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排序方式: 共有166条查询结果,搜索用时 15 毫秒
121.
An efficient application of the Julia–Kocienski coupling for the olefination of aldehydes with resin-bound benzothiazol-2-yl
and 1-phenyl-1H-tetrazol-5-yl sulfones is described. Olefins is generally obtained in high overall yield for the six-reaction steps. 相似文献
122.
Alfréd Menyhárd Gábor Dora Zsuzsanna Horváth Gábor Faludi József Varga 《Journal of Thermal Analysis and Calorimetry》2012,108(2):613-620
Crystallization kinetics of β-nucleated isotactic polypropylene (β-iPP) under isothermal conditions were investigated by differential
scanning calorimetry. iPP was nucleated by a trisamide derivative, namely tris-2,3-dimethyl-hexylamide of trimesic acid (TATA).
In the presence of TATA possessing dual nucleating ability, the formation of the α- and β-form occurs simultaneously. An isothermal
stepwise crystallization method is suggested in this study, which can separate the crystallization process of β- and α-iPP
and consequently their crystallization kinetics can be evaluated separately. The results indicated that the mechanism of crystallization
changes in temperature especially in the vicinity of the upper critical temperature of the formation of the β-phase. In addition,
it was found that the ratio of the growth rates of β- and α-modification determines the characteristics of crystallization
and influences the apparent rate constant of crystallization of both polymorphs. 相似文献
123.
Balogh D Tel-Vered R Freeman R Willner I 《Journal of the American Chemical Society》2011,133(17):6533-6536
Stimuli-triggered wettability of surfaces and controlled uptake and release of substrates by "smart" materials are essential for drug delivery and microfluidic control. A composite "sponge" consisting of bis-aniline-bridged Au nanoparticles (NPs), functionalized with photoisomerizable nitrospiropyran/nitromerocyanine that includes selective imprinted molecular recognition sites for N,N'-bis(3-sulfonatopropyl)-4,4'-bipyridinium (PVS) was electropolymerized on a Au electrode. The system is triggered by photonic and/or electrical signals to yield four different states exhibiting variable binding/release capacities for PVS and controlled wettability of the surface. The electrical/optical uptake and release of PVS to and from the Au NPs "sponge", respectively, is followed by CdSe/ZnS quantum dots, acting as an auxiliary photonic label. 相似文献
124.
Comparison of arsenate, chromate and molybdate binding on schwertmannite: Surface adsorption vs anion-exchange 总被引:3,自引:0,他引:3
J Antelo S Fiol D Gondar R López F Arce 《Journal of colloid and interface science》2012,369(1):338-343
We have synthesized a series of nanocatalysts with different sizes (50-200 nm) for polymerization of 1,3-butadiene (Bd) by immobilizing salicylaldimine cobalt complexes on the mesoporous silica nanoparticles (MSNs). The prepared catalysts have been characterized by infrared (IR) spectra, thermal gravimetric analyses (TGAs), chemical composition analysis, nitrogen adsorption-desorption, scanning electron microscope (SEM), and transmission electron microscope (TEM). The nanocatalysts in combination with methylaluminoxane (MAO) show excellent catalytic efficiency in polymerization of 1,3-butadiene. The results reveal that these nanocatalysts also show higher activity than the homogeneous analog of cobalt complex and the same catalyst on bulky mesoporous silica supporting materials. The yield and the molecular weight of the poly-butadiene product depend on the particle size of the catalyst support. This catalysis process is also a facile way to directly synthesize the polymer/silica composite materials. 相似文献
125.
TY Tang NJ Brooks C Jeworrek O Ces NJ Terrill R Winter RH Templer JM Seddon 《Langmuir : the ACS journal of surfaces and colloids》2012,28(36):13018-13024
Monoacylglycerol based lipids are highly important model membrane components and attractive candidates for drug encapsulation and as delivery agents. However, optimizing the properties of these lipids for applications requires a detailed understanding of the thermodynamic factors governing the self-assembled structures that they form. Here, we report on the effects of hydrostatic pressure, temperature, and water composition on the structural behavior and stability of inverse lyotropic liquid crystalline phases adopted by monolinolein (an unsaturated monoacylglycerol having cis-double bonds at carbon positions 9 and 12) under limited hydration conditions. Six pressure-temperature phase diagrams have been determined using small-angle X-ray diffraction at water contents between 15 wt % and 27 wt % water, in the range 10-40 °C and 1-3000 bar. The gyroid bicontinuous cubic (Q(II)(G)) phase is formed at low pressure and high temperatures, transforming to a fluid lamellar (L(α)) phase at high pressures and low temperature via a region of Q(II)(G)/L(α) coexistence. Pressure stabilizes the lamellar phase over the Q(II)(G) phase; at fixed pressure, increasing the water content causes the coexistence region to move to lower temperature. These trends are consistent throughout the hydration range studied. Moreover, at fixed temperature, increasing the water composition increases the pressure at which the Q(II)(G) to L(α) transition takes place. We discuss the qualitative effect of pressure, temperature, and water content on the stability of the Q(II)(G) phase. 相似文献
126.
Dora Melucci Simona Montalbani Clinio Locatelli 《Central European Journal of Chemistry》2012,10(1):267-276
The present work reports the critical comparison about the employment of three different supporting electrolytes (0.1 mol
L−1 HClO4, 0.01 mol L−1 EDTA-Na2 + 0.06 mol L−1 NaCl + 2.0 mol L−1 HClO4 and 0.1 mol L−1 KSCN + 0.001 mol L−1 HClO4) and their instrumental and chemical optimisation for the simultaneous voltammetric determination of total mercury(II) and
copper(II) in sediments and sea water at gold electrode, especially discussing the reciprocal interference problems. 相似文献
127.
Alfredina Veiga Jos Miro Antnio J. Candeias Paulo Simes Rodrigues Dora Martins Teixeira Vnia S. F. Muralha Jorge Ginja Teixeira 《Journal of Raman spectroscopy : JRS》2014,45(10):947-957
Seventeen Portuguese miniature portraits on copper support from the Évora Museum collection (Portugal) were analyzed in situ and nondestructively by Raman microscopy (RM), SEM‐EDS, and stereomicroscopy. This work constitutes a great breakthrough in the study of miniature paintings from the 17th and 18th centuries, since the chemical information known about this unique kind of paintings are still scarce, and in particular, this exclusive collection was never been subjected to any physicochemical study. In this work, each portrait was examined in detail in order to characterize the pigments palette used by the miniaturists. The μ‐Raman analysis, in particular, guaranteed an exceptional visualization and good individual identification of small grains of pigments and other constituents of the pictorial layer. Using this technique, 19 compounds were identified, including bluish black covellite, a pigment rarely found in oil paintings. SEM‐EDS was used as an important complementary technique to confirm the chemical nature of some pigments and to identify shell gold (gold dust) in some portraits. Overall, the pigments identified in this large set of old paintings are broadly consistent with those mentioned in the painting treatises of that time or reported in other more modern bibliographic sources. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
128.
Stochastic processes with paths in a generalized function algebra are defined and it is shown that there exists an embedding of generalized functional stochastic processes into such ones. Gaussian stochastic processes with paths in an algebra of generalized functions are characterized by their first and second moments and an application to stochastic differential equations is given. 相似文献
129.
130.