Effects on Micro-Surface Texturing of Mg/B4C Matrix Composites Under Dry Sliding Wear Condition

Transactions of the Indian Institute of Metals - The predominant objective of this exploration is analyses of the wear conduct of pure Mg and Mg–B4C (5–15%) composites developed by...     

Quantitative structure-pharmacokinetic relationship modelling.

This article presents the current methods in quantitative structure-pharmacokinetic relationship (QSPkR) modelling along with examples using chemicals of toxicological significance. The common method involves: (i) collecting pharmacokinetic data or determining pharmacokinetic parameters (e.g. elimination half-life, volume of distribution) by fitting to experimental data; and (ii) associating them with the structural features of chemicals using a Free-Wilson model. Such QSPkRs have been developed for a few series of chemicals but their usefulness is limited to the exposure scenario and conditions under which the experimental data were originally collected. The alternative approach involves the development of quantitative structure-property relationship (QSPR) models for parameters, blood:air partition coefficient, tissue:blood partition coefficient, maximal velocity for metabolism and Michaelis affinity constant, of physiologically-based pharmacokinetic (PBPK) models which are useful for conducting species, route, dose and scenario extrapolations of the tissue dose of chemicals. Mechanistic QSPRs are available for predicting tissue:blood and blood:air partition coefficients from molecular structure information of chemicals, whereas such approaches are not currently available for hepatic metabolism parameters. However, at the present time, the pharmacokinetics of inhaled volatile organic chemicals can be simulated adequately by considering the physiological limits of the hepatic extraction ratio (0-1) and molecular structure-based estimates of partition coefficients in the PBPK model. This current state-of-the-art of structure-based modelling of pharmacokinetics will advance with the development of QSPRs for other chemical-specific parameters of PBPK models. Integrated QSPR-PBPK modelling should facilitate the identification of chemicals of a family that possess desired properties of bioaccumulation and blood concentration profile in both test animals and humans.     

Kinetics of polymerisation of furfuryl alcohol in aqueous solution

Kinetic information on the polymerisation of furfuryl alcohol catalysed by Clark-Lubs' aqueous buffer in the pH range of 1.0–2.2 has been derived from the rate of increase of colour intensity measured with a photoelectric colorimeter. The polymerisation reaction is found to be of zero order, with the activation energy increasing exponentially with pH. The time required to reach the extent of reaction at which a resin layer separates out from the aqueous solution decreases with increasing temperature but increases with increasing pH. An exponential expression relating the time for phase separation with temperature and pH has been derived.     

Experimental designs in which each subject is used repeatedly.

Illustrates the fact that in many fields of research, the investigator makes use of experiments in which the same experimental unit (s) is used repeatedly. 1 of the main problems such experiments pose for the researcher is that the observations may not be all statistically independent. In the recent literature, reviewed in this article, several particular forms of statistical dependence between successive observations on the same s have been conceptualized, and the appropriate designs and modes of analysis have been derived. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Steady-state analysis of the variable-speed switched-reluctancemotor drive

The principle of operation of the switched-reluctance motor (SRM) drive demands that the motor and converter be treated as one unit. Little has been done to develop a complete analysis of this motor-converter combination. The authors present an approach to the steady-state analysis of the drive including the effects of stator winding resistance, input filter parameters, and snubber circuits, which are often neglected. The analysis yields current, voltage, torque, and back-EMF (electromotive force) waveforms that provide guidelines to the optimal design of the drive. Experimental verification is provided for a 6/4 pole prototype SRM drive, and it is shown to be in good agreement with the simulation results. It is noted that this approach can be applied to any other motor-converter combination with minimal modification     

Expert system - flat roofs

Director General Paul Fazio and project officer Krishnan Gowri of Research and Computer Applications in the Construction Industry, SIRICON, at Concordia University, Montreal, demonstrate the use of expert systems to give the designer complete control of decision making, whilst automating the process of building code checking, design calculations and information handling.     

A Moment Approach to Evaluation and Optimization of Complex System Reliability

A moment approach to evaluating reliability of complex systems is described. The advantages of this type of model have been discussed in relation to models based simply on probability of failure. The main difficulty of a moment approach is the evaluation of first and second moments of the system failure-time distribution. A proposed theorem considerably alleviates this difficulty. In order to facilitate applying this theorem, approximate expressions for the mean and variance of parallel systems are suggested. The problem of system optimization is then discussed and the technique is illustrated with a bridge network. If the system s-expected life remains unchanged when redundancy is added, the variance of system life always decreases.     

Electroreduction of lauronitrile and stearonitrile

Higher aliphatic amines are extensively used as wetting agents, corrosion inhibitors and as anti-dusting agents. An electrochemical method for preparing laurylamine and stearylamine from their corresponding nitriles using nickel black cathode has been standardised in our laboratories. Both these nitriles underwent smooth reduction in ethanolic sulphuric acid medium to give a yield of around 80% amine for a current efficiency of 40–50%. Galvanostatic polarisation measurements indicated that the reduction is smooth only at lower current densities.     

Immunolymphoscintigraphy in breast cancer: evaluation using 131I-labeled monoclonal antibody B72.3

Resistance to the organophosphates temephos and chlorpyrifos, the carbamate propoxur, the pyrethroid permethrin, and the organochloride DDT was investigated in Tunisian populations of Culex pipiens pipiens (L.) collected between 1990 and 1996. Resistance to temephos was uniformly low, reaching 10-fold in the most resistant population. In contrast, resistance to chlorpyrifos was highly variable, reaching the highest level (> 10,000-fold) recorded worldwide. The chlorpyrifos-resistant populations also were highly resistant to propoxur. Some populations also showed high resistance to permethrin (up to 5,000-fold) and moderate resistance to DDT (approximately 20-fold). Bioassays conducted in the presence of synergists showed that increased detoxification had only a minor role in resistance, although several over-produced esterases known to be involved in organophosphate resistance were detected. To better understand the factors influencing the distribution of resistance in Tunisia, the polymorphism of genes involved in organophosphate resistance (i.e., over-produced esterases and insensitive acetylcholinesterase) was investigated in relation to the genetic structure of populations studied by analyzing the electrophoretic polymorphism of "neutral" genes. Over the area studied, and despite a high level of gene flow, resistance genes showed a patchy distribution. Results are discussed in relation to the selection pressure caused by insecticide treatments.