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排序方式: 共有492条查询结果,搜索用时 15 毫秒
31.
Rottereau M Gimel JC Nicolai T Durand D 《The European physical journal. E, Soft matter》2005,18(1):15-19
The influence of the Brownian step size in off-lattice Monte Carlo simulations of the aggregation and gelation of spheres
is studied. It is found that the kinetics are strongly influenced if the step size is larger than the mean smallest distance
between the sphere surfaces. The structure of the clusters and the gels is influenced, but only over length scales smaller
than the step size. Using large step sizes leads to a narrower size distribution of the clusters. Implications of the present
results are discussed for simulations reported in the literature in which the Brownian step size was chosen equal to the sphere
diameter. 相似文献
32.
Diffusion-limited cluster aggregation and gelation of hard spheres is simulated using off-lattice Monte Carlo simulations.
A comparison is made of the wall-particle correlation function with the particle-particle correlation function over a range
of volume fractions, both for the initial system of randomly distributed spheres and for the final gel state. For randomly
distributed spheres the correlation functions are compared with theoretical results using the Ornstein-Zernike equation and
the Percus-Yevick closure. At high volume fractions (φ > 40%) gelation has little influence on the correlation function, but
for φ < 10% it is a universal function of the distance normalized by correlation length (ξ) of the bulk. The width of the
depletion layer is about 0.5ξ. The concentration increases as a power law from the wall up to r ≈ ξ, where it reaches a weak maximum before decreasing to the bulk value. 相似文献
33.
Berardini N Carle R Schieber A 《Rapid communications in mass spectrometry : RCM》2004,18(19):2208-2216
Polyphenolics were extracted from peels, pulp and kernels of mango fruits (Mangifera indica L. cv. 'Tommy Atkins') and characterized by high-performance liquid chromatography/electrospray ionization mass spectrometry. In the peel 18 gallotannins and five benzophenone derivatives were detected which were tentatively identified as galloylated maclurin and iriflophenone glucosides. Twenty-one and eight gallotannins were found in the kernels and pulp, respectively, whereas no evidence for the presence of benzophenone derivatives was obtained. Gallotannins quantified by the rhodanine assay amounted to 1.4 mg/g dm in the peels (expressed as gallic acid), while only small amounts (0.2 mg/g dm) were found in the pulp. In contrast, mango kernels contained 15.5 mg/g dm and thus proved to be a rich source of gallotannins. 相似文献
34.
López Fontán JL Costa J Ruso JM Prieto G Sarmiento F 《The European physical journal. E, Soft matter》2004,15(2):133-140
The application of a statistical method, the local polynomial regression method, (LPRM), based on a nonparametric estimation of the regression function to determine the critical micelle concentration (cmc) is presented. The method is extremely flexible because it does not impose any parametric model on the subjacent structure of the data but rather allows the data to speak for themselves. Good concordance of cmc values with those obtained by other methods was found for systems in which the variation of a measured physical property with concentration showed an abrupt change. When this variation was slow, discrepancies between the values obtained by LPRM and others methods were found.Received: 2 October 2003, Published online: 25 March 2004PACS:
02.50.-r Probability theory, stochastic processes, and statistics - 82.70.-y Disperse systems; complex fluids 相似文献
35.
Giampiero Mei Almerinda Di Venere Eleonora Nicolai Nicola Rosato Alessandro Finazzi Agro' 《Journal of fluorescence》2003,13(1):33-39
Tryptophan fluorescence is extremely useful to monitor structural conformational transitions in proteins. Denaturant-induced unfolding of azurin and ascorbate oxidase has been studied by dynamic fluorescence measurements in the frequency domain and the results have been interpreted in terms of continuous distribution of lifetimes. The data add new information on the unfolding mechanism that was previously analyzed by steady-state emission spectroscopy. In particular, the existence of multiple, parallel unfolding pathways may be envisaged and correlated, in both cases, to the two protein structures. The effect of metal depletion has been also characterized by fluorescence lifetime measurements. In the case of azurin, a monomeric protein, the data demonstrate that copper removal yields a totally different unfolding pathways with respect to the holo protein, indicating that metal ion plays a fundamental structural role in the wild type, native protein. In the case of ascorbate oxidase a dimer of 140 kDa, only minor effects have been detected by copper removal. However, the analysis of the fluorescence decay in presence of different amounts of guanidinium hydrochloride gives new important insights on the unfolding intermediates. In particular the data support the hypothesis of a partial exposure of an outer layer of dimer at intermediate denaturant concentration. This ability of dynamic fluorescence to pinpoint the presence of structural micro-heterogeneity in the unfolding pathways of proteins demonstrates the greater power of this technique compared to the most commonly used steady-state measurements. 相似文献
36.
We construct maximally supersymmetric gauged N = 16 supergravity in three dimensions, thereby obtaining an entirely new class of anti--de Sitter supergravities. These models apparently cannot be derived from any known higher-dimensional theory and point to the existence of a new type of supergravity beyond D = 11. One of their noteworthy features is a non-Abelian generalization of the duality between scalar and vector fields in three dimensions. Among the possible gauge groups, SO(8) x SO(8) is distinguished as the maximal compact gauge group, but there are also more exotic possibilities such as F(4(-20)) x G2. 相似文献
37.
38.
We study random skew 3D partitions weighted by q
vol
and, specifically, the q → 1 asymptotics of local correlations near various points of the limit shape. We obtain sine-kernel asymptotics for correlations in the bulk of the disordered region, Airy kernel asymptotics near a general point of the frozen boundary, and a Pearcey kernel asymptotics near a cusp of the frozen boundary. 相似文献
39.
40.