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 Title
 Variations of Pericardial Dose at Different Respiratory Status in Accelerated Partial Breast Irradiation (APBI) Using Cyberknife M6™ Multileaf Collimators (CKMLC).
 Creator
 Long, Samanthia C., Shang, Charles, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The purpose of this study is to investigate the changes of the pericardial dose at different respiratory phases and statuses in accelerated partial breast irradiation (APBI) using Cyberknife M6™ multileaf collimators (CKMLC). Anonymous 6 female patient files with respiration gated fourdimensional computed tomography (4DCT) sets, and 6 left breast cancer cases with CT images in freebreathing (FB) and deep inhalation breathhold (BH) were selected. One CT image set from each patient was...
Show moreThe purpose of this study is to investigate the changes of the pericardial dose at different respiratory phases and statuses in accelerated partial breast irradiation (APBI) using Cyberknife M6™ multileaf collimators (CKMLC). Anonymous 6 female patient files with respiration gated fourdimensional computed tomography (4DCT) sets, and 6 left breast cancer cases with CT images in freebreathing (FB) and deep inhalation breathhold (BH) were selected. One CT image set from each patient was planned for APBI in Accuray Multiplan™ 5.2, and respectively compared its pericardial dose with those from CT sets of other respiratory phases. All the comparable CT images were fused in the planning system according to the left chest wall, among which the lung gap anterior to the pericardium varies by the lung expansion. For the purpose of this study, the tumor volume was outlined in the medialower quadrant of the left breast where this lung gap is relatively small. All the plans in this study met the requirements set by the National Surgical Adjuvant Breast and Bowel Project/Radiation Therapy Oncology Group (NSABP/RTOG), specifically protocol B39/RTOG 0413. From the comparisons in this investigation, the mean relative pericardial dose of the BH CT group showed significant or 45% (p < 0.01) lower value than that of FB CT group. However, in FB 4DCT group, 3 of 6 cases indicated a meaningful reduction (p < 0.05) in 100% inhalation phase when compared with the mean dose over other phases. The inconsistent pericardial doses were displayed in FB 4DCT group due to minimal changes in the anterior lung gap of the pericardium, when the diaphragmatic breathing was dominant in those patients.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004518, http://purl.flvc.org/fau/fd/FA00004518
 Subject Headings
 BreastCancerRadiotherapy., BreastCancerTreatment., RadiationMeasurementMethodology., Medical physics.
 Format
 Document (PDF)
 Title
 Validation of a Monte Carlo dose calculation algorithm for clinical electron beams in the presence of phantoms with complex heterogeneities.
 Creator
 Enright, Shayla Landfair, Pella, Silvia, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The purpose of this thesis is to validate the Monte Carlo algorithm for electron radiotherapy in the Eclipse™ treatment planning system (TPS), and to compare the accuracy of the Electron Monte Carlo algorithm (eMC) to the Pencil Beam algorithm (PB) in Eclipse™. Dose distributions from GafChromic™ EBT3 film measurements were compared to dose distributions from eMC and PB treatment plans. Measurements were obtained with 6MeV, 9MeV, and 12MeV electron beams at various depths. A 1 cm thick solid...
Show moreThe purpose of this thesis is to validate the Monte Carlo algorithm for electron radiotherapy in the Eclipse™ treatment planning system (TPS), and to compare the accuracy of the Electron Monte Carlo algorithm (eMC) to the Pencil Beam algorithm (PB) in Eclipse™. Dose distributions from GafChromic™ EBT3 film measurements were compared to dose distributions from eMC and PB treatment plans. Measurements were obtained with 6MeV, 9MeV, and 12MeV electron beams at various depths. A 1 cm thick solid water template with holes for bonelike and lunglike plugs was used to create assorted configurations and heterogeneities. Dose distributions from eMC plans agreed better with the film measurements based on gamma analysis. Gamma values for eMC were between 83%99%, whereas gamma values for PB treatment plans were as low as 38.66%. Our results show that using the eMC algorithm will improve dose accuracy in regions with heterogeneities and should be considered over PB.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004192
 Subject Headings
 Electron beams  Therapeutic use, Image guided radiotherapy, Monte Carlo method, Proton beams  Therapeutic use, Radiation dosimetry, Radiotherapy, High energy
 Format
 Document (PDF)
 Title
 TRANSPORT MEASUREMENTS ON SEMICONDUCTING TCNQ SALTS.
 Creator
 LANE, JOHN EUGENE, Florida Atlantic University, Blakemore, John S., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

This work consists mainly of two parts. First was the development of the necessary experimental techniques for measuring single crystal conductivity of anisotropic charge transfer salts. Difficulties included high impedance problems and limited size of available crystals. Cs2(TCNQ)3 was used as a test material with which to develop these techniques. An extensive investigation was undertaken to study the possibility of intrinsic and extrinsic behavior in this material. The second phase of this...
Show moreThis work consists mainly of two parts. First was the development of the necessary experimental techniques for measuring single crystal conductivity of anisotropic charge transfer salts. Difficulties included high impedance problems and limited size of available crystals. Cs2(TCNQ)3 was used as a test material with which to develop these techniques. An extensive investigation was undertaken to study the possibility of intrinsic and extrinsic behavior in this material. The second phase of this work was the study of TCNQ charge transfer salts in which the donors were structurally related pyridinium ion radicals. Four types of donors were synthesized using a methyl or benzyl substituent along with a cyano group in the 3 or 4 position of the ring. A total of eight compounds were studied including salts of the 1:1 and 1:2 stochiometry. Compaction conductivity was measured for all eight materials along with single crystal conductivity of three of the salts.
Show less  Date Issued
 1977
 PURL
 http://purl.flvc.org/fcla/dt/13835
 Subject Headings
 Charge transfer, Onedimensional conductors, Organic semiconductors, SaltsElectric properties
 Format
 Document (PDF)
 Title
 The tightbinding coherent potential approximation embedded cluster method Monte Carlo approach and approximations to the quadratic KorringaKohnRostoker method.
 Creator
 Horvath, Eva Antoinette, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The coherent potential approximation (CPA) can yield information about the longrange characteristics of an alloy. However, since it is a singlesite theory, the effect of the local environment cannot be taken into account. The CPA can be extended to more than one site using the embedded cluster method, thereby including shortrange order effects. The tightbinding coherentpotential approximation embedded cluster method can be used to generate the densities of states corresponding to all...
Show moreThe coherent potential approximation (CPA) can yield information about the longrange characteristics of an alloy. However, since it is a singlesite theory, the effect of the local environment cannot be taken into account. The CPA can be extended to more than one site using the embedded cluster method, thereby including shortrange order effects. The tightbinding coherentpotential approximation embedded cluster method can be used to generate the densities of states corresponding to all possible configurations of any cluster, but in particular a cluster consisting of an atom and its nearest neighbors. It is then demonstrated that the interaction energies can be calculated and used in conjunction with the Monte Carlo approach to generate the phase diagram of an alloy. In addition, the formalism for two new approximations to the Quadratic KorringaKohnRostoker method is developed and is applied to a system consisting of one metal.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/12321
 Subject Headings
 Physics, Condensed Matter
 Format
 Document (PDF)
 Title
 Theoretical study of binary alloy thin film growth.
 Creator
 Bouwens, Mark R., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Computer simulations of the growth of binary alloy thin films in two and three dimensions were performed using an extension of the Solid on Solid model. Snapshots for a range of interactions and diffusion rates are presented and critically compared to experiment. A wide variety of distinct phases is identified and their growth conditions analyzed. These findings are summarized in a phase diagram. In addition, a fractal analysis of the domains is performed. It is found that for negative...
Show moreComputer simulations of the growth of binary alloy thin films in two and three dimensions were performed using an extension of the Solid on Solid model. Snapshots for a range of interactions and diffusion rates are presented and critically compared to experiment. A wide variety of distinct phases is identified and their growth conditions analyzed. These findings are summarized in a phase diagram. In addition, a fractal analysis of the domains is performed. It is found that for negative interactions the islands are twodimensional, while for positive interactions, regardless of diffusion rate, a fractal dimension of 1.78 is obtained.
Show less  Date Issued
 2011
 PURL
 http://purl.flvc.org/FAU/3174504
 Subject Headings
 Binary systems (Metallurgy), Mathematical models, Thermal diffusivity, Phase diagrams, Phase transformations (Statistical physics)
 Format
 Document (PDF)
 Title
 The relationship between item difficulty and discrimination indices in multiplechoice tests in a physical science course.
 Creator
 Hotiu, Angelica, Jordan, Robin G., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

We have developed a method of quantifying multiplechoice test items in an introductory physical science course in terms of the various tasks required to solve the problem. We assign a numerical level of difficulty to each task so that any question can be assigned a degree of difficulty, which is the sum of the individual levels of difficulty associated in each steps. Using the questions and results from the tests we have investigated the relationship between the degree of difficulty of each...
Show moreWe have developed a method of quantifying multiplechoice test items in an introductory physical science course in terms of the various tasks required to solve the problem. We assign a numerical level of difficulty to each task so that any question can be assigned a degree of difficulty, which is the sum of the individual levels of difficulty associated in each steps. Using the questions and results from the tests we have investigated the relationship between the degree of difficulty of each question and the corresponding discrimination index. Our results indicate that as the degree of difficulty increases so does the capability of the item to discriminate between students with different abilities. There is a maximum degree of difficulty beyond which the discrimination starts to decrease. At that point, test items become too difficult. Thus, it should be possible in future to design items that will provide optimum discrimination.
Show less  Date Issued
 2006
 PURL
 http://purl.flvc.org/fau/fd/FA00000766
 Subject Headings
 Decision making, Curriculum planning, ExaminationsScoring, Educational tests and measurements, Universities and collegesUnited StatesExaminationsDesign and construction
 Format
 Document (PDF)
 Title
 The importance of immobilization and localization of gynecological applicators in high dose rate brachytherapy treatments.
 Creator
 Hyvärinen, Mikko, Pella, Silvia, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Intracavitary high dose rate (HDR) brachytherapy is a form of radiation therapy generally in which a postsurgical tissue margin is treated. The dose gradient of HDR brachytherapy is very steep, and thus small displacements of the applicator, even as small as 1 mm, could potentially cause significant variations of dose which could result in undesired side effects such as overdose of a critical organ. In this retrospective dosimetric study, the variation of dose due to various small range...
Show moreIntracavitary high dose rate (HDR) brachytherapy is a form of radiation therapy generally in which a postsurgical tissue margin is treated. The dose gradient of HDR brachytherapy is very steep, and thus small displacements of the applicator, even as small as 1 mm, could potentially cause significant variations of dose which could result in undesired side effects such as overdose of a critical organ. In this retrospective dosimetric study, the variation of dose due to various small range motions of gynecological applicators is investigated. The results show that the implementation of additional immobilization and localization devices along with other safety measures needs to be further investigated.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004446
 Subject Headings
 Artificial intelligence  Medical applications, Cancer  Intraoperative radiotherapy, Generative organs, Female  Cancer  Treatment, Imaging systems in medicine, Medical physics, Radiosotope brachytherapy
 Format
 Document (PDF)
 Title
 The Advantages of Collimator Optimization for Intensity Modulated Radiation Therapy.
 Creator
 Doozan, Brian, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The goal of this study was to improve dosimetry for pelvic, lung, head and neck, and other cancers sites with aspherical planning target volumes (PTV) using a new algorithm for collimator optimization for intensity modulated radiation therapy (IMRT) that minimizes the xjaw gap (CAX) and the area of the jaws (CAA) for each treatment field. A retroactive study on the effects of collimator optimization of 20 patients was performed by comparing metric results for new collimator optimization...
Show moreThe goal of this study was to improve dosimetry for pelvic, lung, head and neck, and other cancers sites with aspherical planning target volumes (PTV) using a new algorithm for collimator optimization for intensity modulated radiation therapy (IMRT) that minimizes the xjaw gap (CAX) and the area of the jaws (CAA) for each treatment field. A retroactive study on the effects of collimator optimization of 20 patients was performed by comparing metric results for new collimator optimization techniques in Eclipse version 11.0. Keeping all other parameters equal, multiple plans are created using four collimator techniques: CA0, all fields have collimators set to 0°, CAE, using the Eclipse collimator optimization, CAA, minimizing the area of the jaws around the PTV, and CAX, minimizing the xjaw gap. The minimum area and the minimum xjaw angles are found by evaluating each field beam’s eye view of the PTV with ImageJ and finding the desired parameters with a custom script. The evaluation of the plans included the monitor units (MU), the maximum dose of the plan, the maximum dose to organs at risk (OAR), the conformity index (CI) and the number of fields that are calculated to split. Compared to the CA0 plans, the monitor units decreased on average by 6% for the CAX method with a pvalue of 0.01 from an ANOVA test. The average maximum dose remained within 1.1% difference between all four methods with the lowest given by CAX. The maximum dose to the most at risk organ was best spared by the CAA method, which decreased by 0.62% compared to the CA0. Minimizing the xjaws significantly reduced the number of split fields from 61 to 37. In every metric tested the CAX optimization produced comparable or superior results compared to the other three techniques. For aspherical PTVs, CAX on average reduced the number of split fields, lowered the maximum dose, minimized the dose to the surrounding OAR, and decreased the monitor units. This is achieved while maintaining the same control of the PTV.
Show less  Date Issued
 2017
 PURL
 http://purl.flvc.org/fau/fd/FA00004804, http://purl.flvc.org/fau/fd/FA00004804
 Subject Headings
 RadiationDosage., Optical engineering., Medical physics., Imageguided radiation therapy., CancerRadiotherapy., Medical radiologyData processing., MedicineMathematical models.
 Format
 Document (PDF)
 Title
 Terrestrial Absorption in the Sodium D2 Line.
 Creator
 Lammer, Wayne E., Burnett, Clyde R., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

An experimental investigation is described in which a Pepsios high resolution pressure scanning s pectrometer is used to measure the absorption of light due to atomic sodium in the upper atmospher e. Design and construction of the spectrometer will be discussed with attention given to unique features of the instrument which were develo ped in this study. An attempt is made to see if any dependence on the abundance of the sodium can be accounted for by the proximity to the ocean or by the...
Show moreAn experimental investigation is described in which a Pepsios high resolution pressure scanning s pectrometer is used to measure the absorption of light due to atomic sodium in the upper atmospher e. Design and construction of the spectrometer will be discussed with attention given to unique features of the instrument which were develo ped in this study. An attempt is made to see if any dependence on the abundance of the sodium can be accounted for by the proximity to the ocean or by the winds and extreme turbulence developed by tropical storms and hurricanes. It is hoped that this data will compliment the existing data found at other latitudes so that a circulation dependence may be found.
Show less  Date Issued
 1967
 PURL
 http://purl.flvc.org/fau/fd/FA00000786
 Subject Headings
 Airglow, Thermosphere, Atmosphere, Upper, Solar radiation
 Format
 Document (PDF)
 Title
 Synchronization of coupled semiconductor lasers.
 Creator
 London, Michael S., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The synchronization of coupled semiconductor lasers with delay is investigated by numerical simulations of the nonlinear dynamic models complemented by a stability analysis of the linearized system. The equations used in the dissertation are based on the well known "LangKobayashi" model modified to include unidirectional and bidirectional coupling. Stability diagrams are calculated and supplemented by numerically integrated time series. Synchronization is determined and quantified by...
Show moreThe synchronization of coupled semiconductor lasers with delay is investigated by numerical simulations of the nonlinear dynamic models complemented by a stability analysis of the linearized system. The equations used in the dissertation are based on the well known "LangKobayashi" model modified to include unidirectional and bidirectional coupling. Stability diagrams are calculated and supplemented by numerically integrated time series. Synchronization is determined and quantified by computing the crosscorrelation function. It is found that synchronized states are achievable for a wide range of coupling constants and delay times. These findings have implications for experiment and technological applications, notably in cryptography.
Show less  Date Issued
 2011
 PURL
 http://purl.flvc.org/FAU/3318673
 Subject Headings
 Semiconductor lasers, Optical bistability, Nonlinear theories, Diodes, Semiconductor, Mathematical models
 Format
 Document (PDF)
 Title
 Synchronization and phase dynamics of oscillating foils.
 Creator
 Finkel, Cyndee L., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

In this work, a twodimensional model representing the vortices that animals produce, when they are flying/swimming, was constructed. A D{shaped cylinder and an oscillating airfoil were used to mimic these body{shed and wing{generated vortices, respectively. The parameters chosen are based on the Reynolds numbers similar to that which is observed in nature (104). In order to imitate the motion of ying/swimming, the entire system was suspended into a water channel from frictionless air...
Show moreIn this work, a twodimensional model representing the vortices that animals produce, when they are flying/swimming, was constructed. A D{shaped cylinder and an oscillating airfoil were used to mimic these body{shed and wing{generated vortices, respectively. The parameters chosen are based on the Reynolds numbers similar to that which is observed in nature (104). In order to imitate the motion of ying/swimming, the entire system was suspended into a water channel from frictionless air{bearings. The position of the apparatus in the channel was regulated with a linear, closed loop PI controller. Thrust/drag forces were measured with strain gauges and particle image velocimetry (PIV) was used to examine the wake structure that develops. The Strouhal number of the oscillating airfoil was compared to the values observed in nature as the system transitions between the accelerated and steady states... As suggested by previous work, this selfregulation is a result of a limit cycle process that stems from nonlinear periodic oscillations. The limit cycles were used to examine the synchronous conditions due to the coupling of the foil and wake vortices. Noise is a factor that can mask details of the synchronization. In order to control its effect, we study the locking conditions using an analytic technique that only considers the phases.. The results suggest that Strouhal number selection in steady forward natural swimming and flying is the result of a limit cycle process and not actively controlled by an organism. An implication of this is that only relatively simple sensory and control hardware may be necessary to control the steady forward motion of manmade biomimetically propelled vehicles.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fcla/dt/3362333
 Subject Headings
 Mathematical physics, Fluid dynamics, Unsteady flow (Fluid dynamics), Aerofoils, Aerodynamics
 Format
 Document (PDF)
 Title
 Supernovae neutrinos as a probe for neutrino mass and supernovae explosion mechanism.
 Creator
 Gross, Robert Jason, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

In recent years there have been several neutrino detectors built to detect solar, atmospheric, and cosmic neutrinos. In this dissertation, we used a Monte Carlo approach to model both the SuperKamiokande (SuperK) detector in Japan, and the Sudbury Neutrino Observatory (SNO) in Canada. A neutrino flux produced by a supernova code was implemented to simulate a realistic signal. An analysis of the minimum neutrino mass which could be detected was then performed for SuperK which produced...
Show moreIn recent years there have been several neutrino detectors built to detect solar, atmospheric, and cosmic neutrinos. In this dissertation, we used a Monte Carlo approach to model both the SuperKamiokande (SuperK) detector in Japan, and the Sudbury Neutrino Observatory (SNO) in Canada. A neutrino flux produced by a supernova code was implemented to simulate a realistic signal. An analysis of the minimum neutrino mass which could be detected was then performed for SuperK which produced discrepancies for the zero tau mass case when compared to previous work using a smooth emission spectrum as the incident neutrino source. As a result, we reconstructed the neutrino parameters involved in the supernovae explosion mechanism, to correct this discrepancy and determined the minimum mass for a realistic source. The source reconstruction is also useful for empirically determining the explosion mechanism when the next galactic supernova event occurs, since at present, this mechanism is still not entirely understood.
Show less  Date Issued
 2002
 PURL
 http://purl.flvc.org/fau/fd/FADT12031
 Subject Headings
 Physics, Astronomy and Astrophysics
 Format
 Document (PDF)
 Title
 Subjecting the CHIMERA supernova code to two hydrodynamic test problems, (i) Riemann problem and (ii) Point blast explosion.
 Creator
 Ahsan, Abu Salah M., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

A Shock wave as represented by the Riemann problem and a Pointblast explosion are two key phenomena involved in a supernova explosion. Any hydrocode used to simulate supernovae should be subjected to tests consisting of the Riemann problem and the Pointblast explosion. L. I. Sedov's solution of Pointblast explosion and Gary A. Sod's solution of a Riemann problem have been rederived here from one dimensional fluid dynamics equations . Both these problems have been solved by using the idea...
Show moreA Shock wave as represented by the Riemann problem and a Pointblast explosion are two key phenomena involved in a supernova explosion. Any hydrocode used to simulate supernovae should be subjected to tests consisting of the Riemann problem and the Pointblast explosion. L. I. Sedov's solution of Pointblast explosion and Gary A. Sod's solution of a Riemann problem have been rederived here from one dimensional fluid dynamics equations . Both these problems have been solved by using the idea of Selfsimilarity and Dimensional analysis. The main focus of my research was to subject the CHIMERA supernova code to these two hydrodynamic tests. Results of CHIMERA code for both the blast wave and Riemann problem have then been tested by comparing with the results of the analytic solution.
Show less  Date Issued
 2008
 PURL
 http://purl.flvc.org/FAU/172665
 Subject Headings
 Mathematical physics, Continuum mechanics, Number theory, Supernovae, Data processing, Shock waves, Fluid dynamics
 Format
 Document (PDF)
 Title
 Structural, magnetic, and electrical properties of ruthenium oxides.
 Creator
 Leao, Juscelino Batista, Florida Atlantic University, Neumeier, John, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Early reports of antiferromagnetism in CaRuO3 will be discussed within the framework of our recent experiments. We have observed that slight Ru deficiency (∼4%) leads to a weak feature in the magnetic susceptibility. Temperaturedependant timeofflight (TOF) neutron powder diffraction data revealed no longrange magnetic order in the Ruthenium deficient CaRu 0.96O3 sample. More careful analysis of magnetization data indicates that the feature in chi(T) can be attributed to a weak...
Show moreEarly reports of antiferromagnetism in CaRuO3 will be discussed within the framework of our recent experiments. We have observed that slight Ru deficiency (∼4%) leads to a weak feature in the magnetic susceptibility. Temperaturedependant timeofflight (TOF) neutron powder diffraction data revealed no longrange magnetic order in the Ruthenium deficient CaRu 0.96O3 sample. More careful analysis of magnetization data indicates that the feature in chi(T) can be attributed to a weak ferromagnetic phase which forms below an ordering temperature of T = 147 K. This phase is destroyed with Lanthanum doping (∼2%) and annealing in reducing conditions dramatically shifts this feature. Measurements of the magnetic susceptibility versus temperature of the series Ca1xLaxRu 0.96O3 (0 ≤ x ≤ 0.12) led to further study of CaRuO 3 and SrRuO3. The structural parameters of CaRuO 3 and SrRuO3 powder samples, obtained from neutron timeofflight data analysis via Rietveld refinement, will be compared.
Show less  Date Issued
 2002
 PURL
 http://purl.flvc.org/fcla/dt/12954
 Subject Headings
 Ferromagnetism, Ruthenium oxide superconductors, Rietveld method
 Format
 Document (PDF)
 Title
 Structural, electrical and magnetic properties of transition metal nickel oxides.
 Creator
 Wu, Guoqing, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Neutron powder diffraction, high pressure, magnetic susceptibility, and heat capacity measurements, as well as xray powder diffraction and iodometric titration, have been conducted on transition metal nickel oxides (TMOs), representative RuddlesdenPopper (RP) phases Lan+1NinO3n+1 (n = 1, 2, ..., infinity) and holedoped La2xSr xNiO4 (0
Show moreNeutron powder diffraction, high pressure, magnetic susceptibility, and heat capacity measurements, as well as xray powder diffraction and iodometric titration, have been conducted on transition metal nickel oxides (TMOs), representative RuddlesdenPopper (RP) phases Lan+1NinO3n+1 (n = 1, 2, ..., infinity) and holedoped La2xSr xNiO4 (0 < x < 1.2). The first complete study of La 2xSrxNiO4 (0 < x < 1.2) and La n+1NinO3n+1 (n = 2 and 3) phases under high pressure is produced. Strong direct experimental evidence for polaron dominated electrical conduction in these charge transfer (CT) gap La2xSr xNiO4 compounds is provided. Temperature evolution of the crystal structure of La2xSrxNiO4 (x = 1/4 and 1/3) is revealed through neutron powder diffraction, structural relationships among n = 1, 2, and 3 phases are exhibited, and charge density wave (CDW) in multilayer Lan+1NinO3n+1 phases is strongly suggested. No superconductivity is observed at pressures up to 1.6 GPa and temperatures down to 4.2 K.
Show less  Date Issued
 2002
 PURL
 http://purl.flvc.org/fcla/dt/11997
 Subject Headings
 Physics, Condensed Matter
 Format
 Document (PDF)
 Title
 Stochastic processes in the social sciences: markets, prices and wealth distributions.
 Creator
 Romero, Natalia E., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The present work uses statistical mechanics tools to investigate the dynamics of markets, prices, trades and wealth distribution. We studied the evolution of market dynamics in different stages of historical development by analyzing commodity prices from two distinct periods : ancient Babylon, and medieval and early modern England. We find that the firstdigit distributrions of both Babylon and England commodity prices follow Benford's Law, indicating that the data represent empirical...
Show moreThe present work uses statistical mechanics tools to investigate the dynamics of markets, prices, trades and wealth distribution. We studied the evolution of market dynamics in different stages of historical development by analyzing commodity prices from two distinct periods : ancient Babylon, and medieval and early modern England. We find that the firstdigit distributrions of both Babylon and England commodity prices follow Benford's Law, indicating that the data represent empirical observations typically arising from a free market. Further, we find that the normalized prices of both Babylon and England agricultural commodities are characterized by stretched exponential distributions, and exhibit persistent correlations of a power law type over long periods of up to several centuries, in contrast to contemporary markets. Our findings suggest that similar market interactions may underlie the dynamics of ancient agricultural commodity prices, and that these interactions may remain stable across centuries. To further investigate the dynamics of markets, we present the analogy between transfers of money between individuals and the transfer of energy through particle collisions by means of the kinetic theory of gases. We introduce a theoretical framework of how micro rules of trading lead to the emergence of income and wealth distribution. Particularly, we study the effects of different types of distribution of savings/investments among individuals in a society and different welfare/subsidies redistribution policies. Results show that while considering savings propensities, the models approach empirical distributions of wealth quite well. The effect of redistribution better captures specific features of the distributions which earlier models failed to do. Moreover, the models still preserve the exponential decay observed in empirical income distributions reported by tax data and surveys.
Show less  Date Issued
 2012
 PURL
 http://purl.flvc.org/FAU/3352825
 Subject Headings
 Stochastic processes, Mathematical models, Consumption (Economics), Mathematical models, Business cycles, Mathematical models, Statics and dynamics (Social sciences), Mathematical models
 Format
 Document (PDF)
 Title
 Statistical physics for materials classification.
 Creator
 Lassalle, Hugues Jean, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Genetic algorithms (GA) and clustering techniques are used to study and classify materials. An analysis of the convergence speed of GA is carried out using advanced probability theory and random walk concepts. The determination of the groundstate of multicomponent alloys and Ising models with longrange interactions is accomplished using a genetic algorithm. A new GA operator, the domainflip, is introduced and its efficiency is compared to that of traditional GA operators, crossover and...
Show moreGenetic algorithms (GA) and clustering techniques are used to study and classify materials. An analysis of the convergence speed of GA is carried out using advanced probability theory and random walk concepts. The determination of the groundstate of multicomponent alloys and Ising models with longrange interactions is accomplished using a genetic algorithm. A new GA operator, the domainflip, is introduced and its efficiency is compared to that of traditional GA operators, crossover and mutation. The domainflip operator destroys phaseboundaries by flipping all bits of a given domain at the same time. This operator turns out to be crucial in extracting the system from low local minima. Therefore its presence is rather essential to speed up the GA convergence. A study of GA convergence in its last stages, where all chromosomes present in the population are assumed to consist of two wellordered domains, is performed using random walk theory and probability theory. Exact expressions for the average time needed for at least one chromosome to find the groundstate are derived. Also, the probability for two chromosomes to undergo a successful crossover, meaning the result is the groundstate, are given. Finally, clustering techniques, which belong to the field of Data Mining, are applied to the classification of materials. An improved version of the widelyused clustering algorithm, Kmeans, is developed. A comparison of the two clustering techniques on a twodimensional data set shows that the guidepoint approach is more powerful than the Kmeans algorithm. The guidepoint algorithm is used successfully to partition a materials data set. This clustering results in extracting useful information from the data set for which no a priori knowledge was assumed.
Show less  Date Issued
 2002
 PURL
 http://purl.flvc.org/fcla/dt/11998
 Subject Headings
 Physics, Condensed Matter, Engineering, Materials Science, Computer Science
 Format
 Document (PDF)
 Title
 A starting potential for band theory calculations generated from ThomasFermi theory.
 Creator
 Horvath, Eva Antoinette, Florida Atlantic University, Faulkner, J. Samuel, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The purpose of this thesis is to generate a starting potential from ThomasFermi theory and verify that this leads to expedient convergence of the energy eigenvalues. The potential was generated for various elements, representative of the 3d and 4d elements, as well as the simple metals, for different lattice constants. They were inserted into a quadratic KorringaKohnRostoker band theory program. They lead to selfconsistent results at a faster rate than the potentials given by Moruzzi,...
Show moreThe purpose of this thesis is to generate a starting potential from ThomasFermi theory and verify that this leads to expedient convergence of the energy eigenvalues. The potential was generated for various elements, representative of the 3d and 4d elements, as well as the simple metals, for different lattice constants. They were inserted into a quadratic KorringaKohnRostoker band theory program. They lead to selfconsistent results at a faster rate than the potentials given by Moruzzi, Janak, and Williams for lattice constants for which the lattice was not in equilibrium.
Show less  Date Issued
 1988
 PURL
 http://purl.flvc.org/fcla/dt/14487
 Subject Headings
 Energyband theory of solids
 Format
 Document (PDF)
 Title
 Spinfoam dynamics of general relativity.
 Creator
 Chaharsough Shirazi, Atousa, Engle, Jonathan S., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

In this dissertation the dynamics of general relativity is studied via the spinfoam approach to quantum gravity. Spinfoams are a proposal to compute a transition amplitude from a triangulated spacetime manifold for the evolution of quantum 3d geometry via path integral. Any path integral formulation of a quantum theory has two important parts, the measure factor and a phase part. The correct measure factor is obtained by careful canonical analysis at the continuum level. The basic...
Show moreIn this dissertation the dynamics of general relativity is studied via the spinfoam approach to quantum gravity. Spinfoams are a proposal to compute a transition amplitude from a triangulated spacetime manifold for the evolution of quantum 3d geometry via path integral. Any path integral formulation of a quantum theory has two important parts, the measure factor and a phase part. The correct measure factor is obtained by careful canonical analysis at the continuum level. The basic variables in the PlebanskiHolst formulation of gravity from which spinfoam is derived are a Lorentz connection and a Lorentzalgebra valued twoform, called the Plebanski twoform. However, in the final spinfoam sum, one usually sums over only spins and intertwiners, which label eigenstates of the Plebanski twoform alone. The spinfoam sum is therefore a discretized version of a PlebanskiHolst path integral in which only the Plebanski twoform appears, and in which the conne ction degrees of freedom have been integrated out. Calculating the measure factor for Plebanksi Holst formulation without the connection degrees of freedom is one of the aims of this dissertation. This analysis is at the continuum level and in order to be implemented in spinfoams one needs to properly discretize and quantize this measure factor. The correct phase is determined by semiclassical behavior. In asymptotic analysis of the EnglePereiraRovelliLivine spinfoam model, due to the inclusion of more than the usual gravitational sector, more than the usual Regge term appears in the asymptotics of the vertex amplitude. As a consequence, solutions to the classical equations of motion of GR fail to dominate in the semiclassical limit. One solution to this problem has been proposed in which one quantum mechanically imposes restriction to a single gravitational sector, yielding what has been called the “proper” spinfoam model. However, this revised model of quantum gravity, like any proposal for a theory of quantum gravity, must pass certain tests. In the regime of small curvature, one expects a given model of quantum gravity to reproduce the predictions of the linearized theory. As a consistency check we calculate the graviton twopoint function predicted by the Lorentzian proper vertex and examine its semiclassical limit.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004488, http://purl.flvc.org/fau/fd/FA00004488
 Subject Headings
 General relativity (Physics), Gravitation, Mass (Physics), Mathematical physics, Quantum gravity, Quantum theory
 Format
 Document (PDF)
 Title
 Spectroscopic studies of ZnWO4 and doped ZnWO4 single crystals.
 Creator
 Wang, Hong, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

Zinc tungstate (ZnWO4) is promising as a scintillator and laser host material. However, the presence of color centers limit its applications. It has been found that special annealing techniques or doping with metallic elements such as Nb or Sb can bleach the samples (Zhou et al. 1986a, 1986b, 1989). A grouptheoretical analysis of the characteristic lattice vibrational modes for ZnWO4 single crystals is given. The mode assignments have been made. The temperature dependence of the Raman...
Show moreZinc tungstate (ZnWO4) is promising as a scintillator and laser host material. However, the presence of color centers limit its applications. It has been found that special annealing techniques or doping with metallic elements such as Nb or Sb can bleach the samples (Zhou et al. 1986a, 1986b, 1989). A grouptheoretical analysis of the characteristic lattice vibrational modes for ZnWO4 single crystals is given. The mode assignments have been made. The temperature dependence of the Raman spectra has been obtained experimentally in various polarization geometries. Anharmonic contributions and interactions between phonons are discussed. Photoluminescence studies of ZnWO4 (colored, colorfree), ZnWO4: Nb and ZnWO4:Sb have been carried out in the temperature range from 11 to 430 K. All samples show the blue emission band. An IR emission band with a zerophonon line (ZPL) has been found in ZnWO4 colored samples only. The lineshape function of the emission bands has been theoretically studied and compared with the experimental results. Radiative, nonradiative and multiphonon transitions have been investigated in the thermal quenching model. The temperature dependences of the intensity, the frequency and the linewidth of the ZPL have been studied. Using the Single Configurational Coordinate model, the linear coupling between electrons and phonons has been analyzed. The quadratic coupling of electrons and phonons has been studied in the Debye approximation. The coupling of electronic transitions to normal vibrational modes, pseudolocalized vibrational modes and localized modes is also discussed.
Show less  Date Issued
 1993
 PURL
 http://purl.flvc.org/fcla/dt/12346
 Subject Headings
 Physics, Condensed Matter, Physics, Optics, Engineering, Materials Science
 Format
 Document (PDF)