Breakdown voltage improvement in strained InGaAlAs/GaAs FETs

GaAs MESFETs with a surface layer of pseudomorphic InGaAlAs have been fabricated. The compressive strain and wide bandgap in the InGaAlAs layer reduce the impact ionization rate in this layer and improve the breakdown voltage of the device. A 1 μm×75 μm gate device with the pseudomorphic surface layer showed an improvement in gate-to-drain breakdown of over 55% and an improvement in channel breakdown of 50% as compared to a similar device without the pseudomorphic layer. Both devices had a peak transconductance of about 190 mS/mm and a saturation current of about 265 mA/mm     

Mechanistic Studies on the [2 + 2] Photocycloaddition of Deuterium-Labeled Olefins

The mechanism of intramolecular [2 + 2] photocycloaddition of 1b has been investigated. Structure determination of deuterium-labeled photoadducts was accomplished by ²H NMR.     

Laparoscopy for the impalpable testes. Initial experience of one center

Endoscopic treatment of acute pancreatitis has been proposed in different conditions: acute biliary pancreatitis, pancreatitis related to pancreas divisum or in case of pseudocysts. The efficacy of such endoscopic procedure is discussed.     

Femoral nerve block in extracapsular femoral neck fractures

We randomised 50 patients with extracapsular fractures of the femoral neck to receive either a bupivacaine femoral nerve block or systemic analgesia alone. A femoral nerve block was found to be an easy and effective procedure which significantly reduced perioperative analgesic requirements and postoperative morbidity.     

The optimal projection equations with Petersen-Hollot bounds:robust stability and performance via fixed-order dynamic compensationfor systems with structured real-valued parameter uncertainty

A feedback control design problem involving structured real-valued plant parameter uncertainties is considered. A quadratic Lyapunov bound suggested by recent work of I.R. Petersen and C.V. Hollot (1986) is utilized in conjunction with the guaranteed cost approach of S.S.L. Chang and T.K.C. Peng (1972) to guarantee robust stability with robust performance bound. Necessary conditions that generalize the optimal projection equations for fixed-order dynamic compensation are used to characterize the controller that minimizes the performance bound. The design equations thus effectively serve as sufficient conditions for synthesizing dynamic output-feedback controllers that provide robust stability and performance     

On the estimation of uncertain signals using an estimation-detection scheme

An estimation-detection scheme is proposed for the estimation of signals with unknown parameters. The scheme is illustrated by considering the case of a signal with unknown but bounded variance. Two sets of bounds are used to determine two regions of signal uncertainty, and different linear estimators are used for each region. A detector is then used to select the appropriate estimator. Since no a priori information is assumed on the unknown parameters a weighted minimax criterion is used to optimize the detector and the estimators.     

Compact multiple-valued multiplexers using negative differentialresistance devices

Quantum electronic devices with negative differential resistance (NDR) characteristics have been used to design compact multiplexers. These multiplexers may be used either as analog multiplexers where the signal on a single select line selects one out of four analog inputs, or as four-valued logic multiplexers where the select line and the input lines represent one of four quantized signal values and the output line corresponds to the selected input. Any four-valued logic function can be implemented using only four-valued multiplexers (also known as T-gates), and this T-gate uses just 13 devices (transistors) as compared to 44 devices in CMOS. The design of the T-gate was done using a combination of resonant tunneling diodes (RTD's) and heterojunction bipolar transistors (HBT's) with the folded I-V characteristic (NDR characteristic) of the RTD's providing the compact logic implementation and the HBT's providing the gain and isolation. The application of the same design principles to the design of T-gates using other NDR devices such as resonant tunneling hot electron transistors (RHET's) and resonant tunneling bipolar transistors (RTBT's) is also demonstrated     

Numerical Simulation of Natural Convection Flow Over Parabolic Bodies

Steady, two-dimensional and symmetric natural convection flow over parabolic bodies are investigated numerically. The full Navier–Stokes and energy equations were solved using the finite element technique. Solutions for the velocity and temperature distributions are obtained for different values of the flow parameters. In addition, the local and average Nusselt number distributions are obtained and presented. For all cases considered, the following parameters are studied: nose radius of curvature of the parabolic body, Grashof number, and Prandtl number. It was found that as the nose radius of curvature of the parabolic body is increased, the local and average values of the Nusselt number are decreased. On the other hand, an increase in the Grashof or Prandtl number is found to increase the local and average Nusselt number.This paper is dedicated to A. Bany-Youness. He passed away in 2003 and the components of this paper have been collected from his M.Sc. thesis work after his death.     

Ion-exchange chromatography of mono- and divalent cations in natural waters on a weak-acid anion-exclusion column

The regulation of glucose metabolism by glucagon and GLP-1 is well established, but novel functions for these and other proglucagon-derived peptides are less well defined. This paper highlights the diversity of both GLP-1 and glucagon activity by studying the tissue distribution of glucagon and GLP-1 receptor gene expression by both Southern blot analysis of RT-PCR products and nuclease protection assays. By Southern blot analysis of RT-PCR products, GLP-1 receptor mRNA was detected in lung, hypothalamus, hippocampus, cerebral cortex, kidney, pancreas, and throughout the gastrointestinal tract. Glucagon receptor expression was detected in liver, kidney, spleen, thymus, adrenal glands, pancreas, cerebral cortex, lung, and throughout the gastrointestinal tract. Nuclease protection assay revealed glucagon receptor expression to be highest in liver and kidney, whereas GLP-1 receptor expression was only detected by protection assay in lung, stomach, and large bowel. Despite previous evidence that other receptors for proglucagon-derived peptides may exist, no evidence of novel receptors or multiple isoforms of the glucagon and GLP-1 receptors was found, indicating that the two cloned receptors may mediate all the effects of proglucagon-derived peptides, or that novel receptors may share less homology with the glucagon and GLP-1 receptors than previously anticipated.