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81.
Kevin L. White Peng Li Haiqing Yao Riichi Nishimura Hung-Jue Sue 《Rheologica Acta》2014,53(7):571-583
The influence of inter-particle interaction on the rheology of an uncured epoxy containing model α-zirconium phosphate (ZrP) nanoplatelets with aspect ratio of 160 is reported. Epoxy suspensions containing nanoplatelets exfoliated with tetra-n-butyl ammonium hydroxide (TBA), a low molecular weight quaternary ammonium cation, show short-range repulsive potential with weak elastic response at low concentration. At semi-dilute concentrations, the suspensions are solid-like at intermediate frequency and transition to viscous flow for time scales longer than the rotary diffusion process. The weak elasticity at intermediate frequency is attributed to the effect of Brownian motion on the rotational motion of the isolated plates. Suspensions containing nanoplatelets exfoliated with hydrophilic polyetheramine oligomers show similar behaviour to the ZrP-TBA system, but shifted to lower concentration. The rheological behaviour is attributed to steric stabilization of the nanoplatelets by extended oligomer brushes with short-range repulsive interactions. For suspensions containing nanoplatelets exfoliated with hydrophobic polyetheramines with shorter length, there is evidence for elastic response on local length scales and the flow behaviour shows strong history and temperature dependence. Rheological signatures associated with equilibrium nanoplatelet dispersions with repulsive interactions are discussed. 相似文献
82.
83.
利用蛋壳制备丙酸钙的研究 总被引:8,自引:0,他引:8
酸钙是我国近几年发展起来的一种新型食品防腐剂,它对霉菌、好气性芽胞杆菌、革兰氏阴性菌有很好的杀灭作用,而对酵母菌无害,而且对人体无毒、无副作用,还可以抑制黄曲霉素的产生,因而广泛用于面包、糕点等食品的防腐。据联合国粮农组织和世界卫生组织(FAO/WH... 相似文献
84.
Harb HY Collins KD Garcia Altur JV Bowker S Campbell L Procter DJ 《Organic letters》2010,12(23):5446-5449
The use of a silicon stereocontrol element in cyclobutanol and cyclopentanol-forming cyclizations mediated by SmI(2) results in excellent diastereocontrol. The C-Si bond in the products of cyclization provides a versatile handle for further manipulation. An asymmetric route to cyclization substrates involving copper-catalyzed silyl transfer has also been developed. 相似文献
85.
One way of investigating what children learn about animals is to examine, the menial models they reveal through their talk when they come face to face with animal representations. In this study, representations were provided by (a) robotic models in a museum, (b) preserved animals in a museum, and (c) preserved animals borrowed from a museum and presented in a school setting. By recording pupil talk in these three settings and then analyzing the content of the talk for comments about the anatomy of animals, their behaviour, habitat features, and so on, both similarities and significant differences are revealed by this study, depending on the setting. Based on these findings, recommendations are made for science education in both classroom and museum settings. 相似文献
87.
Trent R. Graham Jaehun Chun Gregory K. Schenter Xin Zhang Sue B. Clark Carolyn I. Pearce Kevin M. Rosso 《Magnetic resonance in chemistry : MRC》2022,60(2):226-238
Although nanometer-sized aluminum hydroxide clusters (i.e., ϵ-Al13, [Al13O4(OH)24(H2O)12]7+) command a central role in aluminum ion speciation and transformations between minerals, measurement of their translational diffusion is often limited to indirect methods. Here, 27Al pulsed field gradient stimulated echo nuclear magnetic resonance (PFGSTE NMR) spectroscopy has been applied to the AlO4 core of the ϵ-Al13 cluster with complementary theoretical simulations of the diffusion coefficient and corresponding hydrodynamic radii from a boundary element-based calculation. The tetrahedral AlO4 center of the ϵ-Al13 cluster is symmetric and exhibits only weak quadrupolar coupling, which results in favorable T1 and T2 27Al NMR relaxation coefficients for 27Al PFGSTE NMR studies. Stokes–Einstein relationship was used to relate the 27Al diffusion coefficient of the ϵ-Al13 cluster to the hydrodynamic radius for comparison with theoretical simulations, dynamic light scattering from literature, and previously published 1H PFGSTE NMR studies of chelated Keggin clusters. This first-of-its-kind observation proves that 27Al PFGSTE NMR diffusometry can probe symmetric Al environments in polynuclear clusters of greater molecular weight than previously considered. 相似文献
88.
Schafer Medina Adan Tibbits Gretchen Wall Nathalie A. Ivory Cornelius F. Clark Sue B. Beyenal Haluk 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(3):1021-1030
Journal of Radioanalytical and Nuclear Chemistry - Microliter volumes are used in electrochemical detection and preconcentration of radionuclides to reduce the dose received by researchers and... 相似文献
89.
Micellar aggregates formed following the addition of hexafluoroisopropanol to phospholipid membranes
The addition of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) to aqueous phospholipid membranes leads to perturbation of the bilayer. In the case of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), calorimetric and small-angle X-ray scattering analyses indicate that effects are already apparent at bound molar HFIP/lipid ratios of less than 1:150, with a pronounced decrease in the temperature of the main (gel to liquid crystalline) phase transition and a decrease in the intensity of the first- and second-order scattering reflections. As the HFIP concentration is raised further, at bound molar HFIP/lipid ratios >2:1, uniform isotropic particulate structures are formed with higher intrinsic curvature than the parent liposomes. These observations are supported by the results of thin-film experiments and are consistent with the formation of DMPC/HFIP adducts that are detergent-like in nature. In the case of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) the effects are much less marked, with no blebbing observed over a comparable range of HFIP concentrations. Although HFIP interacts strongly with DOPC membranes, it appears that membrane rupture is not promoted as readily with this lipid. Data from electron microscopy, laser correlation spectroscopy, and marker release experiments suggest that some of the immediate (nonequilibrium) effects of HFIP on membranes are the consequence of microinhomogeneity in water/HFIP mixtures. On the basis of our observations, we propose a model for the interaction of HFIP with phospholipid membranes. 相似文献
90.
La_2Ti_6O_(15)-CeTi_(21)O_(38)-PbTiO_3 ceramics formed in gaseous penetration of La-Ce into PbTiO_3 and their electric properties 总被引:2,自引:0,他引:2
PbTiO3 ceramics, which are typical ferroelectric materials, are useful in various applied fields. For example, it has a very good candidacy for piezoelectric materials for high temperature and high sensibility. In recent years, the studies on doped PbTiO3 ceramics have received consid-erable attention[1—3]. The modified PbTiO3 ceramics doped with Ca2+, Sm3+, Y3+, Ce4+ etc. have some better properties: their Curies temperature decreases, their tetragonal distortion degree de-grades and th… 相似文献