High frequency GaAs switched capacitor filter implemented with GaAs insulated gate FET switches

A switched capacitor filter implemented with 5 mu m GaAs IGFET switches and GaAs MESFET operational amplifiers is presented. The circuit is clocked at 25 MHz. By scaling to 1 mu m IGFETs, a switching speed of about 625 MHz should be attainable. Use of GaAs IGFET switches is shown to greatly reduce power consumption and complexity of the circuit. The low frequency switching instability of the GaAs IGFET is shown to be of no consequence in this application.<>     

Measurement of the thermal expansion coefficient of an all-sapphireoptical cavity

We present measurements of the frequency-temperature dependence of an all-sapphire Fabry-Perot optical cavity to be used as an optical frequency reference. Measurements were made by tracking the frequency of the cavity relative to a second high-stability cryogenic sapphire-spaced cavity-a technique with impressive resolution for measurements of the coefficient of thermal expansion (CTE). Measurements presented here cover the temperature range of 11 K to 26 K. We find that the CTE of the all-sapphire cavity for these temperatures is given by α_cavity=(7.7±0.9)×10^$ -¹³ T/sup (3.23±0.05/)     

"Illusion" of mental health does not explain positive illusions.

Comments on the argument by J. Schedler et al (see record 1994-09623-001) that standard mental health scales appear unable to distinguish between genuine mental health and the illusion of mental health created by psychological defenses. It is asserted that Schedler et al go beyond appropriate empirical and conceptual boundaries by extending their analysis to the body of research known as "positive illusions." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective regulation of protein kinase C isoenzymes by oleic acid in human platelets

Cis-unsaturated fatty acids activate soluble protein kinase C (PKC) in vitro and in intact platelets. The following studies were conducted to determine the effects of oleate on individual isoenzymes of PKC in human platelets. Human platelets were found to contain predominantly PKC alpha, beta I, beta II, and delta with minor immunoreactivity for PKC epsilon, zeta, and eta. In intact platelets, sodium oleate caused a time-dependent redistribution of PKC alpha, beta II, and delta from cytosol to membrane fractions with little effects on PKC beta I. On the other hand, PMA and thrombin induced translocation of all four isoenzymes of PKC. In vitro, oleate partially activated (50% of Vmax) purified calcium-dependent PKC (alpha, beta I, and beta II) with an EC50 of 50 microM whereas it fully activated (100% of Vmax) purified calcium-independent PKC (predominantly delta) with an EC50 of 5 microM. The selective effects of oleate on PKC isoenzymes were investigated in platelet cytosol which contains endogenous PKC and its physiologic substrates. Under these conditions, oleate potently activated calcium-independent PKC causing the phosphorylation of the 40-kDa substrate. Activation of calcium-dependent isoforms occurred only at higher concentrations of oleate. Thus, oleate activates multiple isoenzymes of PKC with predominant effects on calcium-independent PKC.     

Role of NADH/NADPH oxidase-derived H2O2 in angiotensin II-induced vascular hypertrophy

The Maillard reaction between sugar and protein has been postulated as the cause for the browning and arrestment of caries lesions. This reaction has been implicated as the cause for decreased degradability of collagen in vivo. The aim of the present study was to verify the occurrence of the reaction in vivo. Carious and sound dentin samples were taken from extracted human teeth and analyzed for the fluorescence characteristic of the Maillard reaction and oxidation and, by HPLC, for Maillard products. In addition, physiological cross-links were analyzed by HPLC. Oxidation- and Maillard reaction-related fluorescence increased in collagenase digests from carious dentin. Advanced Maillard products (carboxymethyllysine and pentosidine) increased, whereas furosine, a marker for the initial reaction, was not observed consistently. This implies no direct addition of sugars to protein, but rather the addi-tion of smaller metabolites and glycoxidation products. In addition, the physiological cross-links hydroxylysinonorleucine and dihydroxylysinonorleucine decreased in carious dentin. Also for hydroxylysylpyridinoline, a decrease was observed, but not consistently. In conclusion, the caries process modifies amino acids in dentin collagen, which can lead to increased resistance against proteolysis and ultimately to caries arrestment.     

Effective peer responses to impaired nursing practice

Subplate neurons, the first neurons of the cerebral cortex to differentiate and mature, are thought to be essential for the formation of connections between thalamus and cortex, such as the system of ocular dominance columns within layer 4 of visual cortex. To learn more about the requirement for subplate neurons in the formation of thalamocortical connections, we have sought to identify the neurotransmitters and peptides expressed by the specific class of subplate neurons that sends axonal projections into the overlying visual cortex. To label retrogradely subplate neurons, fluorescent latex microspheres were injected into primary visual cortex of postnatal day 28 ferrets, just prior to the onset of ocular dominance column formation. Subsequently, neurons were immunostained with antibodies against glutamate, glutamic acid decarboxylase (GAD-67), parvalbumin, neuropeptide Y (NPY), somatostatin (SRIF), or nitric oxide synthase (NOS). Retrograde labeling results indicate that the majority of subplate neurons projecting into the cortical plate reside in the upper half of the subplate. Combined immunostaining and microsphere labeling reveal that about half of cortically projecting subplate neurons are glutamatergic; most microsphere-labeled subplate neurons do not stain for GAD-67, parvalbumin, NPY, SRIF, or NOS. These observations suggest that subplate neurons can provide a significant glutamatergic synaptic input to the cortical plate, including the neurons of layer 4. If so, excitation from the axons of subplate neurons may be required in addition to that from lateral geniculate nucleus neurons for the activity-dependent synaptic interactions that lead to the formation of ocular dominance columns during development.     

Notch geometry effects in fatigue: A conservative design approach

The understanding of stress concentrators (notches) is an important element in the prevention of failure in components and in the analysis of failures when they occur. This paper examines critically the methods currently used to predict the fatigue strength of components containing notches, with particular attention to the need for a conservative design approach. Current methods, if correctly applied, are shown to give conservative predictions of fatigue limit and high-cycle fatigue strength, and it is shown that the same philosophy can be extended to cover very small notches, including surface roughness. The presentation of these predictions in the form of a “mechanism map” for notch fatigue is advocated as a useful tool for designers. The problems of extending the approach to other types of stress concentrator, such as fillet radii, are discussed.     

A review of hydrodynamic load analysis for submerged structures excited by earthquakes

Analysis of hydrodynamic loads on submerged structures is reviewed in the context of aseismic design of dams, intake towers and offshore platforms. The structures are considered to be flexible, and a linear fluid-structure interaction analysis is developed using the modes of vibration of a structure oscillating in the absence of a surrounding fluid. Particular attention is paid to the significance of fluid compressibility and free surface effects. As an illustration of the influence of these effects, a closed form solution and results are given for a simple rectangular reservoir-dam system. Numerical solutions are also discussed, based on finite element and boundary integral techniques for complex three-dimensional problems.