نشریه علوم دانشگاه خوارزمی
سال چهاردهم شماره 1 (بهار 1393)

The present work was an attempt to investigate the parameters which can affect the process of hydrogel formation in the presence of ultrasound. These parameters were concentration of the reactants (monomers and cross linker)، the reaction medium (solvent، ionic strength، and pH)، and acoustic parameters (power and pulse). The monomers were acrylic acid and acrylamide، and the cross linker was methylene bis acrylamide. The experiments were performed at a constant temperature of 37 °C. Pulsed power ultrasound was irradiated to the reaction mixture from the tip of a probe system. The results showthatultrasonic irradiation significantly reduces the reaction time and increases efficiency. Additionally، increasing glycerol in the solution changes the viscosity of the reaction for the better and increases the reaction rate. However، ionic strength and pH were not significantly effective in this respect. Results showed that ultrasonic acrylic hydrogel are sensitive to pH and temperature. Therefore، these hydrogels is capable for rapid drug absorption and release according to porosity in their structure. These findings provide a better understanding of hydrogel synthesis and enable us to control the pertinent parameters.

The petroleum industry generates large amounts of solid and semisolid wastes known as oily sludges. Oily sludges can be generated in several steps of the petroleum production and refining in the bottom of tanks. The accumulation of oily residues in petroleum industry poses aserious environmental problem. The aim of this research was to evaluate an alternative process of removal of oily sludge from storage tanks that can be carried out by using biosurfactants. One of the most important properties of biosurfactants is reduction of surface tension and formation of oil/water emulsions. In this research، the ability of Pseudomonas aeruginosa PTCC 1570 to produce rhamnolipid was shown and the production of rhamnoilipd was confirmed by TLC and HPLC analysis. The rhamnolipid production started at exponential growth phase and continued during the stationary phase. During investigation of rhamnolipid production on sunflower oil as sole carbon، the results showed that the maximum rhamnolipid reached about 0. 5 g/l. Finally، crude oil recovery from an oil storage tank using produced rhamnolipd was also demonstrated at CMC concentration. An oil recovery of up to 70 % was obtained in a storage tank using this method.

In this study, manganese dioxide nanoparticles were synthesized in the pores of zeolite 13X by supporting method and its morphology and structure were characterized by SEM, XRD, IR and AAS techniques. Decontamination reaction of 2-chloroethyl ethyl sulfide (a mustard agent simulant) was investigated by GC technique. The results of GC analysis showed that 2-CEES was completely absorbed by Nano-MnO2/Zeolite13X composite after 168 hours and converted to less toxic chemical product. Decontamination products formed via hydrolysis were hydroxyl ethyl ethyl sulfide and ethyl vinyl sulfide. Destruction reaction of DMMP nerve agent simulant via 31P NMR analysis showed that this composite after 36 hours demolished almost 32 percent of nerve agent simulant

In this paper، the effect of interface roughness has been studied on spin-dependent electronic transmission in a magnetic tunnel junctions (MTJs). The transfer matrix method and effective mass approximation are used for calcilating the transmission probability. The magnetic double barrier structure consists of two ferromagnetic semiconductor (FMS) barriers which seperated by a nonmagnetic layer that is connected to two nonmagnetic metal electrodes. The different components of spin-dependent transmission probabilities (direct and indirect) have been studied for different thicknesses of quantum which in case that roughness is distributed at the interfaces as some random islands. The results of calculation show that interface roughness effectively affects the electron transport through the double barrier structures. Because scattering and opening the new addition conduction channels have a main effect in reducing of the peak of transmission probabilities. Also، influence of the amount of interface roughness is studied on scattered components of transmission probabilities.

This paper aimed to investigate the relation between the coherent states and the wavelets. So first the standard، generalized and nonlinear coherent states were reviewed and then their properties were presented. As an example of the nonlinear coherent states، the coherent states of a two-dimensional harmonic oscillator on a flat space were examined. Using the Dirac notation، the admissibility condition of the mother wavelets was studied. Then by means of the resolution of the identity of the generalized coherent states and the admissibility condition of the wavelets، a systematic method was presented to calculate the polynomial wavelets. At the end، as an illustrative example، the polynomial wavelets were constructed by using the nonlinear coherent states on a flat space.

The spin-1/2 Ising chain in presence of a magnetic field and the Dzyaloshinskii-Moriya interaction is considered. First، using the rotation operator the model is transformed to the anisotropic spin-1/2 XXZ model in presence of a longitudinal magnetic field and then، using the fermionization technique and mean field approximation، the diagonalized Hamiltonian is obtained. The thermodynamic behavior of the specific heat is studied. It is found that the maximum value of the specific heat shows dual behavior. Specially، in the region of fields less than quantum critical field، it decreases by increasing field but behaves inversely in the region of the magnetic fields more than the quantum critical field. In addition، the magnetization process is studied and it is shown that the Dzyaloshinskii-Moriya interaction influences the magnetization process.

In this paper، we investigated Stark mixing transition rate of muonic deuterium، pionic deuterium، kaonic deuterium and anti protonic deuterium exotic atoms in various density of deuterium and in various initial states. To this end، the effects of Stark mixing were studied by Borie-Leon and SCM models. In order to obtain exact results the experimental data on shift and width of and of exotic atoms were used. The obtained results show considerable transition rate of muonic deuterium in various densities and in various initial state than other exotic atoms.