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An investigation of steric influence on the reactivity of FeV(O)(OH) tautomers in stereospecific C–H hydroxylation (open access)

An investigation of steric influence on the reactivity of FeV(O)(OH) tautomers in stereospecific C–H hydroxylation

Article describes how two new tetradentate N4 ligands (LN4), LN4 = Me2,Me2PyzTACN (1-(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)-4,7-dimethyl-1,4,7-triazacyclononane) and Me2,MeImTACN (1-((1-methyl-1H-imidazol-1-yl)methyl)-4,7-dimethyl-1,4,7-triazacyclononane) have been synthesized and their corresponding Fe(II) complexes [FeII(Me2,Me2PyzTACN)(CF3SO3)2], 1Pz, and [FeII(Me2,MeImTACN)(CF3SO3)2], 1Im, have been prepared and characterized. Based on these labelling studies, the steric influence exerted by each of the ligands towards the relative reactivity of the oxo ligands of the corresponding pair of Fe(V)(O)(OH) tautomers can be derived.
Date: January 5, 2023
Creator: Mitra, Mainak; Brinkmeier, Alexander; Li, Yong; Borrell, Margarida; Call, Arnau; Fillol, Julio Lloret et al.
System: The UNT Digital Library
The Substrate-Independence Theory: Advancing Constructor Theory to Scaffold Substrate Attributes for the Recursive Interaction between Knowledge and Information (open access)

The Substrate-Independence Theory: Advancing Constructor Theory to Scaffold Substrate Attributes for the Recursive Interaction between Knowledge and Information

Article exploring how information and knowledge are absorbed by utilizing Constructor Theory and the Substrate-Independence Theory.
Date: November 30, 2021
Creator: Turner, John R.; Snowden, Dave & Thurlow, Nigel
System: The UNT Digital Library
Multisite phosphorylation of a synthetic peptide derived from the carboxyl terminus of the ribosomal protein S6 (open access)

Multisite phosphorylation of a synthetic peptide derived from the carboxyl terminus of the ribosomal protein S6

Article synthesizing and testing the synthetic peptide AKRRRLSSLRASTSKSESSQK (56-21) which corresponds to the carboxyl-terminal 21 amino acids of human ribosomal protein S6 as a substrate for S6/H4 kinase purified from human placenta. The data suggests that multiple S6 kinases may be required to phosphorylate S6 at all five sites which are modified in vivo.
Date: January 5, 1991
Creator: Brandon, Stanley D. & Masaracchia, Ruthann A.
System: The UNT Digital Library
Intermittent Hypoxic Conditioning Alleviates Post-Traumatic Stress Disorder-Induced Damage and Dysfunction of Rat Visceral Organs and Brain (open access)

Intermittent Hypoxic Conditioning Alleviates Post-Traumatic Stress Disorder-Induced Damage and Dysfunction of Rat Visceral Organs and Brain

Study examines intermittent hypoxic conditioning's (IHC) ability to alleviate harmful PTSD effects on a rat's heart, liver, and brain.
Date: January 5, 2020
Creator: Manukhina, Eugenia B.; Tseilikman, Vadim E.; Karpenko, Marina N.; Pestereva, Nina S.; Tseilikman, Olga B.; Komelkova, Maria V. et al.
System: The UNT Digital Library
Effect of the environment and alloy composition on the electrochemical behavior of Ni-Cr-Mo Alloys (open access)

Effect of the environment and alloy composition on the electrochemical behavior of Ni-Cr-Mo Alloys

Alloy 22 (UNS N06022) is the candidate material for the corrosion resistant, outer barrier of the Yucca Mountain nuclear waste containers. One of the potential corrosion degradation modes of the container is uniform or passive corrosion. Therefore it is of importance to understand the stability of the oxide film, which will control the passive corrosion rate of Alloy 22. Many variables such as temperature, composition and pH of the electrolyte, applied potential, and microstructure and composition of the base metal would determine the thickness and composition of the oxide film. The purpose of this research work was to use electrochemical and surface analysis techniques to explore the influence of solution pH and applied potential on the characteristics of the oxide film formed on Alloy 22 and two experimental alloys containing differing amounts of chromium (Cr) and molybdenum (Mo). Results confirm that bulk metal composition is fundamental to the passive behavior and potential breakdown of the studied alloys. In these preliminary results, welded and non-welded Alloy 22 did not show differences in their anodic behavior.
Date: January 5, 2004
Creator: Hayes, J R; Szmodis, A W; Anderson, K L & Orme, C A
System: The UNT Digital Library
High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST (open access)

High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST

For about two decades, a population of relative small and nearby molecular clouds has been known to exist at high Galactic latitudes. Lying more than 10{sup o} from the Galactic plane, these clouds have typical distances of {approx}150 pc, angular sizes of {approx}1{sup o}, and masses of order tens of solar masses. These objects are passive sources of high-energy {gamma}-rays through cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern sky, we show that typical high-latitude clouds are not bright enough in {gamma}-rays to have been detected by EGRET, but that of order 100 of them will be detectable by the Large Area Telescope (LAT) on GLAST. Thus, we predict a new steady population of {gamma}-ray sources at high Galactic latitudes, perhaps the most numerous after active galactic nuclei.
Date: January 5, 2005
Creator: Torres, D F; Dame, T M & Digel, S W
System: The UNT Digital Library
Search for New Physics at a Super-B Factory (open access)

Search for New Physics at a Super-B Factory

The importance of a Super-B Factory in the search for New Physics, in particular, due to CP-od phase(s) from physics beyond the Standard Model is surveyed. The first point to emphasize is that we know now how to directly measure all three angles of the unitarity triangle very cleanly, i. e. without theoretical assumptions with irreducible theory error {le} 1%; however this requires much more luminosity than is currently available at B-factories. Direct searches via penguin-dominated hadronic modes as well as radiative, pair-leptonic and semi-leptonic decays are also discussed. Null tests of the SM are stressed as these will play a crucial role especially if the effects of BSM phase(s) on B-physics are small.
Date: January 5, 2004
Creator: Browder, T. E. & Soni, A.
System: The UNT Digital Library
Star Formation in High Pressure, High Energy Density Environments: Laboratory Experiments of ISM Dust Analogs (open access)

Star Formation in High Pressure, High Energy Density Environments: Laboratory Experiments of ISM Dust Analogs

Dust grains control the chemistry and cooling, and thus the gravitational collapse of interstellar clouds. Energetic particles, shocks and ionizing radiation can have a profound influence on the structure, lifetime and chemical reactivity of the dust, and therefore on the star formation efficiency. This would be especially important in forming galaxies, which exhibit powerful starburst (supernovae) and AGN (active galactic nucleus) activity. How dust properties are affected in such environments may be crucial for a proper understanding of galaxy formation and evolution. The authors present the results of experiments at LLNL which show that irradiation of the interstellar medium (ISM) dust analog forsterite (Mg{sub 2}SiO{sub 4}) with swift heavy ions (10 MeV Xe) and a large electronic energy deposition amorphizes its crystalline structure, without changing its chemical composition. From the data they predict that silicate grains in the ISM, even in dense and cold giant molecular clouds, can be amorphized by heavy cosmic rays (CR's). This might provide an explanation for the observed absence of crystalline dust in the ISM clouds of the Milky Way galaxy. This processing of dust by CR's would be even more important in forming galaxies and galaxies with active black holes.
Date: January 5, 2005
Creator: van Breugel, W; Bajt, S; Bradley, J; Bringa, E; Dai, Z; Felter, T et al.
System: The UNT Digital Library
Poroelastic Fluid Effects on Shear for Rocks with Soft Anisotropy (open access)

Poroelastic Fluid Effects on Shear for Rocks with Soft Anisotropy

None
Date: January 5, 2004
Creator: Berger, E. L.
System: The UNT Digital Library
How to Determine The Precession of the Inner Accretion Disk in Cygnus X-1 (open access)

How to Determine The Precession of the Inner Accretion Disk in Cygnus X-1

We show that changes in the orientation of the inner accretion disk of Cygnus X-1 affect the shape of the broad Fe K{alpha} emission line emitted from this object, in such a way that eV-level spectral resolution observations (such as those that will be carried out by the ASTRO-E2 satellite) can be used to analyze the dynamics of the disk. We here present a new diagnosis tool, supported by numerical simulations, by which short observations of Cygnus X-1, separated in time, can determine whether its accretion disk actually processes, and if so, determine its period and precession angle. Knowing the precession parameters of Cygnus X-1 would result in a clarification of the origin of such precession, distinguishing between tidal and spin-spin coupling. This approach could also be used for similar studies in other microquasar systems.
Date: January 5, 2005
Creator: Torres, D F; Romero, G E; Barcons, X & Lu, Y
System: The UNT Digital Library
Intracavity, adaptive correction of a high-average-power, solid-state, heat-capacity laser (open access)

Intracavity, adaptive correction of a high-average-power, solid-state, heat-capacity laser

The Solid-State, Heat-Capacity Laser (SSHCL) program at Lawrence Livermore National Laboratory is a multigeneration laser development effort scalable to the megawatt power levels. Wavefront quality is a driving metric of its performance. A deformable mirror with over 100 degrees of freedom situated within the cavity is used to correct both the static and dynamic aberrations sensed with a Shack-Hartmann wavefront sensor. The laser geometry is an unstable, confocal resonator with a clear aperture of 10 cm x 10 cm. It operates in a pulsed mode at a high repetition rate (up to 200 Hz) with a correction being applied before each pulse. Wavefront information is gathered in real-time from a low-power pick-off of the high-power beam. It is combined with historical trends of aberration growth to calculate a correction that is both feedback and feed-forward driven. The overall system design, measurement techniques and correction algorithms are discussed. Experimental results are presented.
Date: January 5, 2005
Creator: LaFortune, K N; Hurd, R L; Brase, J M & Yamamoto, R M
System: The UNT Digital Library
Three-dimensional Global Model Approaches to Understanding Stratospheric Impacts on Tropospheric Ozone (open access)

Three-dimensional Global Model Approaches to Understanding Stratospheric Impacts on Tropospheric Ozone

None
Date: January 5, 2004
Creator: Atherton, C; Bergmann, D; Cameron-Smith, P; Connell, P; Dignon, J; Rotman, D et al.
System: The UNT Digital Library
A novel 3D wavelet based filter for visualizing features in noisy biological data (open access)

A novel 3D wavelet based filter for visualizing features in noisy biological data

We have developed a 3D wavelet-based filter for visualizing structural features in volumetric data. The only variable parameter is a characteristic linear size of the feature of interest. The filtered output contains only those regions that are correlated with the characteristic size, thus denoising the image. We demonstrate the use of the filter by applying it to 3D data from a variety of electron microscopy samples including low contrast vitreous ice cryogenic preparations, as well as 3D optical microscopy specimens.
Date: January 5, 2005
Creator: Moss, W C; Haase, S; Lyle, J M; Agard, D A & Sedat, J W
System: The UNT Digital Library
Nanosecond frame cameras (open access)

Nanosecond frame cameras

The advent of CCD cameras and computerized data recording has spurred the development of several new cameras and techniques for recording nanosecond images. We have made a side by side comparison of three nanosecond frame cameras, examining them for both performance and operational characteristics. The cameras include; Micro-Channel Plate/CCD, Image Diode/CCD and Image Diode/Film; combinations of gating/data recording. The advantages and disadvantages of each device will be discussed.
Date: January 5, 2001
Creator: Frank, A M & Wilkins, P R
System: The UNT Digital Library
Hydra observations of aluminum abundances in the red giants ofthe globular clusters M80 and NGC 6752 (open access)

Hydra observations of aluminum abundances in the red giants ofthe globular clusters M80 and NGC 6752

Aluminum and other metal abundances were determined in 21 red giants in the globular clusters NGC 6752 and M80 as part of a larger study to determine whether the aluminum distribution on the red giant branch is related to the second parameter effect that causes clusters of similar metallicity to display different horizontal branch morphologies. The observations were obtained of the Al I lines near 6700 Angstroms with the CTIO Blanco 4-m telescope and Hydra multi-object spectrograph. The spectra have a resolving power of 18000 or 9400, with typical S/N ratios of 100-200. Mean [Fe/H] values obtained from the spectra are -1.58 for NGC 6751 and -1.73 for M80; this represents the spectroscopic iron abundance determination for M80. Both NGC 6752 and M80 display a spread in aluminum abundance with mean [Al/Fe] ratios of +0.51 and +0.37 respectively. No trend in the variation of the mean AI abundance with position on the giant branch is discernible in either cluster with our small sample.
Date: January 5, 2004
Creator: Suntzeff, N B; Cavallo, R M & Pilachowski, C A
System: The UNT Digital Library
The National Ignition Facility: Laser System, Beam Line Design and Construction (open access)

The National Ignition Facility: Laser System, Beam Line Design and Construction

The construction of the National Ignition Facility (NIF) building and laser beampaths at the Lawrence Livermore National Laboratory has been completed. This 8-year design/construction effort has successfully erected a 450,000 sq ft building and filled its interior with a complex of large-scale optical benches. These benches support all of the large-aperture optic elements of the NIF and the environmentally controlled enclosures that protect each of the 192 laser beamlines as they propagate from the injection laser system, through large aperture amplification stages, and into the target chamber. Even though this facility is very large, nearly 200 m long, 100 m wide, and 30 m tall, stringent mechanical performance requirements have been achieved throughout including temperature control <0.3 C, laser-beam pointing stability on target < 50 {micro}rms, and level 100 surface cleanliness on internal components. This presentation will provide an historical perspective explaining the basis of the design, technical details describing the techniques of construction and a chronological progression of the construction activities from ground breaking to beampath completion.
Date: January 5, 2004
Creator: Sawicki, R H
System: The UNT Digital Library
Image-driven mesh optimization (open access)

Image-driven mesh optimization

We describe a method of improving the appearance of a low vertex count mesh in a manner that is guided by rendered images of the original, detailed mesh. This approach is motivated by the fact that greedy simplification methods often yield meshes that are poorer than what can be represented with a given number of vertices. Our approach relies on edge swaps and vertex teleports to alter the mesh connectivity, and uses the downhill simplex method to simultaneously improve vertex positions and surface attributes. Note that this is not a simplification method--the vertex count remains the same throughout the optimization. At all stages of the optimization the changes are guided by a metric that measures the differences between rendered versions of the original model and the low vertex count mesh. This method creates meshes that are geometrically faithful to the original model. Moreover, the method takes into account more subtle aspects of a model such as surface shading or whether cracks are visible between two interpenetrating parts of the model.
Date: January 5, 2001
Creator: Lindstrom, P & Turk, G
System: The UNT Digital Library
Energy dependence measurements of remmeters and albedo neutron dosimeters at neutron energies of thermal and between 2 keV and 5. 67 MeV (open access)

Energy dependence measurements of remmeters and albedo neutron dosimeters at neutron energies of thermal and between 2 keV and 5. 67 MeV

The instruments tested included a 9-inch sphere Portable Neutron Rem Counter Model PNR-4 manufactured by Eberline Instrument Corporation, Santa Fe, N.M.; an Andersson-Braum type Remmeter; and Hankins-type albedo neutron dosimeters composed of cadmium-enclosed TLDs. The standard neutron source at the NBS reactor was used. The observed and calculated response curves are presented and discussed. (WHK)
Date: January 5, 1977
Creator: Hankins, D. E.
System: The UNT Digital Library
Discovery of a new 2.3 s isomer in the neutron-rich nucleus 174Tm (open access)

Discovery of a new 2.3 s isomer in the neutron-rich nucleus 174Tm

None
Date: January 5, 2005
Creator: Chakrawarthy, R. S.; Walker, P. M.; Smith, M. B.; Andreyev, A. N.; Ashley, S. F.; Ball, G. C. et al.
System: The UNT Digital Library
The National Ignition Facility Wavefront Requirements and Optical Architecture (open access)

The National Ignition Facility Wavefront Requirements and Optical Architecture

With the first four of its eventual 192 beams now executing shots, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is already the world's largest and most energetic laser. The optical system performance requirements that are in place for NIF are derived from the goals of the missions it is designed to serve. These missions include inertial confinement fusion (ICF) research and the study of matter at extreme energy densities and pressures. These mission requirements have led to a design strategy for achieving high quality focusable energy and power from the laser and to specifications on optics that are important for an ICF laser. The design of NIF utilizes a multipass architecture with a single large amplifier type that provides high gain, high extraction efficiency and high packing density. We have taken a systems engineering approach to the practical implementation of this design that specifies the wavefront parameters of individual optics in order to achieve the desired cumulative performance of the laser beamline. This presentation provides a detailed look at the causes and effects of performance degradation in large laser systems and how NIF has been designed to overcome these effects. We will also present results of …
Date: January 5, 2004
Creator: Spaeth, M. L.; Manes, K. R.; Widmayer, C. C.; Williams, W.; Whitman, P. A. & Henesian, M.
System: The UNT Digital Library
Pulse requirements for x-ray diffraction imaging of single biological molecules (open access)

Pulse requirements for x-ray diffraction imaging of single biological molecules

It has been suggested that x-ray free electron lasers will enable single-particle diffraction imaging of biological molecules. In this paper we present a model to estimate the required pulse parameters based on a trade-off between minimizing image degradation due to damage and maximizing the image signal-to-noise ratio. We discuss several means to alleviate the photon requirements, and compare the requirements with existing or planned x-ray sources such as short-pulse x-ray free-electron lasers.
Date: January 5, 2005
Creator: Hau-Riege, S; London, R; Huldt, G & Chapman, H
System: The UNT Digital Library
Magnetorheological Finishing for Imprinting Continuous Phase Plate Structure onto Optical Surfaces (open access)

Magnetorheological Finishing for Imprinting Continuous Phase Plate Structure onto Optical Surfaces

Magnetorheological finishing (MRF) techniques have been developed to manufacture continuous phase plates (CPP's) and custom phase corrective structures on polished fused silica surfaces. These phase structures are important for laser applications requiring precise manipulation and control of beam-shape, energy distribution, and wavefront profile. The MRF's unique deterministic-sub-aperture polishing characteristics make it possible to imprint complex topographical information onto optical surfaces at spatial scale-lengths approaching 1 mm. In this study, we present the results of experiments and model calculations that explore imprinting two-dimensional sinusoidal structures. Results show how the MRF removal function impacts and limits imprint fidelity and what must be done to arrive at a high quality surface. We also present several examples of this imprinting technology for fabrication of phase correction plates and CPPs for use at high fluences.
Date: January 5, 2004
Creator: Menapace, J A; Dixit, S N; Genin, F Y & Brocious, W F
System: The UNT Digital Library
Introduction to the National Ignition Facility (open access)

Introduction to the National Ignition Facility

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. NIF will be the world's largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion and matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear bum, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 10{sup 8} K and 10{sup 11} bar, conditions that exist naturally only in the interior of stars, planets and in nuclear weapons. NIF has completed the first phases of its laser commissioning program. The first four beams of NIF have generated 106 kilojoules of infrared light and over 16 kJ at the third harmonic (351 nm). NIF's target experimental systems are being commissioned and experiments have begun. This paper provides a detailed look the NIF laser systems, laser and optical performance and results from recent laser commissioning shots, and plans for commissioning diagnostics for experiments on NIF.
Date: January 5, 2004
Creator: Moses, E I
System: The UNT Digital Library
Length-Limited Variable-to-Variable Length Codes for High-Performance Entropy Coding (open access)

Length-Limited Variable-to-Variable Length Codes for High-Performance Entropy Coding

Arithmetic coding achieves a superior coding rate when encoding a binary source, but its lack of speed makes it an inferior choice when true high-performance encoding is needed. We present our work on a practical implementation of fast entropy coders for binary messages utilizing only bit shifts and table lookups. To limit code table size we limit our code lengths with a type of variable-to-variable (VV) length code created from source string merging. We refer to these codes as ''merged codes''. With merged codes it is possible to achieve a desired level of speed by adjusting the number of bits read from the source at each step. The most efficient merged codes yield a coder with a worst-case inefficiency of 0.4%, relative to the Shannon entropy. Using a hybrid Golomb-VV Bin Coder we are able to achieve a compression ratio that is competitive with other state-of-the-art coders, at a superior throughput.
Date: January 5, 2004
Creator: Duchaineau, Mark; Senecal, Joshua & Joy, Kenneth I.
System: The UNT Digital Library