Sharif Digital Repository

In the current work, synthesis of an environmental-sensitive superabsorbent hydrogel using γ-rays is described. Grafted polyacrylonitrile onto a homogeneous solution of starch and kappa-Carrageenan hybrid backbones created a smart material with reversible behavior. The reaction parameters (i.e. acrylonitrile, starch and kappa-Carrageenan concentration, as well as γ-irradiation time) affecting the. water absorbency of the. hydrogel were optimized using the. Taguchi method, in order to achieve a hydrogel with high swelling capacity. FTIR spectroscopy was used for confirming the. structure of the final product and the morphology of the synthesized hydrogel was examined by a scanning electron... 

We have performed molecular dynamics simulation on B-DNA duplex (CGCGAATTGCGC) at different temperatures. The DNA was immerged in a salt-water medium with 1 M NaCl concentration to investigate salt effect on the denaturation process. At each temperature, configurational entropy is estimated using the covariance matrix of atom-positional fluctuations, from which the melting temperature (T m) was found to be 349 K. The calculated configuration entropy for different bases shows that the melting process involves more peeling (including fraying from the ends) conformations, and therefore the untwisting of the duplex and peeling states form the transition state of the denaturation process. There... 

Microbial desalination cell (MDC) is a new bio-electrochemical technique which converts chemical energy into electrical energy, and at the same time desalinates water and treats wastewater. In this study, MDC performance and water biofouling conditions were tested as an efficient pretreatment desalination process of reverse osmosis (RO). The experiments were designed in a three-chamber reactor to compare the performance of batch and continuous fed modes, using bio-cathode and synthetic wastewater in four different hydraulic retention times and 17 and 35 g/L NaCl concentrations. According to the results, maximum salt removal of about 52.3% was obtained in the continuously fed MDC at 35 g/L... 

A novel kind of a biopolymer-based superabsorbent composite, salep-g-poly(sodium acrylate)/alumina, was prepared from salep, sodium acrylate, and alumina by aqueous polymerization, using N,N'-methylenebisacrylamide (MBA) as a cross-linker and ammonium persulfate (APS) as an initiator. The reaction parameters [i.e., acrylic acid (AA), MBA, APS amounts, and neutralization percentage of AA as well as alumina/salep weight ratio] affecting the water absorbency of the hydrogel composite were optimized using systematic method to achieve a composite with high swelling capacity as possible. The swelling behavior of optimum superabsorbent composite was measured in various pH solutions. In addition,...