Showing 8 results for Niroomand
Volume 6, Issue 4 (Winter 2022)
Abstract
Abstract
Research subject: In this research, the synthesis method of phenol-formaldehyde resin has been investigated, which can be used in the wood and chipboard industry. This resin is prepared in two forms, Novolac and Resole, which different products are formed by changing the reaction conditions. Resole is used as a liquid adhesive in the wood and chipboard industry.
Research approach: Various parameters are effective in the synthesis of the resin and the properties of the final product such as the molar ratio of formaldehyde to phenol, the pH of the reaction medium, the temperature and time of the reaction, and the amount of water released from the reaction. The synthesis of this material was carried out under reaction conditions with the molar ratio of formaldehyde to phenol from 1.84 to 2.50, the reaction medium pH from 4.0 to 10.85, the reaction temperature from 80 to 100 ◦C, the reaction time from 0.5 to 4 h, and the water output amount in the term of dehydration dimensionless number from 0.18 to 1.02.
Main results: The results showed that the maximum product stability time was obtained for 18 days at the molar ratio of 2, the alkaline medium at pH 9 to 10, the reaction temperature at 90 to 95 ◦C, and reaction time at 2 h. Moreover, viscosity, density, gelation time, and percentage of solids were obtained 180 cP, 1.224 g/cm3, 30 S, and 51.20%, respectively. Product properties were optimized by adding diethylene glycol and urea. The stability time increased to 105 days by adding 8% diethylene glycol and the free formaldehyde amount in the product decreased to 1.29% by adding 4% urea. According to the properties of the created product, the obtained reaction conditions can be used for the mass production of the resin.
Volume 9, Issue 2 (Spring 2018)
Abstract
Aims: The production of biofuels has been one of the promising efforts in biotechnology in the past decades. Unicellular cyanobacteria are widespread phototrophic microorganisms that can be suitable chassis for production of valuable organic materials like biofuels. The aim of this study was the reconstruction and modeling of integrated metabolic network of a cyanobacterium to increase the production of biofuels.
Materials and Methods: In the present computational study, a software for integrating reconstructed metabolic networks was developed to optimize and increase their efficiency and was named as iMet. First, iMet was used to integrate the 3 pre-reconstructed metabolic networks of Synechocystis PCC6803. In the next step, the reconstructed network was modeled to produce 4 types of biofuels, including ethanol, propanol, butanol, and isobutanol.
Findings: The new merged model had 808 reactions and 560 metabolites. The amount of flux or flow in the integrated model was calculated to be 0.0295 hours per hour. This showed a remarkable increase compared to the previous three models. The cells were divided once every 24 hours. The amount of flux of 4 types of alcohol and their maximum theoretical efficiency increased in the integrated model compared to the previous 3 models. The flux of ethanol production was greater in all models than flux of 3 other alcohols, and the ethanol production reactions were closer to the flow or the central flux of carbon.
Conclusion: The analyses of flow equilibrium in the metabolic network coverage show an increase in the production of biofuels and a decrease in the number of blocked reactions in the new model, thereby the efficiency of the developed iMet software is proved.
Volume 11, Issue 4 (12-2022)
Abstract
In this study, the effects of powder and leaf extract of Moringa oleifera on hemolymph factors of Litopenaeus vannamei in response to salinity stress were evaluated. After 8 weeks of feeding with powder (25, 50 and 100g / kg) and extract (0.25, 0.5 and 0.1 g/kg) leaves of Moringa and control treatment without Moringa, all treatments were exposed to short-term salinity stress (5 and 55 ppt). There was a statistically significant difference in total and differential count of homocytes in different dietary treatments in all three normal conditions and under salinity stress of 5 and 55 pp (p<0.05). Under normal conditions and high salinity, shrimps fed with Moringa leaf extract showed higher number of homocytes than other treatments. In stress-free conditions, the number of semi-granular cells in powder and extract treatments was higher than the control group. At 5 ppt, Moringa powder treatments had higher semi-granular and at 55 ppt salinity, the leaf powder group (100 g/kg) and the leaf extract (0.25 g/kg) showed the highest values, respectively. Overall, the results of this study showed the positive effects of using Moringa leaf powder and extract on innate immune system function and exposure to salinity stress in shrimp
Reza Niroomand, Mohammad Hassan Saeedi, Siamak Kazemzadeh Hannani,
Volume 15, Issue 2 (4-2015)
Abstract
Nowadays, computer simulations are becoming more and more important in performance investigation of thermal systems. In this article, radiator of cooling system of diesel engine of ER24PC locomotive is simulated. The radiator is composed of parallel and series arrangement of compact heat exchangers with offset strip fins. It also has two high and low temperature sections. Due to the complexity and compactness of heat transfer plates implemented in the radiator, the simulation is carried out in two steps. First, a relation for coolant-side and air-side heat transfer coefficient is correlated using computational fluid dynamics. Due to vortex shedding phenomenon in the staggered fin arrays, governing equations are solved transiently in two-dimensional space. Appropriate timestep for the transient solution is chosen according to time period of vortex shedding from the surface. In the second step, using the developed computational code, the overall thermal performance of the radiator is simulated as a heat exchanger. Consequently, temperature distribution inside the radiator and its thermal performance are studied. Amount of heat released from the radiator in different flow rates and temperatures of fluid flowing out of radiator are among the outputs of the developed code. Finally, thermal performance curve of radiator is obtained.
Hajar Hassani-Ardekani, Hanieh Niroomand Oscuii,
Volume 16, Issue 6 (8-2016)
Abstract
Molecular Dynamics (MD) method is a computer simulation for studying the physical movements of atoms and molecules of a N-body system by solving classical equations of motion. Here, this method is used to investigate the structural changes of a vital molecular bond in the body. This bond is created by the interaction of P-selectin, expressed on activated endothelium, and its counterpart P-selectin glycoprotein ligand-1 (PSGL-1) which is expressed on leukocytes. Frequent association and dissociation of these bonds allow the leukocyte to roll on the endothelium layer which is a pivotal step in inflammatory responses. Understanding the mechanism underlying the dissociation process of this bond is helpful in pathological researches. Here this process is simulated with MD method using the program NAMD and Visual Molecular Dynamics (VMD). The results indicate that the hydrogen bonds between ion Ca2+ and residue fucose of glycan group of PSGL-1 and also between sulfated tyrosine residues are the most effective bonds in binding.
Mohammad Ali Rasouli, Aboozar Taherizadeh, Mahmood Farzin, Amir Abdolah, Mohammad Reza Niroomand,
Volume 16, Issue 12 (2-2017)
Abstract
Tube spinning or flow forming process is used for manufacturing of seamless tubes widely put into service in advanced industries. The ideal flow for materials entering the deformation zone in this process is extrusion-type flow in axial direction. Very localized deformation zone which is confined by outer materials and forming tools is very important aspect of this process. Therefore, development of defects during the deformation process with undesirable flow of materials can be easily occurred. The main reason of undesirable flow of materials is choosing inappropriate process parameters which results in arising various geometrical and dimensional defects. In this paper, the effects of process parameters on formation and growth of different defects and their correlations with material flow and forming forces in tube spinning of AA6061 was investigated by using design of experiment (DOE) method. The results of experiments show that by applying the optimized values of reduction and feed rate per revolution, these defects can be controlled. Also, by comparing the experimentally measured and theoretically calculated forming forces it can be shown that the larger the deviation of measured forces from calculated ones gets the more severe formation of defects and undesirable materials flow becomes.
Nargess Meghdadi, Hanieh Niroomand-Oscuii, Madjid Soltani,
Volume 18, Issue 4 (8-2018)
Abstract
Cancer is one of the main causes of mortality and morbidity worldwide. Using a single treatment plan for all of the patients is not efficient due to the biological heterogeneity in the individuals. In order to personalize the therapy plan, tumors behavior in each patient must be understood. For this purpose clinical information of the patients are used. Mathematical modeling has gained significant interest in tumor growth investigations, due to its higher flexibility than the other methods. Mass effect and the reaction terms are the key parameters that are investigated in this paper. This is the first time that the effects of these parameters are considered in brain tumor growth modeling and there are few researches that have used only MR images in this area. The mathematical models are used for predicting the growth of brain tumors based on personal MRIs and introducing intracellular fraction into the model. Results of the comparisons show that considering the mass effect in the growth model would improve the prediction. Furthermore, it is necessary to define the optimum formulation for reaction term according to patients' medical information, to be used in the personalized model of tumor growth prediction. The represented approach can be used as a basis for personalizing the therapy plan in patients with brain tumors.
K. Yazdanpanah-Ardakani , H. Niroomand-Oskui ,
Volume 20, Issue 2 (February 2020)
Abstract
Increasing growth of cardiovascular disease treatment caused the occurrence of heart failure for more patients after surviving. This leads to an increase in the need for types of equipment in these patients for struggling heart failure. Ventricular assist pumps have been known as one of the main types of equipment, today. In the present study, a ventricular assist pump has been designed in which its impeller has been designed using the industrial method (point-by-point method). In this study, 7 impellers with different inlet angles (including 10, 15, 20, 30, 35, 40 and 45 degrees) and outlet angle of 25 degrees were designed and analyzed using computational fluid dynamics. The results indicate that all designed impellers in this study can fulfill the physiological requirements according to pressure difference (total head) and flow rate. Meanwhile considering hemolysis as an effective factor in the performance of ventricular assist pumps, the impeller with an inlet angle of 10 degrees is chosen due to the lowest hemolysis index, equal to 0.0045, and complying total head and flow rate, which are equal to 108 and 5, respectively.
