Numerical modeling and experimental measurements of water spray impact and transport over a cylinder

This study compares experimental measurements and numerical simulations of liquid droplets over heated (to a near surface temperature of 423 K) and unheated cylinders. The numerical model is based on an unsteady Reynolds-averaged Navier–Stokes (RANS) formulation using a stochastic separated flow (SSF) approach for the droplets that includes submodels for droplet dispersion, heat and mass transfer, and impact on a solid surface. The details of the droplet impact model are presented and the model is used to simulate water spray impingement on a cylinder. Computational results are compared with experimental measurements using phase Doppler interferometry (PDI). Overall, good agreement is observed between predictions and experimental measurements of droplet mean size and velocity downstream of the cylinder.     

Immobilization ofAzacrown Ligand onto a Fluorophore

Geometric immobilization of azacrown ligand onto a fluorophore is expected to change their binding properties toward ion discrimination. An immobilized azacrown ligand 1 onto anthracene fluorophore senses Al(III), Cu(II) and Ga(III) in ethanol among the metal ions examined. In 100% aqueous solution, ligand 1 shows large CHEF effects with Al(III) and Ga(III) and large CHEQ effect with Hg(II). By comparison, non-immobilized azacrown ligand 2 showed large CHEF effects with Al(III), Ce(III), Ga(III), La(III) and Zn(II) in ethanol.     

Progress toward artificial metalloenzymes: New ligands for transition metal ions and neutral molecules

New nickel catalysts have been developed for the oxidation of alkenes to epoxides, alcohols, aldehydes and ketones. Mechanistic studies indicate that the oxidation reactions are very sensitive to the nature of the catalyst; only certain ligands including salen and the macrocycles cyclam and dioxocyclam render Ni(II) effective as a catalyst. A Ni(III) or Ni(IV)-oxo species has been postulated as the catalytically active oxidant which leads to oxygen atom transfer to alkenes in a stepwise process. Both iodosylbenzene and hypochlorite have been used as terminal oxidants; both systems give high yields of epoxidation of alkenes and varying amounts of C=C bond cleavage products. In order to reach an ultimate goal of hydrocarbon oxidation within a molecular recognition system, new molecular receptors for organic substrates have been investigated. The receptors are constructed from two subunits of cholic acid and display amphophilic character — a hydrophobic exterior and a hydrophilic interior. Conformational properties in the presence of polar guests in CDCl₃ are described.     

Peptide nucleic acid synthesis by novel amide formation

Synthesis of self-activated peptide nucleic acid (PNA) monomers and an efficient method for PNA synthesis using a benzothiazole-2-sulfonyl (Bts) group as an amine-protecting group as well as an acid-activating group are reported. Couplings were complete within 120 min, and the deprotection was performed in 10 min. This Bts strategy provides a high purity PNA oligomer and is appropriate for large-scale synthesis. The results of the 15-mer PNA oligomer are described.     

Development and validation of an ultra‐performance liquid chromatography method for simultaneous analysis of 20 antihistaminics in dietary supplements

The purpose of this study was to develop and validate an ultra‐performance liquid chromatography method for simultaneous analysis of 20 antihistamines (illegal additives) in dietary supplements. The limits of detection and quantitation of the method ranged from 1.5 to 2.5 µg/mL and from 20.0 to 50.0 µg/mL, respectively. The determination coefficient was >0.999, precisions were 0.2–5.1% (intra‐day) and 0.1–8.8% (inter‐day), and accuracies were 84.5–111.2% (intra‐day) and 91.9–112.0% (inter‐day). The mean recoveries of 20 targeted compounds from dietary supplements ranged from 75.4 to 119.3%. The relative standard deviations were <6.6% and complied with established international guidelines. The relative standard deviation of stability was <0.8%. Fifty‐two commercially available dietary supplements were evaluated using this method, and were found to have none of the 20 antihistamines in significant abundance. Copyright © 2014 John Wiley & Sons, Ltd.     

Optical parametric chirped pulse amplification of Cr:forsterite laser pulses in periodically poled stoichiometric LiTaO3 at 1 kHz

The first praseodymium-ytterbium up-conversion ZBLAN fiber laser in an all-fiber ring configuration is reported. The laser operates at 635 nm, is pumped at 835 nm, and consists of only the active ZBLAN fiber and two-fused-fiber couplers. PACS 42.55.Wd; 42.60.By     

Ab initio SCF calculations of the linear infinite chain of LiH according to the pseudo-lattice method

The pseudo-lattice (PL) method has been reformulated for ab initio self-consistent-field (SCF) calculations. The translational symmetries of infinite systems have been applied to the finite model chain by manipulating all the intramolecular and intermolecular Fock matrices. The nuclear repulsion energy has been corrected accordingly. The method has been tested for the linear chain of lithium hydride under the constraint of equidistance between all neighboring lithium and hydrogen atoms. The calculated results of the infinite chain have been compared with those of finite chains of lithium hydride under the same geometric constraint. The equilibrium geometries, band structures, intermolecular stabilization energies and potential curves have been studied. It is found that the infinite systems cannot be described by considering only first nearest neighbor interactions, and the intermolecular interactions must be considered at least up to third nearest neighbors in order to obtain accurate value of force constant of infinite systems. We can conclude from band structures of infinite chains that the boundary effect of the finite model chain is effectively removed by the PL method.