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Co-current rotation of the bulk ions due to the ion orbit loss at the edge of a tokamak plasma  [PDF]
Chengkang Pan,Shaojie Wang,Jing Ou
Physics , 2014, DOI: 10.1088/0029-5515/54/10/103003
Abstract: Flux-surface-averaged momentum loss and parallel rotation of the bulk ions at the edge of a tokamak plasma due to the ion orbit loss are calculated by computing the minimum loss energy of both the trapped and the passing thermal ions. The flux-surface-averaged parallel rotation of the bulk ions is in the co-current direction. The peak of the co-current rotation speed locates inside the last closed flux surface due to the orbit loss of the co-current thermal ions at the very edge of a tokamak plasma. The peaking position moves inward when the ion temperature increases.


中国物理 B , 1998,
Abstract: The destabilization of the poloidal rotation for the species of ions with the poloidally inhomogeneous sources or sinks is studied in multiple ion species tokamak plasmas. Based on the fluid equations, the evolution equation of the poloidal ion rotation speed is derived analytically. The magnitude of the inhomogeneous sources or sinks needed to destabilize the rotation is shown to be proportional to the ion density. It is suggested that the poloidal plasma rotation can be generated by destabilizing the rotation of the minority ions.
On the Differential Rotation of Massive Main Sequence Stars  [PDF]
T. M. Rogers
Physics , 2015,
Abstract: To date, asteroseismology has provided core to surface differential rotation measurements in eight main-sequence stars. These stars, ranging in mass from $\sim$1.5-9$M_\odot$, show rotation profiles ranging from uniform to counter-rotation. Although they have a variety of masses, these stars all have convective cores and overlying radiative regions, conducive to angular momentum transport by internal gravity waves (IGW). Using two-dimensional (2D) numerical simulations we show that angular momentum transport by IGW can explain all of these rotation profiles. We further predict that should high mass, faster rotating stars be observed, the core to envelope differential rotation will be positive, but less than one.
Effects of Circulating Energetic Ions on Geodesic Acoustic Modes with Toroidal Rotation  [PDF]
Haijun Ren,Chao Dong,Paul K. Chu
Physics , 2013,
Abstract: Effects of circulating energetic ions (CEIs) on the geodesic acoustic modes (GAMs) in toroidally rotating tokamaks are theoretically analyzed utilizing the hybrid kinetic-fluid model. The frequencies of GAMs in the presence of toroidal rotation and CEIs are derived by first considering the rigid equilibrium condition. The unperturbed distribution function of CEIs depends on the poloidal angle, eventually influencing the frequencies significantly. The co-CEIs and counter-CEIs do not cancel each other in the balanced tangential neutral beam injection (NBI) case and show destabilizing effect on the zonal flows. The accurate mode frequency and the growth rate are presented.
Measurement of vertebral rotation in adolescent idiopathic scoliosis with low-dose CT in prone position - method description and reliability analysis
Kasim Abul-Kasim, Magnus K Karlsson, Ralph Hasserius, Acke Ohlin
Scoliosis , 2010, DOI: 10.1186/1748-7161-5-4
Abstract: To describe and test the reliability of this new method, compare it with other methods in use and evaluate the influence of body position on the degree of vertebral rotation measured by different radiological methods.Retrospective study.25 consecutive patients with adolescent idiopathic scoliosis scheduled for surgery (17 girls, 8 boys) aged 15 ± 2 years (mean ± SD) were included in the analysis of this study. The degree of the vertebral rotation was in all patients measured according to the method of Perdriolle on standing plain radiographs and on supine CT scanogram, and according to the method of Aaro and Dahlborn on axial CT images in prone position and on magnetic resonance imaging (MRI) in supine position. The measurements were done by one neuroradiologist at two different occasions. Bland and Altman statistical approach was used in the reliability assessment.The reliability of measuring vertebral rotation by axial CT images in prone position was almost perfect with an intraclass correlation coefficient of 0.95, a random error of the intraobserver differences of 2.3°, a repeatability coefficient of 3.2° and a coefficient of variation of 18.4%. Corresponding values for measurements on CT scanogram were 0.83, 5.1°, 7.2°, and 32.8%, respectively, indicating lower reliability of the latter modality and method. The degree of vertebral rotation measured on standing plain radiographs, prone CT scanogram, axial images on CT in prone position and on MRI in supine position were 25.7 ± 9.8°, 21.9 ± 8.3°, 17.4 ± 7.1°, and 16.1 ± 6.5°, respectively. The vertebral rotation measured on axial CT images in prone position was in average 7.5% larger than that measured on axial MRI in supine position.This study has shown that measurements of vertebral rotation in prone position were more reliable on axial CT images than on CT scanogram. The measurement of vertebral rotation on CT (corrected to the pelvic tilt) in prone position imposes lower impact of the recumbent position on th
Main magnetic focus ion source with the radial extraction of ions  [PDF]
V. P. Ovsyannikov,A. V. Nefiodov
Physics , 2015, DOI: 10.1016/j.nimb.2015.11.015
Abstract: In the main magnetic focus ion source, atomic ions are produced in the local ion trap created by the rippled electron beam in focusing magnetic field. Here we present the novel modification of the room-temperature hand-size device, which allows the extraction of ions in the radial direction perpendicular to the electron beam across the magnetic field. The detected X-ray emission evidences the production of Ir$^{44+}$ and Ar$^{16+}$ ions. The ion source can operate as the ion trap for X-ray spectroscopy, as the ion source for the production of highly charged ions and also as the ion source of high brightness.
Differential rotation of main-sequence dwarfs: predicting the dependence on surface temperature and rotation rate  [PDF]
L. L. Kitchatinov,S. V. Olemskoy
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.21126.x
Abstract: Gyrochronology and recent theoretical findings are used to reduce the number of input parameters of differential rotation models. This eventually leads to a theoretical prediction for the surface differential rotation as a function of only two stellar parameters - surface temperature and rotation period - that can be defined observationally. An analytical approximation for this function is suggested. The tendency for the differential rotation to increase with temperature is confirmed. The increase is much steeper for late F-stars compared to G- and K-dwarfs. Slow and fast rotation regimes for internal stellar rotation are identified. A star attains its maximum differential rotation at rotation rates intermediate between these two regimes. The amplitude of the meridional flow increases with surface temperature and rotation rate. The structure of the flow changes considerably between cases of slow and fast rotation. The flow in rapid rotators is concentrated in the boundary layers near the top and bottom of the convection zone with very weak circulation in between.
Differential rotation of main-sequence dwarfs and its dynamo-efficiency  [PDF]
L. L. Kitchatinov,S. V. Olemskoy
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17737.x
Abstract: A new version of a numerical model of stellar differential rotation based on mean-field hydrodynamics is presented and tested by computing the differential rotation of the Sun. The model is then applied to four individual stars including two moderate and two fast rotators to reproduce their observed differential rotation quite closely. A series of models for rapidly rotating ($P_{rot} = 1$ day) stars of different masses and compositions is generated. The effective temperature is found convenient to parameterize the differential rotation: variations with metallicity, that are quite pronounced when the differential rotation is considered as a function of the stellar mass, almost disappear in the dependence of differential rotation on temperature. The differential rotation increases steadily with surface temperature to exceed the largest differential rotation observed to date for the hottest F-stars we considered. This strong differential rotation is, however, found not to be efficient for dynamos when the efficiency is estimated with the standard $C_\Omega$-parameter of dynamo models. On the contrary, the small differential rotation of M-stars is the most dynamo-efficient. The meridional flow near the bottom of the convection zone is not small compared to the flow at the top in all our computations. The flow is distributed over the entire convection zone in slow rotators but retreats to the convection zone boundaries with increasing rotation rate, to consist of two near-boundary jets in rapid rotators. The implications of the change of the flow structure for stellar dynamos are briefly discussed.
Vertebral rotation measurement: a summary and comparison of common radiographic and CT methods
Gabrielle C Lam, Doug L Hill, Lawrence H Le, Jim V Raso, Edmond H Lou
Scoliosis , 2008, DOI: 10.1186/1748-7161-3-16
Abstract: Adolescent Idiopathic Scoliosis (AIS) is a lateral and rotational deformity of the spine, predominantly affecting individuals of age 10 to 17. The progression of AIS occurs during the rapid growth stage due to factors still unknown. Traditionally, measurement of Cobb angles was the primary means of quantifying the severity of AIS in scoliotic patients. However, this method is limited to assessment of the spine in the saggital and coronal planes. More current investigation of vertebral rotation in the axial plane has provided better understanding of AIS as a three-dimensional condition.Recent studies suggest that the coupling relation between vertebral rotation and lateral motion may provide insight into an indicative characteristic of scoliotic spines [1-4]. Other literature has examined rotation of the vertebral column in connection to the etiology of AIS [5,6], as discussed in the Spine-Rib Hypothesis [7] and in evaluating the Neurocentral Junction Hypothesis [8]. Above all, measurement of vertebral rotation is of key significance in the prognosis and treatment of scoliotic curves [9-11]. It may act as an indicator of curve progression, thus being clinically applicable for both preoperative and postoperative assessment [9,12]. The association of vertebral rotation with rib hump has led to techniques that may be applied to school screening programs [13,14]. Furthermore, vertebral rotation measurement is becoming prominent in assisting pre-surgical planning. Inaccurate knowledge of vertebral rotation may lead to unnecessary surgical operations and, in the case of pedicle screws, misplacements that incur risks of spinal cord injury [15]. At the same time, axial rotation has been equally valuable in better understanding the effect of brace treatment or surgical interventions, as evidenced in the studies evaluating Cotrel-Dubousset [16-19] and Harrington instrumentation [20,21].While numerous methods have been developed to measure axial rotation, the techniques explore
The Rotation of Low-Mass Pre-Main-Sequence Stars  [PDF]
Robert D. Mathieu
Physics , 2003,
Abstract: Major photometric monitoring campaigns of star-forming regions in the past decade have provided rich rotation period distributions of pre-main-sequence stars. The rotation periods span more than an order of magnitude in period, with most falling between 1 and 10 days. Thus the broad rotation period distributions found in 100 Myr clusters are already established by an age of 1 Myr. The most rapidly rotating stars are within a factor of 2-3 of their critical velocities; if angular momentum is conserved as they evolve to the ZAMS, these stars may come to exceed their critical velocities. Extensive efforts have been made to find connections between stellar rotation and the presence of protostellar disks; at best only a weak correlation has been found in the largest samples. Magnetic disk-locking is a theoretically attractive mechanism for angular momentum evolution of young stars, but the links between theoretical predictions and observational evidence remain ambiguous. Detailed observational and theoretical studies of the magnetospheric environments will provide better insight into the processes of pre-main-sequence stellar angular momentum evolution.
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