Electromagnetic gyrokinetic simulation of turbulence in torus plasmas

Gyrokinetic simulations of electromagnetic turbulence in magnetically confined torus plasmas including tokamak and heliotron/stellarator are reviewed. Numerical simulation of turbulence in finite beta plasmas is an important task for predicting the performance of fusion reactors and a great challenge in computational science due to multiple spatio-temporal scales related to electromagnetic ion and electron dynamics. The simulation becomes further challenging in non-axisymmetric plasmas. In finite beta plasmas, magnetic perturbation appears and influences some key mechanisms of turbulent transport, which include linear instability and zonal flow production. Linear analysis shows that the ion-temperature gradient (ITG) instability, which is essentially an electrostatic instability, is unstable at low beta and its growth rate is reduced by magnetic field line bending at finite beta. On the other hand, the kinetic ballooning mode (KBM), which is an electromagnetic instability, is destabilized at high beta. In addition, trapped electron modes (TEMs), electron temperature gradient (ETG) modes, and micro-tearing modes (MTMs) can be destabilized. These instabilities are classified into two categories: ballooning parity and tearing parity modes. These parities are mixed by nonlinear interactions, so that, for instance, the ITG mode excites tearing parity modes. In the nonlinear evolution, the zonal flow shear acts to regulate the ITG driven turbulence at low beta. On the other hand, at finite beta, interplay between the turbulence and zonal flows becomes complicated because the production of zonal flow is influenced by the finite beta effects. When the zonal flows are too weak, turbulence continues to grow beyond a physically relevant level of saturation in finite-beta tokamaks. Nonlinear mode coupling to stable modes can play a role in the saturation of finite beta ITG mode and KBM. Since there is a quadratic conserved quantity, evaluating nonlinear transfer of the conserved quantity from unstable modes to stable modes is useful for understanding the saturation mechanism of turbulence

Serum Apolipoprotein M Levels are Correlated with Biomarkers of Coagulation

Background:Apolipoprotein M (ApoM) is bound to high-density lipoprotein (HDL) in plasma, and HDL has anticoagulation effects. However, the association between ApoM and biomarkers of coagulation was unclear. Therefore, we investigated relationships between ApoM and biomarkers of coagulation. Methods: Serum samples from 233 Japanese participants including with diabetes mellitus, hypertension, dyslipidemia, or healthy controls were analyzed. Serum ApoM levels were measured using Enzyme-Linked Immuno-Sorbent Assay(ELISA). Results:Analysis of all 233 participants showed that ApoM levels were positively correlated with age (r＝0.284, p＜0.001), total cholesterol (TC;r＝0.477, p＜0.001), HDL-cholesterol (HDL-C;r＝0.234, p＜0.001) and lowdensity lipoprotein cholesterol (LDL-C;r＝0.331, p＜0.001). Higher ApoM levels were correlated with shorter activated partial thromboplastin time(APTT;r＝－0.226,p＝0.001) and prothrombin time(PT,％;r＝0.326,p＜ 0.001). Separate analysis of the 115 healthy controls showed that ApoM levels were positively correlated with age, TC, HDL-C and LDL-C, and higher ApoM levels were correlated with shorter PT. Conclusion:Serum levels of ApoM may influence biomarkers of coagulation

Turbulent transport of heat and particles in a high ion temperature discharge of the Large Helical Device

Turbulent transport in a high ion temperature discharge of the Large Helical Device (LHD) is investigated by means of electromagnetic gyrokinetic simulations, which include kinetic electrons, magnetic perturbations, and full geometrical effects. Including kinetic electrons enables us to firstly evaluate the particle and the electron heat fluxes caused by turbulence in LHD plasmas. It is found that the electron energy transport reproduces the experimental result, and that the particle flux is negative. The contribution of magnetic perturbation to the transport is small because of very low beta. The turbulence is driven by the ion temperature gradient instability, and the effect of kinetic electrons enhances the growth rate larger than that from the adiabatic electron calculation. The ion energy flux is larger than that observed in the experiment, while the flux is close to the experimental observation when the temperature gradient is reduced 20% in the simulation. This significant sensitivity of the energy flux implies that the profile in the experiment is close to the critical temperature gradient. The critical gradient for turbulent energy flux is similar to that for the linear instability, i.e., the Dimits shift is small. This is because the zonal flow in the LHD is weaker than that in tokamaks

Biometric assessment of deep-sea vent megabenthic communities using multi-resolution 3D image reconstructions

This paper describes a method to survey the distribution of megabenthos over multi-hectare regions of the seafloor. Quantitative biomass estimates are made by combining high-resolution 3D image reconstructions, used to model spatial relationships between representative taxa, with lower-resolution reconstructions taken over a wider area in which the distribution of larger predatory animals can be observed. The method is applied to a region of the Iheya North field that was the target of scientific drilling during the IODP Expedition 331 in 2010. An area of 2.5 ha was surveyed 3 years and 4 months after the site was drilled. More than 100,000 organisms from 6 taxa were identified. The visible effects of drilling on the distribution of megabenthos were confined to a 20 m radius of the artificially created hydrothermal discharges, with the associated densities of biomass lower than observed in nearby naturally discharging areas

Intracrine activity involving NAD-dependent circadian steroidogenic activity governs age-associated meibomian gland dysfunction

新たなイントラクライン機構を用いた加齢性眼疾患治療へ --眼局所のホルモンの加齢変化とサーカディアンリズムが鍵--. 京都大学プレスリリース. 2022-02-14.Canonically, hormones are produced in the endocrine organs and delivered to target tissues. However, for steroids, the concept of tissue intracrinology, whereby hormones are produced in the tissues where they exert their effect without release into circulation, has been proposed, but its role in physiology/disease remains unclear. The meibomian glands in the eyelids produce oil to prevent tear evaporation, which reduces with aging. Here, we demonstrate that (re)activation of local intracrine activity through nicotinamide adenine dinucleotide (NAD+)-dependent circadian 3β-hydroxyl-steroid dehydrogenase (3β-HSD) activity ameliorates age-associated meibomian gland dysfunction and accompanying evaporative dry eye disease. Genetic ablation of 3β-HSD nullified local steroidogenesis and led to atrophy of the meibomian gland. Conversely, reactivation of 3β-HSD activity by boosting its coenzyme NAD+ availability improved glandular cell proliferation and alleviated the dry eye disease phenotype. Both women and men express 3β-HSD in the meibomian gland. Enhancing local steroidogenesis may help combat age-associated meibomian gland dysfunction

Saturated hydraulic conductivity of a volcanic ash soil affected by repulsive potential energy in a multivalent anionic system

Introduction:Acid rain has been a serious problem around the world. The adverse effects of acid rain on soils must be assessed. Because soils have pH-dependent charges, the solution pH affects saturated hydraulic conductivity (K) [1–7]. A volcanic ash soil whose predominant clay minerals are allophane and imogolite contains a substantial pH-dependent charge [8–10]. Its K decreases when a higher- or lower-pH solution percolates [3–6]. When dilute nitrate percolates in the soil, K decreases due to the swelling and dispersion of the soil. On the other hand, when dilute sulfate percolates, K does not decrease; under this condition, the soil neither disperses nor swells [6].Although K is supposed to decrease in response to an increase in electric repulsive force among soil particles, the relationship between K and repulsive potential energy has not been evaluated. The relationship between rheological properties and the potential energy of the interaction between sodium montmorillonite particles was discussed [11]. A numerical solution of the equation for swelling pressure in mixed systems with nonsymmetrical electrolytes was proposed [12]. However, research into repulsive potential energy in multivalent counterion systems has been rare.In this paper, repulsive potential energies for a volcanic ash soil (allophanic Andisol), which is characterized by a number of pH-dependent charges, were evaluated in an NO3–SO4 system at pH’s 3 and 4. In order to determine the mechanism of the change in K of the soil during dilute acid leaching, the relationship between K and the repulsive potential energies was evaluated. Because the acidity in rain is caused mainly by HNO3 and H2SO4, mixed dilute solutions of these acids were used in the experiment