Essential histidyl residues at the active site(s) of sucrose-phosphate synthase from Prosopis juliflora

Antimicrobial resistance in nosocomial isolates is of increasing concern to the clinician, particularly in intensive care units. With more expensive drugs and prolonged periods of hospitalization required, resistance can result in increased healthcare costs. For the patient, infection with multiply resistant strains of bacteria is associated with high mortality rates. This review focuses on the prevalence of nosocomial infections throughout Europe, with particular emphasis on the prevalence of resistance to common antimicrobial agents. The beta-lactams are the most frequently prescribed antimicrobials, and the growing importance of extended spectrum beta-lactamases and the hyperproduction of chromosomal beta-lactamase by stably derepressed mutants in the development of microbial resistance are discussed. Given that the most common reason for modification of an initial empiric antibiotic treatment is the isolation of microorganisms not susceptible to the initial choice of treatment, the results from two European multicenter trials comparing the efficacy of the carbapenems, meropenem, and imipenem/cilastatin, for the treatment of serious nosocomial infections, are appraised. In light of these results, it can be concluded that the carbapenems are effective as initial empiric monotherapy for nosocomial infections because of their broad spectrum of efficacy and stability to beta-lactamases.     

Transformation of state equations to the controllable canonical form

An algorithm is presented for the transformation of the state equations of a linear multivariable system to the controllable canonical form without requiring any matrix inversion.     

Microyield and fracture in polycrystalline MgO

Microyield and plastic flow occurring in polycrystalline MgO prior to fracture at room temperature is examined. It is shown that the initial dislocation activity occurs in the region of grain boundaries at a stress independent of grain size and below the microyield stress. The microyield stress corresponds to the stress necessary for propagating slip across the grain diameter but is below the stress necessary to produce dislocation activity in adjacent grains. The microyield stress obeys a Petch type of relationship with respect to grain size and this is attributed to the variation of dislocation density with grain size. The fracture stress — grain size relationship also follows the Petch equation but indicates that extensive work hardening has occurred prior to fracture.     

Silicon-gate CMOS devices with 300 Å gate oxides

Polycrystalline silicon gate (phosphorus doped) complementary MOS structures were fabricated with gate oxide thicknesses down to 300 Å. Measurements of the oxide fixed charge, Q_ss, and of the back-gate bias dependence of the threshold voltage indicate an absence of phosphorus diffusion through the gate oxide during conventional processing.     

On-line system identification algorithm combining stochastic approximation and pseudoinverse

A new algorithm for on-line system identification is presented combining stochastic approximation with the recursive pseudoinverse algorithm for least squares estimation. It is an extension of Clarke's generalized least squares method, and gives unbiased estimates of the parameters even in the presence of large noise. An example of a simulated second-order process compares the proposed method with three earlier methods.     

Aggregation matrices for a class of low-order models for large-scale systems

A simple technique for aggregation is established for model reduction by projection. This leads to a direct formula for deriving the aggregation matrix. It is shown that aggregation is a generalisation of projection, and the work of Aoki is related to that of Mitra, Davison and Chidambara.     

Intercrystalline cracking,grain-boundary sliding,and delayed elasticity at high temperatures

The hypothesis of an interrelation between grain-boundary sliding and delayed elasticity in polycrystalline materials at high homologous temperatures is used to investigate the conditions conducive to microcracking. It is known that a material may exhibit cracking activity on attaining a critical delayed-elastic strain corresponding to a critical grainboundary sliding displacement. Experimental data on ice at temperatures >0.9T _m are used to verify this concept. The new criterion is then extended to develop simple, selfconsistent equations describing the interdependence of stress, strain, time, temperature, and grain size in predicting the onset of structural degradation due to microcracking and hence possible failure by fracture or rupture. The merit of the theory lies in its ability to forecast explicitly a large number of commonly observed high-temperature phenomena, including superplasticity, brittle-ductile transition, and the stress and temperature dependence of the apparent activation energy for fracture. One derivation makes it clear that cracking occurs when a critical stress depending only on temperature (and independent of grain size) is exceeded. The near constancy of fracture strain in the quasi brittle range can also be predicted     

Thermally stimulated discharge current studies of acrylic-acid-doped polystyrene films

Thermally stimulated discharge currents in thin cylindrical films (30 μm thick) of polystyrene either undoped or doped with acrylic acid were measured under various polarizing conditions. It was found that the undoped samples give rise to a single peak around 105 °C which is due to the release of space charges present in the material. In the doped samples this peak is shifted to 58 °C and another peak appears at around 150 °C. The peak at the lower temperature is due to the superposition of the dipolar peak of the dopant and the space-charge-limited peak of the matrix, whereas the peak at the higher temperature has been attributed to the space charge of the material retained in the double bonds of the dopant, as a result of interaction between the dopant and the matrix.