Analysis of a model for transport of charged particles in a random magnetic field

A model for the transport of charged particles in a random magnetic field is a Volterra integrodifferential equation with a long-range kernel. The integrodifferential equation is solved numerically with the method of Bellman, Kalaba, and Lockett (“Numerical Inversion of the Laplace Transform,” Elsevier, New York, 1966). The results are shown to be in excellent agreement with analytical asymptotic results.     

A two-dimensional cationic lattice built from [Zn6(HPO4)2(PO4)2]2+ clusters

A unique cationic zinc phosphate cluster linked by neutral bifunctional rigid ligands to form a two dimensional framework was synthesized and structurally characterized.     

Superconductivity and magnetism in dilute CdMn alloys. Strong depression in Tc

The superconducting transition temperature in dilute CdMn is depressed by 220K/at.% Mn. The Mn content was determined by Curie constant, resistance and atomic absorption measurements on the same sample. A small amount of the Mn is magnetically passive; the remaining Mn atoms have an effective magnetic moment of 4.80μ_B.     

Environmental effects of the determination of molecular dipole moments by stark spectroscopy

From the orientational Stark splitting in the absorption spectra of parafluoroaniline, the apparent change in dipole moment between the ground state and the first excited singlet state of this molecule isolated in a durene host crystal was found to be about 100% larger than the value reported for the vapor phase. Possible reasons for this difference are given.     

High temperature determination of the rate coefficient for the reaction H2O + CN → HCN + OH

The rate coefficient, k, of the reaction has been determined in the temperature range 2460–2840 K using a shock tube technique. C₂N₂? H₂O? Ar mixtures were heated behind incident shock waves and the CN and OH concentration time histories were monitored simultaneously using broad-band absorption near 388 nm (CN) and narrow-line laser absorption at 306.67 nm (OH). The rate coefficient expression providing the best fit to the data was with uncertainty limits of about ±45% in the temperature range 2460–2840 K. The rate coefficient of the reverse reaction was calculated using detailed balancing, and its extrapolation to lower temperatures was compared with previously published results.     

The Reduction of Organic Compounds with Chromium(II) Salts

Chromium(II) salts can be used for a variety of reductions in organic chemistry; for example, alkyl halides and suitably substituted olefins may both be reduced to alkanes, and alkynes may be converted into trans-olefins. Several epoxyketones are reduced to α,β-unsaturated ketones or β-hydroxyketones, and a nitro steroid was found to give a hydroxy(hydroxyimino) compound. The reduction of alkyl halides is reported to proceed by a free-radical mechanism; the halogen atom that is set free forms a bridge between two chromium atoms.     

In situ studies of the active sites for the water gas shift reaction over Cu-CeO2 catalysts: complex interaction between metallic copper and oxygen vacancies of ceria

New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO2 systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO2 nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuOx/CeO2 sample) were studied. The results from all of the samples indicate that both metallic copper and oxygen vacancies in ceria were involved in the generation of active sites for the WGS reaction. Evidence was found for a synergistic Cu-Ovacancy interaction. This interaction enhances the chemical activity of Cu, and the presence of Cu facilitates the formation of O vacancies in ceria under reaction conditions. Water dissociation occurred on the Ovacancy sites or the Cu-Ovacancy interface. No significant amounts of formate were formed on the catalysts during the WGS reaction. The presence of strongly bound carbonates is an important factor for the deactivation of the catalysts at high temperatures. This work identifies for the first time the active sites for the WGS reaction on Cu-CeO2 catalysts and illustrates the importance of in situ structural studies for heterogeneous catalytic reactions.     

Temporary phosphate tethers: a metathesis strategy to differentiated polyol subunits

[reaction: see text] Studies probing reactivity and selectivity of cross metathesis (CM) with an exocyclic olefin in a P-chiral bicyclo[4.3.1]phosphate triester are described. Studies have revealed a Type III CM reactivity pattern for the exocyclic olefin within this phosphate triester. This versatile method allows for simple, selective manipulation of a P-chiral building block en route to advanced polyol subunits.