The human ocular torsion position response during yaw angular acceleration.
Smith, S T; Curthoys, I S; Moore, S T
1995-07-01
Recent results by Wearne [(1993) Ph.D. thesis] using the scleral search-coil method of measuring eye position indicate that changes in ocular torsion position (OTP) occur during yaw angular acceleration about an earth vertical axis. The present set of experiments, using an image processing method of eye movement measurement free from the possible confound of search coil slippage, demonstrates the generality and repeatability of this phenomenon and examines its possible causes. The change in torsion position is not a linear vestibulo-ocular reflex (LVOR) response to interaural linear acceleration stimulation of the otoliths, but rather the effect is dependent on the characteristics of the angular acceleration stimulus, commencing at the onset and decaying at the offset of the angular acceleration. In the experiments reported here, the magnitude of the angular acceleration stimulus was varied and the torsion position response showed corresponding variations. We consider that the change in torsion position observed during angular acceleration is most likely to be due to activity of the semicircular canals.
35. VERTICAL AND TORSIONAL MOTION FROM EAST TOWER SHOWING ANGULAR ...
35. VERTICAL AND TORSIONAL MOTION FROM EAST TOWER SHOWING ANGULAR DISTORTION APPROACHING 45 DEGREES WITH LAMP POSTS APPEARING TO BE AT EIGHT ANGLES, 7 NOVEMBER 1940, FROM 16MN FILM SHOT BY PROFESSOR F.B. FARQUHARSON, UNIVERSITY OF WASHINGTON. (LABORATORY STUDIES ON THE TACOMA NARROWS BRIDGE, AT UNIVERSITY OF WASHINGTON SEATTLE: UNIVERSITY OF WASHINGTON, DEPARTMENT OF CIVIL ENGINEERING, 1941) - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA
Studies of torsional properties of DNA and nucleosomes using angular optical trapping
NASA Astrophysics Data System (ADS)
Sheinin, Maxim Y.
DNA in vivo is subjected to torsional stress due to the action of molecular motors and other DNA-binding proteins. Several decades of research have uncovered the fascinating diversity of DNA transformations under torsion and the important role they play in the regulation of vital cellular processes such as transcription and replication. Recent studies have also suggested that torsion can influence the structure and stability of nucleosomes---basic building blocks of the eukaryotic genome. However, our understanding of the impact of torsion is far from being complete due to significant experimental challenges. In this work we have used a powerful single-molecule experimental technique, angular optical trapping, to address several long-standing issues in the field of DNA and nucleosome mechanics. First, we utilized the high resolution and direct torque measuring capability of the angular optical trapping to precisely measure DNA twist-stretch coupling. Second, we characterized DNA melting under tension and torsion. We found that torsionally underwound DNA forms a left-handed structure, significantly more flexible compared to the regular B-DNA. Finally, we performed the first comprehensive investigation of the single nucleosome behavior under torque and force. Importantly, we discovered that positive torque causes significant dimer loss, which can have implications for transcription through chromatin.
Quan, Li-Di; Xue, Chao; Shao, Cheng-Gang; Yang, Shan-Qing; Tu, Liang-Cheng; Wang, Yong-Ji; Luo, Jun
2014-01-01
The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to [Formula: see text] at the signal frequency of 2 mHz, which contributes a [Formula: see text] uncertainty to the G value.
Torsional Newton-Cartan geometry from Galilean gauge theory
NASA Astrophysics Data System (ADS)
Banerjee, Rabin; Mukherjee, Pradip
2016-11-01
Using the recently advanced Galilean gauge theory (GGT) we give a comprehensive construction of torsional Newton-Cartan (NC) geometry. The coupling of a Galilean symmetric model with background NC geometry following GGT is illustrated by a free nonrelativistic scalar field theory. The issue of spatial diffeomorphism (Son and Wingate 2006 Ann. Phys. 321 197-224 Banerjee et al 2015 Phys. Rev. D 91 084021) is focussed from a new angle. The expression of the torsionful connection is worked out, which is in complete parallel with the relativistic theory. Also, smooth transition of the connection to its well known torsionless expression is demonstrated. A complete (implicit) expression of the torsion tensor for the NC spacetime is provided where the first-order variables occur in a suggestive way. The well known result for the temporal part of torsion is reproduced from our expression.
Massless fermions and Kaluza--Klein theory with torsion
Wu, Y.; Zee, A.
1984-09-01
A pure Kaluza--Klein theory contains no massless fermion in four-dimensional theory. We investigate the effect of introducing torsion on the internal manifold and find that there are massless fermions. The hope is that given an isometry group the representation to which these fermions belong is fixed, in contrast to the situation in Yang--Mills theory. We show that this is indeed the case, but the representations do not appear to be the ones favored by current theoretical prejudice. The cases with parallelizable torsions on a group manifold as the internal manifold are analyzed in detail.
NASA Astrophysics Data System (ADS)
Meroño, P. A.; Gómez, F. C.; Marín, F.; Zaghar, L.
2017-02-01
One of the widely used processes to measure torsional vibration focuses on the analysis of a square signal from a device set in the machine shaft. The tools used for this purpose usually consist of a toothed wheel connected to an appropriate transducer, of an electromagnetic or optic type, which provides a square wave signal. If the rotation velocity is constant, the signal pulses are the same width, but when the velocity changes, the width of the pulses changes too, lengthening or shortening its width, resulting in a frequency modulated signal. When the shafts of the machines are misaligned angularly, the average speed changes due to variable torque action, so that spectral features of modulated signal show frequency components that are explained by the Bessel Functions. This work shows that these components are caused by a carrying (constant average speed) and a modulator signal (variable turning speed) between the harmonics surrounding the central frequency. Besides, it may also test their relationship with the presence of angular misalignment in the coupled-machine shafts. In addition, an iterative method is applied to construct the frequency spectral diagram of the induced square signal, once the appropriate modulation indices of the Bessel functions have been calculated. To compare and validate the method, different bench tests have been performed using pulse signal and laser interferometry.
Constraining torsion with Gravity Probe B
Mao Yi; Guth, Alan H.; Cabi, Serkan; Tegmark, Max
2007-11-15
It is well-entrenched folklore that all torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally, and consider nonstandard torsion theories in which torsion can be generated by macroscopic rotating objects. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope would be expected to feel torsion. An experiment with a gyroscope (without nuclear spin) such as Gravity Probe B (GPB) can test theories where this is the case. Using symmetry arguments, we show that to lowest order, any torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the parametrized post-Newtonian formalism and provide a concrete framework for further testing Einstein's general theory of relativity (GR). We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B is an ideal experiment for further constraining nonstandard torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters.
Micromechanical torsional digital-to-analog converter for open-loop angular positioning applications
NASA Astrophysics Data System (ADS)
Zhou, Guangya; Tay, Francis E. H.; Chau, Fook Siong; Zhao, Yi; Logeeswaran, VJ
2004-05-01
This paper reports a novel micromechanical torsional digital-to-analog converter (MTDAC), operated in open-loop with digitally controlled precise multi-level tilt angles. The MTDAC mechanism presented is analogous to that of an electrical binary-weighted-input digital-to-analog converter (DAC). It consists of a rigid tunable platform, an array of torsional microactuators, each operating in a two-state (on/off) mode, and a set of connection beams with binary-weighted torsional stiffnesses that connect the actuators to the platform. The feasibility of the proposed MTDAC mechanism was verified numerically by finite element simulations and experimentally with a commercial optical phase-shifting interferometric system. A prototype 2-bit MTDAC was implemented using the poly-MUMPS process achieving a full-scale output tilt angle of 1.92° with a rotation step of 0.64°. This mechanism can be configured for many promising applications, particularly in beam steering-based OXC switches.
New torsion black hole solutions in Poincaré gauge theory
NASA Astrophysics Data System (ADS)
Cembranos, Jose A. R.; Gigante Valcarcel, Jorge
2017-01-01
We derive a new exact static and spherically symmetric vacuum solution in the framework of the Poincaré gauge field theory with dynamical massless torsion. This theory is built in such a form that allows to recover General Relativity when the first Bianchi identity of the model is fulfilled by the total curvature. The solution shows a Reissner-Nordström type geometry with a Coulomb-like curvature provided by the torsion field. It is also shown the existence of a generalized Reissner-Nordström-de Sitter solution when additional electromagnetic fields and/or a cosmological constant are coupled to gravity.
Angular momentum algebra for symbolic expansions in atomic structure theory
NASA Astrophysics Data System (ADS)
Matulioniene, Rasa
Computer programs based on multiconfiguration methods have become standard tools in atomic structure theory. Reliable predictions of atomic properties require very large configuration expansions. The computational resources required often exceed the capabilities of conventional computers. There is a need to restructure existing computer programs to take advantage of modern high-performance computational technology. This dissertation deals with one important aspect of the effort to implement two widely used atomic structure packages (MCHF and GRASP92) on distributed memory parallel computers: the method for handling the angular momentum algebra. In the existing algorithms, the angular integrations required for the Hamiltonian matrix elements are computed for each pair of configurations, even though the results may be identical or very similar for all configurations of a given type. This redundancy leads to a significant increase in computer resource requirements, because the angular matrix elements, which are repeatedly reused in the calculation, need to be stored in computer memory or on disk. At present, the size (and, therefore, accuracy) of the calculations is limited by the large amounts of angular data produced. The aim of the research reported in this dissertation is to provide the theoretical basis for a computational method to curtail the growth of stored angular data with the size of the calculation. The multiconfiguration basis is often generated by one- and two-particle replacements from a reference set to correlation orbitals. The redundancy in the stored angular data could be removed by reformulating the algorithm to treat simultaneously all angular matrix elements that differ only in the quantum numbers of the correlation orbitals. To accomplish this, we expand N- electron matrix elements of a general symmetric two-body scalar operator, an example of which is the Hamiltonian, in terms of two-electron matrix elements. Using diagrammatic methods of
The self-similarity theory of high pressure torsion
Beygelzimer, Yan; Toth, Laszlo S; Ivanisenko, Yulia
2016-01-01
Summary By analyzing the problem of high pressure torsion (HPT) in the rigid plastic formulation, we show that the power hardening law of plastically deformed materials leads to self-similarity of HPT, admitting a simple mathematical description of the process. The analysis shows that the main parameters of HPT are proportional to βq, with β being the angle of the anvil rotation. The meaning of the parameter q is: q = 0 for velocity and strain rate, q = 1 for shear strain and von Mises strain, q = n for stress, pressure and torque (n is the exponent of a power hardening law). We conclude that if the hardening law is a power law in a rotation interval β, self-similar regimes can emerge in HPT if the friction with the lateral wall of the die is not too high. In these intervals a simple mathematical description can be applied based on self-similarity. Outside these ranges, the plasticity problem still has to be solved for each value of β. The results obtained have important practical implications for the proper design and analysis of HPT experiments. PMID:27826500
The self-similarity theory of high pressure torsion.
Beygelzimer, Yan; Kulagin, Roman; Toth, Laszlo S; Ivanisenko, Yulia
2016-01-01
By analyzing the problem of high pressure torsion (HPT) in the rigid plastic formulation, we show that the power hardening law of plastically deformed materials leads to self-similarity of HPT, admitting a simple mathematical description of the process. The analysis shows that the main parameters of HPT are proportional to β (q) , with β being the angle of the anvil rotation. The meaning of the parameter q is: q = 0 for velocity and strain rate, q = 1 for shear strain and von Mises strain, q = n for stress, pressure and torque (n is the exponent of a power hardening law). We conclude that if the hardening law is a power law in a rotation interval β, self-similar regimes can emerge in HPT if the friction with the lateral wall of the die is not too high. In these intervals a simple mathematical description can be applied based on self-similarity. Outside these ranges, the plasticity problem still has to be solved for each value of β. The results obtained have important practical implications for the proper design and analysis of HPT experiments.
Gyrokinetic theory and simulation of angular momentum transport
Waltz, R. E.; Staebler, G. M.; Candy, J.; Hinton, F. L.
2007-12-15
A gyrokinetic theory of turbulent toroidal angular momentum transport as well as modifications to neoclassical poloidal rotation from turbulence is formulated starting from the fundamental six-dimensional kinetic equation. The gyro-Bohm scaled transport is evaluated from toroidal delta-f gyrokinetic simulations using the GYRO code [Candy and Waltz, J. Comput. Phys. 186, 545 (2003)]. The simulations recover two pinch mechanisms in the radial transport of toroidal angular momentum: The slab geometry ExB shear pinch [Dominguez and Staebler, Phys. Fluids B 5, 387 (1993)] and the toroidal geometry 'Coriolis' pinch [Peeters, Angioni, and Strintzi, Phys. Rev. Lett. 98, 265003 (2007)]. The pinches allow the steady state null stress (or angular momentum transport flow) condition required to understand intrinsic (or spontaneous) toroidal rotation in heated tokamak without an internal source of torque [Staebler, Kinsey, and Waltz, Bull. Am. Phys. Soc. 46, 221 (2001)]. A predicted turbulent shift in the neoclassical poloidal rotation [Staebler, Phys. Plasmas 11, 1064 (2004)] appears to be small at the finite relative gyroradius (rho-star) of current experiments.
The two rigid body interaction using angular momentum theory formulae
NASA Astrophysics Data System (ADS)
Boué, Gwenaël
2017-01-01
This work presents an elegant formalism to model the evolution of the full two rigid body problem. The equations of motion, given in a Cartesian coordinate system, are expressed in terms of spherical harmonics and Wigner D-matrices. The algorithm benefits from the numerous recurrence relations satisfied by these functions allowing a fast evaluation of the mutual potential. Moreover, forces and torques are straightforwardly obtained by application of ladder operators taken from the angular momentum theory and commonly used in quantum mechanics. A numerical implementation of this algorithm is made. Tests show that the present code is significantly faster than those currently available in literature.
Álvarez-Asencio, R; Thormann, E; Rutland, M W
2013-09-01
A technique has been developed for the calculation of torsional spring constants for AFM cantilevers based on the combination of the normal spring constant and plate/beam theory. It is easy to apply and allow the determination of torsional constants for stiff cantilevers where the thermal power spectrum is difficult to obtain due to the high resonance frequency and low signal/noise ratio. The applicability is shown to be general and this simple approach can thus be used to obtain torsional constants for any beam shaped cantilever.
Singularity in the Laboratory Frame Angular Distribution Derived in Two-Body Scattering Theory
ERIC Educational Resources Information Center
Dick, Frank; Norbury, John W.
2009-01-01
The laboratory (lab) frame angular distribution derived in two-body scattering theory exhibits a singularity at the maximum lab scattering angle. The singularity appears in the kinematic factor that transforms the centre of momentum (cm) angular distribution to the lab angular distribution. We show that it is caused in the transformation by the…
Sokolovski, D.; Msezane, A.Z.
2004-09-01
A semiclassical complex angular momentum theory, used to analyze atom-diatom reactive angular distributions, is applied to several well-known potential (one-particle) problems. Examples include resonance scattering, rainbow scattering, and the Eckart threshold model. Pade reconstruction of the corresponding matrix elements from the values at physical (integral) angular momenta and properties of the Pade approximants are discussed in detail.
Non-vanishing superpotentials in heterotic string theory and discrete torsion
NASA Astrophysics Data System (ADS)
Buchbinder, Evgeny I.; Ovrut, Burt A.
2017-01-01
We study the non-perturbative superpotential in E 8 × E 8 heterotic string theory on a non-simply connected Calabi-Yau manifold X, as well as on its simply connected covering space tilde{X} . The superpotential is induced by the string wrapping holomorphic, isolated, genus 0 curves. According to the residue theorem of Beasley and Witten, the non-perturbative superpotential must vanish in a large class of heterotic vacua because the contributions from curves in the same homology class cancel each other. We point out, however, that in certain cases the curves treated in the residue theorem as lying in the same homology class, can actually have different area with respect to the physical Kahler form and can be in different homology classes. In these cases, the residue theorem is not directly applicable and the structure of the superpotential is more subtle. We show, in a specific example, that the superpotential is non-zero both on tilde{X} and on X. On the non-simply connected manifold X, we explicitly compute the leading contribution to the superpotential from all holomorphic, isolated, genus 0 curves with minimal area. The reason for the non-vanishing of the superpotental on X is that the second homology class contains a finite part called discrete torsion. As a result, the curves with the same area are distributed among different torsion classes and, hence, do not cancel each other.
NASA Astrophysics Data System (ADS)
Sabbaghianrad, Shima
A commercial Al-7075 alloy was processed by severe plastic deformation (SPD) techniques, namely equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) or a combination of the two processes. After processing, the microstructural properties were examined, microhardness measurements were recorded across the disk diameters, and miniature tensile specimens were pulled to failure at a temperature of 623 K. Using TEM and EBSD techniques, it is demonstrated that the three SPD processing techniques have a potential for producing an ultrafine-grain structure containing reasonably equiaxed grains with high-angle grain boundary misorientations. However, microstructures were refined to different levels depending on the processing operation. It is shown that the most refined grain structure was achieved after processing by a combination of ECAP for 8 passes and HPT. The grain refinement mechanisms are primarily governed by dislocation activities. It is shown that the maximum saturation hardness achieved at high equivalent strains by different processing techniques increases with increasing amounts of deformation and it is the highest after processing by a combination of ECAP for 8 passes and HPT. The saturation hardness values were ˜231 after processing by HPT, ˜249 after processing by ECAP for 4 passes + HPT and ˜273 after processing by ECAP for 8 passes + HPT. Tensile testings show that the elongations to failure increase by increasing the amount of deformation. It is shown that after ECAP for 8 passes + HPT samples of the Al-7075 alloy have lower flow stresses and superplastic elongations up to >1000% when pulling to failure at 623 K. Superplastic elongations were not achieved after processing only by ECAP because of the non-uniform grain size and the presence of many larger grains.
Thin-Walled Beam Theories and Their Applications in the Torsional Strength Analysis of Ship Hulls.
1987-01-01
numerous deep web frames and transverse bulkheads. The system has been utilized in a study of a frigate under an assumed torsional/flexural load, the...transverse bulkheads and r deep web frames. Figure 18 indicates that, despite the poor agreement in twist angle, the axial stress results compare quite...under torsional loads. This will be the case for a typical warship hull, because of the large number of deep web frames and transverse bulkheads. The
Belyaev, Mikhail A.; Rafikov, Roman R.; Stone, James M.
2013-06-10
The nature of angular momentum transport in the boundary layers of accretion disks has been one of the central and long-standing issues of accretion disk theory. In this work we demonstrate that acoustic waves excited by supersonic shear in the boundary layer serve as an efficient mechanism of mass, momentum, and energy transport at the interface between the disk and the accreting object. We develop the theory of angular momentum transport by acoustic modes in the boundary layer, and support our findings with three-dimensional hydrodynamical simulations, using an isothermal equation of state. Our first major result is the identification of three types of global modes in the boundary layer. We derive dispersion relations for each of these modes that accurately capture the pattern speeds observed in simulations to within a few percent. Second, we show that angular momentum transport in the boundary layer is intrinsically nonlocal, and is driven by radiation of angular momentum away from the boundary layer into both the star and the disk. The picture of angular momentum transport in the boundary layer by waves that can travel large distances before dissipating and redistributing angular momentum and energy to the disk and star is incompatible with the conventional notion of local transport by turbulent stresses. Our results have important implications for semianalytical models that describe the spectral emission from boundary layers.
Generalization of Equivalent Crystal Theory to Include Angular Dependence
NASA Technical Reports Server (NTRS)
Ferrante, John; Zypman, Fredy R.
2004-01-01
In the original Equivalent Crystal Theory, each atomic site in the real crystal is assigned an equivalent lattice constant, in general different from the ground state one. This parameter corresponds to a local compression or expansion of the lattice. The basic method considers these volumetric transformations and, in addition, introduces the possibility that the reference lattice is anisotropically distorted. These distortions however, were introduced ad-hoc. In this work, we generalize the original Equivalent Crystal Theory by systematically introducing site-dependent directional distortions of the lattice, whose corresponding distortions account for the dependence of the energy on anisotropic local density variations. This is done in the spirit of the original framework, but including a gradient term in the density. This approach is introduced to correct a deficiency in the original Equivalent Crystal Theory and other semiempirical methods in quantitatively obtaining the correct ratios of the surface energies of low index planes of cubic metals (100), (110), and (111). We develop here the basic framework, and apply it to the calculation of Fe (110) and Fe (111) surface energy formation. The results, compared with first principles calculations, show an improvement over previous semiempirical approaches.
Crystal Field Theory and the Angular Overlap Model Applied to Hydrides of Main Group Elements.
ERIC Educational Resources Information Center
Moore, E. A.
1990-01-01
Described is how crystal field theory and the angular overlap model can be applied to very simple molecules which can then be used to introduce such concepts as bonding orbitals, MO diagrams, and Walsh diagrams. The main-group compounds are used as examples and a switch to the transition metal complexes. (KR)
Dangerous angular Kaluza-Klein/glueball relics in string theory cosmology
Dufaux, J. F.; Kofman, L.; Peloso, M.
2008-07-15
The presence of Kaluza-Klein (KK) particles in the universe is a potential manifestation of string theory cosmology. In general, they can be present in the high temperature bath of the early universe. In particular examples, string theory inflation often ends with brane-antibrane annihilation followed by the energy cascading through massive closed string loops to KK modes which then decay into lighter standard model particles. However, massive KK modes in the early universe may become dangerous cosmological relics if the inner manifold contains warped throat(s) with approximate isometries. In the complimentary picture, in the AdS/CFT dual gauge theory with extra isometries, massive glueballs of various spins become the dangerous cosmological relics. The decay of these angular KK modes/glueballs, located around the tip of the throat, is caused by isometry breaking which results from gluing the throat to the compact Calabi-Yau (CY) manifold. We address the problem of these angular KK particles/glueballs, studying their interactions and decay channels, from the theory side, and the resulting cosmological constraints on the warped compactification parameters, from the phenomenology side. The abundance and decay time of the long-lived nonrelativistic angular KK modes depend strongly on the parameters of the warped geometry, so that observational constraints rule out a significant fraction of the parameter space. In particular, the coupling of the angular KK particles can be weaker than gravitational.
Zhou, Yun Pollak, Eli; Miret-Artés, Salvador
2014-01-14
A second order classical perturbation theory is developed and applied to elastic atom corrugated surface scattering. The resulting theory accounts for experimentally observed asymmetry in the final angular distributions. These include qualitative features, such as reduction of the asymmetry in the intensity of the rainbow peaks with increased incidence energy as well as the asymmetry in the location of the rainbow peaks with respect to the specular scattering angle. The theory is especially applicable to “soft” corrugated potentials. Expressions for the angular distribution are derived for the exponential repulsive and Morse potential models. The theory is implemented numerically to a simplified model of the scattering of an Ar atom from a LiF(100) surface.
... Journal of Urology. 2011;185:2469. Hittelman AB. Neonatal testicular torsion. http://www.uptodate.com/home. Accessed ... 16, 2015. Snyder HM, et al. In utero/neonatal torsion: Observation versus prompt exploration. Journal of Urology. ...
Propagating torsion in the Einstein frame
NASA Astrophysics Data System (ADS)
Popławski, Nikodem J.
2006-11-01
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.
Inverse problems for torsional modes.
Willis, C.
1984-01-01
Considers a spherically symmetric, non-rotating Earth consisting of an isotropic, perfect elastic material where the density and the S-wave velocity may have one or two discontinuities in the upper mantle. Shows that given the velocity throughout the mantle and the crust and given the density in the lower mantle, then the freqencies of the torsional oscillations of one angular order (one torsional spectrum), determine the density in the upper mantle and in the crust uniquely. If the velocity is known only in the lower mantle, then the frequencies of the torsional oscillations of two angular orders uniquely determine both the density and the velocity in the upper mantle and in the crust. In particular, the position and size of the discontinuities in the density and velocity are uniquely determined by two torsional spectra.-Author
NASA Astrophysics Data System (ADS)
Feng, Liang; Zeng, Zhi-ge; Wu, Yong-qian
2013-08-01
In order to test the high dynamic range error beyond one wavelength after the rough polish process, we design a phase retrieval hybrid algorithm based on diffraction angular spectrum theory. Phase retrieval is a wave front sensing method that uses the intensity distribution to reconstruct the phase distribution of optical field. Phase retrieval is established on the model of diffractive propagation and approach the real intensity distribution gradually. In this paper, we introduce the basic principle and challenges of optical surface measurement using phase retrieval, then discuss the major parts of phase retrieval: diffractive propagation and hybrid algorithm. The angular spectrum theory describes the diffractive propagation in the frequency domain instead of spatial domain, which simplifies the computation greatly. Through the theoretical analysis, the angular spectrum in discrete form is more effective when the high frequency part values less and the diffractive distance isn't far. The phase retrieval hybrid algorithm derives from modified GS algorithm and conjugate gradient method, aiming to solve the problem of phase wrapping caused by the high dynamic range error. In the algorithm, phase distribution is described by Zernike polynomials and the coefficients of Zernike polynomials are optimized by the hybrid algorithm. Simulation results show that the retrieved phase distribution and real phase distribution are quite contiguous for the high dynamic range error beyond λ.
NASA Technical Reports Server (NTRS)
Hanson, Donald B.; Parzych, David J.
1993-01-01
This report presents the derivation of a frequency domain theory and working equations for radiation of propeller harmonic noise in the presence of angular inflow. In applying the acoustic analogy, integration over the tangential coordinate of the source region is performed numerically, permitting the equations to be solved without approximation for any degree of angular inflow. Inflow angle is specified in terms of yaw, pitch, and roll angles of the aircraft. Since these can be arbitrarily large, the analysis applies with equal accuracy to propellers and helicopter rotors. For thickness and loading, the derivation is given in complete detail with working equations for near and far field. However, the quadrupole derivation has been carried only far enough to show feasibility of the numerical approach. Explicit formulas are presented for computation of source elements, evaluation of Green's functions, and location of observer points in various visual and retarded coordinate systems. The resulting computer program, called WOBBLE has been written in FORTRAN and follows the notation of this report very closely. The new theory is explored to establish the effects of varying inflow angle on axial and circumferential directivity. Also, parametric studies were performed to evaluate various phenomena outside the capabilities of earlier theories, such as an unsteady thickness effect. Validity of the theory was established by comparison with test data from conventional propellers and Prop Fans in flight and in wind tunnels under a variety of operating conditions and inflow angles.
Ringdahl, Erika; Teague, Lynn
2006-11-15
Each year, testicular torsion affects one in 4,000 males younger than 25 years. Early diagnosis and definitive management are the keys to avoid testicular loss. All prepubertal and young adult males with acute scrotal pain should be considered to have testicular torsion until proven otherwise. The finding of an ipsilateral absent cremasteric reflex is the most accurate sign of testicular torsion. Torsion of the appendix testis is more common in children than testicular torsion and may be diagnosed by the "blue dot sign" (i.e., tender nodule with blue discoloration on the upper pole of the testis). Epididymitis/orchitis is much less common in the prepubertal male, and the diagnosis should be made with caution in this age group. Doppler ultrasonography may be needed for definitive diagnosis; radionuclide scintigraphy is an alternative that may be more accurate but should be ordered only if it can be performed without delay. Diagnosis of testicular torsion is based on the finding of decreased or absent blood flow on the ipsilateral side. Treatment involves rapid restoration of blood flow to the affected testis. The optimal time frame is less than six hours after the onset of symptoms. Manual detorsion by external rotation of the testis can be successful, but restoration of blood flow must be confirmed following the maneuver. Surgical exploration provides definitive treatment for the affected testis by orchiopexy and allows for prophylactic orchiopexy of the contralateral testis. Surgical treatment of torsion of the appendix testis is not mandatory but hastens recovery.
Mass and angular momentum of black holes in low-energy heterotic string theory
NASA Astrophysics Data System (ADS)
Peng, Jun-Jin
2016-04-01
We investigate conserved charges in the low-energy effective field theory describing heterotic string theory. Starting with a general Lagrangian that consists of a metric, a scalar field, a vector gauge field, together with a two-form potential, we derive off-shell Noether potentials of the Lagrangian and generalize the Abbott-Deser-Tekin (ADT) formalism to the off-shell level by establishing one-to-one correspondence between the ADT potential and the off-shell Noether potential. It is proved that the off-shell generalized ADT formalism is conformally invariant. Then, we apply the formulation to compute mass and angular momentum of the four-dimensional Kerr-Sen black hole and the five-dimensional rotating charged black string in the string frame without a necessity to transform the metrics into the Einstein frame.
Nonlinear Hysteretic Torsional Waves
NASA Astrophysics Data System (ADS)
Cabaret, J.; Béquin, P.; Theocharis, G.; Andreev, V.; Gusev, V. E.; Tournat, V.
2015-07-01
We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.
Nonlinear Hysteretic Torsional Waves.
Cabaret, J; Béquin, P; Theocharis, G; Andreev, V; Gusev, V E; Tournat, V
2015-07-31
We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.
Liu, Yuan; Ning, Chuangang
2015-10-14
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li(-), C(-), O(-), F(-), CH(-), OH(-), NH2 (-), O2 (-), and S2 (-) show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.
Abbasi, Mohammad; Karami Mohammadi, Ardeshir
2015-05-01
A relationship based on a nonlocal elasticity theory is developed to investigate the torsional sensitivity and resonant frequency of an atomic force microscope (AFM) with assembled cantilever probe (ACP). This ACP comprises a horizontal cantilever and a vertical extension, and a tip located at the free end of the extension, which makes the AFM capable of topography at sidewalls of microstructures. First, the governing differential equations of motion and boundary conditions for dynamic analysis are obtained by a combination of the basic equations of nonlocal elasticity theory and Hamilton's principle. Afterward, a closed-form expression for the sensitivity of vibration modes has been obtained using the relationship between the resonant frequency and contact stiffness of cantilever and sample. These analysis accounts for a better representation of the torsional behavior of an AFM with sidewall probe where the small-scale effect are significant. The results of the proposed model are compared with those of classical beam theory. The results show that the sensitivities and resonant frequencies of ACP predicted by the nonlocal elasticity theory are smaller than those obtained by the classical beam theory.
Bigoni, D.; Dal Corso, F.; Misseroni, D.; Bosi, F.
2014-01-01
One edge of an elastic rod is inserted into a friction-less and fitting socket head, whereas the other edge is subjected to a torque, generating a uniform twisting moment. It is theoretically shown and experimentally proved that, although perfectly smooth, the constraint realizes an expulsive axial force on the elastic rod, which amount is independent of the shape of the socket head. The axial force explains why screwdrivers at high torque have the tendency to disengage from screw heads and demonstrates torsional locomotion along a perfectly smooth channel. This new type of locomotion finds direct evidence in the realization of a ‘torsional gun’, capable of transforming torque into propulsive force. PMID:25383038
Totenhofer, A J; Connor, J N L; Nyman, Gunnar
2016-03-03
The differential cross section (DCS) for the CH4 + Cl → CH3 + HCl reaction is studied at six total energies where all of the species are in their ground states. The scattering (S) matrix elements have been calculated by the rotating line umbrella method for a dual-level ab initio analytic potential energy surface. We make the first application to this reaction of nearside-farside (NF) and local angular momentum (LAM) techniques, including resummation orders (r) of 0, 1, 2, and 3 for the partial-wave series representation of the full scattering amplitude. We find that resummation usually cleans the NF r = 0 DCSs of unphysical oscillations, especially at small angles. This cleaning effect is typically most pronounced when changing from no resummation (r = 0) to r = 1; further resummations from r = 1 to r = 2 and from r = 2 to r = 3 have smaller effects. The NF DCS analyses show that the reaction is N-dominated at sideward and large angles, whereas at small angles there are oscillations caused by NF interference. The NF LAM analysis provides consistent and complementary information, in particular for the total angular momenta that contribute to the reaction at different scattering angles. The NF analyses also provide justification for simpler N-dominant dynamical theories such as the semiclassical optical model, which provides an explanation for the distorted mirror image effect for the moduli of the S matrix elements and the DCSs, as well as the use of a hard-sphere DCS over limited angular ranges.
Liu, Yuan; Ning, Chuangang
2015-10-14
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li{sup −}, C{sup −}, O{sup −}, F{sup −}, CH{sup −}, OH{sup −}, NH{sub 2}{sup −}, O{sub 2}{sup −}, and S{sub 2}{sup −} show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.
NASA Astrophysics Data System (ADS)
Zhao, Yang; Gong, Yan; Li, Shun; Zhang, Wei
2010-08-01
Off-axis illumination (OAI) technology is widely used to enhance resolution for deep ultraviolet lithography. The realizing methods of OAI include geometrical optics method and physical optics method. However, the former has the disadvantage of weak intensity distribution controlling ability, and the latter introduces simulation errors evidently when dealing with near field diffraction propagation. A diffractive optical element (DOE) designing method using plane wave angular spectrum theory is presented in this paper. Several kinds of OAI modes at near field away from DOE can be realized, and simulation errors and the size of illuminator are also reduced. According to studying the relationships of the sampling point distance of DOE, light beam propagation distance, and the structure of the beam shaping unit, a method of determining the designing parameters is discussed. Using this method, several illumination modes are realized, and simulation results show that all diffraction efficiencies reach up to 84%. The method of DOE manufacturing is analyzed at last, and it is proven to be feasible.
A kinetic theory for nonanalog Monte Carlo algorithms: Exponential transform with angular biasing
Ueki, T.; Larsen, E.W.
1998-11-01
A new Boltzmann Monte Carlo (BMC) equation is proposed to describe the transport of Monte Carlo particles governed by a set of nonanalog rules for the transition of space, velocity, and weight. The BMC equation is a kinetic equation that includes weight as an extra independent variable. The solution of the BMC equation is the pointwise distribution of velocity and weight throughout the physical system. The BMC equation is derived for the simulation of a transmitted current, utilizing the exponential transform with angular biasing. The weight moments of the solution of the BMC equation are used to predict the score moments of the transmission current. (Also, it is shown that an adjoint BMC equation can be used for this purpose.) Integrating the solution of the forward BMC equation over space, velocity, and weight, the mean number of flights per history is obtained. This is used to determine theoretically the figure of merit for any choice of biasing parameters. Also, a maximum safe value of the exponential transform parameter is proposed, which ensure the finite variance of variance estimate (sample variance) for any penetration distance. Finally, numerical results that validate the new theory are provided.
Torsional and rotational couplings in nonrigid molecules
NASA Astrophysics Data System (ADS)
Omiste, Juan J.; Madsen, Lars Bojer
2017-02-01
We analyze theoretically the interplay between the torsional and the rotational motion of an aligned biphenyl-like molecule. To do so, we consider a transition between two electronic states with different internal torsional potentials, induced by means of a resonant laser pulse. The change in the internal torsional potential provokes the motion of the torsional wave packet in the excited electronic state, modifying the structure of the molecule, and hence, its inertia tensor. We find that this process has a strong impact on the rotational wave function, displaying different behavior depending on the electronic states involved and their associated torsional potentials. We describe the dynamics of the system by considering the degree of alignment and the expectation values of the angular momentum operators for the overall rotation of the molecule.
Axions in gravity with torsion
NASA Astrophysics Data System (ADS)
Castillo-Felisola, Oscar; Corral, Cristóbal; Kovalenko, Sergey; Schmidt, Iván; Lyubovitskij, Valery E.
2015-04-01
We study a scenario allowing a solution of the strong charge parity problem via the Peccei-Quinn mechanism, implemented in gravity with torsion. In this framework there appears a torsion-related pseudoscalar field known as the Kalb-Ramond axion. We compare it with the so-called Barbero-Immirzi axion recently proposed in the literature also in the context of the gravity with torsion. We show that they are equivalent from the viewpoint of the effective theory. The phenomenology of these torsion-descended axions is completely determined by the Planck scale without any additional model parameters. These axions are very light and very weakly interacting with ordinary matter. We briefly comment on their astrophysical and cosmological implications in view of the recent BICEP2 and Planck data.
The angular momentum content of dwarf galaxies: new challenges for the theory of galaxy formation
NASA Astrophysics Data System (ADS)
van den Bosch, Frank C.; Burkert, Andreas; Swaters, Rob A.
2001-09-01
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 ΛCDM universe. We find that although the disc mass fractions are significantly smaller than the universal baryon fraction, the total specific angular momenta of the discs are in good agreement with those of dark matter haloes. This suggests that discs form out of only a small fraction of the available baryons, but yet manage to draw most of the available angular momentum. In addition we find that the angular momentum distributions of discs are clearly distinct from those of the dark matter; discs lack predominantly both low and high specific angular momenta. Understanding these findings in terms of a coherent picture for disc formation is challenging. Cooling, feedback and stripping, which are the main mechanisms to explain the small disc mass fractions found, seem unable to simultaneously explain the angular momentum distributions of the discs. In fact, it seems that the baryons that make up the discs must have been born out of angular momentum distributions that are clearly distinct from those of ΛCDM haloes. However, the dark and baryonic mass components experience the same tidal forces, and it is therefore expected that they should have similar angular momentum distributions. Therefore, understanding the angular momentum content of disc galaxies remains an important challenge for our picture of galaxy formation.
Face-seal lubrication. 2: Theory of response to angular misalignement
NASA Technical Reports Server (NTRS)
Ludwig, L. P.; Allen, G. P.
1976-01-01
A theoretical analysis was made of a hypothetical seal operating mode. The hypothetical seal model provides for three degrees of primary ring motion and includes the force and moments induced by primary ring response to seat angular misalignment. This ring response causes a relative angular misalignment between the faces of the primary seal. Hydrodynamic pressure generation is produced by this misalignment. The analysis is based on the Reynolds equation in short bearing form and on a balance of forces and moments that arise from hydrodynamic and secondary seal friction effects. A closed form solution was obtained that can be solved for film thickness and relative angular misalignment.
NASA Astrophysics Data System (ADS)
Freifelder, R.; Prakash, M.; Alexander, John M.
1986-02-01
We examine the application of transition-state theory for fission-fragment angular distributions to composite nuclei near the limits of stability. The possible roles of saddle-point and scission-point configurations are explored. For many heavy-ion reactions that involve large angular momenta, the observed anisotropies are between the predictions of the saddle-point and scisson-point models. Empirical correlations are shown between the effective moments of inertia and the spin and {Z 2}/{A} of the compound nucleus. These correlations provide evidence for a class of transition-state nuclei intermediate between saddle- and scission-point configurations. An important indication of these patterns is that the speed of collective deformation toward fission may well be slow enough to allow for statistical equilibrium in the tilting mode even for configurations well beyond the saddle point.
Hankel, Marlies E-mail: j.n.l.connor@manchester.ac.uk; Connor, J. N. L. E-mail: j.n.l.connor@manchester.ac.uk
2015-07-15
A valuable tool for understanding the dynamics of direct reactions is Nearside-Farside (NF) scattering theory. It makes a decomposition of the (resummed) partial wave series for the scattering amplitude, both for the differential cross section (DCS) and the Local Angular Momentum (LAM). This paper makes the first combined application of these techniques to complex-mode reactions. We ask if NF theory is a useful tool for their identification, in particular, can it distinguish complex-mode from direct-mode reactions? We also ask whether NF theory can identify NF interference oscillations in the full DCSs of complex-mode reactions. Our investigation exploits the fact that accurate quantum scattering matrix elements have recently become available for complex-mode reactions. We first apply NF theory to two simple models for the scattering amplitude of a complex-mode reaction: One involves a single Legendre polynomial; the other involves a single Legendre function of the first kind, whose form is suggested by complex angular momentum theory. We then study, at fixed translational energies, four state-to-state complex-mode reactions. They are: S({sup 1}D) + HD → SH + D, S({sup 1}D) + DH → SD + H, N({sup 2}D) +H{sub 2} → NH + H, and H{sup +} + D{sub 2} → HD + D{sup +}. We compare the NF results for the DCSs and LAMs with those for a state-to-state direct reaction, namely, F + H{sub 2} → FH + H. We demonstrate that NF theory is a valuable tool for identifying and analyzing the dynamics of complex-mode reactions.
Thermoelastic damping in torsion microresonators with coupling effect between torsion and bending
NASA Astrophysics Data System (ADS)
Tai, Yongpeng; Li, Pu; Fang, Yuming
2014-02-01
Predicting thermoelastic damping (TED) is crucial in the design of high Q MEMS resonators. In the past, there have been few works on analytical modeling of thermoelastic damping in torsion microresonators. This could be related to the assumption of pure torsional mode for the supporting beams in the torsion devices. The pure torsional modes of rectangular supporting beams involve no local volume change, and therefore, they do not suffer any thermoelastic loss. However, the coupled motion of torsion and bending usually exists in the torsion microresonator when it is not excited by pure torque. The bending component of the coupled motion causes flexural vibrations of supporting beams which may result in significant thermoelastic damping for the microresonator. This paper presents an analytical model for thermoelastic damping in torsion microresonators with the coupling effect between torsion and bending. The theory derives a dynamic model for torsion microresonators considering the coupling effect, and approximates the thermoelastic damping by assuming the energy loss to occur only in supporting beams of flexural vibrations. The thermoelastic damping obtained by the present model is compared to the measured internal friction of single paddle oscillators. It is found that thermoelastic damping contributes significantly to internal friction for the case of the higher modes at room temperature. The present model is validated by comparing its results with the finite-element method (FEM) solutions. The effects of structural dimensions and other parameters on thermoelastic damping are investigated for the representative case of torsion microresonators.
Noncontact measurement of angular deflection
NASA Technical Reports Server (NTRS)
Bryant, E. L.
1978-01-01
Technique for measuring instantaneous angular deflection of object requires no physical contact. Technique utilizes two flat refractors, converging lens, and different photocell. Distinction of method is its combination of optical and electromechanical components into feedback system in which measurement error is made to approach zero. Application is foreseen in measurement of torsional strain.
Torsionally mediated spin-rotation hyperfine splittings at moderate to high J values in methanol.
Belov, S P; Golubiatnikov, G Yu; Lapinov, A V; Ilyushin, V V; Alekseev, E A; Mescheryakov, A A; Hougen, J T; Xu, Li-Hong
2016-07-14
This paper presents an explanation based on torsionally mediated proton-spin-overall-rotation interaction for the observation of doublet hyperfine splittings in some Lamb-dip sub-millimeter-wave transitions between ground-state torsion-rotation states of E symmetry in methanol. These unexpected doublet splittings, some as large as 70 kHz, were observed for rotational quantum numbers in the range of J = 13 to 34, and K = - 2 to +3. Because they increase nearly linearly with J for a given branch, we confined our search for an explanation to hyperfine operators containing one nuclear-spin angular momentum factor I and one overall-rotation angular momentum factor J (i.e., to spin-rotation operators) and ignored both spin-spin and spin-torsion operators, since they contain no rotational angular momentum operator. Furthermore, since traditional spin-rotation operators did not seem capable of explaining the observed splittings, we constructed totally symmetric "torsionally mediated spin-rotation operators" by multiplying the E-species spin-rotation operator by an E-species torsional-coordinate factor of the form e(±niα). The resulting operator is capable of connecting the two components of a degenerate torsion-rotation E state. This has the effect of turning the hyperfine splitting pattern upside down for some nuclear-spin states, which leads to bottom-to-top and top-to-bottom hyperfine selection rules for some transitions, and thus to an explanation for the unexpectedly large observed hyperfine splittings. The constructed operator cannot contribute to hyperfine splittings in the A-species manifold because its matrix elements within the set of torsion-rotation A1 and A2 states are all zero. The theory developed here fits the observed large doublet splittings to a root-mean-square residual of less than 1 kHz and predicts unresolvable splittings for a number of transitions in which no doublet splitting was detected.
McKown, Benjamin G; Ceriotti, Michele; Womack, Caroline C; Kamarchik, Eugene; Butler, Laurie J; Bowman, Joel M
2013-10-24
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
Torsional Optomechanics of a Levitated Nonspherical Nanoparticle
NASA Astrophysics Data System (ADS)
Hoang, Thai M.; Ma, Yue; Ahn, Jonghoon; Bang, Jaehoon; Robicheaux, F.; Yin, Zhang-Qi; Li, Tongcang
2016-09-01
An optically levitated nanoparticle in vacuum is a paradigm optomechanical system for sensing and studying macroscopic quantum mechanics. While its center-of-mass motion has been investigated intensively, its torsional vibration has only been studied theoretically in limited cases. Here we report the first experimental observation of the torsional vibration of an optically levitated nonspherical nanoparticle in vacuum. We achieve this by utilizing the coupling between the spin angular momentum of photons and the torsional vibration of a nonspherical nanoparticle whose polarizability is a tensor. The torsional vibration frequency can be 1 order of magnitude higher than its center-of-mass motion frequency, which is promising for ground state cooling. We propose a simple yet novel scheme to achieve ground state cooling of its torsional vibration with a linearly polarized Gaussian cavity mode. A levitated nonspherical nanoparticle in vacuum will also be an ultrasensitive nanoscale torsion balance with a torque detection sensitivity on the order of 10-29 N m /√{Hz } under realistic conditions.
Membranes from monopole operators in ABJM theory: Large angular momentum and M-theoretic AdS4/CFT3
NASA Astrophysics Data System (ADS)
Kovacs, Stefano; Sato, Yuki; Shimada, Hidehiko
2014-09-01
We study the duality between M-theory in AdS_4 × S^7/{Z}_k and the ABJM {N}=6 Chern-Simons-matter theory with gauge group U(N) × {U}(N) and level k, taking N large and k of order 1. In this M-theoretic regime the lack of an explicit formulation of M-theory in AdS_4 × S^7/{Z}_k makes the gravity side difficult, while the CFT is strongly coupled and the planar approximation is not applicable. We focus on states on the gravity side with large angular momentum J≫ 1 associated with a single plane of rotation in S^7 and identify their dual operators in the CFT. We show that natural approximation schemes arise on both sides thanks to the presence of the small parameter 1/J. On the AdS side, we use the matrix model of M-theory on the maximally supersymmetric pp-wave background with matrices of size J/k. A perturbative treatment of this matrix model provides a good approximation to M-theory in AdS_4 × S^7/{Z}_k when N^{1/3}≪ J≪ N^{1/2}. On the CFT side, we study the theory on S^2× {R} with magnetic flux J/k. A Born-Oppenheimer-type expansion arises naturally for large J in spite of the theory being strongly coupled. The energy spectra on the two sides agree at leading order. This provides a non-trivial test of the AdS_4/CFT_3 correspondence including near-BPS observables associated with membrane degrees of freedom, thus verifying the duality beyond the previously studied sectors corresponding to either BPS observables or the type IIA string regime.
Bowlin, Paul R; Gatti, John M; Murphy, J Patrick
2017-02-01
The pediatric patient presenting with acute scrotal pain requires prompt evaluation and management given the likelihood of testicular torsion as the underlying cause. Although other diagnoses can present with acute testicular pain, it is important to recognize the possibility of testicular torsion because the best chance of testicular preservation occurs with expeditious management. When testicular torsion is suspected, prompt surgical exploration is warranted. A delay in surgical management should not occur in an effort to obtain confirmatory imaging. When torsion is discovered, the contralateral testicle should undergo fixation to reduce the risk of asynchronous torsion.
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-03-26
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are n(i, f) similar to 10(4)-10(5). We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 10(15) G, where n(i, f) similar to 10(12)-10(13), from the results for n(i, f) similar to 10(4)-10(5). The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).
Tscherbul, T V; Dalgarno, A
2010-11-14
An efficient method is presented for rigorous quantum calculations of atom-molecule and molecule-molecule collisions in a magnetic field. The method is based on the expansion of the wave function of the collision complex in basis functions with well-defined total angular momentum in the body-fixed coordinate frame. We outline the general theory of the method for collisions of diatomic molecules in the (2)Σ and (3)Σ electronic states with structureless atoms and with unlike (2)Σ and (3)Σ molecules. The cross sections for elastic scattering and Zeeman relaxation in low-temperature collisions of CaH((2)Σ(+)) and NH((3)Σ(-)) molecules with (3)He atoms converge quickly with respect to the number of total angular momentum states included in the basis set, leading to a dramatic (>10-fold) enhancement in computational efficiency compared to the previously used methods [A. Volpi and J. L. Bohn, Phys. Rev. A 65, 052712 (2002); R. V. Krems and A. Dalgarno, J. Chem. Phys. 120, 2296 (2004)]. Our approach is thus well suited for theoretical studies of strongly anisotropic molecular collisions in the presence of external electromagnetic fields.
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; ...
2016-03-26
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are n(i, f) similar to 10(4)-10(5). We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one canmore » infer the decay width in more realistic magnetic fields of 10(15) G, where n(i, f) similar to 10(12)-10(13), from the results for n(i, f) similar to 10(4)-10(5). The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).« less
DOE R&D Accomplishments Database
Schwinger, J.
1952-01-26
The commutation relations of an arbitrary angular momentum vector can be reduced to those of the harmonic oscillator. This provides a powerful method for constructing and developing the properties of angular momentum eigenvectors. In this paper many known theorems are derived in this way, and some new results obtained. Among the topics treated are the properties of the rotation matrices; the addition of two, three, and four angular momenta; and the theory of tensor operators.
NASA Astrophysics Data System (ADS)
Zhang, C.; Yuan, H.; Tang, Z.; Quan, W.; Fang, J. C.
2016-12-01
Rotation measurement in an inertial frame is an important technology for modern advanced navigation systems and fundamental physics research. Inertial rotation measurement with atomic spin has demonstrated potential in both high-precision applications and small-volume low-cost devices. After rapid development in the last few decades, atomic spin gyroscopes are considered a promising competitor to current conventional gyroscopes—from rate-grade to strategic-grade applications. Although it has been more than a century since the discovery of the relationship between atomic spin and mechanical rotation by Einstein [Naturwissenschaften, 3(19) (1915)], research on the coupling between spin and rotation is still a focus point. The semi-classical Larmor precession model is usually adopted to describe atomic spin gyroscope measurement principles. More recently, the geometric phase theory has provided a different view of the rotation measurement mechanism via atomic spin. The theory has been used to describe a gyroscope based on the nuclear spin ensembles in diamond. A comprehensive understanding of inertial rotation measurement principles based on atomic spin would be helpful for future applications. This work reviews different atomic spin gyroscopes and their rotation measurement principles with a historical overlook. In addition, the spin-rotation coupling mechanism in the context of the quantum phase theory is presented. The geometric phase is assumed to be the origin of the measurable rotation signal from atomic spins. In conclusion, with a complete understanding of inertial rotation measurements using atomic spin and advances in techniques, wide application of high-performance atomic spin gyroscopes is expected in the near future.
Meana-Pañeda, Rubén; Fernández-Ramos, Antonio
2014-05-07
This work reports a detailed theoretical study of the hydrogen abstraction reactions from ethanol by atomic hydrogen. The calculated thermal rate constants take into account torsional anharmonicity and conformational flexibility, in addition to the variational and tunneling effects. Specifically, the kinetics calculations were performed by using multi-path canonical variational transition state theory with least-action path tunneling corrections, to which we have added the two-dimensional non-separable method to take into account torsional anharmonicity. The multi-path thermal rate constant is expressed as a sum over conformational reaction channels. Each of these channels includes all the transition states that can be reached by internal rotations. The results show that, in the interval of temperatures between 250 and 2500 K, the account for multiple paths leads to higher thermal rate constants with respect to the single path approach, mainly at low and at high temperatures. In addition, torsional anharmonicity enhances the slope of the Arrhenius plot in this range of temperatures. Finally, we show that the incorporation of tunneling into the hydrogen abstraction reactions substantially changes the contribution of each of the transition states to the conformational reaction channel.
NASA Technical Reports Server (NTRS)
Leese, G. E.
1984-01-01
Torsional fatigue testing and data analysis procedures are described. Since there are no standards governing cyclic torsion testing that are generally accepted on a widespread basis by the technical community, the different approaches that dominate current experimental activity, and the ramifications of each are discussed. Particular attention is given to the theoretical and experimental difficulties that have paced refinement and general acceptance of test procedures. Finally, specific quantities and nomenclature modelled after analagous axial fatigue properties are suggested as an effective way to communicate torsional fatigue results until accepted standards are established.
NASA Astrophysics Data System (ADS)
Huang, Changyu; Huang, Yong-Chang; Zhou, Bao-Hua
2015-09-01
We investigate the inner structure of a general S U (2 ) [naturally including S O (3 )] symmetry system—the fermion-gauge field interaction system—and achieve naturally a set of gauge-invariant spin and orbital angular momentum operators of fermion and gauge fields by Noether's theorem in general field theory. Some new relations concerning non-Abelian field strengths are discovered, e.g., the covariant transverse condition, covariant parallel condition (i.e., non-Abelian divergence, non-Abelian curl), and simplified S U (2 ) Coulomb theorem. And we show that the condition that Chen et al. obtained to construct their gauge-invariant angular momentum operators is a result of some fundamental equations in the general field theory. The results obtained in this paper present a new perspective for looking at the overall structure of the gauge field, and provide a new viewpoint to the final resolution of the nucleon spin crisis in the general field theory. Especially, the achieved theory in this paper can calculate the strong interactions with isospin symmetry and solves the serious problem without gauge-invariant angular momenta in strong interaction systems with isospin symmetry, and then the achieved predictions in the calculations can be exactly measured by particle physics experiments due to their gauge invariant properties.
NASA Astrophysics Data System (ADS)
Gültekin, Kemal
2016-03-01
In this study, we give a thorough analysis of a general affine gravity with torsion. After a brief exposition of the affine gravities considered by Eddington and Schrödinger, we construct and analyze different affine gravities based on the determinants of the Ricci tensor, the torsion tensor, the Riemann tensor, and their combinations. In each case we reduce equations of motion to their simplest forms and give a detailed analysis of their solutions. Our analyses lead to the construction of the affine connection in terms of the curvature and torsion tensors. Our solutions of the dynamical equations show that the curvature tensors at different points are correlated via non-local, exponential rescaling factors determined by the torsion tensor.
[Adnexal torsion: three cases].
Sánez, Henry Aristóteles Mateo; Taboada-Pérez, Grecia Carolina; Hernández-Arroyo, Lysandra; Mateo-Madrigal, Melissa; Mateo-Madrigal, Victoria
2013-05-01
Adnexal torsion is a gynecological emergency caused by the torsion of the ovary over its pedicle producing lymphatic and venous stasis, later it develops into ischemia and necrosis, when is not treated. Until recently, the treatment for adnexal torsion has been adnexectomy. This paper report three cases treated successfully with conservative treatment. It is essential to establish a protocol for adnexal torsion management where radical treatments are abandoned and conservative surgeries, such as detorsion and plication, are performed. We suggest as a first choice management adnexal detorsion, in case malignity is suspected to have intraoperative pathologic analysis, and based on the results to decide to preserve the adnexal or remove it for definitive cure.
Testicular Torsion (For Parents)
... ON THIS TOPIC Hernias Ultrasound: Scrotum Undescended Testicles Male Reproductive System PQ: I have a lump on one of ... How to Perform a Testicular Self-Examination Varicocele Male Reproductive System Testicular Torsion Contact Us Print Resources Send to ...
Structural and torsional vibration analysis of a dry screw compressor
NASA Astrophysics Data System (ADS)
Willie, J.; Sachs, R.
2015-08-01
This paper investigates torsional vibration and pulsating noise in a dry screw compressor. The compressor is designed at Gardner Denver (GD) and is oil free and use for mounting on highway trucks. They are driven using a Power Take-Off (PTO) transmission and gear box on a truck. Torque peak fluctuation and noise measurements are done and their sources are investigated and reported in this work. To accurately predict the torsional response (frequency and relative angular deflection and torque amplitude), the Holzer method is used. It is shown that the first torsional frequency is manifested as sidebands in the gear train meshing frequencies and this can lead to noise that is the result of amplitude modulation. Sensitivity analysis of the drive train identifies the weakest link in the drive train that limits the first torsional frequency to a low value. Finally, the significance of higher mode shapes on inter-lobe clearance distribution of the rotors is investigated.
Clark, G
2003-04-28
This report describes a feasibility study. We are interested in calculating the angular and linear velocities of a re-entry vehicle using six acceleration signals from a distributed accelerometer inertial measurement unit (DAIMU). Earlier work showed that angular and linear velocity calculation using classic nonlinear ordinary differential equation (ODE) solvers is not practically feasible, due to mathematical and numerical difficulties. This report demonstrates the theoretical feasibility of using model-based nonlinear state estimation techniques to obtain the angular and linear velocities in this problem. Practical numerical and calibration issues require additional work to resolve. We show that the six accelerometers in the DAIMU are not sufficient to provide observability, so additional measurements of the system states are required (e.g. from a Global Positioning System (GPS) unit). Given the constraint that our system cannot use GPS, we propose using the existing on-board 3-axis magnetometer to measure angular velocity. We further show that the six nonlinear ODE's for the vehicle kinematics can be decoupled into three ODE's in the angular velocity and three ODE's in the linear velocity. This allows us to formulate a three-state Gauss-Markov system model for the angular velocities, using the magnetometer signals in the measurement model. This re-formulated model is observable, allowing us to build an Extended Kalman Filter (EKF) for estimating the angular velocities. Given the angular velocity estimates from the EKF, the three ODE's for the linear velocity become algebraic, and the linear velocity can be calculated by numerical integration. Thus, we do not need direct measurements of the linear velocity to provide observability, and the technique is mathematically feasible. Using a simulation example, we show that the estimator adds value over the numerical ODE solver in the presence of measurement noise. Calculating the velocities in the presence of
NASA Technical Reports Server (NTRS)
Devries, P. L.; George, T. F.
1978-01-01
The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.
Torsional wave propagation in solar tornadoes
NASA Astrophysics Data System (ADS)
Vasheghani Farahani, S.; Ghanbari, E.; Ghaffari, G.; Safari, H.
2017-02-01
Aims: We investigate the propagation of torsional waves in coronal structures together with their collimation effects in the context of magnetohydrodynamic (MHD) theory. The interplay of the equilibrium twist and rotation of the structure, e.g. jet or tornado, together with the density contrast of its internal and external media is studied to shed light on the nature of torsional waves. Methods: We consider a rotating magnetic cylinder embedded in a plasma with a straight magnetic field. This resembles a solar tornado. In order to express the dispersion relations and phase speeds of the axisymmetric magnetohydrodynamic waves, the second-order thin flux tube approximation is implemented for the internal medium and the ideal MHD equations are implemented for the external medium. Results: The explicit expressions for the phase speed of the torsional wave show the modification of the torsional wave speed due to the equilibrium twist, rotation, and density contrast of the tornado. The speeds could be either sub-Alfvénic or ultra-Alfvénic depending on whether the equilibrium twist or rotation is dominant. The equilibrium twist increases the phase speed while the equilibrium rotation decreases it. The good agreement between the explicit versions for the phase speed and that obtained numerically proves adequate for the robustness of the model and method. The density ratio of the internal and external media also play a significant role in the speed and dispersion. Conclusions: The dispersion of the torsional wave is an indication of the compressibility of the oscillations. When the cylinder is rotating or twisted, in contrast to when it only possesses a straight magnetic field, the torsional wave is a collective mode. In this case its phase speed is determined by the Alfvén waves inside and outside the tornado.
Testicular Torsion (For Parents)
... damaged. As a general rule: within about 4-6 hours of the start of the torsion, the testicle can be saved 90% of the time after 12 hours, this drops to 50% after 24 hours, the testicle can be saved only 10% ...
NASA Technical Reports Server (NTRS)
Ihrke, Chris A. (Inventor); Parsons, Adam H. (Inventor); Mehling, Joshua S. (Inventor); Griffith, Bryan Kristian (Inventor)
2012-01-01
A torsion spring comprises an inner mounting segment. An outer mounting segment is located concentrically around the inner mounting segment. A plurality of splines extends from the inner mounting segment to the outer mounting segment. At least a portion of each spline extends generally annularly around the inner mounting segment.
NASA Astrophysics Data System (ADS)
Coppi, B.
2007-11-01
Differentially rotating structures in the prevalent field of a central object have been shown to develop a ``crystal'' magnetic structure resulting from toroidal internal currents and leading to the formation of density ring sequencesootnotetextB. Coppi and F. Rousseau, Ap. J. 641, 458 (2006) rather than disks. Poloidal current densities with appropriate symmetries are found to be connected with angular momentum transport processes represented by an effective viscosity. Jets are suggested to consist of a series of stable ``smoke- rings'' ejected vertically in opposite directions from the central region of the considered ring sequence. A small inward flow velocity is shown to induce a spiral pattern in the magnetic field lines on a selected family of magnetic surfaces. The accretion theoryootnotetextB. Coppi, Nuc. Fus. 42, 1 (2002) of the spontaneous rotation phenomenon in toroidal laboratory plasmas relies on the ejection of angular momentum toward the surrounding material wall, by collisional ballooning modes excited at the edge, whose phase velocity depends on collisionality. The resulting recoil gives rise to the rotation of the main body of the plasma column as other plasma modes (called VTG) provide the needed inward transport of angular momentum. *Sponsored in part by the US D.O.E.
Evaluation of the torsional VOR in weightlessness.
Clarke, A H; Teiwes, W; Scherer, H
1993-01-01
The experimental concept and findings from a recent manned orbital spaceflight are described. Together with ongoing terrestrial and parabolic studies, the present experiment is intended to further our knowledge of the sensory integrative processing of information from the semicircular canals and the otolithic receptors, and to quantify the presumed otolithic adaptation to altered gravito-inertial force environments in a more reliable manner than to date. The experiment included measurement of the basic vestibulo-oculomotor response during active head rotation about each of the three orthogonal axes. Priority was given to the recording of ocular torsion, as elicited by head oscillation about the roll axis, and thus due to the concomitant stimulation of the semicircular canals and otolith receptors. Videooculography was employed for the measurement of eye movements; head movement was measured by three orthogonally arranged angular rate sensors and a triaxial linear accelerometer device. All signals were recorded synchronously on a video/data recorder. Preliminary results indicate alterations in the torsional VOR under zero-g conditions, suggesting an adaptive modification of the torsional VOR gain over the course of the 6-day orbital flight. In addition, the inflight test findings yielded discrepancies between intended and performed head movement, indicating impairment in sensorimotor coordination under prolonged microgravity conditions.
Spin on perinatal testicular torsion.
Samnakay, Naeem; Tudehope, David; Walker, Rosslyn
2006-11-01
We describe a recent case of perinatal testicular torsion at our institution. The presentation, management and outcome of perinatal testicular torsion are quite different to testicular torsion in the general paediatric population. The literature describes a variety of management options for perinatal testicular torsion and these are briefly reviewed. In cases of unilateral perinatal testicular torsin, there is controversy over whether surgery to fix the contralateral testis is required, and if so, the appropriate timing for the surgery. A good understanding of the issues unique to perinatal torsion will facilitate appropriate counseling of parents of affected neonates.
ERIC Educational Resources Information Center
Parker, G. W.
1978-01-01
Discusses, classically and quantum mechanically, the angular momentum induced in the bound motion of an electron by an external magnetic field. Calculates the current density and its magnetic moment, and then uses two methods to solve the first-order perturbation theory equation for the required eigenfunction. (Author/GA)
Torsional anharmonicity in the conformational thermodynamics of flexible molecules
NASA Astrophysics Data System (ADS)
Miller, Thomas F., III; Clary, David C.
We present an algorithm for calculating the conformational thermodynamics of large, flexible molecules that combines ab initio electronic structure theory calculations with a torsional path integral Monte Carlo (TPIMC) simulation. The new algorithm overcomes the previous limitations of the TPIMC method by including the thermodynamic contributions of non-torsional vibrational modes and by affordably incorporating the ab initio calculation of conformer electronic energies, and it improves the conventional ab initio treatment of conformational thermodynamics by accounting for the anharmonicity of the torsional modes. Using previously published ab initio results and new TPIMC calculations, we apply the algorithm to the conformers of the adrenaline molecule.
ERIC Educational Resources Information Center
Shakur, Asif; Sinatra, Taylor
2013-01-01
The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…
Dirican, A; Burak, I; Ara, C; Unal, B; Ozgor, D; Meydanli, M M
2009-01-01
Wandering spleen is characterized by ectopic localization of spleen owing to the lack or weakening of the major splenic ligaments. In present study, two cases with torsion of wandering spleen were reported. The first case was a 30-year-old female who was admitted to emergency department with acute abdominal pain and vomiting. Abdominal Ultrasonography and computed tomography showed a round solid hypodense mass that was located in the left hypochondriac region of abdomen. At laparotomy, the patient was found to have torsion of a wandering spleen with complete infarction and pancreatic tail infarction. Splenectomy and distal pancreatectomy were performed. The second patient was a 19-year-old female. She was admitted to emergency department with abdominal pain. Axial computed tomography (CT) showed pelvic mass that indicated a possibility of a wandering spleen. The wandering spleen was removed with its long pedicle because of infarction. Torsion of wandering spleen must be considered in differential diagnosis of acute abdomen when a palpable painful abdominal mass is present on physical examination, and the spleen is absent in its normal anatomical location on radiological examination (Fig. 4, Ref. 8). Full Text (Free, PDF) www.bmj.sk.
Primordial magnetic fields and dynamos from parity violated torsion
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.
2012-05-01
It is well known that torsion induced magnetic fields may seed galactic dynamos, but the price one pays for that is the conformal and gauge invariance breaks and a tiny photon mass. More recently I have shown [L.C. Garcia de Andrade, Phys. Lett. B 468 (2011) 28] that magnetic fields decay in a gauge invariant non-minimal coupling theory of torsion is slow down, which would allow for dynamo action to take place. In this Letter, by adding a parity violation term of the type Rɛ to the non-coupling term, a magnetic dynamo equation is obtained. From dynamo equation it is shown that torsion terms only appear in the dynamo equation when diffusion in the cosmic plasma is present. Torsion breaks the homogeneity of the magnetic field in the universe. Since Zeldovich anti-dynamo theorem assumes that the spacetime should be totally flat, torsion is responsible for violation of anti-dynamo theorem in 2D spatial dimensions. Contrary to previous results torsion induced primordial magnetic fields cannot seed galactic dynamos since from torsion and diffusion coefficient the decaying time of the magnetic field is 106yrs, which is much shorter than the galaxy age.
Constraining spacetime torsion with the Moon and Mercury
March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone
2011-05-15
We report a search for new gravitational physics phenomena based on Riemann-Cartan theory of general relativity including spacetime torsion. Starting from the parametrized torsion framework of Mao, Tegmark, Guth, and Cabi, we analyze the motion of test bodies in the presence of torsion, and, in particular, we compute the corrections to the perihelion advance and to the orbital geodetic precession of a satellite. We consider the motion of a test body in a spherically symmetric field, and the motion of a satellite in the gravitational field of the Sun and the Earth. We describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general differ from geodesics when torsion is present. We derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of celestial mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter of the satellite. The computed secular variations show how the corrections to the perihelion advance and to the orbital de Sitter effect depend on the torsion parameters. All computations are performed under the assumptions of weak field and slow motion. To test our predictions, we use the measurements of the Moon's geodetic precession from lunar laser ranging data, and the measurements of Mercury's perihelion advance from planetary radar ranging data. These measurements are then used to constrain suitable linear combinations of the torsion parameters.
Development of Torsional and Linear Piezoelectrically Driven Motors
NASA Technical Reports Server (NTRS)
Duong, Khanh; Newton, David; Garcia, Ephrahim
1996-01-01
The development of rotary and linear inchworm-motors using piezoelectric actuators is presented. The motors' design has the advantage of a macro and micro stepper motor with high load and speed. The torsional design is capable of fast angular positioning with micro level accuracy. Additionally, the rotary motor, as designed, can be used as a clutch/brake mechanism. Constructed prototype motors of both types along with their characteristics are presented. The torsional motor consists of a torsional section that provides angular displacement and torque, and two alternating clamping sections which provide the holding force. The motor relies on the principal piezoelectric coupling coefficient (d33) with no torsional elements, increasing its torque capability. The linear motor consists of a longitudinal vibrator that provides displacement and load, and two alternating clamping sections which provide the holding force. This design eliminates bending moment, tension and shear applied to the actuator elements, increase its load capability and life. Innovative flexure designs have been introduced for both motor types. Critical issues that affect the design and performance of the motors are explored and discussed. Experiments are performed demonstrating the motor prototypes based on the aforementioned design considerations.
Torsion effects in braneworld scenarios
Hoff da Silva, J. M.; Rocha, R. da
2010-01-15
We present gravitational aspects of braneworld models endowed with torsion terms both in the bulk and on the brane. In order to investigate a conceivable and measurable gravitational effect, arising genuinely from bulk torsion terms, we analyze the variation in the black hole area by the presence of torsion. Furthermore, we extend the well-known results about consistency conditions in a framework that incorporates brane torsion terms. It is shown, in a rough estimate, that the resulting effects are generally suppressed by the internal space volume. This formalism provides manageable models and their possible ramifications into some aspects of gravity in this context, and cognizable corrections and physical effects as well.
NASA Technical Reports Server (NTRS)
Bradas, James C.; Fennelly, Alphonsus J.; Smalley, Larry L.
1987-01-01
It is shown that a generalized (or 'power law') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley (1982, 1983). This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.
Torsion of Accessory Hepatic Lobe
Natarajan, Saravanan; Jayasudha; Periasamy, Manikandhan; Rangasamy, Saminathan
2017-01-01
An accessory hepatic lobe is a rare congenital anomaly that can undergo torsion and present as an acute surgical emergency. A 5-year-old child admitted as acute abdomen, on laparotomy found to have torsion of accessory lobe of liver, is being reported. PMID:28082782
NASA Technical Reports Server (NTRS)
Herakovich, C. T.
1978-01-01
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.
Torsion-rotation intensities in methanol
NASA Astrophysics Data System (ADS)
Pearson, John
Methanol exists in numerous kinds of astronomical objects featuring a wide range of local conditions. The light nature of the molecule coupled with the internal rotation of the methyl group with respect to the hydroxyl group results in a rich, strong spectrum that spans the entire far-infrared region. As a result, any modest size observational window will have a number of strong methanol transitions. This has made it the gas of choice for testing THz receivers and to extract the local physical conditions from observations covering small frequency windows. The latter has caused methanol to be dubbed the Swiss army knife of astrophysics. Methanol has been increasingly used in this capacity and will be used even more for subsequent investigations into the Herschel archive, and with SOFIA and ALMA. Interpreting physical conditions on the basis of a few methanol lines requires that the molecular data, line positions, intensities, and collision rates, be complete, consistent and accurate to a much higher level than previously required for astrophysics. The need for highly reliable data is even more critical for modeling the two classes of widespread maser action and many examples of optical pumping through the torsional bands. Observation of the torsional bands in the infrared will be a unique opportunity to directly connect JWST observations with those of Herschel, SOFIA, and ALMA. The theory for the intensities of torsion-rotation transitions in a molecule featuring a single internally rotating methyl group is well developed after 70 years of research. However, other than a recent very preliminary and not completely satisfactory investigation of a few CH3OH torsional bands, this theory has never been experimentally tested for any C3V internal rotor. More alarming is a set of recent intensity calibrated microwave measurements that showed deviations relative to calculations of up to 50% in some ground state rotational transitions commonly used by astronomers to extract
Big bounce from spin and torsion
NASA Astrophysics Data System (ADS)
Popławski, Nikodem J.
2012-04-01
The Einstein-Cartan-Sciama-Kibble theory of gravity naturally extends general relativity to account for the intrinsic spin of matter. Spacetime torsion, generated by spin of Dirac fields, induces gravitational repulsion in fermionic matter at extremely high densities and prevents the formation of singularities. Accordingly, the big bang is replaced by a bounce that occurred when the energy density {ɛ ∝ gT^4} was on the order of {n^2/m_Pl^2} (in natural units), where {n ∝ gT^3} is the fermion number density and g is the number of thermal degrees of freedom. If the early Universe contained only the known standard-model particles ( g ≈ 100), then the energy density at the big bounce was about 15 times larger than the Planck energy. The minimum scale factor of the Universe (at the bounce) was about 1032 times smaller than its present value, giving ≈ 50 μm. If more fermions existed in the early Universe, then the spin-torsion coupling causes a bounce at a lower energy and larger scale factor. Recent observations of high-energy photons from gamma-ray bursts indicate that spacetime may behave classically even at scales below the Planck length, supporting the classical spin-torsion mechanism of the big bounce. Such a classical bounce prevents the matter in the contracting Universe from reaching the conditions at which a quantum bounce could possibly occur.
Optical fiber accelerometer based on MEMS torsional micromirror
NASA Astrophysics Data System (ADS)
Zeng, Fanlin; Zhong, Shaolong; Xu, Jing; Wu, Yaming
2008-03-01
A novel structure of optical fiber accelerometer based on MEMS torsional micro-mirror is introduced, including MEMS torsional micro-mirror and optical signal detection. The micro-mirror is a non-symmetric one, which means that the torsional bar supporting the micro-mirror is not located in the axis where the center of the micro-mirror locates. The optical signal detection is composed of PIN diode and dual fiber collimator, which is very sensitive to the coupling angle between the input fiber and output fiber. The detection principle is that acceleration is first transformed into torsional angle of the micro-mirror, then, optical insertion loss of the dual fiber collimator caused by the angle can be received by PIN. So under the flow of acceleration to torsional angle to optical signal attenuation to optical power detection, the acceleration is detected. The theory about sensing and optical signal detect of the device are discussed in this paper. The sensitive structure parameters and performance parameters are calculated by MATLAB. To simulate the static and modal analysis, the finite element analysis, ANSYS, is employed. Based on the above calculation, several optimization methods and the final structure parameters are given. The micro-mirror is completed by using silicon-glass bonding and deep reactive ion etching (DRIE). In the experiment, the acceleration is simulated by electrostatic force and the test results show that the static acceleration detection agrees with the theory analysis very well.
Isolated penile torsion in newborns
Eroglu, Egemen; Gundogdu, Gokhan
2015-01-01
Introduction: We reported on the incidence of isolated penile torsion among our healthy children and our approach to this anomaly. Methods: Between 2011 and 2014, newborn babies with penile torsion were classified according to the angle of torsion. Surgical correction (penile degloving and reattachment for moderate cases and dorsal dartos flap technique in case of resistance) after 6 months was advised to the babies with rotations more than 45°. Results: Among 1000 newborn babies, 200 isolated penile torsions were found, and among these, 43 had torsions more than 45°, and 4 of these had angles greater than 90°. The mean angle of the rotations was found 30.45° (median: 20°). In total, 8 children with 60° torsions were previously circumcised. Surgery was performed on 19 patients, with a mean patient age of 12 ± 2 months. Of these 19, 13 babies were corrected with degloving and reattachment. This technique was not enough on the remaining 6 patients; therefore, derotational dorsal dartos flap was added to correct the torsion. After a mean of 15.6 ± 9.8 months, residual penile rotation, less than 15°, was found only in 2 children. Conclusion: The incidence of isolated penile torsion is 20% in newborns. However, rotation more than 45° angles are seen in 4.3% of male babies. Correction is not necessary in mild degrees, and penile degloving with reattachment is enough in most cases. If the initial correction is insufficient, dorsal dartos flap rotation is easy and effective. Prior circumcision neither disturbs the operative procedure nor affects the outcomes. PMID:26600889
Plastic Behavior and Fracture of Aluminum and Copper in Torsion Tests
Bressan, Jose Divo
2007-04-07
Present work investigates the plastic behavior, work hardening and the beginning of plastic instabilities, of cylindrical specimens deformed by high speed cold plastic torsion tests and at low speed tensile test. The tests were carried out in a laboratory torsion test equipment and an universal tensile test machine. The tensile tests were performed at room temperature in an universal testing machine at low strain rate of 0.034/s. Experimental torsion tests were carried out at constant angular speed that imposed a constant shear strain rate to the specimen. In the tests, the rotation speed were set to 62 rpm and 200 rpm which imposed high strain rates of about 2/s and 6.5/s respectively. The torsion tests performed at room temperature on annealed commercial pure copper and aluminum. Two types of torsion specimen for aluminum were used: solid and tubular. The solid aluminum specimen curves presented various points of maximum torque. The tubular copper specimens showed two points of maximum. Shear bands or shear strain localization at specimen were possibly the mechanism of maximum torque points formation. The work hardening coefficient n and the strain rate sensitivity parameter m were evaluated from the equivalent stress versus strain curve from tensile and torsion tests. The n-value remained constant whereas the m-value increased ten folds for aluminum specimens: from tensile test m= 0.027 and torsion test m= 0.27. However, the hardening curves were sigmoidal.
Toeplitz Operators, Analytic Torsion, and the Hypoelliptic Laplacian
NASA Astrophysics Data System (ADS)
Bismut, Jean-Michel
2016-12-01
The purpose of this paper is to explain how Toeplitz operators can be used in studying asymptotic torsion, and also in the theory of the hypoelliptic Laplacian. The role of the hypoelliptic Laplacian in the explicit computation of orbital integrals will be described. The geodesic flow will be viewed as implementing a dynamical version of Fourier transform.
New supersymmetric index of heterotic compactifications with torsion
NASA Astrophysics Data System (ADS)
Israël, Dan; Sarkis, Matthieu
2015-12-01
We compute the new supersymmetric index of a large class of N=2 heterotic compactifications with torsion, corresponding to principal two-torus bundles over warped K3 surfaces with H-flux. Starting from a UV description as a (0,2) gauged linear sigma-model with torsion, we use supersymmetric localization techniques to provide an explicit expression of the index as a sum over the Jeffrey-Kirwan residues of the one-loop determinant. We finally propose a geometrical formula that gives the new supersymmetric index in terms of bundle data, regardless of any particular choice of underlying two-dimensional theory.
Contribution to the theory of propeller vibrations
NASA Technical Reports Server (NTRS)
Liebers, F
1930-01-01
This report presents a calculation of the torsional frequencies of revolving bars with allowance for the air forces. Calculation of the flexural or bonding frequencies of revolving straight or tapered bars in terms of the angular velocity of revolution. Calculation on the basis of Rayleigh's principle of variation. There is also a discussion of error estimation and the accuracy of results. The author then provides an application of the theory to screw propellers for airplanes and the discusses the liability of propellers to damage through vibrations due to lack of uniform loading.
Torsional wave propagation in multiwalled carbon nanotubes using nonlocal elasticity
NASA Astrophysics Data System (ADS)
Arda, Mustafa; Aydogdu, Metin
2016-03-01
Torsional wave propagation in multiwalled carbon nanotubes is studied in the present work. Governing equation of motion of multiwalled carbon nanotube is obtained using Eringen's nonlocal elasticity theory. The effect of van der Waals interaction coefficient is considered between inner and outer nanotubes. Dispersion relations are obtained and discussed in detail. Effect of nonlocal parameter and van der Waals interaction to the torsional wave propagation behavior of multiwalled carbon nanotubes is investigated. It is obtained that torsional van der Waals interaction between adjacent tubes can change the rotational direction of multiwalled carbon nanotube as in-phase or anti-phase. The group and escape velocity of the waves converge to a limit value in the nonlocal elasticity approach.
NASA Astrophysics Data System (ADS)
Krot, A. M.
2013-09-01
This work develops a statistical theory of gravitating spheroidal bodies to calculate the orbits of planets and explore forms of planetary orbits with regard to the Alfvén oscillating force [1] in the Solar system and other exoplanetary systems. The statistical theory of formation of gravitating spheroidal bodies has been proposed in [2]-[5]. Starting the conception for forming a spheroidal body inside a gas-dust protoplanetary nebula, this theory solves the problem of gravitational condensation of a gas-dust protoplanetary cloud with a view to planetary formation in its own gravitational field [3] as well as derives a new law of the Solar system planetary distances which generalizes the wellknown laws [2], [3]. This work also explains an origin of the Alfvén oscillating force modifying forms of planetary orbits within the framework of the statistical theory of gravitating spheroidal bodies [5]. Due to the Alfvén oscillating force moving solid bodies in a distant zone of a rotating spheroidal body have elliptic trajectories. It means that orbits for the enough remote planets from the Sun in Solar system are described by ellipses with focus in the origin of coordinates and with small eccentricities. The nearby planet to Sun named Mercury has more complex trajectory. Namely, in case of Mercury the angular displacement of a Newtonian ellipse is observed during its one rotation on an orbit, i.e. a regular (century) shift of the perihelion of Mercury' orbit occurs. According to the statistical theory of gravitating spheroidal bodies [2]-[5] under the usage of laws of celestial mechanics in conformity to cosmogonic bodies (especially, to stars) it is necessary to take into account an extended substance called a stellar corona. In this connection the stellar corona can be described by means of model of rotating and gravitating spheroidal body [5]. Moreover, the parameter of gravitational compression α of a spheroidal body (describing the Sun, in particular) has been
Torsional oscillations in dynamo simulations
NASA Astrophysics Data System (ADS)
Wicht, Johannes; Christensen, Ulrich R.
2010-06-01
Cylinders aligned with the planetary rotation axis have a special significance in the dynamics of planetary dynamo regions. The azimuthal Lorentz forces on these geostrophic cylinders is expected to cancel to a large degree, establishing the so-called Taylor state. Deviations from this state take the form of torsional oscillations (TOs) that are supposed to represent important fast flow variations. These oscillations have reportedly been identified in the secular variation signal from the top of Earth's core. We have performed several dynamo simulations at different parameters to check whether Taylor state and TOs can also be identified in a numerical model. Taylor states are approached when viscous effects are small at Ekman numbers of E = 3 × 10-5 or below and Reynolds stresses are kept low by choosing moderate Rayleigh numbers. One-dimensional magnetic Alfvén waves that travel towards the boundaries then become prominent in the motion of the geostrophic cylinders. These waves obey the TO theory but are also damped and modified by other effects. For example, fast variations of likely convective origin remain important in all our simulations. Reynolds stresses may play a more sizable role for the dynamics in Earth's dynamo region than commonly assumed. They may also contribute to the motions of geostrophic cylinders and severely reduce the significance of TOs for the fast core dynamics. The amplitude of TOs amounts to not more than a few percent of the total flow amplitude in the simulations, which renders these motions insignificant for the long-term dynamo process.
Monks, P D D; Connor, J N L; Bouakline, F
2009-04-23
We investigate methods for filtering reaction mechanisms in the angular scattering of the state-to-state reaction, H + D(2)(v(i) = 0, j(i) = 0, m(i) = 0) --> HD(v(f) = 3, j(f) = 0, m(f) = 0) + D, where v(i), j(i), and m(i) and v(f), j(f), and m(f) are initial and final vibrational, rotational, and helicity quantum numbers, respectively. The input to our filtrations is a new set of accurate quantum scattering matrix elements for total energies in the range 1.52-2.50 eV (in steps of 0.01 eV) and for total angular momentum quantum numbers in the range, 0-40, in steps of unity. We filter reaction mechanisms in both the energy domain and the time domain. The time-domain calculations employ the plane wave packet formulation of time-dependent scattering. The theoretical tools used are nearside-farside (NF) analysis of partial wave series for scattering amplitudes, together with NF local angular momentum (LAM) theory. An energy-domain LAM analysis reveals the existence of an important dynamical feature in the N scattering, a "trench" which bisects the (energy, angle) plane. We use the location of this trench to approximately filter two reaction mechanisms. Transformation to the time domain demonstrates that the two reaction mechanisms correspond to direct and delayed (by about 25 fs) scattering. Further analysis, including filtration in the time domain, shows that the pronounced LAM trench arises from the interference of the energy-domain analogues of the time-direct and time-delayed scattering. Our theory and results provide the first successful demonstration of reaction mechanism filtering carried out directly in the (energy, angle) domain. The calculations and results in this paper extend and complement earlier research reported by Monks, Connor, and Althorpe (Monks, P. D. D.; Connor, J. N. L.; Althorpe, S. C. J. Phys. Chem. A 2006, 110, 741; J. Phys. Chem. A 2007, 111, 10302).
Torsional carbon nanotube artificial muscles.
Foroughi, Javad; Spinks, Geoffrey M; Wallace, Gordon G; Oh, Jiyoung; Kozlov, Mikhail E; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D W; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H
2011-10-28
Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated.
Torsional Carbon Nanotube Artificial Muscles
NASA Astrophysics Data System (ADS)
Foroughi, Javad; Spinks, Geoffrey M.; Wallace, Gordon G.; Oh, Jiyoung; Kozlov, Mikhail E.; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D. W.; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H.
2011-10-01
Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated.
Orbital angular momentum in phase space
Rigas, I.; Sanchez-Soto, L.L.; Klimov, A.B.; Rehacek, J.; Hradil, Z.
2011-02-15
Research Highlights: > We propose a comprehensive Weyl-Wigner formalism for the canonical pair angle-angular momentum. > We present a simple and useful toolkit for the practitioner. > We derive simple evolution equations in terms of a star product in the semiclassical limit. - Abstract: A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.
Torsional waves operating in geodynamo and magnetoconvection simulations
NASA Astrophysics Data System (ADS)
Teed, Robert; Jones, Chris; Tobias, Steve
2015-04-01
Torsional waves are a principal feature of the dynamics of the fluid outer core where the Earth's magnetic field is generated. These oscillations are Alfvén waves operating about an equilibrium known as a Taylor state (Taylor, 1963) and they propagate in the cylindrical radial direction. The change in core angular momentum inferred from geomagnetic observations has a measurable impact on the length of the day, and the small decadal variations in the length-of-day signal confirm the existence of torsional oscillations (Holme & de Viron, 2013). Many questions remain unanswered about the exact nature of these waves and this presentation will attempt to address some of these. In order to gain insight we perform three-dimensional spherical dynamo and magnetoconvection simulations in parameter regimes where Earth-like magnetic fields are produced. Many of our simulations produce the desired torsional oscillations, identified by their movement at the correct Alfvén speed, and several show Earth-like core travel times of around 4 years. Our dynamo simulations (Teed et al., 2014) show torsional waves within the tangent cylinder region that also have the ability to pass through this theoretical cylinder. By calculating the driving terms for these waves we find that both the Reynolds force and ageostrophic convection acting through the Lorentz force can be important in driving torsional oscillations. Driven by a desire to reach smaller Ekman numbers and larger magnetic field strengths, which are computationally unattainable in dynamo simulations, we perform, in our follow up work, magnetoconvection simulations (Teed et al., 2015) by imposing a dipolar field on the core-mantle boundary. Under this configuration we find a transition, at low Ekman numbers, to regimes where excitation is found only at the tangent cylinder, is delivered by the Lorentz force and gives rise to a periodic Earth-like wave pattern. This pattern is approximately operating on a 4 to 5 year timescale
Torsional rigidity, isospectrality and quantum graphs
NASA Astrophysics Data System (ADS)
Colladay, Don; Kaganovskiy, Leon; McDonald, Patrick
2017-01-01
We study torsional rigidity for graph and quantum graph analogs of well-known pairs of isospectral non-isometric planar domains. We prove that such isospectral pairs are distinguished by torsional rigidity.
Analysis on volume invariability of metal circular shaft in torsion deformation
NASA Astrophysics Data System (ADS)
Yang, Li-Hong; Zou, Guang-Ping; He, Yun-Zeng; Wang, Hui
2009-12-01
Volume invariability of metal circular shaft in the case of small strain torsion deformation and large strain torsion deformation was, respectively, discussed experimentally and theoretically in this study. In accordance with the elastoplastic theory, it was given that the shear stress did not cause the change of volume in the large strain range. By utilizing torsion experiment with the solid shaft of low carbon steel, it was proved that metal can meet the conditions of the volume invariability in torsion deformation while the cumulative damage was not very serious. Volumetric deformation was analyzed in torsion of circular shaft in the perspective of micromechanics. Finally, Swift effect of solid circular shaft and tubular shaft of brass material were interpreted by using the formulae of elastoplastic critic load obtained from double-limb bar model test presented by Shanley.
Analysis on volume invariability of metal circular shaft in torsion deformation
NASA Astrophysics Data System (ADS)
Yang, Li-Hong; Zou, Guang-Ping; He, Yun-Zeng; Wang, Hui
2010-03-01
Volume invariability of metal circular shaft in the case of small strain torsion deformation and large strain torsion deformation was, respectively, discussed experimentally and theoretically in this study. In accordance with the elastoplastic theory, it was given that the shear stress did not cause the change of volume in the large strain range. By utilizing torsion experiment with the solid shaft of low carbon steel, it was proved that metal can meet the conditions of the volume invariability in torsion deformation while the cumulative damage was not very serious. Volumetric deformation was analyzed in torsion of circular shaft in the perspective of micromechanics. Finally, Swift effect of solid circular shaft and tubular shaft of brass material were interpreted by using the formulae of elastoplastic critic load obtained from double-limb bar model test presented by Shanley.
Torsion effect of swing frame on the measurement of horizontal two-plane balancing machine
NASA Astrophysics Data System (ADS)
Wang, Qiuxiao; Wang, Dequan; He, Bin; Jiang, Pan; Wu, Zhaofu; Fu, Xiaoyan
2017-03-01
In this paper, the vibration model of swing frame of two-plane balancing machine is established to calculate the vibration center position of swing frame first. The torsional stiffness formula of spring plate twisting around the vibration center is then deduced by using superposition principle. Finally, the dynamic balancing experiments prove the irrationality of A-B-C algorithm which ignores the torsion effect, and show that the torsional stiffness deduced by experiments is consistent with the torsional stiffness calculated by theory. The experimental datas show the influence of the torsion effect of swing frame on the separation ratio of sided balancing machines, which reveals the sources of measurement error and assesses the application scope of A-B-C algorithm.
Wandering spleen with chronic torsion.
Misawa, Takeyuki; Yoshida, Kazuhiko; Shiba, Hiroaki; Kobayashi, Susumu; Yanaga, Katsuhiko
2008-04-01
Wandering spleen, a rare clinical entity with a high incidence of splenic torsion and infarction, was preoperatively diagnosed in a 28-year-old woman. Axial computed tomography showed the absence of the spleen in the left subphrenic space and a spleen-like mass in the pelvis, suggestive of a wandering spleen. A coronal contrast-enhanced computed tomography image exhibited the enlarged spleen suspended by elongated, dilated, and somewhat tortuous splenic vessels. Owing to the symptomatic splenomegaly with hypersplenism and chronic torsion, laparoscopic splenectomy was performed.
Jude, Nwashilli N.; Onochie, Nwajei C.
2015-01-01
Wandering spleen is a rare condition that accounts for less than 0.25% of all indications for splenectomy. It is characterized by ectopic localization of the spleen owing to the lack or weakening of its ligaments. Torsion is the most common complication due to its long pedicle and high mobility, which may result in acute abdomen. We report a case of torsion in a wandering spleen in a 28-year-old male presenting with an acute abdomen that was treated by splenectomy. PMID:26620993
Torsion Modified Plasma Screening in Astrophysics
NASA Astrophysics Data System (ADS)
Sivaram, C.; Garcia de Andrade, L. C.
The torsion modified Maxwell-Proca equations when applied to describe a plasma is shown to lead to a correction to the Debye screening length. For hot new born neutron stars the torsion correction is shown to be significant. This effect may provide an indirect evidence for torsion.
Torsional Newton-Cartan geometry from the Noether procedure
NASA Astrophysics Data System (ADS)
Festuccia, Guido; Hansen, Dennis; Hartong, Jelle; Obers, Niels A.
2016-11-01
We apply the Noether procedure for gauging space-time symmetries to theories with Galilean symmetries, analyzing both massless and massive (Bargmann) realizations. It is shown that at the linearized level the Noether procedure gives rise to (linearized) torsional Newton-Cartan geometry. In the case of Bargmann theories the Newton-Cartan form Mμ couples to the conserved mass current. We show that even in the case of theories with massless Galilean symmetries it is necessary to introduce the form Mμ and that it couples to a topological current. Further, we show that the Noether procedure naturally gives rise to a distinguished affine (Christoffel type) connection that is linear in Mμ and torsionful. As an application of these techniques we study the coupling of Galilean electrodynamics to TNC geometry at the linearized level.
Brabson, Tamera L.; Maki, Lynn C.; Newell, Susan M.; Ralphs, S. Christopher
2015-01-01
A 6-month-old male intact Cane Corso mastiff dog was presented for a recent history of vomiting, abdominal pain, and lethargy. A diagnosis of pancreatic torsion was made during abdominal exploratory surgery and was confirmed with histopathology. The dog underwent partial pancreatectomy and recovered with no complications. PMID:25969579
Shaft instantaneous angular speed for blade vibration in rotating machine
NASA Astrophysics Data System (ADS)
Gubran, Ahmed A.; Sinha, Jyoti K.
2014-02-01
Reliable blade health monitoring (BHM) in rotating machines like steam turbines and gas turbines, is a topic of research since decades to reduce machine down time, maintenance costs and to maintain the overall safety. Transverse blade vibration is often transmitted to the shaft as torsional vibration. The shaft instantaneous angular speed (IAS) is nothing but the representing the shaft torsional vibration. Hence the shaft IAS has been extracted from the measured encoder data during machine run-up to understand the blade vibration and to explore the possibility of reliable assessment of blade health. A number of experiments on an experimental rig with a bladed disk were conducted with healthy but mistuned blades and with different faults simulation in the blades. The measured shaft torsional vibration shows a distinct difference between the healthy and the faulty blade conditions. Hence, the observations are useful for the BHM in future. The paper presents the experimental setup, simulation of blade faults, experiments conducted, observations and results.
Electrothermally-Actuated Micromirrors with Bimorph Actuators--Bending-Type and Torsion-Type.
Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che
2015-06-22
Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively.
Electrothermally-Actuated Micromirrors with Bimorph Actuators—Bending-Type and Torsion-Type
Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che
2015-01-01
Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively. PMID:26110409
Optical activity caused by torsion stresses: the case of NaBi(MoO4)2 crystals.
Vasylkiv, Yuriy; Kvasnyuk, Oleksiy; Shopa, Yaroslav; Vlokh, Rostyslav
2013-05-01
We have found that torsion mechanical stresses induce the optical rotation effect in centrosymmetric NaBi(MoO4)2 crystals. We have suggested a description of the effect on the basis of nonlocal linear elasticity theory. It has been shown that the induced optical gyration is proportional to the stress gradient appearing due to the torsion.
Torsional electromechanical quantum oscillations in carbon nanotubes
NASA Astrophysics Data System (ADS)
Cohen-Karni, Tzahi; Segev, Lior; Srur-Lavi, Onit; Cohen, Sidney R.; Joselevich, Ernesto
2006-10-01
Carbon nanotubes can be distinctly metallic or semiconducting depending on their diameter and chirality. Here we show that continuously varying the chirality by mechanical torsion can induce conductance oscillations, which can be attributed to metal-semiconductor periodic transitions. The phenomenon is observed in multiwalled carbon nanotubes, where both the torque and the current are shown to be carried predominantly by the outermost wall. The oscillation period with torsion is consistent with the theoretical shifting of the corners of the first Brillouin zone of graphene across different sub-bands allowed in the nanotube. Beyond a critical torsion, the conductance irreversibly drops due to torsional failure, allowing us to determine the torsional strength of carbon nanotubes. Carbon nanotubes could be ideal torsional springs for nanoscopic pendulums, because electromechanical detection of motion could replace the microscopic detection techniques used at present. Our experiments indicate that carbon nanotubes could be used as electronic sensors of torsional motion in nanoelectromechanical systems.
Gravity: A gauge theory perspective
NASA Astrophysics Data System (ADS)
Nester, James M.; Chen, Chiang-Mei
2016-07-01
The evolution of a generally covariant theory is under-determined. One hundred years ago such dynamics had never before been considered; its ramifications were perplexing, its future important role for all the fundamental interactions under the name gauge principle could not be foreseen. We recount some history regarding Einstein, Hilbert, Klein and Noether and the novel features of gravitational energy that led to Noether’s two theorems. Under-determined evolution is best revealed in the Hamiltonian formulation. We developed a covariant Hamiltonian formulation. The Hamiltonian boundary term gives covariant expressions for the quasi-local energy, momentum and angular momentum. Gravity can be considered as a gauge theory of the local Poincaré group. The dynamical potentials of the Poincaré gauge theory of gravity are the frame and the connection. The spacetime geometry has in general both curvature and torsion. Torsion naturally couples to spin; it could have a significant magnitude and yet not be noticed, except on a cosmological scale where it could have significant effects.
A Novel Permanent Magnetic Angular Acceleration Sensor.
Zhao, Hao; Feng, Hao
2015-07-03
Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s(-2)). Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability.
A Novel Permanent Magnetic Angular Acceleration Sensor
Zhao, Hao; Feng, Hao
2015-01-01
Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s−2). Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability. PMID:26151217
Exact solutions in 3D gravity with torsion
NASA Astrophysics Data System (ADS)
González, P. A.; Vásquez, Yerko
2011-08-01
We study the three-dimensional gravity with torsion given by the Mielke-Baekler (MB) model coupled to gravitational Chern-Simons term, and that possess electric charge described by Maxwell-Chern-Simons electrodynamics. We find and discuss this theory's charged black holes solutions and uncharged solutions. We find that for vanishing torsion our solutions by means of a coordinate transformation can be written as three-dimensional Chern-Simons black holes. We also discuss a special case of this theory, Topologically Massive Gravity (TMG) at chiral point, and we show that the logarithmic solution of TMG is also a solution of the MB model at a fixed point in the space of parameters. Furthermore, we show that our solutions generalize Gödel type solutions in a particular case. Also, we recover BTZ black hole in Riemann-Cartan spacetime for vanishing charge.
Torsional Split Hopkinson Bar Optimization
2012-04-10
is the torsional wave speed . Also, one can relate the torque with the yield stress of the material, as seen in equation 2; where r is the radius of...be equal to the mechanical impedance of the bars. In other words, the product of density, speed of wave and polar moment of inertia must remain...pillow blocks used to mount the incident and transmitter bars are cast iron based- mounted Babbitt-lined bearing split, for 1 in. shaft diameter
Torsion of a wandering spleen.
El Bouhaddouti, Hicham; Lamrani, Jihane; Louchi, Abdellatif; El Yousfi, Mounia; Aqodad, Noureddine; Ibrahimi, Adil; Boubou, Meriem; Kamaoui, Imane; Tizniti, Siham
2010-01-01
Wandering spleen is a rare condition defined as a mobile spleen only attached with its pedicle. It can be complicated by a volvulus, which is a surgical abdominal emergency. Preventing infarction is the aim of a prompt surgery that can preserve the spleen and then proceed to splenopexy. We report a rare case of torsion of a wandering spleen associated with a dolichosigmoοd.
Stability of Thin-Walled Tubes Under Torsion
NASA Technical Reports Server (NTRS)
Donnell, L H
1935-01-01
In this report a theoretical solution is developed for the torsion on a round thin-walled tube for which the walls become unstable. The results of this theory are given by a few simple formulas and curves which cover all cases. The differential equations of equilibrium are derived in a simpler form than previously found, it being shown that many items can be neglected.
Topological design of torsional metamaterials
NASA Astrophysics Data System (ADS)
Vitelli, Vincenzo; Paulose, Jayson; Meeussen, Anne; Topological Mechanics Lab Team
Frameworks - stiff elements with freely hinged joints - model the mechanics of a wide range of natural and artificial structures, including mechanical metamaterials with auxetic and topological properties. The unusual properties of the structure depend crucially on the balance between degrees of freedom associated with the nodes, and the constraints imposed upon them by the connecting elements. Whereas networks of featureless nodes connected by central-force springs have been well-studied, many real-world systems such as frictional granular packings, gear assemblies, and flexible beam meshes incorporate torsional degrees of freedom on the nodes, coupled together with transverse shear forces exerted by the connecting elements. We study the consequences of such torsional constraints on the mechanics of periodic isostatic networks as a foundation for mechanical metamaterials. We demonstrate the existence of soft modes of topological origin, that are protected against disorder or small perturbations of the structure analogously to their counterparts in electronic topological insulators. We have built a lattice of gears connected by rigid beams that provides a real-world demonstration of a torsional metamaterial with topological edge modes and mechanical Weyl modes.
Charged axially-symmetric solution in f( T) gravity theory
NASA Astrophysics Data System (ADS)
Nashed, G. G. L.
2015-01-01
In present article, an axially symmetric tetrad field has been applied to the charged field equations of f( T) gravity theory. Some constraints have been imposed to solve the resulting non-linear partial differential equations. An exact non-vacuum charged solution with three constants of integration is derived. The solution does not have non-trivial scalar torsion, T={T^i}_{jk}{S_i}^{jk}. Total conserved charges, using Poincaré gauge version, are calculated to understand the physical meaning of the three constants of integration. It has been shown that these constants are gravitational mass, angular momentum of the rotating source and charge parameter.
Angular Goos-Hänchen effect in curved dielectric microstructures.
Tran, N H; Dutriaux, L; Balcou, P; Floch, A L; Bretenaker, F
1995-06-01
A macroscopic angular Goos-Hänchen effect at total reflection on curved interfaces is studied experimentally. The results are compared with the complex-angular-momentum model of quasi-critical scattering. An extremum in angular deflection, which has not yet been predicted by any theory other than exact Mie scattering computations, is identified at low size parameters.
Les torsions sur testicules cryptorchides
Gharbi, Mohamed; Amri, Najmeddine; Chambeh, Wahib; Braiek, Salem; Kamel, Rafik El
2010-01-01
Résumé But : La cryptorchidie est une pathologie assez fréquente en urologie. Elle est associée à un risque élevé d’infertilité et de dégénérescence. Elle semble aussi être associée à un risque important de torsion. Cette entité est très peu abordée dans la littérature. Nous rapportons tous les cas de torsion sur testicule cryptorchide observés à notre service dans le but de mieux caractériser cette pathologie et de réduire ainsi le taux d’orchidectomies. Méthodologie : Il s’agit d’une étude rétrospective portant sur tous les cas de torsion sur testicule cryptorchide opérés dans notre service d’urologie entre 1999 et 2007. Les patients ont fait l’objet d’une description basée sur le résumé de leurs observations. Résultats : Les patients étaient âgés de 7 mois à 39 ans. La torsion touchait le testicule droit dans 53 % des cas. Le tableau clinique comportait une douleur au niveau de la région inguinale d’apparition soudaine avec une masse sous-cutanée inflammatoire et douloureuse à ce niveau et surtout un hémiscrotum homolatéral vide. Dans 60 % des cas, le diagnostic était tardif et une orchidectomie a été réalisée. Dans les autre cas, un abaissement du testicule a été réalisé avec orchidopexie controlatéral dans le même temps opératoire. Conclusion : Bien qu’il s’agisse d’une pathologie peu courante, la torsion sur testicule cryptorchide doit être étudiée davantage. Le diagnostic précoce permettra de sauver et d’abaisser le testicule et faciliter ainsi le dépistage d’une éventuelle dégénérescence. PMID:21191497
Premotor neurons encode torsional eye velocity during smooth-pursuit eye movements
NASA Technical Reports Server (NTRS)
Angelaki, Dora E.; Dickman, J. David
2003-01-01
Responses to horizontal and vertical ocular pursuit and head and body rotation in multiple planes were recorded in eye movement-sensitive neurons in the rostral vestibular nuclei (VN) of two rhesus monkeys. When tested during pursuit through primary eye position, the majority of the cells preferred either horizontal or vertical target motion. During pursuit of targets that moved horizontally at different vertical eccentricities or vertically at different horizontal eccentricities, eye angular velocity has been shown to include a torsional component the amplitude of which is proportional to half the gaze angle ("half-angle rule" of Listing's law). Approximately half of the neurons, the majority of which were characterized as "vertical" during pursuit through primary position, exhibited significant changes in their response gain and/or phase as a function of gaze eccentricity during pursuit, as if they were also sensitive to torsional eye velocity. Multiple linear regression analysis revealed a significant contribution of torsional eye movement sensitivity to the responsiveness of the cells. These findings suggest that many VN neurons encode three-dimensional angular velocity, rather than the two-dimensional derivative of eye position, during smooth-pursuit eye movements. Although no clear clustering of pursuit preferred-direction vectors along the semicircular canal axes was observed, the sensitivity of VN neurons to torsional eye movements might reflect a preservation of similar premotor coding of visual and vestibular-driven slow eye movements for both lateral-eyed and foveate species.
Intranatal Torsion of Polydactyly: A Rare Event.
Gupta, Priyanka; Neogi, Sujoy; Shukla, Amlin; Patwari, A K
2016-01-01
Polydactyly is one of the most common anomalies of hand and/or foot. Postnatal torsion of pedunculated polydactyly is a well known complication but intranatal torsion has been infrequently described in published literature. Here, we describe a case of pedunculated ulnar polydactyly which was gangrenous at birth due to intranatal torsion. Controversies surrounding the management of narrow pedicled pedunculated polydactyly by traditional method of suture ligation at base are also discussed.
[A case of neonatal testicular torsion].
Nishizawa, Satoshi; Nanpo, Yoshihito; Kuramoto, Tomomi; Iba, Akinori; Fujii, Reona; Matsumura, Nagahide; Shintani, Yasuyo; Inagaki, Takeshi; Kohjimoto, Yasuo; Hara, Isao
2008-12-01
An infant normally delivered at the 38th week of gestation was referred to our department one day after birth for a firm and painless right hemiscrotal mass with bluish coloration. Since contralateral scrotum showed swelling, we performed emergency surgery on that day. The right spermatic cord was constricted due to extravaginal torsion, and degree and direction of torsion was unclear since the spermatic cord was already organized. Right testis showed irreversible necrotic change, requiring orchiectomy. We confirmed that left testis was intact and performed orchidopexy. Since high incidence of contralateral asymptomatic torsion has been reported in patients with prenatal testicular torsion, emergency surgery should be considered when contralateral scrotum shows abnormal findings.
NASA Astrophysics Data System (ADS)
Ivanov, A. N.; Wellenzohn, M.
2016-02-01
We analyze a spin precession of slow neutrons in the Einstein-Cartan gravity with torsion, chameleon and magnetic field. For the derivation of the Heisenberg equation of motion of the neutron spin we use the effective low-energy potential, derived by Ivanov and Wellenzohn [Phys. Rev. D 92, 125004 (2015)] for slow neutrons, coupled to gravitational, chameleon, and torsion fields to order 1 /m , where m is the neutron mass. In addition to these low-energy interactions we switch on the interaction of slow neutrons with a magnetic field. We show that to linear order approximation with respect to gravitational, chameleon, and torsion fields the Dirac Hamilton operator for fermions (neutrons), moving in spacetimes created by rotating coordinate systems, contains the anti-Hermitian operators of torsion-fermion (neutron) interactions, caused by torsion scalar and tensor space-space-time and time-space-space degrees of freedom. Such anti-Hermitian operators violate C P and T invariance. In the low-energy approximation the C P and T violating torsion-fermion (neutron) interactions appear only to order O (1 /m ). One may assume that in the rotating Universe and galaxies the obtained anti-Hermitian torsion-fermion interactions might be an origin of (i) violation of C P and T invariance in the Universe and (ii) of baryon asymmetry. We show that anti-Hermitian torsion-fermion interactions of relativistic fermions, violating C P and T invariance, (i) cannot be removed by nonunitary transformations of the Dirac fermion wave functions and (ii) are conformal invariant. According to general requirements of conformal invariance of massive particle theories in gravitational fields [see R. H. Dicke, Phys. Rev. 125, 2163 (1962) and A. J. Silenko, Phys. Rev. D 91, 065012 (2015)], conformal invariance of anti-Hermitian torsion-fermion interactions is valid only if the fermion mass is changed by a conformal factor.
Topological invariants and the dynamics of an axial vector torsion field
NASA Astrophysics Data System (ADS)
Drechsler, W.
1983-08-01
A generalized theory of gravitation is discussed which is based on a Riemann-Cartan space-time,U 4, with an axial vector torsion field. Besides Einstein's equations determining the metric of theU 4, a system of nonlinear field equations is established coupling an axial vector source current to the axial vector torsion field. The properties of the solutions of these equations are discussed assuming a London-type condition relating the axial current and torsion field. To characterize the solutions use is made of the Euler and Pontrjagin forms and the associated quadratic curvature invariants for theU 4 space-time. It is found that there exists for a Riemann-Cartan space-time a relation between the zeros of the axial vector torsion field and the singularities of the Pontrjagin invariant, which is analogous to the well-known Hopf relation between the zeros of vector fields and the Euler characteristic.
Torsional Buckling and Writhing Dynamics of Elastic Cables and DNA
Goyal, S; Perkins, N C; Lee, C L
2003-02-14
Marine cables under low tension and torsion on the sea floor can undergo a dynamic buckling process during which torsional strain energy is converted to bending strain energy. The resulting three-dimensional cable geometries can be highly contorted and include loops and tangles. Similar geometries are known to exist for supercoiled DNA and these also arise from the conversion of torsional strain energy to bending strain energy or, kinematically, a conversion of twist to writhe. A dynamic form of Kirchhoff rod theory is presented herein that captures these nonlinear dynamic processes. The resulting theory is discretized using the generalized-method for finite differencing in both space and time. The important kinematics of cross-section rotation are described using an incremental rotation ''vector'' as opposed to traditional Euler angles or Euler parameters. Numerical solutions are presented for an example system of a cable subjected to increasing twist at one end. The solutions show the dynamic evolution of the cable from an initially straight element, through a buckled element in the approximate form of a helix, and through the dynamic collapse of this helix through a looped form.
Czakó, Gábor
2014-06-21
Motivated by a recent experiment [H. Pan and K. Liu, J. Chem. Phys. 140, 191101 (2014)], we report a quasiclassical trajectory study of the O((3)P) + CH4(vk = 0, 1) → OH + CH3 [k = 1 and 3] reactions on an ab initio potential energy surface. The computed angular distributions and cross sections correlated to the OH(v = 0, 1) + CH3(v = 0) coincident product states can be directly compared to experiment for O + CH4(v3 = 0, 1). Both theory and experiment show that the ground-state reaction is backward scattered, whereas the angular distributions shift toward sideways and forward directions upon antisymmetric stretching (v3) excitation of the reactant. Theory predicts similar behavior for the O + CH4(v1 = 1) reaction. The simulations show that stretching excitation enhances the reaction up to about 15 kcal/mol collision energy, whereas the O + CH4(vk = 1) reactions produce smaller cross sections for OH(v = 1) + CH3(v = 0) than those of O + CH4(v = 0) → OH(v = 0) + CH3(v = 0). The former finding agrees with experiment and the latter awaits for confirmation. The computed cold OH rotational distributions of O + CH4(v = 0) are in good agreement with experiment.
Modified teleparallel gravity with higher-derivative torsion terms
NASA Astrophysics Data System (ADS)
Otalora, Giovanni; Saridakis, Emmanuel N.
2016-10-01
We construct F (T ,(∇T) 2,□T ) gravitational modifications, which are novel classes of modified theories arising from higher-derivative torsional terms in the action and are different than their curvature analogue. Applying them in a cosmological framework, we obtain an effective dark energy sector comprised of the novel torsional contributions. We perform a detailed dynamical analysis for two specific examples, extracting the stable late-time solutions and calculating the corresponding observables. We show that the thermal history of the Universe can be reproduced, and it can result in a dark-energy-dominated, accelerating universe, where the dark-energy equation-of-state parameter lies in the quintessence regime, or may exhibit the phantom-divide crossing during the cosmological evolution. Finally, the scale factor behaves asymptotically, either as a power law or as an exponential, in agreement with observations.
Bulk micromachined quasistatic torsional micromirror
NASA Astrophysics Data System (ADS)
Kiessling, Torsten; Wolter, Alexander; Schenk, Harald; Lakner, Hubert
2004-01-01
One dimensional torsional micro mirrors for laser steering applications have been developed and manufactured at Fraunhofer Institute of Photonic Microsystems. Several design variations with rectangular plates are available. The device can be operated in resonant mode and quasistatic mode as well. The device is fabricated out of a BSOI wafer and a second conductive silicon wafer. The structure is assembled by conductive adhesive bonding. Torsional springs connect the mirror plate to the mirror frame mechanically and electrically. Filled isolation trench structures separate volumes of different electrical potentials at the frame and at the deflective mirror respectively. Comb drive structures at both sides of the deflectable mirror and the part of frame located opposite increases capacitance at both mirror half sides. Applying a low level drive voltage between the combs, the mirror can be operated in resonant mode. The second silicon wafer is placed below the deflective mirror and is electrically at ground. Applying a electrical potential of higher level to one side of the deflectable mirror, the mirror can be driven quasistatic and resonant as well. While the drive voltage is applied to one side of the mirror, the comb drive structure of the opposite side can be used for capacitance based position read out.
Angular and axial deformities of the legs of children.
McDonough, M W
1984-12-01
Age is often a determining factor in establishing a treatment program for these axial and angular problems. As can be seen, the deformities of torsion are noticeable from early life. Any tibial torsion should be treated early, but an excessive medial range of motion in the infant leg with a corresponding adequate lateral range of motion of the limb may be cautiously observed. Medial femoral torsion is a normal early finding in the infant thigh. The problem becomes evident as the child matures without the corresponding reduction in femoral torsion, leading to a persistence of fetal or infantile alignment. The gait consequences are usually noticed at 4 to 8 years of age. The angular changes generally are a delayed finding noticed in stance. The bowleg may be associated with marked tibial torsion and picked up early but the Blount's patient has been traditionally definable at 2 years of age. Levin and Drennan may hasten the time of diagnosis with their radiographic criteria. Knock-knee is an alignment disturbance noticed during the early to mid-childhood years, age 4 to 8 years. The diagnosis is important, differentiating physiologic from torsion-related deformities, and treatment, if warranted, should not be delayed. Generally the earlier these problems are discovered, the more optimistic the prognosis. Since the pediatric limb is in a constant state of transition, there will be a perpetual argument as to the need or efficacy of various approaches to the problems of knock-knee and bowleg. If observation is the treatment of choice, the percentage of cases which go on to osteotomies and epiphyseal stapling will continue. For those with axial or angular deformities, degenerative arthritis of the knee may be forthcoming. Swanson, Greene, and Allis warned of problems becoming "unphysiologic." If we consider the epiphyseal malleability, not only to deformity but to correction, we can appreciate Lenoir's comment of "every day the problem goes untreated is a golden
Inelastic torsion of steel I-beams
NASA Astrophysics Data System (ADS)
Pi, Y. L.; Trahair, N. S.
1993-09-01
A nonlinear inelastic analysis of the non-uniform torsion of I-section beams is presented in this paper. Large twist rotations are included in the geometry non-linearity. The nonlinear equilibrium equations of beams in nonuniform torsion have been derived and a finite element procedure has been developed based on the analysis. The elastic-plastic behavior of beams in non-uniform torsion is studied using the finite element procedure and the results are compared with tests. It is found that I-section beams have much larger torsional capacities than can be predicted by linear plastic collapse analysis, and that torsional failure occurs not by the formation of a mechanism but by the tensile rupture of the flanges. A method is proposed for calculating the full plastic non-uniform torque for practical design purposes.
Optically probing torsional superelasticity in spider silks
Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit; Singh, Kamal P.
2013-11-11
We investigate torsion mechanics of various spider silks using a sensitive optical technique. We find that spider silks are torsionally superelastic in that they can reversibly withstand great torsion strains of over 10{sup 2−3} rotations per cm before failure. Among various silks from a spider, we find the failure twist-strain is greatest in the sticky capture silk followed by dragline and egg-case silk. Our in situ laser-diffraction measurements reveal that torsional strains on the silks induce a nano-scale transverse compression in its diameter that is linear and reversible. These unique torsional properties of the silks could find applications in silk-based materials and devices.
Angular Acceleration without Torque?
ERIC Educational Resources Information Center
Kaufman, Richard D.
2012-01-01
Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.
Direct measurement of torsional properties of single fibers
NASA Astrophysics Data System (ADS)
Liu, Dabiao; Peng, Kai; He, Yuming
2016-11-01
In order to characterize the torsional behavior of micron-scale specimens, a direct technique is established based on the principle of torsion balance. The technique applies twist to the specimen and balances the resulting torque against a torsion wire of known torsional rigidity. The torsional rigidity of the torsion wire is determined by a torsion pendulum. To measure the rotation of the torsion wire, a sensitive angle detector, comprising a thin cross-beam attached between the torsion wire and the fiber specimen and a laser displacement sensor, is developed. The presented technique permits the measurement of torque in single fibers as low as 10-9 Nm with a reasonable resolution. Using this technique, torsion tests on micro-diameter copper wires, silver wires and carbon fibers were performed. The longitudinal shear modulus and other torsional properties of these samples, such as yielding shear strength, were obtained.
Investigation of fluctuations in angular velocity in magnetic memory devices
NASA Technical Reports Server (NTRS)
Meshkis, Y. A.; Potsyus, Z. Y.
1973-01-01
The fluctuations in the angular velocity of individual assemblies of a precision mechanical system were analyzed. The system was composed of an electric motor and a magnetic drum which were connected by a flexible coupling. A dynamic model was constructed which took into account the absence of torsion in the rigid shafts of the electric motor drive rotor and the magnetic drum. The motion was described by Lagrange differential equations of the second kind. Curves are developed to show the nature of amplitude fluctuation of the magnetic drum angular velocity at a specific excitation frequency. Additional curves show the amplitudes of fluctuation of the magnetic drum angular velocity compared to the quantity of damping at specific frequencies.
Spinning optical resonator sensor for torsional vibrational applications measurements
NASA Astrophysics Data System (ADS)
Ali, Amir R.; Gatherer, Andrew; Ibrahim, Mariam S.
2016-03-01
Spinning spherical resonators in the torsional vibrational applications could cause a shift in its whispering gallery mode (WGM). The centripetal force acting on the spinning micro sphere resonator will leads to these WGM shifts. An analysis and experiment were carried out in this paper to investigate and demonstrate this effect using different polymeric resonators. In this experiment, centripetal force exerted by the DC-Motor on the sphere induces an elastic deformation of the resonator. This in turn induces a shift in the whispering gallery modes of the sphere resonator. Materials used for the sphere are polydimethylsiloxane (PDMS 60:1 where 60 parts base silicon elastomer to 1 part polymer curing agent by volume) with shear modulus (G≍1kPa), (PDMS 10:1) with shear modulus (G≍300kPa), polymethylmethacrylate (PMMA, G≍2.6×109GPa) and silica (G≍3×1010 GPa). The sphere size was kept constant with 1mm in diameter for all above materials. The optical modes of the sphere exit using a tapered single mode optical fiber that is coupled to a distributed feedback laser. The transmission spectrum through the fiber is monitored to detect WGM shifts. The results showed the resonators with smaller shear modulus G experience larger WGM shift due to the larger mechanical deformation induced by the applied external centripetal force. Also, the results show that angular velocity sensors used in the torsional vibrational applications could be designed using this principle.
Oligothiophene wires: impact of torsional conformation on the electronic structure.
Kislitsyn, D A; Taber, B N; Gervasi, C F; Zhang, L; Mannsfeld, S C B; Prell, J S; Briseno, A L; Nazin, G V
2016-02-14
Charge transport in polymer- and oligomer-based semiconductor materials depends strongly on the structural ordering of the constituent molecules. Variations in molecular conformations influence the electronic structures of polymers and oligomers, and thus impact their charge-transport properties. In this study, we used Scanning Tunneling Microscopy and Spectroscopy (STM/STS) to investigate the electronic structures of different alkyl-substituted oligothiophenes displaying varied torsional conformations on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes self-assemble into chain-like structures, binding to each other via interdigitated alkyl ligands. The molecules adopted distinct planar conformations with alkyl ligands forming cis- or trans- mutual orientations. For each molecule, by using STS mapping, we identify a progression of particle-in-a-box-like states corresponding to the LUMO, LUMO+1 and LUMO+2 orbitals. Analysis of STS data revealed very similar unoccupied molecular orbital energies for different possible molecular conformations. By using density functional theory calculations, we show that the lack of variation in molecular orbital energies among the different oligothiophene conformers implies that the effect of the Au-oligothiophene interaction on molecular orbital energies is nearly identical for all studied torsional conformations. Our results suggest that cis-trans torsional disorder may not be a significant source of electronic disorder and charge carrier trapping in organic semiconductor devices based on oligothiophenes.
Magnetic Torsional Oscillations in Magnetars
Sotani, Hajime; Kokkotas, Kostas D.; Stergioulas, Nikolaos
2009-05-01
We investigate torsional Alfven oscillations of relativistic stars with a global dipole magnetic field, via 2D numerical simulations. We find that a) there exist two families of quasi-periodic oscillations (QPOs) with harmonics at integer multiples of the fundamental frequency, b) the QPOs are long-lived, c) for the chosen form of dipolar magnetic field, the frequency ratio of the lower to upper fundamental QPOs is about 0.6, independent of the equilibrium model or of the strength of the magnetic field, and d) within a representative sample of EOS and of various magnetar masses, the Alfven QPO frequencies are given by accurate empirical relations that depend only on the compactness of the star and on the magnetic field strength. Compared to the observational frequencies, we also obtain an upper limit on the strength of magnetic field of SGR 1806-20 (if is dominated by a dipolar component) between {approx}3 and 7x10{sup 15} Gauss.
New insights into perinatal testicular torsion
Van Kerrebroeck, Philip
2009-01-01
Perinatal testicular torsion is a relatively rare event that remains unrecognized in many patients or is suspected and treated accordingly only after an avoidable loss of time. The authors report their own experience with several patients, some of them quite atypical but instructive. Missed bilateral torsion is an issue, as are partial torsion, possible antenatal signs, and late presentation. These data are discussed together with the existing literature and may help shed new light on the natural course of testicular torsion and its treatment. The most important conclusion is that a much higher index of suspicion based on clinical findings is needed for timely detection of perinatal torsion. It is the authors’ opinion that immediate surgery is mandatory not only in suspected bilateral torsions but also in cases of possible unilateral torsions. There is no place for a more fatalistic “wait-and-see” approach. Whenever possible, even necrotic testes should not be removed during surgery because some endocrine function may be retained. PMID:19856186
Nonlinear backbone torsional pair correlations in proteins
NASA Astrophysics Data System (ADS)
Long, Shiyang; Tian, Pu
2016-10-01
Protein allostery requires dynamical structural correlations. Physical origin of which, however, remain elusive despite intensive studies during last two and half decades. Based on analysis of molecular dynamics (MD) simulation trajectories for ten proteins with different sizes and folds, we found that nonlinear backbone torsional pair (BTP) correlations, which are mainly spatially long-ranged and are dominantly executed by loop residues, exist extensively in most analyzed proteins. Examination of torsional motion for correlated BTPs suggested that such nonlinear correlations are mainly associated aharmonic torsional state transitions and in some cases strongly anisotropic local torsional motion of participating torsions, and occur on widely different and relatively longer time scales. In contrast, correlations between backbone torsions in stable α helices and β strands are mainly linear and spatially short-ranged, and are more likely to associate with harmonic local torsional motion. Further analysis revealed that the direct cause of nonlinear contributions are heterogeneous linear correlations. These findings implicate a general search strategy for novel allosteric modulation sites of protein activities.
Nonlinear backbone torsional pair correlations in proteins
Long, Shiyang; Tian, Pu
2016-01-01
Protein allostery requires dynamical structural correlations. Physical origin of which, however, remain elusive despite intensive studies during last two and half decades. Based on analysis of molecular dynamics (MD) simulation trajectories for ten proteins with different sizes and folds, we found that nonlinear backbone torsional pair (BTP) correlations, which are mainly spatially long-ranged and are dominantly executed by loop residues, exist extensively in most analyzed proteins. Examination of torsional motion for correlated BTPs suggested that such nonlinear correlations are mainly associated aharmonic torsional state transitions and in some cases strongly anisotropic local torsional motion of participating torsions, and occur on widely different and relatively longer time scales. In contrast, correlations between backbone torsions in stable α helices and β strands are mainly linear and spatially short-ranged, and are more likely to associate with harmonic local torsional motion. Further analysis revealed that the direct cause of nonlinear contributions are heterogeneous linear correlations. These findings implicate a general search strategy for novel allosteric modulation sites of protein activities. PMID:27708342
1944-02-01
torsional- divergente problem.which takes into.account the a.erod.ynadicspan - effect. The developments are-based on-the theory of tor- sion of straight...indicat-ethat neglect of the aerodynamic span effect may lead to an appreciable underestimation of the torsional- divergente velocity, the difference
NASA Technical Reports Server (NTRS)
Liebe, Wolfgang
1944-01-01
In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.
Influence of tungsten fiber's slow drift on the measurement of G with angular acceleration method.
Luo, Jie; Wu, Wei-Huang; Xue, Chao; Shao, Cheng-Gang; Zhan, Wen-Ze; Wu, Jun-Fei; Milyukov, Vadim
2016-08-01
In the measurement of the gravitational constant G with angular acceleration method, the equilibrium position of torsion pendulum with tungsten fiber undergoes a linear slow drift, which results in a quadratic slow drift on the angular velocity of the torsion balance turntable under feedback control unit. The accurate amplitude determination of the useful angular acceleration signal with known frequency is biased by the linear slow drift and the coupling effect of the drifting equilibrium position and the room fixed gravitational background signal. We calculate the influences of the linear slow drift and the complex coupling effect on the value of G, respectively. The result shows that the bias of the linear slow drift on G is 7 ppm, and the influence of the coupling effect is less than 1 ppm.
Torsional Resonators Based on Inorganic Nanotubes.
Divon, Yiftach; Levi, Roi; Garel, Jonathan; Golberg, Dmitri; Tenne, Reshef; Ya'akobovitz, Assaf; Joselevich, Ernesto
2017-01-11
We study for the first time the resonant torsional behaviors of inorganic nanotubes, specifically tungsten disulfide (WS2) and boron nitride (BN) nanotubes, and compare them to that of carbon nanotubes. We have found WS2 nanotubes to have the highest quality factor (Q) and torsional resonance frequency, followed by BN nanotubes and carbon nanotubes. Dynamic and static torsional spring constants of the various nanotubes were found to be different, especially in the case of WS2, possibly due to a velocity-dependent intershell friction. These results indicate that inorganic nanotubes are promising building blocks for high-Q nanoelectromechanical systems (NEMS).
Modification of gravity due to torsion
Nair, V. P.; Nikiforova, V.; Randjbar-Daemi, S.; Rubakov, V.
2010-01-01
Modifications of general relativity have been considered as one of the possible ways of addressing some of the outstanding problems related to the large scale gravitational physics. In this contribution we review some of the recent results which are due to the inclusion of dynamical torsion. More specifically we shall discuss the propagation of massive spin-2 particles in flat and curved space times. We shall show that, contrary to what is generally believed, spinning matter is not the sole source of torsion field. A symmetric energy momentum tensor can also couple to torsion degrees of freedom. The massive and massless spin-2 particles mix giving rise to an infrared modification of gravity.
Torsion of wandering spleen and distal pancreas
Sheflin, J.R.; Lee, C.M.; Kretchmar, K.A.
1984-01-01
Wandering spleen is the term applied to the condition in which a long pedicle allows the spleen to lie in an abnormal location. Torsion of a wandering spleen is an unusual cause of an acute abdomen and is rarely diagnosed preoperatively. Associated torsion of the distal pancreas is even more uncommon. The authors describe a patient with torsion of a wandering spleen and distal pancreas, who was correctly diagnosed, and define the merits of the imaging methods used. The initial examination should be /sup 99//sup m/Tc-sulfur colloid liner-spleen scanning.
Angular dynamics of small crystals in viscous flow
NASA Astrophysics Data System (ADS)
Fries, J.; Einarsson, J.; Mehlig, B.
2017-01-01
The angular dynamics of a very small ellipsoidal particle in a viscous flow decouples from its translational dynamics and the particle angular velocity is given by Jeffery's theory. It is known that cuboid particles share these properties. In the literature a special case is most frequently discussed, namely that of axisymmetric particles with a continuous rotation symmetry. Here we compute the angular dynamics of crystals that possess a discrete rotation symmetry and certain mirror symmetries but do not have a continuous rotation symmetry. We give examples of such particles that nevertheless obey Jeffery's theory. However, there are other examples where the angular dynamics is determined by a more general equation of motion.
Inevitable inflation in Einstein-Cartan theory with improved energy-momentum tensor with spin
NASA Technical Reports Server (NTRS)
Fennelly, A. J.; Bradas, James C.; Smalley, Larry L.
1988-01-01
Generalized, or power-law, inflation is shown to necessarily exist for a simple, anisotropic, (Bianchi Type-1) cosmology in the Einstein-Cartan gravitational theory with the Ray-Smalley improved energy momentum tensor with spin. Formal solution of the EC field equations with the fluid equations of motion explicitly shows inflation caused by the RS spin angular kinetic energy density. Shear is not effective in preventing inflation in the ECRS model. The relation between fluid vorticity, torsion, reference axis rotation, and shear ellipsoid precession shows through clearly.
Recurrence of angular cheilitis.
Ohman, S C; Jontell, M; Dahlen, G
1988-08-01
The incidence of recurrence of angular cheilitis following a successful antimicrobial treatment was studied in 48 patients. Clinical assessments including a microbial examination were carried out 8 months and 5 yr after termination of treatment. Eighty percent of the patients reported recurrence of their angular cheilitis on one or more occasions during the observation period. Patients with cutaneous disorders associated with dry skin or intraoral leukoplakia had an increased incidence of recrudescence. Neither the presence of denture stomatitis nor the type of microorganisms isolated from the original lesions of angular cheilitis, i.e. Candida albicans and/or Staphylococcus aureus, were associated with the number of recurrences. The present observations indicate that treatment of the majority of patients with angular cheilitis should be considered in a longer perspective than previously supposed, due to the short lasting therapeutic effects of the antimicrobial therapy.
[Malignant angular cheilitis].
Seoane, J; Vázquez, J; Cazenave, A; de la Cruz Mera, A; Argila, F; Aguado, A
1996-01-01
A case of chronic angular cheilitis is reported. Candida albicans was isolated repeatedly and the process developed into epitheliomatous carcinoma. The etiopathogenic role of Candida albicans and possible mechanism of action are discussed.
Angular velocity discrimination
NASA Technical Reports Server (NTRS)
Kaiser, Mary K.
1990-01-01
Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.
Energy Extraction from Fluid Flow Via Vortex Induced Angular Oscillations
NASA Astrophysics Data System (ADS)
Bhattacharya, Amitabh; Sorathiya, Shahajhan H.
2015-11-01
Using Lattice-Boltzmann simulations, we study angular oscillations of an elliptical cylinder attached to a torsional spring, with the axis placed perpendicular to a uniform flow, at low Reynolds numbers (Re=100 and Re=200). The equilibrium angle and stiffness of the torsional spring is chosen such that the ellipse reaches stable equilibrium at an angle of roughly 45° with respect to the incoming flow. This configuration leads to large unsteady torque due to vortex shedding, which in turn can lead to large oscillations of the ellipse, with several frequency modes. Along with measuring the angular oscillations of the ellipse, we also measure the potential for power-extraction from this setup, by attaching an external angular damper to the axis of the ellipse. For low density ratios, the ellipse tends to oscillate within the first quadrant, while, for higher density ratios, the ellipse, due to its tendency to auto-rotate, undergoes very large oscillations. The ellipse locks on to primary and secondary vortex shedding modes over the range of density ratios studied here. The power output of this setup increases with increasing Reynolds number and density ratio, with peak efficiency of 1.7%.
Sokolovski, D; Akhmatskaya, E; Echeverría-Arrondo, C; De Fazio, D
2015-07-28
State-to-state reactive integral cross sections (ICSs) are often affected by quantum mechanical resonances, especially near a reactive threshold. An ICS is usually obtained by summing partial waves at a given value of energy. For this reason, the knowledge of pole positions and residues in the complex energy plane is not sufficient for a quantitative description of the patterns produced by resonance. Such description is available in terms of the poles of an S-matrix element in the complex plane of the total angular momentum. The approach was recently implemented in a computer code ICS_Regge, available in the public domain [Comput. Phys. Commun., 2014, 185, 2127]. In this paper, we employ the ICS_Regge package to analyse in detail, for the first time, the resonance patterns predicted for integral cross sections (ICSs) of the benchmark F + HD → HF(v' = 3) + D reaction. The v = 0, j = 0, Ω = 0 → v' = 3, j' = 0, 1, 2, and Ω' = 0, 1, 2 transitions are studied for collision energies from 58.54 to 197.54 meV. For these energies, we find several resonances, whose contributions to the ICS vary from symmetric and asymmetric Fano shapes to smooth sinusoidal Regge oscillations. Complex energies of metastable states and Regge pole positions and residues are found by Padé reconstruction of the scattering matrix elements. The accuracy of the ICS_Regge code, relation between complex energies and Regge poles, various types of Regge trajectories, and the origin of the J-shifting approximation are also discussed.
Torsion-induced effects in magnetic nanowires
NASA Astrophysics Data System (ADS)
Sheka, Denis D.; Kravchuk, Volodymyr P.; Yershov, Kostiantyn V.; Gaididei, Yuri
2015-08-01
A magnetic helix wire is one of the simplest magnetic systems which manifests properties of both curvature and torsion. Possible equilibrium magnetization states in the helix wire with different anisotropy directions are studied theoretically. There exist two equilibrium states in the helix wire with easy-tangential anisotropy: a quasitangential magnetization distribution in the case of relatively small curvatures and torsions, and an onion state in the opposite case. The curvature and torsion also essentially influence the spin-wave dynamics in the helix wire, acting as an effective magnetic field. Originated from a geometry-induced effective Dzyaloshinskii interaction, this magnetic field leads to a coupling between the helix chirality and the magnetochirality and breaks mirror symmetry in the spin-wave spectrum: the modification of magnon dispersion relation is linear with respect to the torsion and quadratic with respect to the curvature. All analytical predictions on magnetization statics and dynamics are well confirmed by direct spin-lattice simulations.
The Effect of Acute Superior Oblique Palsy on Torsional Optokinetic Nystagmus in Monkeys
Shan, Xiaoyan; Tian, Jing; Ying, Howard S.; Walker, Mark F.; Guyton, David; Quaia, Christian; Optican, Lance M.; Tamargo, Rafael J.; Zee, David S.
2008-01-01
Purpose To investigate the effects of acquired superior oblique palsy (SOP) and corrective strabismus surgery on torsional optokinetic nystagmus (tOKN) in monkeys. Methods The trochlear nerve was severed intracranially in two rhesus monkeys (M1 and M2). For each monkey, more than 4 months after the SOP, the ipsilateral inferior oblique muscle was denervated and extirpated. For M2, 4 months later, the contralateral inferior rectus muscle was recessed by 2 mm. tOKN was elicited during monocular viewing of a rotating stimulus that was rear projected onto a screen 43.5 cm in front of the animal. Angular rotation of the stimulus about the center was 40 deg/s clockwise or counterclockwise. Results The main findings after trochlear nerve sectioning were (1) the amplitude and peak velocity of torsional quick and slow phases of the paretic eye was less than that in the normal eye for both intorsion and extorsion, and (2) the vertical motion of the paretic eye increased during both torsional slow and quick phases. After corrective inferior oblique surgery, both of these effects were even greater. Conclusions Acquired SOP and corrective inferior oblique–weakening surgery create characteristic patterns of change in tOKN that reflect alterations in the dynamic properties of the extraocular muscles involved in eye torsion. tOKN also provides information complementary to that provided by the traditional Bielschowsky head-tilt test and potentially can help distinguish among different causes of vertical ocular misalignment. PMID:18385059
NASA Astrophysics Data System (ADS)
Schaeffer, Nathanaël.; Jault, Dominique
2016-05-01
Torsional Alfvén waves propagating in the Earth's core have been inferred by inversion techniques applied to geomagnetic models. They appear to propagate across the core but vanish at the equator, exchanging angular momentum between core and mantle. Assuming axial symmetry, we find that an electrically conducting layer at the bottom of the mantle can lead to total absorption of torsional waves that reach the equator. We show that the reflection coefficient depends on GB_r, where Br is the strength of the radial magnetic field at the equator, and G the conductance of the lower mantle there. With Br=7×10-4 T, torsional waves are completely absorbed when they hit the equator if G≃1.3 × 108 S. For larger or smaller G, reflection occurs. As G is increased above this critical value, there is less attenuation and more angular momentum exchange. Our finding dissociates efficient core-mantle coupling from strong ohmic dissipation in the mantle.
Quantum gravity with torsion and non-metricity
NASA Astrophysics Data System (ADS)
Pagani, C.; Percacci, R.
2015-10-01
We study the renormalization of theories of gravity with an arbitrary (torsional and non-metric) connection. The class of actions we consider is of the Palatini type, including the most general terms with up to two derivatives of the metric, but no derivatives of the connection. It contains 19 independent parameters. We calculate the one-loop beta functions of these parameters and find their fixed points. The Holst subspace is discussed in some detail and found not to be stable under renormalization. Some possible implications for ultraviolet and infrared gravity are discussed.
Torsion and geometrostasis in covariant superstrings
Zachos, C.
1985-01-01
The covariant action for freely propagating heterotic superstrings consists of a metric and a torsion term with a special relative strength. It is shown that the strength for which torsion flattens the underlying 10-dimensional superspace geometry is precisely that which yields free oscillators on the light cone. This is in complete analogy with the geometrostasis of two-dimensional sigma-models with Wess-Zumino interactions. 13 refs.
Torsion and buckling of open sections
NASA Technical Reports Server (NTRS)
Wagner, Herbert
1936-01-01
In this paper is a discussion of the general principles for open sections of any shape. In what follows the torsion will be computed and on the basis of the results it will be possible to obtain a proper design of section in each case. The torsion of buckling members for the case where they are centrally loaded, leads to a problem in pure stability and is similar to that of stressed beams.
Magnetic resonance imaging of experimental testicular torsion.
Kaipia, A; Ryymin, P; Mäkelä, E; Aaltonen, M; Kähärä, V; Kangasniemi, M
2005-12-01
We investigated the feasibility of contrast enhanced (CE)-dynamic magnetic resonance imaging (MRI) for the detection of testicular torsion induced hypoperfusion in an experimental rat model. Adult Sprague-Dawley rats were subjected to unilateral testicular torsion of 360 or 720 degrees. After 1 h, the tail veins of the anaesthetized rats were cannulated and T2 -, diffusion-weighted and T1-weighted CE-dynamic MRI were subsequently performed by a 1.5 T MRI scanner. On apparent diffusion coefficient (ADC) images, the region of interest values of the ischaemic and control testes was compared. From CE-dynamic MR images, the maximal slopes of contrast enhancement were calculated and compared. In testicular torsion of 360 degrees, the maximal slope of contrast enhancement was 0.072%/s vs. 0.47%/s in the contralateral control testis (p < 0.001). A torsion of 720 degrees diminished the slope of contrast enhancement to 0.046%/s vs. 0.37%/s in the contralateral testis (p < 0.001). Diminished blood flow during torsion also followed in decreased ADC values in both 360 degrees (12.4% decrease; p < 0.05) and 720 degrees (10.8% decrease; p < 0.001) of torsion. Torsion of the testis causes ipsilateral hypoperfusion and decreased gadolinium uptake in a rat model that can be easily detected and quantified by CE-dynamic MRI. In diffusion-weighted MRI images, acute hypoperfusion results in a slight decrease of ADC values. Our results suggest that CE-dynamic MRI in combination with diffusion-weighted MRI can be used to detect compromised blood flow due to acute testicular torsion.
Attentional Modulation of Eye Torsion Responses
NASA Technical Reports Server (NTRS)
Stevenson, Scott B.; Mahadevan, Madhumitha S.; Mulligan, Jeffrey B.
2016-01-01
Eye movements generally have both reflexive and voluntary aspects, but torsional eye movements are usually thought of as a reflexive response to image rotation around the line of sight (torsional OKN) or to head roll (torsional VOR). In this study we asked whether torsional responses could be modulated by attention in a case where two stimuli rotated independently, and whether attention would influence the latency of responses. The display consisted of rear-projected radial "pinwheel" gratings, with an inner annulus segment extending from the center to 22 degrees eccentricity, and an outer annulus segment extending from 22 degrees out to 45 degrees eccentricity. The two segments rotated around the center in independent random walks, stepping randomly 4 degrees clockwise or counterclockwise at 60 Hz. Subjects were asked to attend to one or the other while keeping fixation steady at the center of the display. To encourage attention on one or the other segment of the display, subjects were asked to move a joystick in synchrony with the back and forth rotations of one part of the image while ignoring the other. Eye torsion was recorded with the scleral search coil technique, sampled at 500 Hz. All four subjects showed roughly 50% stronger torsion responses to the attended compared to unattended segments. Latency varied from 100 to 150 msec across subjects and was unchanged by attention. These findings suggest that attention can influence eye movement responses that are not typically under voluntary control.
NASA Astrophysics Data System (ADS)
Zheng, Jingjing; Meana-Pañeda, Rubén; Truhlar, Donald G.
2013-08-01
partition functions using the torsional eigenvalue summation method. Additional comments: The program package includes a manual, installation script, and input and output files for a test suite. Running time: There are 26 test runs. The running time of the test runs on a single processor of the Itasca computer is less than 2 s. References: [1] MS-T(C) method: Quantum Thermochemistry: Multi-Structural Method with Torsional Anharmonicity Based on a Coupled Torsional Potential, J. Zheng and D.G. Truhlar, Journal of Chemical Theory and Computation 9 (2013) 1356-1367, DOI: http://dx.doi.org/10.1021/ct3010722. [2] MS-T(U) method: Practical Methods for Including Torsional Anharmonicity in Thermochemical Calculations of Complex Molecules: The Internal-Coordinate Multi-Structural Approximation, J. Zheng, T. Yu, E. Papajak, I, M. Alecu, S.L. Mielke, and D.G. Truhlar, Physical Chemistry Chemical Physics 13 (2011) 10885-10907.
Williamson, M.M.; Pratt, G.A.
1999-06-08
The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section. 30 figs.
Williamson, Matthew M.; Pratt, Gill A.
1999-06-08
The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion. The invention also provides a torsional spring consisting of a flexible structure having at least three flat sections each connected integrally with and extending radially from a central section. Each flat section extends axially along the central section from a distal end of the central section to a proximal end of the central section.
The Angular Momentum Dichotomy
NASA Astrophysics Data System (ADS)
Teklu, Adelheid; Remus, Rhea-Silvia; Dolag, Klaus; Burkert, Andreas
2015-02-01
In the context of the formation of spiral galaxies the evolution and distribution of the angular momentum of dark matter halos have been discussed for more than 20 years, especially the idea that the specific angular momentum of the halo can be estimated from the specific angular momentum of its disk (e.g. Fall & Efstathiou (1980), Fall (1983) and Mo et al. (1998)). We use a new set of hydrodynamic cosmological simulations called Magneticum Pathfinder which allow us to split the galaxies into spheroidal and disk galaxies via the circularity parameter ɛ, as commonly used (e.g. Scannapieco et al. (2008)). Here, we focus on the dimensionless spin parameter λ = J |E|1/2 / (G M5/2) (Peebles 1969, 1971), which is a measure of the rotation of the total halo and can be fitted by a lognormal distribution, e.g. Mo et al. (1998). The spin parameter allows one to compare the relative angular momentum of halos across different masses and different times. Fig. 1 reveals a dichotomy in the distribution of λ at all redshifts when the galaxies are split into spheroids (dashed) and disk galaxies (dash-dotted). The disk galaxies preferentially live in halos with slightly larger spin parameter compared to spheroidal galaxies. Thus, we see that the λ of the whole halo reflects the morphology of its central galaxy. For more details and a larger study of the angular momentum properties of disk and spheroidal galaxies, see Teklu et al. (in prep.).
NASA Technical Reports Server (NTRS)
Chutjian, A.; Msezane, A. Z.; Henry, R. J. W.
1983-01-01
Differential electron-scattering cross sections for inelastic excitation of an ion have been measured for the first time. Experiments were carried out in a cross electron-ion beam geometry for the 4(2)S yields 4(2)P transition in Zn II at 75 eV. In addition, differential cross sections were calculated at energies between 15 and 100 eV in a five-state close-coupling approximation in which 4s, 4p, 3d(9)4s(2), 5s, and 4 d states were included. Agreement in shape between theory and experiment at 75 eV is excellent.
Fluidic angular velocity sensor
NASA Technical Reports Server (NTRS)
Berdahl, C. M. (Inventor)
1986-01-01
A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.
Angular Distributions of Synchrotron Radiation in the Nonrelativistic Approximation
NASA Astrophysics Data System (ADS)
Bagrov, V. G.; Loginov, A. S.
2017-03-01
The angular distribution functions of the polarized components of synchrotron radiation in the nonrelativistic approximation are investigated using methods of classical and quantum theory. Particles of zero spin (bosons) and spin 1/2 (electrons) are considered in the quantum theory. It is shown that in the first nonzero approximation the angular distribution functions, calculated by methods of classical and quantum theory, coincide identically. Quantum corrections to the angular distribution functions appear only in the subsequent approximation whereas the total radiated power contains quantum and spin corrections already in the first approximation.
Propagation of torsional waves in pre-stretched composite cylinder with an imperfect interface
NASA Astrophysics Data System (ADS)
Ozturk, A.
2017-02-01
Propagation of torsional waves in pre-stressed circular cylinders is investigated within the framework of the piecewise homogeneous body model with the use of the three-dimensional linearized theory of elastic waves in an initially stressed body. It is assumed that the elasticity relations of the materials of the cylinder components are given through the Murnaghan potential. Numerical results related to the torsional wave dispersion and the influence of the mentioned initial stresses, as well as imperfectness paremeter on this dispersion are presented and discussed.
Evidence for the distribution of angular velocity inside the sun and stars
NASA Technical Reports Server (NTRS)
1972-01-01
A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing the distribution of angular velocity inside the sun and stars.
Optical orbital angular momentum.
Barnett, Stephen M; Babiker, Mohamed; Padgett, Miles J
2017-02-28
We present a brief introduction to the orbital angular momentum of light, the subject of our theme issue and, in particular, to the developments in the 13 years following the founding paper by Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)). The papers by our invited authors serve to bring the field up to date and suggest where developments may take us next.This article is part of the themed issue 'Optical orbital angular momentum'.
Optical orbital angular momentum
NASA Astrophysics Data System (ADS)
Barnett, Stephen M.; Babiker, Mohamed; Padgett, Miles J.
2017-02-01
We present a brief introduction to the orbital angular momentum of light, the subject of our theme issue and, in particular, to the developments in the 13 years following the founding paper by Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)). The papers by our invited authors serve to bring the field up to date and suggest where developments may take us next. This article is part of the themed issue 'Optical orbital angular momentum'.
Optical orbital angular momentum
Barnett, Stephen M.; Babiker, Mohamed; Padgett, Miles J.
2017-01-01
We present a brief introduction to the orbital angular momentum of light, the subject of our theme issue and, in particular, to the developments in the 13 years following the founding paper by Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)). The papers by our invited authors serve to bring the field up to date and suggest where developments may take us next. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069775
Rotational Constants for M-Methylbenzaldehyde a Study in Low Barrier Torsional Splitting
NASA Astrophysics Data System (ADS)
Shirar, Amanda J.; Hotopp, Kelly M.; Wilcox, David S.; Dian, Brian C.
2010-06-01
We present the ground state spectrum for m-methylbenzaldehyde taken with a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. The presence of a methyl rotor on the molecule introduces a threefold internal rotation barrier. Tunneling through this barrier leads to splitting of the torsional energy level degeneracy into A and E states. Theory predicts a low torsional barrier for both the cis and trans conformers, which leads to large splitting in the frequency spectrum. The A states are simulated using the rigid rotor approximation and subsequent distortion terms. In order to predict the E states, a V3 parameter must be determined that correlates to the torsional barrier. All four possible species have been fit and parameters will be presented, including rotational constants, distortion terms and V3 values.
Beam and Torsion Tests of Aluminum-alloy 61S-T Tubing
NASA Technical Reports Server (NTRS)
Moore, R L; Holt, Marshall
1942-01-01
Tests were made to determine the effect of length and the effect of ratios of diameter to wall thickness upon the flexural and torsional moduli of failure of 61S-T aluminum-alloy tubing. The moduli of failure in bending, as determined by tests in which the tubing was loaded on the neutral axis at the one-third points of the span, were found to bear an approximately linear relationship with diameter-thickness ratio and were practically independent of span within the limits investigated. Empirical equations are given describing the relations obtained. The moduli of failure in torsion were found to be dependent upon length as well as upon diameter-thickness ratios. Empirical equations are given for predicting strengths within the range of plastic buckling. Within the elastic range, available torsion theories were found to be satisfactory.
NASA Astrophysics Data System (ADS)
Krak, Michael D.; Dreyer, Jason T.; Singh, Rajendra
2016-03-01
A vehicle clutch damper is intentionally designed to contain multiple discontinuous non-linearities, such as multi-staged springs, clearances, pre-loads, and multi-staged friction elements. The main purpose of this practical torsional device is to transmit a wide range of torque while isolating torsional vibration between an engine and transmission. Improved understanding of the dynamic behavior of the device could be facilitated by laboratory measurement, and thus a refined vibratory experiment is proposed. The experiment is conceptually described as a single degree of freedom non-linear torsional system that is excited by an external step torque. The single torsional inertia (consisting of a shaft and torsion arm) is coupled to ground through parallel production clutch dampers, which are characterized by quasi-static measurements provided by the manufacturer. Other experimental objectives address physical dimensions, system actuation, flexural modes, instrumentation, and signal processing issues. Typical measurements show that the step response of the device is characterized by three distinct non-linear regimes (double-sided impact, single-sided impact, and no-impact). Each regime is directly related to the non-linear features of the device and can be described by peak angular acceleration values. Predictions of a simplified single degree of freedom non-linear model verify that the experiment performs well and as designed. Accordingly, the benchmark measurements could be utilized to validate non-linear models and simulation codes, as well as characterize dynamic parameters of the device including its dissipative properties.
"Angular" plasma cell cheilitis.
da Cunha Filho, Roberto Rheingantz; Tochetto, Lucas Baldissera; Tochetto, Bruno Baldissera; de Almeida, Hiram Larangeira; Lorencette, Nádia Aparecida; Netto, José Fillus
2014-03-17
Plasma cell cheilitis is an extremely rare disease, characterized by erythematous-violaceous, ulcerated and asymptomatic plaques, which evolve slowly. The histological characteristics include dermal infiltrate composed of mature plasmocytes. We report a case of Plasma cell angular cheilitis in a 58-year-old male, localized in the lateral oral commissure.
Endodontic instruments after torsional failure: nanoindentation test.
Jamleh, Ahmed; Sadr, Alireza; Nomura, Naoyuki; Ebihara, Arata; Yahata, Yoshio; Hanawa, Takao; Tagami, Junji; Suda, Hideaki
2014-01-01
This study aimed to evaluate effects of torsional loading on the mechanical properties of endodontic instruments using the nanoindentation technique. ProFile (PF; size 30, taper 04; Dentsply Maillefer, Switzerland) and stainless steel (SS; size 30, taper 02; Mani, Japan) instruments were subjected to torsional test. Nanoindentation was then performed adjacent to the edge of fracture (edge) and at the cutting part beside the shank (shank). Hardness and elastic modulus were measured under 100-mN force on 100 locations at each region, and compared to those obtained from the same regions on new instruments. It showed that PF and SS instruments failed at 559 ± 67 and 596 ± 73 rotation degrees and mean maximum torque of 0.90 ± 0.07 and 0.99 ± 0.05 N-cm, respectively. Hardness and elastic modulus ranged 4.8-6.7 and 118-339 GPa in SS, and 2.7-3.2 and 52-81 GPa in PF. Significant differences between torsion-fractured and new instruments in hardness and elastic modulus were detected in the SS system used. While in PF system, the edge region after torsional fracture had significantly lower hardness and elastic modulus compared to new instruments. The local hardness and modulus of elasticity of endodontic instruments adjacent to the fracture edge are significantly reduced by torsional loading.
Optomechanics based on angular momentum exchange between light and matter
NASA Astrophysics Data System (ADS)
Shi, H.; Bhattacharya, M.
2016-08-01
The subject of optomechanics involves interactions between optical and mechanical degrees of freedom, and is currently of great interest as an enabler of fundamental investigations in quantum mechanics, as well as a platform for ultrasensitive measurement devices. The majority of optomechanical configurations rely on the exchange of linear momentum between light and matter. We will begin this tutorial with a brief description of such systems. Subsequently, we will introduce optomechanical systems based on angular momentum exchange. In this context, optical fields carrying polarization and orbital angular momentum will be considered, while for the mechanics, torsional and free rotational motion will be of relevance. Our overall aims will be to supply basic analyses of some of the existing theoretical proposals, to provide functional descriptions of some of the experiments conducted thus far, and to consider some directions for future research. We hope this tutorial will be useful to both theorists and experimentalists interested in the subject.
The metric on field space, functional renormalization, and metric–torsion quantum gravity
Reuter, Martin Schollmeyer, Gregor M.
2016-04-15
Searching for new non-perturbatively renormalizable quantum gravity theories, functional renormalization group (RG) flows are studied on a theory space of action functionals depending on the metric and the torsion tensor, the latter parameterized by three irreducible component fields. A detailed comparison with Quantum Einstein–Cartan Gravity (QECG), Quantum Einstein Gravity (QEG), and “tetrad-only” gravity, all based on different theory spaces, is performed. It is demonstrated that, over a generic theory space, the construction of a functional RG equation (FRGE) for the effective average action requires the specification of a metric on the infinite-dimensional field manifold as an additional input. A modified FRGE is obtained if this metric is scale-dependent, as it happens in the metric–torsion system considered.
Torsional elasticity and energetics of F1-ATPase.
Czub, Jacek; Grubmüller, Helmut
2011-05-03
F(o)F(1)-ATPase is a rotary motor protein synthesizing ATP from ADP driven by a cross-membrane proton gradient. The proton flow through the membrane-embedded F(o) generates the rotary torque that drives the rotation of the asymmetric shaft of F(1). Mechanical energy of the rotating shaft is used by the F(1) catalytic subunit to synthesize ATP. It was suggested that elastic power transmission with transient storage of energy in some compliant part of the shaft is required for the observed high turnover rate. We used atomistic simulations to study the spatial distribution and structural determinants of the F(1) torsional elasticity at the molecular level and to comprehensively characterize the elastic properties of F(1)-ATPase. Our fluctuation analysis revealed an unexpected heterogeneity of the F(1) shaft elasticity. Further, we found that the measured overall torsional moduli of the shaft arise from two distinct contributions, the intrinsic elasticity and the effective potential imposed on the shaft by the catalytic subunit. Separation of these two contributions provided a quantitative description of the coupling between the rotor and the catalytic subunit. This description enabled us to propose a minimal quantitative model of the F(1) energetics along the rotary degrees of freedom near the resting state observed in the crystal structures. As opposed to the usually employed models where the motor mechanical progression is described by a single angular variable, our multidimensional treatment incorporates the spatially inhomogeneous nature of the shaft and its interactions with the stator and offers new insight into the mechanoenzymatics of F(1)-ATPase.
Li, Zhijie; Wang, Shengjie; Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei; Weber, William J.
2010-07-01
The mechanical behavior of twinned silicon carbide (SiC) nanowires under combined tension-torsion and compression-torsion is investigated using molecular dynamics simulations with an empirical potential. The simulation results show that both the tensile failure stress and buckling stress decrease under combined tension-torsional and combined compression-torsional strain, and they decrease with increasing torsional rate under combined loading. The torsion rate has no effect on the elastic properties of the twinned SiC nanowires. The collapse of the twinned nanowires takes place in a twin stacking fault of the nanowires.
Active structures to reduce torsional vibrations
NASA Astrophysics Data System (ADS)
Matthias, M.; Schlote, D.; Atzrodt, H.
2013-03-01
This paper describes the development of different active measures to reduce torsional vibrations in power trains. The measures are based on concepts developed for active mounts to reduce the transmission of structure-borne sound. To show the potential of these active measures and investigate their mode of operation to influence torsional vibrations, numerical simulations of powertrains with different active measures were done. First experimental results from tests on an experimental (reduced size) power train were used to align the numerical models. The work was done within the project 'LOEWE-Zentrum AdRIA: Adaptronik - Research, Innovation, Application' funded by the German federal state of Hessen, and the Project AKTos: 'Active control of torsional vibrations by coupling elements' placed in the research Framework program 'Navigation and Maritime Technology for the 21st Century' funded by the German Federal Ministry of Economics and Technology.
Transport of torsional stress in DNA
Nelson, Philip
1999-01-01
It is well known that transcription can induce torsional stress in DNA, affecting the activity of nearby genes or even inducing structural transitions in the DNA duplex. It has long been assumed that the generation of significant torsional stress requires the DNA to be anchored, forming a limited topological domain, because otherwise it would spin almost freely about its axis. Previous estimates of the rotational drag have, however, neglected the role of small natural bends in the helix backbone. We show how these bends can increase the drag several thousandfold relative to prior estimates, allowing significant torsional stress even in linear unanchored DNA. The model helps explain several puzzling experimental results on structural transitions induced by transcription of DNA. PMID:10588707
Angular momentum conservation in dipolar energy transfer.
Guo, Dong; Knight, Troy E; McCusker, James K
2011-12-23
Conservation of angular momentum is a familiar tenet in science but has seldom been invoked to understand (or predict) chemical processes. We have developed a general formalism based on Wigner's original ideas concerning angular momentum conservation to interpret the photo-induced reactivity of two molecular donor-acceptor assemblies with physical properties synthetically tailored to facilitate intramolecular energy transfer. Steady-state and time-resolved spectroscopic data establishing excited-state energy transfer from a rhenium(I)-based charge-transfer state to a chromium(III) acceptor can be fully accounted for by Förster theory, whereas the corresponding cobalt(III) adduct does not undergo an analogous reaction despite having a larger cross-section for dipolar coupling. Because this pronounced difference in reactivity is easily explained within the context of the angular momentum conservation model, this relatively simple construct may provide a means for systematizing a broad range of chemical reactions.
Acute Scrotum Caused by Hernia Sac Torsion.
Fukui, Shinji; Aoki, Katsuya; Shimada, Keiji; Samma, Shoji
2016-03-01
A 9-year-old boy was referred to us with an acute pain attack of the left scrotal contents. Ultrasonography showed a normal blood supply to the left testis, suggesting an incarcerated left inguinal hernia. Surgical exploration did not demonstrate an incarcerated left inguinal hernia. After exploration of the left testis, a dark red pedunculated cystic mass, separate from the left testis, was found to be twisted. Immunohistochemical studies of the excised cyst demonstrated torsion of the hernia sac of the peritoneum. In conclusion, we encountered a case of acute scrotum which was probably caused by torsion of the hernia sac.
Acute torsion of a wandering spleen.
Lam, Y; Yuen, Kenny K Y; Chong, L C
2012-04-01
The 'wandering spleen' is a rare condition due to extreme laxity or absence of ligaments that fix the organ in its normal anatomical position within the left upper quadrant. Without early surgical intervention, wandering spleen can lead to torsion and subsequent splenic infarction or rupture. Clinical suspicion plus urgent investigation and intervention are important, so as to salvage the spleen and prevent complications. We present a case of torsion of a wandering spleen in a 21-year-old young woman, who presented with a painful pelvic mass. We also reviewed the literature on this entity.
Wandering spleen with torsion and complete infarction.
Chu, Jianping; Li, Ziping; Luo, Boning; Yang, Jianyong
2011-10-01
Wandering spleen is rare and is associated with a high incidence of splenic torsion and infarction. Presenting symptoms range from an asymptomatic, incidentally palpated abdominal mass to an acutely ill patient. Because wandering spleen is uncommon in the pediatric population, a heightened awareness of the condition is required for accurate diagnosis and appropriate management. We present a case of a 4-year-old girl who presented with acute abdomen and was surgically confirmed to have a wandering spleen with torsion and complete infarction.
Cracked shells under skew-symmetric loading. [Reissner theory
NASA Technical Reports Server (NTRS)
Delale, F.
1981-01-01
The general problem of a shell containing a through crack in one of the principal planes of curvature and under general skew-symmetric loading is considered. By employing a Reissner type shell theory which takes into account the effect of transverse shear strains, all boundary conditions on the crack surfaces are satisfied separately. Consequently, unlike those obtained from the classical shell theory, the angular distributions of the stress components around the crack tips are shown to be identical to the distributions obtained from the plane and anti-plane elasticity solutions. Results are given for axially and circumferentially cracked cylindrical shells, spherical shells, and toroidal shells under uniform in-plane shearing, out of plane shearing, and torsion. The problem is formulated for specially orthostropic materials, therefore, the effect of orthotropy on the results is also studied.
Improved Coating System for High Strength Torsion Bars
1981-04-23
SwW IMPROVED COATING SYSTEM FOR HIGH S- TYPE Of REPORT & PEROo CovERED STRENGTH TORSION BAR Final Report Plastisol Coating System Provides a Cost...8217 mumber) Torsion Bar Plastisol Coating Inorganic Coating Protective Coating Polyvinyl Chloride Coating Polyurethane Coating Corrosion Protection Tape...Bars E. Endurance Test Results for One-third Length Torsion E-1 Bar F. Specification for Application of Plastisol to High F-1 Strength Torsion Bar
Angular momentum relaxation in atom-diatom dilute gas mixtures
NASA Astrophysics Data System (ADS)
Evans, Glenn T.
1987-04-01
The angular momentum relaxation cross sections for a diatomic molecule in a dilute atomic gas are estimated subject to the assumption that the intermolecular torque is dominated by the hard, impulsive contribution (evaluated using Boltzmann kinetic theory for nonspherical molecules). For carbon monoxide in a variety of gases, the kinetic theory derived contribution to the angular momentum cross section is in qualitative agreement with the experimental results of Jameson, Jameson, and Buchi.
NASA Astrophysics Data System (ADS)
de Andrade, L. C. G.
2016-01-01
A generalized dynamo equation in the first order torsion Garcia de Andrade L C (2012 Phys. Lett. B 711 143) has previously been derived. From this equation it is shown that for the 10 kpc scale, torsion gravity is not able to help seed galactic dynamos since the dynamo time is not long enough to take into account structure formation. In this paper, the dynamo equation is extended to second-order torsion terms—but unfortunately, the situation is even worse and the torsion does not seem to help dynamo efficiency. Nevertheless, in the intergalactic magnetic field scale of 1 mpc, the efficiency of the self-induction equation with torsion changes, and even in the first-order torsion case, one obtains large-scale magnetic fields with 109 yr dynamo efficiency. Dynamo efficiency in the case of interstellar matter (ISM) reaches a diffusion time of 1013 yr. This seems to be in contrast with a recent investigation by Bamba et al (2012 J. Cosmol. Astropart. Phys. JCAP05(2010)08) where they obtained, from another type of torsion theory called teleparallelism (A Einstein, Math Annalen (1922)), a large scale intergalactic magnetic field of 10-9 G. If this is not a model-dependent result, there is an apparent contradiction that has to be addressed. It is shown that for dynamo efficiency in astrophysical flow without shear, a strong seed field of 10-11 G is obtained, which is suitable for seeding galactic dynamos. As an example of a non-parity-violating dynamo equation, a magnetic field of the order of 10-27G is obtained as a seed field for the galactic dynamo from the theory of Einstein’s unified teleparallelism. This shows that in certain gravity models, torsion is able to enhance cosmological magnetic fields in view of obtaining better dynamo efficiency. To better compare our work with Bamba et al (2012 J. Cosmol. Astropart. Phys. JCAP05(2010)08), we consider the slow decay of magnetic fields in the teleparallel model. This observation is due to an anonymous referee who
Tussive syncope in a pug with lung-lobe torsion.
Davies, John A; Snead, Elisabeth C R; Pharr, John W
2011-06-01
The most common presenting clinical signs of lung-lobe torsion include dyspnea, tachypnea, lethargy, and anorexia. Tussive syncope secondary to lung-lobe torsion has not been documented. This article describes the presentation, diagnosis, management, and outcome of a pug with tussive syncope secondary to lung-lobe torsion.
Angular cheilitis after tonsillectomy.
England, R J; Lau, M; Ell, S R
1999-08-01
The operation of tonsillectomy requires the oral cavity to be held open mechanically in an unconscious patient, and intra-oral instrumentation to occur. Angular cheilitis may arise as a result of this after operation. This can cause morbidity and delay the re-establishment of a normal diet. The aim of this study was to identify what factors increase the likelihood of developing this problem postoperatively. Sixty patients were randomly selected in a prospective manner. Preoperative, intraoperative and postoperative variables were recorded. The frequency of development of postoperative angular cheilitis was recorded. The prevalence of the condition was related to the prerecorded variables. Parametric analysis showed that the chance of developing angular cheilitis was directly related to the use of diathermy haemostasis (P = 0.05). Logistic regression analysis showed that the odds ratio of developing this complication if diathermy was used is 3.5 (95% confidence intervals 0.99, 12.4) and operation difficulty may also be a relevant variable. No other recorded variables were found to be significant.
Cryptorchid testis with torsion: Inguinoscrotal whirlpool sign
Indiran, Venkatraman
2016-01-01
Non contrast helical computed tomography (CT) study of the abdomen is frequently performed in evaluation of suspected ureteric colic. We present CT images of a young adult male patient who had torsion of an undescended, non-neoplastic testis and describe the “Inguinoscrotal whirlpool sign on CT”. PMID:27555688
Clinical Characteristics of Torsion of the Omentum
Montiel-Jarquin, Alvaro; Lopez-Colombo, Aurelio; Nava, Arnulfo; Juarez-Santiesteban, Rayo; Leyva-Trejo, Hugo; Zamora-Ustaran, Alfonso; García-Carrasco, Mario; Munoz-Guarneros, Margarita
2009-01-01
Background The aim of this paper is to describe clinical aspects of the torsion of the omentum. Methods In this observational, retrospective study, the study group consisted of patients surgically managed for torsion of the omentum, between 1998 and 2008, in a second level medical facility in Mexico. Variables in the study included age, sex, signs and symptoms, body mass index (BMI), treatment and evolution time. Descriptive statistical analysis was employed. Results Eleven patients were confirmed torsion of omentum, 7 (63.63%) women and 4 (36.36%) men, median age 33 (20 to 58) years, BMI > 25.0 in 9 (81.81%), average evolution 6.54, SD 3.47 days. All presented with abdominal pain, 6 (54.54%) with abdominal distension, 4 (36.36%) with ambulatory difficulty, 3 (27.27%) with malaise, and 5 (45.45%) with previous surgery. In all cases diagnosis was made by means of laparotomy, treatment was the resection of the affected segment, and there were no further complications. Conclusions Torsion of the omentum resembles acute appendicitis; abdominal pain and abdominal distension are the most common symptoms. It is often discovered during surgery and it is treated surgically by removal of the affected segment of the omentum. PMID:27942278
He, Li; Li, Huan; Li, Mo
2016-09-01
Photons carry linear momentum and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, whereas transfer of angular momentum induces optical torque. Optical forces including radiation pressure and gradient forces have long been used in optical tweezers and laser cooling. In nanophotonic devices, optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes. In contrast, to date, the angular momentum of light and the optical torque effect have only been used in optical tweezers but remain unexplored in integrated photonics. We demonstrate the measurement of the spin angular momentum of photons propagating in a birefringent waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mechanical effect of photon's polarization degree of freedom and demonstrates its control in integrated photonic devices. Exploiting optical torque and optomechanical interaction with photon angular momentum can lead to torsional cavity optomechanics and optomechanical photon spin-orbit coupling, as well as applications such as optomechanical gyroscopes and torsional magnetometry.
He, Li; Li, Huan; Li, Mo
2016-01-01
Photons carry linear momentum and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, whereas transfer of angular momentum induces optical torque. Optical forces including radiation pressure and gradient forces have long been used in optical tweezers and laser cooling. In nanophotonic devices, optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes. In contrast, to date, the angular momentum of light and the optical torque effect have only been used in optical tweezers but remain unexplored in integrated photonics. We demonstrate the measurement of the spin angular momentum of photons propagating in a birefringent waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mechanical effect of photon’s polarization degree of freedom and demonstrates its control in integrated photonic devices. Exploiting optical torque and optomechanical interaction with photon angular momentum can lead to torsional cavity optomechanics and optomechanical photon spin-orbit coupling, as well as applications such as optomechanical gyroscopes and torsional magnetometry. PMID:27626072
Fakhry, Mohamed A; Shazly, Malak I El
2011-01-01
Purpose To compare torsional versus combined torsional and conventional ultrasound modes in hard cataract surgery regarding ultrasound energy and time and effect on corneal endothelium. Settings Kasr El Aini hospital, Cairo University, and International Eye Hospital, Cairo, Egypt. Methodology Ninety-eight eyes of 63 patients were enrolled in this prospective comparative randomized masked clinical study. All eyes had nuclear cataracts of grades III and IV using the Lens Opacities Classification System III (LOCS III). Two groups were included, each having an equal number of eyes (49). The treatment for group A was combined torsional and conventional US mode phacoemulsification, and for group B torsional US mode phacoemulsification only. Pre- and post-operative assessments included best corrected visual acuity (BCVA), intraocular pressure (IOP), slit-lamp evaluation, and fundoscopic evaluation. Endothelial cell density (ECD) and central corneal thickness (CCT) were measured preoperatively, 1 day, 7 days, and 1 month postoperatively. All eyes were operated on using the Alcon Infiniti System (Alcon, Fort Worth, TX) with the quick chop technique. All eyes were implanted with AcrySof SA60AT (Alcon) intraocular lens (IOL). The main phaco outcome parameters included the mean ultrasound time (UST), the mean cumulative dissipated energy (CDE), and the percent of average torsional amplitude in position 3 (%TUSiP3). Results Improvement in BCVA was statistically significant in both groups (P < 0.001). Comparing UST and CDE for both groups revealed results favoring the pure torsional group (P = 0.002 and P < 0.001 for UST; P = 0.058 and P = 0.009 for CDE). As for %TUSiP3, readings were higher for the pure torsional group (P = 0.03 and P = 0.01). All changes of CCT, and ECD over time were found statistically significant using one-way ANOVA testing (P < 0.001). Conclusion Both modes are safe in hard cataract surgery, however the pure torsional mode showed less US energy used. PMID
Lee, Nam Ki; Park, Soonyong; Yoon, Myung-Han; Kim, Zee Hwan; Kim, Seong Keun
2012-01-14
The role of ring torsion in the enhancement of intramolecular vibrational energy redistribution (IVR) in aromatic molecules was investigated by conducting excitation and dispersed fluorescence spectroscopy of 1,1'-binaphthyl (1,1'-BN) and 2,2'-BN. The dispersed fluorescence spectra of 1,1'-BN in the origin region of S(1)-S(0) were well resolved, which presented 25-27 cm(-1) gaps of torsional mode in the ground state. The overall profile of the dispersed spectra of 1,1'-BN is similar to that of naphthalene. In contrast, the spectra of 2,2'-BN were not resolved due to the multitude of the active torsional modes. In both cases, dissipative IVR was observed to take place with a relatively small excess vibrational energy: 237.5 cm(-1) for 1,1'-BN and 658 cm(-1) for 2,2'-BN, which clearly shows that ring torsion efficiently enhances the IVR rate. Ab initio and density functional theory calculations with medium-sized basis sets showed that the torsional potential of 1,1'-BN has a very flat minimum over the range of torsional angles from ca. 60° to 120°, whereas that of 2,2'-BN showed two well-defined potential minima at ca. 40° and 140°, in resemblance to the case of biphenyl. In this work, we propose that aromatic molecules be classified into "strong" and "weak" torsional hindrance cases: molecules with strong hindrance case show shorter torsional progressions and more effective IVR dynamics than do those with weak hindrance.
Development of a second generation torsion balance based on a spherical superconducting suspension
NASA Astrophysics Data System (ADS)
Hammond, Giles D.; Speake, Clive C.; Matthews, Anthony J.; Rocco, Emanuele; Peña-Arellano, Fabian
2008-02-01
This paper describes the development of a second generation superconducting torsion balance to be used for a precision measurement of the Casimir force and a short range test of the inverse square law of gravity at 4.2K. The instrument utilizes niobium (Nb) as the superconducting element and employs passive damping of the parasitic modes of oscillation. Any contact potential difference between the torsion balance and its surroundings is nulled to within ≈50mV by applying known DC biases and fitting the resulting parabolic relationship between the measured torque and the applied voltage. A digital proportional-integral-derivative servo system has been developed and characterized in order to control the azimuthal position of the instrument. The angular acceleration and displacement noise are currently limited by the capacitive sensor at the level 3×10-8rads-2/√Hz and 30nm/√Hz at 100mHz. The possibility of lossy dielectric coatings on the surface of the torsion balance test masses is also investigated. Our measurements show that the loss angles δ are (1.5±2.3)×10-4 and (2.0±2.2)×10-4 at frequencies of 5 and 10mHz, respectively. These values of loss are not significant sources of error for measurements of the Casimir force using this experimental setup.
Torsion of a Large Appendix Testis Misdiagnosed as Pyocele
Meher, Susanta; Rath, Satyajit; Sharma, Rakesh; Sasmal, Prakash Kumar; Mishra, Tushar Subhadarshan
2015-01-01
Torsion of the appendix testis is not an uncommon cause of acute hemiscrotum. It is frequently misdiagnosed as acute epididymitis, orchitis, or torsion of testis. Though conservative management is the treatment of choice for this condition, prompt surgical intervention is warranted when testicular torsion is suspected. We report a case of torsion of a large appendix testis misdiagnosed as pyocele. Emergency exploration of it revealed a large appendix testis with torsion and early features of gangrene. After excision of the appendix testis, the wound was closed with an open drain. The patient had an uneventful and smooth postoperative recovery. PMID:25861514
Torsion of an intra-abdominal testis.
Lewis; Roller; Parra; Cotlar
2000-09-01
To present a case of torsion of a nonneoplastic intra-abdominal testis with an unusual clinical presentation.A 26-year-old active duty Navy Petty Officer presented to the emergency department on 3 occasions over a 5-day period with lower abdominal pain. Physical examination demonstrated acute tenderness in the left lower quadrant with sugestion of a normal spermatic cord and atrophic testis in the left scrotum. Computed tomography scan demonstrated an intra-abdominal lesion near the internal inguinal ring. The patient underwent surgical exploration through an inguinal incision. Torsion of a nonviable intra-abdominal testis was present. The scrotum contained only the vas deferens and cremasteric muscle. An orchiectomy was performed with removal of the vas deferens and other cord structures.The unusual clinical finding of acute torsion of an intra-abdominal testis, associated with an apparent atrophic scrotal testis, presented a confusing clinical picture. Computed tomography scan did not clarify the issue sufficiently to establish a definite preoperative diagnosis. Clinical suspicion prompted early surgical intervention. Review of the current literature produced 60 reported cases of torsion of an intra-abdominal testis. Two thirds of these involved testicular neoplasm, usually seminoma. Although the clinical presentation varied, most patients had recent onset of lower abdominal pain associated with tenderness and, in half the cases, a mass. Patients almost always presented with an absent scrotal testis on the involved side, and not infrequently reported previous surgery thought to be an orchiectomy.Diagnosis of an intra-abdominal testicular torsion is rare, particularly when no neoplasm is present. A high index of suspicion must be maintained whenever there is abdominal pain and undescended testis. The surgical history and imaging studies may not clarify a confusing clinical picture.
Ultrasonography of Extravaginal Testicular Torsion in Neonates
Bombiński, Przemysław; Warchoł, Stanisław; Brzewski, Michał; Majkowska, Zofia; Dudek-Warchoł, Teresa; Żerańska, Maria; Panek, Małgorzata; Drop, Magdalena
2016-01-01
Summary Background Extravaginal testicular torsion (ETT), also called prenatal or perinatal, occurs prenatally and is present at birth or appears within the first month of life. It has different etiology than intravaginal torsion, which appears later in life. Testicular torsion must be taken into consideration in differential diagnosis of acute scrotum and should be confirmed or ruled out at first diagnostic step. Ultrasonography is a basic imaging modality, however diagnostic pitfalls are still possible. There is still wide discussion concerning management of ETT, which varies from immediate orchiectomy to conservative treatment resulting in testicle atrophy. Material/Methods In this article we present ultrasonographic spectrum of ETT in neonates, which were diagnosed and treated in our hospital during the last 8 years (2008–2015), in correlation with clinical and intraoperative findings. Results Thirteen neonates with ETT were enrolled in the study – 11 patients with a single testicle affected and 2 patients with bilateral testicular torsion. Most common signs on clinical examination were: hardened and enlarged testicle and discoloration of the scrotum. Most common ultrasonographic signs were: abnormal size or echostructure of the affected testicle and absence of the blood flow in Doppler ultrasonography. In 3 patients ultrasound elastography was performed, which appeared very useful in testicle structure assessment. Conclusions Testicular torsion may concern boys even in the perinatal period. Ultrasonographic picture of acute scrotum in young boys may be confused. Coexistence of the abnormal size or echostructure of the torsed testicle with absence of the blood flow in Doppler ultrasonography appear as very specific but late ultrasonographic sings. Ultrasound elastography may be a very useful tool for visualisation of a very common clinical sign – hardening of the necrotic testicle. PMID:27757176
Angular Momentum in Dwarf Galaxies
NASA Astrophysics Data System (ADS)
Del Popolo, A.
We study the ``angular momentum catastrophe" in the framework of interaction among baryons and dark matter through dynamical friction. By means of Del Popolo (2009) model we simulate 14 galaxies similar to those investigated by van den Bosch, Burkert and Swaters (2001), and calculate the distribution of their spin parameters and the angular momenta. Our model gives the angular momentum distribution which is in agreement with the van den Bosch et al. observations. Our result shows that the ``angular momentum catastrophe" can be naturally solved in a model that takes into account the baryonic physics and the exchange of energy and angular momentum between the baryonic clumps and dark matter through dynamical friction.
Zhao, Hao; Feng, Hao
2013-08-12
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.
Optical angular momentum and atoms.
Franke-Arnold, Sonja
2017-02-28
Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors.This article is part of the themed issue 'Optical orbital angular momentum'.
Optical angular momentum and atoms
NASA Astrophysics Data System (ADS)
Franke-Arnold, Sonja
2017-02-01
Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors. This article is part of the themed issue 'Optical orbital angular momentum'.
Angular distributions in multifragmentation
Stoenner, R.W.; Klobuchar, R.L.; Haustein, P.E.; Virtes, G.J.; Cumming, J.B.; Loveland, W.
2006-04-15
Angular distributions are reported for {sup 37}Ar and {sup 127}Xe from 381-GeV {sup 28}Si+Au interactions and for products between {sup 24}Na and {sup 149}Gd from 28-GeV {sup 1}H+Au. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.
Design and analysis of a torsion braid pendulum displacement transducer
NASA Technical Reports Server (NTRS)
Rind, E.; Bryant, E. L.
1981-01-01
The dynamic properties at various temperatures of braids impregnated with polymer can be measured by using the braid as the suspension of a torsion pendulum. This report describes the electronic and mechanical design of a torsional braid pendulum displacement transducer which is an advance in the state of the art. The transducer uses a unique optical design consisting of refracting quartz windows used in conjunction with a differential photocell to produce a null signal. The release mechanism for initiating free torsional oscillation of the pendulum has also been improved. Analysis of the precision and accuracy of the transducer indicated that the maximum relative error in measuring torsional amplitude was approximately 0. A serious problem inherent in all instruments which use a torsional suspension was analyzed: misalignment of the physical and torsional axes of the torsional member which results in modulation of the amplitude of the free oscillation.
Understanding Solar Torsional Oscillations from Global Dynamo Models
NASA Astrophysics Data System (ADS)
Guerrero, G.; Smolarkiewicz, P. K.; de Gouveia Dal Pino, E. M.; Kosovichev, A. G.; Mansour, N. N.
2016-09-01
The phenomenon of solar “torsional oscillations” (TO) represents migratory zonal flows associated with the solar cycle. These flows are observed on the solar surface and, according to helioseismology, extend through the convection zone. We study the origin of the TO using results from a global MHD simulation of the solar interior that reproduces several of the observed characteristics of the mean-flows and magnetic fields. Our results indicate that the magnetic tension (MT) in the tachocline region is a key factor for the periodic changes in the angular momentum transport that causes the TO. The torque induced by the MT at the base of the convection zone is positive at the poles and negative at the equator. A rising MT torque at higher latitudes causes the poles to speed up, whereas a declining negative MT torque at the lower latitudes causes the equator to slow-down. These changes in the zonal flows propagate through the convection zone up to the surface. Additionally, our results suggest that it is the magnetic field at the tachocline that modulates the amplitude of the surface meridional flow rather than the opposite as assumed by flux-transport dynamo models of the solar cycle.
Lattanzi; di Lauro C
1999-12-01
The mechanism of torsional Coriolis interaction of E(1d) and E(2d) vibrational modes in ethane-like molecules is investigated, and it is shown that this coupling can drastically affect the torsional splitting in the degenerate vibrational states. A basic point of our treatment is that the sets of coordinates of head and tail which combine with the + sign to generate E(1d) normal coordinates are in general different from those which combine with the - sign to generate E(2d) normal coordinates. It is shown that the zeta(gamma) torsional Coriolis coefficients calculated by the usual methods of normal mode analysis are related to the vibrational angular momenta within head and tail referred to the internal rotor axis systems. With knowledge of the L and L(-1) matrices it is possible to transform these coefficients for reference to the molecule-fixed frame. It is peculiar that torsional Coriolis matrix elements occur between E(1d) and E(2d) vibrational components with the same x or y orientation in the molecule-fixed frame. The matrix elements of the torsional Coriolis operator and other operators responsible for the end-to-end coupling are determined, and a method for calculating vibration-torsion energies, and then torsional splittings, in degenerate vibrational states is outlined. Detailed calculations require a global model, involving all the degenerate vibrational basis states in a complex mechanism of interactions, but it is shown that useful information can be obtained by means of simplified models. Our semiempirical rule that degenerate vibrational states with a large negative value of the diagonal vibration-rotation Coriolis coefficient are likely to deviate much from the behavior of E(1d) or E(2d) vibrational states, with a sensible decrease of the torsional splittings, is confirmed. Copyright 1999 Academic Press.
Angular displacement measuring device
NASA Technical Reports Server (NTRS)
Seegmiller, H. Lee B. (Inventor)
1992-01-01
A system for measuring the angular displacement of a point of interest on a structure, such as aircraft model within a wind tunnel, includes a source of polarized light located at the point of interest. A remote detector arrangement detects the orientation of the plane of the polarized light received from the source and compares this orientation with the initial orientation to determine the amount or rate of angular displacement of the point of interest. The detector arrangement comprises a rotating polarizing filter and a dual filter and light detector unit. The latter unit comprises an inner aligned filter and photodetector assembly which is disposed relative to the periphery of the polarizer so as to receive polarized light passing the polarizing filter and an outer aligned filter and photodetector assembly which receives the polarized light directly, i.e., without passing through the polarizing filter. The purpose of the unit is to compensate for the effects of dust, fog and the like. A polarization preserving optical fiber conducts polarized light from a remote laser source to the point of interest.
Angular displacement measuring device
NASA Astrophysics Data System (ADS)
Seegmiller, H. Lee B.
1992-08-01
A system for measuring the angular displacement of a point of interest on a structure, such as aircraft model within a wind tunnel, includes a source of polarized light located at the point of interest. A remote detector arrangement detects the orientation of the plane of the polarized light received from the source and compares this orientation with the initial orientation to determine the amount or rate of angular displacement of the point of interest. The detector arrangement comprises a rotating polarizing filter and a dual filter and light detector unit. The latter unit comprises an inner aligned filter and photodetector assembly which is disposed relative to the periphery of the polarizer so as to receive polarized light passing the polarizing filter and an outer aligned filter and photodetector assembly which receives the polarized light directly, i.e., without passing through the polarizing filter. The purpose of the unit is to compensate for the effects of dust, fog and the like. A polarization preserving optical fiber conducts polarized light from a remote laser source to the point of interest.
Orbital angular momentum entanglement
NASA Astrophysics Data System (ADS)
Romero, Mary Jacquiline Romero
Entanglement in higher dimensions is an attractive concept that is a challenge to realise experimentally. To this end, the entanglement of the orbital angular momentum (OAM) of photons holds promise. The OAM state-space is discrete and theoretically unbounded. In the work that follows, we investigate various aspects of OAM entanglement. We show how the correlations in OAM and its conjugate variable, angular position, are determined by phase- matching and the shape of the pump beam in spontaneous parametric down- conversion. We implement tests of quantum mechanics which have been previously done for other variables. We show the Einstein-Podolsky-Rosen paradox for OAM and angle, supporting the incompatibility of quantum mechanics with locality and realism. We demonstrate violations of Bell-type inequalities, thereby discounting local hidden variables for describing the correlations we observe. We show the Hardy paradox using OAM, again highlighting the nonlocal nature of quantum mechanics. We demonstrate violations of Leggett-type inequalities, thereby discounting nonlocal hidden variables for describing correlations. Lastly, we have looked into the entanglement of topological vortex structures formed from a special superposition of OAM modes and show violations of Bell-type inequalities confined to a finite, isolated volume.
Laser-Based Measurement Of Torsional Vibration
NASA Astrophysics Data System (ADS)
Eastwood, P. G.; Halliwell, N. A.
1986-07-01
Investigations of the torsional vibration characteristics of shaft systems which transmit pulsating torques are an important part of a machinery designer's responsibility. Satisfactory operation of such systems depends to a large extent on successful treatment of this vibration problem, since incorrectly or insufficiently controlled torsional oscillations can lead to fatigue failure, rapid bearing wear, gear hammer etc. The problem is particularly severe in engine crankshaft design where numerous failures have been traced to abnormal vibration at "critical" speeds. Traditionally, the monitoring of torsional oscillation has been performed using strain gauges, slip rings and a variety of mechanical and electrical "torsiographs". More recently systems employing slotted discs or toothed wheels together with proximity transducers have been preferred, but a disadvantage arises from all these methods in that they require contact with the rotating component which necessitates "downtime" for transducer attachment. Moreover, physical access to the rotating surface is often restricted thus making the use of such methods impractical. The "cross-beam" laser velocimeter provides a means of measuring torsional vibration by a non-contact method, thus effectively overcoming the disadvantages of previous measurement systems. This well established laser-based instrument provides a time-resolved voltage analogue of shaft tangential surface velocity and laboratory and field tests have shown it to be both accurate and reliable. The versatility of this instrument, however, is restricted by the need for accurate positioning, since the velocimeter must be arranged so that the rotating surface always traverses the beam intersection region, which is typically only a fraction of a millimetre in length. As a consequence use is restricted to components of circular cross section. This paper compares and contrasts the "cross-beam" system with a new laser instrument, the laser torsional vibrometer
Development of a Torsional Seismometer for measuring the rotational oscillations of the Earth.
NASA Astrophysics Data System (ADS)
Madziwa-Nussino, T. G.; Cowsik, R.; Wagoner, K.
2008-12-01
The motivations for the development and characterization of instruments capable of recording the rotations associated with seismic activity and normal mode oscillations were detailed extensively at the 2006 Fall- meeting of the American Geophysical Union in 2006 and in a special workshop at USGS-Menlo Park in 2007. This paper describes the effort and progress we have made in building a new instrument to be used for such measurements. Our prototype has two basic subsystems; a torsional oscillator and an optical lever for angular measurements. The essential idea behind the design maybe briefly stated as follows: A mechanical torsional oscillator with a natural frequency significantly below the lowest normal mode frequencies will couple negligibly to the rotational motions of the earth, even though the housing of the oscillator is firmly fixed to the earth. A sensitive optical lever, fixed to the Earth, observing such a balance can therefore faithfully measure the rotational oscillations of the Earth. The challenges we face in this development are two-fold: (a) the development of a mechanical torsional oscillator with a low enough natural frequency ~10- 3Hz and the fabrication of an optical lever with an angular resolution better than ~10- 6rad·Hz-1/2; (b) to make the instrument robust and field-worthy for the study of near-field strong motions at frequencies higher than ~10-2Hz. The initial implemented design is as follows: the balance bob consists of a circular mirror of diameter ~ 40mm, with its normal in the horizontal plane. The mirror is mounted within an aluminum framework whose moment of inertia may be adjusted as required and also used for capacitive damping of unwanted torsional oscillations. The configuration has a mass of under 50g and a moment of inertia of ~150g·cm2 about the suspension axis. The suspension fiber is made of SS-304 alloy with a cross section of 7μm × 110μm and length ~5cm. The angular frequency of natural oscillations for this
Axial and torsional fatigue behavior of Waspaloy
NASA Technical Reports Server (NTRS)
Zamrik, S.; Mirdamadi, M.; Zahiri, F.
1986-01-01
The cyclic flow response and crack growth behavior of Waspaloy at room temperature and 650 C under tensile loading and torsional loading was studied, for two conditions of Waspaloy: fine grain, large gamma prime size; coarse grain, small gamma prime size. The fine grain material showed 5 to 10 percent hardening after about 10 percent of life, with sequent softening to failure at both themperature levels. The coarse grain material showed either stable response or monotonic softening to failure. Early crack initiation was observed on planes of maximum shear, with eventual branching to principle planes under torsional loading; cracks were always normal to load axis under tensile loading. Also, crack paths were intergranular at 650 C, mostly transgranular at room temperature.
Chronic splenic torsion in two dogs.
Reinhart, Jennifer M; Sherwood, J Matthew; KuKanich, Katherine S; Klocke, Emily; Biller, David S
2015-01-01
A 5 yr old spayed female poodle (case 1) was presented with a 4 mo history of lethargy, inappetence, and nonregenerative anemia. A 5 yr old castrated male French bulldog (case 2) was presented with a 2 wk history of mild abdominal pain, dyschezia, and intermittent anorexia. Both dogs were diagnosed with chronic splenic torsion based on changes in splenic position, echogenicity, and/or echotexture identified on B-mode abdominal ultrasonography, as well as either decreased or absent splenic blood flow on color-flow Doppler ultrasonography. Both dogs underwent splenectomy and had full resolution of clinical signs. Presentation of chronic splenic torsion is variable, and clinical signs can be nonspecific. Abdominal ultrasound with Doppler evaluation is an important diagnostic step that can lead to appropriate surgical intervention and good long-term prognosis.
Wang, Shibo; Niu, Chengchao
2016-01-01
In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T-θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model.
Wang, Shibo; Niu, Chengchao
2016-01-01
In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T–θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model. PMID:26799324
Orbital angular momentum microlaser
NASA Astrophysics Data System (ADS)
Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M.; Feng, Liang
2016-07-01
Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.
Myocardial Rotation and Torsion in Child Growth
Kim, Chang Sin; Park, Sora
2016-01-01
Background The speckle tracking echocardiography can benefit to assess the regional myocardial deformations. Although, previous reports suggested no significant change in left ventricular (LV) torsion with aging, there are certain differences in LV rotation at the base and apex. The purpose of this study was to evaluate the change and relationship of LV rotation for torsion with aging in children. Methods Forty healthy children were recruited and divided into two groups of twenty based on whether the children were preschool-age (2–6 years of age) or school-age (7–12 years of age). After obtaining conventional echocardiographic data, apical and basal short axis rotation were assessed with speckle tracking echocardiography. LV rotation in the basal and apical short axis planes was determined using six myocardial segments along the central axis. Results Apical and basal LV rotation did not show the statistical difference with increased age between preschool- and school-age children. Apical radial strain showed significant higher values in preschool-age children, especially at the anterior (52.8 ± 17.4% vs. 34.7 ± 23.2%, p < 0.02), lateral (55.8 ± 20.4% vs. 36.1 ± 22.7%, p < 0.02), and posterior segments (57.1 ± 17.6% vs. 38.5 ± 21.7%, p < 0.01). The torsion values did not demonstrate the statistical difference between two groups. Conclusion This study revealed the tendency of higher rotation values in preschool-age children than in school-age children. The lesser values of rotation and torsion with increased age during childhood warrant further investigation. PMID:27721953
Fluid driven torsional dipole seismic source
Hardee, Harry C.
1991-01-01
A compressible fluid powered oscillating downhole seismic source device capable of periodically generating uncontaminated horizontally-propagated, shear waves is provided. A compressible fluid generated oscillation is created within the device which imparts an oscillation to a housing when the device is installed in a housing such as the cylinder off an existing downhole tool, thereby a torsional seismic source is established. Horizontal waves are transferred to the surrounding bore hole medium through downhole clamping.
TORSIONAL OSCILLATIONS OF NONBARE STRANGE STARS
Mannarelli, Massimo; Pagliaroli, Giulia; Parisi, Alessandro; Pilo, Luigi; Tonelli, Francesco
2015-12-20
Strange stars are one of the possible compact stellar objects that can form after a supernova collapse. We consider a model of a strange star having an inner core in the color-flavor locked phase surmounted by a crystalline color superconducting (CCSC) layer. These two phases constitute the quarksphere, which we assume to be the largest and heaviest part of the strange star. The next layer consists of standard nuclear matter forming an ionic crust, hovering on the top of the quarksphere and prevented from falling by a strong dipolar electric field. The dipolar electric field arises because quark matter is confined in the quarksphere by the strong interaction, but electrons can leak outside forming an electron layer a few hundred fermi thick separating the ionic crust from the underlying quark matter. The ionic matter and the CCSC matter constitute two electromagnetically coupled crust layers. We study the torsional oscillations of these two layers. Remarkably, we find that if a fraction larger than 10{sup −4} of the energy of a Vela-like glitch is conveyed to a torsional oscillation, the ionic crust will likely break. The reason is that the very rigid and heavy CCSC crust layer will absorb only a small fraction of the glitch energy, leading to a large-amplitude torsional oscillation of the ionic crust. The maximum stress generated by the torsional oscillation is located inside the ionic crust and is very close to the star’s surface. This peculiar behavior leads to a much easier crust cracking than in standard neutron stars.
UBIQUITOUS TORSIONAL MOTIONS IN TYPE II SPICULES
De Pontieu, B.; Hansteen, V. H.; Carlsson, M.; Rouppe van der Voort, L. H. M.; Rutten, R. J.; Watanabe, H.
2012-06-10
Spicules are long, thin, highly dynamic features that jut out ubiquitously from the solar limb. They dominate the interface between the chromosphere and corona and may provide significant mass and energy to the corona. We use high-quality observations with the Swedish 1 m Solar Telescope to establish that so-called type II spicules are characterized by the simultaneous action of three different types of motion: (1) field-aligned flows of order 50-100 km s{sup -1}, (2) swaying motions of order 15-20 km s{sup -1}, and (3) torsional motions of order 25-30 km s{sup -1}. The first two modes have been studied in detail before, but not the torsional motions. Our analysis of many near-limb and off-limb spectra and narrowband images using multiple spectral lines yields strong evidence that most, if not all, type II spicules undergo large torsional modulation and that these motions, like spicule swaying, represent Alfvenic waves propagating outward at several hundred km s{sup -1}. The combined action of the different motions explains the similar morphology of spicule bushes in the outer red and blue wings of chromospheric lines, and needs to be taken into account when interpreting Doppler motions to derive estimates for field-aligned flows in spicules and determining the Alfvenic wave energy in the solar atmosphere. Our results also suggest that large torsional motion is an ingredient in the production of type II spicules and that spicules play an important role in the transport of helicity through the solar atmosphere.
Augat, Peter; Hoegel, Florian; Stephan, Daniel; Hoffmann, Stephanie; Buehren, Volker
2016-11-01
Treatment of distal tibia shaft fractures using intramedullary nailing requires stable fixation of the distal fragment to prevent malunion. Angular stable locking for intramedullary nails pledge to provide increased mechanical stability. This study tested the hypothesis that intramedullary nails with angular stable interlocking screws would have increased construct stiffness, reduced fracture gap movement and enhanced fatigue failure compared to nails with conventional locking having the same diameter. Biomechanical experiments were performed on 24 human cadaveric tibiae which obtained a distal fracture and were fixed by three different techniques: conventional locking with 8- and 10-mm-diameter nails and angular stable locking with 8-mm nails. Stiffness of the implant-bone construct and movement of the fragments were tested under axial loading and torsion. The constructs were tested to failure under cyclic fatigue loading. Analysis of variance and Kaplan-Meier survival analysis were used for statistical assessment. Axial stiffness of the 10-mm nail was about 50% larger compared to both 8-mm nail constructs independent of the type of locking mode (p < 0.01). No differences were found in axial performance between angular stable and conventional locking neither under static nor under cyclic testing conditions (p > 0.5). Angular stability significantly decreased the clearance under torsional load by more than 50% compared to both conventionally locked constructs (p = 0.03). However, due to the larger nail diameter, the total interfragmentary motion was still smallest for the 10-mm nail construct (p < 0.01). Although the 10-mm nail constructs survived slightly longer, differences between groups were minor and not statistically significant (p = 0.4). Our hypothesis that angular stable interlocking of intramedullary nails would improve mechanical performance of distal tibia fracture fixation was not confirmed in a physiologically realistic loading
Neonatal testicular torsion: a systematic literature review.
Nandi, Biplab; Murphy, Feilim Liam
2011-10-01
Neonatal testicular torsion (NTT) is rare and reported salvage rates vary widely both in their cited frequency and plausibility. The timing and necessity of surgery is controversial with different centers arguing for the conservative management of all cases while others argue for prompt exploration for all. Confusion also reigns over the need to fix the contralateral testis. In order to clarify the issue the authors reviewed the literature and found 18 case series of NTT, containing 268 operated cases suitable for analysis. This paper reviews the literature on NTT specifically regarding salvage rates and timing/necessity of surgery. Its primary aim is to produce an overall salvage rate in the operated group. Overall salvage rate was 8.96%, 24 testes. When operation is specified as an emergency, salvage may be as high as 21.7%. While salvage of a testis torted at birth is rare, it is reported. Early asynchronous torsion is also rare but reported. Worryingly, bilateral torsion can present with unilateral signs.Given these findings, we would suggest early surgery with fixation of the contralateral side.
Perinatal testicular torsion and medicolegal considerations.
Massoni, F; Troili, G M; Pelosi, M; Ricci, S
2014-06-01
Perinatal testicular torsion (PTT) is a very complex condition because of rarity of presentation and diagnostic and therapeutic difficulties. In presence of perinatal testicular torsion, the involvement of contralateral testis can be present also in absence of other indications which suggest the bilateral involvement; therefore, occurrences supported by literature do not exclude the use of surgery to avoid the risk of omitted or delayed diagnosis. The data on possible recovery of these testicles are not satisfactory, and treatment consists of an observational approach ("wait-and-see") or an interventional approach. The hypothesis of randomized clinical trials seems impracticable because of rarity of disease. The authors present a case of PTT, analyzing injuries due to clinical and surgical management of these patients, according to medicolegal profile. The delayed diagnosis and the choice of an incorrect therapeutic approach can compromise the position of healthcare professionals, defective in terms of skill, prudence and diligence. Endocrine insufficiency is an unfortunate event. The analysis of literature seems to support, because of high risk, a surgical approach aimed not only at resolution of unilateral pathology or prevention of a relapse, but also at prevention of contralateral testicular torsion.
Polyorchidism with presumed contralateral intrauterine testicular torsion
Leodoro, B.M.; Beasley, S.W.; Stringer, M.D.
2014-01-01
INTRODUCTION Polyorchidism was first described by Blasius in 16701 during a routine autopsy. We report a child with unilateral polyorchidism and a contralateral absent testis, a combination not reported previously. PRESENTATION OF CASE A 2-year-old boy was referred to the outpatient clinic with an impalpable left testis. At laparoscopy, the left vas deferens and testicular vessels ended blindly proximal to a closed internal ring. No gonadal tissue was identified. On the right side, a single vas deferens and testicular vessels were seen entering the internal ring as normal. The right side of the scrotum was explored and two testes were identified within a single tunica vaginalis. DISCUSSION Polyorchidism is rare with a literature search identifying approximately 230 reported cases. Whilst prenatal testicular torsion is increasing being recognized and treated as a surgical emergency,9 prenatal testicular torsion in association with polyorchidism has not been previously reported. CONCLUSION We describe a unique case of a 2-year-old boy with right-sided polyorchidism and an absent left testis associated with a blind ending vas deferens and testicular vessels, presumed secondary to intrauterine testicular torsion. PMID:25462053
Angular dynamics of small crystals in viscous flows
NASA Astrophysics Data System (ADS)
Fries, Johan; Einarsson, Jonas; Mehlig, Bernhard
2016-11-01
The angular dynamics of a very small ellipsoidal particle in a viscous flow decouples from its translational dynamics, and the particle angular velocity is given by Jeffery's theory. It is known that cuboid particles share these properties. In the literature a special case is most frequently discussed, that of axisymmetric particles, with a continuous rotational symmetry. Here we compute the angular dynamics of crystals that possess a discrete rotational symmetry and certain mirror symmetries, but that do not have a continuous rotational symmetry. We give examples of such particles that nevertheless obey Jeffery's theory. But there are other examples where the angular dynamics is determined by a more general equation of motion. Vetenskapsrådet [Grant Number 2013-3992], Formas [Grant Number 2014-585], "Bottlenecks for particle growth in turbulent aerosols" from the Knut and Alice Wallenberg Foundation, Dnr. KAW 2014.0048, MPNS COST Action MP1305 "Flowing matter".
Measurement and analysis of angular velocity variations of twelve-cylinder diesel engine crankshaft
NASA Astrophysics Data System (ADS)
Bulatović, Ž. M.; Štavljanin, M. S.; Tomić, M. V.; Knežević, D. M.; Biočanin, S. Lj.
2011-11-01
This paper presents the procedures for measuring and analyzing the angular velocity variation of twelve-cylinder diesel engine crankshaft on its free end and on the power-output end. In addition, the paper deals with important aspects of the measurement of crankshaft torsional oscillations. The method is based on digital encoders placed at two distances, and one of them is a sensor not inserted directly on the shaft, i.e. a non-contact method with a toothed disc is used. The principle based on toothed disc is also used to measure the actual camshaft angular velocity of in-line compact high-pressure pump the engine is equipped with, and this paper aims to demonstrate the possibility of measuring the actual angular velocity of any rotating shaft in the engine, on which it is physically possible to mount a toothed disc. The method was created completely independently during long-range development and research tests of V46 family engines. This method is specific for its particular adaptability for use on larger engines with extensive vibrations and torsional oscillations. The main purpose of this paper is a practical contribution to all the more interesting research of the use of engine crankshaft angular velocity as a diagnostic tool for identifying the engine irregular running.
Time-dependent photoelectron angular distributions
NASA Astrophysics Data System (ADS)
Wang, Xiangyang
1999-09-01
I show that the angular distribution of electrons photoionized from gas phase targets by short light pulses is time-dependent, when the orbital momentum composition of the photocurrent changes with excitation energy so evolves with the time of detection. A theory of time- dependent photoionization is outlined and general formulas of time-dependent photoelectron flux and angular distribution are given. Two general propagator methods suitable to describe the time-dependent photoionization and scattering processes are developed. The photoionization process is viewed as a local excitation followed by a half scattering. The local excitation process is solved theoretically in a small region around the target core. This approach has been generalized to describe the evolution of a wavepacket in an unbound system. An asymptotic propagator theorem is discovered and used to derive analytic expressions for asymptotic propagators. The origin of the time dependence is explored by parameterizing the time delay and orbital momentum coupling in a two channel model. K-shell photoionization of N2 and CO are calculated with this time- dependent photoionization theory, implemented using a multiple scattering model. Numerical results demonstrate that the time dependence of photoelectron angular distributions is a realistic effect.
Biothermal sensing of a torsional artificial muscle
NASA Astrophysics Data System (ADS)
Lee, Sung-Ho; Kim, Tae Hyeob; Lima, Márcio D.; Baughman, Ray H.; Kim, Seon Jeong
2016-02-01
Biomolecule responsive materials have been studied intensively for use in biomedical applications as smart systems because of their unique property of responding to specific biomolecules under mild conditions. However, these materials have some challenging drawbacks that limit further practical application, including their speed of response and mechanical properties, because most are based on hydrogels. Here, we present a fast, mechanically robust biscrolled twist-spun carbon nanotube yarn as a torsional artificial muscle through entrapping an enzyme linked to a thermally sensitive hydrogel, poly(N-isopropylacrylamide), utilizing the exothermic catalytic reaction of the enzyme. The induced rotation reached an equilibrated angle in less than 2 min under mild temperature conditions (25-37 °C) while maintaining the mechanical properties originating from the carbon nanotubes. This biothermal sensing of a torsional artificial muscle offers a versatile platform for the recognition of various types of biomolecules by replacing the enzyme, because an exothermic reaction is a general property accompanying a biochemical transformation.Biomolecule responsive materials have been studied intensively for use in biomedical applications as smart systems because of their unique property of responding to specific biomolecules under mild conditions. However, these materials have some challenging drawbacks that limit further practical application, including their speed of response and mechanical properties, because most are based on hydrogels. Here, we present a fast, mechanically robust biscrolled twist-spun carbon nanotube yarn as a torsional artificial muscle through entrapping an enzyme linked to a thermally sensitive hydrogel, poly(N-isopropylacrylamide), utilizing the exothermic catalytic reaction of the enzyme. The induced rotation reached an equilibrated angle in less than 2 min under mild temperature conditions (25-37 °C) while maintaining the mechanical properties
Design of a nonlinear torsional vibration absorber
NASA Astrophysics Data System (ADS)
Tahir, Ammaar Bin
Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is usually tuned for a specific resonant frequency or an operating frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies, or for a system with varying excitation frequency. Vibration dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system. In this study, an experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber with geometrically induced cubic stiffness nonlinearity. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, the design optimization of the nonlinear torsional vibration absorber was carried out using an equivalent 2-DOF modal model. The optimality criterion was chosen to be maximization of energy dissipation in the nonlinear absorber attached to the equivalent 2-DOF system. The optimized design parameters of the nonlinear absorber were tested on the original 5-DOF system numerically. A comparison was made between the performance of linear and nonlinear absorbers using the numerical models. The comparison showed the superiority of the nonlinear absorber over its linear counterpart for the given set of primary system parameters as the vibration energy dissipation in the former is
A New Theory of Oscillating Flows
NASA Astrophysics Data System (ADS)
Vladimirov, Vladimir
2010-11-01
A new theory of viscous oscillatory flows has been developed. Our theory represents an adaptation of the Vishik-Lyusternik approach combined with the two-timing and averaging methods. We consider the high Re viscous incompressible flows driven by a vibrating boundary for the simple geometry of a half-space. From the physical viewpoint the considered boundary conditions may be seen as the tangential vibrations of material points of a plane stretchable membrane. The main result is the obtaining of the general, global, and uniformly valid asymptotic solutions of the Navier-Stokes equations. These solutions satisfy general oscillating boundary conditions and three different settings of the scaling parameters (that correspond to the strong, moderate, and weak nonlinearities). We have derived that the streaming part of any solution is governed by either the full Navier-Stokes equations or Stokes' equations (both with the unit Re) as well as by the precisely derived effective boundary conditions. The examples of the spatially periodic vibrations of the boundary and the angular torsional vibrations of an infinite rigid disc have been considered. In the sharp contrast to all previous theories of oscillating flows (see e.g. Batchelor's "Introduction to fluid dynamics," formula 5.13.15) our solutions do not deal with any secular (infinitely growing with the inner normal coordinate) terms. This new approach may be seen as a revolutionary step in the field, since for the very first time it does not use the asymptotic matching procedures and the boundary layer theories.
NASA Astrophysics Data System (ADS)
Gonçalves, Bruno; Ribeiro, Baltazar J.; Pereira, Dante D.; Dias, Mário M.
2016-05-01
In this paper, we focus our attention in the inconsistency that appears when the semi-exact Foldy-Wouthuysen transformation for the Dirac field interacting with space-time torsion field is performed. In order to solve this problem, we present a new involution operator that makes possible to perform the exact transformation when torsion field is present. Such operator has a structure, well known in the literature, composed of the product of an operator that acts in the matrices space and another one that acts in the function space. We also present the bound state of this theory and discuss the possible experimental analysis.
Missed Spermatic Cord Torsion in an Old Man
Seo, Yu Mi; Myung, Na-Hye
2013-01-01
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
Switching mechanism senses angular acceleration
NASA Technical Reports Server (NTRS)
1966-01-01
Switching mechanism actuates an electrical circuit when a predetermined angular acceleration and displacement are reached. A rotor in the mechanism overcomes the restraint of a magnetic detent when the case in which the detent is mounted reaches the predetermined angular acceleration.
Intrinsic Angular Momentum of Light.
ERIC Educational Resources Information Center
Santarelli, Vincent
1979-01-01
Derives a familiar torque-angular momentum theorem for the electromagnetic field, and includes the intrinsic torques exerted by the fields on the polarized medium. This inclusion leads to the expressions for the intrinsic angular momentum carried by the radiation traveling through a charge-free medium. (Author/MA)
Torsion in wandering spleen: CT demonstration of whirl sign.
Priyadarshi, Rajeev N; Anand, Utpal; Kumar, Bindey; Prakash, Vijay
2013-08-01
Wandering spleen is a rare occurrence. Torsion of the splenic pedicle is the major life-threatening complication of this entity. Preoperative diagnosis is based on radiological investigation. We report two consecutive cases, one adult and one child, in whom torsion in a wandering spleen was diagnosed based on a typical whirled appearance of the splenic vessels on computed tomography. We present a review of computed tomographic appearance of splenic torsion, and emphasize the "whirled appearance" as a specific sign for splenic torsion in wandering spleen.
Güneş, Mustafa; Umul, Mehmet; Çelik, Ahmet Orhan; Armağan, Hamit Hakan; Değirmenci, Bumin
2015-01-01
A 17-year-old boy presented with right testicular torsion to the lateral side. Torsion was diagnosed by physical examination; the colour Doppler ultrasonography (CDU) confirmed right testicular torsion with minimal peripheral hydrocele. Transverse and longitudinal examination of the spermatic cord with ultrasound and CDU revealed a counter-clockwise testicular torsion. Manual de-torsion was performed in a clockwise direction (720o) and testicular blood flow and the neutral position of the spermatic cord were confirmed by CDU. We did not encounter a residual twist of the spermatic cord upon surgical exploration. In our experience, ultrasound and CDU may predict the direction of testicular torsion and may allow appropriate management of cases prior to surgery.
Güneş, Mustafa; Umul, Mehmet; Çelik, Ahmet Orhan; Armağan, Hamit Hakan; Değirmenci, Bumin
2015-01-01
A 17-year-old boy presented with right testicular torsion to the lateral side. Torsion was diagnosed by physical examination; the colour Doppler ultrasonography (CDU) confirmed right testicular torsion with minimal peripheral hydrocele. Transverse and longitudinal examination of the spermatic cord with ultrasound and CDU revealed a counter-clockwise testicular torsion. Manual de-torsion was performed in a clockwise direction (720o) and testicular blood flow and the neutral position of the spermatic cord were confirmed by CDU. We did not encounter a residual twist of the spermatic cord upon surgical exploration. In our experience, ultrasound and CDU may predict the direction of testicular torsion and may allow appropriate management of cases prior to surgery. PMID:26425241
NASA Astrophysics Data System (ADS)
Keivani, M.; Abadian, N.; Koochi, A.; Mokhtari, J.; Abadyan, M.
2016-10-01
It has been well established that the physical performance of nanodevices might be affected by the microstructure. Herein, a two-degree-of-freedom model base on the modified couple stress theory is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nanoscanner. Effect of microstructure dependency on the instability parameters is determined as a function of the microstructure parameter, bending/torsion coupling ratio, van der Waals force parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the scanners especially those with long rotational beam elements. Impact of microstructure on instability voltage of the nanoscanner depends on coupling ratio and the conquering bending mode over torsion mode. This effect is more highlighted for higher values of coupling ratio. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nanoscanners.
Energy, momentum and angular momentum conservations in de Sitter gravity
NASA Astrophysics Data System (ADS)
Lu, Jia-An
2016-08-01
In de Sitter (dS) gravity, where gravity is a gauge field introduced to realize the local dS invariance of the matter field, two kinds of conservation laws are derived. The first kind is a differential equation for a dS-covariant current, which unites the canonical energy-momentum (EM) and angular momentum (AM) tensors. The second kind presents a dS-invariant current which is conserved in the sense that its torsion-free divergence vanishes. The dS-invariant current unites the total (matter plus gravity) EM and AM currents. It is well known that the AM current contains an inherent part, called the spin current. Here it is shown that the EM tensor also contains an inherent part, which might be observed by its contribution to the deviation of the dust particle’s world line from a geodesic. All the results are compared to the ordinary Lorentz gravity.
The Torsional Spectrum of Doubly Deuterated Methanol CHD_2OH
NASA Astrophysics Data System (ADS)
Ndao, M.; Coudert, L. H.; Kwabia Tchana, F.; Barros, J.; Margulès, L.; Manceron, Laurent; Roy, P.
2014-06-01
Although the torsional spectrum of several isotopic species of methanol with a symmetrical CH_3 or CD_3 was analyzed some time ago, it is recently, and only for the monodeuterated species CH_2DOH, that such an analysis was extended to the case of an asymmetrical methyl group. In this talk, based on a Fourier transform high-resolution spectrum recorded in the 20 to 670 wn region, the first analysis of the torsional spectrum of doubly deuterated methanol CHD_2OH will be presented. The Q branch of many torsional subbands could be observed and their assignment was initiated using a theoretical torsion-rotation spectrum computed with an approach accounting for the torsion-rotation Coriolis coupling and for the dependence of the generalized inertia tensor on the angle of internal rotation. 46 torsional subbands were thus assigned. For 28 of them, their rotational structure could be assigned and fitted using an effective Hamiltonian expressed as a J(J+1) expansion; and for 2 of them microwave transitions within the lower torsional level could also be included in the analysis. In several cases these analysis revealed that the torsional levels are strongly perturbed. In the talk, the torsional parameters retrieved in the analysis of the torsional subband centers will be discussed. The results of the analysis of the rotational structure of the torsional subbands will be presented and we will also try to understand the nature of the perturbations. At last, preliminary results about the analysis of the microwave spectrum will be presented. El Hilali, Coudert, Konov, and Klee, J. Chem. Phys. 135 (2011) 194309 Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spectrosc. 256 (2009) 204 Quade, Liu, Mukhopadhyay, and Su, J. Mol. Spectrosc. 192 (1998) 378 Pearson, Yu, and Drouin, J. Mol. Spectrosc. 280 (2012) 119
Primary torsion of the greater omentum.
Gul, Y A; Jabbar, M F; Moissinac, K
2001-01-01
Primary or idiopathic greater omental torsion remains a rare cause of acute surgical abdomen in adults and children. The aetiology is as yet unknown and the treatment of choice, once diagnosis is established, is resection of the torted omentum. We report our experience with three such cases encountered over the last five years, two of which were diagnosed and subsequently managed laparoscopically. The performance of diagnostic laparoscopy for acute abdominal pain of an undetermined origin may lead to an increased detection of this condition and subsequent therapeutic intervention.
Maeda, Takenori
1995-11-01
This paper presents an experimental method for the determination of the bending and torsional rigidities of advanced fiber composite laminates with the aid of laser holographic interferometry. The proposed method consists of a four-point bending test and a resonance test. The bending rigidity ratio (D{sub 12}/D{sub 22}) can be determined from the fringe patterns of the four-point bending test. The bending rigidities (D{sub 11} and D{sub 22}) and the torsional rigidity (D{sub 66}) are calculated from the natural frequencies of cantilever plates of the resonance test. The test specimens are carbon/epoxy cross-ply laminates. The adequacy of the experimental method is confirmed by comparing the measured rigidities with the theoretical values obtained from classical lamination theory (CLT) by using the measured tensile properties. The results show that the present method can be used to evaluate the rigidities of orthotropic laminates with reasonably good accuracy.
Non-Riemannian Cosmic Walls as Boundaries of Spinning Matter with Torsion
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.
An example of a plane topological defect solution of linearized Einstein-Cartan (EC) field equation representing a cosmic wall boundary of spinning matter is given. The source of Cartan torsion is composed of two orthogonal lines of static polarized spins bounded by the cosmic plane wall. The Kopczyński-Obukhov-Tresguerres (KOT) spin fluid stress-energy current coincides with thin planar matter current in the static case. Our solution is similar to the Letelier solution of Einstein equation for multiple cosmic strings. Due to this fact we suggest that the lines of spinning matter could be analogous to multiple cosmic spinning string solution in EC theory of gravity. When torsion is turned off, a pure Riemannian cosmic wall is obtained.
Linking the HOMO-LUMO gap to torsional disorder in P3HT/PCBM blends
NASA Astrophysics Data System (ADS)
McLeod, John A.; Pitman, Amy L.; Kurmaev, Ernst Z.; Finkelstein, Larisa D.; Zhidkov, Ivan S.; Savva, Achilleas; Moewes, Alexander
2015-12-01
The electronic structure of [6,6]-phenyl C61 butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT), and P3HT/PCBM blends is studied using soft X-ray emission and absorption spectroscopy and density functional theory calculations. We find that annealing reduces the HOMO-LUMO gap of P3HT and P3HT/PCBM blends, whereas annealing has little effect on the HOMO-LUMO gap of PCBM. We propose a model connecting torsional disorder in a P3HT polymer to the HOMO-LUMO gap, which suggests that annealing helps to decrease the torsional disorder in the P3HT polymers. Our model is used to predict the characteristic length scales of the flat P3TH polymer segments in P3HT and P3HT/PCBM blends before and after annealing. Our approach may prove useful in characterizing organic photovoltaic devices in situ or even in operando.
Maximum magnetic moment to angular momentum conjecture
NASA Astrophysics Data System (ADS)
Barrow, John D.; Gibbons, G. W.
2017-03-01
Conjectures play a central role in theoretical physics, especially those that assert an upper bound to some dimensionless ratio of physical quantities. In this paper we introduce a new such conjecture bounding the ratio of the magnetic moment to angular momentum in nature. We also discuss the current status of some old bounds on dimensionless and dimensional quantities in arbitrary spatial dimension. Our new conjecture is that the dimensionless Schuster-Wilson-Blackett number, c μ /J G1/2 , where μ is the magnetic moment and J is the angular momentum, is bounded above by a number of order unity. We verify that such a bound holds for charged rotating black holes in those theories for which exact solutions are available, including the Einstein-Maxwell theory, Kaluza-Klein theory, the Kerr-Sen black hole, and the so-called STU family of charged rotating supergravity black holes. We also discuss the current status of the maximum tension conjecture, the Dyson luminosity bound, and Thorne's hoop conjecture.
Study of torsional vibrations in an initially stressed composite poroelastic cylinders
NASA Astrophysics Data System (ADS)
Sandhya, Rani B.; Ch, Balu; Malla, Reddy P.
2015-12-01
This paper investigates torsional vibrations in an initially stressed composite poroelastic cylinder in the framework of Biot's theory of wave propagation in poroelastic solids. Poroelastic composite cylinder consists of two concentric cylindrical layers made of different poroelastic materials. The governing equations are formulated from the Biot's incremental deformation theory. The non-dimensional frequency is computed as a function of ratio of thickness to wavelength. The limiting cases of a poroelastic solid cylinder and poroelastic hollow cylinder are discussed. The results are presented graphically for two poroelastic composite cylinders and then compared with the published results.
Standing Torsional Waves in Fluid-Saturated Porous Circular Cylinder
NASA Astrophysics Data System (ADS)
Solorza, S.; Sahay, P. N.
2002-12-01
For dynamic measurement of elastic constants of a porous material saturated with viscous fluid when resonance-bar technique is applied, one also observes attenuation of the wave field. The current practice is to interpret it in terms of solid-viscosity by assuming a viscoelastic rheology for porous material. The likely mechanisms of attenuation in a fluid saturated porous material are: 1) motion of the fluid with respect to the solid frame and 2) viscous loss within the pore fluid. Therefore, it is appropriate to assume a poroelastic rheology and link the observed attenuation value to fluid properties and permeability. In the framework of poroelastic theory, the explicit formula linking attenuation to the properties of solid and fluid constituents and permeability are not worked out yet. In order to established such a link one has to workout solutions of appropriate boundary value problems in such a framework. Here, we have carried out the solution of boundary value problem associated with torsional oscillation of a finite poroelastic circular cylinder, casted in the framework of volume-averaged theory of poroelasticity. Analysing this solution by a perturbative approach we are able to develop explicit expressions for resonance frequency and attenuation for this mode of vibration. It shows how the attenuation is controlled by the permeability and the fluid properties, and how the resonance frequency drops over its value for the dry porous frame due to the effect of the fluid-mass.
Torsional Strengthening of RC Beams Using GFRP Composites
NASA Astrophysics Data System (ADS)
Patel, Paresh V.; Jariwala, Vishnu H.; Purohit, Sharadkumar P.
2016-09-01
Fiber reinforced polymer as an external reinforcement is used extensively for axial, flexural and shear strengthening in structural systems. The strengthening of members subjected to torsion is recently being explored. The loading mechanism of beams located at the perimeter of buildings which carry loads from slabs, joists and beams from one side of the member generates torsion that are transferred from the beams to the columns. In this work an experimental investigation on the improvement of the torsional resistance of reinforced concrete beams using Glass Fiber Reinforced Polymer (GFRP) is presented. Total 24 RC beams have been cast in this work. Ten beams of dimension 150 mm × 150 mm × 1300 mm are subjected to pure torsion while fourteen beams of 150 mm × 150 mm × 1700 mm are subjected to combined torsion and bending. Two beams in each category are designated as control specimen and remaining beams are strengthened by GFRP wrapping of different configurations. Pure torsion on specimens is applied using specially fabricated support mechanism and universal testing machine. For applying combined torsion and bending a loading frame and test set up are fabricated. Measurements of angle of twist at regular interval of torque, torsion at first crack, and ultimate torque, are obtained for all specimens. Results of different wrapping configurations are compared for control and strengthened beams to suggest effective GFRP wrapping configuration.
Hydrostatic self-aligning axial/torsional mechanism
O'Connor, Daniel G.; Gerth, Howard L.
1990-01-01
The present invention is directed to a self-aligning axial/torsional loading mechanism for testing the strength of brittle materials which are sensitive to bending moments. Disposed inside said self-aligning loading mechanism is a frictionless hydrostatic ball joint with a flexure ring to accommodate torsional loads through said ball joint.
Omental torsion in a guinea pig (Cavia porcellus)
Shrubsole-Cockwill, Alana N.; Cockwill, Ken R.N.; Parker, Dennilyn L.
2008-01-01
An adult intact male guinea pig (Cavia porcellus) was presented with gastrointestinal stasis. Radiographic findings demonstrated a gas- and fluid-filled cecum. Treatment was initiated but the animal died shortly after presentation. Gross postmortem revealed omental torsion with vascular thrombosis and necrosis. This is the first report of omental torsion with vascular thrombosis in a domestic animal. PMID:19043488
Mechanical origins of rightward torsion in early chick brain development
NASA Astrophysics Data System (ADS)
Chen, Zi; Guo, Qiaohang; Dai, Eric; Taber, Larry
2015-03-01
During early development, the neural tube of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This torsional deformation is one of the major organ-level left-right asymmetry events in development. Previous studies suggested that bending is mainly due to differential growth, however, the mechanism for torsion remains poorly understood. Since the heart almost always loops rightwards that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is lacking, nor is the mechanical origin of such torsion understood. In our study, experimental perturbations show that the bending and torsional deformations in the brain are coupled and that the vitelline membrane applies an external load necessary for torsion to occur. Moreover, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model and a 3D printed physical model are employed to help interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, and further reveals that the asymmetric development in one organ can induce the asymmetry of another developing organ through mechanics, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''. Z.C. is supported by the Society in Science - Branco Weiss fellowship, administered by ETH Zurich. L.A.T acknowledges the support from NIH Grants R01 GM075200 and R01 NS070918.
[Cardiac herniation and torsion after transpericardial pneumonectomy].
Schummer, W; Hottenrott, A; Nissel, C
2016-07-05
This article presents the case of a 43 year old woman with right-sided lung cancer. She underwent transpericardial pneumonectomy. After an uneventfull surgery, the patient was transferred to the intensive care unit for postoperative monitoring. She was hemodynamically stable and had already been extubated in the OR.On postoperative chest X‑ray a mediastinal shift to the operated side as well as a herniation of the heart into the right chest cavity was detected. While the patient remained hemodynamically stable a computed tomography of the chest was performed which confirmed the diagnosis of cardiac herniation and torsion. The lady underwent rethoracotomy the following day where the heart was repositioned and the pericardial defect was closed. She made an uneventfull recovery.Five years after the pneumonectomy she remains well and is without relapse of lung cancer.Mechanism for cardiac herniation and torsion, the clinical presentation and the typical radiologic signs are discussed. However, the clue to early diagnosis is a high index of clinical suspicion.It is highlighted that a hemodynamically unstable patient under these circumstances demands urgent rethoracotomy.
Curvature and torsion in growing actin networks
Shaevitz, Joshua W; Fletcher, Daniel A
2011-01-01
Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque. PMID:18560043
Curvature and torsion in growing actin networks
NASA Astrophysics Data System (ADS)
Shaevitz, Joshua W.; Fletcher, Daniel A.
2008-06-01
Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque.
Infrared modified gravity with dynamical torsion
Nikiforova, V.; Randjbar-Daemi, S.; Rubakov, V.
2009-12-15
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.
Application of instantaneous angular acceleration to diesel engine fault diagnosis
NASA Astrophysics Data System (ADS)
Ren, Yunpeng; Hu, Tianyou; Liu, Xin
2005-12-01
Diesel engine is a kind of important power generating machine, of which the running state monitoring and fault diagnosis attracts increasing attention. The theory and the method of diesel engine fault diagnosis based on angular acceleration measurement were studied, since angular acceleration contains a lot of information for diesel engine fault diagnosing and its power balance evaluating. USB data acquisition system was designed for the angular acceleration measurement, and it was composed with AVRAT09S8515 micro-processor and PDIUSBD12 USB interface IC. At the same time, the high speed micro-processor AVRAT09S8515 with unique function of automatically capturing the rising or falling edge of square wave was studied, and it was utilized in the diesel engine's crankshaft angular acceleration measuring system. The software and hardware of the whole system was designed, which supplied a whole solution to diesel engine fault diagnosis and power balance evaluation between each cylinder.
Quantum optimal control of photoelectron spectra and angular distributions
NASA Astrophysics Data System (ADS)
Goetz, R. Esteban; Karamatskou, Antonia; Santra, Robin; Koch, Christiane P.
2016-01-01
Photoelectron spectra and photoelectron angular distributions obtained in photoionization reveal important information on, e.g., charge transfer or hole coherence in the parent ion. Here we show that optimal control of the underlying quantum dynamics can be used to enhance desired features in the photoelectron spectra and angular distributions. To this end, we combine Krotov's method for optimal control theory with the time-dependent configuration interaction singles formalism and a splitting approach to calculate photoelectron spectra and angular distributions. The optimization target can account for specific desired properties in the photoelectron angular distribution alone, in the photoelectron spectrum, or in both. We demonstrate the method for hydrogen and then apply it to argon under strong XUV radiation, maximizing the difference of emission into the upper and lower hemispheres, in order to realize directed electron emission in the XUV regime.
Torsion and noninertial effects on a nonrelativistic Dirac particle
Bakke, K.
2014-07-15
We investigate torsion and noninertial effects on a spin-1/2 quantum particle in the nonrelativistic limit of the Dirac equation. We consider the cosmic dislocation spacetime as a background and show that a rotating system of reference can be used out to distances which depend on the parameter related to the torsion of the defect. Therefore, we analyse torsion effects on the spectrum of energy of a nonrelativistic Dirac particle confined to a hard-wall potential in a Fermi–Walker reference frame. -- Highlights: •Torsion effects on a spin- 1/2 particle in a noninertial reference frame. •Fermi–Walker reference frame in the cosmic dislocation spacetime background. •Torsion and noninertial effects on the confinement to a hard-wall confining potential.
Unravelling the structural plasticity of stretched DNA under torsional constraint
NASA Astrophysics Data System (ADS)
King, Graeme A.; Peterman, Erwin J. G.; Wuite, Gijs J. L.
2016-06-01
Regions of the genome are often held under torsional constraint. Nevertheless, the influence of such constraint on DNA-protein interactions during genome metabolism is still poorly understood. Here using a combined optical tweezers and fluorescence microscope, we quantify and explain how torsional constraint influences the structural stability of DNA under applied tension. We provide direct evidence that concomitant basepair melting and helical unwinding can occur in torsionally constrained DNA at forces >~50 pN. This striking result indicates that local changes in linking number can be absorbed by the rest of the DNA duplex. We also present compelling new evidence that an overwound DNA structure (likely P-DNA) is created (alongside underwound structures) at forces >~110 pN. These findings substantiate previous theoretical predictions and highlight a remarkable structural plasticity of torsionally constrained DNA. Such plasticity may be required in vivo to absorb local changes in linking number in DNA held under torsional constraint.
Torsion of wing trusses at diving speeds
NASA Technical Reports Server (NTRS)
Miller, Roy G
1921-01-01
The purpose of this report is to indicate what effect the distortion of a typical loaded wing truss will have upon the load distribution. The case of high angle of incidence may be dismissed immediately from consideration as the loads on the front and rear trusses are balanced, and consequently there will be little angular distortion. A given angular distortion will have the maximum effect upon load distribution in the region of the angle of no-lift, because the slope of the lift curve is highest here, and it is here that the greatest angular distortion will occur, because the load on the front truss acts downward while the load on the rear truss acts upward.
MBL Experiment in Angular Momentum
NASA Astrophysics Data System (ADS)
Gluck, Paul
2002-04-01
Among the series of beautiful take-home experiments designed by A.P. French and J.G. King for MIT students, the one on angular momentum studies the loss and conservation of angular momentum using a small dc motor as generator. Here we describe a version of the experiment that increases its accuracy, enables students to perform detailed rotational dynamics calculations, and sharpens the ability to isolate the region where the collision occurs.
Noncommutative Gauge Theory with Covariant Star Product
Zet, G.
2010-08-04
We present a noncommutative gauge theory with covariant star product on a space-time with torsion. In order to obtain the covariant star product one imposes some restrictions on the connection of the space-time. Then, a noncommutative gauge theory is developed applying this product to the case of differential forms. Some comments on the advantages of using a space-time with torsion to describe the gravitational field are also given.
Relaxation of rotational angular momentum of polar diatomic molecules in simple liquids
Padilla, A.; Perez, J.
2007-03-15
The relaxation processes of rotational angular momentum of polar diatomic molecules diluted in simple liquids are analyzed by applying a non-Markovian relaxation theory to the study of the binary time autocorrelation function of the angular momentum. This non-Markovian theory was previously applied to the study of the infrared and Raman spectroscopy, and also to the analysis of the rotational energy relaxation processes. We have obtained non-Markovian evolution equations for the two-time j-level angular momentum correlation components involved in the angular momentum correlation function. In these equations, the time-dependent angular momentum transfer rates and the pure orientational angular transfer rates are given in terms of the binary time autocorrelation function of the diatomic-solvent anisotropic interaction. The non-Markovian evolution equations converge to Markovian ones in the long time limit, reaching the angular momentum transfer rates in the usual time-independent form. Alternative time scales for the angular relaxation processes, relative to the individual rotational processes as well as to the global decay correlations, are introduced and analyzed. The theory is applied to the study of the angular momentum relaxation processes of HCl diluted in liquid SF{sub 6}, a system for which rotational energy relaxation and infrared and Raman spectroscopy was previously analyzed in the scope of the same theory.
Kawakami, H.; Fujii, T.J.; Morita, Y.
1995-10-01
Fatigue degradation and life prediction for a plain woven glass fabric reinforced polyester under tension/torsion biaxial loadings were investigated. Typical S-N diagrams were given at several biaxial ratios when the biaxial cyclic loads were proportionally applied to the specimens. A fatigue damage accumulation model based on the continuum damage mechanics theory was developed, where modulus decay ratios in tension and shear were used as indicators for damage variables (D). In the model, the damage variables are considered to be second-order tensors. Then, the maximum principal damage variable, D* is introduced. According to the similarity to the principal stress, D* is obtained as the maximum eigen value of damage tensor [D{prime}]. Under proportional tension/torsion loadings, fatigue lives were satisfactorily predicted at any biaxial stress ratios using the present model in which the fatigue characteristics only under uniaxial tension and pure torsion loadings were needed. For a certain biaxial stress ratio, the effect of loading path on the fatigue strength was examined. The experimental result does not show a strong effect of loading path on the fatigue life.
Mordell-Weil torsion in the mirror of multi-sections
NASA Astrophysics Data System (ADS)
Oehlmann, Paul-Konstantin; Reuter, Jonas; Schimannek, Thorsten
2016-12-01
We give further evidence that genus-one fibers with multi-sections are mirror dual to fibers with Mordell-Weil torsion. In the physics of F-theory compactifications this implies a relation between models with a non-simply connected gauge group and those with discrete symmetries. We provide a combinatorial explanation of this phenomenon for toric hypersurfaces. In particular this leads to a criterion to deduce Mordell-Weil torsion directly from the polytope. For all 3134 complete intersection genus-one curves in three-dimensional toric ambient spaces we confirm the conjecture by explicit calculation. We comment on several new features of these models: the Weierstrass forms of many models can be identified by relabeling the coefficient sections. This reduces the number of models to 1024 inequivalent ones. We give an example of a fiber which contains only non-toric sections one of which becomes toric when the fiber is realized in a different ambient space. Similarly a singularity in codimension one can have a toric resolution in one representation while it is non-toric in another. Finally we give a list of 24 inequivalent genus-one fibers that simultaneously exhibit multi-sections and Mordell-Weil torsion in the Jacobian. We discuss a self-mirror example from this list in detail.
NASA Astrophysics Data System (ADS)
Chen, Han; Li, Fuguo; Liu, Jie; Li, Jinghui; Ma, Xinkai; Wan, Qiong
2017-03-01
Systematic experimental studies of microstructure and crystallographic texture of pure titanium during the Single Direction Torsion (SDT) and Alternating Cyclic Torsion (ACT) are carried out at room temperature. The microstructure evolution indicates that the grain size can be refined during SDT, while the grain morphology can be controlled during ACT. Also, lots of {10-12} and few {11-22} twins are observed and their area percentages increase with increasing torsion angles during SDT. The microtexture evolution states that the deformation texture first approaches to the B fiber (0, 90, 0 to 60 deg), and then stays away from B fiber (0, 90, 0 to 60 deg) with increasing plastic strain during SDT. The change of deformation texture is mainly attributed to the appearance of {10-12} twin. However, the deformation texture is always close to B fiber (0, 90, 0 to 60 deg) during ACT. Finally, the effects of different dislocation movements caused by SDT and ACT are discussed. Quantities of subgrains with high density dislocation are observed during SDT while the {10-12} and {11-22} twins intersect with each other, and high density dislocations distribute the twin during ACT.
Torsional suspension system for testing space structures
NASA Technical Reports Server (NTRS)
Reed, Wilmer H., III (Inventor); Gold, Ronald R. (Inventor)
1991-01-01
A low frequency torsional suspension system for testing a space structure uses a plurality of suspension stations attached to the space structure along the length thereof in order to suspend the space structure from an overhead support. Each suspension station includes a disk pivotally mounted to the overhead support, and two cables which have upper ends connected to the disk and lower ends connected to the space structure. The two cables define a parallelogram with the center of gravity of the space structure being vertically beneath the pivot axis of the disk. The vertical distance between the points of attachment of the cables to the disk and the pivot axis of the disk is adjusted to lower the frequency of the suspension system to a level which does not interfere with frequency levels of the space structure, thereby enabling accurate measurement.
Plant-based torsional actuator with memory
NASA Astrophysics Data System (ADS)
Plaza, Nayomi; Zelinka, Samuel L.; Stone, Don S.; Jakes, Joseph E.
2013-07-01
A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg-1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-activated, shape memory twist effect. Over 70% of the twist in a wetted bundle can be locked-in by drying under constraint and then released by rewetting the bundle. Our results indicate that hemicelluloses dominate the shape fixity mechanism and lignin is primarily responsible for remembering the bundle’s original form. The bundles demonstrate proof of a high specific torque actuator with large angles of rotation and shape memory twist capabilities that can be used in microactuators, sensors, and energy harvesters.
Torsional thrust stand for characterization of microthrusters
NASA Astrophysics Data System (ADS)
Cheah, K. H.; Low, K. S.
2016-10-01
This paper describes the setup of a precise thrust stand based on torsional pendulum design for characterizing the performance of microthrusters. Calibration has been carried out by using an improved version of electrostatic calibrator, which produces a wide range of accurate and repeatable calibration force. After the calibration, the thrust stand can resolve constant force from 40μN to 3.4mN and impulse bit from 7μNs to 340μNs. The usefulness of the thrust stand has been demonstrated by measuring the performance of two different microthrusters: a pulsed plasma thruster that produces impulse bit of 23.15μNs and a vaporizing liquid microthruster that produces steady state thrust of 633.5μN.
Experimental Study of Torsional Column Failure
NASA Technical Reports Server (NTRS)
Nile, Alfred S
1939-01-01
Thirty-three 24ST aluminum-alloy 2- by 2- by 0.10-inch channels, with lengths ranging from 10 to 90 inches were tested at Stanford University in compression to obtain an experimental verification of the theoretical formulas for torsional failure developed by Eugene E. Lundquist of the N.A.C.A. The observed critical loads and twist-axis locations were sufficiently close to the values obtained from the formulas to establish the substantial validity of the latter. The differences between observed and computed results were small enough to be accounted for by small and mostly unavoidable differences between actual test conditions and those assumed in deriving the formulas. Some data were obtained from the shorter specimens regarding the growth of the buckles that resulted in local buckling failure.
Torsional ultrasonic transducer computational design optimization.
Melchor, J; Rus, G
2014-09-01
A torsional piezoelectric ultrasonic sensor design is proposed in this paper and computationally tested and optimized to measure shear stiffness properties of soft tissue. These are correlated with a number of pathologies like tumors, hepatic lesions and others. The reason is that, whereas compressibility is predominantly governed by the fluid phase of the tissue, the shear stiffness is dependent on the stroma micro-architecture, which is directly affected by those pathologies. However, diagnostic tools to quantify them are currently not well developed. The first contribution is a new typology of design adapted to quasifluids. A second contribution is the procedure for design optimization, for which an analytical estimate of the Robust Probability Of Detection, called RPOD, is presented for use as optimality criteria. The RPOD is formulated probabilistically to maximize the probability of detecting the least possible pathology while minimizing the effect of noise. The resulting optimal transducer has a resonance frequency of 28 kHz.
Torsion Tests of Stiffened Circular Cylinders
NASA Technical Reports Server (NTRS)
Moore, R L; Wescoat, C
1944-01-01
The design of curved sheet panels to resist shear involves a consideration of several factors: the buckling resistance of the sheet, the stress at which buckling becomes permanent, and the strength which may be developed beyond the buckling limit by tension-field action. Although some experimental as well as theoretical work has been done on the buckling and tension-field phases of this problem, neither of these types of action appears to be very well understood. The problem is of sufficient importance from the standpoint of aircraft design, it is believed, to warrant further experimental investigation. This report presents the results of the first series of torsion tests of stiffened circular cylinders to be completed in connection with this study at Aluminum Research Laboratories. (author)
Management of suspected antenatal torsion: what is the best strategy?
Stone, K T; Kass, E J; Cacciarelli, A A; Gibson, D P
1995-03-01
Currently, management of the newborn with suspected antenatal torsion is somewhat controversial. Many surgeons recommend early surgical exploration within the first few days of life, primarily to avoid errors in diagnosis. However, since the surgical and general anesthetic risks at this age are increased, it might be preferable to defer an operation until risks to the patient are minimized. The optimal solution to this dilemma would be the ability to diagnose torsion and exclude other conditions noninvasively. We present a series of 12 patients 1 to 14 days old who presented with a scrotal mass secondary to suspected antenatal testis torsion. Color Doppler ultrasound in each case demonstrated abnormal testicular blood flow and architecture consistent with testis torsion. Eventual exploration of all 12 patients confirmed prenatal torsion. We conclude that scrotal ultrasound with color Doppler enhancement can accurately identify neonates with antenatal testis torsion and exclude other scrotal pathological conditions. If elected, surgery for torsion can then be deferred until the risks of anesthesia and surgery are improved.
[Torsion and necrosis of epiploic appendices of the large bowel].
Timofeev, M E; Fedorov, E D; Krechetova, A P; Shapoval'iants, S G
2014-01-01
The features of the clinical symptoms was studied, the possibility of laparoscopy in modern diagnosis and treatment of epiploic appendices torsion and necrosis of the large bowel was assessed in the article. It was done the retrospective analysis of the medical records of 87 patients with a diagnosis of epiploic appendices torsion and necrosis of the large bowel. The patients had laparoscopic operations in our hospital in the period from January 1995 to December 2012. The clinical picture, laboratory and instrumental datas in cases of epiploic appendices torsion and necrosis were scarce and nonspecific. An abdominal pain preferentially localized in the lower divisions was the main symptom (97.7%). The instrumental methods did not allow to diagnose the torsion and necrosis of epiploic appendices in the majority of cases and all these techniques were used for the differential diagnosis with other diseases. The assumption of the presence of appendices torsion and necrosis occured just in 34.5% of cases before the operation. Diagnosis of epiploic appendices torsion and necrosis present significant difficulties on prehospital and preoperative stages. The diagnostic laparoscopy is the method of choice in unclear situations and it allows to diagnose the torsion and necrosis of epiploic appendices in 96.6% of cases. Successful surgical treatment by using laparoscopic approach is possible in 90.8% of cases.
Angular momentum evolution during star and planetary system formation
NASA Astrophysics Data System (ADS)
Davies, Claire L.; Greaves, Jane S.
2014-01-01
larger and less massive, consistent with viscous accretion theories and disk dispersal. However, when drawing comparisons between the two regions, the ONC sample appeared to have less massive disks than the Taurus-Auriga sample, even though the population of Taurus-Auriga is older. This may suggest an influence of the birth cloud environment on protoplanetary disk evolution. Finally, the older stars within the ONC were observed to harbour disks that contained more angular momentum than their younger counterparts whereas, in the Taurus-Auriga sample, the amount of angular momentum contained in the older and younger samples was consistent. We suggest that the missing disk angular momentum in the older Taurus-Auriga disks may be contained within yet-undetected planets.
Torsion constraints from cosmological magnetic field and QCD domain walls
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.
2014-10-01
Earlier Kostelecky [Phys. Rev. D 69, 105009 (2004)] has investigated the role of gravitational sector in Riemann-Cartan (RC) spacetime with torsion, in Lorentz and CPT violating (LV) Standard Model extension (SME). In his paper use of quantum electrodynamic (QED) extension in RC spacetime is made. More recently L. C. Garcia de Andrade [Phys. Lett. B 468, 28 (2011)] obtained magnetic field galactic dynamo seeds in the bosonic sector with massless photons, which proved to decay faster than necessary [Phys. Lett. B 711, 143 (2012)] to be able to seed galactic dynamos. In this paper it is shown that by using the fermionic sector of Kostelecky-Lagrangian and torsion written as a chiral current, one obtains torsion and magnetic fields explicitly from a Heisenberg-Ivanenko form of Dirac equation whose solution allows us to express torsion in terms of LV coefficients and magnetic field in terms of fermionic matter fields. When minimal coupling between electromagnetic and torsion fields is used it is shown that the fermionic sector of QED with torsion leads to resonantly amplify magnetic fields which mimics an α2-dynamo mechanism. Fine-tuning of torsion is shown to result in the dynamo reversal, a phenomenon so important in solar physics and geophysics. Of course this is only an analogy since torsion is very weak in solar and geophysics contexts. An analogous expression for the α-effect of mean-field dynamos is also obtained where the α-effect is mimic by torsion. Similar resonant amplification mechanisms connected to early universe have been considered by Finelli and Gruppuso.
Localized Torsional Tension in the DNA of Human Cells
NASA Astrophysics Data System (ADS)
Ljungman, Mats; Hanawalt, Philip C.
1992-07-01
Torsional tension in DNA may be both a prerequisite for the efficient initiation of transcription and a consequence of the transcription process itself with the generation of positive torsional tension in front of the RNA polymerase and negative torsional tension behind it. To examine torsional tension in specific regions of genomic DNA in vivo, we developed an assay using photoactivated psoralen as a probe for unconstrained DNA superhelicity and x-rays as a means to relax DNA. Psoralen intercalates more readily into DNA underwound by negative torsional tension than into relaxed DNA, and it can form interstrand DNA cross-links upon UVA irradiation. By comparing the amount of psoralen-induced DNA cross-links in cells irradiated with x-rays either before or after the psoralen treatment, we examined the topological state of the DNA in specific regions of the genome in cultured human 6A3 cells. We found that although no net torsional tension was detected in the bulk of the genome, localized tension was prominent in the DNA of two active genes. Negative torsional tension was found in the 5' end of the amplified dihydrofolate reductase gene and in a region near the 5' end of the 45S rRNA transcription unit, whereas a low level of positive torsional tension was found in a region near the 3' end of the dihydrofolate reductase gene. These results document an intragenomic heterogeneity of DNA torsional tension and lend support to the twin supercoiled domain model for transcription in the genome of intact human cells.
Factors influencing perceived angular velocity
NASA Technical Reports Server (NTRS)
Kaiser, Mary K.; Calderone, Jack B.
1991-01-01
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).
Nonlinear nonuniform torsional vibrations of bars by the boundary element method
NASA Astrophysics Data System (ADS)
Sapountzakis, E. J.; Tsipiras, V. J.
2010-05-01
In this paper a boundary element method is developed for the nonuniform torsional vibration problem of bars of arbitrary doubly symmetric constant cross-section taking into account the effect of geometrical nonlinearity. The bar is subjected to arbitrarily distributed or concentrated conservative dynamic twisting and warping moments along its length, while its edges are supported by the most general torsional boundary conditions. The transverse displacement components are expressed so as to be valid for large twisting rotations (finite displacement-small strain theory), thus the arising governing differential equations and boundary conditions are in general nonlinear. The resulting coupling effect between twisting and axial displacement components is considered and torsional vibration analysis is performed in both the torsional pre- or post-buckled state. A distributed mass model system is employed, taking into account the warping, rotatory and axial inertia, leading to the formulation of a coupled nonlinear initial boundary value problem with respect to the variable along the bar angle of twist and to an "average" axial displacement of the cross-section of the bar. The numerical solution of the aforementioned initial boundary value problem is performed using the analog equation method, a BEM based method, leading to a system of nonlinear differential-algebraic equations (DAE), which is solved using an efficient time discretization scheme. Additionally, for the free vibrations case, a nonlinear generalized eigenvalue problem is formulated with respect to the fundamental mode shape at the points of reversal of motion after ignoring the axial inertia to verify the accuracy of the proposed method. The problem is solved using the direct iteration technique (DIT), with a geometrically linear fundamental mode shape as a starting vector. The validity of negligible axial inertia assumption is examined for the problem at hand.
Full Angular Profile of the Coherent Polarization Opposition Effect
NASA Technical Reports Server (NTRS)
Mishchenko, Michael I.; Luck, Jean-Marc; Nieuwenhuizen, Theo M.
1999-01-01
We use the rigorous vector theory of weak photon localization for a semi-infinite medium composed of nonabsorbing Rayleigh scatterers to compute the full angular profile of the polarization opposition effect. The latter is caused by coherent backscattering of unpolarized incident light and accompanies the renowned backscattering intensity peak.
Validation of an Automated Torsional and Warping Stress Analysis Program
1992-08-19
AD-A256 035 I HEI| I IIHAI l! VALIDATION OF AN AUTOMATED TORSIONAL AND WARPING STRESS ANALYSIS PROGRAM DI f ELECTE ND OCT 8 1992 A Special Research...7 2.2 Torsional Analysis Case Charts ....................... 8 2.3 Determination of Plane Bending, Torsional ............. 9 and Warping...Fixed-Free 6 W1Ox49 Fixed-Free 7 W6x15 Fixed-Free 8 W8x67 Fixed-Free 9 ClOx20 Fixed-Free 10 C12x30 Fixed-Free 11 C5x9 Fixed-Fire 12 MC18x42 Fixed-Free
Spinning Particles in Scalar-Tensor Gravity with Torsion
Wang, C.-H.
2008-10-10
A new model of neutral spinning particles in scalar-tensor gravity with torsion is developed by using a Fermi coordinates associated with orthonormal frames attached to a timelike curve and Noether identities. We further analyze its equations of motion both in background Brans-Dicke torsion field and the constant pseudo-Riemannian curvature with a constant scalar field. It turns that the particle's spin vector is parallel transport along its wordline in the Brans-Dicke torsion field and de Sitter spacetime. However, the dynamics of the spinning particle cannot completely determined in anti-de Sitter spacetime and it requires a further investigation.
Experimental investigation of cyclic thermomechanical deformation in torsion
NASA Technical Reports Server (NTRS)
Ellis, John R.; Castelli, Michael G.; Bakis, Charles E.
1992-01-01
An investigation of thermomechanical testing and deformation behavior of tubular specimens under torsional loading is described. Experimental issues concerning test accuracy and control specific to thermomechanical loadings under a torsional regime are discussed. A series of shear strain-controlled tests involving the nickel-base superalloy Hastelloy X were performed with various temperature excursions and compared to similar thermomechanical uniaxial tests. The concept and use of second invariants of the deviatoric stress and strain tensors as a means of comparing uniaxial and torsional specimens is also briefly presented and discussed in light of previous thermomechanical tests conducted under uniaxial conditions.
Torsion of a wandering spleen: an unusual abdominal catastrophe.
Riaz ul Haq, Muhammad; Elhassan, Elbagir; Mahdi, Diaa
2014-11-01
Wandering spleen is a rare clinical entity characterised by splenic hypermobility resulting from laxity or maldevelopment of the suspensory gastrosplenic, splenorenal, and phrenicocolic ligaments. Diagnosis is quite difficult, especially in children because of the lack of symptoms and signs until splenic torsion have occurred. An array of investigations is possible but US with color Doppler, CT with intravenous contrast and MRI are frequently being used to diagnose wandering spleen with or without torsion. We present a case of 5 years old child with torsion of wandering spleen to highlight the importance of prompt diagnosis and management.
Acute torsion of wandering spleen: report of one case.
Lien, Chi-Hone; Lee, Hung-Chang; Yeung, Chun-Yan; Chan, Wai-Tao; Wang, Nein-Lu
2009-08-01
Wandering spleen is a rare condition that can lead to splenic infarction or rupture if torsion persists. Early diagnosis and intervention are necessary, and abdominal ultrasonography and abdominal computed tomography are well accepted as the diagnostic imaging modalities. In this study, we present a boy with nic infarction due to acute torsion of a wandering spleen, after initial failure to demonstrate an ectopic spleen. Instead, acute torsion of the wandering spleen with spontaneous partial detorsion was incidentally found by multi-detector row CT with angiography. The patient was managed by splenectomy instead of splenopexy, because poor reperfusion after Laparoscopic detorsion.
Discussion on massive gravitons and propagating torsion in arbitrary dimensions
Hernaski, C. A.; Vargas-Paredes, A. A.; Helayeel-Neto, J. A.
2009-12-15
In this paper, we reassess a particular R{sup 2}-type gravity action in D dimensions, recently studied by Nakasone and Oda, now taking torsion effects into account. Considering that the vielbein and the spin connection carry independent propagating degrees of freedom, we conclude that ghosts and tachyons are absent only if torsion is nonpropagating, and we also conclude that there is no room for massive gravitons. To include these excitations, we understand how to enlarge Nakasone-Oda's model by means of explicit torsion terms in the action and we discuss the unitarity of the enlarged model for arbitrary dimensions.
Generation of angular momentum in cold gravitational collapse
NASA Astrophysics Data System (ADS)
Benhaiem, D.; Joyce, M.; Sylos Labini, F.; Worrakitpoonpon, T.
2016-01-01
During the violent relaxation of a self-gravitating system, a significant fraction of its mass may be ejected. If the time-varying gravitational field also breaks spherical symmetry, this mass can potentially carry angular momentum. Thus, starting initial configurations with zero angular momentum can, in principle, lead to a bound virialised system with non-zero angular momentum. Using numerical simulations we explore here how much angular momentum can be generated in a virialised structure in this way, starting from configurations of cold particles that are very close to spherically symmetric. For the initial configurations in which spherical symmetry is broken only by the Poissonian fluctuations associated with the finite particle number N, with N in range 103 to 105, we find that the relaxed structures have standard "spin" parameters λ ~ 10-3, and decreasing slowly with N. For slightly ellipsoidal initial conditions, in which the finite-N fluctuations break the residual reflection symmetries, we observe values λ ~ 10-2, i.e. of the same order of magnitude as those reported for elliptical galaxies. The net angular momentum vector is typically aligned close to normal to the major semi-axis of the triaxial relaxed structure and of the ejected mass. This simple mechanism may provide an alternative, or complement, to the so-called tidal torque theory for understanding the origin of angular momentum in astrophysical structures.
The Quadratic Spinor Lagrangian, Axial Torsion Current and Generalizations
NASA Astrophysics Data System (ADS)
Da Rocha, R.; Pereira, J. G.
We show that the Einstein-Hilbert, the Einstein-Palatini, and the Holst actions can be derived from the Quadratic Spinor Lagrangian (QSL), when the three classes of Dirac spinor fields, under Lounesto spinor field classification, are considered. To each one of these classes, there corresponds an unique kind of action for a covariant gravity theory. In other words, it is shown to exist a one-to-one correspondence between the three classes of non-equivalent solutions of the Dirac equation, and Einstein-Hilbert, Einstein-Palatini, and Holst actions. Furthermore, it arises naturally, from Lounesto spinor field classification, that any other class of spinor field — Weyl, Majorana, flagpole, or flag-dipole spinor fields — yields a trivial (zero) QSL, up to a boundary term. To investigate this boundary term, we do not impose any constraint on the Dirac spinor field, and consequently we obtain new terms in the boundary component of the QSL. In the particular case of a teleparallel connection, an axial torsion one-form current density is obtained. New terms are also obtained in the corresponding Hamiltonian formalism. We then discuss how these new terms could shed new light on more general investigations.
Interferometric measurement of angular motion
NASA Astrophysics Data System (ADS)
Peña Arellano, Fabián Erasmo; Panjwani, Hasnain; Carbone, Ludovico; Speake, Clive C.
2013-04-01
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°.
Variations in atmospheric angular momentum
NASA Technical Reports Server (NTRS)
Rosen, R. D.; Salstein, D. A.
1981-01-01
Twice-daily values of the atmosphere's angular momentum about the polar axis during the five years from 1976 through 1980 are presented in graphs and a table. The compilation is based on a global data set, incorporating 90 percent of the mass of the atmosphere. The relationship between changes in the angular momentum of the atmosphere and changes in the length of day is described, as are the main sources of error in the data. The variability in angular momentum is revealed in a preliminary fashion by means of a spectral decomposition. The data presented should stimulate comparisons with other measures of the length of day and so provide a basis for greater understanding of Earth-atmosphere interactions.
NASA Astrophysics Data System (ADS)
Gorospe, Alking; Bautista, Zhierwinjay; Shin, Hyung-Seop
2016-10-01
Coated conductor (CC) tapes utilized in high-current-density superconducting cables are commonly subjected to different loading modes, primarily torsion and tension especially in the case of twisted stacked-tape cable. Torsion load can occur due to twisting along the length or when winding the CC tapes around a former, while tension load can occur due to pre-tension when coiled and as a hoop stress when the coil is energized. In this study, electromechanical properties of single CC tapes under torsion load were investigated using a new test apparatus. The results could provide basic information for cable designers to fully characterize stacked cables. Copper-electroplated and brass-laminated CC tapes fabricated with different deposition techniques were subjected to pure torsion and combined tension-torsion loading. The critical current, I c degradation behaviours of CC tapes under torsional deformation were examined. Also, the effect of further external lamination on the I c degradation behaviour of the CC tapes under such loading conditions was investigated. In the case of the combined tension-torsion test, short samples were subjected to twist pitches of 200 mm and 100 mm. Critical parameters including reversible axial stress and strain in such twist pitch conditions were also investigated.
Non-Colinearity of Angular Velocity and Angular Momentum
ERIC Educational Resources Information Center
Burr, A. F.
1974-01-01
Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)
Solar cell angular position transducer
NASA Technical Reports Server (NTRS)
Sandford, M. C.; Gray, D. L. (Inventor)
1980-01-01
An angular position transducer utilizing photocells and a light source is disclosed. The device uses a fully rotatable baffle which is connected via an actuator shaft to the body whose rotational displacement is to be measured. The baffle blocks the light path between the light source and the photocells so that a constant semicircular beam of light reaches the photocells. The current produced by the photocells is fed through a resistor, a differential amplifier measures the voltage drop across the resistor which indicates the angular position of the actuator shaft and hence of the object.
Evidence for changes in the angular velocity of the surface regions of the sun and stars
NASA Technical Reports Server (NTRS)
1972-01-01
A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing changes in the angular velocity of the surface regions of the sun and stars.
Effect of tensile and torsion on GMI in amorphous wire
NASA Astrophysics Data System (ADS)
Blanco, J. M.; Zhukov, A.; Gonzalez, J.
1999-05-01
GMI effect, Δ Z/Z = [ Z( H) - Z( Hmax)]/ Z( Hmax) has been measured in (Fe 0.94Co 0.06) 72.5B 15Si 12.5 wire under tensile, σ ten, and torsional, σ tor, stresses. Generally Δ Z/Z( H) dependence has a non-monotonic shape with a maximum at certain axial magnetic field, Hm. Both tension and torsion modify Δ Z/Z( H) dependence. Application of tension results in an increase of Hm with σ ten. Torsional stress dependence of GMI effect has asymmetry with a maximum at torsion angle, φ, around + 12π/m in as-cast wire, when Δ Z/Z is around 250%. An increase of Δ Z/Zm up to 350% and change of Δ Z/Z(φ) dependence towards a nearly symmetric shape have been observed after Joule heating.
Response characteristics of the human torsional vestibuloocular reflex
NASA Technical Reports Server (NTRS)
Peterka, Robert J.
1992-01-01
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.
Torsional dynamics of steerable needles: modeling and fluoroscopic guidance.
Swensen, John P; Lin, MingDe; Okamura, Allison M; Cowan, Noah J
2014-11-01
Needle insertions underlie a diversity of medical interventions. Steerable needles provide a means by which to enhance existing needle-based interventions and facilitate new ones. Tip-steerable needles follow a curved path and can be steered by twisting the needle base during insertion, but this twisting excites torsional dynamics that introduce a discrepancy between the base and tip twist angles. Here, we model the torsional dynamics of a flexible rod-such as a tip-steerable needle-during subsurface insertion and develop a new controller based on the model. The torsional model incorporates time-varying mode shapes to capture the changing boundary conditions inherent during insertion. Numerical simulations and physical experiments using two distinct setups-stereo camera feedback in semitransparent artificial tissue and feedback control with real-time X-ray imaging in optically opaque artificial tissue-demonstrate the need to account for torsional dynamics in control of the needle tip.
Bilateral perinatal testicular torsion: successful salvage supports emergency surgery.
Granger, Jeremy; Brownlee, Ewan M; Cundy, Thomas P; Goh, Day Way
2016-06-15
Perinatal testicular torsion (PTT) has poor rates of testicular salvage. Although rare, bilateral PTT carries the risk of anorchia. We present a case of a 2-day-old term infant with acute onset right-sided scrotal discolouration and tenderness. The infant was promptly taken to the operating theatre for emergency scrotal exploration. Bilateral extravaginal testicular torsion was identified, with the right testis appearing to have a more established ischaemic appearance compared to that on the left side. Intraoperative findings were representative of metachronous PTT with a short time period of only several hours separating the torsion events. Both testes were detorted and fixated in the scrotum. The infant made an uneventful recovery. Outpatient clinic review at 6 weeks and 6 months postoperatively confirmed no clinical evidence of testicular atrophy. Given the potential for contralateral torsion and the morbidity of anorchia, our experience supports the role for emergency scrotal exploration in suspected PTT.
Spin-torsion effects in the hyperfine structure of methanol
NASA Astrophysics Data System (ADS)
Coudert, L. H.; Gutlé, C.; Huet, T. R.; Grabow, J.-U.; Levshakov, S. A.
2015-07-01
The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.
Spin-torsion effects in the hyperfine structure of methanol
Coudert, L. H. Gutlé, C.; Huet, T. R.; Grabow, J.-U.; Levshakov, S. A.
2015-07-28
The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.
An Inexpensive Torsional Pendulum Apparatus for Rigidity Modulus Measurement.
ERIC Educational Resources Information Center
Tyagi, S.; Lord, A. E., Jr.
1979-01-01
Described is an easy to assemble, and inexpensive, torsional pendulum which gives an accuracy of measurement of the modulus of rigidity, G, comparable to the accuracy obtained with the more expensive commercially available student models. (Author/GA)
Torsion of the Appendix Testis in a Neonate
Krishnan, Arvind; Rich, Mark A.; Swana, Hubert S.
2016-01-01
Torsion of the appendix testis is a rare cause of scrotal swelling in the neonatal period. We present a case of torsion of the appendix testis in a one-day-old male. We discuss the physical examination and radiologic studies used to make the diagnosis. Nonoperative therapy was recommended and the patient has done well. Recognition of this condition in the neonatal period can prevent surgical intervention and its associated risks. PMID:27379193
Cosmic Magnetic Fields from Torsion Modes and Massive Photon Inflation
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.
2014-09-01
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.
Salvage splenopexy for torsion of wandering spleen in a child.
Goyal, Ram Babu; Gupta, Rahul; Prabhakar, Girish; Mathur, Praveen; Mala, Tariq Ahmed
2014-01-01
The wandering spleen is a rare condition characterized by the absence or underdevelopment of one or all of the splenic suspensory ligaments that resulting in increased splenic mobility and rarely torsion. Preventing infarction is the aim of a prompt surgery by splenopexy. We report a case of salvage splenopexy in torsion of a wandering spleen in a three year old girl presented with severe abdominal pain for three days.
Salvage Splenopexy for Torsion of Wandering Spleen in a Child
Goyal, Ram Babu; Prabhakar, Girish; Mathur, Praveen; Mala, Tariq Ahmed
2014-01-01
The wandering spleen is a rare condition characterized by the absence or underdevelopment of one or all of the splenic suspensory ligaments that resulting in increased splenic mobility and rarely torsion. Preventing infarction is the aim of a prompt surgery by splenopexy. We report a case of salvage splenopexy in torsion of a wandering spleen in a three year old girl presented with severe abdominal pain for three days. PMID:24834385
Thermal conductivity and torsional oscillations of solid 4He
NASA Astrophysics Data System (ADS)
Brazhnikov, M. Yu.; Zmeev, D. E.; Golov, A. I.
2012-11-01
Polycrystalline samples of hcp 4He of molar volume Vm = 19.5 cm3 with small amount of 3He impurities were grown in an annular container by the blocked-capillary method. Three concentrations of 3He, x3, were studied: isotopically purified 4He with the estimated x3 < 10-10, commercial `well-grade' helium with x3 ˜ 3.10-7 and a mixture with x3 = 2.5.10-6. Torsional oscillations at two frequencies, 132.5 and 853.6 Hz, and thermal conductivity were investigated before and after annealing. The solid helium under investigation was located not only in the annular container but also in the axial fill line inside two torsion rods and dummy bob of the double-frequency torsional oscillator. The analysis of the frequency shifts upon loading with helium and changing temperatures of different parts of the oscillator suggests that the three techniques probe the properties of solid helium in three different locations: the two different torsion modes respond to the changes of the shear modulus of solid helium in either of the two torsion rods while the thermal conductivity probes the phonon mean free path in solid helium inside the annular container. The temperature and width of the torsional anomaly increase with increasing frequency and x3. The phonon mean free path increases with increasing x3. Annealing typically resulted in an increased phonon mean free path but often in little change in the torsional oscillator response. While the magnitude of the torsional anomaly and phonon mean free path can be very different in different samples, no correlation was found between them.
High angular resolution at LBT
NASA Astrophysics Data System (ADS)
Conrad, A.; Arcidiacono, C.; Bertero, M.; Boccacci, P.; Davies, A. G.; Defrere, D.; de Kleer, K.; De Pater, I.; Hinz, P.; Hofmann, K. H.; La Camera, A.; Leisenring, J.; Kürster, M.; Rathbun, J. A.; Schertl, D.; Skemer, A.; Skrutskie, M.; Spencer, J. R.; Veillet, C.; Weigelt, G.; Woodward, C. E.
2015-12-01
High angular resolution from ground-based observatories stands as a key technology for advancing planetary science. In the window between the angular resolution achievable with 8-10 meter class telescopes, and the 23-to-40 meter giants of the future, LBT provides a glimpse of what the next generation of instruments providing higher angular resolution will provide. We present first ever resolved images of an Io eruption site taken from the ground, images of Io's Loki Patera taken with Fizeau imaging at the 22.8 meter LBT [Conrad, et al., AJ, 2015]. We will also present preliminary analysis of two data sets acquired during the 2015 opposition: L-band fringes at Kurdalagon and an occultation of Loki and Pele by Europa (see figure). The light curves from this occultation will yield an order of magnitude improvement in spatial resolution along the path of ingress and egress. We will conclude by providing an overview of the overall benefit of recent and future advances in angular resolution for planetary science.
Effect of slow rotational diffusion on angular correlations.
NASA Technical Reports Server (NTRS)
Marshall, A. G.; Meares, C. F.
1972-01-01
The theory for perturbed angular correlations of gamma radiation has been extended to include the possibility of adiabatic variation in the interaction Hamiltonian, K, for the intermediate state. The calculation begins from a polycrystalline model. It is shown that adiabatic variation in K introduces a time dependence into the angles which express the orientation of the molecular frame. The relevance of the adiabatic limit to the use of perturbed angular correlations of gamma radiation for study of the motion of radioactive species in viscous media is discussed.
Torsional texturing of superconducting oxide composite articles
Christopherson, Craig John; Riley, Jr., Gilbert N.; Scudiere, John
2002-01-01
A method of texturing a multifilamentary article having filaments comprising a desired oxide superconductor or its precursors by torsionally deforming the article is provided. The texturing is induced by applying a torsional strain which is at least about 0.3 and preferably at least about 0.6 at the surface of the article, but less than the strain which would cause failure of the composite. High performance multifilamentary superconducting composite articles having a plurality of low aspect ratio, twisted filaments with substantially uniform twist pitches in the range of about 1.00 inch to 0.01 inch (25 to 0.25 mm), each comprising a textured desired superconducting oxide material, may be obtained using this texturing method. If tighter twist pitches are desired, the article may be heat treated or annealed and the strain repeated as many times as necessary to obtain the desired twist pitch. It is preferred that the total strain applied per step should be sufficient to provide a twist pitch tighter than 5 times the diameter of the article, and twist pitches in the range of 1 to 5 times the diameter of the article are most preferred. The process may be used to make a high performance multifilamentary superconducting article, having a plurality of twisted filaments, wherein the degree of texturing varies substantially in proportion to the radial distance from the center of the article cross-section, and is substantially radially homogeneous at any given cross-section of the article. Round wires and other low aspect ratio multifilamentary articles are preferred forms. The invention is not dependent on the melting characteristics of the desired superconducting oxide. Desired oxide superconductors or precursors with micaceous or semi-micaceous structures are preferred. When used in connection with desired superconducting oxides which melt irreversibly, it provides multifilamentary articles that exhibit high DC performance characteristics and AC performance markedly
An Axial-Torsional, Thermomechanical Fatigue Testing Technique
NASA Technical Reports Server (NTRS)
Kalluri, Sreeramesh; Bonacuse, Peter J.
1995-01-01
A technique for conducting strain-controlled, thermomechanical, axial-torsional fatigue tests on thin-walled tubular specimens was developed. Three waveforms of loading, namely, the axial strain waveform, the engineering shear strain waveform, and the temperature waveform were required in these tests. The phasing relationships between the mechanical strain waveforms and the temperature and axial strain waveforms were used to define a set of four axial-torsional, thermomechanical fatigue (AT-TMF) tests. Real-time test control (3 channels) and data acquisition (a minimum of 7 channels) were performed with a software program written in C language and executed on a personal computer. The AT-TMF testing technique was used to investigate the axial-torsional thermomechanical fatigue behavior of a cobalt-base superalloy, Haynes 188. The maximum and minimum temperatures selected for the AT-TMF tests were 760 and 316 C, respectively. Details of the testing system, calibration of the dynamic temperature profile of the thin-walled tubular specimen, thermal strain compensation technique, and test control and data acquisition schemes, are reported. The isothermal, axial, torsional, and in- and out-of-phase axial-torsional fatigue behaviors of Haynes 188 at 316 and 760 C were characterized in previous investigations. The cyclic deformation and fatigue behaviors of Haynes 188 in AT-TMF tests are compared to the previously reported isothermal axial-torsional behavior of this superalloy at the maximum and minimum temperatures.
Testicular torsion, oxidative stress and the role of antioxidant therapy.
Dokmeci, Dikmen
2006-01-01
Testicular torsion is a urological syndrome caused mainly by a twist in the spermatic cord. It constitutes a surgical emergency and affects newborns, children and adolescent boys. The torsion must be treated promptly to avoid loss of function of ipsilateral and contralateral testis. This syndrome often leads to infertility of the ipsilateral (torted) and contralateral (not torted) testis,but the mechanisms of cellular injury remain still incompletely understood. The primary pathophysiologic event in testicular torsion is ischemia followed by reperfusion; thus, testicular torsion/detorsion is an ischemia/reperfusion (I/R) injury to the testis. Testicular torsion and detorsion causes morphological and biochemical changes by both ischemia and reperfusion of the tissues. These I/R injury is associated with overgeneration of reactive oxygen species (ROS) and reactive nitrogen species (RNS), and also with a common mechanism to other organs such as brain, heart and kidneys. Although the results are not conclusive and the molecular mechanism by which antioxidants control male fertility have not yet been clearly identified, several antioxidant enzymes and antioxidant drugs have been studied to prevent such I/R injury in testis. As a result, antioxidant therapy may represent a new non-hormonal option within a broader therapeutic strategy in men with ROS-mediated infertility such as testicular torsion.
NASA Technical Reports Server (NTRS)
Houbolt, John C; Brooks, George W
1958-01-01
The differential equations of motion for the lateral and torsional deformations of twisted rotating beams are developed for application to helicopter rotor and propeller blades. No assumption is made regarding the coincidence of the neutral, elastic, and mass axes, and the generality is such that previous theories involving various simplifications are contained as subcases to the theory presented in this paper. Special attention is given the terms which are not included in previous theories. These terms are largely coupling-type terms associated with the centrifugal forces. Methods of solution of the equations of motion are indicated by selected examples.
NASA Technical Reports Server (NTRS)
Houbolt, John C; Brooks, George W
1957-01-01
The differential equations of motion for the lateral and torsional deformations of twisted rotating beams are developed for application to helicopter rotor and propeller blades. No assumption is made regarding the coincidence of the neutral, elastic, and mass axes, and the generality is such that previous theories involving various simplifications are contained as subcases to the theory developed and presented in this paper. Special attention is given to coupling terms not found in previous theories, and methods of solution of the equations of motion are indicated by selected examples.
Angular output of hollow, metal-lined, waveguide Raman sensors
Biedrzycki, Stephen; Buric, Michael P.; Falk, Joel; Woodruff, Steven D.
2012-04-20
Hollow, metal-lined waveguides used as gas sensors based on spontaneous Raman scattering are capable of large angular collection. The collection of light from a large solid angle implies the collection of a large number of waveguide modes. An accurate estimation of the propagation losses for these modes is required to predict the total collected Raman power. We report a theory/experimental comparison of the Raman power collected as a function of the solid angle and waveguide length. New theoretical observations are compared with previous theory appropriate only for low-order modes. A cutback experiment is demonstrated to verify the validity of either theory. The angular distribution of Raman light is measured using aluminum and silver-lined waveguides of varying lengths.
Control of Torsional Vibrations by Pendulum Masses
NASA Technical Reports Server (NTRS)
Stieglitz, Albert
1942-01-01
Various versions of pendulum masses have been developed abroad within the past few years by means of which resonant vibrations of rotating shafts can be eliminated at a given tuning. They are already successfully employed on radial engines in the form of pendulous counterweights. Compared with the commonly known torsional vibration dampers, the pendulum masses have the advantage of being structurally very simple, requiring no internal damping and being capable of completely eliminating certain vibrations. Unexplained, so far, remains the problem of behavior of pendulum masses in other critical zones to which they are not tuned, their dynamic behavior at some tuning other than in resonance, and their effect within a compound vibration system and at simultaneous application of several differently tuned pendulous masses. These problems are analyzed in the present report. The results constitute an enlargement of the scope of application of pendulum masses, especially for in-line engines. Among other things it is found that the natural frequency of a system can be raised by means of a correspondingly tuned pendulum mass. The formulas necessary for the design of any practical version are developed, and a pendulum mass having two different natural frequencies simultaneously is described.
Association between pregnancy and adnexal torsion
Yuk, Jin-Sung; Shin, Ji-Yeon; Park, Won I.; Kim, Dae Woon; Shin, Jung Whan; Lee, Jung Hun
2016-01-01
Abstract The purpose of this study was to determine the effect of pregnancy on adnexal torsion (AT). We conducted a matched case-control study using the Korean Health Insurance Review and Assessment Service–National Inpatients Sample (HIRA-NIS) from 2009 to 2011. AT patients were defined as women with both a diagnostic code (N835) and a surgical code for AT. The AT patients were randomly matched 1:4 with women without AT by age and year of claim. In total, 545 AT cases and 2180 controls were enrolled from a total of 1,843,451 women. After adjustment for such covariates as age, pregnancy was found to be associated with a lower rate of AT (adjusted odds ratio 0.314, 95% confidence interval [CI] 0.237–0.416, P value <0.01) and ovarian hyperstimulation syndrome was associated with a higher rate of AT (adjusted odds ratio 20.091, 95% CI 3.607–111.908, P value <0.01). We found that pregnancy is a negative risk factor for AT. However, a further study is needed to elucidate the mechanisms underlying these results. PMID:27310967
Gascooke, Jason R; Virgo, Edwina A; Lawrance, Warren D
2015-07-28
We have examined the S1←S0 transition of toluene in the region from the 0(0)(0) band to ∼210 cm(-1) above it. The spectrum reveals methyl rotor levels of 0(0) toluene up to m = 6 and of the lowest frequency vibration, 20(1), up to m = 4. The rotor levels of both 20(1) and 0(0) are perturbed by torsion-vibration coupling. The inclusion of torsion-vibration coupling leads to the S1 torsional barrier, V6, being revised from -26.376 cm(-1) to -5.59 cm(-1). The torsion-vibration coupling constant is determined to be 21.1 cm(-1). This situation is the S1 analogue of that recently reported for S0 toluene [Gascooke et al., J. Chem. Phys. 142, 024315 (2015)]. Torsion-vibration coupling alters both the rotor band positions and the rotational contours, which particularly affects the rotational constants associated with motion around the a-axis, about which the methyl group rotates. Every vibrational state (indicated generically by X) will be involved in the corresponding X - X20(1) torsion-vibration coupling; so, this interaction permeates the vib-rotor manifold, providing a mechanism to enhance intramolecular vibrational energy redistribution.
Arbitrarily tunable orbital angular momentum of photons
Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2016-01-01
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM. PMID:27378234
High Orbital Angular Momentum Harmonic Generation
NASA Astrophysics Data System (ADS)
Vieira, J.; Trines, R. M. G. M.; Alves, E. P.; Fonseca, R. A.; Mendonça, J. T.; Bingham, R.; Norreys, P.; Silva, L. O.
2016-12-01
We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions.
Smoothed dissipative particle dynamics with angular momentum conservation
Müller, Kathrin Fedosov, Dmitry A. Gompper, Gerhard
2015-01-15
Smoothed dissipative particle dynamics (SDPD) combines two popular mesoscopic techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved dissipative particle dynamics approach. Despite several advantages of the SDPD method over the conventional DPD model, the original formulation of SDPD by Español and Revenga (2003) [9], lacks angular momentum conservation, leading to unphysical results for problems where the conservation of angular momentum is essential. To overcome this limitation, we extend the SDPD method by introducing a particle spin variable such that local and global angular momentum conservation is restored. The new SDPD formulation (SDPD+a) is directly derived from the Navier–Stokes equation for fluids with spin, while thermal fluctuations are incorporated similarly to the DPD method. We test the new SDPD method and demonstrate that it properly reproduces fluid transport coefficients. Also, SDPD with angular momentum conservation is validated using two problems: (i) the Taylor–Couette flow with two immiscible fluids and (ii) a tank-treading vesicle in shear flow with a viscosity contrast between inner and outer fluids. For both problems, the new SDPD method leads to simulation predictions in agreement with the corresponding analytical theories, while the original SDPD method fails to capture properly physical characteristics of the systems due to violation of angular momentum conservation. In conclusion, the extended SDPD method with angular momentum conservation provides a new approach to tackle fluid problems such as multiphase flows and vesicle/cell suspensions, where the conservation of angular momentum is essential.
Smoothed dissipative particle dynamics with angular momentum conservation
NASA Astrophysics Data System (ADS)
Müller, Kathrin; Fedosov, Dmitry A.; Gompper, Gerhard
2015-01-01
Smoothed dissipative particle dynamics (SDPD) combines two popular mesoscopic techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved dissipative particle dynamics approach. Despite several advantages of the SDPD method over the conventional DPD model, the original formulation of SDPD by Español and Revenga (2003) [9], lacks angular momentum conservation, leading to unphysical results for problems where the conservation of angular momentum is essential. To overcome this limitation, we extend the SDPD method by introducing a particle spin variable such that local and global angular momentum conservation is restored. The new SDPD formulation (SDPD+a) is directly derived from the Navier-Stokes equation for fluids with spin, while thermal fluctuations are incorporated similarly to the DPD method. We test the new SDPD method and demonstrate that it properly reproduces fluid transport coefficients. Also, SDPD with angular momentum conservation is validated using two problems: (i) the Taylor-Couette flow with two immiscible fluids and (ii) a tank-treading vesicle in shear flow with a viscosity contrast between inner and outer fluids. For both problems, the new SDPD method leads to simulation predictions in agreement with the corresponding analytical theories, while the original SDPD method fails to capture properly physical characteristics of the systems due to violation of angular momentum conservation. In conclusion, the extended SDPD method with angular momentum conservation provides a new approach to tackle fluid problems such as multiphase flows and vesicle/cell suspensions, where the conservation of angular momentum is essential.
The Angular Momentum of Baryons and Dark Matter Halos Revisited
NASA Technical Reports Server (NTRS)
Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan
2011-01-01
Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive-mesh refinement (AMR), we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r = 0.1R(sub vir). In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/R(sub vir) > 0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its virialised dark matter halo host. This generic result holds for halos of all masses at all redshifts, as radiative cooling ensures that a significant fraction of baryons remain trapped at the centre of the halos. Despite this injection of angular momentum enriched gas, we predict an amount for stellar discs which is in fair agreement with observations at z=0. This arises because the total specific angular momentum of the baryons (gas and stars) remains close to that of dark matter halos. Indeed, our simulations indicate that any differential loss of angular momentum amplitude between the two components is minor even though dark matter halos continuously lose between half and two-thirds of their specific angular momentum modulus as they evolve. In light of our results, a substantial revision of the standard theory of disc formation seems to be required. We propose a new scenario where gas efficiently carries the angular momentum generated
Scrotal Exploration for Testicular Torsion and Testicular Appendage Torsion: Emergency and Reality
Yu, You; Zhang, Feng; An, Qun; Wang, Long; Li, Chao; Xu, Zhilin
2015-01-01
Background: Scrotal exploration is considered the procedure of choice for acute scrotum. Objectives: We evaluated the importance of early diagnosis and testicular salvage on the therapeutic outcomes of patients with pediatric testicular torsion (TT) and testicular appendage torsion (TAT) in our geographic area. Patients and Methods: We performed a retrospective database analysis of patients who underwent emergency surgery for TT or TAT between January 1996 and June 2009. Patient history, physical examination findings, laboratory test results, color Doppler sonography (CDS) results, and surgical findings were reviewed. Results: A total of 65 cases were included in our analysis. Forty-two cases were followed up for at least 3 months. Testicular tenderness was identified as the major clinical manifestation of TT, while only a few patients with TAT presented with swelling. CDS was an important diagnostic modality. The orchiectomy rate was 71% in the TT group. Conclusions: Cases of acute scrotum require attention in our area. Early diagnosis and scrotal exploration could salvage the testis or preserve normal function without the need for surgery. PMID:26199690
On Dunkl angular momenta algebra
NASA Astrophysics Data System (ADS)
Feigin, Misha; Hakobyan, Tigran
2015-11-01
We consider the quantum angular momentum generators, deformed by means of the Dunkl operators. Together with the reflection operators they generate a subalgebra in the rational Cherednik algebra associated with a finite real reflection group. We find all the defining relations of the algebra, which appear to be quadratic, and we show that the algebra is of Poincaré-Birkhoff-Witt (PBW) type. We show that this algebra contains the angular part of the Calogero-Moser Hamiltonian and that together with constants it generates the centre of the algebra. We also consider the gl( N ) version of the subalge-bra of the rational Cherednik algebra and show that it is a non-homogeneous quadratic algebra of PBW type as well. In this case the central generator can be identified with the usual Calogero-Moser Hamiltonian associated with the Coxeter group in the harmonic confinement.
Achromatic orbital angular momentum generator
NASA Astrophysics Data System (ADS)
Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W.
2014-12-01
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of two glued hollow axicons, is used to introduce a nonuniform rotation of polarization into a linearly polarized input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarization, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of 95% for these three different wavelengths is observed. This device may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed.
Does a Randall-Sundrum Scenario Create the Illusion of a Torsion-Free Universe?
NASA Astrophysics Data System (ADS)
Mukhopadhyaya, Biswarup; Sen, Somasri; Sengupta, Soumitra
2002-08-01
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.
Early onset torsion dystonia (Oppenheim's dystonia)
Kamm, Christoph
2006-01-01
Early onset torsion dystonia (EOTD) is a rare movement disorder characterized by involuntary, repetitive, sustained muscle contractions or postures involving one or more sites of the body. A US study estimated the prevalence at approximately 1 in 30,000. The estimated prevalence in the general population of Europe seems to be lower, ranging from 1 in 330,000 to 1 in 200,000, although precise numbers are currently not available. The estimated prevalence in the Ashkenazi Jewish population is approximately five to ten times higher, due to a founder mutation. Symptoms of EOTD typically develop first in an arm or leg in middle to late childhood and progress in approximately 30% of patients to other body regions (generalized dystonia) within about five years. Distribution and severity of symptoms vary widely between affected individuals. The majority of cases from various ethnic groups are caused by an autosomal dominantly inherited deletion of 3 bp (GAG) in the DYT1 gene on chromosome 9q34. This gene encodes a protein named torsinA, which is presumed to act as a chaperone protein associated with the endoplasmic reticulum and the nuclear envelope. It may interact with the dopamine transporter and participate in intracellular trafficking, although its precise function within the cell remains to be determined. Molecular genetic diagnostic and genetic counseling is recommended for individuals with age of onset below 26 years, and may also be considered in those with onset after 26 years having a relative with typical early onset dystonia. Treatment options include botulinum toxin injections for focal symptoms, pharmacological therapy such as anticholinergics (most commonly trihexiphenydil) for generalized dystonia and surgical approaches such as deep brain stimulation of the internal globus pallidus or intrathecal baclofen application in severe cases. All patients have normal cognitive function, and despite a high rate of generalization of dystonia, 75% of those patients
Investigation of the torsional barrier of EDOT using molecular mechanics and DFT methods.
Durães, Jussara A; da Silva Filho, Demétrio A; Ceschin, Artemis M; Sales, Maria J A; Martins, João B L
2014-08-01
When heterocyclic monomers are polymerized by electrochemical or chemical methods, they form fully conjugated polymers which have a wide range of applications due to their outstanding electronic properties. Among this class of compounds, thiophene derivatives are widely used due to their chemical stability and synthesis flexibility. With the goal to investigate the torsion barrier of polymer chains, a few units of 3,4-ethylenedioxythiophene (EDOT) were chosen and submitted to molecular mechanics (MM), density functional theory (DFT) and coupled cluster CCSD(T) calculations. This study helps to understand the performance and transferability of force fields used in molecular mechanics and molecular dynamics simulations often used to describe structure-property relationships of those systems. Determination of inter-ring torsion angle was performed in a comparative study using both force field, DFT and CCSD(T) methods. A good agreement was noticed between MM and QC results and highlights the importance of the description of the interactions involving the oxygen atoms present in the structure of EDOT. These observations are related to the α,α-coupling that occurs between the monomer units and yields a linear polymer. DFT HOMO and LUMO orbitals were also presented. Finally, UV-vis spectra of EDOT units were obtained using several levels of theory by means of time-dependent DFT calculations (TD-DFT).
Angular Momentum Decomposition for an Electron
Burkardt, Matthias; BC, Hikmat
2009-01-01
We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.
Protective effect of thymoquinone against testicular torsion induced oxidative injury.
Ayan, M; Tas, U; Sogut, E; Caylı, S; Kaya, H; Esen, M; Erdemir, F; Uysal, M
2016-03-01
We aimed to determine the protective effects of thymoquinone (TQ), against ischaemia-reperfusion (I/R) injury in the testis tissue of rats. Twenty-seven male Wistar albino rats were randomly divided into three equal groups as follows: Group I, sham group; Group II, torsion group; and Group III, torsion + thymoquinone group. The ischaemia period was 2 h, and orchiectomy was performed after 30 min of detorsion. Testis tissue sections were analysed with the terminal transferase mediated dUTP-nick end labelling (TUNEL) assay to determine in situ apoptotic DNA fragmentation. Additionally, Caspase 3 and Bax proteins were analysed immunohistochemically. The superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) activity levels in the testis tissue were also measured. The superoxide dismutase activity and malondialdehyde levels in the torsion group were significantly higher than those of the sham group (P < 0.05). Thymoquinone administration significantly reduced these levels. Torsion significantly increased active-Caspase 3 and Bax expression, which was decreased by thymoquinone. The apoptotic index of the torsion group was significantly higher than that of the control group. However, thymoquinone significantly reduced the apoptotic index (P < 0.05). Our results indicate that thymoquinone plays a protective role in oxidative stress induced ischaemia-reperfusion in the testis tissue of rats.
The intermountain power project commissioning - Subsynchronous torsional interaction tests
Wu, C.T.; Peterson, K.J. ); Pinko, R.J.; Kankam, M.D.; Baker, D.H. )
1988-10-01
Subsyncronous torsional vibration as a result of electrochemical interaction between the HVDC controls and a turbine-generator was first discovered during the commissioning of the Square Butte Project in 1977. The level of interaction between the HVDC controls and the turbine-generator depends on several interacting factors: the characteristic torsional frequencies of the turbine-generator, the bandwidth of the HVDC controls and the relative strength of the connecting ac system. For the Intermountain Power Project (IPP), early analysis of these interacting factors indicated that there exist definite potential for subsynchronous oscillation to occur. The calculated torsional frequencies of the IPP units showed that the first mode frequency is 14.0 Hz and is within the typical bandwidth of an HVDC control which is between 10-20 Hz. The HVDC controls, therefore, can influence the torsional stability of the IPP units. Further, the IPP turbine-generators are required to operate isolated on the HVDC rectifier terminal, with no other interconnecting ac network. This ''radial'' mode of operation will result in maximum interaction between the converter station and the IPP units. It became obvious that special measure must be implemented in the design of the IPP HVDC control system to modify its typical characteristics to avoid the occurrence of the subsynchronous oscillation. This paper presents the results of the subsynchronous torsional interaction (SSTI) tests that were performed during the commissioning of the IPP Unit 1 and the HVDC Transmission system.
A torsion quasi-zero stiffness vibration isolator
NASA Astrophysics Data System (ADS)
Zhou, Jiaxi; Xu, Daolin; Bishop, Steven
2015-03-01
A torsion vibration isolator with quasi-zero stiffness (QZS) is proposed to attenuate the transmission of torsional vibration along a shaft system, which also plays a role of coupling between shafts. A pre-compressed cam-roller mechanism is designed to provide torsional negative stiffness that counteracts with the positive torsion stiffness of the vulcanized rubber between shafts. With the design parameters are set to satisfy a unique condition, the stiffness of the isolator delivers a QZS property about the equilibrium position. A nonlinear mathematical model is developed and its dynamic characteristics are further analyzed by using the Harmonic Balance method. A typical folded resonance curve occurs when the vibration amplitude is plotted as the excitation frequency is varied, illustrating a jump phenomenon in the response. The efficiency of vibration attenuation is estimated under a designed torque load, showing that the torsion QZS vibration isolator outperforms the corresponding linear counterpart, especial in low frequency ranges. Furthermore, the torque transmissibility of the QZS isolator is also studied to demonstrate the performance of the QZS isolator when the actual torque deviates from the design load.
Numerical modeling of pendulum dampers in torsional systems
Johnston, P.R.; Shusto, L.M.
1986-01-01
Centrifugal pendulum-design dampers are utilized in torsional systems to reduce the vibration amplitude at certain objectionable torsional speeds. The damper is tuned by proper design of its mass, dimensions, and position on a carrier disk, which is rigidly attached to the torsional system. The effects of the pendulum damper on the response of the torsional system may be included by modifying the structural model to include a separate damper element representing each order of the pendulum damper. The stiffness and mass matrices for a damper element are dependent upon the order of vibration being dampened, the mass, and the geometry of the damper. A general form of the mass and stiffness equations for a simple centrifugal pendulum damper are derived from first principles using Lagrange's equations of motion. The analysis of torsional systems with pendulum dampers utilizing the mass and stiffness properties developed is included in the program SHAMS. SHAMS calculates the steady-state response of a system of springs and masses to harmonic loads using modal superposition. The response of a crankshaft system with and without the pendulum dampers are included as a case study.
Unravelling the structural plasticity of stretched DNA under torsional constraint
King, Graeme A.; Peterman, Erwin J. G.; Wuite, Gijs J. L.
2016-01-01
Regions of the genome are often held under torsional constraint. Nevertheless, the influence of such constraint on DNA–protein interactions during genome metabolism is still poorly understood. Here using a combined optical tweezers and fluorescence microscope, we quantify and explain how torsional constraint influences the structural stability of DNA under applied tension. We provide direct evidence that concomitant basepair melting and helical unwinding can occur in torsionally constrained DNA at forces >∼50 pN. This striking result indicates that local changes in linking number can be absorbed by the rest of the DNA duplex. We also present compelling new evidence that an overwound DNA structure (likely P-DNA) is created (alongside underwound structures) at forces >∼110 pN. These findings substantiate previous theoretical predictions and highlight a remarkable structural plasticity of torsionally constrained DNA. Such plasticity may be required in vivo to absorb local changes in linking number in DNA held under torsional constraint. PMID:27263853
[Torsion of wandering spleen in a teenager: about a case].
Dème, Hamidou; Akpo, Léra Géraud; Fall, Seynabou; Badji, Nfally; Ka, Ibrahima; Guèye, Mohamadou Lamine; Touré, Mouhamed Hamine; Niang, El Hadj
2016-01-01
Wandering or migrating spleen is a rare anomaly which is usually described in children. Complications, which include pedicle torsion, are common and can be life-threatening. We report the case of a 17 year-old patient with a long past medical history of epigastric pain suffering from wandering spleen with chronic torsion of the pedicle. The clinical picture was marked by spontaneously painful epigastric mass, evolved over the past 48 hours. Abdominal ultrasound objectified heterogeneous hypertrophied ectopic spleen in epigastric position and a subcapsular hematoma. Doppler showed a torsion of splenic pedicle which was untwisted 2 turns and a small blood stream on the splenic artery. Abdominal CT scan with contrast injection showed a lack of parenchymal enhancement of large epigastric ectopic spleen and a subcapsular hematoma. The diagnosis of wandering spleen with chronic torsion of the pedicle complicated by necrosis and subcapsular hematoma was confirmed. The patient underwent splenectomy. The postoperative course was uneventful. We here discuss the contribution of ultrasound and CT scan in the diagnosis of wandering spleen with chronic torsion of the pedicle.
Elevated temperature axial and torsional fatigue behavior of Haynes 188
NASA Technical Reports Server (NTRS)
Bonacuse, Peter J.; Kalluri, Sreeramesh
1995-01-01
The results are reported for high-temperature axial and torsional low-cycle fatigue experiments performed at 760 C in air on thin-walled tubular specimens of Haynes 188, a wrought cobalt-based superalloy. Data are also presented for mean coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. This data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME Boiler and Pressure Code), Manson-Halford, modified multiaxiality factor (proposed in this paper), modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The modified multiaxiality factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.
Elevated temperature axial and torsional fatigue behavior of Haynes 188
NASA Technical Reports Server (NTRS)
Bonacuse, Peter J.; Kalluri, Sreeramesh
1992-01-01
The results of high-temperature axial and torsional low-cycle fatigue experiments performed on Haynes 188, a wrought cobalt-base superalloy, are reported. Fatigue tests were performed at 760 C in air on thin-walled tubular specimens at various ranges under strain control. Data are also presented for coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. The data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME boiler and pressure vessel code), Manson-Halford, Modified Multiaxiality Factor (proposed here), Modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The Modified Multiaxiality Factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.
Modelling the torsion of thin metal wires by distortion gradient plasticity
NASA Astrophysics Data System (ADS)
Bardella, Lorenzo; Panteghini, Andrea
2015-05-01
Under small strains and rotations, we apply a phenomenological higher-order theory of distortion gradient plasticity to the torsion problem, here assumed as a paradigmatic benchmark of small-scale plasticity. Peculiar of the studied theory, proposed about ten years ago by Morton E. Gurtin, is the constitutive inclusion of the plastic spin, affecting both the free energy and the dissipation. In particular, the part of the free energy, called the defect energy, which accounts for Geometrically Necessary Dislocations, is a function of Nye's dislocation density tensor, dependent on the plastic distortion, including the plastic spin. For the specific torsion problem, we implement this distortion gradient plasticity theory into a Finite Element (FE) code characterised by implicit (Backward Euler) time integration, numerically robust and accurate for both viscoplastic and rate-independent material responses. We show that, contrariwise to other higher-order theories of strain gradient plasticity (neglecting the plastic spin), the distortion gradient plasticity can predict some strengthening even if a quadratic defect energy is chosen. On the basis of the results of many FE analyses, concerned with (i) cyclic loading, (ii) switch in the higher-order boundary conditions during monotonic plastic loading, (iii) the use of non-quadratic defect energies, and (iv) the prediction of experimental data, we mainly show that (a) including the plastic spin contribution in a gradient plasticity theory is highly recommendable to model small-scale plasticity, (b) less-than-quadratic defect energies may help in describing the experimental results, but they may lead to anomalous cyclic behaviour, and (c) dissipative (unrecoverable) higher-order finite stresses are responsible for an unexpected mechanical response under non-proportional loading.
Two-dimensional angular filter array for angular domain imaging with 3D printed angular filters
NASA Astrophysics Data System (ADS)
Ng, Eldon; Carson, Jeffrey J. L.
2013-02-01
Angular Domain Imaging (ADI) is a technique that is capable of generating two dimensional shadowgrams of attenuating targets embedded in a scattering medium. In ADI, an angular filter array (AFA) is positioned between the sample and the detector to distinguish between quasi-ballistic photons and scattered photons. An AFA is a series of micro-channels with a high aspect ratio. Previous AFAs from our group were constructed by micro-machining the micro-channels into a silicon wafer, limiting the imaging area to a one dimensional line. Two dimensional images were acquired via scanning. The objective of this work was to extend the AFA design to two dimensions to allow for two dimensional imaging with minimal scanning. The second objective of this work was to perform an initial characterization of the imaging capabilities of the 2D AFA. Our approach was to use rapid 3D prototyping techniques to generate an array of micro-channels. The imaging capabilities were then evaluated by imaging a 0.9 mm graphite rod submerged in a scattering media. Contrast was observed to improve when a second angular filter array was placed in front of the sample to mask the incoming light.
Usefulness of T2*-weighted MRI in the detection of adnexal torsion
Kawai, Nobuyuki; Kanematsu, Masayuki; Kawaguchi, Shimpei; Kojima, Toshihisa; Furui, Tatsuro; Morishige, Ken-ichirou; Matsuo, Masayuki
2016-01-01
Background The usefulness of T2*-weighted (T2*W) imaging for the detection of adnexal torsion has yet to be determined. Purpose To assess the usefulness of T2*W imaging for detecting and differentiating adnexal torsion. Material and Methods Eight patients with eight ovaries with torsion and 44 patients with 72 ovaries without torsion were included in this study. All patients underwent 1.5-T magnetic resonance imaging (MRI) including T2*W images. The frequency and distribution of hypointensity on T2*W images were compared between ovaries with torsion and ovaries without torsion. Results Hypointensity on T2*W images was significantly more frequent in ovaries with torsion than in ovaries without torsion (75% vs. 36%; P < 0.05). Among patients with hypointensity on T2*W images, the frequency of diffuse hypointensity was significantly higher in ovaries with torsion than in ovaries without torsion (83% vs. 0%; P < 0.01); whereas the frequency of focal hypointensity was significantly lower in ovaries with torsion than in ovaries without torsion (17% vs. 100%; P < 0.01). Conclusion The presence and distribution of hypointensity on T2*W images may play a supplementary role in the detection of adnexal torsion. PMID:27478621
Kuhn, T; Gullett, J M; Nguyen, P; Boutzoukas, A E; Ford, A; Colon-Perez, L M; Triplett, W; Carney, P R; Mareci, T H; Price, C C; Bauer, R M
2016-06-01
This study examined the reliability of high angular resolution diffusion tensor imaging (HARDI) data collected on a single individual across several sessions using the same scanner. HARDI data was acquired for one healthy adult male at the same time of day on ten separate days across a one-month period. Environmental factors (e.g. temperature) were controlled across scanning sessions. Tract Based Spatial Statistics (TBSS) was used to assess session-to-session variability in measures of diffusion, fractional anisotropy (FA) and mean diffusivity (MD). To address reliability within specific structures of the medial temporal lobe (MTL; the focus of an ongoing investigation), probabilistic tractography segmented the Entorhinal cortex (ERc) based on connections with Hippocampus (HC), Perirhinal (PRc) and Parahippocampal (PHc) cortices. Streamline tractography generated edge weight (EW) metrics for the aforementioned ERc connections and, as comparison regions, connections between left and right rostral and caudal anterior cingulate cortex (ACC). Coefficients of variation (CoV) were derived for the surface area and volumes of these ERc connectivity-defined regions (CDR) and for EW across all ten scans, expecting that scan-to-scan reliability would yield low CoVs. TBSS revealed no significant variation in FA or MD across scanning sessions. Probabilistic tractography successfully reproduced histologically-verified adjacent medial temporal lobe circuits. Tractography-derived metrics displayed larger ranges of scanner-to-scanner variability. Connections involving HC displayed greater variability than metrics of connection between other investigated regions. By confirming the test retest reliability of HARDI data acquisition, support for the validity of significant results derived from diffusion data can be obtained.
Kuhn, T.; Gullett, J. M.; Nguyen, P.; Boutzoukas, A. E.; Ford, A.; Colon-Perez, L. M.; Triplett, W.; Carney, P.R.; Mareci, T. H.; Price, C. C.; Bauer, R. M.
2015-01-01
Introduction This study examined the reliability of high angular resolution diffusion tensor imaging (HARDI) data collected on a single individual across several sessions using the same scanner. Methods HARDI data was acquired for one healthy adult male at the same time of day on ten separate days across a one-month period. Environmental factors (e.g. temperature) were controlled across scanning sessions. Tract Based Spatial Statistics (TBSS) was used to assess session-to-session variability in measures of diffusion, fractional anisotropy (FA) and mean diffusivity (MD). To address reliability within specific structures of the medial temporal lobe (MTL; the focus of an ongoing investigation), probabilistic tractography segmented the Entorhinal cortex (ERc) based on connections with Hippocampus (HC), Perirhinal (PRc) and Parahippocampal (PHc) cortices. Streamline tractography generated edge weight (EW) metrics for the aforementioned ERc connections and, as comparison regions, connections between left and right rostral and caudal anterior cingulate cortex (ACC). Coefficients of variation (CoV) were derived for the surface area and volumes of these ERc connectivity-defined regions (CDR) and for EW across all ten scans, expecting that scan-to-scan reliability would yield low CoVs. Results TBSS revealed no significant variation in FA or MD across scanning sessions. Probabilistic tractography successfully reproduced histologically-verified adjacent medial temporal lobe circuits. Tractography-derived metrics displayed larger ranges of scanner-to-scanner variability. Connections involving HC displayed greater variability than metrics of connection between other investigated regions. Conclusions By confirming the test retest reliability of HARDI data acquisition, support for the validity of significant results derived from diffusion data can be obtained. PMID:26189060
Temperature dependence of angular momentum transport across interfaces
NASA Astrophysics Data System (ADS)
Chen, Kai; Lin, Weiwei; Chien, C. L.; Zhang, Shufeng
2016-08-01
Angular momentum transport in magnetic multilayered structures plays a central role in spintronic physics and devices. The angular momentum currents or spin currents are carried by either quasiparticles such as electrons and magnons, or by macroscopic order parameters such as local magnetization of ferromagnets. Based on the generic interface exchange interaction, we develop a microscopic theory that describes interfacial spin conductance for various interfaces among nonmagnetic metals, ferromagnetic insulators, and antiferromagnetic insulators. Spin conductance and its temperature dependence are obtained for different spin batteries including spin pumping, temperature gradient, and spin Hall effect. As an application of our theory, we calculate the spin current in a trilayer made of a ferromagnetic insulator, an antiferromagnetic insulator, and a nonmagnetic heavy metal. The calculated results on the temperature dependence of spin conductance quantitatively agree with the existing experiments.
Fault diagnosis of planetary gearboxes via torsional vibration signal analysis
NASA Astrophysics Data System (ADS)
Feng, Zhipeng; Zuo, Ming J.
2013-04-01
Torsional vibration signals are theoretically free from the amplitude modulation effect caused by time variant vibration transfer paths due to the rotation of planet carrier and sun gear, and therefore their spectral structure are simpler than transverse vibration signals. Thus, it is potentially easy and effective to diagnose planetary gearbox faults via torsional vibration signal analysis. We give explicit equations to model torsional vibration signals, considering both distributed gear faults (like manufacturing or assembly errors) and local gear faults (like pitting, crack or breakage of one tooth), and derive the characteristics of both the traditional Fourier spectrum and the proposed demodulated spectra of amplitude envelope and instantaneous frequency. These derivations are not only effective to diagnose single gear fault of planetary gearboxes, but can also be generalized to detect and locate multiple gear faults. We validate experimentally the signal models, as well as the Fourier spectral analysis and demodulation analysis methods.
Torsion Strain Effects on Critical Currents of Hts Superconducting Tapes
NASA Astrophysics Data System (ADS)
Takayasu, Makoto; Minervini, Joseph V.; Bromberg, Leslie
2010-04-01
A torsional twist strain effect on the critical current of a thin HTS tape has been found to be well described by a longitudinal strain model taking into account the internal shortening compressive strains accompanied with the tensile longitudinal strains due to a torsional twist. The critical current of a twisted tape is given by the integration of the critical current densities corresponding to the strain distribution over the tape cross-section using axial strain data of the tape. The model is supported with experimental results of YBCO and BSCCO-2223 tapes. It has been also found that torsional twisting effects on the critical currents of a tape composing of the conventional lapped-tape cable and the twisted stacked-tape cable are described by the same equation as that of a twisted single tape.
Complete axial torsion of pregnant uterus with leiomyoma
Sachan, Rekha; Patel, M L; Sachan, Pushpalata; Arora, Anubha
2014-01-01
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
Torsion-balance experiments and ultra-low-mass fields
NASA Astrophysics Data System (ADS)
Terrano, William
2017-01-01
Many of the solutions to outstanding problems in modern cosmology posit new, ultra-light fields. Unifying General Relativity and Quantum Mechanics appears to require new ultra-light fields at some level. Such fields are also invoked to drive inflation and dark energy. Ultra-light fields may also make up much or all of the dark matter density of the universe. Torsion pendulums, a technology that dates to the 18th century, remain one of the most sensitive experimental techniques to search for ultra-light, weakly interacting fields. I will explain how torsion balance experiments can search for beyond-the-standard-model fields using laboratory-based as well as galactic sources, and the important cosmological implications of these measurements. I will also describe a new experimental signature for which certain torsion balance geometries make very sensitive direct dark matter detectors over a broad range of interesting dark matter parameter space.
BCN nanotubes as highly sensitive torsional electromechanical transducers.
Garel, Jonathan; Zhao, Chong; Popovitz-Biro, Ronit; Golberg, Dmitri; Wang, Wenlong; Joselevich, Ernesto
2014-11-12
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.
NASA Technical Reports Server (NTRS)
Herbst, Eric; Winnewisser, G.; Yamada, K. M. T.; Defrees, D. J.; Mclean, A. D.
1989-01-01
A mechanism for the enhanced splitting detected in the millimeter-wave rotational spectra of the first excited S-S stretching state of HSSH (disulfane) has been studied. The mechanism, which involves a potential coupling between the first excited S-S stretching state and excited torsional states, has been investigated in part by the use of ab initio theory. Based on an ab initio potential surface, coupling matrix elements have been calculated, and the amount of splitting has then been estimated by second-order perturbation theory. The result, while not in quantitative agreement with the measured splitting, lends plausibility to the assumed mechanism.
Edge delamination of composite laminates subject to combined tension and torsional loading
NASA Technical Reports Server (NTRS)
Hooper, Steven J.
1990-01-01
Delamination is a common failure mode of laminated composite materials. Edge delamination is important since it results in reduced stiffness and strength of the laminate. The tension/torsion load condition is of particular significance to the structural integrity of composite helicopter rotor systems. Material coupons can easily be tested under this type of loading in servo-hydraulic tension/torsion test stands using techniques very similar to those used for the Edge Delamination Tensile Test (EDT) delamination specimen. Edge delamination of specimens loaded in tension was successfully analyzed by several investigators using both classical laminate theory and quasi-three dimensional (Q3D) finite element techniques. The former analysis technique can be used to predict the total strain energy release rate, while the latter technique enables the calculation of the mixed-mode strain energy release rates. The Q3D analysis is very efficient since it produces a three-dimensional solution to a two-dimensional domain. A computer program was developed which generates PATRAN commands to generate the finite element model. PATRAN is a pre- and post-processor which is commonly used with a variety of finite element programs such as MCS/NASTRAN. The program creates a sufficiently dense mesh at the delamination crack tips to support a mixed-mode fracture mechanics analysis. The program creates a coarse mesh in those regions where the gradients in the stress field are low (away from the delamination regions). A transition mesh is defined between these regions. This program is capable of generating a mesh for an arbitrarily oriented matrix crack. This program significantly reduces the modeling time required to generate these finite element meshes, thus providing a realistic tool with which to investigate the tension torsion problem.
Zgarbová, Marie; Luque, F. Javier; Šponer, Jiří; Cheatham, Thomas E.; Otyepka, Michal; Jurečka, Petr
2013-01-01
We present a refinement of the backbone torsion parameters ε and ζ of the Cornell et al. AMBER force field for DNA simulations. The new parameters, denoted as εζOL1, were derived from quantum-mechanical calculations with inclusion of conformation-dependent solvation effects according to the recently reported methodology (J. Chem. Theory Comput. 2012, 7(9), 2886-2902). The performance of the refined parameters was analyzed by means of extended molecular dynamics (MD) simulations for several representative systems. The results showed that the εζOL1 refinement improves the backbone description of B-DNA double helices and G-DNA stem. In B-DNA simulations, we observed an average increase of the helical twist and narrowing of the major groove, thus achieving better agreement with X-ray and solution NMR data. The balance between populations of BI and BII backbone substates was shifted towards the BII state, in better agreement with ensemble-refined solution experimental results. Furthermore, the refined parameters decreased the backbone RMS deviations in B-DNA MD simulations. In the antiparallel guanine quadruplex (G-DNA) the εζOL1 modification improved the description of non-canonical α/γ backbone substates, which were shown to be coupled to the ε/ζ torsion potential. Thus, the refinement is suggested as a possible alternative to the current ε/ζ torsion potential, which may enable more accurate modeling of nucleic acids. However, long-term testing is recommended before its routine application in DNA simulations. PMID:24058302
Variable Distance Angular Symbology Reader
NASA Technical Reports Server (NTRS)
Schramm, Harry F., Jr. (Inventor); Corder, Eric L. (Inventor)
2006-01-01
A variable distance angular symbology, reader utilizes at least one light source to direct light through a beam splitter and onto a target. A target may be angled relative to the impinging light beam up to and maybe even greater than 45deg. A reflected beam from the target passes through the beam splitter and is preferably directed 90deg relative to the light source through a telecentric lens to a scanner which records an image of the target such as a direct part marking code.
Vaughn, Mark R.; Robinett, III, Rush D.; Phelan, John R.; Van Zuiden, Don M.
1997-01-21
A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.
NASA Technical Reports Server (NTRS)
Kvaternik, R. G.; Kaza, K. R. V.
1976-01-01
The nonlinear curvature expressions for a twisted rotor blade or a beam undergoing transverse bending in two planes, torsion, and extension were developed. The curvature expressions were obtained using simple geometric considerations. The expressions were first developed in a general manner using the geometrical nonlinear theory of elasticity. These general nonlinear expressions were then systematically reduced to four levels of approximation by imposing various simplifying assumptions, and in each of these levels the second degree nonlinear expressions were given. The assumptions were carefully stated and their implications with respect to the nonlinear theory of elasticity as applied to beams were pointed out. The transformation matrices between the deformed and undeformed blade-fixed coordinates, which were needed in the development of the curvature expressions, were also given for three of the levels of approximation. The present curvature expressions and transformation matrices were compared with corresponding expressions existing in the literature.
NASA Astrophysics Data System (ADS)
Abdi, Javad; Keivani, Maryam; Abadyan, Mohamadreza
2016-06-01
The physico-mechanical behavior of nanoscale devices might be microstructure dependent. However, the classical continuum theory cannot correctly predict the microstructure dependency. In this paper, the strain gradient theory is employed to examine the instability characteristics of a nanoscanner with circular geometry. The governing equation of the scanner is derived incorporating the Coulomb and van der Waals (vdW) forces. The influences of applied voltage, squeeze damping and microstructure parameters on the dynamic instability of equilibrium points are studied by plotting the phase portrait and bifurcation diagrams. In the presence of the applied voltage, the phase portrait shows the saddle-node bifurcation while for freestanding scanner a subcritical pitchfork bifurcation is observed. It is concluded that the microstructure parameter enhances the torsional stability.
Determining Angle of Humeral Torsion Using Image Software Technique
Sethi, Madhu; Vasudeva, Neelam
2016-01-01
Introduction Several researches have been done on the measurement of angles of humeral torsion in different parts of the world. Previously described methods were more complicated, not much accurate, cumbersome or required sophisticated instruments. Aim The present study was conducted with the aim to determine the angles of humeral torsion with a newer simple technique using digital images and image tool software. Materials and Methods A total of 250 dry normal adult human humeri were obtained from the bone bank of Department of Anatomy. The length and mid-shaft circumference of each bone was measured with the help of measuring tape. The angle of humeral torsion was measured directly from the digital images by the image analysis using Image Tool 3.0 software program. The data was analysed statistically with SPSS version 17 using unpaired t-test and Spearman’s rank order correlation coefficient. Results The mean angle of torsion was 64.57°±7.56°. On the right side it was 66.84°±9.69°, whereas, on the left side it was found to be 63.31±9.50°. The mean humeral length was 31.6 cm on right side and 30.33 cm on left side. Mid shaft circumference was 5.79 on right side and 5.63 cm on left side. No statistical differences were seen in angles between right and left humeri (p>0.001). Conclusion From our study, it was concluded that circumference of shaft is inversely proportional to angle of humeral torsion. The length and side of humerus has no relation with the humeral torsion. With advancement of digital technology, it is better to use new image softwares for anatomical studies. PMID:27891326
Impact of torsion and stretching on the thermal conductivity of polyethylene strands
NASA Astrophysics Data System (ADS)
Tu, Runchun; Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei
2017-03-01
A single polyethylene chain was reported to have a high metal-like thermal conductivity (TC), which stands in sharp contrast to the thermally insulating feature of common bulk polyethylene materials. This work numerically investigates the impact of torsion and stretching on the TC of polyethylene strands by using equilibrium molecular dynamics simulations. The simulation results show that torsion slightly reduces the TC of a single polyethylene chain. In contrast, the heat conduction of polyethylene strands could be slightly enhanced under torsional loading with a specific torsional angle. Particularly, an apparent improvement of TC of polyethylene strands is achieved by combining torsion and stretching functions. It is found that the TC of torsional polyethylene strands is sensitive to torsional patterns. Our study proposes a specific torsional pattern of polyethylene strands that significantly enhances the heat conduction of the original counterpart. This study will play an essential role in guiding the improvements of thermal conduction property of polymers.
Kodali, Sunil Kumar; Abdullah, Zuhair Saleh; Sharma, Punit; Khan, Muhammad Umar; Naeem, Muhammad
2013-01-01
Torsion of undescended testis, although not uncommon, causes diagnostic difficulties. We here present testicular scintigraphy images of a typical case of torsion of an undescended inguinal testis with disparity between clinical and ultrasonography (USG) findings in the contralateral retractile testis.
Torsional instability in suspension bridges: The Tacoma Narrows Bridge case
NASA Astrophysics Data System (ADS)
Arioli, Gianni; Gazzola, Filippo
2017-01-01
All attempts of aeroelastic explanations for the torsional instability of suspension bridges have been somehow criticised and none of them is unanimously accepted by the scientific community. We suggest a new nonlinear model for a suspension bridge and we perform numerical experiments with the parameters corresponding to the collapsed Tacoma Narrows Bridge. We show that the thresholds of instability are in line with those observed the day of the collapse. Our analysis enables us to give a new explanation for the torsional instability, only based on the nonlinear behavior of the structure.
Coated Fused Silica Fibers for Enhanced Sensitivity Torsion Pendulum
NASA Technical Reports Server (NTRS)
Numata, Kenji; Horowitz, Jordan; Camp, Jordan
2007-01-01
In order to investigate the fundamental thermal noise limit of a torsion pendulum using a fused silica fiber, we systematically measured and modeled the mechanical losses of thin fused silica fibers coated by electrically conductive thin metal films. Our results indicate that it is possible to achieve a thermal noise limit for coated silica lower by a factor between 3 and 9, depending on the silica diameter, compared to the best tungsten fibers available. This will allow a corresponding increase in sensitivity of torsion pendula used for weak force measurements, including the gravitational constant measurement and ground-based force noise testing for the Laser Interferometer Space Antenna (LISA) mission.
Free torsional vibrations of tapered cantilever I-beams
NASA Astrophysics Data System (ADS)
Rao, C. Kameswara; Mirza, S.
1988-08-01
Torsional vibration characteristics of linearly tapered cantilever I-beams have been studied by using the Galerkin finite element method. A third degree polynomial is assumed for the angle of twist. The analysis presented is valid for long beams and includes the effect of warping. The individual as well as combined effects of linear tapers in the width of the flanges and the depth of the web on the torsional vibration of cantilever I-beams are investigated. Numerical results generated for various values of taper ratios are presented in graphical form.
Portal venous thrombosis developing after torsion of a wandering spleen.
Yilmaz, Ö; Kiziltan, R; Almali, N; Aras, A
2017-03-01
Torsion of a wandering spleen is a rare disease. The symptoms and signs of this condition are only present when the splenic pedicle torts. The etiological factors are the congenital absence of the ligaments that hold the spleen in its normal anatomic position, or the relaxation of these ligaments resulting from conditions like trauma and abdominal surgery. We aimed to present a rare case with torsion of wandering spleen that consequently developed thrombosis of portal vein and its branches, taking into consideration the relevant literature.
Wandering spleen with chronic torsion in a patient with thalassaemia.
Ho, Chi Long
2014-12-01
Wandering spleen or splenoptosis is an uncommon entity and often an asymptomatic finding of acute abdomen in the emergency department. A high index of suspicion for splenic torsion is required, particularly in patients with known splenomegaly, as this condition could potentially lead to splenic infarction. Recognition of this condition can help avoid potential confusion with acute abdomen of other aetiologies. Herein, we present a unique case of wandering spleen with chronic torsion, which, to the best of our knowledge, has never been described in an elderly patient with haemoglobin H thalassaemia. We also review the literature for the aetiology and pathogenesis of wandering spleen, and discuss the relevant diagnostic modalities and treatment options.
A monolithically integrated torsional CMOS-MEMS relay
NASA Astrophysics Data System (ADS)
Riverola, M.; Sobreviela, G.; Torres, F.; Uranga, A.; Barniol, N.
2016-11-01
We report experimental demonstrations of a torsional microelectromechanical (MEM) relay fabricated using the CMOS-MEMS approach (or intra-CMOS) which exploits the full foundry inherent characteristics enabling drastic reduction of the fabrication costs and batch production. In particular, the relay is monolithically integrated in the back end of line of a commercial standard CMOS technology (AMS 0.35 μm) and released by means of a simple one-step mask-less wet etching. The fabricated torsional relay exhibits an extremely steep switching behaviour symmetrical about both contact sides with an on-state contact resistance in the k Ω -range throughout the on-off cycling test.
Albino, Giuseppe; Nenna, Rosanna; Corvasce, Antonio; Marucco, Ettore Cirillo
2012-12-01
Cases of torsion of the spermatic cord are rare in men over 30-years-old. Testicular tumors manifest themselves rarely with symptoms of acute scrotum. We report the case of a 38-years-old patient who presented for a suspected left testis torsion. On examination, the testicle was markedly increased in size and painful. The manual derotation made pain dramatically disappear. He came to our attention after about a month asking for an orchidopexy. During the surgery a biopsy was performed. The diagnosis was a Yolk Sac Tumor. A radical inguinal orchiectomy was performed with left hemiscrotal excision, "in block". He performed four cycles of chemotherapy and with no recurrence after 12 months of follow-up. In literature only seven cases of torsion of an intrascrotal testicle with cancer are reported. Our case is the eighth one.
Controlling neutron orbital angular momentum.
Clark, Charles W; Barankov, Roman; Huber, Michael G; Arif, Muhammad; Cory, David G; Pushin, Dmitry A
2015-09-24
The quantized orbital angular momentum (OAM) of photons offers an additional degree of freedom and topological protection from noise. Photonic OAM states have therefore been exploited in various applications ranging from studies of quantum entanglement and quantum information science to imaging. The OAM states of electron beams have been shown to be similarly useful, for example in rotating nanoparticles and determining the chirality of crystals. However, although neutrons--as massive, penetrating and neutral particles--are important in materials characterization, quantum information and studies of the foundations of quantum mechanics, OAM control of neutrons has yet to be achieved. Here, we demonstrate OAM control of neutrons using macroscopic spiral phase plates that apply a 'twist' to an input neutron beam. The twisted neutron beams are analysed with neutron interferometry. Our techniques, applied to spatially incoherent beams, demonstrate both the addition of quantum angular momenta along the direction of propagation, effected by multiple spiral phase plates, and the conservation of topological charge with respect to uniform phase fluctuations. Neutron-based studies of quantum information science, the foundations of quantum mechanics, and scattering and imaging of magnetic, superconducting and chiral materials have until now been limited to three degrees of freedom: spin, path and energy. The optimization of OAM control, leading to well defined values of OAM, would provide an additional quantized degree of freedom for such studies.
Left common basal pyramid torsion following left upper lobectomy/segmentectomy.
Wang, Wei-Li; Cheng, Yen-Po; Cheng, Ching-Yuan; Wang, Bing-Yen
2015-05-01
Lobar or segmental lung torsion is a severe complication of lung resection. To the best of our knowledge, common basal pyramid torsion has never been reported. We describe a case of left basal pyramid torsion after left upper lobectomy and superior segmentectomy, which was successfully treated by thoracoscopic surgery.
Fedoruk, Sergey Ivanov, Evgeny; Smilga, Andrei
2014-05-15
We present simple models of N= 4 supersymmetric mechanics with ordinary and mirror linear (4, 4, 0) multiplets that give a transparent description of Hyper-Kähler with Torsion (HKT), Clifford Kähler with Torsion (CKT), and Octonionic Kähler with Torsion (OKT) geometries. These models are treated in the N= 4 and N=2 superfield approaches, as well as in the component approach. Our study makes manifest that the CKT and OKT supersymmetric sigma models are distinguished from the more simple HKT models by the presence of extra holomorphic torsion terms in the supercharges.
Angular sensitivity for a Fabry-Perot structure incorporating different dielectric materials
NASA Astrophysics Data System (ADS)
Wu, Shangliang; Ye, Yan; Zhou, Yun; Huang, Wenbin; Liu, Yanhua; Qiao, Wen; Wang, Yanyan; Luo, Minghui; Chen, Linsen
2016-11-01
Color filters based on different Fabry-Perot structures are investigated extensively, and incident angle dependency is an important characteristic in practical applications. Here, we investigated a color filter incorporating a Fabry-Perot structure, discussing its reflective angular sensitivity related to refractive index of its dielectric material. By finite difference time domain(FDTD) theory, the refractive index of the dielectric material is found to influence the angular sensitivity greatly while the optical thickness keeps constant. The simulated results shows that the higher the dielectric layer's refractive index is, the more angular insensitive of the reflection will be obtained and a good angular insensitive will achieved when the refractive index is larger than 2.1. Finally, samples with different dielectric layer are fabricated in experiment and the measured results verify influence of the refractive index of dielectric layer on the spectra angular sensitivity, which is helpful for the application of color filter in color display, image sensors and decoration.
NASA Astrophysics Data System (ADS)
Krak, Michael D.; Singh, Rajendra
2016-09-01
Vehicle clutch dampers belong to a family of torsional devices or isolators that contain multi-staged torsional springs, pre-load features, clearances, and multi-staged dry friction elements. Estimation of elastic and dissipative parameters is usually carried out under quasi-static loading and then these static parameters are often assumed when predicting dynamic responses. For the purpose of comparison, this article proposes a new time domain parameter estimation method under dynamic, transient loading conditions. The proposed method assumes a priori knowledge of few nonlinear features based on the design and quasi-static characterization. Angular motion measurements from a component-level laboratory experiment under dynamic loading are utilized. Elastic parameters are first estimated through an instantaneous stochastic linearization technique. A model-based approach and energy balance principle are employed to estimate a combination of viscous and Coulomb damping parameters for seven local (stage-dependent) and global damping formulations for a practical device. The proposed method is validated by comparing time domain predictions from nonlinear models to dynamic measurements. Nonlinear models that utilize the proposed damping formulations are found to be superior to those that solely rely on parameters from a quasi-static experiment.
Linking the HOMO-LUMO gap to torsional disorder in P3HT/PCBM blends
McLeod, John A.; Pitman, Amy L.; Moewes, Alexander; Kurmaev, Ernst Z.; Finkelstein, Larisa D.; Zhidkov, Ivan S.; Savva, Achilleas
2015-12-14
The electronic structure of [6,6]-phenyl C{sub 61} butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT), and P3HT/PCBM blends is studied using soft X-ray emission and absorption spectroscopy and density functional theory calculations. We find that annealing reduces the HOMO-LUMO gap of P3HT and P3HT/PCBM blends, whereas annealing has little effect on the HOMO-LUMO gap of PCBM. We propose a model connecting torsional disorder in a P3HT polymer to the HOMO-LUMO gap, which suggests that annealing helps to decrease the torsional disorder in the P3HT polymers. Our model is used to predict the characteristic length scales of the flat P3TH polymer segments in P3HT and P3HT/PCBM blends before and after annealing. Our approach may prove useful in characterizing organic photovoltaic devices in situ or even in operando.
NASA Technical Reports Server (NTRS)
Hartman, Edwin P; Biermann, David
1938-01-01
The torsional deflection of the blades of three full-scale aluminum-alloy propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10 degree was found at a v/nd of 0.3 and a smaller deflection at higher values of v/nd for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading-transit method used in the previous test.
NASA Technical Reports Server (NTRS)
Hartman, Edwin P.; Biermann, David
1938-01-01
The torsional deflection of the blades of three full-scale duralumin propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10th of a degree was found at V/nD of 0.3 and a smaller deflection at higher values of V/nD for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading transit method used in the previous tests.
Long-wavelength torsional modes of solar coronal plasma structures
NASA Astrophysics Data System (ADS)
Vasheghani Farahani, S.; Nakariakov, V. M.; van Doorsselaere, T.
2010-07-01
Aims: We consider the effects of the magnetic twist and plasma rotation on the propagation of torsional m = 0 perturbations of cylindrical plasma structures (straight magnetic flux tubes) in the case when the wavelength is much longer than the cylinder diameter. Methods: The second order thin flux tube approximation is used to derive dispersion relations and phase relations in linear long-wavelength axisymmetric magnetohydrodynamic waves in uniformly twisted and rotating plasma structures. Results: Asymptotic dispersion relations linking phase speeds with the plasma parameters are derived. When twist and rotation are both present, the phase speed of torsional waves depends upon the direction of the wave propagation, and also the waves are compressible. The phase relations show that in a torsional wave the density and azimuthal magnetic field perturbations are in phase with the axial magnetic field perturbations and anti-phase with tube cross-section perturbations. In a zero-β non-rotating plasma cylinder confined by the equilibrium twist, the density perturbation is found to be about 66 percent of the amplitude of the twist perturbation in torsional waves.
Torsional Oscillations and Waves Projected on the Wall
ERIC Educational Resources Information Center
Bartlett, Albert A.
2008-01-01
The article "Torsional Oscillations with Lorentz Force" by Paul Gluck provides a glimpse into the major world of ancient physics demonstrations in the late 19th and first half of the 20th centuries. The apparatus that was described and similar pieces of apparatus are the basis for many memorable but long forgotten educational demonstrations. The…
Ectopic ovary with torsion: uncommon diagnosis made by ultrasound
Castro, Adham do Amaral e; Morandini, Fernando; Calixto, Caroline Paludo; Barros, Wagner Haese; Nakatani, Edson Tetsuya; Castro, Allan do Amaral e
2017-01-01
Ultrasound is an important diagnostic tool in inguinal hernia and in the evaluation of the contents of the hernia sac. This report presents a case in which ultrasound revealed a herniated ectopic ovary, complicated by torsion of its vascular pedicle, in the right labia majora. We also present a brief discussion of ovarian hernia, its potential complications, and the treatments available. PMID:28298734
Solution of elastoplastic torsion problem by boundary integral method
NASA Technical Reports Server (NTRS)
Mendelson, A.
1975-01-01
The boundary integral method was applied to the elastoplastic analysis of the torsion of prismatic bars, and the results are compared with those obtained by the finite difference method. Although fewer unknowns were used, very good accuracy was obtained with the boundary integral method. Both simply and multiply connected bodies can be handled with equal ease.
New Approaches to Data Acquisitions in a Torsion Pendulum Experiment
ERIC Educational Resources Information Center
Jiang, Daya; Xiao, Jinghua; Li, Haihong; Dai, Qionglin
2007-01-01
In this paper, two simple non-contact and cost-effective methods to acquire data in the student laboratory are applied to investigate the motion of a torsion pendulum. The first method is based on a Hall sensor, while the second makes use of an optical mouse.
Quaternionic Torsion Geometry, Superconformal Symmetry and T-duality
Swann, Andrew
2009-02-02
HyperKaehler metrics with torsion (HKT metrics) are constructed via superconformal symmetry. It is shown how T-duality interpreted as a twist construction for circle actions provides a number of compact simply-connected examples. Further applications of the twist construction are discussed to obtain compact simply-connected HKT manifolds with few symmetries and to construct all HKT nilmanifolds.
A measurement of G with a cryogenic torsion pendulum.
Newman, Riley; Bantel, Michael; Berg, Eric; Cross, William
2014-10-13
A measurement of Newton's gravitational constant G has been made with a cryogenic torsion pendulum operating below 4 K in a dynamic mode in which G is determined from the change in torsional period when a field source mass is moved between two orientations. The source mass was a pair of copper rings that produced an extremely uniform gravitational field gradient, whereas the pendulum was a thin fused silica plate, a combination that minimized the measurement's sensitivity to error in pendulum placement. The measurement was made using an as-drawn CuBe torsion fibre, a heat-treated CuBe fibre, and an as-drawn Al5056 fibre. The pendulum operated with a set of different large torsional amplitudes. The three fibres yielded high Q-values: 82 000, 120 000 and 164 000, minimizing experimental bias from fibre anelasticity. G-values found with the three fibres are, respectively: {6.67435(10),6.67408(15),6.67455(13)}×10(-11) m(3) kg(-1) s(-2), with corresponding uncertainties 14, 22 and 20 ppm. Relative to the CODATA2010 G-value, these are higher by 77, 37 and 107 ppm, respectively. The unweighted average of the three G-values, with the unweighted average of their uncertainties, is 6.67433(13)×10(-11) m(3) kg(-1) s(-2) (19 ppm).
34. VERTICAL AND TORSIONAL MOTION VIEWED FROM EAST TOWER, 7 ...
34. VERTICAL AND TORSIONAL MOTION VIEWED FROM EAST TOWER, 7 NOVEMBER 1940, FROM 16MN FILM SHOT BY PROFESSOR F.B. FARQUHARSON, UNIVERSITY OF WASHINGTON. (LABORATORY STUDIES ON THE TACOMA NARROWS BRIDGE, AT UNIVERSITY OF WASHINGTON (SEATTLE: UNIVERSITY OF WASHINGTON, DEPARTMENT OF CIVIL ENGINEERING, 1941) - Tacoma Narrows Bridge, Spanning Narrows at State Route 16, Tacoma, Pierce County, WA
Protective role of erythropoietin during testicular torsion of the rats.
Yazihan, Nuray; Ataoglu, Haluk; Koku, Naim; Erdemli, Esra; Sargin, Ayse Kose
2007-10-01
Testicular torsion is an important clinical urgency. Similar mechanisms occurred after detorsion of the affected testis as in the ischemia reperfusion (I/R) damage. This study was designed to investigate the effects of erythropoietin (EPO) treatment after unilateral testicular torsion. Fifty male Sprague-Dawley rats were divided into five groups. Group 1 underwent a sham operation of the right testis under general anesthesia. Group 2 was same as sham, and EPO (3,000 IU/kg) infused i.p., group 3 underwent a similar operation but the right testis was rotated 720 degrees clockwise for 1 h, maintained by fixing the testis to the scrotum, and saline infused during the procedure. Group 4 underwent similar torsion but EPO was infused half an hour before the detorsion procedure, and in group 5, EPO was infused after detorsion procedure. Four hours after detorsion, ipsilateral and contralateral testes were taken out for evaluation. Treatment with EPO improved testicular structures in the ipsilateral testis but improvement was less in the contralateral testis histologically, but EPO treatment decreased germ cell apoptosis in both testes following testicular IR. TNF-alpha, IL-1beta, IL-6 and nitrite levels decreased after EPO treatment especially in the ipsilateral testis. We conclude that testicular I/R causes an increase in germ cell apoptosis both in the ipsilateral and contralateral testes. Erythropoietin has antiapoptotic and anti-inflammatory effects following testicular torsion.
Otçu, Selçuk; Durakoğugil, Murat; Orer, Hakan S; Tanyel, Feridun C
2002-10-01
The decrease in blood flow due to the activation of sympathetic system has been suggested to play a role in contralateral testicular deterioration associated with unilateral testicular torsion. Sympathetic nerve discharges (SND) from the genitofemoral nerve were evaluated before and during unilateral testicular torsion. Under urethane anesthesia, arterial blood pressure and SND from splanchnic and right genitofemoral nerves were recorded in 12 male Sprague-Dawley rats, 8 of which were included in subsequent analyses. After control recordings of basal discharges for 2 min the left testis was twisted 720 degrees counterclockwise, and recording was resumed for an additional 30 min. Changes in nerve activity were calculated by measuring the area under the autospectrum curve, and alterations were compared. Following testicular torsion no significant changes were obtained for splanchnic SND, but the amplitude of SND from contralateral genitofemoral nerve showed an overall increase of 21.20+/-7.03% in six rats. This increase lasted about 10-15 min and activities returned to pretorsion levels. In two other rats no significant change was observed in either splanchnic or genitofemoral SND. Ipsilateral testicular torsion results in a transient increase in genitofemoral SND. A possible autonomic reflex mechanism may exist, and it may be activated by noxious stimuli from contralateral side. This reflex mechanism may initiate a series of events that lead to the injury of contralateral testis.
Angular Positioning Sensor for Space Mechanisms
NASA Astrophysics Data System (ADS)
Steiner, Nicolas; Chapuis, Dominique
2013-09-01
Angular position sensors are used on various rotating mechanisms such as solar array drive mechanisms, antenna pointing mechanisms, scientific instruments, motors or actuators.Now a days, potentiometers and encoders are mainly used for angular measurement purposes. Both of them have their own pros and cons.As alternative, Ruag Space Switzerland Nyon (RSSN) is developing and qualifying two innovative technologies of angular position sensors which offer easy implementation, medium to very high lifetime and high flexibility with regards to the output signal shape/type.The Brushed angular position sensor uses space qualified processes which are already flying on RSSN's sliprings for many years. A large variety of output signal shape can be implemented to fulfill customer requirements (digital, analog, customized, etc.).The contactless angular position sensor consists in a new radiation hard Application Specific Integrated Circuit (ASIC) based on the Hall effect and providing the angular position without complex processing algorithm.
Oral candidiasis and angular cheilitis.
Sharon, Victoria; Fazel, Nasim
2010-01-01
Candidiasis, an often encountered oral disease, has been increasing in frequency. Most commonly caused by the overgrowth of Candida albicans, oral candidiasis can be divided into several categories including acute and chronic forms, and angular cheilitis. Risk factors for the development of oral candidiasis include immunosuppression, wearing of dentures, pharmacotherapeutics, smoking, infancy and old age, endocrine dysfunction, and decreased salivation. Oral candidiasis may be asymptomatic. More frequently, however, it is physically uncomfortable, and the patient may complain of burning mouth, dysgeusia, dysphagia, anorexia, and weight loss, leading to nutritional deficiency and impaired quality of life. A plethora of antifungal treatments are available. The overall prognosis of oral candidiasis is good, and rarely is the condition life threatening with invasive or recalcitrant disease.
The Rotation-Torsion Spectrum of CH_2DOH
NASA Astrophysics Data System (ADS)
Hilali, A. El; Coudert, L. H.; Margulès, L.; Motiyenko, R.; Klee, S.
2010-06-01
Due to the asymmetry of the CH_2D group, the internal rotation problem in the partially deuterated species of methanol CH_2DOH is a complicated one as, unlike in the normal species CH_3OH, the inertia tensor depends on the angle of internal rotation. The CH_2DOH species also displays a dense far infrared torsional spectrum difficult to assign. Recently 38 torsional subbands of CH_2DOH have been identified, but for most of them there is neither an assignment nor an analysis of their rotational structure. In this paper an analysis of the rotation-torsion spectrum of CH_2DOH will be presented. The rotational structure of 23 torsional subbands have been assigned. These subbands are Δ v_t &ge 1 perpendicular subbands with a value of v'_t up to 10b and values of K' and K'' ranging from 0 to 9. For all subbands, the Q-branch was assigned, for 3 subbands, the R- and P-branches could also be found. The results of the rotational analysis with an expansion in J(J+1) of the new subbands and of already observed ones will be presented. When available, microwave lines within the lower torsional level, recorded in this work or already measured, were added to the data set. A theoretical approach aimed at calculating the rotation-torsion energy levels has also been developed. It is based on an expansion in terms of rotation-torsion operators with C_s symmetry and accounts for the dependence of the inertia tensor on the angle of internal rotation. This approach will be used to carry out a preliminary global analyses of the wavenumbers and of the frequencies. Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spec. 256 (2009) 204. Quade, Liu, Mukhopadhyay, and Su, J. Mol. Spec. 192 (1998) 378; Mukhopadhyay, J. Mol. Struct. 695-696 (2004) 357. Liu and Quade, J. Mol. Spec. 146 (1991) 252 Mukhopadhyay et al., J. Chem. Phys. 116 (2002) 3710.
Novel Detection of Optical Orbital Angular Momentum
2014-11-16
AFRL-RD-PS- AFRL-RD-PS TR-2014-0045 TR-2014-0045 Novel Detection of Optical Orbital Angular Momentum David Voelz Klipsch...Orbital Angular Momentum FA9451-13-1-0261 GR0004113 David Voelz Klipsch School of ECE New Mexico State University MSC 3-O, PO Box 30001 Las Cruces, NM...1026 . Government Purpose Rights. A light beam carry Orbital Angular Momentum (OAM) has typical wave front and singularity at the optical axis. The
Chirality and the angular momentum of light.
Cameron, Robert P; Götte, Jörg B; Barnett, Stephen M; Yao, Alison M
2017-02-28
Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral light-matter interactions.This article is part of the themed issue 'Optical orbital angular momentum'.
Chirality and the angular momentum of light
NASA Astrophysics Data System (ADS)
Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.; Yao, Alison M.
2017-02-01
Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral light-matter interactions. This article is part of the themed issue 'Optical orbital angular momentum'.
The protective role of erdosteine on testicular tissue after testicular torsion and detorsion.
Koc, Ahmet; Narci, Adnan; Duru, Mehmet; Gergerlioglu, H Serdar; Akaydin, Yesim; Sogut, Sadik
2005-12-01
Testicular torsion and detorsion are important clinical problems for infertile man and oxidative stress may have a role in this clinical situation. The aim of this study was to investigate the protective role of erdosteine, an antioxidant, on unilateral testicular reperfusion injury in rats. The rats were divided into four groups including seven rats in each group: control, torsion, torsion/detorsion and torsion/detorsion+erdosteine. Rats, except the sham operation group, were subjected to left unilateral torsion (720( composite function) rotation in the clockwise direction) without including the epididymis. The experiments were finished after sham operation time for control, 120 min torsion for torsion group and 120 min torsion and 240 min detorsion for torsion/detorsion groups. Bilateral orchiectomy was performed for all groups of rats. The ipsilateral and controlateral testis were divided into two pieces to analyse biochemical parameters and to investigate the light microscopic view. Malondialdehyde level of ipsilateral testis was increased in torsion and torsion/detorsion groups in comparison with the other groups (p < 0.05). Erdosteine treatment ameliorated lipid peroxidation after torsion/detorsion in ipsilateral testis (p < 0.05). Also, xanthine oxidase activity of ipsilateral testis was increased in torsion/detorsion group in comparison with the others (p < 0.05). Nitric oxide (NO) level of ipsilateral testis was higher in all experimental groups than sham operated control group (p < 0.05). Also, NO level of torsion group was increased in comparison with detorsion groups (p < 0.05). Erdosteine treatment caused increased glutathione peroxidase activity in comparison with torsion and torsion/detorsion groups and catalase activity in comparison with the other groups in ipsilateral testis (p < 0.05). Superoxide dismutase activity of ipsilateral testis was higher in torsion/detorsion and torsion/detorsion+erdosteine groups than control and torsion groups (p < 0
Wang, Song; Wang, Fei; Liao, Zhenhua; Wang, Qingliang; Liu, Yuhong; Liu, Weiqiang
2015-10-01
A ball-on-socket contact configuration was designed to simulate an artificial cervical disk in structure. UHMWPE (ultra high molecular weight polyethylene) hot pressed by powders and Ti6Al4V alloy were selected as the material combination of ball and socket. The socket surface was coated by a ~500 nm C-DLC (carbon ion implantation-diamond like carbon) mixed layer to improve its surface nano hardness and wear resistance. The torsional fretting wear behavior of the ball-on-socket model was tested at different angular displacements under 25% bovine serum lubrication with an axial force of 100 N to obtain more realistic results with that in vivo. The fretting running regimes and wear damage characteristics as well as wear mechanisms for both ball and socket were studied based on 2D (two dimension) optical microscope, SEM (scanning electron microscope) and 3D (three dimension) profiles. With the increase of angular displacement amplitude from 1° to 7°, three types of T-θ (Torsional torque-angular displacement amplitude) curves (i.e., linear, elliptical and parallelogram loops) corresponding to running regimes of PSR (partial slip regime), MR (mixed regime) and SR (slip regime) were observed and analyzed. Both the central region and the edge zone of the ball and socket were damaged. The worn surfaces were characterized by wear scratches and wear debris. In addition, more severe wear damage and more wear debris appeared on the central region of the socket at higher angular displacement amplitude. The dominant damage mechanism was a mix of surface scratch, adhesive wear and abrasive wear for the UHMWPE ball while that for the coated socket was abrasive wear by PE particles and some polishing and rolling process on the raised overgrown DLC grains. The frictional kinetic behavior, wear type, damage region and damage mechanism for the ball-on-socket model revealed significant differences with those of a ball-on-flat contact while showing better consistency with that of in
NASA Astrophysics Data System (ADS)
Mehrabi, Reza; Kadkhodaei, Mahmoud; Elahinia, Mohammad
2014-07-01
A three-dimensional phenomenological model based on microplane theory is extended to capture the coupling effects between tension and torsion in complex multiaxial loadings. Inelastic strain in a microplane approach is a component of transformation strain and anisotropic strain. Since the anisotropy effect is induced during martensitic transformation, anisotropic strain is defined as a function of transformation strain. Out-of-plane strain is induced in simple tension and pure torsion in free-end conditions. Anisotropy tensor is experimentally extracted and is used in the proposed model to predict the behavior in multiaxial loading. The ability of this extended microplane model to predict the tension-torsion coupling effects as well as the induced transformation anisotropic behavior of NiTi shape memory alloys is demonstrated. In addition, the microplane model is modified to capture the asymmetric behavior in tension and compression during uniaxial and multiaxial loadings. To this end, numerical correlations between the results of the modified microplane model are compared with experimental results to demonstrate the validity of the extended model.
The torsional mechanical properties of copper nanowires supported by carbon nanotubes
NASA Astrophysics Data System (ADS)
Huan, Hao; Fu, Bing; Ye, Xiang
2017-02-01
The torsional mechanical properties of hollow Cu nanowires supported by carbon nanotubes (CNTs) are studied by all atoms molecular dynamic simulation. It is found that the critical angles of Cu nanowires almost do not decrease when the temperature increases to a limit value, and this invariant feature also has been found as the torsional loading rate is lower than 4.5 ×1012 °s-1. Due to the support of CNTs, Cu nanowires can bear larger torsional angle at low torsional rates and high temperatures compared with those without CNTs, which means the CNTs will increase the torsion-tolerance of Cu nanowires.
Development of a Meso-Scale SMA-Based Torsion Actuator for Image-Guided Procedures.
Sheng, Jun; Gandhi, Dheeraj; Gullapalli, Rao; Simard, J Marc; Desai, Jaydev P
2017-02-01
This paper presents the design, modeling, and control of a meso-scale torsion actuator based on shape memory alloy (SMA) for image-guided surgical procedures. Developing a miniature torsion actuator is challenging, but it opens the possibility of significantly enhancing the robot agility and maneuverability. The proposed torsion actuator is bi-directionally actuated by a pair of antagonistic SMA torsion springs through alternate Joule heating and natural cooling. The torsion actuator is integrated into a surgical robot prototype to demonstrate its working performance in the humid environment under C-Arm CT image guidance.
Angular velocity of a spheroid log rolling in a simple shear at small Reynolds number
NASA Astrophysics Data System (ADS)
Meibohm, Jan; Candelier, Fabien; Rosen, Tomas; Einarsson, Jonas; Lundell, Fredrik; Mehlig, Bernhard
2016-11-01
We analyse the angular velocity of a small neutrally buoyant spheroid log rolling in a simple shear. When the effect of fluid inertia is negligible the angular velocity ω -> equals half the fluid vorticity. We compute by singular perturbation theory how weak fluid inertia reduces the angular velocity in an unbounded shear, and how this reduction depends upon the shape of the spheroid (on its aspect ratio). In addition we determine the angular velocity by direct numerical simulations. The results are in excellent agreement with the theory at small but not too small values of the shear Reynolds number, for all aspect ratios considered. For the special case of a sphere we find ω / s = - 1 / 2 + 0 . 0540Re 3 / 2 where s is the shear rate and Re is the shear Reynolds number. This result differs from that derived by Lin et al. who obtained a numerical coefficient roughly three times larger.
The Angular Momentum of the Solar System
NASA Astrophysics Data System (ADS)
Cang, Rongquin; Guo, Jianpo; Hu, Juanxiu; He, Chaoquiong
2016-05-01
The angular momentum of the Solar System is a very important physical quantity to the formation and evolution of the Solar System. Previously, the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets were only taken into consideration, when researchers calculated the angular momentum of the Solar System. Nowadays, it seems narrow and conservative. Using Eggleton's code, we calculate the rotational inertia of the Sun. Furthermore, we obtain that the spin angular momentum of the Sun is 1.8838 x 10^41 kg m^2 s^-1. Besides the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets, we also account for the orbital angular momentum of the Asteroid Belt, the Kuiper Belt, the Oort Cloud, the Ninth Giant Planet and the Solar Companion. We obtain that the angular momentum of the whole Solar System is 3.3212 x 10^45 kg m^2 s^-1.
Torsion Bounds from CP Violation α2-DYNAMO in Axion-Photon Cosmic Plasma
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.
Years ago Mohanty and Sarkar [Phys. Lett. B 433, 424 (1998)] have placed bounds on torsion mass from K meson physics. In this paper, associating torsion to axions a la Campanelli et al. [Phys. Rev. D 72, 123001 (2005)], it is shown that it is possible to place limits on spacetime torsion by considering an efficient α2-dynamo CP violation term. Therefore instead of Kostelecky et al. [Phys. Rev. Lett. 100, 111102 (2008)] torsion bounds from Lorentz violation, here torsion bounds are obtained from CP violation through dynamo magnetic field amplification. It is also shown that oscillating photon-axion frequency peak is reduced to 10-7 Hz due to torsion mass (or Planck mass when torsion does not propagate) contribution to the photon-axion-torsion action. Though torsion does not couple to electromagnetic fields at classical level, it does at the quantum level. Recently, Garcia de Andrade [Phys. Lett. B 468, 28 (2011)] has shown that the photon sector of Lorentz violation (LV) Lagrangian leads to linear nonstandard Maxwell equations where the magnetic field decays slower giving rise to a seed for galactic dynamos. Torsion constraints of the order of K0≈10-42 GeV can be obtained which are more stringent than the value obtained by Kostelecky et al. A lower bound for the existence of galactic dynamos is obtained for torsion as K0≈10-37 GeV.
Model-based diagnosis of large diesel engines based on angular speed variations of the crankshaft
NASA Astrophysics Data System (ADS)
Desbazeille, M.; Randall, R. B.; Guillet, F.; El Badaoui, M.; Hoisnard, C.
2010-07-01
This work aims at monitoring large diesel engines by analyzing the crankshaft angular speed variations. It focuses on a powerful 20-cylinder diesel engine with crankshaft natural frequencies within the operating speed range. First, the angular speed variations are modeled at the crankshaft free end. This includes modeling both the crankshaft dynamical behavior and the excitation torques. As the engine is very large, the first crankshaft torsional modes are in the low frequency range. A model with the assumption of a flexible crankshaft is required. The excitation torques depend on the in-cylinder pressure curve. The latter is modeled with a phenomenological model. Mechanical and combustion parameters of the model are optimized with the help of actual data. Then, an automated diagnosis based on an artificially intelligent system is proposed. Neural networks are used for pattern recognition of the angular speed waveforms in normal and faulty conditions. Reference patterns required in the training phase are computed with the model, calibrated using a small number of actual measurements. Promising results are obtained. An experimental fuel leakage fault is successfully diagnosed, including detection and localization of the faulty cylinder, as well as the approximation of the fault severity.
Analytical and numerical models to predict the behavior of unbonded flexible risers under torsion
NASA Astrophysics Data System (ADS)
Ren, Shao-fei; Xue, Hong-xiang; Tang, Wen-yong
2016-04-01
This paper presents analytical and numerical models to predict the behavior of unbonded flexible risers under torsion. The analytical model takes local bending and torsion of tensile armor wires into consideration, and equilibrium equations of forces and displacements of layers are deduced. The numerical model includes lay angle, cross-sectional profiles of carcass, pressure armor layer and contact between layers. Abaqus/Explicit quasi-static simulation and mass scaling are adopted to avoid convergence problem and excessive computation time caused by geometric and contact nonlinearities. Results show that local bending and torsion of helical strips may have great influence on torsional stiffness, but stress related to bending and torsion is negligible; the presentation of anti-friction tapes may have great influence both on torsional stiffness and stress; hysteresis of torsion-twist relationship under cyclic loading is obtained by numerical model, which cannot be predicted by analytical model because of the ignorance of friction between layers.
F1 rotary motor of ATP synthase is driven by the torsionally-asymmetric drive shaft
NASA Astrophysics Data System (ADS)
Kulish, O.; Wright, A. D.; Terentjev, E. M.
2016-06-01
F1F0 ATP synthase (ATPase) either facilitates the synthesis of ATP in a process driven by the proton moving force (pmf), or uses the energy from ATP hydrolysis to pump protons against the concentration gradient across the membrane. ATPase is composed of two rotary motors, F0 and F1, which compete for control of their shared γ -shaft. We present a self-consistent physical model of F1 motor as a simplified two-state Brownian ratchet using the asymmetry of torsional elastic energy of the coiled-coil γ -shaft. This stochastic model unifies the physical concepts of linear and rotary motors, and explains the stepped unidirectional rotary motion. Substituting the model parameters, all independently known from recent experiments, our model quantitatively reproduces the ATPase operation, e.g. the ‘no-load’ angular velocity is ca. 400 rad/s anticlockwise at 4 mM ATP. Increasing the pmf torque exerted by F0 can slow, stop and overcome the torque generated by F1, switching from ATP hydrolysis to synthesis at a very low value of ‘stall torque’. We discuss the motor efficiency, which is very low if calculated from the useful mechanical work it produces - but is quite high when the ‘useful outcome’ is measured in the number of H+ pushed against the chemical gradient.
F1 rotary motor of ATP synthase is driven by the torsionally-asymmetric drive shaft
Kulish, O.; Wright, A. D.; Terentjev, E. M.
2016-01-01
F1F0 ATP synthase (ATPase) either facilitates the synthesis of ATP in a process driven by the proton moving force (pmf), or uses the energy from ATP hydrolysis to pump protons against the concentration gradient across the membrane. ATPase is composed of two rotary motors, F0 and F1, which compete for control of their shared γ -shaft. We present a self-consistent physical model of F1 motor as a simplified two-state Brownian ratchet using the asymmetry of torsional elastic energy of the coiled-coil γ -shaft. This stochastic model unifies the physical concepts of linear and rotary motors, and explains the stepped unidirectional rotary motion. Substituting the model parameters, all independently known from recent experiments, our model quantitatively reproduces the ATPase operation, e.g. the ‘no-load’ angular velocity is ca. 400 rad/s anticlockwise at 4 mM ATP. Increasing the pmf torque exerted by F0 can slow, stop and overcome the torque generated by F1, switching from ATP hydrolysis to synthesis at a very low value of ‘stall torque’. We discuss the motor efficiency, which is very low if calculated from the useful mechanical work it produces - but is quite high when the ‘useful outcome’ is measured in the number of H+ pushed against the chemical gradient. PMID:27321713
Semiclassical model for attosecond angular streaking.
Smolarski, M; Eckle, P; Keller, U; Dörner, R
2010-08-16
Attosecond angular streaking is a new technique to achieve unsurpassed time accuracy of only a few attoseconds. Recently this has been successfully used to set an upper limit on the electron tunneling delay time in strong laser field ionization. The measurement technique can be modeled with either the time-dependent Schrödinger equation (TDSE) or a more simple semiclassical approach that describes the process in two steps in analogy to the three-step model in high harmonic generation (HHG): step one is the tunnel ionization and step two is the classical motion in the strong laser field. Here we describe in detail a semiclassical model which is based on the ADK theory for the tunneling step, with subsequent classical propagation of the electron in the laser field. We take into account different ellipticities of the laser field and a possible wavelength-dependent ellipticity that is typically observed for pulses in the two-optical-cycle regime. This semiclassical model shows excellent agreement with the experimental result.
On a finite-state inflow application to flap-lag-torsion damping in hover
NASA Technical Reports Server (NTRS)
De Andrade, Donizeti; Peters, David A.
1992-01-01
An aerodynamic model with a coupled set of generalized dynamic wake equations and hybrid equations of motion for an elastic blade are applied here to a two-blade untwisted stiff in-plane hingeless small-scale model rotor with torsionally soft blades. Blade root offset, precone, blade droop, pitch control stiffness, and blade pitch angle are included in the model rotor. Numerical results show that 3D tip relief effects within the nonuniform steady-state inflow are significant to predict steady-state aerodynamic loads and blade deflections. Eigenvalue results confirm the importance of unsteady 3D aerodynamics in predicting lead-lag damping and frequency. Eigenvector analysis correlations reinforced qualitative and quantitative shortcomings associated with quasi-steady 2D aerodynamic theory for aeroelastic applications in hover.
Numerical Investigation of Flapwise-Torsional Vibration Model of a Smart Section Blade with Microtab
Li, Nailu; Balas, Mark J.; Yang, Hua; ...
2015-01-01
This study presents a method to develop an aeroelastic model of a smart section blade equipped with microtab. The model is suitable for potential passive vibration control study of the blade section in classic flutter. Equations of the model are described by the nondimensional flapwise and torsional vibration modes coupled with the aerodynamic model based on the Theodorsen theory and aerodynamic effects of the microtab based on the wind tunnel experimental data. The aeroelastic model is validated using numerical data available in the literature and then utilized to analyze the microtab control capability on flutter instability case and divergence instabilitymore » case. The effectiveness of the microtab is investigated with the scenarios of different output controllers and actuation deployments for both instability cases. The numerical results show that the microtab can effectively suppress both vibration modes with the appropriate choice of the output feedback controller.« less
Torsional spring is the optimal flexibility arrangement of a flapping wing
NASA Astrophysics Data System (ADS)
Moore, Nick
2015-11-01
While it is understood that flexibility can improve the propulsive performance of flapping wings and fins, the flexibility distribution leading to optimal performance has not been explored. Using 2D small-amplitude theory and a fast Chebyshev method, we examine how thrust depends on the chord-wise distribution of wing stiffness. Through numerical optimization, we find that focusing flexibility at the wing's front, e.g. through a torsional spring, maximizes thrust. A wing with an optimally chosen spring constant typically generates 36% more thrust than a wing of optimal uniform stiffness. These results may relate to material distributions found in nature, such as insect wings, and may apply to the design of biomimetic swimmers and flyers, such as ornithopters.
Torsional spring is the optimal flexibility arrangement for thrust production of a flapping wing
NASA Astrophysics Data System (ADS)
Moore, M. Nicholas J.
2015-09-01
While it is understood that flexibility can improve the propulsive performance of flapping wings and fins, the flexibility distribution leading to optimal performance has not been explored. Using 2D small-amplitude theory and a fast Chebyshev method, we examine how thrust depends on the chord-wise distribution of wing stiffness. Through numerical optimization, we find that focusing flexibility at the wing's front, e.g., through a torsional spring, maximizes thrust. A wing with an optimally chosen spring constant typically generates 36% more thrust than a wing of optimal uniform stiffness. These results may relate to material distributions found in nature, such as insect wings, and may apply to the design of biomimetic swimmers and flyers, such as ornithopters.
Orbital angular momentum: a personal memoir.
Allen, L
2017-02-28
A definitive statement of the model used to describe orbital angular momentum is essentially now available. Its early history, and the interaction of those who played key roles in its development over 20 years ago in its development, is outlined in this Memoir.This article is part of the themed issue 'Optical orbital angular momentum'.
Stellar angular diameters from occultation observations.
NASA Astrophysics Data System (ADS)
Qian, B.-C.
This paper reviews the history of measuring stellar angular diameters from lunar occultation observations and the techniques of data analysis. Several effects which can affect the results of measurement are discussed. The author finds that there may be systematic errors in angular diameters measured by various observatories for Aldebaran.
Angular Momentum Eigenstates for Equivalent Electrons.
ERIC Educational Resources Information Center
Tuttle, E. R.; Calvert, J. B.
1981-01-01
Simple and efficient methods for adding angular momenta and for finding angular momentum eigenstates for systems of equivalent electrons are developed. Several different common representations are used in specific examples. The material is suitable for a graduate course in quantum mechanics. (SK)
Orbital angular momentum: a personal memoir
NASA Astrophysics Data System (ADS)
Allen, L.
2017-02-01
A definitive statement of the model used to describe orbital angular momentum is essentially now available. Its early history, and the interaction of those who played key roles in its development over 20 years ago in its development, is outlined in this Memoir. This article is part of the themed issue 'Optical orbital angular momentum'.
Angular Momentum of Dwarf Galaxies
NASA Astrophysics Data System (ADS)
Butler, Kirsty M.; Obreschkow, Danail; Oh, Se-Heon
2017-01-01
We present measurements of baryonic mass {M}{{b}} and specific angular momentum (sAM) {j}{{b}} in 14 rotating dwarf Irregular (dIrr) galaxies from the LITTLE THINGS sample. These measurements, based on 21 cm kinematic data from the Very Large Array and stellar mass maps from the Spitzer Space Telescope, extend previous AM measurements by more than two orders of magnitude in {M}{{b}}. The dwarf galaxies show systematically higher {j}{{b}} values than expected from the {j}{{b}}\\propto {M}{{b}}2/3 scaling of spiral galaxies, representative of a scale-free galaxy formation scenario. This offset can be explained by decreasing baryon mass fractions {f}{{M}}={M}{{b}}/{M}{dyn} (where {M}{dyn} is the dynamical mass) with decreasing {M}{{b}} (for {M}{{b}}< {10}11 {M}ȯ ). We find that the sAM of neutral atomic hydrogen (H i) alone is about 2.5 times higher than that of the stars. The M–j relation of H i is significantly steeper than that of the stars, as a direct consequence of the systematic variation of the H i fraction with {M}{{b}}.
The angular momentum of the Oort cloud
Weissman, P.R. )
1991-01-01
An evaluation is made of the work of Marochnik et al. (1988), which estimated that the angular momentum of the Oort cloud is 2-3 orders of magnitude greater than the planetary system's total angular momentum. It is noted that most of the angular momentum in the currently observed Oort cloud is the result of the effects of external perturbers over the solar system's history, and it is demonstrated that the total current angular momentum is probably in the 6.0 x 10 to the 50th to 1.1 x 10 to the 51st g sq cm/sec range; original angular momentum was probably a factor of 5 below such values. 21 refs.
The angular momentum of the Oort cloud
NASA Technical Reports Server (NTRS)
Weissman, Paul R.
1991-01-01
An evaluation is made of the work of Marochnik et al. (1988), which estimated that the angular momentum of the Oort cloud is 2-3 orders of magnitude greater than the planetary system's total angular momentum. It is noted that most of the angular momentum in the currently observed Oort cloud is the result of the effects of external perturbers over the solar system's history, and it is demonstrated that the total current angular momentum is probably in the 6.0 x 10 to the 50th to 1.1 x 10 to the 51st g sq cm/sec range; original angular momentum was probably a factor of 5 below such values.
NASA Astrophysics Data System (ADS)
Qi, C.; Kohlstedt, D. L.; Katz, R. F.; Takei, Y.
2013-12-01
Partial melting in Earth mostly occurs at regions undergoing intense deformation. To understand the behavior of partially molten rocks exposed to differential stress, two-phase aggregates consisting of a solid and melt were deformed at high-temperature, high-pressure laboratory conditions. In these experiments, stress-driven melt segregation that leads to the formation of melt-enriched bands has been produced consistently. This segregation process has been successfully reproduced by a theory based on anisotropic viscosity of sheared two-phase aggregates. This theory also predicts a base-state (background), stress-driven melt segregation at the sample-scale. Here we present experimental results from torsion and extrusion experiments designed to test the theoretical predictions. Samples composed of fine-grained San Carlos olivine and uniformly distributed basalt melt were deformed in two different types of experiments at a temperature of 1200°C and a confining pressure of 300 MPa in a gas-medium apparatus. Samples were either sheared in torsion at constant strain rate to a maximum strain of γ ≈ 13 or extruded through a rigid tube at constant differential pressure in a Poiseuille flow geometry. Melt distribution maps obtained from reflected-light optical and backscattered electron micrographs demonstrate that melt migrates radially inward from the outer edge to the center of torsion samples and radially outward from the center to the wall of the tube in extrusion samples. This base-state melt segregation indicates that the partially molten aggregate decompacted (compacted) at the center (outer edge) of torsion samples and at the wall (center) of extrusion samples. Based on the observed melt distribution, we conclude that the compaction/decompaction rate increases with increasing stress, as predicted by the theory. These experimental observations qualitatively agree with the theoretical predictions, with some quantitative discrepancies remaining such as the
The Torsion of Members Having Sections Common in Aircraft Construction
NASA Technical Reports Server (NTRS)
Trayer, George W; March, H W
1930-01-01
Within recent years a great variety of approximate torsion formulas and drafting-room processes have been advocated. In some of these, especially where mathematical considerations are involved, the results are extremely complex and are not generally intelligible to engineers. The principal object of this investigation was to determine by experiment and theoretical investigation how accurate the more common of these formulas are and on what assumptions they are founded and, if none of the proposed methods proved to be reasonable accurate in practice, to produce simple, practical formulas from reasonably correct assumptions, backed by experiment. A second object was to collect in readily accessible form the most useful of known results for the more common sections. Formulas for all the important solid sections that have yielded to mathematical treatment are listed. Then follows a discussion of the torsion of tubular rods with formulas both rigorous and approximate.
MAGNETOSEISMOLOGY: EIGENMODES OF TORSIONAL ALFVEN WAVES IN STRATIFIED SOLAR WAVEGUIDES
Verth, G.; Goossens, M.; Erdelyi, R. E-mail: Marcel.Goossens@wis.kuleuven.b
2010-05-10
There have recently been significant claims of Alfven wave observation in the solar chromosphere and corona. We investigate how the radial and longitudinal plasma structuring affects the observational properties of torsional Alfven waves in magnetic flux tubes for the purposes of solar magnetoseismology. The governing magnetohydrodynamic equations of these waves in axisymmetric flux tubes of arbitrary radial and axial plasma structuring are derived and we study their observable properties for various equilibria in both thin and finite-width magnetic flux tubes. For thin flux tubes, it is demonstrated that observation of the eigenmodes of torsional Alfven waves can provide temperature diagnostics of both the internal and surrounding plasma. In the finite-width flux tube regime, it is shown that these waves are the ideal magnetoseismological tool for probing radial plasma inhomogeneity in solar waveguides.
Omental torsion in a captive polar bear (Ursus maritimus).
Mendez-Angulo, Jose L; Funes, Francisco J; Trent, Ava M; Willette, Michelle; Woodhouse, Kerry; Renier, Anna C
2014-03-01
This is the first case report of an omental torsion in a polar bear (Ursus maritimus). A captive, 23-yr-old, 250-kg, intact female polar bear presented to the University of Minnesota Veterinary Medical Center with a 2-day history of lethargy, depression, and vomiting. Abdominal ultrasound identified large amounts of hyperechoic free peritoneal fluid. Ultrasound-guided abdominocentesis was performed and yielded thick serosanguinous fluid compatible with a hemoabdomen. An exploratory laparotomy revealed a large amount of malodorous, serosanguineous fluid and multiple necrotic blood clots associated with a torsion of the greater omentum and rupture of a branch of the omental artery. A partial omentectomy was performed to remove the necrotic tissue and the abdomen was copiously lavaged. The polar bear recovered successfully and is reported to be clinically well 6 mo later. This condition should be considered as a differential in bears with clinical signs of intestinal obstruction and hemoabdomen.
Bending and Torsion Load Alleviator With Automatic Reset
NASA Technical Reports Server (NTRS)
delaFuente, Horacio M. (Inventor); Eubanks, Michael C. (Inventor); Dao, Anthony X. (Inventor)
1996-01-01
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.
Torsion of a Wandering Spleen Presenting as Acute Abdomen
Chauhan, Narvir Singh; Kumar, Satish
2016-01-01
Summary Background Wandering spleen is a rare condition which if uncorrected, can result in torsion and infarction. Clinical presentation of a wandering spleen can vary from asymptomatic abdominal mass to acute abdominal pain. Radiological investigations play a pivotal role in diagnosis as the clinical diagnosis is usually impossible. Case Report We present a case of wandering spleen with torsion and complete infarction that occurred in a 32-year-old multiparous female. The diagnosis was established preoperatively on colour Doppler and CT of the abdomen with subsequent confirmation on surgery. Conclusions Wandering spleen is a rare clinical condition which can present as acute abdomen. An increased awareness of this entity together with the timely use of ultrasound and CT of the abdomen can play an important role in preoperative diagnosis and surgical management. PMID:27057261
Wandering spleen with chronic torsion in a patient with thalassaemia
Ho, Chi Long
2014-01-01
Wandering spleen or splenoptosis is an uncommon entity and often an asymptomatic finding of acute abdomen in the emergency department. A high index of suspicion for splenic torsion is required, particularly in patients with known splenomegaly, as this condition could potentially lead to splenic infarction. Recognition of this condition can help avoid potential confusion with acute abdomen of other aetiologies. Herein, we present a unique case of wandering spleen with chronic torsion, which, to the best of our knowledge, has never been described in an elderly patient with haemoglobin H thalassaemia. We also review the literature for the aetiology and pathogenesis of wandering spleen, and discuss the relevant diagnostic modalities and treatment options. PMID:25630326
Torsion, parity-odd response, and anomalies in topological states
NASA Astrophysics Data System (ADS)
Parrikar, Onkar; Hughes, Taylor L.; Leigh, Robert G.
2014-11-01
We study the response of a class of topological systems to electromagnetic and gravitational sources, including torsion and curvature. By using the technology of anomaly polynomials, we derive the parity-odd response of a massive Dirac fermion in d =2 +1 and d =4 +1 , which provides a simple model for a topological insulator. We discuss the covariant anomalies of the corresponding edge states, from a Callan-Harvey anomaly inflow, as well as a Hamiltonian spectral flow point of view. We also discuss the applicability of our results to other systems such as Weyl semimetals. Finally, using dimensional reduction from d =4 +1 , we derive the effective action for a d =3 +1 time-reversal invariant topological insulator in the presence of torsion and curvature, and discuss its various physical consequences.
The Ground and First Excited Torsional States of Acetic Acid.
Ilyushin, V. V.; Alekseev, E. A.; Dyubko, S. F.; Podnos, S. V.; Kleiner, I.; Margulès, L.; Wlodarczak, G.; Demaison, J.; Cosléou, J.; Maté, B.; Karyakin, E. N.; Golubiatnikov, G. Yu.; Fraser, G. T.; Suenram, R. D.; Hougen, J. T.
2001-02-01
A global fit of microwave and millimeter-wave rotational transitions in the ground and first excited torsional states (v(t) = 0 and 1) of acetic acid (CH(3)COOH) is reported, which combines older measurements from the literature with new measurements from Kharkov, Lille, and NIST. The fit uses a model developed initially for acetaldehyde and methanol-type internal rotor molecules. It requires 34 parameters to achieve a unitless weighted standard deviation of 0.84 for a total of 2518 data and includes A- and E-species transitions with J torsional interval is available. Copyright 2001 Academic Press.
Torsion Test of a Monocoque Box
NASA Technical Reports Server (NTRS)
Mcpherson, Albert E; Ramberg, Walter; Levy, Samuel
1942-01-01
A monocoque box beam consisting of a 24S-T aluminum-alloy sheet reinforced by four bulkheads and by longitudinal stringers and corner posts was subjected to bending loads as follows: pure bending about the lift axis, cantilever bending about the lift axis, and pure bending about both lift and drag axis. Longitudinal strains were measured for loads up to a load at which permanent set became measurable. The loads were sufficient to produce buckling of the sheet between stringers on the compression side of the box. The only noticeable effect of this buckling was a small increase in extreme-fiber strain on the compression side. The measured strains and measured deflections differed less than 10 percent from those computed from the simple beam theory after taking account of the effective width of the buckled sheet. The effect of the bulkheads on the distribution of stringer strain was negligible.
Genetic and clinical features of primary torsion dystonia
Ozelius, Laurie J.; Bressman, Susan B.
2011-01-01
Primary torsion dystonia (PTD) is defined as a syndrome in which dystonia is the only clinical sign (except for tremor), and there is no evidence of neuronal degeneration or an acquired cause by history or routine laboratory assessment. Seven different loci have been recognized for PTD but only two of the genes have been identified. In this review we will described the phenotypes associated with these loci and discuss the responsible gene. PMID:21168499
Microstructure and texture analyses of polycrystalline ice during hot torsion
NASA Astrophysics Data System (ADS)
Journaux, B.; Montagnat, M.; Gest, L.; Barou, F.; Chauve, T.
2015-12-01
Water ice Ih is a material with very high plastic anisotropy where deformation is mainly accommodated by dislocation glide on the (0001) plane. This anisotropy gives rise to strong strain incompatibilities between grains during deformation, and therefore impacts texture and microstructure evolution. Accurate understanding of ice mechanical properties is significant for several areas of research such as glaciology, planetary sciences, but also in geosciences and metallurgy as ice can be seen as a model material with easier experimental handling at near melting temperatures. In the present study, we used torsion experiments to study non-coaxial shear strain (γ), very common in natural environments, up to very high values of γ. Numerous studies determined microstructure and texture evolution in polycrystalline assemblage submitted to torsion (metallic alloys and geological materials) but a very limited number focused on polycrystalline ice. Full cylinders of randomly oriented polycrystalline ice (grain size ~ 1 mm) were placed in a torsion apparatus and deformed under ductile regime under constant imposed torque at 266K (0.97 Tf). Macroscopic shear was monitored using a LVDT device or a rotary encoder. Several torsion tests with maximal shear strain up to γmax = 1 were performed. Tangent and axial sections were analyzed ex-situ using Automatic Ice Texture Analyzer (AITA) and Electron BackScatter Diffraction (EBSD). We were able to confirm the previously observed bimodal preferred orientation of the basal slip plane. Macroscopic strain evolution γ(t) displays a weakening after γmax = 0.04 (ɛmax ≃ 2 %), due to the beginning of dynamic recrystallization (DRX) processes. EBSD data provide novel informations on the microstructure that suggest very efficient grain boundary migration processes. In particular, we were able to measure differences of intra-granular misorientations density between the two ODF maxima populations that can highlight the role of DRX
Torsional Elastic Property Measurements of Selected Orthodontic Archwires.
1987-01-01
replacing gold in the middle of the century. If the orthodontist wished to have lighter forces over a greater range, he had two choices. First, he...length. The orthodontist was forced to make torque adjustments in small increments with a large, torsionally stiff, stainless steel wire. The concept...slot, respectively) were measured with strain gauges. The expected linear relationship between the torque magnitude and the activation angle was verified
Upright Perception and Ocular Torsion Change Independently during Head Tilt
Otero-Millan, Jorge; Kheradmand, Amir
2016-01-01
We maintain a stable perception of the visual world despite continuous movements of our eyes, head and body. Perception of upright is a key aspect of such orientation constancy. Here we investigated whether changes in upright perception during sustained head tilt were related to simultaneous changes in torsional position of the eyes. We used a subjective visual vertical (SVV) task, modified to track changes in upright perception over time, and a custom video method to measure ocular torsion simultaneously. We tested 12 subjects in upright position, during prolonged (~15 min) lateral head tilts of 20 degrees, and also after the head returned to upright position. While the head was tilted, SVV drifted in the same direction as the head tilt (left tilt: −5.4 ± 1.4° and right tilt: +2.2 ± 2.1°). After the head returned to upright position, there was an SVV aftereffect with respect to the pre-tilt baseline, which was also in the same direction as the head tilt (left tilt: −3.9 ± 0.6° and right tilt: +2.55 ± 1.0°). Neither the SVV drift nor the SVV aftereffect were correlated with the changes in ocular torsion. Using the Bayesian spatial-perception model we show that the pattern of SVV drift and aftereffect in our results could be explained by a drift and an adaptation in sensory inputs that encode head orientation. The fact that ocular torsion (mainly driven by the otoliths) could not account for the perceptual changes suggests that neck proprioception could be the primary source of drift in upright perception during head tilt, and subsequently the aftereffect in upright position. PMID:27909402
Metatarsal torsion in monkeys, apes, humans and australopiths.
Drapeau, Michelle S M; Harmon, Elizabeth H
2013-01-01
This paper presents an analysis of metatarsal torsion in apes, cercopithecoids and humans, compares australopiths with these species, and discusses their inferred foot morphology and function relative to prehensility, arboreality and the presence or absence of a longitudinal arch. Our results show that locomotor modes are reflected in metatarsal torsion values. Apes, which climb vertically with their foot inverted, have hallucal metatarsal heads that are turned toward the other toes and lateral toes that are inverted. Cercopithecoids, which tend to orient their feet in an axis more parallel to the line of motion, present signs of prehensility by having inverted 2nd metatarsals that oppose the hallux, while their two lateral-most metatarsals are strongly everted. Humans, with their rigid feet and longitudinal arches, have all toes that present their plantar surface toward the ground, resulting in hallucal and 2nd metatarsals that are relatively untwisted and the others that are strongly everted. Humans are different from all taxa only for the 2nd and 3rd metatarsal. It is hypothesized that the untwisted 2nd metatarsal reflects the lack of digit opposability of the medial foot and the strongly everted 3rd metatarsal reflects the longitudinal arch. Australopithecus afarensis was characterized by an everted lateral foot, the prerequisite for the development, but not necessarily an indicator, of a longitudinal arch. In Australopithecus africanus, torsion of fragmentary and complete 1st, 2nd, 3rd and 5th metatarsals suggest that the species did not have a foot with monkey- or ape-like prehensile capabilities and did not have a human-like longitudinal arch. In the Swartkrans remains, torsion is consistent with an unprehensile foot. The morphology of the fossils indicates that there was strong selection to orient the plantar surface of the toes facing the ground at the expense of a grasping foot and inversion ability.
Propagation and Reflection of Diffusionless Torsional Waves in a Sphere
NASA Astrophysics Data System (ADS)
Maffei, S.; Jackson, A.
2015-12-01
The magnetohydrodynamics of stars and planetary cores is usually dominated by the overwhelming importance of rotation compared to other forces. Under these conditions the fluid motions are characterized by a strong invariance along the rotation axis. In the presence of a background magnetic field, magnetohydrodynamic oscillations can be triggered. Among these, of particular interest are the torsional waves, azimuthal perturbations of the fluid that are axisymmetric and invariant along the vertical direction. Their periods depend solely on the intensity of the magnetic field component aligned with the radial direction of propagation. As the detection of the fundamental period could constrain the magnetic field intensity in the Earth's outer core there is a long history of attempted detection of torsional waves from geomagnetic data. There is however a fundamental lack of knowledge concerning the propagation and reflection properties of these waves, as observational studies suggests behaviors that are different from theoretical expectations. In particular, recent findings (Gillet et al., 2011) suggest the lack of reflection at the equator and at the rotation axis. Through numerical simulation and analytical techniques we analyze the temporal evolution of diffusionless torsional waves in spherical geometry, with particular attention on the reflection at the equator and the pseudo-reflection at the rotation axis. We develop a novel analytical solution to the torsional wave eigenvalue problem whose behavior at the boundaries helps us to illustrate the meaning of the boundary conditions. Furthermore we find that for any acceptable magnetic background field, reflections at both boundaries are allowed and we illustrate how the WKBJ approximation is an efficient tool for investigating them.
Testicular conditions in athletes: torsion, tumors, and epididymitis.
Sandella, Bradley; Hartmann, Brett; Berkson, David; Hong, Eugene
2012-01-01
Individuals involved in sports are at risk for sustaining various injuries. In addition to musculoskeletal complaints, male athletes are at risk of incurring testicular injuries. These issues can range from an acute emergency such as testicular torsion to indolent testicular tumors. In contrast, epididymitis can present in stages. Presentation and management of testicular complaints can vary depending on the condition. Physicians who provide medical care to athletes need to be competent in diagnosing and managing testicular injuries.
Self-accelerating universe in modified gravity with dynamical torsion
NASA Astrophysics Data System (ADS)
Nikiforova, V.; Randjbar-Daemi, S.; Rubakov, V.
2017-01-01
We consider a model belonging to the class of gravities with dynamical torsion. The model is free of ghosts and gradient instabilities about Minkowski and torsionless Einstein backgrounds. We find that at zero cosmological constant, the model admits a self-accelerating solution with a non-Riemannian connection. Small value of the effective cosmological constant is obtained at the expense of the hierarchy between the dimensionless couplings.
Torsion of the greater omentum: treatment by laparoscopy.
Sánchez, Javier; Rosado, Rafael; Ramírez, Diego; Medina, Pedro; Mezquita, Susana; Gallardo, Andrés
2002-12-01
Four new cases of necrosis of the omentum secondary to torsion are reported. We review the associated signs and symptoms, which are usually those of an acute inflammatory condition in the right lower quadrant (RLQ), very similar to acute appendicitis. Because of acute abdominal pain in the RLQ, along with an uncertain diagnosis, laparoscopic surgery was performed in these cases. Laparoscopy demonstrated the existence of the omental infarction and allowed for complete treatment of the condition without the need for laparotomy.
Intravitreal Phacoemulsification Using Torsional Handpiece for Retained Lens Fragments
Kumar, Vinod; Takkar, Brijesh
2016-01-01
Purpose: To evaluate the results of intravitreal phacoemulsification with torsional hand piece in eyes with posteriorly dislocated lens fragments. Methods: In this prospective, interventional case series, 15 eyes with retained lens fragments following phacoemulsification were included. All patients underwent standard three-port pars plana vitrectomy and intravitreal phacoemulsification using sleeveless, torsional hand piece (OZiL™, Alcon's Infiniti Vision System). Patients were followed up for a minimum of six months to evaluate the visual outcomes and complications. Results: The preoperative best-corrected visual acuity (BCVA) ranged from light perception to 0.3. No complications such as thermal burns of the scleral wound, retinal damage due to flying lens fragments, or difficult lens aspiration occurred during intravitreal phacoemulsification. Mean post-operative BCVA at the final follow-up was 0.5. Two eyes developed cystoid macular edema, which was managed medically. No retinal detachment was noted. Conclusion: Intravitreal phacoemulsification using torsional hand piece is a safe and effective alternative to conventional longitudinal phacofragmentation. PMID:27621783
Friction and shear fracture of an adhesive contact under torsion
NASA Astrophysics Data System (ADS)
Chateauminois, Antoine; Fretigny, Christian; Olanier, Ludovic
2010-02-01
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.
Development of a torsion balance for adhesion measurements
NASA Technical Reports Server (NTRS)
Miyoshi, Kazuhisa; Maeda, Chikayoshi; Masuo, Ryuichi
1988-01-01
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.
Shape sensing for torsionally compliant concentric-tube robots
NASA Astrophysics Data System (ADS)
Xu, Ran; Yurkewich, Aaron; Patel, Rajni V.
2016-03-01
Concentric-tube robots (CTR) consist of a series of pre-curved flexible tubes that make up the robot structure and provide the high dexterity required for performing surgical tasks in constrained environments. This special design introduces new challenges in shape sensing as large twisting is experienced by the torsionally compliant structure. In the literature, fiber Bragg grating (FBG) sensors are attached to needle-sized continuum robots for curvature sensing, but they are limited to obtaining bending curvatures since a straight sensor layout is utilized. For a CTR, in addition to bending curvatures, the torsion along the robots shaft should be determined to calculate the shape and pose of the robot accurately. To solve this problem, in our earlier work, we proposed embedding FBG sensors in a helical pattern into the tube wall. The strain readings are converted to bending curvatures and torsion by a strain-curvature model. In this paper, a modified strain-curvature model is proposed that can be used in conjunction with standard shape reconstruction algorithms for shape and pose calculation. This sensing technology is evaluated for its accuracy and resolution using three FBG sensors with 1 mm sensing segments that are bonded into the helical grooves of a pre-curved Nitinol tube. The results show that this sensorized robot can obtain accurate measurements: resolutions of 0.02 rad/m with a 100 Hz sampling rate. Further, the repeatability of the obtained measurements during loading and unloading conditions are presented and analyzed.
A Rare Emergency: Testicular Torsion in the Inguinal Canal
Şener, Nevzat Can; Bas, Okan; Yesil, Suleyman; Zengin, Kursad; Imamoglu, Abdurrahim
2015-01-01
Objectives. To report our experience and present the largest series of testicular torsion cases in the inguinal canal. Material and Methods. The clinical data of 13 patients with testicular torsion in the inguinal canal treated between 2005 and 2013 were reviewed. Recorded patient age, whether the testes were palpable or not, side of the affected testes, the presence of hernia, ischemia time, and operation outcomes were assessed. Results. Patient age ranged from 8 to 70 months (29.15 ± 20.22). Mean ischemia time was 16.5 ± 21.3 hours. Accompanying inguinal hernia was present in 92% of the cases (12/13). Four of the thirteen patients (30.8%) were treated by orchiectomy because the necrosis was present after prolonged ischemia time. Nine patients (69.2%) were treated by single session orchidopexy. Conclusion. Torsion of testes in the inguinal canal is a rare disease, but with rapid diagnosis, affected testes can be salvaged, but the key factor is to keep this condition in mind. PMID:25654093
Design of a smart superstructure FBG torsion sensor
NASA Astrophysics Data System (ADS)
Miclos, Sorin; Savastru, Dan; Savastru, Roxana; Lancranjan, Ion I.
2015-05-01
The paper presents the results obtained in simulation of a Superstructure Fiber Bragg Grating (SFBG) torsion sensor. The SFBG sensor simulation points to an improved smart composite or metallic parts design to be operated under torsion loads in various applications. SFBG sensor simulation consists of correlating the fiber deformation under applied mechanical loads with the modified FBG characteristic reflection spectrum considering the polarization mode variations. The analyzed SFBG is developed by the selective deposition of on-fiber periodic metal thin films on regular FBGs. The torsion mechanical loads induced shifts in the characteristic reflection spectrum of Bragg wavelength and side bands are analyzed. For obtaining information about an optimal structure of SFBG sensor, simulation is performed for four commercially available photosensitive single mode silica optical fibers having different geometric and optical characteristics, mainly core and clad refractive index values. It is considered that, by using an UV writing technique, Brag gratings are induced into the simulated SFBG. Simulations are performed considering different geometric characteristics of the shaft used as mechanical mount of SFBG. The simulation results are in fairly good agreement with the experimental ones reported in literature.
Optical diagnosis of testicular torsion: feasibility and methodology
NASA Astrophysics Data System (ADS)
Shadgan, Babak; Macnab, Andrew; Stothers, Lynn; Kajbafzadeh, A. M.
2014-03-01
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.
Torsional stiffness degradation and aerostatic divergence of suspension bridge decks
NASA Astrophysics Data System (ADS)
Zhang, Z. T.; Ge, Y. J.; Yang, Y. X.
2013-07-01
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.
LISA technology development using the UF precision torsion pendulum
NASA Astrophysics Data System (ADS)
Apple, Stephen; Chilton, Andrew; Olatunde, Taiwo; Ciani, Giacomo; Mueller, Guido; Conklin, John
2015-04-01
LISA will directly observe low-frequency gravitational waves emitted by sources ranging from super-massive black hole mergers to compact galactic binaries. A laser interferometer will measure picometer changes in the distances between free falling test masses separated by millions of kilometers. A test mass and its associated sensing, actuation, charge control and caging subsystems are referred to as a gravitational reference sensor (GRS). The demanding acceleration noise requirement for the LISA GRS has motivated a rigorous testing campaign in Europe and a dedicated technology mission, LISA Pathfinder, scheduled for launch in the fall of 2015. At the University of Florida we are developing a nearly thermally noise limited torsion pendulum for testing GRS technology enhancements that may improve the performance and/or reduce the cost of the LISA GRS. This experimental facility is based on the design of a similar facility at the University of Trento, and consists of a vacuum enclosed torsion pendulum that suspends mock-ups of the LISA test masses, surrounded by electrode housings. Some of the technologies that will be demonstrated by this facility include a novel TM charge control scheme based on ultraviolet LEDs, an all-optical TM position and attitude sensor, and drift mode operation. This presentation will describe the design of the torsion pendulum facility, its current acceleration noise performance, and the status of the GRS technologies under development.
Ocular torsion before and after 1 hour centrifugation.
Groen, E; De Graaf, B; Bles, W; Bos, J E
1996-01-01
To assess a possible otolith contribution to effects observed following prolonged exposure to hypergravity, we used video oculography to measure ocular torsion during static and dynamic conditions of lateral body tilt (roll) before and after 1 h of centrifugation with a Gx-load of 3 G. Static tilt (from 0 to 57 degrees to either side) showed a 10% decrease in otolith-induced ocular torsion after centrifugation. This implies a reduced gain of the otolith function. The dynamic condition consisted of sinusoidal body roll (frequency 0.25 Hz, amplitude 45 degrees) about an earth horizontal and about an earth vertical axis (respectively, "with" and "without" otolith stimulation). Before centrifugation the gain of the slow component velocity (SCV) was significantly lower "with" otolith stimulation than "without" otolith stimulation. Apparently, the contribution of the otoliths counteracts the ocular torsion response generated by the semicircular canals. Therefore, the observed increase in SCV gain in the condition "with" otolith stimulation after centrifugation, seems in correspondence with the decreased otolith gain in the static condition.
Composite box beam analysis - Theory and experiments
NASA Technical Reports Server (NTRS)
Bauchau, O. A.; Coffenberry, B. S.; Rehfield, L. W.
1987-01-01
Beam theory is widely used as a first approximation in numerous structural applications. When applied to composite beams, the accuracy of beam theory becomes questionable because (1) the shearing and warping deformations become significant, as the shearing stiffness of composite laminates is often very low, and (2) several elastic couplings can occur that strongly influence the behavior of composite beams. The torsional behavior of thin-walled composite beams has important implications for aeronautical structures and is deeply modified by the above nonclassical effects. This paper presents two comprehensive analysis methodologies for composite beams and describes experimental results obtained from a thin-walled, rectangular cross-sectional beam. The theoretical predictions are found in good agreement with the observed twist and strain distributions. Out-of-plane torsional warping of the cross-section is found to be the key factor for an accurate modeling of the torsional behavior of such structures.
Angular momentum and torque described with the complex octonion
Weng, Zi-Hua
2014-08-15
The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of electromagnetic field and of gravitational field can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic) dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory.
Fast torsional waves and strong magnetic field within the Earth's core.
Gillet, Nicolas; Jault, Dominique; Canet, Elisabeth; Fournier, Alexandre
2010-05-06
The magnetic field inside the Earth's fluid and electrically conducting outer core cannot be directly probed. The root-mean-squared (r.m.s.) intensity for the resolved part of the radial magnetic field at the core-mantle boundary is 0.3 mT, but further assumptions are needed to infer the strength of the field inside the core. Recent diagnostics obtained from numerical geodynamo models indicate that the magnitude of the dipole field at the surface of a fluid dynamo is about ten times weaker than the r.m.s. field strength in its interior, which would yield an intensity of the order of several millitesla within the Earth's core. However, a 60-year signal found in the variation in the length of day has long been associated with magneto-hydrodynamic torsional waves carried by a much weaker internal field. According to these studies, the r.m.s. strength of the field in the cylindrical radial direction (calculated for all length scales) is only 0.2 mT, a figure even smaller than the r.m.s. strength of the large-scale (spherical harmonic degree n
Chirality and the angular momentum of light
Götte, Jörg B.; Barnett, Stephen M.; Yao, Alison M.
2017-01-01
Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral light–matter interactions. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069764
Angular momentum in the Local Group
Dunn, A.; Laflamme, R.
1994-04-01
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.
Angular motion estimation using dynamic models in a gyro-free inertial measurement unit.
Edwan, Ezzaldeen; Knedlik, Stefan; Loffeld, Otmar
2012-01-01
In this paper, we summarize the results of using dynamic models borrowed from tracking theory in describing the time evolution of the state vector to have an estimate of the angular motion in a gyro-free inertial measurement unit (GF-IMU). The GF-IMU is a special type inertial measurement unit (IMU) that uses only a set of accelerometers in inferring the angular motion. Using distributed accelerometers, we get an angular information vector (AIV) composed of angular acceleration and quadratic angular velocity terms. We use a Kalman filter approach to estimate the angular velocity vector since it is not expressed explicitly within the AIV. The bias parameters inherent in the accelerometers measurements' produce a biased AIV and hence the AIV bias parameters are estimated within an augmented state vector. Using dynamic models, the appended bias parameters of the AIV become observable and hence we can have unbiased angular motion estimate. Moreover, a good model is required to extract the maximum amount of information from the observation. Observability analysis is done to determine the conditions for having an observable state space model. For higher grades of accelerometers and under relatively higher sampling frequency, the error of accelerometer measurements is dominated by the noise error. Consequently, simulations are conducted on two models, one has bias parameters appended in the state space model and the other is a reduced model without bias parameters.
NASA Technical Reports Server (NTRS)
Angelaki, D. E.; Hess, B. J.
1996-01-01
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).
Rotational Energies in Various Torsional Levels of CH_2DOH
NASA Astrophysics Data System (ADS)
Coudert, L. H.; Hilali, A. El; Margulès, L.; Motiyenko, R. A.; Klee, S.
2012-06-01
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
Wigner functions for the pair angle and orbital angular momentum
NASA Astrophysics Data System (ADS)
Kastrup, H. A.
2016-12-01
The problem of constructing physically and mathematically well-defined Wigner functions for the canonical pair angle θ and angular momentum p is solved. While a key element for the construction of Wigner functions for the planar phase space {(q ,p ) ∈R2} is the Heisenberg-Weyl group, the corresponding group for the cylindrical phase space {(θ ,p ) ∈S1×R } is the Euclidean group E (2 ) of the plane and its unitary representations. Here the angle θ is replaced by the pair (cosθ ,sinθ ) , which corresponds uniquely to the points on the unit circle. The main structural properties of the Wigner functions for the planar and the cylindrical phase spaces are strikingly similar. A crucial role is played by the s i n c function, which provides the interpolation for the discontinuous quantized angular momenta in terms of the continuous classical ones, in accordance with the famous Whittaker cardinal function well known from interpolation and sampling theories. The quantum mechanical marginal distributions for the angle (continuous) and angular momentum (discontinuous) are, as usual, uniquely obtained by appropriate integrations of the (θ ,p ) Wigner function. Among the examples discussed is an elementary system of simple cat states.
Generation and detection of neutron beams with orbital angular momentum
NASA Astrophysics Data System (ADS)
Pushin, Dmitry A.; Barankov, Roman A.; Clark, Charles W.; Huber, Michael G.; Arif, Muhammad; Cory, David G.
2015-05-01
Orbital angular momentum (OAM) states of light, in which photons carry lℏ units of angular momentum along their direction of propagation, are of interest in a variety of applications. The Schrödinger equation for massive particles also supports OAM solutions, and OAM states have been demonstrated with ultracold atoms and electrons. Here we report the first generation and detection of OAM states of neutrons, with l up to 7. These are made using spiral phase plates (SPP), milled out of 6061 aluminum alloy dowels with a high-resolution computer-controlled milling machine. When a SPP is placed in one arm of a Mach-Zehnder neutron interferometer, the interferogram reveals the characteristic patterns of OAM states. Addition of angular momenta is effected by concatenation of SPPs with different values of l; we have found the experimental result 1 + 2 = 3 , in reasonable agreement with theory. The advent of OAM provides an additional, quantized, degree of freedom to neutron interferometry, enlarging the qubit structure available for tests of quantum information processing and foundations of quantum physics.
Angular momentum blockade in nanoscale high-Tc superconducting grains
NASA Astrophysics Data System (ADS)
Mancarella, Francesco; Balatsky, Alexander; Wallin, Mats; Rosengren, Anders; Nordita-Condensed Matter Collaboration; KTH-Theoretical Physics Collaboration
2014-03-01
We discuss the angular momentum blockade in small d-wave SC grains in an external magnetic field. We find abrupt changes in angular momentum state of the condensate (''angular momentum blockade'') as a result of the variation of the external field. The effect represents a direct analog of the Coulomb blockade. We use the Ginzburg-Landau theory to illustrate how the field turns a d-wave order parameter (OP) into a(dx2 -y2 + idxy)-OP. We derive the volume magnetic susceptibility as a function of the field, and corresponding small jumps in magnetization at critical values of the field that should be experimentally observable in SC grains. The observation of these jumps requires a small grain, since their extent is inversely proportional to the number of Cooper pairs in the sample. The general source of instability of the pure d-wave gap is the presence of gap nodes, completely lifted by the secondary OP component. A d + id' -state is chiral and hence has an orbital moment carried by Cooper pairs. We consider fields H <
Classical and quantum chaotic angular-momentum pumps.
Dittrich, T; Dubeibe, F L
2015-03-06
We study directed transport of charge and intrinsic angular momentum by periodically driven scattering in the regime of fast and strong driving. A spin-orbit coupling through a kicked magnetic field confined to a compact region in space leads to irregular scattering and triggers spin flips in a spatially asymmetric manner which allows us to generate polarized currents. The dynamical mechanisms responsible for the spin separation carry over to the quantum level and give rise to spin pumping. Our theory based on the Floquet formalism is confirmed by numerical solutions of the time-dependent inhomogeneous Schrödinger equation with a continuous source term.
Torsion sensors of high sensitivity and wide dynamic range based on a graphene woven structure.
Yang, Tingting; Wang, Yan; Li, Xinming; Zhang, Yangyang; Li, Xiao; Wang, Kunlin; Wu, Dehai; Jin, Hu; Li, Zhihong; Zhu, Hongwei
2014-11-07
Due to its unique electromechanical properties, nanomaterial has become a promising material for use in the sensing elements of strain sensors. Tensile strain is the type of deformation most intensively studied. Torsion is another deformation occurring in everyday life, but is less well understood. In the present study a torsion sensor was prepared by wrapping woven graphene fabrics (GWFs) around a polymer rod at a specific winding angle. The GWF sensor showed an ultra-high sensitivity with a detection limit as low as 0.3 rad m(-1), indicating its potential application in the precise measurement of low torsions. The GWFs were pre-strained before wrapping on polydimethylsiloxane (PDMS) to improve the tolerance of the sensor to high torsion. The microstructure of the GWFs at different torsion levels was monitored using an optical microscope. The results demonstrated the formation of GWF waves and cracks under high torsion, a critical factor in determining the electromechanical properties of a GWF sensor.
NASA Astrophysics Data System (ADS)
Clary, David C.; Meijer, Anthony J. H. M.
2002-06-01
Quantum dynamical calculations have been carried out on the excitation of the torsional vibrations of a protein by collision with a solvent molecule. This energy transfer process represents the first step in the unfolding of the protein. The method developed for this purpose is the torsional close coupling, infinite order sudden approximation. Both time-independent and time dependent methods are used to solve the scattering problem and individual excitation of all the torsional modes of the protein is treated. The method is applied to the excitation of the HIV protein gp41 colliding with a water molecule. This protein has 1101 atoms, 56 amino acids, and 452 torsional modes. A major mode-selective effect is found in the computations: it is much easier to excite backbone torsions than sidechain torsions in the protein. In addition, resonances arise in the collisional process and these complexes involve temporary trapping of the water molecule inside the pockets of the protein.
Kurita, Yoshihisa; Wada, Hiroshi
2011-10-23
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-β (TGF-β) 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-β pathway.
Improving the sensitivity of a torsion pendulum by using an optical spring method
Wang Qinglan; Yeh Hsienchi; Zhou Zebing; Luo Jun
2009-10-15
We present a scheme aiming at improving the sensitivity of a torsion pendulum by means of radiation-pressure-induced optical spring. Two partial-reflective mirrors are installed on the opposite sides of a torsion pendulum, and one high-reflective mirror is mounted at the end of the torsion beam so that two identical Fabry-Perot cavities can be formed and aligned in series. Due to the antisymmetric radiation pressures acting on the opposite sides of the torsion beam, a negative restoring coefficient can be generated within a certain dynamic range, such that both the resultant torsional rigidity and the resonant frequency of the torsion pendulum are reduced, and the minimum detectable response torque in high-frequency region can be reduced accordingly.
Molecular dynamics study of the torsional vibration characteristics of boron-nitride nanotubes
NASA Astrophysics Data System (ADS)
Ansari, R.; Ajori, S.
2014-08-01
In recent years, synthesizing inorganic nanostructures such as boron nitride nanotubes (BNNTs) has led to extensive studies on their exceptional properties. In this study, the torsional vibration behavior of boron-nitride nanotubes (BNNTs) is explored on the basis of molecular dynamics (MD) simulation. The results show that the torsional frequency is sensitive to geometrical parameters such as length and boundary conditions. The axial vibration is found to be induced by torsional vibration of nanotubes which can cause instability in the nanostructure. It is also observed that the torsional frequency of BNNTs is higher than that of their carbon counterpart. Moreover, the shear modulus is predicted by incorporating MD simulation numerical results into torsional vibration frequency obtained through continuum-based model of tubes. Finally, it is seen that the torsional frequency of double-walled boron-nitride nanotubes (DWBNNTs) is between the frequencies of their constituent inner and outer tubes.
Creating an Isotopically Similar Earth and Moon from a Giant Impact with Correct Angular Momentum
NASA Astrophysics Data System (ADS)
Sumpter, William
2017-01-01
The giant-impact hypothesis is the dominant theory as to how the Earth-Moon system was formed, but angular momentum concerns have cast a shadow on its validity. Computer generated impacts have been successful in producing virtual Earth-Moon systems that possess many of the properties of the observed system, but when tasked with addressing the isotopic similarities between the Earth and Moon they result in systems with excessive angular momentum. Evection resonance between the Moon and the Sun has been put forth as a means of removing the excess angular momentum, but this reasoning was rejected by The Royal Society at a special session called to discuss the origin of the Moon. We show here how to use impactor spins to create an impact that preserves all the favorable aspects of previous simulations and produces an Earth-Moon system with the correct angular momentum. Evection resonance is not needed.
Axial and torsional fatigue behavior of a cobalt-base alloy
NASA Technical Reports Server (NTRS)
Bonacuse, Peter J.; Kalluri, Sreeramesh
1991-01-01
In order to develop elevated temperature multiaxial fatigue life prediction models for the wrought cobalt-base alloy, Haynes 188, a multiaxial fatigue data base is required. To satisfy this need, an elevated temperature experimental program on Haynes 188 consisting of axial, torsional, inphase and out of phase axial-torsional fatigue experiments was designed. Elevated temperature axial and torsional fatigue experiments were conducted under strain control on thin wall tubular specimens of Haynes 188 in air. Test results are given.
Torsion Tests of 24S-T Aluminum-alloy Noncircular Bar and Tubing
NASA Technical Reports Server (NTRS)
Moore, R L; Paul, D A
1943-01-01
Tests of 24S-T aluminum alloy have been made to determine the yield and ultimate strengths in torsion of noncircular bar and tubing. An approximate basis for predicting these torsional strength characteristics has been indicated. The results show that the torsional stiffness and maximum shearing stresses within the elastic range may be computed quite closely by means of existing formulas based on mathematical analysis and the membrane analogy.
Gilroy, Richard; Johnson, Philip
2013-01-01
Inferior vena cava (IVC) stenosis and torsion are well-described rare complications following orthotopic liver transplantation (OLT). We present a case of inferior vena cava intermittent torsion and stenosis complicated by compressive regional ascites. To the best of our knowledge, this is the second case of post-OLT regional ascites related compressive IVC stenosis reported and the first reported case of torsion complicated by regional ascites compression. PMID:24386585
3D Curves With a Prescribed Curvature and Torsion for a Flying Robot
Bestaoui, Yasmina
2008-06-12
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.
Application of a boundary element method to the study of dynamical torsion of beams
NASA Technical Reports Server (NTRS)
Czekajski, C.; Laroze, S.; Gay, D.
1982-01-01
During dynamic torsion of beam elements, consideration of nonuniform warping effects involves a more general technical formulation then that of Saint-Venant. Nonclassical torsion constants appear in addition to the well known torsional rigidity. The adaptation of the boundary integral element method to the calculation of these constants for general section shapes is described. The suitability of the formulation is investigated with some examples of thick as well as thin walled cross sections.
Eye torsion and visual tilt are mediated by different binocular processes
NASA Technical Reports Server (NTRS)
Wolfe, J. M.; Held, R.
1979-01-01
Viewing a large, patterned field rotating about the line of sight produces two measurable effects; cyclotorsion of the eyes (torsion) and a perceived displacement of vertical and horizontal (tilt). Experiments examining binocular interaction for these effects show: (1) both effects demonstrate summation in normal individuals and thus both involve a binocular process; (2) the process for tilt is different than for torsion, since summation for torsion is spared in stereodeficient individuals while that for tilt is eliminated.
Extended torsional tests of an interlocked bi-stem satellite boom
NASA Technical Reports Server (NTRS)
Abercrombie, R. A.
1973-01-01
The effect is reported of continued oscillations of a 1.27-cm interlocked bi-stem satellite boom. The test setup oscillated a boom continuously between set torque limits and periodically recorded its hysteresis characteristics. Results showed that repeated oscillations affected torsional characteristics and that torsional rigidity changed as a function of the number of cycles oscillated within certain torque limits. Torsional characteristics changes caused by repeated oscillations were retained.
Supernovae at the Highest Angular Resolution
NASA Technical Reports Server (NTRS)
Dyk, S. Van; Weiler, K.; Sramek, R.; Panagia, N.; Lacey, C.; Montes, M.; Mercaide, J.; Lewin, W.; Fox, D.; Filippenko, A.; Peng, C.
2000-01-01
The study of supernovae (SNe) and their environments in host galaxies at the highest possible angular resolution in a number of wavelength regimes is providing vital clues to the nature of their progenitor stars.
Radially dependent angular acceleration of twisted light.
Webster, Jason; Rosales-Guzmán, Carmelo; Forbes, Andrew
2017-02-15
While photons travel in a straight line at constant velocity in free space, the intensity profile of structured light may be tailored for acceleration in any degree of freedom. Here we propose a simple approach to control the angular acceleration of light. Using Laguerre-Gaussian modes as our twisted beams carrying orbital angular momentum, we show that superpositions of opposite handedness result in a radially dependent angular acceleration as they pass through a focus (waist plane). Due to conservation of orbital angular momentum, we find that propagation dynamics are complex despite the free-space medium: the outer part of the beam (rings) rotates in an opposite direction to the inner part (petals), and while the outer part accelerates, the inner part decelerates. We outline the concepts theoretically and confirm them experimentally. Such exotic structured light beams are topical due to their many applications, for instance in optical trapping and tweezing, metrology, and fundamental studies in optics.
Characterization of the bell-shaped vibratory angular rate gyro.
Liu, Ning; Su, Zhong; Li, Qing; Fu, MengYin; Liu, Hong; Fan, JunFang
2013-08-07
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.
Angular Momentum Theory Applied to Interactions in Solids
1987-02-01
calculation of the matrix elements of the various Interactions Is presented, along with other tables andaids in the computation of thie energy levels...87 8.3 Annotated Bibliography and References ........................ 88 9. MATRIX ELEMENTS OF H3 IN TOTAL A GULAR MOMENTUM STATE FOR THE ELECTRONIC...in Ckq ........... 86 10.1 Matrix Elements of Crystal Field for a Single d Electron in S4 Symmetry
Angular performance measure for tighter uncertainty relations
Hradil, Z.; Rehacek, J.; Klimov, A. B.; Rigas, I.; Sanchez-Soto, L. L.
2010-01-15
The uncertainty principle places a fundamental limit on the accuracy with which we can measure conjugate quantities. However, the fluctuations of these variables can be assessed in terms of different estimators. We propose an angular performance that allows for tighter uncertainty relations for angle and angular momentum. The differences with previous bounds can be significant for particular states and indeed may be amenable to experimental measurement with the present technology.
Relativistic Electron Wave Packets Carrying Angular Momentum
NASA Astrophysics Data System (ADS)
Bialynicki-Birula, Iwo; Bialynicka-Birula, Zofia
2017-03-01
There are important differences between the nonrelativistic and relativistic description of electron beams. In the relativistic case the orbital angular momentum quantum number cannot be used to specify the wave functions and the structure of vortex lines in these two descriptions is completely different. We introduce analytic solutions of the Dirac equation in the form of exponential wave packets and we argue that they properly describe relativistic electron beams carrying angular momentum.
Detection of testicular torsion by magnetic resonance imaging in a rat model.
Landa, H M; Gylys-Morin, V; Mattery, R F; Hajek, P; Krous, H F; Kaplan, G W; Packer, M G
1988-11-01
Testicular torsion is one of the most common pediatric urological emergencies. Incorrect or delayed diagnosis contributes significantly to morbidity. We previously have shown that magnetic resonance displays scrotal contents with great detail using hydrogen concentration weighted and T2 weighted images. Sprague-Dawley rats underwent either unilateral 720-degree testicular torsion or a sham procedure. Magnetic resonance images were obtained at intervals with a 3 or 5-inch surface coil. Scans after surgical torsion showed a characteristic spiral distortion of the fascial planes of the spermatic cord, not seen in the sham animals, as well as a decrease in testicular size with prolonged torsion.
An investigation on the behaviour and stiffness of reinforced concrete slabs subjected to torsion
NASA Astrophysics Data System (ADS)
Nguyen, M. C. T.; Pham, P. T.
2017-01-01
This paper presents an investigation on RC slab under torsion, by both experiment and finite element analysis. The torsion tests were done on three similar square RC slabs with dimensions of 1900×1900×150 mm. The behaviour of slabs at pre-cracking and post-cracking of concrete phases were investigated, via Load-displacement, twisting moment-curvature relationships, and torsional stiffness of slabs. The experimental results are compared with the FEA and the results in literatures. The torsional stiffness of slab at the phase of concrete cracked and steel yield is about 1/25 of the stiffness at the pre-cracking phase.
Yamada, Takeo; Yamamoto, Yuki; Hayamizu, Yuhei; Sekiguchi, Atsuko; Tanaka, Hiroyuki; Kobashi, Kazufumi; Futaba, Don N; Hata, Kenji
2013-04-23
A rational torsion sensing material was fabricated by wrapping aligned single-walled carbon nanotube (SWCNT) thin films onto the surface of a rod with a predetermined and fixed wrapping angle without destroying the internal network of the SWCNTs within the film. When applied as a torsion sensor, torsion could be measured up to 400 rad/meter, that is, more than 4 times higher than conventional optical fiber torsion sensors, by monitoring increases in resistance due to fracturing of the aligned SWCNT thin films.
Trunk rotation monitor using angular velocity sensors.
Seo, A; Uda, S
1997-04-01
To monitor the low back risk imposed by asymmetric postures at workplaces, a method using angular velocity sensors was studied. According to a simple model analysis, trunk rotation could be calculated from the angular velocities measured at both the waist and shoulder and from the inclination of each angular velocity sensor. We thus developed a new detector consisting of an angular velocity sensor (ENC-05D, Murata, Japan) for detecting angular velocity and an acceleration sensor (ADXL05, Analog Devices, USA) for measuring inclination. The precision of the angular velocity sensor was high as the correlation coefficient between the output of the sensor and the true value was 0.9996. When the detectors were affixed to a subject and compared with data measured by a Vicon System 370 (Oxford Metrics, UK), the correlation coefficients between the two methods were 0.949 and 0.815 during model tasks of box transfer and box lifting, respectively. In a model of lifting boxes at different rates, the mean and standard deviation increased according to the task speed. This method was shown to be of practical use for monitoring trunk rotation.
Balint-Kurti, Gabriel G; Vasyutinskii, Oleg S
2009-12-31
A general reactive collision of the type A + B --> C + D is considered where both the collision partners (A and B) or the products (C and D) may possess internal, i.e., spin, orbital or rotational, angular momenta. Compact expressions are derived using a rigorous quantum mechanical analysis for the angular momentum anisotropy of either of the products (C or D) arising from an initially polarized distribution of the reactant angular momentum. The angular momentum distribution of the product is expressed in terms of canonical spherical tensors multiplied by anisotropy-transforming coefficients c(K(i)q(k))(K)(K(r),L). These coefficients act as transformation coefficients between the angular momentum anisotropy of the reactants and that of the product. They are independent of scattering angle but depend on the details of the scattering dynamics. The relationship between the coefficients c(K(i)q(k))(K)(K(r),L) and the body-fixed scattering S matrix is given and the methodology for the quantum mechanical calculation of the anisotropy-transforming coefficients is clearly laid out. The anisotropy-transforming coefficients are amenable to direct experimental measurement in a similar manner to vector correlation and alignment parameters in photodissociation processes. A key aspect of the theory is the use of projections of both reactant and product angular momenta onto the product recoil vector direction. An important new conservation rule is revealed through the analysis, namely that if the state multipole for reactant angular momentum distribution has a projection q(k) onto the product recoil vector the state multipoles for the product angular momentum distribution all have this same projection. Expressions are also presented for the distribution of the product angular momentum when its components are evaluated relative to the space-fixed Z-axis. Notes with detailed derivations of all the formulas are available as Supporting Information.
NASA Technical Reports Server (NTRS)
Johnson, R. A.; Wehrly, T.
1976-01-01
Population models for dependence between two angular measurements and for dependence between an angular and a linear observation are proposed. The method of canonical correlations first leads to new population and sample measures of dependence in this latter situation. An example relating wind direction to the level of a pollutant is given. Next, applied to pairs of angular measurements, the method yields previously proposed sample measures in some special cases and a new sample measure in general.
Zhang, Daixian; Wu, Jianjun; Zhang, Rui; Zhang, Hua; He, Zhen
2013-12-01
A sympathetic resonance theory is analyzed and applied in a newly developed torsional pendulum to measure the micro-impulse produced by a μN 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.
Vacuum static compactified wormholes in eight-dimensional Lovelock theory
Canfora, Fabrizio; Giacomini, Alex
2008-10-15
In this paper, new exact solutions in eight-dimensional Lovelock theory will be presented. These solutions are the vacuum static wormhole, the black hole, and generalized Bertotti-Robinson space-times with nontrivial torsion. All of the solutions have a cross product structure of the type M{sub 5}x{sigma}{sub 3}, where M{sub 5} is a five-dimensional manifold and {sigma}{sub 3} a compact constant curvature manifold. The wormhole is the first example of a smooth vacuum static Lovelock wormhole which is neither Chern-Simons nor Born-Infeld. It will be also discussed how the presence of torsion affects the 'navigableness' of the wormhole for scalar and spinning particles. It will be shown that the wormhole with torsion may act as 'geometrical filter': A very large torsion may 'increase the traversability' for scalars while acting as a 'polarizator' on spinning particles. This may have interesting phenomenological consequences.
Mapping conformational dynamics of proteins using torsional dynamics simulations.
Gangupomu, Vamshi K; Wagner, Jeffrey R; Park, In-Hee; Jain, Abhinandan; Vaidehi, Nagarajan
2013-05-07
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 Ca(2+)-bound to the Ca(2+)-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
Mapping Conformational Dynamics of Proteins Using Torsional Dynamics Simulations
Gangupomu, Vamshi K.; Wagner, Jeffrey R.; Park, In-Hee; Jain, Abhinandan; Vaidehi, Nagarajan
2013-01-01
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
Focal point analysis of torsional isomers of acrylic acid
NASA Astrophysics Data System (ADS)
Alev Çiftçioğlu, Gökçen; Trindle, Carl; Yavuz, Ilhan
2010-10-01
The thermochemistry of acrylic acid has presented challenges owing to its high reactivity, tendency to dimerize in the gas phase, and the existence of two very nearly equal energy conformational isomers. Well-tested thermochemical schemes including G2, G3, G4, and CBS-QB3 agree in the prediction that the s-cis syn structure is the most stable of the torsional isomers, with the s-cis anti form lying 3 kJ mol-1 or less higher in energy. Microwave spectra suggest a value of 0.63 kJ mol-1. The energy barrier between these forms is in the neighbourhood of 25 kJ mol-1 according to a MP2/cc-pVDZ calculation. We present estimates of the relative energies of all four torsional isomers and the rotational barrier based on a variant of the Focal Point Analysis developed by Császár and co-workers. These calculations, extending to the CCSD(T)/cc-pV5Z level, predict that the s-cis anti torsional isomer is the most stable form, in contrast to prior estimates. The s-cis syn form lies about 2.9 kJ mol-1 higher, while the s-trans syn and anti forms lie at about 21.7 and 23.3 kJ mol-1, respectively. We estimate the rotational barrier between the s-cis trans and s-cis anti structures to be about 23.9 kJ mol-1. Error ranges derived from the fit to extrapolation forms suggest that our estimates have an uncertainty of about 0.1 kJ mol-1.
Cross-axis adaptation of torsional components in the yaw-axis vestibulo-ocular reflex
NASA Technical Reports Server (NTRS)
Trillenberg, P.; Shelhamer, M.; Roberts, D. C.; Zee, D. S.
2003-01-01
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
NASA Astrophysics Data System (ADS)
Huang, Yuxin; Xin, Qinkun; Yin, Huabing
2010-06-01
The torsional vibration of vehicle transmission system is heavily concerned with the increase of vehicle speed. The whole powertrain system has to be matched according to the torsional vibration characteristics, especially in developing a new vehicle. The selection of proper elastic coupling has to be made for the torsional vibration match and some frequencies have to be moved out of engine's range . Thus the torsional vibration model of powertrain needs to be built. In the paper a new torsional vibration model is built, which is programmed in the form of a platform. The whole powertrain system torsional vibration model of a vehicle is built firstly with consideration of gear mesh stiffness and engine's excitation in it. The free torsional vibration mode analysis is made and the resonant torques of each lumped inertia in the transmission system are obtained. Secondly the forced vibration of transmission system with the engine's excitation is made and the dynamic torques of each lumped inertias are obtained. Thirdly the process for the torsional vibration analysis is integrated into the optimization process and the selection of elastic coupling for the transmission system is made according the optimization and match results. Fourthly in order to modify the design parameters in the structural design, the sensitivities of inertia and torsional stiffness with reference to eigenvalues are obtained. At last the evaluations of analysis results are made and some suggestions for structural modification for engineers are presented. According to the above study, the conclusion can be made that the new torsional modelling method, the elastic coupling selection method and integration optimization method in the paper are practical and reliabl and these methods play very important roles in torsional vibration analyzing, match and optimization of vehicle transmission system.