Electrical characterization of very-narrow-gap bulk HgCdTe single crystals by variable magnetic field hall measurements

Variable-magnetic-field Hall measurements (0 to 1.5 T) are performed on very-narrow-gap bulk-grown Hg_1−xCd_xTe single crystals (0.165 ≤ x ≤ 0.2) at various temperatures (10 to 300K). The electron densities and mobilities are obtained within the one-carrier (electrons) approximation of the reduced-con-ductivity-tensor scheme. The present data together with the selected data set reported by other workers exhibit a pronounced peak when the electron mobility is plotted against the alloy composition x-value which has been predicted to be due to the effective-mass minimum at the bandgap-crossing (E_g ≈ 0). The observed position (x ≈ 0.165), height (≈4 x 10² m²Vs), and width (≈0.01 in x) of the mobility-peak can be explained by a simple simulation involving only ionized-impurity scattering. A lower bound of the effective mass is introduced as a fitting parameter to be consistent with the finiteness of the observed electron mobility and is found to be of the order of 10⁻⁴ of the mass of a free electron.     

The Effect of Organic Ligands on the Rate of Loss of Phenylmercuric Nitrate into Rubber Closures and Plastic Containers

The effect of the presence of various organic compounds containing a variety of functional groups on the rate of loss of phenylmericuric (PM) nitrate into plastic containers and rubber closures has been investigated. The presence of organic compounds profoundly influenced the loss of the phenylmercuric nitrate, that loss being dependent upon their chemical structure and concentration. This effect explains the unpredictability of the loss of PM nitrate into polymer matrices from pharmaceutical products.     

Effect of beam voltage on the properties of aluminium nitride prepared by ion beam assisted deposition

The effects of nitrogen-beam voltage on the structure, stress, energy band gap and hardness of AIN thin films deposited on Si (111), Si (100) and sapphire (0001) by ion beam assisted deposition (IBAD) are reported. As the nitrogen-beam voltage was increased from 50 to 200 V, the stress and disorder in the AIN films increased as determined by X-ray diffraction, FTIR and Raman spectroscopy. The preferred orientation of the film's c-axis changed from completely normal to the film at 100 V, to a mixture of normal and in the plane of the film at 200 V. For AIN films deposited under the same conditions, the films were more highly oriented on sapphire (0001) than in Si (111). The hardness of the films increased from 18.2 to 23.7 GPa with the nitrogen-beam voltage, and possible reasons for this change in hardness are considered.     

A chemical method for preparation of cobalt oxide thin films

A very simple method has been developed for the preparation of cobalt oxides, CoO(OH) and Co₃O₄, thin films on glass substrates using cobalt(II) chloride and ammonia as reacting agents. These materials were characterized by optical and electrical measurements. CoO(OH) films are insulating and have DC dielectric breakdown at about 3700 V / mm when measurements are made using silver print electrodes placed at various spacings on the film. Electrical resistivity of Co₃O₄ is 2.5 ω m. Analysis of the absorption spectra shows that CoO(OH) and CO₃O₄ have optical band gaps of 2.36 eV and 1.65 eV respectively. Spectral variation of the optical constants of these materials have also been measured.     

An adaptive plasma glucose controller based on a nonlinearinsulin/glucose model

The design of plasma glucose controllers traditionally relies on linear approaches. The implementation of an appropriate nonlinear model of the insulin/glucose regulatory system into an adaptive controller should predict the insulin-dependent glucose removal more reliably and hence provide better control over a wide spectrum of insulin signals. A discretized form of the model leads to a two-step procedure. First, the measured plasma glucose levels associated with the erogeneous glucose infusion rates are used in the estimation of the past removal rates which, in turn, can be expressed as a weighted sum of past insulin inputs and previous values of the removal rate. Parameters of the sum are adjusted on-line by a recursive method of estimation which features a prefiltering of data to account for a corrupting coloured process noise. The same equation is in turn used to predict the time course of the insulin-dependent fractional rate of glucose removal. The performance of the controller. Tested in vivo in three pigs, is presented for various intravenous or subcutaneous rapid injections and staircase infusions of insulin. Plasma glucose is maintained at an average level of 99.9±8.7% of the target value (% set point±coefficient of variation). The controller reacts promptly to large and rapid variations in insulin action. Although control improves with the number of glucose measurements, the prediction of glucose removal allows for some flexibility in the monitoring of the plasma glucose. Sampling frequency varied from a 2 min interval during transient periods to 7 min as steady states were reached