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181.
Macrocyclic complexes of copper, nickel and cobalt were synthesised via template reactions. These 14-membered N6 tetradentate macrocyclic complexes were characterised by magnetic, conductance, electronic and IR spectral studies. The macrocyclic ligand coordinates through the four azomethine nitrogen atoms which are bridged by 2,3-butanedione, moieties, but far IR spectra suggest that the pyridine nitrogens are not coordinated. These macrocyclic complexes are considered to have distorted octahedral configurations. 相似文献
182.
Existence, uniqueness and asymptotic behavior of solutions to integro-differential equations involving monotone operators are discussed. 相似文献
183.
184.
Ahmad I Nawaz SA Afza N Malik A Fatima I Khan SB Ahmad M Choudhary MI 《Chemical & pharmaceutical bulletin》2005,53(8):907-910
Onosmins A (1) and B (2), lipoxygenase inhibitors, have been isolated from Onosma hispida. Their structures were established as 2-[(4-methylbenzyl)amino]benzoic acid (1) and methyl 2-[(4-methylbenzyl)amino]benzoate (2) through spectroscopic studies, including 2D-NMR. The known compounds apigenin (3), 6,4'-dimethoxy-3,5,7-trihydroxyflavone (4), 6,7-dimethoxy-3,5,4'-trihydroxyflavone (5) and apigenin 7-O-beta-D-glucoside (6) are also reported for the first time from this species. Compounds (1) and (2) inhibited lipoxygenase (LOX, EC 1.13.11.12) enzyme in a concentration-dependent fashion with IC50 values of 24.0 and 36.2 microM, respectively. Lineweaver-Burk as well as Dixon plots and their secondary replots indicated that the nature of inhibition was purely a non-competitive type, with K(i) values 22.0 microM and 31.1, respectively. 相似文献
185.
Aziz-Ur-Rehman Malik A Riaz N Ahmad H Nawaz SA Choudhary MI 《Chemical & pharmaceutical bulletin》2005,53(3):263-266
A lignan and two acylphloroglucinols have been isolated from the ethyl acetate soluble fraction of the whole plant of Indigofera hetrantha. Their structures have been assigned on the basis of spectral analysis including 1D and 2D NMR techniques. Compounds 1-3 displayed promising inhibitory potential against enzyme lipoxygenase in concentration-dependent manner. 相似文献
186.
Khan SB Azhar-Ul-Haq Afza N Malik A Khan MT Shah MR Choudhary MI 《Chemical & pharmaceutical bulletin》2005,53(1):86-89
Long-chain esters 1 and 2 have been isolated from the chloroform-soluble fraction of Amberboa ramosa and their structures assigned to be methyl 2beta(2S)-hydroxyl-7(E)-tritriacontenoate (1) and methyl 2beta(2S)-O-beta-D-galactopyranosyl-7(E)-tetratriacontenoate (2). In addition, tricontane (3) and apigenin (4) are also reported for the first time from this species. The structures were assigned on the basis of 1D and 2D NMR techniques. Compounds 1 and 2 showed strong to moderate inhibitory activity against tyrosinase. 相似文献
187.
S-domains and strong S-rings are studied extensively with special emphasis on integral and polynomial ring extensions. The main theorem of this paper is that for a Prüfer domain R, the polynomial ring R[X1,…Xn] in finitely many indeterminates is a strong S-domain. We also prove that any Prüfer υ-multiplication domain is an S-domain. 相似文献
188.
189.
The potential energy surface for spontaneous fission is calculated using realistic density distributions for finite nuclei. Particular emphasis is placed on the region of the potential between the saddle and scission point. The method involves computing the energy of the system using an energy density functional consistent with varible density distributions and nuclear masses and obtained from a statistical many body theory. The results show that there exists an external or scission barrier to the fission process. Lifetimes and mass distributions which are computed using these potential energy surfaces are found to be in adequate agreement with observations for 234U, 236U, 240Pu, 244Cm, 248Cf, and 252Cf. Our predicted upper limit for the spontaneous fission half-lives of elements 112 and 114 is one year but the calculation indicates that these could be considerably shorter than a year. 相似文献
190.