Observation of Runaway Electron Behaviour During Disruptions in LHCD Discharges in the HT‐7 Tokamak

Production of runaway electrons during disruptions has been observed in the HT‐7 Tokamak. The runaway current plateaus, which can carry part of the pre‐disruptive current, are observed in lower‐hybrid current drive (LHCD) limiter discharges. It is found that the runaway current can mitigate the disruptions effectively. We can use gas puffing to increase the line‐averaged density to restrain the runaway electrons and rebuild the plasmas after the disruptions. Detailed observations are presented on the runaway electrons generated following disruptions in the HT‐7 tokamak discharges. The results indicate that the magnetic oscillations play a significant role in the loss of runaway electrons in disruptions. There are two important preconditions to rebuild plasmas by runaway electrons after the disruptions. One of them are weak magnetic oscillations; another one are LHWs (lower‐hybrid waves) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

纤锌矿结构AlInN电子及光学性质的第一性原理研究

本文通过基于密度泛函理论的第一性原理,研究了纤锌矿结构Al1-xInxN在不同In浓度下的稳固结构,以及电子和光学性质的变化规律。研究表明,AlInN不同In浓度的晶格结构都很稳定,说明AlInN的兼容性很好。晶格常数随In浓度的增大不断增大,而混晶的带隙则不断减小。并且随In浓度的增大,混晶在紫外光区的吸收系数、反射系数及折射率增大,吸收边、吸收峰和反射峰蓝移,且这两个峰的峰值减小。AlInN的吸收、反射和折射率曲线在Eg处出现峰值行为,此Eg处的峰值大小随In浓度的增加而增大。当In浓度达到87.5%时,混晶AlInN在紫外光区的吸收、反射和折射能力均达到最强,表明此时的掺杂效果最好。     

青蛙悬浮——一个令人惊奇和充满遐思却只需经典物理知识的实验

利用力学平衡和电磁学方面的知识,系统讨论了电荷、电偶极子、电介质、磁偶极子和顺磁介质不能实现悬浮,而抗磁质介质能够实现稳定悬浮的原因.介绍了盖姆青蛙悬浮实验技术上的细节以及背后简单的物理知识.对青蛙磁悬浮的探讨,不但能引发学生对其应用前景一系列的遐想,也能加深对静电学与磁学知识的理解.     

Deformations of overloaded bands under pH-stable conditions in reversed phase chromatography

It has recently been demonstrated, using mathematical models, how peculiar overloaded band profiles of basic compounds are due to the local pH in the column when using low capacity buffers. In this study, overloaded peak shapes resulting after injection of carefully pH matched samples close to the pK(a) of the chosen solute are investigated primarily on two columns; one hybrid silica C18 column (Kromasil Eternity) and one purely polymeric column (PLRP-S), the latter lacking C18 ligands. It was found that distorted peaks of the basic test compound appear even though there is no difference in pH between the injected sample solution and the eluent; the previous explanation to why these effects occur is based on a pH mismatch. Thus, the unusual band shapes are not due to an initial pH difference. Furthermore, it was observed that the effect does not appear on polymeric columns without C18 ligands, but only on columns with C18 ligands, independently of the base matrix (silica, hybrid silica, polymeric).     

Synthesis, characterization and in vitro antimicrobial study of bioactive polyesters derived from new biobased flame retardant aromatic diacid monomer containing taurine moiety

5-(2-tetrachlorophthalimidoethanesulfonamido) isophthalic acid (6), based on taurine, was simply prepared in three steps. Also a series of novel biologically active polyesters (PEs) were synthesized by the reaction of this monomer with several aromatic diols by step growth polymerization using tosyl chloride (TsCl)/dimethylformamide (DMF)/pyridine (Py) system as a condensing agent. The resulting new polymers were obtained in good to high yields with moderate inherent viscosities. All of the PEs were characterized by FT-IR and some of them were also characterized by ¹H NMR and elemental analyses methods. The thermal stability of PEs was evaluated with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques under a nitrogen atmosphere and it was found that, they have moderate stability. Limiting oxygen index (LOI) of the polymers confirmed that the synthesized compounds have flame retardant properties. Soil bioactivity behavior of the diacid 6 and all of PEs derived from this diacid was investigated in culture media and it was found that synthesized diacid monomer 6 and all PEs have possibility of biodegradation under natural microbial environmental.     

Reciprocating Motion of a Self‐Propelled Object on a Molecular Layer

The mode change of a simple autonomous motor depending on the nature of a monolayer on water is investigated. A camphor disk is floated on a molecular layer of N‐stearoyl‐p‐nitroaniline (C₁₈ANA), which gives a surface‐pressure (π)–area per molecule (A) isotherm with a local maximum and a local minimum. The nature of the camphor motion changes depending on A, and in particular, reciprocating motion is observed at a lower A while cutting out its own trajectory of motion. The characteristic motion of a camphor disk depending on A is discussed in relation to the π–A isotherm of C₁₈ANA and the influence of the molecular interaction between molecules on the driving force of motion.     

Mass Spectrometric Analysis of Site Specific Deuterated Zervamicins

Abstract

Zervamicin is a 16-residue antibiotic peptide produced by Em. salmosynnemata. It belongs to a broad class of α-helical peptides which interact directly with the lipid bilayer. In our strategy to investigate the structure and dynamics of membrane-associated peptides we follow an approach based on site-specific isotope labelling and measurement by means of stable isotope sensitive techniques. We have accurately determined the exact postion of deuterium atoms at Gln-11 of the antibiotic zervamicin-IIB from the FAB collision-induced dissociation FAB-mass spectra of the sodium cationized molecules.     

Phase transitions in triammonium hydrogen disulphate: Crystal structure of an intermediate stable phase at −90°C

Abstract

Triammonium hydrogen disulphate, (NH₄)₃H(SO₄)₂, belongs to the family of crystal structures M₃H(XO₄)₂ (with M = NH₄, K, Rb, Cs, and X = S, Se) which display super protonic phases at elevated temperatures, while at room temperature these are relatively poor proton conductors. The crystal structure of triammonium hydrogen disulphate has been determined by X-ray diffraction at ?90°C and the variation in the characteristics of the hydrogen bond is discussed in comparison with that of the structures at ?110° C and room temperature. It is concluded that the mechanics involving the proton migration in such systems is realised in terms of the variations in the hydrogen bond features with temperature.     

Viscous and inviscid interactions of an oblique shock with a flexible panel

The complex self-sustained oscillations arising from the interaction of an oblique shock with a flexible panel in both the inviscid and viscous regimes have been investigated numerically. The aeroelastic interactions are simulated using either the Euler or the full compressible Navier–Stokes equations coupled to the nonlinear von Karman plate equations. Results demonstrate that for a sufficiently strong shock limit-cycle oscillations emerge from either subcritical or supercritical bifurcations even in the absence of viscous separated flow effects. The critical dynamic pressure diminishes with increasing shock strength and can be much lower than that corresponding to standard panel flutter. Significant changes in panel dynamics were also found as a function of the shock impingement point and cavity pressure. For viscous laminar flow above the panel without a shock, high-frequency periodic oscillations appear due to the coupling of boundary-layer instabilities with high-mode flexural deflections. For a separated shock laminar boundary layer interaction, non-periodic self-excited oscillations arise which can result in a significant reduction in the extent of the time-averaged separation region. This finding suggests the potential use of an aeroelastically tailored flexible panel as a means of passive flow control. Forced panel oscillations, induced by a specified variable cavity pressure underneath the panel, were also found to be effective in reducing separation. For both inviscid and viscous interactions, the significant unsteadiness generated by the fluttering panel propagates along the complex reflected expansion/recompression wave system.