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31.
Polarization transfer under planar mixing conditions is a widely used tool in modern NMR-experiments. In the case of two coupled spins 1/2 or a chain of three or more spins 1/2 with only nearest neighbor couplings, it is only possible to transfer a single magnetization component (longitudinal magnetization in the principle axis system of the planar coupling tensors). However, if all couplings in a three-spin system are non-zero, it turns out that all magnetization components can be efficiently transferred even under strictly planar mixing conditions. In this article a detailed theoretical analysis is presented based on analytical transverse coherence transfer functions and on the underlying commutator algebra. In addition, transverse magnetization transfer is demonstrated experimentally. The results show that in highly coupled spin systems, as for example in the case of partially aligned samples with many residual dipolar couplings, special care has to be taken to avoid phase distortions if planar mixing steps are used. 相似文献
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Glaser SJ 《Angewandte Chemie (International ed. in English)》2001,40(1):147-149
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Micro- and nanotubes of an amorphous carbon nitride material were synthesized by metathesis reactions between cyanuric chloride (C3N3Cl3) and different nitrogen sources, such as Li2(CN2) or Li3(BN2). The intermediate formation of needle-shaped crystals of N(C3N3Cl2)3 was always observed in our reactions, and investigated with respect to their role as a template in the formation of tubes. Chemical analyses of the micro- and nanotubes reveal carbon to nitrogen ratios near 3:4, consistent with the suspected material C3N4. Synthesized carbon nitride materials were thermally stable up to 600 °C in inert atmosphere. They were inspected by a number of physical measurements, mainly using TEM, EDX and IR investigations. 相似文献
35.
Glaser 《Fresenius' Journal of Analytical Chemistry》1892,31(1):285-288
Ohne Zusammenfassung(Mittheilung aus dem Laboratorium der landwirthschaftlichen Versuchsstation für Elsass-Lothringen zu Rufach.) 相似文献
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Oskar Glaser 《Fresenius' Journal of Analytical Chemistry》1907,46(8):531-532
Ohne Zusammenfassung 相似文献
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Nilmini K. Abayasinghe Sibylle Glaser K. Prasanna U. Perera Dennis W. Smith 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5257-5266
Oligoethylene‐end‐capped polylactides were synthesized through the ring‐opening polymerization of L ‐lactide with alcohol‐terminated oligoethylenes as macroinitiators. The polymerization of L ‐lactide was carried out in bulk at 130 °C in the presence of stannous octoate and primary alcohols with four different molecular weights: 350, 425, 550, and 700 g/mol. The end‐capped copolymers that formed had a number‐average molecular weight of approximately 40,000 (weight‐average molecular weight/number‐average molecular weight = 1.7) according to gel permeation chromatography and were highly crystalline in comparison with the similarly formed homopolymer of L ‐lactide. The copolymer structure was characterized by Fourier transform infrared, NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and differential scanning calorimetry analysis. This work focused on developing more crystallizable and hydrolytically stable polylactide derivatives that could potentially be used as compatibilizers in polylactide–polyolefin blends or as nucleating agents for poly(L ‐lactide) or other polyesters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5257–5266, 2005 相似文献