The longitudinal electrical conductivity of metal-matrix composites at cryogenic temperature in the presence of a longitudinal magnetic field

We solve the Boltzmann equation in the relaxation time approximation with parallel E and B fields parallel to the continuous fibres reinforcing a metal matrix. It is shown that this solution is identical to that described by us elsewhere, except for the addition of the cyclotron frequency. The addition of the cyclotron frequency term shows that the electrons follow helical paths as they drift down the composite. The boundary considered is either the external or the internal surface of a cylinder representing the fibre. To apply this solution to metal-matrix composite materials we assumed that the cylindrical fibres are non-conducting cylinders in a matrix of pure crystalline metal. The electron mean free path is never greater than half the fibre separation distance. In a companion paper we discuss the application of this solution to metal-matrix composites.     

Online analysis of in vitro resistance to antimalarial drugs through nonlinear regression

Malaria remains one of the leading causes of morbidity and mortality worldwide which is partly due to the emergence of the parasite resistance to antimalarial drugs. In vitro testing of drugs allows an early detection of resistance. The common parameter used for the monitoring of resistance is the concentration that inhibits 50% of the parasite's activity (IC₅₀). Various methods of calculation are already used but none of them consider new available tools nor display the precision of IC₅₀ estimation. We proposed an approach based on the inhibitory sigmoid E_max model, which is often used in pharmacology, with estimation of IC₅₀ through nonlinear regression using a standard function of the R software. To facilitate the usage of that tool we have developed an online version available on the website ICEstimator (ICEstimator website http://www.antimalarial-icestimator.net/, 2009) [1]. This website is used by various teams in the world and the user can do the analysis without knowing R using the GUI. This article describes version 2.1 of this website and shows illustration on five different real examples.     

ST-Audit: guideline-based automatic auditing of electronic patient records

This work presents the ST-Audit system that audits a patient record for conformance to a particular clinical guideline. The system uses ST-Guide which models a guideline as a set of states and transitions. The audit system tries to find a path in the state/transition diagram that corresponds to the actions taken by the physician, taking into consideration issues such as the unavailability of all the data needed to evaluate the transitions. The system was used to audit an outpatient clinic regarding their procedure for hypertension treatment (using the VI JNC guideline for hypertension), and the results of the number of non-compliant actions were presented and discussed. A follow up auditing showed a small but statistically significant reduction on the number of non-compliant actions for patients treated after the first audit.     

NMR studies of supported metal catalysts

Oxide-supported metals constitute one of the most important classes of heterogeneous catalysts, and for this reason they have been investigated by many techniques: adsorption isotherms, IR of chemisorbed molecules, electron microscopy, EXAFS, etc. However, the fact that they have been studied by so many methods proves that no one technique is totally satisfactory. The physical and chemical properties of sufficiently small particles, in particular their magnetism, must depend on their size, whence the idea of using NMR to study them. Because of the theoretical and technical difficulties associated with the NMR detection of metals, and especially since only a few can be detected, NMR work has been mainly devoted to the indirect study of metallic properties, by the intermediary of easily detected chemisorbed phases (¹H, ¹³C) or of physically adsorbed probes (¹²⁹Xe). However, when the metal can be detected directly (mainly Pt), it is possible to relate the form of the NMR spectrum to the dispersion of the metal and to calculate the electron density of states at the Fermi level.     

Statistiques de la fonction de transfert par trajets multiples pour des largeurs de bande moyennes. Application à la prévision de la qualité

It is shown, from data gathered on three different test links, that multipath transfer functions on a medium bandwidth can be modelled with three parameters. Moreover, the model parameters follow similar probability laws on the three links, thus leading to a universalstatistical model. This statistical model depends on two independent parameters. When the two statistical parameters are known, the outage time of the link can be deduced from the model. A first estimation of these parameters can be inferred from the distribution law of the levels at fixed frequency. The application of the method to two particular cases is presented.     

Scalp Current Density Mapping: Value and Estimation from Potential Data

Scalp current density (SCD) makes possible the identification of scalp sources and sinks of current. SCD is reference independent and its peaks and troughs are sharper than those of the scalp potential (SP). SCD, by comparison to SP, reflects mainly the activity of cortical generators. SCD mapping appears to be a valuable tool to spatially split smeared SP distribution due to simultaneously active generators. The SCD map may be computed from any sufficiently smooth mathematical SP map. An evaluation of the error of SCD estimation is given for a surface spline method of interpolation of SP. An example of the simultaneous use of SP and SCD in the analysis of somatosensory evoked data is given.     

Evaluation of FFT-Based and Moder Parametrc Methods for the Spectral Analysis of Bioprosthetic Valve Sounds

The objective of this paper is to compare the performance of conventional FFT-based (basic periodogram and Welch's method) and modern parametric (all-pole and pole-zero modeling) methods in estimating the spectral distribution of cardiac bioprosthetic valve sounds, and for the extraction of the two most dominant frequency peaks (DFP). These methods were tested for stability by adding random noise and truncating the bioprosthetic valve closing sounds, and for reproducibility by measuring the variance of the spectra obtained from three consecutive recordings of each patient. Results from a group of 11 patients show that the basic periodogram and Steiglitz-McBride's method with maximum entropy (pole-zero modeling) provide the most consistent (minimal variance) estimates of the DFP's of the closing sounds. However, for estimating spectral distributions, the most stable methods appear to be the basic periodogram and Steiglitz-McBride's method with extrapolation to zero. The basic periodogram appears to be the best compromise to estimate both the spectral distribution and the DFP's of the bioprosthetic closing sounds.