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31.
32.
A robust, easy to optimize, and efficient homonuclear correlation NMR experiment for half-integer quadrupolar nuclei in solids is described and has been experimentally tested on anhydrous Na2HPO4-(23Na, S= 3/2 nucleus) and as-synthesized AlPO4-14 (27Al, S= 5/2 nucleus), an aluminophosphate molecular sieve. 相似文献
33.
An activated D-residue of a protected dipeptide when coupled racemizes twice as much as an activated L-residue, which is contrary to the case for couplings of acylamino acids. 相似文献
34.
D'Souza F Chitta R Gadde S Zandler ME Sandanayaka AS Araki Y Ito O 《Chemical communications (Cambridge, England)》2005,(10):1279-1281
A highly stable porphyrin-fullerene conjugate with defined distance and orientation, was formed using a newly developed 'two-point' binding strategy involving axial-coordination and cation-crown ether complexation; photochemical studies performed in benzonitrile revealed efficient charge separation and slow charge-recombination in the supramolecular complex. 相似文献
35.
D.?Mitra S.?Francis L.?VarshneyEmail author 《Journal of Thermal Analysis and Calorimetry》2004,78(3):821-829
DSC and TG studies were carried out on -radiation processed Indian natural products of medicinal importance, namely Ashwagandha (Withania Somnifera), Amla (Emblica Officinalis) and Hartiki (Terminalia chebula). DSC thermoanalytical curves were recorded from 35 to 400°C in air and nitrogen atmosphere. Similarly, TG thermoanalytical curves were taken from 35 to 700°C in air and nitrogen atmosphere. Irradiated products gave significantly different thermoanalytical profiles in comparison to non-irradiated samples. The differences were observed above decomposition temperature of 200°C and were non-linear with respect to radiation dose. Partial oxidation of the products during irradiation in air could be responsible for the observed differences. 相似文献
36.
Christophe Hoarau Alexis Du Fou de Kerdaniel Pierre Grandclaudon Francis Marsais 《Tetrahedron letters》2005,46(49):8573-8577
The efficient and regioselective palladium-catalyzed C-2 arylation of ethyl 4-oxazolecarboxylate 1 with phenyliodide is described. The different parameters (solvent, base, ligand and catalyst) for the optimal conditions of this arylation process have been screened. 相似文献
37.
al-Ktaifani MM Bauer W Bergsträsser U Breit B Francis MD Heinemann FW Hitchcock PB Mack A Nixon JF Pritzkow H Regitz M Zeller M Zenneck U 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(11):2622-2633
Several independent synthetic routes are described leading to the formation of a novel unsaturated tetracyclic phosphorus carbon cage compound tBu4C4P6 (1), which undergoes a light-induced valence isomerization to produce the first hexaphosphapentaprismane cage tBu4C4P6 (2). A second unsaturated isomer tBu4C4P6 (9) of 1 and the bis-[W(CO)5] complex 13 of 1 are stable towards similar isomerization reactions. Another starting material for the synthesis of the hexaphosphapentaprismane cage tBu4C4P6 (2) is the trimeric mercury complex [(tBu4C4P6)Hg]3 (11), which undergoes elimination of mercury to afford the title compound 2. Single-crystal X-ray structural determinations have been carried out on compounds 1, 2, 9, 11, and 13. 相似文献
38.
Yoshim Tokura Richard L. Edelson Francis P. Gasparro 《Photochemistry and photobiology》1993,58(6):822-826
Abstract The effects of cell differentiation and mitogen and phorbol ester stimulation on the formation of 8-methoxypsoralen (8-MOP)-DNA photoadducts in murine T lymphocytes were examined using 3 H-8-MOP. While there were no significant differences in 8-MOP photoadduct formation among BALB/c thymocytes, splenocytes, splenic T cells and MRL/1pr lymph node cells, BALB/c bone marrow cells showed fewer photoadducts than did the lymphocytes. This suggested that proliferating progenitor cells may be resistant to 8-MOP photoadduct formation. Incubation of purified splenic T cells with lectin mitogens for 2 h or with phorbol 12-myristate 13-acetate (PMA) for 2–43 h resulted in reduction of 8-MOP photoadduct formation in the DNA, whereas 64 h cultivation with these agents augmented the photoadduct formation. The reduction of photoadduct formation induced by phytohemagglutinin was restored by the further addition of a protein kinase C (PKC) inhibitor, H-7, to the culture. Thus, it is assumed that the reduction of adduct formation evoked by mitogens and PMA is mediated in part by the activation of PKC in the cells. On the other hand, the augmentation of the adduct formation induced by the longer-period cultures with mitogens and PMA appeared to be caused by down-regulation of PKC. The present study showed that the stimulatory signals in which PKC is presumably involved affect the ability of cells to form 8-MOP-DNA photoadducts. 相似文献
39.
Corine Simonnet-Jégat Francis Robert Francis Sécheresse 《Transition Metal Chemistry》1994,19(3):379-380
Summary The reaction of NH4VO3 with S
2
-2
in ammonia in the presence of 2,2-bipyridine (bipy) and [N(Bu)4]Br gives the mononuclear compound [N(Bu)4][V(O)(S2)2bipy] (1) isolated at room temperature in crystalline form. The X-ray crystal structure determination shows that the vanadium(V) centre is ligated by four sulphur atoms and a nitrogen atom of the bipy ligand forming the equatorial plane of pentagonal bipyramid, an oxygen and the remaining nitrogen atom of the bipy occupying the two apices of the bipyramid. 相似文献
40.
The coupling of subcritical water separation with flame ionization detection (FID) in the split mode has been investigated in this study. In order to keep the FID system stable during subcritical water separation, a Tee union was connected between the separation column and the FID system to split the water flow. The ratio of the water flow to the FID system over the flow-rate to a waste bottle varied depending on the dimension of capillary tubings and the total water flow-rate used. Separations of several carbohydrates, carboxylic acids, and amino acids were performed on commercially available columns using a laboratory-made subcritical water chromatography-FID system. The FID system was very stable in this split mode even at total flow-rate as high as 1.24 ml/min. The linear dynamic range was up to three orders of magnitude and the limit of detection (LOD) ranged from 38 to 111 ng (306-925 ng/microl injected) with split ratios of approximately 1:10 to approximately 1:17 (FID/waste bottle) for several analytes studied. However, the LOD can be significantly lowered by adjusting the dimensions of the restrictors to allow a higher percentage of the total flow to the FID system. 相似文献