In-situ spectro-microscopy on organic films: Mn-Phthalocyanine on Ag(100) (open access)

In-situ spectro-microscopy on organic films: Mn-Phthalocyanine on Ag(100)

Metal phthalocyanines are attracting significant attention, owing to their potential for applications in chemical sensors, solar cells and organic magnets. As the electronic properties of molecular films are determined by their crystallinity and molecular packing, the optimization of film quality is important for improving the performance of organic devices. Here, we present the results of in situ low-energy electron microscopy / photoemission electron microscopy (LEEM/PEEM) studies of incorporation-limited growth [1] of manganese-phthalocyanine (MnPc) on Ag(100) surfaces. MnPc thin films were grown on both, bulk Ag(100) surface and thin Ag(100)/Fe(100) films, where substrate spin-polarized electronic states can be modified through tuning the thickness of the Ag film [2]. We also discuss the electronic structure and magnetic ordering in MnPc thin films, investigated by angle- and spin-resolved photoemission spectroscopy.
Date: August 18, 2013
Creator: A., Al-Mahboob; Vescovo, E. & Sadowski, J.T.
System: The UNT Digital Library
A Search for Dark Matter in Events with One Jet and Missing Transverse Energy in pp-bar Collisions at sqrt(s) = 1.96 TeV (open access)

A Search for Dark Matter in Events with One Jet and Missing Transverse Energy in pp-bar Collisions at sqrt(s) = 1.96 TeV

None
Date: January 18, 2013
Creator: Aaltonen, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A. et al.
System: The UNT Digital Library
Fermi-LAT Study of Gamma-Ray Emission in the Direction of Supernova Remnant W49B (open access)

Fermi-LAT Study of Gamma-Ray Emission in the Direction of Supernova Remnant W49B

None
Date: June 18, 2013
Creator: Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G. et al.
System: The UNT Digital Library
Response of NSTX Liquid Lithium divertor to High Heat Loads (open access)

Response of NSTX Liquid Lithium divertor to High Heat Loads

Samples of the NSTX Liquid Lithium Divertor (LLD) with and without an evaporative Li coating were directly exposed to a neutral beam ex-situ at a power of ~1.5 MW/m2 for 1-3 seconds. Measurements of front face and bulk sample temperature were obtained. Predictions of temperature evolution were derived from a 1D heat flux model. No macroscopic damage occurred when the "bare" sample was exposed to the beam but microscopic changes to the surface were observed. The Li-coated sample developed a lithium hydroxide (LiOH) coating, which did not change even when the front face temperature exceeded the pure Li melting point. These results are consistent with the lack of damage to the LLD surface and imply that heating alone may not expose pure liquid Li if the melting point of surface impurities is not exceeded. This suggests that flow and heat are needed for future PFCs requiring a liquid Li surface. __________________________________________________
Date: July 18, 2012
Creator: Abrams, Tyler; Kallman, J; Kaitaa, R; Foley, E L; Grayd, T K; Kugel, H et al.
System: The UNT Digital Library
Searches for Cosmic-Ray Electron Anisotropies with the Fermi Large Area Telescope (open access)

Searches for Cosmic-Ray Electron Anisotropies with the Fermi Large Area Telescope

None
Date: June 18, 2013
Creator: Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz et al.
System: The UNT Digital Library
Tune Evaluation From Phased BPM Turn-By-Turn Data (open access)

Tune Evaluation From Phased BPM Turn-By-Turn Data

In fast ramping synchrotrons like the Fermilab Booster the conventional methods of betatron tune evaluation from the turn-by-turn data may not work due to rapid changes of the tunes (sometimes in a course of a few dozens of turns) and a high level of noise. We propose a technique based on phasing of signals from a large number of BPMs which significantly increases the signal to noise ratio. Implementation of the method in the Fermilab Booster control system is described and some measurement results are presented.
Date: May 18, 2010
Creator: Alexahin, Y.; Gianfelice-Wendt, E. & Marsh, W.
System: The UNT Digital Library
The evolution of ion charge states in cathodic vacuum arc plasmas: a review (open access)

The evolution of ion charge states in cathodic vacuum arc plasmas: a review

Cathodic vacuum arc plasmas are known to contain multiply charged ions. 20 years after “Pressure Ionization: its role in metal vapour vacuum arc plasmas and ion sources” appeared in vol. 1 of Plasma Sources Science and Technology, it is a great opportunity to re-visit the issue of pressure ionization, a non-ideal plasma effect, and put it in perspective to the many other factors that influence observable charge state distributions, such as the role of the cathode material, the path in the density-temperature phase diagram, the “noise” in vacuum arc plasma as described by a fractal model approach, the effects of external magnetic fields and charge exchange collisions with neutrals. A much more complex image of the vacuum arc plasma emerges putting decades of experimentation and modeling in perspective.
Date: December 18, 2011
Creator: Anders, Andre
System: The UNT Digital Library
The SEMATECH Berkeley MET: extending EUV learning to 16-nm half pitch (open access)

The SEMATECH Berkeley MET: extending EUV learning to 16-nm half pitch

Several high-performing resists identified in the past two years have been exposed at the 0.3-numerical-aperture (NA) SEMATECH Berkeley Microfield Exposure Tool (BMET) with an engineered dipole illumination optimized for 18-nm half pitch. Five chemically amplified platforms were found to support 20-nm dense patterning at a film thickness of approximately 45 nm. At 19-nm half pitch, however, scattered bridging kept all of these resists from cleanly resolving larger areas of dense features. At 18-nm half pitch, none of the resists were are able to cleanly resolve a single line within a bulk pattern. With this same illumination a directly imageable metal oxide hardmask showed excellent performance from 22-nm half pitch to 17-nm half pitch, and good performance at 16-nm half pitch, closely following the predicted aerial image contrast. This indicates that observed limitations of the chemically amplified resists are indeed coming from the resist and not from a shortcoming of the exposure tool. The imageable hardmask was also exposed using a Pseudo Phase-Shift-Mask technique and achieved clean printing of 15-nm half pitch lines and modulation all the way down to the theoretical 12.5-nm resolution limit of the 0.3-NA SEMATECH BMET.
Date: March 18, 2011
Creator: Anderson, Christopher N.; Baclea-an, Lorie Mae; Denham, Paul E.; George, Simi; Goldberg, Kenneth A.; Jones, Michael et al.
System: The UNT Digital Library
Benefits to the U.S. from Physicists Working at Accelerators Overseas (open access)

Benefits to the U.S. from Physicists Working at Accelerators Overseas

None
Date: December 18, 2013
Creator: Anderson, Jacob; Brock, Raymond; Gershtein, Yuri; Hadley, Nicholas; Harrison, Michael; Narain, Meenakshi et al.
System: The UNT Digital Library
A Framework for Incorporating General Domain Knowledge into Latent Dirichlet Allocation using First-Order Logic (open access)

A Framework for Incorporating General Domain Knowledge into Latent Dirichlet Allocation using First-Order Logic

Topic models have been used successfully for a variety of problems, often in the form of application-specific extensions of the basic Latent Dirichlet Allocation (LDA) model. Because deriving these new models in order to encode domain knowledge can be difficult and time-consuming, we propose the Fold-all model, which allows the user to specify general domain knowledge in First-Order Logic (FOL). However, combining topic modeling with FOL can result in inference problems beyond the capabilities of existing techniques. We have therefore developed a scalable inference technique using stochastic gradient descent which may also be useful to the Markov Logic Network (MLN) research community. Experiments demonstrate the expressive power of Fold-all, as well as the scalability of our proposed inference method.
Date: January 18, 2011
Creator: Andrzejewski, D.; Zhu, X.; Craven, M. & Recht, B.
System: The UNT Digital Library
The Impact of Camera Optical Alignments on Weak Lensing Measures for the Dark Energy Survey (open access)

The Impact of Camera Optical Alignments on Weak Lensing Measures for the Dark Energy Survey

None
Date: March 18, 2013
Creator: Antonik, Michelle L.; Bacon, David J.; Bridle, Sarah; Doel, Peter; Brooks, David; Worswick, Sue et al.
System: The UNT Digital Library
The BaBar Detector: Upgrades, Operation and Performance (open access)

The BaBar Detector: Upgrades, Operation and Performance

None
Date: December 18, 2013
Creator: Aubert, Bernard
System: The UNT Digital Library
Management Of Experiments And Data At The National Ignition Facility (open access)

Management Of Experiments And Data At The National Ignition Facility

Experiments, or 'shots', conducted at the National Ignition Facility (NIF) are discrete events that occur over a very short time frame (tens of nanoseconds) separated by many hours. Each shot is part of a larger campaign of shots to advance scientific understanding in high-energy-density physics. In one campaign, scientists use energy from the 192-beam, 1.8-Megajoule pulsed laser in the NIF system to symmetrically implode a hydrogen-filled target, thereby creating conditions similar to the interior of stars in a demonstration of controlled fusion. Each NIF shot generates gigabytes of data from over 30 diagnostics that measure optical, x-ray, and nuclear phenomena from the imploding target. We have developed systems to manage all aspects of the shot cycle. Other papers will discuss the control of the lasers and targets, while this paper focuses on the setup and management of campaigns and diagnostics. Because of the low duty cycle of shots, and the thousands of adjustments for each shot (target type, composition, shape; laser beams used, their power profiles, pointing; diagnostic systems used, their configuration, calibration, settings) it is imperative that we accurately define all equipment prior to the shot. Following the shot, and capture of the data by the automatic control system, …
Date: March 18, 2011
Creator: Azevedo, S; Casey, A; Beeler, R; Bettenhausen, R.; Bond, E.; Chandrasekaran, H. et al.
System: The UNT Digital Library
Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction (open access)

Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction

None
Date: January 18, 2013
Creator: Aznauryan, I. G.; Bashir, A.; Braun, V.; Brodsky, S. J.; Burkert, V. D.; Chang, L. et al.
System: The UNT Digital Library
RELAP5 Application to Accident Analysis of the NIST Research Reactor (open access)

RELAP5 Application to Accident Analysis of the NIST Research Reactor

Detailed safety analyses have been performed for the 20 MW D{sub 2}O moderated research reactor (NBSR) at the National Institute of Standards and Technology (NIST). The time-dependent analysis of the primary system is determined with a RELAP5 transient analysis model that includes the reactor vessel, the pump, heat exchanger, fuel element geometry, and flow channels for both the six inner and twenty-four outer fuel elements. A post-processing of the simulation results has been conducted to evaluate minimum critical heat flux ratio (CHFR) using the Sudo-Kaminaga correlation. Evaluations are performed for the following accidents: (1) the control rod withdrawal startup accident and (2) the maximum reactivity insertion accident. In both cases the RELAP5 results indicate that there is adequate margin to CHF and no damage to the fuel will occur because of sufficient coolant flow through the fuel channels and the negative scram reactivity insertion.
Date: March 18, 2012
Creator: Baek, J.; Cuadra Gascon, A.; Cheng, L. Y. & Diamond, D.
System: The UNT Digital Library
A Note on the Convergence of the Godunov Method for Impact Problems (open access)

A Note on the Convergence of the Godunov Method for Impact Problems

None
Date: April 18, 2012
Creator: Banks, J W
System: The UNT Digital Library
2010 CORRELATED ELECTRON SYSTEMS GORDON RESEARCH CONFERENCE, JUNE 13-18, 2010 For (open access)

2010 CORRELATED ELECTRON SYSTEMS GORDON RESEARCH CONFERENCE, JUNE 13-18, 2010 For

The 2010 Gordon Conference on Correlated Electron Systems will present cutting-edge research on emergent properties arising from strong electronic correlations. The Conference will feature a wide range of topics, such as the role of topology in condensed matter systems, quantum Hall interferometry and non-Abelian statistics, quantum criticality, metal-insulator transition, quantum effects in conductivity, Dirac quasiparticles, and superconductivity in cuprates and pnictides. In addition, we are reserving two sessions for new developments in this field that may arise in the coming year. The Conference will bring together a collection of investigators who are at the forefront of their field, and will provide opportunities for junior scientists and graduate students to present their work in poster format and exchange ideas with leaders in the field. We intend to have talks by established leaders in the field and also by young researchers who have made seminal contributions to various aspects of correlated electron physics, The collegial atmosphere of this Conference, with programmed discussion sessions as well as opportunities for informal gatherings in the afternoons and evenings, provides an avenue for scientists from different disciplines to brainstorm and promotes cross-disciplinary collaborations in the various research areas represented.
Date: June 18, 2010
Creator: Basov, Dmitri
System: The UNT Digital Library
Feature-Based Statistical Analysis of Combustion Simulation Data (open access)

Feature-Based Statistical Analysis of Combustion Simulation Data

We present a new framework for feature-based statistical analysis of large-scale scientific data and demonstrate its effectiveness by analyzing features from Direct Numerical Simulations (DNS) of turbulent combustion. Turbulent flows are ubiquitous and account for transport and mixing processes in combustion, astrophysics, fusion, and climate modeling among other disciplines. They are also characterized by coherent structure or organized motion, i.e. nonlocal entities whose geometrical features can directly impact molecular mixing and reactive processes. While traditional multi-point statistics provide correlative information, they lack nonlocal structural information, and hence, fail to provide mechanistic causality information between organized fluid motion and mixing and reactive processes. Hence, it is of great interest to capture and track flow features and their statistics together with their correlation with relevant scalar quantities, e.g. temperature or species concentrations. In our approach we encode the set of all possible flow features by pre-computing merge trees augmented with attributes, such as statistical moments of various scalar fields, e.g. temperature, as well as length-scales computed via spectral analysis. The computation is performed in an efficient streaming manner in a pre-processing step and results in a collection of meta-data that is orders of magnitude smaller than the original simulation data. This meta-data …
Date: November 18, 2011
Creator: Bennett, J; Krishnamoorthy, V; Liu, S; Grout, R; Hawkes, E; Chen, J et al.
System: The UNT Digital Library
Emergent Photons and Gravitons: The Problem of Vacuum Structure (open access)

Emergent Photons and Gravitons: The Problem of Vacuum Structure

None
Date: June 18, 2013
Creator: Bjorken, J. D.
System: The UNT Digital Library
NEW MATERIALS DEVELOPED TO MEET REGULATORY AND TECHNICAL REQUIREMENTS ASSOCIATED WITH IN-SITU DECOMMISSIONING OF NUCLEAR REACTORS AND ASSOCIATED FACILITIES (open access)

NEW MATERIALS DEVELOPED TO MEET REGULATORY AND TECHNICAL REQUIREMENTS ASSOCIATED WITH IN-SITU DECOMMISSIONING OF NUCLEAR REACTORS AND ASSOCIATED FACILITIES

For the 2010 ANS Embedded Topical Meeting on Decommissioning, Decontamination and Reutilization and Technology, Savannah River National Laboratory's Mike Serrato reported initial information on the newly developed specialty grout materials necessary to satisfy all requirements associated with in-situ decommissioning of P-Reactor and R-Reactor at the U.S. Department of Energy's Savannah River Site. Since that report, both projects have been successfully completed and extensive test data on both fresh properties and cured properties has been gathered and analyzed for a total of almost 191,150 m{sup 3} (250,000 yd{sup 3}) of new materials placed. The focus of this paper is to describe the (1) special grout mix for filling the P-Reactor vessel (RV) and (2) the new flowable structural fill materials used to fill the below grade portions of the facilities. With a wealth of data now in hand, this paper also captures the test results and reports on the performance of these new materials. Both reactors were constructed and entered service in the early 1950s, producing weapons grade materials for the nation's defense nuclear program. R-Reactor was shut down in 1964 and the P-Reactor in 1991. In-situ decommissioning (ISD) was selected for both facilities and performed as Comprehensive Environmental Response, Compensations …
Date: January 18, 2012
Creator: Blankenship, J.; Langton, C.; Musall, J. & Griffin, W.
System: The UNT Digital Library
Demonstrating Structural Adequacy of Nuclear Power Plant Containment Structures for Beyond Design-Basis Pressure Loadings (open access)

Demonstrating Structural Adequacy of Nuclear Power Plant Containment Structures for Beyond Design-Basis Pressure Loadings

ABSTRACT Demonstrating the structural integrity of U.S. nuclear power plant (NPP) containment structures, for beyond design-basis internal pressure loadings, is necessary to satisfy Nuclear Regulatory Commission (NRC) requirements and performance goals. This paper discusses methods for demonstrating the structural adequacy of the containment for beyond design-basis pressure loadings. Three distinct evaluations are addressed: (1) estimating the ultimate pressure capacity of the containment structure (10 CFR 50 and US NRC Standard Review Plan, Section 3.8) ; (2) demonstrating the structural adequacy of the containment subjected to pressure loadings associated with combustible gas generation (10 CFR 52 and 10 CFR 50); and (3) demonstrating the containment structural integrity for severe accidents (10 CFR 52 as well as SECY 90-016, SECY 93-087, and related NRC staff requirements memoranda (SRMs)). The paper describes the technical basis for specific aspects of the methods presented. It also presents examples of past issues identified in licensing activities related to these evaluations.
Date: July 18, 2010
Creator: Braverman, J. I. & Morante, R.
System: The UNT Digital Library
SYNTHESIS AND CHARACTERIZATION OF PROTON CONDUCTORS (open access)

SYNTHESIS AND CHARACTERIZATION OF PROTON CONDUCTORS

The morphological and electrical properties of yttrium (Y) and indium (In) doped barium cerate perovskites of the form BaIn{sub 0.3-x}Y{sub x}Ce{sub 0.7}O{sub 3-{delta}} (with x=0-0.3) prepared by a modified Pechini method were investigated as potential high temperature proton conductors with improved chemical stability. The sinterability increased with the increase of In-doping, and the perovskite phase was found in the BaIn{sub 0.3-x}Y{sub x}Ce{sub 0.7}O{sub 3-{delta}} solid solutions over the range 0 {le} x {le} 0.3. The conductivities decreased (from x to x, insert quantitative values) while the tolerance to wet CO{sub 2} improved for BaIn{sub 0.3-x}Y{sub x}Ce{sub 0.7}O{sub 3-{delta}} samples with an increase of In-doping.
Date: February 18, 2010
Creator: Brinkman, K.
System: The UNT Digital Library
Isospin Splittings of Doubly Heavy Baryons (open access)

Isospin Splittings of Doubly Heavy Baryons

The SELEX Collaboration has reported a very large isospin splitting of doubly charmed baryons. We show that this effect would imply that the doubly charmed baryons are very compact. One intriguing possibility is that such baryons have a linear geometry Q-q-Q where the light quark q oscillates between the two heavy quarks Q, analogous to a linear molecule such as carbon dioxide. However, using conventional arguments, the size of a heavy-light hadron is expected to be around 0.5 fm, much larger than the size needed to explain the observed large isospin splitting. Assuming the distance between two heavy quarks is much smaller than that between the light quark and a heavy one, the doubly heavy baryons are related to the heavy mesons via heavy quark-diquark symmetry. Based on this symmetry, we predict the isospin splittings for doubly heavy baryons including {Xi}{sub cc}, {Xi}{sub bb} and {Xi}{sub bc}. The prediction for the {Xi}{sub cc} is much smaller than the SELEX value. On the other hand, the {Xi}{sub bb} baryons are predicted to have an isospin splitting as large as (6.3 {+-} 1.7) MeV. An experimental study of doubly bottomed baryons is therefore very important to better understand the structure of baryons …
Date: August 18, 2011
Creator: Brodsky, Stanley J.; Guo, Feng-Kun; Hanhart, Christoph & Meissner, Ulf-G.
System: The UNT Digital Library