http://hdl.handle.net/1803/569 Fri, 24 May 2013 06:31:43 GMT 2013-05-24T06:31:43Z http://discoverarchive.vanderbilt.edu:80/jspui/retrieve/3116/Physics.jpg http://hdl.handle.net/1803/569 http://hdl.handle.net/1803/5229 Title: Simulation and optimization of pulsed Chemical Exchange Saturation Transfer for clinical application at 3T Authors: Dewey, Blake Abstract: Chemical Exchange Saturation Transfer (CEST) is often overlooked as a method for the investigation of metabolites in vivo due to the time required to obtain a full spectrum. We investigated the feasibility and optimization of a pulsed CEST technique that interleaves an echo planer imaging (EPI) readout with saturation in order to reduce time. In addition, we incorporated a multi-shot EPI sequence that reduces distortions. To achieve this, computer simulations based on the Bloch equations were used to optimize scan parameters while keeping scan time in the clinical timeframe. To analyze the data, a number of Lorentizian fitting algorithms were investigated to evaluate their ability to isolate CEST contrast. By using a 30 ms pulse at 2 μT, we were able to achieve CEST contrast on the order of 2% and could provide APT maps based on an adapted Lorentzian fitting method. In the process of this fitting, it was also discovered that MTR contrast could also be recovered from the CEST data, allowing for MT and CEST to be acquired at the same time. Mon, 22 Apr 2013 05:00:00 GMT http://hdl.handle.net/1803/5229 2013-04-22T05:00:00Z http://hdl.handle.net/1803/5204 Title: High-energy attosecond-width electron diffraction simulations Authors: Kidd, Daniel Abstract: Electron microscopy has been the recent subject of molecular imaging due to the strength of the electrons' interaction with the target molecule making for a detailed pattern at a small scale.[1] To achieve the best 4D image of the target, one needs sufficient spatial and temporal resolution, the prior being an issue of using electrons in the keV regime as to achieve an optimally small deBroglie wavelength, and the latter being improved by the temporal width of the electron wave packet itself.[2] In order to image the motion of the electronic structure of the target molecule, this width must be within the attosecond regime. In this paper, we use the computational method of time-dependent density functional theory (TDDFT) to model our targets of Beryllium and the Nitrogen molecule, N2 , and an incoming electron wave packet with an energy of 1500 eV. Mon, 22 Apr 2013 05:00:00 GMT http://hdl.handle.net/1803/5204 2013-04-22T05:00:00Z http://hdl.handle.net/1803/5203 Title: An anomalous measurement of delta m31 squared from neutrino oscillations at the Daya Bay Reactor Neutrino Experiment Authors: Burroughs, Hunter Abstract: In 2012, the collaboration overseeing the Daya Bay Reactor Neutrino Experiment announced results which determined the magnitude of the mixing angle \theta_{13} with unprecedented precision. However, no attempt was made in the collaboration’s publications to predict the value of the most relevant mass-squared difference to the observed oscillation, \delta m^2_{31}. This paper presents the results of an analysis which suggests that the Daya Bay data prefers a value of \delta m^2_{31} which is far greater than its presently recognized value. Specifically, it is found that Daya Bay predicts \delta m^2_{31} = 3.53_(-1.07)^(+.74) × 10^(-3) eV^2, where the cited uncertainties correspond to the 99% confidence bounds. This measurement excludes the most precise current measurement of \delta m^2_{31}, the MINOS result, at a 99% confidence level and is in turn excluded by the MINOS data at a 10 \sigma level. The possibility that sterile neutrino effects are the cause of this anomalous result is considered and used to suggest further work. Mon, 22 Apr 2013 05:00:00 GMT http://hdl.handle.net/1803/5203 2013-04-22T05:00:00Z http://hdl.handle.net/1803/5192 Title: Simulating the universe with GPU-accelerated supercomputers: n-body methods, tests, and examples Authors: Wibking, Benjamin Abstract: We demonstrate the acceleration obtained from using GPU/CPU hybrid clusters and supercomputers for N-body simulations of gravity based in part on the author's new code development.  Validation tests are shown for cosmological simulations and for galaxy simulations, along with their respective speedups compared to traditional simulations.  Potential new applications for science enabled by this advance are highlighted. Mon, 22 Apr 2013 05:00:00 GMT http://hdl.handle.net/1803/5192 2013-04-22T05:00:00Z