Theoretical studies of CO hydrogenation to methanol over Cu, Pd, and Pt metals

Theoretical studies of CO hydrogenation to methanol over Cu, Pd, and Pt metals have been carried out using a quasi‐relativistic density‐functional method. The metal surface is simulated by a M₁₀ cluster model. Reaction energies for the elementary steps involved are determined. The activation energies are estimated by the analytic BOC‐MP formula. The results support that these metals are active in CO hydrogenation to methanol. The rate‐determining steps are shown to be different for the metals. The highest activation energies of reaction on the metals fall in the order Cu < Pd < Pt, which corresponds to the order of the catalytic activities of the metals in CO hydrogenation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analyses of distortions and cross modulations in erbium-doped fiberamplifiers

The closed-form expressions of nonlinear Fourier transfer functions are presented for the analyzes of distortions and cross modulations in erbium-doped fiber amplifier (EDFA) systems. Based upon Volterra series and the time-dependent perturbation theory, the transfer functions are obtained after taking account of both the EDFA nonlinearity and chirping effect. Their applications to an AM-SCM and an eight-channel wavelength-division-multiplexed systems are demonstrated     

Microwave-assisted hydrothermal synthesis of coralloid nanostructured nickel hydroxide hydrate and thermal conversion to nickel oxide

Coralloid nanostructured nickel hydroxide hydrate has been successfully synthesized by a simple microwave-assisted hydrothermal process using nickel sulfate hexahydrate as precursor and urea as hydrolysis-controlling agent. A pure coralloid nanostructured nickel oxide can be obtained from the nickel hydroxide hydrate after calcination at 400 °C. The thermal property, structure and morphology of samples were characterized by thermogravimetry (TG), temperature-programmed reduction (TPR), X-ray (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).     

Biological activity of carboxy-terminal gastrin analogs

Amidated forms of gastrin are derived by post-translational processing of a large precursor peptide and stimulate gastric acid secretion via the gastrin/CCK(B) receptor. Non-amidated biosynthetic intermediates may exert biological effects through other mechanisms, but their effect on gastric acid secretion is unclear. Amidated gastrins stimulate acid secretion mainly by releasing histamine from mucosal enterochromaffin-like cells. This study examines the effects on histamine release from the vascularly perfused rat stomach of amidated gastrin-17, COOH-terminal glycine-extended gastrin-17, gastrin-17 extended at the COOH-terminal including the remaining progastrin sequence, and carboxy-terminal progastrin fragments (SAEDEN and GRRSAEDEN). Carboxy-terminal extended gastrins induced histamine release which was inhibited by the gastrin/CCK(B) antagonist L-740,093, but had to be given in concentrations 100-fold higher than amidated gastrin-17 to produce comparable effects. These progastrin-derived peptides are found in high concentrations in some patients with the Zollinger-Ellison syndrome and may contribute to acid hypersecretion and other gastrin/CCK(B) receptor mediated responses.     

Numerical Analysis of Laterally Loaded 3 × 3 to 7 × 3 Pile Groups in Sands

The coupled bridge foundation-superstructure finite-element code FLPIER was employed to predict the lateral response of the single piles and 3 × 3 to 7 × 3 pile groups founded in both loose and medium dense sands. The p-multiplier factors suggested by McVay et al. for laterally loaded pile groups with multiple pile rows were implemented for the predictions. The soil parameters were obtained through a back-analysis procedure based on single pile test results. The latter, as well as the numerical predictions of both the single and group tests, are presented. It was found that the numerical code FLPIER did an excellent job of predicting the response of both the single piles and the 3 × 3 to 7 × 3 pile groups. The latter involved the predictions of lateral load versus lateral deflection of the group, the shears and bending moments developed in the individual piles, and the distributions of the lateral loads in each pile row, which were all in good agreement with the measured results.     

Application of preblasting to high-section top coal caving for steep-thick coal seam

For mining extra-steep-thick coal seam, the sublevel top coal caving is a high efficient method in practical engineering. However, major challenges associated with mining high-section top-coal-caving (HSTCC) are related to the resulting high ground stresses. Inevitability, using the high-section sublevel top coal caving for extra-steep-thick coal seam, the large scale of mined-out area appears. If the prefracture blasting and hydraulic fracture techniques are utilized, the top coal damage and cracks will develop, and the mining complexity will increase, such as seam inclination, continuity, mechanical characteristics of roof and susceptibility of top coal, etc. First, the field conditions of B₁₊₂ seam were investigated at the +588 level of the Weihuliang Underground Mine of China. Subsequently, according to caving mechanism of strata response obtained from several special models including physical simulation tests and numerical simulation models, the prefracture process including blasting and injecting water were analyzed. Then, the prefracture blasting technique was successfully applied to the caving of 52 m-sublevel seam. Finally, the effects were verified by advanced detecting instruments, and the results show these methods and measurements are feasible and valid.     

Very low noise RF nMOSFETs on plastic by substrate thinning and wafer transfer

A very low minimum noise figure (NF/sub min/) of 1.2 dB and a high associated gain of 12.8 dB at 10 GHz were measured for six-finger, 0.18-/spl mu/m radio frequency (RF) metal-oxide semiconductor field-effect transistors mounted on insulating plastic following substrate-thinning (/spl sim/30 /spl mu/m) and wafer transfer. Before this process, the devices had a slightly better RF performance of 1.1-dB NF/sub min/ and a 13.7-dB associated gain. The small RF performance degradation of the active transistors transferred to plastic shows the potential of integrating electronics onto plastic.     

NOLM-NALM fiber ring laser

We study the bidirectional lightwave propagations in an erbium-doped fiber ring laser and an inverted-S fiber ring laser, and observe their optical bistability behaviors. We develop a model for the inverted-S fiber ring laser using nonlinear optical loop mirror and nonlinear amplifying loop mirror (NOLM-NALM) principle, which operates in the nonlinear region. Good agreements between the laser experimental performance and the developed model are achieved. The laser shows good switching and pulse compression capabilities. In addition, the laser model illustrates the route to chaotic operation via period doubling bifurcation, when the input power increases. We also obtain quasi-periodic operation when the laser is amplitude modulated experimentally.     

An extended autocorrelation method for estimation of blood velocity

The conventional autocorrelation method (AM) to estimate the blood velocity for color flow imaging (CFI) is based on the phase estimation of the autocorrelation function. In this paper, a new extended autocorrelation method (EAM) that uses both phase and magnitude of the two dimensional (depth and temporal direction) autocorrelation function for estimating the blood velocity is presented. It is shown that the EAM has similar performance as the cross-correlation method (CCM). Both of them have smaller estimation variance than the AM and have the ability to estimate velocities beyond the Nyquist velocity, but the EAM is more computationally efficient than the CCM. A 2-D blood flow signal with rectilinear velocity including the transit time effect has also been simulated and the results are presented in this paper. For comparison, the EAM and the CCM have been applied to the simulated signals in which the flow velocities are up to four times the Nyquist velocity. The EAM has been further verified by experimental RF data from the subclavian artery     

HIV seroprevalence amongst pregnant women in northeastern Zaire

Heparin co-factor II is in addition to antithrombin III another heparin dependent thrombin inhibitor. This glycoprotein blocks thrombin action not only in haemostasis but also in its other effects. Congenital deficiency of heparin co-factor II was found equally frequently among asymptomatic subjects and patients with thrombotic complications. Although its deficiency probably is not a serious risk factor of thromboembolic disease, it can promote its development in a significant way. The authors describe the case of a child with thrombotic complications and a congenital deficiency of heparin co-factor II.