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91.
Samira Dolati Hosseinali Zarei Riyaz Kharrat 《Journal of Dispersion Science and Technology》2014,35(7):970-983
In this work, two Iranian crude oils diluted in 1-methylnaphthalene (1-MN) were titrated with selected n-alkanes. Subsequently, samples were observed microscopically to determine the onset of asphaltene precipitation. A series of micrographs from de-asphaltening were used to show visible changes of the asphaltene sizes, shapes, and frequencies by addition the n-heptane to the subsamples after 5, 6, 11, and 24 hour lag times. The refractive indices (RI) of the titrated mixtures at different temperatures below and above the onset conditions were measured aiming to establish the asphaltene instability trend. Results show that for the diluted light and heavy crude oils, the onset of asphaltene precipitation is rather a gradual process with an almost constant slope of RI decrease due to the separation of asphaltene clusters from the mixture. This is a kinetically controlled process. Furthermore, the nature of the precipitant is likely to play a notable role. The rate of RI decreasing with temperature was approximately 0.0004/°C for both tested crude oils. 相似文献
92.
Hossein Motavalli Samira Fathezadeh Mojtaba Parhizkar 《International Journal of Theoretical Physics》2011,50(11):3390-3397
We present energy eigenvalues and corresponding eigenfunction of the relativistic Kemmer equation for Dirac oscillator. The
associated ladder operators being established, it is shown that these operators satisfy the commutation relation of the su(1,1)
group. A suitable representation of this group is presented and analytical matrix elements of some functions are obtained. 相似文献
93.
Samira Rahmani-Nezhad Leila Khosravani Mina Saeedi Kouros Divsalar Loghman Firoozpour Yaghoub Pourshojaei 《合成通讯》2013,43(6):741-749
A series of coumarin–resveratrol hybrids, 3-arylcoumarin derivatives 3a–u, were synthesized through the intermolecular condensation reaction of various salicylaldehydes and phenylacetic acids in the presence of 1,4-diazabicyclo[2.2.2]octane under solvent-free conditions. All the synthesized compounds were screened for their inhibitory potency against soybean 15-lipoxygenase. Among them, three compounds (3c, 3j, and 3q) showed good enzyme-inhibitory activities. 相似文献
94.
Issa Yavari Jamil Sheykhahmadi Hamed Saffarian Nooshin Zahedi Samira Bahemmat Mohammad Reza Halvagar 《合成通讯》2013,43(19):2608-2614
AbstractThe four-component reaction among arylhydrazine, alkyl acetoacetate derivatives, alkyl isocyanides, and dialkyl acetylenedicarboxylates, leading to the formation of dialkyl 2-[(Z)-(alkylamino)(3-alkyl-5-oxo-1-phenyl-1,5-dihydro-4H-pyrazol-4-ylidene)methyl] fumarates is described. The structure of target compounds was confirmed using X-ray diffraction study. These pyrazolone derivatives contain a highly twisted exocyclic 1,3-butadiene moiety with skew (??=?87°) geometry. 相似文献
95.
Reported herein is a new protocol for glycosidation of alkyl and aryl thioglycosides in the presence of copper(II) bromide. While the activation with CuBr2 alone was proven suitable for reactive glycosyl donors, the activation of less reactive donors was more efficient in the presence of triflic acid as an additive. A variety of thioglycoside donors in reactions with different glycosyl acceptors were investigated to determine the initial scope of this reaction. 相似文献
96.
Molecular high harmonic generation (MHOHG) is obtained from numerical solution of the time dependent Schrödinger equation (TDSE) for the 3-D one electron linear system exposed to ultrashort (two-cycle) intense (I = 1014 W/cm2) IR laser pulse in order to illustrate and image coherent electron motion on attosecond (1 asec = 10−18 sec) time scale. Such electron motion can occur in electron wavepackets created by nonadiabatic interactions at avoided crossings near conical intersections or by asec photoexcitation. It is found that the MHOHG spectra can monitor electron localization on asec time scale. 相似文献
97.
Sayed A.M. Marzouk Mohamed H. Al-Marzouqi Samira M.S.M. Baomran 《Microchemical Journal》2010,95(2):207-212
The construction, optimization and use of simple and inexpensive gas analyzer for real time measurement of sulfur dioxide in gas streams are described. The analyzer consisted of three main components (i) a custom fabricated hollow fiber membrane (HFM) gas contactor, (ii) carrier solution which absorbs SO2 molecules from the gas stream in the HFM gas contactor and (iii) a flow-through detector placed downstream which continuously measures the changes occurred to the carrier solution upon absorption of SO2 molecules. The significant acidic properties of the produced sulfurous acid suggested pH and conductivity detectors to monitor the decrease in pH or the increase in the conductivity which constituted the basis for quantification of SO2 in the gas line. Aqueous potassium oxalate (10? 1 mol/L) and hydrogen peroxide (10? 3 mol/L) were used as carrier solutions in combination with pH and conductivity detectors, respectively. The analyzer equipped with pH detector provided linear potentiometric response to SO2 concentration up to 1000 ppm with Nernstian slop of 61 mV/log[SO2]. Excellent SO2 recoveries (97–108%) were obtained in the presence of several folds of potentially interfering acidic gases, i.e., CO2 and H2S. The conductivity detector provided linear response up to 2500 ppm. Under optimized conditions, both detectors offered several favorable performance characteristics such as (i) fast response and recovery times, (ii) excellent signal stability and reproducibility (RSD = 0.5%), (iii) intrinsic high selectivity to most common neutral gases, e.g., CH4, N2, O2, CO, etc. The suggested analyzer was applied successfully in monitoring the removal of SO2 from SO2–N2 gas mixtures with hollow fiber membrane contactor using distilled water or aqueous sodium hydroxide as stripping solvents. 相似文献
98.
Textile materials can be treated with some enzymes to improve their functionality. The usual enzymatic treatment hydrolyzes the textile surfaces that leads to increase the functional groups. Here, the polyester/wool fabric as a blend of fibers fabric was selected and treated with the two different types of enzymes to increase the surface activity with a propose of higher nano-TiO(2) adsorption. The fabric was first treated with proteases and lipases to hydrolyze the wool and the polyester surfaces, respectively. It has been then dipped into an ultrasound bath containing nano TiO(2) and cross-linking agent followed by curing. The cross-linking agent, butane tetracarboxylic acid (BTCA), also assisted to enhance the nano-particles adsorption and stabilization on the fabric surface. The self-cleaning properties of the fabrics were examined through evaluating the color removal from the stained fabric with Acid Blue 113. The antibacterial properties were determined by reduction growth of a Gram-negative bacteria E. coli. and the UV protection was assessed by UV-reflectance spectrum. The SEM pictures and EDX spectrums of some samples were also reported. 相似文献
99.
Differential pulse polarography was used for simultaneous determination of Sn2+ and Pb2+. But there is a problem for simultaneous determination and it is high overlapped DPPs of mentioned cations that their determination is impossible in the presence of each other, so multivariate calibration methods as chemomatrics methods were used for this determination. There are some disadvantageous for multivariate calibration methods that can be solved by a new and simple method called net analyte signal standard addition method. This method has some advantages, such as: the use of a full voltammogram, realization in a single step, therefore it does not require calibration and prediction steps and only a few measurements are required for the determination. 相似文献
100.
MP2/aug-cc-pVTZ calculations were carried out on complexes wherein the proton or the lithium cation is located between π-electron systems, or between π-electron and σ-electron units. The acetylene or its fluorine and lithium derivatives act as the Lewis base π-electron species similarly to molecular hydrogen, which acts as the electron donor via its σ-electrons. These complexes may be classified as linked by π-H∙∙∙π/σ hydrogen bonds and π-Li∙∙∙π/σ lithium bonds. The properties of these interactions are discussed, and particularly the Lewis acid units are analyzed, because multi-center π-H or π-Li covalent bonds may occur in these systems. Various theoretical approaches were applied here to analyze the above-mentioned interactions—the Quantum Theory of Atoms in Molecules (QTAIM), the Symmetry-Adapted Perturbation Theory (SAPT) and the Non-Covalent Interaction (NCI) method. 相似文献