[en] Neoclassical transport in a toroidal plasma with finite ion orbits is studied, including for the first time the self-consistent radial electric field. Using a low-noise {delta}f particle simulation, we demonstrate that a deep electric-field well develops in a region with a steep density gradient, because of the self-collision--driven ion flux. We find that the electric field agrees with the standard neoclassical expression, when the toroidal rotation is zero, even for a steep density gradient. Ion thermal transport is modified by the electric-field well in a way which is consistent with the orbit squeezing effect, but smoothed by the finite orbits

[en] For more than a decade, the study of microturbulence driven by ion temperature gradient (ITG) drift instabilities in tokamak devices has been an active area of research in magnetic fusion science for both experimentalists and theorists alike. An important impetus for this avenue of research was the discovery of the radial streamers associated with the ITG modes in the early 1990s using the particle-in-cell (PIC) simulation method. Subsequently, ITG simulations using codes with increasing realism have been made possible by the dramatic increase in computing power. Notable examples were the demonstration of the importance of nonlinearly generated zonal flows in regulating ion thermal transport and the transition from Bohm to gyroBohm scaling with increased device size. In this paper, we will describe an interesting nonlinear physical process, as well as the resulting turbulent transport, that is associated with the interactions between the nonlinear parallel acceleration of the ions and the zonal flow modes. This study was carried out by utilizing a fully parallelized three-dimensional PIC code in global toroidal geometry on the most advanced, modern, massively parallel supercomputers

[en] Electromagnetic gyrokinetic simulation in toroidal geometry is developed based on a fluid-kinetic hybrid electron model. The Alfven wave propagation in a fully global gyrokinetic particle simulation is investigated. In the long-wavelength magnetohydrodynamic limit, shear Alfven wave oscillations, continuum damping, and the appearance of the frequency gap in toroidal geometries are demonstrated. Wave propagation across the magnetic field (kinetic Alfven wave) is examined by comparing the simulation results with the theoretical dispersion relation. Furthermore, finite-beta stabilization of the ion temperature gradient mode and the onset of the kinetic ballooning mode are demonstrated

[en] The purpose of this study is to synthesize and characterize fluorescent polymers, rhodamine B-ethylenediamine-hyaluronan acid (RhB-EA-HA). RhB-EA-HA was successfully synthesized by ester ammonolysis reaction and amidation reaction. Moreover, the structural properties of RhB-EA-HA were characterized by ¹H-NMR spectra, UV-vis spectrometry and Fourier transform infrared spectroscopy (FT-IR). RhB-EA-HA can be grafted on the surface of silica nanomaterials, which may be potential biological functional materials for drug delivery system. (paper)

[en] The nonlocal physics associated with turbulent transport is investigated using global gyrokinetic simulations with realistic parameters in shaped tokamak plasmas. This study focuses on the turbulence spreading through a transport barrier characterized by an equilibrium ExB shear layer. It is found that an ExB shear layer with an experimentally relevant level of the shearing rate can significantly reduce, and sometimes even block, turbulence spreading by reducing the spreading extent and speed. This feature represents a new aspect of transport barrier dynamics. The key quantity in this process is identified as the local maximum shearing rate vertical bar ω_E^max vertical bar, rather than the amplitude of the radial electric field. These simulation studies also extend to radially local physics with respect to the saturation of the ion temperature gradient (ITG) instability, and show that the nonlinear toroidal couplings are the dominant k-space activity in the ITG dynamics, which cause energy transfer to longer wavelength damped modes, forming a downshifted toroidal spectrum in the fully developed turbulence regime

[en] Long-chain alkanoic acids usually form close-packed monolayer films with alkyl chains highly oriented on substrates. Previous studies have reported the adsorption of stearic acid on gold, aluminum, copper, silver, and aluminum oxide. However, there are no reports of stearic acid adsorption on magnetic metals. In this work, the characterization of stearic acid adsorbed on Ni(111) surface has been studied experimentally and with first-principles calculation. The results suggest that the stearic acid is chemically adsorbed on the Ni(111) surface via a bidentate interaction with a distance of about 1.8 A. Besides this, we have also obtained results for the charge transfer and magnetic proximity effect.

[en] Large ion orbits can produce nonlocal neoclassical effects on ion heat transport, the ambipolar radial electric field, and the bootstrap current in realistic toroidal plasmas. Using a global δf particle simulation, it is found that the conventional local, linear gradient-flux relation is broken for the ion thermal transport near the magnetic axis. With regard to the transport level, it is found that details of the ion temperature profile determine whether the transport is higher or lower when compared with the predictions of standard neoclassical theory. Particularly, this nonlocal feature is suggested to exist in the National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, Y.-K. M. Peng et al., Nucl. Fusion 40, 557 (2000)], being consistent with NSTX experimental evidence. It is also shown that a large ion temperature gradient can increase the bootstrap current. When the plasma rotation is taken into account, the toroidal rotation gradient can drive an additional parallel flow for the ions and then additional bootstrap current, either positive or negative, depending on the gradient direction. Compared with the carbon radial force balance estimate for the neoclassical poloidal flow, our nonlocal simulation predicts a significantly deeper radial electric field well at the location of an internal transport barrier of an NSTX discharge

[en] A significant discrepancy of poloidal velocity from conventional theoretical predictions is found in global neoclassical drift-kinetic simulations of magnetic confinement fusion devices. The difference is identified as being due to the presence of large ion orbits. In the case of a large aspect ratio tokamak configuration with steep toroidal flow profiles, a novel heuristic model which estimates this nonlocal effect is presented and shown to be in good agreement with simulation results. The dominant nonlocal mechanisms captured by the model are associated with ion parallel flow modification due to the steep toroidal flow and radial electric field profiles. We compare simulation results with theoretical estimates based on the new model using profiles relevant for the National Spherical Torus Experiment. The carbon poloidal velocity observed in the simulation is in good agreement with the neoclassical theory modified by the newly identified nonlocal effects. (brief communication)

[en] The transmittance of tungsten oxides can be adjusted by oxygen vacancy (V_o) concentration due to its electrochromic property. Here, we report an in-situ observation of resistive switching phenomenon in the oxygen-deficient WO_3-x planar devices. Besides directly identifying the formation/rupture of dark-colored conductive filaments in oxide layer, the stripe-like WO_3-x device demonstrated self-regulated switching behavior during the endurance testing, resulting in highly consistent switching parameters after a stabilizing process. For very high V_os mobility was demonstrated in the WO_3-x film by the pulse experiment, we suggested that the electric-field-induced homogeneous migration of V_os was the physical origin for such unique switching characteristics.

[en] The surface of commercially pure titanium was modified by anodization treatment in a phosphoric acid solution at different voltages: 100 V, 200 V and 300 V. The surface characteristics of anodic TiO₂ layers and their influence on the cell response were investigated. Micrographs by scanning electron microscopy revealed that the dense and uniform oxide layer obtained at 100 V exhibits a nanostructured surface which is similar to the surface of natural tooth cementum. In contrast, porous oxide layers without nanometer features were produced at higher voltages. Thin film x-ray diffraction analysis confirmed the existence of anatase in the oxide layer obtained at 300 V, but not in oxide layers obtained at 100 V and 200 V. The in vitro biocompatibility study of oxide layers demonstrated greater cell adhesion and proliferation of the oxide layer obtained at 100 V compared to the other two kinds of oxide layers.