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Novel Dodecaarylporphyrins: Synthesis and Variable Temperature NMR Studies

Description: An investigation of the synthesis of novel dodecaarylporphyrins using the Suzuki coupling reaction of arylboronic acids with octabromotetraarylporphyrins is reported. Studies of the dynamic properties of these new porphyrins using variable temperature (VT) <SUP>1</SUP>H NMR spectroscopy and molecular mechanics provide interesting insights into their dynamic properties, including the first determination of {beta} aryl rotation in a porphyrin system.
Date: May 5, 1999
Creator: Cancilla, Mark; Lebrilla, Carlito; Ma, Jian-Guo; Medforth, Craig J.; Muzzi, Cinzia M.; Shelnutt, John A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Toward a Molecular-Based Understanding of High-Temperature Solvation Phenomena in Aqueous Electrolyte Solutions

Description: The theoretical treatment of the solvation phenomenon of simple ions in aqueous solutions has been rather difficult, despite the apparent simplicity of the system. Long-range solvent-screened electrostatic interactions, coupled to the large variation (with state conditions) of the dielectric permittivity of water, give rise to a variety of rather complex solvation phenomena including dielectric saturation, electrostriction, and ion association. Notably, ion solvation in high-temperature/pressur… more
Date: October 30, 1999
Creator: Chialvo, A. A.; Cummings, P. T.; Kusalik, P. G. & Simonson, J. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Quartz Channel Fabrication for Electrokinetically Driven Separations

Description: For well resolved electrokinetic separation, we L tilize crystalline quartz to micromachine a uniformly packe Q&iKLmnel. Packing features are posts 5 Vm on a side with:} pm spacing and etched 42 Vm deep. In addition to anisotropic wet etch characteristics for micromachining, quartz propmties are compatible with chemical soiutioits, ekctrokinetic high voltage operation, and stationary phase film depositions. To seal these channels, we employ a room temperature silicon-oxynhride deposition to for… more
Date: December 1, 1998
Creator: Arnold, D.W.; Ashby, C.I.H.; Bailey, C.G.; Kravitz, S.H., Warren, M.E. & Matzke, C.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Combining the Best of Bulk and Surface Micromaching Using Si(111) Substrates

Description: This process combines the best features of bulk ad surface micromachining. It enables the production of stress free, thick, virtually arbitrarily shaped structures with well defiti thick or thin sacrificial layers, high sacrificial layer selectivity and large undercuts using IC compatible, processes. The basis of this approach is the use of dy available {111} oriented substrates. anisotropic Si trench etching, S iN masking and KOH etching.
Date: November 30, 1998
Creator: Fleming, J.G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Recent improvements of a new thermal ionization cavity source for mass spectrometry

Description: Last year, we presented a prototype ion source design for mass spectrometry, which uses a tungsten crucible with a deep cavity for sample loading and enhanced surface ionization; the crucible is heated by high energy electron bombardment. This ion source was named as a thermal ionization cavity (TIC). In this present work, an TIC source has been designed with a vacuum interlock system and translational stage. It is now easier to operate and handle while maximizing sample throughput.
Date: June 1, 1996
Creator: Duan, Y.; Olivares, J. A.; Danen, R. E. & Cleland, T. J.
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Partner: UNT Libraries Government Documents Department
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Fluorinated Dodecaphenylporphyrins: Synthetic and Electrochemical Studies Including the First Evidence of Intramolecular Electron Transfer Between an Fe(II) Porphyrin -Anion Radical and an Fe(I) Porphyrin

Description: Dodecaphenylporphyrins with varying degrees of fluorination of the peripheral phenyl rings (FXDPPS) were synthesized as model compounds for studying electronic effects in nonplan~ porphyrins, and detailed electrochemical studies of the chloroiron(HI) complexes of these compounds were undertaken. The series of porphyrins, represented as FeDPPCl and as FeFXDPPCl where x = 4, 8 (two isomers), 12, 20,28 or 36, could be reversibly oxidized by two electrons in dichloromethane to give n-cation radical… more
Date: October 19, 1998
Creator: D'Souza, Francis; Forsyth, Timothy P.; Fukuzumi, Shunichi; Kadish, Karl M.; Krattinger, Benedicte; Lin, Min et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Radiation Chemistry of Simulated (99)Mo Product

Description: PharrnaceuticaI houses that produce {sup 99}Tc/{sup 99}Tc generators have on occasion received {sup 99}Mo that contained a black precipitate. Addition of sodium hypochlorite to product bottles prior to shipment prevents precipitate formation, indicating the precipitate is a reduced form of Mo. The radiation effects of the dose from {sup 99}Mo on the product and product bottle have been determined by irradiating simulated {sup 99}Mo product solutions with the {sup 60}Co source at Sandia National… more
Date: November 6, 1998
Creator: Carson, S. D.; Garcia, M. J.; McDonald, M. J.; Simpson, R. L. & Tallant, D. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Formation of Chloropyromorphite from Galena (PbS) in the Presence of Hydroxyapatite

Description: Transformation of unstable lead [Pb(ll)] forms into insoluble pyromorphite, [Pb5(P04)3(OH, Cl, F...)], by addition of phosphate to Pb contaminated soil has been proposed as a remediation technology which reduces the mobility and bioavailability of Pb. Under aerobic condition, oxidation of dissolved sulfide increases dissolution of galena (PbS), causing it to become a source of liable Pb forms in soils, sediments and wastes. Thus, a galena ore was reacted with synthetic hydroxyapatite [Ca5(P04)3… more
Date: October 14, 1998
Creator: Ryan, J.A. & Zhang, P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Reduction of sample volume and waste generation in acid/base titrations using microelectrodes

Description: The Analytical Development Section (ADS) has developed microelectrode methods for use with pH titrations and pH determinations. These microelectrode methods offer increased sensitivity and enable analyses to be done with smaller sample and buffer volumes than are used with standard size electrodes. This report establishes the technical validity of the methods and describes the application of these methods to decreased detection limits, decreased waste generation, and decreased radiation exposur… more
Date: March 22, 1996
Creator: Ekechukwu, A.A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Performance of a 13-Stage Development Compressor for the J40-WE-24 Engine at Equivalent Speeds from 30 to 112 Percent of Design

Description: The performance of a 13-stage development compressor for the J40-WE-24 engine has been determined at equivalent speeds from 30 to 112 percent of design. The design total-pressure ratio of 6.0 and the design weight flow of 164 pounds per second were not attained, An analysis was conducted to determine the reasons for the poor performance at the design and over-design speed. The analysis indicated that most of the difficulty could be attributed to the fact that the first stage was overcompromised… more
Date: April 9, 1953
Creator: Hatch, James E.; Lucas, James G. & Finger, Harold B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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INVESTIGATION ON DURABILITY AND REACTIVITY OF PROMISING METAL OXIDE SORBENTS DURING SULFIDATION AND REGENERATION

Description: The main objectives of this research project during this quarter are to investigate effects of hydrogen, moisture, concentrations of H<sub>2</sub> S, and residence time of reaction gas mixtures on equilibrium absorption as well as dynamic absorption of H<sub>2</sub> S into the TU-188 sorbent at 530 o C, and to evaluate effective diffusivity of H<sub>2</sub> S through the sorbent particles, using the newly-fabricated differential reactor.
Date: December 1, 1997
Creator: KWON, K.C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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[Photon Burst Mass Spectrometry Technique.] Final Report

Description: The basic tools have been developed and demonstrated for selective detection of Kr isotopes in the Photon Burst Mass Spectrometry technique. The effort is divided into: photon burst measurements on Mg{sup +} demonstrating high isotopic selectivity, charge exchange of Kr{sup +} with Cs and Rb to produce metastable Kr atoms, development of a diode laser system for photon burst detection of Kr{sup +}, and measurements of photon bursts detection of Kr.
Date: April 1, 1996
Creator: Fairbank, W. M., Jr.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Flight Measurements of the Rudder Control and Sideslip Characteristics of Four Vertical Tail Arrangements on the P-40 Series Airplanes

Description: Report presenting an investigation of rudder trim force change with speed and power, rudder force reversals in sideslips, and rudder positions in sideslips and straight flight of a P-40E airplane. Quantitative measurements of the items were made on three other vertical arrangements.
Date: October 1942
Creator: Johnson, Harold I. & Vensel, Joseph R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Research Activities in Modeling the Selective Oxidation of Hydrocarbons. Final Report

Description: Selective oxidation of organic substrates by oxygen, where all 4 oxidizing equivalents are used productively, remains an unsolved problem in catalysis. In an idealized catalytic cycle that could solve this problem, three separate steps are involved: first oxygen must be rapidly bound, then the O-O bond must be cleaved, and finally each oxo ligand needs to react independently with the substrate regenerating the catalyst. The first and last steps were investigated in this research program. Molecu… more
Date: December 1, 1995
Creator: Rappe, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Quantum chemical studies on the stability of tetramethyl ammonium tetraborohydride

Description: Quantum chemical calculations were performed on tetramethyl ammonium tetraborohydride. The material is of interest chemically as it exists as a molecular ionic solid. Calculations show that there exist low energy barrier pathways to decomposition and, hence, that the stability of the material is largely due to crystal forces. Possible sources of this stability are discussed.
Date: May 1, 1995
Creator: Calef, D.F.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Reactivity of hydrogen with uranium in the presence of Pt

Description: The surface-reaction of di-hydrogen with uranium in the presence of Pt clusters has been studied using scanning tunneling microscopy (STM). Uranium was deposited on highly oriented pyrolytic graphite (HOPG) and annealed at temperatures up to 1200{degrees}C to obtain atomically pyrolytic flat surfaces. Pt clusters were then formed using evaporation from a Pt source onto the surface and subsequent annealing. Hydrogen mainly attacked uranium in the vicinity of Pt clusters and formed hydride. The h… more
Date: July 1, 1997
Creator: Balooch, M. & Siekhaus, W.J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Raman spectroscopic and mass spectrometric investigations of the hydrogen isotopes and isotopically labelled methane

Description: Suitable analytical methods must be tested and developed for monitoring the individual process steps within the fuel cycle of a fusion reactor and for tritium accountability. The utility of laser-Raman spectroscopy accompanied by mass spectrometry with an Omegatron was investigated using the analysis of all hydrogen isotopes and isotopically labeled methanes as an example. The Omegatron is useful for analyzing all hydrogen isotopes mixed with the stable helium isotopes. The application of this … more
Date: February 24, 1997
Creator: Jewett, J.R., Fluor Daniel Hanford
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Copper Catalyzed Sodium Tetraphenylborate, Triphenylborane, Diphenylborinic Acid and Phenylboronic Acid Decomposition Kinetic Studies in Aqueous Alkaline Solutions

Description: This work studied the kinetics of copper-catalyzed decomposition of tetraphenylborate, triphenylborane, diphenylborinic acid and phenylboronic acid (NaTPB, 3PB, 2PB and 1PB, respectively) in aqueous alkaline solution over the temperature range of 25 to 70 degrees C. The statistically designed test matrices added copper sulfate to maximum concentrations of 10 mg/L. The relative rates of decomposition increase in the order of NaTPB < 1PB {tilde} 3PB < 2PB. Dependence of decomposition on the amoun… more
Date: March 15, 1999
Creator: Crawford, C.L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Analysis of hydrodynamic (landau) instability in liquid-propellant combustion at normal and reduced gravity

Description: The burning of liquid propellants is a fundamental combustion problem that is applicable to various types of propulsion and energetic systems. The deflagration process is often rather complex, with vaporization and pyrolysis occurring at the liquid/gas interface and distributed combustion occurring either in the gas phase or in a spray. Nonetheless, there are realistic limiting cases in which combustion may be approximated by an overall reaction at the liquid/gas interface. In one such limit, d… more
Date: October 1997
Creator: Margolis, S. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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