The equation of state of hard hyperspheres in four and five dimensions

The equation of state of hard hyperspheres in four and five dimensions is calculated from the value of the pair correlation function at contact, as determined by Monte Carlo simulations. These results are compared to equations of state obtained by molecular dynamics and theoretical approaches. In all cases the agreement is excellent.     

Synthesis of periphery-functionalized dendritic molecules using polylithiated dendrimers as starting material

A general method for the functionalization of Si-Cl terminated carbosilane dendritic molecules via organolithium or organomagnesium reagents is described. Quantitative exchange of the bromine atoms of 4-bromophenyl-functionalized dendrimers affords polylithiated species that are valuable starting materials for further functionalization, e.g., into pyridyl alcohols. The latter were successfully applied as catalyst precursors in a ruthenium-mediated ring-closure metathesis reaction.     

Fusion Reaction Gas Chromatography

The conventional gas chromatograph is an efficient tool for separating mixtures of volatile compounds into their individual components for quantitative measurement and for preparative isolation of the components. Many compounds, however, are nonvolatile or lack sufficient volatility for gas chromatographic separation. These compounds may contain polar functional groups (i.e.r -COOH, -OH, -NO₂ -NH₂, etc.), which cause low volatility or poor chroma tographic behavior, or ionic groups (i.e., -SO₃Na, R₄NX-SO₄Na, -WNCl, etc.), which are either completely nonvolatile or thermal unstable. Other compounds have too large molecular weights for conventional gas chromatographic separation.     

Condensate splitting in an asymmetric double well for atom chip based sensors

We report on the adiabatic splitting of a Bose-Einstein condensate of 87Rb atoms by an asymmetric double-well potential located above the edge of a perpendicularly magnetized TbGdFeCo film atom chip. By controlling the barrier height and double-well asymmetry, the sensitivity of the axial splitting process is investigated through observation of the fractional atom distribution between the left and right wells. This process constitutes a novel sensor for which we infer a single shot sensitivity to gravity fields of deltag/g approximately 2 x 10(-4). From a simple analytic model, we propose improvements to chip-based gravity detectors using this demonstrated methodology.     

Stereoselective synthesis of tetrahydropyran-3-ones by rearrangement of oxonium ylides generated from metal carbenoids

The synthesis of tetrahydropyran-3-ones by copper-catalysed reactions of diazo ketone tethered allylic ethers has been explored. Product distribution can be explained by the intermediacy of a free ylide or direct rearrangement of a metal-bound ylide equivalent.     

Oscillatory melting temperature of the vortex smectic phase in layered superconductors

We report on transport measurements of YBa 2Cu 3O (7-delta) single crystals with different oxygen contents in the geometry B, J ||ab (J perpendicularB). Our data show that the vortices become confined between the Cu-O planes below a well-defined temperature at which the effective size 2xi of the vortex core is approximately equal to the period of the Cu-O layers. This confinement strongly increases the vortex liquid freezing temperature. A new melting line is found separating a vortex liquid and a smectic phase, which shows an oscillatory field dependence reflecting differences between commensurate and incommensurate smectic states.     

Synthesis of Novel Chiral Diol Ligands for the Enantioselective Reactions

The chiral diols ((,(,((,((-Tetraaryl-1,3-dioxolane-4,5-dimethanols) have been used for the formation of cyclic titanates and similar derivatives of Mg, Al and Zr. These complexes of oxophilic metal centers were employed in catalytic and stiochiometric enantioselective reactions such as enantioselective addition reactions of carbon-centered nucleophiles to aldehydes1, [2+2] cycloadditions2, and Diels-Alder reactions3. So far, the two hydrogen atoms of all this type of diols are in trans form…     

The diffraction of elastic waves by an imperfect fusion bond

We consider diffraction by a semi-infinite crack located alonga fusion interface between two differing elastic media. Twotypes of crack, namely open and partially closed cracks, areinvestigated. An open crack is modelled by a stress-free contactboundary condition and a partially closed crack is modelledby a spring contact boundary condition. For the latter, thejump in the stress across the crack is assumed to be proportionalto the jump in the displacement across the crack. This situationarises in, for example, a K-weld where the fine grain of theparent material (for example, ferritic or forged austeniticsteel) is in stark contrast with the coarse-grained weld metal(for example, austenitic weld metal). In the metal weld thedirection of the grain axis varies through the metal. However,diffraction is a local phenomenon and so the austenitic steelis assumed to have a zonal axis so that it may be modelled bya transversely isotropic composite. The ferritic or forged austeniticsteel will be modelled as an isotropic material.