Showing 8 results for Jamshidian
Volume 12, Issue 1 (12-2020)
Abstract
Abstract
Urinary tract infection is one of the most common and common bacterial infections, accounting for a significant proportion of hospital admissions (about 30-40%). Silver nanoparticles work by releasing silver ions against various bacteria. The fact that bacteria are not resistant to nanoparticles is very important and therefore will affect a wide range of bacteria.
Materials and Methods
In this study, 50 specimens of positive cultures with urinary tract infection referred to Imam Reza Hospital Laboratory in Bojnourd were studied. Resistance and susceptibility of the isolates were determined by disk diffusion method. In this study, antibacterial effects of silver nanoparticles were investigated by microdilution method using aqueous extract of Ganoderma leucidum. Vegetative electron microscopy was used to measure the size and shape of silver nanoparticles. In addition, infrared spectroscopy analysis was performed to investigate possible organic compounds involved in the synthesis of nanoparticles.
Results: The highest antibiotic resistance was related to ampicillin (84%). The resulting nanoparticles were 20 to 45 nm in size.
Conclusion:
The produced nanoparticles have antimicrobial activity and can be a good alternative in the treatment of antibiotic resistant infectious diseases.
Abdolazim Dehghani, Mostafa Jamshidian, Mohammad Saeid Talaei, Mohammad Silani,
Volume 17, Issue 11 (1-2018)
Abstract
The present study investigates the surface energy of metallic nanoplates as the most basic thermodynamic concept of nanostructures using one of the most efficient available computational tools in the field of nanoscience i.e. the molecular dynamics simulations. Whenever physicochemical properties of nanostructures are discussed, the surface energy is one of the key parameters. This parameter has the utmost importance at nanoscale since at this scale the surface to volume ratio is very large and thus there is a significant difference between nanoscale properties and the engineering scale properties. In this study, the surface energy of gold and silver metallic nanoplates using molecular dynamics simulations are investigated and shown to be dependent on size. The surface energy of metallic nanoplates with different thicknesses were calculated and it was shown that for very thin metallic nanoplates with sufficiently small thickness in the order of a few nanometers, the surface energy is dependent on the thickness of nanoplate and the surface energy decreases by reducing the thickness of the nanoplate. By analyzing the excess energy of different layers in very thin nanoplates, it was found that this size-dependent behavior is due to the reduction of excess surface free energy density in surface layers and its increase in the inner layers that overall reduces the surface energy of nanoplate.
Mohammad Mousavion, Mohammad Mashayekhi, Mostafa Jamshidian, Hojjat Badnava,
Volume 18, Issue 7 (11-2018)
Abstract
Recently, the phase field approach has gained popularity as a versatile tool for simulating crack propagation. The purpose of this study is to employ the capabilities of the phase field method for crack growth modeling in complex structures such as porous media. The phase field method does not need predefined cracks and it can simulate curvilinear crack path. This goal is accomplished by replacing the sharp discontinuities with a scalar damage phase field parameter representing the diffuse crack topology. To simulate brittle fracture in this study, the equations of elastic displacement field and fracture phase field are first introduced. Afterwards, using the weak form of the equations, the staggered solution of the equations is performed. To implement the equations in the finite element method, the Abaqus software with User Element Subroutine (UEL) is used. Given that the bone structure is somehow a porous structure, a representative volume element of the bone is selected for phase field simulation. In order to verify the developed model, the tensile test of the single edge notched specimen has been simulated. Subsequently, crack propagation in a porous media with different porosities under tensile loading was simulated. The simulation results illustrate the capability of the phase field method in predicting crack growth in geometrically complex structures. In addition, the load-carrying capacity or the strength of the porous structure continuously decreases with increasing porosity and noteworthy is that such a strength is suddenly decreased around a critical porosity value.
Volume 18, Issue 117 (November 2021)
Abstract
Pectin is a heteropolysaccharide which is widely used as a gelling and stabilizing agent in the food industry. The study aimed to optimize and evaluate the quantity and quality of pectin extraction from apple pomace by acid hydrolysis at high temperatures as a traditional method of the main wastes of the apple juice industries. Extraction efficiency was optimized in the pH from 1.5 to 2, 60 to 90 minutes and 75 to 90 °C by response-surface method (RSM) with using the central composite design. In addition, the esterification degree, amount of galacturonic acid, equivalent weight, methoxyl content, emulsion activity, stability of emulsifier and water/oil holding capacity of pectin were determined under optimal conditions. The results showed that the maximum extraction efficiency (8.83%) was achived at pH 1.5, 90 °C and 90 minutes. The extracted pectin with a degree of esterification of 54% and galacturonic acid 68 mg/g was obtained at optimal conditions. Equivalent weight, methoxyl content, emulsifying activity and water holding capacity of extracted apple pectin were 916, 8.9%, 55.8% and 4, respectively. In overall, it can be possible to obtain different pectin with varying physicochemoical properties with chaning the extraction conditions. Furthermore, the extracted pectin had proper emulsion activity and stability which can be ultilized in different emulsion based products.
S.m. Zareei, M. Jamshidian, Sh. Sepehrirahnama , S. Ziaei-Rad,
Volume 19, Issue 2 (February 2019)
Abstract
Acoustofluidics, the study of acoustics in microfluidic systems, is the basis for analyzing many laboratory applications including the separation of particles, particle sorting, cleaning, and mixing multiphase systems. In this research, a three-dimensional finite element model for particle motion under acoustic radiation force in acoustic microchannels is developed and the interaction of the incident waves with a suspended particle in microchannel is investigated. Using finite element method, the first-order fields due to an applied standing wave are initially calculated and, then, the acoustic radiation force is directly calculated from the second-order perturbation equations. The simulation results for radiation force are first verified against the analytical solution in the Rayleigh limit and, then, examined beyond this limit, for which there is no explicit analytical solution. In addition, the quasi-static motion of a particle under the influence of an applied acoustic standing wave in microchannel is simulated. For simulating particle motion, the acoustic stress on particle surface is calculated and transferred as an input to the laminar flow equations. Then, the drag force is estimated based on the shear stress due to the flow around the particle. The simulation results demonstrate that the particle velocity depends on its position with respect to the wave node at the center of the microchannel. As the particle approaches to the center of microchannel, its velocity decreases until it stops at the center of microchannel.
S.a. Ashrafnia , M. Jamshidian ,
Volume 19, Issue 4 (April 2019)
Abstract
The unique characteristics of nanostructures are mainly due to their large surface to volume ratio. One of the most important quantities in investigating the surface properties of materials is the surface energy. Therefore, calculating the surface energy is necessary for the proper understanding of the behavior and properties of nanostructured materials. The present study investigates the size-dependent surface energy of crystalline nanoparticles and nanocavities of aluminum, silver, copper, and iron. For this purpose, spherical nanoparticles and nanocavities with different radiuses are modeled by molecular dynamics simulations and their surface energy is obtained. The simulation results demonstrate that for nanoparticles and nanocavities with sufficiently small radiuses in the range of a few nanometers, the surface energy depends on the size of the nanostructure. For spherical nanoparticles, the surface energy increases with increasing nanoparticle radius, while for the spherical nanocavities, the surface energy decreases by increasing nanocavity radius. Also, the surface energy variation with size is more intense for nanocavities in comparison with nanoparticles. By increasing the radius, the surface energy of nanoparticles and nanocavities approaches to an asymptotical value, which is the surface energy of a crystalline flat surface or the Gibbs surface energy for the crystallographic surface orientation with the maximum surface energy.
Volume 19, Issue 122 (April 2022)
Abstract
Pectin is used as a coagulant in the food industry due to its thickening properties. Also, the polysaccharide is widely used in the food industry, which is due to its unique technological properties (its gelling properties in the production of jams and like jams such as fruit, etc.). The aim of this study was to optimize and evaluate the quantitative and qualitative evaluation of pectin extraction from apple pomace by microwave and acid extraction method. Microwave extraction efficiency in the pH range of 1.22 to 1.78, time 10.6 to 17.4 minutes and power 320 to 580 W and by acid extraction method in the pH range of 1.5 to 2, time 60 to 90 minutes and temperature of 75 to 90 °C was optimized by the response surface method (RSM). The results showed that in microwave extraction at pH 1.22, time 17.4 minutes and power 580 W and in acid extraction method at pH 1.5, temperature 90 °C and time 90 minutes maximum extraction efficiency (9.17 and 8.83% respectively) were observed. Also, under optimal microwave extraction conditions, pectin with better quality characteristics (higher degree of esterification, galacturonic acid, equivalent weight, methoxyl content, emulsifying activity and water holding capacity) was obtained than the traditional method.
Volume 21, Issue 2 (4-2014)
Abstract
Modern-minded man, as the modern time necessities, believes in the concrete world, and if does not deny metaphysics, he finds it unperceivable and unreachable and hence, ignores some of his potential and spiritual abilities.
Metaphysics form man’s spiritual life, absence of which results in mental nervousness and leads to nihilism, and thus death, men’s inevitable final destiny, appears like a monster. To be away from which and forget it, man requires engaging himself in the concrete, and not reflecting upon death at all.
This paper attempts to investigate the questions as: How does Molavi perceive metaphysics? How does he engage himself with it? And while he follows his religious and spiritual way of thinking, how the face of death is displayed in Molavi’s thoughts?
Molavi’s works represent a human’s perception and experience gained from the Prophets’ teachings which were put into practice in Molavi’s own life. One can find lots of Molavi's couplets dealing with the same, pondering upon which can smooth the harshness of the concrete world in the light of the spiritual world, and generate yet another type of world
