modern research physics

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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.

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in this paper, the effect of rough interface is investigated on spin dependent transmission in a magnetic tunneling junction. For calculating of transmission probability the transfer matrix technique and the approximation of effective mass is used in calculations.  The mentioned magnetic structure includes of two semiconductor ferromagnetic separated by a nonmagnetic layer which is attached to two metal nonmagnetic electrodes. The different components of spin dependent  transmission probability (direct and indirect)   in the presence of roughness is studied while the roughness is distributed as random islands in interfaces. The results of calculations show that roughness  affects the transport of incident electrons through mentioned double barrier structure, effectively. Because the scattering due to roughness of interface and therefore opening addition conduction  channels, results to reduce the peak of incident electrons transmission probability. Also, the effect of percent of interface roughness is studied on component of indirect  transmission probability. 

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Department of Chemistry, Takestan Branch, Islamic Azad University, Takestan, Iran High frequency sound wave, ultrasound, is widely used to facilitate chemical reactions, especially in the polymerization reactions.This paper reports a study which synthesized acrylic hydrogel in the presence of ultrasonic irradiation (20-kHz, power 80%, pulse 8) in a water/glycerol medium. Acrylic acid (AA) and acrylamide (AAm) were used as acrylic monomers, and methylene bisacrylamide (MBA) as the crosslinker. The experiments were performed at a constant temperature of 37 °C. It was found that hydrogel formation is faster in the presence of ultrasound than in its absence. In addition, FT-IR, UV-Vis, and SEM spectroscopy showed that the hydrogel synthesized ultrasonically has a higher swelling capacity and a more uniform and porous structure. It was also discovered that hydrogel formation speeds up at higher quantities of glycerol. However, an increase in crosslinker concentration proved ineffective although it changed the appearance of the hydrogel. The method proposed in this research can be used in the synthesis of biomedical materials and in the development of drug delivery systems.