Sharif Digital Repository

Various ionic liquids (ILs) and their mixtures were coated on the Pt/Al2O3 catalyst and the resulting IL-coated catalysts were used in the synchronous hydrogenation of cyclohexene and acetone. The rate constant (k) and selectivity (S) toward CO hydrogenation were determined for several catalysts in various solvents. The solvatochromic parameters (ETN, normalized polarity parameter; π*, dipolarity-polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) were determined for the used ILs and solvents and the obtained selectivities were modeled based on the solvatochromic parameters of the IL layer and bulk solvent while using the Multiparameter Linear Regression (MLR)... 

Zeolite-based Ag/AgBr and Ag/AgBr/TiO2 photocatalysts were prepared by sol–gel and deposition methods and were characterized. Their photocatalytic activities were evaluated by inactivation of Escherichia (E.) coli and the photodegradation of Acid Blue 92 and potassium permanganate. The composites containing Ag/AgBr showed the antibacterial activity in the dark by releasing Ag+ ions into the medium. The results for inactivation of E. coli indicated that Ag/AgBr/TiO2 modified photocatalyst had better antibacterial activity than Ag/AgBr/zeolite, while zeolite and TiO2/zeolite did not show any antibacterial activity under visible light and dark conditions. Photodecolarization rate was affected... 

Zeolite-based Ag/AgBr and Ag/AgBr/TiO 2 photocatalysts were prepared by sol-gel and deposition methods and were characterized. Their photocatalytic activities were evaluated by inactivation of Escherichia (E.) coli and the photodegradation of Acid Blue 92 and potassium permanganate. The composites containing Ag/AgBr showed the antibacterial activity in the dark by releasing Ag ions into the medium. The results for inactivation of E. coli indicated that Ag/AgBr/TiO 2 modified photocatalyst had better antibacterial activity than Ag/AgBr/zeolite, while zeolite and TiO 2/zeolite did not show any antibacterial activity under visible light and dark conditions. Photodecolarization rate was affected... 

The effect of the corona wind on the natural convection at a rectangular channel was investigated experimentally. The results indicate that the natural convection in the absence of electric/corona wind at obtuse angles outperforms than acute angles and keeps improving by increasing the angle. However, the efficiency of the electric/corona wind at acute angles is higher than obtuse angles. Generally, in the presence of electric/corona wind, heat transfer coefficient was increased. The effect of the electric/corona wind was decreased by raising heat flux. This mainly stems from the fact that the temperature gradient raises the thermal boundary layer and reduces the secondary flow power.... 

Multi-component photocatalysts based on apatite-coated Ag/AgBr/TiO(2) were prepared by the deposition method. The effects of various kinds of apatites, with hydroxyl and fluoro substituents, on photocatalytic activity were investigated. The antibacterial processes in the dark, and under visible light, on two types of bacteria indicate that the multi-composites can inhibit the growth of bacteria by two different mechanisms. TEM images and optical microscopic data demonstrate that by attaching the nanosize catalyst to the outer membrane of the cell, the bacteria could not derive nourishment from surrounding media, i.e. this component acts as bacteria-static. The mechanism for deactivation of... 

Solute-solvent and solvent-solvent interactions were investigated for binary mixtures of an ionic liquid (IL) 2-hydroxy ethylammonium formate as with methanol, ethylene glycol and glycerol. The physicochemical properties of the solvent mixtures at 25 °C, over the whole range of mole fractions, were determined using solvatochromic probes. High normal polarity ( ENT ) in the alcohol-rich region confirms solute-solvent interactions in this medium. Dipolarity/polarizability (π ∗) show a different trend to ENT with a positive deviation from ideal behavior in IL-glycerol mixtures. However, these deviations for other solvent mixtures are insignificant. Contrary to what is observed for ENT and π ∗,... 

The reaction kinetics of 2-bromo-5-nitro thiophene with piperidine was studied in a solvent with a mixture of propan-2-ol with methanol and n-hexane at 25°C. The measured rate coefficients of the reaction demonstrated dramatic variations in propan-2-ol–n-hexane mixtures and mild variations in propan-2-ol–methanol system. The second-order rate coefficients of the reaction, kA, decreased sharply with n-hexane content. The multiparameter correlation of log kA versus molecular-microscopic solvent parameters shows interesting results in these solutions. Linear free energy relationship investigations confirm that polarity has a major effect on the reaction rate and hydrogen bond ability of the... 

Aromatic nucleophilic substitution reaction of 1-fluoro-2,4-dinitrobenzene with para-substituted and meta-substituted anilines was kinetically investigated in the mixtures of ethyl acetate and methanol at room temperature. The correlation of second-order rate coefficients with Hammett's substituent constants yields a fairly linear straight line with negative slope in different mole fractions of ethyl acetate–methanol mixtures. The measured rate coefficients of the reaction demonstrated a dramatic variation in ethyl acetate–methanol mixtures with the increasing mole fraction of ethyl acetate. Linear free energy relationship (LFER) investigations confirm that polarity has a major effect on the... 

Structural and intermolecular interactions of solvatochromic probes 4-nitroaniline, 4-nitroanisole, and Reichardt’s dye were investigated in the binary mixtures of 2-hydroxy ethylammonium formate as an ionic liquid with N,N-dimethyl formamide, dimethyl amine, and dimethyl sulfoxide. Solvatochromic parameters (ETN, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen -bond donor acidity) were determined in ionic liquid mixtures at 25 °C using UV−vis spectroscopy. ETN parameters obtained from absorbance of Reichardt’s dye within various mixtures of ionic liquid were observed to be higher than predicted values from ideal additive... 

Structural and molecular-microscopic properties of the solvatochromic probes 4-nitroaniline, 4-nitroanisole, and Reichardt’s dye were investigated in binary mixtures of ethylammonium propionate with methanol, ethanol, 1-propanol and 2-propanol. Solvatochromic parameters (α, hydrogen-bond donor acidity; β, hydrogen-bond acceptor basicity; π*, dipolarity/polarizability; ENT , normalized polarity parameter) in different binary mixtures of ionic liquid with molecular solvents were determined with UV–Vis spectroscopy. The ENT parameters show nearly ideal trends in all solvent mixtures, but the other parameters show different behavior in the mixtures. The π* parameters show a negative deviation... 

In this paper, a novel temperature-dependent multi-scale method is developed to investigate the role of temperature on surface effects in the analysis of nano-scale materials. In order to evaluate the temperature effect in the micro-scale (atomic) level, the temperature related Cauchy–Born hypothesis is implemented by employing the Helmholtz free energy, as the energy density of equivalent continua relating to the inter-atomic potential. The multi-scale technique is applied in atomistic level (nano-scale) to exhibit the temperature related characteristics. The first Piola–Kirchhoff stress and tangential stiffness tensor are computed, as the first and second derivatives of the free energy... 

In this paper, a numerical model is developed for the fully coupled hydro-mechanical analysis of deformable, progressively fracturing porous media interacting with the flow of two immiscible, compressible wetting and non-wetting pore fluids, in which the coupling between various processes is taken into account. The governing equations involving the coupled solid skeleton deformation and two-phase fluid flow in partially saturated porous media including cohesive cracks are derived within the framework of the generalized Biot theory. The fluid flow within the crack is simulated using the Darcy law in which the permeability variation with porosity because of the cracking of the solid skeleton... 

One of the most popular constitutive rules that correlate the continuum and atomic properties in multi-scale models is the Cauchy–Born (CB) hypothesis. Based on this constitutive law of continuum media, it assumes that all atoms follow the deformation subjected to the boundary of crystal. In this paper, the validity and failure of CB hypothesis are investigated for the silicon nano-structure by comparison of the continuum and atomic properties. In the atomistic level, the stresses and position of atoms are calculated using the molecular dynamics (MD) simulation based on the Tersoff inter-atomic potential. The stresses and strains are compared between the atomistic and continuous media to... 

A combined experimental and computational study was carried out on the gas phase pyrolysis reaction of diallylsulfoxide. Allylalcohol and Thioacrolein were detected as the major products during a unimolecular reaction. Experimental kinetic studies were carried out via a static system over the pressure of 21-55 torr and temperature of 435.2-475.1 K. Based on the experiments, the reaction is homogeneous and proceeds through a zwitterionic intermediate. Computational studies at the DFT (B3LYP) and QCISD(T) levels with 6-311++G(d,p) basis set indicated a two-step concerted pathway as the possible route. Comparison between the experimental and theoretical activation parameters for the most... 

Functionalized magnetic core–zeolitic shell nanocomposites were prepared via hydrothermal and precipitation methods. The products were characterized by vibrating sample magnetometer, X-ray powder diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, and transmission electron microscopy analysis. The growth of mordenite nanocrystals on the outer surface of silica-coated magnetic nanoparticles at the presence of organic templates was well approved. The removal performance and the selectivity of mixed metal ions (Pb2+ and Cd2+) in aqueous solution were investigated via the sorption process. The batch method was employed to study the sorption kinetic,... 

An enhanced media access control (MAC) layer protocol that uses the signaling method benefits of the physical layer in order to provide different levels of quality to different users in optical code-division multiple-access (OCDMA) packet networks is presented. In the proposed network architecture the users are categorized into two classes of service, one having a higher quality level and the other having a lower quality level. Users of each class transmit at the same power level and different from the other classes’ users. Also, the MAC of each user estimates the amount of interference on the channel and adjusts the packet transmission’s time to improve network performance. Through... 

In this paper we propose and analyze the application of generalized optical orthogonal codes (GOOC) in the optical wireless local area networks (OWLAN). A system deploying GOOC can support more users and achieve better BER performance. We evaluate the system performance of GOOC noting practical constraints of OWLAN applications. We consider average and peak power limitations of free space infrared sources, arising from eye safety and device non-linearity restriction. We include the impact of various noises including background-light induced noise in system evaluation. Proper system design requires appropriate selection of GOOC code parameters. We analyze the influence of code parameters on... 

Ab initio, DFT, Monte Carlo statistical mechanics and atom in molecule methods have been applied to investigate the hydrogen bonding effect of protic solvents, apart from the bulk properties, on the reaction of cyclopentadiene and vinyl acetate. The results show that methanol accelerates the rate of the reaction more than water. DFT calculations demonstrate that the interaction of the carbonyl group oxygen atom with solvent molecules in transition state is stronger and more effective than the ether-type oxygen atom. Also, when the solvent molecule is near the oxygen of the carbonyl group the rate of reaction is larger than when it is near the ether-type oxygen. In addition, methanol... 

Background: The seminal plasma is an excellent source for noninvasive detection of spermatogenesis. The seminal plasma of normospermic and azoospermic men has been analyzed for detection of spermatogenesis. Methods: Optical spectroscopy (Attenuated Total Reflectance-Infrared spectroscopy (ATR-IR) and Fourier Transform infrared spectroscopy (FT-IR) has been used to analyze the seminal plasma and the metabolome of seminal plasma for detection of spermatogenesis. Results The seminal plasma of normospermic and azoospermic men has been analyzed by ATR-IR. The results show that there is a pattern variation in the azoospermic men compared to normospermic men. However, the seminal plasma is too...