Sharif Digital Repository

The use of protons and charged particles such as carbon in the treatment of cancerous tumors is one of the new methods of external radiation therapy. Proton therapy can achieve almost the same tumor dose coverage as traditional photon therapy with a greatly reduced dose to the normal organ. The radiation deviations caused by the magnetic field are an effective factor in reducing the dose of vital organs without sacrificing the dose coverage of tumors; Therefore, a new method of proton therapy, called magnetic field-modulated proton therapy, has been proposed, in which the Bragg peak positions of proton beams can be modulated under the cover of predesigned magnetic fields inside cancer... 

Proton precession magnetometers are one of the most sensitive scalar magnetic sensors. Their function is based on Zeeman effect and also nuclear magnetic resonance phenomena. In this project we have designed and implemented needed coils, swithching and signal detection circuits. Because of extremely high sensitivity of this sensor to induced noises and also gradient of earth’s magnetic fileld, detection of precession signal needs design of low noise electronic circuits with special EMC considerations. The implemented system in this project contains different blocks, such as switching circuit and its related control unit, amplifier, filter and frequency meter. Using this system, the obtained... 

Molecular nanomagnets, also known as Single Molecule Magnets (SMMs) are a class of molecules that at low temperature exhibit magnetic hysteresis of pure molecular origin and not related to a cooperative effect. In the past fifteen years they have attracted great interest for their potentiality to act as magnetic memory units and for the many quantum effects in the dynamics of their magnetization. Organization of SMM on surfaces is the first step in order to address the magnetic state of a single molecule or to connect the molecule to a conducting substrate. The complex nature of SMMs and the peculiar origin of their magnetic bistability have been representing for half a decade an obstacle to... 

Obesity is a worldwide growing health challenge affecting ~30% of the world's population. Increased rate of disc degeneration and herniation, low back pain and surgery has been reported in obese individuals. Although obesity-related low back diseases have multifactorial etiology, presumably greater mechanical loads on the spine of heavier individuals during their daily activities may be considered as a risk factor. Likely larger trunk muscle sizes, disc sizes and thus passive stiffness in heavier individuals may however partly or fully offset the effect of their additional body weight on the spinal loads. In absence of in vivo approaches, the present study aims to construct subject-specific... 

This thesis is about multidisciplinary design optimization of MRI ¬controlled robots with a nonlinear model approach in the cardiovascular system and simulates its behavior to reach cancer cells. Such robots, designed to perform medical procedures with minimal side effects to the patient, include a set of ferromagnetic nanoparticles attached to the polymer and disposable drugs such as cancer drugs.The disciplines considered in this issue include structure, hydrodynamics, propulsion, controllability, and trajectory. The proposed model in this study, in addition to the main forces acting on the robot such as magnetic force, hydrodynamics, and apparent weight, also examines other forces due to... 

Using free laccase, enzymatic decolorization of two azo dyes were optimized. The optimum conditions with the aim of maximizing the decolorization of AB92 dye (92.30%) were: dye concentration = 11.85 mg L-1, pH = 5.1, and enzyme concentration = 98.37 mg L-1. While, these conditions to achieve the maximum decolorization yield of DR23 (95.60%) were: dye concentration = 17.68 mg L-1, pH 3.7 and enzyme concentration =97.89 mg L-1.In the second part, the laccase enzyme was covalently immobilized onto GO nanosheets. At the concentration of graphene oxide and laccase enzyme equal to 1 mg mL-1 and 0.9 mg mL-1, respectively, the enzyme loading was 156.5 mg g-1 and the immobilization efficiency was... 

Spin-Transfer Torque Magnetic RAM (STT-MRAM) is known as the most promising replacement for SRAM technology in cache memories. Despite its high-density, non-volatility, near-zero leakage power, and immunity to radiation-induced particle strikes as the major advantages, STT-MRAM-based cache memory suffers from high error rates mainly due to retention failure, read disturbance, and write failure. Despite its high-density, non-volatility, near-zero leakage power, and immunity to radiation as the major advantages, STT-MRAM suffers from high error rates. These errors, which are mainly retention failure, read disturbance, and write failure, are the major reliability challenge in STT-MRAM caches.... 

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... 

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... 

Titanomagnetites are resources of iron and titanium. high level of titanium in titanomagnetites makes using them in iron making processes very difficult. In this work an attempt was made to produce an iron bearing and a titanium bearing product using solid state reduction of Fanouj mine titanomagnetite concentrate. For this purpose, the concentrate was reduced using coal and then was subjected to magnetic separation. In this work, effect of temperature, time, added coal amount, and additive amount on reduction was studied. The result showed that the optimum conditions are 1325 celsius degree, 2.5 hours, 25 percent added coal and 2 percent additive. In optimum conditions a magnetic product... 

Iron oxide nanoparticles were synthesized using microemulsion technique as MRI contrast agents. Utilization of nanoparticles for biological applications and in this case as MRI contrast agents needs particles to be of small size and also narrow size distribution. For this aim, the effect of several parameters on size and size distribution has been studied. These parameters include water/surfactant ratio, precursor’s concentration and amount of polymer employed to improve nanoparticles colloidal stability. XRD, FE-SEM and TEM results reveal that the synthesized nanoparticles had small size (about 10 nm iron oxide core and 20 nm overall diameter) and possessed narrow size distribution (15-21... 

Micro-robotics is one of the currently emerging technologies which has attracted attentions for its probable applications in different fields including biotechnology, diagnosis and treatment in medical engineering as well as general studies in micro-scale science and engineering. Magnetic micro-robotics is considered as the most promising group, primarily due to the biocompatibility of magnetic fields and advances in electronic circuits to produce and control such fields. One critical point in utilizing these robots is their high density in comparison with the working fluid and their tendency to sink. In this thesis, a method to fabricate buoyant magnetic robots has been proposed based on... 

In this work, synthesized Fe3O4 magnetic nanoparticles andcoated with SiO2 to prepare magnetic core-shell nanoparticles. Then immobilized Schiff baseof iron and vanadium complexes on magnetic core-shell nanoparticles was prepared as a recoverable magnetic nano catalysts. These catalysts were named Fe3O4@SiO2@L1@Fe, Fe3O4@SiO2@L2@Fe and Fe3O4@SiO2@L3@V. Furthermore,olefines epoxidation, sulfides and alcohols oxidation were studied with using iron and vanadium magnetic nano catalysts. The supported catalysts were characterized by atomic absorption, FT-IR and UV–Vis spectra.The catalytic performance of the synthesized iron catalyst was tested for the epoxidation of cyclohexene, styrene and... 

Objective: Joint analysis of multi-subject brain imaging datasets has wide applications in biomedical engineering.In these datasets, some sources belong to all subjects (joint), a subset of subjects (partially-joint), or a single subject (individual). In this thesis, this source model is referred to as joint/partiallyjoint/individual multiple datasets unidimensional (JpJI-MDU), and accordingly, a source extraction method is developed.Method: We present a deflation-based algorithm utilizing higher order cumulants to analyze the JpJI-MDU source model. The algorithm maximizes a cost function which leads to an eigenvalue problem solved with thin-SVD (singular value decomposition) factorization.... 

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,... 

Our goal in this research is to fabricate janus micromotors capable of moving in aquious media and being manipulated by an external magnetic field. Such devices were made via attaching magnetic nanoparticles to the surface of magnesium janus motor. The FTIR study proved their existance and physical attraction to the surface of the motors. They were easily navigated through a static magnetic field and janus motors aligned their motion to the direction of magnetic field. The anisotropic geometry of janus micromotors were verified through scaning electron microscope and elemental analysis. Biocompatibility of magnetised janus motors were examined through mtt assay and it was shown that the... 

Modified zeolitic nanostructures were prepared by sol-gel, hydrothermal and coprecipitation methods. At first step, natural zeolite was used as a support for preparing the Ag/AgBr/TiO2 photocatalysts. Their photocatalytic properties were studied by degradation of pollutants and microorganism inactivation at the presence of different illumination source. These processes were mechanistically investigated and the results were explained. At second step, mordenite anocrystals, which synthesized by hydrothermal method, were used as an effective support to prepare the AgX/TiO2/MOR photocatalysts. Photocatalytic degradation of an azo dye performed over these nanocomposites and a mechanism suggested... 

Base isolation is a method for controlling the vibration of structure by modifying the transmission between the source of excitation and the vibration structure.In this thesis, the feasibility of using magnetic field in seismic response control of structures has been investigated. It is tried with the inspiration of magnetic trains. While the old trains ran on the rail lost a large amount of energy because of the friction between the wheels and the rails that decreased the train speed, in the maglev trains with separating them from the rail the friction is reduced to the least amount so that today these trains are able to run with the speed about 550 km/h. It has been tried in two concepts... 

Conventional MRI has been used to diagnose different types of brain injuries. However these methods have generally failed to diagnose mild types of injury. We are working on the specification of mild traumatic brain injury, using diffusion MRI data, based on a multi compartment simulation of white matter tissue. This effort is essential for better understanding of underlying tissue micro-structure changes in patients with trauma. Some studies have been used in similar data fitting approaches in order to estimate axon diameter distribution. Specifically, a comparative study between different Compartment Models has shown that “ActiveAx” model has the best agreement with underlying tissue... 

In recent years, much attention has been paid to the development of biofunctionalized nanoparticles with special magnetic properties for using in clinical imaging. Targeted magnetic materials with high MRI signal intensity can be used in tissue imaging and molecular and cellular detection as valuable tools. The aim of this study has been to synthesize the nanocomposite including the functional gadolinium oxide (Gd2O3) nanoaprticles for MRI contrast agent. Synthesis and in-situ surface modification of ultrasmall Gd2O3 nanoparticles (2.5nm) with PVP was performed by a microwave modified polyol in 5 min. The structure and size of synthesized nanoparticles were studied using X-ray diffraction...