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Showing papers on "Rotation published in 1996"


Journal ArticleDOI
TL;DR: Proper throwing mechanics may enable an athlete to achieve maximum performance with minimum chance of injury by utilising a kinetic chain to generate and transfer energy from the larger body parts to the smaller, more injury-prone upper extremity.
Abstract: Proper throwing mechanics may enable an athlete to achieve maximum performance with minimum chance of injury. While quantifiable differences do exist in proper mechanics for various sports, certain similarities are found in all overhand throws. One essential property is the utilisation of a kinetic chain to generate and transfer energy from the larger body parts to the smaller, more injury-prone upper extremity. This kinetic chain in throwing includes the following sequence of motions: stride, pelvis rotation, upper torso rotation, elbow extension, shoulder internal rotation and wrist flexion. As each joint rotates forward, the subsequent joint completes its rotation back into a cocked position, allowing the connecting segments and musculature to be stretched and eccentrically loaded. Most notable is the external rotation of the shoulder, which reaches a maximum value of approximately 180 degrees. This biomechanical measurement is a combination of true glenohumeral rotation, trunk hyperextension and scapulothoracic motion. Near the time of maximum shoulder external rotation (ERmax), shoulder and elbow musculature eccentrically contract to produce shoulder internal rotation torque and elbow varus torque. Both the shoulder and the elbow are susceptible to injury at this position. At ball release, significant energy and momentum have been transferred to the ball and throwing arm. After ball release, a kinetic chain is used to decelerate the rapidly moving arm with the entire body. Shoulder and elbow muscles produce large compressive forces to resist joint distraction. Both joints are susceptible to injury during arm deceleration.

475 citations


Journal ArticleDOI
31 May 1996-Science
TL;DR: Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths.
Abstract: Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within the solar interior. The nearly uninterrupted observations by the Global Oscillation Network Group (GONG) yield oscillation power spectra with high duty cycles and high signal-to-noise ratios. Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths. A distinctive shear layer just below the surface is discernible at low to mid-latitudes.

367 citations


Journal ArticleDOI
TL;DR: In this paper, the axial trapping forces within optical tweezers arising from Laguerre-Gaussian laser modes were numerically modeled for an 8 μm diameter sphere suspended in water.
Abstract: We numerically model the axial trapping forces within optical tweezers arising from Laguerre–Gaussian laser modes. For an 8 μm diameter sphere suspended in water, the higher-order modes produce an axial trapping force several times larger than that of the fundamental. Partial absorption results in a transfer of the orbital angular momentum from the Laguerre–Gaussian mode to the trapped particle. This results in the rotation of the particle by what may be called an optical spanner (wrench). For an absorption coefficient of α = 5700 m−1 and a laser power of 10 mW, we find that an 8 μm diameter sphere would acquire an angular acceleration of 10 × 104 rad s−2 and a limiting angular velocity of 0.2 rad s−1.

257 citations


Journal ArticleDOI
TL;DR: In this article, a series of simulations of unforced turbulence evolving within a shallow layer of fluid on a rotating sphere are presented, showing that the turbulent evolution in the spherical domain is strongly dependent on numerical and physical conditions.
Abstract: Results from a series of simulations of unforced turbulence evolving within a shallow layer of fluid on a rotating sphere are presented. Simulations show that the turbulent evolution in the spherical domain is strongly dependent on numerical and physical conditions. The independent effects of (1) (hyper)dissipation and initial spectrum, (2) rotation rate, and (3) Rossby deformation radius are carefully isolated and studied in detail. In the nondivergent and nonrotating case, an initially turbulent flow evolves into a vorticity quadrupole at long times, a direct consequence of angular momentum conservation. In the presence of sufficiently strong rotation, the nondivergent long‐time behavior yields a field dominated by polar vortices—as previously reported by Yoden and Yamada. In contrast, the case with a finite deformation radius (i.e., the full spherical shallow‐water system) spontaneously evolves toward a banded configuration, the number of bands increasing with the rotation rate. A direct application of...

236 citations



Journal ArticleDOI
TL;DR: It is shown that inverse and forward cascades of energy can coexist and is relevant to geophysical flows, and contains physics beyond the scope of quasigeostrophic models.
Abstract: Forced rotating turbulence is simulated within a periodic box of small aspect ratio. Critical parameter values are found for the stability of a 2D inverse cascade of energy in the presence of 3D motions at small scales. There is a critical rotation rate below which 2D forcing leads to an equilibrated 3D state, while for a slightly larger rotation rate, 3D forcing drives a 2D inverse cascade. It is shown that inverse and forward cascades of energy can coexist. This study is relevant to geophysical flows, and contains physics beyond the scope of quasigeostrophic models.

177 citations


Patent
06 Sep 1996
TL;DR: In this article, a semiautonomously directed, autonomously controlled, gyroscopically stabilized, horizontal or vertical take off and landing (HOVTOL) flying apparatus is described.
Abstract: A semiautonomously directed, autonomously controlled, gyroscopically stabilized, horizontal or vertical take off and landing (HOVTOL) flying apparatus employing two vertical lift devices equally and longitudinally spaced from the center of gravity of the apparatus; continuously integrated with a drive train apparatus, optional single or multiple power means; congruously connected thereto horizontal thrust devices. Integral to the vertical lift devices; pitch axis control devices situated at the exhaust orifices therein to vector said devices exhaust slip stream by a autonomous flight control system providing pitch stability. The autonomous flight control system providing continuously all flight control of the apparatus and said system being interfaced to a semiautonomous flight director device providing discrete flight direction function codes thereto. The combined effect of the apparatus is: When the power system rotates; coincident rotation of the drive train causes the vertical lift apparatus and horizontal thrust apparatus to counter rotate at right angles simultaneously providing both vertical lift and gyroscopic roll stability and simultaneously providing both horizontal thrust and gyroscopic yaw stability during flight; the continuous control thereof being accomplished by the autonomous flight control system and the directional steering, and function thereof in four axis effected by the semiautonomous flight director device which provides discrete flight function codes to the autonomous flight control system so as to disallow the initiation of negative flight maneuvers and/or functions providing for the safe unskilled pilot operation of the apparatus or any aircraft employing a autopilot having a autonomous digital flight control system.

176 citations



Journal ArticleDOI
TL;DR: In this article, a multiple single frequency laser (MSFL) was proposed for sequential cooling of rotation, translation, and vibration of molecules, which is simpler and more feasible than simply providing a large number of synchronously but independently tunable lasers.
Abstract: A novel scheme is proposed for sequential cooling of rotation, translation, and vibration of molecules. More generally, this scheme manipulates and controls the states and energies of molecules. The scheme, while somewhat complex, is simpler and more feasible than simply providing a large number of synchronously but independently tunable lasers. The key component is a multiple single frequency laser (MSFL) in which a single narrow band pump laser generates an ensemble of resonant ‘‘stimulated Raman’’ (RSR) sidebands (subsequently amplified and selected) in a sample of the molecules to be cooled. Starting with a relatively cold molecular sample (e.g., a supersonic beam of Cs2), the rotation of molecules is cooled by sequential application of P branch electronic transition frequencies transverse to the molecular beam beginning at higher rotational angular momentum J. Then translation of molecules is cooled by application of multiple low J, P, and R branch transition frequencies which counterpropagate with t...

160 citations


Journal ArticleDOI
TL;DR: In this article, the authors numerically study the precessing disk model for superhumps in the SU~UMa subclass of cataclysmic variables, using a two dimensional SPH code specifically designed for thin disk problems.
Abstract: We numerically study the precessing disk model for superhump in the SU~UMa subclass of cataclysmic variables, using a two dimensional SPH code specifically designed for thin disk problems. Two disk simulations for a binary with mass ratio $q=\frac{3}{17}$ (similar to OY~Car) are performed, in order to investigate the Lubow (1991 a,b) tidal resonance instability mechanism. In the first calculation, a disk evolves under steady mass transfer from $L_1$. In the second simulation, mass is added in Keplerian orbit to the inner disk. The two disks follow similar evolutionary paths. However the $L_1$ stream-disk interaction is found to slow the disk's radial expansion and to circularise gas orbits. The initial eccentricity growth in our simulations is exponential at a rate slightly less than predicted by Lubow (1991a). We do not observe a clearing of material from the resonance region via the disk's tidal response to the $m=2$ component of the binary potential as was described in Lubow (1992). Instead the $m=2$ response weakens as the disk eccentricty increases. Both disks reach an eccentric equilibrium state, in which they undergo prograde precession. The rate of viscous energy dissipation in the disks has a periodic excess with a period matching the disk's rotation. The source is identified as a large region in the outer disk, and the mechanism by which it is produced is identified. The time taken for the periodic excess to develop is consistent with the first appearance of superhumps in a superoutburst.

158 citations


Patent
21 Feb 1996
TL;DR: A steerable rotary drilling system comprises a bottom hole assembly which includes, in addition to a drill bit, a modulated bias unit and a control unit including an instrument carrier which is rotatable relative to the bias unit as discussed by the authors.
Abstract: A steerable rotary drilling system comprises a bottom hole assembly which includes, in addition to a drill bit, a modulated bias unit and a control unit including an instrument carrier which is rotatable relative to the bias unit. The bias unit comprises a number of hydraulic actuators spaced apart around the periphery of the unit, each having a movable thrust member which is displaceable outwardly for engagement with the formation. Each actuator can be connected, through a rotatable control valve, to a source of drilling fluid under pressure, the control valve comprising a first part, rotatable with the instrument carrier, which cooperates with a second part which is rotatable with the bias unit. Means are provided to roll stabilize the instrument carrier so that relative rotation between the bias unit and instrument carrier, as the bias unit rotates, causes the valve to operate the actuators in synchronism with rotation of the bias unit so as to apply a lateral bias thereto. In order to neutralize or reduce the net bias applied to the bias unit the instrument carrier may be rotated in various modes instead of being roll stabilized, e.g., it may be rotated at a constant slow speed relative to the bias unit, or at a significantly faster rate so that the actuators do not have time to operate fully. The angular velocity of the carrier may also be varied during its rotation, according to various formulae, in order to vary the net bias. The net bias may also be varied by alternating different modes of carrier rotation.

Patent
21 May 1996
TL;DR: In this paper, an apparatus and method for mixing/agitating microorganism culture bottles includes a wheel in which culture bottles are placed, with the wheel being set at an angle from vertical so that bottles are not inverted during rotation.
Abstract: An apparatus and method for mixing/agitating microorganism culture bottles includes a wheel in which culture bottles are placed, with the wheel being set at an angle from vertical so that bottles are not inverted during rotation. A sensor such as a florescence or colorimetric sensor for carbon dioxide is disposed along the flat bottom surface of each of the bottles. Once during each revolution the bottles pass across a photodiode/light emitting diode pair (for a calorimetric system). A sensor transmits light emitted by the LED to the photodiode. At the same instant, an infrared reflective objective sensor, emitting on a digital rotary encoder, determines the bottle number. The change in sensor transmittance is directly related to cell growth so that bottles positive for growth can be detected by suitable software.

Journal ArticleDOI
TL;DR: In this article, a tilted-ring model is fitted to 21-cm line data taken with the Arecibo Telescope to determine the actual HI distribution and the velocity field in the outermost disk of the spiral galaxy M33, which is one of the main calibrators for the extragalactic distance scale derived through the Tully-Fisher relation.
Abstract: To determine the actual HI distribution and the velocity field in the outermost disk of the spiral galaxy M33, a tilted-ring model is fitted to 21-cm line data taken with the Arecibo Telescope. Since M33 is one of the main calibrators for the extragalactic distance scale derived through the Tully-Fisher relation, the outer disk warping is of interest for a correct determination and deprojection of the galaxy's line width. Even though our best model predicts small effects on the observed line width of M33, we show that similar outer disk warping in galaxies oriented differently along our line of sight could affect the widths considerably. Therefore there may be systematic effects in the determination of the rotation velocities and dynamic masses of spiral galaxies, whose exact value depends also on which method is used for measuring the galaxy's total line width.

Journal ArticleDOI
TL;DR: The objective of this paper is to investigate general solutions having rotating intensity distributions around and along the propagation axis and demonstrate that these solutions are easily obtained in terms of the superposition of Gauss-Laguerre ~GL! modes.
Abstract: Wave fields containing invariant features have recently stimulated the interest of the scientific community. Typical examples of such fields are Gaussian modes, Bessel beams @1#, and wave fronts containing phase dislocations @2#. Bessel beams are solutions of the wave equation that propagate with invariant intensity. Phase dislocations are discontinuities of the phase in a wave front such that the circulation of the phase around its axis is an integral multiple of 2p. Thus, they determine lines of zero intensity in space. Experimental evidences of optical dislocations can be found, for example, in Refs. @3‐5#. It was noted in Refs. @4,6# that, under certain circumstances, an array of dislocations nested in a Gaussian beam rotates by p/2 rad from the waist to the far field, expanding with the host beam. The objective of this paper is to investigate general solutions having rotating intensity distributions around and along the propagation axis. We start by demonstrating that these solutions are easily obtained in terms of the superposition of Gauss-Laguerre ~GL! modes. The rotation rate along the propagation is then derived and the set of all possible solutions presenting a specific total rotation angle is characterized. Finally, we analyze the limit of the rotation rate and present experimental results for optical beams. Let a scalar wave be represented by the function

Journal ArticleDOI
31 May 1996-Science
TL;DR: Rotation profiles averaged over 27-day rotations of the sun reveal the torsional oscillation signal—weak, jetlike features, with amplitudes of 5 meters per second, that are associated with the sunspot latitude activity belts.
Abstract: Doppler velocity observations obtained by the Global Oscillation Network Group (GONG) instruments directly measure the nearly steady flows in the solar photosphere. The sun's differential rotation is accurately determined from single observations. The rotation profile with respect to latitude agrees well with previous measures, but it also shows a slight north-south asymmetry. Rotation profiles averaged over 27-day rotations of the sun reveal the torsional oscillation signal-weak, jetlike features, with amplitudes of 5 meters per second, that are associated with the sunspot latitude activity belts. A meridional circulation with a poleward flow of about 20 meters per second is also evident. Several characteristics of the surface flows suggest the presence of large convection cells.

Journal ArticleDOI
TL;DR: Experimental results on a test system demonstrate that the Moiredeflectometer's sensitivity to rotation and gravitation is already in the range of commercially used inertial sensors and can be increased straightforwardly by orders of magnitude.
Abstract: A different approach to high-precision measurement of rotation, acceleration, and gravitation is presented. Our Moir\'e deflectometer is based on geometric propagation of an atomic (or molecular) beam through a set of three identical gratings. Accelerated movements of the gratings with respect to the atomic beam result in a change of the total transmitted intensity. The device is nondispersive, i.e., atoms with a broad energy distribution and without collimation can be used. Furthermore, rotational and linear (gravitational) acceleration can easily be distinguished and measured simultaneously. In a certain sense the Moir\'e deflectometer represents the classical analog to a quantum-mechanical matter-wave interferometer. Experimental results on a test system demonstrate that its sensitivity to rotation and gravitation is already in the range of commercially used inertial sensors. It can be increased straightforwardly by orders of magnitude. \textcopyright{} 1996 The American Physical Society.

Patent
21 Feb 1996
TL;DR: In this paper, the rotational orientation of a roll stabilizable control unit in a steerable rotary drilling assembly is measured by an instrument carrier rotatably mounted on a support connected to the drill string.
Abstract: A system for controlling the rotation of a roll stabilizable control unit in a steerable rotary drilling assembly comprises an instrument carrier rotatably mounted on a support connected to the drill string. A first rotatable impeller is mounted for rotation by a flow of drilling fluid over the impeller and is coupled to the instrument carrier so as to transmit a torque to it. Sensors carried by the instrument carrier sense the rotational orientation of the instrument carrier and produce a control signal indicative of its rotational orientation, and the torque applied to the instrument carrier by the impeller is controlled, at least partly in response to said signal, so that the instrument carrier can, for example, be roll stabilized if required. A second rotatable impeller is coupled to the instrument carrier for transmitting to it a second torque, which may also be controlled, in the opposite direction to the torque transmitted by the first impeller. The provision of two opposed impellers allows the rotation of the control unit to be controlled over a greater range than is possible with a single impeller.

Journal ArticleDOI
TL;DR: In this article, the authors presented experimental heat transfer results in a two-pass square channel with smooth and ribbed surfaces, where the ribs were placed in a staggered half-V fashion with the rotation orthogonal to the channel axis.
Abstract: This paper presents experimental heat transfer results in a two-pass square channel with smooth and ribbed surfaces. The ribs are placed in a staggered half-V fashion with the rotation orthogonal to the channel axis. The channel orientation varies with respect to the rotation plane. A change in the channel orientation about the rotating frame causes a change in the secondary flow structure and associated flow and turbulence distribution. Consequently, the heat transfer coefficient from the individual surfaces of the two-pass square channel changes. The effects of rotation number on local Nusselt number ratio distributions are presented. Heat transfer coefficients with ribbed surfaces show different characteristics in rotation number dependency from those with smooth surfaces. Results show that staggered half-V ribs mostly have higher heat transfer coefficients than those with 90 and 60 deg continuous ribs. 16 refs., 10 figs.

Patent
10 Jul 1996
TL;DR: In this paper, an apparatus for electrolytic plating of a substrate (44) includes a tank (14) in which a shaft (30) is centrally mounted for rotation about a first axis (28).
Abstract: An apparatus (10) for electrolytic plating of a substrate (44) includes a tank (14) in which a shaft (30) is centrally mounted for rotation about a first axis (28). The shaft carries an arm (40), on the distal end (112) of which is rotatably mounted a fixture wheel (44). The substrate to be plated is carried on the fixture wheel, which rides on an annular track (50) formed on the bottom of the tank around the shaft. A plurality of spaced pins (52) projecting upwardly from the track engage with a plurality of spaced recesses (56) formed about the perimeter (54) of the wheel, so that the wheel rotates about a second axis (64) while revolving around the first axis. The fixture carries a plurality of electrical contact members (46) that contact the substrate. Each contact member is separately supplied with current from a multichannel power supply (22). For each electrical contact member, the fixture includes a separate corresponding conductive brush (162), bushing (142) and lead (48) threaded through the arm and shaft to the corresponding channel of the power supply.

Journal ArticleDOI
TL;DR: In this article, a quantitative analysis of the amplitudes of waves which sample a particular region of the inner core, under Africa, but exhibit various orientations has been conducted to document and characterize the presence of anisotropy in attenuation.
Abstract: During the last decade, the presence of velocity anisotropy inside the inner core, with a fast axis parallel to the Earth's rotation axis, has been well established. The quantitative analysis of the amplitudes of waves which sample a particular region of the inner core, under Africa, but exhibit various orientations allows us to document and characterize the presence of anisotropy in attenuation. The analysis is based on a comparison of both amplitudes and travel times of the PKP(DF) wave, which samples the inner core, and the PKP(BC) wave, which has nearly the same path but bottoms inside the liquid core. The data reveal that the direction of strong attenuation correlates with that of fast velocity. When referred to the same epicentral distance and focal depth, the PKP(DF)/PKP(BC) amplitude ratio are about five times lower for paths tilted by 25° with respect to the Earth rotation axis, than for nearly equatorial paths. A clear negative correlation is observed between travel time and amplitude residuals, when the angle to Earth rotation axis varies. This first quantitative analysis, combined with experimental results on oriented crystals and mushy media, may bring important constraints on the mechanism responsible for anisotropy in the inner core.


Patent
02 Jan 1996
TL;DR: In this paper, a medical retractor has a support shaft on which is threaded a retractor arm drive that supports a retraction arm and a worm with threads that engage peripheral gear teeth of a worm gear.
Abstract: A medical retractor having a support shaft on which is threaded a retractor arm drive that supports a retractor arm. The retractor arm drive includes a worm with threads that engage peripheral gear teeth of a worm gear; and the worm gear is threaded onto the support shaft. Rotating the worm, turns the worm gear and moves the retractor arm drive and retractor arm longitudinally along the support shaft. A stop prevents the support shaft from rotating with the worm gear in response to rotation of the worm.

Journal ArticleDOI
S. C. Cheah1, Hector Iacovides1, D. C. Jackson1, H. Ji1, Brian Launder1 
TL;DR: In this paper, the authors used laser-Doppler anemometry (LDA) to measure the mean and fluctuating flow field in a U-bend of strong curvature, Rc/D = 0.65, that is either stationary or rotating in orthogonal mode.
Abstract: This paper reports results from the use of laser-Doppler anemometry (LDA) to measure the mean and fluctuating flow field in a U-bend of strong curvature, Rc/D = 0.65, that is either stationary or rotating in orthogonal mode (the axis of rotation being parallel to the axis of curvature). The data acquisition system enables a stationary optical fiber probe to collect flow data from a rotating U-bend sweeping past it. Three cases have been examined, all concerning a flow Reynolds number of 100,000; a stationary case, a case of positive rotation (the pressure side of the duct coincides with the outer side of the U-bend) at a rotational number (ΩD/U m ) of 0.2, and a case of negative rotation at a rotational number of -0.2. Measurements have been obtained along the symmetry plane of the duct and also along a plane near the top wall. The most important influence on the development of the mean and turbulence flow fields is exerted by the streamwise pressure gradients that occur over the entry and exit regions of the U-bend. In the stationary case a three-dimensional separation bubble is formed along the inner wall at the 90 deg location and it extends to about two diameters downstream of the bend, causing the generation of high-turbulence levels. Along the outer side, opposite the separation bubble, turbulence levels are suppressed due to streamwise flow acceleration. For the rotation numbers examined, the Coriolis force also has a significant effect on the flow development. Positive rotation doubles the length of the separation bubble and generally suppresses turbulence levels. Negative rotation causes an extra separation bubble at the bend entry, raises turbulence levels within and downstream of the bend, increases velocity fluctuations in the cross-duct direction within the bend, and generates strong secondary motion after the bend exit. It is hoped that the detailed information produced in this study will assist in the development of turbulence models suitable for the numerical computation of flow and heat transfer inside blade-cooling passages.

Patent
18 Jul 1996
TL;DR: A fluid-based torque transfer device as discussed by the authors modulates the amount of torque which is transmitted from an input shaft to an output shaft by applying a magnetic circuit including a coil wound around a core material defining a gap.
Abstract: A fluid-based torque transfer device modulates the amount of torque which is transmitted from an input shaft to an output shaft. The torque transfer device includes a first plate connected to the input shaft. A second plate is connected to the output shaft and spaced from the first plate. A magnetorheological fluid is provided between the first and second plates. A magnetic circuit, including a coil wound around a core material defining a gap, applies a magnetic field to the magnetorheological fluid to variably control the rotation of the second plate in response to the rotation of the first plate. A controller adjusts the current to the coil to vary the magnetic field. Sensors detect at least one of the rotational speed and the torque of the input shaft, the output shaft, vehicle speed, steering direction, throttle position, gear position and brake position. The controller varies the current provided to the coil based thereon. Exemplary applications for the fluid-based torque transfer device include a fuse, a clutch between an engine and a transmission, and a transfer case for four wheel drive powertrains.

Patent
10 Sep 1996
TL;DR: In this article, a perforated baffle attached to the capture shelves prevents cooling fluid from splashing out of the shelves, and a barrier disposed along the inner surface of the rotor wall in the condensing section slows or temporarily stops the flow of cooling fluid prior to reaching the vaporization section.
Abstract: An evaporatively cooled rotor for a gas turbine engine. Each rotor defines an internal cavity which includes a vaporization section that corresponds generally to the blade section of the rotor and a condensing section that corresponds generally to the hub section of the rotor. A radial array of circumferentially disposed capture shelves is provided in the vaporization section for capturing cooling fluid contained within the internal cavity and flowing radially outward under the centrifugal field generated during rotation of the rotor. A barrier disposed along the inner surface of the rotor wall in the condensing section slows or temporarily stops the flow of cooling fluid prior to reaching the vaporization section and a perforated baffle attached to the capture shelves prevents cooling fluid from splashing out of the shelves.

Journal ArticleDOI
TL;DR: In this paper, the orbital angular momentum inherent to light beams with a helical wavefront can be transferred to nonisotropic lenses by inverting one transverse direction of the mode function and the corresponding transfer of angular momentum shows up directly as a frequency shift 2mΩ when the lens system is set in rotation at frequency Ω around the axis.

Journal ArticleDOI
TL;DR: The stellar dynamics of Omega Centauri are inferred from the radial velocities of 469 stars measured with CORAVEL (Mayor et al. 1997) by direct operation on the data as mentioned in this paper.
Abstract: The stellar dynamics of Omega Centauri are inferred from the radial velocities of 469 stars measured with CORAVEL (Mayor et al. 1997). Rather than fit the data to a family of models, we generate estimates of all dynamical functions nonparametrically, by direct operation on the data. The cluster is assumed to be oblate and edge-on but mass is not assumed to follow light. The mean motions are consistent with axisymmetry but the rotation is not cylindrical. The peak rotational velocity is 7.9 km/s at 11 pc from the center. The apparent rotation of Omega Centauri is attributable in part to its proper motion. We reconstruct the stellar velocity ellipsoid as a function of position, assuming isotropy in the meridional plane. We find no significant evidence for a difference between the velocity dispersions parallel and perpendicular to the meridional plane. The mass distribution inferred from the kinematics is slightly more extended than, though not strongly inconsistent with, the luminosity distribution. We also derive the two-integral distribution function f(E,Lz) implied by the velocity data.

Journal ArticleDOI
01 Jul 1996-Spine
TL;DR: It was concluded that the axial rotation is achieved through the activities of agonists, and return to neutral position is because of elastic recoil controlled by agonistic muscles.
Abstract: Study Design. An axial rotation tester was designed and fabricated for the study. This allowed stabilization of seated subjects (hip down) and coupling of shoulders, permitting axial rotation and coupled lateral flexion. Using this device, a flexion-extension free axial rotation was executed for studying its characteristics. Objectives. To determine the mechanism of initiation, sustenance, and execution of axial rotation. This was planned to be done by determining the phasic relationship of various torso muscles in the initiation, execution, and termination of axial rotation. Another objective was to determine the total and relative contribution of torso muscles in axial rotation and the small segments of these activities. Summary of Background Data. There only are a few studies conducted on axial rotation. Generally, these have investigated isometric maximal voluntary contraction in neutral or prerotated postures. The two studies that have reported isokinetic axial rotation have investigated maximal efforts. No study in literature has reported initiation, termination, and execution of unresisted normal velocity axial rotation. Methods. Fifty healthy young subjects executed a full cycle of axial rotation, starting from neutral position to their extreme left, continuing to their extreme right, and finally moving to the neutral posture in one smooth motion without stopping anywhere. The electromyographic results of external obliques, internal obliques, rectus abdominis, pectoralis major, erectores spinae at T 10 and L 3 , and latissimus dorsi were measured bilaterally simultaneously during this trunk rotation. The timing and relative magnitude analyses were done to determine the global and individual muscle contributions in axial rotation. The correlation between electromyographic and anbgular displacement, and non-linear curve fitting regression analyses were performed to decipher individual muscles behavior. Results. The pattern of muscle activation was variable. However, contralateral external obliques, ipsilateral erector spinae, and latissimus dorsi became active before other muscles. These were agonists and the others were antagonists or stabilizers. The agonists contributed 65% of the total electromyographic output, whereas antagonists and stabilizers contributed 35%. The muscle activities during onset and offset periods were biphasic with significantly different slopes. Conclusions. It was concluded that the axial rotation is achieved through the activities of agonists, and return to neutral position is because of elastic recoil controlled by agonistic muscles. A range of approximately 10-15° on either side of the anatomical midsagittal plane involves little muscle effort, but beyond this region, the osteoligamentous structures become stiff and require increasing effort to execute axial rotation.

Journal ArticleDOI
TL;DR: In this article, the authors derived both total flux and velocity-resolved response functions for the CIV 1549 emission line from the data obtained in the 1993 NGC 5548 monitoring campaign.
Abstract: We derive both total flux and velocity-resolved response functions for the CIV 1549 emission line from the data obtained in the 1993 NGC 5548 monitoring campaign. These response functions imply: 1.) the emission region stretches from inside 1 lt-d to outside 10 lt-d, and is probably better described as round than flat; 2.) the velocity field is dominated by a red/blue symmetric component (e.g. 2--d or 3--d random motions, or rotation in a disk) but there is also {\it significant} radial infall. Quantitative modelling indicates that the random speeds are typically a few times as large as the radial speed. However, no simple model gives a completely acceptable fit to the data. These inferences rule out numerous simple and otherwise plausible models for broad line region dynamics, including outflowing winds, radial free-fall, rotation in a disk, or collisionless orbital motion.

Journal ArticleDOI
TL;DR: 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: 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).