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1.
Abolghasem Davoodnia Mehdi Bakavoli Raheleh Moloudi Niloofar Tavakoli-Hoseini Maryam Khashi 《Monatshefte für Chemie / Chemical Monthly》2010,122(3):867-870
Abstract
A simple, efficient, and green method for synthesis of 2,4,6-triarylpyridines by one-pot three-component reaction of acetophenones, aryl aldehydes, and ammonium acetate using 3-methyl-1-(4-sulfonylbutyl)imidazolium hydrogen sulfate [HO3S(CH2)4MIM][HSO4], a Br?nsted-acidic ionic liquid, as an effective and reusable catalyst under solvent-free conditions is described. This method has several advantages, for example simple procedure with an easy work-up, shorter reaction times, and high yields. 相似文献2.
3.
A novel titania sol-gel coating, including tetrabutyl orthototitanat (TBOT) as initial alkoxide, triethanolamine (TEA) as stabilizer, nitric acid as acid catalyst, and polyethylene glycol (PEG, 6000) as binder was prepared for the first time on an anodized aluminium wire and subsequently applied to headspace solid phase microextraction (HS-SPME) of benzene, toluene, ethylbenzene and xylenes (BTEX) with gas chromatography flame ionization detection (GC-FID). The analytical characteristics of the proposed porous titania sol-gel derived TBOT/PEG/TEA (41.6:16.0:42.4) fiber were comparable with reported fibers. The extraction temperature, extraction time, effect of salt addition, desorption temperature and desorption time were optimized. Under the optimized conditions and for all BTEX components, the linearity was from 20 to 800 μg L−1, the RSD was below 8.2% and limit of detections (LODs) were between 5.4 and 14.8 μg L−1. The recovery values were from 86.7% to 94.2% in water samples. The proposed HS-SPME-GC-FID method was successfully applied for the analysis of BTEX compounds from petrochemical wastewater samples. 相似文献
4.
We study arithmetic properties of tangent cones associated to large families of monomial curves obtained by gluing. In particular, we characterize their Cohen-Macaulay and Gorenstein properties and prove that they have non-decreasing Hilbert functions. The results come from a careful analysis of some special Apéry sets of the numerical semigroups obtained by gluing under a condition that we call specific gluing. As a consequence, we complete and extend the results proved by Arslan et al. (in Proc. Am. Math. Soc. 137:2225–2232, 2009) about nice gluings by using different techniques. Our results also allow to prove that for a given numerical semigroup with a non-decreasing Hilbert function and an integer q>1, all extensions of it by q, except a finite number, have non-decreasing Hibert functions. 相似文献
5.
We describe the catalytic activity of the first chimeric ligase containing a foldameric sequence of β- and γ-amino acids. The chimeric backbone provides for the spatial arrangement of all functional groups involved in the formation of the catalytic site to allow efficient catalysis to take place. Our finding indicates significant progress in the field of functionally active artificial motifs. 相似文献
6.
Mohammadpour R Iraji zad A Hagfeldt A Boschloo G 《Physical chemistry chemical physics : PCCP》2011,13(48):21487-21491
In this work, we report on fabrication and characterization of dye-sensitized solar cells based on TiO(2) nanotube/nanoparticle (NT/NP) composite electrodes. TiO(2) nanotubes were prepared by anodization of Ti foil in an organic electrolyte. The nanotubes were chemically separated from the foil, ground and added to a TiO(2) nanoparticle paste, from which composite NT/NP electrodes were fabricated. In the composite TiO(2) films the nanotubes existed in bundles with a length of a few micrometres. By optimizing the amount of NT in the paste, dye-sensitized solar cells with an efficiency of 5.6% were obtained, a 10% improvement in comparison to solar cells with pure NP electrodes. By increasing the fraction of NT in the electrode the current density increased by 20% (from 11.1 to 13.3 mA cm(-2)), but the open circuit voltage decreased from 0.78 to 0.73 V. Electron transport, lifetime and extraction studies were performed to investigate this behavior. A higher fraction of NT in the paste led to more and deeper traps in the resulting composite electrodes. Nevertheless, faster electron transport under short-circuit conditions was found with increased NT content, but the electron lifetime was not improved. The electron diffusion length calculated for short-circuit conditions was increased 3-fold in composite electrodes with an optimized NT fraction. The charge collection efficiency was more than 90% over a wide range of light intensities, leading to improved solar cell performance. 相似文献
7.
Teresa Cortadellas Benítez Raheleh Jafari Santiago Zarzuela Armengou 《Semigroup Forum》2013,86(2):289-320
In this paper, we use the Apéry table of the numerical semigroup associated to an affine monomial curve in order to characterize arithmetic properties and invariants of its tangent cone. In particular, we precise the shape of the Apéry table of a numerical semigroup of embedding dimension 3, when the tangent cone of its monomial curve is Buchsbaum or 2-Buchsbaum, and give new proofs for two conjectures raised by Sapko (Commun. Algebra 29:4759–4773, 2001) and Shen (Commun. Algebra 39:1922–1940, 2001). We also provide a new simple proof in the case of monomial curves for Sally’s conjecture (Numbers of Generators of Ideals in Local Rings, 1978) that the Hilbert function of a one-dimensional Cohen-Macaulay ring with embedding dimension three is non-decreasing. Finally, we obtain that monomial curves of embedding dimension 4 whose tangent cones are Buchsbaum, and also monomial curves of any embedding dimensions whose numerical semigroups are balanced, have non-decreasing Hilbert functions. Numerous examples are provided to illustrate the results, most of them computed by using the NumericalSgps package of GAP (Delgado et al., NumericalSgps-a GAP package, 2006). 相似文献
8.
An efficient palladium catalyst was synthesized using nicotine, benzyl chloride and palladium chloride. The structure of this catalyst was characterized and it was then used for the synthesis of diaryl sufides. A variety of diaryl thioethers were synthesized under relatively mild reaction conditions. This protocol avoids foul‐smelling thiols via cross‐coupling of aryl halides with potassium thiocyanate and all substrates give the corresponding products in good to excellent yields in the presence of low amounts of the catalyst. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
Habibpour Razieh Kashi Eslam Vazirib Raheleh 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(3):532-539
Russian Journal of Physical Chemistry A - The electronic and chemical properties of N-doped hybrid graphene and boron nitride armchair nanoribbons (N-doped a-GBNNRs) in comparison with graphene... 相似文献
10.
F. Mollaamin M. T. Baei M. Monajjemi R. Zhiani B. Honarparvar 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(13):2354-2361
In this study, hydrogen adsorption on the surface of vanadium at various positions (top, bridge, and central sites) was studied,
and the binding energies of hydrogen species adsorbed on vanadium were calculated using density functional theory (DFT) within
the generalized gradient approximation (GGA). The potential of the adsorption of hydrogen on vanadium was examined as a function
of both surface coverage and adsorption site. Our results were in excellent agreement with the experimental values reported
in the literature. The relative stabilities of hydrogen chemisorption were independent of both the transition metal surface
and surface coverage. That is, hydrogen exhibited insignificant selectivity with respect to positions on the metal surface.
Our data on H2/V surface chemisorption revealed that the stablest model for hydrogen adsorption was that on the vertical bridge site. The
adsorption energy for this model was lower than for the other sites. However, adsorption on bridge-hydrogen vacancies was
strong. 相似文献