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1

Can torsion play a role in angular momentum conservation law?  

E-print Network

In Einstein-Cartan theory, by the use of the general Noether theorem, the general covariant angular-momentum conservation law is obtained with the respect to the local Lorentz transformations. The corresponding conservative Noether current is interpreted as the angular momentum tensor of the gravity-matter system including the spin density. It is pointed out that, assuming the tetrad transformation given by eq. (15), torsion tensor can not play a role in the conservation law of angular momentum.

Yishi Duan; Ying Jiang

1998-09-02

2

Can Gravity Probe B usefully constrain torsion gravity theories?  

SciTech Connect

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

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

2007-06-15

3

Universality Principle for Orbital Angular Momentum and Spin in Gravity with Torsion  

E-print Network

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.

H. Kleinert

1998-07-09

4

M-theory moduli spaces and torsion-free structures  

E-print Network

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.

Graña, Mariana

2014-01-01

5

M-theory moduli spaces and torsion-free structures  

E-print Network

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.

Mariana Graña; C. S. Shahbazi

2014-10-31

6

Feedback control of torsion balance in measurement of gravitational constant G with angular acceleration method.  

PubMed

The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to [Formula: see text] at the signal frequency of 2?mHz, which contributes a [Formula: see text] uncertainty to the G value. PMID:24517789

Quan, Li-Di; Xue, Chao; Shao, Cheng-Gang; Yang, Shan-Qing; Tu, Liang-Cheng; Wang, Yong-Ji; Luo, Jun

2014-01-01

7

Feedback control of torsion balance in measurement of gravitational constant G with angular acceleration method  

NASA Astrophysics Data System (ADS)

The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to 7.3× 10^{-7}rad/ sqrt{Hz} at the signal frequency of 2 mHz, which contributes a 0.4 textrm {ppm} uncertainty to the G value.

Quan, Li-Di; Xue, Chao; Shao, Cheng-Gang; Yang, Shan-Qing; Tu, Liang-Cheng; Wang, Yong-Ji; Luo, Jun

2014-01-01

8

On Discrete Symmetries and Torsion Homology in F-Theory  

E-print Network

We study the relation between discrete gauge symmetries in F-theory compactifications and torsion homology on the associated Calabi-Yau manifold. Focusing on the simplest example of a $\\mathbb Z_2$ symmetry, we show that there are two physically distinct ways that such a discrete gauge symmetry can arise. First, compactifications of M-Theory on Calabi-Yau threefolds which support a genus-one fibration with a bi-section are known to be dual to six-dimensional F-theory vacua with a $\\mathbb Z_2$ gauge symmetry. We show that the resulting five-dimensional theories do not have a $\\mathbb Z_2$ symmetry but that the latter emerges only in the F-theory decompactification limit. Accordingly the genus-one fibred Calabi-Yau manifolds do not exhibit discrete torsion. Associated to the bi-section fibration is a Jacobian fibration which does support a section. Compactifying on these related but distinct varieties does lead to a $\\mathbb Z_2$ symmetry in five dimensions and, accordingly, we find explicitly an associated discrete torsion. We identify the expected particle and membrane system of the discrete symmetry in terms of wrapped M2 and M5 branes and present a field-theory description of the physics for both cases in terms of circle reductions of six-dimensional theories. Our results and methods generalise straightforwardly to larger discrete symmetries and to four-dimensional compactifications.

Christoph Mayrhofer; Eran Palti; Oskar Till; Timo Weigand

2014-10-28

9

Continuity of the torsionless limit as a selection rule for gravity theories with torsion  

E-print Network

While one can in principle augment gravity theory with torsion, it is generally thought that any such torsion affects would be too small to be of consequence. Here we show that this cannot in general be the case. We show that the limit of vanishing torsion is not necessarily a continuous one, with the theory obtained in the limit not necessarily coinciding with the theory in which torsion had never been present at all. However, for a standard torsion tensor that is antisymmetric in two of its indices we have found two cases in which the vanishing torsion limit is in fact continuous, namely Einstein gravity and conformal gravity. For other gravity theories of common interest to possess a continuous limit the torsion tensor would need to be antisymmetric in all three of its indices.

Luca Fabbri; Philip D. Mannheim

2014-05-06

10

Constraining torsion with Gravity Probe B  

SciTech Connect

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

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

2007-11-15

11

A simplified approach to apply the theory of critical distances to notched components under torsional fatigue loading  

Microsoft Academic Search

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

Luca Susmel; David Taylor

2006-01-01

12

Parallel spinors and connections with skewsymmetric torsion in string theory \\Lambda  

E-print Network

Parallel spinors and connections with skew­symmetric torsion in string theory \\Lambda Thomas is of importance in string theory, since they are associated with some string solitons (BPS solitons) [42­ plications in the exploration of perturbative and non­perturbative properties of string theory. An important

Friedrich, Thomas

13

Torsional oscillations of neutron stars in scalar-tensor theory of gravity  

E-print Network

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 e...

Silva, Hector O; Berti, Emanuele; Horbatsch, Michael

2014-01-01

14

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

E-print Network

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

Dirk Puetzfeld; Yuri N. Obukhov

2013-08-15

15

Importance of torsion and invariant volumes in Palatini theories of gravity  

NASA Astrophysics Data System (ADS)

We study the field equations of extensions of general relativity formulated within a metric-affine formalism setting torsion to zero (Palatini approach). We find that different (second-order) dynamical equations arise depending on whether torsion is set to zero (i) a priori or (ii) a posteriori, i.e., before or after considering variations of the action. Considering a generic family of Ricci-squared theories, we show that in both cases the connection can be decomposed as the sum of a Levi-Cività connection and terms depending on a vector field. However, while in case (i) this vector field is related to the symmetric part of the connection, in (ii) it comes from the torsion part and, therefore, it vanishes once torsion is completely removed. Moreover, the vanishing of this torsion-related vector field immediately implies the vanishing of the antisymmetric part of the Ricci tensor, which therefore plays no role in the dynamics. Related to this, we find that the Levi-Cività part of the connection is due to the existence of an invariant volume associated with an auxiliary metric h??, which is algebraically related with the physical metric g??.

Olmo, Gonzalo J.; Rubiera-Garcia, D.

2013-10-01

16

Energy and angular momentum in generic F (Riemann) theories  

NASA Astrophysics Data System (ADS)

We construct the conserved charge of generic gravity theories built on arbitrary contractions of the Riemann tensor (but not on its derivatives) for asymptotically (anti)-de Sitter spacetimes. Our construction is a generalization of the Abbott-Deser-Tekin charges of linear and quadratic gravity theories in cosmological backgrounds. As an explicit example we find the energy and angular momentum of the Banados-Teitelboim-Zanelli black hole in the (2+1)-dimensional Born-Infeld gravity.

?entürk, Çetin; ?i?man, Tahsin Ça?r?; Tekin, Bayram

2012-12-01

17

Atomic and Molecular Quantum Theory Course Number: C561 18 Theory of Angular Momentum  

E-print Network

Atomic and Molecular Quantum Theory Course Number: C561 18 Theory of Angular Momentum 1. Why do we (instructor) #12;Atomic and Molecular Quantum Theory Course Number: C561 11. This is the approach we will use, Indiana University 165 c 2003, Srinivasan S. Iyengar (instructor) #12;Atomic and Molecular Quantum Theory

Iyengar, Srinivasan S.

18

Chern-Simons modified gravity as a torsion theory and its interaction with fermions  

SciTech Connect

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.

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

19

Gyrokinetic theory and simulation of angular momentum transport  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

20

Gyrokinetic theory and simulation of angular momentum transport  

SciTech Connect

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

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

2007-12-15

21

A modified theory of gravity with torsion and its applications to cosmology and particle physics  

E-print Network

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 \\textit{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.

Luca Fabbri; Stefano Vignolo

2012-01-26

22

A Modified Theory of Gravity with Torsion and Its Applications to Cosmology and Particle Physics  

NASA Astrophysics Data System (ADS)

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.

Fabbri, Luca; Vignolo, Stefano

2012-10-01

23

Gyrokinetic Theory and Simulation of Angular Momentum Transport  

NASA Astrophysics Data System (ADS)

A gyrokinetic theory of turbulent toroidal angular momentum transport as well as modifications to neoclassical poloidal rotation from turbulence is formulated starting from the fundamental six-dimensional kinetic equation. GyroBohm-scaled transport is evaluated from toroidal gyrokinetic simulations using the GYRO code [1]. The simulations quantify the two pinch mechanisms in the radial transport of toroidal angular momentum: the slab geometry ExB shear pinch [2] and the toroidal geometry ``coriolis'' pinch due to finite parallel velocity [3]. The pinches allow the steady-state null stress (momentum transport) condition required for intrinsic toroidal rotation in heated tokamaks without an internal source of torque [4]. A predicted turbulent shift in the neoclassical poloidal rotation [5] may be significant. [1] J. Candy and R.E. Waltz, J. Comp. Phys. 186, 545 (2003). [2] R.R. Dominguez and G.M. Staebler, Phys. Fluids B5, 387 (1993). [3] A.G. Peeters, et al., Phys. Rev. Lett. 98, 26503 (2007). [4] G.M. Staebler, et al., Bull. Am. Phys. Soc. 46, 221 (2001). [5] G.M. Staebler, Phys. Plasmas 11, 1064 (2004).

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

2007-11-01

24

Mordell-Weil Torsion and the Global Structure of Gauge Groups in F-theory  

E-print Network

We study the global structure of the gauge group $G$ of F-theory compactified on an elliptic fibration $Y$. The global properties of $G$ are encoded in the torsion subgroup of the Mordell-Weil group of rational sections of $Y$. Generalising the Shioda map to torsional sections we construct a specific integer divisor class on $Y$ as a fractional linear combination of the resolution divisors associated with the Cartan subalgebra of $G$. This divisor class can be interpreted as an element of the refined coweight lattice of the gauge group. As a result, the spectrum of admissible matter representations is strongly constrained and the gauge group is non-simply connected. We exemplify our results by a detailed analysis of the general elliptic fibration with Mordell-Weil group $\\mathbb Z_2$ and $\\mathbb Z_3$ as well as a further specialization to $\\mathbb Z \\oplus \\mathbb Z_2$. Our analysis exploits the representation of these fibrations as hypersurfaces in toric geometry.

Christoph Mayrhofer; David R. Morrison; Oskar Till; Timo Weigand

2014-05-14

25

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

ERIC Educational Resources Information Center

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

Dick, Frank; Norbury, John W.

2009-01-01

26

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

SciTech Connect

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

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

2004-09-01

27

Theory of pure rotational transitions in doubly degenerate torsional states of ethane  

NASA Technical Reports Server (NTRS)

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.

Rosenberg, A.; Susskind, J.

1979-01-01

28

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

Microsoft Academic Search

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

Thomas Friedrich; Stefan Ivanov

2001-01-01

29

Dark spinors with torsion in cosmology  

E-print Network

We solve one of the open problems in Einstein-Cartan theory, namely we find a natural matter source whose spin angular momentum tensor is compatible with the cosmological principle. We analyze the resulting evolution equations and find that an epoch of accelerated expansion is an attractor. The torsion field quickly decays in that period. Our results are interpreted in the context of the standard model of cosmology.

Christian G. Boehmer; James Burnett

2008-09-02

30

Dark spinors with torsion in cosmology  

SciTech Connect

We solve one of the open problems in Einstein-Cartan theory, namely, we find a natural matter source whose spin angular momentum tensor is compatible with the cosmological principle. We analyze the resulting evolution equations and find that an epoch of accelerated expansion is an attractor. The torsion field quickly decays in that period. Our results are interpreted in the context of the standard model of cosmology.

Boehmer, Christian G.; Burnett, James [Department of Mathematics, University College London, Gower Street, London, WC1E 6BT (United Kingdom)

2008-11-15

31

Microstructure Evolution and Mechanical Properties of Al-1080 Processed by a Combination of Equal Channel Angular Pressing and High Pressure Torsion  

NASA Astrophysics Data System (ADS)

Equal channel angular pressing (ECAP) and high pressure torsion (HPT) are the most promising severe plastic deformation (SPD) methods. Both methods impose very high strains, leading to extreme work hardening and microstructural refinement. In this paper, billets of Al-1080 were successfully processed by ECAP conducted for up to 10 passes, HPT at an applied pressure of 8 GPa for 5 revolutions, and a combination of ECAP and HPT (ECAP + HPT) at room temperature. The effects of the different SPD processes (ECAP, HPT, and ECAP + HPT) on the evolution of the microstructure and mechanical properties of Al-1080 were investigated. The HPT and ECAP + HPT processes were observed to produce finer grain sizes with greater fractions of high angle grain boundaries (HAGBs) than the ECAP alone. Although the grain sizes after HPT and ECAP + HPT were similar, the ECAP + HPT sample had more dislocations than the HPT sample. HPT after ECAP enhanced the mechanical properties (hardness, tensile strength, and ductility) of the ECAP-processed Al-1080, showing larger dimple size in the tensile fracture surfaces.

El Aal, Mohamed Ibrahim Abd; Yoon, Eun Yoo; Kim, Hyoung Seop

2013-06-01

32

Magnetometer Bias Calibration Based on Relative Angular Position: Theory and Experimental Comparative Evaluation  

E-print Network

Magnetometer Bias Calibration Based on Relative Angular Position: Theory and Experimental for esti- mating the sensor bias of three-axis magnetometers (or any other field sensor). Our approach employs relative angular position measurements to estimate the three-axis magnetometer measurement bias

Eustice, Ryan

33

Maxwell field with Torsion  

E-print Network

We propose a generalizing gauge-invariant model of propagating torsion which couples to the Maxwell field and to charged particles. As a result we have an Abelian gauge invariant action which leads to a theory with nonzero torsion and which is consistent with available experimental data.

R. Fresneda; M. C. Baldiotti; T. S. Pereira

2014-04-11

34

Many-body theory for angular resolved photoelectron spectra of metal clusters  

E-print Network

Angular resolved photoelectron spectra of metal clusters have been experimentally measured for the first time only recently. These measurements have been performed systematically for sodium clusters in a broad range of cluster sizes. This work attracted a lot of attention and was reported practically at all major international cluster conferences because it revealed a very non-trivial behavior of the angular anisotropy parameter with respect to photon energy and provided a method for probing the angular momentum character of the valence orbitals of free nanoclusters. Initial attempts to explain these observations within single particle approximations fail completely. In this Letter we present a consistent many-body theory for the description of angular resolved photoelectron spectra of metal clusters. Jellium model formalism is employed. Our calculations demonstrate the dominant role of the many-body effects in the formation of angular distributions of photoelectrons emitted from sodium clusters and are in a ...

Solov'yov, Andrey V; Ivanov, Vadim K

2009-01-01

35

The Theory of Critical Distances to estimate the static strength of notched samples of Al6082 loaded in combined tension and torsion. Part I: Material cracking behaviour  

Microsoft Academic Search

The present paper is the first of a two-part series reporting an experimental and theoretical study of the fracture of circumferentially notched samples of a commercial aluminium alloy, i.e. Al6082, subjected to tension, torsion and mixed tension\\/torsion loading. The overall aim of the work was to investigate the use of a particular method of failure prediction, known as the Theory

Luca Susmel; David Taylor

2010-01-01

36

Generalization of Equivalent Crystal Theory to Include Angular Dependence  

NASA Technical Reports Server (NTRS)

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.

Ferrante, John; Zypman, Fredy R.

2004-01-01

37

ANGULAR MOMENTUM TRANSPORT BY ACOUSTIC MODES GENERATED IN THE BOUNDARY LAYER. I. HYDRODYNAMICAL THEORY AND SIMULATIONS  

SciTech Connect

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.

Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M., E-mail: rrr@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States)

2013-06-10

38

Propagating torsion in the Einstein frame  

SciTech Connect

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

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

2006-11-15

39

Second order classical perturbation theory for atom surface scattering: Analysis of asymmetry in the angular distribution  

NASA Astrophysics Data System (ADS)

A second order classical perturbation theory is developed and applied to elastic atom corrugated surface scattering. The resulting theory accounts for experimentally observed asymmetry in the final angular distributions. These include qualitative features, such as reduction of the asymmetry in the intensity of the rainbow peaks with increased incidence energy as well as the asymmetry in the location of the rainbow peaks with respect to the specular scattering angle. The theory is especially applicable to "soft" corrugated potentials. Expressions for the angular distribution are derived for the exponential repulsive and Morse potential models. The theory is implemented numerically to a simplified model of the scattering of an Ar atom from a LiF(100) surface.

Zhou, Yun; Pollak, Eli; Miret-Artés, Salvador

2014-01-01

40

Crystal Field Theory and the Angular Overlap Model Applied to Hydrides of Main Group Elements.  

ERIC Educational Resources Information Center

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)

Moore, E. A.

1990-01-01

41

Flexural Torsional Guided Wave Pipe Inspection  

NASA Astrophysics Data System (ADS)

Based on the flexural torsional guided wave theory and its focusing technique, this paper demonstrates the defect detection capability of flexural torsional guided waves on multiple defects with different shapes and axial, circumferential locations in pipe.

Sun, Z.; Zhang, L.; Rose, J. L.

2006-03-01

42

Prospects of detecting spacetime torsion  

E-print Network

How to detect spacetime torsion? In this essay we provide the theoretical basis for an answer to this question. Multipolar equations of motion for a very general class of gravitational theories with nonminimal coupling in spacetimes admitting torsion are given. Our findings provide a framework for the systematic testing of whole classes of theories with the help of extended test bodies. One surprising feature of nonminimal theories turns out to be their potential sensitivity to torsion of spacetime even in experiments with ordinary (not microstructured) test matter.

Puetzfeld, Dirk

2014-01-01

43

Prospects of detecting spacetime torsion  

E-print Network

How to detect spacetime torsion? In this essay we provide the theoretical basis for an answer to this question. Multipolar equations of motion for a very general class of gravitational theories with nonminimal coupling in spacetimes admitting torsion are given. Our findings provide a framework for the systematic testing of whole classes of theories with the help of extended test bodies. One surprising feature of nonminimal theories turns out to be their potential sensitivity to torsion of spacetime even in experiments with ordinary (not microstructured) test matter.

Dirk Puetzfeld; Yuri N. Obukhov

2014-05-16

44

Torsional viscometer  

NSDL National Science Digital Library

Solve the cylindrical Navier-Stokes equations for polymer flow in a torsional viscometer; calculate polymer viscosity from torque; qualitatively evaluate non-Newtonian nature of flow from a second torque data point.

Powell, Adam C., IV

2003-11-14

45

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

NASA Astrophysics Data System (ADS)

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

Cyganski, David; Page, William S.

46

Arc Hyperbolic sine creep theory applied to torsion-tension member of circular cross section  

Microsoft Academic Search

A multiaxial creep theory is presented in this paper which will predict the total deformations of a load-carrying member at any specified time after load. Load-deformation relations are derived based on the assumption that the isochronous stress-strain diagram of the material can be represented by an arc hyperbolic sine function [see, eq (2)]. A closed solution was obtained for the

S. Dharmarajan; O. M. Sidebottom

1963-01-01

47

Degenerate Perturbation Theory Describing the Mixing of Orbital Angular Momentum Modes in Fabry-Perot Cavity Resonators  

E-print Network

Degenerate Perturbation Theory Describing the Mixing of Orbital Angular Momentum Modes in Fabry, in work involving cavity quantum electrodynamics, paraxial theory at the level developed here may-P´erot Cavity Resonators David H. Foster,1 Andrew K. Cook,2 and Jens U. N¨ockel2 1 Deep Photonics Corporation

Nöckelm, Jens

48

Two-Component Spinor Torsion, Curvature Expansions and a Prospect for a New Theory of Dark Energy  

E-print Network

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 connection appears to possess a torsional part which is conveniently taken as a suitable asymmetric contribution. Such a torsional affine contribution thus supplies a gauge-invariant potential that may eventually 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 connection 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 framework may afford locally a new physical characterization of the cosmic dark energy.

J. G. Cardoso

2014-01-29

49

Omental Torsion  

PubMed Central

Torsion of greater omentum is one of the rare causes of acute abdominal pain. It can be primary or secondary. Primary Omental Torsion (POT) occurs because a mobile, thicken segment of omentum rotates around a proximal fixed point in the absence of any associated or secondary intra-abdominal pathology. Secondary omental torsion is associated with a number of pre-existing conditions most common among them is inguinal hernia, other causes include tumours, cysts, internal or external herniation, foci of intra-abdominal inflammation and postsurgical wound or scarring. Torsion of omentum causes twisting of omentum along its long axis resulting in impaired blood supply. This rare condition is more predominant in middle-aged males. It clinically mimics acute appendicitis. It should be kept in mind as a differential diagnosis for acute abdomen. Laparoscopy can aid in diagnosis and management but explorative laparotomy is the definitive and therapeutic procedure of choice. However the condition is not life threatening as omentectomy reduces the inflammation and focus of adhesions within the abdomen. PMID:25121029

R., Arora

2014-01-01

50

Torsional locomotion  

PubMed Central

One edge of an elastic rod is inserted into a friction-less and fitting socket head, whereas the other edge is subjected to a torque, generating a uniform twisting moment. It is theoretically shown and experimentally proved that, although perfectly smooth, the constraint realizes an expulsive axial force on the elastic rod, which amount is independent of the shape of the socket head. The axial force explains why screwdrivers at high torque have the tendency to disengage from screw heads and demonstrates torsional locomotion along a perfectly smooth channel. This new type of locomotion finds direct evidence in the realization of a ‘torsional gun’, capable of transforming torque into propulsive force. PMID:25383038

Bigoni, D.; Dal Corso, F.; Misseroni, D.; Bosi, F.

2014-01-01

51

Alternating torsions in a living '9 + 2' flagellum  

PubMed Central

Live spermatozoa of the Japanese quail were observed as they swam in highly viscous salines. Under these conditions, torsions of the flagellum were readily seen. The torsions had a characteristic magnitude (nominally 180 degrees) and pattern of incidence. As a cycle of bending propagated over it, each position on the flagellum experienced first a sinistral torsion and, later, a restoring dextral torsion. The two zones of torsion were each associated with bending; between them was a torsion-free zone that tended to be straight. The amount of interdoublet sliding needed to generate the torsions may be as little as 10 nm. These dynamic propagating torsions have been detected by following the angular displacements of individual (swollen) mitochondria lying adjacent to the axoneme. It is suggested that torque generation is a primary outcome when the unconstrained '9 + 2' axoneme is activated.

Woolley, D. M.; Vernon, G. G.

1999-01-01

52

Torsion in K-theory for boundary actions on affine buildings of type $\\tA_n$.  

E-print Network

Let $\\Gamma$ be a torsion free lattice in $G = \\PGL(n+1,\\FF)$, where $n\\ge 1$ and $\\FF$ is a non-archimedean local field. Then $\\Gamma$ acts on the Furstenberg boundary $G/P$, where $P$ is a minimal parabolic subgroup of $G$. The identity element $\\id$ in the crossed product $C^*$-algebra $C(G/P)\\rtimes \\Gamma$ generates a class $[\\id]$ in the $K_0$ group of $C(G/P)\\rtimes \\Gamma$. It is shown that $[\\id]$ is a torsion element of $K_0$ and there is an explicit bound for the order of $[\\id]$. The result is proved more generally for groups acting on affine buildings of type $\\tA_n$. For $n=1, 2$ the Euler-Poincaré characteristic $\\chi(\\Gamma)$ annihilates the class $[\\id]$.

Guyan Robertson.; 251-269

53

Photoelectron Angular Distribution from the Disordered Condensed Phase: Theory and Experiment.  

NASA Astrophysics Data System (ADS)

Although the theory of photoemission from single -crystalline solids and ordered overlayers has been studied by almost every available theoretical tool, it is quite surprising that there has not yet been any theoretical investigation of photoemission from the disordered condensed phase. In this work, we address this problem. Starting from first principles, we show that the photoelectron angular distribution from the disordered condensed phase is governed by the same general formula as in the gas phase, i.e., by Yang's formula, and in general, is highly anisotropic. This anisotropy in the angular distribution of the photoelectrons has many far reaching consequences. The most important one is that the theoretical expression for the angle-integrated photoemission intensity, which was first derived by Berglund and Spicer, needs to be modified. Another important consequence is the sensitivity of the photoemission intensity to the polarization of the incoming light: we show that at any incident angle, polarized light leads to a higher photoemission intensity than unpolarized light, with the only exception being at normal incidence where both polarized and unpolarized light lead to the same intensity. In this work, we have developed an extremely accurate technique for the measurement of the condensed phase asymmetry parameter (beta) over all range of photon energies. The behavior of beta at energies around the Cooper minima has a very important application in surface science. Since in this energy region, the beta parameter is very sensitive to the nature of the initial states, its measurements can yield information on the hybrid (bandlike) or atomiclike character of d-valence states of a transition metal at its interface with an elemental semiconductor. An important characteristic of this novel technique is its remarkable resolution. Unlike other surface sensitive tools, such as transmission electron microscopy and diffraction or reflection high energy electron diffraction, which have resolutions at coverages well above 10 ML, this technique has resolution at coverages as low as.05 ML, perhaps as good as that of the scanning tunnelling microscopy. Finally in this work, we show that in the condensed phase, the energy dependence of the beta-parameter at energies near the threshold can yield information about the nature of the continuum waves, i.e., about a quantity which, in general, is very difficult to study experimentally.

Ardehali, Mohammad

54

The explicit representation for the angular flux solution in the simplified P{sub N} (SP{sub N}) theory  

SciTech Connect

The current SP{sub n} theory formulation, via either the asymptotic method or the variational method, does not provide an explicit and calculable representation for the corresponding angular flux solution. It is therefore not possible to reconstruct from the SP{sub n} solution the corresponding angular flux solution, or to extract from a reference transport solution the corresponding SP{sub n} solution. This makes it impossible to calculate the necessary surface discontinuity factors to force consistency between the SP{sub n} solution and the higher level transport solution. Without discontinuity factors, the superiority of SP{sub n} over diffusion could be significantly degraded in practical applications. In this paper we present a different SP{sub n} formulation that provides the explicit angular flux solution such that the physical picture for the SP{sub n} approximation is transparent and the SP{sub n} discontinuity factors can be calculated. (authors)

Chao, Y. A. [Apartment 101, Building 2, 788 Hong Xu Road, Shanghai 201103 (China); Yamamoto, A. [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)

2012-07-01

55

Thermoelastic damping in torsion microresonators with coupling effect between torsion and bending  

NASA Astrophysics Data System (ADS)

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.

Tai, Yongpeng; Li, Pu; Fang, Yuming

2014-02-01

56

Angular dependence of the coercivities of Ba ferrite particulate samples: A comparison between theory and experiments  

Microsoft Academic Search

We measured the angular dependence of coercivity Hc and remnant coercivity Hr of oriented, Co-Ti substituted, plate-like barium ferrite particulate samples. The experimental results were compared to those modelled by a chain of two oblate ellipsoids. By including the effects of the uniaxial magnetocrystalline anisotropy, the shape anisotropy, and the interaction anisotropy of the ellipsoids, the model of a chain

D. H. Han; H. L. Luo; Z. Yang

1995-01-01

57

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

SciTech Connect

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

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

1994-12-31

58

Variable stiffness torsion springs  

NASA Technical Reports Server (NTRS)

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Alhorn, Dean C. (inventor); Polites, Michael E. (inventor)

1995-01-01

59

Variable stiffness torsion springs  

NASA Technical Reports Server (NTRS)

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Alhorn, Dean C. (inventor); Polites, Michael E. (inventor)

1994-01-01

60

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

Microsoft Academic Search

We compute the specific angular momentum distributions for a sample of low-mass disc galaxies observed by Swaters. We compare these distributions to those of dark matter haloes obtained by Bullock et al. from high-resolution N-body simulations of structure formation in a LambdaCDM universe. We find that although the disc mass fractions are significantly smaller than the universal baryon fraction, the

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

2001-01-01

61

The Angular Momentum Content of Dwarf Galaxies: New Challenges for the Theory of Galaxy Formation  

Microsoft Academic Search

We compute the specific angular momentum distributions of a sample of low\\u000amass disk galaxies observed by Swaters. We compare these distributions to those\\u000aof dark matter haloes obtained by Bullock et al. from high resolution N-body\\u000asimulations of structure formation in a LCDM Universe. We find that although\\u000athe disk mass fractions are significantly smaller than the Universal baryon

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

2001-01-01

62

Study on torsional fretting behavior of UHMWPE  

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

63

Effects of high angular momentum on the unimolecular dissociation of CD2CD2OH: theory and comparisons with experiment.  

PubMed

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

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

2013-10-24

64

Membranes from monopole operators in ABJM theory: Large angular momentum and M-theoretic AdS4/CFT3  

NASA Astrophysics Data System (ADS)

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.

Kovacs, Stefano; Sato, Yuki; Shimada, Hidehiko

2014-09-01

65

Role of angular momentum conservation in unimolecular translational energy release: validity of the orbiting transition state theory.  

PubMed

The translational kinetic energy release distribution (KERD) for the halogen loss reaction of the bromobenzene and iodobenzene cations has been reinvestigated on the microsecond time scale. Two necessary conditions of validity of the orbiting transition state theory (OTST) for the calculation of kinetic energy release distributions (KERDs) have been formulated. One of them examines the central ion-induced dipole potential approximation. As a second criterion, an adiabatic parameter is derived. The lower the released translational energy and the total angular momentum, the larger the reduced mass, the rotational constant of the molecular fragment, and the polarizability of the released atom, the more valid is the OTST. Only the low-energy dissociation of the iodobenzene ion (E approximately 0.45 eV, where E is the internal energy above the reaction threshold) is found to fulfill the criteria of validity of the OTST. The constraints that act on the dissociation dynamics have been studied by the maximum entropy method. Calculations of entropy deficiencies (which measure the deviation from a microcanonical distribution) show that the pair of fragments does not sample the whole of the phase space that is compatible with the mere specification of the internal energy. The major constraint that results from conservation of angular momentum is related to a reduction of the dimensionality of the dynamics of the translational motion to a two-dimensional space. A second and minor constraint that affects the KERD leads to a suppression of small translational releases, i.e., accounts for threshold behavior. At high internal energies, the effects of curvature of the reaction path and of angular momentum conservation are intricately intermeddled and it is not possible to specify the share of each effect. PMID:15836111

Gridelet, E; Lorquet, J C; Leyh, B

2005-03-01

66

T-matrix approach and the angular momentum theory in light-scattering problems by ensembles of arbitrarily shaped particles  

NASA Astrophysics Data System (ADS)

Light scattering by a macroscopically anisotropic volume element, which consists of arbitrarily shaped particles with an arbitrary square-integrable probability-density function over orientations, is considered. The T -matrix approach and the quantum theory of angular momentum are used to develop a rigorous analytical method (in terms of the T matrix) for computing the extinction matrix; the extinction, scattering, and absorption cross sections; and the elements of the Mueller matrix of the volume element. The constructive theorem of the existence of the expansion of scattering-matrix elements in a series of Wigner functions for a medium with rotation symmetry is proved. The analytical results are generalized for incident radiation composed of incoherent plane waves with a square-integrable probability-density function over directions of propagation, intensities, and polarization states.

Paramonov, L. E.

1995-12-01

67

Uterine torsion in mares.  

PubMed

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

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

2012-12-01

68

TORSIONAL AND BENDING VIBRATION MEASUREMENT ON ROTORS USING LASER TECHNOLOGY  

Microsoft Academic Search

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

T. J MILES; M LUCAS; N. A HALLIWELL; S. J ROTHBERG

1999-01-01

69

Cyclic torsion testing  

NASA Technical Reports Server (NTRS)

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.

Leese, G. E.

1984-01-01

70

Torsion and Particle Horizons  

NASA Astrophysics Data System (ADS)

Inthe present work we show that the existence of non-vanishing torsion field may solve, at least, one of the problems FRW-cosmology, the particle horizons problem. The field equations of general relativity (GR) are written in a space having non-vanishing torsion, the absolute parallelism (AP) space. An AP-Structure, satisfying the cosmological principle, is used to construct a world model. Energy density and pressure, purely induced by torsion, are defined from the building blocks of the AP-geometry using GR. When these quantities are used in the FRW-dynamical equations, we get a world model free from particle horizons.

Wanas, M. I.; Hassan, H. A.

2014-11-01

71

Nonlinear long-wavelength torsional Alfven waves  

NASA Astrophysics Data System (ADS)

Long-wavelength torsional (Alfven) waves in solar and stellar coronal structures experience geometrical amplification with height and hence are subject to nonlinear effects. We analyse this regime in frames the second order thin flux-tube approximation of Zhugzhda, which describes axisymmetric (sausage) magnetohydrodynamic perturbations of a straight untwisted and non-rotating magnetic flux-tube, representing e.g. a polar plume or a jet, or a coronal loop or a prominence filament. Attention is paid to the compressible motions nonlinearly induced by long-wavelength torsional waves of small, but finite amplitude. We obtained that propagating torsional waves induce compressible perturbations oscillating with double the frequency of the torsional waves. In contrast with plane shear Alfven waves, the amplitude of compressible perturbations is independent of the plasma-beta. Moreover, nonlinear evolution of torsional waves is not affected by the singularity appearing at the height when the local Alfven speed is equal to the sound speed. This result significantly reduces the efficiency of nonlinear cascade, and hence suggests that the present theories of the solar and stellar wind heating and acceleration by Alfven waves, based upon the plane wave theory, require modification.

Nakariakov, Valery

2012-07-01

72

Microstructure and mechanical properties of super-strong nanocrystalline tungsten processed by high-pressure torsion  

E-print Network

, such as equal-chan- nel angular pressing (ECAP) [7], surface mechanical attrition (SMA) [8] and high-pressure torsion (HPT) [9]. HPT has been less investigated than ECAP, and has been applied to a limited number

Wei, Qiuming

73

Joint torsion equals the determinant invariant.  

E-print Network

A determinant in algebraic $K$-theory is associated to any two almost commuting Fredholm operators. On the other hand, one can calculate a homologically defined invariant known as joint torsion. We answer in the affirmative a conjecture of Richard Carey and Joel Pincus, namely that these two invariants agree. In particular, this implies that joint torsion is norm continuous, depends only on the images of the operators modulo trace class, and satisfies the expected Steinberg relations. Moreover, we show that the determinant invariant of two commuting operators can be computed simply as a determinant on a finite dimensional vector space.

Joseph Migler

74

Two-step spacetime deformation induced dynamical torsion  

E-print Network

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.

G Ter-Kazarian

2011-02-12

75

Angular momentum evolution of cool stars: Toward a synthesis of observations and theory before and after the ZAMS  

NASA Astrophysics Data System (ADS)

The coexistence of fast and slowly rotating cool stars in ZAMS clusters - forming distinct sequences in the color vs. rotation period plane - is providing clues to differences in their pre main-sequence angular momentum evolution. This Cool Stars 17 splinter was dedicated to a discussion of new observational and theoretical results that may help discriminate between proposed mechanisms for early angular momentum regulation and help us explain the observed ZAMS dichotomy.

Meibom, S.; Barnes, S. A.; Covey, K.; Jeffries, R. D.; Matt, S.; Morin, J.; Palacios, A.; Reiners, A.; Sicilia-Aguilar, A.; Irwin, J.

2013-02-01

76

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

SciTech Connect

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

Clark, G

2003-04-28

77

Isolated Fallopian Tube Torsion  

PubMed Central

Isolated torsion of the Fallopian tube is a rare gynecological cause of acute lower abdominal pain, and diagnosis is difficult. There are no pathognomonic symptoms; clinical, imaging, or laboratory findings. A preoperative ultrasound showing tubular adnexal masses of heterogeneous echogenicity with cystic component is often present. Diagnosis can rarely be made before operation, and laparoscopy is necessary to establish the diagnosis. Unfortunately, surgery often is performed too late for tube conservation. Isolated Fallopian tube torsion should be suspected in case of acute pelvic pain, and prompt intervention is necessary. PMID:23984132

Kardakis, S.; Barranca, A.; Vitelli, A.; Amore, I.; Trento, F.; Caccia, G.

2013-01-01

78

Gravitation, Cosmology and Space-Time Torsion  

E-print Network

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.

A. V. Minkevich

2007-09-27

79

Nanomechanical torsional resonators for frequency-shift infrared thermal sensing.  

PubMed

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

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

2013-04-10

80

Quantum-mechanical theory including angular momenta analysis of atom-atom collisions in a laser field  

NASA Technical Reports Server (NTRS)

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.

Devries, P. L.; George, T. F.

1978-01-01

81

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

E-print Network

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.

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

2013-04-09

82

Testicular Torsion (For Parents)  

MedlinePLUS

... a prosthetic, or artificial, testicle a few months after surgery. This can help make some boys feel more ... remove the affected testicle. If torsion symptoms appear after a boy is born, the doctor may recommend emergency surgery to correct the testicle. Don't Ignore Symptoms ...

83

Atomic and Molecular Quantum Theory Course Number: C561 18.2 Coupling of angular momentum operators: The Clebsch Gordon  

E-print Network

by constructing a new angular momentum operator in the following fashion: J = i J(i) (18.62) 37. Another important. 32. There is a special case where this is not true: L - S coupling. What happens in this case

Iyengar, Srinivasan S.

84

Torsional anharmonicity in the conformational thermodynamics of flexible molecules  

NASA Astrophysics Data System (ADS)

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

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

85

Torsional fatigue of aramid fibers  

SciTech Connect

An experimental investigation on the shear fatigue process of aramid fibers is presented. Repeated cycles of the torsional deformation are applied on the aramid single fiber and the reduction of the shear modulus of the fiber with an increasing number of the cycles is observed for different strain amplitudes. It has been found that the reduction process of the shear modulus with an increasing number of the repeated cycles depends on the strain amplitude and the effect of the number of cycles is equivalent to that of the strain amplitude on the modulus reduction and they may be superposed like the time-temperature equivalence superposition observed in the viscoelasticity of amorphous polymeric solids. From this relation, the life prediction for the long term use of aramid fibers becomes possible by using this superimposed relation. A simple rate process theory is applied to interpret this fatigue process and to derive the equation for predicting the life cycle number of the loading.

Kawabata, S. [Kyoto Univ. (Japan). Dept. of Polymer Chemistry; Sera, M.

1993-12-31

86

Flexural Longitudinal and Torsional Mode Natural Focusing Phenomena in a Pipe  

NASA Astrophysics Data System (ADS)

Non-axisymmetric guided waves including flexural longitudinal and flexural torsional modes have shown natural focusing characteristics in pipe inspection. A flexural torsional mode theory was developed in this paper based on flexural longitudinal mode theory. Flexural mode experiments were then carried out to show the natural focusing phenomena.

Sun, Z.; Zhang, L.; Rose, J. L.

2004-02-01

87

Torsional actuation with extension-torsion composite coupling and a magnetostrictive actuator  

NASA Astrophysics Data System (ADS)

An analytical-experimental study of using magnetostrictive actuators in conjunction with an extension-torsion coupled composite tube to actuate a rotor blade trailing-edge flap to actively control helicopter vibration is presented. Thin walled beam analysis based on Vlasov theory was used to predict the induced twist and extension in a composite tube with magnetostrictive actuation. The study achieved good correlation between theory and experiment. The Kevlar-epoxy systems showed good correlation between measured and predicted twist values.

Bothwell, Christopher M.; Chandra, Ramesh; Chopra, Inderjit

1995-04-01

88

Nonsingular Dirac particles in spacetime with torsion  

E-print Network

We use the Papapetrou method of multipole expansion to show that a Dirac field in the Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity cannot form singular configurations concentrated on one- or two-dimensional surfaces in spacetime. Instead, such a field describes a nonsingular particle whose spatial dimension is at least on the order of its Cartan radius. In particular, torsion modifies Burinskii's model of the Dirac electron as a Kerr-Newman singular ring of the Compton size, by replacing the ring with a toroidal structure with the outer radius of the Compton size and the inner radius of the Cartan size. We conjecture that torsion produced by spin prevents the formation of singularities from matter composed of quarks and leptons. We expect that the Cartan radius of an electron, ~10^{-27} m, introduces an effective ultraviolet cutoff in quantum field theory for fermions in the ECKS spacetime. We also estimate a maximum density of matter to be on the order of the corresponding Cartan density, ~10^{51} kg m^{-3}, which gives a lower limit for black-hole masses ~10^{16} kg. This limit corresponds to energy ~10^{43} GeV which is 39 orders of magnitude larger than the maximum beam energy currently available at the LHC. Thus, if torsion exists and the ECKS theory of gravity is correct, the LHC cannot produce micro black holes.

Nikodem J. Poplawski

2009-10-07

89

Triorchidism with Torsion  

PubMed Central

Polyorchidism is a rare anomaly; triorchidism is the commonest type and is frequently associated with cryptorchidism, inguinal hernia, and testicular torsion. It is also reported as an increased risk of testicular malignancy. We report a case of 72-year-old man with left supernumerary testes in the left hemiscrotum. He presented with pain in his left hemiscrotum of short duration. Physical examination revealed tender hemiscrotum. Both ultrasound and MRI examinations revealed polyorchidism. One of the testes in the left hemiscrotum revealed features of torsion and hemorrhagic necrosis. Polyorchidism is a rare entity. In most cases, sonography alone is diagnostic of polyorchidism. Magnetic resonance imaging may provide additional information in complicated cases of polyorchidism. PMID:23439922

Kumar, K; Das, D; Shivaraj

2012-01-01

90

Constraining spacetime torsion with the Moon and Mercury  

E-print Network

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.

Riccardo March; Giovanni Bellettini; Roberto Tauraso; Simone Dell'Agnello

2011-01-14

91

Constraining spacetime torsion with the Moon and Mercury  

SciTech Connect

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

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

2011-05-15

92

Gallbladder Torsion: A Diagnostic Challenge  

PubMed Central

80-year-old female presented with clinical findings suggestive of acute cholecystitis. Intraoperatively we discovered a dusky gallbladder with gangrenous patches and gallbladder torsion with 270 degrees clockwise rotation along the longitudinal axis. Gallbladder torsion is a rare cause of acute cholecystitis with less than 500 cases published in the literature. Gallbladder torsion should be included in the list of differential diagnoses in patients suspected of having acute cholecystitis especially when there are inconsistencies between clinical features and imaging. It is worth noting that 3-dimensional reconstructed CT may be useful in preoperative diagnosis of gallbladder torsion. PMID:24949212

Bradshaw, Kimberley; Jeyarajan, Eshwarshanker; Alzubaidy, Rafid; Liew, Victor

2014-01-01

93

Performance of an angular flange aeroelastic wind energy converter  

SciTech Connect

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

Ahmadi, G.

1983-05-01

94

Theoretical-experimental correlation for buckling of composite cylinders under combined compression and torsion  

NASA Technical Reports Server (NTRS)

Comparison between theory and experiment for buckling of laminated graphite-epoxy and boron-epoxy cylinders under combined compression and torsion are presented. The experimental results are compared to a theory by Wu. It is shown that there is excellent agreement between theory and experiment for pure torsional loading (positive and negative), experimental buckling loads for pure compression are well below the predicted values, and good correlation is exhibited between theory and experiment for buckling under combined loading when compared in the form of normalized buckling interaction diagrams in axial-torsional load space.

Herakovich, C. T.

1978-01-01

95

Testicular torsion: A surgical emergency  

SciTech Connect

Testicular torsion is caused by twisting of the spermatic cord, which results in compromised testicular blood flow. The degree of ischemic injury is determined by the severity of arterial compression and the interval between the onset of symptoms and surgical intervention. Torsion usually occurs at puberty, and an anatomic defect known as bell-clapper deformity is usually present. Typical symptoms include acute scrotal pain with associated nausea and vomiting. Up to one-half of patients report previous similar episodes. On examination, the testis is high-riding, tender, swollen and firm. Testicular scan or Doppler ultrasound examination can be helpful in distinguishing torsion from acute epididymitis. Prompt surgical treatment is indicated to reduce the torsion, and bilateral orchiopexy is performed to prevent recurrence. Exocrine function, as determined by semen analysis, is often abnormal after unilateral torsion. 25 references.

Prater, J.M.; Overdorf, B.S. (Surgical Residency Program at Yale University, New Haven, CT (USA))

1991-09-01

96

Transverse nuclear spin relaxation due to director fluctuations in liquid crystals. III. A slow-motional theory for the angular dependence in pulsed experiments  

NASA Astrophysics Data System (ADS)

In the previous article, we have proposed a slow-motional theory for second-order effects of director fluctuations on transverse spin relaxation of quadrupolar nuclei in liquid crystals [D. Frezzato, G.J. Moro, and G. Kothe, J. Chem. Phys. 119, 6931 (2003), preceding paper]. This methodology is now generalized to arbitrary orientations of director and magnetic field. The characteristic functions are evaluated for the free induction decay and the echo intensities in Carr-Purcell-Meiboom-Gill (CPMG) multipulse sequences. From the solution of the corresponding integral equations, the relative magnitude of first and second-order contributions can be assessed. This enables a complete characterization of the angular and pulse spacing dependent transverse relaxation rates observed in CPMG multipulse experiments.

Frezzato, Diego; Kothe, Gerd; Moro, Giorgio J.

2003-10-01

97

LARGE TORSIONAL OSCILLATIONS IN A SUSPENSION BRIDGE: MULTIPLE PERIODIC SOLUTIONS TO A NONLINEAR  

E-print Network

LARGE TORSIONAL OSCILLATIONS IN A SUSPENSION BRIDGE: MULTIPLE PERIODIC SOLUTIONS TO A NONLINEAR of a suspension bridge. We use Leray­Schauder degree theory to prove that, under small periodic external forcing. nonlinear wave equation, torsional oscillations, suspension bridge AMS subject classification. 35B10 PII. S

Moore, Kristen

98

The Theory of Critical Distances to estimate the static strength of notched samples of Al6082 loaded in combined tension and torsion. Part II: Multiaxial static assessment  

Microsoft Academic Search

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

Luca Susmel; David Taylor

2010-01-01

99

Frequency-response analysis of torsional dynamics  

Microsoft Academic Search

This paper introduces a frequency-domain approach for investigation of the phenomenon of torsional dynamics. The Nyquist criterion is adopted by the proposed method to identify stability regions with respect to torsional oscillations. This paper also introduces two performance indices to evaluate torsional dampings and propensity of the system to experience torsional oscillations. The proposed method is an alternative approach to

Ahmadreza Tabesh; Reza Iravani

2004-01-01

100

[Seminoma necrosis by testicular torsion].  

PubMed

The coincidence of a classical scrotal testicular torsion with a scrotal tumor is a rare event. In the case described here the classical histological characteristics of a seminoma were present in addition to clear signs of testicular torsion with fibrin-containing thrombi in the intratesticular capillaries, so that the ischemia time predicted by the pathologists correlated well with the clinical data of 7.5 h for the testicular torsion estimated at the time of the intervention. The intraoperative diagnosis made by the surgeon allowed a rapid response with only a semi-castration, excision of the wound edges and a highest possible amputation of the funiculus. PMID:19859689

Wiedemann, A; Zienkiewicz, T

2010-01-01

101

Magnetic means for the determination of torsional yield strength  

Microsoft Academic Search

In this paper, the yield strength of steels and other materials is typically limited to values determined from uniaxial tension tests. The torsional yield strength, required for the rational design of shafts is generally assumed to be 0.5-0.6 of the tensile value, based on one or another of the several theories of plasticity.

I. J. Garshelis; R. J. Kari; S. Bitar

2003-01-01

102

Deligne-Beilinson cohomology and Abelian link invariants: Torsion case  

SciTech Connect

For the Abelian Chern-Simons field theory, we consider the quantum functional integration over the Deligne-Beilinson cohomology classes and present an explicit path-integral nonperturbative computation of the Chern-Simons link invariants in SO(3){approx_equal}RP{sup 3}, a toy example of a 3-manifold with torsion.

Thuillier, F. [LAPTH, Universite de Savoie, Chemin de Bellevue, BP 110, F-74941 Annecy-le-Vieux Cedex (France)

2009-12-15

103

Origin of solar torsional oscillations  

E-print Network

Helioseismology has revealed many details of solar differential rotation and also its time variation, known as torsional oscillations. So far there is no generally accepted theoretical explanation for torsional oscillations, even though a close relation to the solar activity cycle is evident. On the theoretical side non-kinematic dynamo models (including the Lorentz force feedback on differential rotation) have been used to explain torsional oscillations. In this paper we use a slightly different approach by forcing torsional oscillations in a mean field differential rotation model. Our aim is not a fully self-consistent model but rather to point out a few general properties of torsional oscillations and their possible origin that are independent from a particular dynamo model. We find that the poleward propagating high latitude branch of the torsional oscillations can be explained as a response of the coupled differential rotation / meridional flow system to periodic forcing in mid-latitudes, of either mechanical (Lorentz force) or thermal nature. The speed of the poleward propagation sets constraints on the value of the turbulent viscosity in the solar convection zone to be less than 3x10^8 m^2/s. We also show that the equatorward propagating low latitude branch is very unlikely a consequence of mechanical forcing (Lorentz force) alone, but rather of thermal origin due to the Taylor-Proudman theorem.

Matthias Rempel

2006-10-07

104

Simple torsion test for shear moduli determination of orthotropic composites  

NASA Technical Reports Server (NTRS)

By means of torsion tests performed on test specimens of the same material having a minimum of two different cross sections (flat sheet of different widths), the effective in-plane (G13) and out-of-plane (G23) shear moduli were determined for two composite materials of uniaxial and angleply fiber orientations. Test specimens were 16 plies (nominal 2 mm) thick, 100 mm in length, and in widths of 6.3, 9.5, 12.5, and 15.8 mm. Torsion tests were run under controlled deflection (constant angle of twist) using an electrohydraulic servocontrolled test system. In-plane and out-of-plane shear moduli were calculated from an equation derived in the theory of elasticity which relates applied torque, the torsional angle of twist, the specimen width/thickness ratio, and the ratio of the two shear moduli G13/G23. Results demonstrate that torsional shear moduli, G23 as well as G13, can be determined by simple torsion tests of flat specimens of rectangular cross section. Neither the uniaxial nor angleply composite material were transversely isotropic.

Sumsion, H. T.; Rajapakse, Y. D. S.

1978-01-01

105

Ovarian torsion diagnosed by ultrasonography.  

PubMed

We have reported the ultrasonographic findings in a 9-year-old girl with torsion of a normal ovary. In this and six previously reported cases ultrasonography has shown hypoechoic, solid, intrapelvic masses sometimes containing small cysts. Liquid may be present in the pelvic cul-de-sac, and in one instance an anechoic halo surrounded an infarcted ovary. A second case, a seemingly false-positive ultrasonic diagnosis of ovarian enlargement, illustrated a possible pitfall. Ultrasonography can aid in earlier diagnosis of ovarian torsion, which may permit more ovaries to be salvaged. PMID:3906912

Bowen, A

1985-11-01

106

Torsion bar antenna in the proper reference frame with rotation  

E-print Network

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.

Nakamura, Kouji

2014-01-01

107

A torsional vibration measurement system  

Microsoft Academic Search

At the development stage of automobile construction, many power-train configurations may be considered. Due to complicated coupling mechanisms, the natural frequencies of the combined system are difficult to predict. It is therefore necessary to run tests on automotive subsystems under realistic operating conditions. To fully understand the dynamic behavior, a study of both torsional and translational motions along the driveshaft

Peishuh Wang; Patricia Davies; John M. Starkey; Richard L. Routson

1992-01-01

108

Bistability of a Torsion Magnetometer  

E-print Network

Low-level bistability has been observed in the output from a recently developed novel magnetometer. It is not known whether this behavior is associated with the torsion fiber of the instrument or with the Earth's magnetic field. Whatever its cause, this form of complexity is not widely known.

Randall D. Peters

2002-07-16

109

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

110

Metric-affine $f(R)$-gravity with torsion: an overview  

E-print Network

Torsion and curvature could play a fundamental role in explaining cosmological dynamics. f(R)-gravity with torsion is an approach aimed to encompass in a comprehensive scheme all the Dark Side of the Universe (Dark Energy and Dark Matter). We discuss the field equations in empty space and in presence of perfect fluid matter taking into account the analogy with the metric-affine formalism. The result is that the extra curvature and torsion degrees of freedom can be dealt under the standard of an effective scalar field of fully geometric origin. The initial value problem for such theories is also discussed.

S. Capozziello; S. Vignolo

2009-10-27

111

Simultaneous normal and torsional force measurement by cantilever surface contour analysis  

NASA Astrophysics Data System (ADS)

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

Kumanchik, Lee; Schmitz, Tony; Pratt, Jon

2011-05-01

112

Relativistic Statistical Mechanics with Angular Momentum  

E-print Network

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.

Tadas K Nakamura

2011-12-01

113

Orbital angular momentum in phase space  

SciTech Connect

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.

Rigas, I. [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Sanchez-Soto, L.L., E-mail: lsanchez@fis.ucm.es [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Klimov, A.B. [Departamento de Fisica, Universidad de Guadalajara, 44420 Guadalajara, Jalisco (Mexico); Rehacek, J.; Hradil, Z. [Department of Optics, Palacky University, 17. Listopadu 12, 746 01 Olomouc (Czech Republic)

2011-02-15

114

Electric field in 3D gravity with torsion  

E-print Network

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.

M. Blagojevi?; B. Cvetkovi?

2008-04-11

115

Shaft instantaneous angular speed for blade vibration in rotating machine  

NASA Astrophysics Data System (ADS)

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.

Gubran, Ahmed A.; Sinha, Jyoti K.

2014-02-01

116

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

Microsoft Academic Search

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

Taro Ueki; Edward W Larsen

1998-01-01

117

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

NASA Astrophysics Data System (ADS)

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

Yazadjiev, Stoytcho

2013-01-01

118

Splenic torsion and the prune belly syndrome  

Microsoft Academic Search

Torsion of the spleen is rare, difficult to diagnose, and potentially life-threatening. The simultaneous occurrence of splenic torsion and the prune belly syndrome has been reported only twice in the literature. We report the clinical findings, treatment, and follow-up in a 9-year-old boy with typical features of the prune belly syndrome in whom surgical exploration of the abdomen revealed torsion

Hossein Aliabadi; John Foker; Ricardo Gonzalez

1987-01-01

119

Coupled lateral-torsional-axial vibrations of a helical gear-rotor-bearing system  

NASA Astrophysics Data System (ADS)

Considering the axial and radial loads, a mathematical model of angular contact ball bearing is deduced with Hertz contact theory. With the coupling effects of lateral, torsional and axial vibrations taken into account, a lumped-parameter nonlinear dynamic model of helical gearrotor-bearing system (HGRBS) is established to obtain the transmission system dynamic response to the changes of different parameters. The vibration differential equations of the drive system are derived through the Lagrange equation, which considers the kinetic and potential energies, the dissipative function and the internal/external excitation. Based on the Runge-Kutta numerical method, the dynamics of the HGRBS is investigated, which describes vibration properties of HGRBS more comprehensively. The results show that the vibration amplitudes have obvious fluctuation, and the frequency multiplication and random frequency components become increasingly obvious with changing rotational speed and eccentricity at gear and bearing positions. Axial vibration of the HGRBS also has some fluctuations. The bearing has self-variable stiffness frequency, which should be avoided in engineering design. In addition, the bearing clearance needs little attention due to its slightly discernible effect on vibration response. It is suggested that a careful examination should be made in modelling the nonlinear dynamic behavior of a helical gear-rotor-bearing system.

Li, Chao-Feng; Zhou, Shi-Hua; Liu, Jie; Wen, Bang-Chun

2014-10-01

120

Effects of temperature and torsion speed on torsional properties of single-walled carbon nanotubes  

Microsoft Academic Search

Carbon nanotubes (CNTs) are excellent candidates for torsional elements used in nanoelectro-mechanical systems (NEMS). Simulations show that after being twisted to a certain angle, they buckle and lose their mechanical strength. In this paper, classical molecular dynamics simulations are performed on single-walled carbon nanotubes (CNTs) to investigate the effects of torsion speed and temperature on CNT torsional properties. The AIREBO

A. R. Khoei; E. Ban; P. Banihashemi; M. J. Abdolhosseini Qomi

2011-01-01

121

FAST TRACK COMMUNICATION: f(R) gravity, torsion and non-metricity  

NASA Astrophysics Data System (ADS)

For both f(R) theories of gravity with an independent symmetric connection (no torsion), usually referred to as Palatini f(R) gravity theories, and for f(R) theories of gravity with torsion but no non-metricity, called U4 theories, it has been shown that the independent connection can actually be eliminated algebraically, as long as this connection does not couple to matter. Remarkably, the outcome in both cases is the same theory, which is dynamically equivalent with an ?0 = -3/2 Brans-Dicke theory. It is shown here that even for the most general case of an independent connection with both non-metricity and torsion, one arrives at exactly the same theory as in the more restricted cases. This generalizes the previous results and explains why assuming that either the torsion or the non-metricity vanishing ultimately leads to the same theory. It also demonstrates that f(R) actions cannot support an independent connection which carries dynamical degrees of freedom, irrespective of how general this connection is, at least as long as there is no connection-matter coupling.

Sotiriou, Thomas P.

2009-08-01

122

Premotor neurons encode torsional eye velocity during smooth-pursuit eye movements  

NASA Technical Reports Server (NTRS)

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.

Angelaki, Dora E.; Dickman, J. David

2003-01-01

123

The Angular Momentum of Light  

NASA Astrophysics Data System (ADS)

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.

Andrews, David L.; Babiker, Mohamed

2012-11-01

124

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

SciTech Connect

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

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

2011-05-15

125

Torsional electromechanical quantum oscillations in carbon nanotubes  

E-print Network

Torsional electromechanical quantum oscillations in carbon nanotubes TZAHI COHEN-KARNI1 *, LIOR and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel 2 Chemical Research Support, Weizmann by mechanical torsion4 can induce conductance oscillations, which can be attributed to metal

Joselevich, Ernesto

126

Analytic torsion on spherical factors and tessellations  

E-print Network

The analytic torsion is computed on fixed-point free and non fixed-point free factors (tessellations) of the three--sphere. We repeat the standard computation on spherical space forms (Clifford-Klein spaces) by an improved technique. The transformation to a simpler form of the spectral expression of the torsion on spherical factors effected by Ray is shown to be more general than his derivation implies. It effectively allows the eigenvalues to be considered as squares of integers, and applies also to trivial twistings. The analytic torsions compute to algebraic numbers, as expected. In the case of icosahedral space, the quaternion twisting gives a torsion proportional to the fundamental unit of Q(5^(1/2)). As well as a direct calculation, the torsions are obtained from the lens space values by a character inducing procedure.On tessellations, terms occur due to edge conical singularities.

J. S. Dowker; Peter Chang

2009-04-06

127

Sampling of conformation space in torsion angle dynamics calculations  

NASA Astrophysics Data System (ADS)

Torsion angle dynamics (TAD) performs molecular dynamics simulation using torsion angles instead of Cartesian coordinates as degrees of freedom. TAD algorithms used in conjunction with simulated annealing are one of the common methods for the calculation of three-dimensional protein structures from NMR data. For this application of TAD, unbiased sampling of conformation space is essential. This paper presents a systematic study of the sampling of conformation space in protein structure calculations with the TAD algorithm implemented in the program DYANA, and compares the results with those obtained with a different TAD algorithm in the program CNS. Examples used are unconstrained poly-alanine peptides of length 20 to 100 residues, and the globular protein Antennapedia(C39S) homeodomain, which comprises unstructured polypeptide segments at the two chain termini and was calculated from a high-quality experimental NMR data set. The results show that the different implementations of TAD all have good sampling properties for calculating protein structures that are well-constrained by experimental NMR data. However, if TAD is used for studies of long unconstrained polypeptides, the results obtained in this paper show that the molecule needs to reorient freely in space, and that the total angular and linear momenta of the system are conserved and periodically reset to zero.

Güntert, Peter; Wüthrich, Kurt

2001-08-01

128

Torsional oscillations of strange stars  

E-print Network

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...

Mannarelli, Massimo

2014-01-01

129

Torsion Fields, Propagating Singularities, Nilpotence, Quantum Jumps and the Eikonal Equations  

NASA Astrophysics Data System (ADS)

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.

Rapoport, Diego L.

2010-11-01

130

September 12, 2007 THE ISOMORPHISM PROBLEM FOR TORSION-FREE  

E-print Network

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

131

The Torsion of Spinor Connections and Related Structures  

E-print Network

In this text we introduce the torsion of spinor connections. In terms of the torsion we give conditions on a spinor connection to produce Killing vector fields. We relate the Bianchi type identities for the torsion of spinor connections with Jacobi identities for vector fields on supermanifolds. Furthermore, we discuss applications of this notion of torsion.

Frank Klinker

2006-11-09

132

The Torsion of Spinor Connections and Related Structures  

NASA Astrophysics Data System (ADS)

In this text we introduce the torsion of spinor connections. In terms of the torsion we give conditions on a spinor connection to produce Killing vector fields. We relate the Bianchi type identities for the torsion of spinor connections with Jacobi identities for vector fields on supermanifolds. Furthermore, we discuss applications of this notion of torsion.

Klinker, Frank

2006-11-01

133

The Torsion of Spinor Connections and Related Structures  

Microsoft Academic Search

In this text we introduce the torsion of spinor connections. In terms of the torsion we give conditions on a spinor connection to produce Killing vector fields. We relate the Bianchi type identities for the torsion of spinor connections with Jacobi identities for vector fields on supermanifolds. Furthermore, we discuss applications of this notion of torsion.

Frank Klinker

2006-01-01

134

Torsion Gravity Effects on Charged-Particles and Neutron Interferometers  

E-print Network

Torsion gravitational effects in the quantum interference of charged particles are investigated. The influence of axial torsion in the Schiff-Banhill effect (SB) inside a metallic shell is given. The effect of torsion on the surface of the earth on (SB) experiment is estimated. Torsion gravity effects on the Sagnac phase-shift of neutron interferometry are also computed.

C. Sivaram; L. C. Garcia de Andrade

2001-11-04

135

Validation of an automated torsional and warping stress analysis program  

Microsoft Academic Search

An automated procedure for determining warping and torsional stresses in open steel members was developed by Joseph Palacak, Jr. in 1985. His FORTRAN program, called 'TORSION', determined stresses in wide flange, channel, and single angle members under various longitudinal bending and torsional loadings. In order to validate the 'TORSION' program, twelve test cases were run and compared to the same

Stephen M. Azzinari

1992-01-01

136

Localization of the Einstein group and a nonsingular cosmological model of space-time with torsion  

NASA Astrophysics Data System (ADS)

We consider an Einstein-invariant gauge theory of gravitation (EGT), obtained by localizing the group of motions of a homogeneous static Einstein Universe. Taking into account the cosmological term, we find exact solutions of EGT are as nonsingular homogeneous Isotropic cosmological models with both the metric and the torsion regular. It is shown that EGT satisfies the principle of correspondence with Newton's theory of gravity and with the tetrad theory of gravity in the space of absolute parallelism.

Tunyak, V. N.

1986-10-01

137

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

SciTech Connect

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

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

1999-05-01

138

Invariant torsion and G_2-metrics  

E-print Network

We introduce and study a notion of invariant intrinsic torsion geometry which appears, for instance, in connection with the Bryant-Salamon metric on the spinor bundle over S^3. This space is foliated by six-dimensional hypersurfaces, each of which carries a particular type of SO(3)-structure; the intrinsic torsion is invariant under SO(3). The last condition is sufficient to imply local homogeneity of such geometries, and this allows us to give a classification. We close the circle by showing that the Bryant-Salamon metric is the unique complete metric with holonomy G_2 that arises from SO(3)-structures with invariant intrinsic torsion.

Conti, Diego

2014-01-01

139

Torsional irregularity in multi-story structures  

NASA Astrophysics Data System (ADS)

The purpose of this study is first to determine the conditions for excessive torsional irregularity and then to discuss the validity of code provisions. A parametric investigation is performed on six groups of typical structures with varying shear wall positions, story, and axis numbers. It is found that torsional irregularity coefficients increase as the story numbers decrease, i.e., maximum irregularity coefficients occur for single-story structures. They reach maximum values when the asymmetrical shear walls are placed as close as possible to the centers of mass. However, the results obtained for floor rotations are quite contradictory. A new provisional definition for torsional irregularity coefficient based on floor rotations is proposed.

Özmen, Günay; Girgin, Konuralp; Durgun, Yavuz

2014-09-01

140

Photographic assessment of changes in torsional strabismus.  

PubMed

The horizontal and vertical components of strabismus are measured routinely and relatively easily in the clinical setting using prism-and-cover and/or corneal light reflex tests. The third dimension of ocular alignment, ocular torsion, is more difficult to assess. Objective torsional deviation (cyclotropia) is evaluated qualitatively with fundus examination. For quantitative assessment, however, fundus photography is needed, which may not always be available during a strabismus examination and typically requires pupil dilation. We present a simple, inexpensive photographic technique to assess changes in iris torsion and evaluate its accuracy by comparison with fundus photography. Using a consumer-grade digital camera, basic photographic editing software, and a data worksheet, this technique assesses changes in objective torsion with accuracy and retest variability of both approximately 1 degrees. PMID:20006824

Felius, Joost; Locke, Kirsten G; Hussein, Mohamed A; Stager, David R; Stager, David R

2009-12-01

141

Dark Energy: Is It of Torsion Origin?  

E-print Network

{\\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.

M. I. Wanas

2010-06-10

142

Dirac-harmonic maps with torsion  

E-print Network

We study Dirac-harmonic maps from surfaces to manifolds with torsion, which is motivated from the superstring action considered in theoretical physics. We discuss analytic and geometric properties of such maps and outline an existence result for uncoupled solutions.

Volker Branding

2014-05-20

143

Flow in a torsionally oscillating filled cylinder  

NASA Technical Reports Server (NTRS)

The flow of a liquid in a completely filled cylinder undergoing torsional oscillations about its longitudinal symmetry axis was studied analytically and experimentally. The objective of the studies was to determine the efficacy of the torsional oscillations in mixing the confined liquid. Flow was found to be confined primarily to toroidal cells at the ends of the cylinder. Cell thickness was about equal to the cylinder radius. The use of baffles at the end walls was shown to enhance the mixing process.

Schafer, C. F.

1983-01-01

144

Buckling and postbuckling behaviors of imperfect cylindrical shells subjected to torsion  

Microsoft Academic Search

Buckling and postbuckling behaviors of imperfect cylindrical shell subjected to torsion are investigated. The governing equations are based on the Karman–Donnell-type nonlinear differential equations. A boundary layer theory of shell buckling is applied to obtain the analytic solutions that meet the boundary conditions strictly. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. Numerical

Xiaoqing Zhang; Qiang Han

2007-01-01

145

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

SciTech Connect

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

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

1999-03-01

146

Nonseparable transition state theory for nonzero total angular momentum: Implications for J shifting and application to the OH+H2 reaction  

NASA Astrophysics Data System (ADS)

We report vibration/rotation energies of the OHH2 transition state using the code ``Multimode,'' for total angular momentum J=0, 1, and 4. Rotation is treated in the adiabatic rotation approximation for J=1 and 4, as well as exactly, i.e., including Coriolis coupling, for J=1. State-dependent rotation constants are obtained using the adiabatic rotation energies from the J=0 and 1 calculations and shown to predict accurately the adiabatic rotation rovibrational energies for J=4. These rotation constants are used in new J-shifting calculations of the thermal rate constant for the reaction OH+H2-->H2O+H using results from a previous accurate calculation of the rate constant for J=0 [U. Manthe, T. Seideman, and W. H. Miller, J. Chem. Phys. 99, 10078 (1993); 101, 4759 (1994)]. Comparisons with previous J-shifting and recent centrifugal sudden calculations of the rate constant [D. H. Zhang, J. C. Light, and S-Y. Lee, J. Chem. Phys. 109, 79 (1998)] of this reaction are presented. A modification of the previous centrifugal sudden rate constant is made and shown to yield results that are in good agreement with the new J-shifting calculations. Finally, an assessment of Coriolis coupling is made.

Bowman, Joel M.; Shnider, Heather M.

1999-03-01

147

Infrared and Millimeter-Wave Study of the Four Lowest Torsional States of CH(3)CF(3).  

PubMed

An investigation of the torsion-rotation Hamiltonian of CH(3)CF(3) in the ground vibrational state has been carried out using infrared and mm-wave spectroscopy. With infrared Fourier transform spectroscopy, the weak, torsional overtone (v(6) = 2 <-- 0) has been studied leading to the measurement of 382 frequencies between 405 and 440 cm(-1) at a resolution of 0.005 cm(-1). Torsional splittings on the order of 0.03 cm(-1) were observed. With mm-wave methods, a total of 669 rotational transitions between 50 and 360 GHz have been measured at Doppler-limited resolution in the four lowest torsional states v(6) = 0, 1, 2, 3. The experimental uncertainty attained for an isolated line was better than 10 kHz below 150 GHz, and somewhat larger at higher frequencies. For v(6) = 3, torsional splittings as large as 8.7 MHz were observed. The global data set consisted of the current frequency determinations and the 443 measurements with molecular beam, microwave, and mm-wave methods analyzed by I. Ozier, J. Schroderus, S.-X. Wang, G. A. McRae, M. C. L. Gerry, B. Vogelsanger, and A. Bauder [J. Mol. Spectrosc. 190, 324-340 (1998)]. The observation of mm-wave R-branch transitions for v(6) = 1 led to a change in the J-assignment of the forbidden (Deltak = +/-3) transitions reported earlier for this torsional state. A good fit was obtained by varying 24 parameters in a Hamiltonian that represented both the torsional effects and the sextic splittings. In the earlier work, the large reduced barrier height led to high correlations among several of the torsional distortion constants. With the current measurements, many of these correlations are substantially reduced. Improved effective values were determined for the height V(3) of the hindering barrier and the first-order correction V(6) in the Fourier expansion of the potential function. The dipole function which characterizes the transition moment of the torsional overtone (v(6) = 2 <-- 0) can be written as the product of a single effective dipole constant µ(T)(0,eff) and the appropriate off-diagonal matrix element of (1 - cos 3alpha)/2, where alpha is the torsional angle. From an intensity analysis of the infrared spectrum, it has been determined that |µ(T)(0,eff)| = 85.3(62) mD. A novel approach based on a simple regrouping of angular momentum operators is introduced for decoupling the torsional and rotational degrees of freedom. Copyright 2001 Academic Press. PMID:11148119

Wang; Schroderus; Ozier; Moazzen-Ahmadi; McKellar; Ilyushyn; Alekseev; Katrich; Dyubko

2001-01-01

148

Angular Acceleration without Torque?  

ERIC Educational Resources Information Center

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

Kaufman, Richard D.

2012-01-01

149

Piezoelectric angular acceleration sensor  

Microsoft Academic Search

This paper deals with a piezoelectric angular acceleration sensor, which might be proposed by us, first, as a new concept of the sensor to detect a rotational motion only. In the first part of this paper are dealt with some concrete constructions of this new concept of angular acceleration sensor, composed of piezoelectric transducers. The second part contains their basic

Y. Tomikawa; S. Okada

2003-01-01

150

Angular shear plate  

Microsoft Academic Search

One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative

Mitchell C. Ruda; Alan W. Greynolds; Tilman W. Stuhlinger

2009-01-01

151

Nondipolar photoelectron angular distributions  

SciTech Connect

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

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

1996-12-31

152

Endodontic instruments after torsional failure: nanoindentation test.  

PubMed

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

Jamleh, Ahmed; Sadr, Alireza; Nomura, Naoyuki; Ebihara, Arata; Yahata, Yoshio; Hanawa, Takao; Tagami, Junji; Suda, Hideaki

2014-01-01

153

Metamaterial broadband angular selectivity  

E-print Network

We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each ...

Shen, Yichen

154

Angular velocity discrimination  

NASA Technical Reports Server (NTRS)

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.

Kaiser, Mary K.

1990-01-01

155

Theoretical rotation-torsion spectra of HSOH.  

PubMed

Rotation-torsion spectra of HSOH, involving the vibrational ground state and the fundamental torsional state, have been simulated at T = 300 K. The simulations are carried out with the variational computer program TROVE in conjunction with recently reported ab initio potential energy and electric dipole moment surfaces. HSOH is a near-prolate-symmetric top at equilibrium and the simulated spectra are of perpendicular-band-type with strong R-branch and Q-branch transitions. Recently, an anomalous (b-type-transition)/(c-type-transition) intensity ratio in the vibrational-ground-state (r)Q(K(a))-branches of HSOH has been experimentally observed. Our calculations reproduce correctly the anomaly and show that it originates in the large-amplitude torsional motion of HSOH. We analyze our theoretical results in order to explain the effect and to provide unambiguous (b/c)-type-transition assignments. PMID:20526504

Yachmenev, Andrey; Yurchenko, Sergei N; Jensen, Per; Baum, Oliver; Giesen, Thomas F; Thiel, Walter

2010-08-01

156

Spatial Persistence of Angular Correlations in Amyloid Fibrils  

NASA Astrophysics Data System (ADS)

Using atomic force microscopy height maps, we resolve and quantify torsional fluctuations in one-dimensional amyloid fibril aggregates self-assembled from three different representative polypeptide systems. Furthermore, we show that angular correlation in these nanoscale structures is maintained over several microns, corresponding to many thousands of molecules along the fibril axis. We model disorder in the fibril in respect of both thermal fluctuations and structural defects, and determine quantitative values for the defect density, as well as the energy scales involved in the fundamental interactions stabilizing these generic structures.

Knowles, Tuomas P. J.; Smith, Jeffrey F.; Craig, Aidan; Dobson, Christopher M.; Welland, Mark E.

2006-06-01

157

Shear deformable bars of doubly symmetrical cross section under nonlinear nonuniform torsional vibrations—application to torsional postbuckling configurations and primary resonance excitations  

Microsoft Academic Search

In this paper a boundary element method is developed for the nonuniform torsional vibration problem of bars of arbitrary doubly\\u000a symmetric constant cross section, taking into account the effects of geometrical nonlinearity (finite displacement—small strain\\u000a theory) and secondary twisting moment deformation. The bar is subjected to arbitrarily distributed or concentrated conservative\\u000a dynamic twisting and warping moments along its length, while

E. J. Sapountzakis; V. J. Tsipiras

2010-01-01

158

ME 354, MECHANICS OF MATERIALS LABORATORY TORSION TESTING  

E-print Network

section torsion specimens of 6061-T6 aluminum · Constant-diameter gage section torsion specimens of A36. V. Carefully examine the specimen and fracture surface. Record enough information (in the form

Sniadecki, Nathan J.

159

Validation of an automated torsional and warping stress analysis program  

NASA Astrophysics Data System (ADS)

An automated procedure for determining warping and torsional stresses in open steel members was developed by Joseph Palacak, Jr. in 1985. His FORTRAN program, called 'TORSION', determined stresses in wide flange, channel, and single angle members under various longitudinal bending and torsional loadings. In order to validate the 'TORSION' program, twelve test cases were run and compared to the same cases analyzed using a commonly used manual technique. For this manual technique, the Torsional Analysis Case Charts, developed by Bethlehem Steel were used to compute warping and torsional stresses. Tables comparing the calculated stresses by the 'TORSION' program and the torsion tables were developed. In addition, stress values from the hand-calculated problems were compared to values from GTSTRUDL output. Comparison tables between GTSTRUDL and the hand-calculated values are also presented.

Azzinari, Stephen M.

1992-08-01

160

Thermal Hall Effect and Geometry with Torsion  

E-print Network

We formulate a geometric framework that allows to study momentum and energy transport in non-relativistic systems. It amounts to coupling of the non-relativistic system to the Newton-Cartan geometry with torsion. The approach generalizes the classic Luttinger's formulation of thermal transport. In particular, we clarify the geometric meaning of the fields conjugated to energy and energy current. These fields describe the geometric background with non-vanishing temporal torsion. We use the developed formalism to construct the equilibrium partition function of a non-relativistic system coupled to the NC geometry in 2+1 dimensions and to derive various thermodynamic relations

Andrey Gromov; Alexander G. Abanov

2014-07-10

161

Thermal Hall Effect and Geometry with Torsion  

E-print Network

We formulate a geometric framework that allows to study momentum and energy transport in non-relativistic systems. It amounts to coupling of the non-relativistic system to the Newton-Cartan geometry with torsion. The approach generalizes the classic Luttinger's formulation of thermal transport. In particular, we clarify the geometric meaning of the fields conjugated to energy and energy current. These fields describe the geometric background with non-vanishing temporal torsion. We use the developed formalism to construct the equilibrium partition function of a non-relativistic system coupled to the NC geometry in 2+1 dimensions and to derive various thermodynamic relations

Gromov, Andrey

2014-01-01

162

Evidence for the distribution of angular velocity inside the sun and stars  

NASA Technical Reports Server (NTRS)

A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing the distribution of angular velocity inside the sun and stars.

1972-01-01

163

Torsional fatigue life prediction method for DRAM module  

Microsoft Academic Search

In this study, shear strain controlled torsional test method was developed for torsional fatigue life prediction of DRAM module. The maximum principal strain and its direction was measured using rosette gage during module inserting user environment, and it was verified that shear strain was the dominant driving factor for solder joint failure. Apart from other studies where torsional tests were

Yeo Hoon Yoon; Yong ho Ko; Ho jung Moon; Se Young Yang

2007-01-01

164

Metamaterial broadband angular selectivity  

NASA Astrophysics Data System (ADS)

We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each effective anisotropic layer is constructed from a multilayered metamaterial. We show that by simply changing the structure of the metamaterials, the selective angle can be tuned to a broad range of angles; and, by increasing the number of stacks, the angular transmission window can be made as narrow as desired. As a proof of principle, we realize the idea experimentally in the microwave regime. The angular selectivity and tunability we report here can have various applications such as in directional control of electromagnetic emitters and detectors.

Shen, Yichen; Ye, Dexin; Wang, Li; Celanovic, Ivan; Ran, Lixin; Joannopoulos, John D.; Solja?i?, Marin

2014-09-01

165

Adnexal torsion: review of the literature.  

PubMed

Adnexal torsion is one of a few gynecologic surgical emergencies. Misdiagnosis or delay in treatment can have permanent sequelae including loss of an ovary with effect on future fertility, peritonitis, and even death. A PubMed search was performed between 1985 and 2012 for reviews, comparative studies, and case reports to provide a review of the epidemiology, risk factors, clinical presentation, common laboratory and imaging findings, and treatments of adnexal torsion. Common symptoms of torsion include pain, nausea, and vomiting, with associated abdominal or pelvic tenderness, and may differ in premenarchal and pregnant patients. Laboratory and imaging findings including ultrasound with Doppler analysis, computed tomography, and magnetic resonance imaging can assist in making the diagnosis but should not trump clinical judgment; normal Doppler flow can be observed in up to 60% of adnexal torsion cases. Treatment depends on the individual patient but commonly includes detorsion, even if the adnexae initially seem necrotic, with removal of any associated cysts or salpingo-oophorectomy, because recurrence rates are higher with detorsion alone or detorsion with only cyst aspiration. PMID:24126258

Sasaki, Kirsten J; Miller, Charles E

2014-01-01

166

Torsional vibration reduction using passive nonlinear absorbers  

Microsoft Academic Search

This paper considers the dynamic performance of systems of centrifugal pendulum vibration absorbers that are used to attenuate torsional vibrations in rotating systems. These absorbers, which can be found in certain IC engines and helicopter rotors, consist of movable masses whose centers of mass are kinematically restricted to move along prescribed paths relative to the rotor of interest. The most

Steven W. Shaw; Abdallah Alsuwaiyan

2000-01-01

167

ORIGINAL ARTICLE Torsional Anomalous Retinal Correspondence  

E-print Network

with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry As a result of strabismus, patients may experience diplopia (two images of the same object with different, Massachusetts (PNS, EP). Supplemental digital contents are available for this article. Direct URL citations

Peli, Eli

168

Asymptomatic uterine torsion in a pregnant woman.  

PubMed

Some degree rotation of the gravid uterus in the third trimester of pregnancy is not an abnormal finding. However, extreme uterine torsion of 180° around its cervical junction is a relatively rare event in obstetrical practice. We report here such a case that detected at laparotomy for an emergency cesarean section due to rapture of amniotic membrane. PMID:25278659

Farhadifar, Fariba; Nikkhoo, Bahram; Shahgheibi, Sholeh; Soofizadeh, Nasrin; Rezaie, Masomeh

2014-08-01

169

Test particle acceleration in torsional fan reconnection  

NASA Astrophysics Data System (ADS)

Magnetic reconnection is understood to be a potential mechanism for particle acceleration in astrophysical and space plasmas, especially in solar flares. Torsional fan reconnection is one of the proposed mechanisms for steady-state three-dimensional (3D) magnetic reconnection. By using the magnetic and electric fields for `torsional fan reconnection', the features of test particle acceleration with input parameters for the solar corona are investigated numerically. We show that torsional fan reconnection is potentially an efficient particle accelerator and a proton can gain up to tens of MeV of kinetic energy within only a few milliseconds. Although the final kinetic energy of the accelerated particle depends on the injection position but there exists only one scenario for the particle's trajectory with different initial positions in which the particle is accelerated on the fan plane. Moreover, adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory. These results are compared with those of torsional spine reconnection.

Hosseinpour, M.

2014-12-01

170

Gravitational dispersion in a torsional wave machine  

E-print Network

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.

Rafael de la Madrid; Alejandro Gonzalez; George Irwin

2014-09-01

171

Ideal linear-chain polymers with fixed angular momentum.  

PubMed

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

Brunner, Matthew; Deutsch, J M

2011-07-01

172

6H-SiC microdisk torsional resonators in a "smart-cut" technology  

NASA Astrophysics Data System (ADS)

We report on experimental demonstration of high frequency torsional resonators based on microdisk structures enabled by a "smart-cut" 6H-silicon carbide (6H-SiC) technology. Circular microdisks axially supported by pairs of thin tethers, with diameters of ˜5-15 ?m, exhibit torsional-mode micromechanical resonances with frequency of ˜1-60 MHz, and quality (Q) factors up to 1280 at room temperature in moderate vacuum (˜10 mTorr). Measured intrinsic thermomechanical vibrations of a microdisk with diameter d ? 15.9 ?m (and triangular cross-section tethers with width wT ? 1.5 ?m, length LT ? 2 ?m, and thickness tT ? 0.4 ?m) demonstrate a torque resolution of ST1/2 ? 3.7 × 10-20 (N m)/?Hz, a force sensitivity of SF1/2 ? 5.7fN/?Hz, and an angular displacement sensitivity of S?1/2 ? 4.0 × 10-8 rad/?Hz. By examining devices with varying disk size, different tether shape, width, and length, and by combining experimental data and theoretical calculations, we depict the scaling pathways for ultrasensitive torsional resonant sensors based on this smart-cut 6H-SiC platform.

Yang, Rui; Wang, Zenghui; Lee, Jaesung; Ladhane, Kalyan; Young, Darrin J.; Feng, Philip X.-L.

2014-03-01

173

Design and analysis of a torsion braid pendulum displacement transducer  

NASA Astrophysics Data System (ADS)

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.

Rind, E.; Bryant, E. L.

1981-06-01

174

Evaluation of left ventricular torsion by cardiovascular magnetic resonance  

PubMed Central

Recently there has been considerable interest in LV torsion and its relationship with symptomatic and pre-symptomatic disease processes. Torsion gives useful additional information about myocardial tissue performance in both systolic and diastolic function. CMR assessment of LV torsion is simply and efficiently performed. However, there is currently a wide variation in the reporting of torsional motion and the procedures used for its calculation. For example, torsion has been presented as twist (degrees), twist per length (degrees/mm), shear angle (degrees), and shear strain (dimensionless). This paper reviews current clinical applications and shows how torsion can give insights into LV mechanics and the influence of LV geometry and myocyte fiber architecture on cardiac function. Finally, it provides recommendations for CMR measurement protocols, attempts to stimulate standardization of torsion calculation, and suggests areas of useful future research. PMID:22827856

2012-01-01

175

Design and analysis of a torsion braid pendulum displacement transducer  

NASA Technical Reports Server (NTRS)

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.

Rind, E.; Bryant, E. L.

1981-01-01

176

Angular momentum conservation demonstration  

NSDL National Science Digital Library

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

Berg, Richard E.; Anders, Robert E.

2010-12-23

177

Gears: Determining Angular Velocity  

NSDL National Science Digital Library

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.

AMPS GK-12 Program,

178

Continuous phase transition and critical behaviors of 3D black hole with torsion  

E-print Network

We study the phase transition and the critical behavior of the BTZ black hole with torsion obtained in $(1+2)$-dimensional Poincar\\'{e} gauge theory. According to Ehrenfest's classification, when the parameters in the theory are arranged properly the BTZ black hole with torsion may posses the second order phase transition which is also a smaller mass/larger mass black hole phase transition. Nevertheless, the critical behavior is different from the one in the van der Waals liquid/gas system. We also calculated the critical exponents of the relevant thermodynamic quantities, which are the same as the ones obtained in the Ho\\v{r}ava-Lifshitz black hole and the Born-Infeld black hole.

Meng-Sen Ma; Fang Liu; Ren Zhao

2014-03-03

179

Continuous phase transition and critical behaviors of 3D black hole with torsion  

E-print Network

We study the phase transition and the critical behavior of the BTZ black hole with torsion obtained in $(1+2)$-dimensional Poincar\\'{e} gauge theory. According to Ehrenfest's classification, when the parameters in the theory are arranged properly the BTZ black hole with torsion may posses the second order phase transition which is also a smaller mass/larger mass black hole phase transition. Nevertheless, the critical behavior is different from the one in the van der Waals liquid/gas system. We also calculated the critical exponents of the relevant thermodynamic quantities, which are the same as the ones obtained in the Ho\\v{r}ava-Lifshitz black hole and the Born-Infeld black hole.

Ma, Meng-Sen; Zhao, Ren

2014-01-01

180

Galactic dynamos and slow decay of magnetic fields from torsion modes of Lorentz violation  

NASA Astrophysics Data System (ADS)

Campanelli et al. (2009) [9] have recently shown that electromagnetic fluctuations in Lorentz violation theories Colladay and Kostelecky (1998) [8] along differential rotation may induce galactic dynamo amplification of magnetic fields from primordial seeds. In this Letter, instead of using the Maxwell-Chern-Simmons-Lagrangian used in their paper, one adopts the Lagrangean of the type RFiFk, where R represent the torsion modes, without dynamical curvature. This so-called Minkowski-Cartan spacetime M4 torsion modes, allows us to handle QED vacuum in any Ricci scalar electrodynamics Lagrangean. It is shown that axial-torsion modes electrodynamics allows us to obtain a slow decay of magnetic fields. Thus primordial seed fields are amplified from differential rotation and protogalaxy turbulence as galactic dynamo action. This is mainly due to the fact that the collapse of the protogalaxy induces a strong suppression of the magnetic field decay. Magnetic field anisotropies are also considered. To resume, photon-torsion axial coupling in the quantum electrodynamics (QED) framework in Riemann flat contortioned spacetime may induce galactic dynamos. Fourier space transformation are used to compute electrodynamic equations.

Garcia de Andrade, L. C.

2011-01-01

181

Theories  

NSDL National Science Digital Library

This activity will help the students understand that science theories change in the face of new evidence, but those changes can be slow in coming. Students will observe how scientific theories change over time, Be introduced to the sophistication of the geocentric model and the time it took to change the theory underpinning the heliocentric model, Compare the heliocentric model to the geocentric model.

2010-01-01

182

Galactic dynamos and slow decay of magnetic fields from torsion modes of Lorentz violation  

Microsoft Academic Search

Campanelli et al. (2009) [9] have recently shown that electromagnetic fluctuations in Lorentz violation theories Colladay and Kostelecky (1998) [8] along differential rotation may induce galactic dynamo amplification of magnetic fields from primordial seeds. In this Letter, instead of using the Maxwell–Chern–Simmons–Lagrangian used in their paper, one adopts the Lagrangean of the type RijklFijFkl, where Rijkl represent the torsion modes,

L. C. Garcia de Andrade

2011-01-01

183

Galactic dynamos and slow decay of magnetic fields from torsion modes of Lorentz violation  

Microsoft Academic Search

Campanelli et al. (2009) [9] have recently shown that electromagnetic fluctuations in Lorentz violation theories Colladay and Kostelecky (1998) [8] along differential rotation may induce galactic dynamo amplification of magnetic fields from primordial seeds. In this Letter, instead of using the Maxwell-Chern-Simmons-Lagrangian used in their paper, one adopts the Lagrangean of the type RFiFk, where R represent the torsion modes,

L. C. Garcia de Andrade

2011-01-01

184

Coupled bending and torsional vibration of axially loaded Bernoulli–Euler beams including warping effects  

Microsoft Academic Search

The dynamic transfer matrix method for determining natural frequencies and mode shapes of the bending-torsion coupled vibration of axially loaded thin-walled beams with monosymmetrical cross sections is developed by using a general solution of the governing differential equations of motion based on Bernoulli–Euler beam theory. This method takes into account the effect of warping stiffness and gives allowance to the

Li Jun; Shen Rongying; Hua Hongxing; Jin Xianding

2004-01-01

185

Buckling and Postbuckling Analysis of Shear Deformable Anisotropic Laminated Cylindrical Shells Under Torsion  

Microsoft Academic Search

A postbuckling analysis is presented for a shear deformable anisotropic laminated cylindrical shell of finite length subjected to torsion. The material of each layer of the shell is assumed to be linearly elastic, anisotropic and fiber-reinforced. The governing equations are based on a higher order shear deformation shell theory with von Kármán-Donnell-type of kinematic nonlinearity and including the extension\\/twist, extension\\/flexural

Zhi-Min Li; Hui-Shen Shen

2009-01-01

186

A preliminary study of a torsion balance based on a spherical superconducting suspension  

NASA Astrophysics Data System (ADS)

We present details of the design and construction of a new superconducting, magnetically suspended torsion balance in which the levitation coil and the lift surface of the float lie on the surfaces of concentric spheres. We compare results from calculations of the variation of the inductance with the levitated height and transverse motion of the float with experimental measurements and show that the levitation system is stable. Angular motion of the torsion balance is detected using superconducting pick-up coils whose inductance is modulated by float rotation. The subsequent change in current flowing in the persistent circuit containing the coils is measured using a flux-gate magnetometer. The pick-up coils exert a restoring torque on the float which can be modified by adjusting the persistent current stored. Periods down to 60 s should be obtainable for a current of 2.5 A. Preliminary results of ring-down experiments in He gas at a pressure of 53Pa show that periods of angular oscillations of 24 s with quality factor, Q, of about 200 can be obtained. The moment of inertia of the float is 2 × 10-5 kg m2. The observed period of 24 s indicates that there is an additional restoring torque in the system which may be due to trapped flux. The observed value of Q is consistent with gas damping.

Speake, C. C.; Hammond, G. D.; Trenkel, C.; Rochester, G. K.; Sumner, T. J.

1999-06-01

187

Torsion of the gallbladder in pregnancy  

PubMed Central

Torsion of the gallbladder is a rare condition that is difficult to diagnose preoperatively, but prompt surgical intervention is necessary to avoid possible sepsis and death. A 36-year-old pregnant woman presented to Emergency Department with a constant epigastric pain at 17 weeks of gestation. Abdominal ultrasonography and magnetic resonance imaging demonstrated a distended gallbladder that contained no stones but had mild wall thickening. Laparoscopic cholecystectomy using three ports was performed under the impression of an acalculous cholecystitis. The gallbladder was found to be rotated 180 degrees clockwise on gallbladder mesentery and to be gangrenous. The postoperative course was uneventful and the patient was discharged on the 4th day after surgery. It is important to keep in mind gallbladder torsion in the differential diagnosis from acute cholecystitis when the patient has an acute onset of abdominal pain and a severely distended gallbldder. Prompt cholecystectomy via a laparoscopic approach should be performed. PMID:24368989

Choi, Yoo Shin; Kim, Beom Jin

2013-01-01

188

Fluid driven torsional dipole seismic source  

DOEpatents

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

Hardee, Harry C. (Albuquerque, NM)

1991-01-01

189

ELKO and Dirac Spinors seen from Torsion  

E-print Network

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.

Fabbri, Luca

2014-01-01

190

ELKO and Dirac Spinors seen from Torsion  

E-print Network

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.

Luca Fabbri; Stefano Vignolo

2014-07-30

191

Quantum Heuristics of Angular Momentum  

ERIC Educational Resources Information Center

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)

Levy-Leblond, Jean-Marc

1976-01-01

192

Primary omental torsion diagnosed during hysterectomy  

PubMed Central

Omental torsion is a rare cause of acute abdominal pain. It presents with nonspecific symptoms and signs of an acute abdomen, making it difficult to diagnose preoperatively, because symptoms mimic those caused by other conditions such as appendicitis, cholecystitis, diverticulitis, and other gynecologic diseases. Computed tomography is an effective and useful method to diagnose and exclude other acute abdominal conditions. Our case presented with sudden right upper abdominal pain with tenderness, rebound tenderness, mild fever (37.2?), increased erythrocyte sedimentation rate (37 mm/hr), increased high-sensitivity C-reactive protein level (5.97 mg/dL). Computed tomography showed a large, well-circumscribed heterogeneous fatty mass and a 7.3 cm subserosal myoma. We could not exclude the myoma as the cause of acute abdominal pain, so we performed an emergency operation with suspicion of omental torsion or necrotic degeneration of the myoma. During the operation, we diagnosed primary omental torsion with infarction and subserosal myoma without secondary degeneration.

Park, Chul Min

2014-01-01

193

Primary omental torsion diagnosed during hysterectomy.  

PubMed

Omental torsion is a rare cause of acute abdominal pain. It presents with nonspecific symptoms and signs of an acute abdomen, making it difficult to diagnose preoperatively, because symptoms mimic those caused by other conditions such as appendicitis, cholecystitis, diverticulitis, and other gynecologic diseases. Computed tomography is an effective and useful method to diagnose and exclude other acute abdominal conditions. Our case presented with sudden right upper abdominal pain with tenderness, rebound tenderness, mild fever (37.2?), increased erythrocyte sedimentation rate (37 mm/hr), increased high-sensitivity C-reactive protein level (5.97 mg/dL). Computed tomography showed a large, well-circumscribed heterogeneous fatty mass and a 7.3 cm subserosal myoma. We could not exclude the myoma as the cause of acute abdominal pain, so we performed an emergency operation with suspicion of omental torsion or necrotic degeneration of the myoma. During the operation, we diagnosed primary omental torsion with infarction and subserosal myoma without secondary degeneration. PMID:25264536

Park, Chul Min; Kim, Sung Yob

2014-09-01

194

Isolated Fallopian Tube Torsion in Adolescents  

PubMed Central

Background. Fallopian tube torsion is a rare cause of acute abdomen, occurring commonly in females of reproductive age. It lacks pathognomonic symptoms, signs, or imaging features, thus causing delay in surgical intervention. Case. We report two cases of isolated fallopian tube torsion in adolescent girls. In the first case a 19-year-old patient presented with acute pain in the left iliac region associated with episodes of vomiting for one day and mild tenderness on examination. Laparoscopy revealed left sided twisted fallopian tube associated with hemorrhagic cyst of ovary. The tube was untwisted and salvaged. In another case an 18-year-old virgin girl presented with similar complaints since one week, associated with mild tenderness in the lower abdomen and tender cystic mass on per rectal examination. On laparoscopy right twisted fallopian tube associated with a paratubal cyst was found. Salpingectomy was done as the tube was gangrenous. Conclusion. Fallopian tube torsion, though rare, should be considered in women of reproductive age with unilateral pelvic pain. Early diagnostic laparoscopy is important for an accurate diagnosis and could salvage the tube. PMID:24251052

Rajaram, S.; Bhaskaran, S.; Mehta, S.

2013-01-01

195

Macromolecular conformational dynamics in torsional angle space  

NASA Astrophysics Data System (ADS)

A Brownian dynamics treatment in torsional angle space is presented for the simulation of conformational dynamics of macromolecules with fixed bond lengths and bond angles and with an arbitrary intramolecular potential energy function. The advantages of the torsional angle space treatment over similar treatments (Brownian dynamics or molecular dynamics) in atomic coordinate space are that, first, the number of variables is reduced by roughly a factor of 10 and, second, the integration time step size is increased by 3 to 4 orders of magnitude (because, by confining the treatment to the torsional angle space, the time step size is not limited by the fast oscillation modes of covalent bonds but rather by the slow motion of macromolecular segments whose time scale is roughly 3 to 4 orders of magnitude larger than that of bond oscillations). Consequently, the exploration of global conformational relaxation processes becomes computationally possible. The treatment is tested by studying the folding kinetics of off-lattice chains with fixed bond lengths and bond angles and with prescribed sequences. The present treatment is a general purpose one applicable to all macromolecular conformational relaxation processes (e.g., protein folding kinetics, drug/ligand docking on to target proteins, conformational multiple-minima problems, etc.). It serves as a complement to the molecular dynamics or Brownian dynamics treatments in atomic coordinate space.

He, Siqian; Scheraga, Harold A.

1998-01-01

196

A novel angular acceleration sensor based on the electromagnetic induction principle and investigation of its calibration tests.  

PubMed

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

Zhao, Hao; Feng, Hao

2013-01-01

197

Effects of torsional disorder and position isomerism on two-photon absorption properties of polar chromophore dimers  

NASA Astrophysics Data System (ADS)

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.

Jia, Hai-Hong; Zhao, Ke; Wu, Xiang-Lian

2014-09-01

198

Angular momentum of rotating beams  

NASA Astrophysics Data System (ADS)

Light beams rotating about their axis can be created using rotating optical elements. We analyze the properties of rotating beams by expanding the mode function in eigenfunctions of angular momentum. Both the spin angular momentum, arising from the polarization, and orbital angular momentum, arising from the circulating phase gradient, are considered.

Nienhuis, Gerard

2006-02-01

199

Nanofabricated quartz cylinders for angular  

E-print Network

Nanofabricated quartz cylinders for angular trapping: DNA supercoiling torque detection Christopher nanofabricated quartz cylinders well suited for torque application and detection in an angular optical trap. We that nanofabricated quartz cylinders, when used with an angular trapping instrument, allow direct and simultaneous

Wang, Michelle

200

Torsional Network Model: Normal Modes in Torsion Angle Space Better Correlate with Conformation Changes in Proteins  

NASA Astrophysics Data System (ADS)

We introduce the torsional network model (TNM), an elastic network model whose degrees of freedom are the torsion angles of the protein backbone. Normal modes of the TNM displace backbone atoms including C? maintaining their covalent geometry. For many proteins, low frequency TNM modes are localized in torsion space yet collective in Cartesian space, reminiscent of hinge motions. A smaller number of TNM modes than anisotropic network model modes are enough to represent experimentally observed conformation changes. We observed significant correlation between the contribution of each normal mode to equilibrium fluctuations and to conformation changes, and defined the excess correlation with respect to a simple neutral model. The stronger this excess correlation, the lower the predicted free energy barrier of the conformation change and the fewer modes contribute to the change.

Mendez, Raul; Bastolla, Ugo

2010-06-01

201

Rotation-Induced Breakdown of Torsional Quantum Control  

NASA Astrophysics Data System (ADS)

Control of the torsional angles of nonrigid molecules is key for the development of emerging areas like molecular electronics and nanotechnology. Based on a rigorous calculation of the rotation-torsion-Stark energy levels of nonrigid biphenyl-like molecules, we show that, unlike previously believed, instantaneous rotation-torsion-Stark eigenstates of such molecules, interacting with a strong laser field, present a large degree of delocalization in the torsional coordinate even for the lowest energy states. This is due to a strong coupling between overall rotation and torsion leading to a breakdown of the torsional alignment. Thus, adiabatic control of changes on the planarity of this kind of molecule is essentially impossible unless the temperature is on the order of a few Kelvin.

Coudert, L. H.; Pacios, Luis F.; Ortigoso, Juan

2011-09-01

202

Colliding Wave Solutions in a Symmetric Non-metric Theory  

E-print Network

A method is given to generate the non-linear interaction (collision) of linearly polarized gravity coupled torsion waves in a non-metric theory. Explicit examples are given in which strong mutual focussing of gravitational waves containing impulsive and shock components coupled with torsion waves does not result in a curvature singularity. However, the collision of purely torsion waves displays a curvature singularity in the region of interaction.

Ozay Gurtug; Mustafa Halilsoy

2008-09-22

203

Torsion-Gravity for Dirac fields and their effective phenomenology  

E-print Network

We will consider the torsional completion of gravity for a background filled with Dirac matter fields, studying the weak-gravitational non-relativistic approximation, in view of an assessment about their effective phenomenology: we discuss how the torsionally-induced non-linear interactions among fermion fields in this limit are compatible with all experiments, and remarks on the role of torsion to suggest new physics are given.

Luca Fabbri

2014-01-14

204

An atypical presentation of testicular torsion: a case report.  

PubMed

Testicular torsion is an emergent condition requiring prompt surgical intervention to avoid permanent testicular compromise and death. As its symptoms overlap with other disease processes, diagnosis is sometimes difficult. When considering the presenting symptoms, one must be careful not to ignore unusual causes of torsion and misdiagnose the patient. In this case report we describe an unusual etiology of testicular torsion (traumatic) with an atypical patient presentation (mildly painful) which presented many obstacles before proper diagnosis and treatment. PMID:24294708

Jansen, Robert; Fooks, Henry; Zaslau, Stanley

2013-01-01

205

Missed Spermatic Cord Torsion in an Old Man  

PubMed Central

The fate of testicular salvage in spermatic cord torsion depends on the duration of ischemia and the degree of torsion. Even though spermatic cord torsion (SCT) can occur at any age, it is rarely reported in older patients. If the physician does not pay close attention to this unusual situation, the lack of suspicion for SCT may result in a missed or delayed diagnosis. We report a very uncommon case of missed SCT occurring in a 63-year-old man. PMID:24175049

Seo, Yu Mi; Myung, Na-Hye

2013-01-01

206

The ground electronic state of 1,2-dichloroethane I. Ab initio investigation of the geometrical, vibrational and torsional structure  

NASA Astrophysics Data System (ADS)

The trans and gauche isomers of 1,2-dichloroethane are characterized using ab initio calculations at the MP4(SDQ) level of theory with the full double zeta polarized D95** basis set. The molecular geometry parameters, the torsion potential and the harmonic frequency of the normal modes of vibrations are calculated. The integrated intensity and the rotational type of the infrared fundamental bands also are determined. New labelling of the normal modes of vibration is introduced for the gauche isomer. The relative abundance and stability of both isomers are discussed. The torsional motion is investigated by means of an effective model taking the geometrical relaxation into account and leading to a theoretical torsional spectrum.

El Youssoufi, Y.; Herman, M.; Lievin, J.

207

An extension of the high-resolution millimeter- and submillimeter-wave spectrum of methanol to high angular momentum quantum numbers  

NASA Technical Reports Server (NTRS)

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.

Anderson, Todd; Herbst, Eric; De Lucia, Frank C.

1992-01-01

208

Angular displacement measuring device  

NASA Technical Reports Server (NTRS)

A system for measuring the angular displacement of a point of interest on a structure, such as aircraft model within a wind tunnel, includes a source of polarized light located at the point of interest. A remote detector arrangement detects the orientation of the plane of the polarized light received from the source and compares this orientation with the initial orientation to determine the amount or rate of angular displacement of the point of interest. The detector arrangement comprises a rotating polarizing filter and a dual filter and light detector unit. The latter unit comprises an inner aligned filter and photodetector assembly which is disposed relative to the periphery of the polarizer so as to receive polarized light passing the polarizing filter and an outer aligned filter and photodetector assembly which receives the polarized light directly, i.e., without passing through the polarizing filter. The purpose of the unit is to compensate for the effects of dust, fog and the like. A polarization preserving optical fiber conducts polarized light from a remote laser source to the point of interest.

Seegmiller, H. Lee B. (inventor)

1992-01-01

209

Experimental method for determination of bending and torsional rigidities of advanced composite laminates  

SciTech Connect

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.

Maeda, Takenori [Univ. of Tsukuba, Ibaraki (Japan). Institute of Engineering Mechanics

1995-11-01

210

New Gauge Symmetry in Gravity and the Evanescent Role of Torsion  

E-print Network

If the Einstein-Hilbert action ${\\cal L}_{\\rm EH}\\propto R$ is re-expressed in Riemann-Cartan spacetime using the gauge fields of translations, the vierbein field $h^\\alpha{}_\\mu$, and the gauge field of local Lorentz transformations, the spin connection $A_{\\mu \\alpha}{}^ \\beta $, 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 {\\em new multivalued gauge transformation\\/}. Torsion can be chosen at will by an arbitrary gauge fixing functional. There exist many equivalent ways of specifing the theory, for instance Einstein's traditional way where ${\\cal L}_{\\rm EH}$ is expressed completely in terms of the metric $g_{\\mu \

H. Kleinert

2010-05-10

211

Enhanced angular current intensity from Schottky emitters.  

PubMed

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

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

2010-09-01

212

Torsional fatigue tests of anodized aluminum rods  

Microsoft Academic Search

Fatigue tests in reversed torsion were run on 2024-T351 aluminum-alloy specimens in (1) uncoated state and (2) anodized with\\u000a 0.3 and 0.05-mil (0.0076- and 0.0013-mm) coatings. Tests on both groups were run at low (20–25 percent), medium (55–60 percent),\\u000a and high (86–91 percent) relative humidity. One lot of uncoated specimens was tested that had been polished after machining,\\u000a and one

E. F. Womack; J. H. Wilson; H. H. Mabie

1976-01-01

213

Least squares estimation of curvature and torsion  

Microsoft Academic Search

This work analyzes a new method for curvature and torsion estimation based on local parametric approximation. We show the convergence analysis and noise impact of the method. x(s) = x0(0)s + 12 x 00 (0)s2 + g1(s)s3 y(s) = y0(0)s + 12 y 00 (0)s2 + g2(s)s3 z(s) = z0(0)s + 12 z 00 (0)s2 + g3(s)s3 for the second

THOMAS LEWINER; AO D. GOMES JR; H ´ ELIO LOPES; MARCOS CRAIZER

214

Modelling black holes with angular momentum in loop quantum gravity  

NASA Astrophysics Data System (ADS)

We construct a connection formulation of Kerr isolated horizons. As in the non-rotating case, the model is based on a Chern-Simons theory describing the degrees of freedom on the horizon. The presence of a non-vanishing angular momentum modifies the admissibility conditions for spin network states. Physical states of the system are in correspondence with open intertwiners with total spin matching the angular momentum of the spacetime.

Frodden, Ernesto; Perez, Alejandro; Pranzetti, Daniele; Röken, Christian

2014-12-01

215

Modelling black holes with angular momentum in loop quantum gravity  

E-print Network

We construct a SU(2) connection formulation of Kerr isolated horizons. As in the non-rotating case, the model is based on a SU(2) Chern-Simons theory describing the degrees of freedom on the horizon. The presence of a non-vanishing angular momentum modifies the admissibility conditions for spin network states. Physical states of the system are in correspondence with open intertwiners with total spin matching the angular momentum of the spacetime.

Frodden, Ernesto; Pranzetti, Daniele; Roeken, Christian

2012-01-01

216

Statistical prescission point model of fission fragment angular distributions  

NASA Astrophysics Data System (ADS)

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

John, Bency; Kataria, S. K.

1998-03-01

217

Angular Momentum Transport in Circumplanetary Disks  

NASA Astrophysics Data System (ADS)

The Galilean satellites likely formed in a late-stage accretion disk that persisted around Jupiter after it was fully formed. The structure of this disk is highly dependent on its ability to transport angular momentum. Uncertainty in the level of angular momentum transport has led to competing theories of circumplanetary disk structure. Despite success in other astrophysical contexts, recent studies indicate that the conditions were not suitable for magnetorotational instabilities to develop in circumplanetary disks. However, it has been suggested that baroclinic instabilities can generate turbulence and provide the necessary transport of angular momentum. We present a 1+1D numerical model of the circumplanetary accretion disk that surrounded Jupiter during the epoch of regular satellite formation. An analysis of the radial entropy gradient in this model indicates that baroclinic instabilities can not only develop but persist throughout the majority of the disk. Furthermore, we find evidence for a two-component, gas-starved disk which may help to reconcile the differences in current competing theories of circumplanetary disk structure.

Mitchell, Tyler R.

2014-11-01

218

Angular deflection of rotary nickel titanium files: a comparative study.  

PubMed

A new manufacturing method of twisting nickel titanium wire to produce rotary nickel titanium (RNT) files has recently been developed. The aim of the present study was to evaluate whether the new manufacturing process increased the angular deflection of RNT files, by comparing instruments produced using the new manufacturing method (Twisted Files) versus instruments produced with the traditional grinding process. Testing was performed on a total of 40 instruments of the following commercially available RNT files: Twisted Files (TF), Profile, K3 and M2 (NRT). All instruments tested had the same dimensions (taper 0.06 and tip size 25). Test procedures strictly followed ISO 3630-1. Data were collected and statistically analyzed by means ANOVA test. The results showed that TF demonstrated significantly higher average angular deflection levels (P<0.05), than RNT manufactured by a grinding process. Since angular deflection represent the amount of rotation (and consequently deformation) that a RNT file can withstand before torsional failure, such a significant improvement is a favorable property for the clinical use of the tested RNT files. PMID:20061663

Gambarini, Gianluca; Testarelli, Luca; Milana, Valerio; Pecci, Raffaella; Bedini, Rossella; Pongione, Giancarlo; Gerosa, Roberto; De Luca, Massimo

2009-01-01

219

Torsional Vibration Assessment Using Induction Machine Electromagnetic Torque Estimation  

Microsoft Academic Search

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

Shahin Hedayati Kia; Humberto Henao; GÉrard-AndrÉ Capolino

2010-01-01

220

Massive cerebral infarction after completion pneumonectomy for pulmonary torsion.  

PubMed Central

A case of lower lobe torsion after left upper lobectomy is reported which was complicated by a cerebral infarction after completion pneumonectomy. Results of a small survey in Flanders revealed two additional cases of pulmonary torsion after lobectomy. Images PMID:7878570

Hendriks, J.; Van Schil, P.; De Backer, W.; Hauben, E.; Vanmaele, R.; Van Marck, E.

1994-01-01

221

Infrared modified gravity with dynamical torsion  

SciTech Connect

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

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

2009-12-15

222

Optical measurement of DNA torsional modulus under various stretching forces  

NASA Astrophysics Data System (ADS)

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

Choi, Jaehyuck

2005-03-01

223

Torsional ARC Effectively Expands the Visual Field in Hemianopia  

PubMed Central

Purpose Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonios anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demonstrating a field expansion consistent with torsion we documented torsional strabismus and torsional HARC. Methods Monocular visual fields under binocular fixation conditions were plotted using a custom dichoptic visual field perimeter (DVF). The DVF was also modified to measure perceived visual directions under dissociated and associated conditions across the central 50° diameter field. The field expansion and retinal correspondence of a subject with torsional strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared to that of another exotropic subject with acquired homonymous hemianopia without torsion and to a control subject with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry. Results Torsional ARC documented in the subject with congenital homonymous hemianopia provided a functional binocular field expansion up to 18°. Normal retinal correspondence was mapped for the full 50° visual field in the control subject and for the seeing field of the acquired homonymous hemianopia subject, limiting the functional field expansion benefit. Conclusions Torsional strabismus with ARC, when occurring with homonymous hemianopia provides useful field expansion in the lower and upper fields. Dichoptic perimetry permits documentation of ocular alignment (lateral, vertical and torsional) and perceived visual direction under binocular and monocular viewing conditions. Evaluating patients with congenital or early strabismus for HARC is useful when considering surgical correction, particularly in the presence of congenital homonymous hemianopia. PMID:22885782

Satgunam, PremNandhini; Peli, Eli

2012-01-01

224

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

PubMed Central

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

MATSUMOTO, ATSUSHI; OLSON, WILMA K.

2008-01-01

225

Bulk angular momentum and Hall viscosity in chiral superconductors  

NASA Astrophysics Data System (ADS)

We establish the Berry-phase formulas for the angular momentum (AM) and the Hall viscosity (HV) to investigate chiral superconductors (SCs) in two and three dimensions. The AM is defined by the temporal integral of the antisymmetric momentum current induced by an adiabatic deformation, while the HV is defined by the symmetric momentum current induced by the symmetric torsional electric field. Without suffering from the system size or geometry, we obtain the macroscopic AM Lz=?mN0/2 at zero temperature in full-gap chiral SCs, where m is the magnetic quantum number and N0 is the total number of electrons. We also find that the HV is equal to half the AM at zero temperature not only in full-gap chiral SCs as is well known but also in nodal ones, but its behavior at finite temperature is different in the two cases.

Shitade, Atsuo; Kimura, Taro

2014-10-01

226

Detectability of Torsion Gravity via Galaxy Clustering and Cosmic Shear Measurements  

E-print Network

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.

Stefano Camera; Vincenzo F. Cardone; Ninfa Radicella

2013-11-05

227

Torsional velocity measurements in wire, with application to metal-matrix composites  

NASA Astrophysics Data System (ADS)

A technique is described for measuring torsional wave velocity in (nonferromagnetic) wire with diameters of less than 1 mm. Transduction is noncontacting, via Lorentz forces acting across a gap between transducer and wire, so that velocity can be ''scanned'' along the length of the wire. A double-receiver approach permits the scan to be made in a ''point-by-point'' fashion. The wires are a metal-matrix composite of 6061 aluminum and pitch mesophase graphite. Some data are presented, together with a discussion of the effects of metal-matrix-composite parameters, such as graphite content and porosity, on torsional velocity. An extrapolation of our metal-matrix- composite data yields a value for c44, of the graphite fiber, that was within 1% of a value determined from data of Fischbach and Scrinivasagopalan. Good predictions of experimental results were obtained through use of theory of Hashin and of Achenbach and Herrmann. Some differences, and their implications, between torsional and longitudinal waves propagating in metal-matrix-composite wire are described.

Frost, H. M.; Prout, J. H.; Reed, Robert W.

1982-06-01

228

Detectability of torsion gravity via galaxy clustering and cosmic shear measurements  

NASA Astrophysics Data System (ADS)

Alterations of the gravity Lagrangian introduced in modified torsion gravity theories—also referred to as f(T) gravity—allows for an accelerated expansion in a matter-dominated Universe. In this framework, the cosmic speed-up is driven by an effective "torsion fluid." Besides the background evolution of the Universe, structure formation is also modified because of a time-dependent effective gravitational constant. Here, we investigate the imprints of f(T) gravity on galaxy clustering and weak gravitational lensing to the aim of understanding whether future galaxy surveys could constrain torsion gravity and discriminate between it and standard general relativity. Specifically, we compute Fisher matrix forecasts for two viable f(T) models to both infer the accuracy on the measurement of the model parameters and evaluate the power that a combined clustering and shear analysis will have as a tool for model selection. We find that with such a combination of probes it will indeed be possible to tightly constrain f(T) model parameters. Moreover, the Occam's razor provided by the Bayes factor will allow us to confirm an f(T) power-law extension of the concordance ?CDM model, if a value larger than 0.02 of its power-law slope were measured, whereas in ?CDM it is exactly 0.

Camera, Stefano; Cardone, Vincenzo F.; Radicella, Ninfa

2014-04-01

229

Left Ventricular Torsion Changes Post Kidney Transplantation  

PubMed Central

Background To quantify changes of left ventricular (LV) torsion in patients' pre and post kidney transplantation. Methods A prospective study was conducted on 48 patients who received kidney transplantation for end stage renal disease and without myocardial infarction. The rotation, twist and torsion of LV were studied pre and post kidney transplantation (6 months post transplantation) using velocity vector imaging by echocardiography. The data is expressed as mean ± standard deviation and compared by paired t-test at the p < 0.05 significance level. Results Six months post kidney transplantation, left ventricular ejection fraction (from 40.33 ± 11.42 to 61.00 ± 13.68%), ratio of mitral early and late diastolic filling velocity (from 1.04 ± 0.57 to 1.21 ± 0.52), rotation of basal LV (from 4.48 ± 2.66 to 5.65 ± 2.64 degree), rotation of apical LV (from 4.27 ± 3.08 to 5.50 ± 4.25 degree), LV twist (8.75 ± 4.45 to 11.14 ± 5.25 degree) and torsion (from 1.06 ± 0.54 to 1.33 ± 0.61 degree/cm) were increased significantly (p < 0.05). Interventricular septum thickness (from 11.67 ± 2.39 to 9.67 ± 0.48 mm), left ventricular mass index (from 104.00 ± 16.47 to 95.50 ± 21.44 g/m2), systolic blood pressure (from 143.50 ± 34.99 to 121.50 ± 7.09 mmHg), serum blood urea nitrogen (from 42.40 ± 7.98 to 30.43 ± 13.85 mg/dL) and creatinine (from 4.53 ± 1.96 to 2.73 ± 2.57 mg/dL) were decreased significantly (p < 0.05). Conclusion Kidney transplantation in end stage renal disease without myocardial infarction results in improvement in left ventricular structure, function and myocardial mechanics as detected by echocardiography and velocity vector imaging. Velocity vector imaging provided valuable information for detection and follow-up of cardiac abnormalities in patients with end stage renal disease. PMID:24459564

Deng, Yan; Pandit, Anil; Heilman, Raymond L.; Chakkera, Harini A.; Mazur, Marek J.

2013-01-01

230

Angular Momenta of the Planets.  

National Technical Information Service (NTIS)

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

F. F. Fish

1967-01-01

231

The Angular Gyrus  

PubMed Central

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

2013-01-01

232

High-Pressure Torsion of Ti: Synchrotron characterization of phase volume fraction and domain sizes  

NASA Astrophysics Data System (ADS)

Rods of grade 2 Ti were processed by Equal-Channel Angular Pressing (ECAP) (phi = 120° at 573 K) employing 2, 4 and 6 passes. The same billets were further deformed by High- Pressure Torsion (HPT) at room temperature, varying both the hydrostatic pressure (1 and 6 GPa) and the number of rotations (n = 1 and 5). The ECAP and HPT samples were studied by synchrotron radiation at DESY-Petra III GEMS line. On the ECAP samples, textures were thus determined while for both ECAP and HPT samples the measurements were further analyzed by MAUD. Domain sizes and phase volume fractions were determined as a function of the radial direction of the samples. Alpha and Omega phases were detected in different amounts depending mostly on hydrostatic pressure and shear deformation. These transition phases can be pressure-induced during HPT processing and the results of Vickers microhardness measurements were related to the processing parameters and to the amounts of these phases.

Bolmaro, Raúl E.; Sordi, Vitor L.; Ferrante, Maurizio; Brokmeier, Heinz-Günter; Kawasaki, Megumi; Langdon, Terence G.

2014-08-01

233

Angular momentum - area - proportionality of extremal charged black holes in odd dimensions  

NASA Astrophysics Data System (ADS)

Extremal rotating cohomogeneity-1 black holes in Einstein-Maxwell theory feature two branches. On the branch emerging from the Myers-Perry solutions their angular momentum is proportional to their horizon area, while on the branch emerging from the Tangherlini solutions their angular momentum is proportional to their horizon angular momentum. The transition between these branches occurs at a critical value of the charge, which depends on the value of the angular momentum. However, when a dilaton is included, the angular momentum is always proportional to the horizon area.

Blázquez-Salcedo, Jose Luis; Kunz, Jutta; Navarro-Lérida, Francisco

2013-11-01

234

Pearls and pitfalls in diagnosis of ovarian torsion.  

PubMed

Ovarian torsion is defined as partial or complete rotation of the ovarian vascular pedicle and causes obstruction to venous outflow and arterial inflow. Ovarian torsion is usually associated with a cyst or tumor, which is typically benign; the most common is mature cystic teratoma. Ultrasonography (US) is the primary imaging modality for evaluation of ovarian torsion. US features of ovarian torsion include a unilateral enlarged ovary, uniform peripheral cystic structures, a coexistent mass within the affected ovary, free pelvic fluid, lack of arterial or venous flow, and a twisted vascular pedicle. The presence of flow at color Doppler imaging does not allow exclusion of torsion but instead suggests that the ovary may be viable, especially if flow is present centrally. Absence of flow in the twisted vascular pedicle may indicate that the ovary is not viable. The role of computed tomography (CT) has expanded, and it is increasingly used in evaluation of abdominal pain. Common CT features of ovarian torsion include an enlarged ovary, uterine deviation to the twisted side, smooth wall thickening of the twisted adnexal cystic mass, fallopian tube thickening, peripheral cystic structures, and ascites. Understanding the imaging appearance of ovarian torsion will lead to conservative, ovary-sparing treatment. PMID:18794312

Chang, Hannah C; Bhatt, Shweta; Dogra, Vikram S

2008-01-01

235

[A case of incomplete torsion of the gallbladder due to partial torsion of the gallbladder neck].  

PubMed

A 57-year-old man was admitted to our hospital because of low-grade fever and pain in the right hypochondrium. Abdominal ultrasonographic (US) examination revealed a hyperechoic mass in the body of the gallbladder. The wall of the gallbladder towards the fundus was markedly thickened, while the wall near the gallbladder neck showed no abnormality. Power Doppler and contrast-enhanced CT of the abdomen revealed absence of blood flow in the fundic wall of the gallbladder, however, a contrast-enhanced image of the entire wall was obtained by contrast US, although the blood flow to the fundus was decreased. Torsion of the gallbladder was diagnosed and laparoscopic cholecystectomy was performed. The gallbladder was found to be a wandering gallbladder, Gross I type, and slight counterclockwise torsion was found at the neck of the gallbladder. We report a case of partial torsion of the gallbladder neck, in which the details of the ischemic hemodynamic changes could be observed by contrast-enhanced US. PMID:17984614

Otani, Keisuke; Ueki, Toshiharu; Shimizu, Aiko; Fujimura, Naruhito; Otsuka, Yuichirou; Tohara, Keiji; Matsui, Toshiyuki; Tamura, Tomoaki; Oshige, Kaneto; Iwashita, Akinori

2007-11-01

236

Curvature and torsion in growing actin networks  

E-print Network

Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 seconds. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to ex...

Shaevitz, Joshua W; 10.1088/1478-3975/5/2/026006

2009-01-01

237

Torsional suspension system for testing space structures  

NASA Technical Reports Server (NTRS)

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.

Reed, Wilmer H., III (inventor); Gold, Ronald R. (inventor)

1991-01-01

238

Experimental Evaluation of Torsional Fatigue Strength of Welded Bellows and Application to Design of Fusion Device  

Microsoft Academic Search

Torsional fatigue strength of the welded bellows was evaluated experimentally, aiming the application to a port of a fusion device.The welded bellows revealed elastic torsional buckling and spiral distorsion even under a small angle of torsion. Twisting load never leads the welded bellows to fracture easily so far as the angle of torsion is not excessively large, and the welded

Hideyuki TAKATSU; Masahiro YAMAMOTO; Masatsugu SHIMIZU; Kazuo SUZUKI; Tadashi SONOBE; Yuzo HAYASHI; Gen-ichiro MIZUNO

1984-01-01

239

Coupling and degenerating modes in longitudinal-torsional step horns.  

PubMed

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

Harkness, Patrick; Lucas, Margaret; Cardoni, Andrea

2012-12-01

240

Experimental investigation of cyclic thermomechanical deformation in torsion  

NASA Technical Reports Server (NTRS)

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.

Ellis, John R.; Castelli, Michael G.; Bakis, Charles E.

1992-01-01

241

[Torsion of a hydrosalpinx in a 14-year old].  

PubMed

Lower abdominal pain in women often gives rise to diagnostic problems. We had a 14-year-old girl suffering from acute lower abdominal pain without effect of painkillers. Ultrasound revealed a cystic process in the pelvis. At laparoscopy we saw a right-sided hydrosalpinx with torsion. The hydrosalpinx was removed and afterwards she had no pain. Torsion of a hydrosalpinx is a very rare condition. It is very important that adnexal torsion is diagnosed and treated promptly in order to save the reproductive organs and prevent further complications. PMID:18940159

Sørensen, Rikke Korsgaard

2008-10-01

242

Discussion on massive gravitons and propagating torsion in arbitrary dimensions  

SciTech Connect

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

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

2009-12-15

243

Digital Instrumentation for Angular Velocity and Acceleration  

Microsoft Academic Search

An instrument is described for the measurement of angular velocity and angular acceleration of a rotating shaft, based upon an optical angular transducer and an associated operational digital (pulse rate) system. The angular transducer produces a pulse rate directly proportional to the instantaneous angular velocity and this quantity and its rate of change are processed by the pulse rate system

Alan Dunworth

1969-01-01

244

GENERAL: Coupled flexural-torsional vibration band gap in periodic beam including warping effect  

NASA Astrophysics Data System (ADS)

The propagation of coupled flexural-torsional vibration in the periodic beam including warping effect is investigated with the transfer matrix theory. The band structures of the periodic beam, both including warping effect and ignoring warping effect, are obtained. The frequency response function of the finite periodic beams is simulated with finite element method, which shows large vibration attenuation in the frequency range of the gap as expected. The effect of warping stiffness on the band structure is studied and it is concluded that substantial error can be produced in high frequency range if the effect is ignored. The result including warping effect agrees quite well with the simulated result.

Fang, Jian-Yu; Yu, Dian-Long; Han, Xiao-Yun; Cai, Li

2009-04-01

245

Differential equations of motion for combined flapwise bending, chordwise bending, and torsion of twisted nonuniform rotor blades  

NASA Technical Reports Server (NTRS)

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.

Houbolt, John C; Brooks, George W

1957-01-01

246

Differential equations of motion for combined flapwise bending, chordwise bending, and torsion of twisted nonuniform rotor blades  

NASA Technical Reports Server (NTRS)

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.

Houbolt, John C; Brooks, George W

1958-01-01

247

Chirality and angular momentum in optical radiation  

E-print Network

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

Matt M. Coles; David L. Andrews

2012-03-08

248

Undrained sliding resistance of shallow foundations subjected to torsion  

E-print Network

While the behavior of shallow foundations under vertical load combinations has been the subject of numerous studies, the response of shallow foundations subjected to combined horizontal and torsional loading has received considerably less attention...

Nouri, Hamidreza; Biscontin, Giovanna; Aubeny, Charles P.; ASCE, M.

2014-05-02

249

Humeral torsion and passive shoulder range in elite volleyball players  

Microsoft Academic Search

ObjectivesTo evaluate variations in humeral torsion in elite male volleyball players and determine whether these changes are related to training history, retrospective injury history and volleyball performance.

Laura M. Schwab; Peter Blanch

2009-01-01

250

Response characteristics of the human torsional vestibuloocular reflex  

NASA Technical Reports Server (NTRS)

The characteristics of the response dynamics of the human torsional vestibuloocular reflex were studied during controlled rotations about an earth-horizontal axis. The results extended the frequency range to 2 Hz and identified the nonlinearity of the amplitude response.

Peterka, Robert J.

1992-01-01

251

[Fertility after experimental torsion of the spermatic cord (author's transl)].  

PubMed

In groups of 10 specimens the testicles of 100 Wistar rats were half unilaterally half bilaterally rotated 720 degrees and retorted 1, 2, 4, 6 and 8 hours after torsion. The fertility rate was investigated by copulation experiments following experimental torsion of the spermatic cord. Fertility was demonstrated by pregancy. Independently of torsion period the fertility rate of unilateral contorted specinens was 60% -- like in both control groups. The bilaterally contorted animals were fertile in 40% from the 1 h -- group and in 30% from the 2 hours -- group. If the torsion period was longer than 2 hrs. bilaterally conterted animals were infertile in all cases. There is no influence of unilateral conterted testicle on contralateral uncontorted testicle. PMID:7191168

Ludwig, G; Haselberger, J; Kagelmacher, B

1980-01-01

252

Torsional properties of twisted and machined endodontic files.  

PubMed

The torsional properties of conventionally twisted K-type endodontic files and recently developed machined K-type endodontic files were compared. File sizes 10 through 40 were subjected to torsional load in clockwise and counterclockwise directions independently. Results showed that a statistically significant reduction in clockwise rotation occurred at failure with all of the machined files except size 10. Counterclockwise rotation at failure was also significantly lower for the machined files in sizes 10 through 30. There was no difference in torsional strength between the file types regardless of rotation direction. Therefore, machined files exhibit less ductility than twisted files prior to fracture and may be more susceptible to torsional failure clinically. PMID:2081951

Seto, B G; Nicholls, J I; Harrington, G W

1990-08-01

253

An experimental study of torsional vibration measurement / b  

E-print Network

of operation of the associated instrumentation, and outlining the set-up and calibration procedures. Torsional vibrations can occur in machines that are operating at constant speed, or it can arise while equipment is on a start-up and accelerating up... machines is extensive. Reciprocating engines, partially or fully locked couplings, malfunctioning speed controls, and impzoper gear meshing will produce lasting, steady state torsional excitation to a system, and over a period of time fatigue failure...

French, Robert Sheldon

2012-06-07

254

Usefulness of Doppler sonography in the diagnosis of ovarian torsion  

Microsoft Academic Search

Objective: To assess the predictive value of Doppler sonography in the diagnosis of ovarian torsion and to correlate Doppler results with surgical findings and various clinical characteristics.Design: Retrospective study of discharged inpatients.Setting: An academic community hospital.Patient(s): Twenty-one patients with surgically confirmed ovarian torsion over an 8-year period.Intervention(s): Data were collected on Doppler flow results, ultrasound and surgical findings, patient characteristics,

Joseph E Peña; David Ufberg; Nancy Cooney; André L Denis

2000-01-01

255

Torsional vibration analysis of turbine-generator-blade coupled system  

Microsoft Academic Search

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

O. Matsushita; Namura; T. K. Yoshida; R. Kaneko; A. Okabe

1989-01-01

256

Cosmic Magnetic Fields from Torsion Modes and Massive Photon Inflation  

NASA Astrophysics Data System (ADS)

Earlier Barrow & Tsagas (2008) showed that a slower decay of magnetic fields are present in open Friedmann universes, with traditional Maxwell equations. In their paper magnetic fields of the order of B˜10–33 G which are far below the value required to seed galactic dynamos were obtained. In this paper galactic dynamo seeds of the order of B˜10–23 G are obtained from massive electrodynamics in Einstein–Cartan–Proca (ECP) expanding universe of de Sitter type. Slow decay of magnetic fields in photon-torsion coupling in QED (Garcia de Andrade 2011b) have been recently shown by Garcia de Andrade (2012) also not be able to seed galactic dynamos. Torsion modes are constrained by the field equations. Space-time torsion is shown to be explicitly responsible for the slow decay of cosmic magnetic field. In the absence of massive photon torsion coupling the magnetic field decay is of the order B˜t–3/2, while when torsion is turn on B˜t–1.2. The pure massive-photon-torsion contribution amplifies the magnetic field by Btorsion˜t0.1 which characterizes an extremely slow magnetic dynamo action due to purely torsion gravitational effects. Recently, Barrow et al. (2012) have obtained superadiabatic amplification of B-fields in the Friedmann open cosmology which lies within 10–20 G and 10–12 G which falls very comfortable within limits to seed galactic dynamos. Other simple solutions where B-field decays as B˜a–1, relatively weak photon-torsion coupling approximation. These solutions are obtained for the de Sitter and Friedmann metrics.

Garcia de Andrade, L. C.

2014-09-01

257

Nonminimal torsion-matter coupling extension of f(T) gravity  

NASA Astrophysics Data System (ADS)

We construct an extension of f(T) gravity with the inclusion of a nonminimal torsion-matter coupling in the action. The resulting theory is a novel gravitational modification, since it is different from both f(T) gravity, as well as from the nonminimal curvature-matter-coupled theory. The cosmological application of this new theory proves to be very interesting. In particular, we obtain an effective dark energy sector whose equation-of-state parameter can be quintessence- or phantom-like, or exhibit the phantom-divide crossing, while for a large range of the model parameters the universe enters in a de Sitter, dark-energy-dominated, accelerating phase. Additionally, we can obtain early-time inflationary solutions too, and thus provide a unified description of the cosmological history.

Harko, Tiberiu; Lobo, Francisco S. N.; Otalora, G.; Saridakis, Emmanuel N.

2014-06-01

258

Torsion of the ovary: a known but frequently missed diagnosis.  

PubMed

Torsion of the ovary or fallopian tube is a rare acute gynaecological disorder, seen by different medical specialists. The diverse clinical presentation is one of the main reasons this diagnosis is frequently missed at first presentation. For the preservation of ovarian function it is of utmost importance to diagnose an ovarian torsion at an early stage. We will describe the medical history of three patients with a torsion of one of the ovaries to illustrate the variety of clinical presentation. A medical history of pelvic operations or enlarged ovaries often predisposes to torsion of the ovary or fallopian tube. Treatment policy will differ depending on the stage of life. Ovariopexy can be considered to prevent the ovary from torsion and to maintain its function. Torsion of the ovary is an acute gynaecological disorder with an incidence of 3% in a series of acute gynaecological complaints. It is a disorder in which the ovary and the fallopian tube can be affected, combined as well as separated. Although every specialist is familiar with the disorder, the diagnosis in acute presentation is frequently missed. To bring this entity and its great variability in clinical presentation into focus once again, we will highlight three patients out of a series of 13. Furthermore, we will discuss the possible causes of the disorder and present a proposition for treatment. PMID:19262396

Becker, Jeroen Hubert; de Graaff, Jan; Vos, M Caroline; Vos, Caroline M

2009-06-01

259

Angular distributions of sequentially emitted particles and gamma rays in deep inelastic processes  

SciTech Connect

A general theory for the angular distribution of sequentially emitted particles and gamma rays is developed. Comparison with experimental data allows one to obtain information on the fragment spin and misalignment. Angular distributions of sequentially emitted gammas, alphas, and fission fragments are discussed in detail. It is shown that the experimental data are consistent with the thermal excitation of angular momentum-bearing modes. The anomaly of sequential fission suggests the presence of a prompt or direct fission component. 13 figures.

Moretto, L.G.

1981-01-01

260

The Influence of the Aerodynamic Span Effect on the Magnitude of the Torsional-divergence Velocity and on the Shape of the Corresponding Deflection Mode  

NASA Technical Reports Server (NTRS)

A procedure which takes into account the aerodynamic span effect is given for the determination of the torsional-divergence velocities of monoplanes. The explicit solutions obtained in several cases indicate that the aerodynamic span effect may increase the divergence velocities found by means of the section-force theory by as much as 17 to 40 percent. It is found that the magnitude of the effect increases with increasing degree of stiffness taper and decreases with increasing degree of chord taper. By a slight extension of the present method it is possible to analyze the elastic deformations of wings, and the resultant lift distributions, before torsional divergence occurs.

Hildebrand, Francis B; Reissner, Eric

1944-01-01

261

Premenarchal Ovarian Torsion and Elevated CA-125  

PubMed Central

Background Ovarian tumors are the most common gynecologic malignancy occurring in childhood, with germ cell tumors being most frequent. This contrasts with adults where epithelial tumors account for most ovarian neoplasms. Tumor markers are an integral part of the work up and may guide management. Case A 6 year old girl with a persistent adnexal mass was found to have a highly elevated CA-125. Other tumor markers were normal. Laparoscopy revealed an enlarged, adherent ovary. A minilaparotomy revealed an ovary filled with necrotic material. This necrotic material was excised and the ovary was spared. The pathology was consistent with necrosis. Follow up ultrasound and CA-125 were normal. Summary and Conclusions This case demonstrates for the first time the association of an elevated CA-125 and ovarian torsion in a pediatric patient. This benign finding allowed attempting a conservative ovarian-sparing approach during the surgery even in the presence of a highly elevated CA-125. However, in general, for children CA-125 is of limited utility, as it will not affect the indication for surgical exploration of persistent masses and elevations in CA-125 may discourage ovarian conservation. PMID:19589703

McCarthy, Jenifer D.; Erickson, Kimberly M; Smith, Yolanda R.; Quint, Elisabeth H.

2009-01-01

262

Control of Torsional Vibrations by Pendulum Masses  

NASA Technical Reports Server (NTRS)

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.

Stieglitz, Albert

1942-01-01

263

Torsional vibration reduction using passive nonlinear absorbers  

NASA Astrophysics Data System (ADS)

This paper considers the dynamic performance of systems of centrifugal pendulum vibration absorbers that are used to attenuate torsional vibrations in rotating systems. These absorbers, which can be found in certain IC engines and helicopter rotors, consist of movable masses whose centers of mass are kinematically restricted to move along prescribed paths relative to the rotor of interest. The most common choice for absorber paths are simple circles that are slightly mistuned from the desired order, so that undesirable nonlinear behaviors are avoided when the absorbers undergo large amplitude motions. In this work we consider a range of different path types and tunings, with the goal of optimizing performance over a wide operating range. This analytical study relies on a mathematical model of a rotor fitted with N identical, general-path absorbers, and utilizes perturbation techniques to obtain analytical estimates for the response of the rotor and the absorbers. The results are used to select path parameters based on selected performance measures, and the results are verified via simulation studies. It is shown that slightly overtuned cycloidal paths provide excellent vibration reduction characteristics and prevent the occurrence of nonlinear instabilities and vibration localization in the response of the absorbers.

Shaw, Steven W.; Alsuwaiyan, Abdallah

2000-04-01

264

The Second Torsional State of Acetaldehyde  

NASA Astrophysics Data System (ADS)

We have fit to within experimental accuracy a data set for acetaldehyde obtained by combining 1014 v t = 0, 840 v t = 1, and 430 v t = 2 microwave lines with 420 v t = 1 ? 0 and 404 v t = 2 ? 1 far-infrared lines. The principal additions to the previously treated v t = 0 and v t = 1 microwave data set consist of about 250 new measurements from Barclay, Anderson, and Ziurys and 900 new measurements from Nizhny Novgorod; the v t = 2 measurements include about 400 lines from Nizhny Novgorod and a few lines from various other sources. The previously treated v t = 1 ? 0 far-infrared data set was extended by adding about 200 high- J lines from the 1 ? 0 fundamental band and 400 lines from the 2 ? 1 hot band, all taken from a previously reported Fourier transform spectrum. The final fit, which uses a slightly extended model from the literature. requires 48 parameters to achieve an overall unitless weighted standard deviation of 1.06. The present fit includes essentially all available infrared and microwave transitions involving torsional lexels below the top of the internal rotation barrier.

Belov, S. P.; Tretyakov, M. Y.; Kleiner, I.; Hougen, J. T.

1993-07-01

265

The second torsional state of acetaldehyde  

SciTech Connect

The authors have fit to within experimental accuracy a data set for acetaldehyde obtained by combining 1,014 [nu][sub t] = 0, 840 [nu][sub t] = 1, and 430 [nu][sub t] = 2 microwave lines with 420 [nu][sub t] = 1 [l arrow] 0 and 404 [nu][sub t] = 2 [l arrow] 1 far-infrared lines. The principal additions to the previously treated v[sub t] = 0 and v[sub t] = 1 microwave data set consist of about 250 new measurements from Barclay, Anderson, and Ziurys and 900 new measurements from Nizhny Novgorod; the v[sub t] = 2 measurements include about 400 lines from Nizhny Novgorod and a few lines from various other sources. The previously treated v[sub t] = 1 [l arrow] 0 far-infrared data set was extended by adding about 200 high-J lines from the 1 [l arrow] 0 fundamental band and 400 lines from the 2 [l arrow] 1 hot band, all taken from a previously reported Fourier transform spectrum. The final fit, which uses a slightly extended model from the literature, requires 48 parameters to achieve an overall unitless weighted standard deviation of 1.06. The present fit includes essentially all available infrared and microwave transitions involving torsional levels below the top of the internal rotation barrier.

Belov, S.P.; Tretyakov, M.Yu. (Applied Physics Inst., Nizhny Novgorod (Russian Federation). Microwave Spectroscopy Div.); Kleiner, I. (Univ. Pierre et Marie Curie et C.N.R.S., Paris (France). Lab. de Physique Moleculaire et Applications); Hougen, J.T. (National Inst. of Standards and Technology, Gaithersburg, MD (United States). Molecular Physics Div.)

1993-07-01

266

Factors influencing perceived angular velocity  

NASA Technical Reports Server (NTRS)

Angular velocity perception is examined for rotations both in depth and in the image plane and the influence of several object properties on this motion parameter is explored. Two major object properties are considered, namely, texture density which determines the rate of edge transitions for rotations in depth, i.e., the number of texture elements that pass an object's boundary per unit of time, and object size which determines the tangential linear velocities and 2D image velocities of texture elements for a given angular velocity. Results of experiments show that edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities had an impact on perceived angular velocity; this bias was associated with 2D image velocity rather than 3D tangential velocity. Despite these biases judgements were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter appeared to be good for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).

Kaiser, Mary K.; Calderone, Jack B.

1991-01-01

267

Ground and first excited torsional states of acetamide  

NASA Astrophysics Data System (ADS)

We present a first global study involving rotational levels in the lowest three torsional states of acetamide (CH 3CONH 2). New measurements of this spectrum, consisting of approximately 1600 lines and involving torsion-rotation transitions with J up to 20 and Ka up to 11, have been carried out between 49 and 149 GHz using the millimeter-wave spectrometer in Kharkov. After removing the observed quadrupole hyperfine splittings, the new data were combined with previously published measurements and fitted using a rho-axis-method (RAM) torsion-rotation Hamiltonian in conjunction with a new computer-automated vt and K labeling algorithm. The final fit used 48 parameters to give an overall weighted standard deviation of 0.72 for 759, 587, and 265 lines belonging, respectively, to the ground, first, and second excited torsional states and 95 lines corresponding to ? vt=1 transitions falling in the millimeter wave range. Separate root-mean-square (rms) deviations for the A (25 kHz) and E (27 kHz) species, as well as for the vt=0 state (26 kHz), vt=1 (25 kHz), vt=2 (22 kHz), and ? vt=1 transitions (35 kHz) indicate a similar quality of the fit for the two symmetry species and for the three torsional states. The RAM Hamiltonian was found to have rather good predictive ability when fits of only vt=0 (or only vt=0 and 1) transitions were used to calculate vt=1 (or vt=2) lines. In addition, the combination of this Hamiltonian and the computer-automated vt and K labeling algorithm seems to provide a rather powerful tool for the precise assignment and fitting of torsion-rotation transitions in C3 v internal-rotor molecules with low torsional potential barriers.

Ilyushin, V. V.; Alekseev, E. A.; Dyubko, S. F.; Kleiner, I.; Hougen, J. T.

2004-10-01

268

Evidence for changes in the angular velocity of the surface regions of the sun and stars  

NASA Technical Reports Server (NTRS)

A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing changes in the angular velocity of the surface regions of the sun and stars.

1972-01-01

269

Does a randall-sundrum scenario create the illusion of a torsion-free universe?  

PubMed

We consider spacetime with torsion in a Randall-Sundrum scenario where torsion, identified with the rank-2 Kalb-Ramond field, exists in the bulk together with gravity. While the interactions of both graviton and torsion in the bulk are controlled by the Planck mass, an additional exponential suppression comes for the torsion zero-mode on the visible brane. This may serve as a natural explanation of why the effect of torsion is so much weaker than that of curvature on the brane. The massive torsion modes, on the other hand, are correlated with the corresponding gravitonic modes and may be detectable in TeV-scale experiments. PMID:12225074

Mukhopadhyaya, Biswarup; Sen, Somasri; SenGupta, Soumitra

2002-09-16

270

Variations in atmospheric angular momentum  

NASA Technical Reports Server (NTRS)

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.

Rosen, R. D.; Salstein, D. A.

1981-01-01

271

Phenomenology of preequilibrium angular distributions  

SciTech Connect

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.

Kalbach, C.; Mann, F.M.

1980-05-01

272

Interferometric measurement of angular motion.  

PubMed

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

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

2013-04-01

273

Interferometric measurement of angular motion  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

274

Conservative laparoscopic management of adnexal torsion  

PubMed Central

Objective To evaluate our experience with adnexal torsion (AT) in 36 patients and the outcomes of the patients who were managed conservatively via laparoscopy. Material and Methods A prospective study was conducted on 36 patients who underwent operations for AT via laparoscopy between January 2008 and December 2009. Data including age, previous history, time of onset of symptoms, time of admission to hospital, gray-scale and color Doppler US findings, time interval between hospital admission and surgery, type of intervention, operative findings and postoperative gray-scale and Doppler US findings were recorded. Results In 29 (80.5%) patients, a preoperative diagnosis of AT was confirmed clinically. The mean age of the patients was 26.5, with a range of 11 to 44. Ovarian blood flow was assessed by color Doppler US ultrasonography in 30 patients preoperatively. In 11 (36.6%) patients, this was found to be normal. In 19 (63.3%) patients, ovarian blood flow was found to be pathological or absent. Laparoscopic conservative treatment was performed in 34 patients. In two patients, salpingo-oophorectomy was performed. No thromboembolic complications were seen. Postoperative ultrasonographic examinations confirmed normal ovarian morphology and Doppler blood flow in all patients with no recurrence. Conclusion Early diagnosis and treatment are key factors in managing AT. According to the results of the present study, given its demonstrated safety and benefits, in women of reproductive age, a conservative approach of untwisting the adnexa and salvaging the ovary via laparoscopy should be considered in AT cases in which the time from the onset of symptoms to surgery does not exceed 44 hours, regardless of the color and number of twists. PMID:24591949

Karayalc?n, Rana; Ozcan, Sarp; Ozyer, Sebnem; Var, Turgut; Yesilyurt, Huseyin; Dumanl?, Huseyin; Soysal, Sunullah; Mollamahmutoglu, Leyla; Bat?oglu, Sertac

2011-01-01

275

Non-Colinearity of Angular Velocity and Angular Momentum  

ERIC Educational Resources Information Center

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)

Burr, A. F.

1974-01-01

276

Angular-resolved Photoelectron Spectroscopy of Superatom Orbitals of Fullerenes  

NASA Astrophysics Data System (ADS)

Photoelectron angular distributions from both C60 and C70 were recorded for low laser intensity femtosecond and picosecond pulses. Rich structure is seen for electron kinetic energies that lie below the photon energy. Strong, broad peaks are observed for photoelectron energies corresponding to single-photon ionization of so-called superatom molecular orbitals (SAMOs). The very simple angular distributions measured for these peaks, the close similarity of the spectra observed from C60 and C70, and the comparison with time-dependent density functional theory provide strong support for the SAMO hypothesis.

Johansson, J. Olof; Henderson, Gordon G.; Remacle, Françoise; Campbell, Eleanor E. B.

2012-04-01

277

Kinetic description of electron plasma waves with orbital angular momentum  

SciTech Connect

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

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

2012-11-15

278

Angular momentum in QGP holography  

NASA Astrophysics Data System (ADS)

The quark chemical potential is one of the fundamental parameters describing the quark-gluon plasma produced by sufficiently energetic heavy-ion collisions. It is not large at the extremely high temperatures probed by the LHC, but it plays a key role in discussions of the beam energy scan programmes at the RHIC and other facilities. On the other hand, collisions at such energies typically (that is, in peripheral collisions) give rise to very high values of the angular momentum density. Here we explain that holographic estimates of the quark chemical potential of a rotating sample of plasma can be very considerably improved by taking the angular momentum into account.

McInnes, Brett

2014-10-01

279

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.

280

Elevated temperature axial and torsional fatigue behavior of Haynes 188  

NASA Technical Reports Server (NTRS)

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.

Bonacuse, Peter J.; Kalluri, Sreeramesh

1995-01-01

281

Two-Component Spinors in Spacetimes with Torsionful Affinities  

E-print Network

The essentially unique torsionful version of the classical two-component spinor formalisms of Infeld and van der Waerden is exhibited. 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 connection appears to possess a torsional part which is conveniently taken as a suitable asymmetric contribution. Such a torsional affine contribution thus supplies a gauge-invariant potential that may 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 connection 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. It is pointed out that the new theoretical framework supposedly should afford both a physical characterization of the cosmic dark energy and a description of the propagation of gravitons in torsional regions of the universe.

J. G. Cardoso

2014-01-29

282

Elevated temperature axial and torsional fatigue behavior of Haynes 188  

NASA Technical Reports Server (NTRS)

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

Bonacuse, Peter J.; Kalluri, Sreeramesh

1992-01-01

283

Direct torsional actuation of microcantilevers using magnetic excitation  

NASA Astrophysics Data System (ADS)

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.

Gosvami, Nitya Nand; Nalam, Prathima C.; Exarhos, Annemarie L.; Tam, Qizhan; Kikkawa, James M.; Carpick, Robert W.

2014-09-01

284

Anelastic behavior of a torsion pendulum with a CuBe fiber at low temperature, and implications for a measurement of the gravitational constant  

NASA Astrophysics Data System (ADS)

Using a torsion pendulum, we have investigated the anelastic properties of a CuBe torsion fiber for shear strains in the range 4×10-7 to 3×10-3 at temperatures 4.2K, 77K, and 295K. The fiber was 20 ?m in diameter and 24 cm long, with a torsion constant of 0.033 dyn/cdot cm/cdot rad-1. It suspended an 11 gram azimuthally symmetric torsion pendulum which loaded the fiber to approximately 25% of its tensile strength at room temperature. The natural torsional oscillation frequency of this system was 6.4 mHz. An autocollimator viewing a set of mirrors on the oscillating pendulum served to measure with great accuracy the times at which the pendulum assumed a large set of discrete angular displacements during each oscillation cycle. This enabled a determination of the angular displacement of the pendulum as a function of time to better than a part in 107 of its oscillation amplitude, from which accurate information was obtained on the pendulum's frequency, damping, and harmonic content as functions of the oscillation amplitude. Analysis yields a determination of the fourth order shear elastic constant of CuBe. Expressing the shear potential energy density as: u(/epsilon)=c2?2+c3?3+ c4?4 where ? is the shear strain, the values determined for (c2,/ c3,/ c4) are (25, 0.17, -550) GPa respectively. A striking feature of the fiber's internal friction Q-1 is that it appears to be the sum of two independent components: Q-1=Q I-1(T)+ Q II-1(A) where Q I-1(T) is temperature-dependent, varying by a factor of 3 between 4.2 and 77K, and Q II-1(A) is linearly dependent on amplitude and virtually independent of temperature; its linear dependence on amplitude varied by less than 4% between 4.2K and 77K. Interestingly the measurements of: the linear amplitude-dependent Q II-1, the linear component of the amplitude-dependent frequency shift, and the harmonic content associated with a dissipative hysteresis loop, are consistent with the motion generated by a simple stick-slip mechanism. Such a mechanism may be the result of microplastic behavior associated with the motion of dislocations and/or point defects. For a measurement of the gravitational constant using a torsion pendulum, these fiber-related properties may create a maximal 2-5 ppm systematic error assuming a comprehensive analysis is employed.

Bantel, Michael Kurt

1998-07-01

285

Fractionalization of angular momentum at finite temperature around a magnetic vortex  

SciTech Connect

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.

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

286

Complete axial torsion of pregnant uterus with leiomyoma.  

PubMed

Uterine torsion is defined as a rotation of the uterus of more than 45° along its long axis. It is a rare complication during pregnancy; a common cause of torsion can be uterine myoma. Here we describe the case of a 27-year-old G2P1+0 woman at 15?weeks 3?day pregnancy, who presented to our outpatient department as a case of acute abdomen, in a state of shock. Clinical findings did not correlate with investigation. On lapratomy she was diagnosed as a case of complete axial torsion of pregnant uterus with fundal myoma with massive abruption. Early diagnosis and timely intervention would help in improving both maternal and fetal outcome. PMID:25193815

Sachan, Rekha; Patel, M L; Sachan, Pushpalata; Arora, Anubha

2014-01-01

287

A Case of Torsion of Gravid Uterus Caused by Leiomyoma  

PubMed Central

Uterine torsion during pregnancy is only sporadically reported in the literature. Here we present a case of leiomyoma causing uterine torsion in pregnancy and review the literature on etiology, diagnosis, and management. A 25-years-old primigravida with leiomyoma complicating pregnancy was admitted in our hospital with abdominal pain and uterine tenderness. She underwent emergency LSCS (lower segment cesarean section) for fetal bradycardia. Intraoperatively, the uterus was rotated 180 degrees left to right. Inadvertent incision on the posterior wall was avoided by proper delineation of anatomy. Torsion was corrected by exteriorization of leiomyoma and uterus, and lower segment cesarean was carried out safely. Prompt recognition and management of this condition is necessary for better maternal and fetal outcome. PMID:22567496

Deshpande, Gururaj; Kaul, Rajesh; P., Manjuladevi

2011-01-01

288

Unilateral testicular seminoma with simultaneous contralateral torsion: a case report  

PubMed Central

Introduction Testicular germ cell tumors are the most common malignancies in men. Testicular torsion is also a scrotal phenomenon seen in adolescence and adulthood. The co-occurrence of these two scrotal disorders is extremely rare. Case presentation A 28-year-old East Asian man presented at our hospital with painless bilateral scrotal swelling. Both scrotal ultrasonography and computed tomography findings showed bilateral testicular tumors, and magnetic resonance imaging demonstrated a lack of enhancement in his right testis, indicating a hemorrhagic infarction and a left testicular tumor. After a bilateral orchiectomy, the intraoperative and histopathological findings revealed a left seminoma with a complicating contralateral testicular torsion that had developed with hemorrhagic infarction. Conclusion Testicular germ cell tumor with contralateral torsion is extremely rare. We could differentiate this case from bilateral testicular tumors appropriately using magnetic resonance imaging, and suggest that magnetic resonance imaging examination may be necessary to diagnose bilateral testicular masses. PMID:22800561

2012-01-01

289

Gastrointestinal torsion in a channel catfish (Ictalurus punctatus).  

PubMed

A case of gastrointestinal torsion with dilatation in a farm-raised channel catfish (Ictalurus punctatus) was examined at the Thad Cochran National Warmwater Aquaculture Center (Stoneville, Mississippi, USA). The affected fish was a gravid female broodfish, which displayed pale gills and a markedly distended abdomen. Internal examination revealed that the gastrointestinal tract and ovaries were rotated around each other four times in a counterclockwise direction as viewed in right lateral recumbency. The catfish had a markedly distended gastrointestinal tract, pale liver, hypoplastic spleen, hypoplastic swim bladder, and high volume of ascitic fluid. Blood analysis indicated multiple abnormalities, including severe anemia and metabolic acidosis. The etiology of the torsion was uncertain; however, the presence of a hypoplastic swim bladder most likely allowed for increased movement of the gastrointestinal tract and ovaries. When examining cases of abdominal distention in fish, gastrointestinal torsion can be considered among the differential diagnoses. PMID:12685091

Pasnik, David J; Khoo, Lester; Gaunt, Patricia S

2003-01-01

290

Noninvasive measurement and clinical relevance of myocardial twist and torsion.  

PubMed

Left ventricular (LV) torsion (twisting) and untwisting results in equalization of wall stress and augmentation of pressure generated for a given shortening of sarcomere during the systolic contraction and aids early diastolic relaxation. This is attributed to the dynamic interaction of epicardial and endocardial helical myocardial fibers. Recent advances in noninvasive imaging techniques have enabled us to quantify torsion accurately and reliably in health and disease. LV torsional mechanics are altered in range of clinical conditions from those that cause minimal cardiac architectural changes as seen in hypertension, diabetes mellitus or older age to advanced cardiac remodeling as seen dilated or hypertrophic cardiomyopathy. Therefore, assessment of LV rotational mechanics may be a potentially sensitive marker of cardiac dysfunction and may provide important insights into the pathophysiology of heart failure. PMID:25318986

Pokharel, Parash; Yoon, Andrew J; Bella, Jonathan N

2014-11-01

291

Torsion, AN Alternative to the Cosmological Constant?  

NASA Astrophysics Data System (ADS)

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

Schücker, Thomas; Tilquin, André

2012-12-01

292

Mesoscopic formulas of linear and angular momentum fluxes  

E-print Network

Cosserat theory [E. Cosserat and F. Cosserat, "Th\\'eorie des corps d\\'eformables" (Herman,1909)] is a way to extend a simple Newtonian fluid model or bulk elasticity models to incorporate the underlying mesoscopic structures into the macroscopic theory. However, this theory, which contains asymmetric stress tensor and "couple stress tensor", has been lacking its bottom-up theoretical basis which may correspond to the virial stress formula of Irving-Kirkwood theory of the gas hydrodynamics. Based on the momentum and angular momentum conservation laws, we will present a bottom-up formulation of the Cosserat-type theory in the way adapted to the dense cellular media. Mesoscopic formulas for the stress and couple stress tensors are given, which is reminiscent of the virial stress but without any assumptions about the interactions at the cell-cell interfaces.

Antoine Fruleux; Ken Sekimoto

2014-06-13

293

Chiral symmetries associated with angular momentum  

NASA Astrophysics Data System (ADS)

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.

Bhattacharya, M.; Kleinert, M.

2014-03-01

294

Chiral symmetries associated with angular momentum  

E-print Network

In beginning quantum mechanics courses, symmetries of a physical system are usually introduced as operators which commute with the Hamiltonian. In this article 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 typically 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 article, 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.

M. Bhattacharya; M. Kleinert

2013-11-29

295

Mode conversion of torsional waves generated by electromagnetic acoustic transducer  

NASA Astrophysics Data System (ADS)

Change in group velocity of torsional guided waves induced by mode conversion is investigated for wall-thinning inspection of pipe. The fundamental and second torsional modes are generated and detected by the Lorentz-force-type electromagnetic acoustic transducers (EMATs) in aluminum pipes with fabricated-thinning region. Traveling time of the higher mode in the axial direction varies depending on the thickness of the thinning regions and drops suddenly when the thickness is smaller than the cut-off thickness. From comparison with calculated dispersion relation, the drop is attributed to mode conversion from a higher mode to a lower mode with higher group velocity.

Nurmalia, Nakamura, N.; Ogi, H.; Hirao, M.

2013-01-01

296

Active damping of torsional drillstring vibrations with a hydraulic topdrive  

SciTech Connect

The paper describes the development and field testing of a new active damping system to eliminate stick-slip torsional drillstring vibrations. The system controls the energy flow through a hydraulic top drive and makes it react as a tuned vibration damper. The control algorithm, outlined in the paper, was implemented in software in the electronic control system for the pump unit of the top drive. Dedicated workshop testing allowed for a rapid installation at the rig site. The system was field tested in a deep exploration well in the Barents Sea, and contributed to excellent coring performance by eliminating torsional vibrations while coring hard limestone.

Jansen, J.D.; Steen, L. van den; Zachariassen, E.

1994-12-31

297

Calibrations, torsion classes, and wrapped M-branes  

SciTech Connect

The present work has two goals. The first is to complete the classification of geometries in terms of torsion classes of M-branes wrapping cycles of a Calabi-Yau manifold. The second goal is to give insight into the physical meaning of the torsion class constraints. We accomplish both tasks by defining new energy minimizing calibrations in M-brane backgrounds. When fluxes are turned on, it is these calibrations that are relevant, rather than those which had previously been defined in the context of purely geometric backgrounds.

Fayyazuddin, Ansar [Department of Natural Sciences, Baruch College, City University of New York, New York (United States); Husain, Tasneem Zehra [Jefferson Physical Laboratory, Harvard University, Cambridge, Massachusetts 02138 (United States)

2006-05-15

298

Free torsional vibrations of tapered cantilever I-beams  

NASA Astrophysics Data System (ADS)

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.

Rao, C. Kameswara; Mirza, S.

1988-08-01

299

Torsionally excited methanol in hot molecular cloud cores  

NASA Technical Reports Server (NTRS)

Torsionally excited methanol lines were detected in the direction of four galactic molecular cloud regions by means of scans in the 20-24 GHz interval with the Effelsberg 100 m radiotelescope. Transitions in both the first torsionally excited state, with excitation energies of about 450 K, and the ground state were seen in the direction of the hot, molecular cloud cores of the Orion-KL region, W3(OH), NGC 7538 and W51. The emission in Orion originated from a hot region in the southern ridge cloud 4 arcsec from the hot core. The greatest deviations from LTE occurred when a strong compact continuum source was present.

Menten, K. M.; Walmsley, C. M.; Henkel, C.; Wilson, T. L.; Snyder, L. E.; Hollis, J. M.

1986-01-01

300

Hyperbaric oxygen treatment for unilateral testicular torsion in a child.  

PubMed

Torsion of the testis is a urological emergency most commonly occurring in adolescent boys. Hyperbaric oxygen treatment (HBOT) has been shown to alleviate reperfusion injury in experimental ischaemia of the testis. We report a 13-year-old boy who had prolonged right testicular ischaemia. Despite surgery, the colour of the testis remained poor. He underwent a post-operative course of 10 HBOT over 8 days, with restoration of blood flow on colour Doppler and reduction of oedema. At four-month followup, the testis appeared normal on ultrasonography. To the best of our knowledge, this is the first published case of torsion of the testis treated with HBOT. PMID:25311324

Alp, Bilal Firat; Cebi, Gamze; Ozdemir, Adem; Irkilata, Hasan Cem; Uzun, Günalp

2014-09-01

301

Dynamic nonlinear behavior of torsional resonators in MEMS  

NASA Astrophysics Data System (ADS)

This paper reports the theoretical and experimental characterization of the dynamic behavior of torsional resonators that can be applied to inertial sensors. For the correct operation of the devices it is necessary to model the dynamic behavior of the electrostatically actuated torsional resonators both in the linear and nonlinear range. A complete analytical model is developed in this work including nonlinear terms in the electrostatic stiffness. This provides clear quantitative information about the available linear range of operation and opens the way to exploit the nonlinear range. The model is validated through comparison with experimental data on two 22 µm thick polysilicon resonators having different distances from the underlying electrodes.

Caspani, A.; Comi, C.; Corigliano, A.; Langfelder, G.; Zega, V.; Zerbini, S.

2014-09-01

302

The Angular Momentum of Baryons and Dark Matter Halos Revisited  

NASA Technical Reports Server (NTRS)

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.

Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan

2011-01-01

303

APPLICATION OF WAVELET PACKET ANALYSIS FOR FAULT DETECTION IN ELECTROMECHANICAL SYSTEMS BASED ON TORSIONAL VIBRATION MEASUREMENT  

Microsoft Academic Search

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

X. Li; L. Qu; G. Wen; C. Li

2003-01-01

304

Using torsional vibration analysis as a synergistic method for crack detection in rotating equipment  

Microsoft Academic Search

A non-intrusive torsional vibration method for monitoring and tracking small changes in crack growth of reactor coolant pump shafts is presented in this paper. This method resolves and tracks characteristic changes in the natural torsional vibration frequencies that are associated with shaft crack propagation. The focus of this effort is to develop and apply the torsional vibration shaft cracking monitoring

Mitchell S. Lebold; K. Maynard; K. Reichard; M. Trethewey; D. Bieryla; Clifford Lissenden; David Dobbins

2004-01-01

305

Optimization of a metal honeycomb sandwich beam-bar subjected to torsion and bending  

Microsoft Academic Search

In this paper, we analyze a metal honeycomb sandwich beam\\/torsion bar subjected to combined loading conditions. The cell wall arrangement of the honeycomb core is addressed in the context of maximizing resistance to either bending, torsion, or combined bending and torsion for given dimensions, face sheet thicknesses and core relative density. It is found that the relative contributions of the

A.-J. Wang; D. L. McDowell

2003-01-01

306

The effects of loops on the torsional stiffnesses of rectangular wires: An in vitro study  

Microsoft Academic Search

Various loop designs have been investigated with respect to the increased torsional flexibility given to the wire by their inclusion. The torsional flexibility of the wire was shown to be enlarged from 26% to 63%, depending on loop design. Both variation in wire cross-section and loop geometry will influence torsional stiffness. Wires with small cross-sectional dimensions will show greater flexibility

J. Ødegaard; T. Meling; E. Meling

1996-01-01

307

Controversy concerning the definition of quark and gluon angular momentum  

SciTech Connect

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.

Leader, Elliot [Blackett laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)

2011-05-01

308

A shear-shear torsional beam model for nonlinear aeroelastic analysis of tower buildings  

NASA Astrophysics Data System (ADS)

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.

Piccardo, G.; Tubino, F.; Luongo, A.

2014-09-01

309

Dynamic Finite Element Analysis of Extensional-Torsional Coupled Vibration in Nonuniform Composite Beams  

NASA Astrophysics Data System (ADS)

The application of a Dynamic Finite Element (DFE) technique to the extensional-torsional free vibration analysis of nonuniform composite beams, in the absence of flexural coupling, is presented. The proposed method is a fusion of the Galerkin weighted residual formulation and the Dynamic Stiffness Matrix (DSM) method, where the basis functions of approximation space are assumed to be the closed form solutions of the differential equations governing uncoupled extensional and torsional vibrations of the beam. The use of resulting dynamic trigonometric interpolation (shape) functions leads to a frequency dependent stiffness matrix, representing both mass and stiffness properties of the beam element. Assembly of the element matrices and the application of the boundary conditions then leads to a frequency dependent nonlinear eigenproblem, which is solved to evaluate the system natural frequencies and modes. Two illustrative examples of uniform and tapered cantilevered, Circumferentially Uniform Stiffness ( CUS), hollow, composite beams are presented. The influence of ply fibre-angle on the natural frequencies is also studied. The correctness of the theory and the superiority of the proposed DFE over the contrasting DSM and conventional FEM methods are confirmed by the published results and numerical checks. The discussion of results is followed by some concluding remarks.

Hashemi, Seyed M.; Roach, Andrew

2011-12-01

310

Effects of Torsion on Intervertebral Disc Gene Expression and Biomechanics, Using a Rat Tail Model  

PubMed Central

Study Design In vitro and in vivo rat tail model to assess effects of torsion on intervertebral disc biomechanics and gene expression. Objective Investigate effects of torsion on promoting biosynthesis and producing injury in rat caudal intervertebral discs. Summary of Background Data Torsion is an important loading mode in the disc and increased torsional range of motion is associated with clinical symptoms from disc disruption. Altered elastin content is implicated in disc degeneration, but its effects on torsional loading are unknown. Although effects of compression have been studied, the effect of torsion on intervertebral disc gene expression is unknown. Methods In vitro biomechanical tests were performed in torsion on rat tail motion segments subjected to 4 treatments: elastase, collagenase, genipin, control. In vivo tests were performed on rats with Ilizarov-type fixators implanted to caudal motion segments with five 90-minute loading groups: 1 Hz cyclic torsion to ±5°, ±15°, and ±30°, static torsion to +30°, and sham. Anulus and nucleus tissues were separately analyzed using qRT-PCR for gene expression of anabolic, catabolic, and proinflammatory cytokine markers. Results In vitro tests showed decreased torsional stiffness following elastase treatment and no changes in stiffness with frequency. In vivo tests showed no significant changes in dynamic stiffness with time. Cyclic torsion upregulated elastin expression in the anulus fibrosus. Upregulation of TNF-? and IL-1? was measured at ±30°. Conclusion We conclude that strong differences in the disc response to cyclic torsion and compression are apparent with torsion increasing elastin expression and compression resulting in a more substantial increase in disc metabolism in the nucleus pulposus. Results highlight the importance of elastin in torsional loading and suggest that elastin remodels in response to shearing. Torsional loading can cause injury to the disc at excessive amplitudes that are detectable biologically before they are biomechanically. PMID:20736890

Barbir, Ana; Godburn, Karolyn E.; Michalek, Arthur J.; Lai, Alon; Monsey, Robert D.; Iatridis, James C.

2010-01-01

311

3D numerical simulations of a torsional Alfven waves  

NASA Astrophysics Data System (ADS)

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

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

312

Ultrahigh Torsional Stiffness and Strength of Boron Nitride Jonathan Garel,  

E-print Network

, the stiffest and strongest material discovered so far, in terms of both elastic modulus and tensile strength.1Ultrahigh Torsional Stiffness and Strength of Boron Nitride Nanotubes Jonathan Garel, Itai Leven or CNT bundles markedly decreases their effective stiffness and strength.3,9 CNT-based fibers have still

Hod, Oded

313

Coupled shear-torsional motion of a rubber support system  

Microsoft Academic Search

The finite amplitude, coupled shear-torsional motion of a circular disk supported between identical rubber spring cylinders is studied. The material of the springs is assumed to be an incompressible elastic material. The oscillatory motion oscillatory of the disk is studied for two different cases. In the first case, the material of the spring is assumed to be an incompressible elastic

Ziliang Zhou

1993-01-01

314

Human ocular torsional position before and after unilateral vestibular neurectomy  

Microsoft Academic Search

The static ocular torsional position of both eyes of 23 patients was measured by means of fundus photographs one day before and one week after unilateral vestibular neurectomy for the treatment of acoustic neuroma, Ménière's disease or paroxysmal vertigo. The results showed that in all patients the vestibular neurectomy caused both eyes to tort (i.e. to roll around the visual

I. S. Curthoys; M. J. Dai; G. M. Halmagyi

1991-01-01

315

Experimental investigation on flutter characteristics of composite torsion-box  

Microsoft Academic Search

An experimental investigation on flutter characteristics of a composite torsion-box is presented. Vibration test, wind tunnel flutter test, and the corresponding calculations are conducted. Two models of the same frame are tested, one of them covered with composite skin, the other with aluminum alloy skin of the same thickness. Experimental and calculated date indicate that, for the model with composite

Fenghui Zhu; Tao Qiu

1991-01-01

316

An Uncommon Twist: Isolated Fallopian Tube Torsion in an Adolescent  

PubMed Central

We report a 13-year-old girl with bilateral paratubal cysts and left isolated fallopian tube torsion (IFTT). Paratubal cysts are uncommon in children, and IFTT is a rare complication. Awareness of this entity and prompt surgical intervention could potentially salvage the fallopian tube preserving fertility. PMID:24024061

Kisku, Sundeep; Thomas, Reju Joseph

2013-01-01

317

Acute Abdomen due to Primary Omental Torsion and Infarction  

PubMed Central

Background. Torsion of greater omentum is a quite uncommon cause of acute abdomen. It can be primary or secondary but in both cases omentum twists upon itself and causes omental segmentary or diffuse necrosis. Symptoms are unspecific and preoperative diagnosis is difficult. The widespread and increasing use of computer tomography (CT) in differential diagnosis of acute abdomen can be useful for making a specific diagnosis. Objectives. This work aims to describe primary omental torsion in order to help avoid misdiagnosis, especially with acute appendicitis, which is eventually based solely on a physical examination. Case Report. We present a case of primary omental torsion in a young man and discuss contemporary methods in diagnosis and management of the condition. Conclusions. When a right diagnosis has been posed, possible treatments for omental torsion and necrosis are two: conservative or surgical. Conservative treatment had been rarely carried out because of frequent and important sequelae just like abdominal abscesses. Nowadays, surgical treatment, laparoscopic or laparotomic, is preferred because it is a safe method in diagnosis and management of this condition.

Occhionorelli, S.; Zese, M.; Cappellari, L.; Stano, R.; Vasquez, G.

2014-01-01

318

Optical microshutters and torsional micromirrors for light modulator arrays  

Microsoft Academic Search

The fabrication and operation of surface micromachined light modulators are described. In particular, comb-driven polysilicon microshutters for interrupting a focused laser beam of 5 ?m in diameter are characterized. The shutters are suspended by novel compact meander springs, which favor their application in dense light modulator arrays. Torsional micromirrors working in a reflection mode, having two mirror states, were realized

V. P. Jaecklin; C. Linder; N. F. de Rooij; J.-M. Moret; R. Vuilleumier

1993-01-01

319

The impact of tibial torsion measurements on gait analysis kinematics  

PubMed Central

Objective: To measure and compare tibial torsion values as assessed by goniometry and three-dimensional kinematics. In addition, the impact of each one of these measurements on kinematic and kinetic results for normal gait was determined. Methods: Twenty-three healthy and fully ambulatory patients were assessed, 11 women and 12 men, from 20 to 40 years old. Data were collected at a laboratory for the three-dimensional analysis of movement with 10 cameras and two force plates. Tibial torsion measurements were obtained using goniometry and three-dimensional kinematics based on the Plug-in Gait model. Afterwards, both procedures were compared, and the impact of each result was assessed on the kinematic and kinetic modeling of the knee and ankle. Results: Pearson's linear correlation coefficient (r=0,504) showed a moderate correlation between the three-dimensional kinematics and goniometry, and between the changes in the measurements. Regarding the processed kinematic and kinetic results for every torsion position, no significant differences were noticed among any of the studied variables (p>0.05). Conclusion: Although statistical correlation among tibial torsion angles by goniometry and three-dimensional kinematic were moderate, kinematic and kinetic analysis of the joints did not reveal any significant changes. Level of Evidence I, Diagnostic Studies - Investigating a Diagnostic Test. PMID:25328438

Lucareli, Paulo Roberto Garcia; Santos, Nadia Maria; Godoy, Wagner De; Bernal, Milena Moreira Barreto; Paes, Ângela Tavares; Ramalho, Amancio

2014-01-01

320

Musica II: Torsion Drum, Buzzer, Maraca, Chirper, Flute  

NSDL National Science Digital Library

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.

Workshop, Watsonville E.

2011-01-01

321

On the characteristic torsion of gwistor space R. Albuquerque  

E-print Network

On the characteristic torsion of gwistor space R. Albuquerque rpa@uevora.pt October 24, 2010. Albuquerque 2 G2-twistor for gwistor. Briefly, given M as before, the G2-twistor space of M consists SM may be written as X = Xh + Xv = Xh + L-C X U. (3) #12;R. Albuquerque 3 The tangent sphere bundle

Albuquerque, Rui

322

Torsion-Free Generalized Connections and Heterotic Supergravity  

NASA Astrophysics Data System (ADS)

This work revisits the notions of connection and curvature in generalized geometry, with emphasis on torsion-free generalized connections on a transitive Courant algebroid. As an application, we provide a mathematical derivation of the equations of motion of heterotic supergravity in terms of the Ricci tensor of a generalized metric, inspired by the work of Coimbra, Strickland-Constable and Waldram.

Garcia-Fernandez, Mario

2014-11-01

323

The Torsional and Bending Deflection of Full-Scale Aluminum-Alloy Propeller Blades Under Normal Operating Conditions  

NASA Technical Reports Server (NTRS)

The torsional deflection of the blades of three full-scale aluminum-alloy propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10 degree was found at a v/nd of 0.3 and a smaller deflection at higher values of v/nd for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading-transit method used in the previous test.

Hartman, Edwin P; Biermann, David

1938-01-01

324

Delamination behavior of quasi-isotropic graphite epoxy laminates subjected to tension and torsion loads  

NASA Technical Reports Server (NTRS)

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.

Hinkley, J. A.; Obrien, T. K.

1992-01-01

325

Spin Angular Momentum Imparted by Gravitational Waves  

E-print Network

Following the demonstration that gravitational waves impart linear momentum, it is argued that if they are polarized they should impart angular momentum to appropriately placed 'test rods' in their path. A general formula for this angular momentum is obtained and used to provide expressions for the angular momentum imparted by plane and cylindrical gravitational waves.

M Sharif

2007-01-23

326

Metamaterials-based Salisbury screens with reduced angular sensitivity  

NASA Astrophysics Data System (ADS)

We demonstrate that the incorporation of nonlocal nanowire metamaterials into Salisbury screens allows for a substantial reduction of the dependence of incident angle on the absorption maximum. Realizations of angle-independent Salisbury screens for the near-IR, mid-IR, and GHz frequencies are proposed and their performances are analyzed analytically and numerically. It is shown that nonlocal effective medium theory adequately describes the angular dependence of nanowire-based Salisbury screens.

Wells, Brian M.; Roberts, Christopher M.; Podolskiy, Viktor A.

2014-10-01

327

Stepwise angular spectrum method for curved surface diffraction.  

PubMed

We present a method to calculate wave propagation between arbitrary curved surfaces using a staircase approximation approach. The entire curved surface is divided into multiple subregions and each curved subregion is approximated by a piecewise flat subplane allowing the application of conventional diffraction theory. In addition, in order to reflect the local curvature of each subregion, we apply the phase compensation technique. Analytical expressions are derived based on the angular spectrum method and numerical studies are conducted to validate our method. PMID:24921383

Hwang, Chi-Young; Oh, Seungtaik; Jeong, Il-Kwon; Kim, Hwi

2014-05-19

328

Torsional vibration measurements on rotating shaft system using laser doppler vibrometer  

NASA Astrophysics Data System (ADS)

In this work, a laser torsional vibrameter was used to measure the torsion vibration of a rotating shaft system under electrical network impact. Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) are non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. Furthermore, a highly complex shafting system is analyzed by a modified Riccati torsional transfer matrix. The system is modeled as a chain consisting of an elastic spring with concentrated mass points, and the multi-segments lumped mass model is established for this shafting system. By the modified Riccati torsional transfer matrix method, an accumulated calculation is effectively eliminated to obtain the natural frequencies. The electrical network impacts can activize the torsional vibration of shaft system, and the activized torsion vibration frequencies contained the natural frequencies of shaft system. The torsional vibrations of the shaft system were measured under electrical network impacts in laser Doppler torsional vibrometer. By comparisons, the natural frequencies by measurement were consistent with the values by calculation. The results verify the instrument is robust, user friendly and can be calibrated in situ. The laser torsional vibrometer represents a significant step forward in rotating machinery diagnostics.

Xiang, Ling; Yang, Shixi; Gan, Chunbiao

2012-11-01

329

Torsional instanton effects in quantum gravity  

E-print Network

We show that, in the first order gravity theory coupled to axions, the instanton number of the Giddings-Strominger wormhole can be interpreted as the Nieh-Yan topological index. The axion charge of the baby universes is quantized in terms of the Nieh-Yan integers. Tunneling between universes of different Nieh-Yan charges implies a nonperturbative vacuum state. The associated topological vacuum angle can be identified with the Barbero-Immirzi parameter.

Kaul, Romesh K

2014-01-01

330

Torsional instanton effects in quantum gravity  

E-print Network

We show that, in the first order gravity theory coupled to axions, the instanton number of the Giddings-Strominger wormhole can be interpreted as the Nieh-Yan topological index. The axion charge of the baby universes is quantized in terms of the Nieh-Yan integers. Tunneling between universes of different Nieh-Yan charges implies a nonperturbative vacuum state. The associated topological vacuum angle can be identified with the Barbero-Immirzi parameter.

Romesh K. Kaul; Sandipan Sengupta

2014-11-18

331

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

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

332

Variable Distance Angular Symbology Reader  

NASA Technical Reports Server (NTRS)

A variable distance angular symbology, reader utilizes at least one light source to direct light through a beam splitter and onto a target. A target may be angled relative to the impinging light beam up to and maybe even greater than 45deg. A reflected beam from the target passes through the beam splitter and is preferably directed 90deg relative to the light source through a telecentric lens to a scanner which records an image of the target such as a direct part marking code.

Schramm, Harry F., Jr. (Inventor); Corder, Eric L. (Inventor)

2006-01-01

333

Two-axis angular effector  

DOEpatents

A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.

Vaughn, Mark R. (Albuquerque, NM); Robinett, III, Rush D. (Tijeras, NM); Phelan, John R. (Albuquerque, NM); Van Zuiden, Don M. (Albuquerque, NM)

1997-01-21

334

Inter-Ring and Hexyl Chain Torsional Potentials in Poly (3-HEXYLTHIOPHENE) Oligomers: Scaling with the Length of the Conjugted Polymer Backbone  

NASA Astrophysics Data System (ADS)

Density functional theory calculations are presented for the equilibrium structures and torsional potentials for isolated Poly (3-Hexylthiophene) (P3HT) oligomers up to 12 monomer units (up to 302 atoms). Calculations were performed at B3LYP/6-31++G(d,p) treating both the backbone of thiophene rings and the hexyl chains explicitly. One-dimensional inter-ring torsional potentials were calculated by rotating backbone around the central inter-ring bond and hexyl torsional potentials were calculated rotating n-hexyl group adjacent to the central inter-ring bond for each oligomer. The torsional and electronic properties change significantly for oligomers with 2 to 8 units but reach asymptotic values for a 10 unit P3HT chain, thereby suggesting the 10 unit long oligomer as a molecular model for the extended polymer. For P3HT oligomers having 10 or more units, all the rings and the hexyl groups are approximately coplanar except for one hexyl group at head end. The principal interaction that promotes the coplanarity of the hexyl groups is the attraction of the proximal methylene hydrogens to the sulfur on the adjacent thiophene ring. The cis conformation of the backbone is about 2kT higher than the trans minimum at room temperature. The gauche conformation of the hexyl group is within about half kT of the planar minimum. Therefore conformational polymorphisms of both types will likely be significant in the heterogeneous environment of photovoltaic devices.

Bhatta, Ram S.; Perry, David S.; Yimer, Yeneneh; Tsige, Mesfin

2011-06-01

335

Spin chains and string theory  

Microsoft Academic Search

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

Martin Kruczenski

336

New Aspects of Angular Momentum Quantization in Curved Geometries  

NASA Astrophysics Data System (ADS)

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

Smith, Felix T.

2011-04-01

337

Bending-torsion flutter calculations modified by subsonic compressibility corrections  

NASA Technical Reports Server (NTRS)

A number of calculations of bending-torsion wing flutter are made at two Mach numbers, m=0 (incompressible case) and m=0.7, and results are compared. The air forces employed for the case of m=0.7 are based on Frazer's recalculation of Possio's results, which are derived on the assumption of small disturbances to the main flow. For ordinary wings of normal density and of low bending frequency in comparison with torsion frequency, the compressibility correction to the flutter speed appears to be of the order of a few percent; whereas the correction to flutter speed for high-density wing sections, such as propeller sections, and to the wing-divergence speed in general, may be based on a rule using the (1 - m(2))1/4 factor and, for m=0.7, represents a decrease of the order of 17 percent.

Garrick, I E

1946-01-01

338

Bending and Torsion Load Alleviator With Automatic Reset  

NASA Technical Reports Server (NTRS)

A force transmitting load alleviator apparatus and method are provided for rotatably and pivotally driving a member to be protected against overload torsional and bending (moment) forces. The load alleviator includes at least one bias spring to resiliently bias cam followers and cam surfaces together and to maintain them in locked engagement unless a predetermined load is exceeded whereupon a center housing is pivotal or rotational with respect to a crown assembly. This pivotal and rotational movement results in frictional dissipation of the overload force by an energy dissipator. The energy dissipator can be provided to dissipate substantially more energy from the overload force than from the bias force that automatically resets the center housing and crown assembly to the normally fixed centered alignment. The torsional and bending (moment) overload levels can designed independently of each other.

delaFuente, Horacio M. (Inventor); Eubanks, Michael C. (Inventor); Dao, Anthony X. (Inventor)

1996-01-01

339

Structural plasticity of single chromatin fibers revealed by torsional manipulation  

E-print Network

Magnetic tweezers are used to study the mechanical response under torsion of single nucleosome arrays reconstituted on tandem repeats of 5S positioning sequences. Regular arrays are extremely resilient and can reversibly accommodate a large amount of supercoiling without much change in length. This behavior is quantitatively described by a molecular model of the chromatin 3-D architecture. In this model, we assume the existence of a dynamic equilibrium between three conformations of the nucleosome, which are determined by the crossing status of the entry/exit DNAs (positive, null or negative). Torsional strain, in displacing that equilibrium, extensively reorganizes the fiber architecture. The model explains a number of long-standing topological questions regarding DNA in chromatin, and may provide the ground to better understand the dynamic binding of most chromatin-associated proteins.

Aurelien Bancaud; Natalia Conde e Silva; Maria Barbi; Gaudeline Wagner; Jean-Francois Allemand; Julien Mozziconacci; Christophe Lavelle; Vincent Croquette; Jean-Marc Victor; Ariel Prunell; Jean-Louis Viovy

2007-07-13

340

Quartz crystal microbalance based on torsional piezoelectric resonators  

SciTech Connect

A quartz crystal microbalance (QCM) is described, which is based on a torsional resonator, rather than a conventional thickness-shear resonator. Typical applications are measurements of film thickness in the coating industry and monitoring of biofouling. The torsional QCM is about a factor of 100 less sensitive than the conventional QCM. On the other hand, it can probe film thicknesses in the range of hundreds of microns, which is impossible with the conventional QCM due to viscoelastic artifacts. Data acquisition and data analysis proceed in analogy to the conventional QCM. An indicator of the material's softness can be extracted from the bandwidth of the resonance. Within the small-load approximation, the frequency shift is independent of whether the sample is applied to the face or to the side of the cylinder. Details of the geometry matter if the viscoelastic properties of the sample are of interest.

Buecking, W.; Du, B.; Turshatov, A.; Koenig, A. M.; Reviakine, I.; Bode, B.; Johannsmann, D. [Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Strasse 4, D-38678 Clausthal-Zellerfeld (Germany); Flucon Fluid Control GmbH, Burgstaetter Strasse 6, D-38678 Clausthal-Zellerfeld (Germany); Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Strasse 4, D-38678 Clausthal-Zellerfeld (Germany)

2007-07-15

341

Why has spacetime torsion such negligible effect on our universe?  

E-print Network

We attempt an answer to the question as to why the evolution of four-dimensional universe is governed by spacetime curvature but not torsion. An answer is found if there is an additional compact spacelike dimension with a warped geometry, with torsion caused by a Kalb-Ramond (KR) antisymmetric tensor field in the bulk. Starting from a Randall-Sundrum type of warped extra dimension, and including the inevitable back reaction ensuing from the radius stabilization mechanism, we show that there is always an extra exponential suppression of the KR field on the four-dimensional projection that constitutes our visible universe. The back reaction is found to facilitate the process of such suppression.

Ashmita Das; Biswarup Mukhopadhyaya; Soumitra SenGupta

2014-10-03

342

Why has spacetime torsion such negligible effect on our universe?  

E-print Network

We attempt an answer to the question as to why the evolution of four-dimensional universe is governed by spacetime curvature but not torsion. An answer is found if there is an additional compact spacelike dimension with a warped geometry, with torsion caused by a Kalb-Ramond (KR) antisymmetric tensor field in the bulk. Starting from a Randall-Sundrum type of warped extra dimension, and including the inevitable back reaction ensuing from the radius stabilization mechanism, we show that there is always an extra exponential suppression of the KR field on the four-dimensional projection that constitutes our visible universe. The back reaction is found to facilitate the process of such suppression.

Das, Ashmita; SenGupta, Soumitra

2014-01-01

343

State reversals of optically induced tilt and torsional eye movements  

NASA Technical Reports Server (NTRS)

Alternations of the state of apparent self-motion during observation of a large visual display rotating about the line of sight are associated with alternations in the magnitude of induced tilt and torsional eye rotation. In one experiment, shifts in visually induced tilt during these state alternations are found to be in the opposite direction to corresponding shifts in induced ocular torsion. In a second experiment, the reversals of self-motion perception are shown to be an intravisual phenomenon, independent of competing inputs provided by the vestibular system. These results emphasize the importance of distinguishing between visual and vestibular processes in tilt perception and ocular rotation during human orientation to gravitational vertical.

Finke, R. A.; Held, R.

1978-01-01

344

Calibration of combined bending-torsion fatigue reliability data reduction  

NASA Technical Reports Server (NTRS)

The combined bending-torsion fatigue reliability research machines are described. Three such machines are presently in operation. The calibration of these machines is presented in depth. Fatigue data generated with these machines for SAE 4340 steel grooved specimens subjected to reversed bending and steady torque loading are given. The data reduction procedure is presented. Finally, some comments are made about notch sensitivity and stress concentration as applied to combined fatigue.

Kececioglu, D.; Mcconnell, J. B.

1969-01-01

345

Splenic torsion presenting as a twisted hemorrhagic ovarian cyst.  

PubMed

Torsion of a wandering spleen is rare, usually presenting as an acute abdomen and commonly misdiagnosed. In our case, a 14-year-old girl was diagnosed preoperatively as having a twisted hemorrhagic ovarian cyst. On laparotomy, an infarcted spleen that was twisted on its pedicle was found in the lower abdomen. The patient recovered uneventfully. The clinical spectrum of wandering spleen is discussed briefly. PMID:3880638

Pundaleeka, S K; Zimmers, T E; Nassos, T P

1985-01-01

346

Simple currents versus orbifolds with discrete torsion - a complete classification  

Microsoft Academic Search

We give a complete classification of all simple current modular invariants, extending previous results for (Zp)k to arbitrary centers. We obtain a simple explicit formula for the most general case. Using orbifold techniques to this end, we find a one-to-one correspondence between simple current invariants and subgroups of the center with discrete torsions. As a by-product, we prove the conjectured

M. Kreuzer; A. N. Schellekens

1994-01-01

347

Modelling of Torsion Beam Rear Suspension by Using Multibody Method  

Microsoft Academic Search

The multibody systems analysis has become one of the main simulation techniques to calculate the elasto-kinematics characteristics of a car suspension under wheel loads or to realize complex full vehicle models in order to predict the handling performances or the NVH quality. The modelling of torsion beam rear suspensions—widely adopted in cars belonging to B or C class—presents some problems

G. Fichera; M. Lacagnina; F. Petrone

2004-01-01

348

Fracture and ductility in hot torsion of Nickel  

Microsoft Academic Search

Fracture of Nickel 270 under conditions of warm working and hot working was studied using a hot torsion testing device. Under\\u000a all conditions, fracture initiates as wedge-type cracks at the peak on the torque-twist curve. A hot fracture initiation criterion\\u000a is proposed based on the initial deformation conditions. The higher the temperature and the slower the strain rate, the smaller

E. Shapiro; G. E. Dieter

1971-01-01

349

Ratchetting under tension–torsion loadings: experiments and modelling  

Microsoft Academic Search

This paper is concerned with the mechanical behaviour of 316 austenitic stainless steel under multiaxial loadings and particular attention is paid to ratchetting under tension–torsion non-proportional loadings. First, a series of uniaxial tests and biaxial tests has been carried out in order to calibrate five different cyclic plasticity models based on an isotropic hardening rule and a non-linear kinematic hardening

Laurence Portier; Sylvain Calloch; Didier Marquis; Philippe Geyer

2000-01-01

350

Mass neutrino flavor evolution in spacetime with torsion  

E-print Network

In the framework of the spacetime with torsion, we obtain the flavor evolution equation of the mass neutrino oscillation in vacuum. A comparison with the result of general relativity case, it shows that the flavor evolutionary equations in Riemann spacetime and Weitzenb\\"ock spacetimes are equivalent in the spherical symmetric Schwarzschild spacetime, but turns out to be different in the case of the axial symmetry.

C. M. Zhang

2000-12-06

351

Global geometric torsion estimation in adolescent idiopathic scoliosis.  

PubMed

Several attempts have been made to measure geometrical torsion in adolescent idiopathic scoliosis (AIS) and quantify the three-dimensional (3D) deformation of the spine. However, these approaches are sensitive to imprecisions in the 3D modeling of the anatomy and can only capture the effect locally at the vertebrae, ignoring the global effect at the regional level and thus have never been widely used to follow the progression of a deformity. The goal of this work was to evaluate the relevance of a novel geometric torsion descriptor based on a parametric modeling of the spinal curve as a 3D index of scoliosis. First, an image-based approach anchored on prior statistical distributions is used to reconstruct the spine in 3D from biplanar X-rays. Geometric torsion measuring the twisting effect of the spine is then estimated using a technique that approximates local arc-lengths with parametric curve fitting centered at the neutral vertebra in different spinal regions. We first evaluated the method with simulated experiments, demonstrating the method's robustness toward added noise and reconstruction inaccuracies. A pilot study involving 65 scoliotic patients exhibiting different types of deformities was also conducted. Results show the method is able to discriminate between different types of deformation based on this novel 3D index evaluated in the main thoracic and thoracolumbar/lumbar regions. This demonstrates that geometric torsion modeled by parametric spinal curve fitting is a robust tool that can be used to quantify the 3D deformation of AIS and possibly exploited as an index to classify the 3D shape. PMID:24370854

Kadoury, Samuel; Shen, Jesse; Parent, Stefan

2014-04-01

352

Generalized Hodge dual for torsion in teleparallel gravity  

E-print Network

For teleparallel gravity in four dimensions, Lucas and Pereira have shown that a generalized Hodge dual for torsion tensor can be defined with coefficients determined by mathematical consistency. In this note, we extend their approach to general dimensions. We find that the generalized Hodge dual must be defined twofold, while the first Hodge dual operation coincides exactly with that of LP, the second Hodge dual operation needs new definition required by consistency.

Peng Huang; Fang-Fang Yuan

2014-08-27

353

Ab initio torsional potential and transition frequencies of acetaldehyde  

Microsoft Academic Search

High-level ab initio electronic structure calculations, including extrapolations to the complete basis set limit as well as relativistic and diagonal Born-Oppenheimer corrections, resulted in a torsional potential of acetaldehyde in its electronic ground state. This benchmark-quality potential fully reflects the symmetry and internal rotation dynamics of this molecule [J. Chem. Phys. 117, 6489 (2002)] in the energy range probed by

Attila G. Császár; Viktor Szalay; Maria L. Senent

2004-01-01

354

Effect of inner ring centrifugal displacement on the dynamic characteristics of high-speed angular contact ball bearing  

Microsoft Academic Search

According to the elastic theory the calculating formulas of inner ring centrifugal displacement are inferred, in consideration of inner ring centrifugal displacement the basic equations of angular contact ball bearing are set up, effect of inner ring centrifugal displacement on the dynamic characteristics of high-speed angular contact ball bearings are studied. The results from taking 7012C bearing as an example

Wang Bao-min; Mei Xue-song; Hu Chi-bing; Wu Zai-xin

2010-01-01

355

Friction and shear fracture of an adhesive contact under torsion  

NASA Astrophysics Data System (ADS)

The shear failure or stiction of an adhesive contact between a poly(dimethylsiloxane) (PDMS) rubber and a glass lens has been investigated using a torsional contact configuration. As compared to linear sliding, torsion presents the advantage of inducing a shear failure under a pure mode III condition, while preserving the cylindrical symmetry of the contact. The surface of the transparent PDMS substrate was marked using a network of dots in order to monitor continuously the in-plane surface displacements during the stiction process. Using a previously developed inversion procedure (A. Chateauminois and C. Fretigny, Eur. Phys. J. E 27, 221 (2008)), the corresponding surface shear stress distributions were obtained from the displacement fields. Stiction was found to involve the progressive shrinkage of a central adhesive zone surrounded by an annular microslip region. Adhesion effects were especially evidenced from a stress overshoot at the boundary of the adhesive zone. The experimental data were analysis using an extension to torsional contact of the Maugis-Dugdale approach’s to adhesive contacts which takes into account frictional effects. This model allowed to extract an effective adhesion energy in the presence of friction, which dependence on kinetics effect is briefly discussed.

Chateauminois, Antoine; Fretigny, Christian; Olanier, Ludovic

2010-02-01

356

Torsional wave experiments with a new magnetostrictive transducer configuration.  

PubMed

For the efficient long-range nondestructive structural health inspection of pipes, guided waves have become widely used. Among the various guided wave modes, the torsional wave is most preferred since its first branch is nondispersive. Our objective in this work is to develop a new magnetostrictive transducer configuration to transmit and receive torsional waves in cylindrical waveguides. The conventional magnetostrictive transducer for the generation and measurement of torsional waves consists of solenoid coils and a nickel strip bonded circumferentially to test pipes. The strip must be premagnetized by a permanent magnet before actual measurements. Because of the premagnetization, the transducer is not suitable for the long-term on-line monitoring of pipes buried underground. To avoid the cumbersome premagnetization and to improve the transduction efficiency, we propose a new transducer configuration using several pieces of nickel strips installed at 45 degrees with respect to the pipe axis. If a static bias magnetic field is also applied, the transducer output can be substantially increased. Several experiments were conducted to study the performance of the proposed transducer configuration. The proposed transducer configuration was also applied for damage detection in an aluminum pipe. PMID:16018450

Kim, Yoon Young; Park, Chan Il; Cho, Seung Hyun; Han, Soon Woo

2005-06-01

357

Optical diagnosis of testicular torsion: feasibility and methodology  

NASA Astrophysics Data System (ADS)

Background: Torsion of the testis compromises blood flow through the spermatic cord; testicular ischemia results which if not diagnosed promptly and corrected surgically irrevocably damages the testis. Current diagnostic modalities aimed at rationalizing surgical exploration by demonstrating interruption of spermatic cord blood flow or testicular ischemia have limited applicability. Near infrared spectroscopy (NIRS) offers a non-invasive optical method for detection of ischemia; continuous wave and frequency domain devices have been used experimentally; no device customized for clinical use has been designed. Methods: A miniature spatially resolved NIRS device with light emitting diode light source was applied over the right and left spermatic cord and the difference in oxygen saturation between the two sides measured. Results: In a 14-month old boy with a history of unilateral testicular pain color Doppler ultrasonography was equivocal but the NIRS-derived tissue oxygen saturation index (TSI) was significantly reduced on the left side. Confirmation of torsion of the left testicle was made surgically. Conclusions: Spatially resolved NIRS monitoring of spermatic cord oxygen saturation is feasible in children, adding to prior studies of testicular oxygen saturation in adults. Customized device design and further clinical trials would enhance the applicability of NIRS as a diagnostic entity for torsion.

Shadgan, Babak; Macnab, Andrew; Stothers, Lynn; Kajbafzadeh, A. M.

2014-03-01

358

Direct excitation of resonant torsional Alfven waves by footpoint motions.  

NASA Astrophysics Data System (ADS)

The present paper studies the heating of coronal loops by linear resonant Alfven waves that are excited by the motions of the photospheric footpoints of the magnetic field lines. The analysis is restricted to torsionally polarised footpoint motions in an axially symmetric system so that only torsional Alfven waves are excited. For this subclass of footpoint motions, the Alfven and cusp singularities are absent from the analysis which means that resonant coupling between global modes of the loop and localised oscillations is avoided. Instead, the focus is on the resonances due to the finite extent of the loop in the longitudinal direction: at the radii where Alfven waves travelling back and forth along the length of the loop are in phase with the footpoint motions, the oscillations grow unbounded in ideal MHD. Inclusion of electrical resistivity and viscosity as dissipation mechanisms prevents singular growth and we can look at the steady state in which the energy injected at the photospheric part of the loop is balanced by the energy dissipated at the dissipative layer around the resonance. In this sense, we show that the direct excitation of Alfven waves by torsionally polarised footpoint motions leads to a very efficient heating mechanism for coronal loops, even without resonant coupling to global modes.

Ruderman, M. S.; Berghmans, D.; Goossens, M.; Poedts, S.

1997-04-01

359

Torsional stiffness degradation and aerostatic divergence of suspension bridge decks  

NASA Astrophysics Data System (ADS)

The mechanism of aerostatic torsional divergence (ATD) of long-span suspension bridges is investigated. A theoretical analysis on the basis of a generalized model is presented, showing that the vertical motion of a bridge deck is crucial to the torsional stiffness of the whole suspended system, and that the vertical motion of either cable with a magnitude beyond a certain threshold could result in a sudden degradation of the torsional stiffness of the system. This vertical motion-induced degradation of stiffness is recognized as the main reason for the ATD. Long-span suspension bridges are susceptible to such a type of divergence, especially when they are immersed in turbulent wind fields. The divergences that occur in turbulent wind fields differ significantly from those in smooth wind fields, and the difference is well explained by the generalized model that the loosening of any one cable could result in the vanishing of the part of stiffness provided by the whole cable system. The mechanism revealed in this paper leads to a definition of the critical wind speed of the ATD in a turbulent flow; that is, the one resulting in a vertical motion so large as to loosen either cable to a stressless state. Numerical results from the nonlinear finite-element (FE) analysis of the Xihoumen suspension bridge, in conjunction with observations from wind tunnel tests on an aero-elastic full bridge model, are in support of the viewpoint presented in this study.

Zhang, Z. T.; Ge, Y. J.; Yang, Y. X.

2013-07-01

360

BCN Nanotubes as Highly Sensitive Torsional Electromechanical Transducers.  

PubMed

Owing to their mechanically tunable electronic properties, carbon nanotubes (CNTs) have been widely studied as potential components for nanoelectromechanical systems (NEMS); however, the mechanical properties of multiwall CNTs are often limited by the weak shear interactions between the graphitic layers. Boron nitride nanotubes (BNNTs) exhibit a strong interlayer mechanical coupling, but their high electrical resistance limits their use as electromechanical transducers. Can the outstanding mechanical properties of BNNTs be combined with the electromechanical properties of CNTs in one hybrid structure? Here, we report the first experimental study of boron carbonitride nanotube (BCNNT) mechanics and electromechanics. We found that the hybrid BCNNTs are up to five times torsionally stiffer and stronger than CNTs, thereby retaining to a large extent the ultrahigh torsional stiffness of BNNTs. At the same time, we show that the electrical response of BCNNTs to torsion is 1 to 2 orders of magnitude higher than that of CNTs. These results demonstrate that BCNNTs could be especially attractive building blocks for NEMS. PMID:25275220

Garel, Jonathan; Zhao, Chong; Popovitz-Biro, Ronit; Golberg, Dmitri; Wang, Wenlong; Joselevich, Ernesto

2014-11-12

361

Transverse and torsional modes of vibration of American organ reeds  

NASA Astrophysics Data System (ADS)

A reed from an American reed organ consists of a brass tongue riveted to a frame with an opening just large enough for the reed to pass through during the course of its oscillation. To a first approximation, the reed tongue can be modeled as a cantilever beam of uniform cross section, and the mode frequencies of transverse and torsional modes can be calculated. The reeds used in this study differ from this simple model in several ways, including a nonuniform thickness along the reed length. In addition, the reed includes a curved spoon-like section at the tip of the reed tongue as well as an asymmetric twist at the tip. Transverse and torsional modes of vibration of a mechanically excited reed tongue have been studied using a proximity sensor (variable impedance transducer), a laser vibrometer, and a TV holography system. The motion of the air-driven reed has also been investigated. Although the motion of air-driven reed is dominated by the first transverse mode, some evidence of higher-order transverse modes and torsional modes has been observed. [Work supported by the NSF from REU Grant No. 0139096.

Dirksen, Blake M.; Cottingham, James P.

2002-11-01

362

Effects of High-Frequency Torsional Impacts on Rock Drilling  

NASA Astrophysics Data System (ADS)

High-frequency torsional impact drilling (HFTID) is a new technology which provides stable and efficient drilling. The goal of the present study is to investigate the effects of high-frequency torsional impacts on rock drilling. The impact parameters of the high-frequency torsional impact generator (HFTIG) are obtained by conducting a series of laboratory tests. The results of the tests reveal that the impact time decreases and the impact force increases with increasing impact frequency. The parameters are used as input for simulations of the rock crushing process, and a series of models for investigating the respective performance of HFTID and conventional drilling are developed. In addition, the Drucker-Prager criterion is used to describe the constitutive laws of the rock element, and the equivalent plastic strain criterion is adopted as the damage criterion. The models are run to simulate the dynamic rock crushing processes. The results of the simulations show that increase of the impact frequency results in a significant improvement in the rate of penetration (ROP), and a decrease in the life of the HFTIG. Considering the tool life and ROP, the optimum impact frequency of the HFTIG is 15 Hz. Finally, the performance of the HFTID technique is evaluated.

Zhu, Xiaohua; Tang, Liping; Tong, Hua

2014-07-01

363

Development of a torsion balance for adhesion measurements  

NASA Technical Reports Server (NTRS)

A new torsion balance for study of adhesion in ceramics is discussed. A torsion wire and a linear variable differential transformer are used to monitor load and to measure pull-off force (adhesion force). The investigation suggests that this torsion balance is valuable in studying the interfacial properties of ceramics in controlled environments such as in ultrahigh vacuum. The pull-off forces measured in dry, moist, and saturated nitrogen atmosphere demonstrate that the adhesion of silicon nitride contacts remains low at humidities below 80 percent but rises rapidly above that. The adhesion at saturation is 10 times or more greater than that below 80 percent relative humidity. The adhesion in a saturated atmosphere arises primarily from the surface tension effects of a thin film of water adsorbed on the surface. The surface tension of the water film was 58 x 10 to the minus 5 to 65 x 10 to the minus 5 power. The accepted value for water is 72.7 x 10 to the minus 5 power N/cm. Adhesion characteristics of silicon nitride in contact with metals, like the friction characteristics of silicon carbide to metal contacts, can be related to the relative chemical activity of metals in ultrahigh vacuum. The more active the metal, the higher the adhesion.

Miyoshi, Kazuhisa; Maeda, Chikayoshi; Masuo, Ryuichi

1988-01-01

364

Confirmed testicular torsion in a 67 year old  

PubMed Central

Torsion amongst the elderly population is rarely described. This case presents the oldest surgically confirmed case of testicular torsion, in a 67-year-old male, within the UK. Presenting to the emergency department with a 10-day history of left-sided testicular pain, initially treated with antibiotics. There was no pyrexia or urinary symptoms and negative urine dipstick. In adults above the age of 40, likely diagnoses include epididymo-orchitis, epididymitis, neoplasm or hydrocele. Clinical differentiation with epididymo-orchitis can be difficult in any age range. Clinical signs such as fever, elevated C-reactive protein and positive urine dipstick test are suggestive of epididymo-orchitis/orchitis. This case study demonstrates that testicular torsion can occur at any age, and clinical suspicion should always be high in patients presenting with testicular pain and a negative urine dipstick, regardless of age. Although risk in this subgroup is low, the identification of a potentially reversible testicular abnormality should be of high priority. PMID:24876322

Farrington, Nicola L.; Lucky, Marc A.; Barnes, Thomas; Calvert, Robert

2014-01-01

365

Confirmed testicular torsion in a 67 year old.  

PubMed

Torsion amongst the elderly population is rarely described. This case presents the oldest surgically confirmed case of testicular torsion, in a 67-year-old male, within the UK. Presenting to the emergency department with a 10-day history of left-sided testicular pain, initially treated with antibiotics. There was no pyrexia or urinary symptoms and negative urine dipstick. In adults above the age of 40, likely diagnoses include epididymo-orchitis, epididymitis, neoplasm or hydrocele. Clinical differentiation with epididymo-orchitis can be difficult in any age range. Clinical signs such as fever, elevated C-reactive protein and positive urine dipstick test are suggestive of epididymo-orchitis/orchitis. This case study demonstrates that testicular torsion can occur at any age, and clinical suspicion should always be high in patients presenting with testicular pain and a negative urine dipstick, regardless of age. Although risk in this subgroup is low, the identification of a potentially reversible testicular abnormality should be of high priority. PMID:24876322

Farrington, Nicola L; Lucky, Marc A; Barnes, Thomas; Calvert, Robert

2014-01-01

366

Characterizing conformation changes in proteins through the torsional elastic response.  

PubMed

The relationship between functional conformation changes and thermal dynamics of proteins is investigated with the help of the torsional network model (TNM), an elastic network model in torsion angle space that we recently introduced. We propose and test a null-model of "random" conformation changes that assumes that the contributions of normal modes to conformation changes are proportional to their contributions to thermal fluctuations. Deviations from this null model are generally small. When they are large and significant, they consist in conformation changes that are represented by very few low frequency normal modes and overcome small energy barriers. We interpret these features as the result of natural selection favoring the intrinsic protein dynamics consistent with functional conformation changes. These "selected" conformation changes are more frequently associated to ligand binding, and in particular phosphorylation, than to pairs of conformations with the same ligands. This deep relationship between the thermal dynamics of a protein, represented by its normal modes, and its functional dynamics can reconcile in a unique framework the two models of conformation changes, conformational selection and induced fit. The program TNM that computes torsional normal modes and analyzes conformation changes is available upon request. This article is part of a Special Issue entitled: The emerging dynamic view of proteins: Protein plasticity in allostery, evolution and self-assembly. PMID:23429178

Dos Santos, Helena G; Klett, Javier; Méndez, Raúl; Bastolla, Ugo

2013-05-01

367

Rotation of Electromagnetic Fields and the Nature of Optical Angular Momentum  

PubMed Central

The association of spin and orbital angular momenta of light with its polarization and helical phase fronts is now well established. The problems in linking this with electromagnetic theory, as expressed in Maxwell's equations, are rather less well known. We present a simple analysis of the problems involved in defining spin and orbital angular momenta for electromagnetic fields and discuss some of the remaining challenges. Crucial to our investigation is the duplex symmetry between the electric and magnetic fields. PMID:24808629

Barnett, Stephen M.

2010-01-01

368

Symmetric angular momentum coupling, the quantum volume operator and the 7-spin network: a computational perspective  

E-print Network

A unified vision of the symmetric coupling of angular momenta and of the quantum mechanical volume operator is illustrated. The focus is on the quantum mechanical angular momentum theory of Wigner's 6j symbols and on the volume operator of the symmetric coupling in spin network approaches: here, crucial to our presentation are an appreciation of the role of the Racah sum rule and the simplification arising from the use of Regge symmetry. The projective geometry approach permits the introduction of a symmetric representation of a network of seven spins or angular momenta. Results of extensive computational investigations are summarized, presented and briefly discussed.

Marinelli, Dimitri; Aquilanti, Vincenzo; Anderson, Roger W; Bitencourt, Ana Carla P; Ragni, Mirco

2014-01-01

369

Symmetric angular momentum coupling, the quantum volume operator and the 7-spin network: a computational perspective  

E-print Network

A unified vision of the symmetric coupling of angular momenta and of the quantum mechanical volume operator is illustrated. The focus is on the quantum mechanical angular momentum theory of Wigner's 6j symbols and on the volume operator of the symmetric coupling in spin network approaches: here, crucial to our presentation are an appreciation of the role of the Racah sum rule and the simplification arising from the use of Regge symmetry. The projective geometry approach permits the introduction of a symmetric representation of a network of seven spins or angular momenta. Results of extensive computational investigations are summarized, presented and briefly discussed.

Dimitri Marinelli; Annalisa Marzuoli; Vincenzo Aquilanti; Roger W. Anderson; Ana Carla P. Bitencourt; Mirco Ragni

2014-10-04

370

Preliminary determination of Newtonian gravitational constant with angular acceleration feedback method.  

PubMed

This paper describes the preliminary measurement of the Newtonian gravitational constant G with the angular acceleration feedback method at HUST. The apparatus has been built, and preliminary measurement performed, to test all aspects of the experimental design, particularly the feedback function, which was recently discussed in detail by Quan et al. The experimental results show that the residual twist angle of the torsion pendulum at the signal frequency introduces 0.4?ppm to the value of G. The relative uncertainty of the angular acceleration of the turntable is approximately 100?ppm, which is mainly limited by the stability of the apparatus. Therefore, the experiment has been modified with three features: (i) the height of the apparatus is reduced almost by half, (ii) the aluminium shelves were replaced with shelves made from ultra-low expansion material and (iii) a perfect compensation of the laboratory-fixed gravitational background will be carried out. With these improvements, the angular acceleration is expected to be determined with an uncertainty of better than 10?ppm, and a reliable value of G with 20?ppm or below will be obtained in the near future. PMID:25201996

Xue, Chao; Quan, Li-Di; Yang, Shan-Qing; Wang, Bing-Peng; Wu, Jun-Fei; Shao, Cheng-Gang; Tu, Liang-Cheng; Milyukov, Vadim; Luo, Jun

2014-10-13

371

Angular distributions as lifetime probes  

NASA Astrophysics Data System (ADS)

If new TeV scale particles are discovered, it will be important to determine their width. There is, however, a problematic region, where the width is too small to be determined directly, and too large to generate a secondary vertex. For a collection of colored, spin polarized particles, hadronization depolarizes the particles prior to their decay. The amount of depolarization can be used to probe the lifetime in the problematic region. In this paper we apply this method to a realistic scenario of a top-like particle that can be produced at the LHC. We study how depolarization affects the angular distributions of the decay products and derive an equation for the distributions that is sensitive to the lifetime.

Dror, Jeff Asaf; Grossman, Yuval

2014-06-01

372

PP-waves with torsion: a metric-affine model for the massless neutrino  

NASA Astrophysics Data System (ADS)

In this paper we deal with quadratic metric-affine gravity, which we briefly introduce, explain and give historical and physical reasons for using this particular theory of gravity. Further, we introduce a generalisation of well known spacetimes, namely pp-waves. A classical pp-wave is a 4-dimensional Lorentzian spacetime, which admits a nonvanishing parallel spinor field; here the connection is assumed to be Levi-Civita. This definition was generalised in our previous work to metric compatible spacetimes with torsion and used to construct new explicit vacuum solutions of quadratic metric-affine gravity, namely generalised pp-waves of parallel Ricci curvature. The physical interpretation of these solutions we propose in this article is that they represent a conformally invariant metric-affine model for a massless elementary particle. We give a comparison with the classical model describing the interaction of gravitational and massless neutrino fields, namely Einstein-Weyl theory and construct pp-wave type solutions of this theory. We point out that generalised pp-waves of parallel Ricci curvature are very similar to pp-wave type solutions of the Einstein-Weyl model and therefore propose that our generalised pp-waves of parallel Ricci curvature represent a metric-affine model for the massless neutrino.

Pasic, Vedad; Barakovic, Elvis

2014-10-01

373

Rotational Energies in Various Torsional Levels of CH_2DOH  

NASA Astrophysics Data System (ADS)

Using an approach accounting for the hindered internal rotation of a monodeuterated methyl group, an analysis of the torsional spectrum of the monodeuterated species of methanol CH_2DOH has been carried out recently and led to the assignment of 76 torsional subbands in its microwave, FIR, and IR spectra. Although this approach also allowed us to account for subband centers, the rotational structure of the torsional subbands is not well understood yet. In this paper, we will deal with the rotational energies of CH_2DOH. Analyses of the rotational structure of the available subbands^b have been performed using the polynomial-type expansion introduced in the case of the normal species of methanol. For each subband, FIR or IR transitions and a-type microwave lines, within the lower torsional level, were fitted. The frequencies of the latters were taken from previous investigations or from new measurements carried out from 50 to 950 GHz with the submillimeterwave solid state spectrometer in Lille. Subbands involving lower levels with v_t=0 and K ? 3 could be satisfactorily analyzed. For levels characterized by lower K-values, the expansion fails. In the case of the K=1, v_t=1 level, the frequencies of a-type microwave transitions involving the lower member of the K-type doublet cannot be well reproduced. For K=0 levels with v_t=1 and 2, a large number of terms is needed in the expansion. We will try to understand why the rotational energies of these levels cannot be reproduced. The results of the analyses will be compared to those obtained with a global approach based on the rotation-torsion Hamiltonian of the molecule. [2] El Hilali, Coudert, Konov, and Klee, J. Chem. Phys. 135 (2011) 194309. [3] Ioli, Moruzzi, Riminucci, Strumia, Moraes, Winnewisser, and Winnewisser, J. Mol. Spec. 171 (1995) 130. [4] Quade and Suenram, J. Chem. Phys. 73 (1980) 1127; and Su and Quade, J. Mol. Spec. 134 (1989) 290. [5] Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spec. 256 (2009) 204.

Coudert, L. H.; Hilali, A. El; Margulès, L.; Motiyenko, R. A.; Klee, S.

2012-06-01

374

Evidence that gastropod torsion is driven by asymmetric cell proliferation activated by TGF-? signalling  

PubMed Central

Gastropods are characterized by their asymmetric bodyplan, which develops through a unique ontogenetic process called ‘torsion’. Despite several intensive studies, the driving force of torsion remains to be determined. Although torsion was traditionally believed to be driven by contraction of the retractor muscle connecting the foot and the shell, some recent reports cast doubt on that idea. Here, we report that torsion is accompanied by left–right asymmetric cell proliferation in the mantle epithelium in the limpet Nipponacmea fuscoviridis. Furthermore, we found that pharmacological inhibition of the transforming growth factor-? (TGF-?) signalling pathway, including that of Nodal, blocked torsion. We confirmed that the blocking was brought about through failure of the activation of cell proliferation in the right-hand side of the mantle epithelium, while the retractor muscle apparently developed normally. These results suggest that limpet torsion is driven by left–right asymmetric cell proliferation in the mantle epithelium, induced by the TGF-? pathway. PMID:21525052

Kurita, Yoshihisa; Wada, Hiroshi

2011-01-01

375

Angular correlations in Auger and fluorescence cascades  

NASA Astrophysics Data System (ADS)

Angular correlations in cascades of Auger electrons and X-rays (fluorescence) are discussed. These correlations can be studied by angle-resolved coincidence measurements of two sequential emissions of Auger electrons and/or fluorescence photons. A general expression for the angular correlation function for two sequential radiation is obtained using the density matrix and statistical tensor formalism. As an example, the cascades in inner-shell atomic photoionization and photoexcitation are considered. Spectroscopic and dynamic information which can be gained from angular correlation measurement in cascade transitions is discussed. Finally, the alignment transfer and non-coincidence measurements of the angular distribution of any radiation from a cascade are discussed.

Kabachnik, Nicolai M.

1997-01-01

376

Modular Approach to Physics: Angular Velocity  

NSDL National Science Digital Library

This web page contains an interactive simulation for introductory physics students describing different types of motion in term of angular coordinates. It consists of a moving car, a graph of angular velocity vs. time, and real-time values for areal and angular velocity. The path of the car can be a straight line, a circle, or a parabola with the angular motion given relative to a fixed point. This item is part of a larger collection of physics simulations sponsored by the MAP project (Modular Approach to Physics).

Austin, David; Martin, Brian

2008-08-03

377

Quantum theory on protein folding  

NASA Astrophysics Data System (ADS)

The conformational change of biological macromolecule is investigated from the point of quantum transition. A quantum theory on protein folding is proposed. Compared with other dynamical variables such as mobile electrons, chemical bonds and stretching-bending vibrations the molecular torsion has the lowest energy and can be looked as the slow variable of the system. Simultaneously, from the multi-minima property of torsion potential the local conformational states are well defined. Following the idea that the slow variables slave the fast ones and using the nonadiabaticity operator method we deduce the Hamiltonian describing conformational change. It is shown that the influence of fast variables on the macromolecule can fully be taken into account through a phase transformation of slow variable wave function. Starting from the conformation-transition Hamiltonian the nonradiative matrix element was calculated and a general formulas for protein folding rate was deduced. The analytical form of the formula was utilized to study the temperature dependence of protein folding rate and the curious non-Arrhenius temperature relation was interpreted. By using temperature dependence data the multi-torsion correlation was studied. The decoherence time of quantum torsion state is estimated. The proposed folding rate formula gives a unifying approach for the study of a large class problems of biological conformational change.

Luo, LiaoFu

2014-01-01

378

Continuous Theta Burst Stimulation of Angular Gyrus Reduces Subjective Recollection  

PubMed Central

The contribution of lateral parietal regions such as the angular gyrus to human episodic memory has been the subject of much debate following widespread observations of left parietal activity in healthy volunteers during functional neuroimaging studies of memory retrieval. Patients with lateral parietal lesions are not amnesic, but recent evidence indicates that their memory abilities may not be entirely preserved. Whereas recollection appears intact when objective measures such as source accuracy are used, patients often exhibit reduced subjective confidence in their accurate recollections. When asked to recall autobiographical memories, they may produce spontaneous narratives that lack richness and specificity, but can remember specific details when prompted. Two distinct theoretical accounts have been proposed to explain these results: that the patients have a deficit in the bottom-up capturing of attention by retrieval output, or that they have an impairment in the subjective experience of recollection. The present study aimed to differentiate between these accounts using continuous theta burst stimulation (cTBS) in healthy participants to disrupt function of specific left parietal subregions, including angular gyrus. Inconsistent with predictions of the attentional theory, angular gyrus cTBS did not result in greater impairment of free recall than cued recall. Supporting predictions of the subjective recollection account, temporary disruption of angular gyrus was associated with highly accurate source recollection accuracy but a selective reduction in participants’ rated source confidence. The findings are consistent with a role for angular gyrus in the integration of memory features into a conscious representation that enables the subjective experience of remembering. PMID:25333985

Yazar, Yasemin; Bergstrom, Zara M.; Simons, Jon S.

2014-01-01

379

Angular Power Spectrum in Modular Invariant Inflation Model  

SciTech Connect

A scalar potential of inflation is proposed and the angular power spectra of the adiabatic density perturbations are computed. The potential consists of three scalar fields, S, Y and T, together with two free parameters. By fitting the parameters to cosmological data at the fixed point T = 1, we find that the potential behaves like the single-field potential of S, which slowly rolls down. We further show that the inflation predictions corresponding to this potential provide a good fit to the recent three-year WMAP data, e.g. the spectral index n{sub s} = 0.951.The TT and TE angular power spectra obtained from our model almost completely coincide with the corresponding results obtained from the {lambda}CDM model. We conclude that our model is considered to be an adequate theory of inflation that explains the present data.

Hayashi, Mitsuo J.; Okame, Y.; Takagi, K.; Watanabe, T. [Department of Physics, Tokai University, 1117 Kitakaname, Hiratsuka, 259-1292 (Japan); Hirai, S.; Takami, T. [Department of Digital Games, Osaka Electro-Communication University, 1130-70 Kiyotaki, Shijonawate, Osaka, 575-0063 (Japan)

2008-05-29

380

Secondary-Structure Design of Proteins by a Backbone Torsion Energy  

Microsoft Academic Search

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

Yoshitake Sakae; Yuko Okamoto

2006-01-01

381

The protective role of erdosteine on testicular tissue after testicular torsion and detorsion  

Microsoft Academic Search

Testicular torsion and detorsion are important clinical problems for infertile man and oxidative stress may have a role in\\u000a this clinical situation. The aim of this study was to investigate the protective role of erdosteine, an antioxidant, on unilateral\\u000a testicular reperfusion injury in rats. The rats were divided into four groups including seven rats in each group: control,\\u000a torsion, torsion\\/detorsion

Ahmet Koc; Adnan Narci; Mehmet Duru; H. Serdar Gergerlioglu; Yesim Akaydin; Sadik Sogut

2005-01-01

382

3D Curves With a Prescribed Curvature and Torsion for a Flying Robot  

SciTech Connect

The objective of this paper is to generate a desired flight path to be followed by an flying robot. A curve with discontinuous curvature and torsion is not appropriate for smooth motions for any vehicle architecture. Three different classes of curves are presented. First, constant curvature and torsion followed by a linear variation versus the curvilinear abscissa then a quadratic variation. Finally, the problem of maneuvers between two trim helices of different curvature and torsion is tackled with.

Bestaoui, Yasmina [Informatics, Integrative Biology and Complex Systems, University of Evry 40 Rue de Pelvoux, 91020 Evry Cedex (France)

2008-06-12

383

Interaction between torsional and lateral vibrations in flexible rotor systems with discontinuous friction  

Microsoft Academic Search

In this paper, we analyze the interaction between friction-induced vibrations and self-sustained lateral vibrations caused\\u000a by a mass-unbalance in an experimental rotor dynamic setup. This study is performed on the level of both numerical and experimental\\u000a bifurcation analyses. Numerical analyses show that two types of torsional vibrations can appear: friction-induced torsional\\u000a vibrations and torsional vibrations due to the coupling between

N. Mihajlovi?; N. van de Wouw; P. C. J. N. Rosielle; H. Nijmeijer

2007-01-01

384

The vibrationally adiabatic torsional potential energy surface of trans-stilbene  

Microsoft Academic Search

The effect of vibrational Zero Point Energy (ZPE) on the torsional barriers of trans-stilbene is studied in the adiabatic approximation. The two torsional modes corresponding to phenyl rotation are explicitly separated, and the remaining modes are treated as normal coordinates. ZPE reduces the adiabatic barrier along the in-phase torsion from 198 to 13cm?1. A one-dimensional adiabatic potential for the anti-phase

Praveen D. Chowdary; Todd J. Martinez; Martin Gruebele

2007-01-01

385

Torsional profile of 2,2,2-trifluoroethanol: A theoretical analysis with basis set extrapolation  

NASA Astrophysics Data System (ADS)

The conformational potential for rotation around the C bond C bond O bond H torsional angle of 2,2,2-trifluoroethanol (TFE) has been investigated at second-order Möller-Plesset (MP2) perturbation theory with two series of Dunning's correlation consistent basis sets, cc-pVNZ and aug-cc-pVNZ, N = D, T, Q, and 5. Single-point energy calculations with MP4(SDQ)/(aug-)cc-pVTZ and MP4(SDQT)/cc-pVTZ were also performed. It was found that the geometries of stationary points on this conformational profile are dependent on the basis set size, particularly the torsional angle of the gauche-isomer and the transition structure between the gauche- and anti-isomers (from 61° and 142°, respectively, at cc-pVDZ, to 65° and 149° at aug-cc-pVQZ), requiring at least a aug-cc-pVTZ basis set to be correctly optimized. Additionaly, an even lower barrier height (as low as 0.04 kcal/mol) than that previously calculated by Senent et al. for the conversion of anti-TFE to its more stable (by about 1.95 kcal/mol) gauche-conformer has been obtained, which reinforces the prediction that the main, if not the only, component of TFE in gas phase is its gauche-isomer. The MP2 data were also used in different schemes of basis set extrapolation. Unfortunately, maybe because third-order correlation energy contributions were not considered, these schemes have failed in providing suitable extrapolated energies.

de Amorim, Mauro B.

386

High precision micro-impulse measurements for micro-thrusters based on torsional pendulum and sympathetic resonance techniques  

NASA Astrophysics Data System (ADS)

A sympathetic resonance theory is analyzed and applied in a newly developed torsional pendulum to measure the micro-impulse produced by a ?N s-class ablative pulsed plasma thruster. According to theoretical analysis on the dynamical behaviors of a torsional pendulum, the resonance amplification effect of micro-signals is presented. In addition, a new micro-impulse measurement method based on sympathetic resonance theory is proposed as an improvement of the original single pulse measurement method. In contrast with the single pulse measurement method, the advantages of sympathetic resonance method are significant. First, because of the magnification of vibration signals due to resonance processes, measurement precision for the sympathetic resonance method becomes higher especially in reducing reading error. With an increase in peak number, the relative errors induced by readout of voltage signals decrease to approximately ±1.9% for the sympathetic resonance mode, whereas the relative error in single pulse mode is estimated as ±13.4%. Besides, by using the resonance amplification effect the sympathetic resonance method makes it possible to measure an extremely low-impulse beyond the resolution of a thrust stand without redesigning or purchasing a new one. Moreover, because of the simple operational principle and structure the sympathetic resonance method is much more convenient and inexpensive to be implemented than other high-precision methods. Finally, the sympathetic resonance measurement method can also be applied in other thrust stands to improve further the ability to measure the low-impulse bits.

Zhang, Daixian; Wu, Jianjun; Zhang, Rui; Zhang, Hua; He, Zhen

2013-12-01

387

Stability of elastic bending and torsion of uniform cantilever rotor blades in hover with variable structural coupling  

NASA Technical Reports Server (NTRS)

The stability of elastic flap bending, lead-lag bending, and torsion of uniform, untwisted, cantilever rotor blades without chordwise offsets between the elastic, mass, tension, and areodynamic center axes is investigated for the hovering flight condition. The equations of motion are obtained by simplifying the general, nonlinear, partial differential equations of motion of an elastic rotating cantilever blade. The equations are adapted for a linearized stability analysis in the hovering flight condition by prescribing aerodynamic forces, applying Galerkin's method, and linearizing the resulting ordinary differential equations about the equilibrium operating condition. The aerodynamic forces are obtained from strip theory based on a quasi-steady approximation of two-dimensional unsteady airfoil theory. Six coupled mode shapes, calculated from free vibration about the equilibrium operating condition, are used in the linearized stability analysis. The study emphasizes the effects of two types of structural coupling that strongly influence the stability of hingeless rotor blades. The first structural coupling is the linear coupling between flap and lead-lag bending of the rotor blade. The second structural coupling is a nonlinear coupling between flap bending, lead-lag bending, and torsion deflections. Results are obtained for a wide variety of hingeless rotor configurations and operating conditions in order to provide a reasonably complete picture of hingeless rotor blade stability characteristics.

Hodges, D. H., Roberta.

1976-01-01

388

Femoral torsion: reliability and validity of the trochanteric prominence angle test.  

PubMed

Influence of femoral torsion on femoroacetabular impingement and other hip conditions is not well documented and its assessment by imaging methods during clinical work-up is not routinely performed. We studied whether physical examination could reliably measure or at least screen for gross anomalies of femoral torsion or if appropriate imaging should routinely be performed. Assessing femoral torsion of 45 volunteers using the "trochanteric prominence angle test" and magnetic resonance imaging (MRI), inter- and intra-observer reliability ranged from poor to moderate and agreement with MRI values was only fair. Considering a 5° to 10° difference of femoral torsion as clinically relevant, physical examination failed to match MRI values within ±10° in more than 50%. Arbitrarily defining thresholds for pathological femoral torsion, the "trochanteric prominence angle test" could not recognise torsions outside the >30°/<0° range and diagnosed torsions outside the >20°/<10° range with a sensitivity of 18%-75% and a specificity of 58%-98% only. Physical assessment of femoral torsion using the "trochanteric prominence angle test" does not allow reliable measurement or screening for gross anomalies. We therefore integrate an adapted MRI protocol allowing measurement of femoral torsion within our clinical work up. PMID:22865252

Maier, Claudia; Zingg, Patrick; Seifert, Burkhardt; Sutter, Reto; Dora, Claudio

2012-01-01

389

Measurement of the angular position of a human extremity based on a multifunctional approach  

NASA Astrophysics Data System (ADS)

A novel method for measuring the three-dimensional joint angles of a human extremity simultaneously is presented based on a multifunctional sensing approach. The method proposes a simple and single configuration with minimum sensing elements, which is able to convert obliquity, bending direction and torsion angle to the linear movements of three wires by imitating the status of the skin on the joint using a flexible tube. A prototype is built with three inductances as its outputs, whose results examine the feasibility of the proposed method and give satisfactory accuracy. A simple algorithm to reconstruct three angular parameters is able to provide real-time analysis. The system is multifunctional, easily mountable, low cost and can be used for long-term monitoring of human extremities such as the arm, knee and shoulder.

Quan, Wei; Shida, Katsunori

2007-07-01

390

Optical angular motion sensor, phase 1  

Microsoft Academic Search

The optical angular motion sensor (OAMS) program, phase I, consisted of the design, fabrication, test and analysis of a triaxial angular motion sensor. A brassboard system was fabricated and assembled. It included a transmitter, a receiver assembly and an electronics assembly. The alignment information was transmitted between the transmitter and receiver on three discrete polarized light beams. The detail design

H. T. Braswell; J. W. Fontenot; L. L. Hartley; B. F. Heinrich; W. E. Miller; N. J. Ockman; S. W. Paulson; J. R. Taylor

1975-01-01

391

Angular-Rate Estimation Using Quaternion Measurements  

NASA Technical Reports Server (NTRS)

In most spacecraft (SC) there is a need to know the SC angular rate. Precise angular rate is required for attitude determination, and a coarse rate is needed for attitude control damping. Classically, angular rate information is obtained from gyro measurements. These days, there is a tendency to build smaller, lighter and cheaper SC, therefore the inclination now is to do away with gyros and use other means and methods to determine the angular rate. The latter is also needed even in gyro equipped satellites when performing high rate maneuvers whose angular-rate is out of range of the on board gyros or in case of gyro failure. There are several ways to obtain the angular rate in a gyro-less SC. When the attitude is known, one can differentiate the attitude in whatever parameters it is given and use the kinematics equation that connects the derivative of the attitude with the satellite angular-rate and compute the latter. Since SC usually utilize vector measurements for attitude determination, the differentiation of the attitude introduces a considerable noise component in the computed angular-rate vector.

Azor, Ruth; Bar-Itzhack, Y.; Deutschmann, Julie K.; Harman, Richard R.

1998-01-01

392

Specific Angular Momentum of Extrasolar Planetary Systems  

E-print Network

As the number of known planetary systems increases, the ability to follow-up and characterize the extent of any system becomes limited. This paper considers the use of specific angular momentum as a metric to prioritize future observations. We analyze 431 planets in 367 known extrasolar planetary systems from Butler et al. (2006) (including updates to their online catalog, current to April, 2011) and estimate each system's orbital angular momentum. The range of partition- ing of specific angular momentum in these systems is found to be large, spanning several orders of magnitude. The analysis shows that multi-planet systems tend to have the highest values of specific angular momentum normalized against the planetary masses. This suggests that in high angular momentum systems, the dominant contributors have already been discovered, and that single-planet sys- tems with low observed angular momentum may be the most likely candidates for additional undiscovered companions compared to their high angular momentum, single-planet counterparts. The multi-planet system, GJ 581, is considered as a historical case study to demonstrate the concept, examining how the specific angular momentum of the know planetary system evolved with each discovery.

John C. Armstrong; Shane L. Larson; Rhett R. Zollinger

2007-08-13

393

Angular momentum decomposition of Richardson's pairs  

SciTech Connect

The angular momentum decomposition of pairs obtained using Richardson's exact solution of the pairing Hamiltonian for the deformed {sup 174}Yb nucleus are displayed. The probabilities for low angular momenta of the collective pairs are strikingly different from the ones obtained in the BCS ground state.

Dussel, G. G.; Sofia, H. M. [Departamento de Fisica Juan Jose Giambiagi, Universidad de Buenos Aires and CONICET Ciudad Universitaria, Pabellon 1, 1428 Buenos Aires (Argentina); Departamento de Fisica, Comision Nacional de Energia Atomica, and CONICET Avda. del Lbertador 8250, 1429 Buenos Aires (Argentina)

2008-07-15

394

Fine Aggregate Angularity from Geotechnical Perspective  

Microsoft Academic Search

Particle angularity is an important aspect in the performance of asphalt concrete pavements. When rounded materials are used, the shear strength is reduced resulting in rutting and shoving of the asphalt concrete mixtures. Currently, the Superpave design method stipulates that the fine aggregate angularity (FAA) via AASHTO T304 be used as a test specification for fine aggregate. The objectives of

Stan Vitton; Jason P. Bausano; R. Christopher Williams; Vernon Schafer

2008-01-01

395

The Angular Momentum-Energy Space  

E-print Network

In this paper we shall define and study the angular momentum-energy space for the classical problem of plane-motions of a particle situated in a potential field of a central force. We shall present the angular momentum-energy space for some important cases.

Dan Comanescu

2007-02-09

396

Angular momentum in the global atmospheric circulation  

Microsoft Academic Search

Angular momentum is a variable of central importance to the dynamics of the atmosphere both regionally and globally. Moreover, the angular momentum equations yield a precise description of the dynamic interaction of the atmosphere with the oceans and the solid Earth via various torques as exerted by friction, pressure against the mountains and the nonspherical shape of the Earth, and

Joseph Egger; Klaus Weickmann; Klaus-Peter Hoinka

2007-01-01

397

Amplification of Angular Rotations Using Weak Measurements  

NASA Astrophysics Data System (ADS)

We present a weak measurement protocol that permits a sensitive estimation of angular rotations based on the concept of weak-value amplification. The shift in the state of a pointer, in both angular position and the conjugate orbital angular momentum bases, is used to estimate angular rotations. This is done by an amplification of both the real and imaginary parts of the weak-value of a polarization operator that has been coupled to the pointer, which is a spatial mode, via a spin-orbit coupling. Our experiment demonstrates the first realization of weak-value amplification in the azimuthal degree of freedom. We have achieved effective amplification factors as large as 100, providing a sensitivity that is on par with more complicated methods that employ quantum states of light or extremely large values of orbital angular momentum.

Magaña-Loaiza, Omar S.; Mirhosseini, Mohammad; Rodenburg, Brandon; Boyd, Robert W.

2014-05-01

398

Amplification of Angular Rotations Using Weak Measurements  

E-print Network

We present a weak measurement protocol that permits a sensitive estimation of angular rotations based on the concept of weak-value amplification. The shift in the state of a pointer, in both angular position and the conjugate orbital angular momentum bases, is used to estimate angular rotations. This is done by an amplification of both the real and imaginary parts of the weak-value of a polarization operator that has been coupled to the pointer, which is a spatial mode, via a spin-orbit coupling. Our experiment demonstrates the first realization of weak-value amplification in the azimuthal degree of freedom. We have achieved effective amplification factors as large as 100, providing a sensitivity that is on par with more complicated methods that employ quantum states of light or extremely large values of orbital angular momentum.

Omar S. Magana-Loaiza; Mohammad Mirhosseini; Brandon Rodenburg; Robert W. Boyd

2013-12-10

399

[The functional sport shoe parameter "torsion" within running shoe research--a literature review].  

PubMed

Within the sport shoe area torsion is described as the twisting and decoupling of the rear-, mid- and forefoot along the longitudinal axis of the foot. Studies have shown that running shoes restrict the torsion of the foot and thus they increase the pronation of the foot. Based on the findings, it is recommended to design running shoes, which allow the natural freedom of movement of the foot. The market introduction of the first torsion concept through adidas(R) took place in 1989. Independently of the first market introduction, only one epidemiological study was conducted in the running shoe area. The study should investigate the occurrence of Achilles tendon problems of the athletes running in the new "adidas Torsion(R) shoes". However, further studies quantifying the optimal region of torsionability concerning the reduction of injury incidence are still missing. Newer studies reveal that the criterion torsion only plays a secondary roll regarding the buying decision. Moreover, athletes are not able to perceive torsionability as a discrete functional parameter. It is to register, that several workgroups are dealing intensively with the detailed analysis of the foot movement based on kinematic multi-segment-models. However, scientific as well as popular scientific contributions display that the original idea of the torsion concept is still not completely understood. Hence, the "inverse" characteristic is postulated. The present literature review leads to the deduction that the functional characteristics of the torsion concept are not fully implemented within the running shoe area. This implies the necessity of scientific studies, which investigate the relevance of a functional torsion concept regarding injury prevention based on basic and applied research. Besides, biomechanical studies should analyse systematically the mechanism and the effects of torsion relevant technologies and systems. PMID:20108183

Michel, F I; Kälin, X; Metzger, A; Westphal, K; Schweizer, F; Campe, S; Segesser, B

2009-12-01

400

Cross-axis adaptation of torsional components in the yaw-axis vestibulo-ocular reflex  

NASA Technical Reports Server (NTRS)

The three pairs of semicircular canals within the labyrinth are not perfectly aligned with the pulling directions of the six extraocular muscles. Therefore, for a given head movement, the vestibulo-ocular reflex (VOR) depends upon central neural mechanisms that couple the canals to the muscles with the appropriate functional gains in order to generate a response that rotates the eye the correct amount and around the correct axis. A consequence of these neural connections is a cross-axis adaptive capability, which can be stimulated experimentally when head rotation is around one axis and visual motion about another. From this visual-vestibular conflict the brain infers that the slow-phase eye movement is rotating around the wrong axis. We explored the capability of human cross-axis adaptation, using a short-term training paradigm, to determine if torsional eye movements could be elicited by yaw (horizontal) head rotation (where torsion is normally inappropriate). We applied yaw sinusoidal head rotation (+/-10 degrees, 0.33 Hz) and measured eye movement responses in the dark, and before and after adaptation. The adaptation paradigm lasted 45-60 min, and consisted of the identical head motion, coupled with a moving visual scene that required one of several types of eye movements: (1) torsion alone (-Roll); (2) horizontal/torsional, head right/CW torsion (Yaw-Roll); (3) horizontal/torsional, head right/CCW torsion (Yaw+Roll); (4) horizontal, vertical, torsional combined (Yaw+Pitch-Roll); and (5) horizontal and vertical together (Yaw+Pitch). The largest and most significant changes in torsional amplitude occurred in the Yaw-Roll and Yaw+Roll conditions. We conclude that short-term, cross-axis adaptation of torsion is possible but constrained by the complexity of the adaptation task: smaller torsional components are produced if more than one cross-coupling component is required. In contrast, vertical cross-axis components can be easily trained to occur with yaw head movements.

Trillenberg, P.; Shelhamer, M.; Roberts, D. C.; Zee, D. S.

2003-01-01

401

Fatigue strength of adhesive bonded section beams under torsion  

SciTech Connect

Fatigue strength of adhesive bonded box beams was investigated. From results of the fatigue tests, it was seen that the fatigue strength of bonded beams was higher than that of spot welded beams. Fatigue strength of bonded beams was independent of plate thickness and partition. The flexural rigidity of the box beams in the plane of partition can increase without decrease of torsional rigidity and torsional fatigue strength, if the partition is jointed by adhesive bonding instead of spot welding. Since the fatigue strength and rigidity of adhesive bonded joints can be higher than the spot welded joints in the weight saving structures, it is expected that the structural adhesive joints will be employed more in the automobile body structure. For assuring the introduction of this joint more into the automobile body structures, it is necessary that the fatigue tests on the model members of the actual members used in the automobile body structure are conducted, in addition to those of the simple joints such as tension shear and T-type tension, and the property of the fatigue strength on the adhesive bonded members is known. But, the authors now have little data on fatigue tests of the adhesive bonded members. In the present research to be reported, the fatigue tests on adhesive bonded box beams under torsion, which are typical members in automobile body structure, were carried out and the effects of the presence of longitudinal partition and plate thickness on fatigue strength were investigated. Comparing the results of fatigue tests on adhesive bonded box beams with those on spot welded box beams, the property of fatigue strength on these adhesive bonded box beams was cleared.

Tomioka, Noboru; Kakiage, Masashi; Niisawa, Junetsu; Kitagawa, Hideo [Nihon Univ., Tokyo (Japan). College of Science and Technology

1995-11-01

402

Mapping Conformational Dynamics of Proteins Using Torsional Dynamics Simulations  

PubMed Central

All-atom molecular dynamics simulations are widely used to study the flexibility of protein conformations. However, enhanced sampling techniques are required for simulating protein dynamics that occur on the millisecond timescale. In this work, we show that torsional molecular dynamics simulations enhance protein conformational sampling by performing conformational search in the low-frequency torsional degrees of freedom. In this article, we use our recently developed torsional-dynamics method called Generalized Newton-Euler Inverse Mass Operator (GNEIMO) to study the conformational dynamics of four proteins. We investigate the use of the GNEIMO method in simulations of the conformationally flexible proteins fasciculin and calmodulin, as well as the less flexible crambin and bovine pancreatic trypsin inhibitor. For the latter two proteins, the GNEIMO simulations with an implicit-solvent model reproduced the average protein structural fluctuations and sample conformations similar to those from Cartesian simulations with explicit solvent. The application of GNEIMO with replica exchange to the study of fasciculin conformational dynamics produced sampling of two of this protein’s experimentally established conformational substates. Conformational transition of calmodulin from the Ca2+-bound to the Ca2+-free conformation occurred readily with GNEIMO simulations. Moreover, the GNEIMO method generated an ensemble of conformations that satisfy about half of both short- and long-range interresidue distances obtained from NMR structures of holo to apo transitions in calmodulin. Although unconstrained all-atom Cartesian simulations have failed to sample transitions between the substates of fasciculin and calmodulin, GNEIMO simulations show the transitions in both systems. The relatively short simulation times required to capture these long-timescale conformational dynamics indicate that GNEIMO is a promising molecular-dynamics technique for studying domain motion in proteins. PMID:23663843

Gangupomu, Vamshi K.; Wagner, Jeffrey R.; Park, In-Hee; Jain, Abhinandan; Vaidehi, Nagarajan

2013-01-01

403

Autoamputation of the fallopian tube after chronic adnexal torsion.  

PubMed

Autoamputation of the adnexa, although very rare, can either be congenital or acquired. For affected women it can have future fertility implications. Although in some women it is asymptomatic, in most cases a history of acute followed by chronic pelvic pain can be elicited. This is a case of autoamputation of a fallopian tube after chronic adnexal torsion. We suggest that all patients of reproductive age with acute lower abdominal pain should have a pelvic ultrasound scan and, if symptoms persist, early recourse to laparoscopy. Misdiagnosis can lead to ovarian damage, loss of tubal function, infertility, or chronic pelvic pain. PMID:19249713

Sankaran, Sridevi; Shahid, Anupama; Odejinmi, F

2009-01-01

404

Updated limits on extra dimensions through torsion and LHC data  

NASA Astrophysics Data System (ADS)

It is well known that the inclusion of torsion in the gravitational formalism, leads to four-fermion interactions. Although the coupling constant of this interaction is strongly suppressed in four dimensions, its value is enhanced in models with n extra dimensions. In this context, we reinterpret the recent limits established by LHC experiments to four-fermion contact interactions, to set bounds on the size of the extra dimensions. For n = 2, the limits are comparable to those in the literature, while for n ? 3, the volume of the extra dimensions is strongly constrained.

Castillo-Felisola, Oscar; Corral, Cristobal; Schmidt, Iván; Zerwekh, Alfonso R.

2014-05-01

405

Photoelectronic vibrometer with polarized light. [for torsional vibration measurements  

NASA Technical Reports Server (NTRS)

A seismic torsiometer is described which is based on the reception by a photosensitive transducer of a light flux modulated by a relative rotation of the optical axes of two polaroids. The torsional vibrations of the polaroid fixed to the shaft are transmitted to the other polaroid (which at the same time is the seismic mass of the apparatus) by means of elastic lamellas. The device can work as accelerometer, vibrometer or frequency meter, depending on the value of the ratio between the proper oscillation frequency of the seismic system and the measured vibration frequency.

Kremmer, I.

1974-01-01

406

Sertoli cell tumor in a prepubertal boy mimicking testicular torsion.  

PubMed

A 9-year-old boy presented with left, intermittent testicular pain that was present for 3 days. On physical examination, left testis was grossly enlarged and firm but mildly tender. Serum alpha-fetoprotein and beta-human chorionic gonadotropin levels were within normal range. Color doppler ultrasonography which was performed to rule out testicular torsion revealed an intratesticular mass located at the upper pole of left testis and left radical orchiectomy was performed. The histopathological diagnosis was Sertoli cell tumor. PMID:11112872

Tan, M; Uygur, C; Ozer, E; Erol, D

2000-01-01

407

Torsional Response and Dissipationless Viscosity in Topological Insulators  

E-print Network

We consider the visco-elastic response of the electronic degrees of freedom in 2D and 3D topological insulators (TI). Our primary focus is on the 2D Chern insulator which exhibits a bulk dissipationless viscosity analogous to the quantum Hall viscosity predicted in integer and fractional quantum Hall states. We show that the dissipationless viscosity is the response of a TI to torsional deformations of the underlying lattice geometry. The visco-elastic response also indicates that crystal dislocations in Chern insulators will carry momentum density. We briefly discuss generalizations to 3D which imply that time-reversal invariant TI's will exhibit a quantum Hall viscosity on their surfaces.

Taylor L. Hughes; Robert G. Leigh; Eduardo Fradkin

2011-01-18

408

Torsional dependence of molecular electrical properties and long-range interactions: CH3OH-rare gas systems  

NASA Astrophysics Data System (ADS)

Self-consistent-field (SCF) values are reported for all Cartesian tensor components of the dipole, quadrupole, and octupole moments (?,?,?) and polarizabilities ? and A of the methanol molecule in its staggered, eclipsed, and three intermediate conformations. The methanol geometry was held rigid except for a single internal rotation angle ?, describing the relative orientation of the methyl rotor and the hydroxyl framework. Three different basis sets were used, including a 110 contracted Gaussian set based on the electrical properties (ELP) basis of Dykstra et al. [Adv. Chem. Phys. 75, 37 (1989), and references therein]. It was found that the tensor components ?xxx, ?xyy, Axxx, Axyy, and Ayxy vary as cos 3?, while the components ?yyy, ?yxx, Ayyy, Ayxx, and Axyx vary as sin 3?. All other components of ? and A, as well as all components of ?, ?, show little variation with ?. This dependence was explained using a simple model that treats each property as a sum of a constant, hydroxyl framework contribution and a conformation-dependent, methyl rotor contribution. Torsional averages of these properties were computed from torsional wave functions obtained by diagonalization of the internal axis method (IAM) Hamiltonian. It was found that the large amplitude internal rotation in methanol gives rise to large vibrational effects on the Axxx, Axyy, and Ayxy polarizability components. The conformational dependence of the electrical properties was used to describe the conformational dependence of long-range interactions involving a near-symmetric, nonrigid molecule such as methanol. The leading ?-dependent interaction term was shown to vary as R-8 and R-7 for the induction and dispersion interactions (respectively) between a methanol molecule and a structureless atom. Cartesian tensor expressions are given for the long-range dispersion interaction within second-order perturbation theory, and the leading torsionally dependent interaction is shown to vary as sin3 ? cos 3(?-?), where ?,? are the spherical coordinates of the atom.

Davis, Stephen L.; Dennison, Elizabeth C.

1994-07-01

409

Dynamics of a 3dof torsional system with a dry friction controlled path  

NASA Astrophysics Data System (ADS)

A three-degrees of freedom semi-definite torsional system representing an automotive driveline is studied in presence of a torque converter clutch that manifests itself as a dry friction path. An analytical procedure based on the linear system theory is proposed first to establish the stick-to-slip boundaries. Smoothened and discontinuous Coulomb friction formulations are then applied to the nonlinear system, and the differential governing equations are numerically solved given harmonic torque excitation and a mean load. Time domain histories illustrating dry friction-induced stick-slip motions are predicted for different saturation torques and system parameters. Approximate analytical solutions based on distinct states are also developed and successfully compared with numerical studies. Analysis shows that the conditioning factor associated with the smoothened friction model (hyperbolic tangent) must be carefully selected. Then nonlinear frequency responses are constructed from cyclic time histories and the stick-slip boundaries predictions (as yielded by the linear system theory) are confirmed. In particular, the effect of secondary inertia is analytically and numerically investigated. Results show that the secondary inertia has a significant influence on the dynamic response. A quasi-discontinuous oscillation is found with the conventional bi-linear friction model in which the secondary inertia is ignored. Finally, our methods are successfully compared with two benchmark analytical and experimental studies, as available in the literature on two-degrees of freedom translational systems.

Duan, Chengwu; Singh, Rajendra

2006-02-01

410

How Does the Electromagnetic Field Couple to Gravity, in Particular to Metric, Nonmetricity, Torsion, and Curvature?  

NASA Astrophysics Data System (ADS)

The coupling of the electromagnetic field to gravity is an age-old problem. Presently, there is a resurgence of interest in it, mainly for two reasons: (i) Experimental investigations are under way with ever increasing precision, be it in the laboratory or by observing outer space. (ii) One desires to test out alternatives to Einstein’s gravitational theory, in particular those of a gauge-theoretical nature, like Einstein-Cartan theory or metric-afine gravity.— A clean discussion requires a reflection on the foundations of electrodynamics. If one bases electrodynamics on the conservation laws of electric charge and magnetic flux, one finds Maxwell’s equations expressed in terms of the excitation H = (D,H) and the field strength F = (E,B) without any intervention of the metric or the linear connection of spacetime. In other words, there is still no coupling to gravity. Only the constitutive law H = functional(F) mediates such a coupling. We discuss the different ways of how metric, nonmetricity, torsion, and curvature can come into play here. Along the way, we touch on non-local laws (Mashhoon), non-linear ones (Born-Infeld, Heisenberg-Euler, Pleba?ki), linear ones, including the Abelian axion (Ni), and fid a method for deriving the metric from linear electrodynamics (Toupin, Schönberg). Finally, we discuss possible non-minimal coupling schemes.

Hehl, Friedrich W.; Obukhov, Yuri N.

411

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. II. Inertial detection of angular velocity  

NASA Technical Reports Server (NTRS)

1. The dynamic contribution of otolith signals to three-dimensional angular vestibuloocular reflex (VOR) was studied during off-vertical axis rotations in rhesus monkeys. In an attempt to separate response components to head velocity from those to head position relative to gravity during low-frequency sinusoidal oscillations, large oscillation amplitudes were chosen such that peak-to-peak head displacements exceeded 360 degrees. Because the waveforms of head position and velocity differed in shape and frequency content, the particular head position and angular velocity sensitivity of otolith-ocular responses could be independently assessed. 2. During both constant velocity rotation and low-frequency sinusoidal oscillations, the otolith system generated two different types of oculomotor responses: 1) modulation of three-dimensional eye position and/or eye velocity as a function of head position relative to gravity, as presented in the preceding paper, and 2) slow-phase eye velocity as a function of head angular velocity. These two types of otolith-ocular responses have been analyzed separately. In this paper we focus on the angular velocity responses of the otolith system. 3. During constant velocity off-vertical axis rotations, a steady-state nystagmus was elicited that was maintained throughout rotation. During low-frequency sinusoidal off-vertical axis oscillations, dynamic otolith stimulation resulted primarily in a reduction of phase leads that characterize low-frequency VOR during earth-vertical axis rotations. Both of these effects are the result of an internally generated head angular velocity signal of otolithic origin that is coupled through a low-pass filter to the VOR. No change in either VOR gain or phase was observed at stimulus frequencies larger than 0.1 Hz. 4. The dynamic otolith contribution to low-frequency angular VOR exhibited three-dimensional response characteristics with some quantitative differences in the different response components. For horizontal VOR, the amplitude of the steady-state slow-phase velocity during constant velocity rotation and the reduction of phase leads during sinusoidal oscillation were relatively independent of tilt angle (for angles larger than approximately 10 degrees). For vertical and torsional VOR, the amplitude of steady-state slow-phase eye velocity during constant velocity rotation increased, and the phase leads during sinusoidal oscillation decreased with increasing tilt angle. The largest steady-state response amplitudes and smallest phase leads were observed during vertical/torsional VOR about an earth-horizontal axis. 5. The dynamic range of otolith-borne head angular velocity information in the VOR was limited to velocities up to approximately 110 degrees/s. Higher head velocities resulted in saturation and a decrease in the amplitude of the steady-state response components during constant velocity rotation and in increased phase leads during sinusoidal oscillations. 6. The response characteristics of otolith-borne angular VORs were also studied in animals after selective semicircular canal inactivation. Otolith angular VORs exhibited clear low-pass filtered properties with a corner frequency of approximately 0.05-0.1 Hz. Vectorial summation of canal VOR alone (elicited during earth-vertical axis rotations) and otolith VOR alone (elicited during off-vertical axis oscillations after semicircular canal inactivation) could not predict VOR gain and phase during off-vertical axis rotations in intact animals. This suggests a more complex interaction of semicircular canal and otolith signals. 7. The results of this study show that the primate low-frequency enhancement of VOR dynamics during off-vertical axis rotation is independent of a simultaneous activation of the vertical and torsional "tilt" otolith-ocular reflexes that have been characterized in the preceding paper. (ABSTRACT TRUNCATED).

Angelaki, D. E.; Hess, B. J.

1996-01-01

412

Angular momentum dependence of the nuclear level density parameter  

SciTech Connect

Dependence of nuclear level density parameter on the angular momentum and temperature is investigated in a theoretical framework using the statistical theory of hot rotating nuclei. The structural effects are incorporated by including shell correction, shape, and deformation. The nuclei around Zapprox =50 with an excitation energy range of 30 to 40 MeV are considered. The calculations are in good agreement with the experimentally deduced inverse level density parameter values especially for {sup 109}In, {sup 113}Sb, {sup 122}Te, {sup 123}I, and {sup 127}Cs nuclei.

Aggarwal, Mamta [UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai-Kalina Campus, Mumbai 400 098 (India); Kailas, S. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2010-04-15

413

Does Disk Locking Solve the Stellar Angular Momentum Problem?  

NASA Astrophysics Data System (ADS)

We critically examine the theory of disk locking, which assumes that the angular momentum deposited on an accreting protostar is exactly removed by torques carried along magnetic field lines connecting the star to the disk. In this Letter, we consider that the differential rotation between the star and disk naturally leads to an opening (i.e., disconnecting) of the magnetic field between the two. We find that this significantly reduces the spin-down torque on the star by the disk. Thus, disk locking cannot account for the slow rotation (~10% of breakup speed) observed in several systems and for which the model was originally developed.

Matt, Sean; Pudritz, Ralph E.

2004-05-01

414

Non-Gaussianities in DBI inflation with angular motion  

NASA Astrophysics Data System (ADS)

We study DBI spinflation models with angular potentials that are derived in string theory. We analyze the background dynamics with different parameter sets and study the impact of changing each parameter on inflationary dynamics. It is known that the conversion of the entropy perturbation into the curvature perturbation gives multifield Dirac-Born-Infeld (DBI) inflation models a possibility of satisfying the observational constraints by relaxing the stringent microphysical constraint that disfavors single-field DBI inflation models. We show that our model is excluded by the Planck satellite observations even with the conversion mechanism regardless of the parameter set.

Kidani, Taichi; Koyama, Kazuya

2014-07-01

415

Large Torsional Oscillations in Suspension Bridges Revisited: Fixing an Old Approximation Author(s): P. J. McKenna  

E-print Network

Large Torsional Oscillations in Suspension Bridges Revisited: Fixing an Old Approximation Author to The American Mathematical Monthly. http://www.jstor.org #12;LargeTorsionalOscillations in SuspensionBridges

McKenna, Joseph

416

Turbulent Angular Momentum Transport in Weakly-Ionized Accretion Disks  

E-print Network

Understanding the mechanism that drives accretion has been the primary challenge in accretion disk theory. Turbulence provides a natural means of dissipation and the removal of angular momentum, but firmly establishing its presence in disks proved for many years to be difficult. The realization in the 1990s that a weak magnetic field will destabilize a disk and result in a vigorous turbulent transport of angular momentum has revolutionized the field. Much of accretion disk research now focuses on understanding the implications of this mechanism for astrophysical observations. At the same time, the success of this mechanism depends upon a sufficient ionization level in the disk for the flow to be well-coupled to the magnetic field. Many disks, such as disks around young stars and disks in binary systems that are in quiescence, are too cold to be sufficiently ionized, and so efforts to establish the presence of turbulence in these disks continues. This dissertation focuses on several possible mechanisms for the turbulent transport of angular momentum in weakly-ionized accretion disks: gravitational instability, radial convection and vortices driving compressive motions. It appears that none of these mechanisms are very robust in driving accretion. A discussion is given, based on these results, as to the most promising directions to take in the search for a turbulent transport mechanism that does not require magnetic fields. Also discussed are the implications of assuming that no turbulent transport mechanism exists for weakly-ionized disks.

Bryan Mark Johnson

2005-09-13

417

Relationship between head orientation and torsional eye movements in goldfish during linear acceleration  

NASA Astrophysics Data System (ADS)

We analyzed torsional eye movements of normal goldfish during sinusoidal linear acceleration, altering the orientation of the fish on the linear accelerator in the yaw plane over a range of 90 degrees and in the pitch plane up to 30 degrees. We video-recorded changes of torsional eye movements associated with a body rotation in the yaw and pitch plane and analyzed them frame by frame. In normal fish, we observed clear torsional eye movements for stimuli of 0.1G linear accelerations along the body axis in the horizontal position. Torsion occurred in the opposite direction of resultant force produced by linear acceleration and gravity. Though the amplitude of these compensatory responses increased with increasing magnitude of acceleration up to 0.5 G, the torsion angle did not fully compensate the angle calculated from gravity and linear acceleration. Furthermore, the torsion angle decreased as the longitudinal body axis deviated from the direction of linear acceleration. For the body axis perpendicular to the direction of acceleration, torsional eye movement was still observed. When we tilted the fish in the pitch plane, compensatory eye torsion occurred. The response amplitude to acceleration decreased for both head-up and head-down up to 30 degrees. These results suggested the existence of specific connections between the otolith organ and ocular muscles.

Takabayashi, A.; Ohmura, T.; Mori, S.

418

A discussion on the most general torsion-gravity with electrodynamics for Dirac spinor matter fields  

E-print Network

We consider the most general torsional completion of gravity and electrodynamics with Dirac spinorial matter fields, showing that continuity and consistency constrain torsion to be completely antisymmetric and the model to be parity-invariant and described by either the least-order derivative model or the renormalizable model.

Luca Fabbri

2014-09-06

419

Temporal trends in femoral diaphyseal torsional asymmetry among the Arikara associated with postural behavior.  

PubMed

Average femoral torsion has been reported to differ among populations, and several studies have observed a relatively high prevalence of femoral anteversion asymmetry in Native Americans, especially females. This study investigates sexual dimorphism and temporal trends in femoral torsional asymmetry among the Arikara from the seventeenth to the early nineteenth century. To establish if there are population differences, femoral torsion was first measured using a direct method on a diverse comparative sample of Native Americans from the Southwest, Midwest, and Great Plains as well as American Whites and Blacks. To examine temporal trends among the Arikara, femoral torsion was examined using the orientation of the maximum bending rigidity at subtrochanteric in 154 females and 164 males from three temporal variants of the Arikara Coalescent tradition. There is significant sexual dimorphism in femoral torsional directional and absolute asymmetry among most Native American samples, but not among American Whites and Blacks. Among the Arikara there is significant sexual dimorphism in femoral torsional asymmetry in all three temporal variants, and asymmetry in femoral torsional asymmetry increased significantly from the protohistoric to the early historic period among females. The increased femoral torsional asymmetry is likely associated with a common side-sitting posture observed in historic photographs of Great Plains females. Historic Arikara females may have habitually sat in this compulsory position for extended periods while conducting domestic chores. The dramatic change from the protohistoric to historic period suggests a cultural change in sitting posture among females that was widespread across the Northern Plains. PMID:24861881

Wescott, Daniel J; Cunningham, Deborah L; Hunt, David R

2014-08-01

420

Torsion Property and Cyclic Fatigue Fracture Behavior of Nickel-Titanium Endodontic Instruments  

E-print Network

Torsion Property and Cyclic Fatigue Fracture Behavior of Nickel-Titanium Endodontic Instruments gloomice@163.com, d lczhao@hit.edu.cn Keywords: NiTi alloy; Torsion; Cyclic fatigue; Endodontic instrument play a dominant role in fracture initiation during cyclic fatigue fracture. The cyclic number

Zheng, Yufeng

421

Mechanical and microstructural development of Carrara marble with pre-existing deformation history in torsion experiments  

Microsoft Academic Search

The deformation behaviour of Carrara marble has been studied mostly by performing deformation experiments on initially undeformed samples. In this study, torsion experiments on Carrara marble with a pre-existing deformation history have been conducted and analysed in terms of both mechanical and microstructural development. Torsion experiments have been conducted to deform initially deformed Carrara marble samples until a bulk shear

R. H. C. Bruijn; L. Burlini; K. Kunze

2009-01-01

422

Effective Torsion and Spring Constants in a Hybrid Translational-Rotational Oscillator  

ERIC Educational Resources Information Center

A torsion oscillator is a vibrating system that experiences a restoring torque given by [tau] = -[kappa][theta] when it experiences a rotational displacement [theta] from its equilibrium position. The torsion constant [kappa] (kappa) is analogous to the spring constant "k" for the traditional translational oscillator (for which the restoring force…

Nakhoda, Zein; Taylor, Ken

2011-01-01

423

Deformation of olivine in torsion under hydrous conditions Sylvie Demouchy a,  

E-print Network

Deformation of olivine in torsion under hydrous conditions Sylvie Demouchy a, , Andréa Tommasi Crystal-preferred orientation Seismic anisotropy a b s t r a c t We performed torsional deformation-pressed and then hot-pressed under hydrous conditions, pro- ducing aggregates with average grain sizes of 7 or 15 lm

Tommasi, Andrea

424

[Torsion of the uterus as a complication of second trimester abortion].  

PubMed

A case of uterine torsion obstructing a midtrimester induced abortion is described. As with cases of torsion in late pregnancy which are also rare, the condition was only diagnosed at operation. Meticulous attention to the anatomical details prior to incision of the uterus is required. PMID:1546403

Voigt, S

1992-03-01

425

Robust and real-time torsional eye position calculation using a template-matching technique  

Microsoft Academic Search

Computation of eye rotation about the line of sight (torsion) using image processing techniques has traditionally used cross-correlation of iral signatures sampled from circular arcs centered on the pupil. We have developed a new algorithm that utilizes a template-matching technique to calculate torsional eye position. Iral signatures are obtained from two annuli centered on the pupil center. By assuming that

Danjie Zhu; Steven T. Moore; Theodore Raphan

2004-01-01

426

Stability analysis of rotating blade bending vibration due to torsional excitation  

Microsoft Academic Search

This paper studies the forced vibrations of a flexible rotating blade under the excitation of shaft torsional vibration. A reduced order nonlinear dynamic model is adopted, wherein the torsional vibration degree of freedom is substituted by a simple harmonic motion with a frequency that is function of the system rotating speed. The resulting system of second-order ordinary differential equation with

B. O. Al-Bedoor; A. A. Al-Qaisia

2005-01-01

427

THE EFFECTS OF TORSIONAL ELEMENTS ON THE TRANSIENT PERFORMANCE OF LARGE INDUCTION MOTOR DRIVES  

Microsoft Academic Search

In the modelling of induction motor drives it is common to choose only a first order representation of the torsional elements of the motor drive. When there is a requirement for more detailed information on the behaviour of the torsional elements of the drive a method of analysis is often chosen which inherently suppresses the important features of interaction between

GEORGE W. BUCKLEY

1980-01-01

428

Separation of ferrimagnetic and paramagnetic anisotropies using a high-eld torsion magnetometer  

E-print Network

Separation of ferrimagnetic and paramagnetic anisotropies using a high-®eld torsion magnetometer Fa susceptibility; high ®eld torsion magnetometer; rock magnetism; paramagnetism; ferrimagnetism; AMS 1 a cryogenic magnetometer to determine the susceptibility anisotropy of both ferrimagnetic and Tectonophysics

Utrecht, Universiteit

429

Highly Accurate Beam Torsion Solutions Using the p-Version Finite Element Method  

NASA Technical Reports Server (NTRS)

A new treatment of the classical beam torsion boundary value problem is applied. Using the p-version finite element method with shape functions based on Legendre polynomials, torsion solutions for generic cross-sections comprised of isotropic materials are developed. Element shape functions for quadrilateral and triangular elements are discussed, and numerical examples are provided.

Smith, James P.

1996-01-01

430

The effects of head and trunk position on torsional vestibular and optokinetic eye movements in humans  

Microsoft Academic Search

We measured torsional vestibular and optokinetic eye movements in human subjects with the head and trunk erect, with the head supine and the trunk erect, and with the head and trunk supine, in order to quantify the effects of otolithic and proprioceptive modulation. During active head movements, the torsional vestibulo-ocular reflex (VOR) had significantly higher gain with the head upright

Mark J. Morrow; James A. Sharpe

1993-01-01

431

Increased left ventricular torsion in hypertrophic cardiomyopathy mutation carriers with normal wall thickness  

Microsoft Academic Search

BACKGROUND: Increased left ventricular (LV) torsion has been observed in patients with manifest familial hypertrophic cardiomyopathy (HCM), and is thought to be caused by subendocardial dysfunction. We hypothesize that increased LV torsion is already present in healthy mutation carriers with normal wall thickness. METHODS: Seventeen carriers with an LV wall thickness <10 mm, and seventeen age and gender matched controls

Iris K Rüssel; Wessel P Brouwer; Tjeerd Germans; Paul Knaapen; J Tim Marcus; Jolanda van der Velden; Marco JW Götte; Albert C van Rossum

2011-01-01

432

Effect of Autoclaving on Torsional Moment of Two Nickel-Titanium Endodontic Files.  

National Technical Information Service (NTIS)

The effect of autoclaving on torsional moment of two nickel titanium endodontic files. Aim To evaluate the effects of repeated autoclaving on torsional strength of two nickel titanium (NiTi) rotary endodontic files: Twisted Files (SybronEndo, Orange, CA, ...

B. E. Bergeron, H. W. Roberts, J. B. King, M. J. Mayerchak

2012-01-01

433

Analysis of torsional spectra of molecules with two C3v internal rotors. IV - The torsional potential function for propane-d0 and -d3  

NASA Technical Reports Server (NTRS)

The Raman spectra of gaseous propane-d0 and -d3 have been recorded between 50 and 3500 cm. Considerable torsional data are reported and used to characterize the torsional potential function based on a semirigid model. The average 'effective' V3 for the propanes is found to be 1139 plus or minus 10/cm. The sine-sine coupling term is similar in magnitude but opposite in sign to the cosine-cosine coupling term in propane-d0.

Durig, J. R.; Groner, P.; Griffin, M. G.

1977-01-01

434

Total angular momentum waves for scalar, vector, and tensor fields  

NASA Astrophysics Data System (ADS)

Most calculations in cosmological perturbation theory, including those dealing with the inflationary generation of perturbations, their time evolution, and their observational consequences, decompose those perturbations into plane waves (Fourier modes). However, for some calculations, particularly those involving observations performed on a spherical sky, a decomposition into waves of fixed total angular momentum (TAM) may be more appropriate. Here we introduce TAM waves—solutions of fixed total angular momentum to the Helmholtz equation—for three-dimensional scalar, vector, and tensor fields. The vector TAM waves of given total angular momentum can be decomposed further into a set of three basis functions of fixed orbital angular momentum, a set of fixed helicity, or a basis consisting of a longitudinal (L) and two transverse (E and B) TAM waves. The symmetric traceless rank-2 tensor TAM waves can be similarly decomposed into a basis of fixed orbital angular momentum or fixed helicity, or a basis that consists of a longitudinal (L), two vector (VE and VB, of opposite parity), and two tensor (TE and TB, of opposite parity) waves. We show how all of the vector and tensor TAM waves can be obtained by applying derivative operators to scalar TAM waves. This operator approach then allows one to decompose a vector field into three covariant scalar fields for the L, E, and B components and symmetric-traceless-tensor fields into five covariant scalar fields for the L, VE, VB, TE, and TB components. We provide projections of the vector and tensor TAM waves onto vector and tensor spherical harmonics. We provide calculational detail to facilitate the assimilation of this formalism into cosmological calculations. As an example, we calculate the power spectra of the deflection angle for gravitational lensing by density perturbations and by gravitational waves. We comment on an alternative approach to cosmic microwave background fluctuations based on TAM waves. An accompanying paper will work out three-point functions in terms of TAM waves and their relation to the usual Fourier-space bispectra. Our work may have applications elsewhere in field theory and in general relativity.

Dai, Liang; Kamionkowski, Marc; Jeong, Donghui

2012-12-01

435

Angular momentum dependence of complex fragment emission  

NASA Astrophysics Data System (ADS)

The angular momentum dependence of large fragment production in long-lived reactions is studied by measurements of fragment cross sections from reactions with substantially different angular momentum distributions and the coincident ?-ray multiplicity distributions. The results indicate that the primary l-wave distributions move to larger mean values and decrease in width and skewness with increasing mass symmetry in the decay channel. The results also confirm that the partition of angular momentum kinetic energy relaxed heavy-ion reactions is that expected for a rigidly rotating intermediate.

Sobotka, L. G.; Sarantites, D. G.; Li, Ze; Dines, E. L.; Halbert, M. L.; Hensley, D. C.; Lisle, J. C.; Schmitt, R. P.; Majka, Z.; Nebbia, G.; Griffin, H. C.; Sierk, A. J.

1987-12-01

436

Angular momentum in the Local Group  

SciTech Connect

We briefly review models for the Local Group and the acquisition of its angular momentum. We describe early attempts to understand the origin of the spin of the galaxies discussing the hypothesis that the Local Group has little angular momentum. Finally we show that using Peebles` least action principle there should be a rather large amount of orbital angular momentum compared to the magnitude of the spin of its galaxies. Therefore the Local Group cannot be thought as tidally isolated. Using Peebles` trajectories we give a possible set of trajectories for Local Group galaxies which would predict their spin.

Dunn, A. [Cambridge Univ. (United Kingdom). Inst. of Astronomy; Laflamme, R. [Los Alamos National Lab., NM (United States)

1994-04-01

437

Acute gallbladder torsion - a continued pre-operative diagnostic dilemma  

PubMed Central

Acute gallbladder volvulus continues to remain a relatively uncommon process, manifesting itself usually during exploration for an acute surgical abdomen with a presumptive diagnosis of acute cholecystitis. The pathophysiology is that of mechanical organo-axial torsion along the gallbladder's longitudinal axis involving the cystic duct and cystic artery, and with a pre-requisite of local mesenteric redundancy. The demographic tendency is septua- and octo-genarians of the female sex, and its overall incidence is increasing, this being attributed to increasing life expectancy. We discuss two cases of elderly, fragile women presenting to the emergency department complaining of sudden onset right upper quadrant abdominal pain. Their subsequent evaluation suggested acute cholecystitis. Ultimately both were taken to the operating room where the correct diagnosis of gallbladder torsion was made. Pre-operative diagnosis continues to be a major challenge with only 4 cases reported in the literature diagnosed with pre-operative imaging; the remainder were found intra-operatively. Consequently, a delay in diagnosis can have devastating patient outcomes. Herein we propose a necessary high index of suspicion for gallbladder volvulus in the outlined patient demographic with symptoms and signs mimicking acute cholecystitis. PMID:21489292

2011-01-01

438

Autoantibodies against Leydig cells in patients after spermatic cord torsion.  

PubMed Central

This study is aimed at searching for the presence of circulating antibodies against frozen sections of human testis, ovary and trophoblast in patients that had spermatic cord torsion. Sixty-eight sera samples were studied. Nine patients (13.2%) were positive for organ specific anti-testis autoantibodies. Six patients were positive for antibodies against Leydig cells: five were positive only with the indirect immunofluorescence technique of complement fixing (ITT/CF), the sixth patient was positive only with the indirect immunofluorescence technique (ITT). The other three patients were positive for antibodies against germ line cells: two patients were positive with both techniques, the third was positive only with indirect immunofluorescence technique. Eight of these patients were negative for antibodies against adrenal cortex while only one case was positive with indirect immunofluorescence technique both on adrenal cortex and Leydig cells. Human lyophilized testis absorbed the reactive antibodies against Leydig cells and germ line cells, while adrenal cortex and lyophilized testosterone were ineffective. This study shows the identification of a specific antibody against Leydig cells and germ line cells in patients after spermatic cord torsion. PMID:6362937

Zanchetta, R; Mastrogiacomo, I; Graziotti, P; Foresta, C; Betterle, C

1984-01-01

439

Test particle acceleration in torsional spine magnetic reconnection  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) magnetic reconnection is taking place commonly in astrophysical and space plasmas, especially in solar flares which are rich sources of highly energetic particles. One of the proposed mechanisms for steady-state 3D magnetic reconnection is "torsional spine reconnection". By using the magnetic and electric fields for "torsional spine reconnection", we numerically investigate the features of test particle acceleration with input parameters for the solar corona. We show that efficient acceleration of a relativistic proton is possible near the null point where it can gain up to 100 MeV of kinetic energy within a few milliseconds. However, varying the injection position results in different scenarios for proton acceleration. A proton is most efficiently accelerated when it is injected at the point where the magnetic field lines change their curvature in the fan plane. Moreover, a proton injected far away from the null point cannot be accelerated and, even in some cases, it is trapped in the magnetic field. In addition, adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory.

Hosseinpour, M.

2014-10-01

440

Vertical and torsional VOR in posterior canal occlusion.  

PubMed

The vertical and torsional vestibulo-ocular reflexes (VOR) were investigated in 3 patients with surgical occlusion of the posterior semicircular canal and 1 patient with singular neurectomy, for treatment of refractory paroxysmal positional vertigo. Stimuli comprised sinusoidal oscillation in the coronal ("roll") and sagittal ("pitch") plane as well as in two oblique planes intermediate between pitch in order to stimulate left anterior + right posterior (LARP) and right anterior + left posterior (RALP) canal pairs separately. One case with left side BPPV was investigated pre and post-operatively. Depression of the vertical and torsional VOR gain was seen 1 week postoperatively when the occluded canal was placed in the optimal plane for stimulation at 1 week postoperatively and subsequently gradually recovered. Recordings in other planes suggested that the contralateral posterior canal was also hypofunctioning, a finding which may explain some residual gait unsteadiness in this case. The other 3 cases who were investigated postoperatively all showed a decrease in downward VOR gain in the "on' direction of the operated canal. The data indicate the specificity of the test procedure and underline the prognostic value of comprehensive pre-operative vestibular assessment. PMID:8749162

Kanayama, R; Bronstein, A M; Gresty, M A; Brookes, G B

1995-01-01

441

Asymmetric magnetoimpedance in amorphous microwires due to bias current: Effect of torsional stress  

NASA Astrophysics Data System (ADS)

The influence of torsional stress on the asymmetric magnetoimpedance in a glass-coated negative magnetostrictive amorphous microwire due to bias current is studied theoretically. The longitudinal and off-diagonal impedance components are found assuming a simplified spatial distribution of the magnetoelastic anisotropy induced by the torsional stress. The asymmetry in the field dependence of the impedance components is attributed to the combination of the circular magnetic field produced by the bias current and a helical anisotropy induced by the torsional stress. The asymmetry in the magnetoimpedance and the low-field hysteresis are analyzed as a function of the bias current and torsional stress. It is shown that the application of torsional stress significantly changes the value of the bias current required to suppress the hysteresis effect. The results obtained may be useful for applications in magnetic-field and stress sensors.

Buznikov, N. A.; Antonov, A. S.; Granovsky, A. B.

2014-04-01

442

Torsional Properties of TiNi Shape Memory Alloy Tape for Rotary Actuator  

NASA Astrophysics Data System (ADS)

In order to develop novel shape memory actuators, the torsional deformation of a shape memory alloy (SMA) tape and the actuator models driven by the tape were investigated. The results obtained can be summarized as follows. In the SMA tape subjected to torsion, the martensitic transformation appears along both edges of the tape due to elongation of these elements and grows to the central part. The fatigue life in both the pulsating torsion and alternating torsion is expressed by the unified relationship of the dissipated work in each cycle. Based on an opening and closing door model and a solar-powered active blind model, the two-way rotary driving actuator with a small and simple mechanism can be developed by using torsion of the SMA tape.

Takeda, K.; Tobushi, H.; Mitsui, K.; Nishimura, Y.; Miyamoto, K.

2012-12-01

443

Anomalous Energy Transfer Dynamics due to Torsional Relaxation in a Conjugated Polymer  

NASA Astrophysics Data System (ADS)

In isolated conjugated polymers two explanations are in discussion for the redshift of the emission on a picosecond time scale—exciton energy transfer (EET) between conjugated segments along the chains and conformational changes of these segments themselves, i.e., torsional relaxation. In order to resolve this question we perform femtosecond time-resolved transient absorption measurements of the energy relaxation of poly[3-(2,5-dioctylphenyl)thiophene] in toluene solution. We show that torsional relaxation can be distinguished from EET by site-selectively exciting low-energy conjugated segments. We present a unified model that integrates EET and torsional dynamics. In particular, comparison to ultrafast depolarization measurements shows that torsional dynamics cannot be neglected when analyzing EET dynamics and furthermore reveals that the exciton extends itself by about 2 monomer units during torsional relaxation.

Westenhoff, Sebastian; Beenken, Wichard J. D.; Friend, Richard H.; Greenham, Neil C.; Yartsev, Arkady; Sundström, Villy

2006-10-01

444

Contemporary review of testicular torsion: new concepts, emerging technologies and potential therapeutics.  

PubMed

Testicular torsion is one of the few emergencies in pediatric urology which requires an accurate and timely diagnosis in order to avoid testis loss. It is not an uncommon event affecting a young male population. In fact, testicular torsion is more common than testicular tumors for this same age group, yet testicular torsion has not been given the public attention it deserves as a male health risk. In this review we highlight the new information published over the past four years regarding testicular torsion. We will discuss a variety of topics associated with torsion including: medical legal issues, etiology and genetics, imaging diagnostics, innovative surgical techniques, management controversies, fertility, and new drug therapies. PMID:23044376

DaJusta, Daniel G; Granberg, Candace F; Villanueva, Carlos; Baker, Linda A

2013-12-01

445

Rheology of deformed Carrara marble: Insights from torsion experiments  

NASA Astrophysics Data System (ADS)

Rock deformation experiments are essential for understanding lithosphere dynamics, strain localization processes and deformation mechanisms in polymineral aggregates, as they provide rheological parameters and record fabric development of rock-forming minerals, aiding the geological interpretation of naturally deformed rocks. Carrara marble received significant attention in the rock deformation community due to its homogeneous fabric and low impurities content, making it a laboratory standard. When the torsion actuator was developed for the Paterson-type gas-medium apparatus, it became possible to perform high strain experiments and reach true steady state flow conditions in Carrara marble. At the center of these ground breakings developments stood Luigi Burlini and his students. Their work showed for the first time, the importance of fabric development on steady state flow stress in response to high strain deformation and recrystallization. In the last years of Luigi's life, he and his students took rock deformation studies to a different direction by investigating the effect of initial strain and quantifying the coupling between fabric and flow stress. We present here an overview of the four types of torsion experiment that were performed on Carrara marble with varied pre-existing strain. Earlier torsion experiments on homogeneous Carrara marble provided the framework in which these newer experiments were evaluated. In type I experiments samples were subjected to a torsion deformation leading to a maximum shear strain of 1 to 5, immediately followed by a reversed straining of equal magnitude. In type II and III experiments, a composite sample consisting of a segment of undeformed and one (type II) or two (type III) segment(s) of previously twisted Carrara marble, were deformed. In type IV experiments, a cylindrical segment of dynamically recrystallized Carrara marble was annealed 727 °C for up to five hours at to recover the original grain size without removing the developed texture. Subsequent deformation by torsion revealed the effect of initial texture on peak flow stress. Experimental conditions were designed to activate dislocation creep. Confining pressure was set at 300 MPa, temperature varied from 600 to 800 °C and the applied constant shear strain rate ranged from 3×10-4 to 1×10-3 s-1. Type I to III experiments revealed that reversed deformation recovers sheared grains, with the recovery of shape preferred orientation (SPO) requiring less strain than the recovery of crystallographic preferred orientation (CPO). They also showed that recrystallization is controlled by absolute strain rather than total strain. In terms of rheology, the first three types of experiments highlighted that strain reversal is easier than continued forward deformation (Bauschinger effect), provided sheared relict grains dominate in the fabric. Additionally, bulk sample flow behavior was shown to be dominated by the weakest segment in the composite sample. Type IV experiments quantified the weakening effect of texture at 33-67%, depending on temperature and the degree of initial CPO. All experiments showed that deformed rocks are weaker than their protolith equivalents. Therefore, despite possible alteration of shear direction, or prior grain growth, mylonites will localize strain during the next deformation event.

Bruijn, R. H. C.; Delle Piane, C.; de Raadt, W. S.

2012-04-01

446

Characterization of the bell-shaped vibratory angular rate gyro.  

PubMed

The bell-shaped vibratory angular rate gyro (abbreviated as BVG) is a novel shell vibratory gyroscope, which is inspired by the Chinese traditional bell. It sensitizes angular velocity through the standing wave precession effect. The bell-shaped resonator is a core component of the BVG and looks like the millimeter-grade Chinese traditional bell, such as QianLong Bell and Yongle Bell. It is made of Ni43CrTi, which is a constant modulus alloy. The exciting element, control element and detection element are uniformly distributed and attached to the resonator, respectively. This work presents the design, analysis and experimentation on the BVG. It is most important to analyze the vibratory character of the bell-shaped resonator. The strain equation, internal force and the resonator's equilibrium differential equation are derived in the orthogonal curvilinear coordinate system. When the input angular velocity is existent on the sensitive axis, an analysis of the vibratory character is performed using the theory of thin shells. On this basis, the mode shape function and the simplified second order normal vibration mode dynamical equation are obtained. The coriolis coupling relationship about the primary mode and secondary mode is established. The methods of the signal processing and control loop are presented. Analyzing the impact resistance property of the bell-shaped resonator, which is compared with other shell resonators using the Finite Element Method, demonstrates that BVG has the advantage of a better impact resistance property. A reasonable means of installation and a prototypal gyro are designed. The gyroscopic effect of the BVG is characterized through experiments. Experimental results show that the BVG has not only the advantages of low cost, low power, long work life, high sensitivity, and so on, but, also, of a simple structure and a better impact resistance property for low and medium angular velocity measurements. PMID:23966183

Liu, Ning; Su, Zhong; Li, Qing; Fu, MengYin; Liu, Hong; Fan, JunFang

2013-01-01

447

Characterization of the Bell-Shaped Vibratory Angular Rate Gyro  

PubMed Central

The bell-shaped vibratory angular rate gyro (abbreviated as BVG) is a novel shell vibratory gyroscope, which is inspired by the Chinese traditional bell. It sensitizes angular velocity through the standing wave precession effect. The bell-shaped resonator is a core component of the BVG and looks like the millimeter-grade Chinese traditional bell, such as QianLong Bell and Yongle Bell. It is made of Ni43CrTi, which is a constant modulus alloy. The exciting element, control element and detection element are uniformly distributed and attached to the resonator, respectively. This work presents the design, analysis and experimentation on the BVG. It is most important to analyze the vibratory character of the bell-shaped resonator. The strain equation, internal force and the resonator's equilibrium differential equation are derived in the orthogonal curvilinear coordinate system. When the input angular velocity is existent on the sensitive axis, an analysis of the vibratory character is performed using the theory of thin shells. On this basis, the mode shape function and the simplified second order normal vibration mode dynamical equation are obtained. The coriolis coupling relationship about the primary mode and secondary mode is established. The methods of the signal processing and control loop are presented. Analyzing the impact resistance property of the bell-shaped resonator, which is compared with other shell resonators using the Finite Element Method, demonstrates that BVG has the advantage of a better impact resistance property. A reasonable means of installation and a prototypal gyro are designed. The gyroscopic effect of the BVG is characterized through experiments. Experimental results show that the BVG has not only the advantages of low cost, low power, long work life, high sensitivity, and so on, but, also, of a simple structure and a better impact resistance property for low and medium angular velocity measurements. PMID:23966183

Liu, Ning; Su, Zhong; Li, Qing; Fu, MengYin; Liu, Hong; Fan, JunFang

2013-01-01

448

The effect of humeral torsion on rotational range of motion in the shoulder and throwing performance  

PubMed Central

Several recent studies have found that throwing athletes typically have lower humeral torsion (retroversion) and a greater range of external rotation at the shoulder than non-athletes. How these two parameters are related is debated. This study uses data from a sample of both throwers and non-throwers to test a new model that predicts torsion values from a range of motion data. The model proposes a series of predicted regressions which can help provide new insight into the factors affecting rotational range of motion at the shoulder. Humeral torsion angles were measured from computed tomography scans collected from 25 male subjects. These values are compared to predicted torsion values for the same subjects calculated from both kinematic and goniometric range-of-motion data. Results show that humeral torsion is negatively correlated (goniometric: r = ?0.409, P = 0.047; kinematic: r = ?0.442, P = 0.035) with external rotational range of motion and positively correlated (goniometric: r = 0.741, P < 0.001; kinematic: r = 0.559, P = 0.006) with internal rotational range of motion. The predicted torsion values are highly correlated (goniometric: r = 0.815, P < 0.001; kinematic: r = 0.617, P = 0.006) with actual torsion values. Deviations in the data away from predicted equations highlight significant differences between high torsion and low torsion individuals that may have significant functional consequences. The method described here may be useful for non-invasively assessing the degree of torsion in studies of the evolution and biomechanics of the shoulder and arm, and for testing hypotheses about the etiology of repetitive stress injuries among athletes and others who throw frequently. PMID:22257273

Roach, Neil Thomas; Lieberman, Daniel E; Gill, Thomas J; Palmer, William E; Gill, Thomas J

2012-01-01

449

The trace on the K-theory of group C*-algebras  

Microsoft Academic Search

The canonical trace on the reduced C*-algebra of a discrete group gives rise to a homomorphism from the K-theory of this C^*-algebra to the real numbers. This paper addresses the range of this homomorphism. For torsion free groups, the Baum-Connes conjecture and Atiyah's L2-index theorem implies that the range consists of the integers. If the group is not torsion free,

Thomas Schick

1999-01-01

450

Light Gluino And Tevatroin Dijet Angular Distributions  

E-print Network

We consider the effects of a light gluino on the dijet angular distributions in p - pbar collisions at sqrt(s)=1800 GeV. We show that the slower running of alpha_s and the production q qbar, g g -> Gino Gino do not significantly alter the expected angular distributions. On the other hand, single U, D squark production q g -> Q Gino with subsequent Q -> q g results in dijets whose angular distributions are dramatically different from that in SM. The CDF data on dijet angular distributions with integrated luminosity of 106 pb^(-1) exclude U, D squarks in the mass ranges 170 < m < 650 and 190 < m < 600 GeV, We consider lower energies as well and show that in a future experimental analysis for dijet mass below 240 GeV squarks could be observed or ruled out.

Igor V. Terekhov

1997-02-11

451

The physics of angular momentum radio  

E-print Network

Wireless communications, radio astronomy and other radio science applications are mainly implemented with techniques built on top of the electromagnetic linear momentum (Poynting vector) physical layer. As a supplement and/or alternative to this conventional approach, techniques rooted in the electromagnetic angular momentum physical layer have been advocated, and promising results from proof-of-concept radio communication experiments using angular momentum were recently published. This sparingly exploited physical observable describes the rotational (spinning and orbiting) physical properties of the electromagnetic fields and the rotational dynamics of the pertinent charge and current densities. In order to facilitate the exploitation of angular momentum techniques in real-world implementations, we present a systematic, comprehensive theoretical review of the fundamental physical properties of electromagnetic angular momentum observable. Starting from an overview that puts it into its physical context among ...

Thidé, B; Then, H; Someda, C G; Ravanelli, R A

2014-01-01

452

Angular momentum effects in weak gravitational fields  

E-print Network

It is shown that, contrary to what is normally expected, it is possible to have angular momentum effects on the geometry of space time at the laboratory scale, much bigger than the purely Newtonian effects. This is due to the fact that the ratio between the angular momentum of a body and its mass, expressed as a length, is easily greater than the mass itself, again expressed as a length.

A. Tartaglia

2002-01-02

453

Conservation of the spin and orbital angular momenta in electromagnetism  

NASA Astrophysics Data System (ADS)

We review and re-examine the description and separation of the spin and orbital angular momenta (AM) of an electromagnetic field in free space. While the spin and orbital AM of light are not separately meaningful physical quantities in orthodox quantum mechanics or classical field theory, these quantities are routinely measured and used for applications in optics. A meaningful quantum description of the spin and orbital AM of light was recently provided by several authors, which describes separately conserved and measurable integral values of these quantities. However, the electromagnetic field theory still lacks corresponding locally conserved spin and orbital AM currents. In this paper, we construct these missing spin and orbital AM densities and fluxes that satisfy the proper continuity equations. We show that these are physically measurable and conserved quantities. These are, however, not Lorentz-covariant, so only make sense in the single laboratory reference frame of the measurement probe. The fluxes we derive improve the canonical (nonconserved) spin and orbital AM fluxes, and include a ‘spin–orbit’ term that describes the spin–orbit interaction effects observed in nonparaxial optical fields. We also consider both standard and dual-symmetric versions of the electromagnetic field theory. Applying the general theory to nonparaxial optical vortex beams validates our results and allows us to discriminate between earlier approaches to the problem. Our treatment yields the complete and consistent description of the spin and orbital AM of free Maxwell fields in both quantum-mechanical and field-theory approaches.

Bliokh, Konstantin Y.; Dressel, Justin; Nori, Franco

2014-09-01

454

On Capacity-Maximizing Angular Densities of Multipath in MIMO Channels  

E-print Network

been studied in [2]. The uniform angular density within a sector has been investigated Loyka School of Information Technology and Engineering University of Ottawa 161 Louis Pasteur, Ottawa of multipath in MIMO channels?" using the size-asymptotic theory of Toeplitz matrices for uniform 2-D and 3-D

Loyka, Sergey

455

A detection system with broad angular acceptance for particle identification and angular distribution measurements  

NASA Astrophysics Data System (ADS)

A new detection system for time-optimized heavy-ion angular distribution measurements has been designed and constructed. This device is composed by an ionization chamber with a segmented-grid anode and three position-sensitive silicon detectors. This particular arrangement allows identifying reaction products emitted within a 30° wide angular range with better than 1° angular resolution. As a demonstration of its capabilities, angular distributions of the elastic scattering cross-section and the production of alpha particles in the 7Li+27Al system, at an energy above the Coulomb barrier, are presented.

Carnelli, P. F. F.; Arazi, A.; Ferná