been considered within the flanges only; in the present work the greater effect of shear distortion of the web is included, having previously been considered only in static analysis. The theory predicts three modes of wave propagation, one of which is essentially torsional in character; a second mode may be identified with predominatly flange bending according to the second branch of Timoshenko beam theory whilst a new mode involves individual flange torsion with asymmetric web deformation, and has the lowest phase velocity except at the longest wavelength. An alternative symmetric web deformation is also considered.
Torsional osteotomies of the femur.
Dickschas, Jörg; Harrer, Jörg; Reuter, Benoit; Schwitulla, Judith; Strecker, Wolf
2015-03-01
Various pathologies of the hip or knee, such as patellofemoral malalignment or femoroacetabular impingement may be caused by a femoral torsional deformity. When diagnosed and analyzed, it is treated by femoral torsional osteotomy. Thirty femoral torsional osteotomies in 25 patients were included, the principal symptoms were patellar dislocation in 15 patients, anterior knee pain in 17, and femoroacetabular impingement in two. A computed-tomography-based measurement of the torsional angle was performed in all patients. Japanese Knee Society score, Tegner activity score, Lysholm score, and visual analog scale score were determined before surgery and at follow-up after 41 (6-113) months. Femoral internal torsion was on average 40.9° (29°?-?66°; normal 24°). Surgical treatment consisted of a femoral external torsional osteotomy of on average 13.8° (5°?-?26°). Tegner activity score increased non-significantly (p-value 0.326) from 3.57 to 3.71. Japanese Knee Society score improved significantly from 72 to 87 (p-value 0.004) while Lysholm score rose significantly from 66 to 84 points (p-value 0.004). Pain relief was demonstrated by a significant decrease in the VAS score from 5.6 to 2.4 (p-value 0.007). No further patellar dislocation was reported. Torsional deformities of the femur frequently cause symptoms in the knee or hip joint. After thorough assessment and diagnostic investigation, a femoral external torsional osteotomy provides significant pain relief as well as patellofemoral stability. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:???-???, 2015. PMID:25399673
NSDL National Science Digital Library
Students will learn about the Transit of Venus through reading a NASA press release and viewing a NASA eClips video that describes several ways to observe transits. Then students will study angular measurement by learning about parallax and how astronomers use this geometric effect to determine the distance to Venus during a Transit of Venus. This activity is part of the Space Math multimedia modules that integrate NASA press releases, NASA archival video, and mathematics problems targeted at specific math standards commonly encountered in middle school textbooks. The modules cover specific math topics at multiple levels of difficulty with real-world data and use the 5E instructional sequence.
NASA Astrophysics Data System (ADS)
Shakur, Asif; Sinatra, Taylor
2013-12-01
The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in the physics laboratory. Many traditional physics experiments can now be performed very conveniently in a pedagogically enlightening environment while simultaneously reducing the laboratory budget substantially by using student-owned smartphones.
On the interpretation of combined torsion and tension tests of thin-wall tubes
NASA Technical Reports Server (NTRS)
Prager, W
1948-01-01
General ways of testing thin-wall tubes under combined tension and torsion as a means of checking the various theories of plasticity are discussed. Suggestions also are given for the interpretation of the tests.
Effective fourth order torsion-rotation Hamiltonian parameters of C-13 methanol
Indranath Mukhopadhyay; Kuniaki Nakagawa
1997-01-01
In this work, the effective fourth order Hamiltonian parameters of 13C substituted methanol were determined using microwave (MW), millimeterwave (MMW) and Fourier transform far-infrared (FIR) assigned transitions in the ground and first excited torsional states. The data set consisted of 1060 transitions with the rotational angular momentum J < 13 (with 416 FIR lines). The data set was fitted with
Spectral broadening and diffusion by torsional motion in biphenyl
NASA Astrophysics Data System (ADS)
Beenken, Wichard J. D.; Lischka, Hans
2005-10-01
We have studied biphenyl by time-dependent density-functional theory. In particular, we have analyzed the dependence of singlet excitation energies and transition dipoles on the torsional angle between the phenyl groups. The torsional spectrum has been computed quantum mechanically as well as semiclassically in order to understand how this influences the broadening of absorption and luminescence spectra. Our results are in best agreement with supersonic jet spectroscopy data, but also fit astonishingly well to spectra of biphenyl in condensed phase. Furthermore, we compare the torsional and vibrational relaxation and discuss qualitatively the general consequences for poly-para-phenylenes and related conjugated polymers as poly-thiophenes, considering, in particular, how side chains and solvents may affect the optical spectra.
Spectral broadening and diffusion by torsional motion in biphenyl.
Beenken, Wichard J D; Lischka, Hans
2005-10-01
We have studied biphenyl by time-dependent density-functional theory. In particular, we have analyzed the dependence of singlet excitation energies and transition dipoles on the torsional angle between the phenyl groups. The torsional spectrum has been computed quantum mechanically as well as semiclassically in order to understand how this influences the broadening of absorption and luminescence spectra. Our results are in best agreement with supersonic jet spectroscopy data, but also fit astonishingly well to spectra of biphenyl in condensed phase. Furthermore, we compare the torsional and vibrational relaxation and discuss qualitatively the general consequences for poly-para-phenylenes and related conjugated polymers as poly-thiophenes, considering, in particular, how side chains and solvents may affect the optical spectra. PMID:16238395
Torsional waves propagation in an initially stressed dissipative cylinder
M. M. Selim
2009-03-28
The present paper has been framed to show the effect of damping on the propagation of torsional waves in an initially stressed, dissipative, incompressible cylinder of infinite length. A governing equation has been formulated on Biot's incremental deformation theory. The velocities of torsional waves are obtained as complex ones, in which real part gives the phase velocity of propagation and corresponding imaginary part gives the damping. The study reveals that the damping of the medium has strong effect in the propagation of torsional wave. Since every medium has damping so it is more realistic to use the damped wave equation instead of the undamped wave equation. The study also shows that the velocity of propagation of such waves depend on the presence of initial stress. The influences of damping and initial stresses are shown separately.
Spin and torsion in the very early universe
NASA Astrophysics Data System (ADS)
Bäuerle, G. G. A.; Haneveld, Chr. J.
1983-09-01
In the very early universe with temperature T between 1024 K and 1032 K the gravitational effect of torsion is dominant if particles with spin are sufficiently polarized. The source of the torsion is the spin density and the latter is usually described by a classical theory of Weyssenhoff and Raabe. In this article the spinning particles are described quantum mechanically, i.e. with a Dirac field and the spin density is defined as the source of the torsion. The macroscopic average of the spin density is obtained by the relativistic Wigner function formalism. The expression of the spin density, as derived in this article, is different from the classical one, except when both are zero.
Simple torsion test for shear moduli determination of orthotropic composites
NASA Technical Reports Server (NTRS)
Sumsion, H. T.; Rajapakse, Y. D. S.
1978-01-01
By means of torsion tests performed on test specimens of the same material having a minimum of two different cross sections (flat sheet of different widths), the effective in-plane (G13) and out-of-plane (G23) shear moduli were determined for two composite materials of uniaxial and angleply fiber orientations. Test specimens were 16 plies (nominal 2 mm) thick, 100 mm in length, and in widths of 6.3, 9.5, 12.5, and 15.8 mm. Torsion tests were run under controlled deflection (constant angle of twist) using an electrohydraulic servocontrolled test system. In-plane and out-of-plane shear moduli were calculated from an equation derived in the theory of elasticity which relates applied torque, the torsional angle of twist, the specimen width/thickness ratio, and the ratio of the two shear moduli G13/G23. Results demonstrate that torsional shear moduli, G23 as well as G13, can be determined by simple torsion tests of flat specimens of rectangular cross section. Neither the uniaxial nor angleply composite material were transversely isotropic.
Shuyu, Lin
2002-08-01
Based on the classical torsional and flexural vibrational theory of a slender rod, the prestressed sandwich torsional-flexural composite mode piezoelectric ceramic ultrasonic transducer is studied. This type of transducer consists of the slender metal rods and the longitudinally and tangentially polarized piezoelectric ceramic rings. The resonance frequency equations for the torsional and flexural vibrations in the transducers are derived. The simultaneous resonance of the torsional and flexural vibrations in the transducer is acquired by correcting the length of the metal slender rods resulting from the piezoelectric ceramic elements. The experimental results show that the measured resonance frequencies of the transducers are in good agreement with the computed ones, and the measured resonance frequencies of the torsional and the flexural vibrations in the composite transducers are also in good agreement with each other. PMID:12186032
SPECIAL NATURE OF ORBITAL ANGULAR MOMENTUM
James D. Louck
1963-01-01
The properties of orbital angular momentam operators are examined within ; the framework of the formal theory of angular momentum. It is demonstrated that ; the occurrence of only integral quantum numbers in the orbital theory is a ; consequence of the particular form of the orbital operators. Single-valuedness ; of the eigenfunctions need not be postulated. (auth);
Torsional instability of chiral carbon nanotubes
Dresselhaus, Mildred
In this work we investigate the presence of a torsional instability in single-wall carbon nanotubes which causes small diameter chiral carbon nanotubes to show natural torsion. To obtain insight into the nature of this ...
Torsional carbon nanotube artificial muscles.
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
2011-10-28
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
[Torsion of the appendix testis].
Chou, Y H; Chan, H K; Huang, C N; Huang, C H
1999-06-01
The differential diagnosis of an acute scrotum includes spermatic cord torsion, torsion of a testicular appendage, torsion of spermatocele, epididymitis, orchitis, trauma, hernia, testicular segmental infraction and tumor. Among these, torsion of appendix testis could got dramatic improvement if accurately diagnosed and treated. 5 patients of torsion of appendix testis have been identified in our hospital in the recent 5 years. Ages ranged from 9 to 13 years old (mean age 11). The lesions were on the right side in 2 cases and left side in 3 cases. Duration of scrotal pain ranged from 2 to 7 days (mean of 4 days). The urine analyses were normal in all cases. The white blood counts were all within normal limits with mean of 5.72 x 10(3)/ul. No abnormality in passing urine or other infectious sign could be detected. Doppler ultrasonography or nuclear medicine testicular scan were performed selectively due to clinical availability. The result was equivocal and did not support a definite diagnosis. All 5 cases received surgical treatment. The necrotic testicular appendix was excised and reactive hydrocele treated. All the patients were discharged from the hospital the day after operation and recovered quickly. The pathological report revealed congestion and extensive hemorrhagic necrosis of the testicular appendix. Advances in technology have been helpful in improving the accuracy of diagnosis but technology is not infallible and an over reliance on it can also result in misdiagnosis. Various reports supporting the use of scrotal ultrasound in evaluating cases of acute scrotum pain. Ultrasonography has definitely helped in detecting scrotal pathology but its limitations need to be appreciated. Because of the difficulty of making an accurate diagnosis in acute scrotum, misdiagnosis and delayed operation offer result in disappointment of testis salvage rates. We have supported a policy of early scrotal exploration in any case suspicious of torsion of appendix testis. PMID:10441939
Siklos waves with torsion in 3D
Blagojevi?, M
2014-01-01
Starting from the Siklos waves in general relativity with a cosmological constant, interpreted as gravitational waves on the anti-de Sitter background, a new class of exact torsion waves is constructed in the framework of three-dimensional gravity with propagating torsion. In the asymptotic limit, the geometry of torsion waves takes the anti-de Sitter form. In the sector with massless torsion modes, we found a set of asymptotic conditions that leads to the conformal asymptotic symmetry.
Siklos waves with torsion in 3D
M. Blagojevi?; B. Cvetkovi?
2014-12-05
Starting from the Siklos waves in general relativity with a cosmological constant, interpreted as gravitational waves on the anti-de Sitter background, a new class of exact torsion waves is constructed in the framework of three-dimensional gravity with propagating torsion. In the asymptotic limit, the geometry of torsion waves takes the anti-de Sitter form. In the sector with massless torsion modes, we found a set of asymptotic conditions that leads to the conformal asymptotic symmetry.
Siklos waves with torsion in 3D
NASA Astrophysics Data System (ADS)
Blagojevi?, M.; Cvetkovi?, B.
2014-11-01
Starting from the Siklos waves in general relativity with a cosmological constant, interpreted as gravitational waves on the anti-de Sitter background, a new class of exact torsion waves is constructed in the framework of three-dimensional gravity with propagating torsion. In the asymptotic limit, the geometry of torsion waves takes the anti-de Sitter form. In the sector with massless torsion modes, we found a set of asymptotic conditions that leads to the conformal asymptotic symmetry.
Cartan's Torsion: Necessity and Observational Evidence
Rainer W. Kuhne
2004-02-28
This article starts with the mathematical definition, concrete description, and physical meaning of Cartan's torsion. I proceed with the argumentation that torsion is required for the description of intrinsic spin. Moreover I argue that the duality between curvature and torsion is analogous to the duality between electricity and magnetism. I conclude this article by pointing out that the aligned rotation axes of the galaxies of the Perseus-Pisces supercluster may be interpreted as a topological defect generated by torsion.
A minimal model of Lorentz gauge gravity with dynamical torsion
Cho, Y M; Park, B S
2009-01-01
A new Lorentz gauge gravity model with R^2-type Lagrangian is proposed. In the absence of classical torsion the model admits a topological phase with an arbitrary metric. We analyze the equations of motion in constant curvature space-time background using the Lagrange formalism and demonstrate that the model possesses a minimal set of dynamic degrees of freedom for the torsion. Surprisingly, the number of torsion dynamic degrees of freedom equals the number of physical degrees of freedom for the metric tensor. An interesting feature of the model is that the spin two mode of torsion becomes dynamical essentially due to the non-linear structure of the theory. We perform covariant one-loop quantization of the model for a special case of constant curvature space-time background. We treat the contortion as a quantum field variable whereas the metric tensor is kept as a classical object. We discuss a possible mechanism of an emergent Einstein gravity as a part of the effective theory induced due to quantum dynamics...
Magnetogenesis from axion and dilaton electromagnetism in torsioned spacetime
L. C. G. Andrade
2015-01-09
Recently much controversy has been shed on BICEP 2 experiments for the concerning this validity or not and a possible set of new experiments to detect primordial inflation and gravitational waves. Since gravitational waves imply the existence of primordial magnetic fields in this context, C Bonvin, R Durrer and R Marteens [Phys Rev Lett (2014)] have tried to associate the presence of primordial magnetic fields to BICEP 2 by making use of CMB tensor modes. Here we show that by considering torsion dilatonic lagrangean one obtains cosmological magnetic fields of the order of $B\\sim{10^{-10}G}$ which may seed galactic dynamos. Actually this new result came out of a mistake of a recent paper published by myself in JCAP (2014). These results are more in accordance with Bamba results [JCAP (2014)] in the context of teleparallel theory of gravity with Einstein's distant parallelism and torsion. These results also support Einstein-Cartan sort of theories of gravity from well-known recent data. Another example which supports the use of modified gravities with torsion to investigate magnetogenesis is the alternative exampleof using axions with transmutation into torsion to obtain cosmic magnetic seed bound of $10^{-12}G$.This coincides with the lower bound obtained by Barrow et al [Phys Rev D (2012)] in the interval of $10^{-20}G$ to $10^{-12}G$ in Friedmann universes.
Torsion bar antenna in the proper reference frame with rotation
Kouji Nakamura; Masaki Ando
2014-05-16
The resultant response of the rotating torsion bar antenna for gravitational waves discussed in [M. Ando et al., Phys. Rev. Lett. {\\bf 105} (2010), 161101.] is re-investigate from a general-relativistic point of view. To do this, the equation of motion of a free falling particle in the proper reference frame of a rotating observer is used. As a result, the resultant response derived in the above paper is also valid even when $\\omega_{g}\\sim\\Omega$, where $\\omega_{g}$ and $\\Omega$ are the angular frequencies of gravitational waves and the rotation of the antenna, respectively.
Fetal ovarian cyst decompression to prevent torsion
Timothy M Crombleholme; Sabrina D Craigo; Sara Garmel; Mary E D'Alton
1997-01-01
Background\\/Purpose: Neonates who have ovarian torsion caused by an ovarian cyst often lose their ovary because the torsion and infarction occurred antenatally. Because ultrasound scan has been so effective in diagnosing ovarian cysts in utero, we have a better understanding of their natural history and can select appropriate cases for cyst decompression in utero to prevent torsion. The authors reviewed
Metric-affine $f(R)$-gravity with torsion: an overview
S. Capozziello; S. Vignolo
2009-10-27
Torsion and curvature could play a fundamental role in explaining cosmological dynamics. f(R)-gravity with torsion is an approach aimed to encompass in a comprehensive scheme all the Dark Side of the Universe (Dark Energy and Dark Matter). We discuss the field equations in empty space and in presence of perfect fluid matter taking into account the analogy with the metric-affine formalism. The result is that the extra curvature and torsion degrees of freedom can be dealt under the standard of an effective scalar field of fully geometric origin. The initial value problem for such theories is also discussed.
Torsional wave under initial stress
Sukhendu Dey
1972-01-01
In this paper, the frequency equation for phase velocity of torsional wave in a rod of circular cross section under initial tension has been obtained. The graphs are plotted to compare the velocity with that in the absence of initial tension. Some analytical informations have been obtained for instability of the body under initial compression.
The dynamics and excitation of torsional waves in geodynamo simulations
NASA Astrophysics Data System (ADS)
Teed, R. J.; Jones, C. A.; Tobias, S. M.
2014-02-01
The predominant force balance in rapidly rotating planetary cores is between Coriolis, pressure, buoyancy and Lorentz forces. This magnetostrophic balance leads to a Taylor state where the spatially averaged azimuthal Lorentz force is compelled to vanish on cylinders aligned with the rotation axis. Any deviation from this state leads to a torsional oscillation, signatures of which have been observed in the Earth's secular variation and are thought to influence length of day variations via angular momentum conservation. In order to investigate the dynamics of torsional oscillations (TOs), we perform several 3-D dynamo simulations in a spherical shell. We find TOs, identified by their propagation at the correct Alfvén speed, in many of our simulations. We find that the frequency, location and direction of propagation of the waves are influenced by the choice of parameters. Torsional waves are observed within the tangent cylinder and also have the ability to pass through it. Several of our simulations display waves with core traveltimes of 4-6 yr. We calculate the driving terms for these waves and find that both the Reynolds force and ageostrophic convection acting through the Lorentz force are important in driving TOs.
Xiang-Song Chen; Xiao-Fu Lü; Wei-Min Sun; Fan Wang; T. Goldman
2008-12-23
We reply to the Comment of X. Ji [arXiv:0810.4913] on our paper [PRL 100:232002 (2008)], concerning angular momentum algebra, locality, Lorentz covariance, and measurability of our gauge-invariant description of the spin and orbital angular momentum of quarks and gluons.
Forward models of torsional waves: dispersion and geometric effects
NASA Astrophysics Data System (ADS)
Cox, G. A.; Livermore, P. W.; Mound, J. E.
2014-03-01
Alfvén waves are a set of transverse waves that propagate in an electrically conducting fluid in the presence of an ambient magnetic field. Studies of such waves in the Earth's interior are important because they can be used to make inferences about the structure and physical properties of the core that would otherwise remain inaccessible. We produce 1-D forward models of cylindrical torsional Alfvén waves in the Earth's core, also known as torsional oscillations, and study their evolution in a full sphere and an equatorially symmetric spherical shell. Here, we find that travelling torsional waves undergo significant geometric dispersion that increases with successive reflections from the boundaries such that an initial wave pulse becomes unidentifiable within three transits of the core. Low amplitude wakes trail behind sharply defined pulses during propagation, a phenomenon that we interpret using the failure of Huygens' principle in even dimensions. We investigate the relationship between geometric dispersion and wavelength, concluding that long-wavelength features are more dispersive than short-wavelength features. This result is particularly important because torsional waves that have been inferred in the Earth's core from secular variation are relatively long wavelength, and are therefore likely to undergo significant dispersion within the core. When stress-free boundary conditions on angular velocity are applied, waves are reflected at the equator of the core-mantle boundary with the same sign as the incident wave. Waves that pass through the rotation axis undergo a pseudo-reflection and display a more complicated behaviour due to a phase shift. In an equatorially symmetric shell, we identify a weak reflection at the tangent cylinder due to geometric effects.
Shaft instantaneous angular speed for blade vibration in rotating machine
NASA Astrophysics Data System (ADS)
Gubran, Ahmed A.; Sinha, Jyoti K.
2014-02-01
Reliable blade health monitoring (BHM) in rotating machines like steam turbines and gas turbines, is a topic of research since decades to reduce machine down time, maintenance costs and to maintain the overall safety. Transverse blade vibration is often transmitted to the shaft as torsional vibration. The shaft instantaneous angular speed (IAS) is nothing but the representing the shaft torsional vibration. Hence the shaft IAS has been extracted from the measured encoder data during machine run-up to understand the blade vibration and to explore the possibility of reliable assessment of blade health. A number of experiments on an experimental rig with a bladed disk were conducted with healthy but mistuned blades and with different faults simulation in the blades. The measured shaft torsional vibration shows a distinct difference between the healthy and the faulty blade conditions. Hence, the observations are useful for the BHM in future. The paper presents the experimental setup, simulation of blade faults, experiments conducted, observations and results.
Orbital angular momentum in phase space
Rigas, I. [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Sanchez-Soto, L.L., E-mail: lsanchez@fis.ucm.es [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Klimov, A.B. [Departamento de Fisica, Universidad de Guadalajara, 44420 Guadalajara, Jalisco (Mexico); Rehacek, J.; Hradil, Z. [Department of Optics, Palacky University, 17. Listopadu 12, 746 01 Olomouc (Czech Republic)
2011-02-15
Research Highlights: > We propose a comprehensive Weyl-Wigner formalism for the canonical pair angle-angular momentum. > We present a simple and useful toolkit for the practitioner. > We derive simple evolution equations in terms of a star product in the semiclassical limit. - Abstract: A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.
Quantum Formulation of Fractional Orbital Angular Momentum
J. B. Goette; S. Franke-Arnold; R. Zambrini; Stephen M. Barnett
2006-11-15
The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys. Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values of the orbital angular momentum. This requires the introduction of an additional parameter, the orientation of a phase discontinuity associated with fractional values of the orbital angular momentum. We apply our formalism to the propagation of light modes with fractional orbital angular momentum in the paraxial and non-paraxial regime.
Relativistic Statistical Mechanics with Angular Momentum
Tadas K Nakamura
2011-12-09
The equilibrium distribution function of a relativistic ideal gas has been derived to include the effect of angular momentum. The result agrees with the one obtained from kinetic theory, and consistent with relativistic thermodynamics. The role of angular momentum becomes transparent in this derivation, and the equilibrium distribution can be generalized to accommodate the effect of intrinsic angular momentum. The results here is for a flat spacetime, however, same approach can be applied to static curved spacetimes.
Stability of Thin-Walled Tubes Under Torsion
NASA Technical Reports Server (NTRS)
Donnell, L H
1935-01-01
In this report a theoretical solution is developed for the torsion on a round thin-walled tube for which the walls become unstable. The results of this theory are given by a few simple formulas and curves which cover all cases. The differential equations of equilibrium are derived in a simpler form than previously found, it being shown that many items can be neglected.
Nonlinear electrodynamics in 3D gravity with torsion
Blagojevic, M.; Cvetkovic, B.; Miskovic, O. [Institute of Physics, University of Belgrade, P. O. Box 57, 11001 Belgrade (Serbia); Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4059, Valparaiso (Chile)
2009-07-15
We study exact solutions of nonlinear electrodynamics coupled to three-dimensional gravity with torsion. We show that in any static and spherically symmetric configuration, at least one component of the electromagnetic field has to vanish. In the electric sector of the theory, we construct an exact solution, characterized by the azimuthal electric field. When the electromagnetic action is modified by a topological mass term, we find two types of the self-dual solutions.
Hyttel, Trine E W; Bak, Geske S; Larsen, Solveig B; Løkkegaard, Ellen C L
2015-03-01
The increasing use of de-torsion of the ovaries may result in re-torsion. This review addresses risk of re-torsion and describes preventive strategies to avoid re-torsion in pre-menarcheal girls, and fertile and pregnant women. We clinically reviewed PubMed, Embase, Trip and Cochrane databases. The main outcome measures were re-torsion and viability of ovary with fixation measures. A total of 38 publications including 71 girls, 363 fertile women, and 69 pregnant women were found to be relevant. All studies were case reports or case series, sometimes with non-randomized controls. The studies show considerable heterogeneity in design, population, management and outcome. Only four studies included more than 50 cases. In pregnancy the risk of re-torsion was as high as 19.5-37.5%; among fertile women it was 28.6%. Most articles concluded that fixation of the ovaries to the pelvic sidewall or plication of the ovarian ligament after torsion may prevent re-torsion. In one case a girl experienced re-torsion after ovariopexy. Based on observational studies it seems that de-torsion and fixation of the ovary is a safe procedure that usually ensures maintenance of ovarian function and reduces the risk of recurrence, especially when there are no ovarian cysts or adnexal masses. PMID:25412114
NASA Astrophysics Data System (ADS)
Krot, A. M.
2013-09-01
This work develops a statistical theory of gravitating spheroidal bodies to calculate the orbits of planets and explore forms of planetary orbits with regard to the Alfvén oscillating force [1] in the Solar system and other exoplanetary systems. The statistical theory of formation of gravitating spheroidal bodies has been proposed in [2]-[5]. Starting the conception for forming a spheroidal body inside a gas-dust protoplanetary nebula, this theory solves the problem of gravitational condensation of a gas-dust protoplanetary cloud with a view to planetary formation in its own gravitational field [3] as well as derives a new law of the Solar system planetary distances which generalizes the wellknown laws [2], [3]. This work also explains an origin of the Alfvén oscillating force modifying forms of planetary orbits within the framework of the statistical theory of gravitating spheroidal bodies [5]. Due to the Alfvén oscillating force moving solid bodies in a distant zone of a rotating spheroidal body have elliptic trajectories. It means that orbits for the enough remote planets from the Sun in Solar system are described by ellipses with focus in the origin of coordinates and with small eccentricities. The nearby planet to Sun named Mercury has more complex trajectory. Namely, in case of Mercury the angular displacement of a Newtonian ellipse is observed during its one rotation on an orbit, i.e. a regular (century) shift of the perihelion of Mercury' orbit occurs. According to the statistical theory of gravitating spheroidal bodies [2]-[5] under the usage of laws of celestial mechanics in conformity to cosmogonic bodies (especially, to stars) it is necessary to take into account an extended substance called a stellar corona. In this connection the stellar corona can be described by means of model of rotating and gravitating spheroidal body [5]. Moreover, the parameter of gravitational compression ? of a spheroidal body (describing the Sun, in particular) has been estimated on the basis of the linear size of its kernel, i.e. the thickness of a visible part of the solar corona. Really, NASA' astronomer S. Odenwald in his notice «How thick is the solar corona?» wrote: "The corona actually extends throughout the entire solar system as a "wind" of particles, however, the densist parts of the corona is usually seen not more than about 1-2 solar radii from the surface or about 690,000 to 1.5 million kilometers at the equator. Near the poles, it seems to be a bit flatter..." [6]. In the fact, as mentioned in [5], a recession of plots of dependences of relative brightness of components of spectrum of the Solar corona occurs on distance of 3-3.5 radii from the center, i.e. on 2-2.5 radii from the edge of the solar disk. Thus, accepting thickness of a visible part of the solar corona equal to ? = 2R (here R is radius of the solar disk) we find that r* = R + ? = 3R , where r* =1/ ? . In other words, the parameter of gravitational compression 2 ? =1/ r* of a spheroidal body in case of the Sun with its corona (for which the equatorial radius ofdisk R = 6.955?108 m) can be estimated by the value [2]-[5]: 2.29701177718 10 (m ) (3 ) 1 19 2 2 = ? ? - - R ? . (1) So, the procedure of finding ? is based on the known 3? -rule in the statistical theory. Really, as shown in the monograph [5], namely the solar corona accounting under calculation of perturbed orbit of the planet of Mercury allows to find the estimation of a displacement of perihelion of Mercury' orbit for the one period within the framework of the statistical theory of gravitating spheroidal bodies. As it is known, on a way of specification of the law of Newton using the general relativity theory the Mercury problem solving was found [5]. Nevertheless, from a common position of the statistical theory of gravitating spheroidal bodies the points of view as Leverrier (about existence of an unknown matter) and Einstein (about insufficiency of the theory of Newton) practically differ nothing. Really, there exist plasma as well as gas-dust substance
VSCF in internal coordinates and the calculation of anharmonic torsional mode transitions
NASA Astrophysics Data System (ADS)
Suwan, Iyad; Gerber, R. B.
2010-08-01
The vibrational self-consistent field (VSCF) method assumes separability in normal modes in its usual version. However, the method fails in cases such as soft torsional modes which are better treated by angular variables. We develop VSCF equations based on the assumption of wave function separability in internal coordinates. To test the method, simple illustrative applications to small systems are provided: trans-HONO, cis-HONO, H 2S 2, and H 2O 2. The code directly uses points from ab initio calculations, and the method proves to be accurate for all types of transitions. For typical torsional transitions, the error in the computed frequency is smaller than that of VSCF in normal coordinates. The wave functions for the torsional mode are compared with the corresponding normal mode wave functions. The differences are substantial. The results are encouraging for extension of the model for large polyatomic systems. Work along these lines is in progress.
Cutoff-Free Propagation of Torsional Alfvén Waves Along Thin Magnetic Flux Tubes
Z. E. Musielak; S. Routh; R. Hammer
2007-01-25
Propagation of torsional Alfv\\'en waves along magnetic flux tubes has been extensively studied for many years but no conclusive results regarding the existence of a cutoff frequency for these waves have been obtained. The main purpose of this paper is to derive new wave equations that describe the propagation of linear torsional Alfv\\'en waves along thin and isothermal magnetic flux tubes, and use these wave equations to demonstrate that the torsional wave propagation is not affected by any cutoff frequency. It is also shown that this cutoff-free propagation is independent of different choices of the coordinate systems and wave variables adopted in the previous studies. A brief discussion of implications of this cutoff-free propagation of torsional tube waves on theories of wave heating of the solar and stellar atmospheres is also given.
Coupled lateral-torsional-axial vibrations of a helical gear-rotor-bearing system
NASA Astrophysics Data System (ADS)
Li, Chao-Feng; Zhou, Shi-Hua; Liu, Jie; Wen, Bang-Chun
2014-10-01
Considering the axial and radial loads, a mathematical model of angular contact ball bearing is deduced with Hertz contact theory. With the coupling effects of lateral, torsional and axial vibrations taken into account, a lumped-parameter nonlinear dynamic model of helical gearrotor-bearing system (HGRBS) is established to obtain the transmission system dynamic response to the changes of different parameters. The vibration differential equations of the drive system are derived through the Lagrange equation, which considers the kinetic and potential energies, the dissipative function and the internal/external excitation. Based on the Runge-Kutta numerical method, the dynamics of the HGRBS is investigated, which describes vibration properties of HGRBS more comprehensively. The results show that the vibration amplitudes have obvious fluctuation, and the frequency multiplication and random frequency components become increasingly obvious with changing rotational speed and eccentricity at gear and bearing positions. Axial vibration of the HGRBS also has some fluctuations. The bearing has self-variable stiffness frequency, which should be avoided in engineering design. In addition, the bearing clearance needs little attention due to its slightly discernible effect on vibration response. It is suggested that a careful examination should be made in modelling the nonlinear dynamic behavior of a helical gear-rotor-bearing system.
Premotor neurons encode torsional eye velocity during smooth-pursuit eye movements
NASA Technical Reports Server (NTRS)
Angelaki, Dora E.; Dickman, J. David
2003-01-01
Responses to horizontal and vertical ocular pursuit and head and body rotation in multiple planes were recorded in eye movement-sensitive neurons in the rostral vestibular nuclei (VN) of two rhesus monkeys. When tested during pursuit through primary eye position, the majority of the cells preferred either horizontal or vertical target motion. During pursuit of targets that moved horizontally at different vertical eccentricities or vertically at different horizontal eccentricities, eye angular velocity has been shown to include a torsional component the amplitude of which is proportional to half the gaze angle ("half-angle rule" of Listing's law). Approximately half of the neurons, the majority of which were characterized as "vertical" during pursuit through primary position, exhibited significant changes in their response gain and/or phase as a function of gaze eccentricity during pursuit, as if they were also sensitive to torsional eye velocity. Multiple linear regression analysis revealed a significant contribution of torsional eye movement sensitivity to the responsiveness of the cells. These findings suggest that many VN neurons encode three-dimensional angular velocity, rather than the two-dimensional derivative of eye position, during smooth-pursuit eye movements. Although no clear clustering of pursuit preferred-direction vectors along the semicircular canal axes was observed, the sensitivity of VN neurons to torsional eye movements might reflect a preservation of similar premotor coding of visual and vestibular-driven slow eye movements for both lateral-eyed and foveate species.
The genesis of torsional drillstring vibrations
Brett, J. (Oil and Gas Consultants International Inc., Tulsa, OK (US))
1992-09-01
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.
2D Gravity with Torsion, Oriented Matroids and 2+2 Dimensions
J. A. Nieto; E. A. Leon
2009-09-22
We find a link between oriented matroid theory and 2d gravity with torsion. Our considerations may be useful in the context of noncommutative phase space in a target spacetime of signature (2+2) and in a possible theory of gravity ramification.
Transverse and longitudinal angular momenta of light
Bliokh, Konstantin Y
2015-01-01
We review basic physics and novel types of optical angular momentum. We start with a theoretical overview of momentum and angular momentum properties of generic optical fields, and discuss methods for their experimental measurements. In particular, we describe the well-known longitudinal (i.e., aligned with the mean momentum) spin and orbital angular momenta in polarized vortex beams. Then, we focus on the transverse (i.e., orthogonal to the mean momentum) spin and orbital angular momenta, which were recently actively discussed in theory and observed in experiments. First, the recently-discovered transverse spin angular momenta appear in various structured fields: evanescent waves, interference fields, and focused beams. We show that there are several kinds of transverse spin angular momentum, which differ strongly in their origins and physical properties. We describe extraordinary features of the transverse optical spins and overview recent experiments. In particular, the helicity-independent transverse spin...
NASA Technical Reports Server (NTRS)
Plummer, G. M.; Herbst, E.; De Lucia, F.; Blake, G. A.
1984-01-01
Over 200 rotational lines of methyl formate in its ground (v sub t = 0), symmetric (A) torsional state have been measured in the frequency range 140-550 GHz. Analysis of these and lower frequency transitions permits accurate prediction (below 0.1 MHz) of over 10,000 transitions at frequencies below 600 GHz with angular momentum J lower than 50. The measured spectral lines have permitted identification of over 100 new methyl formate lines in Orion.
Proposed improvements for torsional wave measurements of density and viscosity
Friesel, M.A. [P. O. Box 4094, West Richland, Washington 99353 (United States)] [P. O. Box 4094, West Richland, Washington 99353 (United States)
1996-04-01
A first-order theory has previously been developed to allow the measurements of density and viscosity of fluids using the time-of-flight of torsional waves in immersed waveguides. In this article the theory has been modified to eliminate the need to calculate fluid-independent constants, via the use of two reference fluids. The effects of temperature differences among the reference and test fluids for moderately low temperatures are also examined. The result is a simple matrix equation which can be solved for the unknown fluid density. Fluid viscosity can be determined using an auxiliary equation. {copyright} {ital 1996 American Institute of Physics.}
Gauge invariant coupling of fields to torsion: A string inspired model
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
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.
Power Electronic Devices for Damping Torsional Vibrations
A. M. Miri; T. Zöller; T. Leibfried
Torsional vibrations and resonance problems with synchronous machines are most frequently encountered in rotor systems with long shafts and large inertias constituting a weakly damped mechanical resonator which exhibits a low resonance frequency. It is impossible to obtain a effective mechanical damping for these torsional vibrations, but by using a power electronics device and an inductive or capacitive energy storage
Gravitational waves with torsion in 3D
M. Blagojevi?; B. Cvetkovi?
2014-09-14
We study gravitational waves with torsion as exact vacuum solutions of three-dimensional gravity with propagating torsion. The new solutions are a natural generalization of the plane-fronted gravitational waves in general relativity with a cosmological constant, in the presence of matter.
Gravitational waves with torsion in 3D
Blagojevi?, M
2014-01-01
We study gravitational waves with torsion as exact vacuum solutions of three-dimensional gravity with propagating torsion. The new solutions are a natural generalization of the plane-fronted gravitational waves in general relativity with a cosmological constant, in the presence of matter.
Gravitational waves with torsion in 3D
NASA Astrophysics Data System (ADS)
Blagojevi?, M.; Cvetkovi?, B.
2014-08-01
We study gravitational waves with torsion as exact vacuum solutions of three-dimensional gravity with propagating torsion. The new solutions are a natural generalization of the plane-fronted gravitational waves in general relativity with a cosmological constant, in the presence of matter.
Analytic torsion and holomorphic determinant bundles
Jean-Michel Bismut; Henri Gillet; Christophe Soulé
1988-01-01
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.
Torsional device for remote control steering system
NASA Astrophysics Data System (ADS)
Koyamatsu, Anthony H.; Ono, Owen T.; Hahn, Warren L.
1993-12-01
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.
Light's Orbital Angular Momentum
Miles Padgett; Johannes Courtial; Les Allen
2004-01-01
The realization that light beams can have quantized orbital angular momentum in addition to spin angular momentum has led, in recent years, to novel experiments in quantum mechanics and new methods for manipulating microparticles.
NSDL National Science Digital Library
David Trapp
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.
Stoytcho S. Yazadjiev
2013-01-06
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, non-axisymmetric spacetimes satisfying the Einstein-Maxwell-dilaton-matter equations. In proving the inequalities we assume that the dilaton potential is nonnegative and that the matter energy-momentum tensor satisfies the dominant energy condition.
Optically probing torsional superelasticity in spider silks
Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit; Singh, Kamal P. [Department of Physical Sciences, IISER Mohali, Sector 81, Manauli, Mohali 140306 (India)] [Department of Physical Sciences, IISER Mohali, Sector 81, Manauli, Mohali 140306 (India)
2013-11-11
We investigate torsion mechanics of various spider silks using a sensitive optical technique. We find that spider silks are torsionally superelastic in that they can reversibly withstand great torsion strains of over 10{sup 2?3} rotations per cm before failure. Among various silks from a spider, we find the failure twist-strain is greatest in the sticky capture silk followed by dragline and egg-case silk. Our in situ laser-diffraction measurements reveal that torsional strains on the silks induce a nano-scale transverse compression in its diameter that is linear and reversible. These unique torsional properties of the silks could find applications in silk-based materials and devices.
Statefinder diagnostic in a torsion cosmology
Xin-zhou Li; Chang-bo Sun; Ping Xi
2009-03-27
We apply the statefinder diagnostic to the torsion cosmology, in which an accounting for the accelerated universe is considered in term of a Riemann-Cartan geometry: dynamic scalar torsion. We find that there are some typical characteristic of the evolution of statefinder parameters for the torsion cosmology that can be distinguished from the other cosmological models. Furthermore, we also show that statefinder diagnostic has a direct bearing on the critical points. The statefinder diagnostic divides the torsion parameter $a_1$ into differential ranges, which is in keeping with the requirement of dynamical analysis. In addition, we fit the scalar torsion model to ESSENCE supernovae data and give the best fit values of the model parameters.
Torsional oscillations of longitudinally inhomogeneous coronal loops
T. V. Zaqarashvili; K Murawski
2007-04-03
We explore the effect of an inhomogeneous mass density field on frequencies and wave profiles of torsional Alfven oscillations in solar coronal loops. Dispersion relations for torsional oscillations are derived analytically in limits of weak and strong inhomogeneities. These analytical results are verified by numerical solutions, which are valid for a wide range of inhomogeneity strength. It is shown that the inhomogeneous mass density field leads to the reduction of a wave frequency of torsional oscillations, in comparison to that of estimated from mass density at the loop apex. This frequency reduction results from the decrease of an average Alfven speed as far as the inhomogeneous loop is denser at its footpoints. The derived dispersion relations and wave profiles are important for potential observations of torsional oscillations which result in periodic variations of spectral line widths. Torsional oscillations offer an additional powerful tool for a development of coronal seismology.
Application of the angular correlation formalism to nuclear fission
Herbert Faust
1998-01-01
The angular correlation formalism is applied to calculate angular distributions of fission fragments following light particle induced reactions. The distributions are described by sums over Legendre polynomials, and standard theory is used to calculate statistical tensors to describe the alignment of the compound nucleus, particle parameters and angular correlation coefficients. Comparison with experimental data shows that the importance of higher
Torsion of Noncircular Composite Cylinders
NASA Technical Reports Server (NTRS)
Rouse, Marshall; Hyer, Michael W.; Haynie, Waddy T.
2005-01-01
The paper presents a brief overview of the predicted deformation and failure characteristics of noncircular composite cylinders subjected to torsion. Using a numerical analysis, elliptical cylinders with a minor-to-major diameter ratio of 0.7 are considered. Counterpart circular cylinders with the same circumference as the elliptical cylinders are included for comparison. The cylinders are constructed of a medium-modulus graphite-epoxy material in a quasi-isotropic lay-up. Imperfections generated from the buckling mode shapes are included in the initial cross-sectional geometry of the cylinders. Deformations until first fiber failure, as predicted using the maximum stress failure criterion and a material degradation scheme, are presented. For increasing levels of torsion, the deformations of the elliptical cylinders, in the form of wrinkling of the cylinder wall, occur primarily in the flatter regions of the cross section. By comparison the wrinkling deformations of the circular cylinders are more uniformly distributed around the circumference. Differences in the initial failure and damage progression and the overall torque vs. twist relationship between the elliptical and circular cylinders are presented. Despite differences in the response as the cylinders are being loaded, at first fiber failure the torque and twist for the elliptical and circular cylinders nearly coincide.
Gravitational lenses with angular momentum
NASA Astrophysics Data System (ADS)
Ibanez, J.
1983-08-01
The Einstein (1936), Liebes (1964), Refsdal (1965), and Bourassa et al. (1973, 1975) theories of the effects of gravitational lenses have considered the bending of light as due to the mass distribution of the deflector. The effect of deflector dynamical properties has not been taken into account. The influence of angular momentum in a gravitational lens is presently demonstrated by the bending angle of a photon passing near a rotating body. The expressions used are evaluated for spherical and spheroidal deflectors.
Torsional directed walks, entropic elasticity, and DNA?twist?stiffness
Moroz, J. David; Nelson, Philip
1997-01-01
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. PMID:9405627
Torsional Directed Walks, Entropic Elasticity, and DNA Twist Stiffness
J. David Moroz; Philip Nelson
1997-08-21
DNA and other biopolymers differ from classical polymers due to 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 et al., Science 271 (1996) 1835], 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=120nm and D=50nm. 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.
Torsion Fields, Propagating Singularities, Nilpotence, Quantum Jumps and the Eikonal Equations
NASA Astrophysics Data System (ADS)
Rapoport, Diego L.
2010-11-01
We establish a geometrical theory in terms of torsion fields and their singularities of quantum jumps and of the propagation of wave-front singularities described by the eikonal equation of geometrical optics basic to Fock's theory of gravitation and General Relativity. The latter equations correspond to the wavefront propagation for the Maxwell and Einstein equations. We discuss the genesis of spacetime in terms of these singularities and torsion fields. We introduce the class of solutions of the wave propagation (defined in terms of the metric geometry) and the eikonal equations. The lagrangian functional for quantum jumps defined in terms of the quantum potential is introduced. We give a formula that characterizes the quantum jumps in terms of an extension of the argument principle in complex analysis. We show that the wave propagation in terms of the metric geometry under a change of gauge has a natural expression as a wave propagation in terms of the laplacians associated to a torsion geometry of the Cartan-Weyl type which has an additional interaction first-order torsion term. In this geometry there is a differential one-form trace-torsion term given by the logarithmic differential of (monochromatic) waves. It is shown that quantum jumps are associated with the Cartan-Weyl geometry, through a torsion potential given by the logarithmic differential of the composition of an analytic function -or alternatively a twice differentiable function- with a monochromatic wave function. In particular, if follows that monochromatic wave functions generate torsion. The node sets of monochromatic functions are shown to be the locus for quantum jumps. In the case of the metric being Minkowski or positive-definite, the generalized laplacians corresponding to this torsion geometry, are generators of Brownian motions in which the torsion describes the drift of the Brownian processes. We show that this torsion potential and its singularities due to the nodes of the monochromatic wave functions, gives rise to an Aharonov-Bohm effect. We briefly indicate the role of quantum jumps in establishing a global time and space coordinates in semiclassical General Relativity. We indicate some relations between the present approach to the geometry of quantum jumps, and the problem of topographical representation in visual perception, the Klein bottle, quantum physics and holography.
Torsional properties of distal femoral cortical defects.
Amanatullah, Derek F; Williams, Joel C; Fyhrie, David P; Tamurian, Robert M
2014-03-01
The optimal management of pathologic long bone lesions remains a challenge in orthopedic surgery. The goal of the current study was to investigate the effect of defect depth on the torsional properties of the distal femur. A laterally placed distal metaphyseal cylindrical defect was milled in the cortex of the distal femur in 20 composite models. The proximal extent of the defects was constant. By decreasing the radius of the cylinder that intersected this predefined cord, 4 different radii defining 4 different depths of resection of the distal femur were created for testing: 17%, 33%, 50%, and 67% cortical defects, when normalized to the width of the femur at the level of resection. Each femur was mounted into a hydraulic axial/torsion materials testing machine and each specimen underwent torsional stiffness testing and torsional failure in external rotation. The specimens with less than a 33% cortical loss consistently demonstrated a superiorly oriented spiral fracture pattern, while the specimens with greater than a 50% cortical loss consistently demonstrated an inferiorly oriented transverse fracture pattern. The cortical defects were all statistically (P<.05) less stiff in torsion as the defect grew larger. There was a strong linear correlation between the mean torsional stiffness and cortical defect size (r(2)=0.977). This observation is supported by finite element analysis. The amount of femur remaining is crucial to stability. This biomechanical analysis predicts a critical loss of torsional integrity when a cortical defect approaches 50% of the width of the femur. PMID:24762144
September 12, 2007 THE ISOMORPHISM PROBLEM FOR TORSION-FREE
September 12, 2007 THE ISOMORPHISM PROBLEM FOR TORSION-FREE ABELIAN GROUPS IS ANALYTIC COMPLETE. ROD DOWNEY AND ANTONIO MONTALBÂ´AN Abstract. We prove that the isomorphism problem for torsion-free for countable torsion-free Abelian groups. The question we ask is, given two countable torsion-free Abelian
Magnetic Torsional Oscillations in Magnetars
Sotani, Hajime [Theoretical Astrophysics, University of Tuebingen, 72076, Tuebingen (Germany); Kokkotas, Kostas D. [Theoretical Astrophysics, University of Tuebingen, 72076, Tuebingen (Germany); Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Stergioulas, Nikolaos [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)
2009-05-01
We investigate torsional Alfven oscillations of relativistic stars with a global dipole magnetic field, via 2D numerical simulations. We find that a) there exist two families of quasi-periodic oscillations (QPOs) with harmonics at integer multiples of the fundamental frequency, b) the QPOs are long-lived, c) for the chosen form of dipolar magnetic field, the frequency ratio of the lower to upper fundamental QPOs is about 0.6, independent of the equilibrium model or of the strength of the magnetic field, and d) within a representative sample of EOS and of various magnetar masses, the Alfven QPO frequencies are given by accurate empirical relations that depend only on the compactness of the star and on the magnetic field strength. Compared to the observational frequencies, we also obtain an upper limit on the strength of magnetic field of SGR 1806-20 (if is dominated by a dipolar component) between {approx}3 and 7x10{sup 15} Gauss.
Stationary model of the Universe with torsion
NASA Astrophysics Data System (ADS)
Panzhensky, V. I.
2013-10-01
On a four-dimensional pseudo-Riemannian manifold with the metric of a stationary model of the Universe, we construct a Riemann-Cartan structure with the automorphism group of maximum dimension. The torsion tensor of this structure is the sum of two parts: semisymmetric, aspiring to geometrization of the spin density of matter, and skew-symmetric, determining the torsion of a spatial section. We give a geometric interpretation of the spatial section torsion. We prove that the maximum dimension of the Lie group of automorphisms of a Riemann-Cartan space-time manifold with a semisymmetric or skewsymmetric connection is seven.
Torsional irregularity in multi-story structures
NASA Astrophysics Data System (ADS)
Özmen, Günay; Girgin, Konuralp; Durgun, Yavuz
2014-12-01
The purpose of this study is first to determine the conditions for excessive torsional irregularity and then to discuss the validity of code provisions. A parametric investigation is performed on six groups of typical structures with varying shear wall positions, story, and axis numbers. It is found that torsional irregularity coefficients increase as the story numbers decrease, i.e., maximum irregularity coefficients occur for single-story structures. They reach maximum values when the asymmetrical shear walls are placed as close as possible to the centers of mass. However, the results obtained for floor rotations are quite contradictory. A new provisional definition for torsional irregularity coefficient based on floor rotations is proposed.
Torsional irregularity in multi-story structures
NASA Astrophysics Data System (ADS)
Özmen, Günay; Girgin, Konuralp; Durgun, Yavuz
2014-09-01
The purpose of this study is first to determine the conditions for excessive torsional irregularity and then to discuss the validity of code provisions. A parametric investigation is performed on six groups of typical structures with varying shear wall positions, story, and axis numbers. It is found that torsional irregularity coefficients increase as the story numbers decrease, i.e., maximum irregularity coefficients occur for single-story structures. They reach maximum values when the asymmetrical shear walls are placed as close as possible to the centers of mass. However, the results obtained for floor rotations are quite contradictory. A new provisional definition for torsional irregularity coefficient based on floor rotations is proposed.
Torsion-free generalized connections and Heterotic Supergravity
Mario Garcia-Fernandez
2013-05-26
This work revisits the notions of connection and curvature in generalized geometry, with emphasis on torsion-free generalized connections on a transitive Courant algebroid, compatible with a generalized metric. Non-exact Courant algebroids have been considered recently by R. Rubio in the context of $B_n$-generalised geometry and arise naturally from the theory of generalized reduction of Burzstyn, Cavalcanti and Gualtieri. As an application, we provide a mathematical derivation of the equations of motion of heterotic supergravity, inspired by the work of Coimbra, Strickland-Constable and Waldram.
Czakó, Gábor
2014-06-21
Motivated by a recent experiment [H. Pan and K. Liu, J. Chem. Phys. 140, 191101 (2014)], we report a quasiclassical trajectory study of the O((3)P) + CH4(vk = 0, 1) ? OH + CH3 [k = 1 and 3] reactions on an ab initio potential energy surface. The computed angular distributions and cross sections correlated to the OH(v = 0, 1) + CH3(v = 0) coincident product states can be directly compared to experiment for O + CH4(v3 = 0, 1). Both theory and experiment show that the ground-state reaction is backward scattered, whereas the angular distributions shift toward sideways and forward directions upon antisymmetric stretching (v3) excitation of the reactant. Theory predicts similar behavior for the O + CH4(v1 = 1) reaction. The simulations show that stretching excitation enhances the reaction up to about 15 kcal/mol collision energy, whereas the O + CH4(vk = 1) reactions produce smaller cross sections for OH(v = 1) + CH3(v = 0) than those of O + CH4(v = 0) ? OH(v = 0) + CH3(v = 0). The former finding agrees with experiment and the latter awaits for confirmation. The computed cold OH rotational distributions of O + CH4(v = 0) are in good agreement with experiment. PMID:24952515
Inevitable inflation in Einstein-Cartan theory with improved energy-momentum tensor with spin
NASA Technical Reports Server (NTRS)
Fennelly, A. J.; Bradas, James C.; Smalley, Larry L.
1988-01-01
Generalized, or power-law, inflation is shown to necessarily exist for a simple, anisotropic, (Bianchi Type-1) cosmology in the Einstein-Cartan gravitational theory with the Ray-Smalley improved energy momentum tensor with spin. Formal solution of the EC field equations with the fluid equations of motion explicitly shows inflation caused by the RS spin angular kinetic energy density. Shear is not effective in preventing inflation in the ECRS model. The relation between fluid vorticity, torsion, reference axis rotation, and shear ellipsoid precession shows through clearly.
Dark Energy: Is It of Torsion Origin?
M. I. Wanas
2010-06-10
{\\it "Dark Energy"} is a term recently used to interpret supernovae type Ia observation. In the present work we give two arguments on a possible relation between dark energy and torsion of space-time.
Exact three-dimensional analysis for static torsion of piezoelectric rods
Mohammad Maleki; Mohammad Hasan Naei; Ehsan Hosseinian; Arash Babahaji
Based on the theory of elasticity, exact analytical and numerical solutions of piezoelectric rods under static torsion are studied. In this paper, direct solution method is used. The main scope is to check the extension of validity of assumptions in previous papers that had been made based on linear distribution of electric potential through the cross section and their influences
Beam bending-torsion dynamic stiffness method for calculation of exact vibration modes
W. L. Hallauer; R. Y. L. Liu
1982-01-01
The exact dynamic stiffness matrix is derived for a straight and uniform beam element whose elastic and inertial axes are not coincident. Elementary bending-torsion beam theory is used, and bending translation is restricted to one direction. The element matrix can be used in the dynamic stiffness method for calculation of exact natural frequencies, mode shapes, and generalized masses for planar
Torsional waves and free vibrations of drive systems with stepped shafts
A. Mioduchowski
1986-01-01
In the paper the continuous model of a multi-mass drive system is considered. The method of dynamical analysis is based on the theory of propagation of one dimensional torsional elastic waves. Discussion is presented for the system consisting of N stepped shafts and N+1 rigid bodies. Numerical results are presented for two different systems.
General equations of motion for test particles in space-time with torsion
Chen Fang Pei
1990-01-01
The momentum and spin equations of motion for test particles possessing different spins in space-time with torsion are derived from the most general functional form of LM. The same kinds of equations in general relativity and in Kibble's gauge theory of gravitation are special cases of our equations.
Flow in a torsionally oscillating filled cylinder
NASA Technical Reports Server (NTRS)
Schafer, C. F.
1983-01-01
The flow of a liquid in a completely filled cylinder undergoing torsional oscillations about its longitudinal symmetry axis was studied analytically and experimentally. The objective of the studies was to determine the efficacy of the torsional oscillations in mixing the confined liquid. Flow was found to be confined primarily to toroidal cells at the ends of the cylinder. Cell thickness was about equal to the cylinder radius. The use of baffles at the end walls was shown to enhance the mixing process.
The Torsional Fundamental Band of Methylformate
NASA Astrophysics Data System (ADS)
Tudorie, M.; Ilyushin, V.; Vander Auwera, J.; Pirali, O.; Roy, P.; Huet, T. R.
2011-06-01
Methylformate (HCOOCH_3) is one of the most important molecules in astrophysics, first observed in 1975. The rotational structure of its ground and first excited torsional states are well known from millimeter wave measurements. However, some of the torsional parameters are still not precisely determined because information on the torsional vibrational frequency v_t = 1-0 is missing. To overcome that problem, the far infrared spectrum of HCOOCH_3 was recorded with a 150 m optical path in a White cell and a Bruker IFS 125 HR Fourier transform spectrometer at the AILES beamline of the synchrotron SOLEIL facility. The analysis of the very weak fundamental torsional band v_t = 1-0 observed around 130 Cm-1 was carried out. It led to the first precise determination of the torsional barrier height and the dipole moment induced by the torsional motion. This work is partly supported by the "Programme National de Physico-Chimie du Milieu Interstellaire" (PCMI-CNRS) and by the contract ANR-BLAN-08-0054. R.D. Brown, J.G. Crofts, P.D. Godfrey, F.F. Gardner, B.J. Robinson, J.B. Whiteoak, Astrophys. J. 197 (1975) L29-L31. See V. Ilyushin, A. Kryvda, E. Alekseev, J. Mol. Spectrosc. 255 (2009) 32-38, and references therein.
Migliaccio, Americo A; Della Santina, Charles C; Carey, John P; Minor, Lloyd B; Zee, David S
2006-08-01
We examined how the gain of the torsional vestibulo-ocular reflex (VOR) (defined as the instantaneous eye velocity divided by inverted head velocity) in normal humans is affected by eye position, target distance, and the plane of head rotation. In six normal subjects we measured three-dimensional (3D) eye and head rotation axes using scleral search coils, and 6D head position using a magnetic angular and linear position measurement device, during low-amplitude (approximately 20 degrees ), high-velocity (approximately 200 degrees/s), high-acceleration (approximately 4000 degrees /s2) rapid head rotations or 'impulses.' Head impulses were imposed manually and delivered in five planes: yaw (horizontal canal plane), pitch, roll, left anterior-right posterior canal plane (LARP), and right anterior-left posterior canal plane (RALP). Subjects were instructed to fix on one of six targets at eye level. Targets were either straight-ahead, 20 degrees left or 20 degrees right from midline, at distance 15 or 124 cm from the subject. Two subjects also looked at more eccentric targets, 30 degrees left or 30 degrees right from midline. We found that the vertical and horizontal VOR gains increased with the proximity of the target to the subject. Previous studies suggest that the torsional VOR gain should decrease with target proximity. We found, however, that the torsional VOR gain did not change for all planes of head rotation and for both target distances. We also found a dynamic misalignment of the vertical positions of the eyes during the torsional VOR, which was greatest during near viewing with symmetric convergence. This dynamic vertical skew during the torsional VOR arises, in part, because when the eyes are converged, the optical axes are not parallel to the naso-occipital axes around which the eyes are rotating. In five of six subjects, the average skew ranged 0.9 degrees -2.9 degrees and was reduced to <0.4 degrees by a 'torsional' quick-phase (around the naso-occipital axis) occurring <110 ms after the onset of the impulse. We propose that the torsional quick-phase mechanism during the torsional VOR could serve at least three functions: (1) resetting the retinal meridians closer to their usual orientation in the head, (2) correcting for the 'skew' deviation created by misalignment between the axes around which the eyes are rotating and the line of sight, and (3) taking the eyes back toward Listing's plane. PMID:16545855
Observation of optical torsional stiffness in a high optical power cavity
NASA Astrophysics Data System (ADS)
Fan, Yaohui; Merrill, Lucienne; Zhao, Chunnong; Ju, Li; Blair, David; Slagmolen, Bram; Hosken, David; Brooks, Aidan; Veitch, Peter; Mudge, Damien; Munch, Jesper
2009-02-01
We have observed negative optical torsional rigidity in an 80 m suspended high optical power cavity that would induce the Sidles-Sigg instability as a result of sufficient circulating power. The magnitude of the negative optical spring constant per unit power is a few ?N m/W as the result of the optical torsional stiffness in the yaw mode of a suspended mirror Fabry-Pérot cavity. It has been observed to depend on the g-factor of the cavity which is in agreement with the Sidles-Sigg theory.
Shear and Vorticity in an Accelerating Brans-Dicke Lambda-Universe with Torsion
Marcelo Samuel Berman
2008-08-06
We study accelerating Universes with power-law scale-factors. We include shear and vorticity, a cosmological "constant" term, and spin from torsion, as in Einstein-Cartan's theory when a scalar-field of Brans-Dicke type acts in the model. We find a "no-hair" result, for shear and vorticity; we also make contact with the alternative Machian picture of the Universe. Keywords: Cosmology; Einstein; Brans-Dicke; Cosmological term; Shear; Spin; Vorticity; Inflation; Einstein-Cartan; Torsion; Accelerating Universe
Angular Acceleration without Torque?
ERIC Educational Resources Information Center
Kaufman, Richard D.
2012-01-01
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.
Williamson, M.M.; Pratt, G.A.
1999-06-08
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, Matthew M. (Boston, MA); Pratt, Gill A. (Lexington, MA)
1999-06-08
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.
Beam and Torsion Tests of Aluminum-alloy 61S-T Tubing
NASA Technical Reports Server (NTRS)
Moore, R L; Holt, Marshall
1942-01-01
Tests were made to determine the effect of length and the effect of ratios of diameter to wall thickness upon the flexural and torsional moduli of failure of 61S-T aluminum-alloy tubing. The moduli of failure in bending, as determined by tests in which the tubing was loaded on the neutral axis at the one-third points of the span, were found to bear an approximately linear relationship with diameter-thickness ratio and were practically independent of span within the limits investigated. Empirical equations are given describing the relations obtained. The moduli of failure in torsion were found to be dependent upon length as well as upon diameter-thickness ratios. Empirical equations are given for predicting strengths within the range of plastic buckling. Within the elastic range, available torsion theories were found to be satisfactory.
Renormalizability of the Dirac equation in torsion gravity with nonminimal coupling
NASA Astrophysics Data System (ADS)
Fabbri, Luca; Vignolo, Stefano; Carloni, Sante
2014-07-01
We will consider the torsional completion of gravity for a background filled with Dirac matter fields, studying what happens when fermionic nonminimal coupling is taken into account: we will show that, although nonminimal couplings are usually disregarded because of their ill-defined behavior in ultraviolet regimes, this is due to the fact that torsion is commonly neglected, whereas when torsion is not left aside, even nonminimal couplings behave properly. In detail, we will see that nonminimal coupling allows one to renormalize the Dirac equation even when torsion is taken into consideration and that in some type of nonminimally coupled models parity oddness might be present even in the gravitational sector. In addition, we will show that in the presence of the considered nonminimal coupling, torsion is able to evade cosmological singularities as it can happen in the minimal coupling case and in some other nonminimally coupled theory. In the course of the paper, we shall consider a specific interaction as prototype to study this fermionic nonminimal coupling, but we will try to present results that do not depend on the actual structure of the nonminimal couplings by investigating alternative types of interaction.
Torsion-vibration interactions in the CH{sub 3}-rocking and OH-bending fundamentals of C-13 methanol
Predoi, A.; Lees, R.M. [Univ. of New Brunswick, Fredericton (Canada)
1996-12-31
A review is presented of recent work on the study of the molecular interactions observed in the CH{sub 3}-rocking and OH-bending bands of C-13 methanol. The main aim was to find the interaction constants and to estimate the contributions due to the torsional motion. The modelling was done using a Marquardt algorithm and a second order perturbation theory approach. The frequent Fermi mixing between states of the OH-bending and the first torsionally excited CH{sub 3}-rocking modes make it essential to study these bands jointly and not individually. The pattern of torsion-rotation energies for the OH-bending mode is inverted relative to that of the ground state, implying that the usual Hamiltonian used successfully for the ground state cannot describe the excited state energy manifold. With these findings, the author hope to contribute to better understanding of the torsion-vibration energy structure of the bending modes of methanol.
Torsion-Mediated Interaction between Adjacent Genes
Meyer, Sam; Beslon, Guillaume
2014-01-01
DNA torsional stress is generated by virtually all biomolecular processes involving the double helix, in particular transcription where a significant level of stress propagates over several kilobases. If another promoter is located in this range, this stress may strongly modify its opening properties, and hence facilitate or hinder its transcription. This mechanism implies that transcribed genes distant of a few kilobases are not independent, but coupled by torsional stress, an effect for which we propose the first quantitative and systematic model. In contrast to previously proposed mechanisms of transcriptional interference, the suggested coupling is not mediated by the transcription machineries, but results from the universal mechanical features of the double-helix. The model shows that the effect likely affects prokaryotes as well as eukaryotes, but with different consequences owing to their different basal levels of torsion. It also depends crucially on the relative orientation of the genes, enhancing the expression of eukaryotic divergent pairs while reducing that of prokaryotic convergent ones. To test the in vivo influence of the torsional coupling, we analyze the expression of isolated gene pairs in the Drosophila melanogaster genome. Their orientation and distance dependence is fully consistent with the model, suggesting that torsional gene coupling may constitute a widespread mechanism of (co)regulation in eukaryotes. PMID:25188032
Fourier relationship between angular position and optical orbital angular momentum
Eric Yao; Sonja Franke-Arnold; Johannes Courtial; Stephen Barnett; Miles Padgett
2006-06-15
We demonstrate the Fourier relationship between angular position and angular momentum for a light mode. In particular we measure the distribution of orbital angular momentum states of light that has passed through an aperture and verify that the orbital angular momentum distribution is given by the complex Fourier-transform of the aperture function. We use spatial light modulators, configured as diffractive optical components, to define the initial orbital angular momentum state of the beam, set the defining aperture, and measure the angular momentum spread of the resulting beam. These measurements clearly confirm the Fourier relationship between angular momentum and angular position, even at light intensities corresponding to the single photon level.
Optical Broadband Angular Selectivity
Shen, Yichen
Light selection based purely on the angle of propagation is a long-standing scientific challenge. In angularly selective systems, however, the transmission of light usually also depends on the light frequency. We tailored ...
Metamaterial broadband angular selectivity
Shen, Yichen
We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each ...
Angular velocity discrimination
NASA Technical Reports Server (NTRS)
Kaiser, Mary K.
1990-01-01
Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.
Using ultrasounds for the estimation of the misalignment in plate-plate torsional rheometry
NASA Astrophysics Data System (ADS)
Rodríguez-López, J.; Elvira, L.; Montero de Espinosa Freijo, F.; de Vicente, J.
2013-05-01
A new method to accurately quantify the gap error arising from non-parallelism in plate-plate and cone-plate torsional rheometry is proposed. This method consists in monitoring the ultrasonic pulses sent by a transducer adapted to the rheometer bottom plate. The time of flight (TOF) of the echoes reflected by the rheometer upper plate, while it rotates at small angular velocity having a sample placed between the plates, is measured. As the sample acoustic velocity is constant and known, any variation in the TOF is correlated with changes in the distance between plates and thus, the misalignment is automatically determined.
Torsion-bar antenna in the proper reference frame with rotation
NASA Astrophysics Data System (ADS)
Nakamura, Kouji; Ando, Masaki
2014-09-01
The resultant response of the rotating torsion-bar antenna for gravitational waves discussed in M. Ando et al. [Phys. Rev. Lett. 105, 161101 (2010)] is reinvestigated from a general-relativistic point of view. To do this, the equation of motion of a free-falling particle in the proper reference frame of a rotating observer is used. As a result, the resultant response derived in the above paper is also valid even when ?g˜?, where ?g and ? are the angular frequencies of gravitational waves and the rotation of the antenna, respectively.
THEROLE OF ACTIVE REGIONS IN THEGENERATION OF TORSIONAL OSCILLATIONS
Petrovay, KristÃ³f
relationship between these torsional waves, of wavenumber #24; 2=hemisphere, and the sunspot butter y diagram of torsional waves from f-mode splittings by Kosovichev and Schou (1997), helioseismic observations have propositions of the coexistence of a #24; 1=hemisphere modulation with the torsional waves. Most theoretical
Bavu et al. Torsional waves in a bowed string
New South Wales, University of
Bavu et al. Torsional waves in a bowed string Eric Bavu, John Smith and Joe Wolfe 1 Music Acoustics Bowing a string with a non-zero radius exerts a torque, which excites torsional waves. In general, torsional standing waves have higher fundamental frequencies than do transverse standing waves
THE TRANSITION TO TURBULENCE OF THE TORSIONAL COUETTE FLOW
Paris-Sud XI, UniversitÃ© de
, a primary instability cre- ates a periodic laminar spiral wave pattern in the torsional Couette flow conTHE TRANSITION TO TURBULENCE OF THE TORSIONAL COUETTE FLOW Anne Cros and Patrice Le Gal Institut de gradient is nearly constant and this rotating disk flow is a torsional Couette flow. As in the plane
Intermittent partial adnexal torsion after electrosurgical tubal ligation
Robert A. Sasso
1996-01-01
Intermittent partial adnexal torsion after electrosurgical tubal ligation has been suggested as a cause of chronic pelvic pain. Little is present in the literature describing this entity or its characteristics. Unlike complete torsion of the fallopian tube, ovary, or paratubal cyst, intermittent adnexal torsion is more subtle in both clinical features and laparoscopic findings. It appears to be an underrecognized
Precision Tilt Measurements for a Cryogenic Torsion Balance Scott Yantek
Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group
: August 22, 2012) Abstract Torsion balances allow for high-precision tests of the equivalence principle a basic torsion balance setup with the attrac- tor very close to the test mass. With an appropri- ately]. Today,torsion balances are used to test the equiv- alence principle, which asserts that gravitational
Minimum uncertainty states of angular momentum and angular position
Zambrini, Roberta
Minimum uncertainty states of angular momentum and angular position David T Pegg1 , Stephen M of linear momentum that satisfy the equality in the Heisenberg uncertainty principle for position for position and momentum. The corresponding uncertainty relation for angular momentum and angular position
Matter-antimatter asymmetry and dark matter from torsion
Poplawski, Nikodem J
2011-01-01
We propose a simple scenario which explains the observed matter-antimatter imbalance and the origin of dark matter in the Universe. We use the Einstein-Cartan-Sciama-Kibble theory of gravity which naturally extends general relativity to include the intrinsic spin of matter. The torsion of spacetime generates in the Dirac equation the Hehl-Datta term which is cubic in spinor fields. We show that under the charge-conjugation transformation this term changes sign relative to the mass term. A Dirac spinor and its charge-conjugate therefore satisfy different field equations. Fermions in the presence of torsion have higher energy levels than antifermions, which leads to their decay asymmetry. Such a difference is significant only at extremely high densities that existed in the very early Universe. We propose that this difference caused a mechanism, according to which heavy fermions existing in such a Universe and carrying the baryon number decayed mostly to normal matter, whereas their antiparticles decayed mostly ...
Matter-antimatter asymmetry and dark matter from torsion
NASA Astrophysics Data System (ADS)
Pop?awski, Nikodem J.
2011-04-01
We propose a simple scenario which explains the observed matter-antimatter imbalance and the origin of dark matter in the Universe. We use the Einstein-Cartan-Sciama-Kibble theory of gravity which naturally extends general relativity to include the intrinsic spin of matter. Spacetime torsion produced by spin generates, in the classical Dirac equation, the Hehl-Datta term which is cubic in spinor fields. We show that under a charge-conjugation transformation this term changes sign relative to the mass term. A classical Dirac spinor and its charge conjugate therefore satisfy different field equations. Fermions in the presence of torsion have higher energy levels than antifermions, which leads to their decay asymmetry. Such a difference is significant only at extremely high densities that existed in the very early Universe. We propose that this difference caused a mechanism, according to which heavy fermions existing in such a Universe and carrying the baryon number decayed mostly to normal matter, whereas their antiparticles decayed mostly to hidden antimatter which forms dark matter. The conserved total baryon number of the Universe remained zero.
Matter-antimatter asymmetry and dark matter from torsion
Nikodem J. Poplawski
2011-05-26
We propose a simple scenario which explains the observed matter-antimatter imbalance and the origin of dark matter in the Universe. We use the Einstein-Cartan-Sciama-Kibble theory of gravity which naturally extends general relativity to include the intrinsic spin of matter. Spacetime torsion produced by spin generates, in the classical Dirac equation, the Hehl-Datta term which is cubic in spinor fields. We show that under a charge-conjugation transformation this term changes sign relative to the mass term. A classical Dirac spinor and its charge conjugate therefore satisfy different field equations. Fermions in the presence of torsion have higher energy levels than antifermions, which leads to their decay asymmetry. Such a difference is significant only at extremely high densities that existed in the very early Universe. We propose that this difference caused a mechanism, according to which heavy fermions existing in such a Universe and carrying the baryon number decayed mostly to normal matter, whereas their antiparticles decayed mostly to hidden antimatter which forms dark matter. The conserved total baryon number of the Universe remained zero.
Evidence for the distribution of angular velocity inside the sun and stars
NASA Technical Reports Server (NTRS)
1972-01-01
A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing the distribution of angular velocity inside the sun and stars.
NASA Technical Reports Server (NTRS)
Chutjian, A.; Msezane, A. Z.; Henry, R. J. W.
1983-01-01
Differential electron-scattering cross sections for inelastic excitation of an ion have been measured for the first time. Experiments were carried out in a cross electron-ion beam geometry for the 4(2)S yields 4(2)P transition in Zn II at 75 eV. In addition, differential cross sections were calculated at energies between 15 and 100 eV in a five-state close-coupling approximation in which 4s, 4p, 3d(9)4s(2), 5s, and 4 d states were included. Agreement in shape between theory and experiment at 75 eV is excellent.
The Angular Momentum Dichotomy
NASA Astrophysics Data System (ADS)
Teklu, Adelheid; Remus, Rhea-Silvia; Dolag, Klaus; Burkert, Andreas
2015-02-01
In the context of the formation of spiral galaxies the evolution and distribution of the angular momentum of dark matter halos have been discussed for more than 20 years, especially the idea that the specific angular momentum of the halo can be estimated from the specific angular momentum of its disk (e.g. Fall & Efstathiou (1980), Fall (1983) and Mo et al. (1998)). We use a new set of hydrodynamic cosmological simulations called Magneticum Pathfinder which allow us to split the galaxies into spheroidal and disk galaxies via the circularity parameter ?, as commonly used (e.g. Scannapieco et al. (2008)). Here, we focus on the dimensionless spin parameter ? = J |E|1/2 / (G M5/2) (Peebles 1969, 1971), which is a measure of the rotation of the total halo and can be fitted by a lognormal distribution, e.g. Mo et al. (1998). The spin parameter allows one to compare the relative angular momentum of halos across different masses and different times. Fig. 1 reveals a dichotomy in the distribution of ? at all redshifts when the galaxies are split into spheroids (dashed) and disk galaxies (dash-dotted). The disk galaxies preferentially live in halos with slightly larger spin parameter compared to spheroidal galaxies. Thus, we see that the ? of the whole halo reflects the morphology of its central galaxy. For more details and a larger study of the angular momentum properties of disk and spheroidal galaxies, see Teklu et al. (in prep.).
TORSION ANALYSIS OF FRESH AND AGED CHEESES
Technology Transfer Automated Retrieval System (TEKTRAN)
Torsion gelometry is a fundamental rheological test that can be performed on cheese to provide values of shear stress and shear strain. Six cheese varieties encompassing a wide compositional and age range were analyzed fresh and after aging to determine correlations between casein proteolysis produ...
Torsional wave propagation in reinforced concrete columns
Hidenori Murakami; Junya Yamakawa
1998-01-01
Using a semi-analytical finite element (FE) method, the torsional phase velocity spectra of elastic waves were investigated for reinforced concrete (RC) columns with and without exterior composite layers. An examination of the spectra of these two types of columns shows that the retrofitted columns have a slightly smaller phase velocity in their first mode. In addition, the first mode shapes
Gravitational dispersion in a torsional wave machine
de la Madrid, Rafael; Irwin, George
2014-01-01
We demonstrate that mechanical waves traveling in a torsional, mechanical wave machine exhibit dispersion due to gravity and the discreteness of the medium. We also show that although the dispersion due to discreteness is negligible, the dispersion due to gravity can be easily measured, and can be shown to disappear in a zero-gravity environment.
Gravitational dispersion in a torsional wave machine
Rafael de la Madrid; Alejandro Gonzalez; George Irwin
2014-09-01
We demonstrate that mechanical waves traveling in a torsional, mechanical wave machine exhibit dispersion due to gravity and the discreteness of the medium. We also show that although the dispersion due to discreteness is negligible, the dispersion due to gravity can be easily measured, and can be shown to disappear in a zero-gravity environment.
Gravitational dispersion in a torsional wave machine
NASA Astrophysics Data System (ADS)
de la Madrid, Rafael; Gonzalez, Alejandro; Irwin, George M.
2014-12-01
We demonstrate that mechanical waves traveling in a torsional, mechanical wave machine exhibit dispersion due to gravity and the discreteness of the medium. We also show that although the dispersion due to discreteness is negligible, the dispersion due to gravity can be easily measured and can be shown to disappear in a zero-gravity environment.
Equivariant analytic torsion on Pn Kai KOOHLER
KÃ¶hler, Kai
. The proof of the Riemann-Roch theorem uses a calculation of Gillet, Soul and Zagier [GS1] of the torsion with a special function, which is very similar to the series defining the Gillet-Soul R-genus. 1991 Mathematics of the Gillet-Soul R-function. Keywords: Determinants and determinant line bundles, Arakelov geo- metry
Shear strain localization in torsion experiments
F. Ornelas Marques; L. Burlini
2009-01-01
We used torsion experiments to investigate how mineral composition, grain size and distribution, temperature, scale and fluid content can trigger shear strain localization. The tested synthetic aggregates were composed of one, two or three mineral phases, with a matrix of halite comprising 100% of the sample in the one-phase specimen, 80% of the sample in the two-phase specimens, and 50%
Torsion of a Large Appendix Testis Misdiagnosed as Pyocele
Meher, Susanta; Rath, Satyajit; Sharma, Rakesh; Sasmal, Prakash Kumar; Mishra, Tushar Subhadarshan
2015-01-01
Torsion of the appendix testis is not an uncommon cause of acute hemiscrotum. It is frequently misdiagnosed as acute epididymitis, orchitis, or torsion of testis. Though conservative management is the treatment of choice for this condition, prompt surgical intervention is warranted when testicular torsion is suspected. We report a case of torsion of a large appendix testis misdiagnosed as pyocele. Emergency exploration of it revealed a large appendix testis with torsion and early features of gangrene. After excision of the appendix testis, the wound was closed with an open drain. The patient had an uneventful and smooth postoperative recovery.
Metamaterial broadband angular selectivity
NASA Astrophysics Data System (ADS)
Shen, Yichen; Ye, Dexin; Wang, Li; Celanovic, Ivan; Ran, Lixin; Joannopoulos, John D.; Solja?i?, Marin
2014-09-01
We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each effective anisotropic layer is constructed from a multilayered metamaterial. We show that by simply changing the structure of the metamaterials, the selective angle can be tuned to a broad range of angles; and, by increasing the number of stacks, the angular transmission window can be made as narrow as desired. As a proof of principle, we realize the idea experimentally in the microwave regime. The angular selectivity and tunability we report here can have various applications such as in directional control of electromagnetic emitters and detectors.
Fluidic angular velocity sensor
NASA Technical Reports Server (NTRS)
Berdahl, C. M. (inventor)
1986-01-01
A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.
Jankowiak, Martin; Larkoski, Andrew J.; /SLAC
2012-02-17
We introduce a jet shape observable defined for an ensemble of jets in terms of two-particle angular correlations and a resolution parameter R. This quantity is infrared and collinear safe and can be interpreted as a scaling exponent for the angular distribution of mass inside the jet. For small R it is close to the value 2 as a consequence of the approximately scale invariant QCD dynamics. For large R it is sensitive to non-perturbative effects. We describe the use of this correlation function for tests of QCD, for studying underlying event and pile-up effects, and for tuning Monte Carlo event generators.
Ruda, Mitchell C. (Tucson, AZ); Greynolds, Alan W. (Tucson, AZ); Stuhlinger, Tilman W. (Tucson, AZ)
2009-07-14
One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.
Design and analysis of a torsion braid pendulum displacement transducer
NASA Technical Reports Server (NTRS)
Rind, E.; Bryant, E. L.
1981-01-01
The dynamic properties at various temperatures of braids impregnated with polymer can be measured by using the braid as the suspension of a torsion pendulum. This report describes the electronic and mechanical design of a torsional braid pendulum displacement transducer which is an advance in the state of the art. The transducer uses a unique optical design consisting of refracting quartz windows used in conjunction with a differential photocell to produce a null signal. The release mechanism for initiating free torsional oscillation of the pendulum has also been improved. Analysis of the precision and accuracy of the transducer indicated that the maximum relative error in measuring torsional amplitude was approximately 0. A serious problem inherent in all instruments which use a torsional suspension was analyzed: misalignment of the physical and torsional axes of the torsional member which results in modulation of the amplitude of the free oscillation.
Ideal Linear Chain Polymers with Fixed Angular Momentum
Matthew Brunner; J. M. Deutsch
2010-08-21
The statistical mechanics of a linear non-interacting 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 non-interacting 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.
Curro, John G.; Webb III, Edmund B.; Grest, Gary S.; Weinhold, Jeffrey D.; Putz, Mathias; McCoy, John D.
1999-07-21
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.
Gears: Determining Angular Velocity
NSDL National Science Digital Library
AMPS GK-12 Program,
Students work as engineers and learn to conduct controlled experiments by changing one experimental variable at a time to study its effect on the experiment outcome. Specifically, they conduct experiments to determine the angular velocity for a gear train with varying gear ratios and lengths. Student groups assemble LEGO® MINDSTORMS® NXT robots with variously sized gears in a gear train and then design programs using the NXT software to cause the motor to rotate all the gears in the gear train. They use the LEGO data logging program and light sensors to set up experiments. They run the program with the motor and the light sensor at the same time and analyze the resulting plot in order to determine the angular velocity using the provided physics-based equations. Finally, students manipulate the gear train with different gears and different lengths in order to analyze all these factors and figure out which manipulation has a higher angular velocity. They use the equations for circumference of a circle and angular velocity; and convert units between radians and degrees.
Quasi-steady prediction of coupled bending-torsion flutter under rotating stall
NASA Astrophysics Data System (ADS)
Ananth, S. M.; Kushari, A.; Venkatesan, C.
2013-11-01
A method is presented in this paper to predict cascade flutter under subsonic stalled flow condition in a quasi-steady manner. The ability to predict the occurrence of aeroelastic flutter is highly important from the compressor design point of view. In the present work, the well known Moore-Greitzer compression system model is used to evaluate the flow under rotating stall and the linearized aerodynamic theory of Whitehead is used to estimate the blade loading. The cascade stability is then predicted by solving the structural model, which is posed as a complex eigenvalue problem. The possibility of occurrence of flutter in both bending and torsional modes is considered and the latter is found to be the dominant one, under subsonic stalled flow, for a large range of frequency ratios examined. It is also shown that the design of compressor blades at frequency ratios close to unity may result in rapid initiation of torsional flutter in the presence of stalled flow. A frequency ratio of 0.9 is primarily emphasized for most part of the study as many interesting features are revealed and the results are physically interpreted. Roughly a pitchfork pattern of energy distribution appears to occur between bending mode and torsional mode which ensures that only one flutter mode is possible at any instant in time. A bifurcation from bending flutter to torsional flutter is shown to occur during which the frequency of the two vibrating modes appear to coalesce for a very short period of time.
Continuous phase transition and critical behaviors of 3D black hole with torsion
NASA Astrophysics Data System (ADS)
Ma, Meng-Sen; Liu, Fang; Zhao, Ren
2014-05-01
We study the phase transition and the critical behavior of the BTZ black hole with torsion obtained in (1 + 2)-dimensional Poincaré gauge theory. According to Ehrenfest’s classification, when the parameters in the theory are arranged properly, the BTZ black hole with torsion may possess the second-order phase transition which is also a smaller mass/larger mass black hole phase transition. Nevertheless, the critical behavior is different from the one in the van der Waals liquid/gas system. We also calculated the critical exponents of the relevant thermodynamic quantities, which are the same as the ones obtained in the Ho?ava-Lifshitz black hole and the Born-Infeld black hole.
Quantum Entanglement of High Angular Momenta
Robert Fickler; Radek Lapkiewicz; William N. Plick; Mario Krenn; Christoph Schaeff; Sven Ramelow; Anton Zeilinger
2014-06-06
Single photons with helical phase structures may carry a quantized amount of orbital angular momentum (OAM) and their entanglement is important for quantum information science and fundamental tests of quantum theory. Because there is no theoretical upper limit on how many quanta of OAM a single photon can carry, it is possible to create entanglement between two particles with an arbitrary high difference in the quantum number. By transferring polarization entanglement to OAM with an interferometric scheme, we generate and verify entanglement up to 600 quanta difference in the orbital angular momentum. The only restrictive factors towards higher numbers are current technical limitations. We also experimentally demonstrate that the entanglement of very high OAM can improve the sensitivity of the angular resolution in remote sensing.
Angular analysis of the decay ? b ? ?(? N?) ? + ? -
NASA Astrophysics Data System (ADS)
Böer, Philipp; Feldmann, Thorsten; van Dyk, Danny
2015-01-01
We study the differential decay rate for the rare ? b ? ?(? N?) ? + ? - transition, including a determination of the complete angular distribution, assuming unpolarized ? b baryons. On the basis of a properly chosen parametrization of the various helicity amplitudes, we provide expressions for the angular observables within the Standard Model and a subset of new physics models with chirality-flipped operators. Hadronic effects at low recoil are estimated by combining information from lattice QCD with (improved) form-factor relations in Heavy Quark Effective Theory. Our estimates for large hadronic recoil — at this stage — are still rather uncertain because the baryonic input functions are not so well known, and non-factorizable spectator effects have not been worked out systematically so far. Still, our phenomenological analysis of decay asymmetries and angular observables for ? b ? ?(? N?) ? + ? - reveals that this decay mode can provide new and complementary constraints on the Wilson coefficients in radiative and semileptonic b ? s transitions compared to the corresponding mesonic modes.
A preliminary study of a torsion balance based on a spherical superconducting suspension
NASA Astrophysics Data System (ADS)
Speake, C. C.; Hammond, G. D.; Trenkel, C.; Rochester, G. K.; Sumner, T. J.
1999-06-01
We present details of the design and construction of a new superconducting, magnetically suspended torsion balance in which the levitation coil and the lift surface of the float lie on the surfaces of concentric spheres. We compare results from calculations of the variation of the inductance with the levitated height and transverse motion of the float with experimental measurements and show that the levitation system is stable. Angular motion of the torsion balance is detected using superconducting pick-up coils whose inductance is modulated by float rotation. The subsequent change in current flowing in the persistent circuit containing the coils is measured using a flux-gate magnetometer. The pick-up coils exert a restoring torque on the float which can be modified by adjusting the persistent current stored. Periods down to 60 s should be obtainable for a current of 2.5 A. Preliminary results of ring-down experiments in He gas at a pressure of 53Pa show that periods of angular oscillations of 24 s with quality factor, Q, of about 200 can be obtained. The moment of inertia of the float is 2 × 10-5 kg m2. The observed period of 24 s indicates that there is an additional restoring torque in the system which may be due to trapped flux. The observed value of Q is consistent with gas damping.
Propagation of torsional waves in a prestretched compound hollow circular cylinder
A. Ozturk; S. D. Akbarov
2008-01-01
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
Approximate Torsional Analysis of Multi-layered Tubes with Non-circular Cross-Sections
Benyamin Gholami Bazehhour; Jalil Rezaeepazhand
In this paper an approximate formulation for torsional analysis of tubes with multi-layered non-circular cross-sections is\\u000a presented. A previously presented method based on Bredt’s theory is extended to achieve these formulas. Layers are assumed\\u000a to be isotropic and may possess different thicknesses and material properties. The obtained formulas for shear stress and\\u000a angle of twist are applicable to thin to
Investigations of magnetic hysteresis of barium ferrite using the torsion pendulum method
Richter, H.J.; Hempel, K.A.
1988-11-15
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.
Lorentz Gauge Gravity and Induced Effective Theories
S. W. Kim; D. G. Pak
2005-12-25
We develop the gauge approach based on the Lorentz group to the gravity with torsion. With a Lagrangian quadratic in curvature we show that the Einstein-Hilbert action can be induced from a simple gauge model due to quantum corrections of torsion via formation of a gravito-magnetic condensate. An effective theory of cosmic knots at Planckian scale is proposed.
Xu, L. [Department of Physical Sciences, University of New Brunswick, Saint John, New Brunswick E2L 4L5 (Canada)] [Department of Physical Sciences, University of New Brunswick, Saint John, New Brunswick E2L 4L5 (Canada); Lees, R.M. [Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada)] [Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada); Hougen, J.T. [Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)] [Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
1999-02-01
Equilibrium structural constants and certain torsion{endash}rotation interaction parameters have been determined for methanol and acetaldehyde from {ital ab initio} calculations using GAUSSIAN 94. The substantial molecular flexing which occurs in going from the bottom to the top of the torsional potential barrier can be quantitatively related to coefficients of torsion{endash}rotation terms having a (1{minus}cos&hthinsp;3{gamma}) dependence on torsional angle {gamma}. The barrier height, six equilibrium structural constants characterizing the bottom of the potential well, and six torsion{endash}rotation constants are all compared to experimental parameters obtained from global fits to large microwave and far-infrared data sets for methanol and acetaldehyde. The rather encouraging agreement between the Gaussian and global fit results for methanol seems both to validate the accuracy of {ital ab initio} calculations of these parameters, and to demonstrate that the physical origin of these torsion{endash}rotation interaction terms in methanol lies primarily in structural relaxation with torsion. The less satisfactory agreement between theory and experiment for acetaldehyde requires further study. {copyright} {ital 1999 American Institute of Physics.}
A. Ozturk; S. D. Akbarov
2009-01-01
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
K. Hoki; D. Kröner; J. Manz
2001-01-01
We design a laser pulse which drives a racemate of oriented atropisomers at low temperature to a preferential target enantiomer. The overall laser pulse consists of a series of individual circularly polarized laser pulses which induce corresponding selective transitions between coupled rotational and torsional states. The underlying theory is derived in detail for a model system. It consists of two
Woodcock, H Lee; Moran, Damian; Pastor, Richard W; MacKerell, Alexander D; Brooks, Bernard R
2007-07-01
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 DeltaE = E(equatorial) - E(axial) = 1.42 kcal/mol. When corrected for solvent (by the IEFPCM model), zero-point vibrations and entropy, DeltaG(298) = 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 DeltaE 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 DeltaE by approximately 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. PMID:17554075
Axial and torsional fatigue behavior of Waspaloy
NASA Technical Reports Server (NTRS)
Zamrik, S.; Mirdamadi, M.; Zahiri, F.
1986-01-01
The cyclic flow response and crack growth behavior of Waspaloy at room temperature and 650 C under tensile loading and torsional loading was studied, for two conditions of Waspaloy: fine grain, large gamma prime size; coarse grain, small gamma prime size. The fine grain material showed 5 to 10 percent hardening after about 10 percent of life, with sequent softening to failure at both themperature levels. The coarse grain material showed either stable response or monotonic softening to failure. Early crack initiation was observed on planes of maximum shear, with eventual branching to principle planes under torsional loading; cracks were always normal to load axis under tensile loading. Also, crack paths were intergranular at 650 C, mostly transgranular at room temperature.
Interfacing a torsion pendulum with a microcomputer
Bush, J.A.; Newby, J.W.
1983-02-24
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.
Zhao, Hao; Feng, Hao
2013-01-01
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. PMID:23941911
UBIQUITOUS TORSIONAL MOTIONS IN TYPE II SPICULES
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
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.
Fluid driven torsional dipole seismic source
Hardee, H.C.
1990-08-08
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.
Fluid driven torsional dipole seismic source
Hardee, Harry C. (Albuquerque, NM)
1991-01-01
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.
Torsional Resonance Microscopy and Its Applications
Chanmin Su; Lin Huang; Craig B. Prater; Bharat Bhushan
Torsional resonance microscope provides dynamic information of the tip-sample interaction in lateral dimensions. Since the\\u000a tip displacement amplitude can be as low as subnanometers, it reflects near-field interaction due to different mechanisms,\\u000a such as mechanical, electrical and magnetic interactions. When TRmode is applied in combination with flexural interaction\\u000a such as TappingMode or contact mode it is possible to study the
Ubiquitous torsional motions in type II spicules
De Pontieu, B; van der Voort, L H M Rouppe; Rutten, R J; Hansteen, V H; Watanabe, H
2012-01-01
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, 2. swaying motions of order 15-20 km/s, and 3. torsional motions of order 25-30 km/s. 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 narrow-band images 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. The combined action of the different motions explains the similar morphology of spicule bushes in the ...
Polyorchidism with presumed contralateral intrauterine testicular torsion
Leodoro, B.M.; Beasley, S.W.; Stringer, M.D.
2014-01-01
INTRODUCTION Polyorchidism was first described by Blasius in 16701 during a routine autopsy. We report a child with unilateral polyorchidism and a contralateral absent testis, a combination not reported previously. PRESENTATION OF CASE A 2-year-old boy was referred to the outpatient clinic with an impalpable left testis. At laparoscopy, the left vas deferens and testicular vessels ended blindly proximal to a closed internal ring. No gonadal tissue was identified. On the right side, a single vas deferens and testicular vessels were seen entering the internal ring as normal. The right side of the scrotum was explored and two testes were identified within a single tunica vaginalis. DISCUSSION Polyorchidism is rare with a literature search identifying approximately 230 reported cases. Whilst prenatal testicular torsion is increasing being recognized and treated as a surgical emergency,9 prenatal testicular torsion in association with polyorchidism has not been previously reported. CONCLUSION We describe a unique case of a 2-year-old boy with right-sided polyorchidism and an absent left testis associated with a blind ending vas deferens and testicular vessels, presumed secondary to intrauterine testicular torsion. PMID:25462053
Flexural-torsional buckling initiates idiopathic scoliosis.
Karnezis, Ioannis A
2011-11-01
Initiation of the spinal deformity in idiopathic scoliosis (IS) has been attributed to an abnormal pattern of spinal growth during development. However, recent findings suggest that the earliest observable event in the pathogenesis of IS is a change in the shape of intervertebral discs with alterations in the shape of vertebrae being considered a secondary event. Starting from the previous description of the spinal deformity in IS as 'buckling' of the spine a new hypothesis describing the initial spinal deformity in IS as flexural-torsional buckling, a three-dimensional type of failure of axially loaded columns, is proposed. According to the new hypothesis the initiating event (the earliest observable event) in IS is flexural-torsional buckling developing from the flexible parts (intervertebral discs and ligaments) of the affected spinal motion segments. Since flexural-torsional buckling occurs in columns with a cross-section of one axis of symmetry characterised by a much greater in-plane than out-of-plane bending stiffness the new hypothesis predicts that the initiating condition (the condition promoting the initiation) of IS is 'flexibility anisotropy' namely significantly higher bending stiffness in lateral bending than bending stiffness in flexion-extension of a part of the spine. The parameter of 'flexibility anisotropy' as a factor for initiation of IS has never been suggested or tested before. The present hypothesis has implications in the research on the pathogenesis of IS as well as in the development of new methods for its treatment. PMID:21885198
Aeroelastic considerations for torsionally soft rotors
NASA Technical Reports Server (NTRS)
Mantay, W. R.; Yeager, W. T., Jr.
1986-01-01
A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on conformable rotor performance and loads characteristics. The model articulated rotors included baseline and torsionally soft blades with interchangeable tips. Seven blade tip designs were evaluated on the baseline rotor and six tip designs were tested on the torsionally soft blades. The designs incorporated a systemmatic variation in geometric parameters including sweep, taper, and anhedral. The rotors were evaluated in the NASA Langley Transonic Dynamics Tunnel at several advance ratios, lift and propulsive force values, and tip Mach numbers. A track sensitivity study was also conducted at several advance ratios for both rotors. Based on the test results, tip parameter variations generated significant rotor performance and loads differences for both baseline and torsionally soft blades. Azimuthal variation of elastic twist generated by variations in the tip parameters strongly correlated with rotor performance and loads, but the magnitude of advancing blade elastic twist did not. In addition, fixed system vibratory loads and rotor track for potential conformable rotor candidates appears very sensitive to parametric rotor changes.
Modeling DNA Thermodynamics under Torsional Stress
Wang, Qian; Pettitt, B. Montgomery
2014-01-01
Negatively twisted DNA is essential to many biological functions. Due to torsional stress, duplex DNA can have local, sequence-dependent structural defects. In this work, a thermodynamic model of DNA was built to qualitatively predict the local sequence-dependent mechanical instabilities under torsional stress. The results were compared to both simulation of a coarse-grained model and experiment results. By using the Kirkwood superposition approximation, we built an analytical model to represent the free energy difference ?W of a hydrogen-bonded basepair between the B-form helical state and the basepair opened (or locally melted) state, within a given sequence under torsional stress. We showed that ?W can be well approximated by two-body interactions with its nearest-sequence-neighbor basepairs plus a free energy correction due to long-range correlations. This model is capable of rapidly predicting the position and thermodynamics of local defects in a given sequence. The result qualitatively matches with an in vitro experiment for a long DNA sequence (>4000 basepairs). The 12 parameters used in this model can be further quantitatively refined when more experimental data are available. PMID:24606942
Sutton, Christopher; Gray, Matthew T.; Brunsfeld, Max; Parrish, Robert M.; Sherrill, C. David; Sears, John S.; Brédas, Jean-Luc, E-mail: jean-luc.bredas@chemistry.gatech.edu, E-mail: thomas.koerzdoerfer@uni-potsdam.de [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)] [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Körzdörfer, Thomas, E-mail: jean-luc.bredas@chemistry.gatech.edu, E-mail: thomas.koerzdoerfer@uni-potsdam.de [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States) [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Computational Chemistry, Institute of Chemistry, University of Potsdam, D-14476 Potsdam (Germany)
2014-02-07
We investigate the torsion potentials in two prototypical ?-conjugated polymers, polyacetylene and polydiacetylene, as a function of chain length using different flavors of density functional theory. Our study provides a quantitative analysis of the delocalization error in standard semilocal and hybrid density functionals and demonstrates how it can influence structural and thermodynamic properties. The delocalization error is quantified by evaluating the many-electron self-interaction error (MESIE) for fractional electron numbers, which allows us to establish a direct connection between the MESIE and the error in the torsion barriers. The use of non-empirically tuned long-range corrected hybrid functionals results in a very significant reduction of the MESIE and leads to an improved description of torsion barrier heights. In addition, we demonstrate how our analysis allows the determination of the effective conjugation length in polyacetylene and polydiacetylene chains.
Spin-to-orbital angular momentum conversion in focusing, scattering, and imaging systems
Dainty, Chris
Spin-to-orbital angular momentum conversion in focusing, scattering, and imaging systems Konstantin.bliokh@gmail.com Abstract: We present a general theory of spin-to-orbital angular momentum (AM) conversion of light, C. Manzo, and D. Paparo, "Optical spin-to-orbital angular momentum conversion in inhomogeneous
NASA Technical Reports Server (NTRS)
Anderson, Todd; Herbst, Eric; De Lucia, Frank C.
1992-01-01
The high-resolution laboratory millimeter- and submillimeter-wave spectra of C-12H(3)OH and C-13H(3)OH have been extended to include transitions involving significantly higher angular momentum quantum numbers than studied previously. For C-12H(3)OH, the data set now includes 549 A torsional substate transitions and 524 E torsional substate transitions through J is not greater than 24, exclusive of blends. For C-13H(3)OH the data set now includes 453 A torsional substate transitions and 440 E torsional substate transitions through J is not greater than 24, exclusive of blends. The extended internal axis method Hamiltonian has been used to analyze the transitions to experimental accuracy. The molecular constants determined by this approach have been used to predict accurately the frequencies of many transitions through J = 25 not measured in the laboratory.
Nanofabricated quartz cylinders for angular
Wang, Michelle
Nanofabricated quartz cylinders for angular trapping: DNA supercoiling torque detection Christopher nanofabricated quartz cylinders well suited for torque application and detection in an angular optical trap. We that nanofabricated quartz cylinders, when used with an angular trapping instrument, allow direct and simultaneous
A Vacuum Solution with Torsion in Higher-Derivative Gravity
Kouzou Nishida
2012-09-02
In this paper, we provide a vacuum solution with torsion in quadratic Riemann-curvature gravity. Physically, the solution means that vacuum can have a nonzero vacuum field with large torsion. We show that the Einstein-Hilbert action can be derived if we expand the quadratic curvature of the Lagrangian in a torsion-free Riemannian space-time around a nonzero vacuum field. We also show that the cosmological constant caused by a nonzero vacuum field is equal to zero.
NASA Astrophysics Data System (ADS)
Johnson, Blake N.; Mutharasan, Raj
2011-03-01
Cantilever sensors consisting of only a piezoelectric layer express both bending and torsional modes near ˜25 kHz that persist with reasonable Q-values (˜15) in liquids of high viscosity (>100 cP). Responses of both bending and torsional modes in liquids (1-1019 cP) were measured simultaneously. The bending mode response was more sensitive to mass-change effects than the torsional mode, and the response in liquids <70 cP matched theoretical values within 0.9%. At 1019 cP the bending mode response was within 10.4% of theory. The bending and torsional modes in PEMC can potentially be used simultaneously for bio-chemical sensing in very viscous samples.
Updated Collider Bounds on the Parameters of Dynamical Torsion
Uma Mahanta; Sreerup Raychaudhuri
2003-07-29
We constrain the parameters of dynamical torsion, namely, the torsion-fermion coupling and the torsion mass, by making a careful analysis of current LEP-2 data at several energies, as well as CDF and D0 data from Run-I of the Tevatron. We find that measurements of the forward-backward asymmetry in the e+- e- -> mu+- mu- channel at LEP-2 produce the most restrictive bounds over most of the parameter space,though other measurements, too, have a significant role to play. Our results considerably improve the existing constraints on models with dynamical torsion.
Angular Momentum in Dwarf Galaxies
NASA Astrophysics Data System (ADS)
Del Popolo, A.
We study the ``angular momentum catastrophe" in the framework of interaction among baryons and dark matter through dynamical friction. By means of Del Popolo (2009) model we simulate 14 galaxies similar to those investigated by van den Bosch, Burkert and Swaters (2001), and calculate the distribution of their spin parameters and the angular momenta. Our model gives the angular momentum distribution which is in agreement with the van den Bosch et al. observations. Our result shows that the ``angular momentum catastrophe" can be naturally solved in a model that takes into account the baryonic physics and the exchange of energy and angular momentum between the baryonic clumps and dark matter through dynamical friction.
Fan, Z; Lowe, M J S; Castaings, M; Bacon, C
2008-10-01
Guided torsional waves in a bar with a noncircular cross section have been exploited by previous researchers to measure the density of fluids. However, due to the complexity of the wave behavior in the noncircular cross-sectional shape, the previous theory can only provide an approximate prediction; thus the accuracy of the measurement has been compromised. In this paper, a semianalytical finite element method is developed to model accurately the propagation velocity and leakage of guided waves along an immersed waveguide with arbitrary noncircular cross section. An accurate inverse model is then provided to measure the density of the fluid by measuring the change of the torsional wave speed. Experimental results obtained with a rectangular bar in a range of fluids show very good agreement with the theoretical predictions. Finally, the potentials to use the model for sensor optimization are discussed. PMID:19062840
Maeda, Takenori [Univ. of Tsukuba, Ibaraki (Japan). Institute of Engineering Mechanics
1995-11-01
This paper presents an experimental method for the determination of the bending and torsional rigidities of advanced fiber composite laminates with the aid of laser holographic interferometry. The proposed method consists of a four-point bending test and a resonance test. The bending rigidity ratio (D{sub 12}/D{sub 22}) can be determined from the fringe patterns of the four-point bending test. The bending rigidities (D{sub 11} and D{sub 22}) and the torsional rigidity (D{sub 66}) are calculated from the natural frequencies of cantilever plates of the resonance test. The test specimens are carbon/epoxy cross-ply laminates. The adequacy of the experimental method is confirmed by comparing the measured rigidities with the theoretical values obtained from classical lamination theory (CLT) by using the measured tensile properties. The results show that the present method can be used to evaluate the rigidities of orthotropic laminates with reasonably good accuracy.
Colliding Wave Solutions in a Symmetric Non-metric Theory
Ozay Gurtug; Mustafa Halilsoy
2008-09-22
A method is given to generate the non-linear interaction (collision) of linearly polarized gravity coupled torsion waves in a non-metric theory. Explicit examples are given in which strong mutual focussing of gravitational waves containing impulsive and shock components coupled with torsion waves does not result in a curvature singularity. However, the collision of purely torsion waves displays a curvature singularity in the region of interaction.
The Torsional Spectrum of Doubly Deuterated Methanol CHD_2OH
NASA Astrophysics Data System (ADS)
Ndao, M.; Coudert, L. H.; Kwabia Tchana, F.; Barros, J.; Margulès, L.; Manceron, Laurent; Roy, P.
2014-06-01
Although the torsional spectrum of several isotopic species of methanol with a symmetrical CH_3 or CD_3 was analyzed some time ago, it is recently, and only for the monodeuterated species CH_2DOH, that such an analysis was extended to the case of an asymmetrical methyl group. In this talk, based on a Fourier transform high-resolution spectrum recorded in the 20 to 670 wn region, the first analysis of the torsional spectrum of doubly deuterated methanol CHD_2OH will be presented. The Q branch of many torsional subbands could be observed and their assignment was initiated using a theoretical torsion-rotation spectrum computed with an approach accounting for the torsion-rotation Coriolis coupling and for the dependence of the generalized inertia tensor on the angle of internal rotation. 46 torsional subbands were thus assigned. For 28 of them, their rotational structure could be assigned and fitted using an effective Hamiltonian expressed as a J(J+1) expansion; and for 2 of them microwave transitions within the lower torsional level could also be included in the analysis. In several cases these analysis revealed that the torsional levels are strongly perturbed. In the talk, the torsional parameters retrieved in the analysis of the torsional subband centers will be discussed. The results of the analysis of the rotational structure of the torsional subbands will be presented and we will also try to understand the nature of the perturbations. At last, preliminary results about the analysis of the microwave spectrum will be presented. El Hilali, Coudert, Konov, and Klee, J. Chem. Phys. 135 (2011) 194309 Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spectrosc. 256 (2009) 204 Quade, Liu, Mukhopadhyay, and Su, J. Mol. Spectrosc. 192 (1998) 378 Pearson, Yu, and Drouin, J. Mol. Spectrosc. 280 (2012) 119
Angular displacement measuring device
NASA Technical Reports Server (NTRS)
Seegmiller, H. Lee B. (inventor)
1992-01-01
A system for measuring the angular displacement of a point of interest on a structure, such as aircraft model within a wind tunnel, includes a source of polarized light located at the point of interest. A remote detector arrangement detects the orientation of the plane of the polarized light received from the source and compares this orientation with the initial orientation to determine the amount or rate of angular displacement of the point of interest. The detector arrangement comprises a rotating polarizing filter and a dual filter and light detector unit. The latter unit comprises an inner aligned filter and photodetector assembly which is disposed relative to the periphery of the polarizer so as to receive polarized light passing the polarizing filter and an outer aligned filter and photodetector assembly which receives the polarized light directly, i.e., without passing through the polarizing filter. The purpose of the unit is to compensate for the effects of dust, fog and the like. A polarization preserving optical fiber conducts polarized light from a remote laser source to the point of interest.
Uniaxial angular accelerometers
NASA Astrophysics Data System (ADS)
Seleznev, A. V.; Shvab, I. A.
1985-05-01
The basic mechanical components of an angular accelerometer are the sensor, the damper, and the transducer. Penumatic dampers are simplest in construction, but the viscosity of air is very low and, therefore, dampers with special purpose oils having a high temperature stability (synthetic silicon or organosilicon oils) are most widely used. The most common types of viscous dampers are lamellar with meshed opposed arrays of fixed and movable vanes in the dashpot, piston dampers regulated by an adjustable-length capillary tube, and dampers with paddle wheel in closed tank. Another type of damper is an impact-inertial one with large masses absorbing the rotational energy upon collision with the sensor. Conventional measuring elements are resistive, capacitive, electromagnetic, photoelectric, and penumatic or hydraulic. Novel types of angular accelerometers are based on inertia of gas jets, electron beams, and ion beams, the piezoelectric effect in p-n junctions of diode and transistors, the electrokinetic effect in fluids, and cryogenic suspension of the sensor.
Torsional fatigue tests of anodized aluminum rods
E. F. Womack; J. H. Wilson; H. H. Mabie
1976-01-01
Fatigue tests in reversed torsion were run on 2024-T351 aluminum-alloy specimens in (1) uncoated state and (2) anodized with\\u000a 0.3 and 0.05-mil (0.0076- and 0.0013-mm) coatings. Tests on both groups were run at low (20–25 percent), medium (55–60 percent),\\u000a and high (86–91 percent) relative humidity. One lot of uncoated specimens was tested that had been polished after machining,\\u000a and one
Design and simulation of microspectrometer based on torsional MEMS grating
Bin Yan; Weizheng Yuan; Ruikang Sun; Dayong Qiao; Yiting Yu; Taiping Li
2010-01-01
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
Five Year Retrospective Case Series of Adnexal Torsion
Joy, Smitha; Nayar, Jayashree
2014-01-01
Aims and Objectives: Adnexal torsion is a rare gynaecological emergency that requires an early surgical intervention to save the adnexa from irreversible damage .Our study is about clinical presentation and management approach of adnexal torsion in a tertiary care centre. Study Design: Retrospective study. Materials and Methods: Review of case records during the five years of 2008 November -2013 November in Amrita Institute of Medical Sciences, Kochi, India. Results: Adnexal torsion was found mainly in the reproductive age. Ultrasound was the most commonly used imaging modality. Benign tumours predispose to torsion. Torsion occurred during postovulatory period in many cases. Polycystic ovaries were a risk factor for unexplained torsion in younger age groups. Diagnosis of adnexal torsion was mostly intra operative by direct visualisation of the rotated adnexa. Laparoscopy was the preferred method of surgical intervention. Ovarian conservation was tried in majority of the child bearing age groups. Conclusion: Adnexal torsion is a rare emergency which requires a high index of clinical suspicion for diagnosis as the symptoms are non specific. Imaging helps in diagnosis but most of them are diagnosed intra operatively. Laparoscopic conservative surgery is the preferred surgical approach especially in younger age groups. An early surgical intervention helps in salvaging the adnexa and prevents further complications. PMID:25653994
Energy-Trapping Torsional-Mode Resonators for Liquid Sensing
Huang, Rui
Energy-Trapping Torsional-Mode Resonators for Liquid Sensing Min K. Kang and Rui Huang Department generates compressional waves in the liquid that reflect off the liquid surface and return to the crystal. In this study, we show that torsional-mode resonators may be used for liquid sensing without the depth effect
Torsional waves on the Sun and the activity cycle
B. J. Labonte; R. Howard
1982-01-01
Some properties of the recently-discovered torsional oscillations of the Sun are presented. The detailed relation of this velocity feature to magnetic activity gives evidence that these motions represent a fundamental oscillation within the Sun that is responsible for the solar activity cycle and that they are not a natural consequence of an a-? dynamo. A new torsional oscillation with wave
Direct excitation of resonant torsional Alfven waves by footpoint motions
M. S. Ruderman; David Berghmans; Marcel Goossens; Stefaan Poedts
1997-01-01
The present paper studies the heating of coronal loops by linear resonant Alfven waves that are excited by the motions of the photospheric footpoints of the magnetic field lines. The analysis is restricted to torsionally polarised footpoint motions in an axially symmetric system so that only torsional Alfven waves are excited. For this subclass of footpoint motions, the Alfven and
Torsional waves on the sun and the activity cycle
NASA Technical Reports Server (NTRS)
Labonte, B. J.; Howard, R.
1982-01-01
The detailed relation of the sun's torsional oscillation velocity feature to magnetic activity indicates (1) that these motions represent a fundamental oscillation within the sun which is responsible for the solar activity cycle, and (2) that they are not a natural consequence of an alpha-omega dynamo. It is demonstrated that a solar torsional oscillation with wave number 1/hemisphere exists.
Dynamic viscoelastic behavior of resin cements measured by torsional resonance
Lakes, Roderic
Dynamic viscoelastic behavior of resin cements measured by torsional resonance Y. Papadogiannisa. Dynamic torsional loading was conducted in the frequency range from 1 to 80 Hz. Cement specimens were such as damping of free vibrations, attenuation of propagated waves and the frequency width of a resonance
TORSIONAL VIBRATION REDUCTION IN INTERNAL COMBUSTION ENGINES USING CENTRIFUGAL PENDULUMS
Cheng-Tang Lee; Steven W. Shaw
The goal of the present work is to investigate the performance of tautochronic centrifugal pendulum vibration absorbers (CPVA's) for reducing torsional vibration in internal combustion engines. A mathematical model is first built for the torsional dynamics of an in- line, four-stroke, four-cylinder engine, including the consideration of inertia effects of connecting rods and pistons, gas pressure inside the cylinder chambers,
Long-range excitons in conjugated polymers with ring torsions
Harigaya, Kikuo
Long-range excitons in conjugated polymers with ring torsions Kikuo Harigaya Physical Science) are investigated by the intermediate exciton formalism. Long-range excitons are characterized, and the long-range component of the oscillator strengths is calculated. We nd that ring torsions a ect the long-range excitons
Powerful, multifunctional torsional micromuscles activated by phase transition.
Liu, Kai; Cheng, Chun; Suh, Joonki; Tang-Kong, Robert; Fu, Deyi; Lee, Sangwook; Zhou, Jian; Chua, Leon O; Wu, Junqiao
2014-03-19
Micro bimorph coils driven by a metalinsulator phase transition in VO2 function as powerful torsional muscles. Reversible torsional motion over one million cycles without degradation is demonstrated, with a superior rotational speed up to ca. 200,000 rpm, an amplitude of 500° per mm length, and a power density up to ca. 39 kW kg?¹. PMID:24765648
Precision piezoelectric stepping motor using piezoelectric torsional actuator
NASA Astrophysics Data System (ADS)
Kang, Byung-Woo; Kim, Jaehwan; Cheong, ChaeCheon; Yang, Bo-Won
2001-03-01
This paper deals with a newly developed piezoelectric motor that generates precise stepping motion using a piezoelectric torsional actuator and a pair of one-way clutch bearings. The torsional actuator consists of a piezoelectric cylinder that produces rotation motion invoking shear mode of piezoelectric materials and a torsion bar that magnifies the rotation angle produced from the piezoelectric cylinder. Inner one-way clutch bearing is fit on the torsion bar and outer bearing is mounted outside of the inner bearing such that when the torsion bar rotates in one direction, the inner bearing moves together while the outer one slips. When the torsion bar rotates in opposite direction, the inner bearing slips against the torsion bar while the outer bearing locks the inner bearing so as to accumulate the rotation angle. Because the elaborate piezoelectric torsional actuator functions as the driving source at high frequency, a precise step motion with high speed can be produced. The optimum condition for driving the motor is investigated in terms of excitation frequency, electrical impedance and the location of the bearing set. The rotation speed and torque of the motor is investigated, and 350 rpm and 0.19mNm torque are observed in maximum.
A Patient Presenting with Concurrent Testis Torsion and Epididymal Leiomyoma
Arpali, E.; Tok, A.
2013-01-01
Leiomyomas are the second most common tumors of epididymis. Patients with leiomyomas are sometimes misdiagnosed with testicular tumors. A Case of a patient with a scrotal mass presenting with testicular torsion is reported. Concurrent occurrence of testicular torsion and epididymal leiomyoma is an extremely rare condition. PMID:23781386
Control of the polarity of magnetization vortex by torsion
NASA Astrophysics Data System (ADS)
Wang, Jie; Li, Gui-Ping; Shimada, Takahiro; Fang, Hui; Kitamura, Takayuki
2013-12-01
The switching behavior of vortex polarity in a circular ferromagnetic nanodot subjected to torsion is investigated by using a real space phase field model, which explicitly includes the coupling between magnetization and mechanical strain. It is found that the vortex polarity of the nanodot can be switched by torsion when the sign of the torsion is opposite to that of vortex chirality whereas switching does not take place if the sign of torsion is the same as that of vortex chirality. The magneto-elastic coupling and demagnetization field play a decisive role in the polarity switching, which involves an intriguing interplay of magnetization, strain, and demagnetization. The results suggest another way to control vortex polarity by mechanical torsion other than magnetic field and electric current.
NASA Astrophysics Data System (ADS)
Kasinskii, V.; Kasinskaia, L. I.
2005-06-01
The angular velocities of chromosphere and photosphere are calculated for 1987-1990 on the basis of heliographic coordinates of the chromospheric flares and sunspots (Solar Geophysical Data). The time resolution accepted is 0.25 year. The mean equatorial rotations of chromosphere and photosphere practically coincide. However, the differential coefficients in the chromosphere and photosphere, b, have strongly different behaviour. The value bch - bph change regularly from ``+'' sign to ``-'' sign over two-year interval. Thus, the idea of a torsion like oscillations of ``chromosphere-photosphere'' is supported.
Experimental Evidence for Partonic Orbital Angular Momentum at RHIC
Fields, Douglas E. [University of New Mexico, Department of Physics and Astronomy, Albuquerque, NM 871331 (United States)
2011-12-14
Although one might naively anticipate that the proton, being the lowest baryonic energy state, would be in a L = 0 state, the current theoretical understanding is that it must carry orbital angular momentum in order, for example, to have a non-zero anomalous magnetic moment. I will review the experimental evidence linked theoretically to orbital angular momentum of the proton's constituents from the RHIC experiments and summarize by presenting a challenge to the theory community--to develop a consistent framework which can explain the spin polarization asymmetries seen at RHIC and elsewhere, and give insight to the partonic wave-functions including orbital angular momentum.
Angular Momentum Transport in Circumplanetary Disks
NASA Astrophysics Data System (ADS)
Mitchell, Tyler R.
2014-11-01
The Galilean satellites likely formed in a late-stage accretion disk that persisted around Jupiter after it was fully formed. The structure of this disk is highly dependent on its ability to transport angular momentum. Uncertainty in the level of angular momentum transport has led to competing theories of circumplanetary disk structure. Despite success in other astrophysical contexts, recent studies indicate that the conditions were not suitable for magnetorotational instabilities to develop in circumplanetary disks. However, it has been suggested that baroclinic instabilities can generate turbulence and provide the necessary transport of angular momentum. We present a 1+1D numerical model of the circumplanetary accretion disk that surrounded Jupiter during the epoch of regular satellite formation. An analysis of the radial entropy gradient in this model indicates that baroclinic instabilities can not only develop but persist throughout the majority of the disk. Furthermore, we find evidence for a two-component, gas-starved disk which may help to reconcile the differences in current competing theories of circumplanetary disk structure.
Curvature and torsion in growing actin networks
NASA Astrophysics Data System (ADS)
Shaevitz, Joshua W.; Fletcher, Daniel A.
2008-06-01
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.
2013-01-01
Background and purpose Whether tibial torsion affects the positioning of extramedullary instrumentation and is a possible factor in malalignment of the tibial component in total knee arthroplasty (TKA) is unknown. We assessed the influence of tibial torsion on distal alignment of extramedullary systems for TKA, using the center of the intermalleolar distance as anatomical reference at the ankle joint. Patients and methods We analyzed CT scans of knee and ankle joints of 50 patients with knee osteoarthritis (mean age 73 years, 52 legs). The tibial mechanical axis was identified and translated anteriorly at the level of the medial one-third (proximal AP axis 1), at the medial border of the tibial tuberosity (proximal AP axis 2), and at the level of the talar dome (distal AP axis). The center of the intermalleolar distance and the width of the medial and lateral malleolus were calculated. The proximal AP axes 1 and 2 were translated at the level of the ankle joint and any difference between their alignment and the distal AP axis was calculated as angular and linear values. Results The center of the ankle joint was located, on average 2 mm medial to that of the intermalleolar distance. The distal AP axis was externally rotated by 18° and 27° compared to the proximal AP axes 1 and 2, respectively. Overall, the center of the ankle joint was shifted laterally by 9–11 mm with respect to the proximal AP tibial axes. Interpretation To avoid a varus tibial cut in TKA, extramedullary alignment systems should be aligned more medially at the ankle joint than previously thought, due to the effect of tibial torsion and—to a lesser extent—to the different malleolar width. PMID:23594222
Bulk angular momentum and Hall viscosity in chiral superconductors
NASA Astrophysics Data System (ADS)
Shitade, Atsuo; Kimura, Taro
2014-10-01
We establish the Berry-phase formulas for the angular momentum (AM) and the Hall viscosity (HV) to investigate chiral superconductors (SCs) in two and three dimensions. The AM is defined by the temporal integral of the antisymmetric momentum current induced by an adiabatic deformation, while the HV is defined by the symmetric momentum current induced by the symmetric torsional electric field. Without suffering from the system size or geometry, we obtain the macroscopic AM Lz=?mN0/2 at zero temperature in full-gap chiral SCs, where m is the magnetic quantum number and N0 is the total number of electrons. We also find that the HV is equal to half the AM at zero temperature not only in full-gap chiral SCs as is well known but also in nodal ones, but its behavior at finite temperature is different in the two cases.
Detectability of torsion gravity via galaxy clustering and cosmic shear measurements
NASA Astrophysics Data System (ADS)
Camera, Stefano; Cardone, Vincenzo F.; Radicella, Ninfa
2014-04-01
Alterations of the gravity Lagrangian introduced in modified torsion gravity theories—also referred to as f(T) gravity—allows for an accelerated expansion in a matter-dominated Universe. In this framework, the cosmic speed-up is driven by an effective "torsion fluid." Besides the background evolution of the Universe, structure formation is also modified because of a time-dependent effective gravitational constant. Here, we investigate the imprints of f(T) gravity on galaxy clustering and weak gravitational lensing to the aim of understanding whether future galaxy surveys could constrain torsion gravity and discriminate between it and standard general relativity. Specifically, we compute Fisher matrix forecasts for two viable f(T) models to both infer the accuracy on the measurement of the model parameters and evaluate the power that a combined clustering and shear analysis will have as a tool for model selection. We find that with such a combination of probes it will indeed be possible to tightly constrain f(T) model parameters. Moreover, the Occam's razor provided by the Bayes factor will allow us to confirm an f(T) power-law extension of the concordance ?CDM model, if a value larger than 0.02 of its power-law slope were measured, whereas in ?CDM it is exactly 0.
The laboratory millimeter-wave spectrum of methyl formate in its ground torsional E state
NASA Technical Reports Server (NTRS)
Plummer, G. M.; Herbst, E.; De Lucia, F. C.; Blake, G. A.
1986-01-01
Over 250 rotational transitions of the internal rotor methyl formate (HCOOCH3) in its ground v(t) = 0 degenerate (E) torsional substate have been measured in the millimeter-wave spectral region. These data and a number of E-state lines identified by several other workers have been analyzed using an extension of the classical principal-axis method in the high barrier limit. The resulting rotational constants allow accurate prediction of the v(t) = 0 E substate methyl formate spectrum below 300 GHz between states with angular momentum J not greater than 30 and rotational energy of not more than 350/cm. The calculated transition frequencies for the E state, when combined with the results of the previous analysis of the ground-symmetric, nondegenerate state, account for over 200 of the emission lines observed toward Orion in a recent survey of the 215-265 GHz band.
Intrinsic Angular Momentum of Light.
ERIC Educational Resources Information Center
Santarelli, Vincent
1979-01-01
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)
Yang, Jiashi
2007-07-01
We show that, in a circular cylindrical rod, torsional modes are coupling to extension when the shear deformation associated with the torsional modes is no longer infinitesimal. A set of a couple equations is derived with which the effect of extension on the torsional frequency is examined. The results are useful to the understanding and design of devices operating with torsional modes. PMID:17718339
Torsion Tests of Stiffened Circular Cylinders
NASA Technical Reports Server (NTRS)
Moore, R L; Wescoat, C
1944-01-01
The design of curved sheet panels to resist shear involves a consideration of several factors: the buckling resistance of the sheet, the stress at which buckling becomes permanent, and the strength which may be developed beyond the buckling limit by tension-field action. Although some experimental as well as theoretical work has been done on the buckling and tension-field phases of this problem, neither of these types of action appears to be very well understood. The problem is of sufficient importance from the standpoint of aircraft design, it is believed, to warrant further experimental investigation. This report presents the results of the first series of torsion tests of stiffened circular cylinders to be completed in connection with this study at Aluminum Research Laboratories. (author)
Experimental Study of Torsional Column Failure
NASA Technical Reports Server (NTRS)
Nile, Alfred S
1939-01-01
Thirty-three 24ST aluminum-alloy 2- by 2- by 0.10-inch channels, with lengths ranging from 10 to 90 inches were tested at Stanford University in compression to obtain an experimental verification of the theoretical formulas for torsional failure developed by Eugene E. Lundquist of the N.A.C.A. The observed critical loads and twist-axis locations were sufficiently close to the values obtained from the formulas to establish the substantial validity of the latter. The differences between observed and computed results were small enough to be accounted for by small and mostly unavoidable differences between actual test conditions and those assumed in deriving the formulas. Some data were obtained from the shorter specimens regarding the growth of the buckles that resulted in local buckling failure.
Axisymmetric flow within a torsionally oscillating sphere
NASA Astrophysics Data System (ADS)
Colombini, Marco
2014-02-01
The flow of an incompressible Newtonian fluid inside a torsionally oscillating spherical cavity is considered. The three-dimensional Navier-Stokes and continuity equations are solved by means of a Galerkin projection spectral method, based on a second-order incremental fractional-step approach. Legendre and Jacobi polynomial expansions are used in the zenithal and radial directions, respectively. Axisymmetric solutions are sought for a relatively wide set of the parameters controlling the flow, namely, the Rossby and the Womersley numbers. In particular, the behaviour of the flow for relatively large amplitudes of oscillation is studied, with emphasis on the generation of centrifugal instabilities. Numerical results are compared with experimental observations and semi-analytical solutions in the small-amplitude regime, showing good agreement.
Doxorubicin, DNA torsion, and chromatin dynamics
Yang, Fan; Teves, Sheila S.; Kemp, Christopher J.; Henikoff, Steven
2014-01-01
Doxorubicin is one of the most important anti-cancer chemotherapeutic drugs, being widely used for the treatment of solid tumors and acute leukemias. The action of doxorubicin and other anthracycline drugs has been intensively investigated during the last several decades, but the mechanisms that have been proposed for cell killing remain disparate and controversial. In this review, we examine the proposed models for doxorubicin action from the perspective of the chromatin landscape, which is altered in many types of cancer due to recurrent mutations in chromatin modifiers. We highlight recent evidence for effects of anthracyclines on DNA torsion and chromatin dynamics that may underlie basic mechanisms of doxorubicin-mediated cell death and suggest new therapeutic strategies for cancer treatment. PMID:24361676
Nonlinear Torsional Divergence: Certain Exact Solutions
NASA Astrophysics Data System (ADS)
Dimentberg, M.
1999-08-01
Classical analyses of torsional static instability, or divergence, of airfoils or bridge decks in a fluid flow, based on the use of linearized aerodynamic coefficients, lead to a Sturm-Liouville eigenvalue problem - see, e.g., Bisplinghoff & Ashley (1962). Solution to this problem predicts a critical value of the flow speed, such that exceeding this threshold would lead to unlimited growth of twist angles. Most structures are usually designed so as to exclude this instability completely. In some cases, however, such a design requirement may become violated - for example, if some accident happens with the structure involved. Furthermore, it may sometimes be unreasonable or impractical to impose this requirement for civil engineering structures for the case of a possible very strong storm, which has a small but nonzero probability of occurrence. For all such cases the nonlinear analysis of the postcritical stress/strain state seems to be crucial for predicting structural reliability.
Torsional ultrasonic transducer computational design optimization.
Melchor, J; Rus, G
2014-09-01
A torsional piezoelectric ultrasonic sensor design is proposed in this paper and computationally tested and optimized to measure shear stiffness properties of soft tissue. These are correlated with a number of pathologies like tumors, hepatic lesions and others. The reason is that, whereas compressibility is predominantly governed by the fluid phase of the tissue, the shear stiffness is dependent on the stroma micro-architecture, which is directly affected by those pathologies. However, diagnostic tools to quantify them are currently not well developed. The first contribution is a new typology of design adapted to quasifluids. A second contribution is the procedure for design optimization, for which an analytical estimate of the Robust Probability Of Detection, called RPOD, is presented for use as optimality criteria. The RPOD is formulated probabilistically to maximize the probability of detecting the least possible pathology while minimizing the effect of noise. The resulting optimal transducer has a resonance frequency of 28 kHz. PMID:24882020
Curvature and torsion in growing actin networks
Shaevitz, Joshua W; 10.1088/1478-3975/5/2/026006
2009-01-01
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 seconds. 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 ex...
Torsion-balance probes of fundamental physics
Adelberger, E G
2013-01-01
This white paper is submitted as part of Snowmass2013 (subgroup CF2). The extraordinary sensitivity of torsion-balances can be used to search for the ultra-feeble forces suggested by attempts to unify gravity with the other fundamental interactions. The motivation, the results and their implications as well as the future prospects of this work are summarized. The experiments include tests of the universality of free fall (weak equivalence principle), probes of the short-distance behavior of gravity (inverse-square law tests for extra dimensions and exchange forces from new meV scale bosons), and Planck-scale tests of Lorentz invariance (preferred-frame effects, non-commutative geometries).
Bergamin, O; Straumann, D
2001-07-01
When a human subject is oscillated about the nasooccipital axis and fixes upon targets along the horizontal head-fixed meridian, angular eye velocity includes a vertical component that increases with the horizontal eccentricity of the line-of-sight. This vertical eye movement component is necessary to prevent retinal slip. We asked whether fixation on a near head-fixed target during the same torsional vestibular stimulation would lead to differences of vertical eye movements between the right and the left eye, as the directions of the two lines-of-sight are not parallel during convergence. Healthy human subjects (n = 6) were oscillated (0.3 Hz, +/-30 degrees) about the nasooccipital axis on a three-dimensional motor-driven turntable. Binocular movements were recorded using the dual search coil technique. A head-fixed laser dot was presented 1.4 m (far head-fixed target) or 0.25 m (near head-fixed target) in front of the right eye. We found highly significant (P < 0.01) correlations (R binocular = 0.8, monocular = 0.59) between the convergence angle and the difference of the vertical eye velocity between the two eyes. The slope of the fitted linear regression between the two parameters (s = 0.45) was close to the theoretical slope necessary to prevent vertical retinal slippage (predicted s = 0.5). Covering the left eye did not significantly change the slope (s = 0.52). In addition, there was a marked gain reduction (approximately 35%) of the torsional vestibuloocular reflex (VOR) between viewing the far and the near targets, confirming earlier results by others. There was no difference in torsional gain reduction between the two eyes. Lenses of +3 dpt positioned in front of both eyes to decrease the amount of accommodation did not further change the gain of the torsional VOR. In conclusion, ocular convergence on a near head-fixed target during torsional vestibular stimulation leads to deviations in vertical angular velocity between the two eyes necessary to prevent vertical double vision. The vertical deviation velocity is mainly linked to the amount of convergence, since it also occurs during monocular viewing of the near head-fixed target. This suggests that convergence during vestibular stimulation automatically leads to an alignment of binocular rotation axes with the visual axes independent of retinal slip. PMID:11431493
Random gust response statistics for coupled torsion-flapping rotor blade vibrations.
NASA Technical Reports Server (NTRS)
Gaonkar, G. H.; Hohenemser, K. H.; Yin, S. K.
1972-01-01
An analysis of coupled torsion-flapping rotor blade vibrations in response to atmospheric turbulence revealed that at high rotor advance ratios anticipated for future high speed pure or convertible rotorcraft both flapping and torsional vibrations can be severe. While appropriate feedback systems can alleviate flapping, they have little effect on torsion. Dynamic stability margins have also no substantial influence on dynamic torsion loads. The only effective means found to alleviate turbulence caused torsional vibrations and loads at high advance ratio was a substantial torsional stiffness margin with respect to local static torsional divergence of the retreating blade.
Torsion and noninertial effects on a nonrelativistic Dirac particle
NASA Astrophysics Data System (ADS)
Bakke, K.
2014-07-01
We investigate torsion and noninertial effects on a spin-1/2 quantum particle in the nonrelativistic limit of the Dirac equation. We consider the cosmic dislocation spacetime as a background and show that a rotating system of reference can be used out to distances which depend on the parameter related to the torsion of the defect. Therefore, we analyse torsion effects on the spectrum of energy of a nonrelativistic Dirac particle confined to a hard-wall potential in a Fermi-Walker reference frame.
Torsional ultrasonic technique for LWR liquid-level measurement
Dress, W.B.
1983-01-01
Since 1980, the Instrumentation and Controls Division of ORNL has been involved in the evaluation of sensors using torsional ultrasonic pulses to make level and density measurements, and extensional ultrasonic pulses for temperature measurements and correction of the torsional measurements. Work at ORNL through 1981 demonstrated the feasibility of transmitting torsional pulses in a ribbon of stainless steel and the sensor was used to measure the level of a steam/water interface at 290/sup 0/C and 10 MPa. Subsequent work under the Advanced Two-Phase Instrumentation Program has been directed towards an operational prototype instrument that can be installed in functional power reactor.
Fourier transform spectrum of the second torsional band of hydrazine
NASA Astrophysics Data System (ADS)
Ohashi, Nobukimi; Olson, W. Bruce
1991-02-01
The far-infrared v = 2 ? 0 torsional overtone band has been studied by Fourier transform spectroscopy with an apodized resolution of 0.006 cm -1. About 800 pPK, pQK, rQK, and rRK transitions of 15 subbands with ? K· K? from -8 to 6 were assigned. A global fitting was made with the use of Hougen's group-theoretical formalism to determine 34 molecular parameters in the second torsional state and to obtain a standard deviation 0.001 04 cm -1. Pure torsionalwagging levels in the second torsional state are derived from the tunneling parameters obtained.
Four-fermion interaction from torsion as dark energy
NASA Astrophysics Data System (ADS)
Pop?awski, Nikodem J.
2012-02-01
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.
The Torsion of Box Beams with One Side Lacking
NASA Technical Reports Server (NTRS)
Cambilargiu, E
1940-01-01
The torsion of box beams of rectangular section, the edges of which are strengthened by flanges, and of which one side is lacking, is analyzed by the energy method. The torsional stresses are generally taken up by the bending of the two parallel walls, the rigidity of which is augmented by the third wall. The result was checked experimentally on duralumin and plywood boxes. The torsion recorded was 10 to 30 percent less than that given by the calculation, owing to self-stiffening.
Effect of Spin-Torsion Interaction on Raychaudhuri Equation
NASA Astrophysics Data System (ADS)
Wanas, M. I.; Bakry, M. A.
Raychaudhuri equation is generalized in the parametrized absolute parallelism geometry. This version of absolute parallelism is more general than the conventional one. The generalization takes into account the suggested interaction between the quantum spin of the moving particle and the torsion of the background gravitational field. The generalized Raychaudhuri equation obtained contains some extra terms, depending on the torsion of space-time, that would have some effects on the singularity theorems of general relativity. Under a certain condition, this equation could be reduced to the original Raychaudhuri equation without any need for a vanishing torsion.
Effect of Spin-Torsion Interaction on Raychaudhuri Equation
M. I. Wanas; M. A. Bakry
2008-07-06
Raychaudhuri equation is generalized in the parameterized absolute parallelism geometry. This version of absolute parallelism is more general than the conventional one. The generalization takes into account the suggested interaction between the quantum spin of the moving elementary particle and the torsion of the background gravitational field. The generalized Raychaudhuri equation obtained contains some extra terms, depending on the torsion of space-time, that would have some effects on the singularity theorems of general relativity. Under a certain condition, this equation could be reduced to the original Raychaudhuri equation without any need for a vanishing torsion.
NSDL National Science Digital Library
2010-01-01
This activity will help the students understand that science theories change in the face of new evidence, but those changes can be slow in coming. Students will observe how scientific theories change over time, Be introduced to the sophistication of the geocentric model and the time it took to change the theory underpinning the heliocentric model, Compare the heliocentric model to the geocentric model.
Torsion of an epididymal cyst: a case report and review of the literature.
Erikçi, Volkan; Ho?gör, Münevver; Y?ld?z, Melih; Aksoy, Nail; Okur, Özkan; Örnek, Y?lmazcan; Demircan, Yusuf
2013-01-01
Torsion of an epididymal cyst (EC) on its pedicle is an extremely rare condition that resembles acute testicular torsion. Herein, a boy with EC torsion managed surgically is presented and discussed in light of the relevant literature. The presented child is probably the fourth case of pediatric EC torsion, and to our knowledge, the first report of a child who was known to have EC and was followed conservatively until the occurrence of EC torsion. PMID:24577990
Reexamination of fission fragment angular distributions and the fission process: Formalism
NASA Astrophysics Data System (ADS)
Bond, P. D.
1985-08-01
The theory of fission fragment angular distributions is examined and the universally used expression is found to be valid only under restrictive assumptions. A more general angular distribution formula is derived and applied to recent data of high spin systems. At the same time it is shown that the strong anisotropies observed from such systems can be understood without changing the essential basis of standard fission theory. The effects of reaction mechanisms other than complete fusion on fission fragment angular distributions are discussed and possible angular distribution signatures of noncompound nucleus formation are mentioned.
Smoothed dissipative particle dynamics with angular momentum conservation
NASA Astrophysics Data System (ADS)
Müller, Kathrin; Fedosov, Dmitry A.; Gompper, Gerhard
2015-01-01
Smoothed dissipative particle dynamics (SDPD) combines two popular mesoscopic techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved dissipative particle dynamics approach. Despite several advantages of the SDPD method over the conventional DPD model, the original formulation of SDPD by Español and Revenga (2003) [9], lacks angular momentum conservation, leading to unphysical results for problems where the conservation of angular momentum is essential. To overcome this limitation, we extend the SDPD method by introducing a particle spin variable such that local and global angular momentum conservation is restored. The new SDPD formulation (SDPD+a) is directly derived from the Navier-Stokes equation for fluids with spin, while thermal fluctuations are incorporated similarly to the DPD method. We test the new SDPD method and demonstrate that it properly reproduces fluid transport coefficients. Also, SDPD with angular momentum conservation is validated using two problems: (i) the Taylor-Couette flow with two immiscible fluids and (ii) a tank-treading vesicle in shear flow with a viscosity contrast between inner and outer fluids. For both problems, the new SDPD method leads to simulation predictions in agreement with the corresponding analytical theories, while the original SDPD method fails to capture properly physical characteristics of the systems due to violation of angular momentum conservation. In conclusion, the extended SDPD method with angular momentum conservation provides a new approach to tackle fluid problems such as multiphase flows and vesicle/cell suspensions, where the conservation of angular momentum is essential.
Stress analysis, by photoelastic methods, of a rectangular bar subjected to a torsion load
Rajagopalan, Tiruchengode Chinnappan
1961-01-01
of the required stresses, normal stress and shear stress, can be found out by using shear difference 14 0 s5 %0 Figure 10. Isoclinics of Slice No. 1 gO aO g= so 50 Ro lO Figure 11. Isoclinics of Slice No. 3 16 method. The cantilever bar?under study..., was subjected to a torsional load. From theory (1), it is known that the normal stresses u, 0 x' y' and one of the shearing stresses &, are all equal to zero. Hence z yz' only the other two shear stresses '7, Y, were calculated from the xy xz photoelastic...
Energy conditions in f( T) gravity with non-minimal torsion-matter coupling
NASA Astrophysics Data System (ADS)
Zubair, M.; Waheed, Saira
2015-02-01
The present paper examines the validity of energy bounds in a modified theory of gravity involving non-minimal coupling of torsion scalar and perfect fluid matter. In this respect, we formulate the general inequalities of energy conditions by assuming the flat FRW universe. For the application of these bounds, we particularly focus on two specific models that are recently proposed in literature and also choose the power law cosmology. We find the feasible constraints on the involved free parameters and evaluate their possible ranges graphically for the consistency of these energy bounds.
Energy conditions in $f(T)$ gravity with non-minimal torsion-matter coupling
M. Zubair; Saira Waheed
2015-02-09
The present paper examines the validity of energy bounds in a modified theory of gravity involving non-minimal coupling of torsion scalar and perfect fluid matter. In this respect, we formulate the general inequalities of energy conditions by assuming the flat FRW universe. For the application of these bounds, we particularly focus on two specific models that are recently proposed in literature and also choose the power law cosmology. We find the feasible constraints on the involved free parameters and evaluate their possible ranges graphically for the consistency of these energy bounds.
Energy conditions in $f(T)$ gravity with non-minimal torsion-matter coupling
Zubair, M
2015-01-01
The present paper examines the validity of energy bounds in a modified theory of gravity involving non-minimal coupling of torsion scalar and perfect fluid matter. In this respect, we formulate the general inequalities of energy conditions by assuming the flat FRW universe. For the application of these bounds, we particularly focus on two specific models that are recently proposed in literature and also choose the power law cosmology. We find the feasible constraints on the involved free parameters and evaluate their possible ranges graphically for the consistency of these energy bounds.
NASA Technical Reports Server (NTRS)
Houbolt, John C; Brooks, George W
1957-01-01
The differential equations of motion for the lateral and torsional deformations of twisted rotating beams are developed for application to helicopter rotor and propeller blades. No assumption is made regarding the coincidence of the neutral, elastic, and mass axes, and the generality is such that previous theories involving various simplifications are contained as subcases to the theory developed and presented in this paper. Special attention is given to coupling terms not found in previous theories, and methods of solution of the equations of motion are indicated by selected examples.
NASA Technical Reports Server (NTRS)
Houbolt, John C; Brooks, George W
1958-01-01
The differential equations of motion for the lateral and torsional deformations of twisted rotating beams are developed for application to helicopter rotor and propeller blades. No assumption is made regarding the coincidence of the neutral, elastic, and mass axes, and the generality is such that previous theories involving various simplifications are contained as subcases to the theory presented in this paper. Special attention is given the terms which are not included in previous theories. These terms are largely coupling-type terms associated with the centrifugal forces. Methods of solution of the equations of motion are indicated by selected examples.
Angular dispersion of protons transmitted through thin gold films
NASA Astrophysics Data System (ADS)
Archubi, C.; Denton, C.; Eckardt, J. C.; Lantschner, G. H.; Lovey, F.; Valdés, J.; Parra, C.; Zappa, F.; Arista, N. R.
2004-08-01
The angular distributions of protons travelling through thin polycrystalline gold targets (15 nm) with incident energies in the range of 4-10 keV have been measured. The results confirm previous experiments at higher energies showing deviations from theoretical predictions based on the standard multiple scattering theory. In order to prove that the effect of crystal structure is one of the main causes of these deviations we have performed numerical simulations. To simulate the polycrystalline structure in a realistic way, we have made an analysis of the target by means of transmission electron microscopy (TEM) techniques. Including these characteristics in the simulation, together with the effect of vibrations and crystal disorder we analyzed the corresponding angular distribution. To evaluate the role of channeling, we also measured angular distributions of protons in a 100 gold foil and made the corresponding numerical simulations. The results show the critical influence of the target structure in the angular spectra of transmitted ions.
Angular momentum evolution for galaxies
Pedrosa, Susana
2015-01-01
Using cosmological hydrodynamics simulations we study the angular momentum content of the simulated galaxies in relation with their morphological type. We found that not only the angular momentum of the disk component follow the expected theoretical relation, Mo, Mao & Whiye (1998), but also the spheroidal one, with a gap due to its lost of angular momentum, in agreement with Fall & Romanowsky (2013),. We also found that the galaxy size can plot in one general relation, despite the morphological type, as found by Kravtsov (2013).
Ultrahigh Torsional Stiffness and Strength of Boron Nitride Jonathan Garel,
Hod, Oded
of boron nitride nanotube (BNNT) torsional mechanics. We show that BNNTs exhibit a much stronger mechanical in multiwall BNNT.18,19 Additionally, it has been shown that whereas the spacing between two layers
Considerations on the Sp\\"orer-diagram - torsional wave relationship
Muraközy, J
2014-01-01
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.
Chirality and angular momentum in optical radiation
NASA Astrophysics Data System (ADS)
Coles, Matt M.; Andrews, David L.
2012-06-01
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.
A new hybrid longitudinal-torsional magnetostrictive ultrasonic transducer
NASA Astrophysics Data System (ADS)
Karafi, Mohammad Reza; Hojjat, Yousef; Sassani, Farrokh
2013-06-01
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.
Torsion of the left ventricle during pacing with MRI tagging
NASA Astrophysics Data System (ADS)
Sorger, Jonathan M.; Wyman, Bradley T.; Faris, Owen P.; Hunter, William R.; McVeigh, Elliot R.
2000-04-01
In this study the effects of different pacing protocols on left ventricular (LV) torsion was evaluated over the full cardiac cycle. A systolic and diastolic series of Magnetic Resonance Imaging scans were combined and used to calculate the torsion of the LV. The asynchronous contraction resulting from ventricular pacing interferes with the temporal evolution of LV torsion. From these experiments we have shown that measuring torsion is an extremely sensitive indicator of the existence of ectopic excitation. The torsion of the left ventricle was investigated under three different protocols: (1) Right atrial pacing, (2) Right ventricular pacing and (3) Simultaneous pacing from the right ventricular apex and left ventricular base. The temporal evolution of torsion was determined from tagged magnetic resonance images and was evaluated over the full cardiac cycle. The peak twist Tmax for the RA paced heart was 11.09 (+/- 3.54) degrees compared to 6.06 (+/- 1.65) degrees and 6.09 (+/- 0.68) degrees for the RV and Bi-V paced hearts respectively. While biventricular pacing has been shown to increase the synchrony of contraction, it does not preserve the normal physiological twist patterns of the heart.
Coherent Control of Molecular Torsion and the Active-space Decomposition Method
NASA Astrophysics Data System (ADS)
Parker, Shane Matthew
This dissertation discusses schemes and applications for the strong-field control of molecular torsions as well as introduces the active-space decomposition method. In the first part, a route to realize general control over the torsional motions of a class of biaryl compounds is proposed. Torsion in biaryl compounds--molecules with two aromatic moieties connected by a bond about which the barrier to rotation is small--mediates the electronic coupling between the two rings in the molecule. Thus, by controlling the torsion angle, one also controls the electron transfer and transport rates, the absorption and emission spectra, and the molecule's chirality. In our scheme, a non-resonant half-cycle pulse interacts with the permanent dipole of only one moiety of the pre-oriented biaryl compound. In the non-adiabatic regime, coherent motion is initiated by the half-cycle pulse. In the adiabatic regime, the torsion angle is tuned by the pulse. By properly choosing the parameters and polarization of the half-cycle pulse, we show that free internal rotation can be started or that the molecular chirality can be inverted. Then, with the aid of optimal control theory, we design "deracemizing" control pulses, i.e., control pulses that convert a racemic mixture into an enantiopure mixture. Finally, we explore the potential for this type of control in a single-molecule pulling experiment. In the second part, we describe the active space decomposition method for computing excited states of molecular dimers. In this method, the dimer's wavefunction is expressed as a linear combination of direct products of orthogonal localized monomer states. The adiabatic dimer states are found by diagonalizing the Hamiltonian in this direct product space. Matrix elements between direct product states are computed directly, without ever explicitly forming the dimer wavefunction, thus enabling calculations of dimers with active space sizes that would be otherwise impossible. The decomposed wavefunctions approach the exact dimer wavefunctions in two limiting cases: when there is no coupling between the two monomers and when a full set of monomer states is used. After introducing the method, we apply it to the computation of model Hamiltonians for the singlet fission process.
Plasmons with orbital angular momentum
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
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.
Nonminimal torsion-matter coupling extension of f(T) gravity
NASA Astrophysics Data System (ADS)
Harko, Tiberiu; Lobo, Francisco S. N.; Otalora, G.; Saridakis, Emmanuel N.
2014-06-01
We construct an extension of f(T) gravity with the inclusion of a nonminimal torsion-matter coupling in the action. The resulting theory is a novel gravitational modification, since it is different from both f(T) gravity, as well as from the nonminimal curvature-matter-coupled theory. The cosmological application of this new theory proves to be very interesting. In particular, we obtain an effective dark energy sector whose equation-of-state parameter can be quintessence- or phantom-like, or exhibit the phantom-divide crossing, while for a large range of the model parameters the universe enters in a de Sitter, dark-energy-dominated, accelerating phase. Additionally, we can obtain early-time inflationary solutions too, and thus provide a unified description of the cosmological history.
Flap-lag-torsion aeroelastic stability of a circulation control rotor in forward flight
NASA Technical Reports Server (NTRS)
Chopra, Inderjit; Hong, Chang-Ho
1987-01-01
The aeroelastic stability of a circulation control rotor blade undergoing three degrees of motion (flap, lag, and torsion) is investigated in forward flight. Quasi-steady strip theory is used to evaluate the aerodynamics forces; and the airfoil characteristics are from data tables. The propulsive and the auxiliary power trims are calculated from vehicle and rotor equilibrium equations through the numerical integration of element forces in azimuth as well as in radial directions. The nonlinear time dependent periodic blade response is calculated using an iterative procedure based on Floquet theory. The periodic perturbation equations are solved for stability using Floquet transition matrix theory. The effects of several parameters on blade stability are examined, including advance ratio, collective pitch, thrust level, shaft tilt, structural stiffnesses variation, and propulsive and auxiliary power trims.
Torsional texturing of superconducting oxide composite articles
Christopherson, Craig John (Grafton, MA); Riley, Jr., Gilbert N. (Marlborough, MA); Scudiere, John (Bolton, MA)
2002-01-01
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.
Influence of mistuning on blade torsional flutter
NASA Technical Reports Server (NTRS)
Srinivasan, A. V.
1980-01-01
An analytical technique for the prediction of fan blade flutter was evaluated by utilizing first stage fan flutter data from tests on an advanced high performance engine. The formulation includes both aerodynamic and mechanical coupling among all the blades of the assembly. Mistuning is accounted for in the analysis so that individual blade inertias, frequencies, or damping can be considered. Airfoil stability was predicted by calculating a flutter determinant, the eigenvalues of which indicate the extent of susceptibility to flutter. When blade to blade differences in frequencies are considered, a stable system is predicted for the test points examined. For a tuned system, it was found that torsional flutter can be predicted at a limited number of interblade phase angles. Examination of these phase angles indicated that they were "close" to the condition of acoustic resonance. For the range of Mach numbers and reduced frequencies considered, the so called subcritical flutter cannot be predicted. The essential influence of mechanical coupling among the blades is to change the frequencies of the system with little or no change in damping; however, aerodynamic coupling together with mechanical coupling could change not only frequencies, but also damping in the system, with a trend toward instability.
Novel MEMS torsional mirror optical switch
NASA Astrophysics Data System (ADS)
Yang, Yirong; Liu, Wenping; Wu, Yaming; Yang, Jianyi; Wang, Yuelin
2004-05-01
We have reported a novel 1x2 MEMS optical switch for telecommunication application. A vertical mirror was fabricated by wet anisotropic etching in (110)-oriented silicon wafer. Using DRIE (Deep Reactive Ion Etching) technique, we make a torsional actuator to turn a vertical mirror with a small angle. The actuator was composed of a cantilever beam and two electrodes with curved shape edges. The mirror size was 500 um (L) x 125 um (H) x 50 um (W), and the cantilever dimension was 3000 um (L) x 125 um (H) x 10 um (W). In the optical switch, ball lenses were added in the optics system to extend working distance of fibers. We also fabricated a micro optical platform integrated with the device to simplify the coupling. On the platform, a U-shape groove and fiber clamps were fabricated to accommodate and fix the SMF (single mode fiber). The surface roughness (Ra) of etched mirror was tested below 10 nm. The optical switch was tested on electric and optical characteristics: switching voltage 78.5V, resonance frequency 2.3 kHz, insertion loss 4 - 5 dB, crosstalk 45dB. The device can perform the switching function by the large.
Analytic torsion, vortices and positive Ricci curvature
Berman, Robert J
2010-01-01
We characterize the global maximizers of a certain non-local functional defined on the space of all positively curved metrics on an ample line bundle L over a Kahler manifold X. This functional is an adjoint version, introduced by Berndtsson, of Donaldson's L-functional and generalizes the Ding-Tian functional whose critical points are Kahler-Einstein metrics of positive Ricci curvature. Applications to (1) analytic torsions on Fano manifolds (2) Chern-Simons-Higgs vortices on tori and (3) Kahler geometry are given. In particular, proofs of conjectures of (1) Gillet-Soul\\'e and Fang (concerning the regularized determinant of Dolbeault Laplacians on the two-sphere) (2) Tarantello and (3) Aubin (concerning Moser-Trudinger type inequalities) in these three settings are obtained. New proofs of some results in Kahler geometry are also obtained, including a lower bound on Mabuchi's K-energy and the uniqueness result for Kahler-Einstein metrics on Fano manifolds of Bando-Mabuchi. This paper is a substantially extend...
Control of Torsional Vibrations by Pendulum Masses
NASA Technical Reports Server (NTRS)
Stieglitz, Albert
1942-01-01
Various versions of pendulum masses have been developed abroad within the past few years by means of which resonant vibrations of rotating shafts can be eliminated at a given tuning. They are already successfully employed on radial engines in the form of pendulous counterweights. Compared with the commonly known torsional vibration dampers, the pendulum masses have the advantage of being structurally very simple, requiring no internal damping and being capable of completely eliminating certain vibrations. Unexplained, so far, remains the problem of behavior of pendulum masses in other critical zones to which they are not tuned, their dynamic behavior at some tuning other than in resonance, and their effect within a compound vibration system and at simultaneous application of several differently tuned pendulous masses. These problems are analyzed in the present report. The results constitute an enlargement of the scope of application of pendulum masses, especially for in-line engines. Among other things it is found that the natural frequency of a system can be raised by means of a correspondingly tuned pendulum mass. The formulas necessary for the design of any practical version are developed, and a pendulum mass having two different natural frequencies simultaneously is described.
Angular distributions of sequentially emitted particles and gamma rays in deep inelastic processes
Moretto, L.G.
1981-01-01
A general theory for the angular distribution of sequentially emitted particles and gamma rays is developed. Comparison with experimental data allows one to obtain information on the fragment spin and misalignment. Angular distributions of sequentially emitted gammas, alphas, and fission fragments are discussed in detail. It is shown that the experimental data are consistent with the thermal excitation of angular momentum-bearing modes. The anomaly of sequential fission suggests the presence of a prompt or direct fission component. 13 figures.
Angular momentum evolution during star and planetary system formation
NASA Astrophysics Data System (ADS)
Davies, Claire L.; Greaves, Jane S.
2014-01-01
We focused on analysing the role played by protoplanetary disks in the evolution of angular momentum during star formation. If all the angular momentum contained within collapsing pre-stellar cores was conserved during their formation, proto-stars would reach rotation rates exceeding their break-up velocities before they reached the main sequence (Bodenheimer 1995). In order to avoid this occuring, methods by which proto-stars can lose angular momentum must exist. Angular momentum can be transferred from star to disk via stellar magnetic field lines through a process called magnetic braking (Camenzind 1990; Königl 1991). Alternatively, the stellar angular momentum can be lost from the star-disk system entirely via stellar- or disk-winds (e.g. Pelletier & Pudritz 1992; Matt & Pudritz 2005). The proportion of lost stellar angular momentum retained within the protoplanetary disk is important to studies of planetary system formation. If the bulk motion within the disk remains Keplerian, any increase of angular momentum in the disk causes an outward migration of disk material and an expansion of the disk. Therefore, an increase in disk angular momentum may cause a reduction in the disk surface density, often used to indicate the disk's ability to form planets. We made use of multi-wavelength data available in the literature to directly calculate the stellar and disk angular momenta for two nearby regions of star formation. Namely, these were the densely populated and highly irradiated Orion Nebula Cluster (ONC) and the comparitively sparse Taurus-Auriga region. Due to the limited size of the ONC dataset, we produced an average surface density profile for the region. We modelled the stars as solid body rotators due to their fully convective nature (Krishnamurthi et al. 1997) and assumed the disks are flat and undergo Keplerian rotation about the same rotation axis as the star. We observed the older disks within each of the two star forming regions to be preferentially larger and less massive, consistent with viscous accretion theories and disk dispersal. However, when drawing comparisons between the two regions, the ONC sample appeared to have less massive disks than the Taurus-Auriga sample, even though the population of Taurus-Auriga is older. This may suggest an influence of the birth cloud environment on protoplanetary disk evolution. Finally, the older stars within the ONC were observed to harbour disks that contained more angular momentum than their younger counterparts whereas, in the Taurus-Auriga sample, the amount of angular momentum contained in the older and younger samples was consistent. We suggest that the missing disk angular momentum in the older Taurus-Auriga disks may be contained within yet-undetected planets.
Torsion - Vibration Coupling in the Methyl Rotor Systems
NASA Astrophysics Data System (ADS)
Huang, Meng; McCoy, Anne B.; Miller, Terry A.
2014-06-01
The couplings between the CH stretch and CH{_3} torsion in the methyl rotor have been widely studied in methanol. In this research, we are focusing on the effect of this coupling on the vibrational spectrum in the CH stretch region of the methanol cation - argon cluster, CH{_3}OH{^+}{\\cdot}Ar, and the methyl peroxy radical, CH{_3}OO{\\cdot}. A reduced dimensional analysis including the three CH stretches and the CH{_3} torsion is used to calculate the spectra. The CH stretches are treated as harmonic oscillators whose frequency depends on the torsional angle because of coupling between the CH stretch and CH{_3} torsion. The infrared spectrum of CH{_3}OH{^+}{\\cdot}Ar cluster taken by the Duncan groupshows multiple peak structure in the CH stretch region. In this system, the calculation indicates the coupling between the CH{_3} torsion and CH stretch is relatively strong. The multiple peak structure in the experimental spectrum can be assigned to the CH stretch fundamentals and the combination band involving the CH stretch and the CH{_3} torsion. However, for the methyl peroxy radical, the calculated coupling is very weak. In the CH stretch region of the infrared spectrum of CH{_3}OO{\\cdot} taken by the Lee group, only CH stretch fundamentals with relatively broad rotational contours are observed. The broadened structure of the CH stretch fundamental is possibly caused by sequence band structure from low lying torsional levels which are well populated and shift very little from the origin band. D. S. Perry J. Mol. Spectpsc. 2009, 257, 1-10 J. D. Mosley, J. W. Young, M. A. Duncan 68th International Symosium of Molecular Spectroscopy K.-H. Hsu, Y.-P. Lee, M. Huang, T. A. Miller 68th International Symosium of Molecular Spectroscopy
Errata for cosmological magnetic fields and string dynamo in axion torsioned spacetime
Andrade, L C G
2015-01-01
Recently much controversy has been shed on BICEP 2 experiments for the concerning this validity or not and a possible set of new experiments to detect primordial inflation and gravitational waves. Since gravitational waves imply the existence of primordial magnetic fields in this context, C Bonvin, R Durrer and R Marteens [Phys Rev Lett (2014)] have tried to associate the presence of primordial magnetic fields to BICEP 2 by making use of CMB tensor modes. Here we show that by considering torsion dilatonic lagrangean one obtains cosmological magnetic fields of the order of $B\\sim{10^{-10}G}$ which may seed galactic dynamos. Actually this new result came out of a mistake of a recent paper published by myself in JCAP (2014). These results are more in accordance with Bamba results [JCAP (2014)] in the context of teleparallel theory of gravity with Einstein's distant parallelism and torsion. These results also support Einstein-Cartan sort of theories of gravity from well-known recent data.
Does a randall-sundrum scenario create the illusion of a torsion-free universe?
Mukhopadhyaya, Biswarup; Sen, Somasri; SenGupta, Soumitra
2002-09-16
We consider spacetime with torsion in a Randall-Sundrum scenario where torsion, identified with the rank-2 Kalb-Ramond field, exists in the bulk together with gravity. While the interactions of both graviton and torsion in the bulk are controlled by the Planck mass, an additional exponential suppression comes for the torsion zero-mode on the visible brane. This may serve as a natural explanation of why the effect of torsion is so much weaker than that of curvature on the brane. The massive torsion modes, on the other hand, are correlated with the corresponding gravitonic modes and may be detectable in TeV-scale experiments. PMID:12225074
Truhlar, Donald G
Statistical thermodynamics of bond torsional modes: Tests of separable, almost Practical approximation schemes for calculating partition functions of torsional modes are tested against-dimensional torsion results obtained by eigenvalue summation. The approximate one-dimensional methods tested
Evidence for changes in the angular velocity of the surface regions of the sun and stars
NASA Technical Reports Server (NTRS)
1972-01-01
A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing changes in the angular velocity of the surface regions of the sun and stars.
Structure of an edge-diffraction wave over a wide angular range
Galina V. Bogatiryova; Peter V. Polyanskii
1999-01-01
Experimental data on the angular dependence of the amplitude function of the edge diffraction wave originating behind a metallic knife edge that is illuminated nonenlarged laser beam are represented. It is shown that the scalar diffraction theory approximation (in particular, so-called `Rubinowicz's representation of the Kirhhoff's diffraction integral) is valid up to the diffraction angle approximately 206. Outside this angular
Paraxial Light Beams with Angular Momentum
A. Bekshaev; M. Soskin; M. Vasnetsov
2008-01-01
Fundamental and applied concepts concerning the ability of light beams to carry a certain mechanical angular momentum with respect to the propagation axis are reviewed and discussed. Following issues are included: Historical reference; Angular momentum of a paraxial beam and its constituents; Spin angular momentum and paradoxes associated with it; Orbital angular momentum; Circularly-spiral beams: examples and methods of generation;
Variations in atmospheric angular momentum
NASA Technical Reports Server (NTRS)
Rosen, R. D.; Salstein, D. A.
1981-01-01
Twice-daily values of the atmosphere's angular momentum about the polar axis during the five years from 1976 through 1980 are presented in graphs and a table. The compilation is based on a global data set, incorporating 90 percent of the mass of the atmosphere. The relationship between changes in the angular momentum of the atmosphere and changes in the length of day is described, as are the main sources of error in the data. The variability in angular momentum is revealed in a preliminary fashion by means of a spectral decomposition. The data presented should stimulate comparisons with other measures of the length of day and so provide a basis for greater understanding of Earth-atmosphere interactions.
Elastic effects in torsional oscillators containing solid helium
NASA Astrophysics Data System (ADS)
Beamish, J. R.; Fefferman, A. D.; Haziot, A.; Rojas, X.; Balibar, S.
2012-05-01
A number of recent experiments have used torsional oscillators to study the behavior of solid helium. The oscillator frequencies increased at temperatures below 200 mK, an effect attributed to decoupling of a fraction of the helium mass—the signature of a “supersolid” phase. However, helium's shear modulus also increases below 200 mK and the frequency of a torsional oscillator depends on its elastic properties, as well as on its inertia. In many experiments helium is introduced via a hole in the torsion rod, where its shear modulus contributes to the stiffness of the rod. In oscillators with relatively large torsion rod holes, changes in the helium's shear modulus could produce the entire low temperature frequency shifts that have been interpreted as mass decoupling. For these oscillators we also find that the known elastic properties of helium in the torsion rod can explain the observed TO amplitude dependence (which has been interpreted as a critical velocity) and the TO dissipation peak. However, in other oscillators these elastic effects are small and the observed frequency changes must have a different origin.
Torsion of the Retroperitoneal Kidney: Uncommon or Underreported?
Sosin, Michael; Lumeh, Wuya; Cooper, Matthew
2014-01-01
Vascular torsion in a renal allograft after placement in the retroperitoneum is rare and has only been reported twice in the literature. It is an extrinsically mediated process that occurs at the vascular pedicle resulting in graft compromise and potential loss. Rapid diagnosis and immediate surgical intervention may salvage allograft function. Herein, we present a unique case of a 42-year-old male that developed renal allograft torsion following a second kidney transplant placed in the retroperitoneum. Immediate detorsion did not resolve allograft dysfunction, and a biopsy revealed acute cellular mediated rejection. After antithymocyte globulin treatment, allograft function was salvaged. A review of the current literature shows that the incidence, morbidity, and long term allograft function of intraperitoneal and extraperitoneal torsion are different. As such, torsion of the retroperitoneal kidney demonstrates encouraging allograft salvage rates. Only the third case reported to date, this serves as a contribution to the growing body of literature in retroperitoneal renal torsion and reviews the risks, medication considerations, diagnostic tests, and treatment modalities in a unique disease process. PMID:24551473
Direct torsional actuation of microcantilevers using magnetic excitation
Gosvami, Nitya Nand; Nalam, Prathima C.; Tam, Qizhan; Carpick, Robert W., E-mail: carpick@seas.upenn.edu [Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Exarhos, Annemarie L.; Kikkawa, James M. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)
2014-09-01
Torsional mode dynamic force microscopy can be used for a wide range of studies including mapping lateral contact stiffness, torsional frequency or amplitude modulation imaging, and dynamic friction measurements of various materials. Piezo-actuation of the cantilever is commonly used, but it introduces spurious resonances, limiting the frequency range that can be sampled, and rendering the technique particularly difficult to apply in liquid medium where the cantilever oscillations are significantly damped. Here, we demonstrate a method that enables direct torsional actuation of cantilevers with high uniformity over wide frequency ranges by attaching a micrometer-scale magnetic bead on the back side of the cantilever. We show that when beads are magnetized along the width of the cantilever, efficient torsional actuation of the cantilevers can be achieved using a magnetic field produced from a solenoid placed underneath the sample. We demonstrate the capability of this technique by imaging atomic steps on graphite surfaces in tapping mode near the first torsional resonance of the cantilever in dodecane. The technique is also applied to map the variations in the lateral contact stiffness on the surface of graphite and polydiacetylene monolayers.
Numerical modeling of pendulum dampers in torsional systems
Johnston, P.R.; Shusto, L.M.
1986-01-01
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.
NASA Technical Reports Server (NTRS)
Herbst, Eric; Winnewisser, G.; Yamada, K. M. T.; Defrees, D. J.; Mclean, A. D.
1989-01-01
A mechanism for the enhanced splitting detected in the millimeter-wave rotational spectra of the first excited S-S stretching state of HSSH (disulfane) has been studied. The mechanism, which involves a potential coupling between the first excited S-S stretching state and excited torsional states, has been investigated in part by the use of ab initio theory. Based on an ab initio potential surface, coupling matrix elements have been calculated, and the amount of splitting has then been estimated by second-order perturbation theory. The result, while not in quantitative agreement with the measured splitting, lends plausibility to the assumed mechanism.
Measuring Angular Size and Distance
NSDL National Science Digital Library
This is an activity about measuring angular size and understanding the solar and lunar proportions that result in solar eclipses. Learners will use triangles and proportions to create a shoebox eclipse simulator. They will then apply what they learn about angular size to predict the diameter and distance of one object that can be eclipsed by another. They will also complete three journal assignments to record observations and conceptual understanding. This activity derives from those demonstrated in the NASA CONNECT television series episode, titled Path of Totality.
Angular Momentum in QGP Holography
Brett McInnes
2014-08-25
The quark chemical potential is one of the fundamental parameters describing the Quark-Gluon Plasma produced by sufficiently energetic heavy-ion collisions. It is not large at the extremely high temperatures probed by the LHC, but it plays a key role in discussions of the beam energy scan programmes at the RHIC and other facilities. On the other hand, collisions at such energies typically (that is, in peripheral collisions) give rise to very high values of the angular momentum density. Here we explain that holographic estimates of the quark chemical potential of a rotating sample of plasma can be very considerably improved by taking the angular momentum into account.
Solar cell angular position transducer
NASA Technical Reports Server (NTRS)
Sandford, M. C.; Gray, D. L. (inventors)
1980-01-01
An angular position transducer utilizing photocells and a light source is disclosed. The device uses a fully rotatable baffle which is connected via an actuator shaft to the body whose rotational displacement is to be measured. The baffle blocks the light path between the light source and the photocells so that a constant semicircular beam of light reaches the photocells. The current produced by the photocells is fed through a resistor, a differential amplifier measures the voltage drop across the resistor which indicates the angular position of the actuator shaft and hence of the object.
Angular distribution of electrons elastically scattered from N2.
NASA Technical Reports Server (NTRS)
Shyn, T. W.; Stolarski, R. S.; Carignan, G. R.
1972-01-01
Measurement of the angular distribution of electrons elastically scattered from N2 as a function of energy, utilizing a crossed-beam technique. Measurements have been made of monoenergetic electrons with energies between 5 and 90 eV scattered from a collimated beam of N2 at angles from -114 to +160 deg. The wide angular range of the measurements has enabled the determination of the total elastic-scattering and momentum-transfer cross sections. The measurements are relative and have been normalized to Fisk's (1936) theoretical calculation at 5 eV. The results generally agree well with other published measurements and with theory.
Kinetic description of electron plasma waves with orbital angular momentum
Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2012-11-15
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.
NASA Technical Reports Server (NTRS)
Kvaternik, R. G.; Kaza, K. R. V.
1976-01-01
The nonlinear curvature expressions for a twisted rotor blade or a beam undergoing transverse bending in two planes, torsion, and extension were developed. The curvature expressions were obtained using simple geometric considerations. The expressions were first developed in a general manner using the geometrical nonlinear theory of elasticity. These general nonlinear expressions were then systematically reduced to four levels of approximation by imposing various simplifying assumptions, and in each of these levels the second degree nonlinear expressions were given. The assumptions were carefully stated and their implications with respect to the nonlinear theory of elasticity as applied to beams were pointed out. The transformation matrices between the deformed and undeformed blade-fixed coordinates, which were needed in the development of the curvature expressions, were also given for three of the levels of approximation. The present curvature expressions and transformation matrices were compared with corresponding expressions existing in the literature.
PP-waves with Torsion - a Metric-affine Model for the Massless Neutrino
Pasic, Vedad
2014-01-01
In this paper we deal with quadratic metric-affine gravity, which we briefly introduce, explain and give historical and physical reasons for using this particular theory of gravity. Further, we introduce a generalisation of well known spacetimes, namely pp-waves. A classical pp-wave is a 4-dimensional Lorentzian spacetime, which admits a nonvanishing parallel spinor field; here the connection is assumed to be Levi-Civita. This definition was generalised in our previous work to metric compatible spacetimes with torsion and used to construct new explicit vacuum solutions of quadratic metric-affine gravity, namely generalised pp-waves of parallel Ricci curvature. The physical interpretation of these solutions we propose in this article is that they represent a conformally invariant metric-affine model for a massless elementary particle. We give a comparison with the classical model describing the interaction of gravitational and massless neutrino fields, namely Einstein-Weyl theory and construct pp-wave type sol...
Heat transport as torsional responses and Keldysh formalism in a curved spacetime
NASA Astrophysics Data System (ADS)
Shitade, Atsuo
2014-12-01
We revisit a theory of heat transport in the light of a gauge theory of gravity and find the proper heat current with a corresponding gauge field, which yields the natural definitions of the heat magnetization and the Kubo-formula contribution to the thermal conductivity as torsional responses. We also develop a general framework for calculating gravitational responses by combining the Keldysh and Cartan formalisms. By using this framework, we explicitly calculate these two quantities and reproduce the Wiedemann-Franz law for the thermal Hall conductivity in the clean and non-interacting case. Finally, we discuss an effective action for the quantized thermal Hall effect in (2 +1)-D topological superconductors.
On the discriminant of elliptic curves with non-trivial torsion
Garcia-Selfa, I
2007-01-01
For those elliptic curves defined over the rational with non--trivial torsion subgroup, we find a tight relationship between the torsion subgroup itself and a Galois group naturally arising from the curve.
The effects of torsional-lateral coupling on the dynamics of a gear coupled rotor
Emery, Michael Aaron
2007-04-25
This thesis focuses on the torsional-lateral interactions seen in gear coupled rotors. Of particular interest are cases where the torsional stiffness parameters affect the lateral critical speeds and where lateral stiffness and damping parameters...
Experimental study of ductile fracture of tubes under combined tension/torsion
Johnson, Joseph M. (Joseph Michael)
2007-01-01
This experiment sought to compare the results of an experimental torsion test on a specimen of 1045 steel with a torsion simulation in the ABAQUS FEA software program. A simulation of a tension test on a round bar of 1045 ...
Kim, Hoe Woong; Kwon, Young Eui; Lee, Joo Kyung; Kim, Yoon Young
2013-03-01
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
Near-perfect sorting of orbital angular momentum and angular position states
Boyd, Robert W.
Near-perfect sorting of orbital angular momentum and angular position states of light Malcolm N. O for efficient sorting of photons prepared in states of orbital angular momentum (OAM) and angular position (ANG, "Orbital angular momentum of light and the transfor- mation of Laguerre-Gaussian laser modes," Phys. Rev
Angular output of hollow, metal-lined, waveguide Raman sensors
Biedrzycki, Stephen; Buric, Michael P.; Falk, Joel; Woodruff, Steven D.
2012-04-20
Hollow, metal-lined waveguides used as gas sensors based on spontaneous Raman scattering are capable of large angular collection. The collection of light from a large solid angle implies the collection of a large number of waveguide modes. An accurate estimation of the propagation losses for these modes is required to predict the total collected Raman power. We report a theory/experimental comparison of the Raman power collected as a function of the solid angle and waveguide length. New theoretical observations are compared with previous theory appropriate only for low-order modes. A cutback experiment is demonstrated to verify the validity of either theory. The angular distribution of Raman light is measured using aluminum and silver-lined waveguides of varying lengths.
Torsional stick-slip behavior in WS2 nanotubes.
Nagapriya, K S; Goldbart, Ohad; Kaplan-Ashiri, Ifat; Seifert, Gotthard; Tenne, Reshef; Joselevich, Ernesto
2008-11-01
We experimentally observed atomic-scale torsional stick-slip behavior in individual nanotubes of tungsten disulfide (WS2). When an external torque is applied to a WS2 nanotube, all its walls initially stick and twist together, until a critical torsion angle, at which the outer wall slips and twists around the inner walls, further undergoing a series of stick-slip torque oscillations. We present a theoretical model based on density-functional-based tight-binding calculations, which explains the torsional stick-slip behavior in terms of a competition between the effects of the in-plane shear stiffness of the WS2 walls and the interwall friction arising from the atomic corrugation of the interaction between adjacent WS2 walls. PMID:19113281
Torsional Stick-Slip Behavior in WS2 Nanotubes
NASA Astrophysics Data System (ADS)
Nagapriya, K. S.; Goldbart, Ohad; Kaplan-Ashiri, Ifat; Seifert, Gotthard; Tenne, Reshef; Joselevich, Ernesto
2008-11-01
We experimentally observed atomic-scale torsional stick-slip behavior in individual nanotubes of tungsten disulfide (WS2). When an external torque is applied to a WS2 nanotube, all its walls initially stick and twist together, until a critical torsion angle, at which the outer wall slips and twists around the inner walls, further undergoing a series of stick-slip torque oscillations. We present a theoretical model based on density-functional-based tight-binding calculations, which explains the torsional stick-slip behavior in terms of a competition between the effects of the in-plane shear stiffness of the WS2 walls and the interwall friction arising from the atomic corrugation of the interaction between adjacent WS2 walls.
FREQUENCY FILTERING OF TORSIONAL ALFVEN WAVES BY CHROMOSPHERIC MAGNETIC FIELD
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
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.
A novel low-profile shape memory alloy torsional actuator
NASA Astrophysics Data System (ADS)
Paik, Jamie K.; Hawkes, Elliot; Wood, Robert J.
2010-12-01
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.
The management of tibial torsion in patients with spina bifida.
Fraser, R K; Menelaus, M B
1993-05-01
We reviewed 20 patients with spina bifida who had had surgical management of tibial torsion. Eight had had bilateral procedures and 12 a unilateral procedure, giving a total of 28 limbs for analysis. We performed closed osteoclasis on seven limbs and tibial osteotomy on 21. In the closed osteoclasis group six limbs (85%) had a good result after an average follow-up of nine years (2 to 22). All limbs developed postoperative anteromedial bowing of the tibia which later remodelled. In the tibial osteotomy group 19 (90%) had a good result. The average follow-up was nine years (2 to 28). Complications occurred in seven limbs (33%). We recommend closed osteoclasis of the tibia for the young patient with spina bifida in whom walking is impeded by excessive internal tibial torsion, and supramalleolar tibial osteotomy in the older patient with excessive external tibial torsion and a planovalgus foot. PMID:8496230
Meckel's diverticulum complicated by axial torsion and gangrene
Hadeed, Andrew A.H.; Azar, Robert R.A.; Azar, Nabiel N.A.; Benninger, Brion
2015-01-01
Meckel's diverticulum is a remnant of the omphalomesenteric duct and is the most common congenital anomalies of the gastrointestinal tract. It has been known to mimic different disease states making its diagnosis difficult. Common complications consist of bleeding, intestinal obstruction and inflammation. The patient discussed in this case study was a 29-year-old Hispanic female who presented with right lower quadrant abdominal pain. A CT scan showed a normal appendix, thickened terminal ileum and a high-grade distal small bowel obstruction with a possible closed-loop obstruction. Laparoscopy revealed Meckel's diverticulum with the rare complication of torsion. The mechanism of torsion has been postulated but with little evidence. The purpose of this case report is to discuss the apparent mechanism of axial torsion secondary to the presence of a mesodiverticular band, provide visual evidence at surgery and recommend all Meckel's diverticulum associated with a mesodiverticular band be resected to prevent further complications. PMID:25733669
Angular momentum problem during star formation: Magnetically linked, aligned rotators. II. Results
Mouschovias, T.C.; Morton, S.A.
1985-11-01
Solutions of the three-fragment problem are presented graphically for different values of sigma, the ratio of half the moment of inertia of a fragment to that of the medium between consecutive fragments, namely, for sigma = 0.1, 1.0, and 5.0. The values 0.1 and 5.0 already represent the behavior in the low-sigma and high-sigma limits respectively. Smaller values of sigma represent later stages of contraction of a fragment. The central fragment's angular momentum decreases exponentially in time with an e-folding time tau/sub parallel/ = sigmatau0, where tau0 is the Alfven crossing time between consecutive fragments (typically, tau0 = 10W yr). Resolution of the problem can be achieved in a fraction of the Alfven crossing time in the low-sigma cases, whereas it takes many bounces of the torsional Alfven waves between fragments before the angular momentum problem can be resolved for an individual fragment in the high-sigma cases. Even in the low-sigma cases, however, the problem is regenerated by returning torsional Alfven waves. For star formation to take place in magnetically linked fragments, the magnetic field should decouple from the matter during the low-spin phase: not only a likely, but perhaps an inevitable possiblity because gravity is unopposed by centrifugal forces at that stage.
Intensity Modeling of Methanol in the Torsional Manifold
NASA Astrophysics Data System (ADS)
Xu, Li-Hong; Kleiner, Isabelle
2013-06-01
Methanol is a popular and very important molecule both in astrophysics and atmospheric science, for which reliable line intensities have long been desired by the user communities. Because of the low barrier to the large-amplitude torsional motion, the methanol spectrum is extremely rich and complicated, representing a significant challenge for global modeling. Not until recent years has the torsional manifold of v_t = 0, 1, and 2 levels been successfully globally modeled using a modified version of the BELGI code. The resulting global fit parameters were then used to predict line lists in the THz region, employing both permanent dipole moments and torsional dependence of the dipole moments from ab initio results for the intensity calculations. However, recent direct intensity measurements based on Fourier transform spectra from JPL call for improvement of the intensity model. Thus, we have initiated enhanced modeling of the measured intensities in the torsional manifold using an extended set of dipole moment parameters, including permanent (?_a, ?_b), torsionally dependent (?_{a3n?}, ?_{b3n?}, ?_{c3n?}), and K and J dependent terms. While we are hopeful that this will improve our intensity predictive power, we also foresee challenges in the modeling for the A torsional species since a substantial body of the measured A doublet transitions exhibit either small asymmetry splittings for low K and high J states or are barely to completely unresolved as K increases. The present status of this work is that the existing database still needs some cleaning up to make it consistent with the new code. We hope to report our early intensity fit results at the conference. Xu et. al., J. Mol. Spectrosc. {251} (2008) p305. Xu & Lovas, J. Phys. Chem. Ref. Data {26} (1997) p17. Mekhtiev et. al., J. Mol. Spectrosc. {194} (1999) p171. Brauer et. al., JQSRT {113} (2012) p128.
773revision:2002-01-18modified:2002-01-19 Cotorsion theories cogenerated by 1-free abelian groups
Shelah, Saharon
773revision:2002-01-18modified:2002-01-19 Cotorsion theories cogenerated by 1-free abelian groups of the cotorsion class singly cogenerated by a torsion-free group G. Cotorsion theories were introduced by Salce
[Ischemic testicular necrosis without torsion of the spermatic cord].
Viville, C
1993-01-01
Two diagnoses can be contemplated in case of sudden, painful increase in the volume of a testis: torsion of the spermatic cord and acute orchiepididymitis. Two cases observed in young adults show that acute testicular ischemia may occur without any torsion of the cord, probably due to sudden vascular occlusion. However, except in some infrequent vascular diseases, the etiology of such accidents in young adults in good health is still mysterious. The loss of the involved testis is the rule. Possibilities of treatment are limited at present and render the prognosis for the testis very poor. PMID:7745275
High Sensitivity Torsion Balance Tests for LISA Proof Mass Modeling
S. Schlamminger; C. A. Hagedorn; M. G. Famulare; S. E. Pollack; J. H. Gundlach
2007-02-08
We have built a highly sensitive torsion balance to investigate small forces between closely spaced gold coated surfaces. Such forces will occur between the LISA proof mass and its housing. These forces are not well understood and experimental investigations are imperative. We describe our torsion balance and present the noise of the system. A significant contribution to the LISA noise budget at low frequencies is the fluctuation in the surface potential difference between the proof mass and its housing. We present first results of these measurements with our apparatus.
Gravitational and torsion waves in linearised teleparallel gravity
L. C. Garcia de Andrade
2002-06-03
Spin-2, spin-1 and spin-0 modes in linearised teleparallelism are obtained where the totally skew-symmetric complex contortion tensor generates scalar torsion waves and the symmetric contortion in the last two indices generates gravitational waves as gravitational perturbations of flat spacetime with contortion tensor. A gedanken experiment with this gravitational-torsion wave hitting a ring of spinless particles is proposed which allows us to estimate the contortion of the Earth by making use of data from LISA GW detector. This value coincides with previous value obtained by Nitsch in teleparallelism using another type of experiment.
Elastic torsional buckling of thin-walled composite cylinders
NASA Technical Reports Server (NTRS)
Marlowe, D. E.; Sushinsky, G. F.; Dexter, H. B.
1974-01-01
The elastic torsional buckling strength has been determined experimentally for thin-walled cylinders fabricated with glass/epoxy, boron/epoxy, and graphite/epoxy composite materials and composite-reinforced aluminum and titanium. Cylinders have been tested with several unidirectional-ply orientations and several cross-ply layups. Specimens were designed with diameter-to-thickness ratios of approximately 150 and 300 and in two lengths of 10 in. and 20 in. The results of these tests were compared with the buckling strengths predicted by the torsional buckling analysis of Chao.
The torsional fatigue properties of titanium-alloy spring wire
E. L. Hayman; D. W. Greenwood; B. G. Martin
1977-01-01
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
Torsional rigidity of positively and negatively supercoiled DNA
Selvin, P.R.; Cook, D.N.; Pon, N.G.; Klein, M.P.; Hearst, J.E. (Lawrence Berkeley Lab., CA (United States)); Bauer, W.R. (State Univ. of New York, Stony Brook (United States))
1992-01-03
Time-correlated single-photon counting of intercalated ethidium bromide was used to measure the torsion constants of positively supercoiled, relaxed, and negatively supercoiled pBR322 DNA, which range in superhelix density from +0.042 to {minus}0.123. DNA behaves as coupled, nonlinear torsional pendulums under superhelical stress, and the anharmonic term in the Hamiltonian is approximately 15 percent for root-mean-square fluctuations in twist at room temperature. At the level of secondary structure, positively supercoiled DNA is significantly more flexible than negatively supercoiled DNA. These results exclude certain models that account for differential binding affinity of proteins to positively and negatively supercoiled DNA.
Hyperbaric oxygen treatment for unilateral testicular torsion in a child.
Alp, Bilal Firat; Cebi, Gamze; Ozdemir, Adem; Irkilata, Hasan Cem; Uzun, Günalp
2014-09-01
Torsion of the testis is a urological emergency most commonly occurring in adolescent boys. Hyperbaric oxygen treatment (HBOT) has been shown to alleviate reperfusion injury in experimental ischaemia of the testis. We report a 13-year-old boy who had prolonged right testicular ischaemia. Despite surgery, the colour of the testis remained poor. He underwent a post-operative course of 10 HBOT over 8 days, with restoration of blood flow on colour Doppler and reduction of oedema. At four-month followup, the testis appeared normal on ultrasonography. To the best of our knowledge, this is the first published case of torsion of the testis treated with HBOT. PMID:25311324
Coated Fused Silica Fibers for Enhanced Sensitivity Torsion Pendulum
NASA Technical Reports Server (NTRS)
Numata, Kenji; Horowitz, Jordan; Camp, Jordan
2007-01-01
In order to investigate the fundamental thermal noise limit of a torsion pendulum using a fused silica fiber, we systematically measured and modeled the mechanical losses of thin fused silica fibers coated by electrically conductive thin metal films. Our results indicate that it is possible to achieve a thermal noise limit for coated silica lower by a factor between 3 and 9, depending on the silica diameter, compared to the best tungsten fibers available. This will allow a corresponding increase in sensitivity of torsion pendula used for weak force measurements, including the gravitational constant measurement and ground-based force noise testing for the Laser Interferometer Space Antenna (LISA) mission.
Letian Lin; Taoran Cui; Sean Washburn; Lu-Chang Qin
2011-01-01
We have used a double wall carbon nanotube to build a torsional pendulum. The nanotube worked as a torsional bearing for a metal block. An external electric field was used to rotate the metal block to cause a fully elastic torsional deformation on the nanotube. Nano-beam electron diffraction patterns were taken before and while the nanotube was twisted. By analysis
Mutation of torsion pairs in triangulated categories and its geometric realization
Zhu, Bin
Mutation of torsion pairs in triangulated categories and its geometric realization Yu Zhou and Bin@mails.tsinghua.edu.cn; bzhu@math.tsinghua.edu.cn Abstract The notion of D-mutation of torsion pairs in triangulated categories is introduced. It is proved that the D-mutation of torsion pairs in triangulated
Yang Jiashi
2007-01-01
We show that, in a circular cylindrical rod, torsional modes are coupling to extension when the shear deformation associated with the torsional modes is no longer infinitesimal. A set of a couple equations is derived with which the effect of extension on the torsional frequency is examined. The results are useful to the understanding and design of devices operating with
Calculation for thin-walled closed contours of composite materials in torsion
A. N. Elpat'evskii; N. N. Kurdyumov
1997-01-01
We consider the torsion of closed torsion-box structures made of composite materials (such as airplane wings) under mechanical loads inducing only torsion of the construction without bending. The problem is solved by an energy method and using a conforming displacement method. The derived distribution law for the tangential stresses contains two terms and gives the Bredt formula for the special
Numerical simulation of torsional wave propagation in an elastic-viscoplastic stepped bar
Kaishin Liu
1995-01-01
This paper presents a numerical simulation for the propagation of torsional waves in an elastic-viscoplastic stepped bar subjected to torsional impact at its end surface. The equations governing the dynamic torsional deformation of the stepped bar are solved by means of the method of numerical integration along bicharacteristics. The stability and convergence of the present numerical technique are investigated by
Trapped Torsional Vibrations in Elastic Plates Min K. Kang and Rui Huang
Huang, Rui
was previously used to generate trapped torsional waves in stepped cylinders [13]. This paper presentsTrapped Torsional Vibrations in Elastic Plates Min K. Kang and Rui Huang Department of Aerospace observed that torsional vibrations can be trapped in elastic plates with circular regions of slightly
LARGE TORSIONAL OSCILLATIONS IN A SUSPENSION BRIDGE: MULTIPLE PERIODIC SOLUTIONS TO A NONLINEAR
Moore, Kristen
. nonlinear wave equation, torsional oscillations, suspension bridge AMS subject classification. 35B10 PII. S this claim for the vertical, torsional, and traveling wave motion of suspension bridges can be found in [3LARGE TORSIONAL OSCILLATIONS IN A SUSPENSION BRIDGE: MULTIPLE PERIODIC SOLUTIONS TO A NONLINEAR
THE ROLE OF ACTIVE REGIONS IN THE GENERATION OF TORSIONAL OSCILLATIONS
Petrovay, KristÃ³f
of torsional waves from f -mode splittings by Kosovichev and Schou (1997), helioseismic observations have of the coexistence of a 1/hemisphere modulation with the torsional waves. Most theoretical attempts to interpretTHE ROLE OF ACTIVE REGIONS IN THE GENERATION OF TORSIONAL OSCILLATIONS K. PETROVAY and E. FORGÃCS
Torsional rod wave scattering from tapering between regions of different cross-sections
Helge E. Engan
1999-01-01
Previously (Engan 1998) we have studied the scattering of torsional waves in circular rods with a free surface where the rod diameter is subject to abrupt diameter changes. Here, we discuss the scattering of torsional waves from tapered regions and, in particular, transmission of the fundamental torsional mode. The calculations are based on a mode expansion technique in which propagating
Bianchi groups CBG Abelian Varieties Galois representations Torsion Cohomology of Bianchi Groups and
Sengun, Mehmet Haluk
Bianchi groups CBG Abelian Varieties Galois representations Torsion Cohomology of Bianchi Groups://www.uni-due.de/~hm0074 #12;Bianchi groups CBG Abelian Varieties Galois representations Torsion Outline 1. Bianchi Groups. Dimension #12;Bianchi groups CBG Abelian Varieties Galois representations Torsion Outline 1. Bianchi Groups
Study on Hollow Cylinder Torsional Shear of Dynamic Properties of Two Soils
Ying Nie; Mao-tian Luan; Xiao-wei Tang
The testing is employed to perform cyclic torsional shear test on hollow cylinder sample under isotropic consolidated condition with static and dynamic universal triaxial and torsional shear soil testing apparatus. The authors conducted three dynamic torsional with single sample achieving dynamic properties under three confining pressures with saturated clay and undisturbed silty clay. Special attention was paid to the maximum
Torsion fatigue behavior of unidirectional carbon\\/epoxy and glass\\/epoxy composites
Toshio Ogasawara; Keiji Onta; Shinji Ogihara; Tomohiro Yokozeki; Eiichi Hara
2009-01-01
This paper presents results of the feasibility of carbon\\/epoxy composites (CFRP) as a future helicopter flexbeam material. Torsional behaviors of unidirectional CFRP and glass\\/epoxy composites (GFRP) with the same resin matrix were investigated. The initial torsional rigidity of CFRP was almost identical to that of GFRP. The torsional rigidities calculated using finite element analyses (FEA) agreed with the experimental results:
A MEASUREMENT OF THE GRAVITATIONAL CONSTANT USING A CRYOGENIC TORSION PENDULUM
Newman, Riley D.
A MEASUREMENT OF THE GRAVITATIONAL CONSTANT USING A CRYOGENIC TORSION PENDULUM M.K. Bantel, E of a measurement of G made using a cryogenic torsion pendulum in the `dynamic' (time-of-swing) mode. We have- lation frequency of a thin-plate torsion pendulum due to a pair of ring-shaped source masses positioned
PROGRESS IN THE MEASUREMENT OF THE GRAVITATIONAL CONSTANT USING A CRYOGENIC TORSION PENDULUM
Newman, Riley D.
PROGRESS IN THE MEASUREMENT OF THE GRAVITATIONAL CONSTANT USING A CRYOGENIC TORSION PENDULUM E a cryogenic torsion pendulum in the "dynamic" (time- of-swing) mode. The total metrology contribution to the G- lation frequency of a thin-plate torsion pendulum due to a pair of ring-shaped source masses positioned
Angular Diameters of O- and B-type Stars
NASA Astrophysics Data System (ADS)
Gordon, Kathryn; Gies, Douglas; Schaefer, Gail
2015-01-01
We are observing a sample of 10 O-type stars and 60 B-type stars to determine angular diameters using the Center for High Angular Resolution Astronomy (CHARA) Array, the foremost optical long baseline interferometer in the world. Our goal is to establish accurate stellar parameters to test modern theories of stellar evolution that include rotation. We will combine our stellar angular diameter measurements with flux and line measurements from spectroscopy, projected rotational velocities, and distances to determine radius, effective temperature, luminosity, equatorial rotational velocity, and evolutionary mass. Knowing these properties will allow us to place the stars in a Hertzsprung-Russell diagram and obtain estimates for the age and evolutionary state.
Torsional Splittings in the Band nu9 + nu4 - nu4 of Ethane.
Susskind; Iredell; Blass; Reuter; Halsey; Jennings
1998-11-01
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
A shear-shear torsional beam model for nonlinear aeroelastic analysis of tower buildings
NASA Astrophysics Data System (ADS)
Piccardo, G.; Tubino, F.; Luongo, A.
2014-09-01
In this paper, an equivalent one-dimensional beam model immersed in a three-dimensional space is proposed to study the aeroelastic behavior of tower buildings: linear and nonlinear dynamics are analyzed through a simple but realistic physical modeling of the structure and of the load. The beam is internally constrained, so that it is capable to experience shear strains and torsion only. The elasto-geometric and inertial characteristics of the beam are identified from a discrete model of three-dimensional frame, via a homogenization process. The model accounts for the torsional effect induced by the rotation of the floors around the tower axis; the macroscopic shear strain is produced by bending of the columns, accompanied by negligible rotation of the floors. Nonlinear aerodynamic forces are evaluated through the quasi-steady theory. The first aim is to investigate the effect of mechanical and aerodynamic coupling on the critical galloping conditions. Furthermore, the role of aerodynamic nonlinearities on the galloping post-critical behavior is analyzed through a perturbation solution which permits to obtain a reduced one-dimensional dynamical system, capable of capturing the essential dynamics of the problem.
Flexure-torsion behavior of prismatic beams. I - Section properties via power series
NASA Technical Reports Server (NTRS)
Kosmatka, J. B.
1993-01-01
The behavior of a tip-loaded cantilever beam with an arbitrary cross section is studied using Saint-Venant's semi-inverse method along with a power series solution for the out-of-plane flexure and torsion warping functions. The power series coefficients are determined by solving a set of variationally derived linear algebraic equations. For complex cross sections, the calculated coefficients represented a 'best-fit approximation' to the exact warping function. The resulting warping functions are used to determine the cross-sectional properties (torsion constant, shear correction factors, shear deformation coefficients, and shear center location). A new linear relation is developed for locating the shear center, where the twist rate is zero about the line of shear centers. Moreover, the kinematic relations for a new fully compatible one-dimensional beam theory are developed. Numerical results are presented first to verify the approach and second to provide section data on NACA four-series airfoils not currently found in the literature.
The Angular Momentum of Baryons and Dark Matter Halos Revisited
NASA Technical Reports Server (NTRS)
Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan
2011-01-01
Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive-mesh refinement (AMR), we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r = 0.1R(sub vir). In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/R(sub vir) > 0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its virialised dark matter halo host. This generic result holds for halos of all masses at all redshifts, as radiative cooling ensures that a significant fraction of baryons remain trapped at the centre of the halos. Despite this injection of angular momentum enriched gas, we predict an amount for stellar discs which is in fair agreement with observations at z=0. This arises because the total specific angular momentum of the baryons (gas and stars) remains close to that of dark matter halos. Indeed, our simulations indicate that any differential loss of angular momentum amplitude between the two components is minor even though dark matter halos continuously lose between half and two-thirds of their specific angular momentum modulus as they evolve. In light of our results, a substantial revision of the standard theory of disc formation seems to be required. We propose a new scenario where gas efficiently carries the angular momentum generated by large-scale structure motions deep inside dark matter halos, redistributing it only in the vicinity of the disc.
Controversy concerning the definition of quark and gluon angular momentum
Leader, Elliot [Blackett laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)
2011-05-01
A major controversy has arisen in QCD as to how to split the total angular momentum into separate quark and gluon contributions, and as to whether the gluon angular momentum can itself be split, in a gauge-invariant way, into a spin and orbital part. Several authors have proposed various answers to these questions and offered a variety of different expressions for the relevant operators. I argue that none of these is acceptable and suggest that the canonical expression for the momentum and angular momentum operators is the correct and physically meaningful one. It is then an inescapable fact that the gluon angular momentum operator cannot, in general, be split in a gauge-invariant way into a spin and orbital part. However, the projection of the gluon spin onto its direction of motion, i.e. its helicity is gauge invariant and is measured in deep inelastic scattering on nucleons. The Ji sum rule, relating the quark angular momentum to generalized parton distributions, though not based on the canonical operators, is shown to be correct, if interpreted with due care. I also draw attention to several interesting aspects of QED and QCD, which, to the best of my knowledge, are not commented upon in the standard textbooks on field theory.
Acute Abdomen due to Primary Omental Torsion and Infarction
Occhionorelli, S.; Zese, M.; Cappellari, L.; Stano, R.; Vasquez, G.
2014-01-01
Background. Torsion of greater omentum is a quite uncommon cause of acute abdomen. It can be primary or secondary but in both cases omentum twists upon itself and causes omental segmentary or diffuse necrosis. Symptoms are unspecific and preoperative diagnosis is difficult. The widespread and increasing use of computer tomography (CT) in differential diagnosis of acute abdomen can be useful for making a specific diagnosis. Objectives. This work aims to describe primary omental torsion in order to help avoid misdiagnosis, especially with acute appendicitis, which is eventually based solely on a physical examination. Case Report. We present a case of primary omental torsion in a young man and discuss contemporary methods in diagnosis and management of the condition. Conclusions. When a right diagnosis has been posed, possible treatments for omental torsion and necrosis are two: conservative or surgical. Conservative treatment had been rarely carried out because of frequent and important sequelae just like abdominal abscesses. Nowadays, surgical treatment, laparoscopic or laparotomic, is preferred because it is a safe method in diagnosis and management of this condition. PMID:25431726
TORSION OF RATIONAL ELLIPTIC CURVES OVER QUADRATIC FIELDS II
GonzÃ¡lez, Enrique
. TORNERO Abstract. Let E be an elliptic curve defined over Q and let G = E(Q)tors be the associated torsion by the grant FQMÂ218 and P12ÂFQMÂ2696. 1 #12;2 ENRIQUE GONZÃLEZÂJIMÃ?NEZ AND JOSÃ? M. TORNERO Â· After this
Mechanical properties of orthodontic wires in tension, bending, and torsion.
Drake, S R; Wayne, D M; Powers, J M; Asgar, K
1982-09-01
The mechanical properties of three sizes of stainless steel (SS), nickel-titanium (NT), and titanium-molybdenum (TM) orthodontic wires were studied in tension, bending, and torsion. The wires (0.016 inch, 0.017 by 0.025 inch, and 0.019 by 0.025 inch) were tested in the as-received condition. Tensile testing and stiffness testing machines along with a torsional instrument were used. Mean values and standard deviations of properties were computed. The data were analyzed statistically by analysis of variance using a factorial design. Means were ranked by a Tukey interval calculated at the 95 percent level of confidence. In tension, the stainless steel wires had the least maximum elastic strain or springback, whereas the titanium-molybdenum wires had the most. Higher values of springback indicate the capacity for an increased range of activation clinically. In bending and torsion, the stainless steel wires had the least stored energy at a fixed moment, whereas the nickel-titanium wires had the most. Spring rates in bending and torsion, however, were highest for stainless steel wires and lowest for nickel-titanium wires. A titanium-molybdenum teardrop closing loop delivered less than one half the force of a comparable stainless steel loop for similar activations. PMID:6961793
Musica II: Torsion Drum, Buzzer, Maraca, Chirper, Flute
NSDL National Science Digital Library
Watsonville Environmental Science Workshop
2011-01-01
In this activity, learners use common household items to build musical instruments. This lesson guide includes step-by-step instructions for building five instruments: a torsion drum; buzzer; maraca; chirper; and flute. Basic tools including a drill and clamp are required. Use this activity to help learners explore elements of sound like vibration, sound waves, pitch, amplitude and volume.
Torsion Balance Search for Lorentz-invariance, Dark
Torsion Balance Search for Lorentz-invariance, Dark Energy and Dark Matter Claire Cramer AAPT the Standard Model GR + SM = Lorentz-symmetry breaking??? #12;What about Dark Energy and Dark Matter? We're also not sure what the universe is made of: Dark Energy Dark Matter Ordinary Matter, 4% 96% new
The ground state torsion rotation spectrum of CH2DOH
NASA Astrophysics Data System (ADS)
Pearson, John C.; Yu, Shanshan; Drouin, Brian J.
2012-10-01
The ground state torsion rotation spectrum of CH2DOH has been completely characterized through J = 30 and Ka = 10, 9, 9 in the three torsional sub-states of the ground state; e0, e1, and o1, respectively. Additional a-type assignments are presented to Ka = 11 in each of the torsional sub-states. The data has been analyzed with an empirical power series model as well as an empirical internal axis model. Over 8000 transitions have been assigned and fit with near experimental accuracy over the range of 4-1628 GHz. The characterization of the spectrum allows for a complete set of ground state term values enabling a better understanding of the infrared spectrum. Comparison of the torsional contributions of the Hamiltonian with normal methanol provides great insight into the nature of the asymmetric-top asymmetric-frame internal rotation problem. The comparison with normal methanol also provides a relatively straightforward transformation from the well understood C3V internal rotation problem to the completely asymmetric internal rotation problem. The data and analysis provide some practical wisdom on the impacts of breaking the symmetry and the choice of models for addressing the nearly three fold completely asymmetric internal rotation problem.
PP-waves with torsion and metric-affine gravity
Vedad Pasic; Dmitri Vassiliev
2005-05-31
A classical pp-wave is a 4-dimensional Lorentzian spacetime which admits a nonvanishing parallel spinor field; here the connection is assumed to be Levi-Civita. We generalise this definition to metric compatible spacetimes with torsion and describe basic properties of such spacetimes. We use our generalised pp-waves for constructing new explicit vacuum solutions of quadratic metric-affine gravity.
Torsional Oscillations and Waves Projected on the Wall
ERIC Educational Resources Information Center
Bartlett, Albert A.
2008-01-01
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…
Non-contact torsion sensor using fibre Bragg gratings
Ludi Kruger; Pieter L. Swart; Anatoli A. Chtcherbakov; A. J. van Wyk
2004-01-01
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
Human ocular torsional position before and after unilateral vestibular neurectomy
I. S. Curthoys; M. J. Dai; G. M. Halmagyi
1991-01-01
The static ocular torsional position of both eyes of 23 patients was measured by means of fundus photographs one day before and one week after unilateral vestibular neurectomy for the treatment of acoustic neuroma, Ménière's disease or paroxysmal vertigo. The results showed that in all patients the vestibular neurectomy caused both eyes to tort (i.e. to roll around the visual
Torsion gravity with nonminimally coupled fermionic field: Some cosmological models
NASA Astrophysics Data System (ADS)
Vignolo, Stefano; Carloni, Sante; Fabbri, Luca
2015-02-01
We investigate some cosmological models arising from a nonminimal coupling of a fermionic field to gravity in the geometrical setting of Einstein-Cartan-Sciama-Kibble gravity. In the presence of torsion, we discuss the role played by the nonminimal coupling together with fermionic self-interaction potentials in facing problems such as cosmological singularity, inflation, and dark energy.
The impact of tibial torsion measurements on gait analysis kinematics
Lucareli, Paulo Roberto Garcia; Santos, Nadia Maria; Godoy, Wagner De; Bernal, Milena Moreira Barreto; Paes, Ângela Tavares; Ramalho, Amancio
2014-01-01
Objective: To measure and compare tibial torsion values as assessed by goniometry and three-dimensional kinematics. In addition, the impact of each one of these measurements on kinematic and kinetic results for normal gait was determined. Methods: Twenty-three healthy and fully ambulatory patients were assessed, 11 women and 12 men, from 20 to 40 years old. Data were collected at a laboratory for the three-dimensional analysis of movement with 10 cameras and two force plates. Tibial torsion measurements were obtained using goniometry and three-dimensional kinematics based on the Plug-in Gait model. Afterwards, both procedures were compared, and the impact of each result was assessed on the kinematic and kinetic modeling of the knee and ankle. Results: Pearson's linear correlation coefficient (r=0,504) showed a moderate correlation between the three-dimensional kinematics and goniometry, and between the changes in the measurements. Regarding the processed kinematic and kinetic results for every torsion position, no significant differences were noticed among any of the studied variables (p>0.05). Conclusion: Although statistical correlation among tibial torsion angles by goniometry and three-dimensional kinematic were moderate, kinematic and kinetic analysis of the joints did not reveal any significant changes. Level of Evidence I, Diagnostic Studies - Investigating a Diagnostic Test. PMID:25328438
Fracturing normal to maximum compression: fluid overpressure in torsion experiments
F. Ornelas Marques; L. Burlini
2009-01-01
We carried out torsion experiments in synthetic aggregates of 100% halite and in two-phase synthetic aggregates composed of 70% halite and 30% coarse calcite. The pure halite specimens showed homogeneous shear strain through plastic deformation of halite grains. No brittle yielding was observed, even at microscopic scale. In contrast, the two-phase specimens showed homogeneous deformation at the scale of the
Protective role of erythropoietin during testicular torsion of the rats.
Yazihan, Nuray; Ataoglu, Haluk; Koku, Naim; Erdemli, Esra; Sargin, Ayse Kose
2007-10-01
Testicular torsion is an important clinical urgency. Similar mechanisms occurred after detorsion of the affected testis as in the ischemia reperfusion (I/R) damage. This study was designed to investigate the effects of erythropoietin (EPO) treatment after unilateral testicular torsion. Fifty male Sprague-Dawley rats were divided into five groups. Group 1 underwent a sham operation of the right testis under general anesthesia. Group 2 was same as sham, and EPO (3,000 IU/kg) infused i.p., group 3 underwent a similar operation but the right testis was rotated 720 degrees clockwise for 1 h, maintained by fixing the testis to the scrotum, and saline infused during the procedure. Group 4 underwent similar torsion but EPO was infused half an hour before the detorsion procedure, and in group 5, EPO was infused after detorsion procedure. Four hours after detorsion, ipsilateral and contralateral testes were taken out for evaluation. Treatment with EPO improved testicular structures in the ipsilateral testis but improvement was less in the contralateral testis histologically, but EPO treatment decreased germ cell apoptosis in both testes following testicular IR. TNF-alpha, IL-1beta, IL-6 and nitrite levels decreased after EPO treatment especially in the ipsilateral testis. We conclude that testicular I/R causes an increase in germ cell apoptosis both in the ipsilateral and contralateral testes. Erythropoietin has antiapoptotic and anti-inflammatory effects following testicular torsion. PMID:17690891
Secondary Stresses in Open Box Beams Subjected to Torsion
NASA Technical Reports Server (NTRS)
Kuhn, Paul; Batdorf, S. B.; Brilmyer, Harold G
1944-01-01
In open box beams subjected to torsion, secondary stresses arise owing to lateral bending of the spar caps. The present paper outlines a simple method for estimating the magnitude of these stresses and gives the results of tests of an open box beam in the neighborhood of a discontinuity where the cover changed from the top to the bottom of the box.
On Gravity, Torsion and the Spectral Action Principle
Frank Pfaeffle; Christoph A. Stephan
2011-06-03
We consider compact Riemannian spin manifolds without boundary equipped with orthogonal connections. We investigate the induced Dirac operators and the associated commutative spectral triples. In case of dimension four and totally anti-symmetric torsion we compute the Chamseddine-Connes spectral action, deduce the equations of motions and discuss critical points.
New Approaches to Data Acquisitions in a Torsion Pendulum Experiment
ERIC Educational Resources Information Center
Jiang, Daya; Xiao, Jinghua; Li, Haihong; Dai, Qionglin
2007-01-01
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.
Typical Textures, part 2 FCC Torsion, BCC textures
Rollett, Anthony D.
in torsion; the shear direction points to the left in these figures. a) Nickel at =3.6 b) Copper at =3.5 c with horiz., vertical. #12;16 Fe,Fe-Si rolling fiber plots Note the marked alloy dependence in the alpha
Quaternionic Torsion Geometry, Superconformal Symmetry and T-duality
Swann, Andrew [Department of Mathematics and Computer Science, University of Southern Denmark, Campusvej 55, 5230 Odense M (Denmark)
2009-02-02
HyperKaehler 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.
Compressive and torsional behaviour of Kevlar 49 fibre
S. J. Deteresa; S. R. Allen; R. J. Farris; R. S. Porter
1984-01-01
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
The algebra of discrete torsion - Department of Mathematics, Purdue ...
2004-10-13
Oct 1, 2004 ... the genericity conditions used in [2,3,11,16] to derive the fusion rules. .... Here the final result is that given any Abelian ...... the equivalence of Vafa's and Douglas's picture of discrete torsion, J. High Energy ... II, Nuclear Phys.
INVESTIGATION OF STEEL SAMPLES DESTRUCTION PROCESS UNDER TORSION LOADING
Nizhny Novgorod Branch; Nizhny Novgorod
Acoustical characteristics of steel samples under torsion momentum beyond the elasticity range were investigated. Longitudinal elastic wave propagation velocities V were measured along the axes of every sample which was twisted at some number of turns (from 0 to 5). The relative error of this measurements was equal to 0,01%. The mass of every sample was evaluated by the help
Experimental study of externally prestressed segmental beam under torsion
M. A. Algorafi; A. A. A. Ali; I. Othman; M. S. Jaafar; M. P. Anwar
2010-01-01
Externally prestressed segmental (EPS) concrete beams are widely used in the construction of bridge structures today. The EPS concept has become an attractive tool for rehabilitation and strengthening of existing bridges which have insufficient strength and\\/or excessive deflection and cracking. EPS bridges are affected by combined stresses (bending, shear, normal, and torsion) at the joint interface between the segments. This
Modelling threshold conditions for cracks under tension\\/torsion loading
Yury G. Matvienko; Mike W. Brown; Keith J. Miller
1999-01-01
A model of microstructurally and physically short crack growth, with the threshold criterion for combined tension\\/torsion loading, has been proposed to analyse short crack propagation in medium carbon steel. Tresca's equivalent strain criterion for the high strain range regime and Rankine's criterion for fatigue limit strain range were employed for an analysis of Stage II crack growth. As a result,
34. VERTICAL AND TORSIONAL MOTION VIEWED FROM EAST TOWER, 7 ...
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
Residual strain evolution in steel samples: tension versus torsion
J. R. Bunn; D. Penumadu; C. R. Hubbard
2010-01-01
Torsion provides a unique opportunity to probe mechanical behavior of materials subjected to pure state of shear stress. In this research, identical steel alloy (12L14) hollow cylinder samples are subjected to predetermined amounts of plastic axial and shear strain such that their octahedral shear strain (an invariant) are identical for comparison. Measurements were made at the residual stress measuring facility
A measurement of G with a cryogenic torsion pendulum.
Newman, Riley; Bantel, Michael; Berg, Eric; Cross, William
2014-10-13
A measurement of Newton's gravitational constant G has been made with a cryogenic torsion pendulum operating below 4 K in a dynamic mode in which G is determined from the change in torsional period when a field source mass is moved between two orientations. The source mass was a pair of copper rings that produced an extremely uniform gravitational field gradient, whereas the pendulum was a thin fused silica plate, a combination that minimized the measurement's sensitivity to error in pendulum placement. The measurement was made using an as-drawn CuBe torsion fibre, a heat-treated CuBe fibre, and an as-drawn Al5056 fibre. The pendulum operated with a set of different large torsional amplitudes. The three fibres yielded high Q-values: 82?000, 120?000 and 164?000, minimizing experimental bias from fibre anelasticity. G-values found with the three fibres are, respectively: {6.67435(10),6.67408(15),6.67455(13)}×10(-11)?m(3)?kg(-1)?s(-2), with corresponding uncertainties 14, 22 and 20?ppm. Relative to the CODATA2010 G-value, these are higher by 77, 37 and 107?ppm, respectively. The unweighted average of the three G-values, with the unweighted average of their uncertainties, is 6.67433(13)×10(-11)?m(3)?kg(-1)?s(-2) (19?ppm). PMID:25202000
Phonons with orbital angular momentum
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
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.
NASA Technical Reports Server (NTRS)
Hinkley, J. A.; Obrien, T. K.
1992-01-01
Sixteen and thirty-two ply quasi-isotropic laminates fabricated from AS4/3501-6 were subjected to pure tension, simultaneous tension and torsion, and torsion fatigue. Layups tested were (45 sub n/-45 sub n/O sub n/90 sub n) sub s, with n = 2 or 4. A torsion damage pattern consisting of a localized matrix crack and delaminations was characterized, and the measured torsional stiffnesses were compared with calculated values. It was found that a combination of tension and torsion led to failure at smaller loads than either type of deformation acting alone. Further work is required to determine the exact form of the failure criterion.
NASA Technical Reports Server (NTRS)
Hartman, Edwin P.; Biermann, David
1938-01-01
The torsional deflection of the blades of three full-scale duralumin propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10th of a degree was found at V/nD of 0.3 and a smaller deflection at higher values of V/nD for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading transit method used in the previous tests.
NASA Technical Reports Server (NTRS)
Hartman, Edwin P; Biermann, David
1938-01-01
The torsional deflection of the blades of three full-scale aluminum-alloy propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10 degree was found at a v/nd of 0.3 and a smaller deflection at higher values of v/nd for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading-transit method used in the previous test.
NASA Astrophysics Data System (ADS)
Dai, Y. J.; Huan, Y.; Gao, M.; Dong, J.; Liu, W.; Pan, M. X.; Wang, W. H.; Bi, Z. L.
2015-02-01
A high-resolution micro-torsion tester is developed based on electromagnetism, and the shear modulus of metallic glass fiber (Pd40Cu30Ni10P20) is measured using this tester. The torque is measured by a coil-magnet component and the rotation angle is measured by an inductive angular transducer. The calibration results show that the torque capacity of this tester is 1.1? × ?10?3?N m with resolution of 3? × ?10?8?N m and the rotation angle capacity is 90° with a resolution of 0.01°. A set of metallic glass fibers, with diameter of about 90?µm, are tested using this tester. The average shear modulus is obtained as 20.2?GPa (±6%).
NASA Astrophysics Data System (ADS)
Atwater, S.; Aleksandrova, K.; Werner, V.; von Brentano, P.; Fitzler, A.; Fransen, C.; Linnemann, A.; Terry, J. R.; Fetea, M. S.
2007-10-01
Gamma-gamma coincidences from ^96Mo were detected by the OSIRIS cube spectrometer at the University of Cologne's FN Tandem Accelerator, to identify low-lying M1 transitions between 2+ states using angular correlations. Preliminary analysis of the low energy 2+ to 2+ cascades will be presented. This work was supported by NSF 0555665, Jeffress Fund J-809, and USDOE DE-FG02-91ER-40609 grants.
Achromatic orbital angular momentum generator
NASA Astrophysics Data System (ADS)
Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W.
2014-12-01
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of two glued hollow axicons, is used to introduce a nonuniform rotation of polarization into a linearly polarized input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarization, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of 95% for these three different wavelengths is observed. This device may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed.
Piezoelectric ceramic assembly tubes for torsional actuators
NASA Astrophysics Data System (ADS)
Kim, Chulho; Glazounov, Alexandre E.; Flippen, Luther D.; Pattnaik, Amitav; Zhang, Qi Ming; Lewis, David, III
1999-07-01
The efforts described here are intended to provide a basis for the utilization of novel piezoelectric actuators in smart materials and structures. The actuator design developed in this study is a segmented, piezoelectric tube, with the individual segments driven in a d15 shear mode. The PZT-5A tubes were cut longitudinally in to an even number of equal slender segments. These slender segments were poled individually along their length using a continuous poling technique developed at NRL. The polarization of the poled segments alternates in direction between adjacent segments. The segments were reassembled with a conductive epoxy so that it serves as both joint and electrode. The assembled actuator tubes were evaluated by applying electric field normal to the polarization direction of the segments, demonstrating proof of concept. These solid state prototype devices were driven to precise angular displacement and torque output. Reliability test, including both fatigue and mechanical loading of the device, were conducted. In conjunction with this effort, numerical computation analyses were performed with respect to structural integrity versus segment joint thickness, and the relative effect of cylindrical versus polygonal configurations. These studies facilitated the successful production of prototypes. Projected actuator outputs based on electromechanical test results are also discussed in terms of requirements for noise and vibration control of helicopter rotor blades.
Texture Development During Equal Channel Angular Forging of BCC Metals
Agnew, S.R.
1999-08-08
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.
Li-Hong Xu; J. Fisher; R. M. Lees; H. Y. Shi; J. T. Hougen; J. C. Pearson; B. J. Drouin; G. A. Blake; R. Braakman
2008-01-01
Stimulated by recent THz measurements of the methanol spectrum in one of our laboratories, undertaken in support of NASA programs related to the Herschel Space Observatory (HSO) and the Atacama Large Millimeter Array (ALMA), we have carried out a global analysis of available microwave and high-resolution infrared data for the first three torsional states (?t=0, 1, 2), and for J
The angular momentum of the Oort cloud
P Weissman
1991-01-01
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
Spin Angular Momentum Imparted by Gravitational Waves
M Sharif
2007-01-23
Following the demonstration that gravitational waves impart linear momentum, it is argued that if they are polarized they should impart angular momentum to appropriately placed 'test rods' in their path. A general formula for this angular momentum is obtained and used to provide expressions for the angular momentum imparted by plane and cylindrical gravitational waves.
Angular Momentum Decomposition for an Electron
Burkardt, Matthias; BC, Hikmat
2009-01-01
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.
Angular momentum decomposition for an electron
Burkardt, Matthias; Hikmat, BC [Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003-0001 (United States)
2009-04-01
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.
Photoionization with Orbital Angular Momentum Beams
A. Picón; J. Mompart; J. R. Vázquez de Aldana; L. Plaja; G. F. Calvo; L. Roso
2010-01-01
Intense laser ionization expands Einstein's photoelectric effect rules giving a wealth of phenomena widely studied over the last decades. In all cases, so far, photons were assumed to carry one unit of angular momentum. However it is now clear that photons can possess extra angular momentum, the orbital angular momentum (OAM), related to their spatial profile. We show a complete
What is Orbital Angular Matthias Burkardt
What is Orbital Angular Momentum? Matthias Burkardt burkardt@nmsu.edu New Mexico State University What is Orbital Angular Momentum? Â p.1/22 #12;Motivation polarized DIS: only 30% of the proton spin = 1 quest for the remaining 70% quark orbital angular momentum (OAM) gluon spin gluon OAM How
Photon Orbital Angular Momentum in Astrophysics
Martin Harwit
2003-01-01
Observations of the orbital angular momentum of photons --- a property of electromagnetic radiation that has come to the fore in recent years --- have apparently never been attempted in astronomy. By now it is known from laboratory studies that, in addition to carrying spin angular momentum, individual photons can carry N >> 100 units of orbital angular momentum h\\/2pi
Probes of Orbital Angular Matthias Burkardt
Probes of Orbital Angular Momentum Matthias Burkardt burkardt@nmsu.edu New Mexico State University Las Cruces, NM, 88003, U.S.A. Probes of Orbital Angular Momentum Â p.1/40 #12;Motivation Decomposition carry the nucleon spin? Probes of Orbital Angular Momentum Â p.2/40 #12;Outline The anomalous magnetic
Angular momentum and torque described with the complex octonion
Weng, Zi-Hua
2015-01-01
The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of two fields can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the...
On quantum gauge theories in two dimensions
Edward Witten
1991-01-01
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
Form factors and non-local multiplicative anomaly for fermions with background torsion
NASA Astrophysics Data System (ADS)
de Berredo-Peixoto, G.; Espinosa Maicá, A.
2014-06-01
We analyse the multiplicative anomaly (MA) in the case of quantized massive fermions coupled to a background torsion. The one-loop effective action (EA) can be expressed in terms of the logarithm of the determinant of the appropriate first-order differential operator acting in the spinors space. Simple algebraic manipulations on determinants must be used in order to apply properly the Schwinger-DeWitt technique, or even the covariant perturbation theory (Barvinsky and Vilkovisky, 1990), which is used in the present work. By this method, we calculate the finite non-local quantum corrections, and analyse explicitly the breakdown of those algebraic manipulations on determinants, called by MA. This feature comes from the finite non-local EA, but does not affect the results in the UV limit, in particular, the beta-functions. Similar results were also obtained in previous papers but for different external fields (QED and scalar field).
Generalized Timoshenko Theory of the Variational Asymptotic Beam
Yu, Wenbin
theory with 11 as the extensional strain, 1 as the torsion, as the bending curvatures around x 11 1 2 3 T , column matrix of classical strain measures as defined in Timoshenko beam theory with 11 of transverse strain measures (212 and 213) defined in Timoshenko beam theory R the position vector
Angular Synchronization by Eigenvectors and Semidefinite Programming
Singer, A.
2010-01-01
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
Variable Distance Angular Symbology Reader
NASA Technical Reports Server (NTRS)
Schramm, Harry F., Jr. (Inventor); Corder, Eric L. (Inventor)
2006-01-01
A variable distance angular symbology, reader utilizes at least one light source to direct light through a beam splitter and onto a target. A target may be angled relative to the impinging light beam up to and maybe even greater than 45deg. A reflected beam from the target passes through the beam splitter and is preferably directed 90deg relative to the light source through a telecentric lens to a scanner which records an image of the target such as a direct part marking code.
Vaughn, Mark R. (Albuquerque, NM); Robinett, III, Rush D. (Tijeras, NM); Phelan, John R. (Albuquerque, NM); Van Zuiden, Don M. (Albuquerque, NM)
1997-01-21
A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.
A comparison of four in vivo methods of measuring tibial torsion
MILNER, C. E.; SOAMES, R. W.
1998-01-01
Tibial torsion, twisting of the tibia about its longitudinal axis, varies during development and early childhood. Knowledge of the normal range of tibial torsion at various ages and its accurate clinical measurement is important in the assessment of the extent of a torsional deformity. To evaluate tibial torsion a reliable technique for its measurement in vivo is therefore required. The aim of this study was to determine which of 4 existing in vivo methods of measuring tibial torsion was the most accurate and had the highest repeatability, by comparing them with direct measurement of the tibia. A wide range of mean values for tibial torsion was observed, using the various techniques, with none of the indirect techniques employed having a strong correlation with direct measurement of tibial torsion. The repeatability of the indirect techniques was observed to be low both in cadavers (n=4) and the living (n=3). Since none of the in vivo techniques appear to measure true tibial torsion or be of a reasonable repeatability, alternative easy to use and inexpensive methods need to be developed. Accurate clinical measurement of tibial torsion is important in the assessment of the extent of a torsional deformity. It is recommended that data gained using the methods reviewed here are interpreted with caution. PMID:9758144
NASA Astrophysics Data System (ADS)
von den Hoff, P.; Znakovskaya, I.; Zherebtsov, S.; Kling, M. F.; de Vivie-Riedle, R.
2010-03-01
We outline the details of our new method to calculate angular-dependent ionization probabilities based on electronic structure theory for diatomic and larger systems. To demonstrate its abilities, we compare our calculations to measured ionization probabilities of the four molecules D2, N2, O2 and CO in the strong-field regime. The calculated angular distributions yield better agreement with the experimental data than those obtained from the widely used MO-ADK theory. For CO the measured angular distributions of ionic fragments indicate contributions to the ionization from both the HOMO and the HOMO-1 orbital, an effect that is addressed by the theory.
NASA Astrophysics Data System (ADS)
Li, Si-Jia; Gao, Jun; Cao, Xiang-Yu; Zheng, Gui
2015-04-01
A novel and thin stereometamaterial composed of an orthogonal double-split-ring microstructure, a plane ground with five hemispherical metric surfaces and a coating substrate is proposed and demonstrated to obtain a polarization-insensitive and broadband angular absorption. The mechanism of absorbing electromagnetic wave has been interpreted and investigated by the anti-reflection theory and the surface loss density for the oblique incidence. The absorbing characters have been improved by the five hemispherical metric grounds. The insensitive polarization is proved by the surface current distributions and the angular absorption. It exhibits a broadband angular absorbing range from 6.05 to 13 GHz with the absorption larger than 80 % at the incident angles of 45° theoretically and experimentally. For verification, a stereometamaterial sample with 576 cells is fabricated and measured. Consistent numerical and experimental results have both validated the broadband angular absorption. The design yields advantages of polarized insensitivity, broadband angular absorption and thin microstructure.
MAGNETOSEISMOLOGY: EIGENMODES OF TORSIONAL ALFVEN WAVES IN STRATIFIED 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
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.
The Torsion of Members Having Sections Common in Aircraft Construction
NASA Technical Reports Server (NTRS)
Trayer, George W; March, H W
1930-01-01
Within recent years a great variety of approximate torsion formulas and drafting-room processes have been advocated. In some of these, especially where mathematical considerations are involved, the results are extremely complex and are not generally intelligible to engineers. The principal object of this investigation was to determine by experiment and theoretical investigation how accurate the more common of these formulas are and on what assumptions they are founded and, if none of the proposed methods proved to be reasonable accurate in practice, to produce simple, practical formulas from reasonably correct assumptions, backed by experiment. A second object was to collect in readily accessible form the most useful of known results for the more common sections. Formulas for all the important solid sections that have yielded to mathematical treatment are listed. Then follows a discussion of the torsion of tubular rods with formulas both rigorous and approximate.
Role of short-range electrostatics in torsional potentials.
Darley, Michael G; Popelier, Paul L A
2008-12-18
A force field needs to decide if it should contain a torsional potential or not. A helpful guide to this decision should come from a quantum mechanical energy partitioning. Here we analyze the energy profiles of eight simple molecules (ethane, hydrogen peroxide, hydrazine, methanol, acetaldehyde, formamide, acetamide and N-methylacetamide) subject to rotation around a torsion angle. Coulomb interaction energies between all atom pairs in a molecule are monitored during the rotation. Atoms are defined as finite electron density fragments by quantum chemical topology, a method that enables well-defined short-range interactions (1-2, 1-3 and 1-4). Energy profiles of Coulomb interaction energies mostly counteract the ab initio energy profiles. This and future work strives to settle ambiguities in current force field design. PMID:18800774
Omental torsion in a captive polar bear (Ursus maritimus).
Mendez-Angulo, Jose L; Funes, Francisco J; Trent, Ava M; Willette, Michelle; Woodhouse, Kerry; Renier, Anna C
2014-03-01
This is the first case report of an omental torsion in a polar bear (Ursus maritimus). A captive, 23-yr-old, 250-kg, intact female polar bear presented to the University of Minnesota Veterinary Medical Center with a 2-day history of lethargy, depression, and vomiting. Abdominal ultrasound identified large amounts of hyperechoic free peritoneal fluid. Ultrasound-guided abdominocentesis was performed and yielded thick serosanguinous fluid compatible with a hemoabdomen. An exploratory laparotomy revealed a large amount of malodorous, serosanguineous fluid and multiple necrotic blood clots associated with a torsion of the greater omentum and rupture of a branch of the omental artery. A partial omentectomy was performed to remove the necrotic tissue and the abdomen was copiously lavaged. The polar bear recovered successfully and is reported to be clinically well 6 mo later. This condition should be considered as a differential in bears with clinical signs of intestinal obstruction and hemoabdomen. PMID:24712179
MR evaluation of femoral neck version and tibial torsion.
Koenig, James Karl; Pring, Maya E; Dwek, Jerry R
2012-01-01
Abnormalities of femoral neck version have been associated with a number of hip abnormalities in children, including slipped capital femoral epiphysis, proximal femoral focal deficiency, coxa vara, a deep acetabulum and, rarely, developmental dysplasia of the hip. Orthopedic surgeons also are interested in quantifying the femoral neck anteversion or retroversion in children especially to plan derotational osteotomies. Historically, the angle of femoral version and tibial torsion has been measured with the use of radiography and later by CT. Both methods carry with them the risks associated with ionizing radiation. Techniques that utilize MR are used less often because of the associated lengthy imaging times. This article describes a technique using MRI to determine femoral neck version and tibial torsion with total scan times of approximately 10 min. PMID:21842328
Why has spacetime torsion such negligible effect on the Universe?
NASA Astrophysics Data System (ADS)
Das, Ashmita; Mukhopadhyaya, Biswarup; SenGupta, Soumitra
2014-11-01
We attempt an answer to the question as to why the evolution of a four-dimensional universe is governed by spacetime curvature but not torsion. An answer is found if there is an additional compact spacelike dimension with a warped geometry, with torsion caused by a Kalb-Ramond (KR) antisymmetric tensor field in the bulk. Starting from a Randall-Sundrum type of warped extra dimension, and including the inevitable backreaction ensuing from the radius stabilization mechanism, we show that there is always an extra exponential suppression of the KR field on the four-dimensional projection that constitutes our visible Universe. The backreaction is found to facilitate the process of such suppression.
Structural plasticity of single chromatin fibers revealed by torsional manipulation
Aurelien Bancaud; Natalia Conde e Silva; Maria Barbi; Gaudeline Wagner; Jean-Francois Allemand; Julien Mozziconacci; Christophe Lavelle; Vincent Croquette; Jean-Marc Victor; Ariel Prunell; Jean-Louis Viovy
2007-07-13
Magnetic tweezers are used to study the mechanical response under torsion of single nucleosome arrays reconstituted on tandem repeats of 5S positioning sequences. Regular arrays are extremely resilient and can reversibly accommodate a large amount of supercoiling without much change in length. This behavior is quantitatively described by a molecular model of the chromatin 3-D architecture. In this model, we assume the existence of a dynamic equilibrium between three conformations of the nucleosome, which are determined by the crossing status of the entry/exit DNAs (positive, null or negative). Torsional strain, in displacing that equilibrium, extensively reorganizes the fiber architecture. The model explains a number of long-standing topological questions regarding DNA in chromatin, and may provide the ground to better understand the dynamic binding of most chromatin-associated proteins.
Quartz crystal microbalance based on torsional piezoelectric resonators
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
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.
Transmembrane helix uniformity examined by spectral mapping of torsion angles.
Page, Richard C; Kim, Sanguk; Cross, Timothy A
2008-05-01
The environment and unique balance of molecular forces within lipid bilayers has a profound impact upon the structure, dynamics, and function of membrane proteins. We describe the biophysical foundations for the remarkable uniformity of many transmembrane helices that result from the molecular interactions within lipid bilayers. In fact, the characteristic uniformity of transmembrane helices leads to unique spectroscopic opportunities allowing for phi,psi torsion angles to be mapped directly onto solid state nuclear magnetic resonance (NMR) PISEMA spectra. Results from spectral simulations, the solid state NMR-derived structure of the influenza A M2 proton channel transmembrane domain, and high-resolution crystal structures of 27 integral membrane proteins demonstrate that transmembrane helices tend to be more uniform than previously thought. The results are discussed through the definition of a preferred range of backbone varphi,psi torsion angles for transmembrane alpha helices and are presented with respect to improving biophysical characterizations of integral membrane proteins. PMID:18462683
Torsional conjugate eye movements induced by pupillary light stimulation
Bender, Morris B.; Corin, Morton
1974-01-01
A patient with a brain-stem mass and some evidence of brain-stem dysfunction showed torsional conjugate eye movements after eyelid opening in an illuminated environment, also on pupillary light stimulation. The response appeared after a latency period of 1-2 s, and occurred on stimulation of either the right or left eye. The ocular torsion was always bilateral and often conjugate. The phenomenon, however, varied in the extent, the direction and the symmetry of movement in the two eyes. It is probable that the phenomenon described was due to a disorder in the central, brain-stem mechanism, but the exact anatomical site and physiology are at present imprecise. Images
Dark energy fifth forces in torsion pendulum experiments
Amol Upadhye
2012-10-22
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 Eot-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 Eot-Wash experiment, and show that this experiment will exclude a wide range of quantum-stable models.
Torsion, parity-odd response, and anomalies in topological states
NASA Astrophysics Data System (ADS)
Parrikar, Onkar; Hughes, Taylor L.; Leigh, Robert G.
2014-11-01
We study the response of a class of topological systems to electromagnetic and gravitational sources, including torsion and curvature. By using the technology of anomaly polynomials, we derive the parity-odd response of a massive Dirac fermion in d =2 +1 and d =4 +1 , which provides a simple model for a topological insulator. We discuss the covariant anomalies of the corresponding edge states, from a Callan-Harvey anomaly inflow, as well as a Hamiltonian spectral flow point of view. We also discuss the applicability of our results to other systems such as Weyl semimetals. Finally, using dimensional reduction from d =4 +1 , we derive the effective action for a d =3 +1 time-reversal invariant topological insulator in the presence of torsion and curvature, and discuss its various physical consequences.
Angular momentum generation from holographic Chern-Simons models
NASA Astrophysics Data System (ADS)
Wu, Chaolun
2014-12-01
We study parity-violating effects, particularly the generation of angular momentum density and its relation to the parity-odd and dissipationless transport coefficient Hall viscosity, in strongly-coupled quantum fluid systems in 2+1 dimensions using holographic method. We employ a class of 3+1-dimensional holographic models of Einstein-Maxwell system with gauge and gravitational Chern-Simons terms coupled to a dynamical scalar field. The scalar can condensate and break the parity spontaneously. We find that when the scalar condensates, a non-vanishing angular momentum density and an associated edge current are generated, and they receive contributions from both gauge and gravitational Chern-Simons terms. The angular momentum density does not satisfy a membrane paradigm form because the vector mode fluctuations from which it is calculated are effectively massive. On the other hand, the emergence of Hall viscosity is a consequence of the gravitational Chern-Simons term alone and it has membrane paradigm form. We present both general analytic results and numeric results which take back-reactions into account. The ratio between Hall viscosity and angular momentum density resulting from the gravitational Chern-Simons term has in general a deviation from the universal 1/2 value obtained from field theory and condensed matter physics.