Some new morphological observations on poly-3,3-bis(chlormethyl)-oxacyclobutane

Summary Various aspects of the morphology of both solution and bulk crystallized poly-3,3-bis(chloromethyl)-oxacyclobutane (BCMO) have been studied in order to extend the generality of the current concepts of polymer morphology. In contrast to polyethylene, dark field electron micrographs of BCMO crystals do not reveal significant sectorization. BCMO lamellae do not thicken when annealed on a substrate (viewed in electron microscope or as a sediment mat of single crystals studied by small angle x-ray). The deformation of BCMO crystals is similar to that reported for polyoxymethylene single crystals in almost every respect. The morphology of glass crystallized BCMO can be characterized in terms of many lamellae highly oriented within regions covering several square microns. The thickness and spacing of these lamellae are invariant with the crystallization temperature, but the overall morphology may depend on the melt history of the sample before quenching.

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Zusammenfassung Verschiedene Aspekte der Morphologie von beiden, der l?sungs- und der schmelzkristallisierten Poly-3-, 3-bis-chloromethyl-oxycyclobutane (BCMO) wurden studiert, um die allgemeine Gültigkeit der heute laufenden Konzepte über Polymermorphologie zu erweitern. Im Gegensatz zu Poly?thylen ergibt Dunkelfeld-Elektronenmikrographie von BCMO-Kristallen keine erkennbare Sektorisation. BCMO-Lamellen verdecken sich nicht, wenn sie auf Substrat getempert werden (betrachtet im Elektronenmikroskop oder als sedimentierte Matte von Einzelkristallen untersucht durch Kleinwinkelstreuung). Die Deformation von BCMO-Kristallen ist ?hnlich der, mitgeteilt für Polyoxymethylen-Einzelkristalle in beinahe jeder Hinsicht. Die Morphologie von glaskristallisiertem BCMO kann charakterisiert werden als vielkristallines System hochorientiert innerhalb Bereichen, die mehrere Quadrat-Mikrons bedecken. Die Dicke und die Raumerfüllung dieser Lamellen sind invariant gegenüber der Kristallisationstemperatur, aber die insgesamt erscheinende Morphologie mag von der Schmelzgeschichte der Probe vorm Abschrecken abh?ngen.

     

The Quintile Share Ratio in location analysis

The inequality measure “Quintile Share Ratio” (QSR or sometimes S80/S20) is the primary income inequality measure in the European Union’s set of indicators on social cohesion. An important reason for its adoption as a leading indicator is its simplicity. The Quintile Share Ratio is “The ratio of total income received by the 20% of the population with the highest income (top quintile) to that received by the 20% of the population with the lowest income (lowest quintile)”. The QSR concept is used in this paper in the context of obnoxious facility location where the inequality is in distances to the obnoxious facility. The single facility location problem minimizing the QSR is investigated. The problem is investigated for continuous uniform demand in an area such as a disk, a rectangle, and a line; when demand is generated at a finite set of demand points; and when the facility can be located anywhere on a network. Optimal solution algorithms are devised for demand originating at a finite set of demand points and at nodes of the network. Computational experiments demonstrate the effectiveness of the algorithms.     

Transformation of anionically activated trifluoromethyl groups to heterocycles under mild aqueous conditions

The (hetero)aromatic trifluoromethyl group is present in many biologically active molecules and is generally considered to be chemically stable. In this paper, a convenient one-step synthesis of C-C linked aryl-heterocycles or heteroaryl-heterocycles in good to excellent yields via the reaction of anionically activated trifluoromethyl groups with amino nucleophiles containing a second NH, OH, or SH nucleophile in 1 N sodium hydroxide is reported. The method has high functional group tolerability and is potentially useful in parallel synthesis.     

Efficient Preparative Rentes to 6,6′-Dibromo-2-2′-bipyridine and 6-Bromo-2,2′-bipyridine

The preparation of 6,6′-dibromo-2,2′-bipyridine and 6-bromo-2,2′-bipyridine are described. The dibromo compound was prepared by way of an improved cuprate synthesis resulting in a 72% yield. The monobromo species was prepared from the dibromo compound by way of metal-halogen exchange in 88% yield.     

Determination of organotins in water by micro liquid chromatography–electrospray/ion trap mass spectrometry

Due to the varying toxicity the species of organotins in their widespread applications, it is important for analytical methods to address their speciation. Traditional methods call for the hydrolysis and subsequent derivatization of the organotins before analysis. These methods can be time‐consuming, derivatization can be incomplete and high levels of background interference produce difficulties in identification and quantification. The use is described of a non‐derivatization and non‐hydrolysis micro‐liquid chromatography–electrospray/ion trap mass spectrometry for separation and detection of the organotins. Copyright © 1999 John Wiley & Sons, Ltd.     

Linear convergence of Frank–Wolfe for rank-one matrix recovery without strong convexity

Mathematical Programming - We consider convex optimization problems which are widely used as convex relaxations for low-rank matrix recovery problems. In particular, in several important problems,...