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391.
392.
Carlos Eduardo Bar?o Gisella Maria Zanin Flavio Faria de Moraes 《Journal of inclusion phenomena and macrocyclic chemistry》2011,71(1-2):179-187
BHA (butylated hydroxyanisole) was complexed with ??- and ??-cyclodextrins with the objective of characterizing the thermal stability. From phase solubility diagrams, the association constants for the complexes of ??-CD:BHA and ??-CD:BHA were found as 49.3 and 585 L mol?1, respectively. To increase the thermal stability of BHA, its molecular encapsulation in ??-CD and ??-CD, was tested using molar ratios of 1:1 and 1:2 (BHA:CD) and the complex preparation techniques of kneading and physical mixture. The products of complexation were characterized by differential scanning calorimetry and thermogravimetry, indicating the formation of a BHA:??-CD complex and showing that the release of the complexed BHA occurs in the temperature range of 280?C350 °C, well above the temperature at which BHA sublimates. Dissolution tests have shown that the BHA: ??-CD complex produced by kneading has high efficiency of dissolution and partition coefficient experiments demonstrated that the presence of ??-CD leads to higher concentration of BHA in the organic phase. 相似文献
393.
Liu Z Wang J Kushvaha V Poyraz S Tippur H Park S Kim M Liu Y Bar J Chen H Zhang X 《Chemical communications (Cambridge, England)》2011,47(35):9912-9914
Microwave irradiation can be used to heat conductive materials and metallocene precursors to initiate ultrafast CNT growth. It takes only 15-30 seconds to grow CNTs at room temperature in air, without the need for any inert gas protection and additional feed stock gases. 相似文献
394.
395.
D. Bar 《International Journal of Theoretical Physics》2007,46(10):2626-2657
The double slit experiment (DSE) is known as an important cornerstone in the foundations of physical theories such as Quantum
Mechanics and Special Relativity. A large number of different variants of it were designed and performed over the years. We
perform and discuss here a new version with the somewhat unexpected results of obtaining interference pattern from single-slit
screen. We show using either the Brill’s version of the canonical formulation of general relativity or the linearized version
of it that one may find corresponding and analogous situations in the framework of general relativity. 相似文献
396.
Isonitrile palladium complexes [(RNC)2PdCl2] were prepared and tested in Suzuki reaction of 4-chloroanisol. (AdNC)2PdCl2 was found the most effective catalyst and was used in phenylation of several chloro and bromoaromatic substrates. 相似文献
397.
Richard D. Adams Burjor Captain Eszter Trufan 《Journal of organometallic chemistry》2008,693(24):3593-3602
The compounds Ru3(CO)9(SnPh3)2(NCMe)(μ-H)2 (1), Ru3(CO)10(SnPh3)2(μ-H)2 (2), Ru(CO)4(SnPh3)2 (3) and Ru(CO)4(SnPh3)(H) (4) were obtained from the reaction of Ru3(CO)10(NCMe)2 with HSnPh3 in hexane solvent. Compounds 1, 3 and the new compound Ru3(CO)7(SnPh3)3(NCMe)2(μ-H)3 (5) were obtained from reaction of Ru3(CO)10(NCMe)2 with HSnPh3 in a CH2Cl2 and MeCN solvent mixture. Compound 2 and the new compound Ru3(CO)9(SnPh3)3(μ-H)3 (6) were obtained from reactions of 1 and 5 with CO, respectively. Compounds 2 and 6 eliminated benzene when heated to yield Ru3(CO)10(μ-SnPh2)2 (7) and Ru3(CO)9(μ-SnPh2)3 (8) which contain bridging SnPh2 ligands. Compound 7 was found to react with to yield the adduct, (9) in 59% yield by the addition of groups to two of the Ru-Sn bonds to the bridging SnPh2 ligands. Fenske-Hall molecular orbital calculations were performed to provide an understanding of the metal-metal bonding in the clusters of 7 and 9. Compounds 1, 2, 5, 6, 7 and 9 were characterized structurally by single crystal X-ray diffraction analysis. 相似文献
398.
The correlation between the line shape of Auger peaks and the density of states near the surface has been the subject of recent controversy. In certain cases, it has been possible to obtain the density of states by numerical deconvolution of a KVV peak (Amelio, 1970) or directly using a KLV peak (Cardona et al., 1973). However, the extension of this technique to transition metals (Cu, Zn) has encountered serious difficulties, related to the perturbation created by the presence of localized charges either in the initial or in the final state, although it is not yet clear why this perturbation is strong only in certain cases. The purpose of the present communication is to show a series of results that can throw some light on the abovementioned problem. The main point is that Auger processes of interatomic type, as those occurring in the INS technique of Hagstrum, are free of these perturbations. Recently, the authors have studied the line shape of the Auger peaks of O, C, N and S adsorbed on Cu, Ni and Fe. These results show that only that part of the Auger structure originated by interatomic transitions between substrate and adsorbate atoms can be related to the local density of states (LDOS). The rest of the structure, due to normal intraatomic processes, is dominated by the spectral terms in the final configuration of the ion. This new interpretation allows a separation of perturbation effects and clarifies the contribution of the LDOS to the peak line shape. In this communication, we present the line shape analysis of the L2,3 VV and KVV Auger peaks of Mg and O in MgO. Due to the strong ionic character of this compound, the L2,3 VV peak of Mg++ is mainly due to interatomic processes between Mg++ and O= ions, whereas the KVV peak of O is mainly due to interatomic processes. This analysis shows that good agreement exists between the L2,3VV Mg++ Auger peak and the self-convolution of MgO density of states, whereas the KVV Auger peak of O= is dominated by the spectral terms of the final configuration. Only a small peak in the high energy side of the latter peak can be related to the density of states and could be interpreted as an interatomic transition between two neighboring oxygen ions, in agreement with the interpretation given by others. 相似文献
399.
A large variety of glass and glass ceramics may be obtained by sol-gel process from hydrolysis of tetraethoxysilane. The transformation involves hydrolysis and polycondensation reactions leading to the growth of clusters that eventually collide together to form a gel. The structure and properties of the final product have been found to be strongly dependent on the initial conditions of preparation. Silica nanocomposites based on Fe2O3/SiO2 were prepared with the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 to 30wt.%. 相似文献
400.
Dr. Qiang Liu Niklas Pfriem Dr. Guanhua Cheng Dr. Eszter Baráth Prof. Yue Liu Prof. Johannes A. Lercher 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(3):e202208693
The intracrystalline ionic environment in microporous zeolite can remarkably modify the excess chemical potential of adsorbed reactants and transition states, thereby influencing the catalytic turnover rates. However, a limit of the rate enhancement for aqueous-phase dehydration of alcohols appears to exist for zeolites with high ionic strength. The origin of such limitation has been hypothesized to be caused by the spatial constraints in the pores via, e.g., size exclusion effects. It is demonstrated here that the increase in turnover rate as well as the formation of a maximum and the rate drop are intrinsic consequences of the increasingly dense ionic environment in zeolite. The molecularly sized confines of zeolite create a unique ionic environment that monotonically favors the formation of alcohol-hydronium ion complexes in the micropores. The zeolite microporous environment determines the kinetics of catalytic steps and tailors the impact of ionic strength on catalytic rates. 相似文献