HfO2/AlGaN/GaN structures with HfO2 deposited at ultra low pressure using an e‐beam

We show that HfO₂/AlGaN/GaN structures with HfO₂ layer deposited using an e‐beam in ultra high vacuum are suitable for field effect transistors. The dielectric constant of the HfO₂ was found ε_HfO > 23–24, which is close to the highest re‐ ported values for this material. The leakage current did not exceed 10^–4 A/cm² at the threshold voltage. The comparison of the losses in the samples with and without HfO₂ indicates low concentration of the interface traps. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

M(R-dmet)2] bis(1,2-dithiolenes): a promising new class intermediate between [M(dmit)2] and [M(R,R'-timdt)2] (M = Ni, Pd, Pt)

We report the first examples of metal dithiolenes belonging to the class [M(R-dmet)(2)] [R-dmet = formally monoreduced N-substituted thiazolidine-2,4,5-trithione; R = Et, M = Ni (1), Pd (2), Pt (3)]. A comparative spectroscopic, electrochemical, and density functional theory theoretical investigation indicates that [M(R-dmet)(2)] complexes show features intermediate between those of the dithiolenes belonging to the previously reported classes [M(R,R'-timdt)(2)] and [M(dmit)(2)] (R,R'-timdt = formally monoreduced N,N'-disubstituted imidazolidine-2,4,5-trithione; dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato). UV-vis-near-IR spectroscopy and cyclic voltammetry/differential pulsed voltammetry measurements performed on 1 and 3 proved that the new dithiolenes are stable as neutral, monoanionic, and bianionic species and feature a near-IR electrochromic absorption falling at about 1000 and 1250 nm for neutral and monoanionic species, respectively.     

The use of water-soluble phthalocyanines as textile dyes in nylon/elastane fabric: fastness and antibacterial effectiveness

This work reports on dyeing of nylon/elastane fabric with water-soluble phthalocyanines ( 1-4 ) bearing quinoline 5-sulfonic acid substituents on the peripheral or nonperipheral positions and determining the antibacterial efficiency of the phthalocyanine compounds and the dyed nylon/elastane fabrics. The light, washing, water, perspiration, and rubbing fastness properties of nylon/elastane fabrics dyed with phthalocyanines were also determined. The results showed that all dyed fabrics showed very good wet fastness values. The lightfastness value of the nylon/elastane fabric dyed with phthalocyanine dye ( 1 ) showed a much better value than the others. Also, the antibacterial efficiencies of the dyed nylon fabrics and the dye compounds were investigated against a gram-negative ( Escherichia coli ) and a grampositive ( Staphylococcus aureus ) bacteria by using disc diffusion method. The results showed that the dyed nylon/elastane fabrics and the compounds exhibited antibacterial activities against both bacteria.     

Determining the adsorptive and catalytic properties of strained metal surfaces using adsorption-induced stress

We demonstrate a model for determining the adsorptive and catalytic properties of strained metal surfaces based on linear elastic theory, using first-principles calculations of CO adsorption on Au and K surfaces and CO dissociation on Ru surface. The model involves a single calculation of the adsorption-induced surface stress on the unstrained metal surface, which determines quantitatively how adsorption energy changes with external strain. The model is generally applicable to both transition- and non-transition-metal surfaces, as well as to different adsorption sites on the same surface. Extending the model to both the reactant and transition state of surface reactions should allow determination of the effect of strain on surface reactivity.     

Generalized Method of Separation of Variables on the Nonlinear Elastic-Plastic Wave Motion

The method of separation of variables is developed in addition to the Karman method and the method of characteristics for the wave motion of uniaxial stress in rods. Rate-independent theory is considered and it is shown that the plastic wave speed is independent of the constant n in the stress-strain law. Stresses are determined in explicit forms for two cases.     

Low-frequency noise in monodisperse platinum nanostructures near the percolation threshold

The percolation threshold p ₀ ≈ 0.6 is determined for monodisperse platinum nanostructures with 1.8-nm metallic particles deposited in a monolayer onto an insulating substrate through laser electrodispersion. It is shown that, in the “metallic” state (for p > p ₀), both the magnitude of the noise and its temperature dependence are close to those of pure metallic Pt layers. The frequency dependence of the normalized noise power spectral density is described by the relationship S _I /I ² ～ 1/f ^γ with the exponent γ close to unity. For current densities j ≥ 10⁷?10⁸ A/cm², the noise power spectral density S _I increases more rapidly with a further increase in the current as compared to I ² because of the current generating excess defects. For p < p ₀, the dependence of the conductivity σ on the temperature is adequately described by the standard relationship σ ～ exp[?(T ₀/T)^1/2]. The normalized noise power spectral density S _I /I ² exceeds the corresponding value for a quasi-metallic structure by many orders of magnitude. The noise power spectral density S _I is approximately proportional to the square of the current only for very low currents and increases steeply with a further increase in the current.     

Terpene compounds as drugs. XVI. Characterization of the anabolic 19-nortestosterone 17 -trans, trans- and -cis, trans-homofarnesate

19-Nortestosterone 17β-trans, trans- and -cis, trans-homofarnesate 1 and 2 have been prepared and characterized. Their structure and configuration were identified by mode of formation, elemental analyses, IR. and particularly by NMR. spectra.     

SOME CENTRAL LIMIT THEOREMS FOR SUPER BROWNIAN MOTION

The author proves a central limit theorem for the critical super Brownian motion, which leads to a Gaussian random field. In the transient case the limitingfield is the same as that obtained by Dawson (1977). In the recurrent case it is aspatially uniform field. The author also give a central limit theorem for the weightedoccupation time of the super Brownian motion with underlying dimension numberd 3, completing the results of Iscoe (1986).     

Occupational prolonged organic solvent exposure in shoemakers: brain MR spectroscopy findings

Our purpose was to investigate, by magnetic resonance (MR) spectroscopy, the metabolite changes in the brains of subjects in the shoemaking industry who had been chronically exposed to organic solvents. A total of 49 male subjects and 30 age-matched healthy volunteers underwent detailed neurological and psychiatric examinations. All subjects had long-echo [repetition time (TR) 2000 ms, echo time (TE) 136 ms] single-voxel MR spectroscopy. Voxels (15 x 15 x 15 mm(3)) were placed in the parietal white matter, thalamus, and basal ganglia. N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from thalamus, basal ganglia, and parietal white matter. Cho/Cr ratios in thalamus, basal ganglia, and parietal white matter were found to be significantly increased compared to controls. There was a positive correlation between basal ganglia Cho/Cr ratio and duration of exposure (r = 0.63). MR spectroscopy should be performed to reveal metabolite changes and determine the degree of brain involvement in solvent-related industry workers.