Common Threads in Research Across Disciplines: A Reflection
Date: April 15, 2004
Creator: Matteson, Samuel E.
Description: This University Scholars Day keynote address discusses common threads in research across disciplines. Research lies at the heart of scholarship in all academic disciplines. The author identifies common threads of thought and practice that run through what is called "research". The author identifies six phases that are common to all such scholarly activities (observation, vision, logistics, experiment, assessment, and communication), exploring by example, anecdote and analysis this taxonomy of research as a proposed heuristic for aspiring researchers.
Contributing Partner: UNT Honors College
Permallink:digital.library.unt.edu/ark:/67531/metadc96828/
Comment on "Modification of graphene properties due to electron-beam irradiation"
Date: December 17, 2009
Creator: Jones, Jason D.; Ecton, Philip A.; Mo, Yudong & Pérez, José M.
Description: This article is a comment on another article titled 'Modification of graphene properties due to electron-beam irradiation'. These articles discuss the modification of graphene properties due to electron-beam irradiation.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc83795/
Correlation Function and Generalized Master Equation of Arbitrary Age
Date: June 10, 2005
Creator: Allegrini, Paolo; Aquino, Gerardo; Grigolini, Paolo; Palatella, Luigi; Rosa, Angelo & West, Bruce J.
Description: This article discusses correlation function and generalized master equation of arbitrary age. Abstract: We study a two-state statistical process with a non-Poisson distribution of sojourn times. In accordance with earlier work, we find that this process is characterized by aging and we study three different ways to define the correlation function of arbitrary age of the corresponding dichotomous fluctuation. These three methods yield exact expressions, thus coinciding with the recent result by Godrèche and Luck [J. Stat. Phys. 104, 489 (2001)]. Actually, non-Poisson statistics yields infinite memory at the probability level, thereby breaking any form of Markovian approximation, including the one adopted herein, to find an approximated analytical formula. For this reason, we check the accuracy of this approximated formula by comparing it with the numerical treatment of the second of the three exact expressions. We find that, although not exact, a simple analytical expression for the correlation function of arbitrary age is very accurate. We establish a connection between the correlation function and a generalized master equation of the same age. Thus this formalism, related to models used in glassy materials, allows us to illustrate an approach to the statistical treatment of blinking quantum dots, bypassing the limitations fo ...
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc40401/
Carbon K-shell x-ray and Auger-electron production in hydrocarbons and carbon oxides by 0.6-2.0-MeV protons
Date: May 1, 1987
Creator: Bhalla, R. P.; McDaniel, Floyd Del. (Floyd Delbert), 1942- & Lapicki, G.
Description: This article discusses carbon K-shell x-ray and Auger-electron production in hydrocarbons and carbon oxides by 0.6-2.0-MeV protons. Abstract: Carbon K-shell x-ray and Auger-electron-production cross sections are reported for 0.6-2.0-MeV protons incident on CH4 (methane), C2H2 (acetylene), n-C4H10 (normal butane), i-C4H10 (isobutane), C6H6 (benzene), CO, and CO2. A variable-geometry end-window proportional counter with an alternative procedure for the determination of its transmission was used in collection of the x-ray data. A constant-energy-mode π/4 parallel-plate electrostatic analyzer served in the detection of Auger electrons. K-shell Auger-electron-production cross sections are compared with the predictions of the first Born theory and the perturbed-stationary-state theory which accounts for energy-loss, Coulomb deflection, and relativistic effects (ECPSSR). These data show fair agreement with the ECPSSR theory when the chemical shifts, of the carbon K-shell binding energy in molecules, are included in the calculations. This agreement is even better after effects of intramolecular scattering are considered. Validity of the geometrical model by Matthews and Hopkins [Phys. Rev. Lett. 40, 1326(1978)] is established after a scrutiny of the inelastic cross sections for scattering of Auger-electrons within the molecule and their effective dislocation out of the detector's window. The x-ray cross sections show particularly strong variations with the target molecular ...
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc139493/
Brain, Music, and Non-Poisson Renewal Processes
Date: June 21, 2007
Creator: Bianco, Simone; Ignaccolo, Massimiliano; Rider, Mark S.; Ross, Mary J.; Winsor, Phil & Grigolini, Paolo
Description: This article discusses brain, music, and non-Poisson renewal processes. Abstract: In this paper we show that both music composition and brain function, as revealed by the electroencephalogram (EEG) analysis, are renewal non-Poisson processes living in the nonergodic dominion. To reach this important conclusion the authors process the data with the minimum spanning tree method, so as to detect significant events, thereby building a sequence of times, which is the time series to analyze. The the authors show that in both cases, EEG and music composition, these significant events are the signature of a non-Poisson renewal process. This conclusion is reached using a technique of statistical analysis recently developed by the authors' group, the aging experiment (AE). First, the authors find that in both cases the distances between two consecutive events are described by nonexponential histograms, thereby proving the non-Poisson nature of these processes. The corresponding survival probabilities ψ(t) are well fitted by stretched exponentials [ψ(t) ∝ exp (-(yt)a), with 0.5<a<1.] The second step rests on the adoption of AE, which shows that these are renewal processes. The authors show that the stretched exponential, due to its renewal character, is the emerging tip of an iceberg, whose underwater part has slow ...
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc40398/
Canonical and noncanonical equilibrium distribution
Date: 2001
Creator: Annunziato, Mario; Grigolini, Paolo & West, Bruce J.
Description: This article discusses canonical and noncanonical equilibrium distribution. Abstract: We address the problem of the dynamical foundation of noncanonical equilibrium. We consider, as a source of divergence from ordinary statistical mechanics, the breakdown of the condition of time scale separation between microscopic and macroscopic dynamics. We show that this breakdown has the effect of producing a significant deviation from the canonical prescription. We also show that, while the canonical equilibrium can be reached with no apparent dependence on dynamics, the specific form of noncanonical equilibrium is, in fact, determined by dynamics. We consider the special case where the thermal reservoir driving the system of interest to equilibrium is a generator of intermittent fluctuations. We assess the form of the noncanonical equilibrium reached by the system in this case. Using both theoretical and numerical arguments we demonstrate that Lévy statistics are the best description of the dynamics and that the Lévy distribution is the correct basin of attraction. We show that the correct path to noncanonical equilibrium by means of strictly thermodynamic arguments has not yet been found, and that further research has to be done to establish a connection between dynamics and thermodynamics.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc77164/
Charge-state dependence of K-shell x-ray production in aluminum by 2-12-MeV carbon ions
Date: June 1996
Creator: Sun, H. L.; Yu, Y. C.; Lin, E. K.; Wang, C. W.; Duggan, Jerome L.; Azordegan, A. R. et al
Description: This article discusses charge-state dependence of K-shell x-ray production in aluminum by 2-12-MeV carbon ions. Abstract: Charge-state dependence for K-shell x-ray production cross sections in 13Al bombarded by 2-12-MeV 6C ions with charge states from 2+ to 6+ was measured using a Si(Li) detector. A thin Al target was used to ensure single collision conditions. Contributions of the electron capture as well as direct ionization to the inner-shell ionization were determined by an analysis of the charge-state dependence of the target x-ray production. The measurements are compared with the prediction of the ECPSSR theory using a single-hole fluorescence yield. The ECPSSR theory is based on the perturbed stationary state (PSS) formalism and relativistic efforts (R) for the target electrons, and energy loss (E) and Coulomb deflection (C) of the projectile. In general, this theory gives reasonable agreement with the data for carbon ions without K vacancies while it overpredicts the data for carbon ions with K vacancies. The significant underprediction of the data at the lowest energy is likely associated with the molecular-orbital effect that is not accounted for in the ECPSSR theory.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc139497/
Charge-state dependence of M-shell x-ray production in 67Ho by 2-12-MeV carbon ions
Date: November 1995
Creator: Yu, Y. C.; Sun, H. L.; Duggan, Jerome L.; McDaniel, Floyd Del. (Floyd Delbert), 1942-; Yin, J. Y. & Lapicki, G.
Description: This article discusses charge-state dependence of M-shell x-ray production in 67Ho by 2-12-MeV carbon ions. Abstract: Charge-state dependence of M-shell x-ray production cross sections of 67Ho bombarded by 2-12-MeV carbon ions, with and without K-shell vacancies, were measured using a windowless Si(Li) x-ray detector with a full-width-at-half-maximum resolution of 135 eV at 5.9 keV. Carbon ions of different charge states were produced using a postacceleration, nitrogen gas stripping cell. The carbon ions were then magnetically analyzed to select the desired charge state and energy before entering the target chamber. The total M-shell and Mζ, Mα,β, and Mγ x-ray cross sections were measured. The electron-capture (EC) contributions as well as the direct-ionization (DI) contributions can be determined by making a comprehensive study of the projectile-charge-state dependence of the target x-ray production cross sections for targets in which the single-collision realm is maintained. In this paper, both EC and DI contributions and the total M-shell x-ray production cross sections are compared to both the first Born theory and to the perturbed-stationary-state theory with energy-loss, Coulomb-deflection, and relativistic corrections.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc139496/
Charge transfer equilibria in ambient-exposed epitaxial graphene on (0001) 6 H-SiC
Date: June 5, 2012
Creator: Sidorov, Anton N.; Gaskill, D. Kurt.; Buongiorno Nardelli, Marco; Tedesco, Joseph L.; Myers-Ward, Rachel L.; Eddy, Charles R. et al
Description: This article discusses charge transfer equilibria in ambient-exposed epitaxial graphene on (0001) 6 H-SiC. Abstract: The transport properties of electronic materials have been long interpreted independently from both the underlying bulk-like behavior of the substrate or the influence of ambient gases. This is no longer the case for ultra-thin graphene whose properties are dominated by the interfaces between the active material and its surroundings. Here, the authors show that the graphene interactions with its environments are critical for the electrostatic and electrochemical equilibrium of the active device layers and their transport properties. Based on the prototypical case of epitaxial graphene on (0001) 6 H-SiC and using a combination of 'in-situ' thermoelectric power and resistance measurements and simulations from first principles, the authors demonstrate that the cooperative occurrence of an electrochemically mediated charge transfer from the graphene to air, combined with the peculiar electronic structure of the graphene/SiC interface, explains the wide variation of measured conductivity and charge carrier type found in prior reports.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc132974/
Bose-Einstein Condensates and their Possible Applications in Quantum Computing and Optical Processing
Date: April 3, 2008
Creator: Hodgson, Shane & Eve, Susan Brown
Description: This poster discusses research on Bose-Einstein condensates (BECs) and their possible applications in quantum computing and optical processing. BECs could have a revolutionary impact in the fields of quantum logic and quantum computing, as well as the storage of optical information in a highly compressed state.
Contributing Partner: UNT Honors College
Permallink:digital.library.unt.edu/ark:/67531/metadc86120/