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 Characterization, properties and applications of novel nanostructured hydrogels.

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The characterization, properties and applications of the novel nanostructured microgel (nanoparticle network and microgel crystal) composed of polyNisopropylacrylanmidecoallylamine (PNIPAMcoallylamine) and PNIPAMcoacrylic acid(AA) have been investigated. For the novel nanostructured hydrogels with the two levels of structure: the primary network inside each individual particle and the secondary network of the crosslinked nanoparticles, the new shear modulus, drug release law from hydrogel with heterogeneous structure have been studied. The successful method for calculating the volume fraction related the phase transition of colloid have been obtained. The kinetics of crystallization in an aqueous dispersion of PNIPAM particles has been explored using UVvisible transmission spectroscopy. This dissertation also includes the initial research on the melting behavior of colloidal crystals composed of PNIPAM microgels. Many new findings in this study area have never been reported before. The theoretical model for the columnar crystal growth from the top to bottom of PNIPAM microgel has been built, which explains the growth mechanism of the novel columnar hydrogel colloidal crystals. Since the unique structure of the novel nanostructured hydrogels, their properties are different with the conventional hydrogels and the hardspherelike system. The studies and results in this dissertation have the important significant for theoretical study and valuable application of these novel nanostructured hydrogels. digital.library.unt.edu/ark:/67531/metadc5605/  Charge Collection Studies on Integrated Circuit Test Structures using HeavyIon Microbeams and MEDICI Simulation Calculations
 Ion induced charge collection dynamics within Integrated Circuits (ICs) is important due to the presence of ionizing radiation in the IC environment. As the charge signals defining data states are reduced by voltage and area scaling, the semiconductor device will naturally have a higher susceptibility to ionizing radiation induced effects. The ionizing radiation can lead to the undesired generation and migration of charge within an IC. This can alter, for example, the memory state of a bit, and thereby produce what is called a "soft" error, or Single Event Upset (SEU). Therefore, the response of ICs to natural radiation is of great concern for the reliability of future devices. Immunity to soft errors is listed as a requirement in the 1997 National Technology Roadmap for Semiconductors prepared by the Semiconductor Industry Association in the United States. To design more robust devices, it is essential to create and test accurate models of induced charge collection and transport in semiconductor devices. A heavy ion microbeam produced by an accelerator is an ideal tool to study charge collection processes in ICs and to locate the weak nodes and structures for improvement through hardening design. In this dissertation, the Ion Beam Induced Charge Collection (IBICC) technique is utilized to simulate recoil effects of ions in ICs. These silicon or light ion recoils are usually produced by the elastic scattering or inelastic reactions between cosmic neutrons or protons and the lattice atoms in ICs. Specially designed test structures were experimentally studied, using microbeams produced at Sandia National Laboratories. A new technique, Diffusion Time Resolved IBICC, is first proposed in this work to measure the average arrival time of the diffused charge, which can be related to the first moment (or the average time) of the arrival carrier density at the junction. A 2D device simulation tool, the MEDICI code, and heavyion microbeams are used to calculate and measure charge collection and relative arrival time on stripelike test junctions. The MEDICI simulation is in qualitative and sometimes even quantitative agreement with the microbeam measurements. The amount of charge collection and the magnitude of average arrival time for diffused charge collection can be crucial to understanding and mitigating radiation induced circuit malfunctions during normal IC operations. digital.library.unt.edu/ark:/67531/metadc2469/
 Complexity as a form of transition from dynamics to thermodynamics: Application to sociological and biological processes.
 This dissertation addresses the delicate problem of establishing the statistical mechanical foundation of complex processes. These processes are characterized by a delicate balance of randomness and order, and a correct paradigm for them seems to be the concept of sporadic randomness. First of all, we have studied if it is possible to establish a foundation of these processes on the basis of a generalized version of thermodynamics, of nonextensive nature. A detailed account of this attempt is reported in Ignaccolo and Grigolini (2001), which shows that this approach leads to inconsistencies. It is shown that there is no need to generalize the KolmogorovSinai entropy by means of a nonextensive indicator, and that the anomaly of these processes does not rest on their nonextensive nature, but rather in the fact that the process of transition from dynamics to thermodynamics, this being still extensive, occurs in an exceptionally extended time scale. Even, when the invariant distribution exists, the time necessary to reach the thermodynamic scaling regime is infinite. In the case where no invariant distribution exists, the complex system lives forever in a condition intermediate between dynamics and thermodynamics. This discovery has made it possible to create a new method of analysis of nonstationary time series which is currently applied to problems of sociological and physiological interest. digital.library.unt.edu/ark:/67531/metadc4209/
 Complexity as Aging NonPoisson Renewal Processes
 The search for a satisfactory model for complexity, meant as an intermediate condition between total order and total disorder, is still subject of debate in the scientific community. In this dissertation the emergence of nonPoisson renewal processes in several complex systems is investigated. After reviewing the basics of renewal theory, another popular approach to complexity, called modulation, is introduced. I show how these two different approaches, given a suitable choice of the parameter involved, can generate the same macroscopic outcome, namely an inverse power law distribution density of events occurrence. To solve this ambiguity, a numerical instrument, based on the theoretical analysis of the aging properties of renewal systems, is introduced. The application of this method, called renewal aging experiment, allows us to distinguish if a time series has been generated by a renewal or a modulation process. This method of analysis is then applied to several physical systems, from blinking quantum dots, to the human brain activity, to seismic fluctuations. Theoretical conclusions about the underlying nature of the considered complex systems are drawn. digital.library.unt.edu/ark:/67531/metadc3706/
 A Computer Analysis of Complex GammaRay Spectra
 The purpose of this investigation was to provide a method for determining the relative intensities of all gamma rays in a particular spectrum, and thereby determine the relative transition probabilities. digital.library.unt.edu/ark:/67531/metadc130612/
 The Concept of Collision Strength and Its Applications
 Collision strength, the measure of strength for a binary collision, hasn't been defined clearly. In practice, many physical arguments have been employed for the purpose and taken for granted. A scattering angle has been widely and intensively used as a measure of collision strength in plasma physics for years. The result of this is complication and unnecessary approximation in deriving some of the basic kinetic equations and in calculating some of the basic physical terms. The Boltzmann equation has a fivefold integral collision term that is complicated. Chandrasekhar and Spitzer's approaches to the linear FokkerPlanck coefficients have several approximations. An effective variablechange technique has been developed in this dissertation as an alternative to scattering angle as the measure of collision strength. By introducing the square of the reduced impulse or its equivalencies as a collision strength variable, many plasma calculations have been simplified. The fivefold linear Boltzmann collision integral and linearized Boltzmann collision integral are simplified to threefold integrals. The arbitrary order linear FokkerPlanck coefficients are calculated and expressed in a uniform expression. The new theory provides a simple and exact method for describing the equilibrium plasma collision rate, and a precise calculation of the equilibrium relaxation time. It generalizes bimolecular collision reaction rate theory to a reaction rate theory for plasmas. A simple formula of high precision with wide temperature range has been developed for electron impact ionization rates for carbon atoms and ions. The universality of the concept of collision strength is emphasized. This dissertation will show how Arrhenius' chemical reaction rate theory and Thomson's ionization theory can be unified as one single theory under the concept of collision strength, and how many important physical terms in different disciplines, such as activation energy in chemical reaction theory, ionization energy in Thomson's ionization theory, and the Coulomb logarithm in plasma physics, can be unified into a single one  the threshold value of collision strength. The collision strength, which is a measure of a transfer of momentum in units of energy, can be used to reconcile the differences between Descartes' opinion and Leibnitz's opinion about the "true'' measure of a force. Like Newton's second law, which provides an instantaneous measure of a force, collision strength, as a cumulative measure of a force, can be regarded as part of a law of force in general. digital.library.unt.edu/ark:/67531/metadc4530/
 A Continuously Sensitive Cloud Chamber
 A continuous cloud chamber would be a valuable asset to laboratory work in nuclear and atomic physics. For this reason the construction and investigation of a continuously sensitive diffusion cloud chamber has been undertaken. It is the purpose of this paper to report the design and operating characteristics of such a chamber. digital.library.unt.edu/ark:/67531/metadc97019/
 Cooperationinduced Criticality in Neural Networks
 The human brain is considered to be the most complex and powerful informationprocessing device in the known universe. The fundamental concepts behind the physics of complex systems motivate scientists to investigate the human brain as a collective property emerging from the interaction of thousand agents. In this dissertation, I investigate the emergence of cooperationinduced properties in a system of interacting units. I demonstrate that the neural network of my research generates a series of properties such as avalanche distribution in size and duration coinciding with the experimental results on neural networks both in vivo and in vitro. Focusing attention on temporal complexity and fractal index of the system, I discuss how to define an order parameter and phase transition. Criticality is assumed to correspond to the emergence of temporal complexity, interpreted as a manifestation of nonPoisson renewal dynamics. In addition, I study the transmission of information between two networks to confirm the criticality and discuss how the network topology changes over time in the light of Hebbian learning. digital.library.unt.edu/ark:/67531/metadc283813/
 A Correction Factor for the First Born Approximation
 This thesis looks at a Schroedinger equation and the Born approximation. digital.library.unt.edu/ark:/67531/metadc130574/
 Criticality in Cooperative Systems
 Cooperative behavior arises from the interactions of single units that globally produce a complex dynamics in which the system acts as a whole. As an archetype I refer to a flock of birds. As a result of cooperation the whole flock gets special abilities that the single individuals would not have if they were alone. This research work led to the discovery that the function of a flock, and more in general, that of cooperative systems, surprisingly rests on the occurrence of organizational collapses. In this study, I used cooperative systems based on selfpropelled particle models (the flock models) which have been proved to be virtually equivalent to sociological network models mimicking the decision making processes (the decision making model). The critical region is an intermediate condition between a highly disordered state and a strong ordered one. At criticality the waiting times distribution density between two consecutive collapses shows an inverse power law form with an anomalous statistical behavior. The scientific evidences are based on measures of information theory, correlation in time and space, and fluctuation statistical analysis. In order to prove the benefit for a system to live at criticality, I made a flock system interact with another similar system, and then observe the information transmission for different disturbance values. I proved that at criticality the transfer of information gets the maximal efficiency. As last step, the flock model has been shown that, despite its simplicity, is sufficiently a realistic model as proved via the use of 3D simulations and computer animations. digital.library.unt.edu/ark:/67531/metadc271910/
 Cross Section for the 165/Ho (n, 2n) 164/Ho Reaction at 15.6 MeV
 It was the purpose of this investigation to bring together the ideas and procedures involved in the measurement of (n, 2n) reaction cross sections. Some of the inherent properties of the material under investigation (Holium) are involved in determining these relationships. digital.library.unt.edu/ark:/67531/metadc131148/
 Crystalline Polymorphism of Nitrates
 The purpose of this study was to investigate the polymorphism of a group of related compounds. Special emphasis was placed upon the temperature at which transitions occurred and a possible correlation of these temperatures with other properties of the compounds. digital.library.unt.edu/ark:/67531/metadc97053/
 Cs133 (n,2n) CrossSection at 15.6 and 16.1 MeV
 The intent of this investigation is the determination of the values of the Cs133 (n,2n)Cs132 crosssection at neutron energies of 15.6 and 16.1 MeV. Neutrons of this energy are produced with comparative ease by means of the DT reaction, in which deuterons of energy 500 and 750 keV, respectively, are impingent upon a tritium target. digital.library.unt.edu/ark:/67531/metadc131110/
 DD and DT Neutron Excitation of Energy Levels in Cs133
 The purpose of this experiment was to make positive assignment of the Cs133 energy levels excited by the inelastic scattering of neutrons. digital.library.unt.edu/ark:/67531/metadc130455/
 A Decay Scheme for 164 Ho
 The present investigation was prompted by several considerations. In previous studies there was considerable variance with regard to the reported values for the halflives of the isomeric and ground states in 164 Ho. There was also considerable variance with regard to the values reported for the branching ratios and the relative intensities of the transitions. Thus a further study of the problem was needed. digital.library.unt.edu/ark:/67531/metadc131582/
 Decoherence, Master Equation for Open Quantum Systems, and the Subordination Theory
 This thesis addresses the problem of a form of anomalous decoherence that sheds light into the spectroscopy of blinking quantum dots. The system studied is a twostate system, interacting with an external environment that has the effect of establishing an interaction between the two states, via a coherence generating coupling, called inphasing. The collisions with the environment produce also decoherence, named dephasing. Decoherence is interpreted as the entanglement of the coherent superposition of these two states with the environment. The joint action of inphasing and dephasing generates a Markov master equation statistically equivalent to a random walker jumping from one state to the other. This model can be used to describe intermittent fluorescence, as a sequence of "light on" and "light off" states. The experiments on blinking quantum dots indicate that the sojourn times are distributed with an inverse power law. Thus, a proposal to turn the model for Poisson fluorescence intermittency into a model for nonPoisson fluorescence intermittency is made. The collisionlike interaction of the twostate system with the environment is assumed to takes place at random times rather than at regular times. The time distance between one collision and the next is given by a distribution, called the subordination distribution. If the subordination distribution is exponential, a sequence of collisions yielding no persistence is turned into a sequence of "light on" and "light off" states with significant persistence. If the subordination function is an inverse power law the sequel of "light on" and "light off" states becomes equivalent to the experimental sequences. Different conditions are considered, ranging from predominant inphasing to predominant dephasing. When dephasing is predominant the sequel of "light on" and "light off" states in the time asymptotic limit becomes an inverse power law. If the predominant dephasing involves a time scale much larger than the minimum time scale accessible to the experimental observation, thereby generating persistence, the resulting distribution becomes a MittagLeffler function. If dephasing is predominant, in addition to the inverse power law distribution of "light off" and "light on" time duration, a strong correlation between "light on" and "light off" state is predicted. digital.library.unt.edu/ark:/67531/metadc4812/
 Design and Construction of a Positive RadioFrequency Ion Source for the Production of Negative Ions
 It is the purpose of this paper to present a detailed account of the design and construction of this positiveion source and associated equipment. digital.library.unt.edu/ark:/67531/metadc108015/
 Design and Testing of a Coincidence System
 This paper is concerned with the design, testing and performance of a coincidence system, the proposed North Texas State College accelerator. digital.library.unt.edu/ark:/67531/metadc108113/
 Design and Testing of a Corona Column and a Closed Gas Distribution System for a Tandem Van de Graaff Voltage Generator
 The purpose of this study had been to design and test a corona column and an insulating gas distribution system for a small tandem Van de Graaff. The intent of this paper is to describe the gas handling system and to compare experimentally the effects of corona electrode shape on the corona current carried between adjacent sections of the column. digital.library.unt.edu/ark:/67531/metadc163849/
 Design and Testing of a Positive Ion Accelerator and Necessary Vacuum System
 This thesis is a study of the design and testing of a positive ion accelerator and necessary vacuum system. digital.library.unt.edu/ark:/67531/metadc163830/
 A Determination of the Bothe Depression Factor for Discs in Water
 The purpose of this work is to determine experimentally the depression of the neutron density by a detecting foil. The depression factor is known as the "selfshading" of the foil. digital.library.unt.edu/ark:/67531/metadc130255/
 A Determination of the Fine Structure Constant Using Precision Measurements of Helium Fine Structure
 Spectroscopic measurements of the helium atom are performed to high precision using an atomic beam apparatus and electrooptic laser techniques. These measurements, in addition to serving as a test of helium theory, also provide a new determination of the fine structure constant α. An apparatus was designed and built to overcome limitations encountered in a previous experiment. Not only did this allow an improved level of precision but also enabled new consistency checks, including an extremely useful measurement in 3He. I discuss the details of the experimental setup along with the major changes and improvements. A new value for the J = 0 to 2 fine structure interval in the 23P state of 4He is measured to be 31 908 131.25(30) kHz. The 300 Hz precision of this result represents an improvement over previous results by more than a factor of three. Combined with the latest theoretical calculations, this yields a new determination of α with better than 5 ppb uncertainty, α1 = 137.035 999 55(64). digital.library.unt.edu/ark:/67531/metadc31547/
 A DeuteriumDeuterium Type Neutron Source
 In view of the advantages of its type, the decision to construct a neutron source of the particle accelerator type was made. The purpose of this thesis is to survey the problems encountered in the construction of the source. digital.library.unt.edu/ark:/67531/metadc96980/
 The Dielectric Constant of Galvinoxyl
 The molecules in many substances are know to undergo at characteristic temperatures a change in their rotational freedom in the solid state, signifying either a change in structure of the material of the onset of limited rotation of the molecule about some symmetry axis. The purpose of this research was to determine from dielectric constant measurements over the 100°K420°K temperature range whether or not the organic free radical galvinoxyl and its diamagnetic parent molecule, dihydroxydiphenylmethane, undergo any such transitions. digital.library.unt.edu/ark:/67531/metadc163926/
 Dipole Moments of Diphenyl Compounds with Conjugated Double Bonds
 This thesis is a continuation of a study of molecular moments begun by Joseph T. Fielder. In his paper he discussed the theory and the equipment necessary for such a study. It is the purpose of this paper to set forth modifications of his equipment, to present data obtained with this modified equipment, and to interpret this data. digital.library.unt.edu/ark:/67531/metadc83668/
 Dipole Moments of Olefenic Diesters
 It is the purpose of this paper to present experimental data for the determination of the dielectric constant and the dipole moments for a series of olefenic diesters of the cis and trans configurations. digital.library.unt.edu/ark:/67531/metadc96944/
 Dipole Moments of Olefinic Esters
 It is the purpose of this thesis to investigate the applicability of the Debye equation to measurements dipole moments of polar compounds in dilute solutions of nonpolar solvents more fully than has been done by previous workers at this institution. digital.library.unt.edu/ark:/67531/metadc107828/
 Distribution of Nighttime Fregion Molecular Ion Concentrations and 6300 Å Nightglow Morphology
 The purpose of this study is twofold. The first is to determine the dependence of the molecular ion profiles on the various ionospheric and atmospheric parameters that affect their distributions. The second is to demonstrate the correlation of specific ionospheric parameters with 6300 Å nightglow intensity during periods of magnetically quiet and disturbed conditions. digital.library.unt.edu/ark:/67531/metadc278620/
 The Diurnal Variation of Cosmic Radiation
 The primary purpose of this investigation was to study the diurnal variation of cosmicray intensity. digital.library.unt.edu/ark:/67531/metadc163872/
 A dynamic and thermodynamic approach to complexity.
 The problem of establishing the correct approach to complexity is a very hot and crucial issue to which this dissertation gives some contributions. This dissertation considers two main possibilities, one, advocated by Tsallis and coworkers, setting the foundation of complexity on a generalized, nonextensive , form of thermodynamics, and another, proposed by the UNT Center for Nonlinear Science, on complexity as a new condition that, for physical systems, would be equivalent to a state of matter intermediate between dynamics and thermodynamics. In the first part of this dissertation, the concept of KolmogorovSinai entropy is introduced. The Pesin theorem is generalized in the formalism of Tsallis nonextensive thermodynamics. This generalized form of Pesin theorem is used in the study of two major classes of problems, whose prototypes are given by the Manneville and the logistic map respectively. The results of these studies convince us that the approach to complexity must be made along lines different from those of the nonextensive thermodynamics. We have been convinced that the Lévy walk can be used as a prototype model of complexity, as a condition of balance between order and randomness that yields new phenomena such as aging, and multifractality. We reach the conclusions that these properties must be studied within a dynamic rather than thermodynamic perspective. The second part focuses on the study of the heart beating problem using a dynamic model, the socalled memory beyond memory, based on the Lévy walker model. It is proved that the memory beyond memory effect is more obvious in the healthy heart beating sequence. The concepts of fractal, multifractal, wavelet transformation and wavelet transform maximum modulus (WTMM) method are introduced. Artificial time sequences are generated by the memory beyond memory model to mimic the heart beating sequence. Using WTMM method, the multifratal singular spectrums of the sequences are calculated. It is clear that the sequence with strong memory beyond memory effect has broader singular spectrum.200308 digital.library.unt.edu/ark:/67531/metadc4276/
 The dynamic foundation of fractal operators.
 The fractal operators discussed in this dissertation are introduced in the form originally proposed in an earlier book of the candidate, which proves to be very convenient for physicists, due to its heuristic and intuitive nature. This dissertation proves that these fractal operators are the most convenient tools to address a number of problems in condensed matter, in accordance with the point of view of many other authors, and with the earlier book of the candidate. The microscopic foundation of the fractal calculus on the basis of either classical or quantum mechanics is still unknown, and the second part of this dissertation aims at this important task. This dissertation proves that the adoption of a master equation approach, and so of probabilistic as well as dynamical argument yields a satisfactory solution of the problem, as shown in a work by the candidate already published. At the same time, this dissertation shows that the foundation of Levy statistics is compatible with ordinary statistical mechanics and thermodynamics. The problem of the connection with the KolmogorovSinai entropy is a delicate problem that, however, can be successfully solved. The derivation from a microscopic Liouvillelike approach based on densities, however, is shown to be impossible. This dissertation, in fact, establishes the existence of a striking conflict between densities and trajectories. The third part of this dissertation is devoted to establishing the consequences of the conflict between trajectories and densities in quantum mechanics, and triggers a search for the experimental assessment of spontaneous wavefunction collapses. The research work of this dissertation has been the object of several papers and two books. digital.library.unt.edu/ark:/67531/metadc4235/
 Dynamical Friction Coefficients for Plasmas Exhibiting NonSpherical Electron Velocity Distributions
 This investigation is designed to find the net rate of decrease in the component of velocity parallel to the original direction of motion of a proton moving through an electron gas exhibiting a nonspherical velocity distribution. digital.library.unt.edu/ark:/67531/metadc130480/
 EEG, Alpha Waves and Coherence
 This thesis addresses some theoretical issues generated by the results of recent analysis of EEG time series proving the brain dynamics are driven by abrupt changes making them depart from the ordinary Poisson condition. These changes are renewal, unpredictable and nonergodic. We refer to them as crucial events. How is it possible that this form of randomness be compatible with the generation of waves, for instance alpha waves, whose observation seems to suggest the opposite view the brain is characterized by surprisingly extended coherence? To shed light into this apparently irretrievable contradiction we propose a model based on a generalized form of Langevin equation under the influence of a periodic stimulus. We assume that there exist two different forms of time, a subjective form compatible with Poisson statistical physical and an objective form that is accessible to experimental observation. The transition from the former to the latter form is determined by the brain dynamics interpreted as emerging from the cooperative interaction among many units that, in the absence of cooperation would generate Poisson fluctuations. We call natural time the brain internal time and we make the assumption that in the natural time representation the time evolution of the EEG variable y(t) is determined by a Langevin equation perturbed by a periodic process that in this time representation is hardly distinguishable from an erratic process. We show that the representation of this random process in the experimental time scale is characterized by a surprisingly extended coherence. We show that this model generates a sequence of damped oscillations with a time behavior that is remarkably similar to that derived from the analysis of real EEG's. The main result of this research work is that the existence of crucial events is not incompatible with the alpha wave coherence. In addition to this important result, we find another result that may help our group, or any other research group working on the analysis of brain's dynamics, to prove or to disprove the existence of crucial events. We study the diffusion process generated by fluctuations emerging from the same model after filtering out the alpha coherence, and we study the recursion to the origin. We study the survival probability of this process, namely the probability that up to a given time no recrossing of the origin occurs. We find that this is an inverse power law with a power that depends on whether or not crucial events exist. digital.library.unt.edu/ark:/67531/metadc28389/
 The Effect of Average Grain Size on Polycrystalline Diamond Films
 The work function of hydrogenterminated, polycrystalline diamond was studied using ultraviolet photoelectron spectroscopy. Polycrystalline diamond films were deposited onto molybdenum substrates by electrophoresis for grain sizes ranging from 0.3 to 108 microns. The work function and electron affinity were measured using 21.2 eV photons from a helium plasma source. The films were characterized by xray photoelectron spectroscopy to determine elemental composition and the sp2/sp3 carbon fraction. The percentage of (111) diamond was determined by xray diffraction, and scanning electron microscopy was performed to determine average grain size. The measured work function has a maximum of 5.1 eV at 0.3 microns, and decreases to 3.2 eV at approximately 4 microns. Then the work function increases with increasing grain size to 4.0 eV at 15 microns and then asymptotically approaches the 4.8 eV work function of single crystal diamond at 108 microns. These results are consistent with a 3component model in which the work function is controlled by singlecrystal (111) diamond at larger grain sizes, graphitic carbon at smaller grain sizes, and by the electron affinity for the intervening grain sizes. digital.library.unt.edu/ark:/67531/metadc3164/
 Effect of Sample Geometry on Magnetomorphic Oscillations in the Hall Effect in Cadium at LiquidHelium Temperatures
 This thesis presents observations on sizeeffect oscillations in the Hall effect in an oriented single crystal of highly pure cadmium at liquidhelium temperatures. All measurements were made in transverse magnetic field. digital.library.unt.edu/ark:/67531/metadc130799/
 The Effects of Cesium Deposition and Gas Exposure on the Field Emission Properties of Single Wall and Multiwall Carbon Nanotubes
 The effects of Cs deposition on the field emission (FE) properties of singlewalled carbon nanotube (SWNT) bundles were studied. In addition, a comparative study was made on the effects of O2, Ar and H2 gases on the field emission properties of SWNT bundles and multiwall carbon nanotubes (MWNTs). We observed that Cs deposition decreases the turnon field for FE by a factor of 2.1  2.9 and increases the FE current by 6 orders of magnitude. After Cs deposition, the FE current versus voltage (IV) curves showed nonFowlerNordheim behavior at large currents consistent with tunneling from adsorbate states. At lower currents, the ratio of the slope of the FE IV curves before and after Cs deposition was approximately 2.1. Exposure to N2 does not decrease the FE current, while exposure to O2 decreases the FE current. Our results show that cesiated SWNT bundles have great potential as economical and reliable vacuum electron sources. We find that H2 and Ar gases do not significantly affect the FE properties of SWNTs or MWNTs. O2 temporarily reduces the FE current and increases the turnon voltage of SWNTs. Full recovery of these properties occurred after operation in UHV. The higher operating voltages in an O2 environment caused a permanent decrease of FE current and increase in turnon field of MWNTs. The ratios of the slopes before and after O2 exposure were approximately 1.04 and 0.82 for SWNTs and MWNTs, respectively. SWNTs compared to MWNTs would appear to make more economical and reliable vacuum electron sources. digital.library.unt.edu/ark:/67531/metadc3110/
 Effects of Dissipation on Propagation of Surface Electromagnetic and Acoustic Waves
 With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. with this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. the first part (chapters 2 & 3) of the dissertation deals with the emerging field of plasmonics. Researchers have come up with various designs in an efort to fabricate efficient plasmonic waveguides capable of guiding plasmonic signals. However, the inherent dissipation in the form of Joule losses limits efficient usage of surface plasmon signal. a dielectricmetal¬dielectric planar structure is one of the most practical plasmonic structures that can serve as an efficient waveguide to guide electromagnetic waves along the metaldielectric boundary. I present here a theoretical study of propagation of surface plasmons along a symmetric dielectricmetaldielectric structure and show how proper orientation of the optical axis of the anisotropic substrate enhances the propagation length. an equation for propagation length is derived in a wide range of frequencies. I also show how the frequency of coupled surface plasmons can be modulated by changing the thickness of the metal film. I propose a KronigPenny model for the plasmonic crystal, which in the long wavelength limit, may serve as a homogeneous dielectric substrate with high anisotropy which do not exist for natural optical crystals. in the second part (chapters 4 & 5) of the dissertation, I discuss an interesting effect of extraordinary absorption of acoustic energy due to resonant excitation of Rayleigh waves in a narrow water channel clad between two metal plates. Starting from the elastic properties of the metal plates, I derive a dispersion equation that gives resonant frequencies, which coincide with those observed in the experiment that was performed by Wave Phenomena Group at Polytechnic University of Valencia, Spain. Two eigenmodes with different polarizations and phase velocities are obtained from the dispersion equation. at certain critical aperture of the channel, an interesting cutoff effect, which is unusual for an acoustic wave, is observed for one of the eigenmodes with symmetric distribution of the pressure field. the theoretical prediction of the coupling and synchronization of Rayleigh waves strongly supports the experimentally measured shift of the resonant frequencies in the transmission spectra with channel aperture. the observed high level of absorption may find applications in designing metamaterial acoustic absorbers. digital.library.unt.edu/ark:/67531/metadc115126/
 The Effects of Lead Placement and Sample Shape in the Measurement of Electrical Resistivity
 This thesis is a study of the effects of lead placement and sample shape in the measurement of electrical resistivity. digital.library.unt.edu/ark:/67531/metadc131303/
 Electrical Conductivity in Thin Films
 This thesis deals with electrical conductivity in thin films. Classical and quantum size effects in conductivity are discussed including some experimental evidence of quantum size effects. The component conductivity along the applied electric field of a thin film in a transverse magnetic field is developed in a density matrix method. digital.library.unt.edu/ark:/67531/metadc164055/
 Electron Density and Collision Frequency Studies Using a Resonant Microwave Cavity as a Probe
 Electron densities and collision frequencies were obtained on a number of gases in a dc discharge at low pressures (0.702mm of Hg). These measurements were performed by microwave probing of a filament of the dc discharge placed coaxially in a resonant cavity operating in a TM₀₁₀ mode. The equipment and techniques for making the microwave measurements employing the resonant cavity are described. One of the main features of this investigation is the technique of differentiating the resonance signal of the loaded cavity in order to make accurate measurements of the resonant frequency and halfpower point frequencies. digital.library.unt.edu/ark:/67531/metadc279091/
 Electron Spin Resonance Absorption in Benzophenone Phenylhydrazone Negative Ion
 This thesis reports an electron spin resonance absorption study of the hyperfine interaction between nuclei and a single "nearlyfree" electron in dilute solutions of the benzophenone phenylhydrazone free radical in tetrahydrofuran. digital.library.unt.edu/ark:/67531/metadc131161/
 Electron Transport in Bismuth at Liquid Helium Tempratures
 To obtain information on the band structure of bismuth, galvanomagnetic potentials were measured in a single crystal at liquidhelium and liquidnitrogen temperatures. These measurements were analyzed for information on the different carriers, particularly for the existence of a highmobility band of holes. digital.library.unt.edu/ark:/67531/metadc130512/
 Electrostatic Effects in IIIV Semiconductor Based Metaloptical Nanostructures

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The modification of the band edge or emission energy of semiconductor quantum well light emitters due to image charge induced phenomenon is an emerging field of study. This effect observed in quantum well light emitters is critical for all metaloptics based light emitters including plasmonics, or nanometallic electrode based light emitters. This dissertation presents, for the first time, a systematic study of the image charge effect on semiconductor–metal systems. the necessity of introducing the image charge interactions is demonstrated by experiments and mathematical methods for semiconductormetal image charge interactions are introduced and developed. digital.library.unt.edu/ark:/67531/metadc115090/  Electrostatic Mechanism of Emission Enhancement in Hybrid Metalsemiconductor Lightemitting Heterostructures
 IIIV nitrides have been put to use in a variety of applications including laser diodes for modern DVD devices and for solidstate white lighting. Plasmonics has come to the foreground over the past decade as a means for increasing the internal quantum efficiency (IQE) of devices through resonant interaction with surface plasmons which exist at metal/dielectric interfaces. Increases in emission intensity of an order of magnitude have been previously reported using silver thinfilms on InGaN/GaN MQWs. the dependence on resonant interaction between the plasmons and the light emitter limits the applications of plasmonics for light emission. This dissertation presents a new nonresonant mechanism based on electrostatic interaction of carriers with induced image charges in a nearby metallic nanoparticle. Enhancement similar in strength to that of plasmonics is observed, without the restrictions imposed upon resonant interactions. in this work we demonstrate several key features of this new interaction, including intensitydependent saturation, increase in the radiative recombination lifetime, and strongly inhomogeneous light emission. We also present a model for the interaction based on the aforementioned image charge interactions. Also discussed are results of work done in the course of this research resulting in the development of a novel technique for strain measurement in lightemitting structures. This technique makes use of a spectral fitting model to extract information about electronphonon interactions in the sample which can then be related to strain using theoretical modeling. digital.library.unt.edu/ark:/67531/metadc115113/
 Emergence of Complexity from Synchronization and Cooperation
 The dynamical origin of complexity is an object of intense debate and, up to moment of writing this manuscript, no unified approach exists as to how it should be properly addressed. This research work adopts the perspective of complexity as characterized by the emergence of nonPoisson renewal processes. In particular I introduce two new complex system models, namely the twostate stochastic clocks and the integrateandfire stochastic neurons, and investigate its coupled dynamics in different network topologies. Based on the foundations of renewal theory, I show how complexity, as manifested by the occurrence of nonexponential distribution of events, emerges from the interaction of the units of the system. Conclusion is made on the work's applicability to explaining the dynamics of blinking nanocrystals, neuron interaction in the human brain, and synchronization processes in complex networks. digital.library.unt.edu/ark:/67531/metadc6107/
 Energy Distribution of Sputtered Neutral Atoms from a Multilayer Target
 Energy distribution measurements of sputtered neutral particles contribute to the general knowledge of sputtering, a common technique for surface analysis. In this work emphasis was placed on the measurement of energy distribution of sputtered neutral atoms from different depths. The liquid GaIn eutectic alloy as a sample target for this study was ideal due to an extreme concentration ratio gradient between the top two monolayers. In pursuing this study, the method of sputterinitiated resonance ionization spectroscopy (SIRIS) was utilized. SIRIS employs a pulsed ion beam to initiate sputtering and tunable dye lasers for resonance ionization. Observation of the energy distribution was achieved with a positionsensitive detector. The principle behind the detector's energy resolution is time of flight (TOF) spectroscopy. For this specific detector, programmed time intervals between the sputtering pulse at the target and the ionizing laser pulse provided information leading to the energy distribution of the secondary neutral particles. This experiment contributes data for energy distributions of sputtered neutral particles to the experimental database, required by theoretical models and computer simulations for the sputtering phenomenon. digital.library.unt.edu/ark:/67531/metadc2657/
 Energy Losses of Protons Projected through a Plasma Due to Collisions with Electrons of the Plasma for a Variety of NonMaxwellian Electron Velocity Distributions
 The purpose of this thesis is to study energy losses suffered by protons in traversing a plasma through collision with the electrons of the plasma. For these electrons a variety of nonMaxwellian velocity distributions are assumed. digital.library.unt.edu/ark:/67531/metadc130468/
 An entropic approach to the analysis of time series.
 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 based on the variance of this diffusion process. The variance methods detect the real scaling only if the Gaussian assumption holds true. We call H the scaling exponent detected by the variance methods and d the real scaling exponent. If the time series is characterized by Fractional Brownian Motion, we have H¹d and the scaling can be safely determined, in this case, by using the variance methods. If, on the contrary, the time series is characterized, for example, by Lévy statistics, H ¹ d and the variance methods cannot be used to detect the true scaling. Lévy walk yields the relation d=1/(32H). In the case of Lévy flights, the variance diverges and the exponent H cannot be determined, whereas the scaling d exists and can be established by using the DEA. Therefore, only the joint use of two different scaling analysis methods, the variance scaling analysis and the DEA, can assess the real nature, Gauss or Lévy or something else, of a time series. Moreover, the DEA determines the information content, under the form of Shannon entropy, or of any other convenient entopic indicator, at each time step of the process that, given a sufficiently large number of data, is expected to become diffusion with scaling. This makes it possible to study the regime of transition from dynamics to thermodynamics, nonstationary regimes, and the saturation regime as well. First of all, the efficiency of the DEA is proved with theoretical arguments and with numerical work on artificial sequences. Then we apply the DEA to three different sets of real data, Genome sequences, hard xray solar flare waiting times and sequences of sociological interest. In all these cases the DEA makes new properties, overlooked by the standard method of analysis, emerge. digital.library.unt.edu/ark:/67531/metadc3033/
 Experimental Determination of the Scattering Crosssection of Ogives and Prolate Spheroids at Microwave Frequencies
 Because of the great difficulty of obtaining exact numerical values of crosssection, and because of the inherent uncertainties in interpreting and evaluating the approximate methods, accurate experimental crosssection data would be extremely useful to the radar engineer. It was with this purpose in mind that the present longrange research program in microwave scattering was undertaken. Of immediate interest were the scattering properties of the prolate spheroid, the ogive (formed by rotating the minor segment of a circle around the chord), and, for comparison, the long cylinder. digital.library.unt.edu/ark:/67531/metadc107875/
 Exploration of hierarchical leadership and connectivity in neural networks in vitro.
 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 activation, and information theoretic measures. Together, these methods reveal that global network activity results from ignition by a small group of burst leader neurons, which form a primary circuit that is responsible for initiating most networkwide burst events. Phase delays between leaders and followers reveal information about the nature of the connection between the two. Physical distance from a burst leader appears to be an important factor in follower response dynamics. Information theory reveals that mutual information between neuronal pairs is also a function of physical distance. Activation relationships in developing networks were studied and plating density was found to play an important role in network connectivity development. These measures provide unique views of network connectivity and hierarchical relationship in vitro which should be included in biologically meaningful models of neural networks. digital.library.unt.edu/ark:/67531/metadc9775/