Oxidation kinetics of nitrogen doped TiO(2-δ) thin films

The oxidation kinetics of nitrogen doped, oxygen deficient titanium dioxide thin films has been studied in atmospheres of pure oxygen or nitrogen at 500 °C, 550 °C, and 600 °C, respectively, by means of in situ optical spectroscopy. The thin films show high electronic absorbance in the visible and NIR region, accompanied by a red shift of the absorption edge of about 0.4 eV, e.g., from about 2.9 to 2.5 eV at 600 °C. The time dependent decrease of absorbance due to oxidation is found to follow a parabolic rate law. An activation energy of about 1.96 eV can be obtained from the temperature dependence of the parabolic oxidation rate constant. In the framework of a microscopic oxidation model, this energy barrier is attributed to the diffusion of titanium interstitials in the re-oxidized part of the thin films as a rate-determining process. In addition, an attempt is made to evaluate the kinetics of nitrogen release from the time dependent blue shift of the absorption edge during re-oxidation.     

Defect structure and Fermi-level pinning of BaTiO3 co-doped with a variable-valence acceptor (Mn) and a fixed-valence donor (Y)

Defect structures of BaTiO(3) and the like co-doped with variable-valence acceptors and donors are not clear particularly in transition from acceptor domination to donor domination with increasing oxygen activity. We have, thus, examined the electrical conductivity and thermoelectric power of BaTiO(3) co-doped with a variable-valence acceptor Mn(Mn(Ti)', Mn(Ti)') and a fixed-valence donor Y(Y(ba)·) in different co-doping ratios (m(d)/m(a)) as functions of oxygen activity in the range of -20 < log?a(O(2))≤ 0 at elevated temperatures of 900-1100 °C. Their systematic variations with m(d)/m(a) and log?a(O(2)) are reported, and thereby defect structures of the co-doped BaTiO(3) depending on m(d)/m(a) are determined. It is found that for the co-doping ratio 1 < m(d)/m(a) < 2, the Fermi level is pinned at a few kT's around the deep level of Mn(Ti)' across the otherwise p-type semiconducting log?a(O(2))-region of Mn-singly doped BaTiO(3), and attributed to deep acceptor-shallow donor mutual compensation 2[Mn(Ti)'] + [Mn(Ti)'] ≈ [Y(ba)·], thus turning otherwise p-type semiconducting BaTiO(3) semi-insulating.     

A simple isocratic HPLC method for the simultaneous determination of bioactive components of Scutellariae Radix extract

Scutellariae Radix, the dried root of Scutellaria baicalensis Georgi, has been widely used in Asian countries for the treatment of dermatitis, diarrhoea, inflammatory disease and hepatic disease. A simple, sensitive and precise reversed-phase liquid chromatographic method with isocratic elution was developed to simultaneously determine four bioactive compounds in Scutellariae Radix: baicalein, baicalin, wogonin and wogonoside. Chromatographic analysis was performed on a YMC Pack Pro C(8) column (150?×?4.6?mm(2), 3?μm), with a mobile phase of 0.1% formic acid?:?acetonitrile (70?:?30, v/v) at a flow rate of 1.0?mL?min(-1), and UV detection at 280?nm. Linear behaviour was observed over the investigated concentration range (0.25-10?μg?mL(-1)) for all analytes, with a correlation coefficient of >0.997. The intra- and inter-day precisions were <8.07%, and accuracies were 92.3-102.9%. This method was successfully applied for the analysis of marker compounds for the quality control of Scutellariae Radix extract.     

Pixel based focusing for photoacoustic and ultrasound dual-modality imaging

It is desired that the same imaging functional modules such as beamformation, envelope detection, and digital scan conversion (DSC) are employed for the efficient development of a cross-sectional photoacoustic (PA) and ultrasound (US) dual-modality imaging system. The beamformation can be implemented using either delay-and-sum beamforming (DAS-BF) or adaptive beamforming methods, each with their own advantages and disadvantages for the dual-modality imaging. However, the DSC is always problematic because it causes blurring the fine details of an image, e.g., edges. This paper demonstrates that the pixel based focusing method is suitable for the dual-modality imaging; beamformation is directly conducted on each display pixel and thus DSC is not necessary. As a result, the artifacts by DSC are no longer a problem, so that the proposed method is capable of providing the maximum spatial resolution achievable by DAS-BF. The performance of the proposed method was evaluated through simulation and ex vivo experiments with a microcalcification-contained breast specimen, and the results were compared with those from DAS-BF and adaptive beamforming methods with DSC. The comparison demonstrated that the proposed method effectively overcomes the disadvantages of each beamforming method.     

Characteristic boundary conditions for simulations of compressible reacting flows with multi-dimensional,viscous and reaction effects

A generalized formulation of the characteristic boundary conditions for compressible reacting flows is proposed. The new and improved approach resolves a number of lingering issues of spurious solution behaviour encountered in turbulent reacting flow simulations in the past. This is accomplished (a) by accounting for all the relevant terms in the determination of the characteristic wave amplitudes and (b) by accommodating a relaxation treatment for the transverse gradient terms with the relaxation coefficient properly determined by the low Mach number asymptotic expansion. The new boundary conditions are applied to a comprehensive set of test problems including: vortex-convection; turbulent inflow; ignition front propagation; non-reacting and reacting Poiseuille flows; and counterflow cases. It is demonstrated that the improved boundary conditions perform consistently superior to existing approaches, and result in robust and accurate solutions with minimal acoustic wave interactions at the boundary in hostile turbulent combustion simulation conditions.     

Compositional dependence of the deformation behaviour of ultrahigh-purity Ti–Al alloys

The present study is concerned with the effect of the O and Al concentrations on the deformation behaviour of ultrahigh-purity (UHP) Ti–(48,?50,?52)?at.%?Al alloys using UHP Ti with 30?wt?ppm?O. It has been shown that yield strength increases with increasing O content. Stoichiometric Ti–50?at.%?Al alloys had the lowest yield strength and the highest ductility when the O content was sufficiently low. It is suggested that the deformation mechanism of UHP binary Ti–Al is strongly related to the Al concentration. The deformation substructure of UHP Ti–48?at.%?Al is shown to be dominated by ordinary dislocation as well as deformation twinning and a small portion of superdislocations. The deformation substructure of UHP Ti–50?at.%?Al alloy was similar to that of Ti–48?at.%?Al, but deformation twinning was not observed. Most of dislocation structures of UHP Ti–52?at.%?Al alloy consisted of faulted dipoles. The major deformation mode of UHP Ti–48?at.%?Al and UHP Ti–50?at.%?Al alloys was ordinary dislocation in deformation orientation, which takes advantage of ordinary dislocation slip. However, the major deformation mode in this orientation for UHP Ti–52?at.%?Al alloys was superdislocation slip.     

Electrical conductivity and optical transparency of bacterial cellulose based composite by static and agitated methods

Composites consisting of bacterial cellulose (BC) and ionic conducting polymer (ICP) were prepared. BC was biosynthesized in media at 0, 25, 50 and 100 rpm. ICP was chemically synthesized at different concentrations of ionic salt. The corresponding electrical conductivity of the composites was measured as a function of ionic salt concentration. ICP improved the optical transparency and electrical conductivity of the BC/ICP composites. Morphological images of BC/ICP composites showed that the pore size of the BC pellicle increased while the diameter and density of the BC fibers decreased. The cultivation method was critical in affecting the structure and electrical conductivity of the composites.     

Multiple Degree Reduction and Elevation of Bézier Curves Using Jacobi–Bernstein Basis Transformations

In this article, we find the optimal r times degree reduction of Bézier curves with respect to the Jacobi-weighted L ₂-norm on the interval [0, 1]. This method describes a simple and efficient algorithm based on matrix computations. Also, our method includes many previous results for the best approximation with L ₁, L ₂, and L _∞-norms. We give some examples and figures to demonstrate these methods.     

Ni(0)-promoted activation of Csp2–H and Csp2–O bonds

A dinickel(0)–N₂ complex, stabilized with a rigid acridane-based PNP pincer ligand, was studied for its ability to activate C(sp²)–H and C(sp²)–O bonds. Stabilized by a Ni–μ–N₂–Na⁺ interaction, it activates C–H bonds of unfunctionalized arenes, affording nickel–aryl and nickel–hydride products. Concomitantly, two sodium cations get reduced to Na(0), which was identified and quantified by several methods. Our experimental results, including product analysis and kinetic measurements, strongly suggest that this C(sp²)–H activation does not follow the typical oxidative addition mechanism occurring at a low-valent single metal centre. Instead, via a bimolecular pathway, two powerfully reducing nickel ions cooperatively activate an arene C–H bond and concomitantly reduce two Lewis acidic alkali metals under ambient conditions. As a novel synthetic protocol, nickel(ii)–aryl species were directly synthesized from nickel(ii) precursors in benzene or toluene with excess Na under ambient conditions. Furthermore, when the dinickel(0)–N₂ complex is accessed via reduction of the nickel(ii)–phenyl species, the resulting phenyl anion deprotonates a C–H bond of glyme or 15-crown-5 leading to C–O bond cleavage, which produces vinyl ether. The dinickel(0)–N₂ species then cleaves the C(sp²)–O bond of vinyl ether to produce a nickel(ii)–vinyl complex. These results may provide a new strategy for the activation of C–H and C–O bonds mediated by a low valent nickel ion supported by a structurally rigidified ligand scaffold.

A structurally rigidified nickel(0) complex was found to be capable of cleaving both C(sp²)–H and C(sp²)–O bonds.