排序方式: 共有109条查询结果,搜索用时 46 毫秒
31.
Farhad Panahi Foroogh Bahrami Ali Khalafi-Nezhad 《Journal of the Iranian Chemical Society》2017,14(10):2211-2220
Modification of magnetic nanoparticle surface with l-carnosine dipeptide was developed using a simple chemical process. In order to synthesize this catalyst system, first, magnetic nanoparticles were modified with vinyl groups using trimethoxy(vinyl)silane. Next, the vinyl groups were oxidized with H2O2 to give the epoxy-functionalized MNPs. Reaction of l-carnosine with epoxide rings via amino group resulted in the functionalization of MNPs surface with l-carnosine, covalently. To explore high catalytic activity of this material, l-carnosine grafted on magnetic nanoparticles (Fe3O4@SiO2@LCar; l-CarMNP) was used as a highly efficient heterogeneous nano-organocatalyst in a multicomponent reaction in aqueous medium at room temperature. It was reusable at least for eight times without a significant decrease in its catalytic activity. The catalytic activity of l-CarMNP was compared with other magnetic nano-organocatalyst, and results demonstrate that l-CarMNP has high catalytic activity related to others tested. 相似文献
32.
The effect of micron-sized hydrophobic calcium carbonate particles on the stabilization of polydimethylsiloxane (PDMS)/polyisobutylene (PIB) immiscible model blends is investigated in this study. The analytical splitting of bulk and liquid–liquid interface contributions from the droplet bridging one is successfully performed due to the negligible contribution of hydrophobic microparticles to the bulk rheology of phases. The presence of particles at the fluid–fluid interface is supported by wetting parameter calculation and verified by optical microscopy observations. Moreover, direct visualizations shows that particles are able to form clusters of droplets by simultaneously adsorbing at two fluid–fluid interfaces and glue-dispersed droplets together, probably due to the patchy interactions induced by heterogeneous distribution of particles along the interface. Rheological studies show that the flow-induced coalescence is slowed down upon addition of particles and almost suppressed with the addition of 4 wt% particles. The linear viscoelastic response is modeled to estimate interfacial tension by considering the contribution of particle-induced droplet aggregation in addition to bulk and droplet deformation ones. From linear and nonlinear viscoelastic responses, the improved stability of filled polymer blends is attributed to the interfacial rheology and/or the bridged structure of droplets, even though the interfacial area is not fully covered by particles. Furthermore, Doi–Ohta scaling relations are investigated by employing stress growth response upon step-up of shear flow. 相似文献
33.
Mohsen Nazari Esmaeel Shakerinejad Morteza Nazari D. Andrew S. Rees 《Transport in Porous Media》2013,98(1):223-238
This paper is concerned with the thermal non-equilibrium free convection boundary layer, which is induced by a vertical heated plate embedded in a saturated porous medium. The effect of suction or injection on the free convection boundary layer is also studied. The plate is assumed to have a linear temperature distribution, which yields a boundary layer of constant thickness. On assuming Darcy flow, similarity solutions are obtained for governing the steady laminar boundary layer equations. The reduced Nusselt numbers for both the solid and fluid phases are calculated for a wide range of parameters, and compared with asymptotic analyses. 相似文献
34.
Hamid Reza Abdolmohammadi Abdul Jalil M Khalaf Shirin Panahi Karthikeyan Rajagopal Viet-Thanh Pham Sajad Jafari 《Pramana》2018,90(6):70
Nowadays, designing chaotic systems with hidden attractor is one of the most interesting topics in nonlinear dynamics and chaos. In this paper, a new 4D chaotic system is proposed. This new chaotic system has no equilibria, and so it belongs to the category of systems with hidden attractors. Dynamical features of this system are investigated with the help of its state-space portraits, bifurcation diagram, Lyapunov exponents diagram, and basin of attraction. Also a hardware realisation of this system is proposed by using field programmable gate arrays (FPGA). In addition, an electronic circuit design for the chaotic system is introduced. 相似文献
35.
We use the Bethe ansatz method to investigate the Schrdinger equation for a class of PT-symmetric non-Hermitian Hamiltonians. Elementary exact solutions for the eigenvalues and the corresponding wave functions are obtained in terms of the roots of a set of algebraic equations. Also, it is shown that the problems possess sl(2) hidden symmetry and then the exact solutions of the problems are obtained by employing the representation theory of sl(2) Lie algebra. It is found that the results of the two methods are the same. 相似文献
36.
Atefeh Alimadadi Homayon Ahmad Panahi Faramarz Afshar Taromi Elham Moniri 《Chromatographia》2016,79(5-6):373-373
37.
Maryam Nourisefat Farhad Panahi Marzieh Nabipour Sahar Heidari Ali Khalafi-Nezhad 《Journal of the Iranian Chemical Society》2016,13(10):1853-1865
l-Cysteine-functionalized magnetic nanoparticles (LCMNP) were introduced as an efficient and magnetically separable organocatalyst for the synthesis of 9-(1H-indol-3-yl) xanthen-4-(9H)-one derivatives. This class of compounds was synthesized via a one-pot three-component coupling reaction of 2-hydroxybenzaldehyde, dimedone, and indole in the presence of catalytic amount of LCMNP under mild and green conditions. High yields, short reaction time, easy workup, using environmental friendly conditions, and magnetic reusable catalyst are the advantages of this synthetic methodology. The LCMNP catalyst was reusable in this reaction at least for 6 times without significant decreasing in its catalytic activity. 相似文献
38.
In this work we apply the Dirac method in order to obtain the classical relations for a particle on an ellipsoid. We also determine the quantum mechanical form of these relations by using Dirac quantization. Then by considering the canonical commutation relations between the position and momentum operators in terms of curved coordinates, we try to propose the suitable representations for momentum operator that satisfy the obtained commutators between position and momentum in Euclidean space. We see that our representations for momentum operators are the same as geometric one. 相似文献
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40.
Fariba Tadayon Ali Katebi Abbas Afkhami Yunes Panahi 《International journal of environmental analytical chemistry》2013,93(9):901-915
A new potentiometric sensor for the rapid determination of Hg2+ based on modified carbon paste electrode consisting of room temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), multi-walled carbon nanotubes (MWCNTs), alumina nanoparticles and a synthetic macrocyclic diamide ‘7,10,13-triaza-1-thia-4,16-dioxa-6,14-dioxo-2,3;17,18-dinaphtho-cyclooctadecane’ as an efficient ionophore was constructed. Prepared composite is an ideal paste because it has low drift of potential, high selectivity and fast response time (10 s), which leads to a more stable potential signal. The morphology and properties of electrodes surface were characterised by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. A linear dynamic range of 2.01–2.01 × 107 µg L?1 with detection limit of 1.40 µg L?1 Hg2+ was obtained at pH range of 2.5 to 4.5. The prepared modified electrode shows several advantages such as simple preparation method, high stability of the composite paste, high sensitivity, long-term life time (at least 13 weeks) and remarkable potentiometric reproducibility. The modified electrode was successfully applied for the accurate determination of trace amounts of Hg 2+ in environmental samples. 相似文献