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排序方式: 共有187条查询结果,搜索用时 15 毫秒
1.
Majid M. Heravi Khadijeh Bakhtiari Negar M. Javadi Hossein A. Oskooie Fatemeh F. Bamoharram 《Monatshefte für Chemie / Chemical Monthly》2007,138(5):445-447
Summary. Acetylation of various alcohols and benzyl amine was tested in the presence of H6[PMo9V3O40], a mixed addenda heteropolyacid, in ethyl acetate under reflux condition. Phenols and anilines are not affected under the
reaction conditions. Selective transestrification of alcohols can be achieved in the presence of phenol and aniline derivatives
using this method. 相似文献
2.
Wang J Beton PH Mori N Eaves L Buhmann H Mansouri L Main PC Foster TJ Henini M 《Physical review letters》1994,73(8):1146-1149
3.
Transient streaming potential in a finite length microchannel 总被引:4,自引:0,他引:4
Mansouri A Scheuerman C Bhattacharjee S Kwok DY Kostiuk LW 《Journal of colloid and interface science》2005,292(2):567-580
Pressure-driven flow of an electrolyte solution in a microchannel with charged solid surfaces induces a streaming potential across the microchannel. Such a flow also causes rejection of ions by the microchannel, leading to different concentrations in the feed and permeate reservoirs connecting the capillary, which forms the basis of membrane based separation of electrolytes. Modeling approaches traditionally employed to assess the streaming potential development and ion rejection by capillaries often present a confusing picture of the governing electrochemical transport processes. In this paper, a transient numerical simulation of electrochemical transport process leading to the development of a streaming potential across a finite length circular cylindrical microchannel connecting two infinite reservoirs is presented. The solution based on finite element analysis shows the transient development of ionic concentrations, electric fields, and the streaming potential over the length of the microchannel. The transient analysis presented here resolves several contradictions between the two types of modeling approaches employed in assessing streaming potential development and ion rejection. The simulation results show that the streaming potential across the channel is predominantly set up at the timescale of the developing convective transport, while the equilibrium ion concentrations are developed over a considerably longer duration. 相似文献
4.
5.
The impact of water droplets (diameter 3.6 mm) at a fixed Weber number of 59 on solid surfaces with precisely tailored surface wettabilities was studied experimentally using a high-speed imaging camera at 2500 frames per second. Solid surface wettability was varied using four fractional mixtures of self-assembled monolayers of 1-octadecanethiol and 16-mercaptohexadecanoic acid. The surfaces so obtained are characterized for contact angle and chemical functionality using the axisymmetric drop shape analysis profile (ADSA-P) technique and Fourier transform infrared spectroscopy (FT-IR). Our results correlate the wetting effects of the impacting droplets with the surface energy and contact angle measurements of the tailored surfaces. Literature models for the maximum spreading diameter are employed and compared with those from our experiments. An equation is also proposed for the maximum spreading diameter which makes use of the correct contact angles and results in the least error among the models considered. As a consequence of Young's equation, the correct contact angles to be used for droplet impact dynamics should be the corresponding advancing angles on a smooth substrate of interest. We also conclude that accurate examination of literature models requires careful experimentation on impact dynamic data on well-prepared and characterized surfaces such as those presented here. 相似文献
6.
Surface modified SPIONs‐Cr(VI) ions‐immobilized organic‐inorganic hybrid as a magnetically recyclable nanocatalyst for rapid synthesis of polyhydroquinolines under solvent‐free conditions at room temperature 下载免费PDF全文
In this work, a magnetic hybrid dichromate nanocomposite with triphenylphosphine surface modified superparamagnetic iron oxide nanoparticles (SPIONs) as a recyclable nanocatalyst was designed, prepared and characterized by Fourier transform infrared spectroscopy (FT‐IR) spectra, X‐ray diffraction (XRD) pattern analysis, vibrating sample magnetometer (VSM) curves, X‐ray fluorescence (XRF) analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images and dynamic light scattering (DLS) analysis. Then, it was used in a green and efficient procedure for one‐pot multicomponent synthesis of polyhydroquinoline derivatives by the condensation of aldehydes, dimedone or 1,3‐cyclohexadione, ethyl acetoacetate and ammonium acetate. This protocol includes some new and exceptional advantages such as short reaction times, low catalyst loading, high yields, solvent‐free and room temperature conditions, easy separation and reusability of the catalyst. 相似文献
7.
Az-Eddine El Mansouri 《合成通讯》2019,49(14):1802-1812
The syntheses of N-Alkylpyrimidine derivatives by reacting pyrimidin-2,4-diones with appropriate alkyl halide under microwave irradiation at 400?W were compared to the conventional synthesis route. These methodologies are regioselective and compatible with numerous substrates and furnish the corresponding N-alkylpyrimidines in good yields using a cheap catalyst HMDS/KI in MeCN. A comparison study between these two different modes of heating was investigated. 相似文献
8.
Using a cosmological black hole model proposed recently, we have calculated the quasi-local mass of a collapsing structure
within a cosmological setting due to different definitions put forward in the last decades to see how similar or different
they are. It has been shown that the mass within the horizon follows the familiar Brown–York behavior. It increases, however,
outside the horizon again after a short decrease, in contrast to the Schwarzschild case. Further away, near the void, outside
the collapsed region, and where the density reaches the background minimum, all the mass definitions roughly coincide. They
differ, however, substantially far from it. Generically, we are faced with three different Brown–York mass maxima: near the
horizon, around the void between the overdensity region and the background, and another at cosmological distances corresponding
to the cosmological horizon. While the latter two maxima are always present, the horizon mass maxima is absent before the
onset of the central singularity. 相似文献
9.
Abdolreza Iraj Mansouri Zahra Hassani Mohammad Reza Islami 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1753-1758
2-Aminobenzoic acids or 4-aminobenzoic acid react with dimethyl acetylenedicarboxylate/triphenylphosphine in less than 20 min at 15–25°C to produce new organic phosphorus compounds in good to excellent yields. The conversion occurs with selective N- over O-alkylation of the amino group and isolation of the products is accomplished simply by filtration. 相似文献
10.
The graphene nanosheets/manganese oxide nanoparticles modified glassy carbon electrode (GC/GNSs/MnOx) was simply prepared by casting a thin film of GNSs on the GC electrode surface, followed by performing electrodeposition of MnOx at applied constant potential. The GC/GNSs/MnOx modified electrode shows high catalytic activity toward oxidation of L ‐cysteine. Hydrodynamic amperometry determination of L ‐cysteine gave linear responses over a concentration range up to 120 µM with a detection limit of 75 nM and sensitivity of 27 nA µM?1. The GC/GNSs/MnOx electrode appears to be a highly efficient platform for the development of sensitive, stable and reproducible L ‐cysteine electrochemical sensors. 相似文献