Motion studies of high current arcs using an optical fibre array imaging system

This paper presents an integrated portable measurement system for thestudy of high speed and high temperature unsteady plasma flows such as thosefound in the vicinity of high current switching arcs. The system permits direct andnon-intrusive measurement of arc light emission images with a capture rate of 1million images per second (1MHz), and 8 bit intensity resolution. Novel softwaretechniques are reported to measure arc trajectories. Results are presented on singlehigh current (2kA) discharge events where the electrode and arc runner surfaces areinvestigated using 3D laser scanning methods; such that the position of the arc rootson the runner can be correlated to the measured trajectories. The results showevidence of the cathode arc root stepping along the arc runners<br/

Motion studies of high current arcs using an optical fibre array imaging system

This paper presents an integrated portable measurement system for thestudy of high speed and high temperature unsteady plasma flows such as thosefound in the vicinity of high current switching arcs. The system permits direct andnon-intrusive measurement of arc light emission images with a capture rate of 1million images per second (1MHz), and 8 bit intensity resolution. Novel softwaretechniques are reported to measure arc trajectories. Results are presented on singlehigh current (2kA) discharge events where the electrode and arc runner surfaces areinvestigated using 3D laser scanning methods; such that the position of the arc rootson the runner can be correlated to the measured trajectories. The results showevidence of the cathode arc root stepping along the arc runners<br/

Motion studies of cathode roots in high current arcs using an optical fibre array based imaging system

This paper presents an integrated portable measurement system for the study of high speed and high temperature unsteady plasma flows such as those found in the vicinity of high current switching arcs. The system permits direct and non-intrusive measurement of arc light emission images with a capture rate of 1 million images per second (1MHz), and 8 bit intensity resolution. Novel software techniques are reported to measure arc trajectories. Results are presented on single high current (2kA) discharge events where the electrode and arc runner surfaces are investigated using 3D laser scanning methods; such that the position of the arc roots on the runner can be correlated to the measured trajectories. The results show evidence of the cathode arc root stepping along the arc runners, and regions of where the arc runner is eroded by a stationary arc

Anticancer RuII and RhIII Piano-Stool Complexes that are Histone Deacetylase Inhibitors

The first examples of RuII and RhIII piano-stool complex histone deacetylase (HDAC) inhibitors are presented. The novel complexes have antiproliferative activity against H460 non-small-cell lung carcinoma cells that is comparable to the clinically used HDAC inhibitor suberoylanilide hydroxamic acid (SAHA). Strong evidence for HDAC inhibition as a primary mechanism of action is provided. The complexes reported here represent an important step towards the design of highly active and selective HDAC inhibitors

Calculation of NMR Properties of Solitons in Superfluid 3He-A

Superfluid 3He-A has domain-wall-like structures, which are called solitons. We calculate numerically the structure of a splay soliton. We study the effect of solitons on the nuclear-magnetic-resonance spectrum by calculating the frequency shifts and the amplitudes of the soliton peaks for both longitudinal and transverse oscillations of magnetization. The effect of dissipation caused by normal-superfluid conversion and spin diffusion is calculated. The calculations are in good agreement with experiments, except a problem in the transverse resonance frequency of the splay soliton or in magnetic-field dependence of reduced resonance frequencies.Comment: 15 pages, 10 figures, updated to the published versio

Kinetics of Ordering in Fluctuation-Driven First-Order Transitions: Simulations and Dynamical Renormalization

Many systems where interactions compete with each other or with constraints are well described by a model first introduced by Brazovskii. Such systems include block copolymers, alloys with modulated phases, Rayleigh-Benard Cells and type-I superconductors. The hallmark of this model is that the fluctuation spectrum is isotropic and has a minimum at a nonzero wave vector represented by the surface of a d-dimensional hyper-sphere. It was shown by Brazovskii that the fluctuations change the free energy structure from a $\phi ^{4}$ to a $\phi ^{6}$ form with the disordered state metastable for all quench depths. The transition from the disordered to the periodic, lamellar structure changes from second order to first order and suggests that the dynamics is governed by nucleation. Using numerical simulations we have confirmed that the equilibrium free energy function is indeed of a $\phi ^{6}$ form. A study of the dynamics, however, shows that, following a deep quench, the dynamics is described by unstable growth rather than nucleation. A dynamical calculation, based on a generalization of the Brazovskii calculations shows that the disordered state can remain unstable for a long time following the quench.Comment: 18 pages, 15 figures submitted to PR

Periodic Vortex Structures in Superfluid 3He-A

We discuss the general properties of periodic vortex arrangements in rotating superfluids. The different possible structures are classified according to the symmetry space-groups and the circulation number. We calculate numerically several types of vortex structures in superfluid 3He-A. The calculations are done in the Ginzburg-Landau region, but the method is applicable at all temperatures. A phase diagram of vortices is constructed in the plane formed by the magnetic field and the rotation velocity. The characteristics of the six equilibrium vortex solutions are discussed. One of these, the locked vortex 3, has not been considered in the literature before. The vortex sheet forms the equilibrium state of rotating 3He-A at rotation velocities exceeding 2.6 rad/s. The results are in qualitative agreement with experiments.Comment: 13 pages, 7 figures, http://boojum.hut.fi/research/theory/diagram.htm

Multistable Pulse-like Solutions in a Parametrically Driven Ginzburg-Landau Equation

It is well known that pulse-like solutions of the cubic complex Ginzburg-Landau equation are unstable but can be stabilised by the addition of quintic terms. In this paper we explore an alternative mechanism where the role of the stabilising agent is played by the parametric driver. Our analysis is based on the numerical continuation of solutions in one of the parameters of the Ginzburg-Landau equation (the diffusion coefficient $c$), starting from the nonlinear Schr\"odinger limit (for which $c=0$). The continuation generates, recursively, a sequence of coexisting stable solutions with increasing number of humps. The sequence "converges" to a long pulse which can be interpreted as a bound state of two fronts with opposite polarities.Comment: 13 pages, 6 figures; to appear in PR

Spin-Peierls transition in NaV2O5 in high magnetic fields

We investigate the magnetic field dependence of the spin-Peierls transition in NaV$_2$O$_5$ in the field range 16T-30T. The transition temperature exhibits a very weak variation with the field, suggesting a novel mechanism for the formation of the spin-Peierls state. We argue that a charge ordering transition accompanied by singlet formation is consistent with our observations.Comment: 4 pages, 3 figures, final version to appear in Phys. Rev. B (RC