Reduction of acid chlorides with sodium borohydride in N,N-dimethylformamide: Nature of the reaction intermediate and a method for its conversion to the corresponding aldehyde with minimal alcohol formation

By use of sodium borohydride under the proper reaction conditions, direct conversion of both aliphatic and aromatic acid chlorides to the corresponding aldehyde can be achieved in 80–95% yield.     

A novel reducing agent derived from formic acid and two equivalents of a grignard reagent: Chemoselective reduction of aldehydes

Aldehydes are reduced at a moderate rate by use of a novel reagent obtained by the addition of two molar equivalents of ethylmagnesium bromide to formic acid in tetrahydrofuran solution. Under similar conditions the reduction of ketones proceeds quite slowly.     

Rearrangement of Rare Earth Defects Under Domain Inversion in LiNbO3

Using high resolution excitation-emission spectroscopy we investigated the changes occurring in the optical transition of Er^3? ions in LiNbO₃ during inversion of the ferroelectric axis. In stoichiometric LiNbO₃ we find that a drastic reconfiguration among the different defect sites takes places favoring those centers which have already been dominant in the as-grown sample. The reconfiguration is attributed to changes in the arrangement of the local charge compensators. Furthermore, we find a small shift of the emission transition energy, which is consistent with an increase of the intrinsic electric field. These findings make the Er^3? ions very suitable probes for 3D imaging of domain structures and for in-situ studies of the dynamics of the domain inversion processes and the defect/domain wall interaction.     

Comparative Studies of Er3☎ Ions in LiNbO3 Waveguides Produced by Different Methods

We compare the optical properties of Er^3? in LiNbO₃ waveguides produced by different techniques and find by confocal luminescence microscopy characteristic differences in the excitation and emission transitions. Besides a small redistribution among the regular defect sites, essentially no direct Er^3?—Ti^4? interaction can be observed in Ti^4? diffused waveguides. However a significant shift in transition energies is found, which increases with Ti^4?concentration. Based on earlier results we associate this shift with a decrease in the intrinsic electric field. In addition to a similar shift, we find in Zn^2? diffused waveguides new defect types which suggest a change in direct environment. Finally, in annealed proton exchange waveguides we find no interaction effects at all.     

The scaling of the current voltage characteristics of the YBa2Cu3O7:Y2BaCuO5 composites

We have investigated features in the current voltage (I—V) characteristics of YBa₂Cu₃O₇:Y₂BaCuO₅ composite sinters which indicate the occurrence of a second-order phase transition. For each sinter composition similar families of characteristics are found for a wide range of magnetic fields. The relation between V and I is seen to be of the form V = f(I, ζ(B, T)) where a single parameter ξ contains all of the field and temperature dependence. The locus of points in the B, T plane for which ζ(B, T) is a constant have been examined, and a low field and a high field régime have been identified. Samples of different composition show families of I—V characteristics which scale onto one another in a simple way, hence we are led to suppose the V = f(I, ζ(B, T, p)) where p is the dilution fraction. Data taken at temperatures below the phase transition agrees well with a simple scaling picture of dissipation close to a second order phase transition, with exponents which are independent of magnetic field and composition. Above the transition, however, the behaviour is more complex.     

Wave body interaction in 2D using smoothed particle hydrodynamics (SPH) with variable particle mass

Wave interaction with bodies is an important practical application for smoothed particle hydrodynamics (SPH) which in principle applies to steep and breaking waves without special treatment. However, few detailed tests have been undertaken even with small amplitude waves. In order to reduce computer time a variable particle mass distribution is tested here with fine resolution near the body and coarse resolution further away, while maintaining a uniform kernel size. We consider two well‐defined test cases, in two dimensions, of waves generated by a heaving semi‐immersed cylinder and progressive waves interacting with a fixed cylinder. But first, still water with hydrostatic pressure is tested. The open‐source code SPHysics ( http://www.sphysics.org )^{§Update made here after initial online publication.} is used with a Riemann solver in an Arbitrary Lagrangian–Eulerian formulation. For the heaving cylinder, SPH results for far field wave amplitude and cylinder force show good agreement with the data of Yu and Ursell (J. Fluid Mech. 1961; 11 :529–551). For wave loading on a half‐submerged cylinder the agreement with the experimental data of Dixon et al. (J. Waterway Port Coastal Ocean Div. 1979; 105 :421–438) for the root mean square force is within 2%. For more submerged cases, the results show some discrepancy, but this was also found with other modelling approaches. The sensitivity of results to the value of the slope limiter used in the MUSCL‐based Riemann solver is demonstrated. The variable mass distribution leads to a computer run speedup of nearly 200% in these cases. Copyright © 2011 John Wiley & Sons, Ltd.     

Allylic interactions in organometallics: probing Electronic structure in (η5-C5H5)Fe(CO)2R,R = CH3, η1-C3H5, η1-C5H5.

The He(I) photoelectron spectra of (η⁵-C₅H₅)Fe(CO)₂R, where R = CH₃, η¹-C₃H₅ and η¹-C₅H₅, have been recorded. The lowest lying ion states result from ionization of molecular orbitals with large Fe 3d character; these move to lower anergy when R places double bonds in an allylic relationship to the metal atom. The cyclic voltammetric oxidation potential correlates well with the energies of the lowest ion states. A significant interaction between olefin π orbitals and the allylic metal center is proposed.