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31.
Chen JH Sambol EB Kennealey PT O'Connor RB DeCarolis PL Cory DG Singer S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,171(1):143-150
In cell and tissue samples, water is normally three orders of magnitude more abundant than other metabolites. Thus, water suppression is required in the acquisition of NMR spectra to overcome the dynamic range problem and to recover metabolites that overlap with the broad baseline of the strong water resonance. However, the heterogeneous cellular environment often complicates water suppression and the strong coupling of water to membrane lipids interferes with the NMR detection of membrane associated lipid components. The widely used water suppression techniques including presaturation and double pulsed field gradient selective echo result in more than a 70% reduction in membrane associated lipid components in proton spectra of cells and tissues compared to proton spectra acquired in the absence of water suppression. A water suppression technique based on the combination of selective excitation pulses and pulsed field gradients is proposed to use in the acquisition of high resolution MAS NMR spectra of tissue specimens and cell samples. This pulse sequence methodology enables efficient water suppression for intact cells and tissue samples and eliminates signal loss from cellular metabolites. 相似文献
32.
A modified Polonovski reaction has been employed to N-demethylate several opiate alkaloids in moderate to high yield. This method provides an alternative to traditional N-demethylation procedures which utilize toxic reagents such as cyanogen bromide or expensive reagents such as vinyl chloroformate. The current synthesis involves N-oxide formation, isolation of the corresponding N-oxide hydrochloride, and an FeSO(4).7H(2)O mediated Polonovski reaction to afford the desired secondary amine. 相似文献
33.
Labiche M Orr NA Marqués FM Angélique JC Axelsson L Benoit B Bergmann UC Borge MJ Catford WN Chappell SP Clarke NM Costa G Curtis N D'Arrigo A de Góes Brennand E Dorvaux O Fazio G Freer M Fulton BR Giardina G Grévy S Guillemaud-Mueller D Hanappe F Heusch B Jones KL Jonson B Le Brun C Leenhardt S Lewitowicz M Lopez MJ Markenroth K Mueller AC Nilsson T Ninane A Nyman G de Oliveira F Piqueras I Riisager K Saint Laurent MG Sarazin F Singer SM Sorlin O Stuttgé L 《Physical review letters》2001,86(4):600-603
The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation. 相似文献
34.
Michael Singer 《代数通讯》2013,41(7):639-645
Let G be a finite abelian group of exponent 4. We determine the structure of the terminal value of the summands of gr ZG, as well as the precise point at which this terminal value is reached. 相似文献
35.
Carrie A. Delcomyn Howard S. Weinberg Philip C. Singer 《Journal of chromatography. A》2001,920(1-2):213-219
A user-friendly ion chromatography method in conjunction with a post-column reaction (PCR) achieves practical quantitation limits for the oxyhalides bromate and chlorite of 0.05 μg/l and 0.10 μg/l, respectively. This level of measurement allows for the accurate assessment of bromate contributed to finished drinking waters that have been chlorinated using sodium hypochlorite. The target sensitivity of oxyhalides in the presence of other major ion species typically found in drinking water is achieved by PCR using excess bromide under acidic conditions to form a tribromide species that is detected by ultraviolet spectrometry. The method setup involves non-hazardous materials, as opposed to other recently developed methods that employ somewhat hazardous chemicals for generating the reaction necessary for the detection of bromate at sub-μg/l levels. No pretreatment of the samples is required, other than filtration and quenching of oxidant residual. 相似文献
36.
Zusammenfassung Es wurde der Weinsäuremethylester in einer CarbonatBicarbonatlösung alkalisch verseift und gefunden, daß das erste Methyl 14-mal rascher reagiert als das zweite.Die auf [OH]=1 bezogenen und für 25° geltenden Konstanten der Stufenreaktion sind k1=206 und k2=14·7.Die Methode der Verseifung von Estern mit Alkalicarbonat wurde näher untersucht und an der Hand der Verseifung von Methylacetat überprüft. 相似文献
37.
We obtain the invariants of Witten's topologicalσ-model by gauge fixing a topological action and using BRST symmetry. The fields and the BRST formalism are interpreted geometrically. 相似文献
38.
39.
Mihaela Singer Dr. 《ZDM》2001,33(6):204-217
Dominating information by formation seems to be the only realistic solution to overcome the crisis generated by the higher and higher accumulation of information in each domain. The paper is proposing a model of building structured knowledge able to generate in the child's mind strategies for efficient processing of information. 相似文献
40.
S. Aisinmann L. Singer L. Grünhut J. Treumann A. Martens und D. Holde 《Fresenius' Journal of Analytical Chemistry》1899,38(2):120-122
Ohne Zusammenfassung 相似文献