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NMR Line (nmr + line)
Selected AbstractsNMR search for polymorphic phase transformations in chlorpropamide form-A at high pressuresJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2009sicki Abstract The high-pressure effects on chlorpropamide (C10H13ClN2O3S) form-A have been studied by 1H NMR spectroscopy at high pressures up to 800 MPa in the temperature range 90,300 K. A study of the NMR second moment and spin-lattice relaxation time has been completed by a calculation of the steric hindrances for molecular reorientations and simulations of the second moment of the NMR line by the Monte,Carlo method, which enabled a precise description of molecular dynamics in the compound studied. Reorientations of the methyl group, oscillations and reorientations of the chlorophenyl ring and reorientations of the propyl group have been revealed and respective activation parameters extracted. No phase transformation of the compound form-A has been detected. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1426,1437, 2009 [source] Molecular Dynamics of Podand Studied by Broadband Dielectric and Nuclear Magnetic Resonance Spectroscopies,,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19-20 2007Bakyt Orozbaev Abstract Nuclear magnetic resonance (NMR) and broadband dielectric spectroscopies (BDS) were used to analyze the molecular dynamics in P10.3H Podand. The temperature studies of NMR line and magnetic spin,lattice relaxation times accompanied by DS investigation enabled us to distinguish three main dynamical processes connected with the motions of the P10.3H Podand chains. In the low-temperature region the magnetic relaxation was associated with fast axial C3 rotation of methyl groups. Moreover, two other independent processes were observed and interpreted as (i) segmental motion of both oxyethylene and ethylene units, and (ii) the overall motion involved in the melting process. [source] 55Mn NMR study in magnetically ordered state of perovskite manganitesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2004K. Shimizu Abstract We present NMR results of Pr1,xSrxMnO3 and their lacunar samples, and also present results of the single crystalline layered manganites La1.2Sr1.8Mn2O7 and La1.2Sr1.6Ca0.2Mn2O7. In Pr1,xSrxMnO3, a single resonance line is observed for 0.27 , x , 0.4, which indicates the sample to be in a metallic state. In the Pr and Sr deficient samples, the NMR line arising from Mn2+ is observed. Introducing deficiency to Pr or Sr sites, a charge disproportionation of the type 2Mn3+, Mn2+ + Mn4+ probably occurs. For La1.2Sr1.8Mn2O7 and La1.2Sr1.6Ca0.2Mn2O7 compounds, the NMR spectra under an external field of 1.5 T are broad and spread with several distinct lines in the frequency range 310,420 MHz. This is different from the results of La1,xSrxMnO3 and Pr1,xSrxMnO3 with a metallic state, where a single line has been observed. The distinct NMR lines are ascribed to Mn4+, Mn3+ and metallic phase, taking account of the results for La1,xSrxMnO3 and Pr1,xSrxMnO3. In addition to the NMR line from the metallic phase, the observation of Mn3+ and Mn4+ lines suggests a phase separation at low temperature in La1.2Sr1.8Mn2O7 and La1.2Sr1.6Ca0.2Mn2O7. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis of biodegradable copolymers with low-toxicity zirconium compounds.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Abstract The results of the copolymerization of glycolide with cyclic trimethylene carbonate and 2,2-dimethyltrimethylene carbonate are described. The copolymerization was conducted in the presence of low-toxicity zirconium(IV) acetylacetonate as an initiator. With this kind of initiator, the composition of the comonomer units in the copolymer chains was assumed to be obtained with high efficiency. Despite significant differences in the comonomer reactivity, in copolymers containing comparable amounts of glycolidyl and carbonate sequences, highly randomized chain structures were observed. This effect resulted from strong intermolecular transesterification that proceeded during the studied copolymerization and caused glycolidyl microblock randomization. The assignment of the spectral NMR lines to appropriate comonomer sequences of polymeric chains was performed in the region of methylene protons of glycolidyl units in 1H NMR spectra of the copolymers and in the carbonyl region of carbon spectra. The equations were formulated for a detailed characterization of the obtained copolymer chains, the average lengths of the blocks, and the transesterification and randomization coefficients. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 98,114, 2006 [source] NMR methods applied to anisotropic diffusionMAGNETIC RESONANCE IN CHEMISTRY, Issue 13 2002István Furó Abstract The methodology of NMR experiments intended to measure anisotropic diffusion is reviewed. Experiments of this kind preferably require oriented samples and/or orientation-dependent spin coupling and/or magnetic field gradients in different directions. One strategy of diffusion experiments in anisotropic systems with broad NMR lines employs line narrowing techniques, thereby allowing for efficient gradient encoding/decoding. Depending on the nuclei, spin couplings and samples, the preferred methods vary from decoupling through echo techniques to magic angle sample orientation and spinning. Another avenue to efficient gradient encoding/decoding is through very strong magnetic field gradients. Either way, anisotropic diffusion reveals new structural features as illustrated by a few selected examples in liquid crystals and in biological tissues. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||