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Full-Text Articles in Physics

Independent And Simultaneous Control Of Electromagnetic Wave Properties In Self-Collimating Photonic Crystals Using Spatial Variance, Jesus Javier Gutierrez Jan 2020

Independent And Simultaneous Control Of Electromagnetic Wave Properties In Self-Collimating Photonic Crystals Using Spatial Variance, Jesus Javier Gutierrez

Open Access Theses & Dissertations

Photonic crystals are engineered periodic structures that provide great control over electromagnetic waves. One of these mechanisms is self-collimation, in which the electromagnetic wave travels through the photonic crystal along an axis of the lattice without diffracting or spreading. This mechanism of self-collimation is a dispersion phenomenon, which is dependent on the unit cell's physical and geometrical characteristics. An algorithm for generating spatially variant lattices (SVL) was developed that can change geometrical properties in photonic crystals as a function of position, like unit cell orientation, fill fraction, symmetry, and others in a manner that is smooth, continuous, and virtually ...


Magnetic Nanoparticles For Hyperthermia For Cancer Treatment, Bianca Paola Meneses Brassea Jan 2019

Magnetic Nanoparticles For Hyperthermia For Cancer Treatment, Bianca Paola Meneses Brassea

Open Access Theses & Dissertations

Fe3O4 and NixCu4-x magnetic nanoparticles were synthesized using supercritical conditions of liquids and wet chemistry, respectively. Characterization methods (VSM, SEM, TEM, and magnetic hyperthermia) yielded results that prove feasibility for magnetic hyperthermia for cancer treatment.


Computational Studies On Perovskite-Metallofullerene Interface And Magnetic Properties Of Mn-Based Mixed Olivines, Bethuel Omutiti Khamala Jan 2019

Computational Studies On Perovskite-Metallofullerene Interface And Magnetic Properties Of Mn-Based Mixed Olivines, Bethuel Omutiti Khamala

Open Access Theses & Dissertations

Methyl ammonium lead halide (MAPbX3) perovskite based solar cells have recently emerged as promising class of materials for photovoltaic applications with efficiencies reaching over 22%. Designing interfaces with strong binding is vital to developing efficient, high-performing solar cells. Fullerene-based materials are widely employed as efficient electron acceptors and can serve as electron transporting layer in perovskite based solar cells. We have studied interfaces of methyl ammonium lead iodide MAPbI3 with Sc3N@C80 fullerene and Sc3N@C80PCBM fullerene derivate within the density functional formalism. Different surface terminations and orientations of the methyl ammonium are examined for binding of the fullerene layer ...


Experimental Laser Powder Bed Fusion System For Difficult To Process Metallic Materials, Syed Zia Uddin Jan 2018

Experimental Laser Powder Bed Fusion System For Difficult To Process Metallic Materials, Syed Zia Uddin

Open Access Theses & Dissertations

The focus of this research was twofold, such as development of defect free fabrication parameters for laser powder bed fusion (LPBF) processing of crack prone or difficult to process metallic materials, and study of the temperature dependence of emissivity for some commonly used metal alloy powders in LPBF process. The later objective extends to the implementation of multiwavelength (MW) pyrometer technology for in situ true surface temperature measurement in LPBF process. LPBF is an additive manufacturing (AM) process capable of layer-by-layer manufacturing by successive laser melting of each layer according to CAD data. AM manufacturing has the inherent advantages of ...


Magnetic And Catalytic Properties Of Transition Metal Doped Mos2 Nanocrystals, Luis Martinez Jan 2018

Magnetic And Catalytic Properties Of Transition Metal Doped Mos2 Nanocrystals, Luis Martinez

Open Access Theses & Dissertations

Magnetism and catalytic activity of nanoscale layered two-dimensional (2D) transition metal dichalcogenides (TMDs) have gained an increasing research interest in the recent past. To broaden the current knowledge and understanding on this subject, in this work, together with my collaborators, I study the magnetic and electrocatalytic properties of hydrothermally grown pristine and transition metal doped (10% of Co, Ni, Fe and Mn) 2H-MoS2 nanosheets/nanocrystals (NCs), with the particle size of 25-30 nm. A broad range of experimental measurements such as x-ray diffraction, transmission electron microscopy, x-ray photo absorption spectroscopy, Raman spectroscopy, magnetic, catalytic and electron spin resonance have been ...


Electronic Structure Studies On Transition Metal Containing Endohedral Fullerenes, Carbon Onions And Zinc Sulfide Cages, Shusil Bhusal Jan 2017

Electronic Structure Studies On Transition Metal Containing Endohedral Fullerenes, Carbon Onions And Zinc Sulfide Cages, Shusil Bhusal

Open Access Theses & Dissertations

We present the most stable structures for VXSc3-XN@C2n (where X=1-3 and 2n=70, 76, 78 and 80) using a systematic procedure that involves all possible isomers of the host fullerene cages. Subsequently, a detailed investigation of structural and electronic properties of the lowest energy isomers is performed using density functional theory in combination with large polarized Gaussian basis sets. The search procedure developed involved structural optimizations of thousands of fullerenes and correctly identifies the experimentally observed VSc2N@C80 and V2ScN@C80 isomer as the most stable structures. The structural analysis shows that a few V-doped endohedral fullerenes do ...


Ac Susceptibility And Epr Investigations Of Superspin Dynamics In Manganese Oxide Nanoparticles, Mahesh Koirala Jan 2017

Ac Susceptibility And Epr Investigations Of Superspin Dynamics In Manganese Oxide Nanoparticles, Mahesh Koirala

Open Access Theses & Dissertations

We have investigated the superspin dynamics of 5 nm and 10 nm mixed state Mn3O4 nanoparticles utilizing ac-susceptibility and electron paramagnetic resonance measurements. The out of phase component of the ac-susceptibility measurements show a magnetic anomaly below (T


Raman Microscopic Analysis Of Internal Stress In Boron-Doped Diamond Thin Films, Emma M.A. Sundin Jan 2017

Raman Microscopic Analysis Of Internal Stress In Boron-Doped Diamond Thin Films, Emma M.A. Sundin

Open Access Theses & Dissertations

The correlations between induced stress on undoped and boron-doped diamond (BDD) thin films, sample chemical composition, and fabrication substrate are investigated in this study via confocal Raman microspectroscopic analysis. Stability of BDD films is relevant to fast-scan cyclic voltammetry, as film delamination and dislocation of BDD-coated electrodes that can occur during neurosurgical electrode implantation can negatively impact the biosensing reliability of this technique. Electrodes were fabricated by coating cylindrical tungsten rods using a custom-built chemical vapor deposition reactor. The results of the analysis reveal a direct correlation between regions of pure diamond and enhanced material stress, as well as preferential ...


Label-Free Raman Imaging To Monitor Breast Tumor Signatures, John Ciubuc Jan 2017

Label-Free Raman Imaging To Monitor Breast Tumor Signatures, John Ciubuc

Open Access Theses & Dissertations

Methods built on Raman spectroscopy have shown major potential in describing and discriminating between malignant and benign specimens. Accurate, real-time medical diagnosis benefits in substantial improvements through this vibrational optical method. Not only is acquisition of data possible in milliseconds and analysis in minutes, Raman allows concurrent detection and monitoring of all biological components. Besides validating a significant Raman signature distinction between non-tumorigenic (MCF-10A) and tumorigenic (MCF-7) breast epithelial cells, this study reveals a label-free method to assess overexpression of epidermal growth factor receptors (EGFR) in tumor cells. EGFR overexpression sires Raman features associated with phosphorylated threonine and serine, and ...


Methods For Producing Graphene From Petroleum By-Products, Eva M. Deemer Jan 2017

Methods For Producing Graphene From Petroleum By-Products, Eva M. Deemer

Open Access Theses & Dissertations

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Bragg Gratings In Polarization Maintaining Optical Fiber As Three Dimensional Strain Sensor, Joel Quintana Jan 2017

Bragg Gratings In Polarization Maintaining Optical Fiber As Three Dimensional Strain Sensor, Joel Quintana

Open Access Theses & Dissertations

Fiber-Bragg Gratings (FBG) for Structural Health Monitoring (SHM) have been studied extensively as they offer electrically passive operation, electromagnetic interference (EMI) immunity, high sensitivity and multiplexing as compared to conventional electric strain sensors. FBG sensors written within polarization maintaining (PM) optical fiber offer ad- ditional dimensions of strain measurement, greatly reducing the number of sensors needed to properly monitor a structure. This reduction however, adds complexity to the dis- crimination of the sensorâ??s optical response to its corresponding applied strains. This Dissertation defines the set of algorithms needed to measure planar strain using PM-FBGs exclusively. It defines the minimum ...


Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle Jan 2017

Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle

Open Access Theses & Dissertations

A density functional theory (DFT) study on the geometric and electronic structure of C60 and Sc3N@C80 along with their adsorption on pristine single layer graphene (SLG) is presented. C60 is found to adsorb in two nearly degenerate configurations: (i) with a pentagon facing the SLG, which is the most stable one, and (ii) with a hexagon facing the SLG in a face-to-face perfect alignment, rarely common in Ï?â??Ï? interactions, 0.06 eV higher in energy. The calculated binding energy of 0.76 eV, which includes dispersion effects, is in good agreement with previous theoretical and experimental reports ...


Molecular Dynamics Study On Defect Reduction Strategies Towards The Fabrication Of High Performance Cd1-Xznxte/Cds Solar Cells, Jose Juan Chavez Jan 2015

Molecular Dynamics Study On Defect Reduction Strategies Towards The Fabrication Of High Performance Cd1-Xznxte/Cds Solar Cells, Jose Juan Chavez

Open Access Theses & Dissertations

Cadmium Telluride is a material widely used in terrestrial thin film photovoltaic applications due to its nearly ideal band gap (~1.5 eV) and high absorption coefficient. Due to its low manufacturing cost, this technology has the potential to become a significant energy resource if higher energy conversion efficiencies are achieved. However, the module efficiencies (~14%) are still far from the theoretical maximum (~30%) for this material in a single junction configuration. The reason behind this low performance is attributed to the high number of defects that are present within the device materials. The physics behind the formation mechanisms of ...


Digitally Manufactured Spatially Variant Photonic Crystals, Javier Jair Pazos Jan 2014

Digitally Manufactured Spatially Variant Photonic Crystals, Javier Jair Pazos

Open Access Theses & Dissertations

Metamaterials and photonic crystals are engineered composites that exhibit electromagnetic properties superior to those found in nature. They have been shown to produce novel and useful phenomena that allow extraordinary control over the electromagnetic field. One of these phenomena is self-collimation, an effect observed in photonic crystals in which a beam of light propagates without diffraction and is forced to flow in the direction of the crystal. Self-collimation however, like many of the mechanisms enabled through dispersion engineering, is effective in directions only along the principal axes of the lattice. To this effect, a general purpose synThesis procedure was developed ...


A Study Of Ti-Doped Wo3 Thin Films Using Comparative Theoretical And Experimental Approach, Aurelio Paez Jan 2014

A Study Of Ti-Doped Wo3 Thin Films Using Comparative Theoretical And Experimental Approach, Aurelio Paez

Open Access Theses & Dissertations

Metal oxides like Tungsten Oxide (WO3) are well documented and characterized in the literature, with uses in darkening windows and mirrors, flat computer displays, solar panel cooling, and sensors (of interest in this study). Ti doping of WO3 is less documented and the focus of this study. Sample thin films of pure WO3 and varyingly Ti doped WO3 were prepared using Radio Frequency magnetron sputtering (RF) (13.56 MHz) to grow thin films on a silicon substrate. This study aims to compare multiple Ti doping percentages in WO3 theoretically and then compare with experimental data taken from thin films of ...


The Study Of The Dielectric Properties Of The Endohedral Fullerenes, Shusil Bhusal Jan 2014

The Study Of The Dielectric Properties Of The Endohedral Fullerenes, Shusil Bhusal

Open Access Theses & Dissertations

Dielectric response of the metal nitride fullerenes is studied using the density functional theory at the all-electron level using generalized gradient approximation. The dielectric response is studied by computing the static dipole polarizabilities using the finite field method, i.e. by numerically differentiating the dipole moments with respect to electric field. The endohedral fullerenes studied in this work are Sc3N@C68(6140), Sc3N@C68(6146), Sc3N@C70(7854), Sc3N@C70(7960), Sc3N@C76(17490), Sc3N@C78(22010), Sc3N@C80(31923), Sc3N@C80(31924), Sc3N@C82(39663), Sc3N@C90(43), Sc3N@C90(44), Sc3N@C92(85), Sc3N@C94(121), Sc3N@C96 ...


Structural, Optical And Electrical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Abhilash Kongu Jan 2013

Structural, Optical And Electrical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Abhilash Kongu

Open Access Theses & Dissertations

Hafnium oxide (HfO2) has emerged as the most promising high-k dielectric for Metal-Oxide-Semiconductor (MOS) devices and has been highlighted as the most suitable dielectric materials to replace silicon oxide because of its comprehensive performance. In the present research, yttrium-doped HfO2 (YDH) thin films were fabricated using RF magnetron sputter deposition onto Si (100) and quartz with a variable thickness. Cross-sectional scanning electron microscopy coupled with Filmetrics revealed that film thickness values range from 700 A° to 7500 A°. Electrical properties such as AC Resistivity and current-voltage (I-V) characteristics of YDH films were studied. YDH films that were relatively thin (<1500 A°) crystallized in monoclinic phase while thicker films crystallized in cubic phase. The band gap (Eg) of the films was calculated from the optical measurements. The band gap was found to be ∼5.60 eV for monoclinic while it is ∼6.05 eV for cubic phase of YDH films. Frequency dependence of the electrical resistivity (ρac) and the total conductivity of the films were measured. Resistivity decreased (by three orders of magnitude) with increasing frequency from 100 Hz to 1 MHz, attributed due to the hopping mechanism in YDH films. Whereas, while ρac∼1Ω-m at low frequencies (100 Hz), it decreased to ∼ 104 Ω-cm at higher frequencies (1 MHz). Aluminum (Al) metal electrodes were deposited to fabricate a thin film capacitor with YDH layer as dielectric film thereby employing Al-YDH-Si capacitor structure. The results indicate that the capacitance of the films decrease with increasing film thickness. A detailed analysis of the electrical characteristics of YDH films is presented.


Crystal Structure, Phase, And Optical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Alejandro Ortega Jan 2013

Crystal Structure, Phase, And Optical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Alejandro Ortega

Open Access Theses & Dissertations

Yttrium-doped hafnium oxide (YDH) nanocrystalline films were produced by sputter-deposition at various substrate times and temperatures, to produce YDH films in a wide range of thicknesses, dYDH∼25 to 1100 nm. The deposition was made onto optical grade quartz and sapphire substrates. Samples deposited on sapphire were subject to post-deposition annealing (PDA) at various times (3-24 hr) and temperatures (1100 - 1500 °C). The effect of d[special characters omitted]YDH on the crystal structure, surface/interface morphology and optical properties of YDH films was investigated. X-ray diffraction analyses revealed the formation of monoclinic phase for relatively thin films (<150nm). The evolution towards stabilized cubic phase with increasing dYDH [special characters omitted]is observed. The scanning electron microscopy results indicate the dense, columnar structure of YDH films as a function of dYDH. Spectrophotometry analyses indicate that the grown YDH films are transparent and exhibit interference fringes. The band gap was found to be ∼ 5.60 eV for monoclinic YDH films while distinct separation and an increase in band gap to 6.03 eV is evident with increasing dYDH and formation cubic YDH films. The PDA films band gaps were found to be between 5.31 and 5.72 eV, all of which exhibit secondary gaps. A correlation between growth conditions, annealing, phase evolution, and optical properties of the YDH nanocrystalline thin films is established.


Rbd2po4: Room Temprature Synthesis, Chemical And Structural Stablity Upon Heating, Masoud Mollaee Jan 2013

Rbd2po4: Room Temprature Synthesis, Chemical And Structural Stablity Upon Heating, Masoud Mollaee

Open Access Theses & Dissertations

Monoclinic RbD2PO4 polycrystals were synthesized via the room temperature crystallization of RbH2PO4 dissolved in D2O. Powder x-ray diffraction (XRD) data collected at T=25 ºC indicate that this deuterated compound crystallizes in space group P21/m with unit cell parameters a=7.688í?, b=6.192í?, c=4.781í? and β=109.02°, and is isomorphic with the intermediate-temperature phase of its hydrogenated counterpart rubidium dihydrogen phosphate (RDP). We found no evidence of previously reported [Phase Transitions 80, 17 (2007)] polymorphic phase transition in rubidium dideuterium phosphate (DRDP) upon heating from room temperature to 210 ºC. All lattice parameters vary ...


Surface Plasmon Polaritons And Waveguide Modes At Structured And Inhomogeneous Surfaces, Javier Polanco Jan 2013

Surface Plasmon Polaritons And Waveguide Modes At Structured And Inhomogeneous Surfaces, Javier Polanco

Open Access Theses & Dissertations

In chapter 1, properties of a p-polarized surface plasmon polariton are studied, propagating circumferentially around a portion of a cylindrical interface between vacuum and a metal, a situation investigated earlier by M. V. Berry (J. Phys. A: Math. Gen. 8, (1975) 1952). When the metal is convex toward the vacuum this mode is radiative and consequently is attenuated as it propagates on the cylindrical surface. An approximate analytic solution of the dispersion relation for this wave is obtained by an approach different from the one used by Berry, and plots of the real and imaginary parts of its wave number ...


Raman And Infrared Study Of Electrospun Plla/Pcl Nanofiber Blends For Use In Tissue Engineering, Jose Luis Enriquez Carrejo Jan 2012

Raman And Infrared Study Of Electrospun Plla/Pcl Nanofiber Blends For Use In Tissue Engineering, Jose Luis Enriquez Carrejo

Open Access Theses & Dissertations

Recently, the biomedical engineering field has developed at a very fast pace as improved techniques and materials become available to promote its growth. Consequently, the research in polymeric biomaterials has been highly stimulated by this trend. The goal of the current research is to demonstrate the usefulness of the Raman scattering, Raman mapping, and infrared absorption spectroscopies to tissue engineering, by spectroscopically characterizing blends of PLLA and PCL polymers, which were prepared by electrospinning with and without cell addition. The proposed use of these blends is as primary biomaterials in biodegradable scaffolds used in tissue engineering. Both Raman and infrared ...


High Pressure Synchrotron X-Ray Diffraction Studies Of Superprotonic Transitions In Phosphate Based Solid Acids, Juan Daniel Hermosillo Jan 2012

High Pressure Synchrotron X-Ray Diffraction Studies Of Superprotonic Transitions In Phosphate Based Solid Acids, Juan Daniel Hermosillo

Open Access Theses & Dissertations

Certain phosphate based solid acids, such as CsH2PO4 and RbH2PO4, have been shown to exhibit an abrupt, several-order-of-magnitude increase in their proton conductivity when heated above a temperature threshold. This so called superprotonic behavior allows the above-mentioned materials to function as fuel cell electrolytes at temperatures between 150C and 300C, a remarkable application that attracted significant interest especially from the automobile industry. Yet, the microscopic structures and dynamic mechanisms responsible for this behavior are not fully understood. In fact, until very recently, the very nature of the superprotonic behavior has been debate, with some groups attributing the steep ...


Applications Of Density Functional Theory In Materials Science And Engineering, Manuel Alvarado Jan 2012

Applications Of Density Functional Theory In Materials Science And Engineering, Manuel Alvarado

Open Access Theses & Dissertations

Density Functional Theory (DFT) is a powerful tool that can be used to model various systems in materials science. Our research applies DFT to two problems of interest. First, an organic/inorganic complex dye system known as a Mayan pigment is modeled to determine chemical binding sites, verifying each model with physical data such as UV/Vis spectra. Preliminary studies on palygorskite-based mayan pigments (mayacrom blue, mayacrom purple) show excellent agreement with experimental studies when using a dimer dye geometry binding with tetrahedrally-coordinated aluminum impurity sites in palygorksite. This approach is applied to a sepiolite-based organic/inorganic dye system using ...


A Study Of Wo3 And W0.95ti0.05o3 Thin Films Using Comparative Spectroscopy, James Heyward Howard Jan 2012

A Study Of Wo3 And W0.95ti0.05o3 Thin Films Using Comparative Spectroscopy, James Heyward Howard

Open Access Theses & Dissertations

Tungsten oxide (WO3) is important and well-studied in materials science, particularly for sensor applications. In this research work, we consider the innovation of adding Ti to thin films of this material. Since the characteristics of any such material are strongly dependent on the conditions and methods used in its deposition, the main objective of this project is to provide a detailed spectroscopic characterization by Raman scattering, infrared absorption, and X-ray photoelectron spectroscopy (XPS) of WO3 and of W0.95Ti0.05O3. This characterization will be based on comparison of the morphology and composition of WO3-based thin films, grown by radio frequency ...


Aerosol Characterizaton In El Paso-Juarez Airshed Using Optical Methods, Angel E. Esparza Jan 2011

Aerosol Characterizaton In El Paso-Juarez Airshed Using Optical Methods, Angel E. Esparza

Open Access Theses & Dissertations

The assessment and characterization of atmospheric aerosols and their optical properties are of great significance for several applications such as air pollution studies, atmospheric visibility, remote sensing of the atmosphere, and impacts on climate change. Decades ago, the interest in atmospheric aerosols was primarily for visibility impairment problems; however, recently interest has intensified with efforts to quantify the optical properties of aerosols, especially because of the uncertainties surrounding the role of aerosols in climate change. The main objective of the optical characterization of aerosols is to understand their properties. These properties are determined by the aerosols' chemical composition, size, shape ...


Spectroscopic Study Of The Inhibition Of Calcium Oxalate Calculi By Larrea Tridentata, Luis Alonso Pinales Jan 2010

Spectroscopic Study Of The Inhibition Of Calcium Oxalate Calculi By Larrea Tridentata, Luis Alonso Pinales

Open Access Theses & Dissertations

The causes of urolithiasis include such influences as diet, metabolic disorders, and genetic factors which have been documented as sources that aggravate urinary calculi depositions and aggregations, and, implicitly, as causes of urolithiasis. This study endeavors to detail the scientific mechanisms involved in calcium oxalate calculi formation, and, more importantly, their inhibition under growth conditions imposed by the traditional medicinal approach using the herbal extract, Larrea tridentata. The calculi were synthesized without and with Larrea tridentata infusion by employing the single diffusion gel technique. A visible decrease in calcium oxalate crystal growth with increasing amounts of Larrea tridentata herbal infusion ...


An Ab-Initio Study Of The Elastic Properties Of Important Group Iv Diborides At High Temperatures, Manny Gonzales Jan 2010

An Ab-Initio Study Of The Elastic Properties Of Important Group Iv Diborides At High Temperatures, Manny Gonzales

Open Access Theses & Dissertations

Presented is an ab-initio Molecular Dynamics (MD) study, employing the Density Functional Theory (DFT), of the lattice parameter, thermal expansion coefficients and elastic constants of ZrB2, TiB2 and HfB2 as a function of temperature. The MD trajectories provide the equilibrium lattice parameters at finite temperatures, and the gradient of the energy from these equilibrium solutions is then used to calculate the components of the stiffness tensor. The results for ZrB2 are shown to agree well with reported experimental results for the lattice parameters and elastic constants as a function of temperature.


Computational Modeling Studies Of The Structures And Properties Of Organotin(Iv) And Stannyl-Thioether Systems With Comparisons To X-Ray Crystallography, Michelle R. Stem Joseph Jan 2009

Computational Modeling Studies Of The Structures And Properties Of Organotin(Iv) And Stannyl-Thioether Systems With Comparisons To X-Ray Crystallography, Michelle R. Stem Joseph

Open Access Theses & Dissertations

Controlling the toxic effects of organotin(IV) compounds involves engineering the structure of the molecules to optimize their properties. Molecular engineering, coupled with improved capabilities to generate reliable computational optimization models (COMs), will enable researchers to have greater success at harnessing the highly specific cytotoxicity of organotins. For example, as the thion ligand phenyl groups were replaced with Cl atoms, the S-Sn intramolecularity was strengthened, the bond distance decreased, and the stannyl tetrahedral structure was deformed from its triphenyl conformation. With each substitution, conformation deformations lowered the damaging bioactivity levels of thion. Bonding various ligands to organotin(IV ...


Experimental Study Of The Response Of Semiconductor Detectors For Edxrf Analysis., Sunil Kumar Valaparla Jan 2009

Experimental Study Of The Response Of Semiconductor Detectors For Edxrf Analysis., Sunil Kumar Valaparla

Open Access Theses & Dissertations

This present work relates to the study and characterization of the response function of an energy-dispersive x-ray spectrometer. The problems of energy, efficiency and resolution calibration of the system operating in the energy (5-60 keV) range are discussed. We present the operation characteristics of the portable pyro-electric x-ray generator (COOL-X) and the application of the calibrated response spectrum in the elemental analysis using X-ray Fluorescence (XRF).

We study the response of the Si(Li)-Pin XR-100CR semiconductor detector to low energy photons. The photopeak efficiency was determined experimentally by using radioisotopes and compared against a theoretical efficiency curve. The efficiency ...


Observed Superspin-Glass Behavior In Ni0.5zn0.5fe2o4 Nanoparticles, Antony Adair Jan 2009

Observed Superspin-Glass Behavior In Ni0.5zn0.5fe2o4 Nanoparticles, Antony Adair

Open Access Theses & Dissertations

In this investigation we seek to identify the magnetic behavior of Ni0.5Zn0.5Fe2O4 nanoparticles though AC-susceptibility and DC-magnetization measurements. Powder x-ray diffraction was performed to determine the purity and average diameter ( ~ 9nm) of the particles. Aditionally, structure was confirmed by comparison through the International Centre for Diffraction Data's Powder Diffraction File [52] (PDF # 08-0234).

Zero-field cooled and field cooled DC magnetization measurements (bifurcation and blocking temperature), as well as M(H) hysteresis (below and above the blocking temperature) lead us to initially suggest that the material may in fact be superparamagnetic. However, further investigation of the real AC ...