A nitroxyl-radical-catalyzed oxidation of alcohols using diisopropyl azodicarboxylate (DIAD) as the terminal oxidant is reported. A variety of primary and secondary alcohols including aliphatic, benzylic, and allylic alcohols are efficiently oxidized to their corresponding aldehydes and ketones without overoxidation to carboxylic acid. 1,2-Diols are oxidized to hydroxyl ketones or diketones depending on the amount of DIAD used. 相似文献
Railway companies are encouraged to install platform screen doors (PSDs) for safety reason in Japan. The PSDs might affect train noises in stations, but the effects are not well understood. The aim of the present study is to clarify the effects of PSDs on acoustic characteristics. PSDs can be principally classified by two types, i.e., mobile full-height (MFH) and mobile half-height (MHH). Train noises were recorded in ground and underground train stations with MFH, MHH and without PSDs. The noises were evaluated by noise level, the maximum peak of the interaural cross-correlation function (IACC), and the width of the first decay (WΦ(0)) of the autocorrelation function. Noise level emitted by trains was reduced by PSDs in both aboveground and underground stations. IACC was decreased by PSDs in both ground and underground stations, suggesting that PSDs made train noises more diffused. WΦ(0) was decreased by PSDs in both ground and underground stations, which means that the train noises in station with PSDs have higher spectral centroid, suggesting that the PSDs blocked the lower frequency components of train noises. 相似文献
Annals of the Institute of Statistical Mathematics - Recently, it is becoming more active to apply appropriate statistical methods dealing with missing data in clinical trials. Under not missing at... 相似文献
Summary A selective preconcentration technique for copper using the kerateine gel is described. The gel is prepared by partial oxidation of kerateine which is obtained by reducing the disulphide bonds of wool fiber. Copper is selectively adsorbed on the gel at pH 3.5. It is eluted with 3 M hydrochloric acid and is determined by atomic-absorption spectrometry. This method has been applied to the determination of copper in river water.
Selektive Anreicherung von Kupfer aus wäßriger Lösung mit Hilfe von Keratein-Gel
Zusammenfassung Ein selektives Anreicherungsverfahren für Kupfer mit Hilfe von Keratein-Gel wurde ausgearbeitet. Das Gel wird durch teilweise Oxidation von Keratein hergestellt, das aus Wollfaser durch Reduktion der Disulfidbindungen gewonnen wird. Kupfer wird bei pH 3,5 selektiv an diesem Gel adsorbiert und kann mit 3 M Salzsäure eluiert werden. Die Bestimmung erfolgt mit Hilfe der AAS. Das Verfahren kann zur Kupferbestimmung in Flußwasser angewendet werden.
Proton nuclear magnetic resonance (NMR) spectra were successfully measured in human brain tumor tissues and experimental rat brain tumors. The investigation was performed on clinical materials which consisted of tissue from one normal brain and 36 brain tumors. Normal rat brain tissue and rat glioma implanted in the brain were also analysed. NMR measurements were carried out at the resonance frequency of 99.54 MHz. The proton NMR spectrum of the normal brain consisted of one broad component and eight superimposed sharp peaks. The sharp peaks obtained from the brain tumors varied from those of the normal brain. A decrease in the signal intensity from N-acetyl aspartate was the most common finding in all tumors. Spectral patterns were similar within the same histological types, but varied among the different types. Therefore, 1H-NMR spectra might indicate the metabolism characteristic of each tumor type which would be invaluable for clinical differential dagnosis of brain tumors. 相似文献
The enantioselective total synthesis of (+)‐gracilamine ( 1 ) is described. The strategy features a diastereoselective phenolic coupling reaction followed by a regioselective intramolecular aza‐Michael reaction to construct the ABCE ring system. The configuration at C3a in 1 was controlled by the stereocenter at C9a, which was selectively generated (91 % ee) by an organocatalytic enantioselective aza‐Friedel–Crafts reaction developed by our research group. This synthesis revealed that the absolute configuration of (+)‐gracilamine is 3aR, 4S, 5S, 6R, 7aS, 8R, 9aS. 相似文献
Enzymatic hydrolysis of poly(butylene succinate) (PBS) and poly(butylene succinate‐co‐L ‐lactate) (PBSL) has been studied by using a lipase originated from Pseudomonascepacia. It has been found that the drawn fibers of PBSL are readily hydrolyzed by the action of the lipase, while those of PBS undergo little enzymatic hydrolysis. Since the polymer films of PBS and PBSL are readily hydrolyzed under the same conditions, the enzymatic hydrolysis should depend not only on the crystallinity but also on the molecular orientation. The molecular weight of the samples gradually decreases with incubation time, because nonspecific hydrolysis occurs on the main chains of both PBS and PBSL even in the absence of lipase. The enzymatic hydrolysis of PBS and PBSL gives 4‐hydroxybutyl succinate (HBS) as the main product with traces of succinic acid and butane‐1,4‐diol together with L ‐lactic acid in the case of PBSL. In addition, the hydrolysis rate of the carboxyl end‐capped PBS is much slower than that of the original or hydroxyl end‐capped PBS. These results imply a hydrolysis mechanism involving the preferential exo‐type chain scission from the carboxyl terminals.
Mass remaining of various PBS and PBSL samples as a function of time. 相似文献