Impact of energetic particle orbits on long range frequency chirping of BGK modes

Long range frequency chirping of Bernstein-Greene-Kruskal modes, whose existence is determined by the fast particles, is investigated in cases where these particles do not move freely and their motion is bounded to restricted orbits. An equilibrium oscillating potential, which creates different orbit topologies of energetic particles, is included into the bump-on-tail instability problem of a plasma wave. With respect to fast particles dynamics, the extended model captures the range of particles motion (trapped/passing) with energy and thus represents a more realistic 1D picture of the long range sweeping events observed for weakly damped modes, e.g. global Alfven eigenmodes, in tokamaks. The Poisson equation is solved numerically along with bounce averaging the Vlasov equation in the adiabatic regime. We demonstrate that the shape and the saturation amplitude of the nonlinear mode structure depends not only on the amount of deviation from the initial eigenfrequency but also on the initial energy of the resonant electrons in the equilibrium potential. Similarly, the results reveal that the resonant electrons following different equilibrium orbits in the electrostatic potential lead to different rates of frequency evolution. As compared to the previous model [Breizman B.N. 2010 Nucl. Fusion 50 084014], it is shown that the frequency sweeps with lower rates. The additional physics included in the model enables a more complete 1D description of the range of phenomena observed in experiments.Comment: Submitted to Nuclear Fusion 25/01/201

Do Anionic Titanium Dioxide Nano-Clusters Reach Bulk Band Gap? A Density Functional Theory Study

The electronic properties of both neutral and anionic (TiO2)n (n = 1-10) clusters are investigated by extensive density functional theory calculations. The predicted electron detachment energies and excitation gaps of anionic clusters agree well with the original experimental anion photoelectron spectra (APES). It is shown that the old way to analyze APES tends to overestimate vertical excitation gaps (VGA) of large anionic clusters, due to the nature of multiple electronic origins for the higher APES bands. Moreover, the VGA of anionic TiO2 clusters are evidently smaller than those of neutral clusters, which may also be the case for other metal oxide clusters with high electron affinity

Dynamics of conduction blocks in a model of paced cardiac tissue

We study numerically the dynamics of conduction blocks using a detailed electrophysiological model. We find that this dynamics depends critically on the size of the paced region. Small pacing regions lead to stationary conduction blocks while larger pacing regions can lead to conduction blocks that travel periodically towards the pacing region. We show that this size-dependence dynamics can lead to a novel arrhythmogenic mechanism. Furthermore, we show that the essential phenomena can be captured in a much simpler coupled-map model.Comment: 8 pages 6 figure

Thermally stimulated relaxation and behaviors of oxygen vacancies in SrTiO<inf>3</inf> single crystals with (100), (110) and (111) orientations

Abstract The strontium titanate (SrTiO3) single crystals with different orientations of (100), (110) and (111) were investigated using thermally stimulated depolarization current (TSDC) measurements, which has been proved to be an effective strategy to fundamentally study the relationship between relaxation phenomena and defect chemistry in dielectrics. The origins of different relaxations in SrTiO3 crystals were identified and the activation energy of oxygen vacancies was estimated from TSDC measurements. It was further found that oxygen-treated SrTiO3 crystals exhibit different relaxation behaviors. Noticeable changes of thermal relaxation associated with oxygen vacancies have taken place in relation to the crystalline anisotropy. The SrTiO3 (110) samples display higher concentration and activation energy of oxygen vacancies. First-principles calculations were carried out on SrTiO3 (110) crystals to study the effect of oxygen vacancy on different surface microstructure. From the resulting minimum formation energy of 0.63 eV, it demonstrates that the oxygen vacancies tend to form on the TiO-terminated surfaces. Considering the band structure, oxygen vacancies near the surface contribute to the transition of crystal from insulator to metallic characteristic.</jats:p

Genetic analysis of Aralia cordata thunb by RAPD

In the research, genetic analysis of Aralia cordata Thunb. (Araliaceae) was conducted using randomly amplified polymorphism DNA (RAPD). 161 loci were detected with 12 RAPD primers. Percentage of Polymorphic Band (PPB) varied from 34.78% to 63.35%. All the samples were respectively collected from the eight provinces richest in Aralia cordata Thunb resources in China, including Hunan, Yunnan, Zhejiang, Sichuan, Jiangxi, Anhui, Shanxi and Gansu. The results showed that Hunan Province enjoyed the highest level of genetic differentiation and Gansu was the lowest. The total genetic diversity (HT) of RAPD, intraspecific genetic diversity (HS) and genetic diversity (DST) of the various places was respectively 26.33%, 11.14%, and 49.36%. The differentiation among the species accounted for 98.76% of total genetic diversity (GST). Based on the cluster results of genetic distance, the 8 samples were classified into three groups. It is concluded that Hunan Province enjoyed the highest level of genetic differentiation of Aralia cordata Thunb and Gansu was the lowest, which provides a basis for the taxonomic identification and germplasm resource research of Aralia cordata Thunb in the future.Keywords: Genetic Analysis ; Aralia cordata Thunb.; RAP