Current Search: Department of Physics (x)
View All Items
(21 - 40 of 149)
Pages
- Title
- Atomic displacements in transition metals.
- Creator
- Moghadam, Nassrin Y., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Using the order-N locally-self-consistent multiple scattering (LSMS) method, we carry out first-principles studies of the displacement of atoms from their average sites in the vicinity of a vacancy and transition metal impurities in copper. Our approach is to relax the first nearest neighbor distance and to calculate total energy for a number of relaxed geometries. We then obtain the equilibrium configuration of the nuclei from minimization of the total energy.
- Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/12546
- Subject Headings
- Physics, Condensed Matter
- Format
- Document (PDF)
- Title
- Binary black hole mergers: alternatives to standard puncture initial data and the impact on gravitational waveforms.
- Creator
- Reifenberger, George C., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
We study the evolution of binary black hole initial data schemes as alternatives to the standard puncture construction. These alternatives are based on post-Newtonian expansions that contain realistic gravitational waves. The first scheme is based on a second order post-Newtonian expansion in Arnowitt, Deser, and Misner transverse-traceless (ADMTT) gauge that has been re-summed to approach standard puncture data at the black holes. The other schemes are based on asymptotic matching of the 4...
Show moreWe study the evolution of binary black hole initial data schemes as alternatives to the standard puncture construction. These alternatives are based on post-Newtonian expansions that contain realistic gravitational waves. The first scheme is based on a second order post-Newtonian expansion in Arnowitt, Deser, and Misner transverse-traceless (ADMTT) gauge that has been re-summed to approach standard puncture data at the black holes. The other schemes are based on asymptotic matching of the 4-metrics of two tidally perturbed Schwarzschild solutions to post-Newtonian expansions at different orders. The alternatives are encouraging and lead to quasi-circular orbits and show gravitational radiation from the onset, as well as a reduction of spurious radiation. Deficiencies compared to punctures include more eccentricity during inspiral and larger constraint violations, since the alternative data sets only approximate solutions of Einstein's equations.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fcla/dt/3362577
- Subject Headings
- Black holes (Astronomy), General relativity (Physics), Gravitational waves, Inertia (Mechanics), Mass (Physics), Particles (Nuclear physics)
- Format
- Document (PDF)
- Title
- Binary neutron star mergeres: simulations with arbitrarily spinning stars.
- Creator
- Tsatsin, Petr, Marronetti, Pedro, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits,...
Show moreThe starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits, becoming comparable to those found in evolutions of standard conformally flat, helically symmetric binary initial data. This dissertation presents the first spinning neutron star binary simulations in circular orbits with a orbital eccentricity less then 0.01. The initial data sets corresponding to binaries with spins aligned, zero and anti-aligned with the orbital angular momentum were evolved in time. These simulations show the orbital “hang-up” effect previously seen in binary black holes. Additionally, they show orbital eccentricities that can be up to one order of magnitude smaller than those found in helically symmetric initial sets evolutions.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fau/fd/FA0004067
- Subject Headings
- Astrophysics, Black holes (Astronomy), General relativity (Physics), Gravitational waves, Neutron stars, Particles (Nuclear physics)
- Format
- Document (PDF)
- Title
- Biogenic gas dynamics in peat soil blocks using ground penetrating radar: a comparative study in the laboratory between peat soils from the Everglades and from two northern peatlands in Minnesota and Maine.
- Creator
- Cabolova, Anastasija., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Peatlands cover a total area of approximately 3 million square kilometers and are one of the largest natural sources of atmospheric methane (CH4) and carbon dioxide (CO2). Most traditional methods used to estimate biogenic gas dynamics are invasive and provide little or no information about lateral distribution of gas. In contrast, Ground Penetrating Radar (GPR) is an emerging technique for non-invasive investigation of gas dynamics in peat soils. This thesis establishes a direct comparison...
Show morePeatlands cover a total area of approximately 3 million square kilometers and are one of the largest natural sources of atmospheric methane (CH4) and carbon dioxide (CO2). Most traditional methods used to estimate biogenic gas dynamics are invasive and provide little or no information about lateral distribution of gas. In contrast, Ground Penetrating Radar (GPR) is an emerging technique for non-invasive investigation of gas dynamics in peat soils. This thesis establishes a direct comparison between gas dynamics (i.e. build-up and release) of four different types of peat soil using GPR. Peat soil blocks were collected at peatlands with contrasting latitudes, including the Everglades, Maine and Minnesota. A unique two-antenna GPR setup was used to monitor biogenic gas buildup and ebullition events over a period of 4.5 months, constraining GPR data with surface deformation measurements and direct CH4 and CO2 concentration measurements. The effect of atmospheric pressure was also investigated. This study has implications for better understanding global gas dynamics and carbon cycling in peat soils and its role in climate change.
Show less - Date Issued
- 2010
- PURL
- http://purl.flvc.org/FAU/2974433
- Subject Headings
- Wetland ecology, Wetland ecology, Wetland ecology, Gas dynamics, Soil permeability, Ground penetrating radar, Porous materials, Fluid dynamics
- Format
- Document (PDF)
- Title
- Central Moments of Squeezed States: A Coincidence Statistics Analogue.
- Creator
- Tison, Christopher C., Miller, Warner A., Alsing, Paul M., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
As a subset of quantum optics, single photons are one of the competing physical resources for quantum information processing. When used as carriers of quantum information, they have no equal. For the processing of quantum information, single photons have proven difficult to scale beyond the order of ⇠ 10 photons. The lack of single-photon-level interaction has led to creative approaches which rely on postselection to filter the possible measured outcomes to those which appear as though...
Show moreAs a subset of quantum optics, single photons are one of the competing physical resources for quantum information processing. When used as carriers of quantum information, they have no equal. For the processing of quantum information, single photons have proven difficult to scale beyond the order of ⇠ 10 photons. The lack of single-photon-level interaction has led to creative approaches which rely on postselection to filter the possible measured outcomes to those which appear as though interaction occurred. This approach of post-selection leans heavily on the ability to not only generate but also detect scores of single photons simultaneously and with near perfect efficiency. Our work relaxes the emphasis which has been placed on single photons for quantum information processing to that of states with, in principle, an arbitrary number of photons. Central moment expectations on two-mode squeezed states are shown to exhibit post-selection behavior which reflects the single-photon counterpart. These measures are proven to be robust to loss and return entangled state statistics on average. With naive estimation of the central moment, states with ~ 20 modes are within reach with current technology, closing the gap between quantum states which can and cannot be classically simulated.
Show less - Date Issued
- 2018
- PURL
- http://purl.flvc.org/fau/fd/FA00005951
- Subject Headings
- Squeezed states (Optics), Quantum optics, Photons, Integrated optics
- Format
- Document (PDF)
- Title
- A characterization of the LAP Aquarius Phantom for external LAP laser alignment and magnetic resonance geometric distortion verification for stereotactic radiation surgery patient simulation.
- Creator
- Vergara, Daniel, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The Thesis explores additional applications of LAP's Aquarius external laser alignment verification Phantom by examining geometric accuracy of magnetic resonance images commonly used for planning intracranial stereotactic radiation surgery (ICSRS) cases. The scans were performed with MRI protocols used for ICSRS, and head and neck diagnosis, and their images fused to computerized tomographic (CT) images. The geometric distortions (GDs) were measured against the CT in all axial, sagittal, and...
Show moreThe Thesis explores additional applications of LAP's Aquarius external laser alignment verification Phantom by examining geometric accuracy of magnetic resonance images commonly used for planning intracranial stereotactic radiation surgery (ICSRS) cases. The scans were performed with MRI protocols used for ICSRS, and head and neck diagnosis, and their images fused to computerized tomographic (CT) images. The geometric distortions (GDs) were measured against the CT in all axial, sagittal, and coronal directions at different levels. Using the Aquarius Phantom, one is able to detect GD in ICSRS planning MRI acquisitions, and align the external LAP patient alignment lasers, by following the LAP QA protocol. GDs up to about 2 mm are observed at the distal regions of the longitudinal axis in the SRS treatment planning MR images. Based on the results, one may recommend the use of the Aquarius Phantom to determine if margins should be included for SRS treatment planning.
Show less - Date Issued
- 2012
- PURL
- http://purl.flvc.org/FAU/3352878
- Subject Headings
- Radiotherapy, Techniques, Medical physics, Imaging systems in medicine, Tomographic images, Computerized axial tomography
- Format
- Document (PDF)
- Title
- CHARACTERIZING THE PHYSICAL PROPERTIES OF LIVING CELLS THROUGH MICROFLUIDIC IMPEDANCE SENSING.
- Creator
- Galpayage, Dona Kalpani Nisansala Udeni, Lau, Andy W.C., Du, Sarah E., Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
- Abstract/Description
-
The purpose of this research is to explore and investigate the biophysical properties of living cells using microfluidics based electrical impedance sensing (EIS) technique. It provides a non-invasive approach to detect label-free biological markers in the regulation of cellular activities even at a molecular level. We specifically focus on the development, testing, and theoretical modeling of electrical impedance spectroscopy for neuroblastoma cells and endothelial cells. First, we...
Show moreThe purpose of this research is to explore and investigate the biophysical properties of living cells using microfluidics based electrical impedance sensing (EIS) technique. It provides a non-invasive approach to detect label-free biological markers in the regulation of cellular activities even at a molecular level. We specifically focus on the development, testing, and theoretical modeling of electrical impedance spectroscopy for neuroblastoma cells and endothelial cells. First, we demonstrate that the EIS technique can be used to monitor the progressive mitochondrial fission/fusion modification in genetically modified human neuroblastoma cell lines. Our results characterize quantitatively the abnormal mitochondrial dynamics through the variations in cytoplasm conductivity. Secondly, we employ a real time EIS method to determine the biophysical properties of the junctions which join one endothelial cell with one another in a monolayer of endothelial cells. In particular, we examine the role of the protein, c-MYC oncogene, in the barrier function. Our results show that the downregulation of c-MYC oncogene enhances the endothelial barrier dysfunction associated with inflammation. Finally, we measure and find that the electrical admittance (the reciprocal of the impedance) of the monolayer of endothelial cellular networks exhibits an anomalous power law of the form, Y ∝ ωα, over a wide range of frequency, with the value of the exponent, α, depending on the severity of the inflammation. We attribute the power law to the changes of the intercellular electric permeability between neighboring endothelial cells. Thus, the inflammation gives rise to relatively smaller values of α compared to that of the no-inflammation group. Furthermore, we propose a simple percolation model of a large R-C network to confirm the emergent of power law scaling behavior of the complex admittance, suggesting that the endothelial network behaves as a complex microstructural network and its electrical properties may be simulated by a large R-C network.
Show less - Date Issued
- 2020
- PURL
- http://purl.flvc.org/fau/fd/FA00013595
- Subject Headings
- Microfluidics, Impedance spectroscopy, Cells
- Format
- Document (PDF)
- Title
- Charge Regulation of a Surface Immersed in an Electrolyte Solution.
- Creator
- Acharya, Pramod, Lau, Andy W. C., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
In this thesis, we investigate theoretically a new model of charge regulation of a single charged planar surface immersed in an aqueous electrolyte solution. Assuming that the adsorbed ions are mobile in the charged plane, we formulate a field theory of charge regulation where the numbers of adsorbed ions can be determined consistently by equating the chemical potentials of the adsorbed ions to that of the ions in the bulk. We analyze the mean-field treatment of the model for electrolyte of...
Show moreIn this thesis, we investigate theoretically a new model of charge regulation of a single charged planar surface immersed in an aqueous electrolyte solution. Assuming that the adsorbed ions are mobile in the charged plane, we formulate a field theory of charge regulation where the numbers of adsorbed ions can be determined consistently by equating the chemical potentials of the adsorbed ions to that of the ions in the bulk. We analyze the mean-field treatment of the model for electrolyte of arbitrary valences, and then beyond, where correlation effects are systematically taken into account in a loop expansion. In particular, we compute exactly various one-loop quantities, including electrostatic potentials, ion distributions, and chemical potentials, not only for symmetric (1, 1) electrolyte but also for asymmetric (2, 1) electrolyte, and make use of these quantities to address charge regulation at the one-loop level. We find that correlation effects give rise to various phase transitions in the adsorption of ions, and present phase diagrams for (1, 1) and (2, 1) electrolytes, whose distinct behaviors suggest that charge regulation, at the one-loop level, is no longer universal but depends crucially on the valency of the ions.
Show less - Date Issued
- 2016
- PURL
- http://purl.flvc.org/fau/fd/FA00004560, http://purl.flvc.org/fau/fd/FA00004560
- Subject Headings
- Surface chemistry., Intermolecular forces., Electrodynamics., Quantum field theory.
- Format
- Document (PDF)
- Title
- COMMISSIONING AND ACCEPTANCE TESTING OF A TRUEBEAM LINEAR ACCELERATOR.
- Creator
- Dumitru, Nicolae, Pella, Silvia, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Due to the difficulty of a complex commissioning technique for a multi energetic, multi-modality linear accelerator, I perform all the commissioning and acceptance testing for a TrueBeam linear accelerator with 4 megavoltage (MV) energies of which 2 are flattening filter-free (FFF) and 6 electron energies varying from 6 MeV to 20 MeV. A 2 dimensional (2D) water tank was used for scanning all the required field sizes for all the energies. The one dimensional (1D) water tank was used to collect...
Show moreDue to the difficulty of a complex commissioning technique for a multi energetic, multi-modality linear accelerator, I perform all the commissioning and acceptance testing for a TrueBeam linear accelerator with 4 megavoltage (MV) energies of which 2 are flattening filter-free (FFF) and 6 electron energies varying from 6 MeV to 20 MeV. A 2 dimensional (2D) water tank was used for scanning all the required field sizes for all the energies. The one dimensional (1D) water tank was used to collect all the output factors for all the photon fields sizes small to medium electron field sizes. For the large electron fields sizes, we had to use the 2D water tank. All the collected data was converted into a file type accepted by the planning system (Eclipse) and subsequently imported there. Treatment plans were generated using multiple forms of planning to verify the viability and quality of the beam data commissioned.
Show less - Date Issued
- 2019
- PURL
- http://purl.flvc.org/fau/fd/FA00013301
- Subject Headings
- Linear accelerators, Cancer--Treatment, Radiation dosimetry
- Format
- Document (PDF)
- Title
- Commissioning of 360⁰ Rotational Single Room ProBeam Compact™ (Varian Medical) Pencil Beam Scanning Proton Therapy System.
- Creator
- Fathallah, Shreen Mohamed, Shang, Charles, Muhammad, Wazir, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
- Abstract/Description
-
A clinical commissioning of the first 360 rotational compact Varian ProBeam scanning proton pencil beam (Varian Medical, Palo Alto, CA) system was conducted at the South Florida Proton Therapy Institute (SFPTI). The beam dosimetry and characterizations were the vital section used to verify the consistency of the treatment planning system (TPS) outputs. The integrated depth dose curves were acquired with AP CAX in water phantom utilizing a large PTW Bragg peak chamber; the dose output factors...
Show moreA clinical commissioning of the first 360 rotational compact Varian ProBeam scanning proton pencil beam (Varian Medical, Palo Alto, CA) system was conducted at the South Florida Proton Therapy Institute (SFPTI). The beam dosimetry and characterizations were the vital section used to verify the consistency of the treatment planning system (TPS) outputs. The integrated depth dose curves were acquired with AP CAX in water phantom utilizing a large PTW Bragg peak chamber; the dose output factors measurements were performed by using IBA PCC05 chamber at 1.5 cm water depth applying a single layer 10×10 cm2 beams and 1.1 RBE offset as recommended in TRS 398 report. Widths of the Bragg peaks ranges (Rb80-Ra80) were from 4.07 cm to 30.51 cm for the energy range 70 MeV to 220 MeV. Beam optics such as spot sizes and spot profiles were acquired in-air by using Logos scintillators with a CCD camera and the result data were from 2.33 mm to for 77 MeV to 9.70 mm for 220 MeV. In different field sizes, a comparison between the dose measured using PTW Semiflex and the AcurosPT estimated dose were performed to study the halo effect. All the measured dosimetric parameters showed that the design specifications were well achieved, and the results are suitable for being used as a part of the clinical commissioning and quality assurance program for treating patients.
Show less - Date Issued
- 2021
- PURL
- http://purl.flvc.org/fau/fd/FA00013691
- Subject Headings
- Proton Therapy, Dosimetry
- Format
- Document (PDF)
- Title
- COMPARATIVE PHARMACOKINETICS, BIODISTRIBUTION AND DOSIMETRY OF 212Pb (ALPHA-EMITTER) LABELED ANTIBODY VS PEPTIDE VS SMALL MOLECULE.
- Creator
- Moshiri, Nader Sedeh, Leventouri, Theodora, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
- Abstract/Description
-
With the advent of newly and more reliably designed targeted therapy methods in the past several years, targeted radionuclide therapy has attracted more attentions around the world as a more reliable treatment modality in combination with other well established traditional cancer treatments i.e., external beam radiotherapy and chemotherapy. Alpha particles have a high relative biological effectiveness (RBE) due to their high linear energy transfer (LET). However, to utilize them for...
Show moreWith the advent of newly and more reliably designed targeted therapy methods in the past several years, targeted radionuclide therapy has attracted more attentions around the world as a more reliable treatment modality in combination with other well established traditional cancer treatments i.e., external beam radiotherapy and chemotherapy. Alpha particles have a high relative biological effectiveness (RBE) due to their high linear energy transfer (LET). However, to utilize them for therapeutic purposes, precise human body dosimetry calculation is required. The measurement of their uptake and biodistribution can be quite challenging. Also, due to the complex biology of different types of cells, their shapes and functions, there is not a simple and clear understanding of the mechanism of action that fits all. This study aims to estimate and compare the human organ dosimetry of the alpha emitter, 212Pb, from animal data assuming that it is conjugated with three different types of commonly used targeting nanoparticles. For this purpose, the pre-published animal data of three different radionuclide labeled peptide, antibody, and small molecule carriers were selected and converted to human data. Then a compartmental model was designed for each of them to fit the model to the human data with 212Pb, half-life of 10.64 hours. Once each model reached the desired fit, the area under the curves were extracted then the estimated human organ dosimetry calculations took place via the MIRD scheme. The organ dosimetry results for 212Pb + three different carriers are presented in Tables 14, 17, and 20.
Show less - Date Issued
- 2023
- PURL
- http://purl.flvc.org/fau/fd/FA00014215
- Subject Headings
- Cancer--Treatment, Lead-212, Nuclear Medicine
- Format
- Document (PDF)
- Title
- Comparison of Measured and Computed Lateral Penumbra for a ProteusPlus Pencil Beam Scanning Proton Therapy System.
- Creator
- Leyva, Michael, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The lateral penumbra of a proton pencil beam scanning system (PBS) is of great importance in sparing of organs at risk and normal tissue when treating patients. The purpose of this current work is to measure the lateral penumbra of the Ion Beam Applications (Ion Beam Applications, Louvain‐la‐Neuve, Belgium) ProteusPLUS PBS Proton Therapy System and compare the measurements with the computed results from the RayStation proton treatment planning system. The lateral penumbra (80%-20%) was...
Show moreThe lateral penumbra of a proton pencil beam scanning system (PBS) is of great importance in sparing of organs at risk and normal tissue when treating patients. The purpose of this current work is to measure the lateral penumbra of the Ion Beam Applications (Ion Beam Applications, Louvain‐la‐Neuve, Belgium) ProteusPLUS PBS Proton Therapy System and compare the measurements with the computed results from the RayStation proton treatment planning system. The lateral penumbra (80%-20%) was measured using EBT-3 Gafchromic film in the water tank. The lateral penumbra was studied for various parameters such as range, depth, and air gap. The computed lateral penumbra was found to be higher than the measured lateral penumbra by up to 2.3 mm in the case of depth dependency at 30 cm, and lower by up to 1.18 mm in the case of an air gap of 15 cm.
Show less - Date Issued
- 2019
- PURL
- http://purl.flvc.org/fau/fd/FA00013229
- Subject Headings
- Proton Therapy, Radiotherapy--Measurement, Radiotherapy Planning, Computer-Assisted
- Format
- Document (PDF)
- Title
- A COMPARISON OF SODIUM ABUNDANCES CALCULATED FROM DAYLIGHT ABSORPTION AND TWILIGHT EMISSION IN THE D(2) LINE.
- Creator
- LASHER, RICHARD WILLIAM, Florida Atlantic University, Burnett, Clyde R., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
A method is presented, in which the Pepsios is used to measure abundances of atomic sodium present in the upper atmosphere as calculated from the twilight glow. These abundances are compared with daylight absorption abundances, also measured using the Pepsios. Ten measurements taken during March, 1971 show an average twilight abundance of (6.1 +- 1.8) x 10^9 atoms/cm^2. This compares with an average absorption abundance of (3.3 +- 1.1) x 10^9 atoms/cm^2. These limited data and their attendant...
Show moreA method is presented, in which the Pepsios is used to measure abundances of atomic sodium present in the upper atmosphere as calculated from the twilight glow. These abundances are compared with daylight absorption abundances, also measured using the Pepsios. Ten measurements taken during March, 1971 show an average twilight abundance of (6.1 +- 1.8) x 10^9 atoms/cm^2. This compares with an average absorption abundance of (3.3 +- 1.1) x 10^9 atoms/cm^2. These limited data and their attendant uncertainties reveal no significant discrepancy between twilight and daytime sodium abundances.
Show less - Date Issued
- 1971
- PURL
- http://purl.flvc.org/fcla/dt/13449
- Subject Headings
- Sodium--Spectra, Absorption spectra
- Format
- Document (PDF)
- Title
- Comparison of treatment plans calculated using ray tracing and Monte Carlo algorithms for lung cancer patients having undergone radiotherapy with cyberknife.
- Creator
- Pennington, Andreea, Selvaraj, Raj, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The purpose of this research is to determine the feasibility of introducing the Monte Carlo (MC) dose calculation algorithm into the clinical practice. Unlike the Ray Tracing (RT) algorithm, the MC algorithm is not affected by the tissue inhomogeneities, which are significant inside the chest cavity. A retrospective study was completed for 102 plans calculated using both the RT and MC algorithms. The D95 of the PTV was 26% lower for the MC calculation. The first parameter of conformality, as...
Show moreThe purpose of this research is to determine the feasibility of introducing the Monte Carlo (MC) dose calculation algorithm into the clinical practice. Unlike the Ray Tracing (RT) algorithm, the MC algorithm is not affected by the tissue inhomogeneities, which are significant inside the chest cavity. A retrospective study was completed for 102 plans calculated using both the RT and MC algorithms. The D95 of the PTV was 26% lower for the MC calculation. The first parameter of conformality, as defined as the ratio of the Prescription Isodose Volume to the PTV Volume was on average 1.27 for RT and 0.67 for MC. The results confirm that the RT algorithm significantly overestimates the dosages delivered confirming previous analyses. Correlations indicate that these overestimates are largest for small PTV and/or when the ratio of the volume of lung tissue to the PTV approaches 1.
Show less - Date Issued
- 2014
- PURL
- http://purl.flvc.org/fau/fd/FA00004316
- Subject Headings
- Computer graphics, Diagnostic imaging, Image guided radiation therapy, Lung cancer -- Treatment, Lungs -- Cancer -- Radiotherapy, Monte Carlo method
- Format
- Document (PDF)
- Title
- COMPUTATIONAL ASPECTS OF QUANTUM GRAVITY: NUMERICAL METHODS IN SPINFOAM MODELS.
- Creator
- Qu, Dongxue, Han, Muxin, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
- Abstract/Description
-
Quantum Gravity attempts to unify general relativity (GR) and quantum theory, and is one of the challenging research areas in theoretical physics. LQG is a background-independent and non-perturbative approach towards the theory of quantum gravity. The spinfoam formulation gives the covariant path integral formulation of LQG. The spinfoam amplitude plays a crucial role in the spinfoam formulation by defining the transition amplitude of covariant LQG. It is particularly interesting for testing...
Show moreQuantum Gravity attempts to unify general relativity (GR) and quantum theory, and is one of the challenging research areas in theoretical physics. LQG is a background-independent and non-perturbative approach towards the theory of quantum gravity. The spinfoam formulation gives the covariant path integral formulation of LQG. The spinfoam amplitude plays a crucial role in the spinfoam formulation by defining the transition amplitude of covariant LQG. It is particularly interesting for testing the semiclassical consistency of LQG, because of the connection between the semiclassical approximation of path integral and the stationary phase approximation. The recent semiclassical analysis reveals the interesting relation between spinfoam amplitudes and the Regge calculus, which discretizes GR on triangulations. This relation makes the semiclassical consistency of covariant LQG promising. The spinfoam formulation also provides ways to study the n-point functions of quantum-geometry operators in LQG. Despite the novel and crucial analytic results in the spinfoam formulation, the computational complexity has been obstructed further explorations in spinfoam models. Nevertheless, numerical approaches to spinfoams open new windows to circumvent this obstruction. There has been enlightening progress on numerical computation of the spinfoam amplitudes and the two-point function. The numerical technology should expand the toolbox to investigate LQG.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00013878
- Subject Headings
- Quantum gravity, Quantum theory, Quantum gravity--Mathematics, Theoretical physics
- Format
- Document (PDF)
- Title
- Computational methods in metallic alloys within multiple scattering theory.
- Creator
- Rusanu, Aurelian, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Designing materials, particularly at the nano-scale, is an important scientific research area. It includes a large spectrum of basic science and technological developments. In order to provide results that are relevant to real materials, quantum mechanical simulations involving thousands to millions of atoms must be carried out. The locally self-consistent multiple scattering (LSMS) method is the method of choice for such calculations because it has a technical feature called order-N scaling....
Show moreDesigning materials, particularly at the nano-scale, is an important scientific research area. It includes a large spectrum of basic science and technological developments. In order to provide results that are relevant to real materials, quantum mechanical simulations involving thousands to millions of atoms must be carried out. The locally self-consistent multiple scattering (LSMS) method is the method of choice for such calculations because it has a technical feature called order-N scaling. We describe an implementation of the LSMS for massively parallel supercomputers using k-space and real-space methods. For magnetic materials, the constrained local moment approach and the exchange interaction method are used. We demonstrate our approach by calculating the electronic and magnetic structure of an iron nano-particle embedded in an iron aluminide crystal matrix.
Show less - Date Issued
- 2005
- PURL
- http://purl.flvc.org/fcla/dt/12176
- Subject Headings
- Physics, Condensed Matter
- Format
- Document (PDF)
- Title
- CONSISTENCY OF CT NUMBER AND ELECTRON DENSITY IN TREATMENT PLANNING SYSTEM VERSUS CT SCANNER, AND DOSIMETRIC CONSEQUENCES.
- Creator
- Hana, Evan Makdasy, Pella, Silvia, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The Computer Tomography (CT) scanned images are very important for the Treatment Planning System (TPS) to provide the electron density of the different types of tissues that the radiation penetrates in the path to the tumor to be treated. This electron density is converted to an attenuation coefficient, which varies with tissue for each structure and even varies by the tissue volume. The purpose of this research is to evaluate the CT numbers, and convert them into relative electron densities....
Show moreThe Computer Tomography (CT) scanned images are very important for the Treatment Planning System (TPS) to provide the electron density of the different types of tissues that the radiation penetrates in the path to the tumor to be treated. This electron density is converted to an attenuation coefficient, which varies with tissue for each structure and even varies by the tissue volume. The purpose of this research is to evaluate the CT numbers, and convert them into relative electron densities. Twenty-five patients’ data and CT numbers were evaluated in the CT scanner and in Eclipse and were converted into relative electron density and compared with each other. The differences between the relative electron density in the Eclipse was found to be from 0 up to 6% between tissue equivalent materials, the final result for all equivalent tissue materials was about 2%. For the patients’ data, the percentage difference of CT number versus electron density was found to be high for high relative electron density organs, namely the final average result for the spine was 8%, less for pelvis, and less for rib while for the other organs it was even less. The very lowest was 0.3% compared with 1% which is acceptable for clinical standards.
Show less - Date Issued
- 2019
- PURL
- http://purl.flvc.org/fau/fd/FA00013315
- Subject Headings
- Tomography, X-Ray Computed, Electron density, Radiation dosimetry--Evaluation, Tomography Scanners, X-Ray Computed
- Format
- Document (PDF)
- Title
- Cosmological studies with spatially homogenous models and quantum field effects in Kantowski-Sachs universe.
- Creator
- Sabir, Abdenour, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Perhaps constructing a complete theory of quantum gravity, has been one of the greatest challenges for theoretical physicists in the last few decades, a theory that would reconcile general relativity and quantum mechanics. Addressing this issue, we are drawing a parallel between the Schrodinger and Klein-Gordon equation in quantum mechanics and Schrodinger-based or Klein-Gordon based wave equation in canonical quantum gravity. In particular we analyze the quantum geometrodynamics Schrodinger...
Show morePerhaps constructing a complete theory of quantum gravity, has been one of the greatest challenges for theoretical physicists in the last few decades, a theory that would reconcile general relativity and quantum mechanics. Addressing this issue, we are drawing a parallel between the Schrodinger and Klein-Gordon equation in quantum mechanics and Schrodinger-based or Klein-Gordon based wave equation in canonical quantum gravity. In particular we analyze the quantum geometrodynamics Schrodinger equation for a homogeneous cosmological model and we study the quantum field effects for the &PHgr;6 scalar field in Kantowski-Sachs universe. In essence, we present a unified view of quantum gravity by establishing a parallel between our study and the usual quantum mechanics. Thus, the first part of this dissertation deals with the quantization of Bianchi type IX space-time where the concept of time is derived by imposing the constraints as expectation values over the true dynamical-degrees of freedom of the gravitational field. Thus, we obtained a Schrodinger type wave equation instead of the Wheeler-DeWitt which is associated with the problem of time in quantum gravity [1]. The main technical difference between our proposed equation and other quantum cosmology approaches is in our treatment of the constraints. Ordinarily, the equation cannot be solved simply by separating the coordinates variables, and only under some specific conditions imposed on the background that one may obtain exact analytical expressions. In the second part, we evaluated the one-loop renormalized effective potential for the massive self interacting &PHgr;6 theory the spatially homogenous and anisotropic Kantowki-Sachs Universe. We concluded that regularizing the theory in (3 + 1) dimensional space-time may not be possible. Finally, we looked at the time evolution of the critical temperature that is associated with our model.
Show less - Date Issued
- 2005
- PURL
- http://purl.flvc.org/fau/fd/FADT12125
- Subject Headings
- Physics, General
- Format
- Document (PDF)
- Title
- Critical behavior of forest fires: Theory and numerical simulations.
- Creator
- Lu, Huizong, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Forest fire is an integral part of natural ecosystems. Understanding the mechanisms governing the formation and propagation of forest fire is imperative for effectively managing the natural resources of a forest and minimizing or eliminating damages caused by uncontrolled forest fire. Numerical simulation of two-dimensional forest fires indicates that there is a critical state at which the fire is likely to spread to the entire forest. The effects of wind conditions and multiple tree species...
Show moreForest fire is an integral part of natural ecosystems. Understanding the mechanisms governing the formation and propagation of forest fire is imperative for effectively managing the natural resources of a forest and minimizing or eliminating damages caused by uncontrolled forest fire. Numerical simulation of two-dimensional forest fires indicates that there is a critical state at which the fire is likely to spread to the entire forest. The effects of wind conditions and multiple tree species are studied using numerical simulations and various Mean Field Approximations. Results from the analytical calculations agree well with numerical simulations for square lattice forest fire. Other lattice structures are also investigated. Mathematical models with non-linearly coupled equations are derived to study finite, layered, pseudo-two-dimensional forest fires. Critical states can be predicted by evaluating these non-lineady coupled equations.
Show less - Date Issued
- 2000
- PURL
- http://purl.flvc.org/fcla/dt/12645
- Subject Headings
- Agriculture, Forestry and Wildlife
- Format
- Document (PDF)
- Title
- Detecting the spatiotemporal dynamics of neural activity on the cortical surface: applying anatomically constrained beamforming to EEG.
- Creator
- Murzin, Vyacheslav., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The neurophysiological signals that are recorded in EEG (electroencephalography) and MEG (magnetoencephalography) originate from current flow perpendicular to the cortical surface due to the columnar organization of pyramidal cells in the cortical gray matter. These locations and directions have been used as anatomical constraints for dipolar sources in estimations of neural activity from MEG recordings. Here we extend anatomically constrained beamforming to EEG, which requires a more...
Show moreThe neurophysiological signals that are recorded in EEG (electroencephalography) and MEG (magnetoencephalography) originate from current flow perpendicular to the cortical surface due to the columnar organization of pyramidal cells in the cortical gray matter. These locations and directions have been used as anatomical constraints for dipolar sources in estimations of neural activity from MEG recordings. Here we extend anatomically constrained beamforming to EEG, which requires a more sophisticated forward model than MEG due to the blurring of the electric potential at tissue boundaries, but in contrast to MEG, EEG can account for both tangential and radial sources. Using computed tomography (CT) scans we create a realistic three-layer head model consisting of tessellated surfaces representing the tissue boundaries cerebrospinal fluid-skull, skull-scalp and scalp-air. The cortical gray matter surface, the anatomical constraint for the source dipoles, is extracted from magnetic resonance imaging (MRI) scans. EEG beamforming is implemented in a set of simulated data and compared for three different head models: single sphere, multi-shell sphere and realistic geometry multi-shell model that employs a boundary element method. Beamformer performance is also analyzed and evaluated for multiple dipoles and extended sources (patches). We show that using anatomical constraints with the beamforming algorithm greatly reduces computation time while increasing the spatial accuracy of the reconstructed sources of neural activity. Using the spatial Laplacian instead of the electric potential in combination with beamforming further improves the spatial resolution and allows for the detection of highly correlated sources.
Show less - Date Issued
- 2010
- PURL
- http://purl.flvc.org/FAU/1930497
- Subject Headings
- Sensorimotor integration, Brain mapping, Perceptual-motor processes
- Format
- Document (PDF)
