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941.
This paper considers a Volterra’s population system of fractional order and describes a bi-parametric homotopy analysis method for solving this system. The homotopy method offers a possibility to increase the convergence region of the series solution. Two examples are presented to illustrate the convergence and accuracy of the method to the solution. Further, we define the averaged residual error to show that the obtained results have reasonable accuracy. 相似文献
942.
Mehdi Rafie‐Rad 《Mathematische Nachrichten》2014,287(14-15):1745-1755
An extension of conformal equivalence for Finsler metrics is introduced and called weakly conformal equivalence and is used to define the weakly conformal transformations. The conformal Lichnerowicz‐Obata conjecture is refined to weakly conformal Finsler geometry. It is proved that: If X is a weakly conformal complete vector field on a connected Finsler space (M, F) of dimension , then, at least one of the following statements holds: (a) There exists a Finsler metric F1 weakly conformally equivalent to F such that X is a Killing vector field of the Finsler metric, (b) M is diffeomorphic to the sphere and the Finsler metric is weakly conformally equivalent to the standard Riemannian metric on , and (c) M is diffeomorphic to the Euclidean space and the Finsler metric F is weakly conformally equivalent to a Minkowski metric on . The considerations invite further dynamics on Finsler manifolds. 相似文献
943.
A quaternary ammonium hydroxide–type of anion exchange resin (Amberlite IRA-400) was found to be an effective and reusable catalyst for the synthesis of various 4H-benzo[b]pyran derivatives via a one-pot, three-component condensation in aqueous media. Short reaction time, easy and quick isolation of the products, environmentally friendly procedure, excellent chemoselectivity, and excellent yields are the main advantages of this procedure. 相似文献
944.
2,4,6-Tribromo-1,3,5-trihydroxybenzene (TBTHB) as a reagent was efficiently reacted with 6 molar equivalents of benzothioamides in dimethyl sulfoxide (DMSO), and the corresponding 3,5-diaryl-1,2,4-thiadiazoles were obtained in almost quantitative yields (91–98%) and in short times (15–20 min) with the formation of hexahydroxybenzene as a rather valuable by-product. 相似文献
945.
Seyed Mosayeb Daryanavard Amin Jeppsson‐Dadoun Lars I. Andersson Mahdi Hashemi Mohamed Abdel‐Rehim 《Biomedical chromatography : BMC》2013,27(11):1481-1488
This study presents the use of molecularly imprinted polymer (MIP) as packing material for microextraction by packed syringe (MEPS) to achieve higher extraction selectivity. Pentycaine was used as template for MIP. Development and validation of the determination of lidocaine, ropivacaine, mepivacaine and bupivacaine in human plasma and urine samples utilizing MIP‐MEPS and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) were carried out. The MEPS MIP‐cartridge could be used for 100 extractions before it was discarded. The extraction recovery ranged from 60 to 80%. The correlation coefficients values were >0.999 for all assays using lidocaine, ropivacaine, mepivacaine and bupivacaine in the calibration range 5–2000 nmol/L. The accuracy of the studied compounds, given as a percentage variation from the nominal concentration values, ranged from ‐4.9 to 8.4% using plasma and urine samples. The between‐batch precision, given as the relative standard deviation, at three different concentrations (quality control samples) was ranged from ?4.7 to 14.0% and from 1.8 to 12.7% in plasma and urine, respectively. The lower limit of quantification and limit of detection of the studied substances were 5.0 and 1.0 nm , respectively. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
946.
Mehdi Zeinoddini Khosro Khajeh Saman Hosseinkhani Ali Reza Saeedinia Seyed-Mortaza Robatjazi 《Applied biochemistry and biotechnology》2013,170(2):273-280
The photoprotein aequorin is a calcium-dependent bioluminescent enzyme which is most widely used in biotechnology processes, but this protein is susceptible to aggregation and proteolysis degradation. Various additives such as polyols are known to enhance the stability of proteins and protect them in native folded and functional state. In this work, for study of aequorin stability, the histidine-tagged apoaequorin was expressed in Escherichia coli and purified by nickel chelate affinity chromatography. Kinetics of light emission of purified aequorin upon addition of Ca2+ showed a linear dependency on aequorin concentration. Furthermore, the effect of some stabilisers, such as glycerol, glucose, lactose, terehalose, sucrose and sorbitol on thermostability of recombinant aequorin was measured. Results indicate that the recombinant aequorin is very stable in phosphate buffer including 30 mM sorbitol, since after heat shock of 30 min at different temperatures, a slight decrease in activity was observed. However, flexibility and exposure of tryptophan residues of aequorin to the solvent, in the presence and absence of stabilisers, with respect to fluorescence quenching by acrylamide, indicated identical characterisation. In addition, according to limited proteolysis of aequorin demonstrating that this enzyme is sensitive to proteases as in the presence of 2 ng/ml of protease, aequorin was completely digested. In conclusion, sorbitol increases stability of aequorin with high photoactivity and not effect for flexibility and limited proteolysis of this photoprotein. 相似文献
947.
Hassan Hosseini-Monfared Afsaneh Farrokhi Sohaila Alavi Peter Mayer 《Transition Metal Chemistry》2013,38(3):267-273
A mononuclear dioxo vanadium(V) complex of a hydrazone ONO donor ligand, [VVO2(L1)] (1), was synthesized by the reaction of V2O5 and terephthalic acid with H2L1 in 1:1:1 mol ratio, while an oxo-bridged bis(vanadium(IV)oxo) complex, [μ 2–O–{VIVO(L2)}2] (2), was synthesized by the treatment of isonicotinic acid hydrazide, salicylaldehyde and CoSO4·7H2O with bis(acetylacetonato)oxovanadium(IV) (H2L1 = isonicotinic acid(2-hydroxy-benzylidene)-hydrazide, H2L2 = isonicotinic acid (1-methyl-3-oxo-butylidene)-hydrazide). The complexes were characterized by elemental analyses and spectroscopic methods. The crystal structure of complex 2 was determined by X-ray analysis. The complexes were tested as catalysts for the oxidation of cycloalkenes and benzyl alcohol using H2O2 as terminal oxidant. Excellent selectivity was achieved in the oxidation of cyclohexene. 相似文献
948.
Mousa Ghaemy Seyed Mojtaba Amini Nasab Mehdi Taghavi Marjan Hassanzadeh 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):772-783
A new asymmetric diamine containing diarylimodazole pendant was synthesized from the nucleophilic substitution reaction of 1-fluoro-4-nitrobenzene and 2,4-dihydroxy benzaldehyde in the presence of K2CO3, followed by reaction with benzil and ammonium acetate for the preparation of imidazole ring. This novel diamine was used to prepare poly(amide-ether) (PAE) in reaction with different commercially available dicarboxylic acids via direct polycondensation using triphenyl phosphite and pyridine (Py) as catalyst. The PAEs were fully characterized and their properties such as inherent viscosity, solubility, optical, thermal and kinetics of thermal decomposition, and electrochemical oxidation were investigated. The polymers had inherent viscosity in the range of 0.47–0.65 dL/g and were noncrystalline with excellent solubility in various polar aprotic organic solvents. Their Tg values ranged from 200 to 355°C and 10% weight loss temperature above 450°C in nitrogen and left more than 70% residue at 650°C. The kinetic parameters of thermal degradation such as activation energy, entropy, enthalpy and Gibbs free energy of thermal decomposition have been evaluated using different equations. We also report electrochemical oxidation of the resulting polymers in aqueous solution by using cyclic voltammetry technique on the multi-walled carbon nanotube-modified glassy carbon electrode. 相似文献
949.
Mehrdad Seifali Abbas-Abadi Mehdi Nekoomanesh Haghighi Hamid Yeganeh Babak Bozorgi 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1333-1339
The powder of EX5 grade of high density polyethylene—without any additives—manufactured by Amirkabir petrochemical company was separated by shaker equipment. The separated powder of average diameter ~25, ~62.5, ~87.5, ~112.5, ~137.5, ~175 and the particles >200 μm was tested by a thermogravimetric (TG) analysis instrument in nitrogen atmosphere and heating rates of 10, 20, and 30 °C min?1. In addition, the separated powders were analyzed by a melt flow index (MFI) instrument, and the viscosity average molecular mass (M v) of the powders was tested by a viscometer. Kinetic evaluations were performed by Friedman and Kissinger analysis methods and apparent activation energy for the overall degradation of the powders was determined. The effects of molecular mass, MFI, MFR, and particle size on the degradation TG curve, derivative thermogravimetry curve breadth, and activation energy of thermal degradation were considered. The results showed that the M v of EX5 pipe grade produced by two serial reactors is increased by increasing of the particle size and, MFI is decreased with a little deviation by particle size increasing. The particle size has no obvious effect on the melt flow rate (MFR), and MFR as function of molecular mass distribution does not change very much. The results showed that the powder with bigger particles and higher molecular mass moderately increases the activation energy and shifts the degradation curve to the higher temperatures. 相似文献
950.
Nader Zabarjad-Shiraz Issa Yavari Azizolah Biglari Seyed Ahmad Izadiar Hamid-Reza Bijanzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):3023-3037
Stabilized phosphoranes were synthesized from the reaction between dimethyl acetylenedicarboxylate and amide derivatives in the presence of triphenylphosphine. Dimethylurea containing a phosphorus ylide underwent a smooth reaction in boiling toluene to produce hydantoin and oxo-oxazolidin containing stable phosphorus ylides in good yields. Phosphorus ylides derived from (PhO)3P were not stable and converted to diastereoisomeric phosphonates and phosphorimidate. The nature of the amide derivatives and type of trivalent phosphorus compounds, as well as solvents, determined the distribution of products. 相似文献