Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"Magnetic field gradients"”.
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Correcting the variations of bold signal due to susceptibility-induced magnetic field gradients and its application
Functional magnetic resonance imaging (fMRI) using blood oxygenation level dependent (BOLD) signals is a tool that is currently used in many cognitive neuroscience studies. However, many studies do not consider susceptibility-induced magnetic field gradients. Susceptibility-induced magnetic field …
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Spatial aspects of nuclear magnetic resonance spectroscopy : static and radio-frequency magnetic field gradients in principle and practice
Thesis (Ph. D.)--Massachusetts Institute of Technology, Whitaker College of Health Sciences and Technology, 1997.
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Fundamental and practical limits to image acceleration in parallel magnetic resonance imaging
Imaging speed in conventional magnetic resonance imaging (MRI) is limited by the performance of magnetic field gradients and the rate of power deposition in tissue. Parallel MRI techniques overcome these constraints by exploiting information stored within the spatial sensitivity patterns of …
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Size based separation of submicron nonmagnetic particles through magnetophoresis in structured obstacle arrays
… scalable size based separation technology for nonmagnetic particles in the submicron size range utilizing magnetophoretic forces. When a nonmagnetic particle is immersed in a magnetic fluid and subjected to magnetic field gradients, it behaves like a magnetic hole and experiences magnetic buoyancy …
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Interaction of Nanoparticles with RF, AC, and Static Magnetic Fields in Thermal and Non-Thermal Cancer Therapy Applications
Electromagnetics plays a crucial role in the interdisciplinary science of addressing the complex problem of targeted cancer therapy. Thermal therapies such as radio-frequency and microwave hyperthermia and ablation techniques though effective in ablating tumors are non-target specific. The …
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Radiofrequency detector coil performance maps for parallel MRI applications
… which complements traditional encoding using magnetic field gradients. As the acceleration factor increases, coil design becomes critical to the overall image quality. The quality of a design is commonly judged on how it compares with other coil configurations. A procedure to evaluate the …
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Novel trapping techniques for shaping Bose-Einstein condensates
A combination of radio frequency radiation and magnetic field gradients was used to trap atoms in dressed states. In a magnetic field with a quadrupole minimum. RF fields resonant with the (I F. m)) 11. -1) -- 1, 0) transition trapped the atoms on the surface of a sphere, and gravity caused the …
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Nanoscale magnetic resonance imaging using silicon nanowire oscillators
… describes new techniques for nanometer-scale magnetic resonance imaging. We report methods that enable the use of (1) silicon nanowires as ultrasensitive force transducers for magnetic resonance detection and (2) pulsed magnetic resonance techniques for nanometer-scale imaging and …
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Magnetically enhanced centrifugation for continuous biopharmaceutical processing
… As an integrative technique, high gradient magnetic separation (HGMS), together with the application of functional magnetic particles, provides many advantages over traditional techniques. However, HGMS has a number of drawbacks; and its application is limited because it is inherently a …
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Towards MRI-Guided and Actuated Tetherless Milli-Robots
… patient management and cost effectiveness. Magnetic Resonance Imaging (MRI) is used for pre-operative planning and is also investigated for realtime intra-operative guidance. A new type of technology is emerging that uses the magnetic-field gradients of the MR scanner to maneuver …
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Explorations of quantum decoherence phenomena
… methodology uses liquid-state nuclear magnetic resonance spectroscopy techniques. Initially, a brief discussion of coherent control methods is given. Then, a detailed discussion of the decoherent control methods is presented. These methods describe how strong measurements can be …
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Advanced image reconstruction in parallel magnetic resonance imaging : constraints and solutions.
Imaging speed is a crucial consideration for magnetic resonance imaging (MRI). The speed of conventional MRI is limited by hardware performance and physiological safety measures. "Parallel" MRI is a new technique that circumvents these limitations by utilizing arrays of radiofrequency detector …
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A sub-ppb measurement of the mass of cesium for a new determination of the fine-structure constant
… a passive two-coil system designed for shielding magnetic field gradients. These may prove to be the key enabling technology for a future double Penning trap mass spectrometer.
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Coil performance evaluation based on electrodynamics : tools for hardware design and validation in magnetic resonance imaging
… which complements traditional encoding using magnetic field gradients. As the acceleration factor increases, coil design becomes critical to the overall image quality. The quality of a design is commonly judged on how it compares with other coil configurations. A procedure to evaluate the …
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Magnetophoretic cell clarification
… around a central column to create areas of high magnetic field at the column walls and areas of low magnetic field at the centerline, inducing non-magnetic particles to concentrate at the centerline, where they were removed through a coaxial central outlet tube at the top of the column. Depending …
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Negative magnetophoresis of submicron species in magnetic nanofluids
… the focusing and trapping of submicron, nonmagnetic species immersed in a magnetic nanofluid under applied magnetic fields. Focusing was achieved using two pairs of permanent magnets, which forced submicron fluorescently-tagged polystyrene beads to focus in the region between the two magnet …
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Precision magnetometry and imaging via quantum manipulation of spins in diamond
… various concentrations toward high-performance magnetic field sensing and imaging. First, the wide-field optical magnetic microscopy experiment provides ensemble- NV control via continuous-wave electron spin resonance and camera-based parallel spin-state readout. This microscope offers a factor …
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Magnetohydrodynamic Heat Transfer for Fusion Energy
… heat transfer of up to 10 MW/m2 within strong magnetic fields . Because the two most popular choices for this function (liquid metals and molten salts) are electrically conductive, magnetohydrodynamic effects can alter the fluid flow fields, and therefore heat transfer, in these conditions. The …
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Development of Low Frequency Electron Paramagnetic Resonance Methods and Instrumentation for Biological Applications
… measure tumor physiology. With the addition of magnetic field gradients, the spectral properties of paramagnetic species can be mapped. To facilitate EPR imaging, methods and instrumentation at frequencies between 250 MHz and 1 GHz were developed.</p> <p>At low spin concentrations, the rapid …
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High resolution NMR scattering : the first measurement of spin diffusion rates in a homogeneous solid
… small spatial offsets. Strong pulsed magnetic field gradient techniques were developed for these studies which generate switched gradients with strengths up to 103T /m (a factor of 100 stronger than those commercially available, and a factor of 25 stronger than the highest previously …
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