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261.
Pham TN Masiero S Gottarelli G Brown SP 《Journal of the American Chemical Society》2005,127(46):16018-16019
15N solid-state NMR refocused INADEQUATE spectra of two lipophilic deoxyguanosine derivatives unambiguously identify different intermolecular hydrogen-bonding arrangements that are indicative of either guanine ribbon or quartet self-assembly. The observation of guanine quartet formation in the absence of metal ions is a further example that challenges the accepted dogma that quartet formation requires metal ions. 相似文献
262.
Jiang W Chen C Marinkovic D Tran JA Chen CW Arellano LM White NS Tucci FC 《The Journal of organic chemistry》2005,70(22):8924-8931
[reaction: see text] 2-[4-(tert-Butoxycarbonyl)piperazinyl]benzylidene-tert-butanesulfinamides underwent nucleophilic 1,2-addition with different organometallic reagents to give highly diastereomerically enriched adducts. X-ray crystallography of the resulting alpha-branched N-Boc-2-piperazinylbenzyl-tert-butanesulfinamides confirms different mechanisms depending on the organometallic reagent used. Differential deprotection of the N-Boc and the tert-butanesulfinamides was investigated, and the dehydration byproducts have been identified and characterized. To avoid the formation of byproducts in the acidic deprotection step, the N-tert-butanesulfinamide group was converted to the corresponding N-tert-butanesulfonamide (Bus), which allowed for clean orthogonal deprotection. The efficient synthesis and deprotection of the N-Boc-2-piperazinylbenzyl-tert-butanesulfinamides herein described constitutes an attractive method for extensive structure-activity studies in the search for novel ligands of the human melanocortin 4 receptor. 相似文献
263.
Li YS Wang Y Tran T Perkins A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3032-3037
Organosilane sol-gels have been prepared under different conditions from mercaptopropyltrimethoxysilane (MPTMS) and mercaptopropyltriethoxysilane (MPTES). These sol-gels were applied for the thin film coating on aluminum. Vibrational spectroscopy has been employed to trace and to study the proceeding of the sol-gel formation and the curing of the coated films on Al. Based on the group frequencies as well as their spectral behavior under different conditions, vibrational assignments have been made for most of the observed bands. Surface enhanced Raman scattering has revealed the chemical adsorption of MPTMS sol-gel on silver particles. Recorded reflection and absorption infrared (RAIR) spectra of coated tiles cured at different temperatures have indicated that surface reaction may occur at high temperature. The anticorrosion characters of the coated metals have been evaluated with the measured electrochemical data. Results from cyclic voltammographs have indicated that each layer of sol-gel coating would reduce the redox current across the electrode/electrolyte solution interface. Tafel plots have shown that the anodic current of the coated electrode decreases significantly and the corrosion potentials shift to the positive side. 相似文献
264.
265.
G. Kraus M. Schierhorn Tran thi Van Hong und E. Tuek 《Fresenius' Journal of Analytical Chemistry》1982,312(3):242
Ohne Zusammenfassung
Die Autoren danken Dr. sc. H. J. Deutscher und Dr. W. Weißflog für die Überlassung der Flüssigkristalle sowie Dr. A. Wiegeleben für die Durchführung der calorimetrischen Messungen. 相似文献
Gas-chromatographic separation of dimethylesters of isomeric benzene dicarboxylic acids on liquid crystals
Die Autoren danken Dr. sc. H. J. Deutscher und Dr. W. Weißflog für die Überlassung der Flüssigkristalle sowie Dr. A. Wiegeleben für die Durchführung der calorimetrischen Messungen. 相似文献
266.
267.
Using an oscilloscope the absorbance above a filament atomizer has been measured as a function of the position of the optical axis with respect to the sample position. For the elements investigated (Cd, Pb and Ag) an asymmetrical distribution of the atoms has been found. The vertical velocity of the sample cloud border was constant for each element and twice the horizontal velocity. The experiments have shown that the extension in an open atomizer at atmospheric pressure cannot be described by a pure diffusion process. 相似文献
268.
Tran Van-Nguyen 《Antennas and Propagation, IEEE Transactions on》1972,20(6):776-778
Exact solutions of the transverse resonance equation for a long slot leaky wave antenna have been obtained by numerical analysis and verified by practical results. 相似文献
269.
The confinement properties of a new magnetic shell configuration have been investigated experimentally. The diffusion coefficient D has been determined. 相似文献
270.
C.J. Martoff L. Van Elmbt M. Lebrun M. Schaad U. Straumann P. Truöl K.M. Crowe C. Joseph J.P. Perroud D. Ruegger M.T. Tran J. Deutsch G. Grégoire R. Prieels W. Dahme 《Nuclear Physics A》1984,430(3):557-572
The cross section and angular distribution for the reaction 13C(π+, γ)13N(g.s.) have been measured from 37 to 85° in the laboratory, at a pion energy of 115.5 MeV. The observed cross section ranges from 320 to 660 . These results do not show the large magnitude and wide-angle peaking expected if pre-critical effects due to nascent pion condensation were present. In addition, the observed cross section is less than one-half of the predictions of available theoretical calculations which do not include the pre-critical effect. Data on the reaction 1H(π?, γ)n at Tπ = 116.6 MeV were also obtained for calibration purposes. These data agree with expectations based on knowledge of the inverse reaction and previous measurements. 相似文献