Physics Commons^™

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 …

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 …

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

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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 …

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 …

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 …

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 …

Assessment Of The Applicability Of Terahertz Spectroscopic Breath Sensing Towards Monitoring Type 1 Diabetic Mellitus, Jessica Rose Thomas

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Type 1 diabetes is a condition that cumulatively costs around $14.9 billion in medical expenses every year in the United States. Besides being costly, the monitoring of this disease is invasive, painful, and often embarrassing to the afflicted individual; blood and urine testing is currently the daily method of monitoring blood glucose and ketone levels in the body of type 1 diabetics. Though the use of these samples is standard, another avenue for possibly determining blood glucose has not been completely explored. With over 3000 chemicals reportedly found in exhaled human breath, biomarkers associated with this disorder and many of …

Laser Guide Star Design Project For The Usaf John Bryan State Park Quad Axis Observatory, Nathan Michael Figlewski

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Atmospheric Turbulence has long remained one of the great unsolved problems in physics. Laser guide stars were invented in order for telescopes to overcome atmospheric turbulence while used in combination with adaptive optics. This study focuses on the design and implementation phase of a Rayleigh laser guide star for the John Bryan State Park Observatory, owned and operated by the United States Air Force. Atmospheric simulations, as well as optical modelling of proposed equipment, were completed to optimize the design of this laser guide star. In addition, a novel method for the implementation of the guide star onto this very …

Surface Effects On Critical Dimensions Of Ferromagnetic Nanoparticles, Vartika Chaudhary

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This work studies surface effects on the critical dimensions of ferromagnetic nanoparticles. Iron nanoparticles with different mean diameters from 5.9 nm to 21.4 nm used in this research were prepared by thermal decomposition of iron pentacarbonyl in the presence of oleic acid/octyl ether at Cambridge University, United Kingdom. Heating response of these ferromagnetic nanoparticles suspended in water were measured experimentally during which same amount of iron nanoparticles and di-ionized water were irradiated by an alternating magnetic field and the increase in temperature of these samples was measured. Heating performance of nanoparticles was described in terms of Specific Absorption Rate (SAR) …

Chemical Analysis Of Exhaled Breath By Means Of Terahertz Rotational Spectroscopy, Tianle Guo

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Terahertz spectroscopy, due to the high sensitivity and specificity that it affords, has been incorporated in many fields to aid in the chemical analysis of gases. One potential application is to detect bio-markers in human breath for early diagnosis. Our current aim of our research is to establish a relationship between several chemicals and the glucose levels from human exhaled breath. 20 chemical including Acetone, Carbon monoxide (CO), Methanol were studied. Volunteers' breath samples were processed through a pre-concentration system before being injected into the spectrometer. Initially, a commercial preconcentration system, Entech 7100A, was used. However, due to the limitations …

Thermal Properties Of Magnetic Nanoparticles In External Ac Magnetic Field, Anna Beata Lukawska

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This work studies thermal properties of magnetic nanoparticles in an external ac magnetic field. Dried iron and cobalt nanoparticles were prepared by thermal decomposition of iron pentacarbonyl (Fe(CO)5) and dicobalt octacarbonyl (Co2(CO)8), triscobalt nona(carbonyl)chloride (Co3(CO)9Cl), or tetracaobalt dodecacarbonyl (Co4(CO)12) [1]. The samples had different mean diameters: 5.6 - 21.4 nm for iron and 6.5 - 19.4 nm for cobalt. Each sample was exposed to ac magnetic field and the increase in temperature of the sample was measured. Results were analyzed to find the critical diameters for the transitions from multi-domain to single-domain and from single-domain to superparamagnetic regime. The nanoparticles …

Thin Film Growth Of Dielectric Materials By Pulsed Laser Deposition, Jason Christopher Anders

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Thin films of Sr_yCa_1-yZr_1-xTi_xO₃ (SCZT) with x = 0.8, y = 0.01, CaHf_1-xTi_xO₃ (CHT) with x = 0.8, and _xBiScO₃ - (1-x) BaTiO₃ with x = 0.36 (BSBT(36/64)) showing a high permittivity are useful both in capacitor applications. These dielectric thin films with a SrRuO₃ (SRO) conductive bottom electrodes were prepared by using pulsed laser deposition on <100< La_0.3Sr_0.7Al_0.65Ta_0.35O₃ (LSAT) single crystal substrates. In a search of optimal conditions to achieve epitaxially grown SCZT, CHT, …

Ultraviolet Rayleigh Scatter Imaging For Spatial Temperature Profiles In Atmospheric Microdischarges, James E. Caplinger

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Spatially resolved temperature measurements within a microdischarge in atmospheric pressure air have been conducted using Rayleigh scattering of a pulsed ultraviolet laser. Scattering intensity images were used to generate a radial profile of translational temperature, with the analysis based on the ideal gas inverse relationship of temperature and gas density. Rayleigh scattering results were compared to standard optical emission spectral analyses of N2(C3Πu - B3Πg) bands, where the calculated rotational temperatures from emission were in reasonable agreement with the Rayleigh translational temperature profiles.

Curie Temperature Measurement Of Ferromagnetic Nanoparticles By Using Calorimetry, Xing Zhao

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This Thesis studies the relationship between diameter (size) of ferromagnetic nanoparticles and Curie temperature. Iron nanoparticles with different diameters from 5.9 nm to 21.4 nm were prepared by thermal decomposition of iron pentacarbonyl in the presence of oleic acid/octyl ether at Cambridge University, United Kingdom. Heating response of these ferromagnetic nanoparticles suspended in water were measured experimentally during which the same amount of iron nanoparticles and di-ionized water were subjected to an alternating magnetic field and the increase in temperature of these samples was measured. Heating performance of nanoparticles was described by Specific Absorption Rate (SAR). Heating and cooling rate …

Electromagnetic Characterization Of Af455 With Dna-Ctma In Solvent Blends, Jessica Marie Hendricks

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This work studies the electromagnetic properties of AF455, a two photon dye, DNA bound with cetyltrimethyl ammonium (CTMA), in liquid solvent blends for use in thin film optical filters. The liquid properties of the materials are believed to be transferred to the films. The solvent blends used are ratios of toluene (T) and dimethyl sulfoxide (DMSO). The complex permittivity and permeability of the samples are measured using the short open coaxial line technique in the frequency range of 1.0 x 107 Hz to 2.0 x 109 Hz. In this frequency range, AF455 does not act as a two photon absorber. …

Capturing And Modeling A Three-Dimensional Stationary Noise Source Directivity Pattern With A Dynamic Array In The Near Field, Randy Mieskoski

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The author has studied several legacy landmark methodologies to develop an original measurement technique. Spherical harmonics modeling practices were leveraged to accurately represent a source directivity pattern. In this thesis a lightweight microphone measurement array that was manually maneuvered around a static noise source was employed. The measurement technique consisted of inserting a head-tracker sensor onto the microphone array to allow the location of the captured acoustic Sound Pressure Level (SPL) to be investigated. By leveraging the historical methodologies the acoustic SPL and location data collected with this technique were processes to represent a directivity pattern of the compressor source …

Analytical Chemical Sensing Using High Resolution Terahertz/Submillimeter Wave Spectroscopy, Benjamin L. Moran

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A highly sensitive and selective Terahertz gas sensor used to analyze a complex mixture of Volatile Organic Compounds (VOCs) has been developed. To best demonstrate analytical capabilities of a THz chemical sensor, we chose to perform analytical quantitative analysis of a certified gas mixture using a prototype gas phase chemical sensor that couples a commercial preconcentration system (Entech 7100A) to a custom high resolution THz spectrometer. A Method TO-14A certified mixture of thirty-nine VOCs was purchased. Twenty-six of the thirty-nine chemicals were identified as suitable for THz spectroscopic detection. The Entech 7100A system is designed and marketed as an inlet …

Characterization Of Ceramic Matrix Composite Materials Using Millimeter-Wave Techniques, Matthew Lee Bischoff

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This thesis describes studies that were carried out on Ceramic Matrix Composite (CMC) materials. These materials were provided by the Air Force Research Laboratory for evaluation in the millimeter-wave frequency region with the goal of developing Non-Destructive Evaluation techniques. This thesis centers on describing the measured reflections from an Oxide/Oxide and SiC/SiNC CMC materials. Models were derived from the Fresnel equations to account for the reflected and transmitted waves in these materials. System models were developed to describe the power coupling of the spectra measured in three separate measurement systems. Using these models the complex index of refraction was determined …

Characterization Of Ceramic Composite Materials Using Terahertz Non-Destructive Evaluation Techniques, Lindsay Owens

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The characterization of defects such as rust, voids, etc. on materials and the analysis and prediction of strain and stress induced breakdown are well known applications of non-destructive evaluation (NDE) techniques. THz radiation has been suggested as an effective NDE tool for use in the field of ceramics and ceramic matrix composite materials (CMC), via THz spectroscopy and imaging. The goal of this research is to monitor the progression of thermal and mechanical damage applied to the CMC materials using terahertz spectroscopic imaging in order to create a predictive model that will correlate THz imaging data of these materials to …

Terahertz Time Domain Spectroscopy And Fresnel Coefficient Based Predictive Model, Justin C. Wheatcroft

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An optical material parameter predictive model that accounts for sample to air interfaces was developed. The model predicts how a terahertz time-domain spectroscopy time domain pulse will be affected as it passes through a given thickness of a material. The model assumes a homogenous, linear, isotropic dielectric or semiconductor. The inputs to the model are the real and imaginary refractive indices across the desired frequency band. Different dielectric material's optical parameters were taken from the literature and the predicted time domain pulses were shown. It was also shown that the refractive index and absorption coefficient for samples that were optically …

Electronic And Structural Properties Of Silicene And Graphene Layered Structures, Patrick B. Benasutti

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Graphene is a two-dimensional nanomaterial with useful and novel properties, but it is a material that does not integrate well with the current silicon microchip infrastructure. Silicene could solve this problem, as it is made of silicon yet retains the novel properties that make graphene desirable. This thesis will outline density functional calculations of a newly proposed structure involving the combination of these two materials. The structure includes silicene layered on graphene in such a manner that it composes a superlattice. It will be examined using the ab-initio density functional theory software Quantum Espresso.

This superlattice structure is proposed to …

Photorefractive Thin Films And Polymers For Use In Organic-Inorganic Hybrid Cells, Steven Harris Buller

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Two classes of materials were investigated as possible replacements for the bulk photorefractive windows in inorganic-organic hybrid cells: thin films and polymers. Each material was fabricated and subsequently characterized using two different methods due to their different stages of development. The thin films were characterized by X-ray diffraction while the polymers were characterized by two-beam coupling. Thin films of strontium barium niobate and potassium niobate were grown, using pulsed laser deposition, on four different substrates. It was found that it was possible to grow a thin film of potassium niobate in the correct orientation to replace a bulk photorefractive window. …

On The Quantization Problem In Curved Space, Benjamin Bernard

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The nonrelativistic quantum mechanics of particles constrained to curved surfaces is studied. There is open debate as to which of several approaches is the correct one. After a review of existing literature and the required mathematics, three approaches are studied and applied to a sphere, spheroid, and triaxial ellipsoid.

The first approach uses differential geometry to reduce the problem from a three dimensional problem to a two-dimensional problem. The second approach uses three dimensions and holds one of the separated wavefunctions and its associated coordinate constant. A third approach constrains the particle in a three-dimensional space between two parallel surfaces …

Comparing Us And Chinese High-School Physics Teaching In Terms Of The Use Of Inquiry, Lingbo Qian

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Inquiry based teaching has been widespread in the United States as well as in China in the last two decades. It was implemented by many teachers and shown to be effective in both countries. This study examines the extent to which inquiry-based teaching in high-school physics is practiced in US and China through the use of lesson observations and a survey. Nineteen lessons taught by 19 teachers (9 US and 10 Chinese) were observed (N=19). Results show that both US and Chinese teachers know well about the inquiry-based teaching. However, in practice, little inquiry-based teaching was observed in the two …

Dielectric Constant Measurements Using Atomic Force Microscopy System, Hembathanthirige Yasas Dhanapala

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A new technique to obtain local dielectric constant of thin films was developed using atomic force microscopy system. This technique, in addition to other characterization methods such as AFM imaging and X-Ray diffraction, was used to study, as an example, dielectric constant of thin films of 0.3BiScO3 - 0.7BaTiO3. The thin films were fabricated by using pulsed laser deposition technique under following temperature of the substrate: 6500C, 7000C and 7500C. At each temperature, two different oxygen pressures were used in deposition chamber: 50 mTorr and 100 mTorr. Our goal was to find optimal growth conditions with the highest dielectric constant …

Radio-Frequency Heating Of Magnetic Nanoparticles, Mohammud Zafrullah Jagoo

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In the present study, a power supply capable of converting a direct current into an alternating current was built. The frequency of oscillation of the output current could be varied from 174.8 kHz to 726.0 kHz by setting a set of capacitors in resonance. To this power supply is attached a 20-turns copper coil in the shape of a spiral. Because of the high heat generated in the coil, the latter has to be permanently water-cooled. A vacuum pump removes the air between the sample holder and the coil. A fiber optic temperature sensor with an accuracy of 0.001 K …

The Mechanisms Of Luminescence From Zno Under Electron Irradiation, Devin Marlinjames Todd

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Zinc Oxide has been utilized for centuries in a wide range of applications including medical, food, and materials. It is now that ZnO draws much attention to its potential as a high frequency semiconductor and UV laser. As a result, there has been much investigation into the properties of ZnO and many papers have been published in the area. Despite this fact, there is still much that is unknown about its electronic defect structure. This research investigates the broad region of the Zinc Oxide luminescence spectrum known as the green band, which lies roughly between 480 - 580 nm or …

Characterization Of Structured Nanomaterials Using Terahertz Frequency Radiation, Andrew John Niklas

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Measurements that use terahertz frequency radiation to characterize materials are beneficial for scientists trying to determine the physical parameters that govern the interaction of electromagnetic waves and matter at those frequencies. Results will be presented of time domain terahertz spectroscopy measurements taken in forward and backward scattering directions from vertically aligned arrays of multi-walled carbon nanotubes and thin films of perforated copper. The intent of this research is to both corroborate results from independent research groups conducting similar experiments and to further increase understanding in the scientific community with respect to carbon nanotube reflection phenomena at terahertz frequencies.

Computed Tomography Reconstruction: Investigating The Effect Of Varying Circle Diameter, William F. Sanders Iv

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In Computed Tomography (CT) reconstruction, several methods for determining the intensity of individual pixels from the back-projection of the scanned profiles exist. The standard reconstruction method uses linear interpolation between ray values to determine pixel intensity. This study quantifies the effects of varying circle diameter on the accuracy of an alternative method where the pixel is approximated as a circle and the area contributions calculated.

A library of 104 scans in 3 image families was created by a synthetic CT scanner and reconstructed with circle radii from 0.1 to 1.0 pixel in 0.1 pixel steps. Images were compared against a …