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排序方式: 共有271条查询结果,搜索用时 15 毫秒
31.
Bing-Xin Yang Yi-Han Kao Janos Kirz Chang-Xin Gu R.N. Bhargava D.A. Cammack R.J. Dalby 《Physics letters. A》1985,113(5):283-288
Transmission measurements of the extended X-ray absorption fine structure above the oxygen K-edge have been made by using a new scintillation detection technique. The absorption spectrum is in close resemblance with the total electron yield spectrum recorded at the same time. This new technique is of interest for studies of soft X-ray absorption spectroscopy for thin films of solid materials. 相似文献
32.
Sonia Millán Griselda Sánchez Luz Alicia Fucugauchi Janos H. Fendler 《Molecular Crystals and Liquid Crystals》2013,570(2-4):153-166
A new nematic phase in lyotropic binary liquid crystalline systems consisting of sodium dodecyl sulfate-water was detected, for the first time, in the absence of additives by utilizing positron annihilation techniques. Lyotropic and thermotropic phase transitions were also investigated by the same methods. The positron annihilation parameters have also indicated a better definition of the concentration ranges at which each phase exists in the system studied. Crossed polarized light microscopy was applied to substantiate these results. 相似文献
33.
Grieshaber D Vörös J Zambelli T Ball V Schaaf P Voegel JC Boulmedais F 《Langmuir : the ACS journal of surfaces and colloids》2008,24(23):13668-13676
We developed a new platform at the interface of polyelectrolyte multilayers (PEMs) and electroactive polymers (EAPs) by combining the easy buildup of PEM thin films and the deformation characteristics of the EAPs. The PEM films were made of poly(L-glutamic acid) (PGA) and poly(allylamine hydrochloride) (PAH). After [Fe(CN)6]4- ions (FCIV) were added, cyclic voltammetry (CV) was performed, resulting in a reversible expansion and contraction of the film. The shape change as well as the film buildup prior to the cycling were monitored in situ using the electrochemical quartz crystal microbalance with dissipation monitoring (EC-QCM-D). Electrochemical atomic force microscopy (EC-AFM) images confirmed the rapid shape deformation. The process takes place in an aqueous environment under mild conditions (maximum potential of 600 mV and no pH change), which makes it a promising tool for biomedical applications. In addition, the electrochemically active films are produced using the layer-by-layer (LbL) method that is already established in biotechnology and biomaterials science; therefore, the presented approach can be readily adapted in these areas, bringing about a new possibility for the nanoscale dynamic control of coating thickness in various applications. 相似文献
34.
35.
A numerical investigation is performed addressing the optimal design of stiff structures accounting for uncertainty in loading amplitudes. A minimum volume problem is endowed with a stochastic compliance constraint handling normal distributions and solved adopting mathematical programming. The formulation, originally conceived for a single load case, is extended to handle multiple load cases. Numerical simulations are performed to test the proposed algorithms, pointing out features of the numerical procedures and peculiarities of the stochastic-based optimal solutions achieved for different values of the second-order moments. Comparisons with respect to conventional deterministic layouts are provided as well. 相似文献
36.
Alessandro Marrone Dr. Andrea Renzetti Dr. Paolo De Maria Prof. Stéphane Gérard Dr. Janos Sapi Prof. Antonella Fontana Prof. Nazzareno Re Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11537-11550
The condensation of dialkyl β‐diesters with various aldehydes promoted by TiCl4 has been studied by DFT approaches and experimental methods, including NMR, IR and UV/Vis spectroscopy. Various possible reaction pathways have been investigated and their energy profiles evaluated to find out a plausible mechanism of the reaction. Theoretical results and experimental evidence point to a three‐step mechanism: 1) Ti‐induced formation of the enolate ion; 2) aldol reaction between the enolate ion and the aldehyde, both coordinated to titanium; and 3) intramolecular elimination that leads to a titanyl complex. The presented mechanistic hypothesis allows one to better understand the pivotal role of titanium(IV) in the reaction. 相似文献
37.
38.
Let X and Y be independent identically distributed (i.i.d.) nondegenerate and positive random variables with a common absolutely continuous distribution function F(x). We use the notation Z?=?max(X, Y) and W?=?min(X, Y). In the present paper, we prove that ${\frac{(Z - W)}{(Z + W)}}$ and (Z +?W) are independent if and only if X and Y have gamma distribution. 相似文献
39.
Yuri Park Godwin A. Ayoko Janos Kristof Erzsébet Horváth Ray L. Frost 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1137-1142
High resolution thermogravimetric analysis (TG) has attracted much attention in the synthesis of organoclays and its applications.
In this study, organoclays were synthesised through ion exchange of a single cationic surfactant for sodium ions, and characterised
by methods including X-ray diffraction (XRD) and TG. The changes of surface properties in montmorillonite (MMT) and organoclays
intercalated with surfactant were determined using XRD through the changes in the basal spacing. The TG was applied in this
study to investigate more information of the configuration and structural changes in the organoclays with thermal decomposition.
There are four different decompositions steps in differential thermogravimetric curves. The obtained TG steps are relevant
to the arrangement of the surfactant molecules intercalated in MMT and the thermal analysis indicates the thermal stability
of surfactant modified clays. This investigation provides new insights into the properties of organoclays and is important
in the synthesis and processing of organoclays for environmental applications. 相似文献
40.
Sophie Peeterbroeck Fouad Laoutid Benjamin Swoboda Jos‐Marie Lopez‐Cuesta Nicolas Moreau Janos B. Nagy Michaël Alexandre Philippe Dubois 《Macromolecular rapid communications》2007,28(3):260-264
Nanocomposites based on an ethylene–vinyl acetate copolymer (27 wt.‐% vinyl acetate) and multiwall carbon nanotubes (MWNTs) have been prepared by melt blending and their thermal degradation and flame retardant properties have been evaluated. Special attention has been paid to the influence of the nanotube nature on the flammability properties and more particularly on the time to ignition (TTI) as measured by cone calorimetry. It has been shown that there is a strong influence of the nature of carbon nanotubes on the fire behaviour of the composites, especially previous MWNTs crushing proved to substantially delay the TTI while maintaining much reduced heat release rate (HRR). Such a remarkable behaviour might be explained by the chemical reactivity of radical species present at the surface/extremities of crushed MWNTs during the combustion process.