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The Volatile Matter of Coal

Description: From Introduction Scope of Report: "This bulletin is a report on an investigation of the volatile matter in several typical coals-its composition and amount at different temperatures of volatilization. As the investigation is still in progress and will doubtless include other coals than those already examined, the bulletin may be considered a preliminary report, stating the problems studied, the methods used, and the results thus far obtained."
Date: 1912
Creator: Porter, Horace C. & Ovitz, F. K.
Partner: UNT Libraries Government Documents Department

HYPER-STRANGE HADRONIC MATTER

Description: The binding energy of hyper-strange matter in the hadronic phase is calculated as a function of strangeness fraction in the mean field approximation to a relativistic field theory of matter. This is compared to a calculation of Chin and Kerman for the quark phase.
Date: November 1, 1980
Creator: Glendenning, Norman K.
Partner: UNT Libraries Government Documents Department

An Analysis of Angus Wilson's "No Laughing Matter"

Description: This thesis examines Angus Wilson's novels with particular attention to No Laughing Matter, 1967. The introductory overview of Wilson's first five novels and the examination of No Laughing Matter show that all Wilson's novels are concerned with his protagonists' capacity for self-deception and the ways deception limits freedom of choice. In No Laughing Matter six protagonists try to balance self-deception and freedom both in their lives and in the art forms which interest them. The thesis traces the lives of these six as they fail both as artists and as people. Chapter III of the thesis studies the relationship of fantasy to character in the novel. In No Laughing Matter particularly, the characters reflect the loss of liberty when individuals do not exercise their freedom to choose.
Date: December 1975
Creator: Arnold, Gloria Cockerell
Partner: UNT Libraries

Reducing Zero-point Systematics in Dark Energy Supernova Experiments

Description: We study the effect of filter zero-point uncertainties on future supernova dark energy missions. Fitting for calibration parameters using simultaneous analysis of all Type Ia supernova standard candles achieves a significant improvement over more traditional fit methods. This conclusion is robust under diverse experimental configurations (number of observed supernovae, maximum survey redshift, inclusion of additional systematics). This approach to supernova fitting considerably eases otherwise stringent mission cali- bration requirements. As an example we simulate a space-based mission based on the proposed JDEM satellite; however the method and conclusions are general and valid for any future supernova dark energy mission, ground or space-based.
Date: April 1, 2011
Creator: Faccioli, Lorenzo; Kim, Alex G; Miquel, Ramon; Bernstein, Gary; Bonissent, Alain; Brown, Matthew et al.
Partner: UNT Libraries Government Documents Department

A Study of The Mirror

Description: Because of the lack of authoritative secondary material on the Mirror, the need for deeper study into the content of the Mirror appears necessary. In order to fill this need, this study has been undertaken to provide basic information about the Mirror's subject matter and the attitudes of its contributors.
Date: August 1962
Creator: Heaberlin, Dick M.
Partner: UNT Libraries

Search for Halo Axions

Description: A collaboration of MIT, LLNL, Univ. of Florida, FNAL, UC Berkeley and INR Moscow have built a large-scale RF cavity axion detector. The experiment has been taking production data since February of 1996 and is sensitive enough to detect plausible dark matter axions comprising a reasonable fraction of the mass in our galactic halo. After a brief introduction to axion physics, I discuss details of our instrumentation, our analysis methodology, our run plan and future goals of the experiments.
Date: January 1, 1998
Creator: Daw, E. J., & van Bibber, K.
Partner: UNT Libraries Government Documents Department

Large-scale search for dark-matter axions

Description: Early results from a large-scale search for dark matter axions are presented. In this experiment, axions constituting our dark-matter halo may be resonantly converted to monochromatic microwave photons in a high-Q microwave cavity permeated by a strong magnetic field. Sensitivity at the level of one important axion model (KSVZ) has been demonstrated.
Date: January 1, 1998
Creator: Hagmann, C. A.; Kinion, D.; Stoeffl, W.; Van Bibber, K.; Daw, E. J.; McBride, J. et al.
Partner: UNT Libraries Government Documents Department

The Storage of Organic Matter in Bottom Deposits of Lake Dallas

Description: The purpose of this investigation is to find which season of the year organic matter increases most in the bottom deposits of Lake Dallas, the reason for the increase, and the amount of organic matter increase from year to year. It is hoped that this study will be beneficial in understanding the conditions in artificial reservoirs.
Date: 1941
Creator: Williams, Cyrus Paul
Partner: UNT Libraries

Measurement and Control of Radioactive Particulate Contamination: Summary Report

Description: The following report is meant to review the characteristics of airborne particulate contamination matter, which sets it apart from other phases of the radiation control program and make it necessary to apply to it different concepts, analytical procedures, and control measures.
Date: 1956
Creator: Match, Theodore F.
Partner: UNT Libraries Government Documents Department

Optically Detected Magnetic Resonance Studies on π-conjugated semiconductor systems

Description: Optically Detected Magnetic Resonance (ODMR) techniques were used to investigate the dynamics of excitons and charge carriers in π-conjugated organic semiconductors. Degradation behavior of the negative spin-1/2 electroluminescence-detected magnetic resonance (ELDMR) was observed in Alq3 devices. The increase in the resonance amplitude implies an increasing bipolaron formation during degradation, which might be the result of growth of charge traps in the device. The same behavior of the negative spin-1/2 ELDMR was observed in 2wt% Rubrene doped Tris(8-hydroxyquinolinato)aluminium (Alq3) devices. However, with increasing injection current, a positive spin-1/2 ELDMR, together with positive spin 1 triplet powder patterns at {delta}m{sub S}={+-}1 and {delta}m{sub S}={+-}2, emerges. Due to the similarities in the frequency dependences of single and double modulated ELDMR and the photoluminescence-detected magnetic resonance (PLDMR) results in poly[2-methoxy-5-(2 -ethyl-hexyloxy)-1,4-phenyl ene vinylene] (MEH-PPV) films, the mechanism for this positive spin-1/2 ELDMR was assigned to enhanced triplet-polaron quenching under resonance conditions. The ELDMR in rubrene doped Alq3 devices provides a path to investigate charge distribution in the device under operational conditions. Combining the results of several devices with different carrier blocking properties and the results from transient EL, it was concluded trions not only exist near buffer layer but also exist in the electron transport layer. This TPQ model can also be used to explain the positive spin-1/2 PLDMR in poly(3-hexylthiophene) (P3HT) films at low temperature and in MEH-PPV films at various temperatures up to room temperature. Through quantitative analysis, TE-polaron quenching (TPQ) model is shown having the ability to explain most behaviors of the positive spin-1/2 resonance. Photocurrent detected magnetic resonance (PCDMR) studies on MEH-PPV devices revealed a novel transient resonance signal. The signal may originate from the higher concentration of deep traps near cathode. A quantitative analysis based on this assumption was carried out and found to be consistent with the experimental ...
Date: December 6, 2011
Creator: Chen, Ying
Partner: UNT Libraries Government Documents Department

First principles analysis of lattice dynamics for Fe-based superconductors and entropically-stabilized phases

Description: Modern calculations are becoming an essential, complementary tool to inelastic x-ray scattering studies, where x-rays are scattered inelastically to resolve meV phonons. Calculations of the inelastic structure factor for any value of Q assist in both planning the experiment and analyzing the results. Moreover, differences between the measured data and theoretical calculations help identify important new physics driving the properties of novel correlated systems. We have used such calculations to better and more e#14;ciently measure the phonon dispersion and elastic constants of several iron pnictide superconductors. This dissertation describes calculations and measurements at room temperature in the tetragonal phase of CaFe{sub 2}As{sub 2} and LaFeAsO. In both cases, spin-polarized calculations imposing the antiferromagnetic order present in the low-temperature orthorhombic phase dramatically improves the agreement between theory and experiment. This is discussed in terms of the strong antiferromagnetic correlations that are known to persist in the tetragonal phase. In addition, we discuss a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD), which goes beyond the harmonic approximation to include phonon-phonon interactions and produce a temperature-dependent phonon dispersion. We used this technique to study the HCP to BCC transition in beryllium.
Date: July 20, 2012
Creator: Hahn, Steven
Partner: UNT Libraries Government Documents Department

Structural and magnetic properties and superconductivity in Ba(Fe{sub 1-x}TM{sub x}){sub 2}As{sub 2}

Description: We studied the effects on structural and magnetic phase transitions and the emergence of superconductivity in transition metal substituted BaFe{sub 2}As{sub 2}. We grew four series of Ba(Fe{sub 1-x}TM{sub x}){sub 2}As{sub 2} (TM=Ru, Mn, Co+Cr and Co+Mn) and characterized them by crystallographic, magnetic and transport measurements. We also subjected Ba(Fe{sub 1-x}Cr{sub x}){sub 2}As{sub 2} and Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} to heat treatment to explore what changes might be induced.
Date: July 23, 2012
Creator: Thaler, Alexander
Partner: UNT Libraries Government Documents Department

Structural and magnetic properties of transition metal substituted BaFe{sub 2}As{sub 2} compounds studied by x-ray and neutron scattering

Description: The purpose of my dissertation is to understand the structural and magnetic properties of the newly discovered FeAs-based superconductors and the interconnection between superconductivity, antiferromagnetism, and structure. X-ray and neutron scattering techniques are powerful tools to directly observe the structure and magnetism in this system. I used both xray and neutron scattering techniques on di#11;erent transition substituted BaFe2As2 compounds in order to investigate the substitution dependence of structural and magnetic transitions and try to understand the connections between them.
Date: August 28, 2012
Creator: Kim, Min Gyu
Partner: UNT Libraries Government Documents Department

Electronic structure and f-orbital occupancy in Yb-substituted CeCoIn5

Description: The local structure and 4f orbital occupancy have been investigated in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} via Yb L{sub III}-edge extended x-ray absorption fine structure (EXAFS), Ce and Yb L{sub III}-edge x-ray absorption near-edge structure (XANES), and angle-resolved photoemission spectroscopy (ARPES) measurements. Yb(III) (4f{sup 13}) is the hole analog of Ce(III) (4f{sup 1}). Yb is found to be strongly intermediate-valent in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} throughout the entire doping range, including pure YbCoIn{sub 5}, with an f-hole occupancy for Yb of n{sub f} ≃ 0.3 (i.e. Yb{sup 2.3+}), independent of Yb concentration and independent of temperature down to T = 20 K. In contrast, the f-electron orbital occupancy for Ce remains close to 1 for all Yb concentrations, suggesting that there is no mutual influence on n{sub f} between neighboring Ce and Yb sites. Likewise, ARPES measurements at 12 K have found that the electronic structure along {Gamma} − X is not sensitive to the Yb substitution, suggesting that the Kondo hybridization of Ce f electrons with the conduction band is not affected by the presence of Yb impurities in the lattice. The emerging picture is that in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} there are two networks, interlaced but independent, that couple to the conduction band: one network of Ce ions in the heavy-fermion limit, one network of Yb ions in the strongly intermediate-valent limit. The robustness of the local and electronic structure to doping suggests the absence of charge transfer between the Ce and Yb ions, and may explain the relative robustness of superconductivity for this Ce-site substitution as compared to the In-site substitution.
Date: May 3, 2011
Creator: Booth, C. H.; Durakiewicz, T.; Capan, C.; Hurt, D.; Bianchi, A. D.; Joyce, J.J. et al.
Partner: UNT Libraries Government Documents Department

Itinerant and localized magnetic moments in ferrimagnetic Mn{sub 2}CoGa thin films identified with x-ray magnetic linear dichroism: experiment and ab initio theory

Description: Epitaxial thin films of the half-metallic X{sub a}-compound Mn{sub 2}CoGa (Hg{sub 2}CuTi prototype) were prepared by dc magnetron co-sputtering with different heat treatments on MgO (001) substrates. High-quality #12;lms with a bulk magnetization of 1.95(5) {mu}{sub #22;}B per unit cell were obtained. The average Mn magnetic moment and the Co moment are parallel, in agreement with theory. The x-ray magnetic circular dichroism spectra agree with calculations based on density functional theory and reveal the antiparallel alignment of the two inequivalent Mn moments. X-ray magnetic linear dichroism allows to distinguish between itinerant and localized Mn moments. It is shown that one of the two Mn moments has localized character, whereas the other Mn moment and the Co moment are itinerant.
Date: August 8, 2011
Creator: Meinert, M.; Schmalhorst, J; Klewe, C.; Reiss, G.; Arenholz, E.; Bohnert, T. et al.
Partner: UNT Libraries Government Documents Department

Metal-insulator transition in low dimensional La{sub 0.75}Sr{sub 0.25}VO{sub 3} thin films

Description: We report on the metal-insulator transition that occurs as a function of film thickness in ultrathin La{sub 0.75}Sr{sub 0.25}VO{sub 3} films. The metal-insulator transition displays a critical thickness of 5 unit cell. Above the critical thickness, metallic films exhibit a temperature driven metal-insulator transition with weak localization behavior. With decreasing film thickness, oxygen octahedron rotation in the films increases, causing enhanced electron-electron correlation. The electronelectron correlations in ultrathin films induce the transition from metal to insulator in addition to Anderson localization.
Date: June 15, 2011
Creator: Dao, Tran M.; Mondal, Partha S.; Takamura, Y.; Arenholz, E. & Lee, Jaichan
Partner: UNT Libraries Government Documents Department

Widespread spin polarization effects in photoemission from topological insulators

Description: High-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES) was performed on the three-dimensional topological insulator Bi{sub 2}Se{sub 3} using a recently developed high-efficiency spectrometer. The topological surface state's helical spin structure is observed, in agreement with theoretical prediction. Spin textures of both chiralities, at energies above and below the Dirac point, are observed, and the spin structure is found to persist at room temperature. The measurements reveal additional unexpected spin polarization effects, which also originate from the spin-orbit interaction, but are well differentiated from topological physics by contrasting momentum and photon energy and polarization dependencies. These observations demonstrate significant deviations of photoelectron and quasiparticle spin polarizations. Our findings illustrate the inherent complexity of spin-resolved ARPES and demonstrate key considerations for interpreting experimental results.
Date: June 22, 2011
Creator: Jozwiak, C.; Chen, Y. L.; Fedorov, A. V.; Analytis, J. G.; Rotundu, C. R.; Schmid, A. K. et al.
Partner: UNT Libraries Government Documents Department