Nashrieh Shimi va Mohandesi Shimi Iran
Year:2013 | Volume:32 | Issue:2 (68)|Papers Count:10

Three Nickel (II) complexes of formula [Ni (en)2] (N03)2 (a), [Ni (bpy)2](N03)2 (b) and [Ni (phen)2] (N03)2 (c) (where en=ethylenediamine, bpy=2,2 bipyridine and phen=1,10 phenanthroline) were prepared. The structure of these complexes have been characterized by spectroscopic methods such as infrared, ultraviolet visible and nuclear magnetic resonance and conductivity measurements and elemental analysis. Interaction of these three complexes with calf thymus DNA were carried out using ultraviolet- visible, fluorescence and jell- filterationtachniques. These complexes can denature the DNA at quite low concentrations. Complexes band c having aromatic surface presumably intercalate in DNA. Moreover complex c can cleave the DNA into two parts and interact with both.

In this research, nanoporous poly (vinylidene fluoride) (PVDF) membrane was prepared via Non-solvent Induced Phase Separation (NIPS) method at solution temperature of 75oC and coagulation bath temperature of 20oC. Also, mechanism of PVDF membrane formation (morphology) and its performance (flux of pure water and rejection efficiency of 7 biological compounds) was investigated. In the formation of this membrane, binodal demixing was dominant mechanism and that crystallization and spinodal decomposition caused to form granular structure at membrane surface and rim of macrovoids. Size of membrane pores was measured by Barett-Joyner-Halenda (BJH) method. This method showed that the size of these membrane pores is in nanoscale (i.e. 18-27 nm). Flux of pure water and rejection of the biological compound of blue dextran at pressure of 200 kPa were for this PVDF membrane 23.60 L/m2h and 92.5% respectively that were measured by the use of ultrfiltration apparatus

Suspension polymerization of styrene is an important way to produce polystyrene and expandable polystyrene. In this process, water is used as continues aqueous phase and styrene with additives like initiators are dispersed by agitator. Organic and inorganic stabilizers are used alone or together to stabilize suspension. Viscosity of monomer droplet increases as conversion increases during polymerization. Mean particle size and its distribution of polymer particles are key parameters that should be controlled We used TCP, HEC and PVA to control these parameters in pilot scale reactor in Tabriz petrochemical complex. This research shows that, we should use more TCP than PVA to produce commercial size of EPS. HEC can't stabilize dispersion. But when we use suspension agents together, HEC and TCP show great results. The influence of HEC on particle size distribution is more than PVA. There is no pollution inside reactor when we use TCP. But it is necessary to use optimum amount of PVA to produce less pollution and more commercial size of EPS.

In this work the effect of R22 on methane hydrate formation rate is investigated. R22 and methane are in gas phase. With adding R22 in gas phase the methane hydrate formation rate is increased. Experiments were done at R22 concentrations of 0, 162, 5550, 16000 and 29500 ppm. The results show the initial rate of methane hydrate formation is increased between 36%-64% and the required time for reaching to the equilibrium pressure is decreased with increasing the concentration of R22. Also induction time is decreased in due to encaging R22 in hydrate phase, because with encaging R22 in hydrate phase the equilibrium pressure is decreased and driving force for methane hydrate formation is enhanced.

Exergy analysis is one method for studying of energy efficiency and optimization for systems and machines including dryers. Fluidized bed dryers despite widespread usage have low energy efficiency. Therefore a new method has been proposed that the fluid bed drying has been combined with thick (fix) bed dryer as outlet air from the fluidized bed section is conducted to the thick bed section for drying the other material or same kind material that existed in the first section. Experiments were performed in three temperatures, 50, 60 and 70oC and three bed depth in down, fluidized bed drying, 4, 6 and 8 cm and two beds depth in up, batch bed drying, 6 and 8 cm. The results show that exergy loss of top floor is lower than down floor. And also increasing in bed depth of down floor causes increasing in exergy loss of top floor. But exergy loss of down floor decreases with increasing in bed depth of top floor.

One of the most important methods of gas transmission is using of pipelines. Regards to that most of gas transmission pipelines is in residential areas, the safety consideration for pipelines is very important. In this study, determination of safe distance for sure gas pipelines has been studied. The case study is a sure gas pipeline in BUSHEHR province. Using PHAST Risk software and regards to quantitative risk assessment, safe distance for this pipeline in four wall thickness has determined and the results showed that effects of 2 millimeter change in wall thickness can change safe distance about 60 meter.

Multi-compartment tube mills in closed circuit with air separators are widely used for clinker grinding in cement plants. Ardabil cement plant which produces a pozzolanic type of cement is also using such closed grinding circuits for comminution of clinker, pozzolan and gypsum mixtures with specific ratios to produce cement powder. To simulate grinding circuits of this plant, a large number of samples were collected from various existing streams. In addition, samples were collected from inside of the mills at evenly spaced locations on their longitudinal axis. Then, particle size distribution of samples were determined using sieve analysis and laser diffraction methods and were mass balanced using streams flow rates. The work index and breakage distribution function of mill feed (mixture of clinker, pozzolan and gypsum) were determined in laboratory. These data were used for calibration of simulation models. For circuit simulations, BMCS (BMCS-based Modular Comminution Simulator) software was used which is capable of simulating various comminution circuits. In this article, mathematical models of ball mill and efficiency curve were used for simulation of tube mills and efficiency curve for simulation of air separators. BMCS program for simulation of tube mills uses a population balance model for mathematical description of breakage process and tanks-in-series model for mathematical description of residence time distribution. Also, for simulation of diaphragms and air separator BMCS uses Whiten model for mathematical description of efficiency curve. Whiten model parameters were determined using GA toolbox of MATLAB software. Close agreement between simulation results and actual data indicate accuracy of sampling procedure, validity of models and their calibration and accuracy of predictions made by simulator.

The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of these systems and further increase their acceptance and application in wastewater treatment industries. The objective of this study is comparison between a moving bed membrane bioreactor and a conventional Moving Bed Biofilm Reactor (MBBR). The study was carried out using a hollow fiber micro filtration membrane. The pilot plant consisted of two separated 30 liters reactors with KMT carriers, one with membrane and one without it. The carrier filling fraction was 40%. The synthetic wastewater contained molasses and other salts as nutrient source. The COD of the feed was in three various concent ratios (500-1000-2000 mg/L) with different hydraulic retention times (10-15-20 hr) which responds to organic loading rates between 0.6-4.8 (kg COD / m3d). The removal efficiency of COD for permeate was 92-98%, for biological treatment in the reactor was 89-96% and for conventional MBBR was 87-96%. The MLSS content increased from 4000 to 9230 in the reactor with membrane and decreased from 4000 to 2450 in the conventional MBBR.

At present study, a C-D fragment of bacteriorhodopsin (BR) in recombinant E. coli was expressed. BR mutant gene was synthesized by consideration of E. coli codon usage. The synthesized gene was cloned in pET21a+ expression plasmid at Nde J and Hind 111 restriction sites and expressed under T7 promoter successfully. The expressed protein was analyzed by SDS-PAGE. The effect of temperature (A), induction time (B) and the process time after induction (C), on the protein expression yield (the amount of product per unit dry cell mass) were screened using Yates table analysis. Three factors of A, Band C were significant and optimized by Taguchi method. The optimized condition was as: temperature 37oC, induction time at OD600=0.7 and the process time after induction 4 h. Also, the predicted protein production at optimized condition was 21.54% of total protein. Using the gained optimum condition, the effect of amino acid addition on expression level of recombinant C-D fragment of BR and bacterial growth in E. coli, using M9 culture medium was also investigated. Yates table analysis showed that Threonine, Leucine and Alanine are more effective and so were selected for addition to the culture medium in the fermentor, at two different levels. The results showed that amino acid addition caused increasing in the desired protein productivity, but had little effect on the bacterial growth.

In this research, biosurfactant production (surfactin) by Bacillus subtilis NLlM 0110 has been investigated. This microorganism was isolated from agricultural area of Iran. For surfactin production. The best condition of biosurfactant in shake flask was obtained at 37oC and 250 rpm. In this condition, maximum production of biomass and biosurfactant are 4 and 1.8 g/L. The yield of biosurfactant on biomass (Yp/x), biosurfactant on sucrose (Yp/s), and the volumetric production rate (Y) for shake flask were obtained about 0.45 g/g, 0.18 g/g, and 0.03 g/L.h, respectively. For this microorganism, the production of biosurfactant was proportional to the cell growth representing biosurfactant as a growth-associated product. The produced surfactin showed good surface activity because it is able to reduce the surface tension from 72 mN/m to 25 mN/m. Therefore, the proposed biosurfactant is appropriate candidate for industrial applications.