Metal benzoylpivaloylmethanates. Part II. 1,4-dioxane adducts of copper(II) chelates

Summary 1 : 1 Dioxane adducts of Copper(II) chelates withpara-subtituted benzoylpivaloylmethanes have been synthesized and their u.v., vis., i.r., mass, e.p.r. spectra as well as their magnetic moments and thermal stabilities investigated. Powdered samples of undiluted magnetically adducts were found to give well resolved e.p.r. spectra; the (S = 1) g_| signal being split into nine lines. Magnetic susceptibilities measured down to 4 K did not reveal exchange interactions. The uncommon structure of the e.p.r. spectra is believed to be due to the dimeric structure of the adduct in which an interion dipolar zero-field splitting of the triplet state occurs. The Cu-Cu distance estimated from the e.p.r. D_dd parameter is found to be 7.4 Å.     

Comparative study of breakthrough volumes BTV on various sorbents

Summary Breakthrough volumes on ten sorbents (Chromosorb 102, 104, 105 and 106, Porapak R and S, XAD-2, XAD-7, Tenax GC and Carbosphere) have been determined for vapours of 15 volatile organic compounds (halogenated hydrocarbons, alcohols, etc.). The volumes were determined by an indirect method employing typical chromatographic parameters such as retention volume and peak width.The method seems to be useful for preliminary estimation of adsorption capacity of various sorbents. It is not suitable, however, for the investigation of the effect of various parameters on the breakthrough volume.

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Vergleichende Untersuchung des Durchbruchsvolumens an verschiedenen Sorbentien

Zusammenfassung An 10 verschiedenen Sorbentien (Chromosorb 102, 104, 105, 106; Porapak R und S; XAD-2; XAD-7; Tenax GC; Carbosphere) wurden für 15 flüchtige organische Verbindungen (halogenierte Kohlenwasserstoffe, Alkohole u. a.) die Durchbruchsvolumina bestimmt. Es wurde dafür ein indirektes Verfahren mit typischen chromatographischen Parametern (Retentionsvolumen, Peakbreite) benutzt. Die Methode erscheint nützlich für die vorläufige Abschätzung der Adsorptionskapazität von Sorbentien, eignet sich jedoch nicht für die Untersuchung des Einflusses verschiedener Parameter auf das Durchbruchsvolumen.

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Part of this research was supported by Institute of Oceanology, Polish Academy of Sciences, Gdask, grant MR. I-15.     

Zur Theorie der Überdeckung durch konvexe Körper

Ohne Zusammenfassung     

Pd-Xantphos-catalyzed direct arylation of nucleosides

Direct arylation of the exocyclic amino groups of nucleosides represents a simple approach to N-aryl nucleoside derivatives. To date, one limitation has been that only electron-deficient aryl bromides and triflates possessed adequate reactivity for efficient, direct N-arylation of nucleosides. We demonstrate herein that Pd-Xantphos catalytic systems lead to successful N-arylation of suitably protected 2'-deoxyadenosine and 2'-deoxyguanosine with a wide range of aryl bromides.     

Control of defect concentrations within a semiconductor through adsorption

The technologically useful properties of a crystalline solid depend upon the concentration of defects it contains. Here we show that defect concentrations as deep as 0.5 microm within a semiconductor can be profoundly influenced by gas adsorption. Self-diffusion rates within silicon show that nitrogen atoms adsorbed at less than 1% of a monolayer lead to defect concentrations that vary controllably over several orders of magnitude. The results show that previous measurements of diffusion and defect thermodynamics in semiconductors may have suffered from neglect of adsorption effects.     

A shift sequence based approach for nurse scheduling and a new benchmark dataset

This paper investigates an adaptive constructive method for solving nurse rostering problems. The constraints considered in the problems are categorised into three classes: those that are sequence related, those that are nurse schedule related and those that are roster related. We propose a decomposition approach (to construct solutions) that consists of two stages: (1) to construct high quality sequences for nurses by only considering the sequence constraints, and (2) to iteratively construct schedules for nurses and the overall rosters, based on the sequences built and considering the schedule and roster constraints. In the second stage of the schedule construction, nurses are ordered and selected adaptively according to the quality of the schedules they were assigned to in the last iteration. Greedy local search is carried out during and after the roster construction, in order to improve the (partial) rosters built. We show that the local search heuristic during the roster construction can further improve the constructed solutions for the benchmark problems tested.     

Mixed 2D molecular systems: Mechanic, thermodynamic and dielectric properties

Study of Langmuir monolayers consisting of stearic acid (SA) and dipalmitoylphosphatidylcholine (DPPC) molecules was done by surface pressure-area isotherms (π-A), the Maxwell displacement current (MDC) measurement, X-ray reflectivity (XRR) and atomic force microscopy (AFM) to investigate the selected mechanic, thermodynamic and dielectric properties based on orientational structure of monolayers. On the base of π-A isotherms analysis we explain the creation of stable structures and found optimal monolayer composition. The dielectric properties represented by MDC generated monolayers were analyzed in terms of excess dipole moment, proposing the effect of dipole-dipole interaction. XRR and AFM results illustrate deposited film structure and molecular ordering.