Vertical Instability Research Articles

Instabilities and vertical mixing in river plumes: application to the Bay of Biscay

In the Bay of Biscay (north-east Atlantic), long-living eddies and the frontal activity that they induce substantially contribute to mesoscale and submesoscale dynamics. Tides and river plumes also contribute to frontal activity. Biological productivity is sensitive to river plume fronts and to external forcings (tides and wind). Considering the importance of river plumes, we study here the structure, stability and vertical mixing processes in such river plumes (similar to those generated by the Gironde river). Restratification budget is considered here for evaluating stirring (frontogenetic/frontolytic) or vertical mixing (parametrised here from Ertel potential vorticity mixing) processes. Using high-resolution idealised numerical simulations, we analyse the evolution of the bulge and of the coastal part of this plume and we conduct sensitivity experiments to the river discharge, to southwesterly winds and to M2 tides. The bulge and the coastal current are stable (unstable) in case of moderate (high) river discharge, due to mixed barotropic/baroclinic instabilities. In the unstable case, near surface symmetric and vertical shear instabilities develop in the coastal current and in the core of the bulge where the Rossby number is large. When southwesterly winds blow, the river plume is squeezed near the coast by Ekman transport. The river plume is then subject to frontal symmetric, baroclinic, barotropic and vertical shear instabilities in the coastal part, north of the estuary (its far field). Conversely, in the presence of M2 tides, the river plume is barotropically, baroclinically and symmetrically unstable in its near field. Interior vertical mixing is induced by advective (stirring) and frontogenetic processes. Frontogenesis is dominant in the far-field (in the presence of southwesterlies) or in the near-field (when M2 tide is active). Frontogenesis is important in the far-field region in unforced river plumes (both with moderate and high river discharges). Potential vorticity is eroded in the far-field when southwesterlies blow. This is primarily due to the frictional processes which are dominant at the surface. This study has identified the instabilities which affect a river plume in different cases, and the local turbulent processes which alter the stratification.

The Interaction between Moist Convection and the Atmospheric Circulation in the Tropics

AbstractTheories of the interaction between moist convection and the atmospheric circulation in the tropics are reviewed. Two main schools of thought are highlighted: (i) one that emphasizes the lower-level control of convection through moisture convergence and variations in convective inhibition, and (ii) one that sees convection as an adjustment process in reaction to larger-scale instabilities, referred to as convective quasi-equilibrium theory. Conceptually the two views consider moist convection to have fundamentally different roles in the tropical circulation. In one case the presence of low-level inhibition and the conditional nature of the atmospheric instability allows for convective vertical motion and latent heating to drive and reinforce synoptic-scale disturbances and overturning circulations; in the other case, because low-level inhibition is not acknowledged to be a widespread controlling barrier, convection is believed to balance and dampen vertical instabilities at the rate they are created by larger-scale processes over the vertical extent of the atmosphere. More recently, investigations of the moisture dynamics surrounding organized convective structures have led to an emerging consensus on the theory of convection–circulation coupling in the tropics that acknowledges the important role of lower- to midtropospheric moisture variations, and the significance of moist convection and convective clouds for initiating and establishing circulations. However, the implementation of these new insights in numerical models lags behind. This is exemplified by the apparent inadequacy of climate models to correctly represent decadal variability in the tropical Pacific, a fact that potentially has implications for the confidence in climate change projections based on such models.

Gas and Dust Dynamics in Starlight-heated Protoplanetary Disks

Abstract Theoretical models of the ionization state in protoplanetary disks suggest the existence of large areas with low ionization and weak coupling between the gas and magnetic fields. In this regime hydrodynamical instabilities may become important. In this work we investigate the gas and dust structure and dynamics for a typical T Tauri system under the influence of the vertical shear instability (VSI). We use global 3D radiation hydrodynamics simulations covering all 360° of azimuth with embedded particles of 0.1 and 1 mm size, evolved for 400 orbits. Stellar irradiation heating is included with opacities for 0.1–10 μm sized dust. Saturated VSI turbulence produces a stress-to-pressure ratio of . The value of α is lowest within 30 au of the star, where thermal relaxation is slower relative to the orbital period and approaches the rate below which VSI is cut off. The rise in α from 20 to 30 au causes a dip in the surface density near 35 au, leading to Rossby wave instability and the generation of a stationary, long-lived vortex spanning about 4 au in radius and 40 au in azimuth. Our results confirm previous findings that millimeter-sized grains are strongly vertically mixed by the VSI. The scale height aspect ratio for 1 mm grains is determined to be 0.037, much higher than the value H/r = 0.007 obtained from millimeter-wave observations of the HL Tau system. The measured aspect ratio is better fit by nonideal MHD models. In our VSI turbulence model, the millimeter grains drift radially inwards and many are trapped and concentrated inside the vortex. The turbulence induces a velocity dispersion of ∼12 m s−1 for the millimeter grains, indicating that grain–grain collisions could lead to fragmentation.

TSC simulation of vertical position control by the Bang-bang method on EAST

Vertical instability is a potentially serious hazard for elongated plasma. Many methods have been proposed to control the plasma vertical position. The Bang-bang method, which is designed for the inside coil (IC) voltage mode based on optimal control theory and the RZIp rigid plasma response model, has been successfully used for plasma vertical position control in the EAST 2014 experimental campaign (Wang et al 2016 Fusion Eng. Des. 112 692–8). The Tokamak Simulation Code (TSC) is a numerical model of tokamak plasma and the associated control systems. It studies the evolution of the magnetic field in a rectangular computational domain using the Maxwell magnetohydrodynamic equations for plasma coupled with the boundary conditions to the circuit equations for the poloidal field coils. In this paper, the numerical model of the Bang-bang method has been implemented in the TSC code, which is used to simulate shot 52444. Simulated trajectories of the vertical position, IC voltage, and current fit the experimental data well. On the basis of benchmarked calculation, a numerical investigation of the Bang-bang controller has been performed using the TSC. This controller was able to work with 8 mm random noise and dz = 41.8 mm displacement. As a predictive tool, the TSC code is used to investigate the the maximum controllable vertical displacement value for different maximum current, and evaluate the ability to control the vertical position by the Bang-bang method.

On a Flood-Producing Coastal Mesoscale Convective Storm Associated with the Kor’easterlies: Multi-Data Analyses Using Remotely-Sensed and In-Situ Observations and Storm-Scale Model Simulations

A flood-producing heavy rainfall event occurred at the mountainous coastal region in the northeast of South Korea on 5–6 August 2018, subsequent to extreme heat waves, through a quasi-stationary mesoscale convective system (MCS). We analyzed the storm environment via a multi-data approach using high-resolution (1-km) simulations from the Weather Research and Forecasting (WRF) and in situ/satellite/radar observations. The brightness temperature, from the Advanced Himawari Imager water vapor band, and the composite radar reflectivity were used to identify characteristics of the MCS and associated precipitations. The following factors affected this back-building MCS: low-level convergence by the Korea easterlies (Kor’easterlies), carrying moist air into the coast; strong vertical wind shear, making the updraft tilted and sustained; coastal fronts and back-building convection bands, formed through interactions among the Kor’easterlies, cold pool outflows, and orography; mid-level advection of cold air and positive relative vorticity, enhancing vertical convection and potential instability; and vigorous updraft releasing potential instability. The pre-storm synoptic environment provided favorable conditions for storm development such as high moisture and temperature over the coastal area and adjacent sea, and enhancement of the Kor’easterlies by expansion of a surface high pressure system. Upper-level north-northwesterly winds prompted the MCS to propagate south-southeastward along the coastline.

Tests of the real-time vertical growth rate calculation on EAST**Project supported by the National MCF Energy Research and Development Program of China (Grant No. 2018YFE0302100) and the National Natural Science Foundation of China (Grant Nos. 11705239, 11805236, and 11875291).

In order to measure controllability of vertical instability in EAST, the calculation of model-based vertical growth rate, called rt-gamma, has been successfully carried out in real time. The numerical computing method is adapted from rigid plasma response model in TokSys, which is a widely-used analysis tool for tokamak devices in Matlab environment, but the code is rewritten by taking advantage of GPU parallel computing capability to accelerate the computation. The calculation of rt-gamma is validated by comparing it with the corresponding result generated by TokSys for totally 3508 cases. It is shown that the average absolute value of relative errors is about 0.85%. In addition, the calculation program of rt-gamma has been successfully applied during 2019 EAST campaign. The comparison with experimental results is discussed in this paper. The real-time calculation tool is well able to calculate model-based vertical growth rate, which is convenient for fast and continuous evaluations of EAST control system stability performances.

The coexistence of the streaming instability and the vertical shear instability in protoplanetary disks

The streaming instability is a leading candidate mechanism to explain the formation of planetesimals. However, the role of this instability in the driving of turbulence in protoplanetary disks, given its fundamental nature as a linear hydrodynamical instability, has so far not been investigated in detail. We study the turbulence that is induced by the streaming instability as well as its interaction with the vertical shear instability. For this purpose, we employ the FLASH Code to conduct two-dimensional axisymmetric global disk simulations spanning radii from 1 to 100 au, including the mutual drag between gas and dust as well as the radial and vertical stellar gravity. If the streaming instability and the vertical shear instability start their growth at the same time, we find the turbulence in the dust midplane layer to be primarily driven by the streaming instability. The streaming instability gives rise to vertical gas motions with a Mach number of up to ~10−2. The dust scale height is set in a self-regulatory manner to about 1% of the gas scale height. In contrast, if the vertical shear instability is allowed to saturate before the dust is introduced into our simulations, then it continues to be the main source of the turbulence in the dust layer. The vertical shear instability induces turbulence with a Mach number of ~10−1 and thus impedes dust sedimentation. Nonetheless, we find the vertical shear instability and the streaming instability in combination to lead to radial dust concentration in long-lived accumulations that are significantly denser than those formed by the streaming instability alone. Therefore, the vertical shear instability may promote planetesimal formation by creating weak overdensities that act as seeds for the streaming instability.

A Real-Time Disruption Prediction Tool for VDE on EAST

Vertical displacement event (VDE) is one of the most important events related to disruptions. A real-time disruption prediction tool for VDE is presented in this article. Vertical growth rate is an essential parameter to describe vertical instability, which can be obtained based on the rigid plasma response model. A real-time vertical growth rate calculation system is built, which utilizes graphics process unit (GPU) parallel computation and reflective memory (RFM) boards communication with plasma control system (PCS). Based on real-time vertical growth rate calculation system, an alarm algorithm for detecting vertical instability is integrated into experimental advanced superconducting tokamak (EAST) PCS. It is designed to provide the capabilities of a switching control method and to trigger a warning signal in PCS when uncontrollable vertical instability is detected. Such a disruption prediction tool has been preliminarily applied in the 2019 EAST spring experiment.

Global Simulations of the Vertical Shear Instability with Nonideal Magnetohydrodynamic Effects

Abstract The mechanisms of angular momentum transport and the level of turbulence in protoplanetary disks (PPDs) are crucial for understanding many aspects of planet formation. In recent years, it has been realized that the magneto-rotational instability tends to be suppressed in PPDs due to nonideal magnetohydrodynamic (MHD) effects, and the disk is primarily laminar with accretion driven by magnetized disk winds. In parallel, several hydrodynamic mechanisms have been identified that likely also generate vigorous turbulence and drive disk accretion. In this work, we study the interplay between MHD winds in PPDs with the vertical shear instability (VSI), one of the most promising hydrodynamic mechanisms, through 2D global nonideal MHD simulations with ambipolar diffusion (AD) and ohmic resistivity. For typical disk parameters, MHD winds can coexist with the VSI with accretion primarily wind-driven accompanied by vigorous VSI turbulence. The properties of the VSI remain similar to the unmagnetized case. The wind and overall field configuration are not strongly affected by the VSI turbulence, showing a modest level of variability and corrugation of the midplane current sheet. Weak AD strength or the enhanced coupling between gas and magnetic fields weakens the VSI. The VSI is also weakened with increasing magnetization, and characteristic VSI corrugation modes transition to low-amplitude breathing mode oscillations with strong magnetic fields.

Horizontal shear instabilities in rotating stellar radiation zones

Context. Rotational mixing transports angular momentum and chemical elements in stellar radiative zones. It is one of the key processes for modern stellar evolution. In the past two decades, an emphasis has been placed on the turbulent transport induced by the vertical shear instability. However, instabilities arising from horizontal shear and the strength of the anisotropic turbulent transport that they may trigger remain relatively unexplored. The weakest point of this hydrodynamical theory of rotational mixing is the assumption that anisotropic turbulent transport is stronger in horizontal directions than in the vertical one. Aims. This paper investigates the combined effects of stable stratification, rotation, and thermal diffusion on the horizontal shear instabilities that are obtained and discussed in the context of stellar radiative zones. Methods. The eigenvalue problem describing linear instabilities of a flow with a hyperbolic-tangent horizontal shear profile was solved numerically for a wide range of parameters. When possible, the Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) approximation was applied to provide analytical asymptotic dispersion relations in both the nondiffusive and highly diffusive limits. As a first step, we consider a polar f-plane where the gravity and rotation vector are aligned. Results. Two types of instabilities are identified: the inflectional and inertial instabilities. The inflectional instability that arises from the inflection point (i.e., the zero second derivative of the shear flow) is the most unstable when at a zero vertical wavenumber and a finite wavenumber in the streamwise direction along the imposed-flow direction. While the maximum two-dimensional growth rate is independent of the stratification, rotation rate, and thermal diffusivity, the three-dimensional inflectional instability is destabilized by stable stratification, while it is stabilized by thermal diffusion. The inertial instability is rotationally driven, and a WKBJ analysis reveals that its growth rate reaches the maximum value of √f(1 − f) in the inviscid limit as the vertical wavenumber goes to infinity, where f is the dimensionless Coriolis parameter. The inertial instability for a finite vertical wavenumber is stabilized as the stratification increases, whereas it is destabilized by the thermal diffusion. Furthermore, we found a selfsimilarity in both the inflectional and inertial instabilities based on the rescaled parameter PeN2 with the Péclet number Pe and the Brunt–Väisälä frequency N.

The true axial shoulder projection: Diagnostic aid for acromioclavicular joint dislocation?

Acromioclavicular joint dislocations are common. Differentiating between horizontal and vertical instability is challenging, but possible to diagnose on axial radiographs. No clear consensus for axial radiograph parameters currently exists. We aim to establish a reproducible technique to assess whether an axial radiograph represents a true axial view of the shoulder. One hundred CT scans of normal uninjured shoulders were examined using multiplanar reformatting to assess the distance between the anterior glenoid (reference line) and anterior-most aspect of the acromion in the axial plane. Measurements were repeated and performed by multiple observers to give of intra- and inter-observer reliability. The mean distance from the anterior acromion to the reference line was -2.6 mm (i.e. posteriorly placed) (SD = 5.8 mm, range -16.9-13.2 mm). Most (89%) of the measurements were between 9 and -9 mm to the reference line. Intra-observer reliability was high with Cronbach's α measurement as 0.997. Inter-observer reliability gave a Cronbach's α measurement of 0.959. When the anterior aspect of the acromion lies within 10 mm either side of a line parallel to the scapula blade at the anterior aspect of the glenoid on an axial radiograph, it represents a true axial projection of the glenohumeral joint (GHJ).Level of evidence: IV, Case series.

Self-Acceleration and Instability of Gravity Wave Packets: 3. Three-Dimensional Packet Propagation, Secondary Gravity Waves, Momentum Transport, and Transient Mean Forcing in Tidal Winds.

Dong et al. (2020, https://doi.org/10.1029/2019JD030691) employed a new compressible model to examine gravity wave (GW) self‐acceleration dynamics, instabilities, secondary gravity wave (SGW) generation, and mean forcing for GW packets localized in two dimensions (2D). This paper extends the exploration of self‐acceleration dynamics to a GW packet localized in three dimensions (3D) propagating into tidal winds in the mesosphere and thermosphere. As in the 2D packet responses, 3D GW self‐acceleration dynamics are found to be significant and include 3D GW phase distortions, stalled GW vertical propagation, local instabilities, and SGW and acoustic wave generation. Additional 3D responses described here include refraction by tidal winds, localized 3D instabilities, asymmetric SGW propagation, reduced SGW and acoustic wave responses at higher altitudes relative to 2D responses, and forcing of transient, large‐scale, 3D mean responses that may have implications for chemical and microphysical processes operating on longer time scales.

Lumbar vacuum disc, vertical instability, standalone endoscopic interbody fusion, and other treatments: an opinion based survey among minimally invasive spinal surgeons.

A diseased lumbar intervertebral vacuum disc void of any structurally intact tissue may be vertically unstable. A primary standalone endoscopic decompression and interbody fusion surgery in the treatment of vertical instability in patients with a vacuum disc may be a more reliable treatment than decompression alone. The authors solicited responses to an online survey sent to spine surgeons by email, and chat groups on social media networks, including Facebook, WeChat, WhatsApp, and Linkedin. Descriptive and correlative statistics were employed to count the responses and compare the surgeon's responses recorded on a Likert scale from 1 (disagree) to 10 (agree) or in multiple-choice questions. Surgeons were asked about their familiarity with the concept of vacuum disc and vertical instability and how they would treat such patients. Kappa statistics and linear regression analysis of agreement of incoming responses were performed. A total of 1,165 surgeons accessed the survey. The completion rate was 22.78. The majority surgeons were very familiar with the concept of a "vacuum disc" as a sign of end-stage lumbar degenerative disc disease and a collapsing lumbar motion segment (182/273; 66.7%; Likert score 6.53). The majority of surgeons also thought that vertical instability precedes anterolateral lumbar instability (187/273; 68.5%; Likert score 6.64) and that a vacuum disc may cause vertical instability with symptomatic dynamic foraminal & lateral recess stenosis (222/273; 81%; Likert score 7.48), mechanical back pain (201/273; 73.1%; Likert score 7.48), and may cause sciatica-type low back and leg pain (179/273; 66.3%; Likert score 6.59). The majority of surgeons indicated that vacuum phenomenon on radiographic studies is associated with vertical instability and collapse resulting in dynamic foraminal and lateral recess stenosis and should be treated surgically (199/266; 73.7%; 7 missing responses; Likert score 6.86). Preferred treatments were decompression alone without fusion (P<0.014). There was consensus in support of fusion by TLIF or PLIF with a Likert score of 6.68 (184/266; 69.2%; 7 missing responses). There was no consensus on standalone fusion. Vacuum phenomenon on radiographic studies is associated with a vertical instability and collapse, resulting in dynamic foraminal and lateral recess stenosis that should be treated surgically. Preferred surgical treatments were decompression alone, decompression with interbody fusion using just bone graft, and fusion employing TLIF or PLIF. Further research into the clinical significance of lumbar vacuum disc, vertical instability and its most appropriate surgical treatments if any is necessary.

Violent buckling benefits galactic bars

ABSTRACT Galactic bars are unstable to a vertical buckling instability which heats the disc and in some cases forms a boxy/peanut shaped bulge. We analyse the buckling instability as an application of classical Euler buckling followed by non-linear gravitational Landau damping in the collisionless system. We find that the buckling instability is dictated by the kinematic properties and geometry of the bar. The analytical result is compared to simulations of isolated galaxies containing the disc and dark matter components. Our results demonstrate that violent buckling does not destroy bars while a less energetic buckling can dissolve the bar. The discs that undergo gentle buckling remain stable to bar formation which may explain the observed bar fraction in the local Universe. Our results align with the results from recent surveys.

Optimization design for plasma configuration at the CFETR

Equilibrium is essential in the design of the Chinese Fusion Engineering Test Reactor (CFETR). It is based on the principle underlying various physical and engineering issues, such as vertical instability, core plasma physics, divertor physics and design, etc. Built on the 0-D parameters with elongation κ∼2.0 using the equilibrium code TEQ, series of equilibria with different lower triangularity (range of 0.3–0.8) were constructed. Through iterations with the divertor and blanket structures, we optimized the plasma shape, including, in particular, the position of the X-point, hence obtaining the first acceptable single-null plasma with δ = 0.418. This optimal ITER-like equilibrium has in turn served as the starting point for various other design works. Besides the standard divertor configuration, the quasi-snowflake-plus (QSF+) divertor configurations with different total plasma currents have also been produced, which aimed at controlling excessive heat flux load on the divertor target. The results indicate that the poloidal field (PF) coil system has the capacity to sustain the shape of the QSF+; however, the PF coil system will continue to be optimized with particular attention of the divertor coil.

Systematic errors in the WRF model planetary boundary layer schemes for two contrasting monsoon seasons over the state of Odisha and its neighborhood region

This study evaluates the characteristics of systematic errors (up to day 4) in the planetary boundary layer (PBL) parameterization schemes over the state of Odisha and its neighboring regions for two contrasting monsoon seasons, i.e., 2013 (normal) and 2014 (deficit), using the Weather Research and Forecasting (WRF) model. A total of 1112 numerical experiments are carried out, each with initial conditions from May 28 to September 29 using four PBL schemes, i.e., Yonsei University (YSU), Mellor-Yamada-Nakanishi-Niino (MYNN), Asymmetric Convective Model version 2 (ACM2), and Medium Range Forecast (MRF) with horizontal resolutions of 27 and 9 km with a lead time up to 96 h. It is found that the PBL parameterizations significantly impact the basic atmospheric variables (i.e., wind, temperature, moisture, and rainfall) and associated convective processes such as moist static energy. The wind and rainfall forecast skill of MRF showed better agreement with European Re-Analysis (ERAI). However, YSU has better skills for 2-m temperature and specific humidity compared to others. All PBL schemes produced a moist bias at the surface except MRF. The principle cause of this moist bias with mid tropospheric warming is attributed to inherent tendency of the model to overestimate moist static energy leading to intense vertical motion and convective instability. The magnitude of errors for wind forecast is higher for the deficit year compared to the normal monsoon year. However, the strength of the cross equatorial flow is found to be weaker in all the experiments for both the seasons. In general, the spread and magnitude of errors are large for 2013 (normal) as compared to 2014 (deficit) year.

Revealing the cosmic evolution of boxy/peanut-shaped bulges from HST COSMOS and SDSS

ABSTRACT Vertically thickened bars, observed in the form of boxy/peanut (B/P) bulges, are found in the majority of massive barred disc galaxies in the local Universe, including our own. B/P bulges indicate that their host bars have suffered violent bending instabilities driven by anisotropic velocity distributions. We investigate for the first time how the frequency of B/P bulges in barred galaxies evolves from z = 1 to z ≈ 0, using a large sample of non-edge-on galaxies with masses M⋆ &gt; 1010 M⊙, selected from the HST COSMOS survey. We find the observed fraction increases from $0^{+3.6}_{-0.0}{{\ \rm per\ cent}}$ at z = 1 to $37.8^{+5.4}_{-5.1}$ per cent at z = 0.2. We account for problems identifying B/P bulges in galaxies with low inclinations and unfavourable bar orientations, and due to redshift-dependent observational biases with the help of a sample from the Sloan Digital Sky Survey, matched in resolution, rest-frame band, signal-to-noise ratio and stellar mass and analysed in the same fashion. From this, we estimate that the true fraction of barred galaxies with B/P bulges increases from ∼10 per cent at z ≈ 1 to $\sim 70{{\ \rm per\ cent}}$ at z = 0. In agreement with previous results for nearby galaxies, we find a strong dependence of the presence of a B/P bulge on galaxy stellar mass. This trend is observed in both local and high-redshift galaxies, indicating that it is an important indicator of vertical instabilities across a large fraction of the age of the Universe. We propose that galaxy formation processes regulate the thickness of galaxy discs, which in turn affect which galaxies experience violent bending instabilities of the bar.

Clavicle Elevation or Shoulder Girdle Depression in Acromioclavicular Joint Dislocation: A Radiological Investigation.

Background:The side-comparative coracoclavicular (CC) distance is used to describe the vertical instability component of acute acromioclavicular (AC) joint dislocations. Elevation of the clavicle or a depression of the shoulder girdle can lead to an increased CC distance. The dislocation direction has not yet been investigated and is not included in common classification systems.Hypothesis:Clavicle elevation is primarily responsible for vertical dislocation in AC joint separation.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Weighted and nonweighted bilateral plain anteroposterior views of the shoulder girdles of patients with AC joint dislocations (Rockwood [RW] types III and V), diagnosed in our trauma department between 2001 and 2018, were included in this study. After determining the CC distance, a side-comparative determination of the positions of both the clavicle and shoulder girdle, with reference to the spinal column, was conducted.Results:In total, 245 bilateral plain anteroposterior views were evaluated (RW III, n = 116; RW V, n = 129). All patients showed a side-comparative clavicle elevation (mean ± SD: RW III, 5 ± 14 mm; RW V, 11 ± 17 mm) in weighted and nonweighted views. While no depression of the shoulder girdle was measured in RW III injuries (weighted and nonweighted views, 0 ± 11 mm), dropping of the shoulder girdle in RW V lesions on nonweighted views was observed (–5 ± 11 mm).Conclusion:Vertical dislocation is mostly associated with clavicle elevation in RW III injures, while in high-grade AC joint dislocations (RW V), a combination of clavicle elevation and shoulder girdle depression is present. A significantly greater superior displacement of the clavicle in RW V injuries was seen in weighted views, while a depression of the shoulder girdle could be detected in nonweighted views. For the first time, these results include the dislocation direction in the classification of an AC joint injury. Further studies are needed to investigate the extent to which dislocation types differ in optimal therapy and outcome.

Simulation of disruptions triggered by Vertical Displacement Events (VDE) in tokamak and leading edge effect in plasma energy deposition to material surfaces

The paper describes two major non-linear properties of the vertical instability of a tokamak plasma, which has a vertical elongation: (a) inductive excitation of surface (edge) currents stabilizing the instability and converting it into fast equilibrium evolution, and (b) creation of a wetting zone without the normal component of the magnetic field when the plasma has contact with material surfaces. Two major disruption effects for both mitigated and non-mitigated disruptions, important for JET and ITER, were considered: (a) excitation of vertical disruption during the current quench (i.e., abnormal plasma current ramp down) and (b) related to the wetting zone, potential leading edge effect in plasma energy deposition to the in-vessel tiles during disruptions. Our considerations together with a 2-D version of the VDE (Vertical Disruption Event) code are based on a new mathematical model, called Tokamak MHD (TMHD), as a replacement for the conventional model, a model that cannot solve numerical problems related to extreme plasma anisotropy and negligible mass. The code includes a 3-D model of surface currents on a thin conductive wall and has a well-specified algorithm for extension to vertical disruptions that excite asymmetric kink modes.

Minimally Invasive AC Joint Reconstruction System (MINAR®) in Modified Triple-Button Technique for the Treatment of Acute AC Joint Dislocation.

Acute acromioclavicular (AC) joint dislocation is a frequent sports injury with more than 100 different operation methods described. A total of 65 patients with an acute AC joint dislocation were treated with the modified MINAR® system between 2009 and 2013. Clinical outcome, horizontal and vertical instability, as well as concomitant intraarticular injuries were assessed. We used Zanca, stress and axial X-rays for radiological assessment. A Constant score of 95 (±8.8), University of California Los Angeles Shoulder score (UCLA) of 31 (±4.9), Disabilities of Arm, Shoulder and Hand (DASH) of 9.1 (±14.3), and Visual Analogue Scale (VAS) of 0.9 (±0.126) was found. A total of 30 patients (59%) had no signs of reduction loss, nine patients (18%) a slight loss, 11 patients (22%) a partial loss, and one patient (2%) a total loss. No significant influence on the clinical scores could be shown. The postoperative coracoclavicular (CC) distance negatively affected the Constant (p = 0.007) and UCLA scores (p = 0.035). A longer time interval to surgery had a negative influence on all scores (p ≤ 0.001). We could not find any signs of persistent horizontal instability or intraarticular injuries at follow-up. The MINAR® system promises satisfactory functional and radiological results. When setting the correct indication, patients benefit from an early operation. No persisting horizontal instability was observed following suturing of the AC capsule and the delta fascia.