The epitaxial growth of sputtered silicon layers on differently oriented substrates at low temperature - An electron microscopic study

We investigated epitaxial silicon films deposited on differently oriented substrates by pulsed magnetron sputtering at temperatures of 500-550 °C. Our scanning and transmission electron microscopic as well as electron backscattering investigations show that epitaxial films grow not only on (1 0 0)-oriented substrates, but also on (2 1 0)-, (4 1 1)- and (3 1 1)-oriented ones. A change to the (1 0 0) orientation is found for the growth on (1 1 1)- , (3 2 1)- and close to (1 1 0)-oriented substrates. For these orientations transmission electron microscopic investigations show stacking faults, microtwins and small amorphous inclusions in a region starting at the substrate-film interface up to thicknesses of 150-200 nm. With increasing film thickness above 200 nm the crystalline perfection of the epitaxial layers improves.     

Thermodynamic analysis of the low frequency relaxation time in the smectic A and C phases of a liquid crystal

Pressure-temperature-volume (pVT) measurements were carried out on 2-(4-hexyloxyphenyl)-5-octyl-pyrimidine, a substance exhibiting nematic and smectic A and C polymorphism. Analysis of the longitudinal relaxation times obtained recently for elevated pressures [Czub et al., Z. Naturforsch. A: Phys. Sci. 58, 333 (2003)] was performed for isobaric, isothermal, and isochoric conditions within the two smectic phases. Several relationships linking the dynamical and thermodynamical quantities, derived recently for isotropic glass formers [Roland et al. Rep. Prog. Phys. 68, 1405 (2005)], were found to hold for the liquid crystal, revealing a striking similarity of behaviors for these two types of materials. The parameter gamma characterizing the steepness of the interaction potential was derived in different ways. It is interesting that the liquid crystal gives relaxation time versus TV(-gamma) plots that are linear, unlike results for glass formers, implying that the dynamics of the former is thermally activated.     

Spin physics in few body systems at Nuclotron

The review of the recent results on spin effects in few nucleon systems obtained at LHEP-JINR are presented. The data on the deuteron analyzing powers in different reactions in the wide energy range demonstrate the sensitivity to the spin structure of the light nuclei. The future plans on the studies with polarized deuterons from new polarized ion source at Nuclotron will be reported.     

Phase velocities and attenuations of shear, Lamb, and Rayleigh waves in plate-like tissues submerged in a fluid (L)

In the past several decades, the fields of ultrasound and magnetic resonance elastography have shown promising results in noninvasive estimates of mechanical properties of soft tissues. These techniques often rely on measuring shear wave velocity due to an external or internal source of force and relating the velocity to viscoelasticity of the tissue. The mathematical relationship between the measured velocity and material properties of the myocardial wall, arteries, and other organs with non-negligible boundary conditions is often complicated and computationally expensive. A simple relationship between the Lamb-Rayleigh dispersion and the shear wave dispersion is derived for both the velocity and attenuation. The relationship shows that the shear wave velocity is around 20% higher than the Lamb-Rayleigh velocity and that the shear wave attenuation is about 20% lower than the Lamb-Rayleigh attenuation. Results of numerical simulations in the frequency range 0-500 Hz are presented.     

An Upper Bound for the Poisson Kernel on Higher Rank <Emphasis Type="Italic">NA</Emphasis> Groups

Let S be a semi direct product S=N\rtimes AS=N\rtimes A where N is a connected and simply connected nilpotent Lie group and A is isomorphic with ℝ ^k , k > 1. We obtain an upper bound for the Poisson kernel for the class of second order left-invariant differential operators on S.     

On-line (HPLC-NMR) and off-line phytochemical profiling of the Australian plant, Lasiopetalum macrophyllum

On-line (HPLC-NMR) and off-line (HPLC, NMR and MS) methodologies were used to profile the constituents present in the crude extract of Lasiopetalum macrophyllum. On-flow and stop-flow HPLC-NMR supported the presence of trans-tiliroside and permitted partial identification of cis-tiliroside and 4'-methoxy-trans-tiliroside. Off-line isolation led to the unequivocal identification of four flavanoid glycosides including a new structural derivative, 4'-methoxy-cis-tiliroside. This is the first report of flavonoid glycosides occurring in this plant genus. In addition, a number of structure revisions have been proposed for previously reported flavonoid glycosides that were incorrectly assigned.     

Chemical characteristics and source apportionment of PM_(10) during a brown haze episode in Harbin, China

This study investigates the correlation between PM 10 and meteorological factors such as wind speed, atmospheric visibility, dew point, relative humidity, and ambient temperature during a brown haze episode. In order to identify the potential sources of PM 10 during brown haze episode, respirable particulate matter (PM 10 ) was collected during both non-haze days and haze days and further analyzed for metallic elements, ionic species, and carbonaceous contents. Among them, ionic species contributed 45-64% t...     

Proton mobility and stability of water clusters containing the bisulfate anion, HSO4(-)(H2O)n

Bisulfate water clusters, HSO(4)(-)(H(2)O)(n), have been studied both experimentally by a quadrupole time-of-flight mass spectrometer and by quantum chemical calculations. For the cluster distributions studied, there are some possible "magic number" peaks, although the increase in abundance compared to their neighbours is small. Experiments with size-selected clusters with n = 0-25, reacting with D(2)O at a center-of-mass energy of 0.1 eV, were performed, and it was observed that the rate of hydrogen/deuterium exchange is lower for the smallest clusters (n < 8) than for the larger (n > 11), with a transition taking place in the range n = 8-11. We propose that the protonic defect of the bisulfate ion remains rather stationary unless the degree of hydration reaches a given level. In addition, it was observed that H/D scrambling becomes close to statistically randomized for the larger clusters. Insight into this size dependency was obtained by B3LYP/6-311++G(2d,2p) calculations for HSO(4)(-)(H(2)O)(n) with n = 0-10. In agreement with experimental observations, these calculations suggest pronounced effectiveness of a 'see-saw mechanism' for pendular proton transfer with increasing HSO(4)(-)(H(2)O)(n) cluster size.     

Fabrication and characterization of buckypaper-based nanostructured electrodes as a novel material for biofuel cell applications

The fabrication process of buckypapers (BPs) made from stable suspensions of as-received or functionalized multi-walled carbon nanotubes (MWCNTs) with high purity (97.5 wt%, Baytubes), their characterization and their utilization towards novel biofuel cell electrode applications are reported. The BPs can vary in thickness between 1 μm and 200 μm, are mechanically robust, flexible, stable in solvents, possess high meso-porosities as well as high apparent electrical conductivities of up to 2500 S m(-1). Potentiodynamic measurements of biocathodes based on bilirubin oxidase (BOD)-decorated BPs for the oxygen reduction reaction (ORR) in neutral media (phosphate buffer solution) containing glucose indicate that BP electrodes based on functionalized MWCNTs (fBPs) perform better than BP electrodes of as-received MWCNTs and have high potential as an effective electrode material in biofuel cells and biosensors.     

Phaseguides: a paradigm shift in microfluidic priming and emptying

Phaseguide technology gives complete control over filling and emptying of any type of microfluidic structures, independent of the chamber and channel geometry. The technique is based on a step-wise advancement of the liquid-air interface using the meniscus pinning effect. In this paper, the main effects and parameters underlying the phaseguiding principle are discussed and a demonstration is given of its potential for dead angle filling, spatially controlled phaseguide overflow and sequential phaseguide overflow, all accumulating in a passive valving approach. Phaseguides represent a new direction in microfluidic design thinking that will prove a leap forward towards more simple, flexible and reliable microfluidic systems.