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A Chemical Approach to 3-D Lithographic Patterning of Si and GeNanocrystals (open access)

A Chemical Approach to 3-D Lithographic Patterning of Si and GeNanocrystals

Ion implantation into silica followed by thermal annealingis an established growth method for Si and Ge nanocrystals. Wedemonstrate that growth of Group IV semiconductor nanocrystals can besuppressed by co-implantation of oxygen prior to annealing. For Sinanocrystals, at low Si/O dose ratios, oxygen co-implantation leads to areduction of the average nanocrystal size and a blue-shift of thephotoluminescence emission energy. For both Si and Ge nanocrystals, atlarger Si/O or Ge/O dose ratios, the implanted specie is oxidized andnanocrystals do not form. This chemical deactivation was utilized toachieve patterned growth of Si and Ge nanocrystals. Si was implanted intoa thin SiO2 film on a Si substrate followed by oxygen implantationthrough an electron beam lithographically defined stencil mask. Thermalannealing of the co-implanted structure yields two-dimensionallypatterned growth of Si nanocrystals under the masked regions. We applieda previously developed process to obtain exposed nanocrystals byselective HF etching of the silica matrix to these patterned structures.Atomic force microscopy (AFM) of etched structures revealed that exposednanocrystals are not laterally displaced from their original positionsduring the etching process. Therefore, this process provides a means ofachieving patterned structures of exposed nanocrystals. The possibilitiesfor scaling this chemical-based lithography process to smaller featuresand for extending it to 3-D patterning is discussed.
Date: December 12, 2005
Creator: Sharp, I. D.; Xu, Q.; Yi, D. O.; Liao, C. Y.; Ager, J. W., III; Beeman, J. W. et al.
System: The UNT Digital Library
Chemical Identification of Dubnium as a Decay Product of Element 115 (open access)

Chemical Identification of Dubnium as a Decay Product of Element 115

None
Date: December 12, 2005
Creator: Shaughnessy, D A; Kenneally, J M; Moody, K J; Landrum, J H; Wilk, P A; Stoyer, M A et al.
System: The UNT Digital Library
A Detailed Chemical Kinetic Model for TNT (open access)

A Detailed Chemical Kinetic Model for TNT

None
Date: December 12, 2005
Creator: Pitz, W J & Westbrook, C K
System: The UNT Digital Library
The Development of a Detailed Chemical Kinetic Mechanism for Diisobutylene and Comparison to Shock Tube Ignition Times (open access)

The Development of a Detailed Chemical Kinetic Mechanism for Diisobutylene and Comparison to Shock Tube Ignition Times

None
Date: December 12, 2005
Creator: Metcalfe, W K; Pitz, W J; Curran, H J; Simmie, J M & Westbrook, C K
System: The UNT Digital Library
Enabling HCCI modeling: The RIOT/CMCS Web Service for Automatic Reaction Mechanism Reduction (open access)

Enabling HCCI modeling: The RIOT/CMCS Web Service for Automatic Reaction Mechanism Reduction

New approaches are being developed to facilitate multidisciplinary collaborative research of Homogeneous Charge Compression Ignition (HCCI) combustion processes. In this paper, collaborative sharing of the Range Identification and Optimization Toolkit (RIOT) and related data and models is discussed. RIOT is a developmental approach to reduce the computational complexity of detailed chemical kinetic mechanisms, enabling their use in modeling kinetically-controlled combustion applications such as HCCI. These approaches are being developed and piloted as a part of the Collaboratory for Multiscale Chemical Sciences (CMCS) project. The capabilities of the RIOT code are shared through a portlet in the CMCS portal that allows easy specification and processing of RIOT inputs, remote execution of RIOT, tracking of data pedigree and translation of RIOT outputs (such as the reduced model) to a table view and to the commonly-used CHEMKIN mechanism format. The reduced model is thus immediately ready to be used for more efficient simulation of the chemically reacting system of interest. This effort is motivated by the need to improve computational efficiency in modeling HCCI systems. Preliminary use of the web service to obtain reduced models for this application has yielded computational speedup factors of up to 20 as presented in this paper.
Date: December 12, 2005
Creator: Oluwole, O; Pitz, W J; Schuchardt, K; Rahn, L A; Green, Jr., W H; Leahy, D et al.
System: The UNT Digital Library
The growth of epitaxial uranium oxide observed by micro-Raman spectroscopy (open access)

The growth of epitaxial uranium oxide observed by micro-Raman spectroscopy

Raman spectroscopy can be performed with micrometer resolution and can thus be used to determine the dependence of oxide thickness on the substrate's grain structure or local impurity inclusions. The Raman signal amplitude emitted from an epitaxial uranium oxide layer as a function of oxide thickness has been modeled for light of 632.8 nm wavelength incident on the oxide and reflected from the uranium substrate using the optical properties determined by spectrophotometry. The model shows that the Raman signal increases with oxide thickness and saturates at about 150 nm thickness. The model was compared with the measured Raman signal amplitude of an epitaxial uranium oxide layer growing in air with a known time dependence of oxide growth.
Date: December 12, 2005
Creator: Caculitan, N & Siekhaus, W J
System: The UNT Digital Library
Modeling and Experimental Investigation of Methylcyclohexane Ignition in a Rapid Compression Machine (open access)

Modeling and Experimental Investigation of Methylcyclohexane Ignition in a Rapid Compression Machine

None
Date: December 12, 2005
Creator: Pitz, W J; Naik, C V; Mhaold?in, T N; Westbrook, C K; Curran, H J; Orme, J P et al.
System: The UNT Digital Library
The optical properties of a polished uranium surface and its epitaxial oxide, and the rate of oxide growth determined by spectrophotometry (open access)

The optical properties of a polished uranium surface and its epitaxial oxide, and the rate of oxide growth determined by spectrophotometry

None
Date: December 12, 2005
Creator: Siekhaus, W J & Nelson, A J
System: The UNT Digital Library
POTENTIAL FOR HIGGS PHYSICS AT THE LHC AND SUPER-LHC. (open access)

POTENTIAL FOR HIGGS PHYSICS AT THE LHC AND SUPER-LHC.

The expected sensitivity of the LHC experiments to the discovery of the Higgs boson and the measurement of its properties is presented in the context of both the standard model and the its minimal supersymmetric extension. Prospects for a luminosity-upgraded ''Super-LHC'' are also presented. If it exists, the LHC should discover standard model Higgs boson, measure its mass accurately, and make various measurements of its couplings, spin and CP properties. In the context of the CP-conserving MSSM, the LHC should be able to discover one or more Higgs bosons over the entire m{sub A}-tan {beta} plane, with two or more observable in many cases. The large number of channels available insure a robust discovery and offer many opportunities for additional measurements. Observation of H {yields} {mu}{mu}, measurement of the tri-linear Higgs self-coupling, and various search channels are statistics-limited, and only possible with a luminosity upgrade. A luminosity upgrade would substantially improve some of the coupling measurements and generally extend the sensitivity in the MSSM Higgs plane. Efforts are ongoing to understand the upgrade of the LHC to the Super-LHC.
Date: December 12, 2005
Creator: CRANMER, K.S.
System: The UNT Digital Library
Production of [15O] Water at Low-Energy Proton Cyclotrons (open access)

Production of [15O] Water at Low-Energy Proton Cyclotrons

We report a simple system for producing [15O]H2O from nitrogen-15 in a nitrogen/hydrogen gas target with recycling of the target nitrogen, allowing production on low-energy proton-only accelerators with minimal consumption of isotopically enriched nitrogen-15. The radiolabeled water is separated from the target gas and radiolytically produced ammonia by temporary freezing in a small trap at -40 C.
Date: December 12, 2005
Creator: Powell, James & O'Neil, James P.
System: The UNT Digital Library
Relativistic Bound States (open access)

Relativistic Bound States

The Hamiltonian for Dirac's second-order equation depends nonlinearly on the potential V and the energy E. For this reason the magnetic contribution to the Hamiltonian for s-waves, which has a short range, is attractive for a repulsive Coulomb potential (V > 0) and repulsive for an attractive Coulomb potential (V < 0). Previous studies are confined to the latter case, where strong net attraction near a high-Z nucleus accelerates electrons to velocities close to the speed of light. The Hamiltonian is linear in the product EV/mc{sup 2}. Usually solutions are found in the regime E = mc{sup 2} + {var_epsilon}, where except for high Z, |{var_epsilon}| << mc{sup 2}. Here they show that for V > 0 the attractive magnetic term and the repulsive linear term combine to support a bound state at E = 0.5 mc{sup 2} corresponding to a binding energy E{sub b} = -{var_epsilon} = 0.5 mc{sup 2}.
Date: December 12, 2005
Creator: Ritchie, A. B.
System: The UNT Digital Library
B Decays to Open And Hidden Charm at BaBar (open access)

B Decays to Open And Hidden Charm at BaBar

A wealth of new measurements of hadronic B decays to open charm and charmonium have been performed on the data sample collected by the BaBar experiment at the PEP-II e{sup +}e{sup -} B-factory. We report the first measurement of the rates for inclusive charm production separately for charged and neutral B mesons. Combining measurements of the decay rate of B{sup 0} {yields} D*{sub s}{sup +}D*{sup -} obtained with a partial reconstruction technique and the complete reconstruction of B{sup 0} {yields} D*{sub s}{sup +}D*{sup -} with D{sub s}{sup +} {yields} {phi}{pi}{sup +}, we obtain the most precise measurement of {Beta}(D{sub s}{sup +} {yields} {phi}{pi}{sup +}). We present an update of the measurements of the branching fractions of exclusive B decays to J/{psi}, {psi}(2S), {chi}{sub c1}, {chi}{sub c2} and a kaon or a K*. In addition, we show preliminary results on exclusive decay rates to final states with baryons, or newly-discovered particles, such as D*{sub sJ}(2317), D{sub sJ}(2460){sup +}, and the X(3872).
Date: October 12, 2005
Creator: Ricciardi, S. & /Royal Holloway, U. of London
System: The UNT Digital Library
DIII-D Diagnostic Systems (open access)

DIII-D Diagnostic Systems

None
Date: October 12, 2005
Creator: Boivin, R. L.; Luxon, J. L.; Austin, M. E.; Brooks, N. H.; Burrell, K. H.; Doyle, E. J. et al.
System: The UNT Digital Library
The ICF Status and Plans in the United States (open access)

The ICF Status and Plans in the United States

The United States continues to maintain its leadership in ICF as it moves toward the goal of ignition. The flagship of the program is the National Ignition Facility (NIF) presently under construction at LLNL. Experiments had begun on the first four beams of the National Ignition Facility just at the time of the last IFSA Conference. Several new successful campaigns have been conducted since then in planar hydrodynamics and hohlraums as well as activating the VISAR diagnostic for equation of state experiments. Highlights of these results will be reviewed. Presently, the four beam experimental capability has been suspended while the first eight beams are being installed as the first step in building out the project. Meanwhile, much progress has been made in developing ignition designs for using NIF. An array of designs having several ablator materials have been shown computationally to ignite with energies ranging from the design energy to as low as 1 MJ of laser energy. Alternative direct drive designs in the NIF indirect drive configuration have been developed by LLE. This wide array of design choices has increased the chance of achieving ignition sooner on the facility. Plans are now being developed to begin an ignition experimental …
Date: October 12, 2005
Creator: Moses, E.; Miller, G. & Kauffman, R.
System: The UNT Digital Library
Open and hidden charm production at RHIC and LHC (open access)

Open and hidden charm production at RHIC and LHC

We discuss aspects of open and hidden charm production in hadron-nucleus collisions at RHIC and LHC energies. We first discuss the extraction of the total charm cross section in lower energy collisions and how it compares to next-to-leading order quantum chromodynamics calculations. We then describe calculations of the transverse momentum distributions and their agreement with the shape of the measured STAR transverse momentum distributions. We next explain how shadowing and moderate nuclear absorption can explain the PHENIX J/{psi} dAu/pp ratios.
Date: October 12, 2005
Creator: Vogt, R.
System: The UNT Digital Library
The Pathogenomic Sequence Analysis of B. cereus and B. Thuringiensis isolates closely related to Bacillus anthracis (open access)

The Pathogenomic Sequence Analysis of B. cereus and B. Thuringiensis isolates closely related to Bacillus anthracis

The sequencing and analysis of two close relatives of Bacillus anthracis are reported. AFLP analysis of over 300 isolates of B. cereus, B. thuringiensis and B. anthracis identified two isolates as being very closely related to B. anthracis. One, a B. cereus, BcE33L, was isolated from a zebra carcass in Nambia; the second, a B. thuringiensis, 97-27, was isolated from a necrotic human wound. The B. cereus appears to be the closest anthracis relative sequenced to date. A core genome of over 3,900 genes was compiled for the Bacillus cereus group, including B anthracis. Comparative analysis of these two genomes with other members of the B. cereus group provides insight into the evolutionary relationships among these organisms. Evidence is presented that differential regulation modulates virulence, rather than simple acquisition of virulence factors. These genome sequences provide insight into the molecular mechanisms contributing to the host range and virulence of this group of organisms.
Date: October 12, 2005
Creator: Han, C. S.; Xie, G.; Challacombe, J. F.; Altherr, M. R.; Bhotika, S. S.; Bruce, D. et al.
System: The UNT Digital Library
Pentaquark Searches And Properties of D/SJ Resonances at BaBar (open access)

Pentaquark Searches And Properties of D/SJ Resonances at BaBar

Preliminary results from inclusive searches for strange pentaquark production in e{sup +}e{sup -} interactions at {radical}s = 10.58 GeV using 123 fb{sup -1} of data collected with the BABAR detector are presented. In addition new mass estimates for the D*{sub sJ}(2317){sup +} and D{sub sJ}(2460){sup +} mesons are given. The mesons are studied in e{sup +}e{sup -} {yields} c{bar c} data using 125 fb{sup -1} for the decay to the D{sub s}{sup +} s meson along with one or more {pi}{sup 0}, {pi}{sup +}, or {gamma} particles. A search is also performed for neutral and doubly-charged partners.
Date: October 12, 2005
Creator: Halyo, V.
System: The UNT Digital Library
RADIONUCLIDE DISPERSION RATES BY AEOLIAN, FLUVIAL, AND POROUS MEDIA TRANSPORT (open access)

RADIONUCLIDE DISPERSION RATES BY AEOLIAN, FLUVIAL, AND POROUS MEDIA TRANSPORT

None
Date: October 12, 2005
Creator: Walton, J.; P.Goodell; Beshears, C.; French, D. & Kelts, A.
System: The UNT Digital Library
Study of Inclusive And Exclusive B ---> X/U L Nu Decays And the Measurement of |V(Ub)| With the BaBar Detector (open access)

Study of Inclusive And Exclusive B ---> X/U L Nu Decays And the Measurement of |V(Ub)| With the BaBar Detector

We report studies of B {yields} X{sub u}{ell}{nu} decays, based on a sample of 88 million B{bar B} events recorded with the BABAR detector. From both tagged and untagged B{bar B} events we have isolated inclusive charmless decays in kinematic regions for which the dominant background from B {yields} X{sub c}{ell}{nu} is reduced by making requirements on different variables: the electron energy E{sub l}, the momentum transfer q{sup 2}, and the hadronic mass m{sub X}. Using theoretical calculations we extrapolate to the total decay rate to determine the CKM matrix element |V{sub ub}|. In addition, we have measured the branching fraction for exclusive semileptonic decays, such as B {yields} {pi}({rho}, {omega}, {eta}, a{sub 0}){ell}{nu}. A high signal purity is achieved by selecting events in which a decay of the second B meson is either fully or partially reconstructed.
Date: October 12, 2005
Creator: del Re, D. & /UC, San Diego
System: The UNT Digital Library
A 90-GHz Photoinjector (open access)

A 90-GHz Photoinjector

Photocathode rf guns depend on mode locked laser systems to produce an electron beam at a given phase of the rf. In general, the laser pulse is less than {sigma}{sub z} = 10{sup o} of rf phase in length and the required stability is on the order of {Delta}{phi} = 1{sup o}. At 90 GHz (W-band), these requirements correspond to {sigma}{sub z} = 333 fsec and {Delta}{phi} = 33 fsec. Laser system with pulse lengths in the fsec regime are commercially available, the timing stability is a major concern. We propose a multi-cell W-band photoinjector that does not require a mode locked laser system. Thereby eliminating the stability requirements at W-band. The laser pulse is allowed to be many rf periods long. In principle, the photoinjector can now be considered as a thermionic rf gun. Instead of using an alpha magnet to compress the electron bunch, which would have a detrimental effect on the transverse phase space quality due to longitudinal phase space mixing, we propose to use long pulse laser system and a pair of undulators to produce a low emittance, high current, ultra-short electron bunch for beam dynamics experiments in the 90 GHz regime.
Date: September 12, 2005
Creator: Palmer, D. T.; Hogan, M. J.; Ferrario, M. & Serafini, L.
System: The UNT Digital Library
As-Built Modeling of Ojbects for Performance Assessment (open access)

As-Built Modeling of Ojbects for Performance Assessment

The goal of ''as-built'' computational modeling is to incorporate the most representative geometry and material information for an (fabricated or legacy) object into simulations. While most engineering finite element simulations are based on an object's idealized ''as-designed'' configuration with information obtained from technical drawings or computer-aided design models, ''as-built'' modeling uses nondestructive characterization and metrology techniques to provide the feature information. By incorporating more representative geometry and material features as initial conditions, the uncertainty in the simulation results can be reduced, providing a more realistic understanding of the event and object being modeled. In this paper, key steps and technology areas in the as-built modeling framework are: (1) inspection using non-destructive characterization (NDC) and metrology techniques; (2) data reduction (signal and image processing including artifact removal, data sensor fusion, and geometric feature extraction); and (3) engineering and physics analysis using finite element codes. We illustrate the process with a cylindrical phantom and include a discussion of the key concepts and areas that need improvement. Our results show that reasonable as-built initial conditions based on a volume overlap criteria can be achieved and that notable differences between simulations of the as-built and as-designed configurations can be observed for a given load …
Date: September 12, 2005
Creator: Kokko, E J; Martz, H E; Chinn, D J; Childs, H. R.; Jackson, J A; Chambers, D H et al.
System: The UNT Digital Library
DETERMINATION OF INVENTORIES AND POWER DISTRIBUTIONS FOR THE NSBR. (open access)

DETERMINATION OF INVENTORIES AND POWER DISTRIBUTIONS FOR THE NSBR.

This memo presents the details of the methodology for developing fuel inventories for the NBSR along with power distributions predicted with this set of inventories. Several improvements have been made to the MCNP model of the NBSR since a set of calculations was performed in 2002 in support of the NBSR relicensing and SAR update. One of the most significant changes in the model was to divide the fuel elements into upper and lower halves so the effects of uneven burn between the two halves (due to the shim arms) can be determined. The present set of power distributions are provided for comparison with the previous safety analyses.
Date: September 12, 2005
Creator: Hanson, A. L. & DIAMOND, D. J.
System: The UNT Digital Library
Dust-Particle Transport in Tokamak Edge Plasmas (open access)

Dust-Particle Transport in Tokamak Edge Plasmas

Dust particulates in the size range of 10nm-100{micro}m are found in all fusion devices. Such dust can be generated during tokamak operation due to strong plasma/material-surface interactions. Some recent experiments and theoretical estimates indicate that dust particles can provide an important source of impurities in the tokamak plasma. Moreover, dust can be a serious threat to the safety of next-step fusion devices. In this paper, recent experimental observations on dust in fusion devices are reviewed. A physical model for dust transport simulation, and a newly developed code DUSTT, are discussed. The DUSTT code incorporates both dust dynamics due to comprehensive dust-plasma interactions as well as the effects of dust heating, charging, and evaporation. The code tracks test dust particles in realistic plasma backgrounds as provided by edge-plasma transport codes. Results are presented for dust transport in current and next-step tokamaks. The effect of dust on divertor plasma profiles and core plasma contamination is examined.
Date: September 12, 2005
Creator: Pigarov, A Y; Krasheninnikov, S I; Soboleva, T K & Rognlien, T D
System: The UNT Digital Library
THE FLUORBOARD A STATISTICALLY BASED DASHBOARD METHOD FOR IMPROVING SAFETY (open access)

THE FLUORBOARD A STATISTICALLY BASED DASHBOARD METHOD FOR IMPROVING SAFETY

None
Date: September 12, 2005
Creator: PREVETTE, S.S.
System: The UNT Digital Library