Three new trimeric stilbenes from Gnetum gnemon

Three stilbene trimers (gnemonols D, E, F) were isolated from the root of Gnetum gnemon. The structures were determined by spectroscopic analysis. In addition, the antioxidant activity of the compounds on lipid peroxide inhibition and super oxide scavenging activity were also investigated.     

Cyclopolymerization. V. Monomer design for the synthesis of highly cyclized polymer from unsymmetrical unconjugated dienes: Synthesis and polymerization of N-methyl-N-allylmethacrylamide

N-Methyl-N-allylmethacrylamide (MAMA) was synthesized and polymerized with radical initiators, and the structure of poly-MAMA was studied, in order to establish the concept that difunctional monomers having monofunctional counterparts which do not polymerize are likely to give rise to highly cyclized polymer, if the cyclized polymer is in a lower free-energy level than the monomer. The cyclopolymerizability of MAMA was considerably higher than that of N-allylmethacrylamide, which was previously reported, and its monofunctional counterpart can be polymerized. The extent of cyclization of poly-MAMA was about 93%, even in the polymer obtained by bulk polymerization. The repeating units of poly-MAMA consist mainly of five-membered rings; six-membered rings and pendent methacryl groups were detected in addition as minor repeating components. The monofunctional counterparts of MAMA, i.e., N-methyl-N-n-propylmethacrylamide (MPMA) and N-methyl-N-allylisobutyramide (MAIA), were also synthesized. Neither MPMA nor MAIA showed any tendency toward polymerization under the same experimental conditions as used for MAMA. The results thus obtained all support the concept mentioned above.     

Preparation of novel polymer ligands containing tetraaza macrocyclic schiff base as a highly selective extractant for copper(II)

Three types of the novel polymer ligands in which 6,8,15,17-tetramethyl-dibenzo-5,9,14,18-tetraaza-cyclotetradecene (L) is present as an integral part of the polymer backbone have been prepared. These polymer ligands are oligomers whose polymerization degree may be about five. Their complexing abilities and extractabilities for copper(II) and nickel(II) have been investigated. Among the polymer ligands, Poly-L3, which contains triethyleneglycol bis(p-phenylene) group as a linkage group, was found to be an excellent extractant for copper(II).     

Trace determination of iodide by derivatization and electron-capture gas chromatography

Summary A simple, sensitive and specific method is described for the determination of iodide as pentafluorobenzyl iodide, based on the chemical derivatization of iodide anion with pentafluorobenzyl bromide. The derivative formed in the reaction solution was directly analyzed, without further pretreatment, by gas chromatography with an electroncapture detector. The detection limit was about 1 ng of iodide anion in 0.10 ml of aqueous sample analyzed. Interferences of some common anions with the method were investigated and were proved to be minimal. It was demonstrated that the proposed method is applicable to the determination of iodide in spring water.

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Bestimmung von Iodidspuren durch Derivatisierung und Electron-Capture GC

Zusammenfassung Eine einfache, empfindliche und spezifische Methode wird beschrieben zur Iodidbestimmung als Pentafluorbenzyliodid, die auf der Reaktion von Iodid mit Pentafluorbenzylbromid beruht. Das gebildete Derivat wird direkt ohne weitere Vorbehandlung der GC mit Electron-Capture-Detektion unterworfen. Die Nachweisgrenze liegt bei etwa 1 ng Iodid in 0,1 ml. Störungen durch andere Anionen wurden untersucht und erwiesen sich als unbedeutend. Das Verfahren wurde zur Iodidbestimmung in Quellwasser angewendet.

     

A Special Algorithm for an Additive Model in Data Envelopment Analysis

A special algorithm is presented for the additive model in data envelopment analysis (DEA). The special algorithm first classifies a data set into several subsets. Then the subset is solved by a different algorithmic framework. In simulation studies, the algorithm outperformed available DEA codes. The proposed algorithm can efficiently deal with a large data set.