Copper perchlorate hexahydrate: a highly efficient catalyst for the cyanosilylation of aldehydes

Cu(ClO₄)₂·6H₂O has been found to be an efficient catalyst for cyanosilylation reaction of aldehydes in THF at room temperature with low catalytic loading (1.0 mol%) in short reaction time (mostly within 10 min). Copyright © 2008 John Wiley & Sons, Ltd.     

Cationic Substitution Sites in Mn2+-doped ZnS Nanoparticles

Mn²⁺-doped ZnS nanoparticles of average size 2.5±0.3 nm have been studied and characterized in the dopant concentration range 0.1–0.3% using XRD, EPR, XPS and photoluminescence methods. The experimental results obtained from these studies indicate that the doping of Mn²⁺ occurs primarily at the T _d sites at low dopant concentration, causing the⁴T₁(G) → ⁶A₁(S) transition to take place in the host lattice; the observed decrease in the intensity of photoluminescence at high dopant concentration is due to the setting in of the strong Mn²⁺–Mn²⁺ interaction arising from cluster formation at the highly distorted sites near the particle surface.An erratum to this article can be found at     

Identification of objects in an acoustic wave guide inversion II: Robin–Dirichlet conditions

In this paper we investigate the unknown body problem in a wave guide where one boundary has a pressure release condition and the other an impedance condition. The method used in the paper for solving the unknown body inverse problem is the intersection canonical body approximation (ICBA). The ICBA is based on the Rayleigh conjecture, which states that every point on an illuminated body radiates sound from that point as if the point lies on its tangent sphere. The ICBA method requires that an analytical solution be known exterior to a canonical body in the wave guide. We use the sphere of arbitrary centre and radius in the wave guide as our canonical body. We are lead then to analytically computing the exterior solution for a sphere between two parallel plates. We use the ICBA to construct solutions at points ranging over the suspected surface of the unknown object to reconstruct the unknown object using a least‐squares matching of computed, acoustic field against the measured, scattered field. Copyright © 2005 John Wiley & Sons, Ltd.     

Improvement of mass source/sink for an immersed boundary method

An improved immersed boundary method using a mass source/sink as well as momentum forcing is developed for simulating flows over or inside complex geometries. The present method is based on the Navier–Stokes solver adopting the fractional step method and a staggered Cartesian grid system. A more accurate formulation of the mass source/sink is derived by considering mass conservation of the virtual cells in the fluid crossed by the immersed boundary. Two flow problems (the decaying vortex problem and uniform flow past a circular cylinder) are used to validate the proposed formulation. The results indicate that the accuracy near the immersed boundary is improved by introducing the accurate mass source/sink. Copyright © 2006 John Wiley & Sons, Ltd.     

The study of deNOx catalyst in low temperature using nano-sized supports

The present study pertains to a vanadium/titania-based catalyst for removing nitrogen oxides at a relatively low temperature window. More specially, the present study relates to a vanadium/titania-based catalyst containing VO_x (x < 2.5) and having excellent ability to remove nitrogen oxides at a wide temperature window, particularly at a relatively low temperature window and a process for removing nitrogen oxides using the same. In this study, various TiO₂ supports have been tested to determine the role of support. Raw TiO₂ were examined a variety of physical properties. Also comparing with commercial V₂O₅/TiO₂ catalyst, the activity of various VO_x (x < 2.5)/TiO₂ in this study have quite different values.To find the source of lattice oxygen in vanadium oxides, the effect of calcination conditions on the removal efficiency of nitrogen oxides was examined. When nitrogen instead of air was introduced as a balance gas in calcination step, the activity of catalysts in this study was not changed. That may indicate the source of lattice oxygen in vanadium oxides as that of TiO₂. The results of X-ray photoelectron spectroscope (XPS) revealed that after vanadium oxides loaded the support, TiO₂ was reduced to Ti₂O₃, etc. In the test of calcination temperature of a variety of vanadium/titania-based catalysts, it has been found that TiO₂ supports affects the optimal calcination temperature, indicating that the difference of crystal structure, defect and binding energy in TiO₂ may make inherent VO_x (x < 2.5)/V₂O₅ molar ratios, respectively. Its ratio seems to be an index of activity.     

Inverse problem for N × N hyperbolic systems on the plane and the N-wave interactions

We study regiorously the solvability of the direct and inverse problems associated with Ψ_x–JΨ_y = QΨ,(x,y) ∈ ?², where (i) Ψ is an N × N-matrix-valued function on ?² (N ≦ 2), (ii) J is a constant, real, diagonal N × N matrix with entries, J₁ > J₂ > …? > J_N and (iii) Q is off-diagonal with rapidly decreasing (Schwartz) component functions. In particular we show that the direct problem is always solvable and give a small norm condition for the solvability of the inverse problem. In the particular case that Q is skew Hermitian the inverse problem is solvable without the small norm assumption. Furthermore we show how these results can be used to solve certain Cauchy problems for the associated nonlinear evolution equations. For concreteness we consider the N-wave interactions and show that if a certain norm of Q(x, y, 0) is smallor if Q(x, y, 0) is skew Hermitian the N-wave interations equation has a unique global solution.     

Spin-glass-like phase behaviour in CeNi2−xCuxSn2

We report the results of our investigation in CeNi_2−xCu_xSn₂ (x=0, 0.4, 1.0, 1.6 and 2.0), a new pseudoternary series with CaBe₂Ge₂-type tetragonal structure. Substitution of Cu for Ni leads to a linear increase in the constants a, c and the unit cell volume v. As probed by the low temperature dependence of ac susceptibility χ_ac(T), the T_f temperature, which corresponds to the freezing temperature of the spin-glass clusters, is annihilated above 2.0 K significantly for the samples with x≥1.6. This observation proves conclusively that the Ni-rich samples in the series CeNi_2−xCu_xSn₂ have the advantage of forming the spin-glass-like state.     

Room temperature two-terminal characteristics in silicon nanowires

Quantum effects in silicon nanowires due to one-dimensional carrier confinement were observed at room temperature. Electrical transport properties were measured on narrow thin-silicon-on-insulator wires that were defined by e-beam lithography and further narrowed and thinned down by oxidation to a final thickness of around 3 nm, and a width of 29 nm. The room temperature current-voltage characteristics of the resulting silicon nanowires are shown to exhibit a zero current state may be due to the occurrence of Coulomb blockade.     

A ketogenic diet as a potential novel therapeutic intervention in amyotrophic lateral sclerosis

Background  

The cause of neuronal death in amyotrophic lateral sclerosis (ALS) is uncertain but mitochondrial dysfunction may play an important role. Ketones promote mitochondrial energy production and membrane stabilization.     

Cobalt(III) complexes of ethylenediamine-N,N′-di-S-isobutylacetic acid

A new optically active ONNO-type tetradentate ligand, ethylenediamine-N,N′- di-S-isobutylacetate (SS-eniba), has been synthesized. During the preparation of diaqua cobalt(III) complexes of SS-eniba, [Co(SS-eniba)(H₂O)₂]⁺, the title ligand has coordinated stereospecifically to the cobalt(III) ion to give three isomers, Δ-s-cis, Δ-uns-cis and Λ-uns-cis, which have been isolated and characterized via electronic absorption, circular dichroism (CD), and ¹H NMR spectroscopy, along with elemental analysis data. The preparation of Δ-s-cis-[Co(SS-eniba)Cl₂]⁺ and Δ-s-cis-[Co(SS-eniba)CO₃]⁺ are also reported.