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21.
For swollen polymer networks there is no generally accepted relation between the macroscopic osmotic properties and the scattering behaviour. Detailed information on the relationship between these properties can, however, be deduced from complementary measurements of osmotic and elastic behaviour, small angle neutron and X-ray scattering (SANS and SAXS) and quasi-elastic light scattering. We describe such an investigation in two types of networks, differing in the mechanism of cross-linking. The SANS spectra yield information on the structure, which is generated both by the dynamics of the system and by long range static constraints. The former, arising from thermodynamic concentration fluctuations, governs the macroscopic osmotic and elastic moduli of the swollen network. The static superstructure in the gel reflects local variations in the cross-link density. The resulting concentration polydispersity, <δφ2>/φ2, is determined by the details of the cross-linking procedure. Its concentration dependence as a function of gel swelling can be expressed in terms of the same macroscopic osmotic and elastic variables as those that govern the thermodynamic properties of the gel. 相似文献
22.
Erik Geissler Anne-Marie Hecht Simon Mallam Ferenc Horkay Mikls Zrinyi 《Macromolecular Symposia》1990,40(1):101-108
Small angle neutron scattering measurements were performed on polydimethylsiloxane-toluene solutions and gels at different degrees of swelling. The scattering signal of the gel was decomposed into a solution-like part and a static part. The thermodynamic information obtained from the solution-like part of the signal is compared with macroscopic swelling pressure observations. 相似文献
23.
Liang Chen Yu Fan Jieru Qiu Dr. Régis Laurent Jin Li Prof. Dr. Jérôme Bignon Prof. Dr. Serge Mignani Prof. Dr. Anne-Marie Caminade Prof. Dr. Xiangyang Shi Prof. Dr. Jean-Pierre Majoral 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(26):5903-5910
First-in-class CuII and AuIII metaled phosphorus dendrons were synthesized and showed significant antiproliferative activity against several aggressive breast cancer cell lines. The data suggest that the cytotoxicity increases with reducing length of the alkyl chains, whereas the replacement of CuII with AuIII considerably increases the antiproliferative activity of metaled phosphorus dendrons. Very interestingly, we found that the cell death pathway is related to the nature of the metal complexed by the plain dendrons. CuII metaled dendrons showed a potent caspase-independent cell death pathway, whereas AuIII metaled dendrons displayed a caspase-dependent apoptotic pathway. The complexation of plain dendrons with AuIII increased the cellular lethality versus dendrons with CuII and promoted the translocation of Bax into the mitochondria and the release of Cytochrome C (Cyto C). 相似文献
24.
Rita Simões Christoph Mönninghoff Martha Dlugaj Christian Weimar Isabel Wanke Anne-Marie van Cappellen van Walsum Cornelis Slump 《Magnetic resonance imaging》2013
Magnetic Resonance (MR) white matter hyperintensities have been shown to predict an increased risk of developing cognitive decline. However, their actual role in the conversion to dementia is still not fully understood. Automatic segmentation methods can help in the screening and monitoring of Mild Cognitive Impairment patients who take part in large population-based studies. Most existing segmentation approaches use multimodal MR images. However, multiple acquisitions represent a limitation in terms of both patient comfort and computational complexity of the algorithms. In this work, we propose an automatic lesion segmentation method that uses only three-dimensional fluid-attenuation inversion recovery (FLAIR) images. We use a modified context-sensitive Gaussian mixture model to determine voxel class probabilities, followed by correction of FLAIR artifacts. We evaluate the method against the manual segmentation performed by an experienced neuroradiologist and compare the results with other unimodal segmentation approaches. Finally, we apply our method to the segmentation of multiple sclerosis lesions by using a publicly available benchmark dataset. Results show a similar performance to other state-of-the-art multimodal methods, as well as to the human rater. 相似文献
25.
Paul Servin Régis Laurent Anne-Marie Caminade Jean-Pierre Majoral 《Tetrahedron letters》2007,48(4):579-583
A series of densely functionalized dendrimers is synthesized using two branched monomers of type AB2 and CD2, in which the A function (NH2) reacts with D (CHO) and the B function (Cl) reacts with C (OH). The reaction has been carried out up to the fourth generation possessing 96 end groups and has been obtained in only four steps. 相似文献
26.
Electronic energy relaxation in hollow gold nanospheres (HGNs) was studied using femtosecond time-resolved transient absorption spectroscopy. A range of HGNs having outer diameter-to-shell thickness aspect ratios of 3.5 to 9.5 were synthesized by a galvanic replacement method. The HGNs exhibited electron-phonon relaxation times that decreased from 1.18 ± 0.16 to 0.59 ± 0.08 ps as the aspect ratio increased over this range. The corresponding electron-phonon coupling constants, G, ranged from (1.67 ± 0.22) to (3.33 ± 0.45) × 10(16) W m(-3) K(-1). Electron-phonon coupling was also determined for solid gold nanospheres (SGNs) with diameters spanning 20 nm to 83 nm; no size dependence was observed for these structures. The HGNs with high aspect ratios exhibited larger electron-phonon coupling constants than the SGNs, whose average G value was (1.9 ± 0.2) × 10(16) W m(-3) K(-1). By comparison, low-aspect ratio HGNs exhibited values comparable to SGNs. The electron-phonon coupling of high-aspect ratio HGNs was also influenced by the surrounding fluid dielectric; slightly smaller G values were obtained when methanol was the solvent as opposed to water. This coupling enhancement observed for high-aspect ratio HGNs was attributed to the large surface to volume ratio of these structures, which results in non-negligible contributions from the environment. 相似文献
27.
Max Robba Michel Cugnon De Sevricourt Anne-Marie Godard 《Journal of heterocyclic chemistry》1979,16(6):1175-1180
The cleavage of the pyridazine ring of the acyltetrahydro [1] benzofuro [2,3-d] pyridazones was carried out by hydrolysis, alcoholysis or aminolysis reactions and they affect the lactam 3,4-bond. They lead chiefly to benzofuran derivatives with acid, ester, amide or hydrazide groups in the 2-position and eventually an acylated methylhydrazine group in the 3-position. The cyclization reactions of 3-hydrazinomethylbenzofuran-2-carboxylic acid and its derivatives or ethyl 3-bromome thylbenzofuran-2-carboxylate affords tetrahydrobenzofuropyridazones. The nmr spectra were studied. 相似文献
28.
Rakotondradany F Whitehead MA Lebuis AM Sleiman HF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(19):4771-4780
A new strategy to effect photoinduced control over molecular self-assembly is reported. This strategy uses the reversible trans-cis photoisomerization of a novel azobenzene system, where the trans- and cis-forms self-assemble into dramatically different higher-order structures. The trans-azobenzene form of this molecule associates into infinite hydrogen-bonded linear tapes, while the cis-azobenzene form undergoes hydrogen-bonded self-assembly into cyclic tetramers. This results in a second level of association, where the cis-hydrogen-bonded supramolecular cycles ultimately form long, rod-like aggregates through stacking interactions. 相似文献
29.
30.
Duli C. Jain Denyse De Gale Anne-Marie Sapse 《Journal of computational chemistry》1989,10(8):1031-1037
A continuum and a discrete-continuum models are used to determine the solvation energies of FCH2COO?, FCH2COOH, and F2CHCOO?. For the anions, the continuum model provides results closer to the experiment, while for the acid, the addition of one water molecule improves the continuum-only energy. 相似文献