Swelling behavior of pervaporation membranes in ethanol–water mixtures

Novel hydrophobic composite membranes made of crosslinked poly(dimethylsiloxane) and poly(methyl hydrogen siloxane) (PDMS–PMHS) with various amounts of catalyst were prepared. Pervaporation experiments with water–ethanol mixtures revealed that an optimum ratio of catalyst to polymer base existed. Both swelling behavior and dynamic–mechanical properties of these silicone films were studied. The swelling experiments in different mixtures of ethanol and water determined that ethanol is preferentially sorbed and that the membranes are only capable to absorb a limited quantity of solvent. Equilibrium swelling data were also used in combination with the analysis of the viscoelastic relaxation of the swollen samples to obtain the dependence of the dynamic–mechanical properties of the silicone films on the quantity of permeants sorbed into the membrane. It was observed that the permselective parameters were related with the mobility of the chains and the free volume. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1424–1433, 2000     

Tailored Magnetic Fields in the Melt Extraction of Metallic Filaments

Porous bodies that are resistant to corrosion at high temperatures and thermal shock may be produced from metallic fibers. In order to accomplish reasonable homogeneity and high porosity, the cross-sectional area of the fibers and the width of distribution thereof need to be small. This article studies two techniques for making fibers. Melt extraction out of a crucible yields filaments with a typical diameter ranging from 50 to 200 μm, which is too thick. Also patented for a long time is the extraction from a pendant drop. Even though relatively fine fibers can be manufactured with this method, it never exceeded crucible extraction with respect to industrial importance owing to the low productivity of the process. The present article addresses the drawbacks of both variants of melt extraction of metallic filaments. Because metallic melts are electrically conducting, the use of magnetic fields allows for contactless process optimization. It is well believed that increasing the extraction speed diminishes the fiber diameter. Being not always true, at least in the case of crucible melt extraction, as indicated by the present findings, however, undesired fluid flow, i.e., turbulence, imposes an upper limit on the rotation rate of the extraction wheel. Application of a static magnetic field leads to both higher wheel speed and thinner filaments. The low productivity of extraction from the molten tip of a rod suffers from the fact that only one melt drawing edge can be used. As the bare rod is problematic with respect to heating its tip in contact with the extraction wheel, it is challenging to melt the entire edge of a sheet. A special design of the induction-heating magnetic field is also proposed to solve also this task. This article is based on a presentation given at the International Symposium on Liquid Metal Processing and Casting (LMPC 2007) which occurred in September 2007 in Nancy, France.     

Estimation of cardiac function from computer analysis of thearterial pressure waveform

This paper presents a method for estimating parameters of a cardiovascular model, including the left-ventricular function, using the sequential quadratic programming (SQP) and the least minimum square (LMS) algorithms. In a first stage, a radial arterial-pressure waveform with corresponding cardiac output are used to automatically seek the set of parameters of the diastolic model. Computer simulation of the model using these parameters generate a pressure waveform and a cardiac output very close to those used for the estimation. In a second stage, the estimated arterial load parameters are used to select the best left-ventricular model function, from four different possibilities, and to estimate its optimum parameter values. The method has been tested numerically and applied to real cases, using data obtained from cardiovascular patients. It has also been subjected to preliminary validation using data obtained from laboratory dogs, in which cardiovascular function was artificially altered     

A neutralizing anti-TGF-beta1 antibody promotes proliferation of CD34+Thy-1+ peripheral blood progenitors and increases the number of transduced progenitors

To reduce the time of computation of a motor unit potential (MUP), the shape of intracellular action potential (IAP) and (or) MU anatomy are generally simplified. A method of MUP presentation is suggested. It provides accuracy of the MUPs calculated for any distance and size of rectangular electrodes together with considerably reduced computational load and time. No simplification of the IAP shape or location of muscle fibres of different diameters and lengths is required. The MUP generated by N temporally and spatially dispersed single fibre action potentials is considered to be the output signal of a linear time-shift invariant system for potential generation. The input signal is the first temporal derivative of the IAP. The common impulse response (CIR) is the sum of potentials produced at the electrode by N pairs of dipoles propagating from the motor end-plates to the ends of the corresponding fibres. The potentials of each dipole at the rectangular plate electrode are determined analytically. Thus, the MUP is calculated as a single convolution between the input signal and CIR for a rectangular electrode of any size.     

Liquid metal model experiments on casting and solidification processes

This paper is concerned with laboratory studies using liquid metals with T _melt ≤ 300°C to model the flow of metals in industrial processes. Considering three selected examples the main features of such cold models are described. In the first instance we examine an aluminium alloy investment casting process. The requirement of reducing high flow velocities was achieved by the application of a static magnetic field. Local velocity measurements as well as integrated flow rate determination were carried out using eutectic InGaSn (T _melt = 10°C). Secondly, model experiments were performed on the electromagnetic stirring of liquid metals in a cylindrical cavity. We applied a rotating magnetic field (RMF) and a travelling magnetic field and recorded flow maps by means of ultrasonic Doppler velocimetry. With the goal of an efficient 3D-mixing, measurements were made using a combination of both field types with promising results. Thirdly, we report on systematic studies of the effect of an RMF on the solidification of a PbSn alloy. Directional solidification experiments demonstrate the influence of the electromagnetically driven convection on the resulting microstructure.     

Estimation of Regional Myocardial Blood Flow Using Computed Tomography: A Stochastic Formulation

Previously, we have presented a deterministic formulation for estimation of regional myocardial blood flow (RMBF) using X-ray computed tomography (CT) [1]. Quantitation of RMBF with the deterministic theory requires computing the zeroth and first moments of extrapolated myocardial contrast enhancement (CT numbers versus time) curves. This extrapolation is a potential source of error in the presence of recirculation, especially in myocardial regions with reduced flows. In the present paper, a stochastic approach for parameter estimation is undertaken, which renders an optimal RMBF estimate based upon the least squares error criteria. Random measurement errors are minimized, curve extrapolation is avoided, and the accuracy of RMBF estimates is predicted. The advantages of the stochastic versus the deterministic approach are demonstrated in the results obtained from the in vivo estimation of RMBF in normal and acutely ischemic myocardium of dogs.