Can Gravity Probe B usefully constrain torsion gravity theories?
NASA Astrophysics Data System (ADS)
Flanagan, Éanna É.; Rosenthal, Eran
2007-06-01
In most theories of gravity involving torsion, the source for torsion is the intrinsic spin of matter. Since the spins of fermions are normally randomly oriented in macroscopic bodies, the amount of torsion generated by macroscopic bodies is normally negligible. However, in a recent paper, Mao et al. (arXiv:gr-qc/0608121) point out that there is a class of theories, including the Hayashi-Shirafuji (1979) theory, in which the angular momentum of macroscopic spinning bodies generates a significant amount of torsion. They further argue that, by the principle of action equals reaction, one would expect the angular momentum of test bodies to couple to a background torsion field, and therefore the precession of the Gravity Probe B gyroscopes should be affected in these theories by the torsion generated by the Earth. We show that in fact the principle of action equals reaction does not apply to these theories, essentially because the torsion is not an independent dynamical degree of freedom. We examine in detail a generalization of the Hayashi-Shirafuji theory suggested by Mao et al. called Einstein-Hayashi-Shirafuji theory. There are a variety of different versions of this theory, depending on the precise form of the coupling to matter chosen for the torsion. We show that, for any coupling to matter that is compatible with the spin transport equation postulated by Mao et al., the theory has either ghosts or an ill-posed initial-value formulation. These theoretical problems can be avoided by specializing the parameters of the theory and in addition choosing the standard minimal coupling to matter of the torsion tensor. This yields a consistent theory, but one in which the action equals reaction principle is violated, and in which the angular momentum of the gyroscopes does not couple to the Earth’s torsion field. Thus, the Einstein-Hayashi-Shirafuji theory does not predict a detectable torsion signal for Gravity Probe B. There may be other torsion theories which do.
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.
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
NASA Astrophysics Data System (ADS)
Bai, Y. Z.; Fang, L.; Luo, J.; Yin, H.; Zhou, Z. B.
2015-09-01
The torsion pendulum is widely employed in gravitational experiments as a weak force sensitive instrument, and its resolution is limited by the thermal noise of the pendulum and detection noise of angular deflection. Different kinds of angular deflection transducers are proposed and realized to improve its resolution. A torsion pendulum combined with an electrostatic spring is proposed here in order to improve the measurement sensitivity of angular deflection. Noise analysis and demonstration experiments show that the electrostatic torsion pendulum can relax the requirement of angular deflection detection, which is useful for gravitational experiments with much higher precision requirements.
Is torsion needed in theory of gravity?
Janusz Garecki
2001-03-09
It is known that General Relativity ({\\bf GR}) uses Lorentzian Manifold $(M_4;g)$ as a geometrical model of the physical space-time. $M_4$ means here a four-dimensional differentiable manifold endowed with Lorentzian metric $g$. The metric $g$ satisfies Einstein equations. Since the 1970s many authors have tried to generalize this geometrical model of the physical space-time by introducing torsion and even more general metric-affine geometry. In this paper we discuss status of torsion in the theory of gravity. At first, we emphasize that up to now we have no experimental evidence for the existence of torsion in Nature. Contrary, the all experiments performed in weak gravitational field (Solar System) or in strong regime (binary pulsars) and tests of the Einstein Equivalence Principle ({\\bf EEP}) confirmed {\\bf GR} and Lorentzian manifold $(M_4;g)$ as correct geometrical model of the physical space-time. Then, we give theoretical arguments against introducing of torsion into geometrical model of the physical space-time. At last, we conclude that the general-relativistic model of the physical space-time is sufficient and it seems to be the most satisfactory.
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.
NASA Astrophysics Data System (ADS)
Alexeyev, C. N.; Borshak, E. V.; Volyar, A. V.; Yavorsky, M. A.
2009-09-01
In this paper we consider weakly guiding twisted optical fibres with torsional mechanical stress. We establish the structure of the modes and the propagation constants of such fibres by accounting for the coupling between modes with different azimuthal numbers. It is shown that the principle of the mode formation is based on a sort of selection rule, that allows only the coupling between modes with the same value of total angular momentum. It is demonstrated that the modes are optical vortices bearing the well-defined total angular momentum. Using the obtained mode structure, we show that such twisted fibres transform the incident Gaussian-like mode, possessing spin angular momentum, to the field with orbital angular momentum.
M-theory moduli spaces and torsion-free structures
NASA Astrophysics Data System (ADS)
Graña, Mariana; Shahbazi, C. S.
2015-05-01
Motivated by the description of 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.
M-theory moduli spaces and torsion-free structures
Mariana Graña; C. S. Shahbazi
2015-04-05
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.
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.
The torsion cosmology in Kaluza-Klein theory
Songbai Chen; Jiliang Jing
2009-08-16
We have studied the torsion cosmology model in Kaluza-Klein theory. We considered two simple models in which the torsion vectors are $A_{\\mu}=(\\alpha,0,0,0)$ and $A_{\\mu}=a(t)^2(0,\\beta,\\beta,\\beta)$, respectively. For the first model, the accelerating expansion of the Universe can be not explained without dark energy which is similar to that in the standard cosmology. But for the second model, we find that without dark energy the effect of torsion can give rise to the accelerating expansion of the universe and the alleviation of the well-known age problem of the three old objects for appropriated value of the model parameter $\\beta$. These outstanding features of the second torsion cosmology model have been supported by the Type Ia supernovae (SNIa) data.
Is torsion needed in a theory of gravity? A reappraisal
Janusz Garecki
2011-10-19
It is known that General Relativity ({\\bf GR}) uses a Lorentzian Manifold $(M_4;g)$ as a geometrical model of the physical spacetime. The metric $g$ is required to satisfy Einstein's equations. Since the 1960s many authors have tried to generalize this model by introducing torsion. In this paper we discuss the present status of torsion in a theory of gravity. Our conclusion is that the general-relativistic model of the physical spacetime is sufficient for the all physical applications and it seems to be the best satisfactory.
Metric theory of gravity with torsion in an extra dimension
NASA Astrophysics Data System (ADS)
Shankar, Karthik H.; Balaraman, Anand; Wali, Kameshwar C.
2012-07-01
We consider a theory of gravity with a hidden extra dimension and metric-dependent torsion. A set of physically motivated constraints are imposed on the geometry so that the torsion stays confined to the extra dimension and the extra dimension stays hidden at the level of four-dimensional geodesic motion. At the kinematic level, the theory maps onto general relativity, but the dynamical field equations that follow from the action principle deviate markedly from the standard Einstein equations. We study static spherically symmetric vacuum solutions and homogeneous-isotropic cosmological solutions that emerge from the field equations. In both cases, we find solutions of significant physical interest. Most notably, we find positive mass solutions with naked singularity that match the well-known Schwarzschild solution at large distances but lack an event horizon. In the cosmological context, we find an oscillatory scenario, in contrast to the inevitable singular big bang of the standard cosmology.
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
NASA Astrophysics Data System (ADS)
Mao, Yi; Tegmark, Max; Guth, Alan H.; Cabi, Serkan
2007-11-01
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.
Theory of Angular Momentum This chapter is concerned with a systematic treatment of angular momen-
Satija, Indu
153 CHAPTER 3 Theory of Angular Momentum This chapter is concerned with a systematic treatment of angular momen- tum and related topics. The importance of angular momentum in modern physics can hardly spectroscopy; angular-momentum considerations play an important role in scattering and collision problems
Torsion Wave Solutions in Yang-Mielke Theory of Gravity
Pasic, Vedad
2015-01-01
The approach of metric-affine gravity initially distinguishes it from Einstein's general relativity. Using an independent affine connection produces a theory with 10+64 unknowns. We write down the Yang-Mills action for the affine connection and produce the Yang-Mills equation and the so called complementary Yang-Mills equation by independently varying with respect to the connection and the metric respectively. We call this theory the Yang-Mielke theory of gravity. We construct explicit spacetimes with pp-metric and purely axial torsion and show that they represent a solution of Yang-Mills theory. Finally we compare these spacetimes to existing solutions of metric-affine gravity and present future research possibilities.
Hyperscaling violating black holes in scalar-torsion theories
Kofinas, Georgios
2015-01-01
We study a gravity theory where a scalar field with potential, beyond its minimal coupling, is also coupled through a non-minimal derivative coupling with the torsion scalar which is the teleparallel equivalent of Einstein gravity. This theory provides second order equations of motion and we find large-distance non-perturbative static spherically symmetric four-dimensional solutions. Among them a general class of black hole solutions is found for some range of the parameters/integration constants with asymptotics of the form of hyperscaling violating Lifshitz spacetime with spherical horizon topology. Although the scalar field diverges at the horizon, its energy density and pressures are finite there. From the astrophysical point of view, this solution provides extra deflection of light compared to the Newtonian deflection.
String Theory backgrounds with Torsion in the presence of Fermions and implications for Leptogenesis
NASA Astrophysics Data System (ADS)
Sarkar, Sarben
2015-07-01
Fermions couple in a universal way to the the Kalb-Ramond field which occurs in the gravitational multiplet of string theory. The Kalb-Ramond field is a source of torsion and can provide a background for fermion dynamics. Solutions for this background in terms of the string effective action are discussed and are fixed ’’points” of conformal invariance conditions. Nonperturbative fixed points for the torsion in the absence of matter are shown to be compatible with perturbative fixed points in the presence of matter. Fermion coupling to such backgrounds can lead to both CP and CPT violation. Hence torsion can give a new mechanism for leptogenesis. The presence of anomalies in the Bianchi identity for the torsion, in the presence of matter, is crucial in giving a background solution for the torsion and dilaton with an acceptable cosmology.
Luca Susmel; David Taylor
2006-01-01
In the present study the use of the theory of critical distances (TCD) was extended to notched components subjected to torsional fatigue loading. Initially, using some basic solid-mechanics arguments, it was demonstrated that the reference stress to use for assessing notched components under torsional fatigue loading is the fully-reversed plain torsional fatigue limit. Secondly, some data sets taken from the
The most general ELKOs in torsional f(R)-theories
Fabbri, Luca
2010-01-01
We study f(R)-gravity with torsion in presence of the most general ELKO matter. We check the consistency of the conservation laws with the matter field equations; we discuss some mathematical features of the field equations.
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 want to study angular momentum? 2. We need to study the properties of chemical systems, how is angular the problem.) (b) the angular momentum is conserved in classical mechan- ics and it turns out
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
Scalar-torsion mode in a cosmological model of the Poincaré gauge theory of gravity
Tseng, Huan-Hsin; Lee, Chung-Chi; Geng, Chao-Qiang E-mail: g9522545@oz.nthu.edu.tw
2012-11-01
We investigate the scalar-torsion mode in a cosmological model of the Poincaré gauge theory of gravity. We treat the geometric effect of torsion as an effective quantity, which behaves like dark energy, and study the effective equation of state (EoS) of the model. We concentrate on two cases with the constant curvature solution and positive kinetic energy, respectively. In the former, we find that the torsion EoS has different values in the various stages of the universe. In particular, it behaves like the radiation (matter) EoS of w{sub r} = 1/3 (w{sub m} = 0) in the radiation (matter) dominant epoch, while in the late time the torsion density is supportive for the accelerating universe. In the latter, our numerical analysis shows that in general the EoS has an asymptotic behavior in the high redshift regime, while it could cross the phantom divide line in the low redshift regime.
Torsion and Nonmetricity in Scalar-Tensor Theories of Gravity
Jean-paul Berthias; Bahman Shahid-Saless
1993-03-09
We show that the gravitational field equations derived from an action composed of i) an arbitrary function of the scalar curvature and other scalar fields plus ii) connection-independent kinetic and source terms, are identical whether one chooses nonmetricity to vanish and have non-zero torsion or vice versa.
Silverman, Joseph H.
Definitions Examples from formal groups Galois theory Continuous characters Computation Torsion;Definitions Examples from formal groups Galois theory Continuous characters Computation Nottingham itself;Definitions Examples from formal groups Galois theory Continuous characters Computation Results p
Exaptation and torsion: toward a theory of natural information processing.
Kirby, K G
1998-04-01
Several conundrums are provoked by attempts to provide algorithmic descriptions of natural phenomena. A characteristic feature of natural computation is a breakdown in the formal simulation relation. This is called hermeneutic torsion, and is formally the failure to commute of a diagram describing homomorphisms between dynamical systems. This torsion is a source of computational power. For example, it is deeply involved with phenomena such as exaptation, wherein an existing structure is recruited for a novel function. Exaptation occurs continually at the macromolecular level and is fundamentally nonalgorithmic; our system-theoretic models of computation deal with structural descriptions for which a functional semantics must be assigned in advance, and a natural system continually 'diagonalizes out' of this semantics. This perspective clarifies the nature of computing power and encourages consideration of a new kind of transcomputational complexity. PMID:9648677
Self-gravitating spherically symmetric solutions in scalar-torsion theories
NASA Astrophysics Data System (ADS)
Kofinas, Georgios; Papantonopoulos, Eleftherios; Saridakis, Emmanuel N.
2015-05-01
We study spherically symmetric solutions in scalar-torsion gravity theories in which a scalar field is coupled to torsion with a derivative coupling. We obtain the general field equations from which we extract a decoupled master equation, the solution of which leads to the specification of all other unknown functions. We first obtain an exact solution which represents a new wormholelike solution dressed with a regular scalar field. Then, we find large distance linearized spherically symmetric solutions in which the space asymptotically is anti-de Sitter.
Torsional oscillations of neutron stars in scalar-tensor theory of gravity
NASA Astrophysics Data System (ADS)
Silva, Hector O.; Sotani, Hajime; Berti, Emanuele; Horbatsch, Michael
2014-12-01
We study torsional oscillations of neutron stars in the scalar-tensor theory of gravity using the relativistic Cowling approximation. We compute unperturbed neutron star models adopting realistic equations of state for the neutron star's core and crust. For scalar-tensor theories that allow for spontaneous scalarization, the crust thickness can be significantly smaller than in general relativity. We derive the perturbation equation describing torsional oscillations in scalar-tensor theory, and we solve the corresponding eigenvalue problem to find the oscillation frequencies. The fundamental mode (overtone) frequencies become smaller (larger) than in general relativity for scalarized stellar models. Torsional oscillation frequencies may yield information on the crust microphysics if microphysics effects are not degenerate with strong-gravity effects, such as those due to scalarization. To address this issue, we consider two different models for the equation of state of the crust and we look at the effects of electron screening. The effect of scalarization on torsional oscillation frequencies turns out to be smaller than uncertainties in the microphysics for all spontaneous scalarization models allowed by binary pulsar observations. Our study shows that the observation of quasiperiodic oscillations following giant flares can be used to constrain the microphysics of neutron star crusts, whether spontaneous scalarization occurs or not.
NASA Astrophysics Data System (ADS)
Hehl, Friedrich W.; McCrea, J. Dermott
1986-03-01
Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if, via the field equations, the conservation laws for the material currents are reduced to the contracted Bianchi identities. We first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, we determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model. The Poincaré gauge theory of gravity, like gauge theories of internal groups, has no automatic conservation in the sense defined above. This does not lead to any difficulties in principle. Analogies to 3-dimensional continuum mechanics are stressed throughout the article.
Dangerous Angular KK/Glueball Relics in String Theory Cosmology
J. F. Dufaux; L. Kofman; M. Peloso
2008-07-07
The presence of Kaluza-Klein 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 symmetries, 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 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 non-relativistic 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.
Bases for spin systems and qudits from angular momentum theory
Maurice R. Kibler
2008-10-24
Spin bases of relevance for quantum systems with cyclic symmetry as well as for quantum information and quantum computation are constructed from the theory of angular momentum. This approach is connected to the use of generalized Pauli matrices (in dimension d) arising from a polar decomposition of the group SU(2). Numerous examples are given for d=2, 3 and 4.
Chern-Simons Modified Gravity as a Torsion Theory and its Interaction with Fermions
Alexander, Stephon
2008-01-01
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 interac...
Chern-Simons Modified Gravity as a Torsion Theory and its Interaction with Fermions
Stephon Alexander; Nicolas Yunes
2008-04-10
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 interactions, 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.
Chern-Simons modified gravity as a torsion theory and its interaction with fermions
Alexander, Stephon; Yunes, Nicolas [Institute for Gravity and the Cosmos, Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)
2008-06-15
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.
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.
Angular momentum and light-front scattering theory
Fuda, M.G. (Department of Physics and Astronomy, State University of New York at Buffalo, Buffalo, New York (USA))
1991-09-15
The role of the Leutwyler and Stern spin operator in the angular momentum analysis of light-front scattering theory is analyzed. The equations of formal scattering theory are transformed to the {xi} picture using the unitary operator {ital C}({xi}) recently developed by the author. This operator depends on the two angles which determine the direction of the three-vector part of a lightlike four-vector {xi}. It is shown that an invariant version of light-front perturbation theory developed earlier by the author is related to the standard theory by the unitary operator {ital C}({xi}). It is also shown how to carry out a partial-wave analysis of the Lippmann-Schwinger-like equations obtained by summing a subset of the diagrams of this invariant form of light-front perturbation theory. The analysis presented here makes clear that the {xi} picture overcomes many of the difficulties due to the interaction dependence of light-front angular momentum operators, in particular the difficulties arising from the fact that the individual diagrams of light-front pertubation theory are not rotationally invariant.
Spontaneous generation of angular momentum in holographic theories.
Liu, Hong; Ooguri, Hirosi; Stoica, Bogdan; Yunes, Nicolás
2013-05-24
The Schwarzschild black two-brane in four-dimensional anti-de Sitter space is dual to a finite temperature state in three-dimensional conformal field theory. We show that the solution acquires a nonzero angular momentum density when a gravitational Chern-Simons coupling is turned on in the bulk, even though the solution is not modified. A similar phenomenon is found for the Reissner-Nordström black two-brane with axionic coupling to the gauge field. We discuss interpretation of this phenomenon from the point of view of the boundary three-dimensional conformal field theory. PMID:23745857
Standard Electroweak Interactions in Gravitational Theory with Chameleon Field and Torsion
Ivanov, A N
2015-01-01
We propose a version of a gravitational theory with the torsion field, induced by the chameleon field. Following Hojman et al. Phys. Rev. D17, 3141 (1976) the results, obtained in Phys. Rev. D90, 045040 (2014), are generalised by extending the Einstein gravity to the Einstein-Cartan gravity with the torsion field as a gradient of the chameleon field through a modification of local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant beta_(gamma) is equal to the chameleon-matter coupling constant beta, i.e. beta_(gamma) = beta, the experimental constraints on beta, obtained in terrestrial laboratories by T. Jenke et al. (Phys. Rev. Lett. 112, 115105 (2014)) and by H. Lemmel et al. (Phys. Lett. B743, 310 (2015)), can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage e...
Standard Electroweak Interactions in Gravitational Theory with Chameleon Field and Torsion
A. N. Ivanov; M. Wellenzohn
2015-04-22
We propose a version of a gravitational theory with the torsion field, induced by the chameleon field. Following Hojman et al. Phys. Rev. D17, 3141 (1976) the results, obtained in Phys. Rev. D90, 045040 (2014), are generalised by extending the Einstein gravity to the Einstein-Cartan gravity with the torsion field as a gradient of the chameleon field through a modification of local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant beta_(gamma) is equal to the chameleon-matter coupling constant beta, i.e. beta_(gamma) = beta, the experimental constraints on beta, obtained in terrestrial laboratories by T. Jenke et al. (Phys. Rev. Lett. 112, 115105 (2014)) and by H. Lemmel et al. (Phys. Lett. B743, 310 (2015)), can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage et al. (Phys. Rev. D79, 044028 (2009)), A.-Ch. Davis et al. (Phys. Rev. D80, 064016 (2009), and in references therein, where chameleons induce photons because of direct chameleon-photon transitions in the magnetic fields.
Standard electroweak interactions in gravitational theory with chameleon field and torsion
NASA Astrophysics Data System (ADS)
Ivanov, A. N.; Wellenzohn, M.
2015-04-01
We propose a version of a gravitational theory with a torsion field, induced by the chameleon field. Following Hojman et al. [Phys. Rev. D 17, 3141 (1976)], the results obtained in Phys. Rev. D 90, 045040 (2014) are generalized by extending Einstein gravity to Einstein-Cartan gravity with a torsion field as a gradient of the chameleon field through a modification of the local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant ?? is equal to the chameleon-matter coupling constant ? , i.e., ??=? , the experimental constraints on ? —obtained in terrestrial laboratories by T. Jenke et al. [Phys. Rev. Lett. 112, 115105 (2014)] and by H. Lemmel et al. [Phys. Lett. B 743, 310 (2015)]—can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage et al. [Phys. Rev. D 79, 044028 (2009)], A.-C. Davis et al. [Phys. Rev. D 80, 064016 (2009)], and in references therein, where chameleons induce photons because of direct chameleon-photon transitions in the magnetic fields.
Masson, Eric
2013-05-01
The barriers of torsional isomerization of 13 substituted biphenyls, ranging from 7.4 to 44 kcal mol(-1), were calculated using 9 density functionals (the BP86 and B97D GGAs, the meta-GGA TPSS, hybrids B3LYP, PBE0, ?B97XD, BMK and M06-2X, as well as the double-hybrid B2PLYP), some combined with D and D3 corrections for dispersive interactions, and results were compared with experimental data. As attractive dispersive interactions between substituents had a significant impact on the geometries and stabilities of the ground and transition states of the torsional isomerization pathways, the B3LYP-D, B97-D and TPSS-D3 functionals were identified as the most promising methods, and were used to determine the torsional barriers of 33 other substituted biphenyls with known Gibbs energies of activation (6.0 to 45 kcal mol(-1)). Throughout the 46-member ensemble, results were very accurate relative to experimental values (mean deviation between -0.38 and 0.24 kcal mol(-1)), and narrow distributions of errors were obtained (root-mean-square deviations between 0.14 and 0.16 kcal mol(-1); mean absolute deviations ranging from 0.61 to 0.75 kcal mol(-1)), as long as (1) large triple-? basis sets were used, (2) all conformations were screened at these levels of theory, (3) electronic energies were corrected with zero-point energies and entropic contributions, and (4) solvation effects were taken into account for biphenyl derivatives bearing charged ortho-substituents. With its simple procedures, this study is intended as a benchmark for future determinations of torsional barriers of various biphenyl derivatives. PMID:23493969
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.
A Modified Theory of Gravity with Torsion and Its Applications to Cosmology and Particle Physics
NASA Astrophysics Data System (ADS)
Fabbri, Luca; Vignolo, Stefano
2012-10-01
In this paper we consider the most general least-order derivative theory of gravity in which not only curvature but also torsion is explicitly present in the Lagrangian, and where all independent fields have their own coupling constant: we will apply this theory to the case of ELKO fields, which is the acronym of the German Eigenspinoren des LadungsKonjugationsOperators designating eigenspinors of the charge conjugation operator, and thus they are a Majorana-like special type of spinors; and to the Dirac fields, the most general type of spinors. We shall see that because torsion has a coupling constant that is still undetermined, the ELKO and Dirac field equations are endowed with self-interactions whose coupling constant is undetermined: we discuss different applications according to the value of the coupling constants and the different properties that consequently follow. We highlight that in this approach, the ELKO and Dirac field's self-interactions depend on the coupling constant as a parameter that may even make these non-linearities manifest at subatomic scales.
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 \
Singularity in the Laboratory Frame Angular Distribution Derived in Two-Body Scattering Theory
ERIC Educational Resources Information Center
Dick, Frank; Norbury, John W.
2009-01-01
The laboratory (lab) frame angular distribution derived in two-body scattering theory exhibits a singularity at the maximum lab scattering angle. The singularity appears in the kinematic factor that transforms the centre of momentum (cm) angular distribution to the lab angular distribution. We show that it is caused in the transformation by the…
NASA Astrophysics Data System (ADS)
Lompay, Robert R.; Petrov, Alexander N.
2013-10-01
The present paper continues the work of Lompay and Petrov [J. Math. Phys. 54, 062504 (2013)] where manifestly covariant differential identities and conserved quantities in generally covariant metric-torsion theories of gravity of the most general type have been constructed. Here, we study these theories presented more concretely, setting that their Lagrangians {L} are manifestly generally covariant scalars: algebraic functions of contractions of tensor functions and their covariant derivatives. It is assumed that Lagrangians depend on metric tensor g, curvature tensor R, torsion tensor T and its first {{nabla }}{T} and second {{nabla }}{{nabla }}{T} covariant derivatives, besides, on an arbitrary set of other tensor (matter) fields {\\varphi } and their first {{nabla }}{\\varphi } and second {{nabla }}{{nabla }}{\\varphi } covariant derivatives: {L}= {L}({g},{R}; {T},{{nabla }}{T},{{nabla }}{{nabla }}{T}; {\\varphi },{{nabla }}{\\varphi },{{nabla }}{{nabla }}{\\varphi }). Thus, both the standard minimal coupling with the Riemann-Cartan geometry and non-minimal coupling with the curvature and torsion tensors are considered. The studies and results are as follow: (a) A physical interpretation of the Noether and Klein identities is examined. It was found that they are the basis for constructing equations of balance of energy-momentum tensors of various types (canonical, metrical, and Belinfante symmetrized). The equations of balance are presented. (b) Using the generalized equations of balance, new (generalized) manifestly generally covariant expressions for canonical energy-momentum and spin tensors of the matter fields are constructed. In the cases, when the matter Lagrangian contains both the higher derivatives and non-minimal coupling with curvature and torsion, such generalizations are non-trivial. (c) The Belinfante procedure is generalized for an arbitrary Riemann-Cartan space. (d) A more convenient in applications generalized expression for the canonical superpotential is obtained. (e) A total system of equations for the gravitational fields and matter sources are presented in the form more naturally generalizing the Einstein-Cartan equations with matter. This result, being a one of the more important results itself, is to be also a basis for constructing physically sensible conservation laws and their applications.
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 $\\\
Theory of pure rotational transitions in doubly degenerate torsional states of ethane
NASA Technical Reports Server (NTRS)
Rosenberg, A.; Susskind, J.
1979-01-01
It is shown that pure rotational transitions in doubly degenerate torsional states of C2H6 (with selection rules Delta K = 0, plus or minus 1) are made allowed by Coriolis interaction between torsion and dipole-allowed vibrations. Expressions are presented for integrated intensities from which strengths of lines in the millimeter region can be calculated.
NASA Astrophysics Data System (ADS)
Lompay, Robert R.; Petrov, Alexander N.
2013-06-01
Arbitrary diffeomorphically invariant metric-torsion theories of gravity are considered. It is assumed that Lagrangians of such theories contain derivatives of field variables (tensor densities of arbitrary ranks and weights) up to a second order only. The generalized Klein-Noether methods for constructing manifestly covariant identities and conserved quantities are developed. Manifestly covariant expressions are constructed without including auxiliary structures like a background metric. In the Riemann-Cartan space, the following manifestly generally covariant results are presented: (a) The complete generalized system of differential identities (the Klein-Noether identities) is obtained. (b) The generalized currents of three types depending on an arbitrary vector field displacements are constructed: they are the canonical Noether current, symmetrized Belinfante current, and identically conserved Hilbert-Bergmann current. In particular, it is stated that the symmetrized Belinfante current does not depend on divergences in the Lagrangian. (c) The generalized boundary Klein theorem (third Noether theorem) is proved. (d) The construction of the generalized superpotential is presented in detail, and questions related to its ambiguities are analyzed.
Intrinsic spin requires gravity with torsion and curvature
Nikodem Poplawski
2013-03-29
We show that the intrinsic angular momentum of matter in curved spacetime requires the metric-affine formulation of gravity, in which the antisymmetric part of the affine connection (the torsion tensor) is not constrained to be zero but is a variable in the principle of stationary action. Regarding the tetrad and spin connection (or the metric and torsion tensors) as independent variables gives the correct generalization of the conservation law for the total (orbital plus intrinsic) angular momentum to the presence of the gravitational field. The metric-affine formulation extends general relativity to the simplest theory of gravity with intrinsic spin: the Einstein-Cartan-Sciama-Kibble theory. We also show that teleparallel gravity, which constrains the connection by setting the curvature tensor to zero, is inconsistent with the conservation of the total angular momentum.
L Garcia de Andrade
2011-10-14
Cosmological magnetic helicity has been thought to be a fundamental agent for magnetic field amplification in the universe. More recently Semikoz and Sokoloff [Phys Rev Lett 92 (2004): 131.301.] showed that the weakness of the seed fields did not necessarily imply the weakness of magnetic cosmological helicity. In this paper we present a derivation of dynamo equation based upon the flat torsion photon non-minimal coupling through Riemann-Cartan spacetime. From this derivation one computes the necessary conditions for a flat torsion field to generate a galactic dynamo seed, from the cosmological magnetic helicity. A peculiar feature of this dynamo equation is that the resistivity depends upon the Ricci scalar curvature. This feature is also present in turbulent dynamo models. Here the electrical effective conductivity is obtained by making use of flat torsion modes of a $R(\\Gamma)F^{2}$ Lagrangean where R refers to the Ricci-Cartan spacetime. Power spectrum of the magnetic field is also computed. Lorentz violation appears naturally from birefrigence of photons semi-minimally coupled to torsion. Though Dobado and Maroto [Mod Phys Lett A 12: 3003 (1997)] have previously investigated the role of primordial torsion in the anisotropy of light propagation they made it using the fermionic sector of the QED Lagrangean while we obtained similar results using the photonic sector. They also used the pseudo-trace of torsion while we here work out with the torsion trace itself.
An elastoplastic theory of dislocations as a physical field theory with torsion
NASA Astrophysics Data System (ADS)
Lazar, Markus
2002-03-01
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 is modified near the dislocation core due to the appearance of moment stress. For the first time, we calculate the localized moment stress, the Nye tensor, the elastoplastic energy and the modified Peach-Koehler force of a screw dislocation in this framework. Moreover, we discuss the straightforward analogy between a screw dislocation and a magnetic vortex. The dislocation theory in solids is also considered as a three-dimensional effective theory of gravity.
Bars, I.; Nemeschansky, D.; Yankielowicz, S.
1985-09-01
String theories on a background manifold with torsion are discussed. Candidate vacuum configurations are discussed for ten-dimensional superstrings. These are compactified on M/sub 4/ x K, where M/sub 4/ is four-dimensional and K is some compact six-dimensional manifold. Solutions with non-zero torsion on K are emphasized. The compactification problem is approached both from the effective field theory point of view and directly using string considerations. The construction of string theories in curved space with torsion is then discussed. Particular emphasis is put on the constraints on space-time supersymmetry in the Green-Schwarz approach. Two-dimensional non-linear sigma models are used to describe the propagation of strings in background geometries with torsion. (LEW)
Propagating torsion in the Einstein frame
Poplawski, Nikodem J. [Department of Physics, Indiana University, 727 East Third Street, Bloomington, Indiana 47405 (United States)
2006-11-15
The Einstein-Cartan-Saa theory of torsion modifies the spacetime volume element so that it is compatible with the connection. The condition of connection compatibility gives constraints on torsion, which are also necessary for the consistence of torsion, minimal coupling, and electromagnetic gauge invariance. To solve the problem of positivity of energy associated with the torsionic scalar, we reformulate this theory in the Einstein conformal frame. In the presence of the electromagnetic field, we obtain the Hojman-Rosenbaum-Ryan-Shepley theory of propagating torsion with a different factor in the torsionic kinetic term.
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.
A. S. Garkun; V. I. Kudin; A. V. Minkevich
2008-06-29
Analysis of regular inflationary cosmological models with two torsion functions filled with scalar field with quadratic potential and ultrarelativistic matter is carried out numerically. Properties of different stages of regular inflationary cosmological solutions are studied, restrictions on admissible values of parameters and initial conditions at transition from compression to expansion are found. The structure of extremum surface in space of physical variables is investigated.
The most general ELKO Matter in torsional f(R)-theories
Luca Fabbri; Stefano Vignolo
2011-08-05
We study f(R)-gravity with torsion in presence of the most general ELKO matter, checking the consistency of the conservation laws with the matter field equations; we discuss some mathematical features of the field equations in connection with a cosmological application.
The most general ELKO matter in torsional f(R)-theories
NASA Astrophysics Data System (ADS)
Fabbri, L.; Vignolo, S.
2012-02-01
We study f(R)-gravity with torsion in presence of the most general ELKO matter, checking the consistency of the conservation laws with the matter field equations; we discuss some mathematical features of the field equations in connection with a cosmological application.
a Torsional Topological Invariant
NASA Astrophysics Data System (ADS)
Nieh, H. T.
2008-12-01
Curvature and torsion are the two tensors characterizing a general Riemannian space-time. In Einstein's general theory of gravitation, with torsion postulated to vanish and the affine connection identified to the Christoffel symbol, only the curvature tensor plays the central role. For such a purely metric geometry, two well-known topological invariants, namely the Euler class and the Pontryagin class, are useful in characterizing the topological properties of the space-time. From a gauge theory point of view, and especially in the presence of spin, torsion naturally comes into play, and the underlying space-time is no longer purely metric. We describe a torsional topological invariant, discovered in 1982, that has now found increasing usefulness in recent developments.
Hehl, Friedrich W; Puetzfeld, Dirk
2013-01-01
Ever since E.Cartan in the 1920s enriched the geometric framework of general relativity (GR) by introducing a {\\it torsion} of spacetime, the question arose whether one could find a measurement technique for detecting the presence of a torsion field. Mao et al.(2007) claimed that the rotating quartz balls in the gyroscopes of the Gravity Probe B experiment, falling freely on an orbit around the Earth, should "feel" the torsion. Similarly, March et al.(2011) argue with the precession of the Moon and the Mercury and extend later their considerations to the Lageos satellite.--- A consistent theory of gravity with torsion emerged during the early 1960's as gauge theory of the Poincar\\'e group. This Poincar\\'e gauge theory of gravity incorporates as simplest viable cases the Einstein-Cartan(-Sciama-Kibble) theory (EC), the teleparallel equivalent GR|| of GR, and GR itself. So far, PG and, in particular, the existence of torsion have {\\it not} been experimentally confirmed. However, PG is to be considered as the st...
Inverse problems for torsional modes.
Willis, C.
1984-01-01
Considers a spherically symmetric, non-rotating Earth consisting of an isotropic, perfect elastic material where the density and the S-wave velocity may have one or two discontinuities in the upper mantle. Shows that given the velocity throughout the mantle and the crust and given the density in the lower mantle, then the freqencies of the torsional oscillations of one angular order (one torsional spectrum), determine the density in the upper mantle and in the crust uniquely. If the velocity is known only in the lower mantle, then the frequencies of the torsional oscillations of two angular orders uniquely determine both the density and the velocity in the upper mantle and in the crust. In particular, the position and size of the discontinuities in the density and velocity are uniquely determined by two torsional spectra.-Author
Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M.
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.
Generalization of equivalent crystal theory to include angular dependence
John Ferrante; Fredy R. Zypman
2006-01-01
The original equivalent crystal theory is a semi-empirical method for calculating the configurational energy of atomic systems. Each atomic site in the real crystal with defects is assigned an equivalent lattice constant, in general different from the ground state value. This parameter corresponds to a local compression or expansion of the perfect lattice. The basic method considers these volumetric transformations
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
2015-04-01
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.
Dangerous angular Kaluza-Klein/glueball relics in string theory cosmology
Dufaux, J. F.; Kofman, L.; Peloso, M.
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.
Koh, K B; Dublin, N; Light, T
1995-09-01
A retrospective review of 80 patients who underwent scrotal exploration for presumed testicular torsion is presented. Of these, 67 patients were found to have torsion, and the testicular loss rate was 51%. Patients who experienced delays in scrotal exploration of more than 24 h from onset of symptoms had a testicular loss rate of 71%. These delays arose from both hesitation in seeking medical treatment and misdiagnoses. It is emphasized that an acute scrotum in a child or in an adolescent should be explored early to exclude torsion. PMID:7575294
Angular Momentum Evolution of Young Stars: Toward a Synthesis of Observations, Theory, and Modeling
Keivan G. Stassun; Donald Terndrup
2003-03-17
The aim of this AAS Topical Session was to update the community on the current state of knowledge about the angular momentum evolution of young stars. For newcomers to the subject, the session was intended to provide an introduction and general overview and to highlight emerging issues. For experienced workers in this field, the session provided an opportunity for synthesizing recent developments in observations, theory, and modeling of rotation of young stars and for identifying promising new research directions.
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.
Nonlinear Hysteretic Torsional Waves
NASA Astrophysics Data System (ADS)
Cabaret, J.; Béquin, P.; Theocharis, G.; Andreev, V.; Gusev, V. E.; Tournat, V.
2015-07-01
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 to be 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 types 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.
Batishchev, Pavel A.; Tolstikhin, Oleg I. [Moscow Institute of Physics and Technology, Institutskaya Street 9, Dolgoprudnyi 141700 (Russian Federation); Russian Research Center 'Kurchatov Institute', Kurchatov Square 1, Moscow 123182 (Russian Federation)
2007-06-15
The Siegert pseudostate (SPS) formulation of scattering theory, originally developed by Tolstikhin, Ostrovsky, and Nakamura [Phys. Rev. A, 58, 2077 (1998)] for s-wave scattering in a spherically symmetric finite-range potential, is generalized to nonzero angular momenta. The orthogonality and completeness properties of SPSs are established and SPS expansions for the outgoing-wave Green's function, physical states, and scattering matrix are obtained. The present formulation completes the theory of SPSs in the one-channel case, making its application to three-dimensional problems possible. The results are illustrated by calculations for several model potentials.
Derivation of Einstein-Cartan theory from general relativity
R. J. Petti
2015-05-28
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. This article presents 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. The continuum limit of this sequence of solutions yields Einstein Cartan theory with torsion and the spin torsion relation, not general relativity.
Torsion of a cylinder of partially molten mantle with a spherical inclusion: theory and simulation
Alisic, Laura; Rudge, John F; Katz, Richard F; Wells, Garth N
2015-01-01
The processes that are involved in migration and extraction of melt from the mantle are not yet fully understood. Gaining a better understanding of material properties of partially molten rock could help shed light on the behavior of melt on larger scales in the mantle. In this study, we simulate three-dimensional torsional deformation of a partially molten rock that contains a rigid, spherical inclusion. We compare the computed porosity patterns to those found in recent laboratory experiments. The laboratory experiments show emergence of melt-rich bands throughout the rock sample, and pressure shadows around the inclusion. The numerical model displays similar melt-rich bands only for a small bulk-to-shear-viscosity ratio (five or less). The results are consistent with earlier two-dimensional numerical simulations, however we show that it is easier to form melt-rich bands in three dimensions compared to two. The addition of strain-rate dependence of the viscosity causes a distinct change in the shape of press...
NASA Astrophysics Data System (ADS)
Hansen, J. S.; Daivis, Peter J.; Dyre, Jeppe C.; Todd, B. D.; Bruus, Henrik
2013-01-01
The extended Navier-Stokes theory accounts for the coupling between the translational and rotational molecular degrees of freedom. In this paper, we generalize this theory to non-zero frequencies and wavevectors, which enables a new study of spatio-temporal correlation phenomena present in molecular fluids. To discuss these phenomena in detail, molecular dynamics simulations of molecular chlorine are performed for three different state points. In general, the theory captures the behavior for small wavevector and frequencies as expected. For example, in the hydrodynamic regime and for molecular fluids with small moment of inertia like chlorine, the theory predicts that the longitudinal and transverse intrinsic angular velocity correlation functions are almost identical, which is also seen in the molecular dynamics simulations. However, the theory fails at large wavevector and frequencies. To account for the correlations at these scales, we derive a phenomenological expression for the frequency dependent rotational viscosity and wavevector and frequency dependent longitudinal spin viscosity. From this we observe a significant coupling enhancement between the molecular angular velocity and translational velocity for large frequencies in the gas phase; this is not observed for the supercritical fluid and liquid state points.
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.
Algebraic Torsion in Contact Manifolds
Latschev, Janko
2010-01-01
We extract a nonnegative integer-valued invariant, which we call the "order of algebraic torsion", from the Symplectic Field Theory of a closed contact manifold, and show that its finiteness gives obstructions to the existence of symplectic fillings and exact symplectic cobordisms. A contact manifold has algebraic torsion of order zero if and only if it is algebraically overtwisted (i.e. has trivial contact homology), and any contact 3-manifold with positive Giroux torsion has algebraic torsion of order one (though the converse is not true). We also construct examples for each nonnegative k of contact 3-manifolds that have algebraic torsion of order k but not k - 1, and derive consequences for contact surgeries on such manifolds. The appendix by Michael Hutchings gives an alternative proof of our cobordism obstructions in dimension three using a refinement of the contact invariant in Embedded Contact Homology.
NASA Astrophysics Data System (ADS)
Hanson, Donald B.; Parzych, David J.
1993-03-01
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.
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.
Angular momentum dependent orbital-free density functional theory: Formulation and implementation
NASA Astrophysics Data System (ADS)
Ke, Youqi; Libisch, Florian; Xia, Junchao; Carter, Emily A.
2014-04-01
Orbital-free density functional theory (OFDFT) directly solves for the ground-state electron density. It scales linearly with respect to system size, providing a promising tool for large-scale material simulations. Removal of the orbitals requires use of approximate noninteracting kinetic energy density functionals. If replacing ionic cores with pseudopotentials, removal of the orbitals also requires these pseudopotentials to be local. These are two severe challenges to the capabilities of conventional OFDFT. While main group elements are often well described within conventional OFDFT, transition metals remain intractable due to their localized d electrons. To advance the accuracy and general applicability of OFDFT, we have recently reported a general angular momentum dependent formulation as a next-generation OFDFT. In this formalism, we incorporate the angular momenta of electrons by devising a hybrid scheme based on a muffin tin geometry: inside spheres centered at the ionic cores, the electron density is expanded in a set of atom-centered basis functions combined with an onsite density matrix. The explicit treatment of the angular momenta of electrons provides an important basis for accurately describing the important ionic core region, which is not possible in conventional OFDFT. In addition to the conventional OFDFT total energy functional, we introduce a nonlocal energy term containing a set of angular momentum dependent energies to correct the errors due to the approximate kinetic energy density functional and local pseudopotentials. Our approach greatly increases the accuracy of OFDFT while largely preserving its numerical simplicity. Here, we provide details of the theoretical formulation and practical implementation, including the hybrid scheme, the derivation of the nonlocal energy term, the choice of basis functions, the direct minimization of the total energy, the procedure to determine the angular momentum dependent energies, the force formula with Pulay correction, and the solution to emerging numerical instability. To test the angular momentum dependent OFDFT formalism and its numerical implementations, we calculate a diverse set of properties of the transition metal Ti and compare with different levels of DFT approximation. The results suggest that angular momentum dependent OFDFT ultimately will extend the reliable reach of OFDFT to the rest of the periodic table.
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.
Quaternions, Torsion and the Physical Vacuum: Theories of M. Sachs and G. Shipov Compared
NASA Astrophysics Data System (ADS)
Cyganski, David; Page, William S.
Of several developments of unified field theories in the spirit of Einstein's original objective of a fully geometric description of all classical fields as well as quantum mechanics, two are particularly noteworthy. The works of Mendel Sachs and Gennady Shipov stand apart as major life works comprising tens of papers, several monographs and decades of effort. Direct comparison of these theories is hampered however by differences in notation and conceptual view-point. Despite these differences, there are many parallels between the fundamental mathematical structures appearing in each. In this paper we discuss the main tenets of the two approaches and demonstrate that they both give rise to a factorization of the invariant interval of general relativity.
Axions in gravity with torsion
Castillo-Felisola, Oscar; Kovalenko, Sergey; Schmidt, Ivan; Lyubovitskij, Valery E
2015-01-01
We study a scenario allowing a solution of the strong CP-problem via the Peccei-Quinn mechanism, implemented in gravity with torsion. In this framework there appears a torsion-related pseudoscalar field known as Kalb-Ramond axion. We compare it with the so called Barbero-Immirzi axion recently proposed in the literature also in the context of the gravity with torsion. We show that they are equivalent from the view point of the effective theory. The phenomenology of these torsion-descended axions is completely determined by the Planck scale without any additional model parameters. These axions are very light and very weakly interacting with ordinary matter. We briefly comment on their astrophysical and cosmological implications in view of the recent BICEP2 and Planck data.
Butler, Laurie J.
Effects of High Angular Momentum on the Unimolecular Dissociation of CD2CD2OH: Theory ABSTRACT: This paper explores the dynamics of a highly rotationally and vibrationally excited radical, CD2CD2OH. The radical is produced from the 193 nm photodissociation of 2-bromoethanol-d4, so
Yu, T.; Zheng, J.; Truhlar, D. G.
2011-01-01
We present a new formulation of variational transition state theory (VTST) called multi-structural VTST (MS-VTST) and the use of this to calculate the rate constant for the 1,4-hydrogen shift isomerization reaction of 1-pentyl radical and that for the reverse reaction. MS-VTST uses a multi-faceted dividing surface and provides a convenient way to include the contributions of many structures (typically conformers) of the reactant and the transition state in rate constant calculations. In this particular application, we also account for the torsional anharmonicity. We used the multi-configuration Shepard interpolation method to efficiently generate a semi-global portion of the potential energy surface from a small number of high-level electronic structure calculations using the M06 density functional in order to compute the energies and Hessians of Shepard points along a reaction path. The M06-2X density functional was used to calculate the multi-structural anharmonicity effect, including all of the structures of the reactant, product and transition state. To predict the thermal rate constant, VTST calculations were performed to obtain the canonical variational rate constant over the temperature range 200–2000 K. A transmission coefficient is calculated by the multidimensional small-curvature tunneling (SCT) approximation. The final MS-CVT/SCT thermal rate constant was determined by combining a reaction rate calculation in the single-structural harmonic oscillator approximation (including tunneling) with the multi-structural anharmonicity torsional factor. The calculated forward rate constant agrees very well with experimentally-based evaluations of the high-pressure limit for the temperature range 300–1300 K, although it is a factor of 2.5–3.0 lower than the single-structural harmonic oscillator approximation over this temperature range. We anticipate that MS-VTST will be generally useful for calculating the reaction rates of complex molecules with multiple torsions.
Torsional Oscillations of the Earths's Core
NASA Technical Reports Server (NTRS)
Hide, Raymond; Boggs, Dale H.; Dickey, Jean O.
1997-01-01
Torsional oscillations of the Earth's liquid metallic outer core are investigated by diving the core into twenty imaginary e1qui-volume annuli coaxial with the axis of ratation of the Earth and determining temproal fluctuations in the axial component of angular memonetum of each annulus under the assumption of iso-rotation on cylindrical surfaces.
Thermoelastic damping in torsion microresonators with coupling effect between torsion and bending
NASA Astrophysics Data System (ADS)
Tai, Yongpeng; Li, Pu; Fang, Yuming
2014-02-01
Predicting thermoelastic damping (TED) is crucial in the design of high Q MEMS resonators. In the past, there have been few works on analytical modeling of thermoelastic damping in torsion microresonators. This could be related to the assumption of pure torsional mode for the supporting beams in the torsion devices. The pure torsional modes of rectangular supporting beams involve no local volume change, and therefore, they do not suffer any thermoelastic loss. However, the coupled motion of torsion and bending usually exists in the torsion microresonator when it is not excited by pure torque. The bending component of the coupled motion causes flexural vibrations of supporting beams which may result in significant thermoelastic damping for the microresonator. This paper presents an analytical model for thermoelastic damping in torsion microresonators with the coupling effect between torsion and bending. The theory derives a dynamic model for torsion microresonators considering the coupling effect, and approximates the thermoelastic damping by assuming the energy loss to occur only in supporting beams of flexural vibrations. The thermoelastic damping obtained by the present model is compared to the measured internal friction of single paddle oscillators. It is found that thermoelastic damping contributes significantly to internal friction for the case of the higher modes at room temperature. The present model is validated by comparing its results with the finite-element method (FEM) solutions. The effects of structural dimensions and other parameters on thermoelastic damping are investigated for the representative case of torsion microresonators.
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.
NSDL National Science Digital Library
Wolfgang Christian
The simulation of a rotating wheel below shows the relationship between angular position, angular velocity, and angular acceleration. Graphs of angular position and angular velocity as a function of time are shown.
Face-seal lubrication. 2: Theory of response to angular misalignement
NASA Technical Reports Server (NTRS)
Ludwig, L. P.; Allen, G. P.
1976-01-01
A theoretical analysis was made of a hypothetical seal operating mode. The hypothetical seal model provides for three degrees of primary ring motion and includes the force and moments induced by primary ring response to seat angular misalignment. This ring response causes a relative angular misalignment between the faces of the primary seal. Hydrodynamic pressure generation is produced by this misalignment. The analysis is based on the Reynolds equation in short bearing form and on a balance of forces and moments that arise from hydrodynamic and secondary seal friction effects. A closed form solution was obtained that can be solved for film thickness and relative angular misalignment.
Testicular torsion repair is surgery to untangle a spermatic cord. The spermatic cord is the collection of blood vessels ... the scrotum that lead to the testicles. Testicular torsion develops when the cord twists. This pulling and ...
Testicular Torsion (For Parents)
... torsion happens. If it's before a boy is born, it may be impossible to save the testicle. ... If torsion symptoms appear after a boy is born, the doctor may recommend emergency surgery to correct ...
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.
Gourgiotis, P A
2015-01-01
The existence of torsional and SH surface waves in a half-space of a homogeneous and isotropic material is shown to be possible in the context of the complete Toupin-Mindlin theory of gradient elasticity. This finding is in marked contrast with the well-known result of the classical theory, where such waves do not exist in a homogeneous (isotropic or anisotropic) half-space. In the context of the classical theory, this weakness is usually circumvented by modeling the half-space as a layered structure or as having non-homogeneous properties. On the other hand, employing a simplified version of gradient elasticity (including only one microstructural parameter and an additional surface-energy term), Vardoulakis and Georgiadis (1997), and Georgiadis et al. (2000), showed that such surface waves may exist in a homogeneous half-space only if a certain type of gradient anisotropy is included in the formulation. On the contrary, in the present work, we prove that the complete Toupin-Mindlin theory of isotropic gradie...
Classical density functional theory of solvation in molecular solvents: Angular grid implementation
NASA Astrophysics Data System (ADS)
Gendre, Lionel; Ramirez, Rosa; Borgis, Daniel
2009-06-01
The solvation properties of a solute in a molecular solvent can be obtained by minimization of a position and orientation-dependent free-energy density functional, with the unknown excess term approximated by the angular-dependent direct correlation function of the pure solvent. We show how this function can be extracted from MD simulations of the pure solvent by computing the pair distribution function and solving subsequently the Molecular Ornstein-Zernike equation using angular grids. The corresponding functional can be minimized in the presence of an arbitrary solute on a three-dimensional cubic grid for positions and Gauss-Legendre angular grid for orientations to provide the solvation structure and free-energy. Applications are presented for solvation in acetonitrile.
New Gauge Symmetry in Gravity and the Evanescent Role of Torsion
NASA Astrophysics Data System (ADS)
Kleinert, H.
2011-11-01
If the Einstein-Hilbert action LEH ? R is re-expressed in Riemann-Cartan spacetime using the gauge fields of translations, the vierbein field h? ? , and the gauge field of local Lorentz transformations, the spin connection A???, there exists a new gauge symmetry which permits reshuffling the torsion, partially or totally, into the Cartan curvature term of the Einstein tensor, and back, via a new multivalued gauge transformation. Torsion can be chosen at will by an arbitrary gauge fixing functional. There exist many equivalent ways of specifying the theory, for instance Einstein's traditional way where LEH is expressed completely in terms of the metric g{? ? } = h? ? h{? ? }, and the torsion is zero, or Einstein's teleparallel formulation, where LEH is expressed in terms of the torsion tensor, or an infinity of intermediate ways. As far as the gravitational field in the far-zone of a celestial object is concerned, matter composed of spinning particles can be replaced by matter with only orbital angular momentum, without changing the long-distance forces, no matter which of the various new gauge representations is used.
Vaidya-like exact solutions with torsion
NASA Astrophysics Data System (ADS)
Blagojevi?, M.; Cvetkovi?, B.
2015-05-01
Starting from the Oliva-Tempo-Troncoso black hole, a solution of the Bergshoeff-Hohm-Townsend massive gravity, a class of the Vaidya-like exact vacuum solutions with torsion is constructed in the three-dimensional Poincaré gauge theory. A particular subclass of these solutions is shown to possess the asymptotic conformal symmetry. The related canonical energy contains a contribution stemming from torsion.
Barbosa, Geraldo A. [Department of Electrical Engineering and Computer Science, Center for Photonic Communication and Computing, Northwestern University, 2145 North Sheridan Road, Evanston, Illinois 60208-3118 (United States)
2007-09-15
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.
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.
NASA Astrophysics Data System (ADS)
Hankel, Marlies; Connor, J. N. L.
2015-07-01
A valuable tool for understanding the dynamics of direct reactions is Nearside-Farside (NF) scattering theory. It makes a decomposition of the (resummed) partial wave series for the scattering amplitude, both for the differential cross section (DCS) and the Local Angular Momentum (LAM). This paper makes the first combined application of these techniques to complex-mode reactions. We ask if NF theory is a useful tool for their identification, in particular, can it distinguish complex-mode from direct-mode reactions? We also ask whether NF theory can identify NF interference oscillations in the full DCSs of complex-mode reactions. Our investigation exploits the fact that accurate quantum scattering matrix elements have recently become available for complex-mode reactions. We first apply NF theory to two simple models for the scattering amplitude of a complex-mode reaction: One involves a single Legendre polynomial; the other involves a single Legendre function of the first kind, whose form is suggested by complex angular momentum theory. We then study, at fixed translational energies, four state-to-state complex-mode reactions. They are: S(1D) + HD ? SH + D, S(1D) + DH ? SD + H, N(2D) +H2 ? NH + H, and H+ + D2 ? HD + D+. We compare the NF results for the DCSs and LAMs with those for a state-to-state direct reaction, namely, F + H2 ? FH + H. We demonstrate that NF theory is a valuable tool for identifying and analyzing the dynamics of complex-mode reactions.
Wormholes in spacetime with torsion
Luis A. Anchordoqui
1997-10-21
Analytical wormhole solutions in $U_4$ theory are presented. It is discussed whether the extremely short range repulsive forces, related to the spin angular momentum of matter, could be the ``carrier'' of the exoticity that threads the wormhole throat.
Ovchinnikov, S.Y. [Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy; Macek, J.H. [Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy]|[Oak Ridge National Lab., TN (United States)
1994-12-31
The two-dimensional resonances in the problem of two Coulomb centers are discussed. The ab initio calculation of electron energy and angular distributions of saddle-point and S-promotion electrons for ionization in proton-hydrogen atom collisions are presented. The calculation is based on an outgoing wave Sturmian expansion in the frequency domain. It goes beyond the usual Born-Oppenheimer separation of electron and nuclei motions and displays the ``{upsilon}/2`` peak and the continuum cusp, missing in previous theories.
Classical density functional theory of solvation in molecular solvents: Angular grid implementation
Lionel Gendre; Rosa Ramirez; Daniel Borgis
2009-01-01
The solvation properties of a solute in a molecular solvent can be obtained by minimization of a position and orientation-dependent free-energy density functional, with the unknown excess term approximated by the angular-dependent direct correlation function of the pure solvent. We show how this function can be extracted from MD simulations of the pure solvent by computing the pair distribution function
Physics of detecting torsion and placing limits on its effects
Stoeger, W.R.
1985-10-01
The essential principles of torsion-detection physics are presented, and an evaluation is conducted of several conceivable types of experiments and observations for actually detecting torsion fields, reemphasizing also the evident impossibility of successfully searching for its manifestations among cosmological relics. In particular, a polarized body, with net intrinsic (fundamental-particle) spin, is essential for detecting a torsion field. One which possesses only orbital angular momentum - rotation - or an unpolarized intrinsic spin density will not feel torsion. The fundamental problem in searching for such fields is the extremely small basic unit of the coupling or interaction energy between the torsion field and spin. The best way of maximizing the total interaction energy is to increase the spin density of the source sigma-s and at the same time the spin number SD of the detector. 15 references.
Unified theory for fission path and high angular momentum phenomena of nuclei
Malik, S.S. (Physics Department, Guru Nanak Dev University, Amritsar-143005 (India))
1994-12-01
A unified approach, involving the two-center picture of the nucleus, is proposed for the description of the behavior of nuclei at high angular momentum. This picture involves nine parameters, fixed by solving the system of nine nonlinear equations, obtained from equilibrium constraints. This shape enables us to calculate the potential energy surfaces. For the calculations of shell effects we adopt the Strutinsky formalism. The shell effects play the dominant role in deciding the fission path and the phenomenon of superdeformation in [sup 236]U. The calculated moment of inertia of the isomeric state is close to the observation and hence it supports the theoretical description of its shape.
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.
Analytic Torsion of Z_2-graded Elliptic Complexes
Mathai, Varghese
2010-01-01
We define analytic torsion of Z_2-graded elliptic complexes as an element in the graded determinant line of the cohomology of the complex, generalizing most of the variants of Ray-Singer analytic torsion in the literature. It applies to a myriad of new examples, including flat superconnection complexes, twisted analytic and twisted holomorphic torsions, etc. The definition uses pseudo-differential operators and residue traces. We also study properties of analytic torsion for Z_2-graded elliptic complexes, including the behavior under variation of the metric. For compact odd dimensional manifolds, the analytic torsion is independent of the metric, whereas for even dimensional manifolds, a relative version of the analytic torsion is independent of the metric. Finally, the relation to topological field theories is studied.
Erez Zohar; J. Ignacio Cirac; Benni Reznik
2013-08-28
Quantum simulations of High Energy Physics, and especially of gauge theories, is an emerging and exciting direction in quantum simulations. However, simulations of such theories, compared to simulations of condensed matter physics, must satisfy extra restrictions, such as local gauge and Lorentz invariance. In this paper we discuss these special requirements, and present a new method for quantum simulation of lattice gauge theories using ultracold atoms. This method allows to include local gauge invariance as a fundamental symmetry of the atomic Hamiltonian, arising from natural atomic interactions and conservation laws (and not as a property of a low energy sector). This allows us to implement elementary gauge invariant interactions for three lattice gauge theories: compact QED (U(1)), SU(N) and Z_N, which can be used to build quantum simulators in 1+1 dimensions. We also present a new loop method, which uses the elementary interactions as building blocks in the effective construction of quantum simulations for d+1 dimensional lattice gauge theories (d>1), without having to use Gauss's law as a constraint, as in previous proposals. We discuss in detail the quantum simulation of 2+1 dimensional compact QED and provide a numerical proof of principle. The simplicity of the already gauge invariant elementary interactions of this model suggests it may be useful for future experimental realizations.
NASA Technical Reports Server (NTRS)
Leese, G. E.
1984-01-01
Torsional fatigue testing and data analysis procedures are described. Since there are no standards governing cyclic torsion testing that are generally accepted on a widespread basis by the technical community, the different approaches that dominate current experimental activity, and the ramifications of each are discussed. Particular attention is given to the theoretical and experimental difficulties that have paced refinement and general acceptance of test procedures. Finally, specific quantities and nomenclature modelled after analagous axial fatigue properties are suggested as an effective way to communicate torsional fatigue results until accepted standards are established.
ANGULAR MOMENTUM L Angular Momentum
ANGULAR MOMENTUM L #12;#12;#12;#12;#12;#12;p-6' Angular Momentum Case: A few particles Example: This example emphasizes the fact that the value of the angular momentum of a system of particles depends just for reference.). v v v 1 2 3 Calculate the vector angular momentum of the three-particle system
Miller, William H.
Angular Momentum William H. Mlller Department of Chemistry,and Maferials and Molecular Research Division, 1982; In Final Form: February 8, 1983) It is shown how nonzero total angular momentum is incorporated- aldehyde (1.1) which has a planar transition state: i.e., C, symmetry, and for total angular momentum J = 0
Meana-Pañeda, Rubén; Fernández-Ramos, Antonio
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.
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.
Structural and torsional vibration analysis of a dry screw compressor
NASA Astrophysics Data System (ADS)
Willie, J.; Sachs, R.
2015-08-01
This paper investigates torsional vibration and pulsating noise in a dry screw compressor. The compressor is designed at Gardner Denver (GD) and is oil free and use for mounting on highway trucks. They are driven using a Power Take-Off (PTO) transmission and gear box on a truck. Torque peak fluctuation and noise measurements are done and their sources are investigated and reported in this work. To accurately predict the torsional response (frequency and relative angular deflection and torque amplitude), the Holzer method is used. It is shown that the first torsional frequency is manifested as sidebands in the gear train meshing frequencies and this can lead to noise that is the result of amplitude modulation. Sensitivity analysis of the drive train identifies the weakest link in the drive train that limits the first torsional frequency to a low value. Finally, the significance of higher mode shapes on inter-lobe clearance distribution of the rotors is investigated.
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.
Torsion and soft SUSY breaking
NASA Astrophysics Data System (ADS)
Sander, Tobias
Auxiliary fields in closed string multiplets of type II string compactifications with low energy supersymmetry determine soft supersymmetry breaking terms in the effective action. Building on earlier work, we compute the expectation values of auxiliary fields in hypermultiplets of type IIB models in terms of geometrical data of the compactification manifold, as well as Neveu-Schwarz (NS) fluxes on it. These auxiliary fields are important for computing the soft masses. In the hypermultiplet sector of type IIB theory on manifolds of SU(3)-structure they are identified with purely holomorphic deformations of the NS-NS three-form, together with half-flat deformations of the Calabi-Yau metric. The computation proceeds in three different ways based on 4d supergravity, 10d supergravity, and worldsheet techniques, respectively. The analysis continues with the important generalization to the class of SU(3) x SU(3) compactifications. One motivation for this comes from mirror symmetry considerations: we present evidence that the class of internal SU(3)-manifolds is not closed under mirror symmetry. We argue that in the presence of certain torsion classes nonperturbative corrections of the effective superpotential due to worldsheet instantons become generically important in type IIB theories. The reason is essentially that such torsion implies the presence of a potential driving certain two-cycles in the internal manifold to vanishing size.
Jones, P.L.; Hefter, U.; Mattheus, A.; Witt, J.; Bergmann, K.; Mueller, W.; Meyer, W.; Schinke, R.
1982-09-01
The results of a systematic experimental and theoretical investigation of the differential cross sections for vibronically elastic, rotationally inelastic scattering of Na/sub 2/ from Ne at a center-of-mass collision energy of 190 meV are presented. The experimental cross sections cover the range of rotational transitions ..delta..j = 2 to ..delta..j = 20 for a variety of initial rotational levels including the initially rotationless level j/sub i/ = 0. The data document clearly the major features of rotationally inelastic scattering for collisional systems with steeply repulsive, strongly anisotropic interaction potentials and many energetically open channels, such as main and supernumerary rotational rainbows. The experimental curves are transformed into the center-of-mass reference frame using a constrained minimalization procedure. They are compared with those calculated within the infinite-order sudden approximation from an ab initio potential surface which includes configuration interaction. The results show that the theoretical curves faithfully reproduce both the form and relative magnitudes of the experimental cross sections. An analysis of the sensitivity of the agreement between theory and experiment as the potential is systematically varied indicates that the experimental data place a limit of about +- 5% on the accuracy of the calculated anisotropy. The steepness of the ab initio potential could be varied by -10% or +25% and still lead to an acceptable agreement of calculated and experimental cross sections. The variation of the cross section at the rainbow maximum with ..delta..j and j/sub i/ is shown to be an unreliable test of the accuracy of the potential-energy surface unless a large range of ..delta..j is studied.
Testicular torsion repair - series (image)
Testicular torsion occurs when the testicle, normally attached to the scrotum by a small ligament at its base, becomes ... itself, cutting off its flow of blood. Testicular torsion is considered an emergency. Surgery is usually required, ...
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.
Quaternionic analytic torsion Kai Kohler
KÃ¶hler, Kai
Quaternionic analytic torsion Kai KÂ¨ohler Gregor Weingart April 10, 2001 Abstract We define an (equivariant) quaternionic analytic torsion for anti- selfdual vector bundles on quaternionic KÂ¨ahler manifolds, using ideas by Leung and Yi. We compute this torsion for vector bundles on quaternionic homogeneous
Gravitation, Cosmology and Space-Time Torsion
A. V. Minkevich
2007-09-27
Poincar\\'e gauge theory of gravity offers opportunities to solve some principal problems of general relativity theory and modern cosmology. In the frame of this theory the gravitational interaction can have the repulsion character in the case of usual gravitating matter with positive values of energy density and pressure satisfying energy dominance condition. Cosmological consequences of gravitational repulsion are considered in the case of homogeneous isotropic models in connection with the problem of cosmological singularity and dark energy problem of general relativity theory. Regular Big Bang inflationary scenario with accelerating stage of cosmological expansion at asymptotics and the principal role of space-time torsion in this scenario are discussed.
Torsion And Bending Alleviator
NASA Technical Reports Server (NTRS)
Doebbler, Thomas R.; Kent, Preston E.
1994-01-01
Device couples two shafts while relieving excessive loads between them. Torsion and bending loads between upper and mounting shafts relieved in coupling by ball springs and Belleville springs, respectively. Both sets of springs adjustable so as not to relieve loads below preset limits.
Torsional anharmonicity in the conformational thermodynamics of flexible molecules
NASA Astrophysics Data System (ADS)
Miller, Thomas F., III; Clary, David C.
We present an algorithm for calculating the conformational thermodynamics of large, flexible molecules that combines ab initio electronic structure theory calculations with a torsional path integral Monte Carlo (TPIMC) simulation. The new algorithm overcomes the previous limitations of the TPIMC method by including the thermodynamic contributions of non-torsional vibrational modes and by affordably incorporating the ab initio calculation of conformer electronic energies, and it improves the conventional ab initio treatment of conformational thermodynamics by accounting for the anharmonicity of the torsional modes. Using previously published ab initio results and new TPIMC calculations, we apply the algorithm to the conformers of the adrenaline molecule.
Torsional Oscillations in a Global Solar Dynamo
NASA Astrophysics Data System (ADS)
Beaudoin, P.; Charbonneau, P.; Racine, E.; Smolarkiewicz, P. K.
2013-02-01
We characterize and analyze rotational torsional oscillations developing in a large-eddy magnetohydrodynamical simulation of solar convection (Ghizaru, Charbonneau, and Smolarkiewicz, Astrophys. J. Lett. 715, L133, 2010; Racine et al., Astrophys. J. 735, 46, 2011) producing an axisymmetric, large-scale, magnetic field undergoing periodic polarity reversals. Motivated by the many solar-like features exhibited by these oscillations, we carry out an analysis of the large-scale zonal dynamics. We demonstrate that simulated torsional oscillations are not driven primarily by the periodically varying large-scale magnetic torque, as one might have expected, but rather via the magnetic modulation of angular-momentum transport by the large-scale meridional flow. This result is confirmed by a straightforward energy analysis. We also detect a fairly sharp transition in rotational dynamics taking place as one moves from the base of the convecting layers to the base of the thin tachocline-like shear layer formed in the stably stratified fluid layers immediately below. We conclude by discussing the implications of our analyses with regard to the mechanism of amplitude saturation in the global dynamo operating in the simulation, and speculate on the possible precursor value of torsional oscillations for the forecast of solar-cycle characteristics.
's Constant Using a Torsion Balance with Angular Acceleration Feedback Jens H. Gundlach and Stephen M 98195 (Received 5 June 2000) We measured Newton's gravitational constant G using a new torsion balance previous methods. At the heart of the apparatus is a torsion balance placed on a turntable located between
On Poincaré gauge theory of gravity, its equations of motion, and Gravity Probe B
Friedrich W. Hehl; Yuri N. Obukhov; Dirk Puetzfeld
2013-06-07
Ever since E.Cartan in the 1920s enriched the geometric framework of general relativity (GR) by introducing a {\\it torsion} of spacetime, the question arose whether one could find a measurement technique for detecting the presence of a torsion field. Mao et al.(2007) claimed that the rotating quartz balls in the gyroscopes of the Gravity Probe B experiment, falling freely on an orbit around the Earth, should "feel" the torsion. Similarly, March et al.(2011) argue with the precession of the Moon and the Mercury and extend later their considerations to the Lageos satellite.--- A consistent theory of gravity with torsion emerged during the early 1960's as gauge theory of the Poincar\\'e group. This Poincar\\'e gauge theory of gravity incorporates as simplest viable cases the Einstein-Cartan(-Sciama-Kibble) theory (EC), the teleparallel equivalent GR|| of GR, and GR itself. So far, PG and, in particular, the existence of torsion have {\\it not} been experimentally confirmed. However, PG is to be considered as the standard theory of gravity with torsion because of its very convincing gauge structure.--- Since the early 1970s up to today, different groups have shown more or less independently that torsion couples only to the {\\it elementary particle spin} and under no circumstances to the orbital angular momentum of test particles. This is established knowledge and we reconfirm this conclusion by discussing the energy-momentum law of PG, which has same form for all versions of PG. Therefore, we conclude that, unfortunately, the investigations of Mao et al. and March et al. do not yield any information on torsion.
Constraining spacetime torsion with the Moon and Mercury
March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone
2011-05-15
We report a search for new gravitational physics phenomena based on Riemann-Cartan theory of general relativity including spacetime torsion. Starting from the parametrized torsion framework of Mao, Tegmark, Guth, and Cabi, we analyze the motion of test bodies in the presence of torsion, and, in particular, we compute the corrections to the perihelion advance and to the orbital geodetic precession of a satellite. We consider the motion of a test body in a spherically symmetric field, and the motion of a satellite in the gravitational field of the Sun and the Earth. We describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general differ from geodesics when torsion is present. We derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of celestial mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter of the satellite. The computed secular variations show how the corrections to the perihelion advance and to the orbital de Sitter effect depend on the torsion parameters. All computations are performed under the assumptions of weak field and slow motion. To test our predictions, we use the measurements of the Moon's geodetic precession from lunar laser ranging data, and the measurements of Mercury's perihelion advance from planetary radar ranging data. These measurements are then used to constrain suitable linear combinations of the torsion parameters.
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.
Constraining spacetime torsion with the Moon and Mercury
NASA Astrophysics Data System (ADS)
March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone
2011-05-01
We report a search for new gravitational physics phenomena based on Riemann-Cartan theory of general relativity including spacetime torsion. Starting from the parametrized torsion framework of Mao, Tegmark, Guth, and Cabi, we analyze the motion of test bodies in the presence of torsion, and, in particular, we compute the corrections to the perihelion advance and to the orbital geodetic precession of a satellite. We consider the motion of a test body in a spherically symmetric field, and the motion of a satellite in the gravitational field of the Sun and the Earth. We describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general differ from geodesics when torsion is present. We derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of celestial mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter of the satellite. The computed secular variations show how the corrections to the perihelion advance and to the orbital de Sitter effect depend on the torsion parameters. All computations are performed under the assumptions of weak field and slow motion. To test our predictions, we use the measurements of the Moon’s geodetic precession from lunar laser ranging data, and the measurements of Mercury’s perihelion advance from planetary radar ranging data. These measurements are then used to constrain suitable linear combinations of the torsion parameters.
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.
Torsion of the Testis and its Appendages
R. H. Chapman; A. J. Walton
1972-01-01
In a survey of 101 cases with an index diagnosis of torsion of the testis or its appendage, there were 86 instances of torsion of the testis and 14 of torsion of the hydatid of Morgagni. In 38 of the patients with testicular torsion there were one or more “warning” attacks of pain and swelling, due to torsion which became
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.
Mechanics of ventricular torsion.
Taber, L A; Yang, M; Podszus, W W
1996-06-01
Recent research suggests that left ventricular torsion is an important indicator of cardiac function. We used two theoretical models to study the mechanics of this phenomenon: a compressible cylinder and an incompressible ellipsoid of revolution. The analyses of both models account for large- strain passive and active material behavior, with a muscle fiber angle that varies linearly from endocardium to epicardium. Relative to the end- diastolic configuration, the predicted torsion exhibits several experimentally observed features, including a peak near end systole, rapid untwisting during isovolumic relaxation, and increased twist near the apex. The magnitude of the twist is sensitive to the fiber architecture, the ventricular geometry, and the compressibility and contractility of the myocardium. In particular, the model predicts that the systolic twist increases with increasing compressibility, contractility, and wall thickness, while it decreases with increasing cavity volume. The peak twist approximately doubles (from about 0.02 to 0.04 rad cm(-1)) with a doubling of myocardial compressibility or with a change in the endocardial/epicardial muscle fiber angles from 90/ -90 degrees to 60/ -60 degrees. The twist is less sensitive to changes in contractility and ventricular geometry. These findings provide a basis for interpreting measurements of ventricular torsion in the clinical setting. PMID:9147971
Einstein manifolds with skew torsion
Ilka Agricola; Ana Cristina Ferreira
2013-02-15
This paper is devoted to the first systematic investigation of manifolds that are Einstein for a connection with skew symmetric torsion. We derive the Einstein equation from a variational principle and prove that, for parallel torsion, any Einstein manifold with skew torsion has constant scalar curvature; and if it is complete of positive scalar curvature, it is necessarily compact and it has finite first fundamental group. The longest part of the paper is devoted to the systematic construction of large families of examples. We discuss when a Riemannian Einstein manifold can be Einstein with skew torsion. We give examples of almost Hermitian, almost metric contact, and G2 manifolds that are Einstein with skew torsion. For example, we prove that any Einstein-Sasaki manifold and any 7-dimensional 3-Sasakian manifolds admit deformations into an Einstein metric with parallel skew torsion.
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.
[Management of neonatal testicular torsion].
Mor, Y; Leibovitch, I; Golomb, J; Klavir, S; Jonas, P
1992-09-01
Neonatal testicular torsion is rare, and is distinguished both clinically and anatomically from torsion in the older age group. We describe 2 cases of neonatal torsion treated in different ways, which reflect the current controversy regarding the timing of surgical exploration, the need for orchiectomy, as well as the indications for contralateral orchiopexy. The distinction between prenatal and the postnatal subgroups is emphasized and a policy of treatment is proposed. PMID:1427475
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.
NASA Astrophysics Data System (ADS)
Raoult, M.; Jungen, Ch.
1981-03-01
Multichannel quantum defect theory has been used to calculate the effect of vibrational preionization on the total and partial oscillator strength distributions and photoelectron angular distribution in H2 for excitation between 790 and 760 Å. The total oscillator-strength distribution obtained agrees well with the high-resolution photoionization data of Dehmer and Chupka. The partial oscillator strength resonance profiles are predicted to have different shapes in different vibrational ionization channels, while their widths change little with channel. The preionization resonances are also predicted to affect the angular distribution asymmetry parameters b over a broader range than they affect the oscillator strength distribution. The gross features of the preionization resonances are discussed in terms of approximate solutions of the MQD equations.
Randall-Sundrum scenario with bulk dilaton and torsion
Mukhopadhyaya, Biswarup; Sen, Somasri; SenGupta, Soumitra
2009-06-15
We consider a string-inspired torsion-dilaton-gravity action in a Randall-Sundrum braneworld scenario and show that, in an effective four-dimensional theory on the visible brane, the rank-2 antisymmetric Kalb-Ramond field (source of torsion) is exponentially suppressed. The result is similar to our earlier result in [B. Mukhopadhyaya, S. Sen, and S. SenGupta, Phys. Rev. Lett. 89, 121101 (2002); Phys. Rev. Lett. 89, 259902(E) (2002)], where no dilaton was present in the bulk. This offers an explanation of the apparent invisibility of torsion in our space-time. However, in this case the trilinear couplings {approx}TeV{sup -1} between the dilaton and torsion may lead to new signals in TeV-scale experiments, bearing the stamp of extra warped dimensions.
Torsion Effects in Braneworld Scenarios
J. M. Hoff da Silva; R. da Rocha
2009-12-28
We present gravitational aspects of braneworld models endowed with torsion terms both in the bulk and on the brane. In order to investigate a conceivable and measurable gravitational effect, arising genuinely from bulk torsion terms, we analyze the variation in the black hole area by the presence of torsion. Furthermore, we extend the well known results about consistency conditions in a framework that incorporates brane torsion terms. It is shown, in a rough estimate, that the resulting effects are generally suppressed by the internal space volume. This formalism provides manageable models and their possible ramifications into some aspects of gravity in this context, and cognizable corrections and physical effects as well.
The Dynamics and Excitation of Torsional Waves in Geodynamo Simulations
NASA Astrophysics Data System (ADS)
Jones, C. A.; Teed, R.; Tobias, S.
2013-12-01
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 Alfven 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 travel times of 4 to 6 years. 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 torsional oscillations.
Quaternionic analytic torsion Kai K"ohler
KÃ¶hler, Kai
Quaternionic analytic torsion Kai K We define an (equivariant) quaternionic analytic torsion for anti- selfdual vector bundles on quaternionic K"ahler manifolds, using ideas by Leung and Yi. We compute this torsion for vector bundles
Derivation of Einstein-Cartan theory from general relativity
NASA Astrophysics Data System (ADS)
Petti, Richard
2015-04-01
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 the late 20th century, the consensus view was that Einstein-Cartan theory requires inclusion of torsion without adequate justification, it has no empirical support (though it doesn't conflict with any known evidence), it solves no important problem, and it complicates gravitational theory with no compensating benefit. In 1986 the author published a derivation of Einstein-Cartan theory from general relativity, with no additional assumptions or parameters. Starting without torsion, Poincaré symmetry, classical or quantum spin, or spinors, it derives torsion and its relation to spin from a continuum limit of general relativistic solutions. The present work makes the case that this computation, combined with supporting arguments, constitutes a derivation of Einstein-Cartan theory from general relativity, not just a plausibility argument. This paper adds more and simpler explanations, more computational details, correction of a factor of 2, discussion of limitations of the derivation, and discussion of some areas of gravitational research where Einstein-Cartan theory is relevant.
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)
Manipulating torsional motions of soft dielectric tubes
NASA Astrophysics Data System (ADS)
Shmuel, Gal
2015-05-01
Tubular dielectric elastomers function as actuators by application of a radial voltage difference. This work demonstrates how the applied electric field can be exploited to manipulate their torsional motion. The approach employed considers torsional elastic waves superposed on a finitely deformed configuration, which depends on bias electromechanical loadings. The theory of nonlinear electroelasticity is utilized to derive the corresponding governing equations. These are analyzed analytically and numerically, as functions of the thickness of the tube, the mechanical constraints, and most importantly the applied voltage. The analysis shows how dispersive waves beyond a certain length are filtered across a frequency band, and are significantly accelerated above it. This phenomenon observed to strongly depend on the applied voltage, in a non-linear manner.
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.
The effects of shoes on the torsion and rearfoot motion in running.
Stacoff, A; Kälin, X; Stüssi, E
1991-04-01
Excessive pronation is accepted as a good indicator for various running injuries. The least amount of pronation takes place when running barefoot. The latest investigations show that this is connected to a large torsional movement between forefoot and rearfoot which can be influenced by the shoe sole construction. The shoes which are in use among runners in track and field are basically of two types, running shoes (in general torsionally stiff) and spikes (torsionally flexible). The possibly varying effect of these shoes on the shoe/foot motion in running is not known. The purpose of this investigation was therefore to show whether the pronation angle and the torsion angle differ when running barefoot, with spikes, and with running shoes (forefoot touchdown, N = 9 left and right). A film analysis provided the angular movements of the lower leg, rearfoot, and forefoot as well as pronation and torsion in the frontal plane. The results show that at touchdown the torsional movements with both shoe types are quite different from those of running barefoot. With shoes, the torsion angle is reduced back to zero--with running shoes more than with spikes--and the pronation angle is increased beyond the barefoot values (P less than 0.01). In order to reduce the risk of injury, both shoe types should be improved--the running shoes with respect to torsion and the spikes with respect to pronation. PMID:1676133
NASA Astrophysics Data System (ADS)
Coppi, B.
2007-11-01
Differentially rotating structures in the prevalent field of a central object have been shown to develop a ``crystal'' magnetic structure resulting from toroidal internal currents and leading to the formation of density ring sequencesootnotetextB. Coppi and F. Rousseau, Ap. J. 641, 458 (2006) rather than disks. Poloidal current densities with appropriate symmetries are found to be connected with angular momentum transport processes represented by an effective viscosity. Jets are suggested to consist of a series of stable ``smoke- rings'' ejected vertically in opposite directions from the central region of the considered ring sequence. A small inward flow velocity is shown to induce a spiral pattern in the magnetic field lines on a selected family of magnetic surfaces. The accretion theoryootnotetextB. Coppi, Nuc. Fus. 42, 1 (2002) of the spontaneous rotation phenomenon in toroidal laboratory plasmas relies on the ejection of angular momentum toward the surrounding material wall, by collisional ballooning modes excited at the edge, whose phase velocity depends on collisionality. The resulting recoil gives rise to the rotation of the main body of the plasma column as other plasma modes (called VTG) provide the needed inward transport of angular momentum. *Sponsored in part by the US D.O.E.
... condition also may have problems with: Iron deficiency Vitamin B12 deficiency Folate deficiency Drooping of the corners of the mouth caused by dentures that do not adequately support the facial musculature Signs and Symptoms Angular cheilitis can be found in the corners ...
ERIC Educational Resources Information Center
Shakur, Asif; Sinatra, Taylor
2013-01-01
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…
Tree level Leptogenesis from Kalb-Ramond Torsion Background
de Cesare, M; Sarkar, Sarben
2014-01-01
The effect of torsion in theories of quantum gravity is known to be well described by an axion-like field which couples to matter as well as to gravitation and radiation gauge fields. In this note we consider a particular kind of torsion, arising from the Kalb-Ramond antisymmetric tensor field that appears in the gravitational multiplet of string theory. We investigate the implications for leptogenesis. It is shown that leptogenesis can occur even at tree-level and with only one generation of right-handed Majorana neutrinos, due to CP and CPT violation introduced by the background geometry.
Spherically Symmetric Geometries in and Gravitational Theories
NASA Astrophysics Data System (ADS)
Nashed, Gamal G. L.
2015-05-01
Using the well know relation between Ricci scalar, , and torsion scalar, , that is, , we show that, for any spherically symmetric spacetime whose (i) scalar torsion vanishing, that is, or (ii) total derivative term, that is, with is the contraction of the torsion, vanishing, or (iii) the combination of scalar torsion and total derivative term vanishing, could be solution for and gravitational theories.
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.
The torsional strength of wings
NASA Technical Reports Server (NTRS)
Burgess, C P
1930-01-01
This report describes a simple method for calculating the position of the elastic axis of a wing structure having any number of spars. It is shown that strong drag bracing near the top and bottom of a wing greatly increases the torsional strength. An analytical procedure for finding the contribution of the drag bracing to the torsional strength and stiffness is described, based upon the principle of least work, and involving only one unknown quantity. A coefficient for comparing the torsional rigidity of different wings is derived in this report.
A Meter Stick Torsion Oscillator
NASA Astrophysics Data System (ADS)
Taylor, Ken; Atieno, Chris; O'Brien, Shannon; Stewart, Ben
2008-03-01
This paper discusses a simple experiment in which torsion oscillations are set up in a pivoted meter stick that is balanced by a weight on one side of the axis of rotation and a stretched spring on the other side. By varying the torques applied to the mass-meter-stick-spring system, a non-conventional torsion oscillator can be studied and an expression for the effective torsion constant derived from application of Newton's second law. A rotary motion sensor serves as the axis about which the oscillating rotations occur.
Totenhofer, A J; Noli, C; Connor, J N L
2010-08-21
The differential cross section (DCS) for the I + HI(v(i) = 0, j(i) = 0) --> IH(v(f) = 0, j(f) = 2) + I reaction at a translational energy of 21.3 meV is studied, where v(i), j(i) and v(f), j(f) are vibrational, rotational quantum numbers for the initial and final states respectively. We apply new theoretical developments (since 2001) in nearside-farside (NF) theory to provide insights into intricate oscillatory structures in its DCS. It is shown that a simple physically-meaningful parameterization of the scattering (S) matrix, using a background Gaussian term plus a single Regge pole and a quadratic phase, can reproduce, in the forward and sideward directions, the intricate angular scattering obtained from numerical S matrix elements computed from a quantum Born-Oppenheimer-Centrifugal-Sudden scattering technique. This encouraging result suggests that many S matrix elements obtained from computer-intensive calculations can be parameterized in a similar physically-meaningful way. The manner in which the full and NF DCSs change when the Regge pole becomes progressively less important compared to the Gaussian term is also investigated. We report the first application to reactive scattering of the Hatchell NF decomposition, including resummations of the Legendre partial wave series for the scattering amplitude. The Hatchell NF resummed DCSs are compared with the corresponding Fuller NF resummed DCSs for resummation orders of r = 0, 1, 2 and 3. We find that the Fuller NF decomposition always provides a better physical interpretation of the angular scattering. Resummation usually cleans the NF DCSs of unphysical oscillations, especially in the farside (F) DCSs, with the greatest cleaning effect on going from no resummation (r = 0) to first order resummation (r = 1). Identities are derived which relate the Fuller and Hatchell NF subamplitudes for resummation orders, r > 0, to the NF unresummed subamplitudes, r = 0. These identities help us understand the origin of unexpected peaks, which sometimes appear in NF resummed DCSs, together with a simple procedure to remove them. We report Local Angular Momentum (LAM) and DCS x LAM (CLAM) analyses of the angular scattering for r = 0 and r = 1 using the Fuller NF decomposition. The LAM and CLAM analyses provide complementary (yet consistent) information to that obtained from the NF resummed DCSs. It is shown that the "l window representation", as used to analyse elastic scattering in the presence of strong absorption, is a special case of the general resummation theory developed in this paper. PMID:20498904
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.
Transverse angular momentum of photons
Aiello, Andrea
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.
Transverse angular momentum of photons
Andrea Aiello; Christoph Marquardt; Gerd Leuchs
2010-03-04
We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasi-paraxial 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.
Constraining spacetime torsion with LAGEOS
NASA Astrophysics Data System (ADS)
March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone
2011-11-01
We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We analyze the 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. In the cases of autoparallel and extremal trajectories, we derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of Celestial Mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter. 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 complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters.
Quick phases control ocular torsion during smooth pursuit.
Hess, Bernhard J M; Thomassen, Jakob S
2011-11-01
One of the open questions in oculomotor control of visually guided eye movements is whether it is possible to smoothly track a target along a curvilinear path across the visual field without changing the torsional stance of the eye. We show in an experimental study of three-dimensional eye movements in subhuman primates (Macaca mulatta) that although the pursuit system is able to smoothly change the orbital orientation of the eye's rotation axis, the smooth ocular motion was interrupted every few hundred milliseconds by a small quick phase with amplitude <1.5° while the animal tracked a target along a circle or ellipse. Specifically, during circular pursuit of targets moving at different angular eccentricities (5°, 10°, and 15°) relative to straight ahead at spatial frequencies of 0.067 and 0.1 Hz, the torsional amplitude of the intervening quick phases was typically around 1° or smaller and changed direction for clockwise vs. counterclockwise tracking. Reverse computations of the eye rotation based on the recorded angular eye velocity showed that the quick phases facilitate the overall control of ocular orientation in the roll plane, thereby minimizing torsional disturbances of the visual field. On the basis of a detailed kinematic analysis, we suggest that quick phases during curvilinear smooth tracking serve to minimize deviations from Donders' law, which are inevitable due to the spherical configuration space of smooth eye movements. PMID:21715669
Twisted ultrathin silicon nanowires: A possible torsion electromechanical nanodevice
NASA Astrophysics Data System (ADS)
Garcia, J. C.; Justo, J. F.
2014-11-01
Nanowires have been considered for a number of applications in nanometrology. In such a context, we have explored the possibility of using ultrathin twisted nanowires as torsion nanobalances to probe forces and torques at molecular level with high precision, a nanoscale system analogous to the Coulomb's torsion balance electrometer. In order to achieve this goal, we performed a first-principles investigation on the structural and electronic properties of twisted silicon nanowires, in their pristine and hydrogenated forms. The results indicated that wires with pentagonal and hexagonal cross-sections are the thinnest stable silicon nanostructures. Additionally, all wires followed a Hooke's law behavior for small twisting deformations. Hydrogenation leads to spontaneous twisting, but with angular spring constants considerably smaller than the ones for the respective pristine forms. We observed considerable changes on the nanowire electronic properties upon twisting, which allows to envision the possibility of correlating the torsional angular deformation with the nanowire electronic transport. This could ultimately allow a direct access to measurements on interatomic forces at molecular level.
Torsion of a visceroptosed spleen.
Shende, A; Lanzkowsky, P; Becker, J
1976-01-01
Torsion of the pedicle of a visceroptosed spleen, a rare condition, was diagnosed preoperatively in a 4-year-old girl, with the aid of history, physical examination, blood smear findings, splenic scans with technetium Tc 99m sulfur colloid, and selective angiography. A splenectomy was performed, and the child made an uneventful recovery. This case report illustrates some of the diagnostic and therapeutic considerations pertaining to torsion of the spleen. PMID:1247005
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.
Attard, Phil
Calibration of the torsional spring constant and the lateral photodiode response of frictional simultaneously calibrates the photodiode response to the angular deflection of the cantilever. It does not rely and with an independent measurement of the angle calibration. This nondestructive calibration may be performed with any
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.
Luca Susmel; David Taylor
2010-01-01
This paper is concerned with a novel reformulation of the Theory of Critical Distances (TCD) suitable for estimating static strength of notched ductile materials subjected to multiaxial loading. The main feature of the method proposed and validated here is that the static assessment is performed by directly post-processing the linear-elastic stress fields in the vicinity of crack initiation sites. In
Ghader Rezazadeh; Faraz Khatami; Ahmadali Tahmasebi
2006-01-01
In this paper the electromechanical behavior of a torsional micromirror was investigated using of a static model with considering torsion and bending characteristics of micro-beams. A set of nonlinear equations based on the parallel plate capacitor model was derived to represent the relationships between the applied voltage, torsion angle, and vertical displacement of the torsional micromirror. Step by Step Linearization
Torsional Carbon Nanotube Artificial Muscles
NASA Astrophysics Data System (ADS)
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.
2011-10-01
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.
Torsion bar antenna in the proper reference frame with rotation
Nakamura, Kouji
2014-01-01
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.
Tibiofibular torsion in congenital clubfoot.
Farsetti, Pasquale; Dragoni, Massimiliano; Ippolito, Ernesto
2012-01-01
Tibiofibular torsion was measured by computed tomography in three series of patients affected by congenital clubfoot who were treated with different protocols. The normal leg of unilateral deformities served as the control. For the bilateral cases, only the right side was included in the study. The angle between the bicondylar axis of the tibia and the bimalleolar axis was the index of tibiofibular torsion. There were 34 clubfeet in the first series, treated with a posteromedial release, and 40 clubfeet in the second series, treated with a modified Ponseti method, whereas the third series included 16 clubfeet, treated with the original Ponseti method. All 90 clubfeet were graded at birth as group 3 according to the Manes classification. No patient had previous treatment. The patients of the first and the second series were followed up to maturity, whereas the patients of the third series were followed up to a maximum of 11 years of age. In the congenital clubfoot, the tibia and the fibula were externally rotated, in comparison with the normal leg; in fact, the average value of the angle of tibiofibular torsion was 32.2° in the first series, 23.9° in the second series, and 21.1° in the third series. In the normal tibiae, the average value of the angle of tibiofibular torsion was 21.4°. The difference between the first series and the normal controls was statistically significant, as was the difference between the first one and the other two series. The value of the tibiofibular torsion angle seems to be related to the manipulation technique used to treat clubfoot: when the manipulation does not allow a progressive eversion of the talus underneath the calcaneus, the external tibial torsion increases. At follow-up, an intoeing gait was present in seven treated clubfeet of the first series. In all of them except one, the highest value of the external tibial torsion angle was observed, with a low value of the Kite's angle and/or residual forefoot adduction. In the treated congenital clubfoot, persistent intoeing is not related to the angle of tibial torsion but rather to the amount of correction of calcaneal inversion and residual forefoot adduction. PMID:22027706
Optical activity caused by torsion stresses: the case of NaBi(MoO4)2 crystals.
Vasylkiv, Yuriy; Kvasnyuk, Oleksiy; Shopa, Yaroslav; Vlokh, Rostyslav
2013-05-01
We have found that torsion mechanical stresses induce the optical rotation effect in centrosymmetric NaBi(MoO4)2 crystals. We have suggested a description of the effect on the basis of nonlocal linear elasticity theory. It has been shown that the induced optical gyration is proportional to the stress gradient appearing due to the torsion. PMID:23695320
Torsion Balance Investigation of the Casimir Effect
G. Rajalakshmi
2008-05-08
The presence of finite energy in quantum vacuum has profound implications to physics at the microscopic and macroscopic levels. One of the direct consequences of vacuum energy is the Casimir Force, which is a force of attraction experienced by a pair of infinite planar conductive plates placed in vacuum. Experiments to measure Casimir force have been carried out since the 1950s. This thesis presents a measurement of Casimir force between a flat and a spherical conducting surface using a torsion balance for separations in the range of 1 micron to 8 micron. The details of the construction of the torsion balance apparatus, the experimental procedure and the analysis to obtain the Casimir force as a function of separation are described. There are indications of the finite temperature effects which become important for separations greater than ~ 3microns. The combined import of this experiment with others at shorter distances is to favor the finite temperature theory of Casimir forces. The contributions of this experiment towards bounding the strength of inverse square law short-range violating interactions are presented.
Electrothermally-Actuated Micromirrors with Bimorph Actuators—Bending-Type and Torsion-Type
Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che
2015-01-01
Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively. PMID:26110409
Electrothermally-Actuated Micromirrors with Bimorph Actuators-Bending-Type and Torsion-Type.
Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che
2015-01-01
Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively. PMID:26110409
Weak Forces and Neutrino Oscillations under the standards of Hybrid Gravity with Torsion
Salvatore Capozziello; Luca Fabbri; Stefano Vignolo
2013-11-06
We present a unifying approach where weak forces and neutrino oscillations are interpreted under the same standards of torsional hybrid gravity. This gravitational theory mixes metric and metric-affine formalism in presence of torsion and allows to derive an effective scalar field which gives rise to a running coupling for Dirac matter fields. In this picture, two phenomena occurring at different energy scales can be encompassed under the dynamics of such a single scalar field, which represents the further torsional and curvature degrees of freedom.
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.
Les torsions sur testicules cryptorchides
Gharbi, Mohamed; Amri, Najmeddine; Chambeh, Wahib; Braiek, Salem; Kamel, Rafik El
2010-01-01
Résumé But : La cryptorchidie est une pathologie assez fréquente en urologie. Elle est associée à un risque élevé d’infertilité et de dégénérescence. Elle semble aussi être associée à un risque important de torsion. Cette entité est très peu abordée dans la littérature. Nous rapportons tous les cas de torsion sur testicule cryptorchide observés à notre service dans le but de mieux caractériser cette pathologie et de réduire ainsi le taux d’orchidectomies. Méthodologie : Il s’agit d’une étude rétrospective portant sur tous les cas de torsion sur testicule cryptorchide opérés dans notre service d’urologie entre 1999 et 2007. Les patients ont fait l’objet d’une description basée sur le résumé de leurs observations. Résultats : Les patients étaient âgés de 7 mois à 39 ans. La torsion touchait le testicule droit dans 53 % des cas. Le tableau clinique comportait une douleur au niveau de la région inguinale d’apparition soudaine avec une masse sous-cutanée inflammatoire et douloureuse à ce niveau et surtout un hémiscrotum homolatéral vide. Dans 60 % des cas, le diagnostic était tardif et une orchidectomie a été réalisée. Dans les autre cas, un abaissement du testicule a été réalisé avec orchidopexie controlatéral dans le même temps opératoire. Conclusion : Bien qu’il s’agisse d’une pathologie peu courante, la torsion sur testicule cryptorchide doit être étudiée davantage. Le diagnostic précoce permettra de sauver et d’abaisser le testicule et faciliter ainsi le dépistage d’une éventuelle dégénérescence. PMID:21191497
Excitation and dissipation of torsional modes in solar photospheric magnetic flux tubes
NASA Astrophysics Data System (ADS)
Luo, Q. Y.; Wei, F. S.; Feng, X. S.
2002-11-01
The turbulent excitation of torsional Alfvén waves is presented on the basis of Lighthill-Stein theory. Due to the special properties of torsional modes, we can apply the theory to the inhomogeneous magnetic flux tube embedded in the solar photosphere, to evaluate the wave energy generated from the turbulent source in the convection zone. Torsional wave spectrum distribution along the r coordinate is achieved. In order to estimate the net wave energy transported to the chromosphere, we investigate the wave propagation and dissipation in the photospheric flux tube by simple phase mixing due to the inhomogeneity. Results for several cases with different model parameters are compared. Conclusions are drawn on the significant role of the energy carried by torsional Alfvén waves in the chromospheric and coronal heating, and the wave spectrum may be helpful in understanding the problem of footpoint azimuthal motion of coronal loops.
Simultaneous normal and torsional force measurement by cantilever surface contour analysis
NASA Astrophysics Data System (ADS)
Kumanchik, Lee; Schmitz, Tony; Pratt, Jon
2011-05-01
This study presents an alternative to the current Hooke's law-based force relation between rectangular cantilever deflection and applied force. In the new approach, a transduction constant is presented that (1) includes no cross-talk between torsion and normal force components, (2) is independent of the load application point, and (3) does not depend on the cantilever beam length. Rather than measuring the cantilever deformation at a single point (such as the tip location), it is measured at multiple adjacent points using scanning white light interferometry to provide a three-dimensional description of the cantilever deformation during loading. This measurement, processed by a force relation based on a superposition of deflections derived from Euler-Bernoulli bending theory and St Venant's torsion theory, provides the vertical, axial, and torsional force components simultaneously. Experimental results are compared to force predictions for the vertical and torsional components using macro-scale cantilevers under mass loading. An uncertainty analysis is also provided.
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.
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.
On determining G using a cryogenic torsion pendulum
NASA Astrophysics Data System (ADS)
Newman, R. D.; Bantel, M. K.
1999-06-01
A measurement of G which will use a torsion pendulum in the `dynamic' (time-of-swing) mode, measuring the influence of field source masses on the pendulum's oscillation period, is being prepared at UC Irvine. Features of the design include: (i) operation at cryogenic temperature (2 K) to reduce thermal noise and increase frequency stability and for ease of magnetic shielding, (ii) large pendulum oscillation amplitudes to increase signal-to-noise ratio and reduce the effect of amplitude-determination error, (iii) use of a pair of source mass rings to produce an extremely uniform field gradient; and (iv) use of a thin quartz plate as a torsion pendulum to minimize sensitivity to pendulum density inhomogeneity and dimensional uncertainties. The `dynamic' method to be used has the great advantage of requiring no angular displacement measurement or calibrating force, but, as pointed out by Kuroda, the method is subject to systematic error associated with the anelastic properties of a torsion fibre. We demonstrate that, for the linear anelasticity discussed by Kuroda, the fractional error introduced by anelasticity in such measurements of G is bounded by 0icons/Journals/Common/le" ALT="le" ALIGN="TOP"/>icons/Journals/Common/delta" ALT="delta" ALIGN="TOP"/> G/Gicons/Journals/Common/le" ALT="le" ALIGN="TOP"/> 1/2 Q-1, where Q is the torsional oscillation quality factor of the pendulum. We report detailed studies of anelasticity in candidate fibre materials at low temperature, concluding that anelastic behaviour should not limit our G measurement at a level of a few ppm.
Exact solutions in 3D gravity with torsion
NASA Astrophysics Data System (ADS)
González, P. A.; Vásquez, Yerko
2011-08-01
We study the three-dimensional gravity with torsion given by the Mielke-Baekler (MB) model coupled to gravitational Chern-Simons term, and that possess electric charge described by Maxwell-Chern-Simons electrodynamics. We find and discuss this theory's charged black holes solutions and uncharged solutions. We find that for vanishing torsion our solutions by means of a coordinate transformation can be written as three-dimensional Chern-Simons black holes. We also discuss a special case of this theory, Topologically Massive Gravity (TMG) at chiral point, and we show that the logarithmic solution of TMG is also a solution of the MB model at a fixed point in the space of parameters. Furthermore, we show that our solutions generalize Gödel type solutions in a particular case. Also, we recover BTZ black hole in Riemann-Cartan spacetime for vanishing charge.
Orbital angular momentum in phase space
Rigas, I.; Sanchez-Soto, L.L.; Klimov, A.B.; Rehacek, J.; Hradil, Z.
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.
Electric field in 3D gravity with torsion
M. Blagojevi?; B. Cvetkovi?
2008-09-01
It is shown that in static and spherically symmetric configurations of the system of Maxwell field coupled to 3D gravity with torsion, at least one of the Maxwell field components has to vanish. Restricting our attention to the electric sector of the theory, we find an interesting exact solution, corresponding to the azimuthal electric field. Its geometric structure is to a large extent influenced by the values of two different central charges, associated to the asymptotic AdS structure of spacetime.
[Torsion of the pregnant uterus].
Ilic, V
1976-01-01
Torsion of a 6-month gravid uterus in a secundigravida, showing the clinical shape of an acute abdomen and shock, is described. The uterus was twisted 180 degrees from left to right, with a retroplacental haematoma and dead foetus. The symptoms occurred while the patient was sleeping. Sectio caesarea was performed and no other pathologic changes were found in the uterus, ovaries, or minor pelvis. PMID:1027930
Modeling slender viscoelastic jets and fibers with torsion
Cao, J.
1992-01-01
All thin-filament models to date are torsionless and consider only leading-order approximations in a slender asymptotic sense. This dissertation first presents a higher-order perturbation theory for slender viscoelastic jets and fibers, which allows full consideration of axisymmetric torsion. It then illustrates the practical applications of this higher-order perturbation theory through four practical examples. The steady equations through three orders for all four examples are solved to illustrate several points: (1) it is necessary to go to the higher-order corrections in order to check the leading-order approximation or to consider the torsional coupling; (2) many leading-order steady solutions are asymptotically valid and robust to neglected higher-order physical effects (the higher-order corrections are computed and found being small); (3) other leading-order solutions are invalid in the presence of higher-order effects; specifically, it is shown that corrections due to weak elastic relaxation can be as large as the Newtonian leading-order approximation; (4) it is straightforward using this higher-order perturbation theory to determine if a particular leading-order solution is a valid approximation of physical behavior; (5) torsion can have effect on both the mathematical structure of the model and higher-order corrections of the leading-order approximations.
Spin Quantum Number or Rest Angular Momentum
H. Razmi; A. MohammadKazemi
2013-08-01
Considering the fundamental origins of Klein-Gordon and Dirac equations, Thomas precession, and the photon spin, it is clear that the origin of spin angular momentum refers to relativity than quantum theory; so, when introducing spin, it is better to know it as rest angular momentum than as an intrinsic quantum quantity.
Ganatra, Nirmal Kirtikumar
2004-09-30
Torsional vibration is an oscillatory angular twisting motion in the rotating members of a system. It can be deemed quite dangerous in that it cannot be detected as easily as other forms of vibration, and hence, subsequent failures that it leads...
Newman, Riley D.
's environment, using a charcoal "cryopump" near the pendulum to supplement an ion pump operating at room is the angular orientation of the pendulum relative to a field source and the peak torque is N0 = pca. Here pc materials. The ratio of the torque amplitude pca to the pendulum's torsion constant gives a dimensionless
Ghader Rezazadeh; Faraz Khatami; Ahmadali Tahmasebi
2007-01-01
In this paper the electromechanical behavior of a torsional micromirror was investigated using of a static model with considering\\u000a torsion and bending characteristics of micro-beams. A set of nonlinear equations based on the parallel plate capacitor model\\u000a was derived to represent the relationships between the applied voltage, torsion angle, and vertical displacement of the torsional\\u000a micromirror. Step by step linearization
An analysis of traction drive torsional stiffness
NASA Technical Reports Server (NTRS)
Rohn, D. A.; Loewenthal, S. H.
1983-01-01
The tangential compliance of elastic bodies in concentrated contact applied to traction drive elements to determine their torsional stiffness was analyzed. Static loading and rotating conditions are considered. The effects of several design variables are shown. The theoretical torsional stiffness of a fixed ratio multiroller drive is computed and compared to experimental values. It is shown that the torsional compliance of the traction contacts themselves is a relatively small portion of the overall drive system compliance.
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.
J.-M. Huang; A. Q. Liu; Z. L. Deng; Q. X. Zhang; J. Ahna; A. Asundi
2004-01-01
A general theoretical model using the coupling effect between the torsion and bending is presented in this paper, which characterizes the static properties of the electrostatic torsional micromirror, especially its pull-in effect. A set of normalized equations governing the static actuation properties of the torsional micromirror based on the parallel plate capacitor model is derived to demonstrate the relationships between
Twisted torsion invariants and link concordance
Cha, Jae Choon
2010-01-01
The twisted torsion of a 3-manifold is well-known to be zero whenever the corresponding twisted Alexander module is non-torsion. Under mild extra assumptions we introduce a new twisted torsion invariant which is always non-zero. We show how this torsion invariant relates to the twisted intersection form of a bounding 4-manifold, generalizing a theorem of Milnor. Using this result, we give new obstructions to 3-manifolds being homology cobordant and to links being concordant. These obstructions are sufficiently strong to detect that the Bing double of the figure eight knot is not slice.
Hidden torsion, 3-manifolds, and homology cobordism
Cha, Jae Choon
2011-01-01
This paper continues our exploration of homology cobordism of 3-manifolds using our recent results on Cheeger-Gromov rho-invariants associated to amenable representations. We introduce a new type of torsion in 3-manifold groups we call hidden torsion, and an algebraic approximation we call local hidden torsion. We construct infinitely many hyperbolic 3-manifolds which have local hidden torsion in the transfinite lower central subgroup. By realizing Cheeger-Gromov invariants over amenable groups, we show that our hyperbolic 3-manifolds are not pairwise homology cobordant, yet remain indistinguishable by any prior known homology cobordism invariants.
Torsion and supersymmetry breaking
NASA Astrophysics Data System (ADS)
Lawrence, Albion; Sander, Tobias; Schulz, Michael B.; Wecht, Brian
2008-07-01
We identify the auxiliary fields in the hypermultiplets of type IIB string theory compactified on a Calabi-Yau manifold, using a combination of worldsheet and supergravity techniques. The SUSY-breaking squark and gaugino masses in type IIB models depend on these auxiliary fields, which parametrize deformations away from a pure Calabi-Yau compactification to one with NS-NS 3-form flux and SU(3) × SU(3) structure. Worldsheet arguments show that such compactifications are generically globally nongeometric. Our results, combined with earlier results for type IIA compactifications, imply that these deformations are the mirrors of NS-NS 3-form flux, in accord with work from the supergravity point of view. Using the worldsheet current algebra, we explain why mirror symmetry may continue to hold in the presence of fluxes breaking the symmetries (e.g., (2,2) SUSY) on which mirror symmetry is typically taken to depend. Finally, we give evidence that nonperturbative worldsheet effects (such as worldsheet instantons) provide important corrections to the supergravity picture in the presence of auxiliary fields for Kähler moduli.
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...
Vertical, horizontal, and torsional eye movement responses to head roll in the squirrel monkey
S. H. Seidman; L. Telford; G. D. Paige
1995-01-01
The vestibulo-ocular reflex (VOR) serves to stabilize images on the retina by rotating the eyes in the direction which opposes angular (aVOR) or linear (1VOR) head movement. The aVOR responds to rotations in any plane. Head rotations about the naso-occipital axis (roll) are accompanied by compensatory torsional eye movements, with gains typically less than 0.7. However, geometric considerations suggest that
A Novel Permanent Magnetic Angular Acceleration Sensor
Zhao, Hao; Feng, Hao
2015-01-01
Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s?2). Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability. PMID:26151217
Torsional Buckling and Writhing Dynamics of Elastic Cables and DNA
Goyal, S; Perkins, N C; Lee, C L
2003-02-14
Marine cables under low tension and torsion on the sea floor can undergo a dynamic buckling process during which torsional strain energy is converted to bending strain energy. The resulting three-dimensional cable geometries can be highly contorted and include loops and tangles. Similar geometries are known to exist for supercoiled DNA and these also arise from the conversion of torsional strain energy to bending strain energy or, kinematically, a conversion of twist to writhe. A dynamic form of Kirchhoff rod theory is presented herein that captures these nonlinear dynamic processes. The resulting theory is discretized using the generalized-method for finite differencing in both space and time. The important kinematics of cross-section rotation are described using an incremental rotation ''vector'' as opposed to traditional Euler angles or Euler parameters. Numerical solutions are presented for an example system of a cable subjected to increasing twist at one end. The solutions show the dynamic evolution of the cable from an initially straight element, through a buckled element in the approximate form of a helix, and through the dynamic collapse of this helix through a looped form.
NASA Astrophysics Data System (ADS)
Andrews, David L.; Babiker, Mohamed
2012-11-01
Preface D. L. Andrews and M. Babiker; 1. Light beams carrying orbital angular momentum J. B. Götte and S. M. Barnett; 2. Vortex transformation and vortex dynamics in optical fields G. Molina-Terriza; 3. Vector beams in free space E. J. Galvez; 4. Optical beams with orbital angular momentum in nonlinear media A. S. Desyatnikov and Y. S. Kivshar; 5. Ray optics, wave optics and quantum mechanics G. Nienhuis; 6. Quantum formulation of angle and orbital angular momentum J. B. Götte and S. M. Barnett; 7. Dynamic rotational frequency shift I. Bialynicki-Birula and Z. Bialynicka-Birula; 8. Spin-orbit interactions of light in isotropic media K. Y. Bliokh, A. Aiello and M. A. Alonso; 9. Quantum electrodynamics, angular momentum and chirality D. L. Andrews and M. Babiker; 10. Trapping of charged particles by Bessel beams I. Bialynicki-Birula, Z. Bialynicka-Birula and N. Drozd; 11. Theory of atoms in twisted light M. Babiker, D. L. Andrews and V. E. Lembessis; 12. An experimentalist's introduction to orbital angular momentum for quantum optics J. Romero, D. Giovannini, S. Franke-Arnold and M. J. Padgett; 13. Measurement of light's orbital angular momentum M. P. J. Lavery, J. Courtial and M. J. Padgett; 14. Efficient generation of optical twisters using helico-conical beams V. R. Daria, D. Palima and J. Glückstad; 15. Self similar modes of coherent diffusion with orbital angular momentum O. Firstenberg, M. Shuker, R. Pugatch and N. Davidson; 16. Dimensionality of azimuthal entanglement M. van Exter, E. Eliel and H. Woerdman; Index.
Torsion, Scalar Field and f(\\mathcal{R}) Gravity
Prasanta Mahato
2008-02-14
The role of torsion and a scalar field $\\phi$ in gravitation in the background of a particular class of the Riemann-Cartan geometry is considered here. Some times ago, a Lagrangian density with Lagrange multipliers has been proposed by the author which has been obtained by picking some particular terms from the SO(4,1) Pontryagin density, where the scalar field $\\phi$ causes the de Sitter connection to have the proper dimension of a gauge field. Here it has been shown that the divergence of the axial torsion gives the Newton's constant and the scalar field becomes a function of the Ricci scalar $\\mathcal{R}$. The starting Lagrangian then reduces to a Lagrangian representing the metric $f(\\mathcal{R})$ gravity theory.
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.
Possible Generalizations within Braneworld Scenarios: Torsion fields
J M Hoff da Silva; Roldao da Rocha
2010-12-09
In this Chapter we introduce the aspects in which torsion can influence the formalism of braneworld scenarios in general, and also how it is possible to measure such kind of effects, namely, for instance, the blackstring transverse area corrections and variation of quasar luminosity due to those corrections. We analyze the projected effective Einstein equation in a 4-dimensional arbitrary manifold embedded in a 5-dimensional Riemann-Cartan manifold. The Israel-Darmois matching conditions are investigated, in the context where the torsion discontinuity is orthogonal to the brane. Unexpectedly, the presence of torsion terms in the connection does not modify such conditions whatsoever, despite of the modification in the extrinsic curvature and in the connection. Then, by imposing the Z2-symmetry, the Einstein equation obtained via Gauss-Codazzi formalism is extended, in order to now encompass the torsion terms. We also show that the factors involving contorsion change drastically the effective Einstein equation on the brane, as well as the effective cosmological constant. Also, we present gravitational aspects of braneworld models endowed with torsion terms both in the bulk and on the brane. In order to investigate a conceivable and measurable gravitational effect, arising genuinely from bulk torsion terms, we analyze the variation in the black hole area by the presence of torsion. Furthermore, we extend the well known results about consistency conditions in a framework that incorporates brane torsion terms. It is shown, in a rough estimate, that the resulting effects are generally suppressed by the internal space volume.
Gamal G. L. Nashed
2009-10-27
The energy-momentum tensor, which is coordinate independent, is used to calculate energy, momentum and angular-momentum of two different tetrad fields. Although, the two tetrad fields reproduce the same space-time their energies are different. Therefore, a regularized expression of the gravitational energy-momentum tensor of the teleparallel equivalent of general relativity, (TEGR), is used to make the energies of the two tetrad fields equal. The definition of the gravitational energy-momentum is used to investigate the energy within the external event horizon. The components of angular-momentum associated with these space-times are calculated. In spite that we use a static space-times, we get a non-zero component of angular-momentum! Therefore, we derive the killing vectors associated with these space-times using the definition of the Lie derivative of a second rank tensor in the framework of the TEGR to make the picture more clear.
Optically probing torsional superelasticity in spider silks
Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit; Singh, Kamal P.
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
NASA Astrophysics Data System (ADS)
Li, Xin-zhou; Sun, Chang-bo; Xi, Ping
2009-04-01
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 a1 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.
Torsion Profiling of Proteins Using Magnetic Particles
van Reenen, A.; Gutiérrez-Mejía, F.; van IJzendoorn, L.J.; Prins, M.W.J.
2013-01-01
We report a method to profile the torsional spring properties of proteins as a function of the angle of rotation. The torque is applied by superparamagnetic particles and has been calibrated while taking account of the magnetization dynamics of the particles. We record and compare the torsional profiles of single Protein G-Immunoglobulin G (IgG) and IgG-IgG complexes, sandwiched between a substrate and a superparamagnetic particle, for torques in the range between 0.5 × 103 and 5 × 103 pN·nm. Both molecular systems show torsional stiffening for increasing rotation angle, but the elastic and inelastic torsion stiffnesses are remarkably different. We interpret the results in terms of the structural properties of the molecules. The torsion profiling technique opens new dimensions for research on biomolecular characterization and for research on bio-nanomechanical structure-function relationships. PMID:23473490
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.
Some solutions with torsion in Chern-Simons gravity and observable effects
F. Canfora
2008-07-02
It is shown that in all odd dimensional Chern-Simons theories states in which the torsion is non zero (but it can approach smoothly to zero outside suitable regions) do exist. Some possible observational effects related to neutrino oscillations are pointed out. In the theory of continuum media (in which suitable defects can be described by localized non vanishing torsion) "the gravitational intuition" is a rather useful tool to describe the physical effects of such defects. A possible astrophysical application is shortly described.
Transverse and longitudinal angular momenta of light
NASA Astrophysics Data System (ADS)
Bliokh, Konstantin Y.; Nori, Franco
2015-08-01
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 inherent in edge evanescent waves offers robust spin-direction coupling at optical interfaces (the quantum spin Hall effect of light). Second, we overview the transverse orbital angular momenta of light, which can be both extrinsic and intrinsic. These two types of the transverse orbital angular momentum are produced by spatial shifts of the optical beams (e.g., in the spin Hall effect of light) and their Lorentz boosts, respectively. Our review is underpinned by a unified theory of the angular momentum of light based on the canonical momentum and spin densities, which avoids complications associated with the separation of spin and orbital angular momenta in the Poynting picture. It allows us to construct a comprehensive classification of all known optical angular momenta based on their key parameters and main physical properties.
Angular and axial deformities of the legs of children.
McDonough, M W
1984-12-01
Age is often a determining factor in establishing a treatment program for these axial and angular problems. As can be seen, the deformities of torsion are noticeable from early life. Any tibial torsion should be treated early, but an excessive medial range of motion in the infant leg with a corresponding adequate lateral range of motion of the limb may be cautiously observed. Medial femoral torsion is a normal early finding in the infant thigh. The problem becomes evident as the child matures without the corresponding reduction in femoral torsion, leading to a persistence of fetal or infantile alignment. The gait consequences are usually noticed at 4 to 8 years of age. The angular changes generally are a delayed finding noticed in stance. The bowleg may be associated with marked tibial torsion and picked up early but the Blount's patient has been traditionally definable at 2 years of age. Levin and Drennan may hasten the time of diagnosis with their radiographic criteria. Knock-knee is an alignment disturbance noticed during the early to mid-childhood years, age 4 to 8 years. The diagnosis is important, differentiating physiologic from torsion-related deformities, and treatment, if warranted, should not be delayed. Generally the earlier these problems are discovered, the more optimistic the prognosis. Since the pediatric limb is in a constant state of transition, there will be a perpetual argument as to the need or efficacy of various approaches to the problems of knock-knee and bowleg. If observation is the treatment of choice, the percentage of cases which go on to osteotomies and epiphyseal stapling will continue. For those with axial or angular deformities, degenerative arthritis of the knee may be forthcoming. Swanson, Greene, and Allis warned of problems becoming "unphysiologic." If we consider the epiphyseal malleability, not only to deformity but to correction, we can appreciate Lenoir's comment of "every day the problem goes untreated is a golden opportunity lost forever." Early, gentle conservative therapy, using splints and casting, is an approach which should be considered in appropriate early problems. PMID:6536411
Torsion Balance Search for Lorentz-invariance, Dark
Torsion Balance Search for Lorentz-invariance, Dark Energy and Dark Matter Claire Cramer AAPT of unpolarized matter another particle's spin #12;Torsion balances Coulomb's torsion balance: A high precision-plated · magnetically shielded · 4 mirrors 2.6 cm #12;#12;The torsion balance apparatus feet pendulum magnetic shielding
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 MONTALB´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
A study of the static characteristics of a torsional micromirror
X. M. Zhang; F. S. Chau; C. Quan; Y. L. Lam; A. Q. Liu
2001-01-01
Torsional micromirror has been widely used in many applications as diverse as optical communication, laser scanning related and spatial light modulator related applications. In different applications the torsional micromirror may have different arrangements. A general analysis of the static characteristics of the torsional micromirror, especially its snap-down effect, is able to simplify the design of torsional micromirror.This paper describes the
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.
Bovine uterine torsion: 164 hospital referral cases.
Frazer, G S; Perkins, N R; Constable, P D
1996-10-01
Uterine torsion is more common in the cow than any other domestic species. The etiopathogenesis of the condition remains open to speculation. Available hospital referral records of bovine uterine torsions (n = 164) were collated, and additional comparisons for season, age and breed were made using the VDMP data base of 24 North American veterinary schools. There was no effect of season. Brown Swiss cows were at a significantly higher risk (P = 0.0001), while Hereford, Angus, and Jersey cows were at a lower risk for uterine torsion when compared with Holstein-Friesian cows, the largest breed population (P = 0.01). Most cows (81%) were at term. Clinical signs of torsion included fever (23%), tachycardia (93%), tachypnea (94%), straining (23%), anorexia (18%) and vaginal discharge (13%). In 34% of the cases the torsion was precervical, with no vaginal involvement being noted. The severity of the torsion was predominately 180 to 270 degrees (57%) and 271 to 360 degrees (22%). Counter-clockwise torsion was present in 63% of the cases. Vaginal delivery was possible after manual correction (20%) or rolling of the cow (18%). Cesarean section was performed immediately in 35% of the cases, after failed detorsion attempts in 7%, and due to failure of the cervix to dilate following successful correction of the torsion in 20%. Calf birth weights exceeded breed means in 89% of the cases, and a significantly greater proportion (63%) of the fetuses were male. Fetal survival rate was 24% (14% of dead fetuses were emphysematous), and the cow survival rate was 78% (10% were euthanized). The fetal membrane retention rate was 57%. It was found that large term fetuses appear to predispose a cow to uterine torsion. PMID:16727939
Torsional oscillations of strange stars
NASA Astrophysics Data System (ADS)
Mannarelli, Massimo
2014-11-01
Strange stars are one of the hypothetical compact stellar objects that can be formed after a supernova explosion. The existence of these objects relies on the absolute stability of strange collapsed quark matter with respect to standard nuclear matter. We discuss simple models of strange stars with a bare quark matter surface, thus standard nuclear matter is completely absent. In these models an electric dipole layer a few hundreds Fermi thick should exist close to the star surface. Studying the torsional oscillations of the electrically charged layer we estimate the emitted power, finding that it is of the order of 1045 erg/s, meaning that these objects would be among the brightest compact sources in the heavens. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. Although part of the radiated power should be absorbed by the electrosphere surrounding the strange star, a sizable fraction of photons should escape and be detectable.
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.
Partonic orbital angular momentum
NASA Astrophysics Data System (ADS)
Arash, Firooz; Taghavi-Shahri, Fatemeh; Shahveh, Abolfazl
2013-04-01
Ji's decomposition of nucleon spin is used and the orbital angular momentum of quarks and gluon are calculated. We have utilized the so called valon model description of the nucleon in the next to leading order. It is found that the average orbital angular momentum of quarks is positive, but small, whereas that of gluon is negative and large. Individual quark flavor contributions are also calculated. Some regularities on the total angular momentum of the quarks and gluon are observed.
A torsion balance for probing a non-standard force in the sub-micrometre range
Masuda, M; Araya, A
2015-01-01
We report the performance of an instrument that employs a torsion balance for probing a non-standard force in the sub-micrometre range. High sensitivity is achieved by using a torsion balance that has a long torsional period, strong magnetic damping of all vibrational motions and a feedback system that employs an optical lever. In torsion balance experiments, the distance fluctuations during measurements and the accuracy to which the absolute distance is determined are crucial for determining the sensitivity of the balance to a macroscopic force in the sub-micrometre range. We have estimated the root mean square amplitude of the distance fluctuation to be 18 nm by considering the effects due to seismic motions, tilt motions, residual angular fluctuations and thermal fluctuations. We have also estimated the error of the absolute distance to be 13 nm and the statistical error of the force to be 3.4$\\times$10$^{-12}$ N by measuring the electrostatic forces. As a result of this systematic study, we have evaluated...
Torsion in extra dimensions and one-loop observables
NASA Astrophysics Data System (ADS)
Castillo-Felisola, Oscar; Corral, Cristóbal; Kovalenko, Sergey; Schmidt, Iván
2014-07-01
We study gravity with torsion in extra dimensions and derive an effective four-dimensional theory containing four-fermion contact operators at the fundamental scale of quantum gravity in the TeV range. These operators may have an impact on the low-energy observables and can manifest themselves or can be constrained in precision measurements. We calculate possible contributions of these operators to some observables at the one-loop level. We show that the existing precision data on the lepton decay mode of Z boson set limits on the fundamental scale of the gravity and compactification radius, which are more stringent than the limits previously derived in the literature.
Quantum gravity with torsion and non-metricity
NASA Astrophysics Data System (ADS)
Pagani, C.; Percacci, R.
2015-10-01
We study the renormalization of theories of gravity with an arbitrary (torsional and non-metric) connection. The class of actions we consider is of the Palatini type, including the most general terms with up to two derivatives of the metric, but no derivatives of the connection. It contains 19 independent parameters. We calculate the one-loop beta functions of these parameters and find their fixed points. The Holst subspace is discussed in some detail and found not to be stable under renormalization. Some possible implications for ultraviolet and infrared gravity are discussed.
Dislocations and torsion in graphene and related systems
NASA Astrophysics Data System (ADS)
de Juan, Fernando; Cortijo, Alberto; Vozmediano, María A. H.
2010-04-01
A continuum model to study the influence of dislocations on the electronic properties of condensed matter systems is described and analyzed. The model is based on a geometrical formalism that associates a density of dislocations with the torsion tensor and uses the technique of quantum field theory in curved space. When applied to two-dimensional systems with Dirac points like graphene we find that dislocations couple in the form of vector gauge fields similar to these arising from curvature or elastic strain. We also describe the ways to couple dislocations to normal metals with a Fermi surface.
Quantum gravity with torsion and non-metricity
Carlo Pagani; Roberto Percacci
2015-06-09
We study the renormalization of theories of gravity with an arbitrary (torsionful and non-metric) connection. The class of actions we consider is of the Palatini type, including the most general terms with up to two derivatives of the metric, but no derivatives of the connection. It contains 19 independent parameters. We calculate the one loop beta functions of these parameters and find their fixed points. The Holst subspace is discussed in some detail and found not to be stable under renormalization. Some possible implications for ultraviolet and infrared gravity are discussed.
Twirling Elastica: Kinks, Viscous Drag, and Torsional Stress
Stephan A. Koehler; Thomas R. Powers
2000-12-13
Biological filaments such as DNA or bacterial flagella are typically curved in their natural states. To elucidate the interplay of viscous drag, twisting, and bending in the overdamped dynamics of such filaments, we compute the steady-state torsional stress and shape of a rotating rod with a kink. Drag deforms the rod, ultimately extending or folding it depending on the kink angle. For certain kink angles and kink locations, both states are possible at high rotation rates. The agreement between our macroscopic experiments and the theory is good, with no adjustable parameters.
Torsion-induced effects in magnetic nanowires
NASA Astrophysics Data System (ADS)
Sheka, Denis D.; Kravchuk, Volodymyr P.; Yershov, Kostiantyn V.; Gaididei, Yuri
2015-08-01
A magnetic helix wire is one of the simplest magnetic systems which manifests properties of both curvature and torsion. Possible equilibrium magnetization states in the helix wire with different anisotropy directions are studied theoretically. There exist two equilibrium states in the helix wire with easy-tangential anisotropy: a quasitangential magnetization distribution in the case of relatively small curvatures and torsions, and an onion state in the opposite case. The curvature and torsion also essentially influence the spin-wave dynamics in the helix wire, acting as an effective magnetic field. Originated from a geometry-induced effective Dzyaloshinskii interaction, this magnetic field leads to a coupling between the helix chirality and the magnetochirality and breaks mirror symmetry in the spin-wave spectrum: the modification of magnon dispersion relation is linear with respect to the torsion and quadratic with respect to the curvature. All analytical predictions on magnetization statics and dynamics are well confirmed by direct spin-lattice simulations.
Elko Spinor Model with Torsion and Cosmology
NASA Astrophysics Data System (ADS)
Kouwn, Seyen; Lee, Joohan; Lee, Tae Hoon; Oh, Phillial
2013-08-01
We investigate the cosmology of ELKO spinor model when minimal coupling with torsion is included. Unlike the Dirac spinor which interacts only with the totally anti-symmetric components of torsion tensor, we find the interaction of the time component of the trace of torsion tensor with ELKO spinor provides different aspects of cosmology with fermions. We discuss a couple of cases with given potentials of ELKO spinor which can result in interesting cosmological consequences. Especially, we show that there exists an exact cosmological solution in which the universe began its acceleration only recently and this solution is an attractor. This corresponds to specific forms of torsion and potential with a mild fine-tuning which can address the coincidence problem.
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.
Ocular torsion on earth and in weightlessness
NASA Technical Reports Server (NTRS)
Young, L. R.; Lichtenberg, B. K.; Arrott, A. P.; Crites, T. A.; Oman, C. M.; Edelman, E. R.
1981-01-01
Otolith function is studied by means of measurements of ocular torsion under various acceleration environments on earth and in weightlessness. Photographic measurements of ocular torsion as indicated by the rotation of landmarks on the iris with respect to head-fixed fiducial marks were obtained in subjects undergoing horizontal linear acceleration in a ground-based version of the space sled, lateral acceleration from weightlessness during pullout from the free-fall portion of parabolic flight, and optokinetic stimulation about the roll axis in the supine position in the laboratory and during weightlessness. The responses of ocular torsion to horizontal acceleration are in agreement with a simple low-order linear system with a dominant time constant of 0.33 sec, with a transfer function fit by a model with a pure delay of 0 to 400 msec and a first-order lag. In the pullout experiment, torsion was not observed in response to the onset of acceleration in the right-ear-down position, although it was present in response to the lateral stimulus. Results of the roll vection experiments indicate the independence of ocular torsion and visually induced tilt. In addition, an automatic video system using a soft contact lens target is presented which has been developed for ocular torsion measurements.
Calculations of the C(1)?C(?) torsional barrier in styrene. Comparison with experiment
NASA Astrophysics Data System (ADS)
Schaefer, Ted; Penner, Glenn H.
1985-03-01
Computations of the geometry optimized conformational energies of styrene at the STO 3G, 4-21G, and 4-31G levels of molecular orbital theory, bear out vibronic level fluorescence spectra showing a large fourfold component for the internal torsional potential function.
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
NASA Astrophysics Data System (ADS)
Czakó, Gábor
2014-06-01
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(3P) + 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.
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.
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.
CONVERVATION OF ANGULAR MOMENTUM A rotating bicycle wheel has angular
CONVERVATION OF ANGULAR MOMENTUM A rotating bicycle wheel has angular momentum, which is a property a larger angular momentum at a given speed. Angular momentum is characterized by both size and direction momentum. This means that any change in angular momentum within the system must be accompanied by an equal
Strong field coherent control of molecular torsions—Analytical models
NASA Astrophysics Data System (ADS)
Ashwell, Benjamin A.; Ramakrishna, S.; Seideman, Tamar
2015-08-01
We introduce analytical models of torsional alignment by moderately intense laser pulses that are applicable to the limiting cases of the torsional barrier heights. Using these models, we explore in detail the role that the laser intensity and pulse duration play in coherent torsional dynamics, addressing both experimental and theoretical concerns. Our results suggest strategies for minimizing the risk of off-resonant ionization, noting the qualitative differences between the case of torsional alignment subject to a field-free torsional barrier and that of torsional alignment of a barrier-less system (equivalent to a 2D rigid rotor). We also investigate several interesting torsional phenomena, including the onset of impulsive alignment of torsions, field-driven oscillations in quantum number space, and the disappearance of an alignment upper bound observed for a rigid rotor in the impulsive torsional alignment limit.
Strong field coherent control of molecular torsions-Analytical models.
Ashwell, Benjamin A; Ramakrishna, S; Seideman, Tamar
2015-08-14
We introduce analytical models of torsional alignment by moderately intense laser pulses that are applicable to the limiting cases of the torsional barrier heights. Using these models, we explore in detail the role that the laser intensity and pulse duration play in coherent torsional dynamics, addressing both experimental and theoretical concerns. Our results suggest strategies for minimizing the risk of off-resonant ionization, noting the qualitative differences between the case of torsional alignment subject to a field-free torsional barrier and that of torsional alignment of a barrier-less system (equivalent to a 2D rigid rotor). We also investigate several interesting torsional phenomena, including the onset of impulsive alignment of torsions, field-driven oscillations in quantum number space, and the disappearance of an alignment upper bound observed for a rigid rotor in the impulsive torsional alignment limit. PMID:26277138
Spinflation with Angular Potentials
Ruth Gregory; Dariush Kaviani
2012-05-29
We investigate in detail the cosmological consequences of realistic angular dependent potentials in the brane inflation scenario. Embedding a warped throat into a compact Calabi-Yau space with all moduli stabilized breaks the no-scale structure and induces angular dependence in the potential of the probe D3-brane. We solve the equations of motion from the DBI action in the warped deformed conifold including linearized perturbations around the imaginary self-dual solution. Our numerical solutions show that angular dependence is a next to leading order correction to the dominant radial motion of the brane, however, just as angular motion typically increases the amount of inflation (spinflation), having additional angular dependence also increases the amount of inflation. We also derive an analytic approximation for the number of e-foldings along the DBI trajectory in terms of the compactification parameters.
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
The millimeter-wave spectrum of acetaldehyde in its two lowest torsional states
NASA Astrophysics Data System (ADS)
Liang, W.; Baker, John G.; Herbst, Eric; Booker, Randy A.; De Lucia, Frank C.
1986-12-01
A large number of new millimeter-wave spectral lines of gaseous acetaldehyde have been measured at frequencies up to 250 GHz. These lines arise from rotational transitions of acetaldehyde in its two lowest ( vt = 0,1) torsional states and involve angular momentum quantum numbers J ? 12 and K ? 10. A global data set consisting of 562 lines has been obtained by combining the millimeter-wave lines with previously measured lower frequency data involving the two lowest torsional states. This data set has been analyzed via an internal axis method previously used to study the spectra of CH 3OH and CH 3SH. The root-mean-square deviation of the fit is only 685 kHz. An analogous least-squares fit to 335 vt = 0 lines yields a root-mean-square deviation of 269 kHz.
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.
Torsional oscillations of strange stars
Massimo Mannarelli
2014-09-12
Strange stars are one of the hypothetical compact stellar objects that can be formed after a supernova explosion. The existence of these objects relies on the absolute stability of strange {\\it collapsed} quark matter with respect to standard nuclear matter. We discuss simple models of strange stars with a bare quark matter surface, thus standard nuclear matter is completely absent. In these models an electric dipole layer a few hundreds Fermi thick should exist close to the star surface. Studying the torsional oscillations of the electrically charged layer we estimate the emitted power, finding that it is of the order of $10^{45}$ erg/s, meaning that these objects would be among the brightest compact sources in the heavens. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. Although part of the radiated power should be absorbed by the electrosphere surrounding the strange star, a sizable fraction of photons should escape and be detectable.
Detectability of Torsion Gravity via Galaxy Clustering and Cosmic Shear Measurements
Camera, Stefano; Radicella, Ninfa
2013-01-01
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 amongst 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 constrai...
Non-Topological Gauss-Bonnet type model of gravity with torsion
H. Niu; D. G. Pak
2008-03-06
A non-topological Lorentz gauge model of gravity with torsion based on Gauss-Bonnet type Lagrangian is considered. The Lagrangian differs from the Lovelock term in four-dimensional space-time and has a number of interesting features. We demonstrate that the model admits a propagating torsion unlike the case of the topological Lovelock gravity. Due to additional symmetries of the proposed Gauss-Bonnet type Lagrangian the torsion has a reduced set of dynamical degrees of freedom corresponding to the spin two field, U(1) gauge vector field and spin zero field. A remarkable feature is that the kinetic part of the Hamiltonian containing the spin two field is positively defined. We perform one-loop quantization of the model for a special case of constant Riemann curvature space-time background treating the torsion as a quantum field variable. We discuss a possible mechanism of emergent Einstein gravity as an effective theory which can be induced due to quantum dynamics of torsion.
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.
NASA Technical Reports Server (NTRS)
Liebe, Wolfgang
1944-01-01
In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.
Fission fragment angular distributions
Bond, P.D.
1985-01-01
Many recent papers have found that calculations with the standard angular distribution formula for fission fragments from compound nuclei do not reproduce the strong anisotropies observed in the decay of high spin systems. They conclude that a noncompound nuclear process must exist for some partial waves and postulate an ad-hoc angular distribution for this process in order to reproduce the strong anisotropies. It is the purpose of this contribtion to demonstrate that much of the data are, in fact, consistent with compound nucleus formation and to emphasize that the standard model is not a generally valid way to calculate fission fragment angular distributions from a compound nucleus.
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.
Li, Zhijie; Wang, Shengjie; Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei; Weber, William J.
2010-07-01
The mechanical behavior of twinned silicon carbide (SiC) nanowires under combined tension-torsion and compression-torsion is investigated using molecular dynamics simulations with an empirical potential. The simulation results show that both the tensile failure stress and buckling stress decrease under combined tension-torsional and combined compression-torsional strain, and they decrease with increasing torsional rate under combined loading. The torsion rate has no effect on the elastic properties of the twinned SiC nanowires. The collapse of the twinned nanowires takes place in a twin stacking fault of the nanowires.
The metric on field space, functional renormalization, and metric-torsion quantum gravity
Reuter, Martin
2015-01-01
Searching for new non-perturbatively renormalizable quantum gravity theories, functional renormalization group (RG) flows are studied on a theory space of action functionals depending on the metric and the torsion tensor, the latter parameterized by three irreducible component fields. A detailed comparison with Quantum Einstein-Cartan Gravity (QECG), Quantum Einstein Gravity (QEG), and "tetrad-only" gravity, all based on different theory spaces, is performed. It is demonstrated that, over a generic theory space, the construction of a functional RG equation (FRGE) for the effective average action requires the specification of a metric on the infinite-dimensional field manifold as an additional input. A modified FRGE is obtained if this metric is scale-dependent, as it happens in the metric-torsion system considered.
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
Endodontic instruments after torsional failure: nanoindentation test.
Jamleh, Ahmed; Sadr, Alireza; Nomura, Naoyuki; Ebihara, Arata; Yahata, Yoshio; Hanawa, Takao; Tagami, Junji; Suda, Hideaki
2014-01-01
This study aimed to evaluate effects of torsional loading on the mechanical properties of endodontic instruments using the nanoindentation technique. ProFile (PF; size 30, taper 04; Dentsply Maillefer, Switzerland) and stainless steel (SS; size 30, taper 02; Mani, Japan) instruments were subjected to torsional test. Nanoindentation was then performed adjacent to the edge of fracture (edge) and at the cutting part beside the shank (shank). Hardness and elastic modulus were measured under 100-mN force on 100 locations at each region, and compared to those obtained from the same regions on new instruments. It showed that PF and SS instruments failed at 559?±?67 and 596?±?73 rotation degrees and mean maximum torque of 0.90?±?0.07 and 0.99?±?0.05?N-cm, respectively. Hardness and elastic modulus ranged 4.8-6.7 and 118-339?GPa in SS, and 2.7-3.2 and 52-81?GPa in PF. Significant differences between torsion-fractured and new instruments in hardness and elastic modulus were detected in the SS system used. While in PF system, the edge region after torsional fracture had significantly lower hardness and elastic modulus compared to new instruments. The local hardness and modulus of elasticity of endodontic instruments adjacent to the fracture edge are significantly reduced by torsional loading. PMID:24610598
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.
Torsion system for creep testing with multiple stress reversals
NASA Technical Reports Server (NTRS)
Lilienthal, P. A.
1969-01-01
Torsion system proves exploratory data on accelerated creep due to multiple stress reversals. Torsional testing of tubular specimens is best suited for reversed stress creep tests since large strains are obtainable while maintaining specimen geometry.
Active structures to reduce torsional vibrations
NASA Astrophysics Data System (ADS)
Matthias, M.; Schlote, D.; Atzrodt, H.
2013-03-01
This paper describes the development of different active measures to reduce torsional vibrations in power trains. The measures are based on concepts developed for active mounts to reduce the transmission of structure-borne sound. To show the potential of these active measures and investigate their mode of operation to influence torsional vibrations, numerical simulations of powertrains with different active measures were done. First experimental results from tests on an experimental (reduced size) power train were used to align the numerical models. The work was done within the project 'LOEWE-Zentrum AdRIA: Adaptronik - Research, Innovation, Application' funded by the German federal state of Hessen, and the Project AKTos: 'Active control of torsional vibrations by coupling elements' placed in the research Framework program 'Navigation and Maritime Technology for the 21st Century' funded by the German Federal Ministry of Economics and Technology.
Torsional Behavior of Axonal Microtubule Bundles.
Lazarus, Carole; Soheilypour, Mohammad; Mofrad, Mohammad R K
2015-07-21
Axonal microtubule (MT) bundles crosslinked by microtubule-associated protein (MAP) tau are responsible for vital biological functions such as maintaining mechanical integrity and shape of the axon as well as facilitating axonal transport. Breaking and twisting of MTs have been previously observed in damaged undulated axons. Such breaking and twisting of MTs is suggested to cause axonal swellings that lead to axonal degeneration, which is known as "diffuse axonal injury". In particular, overstretching and torsion of axons can potentially damage the axonal cytoskeleton. Following our previous studies on mechanical response of axonal MT bundles under uniaxial tension and compression, this work seeks to characterize the mechanical behavior of MT bundles under pure torsion as well as a combination of torsional and tensile loads using a coarse-grained computational model. In the case of pure torsion, a competition between MAP tau tensile and MT bending energies is observed. After three turns, a transition occurs in the mechanical behavior of the bundle that is characterized by its diameter shrinkage. Furthermore, crosslink spacing is shown to considerably influence the mechanical response, with larger MAP tau spacing resulting in a higher rate of turns. Therefore, MAP tau crosslinking of MT filaments protects the bundle from excessive deformation. Simultaneous application of torsion and tension on MT bundles is shown to accelerate bundle failure, compared to pure tension experiments. MAP tau proteins fail in clusters of 10-100 elements located at the discontinuities or the ends of MT filaments. This failure occurs in a stepwise fashion, implying gradual accumulation of elastic tensile energy in crosslinks followed by rupture. Failure of large groups of interconnecting MAP tau proteins leads to detachment of MT filaments from the bundle near discontinuities. This study highlights the importance of torsional loading in axonal damage after traumatic brain injury. PMID:26200859
Omental Torsion After Repeated Abdominal Blunt Trauma
Hosseinpour, Mehrdad; Abdollahi, Azadeh; Jazayeri, Hoda; Talari, Hamid Reza; Sadeghpour, Ahmad
2012-01-01
Omental torsion is caused by the rotation of the greater omentum on its axis which may lead to tissue infarction and necrosis. It is a rare cause of acute abdomen. Signs, symptoms and paraclinical data are not specific. The patients usually undergo laparotomy for acute abdomen of poorly defined origin. High index of suspicious is required for the diagnosis of this entity. The diagnosis is usually confirmed after an explorative laparotomy. We present clinical characteristics and imaging findings of omental torsion in a young man following repeated blunt abdominal trauma. PMID:24396748
Primary omental torsion: A case report
Scabini, Stefano; Rimini, Edoardo; Massobrio, Andrea; Romairone, Emanuele; Linari, Chiara; Scordamaglia, Renato; Marini, Luisito De; Ferrando, Valter
2011-01-01
A patient presented with an acute abdomen at the Emergency Department. The patient, a 69-year-old man, was admitted and underwent surgery with a provisional diagnosis of acute appendicitis. During surgery, omental torsion was diagnosed and the involved omentum was removed. The patient had no previous surgical history. Omental torsion is a rare cause of acute abdomen in children and adults who may present with various signs and symptoms; a preoperative diagnosis may therefore be difficult and can usually only be established during surgery. PMID:22110847
Torsion, a multivalued gauge degree of freedom in Einstein's gravity
NASA Astrophysics Data System (ADS)
Kleinert, H.
2011-07-01
We show that there is an entire gauge symmetry of a novel kind which interpolates between an infinity of formulations of the laws of gravity, ranging from Einsteins pure curvature formulation to a pure torsion formulation in a teleparallel geometry. As a consequence, torsion and curvature are not independent and that torsion is an alternative description of curvature in gravity.
Angular Momentum Operator Identities G I. Orbital Angular Momentum
Simons, Jack
Angular Momentum Operator Identities G I. Orbital Angular Momentum A particle moving with momentum p at a position r relative to some coordinate origin has so-called orbital angular momentum equal to L = r x p . The three components of this angular momentum vector in a cartesian coordinate system
NASA Astrophysics Data System (ADS)
Spano, Frank C.
2001-01-01
Within a density matrix framework, an analytical expression for the optical-optical double resonance (OODR) line shape for a molecule in the presence of a strong coupling laser is derived. The coupling laser is tuned to a transition between the upper level in the OODR sequence and another excited level which is not part of the OODR sequence. The pump and probe lasers are treated perturbatively, while the coupling laser is treated exactly. The line shape reveals sub-Doppler Autler-Townes (AT) splitting of the states |J,m> within the highest excited level. The splitting depends on |m|(m) for linearly (circularly) polarized coupling fields. m-state selectivity and therefore alignment and orientation of the angular momentum can be achieved by tuning the probe laser in the presence of a coupling field which is sufficiently strong to resolve the m-dependent AT splittings. m selectivity is analyzed for e and f parity 1?g levels in diatomic molecules. A method to orient nonpolar diatomics using circularly polarized lasers is proposed.
J. Murín; V. Kutiš
2008-01-01
In this paper an effective finite element of constant stiffness is developed for torsion with warping of both open- and closed-shape cross-sections. The secondary torsion moment deformation effect has been taken into account. The local element stiffness matrix that describes torsion with warping of both open- and closed-shape cross-sections has been derived using an analogy between torsion with warping (including
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.).
Sokolovski, D; Akhmatskaya, E; Echeverría-Arrondo, C; De Fazio, D
2015-07-28
State-to-state reactive integral cross sections (ICSs) are often affected by quantum mechanical resonances, especially near a reactive threshold. An ICS is usually obtained by summing partial waves at a given value of energy. For this reason, the knowledge of pole positions and residues in the complex energy plane is not sufficient for a quantitative description of the patterns produced by resonance. Such description is available in terms of the poles of an S-matrix element in the complex plane of the total angular momentum. The approach was recently implemented in a computer code ICS_Regge, available in the public domain [Comput. Phys. Commun., 2014, 185, 2127]. In this paper, we employ the ICS_Regge package to analyse in detail, for the first time, the resonance patterns predicted for integral cross sections (ICSs) of the benchmark F + HD ? HF(v' = 3) + D reaction. The v = 0, j = 0, ? = 0 ? v' = 3, j' = 0, 1, 2, and ?' = 0, 1, 2 transitions are studied for collision energies from 58.54 to 197.54 meV. For these energies, we find several resonances, whose contributions to the ICS vary from symmetric and asymmetric Fano shapes to smooth sinusoidal Regge oscillations. Complex energies of metastable states and Regge pole positions and residues are found by Padé reconstruction of the scattering matrix elements. The accuracy of the ICS_Regge code, relation between complex energies and Regge poles, various types of Regge trajectories, and the origin of the J-shifting approximation are also discussed. PMID:26112337
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. PMID:25861514
Torsional electromechanical quantum oscillations in carbon nanotubes
Joselevich, Ernesto
Torsional electromechanical quantum oscillations in carbon nanotubes TZAHI COHEN-KARNI1 *, LIOR electromechanical detection of motion could replace the microscopic detection techniques used at present. Our in nanoelectro-mechanical systems11. Owing to the promise of carbon nanotubes for application
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...
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.
Joining and forming using torsional ultrasonic principles.
Frost, M
2009-10-01
Developments in torsional ultrasonic joining mean that it is now used in a diverse range of joining, forming, selective weakening and "break-off" applications in the medical device industry.The principles and benefits of the technique are described together with application examples. PMID:20302140
Dispensing system eliminates torsion in deployed hoses
NASA Technical Reports Server (NTRS)
1965-01-01
Dispensing system uses a rotating drum, transfer arm, and stationary drum to deploy, reel in, and store an attached hose. This system which eliminates torsion and minimizes strain and wear of flexible hoses, is used for handling flexible cables that have one end permanently attached to an outlet or connector.
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.
a Rotatable Torsion Balance for a New Test of the Equivalence Principle.
NASA Astrophysics Data System (ADS)
Beilby, Mark Alfred
1995-01-01
An improved rotatable torsion balance has been built at UC Irvine to be used for a new test of the equivalence of inertial and gravitational mass, with the ability to use both the earth and the sun as acceleration sources. The suspended torsion balance body contains four cylindrical test masses of copper and four of lead press-fit into a cylindrical aluminum body in a highly stable configuration designed to minimize its mass multipole moments. The balance body is trimmed to reduce measured undesired mass moments due to inhomogeneities in the materials and to manufacturing imperfections. To reduce thermal noise, the balance body is suspended by an 80 cm long quartz fiber, which has a high Q. A Q of about 300,000 for a 20 micron diameter bare quartz fiber at 3.6 mHz has been achieved, corresponding to an amplitude damping time of about one year. The instrument is operated in a turn/stop mode in which it is rotated to a new position, then stopped for data taking. To prevent inelastic strain of the torsion fiber when the instrument is rotated, the balance body is gently forced to co-rotate with its housing by a small spinning horizontal magnetic field servoed to the angular readout. This balance was used to measure the fractional difference in acceleration between lead and copper towards the sun to a part in 10 ^{11}, with the resulting data consistent with Newtonian gravitation.
Development of a second generation torsion balance based on a spherical superconducting suspension.
Hammond, Giles D; Speake, Clive C; Matthews, Anthony J; Rocco, Emanuele; Peña-Arellano, Fabian
2008-02-01
This paper describes the development of a second generation superconducting torsion balance to be used for a precision measurement of the Casimir force and a short range test of the inverse square law of gravity at 4.2 K. The instrument utilizes niobium (Nb) as the superconducting element and employs passive damping of the parasitic modes of oscillation. Any contact potential difference between the torsion balance and its surroundings is nulled to within approximately 50 mV by applying known DC biases and fitting the resulting parabolic relationship between the measured torque and the applied voltage. A digital proportional-integral-derivative servo system has been developed and characterized in order to control the azimuthal position of the instrument. The angular acceleration and displacement noise are currently limited by the capacitive sensor at the level 3x10(-8) rad s(-2)/ squarerootHz and 30 nm/ squarerootHz at 100 mHz. The possibility of lossy dielectric coatings on the surface of the torsion balance test masses is also investigated. Our measurements show that the loss angles delta are (1.5+/-2.3)x10(-4) and (2.0+/-2.2)x10(-4) at frequencies of 5 and 10 mHz, respectively. These values of loss are not significant sources of error for measurements of the Casimir force using this experimental setup. PMID:18315325
Creation of photonic orbital angular momentum by distributed volume turbulence.
Oesch, Denis W; Sanchez, Darryl J; Gallegos, Anita L; Holzman, Jason M; Brennan, Terry J; Smith, Julie C; Gibson, William J; Farrell, Tom C; Kelly, Patrick R
2013-03-11
In previous work, we presented theory of how atmospheric turbulence can impart orbital angular momentum to propagating optical waves. In this paper we provide the first experimental demonstration of the detection of orbital angular momentum from distributed volume turbulence through the identification of well-defined, turbulence-induced, optical vortex trails in Shack-Hartmann wave front sensor measurements. PMID:23482115
NASA Technical Reports Server (NTRS)
Mccomb, Harvey G , Jr
1957-01-01
A theoretical investigation has been made of the Saint-Venant torsion of certain composite bars. These bars are composed of two materials -- one material in the form of a thin-walled cylindrical shell and the other material in the form of a core which fills the interior of the shell and is bonded to it. An approximate boundary-value problem is formulated on assumptions similar to those of the theory of torsion of hollow thin-walled shells (Bredt theory). This boundary-value problem is solved exactly for a rectangular cross section and approximately for slender triangular and diamond cross sections. Results for the torsional stiffness constants are presented graphically.
Gutiérrez-Medina, Braulio; Fehr, Adrian N; Block, Steven M
2009-10-01
Kinesin is a homodimeric motor with two catalytic heads joined to a stalk via short neck linkers (NLs). We measured the torsional properties of single recombinant molecules by tracking the thermal angular motions of fluorescently labeled beads bound to the C terminus of the stalk. When kinesin heads were immobilized on microtubules (MTs) under varied nucleotide conditions, we observed bounded or unbounded angular diffusion, depending on whether one or both heads were attached to the MT. Free rotation implies that NLs act as swivels. From data on constrained diffusion, we conclude that the coiled-coil stalk domains are approximately 30-fold stiffer than its flexible "hinge" regions. Surprisingly, while tracking processive kinesin motion at low ATP concentrations, we observed occasional abrupt reversals in the directional orientations of the stalk. Our results impose constraints on kinesin walking models and suggest a role for rotational freedom in cargo transport. PMID:19805111
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.
Cracked shells under skew-symmetric loading. [Reissner theory
NASA Technical Reports Server (NTRS)
Delale, F.
1981-01-01
The general problem of a shell containing a through crack in one of the principal planes of curvature and under general skew-symmetric loading is considered. By employing a Reissner type shell theory which takes into account the effect of transverse shear strains, all boundary conditions on the crack surfaces are satisfied separately. Consequently, unlike those obtained from the classical shell theory, the angular distributions of the stress components around the crack tips are shown to be identical to the distributions obtained from the plane and anti-plane elasticity solutions. Results are given for axially and circumferentially cracked cylindrical shells, spherical shells, and toroidal shells under uniform in-plane shearing, out of plane shearing, and torsion. The problem is formulated for specially orthostropic materials, therefore, the effect of orthotropy on the results is also studied.
Angular momentum in spin-phonon processes
NASA Astrophysics Data System (ADS)
Garanin, D. A.; Chudnovsky, E. M.
2015-07-01
Quantum theory of spin relaxation in the elastic environment is revised with account of the concept of a phonon spin recently introduced by Zhang and Niu [L. Zhang and Q. Niu, Phys. Rev. Lett. 112, 085503 (2014), 10.1103/PhysRevLett.112.085503]. Similar to the case of the electromagnetic field, the division of the angular momentum associated with elastic deformations into the orbital part and the part due to phonon spins proves to be useful for the analysis of the balance of the angular momentum. Such analysis sheds important light on microscopic processes leading to the Einstein-de Haas effect.
Fedoruk, Sergey, E-mail: fedoruk@theor.jinr.ru; Ivanov, Evgeny, E-mail: eivanov@theor.jinr.ru [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna, Moscow Region (Russian Federation)] [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna, Moscow Region (Russian Federation); Smilga, Andrei, E-mail: smilga@subatech.in2p3.fr [SUBATECH, Université de Nantes, 4 rue Alfred Kastler, BP 20722, Nantes 44307 (France)] [SUBATECH, Université de Nantes, 4 rue Alfred Kastler, BP 20722, Nantes 44307 (France)
2014-05-15
We present simple models of N= 4 supersymmetric mechanics with ordinary and mirror linear (4, 4, 0) multiplets that give a transparent description of Hyper-Kähler with Torsion (HKT), Clifford Kähler with Torsion (CKT), and Octonionic Kähler with Torsion (OKT) geometries. These models are treated in the N= 4 and N=2 superfield approaches, as well as in the component approach. Our study makes manifest that the CKT and OKT supersymmetric sigma models are distinguished from the more simple HKT models by the presence of extra holomorphic torsion terms in the supercharges.
Gears: Determining Angular Velocity
NSDL National Science Digital Library
2014-09-18
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.
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.
Transfer of angular momentum to matter from acoustical vortices in free space.
Volke-Sepúlveda, Karen; Santillán, Arturo O; Boullosa, Ricardo R
2008-01-18
An experimental demonstration of the mechanical transfer of orbital angular momentum to matter from acoustical vortices in free field is presented. Vortices with topological charges l=+/-1 and l=+/-2 were generated and a torsion pendulum was used to study the angular momentum transfer to hanging disks of several sizes. This allowed us to make a comparative study of the effective acoustical torque in terms of topological charge of the vortex, the disk radius, and its position along the main propagation axis. A theoretical discussion of the generated sound fields is also provided. PMID:18232874
Transfer of Angular Momentum to Matter from Acoustical Vortices in Free Space
NASA Astrophysics Data System (ADS)
Volke-Sepúlveda, Karen; Santillán, Arturo O.; Boullosa, Ricardo R.
2008-01-01
An experimental demonstration of the mechanical transfer of orbital angular momentum to matter from acoustical vortices in free field is presented. Vortices with topological charges l=±1 and l=±2 were generated and a torsion pendulum was used to study the angular momentum transfer to hanging disks of several sizes. This allowed us to make a comparative study of the effective acoustical torque in terms of topological charge of the vortex, the disk radius, and its position along the main propagation axis. A theoretical discussion of the generated sound fields is also provided.
Torsion of DNA modeled as a heterogeneous fluctuating rod
NASA Astrophysics Data System (ADS)
Argudo, David; Purohit, Prashant K.
2014-01-01
We discuss the statistical mechanics of a heterogeneous elastic rod with bending, twisting and stretching. Our model goes beyond earlier works where only homogeneous rods were considered in the limit of high forces and long lengths. Our methods allow us to consider shorter fluctuating rods for which boundary conditions can play an important role. We use our theory to study structural transitions in torsionally constrained DNA where there is coexistence of states with different effective properties. In particular, we examine whether a newly discovered left-handed DNA conformation called L-DNA is a mixture of two known states. We also use our model to investigate the mechanical effects of the binding of small molecules to DNA. For both these applications we make experimentally falsifiable predictions.
Angular momentum conservation in dipolar energy transfer.
Guo, Dong; Knight, Troy E; McCusker, James K
2011-12-23
Conservation of angular momentum is a familiar tenet in science but has seldom been invoked to understand (or predict) chemical processes. We have developed a general formalism based on Wigner's original ideas concerning angular momentum conservation to interpret the photo-induced reactivity of two molecular donor-acceptor assemblies with physical properties synthetically tailored to facilitate intramolecular energy transfer. Steady-state and time-resolved spectroscopic data establishing excited-state energy transfer from a rhenium(I)-based charge-transfer state to a chromium(III) acceptor can be fully accounted for by Förster theory, whereas the corresponding cobalt(III) adduct does not undergo an analogous reaction despite having a larger cross-section for dipolar coupling. Because this pronounced difference in reactivity is easily explained within the context of the angular momentum conservation model, this relatively simple construct may provide a means for systematizing a broad range of chemical reactions. PMID:22194572
Angular Size in a Static Universe
David F. Crawford
1994-07-11
In principle the geometry of the universe can be investigated by measuring the angular size of known objects as a function of distance. Thus the distribution of angular sizes provides a critical test of the stable and static model of the universe described by Crawford (1991,1993) that has a simple and explicit relationship between the angular size of an object and its redshift. The result is that the agreement with observations of galactic diameters and the size of double radio sources with the static model is much better than the standard (Big Bang) theory without evolution. However there is still a small discrepancy at large redshifts that could be due to selection effects.
Laser-Based Measurement Of Torsional Vibration
NASA Astrophysics Data System (ADS)
Eastwood, P. G.; Halliwell, N. A.
1986-07-01
Investigations of the torsional vibration characteristics of shaft systems which transmit pulsating torques are an important part of a machinery designer's responsibility. Satisfactory operation of such systems depends to a large extent on successful treatment of this vibration problem, since incorrectly or insufficiently controlled torsional oscillations can lead to fatigue failure, rapid bearing wear, gear hammer etc. The problem is particularly severe in engine crankshaft design where numerous failures have been traced to abnormal vibration at "critical" speeds. Traditionally, the monitoring of torsional oscillation has been performed using strain gauges, slip rings and a variety of mechanical and electrical "torsiographs". More recently systems employing slotted discs or toothed wheels together with proximity transducers have been preferred, but a disadvantage arises from all these methods in that they require contact with the rotating component which necessitates "downtime" for transducer attachment. Moreover, physical access to the rotating surface is often restricted thus making the use of such methods impractical. The "cross-beam" laser velocimeter provides a means of measuring torsional vibration by a non-contact method, thus effectively overcoming the disadvantages of previous measurement systems. This well established laser-based instrument provides a time-resolved voltage analogue of shaft tangential surface velocity and laboratory and field tests have shown it to be both accurate and reliable. The versatility of this instrument, however, is restricted by the need for accurate positioning, since the velocimeter must be arranged so that the rotating surface always traverses the beam intersection region, which is typically only a fraction of a millimetre in length. As a consequence use is restricted to components of circular cross section. This paper compares and contrasts the "cross-beam" system with a new laser instrument, the laser torsional vibrometer. The optical geometry employed in this new instrument offers a means of producing a hand held laser tool which the operator can simply "point" at the rotating surface of interest. Other important advantages include Insensitivity to operator or shaft radial movement and the ability to measure torsional oscillations of any rotating component of arbitrary cross-section.
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
Spinors on a curved noncommutative space: coupling to torsion and the Gross–Neveu model
NASA Astrophysics Data System (ADS)
Buri?, Maja; Madore, John; Nenadovi?, Luka
2015-09-01
We analyse the Dirac action on the truncated Heisenberg algebra and in particular, the nonminimal couplings to the background gravitational field. By projection to the Heisenberg algebra we obtain a renormalisable model: the noncommutative extension of the Gross–Neveu model. This result indicates that, as on the commutative curved backgrounds, nonminimal couplings with torsion and curvature are necessary (and sufficient) for renormalisability of scalar and spinor theories on the curved noncommutative spaces.
Metric-scalar gravity with torsion and the measurability of the non-minimal coupling
A. Accioly; H. Blas
2006-08-29
The "measurability" of the non-minimal coupling is discussed by considering the correction to the Newtonian static potential in the semi-classical approach. The coefficient of the "gravitational Darwin term" (GDT) gets redefined by the non-minimal torsion-scalar couplings. Based on a similar analysis of the GDT in the effective field theory approach to non-minimal scalar we conclude that for reasonable values of the couplings the correction is very small.
Wrinkling Behaviors of Gossamer Structure with Stretched Annulus-Shape under In-Plane Torsion
C. G. Wang; H. F. Tan; X. W. Du; X. D. He
2008-01-01
In this paper, an out-of-plane wrinkling function is constructed and then is introduced to the buckling theory to complete the wrinkling analysis. Two key techniques (initial imperfection and prestress) are then introduced to the shell model to perform the post-wrinkling numerical analysis of the annulus-shaped membrane under in-plane torsion. The numerical analysis is also performed to evaluate the effects of
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.
Angular momentum of the atmosphere Variations of atmospheric relative angular
O'Gorman, Paul
Angular momentum of the atmosphere #12;Variations of atmospheric relative angular momentum OCW Schematic of dynamic angular momentum transports and surface torques #12;NCEP reanalysis imbalance -30 0 30 60 0.2 0.8 JJA DJF #12;Northward flux of momentum (m2s-2) Peixoto and Oort, Fig 11
NASA Astrophysics Data System (ADS)
Wormer, Paul E. S.; Paldus, Josef
Starting from the simplest possible building blocks--a ket, a bra, a time-reversed ket, and a time-reversed bra--a diagrammatic formalism is developed for angular momentum coupling problems. The formalism comprises Clebsch-Gordan coefficients as well as 3jm-symbols. The idea of constructing invariants (internal lines) by contracting contragredient pairs of quantities is emphasized throughout. The Clebsch-Gordan series, and its extension to the coupling of more than two angular momenta, is introduced algebraically and diagrammatically. Recoupling between bases obtained in different coupling schemes is introduced and the connection between recoupling coefficients and irreducible 3nj-symbols is derived diagrammatically. The well-known diagrammatic rules due to Jucys and co-workers are derived by group theoretical means and simple rules for their practical exploitation are presented.
Chronic splenic torsion in two dogs.
Reinhart, Jennifer M; Sherwood, J Matthew; KuKanich, Katherine S; Klocke, Emily; Biller, David S
2015-01-01
A 5 yr old spayed female poodle (case 1) was presented with a 4 mo history of lethargy, inappetence, and nonregenerative anemia. A 5 yr old castrated male French bulldog (case 2) was presented with a 2 wk history of mild abdominal pain, dyschezia, and intermittent anorexia. Both dogs were diagnosed with chronic splenic torsion based on changes in splenic position, echogenicity, and/or echotexture identified on B-mode abdominal ultrasonography, as well as either decreased or absent splenic blood flow on color-flow Doppler ultrasonography. Both dogs underwent splenectomy and had full resolution of clinical signs. Presentation of chronic splenic torsion is variable, and clinical signs can be nonspecific. Abdominal ultrasound with Doppler evaluation is an important diagnostic step that can lead to appropriate surgical intervention and good long-term prognosis. PMID:25955145
On gauged linear sigma models with torsion
Crichigno, P Marcos
2015-01-01
We study a broad class of two dimensional gauged linear sigma models (GLSMs) with off-shell N=(2,2) supersymmetry that flow to nonlinear sigma models (NLSMs) on noncompact geometries with torsion. These models arise from coupling chiral, twisted chiral, and semichiral multiplets to known as well as to a new N=(2,2) vector multiplet, the constrained semichiral vector multiplet (CSVM). We discuss three kinds of models, corresponding to torsionful deformations of standard GLSMs realizing Kahler, hyperkahler, and Calabi-Yau manifolds. The (2,2) supersymmetry guarantees that these spaces are generalized Kahler. Our analysis of the geometric structure is performed at the classical level, but we also discuss quantum aspects such as R-symmetry anomalies. We provide an explicit example of a generalized Kahler structure on the conifold.
On gauged linear sigma models with torsion
P. Marcos Crichigno; Martin Ro?ek
2015-07-14
We study a broad class of two dimensional gauged linear sigma models (GLSMs) with off-shell N=(2,2) supersymmetry that flow to nonlinear sigma models (NLSMs) on noncompact geometries with torsion. These models arise from coupling chiral, twisted chiral, and semichiral multiplets to known as well as to a new N=(2,2) vector multiplet, the constrained semichiral vector multiplet (CSVM). We discuss three kinds of models, corresponding to torsionful deformations of standard GLSMs realizing Kahler, hyperkahler, and Calabi-Yau manifolds. The (2,2) supersymmetry guarantees that these spaces are generalized Kahler. Our analysis of the geometric structure is performed at the classical level, but we also discuss quantum aspects such as R-symmetry anomalies. We provide an explicit example of a generalized Kahler structure on the conifold.
Torsion and transverse bending of cantilever plates
NASA Technical Reports Server (NTRS)
Reissner, Eric; Stein, Manuel
1951-01-01
The problem of combined bending and torsion of cantilever plates of variable thickness, such as might be considered for solid thin high-speed airplane or missile wings, is considered in this paper. The deflections of the plate are assumed to vary linearly across the chord; minimization of the potential energy by means of the calculus of variations then leads to two ordinary linear differential equations for the bending deflections and the twist of the plate. Because the cantilever is analyzed as a plate rather than as a beam, the effect of constraint against axial warping in torsion is inherently included. The application of this method to specific problems involving static deflection, vibration, and buckling of cantilever plates is presented. In the static-deflection problems, taper and sweep are considered.
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.
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.
ELKO and Dirac spinors seen from torsion
NASA Astrophysics Data System (ADS)
Fabbri, Luca; Vignolo, Stefano
2014-09-01
In this paper, the recently-introduced ELKO and the well-known Dirac spinor fields will be compared. However, instead of comparing them under the point of view of their algebraic properties or their dynamical features, we will proceed by investigating the analogies and similarities in terms of their geometrical character viewed from the perspective of torsion. The paper will be concluded by sketching some consequences for the application to cosmology and particle physics.
ELKO and Dirac Spinors seen from Torsion
Fabbri, Luca
2014-01-01
In this paper, the recently-introduced ELKO and the well-known Dirac spinor fields will be compared; however, instead of comparing them under the point of view of their algebraic properties or their dynamical features, we will proceed by investigating the analogies and similarities in terms of their geometrical character view from the perspective of torsion. The paper will be concluded by sketching some consequences for the application to cosmology and particle physics.
ELKO and Dirac Spinors seen from Torsion
Luca Fabbri; Stefano Vignolo
2014-09-01
In this paper, the recently-introduced ELKO and the well-known Dirac spinor fields will be compared; however, instead of comparing them under the point of view of their algebraic properties or their dynamical features, we will proceed by investigating the analogies and similarities in terms of their geometrical character viewed from the perspective of torsion. The paper will be concluded by sketching some consequences for the application to cosmology and particle physics.
Investigation Of Tapered Tension/Torsion Strap
NASA Technical Reports Server (NTRS)
Louie, Alexander
1991-01-01
Tapered strap provides more torque than parallel one. Report describes theoretical and experimental-investigation of simplified model of tension/torsion strap. Proposed for use in helicopter rotor blade to hold otherwise freely pitching blade tip inward against centrifugal force and to apply torque about pitch axis to regulate pitching motions of tip. Intended to improve aerodynamic performances of rotors and to reduce vibrations.
UBIQUITOUS TORSIONAL MOTIONS IN TYPE II SPICULES
De Pontieu, B.; Hansteen, V. H.; Carlsson, M.; Rouppe van der Voort, L. H. M.; Rutten, R. J.; Watanabe, H.
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.
Quantum Heuristics of Angular Momentum
ERIC Educational Resources Information Center
Levy-Leblond, Jean-Marc
1976-01-01
Discusses the quantization of angular momentum components, Heisenberg-type inequalities for their spectral dispersions, and the quantization of the angular momentum modulus, without using operators or commutation relations. (MLH)
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.
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
Perinatal testicular torsion and medicolegal considerations.
Massoni, F; Troili, G M; Pelosi, M; Ricci, S
2014-06-01
Perinatal testicular torsion (PTT) is a very complex condition because of rarity of presentation and diagnostic and therapeutic difficulties. In presence of perinatal testicular torsion, the involvement of contralateral testis can be present also in absence of other indications which suggest the bilateral involvement; therefore, occurrences supported by literature do not exclude the use of surgery to avoid the risk of omitted or delayed diagnosis. The data on possible recovery of these testicles are not satisfactory, and treatment consists of an observational approach ("wait-and-see") or an interventional approach. The hypothesis of randomized clinical trials seems impracticable because of rarity of disease. The authors present a case of PTT, analyzing injuries due to clinical and surgical management of these patients, according to medicolegal profile. The delayed diagnosis and the choice of an incorrect therapeutic approach can compromise the position of healthcare professionals, defective in terms of skill, prudence and diligence. Endocrine insufficiency is an unfortunate event. The analysis of literature seems to support, because of high risk, a surgical approach aimed not only at resolution of unilateral pathology or prevention of a relapse, but also at prevention of contralateral testicular torsion. PMID:24826979
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.
NASA Astrophysics Data System (ADS)
Jia, Hai-Hong; Zhao, Ke; Wu, Xiang-Lian
2014-09-01
Two-photon absorption properties of a push-pull molecule and its covalent dimers have been studied by density functional response theory in combination with polarizable continuum model. A set of constrained geometries with different torsional angles are optimized and used to calculate two-photon absorption spectra. It is found that the torsional disorder could possibly produce the experimental two-photon absorption additive behavior. We have also designed a series of covalent dimers and investigated the effects of position isomerism. Our results suggest that the cooperative two-photon absorption enhancement can be achieved when the subunits are substituted in closer proximity and have larger interchromophore angle.
Torsional and biaxial (tension-torsion) fatigue damage mechanisms in Waspaloy at room temperature
NASA Technical Reports Server (NTRS)
Jayaraman, N.; Ditmars, M. M.
1989-01-01
Strain controlled torsional and biaxial (tension-torsion) low cycle fatigue behavior of Waspaloy was studied at room temperature as a function of heat treatment. Biaxial tests were conducted under proportional and nonproportional cyclic conditions. The deformation behavior under these different cyclic conditions was evaluated by slip trace analysis. For this, a Schmidt-type factor was defined for multiaxial loading conditions, and it was shown that when the slip deformation is predominant, nonproportional cycles are more damaging than proportional or pure axial or torsional cycles. This was attributed to the fact that under nonproportional cyclic conditions, deformation was through multiple slip, as opposed to single slip for other loading conditions, which gave rise to increased hardening. The total life for a given test condition was found to be independent of heat treatment. This was interpreted as being due to the differences in the cycles to initiation and propagation of cracks.
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.
Coherent Control of Angular Momentum Transfer in Resonant Two-Photon Light-Matter Interaction
Malik, D. A.; Kimel, A. V.; Kirilyuk, A.; Rasing, Th.; Zande, W. J. van der
2010-04-02
We show experimentally and theoretically that a polarization-shaped femtosecond laser pulse with a zero net angular momentum creates a net angular momentum in atomic rubidium during resonant two-photon excitation. The necessary conditions for the creation of a nonzero angular momentum as well as the excitation efficiencies are analyzed in the framework of second-order time-dependent perturbation theory.
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.
Güne?, Mustafa; Umul, Mehmet; Çelik, Ahmet Orhan; Arma?an, Hamit Hakan; De?irmenci, Bumin
2015-01-01
A 17-year-old boy presented with right testicular torsion to the lateral side. Torsion was diagnosed by physical examination; the colour Doppler ultrasonography (CDU) confirmed right testicular torsion with minimal peripheral hydrocele. Transverse and longitudinal examination of the spermatic cord with ultrasound and CDU revealed a counter-clockwise testicular torsion. Manual de-torsion was performed in a clockwise direction (720o) and testicular blood flow and the neutral position of the spermatic cord were confirmed by CDU. We did not encounter a residual twist of the spermatic cord upon surgical exploration. In our experience, ultrasound and CDU may predict the direction of testicular torsion and may allow appropriate management of cases prior to surgery. PMID:26425241
Swanson, W.J.
1998-12-01
An experimental investigation was conducted to develop a method of predicting cylinder indicated torques in a reciprocating engine by measurement of crankshaft angular velocity fluctuations. Cylinder indicated pressures were measured for all three cylinders of a two-stroke Diesel engine with pressure transducers. Time-resolved angular position was measured at the crankshaft front and at the flywheel. A six degree-of-freedom torsional crankshaft model was developed. Two solution methods are described to solve the equations of motion: a time-marching ODE solver, and a Finite Element solution in the time domain. Using these methods with the measured cylinder torques, the angular positions are predicted and compared to measured angular positions for model calibration. An inverse solution method was developed to determine the cylinder indicated torques from the measured angular position at the crankshaft endpoints. The method is theoretically demonstrated to be useful for explicit solutions for two-stroke engines up to three cylinders, and four-stroke engines up to four cylinders. Experimental results show that the method is useful in predicting cylinder indicated torques from angular velocity measurements.
Angular distributions in multifragmentation
Stoenner, R.W.; Klobuchar, R.L.; Haustein, P.E.; Virtes, G.J.; Cumming, J.B.; Loveland, W.
2006-04-15
Angular distributions are reported for {sup 37}Ar and {sup 127}Xe from 381-GeV {sup 28}Si+Au interactions and for products between {sup 24}Na and {sup 149}Gd from 28-GeV {sup 1}H+Au. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.
Kannengießer, Raphaela; Lach, Marcel J; Stahl, Wolfgang; Nguyen, Ha Vinh Lam
2015-06-22
The gas-phase structures and parameters describing acetyl methyl torsion of N-ethylacetamide are determined with high accuracy, using a combination of molecular beam Fourier-transform microwave spectroscopy and quantum chemical calculations. Conformational studies at the MP2 level of theory yield four minima on the energy surface. The most energetically favorable conformer, which possesses C1 symmetry, is assigned. Due to the torsional barrier of 73.4782(1) cm(-1) of the acetyl methyl group, fine splitting up to 4.9 GHz is found in the spectrum. The conformational structure is not only confirmed by the rotational constants, but also by the orientation of the internal rotor. The (14) N quadrupole hyperfine splittings are analyzed and the deduced coupling constants are compared with the calculated values. PMID:25916631
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.
Ovarian torsion: opportunities to improve clinical management.
Bharathan, R; Ramsawak, L; Kelly, A
2012-10-01
Ovarian torsion is an uncommon condition which may affect women of any age. In a significant number of women, it may be associated with a concomitant pathology such as a cyst. Presently, there is no single diagnostic tool with significant predictive value. Multimodal diagnostic tools hold promise of early accurate diagnosis; prospective studies are required to assess the validity of such tools. This would enable wider application of ovarian function preserving procedures. Further, an assessment of the psychological impact of oophorectomy should be studied in order to facilitate the optimal tailored care. PMID:22943718
The normal development of tibial torsion
Leif P. Kristiansen; Ragnhild B. Gunderson; Harald Steen; Olav Reikerås
2001-01-01
. \\u000a Objective: Pathological rotation of the leg is a well-known problem in paediatric orthopaedics. In this study the normal development\\u000a of tibial torsion during growth was evaluated by computed tomography (CT). \\u000a \\u000a \\u000a \\u000a Design: Seventy-eight normal individuals (52 children, 26 adults) aged 3–51 years were examined with CT. In axial scans the angle\\u000a between a line tangential to the posterior part of the
Laboratory Tests of Gravitational Physics Using a Cryogenic Torsion Pendulum
NASA Astrophysics Data System (ADS)
Berg, E. C.; Bantel, M. K.; Cross, W. D.; Inoue, T.; Newman, R. D.; Steffen, J. H.; Moore, M. W.; Boynton, P. E.
2006-02-01
Progress and plans are reported for a program of gravitational physics experiments using cryogenic torsion pendula undergoing large amplitude torsional oscillation. The program includes a UC Irvine project to measure the gravitational constant G and joint UC Irvine-U. Washington projects to test the gravitational inverse square law at a range of about 10 cm and to test the weak equivalence principle.
TORSIONAL STRENGTHENING OF SPANDREL BEAMS WITH COMPOSITE LAMINATES
Pedro Salom; NC Janos Gergely; David T. Young
The present paper describes the experimental and analytical findings of a project focused on the structural strengthening of reinforced concrete (RC) spandrel beams using carbon fiber reinforced polymer (CFRP) composite laminates, and subjected to pure torsion. Current torsional strengthening and repair methods are time and resource intensive, and quite often very intrusive. The proposed method however, uses composite laminates to
Quantum Gravity Effect in Torsion Driven Inflation and CP violation
Sayantan Choudhury; Barun Kumar Pal; Banasri Basu; Pratul Bandyopadhyay
2015-10-10
We have derived an effective potential for inflationary scenario from torsion and quantum gravity correction in terms of the scalar field hidden in torsion. A strict bound on the CP violating $\\theta$ parameter, ${\\cal O}(10^{-10})<\\theta<{\\cal O}(10^{-9})$ has been obtained, using {\\tt Planck+WMAP9} best fit cosmological parameters.
Modeling Torsion of Blood Vessels in Surgical Simulation and Planning
Leow, Wee Kheng
Modeling Torsion of Blood Vessels in Surgical Simulation and Planning Hao LI a,1 , Wee Kheng LEOW a hybrid approach for modeling torsion of blood vessels that undergo deformation and joining. The proposed model takes 3D mesh of the blood vessel as input. It first fits a generalized cylinder to extract
COUPLED BENDING TORSIONAL VIBRATION OF ROTORS USING FINITE ELEMENT
M. A. Mohiuddin; Y. A. Khulief
1999-01-01
The finite element formulation of the dynamic model of a rotor-bearing system is presented. The elastodynamic model of coupled bending and torsional motions of the rotating shaft is derived using the Lagrangian approach. The model accounts for the gyroscopic effects as well as the inertia coupling between bending and torsional deformations. A reduced order model is obtained using modal truncation.
Coupled Bending Torsional Vibration of Rotors Using Finite Element
M. A. Mohiuddin; Y. A. Khulief
1999-01-01
The finite element formulation of the dynamic model of a rotor-bearing system is presented. The elastodynamic model of coupled bending and torsional motions of the rotating shaft is derived using the Lagrangian approach. The model accounts for the gyroscopic effects as well as the inertia coupling between bending and torsional deformations. A reduced order model is obtained using modal truncation.
Laboratory Tests of Gravitational Physics Using a Cryogenic Torsion Pendulum
E. C. Berg; J. H. Steffen; M. K. Bantel; P. E. Boynton; W. D. Cross; T. Inoue; M. W. Moore; R. D. Newman
2004-05-18
Progress and plans are reported for a program of gravitational physics experiments using cryogenic torsion pendula undergoing large amplitude torsional oscillation. The program includes a UC Irvine project to measure the gravitational constant G and joint UC Irvine - U. Washington projects to test the gravitational inverse square law at a range of about 10 cm and to test the weak equivalence principle.
Singlewall Carbon Nanotubes as Torsional Springs in a Nanoelectromechanical Device
NASA Astrophysics Data System (ADS)
Hall, A. R.
2005-03-01
Nanoelecromechnical devices have been fabricated that utilize an individual singlewall carbon nanotube as a torsional spring for a fully suspended, lithographed metal platform. The torsional properties of the structure were measured through repeated deflection with a scanning probe tip. We discuss results of such measurements as well as progress towards high Q oscillator behavior and integrated device arrays.
Torsional Vibration Assessment Using Induction Machine Electromagnetic Torque Estimation
Shahin Hedayati Kia; Humberto Henao; GÉrard-AndrÉ Capolino
2010-01-01
Mechanical anomalies such as load troubles, great torque dynamic variations, and torsional oscillations result in the shaft fatigue of electrical machine and other mechanical parts such as bearings and gearboxes. Particularly, the torsional vibration may attain a significant level at resonant frequencies which damage or cause additional lifetime consumption of mechanical parts. In this way, this paper proposes a noninvasive
A Cheeger-Müller theorem for symmetric bilinear torsions
Guangxiang Su; Weiping Zhang
2008-01-01
The authors establish a Cheeger-Müller type theorem for the complex valued analytic torsion introduced by Burghelea and Haller\\u000a for flat vector bundles carrying nondegenerate symmetric bilinear forms. As a consequence, they prove the Burghelea-Haller\\u000a conjecture in full generality, which gives an analytic interpretation of (the square of) the Turaev torsion.
TORSIONAL VIBRATION REDUCTION IN INTERNAL COMBUSTION ENGINES USING
Shaw, Steven W.
engines. A mathematical model is first built for the torsional dynamics of an in- line, four-stroke, four-line, four-stroke engine. The papers by Denman (1992), Cronin (1992) and Borowski et al. (1991) describeTORSIONAL VIBRATION REDUCTION IN INTERNAL COMBUSTION ENGINES USING CENTRIFUGAL PENDULUMS Cheng
Ultrahigh Torsional Stiffness and Strength of Boron Nitride Jonathan Garel,
Joselevich, Ernesto
Ultrahigh Torsional Stiffness and Strength of Boron Nitride Nanotubes Jonathan Garel, Itai Leven of boron nitride nanotube (BNNT) torsional mechanics. We show that BNNTs exhibit a much stronger mechanical in nanoelectromechanical systems (NEMS), fibers, and nanocomposites. KEYWORDS: Nanotube, boron nitride (BN), atomic force
PLASTIC TORSION AND RELATED PROBLEMS FRANCOIS ALOUGES AND ANTONIO DESIMONE
Alouges, FranÃ§ois
PLASTIC TORSION AND RELATED PROBLEMS FRANCÂ¸OIS ALOUGES AND ANTONIO DESIMONE Abstract. A simple buckling of thin film blisters are also discussed. 1. Introduction A classical problem in Plasticity (more of Matlab code provided herein will entice many to experiment with plastic torsional loads, isotropic thin
Torsional Control by Intense Pulses S. Ramakrishna and Tamar Seideman*
Seideman, Tamar
are the Cartesian compo- nents of the polarizability tensor [1(a)]. In terms of the body-fixed Cartesian coordinates. Torsional control is applied to manipulate charge transfer events, hence introducing a potential route of simultaneously controlling also their torsional motions. In particular, we illustrate numerically the appli
Bradas, J.C.
1986-01-01
The aim of this treatise is to examine the behavior of a standard Bianchi Type I universe modeled as a fluid with expansion, shear, and vorticity and to see what effects torsion has on the behavior of the model. It is shown that a generalized (or power law) inflationary phase arises naturally and inevitably in a cosmology modeled as a Bianchi Type I anisotropic model in the self-consistent Einstein-Cartan gravitational theory with the improved Stress-Energy-Momentum-Tensor (SEMT) with spin density of Ray and Smalley. This is made explicit by 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 allipsoid. Shear is not effective in damping the inflation.
Torsion and noninertial effects on a nonrelativistic Dirac particle
Bakke, K., E-mail: kbakke@fisica.ufpb.br
2014-07-15
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. -- Highlights: •Torsion effects on a spin- 1/2 particle in a noninertial reference frame. •Fermi–Walker reference frame in the cosmic dislocation spacetime background. •Torsion and noninertial effects on the confinement to a hard-wall confining potential.
Angular Dependences of Third Harmonic Generation from Microdroplets
J. Kasparian; B. Krämer; J. P. Dewitz; S. Vajda; P. Rairoux; B. Vezin; V. Boutou; T. Leisner; W. Hübner; J. P. Wolf; L. Wöste; K. H. Bennemann
1997-01-01
We present experimental and theoretical results for the angular dependence of third harmonic generation of water droplets in the micrometer range (size parameter 62
Experimental Evidence for Partonic Orbital Angular Momentum at RHIC
Fields, Douglas E.
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.
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.
Twisted anisotropic fibers for robust orbital-angular-momentum-based information transmission
NASA Astrophysics Data System (ADS)
Barshak, E. V.; Alexeyev, C. N.; Lapin, B. P.; Yavorsky, M. A.
2015-03-01
We study the light propagation in the twisted anisotropic optical fibers endowed with torsional mechanical stress by obtaining the analytical solution of the vector wave equation. We show that at certain interplay between fiber parameters optical vortex beams of topological charge ? =0 ,±1 ,±2 ,... become the modes of the fibers in question. To explain the splitting of the optical vortex propagation constants we introduce the notions of orbital birefringence and optical Zeeman effect. Moreover, we unveil that induced by torsional stress circular birefringence makes the vortex beams with the well-defined orbital angular momentum robust against small perturbations characterized by both constant and spatially varying orientation of a director. We believe that such fibers can be successfully utilized for the long-range robust transmission of information encoded in the light's orbital degrees of freedom.
Detecting the crankshaft torsional vibration of diesel engines for combustion related diagnosis
NASA Astrophysics Data System (ADS)
Charles, P.; Sinha, Jyoti K.; Gu, F.; Lidstone, L.; Ball, A. D.
2009-04-01
Early fault detection and diagnosis for medium-speed diesel engines is important to ensure reliable operation throughout the course of their service. This work presents an investigation of the diesel engine combustion related fault detection capability of crankshaft torsional vibration. The encoder signal, often used for shaft speed measurement, has been used to construct the instantaneous angular speed (IAS) waveform, which actually represents the signature of the torsional vibration. Earlier studies have shown that the IAS signal and its fast Fourier transform (FFT) analysis are effective for monitoring engines with less than eight cylinders. The applicability to medium-speed engines, however, is strongly contested due to the high number of cylinders and large moment of inertia. Therefore the effectiveness of the FFT-based approach has further been enhanced by improving the signal processing to determine the IAS signal and subsequently tested on a 16-cylinder engine. In addition, a novel method of presentation, based on the polar coordinate system of the IAS signal, has also been introduced; to improve the discrimination features of the faults compared to the FFT-based approach of the IAS signal. The paper discusses two typical experimental studies on 16- and 20-cylinder engines, with and without faults, and the diagnosis results by the proposed polar presentation method. The results were also compared with the earlier FFT-based method of the IAS signal.
Detectability of Torsion Gravity via Galaxy Clustering and Cosmic Shear Measurements
Stefano Camera; Vincenzo F. Cardone; Ninfa Radicella
2014-04-10
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 amongst 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 $\\Lambda{\\rm CDM}$ model, were a value larger than 0.02 of its power-law slope measured, whereas in $\\Lambda{\\rm CDM}$ it is exactly 0.
NASA Astrophysics Data System (ADS)
Bai, Cheng; Huang, Jin
2014-05-01
Electrostatically driven torsional micromirrors are suitable for optical microelectromechanical systems due to their good dynamic response, low adhesion, and simple structure for large-scale-integrated applications. For these devices, how to eliminate the excessive residual vibration in order to achieve more accurate positioning and faster switching is an important research topic. Because of the known nonlinearity issues, traditional shaping techniques based on linear theories are not suitable for nonlinear torsional micromirrors. In addition, due to the difficulties in calculating energy dissipation, the existing nonlinear command shaping techniques using energy method have neglected the effect of damping. We analyze the static and dynamic behavior of the electrostatically actuated torsional micromirrors. Based on the response of these devices, a multistep-shaping control considering the damping effects and the nonlinearity is proposed. Compared to the conventional closed-loop control, the proposed multistep-shaping control is a feedforward approach which can yield a good enough performance without extra sensors and actuators. Simulation results show that, without changing the system structure, the preshaping input reduces the settling time from 4.3 to 0.97 ms, and the overshoot percentage of the mirror response is decreased from 33.2% to 0.2%.
Torsion of wing trusses at diving speeds
NASA Technical Reports Server (NTRS)
Miller, Roy G
1921-01-01
The purpose of this report is to indicate what effect the distortion of a typical loaded wing truss will have upon the load distribution. The case of high angle of incidence may be dismissed immediately from consideration as the loads on the front and rear trusses are balanced, and consequently there will be little angular distortion. A given angular distortion will have the maximum effect upon load distribution in the region of the angle of no-lift, because the slope of the lift curve is highest here, and it is here that the greatest angular distortion will occur, because the load on the front truss acts downward while the load on the rear truss acts upward.
Nanofabricated quartz cylinders for angular
Cai, Long
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 made the cylinder axis perpendicular to the extraordinary axis of the quartz crystal and chemically
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)
2013-01-01
There is considerable interest in the structural and functional properties of the angular gyrus (AG). Located in the posterior part of the inferior parietal lobule, the AG has been shown in numerous meta-analysis reviews to be consistently activated in a variety of tasks. This review discusses the involvement of the AG in semantic processing, word reading and comprehension, number processing, default mode network, memory retrieval, attention and spatial cognition, reasoning, and social cognition. This large functional neuroimaging literature depicts a major role for the AG in processing concepts rather than percepts when interfacing perception-to-recognition-to-action. More specifically, the AG emerges as a cross-modal hub where converging multisensory information is combined and integrated to comprehend and give sense to events, manipulate mental representations, solve familiar problems, and reorient attention to relevant information. In addition, this review discusses recent findings that point to the existence of multiple subdivisions in the AG. This spatial parcellation can serve as a framework for reporting AG activations with greater definition. This review also acknowledges that the role of the AG cannot comprehensibly be identified in isolation but needs to be understood in parallel with the influence from other regions. Several interesting questions that warrant further investigations are finally emphasized. PMID:22547530
Author's personal copy The effect of excessive tibial torsion on the capacity of muscles
Delp, Scott
of soleus to extend the knee; however, the effects of excess external torsion on the capacity of other. Analysis of the model confirmed that excessive external torsion reduces the extension capacity of soleus affected by excessive tibial torsion. With a tibial torsion deformity of 308, the capacities of soleus
Localized Torsional Tension in the DNA of Human Cells
NASA Astrophysics Data System (ADS)
Ljungman, Mats; Hanawalt, Philip C.
1992-07-01
Torsional tension in DNA may be both a prerequisite for the efficient initiation of transcription and a consequence of the transcription process itself with the generation of positive torsional tension in front of the RNA polymerase and negative torsional tension behind it. To examine torsional tension in specific regions of genomic DNA in vivo, we developed an assay using photoactivated psoralen as a probe for unconstrained DNA superhelicity and x-rays as a means to relax DNA. Psoralen intercalates more readily into DNA underwound by negative torsional tension than into relaxed DNA, and it can form interstrand DNA cross-links upon UVA irradiation. By comparing the amount of psoralen-induced DNA cross-links in cells irradiated with x-rays either before or after the psoralen treatment, we examined the topological state of the DNA in specific regions of the genome in cultured human 6A3 cells. We found that although no net torsional tension was detected in the bulk of the genome, localized tension was prominent in the DNA of two active genes. Negative torsional tension was found in the 5' end of the amplified dihydrofolate reductase gene and in a region near the 5' end of the 45S rRNA transcription unit, whereas a low level of positive torsional tension was found in a region near the 3' end of the dihydrofolate reductase gene. These results document an intragenomic heterogeneity of DNA torsional tension and lend support to the twin supercoiled domain model for transcription in the genome of intact human cells.
Torsion-balance probes of fundamental physics
E. G. Adelberger
2013-08-14
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).
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.
Torsion, Scalar Field, Mass and FRW Cosmology
Prasanta Mahato
2006-03-31
In the Einstein-Cartan space $U_4$, an axial vector torsion together with a scalar field connected to a local scale factor have been considered. By combining two particular terms from the SO(4,1) Pontryagin density and then modifying it in a SO(3,1) invariant way, we get a Lagrangian density with Lagrange multipliers. Then under FRW-cosmological background, where the scalar field is connected to the source of gravitation, the Euler-Lagrange equations ultimately give the constancy of the gravitational constant together with only three kinds of energy densities representing mass, radiation and cosmological constant. The gravitational constant has been found to be linked with the geometrical Nieh-Yan density.
Torsional suspension system for testing space structures
NASA Technical Reports Server (NTRS)
Reed, Wilmer H., III (inventor); Gold, Ronald R. (inventor)
1991-01-01
A low frequency torsional suspension system for testing a space structure uses a plurality of suspension stations attached to the space structure along the length thereof in order to suspend the space structure from an overhead support. Each suspension station includes a disk pivotally mounted to the overhead support, and two cables which have upper ends connected to the disk and lower ends connected to the space structure. The two cables define a parallelogram with the center of gravity of the space structure being vertically beneath the pivot axis of the disk. The vertical distance between the points of attachment of the cables to the disk and the pivot axis of the disk is adjusted to lower the frequency of the suspension system to a level which does not interfere with frequency levels of the space structure, thereby enabling accurate measurement.
Experimental investigation of cyclic thermomechanical deformation in torsion
NASA Technical Reports Server (NTRS)
Ellis, John R.; Castelli, Michael G.; Bakis, Charles E.
1992-01-01
An investigation of thermomechanical testing and deformation behavior of tubular specimens under torsional loading is described. Experimental issues concerning test accuracy and control specific to thermomechanical loadings under a torsional regime are discussed. A series of shear strain-controlled tests involving the nickel-base superalloy Hastelloy X were performed with various temperature excursions and compared to similar thermomechanical uniaxial tests. The concept and use of second invariants of the deviatoric stress and strain tensors as a means of comparing uniaxial and torsional specimens is also briefly presented and discussed in light of previous thermomechanical tests conducted under uniaxial conditions.
Discussion on massive gravitons and propagating torsion in arbitrary dimensions
Hernaski, C. A.; Vargas-Paredes, A. A.; Helayeel-Neto, J. A.
2009-12-15
In this paper, we reassess a particular R{sup 2}-type gravity action in D dimensions, recently studied by Nakasone and Oda, now taking torsion effects into account. Considering that the vielbein and the spin connection carry independent propagating degrees of freedom, we conclude that ghosts and tachyons are absent only if torsion is nonpropagating, and we also conclude that there is no room for massive gravitons. To include these excitations, we understand how to enlarge Nakasone-Oda's model by means of explicit torsion terms in the action and we discuss the unitarity of the enlarged model for arbitrary dimensions.
Coupling and degenerating modes in longitudinal-torsional step horns.
Harkness, Patrick; Lucas, Margaret; Cardoni, Andrea
2012-12-01
Longitudinal-torsional vibration is used and proposed for a variety of ultrasonic applications including motors, welding, and rock-cutting. To obtain this behavior in an ultrasonic step horn one can either, (i) couple the longitudinal and torsional modes of the horn by incorporating a ring of diagonal slits in the thick base section or, (ii) place helical flutes in the thin stem section to degenerate the longitudinal mode into a modified behavior with a longitudinal-torsional motion. This paper compares the efficacy of these two design approaches using both numerical and experimental techniques. PMID:22770885
Angular momentum & spin January 8, 2002
Landstreet, John D.
Angular momentum & spin January 8, 2002 1 Angular momentum Angular momentum appears as a very properties of this quantity. 1.1 Definitions The classical definition of the angular momentum of a particle¯h, the quantum mechanical operator for angular momentum becomes L = -i¯h(r × ), for example Lz = -i¯h(x y - y x
The quadratic spinor Lagrangian, axial torsion current, and generalizations
Roldao da Rocha; J. G. Pereira
2007-03-13
We show that the Einstein-Hilbert, the Einstein-Palatini, and the Holst actions can be derived from the Quadratic Spinor Lagrangian (QSL), when the three classes of Dirac spinor fields, under Lounesto spinor field classification, are considered. To each one of these classes, there corresponds a unique kind of action for a covariant gravity theory. In other words, it is shown to exist a one-to-one correspondence between the three classes of non-equivalent solutions of the Dirac equation, and Einstein-Hilbert, Einstein-Palatini, and Holst actions. Furthermore, it arises naturally, from Lounesto spinor field classification, that any other class of spinor field (Weyl, Majorana, flagpole, or flag-dipole spinor fields) yields a trivial (zero) QSL, up to a boundary term. To investigate this boundary term we do not impose any constraint on the Dirac spinor field, and consequently we obtain new terms in the boundary component of the QSL. In the particular case of a teleparallel connection, an axial torsion 1-form current density is obtained. New terms are also obtained in the corresponding Hamiltonian formalism. We then discuss how these new terms could shed new light on more general investigations.
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.
Peter Baekler; Friedrich W. Hehl
2011-10-17
Recently, gravitational gauge theories with torsion have been discussed by an increasing number of authors from a classical as well as from a quantum field theoretical point of view. The Einstein-Cartan(-Sciama-Kibble) Lagrangian has been enriched by the parity odd pseudoscalar curvature (Hojman, Mukku, and Sayed) and by torsion square and curvature square pieces, likewise of even and odd parity. (i) We show that the inverse of the so-called Barbero-Immirzi parameter multiplying the pseudoscalar curvature, because of the topological Nieh-Yan form, can only be appropriately discussed if torsion square pieces are included. (ii) The quadratic gauge Lagrangian with both parities, proposed by Obukhov et al. and Baekler et al., emerges also in the framework of Diakonov et al.(2011). We establish the exact relations between both approaches by applying the topological Euler and Pontryagin forms in a Riemann-Cartan space expressed for the first time in terms of irreducible pieces of the curvature tensor. (iii) Only in a Riemann-Cartan spacetime, that is, in a spacetime with torsion, parity violating terms can be brought into the gravitational Lagrangian in a straightforward and natural way. Accordingly, Riemann-Cartan spacetime is a natural habitat for chiral fermionic matter fields.
Hoffmann, Stefanie; Gerber, Claus; von Oldenburg, Geert; Kessler, Manuel; Stephan, Daniel; Augat, Peter
2015-04-01
To extend the indications of intramedullary nails for distal or proximal fractures, nails with angle stable locking options have been developed. Studies on the mechanical efficacy of these systems have been inconsistent likely due to confounding variables such as number, geometry, or orientation of the screws, as well as differences in the loading mode. Therefore, the aim of this study was to quantify the effect of angular stability on the mechanical performance of intramedullary nails. The results could then be compared with the effects of various locking screw parameters and loading modes. A generic model was developed consisting of artificial bone material and titanium intramedullary nail that provided the option to systematically modify the locking screw configuration. Using a base configuration, the following parameters were varied: number of screws, distance and orientation between screws, blocking of screws, and simulation of freehand locking. Tension/compression, torsional, and bending loads were applied. Stiffness and clearance around the zero loading point were determined. Angular stability had no effect on stiffness but completely blocked axial clearance (p=0.003). Simulation of freehand locking reduced clearance for all loading modes by at least 70% (p<0.003). The greatest increases in torsional and bending stiffness were obtained by increasing the number of locking screws (up to 80%, p<0.001) and by increasing the distance between them (up to 70%, p<0.001). In conclusion, our results demonstrate that the mechanical performance of IM nailing can be affected by various locking parameters of which angular stability is only one. While angular stability clearly reduces clearance of the screw within the nail, mechanical stiffness depends more on the number of screws and their relative distance. Thus, optimal mechanical performance in IM nailing could potentially be obtained by combining angular stability with optimal arrangement of locking screws. PMID:25581739
Application of instantaneous angular acceleration to diesel engine fault diagnosis
NASA Astrophysics Data System (ADS)
Ren, Yunpeng; Hu, Tianyou; Liu, Xin
2005-12-01
Diesel engine is a kind of important power generating machine, of which the running state monitoring and fault diagnosis attracts increasing attention. The theory and the method of diesel engine fault diagnosis based on angular acceleration measurement were studied, since angular acceleration contains a lot of information for diesel engine fault diagnosing and its power balance evaluating. USB data acquisition system was designed for the angular acceleration measurement, and it was composed with AVRAT09S8515 micro-processor and PDIUSBD12 USB interface IC. At the same time, the high speed micro-processor AVRAT09S8515 with unique function of automatically capturing the rising or falling edge of square wave was studied, and it was utilized in the diesel engine's crankshaft angular acceleration measuring system. The software and hardware of the whole system was designed, which supplied a whole solution to diesel engine fault diagnosis and power balance evaluation between each cylinder.
An investigation of torsional design procedures applied to lightweight concrete members
Tanner, Richard Bertrand
1962-01-01
e e ~ e o o a e e a o a a a o e o o a o a a 54 i 0. Tensile Strength Analysis 57 i i. Modulus of Rigidity Analysis LIST OF FIGURES Figure Page Stress Variations for Elastic and Plastic Theories o a 2 4, 8, Diagram for Developing Andersen... the torsion changes or must be duplicated in the reverse direction to resist both cases. s The first American to enter the field was Andersen with reports in i935, (5), f937, (6), and 1938, (7). He presented an analysis and 9 design method based...
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.
An Inexpensive Torsional Pendulum Apparatus for Rigidity Modulus Measurement.
ERIC Educational Resources Information Center
Tyagi, S.; Lord, A. E., Jr.
1979-01-01
Described is an easy to assemble, and inexpensive, torsional pendulum which gives an accuracy of measurement of the modulus of rigidity, G, comparable to the accuracy obtained with the more expensive commercially available student models. (Author/GA)
Uncommon cause of acute pelvic pain: isolated torsion of hydrosalpinx.
Ait Benkaddour, Y; Bennani, R; Aboulfalah, A; Abbassi, H
2009-12-01
Isolated torsion of hydrosalpinx is a rare cause of acute pelvic pain. Pre-operative diagnosis is very difficult because of non specific clinical presentation. Definitive diagnosis is always made at surgical exploration performed for suspected adnexal torsion and salpingectomy is performed in the majority of cases. A 34-year-old woman was admitted for acute pelvic pain with nausea and vomiting. Vaginal examination revealed a right adnexal tender mass and ultrasound revealed a well circumscribed right adnexal cystic mass. Surgical exploration has revealed torsion of a right hydrosalpinx and right salpingectomy was performed. Differential diagnosis between adnexal and tubal torsion is very difficult, however both should be managed by rapid surgical exploration which an allow precocious diagnosis and conservative treatment. PMID:20690282
Spin-torsion effects in the hyperfine structure of methanol
NASA Astrophysics Data System (ADS)
Coudert, L. H.; Gutlé, C.; Huet, T. R.; Grabow, J.-U.; Levshakov, S. A.
2015-07-01
The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.
Spin-torsion effects in the hyperfine structure of methanol.
Coudert, L H; Gutlé, C; Huet, T R; Grabow, J-U; Levshakov, S A
2015-07-28
The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling. PMID:26233126
Torsion effect on fully developed flow in a helical pipe
NASA Technical Reports Server (NTRS)
Kao, Hsiao C.
1987-01-01
Two techniques, a series expansion method of perturbed Poiseuille flow valid for low Dean numbers and a solution of the complete Navier-Stokes equation applicable to intermediate Dean values, are used to investigate the torsion effect on the fully developed laminar flow in a helical pipe of constant circular cross section. For the secondary flow patterns, the results show that the presence of torsion can produce a significant effect if the ratio of the curvature to the torsion is of order unity. The secondary flow is distorted in these cases. It is noted that the torsion effect is, however, usually small, and that the secondary flow has the usual pattern of a pair of counter-rotating vortices of nearly equal strength.
Torsion of the greater omentum: A rare preoperative diagnosis
Tandon, Ankit Anil; Lim, Kian Soon
2010-01-01
Torsion of the greater omentum is a rare acute abdominal condition that is seldom diagnosed preoperatively. We report the characteristic computed tomography (CT) scan findings and the clinical implications of this unusual diagnosis in a 41-year-old man, who also had longstanding right inguinal hernia. Awareness of omental torsion as a differential diagnosis in the acute abdomen setting is necessary for correct patient management. PMID:21423906
Thermal conductivity and torsional oscillations of solid 4He
NASA Astrophysics Data System (ADS)
Brazhnikov, M. Yu.; Zmeev, D. E.; Golov, A. I.
2012-11-01
Polycrystalline samples of hcp 4He of molar volume Vm = 19.5 cm3 with small amount of 3He impurities were grown in an annular container by the blocked-capillary method. Three concentrations of 3He, x3, were studied: isotopically purified 4He with the estimated x3 < 10-10, commercial `well-grade' helium with x3 ˜ 3.10-7 and a mixture with x3 = 2.5.10-6. Torsional oscillations at two frequencies, 132.5 and 853.6 Hz, and thermal conductivity were investigated before and after annealing. The solid helium under investigation was located not only in the annular container but also in the axial fill line inside two torsion rods and dummy bob of the double-frequency torsional oscillator. The analysis of the frequency shifts upon loading with helium and changing temperatures of different parts of the oscillator suggests that the three techniques probe the properties of solid helium in three different locations: the two different torsion modes respond to the changes of the shear modulus of solid helium in either of the two torsion rods while the thermal conductivity probes the phonon mean free path in solid helium inside the annular container. The temperature and width of the torsional anomaly increase with increasing frequency and x3. The phonon mean free path increases with increasing x3. Annealing typically resulted in an increased phonon mean free path but often in little change in the torsional oscillator response. While the magnitude of the torsional anomaly and phonon mean free path can be very different in different samples, no correlation was found between them.
[Prelabour uterine torsion complicated by partial abruption and fetal death].
Agar, N; Canis, M; Accoceberry, M; Bourdel, N; Lafaye, A-L; Gallot, D
2014-06-01
Uterine torsion is a rare obstetrical complication whose diagnosis remains challenging. We report a case of 180 degrees dextrogyre torsion at 36(+5) weeks of gestation complicated by partial abruption and in utero fetal death. Emergency cesarean section was performed through an unintentional posterior hysterotomy. Literature reports a few similar cases. Vertical hysterotomy should be advised in this context avoiding incision on lateral sides associated with increased risk of vascular or ureteral injury. PMID:24411298
Torsional vibration analysis of turbine-generator-blade coupled system
O. Matsushita; Namura; T. K. Yoshida; R. Kaneko; A. Okabe
1989-01-01
Turbine-generator sets are major components of electricity generating power plants. Pretwisted turbine blades, fixed on a rotating shaft by means of mounting disks, vibrate in both tangential and axial directions. The tangential component of blade vibrations is coupled with torsional vibrations of the shaft. This problem of a coupled shaft-blade torsional vibration in turbine-generator sets requires an equivalent reduction modeling
Killing tensors with nonvanishing Haantjes torsion and integrable systems
NASA Astrophysics Data System (ADS)
Tsiganov, Andrey V.
2015-07-01
The second-order integrable Killing tensor with simple eigenvalues and vanishing Haantjes torsion is the key ingredient in construction of Liouville integrable systems of Stäckel type. We present two examples of the integrable systems on three-dimensional Euclidean space associated with the second-order Killing tensors possessing nontrivial torsion. Integrals of motion for these integrable systems are the second- and fourth-order polynomials in momenta, which are constructed using a special family of the Killing tensors.
Torsional response of relativistic fermions in 2 + 1 dimensions
NASA Astrophysics Data System (ADS)
Valle, Manuel
2015-07-01
We consider the equilibrium partition function of an ideal gas of Dirac fermions minimally coupled to torsion in 2 + 1 dimensions. We show that the energy-momentum tensor reproduces the Hall viscosity and other parity violating terms of first order in the torsion. We also consider the modifications of the constitutive relations, and classify the corresponding susceptibilities. An entropy current consistent with zero production of entropy in equilibrium is constructed.
Changes in gravitational state cause changes in ocular torsion
NASA Technical Reports Server (NTRS)
Diamond, S. G.; Markham, C. H.
1998-01-01
Gravity-responsive eye torsion was studied simultaneously in both eyes during parabolic flight to determine the effects of weightlessness. Observed effects were that torsional position of eyes in the 1G states between parabolas was offset from the baseline positions obtained prior to the onset of parabolas, responses to hyper- and hypogravity were seen in most subjects, and responses were consistent within subjects but varied between subjects.
Non-Abelian anomalies on a curved space with torsion
Cognola, G.; Giacconi, P.
1989-05-15
Using path-integral methods and /zeta/-function regularization a nonperturbative derivation of non-Abelian-covariant and consistent anomalies on a curved space with torsion is given. All terms depending on torsion, that one has in the expression of the consistent anomaly, can be eliminated by adding suitable counterterms to the Lagrangian density. In this way, the well-known result of Bardeen is recovered. The so-called ''covariant anomaly'' will be discussed too.
Torsional chiral magnetic effect in Weyl semimetal with topological defect
Sumiyoshi, Hiroaki
2015-01-01
We propose a torsional response raised by lattice dislocation in Weyl semimetals akin to chiral magnetic effect; i.e. a fictitious magnetic field arising from screw or edge dislocation induces charge current. We demonstrate that, in sharp contrast to the usual chiral magnetic effect which vanishes in real solid state materials, the torsional chiral magnetic effect exists even for realistic lattice models, which implies the experimental detection of the effect via the measurement of the nonlocal resistivity in Weyl semimetal materials.
An experimental investigation of a general quadrilateral torsion box
Champlin, James Lund
1961-01-01
i9'kl & 9~3 AN EXPERIMENTAL INVESTIGATION OF A GENERAL QUADRILATERAL TORSION BOX A Thesis by JAMES LUND CHAMPLIN Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1961 Major Subject: Aeronautical Engineering AN EXPERIMENTAL INVESTIGATION OF A GENERAL QUADRILATERAL TORSION BOX A Thesis By JAMES LUND CHAMPLIN Approved as to style and content by: (Chairman of Committee) (Head...
An experimental study of torsional vibration measurement / b
French, Robert Sheldon
1981-01-01
AN EXPERIMENTAL STUDY OF TORSIONAL VIBRATION MEASUREMENT A Thesis by ROBERT SHELDON FRENCH Submitted to the Graduate College of Texas A&M Uniuersity in partial fulfillment of the requirement of the degree of MASTER OF SCIENCE August 1981... biajor Subject: Mechanical Engineering AN EXPERIMENTAL STUDY OF TORSIONAL VIBRATION MEASUREMENT A Thesis by ROBERT SHELDON FRENCH Approved as to style and content by: , ' (Chairman of Committee) (Mem ) ( er) (Member) (H d of Department) August...
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.
Automated angular momentum recoupling algebra
Williams, H.T. . Dept. of Physics); Silbar, R.R. )
1990-01-01
We describe a code, RACAH, for algebraic solution of angular momentum recoupling problems. The general problem is to find an optimal path from one binary tree (representing the angular momentum coupling scheme for the reduced matrix element) to another (representing the sub-integrals and spin sums to be done). RACAH is implemented on a MS-DOS microcomputer, using the SCHEME dialect of LISP. 6 refs.
Analysis of torsional oscillations using an artificial neural network
Hsu, Y.Y.; Jeng, L,H. (Dept. of Electrical Engineering, National Taiwan Univ., Taipei (Taiwan, Province of China))
1992-12-01
In this paper, a novel approach using an artificial neural network (ANN) is proposed for the analysis of torsional oscillations in a power system. In the developed artificial neural network, those system variables such as generator loadings and capacitor compensation ratio which have major impacts on the damping characteristics of torsional oscillatio modes are employed as the inputs. The outputs of the neural net provide the desired eigenvalues for torsional modes. Once the connection weights of the neural network have been learned using a set of training data derived off-line, the neural network can be applied to torsional analysis in real-time situations. To demonstrate the effectiveness of the proposed neural net, torsional analysis is performed on the IEEE First Benchmark Model. It is concluded from the test results that accurate assessment of the torsional mode eigenvalues can be achieved by the neural network in a very efficient manner. Thereofore, the proposed neural network approach can serve as a valuable tool to system operators in conducting SSR analysis in operational planning.
Torsional eye movements during psychophysical testing with rotating patterns.
Ibbotson, M R; Price, N S C; Das, V E; Hietanen, M A; Mustari, M J
2005-01-01
Torsional eye movements were measured while subjects viewed a large, high contrast windmill pattern rotating at 53 degrees /s or a small (5 degrees diameter) dot pattern rotating at 115 degrees /s. Both stimuli generated rotational eye movements consisting of torsional optokinetic nystagmus (tOKN) superimposed on a slow torsional drift in the direction of pattern rotation. With the wide-field windmill stimulus, torsional drifts of up to 7 degrees over 20 s were found. The dot pattern produced drifts of up to 2 degrees over 5-20 s. In both cases, the slow-phase speeds during tOKN were low (0.5-1 degrees /s). We conclude that reductions in slip speed are minimal with rotating stimuli, so torsional eye speeds will have a minimal effect on investigations of rotational motion aftereffect strength and perceived speed. While the slow-phase tOKN gain is low, the slow drift in torsional eye position will have significant effects on psychophysical results when the tests rely on keeping selected regions of the stimulus confined to specific areas of the retina, as is the case for phantom or remote motion aftereffects. PMID:15551078
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.
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.
Relaxation of rotational angular momentum of polar diatomic molecules in simple liquids
Padilla, A.; Perez, J.
2007-03-15
The relaxation processes of rotational angular momentum of polar diatomic molecules diluted in simple liquids are analyzed by applying a non-Markovian relaxation theory to the study of the binary time autocorrelation function of the angular momentum. This non-Markovian theory was previously applied to the study of the infrared and Raman spectroscopy, and also to the analysis of the rotational energy relaxation processes. We have obtained non-Markovian evolution equations for the two-time j-level angular momentum correlation components involved in the angular momentum correlation function. In these equations, the time-dependent angular momentum transfer rates and the pure orientational angular transfer rates are given in terms of the binary time autocorrelation function of the diatomic-solvent anisotropic interaction. The non-Markovian evolution equations converge to Markovian ones in the long time limit, reaching the angular momentum transfer rates in the usual time-independent form. Alternative time scales for the angular relaxation processes, relative to the individual rotational processes as well as to the global decay correlations, are introduced and analyzed. The theory is applied to the study of the angular momentum relaxation processes of HCl diluted in liquid SF{sub 6}, a system for which rotational energy relaxation and infrared and Raman spectroscopy was previously analyzed in the scope of the same theory.
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.
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.
NASA Astrophysics Data System (ADS)
Gascooke, Jason R.; Virgo, Edwina A.; Lawrance, Warren D.
2015-07-01
We have examined the S1?S0 transition of toluene in the region from the 00 0 band to ˜210 cm-1 above it. The spectrum reveals methyl rotor levels of 00 toluene up to m = 6 and of the lowest frequency vibration, 201, up to m = 4. The rotor levels of both 201 and 00 are perturbed by torsion-vibration coupling. The inclusion of torsion-vibration coupling leads to the S1 torsional barrier, V6, being revised from -26.376 cm-1 to -5.59 cm-1. The torsion-vibration coupling constant is determined to be 21.1 cm-1. This situation is the S1 analogue of that recently reported for S0 toluene [Gascooke et al., J. Chem. Phys. 142, 024315 (2015)]. Torsion-vibration coupling alters both the rotor band positions and the rotational contours, which particularly affects the rotational constants associated with motion around the a-axis, about which the methyl group rotates. Every vibrational state (indicated generically by X) will be involved in the corresponding X - X201 torsion-vibration coupling; so, this interaction permeates the vib-rotor manifold, providing a mechanism to enhance intramolecular vibrational energy redistribution.
Gascooke, Jason R; Virgo, Edwina A; Lawrance, Warren D
2015-07-28
We have examined the S1?S0 transition of toluene in the region from the 00 (0) band to ?210 cm(-1) above it. The spectrum reveals methyl rotor levels of 0(0) toluene up to m = 6 and of the lowest frequency vibration, 20(1), up to m = 4. The rotor levels of both 20(1) and 0(0) are perturbed by torsion-vibration coupling. The inclusion of torsion-vibration coupling leads to the S1 torsional barrier, V6, being revised from -26.376 cm(-1) to -5.59 cm(-1). The torsion-vibration coupling constant is determined to be 21.1 cm(-1). This situation is the S1 analogue of that recently reported for S0 toluene [Gascooke et al., J. Chem. Phys. 142, 024315 (2015)]. Torsion-vibration coupling alters both the rotor band positions and the rotational contours, which particularly affects the rotational constants associated with motion around the a-axis, about which the methyl group rotates. Every vibrational state (indicated generically by X) will be involved in the corresponding X - X20(1) torsion-vibration coupling; so, this interaction permeates the vib-rotor manifold, providing a mechanism to enhance intramolecular vibrational energy redistribution. PMID:26233135
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.
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.
The angular momentum of the gravitational field and the Poincare group
J. W. Maluf; S. C. Ulhoa; F. F. Faria; J. F. da Rocha-Neto
2006-09-06
We redefine the gravitational angular momentum in the framework of the teleparallel equivalent of general relativity. In similarity to the gravitational energy-momentum, the new definition for the gravitational angular momentum is coordinate independent. By considering the Poisson brackets in the phase space of the theory, we find that the gravitational energy-momentum and angular momentum correspond to a representation of the Poincar\\'e group. This result allows us to define Casimir type invariants for the gravitational field.
Coherent control of angular momentum transfer in resonant two-photon light-matter interaction.
Malik, D A; Kimel, A V; Kirilyuk, A; Rasing, Th; van der Zande, W J
2010-04-01
We show experimentally and theoretically that a polarization-shaped femtosecond laser pulse with a zero net angular momentum creates a net angular momentum in atomic rubidium during resonant two-photon excitation. The necessary conditions for the creation of a nonzero angular momentum as well as the excitation efficiencies are analyzed in the framework of second-order time-dependent perturbation theory. PMID:20481880
Full Angular Profile of the Coherent Polarization Opposition Effect
NASA Technical Reports Server (NTRS)
Mishchenko, Michael I.; Luck, Jean-Marc; Nieuwenhuizen, Theo M.
1999-01-01
We use the rigorous vector theory of weak photon localization for a semi-infinite medium composed of nonabsorbing Rayleigh scatterers to compute the full angular profile of the polarization opposition effect. The latter is caused by coherent backscattering of unpolarized incident light and accompanies the renowned backscattering intensity peak.
ON GROUP THEORETICAL ASPECTS AND SYMMETRIES OF ANGULAR MOMENTUM
Krattenthaler, Christian
coe#cients in terms of generalized hypergeometric functions of unit argument. Early studies [4, generalized hypergeometric series, Kampâ??e de Fâ??eriet functions. 1 #12; 2 Jucys and Bandzaitis [13] being Theory of Angular Momentum (QTAM) were related to the hypergeometric functions [1], [2] and the use
Calculating limits for torsion and tensile loads on drill pipe
Bailey, E.I.; Smith, J.E.
1998-02-01
Drill pipe used for drilling horizontal and extended reach holes experiences much higher torsional and tensile loads than normally seen while drilling vertical holes. This is particularly true for rigs with top drives vs. rigs with rotary tables. When pipe is rotated while pulling out of the hole, which is commonly done on top drive rigs, the drill pipe can experience high tensile and torsional loading simultaneously. These conditions increase the probability of overload on tool joints and require that the drill pipe and tool joint selection process include consideration of combined loading. Calculating the required drill pipe strength for vertical holes is straightforward and spelled out in Section 5 of API RP7G. In vertical hole applications, pipe is almost always selected for its tensile capacity and the torsional strength of the pipe generally does not require special consideration. In Section 4 of API Sec 7, API recommends that the tool joints have a torsional strength of 80% of the pipe`s torsional strength; this is usually adequate. The torsional strength and tensile strength of commonly used drill pipe and tool joint combinations are tabulated in Tables 2 through 10 of API RP7G. Appendix A.8.3 in API RP7G shows a method for plotting a graphical representation of the combined torsional and tensile operational limits of tool joints. How to calculate the limits of the drill pipe tube is shown in Appendix A.9.2. This paper defines terms and limits, and discusses building and using a diagram to determine safe loads.
Angular momentum of isolated systems
Adam D. Helfer
2007-09-07
Penrose's twistorial approach to the definition of angular momentum at null infinity is developed so that angular momenta at different cuts can be meaningfully compared. This is done by showing that the twistor spaces associated with different cuts of scri can be identified as manifolds (but not as vector spaces). The result is a well-defined, Bondi-Metzner-Sachs-invariant notion of angular momentum in a radiating space-time; the difficulties and ambiguities previously encountered are attached to attempts to express this in special-relativistic terms, and in particular to attempts to identify a single Minkowski space of origins. Unlike the special-relativistic case, the angular momentum cannot be represented by a purely j=1 quantity M_{ab}, but has higher-j contributions as well. Applying standard kinematic prescriptions, these higher-j contributions are shown to correspond precisely to the shear. Thus it appears that shear and angular momentum should be regarded as different aspects of a single unified concept.
Week 11: Chapter 11 Angular Momentum
1 Week 11: Chapter 11 Angular Momentum The Vector Product There are instances where the product i j j i i j k Angular Momentum Consider a particle of mass m located at the vector position p r F r r p r p p r Angular Momentum, cont The instantaneous angular momentum
ANGULAR MOMENTUM: AN APPROACH TO COMBINATORIAL SPACETIME
Baez, John
ANGULAR MOMENTUM: AN APPROACH TO COMBINATORIAL SPACEÂTIME ROGER PENROSE I want to describe an ideaÂtime in a very intimate way, is in angular momentum. The idea here, then, is to start with the concept of angular momentum--- here one has a discrete spectrum---and use the rules for combining angular This paper
Investigation of the torsional barrier of EDOT using molecular mechanics and DFT methods.
Durães, Jussara A; da Silva Filho, Demétrio A; Ceschin, Artemis M; Sales, Maria J A; Martins, João B L
2014-08-01
When heterocyclic monomers are polymerized by electrochemical or chemical methods, they form fully conjugated polymers which have a wide range of applications due to their outstanding electronic properties. Among this class of compounds, thiophene derivatives are widely used due to their chemical stability and synthesis flexibility. With the goal to investigate the torsion barrier of polymer chains, a few units of 3,4-ethylenedioxythiophene (EDOT) were chosen and submitted to molecular mechanics (MM), density functional theory (DFT) and coupled cluster CCSD(T) calculations. This study helps to understand the performance and transferability of force fields used in molecular mechanics and molecular dynamics simulations often used to describe structure-property relationships of those systems. Determination of inter-ring torsion angle was performed in a comparative study using both force field, DFT and CCSD(T) methods. A good agreement was noticed between MM and QC results and highlights the importance of the description of the interactions involving the oxygen atoms present in the structure of EDOT. These observations are related to the ?,?-coupling that occurs between the monomer units and yields a linear polymer. DFT HOMO and LUMO orbitals were also presented. Finally, UV-vis spectra of EDOT units were obtained using several levels of theory by means of time-dependent DFT calculations (TD-DFT). PMID:25116151
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.
Phenomenology of preequilibrium angular distributions
Kalbach, C.; Mann, F.M.
1980-05-01
The systematics of continuum angular distributions from a wide variety of light ion nuclear reactions have been studied. To first order, the shape of the angular distributions have been found to depend only on the energy of the outgoing particle and on the division of the cross section into multi-step direct and multi-step compound parts. The angular distributions can be described in terms of Legendre polynomials with the reduced polynomial coefficients exhibiting a simple dependence on the outgoing particle energy. Two integer and four continuous parameters with universal values are needed to describe the coefficients for outgoing energies of 2 to 60 MeV in all the reaction types studied. This parameterization combined with a modified Griffin model computer code permits the calculation of double differential cross sections for light ion continuum reactions where no data is available.
Energy, angular momentum, superenergy and angular supermomentum in conformal frames
Mariusz P. Dabrowski; Janusz Garecki
2007-12-14
We find the rules of the conformal transformation for the energetic quantities such as the Einstein energy-momentum complex, the Bergmann-Thomson angular momentum complex, the superenergy tensor, and the angular supermomentum tensor of gravitation and matter. We show that the conformal transformation rules for the matter parts of both the Einstein complex and the Bergmann-Thomson complex are fairly simple, while the transformation rules for their gravitational parts are more complicated. We also find that the transformational rules of the superenergy tensor of matter and the superenergy tensor of gravity are quite complicated except for the case of a pure gravity. In such a special case the superenergy density as well as the sum of the superenergy density and the matter energy density are invariants of the conformal transformation. Besides, in that case, a conformal invariant is also the Bel-Robinson tensor which is a part of the superenergy tensor. As for the angular supermomentum tensor of gravity - it emerges that its transformational rule even for a pure gravity is quite complicated but this is not the case for the angular supermomentum tensor of matter. Having investigated some technicalities of the conformal transformations, we also find the conformal transformation rule for the curvature invariants and, in particular, for the Gauss-Bonnet invariant in a spacetime of arbitrary dimension.
Non-Colinearity of Angular Velocity and Angular Momentum
ERIC Educational Resources Information Center
Burr, A. F.
1974-01-01
Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)
Cordonier-Tello, Fabrizio; Mella, Patricio; Rodríguez, Eduardo
2015-01-01
In stark contrast with the three-dimensional case, higher-dimensional Chern-Simons theories can have non-topological, propagating degrees of freedom. Finding those vacua that allow for the propagation of linear perturbations, however, proves to be surprisingly challenging. The simplest solutions are somehow "hyper-stable," and preclude the construction of realistic, four-dimensional physical models. In the context of Chern-Simons gravity, we show that endowing the vacuum with torsion can be helpful to overcome this problem. In particular, we consider a five-dimensional Chern-Simons gravity theory, off-shell gauge-invariant under the Weyl subgroup of the conformal group. We find a Lorentz-flat vacuum with non-vanishing torsion, which gives rise to propagating degrees of freedom on a Randall-Sundrum brane universe. On the brane, torsion vanishes in all the four-dimensional directions, and the metric perturbations propagate as standard gravitational waves on a four-dimensional Minkowski background. In the non-pe...
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.
Two-component spinors in spacetimes with torsionful affinities
NASA Astrophysics Data System (ADS)
Cardoso, J. G.
2015-01-01
The essentially unique torsionful version of the classical two-component spinor formalisms of Infeld and van der Waerden is presented. All the metric spinors and connecting objects that arise here are formally the same as the ones borne by the traditional formalisms. Any spin-affine connexion appears to possess a torsional part which is conveniently chosen as a suitable asymmetric contribution. Such a torsional affine contribution thus supplies a gauge-invariant potential that can eventually be taken to carry an observable character, and thereby effectively takes over the role of any trivially realizable symmetric contribution. The overall curvature spinors for any spin-affine connexion accordingly emerge from the irreducible decomposition of a mixed world-spin object which in turn comes out of the action on elementary spinors of a typical torsionful second-order covariant derivative operator. Explicit curvature expansions are likewise exhibited which fill in the gap related to their absence from the literature. It is then pointed out that the utilization of the torsionful spinor framework may afford locally some new physical descriptions.
Microelectromechanical Systems Resonator Utilizing Torsional-to-Transverse Vibration Conversion
NASA Astrophysics Data System (ADS)
Kiso, Masaya; Okada, Mitsuhiro; Tamano, Akimasa; Fujiura, Hideaki; Miyauchi, Hideo; Niki, Kazuya; Tanigawa, Hiroshi; Suzuki, Kenichiro
2011-06-01
A silicon microelectromechanical systems (MEMS) resonator utilizing the torsional-to-transverse vibration conversion is designed, fabricated and evaluated. The resonant frequency for the torsional modes mostly depends on only beam length, providing a large tolerance in the fabrication process. It has been, however, a critical issue to investigate the mechanism for generating the torsional vibration and the reduction of motional resistance. We propose a new beam structure, in which four torsion beams are vibrated by twist force generated by a transverse beam. The novel process for fabricating resonators provides a narrow gap surrounded by flat surfaces, which can reduce the motional resistance. The fabricated resonators are measured with a laser-Doppler (LD) vibrometer. The scanning function of the LD vibrometer confirms the torsional-to-transverse vibration conversion has been successfully achieved. The measured resonant frequency, 10.96 MHz, is in good agreement with the simulated one. The Q-factor has been also measured to be as high as 2.2 ×104 in vacuum. The electrical characteristic is evaluated with an impedance analyzer. At the resonant frequency, the extracted motional resistance for the 0.5-µm-gap resonator is 2.0 M?, which is greatly reduced, owing to the narrow gap effect, from that of the 1-µm-gap resonator. The temperature coefficient of the resonant frequency between -40 and 85 °C, has been measured to be -24.4 ppm/deg. The resonant frequency linearly decreases as the temperature rises.
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.
Two-Component Spinors in Spacetimes with Torsionful Affinities
J. G. Cardoso
2015-01-23
The essentially unique torsionful version of the classical two-component spinor formalisms of Infeld and van der Waerden is presented. All the metric spinors and connecting objects that arise here are formally the same as the ones borne by the traditional formalisms. Any spin-affine connexion appears to possess a torsional part which is conveniently chosen as a suitable asymmetric contribution. Such a torsional affine contribution thus supplies a gauge-invariant potential that can eventually be taken to carry an observable character, and thereby effectively takes over the role of any trivially realizable symmetric contribution. The overall curvature spinors for any spin-affine connexion accordingly emerge from the irreducible decomposition of a mixed world-spin object which in turn comes out of the action on elementary spinors of a typical torsionful second-order covariant derivative operator. Explicit curvature expansions are likewise exhibited which fill in the gap related to their absence from the literature. It is then pointed out that the utilization of the torsionful spinor framework may afford locally some new physical descriptions.
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.
Elevated temperature axial and torsional fatigue behavior of Haynes 188
NASA Technical Reports Server (NTRS)
Bonacuse, Peter J.; Kalluri, Sreeramesh
1995-01-01
The results are reported for high-temperature axial and torsional low-cycle fatigue experiments performed at 760 C in air on thin-walled tubular specimens of Haynes 188, a wrought cobalt-based superalloy. Data are also presented for mean coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. This data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME Boiler and Pressure Code), Manson-Halford, modified multiaxiality factor (proposed in this paper), modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The modified multiaxiality factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.
Elevated temperature axial and torsional fatigue behavior of Haynes 188
NASA Technical Reports Server (NTRS)
Bonacuse, Peter J.; Kalluri, Sreeramesh
1992-01-01
The results of high-temperature axial and torsional low-cycle fatigue experiments performed on Haynes 188, a wrought cobalt-base superalloy, are reported. Fatigue tests were performed at 760 C in air on thin-walled tubular specimens at various ranges under strain control. Data are also presented for coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. The data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME boiler and pressure vessel code), Manson-Halford, Modified Multiaxiality Factor (proposed here), Modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The Modified Multiaxiality Factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.
Modelling the torsion of thin metal wires by distortion gradient plasticity
NASA Astrophysics Data System (ADS)
Bardella, Lorenzo; Panteghini, Andrea
2015-05-01
Under small strains and rotations, we apply a phenomenological higher-order theory of distortion gradient plasticity to the torsion problem, here assumed as a paradigmatic benchmark of small-scale plasticity. Peculiar of the studied theory, proposed about ten years ago by Morton E. Gurtin, is the constitutive inclusion of the plastic spin, affecting both the free energy and the dissipation. In particular, the part of the free energy, called the defect energy, which accounts for Geometrically Necessary Dislocations, is a function of Nye's dislocation density tensor, dependent on the plastic distortion, including the plastic spin. For the specific torsion problem, we implement this distortion gradient plasticity theory into a Finite Element (FE) code characterised by implicit (Backward Euler) time integration, numerically robust and accurate for both viscoplastic and rate-independent material responses. We show that, contrariwise to other higher-order theories of strain gradient plasticity (neglecting the plastic spin), the distortion gradient plasticity can predict some strengthening even if a quadratic defect energy is chosen. On the basis of the results of many FE analyses, concerned with (i) cyclic loading, (ii) switch in the higher-order boundary conditions during monotonic plastic loading, (iii) the use of non-quadratic defect energies, and (iv) the prediction of experimental data, we mainly show that (a) including the plastic spin contribution in a gradient plasticity theory is highly recommendable to model small-scale plasticity, (b) less-than-quadratic defect energies may help in describing the experimental results, but they may lead to anomalous cyclic behaviour, and (c) dissipative (unrecoverable) higher-order finite stresses are responsible for an unexpected mechanical response under non-proportional loading.
Bastrukov, S I; Molodtsova, I V; Wu, E H; Chen, G T; Lan, S H
2009-01-01
The Lorentz-force-driven global torsional nodeless vibrations of the neutron star model with Ferraro's form of axisymmetric nonhomogeneous poloidal internal and dipolar external magnetic field are investigated. Making use of the energy variational method of magneto-solid-mechanical theory of perfectly conducting elastic medium threaded by magnetic field, the one-parametric spectral formula for the frequency of this toroidal Alfv\\'en vibrational mode is obtained and compared with the frequency spectrum of such a mode in the neutron star with homogeneous internal and dipolar external magnetic field that has early been analytically derived in similar manner. The relevance of considered asteroseismic model to quasi-periodic oscillations discovered in the X-ray flux during the giant flare of SGR 1806-20 and SGR 1900+14 and interpreted as being produced by torsional seismic vibrations about magnetic axis of underlying magnetar is discussed.
Kinetic description of electron plasma waves with orbital angular momentum
Mendonca, J. T.
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.
Angular momentum non conserving symmetries in bosonic models
L. Fortunato; W. A. de Graaf
2011-02-23
The Levi-Malcev decomposition is applied to bosonic models of quantum mechanics based on unitary Lie algebras u(2), u(2)+u(2), u(3) and u(4) to clearly disentangle semisimple subalgebras. The theory of weighted Dynkin diagrams is then applied to identify conjugacy classes of relevant A_1 subalgebras allowing to introduce a complete classification of new angular momentum non conserving (AMNC) dynamical symmetries. The tensor analysis of the whole algebra based on the new "angular momentum" operators reveals unexpected spinors to occur in purely bosonic models. The new chains of subalgebra can be invoked to set up ANMC bases for diagonalization.
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 ...
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...
Edge delamination of composite laminates subject to combined tension and torsional loading
NASA Technical Reports Server (NTRS)
Hooper, Steven J.
1990-01-01
Delamination is a common failure mode of laminated composite materials. Edge delamination is important since it results in reduced stiffness and strength of the laminate. The tension/torsion load condition is of particular significance to the structural integrity of composite helicopter rotor systems. Material coupons can easily be tested under this type of loading in servo-hydraulic tension/torsion test stands using techniques very similar to those used for the Edge Delamination Tensile Test (EDT) delamination specimen. Edge delamination of specimens loaded in tension was successfully analyzed by several investigators using both classical laminate theory and quasi-three dimensional (Q3D) finite element techniques. The former analysis technique can be used to predict the total strain energy release rate, while the latter technique enables the calculation of the mixed-mode strain energy release rates. The Q3D analysis is very efficient since it produces a three-dimensional solution to a two-dimensional domain. A computer program was developed which generates PATRAN commands to generate the finite element model. PATRAN is a pre- and post-processor which is commonly used with a variety of finite element programs such as MCS/NASTRAN. The program creates a sufficiently dense mesh at the delamination crack tips to support a mixed-mode fracture mechanics analysis. The program creates a coarse mesh in those regions where the gradients in the stress field are low (away from the delamination regions). A transition mesh is defined between these regions. This program is capable of generating a mesh for an arbitrarily oriented matrix crack. This program significantly reduces the modeling time required to generate these finite element meshes, thus providing a realistic tool with which to investigate the tension torsion problem.
NASA Astrophysics Data System (ADS)
Klopper, Wim; Schütz, Martin; Lüthi, Hans P.; Leutwyler, Samuel
1995-07-01
A torsional potential energy surface for the cyclic water trimer was calculated at the level of second-order Møller-Plesset perturbation theory. For the construction of this ab initio surface, the first-order wave function was expanded in a many-electron basis which linearly depends on the interelectronic coordinates r12. The one-electron basis of Gaussian orbitals was calibrated on the water monomer and dimer to ensure that the ab initio surface computed represents the (near- ) basis set limit for the level of theory applied. The positions of the free O—H bonds are described by three torsional angles. The respective three-dimensional torsional space was investigated by 70 counterpoise corrected single-point calculations for various values of these angles, providing a grid to fit an analytical representation of the potential energy surface. The four symmetry unique stationary points previously found at the Hartree-Fock and conventional Møller-Plesset levels [Schütz et al., J. Chem. Phys. 99, 5228 (1993)] were studied in detail: Relative energies of the structures were calculated by applying second-order Møller-Plesset and coupled cluster methods; harmonic vibrational frequencies were calculated at the second-order Møller-Plesset level with a 6-311++G(d,p) basis set at these stationary points. It is expected that the present torsional potential energy surface for the water trimer will play an important role in the understanding of the vibrational transitions observed by far-infrared vibration-rotation-tunneling spectroscopy in terms of a nearly free pseudorotational interconversion on a cyclic vibrational-tunneling path.
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
Left-sided omental torsion with inguinal hernia
Hirano, Yasumitsu; Oyama, Kaeko; Nozawa, Hiroshi; Hara, Takuo; Nakada, Koichi; Hada, Masahiro; Takagi, Takeshi; Hirano, Makoto
2006-01-01
We report a case of surgically proved left-sided torsion of the greater omentum that caused secondary by untreated inguinal hernia. Case A 36-year-old man presented to our hospital with abdominal pain. He had been diagnosed with a left inguinal hernia, but he had not received any treatments. Contrast-enhanced computed tomography (CT) of the abdomen showed a large fat density mass below the Sigmoid colon and left inguinal hernia with incarcerated fat. Exploratory laparotomy revealed torsion of the greater omentum with small bloody ascites. The greater omentum was twisted into one and a half circles and entered into a left inguinal hernia. An omentectomy with a repair of left inguinal hernia was performed. A resected omentum was submitted for pathological examination, which showed hemorrhagic infarction. Omental torsion is a rare cause of acute abdominal pain but should be included in the differential diagnoses of acute abdomen, especially in patients with untreated inguinal hernia. PMID:16489689
Graphene-based torsional resonator from molecular-dynamics simulation
NASA Astrophysics Data System (ADS)
Jiang, Jin-Wu; Wang, Jian-Sheng
2011-12-01
Molecular-dynamics simulations are performed to study graphene-based torsional mechanical resonators. The quality factor is calculated by QF=??/2?, where the frequency ? and lifetime ? are obtained from the correlation function of the normal mode coordinate. Our simulations reveal the radius dependence of the quality factor as QF=2628/(22R- 1+0.004R2), which yields a maximum value at some proper radius R. This maximum point is due to the strong boundary effect in the torsional resonator, as disclosed by the temperature distribution in the resonator. Resulting from the same boundary effect, the quality factor shows a power law temperature dependence with power factors below 1.0. The theoretical results supply some valuable information for the manipulation of the quality factor in future experimental devices based on the torsional mechanical resonator.
``Quasi-complete'' mechanical model for a double torsion pendulum
NASA Astrophysics Data System (ADS)
De Marchi, Fabrizio; Pucacco, Giuseppe; Bassan, Massimo; De Rosa, Rosario; Di Fiore, Luciano; Garufi, Fabio; Grado, Aniello; Marconi, Lorenzo; Stanga, Ruggero; Stolzi, Francesco; Visco, Massimo
2013-06-01
We present a dynamical model for the double torsion pendulum nicknamed “PETER,” where one torsion pendulum hangs in cascade, but off axis, from the other. The dynamics of interest in these devices lies around the torsional resonance, that is at very low frequencies (mHz). However, we find that, in order to properly describe the forced motion of the pendulums, also other modes must be considered, namely swinging and bouncing oscillations of the two suspended masses, that resonate at higher frequencies (Hz). Although the system has obviously 6+6 degrees of freedom, we find that 8 are sufficient for an accurate description of the observed motion. This model produces reliable estimates of the response to generic external disturbances and actuating forces or torques. In particular, we compute the effect of seismic floor motion (“tilt” noise) on the low frequency part of the signal spectra and show that it properly accounts for most of the measured low frequency noise.
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.; Verth, G.; Jess, D. B.
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.
Carter Constant and Angular Momentum
Sajal Mukherjee; Rajesh Kumble Nayak
2015-07-05
We investigate the carter like constant for a particle in a non relativistic dipolar field. This special case is a missing link between carter constant in stationary axially symmetric spacetime such as Kerr solution and its possible Newtonian counterpart. We use this system to carry over the definition of angular momentum from Newtonian mechanics to relativistic stationary axially symmetric stationary spacetime.
Unified Angular Momentum of Dyons
Shalini Dangwal; P. S. Bisht; O. P. S. Negi
2006-08-22
Unified quaternionic angular momentum for the fields of dyons and gravito-dyons has been developed and the commutation relations for dynamical variables are obtained in compact and consistent manner. Demonstrating the quaternion forms of unified fields of dyons (electromagnetic fields) and gravito-dyons (gravito-Heavisidian fields of linear gravity), corresponding quantum equations are reformulated in compact, simpler and manifestly covariant way.
Fractionalization of angular momentum at finite temperature around a magnetic vortex
Sitenko, Yu.A. [Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 14-b Metrologichna str., Kyiv 03143 (Ukraine) and Physics Department, National Taras Shevchenko University of Kyiv, 2 Academician Glushkov ave., Kyiv 03127 (Ukraine)]. E-mail: yusitenko@bitp.kiev.ua; Vlasii, N.D. [Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 14-b Metrologichna str., Kyiv 03143 (Ukraine); Physics Department, National Taras Shevchenko University of Kyiv, 2 Academician Glushkov ave., Kyiv 03127 (Ukraine)
2007-04-15
Ambiguities in the definition of angular momentum of a quantum-mechanical particle in the presence of a magnetic vortex are reviewed. We show that the long-standing problem of the adequate definition is resolved in the framework of the second-quantized theory at nonzero temperature. Planar relativistic Fermi gas in the background of a point-like magnetic vortex with arbitrary flux is considered, and we find thermal averages, quadratic fluctuations, and correlations of all observables, including angular momentum, in this system. The kinetic definition of angular momentum is picked out unambiguously by the requirement of plausible behaviour for the angular momentum fluctuation and its correlation with fermion number.
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.
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.
Coupled bending-bending-torsion flutter of a mistuned cascade with nonuniform blades
NASA Technical Reports Server (NTRS)
Kaza, K. R. V.; Kielb, R. E.
1982-01-01
A set of aeroelastic equations describing the motion of an arbitrarily mistuned cascade with flexible, pretwisted, nonuniform blades is developed using an extended Hamilton's principle. The derivation of the equations has its basis in the geometric nonlinear theory of elasticity in which the elongations and shears are negligible compared to unity. A general expression for foreshortening of a blade is derived and is explicity used in the formulation. The blade aerodynamic loading in the subsonic and supersonic flow regimes is obtained from two dimensional, unsteady, cascade theories. The aerodynamic, inertial and structural coupling between the bending (in two planes) and torsional motions of the blade is included. The equations are used to investigate the aeroelastic stability and to quantify the effect of frequency mistuning on flutter in turbofans. Results indicate that a moderate amount of intentional mistuning has enough potential to alleviate flutter problems in unshrouded, high aspect ratio turbofans.
Coupled bending-bending-torsion flutter of a mistuned cascade with nonuniform blades
NASA Technical Reports Server (NTRS)
Kaza, K. R. V.; Kielb, R. E.
1982-01-01
A set of aeroelastic equations describing the motion of an arbitrarily mistuned cascade with flexible, pretwisted, nonuniform blades is developed using an extended Hamilton's principle. The derivation of the equations has its basis in the geometric nonlinear theory of elasticity in which the elongations and shears are negligible compared to unity. A general expression for foreshortening of a blade is derived and is explicitly used in the formulation. The blade aerodynamic loading in the subsonic and supersonic flow regimes is obtained from two-dimensional, unsteady, cascade theories. The aerodynamic, inertial and structural coupling between the bending (in two planes) and torsional motions of the blade is included. The equations are used to investigate the aeroelastic stability and to quantify the effect of frequency mistuning on flutter in turbofans. Results indicate that a moderate amount of intentional mistuning has enough potential to alleviate flutter problems in unshrouded, high-aspect-ratio turbofans.
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.
Spin connection as Lorentz gauge field: propagating torsion
Cianfrani, Francesco; Scopelliti, Vincenzo
2015-01-01
We propose a modified gravitational action containing besides the Einstein-Hilbert term some quadratic contributions resembling the Yang-Mills lagrangian for the spin connections. We outline how a propagating torsion arises and we solve explicitly the linearised equations of motion on a Minkowski background. We identify among torsion components six degrees of freedom: one is carried by a pseudo-scalar particle, five by a tachyon field. By adding spinor fields, we point out how only the pseudo-scalar particle couples directly with fermions and we evaluate the associated coupling constant, which is suppressed by the ratio between fermion and Planck masses.
Spin connection as Lorentz gauge field: propagating torsion
Francesco Cianfrani; Giovanni Montani; Vincenzo Scopelliti
2015-05-05
We propose a modified gravitational action containing besides the Einstein-Hilbert term some quadratic contributions resembling the Yang-Mills lagrangian for the spin connections. We outline how a propagating torsion arises and we solve explicitly the linearised equations of motion on a Minkowski background. We identify among torsion components six degrees of freedom: one is carried by a pseudo-scalar particle, five by a tachyon field. By adding spinor fields, we point out how only the pseudo-scalar particle couples directly with fermions and we evaluate the associated coupling constant, which is suppressed by the ratio between fermion and Planck masses.
Free torsional vibrations of tapered cantilever I-beams
NASA Astrophysics Data System (ADS)
Rao, C. Kameswara; Mirza, S.
1988-08-01
Torsional vibration characteristics of linearly tapered cantilever I-beams have been studied by using the Galerkin finite element method. A third degree polynomial is assumed for the angle of twist. The analysis presented is valid for long beams and includes the effect of warping. The individual as well as combined effects of linear tapers in the width of the flanges and the depth of the web on the torsional vibration of cantilever I-beams are investigated. Numerical results generated for various values of taper ratios are presented in graphical form.
Torsional rigidity of positively and negatively supercoiled DNA.
Selvin, P R; Cook, D N; Pon, N G; Bauer, W R; Klein, M P; Hearst, J E
1992-01-01
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 -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. PMID:1553534
High pressure torsion of Cu-based metallic glasses
NASA Astrophysics Data System (ADS)
Hóbor, S.; Kovács, Zs; Zhilyaev, A. P.; Varga, L. K.; Szabó, P. J.; Révész, Á.
2010-07-01
Cu-Zr-Ti metallic glass was subjected to high pressure torsion applying different revolution times (180s, 120s, 60s). Both deformation and deformation rate dependent microstructural and thermal properties were characterized by scanning electron microscopy, X-ray diffraction and calorimetry, respectively. In order to estimate the temperature rise in the metallic glass during high pressure torsion, quasi three-dimensional heat conduction equation with a source term was considered. Solutions indicate that the saturation temperature strongly depends on the revolution time, i. e. on the deformation rate.
The Accelerating Expansion of the Universe and Torsion Energy
M. I. Wanas
2008-02-27
In the present work, it is shown that the problem of the accelerating expansion of the Universe can be directly solved by applying Einstein geometrization philosophy in a wider geometry. The geometric structure used to fulfil the aim of the work is a version of Absolute Parallelism geometry in which curvature and torsion are simultaneously non vanishing objects. It is shown that, while the energy corresponding to the curvature of space- time gives rise to an attractive force, the energy corresponding to the torsion indicates the presence of a repulsive force. A fine tuning parameter can be adjusted to give the observed phenomena.
Inflation in $R + R^2$ Gravity with Torsion
Chih-Hung Wang; Yu-Huei Wu
2009-02-06
We examine an inflationary model in $R + R^2$ gravity with torsion, where $R^2$ denotes five independent quadratic curvature invariants; it turns out that only two free parameters remain in this model. We show that the behavior of the scale factor $a(t)$ is determined by two scalar fields, axial torsion $\\chi(t)$ and the totally anti-symmetric curvature $E(t)$, which satisfy two first-order differential equations. Considering $\\dot{\\chi}\\approx 0$ during inflation leads to a power-law inflation: $a \\sim (t+ A)^p$ where $1inflation, $\\chi$ and $E$ will enter into an oscillatory phase.
X. Li; L. Qu; G. Wen; C. Li
2003-01-01
This paper primarily focuses on detecting electrical faults in turbine generator sets by monitoring torsional vibrations with the help of the non-contact measurement technique and analysing the data acquired from torsional vibration meter. Torsional vibrations in shaft trains can be excited by periodic excitation due to a variety of electromagnetic disturbances or unsteady flow in large steam turbine generator sets
The torsional and asymmetry splittings in HSOH Koichi M.T. Yamada a,*, Per Jensen b
Giesen, Thomas
The torsional and asymmetry splittings in HSOH Koichi M.T. Yamada a,*, Per Jensen b , Stephen C. Winnewisser, P. Jensen, J. Mol. Struct. 695Â696 (2004) 323] to explain the torsional splittings observed, Winnewisser, and Jensen [1] (hereinafter denoted YWJ) presented analytical expressions for the torsional
Tension/torsion loading of composite laminates with free-edge boundary conditions
NASA Technical Reports Server (NTRS)
Hooper, Steven J.; Hagemeier, Rick; Ramaprasad, Srinivasan
1991-01-01
A finite element analysis of a family of quasi-isotropic graphite/epoxy laminates was conducted for tension, torsion, and combined tension/torsion loading. The model was employed to investigate the effects of delaminations on torsional stiffness and also to evaluate the total strain energy release rates associated with these delaminations.
QUASI-STATIC AND DYNAMIC TORSION TESTING OF CERAMIC COATINGS USING HIGH-SPEED PHOTOGRAPHY
Espinosa, Horacio D.
QUASI-STATIC AND DYNAMIC TORSION TESTING OF CERAMIC COATINGS USING HIGH-SPEED PHOTOGRAPHY François were performed on a Kolsky bar apparatus modified for torsion loading. High-speed photography was used-static and dynamic loading. A Kolsky bar [6] modified for torsional loading was used. High-Speed Photography
Left common basal pyramid torsion following left upper lobectomy/segmentectomy.
Wang, Wei-Li; Cheng, Yen-Po; Cheng, Ching-Yuan; Wang, Bing-Yen
2015-05-01
Lobar or segmental lung torsion is a severe complication of lung resection. To the best of our knowledge, common basal pyramid torsion has never been reported. We describe a case of left basal pyramid torsion after left upper lobectomy and superior segmentectomy, which was successfully treated by thoracoscopic surgery. PMID:24948781
Angular distributions of Ar reflected from molten metal surfaces
Muis, A.; Manson, J.R. [Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 (United States)] [Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 (United States)
1999-07-01
Recent experimental measurements of the angular distributions of monoenergetic beams of Ar atoms, with incident energies of up to 1 eV scattered from a molten In surface, are compared with calculated intensities. The data are described by classical scattering theory and the agreement indicates that the shapes of the lobes are dominated by single collisions with the surface, and the interaction potential has a smooth repulsive barrier similar to that commonly used to describe rare-gas scattering from crystalline metals. The attractive adsorption well of the interaction potential is considered, and is shown to have significant effects on the angular distributions at low incident energy. The dependence of the angular distributions on surface temperature is also well described. {copyright} {ital 1999 American Institute of Physics.}
Chiral symmetries associated with angular momentum
NASA Astrophysics Data System (ADS)
Bhattacharya, M.; Kleinert, M.
2014-03-01
In quantum mechanics courses, symmetries of a physical system are usually introduced as operators which commute with the Hamiltonian. In this paper we will consider chiral symmetries which anticommute with the Hamiltonian. Typically, introductory courses at the (under)graduate level do not discuss these simple, useful and beautiful symmetries at all. The first time a student encounters them is when the Dirac equation is discussed in a course on relativistic quantum mechanics, or when particle-hole symmetry is studied in the context of superconductivity. In this paper, we will show how chiral symmetries can be simply elucidated using the theory of angular momentum, which is taught in virtually all introductory quantum mechanics courses.
Orbital angular momentum entanglement in turbulence
Alpha Hamadou Ibrahim; Filippus S. Roux; Melanie McLaren; Thomas Konrad; Andrew Forbes
2013-06-27
The turbulence induced decay of orbital angular momentum (OAM) entanglement between two photons is investigated numerically and experimentally. To compare our results with previous work, we simulate the turbulent atmosphere with a single phase screen based on the Kolmogorov theory of turbulence. We consider two different scenarios: in the first only one of the two photons propagates through turbulence, and in the second both photons propagate through uncorrelated turbulence. Comparing the entanglement evolution for different OAM values, we found the entanglement to be more robust in turbulence for higher OAM values. We derive an empirical formula for the distance scale at which entanglement decays in term of the scale parameters and the OAM value.
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.
The missing angular momentum of superconductors
NASA Astrophysics Data System (ADS)
Hirsch, J. E.
2008-06-01
We point out that the Meissner effect, the process by which a superconductor expels magnetic field from its interior, represents an unsolved puzzle within the London-Bardeen-Cooper-Schrieffer theoretical framework used to describe the physics of conventional superconductors, because it appears to give rise to non-conservation of angular momentum. Possible ways to avoid this inconsistency within the conventional theory of superconductivity are argued to be far-fetched. Consequently, we argue that unless/until a consistent explanation is put forth, the existence of the Meissner effect represents an anomaly that casts doubt on the validity of the conventional framework. Instead, we point out that three elements of the unconventional theory of hole superconductivity (that are not part of the conventional theory) allow for a consistent explanation of the Meissner effect, namely: (i) that the charge distribution in superconductors is macroscopically inhomogeneous, (ii) that superconducting electrons reside in mesoscopic orbits of radius 2?L (?L = London penetration depth), and (iii) that spin-orbit coupling plays an essential role in superconductivity.
Torsional and bending rigidity of the double helix from data on small DNA rings.
Frank-Kamenetskii, M D; Lukashin, A V; Anshelevich, V V; Vologodskii, A V
1985-02-01
We have calculated the variance of equilibrium distribution of a circular wormlike polymer chain over the writhing number, [Wr)2), as a function of the number of Kuhn statistical segments, n. For large n these data splice well with our earlier results obtained for a circular freely jointed polymer chain. Assuming that [delta Lk)2) = [delta Tw)2) we have compared our results with experimental data on the chain length dependence of the [delta Lk)2) value recently obtained by Horowitz and Wang for small DNA rings. This comparison has shown an excellent agreement between theory and experiment and yielded a reliable estimate of the torsional and bending rigidity parameters. Namely, the torsional rigidity constant is C = 3.0.10(-19) erg cm, and the bending rigidity as expressed in terms of the DNA persistence length is a = 500 A. The obtained value of C agrees well with earlier estimates by Shore and Baldwin as well as by Horowitz and Wang whereas the a value is in accord with the data of Hagerman. We have found the data of Shore and Baldwin on the chain length dependence of the [delta Lk)2) value to be entirely inconsistent with our theorectical results. PMID:3916932
A shear-shear torsional beam model for nonlinear aeroelastic analysis of tower buildings
NASA Astrophysics Data System (ADS)
Piccardo, G.; Tubino, F.; Luongo, A.
2015-08-01
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.
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.
Gravitational energy for GR and Poincaré gauge theories: A covariant Hamiltonian approach
NASA Astrophysics Data System (ADS)
Chen, Chiang-Mei; Nester, James M.; Tung, Roh-Suan
2015-08-01
Our topic concerns a long standing puzzle: The energy of gravitating systems. More precisely we want to consider, for gravitating systems, how to best describe energy-momentum and angular momentum/center-of-mass momentum (CoMM). It is known that these quantities cannot be given by a local density. The modern understanding is that (i) they are quasi-local (associated with a closed 2-surface), (ii) they have no unique formula, (iii) they have no reference frame independent description. In the first part of this work, we review some early history, much of it not so well known, on the subject of gravitational energy in Einstein's general relativity (GR), noting especially Noether's contribution. In the second part, we review (including some new results) much of our covariant Hamiltonian formalism and apply it to Poincaré gauge theories of gravity (PG), with GR as a special case. The key point is that the Hamiltonian boundary term has two roles, it determines the quasi-local quantities, and furthermore, it determines the boundary conditions for the dynamical variables. Energy-momentum and angular momentum/CoMM are associated with the geometric symmetries under Poincaré transformations. They are best described in a local Poincaré gauge theory. The type of spacetime that naturally has this symmetry is Riemann-Cartan spacetime, with a metric compatible connection having, in general, both curvature and torsion. Thus our expression for the energy-momentum of physical systems is obtained via our covariant Hamiltonian formulation applied to the PG.
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.
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.
Angular-Momentum-Compensating Servomechanism
NASA Technical Reports Server (NTRS)
Marchetto, Carl A.
1988-01-01
Servomechanism for rotating an instrumentation platform isolates supporting vehicle or stationary platform from reaction torques producedby rotations. Prevents aiming of instrument from disturbing vehicle or other instrument platforms. Rotating oppositely to instrument platform, reaction wheel, motor, and gear 1 have angular momentum equal and opposite to gear 2, output shaft, and platform. External torque reaction to rotation of platform canceled. Although spur gears appear in schematic diagram, gear train made of spline gears.
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)
Hinkley, J. A.; O'Brien, T. K.
1991-01-01
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/0 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.
Angular momentum generation by parity violation
Liu, Hong
We generalize our holographic derivation of spontaneous angular momentum generation in 2 + 1 dimensions in several directions. We consider cases when a parity-violating perturbation responsible for the angular momentum ...
Paraxial Light Beams with Angular Momentum
A. Bekshaev; M. Soskin; M. Vasnetsov
2008-01-15
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; Orbital angular momentum and the intensity moments; Symmetry breakdown and decomposition of the orbital angular momentum; Mechanical models of the vortex light beams; Mechanical action of the beam angular momentum; Rotational Doppler effect, its manifestation in the image rotation; Spectrum of helical harmonics and associated problems; Non-collinear rotational Doppler effect; Properties of a beam forcedly rotating around its own axis. Research prospects and ways of practical utilization of optical beams with angular momentum.
Musica II: Torsion Drum, Buzzer, Maraca, Chirper, Flute
NSDL National Science Digital Library
2014-09-12
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.
Exotic torsion, Frobenius splitting and the slope spectral sequence
Kirti Joshi
2001-01-01
In this note we show that Frobenius split smooth, projective threefolds are Hodge-Witt (using a criterion for the degeneration of the slope spectral sequence of smooth projective threefolds which we prove), and that smooth, projective Frobenius split varieties do not have exotic torsion in their slope spectral sequence. We also record a few simple observations on Frobenius split threefolds. This
Torsionally-gravitating charged matter fields and quanta
NASA Astrophysics Data System (ADS)
Fabbri, Luca
2015-10-01
In the present article we shall consider the torsional completion of a gravitational background that is filled with electrodynamically interacting material fields, taken to be of fermionic type, eventually deriving properties like the impossibility of singularities and the possibility of confinement, both necessary for a correct quantum description.
Testicular torsion in a patient with Cohen syndrome
Y?lmaz, Ömer; Ye?ildal, Cumhur; Malkoç, Ercan; Soydan, Hasan
2015-01-01
Cohen syndrome is an extremely rare autosomal recessive disorder. A 12-year-old boy with Cohen syndrome applied to a primary health care center because of severe pain in the left groin and was diagnosed with epididymo-orchitis. Despite the administered the antibiotic treatment, pain increased. Therefore, the family brought the patient to the emergency department 16 h after the first diagnosis. The patient had mild mental retardation, myopia, and craniofacial dysmorphism, which are components of Cohen syndrome. There was no blood flow on the left testicle at color Doppler ultrasonography. Further, scrotal exploration was performed because of a high risk of torsion. The left testicle was torsioned, and the color was dark blue. Revascularization could not be achieved by detorsion; left orchiectomy and right testicular fixation were then conducted. In conclusion, to the best of our knowledge, this is the first reported case of testicular torsion in Cohen syndrome. If a patient with this syndrome has acute groin pain, testicular torsion should be immediately ruled out with Doppler ultrasonography. These patients may not clearly and correctly express themselves because of mild mental retardation. Moreover, detailed genitourinary, particularly testicular examination may clarify the omitted pathologies and make them well known in future in this syndrome.
Nanoscopic liquid bridges exposed to a torsional strain.
Sacquin-Mora, Sophie; Fuchs, Alain H; Schoen, Martin
2003-12-01
In this paper we investigate the response to a torsional strain of a molecularly thin film of spherically symmetric molecules confined to a chemically heterogeneous slit pore by means of Monte Carlo simulations in the grand canonical ensemble. The slit pore comprises two identical plane-parallel solid substrates, the fluid-substrate interaction is purely repulsive except for elliptic regions attracting fluid molecules. Under favorable thermodynamic conditions the confined film consists of fluid bridges where the molecules are preferentially adsorbed by the attractive elliptic regions, and span the gap between the opposite substrate surfaces. By rotating the upper substrate while holding the lower one in position, bridge phases can be exposed to a torsional strain 0< or =theta< or =pi/2 and the associated torsional stress T(theta) of the (fluidic) bridge phases can be calculated from molecular expressions. The obtained stress curve T(theta)(theta) is qualitatively similar to the one characteristic of sheared confined films: as the torsion strain increases, T(theta) rises to a maximum (yield point) and then decays monotonically to zero. By changing the ellipses' aspect ratio while keeping their area constant, we also investigate the influence of the attractive elliptic patterns' shape on T(theta)(theta). PMID:14754265
BCN Nanotubes as Highly Sensitive Torsional Electromechanical Transducers
Joselevich, Ernesto
BCN Nanotubes as Highly Sensitive Torsional Electromechanical Transducers Jonathan Garel, Chong for nanoelectromechanical systems (NEMS); however, the mechanical properties of multiwall CNTs are often limited by the weak interlayer mechanical coupling, but their high electrical resistance limits their use as electromechanical
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…
Torsion of an Epiploic Appendix Pretending as Acute Appendicitis
Malik, Kamran Ahmad
2010-01-01
Torsion of an epiploic appendix is a rare surgical entity. Its unusual symptomatology, wide variation in physical findings and the absence of helpful laboratory and radiological studies makes it very difficult to diagnose pre-operatively. This is a report of this rare entity found in a patient upon diagnostic laparoscopy performed for suspected acute appendicitis. PMID:22043343
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.
Torsional Directed Walks, Entropic Elasticity, and DNA Twist Stiffness
Nelson, Philip
, biology, and even finance. The discovery that polymer conformations afford a concrete realization #12; Abstract: DNA and other biopolymers differ from classical polymers due to their torsional the birth of polymer physics [1]. Remarkably, it has recently become possible to apply minuscule forces
THEROLE OF ACTIVE REGIONS IN THEGENERATION OF TORSIONAL OSCILLATIONS
Petrovay, Kristóf
;. The characteristic amplitude of the oscillations is order of 0:1 %, or a few nHz. Since the #12;rst seismic detection). With these methods the depth depen- dence of these motions could also be studied. It was found that the motions attempts to interpret the torsional oscillations at- tribute them to some feedback e#11;ect of the magnetic
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
Total Curvature and Total Torsion of Knotted Patrick Plunkett
California at Santa Barbara, University of
. To understand better the statistical mechanics of polymers under these specific conditions we use numericalTotal Curvature and Total Torsion of Knotted Polymers Patrick Plunkett Michael Piatek Akos Dobay work on radius of gyration and average crossing number has demonstrated that polymers with fixed
Optical MEMS devices based on micromachined torsion structure
NASA Astrophysics Data System (ADS)
Wu, Yaming; Xu, Jing; Li, Sihua; Wan, Zhujun; Mu, Canjun
2008-03-01
Optical MEMS components with optical fiber inputs and outputs are the most important kinds of optical MEMS devices because of their applications in optical communication industry and fiber-optic sensors. Efficient optical coupling is the key to develop optical MEMS devices for optical communication and sensing, however, efficient coupling between MEMS actuators or sensing structures and optical fibers is a challenging job. Besides high performance MEMS actuators and coupling micro-optics are needed, the MEMS structures should adapt to coupling micro-optics. The torsion MEMS micro-mirrors and gratings can couple with fiber collimators at low insertion loss, therefore, the torsion MEMS structure is a good choice for optical MEMS devices, especially for continuous or multi-level controlled devices. In this paper, we report three kinds of optical MEMS devices based on silicon torsion micro structure, MEMS variable optical attenuator (VOA), 1×8 MEMS optical switch and high-speed MEMS torsion blazed grating , which have been developed recently in our optical MEMS research group. The three devices are coupled with optical fibers by optical fiber collimators, so low loss coupling can be achieved.
Coupled bending, longitudinal and torsional vibrations of a cracked rotor
A. K. Darpe; K. Gupta; A. Chawla
2004-01-01
The coupling between longitudinal, lateral and torsional vibrations is studied together for a rotating cracked shaft. These coupling mechanisms have been studied here with a response-dependent non-linear breathing crack model. Most of the earlier work on coupled vibrations due to crack has been either on stationary shaft or on rotating shaft with open crack model. The stiffness matrix of a
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.
Torsional vibration monitoring using induction machine electromagnetic torque estimation
Shahin Hedayati Kia; Humberto Henao; Gérard-André Capolino
2008-01-01
The heavy duty drives need a continuous monitoring to avoid sudden loss of operation. In these systems, the mechanical anomalies like load troubles, great torque dynamic variations and torsional oscillations, result in the fatigue of the shaft driving electrical machine and other mechanical parts as bearings and gearboxes. Then, the permanent on-site mechanical performance has to be evaluated to predict
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
Combined torsional buckling of multi-walled carbon nanotubes
Y. J. Lu; X. Wang
2006-01-01
This paper reports the results of an investigation on combined torsional buckling of an individual multi-walled carbon nanotube (MWNT) under combined torque and axial loading. Here, a multiple shell model is adopted and the effect of van der Waals forces between two adjacent tubes is taken into account. According to the ratio of radius to thickness, MWNTs discussed in this
Transport of Torsional Stress in DNA Philip Nelson
Nelson, Philip
a role in gene regulation the twin supercoiled domain model" 2 . Transcription causes axial rotation It is well known that transcription can induce torsional stress in DNA, a ecting the activity of nearby genes.g. methylation, and each of these viewpoints is important for understanding some aspects of gene function