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Articles 121 - 150 of 227
Full-Text Articles in Physics
Hard-Sphere-Like Dynamics In Highly Concentrated Alpha-Crystallin Suspensions, Preeti Vodnala, Laurence Lurio, Michael C. Vega, Elizabeth Gaillard
Hard-Sphere-Like Dynamics In Highly Concentrated Alpha-Crystallin Suspensions, Preeti Vodnala, Laurence Lurio, Michael C. Vega, Elizabeth Gaillard
Faculty Peer-Reviewed Publications
The dynamics of concentrated suspensions of the eye-lens protein alpha crystallin have been measured using x-ray photon correlation spectroscopy. Measurements were made at wave vectors corresponding to the first peak in the hard-sphere structure factor and volume fractions close to the critical volume fraction for the glass transition. Langevin dynamics simulations were also performed in parallel to the experiments. The intermediate scattering function f(q,τ) could be fit using a stretched exponential decay for both experiments and numerical simulations. The measured relaxation times show good agreement with simulations for polydisperse hard-sphere colloids.
The Influence Of A Surface On Hysteresis Loops For Single-Domain Ferromagnetic Nanoparticles, Saad Alsari
The Influence Of A Surface On Hysteresis Loops For Single-Domain Ferromagnetic Nanoparticles, Saad Alsari
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The influence of surface effects on a hysteresis loop for single domain, ferromagnetic nanoparticles was examined. Theoretical equations were derived to describe the magnetic behavior of the domains and a MATLAB program was used to solve them. M-H curves were calculated for the case when a magnetic field is applied in the favorable magnetization direction (easy axis). In contrast, the calculations show there were no hysteresis loops when the magnetic field was applied perpendicular to the easy axis. Our studies showed how parameters of the surface such as a associated with saturation magnetization near the surface of nanoparticles and Ks …
Establishing A Quality Assurance Routine For Digital Imaging, Sulaiman Rana Al
Establishing A Quality Assurance Routine For Digital Imaging, Sulaiman Rana Al
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In the clinical medical physics field, Quality Assurance (QA) is a fundamental topic to insure patient safety and effective treatment. In recent years, the imaging hardware for diagnostic x-rays has been shifting to fully digital detectors. However, the quality assurance tests for such detectors in the clinical setting is still under development. In the Medical Imaging Department of Kettering Hospital (Kettering, OH), the currently accepted method of performing QA on detectors is to use an extensive set of tests suggested by the manufacturer. This set of tests requires about 90 minutes, which is too long for daily use. The goal …
Determination Of Dose Effects When Including Attenuation Of The Treatment Table Into Treatment Planning Computer Modeling, Abdullah Alshamrany
Determination Of Dose Effects When Including Attenuation Of The Treatment Table Into Treatment Planning Computer Modeling, Abdullah Alshamrany
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During radiation treatment, the patient commonly lies on a horizontal treatment table called a couch. The material used for the couch is chosen during the manufacturing process so as to minimize the effect of the couch on dose delivery, but it still has an effect. In addition to couch attenuation on the beam, the modern approach of using multiple beam angles for dose delivery makes treatment planning in the presence of the couch more challenging. However, the effect of the couch is not always considered when creating treatment plans, generally due to treatment planning software limitations. In this evaluation, the …
Electromagnetic Properties Of Fractal Antennas, Jordan Jeffrey Ewing
Electromagnetic Properties Of Fractal Antennas, Jordan Jeffrey Ewing
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Finite element method analysis is used to conduct electromagnetic simulations to characterize fractal antennas. This work considers wire (1D) antennas such as the triadic Koch curve, zig zag, and quadratic Koch curve of varying heights, iterations, and cross-sectional areas. Carpet (2D) antennas, including the Sierpinksi carpet, of varying heights, iterations, and deterministic and stochastic iterations are analyzed. The antenna shapes were generated in MATLAB and then modeled with finite element analysis using COMSOL Multiphysics®. The focus of this study is to determine what role various fractal patterns and iterations have on the S11 return loss and far field radiation patterns. …
A Parallel Spectral Method Approach To Model Plasma Instabilities, Kevin S. Scheiman
A Parallel Spectral Method Approach To Model Plasma Instabilities, Kevin S. Scheiman
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The study of solar-terrestrial plasma is concerned with processes in magnetospheric, ionospheric, and cosmic-ray physics involving different particle species and even particles of different energy within a single species. Instabilities in space plasmas and the earth's atmosphere are driven by a multitude of free energy sources such as velocity shear, gravity, temperature anisotropy, electron, and, ion beams and currents. Microinstabilities such as Rayleigh-Taylor and Kelvin-Helmholtz instabilities are important for the understanding of plasma dynamics in presence of magnetic field and velocity shear. Modeling these turbulences is a computationally demanding processes; requiring large memory and suffer from excessively long runtimes. Previous …
Molecular Dynamics Study Of Hydrogen Trapping And Helium Clustering In Tungsten, Ashok Gurung
Molecular Dynamics Study Of Hydrogen Trapping And Helium Clustering In Tungsten, Ashok Gurung
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The field of plasma confinement and path toward achieving thermonuclear fusion started with experimental devices like tokamak and has evolved into other more complex variants of magnetic plasma confinement such as stellarator and spherical-tokamaks. As the plasma confinement machines advance towards higher temperature and plasma density (thermonuclear fusion conditions) the role and nature of plasma-wall interaction such as possible edge plasma regimes, particle recycling at the walls and its consequence for erosion, migration and re-deposition of wall material and impurity generation, transport and radiation as well as issues of particle exhaust continues to be a dominant limiting factor due to …
Modelling Parallel Overhead From Simple Run-Time Records, Siegfried Höfinger, Ernst Haunschmid
Modelling Parallel Overhead From Simple Run-Time Records, Siegfried Höfinger, Ernst Haunschmid
Michigan Tech Publications
A number of scientific applications run on current HPC systems would benefit from an approximate assessment of parallel overhead. In many instances a quick and simple method to obtain a general overview on the subject is regarded useful auxiliary information by the routine HPC user. Here we present such a method using just execution times for increasing numbers of parallel processing cores. We start out with several common scientific applications and measure the fraction of time spent in MPI communication. Forming the ratio of MPI time to overall execution time we obtain a smooth curve that can be parameterized by …
Effect Of Thermodenuding On The Structure Of Nascent Flame Soot Aggregates, Janarjan Bhandari, Swarup China, Timothy Onasch, Lindsay Wolff, Andrew Lambe, Paul Davidovits, Claudio Mazzoleni, Et Al.
Effect Of Thermodenuding On The Structure Of Nascent Flame Soot Aggregates, Janarjan Bhandari, Swarup China, Timothy Onasch, Lindsay Wolff, Andrew Lambe, Paul Davidovits, Claudio Mazzoleni, Et Al.
Michigan Tech Publications
The optical properties (absorption and scattering) of soot particles depend on soot size and index of refraction, but also on the soot complex morphology and the internal mixing with materials that can condense on a freshly emitted (nascent) soot particle and coat it. This coating can affect the soot optical properties by refracting light, or by changing the soot aggregate structure. A common approach to studying the effect of coating on soot optical properties is to measure the absorption and scattering coefficients in ambient air, and then measure them again after removing the coating using a thermodenuder. In this approach, …
Detection And Analysis Of Polyurethane Biodegradation Due To Cryptococcus Laurentii, Tyler Jacob Zicht
Detection And Analysis Of Polyurethane Biodegradation Due To Cryptococcus Laurentii, Tyler Jacob Zicht
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Current United States aircraft are equipped with a multitude of protective coatings on the interior and exterior of the vehicle, ultimately enhancing their ability to ensure a safe and effective mission. Aircraft, over the course of their lifetime, will experience impact, corrosion, weathering, and microbial damage to its defensive structures, rendering it vulnerable to attacks. Damaged coatings are then repaired on the aircraft once detected in inspection or replaced in accordance to the lifecycle of the material on the aircraft. However potentially harmful threats such as bacteria are not considered by the Air Force to be dangerous. Therefore, the purpose …
Adaptive Optics System Baseline Modeling For A Usaf Quad Axis Telescope, Nathaniel R. Morris
Adaptive Optics System Baseline Modeling For A Usaf Quad Axis Telescope, Nathaniel R. Morris
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Atmospheric turbulence has afflicted accurate observations of celestial bodies since man first gazed upon the stars. In this past century, the technology of adaptive optics was invented to help compensate for the optical distortions that atmospheric turbulence causes. As part of that technology, artificial guide stars, wave front sensors, deformable mirrors, and other optical components were developed to correct these wave aberrations. The purpose of this study focuses on the modeling and configuration of an adaptive optics system that is appropriate for the John Bryan Observatory Quad Axis Telescope System (JBO-Q), which is funded by the United States Air Force. …
Determination Of The Shape Of A Flattening Filter Free (Fff) Radiation Beam When Modified By A Physical Wedge, Kalel Alsaeed
Determination Of The Shape Of A Flattening Filter Free (Fff) Radiation Beam When Modified By A Physical Wedge, Kalel Alsaeed
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The determination of a flattening filter free (FFF) beam profile when the collimator is intentionally modified to incorporate a physical wedge. Specifically, radiation beam profiles change shape when a metallic wedge is placed in the path of the beam. Examination of this unknown is necessary to ascertain whether a physical wedge is clinically beneficial for applications involving FFF beams. The aim of this study is to determine if the radiation profile of a flattening filter free beam having a physical wedge is comparable to a beam with a flattening filter, with the same wedge inserted. This research involves measurement of …
Extraordinary Optical Transmission In Aligned Carbon Nanotube Devices At Terahertz Frequencies., Shaikhah F. Almousa
Extraordinary Optical Transmission In Aligned Carbon Nanotube Devices At Terahertz Frequencies., Shaikhah F. Almousa
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In the phenomenon known as extraordinary optical transmission (EOT), a narrow band of selected frequencies are transmitted when incident on an array of subwavelength periodic apertures where the resonant frequency is determined by the geometry of the array of apertures and optical properties of the metal-dielectric interface. This takes place due to the excitation of surface plasmon polaritons (SPPs) at the metal and dielectric interface. Using the COMSOL Multiphysics software RF Module, a unit cell of a carbon nanotube (CNT) based EOT device is modeled in order to verify theoretical calculations of the resonant frequency using S-parameter calculations. The simulation …
Multiscale Modeling Of Carbon Nanotube Synthesis In A Catalytic Chemical Vapor Deposition Reactor, Jonathan Troville
Multiscale Modeling Of Carbon Nanotube Synthesis In A Catalytic Chemical Vapor Deposition Reactor, Jonathan Troville
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The bottom-up analysis of Carbon Nanotube synthesis is not well understood. Specifically, the question as to how carbon adsorbs to a substrate inclusive of a supported catalyst may lead to the energetically favorable structure of a hexagonal close- packed structure along the wall, or walls, of the tube. A first time simulation using COMSOL Multiphysics has been generated in order to capture the gas-phase mech- anism which leads to carbon production. It is thought that the carbon adsorbs and the walls are formed from the bottom up and the inside out for multi-wall CNTs. The studies involved accurately setting up …
Towards A Prediction Of Landscape Evolution From Chemical Weathering And Soil Production, Eric Alan Jackson
Towards A Prediction Of Landscape Evolution From Chemical Weathering And Soil Production, Eric Alan Jackson
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The time evolution of a periodic landscape under the influence of chemical weathering and physical erosion is computed. The model used incorporates weathering and soil production as a flux limited reaction controlled by groundwater flow. Scaling of the flow rate is obtained from a percolation theoretic treatment. The erosion of the soil material produced by this process is modeled by the diffusion of elevation, as consistent with downslope soil transport proportional to the tangent of the angle of the topography, and application of the equation of continuity to surface soil transport. Three initial topographies are examined over a periods of …
Thermoelectrical Properties Of Covetics, S. M. Sarif Rana
Thermoelectrical Properties Of Covetics, S. M. Sarif Rana
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Covetics are hybrid materials fabricated by fusing carbon with metals in an induction furnace. There is an indication that covetics have better thermal and electrical proper-ties in comparison with pure metals. The main goal of this research is to study thermal transport in covetics measured by specific absorption rate using calorimetry. In addition, temperature distribution has been measured along the both metal and covetic wires carrying currents of 5 A and 10 A, respectively. The first set of copper covetic (Cu cov) samples with nominal content of 36 at% carbon were prepared by Third Millennium Materials Company (TMMC) in the …
Terahertz Molecular Spectroscopy As A Tool For Analytical Probing Of Cellular Metabolism, Mitchell Cameron Paul
Terahertz Molecular Spectroscopy As A Tool For Analytical Probing Of Cellular Metabolism, Mitchell Cameron Paul
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Terahertz spectroscopy has found use as an analytical tool in determining chemical composition of exhaled human breath. This thesis demonstrates a novel application of this technology - analytical sensing of gaseous metabolic products of several types of human cell cultures. An innovative experimental system was developed for probing cellular metabolism using terahertz [THz] rotational spectroscopy. Gaseous emissions of cell cultures were analyzed and compared between several cell types. Cancerous and healthy lung cells as well as cancerous liver cells were studied. This technique carries a lot of promise as a noninvasive method of distinguishing between cell types and identifying cell …
Experimental Investigation Of A Parametric Excitation Of Whistler Waves, Nathan E. Zechar
Experimental Investigation Of A Parametric Excitation Of Whistler Waves, Nathan E. Zechar
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Previous theoretical work has shown that a parametric interaction between electrostatic lower oblique resonance (LOR) and ion acoustic waves (IAW) can produce electromagnetic whistler waves in a cold magnetized plasma. It was also demonstrated theoretically that this interaction can more efficiently generate electromagnetic whistler waves than by direct excitation using a conventional loop antenna. For the purpose of experimentally validating the above result, an experimental facility was designed and constructed utilizing a vacuum chamber, electromagnets, and a helicon plasma source array capable of producing a volume of plasma with high density and spatial uniformity. Additionally, positioning equipment and plasma diagnostics …
Terahertz Molecular Spectroscopy As A Tool For Analytical Probing Of Cellular Metabolism, Mitchell Cameron Paul
Terahertz Molecular Spectroscopy As A Tool For Analytical Probing Of Cellular Metabolism, Mitchell Cameron Paul
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Terahertz spectroscopy has found use as an analytical tool in determining chemical composition of exhaled human breath. This thesis demonstrates a novel application of this technology - analytical sensing of gaseous metabolic products of several types of human cell cultures. An innovative experimental system was developed for probing cellular metabolism using terahertz [THz] rotational spectroscopy. Gaseous emissions of cell cultures were analyzed and compared between several cell types. Cancerous and healthy lung cells as well as cancerous liver cells were studied. This technique carries a lot of promise as a noninvasive method of distinguishing between cell types and identifying cell …
A Study Of Alkali-Resistant Materials For Use In Atomic Physics Based Systems, Aaron Thomas Fletcher
A Study Of Alkali-Resistant Materials For Use In Atomic Physics Based Systems, Aaron Thomas Fletcher
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Due to shortcomings in emerging alkali-based atomic physics based systems, a need to investigate alkali resistant materials has arisen. There is interest in alkali based systems such as atomic clocks and diode pumped alkali laser (DPAL) systems. In the case of atomic clocks and DPALs, alkali metal vapor, such as Rb, is the active part of the systems. The alkali vapor is confined in some manner of housing, but the transmission of electromagnetic radiation is required in the cells. This requires the incorporation of windows into the cell. The current window material, however, have been shown to degrade over time, …
Conditions For Super-Adiabatic Droplet Growth After Entrainment Mixing, Fan Yang, Raymond Shaw, Huiwen Xue
Conditions For Super-Adiabatic Droplet Growth After Entrainment Mixing, Fan Yang, Raymond Shaw, Huiwen Xue
Michigan Tech Publications
Cloud droplet response to entrainment and mixing between a cloud and its environment is considered, accounting for subsequent droplet growth during adiabatic ascent following a mixing event. The vertical profile for liquid water mixing ratio after a mixing event is derived analytically, allowing the reduction to be predicted from the mixing fraction and from the temperature and humidity for both the cloud and environment. It is derived for the limit of homogeneous mixing. The expression leads to a critical height above the mixing level: at the critical height the cloud droplet radius is the same for both mixed and unmixed …
Surface Effect Of Ferromagnetic Nanoparticles On Transition Between Single- And Multi-Domain Structure Or Between Single-Domain Structure And Superparamagnetic Phase, Hind Adawi
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Surface effects on critical dimensions of ferromagnetic nanoparticles were studied. Algebraic equations were derived and numerically solved for critical radius RC2 of ferromagnetic nanoparticles describing the transition between single- and multi-domain magnetic structure. Results were analyzed to illustrate the effect of surface parameters related to saturation magnetization a, exchange interaction ß, and anisotropy KS on the critical radius of nanoparticles with a core value of anisotropy KV. Available experimental data for MnBi, FePt, and CoPt or for Fe nanoparticles were used as examples of nanoparticles with high and low values of KV, respectively. Our studies clearly show that discrepancies existing …
Social Network Analysis And The Representation Of Female Students In Introductory Undergraduate Physics, Sarah Teresa Hierath
Social Network Analysis And The Representation Of Female Students In Introductory Undergraduate Physics, Sarah Teresa Hierath
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Physics Education Research has begun to focus on the learning habits, success, and connections of students in physics classrooms using Social Network Analysis (SNA). SNA is an important tool in studying classroom dynamics because it can be used to map the social structure of a classroom's interactions and to aid in understanding how students work and study together. This study presents network diagrams, statistics, centrality measures, and conceptual understanding correlations for 7 different sections of introductory physics. Centrality measures were determined from a first and last week survey in which students were asked to indicate their study partners within the …
Terahertz Spectroscopic Breath Analysis As A Viable Analytical Chemical Sensing Technique, Robert M. Schueler
Terahertz Spectroscopic Breath Analysis As A Viable Analytical Chemical Sensing Technique, Robert M. Schueler
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The ability to quantify trace chemicals in human breath enables the possibility of identifying breath biomarkers to aid in diagnosis. The vast majority of the studies in the analytical breath analysis rely on GC-MS techniques for quantification of the human breath composition1,2,3,4. THz spectroscopy of breath is rapid, sensitive, and highly specific molecular identification in complex mixtures containing 10-100 analytes with near `absolute' specificity. THz spectroscopic breath analyzers require chemical preconcentration. A newly developed custom preconcentrator was constructed and compared in its performance to a commercial system. Unlike the commercial counterpart, the new system does not require cryogenic liquids, is …
A Social Network Analysis Of An Introductory Calculus-Based Physics Class With Comparisons Of Traditional And Non-Traditional Students, Fci Scores, And Network Centralities, Emily Sandt
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The use of social network analysis in physics education research seeks to advance understanding of how students' collaborative tendencies influence trends of learning. Common useful measurements are network size, density of connections, and centrality measures that describe the importance of nodes' positions. This study compared four different centrality measures at the beginning and end of seven sections of an introductory calculus-based physics course. The Force Concept Inventory was used as a measure of conceptual learning at pre- and post-course administrations. The main focus of this study was to identify if differences in network centralities and conceptual learning/knowledge exist with respect …
Correlations Between Introductory Students’ Attitudes About Physics And Conceptual Understanding, Raym Alzahrani
Correlations Between Introductory Students’ Attitudes About Physics And Conceptual Understanding, Raym Alzahrani
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The purpose of this study is to measure correlations between the students’ incoming attitudes, beliefs and expectations about physics and their conceptual understanding. The study presents a profile of the attitudes and beliefs for Wright State University students who enrolled in calculus-based General Physics I courses during academic years 2014-2015 and 2015-2016. Students’ initial and final attitudes, measured using the CLASS, are correlated with initial and final conceptual gain, measured using the Force Concept Inventory. Students’ initial attitudes (Opre) was correlated with students’ gain (FCIgain) in many sections. Correlations between students’ final attitudes (Opost) and their conceptual understanding (FCIpost), reported …
High Powered Pulsed Terahertz Light Generation From Superconducting Antenna Arrays, Nicholas C. Padgett
High Powered Pulsed Terahertz Light Generation From Superconducting Antenna Arrays, Nicholas C. Padgett
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Terahertz radiation is invaluable for use in spectroscopy and imaging work due to its nondestructive nature. It has become a key focus for those wishing to develop sensors capable of detecting weapons and narcotics unobtrusively and at a distance as well as characterizing materials and identifying defects. An ultrafast pulsed (femtoseconds) laser incident on a superconducting ring has been predicted to cause the emission of terahertz (THz) radiation. It is theorized that the radiation is a result of the supercurrent being modulated by the breaking and recombining of Cooper pairs on the order of picoseconds, where the time scale determines …
Millimeter – Wave/Terahertz Chirped Michelson Interferometer Techniques For Sub Surface Sensing, Dinesh Amal Mirando
Millimeter – Wave/Terahertz Chirped Michelson Interferometer Techniques For Sub Surface Sensing, Dinesh Amal Mirando
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Over the last couple of decades, the field of millimeter-wave (mmW) and terahertz (THz) radiation has seen an accelerated growth thanks to developments in high quality mmW/THz sensors. These developments have contributed to many useful applications in the fields of medicine, security, construction, etc. Non-destructive evaluations such as the detection of defects in materials is currently one of the major applications of mmW/THz radiation. These evaluations are performed using mmW/THz continuous-wave radar systems. In this study, we discuss how Frequency Modulated Continuous Wave (FMCW) techniques can enhance sensing applications through the use of a Michelson interferometer. This allows multiple objects …
Heating Power Of Coated Fecov Magnetic Nanoparticles, Hanaa Ali Alshammari
Heating Power Of Coated Fecov Magnetic Nanoparticles, Hanaa Ali Alshammari
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The effect of coatings on the heating curves of magnetic nanoparticles was studied in this Thesis. Iron cobalt vanadium (FeCoV) nanoparticles with oxide (CoOFe2O3) and graphite (C) coating to prevent oxidation, were synthesized through thermal plasma processing method. The magnetic nanoparticles had an average diameter of 30 nm. In the case of FeCoV with oxide coating, the initial diameter of the pure FeCoV nanoparticles on average was 30 nm but after oxidation 5 nm thick oxide layer was created. As a result of this oxidation, the magnetic core of FeCoV nanoparticles was shrunk from 30 nm to 20 nm in …
Use Of Clearview Gel Dosimeter For Quality Assurance And Testing Of Stereotactic Radiosurgery, Erik Joseph-Leonard Courter
Use Of Clearview Gel Dosimeter For Quality Assurance And Testing Of Stereotactic Radiosurgery, Erik Joseph-Leonard Courter
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There exists a lack of accurate, reproducible three-dimensional dosimetry techniques for stereotactic radiosurgery (SRS) commissioning and quality assurance. This experiment evaluates the use of ClearView gel dosimeters as an alternative to current methods for small field dosimetry in SRS testing. ClearView differs from other gel dosimeters in that it uses tetrazolium salt in its chemical make-up in place of traditional Fricke-type compounds. Using a Varian TrueBeam radiotherapy system to deliver the radiation, three vials of ClearView gel dosimeter were tested in three different dose delivery scenarios. The first test examined the dosimeter's response to a static beam with the dose …