Relationships between the Prediction of Linear MHD Stability Criteria and the Experiment in LHD

We analyze the relationship between the experimentally observed pressure gradients at resonant rational surfaces and the theoretically predicted ideal magnetohydrodynamics (MHD) unstable region of global modes in the large helical device (LHD). According to the stability analysis of the ideal MHD modes with a low toroidal mode number, we find that the ideal MHD mode gives a constraint on the operational regime of the pressure gradients in the core. In the edge, a clear saturation of the pressure gradients due to the ideal MHD instability has not been observed up to the high beta regime around 3% as the volume-averaged toridal beta value, where global ideal MHD modes are predictedto be unstable

Onset of instability with collapse observed in relatively high density and medium beta regions of LHD

Edge MHD instabilities with pressure collapse are found in relatively high beta and low magnetic Reynolds number regions with a magnetic axis torus outward-shifted configuration of the large helical device (LHD), and characteristics and onset conditions of the instability are investigated. The instability has a radial structure with an odd parity around the resonant surface, which is different from that of the interchange instability typically observed in the LHD. The onset condition dependence on the magnetic axis location shows that the onset beta increases as the magnetic axis location moves more torus inwardly, and the instability appears only in limited configurations where the magnetic axis is located between 3.65 and 3.775 m. In such configurations, the resonant surface location is close to an index of the plasma boundary. This fact suggests that the distance between the resonant surface location and the plasma boundary plays an important role in the onset, and a possibility that the instability is driven by an external mode

Association of schizophrenia onset age and white matter integrity with treatment effect of D-cycloserine : a randomized placebo-controlled double-blind crossover study

Background: It has been reported that drugs which promote the N-Methyl-D-aspartate-type glutamate receptor function by stimulating the glycine modulatory site in the receptor improve negative symptoms and cognitive dysfunction in schizophrenia patients being treated with antipsychotic drugs. Methods: We performed a placebo-controlled double-blind crossover study involving 41 schizophrenia patients in which D-cycloserine 50 mg/day was added-on, and the influence of the onset age and association with white matter integrity on MR diffusion tensor imaging were investigated for the first time. The patients were evaluated using the Positive and Negative Syndrome Scale (PANSS), Scale for the Assessment of Negative Symptoms (SANS), Brief Assessment of Cognition in Schizophrenia (BACS), and other scales. Results: D-cycloserine did not improve positive or negative symptoms or cognitive dysfunction in schizophrenia. The investigation in consideration of the onset age suggests that D-cycloserine may aggravate negative symptoms of early-onset schizophrenia. The better treatment effect of D-cycloserine on BACS was observed when the white matter integrity of the sagittal stratum/ cingulum/fornix stria terminalis/genu of corpus callosum/external capsule was higher, and the better treatment effect on PANSS general psychopathology (PANSS-G) was observed when the white matter integrity of the splenium of corpus callosum was higher. In contrast, the better treatment effect of D-cycloserine on PANSS-G and SANS-IV were observed when the white matter integrity of the posterior thalamic radiation (left) was lower. Conclusion: It was suggested that response to D-cycloserine is influenced by the onset age and white matter integrity

Impact of a resonant magnetic perturbation field on impurity radiation, divertor footprint, and core plasma transport in attached and detached plasmas in the Large Helical Device

The effects of resonant magnetic perturbation (RMP) field on impurity radiation, divertor footprint distribution, and core plasma transport are investigated in the detachment discharges of the Large Helical Device (LHD). The RMP with m/n  =  1/1 mode creates an edge magnetic island in the stochastic layer, which enhances the impurity emission from low charge states, C2+ and C3+, and then triggers a detachment transition. Emission from the higher charge states, C4+ and C5+, implies enhanced penetration of impurities during the detachment phase with RMP. The toroidal divertor particle flux distribution exhibits n  =  1 mode structure in both the attached and detached phases, but with a large toroidal phase shift between the two phases. The distribution in the attached phase is well correlated with the magnetic footprint of field line connection length calculated by the vacuum approximation. During the detached phase, however, the phase shift is not well explained by the vacuum approximation, where a significant plasma response to the external RMP is observed. The energy confinement time becomes systematically shorter with RMP application due to the shrinkage of plasma volume caused by the edge magnetic island. On the other hand, the pressure profile during detachment with RMP is found to be more peaked than without RMP. The analysis using the core transport code TASK3D, considering the heating profiles of neutral beam injection, shows no significant transport degradation during detachment with RMP application, even with the enhanced radiation, reduced divertor flux, and possible impurity penetration

Simultaneous excitation of the snake-like oscillations and the m/n = 1/1 resistive interchange modes around the iota = 1 rational surface just after hydrogen pellet injections in LHD plasmas

Two types of oscillation phenomena are found just after hydrogen ice pellet injections in the Large Helical Device (LHD). Oscillation phenomena appear when the deposition profile of a hydrogen ice pellet is localized around the rotational transform ι = 1 rational surface. At first, damping oscillations (type-I) appear only in the soft X-ray (SX) emission. They are followed by the second type of oscillations (type-II) where the magnetic fluctuations and density fluctuations synchronized to the SX fluctuations are observed. Both oscillations have poloidal/toroidal mode number, m/n = 1/1. Since the type-II oscillations appear when the local pressure is large and/or the local magnetic Reynold\u27s number is small, it is reasonable that type-II oscillations are caused by the resistive interchange modes. Because both types of oscillations appear simultaneously at slightly different locations and with slightly different frequencies, it is certain that type-I oscillations are different from type-II oscillations, which we believe is the MHD instability. It is possible that type-I oscillations are caused by the asymmetric concentration of the impurities. The type-I oscillations are similar to the impurity snake phenomena observed in tokamaks though type-I oscillations survive only several tens of milliseconds in LHD

Distorted magnetic island formation during slowing down to mode locking in helical plasmas

We report the first observation of the formation of a magnetic island before the occurrence of mode locking in helical plasma. New analysis and observation techniques applied to the ECE signal and poloidal flow in LHD experiments yield the following results. (i) A magnetic island structure is present, rotating at the end of the rotating phase. (ii) The rotation speed of the island is not uniform in space and time. The rotation of the island changes significantly at the end of the rotating phase, and the deformation increases until the mode is locked

Characteristics of MHD instabilities limiting the beta value in LHD

Effects of low-n magnetohydrodynamic instabilities on plasma performance have been assessed in the regime where an achieved beta value is limited by instabilities. The unstable regime of an ideal interchange mode is characterized by enhanced magnetic hill and reduced magnetic shear. Experiments have clarified that (i) low-n modes are significantly destabilized in the ideal-unstable configurations and lead to degradation of central beta by at most 60%, and (ii) the degree of their damages strongly depends on the mode rotation velocity. The occurrence of the minor collapse is independent of an existence of an error field

B cell-derived GABA elicits IL-10⁺ macrophages to limit anti-tumour immunity

GABAを標的とする抗腫瘍免疫機構 --代謝産物を介した免疫細胞間制御の一端を解明--. 京都大学プレスリリース. 2021-11-10.Small, soluble metabolites not only are essential intermediates in intracellular biochemical processes, but can also influence neighbouring cells when released into the extracellular milieu1-3. Here we identify the metabolite and neurotransmitter GABA as a candidate signalling molecule synthesized and secreted by activated B cells and plasma cells. We show that B cell-derived GABA promotes monocyte differentiation into anti-inflammatory macrophages that secrete interleukin-10 and inhibit CD8⁺ T cell killer function. In mice, B cell deficiency or B cell-specific inactivation of the GABA-generating enzyme GAD67 enhances anti-tumour responses. Our study reveals that, in addition to cytokines and membrane proteins, small metabolites derived from B-lineage cells have immunoregulatory functions, which may be pharmaceutical targets allowing fine-tuning of immune responses

Effects of Resonant Magnetic Perturbation on Particle Transport in LHD

In this study, the effects of resonant magnetic perturbation (RMP) on particle transport are investigated in Large Helical device (LHD). The magnetic configuration is selected to be the outwardly shifted configuration, for which the magnetic axis position (Rax) is 3.9 m. At Rax = 3.9 m, the main plasma is surrounded by a thick ergodic layer, with width of about 30% of the plasma minor radius. The perturbation mode m/n = 1/1, where m and n are poloidal and toroidal mode numbers, is applied. The resonant layer is around the last closed flux surface. With RMP, a region in which both the connection and Kolmogorov lengths are finite and the magnetic field is ergodic forms; this region extends inside the main plasma. In the low-collisionality regime, where νh* 1), a clear difference in particle transport is found. A clear difference in turbulence is also observed, suggesting that turbulence plays a significant role in particle transport in the high-collisionality regime both with and without RMP