Sodium Phosphaethynolate as a Building Block for Heterocycles

Phosphorus‐containing heterocycles have evolved from laboratory curiosities to functional components, such as ligands in catalytically active metal complexes or molecular constituents in electronic devices. The straightforward synthesis of functionalized heterocycles on a larger scale remains a challenge. Herein, we report the use of the phosphaethynolate (OCP)^? anion as a building block for various sterically unprotected and functionalized hydroxy substituted phosphorus heterocycles. Because the resulting heterocycles are themselves anions, they are building blocks in their own right and allow further facile functionalization. This property may be of interest in coordination chemistry and material science.     

Simulation-based confidence bounds for two-stage stochastic programs

This paper provides a rigorous asymptotic analysis and justification of upper and lower confidence bounds proposed by Dantzig and Infanger (A probabilistic lower bound for two-stage stochastic programs, Stanford University, CA, 1995) for an iterative sampling-based decomposition algorithm, introduced by Dantzig and Glynn (Ann. Oper. Res. 22:1–21, 1990) and Infanger (Ann. Oper. Res. 39:41–67, 1992), for solving two-stage stochastic programs. The paper provides confidence bounds in the presence of both independent sampling across iterations, and when common samples are used across different iterations. Confidence bounds for sample-average approximation then follow as a special case. Extensions of the theory to cover use of variance reduction and the dropping of cuts are also presented. An extensive empirical investigation of the performance of these bounds establishes that the bounds perform reasonably on realistic problems.

     

Comparison of DNA Hybridization at Rotating and Heated Gold Disk Electrodes

This paper reports about the influence of temperature, hybridization time and convection upon the detection of osmium tetroxide bipyridine‐labeled target oligonucleotides at rotating gold disk (RDE) and heated low temperature co‐fired ceramics (LTCC) gold disk electrodes. We used mixed self‐assembled monolayers of hexathiol‐linked probe oligonucleotides and mercaptohexanol on the gold surface of the electrodes for the hybridization detection of the labeled targets by means of square‐wave voltammetry. Due to protective strands, the osmium tetroxide‐modified target strands were still able to hybridize with the immobilized probe strands. The hybridization of such osmium tetroxide bipyridine‐modified target strands with thiol‐linked probe strands immobilized on gold yielded large reversible square‐wave‐voltammetric signals. Rotation speed and, hence, mass transport due to convection has only marginal effects. On the other hand, temperature affects greatly the hybridization step as indicated by both heated LTCC electrode in cold and RDE in warm hybridization solution. Calculated detection limits of 3.6 and 3.1 nM targets at the RDE and the LTCC electrode, respectively, have been almost the same at both types of electrodes. Applying an appropriate temperature during hybridization is more important than mechanically enhanced mass transport.     

Understanding the leaching properties of heterogenized catalysts: a combined solid-state and PHIP NMR study

Para-hydrogen induced polarization (PHIP) NMR in solution, combined with solid-state NMR, can be efficiently employed for the highly sensitive in-situ detection of the leaching properties of immobilized catalysts. The knowledge of this property is important for possible applications of PHIP experiments in medicine, biology or industry, where leached catalysts poison the solution of hyperpolarized products. As experimental example Wilkinson's catalyst RhCl(PPh(3))(3) (1) immobilized on mesoporous silica is chosen. As model reaction the hydrogenation of styrene in solvents with different polarities (methanol-d(4), acetone-d(6) and benzene-d(6)) is used. A (31)P solid-state MAS-NMR study reveals that there are two different species of catalysts on the silica, namely coordinatively bound catalysts and physisorbed catalyst. Only the second species exhibits substantial leaching, which is visible in a strong PHIP enhancement of the reaction product.     

On cobordism of manifolds with corners

This work sets up a cobordism theory for manifolds with corners and gives an identification with the homotopy of a certain limit of Thom spectra. It thereby creates a geometrical interpretation of Adams-Novikov resolutions and lays the foundation for investigating the chromatic status of the elements so realized. As an application, Lie groups together with their left invariant framings are calculated by regarding them as corners of manifolds with interesting Chern numbers. The work also shows how elliptic cohomology can provide useful invariants for manifolds of codimension 2.

     

The Solubility of Bis(cyclopentadienyl)samarium(II) and Implications for the Reaction of Samarium Metal with Bis(cyclopentadienyl)mercury(II)

Bis(cyclopentadienyl)samarium(II) has been shown to be insoluble in thf : ether mixtures, hence it cannot be isolated as a soluble product from the reaction of samarium with HgCp₂ in thf : ether.     

The nature of physics

The Doppler shift in frequency of an ionospherically reflected radio wave can be used to study various ionospheric disturbances. In this article the experimental arrangement for measuring such a shift is described, and examples of frequency shifts associated with solar flares, geomagnetic variations and travelling disturbances are discussed.