Sharif Digital Repository

NMR spectroscopy as a powerful technique is often used to investigate on structural and conformational studies on proteins and drug compounds. In this work, conformations and structural properties of drug compounds and some nucleoside derivations have been studied using advanced NMR techniques including H-H COSY, HMQC, HMBC and NOESY and quantum based calculations.Experimental analysis on Valsartan show that there are two simultaneous conformers (M and m) with unequal population in M-m type solvents and two stable conformers (N and n) in the N-n type solvents. As the results show, different intramolecular hydrogen bond is the reason for stability af all available conformers. In the... 

In this project rotational barrier around the C-N bond in 4-ethyle-morpholine- carboxylate has been studied using DNMR spectroscopy. Spectra were taken at variable temperature, and then with simulation of bandshape broadening pattern at coalescence region, rate constants of exchange were obtained for all temperatures. For simulation of line-shape broadening Spinworks software was used, that with two interfaces made possible simulation with two bandshape simulator programs, DNMR and MEXICO. The rate constants obtained from simulations, were used for calculation of thermodynamic activation parameters (∆G#, ∆H#, ∆S# and Ea). ∆G# 298 value of 13.66 Kcal/mol for 4-ethyle-morpholine- carboxylate... 

In this project, investigation of C-N internal rotation in ethyl tetrahydro-1(2H)-pyridine carbdithioate and ethyl 1-pyrrolidine carbodithioate were investigated by dynamic nuclear magnetic resonance spectroscopy. The 1HNMR and 13CNMR spectra were taken at the variable tempratures around the coalescence temprature. Thermodynamic parameters were calculated by analysing the spectra and the outcomes were compared by the theoretical results. For ethyl tetrahydro-1(2H)-pyridine carbdithioate ∆G‡ was 14.3 (kcal/mol) and for ethyl 1-pyrrolidine carbodithioate ∆G‡ was 17.0 (kcal/mol) which were in accordance with the theoretical results. The analysis were done by the Spinworks program which... 

The present work illustrates the results of an experimental study of ferrofluid flow in a tube subjected to a constant heat flux on its wall and filled with permeable material under the effect of magnetic field. The aim of this project is investigating the enhancement of heat transfer and obtaining a uniform temperature distribution inside the pipe. In order to achieve this, a porous medium with a porosity of 0.39 and ferrofluid with volume fractions of 0.6, 1.0 and 1.5 are used simultaneously, in the presence of magnetic field. The experiments are held for four different Reynolds numbers of 147.1, 167.3, 184.3 and 205.1. Also, four various modes of the oscillatory magnetic field are applied... 

The aim of this study was to investigate the rate of increase in temperature of a phantom equivalent to body tissue by different groups of magnetic iron nanoparticles in the external magnetic field to kill cancer cells based on the hyperthermia method. To achieve this goal, three groups of dextran magnetic nanoparticles with different properties and reduced iron oxide-graphene oxide magnetic nanoparticles by M-rGO supercritical synthesis method were used. After XRD, FTIR, SEM, FESEM, VSM, TEM characterization tests, these materials were placed in a phantom made of agarose gel and with the same properties, in a magnetic field with fixed characteristics for all groups and during the process of... 

The main methods have been used clinically for cancer treatment are included: surgery, chemotherapy, radiation therapy and hyperthermia. Hyperthermia (heat therapy) treatment method in which by raising the temperature of the tumor it removed. Magnetic hyperthermia is known as a kind of hyperthermia that have been represent appropriate results. In this study, using iron oxide nanoparticle coated with graphene for cancer treatment under a magnetic field of the laser. In the first stage, graphene oxide nanosheets and nanoparticles Magntayt are synthesized by chemical oxidation and co-precipitation, respectively. At the end, the nanoparticles on the substrate of graphene layer is obtained... 

Donor-acceptor adducts of selenium dioxide were formed with tree aromatic amines, two aliphatic amines and tree pyridine like bases. Characterization of these adducts were done through UV-Vis Spectrophotometer and IR Spectrophotometer and NMR Spectroscopy. In addition, the stoichiometry of these adducts were identified by elemental analysis (CHN). To approve the existence of selenium, Atomic absorption instrument was used.The results obtained from the entioned methods show that the adduct formation between selenium dioxide with amines and pyridine like bases are in following order: p-phenylen diamine.SeO2>NH5.SeO2,en.SeO2,cyclohexylamine.SeO2,... 

A novel magnetic heterogeneous copper catalyst was synthesized by immobilization ofcopper ion onto the triazole functionalized Fe3O4. The catalyst was fully characterized by FTIR, TGA, CHN, SEM, TEM, EDX and atomic adsorption spectroscopy. The resulting catalystwas used in the synthesis of 1,2,3-triazoles via one-pot three component reaction of alkynes,alkyl halides, sodium azides under green condition. The catalyst was reused for ten times andno significant loss of activity was observed. Supported gold (III) on poly(ionic liquid) coated on magnetic nanoparticles produced a highly active, stablerecoverable and high loading for the synthesis of propargylamines (A3 coupling reaction) under... 

In this thesis we have been mainly interested in studying Single Impurity Anderson model (SIAM) in Dirac fermions. Although this model seems to be simple, the rich physics of SIAM can not be underestimated. In this thesis we were interested in Dirac materials, systems which their low energy excitations are described by Dirac equation.Therefore, considering Dirac material in two dimensions(2D), we briefly review the distinct features of one atom thick layer of carbon. In addition, we will explain the effective Hamiltonian of Bismuth near L point which is considered a three dimensional(3D) Dirac material. Because of very strong spin-orbit interaction, bismuth is a key element in topological... 

Flying has fascinated mankind for ages. Nowadays, planar actuators are performing the same task as that, once a dream, of a flying magic carpet found in Persian mythology. Magnetically levitated planar actuators (MLPAs) consist of two parts; a moving part, and a stationary part. In most applications the moving part which is an array of permanent magnets (PMs) produces a magnetic flux density in the air-gap, and the stationary part, an array of current carrying coils, produces force and torque when it is exposed to the magnetic flux of the PM array. These actuators have been utilized in industry in applications where precise positioning is important. In recent years however, they have found... 

The good performance in cooling, especially in systems with small dimensions, is one of the critical needs of many industries. Heat transfer around sphere in all systems that contain particles, is important. Many methods have been proposed to improve the heat transfer rate but using nanofluids is one of the ways that has attracted more attention than others. Ferrofluids have magnetic properties in addition to nanofluids properties and this has a significant impact in increasing the heat transfer rate. Controlling heat transfer by magnetic field is one of the unique characteristics of this fluid. The project aim is to investigate the effect of magnetic field on heat transfer around sphere in... 

Among different mechanisems for ambient energy harvesters, energy harvesting systems by means of magnetic shape memory alloys are noted due to their long life time, large strain amplitudes and the ability to operate at low frequencies. Strain change in these systems, changes the MSMA magnetization resulting change in the magnetic flux leading to inducing voltage by means of pickup coil. in the commercial systems, magnetic flux path is created by inserting an MSMA specimen in the air gap of ferromagnetic core and generation of bias magnetic field by means of the permanent magnet or electromagnet. In this proposed research, a thermodynamic based constitutive model is selected for the mdeling... 

In the presented dissertation an analytical model is developed for the air gap flux density and the cogging torque in the axial flux surface-mounted PM machines. The slotting effect is taken into account in the magnetic flux distribution.The model is derived from solving the 2D Poisson' equation in the slotted air gap. To simplify the solution process, the concept of the uniqueness theorem is used to replace the slotted air gap by a slotless one and some surface current distribution. In addition, the separation of variables method is applied to the analytical solution of the Poisson equation. However, the proposed 2D analytical model is developed for the quasi 3D model by the well-known... 

Magnetic Shape Memory Alloys (MSMAs) are a category of active materials which can be excited by magnetic field. These alloys have been used in sensor and actuator applications recently. MSMAs posses special properties such as large magnetic field-induced strains (up to %10) and high actuation frequency (about 1kHz), while ordinary Shape Memory Alloys can’t act in frequencies above 5Hz due to the time involved with heat transformation. In this thesis, MSMAs are modeled by means of incremental modelling which is a useful method in analysis of nonlinear behaviour of materials. Furthermore, stress-strain curve of MSMA is approximated using an analytical expression whose parameters can simply be... 

Harvesting energy from renewable sources in nature, such as wind energy, solar energy, water energy and vibrations has always attracted researchers. There exist different ways to harvest energy from environmental vibrations. In this thesis, energy harvesting via Magnetic Shape Memory Alloys (MSMAs) has been taken into account due to important advantages of these alloys, such as their long fatigue life and good performance at high amplitudes and low frequencies.In this system, applying strain on alloy changes the magnetization and this change generates voltage in the pick-up coil around the MSMA. On the other hand, since the strain-magnetization relation is nonlinear and hysteresis,... 

Magnetic shape memory alloys (MSMAs) are a new class of smart materials that exhibit characteristics of large recoverable strains and high frequency. These unique characteristics, make MSMAs interesting materials for applications such as actuators, sensors, and energy harvesters. This thesis presents a three-dimensional phenomenological constitutive model for MSMAs, developed within the framework of irreversible continuum thermodynamics. To this end, a proper set of internal variables is introduced to reflect the microstructural consequences on the material macroscopic behavior. Moreover, a stress-dependent thermodynamic force threshold needed for variant reorientation is introduced which... 

Magnetic shape memory alloys (MSMAs) are a new kind of smart materials which are great alternatives for energy harvesting systems due to some unmatched characteristics such as reversible large strain, high cycle fatigue and fast time response. In this work, an energy harvesting system using MSMA is studied. For this goal, a 3-D thermodynamic-based MSMA model is applied for predicting magnetomechanical behavior of the MSMA sample which is used in the energy harvester system. Since demagnetization effect, which has a great influence on the model’s outputs, has been neglected in the selected MSMA model, a new approach is presented for inserting demagnetization coefficients, regarding to the... 

The purpose of this project is modeling and solving equation of an open cycle system based on MHD generator in order to achiving geometrical properties of generator shuch as length and cross sections of channel and extractable electrical power. In this work hydrogen is used as initial fuel and it’s combustion product near oxygen as working fluid in an open cycle system concluding of combustion chamber, convergence nozzle, farady generator with separated electrod’s and constant mach number and also diffuser. Motion of fluid is considered one dimentional and direction of magnetic field with magnitude of 2 tesla is assumed to be perpendicular to motion and electrical current directs. For... 

Magnetic gels and ferrogels are smart composite materials made by combining magnetic particles in a polymer matrix. These materials have been considered due to their special properties such as deformation and change of mechanical properties in the presence of external magnetic field. Having polymer properties along with the magnetic properties of metals, have led these materials to many uses such as drug delivery and artificial muscles. The increasing use of these materials has led researchers to continue research in the field of modeling ferrogels. Due to the porous nature of ferrogels, the ability to absorb a lot of liquid and their large deformations in the magnetic field, modeling of... 

Magnetic shape memory alloys (MSMAs) are a new class of smart materials which exhibit properties such as large reversible strains and high performance frequencies. These unique properties, offer magnetic shape memory alloys as an option in applications such as actuators, sensors and energy harvesters. In this thesis, the equations of magnetic shape memory alloys by considering nonlinear terms of Von karaman in strain-displacement relations, is expanded by using the theory of thin plates in two dimensions which can be used for plate equations with any boundary conditions by applying elastic boundary. In order to verify the obtained model, the equations of motions of magnetic shape memory...