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saifkordi--aliakbar
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Experimental Study of the β-CD-g-PG Hybrid Nanostructure On Phase Solubilityof Hydrophobic Drug
, M.Sc. Thesis Sharif University of Technology ; 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...
Investigation of mass transfer coefficient under jetting conditions in a liquid-liquid extraction system
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 29, Issue 1 , 2010 , Pages 1-12 ; 10219986 (ISSN) ; Omidkhah, M. R ; Bastani, D ; Saifkordi, A. A ; Sharif University of Technology
2010
Abstract
In this research mass transfer coefficient under jetting regime in different directions (from dispersed to continuous and continuous to dispersed phase) has been studied using an experimental setup. n-Butanol-succinic acid-water with low interfacial tension has been selected as experimental chemical system. The effects of various parameters such as jet velocity, nozzle diameter and the height of the continuous phase above the nozzle, on mass transfer coefficient have been investigated. A correlation has also been derived in order to predict the mass transfer coefficient as a function of physical properties of both phases and aforementioned parameters. Based on the experimental results, mass...
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) ; 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) ; 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 ; 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 ; 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) ; 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) ; 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 ; 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...
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) ; 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) ; 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 ; 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
Microstructure and Mechanical Properties of Two-step TLP Bonded 304 Stainless Steel with a Cobalt base Interlayer
, M.Sc. Thesis Sharif University of Technology ; 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...
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 ; 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...
Spot Resistance Welding of St12 and HSLA Steels in Different Thicknesses
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amirhosein (Supervisor) ; Ekrami, Aliakbar (Supervisor)
Abstract
High-strength low alloy (HSLA) E275 developed specifically for automotive application. Also St12 Steel is used in autobodies. On the other hand the resistance spot weld of dissimilar materials is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. The influence of the primary welding parameters affecting the heat input such as; current and time on the morphology, fracture mode, microhardness, and tensile shear load bearing capacity of dissimilar welds between HSLA E275 steel and St12 steel in two different thicknesses (1,2 mm) has been investigated in this study which consisted six group. The...
Investigation on Wettability Alteration of Reservoir Rocks by Functionalized Silica Nanoparticles using Molecular Dynamics Simulations
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Aliasghar (Supervisor) ; Seyfkordi, Aliakbar (Supervisor)
Abstract
The properties of 3 nm-diameter fluorinated silica nanoparticles with different coverage percent of CF3 groups as water and oil repellents were investigated at the water-rock and decane-rock interface using molecular dynamics simulation. Simulating a pore of rock in presence of water and decane molecules separately, resulted in liquid bridging for both of liquids. The density profiles of liquids in the pore clearly show several highly ordered layers packing of the molecules close to the rock surface. Distribution of liquid molecules around the nanoparticles is much influenced with increasing CF3 groups on the nanoparticle surface. Results show that adsorption of functionalized silica...
Fuzzy Dark Matter and its Impacts on the Structure and Statistics of Halos
, Ph.D. Dissertation Sharif University of Technology ; Abolhasani, Aliakbar (Supervisor) ; Namjoo, Mohammad Hossein (Supervisor)
Abstract
According to the standard model of cosmology, around 26% of the universe’s energy content consists of a type of cold matter with minimal non-gravitational interaction, known as ”dark matter.” The standard ”cold dark matter” (CDM) can successfully explain observations across various scales. However, it faces challenges on small (galactic) scales, such as the ”core-cusp problem,” ”the missing satellite problem,” and ”the too-big-to-fail problem.” Fuzzy dark matter is a promising candidate for dark matter. It is characterized by its ultra-light mass, which gives rise to wave effects at astrophysical scales. These effects offer potential solutions to small-scale issues. In this thesis, we...
Corrosion and Crack Monitoring of Pipelines Using an Equivalent Electrical and Bond Graph Model
, M.Sc. Thesis Sharif University of Technology ; Khayyat, Amir Aliakbar (Supervisor) ; Zabihollah, Abolghasem (Co-Advisor)
Abstract
Pipeline systems have a major role in civil infrastructure for transportation of energy sources including, petroleum, natural gas, and water. As most pipelines are located in hard-access location such as underground and sea as well as mountains, they are vulnerable to corrosion, cracks and thus, unpredictable failure. Failure of pipelines not only costs millions of dollars but also causes environmental damage, requiring continuous health monitoring systems to provide early detection and early warning of flaws such as corrosion and leaks. Structural health monitoring based on ultrasonic guided waves is used in structures as plates, composites, rods, piping and tubing. This research aims to...
General noise considerations of amplified photons in lightwave systems with optically bistable elements
, Article Proceedings - 10th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2010, 12 September 2010 through 14 September 2010 ; 2010 , Pages 93-95 ; 9781424469970 (ISBN) ; Naqavi, A ; Mehrany, K ; Mousavi, S. M ; Aliakbar, J ; Mousavi, S. M ; Sharif University of Technology
2010
Abstract
An optical amplifier followed by a bistable element has been statistically analyzed before [1]. In this manuscript, output noise analysis represents, then signal to noise ratios (SNR) are calculated either for input or output. It will be shown that noise reduction, can be achieved by a proper selection of parameters
Experimental Investigation and CFD Simulation of the Flow Pattern of the FCC's Fluidized Bed Regenerator
, M.Sc. Thesis Sharif University of Technology ; 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...