A short catalytic enantioselective synthesis of the vascular antiinflammatory eicosanoid (11R,12S)-oxidoarachidonic acid

[reaction: see text] An effective pathway is described for the synthesis of (11R, 12S)-oxidoarachidonic acid (1) from the achiral precursors shown.     

Particle collision rate in turbulent flow

The fluctuating relative motion of two solid particles or liquid drops in a turbulent gas flow is analysed, yielding an expression for collision rate as a function of the particle concentration and relaxation times and the turbulence intensity and scale. Unlike earlier theories, particles of intermediate size are included, having approach velocities neither well-correlated nor completely independent.     

The millimeter wave spectrum of phosphorus oxychloride

Millimeter wave rotational spectra of phosphorus oxychloride (OPCl₃) in the ground and excited vibrational states have been recorded and analyzed. The v₅ = 1 and v₆ = 1 state spectra show large splittings due to l resonance and the effect of the 2, -1 term r_t. Coriolis constants have been obtained for the two lowest degenerate states. The spectra of the asymmetric top species OP³⁵Cl₂³⁷Cl have been analyzed and centrifugal distortion constants obtained. These have been used to determine the harmonic force field of the molecule.     

Axially symmetric plumes at large Prandtl numbers

Summary The natural convection from a point source of heat is developed in an asymptotic series for moderate to large values of the Prandtl number.

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Zusammenfassung Die natürliche Konvektion von einer punktförmigen Wärmequelle wird in einer asymptotrischen Reihe für grosse und mässige Werte der Prandtl'schen Zahl dargestellet.

     

Parity violation observed in the beta decay of magnetically trapped 82Rb atoms

Laser cooling and atomic trapping techniques have been employed to confine polarized 82Rb atoms ( T1/2 = 75 s) in a magnetic time-orbiting-potential (TOP) trap. We have observed the parity-violating correlation between the emitted positron momentum and the parent nuclear spin as a continuous function of angle and positron energy for this pure Gamow-Teller (GT) transition. These proof-of-principle measurements demonstrate the utility of exploring fundamental symmetries in a TOP trap and the steps required to improve sensitivity in the search for physics beyond the standard model.     

Influence of strain rate and temperature on necking transition in a polydomain smectic main chain elastomer

Smectic main‐chain liquid crystalline elastomers (MCLCE) with polydomain morphology are rare examples of elastomers that can form a neck and undergo cold drawing under tension. However, not all previous studies of the mechanical behavior of smectic MCLCE reported neck formation. The mechanical response of a polydomain smectic MCLCE has therefore been characterized by elongation at varying strain rates and temperatures to identify factors favoring mechanical instability. Yielding and neck formation are increasingly favored as the strain rate increases at constant temperature, or as the temperature decreases toward T_g. As cold drawing proceeds, significant creep occurs continuously within the neck, in contrast to the behavior of certain linear polymers that exhibit a “natural” draw ratio. Thermal imaging during elongation indicates that viscous heating is not a prerequisite for neck formation. Rather, inherent softening of the material during yielding due to morphological changes leads to an enhanced rate of deformation and contraction at the neck. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Instrumental neutron activation analysis,a technique for measurement of Se,Hg, Fe,Zn, K,Mn, Br,and the Hg:Se ratio in brain tissue samples with results from the Memory and Aging Project (MAP)

An INAA method for measurement of Se, Hg, Fe, Cr, Zn, Mn, K, and Br in autopsy cerebellum, anterior putamen, white matter, mid-frontal cortex, and inferior temporal lobe. Se, Hg, Fe, Cr, and Zn were measured autopsy samples collected from participants of the Memory and Aging Project. The first study examined the association between seafood consumption, brain Hg and Se, Apolipoprotein E (APOE-ε4) status, and brain neuropathology. Following the initial study, the samples were archived. A subsequent method was developed to measure Mn, K, and Br in the archived brain tissue samples.     

CONCERNING THE ORIGIN OF CHARGE AT THE POLYSTYRENE PARTICLE/WATER INTERFACE

The electrophoretic mobility behavior of well-characterized polystyrene latex particles, carrying one type of surface functional endgroups, has been studied as a function of pH. At low pH, the interaction of protons with the functional endgroups increased in the order: Hydroxyl > carboxyl > sulfate; at high pH the order of interaction was reversed; and at intermediate pH no interactions were observed. The particles of the polystyrene latexes in their different forms at the intermediate pH range, dispersed in deionized water, all exhibited the same mobility irrespective of the functional endgroup. The origin of charge in these systems is explained as being the result of either the preferential adsorption of hydroxyl ions or an electron - injection mechanism due to the overlap of local intrinsic molecular - ion states in polystyrene and water. At low concentrations of functional endgroups, the surface properties of the polystyrene latexes are largely dependent upon the hydrophobic nature of the surface.     

A molecular simulation study of a cyclic siloxane with attached biphehylyl 4-allyloxybenzoate mesogens

A molecular simulation study of a cyclic siloxane macromolecule based on a pentamethylcyclosiloxane core and biphenylyl 4-allyloxybenzoate mesogenic units is reported. Molecular dynamics and semi-empirical calculations were used to provide insight into the conformation and the dielectric properties of the material. Out of three proposed conformations of the molecules, a cylindrical conformation was found to be the most probable. The intermolecular interactions were found to be optimized for the case where the mesogenic groups were planar and parallel to each other. The calculated mesogen length and inter-mesogen distances were consistent with available X-ray data. Electrostatic interactions were found to make a very significant contribution to the total energy. For the cylindrical model, the major component of the dipole was calculated to be along the long axis of the molecules. This is consistent with the alignment of the molecules parallel to a low frequency applied electric field as found experimentally.