Plasma and cerebrospinal fluid concentration of phenylacetic acid in humans and monkeys

A rapid and reliable mass-fragmentographic method for assay of plasma and cerebrospinal fluid (CSF) concentrations of free and conjugated phenylacetic acid (PAA) is described. The method is used to compare plasma and CSF concentrations of PAA in humans and monkeys. Both packed and capillary columns are used. In humans approximately 45% of total plasma PAA is conjugated in contrast to approximately 60% in monkeys. Both free and conjugated PAA concentrations tend to be higher in monkeys than in humans. Plasma mean concentration of total PAA in humans and monkeys are, respectively, 459.1 and 838 ng/ml. Approximately 55 and 25% of total PAA in the CSF are conjugated in humans and monkeys, respectively. Total PAA mean concentrations in human and monkey CSF are 41.6 and 84.2 ng/ml. Because over 90% of total urine PAA in humans is conjugated, it is concluded that over 50% of urine phenylacetylglutamine may be derived from kidney conjugation of free plasma PAA and/or from the kidney's preferential filtration of conjugated PAA as contrasted with free PAA.     

The additive subgroup generated by a polynomial

SupposeR is a prime ring with the centerZ and the extended centroidC. Letp(x ₁, …,x _n) be a polynomial overC in noncommuting variablesx ₁, …,x _n. LetI be a nonzero ideal ofR andA be the additive subgroup ofRC generated by {p(a ₁, …,a _n):a ₁, …,a _n ∈I}. Then eitherp(x ₁, …,x _n) is central valued orA contains a noncentral Lie ideal ofR except in the only one case whereR is the ring of all 2 × 2 matrices over GF(2), the integers mod 2.     

Effects of electrical and temperature stress on polysilicon resistors for CMOS technology applications

The effects of electrical and temperature stress on polysilicon resistors for CMOS technology applications are studied. Under a fixed square number, the peak current density (J_peak) is increased with decreasing the polysilicon resistor width W. The time-to-fail value of the polysilicon resistor is decreased with increasing the electrical and temperature stress. A simple empirical formula is proposed in this study to predict the maximum current density (J ) and lifetime of polysilicon resistors. Under a fixed current density (1.0 × 10⁶A cm ^{− 2}), the activation energies (E_a) for n ⁺ andp ⁺ polysilicon resistors at different temperatures are 0.67 and 0.48 eV, respectively. In addition, at a fixed temperature of 473 K, the current factors for n ⁺ andp ⁺ polysilicon resistors are 1.57 × 10 ^{− 5}and 1.30 × 10 ^{− 5}cm² / A, respectively, under different current densities. Therefore, these precise reliability performances offer promise for ULSI design and fabrication.     

Positronium quenching reactions and diffusion in solutions

The temperature effect on positronium quenching rates for p-benzoquinone and iodine in several solvents was determined. The quenching rate constantk ₁ follows ak ₁∝1/η relationship better than thek ₁∝T/η one, predicted by ordinary theory. A simple theoretical treatment based on diffusion theory shows that the temperatureT of the solute, positronium, may not be the same as the temperature of the solvent if the positronium is not fully thermalized. This temperature is found to be about twice the room temperature for the solvents investigated. The findings further support the theory that positronium reactions are “diffusion controlled” in liquid solutions. The activation energies of all the positronium reactions studied are either negligible or less than 0.1 eV.     

Ag/SiO2: a novel catalyst with high activity and selectivity for hydrogenation of chloronitrobenzenes

Ag/SiO2 prepared by an in situ reduction method are found, for the first time, to be highly effective and recyclable catalysts for the selective hydrogenation of a range of chloronitrobenzes to their corresponding chloroanilines, which are of great potential as industrially viable and cheap novel catalysts for the production of chloroanilines.     

Stochastic extensions to necessary conditions in the theory of the calculus of variations

A stochastic version of the modified Young's generalized necessary conditions in the calculus of variations is given in this paper. It is based on an extension of Minkowski's theorem on the existence of a flat support for a convex figure, and it generalizes the necessary conditions of Weierstrass and Euler in the classical theory of the calculus of variations to a class of admissible curves which are expressible in terms of a finite number of random parameters. The integrals which we consider here are in the general Denjoy sense, except those with respect to the random parameters, which exist in the Lebesgue sense defined on a probability space. The importance of our stochastic analysis lies in the completion that a minimum not attained in the classical sense may be, and frequently is, attained in the stochastic case.This research was supported in part by the National Science Foundation under Grants Nos. GK-1834X and GK-31229     

Slow and fast light in quantum-well and quantum-dot semiconductor optical amplifiersInvited Paper

Slow and fast light in quantum-well (QW) and quantum-dot (QD) semiconductor optical amplifiers (SOAs) using nonlinear quantum optical effects are presented. We demonstrate electrical and optical controls of fast light using the coherent population oscillation (CPO) and four wave mixing (FWM) in the gain regime of QW SOAs. We then consider the dependence on the wavelength and modal gain of the pump in QW SOAs. To enhance the tunable photonic delay of a single QW SOA, we explore a serial cascade of multiple amplifiers. A model for the number of QW SOAs in series with variable optical attenuation is developed and matched to the experimental data. We demonstrate the scaling law and the bandwidth control by using the serial cascade of multiple QW SOAs. Experimentally, we achieve a phase change of 160° and a scaling factor of four at 1 GHz using the cascade of four QW SOAs. Finally, we investigate CPO and FWM slow and fast light of QD SOAs. The experiment shows that the bandwidth of the time delay as a function of the modulation frequency changes in the absorption and gain regimes due to the carrier-lifetime variation. The tunable phase shift in QD SOA is compared between the ground- and first excited-state transitions with different modal gains.     

Employing injection-locked Fabry–Perot laser diodes to improve bidirectional WDM–PON performances

We proposed and demonstrated a bidirectional wavelength-division-multiplexing (WDM)–passive optical network (PON) employing injection-locked Fabry–Perot laser diodes (FP LDs) at both transmitting sites, and adaptive filters at both receiving sites. Injection-locked FP LDs, a particularly inexpensive option, are used to replace the conventional distributed feedback (DFB) LDs in WDM–PON. Adaptive filters are attractive because they can track the variations and compensate the nonlinear distortions. Transmission performance over 20 km of a standard single-mode fiber (SMF) was investigated. Improved performance of bit error rate (BER), better and clear eye diagram were achieved in our proposed WDM–PON.     

A rapid and precise probe for measurement of liquid xenon polarization

The relaxation time of liquid (129)Xe is very long (>15 min) and the signal at thermal equilibrium is weak. Therefore, determination of the absolute polarization enhancement of hyperpolarized (129)Xe by direct measurement is tedious. We demonstrate a fast and precise alternative, based on the dipolar field created by liquid hyperpolarized (129)Xe contained in a cylindrical sample tube. The dipolar field is homogeneous in the bulk of the tube and adds to the external field, causing a shift in the Larmor frequencies of all nuclear spins. We show that the frequency shift of the proton in CHCl(3) (chloroform), which dissolves homogeneously in xenon over a fairly broad temperature range, is an excellent probe for (129)Xe polarization. Frequency measurements are precise and the experiment is much faster than by direct measurement. Furthermore the (129)Xe polarization is minimally disturbed since no rf pulses are applied directly to (129)Xe and since chloroform is a fairly weak source of (129)Xe relaxation. The experiments are reproducible and require only standard NMR instrumentation.