Effects of edge biasing on blob dynamics and associated transport in the edge of the J-TEXT tokamak

Effects of edge radial electric field Er and Er × B flow shear on edge turbulence and turbulent transport, in particular, on large-scale blobs and blobby transport have been investigated in the positive and negative biasing discharges in the J-TEXT tokamak. The results show that under certain conditions, the positive electrode biasing induces better plasma confinement than the negative biasing. Further studies reveal that in addition to flow shear effects on blob dynamics, the local radial electric field at the edge region plays a significant role in repulsion of the blobs and associated transport, leading to improvement of particle confinement when the outward motion of the blobs is blocked. The results are in accordance with theoretical predictions.

Inverse centrifugal effect induced by collective motion of vortices in rotating thermal convection

When a fluid system is subject to strong rotation, centrifugal fluid motion is expected, i.e., denser (lighter) fluid moves outward (inward) from (toward) the axis of rotation. Here we demonstrate, both experimentally and numerically, the existence of an unexpected outward motion of warm and lighter vortices in rotating thermal convection. This anomalous vortex motion occurs under rapid rotations when the centrifugal buoyancy is sufficiently strong to induce a symmetry-breaking in the vorticity field, i.e., the vorticity of the cold anticyclones overrides that of the warm cyclones. We show that through hydrodynamic interactions the densely distributed vortices can self-aggregate into coherent clusters and exhibit collective motion in this flow regime. Interestingly, the correlation of the vortex velocity fluctuations within a cluster is scale-free, with the correlation length being proportional ( ≈ 30%) to the cluster length. Such long-range correlation leads to the counterintuitive collective outward motion of warm vortices. Our study brings insights into the vortex dynamics that are widely present in nature.

Evolution from mitral annular dysfunction to severe mitral regurgitation in Barlow’s disease

OBJECTIVES Barlow’s disease (BD) is characterized by thick, redundant mitral valve (MV) leaflets, which can lead to prolapse and significant mitral regurgitation (MR). MV annular abnormalities are also commonly observed and increasingly recognized as possible primary pathology, with leaflet thickening being secondary to increased stress on the MV apparatus. To provide more insights into this hypothesis, the evolution of MV abnormalities over time in patients with BD was assessed. METHODS A total of 64 patients (54 ± 12 years, 72% male) with BD who underwent MV surgery and had multiple transthoracic echocardiograms (TTE) before surgery were included. In total, 186 TTE were analysed (median time interval 4.2, interquartile range 2.2–6.5 years) including specific MV characteristics. RESULTS At baseline, MV leaflet length, thickness, billowing height and annular diameter were larger in patients with BD compared to 59 healthy subjects. Systolic outward motion (curling) of the annulus was observed in 77% and severe mitral annular disjunction (≥5 mm) in 38% of patients with BD. Forty (63%) patients had MR grade I–II and 24 (37%) MR grade III–IV; at baseline, the 2 groups only differed in left atrial volume and in thickness and billowing height of the posterior leaflet, showing comparable MV annular abnormalities and dilatation despite different grades of MR. Over time, MV annulus diameter, leaflet length and billowing height increased significantly along with MR grade. CONCLUSIONS In patients with BD, MV annulus abnormalities are present at an early stage and precede the development of significant MR, suggesting their substantial role in the pathophysiology of this disease and as an important target for surgical treatment.

Inverse centrifugal effect induced by collective motion of vortices in rotating turbulent convection

When a fluid system is subject to strong rotation, centrifugal fluid motion is expected, i.e., denser (lighter) fluid moves outward (inward) from (toward) the axis of rotation. Here we demonstrate, both experimentally and numerically, the existence of an unexpected outward motion of warm and lighter vortices in rotating turbulent convection. This anomalous vortex motion occurs under rapid rotations when the centrifugal buoyancy is sufficiently strong to induce a symmetry-breaking in the vorticity field, i.e., the vorticity of the cold anticyclones overrides that of the warm cyclones. We show that through hydrodynamic interactions the densely populated vortices can self-aggregate into coherent clusters and exhibit collective motion in this flow regime. Interestingly, the correlation of the vortex velocity fluctuations within a cluster is scale-free, with the correlation length being about 30% of the cluster length. Such long-range correlation leads to the collective outward motion of cyclones. Our study provides new understanding of vortex dynamics that are widely present in nature.

Deciphering collaborative sidechain motions in proteins during molecular dynamics simulations

The dynamic structure of proteins is essential for their functions and may include large conformational transitions which can be studied by molecular dynamics (MD) simulations. However, details of these transitions are difficult to automatically track. To facilitate their analysis, we developed two scores of correlation between sidechain dihedral angles. The CIRCULAR and OMES scores are computed from, respectively, dihedral angle values and rotamer distributions. As a case study, we applied our methods to an activation-like transition of the chemokine receptor CXCR4, observed during accelerated MD simulations. The principal component analysis of the correlation matrices was consistent with the networking structure of the top ranking pairs. Both scores identify a set of residues whose “collaborative” sidechain rotamerization immediately preceded or accompanied the conformational transition of CXCR4. Detailed analysis of the sequential order of these rotamerizations suggests that an allosteric mechanism, involving the outward motion of an asparagine residue in transmembrane helix 3, might be a prerequisite to the large scale conformational transition of CXCR4. This case study provides the proof-of-concept that the correlation methods developed here are valuable exploratory techniques to help decipher complex reactional pathways.

Revealing the tidal scars of the Small Magellanic Cloud

ABSTRACT Due to their close proximity, the Large and Small Magellanic Clouds (LMC/SMC) provide natural laboratories for understanding how galaxies form and evolve. With the goal of determining the structure and dynamical state of the SMC, we present new spectroscopic data for ∼3000 SMC red giant branch stars observed using the AAOmega spectrograph at the Anglo-Australian Telescope. We complement our data with further spectroscopic measurements from previous studies that used the same instrumental configuration as well as proper motions from the Gaia Data Release 2 catalogue. Analysing the photometric and stellar kinematic data, we find that the SMC centre of mass presents a conspicuous offset from the velocity centre of its associated H i gas, suggesting that the SMC gas is likely to be far from dynamical equilibrium. Furthermore, we find evidence that the SMC is currently undergoing tidal disruption by the LMC within 2 kpc of the centre of the SMC, and possibly all the way into the very core. This is revealed by a net outward motion of stars from the SMC centre along the direction towards the LMC and an apparent tangential anisotropy at all radii. The latter is expected if the SMC is undergoing significant tidal stripping, as we demonstrate using a suite of N-body simulations of the SMC/LMC system disrupting around the Milky Way. Our results suggest that dynamical models for the SMC that assume a steady state will need to be revisited.

Silent VLPs At Stromboli: Implications For Slug Vs. Plug

<p>Very long period (VLP) seismic signals observed in volcanic environments are thought to be produced by magma and gas flow through conduits. Stromboli Volcano, Italy, typically produces hundreds of VLPs per day. These have been generally attributed to the flow of gas slugs through the shallow plumbing system and thus linked to the mechanism thought to drive Strombolian explosions. During a 6-day-long seismo-acoustic campaign in May 2018 (a period characterized by relatively low activity) we recorded 1900+ seismic events, the majority of which have significant energy in the VLP (2-100 s) band. We used a coincident STA/LTA trigger to identify seismic events in continuous waveform data and then used the PeakMatch algorithm (Rodgers et al., 2015) to identify seismic multiplets, with a focus on VLPs. To identify explosions, we applied the same coincident trigger to infrasound data, and manually identified gas jetting events using spectrograms and high-pass-filtered (20 Hz) waveforms. </p><p> </p><p>We identified ~250 explosions and ~600 jetting events. Seismic multiplet analysis identified two main families of repeating events. Family 1 (F1) has over 500 events and Family 2 (F2) has over 150 events based on a 0.7 correlation threshold. We find that F1 VLPs coincide in time with ~6% of explosions and ~0.8% of jetting events and F2 VLPs coincide in time with ~28% of explosions and ~2.7% of jetting events (we term these “silent VLPs”). These VLPs do not correspond with lava effusion (Marchetti and Ripepe, 2005; Ripepe et al., 2015). F2 have a higher dominant period (8-10 s) compared to F1 (3-4 s). The repeating VLPs are part of a broadband signal and the higher frequencies start after the VLP. VLP peak amplitudes are generally larger for F1 events. The dip of the VLP particle motion roughly locates the F1 and F2 VLP source centroids beneath the active crater and are stable throughout the dataset. Both VLP displacements show a small outward, large inward, and subsequent large outward motion from the crater. The lack of explosions relative to repeating VLPs does not support the slug model, where a slug rises through a conduit, generates a VLP through interactions with changes in conduit geometry, and then bursts at the lava free surface. Our observations support the plug model (Suckale et al., 2016). We suggest the “silent” VLPs are generated when the gas bubbles interact with and move into the semipermeable plug. Then the plug behaves as a mechanical filter for gas escape and allows for passive and explosive escape mechanisms.</p>

The largest Crab glitch and the vortex creep model

The Crab pulsar displayed its largest glitch on 2017 November. An extended initial spin-up phase of this largest glitch was resolved, for the first time with high cadence of observations both in radio and X-rays on a time-scale of 2 d. A combination of crustquake and vortex unpinning models is invoked to account for the extended spin-up, magnitude, and post-glitch relaxation characteristics of this glitch. We evaluate the extended spin-up followed by the familiar spin-down as due to the creep response to the initial induced inward motion of some vortex lines pinned to broken crustal plates moving inward towards the rotation axis, together with the common and familiar post-glitch creep response to the sudden outward motion of vortices unpinned at the glitch. Our analysis confirms that the number of unpinned vortices participating in glitches are similar in all Crab glitches, and within an order of magnitude in all glitches from all pulsars. This typical number of unpinned vortices is related to the broken plate size in quakes as triggers for vortex unpinning avalanches. The physical determinant of this universal broken plate size is in turn the critical strain angle in the neutron star crust. Occurrence of this largest Crab glitch after a relatively long inactive period is consistent with accumulation of the pinned vorticity to be tapped.

PENCAK SILAT AMENG TIMBANGAN DI JAWA BARAT: HUBUNGAN ANTARA AJARAN DAN GERAK AMENG TIMBANGAN

Pencak silat Ameng Timbangan diciptakan R. Moezni Anggakoesoemah bersumber pada ajaran Timbangan. Ajaran Timbangan bukanlah petunjuk teknis untuk melakukan jurus tertentu, melainkan ajaran kerohanian Islam. Di dalamnya dibahas mengenai trilogi Islam, yaitu Iman-Islam-Ihsan. Ajaran ini menjadi jiwa dalam gerak lahiriah Ameng Timbangan. Masalahnya bagaimana teks ajaran itu menjelma menjadi gerak Ameng Timbangan. Tujuan penelitian adalah menjelaskan teks ajaran Timbangan menjadi gerak Ameng Timbangan. Adapun metodenya digunakan metode deskripsi,yang menggambarkan data apa adanya. Bentuk Ajaran Timbangan disusun dalam bentuk puisi dan prosa yang disebut teks Naskah Timbangan, karena itu digunakan pula metode analisis isi.Teknik penelitiannya wawancara mendalam dan partisipasi (ikut serta latihan Ameng Timbangan). Simpulannya Ajaran Timbangan berisi pelajaran rohani, sedangkan Ameng Timbangan menitikberatkan pada pelajaran lahiriah. Pengolahan lahiriah dalam bentuk olah raga dan olah rasa memberikan ruang untuk membangkitkan kemampuan dan kekuatan naluri beladiri. Hubungan keduanya merupakan hubungan kesatuan yang saling melengkapi. Pencak Silat Ameng Timbangan created by R. Moezni Anggakoesoemah derived from the teachings called Timbangan. The Sci-op Teachings are not technical guidelines for performing a specific moment, but rather the spiritual teaching of Islam, discussed about the Islamic trilogy, namely Iman-Islam-Ikhsan. It is this doctrine which then becomes the soul or spirit in the outward motion called Ameng Timbangan. The main problem is how the text containing the teachings is transformed into a motion called Ameng Timbangan. The main purpose of the study is to explain the text of the Timbangan teaching to the motion of Ameng Timbangan. In order to achieve these objectives the writer used description method, which describes the data. Forms of AjaranTimbangan are arranged in the form of poetry and prose called script of Naskah Timbangan, then used the method of content analysis. The research technique are in-depth interview, and participation (participate in Ameng Timbangan training). The conclusion are the Doctrine and Ameng Timbangan is a unity. The Timbangan Teachings contain spiritual lessons while Ameng Timbangan focuses on outer lessons. External processing in the form of sports and taste provide space to awaken the ability and strength of martial instinct. Their relationship is a complementary relationship.

A study on evolved stars by simultaneous observations of H2O and SiO masers using KVN

The Korean VLBI Network (KVN) is a unique millimeter VLBI system which is consisted of three 21 m telescopes with relatively short baselines. We present the preliminary results of simultaneous monitoring observations of the 22.2 GHz H2O and 43.1/42.8/86.2/129.3 GHz SiO masers based on the KVN Key Science Project (KSP). We obtained the astrometrically registered maps of the H2O and SiO masers toward nine evolved stars using the source frequency phase referencing method (SFPR). The SFPR maps of the H2O and SiO masers enabled us to investigate the spatial structure and kinematics from the SiO to H2O maser regions including the development of an outward motion from the ring-like or elliptical structures of SiO masers to the asymmetric structures of the 22.2 GHz H2O maser features. In particular, the 86.2/129.3 GHz SiO (v=1, J=2–1 and J=3–2) masers were clearly imaged toward several objects for the first time. The SiO v=1, J=3–2 maser shows different distributions compared to those of the SiO v=1, 2, J=1–0 and v=1, J=2–1 masers implying a different physical condition.