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1.
S. Kwieciński M. Weychert A. Jasiński P. Kulinowski I. Wawer E. Sieradzki 《Applied magnetic resonance》2002,22(1):23-29
The disintegration of bromhexin tablets was monitored by magnetic resonance imaging. The fast imaging method FLASH with spoiling
gradients was used to obtain images of the tablets in short time intervals. The rate of the disintegration depends on the
preparation method, kind and percentage of the carrier (polyethylene glycol, lactose). Solid dispersion with slow evaporation
of solvent yields materials with decreased dissolution rate. Increasing molecular mass of polyethylene glycol and its percentage
content also hampers disintegration. 相似文献
2.
Based on the SU(n)-algebra the Markoff master equation in discrete product space is reformulated to explicitly deal with composite systems. The resulting local (single node) and nonlocal (multi-node) state parameters allow a systematic approach to non-classical features of the state, like variance and covariance tensors. For local optical driving forces, inter-node interactions, and local damping channels the solution of the master equation is unraveled into stochastic quantum trajectories. Sampling leads to a joint distribution function in terms of those state parameters. Its linear moments define the ensemble-density matrix. The average variance and covariance are in terms of non-linear moments, which should be distinguished from their entirely statistical counterpairs. Non-classicality of the network dynamics is shown to reflect itself in the luminescence-photonstatistics. 相似文献
3.
Maciej PisklakFranciszek Herold Romana Anulewicz-OstrowskaIwona Wawer 《Journal of Molecular Structure》2002,605(1):85-92
13C cross-polarisation magic angle spinning NMR data have been reported for four derivatives of 4-aryl-octahydro-pyrido[1,2-c]pyrimidine-1,3-dione and the X-ray diffraction data for two (with 2′-Me and 2′-OMe). The crystal structures show the presence of centrosymmetric cyclic dimers with intermolecular C1O?H-N or C3O?H-N hydrogen bonds, the configuration at the chiral centres (C4 and C4a) was determined as RR (SS). The twisting of aromatic ring at C4 with respect to the pyrido[1,2-c]pyrimidine skeleton is about 68-109°. 相似文献
4.
Cross-polarization (CP) magic angle spinning (MAS) solid-state 13C NMR spectra of five steroidal sapogenins: tigogenin ((25R)-5alpha-spirostan-3beta-ol), hecogenin (3beta-hydroxy-(25R)-5alpha-spirostan-12-one), diosgenin ((delta5-(25R)-5alpha-spirosten-3beta-ol), sarsasapogenin ((25S)-55beta-spirostan-3beta-ol), and smilagenin ((25R)-5beta-spirostan-3beta-ol) were recorded. The solid-state chemical shifts are almost the same as for solution, which indicate that confirmations of sapogenins are similar in both phases. The doubling of some resonances in the spectra of solid diosgenin shows that there are two molecules in the crystallographic asymmetric unit. The cross-polarization time constants T(CP) and relaxation times in the rotating frame T(1rho)H were obtained from the variable-contact cross-polarization experiments for tigogenin and diosgenin. The values of T(CH) for methyl carbons indicate fast rotation of methyl groups and are close (0.30-0.35 ms), suggesting that the interaction with their intramolecular neighbors is similar. The values of T(1rho)H for carbons of tigogenin are longer than of diosgenin. Very efficient cross-polarization dynamics results in short time required for obtaining a spectrum of sapogenin of remarkably good quality. 相似文献
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A Szelejewska-Wo?niakowska Z Chilmonczyk A Le? J Cybulski I Wawer 《Solid state nuclear magnetic resonance》1999,14(1):59-65
13C cross-polarization (CP) magic angle spinning (MAS) solid state NMR spectra of hydrochlorides and perchlorates of buspirone analogues (2-5) were recorded. In the spectra for each compound, one set of signals appeared, in agreement with single crystal X-ray diffraction data indicating the presence of one molecule per crystal unit. The resonances of 2-5 hydrochlorides were assigned by comparison with the solution chemical shifts. For perchlorate 2b and diperchlorate 2c, the reasonable assignment of signals was made with the aid of the theoretical studies. Ab initio calculations of the carbon shieldings were performed by means of the GIAO-CHF method for two model systems: perchlorate and diperchlorate of quinoline-(N-methyl)piperazine. As no remarkable differences between carbon chemical shifts of hydrochlorides 3-5 in solid state and in solution were observed, it was concluded that in solution these compounds adopted the same conformation as in the solid state. 相似文献
7.
Romana Anulewicz Iwona Wawer Boguslawa Piekarska-Bartoszewicz Andrzej Temeriusz 《Journal of carbohydrate chemistry》2013,32(6):617-628
ABSTRACT The X-ray diffraction analysis of methyl 3,4,6-tri-O-acetyl-2-deoxy-(3-phenylureido)-β-D-glucopyranoside was performed and showed that the molecules are associated by two NHz.O=C hydrogen bonds. One molecule with disorder of an acetyl group at C-4 was found in the asymmetric crystal unit. The signals in 13C CPMAS NMR spectrum are duplicated indicating that local symmetry is lower than those of the crystal. 相似文献
8.
Katarzyna Paradowska Micha Wolniak Maciej Pisklak Jan A. Gliski Matthew H. Davey Iwona Wawer 《Solid state nuclear magnetic resonance》2008,34(4):202-209
Oxindole alkaloids, isolated from the bark of Uncaria tomentosa [Willd. ex Schult.] Rubiaceae, are considered to be responsible for the biological activity of this herb. Five pentacyclic and two tetracyclic alkaloids were studied by solid-state NMR and theoretical GIAO DFT methods. The 13C and 15N CPMAS NMR spectra were recorded for mitraphylline, isomitraphylline, pteropodine (uncarine C), isopteropodine (uncarine E), speciophylline (uncarine D), rhynchophylline and isorhynchophylline. Theoretical GIAO DFT calculations of shielding constants provide arguments for identification of asymmetric centers and proper assignment of NMR spectra. These alkaloids are 7R/7S and 20R/20S stereoisomeric pairs. Based on the 13C CP MAS chemical shifts the 7S alkaloids (δ C3 70–71 ppm) can be easily and conveniently distinguished from 7R (δC3 74.5–74.9 ppm), also 20R (δC20 41.3–41.7 ppm) from the 20S (δC20 36.3–38.3 ppm). The epiallo-type isomer (3R, 20S) of speciophylline is characterized by a larger 15N MAS chemical shift of N4 (64.6 ppm) than the allo-type (3S, 20S) of isopteropodine (δN4 53.3 ppm). 15N MAS chemical shifts of N1–H in pentacyclic alkaloids are within 131.9–140.4 ppm. 相似文献
9.
M. Getsova D. Todorovsky V. Enchev I. Wawer 《Monatshefte für Chemie / Chemical Monthly》2007,138(5):389-401
Summary. Cerium(III/IV) and Ce(IV)–Ti(IV) citric complexes were synthesized in ethylene glycol medium under conditions similar to those
of the polymerized complex method (PCM). Solution phase 1H, 13C NMR, solid state 13C CP MAS NMR and IR spectroscopy, and X-ray powder diffractometry were used to characterize the composition and structure
of the synthesized products. Thermal decomposition of the isolated complexes was studied and a scheme of the processes taking
place is proposed. Complexes of Ce(III) can be prepared at low temperature (40°C), only. In the presence of Ti(IV) ions, the
oxidation takes place even at this temperature. A mixed-metal nature of the Ce(IV)–Ti(IV) complexes is established. The comparison
between their composition and the one of analogous lanthanide(III)–Ti(IV) citrates contributes to the elucidation of the complexation
process mechanism in the case of the PCM application. The increased charge of the complexation agent in the Ce4+–Ti4+ complex (in comparison with Ln
3+–Ti4+ citrates) is “compensated” by the increase of the relative number of the ligands with deprotonated OH group. 相似文献
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