A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.     

Determination of amount of N2O impurity in nitric oxide by spectrophotometric analysis

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 2, pp. 283–286, February, 1988.     

Multiple absorption and dissociation of trifluoromethylhypofluorite under the effect of pulsed CO2 laser radiation

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 753–758, May, 1991.     

Mechanisms of defibrillation by standing waves in the bidomain ventricular tissue with voltage applied in an external bath

Standing waves of depolarisation produced by periodic low-voltage driving eliminate propagation activity in the heart, thus providing a defibrillating effect. The phenomenon cannot be reproduced by mono- or bidomain models of cardiac tissue, where voltage perturbations decay exponentially with a space constant λ₁≈1 mm. Extension of the bidomain model taking into account effects of the external bathing medium allows simulation of the standing waves which eliminate spiral wave activity in the tissue. Mechanisms of such a defibrillating effect can be explained by the existence of an additional, unusually long space constant, λ₂≈20 mm, in the bidomain model with a bath, which emerges due to redistribution of the applied voltage by the external conductive medium.     

Collisional dissociation for difluoromethylene bishypofluorite on excitation by a pulsed CO2 laser

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 951–954, June, 1991.     

Justification of the Kirchhoff hypotheses and error estimation for two-dimensional models of anisotropic and inhomogeneous plates, including laminated plates

Asymptotic analysis of the problem describing deformation ofa thin cylindrical plate with clamped lateral side is performed.The problem is considered under the most general statement withthe plate being laminated and consisting of an arbitrary numberof nonhomogeneous and anisotropic (21 elastic moduli) layers.Explicit integral representations of the differential operatorswhich form the two-dimensional model of the plate are derived.In the case when the elastic moduli of each of the layers areconstant, these integral representations turn into algebraicones. The asymptotic procedure is justified with the help ofa weighted inequality of Korn's type. The error estimates obtainedgive a rigorous mathematical proof of both of Kirchhoff's hypotheses(kinematic and static) and shed light on the well-known intrinsicinconsistency of two of the hypotheses.     

Can colliding nerve pulses be reflected?

A new effect not previously observed is predicted on the basis of numerical experiments with the Hodgkin-Huxley equations [A. L. Hodgkin and A. F. Huxley, J. Physiol. 117, 500 (1952)], which describe quantitatively the dynamics of generation, propagation and interaction of nerve pulses: colliding nerve pulse reflection. The range of governing parameters in which the effect might be revealed in real experiments is indicated. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 7, 553–558 (10 April 1997)     

Beyond the Kuramoto-Zel’dovich theory: Steadily rotating concave spiral waves and their relation to the echo phenomenon

In numerical experiments with the Fitzhugh-Nagumo set of reaction-diffusion equations describing two-dimensional excitable media, unusual solutions are found that correspond to a concave spiral wave steadily rotating round a circular obstacle in a finite-size medium. Such a wave arises in the region of parameters corresponding to the solitonlike regime (see text); it appears due to the interaction between the peripheral areas of a “seed” spiral wave with a convex front and the echo waves incoming from the outer boundaries of a medium. The solutions obtained are in contradiction with intuition and represent a numerical counterexample to the known theories that forbid steadily moving excitation waves with concave fronts. Nevertheless, a concave spiral wave is a stable object; being transformed to the usual spiral wave with a convex front by suppressing echo at the outer boundaries of the medium, it is again recovered upon restoring the echo conditions. In addition to the single-arm spiral concave wave, solutions are obtained that describe multiarm waves of this type; for this reason, the concave fronts of these waves are a coarse property.     

Enhanced self-termination of re-entrant arrhythmias as a pharmacological strategy for antiarrhythmic action

Ventricular tachycardia and fibrillation are potentially lethal cardiac arrhythmias generated by high frequency, irregular spatio-temporal electrical activity. Re-entrant propagation has been demonstrated as a mechanism generating these arrhythmias in computational and in vitro animal models of these arrhythmias. Re-entry can be idealised in homogenous isotropic virtual cardiac tissues as spiral and scroll wave solutions of reaction-diffusion equations. A spiral wave in a bounded medium can be terminated if its core reaches a boundary. Ventricular tachyarrhythmias in patients are sometimes observed to spontaneously self-terminate. One possible mechanism for self-termination of a spiral wave is meander of its core to an inexcitable boundary. We have previously proposed the hypothesis that the spatial extent of meander of a re-entrant wave in the heart can be directly related to its probability of self-termination, and so inversely related to its lethality. Meander in two-dimensional virtual ventricular tissues based on the Oxsoft family of cell models, with membrane excitation parameters simulating the inherited long Q-T syndromes has been shown to be consistent with this hypothesis: the largest meander is seen in the syndrome with the lowest probability of death per arrhythmic episode. Here we extend our previous results to virtual tissues based on the Luo-Rudy family of models. Consistent with our hypothesis, for both families of models, whose different ionic mechanisms produce different patterns of meander, the LQT virtual tissue with the larger meander simulates the syndrome with the lower probability of death per episode. Further, we search the parameter space of the repolarizing currents to find their conductance parameter values that give increased meander of spiral waves. These parameters may provide targets for antiarrhythmic drugs designed to act by increasing the likelihood of self-termination of re-entrant arrhythmias. (c) 2002 American Institute of Physics.