Reliability block diagram simulation techniques applied to the IEEE Std. 493 standard network

This is one of a series of papers discussing the application and accuracy of different analysis techniques supporting the determination of industrial and commercial power system reliability and availability. There is a need recognized in the power industry to identify and utilize a standard tool, or a set of tools, to analyze the reliability of power systems. Historically, the results of applying different reliability methodologies and tools varied significantly, and comparisons were difficult. The Reliability Analysis Techniques Working Group of the Gold Book (IEEE Std. 493-1997) developed a standard network to enable comparison of analytical techniques. This paper describes the approach of simulations via reliability block diagrams as applied to the Gold Book standard network. Reliability indexes of the load points are presented, and are compared with ones obtained from other techniques in the series to determine the accuracy.     

Simultaneous multiple substrate tag detection with ESI-ion trap MS for in vivo bacterial enzyme activity profiling

A bacterial identification method in which multiple enzyme activities are measured simultaneously and in vivo with electrospray ionization-mass spectrometry (ESI-MS) is described. Whole-cell bacteria are immobilized onto a filter support and incubated with a mixture of substrates. Each substrate is chosen to measure a specific enzyme activity of a targeted bacterium and to produce a tag of unique molecular weight. After a predetermined incubation time, the solution is filtered, and the supernatant consisting of a mixture of released tags and unhydrolyzed substrates is directly analyzed, without chromatographic separation, by ESI-MS. Bacteria remain viable on the filter for further analyses. The method was tested by measuring the aminopeptidase activity of the bacteria Escherichia coli, Bacillus subtilis, Bacillus cereus, and Pseudomonas aeruginosa. The resulting aminopeptidase enzyme profiles allowed the differentiation between the four bacteria tested. The method is rapid, since a multiplex advantage is realized when assaying for multiple enzymes, and it is amenable to automation via a flow injection analysis setup.     

Analysis and Optomechanical Characterisation of a MEMS Micromirror Device

Abstract:  Advances in our analysis and characterisation of a micro-electromechanical system (MEMS) micromirror device are presented. The micromirror device, to be used as an integral component of an interferometer, has a characteristic dimension of 510  μ m and operates in a dynamic mode with maximum out-of-plane displacements in the order of 10  μ m at oscillation frequencies of up to 1.3 kHz. Developments are carried out by analytical, computational and experimental methods. Analytical and computational nonlinear geometrical models are developed in order to determine the optimal loading-displacement operational characteristics of the micromirror. Because of the operational mode of the micromirror, the experimental characterisation of its loading-displacement transfer function requires utilisation of advanced optical metrology methods. Optoelectronic holographic microscopy (OEHM) methodologies, based on multiple wavelengths being developed to perform such characterisation, are described. The micromirror device is suitable for optical phase measurements and applicable to development of miniaturised optical metrology systems for characterisation of shapes and deformations.     

Aberrant cell division and random FtsZ ring positioning in Escherichia coli cpxA* mutants

In Escherichia coli, certain mutations in the cpxA gene (encoding a sensor kinase of a two-component signal transduction system) randomize the location of FtsZ ring assembly and dramatically affect cell division. However, deletion of the cpxRA operon, encoding the sensor kinase and its cognate regulator CpxR, has no effect on division site biogenesis. It appears that certain mutant sensor kinases (CpxA*) either exhibit hyperactivity on CpxR or extend their signalling activity to one or more noncognate response regulators involved in cell division.     

Biological response to different diets of fermented and unfermented mixtures of flour and cereal brans

The objective of this study was to biologically evaluate eight mixtures of flour and brans prepared with non‐conventional foods popularly denominated ‘multimixtures’, which differed from each other in terms of type of bran (wheat or rice), presence or absence of cassava leaf powder and submission or non‐submission to a solid‐state fermentation with Saccharomyces cerevisiae for 6 h/30 °C, utilising female Wistar/UFPEL rats. Biological indices determined were food efficiency ratio (FER), protein efficiency ratio (PER), net protein efficiency ratio (NPR) and in vivo digestibility. Liver, spleen and kidney specimens were collected at the end of the experiment. In vivo digestibility of diets containing multimixtures formulated with wheat bran was superior to diets containing rice bran, presenting values from 76.5% to 82.8%, which corresponds to up to 85% of casein digestibility. The results allowed the conclusion that fermentation tended to improve food efficiency, but did not influence in vivo digestibility.     

Shear-induced boundary film formation from dialkyl sulfides on copper

The friction of a copper surface, which is exposed to diethyl disulfide (DEDS), dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS) while rubbing by a tungsten carbide pin, are explored in an ultrahigh vacuum tribometer to investigate the effect of the sulfur-to-carbon stoichiometry on gas-phase lubrication. Surface analyses by Auger spectroscopy of the wear scars after rubbing reveal that the amount of sulfur increases with sulfur content of the gas-phase lubricant, as anticipated. It is found that the friction reduction depends on the normal load, where the friction coefficient tends to decrease more at lower loads, and that the load at which the most friction-reducing tribofilm is formed depends on the stoichiometry of the gas-phase lubricant. DEDS (with a sulfur to carbon ratio of 0.5) only reduces the friction coefficient to a minimum value of ～0.28 at a normal load of 0.25 N, for DMDS (S/C = 1.0) friction is reduced to ～0.28 for loads below ～0.7 N, and DMTS (S/C = 1.5) reduces friction to this value for all loads tested.