In vitro measurement of myocardial impedivity anisotropy with a miniature rectangular tube

Due to rapid change of fiber orientation, it is difficult to measure myocardial impedivity separately in a longitudinal or transverse fiber direction without mutual influence in the two directions. Previously published values of the longitudinal and the transverse myocardial impedivity were derived indirectly from measurements that mixed the impedivity in all directions. Those values are questionable because the derivations were based on a simplified uniform myocardial fiber model. In this paper, a miniature rectangular tube was devised to facilitate direct measurement of myocardial impedivity in a uniform fiber direction. The average transverse-to-longitudinal ratio of the measured in vitro swine myocardial impedivity was about 1.66 from 1 Hz to 1 kHz and dropped to 1.25 at 1 MHz. The result is important for accurate modeling of the electrical property of myocardium in biomedical research of radio-frequency cardiac catheter ablation.     

Thermophysical Properties of Binary and Ternary Fluid Mixtures from Dynamic Light Scattering

Several thermophysical properties of R507, a binary refrigerant mixture, and R404A, a ternary mixture, have been determined by dynamic light scattering (DLS), in both the liquid and the vapor states, along the saturation line approaching the vapor–liquid critical point. Data for the thermal diffusivitya and sound speed c _S cover a range of temperatures down to 270K, and data for the surface tension and kinematic viscosity down to 230K. For both mixtures the behavior of all properties determined can be correlated well by the mass-weighted sum of the respective pure component data, when all data are represented as a function of the reduced temperature.     

Is there the potential for an epidemic of variant Creutzfeldt–Jakob disease via blood transfusion in the UK?

The discovery of three individuals suspected to have contracted variant Creutzfeldt-Jakob disease (vCJD) through blood transfusions has heightened concerns that a secondary epidemic via human-to-human transmission could occur in the UK. The Department of Health responded immediately to this threat by banning those who had received blood transfusions since 1980 from donating blood. In this paper, we conduct a sensitivity analysis to explore the potential size of a blood-borne vCJD epidemic and investigate the effectiveness of public health interventions. A mathematical model was developed together with an expression for the basic reproduction number (R0). The sensitivity of model predictions to unknown parameters determining the transmission of vCJD via infected blood was assessed under pessimistic modelling assumptions. We found that the size of the epidemic (up until 2080) was bounded above by 900 cases, with self-sustaining epidemics (R0>1) also possible; but the scenarios under which such epidemics could arise were found to be biologically implausible. Under optimistic assumptions, public health interventions reduced the upper bound to 250 and further still when only biologically plausible scenarios were considered. Our results support the belief that scenarios leading to large or self-sustaining epidemics are possible but unlikely, and that public health interventions were effective.     

G?rungserscheinungen

Ohne Zusammenfassung     

Thermophysical Properties of Fluids from Dynamic Light Scattering

In a continuous development for more than three decades, dynamic light scattering (DLS) has evolved into a versatile and powerful technique for the determination of transport and other thermophysical properties of fluids. The success is founded on its application in a macroscopic thermodynamic equilibrium, i.e., without the need for employing external gradients, to determine a large variety of properties, which can be derived, in some instances even simultaneously, by an appropriate experimental approach and a corresponding signal analysis. The principles, essential features, and variants of the technique are reviewed, and a survey on the determination of various desired transport and thermophysical properties is given, both for the application of light scattering from bulk fluids and for the variant of surface light scattering (SLS). The stage of development and the corresponding uncertainties are discussed for the measurement of the individual quantities, and the performance of the method is demonstrated by representative experimental results for relevant fluids.     

A fully automatic peak-search program for the evaluation of Gauss-shaped diffraction patterns

Diffraction patterns (X-rays or neutrons) often contain regions of overlapping, unresolved peaks. When using energy-dispersive techniques with solid state detectors the degree of overlap is especially high because of the poor resolution of such detectors. Profile analysis then offers the possibility to overcome, or at least reduce this drawback. In this paper a peak-search program is represented for fully automatic separation of the individual peaks. Only the instrumental parameter fwhm (full width at half-maximum) and the recorded spectrum are required as input for the program. Results are given for orthorhombic MnSO₄.