Discovery of TeV Gamma-Ray Emission from the Cygnus Region (open access)

Discovery of TeV Gamma-Ray Emission from the Cygnus Region

The diffuse gamma radiation arising from the interaction of cosmic ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of the cosmic rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes Milagro the most sensitive instrument available for the study of large, low surface brightness sources such as the diffuse gamma radiation arising from interactions of cosmic radiation with interstellar matter. In this paper we present spatial and flux measurements of TeV gamma-ray emission from the Cygnus Region. The TeV image shows at least one new source MGRO J2019+37 as well as correlations with the matter density in the region as would be expected from cosmic-ray proton interactions. However, the TeV gamma-ray flux as measured at {approx}12 TeV from the Cygnus region (after excluding MGRO J2019+37) exceeds that predicted from a conventional model of cosmic ray production and propagation. This observation indicates the existence of either hard-spectrum cosmic-ray sources and/or other sources of TeV gamma rays in the region.
Date: November 28, 2006
Creator: Abdo, A. A.; Allen, B.; Berley, D.; Blaufuss, E.; Casanova, S.; Chen, C. et al.
System: The UNT Digital Library
Low Mach Number Modeling of Type Ia Supernovae. II. EnergyEvolution (open access)

Low Mach Number Modeling of Type Ia Supernovae. II. EnergyEvolution

The convective period leading up to a Type Ia supernova (SNIa) explosion is characterized by very low Mach number flows, requiringhydrodynamical methods well-suited to long-time integration. We continuethe development of the low Mach number equation set for stellar scaleflows by incorporating the effects of heat release due to externalsources. Low Mach number hydrodynamics equations with a time-dependentbackground state are derived, and a numerical method based on theapproximate projection formalism is presented. We demonstrate throughvalidation with a fully compressible hydrodynamics code that this lowMach number model accurately captures the expansion of the stellaratmosphere as well as the local dynamics due to external heat sources.This algorithm provides the basis for an efficient simulation tool forstudying the ignition of SNe Ia.
Date: March 28, 2006
Creator: Almgren, Ann S.; Bell, John B.; Rendleman, Charles A. & Zingale,Mike
System: The UNT Digital Library
A grating-less, fiber-based oscillator that generates 25 nJ pulses (open access)

A grating-less, fiber-based oscillator that generates 25 nJ pulses

We report a passively mode-locked fiber-based oscillator that has no internal dispersion-compensating gratings. This design, the first of its kind, produces 25 nJ pulses at 80 MHz with the pulses compressible to 150 fs. The pulses appear to be self-similar and initial data imply that their energy is further scalable.
Date: December 28, 2006
Creator: An, J; Kim, D; Dawson, J W; Messerly, M J & Barty, C J
System: The UNT Digital Library
Magnetocentrifugal Winds in 3D: Nonaxisymmetric Steady State (open access)

Magnetocentrifugal Winds in 3D: Nonaxisymmetric Steady State

Outflows can be loaded and accelerated to high speeds along rapidly rotating, open magnetic field lines by centrifugal forces. Whether such magnetocentrifugally driven winds are stable is a longstanding theoretical problem. As a step towards addressing this problem, we perform the first large-scale 3D MHD simulations that extend to a distance {approx} 10{sup 2} times beyond the launching region, starting from steady 2D (axisymmetric) solutions. In an attempt to drive the wind unstable, we increase the mass loading on one half of the launching surface by a factor of {radical}10, and reduce it by the same factor on the other half. The evolution of the perturbed wind is followed numerically. We find no evidence for any rapidly growing instability that could disrupt the wind during the launching and initial phase of propagation, even when the magnetic field of the magnetocentrifugal wind is toroidally dominated all the way to the launching surface. The strongly perturbed wind settles into a new steady state, with a highly asymmetric mass distribution. The distribution of magnetic field strength is, in contrast, much more symmetric. We discuss possible reasons for the apparent stability, including stabilization by an axial poloidal magnetic field, which is required to bend …
Date: November 28, 2006
Creator: Anderson, Jeffrey M.; Li, Zhi-Yun; /Virginia U., Astron. Dept.; Krasnopolsky, Ruben; /Toronto U., Astron. Dept.; Blandford, Roger D. et al.
System: The UNT Digital Library
Measurement of B decays to phi K gamma (open access)

Measurement of B decays to phi K gamma

We measure the branching fraction of the radiative B{sup -} decay {Beta}(B{sup -} {yields} {phi}K{sup -}{gamma}) = (3.46 {+-} 0.57{sub -0.37}{sup +0.39}) x 10{sup -6}, and set an upper limit on the radiative {bar B}{sup 0} decay {Beta}({bar B}{sup 0} {yields} {phi}{bar K}{sup 0}{gamma}) < 2.71 x 10{sup -6} at 90% confidence level. We also measure the direct CP asymmetry of the B{sup -} {yields} {phi}K{sup -}{gamma} mode {Alpha}{sub CP} = (-26.4 {+-} 14.3 {+-} 4.8)%. The uncertainties are statistical and systematic, respectively. These measurements are based on 207 fb{sup -1} of data collected at the {Upsilon}(4S) resonance with the BABAR detector.
Date: July 28, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Measurements of the Decays B0->D0barppbar, B0->D*0ppbar, B0->D-ppbar\pi+, and B0->D*-ppbar\pi+ (open access)

Measurements of the Decays B0->D0barppbar, B0->D*0ppbar, B0->D-ppbar\pi+, and B0->D*-ppbar\pi+

The authors present measurements of branching fractions of B{sup 0} decays to multi-body final states containing protons, based on 232 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. They measure the branching fractions {Beta}(B{sup 0} {yields} {bar D}{sup 0} p{bar p}) = (1.13 {+-} 0.06 {+-} 0.08) x 10{sup -4} {Beta}(B{sup 0} {yields} {bar D}*{sup 0} p{bar p}) = (1.01 {+-} 0.10 {+-} 0.09) x 10{sup -4}, {Beta}(B{sup 0} {yields} D{sup -} p{bar p}{pi}{sup +}) = (3.38 {+-} 0.14 {+-} 0.29) x 10{sup -4}, and {Beta}(B{sup 0} {yields} D*{sup -} p{bar p}{pi}{sup +}) = (4.81 {+-} 0.22 {+-} 0.44) x 10{sup -4} where the first error is statistical and the second systematic. They present a search for the charmed pentaquark state, {Theta}{sub c}(3100) observed by H1 and put limits on the branching fraction {Beta}(B{sup 0} {yields} {Theta}{sub c}{bar p}{pi}{sup +}) x {Beta}({Theta}{sub c} {yields} D*{sup -}p) < 14 x 10{sup -6} and {Beta}(B{sup 0} {yields} {Theta}{sub c}{bar p}{pi}{sup +}) x {Beta}({Theta}{sub c} {yields} D{sup -}p) < 9 x 10{sup -6}. Upon investigation of the decay structure of the above four B{sup 0} decay modes, they see an enhancement at low …
Date: July 28, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Measurment of B Decays to phi K gamma (open access)

Measurment of B Decays to phi K gamma

The authors search for the decays B{sup -} {yields} {phi}K{sup -}{gamma} and {bar B}{sup 0} {yields} {phi}{bar K}{sup 0}{gamma} in a data sample of 228 million B{bar B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector. They measure the branching fraction {Beta}(B{sup -} {yields} {phi}K{sup -}{gamma}) = (3.5 {+-} 0.6 {+-} 0.4) x 10{sup -6} and set an upper limit {Beta}({bar B}{sup 0} {yields} {phi}{bar K}{sup 0}{gamma}) < 2.7 x 10{sup -6} at the 90% confidence level. They also measure the direct CP asymmetry in B{sup -} {yields} {phi}K{sup -}{gamma}, {Alpha}{sub CP} = (-26 {+-} 14 {+-} 5)%. The uncertainties are statistical and systematic, respectively.
Date: November 28, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Search for the Baryon and Lepton Number Violating Decays tau to Lambda h (open access)

Search for the Baryon and Lepton Number Violating Decays tau to Lambda h

The authors have searched for the violation of baryon number B and lepton number L in the (B-L)-conserving modes {tau}{sup -} {yields} {bar {Lambda}}{sup 0}{pi}{sup -} and {tau}{sup -} {yields} {bar {Lambda}}{sup 0}K{sup -} as well as the (B-L)-violating modes {tau}{sup -} {yields} {Lambda}{sup 0}{pi}{sup -} and {tau}{sup -} {yields} {Lambda}{sup 0}K{sup -} using 237 fb{sup -1} of data collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring. They do not observe any signal and determine preliminary upper limits on the branching fractions {Beta}({tau}{sup -} {yields} {bar {Lambda}}{sup 0}{pi}{sup -}) < 5.9 x 10{sup -8}, {Beta}({tau}{sup -} {yields} {Lambda}{sup 0}{pi}{sup -}) < 5.8 x 10{sup -8}, {Beta}({tau}{sup -} {yields} {bar {Lambda}}{sup 0}K{sup -}) < 7.2 x 10{sup -8}, and {Beta}({tau}{sup -} {yields} {Lambda}{sup 0}K{sup -}) < 15 x 10{sup -8} at 90% confidence level.
Date: November 28, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Three-dimensional architecture of hair-cell linkages as revealedby electron-microscopic tomography (open access)

Three-dimensional architecture of hair-cell linkages as revealedby electron-microscopic tomography

The senses of hearing and balance rest upon mechanoelectrical transduction by the hair bundles of hair cells in the inner ear. Located at the apical cellular surface, each hair bundle comprises several tens of stereocilia and a single kinocilium that are interconnected by extracellular proteinaceous links. Using electron-microscopic tomography of bullfrog saccular sensory epithelia, we examined the three-dimensional structures of ankle or basal links, kinociliary links, and tip links. We observed clear differences in the dimensions and appearances of the three links. We found two distinct populations of tip links suggestive of the involvement of two proteins or splice variants. We noted auxiliary links connecting the upper portions of tip links to the taller stereocilia. Tip links and auxiliary links show a tendency to adopt a globular conformation when disconnected from the membrane surface.
Date: July 28, 2006
Creator: Auer, Manfred; Koster, Bram; Ziese, Ulrike; Bajaj, Chandrajit; Volkmann, Niels; Wang, Da Neng et al.
System: The UNT Digital Library
Estimating Missing Features to Improve Multimedia Information Retrieval (open access)

Estimating Missing Features to Improve Multimedia Information Retrieval

Retrieval in a multimedia database usually involves combining information from different modalities of data, such as text and images. However, all modalities of the data may not be available to form the query. The retrieval results from such a partial query are often less than satisfactory. In this paper, we present an approach to complete a partial query by estimating the missing features in the query. Our experiments with a database of images and their associated captions show that, with an initial text-only query, our completion method has similar performance to a full query with both image and text features. In addition, when we use relevance feedback, our approach outperforms the results obtained using a full query.
Date: September 28, 2006
Creator: Bagherjeiran, A.; Love, N. S. & Kamath, C.
System: The UNT Digital Library
Equation of state for high explosives detonation products with explicit polar and ionic species (open access)

Equation of state for high explosives detonation products with explicit polar and ionic species

We introduce a new thermodynamic theory for detonation products that includes polar and ionic species. The new formalism extends the domain of validity of the previously developed EXP6 equation of state library and opens the possibility of new applications. We illustrate the scope of the new approach on PETN detonation properties and water ionization models.
Date: June 28, 2006
Creator: Bastea, S; Glaesemann, K R & Fried, L E
System: The UNT Digital Library
The DART Imaging And CaT Survey of the Fornax Dwarf Spheroidal Galaxy (open access)

The DART Imaging And CaT Survey of the Fornax Dwarf Spheroidal Galaxy

As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES* GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. Fornax dSph has had a complicated evolution and contains significant numbers of young, intermediate age and old stars. We investigate the relation between these different components by studying their photometric, kinematic and abundance distributions. We re-derived the structural parameters of the Fornax dwarf spheroidal using our wide field imaging covering the galaxy out to its tidal radius, and analyzed the spatial distribution of the Fornax stars of different ages as selected from Colour-Magnitude Diagram analysis. We have obtained accurate velocities and metallicities from spectra in the Ca II triplet wavelength region for 562 Red Giant Branch stars which have velocities consistent with membership in Fornax dwarf spheroidal. We have found evidence for the presence of at least three distinct stellar components: a young population (few 100 Myr old) concentrated in the center of the galaxy, visible as a Main Sequence in the Colour-Magnitude Diagram; an intermediate age population (2-8 Gyr old); and an ancient population (> …
Date: August 28, 2006
Creator: Battaglia, Giuseppina; Tolstoy, E.; Helmi, A.; Irwin, M. J.; Letarte, B.; Jablonka, P. et al.
System: The UNT Digital Library
Characterization of Recompressed Spall in Copper Gas Gun Targets (open access)

Characterization of Recompressed Spall in Copper Gas Gun Targets

Complementary experiments and simulations are conducted to characterize the microstructure and mechanisms involved in recompression of spalled ductile metals. Soft capture experiments performed on copper targets in a gas gun include a dense secondary plate spaced behind the customary flyer to recompress the voids in the wake of the spall induced by the flyer. Control experiments are run without the secondary plate to obtain spall damage without recompression. The simulations feature explicit representation of void nucleating particles in a narrow strip of material spanning the flyer package and target. Analysis of the spall closure in the simulations reveals the void collapse mechanisms and the origin of features observed experimentally. The experiments and simulations show little trace of the prior voids, and a thin ribbon of highly strained material is the only readily observable remnant of the spall surface.
Date: August 28, 2006
Creator: Becker, R.; Cazamias, J. & LeBlanc, M.
System: The UNT Digital Library
Refrigerator Efficiency in Ghana: Tailoring an appliance markettransformation program design for Africa (open access)

Refrigerator Efficiency in Ghana: Tailoring an appliance markettransformation program design for Africa

A simple replication of developed country applianceefficiency labels and standards is unlikely to be feasible in Ghana andmany other countries in Africa. Yet by creatively modifying the developedcountry appliance efficiency market transformation model, it should bepossible to achieve dramatic energy use reductions. As was true indeveloped countries in the previous two decades, refrigeration efficiencyimprovements provide the greatest energy savings potential in theresidential electricity sector in Ghana. Although Ghana, like manyAfrican countries may impose standards on imports since Ghana does nothave manufacturing facilities for appliances in country. This approachmay hurt some consumers who patronize a very diverse market of usedappliances imported from Europe. We discuss how meeting the challenges ofthe Ghanaian market will require modification of the usual energyefficiency labeling and standards paradigm. But once a refrigeratormarket transformation is accomplished in Ghana, we estimate an averageenergy savings potential of 550 kWh/refrigerator/year, and a monetarysavings of more than $35/refrigerator/year. We discuss how this modifiedrefrigerator efficiency market transformation may occur in the Ghanaiancontext. If successful, this market transformation is likely to be anexample for many other African countries.
Date: February 28, 2006
Creator: Ben Hagan, Essel; Van Buskirk, Robert; Ofosu-Ahenkorah, Alfred & McNeil, Michael A.
System: The UNT Digital Library
SciDAC Visualization and Analytics Center for EnablingTechnology (open access)

SciDAC Visualization and Analytics Center for EnablingTechnology

The SciDAC2 Visualization and Analytics Center for EnablingTechnologies (VACET) began operation on 10/1/2006. This document, dated11/27/2006, is the first version of the VACET project management plan. Itwas requested by and delivered to ASCR/DOE. It outlines the Center'saccomplishments in the first six weeks of operation along with broadobjectives for the upcoming future (12-24 months).
Date: November 28, 2006
Creator: Bethel, E. Wes; Johnson, Chris; Joy, Ken; Ahern, Sean; Pascucci,Valerio; Childs, Hank et al.
System: The UNT Digital Library
Ruthenium / aerogel nanocomposits via Atomic Layer Deposition (open access)

Ruthenium / aerogel nanocomposits via Atomic Layer Deposition

We present a general approach to prepare metal/aerogel nanocomposites via template directed atomic layer deposition (ALD). In particular, we used a Ru ALD process consisting of alternating exposures to bis(cyclopentadienyl)ruthenium (RuCp{sub 2}) and air at 350 C to deposit metallic Ru nanoparticles on the internal surfaces of carbon and silica aerogels. The process does not affect the morphology of the aerogel template and offers excellent control over metal loading by simply adjusting the number of ALD cycles. We also discuss the limitations of our ALD approach, and suggest ways to overcome these.
Date: August 28, 2006
Creator: Biener, J.; Baumann, T. F.; Wang, Y.; Nelson, E. J.; Kucheyev, S. O.; Hamza, A. V. et al.
System: The UNT Digital Library
Comment on "Methodology and results of calculating Central California surface temperature trends: evidence of human-induced climate change?" by Christy et al. (2006) (open access)

Comment on "Methodology and results of calculating Central California surface temperature trends: evidence of human-induced climate change?" by Christy et al. (2006)

Understanding the causes of observed regional temperature trends is essential to projecting the human influences on climate, and the societal impacts of these influences. In their recent study, Christy et al. (2006, hereinafter CRNG06) hypothesized that the presence of irrigated soils is responsible for rapid warming of summer nights occurring in California's Central Valley over the last century (1910-2003), an assumption that rules out any significant effect due to increased greenhouse gases, urbanization, or other factors in this region. We question this interpretation, which is based on an apparent contrast in summer nighttime temperature trends between the San Joaquin Valley ({approx} +0.3 {+-} 0.1 C/decade) and the adjacent western slopes of the Sierra Nevada (-0.25 {+-} 0.15 C/decade), as well as the amplitude, sign and uncertainty of the Sierra nighttime temperature trend itself. We, however, do not dispute the finding of other Sierra and Valley trends. Regarding the veracity of the apparent Sierra nighttime temperature trend, CRNG06 generated the Valley and Sierra time-series using a meticulous procedure that eliminates discontinuities and isolates homogeneous segments in temperature records from 41 weather stations. This procedure yields an apparent cooling of about -0.25 {+-} 0.15 C/decade in the Sierra region. However, because removal …
Date: March 28, 2006
Creator: Bonfils, C; Duffy, P & Lobell, D
System: The UNT Digital Library
New Perspectives for QCD from AdS/CFT (open access)

New Perspectives for QCD from AdS/CFT

The AdS/CFT correspondence between conformal field theory and string states in an extended space-time has provided new insights into not only hadron spectra, but also their light-front wavefunctions. We show that there is an exact correspondence between the fifth-dimensional coordinate of anti-de Sitter space z and a specific impact variable {zeta} which measures the separation of the constituents within the hadron in ordinary space-time. This connection allows one to predict the form of the light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and scattering amplitudes. A new relativistic Schroedinger light-cone equation is found which reproduces the results obtained using the fifth-dimensional theory.
Date: July 28, 2006
Creator: Brodsky, Stanley J.
System: The UNT Digital Library
Laboratory measurements of the x-ray line emission from neon-like Fe XVII (open access)

Laboratory measurements of the x-ray line emission from neon-like Fe XVII

The authors have conducted a systematic study of the dominant x-ray line emission from Fe XVII. These studies include relative line intensities in the optically thin limit, intensities in the presence of radiation from satellite lines from lower charge states of iron, and the absolute excitation cross sections of some of the strongest lines. These measurements were conducted at the Lawrence Livermore National Laboratory electron beam ion trap facility using crystal spectrometers and a NASA-Goddard Space Flight Center microcalorimeter array.
Date: April 28, 2006
Creator: Brown, G V; Beiersdorfer, P; Chen, H; Scofield, J; Boyce, K R; Kelley, R L et al.
System: The UNT Digital Library
Multiscale Thermohydrologic Model Supporting the Licence Application for the Yucca Mountain Repository (open access)

Multiscale Thermohydrologic Model Supporting the Licence Application for the Yucca Mountain Repository

The MultiScale ThermoHydrologic Model (MSTHM) predicts thermal-hydrologic (TH) conditions within emplacement tunnels (drifts) and in the adjoining host rock at Yucca Mountain, Nevada, which is the proposed site for a radioactive waste repository in the US. Because these predictions are used in the performance assessment of the Yucca Mountain repository, they must address the influence of variability and uncertainty of the engineered- and natural-system parameters that significantly influence those predictions. Parameter-sensitivity studies show that the MSTHM predictions adequately propagate the influence of parametric variability and uncertainty. Model-validation studies show that the influence of conceptual-model uncertainty on the MSTHM predictions is insignificant compared to that of parametric uncertainty, which is propagated through the MSTHM.
Date: March 28, 2006
Creator: Buscheck, T.A>; Sun, Y. & Hao, Y.
System: The UNT Digital Library
Heterogeneous precipitation of Cu in Fe-Cu alloys (open access)

Heterogeneous precipitation of Cu in Fe-Cu alloys

None
Date: August 28, 2006
Creator: Caro, M & Caro, A
System: The UNT Digital Library
Beam interaction measurements with a Retarding Field Analyzer (open access)

Beam interaction measurements with a Retarding Field Analyzer

A Retarding Field Analyzer (RFA) was designed and inserted in a drift region of a magnetic transport section of the High Current Experiment (HCX). It measures ions or electrons resulting from the beam interaction with the background gas and walls. The ions are expelled during the beam by the space-charge beam potential, and the electrons are expelled mainly at the end of the beam, when the beam potential decays. The measured electrons have a Maxwellian energy distribution and the measured ions have an energy distribution that gives the information of the beam profile, details will be presented and discussed.
Date: March 28, 2006
Creator: Covo, M K; Molvik, A W; Friedman, A; Barnard, J J; Seidl, P; Logan, B G et al.
System: The UNT Digital Library
Sulfur K-Edge XAS and DFT Calculations on [Fe4S4]2+Clusters: Effects of H-bonding and Structural Distortion on Covalency and SpinTopology (open access)

Sulfur K-Edge XAS and DFT Calculations on [Fe4S4]2+Clusters: Effects of H-bonding and Structural Distortion on Covalency and SpinTopology

Sulfur K-edge X-ray absorption spectroscopy of a hydrogen-bonded elongated [Fe{sub 4}S{sub 4}]{sup 2+} cube is reported. The data show that this synthetic cube is less covalent than a normal compressed cube with no hydrogen bonding. DFT calculations reveal that the observed difference in electronic structure has significant contributions from both the cluster distortion and from hydrogen bonding. The elongated and compressed Fe{sub 4}S{sub 4} structures are found to have different spin topologies (i.e., orientation of the delocalized Fe{sub 2}S{sub 2} subclusters which are antiferromagnetically coupled to each other). It is suggested that the H-bonding interaction with the counterion does not contribute to the cluster elongation. A magneto-structural correlation is developed for the Fe{sub 4}S{sub 4} cube that is used to identify the redoxactive Fe{sub 2}S{sub 2} subclusters in active sites of HiPIP and ferredoxin proteins involving these clusters.
Date: September 28, 2006
Creator: Dey, A.; Roche, C. L.; Walters, M. A.; Hodgson, K. O.; Hedman, B.; Solomon, E. I. et al.
System: The UNT Digital Library
Sulfur K-Edge XAS and DFT Calculations on NitrileHydratase: Geometric and Electronic Structure of the Non-heme Iron Active Site (open access)

Sulfur K-Edge XAS and DFT Calculations on NitrileHydratase: Geometric and Electronic Structure of the Non-heme Iron Active Site

The geometric and electronic structure of the active site of the non-heme iron enzyme nitrile hydratase (NHase) is studied using sulfur K-edge XAS and DFT calculations. Using thiolate (RS{sup -})-, sulfenate (RSO{sup -})-, and sulfinate (RSO{sub 2}{sup -})-ligated model complexes to provide benchmark spectral parameters, the results show that the S K-edge XAS is sensitive to the oxidation state of S-containing ligands and that the spectrum of the RSO- species changes upon protonation as the S-O bond is elongated (by {approx}0.1 {angstrom}). These signature features are used to identify the three cysteine residues coordinated to the low-spin Fe{sup III} in the active site of NHase as CysS{sup -}, CysSOH, and CysSO{sub 2}{sup -} both in the NO-bound inactive form and in the photolyzed active form. These results are correlated to geometry-optimized DFT calculations. The pre-edge region of the X-ray absorption spectrum is sensitive to the Z{sub eff} of the Fe and reveals that the Fe in [FeNO]{sup 6} NHase species has a Z{sub eff} very similar to that of its photolyzed Fe{sup III} counterpart. DFT calculations reveal that this results from the strong {pi} back-bonding into the {pi}* antibonding orbital of NO, which shifts significant charge from the formally t{sub …
Date: September 28, 2006
Creator: Dey, Abhishek; Chow, Marina; /Stanford U., Chem. Dept.; Taniguchi, Kayoko; /Wako, RIKEN; Lugo-Mas, Priscilla et al.
System: The UNT Digital Library