Determination of carvedilol in human cardiac tissue by high-performance liquid chromatography

A new high-performance liquid chromatographic method has been developed for the determination of the beta-receptor blocker carvedilol in human cardiac tissue. After homogenizing tissue samples in a microdismembrator, carvedilol and the internal standard naftopidil are extracted with acetone. The extract is evaporated to dryness and reconstituted in a potassium acetate buffer of pH 3.5. Samples are cleaned up with solid-phase extraction columns. Carvedilol and the internal standard show recoveries of 69.8 +/- 12.2% and 63.9 +/- 9.34%, respectively. The linearity range for carvedilol is 0.01-0.35 ng/mg (parts per billion) tissue (wet weight), and the limit of quantitation is 0.01 ng/mg. The percentage coefficient of variation of the intra-assay varies between 1.45 and 5.38% and the interassay between 4.25 and 6.96%. To use as an application of the assay, the cardiac carvedilol tissue level in a patient on oral carvedilol therapy for congestive heart failure is reported.     

Recent results from the TCV tokamak

During the first two years of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1.0B _tor1.46T,I _p800kA,k2.05, –0.71. A new shape control algorithm, based on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates up to 1000s^–1 have been stabilized using the external coil system. Ohmic H-modes with Troyon factors ( _tor aB/I _p) up to two and densities up to 2.25×10²⁰m^–3, corresponding to the Greenwald limit, have been obtained in diverted discharges. Limiter H-modes with line averaged electron densities up to 1.7×10²⁰m^–3 have been obtained in elongated D-shaped plasmas with 360 kAI _P600 kA.Presented at 17^th Symposium Plasma Physics and Technology, Prague, June 13–16, 1995.This work was partly supported by the Fonds National Suisse de la Recherche Scientifique.     

Electrohydrodynamic instabilities in nematic liquid crystals under dichotomous parametric modulation

The onset of EHD instabilities in nematic liquid crystals driven by parametric modulation is investigated starting with the one-dimensional linear model of Dubois-Violette. The superposition of a constant electric field with a dichotomous (stochastic or periodic) field as well as the superposition of two dichotomous stochastic fields (pregaussian noise) are considered in detail. The experimentally observed discontinuous behaviour of the threshold (direct transition towards chaos) above a critical strength of the driving field and the dependence of the threshold curve on the correlation time of the noise can be explained qualitatively. Experiments to complete the phase diagram are proposed.     

Semiprimality and Nilpotency of Nonassociative Rings Satisfying x(yz) = y(zx)

In this article we study nonassociative rings satisfying the polynomial identity x(yz) = y(zx), which we call “cyclic rings.” We prove that every semiprime cyclic ring is associative and commutative and that every cyclic right-nilring is solvable. Moreover, we find sufficient conditions for the nilpotency of cyclic right-nilrings and apply these results to obtain sufficient conditions for the nilpotency of cyclic right-nilalgebras.     

One-dimensional random field Ising model and discrete stochastic mappings

Previous results relating the one-dimensional random field Ising model to a discrete stochastic mapping are generalized to a two-valued correlated random (Markovian) field and to the case of zero temperature. The fractal dimension of the support of the invariant measure is calculated in a simple approximation and its dependence on the physical parameters is discussed.Contribution to the symposium Statistical Mechanics of Phase Transitions—Mathematical and Physical Aspects, Trebo, CSSR, September 1–6, 1986.     

Laser diffraction by periodic dynamic patterns in anisotropic fluids

This paper describes the application of a laser diffraction technique to the study of electroconvection in nematic liquid crystal cells. It allows a real-time quantitative access to pattern wave lengths and amplitudes. The diffraction profile of the spatial periodic pattern is calculated and compared quantitatively to experimental intensity profiles. For small director tilt amplitudes , the phase grating generated in normally incident undeflected light and the first order term correction from light deflection is derived analytically. It yields an dependence of the diffracted intensity I on the amplitude of director deflections. For larger director tilt amplitudes, phase and amplitude modulations of deflection of light in the inhomogeneous director field are calculated numerically. We apply the calculations to the determination of the director deflection and measure growth and decay rates of the dissipative patterns under periodic excitation. Real time analysis of pattern amplitudes under stochastic excitation is demonstrated.Received: 23 May 2003, Published online: 2 October 2003PACS: 42.70.Df Liquid crystals - 47.20.-k Hydrodynamic stability - 78.20.-e Optical properties of bulk materials and thin films     

Adaptive λ-tracking-control for relative degree two systems with application to bio-inspired sensors

This paper deals with the (adaptive) control of a sensory system, which is inspired by biological ideas concerning the behaviour of a tactile hair or sensillum. The cells for reception of vibrations adjust their sensibility to a continuing excitement, such that this permanent excitation of the whole system tends to the rest position. Hence, this biological paradigm demonstrates a fundamental principle: adaption. In general, one cannot expect to have complete information about a sophisticated mechanical or biological system, but instead only structural properties (e.g. minimum phase condition, strict relative degree) are known. Therefore, the method of adaptive control is chosen in this paper. The aim is to design a universal adaptive controller, which learns from the behaviour of the system, so automatically adjusts its parameters and achieves a pre-specified control objective. Since we deal with a non-linearly perturbed multi-input, multi-output system, which is not necessarily autonomous, particular attention is paid to the λ-tracking control objective. Simple adaptive servomechanisms, which achieve tracking of a given reference signal for any pre-specified accuracy (tracking-error) λ, are introduced. We stress that the introduced adaptive controllers consist of very simple feedback mechanisms and adaptation rules. These controllers are only based on information about the output of the system – no knowledge of system parameters is required.