Measurement of γp→K + Λ and γp→K + Σ 0 at photon energies up to 1.47 GeV

The reactions pK ⁺ and pK ^{+ 0} have been measured with the multiparticle detector system SAPHIR at ELSA in Bonn. Besides the differential cross sections the polarization and, for the first time, the ⁰ polarization have been determined in a photon induced reaction. All data are presented as functions of the photon energy (from threshold up to 1.47 GeV) and of the kaon production angle (0°–180°). The polarization of both and ⁰ is substantial at all energies and varies strongly with the production angle.This work is supported by the Bundesminister für Forschung und Technologie (BMFT), FK 06 BN 621 I     

Iterative bounds on the relative value vector in undiscounted Markov renewal programming

The functional equations of Markov renewal programming with a scalar again rateg are v=max [q (f)–gT (f)+P(f) v;f A] whereA is the Cartesian product set of allowed policies. When there functional equations are solved iteratively, convergent upper and lower bounds on the gain rateg were given by the author in J. Math. Anal. Appl. 34, 1971, 495–501. In this paper, an augmented iterative scheme is exhibited which supplies convergent upper and lower bounds on the value vector v as well.

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Zusammenfassung Die Funktionalgleichungen für undiskontierte Markoffsche Erneuerungsprogramme mit skalarem Durschnittsgewinng lauten v=max [q (f)–gT (f)+P (f)v;f A] wobeiA die Menge der zulässigen Politiken ist. Konvergierende obere und untere Schranken für den Durchschnittsgewinn wurden vom Autor in J. Math. Anal. Appl. 34, 1971, 495–501 hergeleitet. In dieser Arbeit wird ein verbessertes iteratives Verfahren vorgestellt, das auch konvergierende obere und untere Schranken für den relativen Gewinn liefert.

     

Complexing effects in the solvent extraction of thallium(I) 2-mercaptobenzothiazole

Studies of the extraction of thallum(l) from aqueous solution in the absence and presence of aqueous complexing agents into chloroform containing 2-mercaptobenzothiazole are described. Fluoride, chloride, bromide, iodide, thiocyanair, cyanide, and sulfate were employed as aqueous complexing agents. A number of the participating species were identified and association constants are estimated.     

Electro-optic scattering from nitrocellulose solutions

Measurements have been made of the light intensity scattered from dilute solutions of a sample of nitrocellulose ($\text{M}{}_{\mathrm{w}}\text{= 460,000}$) in acetone, both in the absence and presence of a.c. and d.c. electric fields. In an earlier study, owing to a mathematical slip and a false interpretation of an experimental parameter, other workers [5] interpreted similar measurements in terms of a freely rotating polar chain model. It is shown herein that this cannot be so and that the molecules of nitrocellulose of this order of molecular weight and in this type of solvent are better regarded as extremely stiff and extended.     

A two-sided short-recurrence extended Krylov subspace method for nonsymmetric matrices and its relation to rational moment matching

The Lagrange interpolation problem on spaces of symmetric bivariate polynomials is considered to reduce the interpolation problem to problems of approximately half dimension. The Berzolari-Radon construction is adapted to these kinds of problems by considering nodes placed on symmetric lines or symmetric pairs of lines. A Newton formula for the symmetric interpolant using the Berzolari-Radon construction is proposed.     

Anomalous lattice response at the Mott transition in a quasi-2D organic conductor

Discontinuous changes of the lattice parameters at the Mott metal-insulator transition are detected by high-resolution dilatometry on deuterated crystals of the layered organic conductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. The uniaxial expansivities uncover a striking and unexpected anisotropy, notably a zero effect along the in-plane c axis along which the electronic interactions are relatively strong. A huge thermal expansion anomaly is observed near the end point of the first-order transition line enabling us to explore the critical behavior with very high sensitivity. The analysis yields critical fluctuations with an exponent alpha approximately 0.8+/-0.15 at odds with the novel criticality recently proposed for these materials [Kagawa et al., Nature (London) 436, 534 (2005)]. Our data suggest an intricate role of the lattice degrees of freedom in the Mott transition for the present materials.     

Acid‐Catalyzed Oxidative Radical Addition of Ketones to Olefins

Based on a mechanistic study, we have discovered a Brønsted acid catalyzed formation of ketone radicals. This is believed to proceed via thermally labile alkenyl peroxides formed in situ from ketones and hydroperoxides. The discovery could be utilized to develop a multicomponent radical addition of unactivated ketones and tert‐butyl hydroperoxide to olefins. The resulting γ‐peroxyketones are synthetically useful intermediates that can be further transformed into 1,4‐diketones, homoaldol products, and alkyl ketones. A one‐pot reaction yielding a pharmaceutically active pyrrole is also described.