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81.
82.
Mahnaz Enayati-Jazi Mehran Solati-Hashjin Ali Nemati Farhad Bakhshi 《Superlattices and Microstructures》2012
Hydroxyapatite/titania nanocomposites were successfully synthesized by in situ precipitation of precursor matters from hydroxyapatite and titania at 70 °C with different hydroxyapatite/titania ratios. X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface, scanning and transmission electron microscopes were employed to characterize the prepared nanocomposite powders. X-ray diffraction results indicated that hydroxyapatite and anatase (TiO2) were the major crystalline phases. By increasing the amount of titania nano-particles, Fourier transform infrared spectroscopy revealed that (PO4)3− bands at 567, 1033 cm−1 decreased. Brunauer–Emmett–Teller surface results also showed a reduction in surface areas of nanocomposites. Transmission electron microscope observations revealed that the aspect ratio of hydroxyapatite/TiO2 nanocrystals increased by increasing TiO2 proportion in nanocomposites. The observed nanorod crystals tended to thin, elongated and plate-like in shape. 相似文献
83.
Ammonium acetate and basic alumina catalyzed efficiently the Knoevenagel condensation of aldehydes and ketones with active methylene compounds under solvent-free condition where olefinic products were obtained in high yields. 相似文献
84.
Partially hydrogenated binaphthol monophosphoric acids were prepared via an improved four-step sequence. It is demonstrated that typical protection and deprotection of the phenolic groups are dispensable. The vinyl-substituted derivative has been polymerized to give a novel polymerized organocatalyst. 相似文献
85.
Zeolite Y modified by cesium and magnesium ions was prepared by ion-exchange and impregnation methods, and its activity in the cyanoethylation of aliphatic and aromatic alcohols and amines was investigated. During the preparation of some samples, the transformation of zeolite Y into a pollucite-type phase occurred. This phase exhibited good activity in the cyanoethylation of aliphatic alcohols. The prepared solids modified by the impregnation method were more active than the ion-exchanged solids. The activities of the catalysts, in contrast to other basic solids, were scarcely affected by the presence of air or moisture. A correlation between catalyst basicity and catalytic activity is discussed. The catalysts were characterized by X-ray diffraction, volumetric nitrogen adsorption surface area measurement, and CO2 temperature-programmed desorption. Scanning electron microscopy revealed that the particles of the modified nanocatalysts were < 40 nm. The reaction of acrylonitrile with linear alcohols in the presence of the catalysts was accelerated by microwave irradiation. 相似文献
86.
A new artificial neural network solution approach is proposed to solve combinatorial optimization problems. The artificial neural network is called the Tabu Machine because it has the same structure as the Boltzmann Machine does but uses tabu search to govern its state transition mechanism. Similar to the Boltzmann Machine, the Tabu Machine consists of a set of binary state nodes connected with bidirectional arcs. Ruled by the transition mechanism, the nodes adjust their states in order to search for a global minimum energy state. Two combinatorial optimization problems, the maximum cut problem and the independent set problem, are used as examples to conduct a computational experiment. Without using overly sophisticated tabu search techniques, the Tabu Machine outperforms the Boltzmann Machine in terms of both solution quality and computation time. 相似文献
87.
Ali Mirabi-semnakolaii Parandis Daneshgar Ali Akbar Moosavi-Movahedi Mehdi Rezayat Parviz Norouzi Ali Nemati Mohammad Farhadi 《Journal of Solid State Electrochemistry》2011,15(9):1953-1961
A novel voltammetric method for the determination of trifluralin is proposed based on a composit of carbon paste and copper
nanowire as a sensitive sensor. The presence of copper nanowire in the composite film enhance the conductivity and as a result
increased the electron transfer rate constant and so the current will increase. The composite exhibits a promising higher
electrocatalytic activity towards the oxidation of trifluralin in pH 4.0 aqueous solution. The reduction peak currents of
trifluralin increased remarkably and the reduction peak potential shifted positively at the nanostructuring electrode, compared
with that at a bare CPE which show the enhanced effect of nanowire. The support electrolyte to provide a more defined and
intense peak current for trifluraline determination was 0.05 mol L−1 phosphate buffer at pH 4.0. The fast Fourier transform square wave voltammetry was used as a new electrochemical technique
in flow injection system to abtain more sensitivity by application of discrete fast Fourier transform method by background
subtraction and two-dimensional integration of the electrode response over a selected potential range and time window, the
signal-to-noise ratio has significantly increased and made the sensivity to be higher than other methods. The effective parameters
such as frequency, amplitude, and pH were optimized to get the best sensitivity. As a result, the sensor showed a valuable
response in linear concentration range of 100–0.02 nmol L−1 with a (limit of detection) LOD of 0.008 nmol L−1 and (limit of quantification) LOQ of 0.15 nmol L−1 for trifluralin. A good recovery was obtained for assay spiked urine samples and a good quantification of trifluralin was
achieved in soil samples. 相似文献
88.
Two new cobalt (II) and cobalt (III) complexes of a terpyridine based ligand, (4′-(2-thienyl)-2,2′;6′,2″-terpyridine (L)), were synthesized. Each complex has two units of the tridentate ligand. The complexes were fully characterized by spectroscopic methods as well as CHN analysis. Moreover, their solid state structures were determined by single crystal X-ray diffraction. The cobaltous complex has the formula [Co(L)2](NO3)2·2CH3OH·H2O (1), whereas the cobaltic complex shows the formula [Co(L)2](NO3)3·2CH3OH (2). Both complexes were tested as homogenous catalysts for the oxidation of a variety of aliphatic and aromatic alcohols utilizing aqueous hydrogen peroxide in water media. The Co(II) complex showed more activity in comparison with its isostructural Co(III) species. The results show that the aromatic alcohols were oxidized with higher conversions and selectivity compared to the aliphatic substrates, possibly due to their conjugation systems which thermodynamically stabilized the carbonyl products. 相似文献
89.
In a graph G, a set D of vertices is said to be a monopoly if any vertex ${v\in V(G) \setminus D}$ has at least deg(v)/2 neighbors in D. A strict monopoly is defined similarly when we replace deg(v)/2 by deg(v)/2 + 1 for any vertex v whose degree is even number. By the monopoly size (resp. strict monopoly size) of G we mean the smallest cardinality of a monopoly (resp. strict monopoly) in G. We first discuss the basic bounds for the monopoly and strict monopoly size of graphs. In the second section we show relationships between matchings and monopolies and present some upper bounds for the monopoly and strict monopoly size of graphs in terms of the matching number of graphs. The third section is devoted to presenting some lower bounds for the monopoly size of graphs in terms of the even-girth and odd-girth of graphs. 相似文献
90.
Nemati Azadeh Sayyahi Soheil Zare-Shahabadi Vahid Anaraki-Ardakani Hossein 《Research on Chemical Intermediates》2020,46(7):3397-3411
Research on Chemical Intermediates - In this study, we examined the catalytic role of low rhodium embedded onto MOF-5 as a hard template, in the ring opening reaction of epoxides with N3?... 相似文献