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21.
R. Anil Rugunanan Michael E. Brown 《Journal of Thermal Analysis and Calorimetry》1991,37(6):1193-1211
Thermogravimetry (TG) and differential scanning calorimetry (DSC) have been used to examine the thermal behaviour, in N2 and in air, of the Si/Sb2O3, Si/KNO3, Si/Fe2O3 and Si/SnO2 pyrotechnic systems, in relation to the behaviour of the individual constituents.TG curves for Si powder, heated alone in air, showed that limited oxidation of Si occurred above 700°. In N2, Sb2O3 sublimed completely between 500 and 900° and, in air, sublimation was accompanied by oxidation to Sb2O4. The Sb2O4 decomposed at higher temperatures. DSC curves for KNO3 heated in N2 showed the usual crystalline transition and melting endotherms followed by endothermic decomposition between 400 and 950°. DSC and TG curves of SnO2and Fe2O3 revealed no thermal events when samples were heated to 1000° in either N2 or air.For the Si/Sb2O3 system, the oxidation of Si by Sb2O3 between 590 and 700°, was complicated by sublimation of Sb2O3 in N2 and also by the oxidation of Sb2O3 in air. No thermal events were observed for the Si/SnO2and Si/Fe2O3 systems when heated under a variety of conditions in either N2 or in air, although these systems do sustain combustion on suitable ignition. In the Si/KNO3 system, oxidation of Si occurs in a KNO3 melt at temperatures above 560° in nitrogen and in air.
Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60th birthday 相似文献
Zusammenfassung Mittels TG und DSC wurde das thermische Verhalten der pyrotechnischen Systeme Si/Sb2O3, Si/KNO3, Si/Fe2O3 und Si/SnO2in N2 und in Luft im Vergleich zum Verhalten der einzelnen Komponenten untersucht.TG-Aufnahmen über das Erhitzen von Si-Pulver in Luft zeigten eine begrenzte Oxidation von Silizium oberhalb 700°C. Sb2O3 sublimiert in Stickstoff vollständig zwischen 500 und 900°C, in Luft wird die Sublimation durch Oxidation zu Sb2O4 begleitet. Sb2O4 zersetzt sich bei höheren Temperaturen. DSC-Aufnahmen für KNO3 in N2 zeigen die gewohnten Umwandlungs- und Schmelzendothermen, gefolgt von einer endothermen Zersetzung zwischen 400 und 950°C. Die DSC- und TG-Kurven für SnO2und Fe2O3 zeigen bei Erhitzen bis 1000°C weder in N2 noch in Luft den Verlauf thermische Prozesse an.Bei dem System Si/Sb2O3 spielt sich neben der Oxidation von Si durch Sb2O3 zwischen 590 und 700°C auch eine Sublimation von Sb2O3 in N2 sowie eine Oxidation von Sb2O3 in Luft ab. Für die Systeme Si/SnO2und Si/Fe2O3 konnten durch Erhitzen unter einer Reihe von Bedingungen weder in Luft noch in N2 Thermoprozesse nachgewiesen werden, obwohl diese Systeme nach geeigneter Zündung den Brennvorgang aufrechterhalten. Im System Si/KNO3 erfolgt sowohl in N2 als auch in Luft oberhalb 560°C die Oxidation von Si in der KNO3-Schmelze.
Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60th birthday 相似文献
22.
Vyas S Pradhan SD Pavaskar NR Lachke A 《Applied biochemistry and biotechnology》2004,118(1-3):177-188
Various cellulosic substrates were examined for bound water content by differential thermal analysis (DTA) and thermogravimetry (TG). Samples were heated in the range of 30-100 degrees C at a rate of 3 degrees C/min. DTA vaporization curves for different cellulose samples indicated that the bound water (Wf) was vaporized at higher temperature than free water (Wf) at the surface. Weight loss was observed in two stages, corresponding to Wf and Wb in TG curves. The bound water content was dependent on the degree of crystallinity of cellulose. Among different cellulosic substrates, Walseth cellulose showed the highest bound water content, and it also was found to be the least crystalline. The alkaline-active, alkali-stable cellulase was obtained from the alkalotolerant Fusarium sp. The substrate specificity and viscometric characteristics confirmed the enzyme to be an endoglucanase. The Wb content of Walseth cellulose was lowered during the enzymatic hydrolysis. The possible application of bound water analysis in understanding the hydrolysis of cellulosic substrates of different crystallinity is discussed. 相似文献
23.
The reactions of various main-group metal hydrides with 1-halo-5-hexenes and with 1-halo-2,2-dlmethyl-5-hexenes produce both straight chain and cyclized reduction products. The formation of cyclic hydrocarbons clearly indicates the presence of radical intermediates during the course of these reactions. 相似文献
24.
Order - Cover-incomparability graphs (C-I graphs) are graphs whose edge-set is the union of edge-sets of the incomparability graph and the cover graph of some poset. C-I graphs captured attention... 相似文献
25.
The conformational properties of the furanose ring of purine- and pyrimidine--nucleosides and-nucleotides are studied quantum-mechanically with the help of the PCILO method, using the pseudorotational concept. The computations point to the existence of two stable conformational zones centered around the C(3)-endo and C(2)-endo conformations which in the isolated furanose ring are separated by barriers of the order of 4 kcal/mole. In nucleosides one of the barriers (the one running through the O(1)-exo-C(2)-exo path) becomes very high. A detailed study is made of the relation between the phase angle of pseudorotation, P, and the torsion angle about the glycosyl bond,
CN. A very satisfactory agreement with the available experimental data is observed.
This research was supported by the R.C.P. 173 and the A.T.P. A 655-2303 of the C.N.R.S. 相似文献
Zusammenfassung Die Konformationseigenschaften des Furanoserings in -Nucleosiden und Nucleotiden von Purin und Pyrimidin werden nach der PCILO-Methode unter Berücksichtigung der pseudorotatorischen Betrachtungsweise studiert. Die Rechnung läßt auf die Existenz zweier stabiler Konformationszonen schließen, die in der Umgebung der C(2)-endo und der C(3)-endo Konformationen liegen, und die im isolierten Furanosering durch Energiebarrieren der Größenordnung von 4 kcal/mol voneinander getrennt sind. In Nucleosiden wird eine der Barrieren (die durch den Weg O(1)-exo-C(2)-exo gekennzeichnete) sehr hoch. Die Relation zwischen dem Phasenwinkel der Pseudorotation, P, und dem Drehwinkel um die Glycosylbindung, CN, wird einer eingehenden Untersuchung unterworfen. Man beobachtet eine sehr zufriedenstellende Übereinstimmung mit den verfügbaren experimentellen Daten.
Résumé Les propriétés conformationnelles du noyau furanose des -nucleosides et nucleotides des purines et pyrimidines sont étudiées par la méthode PCILO en faisant appel au concept de la pseudorotation. Les calculs indiquent l'existence de deux zones de conformations stables, centrées autour des conformations C(2)-endo et C(3)-endo, qui sont dans le sucre isolé séparées par des barrières de l'ordre de 4 kcal/mole. Dans les nucleosides, l'une de ces barrières (celle qui passe par le chemin O(1)-exo-C(2)-exo) devient très élevée. Une étude détaillée est effectuée sur la relation entre l'angle de phase de la pseudorotation P et l'angle de torsion autour de la liaison glycosylique, CN. Un excellent accord avec les données expérimentales disponibles est observé.
This research was supported by the R.C.P. 173 and the A.T.P. A 655-2303 of the C.N.R.S. 相似文献
26.
The biomimetic reduction of anti-inflammatory drug, nimesulide (1) with sodium borohydride catalyzed by 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides [TAPFe(III)Cl] has been studied in organic solvents under anaerobic and aerobic conditions. 相似文献
27.
Rathore N. S. Pabby Anil Kumar Venugopalan A. K. 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(3):543-549
Hydrated iron oxide or amorphous-Fe2O3·3.5 H2O (HFeO), hydrated titanium oxide (HTiO) and hydrated thorium oxide (HThO) were synthesized and their applicability for the decontamination of intermediate level liquid wastes (ILLW) was tested. The sorption of a few actinides like plutonium and americium on HFeO, 137Cs and 106Ru on HTiO and 90Sr on HThO was investigated as a function of pH, time and loading capacity of the hydrous oxide with metal ions. The influence of the total dissolved salt content was also monitored. Some of these parameters influenced the sorption behavior significantly. The radiation stability of these inorganic sorbents were studied by irradiating them up to 48 Mrad. Adsorbed actinides and fission products were successfully eluted from HFeO and from the mix-bed of HTiO and HThO by 0.5M nitric acid.The authors wish to thank Shri R. D. Changarani, Chief Superintendent NRG Facilities and Shri P. K. Dey, Head FRD for their valuable advice and constant support. 相似文献
28.
Anil Kumar PG Pregosin PS Schmid TM Consiglio G 《Magnetic resonance in chemistry : MRC》2004,42(9):795-800
Three new salts of Rh(I), [Rh(1,5-COD)(Biphemp)]X, Biphemp = (6,6'-dimethylbiphenyl-2,2'-diyl)bis(diphenylphosphine), X = BF4-, 2a, PF6-, 2b, and CF3SO3-, 2c, were prepared and studied using PGSE diffusion, 1H-19F HOESY and inverse 103Rh (amongst other) NMR methods. Although the immediate coordination sphere of the cation does not sense the change in the anion, the PGSE diffusion and 1H-19F HOESY data suggest that, in addition to some ion pairing, each of the anions in 2 demonstrates selectivity in its approach towards the cation. 相似文献
29.
Pharmaceutical counterfeiting 总被引:2,自引:0,他引:2
Deisingh AK 《The Analyst》2005,130(3):271-279
Pharmaceutical counterfeiting is becoming a serious problem both in developed and developing countries. This paper considers the extent of the problem and provides several examples of drugs which have been counterfeited. Additionally, the effects of counterfeit products on consumers, health care providers, drug manufacturers and governments are discussed. Several of the currently used methods of detection are described and these include near-infrared spectroscopy, Raman spectroscopy, isotopic characterization, tensiography, chromatographic and mass spectrometric approaches. Finally, anti-counterfeiting measures such as the use of holograms, tracers and taggants and electronic tracking are summarized. 相似文献
30.