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71.
Water in protein/water mixtures can be described in terms of bound water and free water, by exchange between these two states, and by its exchange with appropriate sites on the protein. 1H-NMR diffusion and relaxation measurements provide insights into the mobility of these states. T2 relaxation-time dispersions (i.e., T2 relaxation times at different echo pulse spacings) reveal additional information about exchange. We present a comprehensive set of diffusion and T2 dispersion measurements on casein gels for which the protein/water ratio ranges from 0.25 to 0.5. The combination of these methods, taken in conjunction with concentration dependence, allows a good estimate of the parameters required to fit the data with Luz/Meiboom and Carver/Richards models for relaxation and chemical exchange. We compare the exchange (a) between water and protein and (b) between free water and bound water. Further, we attempt to distinguish chemical site exchange and diffusion/susceptibility exchange. 相似文献
72.
Konstanze R. Hahn Antonio Tricoli Gianluca Santarossa Angelo Vargas Alfons Baiker 《Surface science》2011,605(15-16):1476-1482
The composition and thermodynamic stability of the (110) surface of Sn1 - xTixO2 rutile solid solutions was investigated as a function of Ti-distribution and content up to the formation of a full TiO2 surface monolayer. The bulk and (110) surface properties of Sn1 - xTixO2 were compared to that of the pure SnO2 and TiO2 crystal. A large supercell of 720 atoms and a localized basis set based on the Gaussian and plane wave scheme allowed the investigation of very low Ti-content and symmetry. For the bulk, optimization of the crystal structure confirmed that up to a Ti-content of 3.3 at.%, the lattice parameters (a, c) of SnO2 do not change. Increasing further the Ti-content decreased both lattice parameters down to those of TiO2. The surface energy of these solid solutions did not change for Ti-substitution in the bulk of up to 20 at.%. In contrast, substitution in the surface layer rapidly decreased the surface energy from 0.99 to 0.74 J/m2 with increasing Ti-content from 0 to 20 at.%. As a result, systems with Ti atoms distributed in the surface (surface enrichment) had always lower energies and thus were thermodynamically more favorable than those with Ti homogeneously distributed in the bulk. This was attributed to the lower energy necessary to break the TiO bonds than SnO bonds in the surface layer. In fact, distributing the Ti atoms homogeneously or segregated in the (110) surface led to the same surface energy indicating that restructuring of the surface bond lengths has minimal impact on thermodynamic stability of these rutile systems. As a result, a first theoretical prediction of the composition of Sn1 - xTixO2 solid solutions is proposed. 相似文献
73.
74.
Antje Gottwald Dieter Jehnichen Doris Pospiech Peter Friedel Andreas Janke 《Journal of Macromolecular Science: Physics》2013,52(5-6):549-562
Multiblock copolymers (MBCPs) consisting of polysulfone (PSU) segments and segments of the liquid crystalline poly(ethyleneterephthalate-co-oxybenzoate) (PET/HBA) form rather complex morphologies. Scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM) investigations of two block copolymers with significantly different block molecular weights proved the existence of both macro-and microphase separation. These morphologies, existing on different length scales, were found to be superimposed in the samples. A suitable fractionation procedure was used to suppress macrophase separation. Then, it was found that microphase separation is controlled by the segment molecular weights. 相似文献
75.
W. Hufenbach B. Grüber R. Gottwald M. Lepper B. Zhou 《Mechanics of Composite Materials》2009,45(4):359-368
For analyzing the stress, strain, and displacement fields in thick-walled anisotropic multilayered composites, sophisticated
semianalytical solution methods based on a first-order shear deformation theory have been developed at the Insitut für Leichtbau
und Kunststofftechnik and validated in a great number of numerical finite-element simulations and extensive experimental tests.
A comparison of results obtained by the different methods for general multilayered composites made from unidirectional, bidirectional,
and textile-reinforced layers show a good agreement. 相似文献
76.
W. Gottwald 《Fresenius' Journal of Analytical Chemistry》1957,156(3):199-201
Ohne Zusammenfassung 相似文献
77.
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79.
We investigate the drift of a spiral wave core in a homogeneous excitable medium under the influence of a periodic stimulation by wave trains close to the core. Two important results were found. First, as opposed to existing theories of spiral wave drift, we observe drift induced by wave trains with periods larger than the period of the freely rotating spiral wave. Second, when investigating the drift of meandering spirals we found that the property of meandering of spirals is not robust against periodic stimulations. Simple phenomenological arguments are provided to explain these observations. (c) 2001 American Institute of Physics. 相似文献
80.