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Core-Shell Based Metamaterials: Fabrication Protocol and Optical Properties

Description: The objective of this study is to examine core-shell type plasmonic metamaterials aimed at the development of materials with unique electromagnetic properties. The building blocks of metamaterials under study consist of gold as a metal component, and silica and precipitated calcium carbonate (PCC) as the dielectric media. The results of this study demonstrate important applications of the core-shells including scattering suppression, airborne obscurants made of fractal gold shells, photomodific… more
Date: December 2017
Creator: De Silva, Vashista C
Partner: UNT Libraries
open access

Model for Long-range Correlations in DNA Sequences

Description: We address the problem of the DNA sequences developing a "dynamical" method based on the assumption that the statistical properties of DNA paths are determined by the joint action of two processes, one deterministic, with long-range correlations, and the other random and delta correlated. The generator of the deterministic evolution is a nonlinear map, belonging to a class of maps recently tailored to mimic the processes of weak chaos responsible for the birth of anomalous diffusion. It is assu… more
Date: December 1996
Creator: Allegrini, Paolo
Partner: UNT Libraries
open access

The Stopping Power of Amorphous and Channelled Silicon at All Energies as Computed with the Binary Encounter Approximation

Description: This thesis utilizes the binary encounter approximation to calculate the stopping power of protons penetrating silicon. The main goal of the research was to make predictions of the stopping power of silicon for low-energy and medium-energy channelled protons, in the hope that this will motivate experiments to test the theory developed below. In attaining this goal, different stopping power theories were compared and the binary encounter approach was applied to random (non-channelled) and high-e… more
Date: December 1994
Creator: Bickel, David, 1970-
Partner: UNT Libraries
open access

Experimental Synchronization of Chaotic Attractors Using Control

Description: The focus of this thesis is to theoretically and experimentally investigate two new schemes of synchronizing chaotic attractors using chaotically operating diode resonators. The first method, called synchronization using control, is shown for the first time to experimentally synchronize dynamical systems. This method is an economical scheme which can be viably applied to low dimensional dynamical systems. The other, unidirectional coupling, is a straightforward means of synchronization which ca… more
Date: December 1994
Creator: Newell, Timothy C. (Timothy Charles)
Partner: UNT Libraries
open access

Magneto-Optical and Chaotic Electrical Properties of n-InSb

Description: This thesis investigation concerns the optical and nonlinear electrical properties of n-InSb. Two specific areas have been studied. First is the magneto-optical study of magneto-donors, and second is the nonlinear dynamic study of nonlinear and chaotic oscillations in InSb. The magneto-optical study of InSb provides a physical picture of the magneto-donor levels, which has an important impact on the physical model of nonlinear and chaotic oscillations. Thus, the subjects discussed in this thesi… more
Date: December 1991
Creator: Song, Xiang-Ning
Partner: UNT Libraries
open access

Accelerator Mass Spectrometry Studies of Highly Charged Molecular Ions

Description: The existence of singly, doubly, and triply charged diatomic molecular ions was observed by using an Accelerator Mass Spectrometry (AMS) technique. The mean lifetimes of 3 MeV boron diatomic molecular ions were measured. No isotopic effects on the mean lifetimes of boron diatomic molecules were observed for charge state 3+. Also, the mean lifetime of SiF^3+ was measured.
Date: December 1994
Creator: Kim, Yong-Dal
Partner: UNT Libraries

Microwave Cavity Test for Superconductivity

Description: The first part of this paper describes the Meissner effect in superconductors which serves as the most definitive evidence for superconductivity. It is shown that the microwave perturbation technique may be used to demonstrate this effect. By measuring the changes of resonant frequency and inverse quality factor Q of a microwave cavity with a small volume of sample loading, the Meissner effect can be shown by using the Slater perturbation equation. The experimental system is described with deta… more
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Date: December 2001
Creator: Tang, Shan
Partner: UNT Libraries

The Stopping of Energetic Si, P and S Ions in Ni, Cu, Ge and GaAs Targets

Description: Accurate knowledge of stopping powers is essential for these for quantitative analysis and surface characterization of thin films using ion beam analysis (IBA). These values are also of interest in radiobiology and radiotherapy, and in ion- implantation technology where shrinking feature sizes puts high demands on the accuracy of range calculations. A theory that predicts stopping powers and ranges for all projectile-target combinations is needed. The most important database used to report the … more
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Date: December 2001
Creator: Nigam, Mohit
Partner: UNT Libraries
open access

A Statistical Study of Hard X-Ray Solar Flares

Description: The results of a statistical study of hard x-ray solar flares are presented in this dissertation. Two methods of analysis were used, the Diffusion Entropy (DE) method coupled with an analysis of the data distributions and the Rescaled Range (R/S) Method, sometimes referred to as "Hurst's method". Chapter one provides an introduction to hard x-ray flares within the context of the solar environment and a summary of the statistical paradigms solar astronomers currently work under. Chapter two pres… more
Date: December 2001
Creator: Leddon, Deborah L.
Partner: UNT Libraries
open access

An entropic approach to the analysis of time series.

Description: Statistical analysis of time series. With compelling arguments we show that the Diffusion Entropy Analysis (DEA) is the only method of the literature of the Science of Complexity that correctly determines the scaling hidden within a time series reflecting a Complex Process. The time series is thought of as a source of fluctuations, and the DEA is based on the Shannon entropy of the diffusion process generated by these fluctuations. All traditional methods of scaling analysis, instead, are base… more
Date: December 2001
Creator: Scafetta, Nicola
Partner: UNT Libraries
open access

A Comprehensive Model for the Rotational Spectra of Propyne CH₃CCH in the Ground and V₁₀=1,2,3,4,5 Vibrational States

Description: The energy states of C₃ᵥ symmetric top polyatomic molecules were studied. Both classical and quantum mechanical methods have been used to introduce the energy states of polyatomic molecules. Also, it is shown that the vibration-rotation spectra of polyatomic molecules in the ground and excited vibrational states can be predicted by group theory. A comprehensive model for predicting rotational frequency components in various v₁₀ vibrational levels of propyne was developed by using perturbation t… more
Date: December 1986
Creator: Rhee, Won Myung
Partner: UNT Libraries
open access

Investigation of the Linear and Nonlinear Optical Properties of InSb

Description: Highly sensitive magneto-optical techniques have been used to investigate weak linear and nonlinear optical absorption mechanisms in p- and n-type InSb. As a result, new absorption processes involving both impurities and free carriers have been identified and studied in detail. For p-InSb, magneto-optical spectra has been obtained over a wide range of temperatures and photon energies. The spectra obtained at higher sample temperatures are seen to result from combined-resonance transitions of fr… more
Date: December 1984
Creator: Littler, C. L.
Partner: UNT Libraries
open access

Fluid Spheres in General Relativity: Exact Solutions and Applications to Astrophysics

Description: Exact solutions to Einstein's field equations in the presence of matter are presented. A one parameter family of interior solutions for a static fluid is discussed. It is shown that these solutions can be joined to the Schwarzschild exterior, and hence represent fluid spheres of finite radius. Contained within this family is a set of solutions which are gaseous spheres defined by the vanishing of the density at the surface. One such solution yields an analytic expression which corresponds to th… more
Date: December 1978
Creator: Whitman, Patrick G.
Partner: UNT Libraries
open access

Detection of the Resonant Vibration of the Cellular Membrane Using Femtosecond Laser Pulses

Description: An optical detection technique is developed to detect and measure the resonant vibration of the cellular membrane. Biological membranes are active components of living cells and play a complex and dynamic role in life processes. They are believed to have oscillation modes of frequencies in the range of 1 to 1000 GHz. To measure such a high-frequency vibration, a linear laser cavity is designed to produce a train of femtosecond pulses of adjustable repetition rate. The method is then directly ap… more
Date: December 1989
Creator: Jamasbi, Nooshin
Partner: UNT Libraries
open access

K-, L-, and M-Shell X-Ray Production Cross Sections for Beryllium, Aluminum and Argon Ions Incident Upon Selected Elements

Description: Incident 0.5 to 2.5 MeV charged particle beams were used to ionize the inner-shells of selected targets and study their subsequent emission of characteristic x-rays. ⁹Be⁺ ions were used to examine K-shell x-ray production from thin F, Na, Al, Si, P, Cl, and K targets, L-shell x-ray production from thin Cu, An, Ge, Br, Zr and Ag targets, and M-shell x-ray production from thin Pr, Nd, Eu, Dy, Ho, Hf, W, Au, Pb and Bi targets. L-shell x-ray production cross sections were also measured for ²⁷Al⁺ io… more
Date: December 1986
Creator: Price, Jack Lewis
Partner: UNT Libraries
open access

Investigation of the Interaction of CO Laser Radiation with n-InSb

Description: The Shubnikov-de Haas magneto-resistance oscillations and photoconductivity were experimentally studied in order to investigate the interaction of CO laser radiation with n-InSb at liquid helium temperatures. The roles of various absorption mechanisms on these effects were considered, particularly near the intrinsic band edge. From these measurements an effective electron temperature Tₑ was defined that increased or decreased under illumination, depending upon the strength of the applied electr… more
Date: December 1982
Creator: Hanes, Larry Kenneth
Partner: UNT Libraries
open access

Anomalous Behavior in the Rotational Spectra of the v₈=2 and the v₈=3 Vibrations for the ¹³C and ¹⁵N Tagged Isotopes of the CH₃CN Molecule in the Frequency Range 17-95 GHz

Description: The rotational microwave spectra of the three isotopes (^13CH_3^12C^15N, ^12CH_3^13C^15N, and ^13CH_3^13C^15N) of the methyl cyanide molecule in the v_8=3, v_8=2, v_7=1 and v_4=1 vibrational energy levels for the rotational components 1£J£5 (for a range of frequency 17-95 GHz.) were experimentally and theoretically examined. Rotational components in each vibration were measured to determine the mutual interactions in each vibration between any of the vibrational levels investigated. The method … more
Date: December 1990
Creator: Al-Share, Mohammad A. (Mohammad Abdel)
Partner: UNT Libraries
open access

Theoretical and Experimental Linewidth Parameters in the Rotational Spectrum of Nitrogen Dioxide

Description: Contributions to the second order collision efficiency function S ⁽²⁾ (b), used in semiclassical perturbation approaches to pressure broadening of microwave and infrared spectra, due to several leading terms, dipole and quadrupole components, in the expansion of the intermolecular interaction energy are derived by method of irreducible spherical tensor operators for molecules of arbitrary symmetry. Results are given explicitly in terms of dipole and quadrupole line strengths. General expression… more
Date: December 1982
Creator: Moazzen-Ahmadi, Mohamad Nasser
Partner: UNT Libraries
open access

Inversion-Asymmetry Splitting of the Conduction Band in N-Type Indium Antimonide

Description: The origin of the Shubnikov-de Haas effect, the strain theory developed by Bir and Pikus, and a simple, classical beating-effects model are discussed. The equipment and the experimental techniques used in recording the Shubnikov-de Haas oscillations of n-type indium antimonite are described. The analysis of the experimental data showed that the angular anisotropy of the period of SdH oscillations at zero stress was unmeasurable for low concentration samples as discussed by other workers. Thus t… more
Date: December 1976
Creator: Bajaj, Bhushan D.
Partner: UNT Libraries
open access

K-Shell Ionization Cross Sections of Selected Elements from Fe to As for Proton Bombardment from 0.5 to 2.0 MeV

Description: The problem with which this investigation is concerned is that of making experimental measurements of proton-induced K-shell x-ray production cross sections and to study the dependence of these cross sections upon the energy of the incident proton. The measurements were made by detection of the characteristic x-rays emitted as a consequence of the ionization of the K-shell of the atom. The method for relating this characteristic x-ray emission to the x-ray production cross section is discussed … more
Date: December 1973
Creator: Lear, Richard Dean
Partner: UNT Libraries
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K-Shell Ionization Cross Sections For Elements Se To Pd: 0.4 To 2.0 MeV

Description: K-Shell ionization cross section for protons over the energy range of 0.4 to 2.0 MeV have been measured on thin targets of the elements Se, Br, Rb, Sr, Y, Mo and Pd. Total x-ray and ionization cross sections for the K-shell are reported. The experimental values of the ionization cross sections are compared to the non-relativistic plane-wave Born approximation, the binary-encounter approximation, the constrained binary-encounter approximation, and the plane-wave Born approximation with correctio… more
Date: December 1974
Creator: Criswell, Tommy L.
Partner: UNT Libraries
open access

Exploration of hierarchical leadership and connectivity in neural networks in vitro.

Description: Living neural networks are capable of processing information much faster than a modern computer, despite running at significantly lower clock speeds. Therefore, understanding the mechanisms neural networks utilize is an issue of substantial importance. Neuronal interaction dynamics were studied using histiotypic networks growing on microelectrode arrays in vitro. Hierarchical relationships were explored using bursting (when many neurons fire in a short time frame) dynamics, pairwise neuronal a… more
Date: December 2008
Creator: Ham, Michael I.
Partner: UNT Libraries
open access

Ultrasensitive Technique for Measurement of Two-Photon Absorption

Description: Intensive demands have arisen to characterize nonlinear optical properties of materials for applications involving optical limiters, waveguide switches and bistable light switches. The technique of Pulse Delay Modulation is described which can monitor nonlinear changes in transmission with shot noise limited signal-to-noise ratios even in the presence of large background signals. The theoretical foundations of the experiment are presented followed by actual measurements of beam depletion due to… more
Date: December 1991
Creator: Miller, Steven A. (Steven Alan)
Partner: UNT Libraries
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