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in creator/contributor: "USDOE Director, Office of Science. Office of Basic Energy Sciences. Chemical Sciences, Geosciences, and Biosciences Division"  
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Carbon microstructures for electrochemical studies

Description: Thin layers of photoresist were spin coated onto silicon wafers, and then carbonized to form smooth carbon films by heating in nitrogen for 1 hour at temperatures between 600 to 1100 C. Well-defined carbon microstructures on Si wafers that are being considered for electrodes in a microbattery concept were obtained by additional processing steps involving patterning and lithography of the photoresist prior to carbonization. The status of the fabrication of carbon microelectrodes obtained by pyro… more
Date: June 22, 2001
Creator: Kostecki, Robert; Song, Xiang Yun & Kinoshita, Kim
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Effect of catalyst structure on oxidative dehydrogenation of ethane and propane on alumina-supported vanadia

Description: The catalytic properties of Al2O3-supported vanadia with a wide range of VOx surface density (1.4-34.2 V/nm2) and structure were examined for the oxidative dehydrogenation of ethane and propane. UV-visible and Raman spectra showed that vanadia is dispersed predominantly as isolated monovanadate species below {approx}2.3 V/nm2. As surface densities increase, two-dimensional polyvanadates appear (2.3-7.0 V/nm2) along with increasing amounts of V2O5 crystallites at surface densities above 7.0 V/nm… more
Date: September 11, 2001
Creator: Argyle, Morris D.; Chen, Kaidong; Bell, Alexis T. & Iglesia, Enrique
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Studies of N{sub 2}0 adsorption and decomposition on Fe-ZSM-5

Description: The interactions of N2O with H-ZSM-5 and Fe-ZSM-5 have been investigated using infrared spectroscopy and temperature-programmed reaction. Fe-ZSM-5 samples with Fe/Al ratios of 0.17 and 0.33 were prepared by solid-state exchange. It was determined that most of the iron in the samples of Fe-ZSM-5 is in the form of isolated cations, which have exchanged with Bronsted acid H+ in H-ZSM-5. The infrared spectrum of N2O adsorbed on H-ZSM-5 at 298 K exhibits bands at 2226 and 1308 cm-1 associated with v… more
Date: March 8, 2002
Creator: Wood, Benjamin R.; Reimer, Jeffrey A. & Bell, Alexis T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Structure of the Mn complex in photosystem II: Insights from x-ray spectroscopy

Description: We have used Mn K-edge absorption and Kb emission spectroscopies to determine the oxidation states of the Mn complex in the various S-states. We have started exploring the new technique of resonant inelastic X-ray scattering spectroscopy (RIXS); this technique can be characterized as a Raman process that uses K-edge energies (1s to 4p, {approx}6550 eV) to obtain L-edge-like spectra (2p to 3d, {approx}650 eV). The relevance of these data to the oxidation states and structure of the Mn complex is… more
Date: April 2, 2002
Creator: Yachandra, Vittal K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Colloid facilitated transport in fractured rocks: parameter estimation and comparison with experimental data

Description: Colloid-facilitated migration of plutonium in fractured rock has been implicated in both field and laboratory studies. Other reactive radionuclides may also experience enhanced mobility due to groundwater colloids. Model prediction of this process is necessary for assessment of contaminant boundaries in systems for which radionuclides are already in the groundwater and for performance assessment of potential repositories for radioactive waste. Therefore, a reactive transport model is developed … more
Date: January 10, 2003
Creator: Viswanthan, H. S.; Wolfsberg, A. V.; Reimus, P. W.; Ware, D. & Lu, G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Improved self-absorption correction for extended x-ray absorption fine-structure measurements

Description: Extended x-ray absorption fine-structure (EXAFS) data collected in the fluorescence mode are susceptible to an apparent amplitude reduction due to the self-absorption of the fluorescing photon by the sample before it reaches a detector. Previous treatments have made the simplifying assumption that the effect of the EXAFS on the correction term is negligible, and that the samples are in the thick limit. We present a nearly exact treatment that can be applied for any sample thickness or concentra… more
Date: June 4, 2003
Creator: Booth, C.H. & Bridges, F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Nanosecond and femtosecond laser ablation of brass: Particulate and ICPMS measurements

Description: Femtosecond and nanosecond lasers were compared for ablating brass alloys. All operating parameters from both lasers were equal except for the pulse duration. The ablated aerosol vapor was collected on silicon substrates for particle size measurements or sent into an inductively coupled plasma mass spectrometer. The diameters and size distribution of particulates were measured from scanning electron microscope (SEM) images of the collected ablated aerosol. SEM measurements showed that particles… more
Date: November 1, 2003
Creator: Liu, C.; Mao, X.L.; Mao, S.; Zeng, X.; Greif, R. & Russo, R.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Self-Consistent Approach for Calculating the Effective Hydraulic Conductivity of a Bimodal, Heterogeneous Medium

Description: In this paper, we consider an approach for estimating the effective hydraulic conductivity of a 3D medium with a binary distribution of local hydraulic conductivities. The medium heterogeneity is represented by a combination of matrix medium conductivity with spatially distributed sets of inclusions. Estimation of effective conductivity is based on a self-consistent approach introduced by Shvidler (1985). The tensor of effective hydraulic conductivity is calculated numerically by using a simple… more
Date: January 2, 2004
Creator: Pozdniakov, Sergey & Tsang, Chin-Fu
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Conditions necessary for capillary hysteresis in porous media: Tests of grain-size and surface tension influences

Description: Hysteresis in the relation between water saturation and matric potential is generally regarded as a basic aspect of unsaturated porous media. However, the nature of an upper length scale limit for saturation hysteresis has not been previously addressed. Since hysteresis depends on whether or not capillary rise occurs at the grain scale, this criterion was used to predict required combinations of grain size, surface tension, fluid-fluid density differences, and acceleration in monodisperse syste… more
Date: March 12, 2004
Creator: Tokunaga, Tetsu K.; Olson, Keith R. & Wan, Jiamin
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion

Description: Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and t… more
Date: March 23, 2004
Creator: Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph & Russo, Richard E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Hexavalent uranium diffusion into soils from concentrated acidic and alkaline solutions

Description: Uranium contamination of soils and sediments often originates from acidic or alkaline waste sources, with diffusion being a major transport mechanism. Measurements of U(VI) diffusion from initially pH 2 and pH 11 solutions into a slightly alkaline Altamont soil and a neutral Oak Ridge soil were obtained through monitoring uptake from boundary reservoirs and from U concentration profiles within soil columns. The soils provided pH buffering, resulting in diffusion at nearly constant pH. Micro x-r… more
Date: March 29, 2004
Creator: Tokunaga, Tetsu K.; Wan, Jiamin; Pena, Jasquelin; Sutton, Stephen R. & Newville, Matthew
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Identifying the sources of subsurface contamination at the Hanford site in Washington using high-precision uranium isotopic measurements

Description: In the mid-1990s, a groundwater plume of uranium (U) was detected in monitoring wells in the B-BX-BY Waste Management Area (WMA) at the Hanford Site in Washington. This area has been used since the late 1940s to store high-level radioactive waste and other products of U fuel-rod processing. Using multiple collector ICP source magnetic sector mass spectrometry (MC ICPMS) high precision uranium isotopic analyses were conducted of samples of vadose zone contamination and of groundwater. The ratios… more
Date: March 30, 2004
Creator: Christensen, John N.; Dresel, P. Evan; Conrad, Mark E.; Maher, Kate & DePaolo, Donald J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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X-ray absorption studies of the local structure and f-level occupancy in CeIr(1-x)Rh(x)In(5)

Description: The CeIr{sub 1-x}Rh{sub x}In{sub 5} series exhibits a range of interesting phenomena, including heavy-fermion superconductivity, non-Fermi liquid behavior, and concomitant antiferromagnetism (AF) and superconductivity (SC). In the low-Rh concentration range (0.1 {ge} x {ge} 0.5), specific heat measurements show a broad anomaly, suggestive of gross phase separation. We have performed x-ray absorption experiments at the Ce L{sub III}, Ir L{sub III}, and Rh K-edges as a function of Rh concentratio… more
Date: April 15, 2004
Creator: Daniel, M.; Han, S. W.; Booth, C. H.; Cornelius, A. L.; Pagliuso, P. G.; Sarrao, J. L. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Complex potential surface for the {sup 2}B{sub 1} metastable state of the water anion

Description: The potential energy surface corresponding the complex resonance energy of the 2B1 Feshbach resonance state of the water anion is constructed in its full dimensionality. Complex Kohn variational scattering calculations are used to compute the resonance width, while large-scale Configuration Interaction calculations are used to compute the resonance energy. Near the equilibrium geometry, an accompanying ground state potential surface is constructed from Configuration Interaction calculations tha… more
Date: April 23, 2004
Creator: Haxton, Daniel J.; Zhang, Zhiyong; McCurdy, C. William & Rescigno, Thomas N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Solving the three-body Coulomb breakup problem using exterior complex scaling

Description: Electron-impact ionization of the hydrogen atom is the prototypical three-body Coulomb breakup problem in quantum mechanics. The combination of subtle correlation effects and the difficult boundary conditions required to describe two electrons in the continuum have made this one of the outstanding challenges of atomic physics. A complete solution of this problem in the form of a ''reduction to computation'' of all aspects of the physics is given by the application of exterior complex scaling, a… more
Date: May 17, 2004
Creator: McCurdy, C. W.; Baertschy, M. & Rescigno, T. N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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