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    Experimental Investigation and CFD Simulation of the Flow Pattern of the FCC's Fluidized Bed Regenerator

    , M.Sc. Thesis Sharif University of Technology Azarnivand, Abbas (Author) ; Dehkordi, Asghar Molaei (Supervisor) ; Seifkordi, Aliakbar (Supervisor) ; Behjat, Yaghoub (Supervisor)
    Abstract
    Hydrodynamic behavior of gas-solid fluidization in large-diameter beds like FCC regenerator exhibits complex aspects. To investigate the gas-solid flow pattern of UOP's combustor-style FCC regenerator, a lab-scale regenerator was designed by a downscale factor of 0.045. The regenerator's operation and fluidization of FCC particles through it was examined and pressure axial distributions were measured and analyzed at different superficial air velocities. 3D CFD simulation of the regenerator was performed with Eulerian-Eulerian approach to investigate the effects of operating conditions, including superficial air velocity, catalyst mass flux, presence of recirculated catalyst, and the... 

    Facilitation of Transscleral Drug Delivery

    , M.Sc. Thesis Sharif University of Technology Mousavi Khamene, Zeynab (Author) ; Abdekhodaie, Mohammad Jafar (Supervisor) ; Seifkordi, Aliakbar (Supervisor) ; Ahmadieh, Hamid (Co-Supervisor)
    Abstract
    In the present research the methods and challenges to ocular drug delivery have been investigated with more emphasis on ocular diseases that do not have any approved treatment. Periocular route is a promising alternative to the common routes of ocular drug delivery especially for treatment of posterior eye diseases. Based on barriers for efficient drug delivery to the eye, magnetic drug targeting revealed to be influential to eliminate some obstacles of this route which has not been worked before. It is hypothesized that the particles can pulled into the eye or will be trapped inside the sclera tissue or even if it is not happened, they can stay behind the sclera and magnetic force can... 

    Comparison of gas phase intrinsic properties of cytosine and thymine nucleobases with their O-alkyl adducts: Different hydrogen bonding preferences for thymine versus O-alkyl thymine

    , Article Journal of Molecular Modeling ; Volume 19, Issue 8 , 2013 , Pages 2993-3005 ; 16102940 (ISSN) Aliakbar Tehrani, Z ; Fattahi, A ; Sharif University of Technology
    2013
    Abstract
    In recent years, there has been increasing interest in damaged DNA and RNA nucleobases. These damaged nucleobases can cause DNA mutation, resulting in various diseases such as cancer. Alkylating agents are mutagenic and carcinogenic in a variety of prokaryotic and eukaryotic organisms. The present study employs density functional theory (DFT/B3LYP) with the 6-311++G(d,p) basis set to investigate the effect of chemical damage in O-alkyl pyrimidines such as O4-methylthymine, O2-methylcytosine and O 2-methylthymine. We compared the intrinsic properties, such as proton affinities, gas phase acidities, equilibrium tautomerization and nucleobase pair's hydrogen bonding properties, of these... 

    Conformational aspects of glutathione tripeptide: Electron density topological & natural bond orbital analyses

    , Article Structural Chemistry ; Volume 24, Issue 1 , 2013 , Pages 147-158 ; 10400400 (ISSN) Aliakbar Tehrani, Z ; Fattahi, A ; Sharif University of Technology
    2013
    Abstract
    Glutathione tripeptide (γ-glutamyl-cysteinyl-glycine) is a flexible molecule and its conformational energy landscape is strongly influenced by forming intramolecular hydrogen bond, its charge and the environment. This study employs DFT-B3LYP method with the 6-31+G (d,p) basis set to carry out conformational analysis of neutral, zwitterionic, cationic, and anionic forms of glutathione. In analyzing the structural characteristics of these structures, intramolecular hydrogen bonds were identified and characterized in details by topological parameters such as electron density ρ(r) and Laplacian of electron density Δ2 ρ(r) from Bader's atom in molecules theory. Charge transfer energies based on... 

    Dynamical Systems Approach to Interacting Dark Energy Models

    , M.Sc. Thesis Sharif University of Technology Pirayesh, Behnam (Author) ; Abolhassani, Aliakbar (Supervisor)
    Abstract
    This thesis studies the possible solution to the H0 tension via a dynamical systems approach. The early dark energy (IDE) scenario can somewhat alleviate the Hubble constant tension. On the other hand, postulating a new subdominant EDE in the pre – recombination Universe can also resolve the H0 tension. We introduce a novel model to interweave the early dark energy(EDE) and interacting dark energy-dark matter (IDE) scenarios. In this scenario, the early dark energy emerges naturally by changing the topological class of the phase portrait of the universe dynamics. In particular, an EDE component contributing only 10% of the matter density of the Universe—preferably in the vicinity of the... 

    Mechanical Properties of TLP bonded SS304 by Two Steps Heating

    , M.Sc. Thesis Sharif University of Technology Bahrehmand, Mohammadreza (Author) ; Ekrami, Aliakbar (Supervisor)
    Abstract
    Austenitic stainless steels are the most common kinds of stainless steels. Although these alloys are generally very weldable, there are some problems in join- ing of them using fusion welding. Solidification and liquation cracking or corrosion at grain bound- aries in the heat-affected zone are examples of these problems. Transient liquid phase (TLP) bonding is an important variation of diffusion bonding that has the potential to overcome this problems. Two-step TLP bonding is an ingenious development to form non-planar interface. This method consists of a short-time high temperature heating to melt interlayer followed by isothermal solidification of liquid phase at a lower temperature. In... 

    Influence of metal complexation on acidity of cytosine nucleosides: Part I, Li +, Na + and K + cation

    , Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 535-545 ; 10263098 (ISSN) Aliakbar Tehrani, Z ; Fattahi, A ; Pourjavadi, A ; Sharif University of Technology
    2012
    Abstract
    Gas-phase acidities of nucleosides, combined with the knowledge of deprotonation sites, could improve our understanding of chemical reactions to biological systems. In this paper, we mainly focus our attention on the influence of cation coordination on acidities of multiple sites in cytosine nucleosides. The acidities of multiple sites in M +-L (where L represents cytosine nucleosides and M + is an alkali metal ion, including Li +, Na + and K +) complexes have been investigated theoretically, employing B3LY P6-311++G(d,p) basis sets. The geometrical characters, gas-phase acidities, sugar puckering and electronic properties of non-deprotonated and/or deprotonated complexes have been... 

    Conformational behavior and potential energy profile of gaseous histidine

    , Article Journal of Molecular Structure: THEOCHEM ; Volume 960, Issue 1-3 , November , 2010 , Pages 73-85 ; 01661280 (ISSN) Aliakbar Tehrani, Z ; Tavasoli, E ; Fattahi, A ; Sharif University of Technology
    2010
    Abstract
    Histidine as a natural amino acid is found to be biologically important and is known to function as a nucleophile or enzyme co-factor, or in proton transfer process. The properties of gaseous aromatic amino acid histidine depend on the structural forms it may take in gas-phase. Ab initio method has been used to characterize the gas-phase conformer/tautomers of histidine. Wide range of possible structures for histidine was surveyed at the MM level, and then the geometries of the unique conformers were refined at the B3LYP/6-311++G (d,p) levels. At this theoretical level, 25 conformers were located for both tautomers of histidine i.e., His [NπH] and His [NτH]. The MM level provides a poor... 

    Warm Inflation Model in Effective Field Theory of Axion Monodromy

    , M.Sc. Thesis Sharif University of Technology Ghomi Shurkai, Reza (Author) ; Abolhassani, Aliakbar (Supervisor)
    Abstract
    Temerature fluctuation of the Cosmic Microwave Background (CMB) is one of the key observebles of the modern cosmology. Today, it is widely believed that quantum fluctuation that are stretched to horizon scales during a period of acceleration expansion -- at the onset of evolution of the universe-- are responsible for these perturbations. In the simplest scenarios of the inflation, a scalar field is responsible for both nearly expansional expansion of the universe and the proimordial fluctuations. In this thesis, we investigate the models of inflation with an additional light degree of freedom. In particular, we employ the method of the Effective Field Theory to study the general structure... 

    Investigation into some parameters affecting pectin gel quality

    , Article Scientia Iranica ; Volume 14, Issue 2 , 2007 , Pages 174-179 ; 10263098 (ISSN) Ebrahimi, B ; Alemzadeh, I ; Seifkordi, S. K ; Sharif University of Technology
    Sharif University of Technology  2007
    Abstract
    In this research, gel production from the extracted pectin gel of shahroud sugar beet pulp has been investigated. The pectin extractions were performed in a cold alkaline solution and a hot acid solution, respectively. The effects of different parameters, such as percent of sugar, pectin concentration, calcium content and quantity of peroxidase enzyme, hardness and content of water absorbed by the gel, were studied. Optimum conditions for production of favorable gel, from extracted pectin in this research are, as follows: Percent of sugar (glucose): 15%, peroxidase enzyme content: (pectin unit) 170 pu/g of pectin, pectin concentration (if only gel water uptake is important): 10%, pectin... 

    Computational investigation of thermochemical properties of non-natural C-nucloebases: Different hydrogen-bonding preferences for non-natural Watson-Crick base pairs

    , Article Structural Chemistry ; Volume 24, Issue 4 , 2013 , Pages 1015-1025 ; 10400400 (ISSN) Aliakbar Tehrani, Z ; Shakourian Fard, M ; Fattahi, A ; Sharif University of Technology
    2013
    Abstract
    In the present density functional theory study, we have compared intrinsic properties of non-natural nucleobases (acA, acG, acC, and acT nucleobases) such as proton affinities, gas phase acidities, tautomerization, and hydrogen-bonding properties with those in normal Watson-Crick nucleobases (A, G, C, T nucleobases). The hydrogen-bonding interactions in non-natural and Watson-Crick base pairs were studied at B3LYP/6-311++G (d,p) level regarding their geometries, energies, and topological features of the electron density. The quantum theory of atoms-in-molecule (QTAIM) and natural bond orbital (NBO) analyses were employed to elucidate the interaction characteristics in base pairs. The... 

    DFT study of the interaction of cytidine and 2′-deoxycytidine with Li+, Na+, and K+: effects of metal cationization on sugar puckering and stability of the N-glycosidic bond

    , Article Carbohydrate Research ; Volume 344, Issue 6 , 2009 , Pages 771-778 ; 00086215 (ISSN) Aliakbar Tehrani, Z ; Fattahi, A. R ; Pourjavadi, A ; Sharif University of Technology
    2009
    Abstract
    Density functional theory (DFT) calculations were performed at the B3LYP level with a 6-311++G(d,p) basis set to systematically explore the geometrical multiplicity and binding strength for complexes formed by Li+, Na+, and K+ with cytidine and 2′-deoxycytidine. All computational studies indicate that the metal ion affinity (MIA) decreases from Li+ to Na+ and K+ for cytosine nucleosides. For example, for cytidine the affinity for the above metal ions are 79.5, 55.2, and 41.8 and for 2′-deoxycytidine, 82.8, 57.4, and 42.2 kcal/mol, respectively. It is also interesting to mention that linear correlations between calculated MIA values and the atomic numbers (Z) of the above metal ions were... 

    Non-linear Effects on "linear point" through Analytical Methods

    , M.Sc. Thesis Sharif University of Technology Farhadi Mahalli, Nematollah (Author) ; Abolhassani, Aliakbar (Supervisor)
    Abstract
    By studying of simulations, it can be seen that the linear point (LP), a point lies midway between the scales associated with the peak and the dip in the correlation function on BAO scales, is a useful window into cosmology and large scale structures rather than baryonic echo peak. Some fundamental features of the LP, been unaffected by redshift space distortions and gravitational non-linear effects, has made it important. I want to find evidences to stability of the LP by utilizing Standard Perturbation Theory through my thesis  

    Liquid-Liquid equilibrium data, density, viscosity, and interfacial tension of ternary system (Toluene-Acetic Acid-Water) at 298.15 K: Experiment and correlation

    , Article Journal of Chemical and Engineering Data ; Volume 62, Issue 12 , 2017 , Pages 4133-4143 ; 00219568 (ISSN) Memari, M ; Molaei Dehkordi, A ; Seifkordi, A. A ; Sharif University of Technology
    2017
    Abstract
    Liquid-liquid equilibrium (LLE) data, density, viscosity, and interfacial tension for the ternary system of toluene-acetic acid-water were measured at 298.15 K and 101.7 kPa. The Othmer-Tobias and the Hand correlations were used to check the reliability of the experimental tie-lines. Moreover, the distribution coefficient and the separation factor were explored. It was found from the experimental results that a maximum separation factor value happens at an acetic acid mass fraction of 0.02 in the organic phase. Density, viscosity, and interfacial tension were correlated using the appropriate correlations such that the predicted results have excellent agreement with the experimental data. The... 

    Microstructure and Mechanical Properties of Two-step TLP Bonded 304 Stainless Steel with a Cobalt base Interlayer

    , M.Sc. Thesis Sharif University of Technology Amini, Ali (Author) ; Pouranvari, Majid (Supervisor) ; Ekrami, Aliakbar (Supervisor)
    Abstract
    Considering the wide applications of 304 stainless steel in various industries and the existing literature on transient liquid phase bonding of stainless steels with a variety of interlayers, the present work aimed to reduce the bonding time by using a two step bonding method. Faster bonding reduces both energy consumption during bonding and the base metal grain growth. It also leads to a lower reduction in the base metal and joint strength.Due to the melting point of the interlayer, different durations and a temperature of 1200°C were selected for the first step. This temperature was maintained for a specified period of time before it sharply dropped to and remained at 1180°C (the... 

    Separation of CO2/CH4 through alumina-supported geminal ionic liquid membranes

    , Article Journal of Membrane Science ; Vol. 455 , 2014 , pp. 229-235 ; ISSN: 03767388 Shahkaramipour, N ; Adibi, M ; Seifkordi, A. A ; Fazli, Y ; Sharif University of Technology
    2014
    Abstract
    Interesting properties of ionic liquids lead to their application as sub-component of membrane structures. Supported ionic liquid membranes (SILMs) are porous membranes whose pores are saturated with ionic liquids. Two ionic liquids, pr[mim]2[Tf2N]2 [1,3-di(3-methyl-imidazolium) propane bis(trifluoromethylsulfonyl) imide] and, h[mim]2 [Tf2N]2 [(1,6-di(3-methylimidazolium)hexane bis(trifluoromethylsulfonyl)imide)], were synthesized in our laboratory and stabilized on an alumina porous support. Permeability and permselectivity of carbon dioxide and methane using membranes containing these ionic liquids were then measured. The experiments were performed in the pressure range of 10-50kPa and... 

    Preparation and investigation the release behaviour of wax microspheres loaded with salicylic acid

    , Article Journal of Microencapsulation ; Volume 26, Issue 6 , 2009 , Pages 485-492 ; 02652048 (ISSN) Gifani, A ; Taghizadeh, M ; Seifkordi, A. A ; Ardjmand, M ; Sharif University of Technology
    2009
    Abstract
    Salicylic acid-beeswax microspheres were prepared by melt dispersion technique. The effects of formulation parameters on the microscopic characteristic, drug loading and cumulative amount of released drug were investigated by experimental design. Results showed that all of the microparticles were spherical with porous surfaces. The average size of microspheres was 2448 m, the drug content was in the range of 2245 and the encapsulation efficiency was 4693. Drug loading was influenced by emulsification speed as a main factor. All the microspheres had a burst release initially. The emulsifier concentration did not have a significant effect on drug release. The release behaviour of microspheres... 

    Gum tragacanth gels as a new supporting matrix for immobilization of whole-cell

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 24, Issue 4 , 2005 , Pages 1-7 ; 10219986 (ISSN) Otady, M ; Vaziri, A ; Seifkordi, A. A ; Kheirolomoom, A ; Sharif University of Technology
    2005
    Abstract
    We introduce a new smooth, non-toxic, biocompatible method for cross-linking of gum tragacanth (GT), a polysaccharide of natural origin, in order to serve as a new supporting matrix for immobilization systems. The modified gum is used as a matrix for the catalysis of the conversion of benzyl penicillin to 6-aminopenicillanic acid (6-APA) by means of Escherichia coli ATCC11105 with penicillin G acylase (PGA) activity. The results show that GT beads can not only serve as a proper matrix for immobilization, but show enhanced hydrolysis rate and stability compared to other immobilization systems used for this reaction. This signifies the potential of GT as a biocompatible matrix for... 

    Experimental Study of the β-CD-g-PG Hybrid Nanostructure On Phase Solubilityof Hydrophobic Drug

    , M.Sc. Thesis Sharif University of Technology Asadi, Farshid (Author) ; Saifkordi, Aliakbar (Supervisor) ; Vossoughi, Manouchehr (Supervisor)
    Abstract
    Some widely used drugs such as paclitaxel (PTX) are poorly water soluble. The clinical use of PTX with solubilizer causes side effects. These problems limited its application in treatments. In this work has been studied the effect of β-CD-g-PG (HPCD) hybrid nanomaterials, conjugated PG branches onto β-CD core, on the water solubility of PTX. First HPCD has been synthesized. Then the inclusion complex of PTX with HPCD was prepared. The inclusion complex efficiency for PTX:HPCD complex in 1:25 mole ratio was 87%. Then solubility of PTX with HPCD in water has been determined, showing Ap type phase solubility diagram. Then stability constants were calculated. The first order and second order... 

    Designing and Fabrication of a Wearable Colorimetric Biosensor Based on Polyvinyl Alcohol Hydrogel with the Help of Machine Learning to Detect Glucose Concentration and PH Level of Body Sweat

    , M.Sc. Thesis Sharif University of Technology Chenani, Hossein (Author) ; Simchi, Abdolreza (Supervisor) ; Ekrami, Aliakbar (Supervisor)
    Abstract
    Simultaneous detection of pH and glucose levels in sweat is a promising tool for early skin disease detection and diabetes diagnosis. Hydrogels have attracted a lot of attention in the field of wearable biosensors due to sweat absorption capability, biocompatibility, and the ability to store enzymes and reagents in their cavities. In this research, we have presented an innovative wearable colorimetric biosensor based on polyvinyl alcohol (PVA) hydrogel, which can simultaneously measure pH level (in the range of 3-9) and glucose concentration (in the range of 0.025-0.5 mM) of sweat with the help of machine learning (ML). This wearable sensor consists of two main parts: sensors and a patch, in...