Preparation of the Borane (Fmes)BH2 and its Utilization in the FLP Reduction of Carbon Monoxide and Carbon Dioxide

Treatment of 1,3,5‐tris(trifluoromethyl)benzene with n‐BuLi, followed by H₃B?SMe₂ and subsequent hydride removal gave the (Fmes)BH₂ reagent, which was isolated as a SMe₂ stabilized monomer or a ligand free (μ‐H)₂‐bridged dimer. Reaction with Mes₂P(vinyl) gave the respective ethylene‐bridged P/B(Fmes)H FLP. It reduced carbon monoxide to the formyl stage and carbon dioxide to the formaldehyde oxidation state. Most new compounds were characterized by X‐ray diffraction.     

Multi‐Component Synthesis of Rare 1,3‐Dihydro‐1,3‐azaborinine Derivatives: Application of a Bora‐Nazarov Type Reaction

The twofold hydroboration products of (Fmes)BH₂?SMe₂ with a series of alkynes (2‐butyne, arylethynes) react with two molar equiv of 2,6‐dimethylphenyl isocyanide (CN‐Xyl) at 80 °C to give rare examples of 1,3‐azaborinine derivatives. A mechanistic study revealed a reaction course involving insertion of one isonitrile followed by a bora‐Nazarov type ring‐closure reaction and subsequent isonitrile insertion to give the respective 1,3‐dihydro‐1,3‐azaborinines 5 .     

Layering and position-dependent diffusive dynamics of confined fluids

We study the diffusive dynamics of a hard-sphere fluid confined between parallel smooth hard walls. The position-dependent diffusion coefficient normal to the walls is larger in regions of high local packing density. High density regions also have the largest available volume, consistent with the fast local diffusivity. Indeed, local and global diffusivities as a function of the Widom insertion probability approximately collapse onto a master curve. Parallel and average normal diffusivities are strongly coupled at high densities and deviate from bulk fluid behavior.     

Capacity limits of information transport in fiber-optic networks

The instantaneous optical Kerr effect in optical fibers is a nonlinear phenomenon that can impose limits on the ability of fiber-optic communication systems to transport information. We present here a conservative estimate of the "fiber channel" capacity in an optically routed network. We show that the fiber capacity per unit bandwidth for a given distance significantly exceeds current record experimental demonstrations.     

Endor frequencies of randomly oriented triplets by electron spin echo spectroscopy

ENDOR frequencies of randomly oriented triplets have been measured from the fast Fourier transform of electron spin echo envelope modulation. Important experimental conditions are low temperatures, high microwave power and long phase memory time in a proper form of solvent. The technique is exemplified by using diphenylmethylenes in rigid glasses, polycrystalline forms and single crystals of benzophenones.     

Microchemical characterization of paintings — A case study

Summary The fundamental importance of scientific research for the preservation and restoration of works of art is uncontestable. The methods described in this paper, such as light microscopy, microchemical tests, emission spectroscopy, chromatography, scanning electron analysis, electron microprobe analysis and infrared spectroscopy, are of special significance in this filed. Nevertheless a better understanding of the problems that arise out of new special questions of art history can be obtained only by the right interpretation of the data obtained by scientific methods.

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Mikrochemische Charakterisierung von Gemälden

Zusammenfassung Die grundlegende Bedeutung wissenschaftlicher Forschung für die Erhaltung und Restaurierung von Kunstwerken ist unbestritten. Die hier beschriebenen Methoden (Lichtmikroskopie, mikrochemische Reaktionen, Emissionsspektroskopie, Chromatographie, Rasterelektronen-Analyse und Infrarotspektroskopie) sind hierfür von zunehmender Bedeutung. Sie ermöglichen ein besseres Verständnis neuerer kunsthistorischer Probleme nur durch die richtige Interpretation der Ergebnisse wissenschaftlicher Methoden.

     

Paracrystalline order in polymers

Summary A brief review of one and three dimensional models of paracrystalline superstructures in polymers, as used for analysing the small angle scattering, is given.

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Zusammenfassung Es wird ein knapper überblick über die bei der Analyse der Kleinwinkelstreuung von Polymeren verwendeten einund dreidimensionalen Modelle der Überstruktur gegeben.

     

Isocamphananaloge mandelsäure

The synthesis of some new potentially, nitrogenefree spasmolytics is described. Formally the benzene nucleus in some mandelic acid esters, known by their mild spasmolytic activity, is substituted for the isocamphane bicyclus by a) SeO₂ oxidation of 1-(3,3-Dimethyl-2-exo-norbornyl)-ethanone (5) to the corresponding ketoaldehyde6, b) oxidation of6 to the isocamphane analogous mandelic acid4 and c) esterification of derivatives of4 with isoamylalcohol and benzylalcohol. Attemps to dehydrate the methylester7 to camphenylideneacetic acid methylester (12) by various methods failed, probably because of the ring strain.

Teil der Diplomarbeit vonB. Blach, Universität Wien 1981.     

Accurate values for the nonrelativistic energies of the lowest singlet and triplet S-states of the4He-Isotop

Accurate lower and upper bounds for the nonrelativistic lowest energies¹ E ₀ and³ E ₀ of the singlet and triplet-system of the⁴He-Isotop are calculated with the linearized method of variance minimization. The same was done for¹ E ₁ the energy of the first excitedS-state 2¹ S. The results especially for¹ E ₀ and³ E ₀ in a.u. are −2.9033076997₅ ≤¹ E ₀ ≤ −2.9033076921₈ −2.1749324263₇ ≤³ E ₀ ≤ −2.1749324245₉ i.e. the values are determined with an absolute error smaller than 0.00167 cm⁻¹ for¹ E ₀ and 0.00039 cm⁻¹ for³ E ₀.