Electromagnetic gyrokinetic turbulence in finite-beta helical plasmas

A saturation mechanism for microturbulence in a regime of weak zonal flow generation isinvestigated by means of electromagnetic gyrokinetic simulations. The study identifies a newsaturation process of the kinetic ballooning mode (KBM) turbulence originating from the spatial structure of the KBM instabilities in a finite-beta Large Helical Device (LHD) plasma.Specifically, the most unstable KBM in LHD has an inclined mode structure with respect to the mid-plane of a torus, i.e., it has a finite radial wave-number in flux tube coordinates, in contrast to KBMs in tokamaks as well as ion-temperature gradient modes in tokamaks and helical systems. The simulations reveal that the growth of KBMs in LHD is saturated by nonlinear interactions of oppositely inclined convection cells through mutual shearing as well as by the zonal flow. The saturation mechanism is quantitatively investigated by analysis of the nonlinear entropy transfer that shows not only the mutual shearing but also a self-interaction with an elongated mode structure along the magnetic field line

Plasma beta dependence of turbulent transport suggesting an advantage of weak magnetic shear from local and global gyrokinetic simulations

A higher plasma β is desirable for realizing high performance fusion reactor, in fact, one of the three goals of JT-60SA project is to achieve a high-β regime. We investigate key physical processes that regulate the β dependence of turbulent transport in L-mode plasmas by means of both local and global gyrokinetic simulations. From local simulations, we found that the turbulent transport does not decrease as β increases, because the electromagnetic stabilizing effect is canceled out by the increase of the Shafranov shift. This influence of the Shafranov shift is suppressed when the magnetic shear is weak, and thus the electromagnetic stabilization is prominent in weak shear plasmas, suggesting an advantage of weak magnetic shear plasmas for achieving a high-β regime. In high β regime, local gyrokinetic simulations are suffered from the non-saturation of turbulence level. In global simulations, by contrast, the electromagnetic turbulence gets saturated by the entropy advection in the radial direction to avoid the zonal flow erosion due to magnetic fluctuations. This breakthrough enables us to explore turbulent transport at a higher β regime by gyrokinetic simulations

Effects of Flavonoids Isolated From Orange Jasmine (Murraya Paniculata [L.] Jack.) on Histamine Release From Mast Cells

Murraya paniculata [L.] Jack. (Kemuning) is a plant that grows widely in some areas of Indonesia. Studies related to this plant have been widely explored especially isolation of its active compounds. The plant contents several active compounds such as flanovoids. In the study, three flavonoid isolated from M. paniculata were evaluated for their effect on histamine release from mast cells (RBL-2H3 cells). These compounds were 3,3',4',5,5',6,7,8-octamethoxyflavone; 3,3',4',5,5',6,7-heptamethoxyflavone and 3, 3', 4', 5, 5', 7–hexamethoxyflavone. The histamine inducers used in the study were DNP24-BSA dan thapsigargin, inducing the histamine release immunologically and non-immunologically, respectively. In the study, heptamethoxyflavone and hexamethoxyflavone did not influence the histamine release from mast cells significantly. However, octamethoxyflavone could increase the histamine release from RBL-2H3 cells in absence and presence the histamine inducers. The flavanoid could increase the release of histamine up to 50 %. Based on the results, polymethoxy moieties at the structure of flavonoid have a significant role to emerge the histamine-release stimulating effect from mast cells

Comparison of Cytotoxic and Antiproliferative Effects of Benzylidenecyclopentanone Analogues of Curcumin on RBL-2H3 Cells

Curcumin is a natural yellow pigment isolated from the rhizomes of Curcuma longa L. (turmeric), and has several pharmacological effects and no toxicity in both in animal and human clinical study. However, the problem of curcumin is its stability because of its active methylene moiety. Modification of this moiety to cyclopentanone is expected to increase the stability. Previous study reported that benzylidenecyclopentanone analogues of curcumin showed inhibitory effect on histamine release from RBL-2H3 (rat basophilic leukemia) cells, a tumor analog of mast cells. One of them, the hydroxy-methoxy analog (PGV-0), showed more potent effect than that of curcumin. In the present study, some benzylidenecyclopentanone analogues of curcumin were evaluated for their effects on the viability and proliferation of RBL-2H3 cells. Viable cells were counted under a light microscope with a cells-counting chamber or using the cell viability reagent WST-1. The results showed that mast cell viability and histamine content were not affected by curcumin and benzylidene cyclopentanone for 30 min incubation, however, impaired for overnight incubation. The hydroxy-dimethyl benzylidene analog (PGV-1) strongly decreased the mast cells viability for overnight incubation, and its effect was highest among the other analogues. In the proliferation study, this compound also strongly inhibited the proliferation of mast cells, whereas curcumin and hydroxy-methoxy benzylidene analog inhibited the proliferation slightly. There were no inhibitory effects on mast cells proliferation treated by dibenzylidene; dihydroxybenzylidene; and hydroxy-diethylbenzylidene cyclopentanone. Keywords : viability, proliferation, curcumin, benzylidene cyclopentanone, RBL-2H3 cell