"Tethered" Ru(II) catalysts for asymmetric transfer hydrogenation of ketones

Stereochemically well-defined ruthenium(II) catalysts have been applied to the asymmetric transfer hydrogenation of a series of ketones. In one case, statistical experimental design was employed to optimize the enantiomeric excess of the product. In the case of the TsDPEN-based systems, the replacement of trans-1,2-diphenyl substitution with cis-, or deletion of one of the phenyl groups, results in significant deterioration of the enantiomeric excess. A new method is described for the synthesis of tethered amino alcohol-containing catalysts.     

Tumor cell toxicity of hypericin and related analogs

A series of hypericin analogs were found to differ in their cytotoxic activity induced by ambient light levels. These analogs vary in their ability to partition into cells, to generate singlet oxygen as well as in other photophysical properties. The data suggest that the biological activity of hypericin is due to a combination of factors whose roles may vary under different circumstances.     

Synthesis and preliminary studies on a novel class of soluble amino alcohol reagents based on methacrylate copolymers

A class of soluble polymers containing chiral β-amino alcohol ligands, based on methacryate copolymers, are described. The use of copolymers permits the selective introduction of material to control the solubility and a functional group in a controllable ratio and polymer length. The application of the supported polymers to diethylzinc additions is described.     

Infinite series of combinatorially regular polyhedra in three-space

The paper discusses polyhedral realizations in ordinary Euclidean 3-space of Coxeter's regular skew polyhedra {4, p|4 ^p/2]–1} and their duals on an orientable surface of genus 2 ^p–3(p–4)+1. Our considerations are based on work of Coxeter, Ringel and McMullen et al., revealing that certain polyhedral manifolds discovered by the last three authors are in fact the polyhedra in question. We also describe Kepler-Poinsot-type polyhedra in 3-space obtained by projections from Coxeter's regular skew star-polyhedra in 4 dimensions.     

Natural Selection: Interactive Subset Creation

Abstract

Visualization is a critical technology for understanding complex, data-rich systems. Effective visualizations make important features of the data immediately recognizable and enable the user to discover interesting and useful results by highlighting patterns. A key element of such systems is the ability to interact with displays of data by selecting a subset for further investigation. This operation is needed for use in linked views systems and in drill-down analysis. It is a common manipulation in many other systems and is as ubiquitous as selecting icons in a desktop graphical user interface (GUI). It is therefore surprising to note that little research has been done on how selection can be implemented. This article addresses this omission, presenting a taxonomy for selection mechanisms and discussing the interactions between branches of the taxonomy.     

The two Pappus-tori

Two polyhedral embeddings of the regular maps {3, 6}_3,0 and {6, 3}_3,0 in E ³ are given. They are the smallest combinatorially regular tori of type {3, 6} and {6, 3} embedded in E ³, and their automorphism group is that of the famous Pappus-configuration.     

Gitterpunkte und Volumen-Oberfläche-Verhältnis konvexer Mengen

Ohne ZusammenfassungW.Fenchel zum 65. Geburtstag gewidmet     

Zur simultanen homogenen diophantischen Approximation III

Ohne Zusammenfassung