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121.
The crude saponin obtainable from Marsilea minuta Linn on acid hydrolysis yielded a mixture of sapogenols. The major sapogenol named Marsileagenin A was found to be a hexahydroxy triterpene of oleanene series. From a study of various spectrometric data together with chemical reactions the structure of this sapogenol has been assigned as olean-12-ene-2α, 3β, 16β, 21β, 22α, 28-hexol (1a). 相似文献
122.
G. Spiteller A. Chatterjee A. Bhattacharya A. Deb 《Monatshefte für Chemie / Chemical Monthly》1962,93(5):1220-1234
Zusammenfassung Kopsin und seine Derivate geben charakteristische Massenspektren. Wegen der Schwerflüchtigkeit des Kopsins ist es nicht möglich, mit der üblichen Aufnahmetechnik reproduzierbare Massenspektren zu erhalten. Dagegen gelingt es, durch direkte Einführung der Substanz in die Ionenquelle reproduzierbare und auswertbare Spektren aufzunehmen.Durch Deutung der Massenspektren, sowie älterer und neuerer Ergebnisse der chemischen Untersuchung, kann gezeigt werden, daß Kopsin ein aus sieben Ringen aufgebautes, dem Aspidospermin ähnliches Alkaloid ist.Mit 1 Abbildung 相似文献
123.
Mohit L. Deb 《Tetrahedron letters》2007,48(12):2159-2163
Synthesis of some novel 3-alkylated indoles via an uncatalyzed Michael addition of indoles using three components in one-pot solvent-free conditions is reported. The mechanism was established by performing the reaction in two steps. The reaction was also studied in different solvents and an important solvent effect was noticed. 相似文献
124.
N-hydroxy-N,N′-diphenylcinnamamidine (HDPCA) forms a blue-violet coloured 1:2 complex (metal:ligand) with vanadium(V), which can be quantitatively extracted into chloroform from 1.0–9.5M acetic acid medium. Based on this colour reaction, a sensitive and highly selective method for the spectrophotometric determination of microgram quantities of vanadium(V) has been developed. The complex shows maximum absorption at 570 nm and obeys Beer's law in the vanadium concentration range 0.6–12.5 μg/ml. The method has been applied to alloy steels. 相似文献
125.
Swapan K. Ghosh Alok Samanta B. M. Deb 《International journal of quantum chemistry》1997,62(5):461-465
A new local density functional approach for the calculation of correlation energies of many-electron atomic systems is proposed by using the exact results for the correlation energy of a two-electron system bound by a harmonic oscillator external potential. This is motivated by the fact that the correlation energy is a universal functional of the electron density, and the form of this functional is independent of the external potential. The calculated numerical results for the correlation energies show very good agreement with the standard values reported in the literature. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62: 461–465, 1997 相似文献
126.
A nonperturbative, time-dependent (TD) quantum mechanical approach is described for studying the collision dynamics between the He atom and a fully stripped ion. The method combines quantum fluid dynamics and density functional theory to solve two coupled equations: one for the trajectory of the projectile nucleus and the other for the electronic charge distribution of the target atom. The computed TD and frequency-dependent properties provide detailed features of the collision process. Inelastic and ionization cross sections are also reported. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 251–271, 1998 相似文献
127.
Transport in Porous Media - In this paper, an approximate integral equation solution for a horizontal, unsteady flow of two viscous incompressible fluids is derived. Wettability variation of the... 相似文献
128.
Dipak Ghosh Argha Deb Md. Azizar Rahman Abdul Kayum Jafry Jayita Ghosh 《The European Physical Journal A - Hadrons and Nuclei》2000,8(1):97-101
An analysis of 16O-AgBr interaction data at 60A GeV in terms of factorial correlators is presented. The correlated moments are found to increase
with decreasing bin-bin separation D, following a power law within the region D
1. The data are also consistent with the dimension-independent scaling relation proposed by Seixas.
Received: 5 October 1998 / Accepted: 20 April 2000 相似文献
129.
Importance of shattering fragmentation in the surface-induced dissociation of protonated octaglycine
Kyoyeon Park Bipasha Deb Kihyung Song William L. Hase 《Journal of the American Society for Mass Spectrometry》2009,20(6):939-948
A QM + MM direct chemical dynamics simulation was performed to study collisions of protonated octaglycine, gly8-H+, with the diamond {111} surface at an initial collision energy E
i
of 100 eV and incident angle θ
i
of 0° and 45°. The semiempirical model AM1 was used for the gly8-H+ intramolecular potential, so that its fragmentation could be studied. Shattering dominates gly8-H+ fragmentation at θ
i
= 0°, with 78% of the ions dissociating in this way. At θ
i
= 45° shattering is much less important. For θ
i
= 0° there are 304 different pathways, many related by their backbone cleavage patterns. For the θ
i
= 0° fragmentations, 59% resulted from both a-x and b-y cleavages, while for θ
i
= 45° 70% of the fragmentations occurred with only a-x cleavage. For θ
i
= 0°, the average percentage energy transfers to the internal degrees of freedom of the ion and the surface, and the energy
remaining in ion translation are 45%, 26%, and 29%. For 45° these percentages are 26%, 12%, and 62%. The percentage energy-transfer
to ΔE
int
for θ
i
= 0° is larger than that reported in previous experiments for collisions of des-Arg1-bradykinin with a diamond surface at the same θ
i
. This difference is discussed in terms of differences between the model diamond surface used in the simulations and the diamond
surface prepared for the experiments. 相似文献
130.