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…

Supersonic flow past oscillating airfoils including nonlinear thickness effects

NASA Technical Reports Server (NTRS)

Van Dyke, Milton D

1954-01-01

A solution to second order in thickness is derived for harmonically oscillating two-dimensional airfoils in supersonic flow. For slow oscillations of an arbitrary profile, the result is found as a series including the third power of frequency. For arbitrary frequencies, the method of solution for any specific profile is indicated, and the explicit solution derived for a single wedge. Nonlinear thickness effects are found generally to reduce the torsional damping, and so enlarge the range of Mach numbers within which torsional instability is possible.

33. VERTICAL AND TORSIONAL OSCILLATIONS, 3/4 VIEW, 7 NOVEMBER 1940, ...

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

33. VERTICAL AND TORSIONAL OSCILLATIONS, 3/4 VIEW, 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

Diagnostic evaluation of ovarian torsion: An analysis of pediatric patients using the Nationwide Emergency Department Sample.

PubMed

Rialon, Kristy L; Wolf, Steven; Routh, Jonathan C; Adibe, Obinna O

2017-04-01

Ultrasonography (US) is the diagnostic modality of choice during work-up for ovarian torsion, although computed tomography (CT) may be used. We examined the utilization of CT in girls with ovarian torsion, and determined which patients are most likely to undergo this study. The Nationwide Emergency Department Sample dataset was searched for patients <18 years who presented with ovarian torsion from 2006 to 2012. Hospitals were categorized by the volume of pediatric patients seen. A total of 1279 patients were identified. Seven hundred twelve (56%) were seen at adult hospitals, 154 (12%) at pediatric privileged, and 413 (32%) at pediatric hospitals. Patients cared for in a pediatric or pediatric privileged hospital had more US alone performed to diagnose ovarian torsion (p < 0.01). Girls seen at pediatric hospitals are more likely to undergo US for work-up of ovarian torsion. Copyright © 2016 Elsevier Inc. All rights reserved.

Flutter and oscillating air-force calculations for an airfoil in two-dimensional supersonic flow

NASA Technical Reports Server (NTRS)

Garrick, I E; Rubinow, S I

1946-01-01

A connected account is given of the Possio theory of non-stationary flow for small disturbances in a two-dimensional supersonic flow and of its application to the determination of the aerodynamic forces on an oscillating airfoil. Further application is made to the problem of wing flutter in the degrees of freedom - torsion, bending, and aileron rotations. Numerical tables for flutter calculations are provided for various values of the Mach number greater than unity. Results for bending-torsion wing flutter are shown in figures and are discussed. The static instabilities of divergence and aileron reversal are examined as is a one-degree-of-freedom case of torsional oscillatory instability.

Diesel engine torsional vibration control coupling with speed control system

NASA Astrophysics Data System (ADS)

Guo, Yibin; Li, Wanyou; Yu, Shuwen; Han, Xiao; Yuan, Yunbo; Wang, Zhipeng; Ma, Xiuzhen

2017-09-01

The coupling problems between shafting torsional vibration and speed control system of diesel engine are very common. Neglecting the coupling problems sometimes lead to serious oscillation and vibration during the operation of engines. For example, during the propulsion shafting operation of a diesel engine, the oscillation of engine speed and the severe vibration of gear box occur which cause the engine is unable to operate. To find the cause of the malfunctions, a simulation model coupling the speed control system with the torsional vibration of deformable shafting is proposed and investigated. In the coupling model, the shafting is simplified to be a deformable one which consists of several inertias and shaft sections and with characteristics of torsional vibration. The results of instantaneous rotation speed from this proposed model agree with the test results very well and are successful in reflecting the real oscillation state of the engine operation. Furthermore, using the proposed model, the speed control parameters can be tuned up to predict the diesel engine a stable and safe running. The results from the tests on the diesel engine with a set of tuned control parameters are consistent with the simulation results very well.

Solar array stepping to minimize array excitation

NASA Technical Reports Server (NTRS)

Bhat, Mahabaleshwar K. P. (Inventor); Liu, Tung Y. (Inventor); Plescia, Carl T. (Inventor)

1989-01-01

Mechanical oscillations of a mechanism containing a stepper motor, such as a solar-array powered spacecraft, are reduced and minimized by the execution of step movements in pairs of steps, the period between steps being equal to one-half of the period of torsional oscillation of the mechanism. Each pair of steps is repeated at needed intervals to maintain desired continuous movement of the portion of elements to be moved, such as the solar array of a spacecraft. In order to account for uncertainty as well as slow change in the period of torsional oscillation, a command unit may be provided for varying the interval between steps in a pair.

Propulsion of a flapping and oscillating airfoil

NASA Technical Reports Server (NTRS)

Garrick, I E

1937-01-01

Formulas are given for the propelling or drag force experience in a uniform air stream by an airfoil or an airfoil-aileron combination, oscillating in any of three degrees of freedom; vertical flapping, torsional oscillations about a fixed axis parallel to the span, and angular oscillations of the aileron about a hinge.

Torque balance, Taylor's constraint and torsional oscillations in a numerical model of the geodynamo

NASA Astrophysics Data System (ADS)

Dumberry, Mathieu; Bloxham, Jeremy

2003-11-01

Theoretical considerations and observations suggest that, to a first approximation, the Earth's dynamo is in a quasi-Taylor state, where the axial Lorentz torque on cylindrical surfaces co-axial with the rotation axis vanishes, except for the part involved in torsional oscillations. The latter are rigid azimuthal accelerations of cylindrical surfaces which oscillate with typical periods of decades. We present a solution of a numerical model of the geodynamo in which rigid accelerations of cylinder surfaces are observed. The underlying dynamic state in the model is not a Taylor state because the Reynolds stresses and viscous torque remain large and provide an effective way to balance a large Lorentz torque. This is a consequence of the limited parameter regime which can be attained numerically. Nevertheless, departures in the torque equilibrium are primarily counterbalanced by rigid accelerations of cylindrical surfaces, which, in turn, excite rigid azimuthal oscillations of the surfaces. We show that the azimuthal motion is indeed quasi-rigid, though the torsional oscillations that are produced in the model probably differ from those in the Earth's core because of the large influence of the Reynolds stresses on their dynamics. We also show that the continual excitation of rigid cylindrical accelerations is produced by the advection of the non-axisymmetric structure of the fields by a mean differential rotation of the cylindrical surfaces which produces disconnections and reconnections and continual fluctuations in the Lorentz torque and Reynolds stresses. We propose that the torque balance in Earth's core may evolve in a similar chaotic fashion, except that the influence of the Reynolds stresses is probably weaker. If this is the case, the Lorentz torque on a cylindrical surface is continually fluctuating, even though its time-averaged value vanishes and satisfies Taylor's constraint. Rigid accelerations of cylindrical surfaces are continually excited by the fluctuations in the Lorentz torque, and the torsional oscillations observed in the geomagnetic data are a mixture of forced and free oscillations.

NIST torsion oscillator viscometer response: Performance on the LeRC active vibration isolation platform

NASA Technical Reports Server (NTRS)

Berg, Robert F.; Grodsinsky, Carlos M.

1992-01-01

Critical point viscosity measurements are limited to their reduced temperature approach to T(sub c) in an Earth bound system, because of density gradients imposed by gravity. Therefore, these classes of experiments have been proposed as good candidates for 'microgravity' science experiments where this limitation is not present. The nature of these viscosity measurements dictate hardware that is sensitive to low frequency excitations. Because of the vibratory acceleration sensitivity of a torsion oscillator viscometer, used to acquire such measurements, a vibration isolation sensitivity test was performed on candidate 'microgravity' hardware to study the possibility of meeting the stringent oscillatory sensitivity requirements of a National Institute of Standards and Technology (NIST) torsion oscillator viscometer. A prototype six degree of freedom active magnetic isolation system, developed at NASA Lewis Research Center, was used as the isolation system. The ambient acceleration levels of the platform were reduced to the noise floor levels of its control sensors, about one microgravity in the 0.1 to 10 Hz bandwidth.

Electromagnetic torques in the core and resonant excitation of decadal polar motion

NASA Astrophysics Data System (ADS)

Mound, Jon E.

2005-02-01

Motion of the rotation axis of the Earth contains decadal variations with amplitudes on the order of 10 mas. The origin of these decadal polar motions is unknown. A class of rotational normal modes of the core-mantle system termed torsional oscillations are known to affect the length of day (LOD) at decadal periods and have also been suggested as a possible excitation source for the observed decadal polar motion. Torsional oscillations involve relative motion between the outer core and the surrounding solid bodies, producing electromagnetic torques at the inner-core boundary (ICB) and core-mantle boundary (CMB). It has been proposed that the ICB torque can explain the excitation of the approximately 30-yr-period polar motion termed the Markowitz wobble. This paper uses the results of a torsional oscillation model to calculate the torques generated at Markowitz and other decadal periods and finds, in contrast to previous results, that electromagnetic torques at the ICB can not explain the observed polar motion.

The role of nonlinear torsional contributions on the stability of flexural-torsional oscillations of open-cross section beams

NASA Astrophysics Data System (ADS)

Di Egidio, Angelo; Contento, Alessandro; Vestroni, Fabrizio

2015-12-01

An open-cross section thin-walled beam model, already developed by the authors, has been conveniently simplified while maintaining the capacity of accounting for the significant nonlinear warping effects. For a technical range of geometrical and mechanical characteristics of the beam, the response is characterized by the torsional curvature prevailing over the flexural ones. A Galerkin discretization is performed by using a suitable expansion of displacements based on shape functions. The attention is focused on the dynamic response of the beam to a harmonic force, applied at the free end of the cantilever beam. The excitation is directed along the symmetry axis of the beam section. The stability of the one-component oscillations has been investigated using the analytical model, showing the importance of the internal resonances due to the nonlinear warping coupling terms. Comparison with the results provided by a computational finite element model has been performed. The good agreement among the results of the analytical and the computational models confirms the effectiveness of the simplified model of a nonlinear open-cross section thin-walled beam and overall the important role of the warping and of the torsional elongation in the study of the one-component dynamic oscillations and their stability.

Peculiar torsion dynamical response of spider dragline silk

NASA Astrophysics Data System (ADS)

Liu, Dabiao; Yu, Longteng; He, Yuming; Peng, Kai; Liu, Jie; Guan, Juan; Dunstan, D. J.

2017-07-01

The torsional properties of spider dragline silks from Nephila edulis and Nephila pilipes spiders are investigated by using a torsion pendulum technique. A permanent torsional deformation is observed after even small torsional strain. This behaviour is quite different from that of the other materials tested here, i.e., carbon fiber, thin metallic wires, Kevlar fiber, and human hair. The spider dragline thus displays a strong energy dissipation upon the initial excitation (around 75% for small strains and more for a larger strain), which correspondingly reduces the amplitude of subsequent oscillations around the new equilibrium position. The variation of torsional stiffness in relaxation dynamics of spider draglines for different excitations is also determined. The experimental result is interpreted in the light of the hierarchical structure of dragline silk.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubey, P., E-mail: purushd@barc.gov.in; Sharma, V. K.; Mitra, S.

Synthetic hydroxyapatite (HAp) is an important material in biomedical engineering due to its excellent biocompatibility and bioactivity. Here we report dynamics of cetyltrimethylammonium bromide (CTAB) in HAp composite, prepared by co-precipitation method, as studied by quasielastic neutron scattering (QENS) technique. It is found that the observed dynamics involved two time scales associated with fast torsional motion and segmental motion of the CTAB monomers. In addition to segmental motion of the hydrogen atoms, few undergo torsional motion as well. Torsional dynamics was described by a 2-fold jump diffusion model. The segmental dynamics of CTAB has been described assumimg the hydrogen atomsmore » undergoing diffusion inside a sphere of confined volume. While the diffusivity is found to increase with temperature, the spherical volumes within which the hydrogen atoms are undergoing diffusion remain almost unchanged.« less

Femtosecond pump-probe photoionization-photofragmentation spectroscopy: photoionization-induced twisting and coherent vibrational motion of azobenzene cation.

PubMed

Ho, Jr-Wei; Chen, Wei-Kan; Cheng, Po-Yuan

2009-10-07

We report studies of ultrafast dynamics of azobenzene cation using femtosecond photoionization-photofragmentation spectroscopy. In our experiments, a femtosecond pump pulse first produces an ensemble of azobenzene cations via photoionization of the neutrals. A delayed probe pulse then brings the evolving ionic system to excited states that ultimately undergo ion fragmentation. The dynamics is followed by monitoring either the parent-ion depletion or fragment-ion formation as a function of the pump-probe delay time. The observed transients for azobenzene cation are characterized by a constant ion depletion modulated by a rapidly damped oscillatory signal with a period of about 1 ps. Theoretical calculations suggest that the oscillation arises from a vibration motion along the twisting inversion coordinate involving displacements in CNNC and phenyl-ring torsions. The oscillation is damped rapidly with a time constant of about 1.2 ps, suggesting that energy dissipation from the active mode to bath modes takes place in this time scale.

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 initial design is ~3×10-2 rad·s-1, which corresponds to a period of ~200s or a frequency of ~5×10-3Hz, i.e. significantly smaller than the frequencies of interest. The second subsystem is a robust yet sensitive optical lever which consists of a slit illuminated by a high intensity LED (50,000mcd) emitting in a forward cone of angle ~7°. The slit is located at the focal plane of a lens of aperture f=200mm. This optical design ensures that the image quality and the angular displacement of the image due to motions of the mirror are sensibly independent of changes in the temperature of the surroundings. The optical image falls on a position sensitive diode whose positional accuracy is ≈3×10-5 mm· Hz-1/2 which corresponds to an angular displacement of the mirror by ≈7.5×10-8 rad·Hz-1/2 Currently we are working to improve the seismometer by adding a position control system to help us acquire reliable data in the presence of torsional oscillations. We are also shielding the system from noise due to radiometric and convective currents. We will report on the performance of this balance operated in the basement of a building at the university.

Existence of Torsional Solitons in a Beam Model of Suspension Bridge

NASA Astrophysics Data System (ADS)

Benci, Vieri; Fortunato, Donato; Gazzola, Filippo

2017-11-01

This paper studies the existence of solitons, namely stable solitary waves, in an idealized suspension bridge. The bridge is modeled as an unbounded degenerate plate, that is, a central beam with cross sections, and displays two degrees of freedom: the vertical displacement of the beam and the torsional angles of the cross sections. Under fairly general assumptions, we prove the existence of solitons. Under the additional assumption of large tension in the sustaining cables, we prove that these solitons have a nontrivial torsional component. This appears relevant for security since several suspension bridges collapsed due to torsional oscillations.

Human Subject Effects on Torsion Pendulum Oscillations: Further Evidence of Mediation by Convection Currents.

PubMed

Hammerschlag, Richard; Linda Baldwin, Ann; Schwartz, Gary E

When a human subject sits beneath a wire mesh, hemispheric torsion pendulum (TP) a rapid-onset series of oscillations at frequencies both higher and lower than the fundamental frequency of the TP have been consistently observed. This study was designed to replicate and extend prior findings that suggest the human subject effect on TP behavior is due to subject-generated, heat-induced convection currents. Effects on pendulum behavior were tested after draping an aluminized "space blanket" over the subject and by replacing the subject with a thermal mattress pad shaped to approximate the human form. Experiments were performed in a basic science university research laboratory. Real-time recordings and Fast Fourier Transform frequency spectra of pendulum oscillatory movement. The space blanket blocked, while the mattress pad mimicked, the human subject induced complex array of pendulum oscillations. Our findings support and strengthen previous results that suggest the effects of human subjects on behavior of a torsion pendulum are mediated by body-heat-induced air convection rather than an unknown type of biofield. Copyright © 2016 Elsevier Inc. All rights reserved.

Bulk Modulus Relaxation in Partially Molten Dunite?

NASA Astrophysics Data System (ADS)

Jackson, I.; Cline, C. J., II

2016-12-01

Synthetic solgel-derived Fo90 olivine was mixed with 3.5 wt % basaltic glass and hot-pressed within Ni/Fe foil to produce a dense aggregate expected to contain a small melt fraction at temperatures ≥ 1100°C. This specimen was precision ground and tested in both torsional and flexural forced oscillation to determine the relaxation behavior of both shear (G) and bulk (K) moduli at seismic frequencies. A recent upgrade of our experimental facility allows such measurements to be made without alteration of the driver/detector geometry, and uses an oscillating bending force rather than a bending moment, as previously described. The torsional and flexural tests were conducted in a gas apparatus at 200 MPa confining pressure, with oscillation periods ranging between 1 and 1000 s, during slow staged-cooling from 1300 to 25°C. Shear modulus and associated dissipation data are consistent with those for melt-bearing olivine specimens previously tested in torsion, with a pronounced dissipation peak superimposed on high-temperature background within the 1-1000 s observational window at temperatures of 1100-1200°C. A filament elongation model relates the observed flexural measurements to the variations along the experimental assembly of the complex Young's modulus (E*), bending moment and diametral moment of inertia. With E* given by 1/E*=1/(3G*) + 1/(9K*), and the complex shear modulus (G*) derived from torsional oscillation, any relaxation of K can be identified. Preliminary modeling shows that the viscoelastic properties in flexure are broadly consistent with those expected from the shear-mode viscoelasticity with anharmonic (real) values of K. However, some discrepancies between modeled results and flexure data at super-solidus temperatures require further investigation of possible differences in shear modulus relaxation between the torsional and flexural modes, and of potential relaxation of the bulk modulus through stress-induced changes in melt redistribution and/or proportions of coexisting crystalline and melt phases.

Relaxation of the bulk modulus in partially molten dunite?

NASA Astrophysics Data System (ADS)

Cline, C. J.; Jackson, I.

2016-11-01

To address the possibility of melt-related bulk modulus relaxation, a forced oscillation experiment was conducted at seismic frequencies on a partially molten synthetic dunite specimen (melt fraction = 0.026) utilizing the enhanced capacity of the Australian National University attenuation apparatus to operate in both torsional and flexural oscillation modes. Shear modulus and dissipation data are consistent with those for melt-bearing olivine specimens previously tested in torsion, with a pronounced dissipation peak superimposed on high-temperature background. Flexural data exhibit a monotonic decrease in complex Young's modulus with increasing temperature under transsolidus temperatures. The observed variation of Young's modulus is well described by the relationship 1/E 1/3G, without requiring relaxation of the bulk modulus. At high homologous temperatures, when shear modulus is low, extensional and flexural oscillation measurements have little resolution of bulk modulus, and thus, only pressure oscillation measurements can definitively constrain bulk properties at these conditions.

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

NASA Astrophysics Data System (ADS)

Bantel, Michael Kurt

1998-07-01

Using a torsion pendulum, we have investigated the anelastic properties of a CuBe torsion fiber for shear strains in the range 4×10-7 to 3×10-3 at temperatures 4.2K, 77K, and 295K. The fiber was 20 μm in diameter and 24 cm long, with a torsion constant of 0.033 dyn/cdot cm/cdot rad-1. It suspended an 11 gram azimuthally symmetric torsion pendulum which loaded the fiber to approximately 25% of its tensile strength at room temperature. The natural torsional oscillation frequency of this system was 6.4 mHz. An autocollimator viewing a set of mirrors on the oscillating pendulum served to measure with great accuracy the times at which the pendulum assumed a large set of discrete angular displacements during each oscillation cycle. This enabled a determination of the angular displacement of the pendulum as a function of time to better than a part in 107 of its oscillation amplitude, from which accurate information was obtained on the pendulum's frequency, damping, and harmonic content as functions of the oscillation amplitude. Analysis yields a determination of the fourth order shear elastic constant of CuBe. Expressing the shear potential energy density as: u(/epsilon)=c2ɛ2+c3ɛ3+ c4ɛ4 where ɛ is the shear strain, the values determined for (c2,/ c3,/ c4) are (25, 0.17, -550) GPa respectively. A striking feature of the fiber's internal friction Q-1 is that it appears to be the sum of two independent components: Q-1=Q I-1(T)+ Q II-1(A) where Q I-1(T) is temperature-dependent, varying by a factor of 3 between 4.2 and 77K, and Q II-1(A) is linearly dependent on amplitude and virtually independent of temperature; its linear dependence on amplitude varied by less than 4% between 4.2K and 77K. Interestingly the measurements of: the linear amplitude-dependent Q II-1, the linear component of the amplitude-dependent frequency shift, and the harmonic content associated with a dissipative hysteresis loop, are consistent with the motion generated by a simple stick-slip mechanism. Such a mechanism may be the result of microplastic behavior associated with the motion of dislocations and/or point defects. For a measurement of the gravitational constant using a torsion pendulum, these fiber-related properties may create a maximal 2-5 ppm systematic error assuming a comprehensive analysis is employed.

A swing driven by liquid crystals

NASA Astrophysics Data System (ADS)

Cheng, Cheng

Angular momentum in liquid crystals exists as flow, director reorientation, etc. However, it is hard to observe and measure angular momentum in liquid crystals by a direct mechanical approach. Torsion pendulum is a general tool to measure angular momentum by torque balance. Our torsion pendulum can harvest the angular momentum in liquid crystals to make it observable. The oscillation of the pendulum keeps increasing by constructively adding a small angular momentum of liquid crystals each period at the resonant frequency of the pendulum. Its similar to a swing driven by a force at its resonant frequency. For the torsion pendulum, a cage made of two aluminum discs, in which a liquid crystal cell is placed, is suspended between two thin tungsten wires. A gold mirror, which is a part of the optical lever system, is attached on one tungsten wire. As first demonstration, we fabricate a circular hybrid liquid crystal cell, which can induce concentric backflows to generate angular momentum. The alignment on the planar substrate is concentric and tangential. Due to the coupling between director rotation and flow, the induced backflow goes around the cell when we add electrical pulses between top and bottom substrates. The oscillation is observed by a position sensitive detector and analyzed on the basis of Eriksen-Leslie theory. With vacuum condition and synchronous driving system, the oscillation signal is improved. We demonstrate that this torsion pendulum can sensitively detect the angular momentum in liquid crystals.

Differential rotation of chromosphere and photosphere in the rising phase of N22 cycle of the Sun: torsional oscillations

NASA Astrophysics Data System (ADS)

Kasinskii, V.; Kasinskaia, L. I.

2005-06-01

The angular velocities of chromosphere and photosphere are calculated for 1987-1990 on the basis of heliographic coordinates of the chromospheric flares and sunspots (Solar Geophysical Data). The time resolution accepted is 0.25 year. The mean equatorial rotations of chromosphere and photosphere practically coincide. However, the differential coefficients in the chromosphere and photosphere, b, have strongly different behaviour. The value bch - bph change regularly from ``+'' sign to ``-'' sign over two-year interval. Thus, the idea of a torsion like oscillations of ``chromosphere-photosphere'' is supported.

Research on torsional vibration modelling and control of printing cylinder based on particle swarm optimization

NASA Astrophysics Data System (ADS)

Wang, Y. M.; Xu, W. C.; Wu, S. Q.; Chai, C. W.; Liu, X.; Wang, S. H.

2018-03-01

The torsional oscillation is the dominant vibration form for the impression cylinder of printing machine (printing cylinder for short), directly restricting the printing speed up and reducing the quality of the prints. In order to reduce torsional vibration, the active control method for the printing cylinder is obtained. Taking the excitation force and moment from the cylinder gap and gripper teeth open & closing cam mechanism as variable parameters, authors establish the dynamic mathematical model of torsional vibration for the printing cylinder. The torsional active control method is based on Particle Swarm Optimization(PSO) algorithm to optimize input parameters for the serve motor. Furthermore, the input torque of the printing cylinder is optimized, and then compared with the numerical simulation results. The conclusions are that torsional vibration active control based on PSO is an availability method to the torsional vibration of printing cylinder.

Development of a New Nondestructive Inspection Strategy for Corroded Multistrand Anchor Cables

DTIC Science & Technology

2016-07-01

perimeter wires (bottom). Torsional Guided Wave. Experiments also indicate the presence of a propagating torsional mode approximately 1.4 Mhz. This...mode is identified as torsional because it does not appear to undergo dispersion as it propagates. While this mode has been identified in a large...number of tests, it does not appear to be as robust in terms of its sensitivity to transducer coupling. Torsional modes ranges have been limited to

Torsional vibration measurements on rotating shaft system using laser doppler vibrometer

NASA Astrophysics Data System (ADS)

Xiang, Ling; Yang, Shixi; Gan, Chunbiao

2012-11-01

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

Torsional tapping atomic force microscopy for molecular resolution imaging of soft matter

NASA Astrophysics Data System (ADS)

Hobbs, Jamie; Mullin, Nic

2012-02-01

Despite considerable advances in image resolution on challenging, soft systems, a method for obtaining molecular resolution on `real' samples with significant surface roughness has remained elusive. Here we will show that a relatively new technique, torsional tapping AFM (TTAFM), is capable of imaging with resolution down to 3.7 Angrstrom on the surface of `bulk' polymer films [1]. In TTAFM T-shaped cantilevers are driven into torsional oscillation. As the tip is offset from the rotation axis this provides a tapping motion. Due to the high frequency and Q of the oscillation and relatively small increase in spring constant, improved cantilever dynamics and force sensitivity are obtained. As the tip offset from the torsional axis is relatively small (typically 25 microns), the optical lever sensitivity is considerably improved compared to flexural oscillation. Combined these give a reduction in noise floor by a factor of 12 just by changing the cantilever geometry. The ensuing low noise allows the use of ultra-sharp `whisker' tips with minimal blunting. As the cantilevers remain soft in the flexural axis, the force when imaging with error is also reduced, further protecting the tip. We will show that this combination allows routine imaging of the molecular structure of semicrystalline polymer films, including chain folds, loose loops and tie-chains in polyethylene, and the helical conformation of polypropylene within the crystal, using a standard, commercial AFM. [4pt] [1] N Mullin, JK Hobbs, PRL 107, 197801 (2011)

Dynamic characteristics of rotor blades with pendulum absorbers

NASA Technical Reports Server (NTRS)

Murthy, V. R.; Goglia, G. L.

1977-01-01

The point transmission matrix for a vertical plane pendulum on a rotating blade undergoing combined flapwise bending, and chordwise bending and torsion is derived. The equilibrium equation of the pendulum is linearized for small oscillations about the steady state. A FORTRAN program was written for the case of a vertical plane pendulum attached to a uniform blade with flapwise bending degree of freedom for cantilever boundary conditions. The frequency has a singular value right at the uncoupled pendulum natural frequency and thus introduces two frequencies corresponding to the nearest natural frequency of the blade without pendulum. In both of these modes it was observed that the pendulum deflection is large. One frequency can be thought of as a coupled pendulum frequency and the other as a coupled bending and pendulum frequency.

On searching for observational manifestations of Alfvén waves in solar faculae

NASA Astrophysics Data System (ADS)

Kobanov, N. I.; Chupin, S. A.; Chelpanov, A. A.

2017-12-01

In an effort to detect torsional oscillations, we have studied the periodic half-width variations for several spectral lines in solar faculae. The duration of the series being analyzed was from 40 to 150 min. We have determined the dominant frequencies and amplitudes of the half-width oscillations and considered their phase relations to the intensity and line-of-sight velocity oscillations. Five-minute profile halfwidth oscillations with a peak-to-peak amplitude of ˜10 m ˚A are recorded with confidence in the upperphotospheric Si I 10 827 ˚A line in faculae. The chromospheric He I 10 830 A˚ and Hα line profiles shows ˜40-60 m ˚A variations in two frequency bands, 2.5-4 and 1-1.9 mHz. No center-to-limb dependence that, according to the theory, must accompany the torsional oscillations has been revealed in the behavior of the oscillation amplitudes. According to present views, these variations cannot be caused by periodic temperature and magnetic field changes. Our observations do not allow us to explain these variations by the sausage mode action either, which should manifest itself at the double frequency.

Oscillation control system for electric motor drive

DOEpatents

Slicker, James M.; Sereshteh, Ahmad

1988-01-01

A feedback system for controlling mechanical oscillations in the torsionally complaint drive train of an electric or other vehicle. Motor speed is converted in a processor to estimate state signals in which a plant model which are used to electronically modify thetorque commands applied to the motor.

The nonlinear instability in flap-lag of rotor blades in forward flight

NASA Technical Reports Server (NTRS)

Tong, P.

1971-01-01

The nonlinear flap-lag coupled oscillation of torsionally rigid rotor blades in forward flight is examined using a set of consistently derived equations by the asymptotic expansion procedure of multiple time scales. The regions of stability and limit cycle oscillation are presented. The roles of parametric excitation, nonlinear oscillation, and forced excitation played in the response of the blade are determined.

Test of spatial isotropy using a cryogenic torsion pendulum

NASA Technical Reports Server (NTRS)

Phillips, Peter R.

1987-01-01

Motion of the earth through the cosmic neutrino background, or through certain kinds of vacuum states, produces a term of the form g(sigma) x v in the energy of an electron. To search for such a term, a cryogenic torsion pendulum carrying a transversely polarized magnet was used. Superconducting shields reduced magnetic torques. A sigma x v term would produce a sinusoidal oscillation of the pendulum with a period of one sidereal day. Such an oscillation was not detected, and a new limit of 8.5 x 10 to the -18th eV has been set for the splitting of the spin states of an electron at rest on the earth.

Oscillation control system for electric motor drive

DOEpatents

Slicker, J.M.; Sereshteh, A.

1988-08-30

A feedback system for controlling mechanical oscillations in the torsionally complaint drive train of an electric or other vehicle. Motor speed is converted in a processor to estimate state signals in which a plant model which are used to electronically modify the torque commands applied to the motor. 5 figs.

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.

Hybrid fuzzy sliding mode control for motorised space tether spin-up when coupled with axial and torsional oscillation

NASA Astrophysics Data System (ADS)

Chen, Yi; Cartmell, Matthew

2010-03-01

A specialised hybrid controller is applied to the control of a motorised space tether spin-up space coupled with an axial and a torsional oscillation phenomenon. A seven-degree-of-freedom (7-DOF) dynamic model of a motorised momentum exchange tether is used as the basis for interplanetary payload exchange in the context of control. The tether comprises a symmetrical double payload configuration, with an outrigger counter inertia and massive central facility. It is shown that including axial and torsional elasticity permits an enhanced level of performance prediction accuracy and a useful departure from the usual rigid body representations, particularly for accurate payload positioning at strategic points. A simulation with given initial condition data has been devised in a connecting programme between control code written in MATLAB and dynamics simulation code constructed within MATHEMATICA. It is shown that there is an enhanced level of spin-up control for the 7-DOF motorised momentum exchange tether system using the specialised hybrid controller.

Study of torsion oscillations of pumping unit shafts

NASA Astrophysics Data System (ADS)

Loginovskikh, V. M.; Cherentsov, D. A.; Voronin, K. S.; Pirogov, S. P.

2018-05-01

The method of detuning from resonant frequencies is an effective method of reducing the vibration activity of the HA at the design stage, which allows selecting the necessary operating mode for the HA, which will provide the necessary reliability of operation. In this connection, works in the field of increasing the vibration protection of NA are relevant. All calculations are based on the dynamic model of free torsional vibrations of the pumping unit, for which the oscillation equation was derived on the basis of Lagrange equations of the second kind, where the angle of rotation of the rotor was taken as the generalized coordinate. Next, expressions were obtained for the determination of the potential and kinetic energies that take into account all the characteristics of the shaft and the disk of the rotor HA; in particular, for the first time the mass of the shaft is taken into account. Then an expression was obtained for determining the frequencies of free torsional oscillations and the equation of motion of the rotor HA. Knowing the parameters of the oscillatory motion makes it possible to estimate the stresses that arise when the shaft rotates. The following is a case of a sudden stop of the shaft, for example, when the support is destroyed, and a graph is obtained from which the main conclusions are drawn.

Observation and control of coherent torsional dynamics in a quinquethiophene molecule.

PubMed

Cirmi, Giovanni; Brida, Daniele; Gambetta, Alessio; Piacenza, Manuel; Della Sala, Fabio; Favaretto, Laura; Cerullo, Giulio; Lanzani, Guglielmo

2010-07-28

By applying femtosecond pump-probe spectroscopy to a substituted quinquethiophene molecule in solution, we observe in the time domain the coherent torsional dynamics that drives planarization of the excited state. Our interpretation is based on numerical modeling of the ground and excited state potential energy surfaces and simulation of wavepacket dynamics, which reveals two symmetric excited state deactivation pathways per oscillation period. We use the acquired knowledge on torsional dynamics to coherently control the excited state population with a pump-dump scheme, exploiting the non-stationary Franck-Condon overlap between ground and excited states.

Electromagnetic signals from bare strange stars

NASA Astrophysics Data System (ADS)

Mannarelli, Massimo; Pagliaroli, Giulia; Parisi, Alessandro; Pilo, Luigi

2014-05-01

The crystalline color superconducting phase is believed to be the ground state of deconfined quark matter for sufficiently large values of the strange quark mass. This phase has the remarkable property of being more rigid than any known material. It can therefore sustain large shear stresses, supporting torsional oscillations of large amplitude. The torsional oscillations could lead to observable electromagnetic signals if strange stars have a crystalline color superconducting crust. Indeed, considering a simple model of a strange star with a bare quark matter surface, it turns out that a positive charge is localized in a narrow shell about ten Fermi thick beneath the star surface. The electrons needed to neutralize the positive charge of quarks spill in the star exterior forming an electromagnetically bounded atmosphere hundreds of Fermi thick. When a torsional oscillation is excited, for example by a stellar glitch, the positive charge oscillates with typical kHz frequencies, for a crust thickness of about one-tenth of the stellar radius, to hundreds of Hz, for a crust thickness of about nine-tenths of the stellar radius. Higher frequencies, of the order of few GHz, can be reached if the star crust is of the order of a few centimeters thick. We estimate the emitted power considering emission by an oscillating magnetic dipole, finding that it can be quite large, of the order of 1045 erg/s for a thin crust. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. The radiated photons will be in part absorbed by the electronic atmosphere, but a sizable fraction of them should be emitted by the star.

Proposal for quantum many-body simulation and torsional matter-wave interferometry with a levitated nanodiamond

NASA Astrophysics Data System (ADS)

Ma, Yue; Hoang, Thai M.; Gong, Ming; Li, Tongcang; Yin, Zhang-qi

2017-08-01

Hybrid spin-mechanical systems have great potential in sensing, macroscopic quantum mechanics, and quantum information science. In order to induce strong coupling between an electron spin and the center-of-mass motion of a mechanical oscillator, a large magnetic gradient usually is required, which is difficult to achieve. Here we show that strong coupling between the electron spin of a nitrogen-vacancy (NV) center and the torsional vibration of an optically levitated nanodiamond can be achieved in a uniform magnetic field. Thanks to the uniform magnetic field, multiple spins can strongly couple to the torsional vibration at the same time. We propose utilizing this coupling mechanism to realize the Lipkin-Meshkov-Glick (LMG) model by an ensemble of NV centers in a levitated nanodiamond. The quantum phase transition in the LMG model and finite number effects can be observed with this system. We also propose generating torsional superposition states and realizing torsional matter-wave interferometry with spin-torsional coupling.

Modeling and Control of a Trailing Wire Antenna Towed by an Orbiting Aircraft

DTIC Science & Technology

1992-09-01

do not induce significant oscillations in the wire. The development of the dynamic model also assumed that wire bending , torsion and stretching...it was reasonable to assume that the wire bending forces did not contribute significantly to the oscillations. 8= (4.54)8EI pg=0.005176 ibf in E

Influence of torsional-lateral coupling on stability behavior of geared rotor systems

NASA Technical Reports Server (NTRS)

Schwibinger, P.; Nordmann, R.

1987-01-01

In high-performance turbomachinery trouble often arises because of unstable nonsynchronous lateral vibrations. The instabilities are mostly caused by oil-film bearings, clearance excitation, internal damping, annular pressure seals in pumps, or labyrinth seals in turbocompressors. In recent times the coupling between torsional and lateral vibrations has been considered as an additional influence. This coupling is of practical importance in geared rotor systems. The literature describes some field problems in geared drive trains where unstable lateral vibrations occurred together with torsional oscillations. This paper studies the influence of the torsional-lateral coupling on the stability behavior of a simple geared system supported by oil-film bearings. The coupling effect is investigated by parameter studies and a sensitivity analysis for the uncoupled and coupled systems.

An Experimental Investigation Into the Feasibility of Measuring Static and Dynamic Aerodynamic Derivatives in the DSTO Water Tunnel

DTIC Science & Technology

2013-08-01

The SDM was subjected to forced small (0.5) sinusoidal pitching oscillations and derivatives were computed from measured model loads, angles of... aluminium alloy when subjected to both tensile and torsional loading. He joined the Aeronautical Research Laboratories (now called the Defence...oscillations and derivatives were computed from measured model loads, angles of attack, reduced frequency of oscillation and aircraft geometrical parameters

Ultrasonic Spot and Torsion Welding of Aluminum to Titanium Alloys: Process, Properties and Interfacial Microstructure

NASA Astrophysics Data System (ADS)

Balle, Frank; Magin, Jens

Hybrid lightweight structures shape the development of future vehicles in traffic engineering and the aerospace industry. For multi-material concepts made out of aluminum and titanium alloys, the ultrasonic welding technique is an alternative effective joining technology. The overlapped structures can be welded in the solid state, even without gas shielding. In this paper the conventional ultrasonic spot welding with longitudinal oscillation mode is compared to the recent ultrasonic torsion welding with a torsional mode at 20 kHz working frequency. For each technique the process parameters welding force, welding energy and oscillation amplitude were optimized for the hybrid joints using design of experiments. Relationships between the process parameters, mechanical properties and related welding zone should be understood. Central aspects of the research project are microscopic studies of the joining zone in cross section and extensive fracture surface analysis. Detailed electron microscopy and spectroscopy of the hybrid interface help to understand the interfacial formation during ultrasonic welding as well as to transfer the gained knowledge for further multi-metal joints.

Alfven seismic vibrations of crustal solid-state plasma in quaking paramagnetic neutron star

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bastrukov, S.; Xu, R.-X.; Molodtsova, I.

2010-11-15

Magneto-solid-mechanical model of two-component, core-crust, paramagnetic neutron star responding to quake-induced perturbation by differentially rotational, torsional, oscillations of crustal electron-nuclear solid-state plasma about axis of magnetic field frozen in the immobile paramagnetic core is developed. Particular attention is given to the node-free torsional crust-against-core vibrations under combined action of Lorentz magnetic and Hooke's elastic forces; the damping is attributed to Newtonian force of shear viscose stresses in crustal solid-state plasma. The spectral formulas for the frequency and lifetime of this toroidal mode are derived in analytic form and discussed in the context of quasiperiodic oscillations of the x-ray outburst fluxmore » from quaking magnetars. The application of obtained theoretical spectra to modal analysis of available data on frequencies of oscillating outburst emission suggests that detected variability is the manifestation of crustal Alfven's seismic vibrations restored by Lorentz force of magnetic field stresses.« less

Dynamics and Manipulation of Nanomagnets

NASA Astrophysics Data System (ADS)

Cai, Liufei

This thesis presents my work on the spin dynamics of nanomagnets and investigates the possibility of manipulating nanomagnets by various means. Most of the work has been published. Some has been submitted for publication. The structure of this thesis is as follows. In Chapter 1, I present the theory of manipulation of a nanomagnet by rotating ac fields whose frequency is time dependent. Theory has been developed that maps the problem onto Landau-Zener problem. For the linear frequency sweep the switching phase diagrams are obtained on the amplitude of the ac field and the frequency sweep rate. Switching conditions have been obtained numerically and analytically. For the nonlinear frequency sweep, the optimal time dependence of the frequency is obtained analytically with account of damping that gives the fastest controllable switching of the magnetization. In Chapter 2, interaction between a nanomagnet and a Josephson junction has been studied. The I-V curve of the Josephson junction in the proximity of a nanomagnet shows Shapiro-like steps due to the ac field generated by the precessing magnetic moment. Possibility of switching of the magnetic moment by a time-linear voltage in the Josephson junction is demonstrated. Realization of the optimal switching is suggested that employs two perpendicular Josephson junctions with time-dependent voltage signals. The result is shown to be robust against voltage noises. Quantum-mechanical coupling between the nanomagnet considered as a two-level system and a Josephson junction has been studied and quantum oscillations of the populations of the spin states have been computed. In Chapter 3, the switching dynamics of a nanomagnet embedded in a torsional oscillator that serves as a conducting wire for a spin current has been investigated. Generalized Slonczewski's equation is derived. The coupling of the nanomagnet, the torsional oscillator and the spin current generates a number of interesting phenomena. The mechanically-assisted magnetization switching is studied, in which the magnetization can be reversed by tilting the torsional oscillator. The effect of the torsional oscillator on the switching of the magnetization in the presence of spin-polarized current is computed. Combined effects of the spin current and a mechanical kick of the torsional oscillator have been studied. In Chapter 4, skyrmion dynamics and interaction of the skyrmion with an electron have been studied. Corrections to the spin texture of the skyrmion due to the crystal lattice have been computed. Due to the lattice effects the skyrmion collapses in clean ferromagnetic and anti-ferromagnetic materials. The lifetime of the skyrmion has been computed numerically and compared with analytical theory. In doped anti-ferromagnetic materials the weak attraction between a skyrmion and an electron may generate a bound state. In Chapter 5, experimental results of the NIST group on magnetic multilayer microcantilevers have been analyzed. Theoretical framework has been suggested that explains the observed strong damping effect of the platinum layer on the mechanical oscillations of Py-Pt bilayer cantilevers. The strong spin-orbit coupling of platinum is shown to impede the motion of the domain wall in permalloy and to dramatically increase the damping of the cantilever motion.

On the Possibility to Construct Gravitational Eye

NASA Astrophysics Data System (ADS)

Chen, Ying-Tian

2007-05-01

The possibility of modifying a conventional Cavendish torsion pendulum into a half-armed pendulum oscillator to measure the horizontal gravitational acceleration is discussed. A new kind of gravitational detector, gravieye, as we named, can be made by a proper combination of such oscillators to ``see'' remote objects and to be used, e.g. to detect the movement of huge mass at a long distance.

Activation barrier scaling and crossover for noise-induced switching in micromechanical parametric oscillators.

PubMed

Chan, H B; Stambaugh, C

2007-08-10

We explore fluctuation-induced switching in parametrically driven micromechanical torsional oscillators. The oscillators possess one, two, or three stable attractors depending on the modulation frequency. Noise induces transitions between the coexisting attractors. Near the bifurcation points, the activation barriers are found to have a power law dependence on frequency detuning with critical exponents that are in agreement with predicted universal scaling relationships. At large detuning, we observe a crossover to a different power law dependence with an exponent that is device specific.

Fluid-structure interaction of a rolling restrained body of revolution at high angles of attack

NASA Astrophysics Data System (ADS)

Degani, D.; Ishay, M.; Gottlieb, O.

2017-03-01

The current work investigates numerically rolling instabilities of a free-to-roll slender rigid-body of revolution placed in a wind tunnel at a high angle of attack. The resistance to the roll moment is represented by a linear torsion spring and equivalent linear damping representing friction in the bearings of a simulated wind tunnel model. The body is subjected to a three-dimensional, compressible, laminar flow. The full Navier-Stokes equations are solved using the second-order implicit finite difference Beam-Warming scheme, adapted to a curvilinear coordinate system, whereas the coupled structural second order equation of motion for roll is solved by a fourth-order Runge-Kutta method. The body consists of a 3.5-diameter tangent ogive forebody with a 7.0-diameter long cylindrical afterbody extending aft of the nose-body junction to x/D = 10.5. We describe in detail the investigation of three angles of attack 20°, 40°, and 65°, at a Reynolds number of 30 000 (based on body diameter) and a Mach number of 0.2. Three distinct configurations are investigated as follows: a fixed body, a free-to-roll body with a weak torsion spring, and a free-to-roll body with a strong torsion spring. For each angle of attack the free-to-roll configuration portrays a distinct and different behavior pattern, including bi-stable limit-cycle oscillations. The bifurcation structure incorporates both large and small amplitude periodic roll oscillations where the latter lose their periodicity with increasing stiffness of the restraining spring culminating with distinct quasiperiodic oscillations. We note that removal of an applied upstream disturbance for a restrained body does not change the magnitude or complexity of the oscillations or of the flow patterns along the body. Depending on structure characteristics and flow conditions even a small rolling moment coefficient at the relatively low angle of attack of 20° may lead to large amplitude resonant roll oscillations.

Harvesting electrical energy from torsional thermal actuation driven by natural convection.

PubMed

Kim, Shi Hyeong; Sim, Hyeon Jun; Hyeon, Jae Sang; Suh, Dongseok; Spinks, Geoffrey M; Baughman, Ray H; Kim, Seon Jeong

2018-06-07

The development of practical, cost-effective systems for the conversion of low-grade waste heat to electrical energy is an important area of renewable energy research. We here demonstrate a thermal energy harvester that is driven by the small temperature fluctuations provided by natural convection. This harvester uses coiled yarn artificial muscles, comprising well-aligned shape memory polyurethane (SMPU) microfibers, to convert thermal energy to torsional mechanical energy, which is then electromagnetically converted to electrical energy. Temperature fluctuations in a yarn muscle, having a maximum hot-to-cold temperature difference of about 13 °C, were used to spin a magnetic rotor to a peak torsional rotation speed of 3,000 rpm. The electromagnetic energy generator converted the torsional energy to electrical energy, thereby producing an oscillating output voltage of up to 0.81 V and peak power of 4 W/kg, based on SMPU mass.

High-resolution spectroscopy of the C-N stretching band of methylamine

NASA Astrophysics Data System (ADS)

Lees, Ronald M.; Sun, Zhen-Dong; Billinghurst, B. E.

2011-09-01

The C-N stretching infrared fundamental of CH3NH2 has been investigated by high-resolution laser sideband and Fourier transform synchrotron spectroscopy to explore the energy level structure and to look for possible interactions with high-lying torsional levels of the ground state and other vibrational modes. The spectrum is complicated by two coupled large-amplitude motions in the molecule, the CH3 torsion and the NH2 inversion, which lead to rich spectral structure with a wide range of energy level splittings and relative line intensities. Numerous sub-bands have been assigned for K values ranging up to 12 for the stronger a inversion species for the vt = 0 torsional state, along with many of the weaker sub-bands of the s species. The C-N stretching sub-state origins have been determined by fitting the upper-state term values to J(J + 1) power-series expansions. For comparison with the ground-state behaviour, both ground and C-N stretch origins have been fitted to a phenomenological Fourier series model that produces an interesting pattern with the differing periodicities of the torsional and inversion energies. The amplitude of the torsional energy oscillation increases substantially for the C-N stretch, while the amplitude of the inversion energy oscillation is relatively unchanged. Independent inertial scale factors ρ were fitted for the torsion and the inversion and differ significantly in the upper state. The C-N stretching vibrational energy is determined to be 1044.817 cm-1, while the effective upper state B-value is 0.7318 cm-1. Several anharmonic resonances with vt = 4 ground-state levels have been observed and partially characterized. A variety of J-localized level-crossing resonances have also been seen, five of which display forbidden transitions arising from intensity borrowing that allow determination of the interaction coupling constants.

How the embryonic brain tube twists

NASA Astrophysics Data System (ADS)

Chen, Zi; Guo, Qiaohang; Forsch, Nickolas; Taber, Larry

2014-03-01

During early development, the tubular brain of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This deformation is one of the major organ-level symmetry-breaking events in development. Available evidence suggests that bending is caused by differential growth, but the mechanism for torsion remains poorly understood. Since the heart almost always loops in the same direction that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is virtually nonexistent, 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. In addition, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model is used to interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''.

Search for supersolidity in solid 4He using multiple-mode torsional oscillators

PubMed Central

Eyal, Anna; Mi, Xiao; Talanov, Artem V.; Reppy, John D.

2016-01-01

In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid 4He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941–1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid 4He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the 4He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853–856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid 4He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the 4He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state. PMID:27222579

Torsional Vibration in the National Wind Technology Center’s 2.5-Megawatt Dynamometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sethuraman, Latha; Keller, Jonathan; Wallen, Robb

2016-08-31

This report documents the torsional drivetrain dynamics of the NWTC's 2.5-megawatt dynamometer as identified experimentally and as calculated using lumped parameter models using known inertia and stiffness parameters. The report is presented in two parts beginning with the identification of the primary torsional modes followed by the investigation of approaches to damp the torsional vibrations. The key mechanical parameters for the lumped parameter models and justification for the element grouping used in the derivation of the torsional modes are presented. The sensitivities of the torsional modes to different test article properties are discussed. The oscillations observed from the low-speed andmore » generator torque measurements were used to identify the extent of damping inherently achieved through active and passive compensation techniques. A simplified Simulink model of the dynamometer test article integrating the electro-mechanical power conversion and control features was established to emulate the torque behavior that was observed during testing. The torque response in the high-speed, low-speed, and generator shafts were tested and validated against experimental measurements involving step changes in load with the dynamometer operating under speed-regulation mode. The Simulink model serves as a ready reference to identify the torque sensitivities to various system parameters and to explore opportunities to improve torsional damping under different conditions.« less

Direct torsional actuation of microcantilevers using magnetic excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gosvami, Nitya Nand; Nalam, Prathima C.; Tam, Qizhan

2014-09-01

Torsional mode dynamic force microscopy can be used for a wide range of studies including mapping lateral contact stiffness, torsional frequency or amplitude modulation imaging, and dynamic friction measurements of various materials. Piezo-actuation of the cantilever is commonly used, but it introduces spurious resonances, limiting the frequency range that can be sampled, and rendering the technique particularly difficult to apply in liquid medium where the cantilever oscillations are significantly damped. Here, we demonstrate a method that enables direct torsional actuation of cantilevers with high uniformity over wide frequency ranges by attaching a micrometer-scale magnetic bead on the back side ofmore » the cantilever. We show that when beads are magnetized along the width of the cantilever, efficient torsional actuation of the cantilevers can be achieved using a magnetic field produced from a solenoid placed underneath the sample. We demonstrate the capability of this technique by imaging atomic steps on graphite surfaces in tapping mode near the first torsional resonance of the cantilever in dodecane. The technique is also applied to map the variations in the lateral contact stiffness on the surface of graphite and polydiacetylene monolayers.« less

The accuracy of serum interleukin-6 and tumour necrosis factor as markers for ovarian torsion.

PubMed

Cohen, S B; Wattiez, A; Stockheim, D; Seidman, D S; Lidor, A L; Mashiach, S; Goldenberg, M

2001-10-01

The aim of this study was to investigate a possible role for interleukin-6 (IL-6) and tumour necrosis factor (TNF-alpha) as pre-operative markers for the diagnosis of ovarian torsion. Twenty consecutive patients admitted to the gynaecological emergency room with suspected clinical diagnosis of ovarian torsion were prospectively assigned to the study. Blood samples were drawn pre-operatively and examined for serum concentrations of IL-6 and TNF-alpha. Surgeons were blinded to laboratory results prior to laparoscopy. The pre-operative diagnosis of ovarian torsion was confirmed during an urgent diagnostic laparoscopy in 8 (40%) patients. The surgical diagnosis among the remaining 12 patients was a large ovarian cyst not in torsion. In six out of eight (75.0%) patients with ovarian torsion serum IL-6 concentrations were elevated. None of the 12 patients without torsion had elevated serum IL-6 concentrations. This difference was statistically significant (P < 0.001). There was no significant difference in the proportion of women with elevated serum TNF-alpha concentrations, two of eight (25.0%) patients with torsion and four of 12 (33.3%) control cases. Elevated serum IL-6 concentrations, but not serum TNF-alpha concentrations, were significantly associated with the occurrence of ovarian torsion. In patients with vague clinical signs of ovarian torsion, serum IL-6 might help to distinguish which patients should undergo diagnostic laparoscopy.

Kinematic principles of primate rotational vestibulo-ocular reflex. II. Gravity-dependent modulation of primary eye position

NASA Technical Reports Server (NTRS)

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

1997-01-01

The kinematic constraints of three-dimensional eye positions were investigated in rhesus monkeys during passive head and body rotations relative to gravity. We studied fast and slow phase components of the vestibulo-ocular reflex (VOR) elicited by constant-velocity yaw rotations and sinusoidal oscillations about an earth-horizontal axis. We found that the spatial orientation of both fast and slow phase eye positions could be described locally by a planar surface with torsional variation of <2.0 +/- 0.4 degrees (displacement planes) that systematically rotated and/or shifted relative to Listing's plane. In supine/prone positions, displacement planes pitched forward/backward; in left/right ear-down positions, displacement planes were parallel shifted along the positive/negative torsional axis. Dynamically changing primary eye positions were computed from displacement planes. Torsional and vertical components of primary eye position modulated as a sinusoidal function of head orientation in space. The torsional component was maximal in ear-down positions and approximately zero in supine/prone orientations. The opposite was observed for the vertical component. Modulation of the horizontal component of primary eye position exhibited a more complex dependence. In contrast to the torsional component, which was relatively independent of rotational speed, modulation of the vertical and horizontal components of primary position depended strongly on the speed of head rotation (i.e., on the frequency of oscillation of the gravity vector component): the faster the head rotated relative to gravity, the larger was the modulation. Corresponding results were obtained when a model based on a sinusoidal dependence of instantaneous displacement planes (and primary eye position) on head orientation relative to gravity was fitted to VOR fast phase positions. When VOR fast phase positions were expressed relative to primary eye position estimated from the model fits, they were confined approximately to a single plane with a small torsional standard deviation ( approximately 1.4-2.6 degrees). This reduced torsional variation was in contrast to the large torsional spread (well >10-15 degrees ) of fast phase positions when expressed relative to Listing's plane. We conclude that primary eye position depends dynamically on head orientation relative to space rather than being fixed to the head. It defines a gravity-dependent coordinate system relative to which the torsional variability of eye positions is minimized even when the head is moved passively and vestibulo-ocular reflexes are evoked. In this general sense, Listing's law is preserved with respect to an otolith-controlled reference system that is defined dynamically by gravity.

Nonhydrodynamic Characteristics of the Oscillating Screen Viscometer

NASA Technical Reports Server (NTRS)

Berg, Robert F.; Moldover, Michael R.

1993-01-01

Extraction of the viscosity from the oscillating screen's response function requires knowledge of it resonance frequency omega(sub 0) and of the prefactor k(sub tr)/k(theta), where k(sub tr) is a transducer coefficient and k(sub theta) is the torsion spring constant. The determination of these parameters is described. The effect of a possible anomaly in the dielectric constant near the critical point of xenon will be negligible.

Generalization of the Förster resonance energy transfer theory for quantum mechanical modulation of the donor-acceptor coupling

NASA Astrophysics Data System (ADS)

Jang, Seogjoo

2007-11-01

The Förster resonance energy transfer theory is generalized for inelastic situations with quantum mechanical modulation of the donor-acceptor coupling. Under the assumption that the modulations are independent of the electronic excitation of the donor and the acceptor, a general rate expression is derived, which involves two dimensional frequency-domain convolution of the donor emission line shape, the acceptor absorption line shape, and the spectral density of the modulation of the donor-acceptor coupling. For two models of modulation, detailed rate expressions are derived. The first model is the fluctuation of the donor-acceptor distance, approximated as a quantum harmonic oscillator coupled to a bath of other quantum harmonic oscillators. The distance fluctuation results in additional terms in the rate, which in the small fluctuation limit depend on the inverse eighth power of the donor-acceptor distance. The second model is the fluctuation of the torsional angle between the two transition dipoles, which is modeled as a quantum harmonic oscillator coupled to a bath of quantum harmonic oscillators and causes sinusoidal modulation of the donor-acceptor coupling. The rate expression has new elastic and inelastic terms, depending sensitively on the value of the minimum energy torsional angle. Experimental implications of the present theory and some of the open theoretical issues are discussed.

Human ocular torsion during parabolic flights: an analysis with scleral search coil

NASA Technical Reports Server (NTRS)

Cheung, B. S.; Money, K.; Howard, I.; Kirienko, N.; Johnson, W.; Lackner, J.; Dizio, P.; Evanoff, J.

1992-01-01

Rotation of the eyes about the visual axis is known as ocular torsion. A lateral inclination (a "roll") of the head induces ocular torsion in the opposite direction, a response known as ocular counterrolling. For six subjects, we recorded the static (head still) and dynamic (head in oscillatory roll motion) ocular torsion in normal 1 g condition and also during the microgravity and hypergravity periods of parabolic flight, using the electromagnetic scleral search coil technique. With the head still, the direction and magnitude of torsion that occurred in response to microgravity and hypergravity differed substantially from one individual to another, but there was a significant difference in torsional magnitude between the microgravity and hypergravity periods, for all static head positions including the upright position. Under normal 1 g conditions, counterrolling compensated for about 16% of (voluntary) static head roll, while dynamic counterroll was much larger, up to 36% of head roll at 0.55 Hz. With increasing frequency of head oscillation between 0.33 Hz and 0.55 Hz, the gain of counterrolling increased and there was no change in the phase relationship. The gain of dynamic counterroll (in response to voluntary head rolling) was not significantly less in hypogravity, suggesting that on the ground at these frequencies the contribution of gravity and gravity receptors to this reflex is redundant: this reflex is probably driven by the semicircular canals. In some subjects, the torsional displacement in microgravity is accompanied by micro-torsional oscillatory motion.

A high-sensitivity torsional pendulum for polymeric films and fibres

NASA Technical Reports Server (NTRS)

Aghili-Kermani, H.; Obrien, T.; Armeniades, C. D.; Roberts, J. M.

1976-01-01

A free oscillation torsion pendulum is described, which has been designed to measure accurately the dynamic shear modulus and logarithmic decrement of polymeric thin films and fibers, at frequencies of 0.1 to 10 Hz and a temperature range of 4.2 to 450 K. The instrument can also provide in situ tensile deformations of up to 5%. The specimen geometry necessary to obtain reliable modulus measurements with thin films is discussed, and typical data are presented which exhibit hitherto unreported relaxation processes, discernible by this instrument.

Effect of wind tunnel acoustic modes on linear oscillating cascade aerodynamics

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1993-01-01

The aerodynamics of a biconvex airfoil cascade oscillating in torsion is investigated using the unsteady aerodynamic influence coefficient technique. For subsonic flow and reduced frequencies as large as 0.9, airfoil surface unsteady pressures resulting from oscillation of one of the airfoils are measured using flush-mounted high-frequency-response pressure transducers. The influence coefficient data are examined in detail and then used to predict the unsteady aerodynamics of a cascade oscillating at various interblade phase angles. These results are correlated with experimental data obtained in the traveling-wave mode of oscillation and linearized analysis predictions. It is found that the unsteady pressure disturbances created by an oscillating airfoil excite wind tunnel acoustic modes which have detrimental effects on the experimental data. Acoustic treatment is proposed to rectify this problem.

Viscosity Difference Measurements for Normal and Para Liquid Hydrogen Mixtures

NASA Technical Reports Server (NTRS)

Webeler, R.; Bedard, F.

1961-01-01

The absence of experimental data in the literature concerning a viscosity difference for normal and equilibrium liquid hydrogen may be attributed to the limited reproducibility of "oscillating disk" measurements in a liquid-hydrogen environment. Indeed, there is disagreement over the viscosity values for equilibrium liquid hydrogen even without proton spin considerations. Measurements presented here represent the first application of the piezoelectric alpha quartz torsional oscillator technique to liquid-hydrogen viscosity measurements.

Dirac oscillator interacting with a topological defect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carvalho, J.; Furtado, C.; Moraes, F.

In this work we study the interaction problem of a Dirac oscillator with gravitational fields produced by topological defects. The energy levels of the relativistic oscillator in the cosmic string and in the cosmic dislocation space-times are sensible to curvature and torsion associated to these defects and are important evidence of the influence of the topology on this system. In the presence of a localized magnetic field the energy levels acquire a term associated with the Aharonov-Bohm effect. We obtain the eigenfunctions and eigenvalues and see that in the nonrelativistic limit some results known in standard quantum mechanics are reached.

Imprints of superfluidity on magnetoelastic quasiperiodic oscillations of soft gamma-ray repeaters.

PubMed

Gabler, Michael; Cerdá-Durán, Pablo; Stergioulas, Nikolaos; Font, José A; Müller, Ewald

2013-11-22

Our numerical simulations show that axisymmetric, torsional, magnetoelastic oscillations of magnetars with a superfluid core can explain the whole range of observed quasiperiodic oscillations (QPOs) in the giant flares of soft gamma-ray repeaters. There exist constant phase QPOs at f is < or approximately equal to 150 Hz and resonantly excited high-frequency QPOs (f>500 Hz), in good agreement with observations. The range of magnetic field strengths required to match the observed QPO frequencies agrees with that from spin-down estimates. These results suggest that there is at least one superfluid species in magnetar cores.

Reducing the data: Analysis of the role of vascular geometry on blood flow patterns in curved vessels

NASA Astrophysics Data System (ADS)

Alastruey, Jordi; Siggers, Jennifer H.; Peiffer, Véronique; Doorly, Denis J.; Sherwin, Spencer J.

2012-03-01

Three-dimensional simulations of blood flow usually produce such large quantities of data that they are unlikely to be of clinical use unless methods are available to simplify our understanding of the flow dynamics. We present a new method to investigate the mechanisms by which vascular curvature and torsion affect blood flow, and we apply it to the steady-state flow in single bends, helices, double bends, and a rabbit thoracic aorta based on image data. By calculating forces and accelerations in an orthogonal coordinate system following the centreline of each vessel, we obtain the inertial forces (centrifugal, Coriolis, and torsional) explicitly, which directly depend on vascular curvature and torsion. We then analyse the individual roles of the inertial, pressure gradient, and viscous forces on the patterns of primary and secondary velocities, vortical structures, and wall stresses in each cross section. We also consider cross-sectional averages of the in-plane components of these forces, which can be thought of as reducing the dynamics of secondary flows onto the vessel centreline. At Reynolds numbers between 50 and 500, secondary motions in the directions of the local normals and binormals behave as two underdamped oscillators. These oscillate around the fully developed state and are coupled by torsional forces that break the symmetry of the flow. Secondary flows are driven by the centrifugal and torsional forces, and these are counterbalanced by the in-plane pressure gradients generated by the wall reaction. The viscous force primarily opposes the pressure gradient, rather than the inertial forces. In the axial direction, and depending on the secondary motion, the curvature-dependent Coriolis force can either enhance or oppose the bulk of the axial flow, and this shapes the velocity profile. For bends with little or no torsion, the Coriolis force tends to restore flow axisymmetry. The maximum circumferential and axial wall shear stresses along the centreline correlate well with the averaged in-plane pressure gradient and the radial displacement of the peak axial velocity, respectively. We conclude with a discussion of the physiological implications of these results.

Laser Raman spectroscopy of the effect of solvent on the low-frequency oscillations of organic molecules

NASA Astrophysics Data System (ADS)

Brandt, N. N.; Chikishev, A. Yu.; Dolgovskii, V. I.; Lebedenko, S. I.

2007-09-01

The effect of solvent on low-frequency oscillations is studied using an example of the 1,1,2,2-tetrachloroethane (TCE) and 1,1,2,2-tetrabromoethane (TBE) molecules, which exhibit torsional oscillations in the terahertz range. Dimethylsulfoxide (DMSO) and carbon tetrachloride (CTC) are used as solvents. It is demonstrated that a decrease in the concentration of the substance under study in the TBE/CTC, TCE/DMSO, and TCE/CTC mixtures leads to a frequency shift of the low-frequency oscillation. The shift is not observed in the TBE/DMSO mixture but a decrease in the TBE concentration causes significant broadening of the low-frequency line.

Fourier transform synchrotron spectroscopy of the in-plane methyl-rocking band of CD3OH

NASA Astrophysics Data System (ADS)

Lees, R. M.; Xu, Li-Hong; Gao, Song; Billinghurst, B. E.

2015-09-01

Infrared Fourier transform spectra of the 12CD3OH isotopologue of methanol recorded at the Canadian Light Source synchrotron have been investigated in the 750-950 cm-1 region to explore the torsional energy pattern of the in-plane methyl-rocking mode. The in-plane CD3-rocking band is primarily of parallel a-type character with relatively widely spaced K-structure, and the central Q-branch region is well-resolved. Sub-bands have been assigned for the vt = 0 ground torsional state from K = 0 to 15 for both A and E torsional species, as well as a number of sub-bands in the vt = 1 excited torsional state. A variety of perturbations due to asymmetry-induced, anharmonic Fermi and level-crossing resonances is seen in the spectra. Mapping of K-reduced torsional energies determined from the upper-state term values shows that the K-dependence is severely distorted from the usual pattern of smoothly oscillating, near-sinusoidal interlocking τ-curves. Although the K = 0 levels are nominally inverted for vt = 0, the torsional splitting is very small with the A level higher than the E level by only 0.625 cm-1, and the anomalous behavior precludes a definite conclusion about torsional inversion. However, the range of variation with K of the vt = 0 CD3-rocking τ-curves is about half that of the ground vibrational state, similar to previous observations for CH3OH isotopologues, suggesting a comparable reduction of about 25% in the effective torsional barrier height for the in-plane rocking mode.

Thermal convection of liquid sodium in inclined cylinders

NASA Astrophysics Data System (ADS)

Khalilov, Ruslan; Kolesnichenko, Ilya; Pavlinov, Alexander; Mamykin, Andrey; Shestakov, Alexander; Frick, Peter

2018-04-01

The effect of inclination on the low Prandtl number turbulent convection in a cylinder of unit aspect ratio was studied experimentally. The working fluid was sodium (Prandtl number Pr =0.0094 ), the measurements were performed for a fixed Rayleigh number Ra =(1.47 ±0.03 ) ×107 , and the inclination angle varied from β =0∘ (the Rayleigh-Bénard convection, the temperature gradient is vertical) up to β =90∘ (the applied temperature gradient is horizontal) with a step Δ β =10∘ . The effective axial heat flux characterized by the Nusselt number is minimal at β =0∘ and demonstrates a smooth growth with the increase of the cylinder inclination, reaching a maximum at angle β ≈70∘ and decreasing with a further increase of β . The maximal value of the normalized Nusselt number Nu (β )/Nu (0 ) was 1.21. In general, the dependence of Nu (β ) in a cylinder with unit aspect ratio is similar to what was observed in sodium convection in inclined long cylinders but is much weaker. The structure of the flow undergoes a significant transformation with inclination. Under moderate inclination (β ≲30∘ ), the fluctuations are strong and are provided by regular oscillations of large-scale circulation (LSC) and by turbulence. Under large inclination (β >60∘ ), the LSC is regular and the turbulence is weak, while in transient regimes (30∘<β <60∘ ), the LSC fluctuations are weak and the turbulence decreases with inclination. The maximum Nusselt number corresponds to the border of transient and large inclinations. We find the first evidence of strong LSC fluctuations in low Prandtl number convective flow under moderate inclination. The rms azimuthal fluctuations of LSC, about 27∘ at β =0∘ , decrease almost linearly up to β =30∘ , where they are about 9∘. The angular fluctuations in the vicinity of the end faces are much stronger (about 37∘ at β =0∘ ) and weakly decrease up to β =20∘ . The strong anticorrelation of the fluctuations in two halves of the cylinder indicates the torsional character of LSC fluctuations. At β =30∘ , the intensity of the oscillations at the periphery of the cylinder falls sharply to the level of oscillations in the central plane and the anticorrelation disappears; the torsional fluctuations vanish.

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.

Association of Torsion With Testicular Cancer: A Retrospective Study.

PubMed

Uguz, Sami; Yilmaz, Sercan; Guragac, Ali; Topuz, Bahadır; Aydur, Emin

2016-02-01

Testicular torsion is a medical emergency that usually requires surgical exploration. However, testicular malignancy has been anecdotally reported with the association of torsion in surgical specimens, and the published data remain scant on the association of torsion with testicular tumors. By retrospective medical record review, we identified 32 patients who had been diagnosed with testicular torsion, 20 of whom had undergone orchiectomy. Of these 20 patients, 2 were diagnosed with a malignancy. Our study, the largest case series to date, has shown an association between testicular torsion and testicular cancer of 6.4%. Testicular torsion is a medical emergency that usually requires surgical exploration. However, testicular malignancy has been anecdotally reported in association with torsion in surgical specimens. However, the published data remain scant on the association between torsion and the presence of testicular tumors. The present retrospective study explored the association between torsion and testicular cancer in patients with testicular torsion undergoing orchiectomy during scrotal exploration. A medical record review was performed of patients who had had a diagnosis of testicular torsion from January 2003 to February 2015. The clinicopathologic characteristics of the patients were recorded. A total of 32 patients were identified. Their mean age was 21.1 years (range, 7-39 years). All the patients had unilateral testicular torsion, which affected the left side in 17 and the right side in 15. Manual detorsion was successful in 6 patients, and 26 patients underwent emergency surgery with testicular detorsion (6 fixation surgery and 20 orchiectomy). The type of incision was scrotal in 6, inguinal in 10, and unspecified in 4. Pathologic examination of the orchiectomy specimens showed malignancy in 2 cases (seminoma and malign mixed germ cell tumor). To the best of our knowledge, the present single-center case series is the largest case series to date of testicular torsion and showed an association between testicular torsion and testicular cancer of 6.4%. However, further larger series of the association between testicular torsion and cancer are needed to explore the relationship between testicular torsion and testicular cancer. Copyright © 2016 Elsevier Inc. All rights reserved.

A molecular symmetry analysis of the electronic states and transition dipole moments for molecules with two torsional degrees of freedom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obaid, R.; Applied Chemistry Department, Palestine Polytechnic University, Hebron, Palestine; Leibscher, M., E-mail: monika.leibscher@itp.uni-hannover.de

2015-02-14

We present a molecular symmetry analysis of electronic states and transition dipole moments for molecules which undergo large amplitude intramolecular torsions. The method is based on the correlation between the point group of the molecule at highly symmetric configurations and the molecular symmetry group. As an example, we determine the global irreducible representations of the electronic states and transition dipole moments for the quinodimethane derivative 2-[4-(cyclopenta-2,4-dien-1-ylidene)cyclohexa-2,5-dien-1-ylidene]-2H-1, 3-dioxole for which two torsional degrees of freedom can be activated upon photo-excitation and construct the resulting symmetry adapted transition dipole functions.

Raman spectroscopic study of reaction dynamics

NASA Astrophysics Data System (ADS)

MacPhail, R. A.

1990-12-01

The Raman spectra of reacting molecules in liquids can yield information about various aspects of the reaction dynamics. The author discusses the analysis of Raman spectra for three prototypical unimolecular reactions, the rotational isomerization of n-butane and 1,2-difluoroethane, and the barrierless exchange of axial and equatorial hydrogens in cyclopentane via pseudorotation. In the first two cases the spectra are sensitive to torsional oscillations of the gauche conformer, and yield estimates of the torsional solvent friction. In the case of cyclopentane, the spectra can be used to discriminate between different stochastic models of the pseudorotation dynamics, and to determine the relevant friction coefficients.

Coulomb's Electrical Measurements. Experiment No. 14.

ERIC Educational Resources Information Center

Devons, Samuel

Presented is information related to the life and work of Charles Coulomb as well as detailed notes of his measurements of the distribution of electricity on conductors. The two methods that he used (the large torsion balance, and the timing of "force" oscillations) are described. (SA)

Experimental evidence for flux-lattice melting. [in high-Tc superconductors

NASA Technical Reports Server (NTRS)

Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.

1991-01-01

A low-frequency torsional oscillator has been used to search for flux-lattice melting in an untwinned single crystal of YBa2Cu3O(7-delta). The damping of the oscillator was measured as a function of temperature, for applied magnetic fields in the range H = 0.1-2.3 T. A remarkably sharp damping peak has been located. It is suggested that the temperature of the peak corresponds to the melting point of the Abrikosov flux lattice.

Comparison of torsional and microburst longitudinal phacoemulsification: a prospective, randomized, masked clinical trial.

PubMed

Vasavada, Abhay R; Raj, Shetal M; Patel, Udayan; Vasavada, Vaishali; Vasavada, Viraj

2010-01-01

To compare intraoperative performance and postoperative outcome of three phacoemulsification technologies in patients undergoing microcoaxial phacoemulsification through 2.2-mm corneal incisions. The prospective, randomized, single-masked study included 360 eyes randomly assigned to torsional (Infiniti Vision System; Alcon Laboratories, Fort Worth, TX), microburst with longitudinal (Infiniti), or microburst with longitudinal (Legacy Everest, Alcon Laboratories) ultrasound. Assessments included surgical clock time, fluid volume, and intraoperative complications, central corneal thickness on day 1 and months 1 and 3 postoperatively, and endothelial cell density at 3 months postoperatively. Comparisons among groups were conducted. Torsional ultrasound required significantly less surgical clock time and fluid volume than the other groups. There were no intraoperative complications. Change in central corneal thickness and endothelial cell loss was significantly lower in the torsional ultrasound group at all postoperative visits (P < .001, Kruskal-Wallis test) compared to microburst longitudinal ultrasound modalities. Torsional ultrasound demonstrated quantitatively superior intraoperative performance and showed less increase in corneal thickness and less endothelial cell loss compared to microburst longitudinal ultrasound. Copyright 2010, SLACK Incorporated.

Torsional vibration characteristic study of the grid-connected DFIG wind turbine

NASA Astrophysics Data System (ADS)

Yu, Songtao; Xie, Da; Wu, Wangping; Gu, Chenghong; Li, Furong

2017-01-01

This paper studies the torsional vibration characteristics of the grid-connected doubly-fed induction generator (DFIG) wind turbine by small signal analysis method. Firstly a detailed small-signal stability union model of the grid-connected DFIG wind turbine is developed, including the mechanical system and electrical system. To study the dynamic characteristic of the blade, gearbox, low speed and high speed shafts, a three mass shaft model for the mechanical system is adopted. At the same time, small signal models of DFIG, the voltage source converter (VSC) and the transmission line of the electrical system are developed respectively. Then, through calculating the eigenvalues of the state matrix A and the corresponding participation factors, the modal analysis is conducted in the shaft torsional vibration issues. And the impact of the system parameters including the series compensation capacitor, the flat-wave reactor, the PI parameters, especially the speed controller of generator rotor on shaft torsional vibration are discussed. The results show that the speed controller strengthens association between the mechanical system and the electrical system, and also produces a low-frequency oscillation mode.

High-frequency torsional Alfvén waves as an energy source for coronal heating

PubMed Central

Srivastava, Abhishek Kumar; Shetye, Juie; Murawski, Krzysztof; Doyle, John Gerard; Stangalini, Marco; Scullion, Eamon; Ray, Tom; Wójcik, Dariusz Patryk; Dwivedi, Bhola N.

2017-01-01

The existence of the Sun’s hot atmosphere and the solar wind acceleration continues to be an outstanding problem in solar-astrophysics. Although magnetohydrodynamic (MHD) modes and dissipation of magnetic energy contribute to heating and the mass cycle of the solar atmosphere, yet direct evidence of such processes often generates debate. Ground-based 1-m Swedish Solar Telescope (SST)/CRISP, Hα 6562.8 Å observations reveal, for the first time, the ubiquitous presence of high frequency (~12–42 mHz) torsional motions in thin spicular-type structures in the chromosphere. We detect numerous oscillating flux tubes on 10 June 2014 between 07:17 UT to 08:08 UT in a quiet-Sun field-of-view of 60” × 60” (1” = 725 km). Stringent numerical model shows that these observations resemble torsional Alfvén waves associated with high frequency drivers which contain a huge amount of energy (~105 W m−2) in the chromosphere. Even after partial reflection from the transition region, a significant amount of energy (~103 W m−2) is transferred onto the overlying corona. We find that oscillating tubes serve as substantial sources of Alfvén wave generation that provide sufficient Poynting flux not only to heat the corona but also to originate the supersonic solar wind. PMID:28256538

Wind tunnel wall effects in a linear oscillating cascade

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1991-01-01

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flow field, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity - the airfoil to airfoil variation in unsteady surface pressure - is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions.

Effect of Dynamic Rolling Oscillations on Twin Tail Buffet Response

NASA Technical Reports Server (NTRS)

Sheta, Essam F.; Kandil, Osama A.

1999-01-01

The effect of dynamic rolling oscillations of delta-wing/twin-tail configuration on twin-tail buffet response is investigated. The computational model consists of a sharp-edged delta wing of aspect ratio one and swept-back flexible twin tail with taper ratio of 0.23. The configuration model is statically pitched at 30 deg. angle of attack and then forced to oscillate in roll around the symmetry axis at a constant amplitude of 4 deg. and reduced frequency of pi and 2(pi). The freestream Mach number and Reynolds number are 0.3 and 1.25 million, respectively. This multidisciplinary problem is solved using three sets of equations on a dynamic multi-block grid structure. The first set is the unsteady, full Navier-Stokes equations, the second set is the aeroelastic equations for coupled bending and torsion vibrations of the tails, and the third set is the grid-displacement equations. The configuration is investigated for inboard position of the twin tails which corresponds to a separation distance between the twin tails of 33% wing span. The computed results are compared with the results of stationary configuration, which previously have been validated using experimental data. The results conclusively showed that the rolling oscillations of the configuration have led to higher loads, higher deflections, and higher excitation peaks than those of the stationary configuration. Moreover, increasing the reduced frequency has led to higher loads and excitation peaks and lower bending and torsion deflections and acceleration.

Aerodynamics of a linear oscillating cascade

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1990-01-01

The steady and unsteady aerodynamics of a linear oscillating cascade are investigated using experimental and computational methods. Experiments are performed to quantify the torsion mode oscillating cascade aerodynamics of the NASA Lewis Transonic Oscillating Cascade for subsonic inlet flowfields using two methods: simultaneous oscillation of all the cascaded airfoils at various values of interblade phase angle, and the unsteady aerodynamic influence coefficient technique. Analysis of these data and correlation with classical linearized unsteady aerodynamic analysis predictions indicate that the wind tunnel walls enclosing the cascade have, in some cases, a detrimental effect on the cascade unsteady aerodynamics. An Euler code for oscillating cascade aerodynamics is modified to incorporate improved upstream and downstream boundary conditions and also the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic predictions of the code, and the computational unsteady aerodynamic influence coefficient technique is shown to be a viable alternative for calculation of oscillating cascade aerodynamics.

Model-based analysis of the torsional loss modulus in human hair and of the effects of cosmetic processing.

PubMed

Wortmann, Franz J; Wortmann, Gabriele; Haake, Hans-Martin; Eisfeld, Wolf

Torsional analysis of single human hairs is especially suited to determine the properties of the cuticle and its changes through cosmetic processing. The two primary parameters, which are obtained by free torsional oscillation using the torsional pendulum method, are storage ( G ') and loss modulus ( G ″). Based on previous work on G ', the current investigation focuses on G ″. The results show an increase of G ″ with a drop of G ' and vice versa , as is expected for a viscoelastic material well below its glass transition. The overall power of G ″ to discriminate between samples is quite low. This is attributed to the systematic decrease of the parameter values with increasing fiber diameter, with a pronounced correlation between G ″ and G '. Analyzing this effect on the basis of a core/shell model for the cortex/cuticle structure of hair by nonlinear regression leads to estimates for the loss moduli of cortex ( G ″ co ) and cuticle ( G ″ cu ). Although the values for G ″ co turn out to be physically not plausible, due to limitations of the applied model, those for G ″ cu are considered as generally realistic against relevant literature values. Significant differences between the loss moduli of the cuticle for the different samples provide insight into changes of the torsional energy loss due to the cosmetic processes and products, contributing toward a consistent view of torsional energy storage and loss, namely, in the cuticle of hair.

A Rare Case of Splenic Torsion with Sigmoid Volvulus in a 14-Year-Old Girl.

PubMed

Ahmadi, Hamid; Tehrani, Mahdieh Mohammad Khan

2016-01-01

Wandering spleen is an uncommon entity in adults and has been described only rarely with sigmoid volvulus, that rarely affects children and adolescents. It is usually described in adults.Wandering spleen characterized by the abnormal location of the spleen, caused by incomplete fusion of the four primary splenic ligaments, allowing the spleen to be mobile within the abdomen.The wandering spleen can lead to torsion and subsequent splenic infarction or rupture. Clinical suspicion plus urgent investigation and intervention are important. We present a rare clinical case of acute abdomen due to torsion of wandering spleen and volvulus of sigmoid in a 14-year-old girl presented with painful periumbilical mass. Detorsion of sigmoid occurred while undergoing exploratory laparotomy and splenectomy was performed. The possibility of torsion and its complication like gastric, pancreas tail and colon volvulus should be kept in mind in the differential diagnosis of the acute abdomen to avoid serious complications.

Compressible viscous flows generated by oscillating flexible cylinders

NASA Astrophysics Data System (ADS)

Van Eysden, Cornelis A.; Sader, John E.

2009-01-01

The fluid dynamics of oscillating elastic beams underpin the operation of many modern technological devices ranging from micromechanical sensors to the atomic force microscope. While viscous effects are widely acknowledged to have a strong influence on these dynamics, fluid compressibility is commonly neglected. Here, we theoretically study the three-dimensional flow fields that are generated by the motion of flexible cylinders immersed in viscous compressible fluids and discuss the implications of compressibility in practice. We consider cylinders of circular cross section and flat blades of zero thickness that are executing flexural and torsional oscillations of arbitrary wave number. Exact analytical solutions are derived for these flow fields and their resulting hydrodynamic loads.

Oscillating Cascade Aerodynamics at Large Mean Incidence Angles

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.

1997-01-01

In a cooperative program with Pratt & Whitney, researchers obtained fundamental separated flow unsteady aerodynamic data in the NASA Lewis Research Center's Oscillating Cascade. These data fill a void that has hindered the understanding and prediction of subsonic and transonic stall flutter. For small-amplitude torsional oscillations, unsteady pressure distributions were measured on airfoils with cross sections representative of an advanced, low-aspect-ratio fan blade. Data were obtained for two mean incidence angles with a subsonic inflow. At high mean incidence angles (alpha = 10 deg), the mean flow separated at the leading edge and reattached at about 40 percent of the chord. For comparison purposes, data were also obtained for a low incidence angle (a = 0 deg) attached flow.

Slip measurement in a frictional connection by torsional LDV

NASA Astrophysics Data System (ADS)

Schäfer, Günter; Lohrengel, Armin; Hilgermann, Jan Lukas

2016-06-01

Frictional shaft-hub connections are often used in drive train applications. The classic version is fitted by a temperature difference between the cold shaft und the hot hub, or simply axial press-fitted at room temperature. The critical point in this type of connection is the contact pressure at the edge of the hub regarding the relative deformation between the shaft and the hub under dynamic operating loads. Another innovative version, the internal press-fit, leads to a tolerance insensitive lightweight design using a tube as shaft and a controlled plastic deformation by internal high pressure. The internal press-fit connection is a special research topic at the IMW, TU Clausthal. The use of internal high pressure allows to trigger the contact pressure at the edge of the hub on an optimum value. The product of contact pressure and slipway is the key value to determine the fatigue resistance and load capacity of this kind of connection. /1/ and /2/ defined a critical range of slipway amplitudes between 5 and 25 µm for fretting. The normal use and main function of a shaft-hub connection is the transmission of torque. Regarding the different torsional stiffness of the shaft and the hub, there will be a difference in deformation in the contact zone between the shaft and the hub, which is necessary to measure on a probe under oscillating torque load. The measurement on the test-rig in /3/ was done with a POLYTEC torsional LDV (controller OFV-4000, sensor head OFV-400). In general the continuously oscillating torque load allowed a serial measurement of the torsional movement of the shaft and the hub. The difference of the two maximum values is the expected slipway between the two parts in the critical zone at the edge of the hub. The main benefits of the Torsional LDV in this application are the very small measuring point (next to the contact), no influence on the probe, no special preparation of the probe and a really good resolution. The paper gives an overview to the technical background of the measured value, to the measuring setup, to the other used measuring techniques and to the measuring results.

A novel torsional exciter for modal vibration testing of large rotating machinery

NASA Astrophysics Data System (ADS)

Sihler, Christof

2006-10-01

A novel exciter for applying a dynamic torsional force to a rotating structure is presented in this paper. It has been developed at IPP in order to perform vibration tests with shaft assemblies of large flywheel generators (synchronous machines). The electromagnetic exciter (shaker) needs no fixture to the rotating shaft because the torque is applied by means of the stator winding of an electrical machine. Therefore, the exciter can most easily be applied in cases where a three-phase electrical machine (a motor or generator) is part of the shaft assembly. The oscillating power for the shaker is generated in a separate current-controlled DC circuit with an inductor acting as a buffer storage of magnetic energy. An AC component with adjustable frequency is superimposed on the inductor current in order to generate pulsating torques acting on the rotating shaft with the desired waveform and frequency. Since this torsional exciter does not require an external power source, can easily be installed (without contact to the rotating structure) and provides dynamic torsional forces which are sufficient for multi-megawatt applications, it is best suited for on-site tests of large rotating machinery.

Coronal magnetohydrodynamic waves and oscillations: observations and quests.

PubMed

Aschwanden, Markus J

2006-02-15

Coronal seismology, a new field of solar physics that emerged over the last 5 years, provides unique information on basic physical properties of the solar corona. The inhomogeneous coronal plasma supports a variety of magnetohydrodynamics (MHD) wave modes, which manifest themselves as standing waves (MHD oscillations) and propagating waves. Here, we briefly review the physical properties of observed MHD oscillations and waves, including fast kink modes, fast sausage modes, slow (acoustic) modes, torsional modes, their diagnostics of the coronal magnetic field, and their physical damping mechanisms. We discuss the excitation mechanisms of coronal MHD oscillations and waves: the origin of the exciter, exciter propagation, and excitation in magnetic reconnection outflow regions. Finally, we consider the role of coronal MHD oscillations and waves for coronal heating, the detectability of various MHD wave types, and we estimate the energies carried in the observed MHD waves and oscillations: Alfvénic MHD waves could potentially provide sufficient energy to sustain coronal heating, while acoustic MHD waves fall far short of the required coronal heating rates.

Investigation of oscillating cascade aerodynamics by an experimental influence coefficient technique

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Fleeter, Sanford

1988-01-01

Fundamental experiments are performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate the torsion mode unsteady aerodynamics of a biconvex airfoil cascade at realistic values of the reduced frequency for all interblade phase angles at a specified mean flow condition. In particular, an unsteady aerodynamic influence coefficient technique is developed and utilized in which only one airfoil in the cascade is oscillated at a time and the resulting airfoil surface unsteady pressure distribution measured on one dynamically instrumented airfoil. The unsteady aerodynamics of an equivalent cascade with all airfoils oscillating at a specified interblade phase angle are then determined through a vector summation of these data. These influence coefficient determined oscillation cascade data are correlated with data obtained in this cascade with all airfoils oscillating at several interblade phase angle values. The influence coefficients are then utilized to determine the unsteady aerodynamics of the cascade for all interblade phase angles, with these unique data subsequently correlated with predictions from a linearized unsteady cascade model.

Study on Active Suppression Control of Drivetrain Oscillations in an Electric Vehicle

NASA Astrophysics Data System (ADS)

Huang, Lei; Cui, Ying

2017-07-01

Due to the low damping in a central driven electric vehicle and lack of passive damping mechanisms as compared with a conventional vehicle, the vehicle may endure torsional vibrations which may deteriorates the vehicle’s drivability. Thus active damping control strategy is required to reduce the undesirable oscillations in an EV. In this paper, the origin of the vibration and the design of a damping control method to suppress such oscillations to improve the drivability of an EV are studied. The traction motor torque that is given by the vehicle controller is adjusted according to the acceleration rate of the motor speed to attenuate the resonant frequency. Simulations and experiments are performed to validate the system. The results show that the proposed control system can effectively suppress oscillations and hence improve drivability.

High-resolution Fourier transform synchrotron spectroscopy of the C-S stretching band of methyl mercaptan, CH332SH

NASA Astrophysics Data System (ADS)

Lees, R. M.; Xu, Li-Hong; Billinghurst, B. E.

2016-01-01

The C-S stretching fundamental band of 12CH332SH, the principal isotopologue of methyl mercaptan, has been investigated by Fourier transform infrared spectroscopy on the Far-Infrared beamline at the Canadian Light Source synchrotron. The band is centered around 710 cm-1 and shows well-resolved a-type parallel structure. Most of the A and E spectral sub-bands have been assigned up to K = 12 for the vt = 0 torsional state and K = 9 for the vt = 1 state, along with a smaller variety of sub-bands for vt = 2. C-S stretching energy term values have been determined employing known ground-state energies, and have been fitted to series expansions in powers of J(J + 1) to determine the substate origins. The origins have in turn been fitted to a Fourier model to characterize the oscillatory torsional energy structure of the C-S stretching state. The amplitude of oscillation of the vt = 0 torsional curves is significantly larger for the C-S stretch state compared to the ground state. A strategy devised to relate this amplitude to an effective torsional barrier height indicates a decrease of about 7% in the effective V3 for the C-S stretch. The vibrational frequency determined for the stretching fundamental from the Fourier fit is 710.3 cm-1. The C-S stretching manifold is crossed by excited vt = 4 torsional levels of the ground state, and strong torsion-vibrational resonant coupling is observed via perturbations in the spectrum together with forbidden sub-bands induced by mixing and intensity borrowing.

Single-molecule study of the DNA denaturation phase transition in the force-torsion space.

PubMed

Salerno, D; Tempestini, A; Mai, I; Brogioli, D; Ziano, R; Cassina, V; Mantegazza, F

2012-09-14

We use the "magnetic tweezers" technique to show the structural transitions that the DNA undergoes in the force-torsion space. In particular, we focus on the regions corresponding to negative supercoiling. These regions are characterized by the formation of the so-called denaturation bubbles, which play an essential role in the replication and transcription of DNA. We experimentally map the region of the force-torsion space where the denaturation takes place. We observe that large fluctuations in DNA extension occur at one of the boundaries of this region, i.e., when the formation of denaturation bubbles and of plectonemes compete. To describe the experiments, we introduce a suitable extension of the classical model. The model correctly describes the position of the denaturation regions, the transition boundaries, and the measured values of the DNA extension fluctuations.

Single-Molecule Study of the DNA Denaturation Phase Transition in the Force-Torsion Space

NASA Astrophysics Data System (ADS)

Salerno, D.; Tempestini, A.; Mai, I.; Brogioli, D.; Ziano, R.; Cassina, V.; Mantegazza, F.

2012-09-01

We use the “magnetic tweezers” technique to show the structural transitions that the DNA undergoes in the force-torsion space. In particular, we focus on the regions corresponding to negative supercoiling. These regions are characterized by the formation of the so-called denaturation bubbles, which play an essential role in the replication and transcription of DNA. We experimentally map the region of the force-torsion space where the denaturation takes place. We observe that large fluctuations in DNA extension occur at one of the boundaries of this region, i.e., when the formation of denaturation bubbles and of plectonemes compete. To describe the experiments, we introduce a suitable extension of the classical model. The model correctly describes the position of the denaturation regions, the transition boundaries, and the measured values of the DNA extension fluctuations.

Reverse left ventricular remodeling after acute myocardial infarction: the prognostic impact of left ventricular global torsion.

PubMed

Spinelli, Letizia; Morisco, Carmine; Assante di Panzillo, Emiliano; Izzo, Raffaele; Trimarco, Bruno

2013-04-01

Reverse left ventricular (LV) remodeling (>10 % reduction in LV end-systolic volume) may occur in patients recovering for acute ST-elevation myocardial infarction (STEMI), undergoing percutaneous revascularization of infarct-related coronary artery (PCI). To detect whether LV global torsion obtained by two-dimensional speckle-tracking echocardiography was predictive of reverse LV remodeling, 75 patients with first anterior wall STEMI were studied before (T1) and after PCI (T2) and at 6-month follow-up. Two-year clinical follow-up was also accomplished. LV volumes and both LV sphericity index and conic index were obtained by three-dimensional echocardiography. Reverse remodeling was observed in 25 patients (33 %). By multivariate analysis, independent predictors of reverse LV remodeling were: LV conic index, T2 LV torsion and Δ torsion (difference between T2 and T1 LV torsion expressed as percentage of this latter). According to receiver operating characteristic analysis, 1.34°/cm for T2 LV torsion (sensitivity 88 % and specificity 80 %) and 54 % for Δ torsion (sensitivity 92 % and specificity 82 %) were the optimal cutoff values in predicting reverse LV remodeling. In up to 24 month follow-up, 4 non-fatal re-infarction, 7 hospitalization for heart failure and 4 cardiac deaths occurred. By multivariate Cox analysis, the best variable significantly associated with event-free survival rate was reverse LV remodeling with a hazard ratio = 9.9 (95 % confidence interval, 7.9-31.4, p < 0.01). In conclusion, reverse LV remodeling occurring after anterior wall STEMI is associated with favorable long-term outcome. The improvement of global LV torsion following coronary artery revascularization is the major predictor of reverse LV remodeling.

Transverse vs torsional ultrasound: prospective randomized contralaterally controlled study comparing two phacoemulsification-system handpieces.

PubMed

Assil, Kerry K; Harris, Lindsay; Cecka, Jeannie

2015-01-01

To compare surgical efficiency and multiple early clinical outcome variables in eyes undergoing phacoemulsification using either transversal or torsional ultrasound systems. Assil Eye Institute, Beverly Hills, CA, USA. Prospective, randomized, clinician-masked, contralaterally controlled single-center evaluation. Patients seeking cataract removal in both eyes with implantation of multifocal intraocular lenses were randomly assigned to one of two treatment rooms for phacoemulsification with either a transverse ultrasound system or torsional handpiece system. The contralateral eye was treated at a later date with the alternate device. A total of 54 eyes of 27 patients having similar degrees of cataract, astigmatism, and visual potential were included. All operative data were collected for analysis, and patients were followed for 3 months after surgery. Similar visual acuity was reported at all postoperative visits between the two groups. Mean phacoemulsification time and total power required were both significantly lower with the transverse system than with the torsional technique (P<0.05 for both). Similarly, mean total balanced salt solution used was significantly less with the transverse system vs torsional (P<0.05). Postoperative safety demonstrated significantly lower endothelial cell loss at 1 day and 1 month (P<0.05) with transverse vs torsional. Macular swelling was less at 1 week, 1 month, and 3 months with transverse vs torsional, although the difference did not achieve significance (P=0.1) at any single time point. Clinically detectable corneal edema was reported less frequently at all postoperative time points with the transverse system. The transverse ultrasound system was found to be possibly associated with less balanced salt-solution use, less phacoemulsification time, and less power required than the torsional phaco system. Postoperative data suggested that improved phaco efficiency may translate to a better overall safety profile for the patient.

Method for spatially modulating X-ray pulses using MEMS-based X-ray optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez, Daniel; Shenoy, Gopal; Wang, Jin

A method and apparatus are provided for spatially modulating X-rays or X-ray pulses using microelectromechanical systems (MEMS) based X-ray optics. A torsionally-oscillating MEMS micromirror and a method of leveraging the grazing-angle reflection property are provided to modulate X-ray pulses with a high-degree of controllability.

How the embryonic chick brain twists.

PubMed

Chen, Zi; Guo, Qiaohang; Dai, Eric; Forsch, Nickolas; Taber, Larry A

2016-11-01

During early development, the tubular embryonic chick brain undergoes a combination of progressive ventral bending and rightward torsion, one of the earliest organ-level left-right asymmetry events in development. Existing evidence suggests that bending is caused by differential growth, but the mechanism for the predominantly rightward torsion of the embryonic brain tube remains poorly understood. Here, we show through a combination of in vitro experiments, a physical model of the embryonic morphology and mechanics analysis that the vitelline membrane (VM) exerts an external load on the brain that drives torsion. Our theoretical analysis showed that the force is of the order of 10 micronewtons. We also designed an experiment to use fluid surface tension to replace the mechanical role of the VM, and the estimated magnitude of the force owing to surface tension was shown to be consistent with the above theoretical analysis. We further discovered that the asymmetry of the looping heart determines the chirality of the twisted brain via physical mechanisms, demonstrating the mechanical transfer of left-right asymmetry between organs. Our experiments also implied that brain flexure is a necessary condition for torsion. Our work clarifies the mechanical origin of torsion and the development of left-right asymmetry in the early embryonic brain. © 2016 The Author(s).

[The adnexal torsion in children].

PubMed

Khemakhem, Rachid; Barhoumi, Amel; Matoussi, Nadia; Hidouri, Saida; Ghorbel, Sofiane; Nouira, Faouzi; Jlidi, Said; Ben Becheur, Saida; Chaouachi, Béji

2008-05-01

Adnexal torsion is the most frequent gynaecological emergency in children. It requires an early diagnosis and an urgent surgical treatment. to study the clinical, paraclinical and therapeutic aspect of adnexal torsion in paediatric population. This is a retrospective review of nine girls with the diagnosis of ovarian torsion observed over a 7 years period (January 1999 to December 2005). The average age is 9 years (extreme 6 to 13 years). This pathology was located in 5 cases on the right side and in 3 cases on the left side; a case of bilateral torsion of poly-cystic ovary was encountered in a girl with down syndrome. Clinical presentation is made in all the cases by abdominal pains and vomiting. The disorders of the transit and the urinary signs are associated in 3 and 2 cases respectively, the clinical examination objectified a pelvic defense in all the cases and an abdominal mass in 2 cases. Pelvic ultra-sonography was made in 6 observations and give the diagnosis of torsion of the ovary in 4 cases, whereas it was doubtful in the 2 remaining cases when an ovarian mass was observed. In the 3 remaining cases, this examination was not performed since one the diagnosis of acute appendicitis was retained and the patient operated in emergency. All the children of our series were operated; in 1/3 of the cases we found a necrosis of the ovary. 4 cases out of 9 present a torsion on pathologic ovary (cyst, dysplasia), whereas in the 5 remaining cases, we noted a torsion on healthy ovary. 4 young girls have undergoes a annexectomy, of which one was bilateral. The evolution was favorable in all the cases. Adnexal torsion is a surgical emergency that need an early diagnosis and management to preserve ovarian function in girls and Doppler sonography every must be done every time there is a pelvic pain without fever in girls

Cardiac Rotational Mechanics As a Predictor of Myocardial Recovery in Heart Failure Patients Undergoing Chronic Mechanical Circulatory Support: A Pilot Study.

PubMed

Bonios, Michael J; Koliopoulou, Antigone; Wever-Pinzon, Omar; Taleb, Iosif; Stehlik, Josef; Xu, Weining; Wever-Pinzon, James; Catino, Anna; Kfoury, Abdallah G; Horne, Benjamin D; Nativi-Nicolau, Jose; Adamopoulos, Stamatis N; Fang, James C; Selzman, Craig H; Bax, Jeroen J; Drakos, Stavros G

2018-04-01

Impaired qualitative and quantitative left ventricular (LV) rotational mechanics predict cardiac remodeling progression and prognosis after myocardial infarction. We investigated whether cardiac rotational mechanics can predict cardiac recovery in chronic advanced cardiomyopathy patients. Sixty-three patients with advanced and chronic dilated cardiomyopathy undergoing implantation of LV assist device (LVAD) were prospectively investigated using speckle tracking echocardiography. Acute heart failure patients were prospectively excluded. We evaluated LV rotational mechanics (apical and basal LV twist, LV torsion) and deformational mechanics (circumferential and longitudinal strain) before LVAD implantation. Cardiac recovery post-LVAD implantation was defined as (1) final resulting LV ejection fraction ≥40%, (2) relative LV ejection fraction increase ≥50%, (iii) relative LV end-systolic volume decrease ≥50% (all 3 required). Twelve patients fulfilled the criteria for cardiac recovery (Rec Group). The Rec Group had significantly less impaired pre-LVAD peak LV torsion compared with the Non-Rec Group. Notably, both groups had similarly reduced pre-LVAD LV ejection fraction. By receiver operating characteristic curve analysis, pre-LVAD peak LV torsion of 0.35 degrees/cm had a 92% sensitivity and a 73% specificity in predicting cardiac recovery. Peak LV torsion before LVAD implantation was found to be an independent predictor of cardiac recovery after LVAD implantation (odds ratio, 0.65 per 0.1 degrees/cm [0.49-0.87]; P =0.014). LV rotational mechanics seem to be useful in selecting patients prone to cardiac recovery after mechanical unloading induced by LVADs. Future studies should investigate the utility of these markers in predicting durable cardiac recovery after the explantation of the cardiac assist device. © 2018 American Heart Association, Inc.

Torsional Oscillations with Lorentz Force

ERIC Educational Resources Information Center

Gluck, Paul

2007-01-01

We have built a device that uses the Lorentz force on a current-carrying wire situated in a magnetic field, F = I L x B, in order to demonstrate a slowly varying alternating current by means of an optical lever. The apparatus consists of a horseshoe magnet, a length of thin enamel-coated wire (ours was 0.3 mm thick), a signal generator, a…

High-frequency performance for a spiral-shaped piezoelectric bimorph

NASA Astrophysics Data System (ADS)

Huang, Fang Sheng; Feng, Zhi Hua; Ma, Yu Ting; Pan, Qiao Sheng; Zhang, Lian Sheng; Liu, Yong Bin; He, Liang Guo

2018-04-01

Piezoelectric cantilever is suitable as an actuator for micro-flapping-wing aircraft. Higher resonant frequency brings about stronger flight energy, and the flight amplitude can be compensated by displacement-amplification mechanism, such as lever. To obtain a higher resonant frequency, straight piezoelectric bimorph was rolled into spiral-shaped piezoelectric bimorph with identical effective length in this study, which is verified in COMSOL simulations. Simulation results show that compared with the straight piezoelectric bimorph, the spiral-shaped piezoelectric bimorph with two turns has higher inherent frequencies (from 204.79 Hz to 504.84 Hz in terms of axial oscillation mode, and from 319.77 Hz to 704.48 Hz in terms of tangential torsional mode). The spiral-shaped piezoelectric bimorph is fabricated by a precise laser cutting process and consists of two turns with effective length of 60 mm, width of 2.5 mm, and thickness of 1.6 mm, respectively. With the excitation voltage of 100 Vpp applying an electric field across the thickness of the bimorph, the tip displacement of the actuator in the axial oscillation and tangential torsional modes are 85 μm and 15 μm, respectively.

SOLAR MERIDIONAL FLOW IN THE SHALLOW INTERIOR DURING THE RISING PHASE OF CYCLE 24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Junwei; Bogart, R. S.; Kosovichev, A. G.

2014-07-01

Solar subsurface zonal- and meridional-flow profiles during the rising phase of solar cycle 24 are studied using the time-distance helioseismology technique. The faster zonal bands in the torsional-oscillation pattern show strong hemispheric asymmetries and temporal variations in both width and speed. The faster band in the northern hemisphere is located closer to the equator than the band in the southern hemisphere and migrates past the equator when the magnetic activity in the southern hemisphere is reaching maximum. The meridional-flow speed decreases substantially with the increase of magnetic activity, and the flow profile shows two zonal structures in each hemisphere. Themore » residual meridional flow, after subtracting a mean meridional-flow profile, converges toward the activity belts and shows faster and slower bands like the torsional-oscillation pattern. More interestingly, the meridional-flow speed above latitude 30° shows an anti-correlation with the poleward-transporting magnetic flux, slower when the following-polarity flux is transported and faster when the leading-polarity flux is transported. It is expected that this phenomenon slows the process of magnetic cancellation and polarity reversal in high-latitude areas.« less

Experimental Testicular Torsion in a Rat Model: Effects of Treatment with Pausinystalia macroceras on Testis Functions.

PubMed

Ikebuaso, Afamefuna Donatus; Yama, Oshiozokhai Eboetse; Duru, F I O; Oyebadejo, S A

2012-10-01

Testicular torsion is a medical emergency with catastrophic sequelae that deserves the same treatment considerations and concerted efforts in research as any other complicated medical condition. The aim of this study was to investigate the effect of Pausinystalia macroceras (PM) bark extract on sperm quality and serum testosterone levels in testicular torsion in a rat model. Sixty-five (65) mature male Wistar rats apportioned randomly into four experimental groups of A to C; were further divided into four subgroups according to duration of torsion. Group D were the normal regular rats. Each group/subgroup comprised five rats. Testis maintained in the torted position (T) for 1, 2, 3 and 4 hr in Group A (subgroups: AT1+PM, AT2+PM, AT3+PM, and AT4+PM). Group B (sub- groups: B1+PM, B2+PM, B3+PM, B4+PM) were sham-operated animals, which did not undergo torsion and served as the sham control group. Group C subgroups: CT1, CT2, CT3 and CT4 were torted as in A. All animals (except groups C and D) were treated by PM extract (0.1 g/kg b.w. per day) for 56 days. Group D rats were fed distilled water. Serum testosterone concentrations and sperm quality (motility and count) were measured. Analyses of variance with Scheffe's post-hoc test were carried out on the data. PM extract had a positive effect (significant; p < 0.5) on the sperm count and motility in rats with testicular torsion compared to those not receiving the extract. There was also an increase in serum testosterone levels in the former groups. Treatment of rats following testicular torsion result to the enhancement of sperm production in comparison with untreated rats.

Quasi-periodic oscillations in superfluid, relativistic magnetars with nuclear pasta phases

NASA Astrophysics Data System (ADS)

Passamonti, Andrea; Pons, José A.

2016-12-01

We study the torsional magneto-elastic oscillations of relativistic superfluid magnetars and explore the effects of a phase transition in the crust-core interface (nuclear pasta) which results in a weaker elastic response. Exploring various models with different extension of nuclear pasta phases, we find that the differences in the oscillation spectrum present in purely elastic modes (weak magnetic field) are smeared out with increasing strength of the magnetic field. For magnetar conditions, the main characteristic and features of models without nuclear pasta are preserved. We find, in general, two classes of magneto-elastic oscillations which exhibit a different oscillation pattern. For Bp < 4 × 1014 G, the spectrum is characterized by the turning points and edges of the continuum which are mostly confined into the star's core, and have no constant phase. Increasing the magnetic field, we find, in addition, several magneto-elastic oscillations which reach the surface and have an angular structure similar to crustal modes. These global magneto-elastic oscillations show a constant phase and become dominant when Bp > 5 × 1014 G. We do not find any evidence of fundamental pure crustal modes in the low-frequency range (below 200 Hz) for Bp ≥ 1014 G.

Nanonewton thrust measurement of photon pressure propulsion using semiconductor laser

NASA Astrophysics Data System (ADS)

Iwami, K.; Akazawa, Taku; Ohtsuka, Tomohiro; Nishida, Hiroyuki; Umeda, Norihiro

2011-09-01

To evaluate the thrust produced by photon pressure emitted from a 100 W class continuous-wave semiconductor laser, a torsion-balance precise thrust stand is designed and tested. Photon emission propulsion using semiconductor light sources attract interests as a possible candidate for deep-space propellant-less propulsion and attitude control system. However, the thrust produced by photon emission as large as several ten nanonewtons requires precise thrust stand. A resonant method is adopted to enhance the sensitivity of the biflier torsional-spring thrust stand. The torsional spring constant and the resonant of the stand is 1.245 × 10-3 Nm/rad and 0.118 Hz, respectively. The experimental results showed good agreement with the theoretical estimation. The thrust efficiency for photon propulsion was also defined. A maximum thrust of 499 nN was produced by the laser with 208 W input power (75 W of optical output) corresponding to a thrust efficiency of 36.7%. The minimum detectable thrust of the stand was estimated to be 2.62 nN under oscillation at a frequency close to resonance.

Transverse vs torsional ultrasound: prospective randomized contralaterally controlled study comparing two phacoemulsification-system handpieces

PubMed Central

Assil, Kerry K; Harris, Lindsay; Cecka, Jeannie

2015-01-01

Purpose To compare surgical efficiency and multiple early clinical outcome variables in eyes undergoing phacoemulsification using either transversal or torsional ultrasound systems. Setting Assil Eye Institute, Beverly Hills, CA, USA. Design Prospective, randomized, clinician-masked, contralaterally controlled single-center evaluation. Patients and methods Patients seeking cataract removal in both eyes with implantation of multifocal intraocular lenses were randomly assigned to one of two treatment rooms for phacoemulsification with either a transverse ultrasound system or torsional handpiece system. The contralateral eye was treated at a later date with the alternate device. A total of 54 eyes of 27 patients having similar degrees of cataract, astigmatism, and visual potential were included. All operative data were collected for analysis, and patients were followed for 3 months after surgery. Results Similar visual acuity was reported at all postoperative visits between the two groups. Mean phacoemulsification time and total power required were both significantly lower with the transverse system than with the torsional technique (P<0.05 for both). Similarly, mean total balanced salt solution used was significantly less with the transverse system vs torsional (P<0.05). Postoperative safety demonstrated significantly lower endothelial cell loss at 1 day and 1 month (P<0.05) with transverse vs torsional. Macular swelling was less at 1 week, 1 month, and 3 months with transverse vs torsional, although the difference did not achieve significance (P=0.1) at any single time point. Clinically detectable corneal edema was reported less frequently at all postoperative time points with the transverse system. Conclusion The transverse ultrasound system was found to be possibly associated with less balanced salt-solution use, less phacoemulsification time, and less power required than the torsional phaco system. Postoperative data suggested that improved phaco efficiency may translate to a better overall safety profile for the patient. PMID:26345628

Experimental determination of unsteady blade element aerodynamics in cascades. Volume 1: Torsion mode cascade

NASA Technical Reports Server (NTRS)

Riffel, R. E.; Rothrock, M. D.

1980-01-01

A two dimensional cascade of harmonically oscillating airfoils was designed to model a near tip section from a rotor which was known to have experienced supersonic torsional flutter. This five bladed cascade had a solidity of 1.17 and a setting angle of 1.07 rad. Graphite epoxy airfoils were fabricated to achieve the realistically high reduced frequency level of 0.44. The cascade was tested over a range of static pressure ratios approximating the blade element operating conditions of the rotor along a constant speed line which penetrated the flutter boundary. The time-steady and time-unsteady flow field surrounding the center cascade airfoil were investigated. The effects of reduced solidity and decreased setting angle on the flow field were also evaluated.

The Protective Effects of Alpha-Lipoic Acid and Coenzyme Q10 Combination on Ovarian Ischemia-Reperfusion Injury: An Experimental Study.

PubMed

Tuncer, Ahmet Ali; Bozkurt, Mehmet Fatih; Koken, Tulay; Dogan, Nurhan; Pektaş, Mine Kanat; Baskin Embleton, Didem

2016-01-01

Objective. This study aims to evaluate whether alpha-lipoic acid and/or coenzyme Q10 can protect the prepubertal ovarian tissue from ischemia-reperfusion injury in an experimental rat model of ovarian torsion. Materials and Methods. Forty-two female preadolescent Wistar-Albino rats were divided into 6 equal groups randomly. The sham group had laparotomy without torsion; the other groups had torsion/detorsion procedure. After undergoing torsion, group 2 received saline, group 3 received olive oil, group 4 received alpha-lipoic acid, group 5 received coenzyme Q10, and group 6 received both alpha-lipoic acid and coenzyme Q10 orally. The oxidant-antioxidant statuses of these groups were compared using biochemical measurement of oxidized/reduced glutathione, glutathione peroxidase and malondialdehyde, pathological evaluation of damage and apoptosis within the ovarian tissue, and immunohistochemical assessment of nitric oxide synthase. Results. The left ovaries of the alpha-lipoic acid + coenzyme Q10 group had significantly lower apoptosis scores and significantly higher nitric oxide synthase content than the left ovaries of the control groups. The alpha-lipoic acid + coenzyme Q10 group had significantly higher glutathione peroxidase levels and serum malondialdehyde concentrations than the sham group. Conclusions. The combination of alpha-lipoic acid and coenzyme Q10 has beneficial effects on oxidative stress induced by ischemia-reperfusion injury related to ovarian torsion.

Flow over a traveling wavy foil with a passively flapping flat plate

NASA Astrophysics Data System (ADS)

Liu, Nansheng; Peng, Yan; Liang, Youwen; Lu, Xiyun

2012-05-01

Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The study reveals that the passively oscillating flat plate contributes half of the propulsive force. The flexibility, represented by the nondimensional natural frequency F, plays a very important role in the movement and propulsive force generation of the whole body. When the plate is too flexible, the drag force is observed. As the flat plate becomes more rigid, the propulsive force that is generated when the undulation is confined to last part of the wavy foil becomes larger. The steady movement occurs at F=5. These results are consistent with the observations of some swimming animals in nature.

A micro-machined gyroscope for rotating aircraft.

PubMed

Yan, Qingwen; Zhang, Fuxue; Zhang, Wei

2012-01-01

In this paper we present recent work on the design, fabrication by silicon micromachining, and packaging of a new gyroscope for stabilizing the autopilot of rotating aircraft. It operates based on oscillation of the silicon pendulum between two torsion girders for detecting the Coriolis force. The oscillation of the pendulum is initiated by the rolling and deflecting motion of the rotating carrier. Therefore, the frequency and amplitude of the oscillation are proportional to the rolling frequency and deflecting angular rate of the rotating carrier, and are measured by the sensing electrodes. A modulated pulse with constant amplitude and unequal width is obtained by a linearizing process of the gyroscope output signal and used to control the deflection of the rotating aircraft. Experimental results show that the gyroscope has a resolution of 0.008 °/s and a bias of 56.18 °/h.

Torque Sensor Based on Tunnel-Diode Oscillator

NASA Technical Reports Server (NTRS)

Chui, Talso; Young, Joseph

2008-01-01

A proposed torque sensor would be capable of operating over the temperature range from 1 to 400 K, whereas a typical commercially available torque sensor is limited to the narrower temperature range of 244 to 338 K. The design of this sensor would exploit the wide temperature range and other desirable attributes of differential transducers based on tunnel-diode oscillators as described in "Multiplexing Transducers Based on Tunnel-Diode Oscillators". The proposed torque sensor would include three flexural springs that would couple torque between a hollow outer drive shaft and a solid inner drive shaft. The torque would be deduced from the torsional relative deflection of the two shafts, which would be sensed via changes in capacitances of two capacitors defined by two electrodes attached to the inner shaft and a common middle electrode attached to the outer shaft.

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

NASA Technical Reports Server (NTRS)

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

1996-01-01

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

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.

Development of a second generation torsion balance based on a spherical superconducting suspension.

PubMed

Hammond, Giles D; Speake, Clive C; Matthews, Anthony J; Rocco, Emanuele; Peña-Arellano, Fabian

2008-02-01

This paper describes the development of a second generation superconducting torsion balance to be used for a precision measurement of the Casimir force and a short range test of the inverse square law of gravity at 4.2 K. The instrument utilizes niobium (Nb) as the superconducting element and employs passive damping of the parasitic modes of oscillation. Any contact potential difference between the torsion balance and its surroundings is nulled to within approximately 50 mV by applying known DC biases and fitting the resulting parabolic relationship between the measured torque and the applied voltage. A digital proportional-integral-derivative servo system has been developed and characterized in order to control the azimuthal position of the instrument. The angular acceleration and displacement noise are currently limited by the capacitive sensor at the level 3x10(-8) rad s(-2)/ squarerootHz and 30 nm/ squarerootHz at 100 mHz. The possibility of lossy dielectric coatings on the surface of the torsion balance test masses is also investigated. Our measurements show that the loss angles delta are (1.5+/-2.3)x10(-4) and (2.0+/-2.2)x10(-4) at frequencies of 5 and 10 mHz, respectively. These values of loss are not significant sources of error for measurements of the Casimir force using this experimental setup.

Predator-prey model for the self-organization of stochastic oscillators in dual populations

NASA Astrophysics Data System (ADS)

Moradi, Sara; Anderson, Johan; Gürcan, Ozgür D.

2015-12-01

A predator-prey model of dual populations with stochastic oscillators is presented. A linear cross-coupling between the two populations is introduced following the coupling between the motions of a Wilberforce pendulum in two dimensions: one in the longitudinal and the other in torsional plain. Within each population a Kuramoto-type competition between the phases is assumed. Thus, the synchronization state of the whole system is controlled by these two types of competitions. The results of the numerical simulations show that by adding the linear cross-coupling interactions predator-prey oscillations between the two populations appear, which results in self-regulation of the system by a transfer of synchrony between the two populations. The model represents several important features of the dynamical interplay between the drift wave and zonal flow turbulence in magnetically confined plasmas, and a novel interpretation of the coupled dynamics of drift wave-zonal flow turbulence using synchronization of stochastic oscillator is discussed.

Is there a connection between Earth's core and climate at multidecadal time scales?

NASA Astrophysics Data System (ADS)

Lambert, Sébastien; Marcus, Steven; de Viron, Olivier

2017-04-01

The length-of-day (LOD) undergoes multidecadal variations of several milliseconds (ms) attributed to changes in the fluid outer core angular momentum. These variations resemble a quasi-periodic oscillation of duration 60 to 70 years, although the periodicity (and its accurate length) are disputable because of the relatively short observational time span and the lower quality of the observations before the 20th century. Interestingly, similar variations show up in various measured or reconstructed climate indices including the sea surface (SST) and surface air (SAT) temperatures. It has been shown in several studies that LOD variations lead SST and SAT variations by a few years. No clear scenarios have been raised so far to explain the link between external, astronomical forcing (e.g., Solar wind), Earth's rotation (core-driven torsional) oscillations, and Earth's surface processes (climate variations) at these time scales. Accumulating evidence, however, suggests the centrifugal tides generated by multidecadal LOD variations as a 'valve' to control the transfer of thermal energy from the lithosphere to the surface via geothermal fluxes. This hypothesis is supported by recent studies reporting significant correlations between tidal and rotational excitation and seafloor and surface volcanism. In this study, we extend recent works from us and other independent authors by re-assessing the correlations between multidecadal LOD, climate indices, Solar and magnetic activities, as well as gridded data including SST, SAT, and cloud cover. We pay a special attention to the time lags: when a significant correlation is found, the value of the lag may help to discriminate between various possible scenarios. We locate some `hot spots', particularly in the Atlantic ocean and along the trajectory of the upper branch of the Atlantic meridional overturning circulation (AMOC), where the 70-yr oscillation is strongly marked. In addition, we discuss the possibility for centrifugal tides generated by multidecadal LOD variations to activate geothermal activity on the seafloor or to affect the global conveyor belt circulation.

Cosmological singularities and bounce in Cartan-Einstein theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lucat, Stefano; Prokopec, Tomislav, E-mail: s.lucat@students.uu.nl, E-mail: t.prokopec@uu.nl

We consider a generalized Einstein-Cartan theory, in which we add the unique covariant dimension four operators to general relativity that couples fermionic spin current to the torsion tensor (with an arbitrary strength). Since torsion is local and non-dynamical, when integrated out it yields an effective four-fermion interaction of the gravitational strength. We show how to renormalize the theory, in the one-loop perturbative expansion in generally curved space-times, obtaining the first order correction to the 2PI effective action in Schwinger-Keldysh ( in-in ) formalism. We then apply the renormalized theory to study the dynamics of a collapsing universe that begins inmore » a thermal state and find that—instead of a big crunch singularity—the Universe with torsion undergoes a bounce . We solve the dynamical equations (a) classically (without particle production); (b) including the production of fermions in a fixed background in the Hartree-Fock approximation and (c) including the quantum backreaction of fermions onto the background space-time. In the first and last cases the Universe undergoes a bounce. The production of fermions due to the coupling to a contracting homogeneous background speeds up the bounce, implying that the quantum contributions from fermions is negative, presumably because fermion production contributes negatively to the energy-momentum tensor. When compared with former works on the subject, our treatment is fully microscopic (namely, we treat fermions by solving the corresponding Dirac equations) and quantum (in the sense that we include fermionic loop contributions).« less

Cosmological singularities and bounce in Cartan-Einstein theory

NASA Astrophysics Data System (ADS)

Lucat, Stefano; Prokopec, Tomislav

2017-10-01

We consider a generalized Einstein-Cartan theory, in which we add the unique covariant dimension four operators to general relativity that couples fermionic spin current to the torsion tensor (with an arbitrary strength). Since torsion is local and non-dynamical, when integrated out it yields an effective four-fermion interaction of the gravitational strength. We show how to renormalize the theory, in the one-loop perturbative expansion in generally curved space-times, obtaining the first order correction to the 2PI effective action in Schwinger-Keldysh (in-in) formalism. We then apply the renormalized theory to study the dynamics of a collapsing universe that begins in a thermal state and find that—instead of a big crunch singularity—the Universe with torsion undergoes a bounce. We solve the dynamical equations (a) classically (without particle production); (b) including the production of fermions in a fixed background in the Hartree-Fock approximation and (c) including the quantum backreaction of fermions onto the background space-time. In the first and last cases the Universe undergoes a bounce. The production of fermions due to the coupling to a contracting homogeneous background speeds up the bounce, implying that the quantum contributions from fermions is negative, presumably because fermion production contributes negatively to the energy-momentum tensor. When compared with former works on the subject, our treatment is fully microscopic (namely, we treat fermions by solving the corresponding Dirac equations) and quantum (in the sense that we include fermionic loop contributions).

Design and static structural analysis of a race car chassis for Formula Society of Automotive Engineers (FSAE) event

NASA Astrophysics Data System (ADS)

Mohamad, M. L.; Rahman, M. T. A.; Khan, S. F.; Basha, M. H.; Adom, A. H.; Hashim, M. S. M.

2017-10-01

The main purpose of this study is to make improvement for the UniMAP Automotive Racing Team car chassis which has several problems associated with the chassis must be fixed and some changes are needed to be made in order to perform well. This study involves the process of designing three chassis that are created based on the rules stated by FSAE rules book (2017/2018). The three chassis will undergo analysis test that consists of five tests which are main roll hoop test, front roll hoop test, static shear, side impact, static torsional loading and finally one of them will be selected as the best design in term of Von Mises Stress and torsional displacement. From the results obtained, the new selected chassis design which also declared as the new improved design poses the weight of 27.66 kg which was decreased by 16.7% from the existing chassis (32.77 kg). The torsional rigidity of the improved chassis increased by 37.74%.

Role of passive deformation on propulsion through a lumped torsional flexibility model

NASA Astrophysics Data System (ADS)

Arora, Nipun; Gupta, Amit

2016-11-01

Scientists and biologists have been affianced in a deeper examination of insect flight to develop an improved understanding of the role of flexibility on aerodynamic performance. Here, we mimic a flapping wing through a fluid-structure interaction framework based upon a lumped torsional flexibility model. The developed fluid and structural solvers together determine the aerodynamic forces and wing deformation, respectively. An analytical solution to the simplified single-spring structural dynamics equation is established to substantiate simulations. It is revealed that the dynamics of structural deformation is governed by the balance between inertia, stiffness and aerodynamics, where the former two oscillate at the plunging frequency and the latter oscillates at twice the plunging frequency. We demonstrate that an induced phase difference between plunging and passive pitching is responsible for a higher thrust coefficient. This phase difference is also shown to be dependent on aerodynamics to inertia and natural to plunging frequency ratios. For inertia dominated flows, pitching and plunging always remain in phase. As the aerodynamics dominates, a large phase difference is induced which is accountable for a large passive deformation and higher thrust. Authors acknowledge the financial support received from the Aeronautics Research and Development Board (ARDB) under SIGMA Project No. 1705 and thank the IIT Delhi HPC facility for computational resources.

High resolution spectroscopy of 1,2-difluoroethane in a molecular beam: A case study of vibrational mode-coupling

NASA Astrophysics Data System (ADS)

Mork, Steven W.; Miller, C. Cameron; Philips, Laura A.

1992-09-01

The high resolution infrared spectrum of 1,2-difluoroethane (DFE) in a molecular beam has been obtained over the 2978-2996 cm-1 spectral region. This region corresponds to the symmetric combination of asymmetric C-H stretches in DFE. Observed rotational fine structure indicates that this C-H stretch is undergoing vibrational mode coupling to a single dark mode. The dark mode is split by approximately 19 cm-1 due to tunneling between the two identical gauche conformers. The mechanism of the coupling is largely anharmonic with a minor component of B/C plane Coriolis coupling. Effects of centrifugal distortion along the molecular A-axis are also observed. Analysis of the fine structure identifies the dark state as being composed of C-C torsion, CCF bend, and CH2 rock. Coupling between the C-H stretches and the C-C torsion is of particular interest because DFE has been observed to undergo vibrationally induced isomerization from the gauche to trans conformer upon excitation of the C-H stretch.

Steady Flow Generated by a Core Oscillating in a Rotating Spherical Cavity

NASA Astrophysics Data System (ADS)

Kozlov, V. G.; Subbotin, S. V.

2018-01-01

Steady flow generated by oscillations of an inner solid core in a fluid-filled rotating spherical cavity is experimentally studied. The core with density less than the fluid density is located near the center of the cavity and is acted upon by a centrifugal force. The gravity field directed perpendicular to the rotation axis leads to a stationary displacement of the core from the rotation axis. As a result, in the frame of reference attached to the cavity, the core performs circular oscillation with frequency equal to the rotation frequency, and its center moves along a circular trajectory in the equatorial plane around the center of the cavity. For the differential rotation of the core to be absent, one of the poles of the core is connected to the nearest pole of the cavity with a torsionally elastic, flexible fishing line. It is found that the oscillation of the core generates axisymmetric azimuthal fluid flow in the cavity which has the form of nested liquid columns rotating with different angular velocities. Comparison with the case of a free oscillating core which performs mean differential rotation suggests the existence of two mechanisms of flow generation (due to the differential rotation of the core in the Ekman layer and due to the oscillation of the core in the oscillating boundary layers).

Influence of cross-sectional design and dimension on mechanical behavior of nickel-titanium instruments under torsion and bending: a numerical analysis.

PubMed

Zhang, En-Wei; Cheung, Gary S P; Zheng, Yu-Feng

2010-08-01

The aim of this study was to examine the influence of the cross-sectional configuration and dimensions (size and taper) on the torsional and bending behavior of nickel-titanium rotary instruments, taking into account the nonlinear mechanical properties of material. Ten cross-sectional configurations, square, triangular, U-type, S-type (large and small), convex-triangle, and 4 proprietary ones (Mani NRT and RT2, Quantec, and Mtwo), were analyzed under torsion or bending by using a 3-dimensional finite element method. The von Mises stresses were correlated with the critical values for various phases of the nickel-titanium material. Different loading conditions led to unequal patterns of stress distribution. Increasing the applied torque or bending angle resulted in a rise in the corresponding stresses in the instrument. Favorable stress distribution without dangerous stress concentration was observed if the material was undergoing superelastic transformation at that applied load. The ultimate strength of the material was not exceeded when the instrument was bent up to a 50-degree curvature. On the other hand, when a torsional moment of greater than 1.0 N*mm was applied, the maximum stresses developed in some designs would exceed the ultimate strength of the material. Little variation in the von Mises stresses was observed for instruments of different nominal sizes and tapers on bending to similar extent. The cross-sectional design has a greater impact than taper or size of the instrument on the stresses developed in the instrument under either torsion or bending. Certain cross-sectional configurations are prone to fracture by excess torsional stresses. Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Unsteady aerodynamics of an oscillating cascade in a compressible flow field

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; Boldman, Donald R.; Fleeter, Sanford

1987-01-01

Fundamental experiments were performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate and quantify the unsteady aerodynamics of a cascade of biconvex airfoils executing torsion-mode oscillations at realistic reduced frequencies. Flush-mounted, high-response miniature pressure transducers were used to measure the unsteady airfoil surface pressures. The pressures were measured for three interblade phase angles at two inlet Mach numbers, 0.65 and 0.80, and two incidence angles, 0 and 7 deg. The time-variant pressures were analyzed by means of discrete Fourier transform techniques, and these unique data were then compared with predictions from a linearized unsteady cascade model. The experimental results indicate that the interblade phase angle had a major effect on the chordwise distributions of the airfoil surface unsteady pressure, and that reduced frequency, incidence angle, and Mach number had a somewhat less significant effect.

Dynamic torsional misalignment of eyes during laser in-situ keratomileusis.

PubMed

Shajari, Mehdi; Bühren, Jens; Kohnen, Thomas

2016-05-01

To determine the amount and characteristics of dynamic torsional misalignment of eyes during excimer ablation in laser in-situ keratomileusis (LASIK). Retrospective trial for evaluation of dynamic intraoperative torsional misalignment of 179 eyes that underwent LASIK for correction of myopia and/or astigmatism. Patients were treated with the Keracor 217z excimer laser implementing 25 Hz dynamic eye tracker ACE 100 (both Technolas Perfect Vision, Munich, Germany). From dynamic torsional misalignments, temporal power spectra were obtained by Fourier analysis up to a frequency of 12.5 Hz and an amplitude of ±15° from initial torsional status (limited by the tracking system). The f90, f95, and f99 criteria were defined as the frequency below which 90 %, 95 %, and 99 % of misalignments occur. A Wilcoxon rank sum test was performed to detect differences of f90, f95, and f99 in groups' gender, age, and eye (if both eyes underwent surgery at same day). Multiple regression analysis (MRA) was performed to evaluate possible preoperative predictors of f90, f95, and f99. Fourier analysis showed a dominance of high-frequency, low-power dynamic torsional misalignment. Mean f95 threshold of rotational movements was 4.89±2.12 Hz (median 4.54, ranging from 0.44 to 9.23 Hz). Wilcoxon rank sum test showed no differences in f90, f95, and f99 between groups' gender, age, and eye. MRA revealed age, gender, and optical zone as preoperative predictors on intraoperative f90, f95, and f99. Dynamic intraoperative torsional misalignments of eyes undergoing LASIK are dominated by low-frequency (slow), high-power (large) movements, with 95 % being slower than 4.89Hz regarding the spectrum analyzed (0-12.5Hz, ±15°). Movements can be predicted preoperatively by eye treated, patients' gender, and age in pre-LASIK diagnostics.

Experimental Testicular Torsion in a Rat Model: Effects of Treatment with Pausinystalia macroceras on Testis Functions

PubMed Central

Ikebuaso, Afamefuna Donatus; Yama, Oshiozokhai Eboetse; Duru, F.I.O.; Oyebadejo, S.A.

2012-01-01

Background Testicular torsion is a medical emergency with catastrophic sequelae that deserves the same treatment considerations and concerted efforts in research as any other complicated medical condition. The aim of this study was to investigate the effect of Pausinystalia macroceras (PM) bark extract on sperm quality and serum testosterone levels in testicular torsion in a rat model. Methods Sixty–five (65) mature male Wistar rats apportioned randomly into four experimental groups of A to C; were further divided into four subgroups according to duration of torsion. Group D were the normal regular rats. Each group/subgroup comprised five rats. Testis maintained in the torted position (T) for 1, 2, 3 and 4 hr in Group A (subgroups: AT1+PM, AT2+PM, AT3+PM, and AT4+PM). Group B (sub- groups: B1+PM, B2+PM, B3+PM, B4+PM) were sham–operated animals, which did not undergo torsion and served as the sham control group. Group C subgroups: CT1, CT2, CT3 and CT4 were torted as in A. All animals (except groups C and D) were treated by PM extract (0.1 g/kg b.w. per day) for 56 days. Group D rats were fed distilled water. Serum testosterone concentrations and sperm quality (motility and count) were measured. Analyses of variance with Scheffe's post-hoc test were carried out on the data. Results PM extract had a positive effect (significant; p < 0.5) on the sperm count and motility in rats with testicular torsion compared to those not receiving the extract. There was also an increase in serum testosterone levels in the former groups. Conclusion Treatment of rats following testicular torsion result to the enhancement of sperm production in comparison with untreated rats. PMID:23926549

Use of the Thin-Walled Torsion Specimen

DTIC Science & Technology

1992-08-01

similar to the 316 stainless steel but the shear, stress shows a region of lower 16 strain hardening during the reversal. This behavor has been observed...oscillations and match the axial stress seen in experiment. Among these proposals are: the use of the Green -Naghdi stress rate,22 and the formulation of...other references on the topic. In this section, calculations using Jaumann, Green -Naghdi, and plastic spin motivated stress rates ap- plied to

Advances in Time-Distance Helioseismology

NASA Technical Reports Server (NTRS)

Duvall, Thomas L., Jr.; Beck, John G.; Gizon, Laurent; Kosovichev, Alexander F.; Oegerle, William (Technical Monitor)

2002-01-01

Time-distance helioseismology is a way to measure travel times between surface locations for waves traversing the solar interior. Coupling the travel with an extensive modeling effort has proven to be a powerful tool for measuring flows and other wave speed inhomogeneities in the solar interior. Problems receiving current attention include studying the time variation of the meridional circulation and torsional oscillation and active region emergence and evolution, current results on these topics will be presented.

NASA's Preparations for ESA's L3 Gravitational Wave Mission

NASA Technical Reports Server (NTRS)

Stebbins, Robin

2016-01-01

Telescope Subsystem - Jeff Livas (GSFC): Demonstrate pathlength stability, straylight and manufacturability. Phase Measurement System - Bill Klipstein (JPL): Key measurement functions demonstrated. Incorporate full flight functionality. Laser Subsystem - Jordan Camp (GSFC): ECL master oscillator, phase noise of fiber power amplifier, demonstrate end-to-end performance in integrated system, lifetime. Micronewton Thrusters - John Ziemer (JPL): Propellant storage and distribution, system robustness, manufacturing yield, lifetime. Arm-locking Demonstration - Kirk McKenzie (JPL): Studying a demonstration of laser frequency stabilization with GRACE Follow-On. Torsion Pendulum - John Conklin (UF): Develop U.S. capability with GRS and torsion pendulum test bed. Multi-Axis Heterodyne Interferometry - Ira Thorpe (GSFC): Investigate test mass/optical bench interface. UV LEDs - John Conklin+ (UF): Flight qualify UV LEDs to replace mercury lamps in discharging system. Optical Bench - Guido Mueller (UF): Investigate alternate designs and fabrication processes to ease manufacturability. LISA researchers at JPL are leading the Laser Ranging Interferometer instrument on the GRACE Follow-On mission.

Hydrodynamic Force on a Cylinder Oscillating at Low Frequency

NASA Technical Reports Server (NTRS)

Berg, Robert F.; Yao, Minwu; Panzarella, Charles H.

2007-01-01

The hydrodynamic force on a cylinder oscillating transversely to its axis is a nonlinear function of the displacement amplitude x0. We report measurements and numerical calculations of the force at frequencies low enough that delta > R, where delta is the viscous penetration length and R is the cylinder radius. For small amplitudes, the numerically calculated Fourier transform of the force per unit length, F(sub small), agrees with Stokes' analytical calculation. For larger amplitudes, the force per unit length found by both calculation and measurement is F = F(sub small)C (x(sub 0)/delta,R/delta). The complex function C depends only weakly on R/delta, indicating that x0/delta is more appropriate as a scaling variable than the Keulegan-Carpenter number KC = pi*x(sub 0)/R. The measurements used a torsion oscillator driven at frequencies from 1 to 12 Hz while immersed in dense xenon. The oscillator comprised cylinders with an effective radius of R = 13.4 micron and oscillation amplitudes as large as x(sub 0)/delta = 4 (corresponding to KC as large as 71). The calculations used similar conditions except that the amplitudes were as large as x0/delta = 28.

Geomagnetic field and length-of-day fluctuations at decadal and subdecadal time scales. A plea for looking beyond the atmosphere for partners in Earth's rotation

NASA Astrophysics Data System (ADS)

Demetrescu, C.; Dobrica, V.; Stefan, C.

2017-12-01

A rich scientific literature is linking length-of-day (LOD) fluctuations to geomagnetic field and flow oscillations in the fluid outer core. We demostrate that the temporal evolution of the geomagnetic field shows the existence of several oscillations at decadal, inter-decadal, and sub-centennial time scales that superimpose on a so-called inter-centennial constituent. We show that while the subcentennial oscillations of the geomagnetic field, produced by torsional oscillations in the core, could be linked to oscillations of LOD at a similar time scale, the oscillations at decadal and sub-decadal time scales, of external origin, can be found in LOD too. We discuss these issues from the perspective of long time-span main field models (gufm1 - Jackson et al., 2000; COV-OBS - Gillet et al., 2013) that are used to retrieve time series of geomagnetic elements in a 2.5x2.5° network. The decadal and sub-decadal constituents of the time series of annual values in LOD and geomagnetic field were separated in the cyclic component of a Hodrick-Prescott filtering applied to data, and shown to highly correlate to variations of external sources such as the magnetospheric ring current.

Large Deformation of an Elastic Rod with Structural Anisotropy Subjected to Fluid Flow

NASA Astrophysics Data System (ADS)

Hassani, Masoud; Mureithi, Njuki; Gosselin, Frederick

2015-11-01

In the present work, we seek to understand the fundamental mechanisms of three-dimensional reconfiguration of plants by studying the large deformation of a flexible rod in fluid flow. Flexible rods made of Polyurethane foam and reinforced with Nylon fibers are tested in a wind tunnel. The rods have bending-torsion coupling which induces a torsional deformation during asymmetric bending. A mathematical model is also developed by coupling the Kirchhoff rod theory with a semi-empirical drag formulation. Different alignments of the material frame with respect to the flow direction and a range of structural properties are considered to study their effect on the deformation of the flexible rod and its drag scaling. Results show that twisting causes the flexible rods to reorient and bend with the minimum bending rigidity. It is also found that the drag scaling of the rod in the large deformation regime is not affected by torsion. Finally, using a proper set of dimensionless numbers, the state of a bending and twisting rod is characterized as a beam undergoing a pure bending deformation.

Calibration of the Oscillating Screen Viscometer

NASA Technical Reports Server (NTRS)

Berg, Robert F.; Moldover, Michael R.

1993-01-01

We have devised a calibration procedure for the oscillating screen viscometer which can provide the accuracy needed for the flight measurement of viscosity near the liquid-vapor critical point of xenon. The procedure, which makes use of the viscometer's wide bandwidth and hydrodynamic similarity, allows the viscometer to be self-calibrating. To demonstrate the validity of this procedure we measured the oscillator's transfer function under a wide variety of conditions. We obtained data using CO2 at temperatures spanning a temperature range of 35 K and densities varying by a factor of 165, thereby encountering viscosity variations as great as 50%. In contrast the flight experiment will be performed over a temperature range of 29 K and at only a single density, and the viscosity is expected to change by less than 40%. The measurements show that, after excluding data above 10 Hz (where frequency-dependent corrections are poorly modeled) and making a plausible adjustment to the viscosity value used at high density, the viscometer's behavior is fully consistent with the use of hydrodynamic similarity for calibration. Achieving this agreement required understanding a 1% anelastic effect present in the oscillator's torsion fiber.

Vorticity Transport on a Flexible Wing in Stall Flutter

NASA Astrophysics Data System (ADS)

Akkala, James; Buchholz, James; Farnsworth, John; McLaughlin, Thomas

2014-11-01

The circulation budget within dynamic stall vortices was investigated on a flexible NACA 0018 wing model of aspect ratio 6 undergoing stall flutter. The wing had an initial angle of attack of 6 degrees, Reynolds number of 1 . 5 ×105 and large-amplitude, primarily torsional, limit cycle oscillations were observed at a reduced frequency of k = πfc / U = 0 . 1 . Phase-locked stereo PIV measurements were obtained at multiple chordwise planes around the 62.5% and 75% spanwise locations to characterize the flow field within thin volumetric regions over the suction surface. Transient surface pressure measurements were used to estimate boundary vorticity flux. Recent analyses on plunging and rotating wings indicates that the magnitude of the pressure-gradient-driven boundary flux of secondary vorticity is a significant fraction of the magnitude of the convective flux from the separated leading-edge shear layer, suggesting that the secondary vorticity plays a significant role in regulating the strength of the primary vortex. This phenomenon is examined in the present case, and the physical mechanisms governing the growth and evolution of the dynamic stall vortices are explored. This work was supported by the Air Force Office of Scientific Research through the Flow Interactions and Control Program monitored by Dr. Douglas Smith, and through the 2014 AFOSR/ASEE Summer Faculty Fellowship Program (JA and JB).

Melting of the Abrikosov flux lattice in anisotropic superconductors

NASA Technical Reports Server (NTRS)

Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.

1992-01-01

It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.

Investigation of Periodic Pitching through the Static Stall Angle of Attack.

DTIC Science & Technology

1987-03-01

been completed to characterize and predict the dynamic stall process. In 1968 Ham (Ref 11) completed a study to explain the torsional oscillation of...peak values of l.:t and moment could be predicted accurately, but the model did not predict when the peaks would occur. Another problem with the...model was that it required input from experimental results to tell when leading edge vortex separation occurred. The prediction of when vortex shedding

Actin-based motility propelled by molecular motors

NASA Astrophysics Data System (ADS)

Upadyayula, Sai Pramod; Rangarajan, Murali

2012-09-01

Actin-based motility of Listeria monocytogenes propelled by filament end-tracking molecular motors has been simulated. Such systems may act as potential nanoscale actuators and shuttles useful in sorting and sensing biomolecules. Filaments are modeled as three-dimensional elastic springs distributed on one end of the capsule and persistently attached to the motile bacterial surface through an end-tracking motor complex. Filament distribution is random, and monomer concentration decreases linearly as a function of position on the bacterial surface. Filament growth rate increases with monomer concentration but decreases with the extent of compression. The growing filaments exert push-pull forces on the bacterial surface. In addition to forces, torques arise due to two factors—distribution of motors on the bacterial surface, and coupling of torsion upon growth due to the right-handed helicity of F-actin—causing the motile object to undergo simultaneous translation and rotation. The trajectory of the bacterium is simulated by performing a force and torque balance on the bacterium. All simulations use a fixed value of torsion. Simulations show strong alignment of the filaments and the long axis of the bacterium along the direction of motion. In the absence of torsion, the bacterial surface essentially moves along the direction of the long axis. When a small amount of the torsion is applied to the bacterial surface, the bacterium is seen to move in right-handed helical trajectories, consistent with experimental observations.

[Axial torsion and gangrene of Meckel's diverticulum: case report].

PubMed

2015-01-01

Meckel's diverticulum (MD) is the most prevalent congenital anomaly of small intestine. It develops due to the incomplete obliteration of omphalomesenterict duct which normally undergoes obliteration during the seventh week of gestation. In the majority of cases MD is asymptomatic but it may cause various complications, such as bleeding, intestinal obstruction and inflammation. Cases of umbilical sinuses, fistulas and neoplasms related with MD have been reported, but extremely rare gangrene due to its axial torsion, especially in children, as is the case of our patients. An 11-year-old boy admitted to hospital due to 24 hours epigastric pain, vomiting and malaise. After a complete physical examination, and appropriate pre-surgical laboratory and radiographic tests, surgical exploration was performed with a midline abdominal incision. On 60th cm proximal to the ileocecal valve we found a long and in a narrow based ganrenous MD with axial torsion and fibrotic cord extending from the tip of MD to the ileal mesentery. Surrounding ileum had normal appearance. A demarcation and subsequent resection of MD and the surrounding ileum was performed with end-to-end ileal anastomosis. Postoperative recovery was successful and the patient was discharged after six days. Axial torsion of MD is presented with non-specific abdominal symptoms and difficult preoperative diagnosis. The choice of diagnosis and therapy is surgical exploration and resection of MD.

Emergent Oscillations in Networks of Stochastic Spiking Neurons

PubMed Central

van Drongelen, Wim; Cowan, Jack D.

2011-01-01

Networks of neurons produce diverse patterns of oscillations, arising from the network's global properties, the propensity of individual neurons to oscillate, or a mixture of the two. Here we describe noisy limit cycles and quasi-cycles, two related mechanisms underlying emergent oscillations in neuronal networks whose individual components, stochastic spiking neurons, do not themselves oscillate. Both mechanisms are shown to produce gamma band oscillations at the population level while individual neurons fire at a rate much lower than the population frequency. Spike trains in a network undergoing noisy limit cycles display a preferred period which is not found in the case of quasi-cycles, due to the even faster decay of phase information in quasi-cycles. These oscillations persist in sparsely connected networks, and variation of the network's connectivity results in variation of the oscillation frequency. A network of such neurons behaves as a stochastic perturbation of the deterministic Wilson-Cowan equations, and the network undergoes noisy limit cycles or quasi-cycles depending on whether these have limit cycles or a weakly stable focus. These mechanisms provide a new perspective on the emergence of rhythmic firing in neural networks, showing the coexistence of population-level oscillations with very irregular individual spike trains in a simple and general framework. PMID:21573105

Seismic sources

DOEpatents

Green, M.A.; Cook, N.G.W.; McEvilly, T.V.; Majer, E.L.; Witherspoon, P.A.

1987-04-20

Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Longitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements for more than about one minute. 9 figs.

Comparison of Electrostatic Fins with Piezoelectric Impact Hammer Techniques to Extend Impulse Calibration Range of a Torsional Thrust Stand (Preprint)

DTIC Science & Technology

2011-03-23

prac- tical max impulse to 1mNs. The newly developed Piezo - electric Impact Hammer (PIH) calibration system over- comes geometric limits of ESC...the fins to behave as part of an LRC circuit which results in voltage oscillations. By adding a resistor in series between the pulse generator and...series resistor as well as the effects of no loading on the pulse generator. III. PIEZOELECTRIC IMPACT HAMMER SYSTEM The second calibration method tested

Influence of tungsten fiber’s slow drift on the measurement of G with angular acceleration method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Jie; Wu, Wei-Huang; Zhan, Wen-Ze

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 ofmore » 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.« less

Influence of tungsten fiber's slow drift on the measurement of G with angular acceleration method.

PubMed

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.

Influence of tungsten fiber's slow drift on the measurement of G with angular acceleration method

NASA Astrophysics Data System (ADS)

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.

Predator-prey model for the self-organization of stochastic oscillators in dual populations

NASA Astrophysics Data System (ADS)

Moradi, Sara; Anderson, Johan; Gürcan, Ozgur D.

A predator-prey model of dual populations with stochastic oscillators is presented. A linear cross-coupling between the two populations is introduced that follows the coupling between the motions of a Wilberforce pendulum in two dimensions: one in the longitudinal and the other in torsional plain. Within each population a Kuramoto type competition between the phases is assumed. Thus, the synchronization state of the whole system is controlled by these two types of competitions. The results of the numerical simulations show that by adding the linear cross-coupling interactions predator-prey oscillations between the two populations appear which results in self-regulation of the system by a transfer of synchrony between the two populations. The model represents several important features of the dynamical interplay between the drift wave and zonal flow turbulence in magnetically confined plasmas, and a novel interpretation of the coupled dynamics of drift wave-zonal flow turbulence using synchronization of stochastic oscillator is discussed. Sara Moradi has benefited from a mobility grant funded by the Belgian Federal Science Policy Office and the MSCA of the European Commission (FP7-PEOPLE-COFUND-2008 nº 246540).

Propulsive performance of pitching foils with variable chordwise flexibility

NASA Astrophysics Data System (ADS)

Zeyghami, Samane; Moored, Keith; Lehigh University Team

2017-11-01

Many swimming and flying animals propel themselves efficiently through water by oscillating flexible fins. These fins are not homogeneously flexible, but instead their flexural stiffness varies along their chord and span. Here we seek to evaluate the effect stiffness profile on the propulsive performance of pitching foils. Stiffness profile characterizes the variation in the local fin stiffness along the chord. To this aim, we developed a low order model of a functionally-graded material where the chordwise flexibility is modeled by two torsional springs along the chordline and the stiffness and location of the springs can be varied arbitrarily. The torsional spring structural model is then strongly coupled to a boundary element fluid model to simulate the fluid-structure interactions. Keeping the leading edge kinematics unchanged, we alter the stiffness profile of the foil and allow it to swim freely in response to the resulting hydrodynamic forces. We then detail the dependency of the hydrodynamic performance and the wake structure to the variations in the local structural properties of the foil.

Responses to rotating linear acceleration vectors considered in relation to a model of the otolith organs. [human oculomotor response to transverse acceleration stress

NASA Technical Reports Server (NTRS)

Benson, A. J.; Barnes, G. R.

1973-01-01

Human subjects were exposed to a linear acceleration vector that rotated in the transverse plane of the skull without angular counterrotation. Lateral eye movements showed a sinusoidal change in slow phase velocity and an asymmetry or bias in the same direction as vector rotation. A model is developed that attributes the oculomotor response to otolithic mechanisms. It is suggested that the bias component is the manifestation of torsion of the statoconial plaque relative to the base of the utricular macula and that the sinusoidal component represents the translational oscillation of the statoconia. The model subsumes a hypothetical neural mechanism which allows x- and y-axis accelerations to be resolved. Derivation of equations of motion for the statoconial plaque in torsion and translation, which take into account forces acting in shear and normal to the macula, yield estimates of bias and sinusoidal components that are in qualitative agreement with the diverse experimental findings.

High frequency variations of the main magnetic field: convergence of observations and theory (Petrus Peregrinus Medal Lecture)

NASA Astrophysics Data System (ADS)

Jault, Dominique

2013-04-01

Understanding the main magnetic field variations has been hindered by the discrepancy between the periods (from months to years) of the simplest linear wave phenomena and the relatively long time intervals (10 to 100 years) over which magnetic field changes can be confidently monitored. A theoretical description of short-period waves within the Earth's fluid core is at hand. Quasi-geostrophic inertial waves (akin to Rossby waves in the atmosphere) are slightly modified in the presence of magnetic fields and torsional oscillations consist of differential motion between coaxial rigid cylindrical annuli. Torsional oscillations are sensitive to the whole magnetic field that they shear in the course of their propagation. From their modelling, we have thus gained an estimate for the magnetic field strength in the core interior. There is now ongoing work to extend the theoretical framework to longer times. Furthermore, data collected from the Swarm constellation of three satellites to be launched this year by ESA will permit to better separate the internal and external magnetic signals. We may thus dream to detect quasi-geostrophic inertial waves. As the spectral ranges of theoretical models and observations begin to overlap, we can now go beyond the understanding of the magnetic field variations as the juxtaposition of partial models, arranged as a set of nested Matryoshka dolls. This talk will give illustrations for this statement, among which the question of induction in the lower mantle.

The Adiabatic Invariant of the n-Degree-of-Freedom Harmonic Oscillator

ERIC Educational Resources Information Center

Devaud, M.; Leroy, V.; Bacri, J.-C.; Hocquet, T.

2008-01-01

In this graduate-level theoretical paper, we propose a general derivation of the adiabatic invariant of the n-degree-of-freedom harmonic oscillator, available whichever the physical nature of the oscillator and of the parametrical excitation it undergoes. This derivation is founded on the use of the classical Glauber variables and ends up with…

Femtosecond coherent nuclear dynamics of excited tetraphenylethylene: Ultrafast transient absorption and ultrafast Raman loss spectroscopic studies

NASA Astrophysics Data System (ADS)

Kayal, Surajit; Roy, Khokan; Umapathy, Siva

2018-01-01

Ultrafast torsional dynamics plays an important role in the photoinduced excited state dynamics. Tetraphenylethylene (TPE), a model system for the molecular motor, executes interesting torsional dynamics upon photoexcitation. The photoreaction of TPE involves ultrafast internal conversion via a nearly planar intermediate state (relaxed state) that further leads to a twisted zwitterionic state. Here, we report the photoinduced structural dynamics of excited TPE during the course of photoisomerization in the condensed phase by ultrafast Raman loss (URLS) and femtosecond transient absorption (TA) spectroscopy. TA measurements on the S1 state reveal step-wise population relaxation from the Franck-Condon (FC) state → relaxed state → twisted state, while the URLS study provides insights on the vibrational dynamics during the course of the reaction. The TA spectral dynamics and vibrational Raman amplitudes within 1 ps reveal vibrational wave packet propagating from the FC state to the relaxed state. Fourier transformation of this oscillation leads to a ˜130 cm-1 low-frequency phenyl torsional mode. Two vibrational marker bands, Cet=Cet stretching (˜1512 cm-1) and Cph=Cph stretching (˜1584 cm-1) modes, appear immediately after photoexcitation in the URLS spectra. The initial red-shift of the Cph=Cph stretching mode with a time constant of ˜400 fs (in butyronitrile) is assigned to the rate of planarization of excited TPE. In addition, the Cet=Cet stretching mode shows initial blue-shift within 1 ps followed by frequency red-shift, suggesting that on the sub-picosecond time scale, structural relaxation is dominated by phenyl torsion rather than the central Cet=Cet twist. Furthermore, the effect of the solvent on the structural dynamics is discussed in the context of ultrafast nuclear dynamics and solute-solvent coupling.

Femtosecond coherent nuclear dynamics of excited tetraphenylethylene: Ultrafast transient absorption and ultrafast Raman loss spectroscopic studies.

PubMed

Kayal, Surajit; Roy, Khokan; Umapathy, Siva

2018-01-14

Ultrafast torsional dynamics plays an important role in the photoinduced excited state dynamics. Tetraphenylethylene (TPE), a model system for the molecular motor, executes interesting torsional dynamics upon photoexcitation. The photoreaction of TPE involves ultrafast internal conversion via a nearly planar intermediate state (relaxed state) that further leads to a twisted zwitterionic state. Here, we report the photoinduced structural dynamics of excited TPE during the course of photoisomerization in the condensed phase by ultrafast Raman loss (URLS) and femtosecond transient absorption (TA) spectroscopy. TA measurements on the S 1 state reveal step-wise population relaxation from the Franck-Condon (FC) state → relaxed state → twisted state, while the URLS study provides insights on the vibrational dynamics during the course of the reaction. The TA spectral dynamics and vibrational Raman amplitudes within 1 ps reveal vibrational wave packet propagating from the FC state to the relaxed state. Fourier transformation of this oscillation leads to a ∼130 cm -1 low-frequency phenyl torsional mode. Two vibrational marker bands, C et =C et stretching (∼1512 cm -1 ) and C ph =C ph stretching (∼1584 cm -1 ) modes, appear immediately after photoexcitation in the URLS spectra. The initial red-shift of the C ph =C ph stretching mode with a time constant of ∼400 fs (in butyronitrile) is assigned to the rate of planarization of excited TPE. In addition, the C et =C et stretching mode shows initial blue-shift within 1 ps followed by frequency red-shift, suggesting that on the sub-picosecond time scale, structural relaxation is dominated by phenyl torsion rather than the central C et =C et twist. Furthermore, the effect of the solvent on the structural dynamics is discussed in the context of ultrafast nuclear dynamics and solute-solvent coupling.

Dynamics of axial torsional libration under the mantle-inner core gravitational interaction

NASA Astrophysics Data System (ADS)

Chao, B. F.

2017-01-01

The aims of this paper are (i) formulating the dynamics of the mantle-inner core gravitational (MICG) interaction in terms of the spherical-harmonic multipoles of mass density. The modeled MICG system is composed of two concentric rigid bodies (mantle and inner core) of near-spherical but otherwise heterogeneous configuration, with a fluid outer core in between playing a passive role. We derive the general equation of motion for the vector rotation but only focus on the polar component that describes the MICG axial torsional libration. The torsion constant and hence the square of the natural frequency of the libration is proportional to the product of the equatorial ellipticities of the mantle and inner-core geoid embodied in their multipoles (of two different types) of degree 2 and order 2 (such as the Large Low-Shear-Velocity Provinces above the core-mantle boundary) and (ii) studying the geophysical implications upon equating the said MICG libration to the steady 6 year oscillation that are observed in the Earth's spin rate or the length-of-day variation (ΔLOD). In particular, the MICG torsion constant is found to be Γ>˜z = CIC σz2 ≈ 6.5 × 1019 N m, while the inner core's (BIC - AIC) ≈ 1.08 × 1031 kg m2 gives the inner core triaxiality (BIC - AIC)/CIC ≈ 1.8 × 10-4, about 8 times the whole-Earth value. It is also asserted that the required inner-core ellipticity amounts to no more than 140 m in geoid height, much smaller than the sensitivity required for the seismic wave travel time to resolve the variation of the inner core.

Accelerated and Airy-Bloch oscillations

NASA Astrophysics Data System (ADS)

Longhi, Stefano

2016-09-01

A quantum particle subjected to a constant force undergoes an accelerated motion following a parabolic path, which differs from the classical motion just because of wave packet spreading (quantum diffusion). However, when a periodic potential is added (such as in a crystal) the particle undergoes Bragg scattering and an oscillatory (rather than accelerated) motion is found, corresponding to the famous Bloch oscillations (BOs). Here, we introduce an exactly-solvable quantum Hamiltonian model, corresponding to a generalized Wannier-Stark Hamiltonian Ĥ, in which a quantum particle shows an intermediate dynamical behavior, namely an oscillatory motion superimposed to an accelerated one. Such a novel dynamical behavior is referred to as accelerated BOs. Analytical expressions of the spectrum, improper eigenfunctions and propagator of the generalized Wannier-Stark Hamiltonian Ĥ are derived. Finally, it is shown that acceleration and quantum diffusion in the generalized Wannier-Stark Hamiltonian are prevented for Airy wave packets, which undergo a periodic breathing dynamics that can be referred to as Airy-Bloch oscillations.

Recent development of the passive vibration control method

NASA Astrophysics Data System (ADS)

Ishida, Yukio

2012-05-01

This paper introduces new passive vibration suppression methods developed recently in our laboratory. First, two methods used to suppress steady-state resonances are explained. One is the improvement of the efficiency of a ball balancer. A simple method to eliminate the influence of friction of balls and to improve its efficiency is introduced. The other is an effective method that utilizes the discontinuous spring characteristics. Secondly, a method to eliminate unstable ranges in rotor systems is explained. Unstable ranges in an asymmetrical shaft, and in a hollow rotor partially filled with liquid, are eliminated by the discontinuous spring characteristics. Thirdly, a method to suppress self-excited oscillations is explained. Self-excited oscillations due to internal damping and rubbing are discussed. Finally, the methods of using a pendulum or roller type absorbers to suppress torsional vibrations are explained.

Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. I. Frequency-specific recovery of horizontal VOR after inactivation of the lateral semicircular canals

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Hess, B. J.; Arai, Y.; Suzuki, J.

1996-01-01

1. The adaptive plasticity of the vestibuloocular reflex (VOR) following a selective lesion of the peripheral vestibular organs was investigated in rhesus monkeys whose lateral semicircular canals were inactivated by plugging of the canal lumen in both ears. Gain and phase of horizontal, vertical, and torsional slow-phase eye velocity were determined from three-dimensional eye movement recordings obtained acutely after the plugging operation, as well as in regular intervals up to 10 mo later. 2. Acutely after plugging, horizontal VOR was minimal during yaw rotation with gains of < 0.1 at all frequencies. Horizontal VOR gain gradually increased over time, reaching gains of 0.4-0.5 for yaw oscillations at 1.1 Hz approximately 5 mo after lateral canal inactivation. This response recovery was strongly frequency dependent: horizontal VOR gains were largest at the highest frequency tested and progressively decreased for lower frequencies. Below approximately 0.1 Hz, no consistent horizontal VOR could be elicited even 10 mo after plugging. 3. The frequency-dependent changes in gain paralleled changes in horizontal VOR phase. Below approximately 0.1-0.05 Hz large phase leads were present, similarly as in semicircular canal primary afferents. Smaller phase leads were also present at higher frequencies, particularly at 1.1 Hz (the highest frequency tested). 4. Consistent with the afferent-like dynamics of the adapted horizontal VOR, per- and postrotatory horizontal responses to constant-velocity yaw rotations were short lasting. Time constants of the slow-phase eye velocity envelope of the horizontal postrotatory nystagmus were approximately 2 s. Nonetheless, a consistent horizontal optokinetic afternystagmus was evoked in plugged animals. 5. A torsional component that was absent in intact animals was consistently present during yaw rotation acutely after lateral canal inactivation and remained approximately constant thereafter. The frequency response characteristics of this torsional component resembled those of the adapted horizontal slow-phase responses: gain decreased and large phase leads were introduced at frequencies below approximately 0.05-0.1 Hz. Torsional responses elicited by roll oscillations in supine position, on the other hand, were indistinguishable in their dynamics from intact animals. No consistent vertical nystagmus was elicited during yaw rotation. 6. Our results show that there is a slow, frequency-specific recovery of horizontal VOR after selective inactivation of the lateral semicircular canals. Both the spatial organization and the dynamic properties of the adapted VOR responses are distinctly different from responses in intact animals, suggesting complex changes in the underlying vestibuloocular circuitry.

Evidence for initiation of frictional partial slip as the mechanism behind nonlinear stress-strain hysteresis in rock fractures under seismic-frequency torsion

NASA Astrophysics Data System (ADS)

Saltiel, S.; Bonner, B. P.; Delbridge, B. G.; Ajo Franklin, J. B.

2016-12-01

We have adapted a low-frequency (0.1 - 64 Hz) torsional apparatus to explore the pure shear behavior of rock fractures under low normal stresses, simulating low effective stress environments - shallow depths and/or under high pore pressures. The instrument is unique in this ability to measure under very low confinement as well as to probe partial slip on the outside of asperities, before full slip nucleation occurs. Using a sinusoidal oscillation around this condition, we can probe the stress-strain constitutive relation at a range of strain amplitudes and the rate-dependence of the initiation of asperity slip. We find different, nonlinear, stress-strain constitutive relations for dolomite, rhyolite, and granite fractured samples, but all show softening at high strain amplitudes (above microstrain or micron-scale displacement). All measured samples exhibit qualitatively similar time-series hysteresis loops and frequency-dependence. The low frequency stress-strain loops stiffen at the high strain static end of the sinusoidal oscillation. This shape is determined by harmonic generation in the strain, while the stress signal has low power in harmonics, confirming that the driver and electronics are not the source of this nonlinearity. We also observe that this stiffening cusp does not occur as frequency increases above 8 Hz (opposite to normal dispersion seen at higher normal stresses). We monitor the fracture surface wear with repeated cycles to show the extent of slip on mapped asperities. These observations suggest that a rate dependent, healing, process causes the nonlinear responce of fracture faces under low normal stress to periodic shear. We propose that static friction at the low strain-rate part of the cycle, when given enough time at low oscillation frequencies, causes this stiffening cusp shape in the hysteretic stress-strain curve. An analytic model with idealized contact area is used to constrain the rate-state friction constitutive model parameters needed to provide this dynamic behavior.

Nonlinear Curvature Expressions for Combined Flapwise Bending, Chordwise Bending, Torsion and Extension of Twisted Rotor Blades

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.

Atomistic Simulation of Interstitial Dislocation Loop Evolution under Applied Stresses in BCC Iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Xue Hao; Wang, Dong; Setyawan, Wahyu

Evolution of an interstitial 1/2⟨111⟩ dislocation loop under tensile, shear, and torsion stresses is studied with molecular statics method. Under a tensile stress, the dependence of ultimate tensile strength on size of loop is calculated. The formation of small shear loops around the initial prismatic loop is confirmed as an intermediate state to form the final dislocation network. Under a shear stress, the rotation of a loop is observed not only by a change of the habit plane but also through a transformation between a shear and a prismatic loop. Under torsion, a perfect BCC crystal may undergo a BCCmore » to FCC or BCC to HCP transformation. The present work indicates that a 1/2⟨111⟩ loop can delay these transformations, resulting in the formation of micro-crack on the surface.« less

AC losses in (Bi,Pb) 2Sr 2Ca 2Cu 3O x tapes

NASA Astrophysics Data System (ADS)

D'Anna, G.; Indenbom, M. V.; André, M.-O.; Benoit, W.; Grivel, J.-C.; Hensel, B.; Flükiger, R.

1994-05-01

A double peak structure is observed in the AC losses of (Bi,Pb) 2Sr 2Ca 2Cu 3O x silver-sheathed tapes using a torsion-pendulum oscillator. The low-temperature peak is associated to the intragrain flux expulsion, while the high-temperature peak results from a macroscopic current path around the whole sample due to a well-coupled fraction of the grains. The flux pinning by the dislocations forming small-angle grain boundaries is suggested to control the transport current.

Torsional Alfv\\xE9n resonances as an efficient damping mechanism for non-radial oscillations in red giant stars

NASA Astrophysics Data System (ADS)

Loi, Shyeh Tjing; Papaloizou, John C. B.

2017-05-01

Stars are self-gravitating fluids in which pressure, buoyancy, rotation and magnetic fields provide the restoring forces for global modes of oscillation. Pressure and buoyancy energetically dominate, while rotation and magnetism are generally assumed to be weak perturbations and often ignored. However, observations of anomalously weak dipole mode amplitudes in red giant stars suggest that a substantial fraction of these are subject to an additional source of damping localized to their core region, with indirect evidence pointing to the role of a deeply buried magnetic field. It is also known that in many instances, the gravity-mode character of affected modes is preserved, but so far, no effective damping mechanism has been proposed that accommodates this aspect. Here we present such a mechanism, which damps the oscillations of stars harbouring magnetised cores via resonant interactions with standing Alfvén modes of high harmonic index. The damping rates produced by this mechanism are quantitatively on par with those associated with turbulent convection, and in the range required to explain observations, for realistic stellar models and magnetic field strengths. Our results suggest that magnetic fields can provide an efficient means of damping stellar oscillations without needing to disrupt the internal structure of the modes, and lay the groundwork for an extension of the theory of global stellar oscillations that incorporates these effects.

Experimental investigation of unsteady flows at large incidence angles in a linear oscillating cascade

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; King, Aaron J.; Capece, Vincent R.; El-Aini, Yehia M.

1996-01-01

The aerodynamics of a cascade of airfoils oscillating in torsion about the midchord is investigated experimentally at a large mean incidence angle and, for reference, at a low mean incidence angle. The airfoil section is representative of a modern, low aspect ratio, fan blade tip section. Time-dependent airfoil surface pressure measurements were made for reduced frequencies up to 0.8 for out-of-phase oscillations at Mach numbers up to 0.8 and chordal incidence angles of 0 deg and 10 deg. For the 10 deg chordal incidence angle, a separation bubble formed at the leading edge of the suction surface. The separated flow field was found to have a dramatic effect on the chordwise distribution of the unsteady pressure. In this region, substantial deviations from the attached flow data were found with the deviations becoming less apparent in the aft region of the airfoil for all reduced frequencies. In particular, near the leading edge the separated flow had a strong destabilizing influence while the attached flow had a strong stabilizing influence.

Oscillating cascade aerodynamics at large mean incidence

NASA Technical Reports Server (NTRS)

Buffum, Daniel H.; King, Aaron J.; El-Aini, Yehia M.; Capece, Vincent R.

1996-01-01

The aerodynamics of a cascade of airfoils oscillating in torsion about the midchord is investigated experimentally at a large mean incidence angle and, for reference, at a low mean incidence angle. The airfoil section is representative of a modern, low aspect ratio, fan blade tip section. Time-dependent airfoil surface pressure measurements were made for reduced frequencies of up to 1.2 for out-of-phase oscillations at a Mach number of 0.5 and chordal incidence angles of 0 deg and 10 deg; the Reynolds number was 0.9 x l0(exp 6). For the 10 deg chordal incidence angle, a separation bubble formed at the leading edge of the suction surface. The separated flow field was found to have a dramatic effect on the chordwise distribution of the unsteady pressure. In this region, substantial deviations from the attached flow data were found with the deviations becoming less apparent in the aft region of the airfoil for all reduced frequencies. In particular, near the leading edge the separated flow had a strong destabilizing influence while the attached flow had a strong stabilizing influence.

Testing the gravitational inverse-square law at centimeter scales

NASA Astrophysics Data System (ADS)

Bonicalzi, Ricco

Many attempts to unify gravity with the Standard Model entail a gravitational inverse-square-law violation (ISLV) at some low level. This dissertation reports on the initial phase of a torsion-pendulum null experiment searching for such a violation in the interaction between two macroscopic bodies with a characteristic separation of 12 cm. Central to the experimental design is the special configuration of the mass distributions of both the pendulum and source mass to provide high-sensitivity to the horizontal gradient of the Laplacian of the interaction potential (a signature of ISLV), while strongly suppressing coupling through Newtonian gravity. Specifically, this design ensures that gravitational systematic effects arise only at second order in the fabrication errors of the pendulum and source mass. A key aspect of this work is the choice of the second-harmonic amplitude of pendulum oscillation as the torque observable, instead of the traditional oscillation frequency. This relatively recent torsion-pendulum method is markedly less sensitive to changes in torsion-fiber temperature and enables the ambient-temperature instrumentation of the initial phase to achieve necessary noise performance without heroic efforts to stabilize temperature. As details of the second-harmonic method have not yet been published, the presentation here dwells on a number of subtleties involved in analyzing the data. Experimental results are reported assuming a Yukawa-type interaction anomaly, where a is the strength of the Yukawa term relative to Newtonian gravity. A preliminary set of 34 data runs, each around a day in duration, produced a value of alpha = (-6.3 +/- 7.5) x 10-5. In the absence of significant systematic effects, even this interim result would have placed tighter bounds on ISLV than previously appearing in the literature. Unfortunately, an accelerated Department of Energy deadline for demolition of our Hanford laboratory facility compelled a shift of focus to the principal phase of this experiment before resolving two apparently marginal, but significant sources of systematic error. These and resolved systematic effects are discussed in the context of the second-harmonic method.

Investigating the relationship between internal tibial torsion and medial collateral ligament injury in patients undergoing knee arthroscopy due to tears in the posterior one third of the medial meniscus.

PubMed

Guler, Olcay; Isyar, Mehmet; Karataş, Dilek; Ormeci, Tugrul; Cerci, Halis; Mahirogulları, Mahir

2016-08-01

To evaluate the relationship between medial collateral ligament (MCL) injury and degree of internal tibial torsion in patients who had undergone arthroscopic resection due to tears in the posterior one third of the medial meniscus. Seventy-one patients were allocated into two groups with respect to foot femur angle (FFA) and transmalleolar angle (TMA) (Group 1 31 patients with FFA<8° and Group 2 40 patients with FFA≥8°). The groups were compared in terms of valgus instability, Lysholm score, magnetic resonance view, FFA, and TMA, both before and after the operation. Lysholm scores were higher in Group 2 at both postoperative week 1 (p<0.001) and month 1 (p=0.045) relative to Group 1. Preoperative cartilage injury was encountered more frequently in Group 1 (p=0.037) than in Group 2. MCL injury was detected more frequently in Group 1 compared to Group 2 postoperatively at week 1 (p=0.001). We conclude that FFA and TFA, indicators of internal tibial torsion, may serve as markers for foreseeing clinical improvement and complications following arthroscopic surgery. level III retrospective comparative study. Copyright © 2015 Elsevier B.V. All rights reserved.

Calculations on the forces and moments for an oscillating wing-aileron combination in two-dimensional potential flow at sonic speed

NASA Technical Reports Server (NTRS)

Nelson, Herbert C; Berman, Julian H

1953-01-01

The linearized theory for compressible unsteady flow is used, as suggested in recent contributions to the subject, to obtain the velocity potential and the lift and moment for a thin harmonically oscillating, two-dimensional wing-aileron combination moving at sonic speed. The velocity potential is derived by considering the sonic case as the limit of the linearized supersonic theory. From the velocity potential explicit expressions for the lift and moment are developed for vertical translation and pitching of the wing and rotation of the aileron. The sonic results are compared and found to be consistent with previously obtained subsonic and supersonic results. Several figures are presented showing the variation of lift and moment with reduced frequency and Mach number and the influence of Mach number on some cases of bending-torsion flutter.

Erythropoietin and sildenafil protect against ischemia/reperfusion injury following testicular torsion in adult rats.

PubMed

Kostakis, Ioannis D; Zavras, Nick; Damaskos, Christos; Sakellariou, Stratigoula; Korkolopoulou, Penelope; Misiakos, Evangelos P; Tsaparas, Petros; Vaos, George; Karatzas, Theodoros

2017-06-01

Testicular torsion/detorsion causes severe tissue damage due to ischemia/reperfusion injury. The present study investigated the protective effect of erythropoietin and sildenafil against ischemia/reperfusion injury following unilateral testicular torsion/detorsion in adult rats. A total of 28 adult male rats were included, and were divided into the following groups: Group A (n=5), sham operated; groups B (n=5), C (n=5), D (n=5) and E (n=8), undergoing right testis torsion and detorsion after 90 min. Group B received no drug treatment. Rats in the groups C and D received low-dose (1,000 IU/kg) or high-dose (3,000 IU/kg) erythropoietin, while those in group E received sildenafil (0.7 mg/kg), through intraperitoneal injection after 60 min of torsion. The right testis was extracted 24 h after detorsion, and the tissue was subjected to histopathological examination and immunohistochemical assessment of cleaved caspase-3 expression. Histological alterations and the quality of spermatogenesis were scored according to the Cosentino and the Johnsen scoring systems, respectively. The results demonstrated normal testicular architecture in group A, while the other groups showed ischemic cellular damages, with the worst scores observed in group B. Groups D and E presented better scores compared with group C. Regarding the quality of spermatogenesis, the best scores were observed in group A, and the worst in group B. Groups C, D and E presented similar results, which were improved in comparison to group B, however, not compared to group A. Furthermore, cleaved caspase-3 levels were lower in groups A, D and E, with equal results observed. Group C had higher levels of cleaved caspase-3 compared with these groups, but lower than group B, which presented the highest cleaved caspase-3 levels. In conclusion, erythropoietin and sildenafil protect testis from ischemia/reperfusion injury by decreasing cellular damage and attenuating apoptosis.

Erythropoietin and sildenafil protect against ischemia/reperfusion injury following testicular torsion in adult rats

PubMed Central

Kostakis, Ioannis D.; Zavras, Nick; Damaskos, Christos; Sakellariou, Stratigoula; Korkolopoulou, Penelope; Misiakos, Evangelos P.; Tsaparas, Petros; Vaos, George; Karatzas, Theodoros

2017-01-01

Testicular torsion/detorsion causes severe tissue damage due to ischemia/reperfusion injury. The present study investigated the protective effect of erythropoietin and sildenafil against ischemia/reperfusion injury following unilateral testicular torsion/detorsion in adult rats. A total of 28 adult male rats were included, and were divided into the following groups: Group A (n=5), sham operated; groups B (n=5), C (n=5), D (n=5) and E (n=8), undergoing right testis torsion and detorsion after 90 min. Group B received no drug treatment. Rats in the groups C and D received low-dose (1,000 IU/kg) or high-dose (3,000 IU/kg) erythropoietin, while those in group E received sildenafil (0.7 mg/kg), through intraperitoneal injection after 60 min of torsion. The right testis was extracted 24 h after detorsion, and the tissue was subjected to histopathological examination and immunohistochemical assessment of cleaved caspase-3 expression. Histological alterations and the quality of spermatogenesis were scored according to the Cosentino and the Johnsen scoring systems, respectively. The results demonstrated normal testicular architecture in group A, while the other groups showed ischemic cellular damages, with the worst scores observed in group B. Groups D and E presented better scores compared with group C. Regarding the quality of spermatogenesis, the best scores were observed in group A, and the worst in group B. Groups C, D and E presented similar results, which were improved in comparison to group B, however, not compared to group A. Furthermore, cleaved caspase-3 levels were lower in groups A, D and E, with equal results observed. Group C had higher levels of cleaved caspase-3 compared with these groups, but lower than group B, which presented the highest cleaved caspase-3 levels. In conclusion, erythropoietin and sildenafil protect testis from ischemia/reperfusion injury by decreasing cellular damage and attenuating apoptosis. PMID:28587411

Torsional vibrations of shafts of mechanical systems

NASA Astrophysics Data System (ADS)

Gulevsky, V. A.; Belyaev, A. N.; Trishina, T. V.

2018-03-01

The aim of the research is to compare the calculated dependencies for determining the equivalent rigidity of a mechanical system and to come to an agreement on the methods of compiling dynamic models for systems with elastic reducer couplings in applied and classical oscillation theories. As a result of the analysis, it was revealed that most of the damage in the mechanisms and their details is due to the appearance of oscillations due to the dynamic impact of various factors: shock and alternating loads, unbalanced parts of machines, etc. Therefore, the designer at the design stage, and the engineer in the process of operation should provide the possibility of regulating the oscillatory processes both in details and machines by means of creating rational designs, as well as the use of special devices such as vibration dampers, various vibrators with optimal characteristics. A method is proposed for deriving a formula for determining the equivalent stiffness of a double-mass oscillating system of a multistage reducer with elastic reducer links without taking into account the internal losses and inertia of its elements, which gives a result completely coinciding with the result obtained by the classical theory of small mechanical oscillations and allows eliminating formulas for reducing the moments of inertia of the flywheel masses and the stiffness of the shafts.

Grain size-sensitive viscoelastic relaxation and seismic properties of polycrystalline MgO

NASA Astrophysics Data System (ADS)

Barnhoorn, A.; Jackson, I.; Fitz Gerald, J. D.; Kishimoto, A.; Itatani, K.

2016-07-01

Torsional forced-oscillation experiments on a suite of synthetic MgO polycrystals, of high-purity and average grain sizes of 1-100 µm, reveal strongly viscoelastic behavior at temperatures of 800-1300°C and periods between 1 and 1000 s. The measured shear modulus and associated strain energy dissipation both display monotonic variations with oscillation period, temperature, and grain size. The data for the specimens of intermediate grain size have been fitted to a generalized Burgers creep function model that is also broadly consistent with the results for the most coarse-grained specimen. The mild grain size sensitivity for the relaxation time τL, defining the lower end of the anelastic absorption band, is consistent with the onset of elastically accommodated grain boundary sliding. The upper end of the anelastic absorption band, evident in the highest-temperature data for one specimen only, is associated with the Maxwell relaxation time τM marking the transition toward viscous behavior, conventionally ascribed a stronger grain size sensitivity. Similarly pronounced viscoelastic behavior was observed in complementary torsional microcreep tests, which confirm that the nonelastic strains are mainly recoverable, i.e., anelastic. With an estimated activation volume for the viscoelastic relaxation, the experimentally constrained Burgers model has been extrapolated to the conditions of pressure and temperature prevailing in the Earth's uppermost lower mantle. For a plausible grain size of 10 mm, the predicted dissipation Q-1 ranges from 10-3 to 10-2 for periods of 3-3000 s. Broad consistency with seismological observations suggests that the lower mantle ferropericlase phase might account for much of its observed attenuation.

The three-dimensional wake of a cylinder undergoing a combination of translational and rotational oscillation in a quiescent fluid

NASA Astrophysics Data System (ADS)

Nazarinia, M.; Lo Jacono, D.; Thompson, M. C.; Sheridan, J.

2009-06-01

Previous two-dimensional numerical studies have shown that a circular cylinder undergoing both oscillatory rotational and translational motions can generate thrust so that it will actually self-propel through a stationary fluid. Although a cylinder undergoing a single oscillation has been thoroughly studied, the combination of the two oscillations has not received much attention until now. The current research reported here extends the numerical study of Blackburn et al. [Phys. Fluids 11, L4 (1999)] both experimentally and numerically, recording detailed vorticity fields in the wake and using these to elucidate the underlying physics, examining the three-dimensional wake development experimentally, and determining the three-dimensional stability of the wake through Floquet stability analysis. Experiments conducted in the laboratory are presented for a given parameter range, confirming the early results from Blackburn et al. [Phys. Fluids 11, L4 (1999)]. In particular, we confirm the thrust generation ability of a circular cylinder undergoing combined oscillatory motions. Importantly, we also find that the wake undergoes three-dimensional transition at low Reynolds numbers (Re≃100) to an instability mode with a wavelength of about two cylinder diameters. The stability analysis indicates that the base flow is also unstable to another mode at slightly higher Reynolds numbers, broadly analogous to the three-dimensional wake transition mode for a circular cylinder, despite the distinct differences in wake/mode topology. The stability of these flows was confirmed by experimental measurements.

Synchronous Chaos and Broad Band Gamma Rhythm in a Minimal Multi-Layer Model of Primary Visual Cortex

PubMed Central

Battaglia, Demian; Hansel, David

2011-01-01

Visually induced neuronal activity in V1 displays a marked gamma-band component which is modulated by stimulus properties. It has been argued that synchronized oscillations contribute to these gamma-band activity. However, analysis of Local Field Potentials (LFPs) across different experiments reveals considerable diversity in the degree of oscillatory behavior of this induced activity. Contrast-dependent power enhancements can indeed occur over a broad band in the gamma frequency range and spectral peaks may not arise at all. Furthermore, even when oscillations are observed, they undergo temporal decorrelation over very few cycles. This is not easily accounted for in previous network modeling of gamma oscillations. We argue here that interactions between cortical layers can be responsible for this fast decorrelation. We study a model of a V1 hypercolumn, embedding a simplified description of the multi-layered structure of the cortex. When the stimulus contrast is low, the induced activity is only weakly synchronous and the network resonates transiently without developing collective oscillations. When the contrast is high, on the other hand, the induced activity undergoes synchronous oscillations with an irregular spatiotemporal structure expressing a synchronous chaotic state. As a consequence the population activity undergoes fast temporal decorrelation, with concomitant rapid damping of the oscillations in LFPs autocorrelograms and peak broadening in LFPs power spectra. We show that the strength of the inter-layer coupling crucially affects this spatiotemporal structure. We predict that layer VI inactivation should induce global changes in the spectral properties of induced LFPs, reflecting their slower temporal decorrelation in the absence of inter-layer feedback. Finally, we argue that the mechanism underlying the emergence of synchronous chaos in our model is in fact very general. It stems from the fact that gamma oscillations induced by local delayed inhibition tend to develop chaos when coupled by sufficiently strong excitation. PMID:21998568

Nanoscopic dynamics in hybrid hydroxyapatite-CTAB composite

NASA Astrophysics Data System (ADS)

Dubey, P. S.; Sharma, V. K.; Mitra, S.; Verma, G.; Hassan, P. A.; Dutta, B.; Johnson, M.; Mukhopadhyay, R.

2017-06-01

Synthetic hydroxyapatite (HAp) is an important material in biomedical engineering due to its excellent biocompatibility and bioactivity. HAp nanoparticles were synthesized by the co-precipitation method using cetyltrimethylammonium bromide (CTAB) micelles as a template and are characterized using x-ray diffraction, electron microscopy, and thermal gravimetric measurements. Transmission electron microscope (TEM) demonstrates the formation of rod-shaped HAp. Dynamics of CTAB in HAp-CTAB composite as studied by using quasielastic neutron scattering (QENS) technique is reported here. HAp-CTAB composite provides an ideal system for studying the dynamics of CTAB micelles without any aqueous media. QENS data indicate that the observed dynamics are reminiscent of localized motions in ionic micellar systems, consisting of segmental and fast torsional motions. Segmental dynamics has been described with a model, in which hydrogen atoms in the alkyl chain undergoes localized translation diffusion and the CH3 unit associated with the head group undergo 3-fold jump rotation. Within this model, the hydrogen atoms in the alkyl chain undergo diffusion within spherical domains having different radii and diffusivities. A simple linear distribution of the radius and diffusivity has been assumed, in which the CH2 unit nearest to the head group has the least value and the ones furthest from the head group, that is, at the end of the alkyl chain has the largest value. The fast torsional motion is described by a 2-fold jump rotation model. Quantitative estimate of the different parameters characterizing various dynamical motions active within the time scale of the instrument is also presented. We have provided a detailed description of the observed dynamical features in hybrid HAp-CTAB composite, a potential candidate for biomedical applications.

Chaotic non-planar vibrations of the thin elastica. Part I: Experimental observation of planar instability

NASA Astrophysics Data System (ADS)

Cusumano, J. P.; Moon, F. C.

1995-01-01

In this two-part paper, the results of an investigation into the non-linear dynamics of a flexible cantilevered rod (the elastica) with a thin rectangular cross-section are presented. An experimental examination of the dynamics of the elastica over a broad parameter range forms the core of Part I. In Part II, the experimental work is related to a theoretical study of the mechanics of the elastica, and the study of a two-degree-of-freedom model obtained by modal projection. The experimental system used in this investigation is a rod with clamped-free boundary conditions, forced by sinusoidally displacing the clamped end. Planar periodic motions of the driven elastica are shown to lose stability at distinct resonant wedges, and the resulting motions are shown in general to be non-planar, chaotic, bending-torsion oscillations. Non-planar motions in all resonances exhibit energy cascading and dynamic two-well phenomena, and a family of asymmetric, bending-torsion non-linear modes is discovered. Correlation dimension calculations are used to estimate the number of active degrees of freedom in the system.

A method of measuring micro-impulse with torsion pendulum based on multi-beam laser heterodyne

NASA Astrophysics Data System (ADS)

Li, Yan-Chao; Wang, Chun-Hui

2012-02-01

In this paper, we propose a novel method of multi-beam laser heterodyne measurement for micro-impulse. The measurement of the micro-impulse, which is converted into the measurement of the small tuning angle of the torsion pendulum, is realized by considering the interaction between pulse laser and working medium. Based on Doppler effect and heterodyne technology, the information regarding the small tuning angle is loaded to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, thereby obtaining many values of the small tuning angle after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, the small tuning angle can be obtained accurately and the value of the micro-impulse can eventually be calculated. Using Polyvinylchlorid+2%C as a working medium, this novel method is used to simulate the value of the micro-impulse by MATLAB which is generated by considering the interaction between the pulse laser and the working medium, the obtained result shows that the relative error of this method is just 0.5%.

FTIR Synchrotron Spectroscopy of the Asymmetric C-H Stretching Bands of Methyl Mercaptan (CH3SH) - a Perplexity of Perturbations

NASA Astrophysics Data System (ADS)

Lees, Ronald M.; Xu, Li-Hong; Reid, Elias M.; Thapaliya, Bishnu P.; Dawadi, Mahesh B.; Perry, David S.; Twagirayezu, Sylvestre; Billinghurst, Brant E.

2016-06-01

The infrared Fourier transform spectrum of the asymmetric C-H stretching bands of CH3SH has been recorded in the 2950-3100 cm-1 region at Doppler limited resolution using synchrotron radiation at the FIR beamline of the Canadian Light Source in Saskatoon. Assignment of numerous torsion-rotation sub-bands for the asymmetric stretches has revealed a surprising pseudo-symmetric behavior, in which each band is seen in only one of the two possible ΔK selection rules. The upper states of the two asymmetric stretching vibrational bands thus appear to behave more like l = ± 1 components of a degenerate E state of a symmetric top rather than distinct vibrational states. The two components are separated by about 1.5 cm-1 at K = 0, and then diverge linearly at higher K with torsional oscillation amplitude similar to that of the ground state of about 1.3 cm-1. The divergence is consistent with an a-type Coriolis splitting picture with an effective Coriolis constant ζ ≈ 0.075.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raston, Paul L., E-mail: paul.raston@adelaide.edu.au; Douberly, Gary E.; Jäger, Wolfgang

Methanol is one of the simplest molecules that undergo torsional oscillations, and so it has been extensively studied in the gas phase by various spectroscopic techniques. At 300 K, a large number of rotational, torsional, and vibrational energy levels is populated, and this makes for a rather complicated spectrum, which is still not fully understood. It is expected that in going from 300 K to 0.4 K (the temperature of helium nanodroplets) the population distribution of methanol will mainly collapse into two states; the J{sub K} = 0{sub 0} state for the A{sub 1} nuclear spin symmetry species (with I{submore » CH{sub 3}} = 3/2), and the J{sub K} = 1{sub −1} state for the E species (I{sub CH{sub 3}} = 1/2). This results in a simplified spectrum that consists of narrow a-type (ΔK = 0) lines and broader b- and c-type (ΔK = ±1) lines. We have recorded the rotovibrational spectrum of CH{sub 3}OH in the OH stretching, CH{sub 3} stretching and bending, CH{sub 3} rocking, and CO stretching regions, and have firmly assigned five bands (v{sub 1}, v{sub 2}, v{sub 3}, v{sub 7}, and v{sub 8}), and tentatively assigned five others (v{sub 9}, 2v{sub 4}, v{sub 4} + v{sub 10}, 2v{sub 10}, and v{sub 4} + v{sub 5}). To our knowledge, the transitions we have assigned within the v{sub 4} + v{sub 10}, 2v{sub 10}, and v{sub 4} + v{sub 5} bands have not yet been assigned in the gas phase, and we hope that considering the very small “matrix” shift in helium nanodroplets (<1 cm{sup −1} for most subband origins of CH{sub 3}OH), those made here can aid in their gas phase identification. Microwave-infrared double resonance spectroscopy was used to confirm the initially tentative a-type infrared assignments in the OH stretching (v{sub 1}) band of A{sub 1} species methanol, in addition to revealing “warm” b-type lines. From a rotovibrational analysis, the B rotational constant is found to be reduced quite significantly (56%) with respect to the gas phase, and the torsional tunneling splittings are relatively unaffected and are at most reduced by 16%. While most rovibrational peaks are Lorentzian shaped, and those which are significantly perturbed by vibrational coupling in the gas phase are additionally broadened, the narrowest ΔJ = +1 peaks are asymmetric, and a skew-type analysis suggests that the response time of the helium solvent upon excitation is of the order of 1 ns.« less

Properties of oscillating refractive optical wings with one reflective surface

NASA Astrophysics Data System (ADS)

Artusio-Glimpse, Alexandra B.; Swartzlander, Grover A.

2013-09-01

A new modality for optical micromanipulation is under investigation. Optical wings are shaped refractive objects that experience a force and torque owing to the reflection and transmission of uniform light at the object surface. We present wing designs that provide a restoring torque that returns the wing to a source facing orientation while preserving efficient thrust from radiation pressure. The torsional stiffness and orbital period of a set of optical wing cross-sectional shapes are determined from numerical ray-tracing analyses. These results demonstrate the potential to develop an efficient optomechanical device for applications in microbiology and space flight systems.

Effect of noise reducing components on nose landing gear stability for a mid-size aircraft coupled with vortex shedding and freeplay

NASA Astrophysics Data System (ADS)

Eret, Petr; Kennedy, John; Bennett, Gareth J.

2015-10-01

In the pursuit of quieter aircraft, significant effort has been dedicated to airframe noise identification and reduction. The landing gear is one of the main sources of airframe noise on approach. The addition of noise abatement technologies such as fairings or wheel hub caps is usually considered to be the simplest solution to reduce this noise. After touchdown, noise abatement components can potentially affect the inherently nonlinear and dynamically complex behaviour (shimmy) of landing gear. Moreover, fairings can influence the aerodynamic load on the system and interact with the mechanical freeplay in the torque link. This paper presents a numerical study of nose landing gear stability for a mid-size aircraft with low noise solutions, which are modelled by an increase of the relevant model structural parameters to address a hypothetical effect of additional fairings and wheel hub caps. The study shows that the wheel hub caps are not a threat to stability. A fairing has a destabilising effect due to the increased moment of inertia of the strut and a stabilising effect due to the increased torsional stiffness of the strut. As the torsional stiffness is dependent on the method of attachment, in situations where the fairing increases the torsional inertia with little increase to the torsional stiffness, a net destabilising effect can result. Alternatively, it is possible that for the case that if the fairing were to increase equally both the torsional stiffness and the moment of inertia of the strut, then their effects could be mutually negated. However, it has been found here that for small and simple fairings, typical of current landing gear noise abatement design, their implementation will not affect the dynamics and stability of the system in an operational range (Fz ≤ 50 000 N, V ≤ 100 m/s). This generalisation is strictly dependent on size and installation methods. The aerodynamic load, which would be influenced by the presence of fairings, was modelled using a simple vortex shedding oscillator acting on the strut. The stability boundary was found to remain unaltered by vortex shedding. Significantly however, the addition of freeplay in the torque link was found to cause shimmy over the more typical operating conditions studied here. Unlike the no-freeplay case, there was a suppressed stabilising effect of increased torsional stiffness of the strut caused by the presence of fairing. No interaction between the vortex shedding and the freeplay on the stability threshold was observed.

Nonlinear equations of motion for the elastic bending and torsion of twisted nonuniform rotor blades

NASA Technical Reports Server (NTRS)

Hodges, D. H.; Dowell, E. H.

1974-01-01

The equations of motion are developed by two complementary methods, Hamilton's principle and the Newtonian method. The resulting equations are valid to second order for long, straight, slender, homogeneous, isotropic beams undergoing moderate displacements. The ordering scheme is based on the restriction that squares of the bending slopes, the torsion deformation, and the chord/radius and thickness/radius ratios are negligible with respect to unity. All remaining nonlinear terms are retained. The equations are valid for beams with mass centroid axis and area centroid (tension) axis offsets from the elastic axis, nonuniform mass and stiffness section properties, variable pretwist, and a small precone angle. The strain-displacement relations are developed from an exact transformation between the deformed and undeformed coordinate systems. These nonlinear relations form an important contribution to the final equations. Several nonlinear structural and inertial terms in the final equations are identified that can substantially influence the aeroelastic stability and response of hingeless helicopter rotor blades.

Sloshing dynamics modulated fluid angular momentum and moment fluctuations driven by orbital gravity gradient and jitter accelerations in microgravity

NASA Technical Reports Server (NTRS)

Hung, R. J.; Pan, H. L.

1995-01-01

The dynamical behavior of spacecraft propellant affected by the asymmetric combined gravity gradient and jitter accelerations, in particular the effect of surface tension on partially-filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank has been investigated. Three different cases of orbital accelerations: (1) gravity gradient-dominated, (2) equally weighted between gravity gradient and jitter, and (3) gravity jitter-dominated accelerations are studied. The results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient-dominated accelerations provide a torsional moment with tidal motion of bubble oscillations in the rotating dewar. The results are clearly seen from the twisting shape of the bubble oscillations driven by gravity gradient-dominated acceleration. The results of slosh wave excitation along the liquid-vapor interface induced by gravity jitter-dominated acceleration indicate the results of bubble motion in a manner of down-and-up and leftward-and-rightward movement of oscillation when the bubble is rotating with respect to rotating dewar axis. Fluctuations of angular momentum, fluid moment and bubble mass center caused by slosh wave excitations driven by gravity gradient acceleration or gravity jitter acceleration are also investigated.

Torsion and bending imposed on a new anterior cruciate ligament prosthesis during knee flexion: an evaluation method.

PubMed

Gely, P; Drouin, G; Thiry, P S; Tremblay, G R

1984-11-01

A new composite prosthesis was recently proposed for the anterior cruciate ligament. It is implanted in the femur and the tibia through two anchoring channels. Its intra-articular portion, composed of a fiber mesh sheath wrapped around a silicone rubber cylindrical core, reproduces satisfactorily the ligament response in tension. However, the prosthesis does not only undergo elongation. In addition, it is submitted to torsion in its intra-articular portion and bending at its ends. This paper presents a new method to evaluate these two types of deformations throughout a knee flexion by means of a geometric model of the implanted prosthesis. Input data originate from two sources: (i) a three-dimensional anatomic topology of the knee joint in full extension, providing the localization of the prosthesis anchoring channels, and ii) a kinematic model of the knee describing the motion of these anchoring channels during a physiological flexion of the knee joint. The evaluation method is independent of the way input data are obtained. This method, applied to a right cadaveric knee, shows that the orientation of the anchoring channels has a large effect on the extent of torsion and bending applied to the implanted prosthesis throughout a knee flexion, especially on the femoral side. The study suggests also the best choice for the anchoring channel axes orientation.

Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. II Spatiotemporal properties of the adapted slow-phase eye velocity

NASA Technical Reports Server (NTRS)

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

1996-01-01

1. The ability of the vestibuloocular reflex (VOR) to undergo adaptive modification after selective changes in the peripheral vestibular system was investigated in rhesus monkeys by recording three-dimensional eye movements before and after inactivation of selective semicircular canals. In the preceding paper we showed that the horizontal VOR gain evoked by passive yaw oscillations after lateral semicircular canal inactivation recovers gradually over time in a frequency-specific manner. Here we present the spatial tuning of the adapted slow-phase eye velocity and describe its spatiotemporal properties as a function of time after canal inactivation. 2. The spatial organization of the VOR was investigated during oscillations at different head positions in the pitch, roll, and yaw planes, as well as in the right anterior/left posterior and left anterior/right posterior canal planes. Acutely after bilateral inactivation of the lateral semicircular canals, a small horizontal response could still be elicited that peaked during rotations in pitched head positions that would maximally stimulate vertical semicircular canals. In addition, the phase of horizontal slow-phase velocity abruptly reversed through 180 degrees at positions close to upright, similarly to torsional slow-phase velocity. These spatial response properties suggest that the small, residual horizontal response components that are present acutely after plugging of both lateral canals originate from vertical semicircular canal signals. 3. As the horizontal response amplitude increased over time, consistent changes were also observed in the spatiotemporal tuning of horizontal slow-phase velocity. 1) The spatiotemporal response properties of horizontal slow-phase velocity acquired noncosine tuning characteristics, primarily in the pitch plane, in the right anterior/left posterior and left anterior/right posterior canal planes. Accordingly, horizontal response amplitude was nonzero during rotation in any head position in these planes and response phase varied significantly as a function of head orientation. 2) The peak horizontal response amplitude shifted spatially over time, such that 5-10 mo after plugging it was maximal during rotations at head positions close to upright. 4. In parallel to these unique spatiotemporal response properties characterizing the adapted horizontal VOR, torsional slow-phase velocity also exhibited small spatiotemporal changes after lateral canal inactivation that tended to precede in time the changes associated with the horizontal response components. In contrast, vertical slow-phase velocity in the plugged animals was unaltered and continued to be characterized by cosine-tuned spatial properties in three dimensions. 5. Recovery of the horizontal response gain during yaw oscillations in upright position, as well as the unique, noncosine spatiotemporal characteristics of the adapted horizontal VOR, were also observed in an animal with all but one vertical semicircular canals inactivated. There was, however, no sign of VOR gain recovery up to 2 mo after all semicircular canals were inactivated. These results suggest that the observed recovery of horizontal VOR is at least partly due to signals originating from the remaining intact vertical canal(s). Even in the presence of a single intact vertical canal, the improvement in horizontal gaze stability is at least partly restored through spatiotemporal changes in the processing of vestibuloocular signals that improve the gain and spatial tuning of horizontal VOR at the expense of temporal response properties.

MEMS infrared approaches to detector based on nonlinear oscillation and wavelength selective emitter using surface plasmon polariton

NASA Astrophysics Data System (ADS)

Sasaki, Minoru; Kumagai, Shinya

2014-03-01

The suspended MEMS structure is suitable for reducing the energy loss due to the thermal conduction. There is the possibility that IR photon energy can be well-controlled to generate some physical effects. A new method bases on the nonlinear oscillation for the detector. The thin film torsional spring exhibits a large hard spring effect when the deflection occurs in the out-of-plane direction of the film. When IR is absorbed, the resonator bends due to the thermal expansion. The torsional spring becomes harder increasing the resonant frequency. The frequency measurement is suited for the precise sensing. The device response is measured using the laser (wavelength of 650nm). The resonant frequency is 88-94kHz. Q factor is about 1600 in vacuum (1Pa). The sensitivity is -0.144[kHz/(kW/m2)]. As for the emitter, nondispersive IR gas sensor is considered. The molecules have their intrinsic absorptions. CO2 absorbs the wavelength 4.2- 4.3μm. The major incandescent light bulbs have the broad spectrum emitting IR which is not used for gas sensing. The wavelength selectivity at the gas bandwidth will improve the efficiency. A new principle uses the microheater placed facing to the grating. SPP is excited carrying IR energy on the grating surface. IR emission is the reverse process of excitation occurring at the output end. The emission spectra show SPP related peak having the width of 190nm. When the input power increases from 0.3 to 1.9W, the peak at wavelength of 3.5μm becomes clearer.

Inner Core Tilt and Polar Motion: Probing the Dynamics Deep Inside the Earth

NASA Astrophysics Data System (ADS)

Dumberry, M.; Bloxham, J.

2003-12-01

A tilted inner core permits exchange of angular momentum between the core and the mantle through gravitational and pressure torques and, as a result, changes in the direction of Earth's axis of rotation with respect to the mantle. Some of the observed variations in the direction of Earth's rotation could then be caused by equatorial torques on the inner core which tilt the latter out of its alignment with the mantle. In this work, we investigate whether such a scenario could explain the decade polar motion known as the Markowitz wobble. We show that a decade polar motion of the same amplitude as the observed Markowitz wobble requires a torque of 1020 N m which tilts the inner core by 0.07 degrees. This result critically depends on the viscosity of the inner core; for a viscosity less than 5 x 1017 Pa s, larger torques are required. A torque of 1020 N m with decadal periodicity can perhaps be produced by electromagnetic coupling between the inner core and a component of the flow in the outer core known as torsional oscillations, provided that the radial magnetic field at the inner core boundary is on the order of 3 to 4 mT and satisfies certain geometrical constraints. The resulting polar motion thus produced is eccentric and polarized, in agreement with the observations. Our model suggests that equatorial torques at the inner core boundary might also excite the Chandler wobble, provided shorter wavelength torsional oscillations with higher natural frequencies have enough power or provided there exists another physical mechanism that can generate a large torque at a 14 month period.

Rayleigh-type parametric chemical oscillation.

PubMed

Ghosh, Shyamolina; Ray, Deb Shankar

2015-09-28

We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

Creation and perturbation of planar networks of chemical oscillators

PubMed Central

Tompkins, Nathan; Cambria, Matthew Carl; Wang, Adam L.; Heymann, Michael; Fraden, Seth

2015-01-01

Methods for creating custom planar networks of diffusively coupled chemical oscillators and perturbing individual oscillators within the network are presented. The oscillators consist of the Belousov-Zhabotinsky (BZ) reaction contained in an emulsion. Networks of drops of the BZ reaction are created with either Dirichlet (constant-concentration) or Neumann (no-flux) boundary conditions in a custom planar configuration using programmable illumination for the perturbations. The differences between the observed network dynamics for each boundary condition are described. Using light, we demonstrate the ability to control the initial conditions of the network and to cause individual oscillators within the network to undergo sustained period elongation or a one-time phase delay. PMID:26117136

Wheels within Wheels: Hamiltonian Dynamics as a Hierarchy of Action Variables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perkins, Rory J.; Bellan, Paul M.

2010-09-17

In systems where one coordinate undergoes periodic oscillation, the net displacement in any other coordinate over a single period is shown to be given by differentiation of the action integral associated with the oscillating coordinate. This result is then used to demonstrate that the action integral acts as a Hamiltonian for slow coordinates providing time is scaled to the 'tick time' of the oscillating coordinate. Numerous examples, including charged particle drifts and relativistic motion, are supplied to illustrate the varied application of these results.

Primary splenic torsion in dogs: 102 cases (1992-2014).

PubMed

DeGroot, Whitney; Giuffrida, Michelle A; Rubin, Jacob; Runge, Jeffrey J; Zide, Amy; Mayhew, Philipp D; Culp, William T N; Mankin, Kelley Thieman; Amsellem, Pierre M; Petrukovich, Brandi; Ringwood, P Brendon; Case, J Brad; Singh, Ameet

2016-03-15

To determine the percentage of dogs surviving to hospital discharge and identify factors associated with death prior to hospital discharge among dogs undergoing surgery because of primary splenic torsion (PST). Retrospective case series. 102 client-owned dogs. Medical records of dogs with a confirmed diagnosis of PST that underwent surgery between August 1992 and May 2014 were reviewed. History, signalment, results of physical examination and preoperative bloodwork, method of splenectomy, concurrent surgical procedures, perioperative complications, duration of hospital stay, splenic histopathologic findings, and details of follow-up were recorded. Best-fit multivariate logistic regression was performed to identify perioperative factors associated with survival to hospital discharge. 93 of the 102 (91.2%) dogs survived to hospital discharge. German Shepherd Dogs (24/102 [23.5%]), Great Danes (15/102 [14.7%]), and English Bulldogs (12/102 [11.8%]) accounted for 50% of cases. Risk factors significantly associated with death prior to hospital discharge included septic peritonitis at initial examination (OR, 32.4; 95% confidence interval [CI], 2.1 to 502.0), intraoperative hemorrhage (OR, 22.6; 95% CI, 1.8 to 289.8), and postoperative development of respiratory distress (OR, 35.7; 95% CI, 2.7 to 466.0). Histopathologic evidence of splenic neoplasia was not found in any case. Results suggested that the prognosis for dogs undergoing splenectomy because of PST was favorable. Several risk factors for death prior to discharge were identified, including preexisting septic peritonitis, intraoperative hemorrhage, and postoperative development of respiratory distress.

Rotational spectrum and structure of the T-shaped cyanoacetylene carbon dioxide complex, HCCCN⋯CO2

NASA Astrophysics Data System (ADS)

Kang, Lu; Davis, Philip; Dorell, Ian; Li, Kexin; Oncer, Onur; Wang, Lucy; Novick, Stewart E.; Kukolich, Stephen G.

2017-12-01

The rotational spectrum of the T-shaped cyanoacetylene carbon dioxide dimer, HCCCN⋯CO2, was measured using two Balle-Flygare Fourier transform microwave (FTMW) spectrometers between 1.4 GHz and 25 GHz. Only the Ka = 0, 2, 4 branches of spectrum from J‧ = 1 ← 0 to J″ = 16 ← 15 transitions were observed. The vanishing of the Ka = 1, 3, … transitions demonstrates a C2v symmetry complex with a T-shaped alignment of the subunits. The spectroscopic constants were fit using Pickett's SPFIT/SPCAT suite of programs obtaining: A0 = 11273(18) MHz, B0 = 764.088(21) MHz, C0 = 716.254(21) MHz, ΔJ = 0.50329(34) kHz, ΔJK = 0.120867(11) MHz, ΔK = -28.17(36) MHz, δJ = 0.0613(21) kHz, δK = 44.25(95) kHz, ΦJ = 0.0053(12) Hz, ΦJK = 9.820(55) Hz, ΦKJ = -0.59325(72) kHz, ΦK = -2.3719(53) MHz, ϕJ = 0.0398(42) Hz, ϕJK = 6.9(9) Hz, and ϕK = -3.592(13) kHz. The 14N nuclear quadrupole coupling constants were fit to χaa = -4.12753(38) MHz and χbb - χcc = 0.103(15) MHz. The small negative inertial defect, Δ0 = -0.66(12) u Å2, indicates a vibrationally averaged planar complex with non-negligible low frequency out-of-plane vibrations. While maintaining near-planar orientation, both binding partners exhibit large-amplitude bending vibrations within the plane. To deal with the intermolecular dynamics, a torsional oscillation model was developed in this work for the structural analysis. According to this model, the vibrational bending amplitude for HCCCN torsional angle is 10.(1)°, with the a-axis of complex; CO2 subtending a 5.4(5)° torsional oscillation angle with the b molecular axis. The van der Waals bond length is 3.0137(3) Å. The stretching force constant, ks = 3.9 N/m, and the stretching frequency, νs = 53 cm-1, for the van der Waals bond were calculated using the pseudo-diatomic model. High-level MP2 and DFT calculations of structural parameters, rotational constants, and 14N quadrupole coupling strengths were made and the results compared with experimental results.

Generation of Magnetohydrodynamic Waves in Low Solar Atmospheric Flux Tubes by Photospheric Motions

NASA Astrophysics Data System (ADS)

Mumford, S. J.; Fedun, V.; Erdélyi, R.

2015-01-01

Recent ground- and space-based observations reveal the presence of small-scale motions between convection cells in the solar photosphere. In these regions, small-scale magnetic flux tubes are generated via the interaction of granulation motion and the background magnetic field. This paper studies the effects of these motions on magnetohydrodynamic (MHD) wave excitation from broadband photospheric drivers. Numerical experiments of linear MHD wave propagation in a magnetic flux tube embedded in a realistic gravitationally stratified solar atmosphere between the photosphere and the low choromosphere (above β = 1) are performed. Horizontal and vertical velocity field drivers mimic granular buffeting and solar global oscillations. A uniform torsional driver as well as Archimedean and logarithmic spiral drivers mimic observed torsional motions in the solar photosphere. The results are analyzed using a novel method for extracting the parallel, perpendicular, and azimuthal components of the perturbations, which caters to both the linear and non-linear cases. Employing this method yields the identification of the wave modes excited in the numerical simulations and enables a comparison of excited modes via velocity perturbations and wave energy flux. The wave energy flux distribution is calculated to enable the quantification of the relative strengths of excited modes. The torsional drivers primarily excite Alfvén modes (≈60% of the total flux) with small contributions from the slow kink mode, and, for the logarithmic spiral driver, small amounts of slow sausage mode. The horizontal and vertical drivers primarily excite slow kink or fast sausage modes, respectively, with small variations dependent upon flux surface radius.

Photoisomerization pathways and Raman activity of 1,1'-difluorostilbene

NASA Astrophysics Data System (ADS)

Dobryakov, A. L.; Quick, M.; Richter, C.; Knie, C.; Ioffe, I. N.; Granovsky, A. A.; Mahrwald, R.; Ernsting, N. P.; Kovalenko, S. A.

2017-01-01

The photoisomerization of 1,1'-difluorostilbene, following S0→S1 optical excitation in solution, was studied with femtosecond broadband transient absorption and stimulated Raman spectroscopy, and by quantum-chemical calculations. In n-hexane, trans-to-cis (t →c ) isomerization starts with Franck-Condon relaxation (τ1 t = 0.07 ps) followed by nearly barrierless torsion around the ethylenic bond (τ2 t ≈ 0.3 ps) to a perpendicular conformation P. About 50% of the excited molecules are trapped in P, while others reach the S1(cis) conformation adiabatically. For the opposite cis-to-trans (c →t ) path, the dynamics in n-hexane (τ1 c = 0.04 ps, τ2 c = 0.7 ps) suggest a 5 kJ/mol barrier between the relaxed S1(cis) and P states. The subsequent P decay with τ3 = 0.4 ps is followed by much slower ground-state recovery (τ4 ≈ 3 ps), indicating an intermediate state X. The t →P and c →P torsion depend on solvent viscosity and polarity, whereas the P →X →S0 relaxation and residual torsion is viscosity-independent but still polarity-dependent. Photoisomerization yields are derived from the transient absorption data and compared to those from actinometric measurements. Low-frequency oscillations in the transient signal are assigned to nuclei motions. Transient and stationary stimulated Raman spectra are compared to calculations. Early Franck-Condon Raman spectra differ from those of the quasistationary trans or cis S1 state. The photoisomerization behavior of stilbene and vinyl-substituted derivatives is compared and the general features are discussed.

The role of shock induced trailing-edge separation in limit cycle oscillations

NASA Technical Reports Server (NTRS)

Cunningham, Atlee M., Jr.

1989-01-01

The potential role of shock induced trailing edge separation (SITES) in limit cycle oscillations (LCO) was established. It was shown that the flip-flop characteristics of transition to and from SITES as well as its hysteresis could couple with wing modes with torsional motion and low damping. This connection led to the formulation of a very simple nonlinear math model using the linear equations of motion with a nonlinear step forcing function with hysteresis. A finite difference solution with time was developed and calculations were made for the F-111 TACT were used to determine the step forcing function due to SITES transition. Since no data were available for the hysteresis, a parameter study was conducted allowing the hysteresis effect to vary. Very small hysteresis effects, which were within expected bounds, were required to obtain reasonable response levels that essentially agreed with flight test results. Also in agreement with wind tunnel tests, LCO calculations for the 1/6 scale F-111 model showed that the model should have not experienced LCO.

Kinematics and Flow Evolution of a Flexible Wing in Stall Flutter

NASA Astrophysics Data System (ADS)

Farnsworth, John; Akkala, James; Buchholz, James; McLaughlin, Thomas

2014-11-01

Large amplitude stall flutter limit cycle oscillations were observed on an aspect ratio six finite span NACA0018 flexible wing model at a free stream velocity of 23 m/s and an initial angle of attack of six degrees. The wing motion was characterized by periodic oscillations of predominately a torsional mode at a reduced frequency of k = 0.1. The kinematics were quantified via stereoscopic tracking of the wing surface with high speed camera imaging and direct linear transformation. Simultaneously acquired accelerometer measurements were used to track the wing motion and trigger the collection of two-dimensional particle image velocimetry field measurements to the phase angle of the periodic motion. Aerodynamically, the flutter motion is driven by the development and shedding of a dynamic stall vortex system, the evolution of which is characterized and discussed. This work was supported by the AFOSR Flow Interactions and Control Portfolio monitored by Dr. Douglas Smith and the AFOSR/ASEE Summer Faculty Fellowship Program (JA and JB).

EMTP; A powerful tool for analyzing power system transients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, W.; Cotcher, D.; Ruiu, D.

1990-07-01

This paper reports on the electromagnetic transients program (EMTP), a general purpose computer program for simulating high-speed transient effects in electric power systems. The program features an extremely wide variety of modeling capabilities encompassing electromagnetic and electromechanical oscillations ranging in duration from microseconds to seconds. Examples of its use include switching and lightning surge analysis, insulation coordination, shaft torsional oscillations, ferroresonance, and HVDC converter control and operation. In the late 1960s Hermann Dommel developed the EMTP at Bonneville Power Administration (BPA), which considered the program to be the digital computer replacement for the transient network analyzer. The program initially comprisedmore » about 5000 lines of code, and was useful primarily for transmission line switching studies. As more uses for the program became apparent, BPA coordinated many improvements to the program. As the program grew in versatility and in size, it likewise became more unwieldy and difficult to use. One had to be an EMTP aficionado to take advantage of its capabilities.« less

Seismic sources

DOEpatents

Green, Michael A.; Cook, Neville G. W.; McEvilly, Thomas V.; Majer, Ernest L.; Witherspoon, Paul A.

1992-01-01

Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Logitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole relative to a stator that is clamped to the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements at a power level that causes heating to over 150.degree. C. within one minute of operation, but energizing the elements for no more than about one minute.

Improved Control Strategy for Subsynchronous Resonance Mitigation with Fractional-order PI Controller

NASA Astrophysics Data System (ADS)

Raju, D. Koteswara; Umre, Bhimrao S.; Junghare, A. S.; Chitti Babu, B.

2016-12-01

This paper explores a robust Fractional-order PI (FOPI) controller to diminish Subsynchronous Resonance (SSR) using Static Synchronous series compensator (SSSC). The diminution of SSR is accomplished by increasing the network damping with the injection of voltage of subsynchronous component into the line at those frequencies which are proximate to the torsional mode frequency of the turbine-generator shaft. The voltage of subsynchronous frequency component is extracted from the transmission line and further the similar quantity of series voltage is injected by SSSC into the line to make the current of subsynchronous frequency component to zero which is the major source of oscillations in the turbine-generator shaft. The insertion and fine tuning of Fractional-order PI controller in the control scheme of SSSC the subsynchronous oscillations are reduced to 4 % as compared to conventional PI controller. The studied system is modelled and simulated using MATLAB-Simulink and the results are analysed to show the precision and robustness of the proposed control strategy.

Studies of Sub-Synchronous Oscillations in Large-Scale Wind Farm Integrated System

NASA Astrophysics Data System (ADS)

Yue, Liu; Hang, Mend

2018-01-01

With the rapid development and construction of large-scale wind farms and grid-connected operation, the series compensation wind power AC transmission is gradually becoming the main way of power usage and improvement of wind power availability and grid stability, but the integration of wind farm will change the SSO (Sub-Synchronous oscillation) damping characteristics of synchronous generator system. Regarding the above SSO problem caused by integration of large-scale wind farms, this paper focusing on doubly fed induction generator (DFIG) based wind farms, aim to summarize the SSO mechanism in large-scale wind power integrated system with series compensation, which can be classified as three types: sub-synchronous control interaction (SSCI), sub-synchronous torsional interaction (SSTI), sub-synchronous resonance (SSR). Then, SSO modelling and analysis methods are categorized and compared by its applicable areas. Furthermore, this paper summarizes the suppression measures of actual SSO projects based on different control objectives. Finally, the research prospect on this field is explored.

Discovery of Short-Timescale Oscillations in the Transition Region by CLASP

NASA Technical Reports Server (NTRS)

Kubo, M.; Katsukawa, Y.; Kano, R.; Winebarger, A.; Kobayashi, K.; Ishikawa, R.; Narukage, N.; Bando, T.; Suematsu, Y.; Giono, G.;

Viscosity Measurement for Tellurium Melt

NASA Technical Reports Server (NTRS)

Lin, Bochuan; Li, Chao; Ban, Heng; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

2006-01-01

The viscosity of high temperature Te melt was measured using a new technique in which a rotating magnetic field was applied to the melt sealed in a suspended ampoule, and the torque exerted by rotating melt flow on the ampoule wall was measured. Governing equations for the coupled melt flow and ampoule torsional oscillation were solved, and the viscosity was extracted from the experimental data by numerical fitting. The computational result showed good agreement with experimental data. The melt velocity transient initiated by the rotating magnetic field reached a stable condition quickly, allowing the viscosity and electrical conductivity of the melt to be determined in a short period.

Tests of the Weak Equivalence Principal Below Fifty Microns

NASA Astrophysics Data System (ADS)

Leopardi, Holly; Hoyle, C. D.; Smith, Dave; Cardenas, Crystal; Harter, Andrew Conrad

2014-03-01

Due to the incompatibility of the Standard Model and General Relativity, tests of gravity remain at the forefront of experimental physics research. The Weak Equivalence Principle (WEP), which states that in a uniform gravitational field all objects fall with the same acceleration regardless of composition, total mass, or structure, is fundamentally the result of the equality of inertial mass and gravitational mass. The WEP has been effectively studied since the time of Galileo, and is a central feature of General Relativity; its violation at any length scale would bring into question fundamental aspects of the current model of gravitational physics. A variety of scenarios predict possible mechanisms that could result in a violation of the WEP. The Humboldt State University Gravitational Physics Laboratory is using a torsion pendulum with equal masses of different materials (a ``composition dipole'' configuration) to determine whether the WEP holds below the 50-micron distance scale. The experiment will measure the twist of a torsion pendulum as an attractor mass is oscillated nearby in a parallel-plate configuration, providing a time varying torque on the pendulum. The size and distance dependence of the torque variation will provide means to determine deviations from accepted models of gravity on untested distance scales. P.I.

UNDERSTANDING SOLAR TORSIONAL OSCILLATIONS FROM GLOBAL DYNAMO MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerrero, G.; Smolarkiewicz, P. K.; Pino, E. M. de Gouveia Dal

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 atmore » 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.« less

Photoisomerization around a fulvene double bond: coherent population transfer to the electronic ground state?

PubMed

Ioffe, Ilya; Dobryakov, Alexander L; Granovsky, Alexander A; Ernsting, Nikolaus P; Lustres, J Luis Pérez

2011-07-11

Photoisomerization around a central fulvene-type double bond is known to proceed through a conical intersection at the perpendicular geometry. The process is studied with an indenylidene-dihydropyridine model compound, allowing the use of visible excitation pulses. Transient absorption shows that 1) stimulated emission shifts to the red and loses oscillator strength on a 50 fs timescale, and 2) bleach recovery is highly nonexponential and not affected by solvent viscosity or methyl substitution at the dihydropyridine ring. Quantum-chemical calculations are used to explain point 1 as a result of initial elongation of the central C=C bond with mixing of S(2) and S(1) states. From point 2 it is concluded that internal conversion of S(1)→S(0) does not require torsional motion to the fully perpendicular state. The S(1) population appears to encounter a sink on the torsional coordinate before the conical intersection is reached. Rate equations cannot model the observed ground-state recovery adequately. Instead the dynamics are best described with a strongly damped oscillatory contribution, which could indicate coherent S(1)-S(0) population transfer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synchronous Oscillations in Microtubule Polymerization

NASA Astrophysics Data System (ADS)

Carlier, M. F.; Melki, R.; Pantaloni, D.; Hill, T. L.; Chen, Y.

1987-08-01

Under conditions where microtubule nucleation and growth are fast (i.e., high magnesium ion and tubulin concentrations and absence of glycerol), microtubule assembly in vitro exhibits an oscillatory regime preceding the establishment of steady state. The amplitude of the oscillations can represent >50% of the maximum turbidity change and oscillations persist for up to 20 periods of 80 s each. Oscillations are accompanied by extensive length redistribution of microtubules. Preliminary work suggests that the oscillatory kinetics can be simulated using a model in which many microtubules undergo synchronous transitions between growing and rapidly depolymerizing phases, complicated by the kinetically limiting rate of nucleotide exchange on free tubulin.

Spin-oscillator model for the unzipping of biomolecules by mechanical force.

PubMed

Prados, A; Carpio, A; Bonilla, L L

2012-08-01

A spin-oscillator system models unzipping of biomolecules (such as DNA, RNA, or proteins) subject to an external force. The system comprises a macroscopic degree of freedom, represented by a one-dimensional oscillator, and internal degrees of freedom, represented by Glauber spins with nearest-neighbor interaction and a coupling constant proportional to the oscillator position. At a critical value F(c) of an applied external force F, the oscillator rest position (order parameter) changes abruptly and the system undergoes a first-order phase transition. When the external force is cycled at different rates, the extension given by the oscillator position exhibits a hysteresis cycle at high loading rates, whereas it moves reversibly over the equilibrium force-extension curve at very low loading rates. Under constant force, the logarithm of the residence time at the stable and metastable oscillator rest position is proportional to F-F(c) as in an Arrhenius law.

Baryogenesis via particle-antiparticle oscillations

DOE PAGES

Ipek, Seyda; March-Russell, John

2016-06-29

CP violation, which is crucial for producing the baryon asymmetry of the Universe, is enhanced in particle-antiparticle oscillations. We study particle-antiparticle oscillations [of a particle with mass O(100GeV)] with CP violation in the early Universe in the presence of interactions with O(ab-fb) cross sections. We show that if baryon-number-violating interactions exist, a baryon asymmetry can be produced via out-of-equilibrium decays of oscillating particles. As a concrete example we study a U(1)R-symmetric, R-parity-violating supersymmetry model with pseudo-Dirac gauginos, which undergo particle-antiparticle oscillations. Hence, taking bino to be the lightest U(1) R-symmetric particle, and assuming it decays via baryon-number-violating interactions, we showmore » that bino-antibino oscillations can produce the baryon asymmetry of the Universe.« less

Vertical vibration and shape oscillation of acoustically levitated water drops

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, D. L.; Xie, W. J.; Yan, N.

2014-09-08

We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

Unsteady Aerodynamic Response of a Linear Cascade of Airfoils in Separated Flow

NASA Technical Reports Server (NTRS)

Capece, Vincent R.; Ford, Christopher; Bone, Christopher; Li, Rui

2004-01-01

The overall objective of this research program was to investigate methods to modify the leading edge separation region, which could lead to an improvement in aeroelastic stability of advanced airfoil designs. The airfoil section used is representative of current low aspect ratio fan blade tip sections. The experimental potion of this study investigated separated zone boundary layer from removal through suction slots. Suction applied to a cavity in the vicinity of the separation onset point was found to be the most effective location. The computational study looked into the influence of front camber on flutter stability. To assess the influence of the change in airfoil shape on stability the work-per-cycle was evaluated for torsion mode oscillations. It was shown that the front camberline shape can be an important factor for stabilizing the predicted work-per-cycle and reducing the predicted extent of the separation zone. In addition, data analysis procedures are discussed for reducing data acquired in experiments that involve periodic unsteady data. This work was conducted in support of experiments being conducted in the NASA Glenn Research Center Transonic Flutter Cascade. The spectral block averaging method is presented. This method is shown to be able to account for variations in airfoil oscillation frequency that can occur in experiments that force oscillate the airfoils to simulate flutter.

Transient Torque Method: A Fast and Non-Intrusive Technique to Simultaneously Determine Viscosity and Electrical Conductivity of Semiconducting and Metallic Melts

NASA Technical Reports Server (NTRS)

Li, C.; Ban, H.; Lin, B.; Scripa, R. N.; Su, C.; Lehoczky, S. L.; Zhu, S.

2003-01-01

A transient torque method was developed to rapidly and simultaneously determine the viscosity and electrical conductivity of semiconducting or metallic melts. The experimental setup is similar to that for the oscillation cup technique. The melt sample is sealed inside a fused silica ampoule, and the ampoule is suspended by a long quartz fiber to form a torsional oscillation system. A rotating magnetic field is used to induce a rotating flow in the conductive melt, which causes the ampoule to rotate along its axis. A sensitive angular detector is used to measure the deflection angle of the ampoule. Based on the transient behavior of the deflection angle as the rotating magnetic field is applied, the electrical conductivity and viscosity of the melt can be obtained simultaneously by numerically fitting the data to a set of governing equations. The transient torque viscometer was applied successfully to measure the viscosity and electrical conductivity of high purity mercury at 53.4 C. The results were in excellent agreement with the published data. The main advantage of the technique is that the measurement can be completed in one or two minutes, as opposed to the one or two-hour measurement time required by the oscillation cup technique. The method is non-intrusive; capable of rapid measurement of the viscosity of toxic, high vapor pressure melts at elevated temperatures. In addition, the transient torque viscometer can also be operated as an oscillation cup viscometer if desired.

Search for quasi-periodic signals in magnetar giant flares. Bayesian inspection of SGR 1806-20 and SGR 1900+14

NASA Astrophysics Data System (ADS)

Pumpe, Daniel; Gabler, Michael; Steininger, Theo; Enßlin, Torsten A.

2018-02-01

Quasi-periodic oscillations (QPOs) discovered in the decaying tails of giant flares of magnetars are believed to be torsional oscillations of neutron stars. These QPOs have a high potential to constrain properties of high-density matter. In search for quasi-periodic signals, we study the light curves of the giant flares of SGR 1806-20 and SGR 1900+14, with a non-parametric Bayesian signal inference method called D3PO. The D3PO algorithm models the raw photon counts as a continuous flux and takes the Poissonian shot noise as well as all instrument effects into account. It reconstructs the logarithmic flux and its power spectrum from the data. Using this fully noise-aware method, we do not confirm previously reported frequency lines at ν ≳ 17 Hz because they fall into the noise-dominated regime. However, we find two new potential candidates for oscillations at 9.2 Hz (SGR 1806-20) and 7.7 Hz (SGR 1900+14). If these are real and the fundamental magneto-elastic oscillations of the magnetars, current theoretical models would favour relatively weak magnetic fields B̅ 6× 1013-3 × 1014 G (SGR 1806-20) and a relatively low shear velocity inside the crust compared to previous findings. Data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A61

Experimental test of the viscous anisotropy hypothesis for partially molten rocks

PubMed Central

Qi, Chao; Kohlstedt, David L.; Katz, Richard F.; Takei, Yasuko

2015-01-01

Chemical differentiation of rocky planets occurs by melt segregation away from the region of melting. The mechanics of this process, however, are complex and incompletely understood. In partially molten rocks undergoing shear deformation, melt pockets between grains align coherently in the stress field; it has been hypothesized that this anisotropy in microstructure creates an anisotropy in the viscosity of the aggregate. With the inclusion of anisotropic viscosity, continuum, two-phase-flow models reproduce the emergence and angle of melt-enriched bands that form in laboratory experiments. In the same theoretical context, these models also predict sample-scale melt migration due to a gradient in shear stress. Under torsional deformation, melt is expected to segregate radially inward. Here we present torsional deformation experiments on partially molten rocks that test this prediction. Microstructural analyses of the distribution of melt and solid reveal a radial gradient in melt fraction, with more melt toward the center of the cylinder. The extent of this radial melt segregation grows with progressive strain, consistent with theory. The agreement between theoretical prediction and experimental observation provides a validation of this theory. PMID:26417107

Experimental test of the viscous anisotropy hypothesis for partially molten rocks.

PubMed

Qi, Chao; Kohlstedt, David L; Katz, Richard F; Takei, Yasuko

2015-10-13

Chemical differentiation of rocky planets occurs by melt segregation away from the region of melting. The mechanics of this process, however, are complex and incompletely understood. In partially molten rocks undergoing shear deformation, melt pockets between grains align coherently in the stress field; it has been hypothesized that this anisotropy in microstructure creates an anisotropy in the viscosity of the aggregate. With the inclusion of anisotropic viscosity, continuum, two-phase-flow models reproduce the emergence and angle of melt-enriched bands that form in laboratory experiments. In the same theoretical context, these models also predict sample-scale melt migration due to a gradient in shear stress. Under torsional deformation, melt is expected to segregate radially inward. Here we present torsional deformation experiments on partially molten rocks that test this prediction. Microstructural analyses of the distribution of melt and solid reveal a radial gradient in melt fraction, with more melt toward the center of the cylinder. The extent of this radial melt segregation grows with progressive strain, consistent with theory. The agreement between theoretical prediction and experimental observation provides a validation of this theory.

Translational velocity oscillations of piston generated vortex rings

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Arakeri, J. H.; Shankar, P. N.

1995-11-01

Experimental results are presented that show that the translational velocities of piston generated vortex rings often undergo oscillations, similar to those recently discovered for drop generated rings. An attempt has been made to minimize uncertainties by utilizing both dye and hydrogen bubbles for visualization and carefully repeating measurements on the same ring and on different realizations under the same nominal piston conditions. The results unambiguously show that under most conditions, both for laminar and turbulent rings and for rings generated from pipes and orifices, the oscillations are present. The present results, together with the earlier results on drop generated rings, give support to the view that translational velocity oscillations are probably an inherent feature of translating vortex ring fields.

Effect of torsional stiffness and inertia on the dynamics of low aspect ratio flapping wings.

PubMed

Xiao, Qing; Hu, Jianxin; Liu, Hao

2014-03-01

Micro air vehicle-motivated aerodynamics in biological flight has been an important subject in the past decade. Inspired by the novel flapping wing mechanisms in insects, birds and bats, we have carried out a numerical study systematically investigating a three-dimensional flapping rigid wing with passively actuated lateral and rotational motion. Distinguishing it from the limited existing studies, this work performs a systematic examination on the effects of wing aspect ratio (AR = 1.0 to infinity), inertia (density ratio σ = 4-32), torsional stiffness (frequency ratio F = 1.5-10 and infinity) and pivot point (from chord-center to leading edge) on the dynamics response of a low AR rectangular wing under an initial zero speed flow field condition. The simulation results show that the symmetry breakdown of the flapping wing results in a forward/backward motion with a rotational pitching. When the wing reaches its stable periodic state, the induced pitching frequency is identical to its forced flapping frequency. However, depending on various kinematic and dynamic system parameters, (i.e. flapping frequency, density ratio and pitching axis), the lateral induced velocity shows a number of different oscillating frequencies. Furthermore, compared with a one degree of freedom (DoF) wing in the lateral direction only, the propulsion performance of such a two DoF wing relies very much on the magnitude of torsional stiffness adding on the pivot point, as well as its pitching axis. In all cases examined here, thrust force and moment generated by a long span wing is larger than that of a short wing, which is remarkably linked to the strong reverse von Kármán vortex street formed in the wake of a wing.

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

PubMed Central

Zhao, Hao; Feng, Hao

2013-01-01

An angular acceleration sensor can be used for the dynamic analysis of human and joint motions. In this paper, an angular acceleration sensor with novel structure based on the principle of electromagnetic induction is designed. The method involves the construction of a constant magnetic field by the excitation windings of sensor, and the cup-shaped rotor that cut the magnetic field. The output windings of the sensor generate an electromotive force, which is directly proportional to the angular acceleration through the electromagnetic coupling when the rotor has rotational angular acceleration. The mechanical structure and the magnetic working circuit of the sensor are described. The output properties and the mathematical model including the transfer function and state-space model of the sensor are established. The asymptotical stability of the sensor when it is working is verified by the Lyapunov Theorem. An angular acceleration calibration device based on the torsional pendulum principle is designed. The method involves the coaxial connection of the angular acceleration sensor, torsion pendulum and a high-precision angle sensor, and then an initial external force is applied to the torsion pendulum to produce a periodic damping angle oscillation. The angular acceleration sensor and the angle sensor will generate two corresponding electrical signals. The sensitivity coefficient of the angular acceleration sensor can be obtained after processing these two-channel signals. The experiment results show that the sensitivity coefficient of the sensor is about 17.29 mv/Krad·s2. Finally, the errors existing in the practical applications of the sensor are discussed and the corresponding improvement measures are proposed to provide effective technical support for the practical promotion of the novel sensor. PMID:23941911

Large-scale photospheric motions determined from granule tracking and helioseismology from SDO/HMI data

NASA Astrophysics Data System (ADS)

Roudier, Th.; Švanda, M.; Ballot, J.; Malherbe, J. M.; Rieutord, M.

2018-04-01

Context. Large-scale flows in the Sun play an important role in the dynamo process linked to the solar cycle. The important large-scale flows are the differential rotation and the meridional circulation with an amplitude of km s-1 and few m s-1, respectively. These flows also have a cycle-related components, namely the torsional oscillations. Aim. Our attempt is to determine large-scale plasma flows on the solar surface by deriving horizontal flow velocities using the techniques of solar granule tracking, dopplergrams, and time-distance helioseismology. Methods: Coherent structure tracking (CST) and time-distance helioseismology were used to investigate the solar differential rotation and meridional circulation at the solar surface on a 30-day HMI/SDO sequence. The influence of a large sunspot on these large-scale flows with a specific 7-day HMI/SDO sequence has been also studied. Results: The large-scale flows measured by the CST on the solar surface and the same flow determined from the same data with the helioseismology in the first 1 Mm below the surface are in good agreement in amplitude and direction. The torsional waves are also located at the same latitudes with amplitude of the same order. We are able to measure the meridional circulation correctly using the CST method with only 3 days of data and after averaging between ± 15° in longitude. Conclusions: We conclude that the combination of CST and Doppler velocities allows us to detect properly the differential solar rotation and also smaller amplitude flows such as the meridional circulation and torsional waves. The results of our methods are in good agreement with helioseismic measurements.

Computational Investigation and Validation of Twin-Tail Buffet Response Including Dynamics and Control

NASA Technical Reports Server (NTRS)

Kandil, Osama A.

1998-01-01

Multidisciplinary tools for prediction of single rectangular-tail buffet are extended to single swept-back-tail buffet in transonic-speed flow, and multidisciplinary tools for prediction and control of twin-tail buffet are developed and presented. The configuration model consists of a sharp-edged delta wing with single or twin tails that are oriented normal to the wing surface. The tails are treated as cantilevered beams fixed at the root and allowed to oscillate in both bending and torsion. This complex multidisciplinary problem is solved sequentially using three sets of equations on a dynamic single or multi-block grid structure. The first set is the unsteady, compressible, Reynolds-averaged Navier-Stokes equations which are used for obtaining the flow field vector and the aerodynamic loads on the tails. The Navier-Stokes equations are solved accurately in time using the implicit, upwind, flux-difference splitting, finite volume scheme. The second set is the coupled bending and torsion aeroelastic equations of cantilevered beams which are used for obtaining the bending and torsion deflections of the tails. The aeroelastic equations'are solved accurately in time using, a fifth-order-accurate Runge-Kutta scheme. The third set is the grid-displacement equations and the rigid-body dynamics equations, which are used for updating the grid coordinates due to the tail deflections and rigid-body motions. The tail-buffet phenomenon is predicted for highly-swept, single vertical tail placed at the plane of geometric symmetry, and for highly-swept, vertical twin tails placed at three different spanwise separation distances. The investigation demonstrates the effects of structural inertial coupling and uncoupling of the bending and torsion modes of vibration, spanwise positions of the twin-tail, angle of attack, and pitching and rolling dynamic motions of the configuration model on the tail buffet loading and response. The fundamental issue of twin-tail buffet alleviation is addressed using two active flow-control methods. These methods are the tangential leading-edge blowing and the flow suction from the leading-edge vortex cores along their paths. Qualitative and quantitative comparisons with the available experimental data are presented. The comparisons indicate that the present multidisciplinary aeroelastic analysis tools are robust, accurate and efficient.

Nonlinear dynamical analysis of an aeroelastic system with multi-segmented moment in the pitch degree-of-freedom

NASA Astrophysics Data System (ADS)

Vasconcellos, Rui; Abdelkefi, Abdessattar

2015-01-01

The effects of a multi-segmented nonlinearity in the pitch degree of freedom on the behavior of a two-degree of freedom aeroelastic system are investigated. The aeroelastic system is free to plunge and pitch and is supported by linear translational and nonlinear torsional springs and is subjected to an incoming flow. The unsteady representation based on the Duhamel formulation is used to model the aerodynamic loads. Using modern method of nonlinear dynamics, a nonlinear characterization is performed to identify the system's response when increasing the wind speed. It is demonstrated that four sudden transitions take place with a change in the system's response. It is shown that, in the first transition, the system's response changes from simply periodic (only main oscillating frequency) to two periods (having the main oscillating frequency and its superharmonic of order 2). In the second transition, the response of the system changes from two periods (having the main oscillating frequency and its superharmonic of order 2) to a period-1. The results also show that the third transition is accompanied by a change in the system's response from simply periodic to two periods (having the main oscillating frequency and its superharmonic of order 3). After this transition, chaotic responses take place and then the fourth transition is accompanied by a sudden change in the system's response from chaotic to two periods (having the main oscillating frequency and its superharmonic of order 3). The results show that these transitions are caused by the tangential contact between the trajectory and the multi-segmented nonlinearity boundaries and with a zero-pitch speed incidence. This observation is associated with the definition of grazing bifurcation.

Prediction of advanced endovascular stent graft rotation and its associated morbidity and mortality.

PubMed

Crawford, Sean A; Sanford, Ryan M; Doyle, Matthew G; Wheatcroft, Mark; Amon, Cristina H; Forbes, Thomas L

2018-01-29

Advanced endovascular aneurysm repair (EVAR) with fenestrated and branched stent grafts is increasingly being used to repair complex aortic aneurysms; however, these devices can rotate unpredictably during deployment, leading to device misalignment. The objectives of this study were to quantify the short-term clinical outcomes in patients with intraoperative stent graft rotation and to identify quantitative anatomic markers of the arterial geometry that can predict stent graft rotation preoperatively. A prospective study evaluating all patients undergoing advanced EVAR was conducted at two university-affiliated hospitals between November 2015 and December 2016. Stent graft rotation (defined as ≥10 degrees) was measured on intraoperative fluoroscopic video of the deployment sequence. Standard preoperative computed tomography angiography imaging was used to calculate the geometric properties of the arterial anatomy. Any in-hospital and 30-day complications were prospectively documented, and a composite outcome of any end-organ ischemia or death was used as the primary end point. Thirty-nine patients undergoing advanced EVAR were enrolled in the study with a mean age of 75 years (interquartile range [IQR], 71-80 years) and a mean aneurysm diameter of 64 mm (IQR, 59-65 mm). The incidence of stent graft rotation was 37% (n = 14), with a mean rotation of 25 degrees (IQR, 21-28 degrees). A nominal logistic regression model identified iliac artery torsion, volume of iliac artery calcification, and stent graft length as the primary predictive factors. The total net torsion and the total volume of calcific plaque were higher in patients with stent graft rotation, 8.9 ± 0.8 mm -1 vs 4.1 ± 0.5 mm -1 (P < .0001) and 1054 ± 144 mm 3 vs 525 ± 83 mm 3 (P < .01), respectively. The length of the implanted stent grafts was also higher in patients with intraoperative rotation, 172 ± 9 mm vs 156 ± 8 mm (P < .01). The composite outcome of any end-organ ischemia or death was also substantially higher in patients with stent graft rotation (36% vs 0%; P = .004). In addition, patients with stent graft rotation had significantly higher combined rates of type Ib and type III endoleaks (43% vs 8%; P = .03). Patients with intraoperative stent graft rotation have a significantly higher rate of severe postoperative complications, and this is strongly associated with higher levels of iliac artery torsion, calcification, and stent graft length. These findings suggest that preoperative quantitative analysis of iliac artery torsion and calcification may improve risk stratification of patients before advanced EVAR. Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

High Temperature Fatigue Properties Research of GH4169 under Multiaxial Cyclic Loading

NASA Astrophysics Data System (ADS)

Ma, Shaojun; Tong, Dihua; Li, Liyun; Cheng, Yangyang; Hu, Benrun; Chen, Bo

2018-03-01

The high temperature (550°C and 650°C) fatigue properties of GH4169 for thin-wall tube specimen are investigated under uniaxial tension, uniaxial torsion, proportional tension-torsion and nonproportional tension-torsion. All tests are strain-controlled. The results indicate that the shape of the hysteresis loops of uniaxial tension, uniaxial torsion and proportional tension-torsion are similar, but hysteresis loop of non-proportional tension-torsion has distortion; the cyclic softening behavior is shown for GH4169 under uniaxial tension, uniaxial torsion and proportional tension-torsion, but the cyclic hardening behavior is shown for the first several cycles of nonproportional tension-torsion.

Drop Ejection From an Oscillating Rod

NASA Technical Reports Server (NTRS)

Wilkes, E. D.; Basaran, O. A.

1999-01-01

The dynamics of a drop of a Newtonian liquid that is pendant from or sessile on a solid rod that is forced to undergo time-periodic oscillations along its axis is studied theoretically. The free boundary problem governing the time evolution of the shape of the drop and the flow field inside it is solved by a method of lines using a finite element algorithm incorporating an adaptive mesh. When the forcing amplitude is small, the drop approaches a limit cycle at large times and undergoes steady oscillations thereafter. However, drop breakup is the consequence if the forcing amplitude exceeds a critical value. Over a wide range of amplitudes above this critical value, drop ejection from the rod occurs during the second oscillation period from the commencement of rod motion. Remarkably, the shape of the interface at breakup and the volume of the primary drop formed are insensitive to changes in forcing amplitude. The interface shape at times close to and at breakup is a multi-valued function of distance measured along the rod axis and hence cannot be described by recently popularized one-dimensional approximations. The computations show that drop ejection occurs without the formation of a long neck. Therefore, this method of drop formation holds promise of preventing formation of undesirable satellite droplets.

Prediction of unsteady separated flows on oscillating airfoils

NASA Technical Reports Server (NTRS)

Mccroskey, W. J.

1978-01-01

Techniques for calculating high Reynolds number flow around an airfoil undergoing dynamic stall are reviewed. Emphasis is placed on predicting the values of lift, drag, and pitching moments. Methods discussed include: the discrete potential vortex method; thin boundary layer method; strong interaction between inviscid and viscous flows; and solutions to the Navier-Stokes equations. Empirical methods for estimating unsteady airloads on oscillating airfoils are also described. These methods correlate force and moment data from wind tunnel tests to indicate the effects of various parameters, such as airfoil shape, Mach number, amplitude and frequency of sinosoidal oscillations, mean angle, and type of motion.

Noise-induced transitions in a double-well oscillator with nonlinear dissipation.

PubMed

Semenov, Vladimir V; Neiman, Alexander B; Vadivasova, Tatyana E; Anishchenko, Vadim S

2016-05-01

We develop a model of bistable oscillator with nonlinear dissipation. Using a numerical simulation and an electronic circuit realization of this system we study its response to additive noise excitations. We show that depending on noise intensity the system undergoes multiple qualitative changes in the structure of its steady-state probability density function (PDF). In particular, the PDF exhibits two pitchfork bifurcations versus noise intensity, which we describe using an effective potential and corresponding normal form of the bifurcation. These stochastic effects are explained by the partition of the phase space by the nullclines of the deterministic oscillator.

Planet Formation in Binary Star Systems

NASA Astrophysics Data System (ADS)

Martin, Rebecca

About half of observed exoplanets are estimated to be in binary systems. Understanding planet formation and evolution in binaries is therefore essential for explaining observed exoplanet properties. Recently, we discovered that a highly misaligned circumstellar disk in a binary system can undergo global Kozai-Lidov (KL) oscillations of the disk inclination and eccentricity. These oscillations likely have a significant impact on the formation and orbital evolution of planets in binary star systems. Planet formation by core accretion cannot operate during KL oscillations of the disk. First, we propose to consider the process of disk mass transfer between the binary members. Secondly, we will investigate the possibility of planet formation by disk fragmentation. Disk self gravity can weaken or suppress the oscillations during the early disk evolution when the disk mass is relatively high for a narrow range of parameters. Thirdly, we will investigate the evolution of a planet whose orbit is initially aligned with respect to the disk, but misaligned with respect to the orbit of the binary. We will study how these processes relate to observations of star-spin and planet orbit misalignment and to observations of planets that appear to be undergoing KL oscillations. Finally, we will analyze the evolution of misaligned multi-planet systems. This theoretical work will involve a combination of analytic and numerical techniques. The aim of this research is to shed some light on the formation of planets in binary star systems and to contribute to NASA's goal of understanding of the origins of exoplanetary systems.

A search for muon neutrino to electron neutrino oscillations at Δm 2 > 0.1 eV 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patterson, Ryan Benton

2007-11-01

The evidence is compelling that neutrinos undergo flavor change as they propagate. In recent years, experiments have observed this phenomenon of neutrino oscillations using disparate neutrino sources: the sun, fission reactors, accelerators, and secondary cosmic rays. The standard model of particle physics needs only simple extensions - neutrino masses and mixing - to accommodate all neutrino oscillation results to date, save one. The 3.8σ-significantmore » $$\\bar{v}$$ e excess reported by the LSND collaboration is consistent with $$\\bar{v}$$ μ →$$\\bar{v}$$ e oscillations with a mass-squared splitting of Δm 2 ~ 1 eV 2. This signal, which has not been independently verified, is inconsistent with other oscillation evidence unless more daring standard model extensions (e.g. sterile neutrinos) are considered.« less

Harmonic uniflow engine

DOEpatents

Bennett, Charles L.

2016-03-22

A reciprocating-piston uniflow engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. When released, the inlet valve head undergoes a single oscillation past the equilibrium position to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. In other embodiments, the harmonic oscillator arrangement of the inlet valve enables the uniflow engine to be reversibly operated as a uniflow compressor.

Spectral variation during one quasi-periodic oscillation cycle in the black hole candidate H1743-322

NASA Astrophysics Data System (ADS)

Sarathi Pal, Partha; Debnath, Dipak; Chakrabarti, Sandip Kumar

2016-07-01

From the nature of energy dependence of the power density spectra, it is believed that the oscillation of the Compton cloud may be related to low frequency quasi-periodic oscillations (LFQPOs). In the context of two component advective flow (TCAF) solution, the centrifugal pressure supported boundary layer of a transonic flow acts as the Compton cloud. This region undergoes resonance oscillation when cooling time scale roughly agrees with infall time scale as matter crosses this region. By carefully separating photons emitted at different phases of a complete oscillation, we establish beyond reasonable doubt that such an oscillation is the cause of LFQPOs. We show that the degree of Comptonization and therefore the spectral properties of the flow oscillate systematically with the phase of LFQPOs. We analysis the properties of a 0.2Hz LFQPO exhibited by a black hole candidate H 1743-322 using the 3-80 keV data from NuSTAR satellite. This object was chosen because of availability of high quality data for a relatively low frequency oscillation, rendering easy phase-wise of separation of the light curve data.

An oscillating dynamic model of collective cells in a monolayer

NASA Astrophysics Data System (ADS)

Lin, Shao-Zhen; Xue, Shi-Lei; Li, Bo; Feng, Xi-Qiao

2018-03-01

Periodic oscillations of collective cells occur in the morphogenesis and organogenesis of various tissues and organs. In this paper, an oscillating cytodynamic model is presented by integrating the chemomechanical interplay between the RhoA effector signaling pathway and cell deformation. We show that both an isolated cell and a cell aggregate can undergo spontaneous oscillations as a result of Hopf bifurcation, upon which the system evolves into a limit cycle of chemomechanical oscillations. The dynamic characteristics are tailored by the mechanical properties of cells (e.g., elasticity, contractility, and intercellular tension) and the chemical reactions involved in the RhoA effector signaling pathway. External forces are found to modulate the oscillation intensity of collective cells in the monolayer and to polarize their oscillations along the direction of external tension. The proposed cytodynamic model can recapitulate the prominent features of cell oscillations observed in a variety of experiments, including both isolated cells (e.g., spreading mouse embryonic fibroblasts, migrating amoeboid cells, and suspending 3T3 fibroblasts) and multicellular systems (e.g., Drosophila embryogenesis and oogenesis).

External torsion in a proximal tibia and internal torsion in a distal tibia occur independently in varus osteoarthritic knees compared to healthy knees.

PubMed

Mochizuki, Tomoharu; Tanifuji, Osamu; Koga, Yoshio; Hata, Ryosuke; Mori, Takahiro; Nishino, Katsutoshi; Sato, Takashi; Kobayashi, Koichi; Omori, Go; Sakamoto, Makoto; Tanabe, Yuji; Endo, Naoto

2017-05-01

The relative torsional angle of the distal tibia is dependent on a deformity of the proximal tibia, and it is a commonly used torsional parameter to describe deformities of the tibia; however, this parameter cannot show the location and direction of the torsional deformity in the entire tibia. This study aimed to identify the detailed deformity in the entire tibia via a coordinate system based on the diaphysis of the tibia by comparing varus osteoarthritic knees to healthy knees. In total, 61 limbs in 58 healthy subjects (age: 54 ± 18 years) and 55 limbs in 50 varus osteoarthritis (OA) subjects (age: 72 ± 7 years) were evaluated. The original coordinate system based on anatomic points only from the tibial diaphysis was established. The evaluation parameters were 1) the relative torsion in the distal tibia to the proximal tibia, 2) the proximal tibial torsion relative to the tibial diaphysis, and 3) the distal tibial torsion relative to the tibial diaphysis. The relative torsion in the distal tibia to the proximal tibia showed external torsion in both groups, while the external torsion was lower in the OA group than in the healthy group (p < 0.0001). The proximal tibial torsion relative to the tibial diaphysis had a higher external torsion in the OA group (p = 0.012), and the distal tibial torsion relative to the tibial diaphysis had a higher internal torsion in the OA group (p = 0.004) in comparison to the healthy group. The reverse torsional deformity, showing a higher external torsion in the proximal tibia and a higher internal torsion in the distal tibia, occurred independently in the OA group in comparison to the healthy group. Clinically, this finding may prove to be a pathogenic factor in varus osteoarthritic knees. Level Ⅲ. Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

Acoustical studies of the American reed organ

NASA Astrophysics Data System (ADS)

Cottingham, James P.

2004-05-01

The reed organ enjoyed a period of great popularity in North America which reached a peak in the late 19th century, when thousands of instruments per year were manufactured and sold in the United States and Canada. Displaced by the emergence of the upright piano, the reed organ had very much fallen out of favor by 1929. In the past decade a number of acoustical investigations have been undertaken on the instrument known as the American reed organ. Observations of reed motion and velocity have been made with electronic proximity sensors and a laser vibrometer system. The variation of the frequency and amplitude of reed vibration as a function of blowing pressure has been explored in some detail and the results compared with predictions of a simple theoretical model. Measurements have been made of the spectrum of the near-field sound including the effects of changes in dimensions of the reed cell. While most treatments of free reed oscillation approximate the reed vibration as a sinusoidal oscillation of a cantilever beam in the fundamental transverse mode, recently some evidence of higher transverse modes and torsional modes of vibration have been observed.

Spin precession experiments for light axionic dark matter

NASA Astrophysics Data System (ADS)

Graham, Peter W.; Kaplan, David E.; Mardon, Jeremy; Rajendran, Surjeet; Terrano, William A.; Trahms, Lutz; Wilkason, Thomas

2018-03-01

Axionlike particles are promising candidates to make up the dark matter of the Universe, but it is challenging to design experiments that can detect them over their entire allowed mass range. Dark matter in general, and, in particular, axionlike particles and hidden photons, can be as light as roughly 10-22 eV (˜10-8 Hz ), with astrophysical anomalies providing motivation for the lightest masses ("fuzzy dark matter"). We propose experimental techniques for direct detection of axionlike dark matter in the mass range from roughly 10-13 eV (˜102 Hz ) down to the lowest possible masses. In this range, these axionlike particles act as a time-oscillating magnetic field coupling only to spin, inducing effects such as a time-oscillating torque and periodic variations in the spin-precession frequency with the frequency and direction of these effects set by the axion field. We describe how these signals can be measured using existing experimental technology, including torsion pendulums, atomic magnetometers, and atom interferometry. These experiments demonstrate a strong discovery capability, with future iterations of these experiments capable of pushing several orders of magnitude past current astrophysical bounds.

Chaotic behavior in Casimir oscillators: A case study for phase-change materials.

PubMed

Tajik, Fatemeh; Sedighi, Mehdi; Khorrami, Mohammad; Masoudi, Amir Ali; Palasantzas, George

2017-10-01

Casimir forces between material surfaces at close proximity of less than 200 nm can lead to increased chaotic behavior of actuating devices depending on the strength of the Casimir interaction. We investigate these phenomena for phase-change materials in torsional oscillators, where the amorphous to crystalline phase transitions lead to transitions between high and low Casimir force and torque states, respectively, without material compositions. For a conservative system bifurcation curve and Poincare maps analysis show the absence of chaotic behavior but with the crystalline phase (high force-torque state) favoring more unstable behavior and stiction. However, for a nonconservative system chaotic behavior can take place introducing significant risk for stiction, which is again more pronounced for the crystalline phase. The latter illustrates the more general scenario that stronger Casimir forces and torques increase the possibility for chaotic behavior. The latter is making it impossible to predict whether stiction or stable actuation will occur on a long-term basis, and it is setting limitations in the design of micronano devices operating at short-range nanoscale separations.

A model for flexi-bar to evaluate intervertebral disc and muscle forces in exercises.

PubMed

Abdollahi, Masoud; Nikkhoo, Mohammad; Ashouri, Sajad; Asghari, Mohsen; Parnianpour, Mohamad; Khalaf, Kinda

2016-10-01

This study developed and validated a lumped parameter model for the FLEXI-BAR, a popular training instrument that provides vibration stimulation. The model which can be used in conjunction with musculoskeletal-modeling software for quantitative biomechanical analyses, consists of 3 rigid segments, 2 torsional springs, and 2 torsional dashpots. Two different sets of experiments were conducted to determine the model's key parameters including the stiffness of the springs and the damping ratio of the dashpots. In the first set of experiments, the free vibration of the FLEXI-BAR with an initial displacement at its end was considered, while in the second set, forced oscillations of the bar were studied. The properties of the mechanical elements in the lumped parameter model were derived utilizing a non-linear optimization algorithm which minimized the difference between the model's prediction and the experimental data. The results showed that the model is valid (8% error) and can be used for simulating exercises with the FLEXI-BAR for excitations in the range of the natural frequency. The model was then validated in combination with AnyBody musculoskeletal modeling software, where various lumbar disc, spinal muscles and hand muscles forces were determined during different FLEXI-BAR exercise simulations. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Investigation of conditions for the generation and propagation of low-frequency disturbances in the troposphere

NASA Astrophysics Data System (ADS)

Mordvinov, V. I.; Devyatova, E. V.; Kochetkova, O. S.; Oznobikhina, O. A.

2013-01-01

Low-frequency disturbances responsible for the excitation of torsional oscillations—variations in the zonal mean flow intensity with a characteristic scale of 15-20 days—propagating along the meridian at mid and low latitudes of both hemispheres are investigated [1]. As data observed over the eastern parts of continents and the western parts of oceans are processed with the lag correlation statistics, traveling waves intersecting the eastern parts of continents from northwest to southeast and then returning to the north along the ocean coasts are identified. In this case, trains of anomalies oriented in the zonal direction periodically appear and are destructed in the western parts of continents. The simulation of the propagation of disturbances in the quasi-geostrophic approximation made it possible to explain the specific features of lag correlation statistics over continents by the dispersion of two-dimensional Rossby waves from traveling sources. The turnover of disturbances over Asia and wave trains to the west from the pole were reproduced. Torsional oscillations caused by the dispersion of two-dimensional Rossby waves have a characteristic form of inclined bands in the latitude-time diagram, whose steepness is controlled by the velocity of displacement of the vorticity source along the meridian.

Constraining torsion with Gravity Probe B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao Yi; Guth, Alan H.; Cabi, Serkan

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) suchmore » 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.« less

Quantum Zeno Effect in the Strong Measurement Regime of Circuit Quantum Electrodynamics

DTIC Science & Technology

2016-05-17

andNV centers [16]. In driven superconducting qubits, the QZEhas been indirectly inferred from the transition between coherent Rabi oscillations and...qubit will undergo sinusoidal Rabi oscillations between states at frequency pW 2 , whereΩ depends on the strength of the resonant drive. Repeated...where the qubit dynamics dependmainly on qubit drive andmeasurement strength. Because of the presence of the Rabi drive, this treatment is only valid

Constraining properties of high-density matter in neutron stars with magneto-elastic oscillations

NASA Astrophysics Data System (ADS)

Gabler, Michael; Cerdá-Durán, Pablo; Stergioulas, Nikolaos; Font, José A.; Müller, Ewald

2018-05-01

We discuss torsional oscillations of highly magnetized neutron stars (magnetars) using two-dimensional, magneto-elastic-hydrodynamical simulations. Our model is able to explain both the low- and high-frequency quasi-periodic oscillations (QPOs) observed in magnetars. The analysis of these oscillations provides constraints on the breakout magnetic-field strength, on the fundamental QPO frequency, and on the frequency of a particularly excited overtone. By performing a new set of simulations, we are able to derive for the first time empirical relations for a self consistent model including a superfluid core which describe these constraints quantitatively. We use these relations to generically constrain properties of high-density matter in neutron stars, employing Bayesian analysis. In spite of current uncertainties and computational approximations, our model-dependent Bayesian posterior estimates for SGR 1806-20 yield a magnetic-field strength \\bar{B}˜ 2.1^{+1.3}_{-1.0}× 10^{15} G and a crust thickness of Δ r = 1.6^{+0.7}_{-0.6} km, which are both in remarkable agreement with observational and theoretical expectations, respectively (1σ error bars are indicated). Our posteriors also favour the presence of a superfluid phase in the core, a relatively low stellar compactness, M/R < 0.19, indicating a relatively stiff equation of state and/or low-mass neutron star, and high shear speeds at the base of the crust, cs > 1.4 × 108 cm s-1. Although the procedure laid out here still has large uncertainties, these constraints could become tighter when additional observations become available.

The extratropical 40-day oscillation in the UCLA general circulation model. Part 1: Atmospheric angular momentum

NASA Technical Reports Server (NTRS)

Marcus, S. L.; Ghil, M.; Dickey, J. O.

1994-01-01

Variations in atmospheric angular momentum (AAM) are examined in a three-year simulation of the large-scale atmosphere with perpetual January forcing. The simulation is performed with a version of the University of California at Los Angeles (UCLA) general circulation model that contains no tropical Madden-Julian Oscillation (MJO). In addition, the results of three shorter experiments with no topography are analyzed. The three-year standard topography run contains no significant intraseasonal AAM periodicity in the tropics, consistent with the lack of the MJO, but produces a robust, 42-day AAM oscillation in the Northern Hemisphere (NH) extratropics. The model tropics undergoes a barotropic, zonally symmetric oscillation, driven by an exchange of mass with the NH extratropics. No intraseasonal periodicity is found in the average tropical latent heating field, indicating that the model oscillation is dynamically rather than thermodynamically driven. The no-mountain runs fail to produce an intraseasonal AAM oscillation, consistent with a topographic origin for the NH extratropical oscillation in the standard model. The spatial patterns of the oscillation in the 500-mb height field, and the relationship of the extratropical oscillation to intraseasonal variations in the tropics, will be discussed in Part 2 of this study.

Investigation of the torsional stiffness of flexible disc coupling

NASA Astrophysics Data System (ADS)

Buryy, A.; Simonovsky, V.; Obolonik, V.

2017-08-01

Calculation of flexible coupling torsional stiffness is required when analyzing the torsional vibrations of the reciprocating machinery train. While having the lowest torsional stiffness of all the elements of the train, flexible coupling has a significant influence on the natural frequencies of torsional vibration. However, considering structural complexity of coupling, precise definition of its torsional stiffness is quite a difficult task. The paper presents a method for calculating the torsional stiffness of flexible disc coupling based on the study of its finite element model response under the action of torque. The analysis of the basic parameters that quantitatively and qualitatively affect the coupling torsional stiffness has been also provided. The results of the calculation as well as model adequacy, sufficient for practical application, have been confirmed at the experimental measurement of flexible disc coupling torsional stiffness. The obtained elastic characteristics (dependences of applied torque and torsional stiffness versus twist angle) are nonlinear in the initial stage of loading. This feature should be taken into account when creating reliable mathematical models of torsional vibrations of reciprocating machinery trains containing flexible disc couplings.

Dissociation dynamics of 3- and 4-nitrotoluene radical cations: Coherently driven C-NO2 bond homolysis

NASA Astrophysics Data System (ADS)

Ampadu Boateng, Derrick; Gutsev, Gennady L.; Jena, Puru; Tibbetts, Katharine Moore

2018-04-01

Monosubstituted nitrotoluenes serve as important model compounds for nitroaromatic energetic molecules such as trinitrotoluene. This work investigates the ultrafast nuclear dynamics of 3- and 4-nitrotoluene radical cations using femtosecond pump-probe measurements and the results of density functional theory calculations. Strong-field adiabatic ionization of 3- and 4-nitrotoluene using 1500 nm, 18 fs pulses produces radical cations in the ground electronic state with distinct coherent vibrational excitations. In both nitrotoluene isomers, a one-photon excitation with the probe pulse results in NO2 loss to form C7H7+, which exhibits out-of-phase oscillations in yield with the parent molecular ion. The oscillations in 4-nitrotoluene with a period of 470 fs are attributed to the torsional motion of the NO2 group based on theoretical results showing that the dominant relaxation pathway in 4-nitrotoluene radical cations involves the rotation of the NO2 group away from the planar geometry. The distinctly faster oscillation period of 216 fs in 3-nitrotoluene is attributed to an in-plane bending motion of the NO2 and CH3 moieties based on analysis of the normal modes. These results demonstrate that coherent nuclear motions determine the probability of C-NO2 homolysis in the nitrotoluene radical cations upon optical excitation within several hundred femtoseconds of the initial ionization event.

Theory and Simulation of A Novel Viscosity Measurement Method for High Temperature Semiconductor

NASA Technical Reports Server (NTRS)

Lin, Bochuan; Li, Chao; Ban, Heng; Scripa, Rose; Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)

2002-01-01

The properties of molten semiconductors are good indicators for material structure transformation and hysteresis under temperature variations. Viscosity, as one of the most important properties, is difficult to measure because of high temperature, high pressure, and vapor toxicity of melts. Recently, a novel method was developed by applying a rotating magnetic field to the melt sealed in a suspended quartz ampoule, and measuring the transient torque exerted by rotating melt flow on the ampoule wall. The method was designed to measure viscosity in short time period, which is essential for evaluating temperature hysteresis. This paper compares the theoretical prediction of melt flow and ampoule oscillation with the experimental data. A theoretical model was established and the coupled fluid flow and ampoule torsional vibration equations were solved numerically. The simulation results showed a good agreement with experimental data. The results also showed that both electrical conductivity and viscosity could be calculated by fitting the theoretical results to the experimental data. The transient velocity of the melt caused by the rotating magnetic field was found reach equilibrium in about half a minute, and the viscosity of melt could be calculated from the altitude of oscillation. This would allow the measurement of viscosity in a minute or so, in contrast to the existing oscillation cup method, which requires about an hour for one measurement.

Understanding photoluminescence of metal nanostructures based on an oscillator model.

PubMed

Cheng, Yuqing; Zhang, Weidong; Zhao, Jingyi; Wen, Te; Hu, Aiqin; Gong, Qihuang; Lu, Guowei

2018-08-03

Scattering and absorption properties of metal nanostructures have been well understood based on the classic oscillator theory. Here, we demonstrate that photoluminescence of metal nanostructures can also be explained based on a classic model. The model shows that inelastic radiation of an oscillator resembles its resonance band after external excitation, and is related to the photoluminescence from metallic nanostructures. The understanding based on the classic oscillator model is in agreement with that predicted by a quantum electromagnetic cavity model. Moreover, by correlating a two-temperature model and the electron distributions, we demonstrate that both one-photon and two-photon luminescence of the metal nanostructures undergo the same mechanism. Furthermore, the model explains most of the emission characteristics of the metallic nanostructures, such as quantum yield, spectral shape, excitation polarization and power dependence. The model based on an oscillator provides an intuitive description of the photoluminescence process and may enable rapid optimization and exploration of the plasmonic properties.

Phytoluminographic Detection of Dynamic Variations in Leaf Gaseous Conductivity 1

PubMed Central

Ellenson, James L.

1985-01-01

Gas exchange and plant luminescence (delayed light emission) of a single red kidney bean leaf undergoing synchronous oscillations in gas exchange were recorded and analyzed. Introduction of 1.1 microliter per liter SO2 during these oscillations produced increases in plant luminescence that, when averaged over a portion of the leaf, oscillated in phase with the gas exchange oscillations. However, examination of a video record of the plant luminescence showed not only that luminescence intensities tended to be localized within discrete areas of the leaf, but that the time-dependence of luminescence intensities within these regions varied considerably from the period, amplitude, and often phase of the overall gas exchange oscillations. The video recording also showed that changes in luminescence intensities appeared to migrate across the leaf in wave-like patterns. These data are interpreted in terms of localized fluctuations in gaseous conductances of the leaf. Images Fig. 3 PMID:16664350

Dynamics of vortex domain walls in ferromagnetic nanowires - A possible method for chirality manipulation

NASA Astrophysics Data System (ADS)

Li, Y.; Lu, Z.; Chen, C.; Cheng, M.; Yin, H.; Wang, W.; Li, C.; Liu, Y.; Xiong, R.; Shi, J.

2018-06-01

The dynamic behaviors of vortex domain walls (VDWs) in ferromagnetic nanowires driven by a magnetic field above Walker breakdown field (Hw) were investigated using micromagnetic simulation. It was found when nanowire has proper geometrical dimensions, the VDW may oscillate in a chirality invariant mode or a chirality switching mode depending on applied field and damping constant. At fixed damping constant, the oscillation mode can be controlled by applied field - with the increase of applied field, the oscillation of VDW change from a chirality invariant mode to a variant one. As the oscillation of VDW changes from chirality invariant regime to chirality switching regime, the oscillation frequency and amplification will undergo an abnormal change, which may offer a fingerprint for the switch of oscillation mode. Our finding proposes a simple way to control the chirality of a VDW by properly manipulating nanowire geometry and applied field, which may have important applications in VDW-based devices.

Nonspherical liquid droplet falling in air

NASA Astrophysics Data System (ADS)

Sahu, Kirti; Agrawal, Meenu; A. R, Premlala; Tripathi, Manoj; Karri, Badarinath; Kirti Sahu Collaboration

2017-11-01

The dynamics of an initially nonspherical liquid droplet falling in air under the action of gravity is investigated via three-dimensional numerical simulations of the Navier-Stokes and continuity equations in the inertial regime. The surface tension is considered to be high enough so that a droplet does not undergo break-up. Vertically symmetric oscillations which decay with time are observed for low inertia. The amplitude of these oscillations increases for high Gallilei numbers and the shape asymmetry in the vertical direction becomes prominent. The reason for this asymmetry has been attributed to the higher aerodynamic inertia. Moreover, even for large inertia, no path deviations/oscillations are observed.

Nonspherical liquid droplet falling in air

NASA Astrophysics Data System (ADS)

Agrawal, Meenu; Premlata, A. R.; Tripathi, Manoj Kumar; Karri, Badarinath; Sahu, Kirti Chandra

2017-03-01

The dynamics of an initially nonspherical liquid droplet falling in air under the action of gravity is investigated via three-dimensional numerical simulations of the Navier-Stokes and continuity equations in the inertial regime. The surface tension is considered to be high enough so that a droplet does not undergo breakup. Vertically symmetric oscillations which decay with time are observed for low inertia. The amplitude of these oscillations increases for high Gallilei numbers and the shape asymmetry in the vertical direction becomes prominent. The reason for this asymmetry has been attributed to the higher aerodynamic inertia. Moreover, even for large inertia, no path deviations or oscillations are observed.

Classification of the nonlinear dynamics and bifurcation structure of ultrasound contrast agents excited at higher multiples of their resonance frequency

NASA Astrophysics Data System (ADS)

Sojahrood, Amin Jafari; Kolios, Michael C.

2012-07-01

Through numerical simulation of the Hoff model we show that when ultrasound contrast agents (UCAs) are excited at frequencies which are close to integer (m>2) multiples of their natural resonance frequency, the bifurcation structure of the UCA oscillations as a function of pressure may be characterized by 3 general distinct regions. The UCA behavior starts with initial period one oscillations which undergoes a saddle node bifurcation to m coexisting attractors for an acoustic pressure above a threshold, P. Further increasing the pressure above a second threshold P, is followed by a sudden transition to period 1 oscillations.

Solvation and Evolution Dynamics of an Excess Electron in Supercritical CO2

NASA Astrophysics Data System (ADS)

Wang, Zhiping; Liu, Jinxiang; Zhang, Meng; Cukier, Robert I.; Bu, Yuxiang

2012-05-01

We present an ab initio molecular dynamics simulation of the dynamics of an excess electron solvated in supercritical CO2. The excess electron can exist in three types of states: CO2-core localized, dual-core localized, and diffuse states. All these states undergo continuous state conversions via a combination of long lasting breathing oscillations and core switching, as also characterized by highly cooperative oscillations of the excess electron volume and vertical detachment energy. All of these oscillations exhibit a strong correlation with the electron-impacted bending vibration of the core CO2, and the core-switching is controlled by thermal fluctuations.

Model for the dynamics of two interacting axisymmetric spherical bubbles undergoing small shape oscillations

PubMed Central

Kurihara, Eru; Hay, Todd A.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.

2011-01-01

Interaction between acoustically driven or laser-generated bubbles causes the bubble surfaces to deform. Dynamical equations describing the motion of two translating, nominally spherical bubbles undergoing small shape oscillations in a viscous liquid are derived using Lagrangian mechanics. Deformation of the bubble surfaces is taken into account by including quadrupole and octupole perturbations in the spherical-harmonic expansion of the boundary conditions on the bubbles. Quadratic terms in the quadrupole and octupole amplitudes are retained, and surface tension and shear viscosity are included in a consistent manner. A set of eight coupled second-order ordinary differential equations is obtained. Simulation results, obtained by numerical integration of the model equations, exhibit qualitative agreement with experimental observations by predicting the formation of liquid jets. Simulations also suggest that bubble-bubble interactions act to enhance surface mode instability. PMID:22088009

Properties of quasi-periodic oscillations in accreting magnetic white dwarfs

NASA Technical Reports Server (NTRS)

Wu, Kinwah; Chanmugam, G.; Shaviv, G.

1992-01-01

Previous studies of time-dependent accretion onto magnetic white dwarfs, in which the cooling was assumed to be due to bremsstrahlung emission, have shown that the accretion shock undergoes oscillations. However, when cyclotron cooling is also included, the oscillations are damped for sufficiently strong magnetic fields. Here we demonstrate that the oscillations can be sustained by accretion-fluctuation-induced excitations. The frequency of the QPOs are shown to increase quadratically with the magnetic field strength. We interpret the oscillations as a two-phase process in which bremsstrahlung cooling dominates in one half-cycle and cyclotron cooling in the other. Such a process may have very different consequences compared to a single-phase process where the functional form of the cooling is essentially the same throughout the cycle. If in the two-phase process damping occurs mainly in the cyclotron cooling half-cycle, there will be a universal effective damping factor which tends to suppress all oscillation modes indiscriminately. The oscillations of the accretion shock also could be a limit cycle process in which the system vacillates between two branches.

DNA-DNA interaction beyond the ground state

NASA Astrophysics Data System (ADS)

Lee, D. J.; Wynveen, A.; Kornyshev, A. A.

2004-11-01

The electrostatic interaction potential between DNA duplexes in solution is a basis for the statistical mechanics of columnar DNA assemblies. It may also play an important role in recombination of homologous genes. We develop a theory of this interaction that includes thermal torsional fluctuations of DNA using field-theoretical methods and Monte Carlo simulations. The theory extends and rationalizes the earlier suggested variational approach which was developed in the context of a ground state theory of interaction of nonhomologous duplexes. It shows that the heuristic variational theory is equivalent to the Hartree self-consistent field approximation. By comparison of the Hartree approximation with an exact solution based on the QM analogy of path integrals, as well as Monte Carlo simulations, we show that this easily analytically-tractable approximation works very well in most cases. Thermal fluctuations do not remove the ability of DNA molecules to attract each other at favorable azimuthal conformations, neither do they wash out the possibility of electrostatic “snap-shot” recognition of homologous sequences, considered earlier on the basis of ground state calculations. At short distances DNA molecules undergo a “torsional alignment transition,” which is first order for nonhomologous DNA and weaker order for homologous sequences.

Variable stiffness torsion springs

NASA Astrophysics Data System (ADS)

Alhorn, Dean C.; Polites, Michael E.

1994-05-01

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

Variable stiffness torsion springs

NASA Technical Reports Server (NTRS)

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

1995-01-01

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

Variable stiffness torsion springs

NASA Astrophysics Data System (ADS)

Alhorn, Dean C.; Polites, Michael E.

1995-08-01

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

Variable stiffness torsion springs

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

Incidence and predictive factors of isolated neonatal penile glanular torsion.

PubMed

Sarkis, Pierrot E; Sadasivam, Muthurajan

2007-12-01

To determine the incidence of isolated neonatal penile glanular torsion, describe the basic characteristics, and explore the relationship between foreskin and glans torsion. A prospective survey was conducted of all male newborns admitted to nursery after delivery, or neonates less than 3 months presenting for circumcision. Cases with associated genital malformations were excluded. The incidence of isolated neonatal penile torsion was 27% (95% CI: 22.2%-31.84%), to the left in 99% of cases. In 3.5% of cases, the penis had an angle <10 degrees, and 9.5% >20 degrees. Using Spearman's correlational coefficient, deviation of penile raphe from the midline at the foreskin tip had a better correlation with glans torsion than deviation of raphe at the coronal sulcus (0.727 vs 0.570; both significant at p<0.01). Isolated neonatal penile torsion is more common than reported. The median raphe of the penis may be normal and mask unexpected glans torsion. Median raphe torsion at foreskin tip can be used as a predictor for glans torsion. Clinical significance and relation to adult penile torsion are beyond the scope of the study.

Torsion limits from t t macr production at the LHC

NASA Astrophysics Data System (ADS)

de Almeida, F. M. L.; de Andrade, F. R.; do Vale, M. A. B.; Nepomuceno, A. A.

2018-04-01

Torsion models constitute a well-known class of extended quantum gravity models. In this work, one investigates the phenomenological consequences of a torsion field interacting with top quarks at the LHC. A torsion field could appear as a new heavy state characterized by its mass and couplings to fermions. This new state would form a resonance decaying into a top antitop pair. The latest ATLAS t t ¯ production results from LHC 13 TeV data are used to set limits on torsion parameters. The integrated luminosity needed to observe torsion resonance at the next LHC upgrades are also evaluated, considering different values for the torsion mass and its couplings to Standard Model fermions. Finally, prospects for torsion exclusion at the future LHC phases II and III are obtained using fast detector simulations.

Twofold Transition in PT-symmetric Coupled Oscillators

DTIC Science & Technology

2013-12-26

theoretical model exhibits two PT transitions depending on the size of the coupling parameter . For small , the PT symmetry is broken and the system is...small , the PT symmetry is broken and the system is not in equilibrium, but when becomes sufficiently large, the system undergoes a transition to...an equilibrium phase in which the PT symmetry is unbroken. For very large , the system undergoes a second transition and is no longer in

The human brain pacemaker: Synchronized infra-slow neurovascular coupling in patients undergoing non-pulsatile cardiopulmonary bypass.

PubMed

Zanatta, Paolo; Toffolo, Gianna Maria; Sartori, Elisa; Bet, Anna; Baldanzi, Fabrizio; Agarwal, Nivedita; Golanov, Eugene

2013-05-15

In non-pulsatile cardiopulmonary bypass surgery, middle cerebral artery blood flow velocity (BFV) is characterized by infra-slow oscillations of approximately 0.06Hz, which are paralleled by changes in total EEG power variability (EEG-PV), measured in 2s intervals. Since the origin of these BFV oscillations is not known, we explored their possible causative relationships with oscillations in EEG-PV at around 0.06Hz. We monitored 28 patients undergoing non-pulsatile cardiopulmonary bypass using transcranial Doppler sonography and scalp electroencephalography at two levels of anesthesia, deep (prevalence of burst suppression rhythm) and moderate (prevalence of theta rhythm). Under deep anesthesia, the EEG bursts suppression pattern was highly correlative with BFV oscillations. Hence, a detailed quantitative picture of the coupling between electrical brain activity and BFV was derived, both in deep and moderate anesthesia, via linear and non linear processing of EEG-PV and BFV signals, resorting to widely used measures of signal coupling such as frequency of oscillations, coherence, Granger causality and cross-approximate entropy. Results strongly suggest the existence of coupling between EEG-PV and BFV. In moderate anesthesia EEG-PV mean dominant frequency is similar to frequency of BFV oscillations (0.065±0.010Hz vs 0.045±0.019Hz); coherence between the two signals was significant in about 55% of subjects, and the Granger causality suggested an EEG-PV→BFV causal effect direction. The strength of the coupling increased with deepening anesthesia, as EEG-PV oscillations mean dominant frequency virtually coincided with the BFV peak frequency (0.062±0.017Hz vs 0.060±0.024Hz), and coherence became significant in a larger number (65%) of subjects. Cross-approximate entropy decreased significantly from moderate to deep anesthesia, indicating a higher level of synchrony between the two signals. Presence of a subcortical brain pacemaker that drives vascular infra-slow oscillations in the brain is proposed. These findings allow to suggest an original hypothesis explaining the mechanism underlying infra-slow neurovascular coupling. Copyright © 2013 Elsevier Inc. All rights reserved.

Torsion and buckling of open sections

NASA Technical Reports Server (NTRS)

Wagner, H; Pretschner, W

1936-01-01

Following an abstract of the well-known theory of torsion in compression, the writers give directions for the practical calculation of the values of C(sub BT) (resistance to flexure and torsion) and i(sub SP(exp 2)), which determine the torsion. The second part treats the experiments in support of the theory of torsion of plain and flanged angle sections.

Molecular mechanical studies of DNA flexibility: Coupled backbone torsion angles and base-pair openings

PubMed Central

Keepers, Joe W.; Kollman, Peter A.; Weiner, Paul K.; James, Thomas L.

1982-01-01

Molecular mechanics studies have been carried out on “B-DNA-like” structures of [d(C-G-C-G-A-A-T-T-C-G-C-G)]2 and [d(A)]12·[d(T)]12. Each of the backbone torsion angles (ψ, φ, ω, ω′, φ′) has been “forced” to alternative values from the normal B-DNA values (g+, t, g-, g-, t conformations). Compensating torsion angle changes preserve most of the base stacking energy in the double helix. In a second part of the study, one purine N3-pyrimidine N1 distance at a time has been forced to a value of 6 Å in an attempt to simulate the base opening motions required to rationalize proton exchange data for DNA. When the 6-Å constraint is removed, many of the structures revert to the normal Watson-Crick hydrogen-bonded structure, but a number are trapped in structures ≈5 kcal/mol higher in energy than the starting B-DNA structure. The relative energy of these structures, some of which involve a non-Watson-Crick thymine C2(carbonyl)[unk]adenine 6NH2 hydrogen bond, are qualitatively consistent with the ΔH for a “base pair-open state” suggested by Mandal et al. of 4-6 kcal/mol [Mandal, C., Kallenbach, N. R. & Englander, S. W. (1979) J. Mol. Biol. 135, 391-411]. The picture of DNA flexibility emerging from this study depicts the backbone as undergoing rapid motion between local torsional minima on a nanosecond time scale. Backbone motion is mainly localized within a dinucleoside segment and generally not conformationally coupled along the chain or across the base pairs. Base motions are much smaller in magnitude than backbone motions. Base sliding allows imino N—H exchange, but it is localized, and only a small fraction of the N—H groups is exposed at any one time. Stacking and hydrogen bonding cause a rigid core of bases in the center of the molecule accounting for the hydrodynamic properties of DNA. PMID:6957879

Comparative analysis of corneal morphological changes after transversal and torsional phacoemulsification through 2.2 mm corneal incision.

PubMed

Assaf, Ahmed; Roshdy, Maged Maher

2013-01-01

This paper compares and evaluates the corneal morphological changes occurring after cataract surgery through a 2.2 mm corneal incision. We use two platforms for comparison and evaluation, transversal and torsional phacoemulsification. This study includes 139 consecutive cataractous eyes (nuclear color 2-4, according to the Lens Opacities Classification System III [LOCSIII]) of 82 patients undergoing cataract surgery through a 2.2 mm corneal incision. Two different phacoemulsification platforms were used and assigned randomly: we used the WhiteStar Signature(®) system with the Ellips™ FX transversal continuous ultrasound (US) mode for group I (mean age: 65.33 ± 6.97 years), and we used the Infiniti(®) system with the OZil(®) Intelligent Phaco (IP) torsional US mode for group II (mean age: 64.02 ± 7.55 years). The corneal endothelium and pachymetry were evaluated preoperatively and at 1 month postoperatively. Incision size changes were also evaluated. All surgeries were uneventful. Before intraocular lens implantation, the mean incision size was 2.24 ± 0.06 mm in both groups (P = 0.75). In terms of corneal endothelial cell density, neither preoperative (I vs II: 2304.1 ± 122.5 cell/mm(2) vs 2315.6 ± 83.1 cell/mm(2), P = 0.80) nor postoperative (I vs II: 2264.1 ± 124.3 cell/mm(2) vs 2270.3 ± 89.9 cell/mm(2), P = 0.98) differences between the groups were statistically significant. The mean endothelial cell density loss was 1.7% ± 1.6% and 2.0% ± 1.4% in groups I and II, respectively. Furthermore, no significant differences between groups I and II were found preoperatively (P = 0.40) and postoperatively (P = 0.68) in central pachymetry. With surgery, the mean increase in central pachymetry was 28.1 ± 23.6 μm and 24.0 ± 24.0 μm in groups I and II, respectively (P = 0.1). Ellips™ FX transversal and OZil(®) IP torsional phacoemulsification modes are safe for performing cataract surgery, inducing minimal corneal thickness and endothelial changes.

Comparative analysis of corneal morphological changes after transversal and torsional phacoemulsification through 2.2 mm corneal incision

PubMed Central

Assaf, Ahmed; Roshdy, Maged Maher

2013-01-01

Purpose This paper compares and evaluates the corneal morphological changes occurring after cataract surgery through a 2.2 mm corneal incision. We use two platforms for comparison and evaluation, transversal and torsional phacoemulsification. Patients and methods This study includes 139 consecutive cataractous eyes (nuclear color 2–4, according to the Lens Opacities Classification System III [LOCSIII]) of 82 patients undergoing cataract surgery through a 2.2 mm corneal incision. Two different phacoemulsification platforms were used and assigned randomly: we used the WhiteStar Signature® system with the Ellips™ FX transversal continuous ultrasound (US) mode for group I (mean age: 65.33 ± 6.97 years), and we used the Infiniti® system with the OZil® Intelligent Phaco (IP) torsional US mode for group II (mean age: 64.02 ± 7.55 years). The corneal endothelium and pachymetry were evaluated preoperatively and at 1 month postoperatively. Incision size changes were also evaluated. Results All surgeries were uneventful. Before intraocular lens implantation, the mean incision size was 2.24 ± 0.06 mm in both groups (P = 0.75). In terms of corneal endothelial cell density, neither preoperative (I vs II: 2304.1 ± 122.5 cell/mm2 vs 2315.6 ± 83.1 cell/mm2, P = 0.80) nor postoperative (I vs II: 2264.1 ± 124.3 cell/mm2 vs 2270.3 ± 89.9 cell/mm2, P = 0.98) differences between the groups were statistically significant. The mean endothelial cell density loss was 1.7% ± 1.6% and 2.0% ± 1.4% in groups I and II, respectively. Furthermore, no significant differences between groups I and II were found preoperatively (P = 0.40) and postoperatively (P = 0.68) in central pachymetry. With surgery, the mean increase in central pachymetry was 28.1 ± 23.6 μm and 24.0 ± 24.0 μm in groups I and II, respectively (P = 0.1). Conclusion Ellips™ FX transversal and OZil® IP torsional phacoemulsification modes are safe for performing cataract surgery, inducing minimal corneal thickness and endothelial changes. PMID:23326184

A new twist in the photophysics of the GFP chromophore: a volume-conserving molecular torsion couple† †Electronic supplementary information (ESI) available: Synthetic methods and characterization; fluorescence up-conversion data; additional computational details; Cartesian coordinates of key structures; photochemical isomerization data; data for the anion of I. See DOI: 10.1039/c7sc04091a

PubMed Central

Conyard, Jamie; Heisler, Ismael A.; Chan, Yohan; Bulman Page, Philip C.

2018-01-01

The simple structure of the chromophore of the green fluorescent protein (GFP), a phenol and an imidazolone ring linked by a methyne bridge, supports an exceptionally diverse range of excited state phenomena. Here we describe experimentally and theoretically the photochemistry of a novel sterically crowded nonplanar derivative of the GFP chromophore. It undergoes an excited state isomerization reaction accompanied by an exceptionally fast (sub 100 fs) excited state decay. The decay dynamics are essentially independent of solvent polarity and viscosity. Excited state structural dynamics are probed by high level quantum chemical calculations revealing that the fast decay is due to a conical intersection characterized by a twist of the rings and pyramidalization of the methyne bridge carbon. The intersection can be accessed without a barrier from the pre-twisted Franck–Condon structure, and the lack of viscosity dependence is due to the fact that the rings twist in the same direction, giving rise to a volume-conserving decay coordinate. Moreover, the rotation of the phenyl, methyl and imidazolone groups is coupled in the sterically crowded structure, with the methyl group translating the rotation of one ring to the next. As a consequence, the excited state dynamics can be viewed as a torsional couple, where the absorbed photon energy leads to conversion of the out-of-plane orientation from one ring to the other in a volume conserving fashion. A similar modification of the range of methyne dyes may provide a new family of devices for molecular machines, specifically torsional couples. PMID:29675225

Symbolic generation of elastic rotor blade equations using a FORTRAN processor and numerical study on dynamic inflow effects on the stability of helicopter rotors

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.

1986-01-01

The process of performing an automated stability analysis for an elastic-bladed helicopter rotor is discussed. A symbolic manipulation program, written in FORTRAN, is used to aid in the derivation of the governing equations of motion for the rotor. The blades undergo coupled bending and torsional deformations. Two-dimensional quasi-steady aerodynamics below stall are used. Although reversed flow effects are neglected, unsteady effects, modeled as dynamic inflow are included. Using a Lagrangian approach, the governing equations are derived in generalized coordinates using the symbolic program. The program generates the steady and perturbed equations and writes into subroutines to be called by numerical routines. The symbolic program can operate on both expressions and matrices. For the case of hovering flight, the blade and dynamic inflow equations are converted to equations in a multiblade coordinate system by rearranging the coefficients of the equations. For the case of forward flight, the multiblade equations are obtained through the symbolic program. The final multiblade equations are capable of accommodating any number of elastic blade modes. The computer implementation of this procedure consists of three stages: (1) the symbolic derivation of equations; (2) the coding of the equations into subroutines; and (3) the numerical study after identifying mass, damping, and stiffness coefficients. Damping results are presented in hover and in forward flight with and without dynamic inflow effects for various rotor blade models, including rigid blade lag-flap, elastic flap-lag, flap-lag-torsion, and quasi-static torsion. Results from dynamic inflow effects which are obtained from a lift deficiency function for a quasi-static inflow model in hover are also presented.

Discrete Torsion, (Anti) de Sitter D4-Brane and Tunneling

NASA Astrophysics Data System (ADS)

Singh, Abhishek K.; Pandey, P. K.; Singh, Sunita; Kar, Supriya

2014-06-01

We obtain quantum geometries on a vacuum created pair of a (DDbar)3-brane, at a Big Bang singularity, by a local two form on a D4-brane. In fact our analysis is provoked by an established phenomenon leading to a pair creation by a gauge field at a black hole horizon by Stephen Hawking in 1975. Importantly, the five dimensional microscopic black holes are described by an effective non-perturbative curvature underlying a discrete torsion in a second order formalism. In the case for a non-propagating torsion, the effective curvature reduces to Riemannian, which in a low energy limit may describe Einstein vacuum in the formalism. In particular, our analysis suggests that a non-trivial space begin with a hot de Sitter brane-Universe underlying a nucleation of a vacuum pair of (DDbar)-instanton at a Big Bang. A pair of instanton nucleats a D-particle which in turn combines with an anti D-particle to describe a D-string and so on. The nucleation of a pair of higher dimensional pair of brane/anti-brane from a lower dimensional pair may be viewed via an expansion of the brane-Universe upon time. It is in conformity with the conjecture of a branes within a brane presumably in presence of the non-zero modes of two form. Interestingly, we perform a thermal analysis underlying various emergent quantum de Sitter vacua on a D4-brane and argue for the plausible tunneling geometries underlying a thermal equilibrium. It is argued that a de Sitter Schwarzschild undergoes quantum tunneling to an AdS-brane Schwarzschild via Nariai and de Sitter topological black hole.

The Microwave Spectrum of Partially Deuterated Species of Dimethyl Ether

NASA Astrophysics Data System (ADS)

Lauvergnat, D.; Margulès, L.; Motiyenko, R. A.; Guillemin, J.-C.; Coudert, L. H.

2011-06-01

Dimethyl ether is a molecule of astrophysical interest spectroscopically well characterized. It is one of the simplest molecules with two methyl groups undergoing large amplitude internal rotations. Due to deuterium enrichment in the interstellar medium, one can reasonably expect that partially deuterated species of dimethyl ether might be detected. However, there are no spectroscopic results about the microwave spectrum of such species. A theoretical calculation of the rotation-torsion energy levels of the partially deuterated species of dimethyl ether has been undertaken aided by ab initio calculations. The approach accounts for the complicated torsion-rotation interactions displayed by this molecule and for the fact that deuteration leads to changes of the bidimensional internal rotation effective potential energy surface. Due to zero-point energy contributions from the 19 small amplitude vibrational modes, this surface no longer displays G36 symmetry. Rotation-torsion energy levels are computed treating the two angles of internal rotation as active coordinates and evaluating Hamiltonian matrix elements with the help of Gaussian quadrature. It is hoped that the present results will allow us to understand the microwave spectrum of the mono deuterated species CH_2DOCH_3 which has been recorded in Lille with the new sub millimeter wave spectrometer (150--950 GHz) based on harmonic generation of solid-state sources. [2] Snyder, Buhl, and Schwartz, Astrophys. J. Letters 191 (1974) L79. [3] Endres, Drouin, Pearson, Müller, Lewen, Schlemmer, and Giesen, A&A 504 (2009) 635. [4] Solomon and Woolf, Astrophys. J. Letters 180 (1973) L89. [5] Lauvergnat and Nauts, J. Chem. Phys. 116 (2002) 8560; and Light and Bačić, J. Chem. Phys. 87 (1987) 4008.

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. III. Responses To translation

NASA Technical Reports Server (NTRS)

Angelaki, D. E.

1998-01-01

The three-dimensional (3-D) properties of the translational vestibulo-ocular reflexes (translational VORs) during lateral and fore-aft oscillations in complete darkness were studied in rhesus monkeys at frequencies between 0.16 and 25 Hz. In addition, constant velocity off-vertical axis rotations extended the frequency range to 0.02 Hz. During lateral motion, horizontal responses were in phase with linear velocity in the frequency range of 2-10 Hz. At both lower and higher frequencies, phase lags were introduced. Torsional response phase changed more than 180 degrees in the tested frequency range such that torsional eye movements, which could be regarded as compensatory to "an apparent roll tilt" at the lowest frequencies, became anticompensatory at all frequencies above approximately 1 Hz. These results suggest two functionally different frequency bandwidths for the translational VORs. In the low-frequency spectrum (<<0.5 Hz), horizontal responses compensatory to translation are small and high-pass-filtered whereas torsional response sensitivity is relatively frequency independent. At higher frequencies however, both horizontal and torsional response sensitivity and phase exhibit a similar frequency dependence, suggesting a common role during head translation. During up-down motion, vertical responses were in phase with translational velocity at 3-5 Hz but phase leads progressively increased for lower frequencies (>90 degrees at frequencies <0.2 Hz). No consistent dependence on static head orientation was observed for the vertical response components during up-down motion and the horizontal and torsional response components during lateral translation. The frequency response characteristics of the translational VORs were fitted by "periphery/brain stem" functions that related the linear acceleration input, transduced by primary otolith afferents, to the velocity signals providing the input to the velocity-to-position neural integrator and the oculomotor plant. The lowest-order, best-fit periphery/brain stem model that approximated the frequency dependence of the data consisted of a second order transfer function with two alternating poles (at 0.4 and 7.2 Hz) and zeros (at 0.035 and 3.4 Hz). In addition to clearly differentiator dynamics at low frequencies (less than approximately 0.5 Hz), there was no frequency bandwidth where the periphery/brain stem function could be approximated by an integrator, as previously suggested. In this scheme, the oculomotor plant dynamics are assumed to perform the necessary high-frequency integration as required by the reflex. The detailed frequency dependence of the data could only be precisely described by higher order functions with nonminimum phase characteristics that preclude simple filtering of afferent inputs and might be suggestive of distributed spatiotemporal processing of otolith signals in the translational VORs.

Closed-loop suppression of chaos in nonlinear driven oscillators

NASA Astrophysics Data System (ADS)

Aguirre, L. A.; Billings, S. A.

1995-05-01

This paper discusses the suppression of chaos in nonlinear driven oscillators via the addition of a periodic perturbation. Given a system originally undergoing chaotic motions, it is desired that such a system be driven to some periodic orbit. This can be achieved by the addition of a weak periodic signal to the oscillator input. This is usually accomplished in open loop, but this procedure presents some difficulties which are discussed in the paper. To ensure that this is attained despite uncertainties and possible disturbances on the system, a procedure is suggested to perform control in closed loop. In addition, it is illustrated how a model, estimated from input/output data, can be used in the design. Numerical examples which use the Duffing-Ueda and modified van der Pol oscillators are included to illustrate some of the properties of the new approach.

Rotating non-Boussinesq convection: oscillating hexagons

NASA Astrophysics Data System (ADS)

Moroz, Vadim; Riecke, Hermann; Pesch, Werner

2000-11-01

Within weakly nonlinear theory hexagon patterns are expected to undergo a Hopf bifurcation to oscillating hexagons when the chiral symmetry of the system is broken. Quite generally, the oscillating hexagons are expected to exhibit bistability of spatio-temporal defect chaos and periodic dynamics. This regime is described by the complex Ginzburg-Landau equation, which has been investigated theoretically in great detail. Its complex dynamics have, however, not been observed in experiments. Starting from the Navier-Stokes equations with realistic boundary conditions, we derive the three coupled real Ginzburg-Landau equations describing hexagons in rotating non-Boussinesq convection. We use them to provide quantitative results for the wavenumber range of stability of the stationary hexagons as well as the range of existence and stability of the oscillating hexagons. Our investigation is complemented by direct numerical simulations of the Navier-Stokes equations.

Role of S waves and Love waves in coseismic permeability enhancement

NASA Astrophysics Data System (ADS)

Wang, Chi-yuen; Chia, Yeeping; Wang, Pei-ling; Dreger, Douglas

2009-05-01

The 2008 M7.9 Wenchuan earthquake in Sichuan, China, caused water level to oscillate and undergo sustained changes in Taiwan, ˜2000 km away from the epicenter. Here we use the responses in three wells recorded at high sampling rate (1 Hz) and the broadband seismograms from a nearby station to document, for the first time, that the major water-level responses associated with Rayleigh waves were preceded by small oscillations that occurred concurrently with S waves and Love waves. We also show that the groundwater flow associated with these small oscillations may be strong enough to remove blockades from sediment pores to enhance aquifer permeability and to facilitate the later major responses.

Effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy

NASA Astrophysics Data System (ADS)

Wu, Wenqian; Guo, Lin; Liu, Bin; Ni, Song; Liu, Yong; Song, Min

2017-12-01

The effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy have been investigated. The torsional deformation generates a gradient microstructure distribution due to the gradient torsional strain. Both dislocation activity and deformation twinning dominated the torsional deformation process. With increasing the torsional equivalent strain, the microstructural evolution can be described as follows: (1) formation of pile-up dislocations parallel to the trace of {1 1 1}-type slip planes; (2) formation of Taylor lattices; (3) formation of highly dense dislocation walls; (3) formation of microbands and deformation twins. The extremely high deformation strain (strained to fracture) results in the activation of wavy slip. The tensile strength is very sensitive to the torsional deformation, and increases significantly with increasing the torsional angle.

Femtosecond Heterodyne Transient Grating Studies of Nonradiative Decay of the S2 (11Bu+) State of Peridinin: Detection and Spectroscopic Assignment of an Sx Intermediate State

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Bishop, Michael M.; Roscioli, Jerome D.; Lafountain, Amy M.; Frank, Harry A.; Beck, Warren F.

Femtosecond heterodyne transient grating spectroscopy was employed to investigate the nonradiative relaxation dynamics of peridinin from the S2 state to the S1 (21Ag-) state in methanol. A global target analysis indicates that S2 decays in 12 fs to populate an intermediate state, Sx. The absorption and dispersion components of the transient grating signal exhibit a response that is very similar to that of β-carotene in benzonitrile solution. Numerical simulation of the experimental data indicates that the excited state absorption transition from Sx has a larger oscillator strength than that of S1, which rules out an assignment of Sx to a vibrationally excited S1 state. The lifetime of Sx is found to be strongly dependent on the polar solvation timescale. This result indicates that nonradiative decay from Sx to S1 involves large-amplitude torsional motions and a concomitant formation of intramolecular charge transfer character. The present work provides the first evidence that peridinin has an ultrashort S2 lifetime owing to the onset of torsional motions and shows that the Sx acts as an active state for excitation energy transfer to chlorophyll in light-harvesting proteins. Work supported by the Photosynthetic Systems program of U.S. Department of Energy under Award Number DE-SC0010847.

Dissociation of frontal-midline delta-theta and posterior alpha oscillations: A mobile EEG study.

PubMed

Liang, Mingli; Starrett, Michael J; Ekstrom, Arne D

2018-04-22

Numerous reports have demonstrated low-frequency oscillations during navigation using invasive recordings in the hippocampus of both rats and human patients. Given evidence, in some cases, of low-frequency synchronization between midline cortex and hippocampus, it is also possible that low-frequency movement-related oscillations manifest in healthy human neocortex. However, this possibility remains largely unexplored, in part due to the difficulties of coupling free ambulation and effective scalp EEG recordings. In the current study, participants freely ambulated on an omnidirectional treadmill and explored an immersive virtual reality city rendered on a head-mounted display while undergoing simultaneous wireless scalp EEG recordings. We found that frontal-midline (FM) delta-theta (2-7.21 Hz) oscillations increased during movement compared to standing still periods, consistent with a role in navigation. In contrast, posterior alpha (8.32-12.76 Hz) oscillations were suppressed in the presence of visual input, independent of movement. Our findings suggest that FM delta-theta and posterior alpha oscillations arise at independent frequencies, under complementary behavioral conditions, and, at least for FM delta-theta oscillations, at independent recordings sites. Together, our findings support a double dissociation between movement-related FM delta-theta and resting-related posterior alpha oscillations. Our study thus provides novel evidence that FM delta-theta oscillations arise, in part, from real-world ambulation, and are functionally independent from posterior alpha oscillations. © 2018 Society for Psychophysiological Research.

Torsional Splitting in the Degenerate Vibrational States of (70)Ge(2)H(6): Rotation-Torsion Analysis of the nu(7) and nu(9) Fundamentals.

PubMed

Lattanzi; di Lauro C; Bürger; Mkadmi

2000-09-01

The rotational and torsional structure of the nu(7) and nu(9) degenerate fundamentals of (70)Ge(2)H(6) has been analyzed under high resolution. The torsional structure of both v(7) = 1 and v(9) = 1 states can be fitted by a simple one-parameter formula. The x,y-Coriolis interaction with the parallel nu(5) fundamental was accounted for in the analysis of nu(7). A strong perturbation of the J structure of the E(3s) torsional component of the KDeltaK = -2 subbranches of nu(9) can be explained by the resonance with an E(3s) excited level of the pure torsional manifold. The perturber is centered at 361.58 cm(-1), very close to the value estimated with a barrier height of 285 cm(-1). This confirms that the fundamental torsional wavenumber is close to 103 cm(-1), in good agreement with the "ab initio" prediction. The torsional splittings of all the infrared active degenerate fundamentals, nu(7), nu(8), and nu(9), follow the trend predicted by theory, and have been fitted by exploratory calculations accounting only for the torsional Coriolis-coupling mechanism of all degenerate vibrational fundamentals in several torsional states. This confirms that torsional Coriolis coupling is the dominant mechanism responsible for the decrease of the torsional splitting in the degenerate vibrational states. A higher value of the barrier had to be used for the nu(9) mode. Copyright 2000 Academic Press.

Ultrafast Nonradiative Decay and Excitation Energy Transfer by Carotenoids in Photosynthetic Light-Harvesting Proteins

NASA Astrophysics Data System (ADS)

Ghosh, Soumen

This dissertation investigates the photophysical and structural dynamics that allow carotenoids to serve as efficient excitation energy transfer donor to chlorophyll acceptors in photosynthetic light harvesting proteins. Femtosecond transient grating spectroscopy with optical heterodyne detection has been employed to follow the nonradiative decay pathways of carotenoids and excitation energy transfer to chlorophylls. It was found that the optically prepared S2 (11Bu+) state of beta-carotene decays in 12 fs fs to populate an intermediate electronic state, Sx, which then decays nonradiatively to the S 1 state. The ultrafast rise of the dispersion component of the heterodyne transient grating signal reports the formation of Sx intermediate since the rise of the dispersion signal is controlled by the loss of stimulated emission from the S2 state. These findings were extended to studies of peridinin, a carbonyl substituted carotenoid that serves as a photosynthetic light-harvesting chromophore in dinoflagellates. Numerical simulations using nonlinear response formalism and the multimode Brownian oscillator model assigned the Sx intermediate to a torsionally distorted structure evolving on the S2 potential surface. The decay of the Sx state is promoted by large amplitude out-of-plane torsional motions and is significantly retarded by solvent friction owing to the development of an intramolecular charge transfer character in peridinin. The slowing of the nonradiative decay allows the Sx state to transfer significant portion of the excitation energy to chlorophyll a acceptors in the peridinin-chlorophyll a protein. The results of heterodyne transient grating study on peridinin-chlorophyll a protein suggests two distinct energy transfer channels from peridinin to chlorophyll a: a 30 fs process involving quantum coherence and delocalized peridinin-Chl states and an incoherent, 2.5 ps process involving the distorted S2 state of peridinin. The torsional evolution on the S2 state is accompanied by the formation of an ICT character and dynamic exciton localization, which controls the mechanism of excitation energy transfer to chlorophyll a acceptors in the peridinin-chlorophyll a protein.

Normal Mode Analysis of Ambient-Noise Induced Free Oscillations of a Slender Medieval Masonry Tower in Bologna (Italy)

NASA Astrophysics Data System (ADS)

Morelli, A.; Azzara, R. M.; Cavaliere, A.; Zaccarelli, L.

2014-12-01

Analysis of the oscillations of buildings — either excited by earthquakes or by ambient noise — has become an effective tool to evaluate the response of such structures to strong ground motion, and hence to assess their seismic vulnerability. Response to small-amplitude ground motion may also provide crucial information on the elastic and anelastic properties of a structure — essential in the case of historical buildings — and constrain numerical full dynamic structural analyses. We report about an analysis carried out for a tall medieval monumental building in the urban center of the Norther Italian city of Bologna. Seismic monitoring, carried on for six months using field seismic instrumentation, has revealed the response to ambient noise, and has allowed to reconstruct, with high detail, the free oscillation modes of the tower. At 97 meters, the XII-century tower of the Asinelli is the tallest masonry building in Europe, and the most slender. We measured the fundamental, and several higher-order, flexural normal modes of oscillation, as well as the fundamental torsional mode. Asymmetry due to non-coincidence of centers of mass and of stiffness produces slightly different modal frequencies of oscillation in two orthogonal directions, consistently with dynamical modeling. Horizontal particle-motion polarization plots show the cyclic energy transfer between two degrees of freedom of the system. The Asinelli spectral signature can also be easily recognized in the motion recorded at the base of nearby Garisenda. We verify that there is correlation of spectral amplitudes with time of the day — in agreement with expected time-variance of anthropic disturbance —- but also with wind velocity and, intriguingly, with temperature variations inside the buidings. We are using these data to adjust the numerical dynamical models of the buildings, to examine time variations of behavior, and to identify the origin of anthropogenic sources of vibration in view of their possible mitigation.

Interaction of a magnetic island chain in a tokamak plasma with a resonant magnetic perturbation of rapidly oscillating phase

NASA Astrophysics Data System (ADS)

Fitzpatrick, Richard

2017-12-01

An investigation is made into the interaction of a magnetic island chain, embedded in a tokamak plasma, with an externally generated magnetic perturbation of the same helicity whose helical phase is rapidly oscillating. The analysis is similar in form to the classic analysis used by Kapitza [Sov. Phys. JETP 21, 588 (1951)] to examine the angular motion of a rigid pendulum whose pivot point undergoes rapid vertical oscillations. The phase oscillations are found to modify the existing terms, and also to give rise to new terms, in the equations governing the secular evolution of the island chain's radial width and helical phase. An examination of the properties of the new secular evolution equation reveals that it is possible to phase-lock an island chain to an external magnetic perturbation with an oscillating helical phase in a stabilizing phase relation provided that the amplitude, ɛ, of the phase oscillations (in radians) is such that |J0(ɛ )|≪1 , and the mean angular frequency of the perturbation closely matches the natural angular frequency of the island chain.

Effects of the fluid flows on enzymatic chemical oscillations

NASA Astrophysics Data System (ADS)

Shklyaev, Oleg; Yashin, Victor; Balazs, Anna

2017-11-01

Chemical oscillations are ubiquitous in nature and have a variety of promising applications. Usually, oscillating chemical systems are analyzed within the context of a reaction-diffusion framework. Here, we examine how fluid flows carrying the reactants can be utilized to modulate the negative feedback loops and time delays that promote chemical oscillations. We consider a model where a chemical reaction network involves two species, X and Y, which undergo transformations catalyzed by respective enzymes immobilized at the bottom wall of a fluid-filled microchamber. The reactions with the enzymes provide a negative feedback in the chemically oscillating system. In particular, the first enzyme, localized on the first patch, promotes production of chemical X, while the second enzyme, immobilized on the second patch, promotes production of chemical Y, which inhibits the production of chemical X. The separation distance between the enzyme-coated patches sets the time delay required for the transportation of X and Y. The chemical transport is significantly enhanced if convective fluxes accompany the diffusive ones. Therefore, the parameter region where oscillations are present is modified. The findings provide guidance to designing micro-scale chemical reactors with improved functionalities.

Vocal fold tissue failure: preliminary data and constitutive modeling.

PubMed

Chan, Roger W; Siegmund, Thomas

2004-08-01

In human voice production (phonation), linear small-amplitude vocal fold oscillation occurs only under restricted conditions. Physiologically, phonation more often involves large-amplitude oscillation associated with tissue stresses and strains beyond their linear viscoelastic limits, particularly in the lamina propria extracellular matrix (ECM). This study reports some preliminary measurements of tissue deformation and failure response of the vocal fold ECM under large-strain shear The primary goal was to formulate and test a novel constitutive model for vocal fold tissue failure, based on a standard-linear cohesive-zone (SL-CZ) approach. Tissue specimens of the sheep vocal fold mucosa were subjected to torsional deformation in vitro, at constant strain rates corresponding to twist rates of 0.01, 0.1, and 1.0 rad/s. The vocal fold ECM demonstrated nonlinear stress-strain and rate-dependent failure response with a failure strain as low as 0.40 rad. A finite-element implementation of the SL-CZ model was capable of capturing the rate dependence in these preliminary data, demonstrating the model's potential for describing tissue failure. Further studies with additional tissue specimens and model improvements are needed to better understand vocal fold tissue failure.

The sleep slow oscillation as a traveling wave.

PubMed

Massimini, Marcello; Huber, Reto; Ferrarelli, Fabio; Hill, Sean; Tononi, Giulio

2004-08-04

During much of sleep, virtually all cortical neurons undergo a slow oscillation (<1 Hz) in membrane potential, cycling from a hyperpolarized state of silence to a depolarized state of intense firing. This slow oscillation is the fundamental cellular phenomenon that organizes other sleep rhythms such as spindles and slow waves. Using high-density electroencephalogram recordings in humans, we show here that each cycle of the slow oscillation is a traveling wave. Each wave originates at a definite site and travels over the scalp at an estimated speed of 1.2-7.0 m/sec. Waves originate more frequently in prefrontal-orbitofrontal regions and propagate in an anteroposterior direction. Their rate of occurrence increases progressively reaching almost once per second as sleep deepens. The pattern of origin and propagation of sleep slow oscillations is reproducible across nights and subjects and provides a blueprint of cortical excitability and connectivity. The orderly propagation of correlated activity along connected pathways may play a role in spike timing-dependent synaptic plasticity during sleep.

Robust ion current oscillations under a steady electric field: An ion channel analog.

PubMed

Yan, Yu; Wang, Yunshan; Senapati, Satyajyoti; Schiffbauer, Jarrod; Yossifon, Gilad; Chang, Hsueh-Chia

2016-08-01

We demonstrate a nonlinear, nonequilibrium field-driven ion flux phenomenon, which unlike Teorell's nonlinear multiple field theory, requires only the application of one field: robust autonomous current-mass flux oscillations across a porous monolith coupled to a capillary with a long air bubble, which mimics a hydrophobic protein in an ion channel. The oscillations are driven by the hysteretic wetting dynamics of the meniscus when electro-osmotic flow and pressure driven backflow, due to bubble expansion, compete to approach zero mass flux within the monolith. Delayed rupture of the film around the advancing bubble cuts off the electric field and switches the monolith mass flow from the former to the latter. The meniscus then recedes and repairs the rupture to sustain an oscillation for a range of applied fields. This generic mechanism shares many analogs with current oscillations in cell membrane ion channel. At sufficiently high voltage, the system undergoes a state transition characterized by appearance of the ubiquitous 1/f power spectrum.

Creating Reconfigurable Materials Using ``Colonies'' of Oscillating Polymer Gels

NASA Astrophysics Data System (ADS)

Deb, Debabrata; Dayal, Pratyush; Kuksenok, Olga; Balazs, Anna

2013-03-01

Species ranging from single-cell organisms to social insects can undergo auto-chemotaxis, where the entities move towards a chemo-attractant that they themselves emit. This mode of signaling allows the organisms to form large-scale structures. Using computational modeling, we show that millimeter-sized polymer gels can display similar auto-chemotaxis. In particular, we demonstrate that gels undergoing the self-oscillating Belousov-Zhabotinsky (BZ) reaction not only respond to a chemical signal from the surrounding solution, but also emit this signal and thus, multiple gel pieces can spontaneously self-aggregate. We focus on the collective behavior of ``colonies'' of BZ gels and show that communication between the individual pieces critically depends on all the neighboring gels. We isolate the conditions at which the BZ gels can undergo a type of self-recombining: if a larger gel is cut into distinct pieces that are moved relatively far apart, then their auto-chemotactic behavior drives them to move and autonomously recombine into a structure resembling the original, uncut sample. These findings reveal that the BZ gels can be used as autonomously moving building blocks to construct multiple structures and thus, provide a new route for creating dynamically reconfigurable materials.

[Penile torsion. Case report].

PubMed

Arch Canas, Albert; Gutiérfz del Pozo, Rafael

2006-01-01

To report the clinical characteristics and therapeutic options of penile torsion. We report the case of a male with asymptomatic penile torsion as an incidental finding after consultation for other reasons. The patient was treated conservatively because it was not an important aesthetic trouble and it was asymptomatic. Penile torsion is rare. Surgical treatment is reserved for very important degrees of torsion, symptomatic patients or, when patient feels discomfort with the aesthetic alteration.

Development of a Meso-Scale SMA-Based Torsion Actuator for Image-Guided Procedures.

PubMed

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.

Development of a Meso-Scale SMA-Based Torsion Actuator for Image-Guided Procedures

PubMed Central

Sheng, Jun; Gandhi, Dheeraj; Gullapalli, Rao; Simard, J. Marc; Desai, Jaydev P.

2016-01-01

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. PMID:28210189

Quasi-periodic oscillations in short recurring bursts of magnetars SGR 1806–20 and SGR 1900+14 observed with RXTE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huppenkothen, D.; Heil, L. M.; Watts, A. L.

2014-11-10

Quasi-periodic oscillations (QPOs) observed in the giant flares of magnetars are of particular interest due to their potential to open up a window into the neutron star interior via neutron star asteroseismology. However, only three giant flares have been observed. We therefore make use of the much larger data set of shorter, less energetic recurrent bursts. Here, we report on a search for QPOs in a large data set of bursts from the two most burst-active magnetars, SGR 1806-20 and SGR 1900+14, observed with Rossi X-ray Timing Explorer. We find a single detection in an averaged periodogram comprising 30 burstsmore » from SGR 1806–20, with a frequency of 57 Hz and a width of 5 Hz, remarkably similar to a giant flare QPO observed from SGR 1900+14. This QPO fits naturally within the framework of global magneto-elastic torsional oscillations employed to explain giant flare QPOs. Additionally, we uncover a limit on the applicability of Fourier analysis for light curves with low background count rates and strong variability on short timescales. In this regime, standard Fourier methodology and more sophisticated Fourier analyses fail in equal parts by yielding an unacceptably large number of false-positive detections. This problem is not straightforward to solve in the Fourier domain. Instead, we show how simulations of light curves can offer a viable solution for QPO searches in these light curves.« less

Transient Torque Method: A Fast and Nonintrusive Technique to Simultaneously Determine Viscosity and Electrical Conductivity of Semiconducting and Metallic Melts

NASA Technical Reports Server (NTRS)

Li, C.; Ban, H.; Lin, B.; Scripa, R. N.; Su, C.-H.; Lehoczky, S. L.; Zhu, S.

2004-01-01

A transient torque method was developed to rapidly and simultaneously determine the viscosity and electrical conductivity of liquid metals and molten semiconductors. The experimental setup of the transient torque method is similar to that of the oscillation cup method. The melt sample is sealed inside a fused silica ampoule, and the ampoule is suspended by a long quartz fiber to form a torsional oscillation system. A rotating magnetic field is used to induce a rotating flow in the conductive melt, which causes the ampoule to rotate around its vertical axis. A sensitive angular detector is used to measure the deflection angle of the ampoule. Based on the transient behavior of the deflection angle as the rotating magnetic field is applied, the electrical conductivity and viscosity of the melt can be obtained simultaneously by numerically fitting the data to a set of governing equations. The transient torque viscometer was applied successfully to measure the viscosity and electrical conductivity of high purity mercury at 53.4 C. The results were in excellent agreement with published data. The method is nonintrusive; capable of rapid measurement of the viscosity of toxic, high vapor pressure melts at elevated temperatures. In addition, the transient torque viscometer can also be operated as an oscillation cup viscometer to measure just the viscosity of the melt or as a rotating magnetic field method to determine the electrical conductivity of a melt or a solid if desired.

Modeling and analysis of friction clutch at a driveline for suppressing car starting judder

NASA Astrophysics Data System (ADS)

Li, Liping; Lu, Zhaijun; Liu, Xue-Lai; Sun, Tao; Jing, Xingjian; Shangguan, Wen-Bin

2018-06-01

Car judder is a kind of back-forth vibration during vehicle starting which caused by the torsional oscillation of the driveline. This paper presents a systematic study on the dynamic response characteristics of the clutch driven disc for suppression of the judder during vehicle starting. Self-excited vibration behavior of the clutch driven disc is analyzed based on the developed 4DOF non-linear multi-body dynamic model of the clutch driving process considering stick-slip characteristics and using Karnopp friction models. Physical parameters of a clutch determining the generations of the judder behaviors are discussed and the revised designs of the driven disc of a clutch for suppression of the judder are consequently investigated and validated with experiments for two real cars.

Dielectric Constant Measurements of Solid 4He

NASA Astrophysics Data System (ADS)

Yin, L.; Xia, J. S.; Huan, C.; Sullivan, N. S.; Chan, M. H. W.

2011-03-01

Careful measurements of the dielectric properties of solid 4He have been carried out down to 35 mK, considerably lower than the temperature range of previous studies. The sample was prepared from high purity gas with 3He concentrations of the order of 200 ppb and were formed by the blocked capillary method. The molar volume of the sample was 20.30 cm3. The dielectric constant of the samples was found to be independent of temperature down to 120 mK before showing a continuous increase with decreasing temperature and saturating below 50 mK. The total increase in ɛ is 2 parts in 10-5. The temperature dependence of ɛ mimics the increase in the resonant frequency found in the torsional oscillator studies and also the increase found in the shear modulus measurements.

Improving the sensitivity of a torsion pendulum by using an optical spring method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Qinglan; Yeh Hsienchi; Zhou Zebing

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 pendulummore » are reduced, and the minimum detectable response torque in high-frequency region can be reduced accordingly.« less

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

PubMed

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

2009-12-01

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

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

Can Gravity Probe B usefully constrain torsion gravity theories?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flanagan, Eanna E.; Rosenthal, Eran

2007-06-15

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

Inter-study reproducibility of left ventricular torsion and torsion rate quantification using MR myocardial feature tracking.

PubMed

Kowallick, Johannes T; Morton, Geraint; Lamata, Pablo; Jogiya, Roy; Kutty, Shelby; Lotz, Joachim; Hasenfuß, Gerd; Nagel, Eike; Chiribiri, Amedeo; Schuster, Andreas

2016-01-01

To determine the inter-study reproducibility of MR feature tracking (MR-FT) derived left ventricular (LV) torsion and torsion rates for a combined assessment of systolic and diastolic myocardial function. Steady-state free precession (SSFP) cine LV short-axis stacks were acquired at 9:00 (Exam A), 9:30 (Exam B), and 14:00 (Exam C) in 16 healthy volunteers at 3 Tesla. SSFP images were analyzed offline using MR-FT to assess rotational displacement in apical and basal slices. Global peak torsion, peak systolic and peak diastolic torsion rates were calculated using different definitions ("twist", "normalized twist" and "circumferential-longitudinal (CL) shear angle"). Exam A and B were compared to assess the inter-study reproducibility. Morning and afternoon scans were compared to address possible diurnal variation. The different methods showed good inter-study reproducibility for global peak torsion (intraclass correlation coefficient [ICC]: 0.90-0.92; coefficient of variation [CoV]: 19.0-20.3%) and global peak systolic torsion rate (ICC: 0.82-0.84; CoV: 25.9-29.0%). Conversely, global peak diastolic torsion rate showed little inter-study reproducibility (ICC: 0.34-0.47; CoV: 40.8-45.5%). Global peak torsion as determined by the CL shear angle showed the best inter-study reproducibility (ICC: 0.90;CoV: 19.0%). MR-FT results were not measurably affected by diurnal variation between morning and afternoon scans (CL shear angle: 4.8 ± 1.4°, 4.8 ± 1.5°, and 4.1 ± 1.6° for Exam A, B, and C, respectively; P = 0.21). MR-FT based derivation of myocardial peak torsion and peak systolic torsion rate has high inter-study reproducibility as opposed to peak diastolic torsion rate. The CL shear angle was the most reproducible parameter independently of cardiac anatomy and may develop into a robust tool to quantify cardiac rotational mechanics in longitudinal MR-FT patient studies. © 2015 Wiley Periodicals, Inc.

Determination of the Glass-Transition Temperature of GRPS and CFRPS Using a Torsion Pendulum in Regimes of Freely Damped Vibrations and Quasi-Stastic Torsion of Specimens

NASA Astrophysics Data System (ADS)

Startsev, V. O.; Lebedev, M. P.; Molokov, M. V.

2018-03-01

A method to measure the glass-transition temperature of polymers and polymeric matrices of composite materials with the help of an inverse torsion pendulum over a wide range of temperatures is considered combining the method of free torsional vibrations and a quasi-static torsion of specimens. The glass-transition temperature Tg of a KMKS-1-80. T10 fiberglass, on increasing the frequency of freely damped torsional vibrations from 0.7 to 9.6 Hz, was found to increase from 132 to 140°C. The value of Tg of these specimens, determined by measuring the work of their torsion through a small fixed angle was 128.6°C ± 0.8°C. It is shown that the use of a torsion pendulum allows one to determine the glass-transition temperature of polymeric or polymer matrices of PCMs in dynamic and quasi-static deformation regimes of specimens.

Frequency-dependent solvent friction and torsional damping in liquid 1,2-difluoroethane

NASA Astrophysics Data System (ADS)

MacPhail, Richard A.; Monroe, Frances C.

1991-04-01

We have used Raman spectroscopy to study the torsional dynamics, rotational dynamics, and conformational solvation energy of liquid 1,2-difluoroethane. From the Raman intensities, we obtain Δ H(g-t) = -2.4±0.1 kcal/mol, indicating strong dipolar solvation of the gauche conformer. We analyze the Raman linewidths of the CCF bending bands to obtain the zero-frequency torsional damping coefficient or well friction for the gauche conformer, and from the linewidth of the torsion band we obtain the friction evaluated at the torsional frequency. The zero-frequency well friction shows deviations from hydrodynamic behavior reminiscent of those observed for barrier friction, whereas the high-frequency friction is considerably smaller in magnitude and independent of temperature and viscosity. The zero-frequency torsional friction correlates linearly with the rotational friction. It is argued that the small amplitude of the torsional fluctuations emphasizes the short distance, or high wavevector components of the solvent friction. Dielectric friction apparently does not contribute to the torsional friction at the observed frequencies.

Effects of {10-12} Twins on Dynamic Torsional Properties of Extruded AZ31 Magnesium Alloy

NASA Astrophysics Data System (ADS)

Lee, Jong Un; Song, Seok Weon; Kim, Yongjin; Kim, Sang-Hoon; Kim, Ye Jin; Park, Sung Hyuk

2018-03-01

Effects of initial twins on dynamic torsional properties of extruded AZ31 alloy were investigated by introducing {10-12} twins into it through precompression to 3 and 6% strains along the extrusion direction and performing torsional testing at a strain rate of 1.4 × 103 s-1 using a torsional Kolsky bar system. The as-extruded sample without twins showed higher dynamic torsional properties than the precompressed samples with many initial twins; the maximum shear strength and fracture shear strain decreased with increasing amount of initial twins. In the as-extruded sample, twinning occurred vigorously throughout the gage section of the tubular specimen during high-strain-rate torsional tests, resulting in heavily deformed morphology, many macrocracks, and rough fractured surfaces. The increased amount of initial twins suppressed the twinning behavior and localized the applied torsional deformation; this resulted in an almost unchanged sample shape, no secondary cracks, and a flat fracture plane, thereby deteriorating the dynamic torsional properties of the extruded alloy.

Cumulative Axial and Torsional Fatigue: An Investigation of Load-Type Sequencing Effects

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

2000-01-01

Cumulative fatigue behavior of a wrought cobalt-base superalloy, Haynes 188 was investigated at 538 C under various single-step sequences of axial and torsional loading conditions. Initially, fully-reversed, axial and torsional fatigue tests were conducted under strain control at 538 C on thin-walled tubular specimens to establish baseline fatigue life relationships. Subsequently, four sequences (axial/axial, torsional/torsional, axial/torsional, and torsional/axial) of two load-level fatigue tests were conducted to characterize both the load-order (high/low) and load-type sequencing effects. For the two load-level tests, summations of life fractions and the remaining fatigue lives at the second load-level were computed by the Miner's Linear Damage Rule (LDR) and a nonlinear Damage Curve Approach (DCA). In general, for all four cases predictions by LDR were unconservative. Predictions by the DCA were within a factor of two of the experimentally observed fatigue lives for a majority of the cumulative axial and torsional fatigue tests.

The vibrationally adiabatic torsional potential energy surface of trans-stilbene

NASA Astrophysics Data System (ADS)

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

2007-05-01

The effect of vibrational Zero Point Energy (ZPE) on the torsional barriers of trans-stilbene is studied in the adiabatic approximation. The two torsional modes corresponding to phenyl rotation are explicitly separated, and the remaining modes are treated as normal coordinates. ZPE reduces the adiabatic barrier along the in-phase torsion from 198 to 13 cm -1. A one-dimensional adiabatic potential for the anti-phase torsion, including the ZPE of the in-phase torsion, reduces the adiabatic barrier from 260 to 58 cm -1. Comparison with recent electronic structure benchmark calculations suggests that vibrational corrections play a significant role in trans-stilbene's experimentally observed planar structure.

Should Torsion Balance Technique Continue to be Taught to Pharmacy Students?

PubMed

Bilger, Rhonda; Chereson, Rasma; Salama, Noha Nabil

2017-06-01

Objective. To determine the types of balances used in compounding pharmacies: torsion or digital. Methods. A survey was mailed to the pharmacist-in-charge at 698 pharmacies, representing 47% of the pharmacies in Missouri as of July 2013. The pharmacies were randomly selected and stratified by region into eight regions to ensure a representative sample. Information was gathered regarding the type and use of balances and pharmacists' perspectives on the need to teach torsion balance technique to pharmacy students. Results. The response rate for the survey was 53.3%. Out of the total responses received, those pharmacies having a torsion balance, digital balance or both were 46.8%, 27.4% and 11.8%, respectively. About 68.3% of respondents compound prescriptions. The study showed that 52% of compounding pharmacies use torsion balances in their practice. Of those with a balance in their pharmacy, 65.6% favored continuation of torsion balance instruction. Conclusions. Digital balances have become increasingly popular and have replaced torsion balances in some pharmacies, especially those that compound a significant number of prescriptions. The results of this study indicate that torsion balances remain integral to compounding practice. Therefore, students should continue being taught torsion balance technique at the college.

Should Torsion Balance Technique Continue to be Taught to Pharmacy Students?

PubMed Central

Bilger, Rhonda; Chereson, Rasma

2017-01-01

Objective. To determine the types of balances used in compounding pharmacies: torsion or digital. Methods. A survey was mailed to the pharmacist-in-charge at 698 pharmacies, representing 47% of the pharmacies in Missouri as of July 2013. The pharmacies were randomly selected and stratified by region into eight regions to ensure a representative sample. Information was gathered regarding the type and use of balances and pharmacists’ perspectives on the need to teach torsion balance technique to pharmacy students. Results. The response rate for the survey was 53.3%. Out of the total responses received, those pharmacies having a torsion balance, digital balance or both were 46.8%, 27.4% and 11.8%, respectively. About 68.3% of respondents compound prescriptions. The study showed that 52% of compounding pharmacies use torsion balances in their practice. Of those with a balance in their pharmacy, 65.6% favored continuation of torsion balance instruction. Conclusions. Digital balances have become increasingly popular and have replaced torsion balances in some pharmacies, especially those that compound a significant number of prescriptions. The results of this study indicate that torsion balances remain integral to compounding practice. Therefore, students should continue being taught torsion balance technique at the college. PMID:28720913

Improving Tensile and Compressive Properties of an Extruded AZ91 Rod by the Combined Use of Torsion Deformation and Aging Treatment

PubMed Central

Song, Bo; Wang, Chunpeng; Guo, Ning; Pan, Hucheng; Xin, Renlong

2017-01-01

In this study, AZ91 magnesium alloy rods were used to investigate the effects of torsion deformation on microstructure and subsequent aging behavior. Extruded AZ91 rod has a uniform microstructure and typical fiber texture. Torsion deformation can generate a gradient microstructure on the cross-section of the rod. After torsion, from the center to the edge in the cross-section of the rod, both stored dislocations and area fraction of {10-12} twins gradually increase, and the basal pole of the texture tends to rotate in the ED direction. Direct aging usually generates coarse discontinuous precipitates and fine continuous precipitates simultaneously. Both twin structures and dislocations via torsion deformation can be effective microstructures for the nucleation of continuous precipitates during subsequent aging. Thus, aging after torsion can promote continuous precipitation and generate gradient precipitation characteristics. Both aging treatment and torsion deformation can reduce yield asymmetry, and torsion deformation enhances the aging hardening effect by promoting continuous precipitation. Therefore, combined use of torsion deformation and aging treatment can effectively enhance the yield strength and almost eliminate the yield asymmetry of the present extruded AZ91 rod. Finally, the relevant mechanisms are discussed. PMID:28772638

Faraday Rotation and Primordial Magnetic Fields Constraints on Ultraviolet Lorentz Violation with Spacetime Torsion

NASA Astrophysics Data System (ADS)

de Andrade, L. C. Garcia

Recently Kahniashvili et al.9 presented a unified treatment for ultraviolet Lorentz violation (LV) testing through electromagnetic wave propagation in magnetized plasmas, based on dispersion and rotation measured data. Based on the fact discovered recently by Kostelecky et al., 3 that LV may place constraints on spacetime torsion, in this paper it is shown that on the limit of very low frequency torsion waves, it is possible to constraint torsion from Faraday rotation and CMB on a similar fashion as Minkowski spacetime plus torsion. Here, the Maxwells modified equations are obtained by a perturbative method introduced by de Sabbata and Gasperini [Introduction to Gravitation (World Scientific, 1980)]. Torsion is constraint to QCMB≈10-18 GeV which is not so stringent as the 10-31 GeV obtained by Kostelecky et al. However, Gamma-Ray Bursts (GRBs) may lead to the more string value obtained by Kostelecky et al.Another interesting constraint on torsion is shown to be placed by galactic dynamo seed magnetic fields. For torsion effects be compatible with the galactic dynamo seeds, one obtains a torsion constraint of 10-33 GeV which is two orders of magnitude more stringent that the above Kostelecky et al. limit.

[Correlation analysis on the disorders of patella-femoral joint and torsional deformity of tibia].

PubMed

Sun, Zhen-Jie; Yuan, Yi; Liu, Rui-Bo

2015-03-01

To reveal the possible mechanism involved in patella-femoral degenerative arthritis (PFDA) in- duced by torsion-deformity of tibia via analyzing the relationship between torsion-deformity of the tibia in patients with PFDA and the disorder of patella-femoral joint under the static and dynamic conditions. From October 2009 to October 2010, 50 patients (86 knees, 24 knees of male patients and 62 knees of female patients) with PFDA were classified as disease group and 16 people (23 knees, 7 knees of males and 16 knees of females) in the control group. The follow indexes were measured: the torsion-angle of tibia on CT scanning imagings, the patella-femoral congruence angle and lateral patella-femoral angle under static and dynamic conditions when the knee bent at 30 degrees of flexion. Based on the measurement results, the relationship between the torsion-deformity of tibias and the disorders of patella-femoral joints in patients with PFDA were analyzed. Finally,the patients were divided into three groups including large torsion-angle group, small torsion-angle group and normal group according to the size of torsion-angle, in order to analyze the relationship between torsion-deformity and disorders of patella-femoral joint, especially under the dynamic conditions. Compared with patients without PFDA, the ones with PFDA had bigger torsion-angle (30.30 ± 7.11)° of tibia, larger patella-femoral congruence angle (13.20 ± 3.94)° and smaller lateral patella-femoral angle (12.30 ± 3.04)°. The congruence angle and lateral patella-femoral angle under static and dynamic conditions had statistical differences respectively in both too-big torsion-angle group and too-small torsion-angle group. The congruence angle and lateral patella-femoral angle under static and dynamic conditions had no statistical differences in normal torsion-angle group. Torsion-deformity of tibia is the main reason for disorder of patella-femoral joint in the patients with PFDA. Torsion-deformity of tibia is always accompanied by instability of patella-femoral joint,especially under the dynamic condition, thus causing PFDA. It can not only provide arrangement information and degenerative condition of patella-femoral joint,but also provide guidance through the analysis on the relationship for better clinical prevention and early treatment of degenerative bone and joint disease.

Newton-Cartan gravity and torsion

NASA Astrophysics Data System (ADS)

Bergshoeff, Eric; Chatzistavrakidis, Athanasios; Romano, Luca; Rosseel, Jan

2017-10-01

We compare the gauging of the Bargmann algebra, for the case of arbitrary torsion, with the result that one obtains from a null-reduction of General Relativity. Whereas the two procedures lead to the same result for Newton-Cartan geometry with arbitrary torsion, the null-reduction of the Einstein equations necessarily leads to Newton-Cartan gravity with zero torsion. We show, for three space-time dimensions, how Newton-Cartan gravity with arbitrary torsion can be obtained by starting from a Schrödinger field theory with dynamical exponent z = 2 for a complex compensating scalar and next coupling this field theory to a z = 2 Schrödinger geometry with arbitrary torsion. The latter theory can be obtained from either a gauging of the Schrödinger algebra, for arbitrary torsion, or from a null-reduction of conformal gravity.

Further studies of stall flutter and nonlinear divergence of two-dimensional wings

NASA Technical Reports Server (NTRS)

Dugundji, J.; Chopra, I.

1975-01-01

An experimental investigation is made of the purely torsional stall flutter of a two-dimensional wing pivoted about the midchord, and also of the bending-torsion stall flutter of a two-dimensional wing pivoted about the quarterchord. For the purely torsional flutter case, large amplitude limit cycles ranging from + or - 11 to + or - 160 degrees were observed. Nondimensional harmonic coefficients were extracted from the free transient vibration tests for amplitudes up to 80 degrees. Reasonable nondimensional correlation was obtained for several wing configurations. For the bending-torsion flutter case, large amplitude coupled limit cycles were observed with torsional amplitudes as large as + or - 40 degrees. The torsion amplitudes first increased, then decreased with increasing velocity. Additionally, a small amplitude, predominantly torsional flutter was observed when the static equilibrium angle was near the stall angle.

Automatic Fourier transform and self-Fourier beams due to parabolic potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yiqi, E-mail: zhangyiqi@mail.xjtu.edu.cn; Liu, Xing; Belić, Milivoj R., E-mail: milivoj.belic@qatar.tamu.edu

We investigate the propagation of light beams including Hermite–Gauss, Bessel–Gauss and finite energy Airy beams in a linear medium with parabolic potential. Expectedly, the beams undergo oscillation during propagation, but quite unexpectedly they also perform automatic Fourier transform, that is, periodic change from the beam to its Fourier transform and back. In addition to oscillation, the finite-energy Airy beams exhibit periodic inversion during propagation. The oscillating period of parity-asymmetric beams is twice that of the parity-symmetric beams. Based on the propagation in parabolic potential, we introduce a class of optically-interesting beams that are self-Fourier beams—that is, the beams whose Fouriermore » transforms are the beams themselves.« less

Rat disc torsional mechanics: effect of lumbar and caudal levels and axial compression load.

PubMed

Espinoza Orías, Alejandro A; Malhotra, Neil R; Elliott, Dawn M

2009-03-01

Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior to evaluate changes after model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Cadaveric biomechanical study. Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. The apparent torsional modulus was higher in the lumbar region than in the caudal region: 0.081+/-0.026 (MPa/degrees, mean+/-SD) for lumbar axially loaded; 0.066+/-0.028 for caudal axially loaded; 0.091+/-0.033 for lumbar in pure torsion; and 0.056+/-0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/degrees. Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics.

Ozil IP torsional mode versus combined torsional/longitudinal microcoaxial phacoemulsification.

PubMed

Helvacioglu, Firat; Tunc, Zeki; Yeter, Celal; Oguzhan, Hasan; Sencan, Sadik

2012-01-01

To compare the safety and efficacy of microcoaxial phacoemulsification surgeries performed with the Ozil Intelligent Phaco (IP) torsional mode and combined torsional/longitudinal ultrasound (US) mode using the Infiniti Vision System (Alcon Laboratories). In this prospective randomized comparative study, 60 eyes were assigned to 2.2-mm microcoaxial phacoemulsification using the Ozil IP torsional mode (group 1) or combined torsional/longitudinal US mode (group 2). The primary outcome measures were US time (UST), cumulative dissipated energy (CDE), longitudinal and torsional ultrasound amplitudes, mean operation time, mean volume of balanced salt solution (BSS) used, and surgical complications. Both groups included 30 eyes. Mean UST, CDE, and longitudinal and torsional ultrasound amplitudes in group 1 were 1 minute 15±34.33 seconds, 8.74±5.64, 0.43±0.74, and 25.56±8.56, respectively, and these parameters in group 2 were 1 minute 40±51.44 seconds, 9.28±5.99, 3.64±1.55, and 3.71±1.34, respectively. UST and longitudinal amplitudes were found to be significantly low in group 1 (p<0.001, p<0.001), whereas torsional amplitude was found to be significantly high in this group (p=0.001). Mean volumes of BSS used in groups 1 and 2 were 63.30±18.00 cc and 84.50±28.65 cc, respectively (p=0.001). The Ozil IP torsional mode may provide more effective lens removal than the combined torsional/longitudinal US mode with a lower UST and volume of BSS used.

Torsional ARC Effectively Expands the Visual Field in Hemianopia

PubMed Central

Satgunam, PremNandhini; Peli, Eli

2012-01-01

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

Eye-Safe Lidar

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1989-01-01

Laser infrared radar (lidar) undergoing development harmless to human eyes, consists almost entirely of solid-state components, and offers high range resolution. Operates at wavelength of about 2 micrometers. If radiation from such device strikes eye, almost completely absorbed by cornea without causing damage, even if aimed directly at eye. Continuous-wave light from laser oscillator amplified and modulated for transmission from telescope. Small portion of output of oscillator fed to single-mode fiber coupler, where mixed with return pulses. Intended for remote Doppler measurements of winds and differential-absorption measurements of concentrations of gases in atmosphere.

UNIVERSE IN A BLACK HOLE IN EINSTEIN–CARTAN GRAVITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popławski, Nikodem, E-mail: NPoplawski@newhaven.edu

The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least action. The coupling between the spin of elementary particles and torsion in the Einstein–Cartan theory of gravity generates gravitational repulsion at extremely high densities in fermionic matter, approximated as a spin fluid, and thus avoids the formation of singularities in black holes. The collapsing matter in a black hole should therefore bounce at a finite density and then expand into a new region of space onmore » the other side of the event horizon, which may be regarded as a nonsingular, closed universe. We show that quantum particle production caused by an extremely high curvature near a bounce can create enormous amounts of matter, produce entropy, and generate a finite period of exponential expansion (inflation) of this universe. This scenario can thus explain inflation without a scalar field and reheating. We show that, depending on the particle production rate, such a universe may undergo several nonsingular bounces until it has enough matter to reach a size at which the cosmological constant starts cosmic acceleration. The last bounce can be regarded as the big bang of this universe.« less

Universe in a Black Hole in Einstein-Cartan Gravity

NASA Astrophysics Data System (ADS)

Popławski, Nikodem

2016-12-01

The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least action. The coupling between the spin of elementary particles and torsion in the Einstein-Cartan theory of gravity generates gravitational repulsion at extremely high densities in fermionic matter, approximated as a spin fluid, and thus avoids the formation of singularities in black holes. The collapsing matter in a black hole should therefore bounce at a finite density and then expand into a new region of space on the other side of the event horizon, which may be regarded as a nonsingular, closed universe. We show that quantum particle production caused by an extremely high curvature near a bounce can create enormous amounts of matter, produce entropy, and generate a finite period of exponential expansion (inflation) of this universe. This scenario can thus explain inflation without a scalar field and reheating. We show that, depending on the particle production rate, such a universe may undergo several nonsingular bounces until it has enough matter to reach a size at which the cosmological constant starts cosmic acceleration. The last bounce can be regarded as the big bang of this universe.

Optically probing torsional superelasticity in spider silks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit

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-basedmore » materials and devices.« less

Many-body and spin-orbit aspects of the alternating current phenomena

NASA Astrophysics Data System (ADS)

Glenn, Rachel M.

The thesis reports on research in the general field of light interaction with matter. According to the topics addressed, it can be naturally divided into two parts: Part I, many-body aspects of the Rabi oscillations which a two-level systems undergoes under a strong resonant drive; and Part II, absorption of the ac field between the spectrum branches of two-dimensional fermions that are split by the combined action of Zeeman and spin-orbit (SO) fields. The focus of Part I is the following many-body effects that modify the conventional Rabi oscillations: Chapter 1, coupling of a two-level system to a single vibrational mode of the environment. Chapter 2, correlated Rabi oscillations in two electron-hole systems coupled by tunneling with strong electron-hole attraction. In Chapter 1, a new effect of Rabi-vibronic resonance is uncovered. If the frequency of the Rabi oscillations, OR, is close to the frequency o0 of the vibrational mode, the oscillations acquire a collective character. It is demonstrated that the actual frequency of the collective oscillations exhibits a bistable behavior as a function of OR - o0. The main finding in Chapter 2 is, that the Fourier spectrum of the Rabi oscillations in two coupled electron-hole systems undergoes a strong transformation with increasing O R. For OR smaller than the tunneling frequency, the spectrum is dominated by a low-frequency (<< OR ) component and contains two additional weaker lines; conventional Rabi oscillations are restored only as OR exceeds the electron-hole attraction strength. The highlight of Part II is a finding that, while the spectrum of absorption between either Zeeman-split branches or SO-split branches is close to a delta-peak, in the presence of both, it transforms into a broad line with singular behavior at the edges. In particular, when the magnitudes of Zeeman and SO are equal, absorption of very low (much smaller than the splitting) frequencies become possible. The shape of the absorption spectrum is highly anisotropic with respect to the exciting field. This peculiar behavior of the absorption is also studied in wire geometry, where the interplay between two couplings (Zeeman and spin-orbit splitting) affects the shape of numerous absorption peaks.

The 2004 Hyperflare from SGR 1806-20: Further Evidence for Global Torsional Vibrations

NASA Technical Reports Server (NTRS)

Strohmayer, Tod E.; Watts, Anna L.

2006-01-01

We report an analysis of the archival Rossi X-ray Timing Explorer (RXTE) data from the December 2004 hyperflare from SGR 1806-20. In addition to the approx. equal to 90 Hz QPO first discovered by Israel et al., we report the detection of higher frequency oscillations at approx. equal to 150, 625, and 1,835 Hz. In addition to these frequencies there are indications of oscillations at approx. equal to 720, and 2,384 Hz, but with lower significances. The 150 Hz QPO has a width (FWHM) of about 17 Hz, an average amplitude (rms) of 6.5%, and is detected in average power spectra centered on the rotational phase of the strongest peak in the pulse profile. This is approximately half a rotational cycle from the phase at which the 90 Hz QPO is strongly detected. The 625 Hz oscillation was first detected in an average power spectrum from nine successive cycles beginning approximately 180 s after the initial hard spike. It has a width (FWHM) of approx. equal to 2 Hz and an average amplitude (rms) during this interval of 9%. We find a strong detection of the 625 Hz oscillation in a pair of successive rotation cycles beginning about 230 s after the start of the flare. In these cycles we also detect the 1,835 Hz QPO with the 625 Hz oscillation. The rotational phase in which the 625 Hz &PO is detected is similar to that for the 90 Hz QPO, indeed, this feature is seen in the same average power spectrum. During the time the 625 Hz QPO is detected we also confirm the simultaneous presence of 30 and 92 Hz QPOs, first reported by Israel et al. The centroid frequency of the 625 Hz QPO detected with RXTE is within 1 Hz of the M 626 Hz oscillation recently found in RHESSI data from this hyperflare by Watts & Strohmayer, however, the two detections were made in different phase and energy intervals. Nevertheless, we argue that the two results likely represent detections of the same oscillation frequency intrinsic to the source, but we comment on some of the difficulties in making direct comparisons between the RXTE and RHESSI measurements

Nonsmooth modal analysis of a N-degree-of-freedom system undergoing a purely elastic impact law

NASA Astrophysics Data System (ADS)

Legrand, Mathias; Junca, Stéphane; Heng, Sokly

2017-04-01

The dynamics of a N-degree-of-freedom autonomous oscillator undergoing an energy-preserving impact law on one of its masses is investigated in the light of nonlinear modal analysis. The impacted rigid foundation provides a natural Poincaré section of the investigated system from which is formulated a smooth First Return Map well-defined away from the grazing trajectory. In order to focus on the impact-induced nonlinearity, the oscillator is assumed linear. Continuous one-parameter families of T-periodic orbits featuring one impact per period and lying on two-dimensional invariant manifolds in the state-space are shown to exist. The geometry of these piecewise-smooth manifolds is such that a linear "flat" portion (on which contact is not activated) is continuously attached to a purely nonlinear portion (on which contact is activated once per period) exhibiting a velocity discontinuity through a grazing orbit. These features explain the newly introduced terminology "Nonsmooth modal analysis". The stability of the periodic orbits lying on the invariant manifolds is also explored by calculating the eigenvalues of the linearized First Return Map. Internal resonances and multiple impacts per period are not addressed in this work. However, the pre-stressed case is succinctly described and extensions to multiple oscillators as well as self-contact are discussed.

Torsional splittings in the diode laser slit-jet spectra of the ν6 fundamental of 1-chloro-1,1-difluoroethane (HCFC-142b)

NASA Astrophysics Data System (ADS)

di Lauro, Carlo; D'Amico, Giuseppe; Snels, Marcel

2009-04-01

High resolution infrared spectra (0.001 cm -1 FWHM) have been measured for mixtures of 1-chloro-1,1-difluoroethane in Ne, expanded in a supersonic planar jet. The ν6 fundamental, infrared active with a dominant parallel transition moment, exhibits a remarkable splitting of about 0.035 cm -1 for both 35Cl and 37Cl isotopomers. Several mechanisms of interaction of ν6 with states with high torsional excitation are critically examined to explain the observed effect. It is concluded that the observed torsional splitting patterns can be explained in terms of a torsional Coriolis interaction between ν6 and a highly excited torsional mode, 6 ν18. A full numerical analysis, performed including a torsional Coriolis term in the Hamiltonian, shows that the interaction mechanism requires a torsional barrier height of about 1270 cm -1.

Nonminimal couplings, gravitational waves, and torsion in Horndeski's theory

NASA Astrophysics Data System (ADS)

Barrientos, José; Cordonier-Tello, Fabrizio; Izaurieta, Fernando; Medina, Perla; Narbona, Daniela; Rodríguez, Eduardo; Valdivia, Omar

2017-10-01

The Horndeski Lagrangian brings together all possible interactions between gravity and a scalar field that yield second-order field equations in four-dimensional spacetime. As originally proposed, it only addresses phenomenology without torsion, which is a non-Riemannian feature of geometry. Since torsion can potentially affect interesting phenomena such as gravitational waves and early universe inflation, in this paper we allow torsion to exist and propagate within the Horndeski framework. To achieve this goal, we cast the Horndeski Lagrangian in Cartan's first-order formalism and introduce wave operators designed to act covariantly on p -form fields that carry Lorentz indices. We find that nonminimal couplings and second-order derivatives of the scalar field in the Lagrangian are indeed generic sources of torsion. Metric perturbations couple to the background torsion, and new torsional modes appear. These may be detected via gravitational waves but not through Yang-Mills gauge bosons.

Historical Variations in Inner Core Rotation and Polar Motion at Decade Timescales

NASA Astrophysics Data System (ADS)

Dumberry, M.

2005-12-01

Exchanges of angular momentum between the mantle, the fluid core and the solid inner core result in changes in the Earth's rotation. Torques in the axial direction produce changes in amplitude, or changes in length of day, while torques in the equatorial direction lead to changes in orientation of the rotation vector with respect to the mantle, or polar motion. In this work, we explore the possibility that a combination of electromagnetic and gravitational torques on the inner core can reproduce the observed decadal variations in polar motion known as the Markowitz wobble. Torsional oscillations, which involve azimuthal motions in the fluid core with typical periods of decades, entrain the inner core by electromagnetic traction. When the inner core is axially rotated, its surfaces of constant density are no longer aligned with the gravitational potential from mantle density heterogeneities, and this results in a gravitational torque between the two. The axial component of this torque has been previously described and is believed to be partly responsible for decadal changes in length of day. In this work, we show that it has also an equatorial component, which produces a tilt of the inner core and results in polar motion. The polar motion produced by this mechanism depends on the density structure in the mantle, the rheology of the inner core, and the time-history of the angle of axial misalignment between the inner core and the mantle. We reconstruct the latter using a model of torsional oscillations derived from geomagnetic secular variation. From this time-history, and by using published models of mantle density structure, we show that we can reproduce the salient characteristics of the Markowitz wobble: an eccentric decadal polar motion of 30-50 milliarcsecs oriented along a specific longitude. We discuss the implications of this result, noting that a match in both amplitude and phase of the observed Markowitz wobble allows the recovery of the historical rotational variations of the inner core, and also provides constraints on structure, rheology and dynamics of the Earth's deep interior that cannot be observed directly.

Anharmonic Vibrations of an "Ideal" Hooke's Law Oscillator

ERIC Educational Resources Information Center

Thomchick, John; McKelvey, J. P.

1978-01-01

Presents a model describing the vibrations of a mass connected to fixed supports by "ideal" Hooke's law springs which may serve as a starting point in the study of the properties of irons in a crystal undergoing soft mode activated transition. (SL)

Ovarian torsion in a three-year-old girl.

PubMed

Ochsner, Todd Justin; Roos, Joel A; Johnson, Andrew S; Henderson, Janet L

2010-05-01

Ovarian torsion is the fifth most encountered gynecological emergency requiring surgery. Representing only 2.7% of surgical emergencies, it is an entity that is worth being familiar with in the emergency department (ED). Untreated ovarian torsion may result in loss of ovarian function, tissue necrosis, and death from thromboembolism or sepsis. Presenting with vague symptoms and abdominal pain, diagnosing ovarian torsion can be difficult, especially in children. The objective of this article is to present a case of pediatric ovarian torsion and to review its epidemiology, diagnosis, and treatment. A 3-year-old girl presented to the ED with vomiting, fever, anorexia, and abdominal pain. Initially diagnosed with appendicitis by physical examination and computed tomography scan, this patient was taken to the operating room for surgical exploration. The patient was subsequently found to have ovarian torsion, which was treated appropriately. Although a rare phenomenon, this case serves to increase awareness of the clinical presentation of ovarian torsion in the pediatric patient. Abdominal pain in the female child represents a challenging differential diagnosis, for which a physician must consider ovarian torsion. Copyright (c) 2010. Published by Elsevier Inc.

Lower-extremity rotational profile and toe-walking in preschool children with autism spectrum disorder.

PubMed

Arik, Atilla; Aksoy, Cemalettin; Aysev, Ayla; Akçakin, Melda

2018-04-24

The aim of this study was to establish the torsional and toe-walking profiles of children with autism spectrum disorder (ASD), and to analyze the correlations between torsion, toe-walking, autism severity score, and age. In total, 79 consecutive children with autism were examined to determine their hip rotations, thigh-foot angle, degree of toe-walking, and autism severity. Femoral and tibial torsion values, of the preschool patients, were compared statistically with age-matched controls. The hip rotation profile of the patients was similar to the normal group. Nearly a half of the patients with ASD present excessive external tibial torsion. The difference in the tibial torsion between patients and normal children was statistically significant. A weak correlation was found only between tibial torsion and the autism severity score, but no correlation was found between the other parameters. External tibial torsion is the cardinal and persistent orthopedic manifestation among patients with ASD. Toe-walking is the second most common such manifestation and is an independent orthopedic feature in these patients. External tibial torsion may potentially contribute toward the described gait abnormalities in patients with ASD.

Instability of ocular torsion in zero gravity - Possible implications for space motion sickness

NASA Technical Reports Server (NTRS)

Diamond, Shirley G.; Markham, Charles H.; Money, Ken E.

1990-01-01

It is proposed that study of the eye torsion reflex and its behavior under novel gravitational states may possibly provide the basis for a long-sought test to predict space motion sickness (SMS). Measures of eye torsion such as ocular counterrolling and spontaneous eye torsion, were examined during hypo- and hypergravity in parabolic flight on the NASA KC-135 aircraft. Ten subjects, including two astronauts, one who had experienced SMS and one who had not, were ranked according to scores of torsional inability at 0 G and divided into two equal groups of high and low susceptibility to SMS. At 1.8 G the groups were significantly different in both the instability measure and the measure of torsional ability. No differences were detected in eye torsion in either 0 G or 1.8 G and none of the tests were significantly different in 1 G. Results suggest that tests of eye torsion on the KC-135 might differentiate those who would experience SMS from those who would not, although it is noted that this is not yet proven.

Torsional actuator motor using solid freeform fabricated PZT ceramics

NASA Astrophysics Data System (ADS)

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

2004-07-01

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

Some Properties and Uses of Torsional Overlap Integrals

NASA Astrophysics Data System (ADS)

Mekhtiev, Mirza A.; Hougen, Jon T.

1998-01-01

The first diagonalization step in a rho-axis-method treatment of methyl-top internal rotation problems involves finding eigenvalues and eigenvectors of a torsional Hamiltonian, which depends on the rotational projection quantum numberKas a parameter. Traditionally the torsional quantum numbervt= 0, 1, 2···is assigned to eigenfunctions of givenKin order of increasing energy. In this paper we propose an alternative labeling scheme, using the torsional quantum numbervT, which is based on properties of theK-dependent torsional overlap integrals . In particular, the quantum numbervTis assigned in such a way that torsional wavefunctions |vT,K> vary as slowly as possible whenKchanges by unity. Roughly speaking,vT=vtfor torsional levels below the barrier, whereasvTis more closely related to the free-rotor quantum number for levels above the barrier. Because of the latter fact, we believevTwill in general be a physically more meaningful torsional quantum number for levels above the barrier. The usefulness of overlap integrals for qualitative prediction of torsion-rotation band intensities and for rationalizing the magnitudes of perturbations involving some excitation of the small-amplitude vibrations in an internal rotor problem is also discussed.

Critical current degradation behaviour of GdBCO CC tapes in pure torsion and combined tension-torsion modes

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.

Humeral torsion revisited: a functional and ontogenetic model for populational variation.

PubMed

Cowgill, Libby W

2007-12-01

Anthropological interest in humeral torsion has a long history, and several functional explanations for observed variation in the orientation of the humeral head have been proposed. Recent clinical studies have revived this topic by linking patterns of humeral torsion to habitual activities such as overhand throwing. However, the precise functional implications and ontogenetic history of humeral torsion remain unclear. This study examines the ontogeny of humeral torsion in a large sample of primarily immature remains from six different skeletal collections (n = 407). The results of this research confirm that humeral torsion displays consistent developmental variation within all populations of growing children; neonates display relatively posteriorly oriented humeral heads, and the level of torsion declines steadily into adulthood. As in adults, variation in the angle of humeral torsion in immature individuals varies by population, and these differences arise early in development. However, when examined in the context of the developing muscles of the shoulder complex, it becomes apparent that variation in the angle of humeral torsion is not necessarily related to specific habitual activities. Variability in this feature is more likely caused by a generalized functional imbalance between muscles of medial and lateral rotation that can be produced by a wide variety of upper limb activity patterns during growth. (c) 2007 Wiley-Liss, Inc.

Static vacuum solutions on curved space-times with torsion

NASA Astrophysics Data System (ADS)

Shabani, Hamid; Ziaie, Amir Hadi

2018-06-01

The Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity naturally extends Einstein’s general relativity (GR) to include intrinsic angular momentum (spin) of matter. The main feature of this theory consists of an algebraic relation between space-time torsion and spin of matter, which indeed deprives the torsion of its dynamical content. The Lagrangian of ECKS gravity is proportional to the Ricci curvature scalar constructed out of a general affine connection so that owing to the influence of matter energy-momentum and spin, curvature and torsion are produced and interact only through the space-time metric. In the absence of spin, the space-time torsion vanishes and the theory reduces to GR. It is however possible to have torsion propagation in vacuum by resorting to a model endowed with a nonminimal coupling between curvature and torsion. In the present work we try to investigate possible effects of the higher order terms that can be constructed from space-time curvature and torsion, as the two basic constituents of Riemann-Cartan geometry. We consider Lagrangians that include fourth-order scalar invariants from curvature and torsion and then investigate the resulting field equations. The solutions that we find show that there could exist, even in vacuum, nontrivial static space-times that admit both black holes and naked singularities.

Rat Disc Torsional Mechanics: Effect of Lumbar and Caudal Levels and Axial Compression Load

PubMed Central

Elliott, Dawn M; Espinoza Orías, Alejandro A; Malhotra, Neil R

2009-01-01

Background Context Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior in order to evaluate changes following model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Purpose Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Study Design Cadaveric biomechanical study. Methods Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. Results The apparent torsional modulus was higher in the lumbar region than in the caudal region,: 0.081±0.026 (MPa/°, Mean±SD) for lumbar axially loaded; 0.066±0.028 caudal axially loaded; 0.091±0.033 for lumbar in pure torsion; and 0.056±0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/°. Conclusions Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics. PMID:18495544

Femoral Shaft Torsion in Injured and Uninjured Ballet Dancers and Its Association with Other Hip Measures: A Cross-sectional Study.

PubMed

Hafiz, Eliza; Hiller, Claire E; Nicholson, Leslie L; Nightingale, Elizabeth J; Grimaldi, Alison; Refshauge, Kathryn M

2016-03-01

Low range femoral torsion, termed "lateral shaft torsion," has been associated with greater range of hip external rotation and turnout in dancers. It is also hypothesized that achieving greater turnout at the hip minimizes torsion at the knee, shank, ankle, and foot, and consequently reduces incidence of lower limb injuries. The primary aims of this study were to investigate: 1. differences in range of femoral shaft torsion between dancers with and without lower limb injuries; and 2. the relationship between femoral shaft torsion, hip external rotation range, and turnout. A secondary aim was to examine the relationship between femoral shaft torsion and other hip measures: hip strength, lower limb joint hypermobility, hip stability, and foot progression angle, as explanatory variables. Demographic, dance, and injury data were collected, along with physical measures of femoral shaft torsion, hip rotation range of motion, and turnout. Hip strength, control, lower limb hypermobility, and foot progression angle were also measured. Eighty female dancers, 50 with lower limb injury (20.7 ± 4.8 years of age) and 30 without lower limb injury (17.8 ± 4.1 years of age), participated in the study. There was no difference in range of femoral shaft torsion between the groups (p = 0.941). Femoral shaft torsion was weakly correlated with range of hip external rotation (r = -0.034, p = 0.384) and turnout (r = -0.066, p = 0.558). Injured dancers had a significantly longer training history than non-injured dancers (p = 0.001). It was concluded that femoral shaft torsion does not appear to be associated with the overall incidence of lower limb injury in dancers or to be a primary factor influencing extent of turnout in this population.

Feasibility of using near-infrared spectroscopy to diagnose testicular torsion: an experimental study in sheep.

PubMed

Capraro, Geoffrey A; Mader, Timothy J; Coughlin, Bret F; Lovewell, Carolanne; St Louis, Myron R L; Tirabassi, Michael; Wadie, George; Smithline, Howard A

2007-04-01

To assess whether near-infrared spectroscopy can detect testicular hypoxia in a sheep model of testicular torsion within 6 hours of experimental torsion. This was a randomized, controlled, nonblinded study. Trans-scrotal, near-infrared, spectroscopy-derived testicular tissue saturation of oxygen values were obtained from the posterior hemiscrota of 6 anesthetized sheep at baseline and every 15 minutes for 6 hours after either experimental-side, 720-degree, unilateral, medial testicular torsion and orchidopexy or control-side sham procedure with orchidopexy and then for 75 minutes after reduction of torsion and pexy. Color Doppler ultrasonography was performed every 30 minutes to confirm loss of vascular flow on the experimental side, return of flow after torsion reduction, and preserved flow on the control side. Near infrared spectroscopy detected a prompt, sustained reduction in testicular tissue saturation of oxygen after experimental torsion. Further, it documented a rapid return of these values to pretorsion levels after reduction of torsion. Experimental-side testicular tissue saturation of oxygen fell from a median value of 59% (interquartile range [IQR] 57% to 69%) at baseline to 14% (IQR 11% to 29%) at 2.5 hours of torsion, and postreduction values were approximately 70%. Control-side testicular tissue saturation of oxygen values increased from a median value of 67% (IQR 59% to 68%) at baseline to 77% (IQR 77% to 94%) at 2.5 hours and remained at approximately 80% for the entire protocol. The difference in median testicular tissue saturation of oxygen between experimental and control sides, using the Friedman test, was found to be significant (P=.017). This study demonstrates the feasibility, in a sheep model, of using near-infrared spectroscopy for the noninvasive diagnosis of testicular torsion and for quantification of reperfusion after torsion reduction. The applicability of these findings, from an animal model using complete torsion, to the clinical setting remains to be established.

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 movements.

An Assessment of Cumulative Axial and Torsional Fatigue in a Cobalt-Base Superalloy

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

2010-01-01

Cumulative fatigue under axial and torsional loading conditions can include both load-order (higMow and low/high) as well as load-type sequence (axial/torsional and torsional/axial) effects. Previously reported experimental studies on a cobalt-base superalloy, Haynes 188 at 538 C, addressed these effects. These studies characterized the cumulative axial and torsional fatigue behavior under high amplitude followed by low amplitude (Kalluri, S. and Bonacuse, P. J., "Cumulative Axial and Torsional Fatigue: An Investigation of Load-Type Sequance Effects," in Multiaxial Fatigue and Deformation: Testing and Prediction, ASTM STP 1387, S. Kalluri, and P. J. Bonacuse, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2000, pp. 281-301) and low amplitude followed by high amplitude (Bonacuse, P. and Kalluri, S. "Sequenced Axial and Torsional Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading," Biaxial/Multiaxial Fatigue and Fracture, ESIS Publication 31, A. Carpinteri, M. De Freitas, and A. Spagnoli, Eds., Elsevier, New York, 2003, pp. 165-182) conditions. In both studies, experiments with the following four load-type sequences were performed: (a) axial/axial, (b) torsional/torsional, (c) axial/torsional, and (d) torsional/axial. In this paper, the cumulative axial and torsional fatigue data generated in the two previous studies are combined to generate a comprehensive cumulative fatigue database on both the load-order and load-type sequence effects. This comprehensive database is used to examine applicability of the Palmgren-langer-Miner linear damage rule and a nonlinear damage curve approach for Haynes 188 subjected to the load-order and load-type sequencing described above. Summations of life fractions from the experiments are compared to the predictions from both the linear and nonlinear cumulative fatigue damage approaches. The significance of load-order versus load-type sequence effects for axial and torsional loading conditions is discussed. Possible reasons for the observed differences between the computed and observed summations of cycle fractions are rationalized in terms of the observed ever lutions of cyclic axial and shear stress ranges in the cumulative fatigue tests.

Mannitol has a protective effect on testicular torsion: An experimental rat model.

PubMed

Kurt, Omer; Yazici, Cenk Murat; Erboga, Mustafa; Turan, Cuneyt; Bozdemir, Yeliz; Akbas, Alpaslan; Turker, Polat; Aktas, Cevat; Aydin, Murat; Yesildag, Ebru

2016-06-01

Testicular torsion is an emergency condition that causes testicular injury. Any treatment opportunity reducing the destructive effect of testicular torsion is important for the future life of patients. In this experimental study we investigated the protective effect of mannitol on ischemia-reperfusion (I/R) injury in a rat testes torsion model. In total, 32 male Sprague Dawley rats were included. Four experimental groups included eight rats each. Group A was a sham group in which the right testis was brought out through a scrotal incision and then replaced in the scrotum without torsion. In Group B, the right testis was torsioned, by rotating 720° clockwise and fixed to the scrotum with no treatment. In Group C, the same testicular torsion process was performed with saline infusion just after testicular torsion. In group D, mannitol infusion was used just after testicular torsion. Testicles were detorsioned after 3 h and left inside for more than 2 h before orchiectomy. Histopathological, immunohistochemical, and biochemical analyses were performed. Testicular architecture was disturbed significantly in the torsion groups without mannitol infusion. However, testicular tissue structure was significantly better in the mannitol-treated group, demonstrating a protective effect. Similar findings were also shown for the proliferating cell nuclear antigen (PCNA) index and antioxidant activity; both were higher in the mannitol group than in the no-treatment and saline groups (p < 0.01). The apoptotic index was also significantly lower in the mannitol-treated group compared with the no treatment and saline groups (p < 0.01). The seminiferous tubule structure in testicular torsion without mannitol treatment was significantly disturbed, whereas the structural disruption was considerably less in the mannitol group. Mannitol treatment also decreased reactive oxygen radical levels significantly and was able to decrease apoptosis. These results were consistent with other organ model studies that evaluated the protective effects of mannitol treatment in I/R injury. Mannitol infusion had a protective effect against I/R injury in testicular torsion in rats. This experimental study may guide clinicians to evaluate the effectiveness of mannitol in human testicular torsion. Copyright © 2016 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

Validation of color Doppler ultrasonography for evaluating the uterine blood flow and perfusion during late normal pregnancy and uterine torsion in buffaloes.

PubMed

Hussein, Hassan A

2013-04-15

The aim of this study was to verify the efficacy of color Doppler ultrasonography for diagnosis of degree and duration of uterine torsion in buffaloes. In Assiut province/Upper Egypt, 65 buffaloes (37 with uterine torsion, 28 with normal late pregnancy) were examined clinically and using Doppler ultrasonography. The Doppler indices including resistance index (RI), pulsatility index (PI), time-averaged maximum velocity (TAMV), and blood flow volume (BFV) in the arteries ipsilateral to the uterine torsion (IPUT) and in arteries contralateral to the uterine torsion (COUT) were recorded. Methods of correction were documented along with dam and calf survival. Torsion was recorded postcervically with vaginal involvement in 35/37 (94.6%) of the cases. The degrees of uterine torsion were light and high in 9/37 (24.3%) and 28/37 (75.7%) of the cases, respectively (P = 0.001). Right uterine torsion was present in 36/37 (97.3%) of the cases (P = 0.0001). Pulsatility index, RI, TAMV, and BFV in IPUT and COUT did not differ significantly (P > 0.05) in normal late pregnancy. The PI and RI in IPUT were significantly higher (P < 0.01) than in COUT, and the TAMV and BFV in IPUT were less (P < 0.001) than that in COUT in uterine torsion. The PI and RI of torsion cases in IPUT were higher (P < 0.001) than that in normal pregnancy. Time-averaged maximum velocity and BFV in torsion cases were lower (P < 0.01) than that of normal pregnancy in IPUT. There was approximately 50% of RI and PI higher than in light degree uterine torsion in IPUT (P < 0.001). Consequently, TAMV and BFV were greatly lower (P < 0.0001) than that in light degree in IPUT. Pulsatility index and RI were positively correlated (r = 0.856; P < 0.001) with the duration and degree of the uterine torsion, and TAMV and BFV were negatively correlated (r = -0.763; P < 0.001). In all cases of uterine torsion the uterine flow velocity waveform showed high systolic flow and absence of early diastolic flow and poor uterine and placentomal blood perfusion. In conclusion, depicting blood flow within the middle uterine artery using color Doppler sonography could be helpful in correct diagnosis of duration and degree of uterine torsion and concurrently predicting the viability of the fetus and dam. Copyright © 2013 Elsevier Inc. All rights reserved.

The incidence of isolated penile torsion in North India: A study of 5,018 male neonates.

PubMed

Bhat, Amilal; Bhat, Mahakshit; Kumar, Vinay; Goyal, Suresh; Bhat, Akshita; Patni, Madhu

2017-10-01

Congenital penile torsion is a three-dimensional deformity with helical rotation of the distal corporal bodies with the penile crurae remaining fixed to the pubic rami. The first case of congenital penile torsion (hypospadias) was described in 1857. Isolated penile torsion is an under-reported anomaly. The reported incidence of isolated penile torsion is 1.7-27% and severe torsion is 0.7%. There are no studies available from Indian subcontinent on the incidence of isolated penile torque. The objective of this study was to determine the overall incidence of isolated penile torque in a north Indian population. A prospective study of deliveries of male children was conducted at our institute between April 2014 and June 2015. Penile torsion was measured using a small protractor either by the deviation of the median raphae or the direction of the meatus. Data were collected on the incidence of congenital isolated penile torsion, including the degree and direction (left or right) of torsion. Torsion was classified as mild (<450), moderate (450-900), and severe (>900). Statistical analysis was done using the chi-square test with variables of age and parity of the mother and weight of the child. There were 99 cases of isolated penile torque among 5018 male neonates assessed for penile torque. The incidence of isolated penile torque was 19.7 per 1000 births. The degree of torsion varied from 30 to 110° (average 51.46°). Seventy-nine percent (79%) of them had left side and 21% had right side torque (4:1). The degree of torsion was mild in 30%, with 20% having left side torque and 10% having right side torque (2:1). A moderate degree of torsion was seen in 69%: 84% of them had left torque and only 16% had right sided torque (5:1). Only one patient had severe left torque. The incidence of isolated congenital penile torsion was highest in the maternal age group of >30 years followed by the 26-30-year age group, and was lowest in 21-25 year age group. In multiparous women, the incidence of isolated congenital penile torsion was highest (2.54%), and it was lowest in primiparous women (1.36%). The incidence of isolated penile torsion was 1.97% and the left-to-right ratio was 3:1, but for moderate torque it was 5:1. There was a strong association between incidence of penile torque with the age of the mother (p = 0.012) and parity (p = 0.008) but not with the weight of the baby (p = 0.415). Copyright © 2017 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

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.

A current-driven resistive instability and its nonlinear effects in simulations of coaxial helicity injection in a tokamak

DOE PAGES

Hooper, E. B.; Sovinec, C. R.

2016-10-06

An instability observed in whole-device, resistive magnetohydrodynamic simulations of the driven phase of coaxial helicity injection in the National Spherical Torus eXperiment is identified as a current-driven resistive mode in an unusual geometry that transiently generates a current sheet. The mode consists of plasma flow velocity and magnetic field eddies in a tube aligned with the magnetic field at the surface of the injected magnetic flux. At low plasma temperatures (~10–20 eV), the mode is benign, but at high temperatures (~100 eV) its amplitude undergoes relaxation oscillations, broadening the layer of injected current and flow at the surface of themore » injected toroidal flux and background plasma. The poloidal-field structure is affected and the magnetic surface closure is generally prevented while the mode undergoes relaxation oscillations during injection. Furthermore, this study describes the mode and uses linearized numerical computations and an analytic slab model to identify the unstable mode.« less

Stall Flutter Control of a Smart Blade Section Undergoing Asymmetric Limit Oscillations

DOE PAGES

Li, Nailu; Balas, Mark J.; Nikoueeyan, Pourya; ...

2016-01-01

Stall flutter is an aeroelastic phenomenon resulting in unwanted oscillatory loads on the blade, such as wind turbine blade, helicopter rotor blade, and other flexible wing blades. While the stall flutter and related aeroelastic control have been studied theoretically and experimentally, microtab control of asymmetric limit cycle oscillations (LCOs) in stall flutter cases has not been generally investigated. This paper presents an aeroservoelastic model to study the microtab control of the blade section undergoing moderate stall flutter and deep stall flutter separately. The effects of different dynamic stall conditions and the consequent asymmetric LCOs for both stall cases are simulatedmore » and analyzed. Then, for the design of the stall flutter controller, the potential sensor signal for the stall flutter, the microtab control capability of the stall flutter, and the control algorithm for the stall flutter are studied. Lastly, the improvement and the superiority of the proposed adaptive stall flutter controller are shown by comparison with a simple stall flutter controller.« less

Chemotaxis of active, self-oscillating polymer gels in solution

NASA Astrophysics Data System (ADS)

Dayal, Pratyush; Bhattacharya, Amitabh; Kuksenok, Olga; Balazs, Anna C.

2012-02-01

Fighting, fleeing and feeding are hallmarks of all living things; all these activities require some degree of mobility. Herein, we undertake the first computational study of self-oscillating polymer gels and show that this system can ``communicate'' to undergo a biomimetic, collective response to small-scale chemical changes. In this study we harness unique properties of polymer gels that undergo oscillatory Belousov-Zhabotinsky (BZ) reaction. The activator for the reaction is generated within these BZ cilia and diffuses between the neighboring gels. In order to simulate the dynamics of the BZ gels in surrounding fluid we have developed a nonlinear hybrid 3D model which captures the elasto-dynamics of polymer gel and diffusive exchange of BZ reagents between the gel and the fluid. We illustrate that multiple BZ gels in solution exhibit a distinct form of chemotaxis, moving towards the highest activator concentration in the solution. Similar ability to sense and move in response to chemical gradients constitutes a vital function in simple organisms, enabling them to find food and flee from poisons.

Harmonic engine

DOEpatents

Bennett, Charles L.; Sewall, Noel; Boroa, Carl

2014-08-19

An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into of the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. Upon releasing the inlet valve the inlet valve head undergoes a single oscillation past the equilibrium positio to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. Protrusions carried either by the inlet valve head or piston head are used to bump open the inlet valve from the closed position and initiate the single oscillation of the inlet valve head, and protrusions carried either by the outlet valve head or piston head are used to close the outlet valve ahead of the bump opening of the inlet valve.

Protective effect of sildenafil citrate on contralateral testis injury after unilateral testicular torsion/detorsion.

PubMed

Yíldíz, Hamit; Durmus, Ali Said; Simşek, Halil; Yaman, Mine

2011-01-01

This study was designed to investigate prevention of contralateral testicular injury with sildenafil citrate after unilateral testicular torsion/detorsion. Thirty-seven adult male rats were divided into four groups: sham operated (group 1, n = 7), torsion/detorsion + saline (group 2, n = 10), torsion/detorsion + 0.7 mg of sildenafil citrate (group 3, n = 10) and torsion/detorsion + 1.4 mg of sildenafil citrate (group 4, n = 10). Unilateral testicular torsion was created by rotating the right testis 720º in a clockwise direction for 2 h in other groups, except for group 1, which was served as sham group. After torsion (2 h) and detorsion (2 h) periods, rats were killed. The level of reduced glutathion (GSH) (p < 0.05) and the activities of catalase (p < 0.01) and glutathione peroxidase (p < 0.05) in the contralateral testis from group 2 were significantly lower and nitric oxide (NO) (p < 0.05) level in the contralateral testis were significantly higher than those of group 1. Administration of low-dose sildenafil citrate (group 3) prevented the increases in malondialdehyde and NO levels and decreases in glutathione peroxidase activities and GSH values induced by testicular torsion. However, administration of high-dose sildenafil citrate (group 4) had no effect on these testicular parameters (p > 0.05). Histopathological changes were detected in groups 2, 3 and 4. These results suggest that biochemically and histologically torsion/detorsion injury occurs in the contralateral testis following 2-h torsion and 2-h detorsion and that administration of low-dose sildenafil citrate before detorsion prevents ischemia/reperfusion cellular damage in testicular tissue.

Constraints on spatially oscillating sub-mm forces from the Stanford Optically Levitated Microsphere Experiment data

NASA Astrophysics Data System (ADS)

Antoniou, I.; Perivolaropoulos, L.

2017-11-01

A recent analysis by one of the authors [L. Perivolaropoulos, Phys. Rev. D 95, 084050 (2017), 10.1103/PhysRevD.95.084050] has indicated the presence of a 2 σ signal of spatially oscillating new force residuals in the torsion balance data of the Washington experiment. We extend that study and analyze the data of the Stanford Optically Levitated Microsphere Experiment (SOLME) [A. D. Rider et al., Phys. Rev. Lett. 117, 101101 (2016), 10.1103/PhysRevLett.117.101101] (kindly provided by A. D. Rider et al.) searching for sub-mm spatially oscillating new force signals. We find a statistically significant oscillating signal for a force residual of the form F (z )=α cos (2/π λ z +c ) where z is the distance between the macroscopic interacting masses (levitated microsphere and cantilever). The best fit parameter values are α =(1.1 ±0.4 )×10-17N , λ =(35.2 ±0.6 ) μ m . Monte Carlo simulation of the SOLME data under the assumption of zero force residuals has indicated that the statistical significance of this signal is at about 2 σ level. The improvement of the χ2 fit compared to the null hypothesis (zero residual force) corresponds to Δ χ2=13.1 . There are indications that this previously unnoticed signal is indeed in the data but is most probably induced by a systematic effect caused by diffraction of non-Gaussian tails of the laser beam. Thus the amplitude of this detected signal can only be useful as an upper bound to the amplitude of new spatially oscillating forces on sub-mm scales. In the context of gravitational origin of the signal emerging from a fundamental modification of the Newtonian potential of the form Veff(r )=-G M/r (1 +αOcos (2/π λ r +θ ))≡VN(r )+Vosc(r ) , we evaluate the source integral of the oscillating macroscopically induced force. If the origin of the SOLME oscillating signal is systematic, the parameter αO is bounded as αO<107 for λ ≃35 μ m . Thus, the SOLME data cannot provide useful constraints on the modified gravity parameter αO. However, the constraints on the general phenomenological parameter α (α <0.3 ×10-17N at 2 σ ) can be useful in constraining other fifth force models related to dark energy (chameleon oscillating potentials etc.).

Effects of axial compression and rotation angle on torsional mechanical properties of bovine caudal discs.

PubMed

Bezci, Semih E; Klineberg, Eric O; O'Connell, Grace D

2018-01-01

The intervertebral disc is a complex joint that acts to support and transfer large multidirectional loads, including combinations of compression, tension, bending, and torsion. Direct comparison of disc torsion mechanics across studies has been difficult, due to differences in loading protocols. In particular, the lack of information on the combined effect of multiple parameters, including axial compressive preload and rotation angle, makes it difficult to discern whether disc torsion mechanics are sensitive to the variables used in the test protocol. Thus, the objective of this study was to evaluate compression-torsion mechanical behavior of healthy discs under a wide range of rotation angles. Bovine caudal discs were tested under a range of compressive preloads (150, 300, 600, and 900N) and rotation angles (± 1, 2, 3, 4, or 5°) applied at a rate of 0.5°/s. Torque-rotation data were used to characterize shape changes in the hysteresis loop and to calculate disc torsion mechanics. Torsional mechanical properties were described using multivariate regression models. The rate of change in torsional mechanical properties with compression depended on the maximum rotation angle applied, indicating a strong interaction between compressive stress and maximum rotation angle. The regression models reported here can be used to predict disc torsion mechanics under axial compression for a given disc geometry, compressive preload, and rotation angle. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of torsional and longitudinal modes using phacoemulsification parameters.

PubMed

Rekas, Marek; Montés-Micó, Robert; Krix-Jachym, Karolina; Kluś, Adam; Stankiewicz, Andrzej; Ferrer-Blasco, Teresa

2009-10-01

To compare phacoemulsification parameters of torsional and longitudinal ultrasound modes. Ophthalmology Department, Military Health Service Institute, Warsaw, Poland. This prospective study evaluated eyes 1, 7, and 30 days after phacoemulsification with an Infiniti Vision System using the torsional or longitudinal ultrasound (US) mode. Cataract classification was according to the Lens Opacities Classification System II. Nucleus fragmentation was by the phaco-chop and quick-chop methods. Primary outcome measures were phaco time, mean phaco power, mean torsional amplitude, and aspiration time. Total energy, defined as cumulative dissipated energy (CDE) x aspiration time, and the effective coefficient, defined as aspiration time/phaco time, were also calculated. Four hundred eyes were evaluated. The CDE was statistically significantly lower in the torsional mode for nucleus grades I, II, and III (P<.001) but not for grade IV (P>.05). Aspiration time was statistically significantly shorter in the torsional mode than in the longitudinal mode for nucleus grades III and IV (P<.05). Total energy was significantly lower in the torsional mode for all nucleus densities (P<.05). The effective coefficient was significantly lower in the longitudinal mode except for nucleus grade I (P<.05). Torsional phacoemulsification was more effective than longitudinal phacoemulsification in the amount of applied fluid and the quantity of US energy expended. With the torsional method, it was possible to maintain a constant ratio of amount of fluid flow to quantity of US energy used, regardless of nucleus density.

Effects of temperature, loading rate and nanowire length on torsional deformation and mechanical properties of aluminium nanowires investigated using molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Sung, Po-Hsien; Wu, Cheng-Da; Fang, Te-Hua

2012-05-01

Single-crystal aluminium nanowires under torsion are studied using molecular dynamics simulations based on the many-body tight-binding potential. The effects of temperature, loading rate and nanowire length are evaluated in terms of atomic trajectories, potential energy, von Mises stress, a centrosymmetry parameter, torque, shear modulus and radial distribution function. Simulation results clearly show that torsional deformation begins at the surface, extends close to the two ends and finally diffuses to the middle part. The critical torsional angle which represents the beginning of plastic deformation varies with different conditions. Before the critical torsional angle is reached, the potential energy and the torque required for the deformation of a nanowire significantly increase with the torsional angle. The critical torsional angle increases with increasing nanowire length and loading rate and decreasing temperature. The torque required for the deformation decreases and the shear modulus increases with increasing nanowire length. For higher temperatures and higher loading rates, torsional buckling more easily occurs at the two ends of a nanowire, whereas it occurs towards the middle part at or below room temperature with lower loading rates. Geometry instability occurs before material instability (buckling) for a long nanowire.

Electrophysiological examination and high frequency ultrasonography for diagnosis of radial nerve torsion and compression

PubMed Central

Shi, Miao; Qi, Hengtao; Ding, Hongyu; Chen, Feng; Xin, Zhaoqin; Zhao, Qinghua; Guan, Shibing; Shi, Hao

2018-01-01

Abstract This study aims to evaluate the value of electrophysiological examination and high frequency ultrasonography in the differential diagnosis of radial nerve torsion and radial nerve compression. Patients with radial nerve torsion (n = 14) and radial nerve compression (n = 14) were enrolled. The results of neurophysiological and high frequency ultrasonography were compared. Electrophysiological examination and high-frequency ultrasonography had a high diagnostic rate for both diseases with consistent results. Of the 28 patients, 23 were positive for electrophysiological examination, showing decreased amplitude and decreased conduction velocity of radial nerve; however, electrophysiological examination cannot distinguish torsion from compression. A total of 27 cases showed positive in ultrasound examinations among all 28 cases. On ultrasound images, the nerve was thinned at torsion site whereas thickened at the distal ends of torsion. The diameter and cross-sectional area of torsion or compression determined the nerve damage, and ultrasound could locate the nerve injury site and measure the length of the nerve. Electrophysiological examination and high-frequency ultrasonography can diagnose radial neuropathy, with electrophysiological examination reflecting the neurological function, and high-frequency ultrasound differentiating nerve torsion from compression. PMID:29480857

Neutrino oscillation tomography of the Earth with KM3NeT-ORCA

NASA Astrophysics Data System (ADS)

Bourret, Simon; Coelho, João A. B.; Van Elewyck, Véronique; KM3NeT Collaboration

2017-09-01

KM3NeT-ORCA is a water-Cherenkov neutrino detector designed for studying the oscillations of atmospheric neutrinos, with the primary objective of measuring the neutrino mass ordering. Atmospheric neutrinos crossing the Earth undergo matter effects, modifying the pattern of their flavour oscillations. The study of the angular and energy distribution of neutrino events in ORCA can therefore provide tomographic information on the Earth’s interior with an independent technique, complementary to the standard geophysics methods. Preliminary estimations based on a full Monte Carlo simulation of the detector response show that after ten years of operation the electron density can be measured with a precision of 3-5% in the mantle and 7-10% in the outer core - depending on the mass ordering.

Circadian desynchronization

PubMed Central

Granada, Adrián E.; Cambras, Trinitat; Díez-Noguera, Antoni; Herzel, Hanspeter

2011-01-01

The suprachiasmatic nucleus (SCN) coordinates via multiple outputs physiological and behavioural circadian rhythms. The SCN is composed of a heterogeneous network of coupled oscillators that entrain to the daily light–dark cycles. Outside the physiological entrainment range, rich locomotor patterns of desynchronized rhythms are observed. Previous studies interpreted these results as the output of different SCN neural subpopulations. We find, however, that even a single periodically driven oscillator can induce such complex desynchronized locomotor patterns. Using signal analysis, we show how the observed patterns can be consistently clustered into two generic oscillatory interaction groups: modulation and superposition. In seven of 17 rats undergoing forced desynchronization, we find a theoretically predicted third spectral component. Combining signal analysis with the theory of coupled oscillators, we provide a framework for the study of circadian desynchronization. PMID:22419981

High-Speed Rainbow Schlieren Visualization of an Oscillating Helium Jet Undergoing Gravitational Change

NASA Technical Reports Server (NTRS)

Leptuch, Peter A.; Agrawal, Ajay K.

2005-01-01

Rainbow schlieren deflectometry combined with high-speed digital imaging was used to study buoyancy effects on flow structure of a helium jet discharged vertically into air. The experimental data were taken using the 2.2-sec drop tower facility at the NASA John H. Glenn Research Center in Cleveland, Ohio. The test conditions pertained to jet Reynolds number of 490 and jet Richardson number of 0.11, for which buoyancy is often considered unimportant. Experimental results show global oscillations at a frequency of 27 Hz in Earth gravity. In microgravity, the jet oscillations vanished and the jet width increased. Results provide a direct physical evidence of the importance of buoyancy on the flow structure of low-density gas jets at a Richardson number considered too small to account for gravity.

Structural evolution of nanoscale metallic glasses during high-pressure torsion: A molecular dynamics analysis

NASA Astrophysics Data System (ADS)

Feng, S. D.; Jiao, W.; Jing, Q.; Qi, L.; Pan, S. P.; Li, G.; Ma, M. Z.; Wang, W. H.; Liu, R. P.

2016-11-01

Structural evolution in nanoscale Cu50Zr50 metallic glasses during high-pressure torsion is investigated using molecular dynamics simulations. Results show that the strong cooperation of shear transformations can be realized by high-pressure torsion in nanoscale Cu50Zr50 metallic glasses at room temperature. It is further shown that high-pressure torsion could prompt atoms to possess lower five-fold symmetries and higher potential energies, making them more likely to participate in shear transformations. Meanwhile, a higher torsion period leads to a greater degree of forced cooperative flow. And the pronounced forced cooperative flow at room temperature under high-pressure torsion permits the study of the shear transformation, its activation and characteristics, and its relationship to the deformations behaviors. This research not only provides an important platform for probing the atomic-level understanding of the fundamental mechanisms of high-pressure torsion in metallic glasses, but also leads to higher stresses and homogeneous flow near lower temperatures which is impossible previously.

Ultrasonographic identification of nerve pathology in neuralgic amyotrophy: Enlargement, constriction, fascicular entwinement, and torsion.

PubMed

Arányi, Zsuzsanna; Csillik, Anita; Dévay, Katalin; Rosero, Maja; Barsi, Péter; Böhm, Josef; Schelle, Thomas

2015-10-01

The aim of this study was to characterize the ultrasonographic findings on nerves in neuralgic amyotrophy. Fourteen patients with neuralgic amyotrophy were examined using high-resolution ultrasound. Four types of abnormalities were found: (1) focal or diffuse nerve/fascicle enlargement (57%); (2) incomplete nerve constriction (36%); (3) complete nerve constriction with torsion (50%; hourglass-like appearance); and (4) fascicular entwinement (28%). Torsions were confirmed intraoperatively and were seen on the radial nerve in 85% of patients. A significant correlation was found between no spontaneous recovery of nerve function and constriction/torsion/fascicular entwinement (P = 0.007). Ultrasonographic nerve pathology in neuralgic amyotrophy varies in order of severity from nerve enlargement to constriction to nerve torsion, with treatment ranging from conservative to surgical. We postulate that the constriction caused by inflammation is the precursor of torsion and that development of nerve torsion is facilitated by the rotational movements of limbs. © 2015 Wiley Periodicals, Inc.

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.

Coupled out of plane vibrations of spiral beams for micro-scale applications

NASA Astrophysics Data System (ADS)

Amin Karami, M.; Yardimoglu, Bulent; Inman, Daniel J.

2010-12-01

An analytical method is proposed to calculate the natural frequencies and the corresponding mode shape functions of an Archimedean spiral beam. The deflection of the beam is due to both bending and torsion, which makes the problem coupled in nature. The governing partial differential equations and the boundary conditions are derived using Hamilton's principle. Two factors make the vibrations of spirals different from oscillations of constant radius arcs. The first is the presence of terms with derivatives of the radius in the governing equations of spirals and the second is the fact that variations of radius of the beam causes the coefficients of the differential equations to be variable. It is demonstrated, using perturbation techniques that the derivative of the radius terms have negligible effect on structure's dynamics. The spiral is then approximated with many merging constant-radius curved sections joined together to approximate the slow change of radius along the spiral. The equations of motion are formulated in non-dimensional form and the effect of all the key parameters on natural frequencies is presented. Non-dimensional curves are used to summarize the results for clarity. We also solve the governing equations using Rayleigh's approximate method. The fundamental frequency results of the exact and Rayleigh's method are in close agreement. This to some extent verifies the exact solutions. The results show that the vibration of spirals is mostly torsional which complicates using the spiral beam as a host for a sensor or energy harvesting device.

Excited stilbene: intramolecular vibrational redistribution and solvation studied by femtosecond stimulated Raman spectroscopy.

PubMed

Weigel, A; Ernsting, N P

2010-06-17

Excited-state relaxation of cis- and trans-stilbene is traced with femtosecond stimulated Raman spectroscopy, exploiting S(n) <-- S(1) resonance conditions. For both isomers, decay in Raman intensity, shift of spectral positions, and broadening of the bands indicate intramolecular vibrational redistribution (IVR). In n-hexane this process effectively takes 0.5-0.7 ps. Analysis of the intensity decay allows us to further distinguish two phases for trans-stilbene: fast IVR within a subset of modes (approximately 0.3 ps) followed by slower equilibration over the full vibrational manifold (approximately 0.9 ps). In acetonitrile IVR completes with 0.15 ps; this acceleration may originate from symmetry breakage induced by the polar solvent. Another process, dynamic solvation by acetonitrile, is seen as spectral narrowing and characteristic band shifts of the C=C stretch and phenyl bending modes with 0.69 ps. Wavepacket motion is observed in both isomers as oscillation of low-frequency bands with their pertinent mode frequency (90 or 195 cm(-1) in trans-stilbene; 250 cm(-1) in cis-stilbene). Anharmonic coupling shows up as a modulation of high-frequency peak positions by phenyl/ethylene torsion modes of 57 and 90 cm(-1). Decay and shift of the 90 cm(-1) inverse Raman band within the first 0.3 ps suggests a gradual involvement of phenyl/ethylene torsion in relaxation. In cis- and trans-stilbene, low-frequency spectral changes are found within 0.15 ps, indicating an additional ultrafast process.

Evaluation of a high-torque backlash-free roller actuator

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.

1988-01-01

The results are presented of a test program that evaluated the stiffness, accuracy, torque ripple, frictional losses, and torque holding capability of a 16:1 ratio, 430 N-m (320 ft-lb) planetary roller drive for a potential space vehicle actuator application. The drive's planet roller supporting structure and bearings were found to be the largest contributors to overall drive compliance, accounting for more than half the total. In comparison, the traction roller contacts themselves contributed only 9 percent of the drive's compliance based on an experimentally verified stiffnesss model. Torque ripple tests showed the drive to be extremely smooth, actually providing some damping of input torsional oscillations. The drive also demonstrated the ability to hold static torque with drifts of 7 arc sec or less over a 24-hour period at 35 percent of full load.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Jun, E-mail: pengjun@cimm.com.cn; Zhang, Li, E-mail: zhangli@cimm.com.cn; School of Instrumentation Science and Opto-electronics Engineering, Beihang University, Beijing

The moment of inertia calibration system is developed by Changcheng Institute of Metrology and Measurement (CIMM). Rotation table - torsional spring system is used to generate angular vibration, and laser vibrometer is used to measure rotational angle and the vibration period. The object to be measured is mounted on the top of the rotation table. The air-bearing system is elaborately manufactured which reduce the friction of the angular movement and increase measurement accuracy. Heterodyne laser interferometer collaborates with column diffraction grating is used in the measurement of angular movement. Experiment shows the method of measuring oscillating angle and period introducedmore » in this paper is stable and the time resolution is high. When the air damping effect can’t be neglected in moment of inertia measurement, the periodic waveform area ratio method is introduced to calculate damping ratio and obtain the moment of inertia.« less

Torsion balances with fibres of zero length

NASA Astrophysics Data System (ADS)

Speake, Clive C.; Collins, Christopher J.

2018-04-01

Torsion balances have good immunity to tilt and low rotational stiffness. However precise control of the position of the suspended torsion 'bob' is difficult in the presence of ground vibrations and tilt and this is a limiting factor in applications where Casimir forces or putative non-Newtonian short-range forces are being measured. We describe how the desirable characteristics of torsion balances can be reproduced in a rigid body that is suspended using applied forces rather than a torsion fibre. The suspension system can then provide a more precise control of the degrees of freedom of the suspended body. We apply these ideas to a superconducting levitated torsion balance, developed by the authors, and a generic electrostatic suspension. We present results of preliminary experiments that provide support for our analyses.

Torsional Properties of TiNi Shape Memory Alloy Tape for Rotary Actuator

NASA Astrophysics Data System (ADS)

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

2012-12-01

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

MSTor version 2013: A new version of the computer code for the multi-structural torsional anharmonicity, now with a coupled torsional potential

NASA Astrophysics Data System (ADS)

Zheng, Jingjing; Meana-Pañeda, Rubén; Truhlar, Donald G.

2013-08-01

We present an improved version of the MSTor program package, which calculates partition functions and thermodynamic functions of complex molecules involving multiple torsions; the method is based on either a coupled torsional potential or an uncoupled torsional potential. The program can also carry out calculations in the multiple-structure local harmonic approximation. The program package also includes seven utility codes that can be used as stand-alone programs to calculate reduced moment of inertia matrices by the method of Kilpatrick and Pitzer, to generate conformational structures, to calculate, either analytically or by Monte Carlo sampling, volumes for torsional subdomains defined by Voronoi tessellation of the conformational subspace, to generate template input files for the MSTor calculation and Voronoi calculation, and to calculate one-dimensional torsional partition functions using the torsional eigenvalue summation method. Restrictions: There is no limit on the number of torsions that can be included in either the Voronoi calculation or the full MS-T calculation. In practice, the range of problems that can be addressed with the present method consists of all multitorsional problems for which one can afford to calculate all the conformational structures and their frequencies. Unusual features: The method can be applied to transition states as well as stable molecules. The program package also includes the hull program for the calculation of Voronoi volumes, the symmetry program for determining point group symmetry of a molecule, and seven utility codes that can be used as stand-alone programs to calculate reduced moment-of-inertia matrices by the method of Kilpatrick and Pitzer, to generate conformational structures, to calculate, either analytically or by Monte Carlo sampling, volumes of the torsional subdomains defined by Voronoi tessellation of the conformational subspace, to generate template input files, and to calculate one-dimensional torsional 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.

A 55-Year-Old Man with Right Testicular Pain: Too Old for Torsion?

PubMed

Tang, Yu Ho; Yeung, Victor Hip Wo; Chu, Peggy Sau Kwan; Man, Chi Wai

2017-02-01

Testicular torsion is predominantly a disease of adolescence, but age itself should not be an exclusion criterion for the diagnosis. A lack of suspicion for testicular torsion in older patients may result in a missed or delayed diagnosis which jeopardizes the chance of testicular salvage. In this article, we report a case of testicular torsion in a 55-year-old Chinese man.

Magnesium: does it reduce ischemia/reperfusion injury in an adnexal torsion rat model?

PubMed Central

Celik Kavak, Ebru; Gulcu Bulmus, Funda; Bulmus, Ozgur; Kavak, Salih Burcin; Kocaman, Nevin

2018-01-01

Aim The aim of the present study was to assess the protective effects of magnesium sulfate (MgSO4) on ischemia/reperfusion (I/R) induced ovarian damage in a rat ovarian torsion model. Methods Forty-two female Sprague Dawley rats were included in the study. They were divided into six groups as Group 1, sham; Group 2, bilateral ovarian torsion; Group 3, bilateral ovarian torsion–detorsion; Group 4, MgSO4–sham; Group 5, MgSO4–bilateral ovarian torsion; Group 6, bilateral ovarian torsion–MgSO4–detorsion. Both torsion and detorsion periods lasted 3 hours. In Groups 4, 5 and 6, MgSO4 (600 mg/kg) was administered by intraperitoneal route 30 minutes before sham operation, torsion and detorsion, respectively. At the end of the study period, both ovaries were removed. One of the ovaries was used for histopathological analyses and the other for biochemical analyses. Results In the torsion–detorsion group, all the histopathological scores were higher compared to the sham and torsion only group (p<0.05). Administration of MgSO4 only caused significant decrease in the inflammatory cell scores of the torsion–detorsion group (p<0.05). MgSO4, whether given before torsion or before detorsion, suppressed malondialdehyde levels when compared to the untreated groups (p<0.01 and p<0.001, respectively). Glutathione peroxidase activities were significantly higher in the MgSO4 applied torsion and detorsion groups than Groups 2 and 3 (p<0.05, for both). Administration of MgSO4 also caused an increase in glutathione levels in the torsion and detorsion groups compared to the torsion only and detorsion only groups (p<0.05, for both). Also, total oxidant status levels decreased in the MgSO4 applied torsion and detorsion groups compared to the untreated corresponding ones (p<0.01 and p<0.001, respectively). MgSO4 significantly decreased the Oxidative Stress Index levels in the torsion–detorsion group compared to Group 2 (p<0.001). Conclusion Histopathological and biochemical analysis revealed that prophylactic treatment with MgSO4 reduces the changes observed in I/R injury in a rat model. PMID:29535502

Chiral dynamos and magnetogenesis induced by torsionful Maxwell-Chern Simons electrodynamics

NASA Astrophysics Data System (ADS)

de Andrade, L. C. Garcia

2018-03-01

Recently chiral anomalous currents have been investigated by Boyarsky et al. and Brandenburg et al. with respect to applications to the early universe. In this paper we show that these magnetic field anomalies, which can give rise to dynamo magnetic field amplification can also be linked to spacetime torsion through the use of a chemical potential and Maxwell electrodynamics with torsion firstly proposed by de Sabbata and Gasperini. When the axial torsion is constant this electrodynamics acquires the form of a Maxwell-Chern-Simmons (MCS) equations where the chiral current appears naturally and the zero component of torsion plays the role of a chemical potential, while the other components play the role of anisotropic conductivity. The chiral dynamo equation in torsionful spacetime is derived here from MSC electrodynamics. Here we have used a recently derived a torsion LV bound of T0˜ {10^{-26}} GeV and the constraint that this chiral magnetic field is a seed for galactic dynamo. This estimate is weaker than the one obtained from the chiral battery seed of ˜ {10^{30}} G without making use of Cartan torsion. The torsion obtained here was derived at 500 pc coherence scale. When a chiral MF is forced to seed a galactic dynamo one obtains a yet weaker MF, of the order of B˜ {10^{12}} G, which is the value of a MF at nucleosynthesis. By the use of chiral dynamo equations from parity-violating torsion one obtains a seed field of B˜ {10^{27}} G, which is a much stronger MF closer to the one obtained by making use of chiral batteries. Chiral vortical currents in non-Riemannian spacetimes derived in Riemannian spaces previously by Flaschi and Fukushima are extended to include minimal coupling with torsion. The present universe yields B˜ {10^{-24}} G, still sufficient to seed galactic dynamos.

Ghrelin and NUCB2/Nesfatin-1 expression in unilateral testicular torsion-induced rats with and without N-acetylcysteine.

PubMed

Sarac, M; Bakal, U; Tartar, T; Kuloglu, T; Yardim, M; Artas, G; Aydin, S; Kazez, A

2017-08-15

Testicular torsion (TT) is a common urological problem in the field of pediatric surgery. The degree and duration of torsion determines the degree of testicular damage; however, its effects on the expression of octanoylated ghrelin and nucleobindin 2 (NUCB2) /nesfatin-1 synthetized from testicular tissue remain unclear. We explored the effects of experimentally induced unilateral TT on serum and contralateral testicular tissue ghrelin and NUCB2/nesfatin-1 levels, and determined whether N-acetyl cysteine (NAS) treatment had any effects on their expression. A total of 42 Wistar Albino strain rats were divided into 7 groups: Group (G) I control, GII sham, GIII 12-hour torsion, GIV 12-hour torsion + detorsion + 100 mg/kg NAS, GV 24-hour torsion, GVI 24-hour torsion + detorsion + 100 mg/kg NAS, and GVII 100 mg/kg NAS. Octanoylated ghrelin and NUCB2/nesfatin-1 concentrations were evaluated in serum using the ELISA method and in testicular tissue with immunohistochemical methods. Immunoreactivity of octanoylated ghrelin significantly increased in GI compared to GIII, GV, and GVI (p<0.05). NUCB2/nesfatin-1 immunoreactivity increased in GV and GVIII relative to GI (p<0.05). In the 12-hour torsion group, a significant decrease in octanoylated ghrelin levels with NAS treatment was observed; however, in the 24-hour torsion group, a significant decrease was not observed. In the 12-hour torsion + NAS treatment group, a significant change was not observed in NUCB2/nesfatin-1 expression. Following 24-hour torsion, an increase in NUCB2/nesfatin-1 levels was observed, and NAS treatment did not reverse this increase. It was determined that increases in the expression of octanoylated ghrelin and NUCB2/nesfatin-1, the latter of which was a result of TT, reflect damage in this tissue. Importantly, NAS treatment could prevent this damage. Thus, there may be a clinical application for the combined use of NAS and octanoylated ghrelin in preventing TT-related infertility.

Computational Test Cases for a Rectangular Supercritical Wing Undergoing Pitching Oscillations

NASA Technical Reports Server (NTRS)

Bennett, Robert M.; Walker, Charlotte E.

1999-01-01

Proposed computational test cases have been selected from the data set for a rectangular wing of panel aspect ratio two with a twelve-percent-thick supercritical airfoil section that was tested in the NASA Langley Transonic Dynamics Tunnel. The test cases include parametric variation of static angle of attack, pitching oscillation frequency, and Mach numbers from subsonic to transonic with strong shocks. Tables and plots of the measured pressures are presented for each case. This report provides an early release of test cases that have been proposed for a document that supplements the cases presented in AGARD Report 702.

A fluid-mechanical sewing machine

NASA Astrophysics Data System (ADS)

Lister, John; Chiu-Webster, Sunny

2004-11-01

It is a breakfast-table experience that when a viscous fluid thread falls a sufficient height onto a stationary horizontal surface the thread is undergoes a coiling instability. We describe experimental observations of a viscous thread falling onto a steadily moving horizontal belt. Low (or zero) belt speeds produce coiling as expected. High belt speeds produce a steady thread, whose shape is well-predicted by theory for a stretching catenary with surface tension and inertia. Intermediate belt speeds show various modes of oscillation, which produce a variety of `stitching' patterns on the belt. The onset of oscillations is predicted theoretically.

Guidelines for Computing Longitudinal Dynamic Stability Characteristics of a Subsonic Transport

NASA Technical Reports Server (NTRS)

Thompson, Joseph R.; Frank, Neal T.; Murphy, Patrick C.

2010-01-01

A systematic study is presented to guide the selection of a numerical solution strategy for URANS computation of a subsonic transport configuration undergoing simulated forced oscillation about its pitch axis. Forced oscillation is central to the prevalent wind tunnel methodology for quantifying aircraft dynamic stability derivatives from force and moment coefficients, which is the ultimate goal for the computational simulations. Extensive computations are performed that lead in key insights of the critical numerical parameters affecting solution convergence. A preliminary linear harmonic analysis is included to demonstrate the potential of extracting dynamic stability derivatives from computational solutions.

Electronic theoretical study on the influence of torsional deformation on the electronic structure and optical properties of BN-doped graphene

NASA Astrophysics Data System (ADS)

Fan, Dazhi; Liu, Guili; Wei, Lin

2018-06-01

Based on the density functional theory, the effect of torsional deformation on the electronic structure and optical properties of boron nitride (BN)-doped graphene is studied by using the first-principles calculations. The band structure calculations show that the intrinsic graphene is a semi-metallic material with zero band gap and the torsional deformation has a large effect on its band gap, opening its band gap and turning it from the semi-metal to the medium band gap semiconductor. The doping of BN in graphene makes its band gap open and becomes a medium band gap semiconductor. When it is subjected to a torsional effect, it is found to have a weak influence on its band gap. In other words, the doping of BN makes the changes of the band gap of graphene no longer sensitive to torsional deformation. Optical properties show that the doping of BN leads to a significant decrease in the light absorption coefficient and reflectivity of the graphene at the characteristic peak and that of BN-doped graphene system is also weakened by torsional deformation at the characteristic peak. In the absorption spectrum, the absorption peaks of the doping system of the torsion angle of 2-20∘ are redshifted compared with that of the BN-doped system (the torsion angle is 0∘). In the reflection spectrum, the two reflection peaks are all redshifted relative to that of the BN-doped system (the torsion angle is 0∘) and when the torsion angle exceeds 12∘, the size relationship between the two peaks is interchanged. The results of this paper are of guiding significance for the study of graphene-based nanotube devices in terms of deformation.

Comparison of animal discs used in disc research to human lumbar disc: torsion mechanics and collagen content.

PubMed

Showalter, Brent L; Beckstein, Jesse C; Martin, John T; Beattie, Elizabeth E; Espinoza Orías, Alejandro A; Schaer, Thomas P; Vresilovic, Edward J; Elliott, Dawn M

2012-07-01

Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these with the human disc. To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar discs, and cow, rat, and mouse caudal discs. Collagen content was measured and normalized by dry weight for the same discs except the rat and the mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human discs. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Disc torsion mechanics are comparable with human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented are useful for selecting and interpreting results for animal disc models. Structural organization of the fiber angle may explain the differences that were noted between species after geometric normalization.

Practical Methods for Including Torsional Anharmonicity in Thermochemical Calculations on Complex Molecules: The Internal-Coordinate Multi-Structural Approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, J.; Yu, T.; Papajak, E.

2011-01-01

Many methods for correcting harmonic partition functions for the presence of torsional motions employ some form of one-dimensional torsional treatment to replace the harmonic contribution of a specific normal mode. However, torsions are often strongly coupled to other degrees of freedom, especially other torsions and low-frequency bending motions, and this coupling can make assigning torsions to specific normal modes problematic. Here, we present a new class of methods, called multi-structural (MS) methods, that circumvents the need for such assignments by instead adjusting the harmonic results by torsional correction factors that are determined using internal coordinates. We present three versions ofmore » the MS method: (i) MS-AS based on including all structures (AS), i.e., all conformers generated by internal rotations; (ii) MS-ASCB based on all structures augmented with explicit conformational barrier (CB) information, i.e., including explicit calculations of all barrier heights for internal-rotation barriers between the conformers; and (iii) MS-RS based on including all conformers generated from a reference structure (RS) by independent torsions. In the MS-AS scheme, one has two options for obtaining the local periodicity parameters, one based on consideration of the nearly separable limit and one based on strongly coupled torsions. The latter involves assigning the local periodicities on the basis of Voronoi volumes. The methods are illustrated with calculations for ethanol, 1-butanol, and 1-pentyl radical as well as two one-dimensional torsional potentials. The MS-AS method is particularly interesting because it does not require any information about conformational barriers or about the paths that connect the various structures.« less

Practical methods for including torsional anharmonicity in thermochemical calculations on complex molecules: the internal-coordinate multi-structural approximation.

PubMed

Zheng, Jingjing; Yu, Tao; Papajak, Ewa; Alecu, I M; Mielke, Steven L; Truhlar, Donald G

2011-06-21

Many methods for correcting harmonic partition functions for the presence of torsional motions employ some form of one-dimensional torsional treatment to replace the harmonic contribution of a specific normal mode. However, torsions are often strongly coupled to other degrees of freedom, especially other torsions and low-frequency bending motions, and this coupling can make assigning torsions to specific normal modes problematic. Here, we present a new class of methods, called multi-structural (MS) methods, that circumvents the need for such assignments by instead adjusting the harmonic results by torsional correction factors that are determined using internal coordinates. We present three versions of the MS method: (i) MS-AS based on including all structures (AS), i.e., all conformers generated by internal rotations; (ii) MS-ASCB based on all structures augmented with explicit conformational barrier (CB) information, i.e., including explicit calculations of all barrier heights for internal-rotation barriers between the conformers; and (iii) MS-RS based on including all conformers generated from a reference structure (RS) by independent torsions. In the MS-AS scheme, one has two options for obtaining the local periodicity parameters, one based on consideration of the nearly separable limit and one based on strongly coupled torsions. The latter involves assigning the local periodicities on the basis of Voronoi volumes. The methods are illustrated with calculations for ethanol, 1-butanol, and 1-pentyl radical as well as two one-dimensional torsional potentials. The MS-AS method is particularly interesting because it does not require any information about conformational barriers or about the paths that connect the various structures.

The Effects of Torsional Preloading on the Torsional Resistance of Nickel-titanium Instruments.

PubMed

Oh, Seung-Hei; Ha, Jung-Hong; Kwak, Sang Won; Ahn, Shin Wook; Lee, WooCheol; Kim, Hyeon-Cheol

2017-01-01

This study evaluated the effect of torsional preloading on the torsional resistance of nickel-titanium (NiTi) endodontic instruments. WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) and ProTaper Universal F2 (Dentsply Maillefer) files were used. The ultimate torsional strength until fracture was determined for each instrument. In the phase 1 experiment, the ProTaper and WaveOne files were loaded to have a maximum load from 2.0 up to 2.7 or 2.8 Ncm, respectively. In the phase 2 experiment, the number of repetitions of preloading for each file was increased from 50 to 200, whereas the preloading torque was fixed at 2.4 Ncm. Using torsionally preloaded specimens from phase 1 and 2, the torsional resistances were calculated to determine the ultimate strength, distortion angle, and toughness. The results were analyzed using 1-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of 5 specimens per group were examined under a scanning electron microscope. All preloaded groups showed significantly higher ultimate strength than the unpreloaded groups (P < .05). There was no significant difference among all groups for distortion angle and toughness. Although WaveOne had no significant difference between the repetition groups for ultimate strength, fracture angle, and toughness, ProTaper had a higher distortion angle and toughness in the 50-repetition group compared with the other repetition groups (P < .05). Scanning electron microscopic examinations of the fractured surface showed typical features of torsional fracture. Torsional preloading within the ultimate values could enhance the torsional strength of NiTi instruments. The total energy until fracture was maintained constantly, regardless of the alloy type. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Determining optimal torsional ultrasound power for cataract surgery with automatic longitudinal pulses at maximum vacuum ex vivo.

PubMed

Ronquillo, Cecinio C; Zaugg, Brian; Stagg, Brian; Kirk, Kevin R; Gupta, Isha; Barlow, William R; Pettey, Jeff H; Olson, Randall J

2014-12-01

To determine the optimal longitudinal power settings for Infiniti OZil Intelligent Phaco (IP) at varying torsional amplitude settings; and to test the hypothesis that increasing longitudinal power is more important at lower torsional amplitudes to achieve efficient phacoemulsification. Laboratory investigation. setting: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. procedure: Individual porcine nuclei were fixed in formalin, then cut into 2.0 mm cubes. Lens cube phacoemulsification was done using OZil IP at 60%, 80%, and 100% torsional amplitude with 0%, 10%, 20%, 30%, 50%, 75%, or 100% longitudinal power. All experiments were done using a 20 gauge 0.9 mm bent reverse bevel phaco tip at constant vacuum (550 mm Hg), aspiration rate (40 mL/min), and bottle height (50 cm). main outcome measure: Complete lens particle phacoemulsification (efficiency). Linear regression analysis showed a significant increase in efficiency with increasing longitudinal power at 60% torsional amplitude (R(2) = 0.7269, P = .01) and 80% torsional amplitude (R(2) = 0.6995, P = .02) but not at 100% amplitude (R(2) = 0.3053, P = .2). Baseline comparison of 60% or 80% vs 100% torsional amplitude without longitudinal power showed increased efficiency at 100% (P = .0004). Increasing longitudinal power to 20% abolished the efficiency difference between 80% vs 100% amplitudes. In contrast, 75% longitudinal power abolished the efficiency difference between 60% vs 100% torsional amplitudes. Results suggest that longitudinal power becomes more critical at increasing phacoemulsification efficiencies at torsional amplitudes less than 100%. Increasing longitudinal power does not further increase efficiency at maximal torsional amplitudes. Copyright © 2014 Elsevier Inc. All rights reserved.

Optical monitoring of testicular torsion using a miniaturized near infrared spectroscopy sensor

NASA Astrophysics Data System (ADS)

Shadgan, Babak; Kajbafzadeh, Majid; Nigro, Mark; Kajbafzadeh, A. M.; Macnab, Andrew

2017-02-01

Background: Testicular torsion is an acute urological emergency occurring in children and adolescents. Accurate and fast diagnosis is important as the resulting ischemia can destroy the testis. Currently, Doppler ultrasound is the preferred diagnostic method. Ultrasound is not readily available in all centers which may delay surgical treatment. In this study, a rat model was used to examine the feasibility and sensitivity of using spatially-resolved near infrared spectroscopy (SR-NIRS) with a custom-made miniaturized optical sensor probe to detect and study changes in testicular hemodynamics and oxygenation during three degrees of induced testicular torsion, and after detorsion. Methods: Eight anesthetized rats (16 testes) were studied using SR-NIRS with the miniaturized optical probe applied directly onto the surface of the surgically exposed testis during 360, 720 and 1080 degrees of torsion followed by detorsion. Oxygenated, deoxygenated and total hemoglobin and TOI% were studied pre-and post-manipulations. Results: NIRS monitoring reflected acute testicular ischemia and hypoxia on induction of torsion, and tissue reperfusionreoxygenation after detorsion. Testicular torsion at 720 degrees induced the maximum observed degree of hypoxic changes. In all cases, rhythmic changes were observed in the NIRS signals before inducing torsion; these disappeared after applying 360 degrees of torsion and did not reappear after detorsion. Conclusion: This animal study indicates that SR-NIRS monitoring of the testes using a directly applied miniature sensor is a feasible and sensitive method to detect testicular ischemia and hypoxia immediately after torsion occurs, and testicular reperfusion upon detorsion. This study offers the potential for a SR-NIRS system with a miniaturized sensor to be explored further as a rapid, noninvasive, optical method for detecting testicular torsion in children.

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

PubMed

Bezci, Semih E; Eleswarapu, Ananth; Klineberg, Eric O; O'Connell, Grace D

2018-02-12

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Comparison of Animal Discs Used in Disc Research to Human Lumbar Disc: Torsion Mechanics and Collagen Content

PubMed Central

Showalter, Brent L.; Beckstein, Jesse C.; Martin, John T.; Beattie, Elizabeth E.; Orías, Alejandro A. Espinoza; Schaer, Thomas P.; Vresilovic, Edward J.; Elliott, Dawn M.

2012-01-01

Study Design Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these to the human disc. Objective To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. Summary of Background Data There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Methods Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar, and cow, rat, and mouse caudal. Collagen content was measured and normalized by dry weight for the same discs except the rat and mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Results Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Conclusion Disc torsion mechanics are comparable to human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented is useful for selecting and interpreting results for animal models of the disc. Structural composition of the disc, such as initial fiber angle, may explain the differences that were noted between species after geometric normalization. PMID:22333953

Quantitative characterization of the (D2O)3 torsional manifold by terahertz laser spectroscopy and theoretical analysis

NASA Astrophysics Data System (ADS)

Viant, Mark R.; Brown, Mac G.; Cruzan, Jeff D.; Saykally, Richard J.; Geleijns, Michel; van der Avoird, Ad

1999-03-01

We report the measurement of two new perpendicular (D2O)3 torsional bands by terahertz laser vibration-rotation-tunneling (VRT) spectroscopy of a planar pulsed supersonic expansion. The first (28.0 cm-1) band corresponds to the k=±2l←0 transition, and is the lowest frequency vibrational spectrum observed for a water cluster. The second (81.8 cm-1) band originates in the first excited torsional state, and has been assigned as k=3u←±1l. An effective three-dimensional Hamiltonian is derived to describe the rotational structure of each torsional state. Degenerate torsional levels with k=±1 and k=±2 exhibit a Coriolis splitting linear in K implying the presence of vibrational angular momentum, and a second-order splitting from off-diagonal coupling between degenerate sublevels with +|k| and -|k|. With this effective Hamiltonian we fit a total of 554 rovibrational transitions in five different bands connecting the lowest nine torsional states, with a rms residual of 1.36 MHz. The data set comprises the two new VRT bands together with the 41.1 cm-1 parallel band, the 89.6 cm-1 parallel band, and the 98.1 cm-1 perpendicular band. This analysis provides a comprehensive characterization of the torsional energy levels in (D2O)3 up to 100 cm-1 above the zero-point energy, and confirms the torsional assignments for all five (D2O)3 VRT bands observed to date. Moreover, it vindicates the adiabatic separation of the trimer torsional and hydrogen bond stretch/bend vibrational modes which underlies the torsional model.

Response of pendulums to complex input ground motion

USGS Publications Warehouse

Graizer, V.; Kalkan, E.

2008-01-01

Dynamic response of most seismological instruments and many engineering structures to ground shaking can be represented via response of a pendulum (single-degree-of-freedom oscillator). In most studies, pendulum response is simplified by considering the input from uni-axial translational motion alone. Complete ground motion however, includes not only translational components but also rotations (tilt and torsion). In this paper, complete equations of motion for three following types of pendulum are described: (i) conventional (mass-on-rod), (ii) mass-on-spring type, and (iii) inverted (astatic), then their response sensitivities to each component of complex ground motion are examined. The results of this study show that a horizontal pendulum similar to an accelerometer used in strong motion measurements is practically sensitive to translational motion and tilt only, while inverted pendulum commonly utilized to idealize multi-degree-of-freedom systems is sensitive not only to translational components, but also to angular accelerations and tilt. For better understanding of the inverted pendulum's dynamic behavior under complex ground excitation, relative contribution of each component of motion on response variants is carefully isolated. The systematically applied loading protocols indicate that vertical component of motion may create time-dependent variations on pendulum's oscillation period; yet most dramatic impact on response is produced by the tilting (rocking) component. ?? 2007 Elsevier Ltd. All rights reserved.

Coordinated Control of Three-Dimensional Components of Smooth Pursuit to Rotating and Translating Textures.

PubMed

Edinger, Janick; Pai, Dinesh K; Spering, Miriam

2017-01-01

The neural control of pursuit eye movements to visual textures that simultaneously translate and rotate has largely been neglected. Here we propose that pursuit of such targets-texture pursuit-is a fully three-dimensional task that utilizes all three degrees of freedom of the eye, including torsion. Head-fixed healthy human adults (n = 8) tracked a translating and rotating random dot pattern, shown on a computer monitor, with their eyes. Horizontal, vertical, and torsional eye positions were recorded with a head-mounted eye tracker. The torsional component of pursuit is a function of the rotation of the texture, aligned with its visual properties. We observed distinct behaviors between those trials in which stimulus rotation was in the same direction as that of a rolling ball ("natural") in comparison to those with the opposite rotation ("unnatural"): Natural rotation enhanced and unnatural rotation reversed torsional velocity during pursuit, as compared to torsion triggered by a nonrotating random dot pattern. Natural rotation also triggered pursuit with a higher horizontal velocity gain and fewer and smaller corrective saccades. Furthermore, we show that horizontal corrective saccades are synchronized with torsional corrective saccades, indicating temporal coupling of horizontal and torsional saccade control. Pursuit eye movements have a torsional component that depends on the visual stimulus. Horizontal and torsional eye movements are separated in the motor periphery. Our findings suggest that translational and rotational motion signals might be coordinated in descending pursuit pathways.

Assessment of radial torsion using computed tomography in dogs with and without antebrachial limb deformity.

PubMed

Kroner, Kevin; Cooley, Katie; Hoey, Seamus; Hetzel, Scott J; Bleedorn, Jason A

2017-01-01

To evaluate the reliability of radial torsion assessment in dogs using computed tomography (CT). Cadaveric and retrospective observational clinical study. Thoracic limbs (n = 40) from bilateral normal cadaveric canine specimens (10 pairs) and unilateral antebrachial angular limb deformity (ALD) dogs (10 uniapical and 10 biapical deformities). Limbs were evaluated using CT. Frontal, sagittal, and axial plane (torsion) values were obtained using published guidelines and compared between groups and limbs. Radial torsion reliability was assessed among 3 observers using intraclass correlation coefficients (ICC). The mean (±SD) radial torsion of normal dogs was 3.6° ± 6.4° and contained a significant right to left limb variation of 2.6°. Mean radial torsion in uniapical ALD limbs (3.6° ± 18.7°) was not significantly different from biapical ALD limbs (8.9° ± 17.9°). There was a wide range of torsion values in normal and ALD limbs. The interobserver reliability was excellent (ICC > 0.8) for normal dogs, good (0.73) for uniapical, and excellent (0.89) for biapical ALD limbs. The intraobserver reliability was excellent (>0.8) for all groups. There was a small side-to-side variation of radial torsion in normal dogs. With directed training, torsion assessment using CT is reliable in dogs with and without antebrachial bone deformity. © 2016 The American College of Veterinary Surgeons.

Chemomechanical synchronization in heterogeneous self-oscillating gels

NASA Astrophysics Data System (ADS)

Yashin, Victor V.; Balazs, Anna C.

2008-04-01

Using computational modeling, we introduce patches of self-oscillating gels undergoing the Belousov-Zhabotinsky (BZ) reaction into a nonreactive polymer network and thereby demonstrate how these BZ gels can be harnessed to impart remarkable functionality to the entire system. By first focusing on two adjacent patches of BZ gels, we show that the patches’ oscillations can become synchronized in phase or out of phase, with the oscillation frequency depending on the synchronization mode and the spatial separation between these domains. We then apply these results to an array of five adjacent BZ patches and by varying the distance between these pieces, we dramatically alter the dynamical behavior of the patterned gel. For example, the sample can be made to exhibit a unidirectional traveling wave or display a concerted expansion and contraction, properties that are valuable for creating gel-based devices, such as micropumps and microactuators. The findings point to a “modular” design approach, which can impart different functionality simply by arranging identical pieces of BZ gels into distinct spatial arrangements within a polymer matrix.

Intermittent Ovarian Torsion in Pregnancy

PubMed Central

Young, Randall; Cork, Kelly

2017-01-01

Ovarian torsion during pregnancy is a fairly uncommon complication with a high patient morbidity and fetal mortality if not immediately treated. Ovarian torsion should be considered a clinical diagnosis, and a high level of clinical suspicion is needed by the practitioner to ensure that this diagnosis is not missed. We present an unusual case of intermittent ovarian torsion discussing both the presentation and the operative and post-operative management. PMID:29849404

The effect of neck torsion on postural stability in subjects with persistent whiplash.

PubMed

Yu, Li-Ju; Stokell, Raina; Treleaven, Julia

2011-08-01

Dysfunction of cervical receptors in neck disorders has been shown to lead to disturbances in postural stability. The neck torsion manoeuvre used in the smooth pursuit neck torsion (SPNT) test is thought to be a specific measure of neck afferent dysfunction on eye movement in those with neck pain. This study aimed to determine whether neck torsion could change balance responses in those with persistent whiplash-associated disorders (WADs). Twenty subjects with persistent WAD and 20 healthy controls aged between 18 and 50 years stood on a computerised force plate with eyes closed in comfortable stance under 5 conditions: neutral head, head turned to left and right and neck torsion to left and right. Root mean square (rms) amplitude of sway was measured in the anterior-posterior (AP) and medial-lateral (ML) directions. The whiplash group had significantly greater rms amplitude in the AP direction following neck torsion compared to the control group (p < 0.03). The results show that the neck torsion manoeuvre may lead to greater postural deficits in individuals with persistent WAD and provides further evidence of neck torsion to identify abnormal cervical afferent input, as an underlying cause of balance disturbances in WAD. Further research is warranted. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

FIR Synchrotron Spectroscopy of High Torsional Levels of CD_3OH: the Tau of Methanol

NASA Astrophysics Data System (ADS)

Lees, Ronald M.; Xu, Li-Hong; Billinghurst, Brant E.

2015-06-01

Sub-bands involving high torsional levels of the CD_3OH isotopologue of methanol have been analyzed in Fourier transform spectra recorded at the Far-Infrared beamline of the Canadian Light Source synchrotron in Saskatoon. Energy term values for A and E torsional species of the third excited torsional state, v_t = 3, are now almost complete up to rotational levels K = 15, and thirteen substates have so far been identified for v_t = 4. The spectra show interesting close groupings of high-v_t sub-bands related by Dennison's torsional symmetry label τ, rather than A and E, that can be understood in terms of a simple and universal free-rotor "spectral predictor" chart. Transitions between states on the same free rotor curve have torsional overlap matrix elements close to unity, so give rise to strong sub-bands providing radiative routes for rapid population transfer through the high torsional manifold. Where the energy curves for the v_t = 3 and 4 ground-state torsional levels pass through the excited vibrational states, strong resonances can occur and a number of anharmonic and Coriolis interactions have been detected through perturbations to the spectra and appearance of forbidden transitions due to strong mixing and intensity borrowing.

Isolated torsion of fallopian tube in a post-menopausal patient: a case report.

PubMed

Ozgun, Mahmut Tuncay; Batukan, Cem; Turkyilmaz, Cagdas; Serin, Ibrahim Serdar

2007-07-20

Isolated fallopian tube torsion after menopause is a rare condition. Here we report the second case of isolated fallopian tube torsion in a post-menopausal woman. A 55-year-old post-menopausal woman presented with right lower abdominal pain. Sonography depicted a simple cystic mass adjacent to the right uterine border. Laparatomy revealed torsion of the right fallopian tube together with a paraovarian cyst. Total abdominal hysterectomy and bilateral salpingo-oophorectomy was performed. Histopathological examination revealed a simple paraovarian cyst with severe congestion, necrosis and hemorrhage. Tubal torsion should be considered in the differential diagnosis of acute lower abdominal pain, even in post-menopausal women.

Aeroelastic equations of motion of a Darrieus vertical-axis wind-turbine blade

NASA Technical Reports Server (NTRS)

Kaza, K. R. V.; Kvaternik, R. G.

1979-01-01

The second-degree nonlinear aeroelastic equations of motion for a slender, flexible, nonuniform, Darrieus vertical-axis wind turbine blade which is undergoing combined flatwise bending, edgewise bending, torsion, and extension are developed using Hamilton's principle. The blade aerodynamic loading is obtained from strip theory based on a quasi-steady approximation of two-dimensional incompressible unsteady airfoil theory. The derivation of the equations has its basis in the geometric nonlinear theory of elasticity and the resulting equations are consistent with the small deformation approximation in which the elongations and shears are negligible compared to unity. These equations are suitable for studying vibrations, static and dynamic aeroelastic instabilities, and dynamic response. Several possible methods of solution of the equations, which have periodic coefficients, are discussed.

Minocycline Attenuates Depressive-Like Behaviour Induced by Rat Model of Testicular Torsion: Involvement of Nitric Oxide Pathway.

PubMed

Saravi, Seyed Soheil Saeedi; Mousavi, Seyyedeh Elaheh; Saravi, Seyed Sobhan Saeedi; Dehpour, Ahmad Reza

2016-04-01

Testicular torsion/detorsion (T/D) can induce depression in pre- and post-pubertal patients. This study was conducted to investigate the psychological impact of testicular torsion and mechanism underlying its depressive-like behaviour, as well as antidepressant-like activity of minocycline and possible involvement of nitric oxide (NO)/cyclic GMP pathway in this paradigm in male rats undergoing testicular T/D. Unilateral T/D was performed in 36 male adult Wistar rats, and different doses of minocycline were injected alone or combined with N(ω) -nitro-l-arginine methyl ester (l-NAME), non-specific NO synthase (NOS) inhibitor; aminoguanidine (AG), specific inducible NOS inhibitor; l-arginine, an NO precursor; and selective PDE5I, sildenafil. After assessment of locomotor activity in open-field test, immobility times were recorded in the forced swimming test (FST). Moreover, 30 days after testicular T/D, testicular venous testosterone and serum nitrite concentrations were measured. A correlation was observed between either a decrease in plasma testosterone or an increase in serum nitrite concentrations with prolongation in immobility time in the testicular T/D-operated rats FST. Minocycline (160 mg/kg) exerted the highest significant antidepressant-like effect in the operated rats in the FST (p < 0.001). Furthermore, combination of subeffective doses of minocycline (80 mg/kg) and either l-NAME (10 mg/kg) or AG (50 mg/kg) demonstrated a significant robust antidepressant-like activity in T/D group (p < 0.01). Consequently, NO/cGMP pathway was involved in testicular T/D-induced depressive-like behaviour and antidepressant-like activity of minocycline in the animal model. Moreover, a contribution was observed between either decreased testosterone or elevated serum nitrite levels and depressive-like behaviour following testicular T/D. © 2015 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Research on torsional friction behavior and fluid load support of PVA/HA composite hydrogel.

PubMed

Chen, Kai; Zhang, Dekun; Yang, Xuehui; Cui, Xiaotong; Zhang, Xin; Wang, Qingliang

2016-09-01

Hydrogels have been extensively studied for use as synthetic articular cartilage. This study aimed to investigate (1) the torsional friction contact state and the transformation mechanism of PVA/HA composite hydrogel against CoCrMo femoral head and (2) effects of load and torsional angle on torsional friction behavior. The finite element method was used to study fluid load support of PVA/HA composite hydrogel. Results show fluid loss increases gradually of PVA/HA composite hydrogel with torsional friction time, leading to fluid load support decreases. The contact state changes from full slip state to stick-slip mixed state. As the load increases, friction coefficient and adhesion zone increase gradually. As the torsional angle increases, friction coefficient and slip trend of the contact interface increase, resulting in the increase of the slip zone and the reduction of the adhesion zone. Fluid loss increases of PVA/HA composite hydrogel as the load and the torsional angle increase, which causes the decrease of fluid load support and the increase of friction coefficient. Copyright © 2016 Elsevier Ltd. All rights reserved.

Complete body-neck torsion of the gallbladder: a case report.

PubMed

Pu, Ta-Wei; Fu, Chun-Yu; Lu, Huai-En; Cheng, Wei-Tung

2014-10-14

Gallbladder torsion is a rare, acute abdominal disease. It was first reported by Wendell in 1898. Since then, only 500 cases have been reported. Gallbladder torsion occurs in all age groups, although it usually appears in the latter stages of life. The occurrence ratio between women and men is 3:1. Most cases are diagnosed during surgery. The main treatment is surgical detorsion and cholecystectomy. Despite progress in radiologic imaging diagnosis, it is not easy to obtain a precise preoperative diagnosis of gallbladder torsion. In previous reports, only 9.8% of all gallbladder torsion cases were diagnosed preoperatively. We present a case of acute body-neck gallbladder torsion in an elderly man, and we review the radiologic findings of magnetic resonance imaging, computed tomography, and ultrasonography. The radiologic findings in the present case were helpful in obtaining a preoperative diagnosis of gallbladder torsion. The diagnosis was confirmed by T2-weighted magnetic resonance images, which showed an intra-gallbladder segment located between the body and neck of the gallbladder, with a notable crease within this segment.

Is ursodeoxycholic acid crucial for ischemia/reperfusion-induced ovarian injury in rat ovary?

PubMed

Akdemir, Ali; Sahin, Cagdas; Erbas, Oytun; Yeniel, Ahmet O; Sendag, Fatih

2015-08-01

Ursodeoxycholic acid is frequently used in cholestatic liver diseases. Also, it protects hepatocytes against oxidative stress induced by hydrophobic bile acids. We investigated the anti-oxidative effect of ursodeoxycholic acid on ischemia/reperfusion injury after ovarian de-torsion in rats. We designed five study groups. Group 1 (n = 6): Sham-operated group; group 2 (n = 6): torsion group; group 3 (n = 6): torsion and ursodeoxycholic acid, group 4 (n = 7): torsion/de-torsion group; and group 5 (n = 7): torsion/de-torsion and ursodeoxycholic acid. After that, ovarian samples were obtained and examined histologically and tissue levels of malondialdehyde were measured. Follicular degeneration, edema and inflammatory cells were significantly decreased in groups 3 and 5 in comparison with groups 2 and 4. Also, groups 4 and 5 were compared in terms of vascular congestion and hemorrhage and these were found to be significantly decreased in group 5. In addition, levels of malondialdehyde were significantly decreased in groups 3 and 5 in comparison with groups 2 and 4. We concluded that ursodeoxycholic acid might be useful to protect the ovary against ischemia and reperfusion injury.

Quantum Rotational Effects in Nanomagnetic Systems

NASA Astrophysics Data System (ADS)

O'Keeffe, Michael F.

Quantum tunneling of the magnetic moment in a nanomagnet must conserve the total angular momentum. For a nanomagnet embedded in a rigid body, reversal of the magnetic moment will cause the body to rotate as a whole. When embedded in an elastic environment, tunneling of the magnetic moment will cause local elastic twists of the crystal structure. In this thesis, I will present a theoretical study of the interplay between magnetization and rotations in a variety of nanomagnetic systems which have some degree of rotational freedom. We investigate the effect of rotational freedom on the tunnel splitting of a nanomagnet which is free to rotate about its easy axis. Calculating the exact instanton of the coupled equations of motion shows that mechanical freedom of the particle renormalizes the easy axis anisotropy, increasing the tunnel splitting. To understand magnetization dynamics in free particles, we study a quantum mechanical model of a tunneling spin embedded in a rigid rotor. The exact energy levels for a symmetric rotor exhibit first and second order quantum phase transitions between states with different values the magnetic moment. A quantum phase diagram is obtained in which the magnetic moment depends strongly on the moments of inertia. An intrinsic contribution to decoherence of current oscillations of a flux qubit must come from the angular momentum it transfers to the surrounding body. Within exactly solvable models of a qubit embedded in a rigid body and an elastic medium, we show that slow decoherence is permitted if the solid is macroscopically large. The spin-boson model is one of the simplest representations of a two-level system interacting with a quantum harmonic oscillator, yet has eluded a closed-form solution. I investigate some possible approaches to understanding its spectrum. The Landau-Zener dynamics of a tunneling spin coupled to a torsional resonator show that for certain parameter ranges the system exhibits multiple Landau-Zener transitions. These transitions coincide in time with changes in the oscillator dynamics. A large number of spins on a single oscillator coupled only through the in-phase oscillations behaves as a single large spin, greatly enhancing the spin-phonon coupling.

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.

Integrability conditions for Killing-Yano tensors and maximally symmetric spaces in the presence of torsion

NASA Astrophysics Data System (ADS)

Batista, Carlos

2015-04-01

The integrability conditions for the existence of Killing-Yano tensors or, equivalently, covariantly closed conformal Killing-Yano tensors, in the presence of torsion are worked out. As an application, all metrics and torsions compatible with the existence of a Killing-Yano tensor of order n -1 are obtained. Finally, the issue of defining a maximally symmetric space with respect to connections with torsion is addressed.

Damping system for torsion modes of mirror isolation filters in TAMA300

NASA Astrophysics Data System (ADS)

Arase, Y.; Takahashi, R.; Arai, K.; Tatsumi, D.; Fukushima, M.; Yamazaki, T.; Fujimoto, Masa-Katsu; Agatsuma, K.; Nakagawa, N.

2008-07-01

The seismic attenuation system (SAS) in TAMA300 consists of a three-legged inverted pendulum and mirror isolation filters in order to provide a high level of seismic isolation. However, the mirror isolation filters have torsion modes with long decay time which disturb the interferometer operation for about half an hour if they get excited. In order to damp the torsion modes of the filters, we constructed a digital damping system using reflective photosensors with a large linear range. This system was installed to all of four SASs. By damping of the target torsion modes, the effective quality factors of the torsion modes are reduced to less than 10 or to unmeasurable level. This system is expected to reduce the inoperative period by the torsion mode excitation, and thus will contribute to improve the duty time of the gravitational wave detector.

Ionic polymer-metal composite torsional sensor: physics-based modeling and experimental validation

NASA Astrophysics Data System (ADS)

Aidi Sharif, Montassar; Lei, Hong; Khalid Al-Rubaiai, Mohammed; Tan, Xiaobo

2018-07-01

Ionic polymer-metal composites (IPMCs) have intrinsic sensing and actuation properties. Typical IPMC sensors are in the shape of beams and only respond to stimuli acting along beam-bending directions. Rod or tube-shaped IPMCs have been explored as omnidirectional bending actuators or sensors. In this paper, physics-based modeling is studied for a tubular IPMC sensor under pure torsional stimulus. The Poisson–Nernst–Planck model is used to describe the fundamental physics within the IPMC, where it is hypothesized that the anion concentration is coupled to the sum of shear strains induced by the torsional stimulus. Finite element simulation is conducted to solve for the torsional sensing response, where some of the key parameters are identified based on experimental measurements using an artificial neural network. Additional experimental results suggest that the proposed model is able to capture the torsional sensing dynamics for different amplitudes and rates of the torsional stimulus.

Torsion of partial cleft of ear lobule.

PubMed

Kumaraswamy, M; Waiker, Veena P

2014-02-01

Torsion is a well-known phenomenon involving organs with long mesentery. Torsion in the ear lobule is rare. Ear lobule is very well vascularized. In cases of partial cleft ear lobule, there is a small segment of lobule inferior to the cleft which is vascularized through the pedicles on either side of the cleft. A lady aged 89 years presented with discoloration of the ear lobule. She was diagnosed as having gangrene of the central part of lobule. The segment of the lobule had undergone more than 360° torsion. She underwent debridement of gangrenous part and lobuloplasty. In our case laxity of the stretched lobule caused the torsion of the segment followed by gangrene. This rare complication indicates the need for correction of the cleft lobule not only for esthetic purpose, but also for the prevention of torsion. Copyright © 2013 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

Torsion Profiling of Proteins Using Magnetic Particles

PubMed Central

van Reenen, A.; Gutiérrez-Mejía, F.; van IJzendoorn, L.J.; Prins, M.W.J.

2013-01-01

We report a method to profile the torsional spring properties of proteins as a function of the angle of rotation. The torque is applied by superparamagnetic particles and has been calibrated while taking account of the magnetization dynamics of the particles. We record and compare the torsional profiles of single Protein G-Immunoglobulin G (IgG) and IgG-IgG complexes, sandwiched between a substrate and a superparamagnetic particle, for torques in the range between 0.5 × 103 and 5 × 103 pN·nm. Both molecular systems show torsional stiffening for increasing rotation angle, but the elastic and inelastic torsion stiffnesses are remarkably different. We interpret the results in terms of the structural properties of the molecules. The torsion profiling technique opens new dimensions for research on biomolecular characterization and for research on bio-nanomechanical structure-function relationships. PMID:23473490

Torsion of a nongravid uterus with a large ovarian cyst: usefulness of contrast MR image.

PubMed

Matsumoto, Hiroki; Ohta, Tsuyoshi; Nakahara, Kenji; Kojimahara, Takanobu; Kurachi, Hirohisa

2007-01-01

Torsion of a nongravid uterus is extremely rare. Most cases of uterine torsion occur during pregnancy. Here we report a case of nongravid uterus torsion with a large adnexal mass. A 73-year-old woman presented at the emergency room with acute abdominal pain. A preoperative diagnosis of torsion of an ovarian cyst was made and laparotomy was performed. The left ovary was twisted 360 degrees in a clockwise rotation, and the uterine corpus had also undergone a 360 degrees rotation. Total abdominal hysterectomy and bilateral salpingo-oophorectomy were carried out. Although a preoperative diagnosis of uterine torsion was not possible, it is noteworthy that in the contrast-enhanced magnetic resonance images the uterine cervix was intensely enhanced, while the uterine corpus was not. This is the first report to show the magnetic resonance imaging findings of a twisted uterus. Copyright (c) 2007 S. Karger AG, Basel.

Solar filament material oscillations and drainage before eruption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bi, Yi; Jiang, Yunchun; Yang, Jiayan

Both large-amplitude longitudinal (LAL) oscillations and material drainage in a solar filament are associated with the flow of material along the filament axis, often followed by an eruption. However, the relationship between these two motions and a subsequent eruption event is poorly understood. We analyze a filament eruption using EUV imaging data captured by the Atmospheric Imaging Array on board the Solar Dynamics Observatory and the Hα images from the Global Oscillation Network Group. Hours before the eruption, the filament was activated, with one of its legs undergoing a slow rising motion. The asymmetric activation inclined the filament relative tomore » the solar surface. After the active phase, LAL oscillations were observed in the inclined filament. The oscillation period increased slightly over time, which may suggest that the magnetic fields supporting the filament evolve to be flatter during the slow rising phase. After the oscillations, a significant amount of filament material was drained toward one filament endpoint, followed immediately by the violent eruption of the filament. The material drainage may further support the change in magnetic topology prior to the eruption. Moreover, we suggest that the filament material drainage could play a role in the transition from a slow to a fast rise of the erupting filament.« less

The g - 2 muon anomaly in di-muon production with the torsion in LHC

NASA Astrophysics Data System (ADS)

Syromyatnikov, A. G.

2016-06-01

It was considered within the framework of the conformal gauge gravitational theory CGTG coupling of the standard model fermions to the axial torsion and preliminary discusses the impact of extra dimensions, in particular, in a five-dimensional space-time with Randall-Sundrum metric, where the fifth dimension is compactified on an S1/Z 2 orbifold, which as it turns out is conformally to the fifth dimension flat Euclidean space with permanent trace of torsion, with a compactification radius R in terms of the radius of a CGTG gravitational screening, through torsion in a process Z → μ+μ- and LHC data. In general, have come to the correct set of the conformal calibration curvature the Faddeev-Popov diagram technique type, that follows directly from dynamics. This leads to the effect of restrictions on neutral spin currents of gauge fields by helicity and the Regge’s form theory. The diagrams reveals the fact of opening of the fine spacetime structure in a process pp → γ/Z/T → μ+μ- with a center-of-mass energy of 14TeV, indicated by dotted lines and texture columns, as a result of p-p collision on 1.3 ṡ 10-18cm scales from geometric shell gauge bosons of the SM continued by the heavy axial torsion resonance, and even by emerging from the inside into the outside of the ultra-light (freely-frozen in muon’s spin) axial torsion. We then evaluate the contribution of the torsion to the muon anomaly to derive new constraints on the torsion parameters. It was obtained that on the πN scattering through the exchange of axial torsion accounting, the nucleon anomalous magnetic moment in the eikonal phase leads to additive additives which is responsible for the spin-flip in the scattering process, the scattering amplitude is classical and characterized by a strong the torsion coupling ηT≅1. So the scattering of particles, occurs as on the Coulomb center with the charge fT This is the base model which is the g-2 muon anomaly. The muon anomaly contribution due to the heavy axial vector torsion arises from coupling the muon with torsion as external field. This leads to negative energy additive to mass of muons which makes the missing part of the g-2 muon anomaly. It takes place at reasonable values of the transverse front size of the exact solution CGTG equations types of torsion waves with the spin-flip close to the size of the Compton length muon.

Anomalous torsional tripling in the ν9 and ν10 CH3-deformation modes of ethane 12CH313CH3

NASA Astrophysics Data System (ADS)

Lattanzi, F.; di Lauro, C.

2017-12-01

We have investigated the anomalous torsional behavior in the coupled ν9 and ν10 vibrational fundamentals of 12CH313CH3, both states exhibiting a splitting into three components, instead of two, only in those rotational levels which are very close to resonance. We conclude that the intrinsic additional splitting, which occurs in the E-torsional components, for these two vibrational states is too small to be detected in the high resolution infrared spectrum, but it is substantively enhanced by their coupling. It is shown that this effect requires the simultaneous action of torsion independent operators, such as Fermi-type and z-Coriolis, not allowed in the more symmetric isotopologue 12CH312CH3, and torsion dependent operators, such as torsional-Coriolis, connecting the two vibrational states. Our conclusions lead to a simple model for the coupling of ν9 and ν10, with effective Fermi-type matrix elements W for the A-torsional components, and W ± w for the two pairs of E-torsional components. This causes the additional splitting in the E-pairs. This model is consistent with the mechanism causing the Coriolis-dependent decrease of the A-E torsional splitting in degenerate vibrational states. Exploratory calculations were performed making use of results from a normal mode analysis, showing that the effects predictable by the proposed model are of the correct order of magnitude compared to the observed features, with coupling parameter values reasonably consistent with those determined by the least squares fit of the observed transition wavenumbers.

Intraoperative performance and postoperative outcome comparison of longitudinal, torsional, and transversal phacoemulsification machines.

PubMed

Christakis, Panos G; Braga-Mele, Rosa M

2012-02-01

To compare the intraoperative performance and postoperative outcomes of 3 phacoemulsification machines that use different modes. Kensington Eye Institute, Toronto, Ontario, Canada. Comparative case series. This chart and video review comprised consecutive eligible patients who had phacoemulsification by the same surgeon using a Whitestar Signature Ellips-FX (transversal), Infiniti-Ozil-IP (torsional), or Stellaris (longitudinal) machine. The review included 98 patients. Baseline characteristics in the groups were similar; the mean nuclear sclerosis grade was 2.0 ± 0.8. There were no significant intraoperative complications. The torsional machine averaged less phacoemulsification needle time (83 ± 33 seconds) than the transversal (99 ± 40 seconds; P=.21) or longitudinal (110 ± 45 seconds; P=.02) machines; the difference was accentuated in cases with high-grade nuclear sclerosis. The torsional machine had less chatter and better followability than the transversal or longitudinal machines (P<.001). The torsional and longitudinal machines had better anterior chamber stability than the transversal machine (P<.001). Postoperatively, the torsional machine yielded less central corneal edema than the transversal (P<.001) and longitudinal (P=.04) machines, corresponding to a smaller increase in mean corneal thickness (torsional 5%, transversal 10%, longitudinal 12%; P=.04). Also, the torsional machine had better 1-day postoperative visual acuities (P<.001). All 3 phacoemulsification machines were effective with no significant intraoperative complications. The torsional machine outperformed the transversal and longitudinal machines, with a lower mean needle time, less chatter, and improved followability. This corresponded to less corneal edema 1 day postoperatively and better visual acuity. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Isolated fallopian tube torsion in pediatric and adolescent females: a retrospective review of 15 cases at a single institution.

PubMed

Casey, Rachel K; Damle, Lauren F; Gomez-Lobo, Veronica

2013-06-01

To identify and review cases of isolated fallopian tube torsion (FTT) at our institution to further characterize diagnosis and management. Retrospective review. Tertiary care medical center. Case series of pediatric and adolescent females, <21 years old, with operatively diagnosed isolated fallopian tube torsion from our institution. None. Isolated fallopian tube torsion. Fifteen cases of isolated fallopian tube torsion were identified based on intraoperative diagnosis. Patient ages ranged from 8-15 years old, mean age of 12. Fourteen patients (93%) presented with abdominal pain, 8 (53%) localized to the side of associated torsion. Ultrasonography reports described a tubular structure in 4 patients and an associated ovarian or paraovarian cyst in eleven patients. Suspicion of fallopian tube torsion was only described for those patients with a tubular structure described on ultrasonography report. Intraoperatively, 7 patients (47%) were found to have no associated pathology and 8 (53%) were found to have associated cyst or hydrosalpinx. Eight (53%) patients underwent salipingectomy and 7 (47%) underwent reversal of torsion with drainage of associated cyst or cystectomy. Isolated fallopian tube torsion is a rare condition that seems to occur in younger adolescents. Vague clinical presentation contributes to low preoperative suspicion. Preoperative suspicion may be increased based on radiographic findings of an enlarged tubular structure or an adjacent normal ovary. Management may be considered nonemergent and salpingectomy is controversial. Long-term fertility outcomes must be further assessed for more definitive decisions regarding surgical management. Copyright © 2013 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

Left ventricular torsional mechanics and myocardial iron load in beta-thalassaemia major: a potential role of titin degradation.

PubMed

Chen, Mei-Pian; Li, Shu-Na; Lam, Wendy W M; Ho, Yuen-Chi; Ha, Shau-Yin; Chan, Godfrey C F; Cheung, Yiu-Fai

2014-04-12

Iron may damage sarcomeric proteins through oxidative stress. We explored the left ventricular (LV) torsional mechanics in patients with beta-thalassaemia major and its relationship to myocardial iron load. Using HL-1 cell and B6D2F1 mouse models, we further determined the impact of iron load on proteolysis of the giant sarcomeric protein titin. In 44 thalassaemia patients aged 25 ± 7 years and 38 healthy subjects, LV torsion and twisting velocities were determined at rest using speckle tracking echocardiography. Changes in LV torsional parameters during submaximal exercise testing were further assessed in 32 patients and 17 controls. Compared with controls, patients had significantly reduced LV apical rotation, torsion, systolic twisting velocity, and diastolic untwisting velocity. T2* cardiac magnetic resonance findings correlated with resting diastolic untwisting velocity. The increments from baseline and resultant LV torsion and systolic and diastolic untwisting velocities during exercise were significantly lower in patients than controls. Significant correlations existed between LV systolic torsion and diastolic untwisting velocities in patients and controls, both at rest and during exercise. In HL-1 cells and ventricular myocardium of B6D2F1 mice overloaded with iron, the titin-stained pattern of sarcomeric structure became disrupted. Gel electrophoresis of iron-overloaded mouse myocardial tissue further showed significant decrease in the amount of titin isoforms and increase in titin degradation products. Resting and dynamic LV torsional mechanics is impaired in patients with beta-thalassaemia major. Cell and animal models suggest a potential role of titin degradation in iron overload-induced alteration of LV torsional mechanics.

Isolated penile torsion in newborns.

PubMed

Eroglu, Egemen; Gundogdu, Gokhan

2015-01-01

We reported on the incidence of isolated penile torsion among our healthy children and our approach to this anomaly. 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°. 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. 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.

Non-minimally coupled scalar field cosmology with torsion

NASA Astrophysics Data System (ADS)

Cid, Antonella; Izaurieta, Fernando; Leon, Genly; Medina, Perla; Narbona, Daniela

2018-04-01

In this work we present a generalized Brans-Dicke lagrangian including a non-minimally coupled Gauss-Bonnet term without imposing the vanishing torsion condition. In the resulting field equations, the torsion is closely related to the dynamics of the scalar field, i.e., if non-minimally coupled terms are present in the theory, then the torsion must be present. For the studied lagrangian we analyze the cosmological consequences of an effective torsional fluid and we show that this fluid can be responsible for the current acceleration of the universe. Finally, we perform a detailed dynamical system analysis to describe the qualitative features of the model, we find that accelerated stages are a generic feature of this scenario.

Methamphetamine use can mimic testicular torsion.

PubMed

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

2013-09-01

We report the case of a patient presenting with the classic clinical appearance of testicular torsion. Ultrasound showed testicular ischemia supporting the clinical diagnosis, but the lack of visualization of spermatic cord torsion was of concern. An attempt of clinical detorsion was considered unsuccessful and the patient was explored. No torsion was found. On postoperative review of the patient's medical history, we found methamphetamine use, with a positive urine test at the time of his emergent consultation for the scrotal pain episode. The use of amphetamines has been previously reported as the cause of ischemia of multiple organs, but we could not find previous reports of involvement of the testis mimicking torsion. Copyright © 2013 Wiley Periodicals, Inc.

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.

Direct observation of methyl rotor and vib-rotor states of S0 toluene: a revised torsional barrier due to torsion-vibration coupling.

PubMed

Gascooke, Jason R; Virgo, Edwina A; Lawrance, Warren D

2015-01-14

We report a two dimensional, laser induced fluorescence study of the lowest 345 cm(-1) region of S0 toluene. Methyl rotor levels of 00 up to m = 6 and of 201 up to m = 4 are observed. The rotor levels of 00 and 201 have quite different energy spacings that are well fit by a model that includes strong torsion-vibration coupling between them. The model requires that the rotor barrier height be revised from -4.84 cm(-1) (methyl hydrogens in a staggered conformation) to +1.57 cm(-1) (eclipsed conformation). However, the 3a2″ state lies below the 3a1″ state as expected for a staggered conformation due to energy shifts associated with the torsion-vibration coupling. It is shown that the rotor wave-functions exhibit little localization at the torsional energy minima. The variation in the m = 0 wavefunction probability distribution with torsional angle is shown to be very similar for the previously accepted negative V6 value and the torsion-vibration coupling model as this coupling shifts the phase of the wavefunction by 30° compared with its phase for V6 alone. The presence of a strong Δυ = ± 1 torsion-vibration coupling involving the lowest frequency vibrational mode provides a potential pathway for rapid intramolecular vibrational energy redistribution at higher energies.

Decreased Left Ventricular Torsion and Untwisting in Children with Dilated Cardiomyopathy

PubMed Central

Jin, Seon Mi; Bae, Eun Jung; Choi, Jung Yun; Yun, Yong Soo

2007-01-01

The purpose of this study was to analyze left ventricular (LV) torsion and untwisting, and to evaluate the correlation between torsion and other components of LV contraction in children with dilated cardiomyopathy (DCM). Segmental and global rotation, rotational rate (Vrot) were measured at three levels of LV using the two-dimensional (2D) speckle tracking imaging (STI) method in 10 DCM patients (range 0.6-15 yr, median 6.5 yr, 3 females) and 17 age- and sex-matched normal controls. Global torsion was decreased in DCM (peak global torsion; 10.9±4.6° vs. 0.3±2.1°, p<0.001). Loss of LV torsion occurred mainly by the diminution of counterclockwise apical rotation and was augmented by somewhat less reduction in clockwise basal rotation. In DCM, the normal counterclockwise apical rotation was not observed, and the apical rotation about the central axis was clockwise or slightly counterclockwise (peak apical rotation; 5.9±4.1° vs. -0.9±3.1°, p<0.001). Systolic counterclockwise Vrot and early diastolic clockwise Vrot at the apical level were decreased or abolished. In DCM, decreased systolic torsion and loss of early diastolic recoil contribute to LV systolic and diastolic dysfunction. The STI method may facilitate the serial evaluation of the LV torsional behavior in clinical settings and give new biomechanical concepts for better management of patients with DCM. PMID:17728501

Cyclic Axial-Torsional Deformation Behavior of a Cobalt-Base Superalloy

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1995-01-01

The cyclic, high-temperature deformation behavior of a wrought cobalt-base super-alloy, Haynes 188, is investigated under combined axial and torsional loads. This is accomplished through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue database has been generated on Haynes 188 at 760 C. Cyclic loading tests have been conducted on uniform gage section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. The fatigue behavior of Haynes 188 at 760 C under axial, torsional, and combined axial-torsional loads and the monotonic and cyclic deformation behaviors under axial and torsional loads have been previously reported. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress ,versus engineering shear strain, axial strain versus engineering shear strain. and axial stress versus shear stress spaces are presented for cyclic in-phase and out-of-phase axial-torsional tests. For in-phase tests, three different values of the proportionality constant lambda (the ratio of engineering shear strain amplitude to axial strain amplitude, are examined, viz. 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, phi (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90 degrees with lambda equals 1.73. The cyclic hardening behaviors of all the tests conducted on Haynes 188 at 760 C are evaluated using the von Mises equivalent stress-strain and the maximum shear stress-maximum engineering shear strain (Tresca) curves. Comparisons are also made between the hardening behaviors of cyclic axial, torsional, and combined in-phase (lambda = 1.73 and phi = 0) and out-of-phase (lambda = 1.73 and phi = 90') axial-torsional fatigue tests. These comparisons are accomplished through simple Ramberg-Osgood type stress-strain functions for cyclic, axial stress-strain and shear stress-engineering shear strain curves.

Observation of Bloch oscillations in complex PT-symmetric photonic lattices

PubMed Central

Wimmer, Martin; Miri, Mohammed-Ali; Christodoulides, Demetrios; Peschel, Ulf

2015-01-01

Light propagation in periodic environments is often associated with a number of interesting and potentially useful processes. If a crystalline optical potential is also linearly ramped, light can undergo periodic Bloch oscillations, a direct outcome of localized Wannier-Stark states and their equidistant eigenvalue spectrum. Even though these effects have been extensively explored in conservative settings, this is by no means the case in non-Hermitian photonic lattices encompassing both amplification and attenuation. Quite recently, Bloch oscillations have been predicted in parity-time-symmetric structures involving gain and loss in a balanced fashion. While in a complex bulk medium, one intuitively expects that light will typically follow the path of highest amplification, in a periodic system this behavior can be substantially altered by the underlying band structure. Here, we report the first experimental observation of Bloch oscillations in parity-time-symmetric mesh lattices. We show that these revivals exhibit unusual properties like secondary emissions and resonant restoration of PT symmetry. In addition, we present a versatile method for reconstructing the real and imaginary components of the band structure by directly monitoring the light evolution during a cycle of these oscillations. PMID:26639941

Peripheral Circadian Clock Rhythmicity Is Retained in the Absence of Adrenergic Signaling

PubMed Central

Reilly, Dermot F.; Curtis, Anne M.; Cheng, Yan; Westgate, Elizabeth J.; Rudic, Radu D.; Paschos, Georgios; Morris, Jacqueline; Ouyang, Ming; Thomas, Steven A.; FitzGerald, Garret A.

2009-01-01

Objective The incidence of heart attack and stroke undergo diurnal variation. Molecular clocks have been described in the heart and the vasculature; however it is largely unknown how the suprachiasmatic nucleus (SCN) entrains these peripheral oscillators. Methods and Results Norepinephrine and epinephrine, added to aortic smooth muscle cells (ASMCs) in vitro, altered Per1, E4bp4, and dbp expression and altered the observed oscillations in clock gene expression. However, oscillations of Per1, E4bp4, dbp, and Per2 were preserved ex vivo in the aorta, heart, and liver harvested from dopamine β-hydroxylase knockout mice (Dbh−/−) that cannot synthesize either norepinephrine or epinephrine. Furthermore, clock gene oscillations in heart, liver, and white adipose tissue phase shifted identically in Dbh−/− mice and in Dbh+/− controls in response to daytime restriction of feeding. Oscillation of clock genes was similarly preserved ex vivo in tissues from Dbh+/− and Dbh−/− chronically treated with both propranolol and terazosin, thus excluding compensation by dopamine in Dbh−/− mice. Conclusions Although adrenergic signaling can influence circadian timing in vitro, peripheral circadian rhythmicity is retained despite its ablation in vivo. PMID:17975121

Observation of Bloch oscillations in complex PT-symmetric photonic lattices

NASA Astrophysics Data System (ADS)

Wimmer, Martin; Miri, Mohammed-Ali; Christodoulides, Demetrios; Peschel, Ulf

2015-12-01

Light propagation in periodic environments is often associated with a number of interesting and potentially useful processes. If a crystalline optical potential is also linearly ramped, light can undergo periodic Bloch oscillations, a direct outcome of localized Wannier-Stark states and their equidistant eigenvalue spectrum. Even though these effects have been extensively explored in conservative settings, this is by no means the case in non-Hermitian photonic lattices encompassing both amplification and attenuation. Quite recently, Bloch oscillations have been predicted in parity-time-symmetric structures involving gain and loss in a balanced fashion. While in a complex bulk medium, one intuitively expects that light will typically follow the path of highest amplification, in a periodic system this behavior can be substantially altered by the underlying band structure. Here, we report the first experimental observation of Bloch oscillations in parity-time-symmetric mesh lattices. We show that these revivals exhibit unusual properties like secondary emissions and resonant restoration of PT symmetry. In addition, we present a versatile method for reconstructing the real and imaginary components of the band structure by directly monitoring the light evolution during a cycle of these oscillations.

Three-Dimensional Rotation, Twist and Torsion Analyses Using Real-Time 3D Speckle Tracking Imaging: Feasibility, Reproducibility, and Normal Ranges in Pediatric Population.

PubMed

Zhang, Li; Zhang, Jing; Han, Wei; Gao, Jun; He, Lin; Yang, Yali; Yin, Ping; Xie, Mingxing; Ge, Shuping

2016-01-01

The specific aim of this study was to evaluate the feasibility, reproducibility and maturational changes of LV rotation, twist and torsion variables by real-time 3D speckle-tracking echocardiography (RT3DSTE) in children. A prospective study was conducted in 347 consecutive healthy subjects (181 males/156 females, mean age 7.12 ± 5.3 years, and range from birth to 18-years) using RT 3D echocardiography (3DE). The LV rotation, twist and torsion measurements were made off-line using TomTec software. Manual landmark selection and endocardial border editing were performed in 3 planes (apical "2"-, "4"-, and "3"- chamber views) and semi-automated tracking yielded LV rotation, twist and torsion measurements. LV rotation, twist and torsion analysis by RT 3DSTE were feasible in 307 out of 347 subjects (88.5%). There was no correlation between rotation or twist and age, height, weight, BSA or heart rate, respectively. However, there was statistically significant, but very modest correlation between LV torsion and age (R2 = 0.036, P< 0.001). The normal ranges were defined for rotation and twist in this cohort, and for torsion for each age group. The intra-observer and inter-observer variabilities for apical and basal rotation, twist and torsion ranged from 7.3% ± 3.8% to 12.3% ± 8.8% and from 8.8% ± 4.6% to 15.7% ± 10.1%, respectively. We conclude that analysis of LV rotation, twist and torsion by this new RT3D STE is feasible and reproducible in pediatric population. There is no maturational change in rotation and twist, but torsion decreases with age in this cohort. Further refinement is warranted to validate the utility of this new methodology in more sensitive and quantitative evaluation of congenital and acquired heart diseases in children.

Torsional ultrasound mode versus combined torsional and conventional ultrasound mode phacoemulsification for eyes with hard cataract.

PubMed

Fakhry, Mohamed A; El Shazly, Malak I

2011-01-01

To compare torsional versus combined torsional and conventional ultrasound modes in hard cataract surgery regarding ultrasound energy and time and effect on corneal endothelium. Kasr El Aini hospital, Cairo University, and International Eye Hospital, Cairo, Egypt. 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). 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). Both modes are safe in hard cataract surgery, however the pure torsional mode showed less US energy used.

Torsional ultrasound mode versus combined torsional and conventional ultrasound mode phacoemulsification for eyes with hard cataract

PubMed Central

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:21792288

Axial and Torsional Load-Type Sequencing in Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

2001-01-01

The experiments described herein were performed to determine whether damage imposed by axial loading interacts with damage imposed by torsional loading. This paper is a follow on to a study that investigated effects of load-type sequencing on the cumulative fatigue behavior of a cobalt base superalloy, Haynes 188 at 538 C Both the current and the previous study were used to test the applicability of cumulative fatigue damage models to conditions where damage is imposed by different loading modes. In the previous study, axial and torsional two load level cumulative fatigue experiments were conducted, in varied combinations, with the low-cycle fatigue (high amplitude loading) applied first. In present study, the high-cycle fatigue (low amplitude loading) is applied initially. As in the previous study, four sequences (axial/axial, torsion/torsion, axial/torsion, and torsion/axial) of two load level cumulative fatigue experiments were performed. The amount of fatigue damage contributed by each of the imposed loads was estimated by both the Palmgren-Miner linear damage rule (LDR) and the non-linear damage curve approach (DCA). Life predictions for the various cumulative loading combinations are compared with experimental results.

Effect of Relative Marker Movement on the Calculation of the Foot Torsion Axis Using a Combined Cardan Angle and Helical Axis Approach

PubMed Central

Graf, Eveline S.; Wright, Ian C.; Stefanyshyn, Darren J.

2012-01-01

The two main movements occurring between the forefoot and rearfoot segment of a human foot are flexion at the metatarsophalangeal joints and torsion in the midfoot. The location of the torsion axis within the foot is currently unknown. The purpose of this study was to develop a method based on Cardan angles and the finite helical axis approach to calculate the torsion axis without the effect of flexion. As the finite helical axis method is susceptible to error due to noise with small helical rotations, a minimal amount of rotation was defined in order to accurately determine the torsion axis location. Using simulation, the location of the axis based on data containing noise was compared to the axis location of data without noise with a one-sample t-test and Fisher's combined probability score. When using only data with helical rotation of seven degrees or more, the location of the torsion axis based on the data with noise was within 0.2 mm of the reference location. Therefore, the proposed method allowed an accurate calculation of the foot torsion axis location. PMID:22666303

Development of a method for measuring femoral torsion using real-time ultrasound.

PubMed

Hafiz, Eliza; Hiller, Claire E; Nicholson, Leslie L; Nightingale, E Jean; Clarke, Jillian L; Grimaldi, Alison; Eisenhuth, John P; Refshauge, Kathryn M

2014-07-01

Excessive femoral torsion has been associated with various musculoskeletal and neurological problems. To explore this relationship, it is essential to be able to measure femoral torsion in the clinic accurately. Computerized tomography (CT) and magnetic resonance imaging (MRI) are thought to provide the most accurate measurements but CT involves significant radiation exposure and MRI is expensive. The aim of this study was to design a method for measuring femoral torsion in the clinic, and to determine the reliability of this method. Details of design process, including construction of a jig, the protocol developed and the reliability of the method are presented. The protocol developed used ultrasound to image a ridge on the greater trochanter, and a customized jig placed on the femoral condyles as reference points. An inclinometer attached to the customized jig allowed quantification of the degree of femoral torsion. Measurements taken with this protocol had excellent intra- and inter-rater reliability (ICC2,1 = 0.98 and 0.97, respectively). This method of measuring femoral torsion also permitted measurement of femoral torsion with a high degree of accuracy. This method is applicable to the research setting and, with minor adjustments, will be applicable to the clinical setting.

Torsional Tribological Behavior and Torsional Friction Model of Polytetrafluoroethylene against 1045 Steel

PubMed Central

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

ALFVÉN WAVES IN SIMULATIONS OF SOLAR PHOTOSPHERIC VORTICES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shelyag, S.; Cally, P. S.; Reid, A.

Using advanced numerical magneto-hydrodynamic simulations of the magnetized solar photosphere, including non-gray radiative transport and a non-ideal equation of state, we analyze plasma motions in photospheric magnetic vortices. We demonstrate that apparent vortex-like motions in photospheric magnetic field concentrations do not exhibit 'tornado'-like behavior or a 'bath-tub' effect. While at each time instance the velocity field lines in the upper layers of the solar photosphere show swirls, the test particles moving with the time-dependent velocity field do not demonstrate such structures. Instead, they move in a wave-like fashion with rapidly changing and oscillating velocity field, determined mainly by magnetic tensionmore » in the magnetized intergranular downflows. Using time-distance diagrams, we identify horizontal motions in the magnetic flux tubes as torsional Alfvén perturbations propagating along the nearly vertical magnetic field lines with local Alfvén speed.« less

Development of an unsteady aerodynamics model to improve correlation of computed blade stresses with test data

NASA Technical Reports Server (NTRS)

Gangwani, S. T.

1985-01-01

A reliable rotor aeroelastic analysis operational that correctly predicts the vibration levels for a helicopter is utilized to test various unsteady aerodynamics models with the objective of improving the correlation between test and theory. This analysis called Rotor Aeroelastic Vibration (RAVIB) computer program is based on a frequency domain forced response analysis which utilizes the transfer matrix techniques to model helicopter/rotor dynamic systems of varying degrees of complexity. The results for the AH-1G helicopter rotor were compared with the flight test data during high speed operation and they indicated a reasonably good correlation for the beamwise and chordwise blade bending moments, but for torsional moments the correlation was poor. As a result, a new aerodynamics model based on unstalled synthesized data derived from the large amplitude oscillating airfoil experiments was developed and tested.

Spontaneous Scalarization: Dead or Alive?

NASA Astrophysics Data System (ADS)

Berti, Emanuele; Crispino, Luis; Gerosa, Davide; Gualtieri, Leonardo; Horbatsch, Michael; Macedo, Caio; Okada da Silva, Hector; Pani, Paolo; Sotani, Hajime; Sperhake, Ulrich

2015-04-01

In 1993, Damour and Esposito-Farese showed that a wide class of scalar-tensor theories can pass weak-field gravitational tests and exhibit nonperturbative strong-field deviations away from General Relativity in systems involving neutron stars. These deviations are possible in the presence of ``spontaneous scalarization,'' a phase transition similar in nature to spontaneous magnetization in ferromagnets. More than twenty years after the original proposal, binary pulsar experiments have severely constrained the possibility of spontaneous scalarization occurring in nature. I will show that these experimental constraints have important implications for the torsional oscillation frequencies of neutron stars and for the so-called ``I-Love-Q'' relations in scalar-tensor theories. I will also argue that there is still hope to observe strong scalarization effects, despite the strong experimental bounds on the original mechanism. In particular, I will discuss two mechanisms that could produce strong scalarization in neutron stars: anisotropy and multiscalarization. This work was supported by NSF CAREER Award PHY-1055103.

On the Possibilities of Predicting Geomagnetic Secular Variation with Geodynamo Modeling

NASA Technical Reports Server (NTRS)

Kuang, Wei-Jia; Tangborn, Andrew; Sabaka, Terrance

2004-01-01

We use our MoSST core dynamics model and geomagnetic field at the core-mantle boundary (CMB) continued downward from surface observations to investigate possibilities of geomagnetic data assimilation, so that model results and current geomagnetic observations can be used to predict geomagnetic secular variation in future. As the first attempt, we apply data insertion technique to examine evolution of the model solution that is modified by geomagnetic input. Our study demonstrate that, with a single data insertion, large-scale poloidal magnetic field obtained from subsequent numerical simulation evolves similarly to the observed geomagnetic variation, regardless of the initial choice of the model solution (so long it is a well developed numerical solution). The model solution diverges on the time scales on the order of 60 years, similar to the time scales of the torsional oscillations in the Earth's core. Our numerical test shows that geomagnetic data assimilation is promising with our MoSST model.

The Complex Dynamics of the Precessing Vortex Rope in a Straight Diffuser

NASA Astrophysics Data System (ADS)

Stuparu, Adrian; Susan-Resiga, Romeo

2016-11-01

The decelerated swirling flow in the discharge cone of Francis turbines operated at partial discharge develops a self-induced instability with a precessing helical vortex (vortex rope). In an axisymmetric geometry, this phenomenon is expected to generate asynchronous pressure fluctuations as a result of the precessing motion. However, numerical and experimental data indicate that synchronous (plunging) fluctuations, with a frequency lower than the precessing frequency, also develops as a result of helical vortex filament dynamics. This paper presents a quantitative approach to describe the precessing vortex rope by properly fitting a three-dimensional logarithmic spiral model with the vortex filament computed from the velocity gradient tensor. We show that the slope coefficient of either curvature or torsion radii of the helix is a good indicator for the vortex rope dynamics, and it supports the stretching - breaking up - bouncing back mechanism that may explain the plunging oscillations.

Growth structure and superconductivity of Bi1.7Bi0.3Sr2Ca2Cu3O10+δ ceramics synthesized from glass-crystal precursors processed in solar type ovens

NASA Astrophysics Data System (ADS)

Acrivos, J. V.; Gulamova, D. D.; Chigvinadze, J. G.; Loy, D.

2010-03-01

The growth structure as well as the superconductivity of Bi/Pb2223 alloys is reported. Periodic lattice distortions (PLD) along the ab plane diagonal, direction of superconducting transport at the transition temperature, Tc=107K are found to dominate the growth. Trransport induced by the PLD may be responsible for the sharp Tc transitions, and the bursts of frequency and Abrikosov oscillations observed above the transition temperature up to 150K. Chemical synthesis in a heliostat oven was followed by fast quenching of the melt and annealing at 840-850K, XRD near the Cu K-edge, and Tc measured by axial-torsional vibrations in transverse magnetic fields. Tc and phaase purity obtained by green solid state chemistry, in a solar spectrum, will be discussed.

Spontaneous chiral symmetry breaking in metamaterials

NASA Astrophysics Data System (ADS)

Liu, Mingkai; Powell, David A.; Shadrivov, Ilya V.; Lapine, Mikhail; Kivshar, Yuri S.

2014-07-01

Spontaneous chiral symmetry breaking underpins a variety of areas such as subatomic physics and biochemistry, and leads to an impressive range of fundamental phenomena. Here we show that this prominent effect is now available in artificial electromagnetic systems, enabled by the advent of magnetoelastic metamaterials where a mechanical degree of freedom leads to a rich variety of strong nonlinear effects such as bistability and self-oscillations. We report spontaneous symmetry breaking in torsional chiral magnetoelastic structures where two or more meta-molecules with opposite handedness are electromagnetically coupled, modifying the system stability. Importantly, we show that chiral symmetry breaking can be found in the stationary response of the system, and the effect is successfully demonstrated in a microwave pump-probe experiment. Such symmetry breaking can lead to a giant nonlinear polarization change, energy localization and mode splitting, which provides a new possibility for creating an artificial phase transition in metamaterials, analogous to that in ferrimagnetic domains.

Spontaneous chiral symmetry breaking in metamaterials.

PubMed

Liu, Mingkai; Powell, David A; Shadrivov, Ilya V; Lapine, Mikhail; Kivshar, Yuri S

2014-07-18

Spontaneous chiral symmetry breaking underpins a variety of areas such as subatomic physics and biochemistry, and leads to an impressive range of fundamental phenomena. Here we show that this prominent effect is now available in artificial electromagnetic systems, enabled by the advent of magnetoelastic metamaterials where a mechanical degree of freedom leads to a rich variety of strong nonlinear effects such as bistability and self-oscillations. We report spontaneous symmetry breaking in torsional chiral magnetoelastic structures where two or more meta-molecules with opposite handedness are electromagnetically coupled, modifying the system stability. Importantly, we show that chiral symmetry breaking can be found in the stationary response of the system, and the effect is successfully demonstrated in a microwave pump-probe experiment. Such symmetry breaking can lead to a giant nonlinear polarization change, energy localization and mode splitting, which provides a new possibility for creating an artificial phase transition in metamaterials, analogous to that in ferrimagnetic domains.

The collapse of Tacoma Narrows Bridge: a piece to the puzzle

NASA Astrophysics Data System (ADS)

Walther, J. H.; Christensen, D. S.; Malthe, M. G.; Roenne, M.; Spietz, H. J.; Larsen, A.; Larsen, S. V.

2017-11-01

On Nov. 7th 1940 the newly constructed Tacoma Narrows Bridge collapsed due to excessive torsional oscillations caused by the formation and shedding of large coherent vortices. The subsequent wind tunnel tests conducted on both section- and full bridge models concluded that the bridge should have collapsed at a wind speed corresponding to approximately half of the wind speed at the day of the collapse. This discrepancy questions our understanding of the phenomena responsible for the failure of the bridge. The present study aims at clarifying this ``mystery'' by considering historical records made available by the US coast guards, and by performing wind tunnel tests and detailed numerical flow simulations. Our findings indicate that the discrepancy is caused by an until now unnoticed yawed wind direction relative to the bridge, which was present at the day of the collapse. Danish Council for Independent Research Grant No. 4184-00349B.

The ferromagnetic monolayer Fe(110) on W(110)

NASA Astrophysics Data System (ADS)

Gradmann, U.; Liu, G.; Elmers, H. J.; Przybylski, M.

1990-07-01

Ferromagnetic order in the pseudomorphic monolayer Fe(110) on W(110) was analyzed experimentally using Conversion Electron Mössbauer Spectroscopy (CEMS) and Torsion Oscillation Magnetometry (TOM). The monolayer is thermodynamically stable, crystallizes to large monolayer patches at elevated temperatures and therefore forms an excellent approximation to the ideal monolayer structure. It is ferromagnetic below a Curie-temperature T c,mono, which is given by (282±3) K for the Ag-coated layer, (290±10) K for coating by Cu, Ag or Au and ≈210 K for the free monolayer. For the Ag-coated monolayer, ground state hyperfine field B hf (0)=(11.9±0.3) T and magnetic moment per atom μ=2.53 μB could be determined, in fair agreement with theoretical predictions. Unusual properties of the phase transition are detected by the combination of both experimental techniques. Strong magnetic anisotropies, which are essential for ferromagnetic order, are determined by CEMS.

Observational information for f(T) theories and dark torsion

NASA Astrophysics Data System (ADS)

Bengochea, Gabriel R.

2011-01-01

In the present work we analyze and compare the information coming from different observational data sets in the context of a sort of f(T) theories. We perform a joint analysis with measurements of the most recent type Ia supernovae (SNe Ia), Baryon Acoustic Oscillation (BAO), Cosmic Microwave Background radiation (CMB), Gamma-Ray Bursts data (GRBs) and Hubble parameter observations (OHD) to constraint the only new parameter these theories have. It is shown that when the new combined BAO/CMB parameter is used to put constraints, the result is different from previous works. We also show that when we include Observational Hubble Data (OHD) the simpler ΛCDM model is excluded to one sigma level, leading the effective equation of state of these theories to be of phantom type. Also, analyzing a tension criterion for SNe Ia and other observational sets, we obtain more consistent and better suited data sets to work with these theories.

New observational constraints on f ( T ) gravity from cosmic chronometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nunes, Rafael C.; Pan, Supriya; Saridakis, Emmanuel N., E-mail: nunes@ecm.ub.edu, E-mail: span@iiserkol.ac.in, E-mail: Emmanuel_Saridakis@baylor.edu

2016-08-01

We use the local value of the Hubble constant recently measured with 2.4% precision, as well as the latest compilation of cosmic chronometers data, together with standard probes such as Supernovae Type Ia and Baryon Acoustic Oscillation distance measurements, in order to impose constraints on the viable and most used f ( T ) gravity models, where T is the torsion scalar in teleparallel gravity. In particular, we consider three f ( T ) models with two parameters, out of which one is independent, and we quantify their deviation from ΛCDM cosmology through a sole parameter. Our analysis reveals thatmore » for one of the models a small but non-zero deviation from ΛCDM cosmology is slightly favored, while for the other models the best fit is very close to ΛCDM scenario. Clearly, f ( T ) gravity is consistent with observations, and it can serve as a candidate for modified gravity.« less

Some Investigations of the General Instability of Stiffened Metal Cylinders VII : Stiffened Metal Cylinders Subjected to Combined Bending and Torsion

NASA Technical Reports Server (NTRS)

1943-01-01

This report summarizes the work that has been carried on in the experimental investigation of the problem of the general instability of stiffened metal cylinders subjected to combined bending and torsion at the C.I.T. This part of the investigation included tests on 26 sheet-covered specimens. An interaction curve for the case of combined bending and torsion is presented. The results of tests of 17 specimens subjected to pure torsion are also given.

Isolated torsion of fallopian tube during pregnancy; report of two cases.

PubMed

Yalcin, O T; Hassa, H; Zeytinoglu, S; Isiksoy, S

1997-08-01

Isolated torsion of fallopian tube is very uncommon during pregnancy. Predisposing factors for torsion are hydrosalpinx, prior tubal operation, pelvic congestion, ovarian and paraovarian masses and trauma. Although the most important clinical symptom is abdominal pain in lower quadrants, the diagnosis is usually established during the operation performed for acute abdomen and salpingectomy is almost always necessary. Two cases of torsion of fallopian tube during pregnancy, one with hydrosalpinx, the other with paratubal cyst are presented and symptoms and predisposing factors are discussed.

Sporadic adult onset primary torsion dystonia is a genetic disorder by the temporal discrimination test.

PubMed

Kimmich, Okka; Bradley, David; Whelan, Robert; Mulrooney, Nicola; Reilly, Richard B; Hutchinson, Siobhan; O'Riordan, Sean; Hutchinson, Michael

2011-09-01

Adult-onset primary torsion dystonia is an autosomal dominant disorder with markedly reduced penetrance; patients with sporadic adult-onset primary torsion dystonia are much more prevalent than familial. The temporal discrimination threshold is the shortest time interval at which two stimuli are detected to be asynchronous and has been shown to be abnormal in adult-onset primary torsion dystonia. The aim was to determine the frequency of abnormal temporal discrimination thresholds in patients with sporadic adult-onset primary torsion dystonia and their first-degree relatives. We hypothesized that abnormal temporal discrimination thresholds in first relatives would be compatible with an autosomal dominant endophenotype. Temporal discrimination thresholds were examined in 61 control subjects (39 subjects <50 years of age; 22 subjects >50 years of age), 32 patients with sporadic adult-onset primary torsion dystonia (cervical dystonia n = 30, spasmodic dysphonia n = 1 and Meige's syndrome n = 1) and 73 unaffected first-degree relatives (36 siblings, 36 offspring and one parent) using visual and tactile stimuli. Z-scores were calculated for all subjects; a Z > 2.5 was considered abnormal. Abnormal temporal discrimination thresholds were found in 1/61 (2%) control subjects, 27/32 (84%) patients with adult-onset primary torsion dystonia and 32/73 (44%) unaffected relatives [siblings (20/36; 56%), offspring (11/36; 31%) and one parent]. When two or more relatives were tested in any one family, 22 of 24 families had at least one first-degree relative with an abnormal temporal discrimination threshold. The frequency of abnormal temporal discrimination thresholds in first-degree relatives of patients with sporadic adult-onset primary torsion dystonia is compatible with an autosomal dominant disorder and supports the hypothesis that apparently sporadic adult-onset primary torsion dystonia is genetic in origin.

Thermal study of longitudinal and torsional ultrasound phacoemulsification: tracking the temperature of the corneal surface, incision, and handpiece.

PubMed

Jun, Bokkwan; Berdahl, John P; Kim, Terry

2010-05-01

To evaluate the change and difference in the corneal surface, incision, and handpiece temperatures during longitudinal and torsional ultrasound (US) phacoemulsification with standard incisions (2.75 mm) and microincisions (2.20 mm) and the thermal effect on wounds. Department of Ophthalmology, Duke University, Durham, North Carolina, USA. In this prospective study, human cadaver eyes had simulated phacoemulsification. Group 1 had a 2.75 mm incision with 100% longitudinal US; Group 2, a 2.20 mm incision with 100% longitudinal US; Group 3, a 2.75 mm incision with 100% torsional US; and Group 4, a 2.20 mm incision with 100% torsional US. During phacoemulsification, the corneal incision was evaluated by surgical microscopy and scanning electron microscopy (SEM) and images of the corneal surface, incision, and handpiece were captured with an infrared camera. Twelve eyes (3 each group) were evaluated. The maximum incision temperature was higher in the longitudinal groups than in the torsional groups. With the same US modality, the maximum microincision temperature was higher than the maximum standard incision temperature. After application of full power for 40 seconds, wound burn was observed in all eyes in the longitudinal groups and no eyes in the torsional groups. On SEM, there was more extensive loss of Descemet membrane in the longitudinal groups than in the torsional groups. Incision temperature was influenced by US modality and was significantly lower with torsional US than with longitudinal US. Using torsional US with smaller incisions may decrease the risk for wound burn in eyes with denser cataracts. (c) 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

On the relationship between tibia torsional deformation and regional muscle contractions in habitual human exercises in vivo.

PubMed

Yang, Peng-Fei; Kriechbaumer, Andreas; Albracht, Kirsten; Sanno, Maximilian; Ganse, Bergita; Koy, Timmo; Shang, Peng; Brüggemann, Gert-Peter; Müller, Lars Peter; Rittweger, Jörn

2015-02-05

The mechanical relationship between bone and muscle has been long recognized. However, it still remains unclear how muscles exactly load on bone. In this study, utilizing an optical segment tracking technique, the in vivo tibia loading regimes in terms of tibia segment deformation in humans were investigated during walking, forefoot and rear foot stair ascent and running and isometric plantar flexion. Results suggested that the proximal tibia primarily bends to the posterior aspect and twists to the external aspect with respect to the distal tibia. During walking, peak posterior bending and peak torsion occurred in the first half (22%) and second half (76%) of the stance phase, respectively. During stair ascent, two noticeable peaks of torsion were found with forefoot strike (38% and 82% of stance phase), but only one peak of torsion was found with rear foot strike (78% of stance phase). The torsional deformation angle during both stair ascent and running was larger with forefoot strike than rear foot strike. During isometric plantar flexion, the tibia deformation regimes were characterized more by torsion (maximum 1.35°) than bending (maximum 0.52°). To conclude, bending and torsion predominated the tibia loading regimes during the investigated activities. Tibia torsional deformation is closely related to calf muscle contractions, which further confirm the notion of the muscle-bone mechanical link and shift the focus from loading magnitude to loading regimes in bone mechanobiology. It thus is speculated that torsion is another, yet under-rated factor, besides the compression and tension, to drive long bone mechano-adaptation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Muscular Basis of Whisker Torsion in Mice and Rats.

PubMed

Haidarliu, Sebastian; Bagdasarian, Knarik; Shinde, Namrata; Ahissar, Ehud

2017-09-01

Whisking mammals move their whiskers in the rostrocaudal and dorsoventral directions with simultaneous rolling about their long axes (torsion). Whereas muscular control of the first two types of whisker movement was already established, the anatomic muscular substrate of the whisker torsion remains unclear. Specifically, it was not clear whether torsion is induced by asymmetrical operation of known muscles or by other largely unknown muscles. Here, we report that mystacial pads of newborn and adult rats and mice contain oblique intrinsic muscles (OMs) that connect diagonally adjacent vibrissa follicles. Each of the OMs is supplied by a cluster of motor end plates. In rows A and B, OMs connect the ventral part of the rostral follicle with the dorsal part of the caudal follicle. In rows C-E, in contrast, OMs connect the dorsal part of the rostral follicle to the ventral part of the caudal follicle. This inverse architecture is consistent with previous behavioral observations [Knutsen et al.: Neuron 59 (2008) 35-42]. In newborn mice, torsion occurred in irregular single twitches. In adult anesthetized rats, microelectrode mediated electrical stimulation of an individual OM that is coupled with two adjacent whiskers was sufficient to induce a unidirectional torsion of both whiskers. Torsional movement was associated with protracting movement, indicating that in the vibrissal system, like in the ocular system, torsional movement is mechanically coupled to horizontal and vertical movements. This study shows that torsional whisker rotation is mediated by specific OMs whose morphology and attachment sites determine rotation direction and mechanical coupling, and motor innervation determines rotation dynamics. Anat Rec, 300:1643-1653, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Thermal characterization of phacoemulsification probes operated in axial and torsional modes.

PubMed

Zacharias, Jaime

2015-01-01

To analyze temperature increases and identify potential sources of heat generated when sleeved and sleeveless phacoemulsification probes were operated in axial and torsional modes using the Infiniti Vision System with the Ozil torsional handpiece. Phacodynamics Laboratory, Pasteur Ophthalmic Clinic, Santiago, Chile. Experimental study. Two computer-controlled thermal transfer systems were developed to evaluate the contribution of internal metal stress and tip-to-sleeve friction on heat generation during phacoemulsification using axial and torsional ultrasound modalities. Both systems incorporated infrared thermal imaging and used a black-body film to accurately capture temperature measurements. Axial mode was consistently associated with greater temperature increases than torsional mode whether tips were operated with or without sleeves. In tests involving bare tips, axial mode and torsional mode peaked at 51.7°C and 34.2°C, respectively. In an example using sleeved tips in which a 30.0 g load was applied for 1 second, temperatures for axial mode reached 45°C and for torsional mode, 38°C. Friction between the sleeved probe and the incisional wall contributed more significantly to the temperature increase than internal metal stress regardless of the mode used. In all experiments, the temperature increase observed with axial mode was greater than that observed with torsional mode, even when conditions such as power or amplitude and flow rate were varied. Tip-to-sleeve friction was a more dominant source of phaco probe heating than internal metal stress. The temperature increase due to internal metal stress was greater with axial mode than with torsional mode. Dr. Zacharias received research funding from Alcon Laboratories, Inc., to conduct this study. He has no financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Influence of cyclic torsional preloading on cyclic fatigue resistance of nickel - titanium instruments.

PubMed

Pedullà, E; Lo Savio, F; Boninelli, S; Plotino, G; Grande, N M; Rapisarda, E; La Rosa, G

2015-11-01

To evaluate the effect of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments constructed from conventional nickel-titanium (NiTi), M-Wire or CM-Wire. Eighty new size 25, 0.06 taper Mtwo instruments (Sweden & Martina), size 25, 0.06 taper HyFlex CM (Coltene/Whaledent, Inc) and X2 ProTaper Next (Dentsply Maillefer) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured, and 0% (n = 10), 25%, 50% and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630-1 for each brand. The twenty files tested for every extent of preload were subjected to 20 or 40 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 60° angle of curvature and 5 mm of radius of curvature. Data were analysed using two-way analysis of variance. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were analysed by two-way analyses of variance. Preload repetitions did not influence the cyclic fatigue of the three brands; however, the 25%, 50% and 75% torsional preloading significantly reduced the fatigue resistance of all instruments tested (P < 0.01, P < 0.001 and P < 0.0001, respectively) except for the HyFlex CM preloaded with 25% of the maximum torsional strength (P > 0.05). Torsional preloads reduced the cyclic fatigue resistance of conventional and treated (M-wire and CM-wire) NiTi rotary instruments except for size 25, 0.06 taper HyFlex CM instruments with a 25% of torsional preloading. © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Investigations on bending-torsional vibrations of rotor during rotor-stator rub using Lagrange multiplier method

NASA Astrophysics Data System (ADS)

Mokhtar, Md Asjad; Kamalakar Darpe, Ashish; Gupta, Kshitij

2017-08-01

The ever-increasing need of highly efficient rotating machinery causes reduction in the clearance between rotating and non-rotating parts and increase in the chances of interaction between these parts. The rotor-stator contact, known as rub, has always been recognized as one of the potential causes of rotor system malfunctions and a source of secondary failures. It is one of few causes that influence both lateral and torsional vibrations. In this paper, the rotor stator interaction phenomenon is investigated in the finite element framework using Lagrange multiplier based contact mechanics approach. The stator is modelled as a beam that can respond to axial penetration and lateral friction force during the contact with the rotor. It ensures dynamic stator contact boundary and more realistic contact conditions in contrast to most of the earlier approaches. The rotor bending-torsional mode coupling during contact is considered and the vibration response in bending and torsion are analysed. The effect of parameters such as clearance, friction coefficient and stator stiffness are studied at various operating speeds and it has been found that certain parameter values generate peculiar rub related features. Presence of sub-harmonics in the lateral vibration frequency spectra are prominently observed when the rotor operates near the integer multiple of its lateral critical speed. The spectrum cascade of torsional vibration shows the presence of bending critical speed along with the larger amplitudes of frequencies close to torsional natural frequency of the rotor. When m × 1/n X frequency component of rotational frequency comes closer to the torsional natural frequency, stronger torsional vibration amplitude is noticed in the spectrum cascade. The combined information from the stator vibration and rotor lateral-torsional vibration spectral features is proposed for robust rub identification.

Dynamic properties of combustion instability in a lean premixed gas-turbine combustor.

PubMed

Gotoda, Hiroshi; Nikimoto, Hiroyuki; Miyano, Takaya; Tachibana, Shigeru

2011-03-01

We experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. A nonlinear time series analysis in combination with a surrogate data method clearly reveals that as the equivalence ratio increases, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. We also show that a nonlinear forecasting method is useful for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor, which has not been addressed in the fields of combustion science and physics.

Raman spectra of gases. XVI - Torsional transitions in ethanol and ethanethiol

NASA Technical Reports Server (NTRS)

Durig, J. R.; Bucy, W. E.; Wurrey, C. J.; Carreira, L. A.

1975-01-01

The Raman spectra of gaseous ethanol and ethanethiol have been investigated. Thiol torsional fundamentals for the gauche conformer of EtSH and EtSD have been observed and the asymmetric potential function for this vibration has been calculated. Methyl torsional transitions and overtones have also been observed for both of these molecules. Barriers to internal rotation for the methyl top are calculated to be 3.77 and 3.84 kcal/mol for the EtSH and EtSD compounds, respectively. Hydroxyl torsional fundamentals were observed at 207 and 170 per cm in the EtOH and EtOD spectra, respectively. Overtones of the methyl torsion in both molecules yield a barrier to internal rotation of 3.62 kcal/mol for the gauche conformer.

Torsion effect on fully developed flow in a helical pipe

NASA Technical Reports Server (NTRS)

Kao, Hsiao C.

1987-01-01

Two techniques, a series expansion method of perturbed Poiseuille flow valid for low Dean numbers and a solution of the complete Navier-Stokes equation applicable to intermediate Dean values, are used to investigate the torsion effect on the fully developed laminar flow in a helical pipe of constant circular cross section. For the secondary flow patterns, the results show that the presence of torsion can produce a significant effect if the ratio of the curvature to the torsion is of order unity. The secondary flow is distorted in these cases. It is noted that the torsion effect is, however, usually small, and that the secondary flow has the usual pattern of a pair of counter-rotating vortices of nearly equal strength.

Seismic performance of square RC bridge columns under combined loading including torsion with low shear.

DOT National Transportation Integrated Search

2009-12-01

During earthquake excitations, reinforced concrete bridge columns can be subjected to a combination of axial load, shear force, : flexural moments, and torsional moments. The torsional moment can be much more significant in columns of bridges that ar...

A 2-DOF microstructure-dependent model for the coupled torsion/bending instability of rotational nanoscanner

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.

Acute abdomen due to ovarian congestion caused by coiling of the fallopian tube accompanied by paratubal cyst around the utero-ovarian ligament.

PubMed

Kim, Juyoung; Park, Daehyun; Han, Won Bo; Jeong, Hyangjin; Park, Youngse

2014-07-01

Torsion of uterine adnexa is an important cause of acute abdominal pain in females. The main organ which can cause torsion is the ovaries, but torsions of the fallopian tube, subserosal myoma, paratubal cyst, and even the uterine body have been reported. The incidence of isolated fallopian tubal torsion is very rare. Even more rarely, it can coil around nearby organs such as the utero-ovarian ligament, showing similar clinical manifestations with those of adnexal torsion. We experienced an extremely rare case of acute abdomen induced by ovarian congestion triggered by the fallopian tube accompanying a paratubal cyst coiling around the utero-ovarian ligament. The right paratubal cyst was misinterpreted as being part of a cystic component of the left ovary on preoperative sonographic examination, and the coiling of the right fallopian tube accompanying the paratubal cyst was misdiagnosed as torsion of the right ovary. We report this rare case with a brief literature review.

Acute abdomen due to ovarian congestion caused by coiling of the fallopian tube accompanied by paratubal cyst around the utero-ovarian ligament

PubMed Central

Kim, Juyoung; Park, Daehyun; Han, Won Bo; Jeong, Hyangjin

2014-01-01

Torsion of uterine adnexa is an important cause of acute abdominal pain in females. The main organ which can cause torsion is the ovaries, but torsions of the fallopian tube, subserosal myoma, paratubal cyst, and even the uterine body have been reported. The incidence of isolated fallopian tubal torsion is very rare. Even more rarely, it can coil around nearby organs such as the utero-ovarian ligament, showing similar clinical manifestations with those of adnexal torsion. We experienced an extremely rare case of acute abdomen induced by ovarian congestion triggered by the fallopian tube accompanying a paratubal cyst coiling around the utero-ovarian ligament. The right paratubal cyst was misinterpreted as being part of a cystic component of the left ovary on preoperative sonographic examination, and the coiling of the right fallopian tube accompanying the paratubal cyst was misdiagnosed as torsion of the right ovary. We report this rare case with a brief literature review. PMID:25105111

Modeling the Elastic and Damping Properties of the Multilayered Torsion Bar-Blade Structure of Rotors of Light Helicopters of the New Generation 2. Finite-Element Approximation of Blades and a Model of Coupling of the Torsion Bar with the Blades

NASA Astrophysics Data System (ADS)

Paimushin, V. N.; Shishkin, V. M.

2016-01-01

A rod-shape finite element with twelve degrees of freedom is proposed for modeling the elastic and damping properties of rotor blades with regard to their geometric stiffness caused by rotation of the rotor. A model of coupling of the torsion bar with blades is developed based on the hypothesis of linear deplanation of the connecting section of the torsion bar and a special transition element to ensure the compatibility of displacements of the torsion bar and blades upon their vibrations in the flapping and rotation planes. Numerical experiments were carried out to test and assess the validity of the model developed. Suggestions are made for ensuring unconditional stability of the iteration method in a subspace in determining the specified number of modes and frequencies of free vibrations of the torsion bar-blade structure.

Effects of torsion on the thermal conductivity of multi-layer graphene

NASA Astrophysics Data System (ADS)

Si, Chao; Lu, Gui; Cao, Bing-Yang; Wang, Xiao-Dong; Fan, Zhen; Feng, Zhi-Hai

2017-05-01

This work employs the equilibrium molecular dynamics method to study the effects of torsion on the thermal conductivity of multi-layer graphene. Thermal conductivities of twisted 10-layer 433.91 × 99.68 Å2 graphene with torsion angles of 0°, 11.25°, 22.5°, 33.75°, 45°, 67.5°, 90°, 112.5°, and 135° are calculated. The corresponding radial distribution functions and nearest atomic distances are calculated to reveal the effects of torsion on lattice structures. The spectral energy density (SED) method is utilized to analyze the phonon transport properties. It is very interesting that the thermal conductivity of multi-layer graphene decreases slightly at first and then increases with the increasing torsion angle, and the valley is located at θG = 22.5° with the lowest thermal conductivity of 4692.40 W m-1 K-1. The torsion effect can be considered as a combination of the compression effect and the dislocation effect. Further SED analysis confirms that the effect of dislocation on thermal conductivities can be negligible, while the compression effect decreases the phonon lifetimes of flexural out-of-plane acoustic (ZA) branches and increases the ZA group velocities and the phonon specific heat. The decrease becomes dominated when the torsion angle is small, whereas the increase becomes more and more dominated when the torsion angle becomes larger, which are responsible for the reported variation of thermal conductivities.

Protective effects of udenafil citrate, piracetam and dexmedetomidine treatment on testicular torsion/detorsion-induced ischaemia/reperfusion injury in rats.

PubMed

Tuglu, D; Yuvanc, E; Ozan, T; Bal, F; Yilmaz, E; Atasoy, P; Kisa, U; Batislam, E

2016-08-01

The aim of this study was to investigate the antioxidant properties of udenafil citrate (1.4 mg kg(-1) -2.8 mg kg(-1) ), dexmedetomidine 25 μg kg(-1) and piracetam 200 mg kg(-1) administered on ipsilateral/contralateral testes after ischaemia in a rat model of testicular torsion/detorsion (T/D) and define its protective effect histologically. Fifty-six Wistar albino rats were included and randomly assigned into 6 groups. No intervention was performed in control group (Group 1, n = 8) and in torsion/detorsion group, (Group 2, n = 8). Udenafil 1.4 mg kg(-1) was given to torsion/detorsion group (Group 3, n = 10), udenafil 2.8 mg kg(-1) was given to torsion/detorsion group (Group 4, n = 10), piracetam 200 mg kg(-1) was given to torsion/detorsion group (Group 5, n = 10) and dexmedetomidine 25 μg kg(-1) was given to torsion/detorsion group (Group 6, n = 10) intraperitoneally after 60 mins of testicular torsion. Biochemical and histopathological testicular injury were evaluated. When the tissue was examined by TOS values, Group 3, Group 4 and Group 5 were significantly lower than Group 2. In contrary Group 6 values were significantly higher than Group 2. The increasing doses of udenafil demonstrated antioxidant properties on the testis tissue and histopathological that protects the testicles. © 2015 Blackwell Verlag GmbH.

Torsional stress impedance and magneto-impedance in (Co0.95Fe0.05)72.5 Si12.5B15 amorphous wire with helical induced anisotropy

NASA Astrophysics Data System (ADS)

Blanco, J. M.; Zhukov, A. P.; González, J.

1999-12-01

The magneto-impedance effect icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/ZH = [Z(H)-Z(Hmax)]/Z(Hmax) has been measured in (Fe0.95Co0.05)72.5B15Si12.5 wire under torsion stress, icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> (torsion angle per unit length) with axial magnetic field (H) as parameter. Without stress (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)H(H) dependence has a non-monotonous shape with first an increase of total impedance Z and then a decrease, i.e. shows a maximum at certain axial magnetic field Hm. It was found that the torsion stress dependence of electrical impedance (torsion impedance), (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> = [Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>)-Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>max)]/Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>max), has asymmetric character with a clear maximum at torsion angle, icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> around 7icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> rad m-1 in as-cast wire, while (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> reaches a maximum around 170%. Thermal treatments under torsion stress (without and with a previous annealing stage) develop a helical anisotropy on the amorphous wire, which drastically modifies the (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> response. Such treatments were carried out by using current annealing which resulted in a drastic increase of the maximum (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> up to 225%, and a change of torsion dependence of icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z with a tendency to a finally symmetric dependence of (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/>(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>). The maximum (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> ratio, (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> m, was obtained under torsion stress of icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> = 20icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> rad m-1 (in a torsion annealed sample) and = 11 rad m-1 (with pre-annealing and torsion annealing). Observed dependences were explained taking into account the frozen-in magneto-elastic anisotropy owing to the internal stress distribution during the fabrication process, the helical anisotropies induced by the torsion strain and that developed by thermal treatment under torsion stress (torsion annealing). The differences in the shape and intensity of the maximum ( Z/Z) m between the torsion annealed and pre-annealed and torsion annealed samples should be ascribed to the visco-elastic character of the helical anisotropy induced by torsion stress.

Standardized education and parental awareness are lacking for testicular torsion.

PubMed

Friedman, Ariella A; Ahmed, Haris; Gitlin, Jordan S; Palmer, Lane S

2016-06-01

Testicular torsion leads to orchiectomy in 30-50% of cases, which may cause psychological upset and parental guilt over a potentially avertable outcome. Presentation delay is an important modifiable cause of orchiectomy; yet, families are not routinely educated about torsion or its urgency. The present study assessed parental knowledge regarding acute scrotal pain. An anonymous survey was distributed to parents in Urology and ENT offices, asking about their children's gender and scrotal pain history, urgency of response to a child's acute scrotal pain, and familiarity with testicular torsion. Surveys of 479 urology and 59 ENT parents were analyzed. The results between the two were not statistically different. Among the urology parents, 34% had heard of testicular twisting/torsion, most commonly through friends, relatives or knowing someone with torsion (35%); only 17% were informed by pediatricians (Summary Figure). Parents presenting for a child's scrotal pain were significantly more likely to have heard of torsion (69%) than those presenting for other reasons (30%, OR 5.24, P < 0.0001). Only 13% of parents of boys had spoken with their children about torsion. Roughly three quarters of them would seek emergent medical attention - by day (75%) or night (82%) - for acute scrotal pain. However, urgency was no more likely among those who knew about torsion. This was the first study to assess parental knowledge of the emergent nature of acute scrotal pain in a non-urgent setting, and most closely approximating their level of knowledge at the time of pain onset. It also assessed parents' hypothetical responses to the scenario, which was markedly different than documented presentation times, highlighting a potential area for improvement in presentation times. Potential limitations included lack of respondent demographic data, potential sampling bias of a population with greater healthcare knowledge or involvement, and assessment of parents only. Parental knowledge of testicular torsion was lacking, suggesting both ineffective education in the well-child setting and inappropriately timed education during or after pain occurrence. Awareness was most commonly anecdotal or taught unreliably, as even familiar parents were no more likely to seek emergent attention. Therefore, standardized, effective parental education on testicular torsion and the need for prompt presentation is needed, as is improvement in the quality of information taught in the healthcare setting. Further assessment of knowledge among preadolescent and adolescent boys regarding testicular torsion is warranted. It is hopeful that pre-hospital delay may be minimized and greater rates of testicular salvageability may be achieved through these efforts. Copyright © 2016 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

Using a respiratory navigator significantly reduces variability when quantifying left ventricular torsion with cardiovascular magnetic resonance.

PubMed

Hamlet, Sean M; Haggerty, Christopher M; Suever, Jonathan D; Wehner, Gregory J; Andres, Kristin N; Powell, David K; Charnigo, Richard J; Fornwalt, Brandon K

2017-03-01

Left ventricular (LV) torsion is an important indicator of cardiac function that is limited by high inter-test variability (50% of the mean value). We hypothesized that this high inter-test variability is partly due to inconsistent breath-hold positions during serial image acquisitions, which could be significantly improved by using a respiratory navigator for cardiovascular magnetic resonance (CMR) based quantification of LV torsion. We assessed respiratory-related variability in measured LV torsion with two distinct experimental protocols. First, 17 volunteers were recruited for CMR with cine displacement encoding with stimulated echoes (DENSE) in which a respiratory navigator was used to measure and then enforce variability in end-expiratory position between all LV basal and apical acquisitions. From these data, we quantified the inter-test variability of torsion in the absence and presence of enforced end-expiratory position variability, which established an upper bound for the expected torsion variability. For the second experiment (in 20 new, healthy volunteers), 10 pairs of cine DENSE basal and apical images were each acquired from consecutive breath-holds and consecutive navigator-gated scans (with a single acceptance position). Inter-test variability of torsion was compared between the breath-hold and navigator-gated scans to quantify the variability due to natural breath-hold variation. To demonstrate the importance of these variability reductions, we quantified the reduction in sample size required to detect a clinically meaningful change in LV torsion with the use of a respiratory navigator. The mean torsion was 3.4 ± 0.2°/cm. From the first experiment, enforced variability in end-expiratory position translated to considerable variability in measured torsion (0.56 ± 0.34°/cm), whereas inter-test variability with consistent end-expiratory position was 57% lower (0.24 ± 0.16°/cm, p < 0.001). From the second experiment, natural respiratory variability from consecutive breath-holds translated to a variability in torsion of 0.24 ± 0.10°/cm, which was significantly higher than the variability from navigator-gated scans (0.18 ± 0.06°/cm, p = 0.02). By using a respiratory navigator with DENSE, theoretical sample sizes were reduced from 66 to 16 and 26 to 15 as calculated from the two experiments. A substantial portion (22-57%) of the inter-test variability of LV torsion can be reduced by using a respiratory navigator to ensure a consistent breath-hold position between image acquisitions.

An instrument for direct observations of seismic and normal-mode rotational oscillations of the Earth

PubMed Central

Cowsik, R.

2007-01-01

The rotations around the vertical axis associated with the normal mode oscillations of the Earth and those induced by the seismic and other disturbances have been very difficult to observe directly. Such observations will provide additional information for 3D modeling of the Earth and for understanding earthquakes and other underground explosions. In this paper, we describe the design of an instrument capable of measuring the rotational motions associated with the seismic oscillations of the Earth, including the lowest frequency normal mode at ν ≈ 3.7 × 10−4 Hz. The instrument consists of a torsion balance with a natural frequency of ν0 ≈ 1.6 × 10−4 Hz, which is observed by an autocollimating optical lever of high angular resolution and dynamic range. Thermal noise limits the sensitivity of the apparatus to amplitudes of ≈ 1.5 × 10−9 rad at the lowest frequency normal mode and the sensitivity improves as ν−3/2 with increasing frequency. Further improvements in sensitivity by about two orders of magnitude may be achieved by operating the balance at cryogenic temperatures. Alternatively, the instrument can be made more robust with a reduced sensitivity by increasing ν0 to ≈10−2 Hz. This instrument thus complements the ongoing effort by Igel and others to study rotational motions using ring laser gyroscopes and constitutes a positive response to the clarion call for developments in rotation seismology by Igel, Lee, and Todorovska [H. Igel, W.H.K. Lee and M.I. Todorovska, AGU Fall Meeting 2006, Rotational Seismology Sessions: S22A,S23B, Inauguration of the International Working Group on Rotational Seismology (IWGoRS)]. PMID:17438268

Experimental study of firing death in a network of chaotic FitzHugh-Nagumo neurons

NASA Astrophysics Data System (ADS)

Ciszak, Marzena; Euzzor, Stefano; Arecchi, F. Tito; Meucci, Riccardo

2013-02-01

The FitzHugh-Nagumo neurons driven by a periodic forcing undergo a period-doubling route to chaos and a transition to mixed-mode oscillations. When coupled, their dynamics tend to be synchronized. We show that the chaotically spiking neurons change their internal dynamics to subthreshold oscillations, the phenomenon referred to as firing death. These dynamical changes are observed below the critical coupling strength at which the transition to full chaotic synchronization occurs. Moreover, we find various dynamical regimes in the subthreshold oscillations, namely, regular, quasiperiodic, and chaotic states. We show numerically that these dynamical states may coexist with large-amplitude spiking regimes and that this coexistence is characterized by riddled basins of attraction. The reported results are obtained for neurons implemented in the electronic circuits as well as for the model equations. Finally, we comment on the possible scenarios where the coupling-induced firing death could play an important role in biological systems.

Tests of Mach's Principle With a Mechanical Oscillator

NASA Technical Reports Server (NTRS)

Millis, Marc G. (Technical Monitor); Cramer, John G.; Fey, Curran W.; Casissi, Damon V.

2004-01-01

James F. Woodward has made a prediction, based on Sciama's formulation of Mach's Principle in the framework of general relativity, that in the presence of an energy flow the inertial mass of an object may undergo sizable variations, changing as the second time derivative of the energy. We describe an attempt to test for the predicted effect with a charging capacitor, using a technique that does not require an unbalanced force or any local violation of Newton s 3rd law of motion. We attempt to observe: (1) the gravitational effect of the varying mass and (2) the effect of the mass variation on a driven harmonic oscillator with the charging capacitor as the oscillating mass. We report on the predicted effect, the design and implementation of the measurement apparatus, and initial experience with the apparatus. At this time, however, we will not report on observations of the presence or absence of the Woodward effect.

GONG Catalog of Solar Filament Oscillations Near Solar Maximum

NASA Astrophysics Data System (ADS)

Luna, M.; Karpen, J.; Ballester, J. L.; Muglach, K.; Terradas, J.; Kucera, T.; Gilbert, H.

2018-06-01

We have cataloged 196 filament oscillations from the Global Oscillation Network Group Hα network data during several months near the maximum of solar cycle 24 (2014 January–June). Selected examples from the catalog are described in detail, along with our statistical analyses of all events. Oscillations were classified according to their velocity amplitude: 106 small-amplitude oscillations (SAOs), with velocities <10 {km} {{{s}}}-1, and 90 large-amplitude oscillations (LAOs), with velocities >10 {km} {{{s}}}-1. Both SAOs and LAOs are common, with one event of each class every two days on the visible side of the Sun. For nearly half of the events, we identified their apparent trigger. The period distribution has a mean value of 58 ± 15 minutes for both types of oscillations. The distribution of the damping time per period peaks at τ/P = 1.75 and 1.25 for SAOs and LAOs, respectively. We confirmed that LAO damping rates depend nonlinearly on the oscillation velocity. The angle between the direction of motion and the filament spine has a distribution centered at 27° for all filament types. This angle agrees with the observed direction of filament-channel magnetic fields, indicating that most of the cataloged events are longitudinal (i.e., undergo field-aligned motions). We applied seismology to determine the average radius of curvature in the magnetic dips, R ≈ 89 Mm, and the average minimum magnetic field strength, B ≈ 16 G. The catalog is available to the community online and is intended to be expanded to cover at least 1 solar cycle.

A Prospective Study of Age-dependent Changes in Propofol-induced Electroencephalogram Oscillations in Children.

PubMed

Lee, Johanna M; Akeju, Oluwaseun; Terzakis, Kristina; Pavone, Kara J; Deng, Hao; Houle, Timothy T; Firth, Paul G; Shank, Erik S; Brown, Emery N; Purdon, Patrick L

2017-08-01

In adults, frontal electroencephalogram patterns observed during propofol-induced unconsciousness consist of slow oscillations (0.1 to 1 Hz) and coherent alpha oscillations (8 to 13 Hz). Given that the nervous system undergoes significant changes during development, anesthesia-induced electroencephalogram oscillations in children may differ from those observed in adults. Therefore, we investigated age-related changes in frontal electroencephalogram power spectra and coherence during propofol-induced unconsciousness. We analyzed electroencephalogram data recorded during propofol-induced unconsciousness in patients between 0 and 21 yr of age (n = 97), using multitaper spectral and coherence methods. We characterized power and coherence as a function of age using multiple linear regression analysis and within four age groups: 4 months to 1 yr old (n = 4), greater than 1 to 7 yr old (n = 16), greater than 7 to 14 yr old (n = 30), and greater than 14 to 21 yr old (n = 47). Total electroencephalogram power (0.1 to 40 Hz) peaked at approximately 8 yr old and subsequently declined with increasing age. For patients greater than 1 yr old, the propofol-induced electroencephalogram structure was qualitatively similar regardless of age, featuring slow and coherent alpha oscillations. For patients under 1 yr of age, frontal alpha oscillations were not coherent. Neurodevelopmental processes that occur throughout childhood, including thalamocortical development, may underlie age-dependent changes in electroencephalogram power and coherence during anesthesia. These age-dependent anesthesia-induced electroencephalogram oscillations suggest a more principled approach to monitoring brain states in pediatric patients.

Hydrostatic self-aligning axial/torsional mechanism

DOEpatents

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.

Extended Reissner-Nordström solutions sourced by dynamical torsion

NASA Astrophysics Data System (ADS)

Cembranos, Jose A. R.; Valcarcel, Jorge Gigante

2018-04-01

We find a new exact vacuum solution in the framework of the Poincaré Gauge field theory with massive torsion. In this model, torsion operates as an independent field and introduces corrections to the vacuum structure present in General Relativity. The new static and spherically symmetric configuration shows a Reissner-Nordström-like geometry characterized by a spin charge. It extends the known massless torsion solution to the massive case. The corresponding Reissner-Nordström-de Sitter solution is also compatible with a cosmological constant and additional U (1) gauge fields.

Ovarian torsion: diagnostic features on CT and MRI with pathologic correlation.

PubMed

Duigenan, Shauna; Oliva, Esther; Lee, Susanna I

2012-02-01

The CT and MRI features of ovarian torsion are illustrated with gross pathologic correlation. Ovarian enlargement with or without an underlying mass is the finding most frequently associated with torsion, but it is nonspecific. A twisted pedicle, although not often detected on imaging, is pathognomonic when seen. Subacute ovarian hemorrhage and abnormal enhancement is usually seen, and both features show characteristic patterns on CT and MRI. Ipsilateral uterine deviation can also be seen. Diagnostic pitfalls that may mimic ovarian torsion and observations for discriminating them are discussed.

A cost-effective, accurate machine for testing the torsional strength of sheep long bones.

PubMed

Jämsä, T; Jalovaara, P

1996-07-01

A cost-effective torsional testing machine for sheep long bones was constructed. The machine was fabricated on a disused standard turning lathe. The angular speed used was 6.5 degrees/s. A precision amplifier using modern low-noise, low-drift operational amplifiers was developed. The maximum torsional load was 250 Nm, the sensitivity 0.5 Nm and the total machine inaccuracy less than 1.0%. The standard error of torsional testing was 3.0% when seven pairs of intact sheep tibiae were tested.

Torsion sensing setup based on a Mach-Zehnder interferometer with photonics crystal fiber

NASA Astrophysics Data System (ADS)

Pacheco-Chacon, Eliana I.; Gallegos-Arellano, E.; Sierra-Hernandez, Juan M.; Rojas-Laguna, Roberto; Estudillo-Ayala, Julian M.; Hernandez, Emmanuel; Jauregui-Vazquez, D.; Hernandez-Garcia, J. C.

2017-02-01

A torsion experimental sensing setup based on a Mach-Zehnder interferometer (MZI) with photonics crystal fiber is presented. The MZI was fabricated by fusion splicing a piece of photonic crystal fiber (PCF) between two segments of a single-mode fiber (SMF). Here, a spectral MZI fringe shifting is induced by applying torsion over the SMF-PCF-SMF. As a result a torsion sensitivity of 35.79 pm/ and a high visibility of 10 dB were achieved. Finally, it is shown that the sensing arrangement is compact and robust.

Use of optical coherence topography for objective assessment of fundus torsion.

PubMed

Sophocleous, Sophocles

2017-02-23

Objective assessment of fundus torsion is currently performed with indirect ophthalmoscopy or fundus photography. Using the infrared image of the macular scan of the optical coherence tomography one can assess the presence and amount of fundus torsion. In addition, the line scan through the fovea can be used as a reference to confirm the position of the foveal pit in relation to the optic nerve head. Two cases are used to demonstrate how to assess fundus torsion with the use of the optical coherence tomography. 2017 BMJ Publishing Group Ltd.

TT-Cut Torsional Quartz Crystal Resonators of Free-Free Bar-Type

NASA Astrophysics Data System (ADS)

Kawashima, Hirofumi; Nakazato, Mitsuhiro

1994-05-01

This paper describes a TT-cut torsional quartz crystal resonator of free-free bar type. An object of this paper is to clarify the frequency temperature behavior, series resistance and a quality factor for TT-cut torsional quartz crystal resonators of free-free bar-type. The analysis results are then compared with the measured data. The principal results indicate that the calculated values of frequency temperature behavior for resonators of free-free bar-type agree comparatively well with the measured ones. Similar to the torsional resonators of tuning fork-type, a torsional quartz crystal resonator of free-free bar-type is also found to have an absolute value of the second order temperature coefficient β smaller than half a value of that for a flexural mode quartz crystal resonator.

Nature of the ``yield tooth'' under torsion in plastic-deformed whiskers

NASA Astrophysics Data System (ADS)

Bataronov, I. L.; Belikov, A. M.; Drozhzhin, A. I.; Roshchupkin, A. M.

1987-07-01

The plastic torsion of whiskers with high Peierls barriers has been studied. As the samples for the studies we chose p-type germanium whiskers with <111> growth axis. The diameter of the whisker was (5 60)·10-6 m and the gauge length was (1 4)·10-3 m. The whiskers were dislocation-free in the initial state. Within the framework of the continuum model developed by us for the plastic deformation of whiskers under torsion, we analyze the anomalies of the torsional stress-strain diagram under different testing conditions and with preliminary deformation. The “flow tooth” during the torsion of a whisker is attributable to the nonuniform distribution of dislocations over the cross section of the whisker and high barriers to the dislocation motion.

Biomechanical comparison of straight DCP and helical plates for fixation of transverse and oblique bone fractures.

PubMed

Aksakal, Bunyamin; Gurger, Murat; Say, Yakup; Yilmaz, Erhan

2014-01-01

Biomechanical comparison of straight DCP and helical plates for fixation of transversal and oblique tibial bone fractures were analyzed and compared to each other by axial compression, bending and torsion tests. An in vitro osteosynthesis of transverse (TF) and oblique bone fracture (OF) fixations have been analysed on fresh sheep tibias by using the DCP and helical compression plates (HP). Statistically significant differences were found for both DCP and helical plate fixations under axial compression, bending and torsional loads. The strength of fixation systems was in favor of DC plating with exception of the TF-HP fixation group under compression loads and torsional moments. The transvers fracture (TF) stability was found to be higher than that found in oblique fracture (OF) fixed by helical plates (HP). However, under torsional testing, compared to conventional plating, the helical plate fixations provided a higher torsional resistance and strength. The maximum stiffness at axial compression loading and maximum torsional strength was achieved in torsional testing for the TF-HP fixations. From in vitro biomechanical analysis, fracture type and plate fixation system groups showed different responses under different loadings. Consequently, current biomechanical analyses may encourage the usage of helical HP fixations in near future during clinical practice for transverse bone fractures.

Clinical and imaging features in lung torsion and description of a novel imaging sign.

PubMed

Hammer, Mark M; Madan, Rachna

2018-04-01

We set out to identify the clinical and imaging features seen in lung torsion, a rare but emergent diagnosis leading to vascular compromise of a lobe or entire lung. We retrospectively identified 10 patients with torsion who underwent chest CT. We evaluated each case for the presence of bronchial obstruction and abnormal fissure orientation. In seven patients who underwent contrast-enhanced CTs, we assessed for the presence of the antler sign, a novel sign seen on axial images demonstrating abnormal curvature of the artery and branches originating on one side. Five patients had right middle lobe (RML) torsion after right upper lobectomy, and the remaining occurred following thoracentesis, aortic surgery, or spontaneously. Chest CTs demonstrated bronchial obstruction in eight cases and presence of abnormal fissure orientation in four patients. The antler sign was present in three patients with whole-lung torsion and one patient with lobar torsion; vascular swirling was seen on 3-D images in all seven patients with contrast-enhanced CTs. Lung parenchymal imaging findings in lung torsion may be non-specific. Identification of the antler sign on contrast-enhanced chest CT, in combination with other signs such as bronchial obstruction and abnormal fissure orientation, indicates rotation of the bronchovascular pedicle. The presence of this sign should prompt further evaluation with 3-dimensional reconstructions.

Torsional strength of computer-aided design/computer-aided manufacturing-fabricated esthetic orthodontic brackets.

PubMed

Alrejaye, Najla; Pober, Richard; Giordano Ii, Russell

2017-01-01

To fabricate orthodontic brackets from esthetic materials and determine their fracture resistance during archwire torsion. Computer-aided design/computer-aided manufacturing technology (Cerec inLab, Sirona) was used to mill brackets with a 0.018 × 0.025-inch slot. Materials used were Paradigm MZ100 and Lava Ultimate resin composite (3M ESPE), Mark II feldspathic porcelain (Vita Zahnfabrik), and In-Ceram YZ zirconia (Vita Zahnfabrik). Ten brackets of each material were subjected to torque by a 0.018 × 0.025-inch stainless steel archwire (G&H) using a specially designed apparatus. The average moments and degrees of torsion necessary to fracture the brackets were determined and compared with those of commercially available alumina brackets, Mystique MB (Dentsply GAC). The YZ brackets were statistically significantly stronger than any other tested material in their resistance to torsion (P < .05). The mean torques at failure ranged from 3467 g.mm for Mark II to 11,902 g.mm for YZ. The mean torsion angles at failure ranged from 15.3° to 40.9°. Zirconia had the highest torsional strength among the tested esthetic brackets. Resistance of MZ100 and Lava Ultimate composite resin brackets to archwire torsion was comparable to commercially available alumina ceramic brackets.

Torsion of the fallopian tube--a late complication of sterilisation.

PubMed

Sivanesaratnam, V

1986-02-01

Torsion of an intact fallopian tube, unaccompanied by torsion of the ipsilateral ovary, was noted as a complication of bilateral tubal occlusion by the Pomeroy method in a 45-year old Indian woman. The sterilization was performed 5 years previously, at the time of Cesarean section delivery. The patient presented with a history of pain in the right iliac fossa. Laparotomy showed that the distal segment of the right fallopian tube was twisted 3 times on the distal mesosalpinx and appeared tense and gangrenous. The right ovary was normal and a 2 cm gap was noted between the proximal and distal segments of the tube. As a rare complication of the Pomeroy method, the gap in the tube can allow the distal mesosalpinx to act as a pedicle, and with a long mesosalpinx, the fimbriated segment of the tube lies free and may swing and twist to produce torsion. The occurrence of torsion is further promoted by a vascular disturbance leading to venous congestion, edema, and increased weight of the free fimbrial end of the tube. In those patients with a history of sterilization, torsion of the fallopian tube should be considered in the differential diagnosis of acute lower abdominal pain. Torsion of the fallopian tube has also been reported following other methods of tubal occlusion, including cautery and clips.

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.

Gravitationally bound BCS state as dark matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexander, Stephon; Cormack, Sam, E-mail: stephon_alexander@brown.edu, E-mail: samuel.c.cormack.gr@dartmouth.edu

2017-04-01

We explore the possibility that fermionic dark matter undergoes a BCS transition to form a superfluid. This requires an attractive interaction between fermions and we describe a possible source of this interaction induced by torsion. We describe the gravitating fermion system with the Bogoliubov-de Gennes formalism in the local density approximation. We solve the Poisson equation along with the equations for the density and gap energy of the fermions to find a self-gravitating, superfluid solution for dark matter halos. In order to produce halos the size of dwarf galaxies, we require a particle mass of ∼ 200 eV. We findmore » a maximum attractive coupling strength before the halo becomes unstable. If dark matter halos do have a superfluid component, this raises the possibility that they contain vortex lines.« less

Rabi oscillations in the dissociative continuum: Rotation and alignment effects

NASA Astrophysics Data System (ADS)

Granucci, Giovanni; Magnier, Sylvie; Persico, Maurizio

2002-01-01

We have simulated a set of experiments in which Rabi oscillations are induced in bound-free and free-free transitions of a diatomic molecule. Dissociative vibrational states belonging to different electronic terms are involved. We show analytically and confirm computationally that a simple relationship exists between the one-dimensional dynamics of a molecule with fixed orientation with respect to the polarization of the radiation field and the three-dimensional dynamics of a rotating system. It is demonstrated that sufficiently short laser pulses can induce oscillations in the probabilities of two coupled electronic states, and in the yields of the respective dissociation products, as functions of the radiation intensity. As a result of molecular rotation the oscillations are damped but not washed out. The initial thermal distribution on several rotational levels has a negligible effect on the photodissociation yields and other experimentally relevant quantities. Since the molecule undergoes a strong alignment along the polarization axis of the laser field, the ejection of atoms and ions is anisotropic. We have chosen the well known diatomic ion Na2+ as a convenient example.

Ultrasound acoustic energy for microbubble manipulation

NASA Astrophysics Data System (ADS)

Bakhtiari-Nejad, Marjan; Elnahhas, Ahmed; Jung, Sunghwan; Shahab, Shima

2017-04-01

Many bio-medical applications entail the problems of spatially manipulating of bubbles by means of acoustic radiation. The examples are ultrasonic noninvasive-targeted drug delivery and therapeutic applications. This paper investigates the nonlinear coupling between radial pulsations, axisymmetric modes of shape oscillations and translational motion of a single spherical gas bubble in a host liquid, when it is subjected to an acoustic pressure wave field. A mathematical model is developed to account for both small and large amplitudes of bubble oscillations. The coupled system dynamics under various conditions is studied. Specifically, oscillating behaviors of a bubble (e.g. the amplitudes and instability of oscillations) undergoing resonance and off-resonance excitation in low- and high- intensity acoustic fields are studied. Instability of the shape modes of a bubble, which is contributing to form the translational instability, known as dancing motion, is analyzed. Dynamic responses of the bubble exposed to low- and high-intensity acoustic excitation are compared in terms of translational motion and surface shape of the bubble. Acoustic streaming effects caused by radial pulsations of the bubble in the surrounding liquid domain are also reported.

Wing Rock Motion and its Flow Mechanism over a Chined-Body Configuration

NASA Astrophysics Data System (ADS)

Wang, Yankui; Li, Qian; Shi, Wei

2015-11-01

Wing rock motion is one kind of uncommanded oscillation around the body axis over the most of the aircraft at enough high angle of attack and has a strong threat to the flight safety. The purpose of this paper is to investigate the wing rock motion over a typical body-wing configuration with a chined fuselage at fixed angle of attack firstly and four kinds of wing rock motion are revealed based on the flow phenomena, namely non-oscillation, lateral deflection, limit-cycle oscillation and irregular oscillation. Simultaneously, some special relationship between the wing rock motion and the flow over the chined body configuration are discussed. In addition, the evolution of wing rock motion and its corresponding flows when the model undergoes pitching up are also given out. All the experiments have been conducted in a low-speed wind tunnel at a Reynolds number of 1.87*10E5 and angle of attack from 0deg to 65deg. National Natural Science Foundation of China(11472028) and Open fund from State Key Laboratory of Aerodynamics.

Oscillating flow and heat transfer in a channel with sudden cross section change

NASA Technical Reports Server (NTRS)

Ibrahim, Mounir; Hashim, Waqar

1993-01-01

We have computationally examined oscillating flow (zero mean) between two parallel plates with a sudden change in cross section. The flow was assumed to be laminar incompressible with the inflow velocity uniform over the channel cross section but varying sinusoidally with time. The cases studied cover wide ranges of Re(sub max) (from 187.5 to 2000), Va (from 1 to 10.66), the expansion ratio (1:2 and 1:4) and A(sub r) (2 and 4). Also, three different geometric cases were discussed: (1) asymmetric expansion/contraction; (2) symmetric expansion/contraction; and (3) symmetric blunt body. For these oscillating flow conditions, the fluid undergoes sudden expansion in one-half of the cycle and sudden contraction inthe other half. The instantaneous friction factor, for some ranges of Re(sub max) and Va, deviated substantially from the steady-state friction factor for the same flow parameters. A region has been identified below which the flow is laminar quasi-steady. A videotape showing computer simulations of the oscillating flow demonstrates the usefulness of the current analyses in providing information on the transient hydraulic phenomena.

Optimal viscous damping of vibrating porous cylinders

NASA Astrophysics Data System (ADS)

Jafari Kang, Saeed; Masoud, Hassan

2017-11-01

We theoretically study small-amplitude oscillations of permeable cylinders immersed in an unbounded fluid. Specifically, we examine the effects of permeability and oscillation frequency on the damping coefficient, which is proportional to the power required to sustain the vibrations. Cylinders of both circular and non-circular cross-sections undergoing transverse and rotational vibrations are considered. Our calculations indicate that the damping coefficient often varies non-monotonically with the permeability. Depending on the oscillation period, the maximum damping of a permeable cylinder can be many times greater than that of an otherwise impermeable one. This might seem counter-intuitive at first since generally the power it takes to steadily drag a permeable object through the fluid is less than the power needed to drive the steady motion of the same but impermeable object. However, the driving power (or damping coefficient) for oscillating bodies is determined by not only the amplitude of the cyclic fluid force experienced by them but also by the phase shift between the force and their periodic motion. An increase in the latter is responsible for excess damping coefficient of vibrating porous cylinders.

Linear Transformation of the Polarization Modes in Coiled Optical Spun-Fibers with Strong Unperturbed Linear Birefringence. I. Nonresonant Transformation

NASA Astrophysics Data System (ADS)

Malykin, G. B.; Pozdnyakova, V. I.

2018-03-01

A linear transformation of orthogonal polarization modes in coiled optical spun-fibers with strong unperturbed linear birefringence, which causes the emergence of the dependences of the integrated elliptical birefringence and the ellipticity and azimuth of the major axis of the ellipse, as well as the polarization state of radiation (PSR), on the length of optical fiber has been considered. Optical spun-fibers are subjected to a strong mechanical twisting, which is frozen into the structure of the optical fiber upon cooling, in the process of being drawn out from the workpiece. Since the values of the local polarization parameters of coiled spunwaveguides vary according to a rather complex law, the calculations were carried out by numerical modeling of the parameters of the Jones matrices. Since the rotation speed of the axes of the birefringence is constant on a relatively short segment of a coiled optical spun-fiber in the accompanying torsion (helical) coordinate system, the so-called "Ginzburg helical polarization modes" (GHPMs)—two mutually orthogonal ellipses with the opposite directions of traversal, the axis of which rotate relative to the fixed coordinate system uniformly and unidirectionally—are approximately the local normal polarization modes of such optical fiber. It has been shown that, despite the fact that the unperturbed linear birefringence of the spun-fibers significantly exceeds the linear birefringence, which is caused by the winding on a coil, the integral birefringence of an extended segment of such a fiber coincides in order of magnitude with the linear birefringence, which is caused by the winding on the coil, and the integral polarization modes tend asymptotically to circular ones. It has been also shown that the values of the circular birefringence of twisted single-mode fibers, which were calculated in a nonrotating and torsion helical coordinate systems, differ significantly. It has been shown that the polarization phenomena occur in the process of linear transformation of local polarization modes, which lead to small quasi-harmonic oscillations of the birefringence integral parameters of the optical spun-fibers, which depend on their length, and the period of these oscillations is approximately equal to half of the effective period of polarization beating.