Enantiomeric discrimination : II. Incorporation of chiral amines platinum complexes. Crystal and molecular structure of (chloro)-(methyl)((+)-2S,3S-O-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)platinum(II)

Diastereomeric platinum complexes of formula [Pt(chelate)CH₃L]ClO₄ have been prepared, where (chelate) is disphosphineligand, either 2S ,3S-bis(diphenylphosphino)butane, or (+)-2S, 3S-O-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)butane)platinum(II) has shown that the compound crystallises in space group P2₁2₁2₁, with cell dimensions a 16.282(4), b 16.995(4) and c 10.973(2) Å. Full-matrix least-squares refinement on aF, using 2504 observations and 170 variables, converged at R  0.0605. The coordination at the Pt atom is square planar, with Pt—P distances of 2.322(4) and 2.233(4) Å. Pt—Cl and Pt—C were 2.323(5) and 2.17(1) Å respectively. The seven-membered chelate ring adopts a twisted chair conformation. Enantiomeric discrimation in these Pt-amine systems is discussed with reference to the solid state structure of the complex.     

A practical second-order electromagnetic model in the quasi-specular regime based on the curvature of a 'good-conducting' scattering surface

This letter presents an approximate second-order electromagnetic model where polarization coefficients are surface dependent up to the curvature order in the quasi-specular regime. The scattering surface is considered 'good-conducting' as opposed to the case for our previous derivation where perfect conductivity was assumed. The model reproduces dynamically, depending on the properties of the scattering surface, the tangent-plane (Kirchhoff) or the first-order small-perturbation (Bragg) limits. The convergence is assumed to be ensured by the surface curvature alone. This second-order model is shown to be consistent with the small-slope approximation of Voronovich (SSA-1+SSA-2) for perfectly conducting surfaces. Our model differs from SSA-1 + SSA-2 in its dielectric expression, to correct for a full convergence toward the tangent-plane limit under the 'good-conducting' approximation. This new second-order formulation is simple because it involves a single integral over the scattering surface and therefore it is suitable for a vast array of analytical and numerical applications in quasi-specular applications.     

Fermi surface studies of non-dilute disordered alloys by positron experiments

The technique of positron annihilation experiments as applied to the study of Fermi surfaces in metals and alloys is briefly reviewed. The angular correlation of the two annihilation photons is directly related to the momentum distribution of the positron-electron system; breaks in this distribution reflect the size and shape of the Fermi surface. Recent two-dimensional angular correlation measurements designed to study the Fermi surface of Cu?Al and Cu?Zn alloys are presented, and are compared with theoretical predictions.     

Beitrag zur Berechnung des Wärmeüberganges und Druckabfalles laminarer Einlaufströmungen

Zusammenfassung In der vorliegenden Arbeit wurden Wärmeübergang und Druckabfall nichtausgebildeter Laminarströmung in Rohren und ebenen Kanälen berechnet. Hierzu wurden exakte Methoden der Grenzschichttheorie, wie sie zur Berechnung der Geschwindigkeitsverteilung üblich sind, auf die Berechnung der Temperaturverteilung übertragen. Diese Methoden bestehen darin, daß man eine Entwicklung von vorn ansetzt, die vom Eintrittsquerschnitt an gültig ist, und eine Entwicklung von hinten, die in größerer Entfernung vom Eintrittsquerschnitt an gilt. In dem Bereich, wo weder die Entwicklung von vorn noch die Entwicklung von hinten gültig sind, weil nicht genügend Glieder zur Verfügung stehen, erzielt man durch Interpolation brauchbare Ergebnisse. Die in der Arbeit beschriebenen Methoden sind auch geeignet, den Wärmeübergang und Druckabfall in Ringspalten zu berechnen. Das wird jedoch eine erhebliche Rechenarbeit erfordern, weil als weiterer Parameter noch das Verhältnis der Radien des inneren und des äußeren Rohres auftritt.Auszug aus der von der Fakultät für Maschinenwesen der Technischen Hochschule Karlsruhe genehmigten Dissertation des Verfassers.     

Zwei neue Oxopalladate: BaPdNd2O5 und BaPdSm2O5 mit planar koordinierten Pd2+-Ionen

Single crystals of BaPdNd₂O₅ (A), BaPdSm₂O₅ (B) and BaCuNd₂O₅ (C) were prepared by solid state reaction using BaCl₂ as a fusing assistant (A, B) or by high temperature Laser technique (C). X-ray investigations show tetragonal symmetry with A:a=6.7387 (5),c=5.9002 (25) Å, B:a=6.6667 (13),c=5.8800 (6) Å (space group D _4h ⁵ ?P4/mbm,Z=2). The formerly investigated compound (C) is refined here by single crystal data. (A) and (B) belong to the BaPtNd₂O₅-type. The results are discussed.