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991.
Tangestaninejad S Mirkhani V Moghadam M Mohammadpoor-Baltork I Shams E Salavati H 《Ultrasonics sonochemistry》2008,15(4):438-447
Vanadium polyoxometalate (PVMo) supported on mesoporous MCM-41, MCM-41-NH(2), as efficient and heterogeneous catalysts, with large surface area, for hydrocarbon oxidation with hydrogen peroxide is reported. Oxidation of the alkenes and alkanes gave product selectivities, which are similar to those observed for corresponding homogeneous catalyst. PVMo-MCM was prepared by introduction of PVMo into the mesoporous molecule sieves of MCM-41 by impregnation and adsorption techniques. The samples were characterized by X-ray diffraction (XRD), thermal gravimetric-differential thermal analysis (TG-DTA), FT-IR, scanning electron microscopy (SEM), UV-Vis and cyclic voltametry (CV). Ultrasonic irradiation has a particular effect on MCM-41 structural uniformity and reduced the reaction times and improved the product yields. In addition, the solid catalysts could be recovered and reused several times without loss of its activity. 相似文献
992.
Mehrabi H 《Ultrasonics sonochemistry》2008,15(4):279-282
The reaction of 6-acylmethylphenanthridines with isoamyl nitrite results alpha-oximino-6-acylmethylphenanthridines in 73-95% yields in DMF under ultrasound irradiation. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields. 相似文献
993.
Ebrahim Paimozd Ali Ghasemi Abdolhamid Jafari Hassan Sheikh 《Journal of magnetism and magnetic materials》2008
BaFe12O19 powders with nanocrystalline size were prepared by sol–gel techniques. Nitric, hydrochloric, acetic and stearic acid were used to improve the magnetic properties. Amorphous gels were formed with Fe/Ba molar ratio of 10.5. Then powders were obtained by subsequent heat treatment at 800–1000 °C for 1 h. Barium ferrite powder was also synthesized by solid state reaction at 1210 °C. X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM) experiments were conducted to evaluate structural properties of the samples. The value of the effective magnetic susceptibility was measured. The results show that the magnetoplumbite structure was formed in all of the powders. The TEM observation showed that the minimum particle size (20 nm) was produced with the stearic acid catalyst. The highest value of the effective magnetic susceptibility was achieved also using stearic acid. 相似文献
994.
Hossein Farajollahi 《International Journal of Theoretical Physics》2008,47(6):1479-1489
A cosmological time variable is emerged from the Hamiltonian formulation of Friedmann model to measure the evolution of dynamical
observables in the theory. A set of observables has been identified for the theory on the null hypersurfaces that its evolution
is with respect to the volume clock introduced by the cosmological time variable. 相似文献
995.
Mohammad Hossein Zhoolideh Haghighi Sohrab Rahvar Mohammad Reza Rahimi Tabar 《Entropy (Basel, Switzerland)》2021,23(9)
We study the statistical mechanics of binary systems under the gravitational interaction of the Modified Newtonian Dynamics (MOND) in three-dimensional space. Considering the binary systems in the microcanonical and canonical ensembles, we show that in the microcanonical systems, unlike the Newtonian gravity, there is a sharp phase transition, with a high-temperature homogeneous phase and a low-temperature clumped binary one. Defining an order parameter in the canonical systems, we find a smoother phase transition and identify the corresponding critical temperature in terms of the physical parameters of the binary system. 相似文献
996.
The kinetic study and mechanism of the permanganic oxidation of L‐glutamine in sulfuric acid has been carried out both in the absence and presence of silver (I) using a spectrophotometric technique. Activation parameters have been evaluated using the Arrhenius and Eyring plots. Mechanisms consistent with the observed kinetic data have been proposed and discussed. The overall rate expression for the oxidation may be written as In the presence of silver (I) the rate law is The reaction appears to involve an acid catalyzed and data showed role of water molecules in the rate‐determining step is proton transfer which satisfies Bunnett's theory. A mechanism satisfying the various kinetic parameters has been proposed. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 95–102, 1999 相似文献
997.
998.
We use a method recently devised by Bolle to establish the existence of an infinite number of solutions for various non-homogeneous
boundary value problems. In particular, we consider second order systems, Hamiltonian systems as well as semi-linear partial
differential equations. The non-homogeneity can originate in the equation but also from the boundary conditions. The results
are more satisfactory than those obtained by the standard “Perturbation from Symmetry” method that was developed – in various forms – in the early eighties by Bahri–Berestycki, Struwe and Rabinowitz.
Received: 13 August 1998 / Revised version: 6 July 1999 相似文献
999.
The conditions of processing and gas sensing of polyaniline (PANi) blends with polyvinyl acetate (PVAc), polystyrene (PS) and polyvinyl chloride (PVC) were investigated. Flexible, free‐standing and stretchable films of various blends compositions were obtained by casting. The mechanisms of the conducting blends response to a selection of gases and vapours were investigated using two techniques: measurement of conductance and mass changes using a four‐point probe method and X‐ray fluorescence (XRF) device, respectively. These responses to toxic gases and vapours are better explained by polymer blends than homopolymers. Prepared films were exposed to hydrogen halides, hydrogen cyanide, halogens, monochloroacetic acid (MCAA), 1‐3‐5 trichloromethyl benzene (TCMB), methylbenzyl bromide (MBB), bromoacetone (BA) and cyanogen bromide (CB). The changes in conductivity of various polymer frequently observed are partly due to one stage in the two‐stage sorption perhaps involving the swelling of the polymer and then diffusion of gases into polymer chains. The swelling of polymers is a slow process, therefore, we have pre‐swelled polymer films which tend to decrease the response times of blends in respect to gases. The structures of the blends are examined by STA (TGA & DSC) and SEM studies. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
1000.
Ghobadian Roshanak Esfandyari Roghaieh Nadri Hamid Moradi Alireza Mahdavi Mohammad Akbarzadeh Tahmineh Khaleghzadeh-Ahangar Hossein Edraki Najmeh Sharifzadeh Mohammad Amini Mohsen 《Molecular diversity》2020,24(1):211-223
Molecular Diversity - Inhibition of butyrylcholinesterase (BChE) might be a useful therapeutic target for Alzheimer’s disease (AD). A new series of 1,2,3,4-tetrahydro-9H-carbazole derivatives... 相似文献