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The low temperature properties of (Dy{sub 1-x}Er{sub x})Ni{sub 2} alloys

Description: The study of rare earth magnetic properties is undertaken to further the understanding of critical phenomena and the mechanism of magnetic ordering in solids. There is a great variety of magnetic ordering observed in the rare earth compounds, thus providing an insight to phenomena such as heat capacity, magnetostriction and crystal fields. Studies began on the magnetic properties of the rare earths and their compounds in the 1950`s.
Date: July 27, 1994
Creator: Gailloux, M.
Partner: UNT Libraries Government Documents Department
open access

Directional solidification of the alumina-zirconia ceramic eutectic system

Description: It is possible to produce alumina-zirconia ceramic samples through existing solidification techniques. The resulting microstructures typically consist of rods of zirconia in an alumina matrix, although a lamellar structure has been noted in some cases. In nearly all cases, colony growth was present which may possibly result from grain size, repeated nucleation events, and lamellar oscillations. In the same vein, it appears that the amount of impurities within the system might be the underlying … more
Date: July 27, 1994
Creator: Boldt, C.
Partner: UNT Libraries Government Documents Department
open access

Novel absorption detection techniques for capillary electrophoresis

Description: Capillary electrophoresis (CE) has emerged as one of the most versatile separation methods. However, efficient separation is not sufficient unless coupled to adequate detection. The narrow inner diameter (I.D.) of the capillary column raises a big challenge to detection methods. For UV-vis absorption detection, the concentration sensitivity is only at the {mu}M level. Most commercial CE instruments are equipped with incoherent UV-vis lamps. Low-brightness, instability and inefficient coupling o… more
Date: July 27, 1994
Creator: Xue, Y.
Partner: UNT Libraries Government Documents Department
open access

Development of novel separation techniques for biological samples in capillary electrophoresis

Description: This dissertation includes three different topics: general introduction of capillary electrophoresis (CE); gradient in CE and CE in biological separations; and capillary gel electrophoresis (CGE) for DNA separation. Factors such as temperature, viscosity, pH, and the surface of capillary walls affecting the separation performance are demonstrated. A pH gradient between 3.0 and 5.2 is useful to improve the resolution among eight different organic acids. A flow gradient due to the change in the c… more
Date: July 27, 1994
Creator: Chang, H. T.
Partner: UNT Libraries Government Documents Department
open access

Theoretical study of the noble metals on semiconductor surfaces and Ti-base shape memory alloys

Description: The electronic and structural properties of the ({radical}3 {times} {radical}3) R30{degrees} Ag/Si(111) and ({radical}3 {times} {radical}3) R30{degrees} Au/Si(111) surfaces are investigated using first principles total energy calculations. We have tested almost all experimentally proposed structural models for both surfaces and found the energetically most favorable model for each of them. The lowest energy model structure of the ({radical}3 {times} {radical}3) R30{degrees} Ag/Si(111) surface c… more
Date: July 27, 1994
Creator: Ding, Yungui
Partner: UNT Libraries Government Documents Department
open access

Selenophene transition metal complexes

Description: This research shows that selenophene transition metal complexes have a chemistry that is similar to their thiophene analogs. Selenophene coordination has been demonstrated and confirmed by molecular structure in both the {eta}{sup 5}- and the {eta}{sup 1}(Se)-coordination modes. The reaction chemistry of selenophene complexes closely resembles that of the analogous thiophene complexes. One major difference, however, is that selenophene is a better donor ligand than thiophene making the selenoph… more
Date: July 27, 1994
Creator: White, C. J.
Partner: UNT Libraries Government Documents Department
open access

Dynamic NMR studies of restricted arene rotation in the chromiu tricarbonyl thiophene and selenophene complexes

Description: This thesis contains the results of organometallic studies of thiophene and selenophene coordination in transition metal complexes. Chromium tricarbonyl complexes of thiophene, selenophene, and their alkyl-substituted derivatives were prepared and variable-temperature {sup 13}C NMR spectra of these complexes were recorded in dimethyl ether. Bandshape analyses of these spectra yielded activation parameters for restricted rotation of the thiophene and selenophene ligands in these complexes. Exten… more
Date: May 27, 1994
Creator: Sanger, M. J.
Partner: UNT Libraries Government Documents Department
open access

Quantum dynamical phenomena of independent electrons in semiconductor superlattices subject to a uniform electric field

Description: This report discusses the following topics: Bloch oscillations and other dynamical phenomena of electrons in semiconductor superlattices; solvable dynamical model of an electron in a one-dimensional aperiodic lattice subject to a uniform electric field; and quantum dynamical phenomena of electrons in aperiodic semiconductor superlattices.
Date: July 27, 1994
Creator: Bouchard, A. M.
Partner: UNT Libraries Government Documents Department
open access

Photodissociation and photoionization of organosulfur radicals

Description: The dynamics of S({sup 3}P{sub 2,1,0}, {sup 1}D{sub 2}) production from the 193 nm photodissociation of CH{sub 3}SCH{sub 3}, H{sub 2}S and CH{sub 3}SH have been studied using 2 + 1 resonance-enhanced multiphoton ionization (REMPI) techniques. The 193 nm photodissociation cross sections for the formation of S from CH{sub 3}S and HS initially prepared in the photodissociation of CH{sub 3}SCH{sub 3} and H{sub 2}S are estimated to be 1 {times} 10{sup {minus}18} and 1.1 {times} 10{sup {minus}18} cm{… more
Date: May 27, 1994
Creator: Hsu, Chia-Wei
Partner: UNT Libraries Government Documents Department
open access

Studies of selenium and xenon in inductively coupled plasma mass spectrometry

Description: Since its development, inductively coupled plasma mass spectrometry (ICP-MS) has been a widely used analytical technique. ICP-MS offers low detection limits, easy determination of isotope ratios, and simple mass spectra from analyte elements. ICP-MS has been successfully employed for many applications including geological, environmental, biological, metallurgical, food, medical, and industrial. One specific application important to many areas of study involves elemental speciation by using ICP-… more
Date: July 27, 1994
Creator: Bricker, T.
Partner: UNT Libraries Government Documents Department
open access

Distribution-independent hierarchicald N-body methods

Description: The N-body problem is to simulate the motion of N particles under the influence of mutual force fields based on an inverse square law. The problem has applications in several domains including astrophysics, molecular dynamics, fluid dynamics, radiosity methods in computer graphics and numerical complex analysis. Research efforts have focused on reducing the O(N{sup 2}) time per iteration required by the naive algorithm of computing each pairwise interaction. Widely respected among these are the… more
Date: July 27, 1994
Creator: Aluru, S.
Partner: UNT Libraries Government Documents Department
open access

Classical Inspiration and Modern Expression: Greek Art Turned Fauve, Constructivist, Dada, and Pop

Description: Senior colloquium written by a student in the UNT Honors College discussing Greek sculpture and architecture as filtered through the Fauve, Constructivist, Dada, and Pop artistic movements. The author takes examples of Grecian sculpture, recreates them in each of the other styles, and discusses the results.
Date: April 27, 1991
Creator: Capen, Sheri
Partner: UNT Honors College
open access

Applications of electrochemically-modulated liquid chromatography (EMLC): Separations of aromatic amino acids and polycyclic aromatic hydrocarbons

Description: The research in this thesis explores the separation capabilities of a new technique termed electrochemically-modulated liquid chromatography (EMLC). The thesis begins with a general introduction section which provides a literature review of this technique as well as a brief background discussion of the two research projects in each of the next two chapters. The two papers which follow investigate the application of EMLC to the separation of a mixture of aromatic amino acids and of a mixture of … more
Date: March 27, 1998
Creator: Deng, L.
Partner: UNT Libraries Government Documents Department
open access

Zintl cluster chemistry in the alkali-metal-gallium systems

Description: Previous research into the alkali-metal-gallium systems has revealed a large variety of networked gallium deltahedra. The clusters are analogues to borane clusters and follow the same electronic requirements of 2n+2 skeletal electrons for closo-deltahedra. This work has focused on compounds that do not follow the typical electron counting rules. The first isolated gallium cluster was found in Cs{sub 8}Ga{sub 11}. The geometry of the Ga{sub 11}{sup 7{minus}} unit is not deltahedral but can be de… more
Date: March 27, 1998
Creator: Henning, R.
Partner: UNT Libraries Government Documents Department
open access

Nuclear magnetic resonance: Its role as a microscopic probe of the electronic and magnetic properties of High-{Tc} superconductors and related materials

Description: NMR experiments are reported for Sr{sub 2}CuO{sub 2}Cl{sub 2}, HgBa{sub 2}CuO{sub 4+d}, YNi{sub 2}B{sub 2}C and YBa{sub 2}Cu{sub 3}O{sub 7}. NMR studies typify three different aspects of microscopic properties of HTSC. In non-superconducting antiferromagnetic (AF) prototype Sr{sub 2}CuO{sub 2}Cl{sub 2}, we used NMR to investigate Cu{sup 2+} correlated spin dynamics and AF phase transition in CuO2 layers. In the superconductors, we used NMR both to investigate the electronic properties of the Fe… more
Date: December 27, 1995
Creator: Suh, Byoung Jin
Partner: UNT Libraries Government Documents Department
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