Synthesis and characterization of ammonium molybdophosphate–silica nano-composite (AMP–SiO2) as a prospective sorbent for the separation of 137Cs from nuclear waste

The ammonium molybdophosphate–silica (AMP–SiO₂) nano-composites were prepared by sol–gel method. The material synthesized was nanocrystalline, with average crystallite size of primary particles in the range of 10–25 nm. Small angle X-ray scattering showed presence of mass fractal aggregates made of small particles with rough pore boundaries. To realize the scope of using AMP–SiO₂ nano-composites sorbent for removal of ¹³⁷Cs from nuclear waste solutions, its adsorption characteristics for cesium were evaluated. It was found that the AMP–SiO₂ nanocomposites were amenable for column operation, have high affinity for Cs, and possess very high adsorption capacity for Cs. From the perspective of separation of ¹³⁷Cs from acidic radioactive waste solution, AMP–SiO₂ nanocomposite holds significant promise.     

CO sensor derived from mesostructured Au-doped SnO2 thin film

Pure and Au-doped mesostructured SnO₂ thin films were successfully prepared by using non-ionic surfactant Brij-58 (polyoxyethylene acyl ether) as organic template and tin tetrachloride and hydrogen tetrachloroaurate(III) trihydrate as inorganic precursor. Thin films were deposited onto the glass substrates at 450 °C by simple spray pyrolysis technique. The novel mesostructured tin oxide thin films with different Au concentration exhibit highly selective response towards CO. The correlation of the Au incorporation in the mesostructure with particular morphology and gas sensing behavior is discussed using scanning electron microscopy (SEM), X-ray diffraction (XRD), BET surface area and transmission electron microscopy (TEM) studies.     

Guidelines for using variable selection techniques in data envelopment analysis

Model misspecification has significant impacts on data envelopment analysis (DEA) efficiency estimates. This paper discusses the four most widely-used approaches to guide variable specification in DEA. We analyze efficiency contribution measure (ECM), principal component analysis (PCA-DEA), a regression-based test, and bootstrapping for variable selection via Monte Carlo simulations to determine each approach’s advantages and disadvantages. For a three input, one output production process, we find that: PCA-DEA performs well with highly correlated inputs (greater than 0.8) and even for small data sets (less than 300 observations); both the regression and ECM approaches perform well under low correlation (less than 0.2) and relatively larger data sets (at least 300 observations); and bootstrapping performs relatively poorly. Bootstrapping requires hours of computational time whereas the three other methods require minutes. Based on the results, we offer guidelines for effectively choosing among the four selection methods.     

Lewis Acid Catalyzed,Selective Cyclopropane‐Ring Opening in Ingol Diterpene Derivatives

Lewis acid mediated skeletal rearrangement of the ingol diterpenoids 1 and 4 via regio‐ and stereospecific cyclopropane‐ring opening afforded the four new compounds 2, 3, 5 , and 6 , named nivulianol A–D (Scheme 1). Their structures were established by means of IR, MS, and in‐depth NMR spectroscopic analyses. The rearranged congeners were tested for lipopolysaccharide (LPS)‐induced prostaglandin (PG) E₂ (cyclooxygenase‐2) inhibition. Thereby, nivulianol B (=(1S*,2E,4R*,5S*,7Z,9S*,11R,13S*,14S*)‐14‐acetoxy‐5‐methoxy‐3,9,13‐trimethyl‐6‐(1‐methylethenyl)‐10‐oxo‐15‐oxatricyclo[9.3.1.0^1,11]pentadeca‐2,7‐dien‐4‐yl (2Z)‐2‐methylbut‐2‐enoate; 3 ) was found to be significantly active, with an IC₅₀ value of 36.3 μg/ml.     

Free convection effects on HMD horizontal channel flow with Hallcurrents

An exact solution of MHD channel flow between two horizontal parallel plates taking into account free convection currents and the Hall currents is presented. Solutions for the primary and secondary velocity, the induced magnetic field, the skin friction, and the temperature are derived. The velocity field and magnetic field are shown on graphs, and the values of the skin friction and the rate of heat transfer are indicated on tables. The results are discussed in terms of the hall parameter, the Hartmann number, and the Grashof number     

Bio‐based hyperbranched polyurethane/clay nanocomposites: adhesive,mechanical, and thermal properties

The unison of vegetable oil‐based hyperbranched polymers with nanotechnology can unhook myriad of avant‐garde applications of such materials. Thus Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/clay nanocomposites and their performance, with special reference to adhesive strength, are reported for the first time. The nanocomposites of the hyperbranched polyurethane with organically modified nanoclay were obtained by ex situ solution technique and cured by bisphenol‐A‐based epoxy with poly(amido amine) hardener system. The partially exfoliated and well‐distributed structure of nanoclay was confirmed by XRD, SEM, and TEM studies. FTIR spectra indicate the presence of H‐bonding between nanoclay and the polymer matrix. Two times improvement in the adhesive strength and scratch hardness, 10 MPa increments in the tensile strength and 112°C more thermo‐stability have been observed without much affecting the impact resistance, bending, and elongation at break of the nanocomposites compared to the pristine epoxy modified HBPU system. Thus, the resulted nanocomposites are promising materials for different advanced applications including adhesive. Copyright © 2009 John Wiley & Sons, Ltd.     

Integral motives and special values of zeta functions

For each field , we define a category of rationally decomposed mixed motives with -coefficients. When is finite, we show that the category is Tannakian, and we prove formulas relating the behaviour of zeta functions near integers to certain groups.

     

Unusual redox and chemical properties of N4-substituted pyridoxal thiosemicarbazone copper(II) complexes: their preparation,properties and reactivities

Summary New copper(II) complexes with pyridoxal N⁴-methylthiosemicarbazone (H₂Methsa), N⁴-ethylthiosemicarbazone (H₂Etthsa) and N⁴-phenylthiosemicarbazone (H₂Phthsa) have been prepared and characterized by analytical, magnetic, spectral, e.s.r. and electrochemical methods. All the compounds exhibit normal magnetic moments at room temperature. The variable temperature magnetic moments, however, show the presence of very weak intramolecular antiferromagnetic interaction (–2J = ca. 30cm^-1) between the copper(II) centres in the complexes. The e.s.r. spectra at 77 K in DMSO indicate the presence of a mixture of monomers and dimers consistent with the dissociation of the complexes. Electrochemical studies in non-aqueous solvents show that the complexes undergo a quasi-reversible one electron facile reduction at markedly low negative potentials versus saturated calomel electrode (s.c.e.).     

Manipulating valence and core electronic excitations of a transition-metal complex using UV/Vis and X-ray cavities

We demonstrate how optical cavities can be exploited to control both valence- and core-excitations in a prototypical model transition metal complex, ferricyanide ([Fe(iii)(CN)₆]³⁻), in an aqueous environment. The spectroscopic signatures of hybrid light-matter polariton states are revealed in UV/Vis and X-ray absorption, and stimulated X-ray Raman signals. In an UV/Vis cavity, the absorption spectrum exhibits the single-polariton states arising from the cavity photon mode coupling to both resonant and off-resonant valence-excited states. We further show that nonlinear stimulated X-ray Raman signals can selectively probe the bipolariton states via cavity-modified Fe core-excited states. This unveils the correlation between valence polaritons and dressed core-excitations. In an X-ray cavity, core-polaritons are generated and their correlations with the bare valence-excitations appear in the linear and nonlinear X-ray spectra.

We demonstrate how optical cavities can be exploited to control both valence- and core-excitations in a prototypical model transition metal complex, ferricyanide ([Fe(iii)(CN)₆]³⁻), in an aqueous environment.