An ampD gene in Pseudomonas aeruginosa encodes a negative regulator of AmpC beta-lactamase expression

The ampD and ampE genes of Pseudomonas aeruginosa PAO1 were cloned and characterized. These genes are transcribed in the same orientation and form an operon. The deduced polypeptide of P. aeruginosa ampD exhibited more than 60% similarity to the AmpD proteins of enterobacteria and Haemophilus influenzae. The ampD product transcomplemented Escherichia coli ampD mutants to wild-type beta-lactamase expression.     

A study of thermal conductivity of structural ceramic materials. Part I. State of research of thermal conductivity of structural materials

At the present time, experiment is a reliable method for studying the thermal conductivity of new ceramic materials and especially refractories. However, the range and possibilities of existing devices do not meet the requirements for measuring thermal conductivity, especially at a high temperature. At very high thermal loads under the conditions of formation of surface columnar crystal structures, thermoelastic stresses, disturbances in vibration of the elementary lattice, and other phenomena, the thermal conductivity can be a function of the temperature drop. The present paper concerns the physical fundamentals of heat conduction in current ceramic materials and refractories based on MgO, A1₂O₃, and Si₃N₄. The classical stationary and nonstationary methods for determining thermal conductivity are considered. Special attention is devoted high-temperature processes and the difficulties arising in this case. It is recommended to solve high-temperature problems by using methods based on solving inverse problems of heat conduction     

Point light source detection characteristics of a SEC vidicon digital TV camera

Optimization of the point source detection properties of a Secondary Electron Conduction (SEC) vidicon TV camera tube as a detector of point light sources such as star fields or certain optical spectra requires the accurate determination of peak height, half-peak width, background, and location of the point image. Two perpendicular Gaussian curves have been used to define a point image, allowing changes in the parameters of these Gaussian curves to be used in the study of SEC vidicon point source properties as a function of electrical and optical parameters. Peak height was shown to depend on priming time and a method was developed to reduce the priming time by almost an order of magnitude by momentarily raising the target voltage during priming. Power supply specifications needed for 0.1 pixel (picture element) addressing accuracy were found to be +/-0.03 V. Focus current was optimized to obtain the best sensitivity and resolution over the entire target. Peak height, background, and half-peak width were found to be strongly dependent on readout beam current. Target voltage, over the limited range examined, was found to affect only the gain without compromising other image parameters, so that any value could be used, consistent with gain and sensitivity required.     

Single-crystalline Si grown on single-crystalline Gd2O3 by modified solid-phase epitaxy

We investigate molecular beam epitaxial overgrowth of Si template layers produced by different approaches on single-crystalline oxide grown on Si(111). Three approaches based on modified solid-phase epitaxy were found to be suitable for the subsequent Si epitaxial overgrowth. The crystalline quality and interface properties of single-crystalline silicon on single-crystalline oxide grown on Si(111) make the obtained structures suitable for silicon-on-insulator applications. First measurements of electrical properties of p-type samples indicate good electrical properties of the top Si layer. Supplemental investigations demonstrate that Si layers with thickness in the range of 10 nm remain stable during thermal annealing up to 900 °C in an ultra-high vacuum.     

A study of heat conduction in structural ceramic materials. Part III. Mathematical model of measuring cell

The process of heat propagation in a specimen is considered in an approximation of a one-dimensional heat flow with side leakages of heat. They are modelled as a function of the heat sources (sinks). The chosen stationary heating and the temperature field in the specimen are described by a nonlinear one-dimensional differential equation. The boundary conditions and the source function are determined from experimental data. The nonlinear one-dimensional differential equation is used in an implicit identification method and solved numerically; a minimum of the quality criterion is determined at each iteration step in the search procedure. The identification procedure is performed by explicit and implicit methods of solution of inverse problems of heat conduction. A numerical simulation has shown that the method of component-wise minimization is the most efficient. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 39–42, April, 2000. Part I appeared in No. 8, 1999, and Part II in No. 2, 2000.     

Studies of heat conduction in structural ceramic materials. Part II. A study based of the solution of inverse problems of heat conduction

The process of energy transfer in refractory materials is studied under conditions of intense high-temperature heating. The coefficients of inverse problems of heat conduction (IPHC) are analyzed. The extremum coefficients of IPHC are determined and classified as explicit and implicit in accordance with the methods used for their estimation. Coefficient-type IPHC make it possible to bring the processing of results as close as possible to the measuring cell and to diminish the effect of errors of measurement on the solution of the problems and to increase simultaneously the efficiency of the experiments. A method for performing physical experiments, high-temperature heating sources, and measuring cells are described. The boundaries of the confidence interval of the instrumental error are shown. Results of single measurements of the thermal conductivity of MgO-base ceramics in an optical furnace are presented. Computation of the errors shows that the total relative instrumental error of measurement of the thermal conductivity is quite acceptable for high-temperature studies. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 2, pp. 33–43, February, 2000. For the beginning of the series see No. 8 of 1999, p. 22.