Nashrieh Shimi va Mohandesi Shimi Iran
Year:2020 | Volume:38 | Issue:4 (94)|Papers Count:28

In this review article, the potential functions of the reactive force field ReaxFF used in reactive molecular dynamics (RMD) simulations are introduced and described. This force field with its special potential functions is used to simulate chemical reaction systems with accuracies close to those of quantum chemical calculations within reasonable computation times, even with about one million atoms on high-performance computing facilities. Variations of the partial charges of atoms during chemical reactions can also be calculated and probed within RMD simulations with accuracies very close to those calculated by density functional methods. In addition to the general potential functions incorporated in non-reactive force fields, in ReaxFF force field, there are a number of special (usually complex) potential functions describing details of the bonding structures and charge states of atoms in different coordination states and chemical and solvent environments. All of these potential functions are described in this paper, and examples are calculated and plotted to demonstrate clearly their behavior and their corresponding chemical and physical backgrounds. Finally, important evolutions of the ReaxFF force field and a few of its applications have been presented.

In this study, graphene-based nanostructures were simulated using computational quantum chemistry methods and individual interactions of isoelectronic ions sodium and fluoride with inner and outer faces of them have been studied. Also, simultaneous interactions of these ions with inner and outer faces of nanostructures have been investigated with two models. In the first model, fluoride ion with outer face and sodium ion with the inner face of nanostructures interact simultaneously and in the second model, positions of ions were exchanged to study the effect of this on binding energies of the ternary complexes. Results indicate that binding energies in the first model are larger than the second one by an average 1. 90 kcal mol-1. Indeed, a decrease of electron delocalization/increase of electron delocalization in the central ring of nanostructures is good for the interaction of ions with the outer face of them in the first model/second model. Results propose that graphene-based nanostructures due to unique structural and electronic properties are good beds for interactions of ions and can be considered as sodium-ion batteries. Also, the growth of curvature of nanostructures leads to better functionalization of their outer faces through ions with a negative charge and can optimize their performance as ion batteries using changing electronic cloud densities of their walls.

For the first time, a novel and efficient Magnetic Multi-Wall Carbon NanoTube (MMWCNT) was introduced as a novel sorbent for Solid-Phase Extraction (SPE) coupled with ElectroThermal Atomic Absorption Spectrometry (ET-AAS) for sensitive determination of vanadium (V) in environmental water samples. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Energy-Dispersive X-ray analysis (EDX), Vibrating Sample Magnetometry (VSM), and Fourier Transform-InfraRed (FT-IR) spectroscopy were applied to characterize the prepared nanoparticles. A unique and attractive property of this method is that magnetic adsorbents can be simply isolated from sample solutions by an external magnetic field without using a centrifuge. N-Benzoyl-N-phenylhydroxylamine (BPHA) was used as a complexing agent for extraction of the analyte into the solid phase. The extracted complex was injected into the instrument for analysis. Initially, effective parameters controlling the performance of the extraction process were evaluated and optimized. Under the optimized condition, the calibration curve showed linearity in the range of 25-2000 ng mL-1 with a regression coefficient corresponding to 0. 997. Limits of detection (LOD, S/N = 3) and relative standard deviations were 8 ng mL-1 and 3. 9 % (n = 6) respectively. The proposed method was successfully applied for the preconcentration and trace determination of V in environmental water samples while the accuracy was approved by analyzing relative recovery experiments as well as a standards reference material.

In the present work, Graphene Oxide (GO) was modified by in-situ polymerization in the presence of methylmethacryalte and was used to improve the dispersion of GO nanoparticles as well as mechanical properties in polymethylmethacryalte (PMMA) matrix. Fourier Transform InfraRed (FT-IR) technique was used to confirm the successful modification of GO. PMMA nanocomposites were prepared by melting method and Thermal Gravimetric Analysis (TGA) and Field Emission Scanning Electron Microscopy (FESEM) techniques were applied in order to characterize the prepared nanocomposites. Also, the effect of GO percentage and processing parameters were studied by Taguchi Design of Experiment. (GO content: 0, 2, and 4 wt%, injection pressure: 40, 60, and 80 MPa, holding pressure: 60, 80, and 100 MPa, and holding pressure time: 1, 2. 5, and 4 s were mentioned as the variable parameters). To investigate the mechanical properties of nanocomposites tensile strength, hardness, and impact tests were carried out.

Copper Oxide(CuO) nanoparticles and nanoporous silica such as MCM-41 and SBA-15 were synthesized and characterized by Fourier Transform InfraRed (FT-IR) spectroscopy, X-Ray Diffraction (XRD), and Sscanning Electron Microscopy (SEM). The synthesized copper oxide nanocatalyst was applied in allylic oxidation of cycloolefinsvia C– H bonds activation by tert-butyl-p-nitrobenzoperoxoate as oxidant and in the presence of nanoporous silica as additive. Allylic esters were obtained in good yields (up to 90%) and reasonable reaction times. Also, the recovered catalyst was applicable in the allylic oxidation reaction for four times without loss in catalytic reactivity and yield. The structure of tert-butyl-p-nitrobenzoperoxoate and allylic esters were characterized by 1HNMR, and 13CNMR spectroscopy.

Cellulose nanowhisker produced from acid hydrolysis of cotton linter and used as starting material for fabrication of a new polymer-supported palladium complex. It is firstly, grafted by citric acid and then loaded by Palladium complex. Successful fabrication of Palladium complex supported polymer confirmed using FT-IR and NMR spectroscopy. Thermal behavior and crystalline structure of the resulting composite evaluated by TGA and XRD techniques. The results showed that composite has higher thermal stability and lower crystallinity in comparison with unmodified cellulose nanowhisker. Finally, the potential application of the synthesized cellulose nanowhisker-graft-citric acid/palladium complex as a photocatalyst for degradation of 2, 4-dichlorophenol was examined. The results showed that the polymer-supported Palladium complex could be an effective photocatalyst with a narrow bandgap. It could eliminate 2, 4-dichlorophenol after 300 min illumination.

AgBr-Bi24Br10O31 nanosheets were prepared by a facile single-step co-precipitation method at the presence of 1-Butyl-3-methylimidazolium bromide ([BMIM]Br) ionic liquid (IL) as the bromide source and template agent. The products were well characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Diffuse Reflectance Spectroscopy (DRS), nitrogen adsorption-desorption isotherms (BET), Fourier Transform InfraRed (FT-IR) spectroscopy, and Scanning Electron Microscopy (TEM). The XRD pattern well confirmed the presence of both Bi24O31Br10 and AgBr crystalline phases in the structure. In addition, the SEM micrographs indicated that the sample has sheet-like morphology, and the thickness of the sheets is below 100 nm. According to the photocatalytic experiments, the product was incredibly efficient for the degradation of Acid Blue 92 (AB92) solutions under visible light. Also, the results of recycling experiments implied the high capacity of the prepared nanosheets for the repeated treatment of the wastewater solution which is great of importance for being introduced a catalyst in practical applications.

A highly efficient, simple, convenient, and eco-friendly methodology for the synthesis of 1, 4-dihydropyridines has been demonstrated. A biodegradable, polymer-supported catalyst, PEG– SO3H, was applied for the synthesis of 1, 4-dihydropyridines via the Hantzsch-type condensation reaction under solvent-free conditions. The PEG-SO3H acts as an acidic mediator to facilitate the Hantzsch-type condensation and at the same time as the reaction solvent. The significant advantages of this methodology are high yields of products, short reaction time, the economic viability of the catalyst, handling of the catalyst, ease of preparation of the catalyst, and ease of product isolation. Furthermore, the solvent-free preparation of 1, 4-DHPs is an environmentally benign method. The products were characterized by FT-IR and 1H NMR spectroscopy, and by comparison with authentic samples.

Efficient functionalization of Fumed silica by sulfonamides via copper-catalyzed Huisgen 1, 3-dipolar cycloaddition (Click) reaction has been reported. Functionalization of Fumed silica by 3-azidopropyl groups leads to the formation of azide moiety as building blocks for Click reaction. Propargylation of three commercial sulfonamides (sulfadiazine, sulfadimidine, and sulfaquinoxaline), with propargyl bromide, leads to the formation of another building block for Click reaction. The Click reaction was catalyzed by freshly prepared Copper(I) iodide in DMF at room temperature after 72 hours. Antimicrobial activities of sulfonamides functionalized Fumed silica were measured against Staphylococcus aureus as gram-positive bacteria and Escherichia coli as gram-negative bacteria and checked by their Zeta potentials.

Styrene derivatives are important structural units in the chemistry of organic compounds. Since the nuclear attack on a triple bond is not carried out, the use of palladium catalyst is considered a suitable route for the activation of these compounds. In this study, a new pathway for the preparation of styrene derivatives using alcohols As a source of active vinyl and boronic acids, it has been reported as a source of activated Ariel. Optimum reaction conditions include the catalytic system of tris (diphenzilindenson) palladium / 1 and 4-bis (phenylphosphine) butane as a ligand and a mixture of dimethyl acetamide/water as a solvent. The study of variation reacted that the presence of fatal electron and electron components in the structure of boronic acids ariel is very well suited to the reaction conditions. In addition, the selectivity test reacts that the reaction product is predominantly cysteine.

In this research, a theoretical study on the cycloaddition reaction of the C20 fullerene and certain fused bicyclic aromatic compounds including naphthalene, 2-methoxynaphthalene, 2-nitronaphthalene, quinoline, and isoquinoline was carried out with the aims of functionalization possibility of the fullerene and investigation of the reactivity and regioselectivity. For this purpose, the [4+2] cycloaddition reaction between the above mentioned aromatic systems and fullerene was studied in which, the fullerene and aromatic systems act as dienophile and diene, respectively. Except for the naphthalene, two possible reaction paths were considered for the aromatic systems in which, the substituent-or heteroatom-containing ring reacts in one path and the ring without substituent or heteroatom reacts in another one. The thermodynamic and kinetic parameters of each reaction path were calculated using optimization of the reactants, products, and transition states geometries. In order to study the reactivity of different positions of the naphthalene, 2-nitronaphthalene, 2-methoxynaphthalene, quinoline, and isoquinoline, three different methods were used including calculation of the Parr as well as Fukui functions and the value of the contribution of different atoms in the HOMO of the aromatic system. The results indicated that the Fukui functions can completely describe the reactivity of different positions of the above aromatic compounds. Also, the Parr functions and the contribution value of different atoms in HOMO can satisfactorily describe the reactivities in the corresponding cycloaddition reactions. The Global Electron Density Transfer (GEDT) value was also calculated for the reactions and the results revealed that the reactions are polar in character and the electron density is transferred from the aromatic compound toward the fullerene. Finally, the calculation of the synchronicity showed that the reactions of fullerene with the naphthalene and the heteroatom-containing ring in the quinoline and isoquinoline are more synchronous in comparison to the other ones.

Cross-coupling reactions employing transition metals as catalysts have become an important approach for the construction of C-C and C-heteroatom bonds. Traditionally, aryl halides have been used as one of the coupling partners in these kinds of reactions. However, these compounds are generally environmental pollutants and many of them are expensive. Thus, looking for safe and cheap alternatives for these compounds is of high interest from both laboratory and industry point of view. In recent years, nitroarenes have been reported to be active substrates in the cross-coupling reactions activated by some transition metals such as copper, palladium, or rhodium. Herein, the recent advances in cross-coupling reactions starting from nitroarenes has been reviewed.

Sodium lauryl ether is a surfactant that is used as a viscosity agent in bleaching fluid. But in certain chemical environments, the concentration of this surfactant decreases over time. This decrease in concentration changes the chemical and physical properties of the product. In this study, considering the effective parameters on the decomposition rate of sodium lauryl ether sulfate, including temperature, time, sodium lauryl ether sulfate concentration, sodium hydroxide, and sodium hypochlorite concentrations, the decomposition rate of Sodium lauryl ether sulfate was obtained using high-performance liquid chromatography and two-phase titration, and with the aid of kinetic ratios, the constant rate and degradation reaction order were calculated. The obtained results showed that the reaction order of Sodium Lauryl Ether Sulfate surfactant decomposition relative to NaOH concentration is first order. On the other hand, the reaction order of Sodium Lauryl Ether Sulfate relative to its concentration is first order. Then the reaction order of Sodium Lauryl Ether Sulfate surfactant decomposition was obtained at three temperatures of 4, 20, and 47 ° C. These results can be used in selecting conditions that lead to increased product shelf life as well as determining the expiration date of the bleach product.

Schiff base ligands provide a platform for the development of suitable ligands for coordination to transitional metal ions. In this research, synthesis, characterization, and photophysical properties of three zinc complexes with Schiff bases ligands derived from ortho-vanillin are investigated. 6-Methoxy-2-[(E)-Aryliminomethyl]-phenol (Aryl = Phenyl; 2, 6-dimethyl; 2, 6-diisopropylphenyl), comprising L1-3 ligands, and the corresponding zinc complexes [Zn(Ln)2, n=1-3] were synthesized. The complexes were characterized using infrared, ultraviolet, and nuclear magnetic resonance spectroscopy techniques. The complexes show interesting photophysical properties. In the absorption spectra of the zinc complexes, the observed high-intensity peaks are attributed to the intra ligand p-p < /em>*, originating from ortho-vanillin and aromatic rings. All three zinc complexes feature emission bands in dichloromethane, while only two metal complexes are emissive in the solid-state.

In the present study, Dispersive Liquid-Liquid Microextraction (DLLME) method coupled with UV-Vis spectrophotometry was used for pre-concentration and measurement of fentanyl in water, plasma, and urine samples. 10mL of water sample containing fentanyl adjusted by phosphate buffer at pH 10 and placed in a 15-millimeter-glass tube with a conical end. Then, usinga microsyringe, a chloroform solution containing aliquot 336s was rapidly injected into the solution, and then a cloudy solution was created. At this stage, the resulting product was extracted into tiny drops of chloroform. Next, the mixture was centrifuged for a specific time and the organic phase was deposited at the tube. After eliminating the upper aqueous phase, the residual organic phase was taken with a microsyringe and placed into a micro-cell of quartz and its adsorption in comparison with the control solution in the wavelengths (fentanyl 265 nm) was read. In this method, conventional dispersive solvents are not used to disperse the extracted solvent because the injectable aliquot336s, along with chloroform, other than creating cation along with ion pairs with solution, plays a role as a dispersive solvent for the formation of a cloud solution, which not only results in dispersive liquid-liquid microextraction, but also considers as a green method. The detection limit of the method to measure fentanyl was 0/002 mg/L respectively, and the calibration curve was linear in the range of 0/01-52mg/L. The relative standard deviations(at n=7) for the extraction of fentanyl (3. 5 ng/mL), was 2. 7 %, and the enrichment factors was 55. 5. Simplicity, being fast, low cost, and high pre-concentration factor are some of the advantages of the present method. Complex devices have been used for almost all measurements of Fentanyl. Some figures relating to the suitability of this method are comparable to those reported previously.

The time of flight mass spectrometry is an efficient technique for the identification and characterization of chemical materials. In this method, the ions produced by the interaction of laser radiation with the sample, are accelerated in the ionization region and after obtaining enough kinetic energy are separated from each other in the absence of an electrical field based on their mass to charge ratio in a flight tube and then, reach to the detector at different times. In this work, the time of flight mass spectra of several inorganic complexes such as [Co(H2O)6](NO3)2, [Co(H2O)7]SO4, [Co(NH3)5Cl]Cl2, [Co(NH3)4CO3]NO3, [Fe(H2O)6]SO4 and [Fe(H2O)7](NO3)3 were recorded using the desorption-ionization (LDI) of sample on the aluminum plate. The laser light with a wavelength of 1064 nm (infrared region) was used for the LDI. Comparison of the recorded mass spectra of Co complexes with H2O ligands with those of Co complexes with NH3 ligands showed that the metal-oxygen bond is stronger than the metal-nitrogen bond because the different ionic species containing the metal-oxygen bonds are seen in the mass spectra of complexes containing H2O as a ligand. The absence of the peak related to the intact complex in the recorded mass spectra showed that these complexes have not stability against the laser radiation. Also, the effect of different counterions on the mass spectra of complexes with the same metal and ligands was investigated and it was found that the mass spectra are independent of the kind of counterion.

In this study, the chemical adsorption modeling of CO2 in the fixed bed column is determined. In the adsorbent modeling, the granules are assumed to be spherical, and by writing the mass balance around a radial element, a partial differential equation has obtained that shows the variation in adsorption versus the direction of radius and time. By applying the boundary conditions and initial condition in terms of the physics of the problem, this equation can be solved, but due to the complexity of its analytical solution, the equations were solved using a combination of the method of lines and finite difference methods. For the modeling of the fixed bed column, the column is aligned along with the height, and by writing the mass balance around it, the partial differential equation is obtained. In order to ensure the modeling process, the model has been verified using experimental data and numerical modeling of the Kelvin Odafe Yoro model. Finally, parametric studies have been done on the chemical adsorption of CO2 in the fixed bed column. The amount of R2 in the CO2 breakthrough curves on polyaspartamide and in the experimental and simulated equilibrium amount of CO2 adsorbed by polyaspartamide at the time is 0. 99 and RMSE is approximately 10% for them.

Membrane processes are among the common methods for water sweetening and desalination, however, due to the cost and energy consumption, membrane processes are more suitable and have more practical applications. Designing of membranes in different shapes and dimensions, performing of separation process at room temperature, minimum consumption of chemical materials including solvents, and other additives are among the advantages of membrane process in respect to classical and common separation processes. Different membrane processes are used for water sweetening including reverse osmosis, electrodialysis, microfiltration, ultrafiltration, and nanofiltration membrane processes in which the reverse osmosis and electrodialysis methods are more important. Polymers are commonly used as membranes for the water sweetening industry, and due to their versatile structures and properties have a specific position in such a way that their applications are growing steadily. The most suitable and efficient polymeric membranes applied in the country are cellulose acetate, polyamide composite membranes, polysulfone, polyethylene, polypropylene, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride, and polydimethylsiloxane. There are different methods for improving the efficiency of polymeric membranes in the water desalination process in which preparation of copolymers and polymer blends, chemical modifications on the polymeric structure or their chemical functionalization, preparation of composites, and physical or chemical modifications on the surface of some polymers are more important that should be resulted in a suitable collection of physical, hydrophobic, chemical, thermal, and hydrolytic stability of the polymer and also led to remarkable flux and salt rejection. In this article, different membrane processes, and polymers that are applying in this industry is briefly introduced.

Alcohol dehydration is accomplished by various processes, especially pervaporation with increased attention and applications. Many hydrophilic polymeric membranes have been prepared and used for alcohol dehydration. Polyvinyl alcohol (PVA) is one of the most important polymeric membranes in this regard. In this study, modification of the prepared polyvinyl alcohol membranes by blending method them with Agarose (Aga) in order to achieve higher separation performance is studied. PVA/Aga blended membranes are prepared and used for separation of ethanol/water solution using pervaporation process. The structure of the membranes was investigated using SEM and contact angle tests. In the carried out experiments, pervaporation operating temperature and pressure are kept fixed at 30 ° C and-830 mbar abs, respectively, and effects of the feed composition and the blending ratio on the membrane separation parameters are studied. The results showed that membranes have enhanced separation performance for water/ethanol mixtures. The highest selectivity as infinity and flux of 0. 243 kg/m2h was obtained for the 50 wt. % Aga membrane and the feed mixture of 30 wt. %. The 60 wt. % Aga membrane selectivity and flux for dehydration of the feed mixture containing 70 wt. % ethanol are obtained as infinity and 0. 838kg/m2h, respectively.

Potassium Khor-Biabanak is a rich source of magnesium, calcium, potassium, and sodium. In this research, we tried to separate and precipitation of their calcium and magnesium in the presence of other cations and anions using oxalic acid as a precipitator. Before the experimental phase, simulation of the reactions, and prediction of the results were performed using Stabalk modeling software. Based on the data processing of this software and also the obtained experimental results, the best molar ratio of oxalic acid to calcium and magnesium obtained for calcium separation from saline were 1. 05: 1 and 1. 25: 1, respectively. The obtained analyzes showed that using this method, separation of 87% of calcium and 88% of magnesium from saline is possible and 95% and 94% purity for extracted calcium and magnesium oxalate salt are available, respectively.

Energy conservation is becoming increasingly important as the cost of fuel continuously rises. The two-phase closed thermosyphons are handy tools in the heat transfer process. In this study, the effect of affecting parameters on a two-phase closed thermosyphon's thermal performance was investigated experimentally. A copper pipe with a length of one meter and an inside diameter of 20 mm was constructed. Distilled water was used as a working fluid for this research. Many experiments were carried out for the inclination angle range of 5º – 90º , input heat between 100 to 300 W, aspect ratio 13, 16. 5, 20, and filling ratios of 25% to 70%. An experimental correlation derived from all of the results shows that the thermal efficiency increase with the increase of the filling ratio, mass flow rate of the coolant, and input heat and decreases with the rise in the inclination angle and aspect ratio. The highest thermal efficiency is obtained at input power 200 W, inclination angle 60, aspect ratio 16. 5, and the filling ratio 50%. The geyser boiling has been investigated by examining the time variations of the outlet water temperature from the condenser jacket. At an input power of 100W, geyser boiling occurs, but if input power equal to or greater than 150 W combined, boiling will be observed. An empirical relationship for the period of temperature variations caused by boiling was presented. The results show that the geyser boiling period was shorter for higher input power, cooling water flow rate, and inclination angles.

In the present study, an efficient two-step thermal cracking process has been investigated for the conversion of refinery fuel oil to value-added products viz. olefins and liquid fuels. In the first step of the process, the low-ranked heavy feedstock was thermally treated in the liquid phase at completely mild operating conditions in order to remove undesirable species and obtain suitable products which indicates high potential for utilization as a feedstock in olefin units. The thermal treatment process was carried out at three different temperatures of 360, 400, and 440 ° C. The activation energy was found to be 68. 5 kJ/mol on the basis of the Arrhenius equation. Thermal analysis using the isoconversional Kissinger model at four temperature programs on the heavy feedstock led to an activation energy of 59. 9 kJ/mol for the decomposition of the refinery fuel oil, being in reasonable agreement with that from the Arrhenius equation. More than 90% of the heavy feedstock was converted at 440 ° C to products (mainly liquid products with a yield above 76 wt%). The obtained product was applied as a proper feedstock in the subsequent thermal cracking step, which was performed in vapor phase within a wider range of temperatures (550– 750 ° C). The yield of olefins in this step at 750 ° C was more than 88 wt% based on the dry gas composition and more than 45 wt% based on the applied feedstock. By decreasing the temperature, the reaction tended to produce liquids than gases particularly gasoline and diesel fuel, such that at 550 ° C, only 1 wt% of the obtained products were gaseous.

Having information on the chemical composition of hydrocarbon mixtures (the amount of paraffinic, naphthenic, and aromatics) is still a challenging problem in the area of reservoir fluids. Methods for determining these compositions include experimental techniques and empirical models. Laboratory methods are accurate, but they are costly and time-consuming. Therefore, researchers have tried to use empirical models instead of using laboratory methods. Generally, these models include two or more characteristic parameters such as Refractive Index (RI), normal boiling point (Tb), density in standard conditions (d), carbon to hydrogen ratio (CH), Watson coefficient (K), and viscosity-gravity constant(VGC). The problem with the proposed models is that for finding the compositions the mentioned characteristic parameters must be available, but usually, these parameters are not specified for petroleum cuts, therefore, in practice, the determination of chemical composition is difficult. In this research, we have tried to select parameters for the construction of a model that does not have this limitation. Selected parameters were MW, SG, and Tb which are molecular weight, specific gravity, and normal boiling point respectively. These parameters are commonly available for petroleum cuts, therefore for the determination of the composition of oil cuts, another specific characteristic parameter is not necessary. In this study, the neural network and the SAFT family equation of state have been used to determine the model for estimating the composition of families. For the development of this model, for synthetic cuts consisting of paraffinic, naphthenic, and aromatic, the specific gravity and normal boiling point values were determined using the PC-SAFT state equation. Finally, a neural network model was implemented on these data. In the end, the ability of the model for estimation has been tested using a series of evaluation data for oil cuts. The results indicate that the proposed model predicts the families present in the cuts effectively.

Since the inhibition of gas hydrates is very important in gas transfer, in this study the effect of temperature and material of cetyl trimethyl ammonium bromide as an inhibitor on the formation of tetrahydrofuran hydrates has been investigated. First, tetrahydrofuran hydrates were investigated in 2. 5, 3, 3. 5, and 4 degrees Celsius and 15, 20, 25, 30% by weight of tetrahydrofuran at atmospheric pressure, while the induction time and pure hydrate equilibrium were determined. Then experiments were carried out in the presence of 0. 5, 1, 1. 5, and 2 wt. % of cetyl Teri methyl ammonium bromide as a hydrate inhibitor, and the effects of cetyl trimethyl ammonium bromide on the induction time as well as the kinetics of hydrate formation were studied. The results show that at a constant temperature over time, the addition of cetyl trimethyl ammonium bromide increased to the induction time hydrate. more ever, in some concentrations of inhibitory substances, the inhibitory role has been lost and the induction time has decreased. By detecting the kinetic diagram of the hydrate formation, additionally, it was found that the heat released during the formation of the hydrate was reduced by the addition of the inhibitor and the nucleation time also increased.

Microbial Fuel Cells (MFCs) are considered as one of the renewable energy sources. In the meantime, Sediment Microbial Fuel Cells (SMFCs) have a special place, especially in areas where nutrient-rich precipitates are used to grow microorganisms. One of the ways to produce renewable and non-destructive energy using the energy found in biomass resources is the microbial fuel cell. In this research, conductive metal brushes with high effective surface were evaluated as cathodes in sedimentary microbial fuel cells. In this work, the performance of SMFCs in electric power generation, as well as the resistance and durability of electrodes for four brushes of iron, stainless steel, rice, and copper, were studied. The results showed the lowest and highest corrosion rates of stainless steel and iron, respectively. The highest power density was obtained from SMFCs using copper brush cathode, which was equal to (382µ W/cm2) and the lowest value for cathodic brushes Brass (19. 24µ W/cm2) was reported.

Preserving the level of calcium concentration in the blood is a dynamic process that is carried out through the interaction of several organs such as the intestine, kidney, and parathyroid glands. Human parathyroid hormone (hPTH) increases blood calcium level by increasing intestinal absorption of calcium and decreasing renal excretion. Therefore, this hormone is used for the treatment of osteoporosis and diseases of the disorders in parathyroid gland function. In this research, the plasmid pUC 57 and strain of E. coli DH5α are used for cloning and the plasmid pET 32a (+) and strain of E. coli BL21 are used for protein expression. In this study, protein production was carried out in a 1 L batch Erlenmeyer and in a 10 L fed-batch mixed bioreactor. The results of this research showed that the amounts of biomass and recombinant human parathyroid hormone were about 6. 5 g/l and 1. 7 g/l in shake flasks after 16 h. Also, our results showed the amounts of biomass and recombinant human parathyroid hormone were about 81 g/l and 22 g/l in the fed-batch bioreactor after 12 h, respectively. Finally, the production of recombinant human parathyroid hormone was confirmed by SDS-PAGE and western blot analyses. However, in this research, the presence of a protein band in the 37 kDa region indicates the correct expression of the parathyroid hormone. According to the successful production of human parathyroid hormone in this study, as well as the advantages of Escherichia coli as a host, it seems that this method can be a good alternative to producing this valuable drug.

In this study, in order to optimize the production of lipase from Rhizopus oryzae in the liquid culture medium, the design of the experiment was carried out by using the response surface methodology to the central operating state by the design expert 7. 0. 0 software. Fermentation was performed by selecting the parameters including the mass ratio of carbon source to nitrogen source, the agitation speed, and the initial pH in the range of variation (0. 2-1), (100-250), (5-8) respectively. The experiments were carried out by using the olive oil stimulus as a carbon source at 32 ° C. The activity amount of the lipase enzyme was measured by titration of the free fatty acids (NaOH 0. 1 molar as a titrant) and the mass of biomass was calculated by the gravity method. (Responses: Enzyme activity and the bulk of mass both produced after 48 and 96 hours). The statistical analysis of the experimental data was obtained from measuring the activity of the lipase enzyme, indicates that the models presented with 95% confidence for enzyme activity after 48 hours of cultivation have the desired effect of increasing the agitation and the alkalinity of the culture. It also shows that It is desirable to increase the agitation of the stirrer and reduce the mass ratio of the carbon source to the nitrogen source for the activity of the lipase enzyme after 96 hours of cultivation. Optimum fermentation conditions of lipase enzyme, respectively, the ratio of carbon source to nitrogen source 0. 4, agitation 100 (rpm) and initial pH 8, with the production of the highest activity of the extracellular lipase enzyme (2. 48, 4. 89)(U/ml) was obtained after 48 and 96 h cultivation which shows a more efficient process than previous similar researches.

One of the problems in the biotechnology industry is the discrepancy between the experimental results and the pilot results. Therefore, in this research, the scale-up of bioreactors as one of the main issues in the industrialization of laboratory research is discussed. In this research, scale-up calculations based on Reynolds number and momentum factors, blade speed (NDi and N), and constant mass transfer mass coefficient (KLa) are investigated. Since simulations of these criteria are manually time-consuming, computer simulation is essential. Therefore, in the present study, the scale-up of mixed bioreactors was simulated by excel software. Results of this research for scale-up of a bioreactor from 100 liters to 125 liters and from 80 liters to 10000 with other researchers were compared and confirmed. However, using this software, you can make the optimization on a larger scale in the shortest possible time, which reduces costs such as optimization costs, labor costs, and more. Also, the use of this software can help engineers to make predictions on larger-scale production.