Monte Carlo study of the two-dimensional spin-1/2 XY model

The generalized Trotter formula is used to map the two-dimensional spin-1/2 XY model onto a three-dimensional Ising model with complicated many-spin interactions. This relationship is used to construct an efficient Monte Carlo algorithm. Simulation data for the specific heat and vortex correlation functions give strong evidence for the existence of a phase transition.     

Fluctuation measurements with emissive probes in tokamaks

A new probe head, composed of two electro-emissive probes and two Langmuir probes has been designed to measure edge fluctuations in the CASTOR tokamak. In this contribution, only one Langmuir and one electron-emissive probe are used to measure the temperature and potential fluctuations and the phase angle between them.     

A novel approach to direct measurement of the plasma potential

A novel probe and approach to the direct measurements of the plasma potential in a strong magnetic field is suggested. The principle of this method is to reduce the electron saturation current to the same magnitude as that of the ion saturation current. In this case, the floating potential of the probe becomes indentical to the plasma potential. This goal is attained by a shield, which screens off an adjustable part of the electron current from the probe collector due to the much smaller gyro-radius of the electrons. First systematic measurements have been perfomred in the CASTOR tokamak.     

New NHR Techniques for Structure Determination and Resonance Assignments of Complex Carbohydrates

Abstract

This paper describes several new NMR techniques for structure determination and spectral assignment of polysaccharides. Positions of linkages between sugar units can be determined unambigously and with high sensitivity using a modified version of the well known INEPT experiment. A new two-dimensional experiment is shown to provide excellent resolution and sensitivity in correlating ¹H and ¹³C chemical shifts.     

Development and validation of a liquid chromatography-electrospray tandem mass spectrometry method for mebendazole and its metabolites hydroxymebendazole and aminomebendazole in sheep liver

A quantitative liquid chromatography-electrospray tandem mass spectrometry method for the determination of mebendazole and its hydrolysed and reduced metabolites in sheep liver has been developed and validated. The benzimidazole substances were extracted with ethyl acetate after the sample mixture had been made alkaline. The HPLC separation was performed on a reversed-phase C18 column with gradient elution using a mobile phase consisting of water containing 0.1% formic acid and acetonitrile. The analytes were detected after atmospheric pressure electrospray ionization on a tandem quadrupole mass spectrometer in MS-MS mode. The components were measured by the MS-MS transitions of the molecular ion to the two most abundant daughter ions. The detection limits are lower than 1 microg kg(-1). For this application, the validation limit was set at 50 microg kg(-1). The examined validation parameters were in accordance with the permitted tolerances ranges stipulated in the proposed new European validation criteria for residue surveillance. For the three analytes, the overall recovery was higher than 90%. The RSD for the repeatability ranged from 5 to 11%. The range for the within-laboratory reproducibility was between 2 and 17%. The decision limits for mebendazole, the hydrolysed and the reduced metabolite were 56.6, 61.8 and 64.2 microg kg(-1), respectively. The detection capabilities for these substances were 60.0, 86.1 and 90.9 microg kg(-1), respectively.     

Mathematical model of suspension flocculation kinetics

A mathematical model of suspension flocculation kinetics which describes its evolution in a wide time interval, and later stages is presented. The rate constant of floc formation has been found. The calculated dependence of particle number in volume unit on time correlates well with experimental data.