Effects of Steady Flow on Magnetoacoustic-Gravity Surface Waves: I. The Weak Field Case

Magnetoacoustic gravity (MAG) waves have been studied for some time. In this article, we investigate the effect that a shear flow at a tangential discontinuity embedded in a gravitationally stratified and magnetised plasma has on MAG surface waves. The dispersion relation found is algebraically analogous to the relation of the non-flow cases obtained by Miles and Roberts (Solar Phys.141, 205, 1992), except for the introduction of a Doppler-shifted frequency for the eigenvalue. This feature, however, introduces rather interesting physics, including the asymmetric presence of forward- and backward-propagating surface waves. We find that increasing the equilibrium flow speed leads to a shift in the permitted regions of propagation for surface waves. For most wave number combinations this leads to the fast mode being completely removed, as well as more limited phase speed regimes for slow-mode propagation. We also find that upon increasing the flow, the phase speeds of the backward propagating waves are increased. Eventually, at high enough flow speeds, the wave’s direction of propagation is reversed and is in the positive direction. However, the phase speed of the forward-propagating wave remains mainly the same. For strong enough flows we find that the Kelvin–Helmholtz instability can also occur when the forward- and backward-propagating modes couple

Systematic assessment of the growth plates of the wrist in young gymnasts: Development and validation of the Amsterdam MRI assessment of the Physis (AMPHYS) protocol

Objectives To develop and validate a protocol for MRI assessment of the distal radial and ulnar periphyseal area in gymnasts and non-gymnasts. Methods Twenty-four gymnasts with wrist pain, 18 asymptomatic gymnasts and 24 non-gymnastic controls (33 girls) underwent MRI of the wrist on a 3T scanner. Sequences included coronal proton density-weighted images with and without fat saturation, and three-dimensional water-selective cartilage scan and T2 Dixon series. Skeletal age was determined using hand radiographs. Three experienced musculoskeletal radiologists established a checklist of possible (peri)physeal abnormalities based on literature an

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Prospective assessment of interobserver agreement for defecography in fecal incontinence

OBJECTIVE. The primary aim of our study was to determine the interobserver agreement of defecography in diagnosing enterocele, anterior rectocele, intussusception, and anismus in fecal-incontinent patients. The subsidiary aim was to evaluate the influence of level of experience on interpreting defecography. SUBJECTS AND METHODS. Defecography was performed in 105 consecutive fecalincontinent patients. Observers were classified by level of experience and their findings were compared with the findings of an expert radiologist. The quality of the expert radiologist's findings was evaluated by an intraobserver agreement procedure. RESULTS. Intraobserver agreement was good to very good except for anismus: incomplete evacuation after 30 sec (K, 0.55) and puborectalis impression (K, 0.54). Interobserver agreement for enterocele and rectocele was good (K, 0.66 for both) and for intussusception, fair (K, 0.29). Interobserver agreement for anismus: incomplete evacuation after 30 sec was moderate (K, 0.47), and for anismus: puborectalis impression was fair (K, 0.24). Agreement in grading of enterocele and rectocele was good (K, 0.64 and 0.72, respectively) and for intussusception, fair (K, 0.39). Agreement separated by experience level was very good for rectocele (K, 0.83) and grading of rectoceles (K, 0.83) and moderate for intussusception (K, 0.44) at the most experienced level. For enterocele and grading, experience level did not influence the reproducibility. CONCLUSION. Reproducibility for enterocele, anterior rectocele, and severity grading is good, but for intussusception is fair to moderate. For anismus, the diagnosis of incomplete evacuation after 30 sec is more reproducible than puborectalis impression. The level of experience seems to play a role in diagnosing anterior rectocele and its grading and in diagnosing intussusceptio

Selecting an outcome measure for evaluating treatment in fecal incontinence

PURPOSE: Various outcome measures exist to evaluate treatment in fecal incontinence, including descriptive, severity (fecal incontinence scoring systems), and impact (quality-of-life questionnaires) and diagnostic measures. We studied associations between changes after treatment for a number of outcome measures and compared them to patients' subjective perception of relief. METHODS: We analyzed data of 66 patients (92 percent female; mean age, 62 years) (Vaizey score, Wexner score, two impact scales, utility, resting pressure, and maximal incremental squeeze pressure) at baseline and after physiotherapy. In a standardized interview by phone, we asked patients to compare their situation before and after treatment. Correlations between changes in outcome measures were calculated. These changes were compared with patients' subjective perception. RESULTS: There was a high correlation between the changes in the Vaizey and the Wexner scores (r = 0.94, P <0.01). Changes in Vaizey and Wexner scores correlated moderately with changes in maximum incremental squeeze pressure (r = -0.29, -0-30, both P <0.05). Changes in utility and resting pressure were not correlated with changes in any of the other measurements (all r values between -0.086 and 0. 18). Average severity scores (Vaizey and Wexner) were I point lower for patients who rated their situation as worse or equal (62 percent), 4 points lower for patients who reported their situation to be better (21 percent), and 9 points lower in patients who rated their situation much better (17 percent) (P <.05). CONCLUSION: Severity measures are best related to patients' subjective perception of relie