Column fractionation of acrylonitrile-styrene copolymers

An acrylonitrile-styrene copolymer having 51.4 wt % acrylonitrile content was fractionated using dimethylformamide and a toluene–n-propanol mixture as solvent and nonsolvent, respectively. From characterization of the fractions, it is shown that the copolymer was fractionated principally in accordance with composition. The weight distribution curve of the copolymer was expressed as a function of both molecular weight and chemical composition on a two-dimensional contour map. The same plotting technique was applied to a copolymer having nearly the azeotropic composition.     

Selective separation of water–alcohol binary mixture through poly(maleimide-co-acrylonitrile) membrane

Separation of various alcohols and water through a membrane was carried out by means of a hydrogen-bonding interaction. A membrane obtained from poly(maleimide-co-acrylonitrile) was effective for a selective separation of water from aqueous alcohol solution by pervaporation technique. Spectroscopic analyses verified that this high selectivity was attributed to the hydrogen-bonding interaction between water and maleimide units in the membrane.     

The structure of neopeptins,inhibitors of fungal cell wall biosynthesis

The structures of neopeptins A (1), B (2), and C (3) were elucidated on the basis of chemical and spectroscopic evidences.     

Identification of the source of the crude drug Tu-zhu-ye using low-temperature plasma ashing

Tu-zhu-ye is a Korean crude drug for use as a diuretic but its plant source has not been identified. The present work has been attempted for identification of the original plant using specimens collected both at Seoul and Taegu, Korea, their mineral microstructures being examined after ashing the specimens by a low-temperature method with high-frequency oxygen plasma. A preliminary survey of the specimens with the naked eye suggested that the Tu-zhu-ye was near to Phyllostachys or its closely related bamboo species. Several specimens, namely, Phyllostachys heterocyclaMitf. var. pubescensOhwi, Phyllostachys nigraMunro var. henonisStapf, Phyllostachys bambusoidesSieb. et Zucc. and Bambusa multiplexRaeuschel were therefore ashed by the low-temperature method and the comparative microscopic studies with the resultant ashed tissues concluded that the “Tu-zhu-ye” from Seoul was perfectly identical with Phyllostachys nigraMunro var. henonisStapf. A further investigation is continued for the specimen from Taegu since it is different from any other specimens provided for the present work.     

Rotons and the gross-pitaevskii equation

With a plausible assumption for ψ(r), a bubble-solution of the GP-equation in the three-dimensional case is obtained. The relation between a roton and a “bubble” is examined. The roton spectrum is derived in order to test the suggested theory of condensate wavefunctions.     

Determination of nitrate in natural waters by flow-injection analysis

Summary Nitrate was determined in natural water samples by flow-injection spectrophotometry. It was reduced to nitrite with copperized cadmium and the nitrite thus produced reacted with p-aminoacetophenone and m-phenylenediamine. The limit of detection was about 1.5 g l^–1 for sample injections of 650 l. The sampling rate was about 40 samples h^–1 and the relative standard deviation was above 1% for 0.1–0.3 mg l^–1 nitratenitrogen. Nitrite present in the sample was determined separately and subtracted.

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Nitratbestimmung in natürlichen Wässern mit Hilfe der Fließinjektions-Analyse

Zusammenfassung Nitrat wird bei dieser Methode mit Hilfe einer Cu/Cd-Reduktionssäule zu Nitrit reduziert, das mit p-Aminoacetophenon und m-Phenylendiamin zur Reaktion gebracht wird. Die gebildete Verbindung wird spektral-photometrisch gemessen. Die Nachweisgrenze beträgt etwa 1,5 g/l bei injizierten Probevolumina von 650 l. Der Probendurchsatz beträgt 40/h. Die relative Standardabweichung liegt über 1% bei 0,1–0,3 mg/l Nitrat-Stickstoff. Vorhandenes Nitrit wird gesondert bestimmt und abgezogen.

     

Sustainable domino Michael reaction catalyzed by a Brønsted base on silica gel: synthesis of bicyclo[2.2.2]octane-2,5-dione derivatives

Domino Michael reactions of oxophorone and its derivatives 4 with Michael partners 3 have been effected to give bicyclo[2.2.2]octane-2,5-dione derivatives 7 by a catalytic amount of a Brønsted base (NMAP-Li) generated from N-methylaminopropylated silica gel (NMAP) and n-BuLi. The NMAP pellets were efficiently reused up to six times in 86% average yield.