Melting of bcc Transition Metals and Icosahedral Clustering (open access)

Melting of bcc Transition Metals and Icosahedral Clustering

In contrast to polyvalent metals, transition metals have low melting slopes(dT/dP) that are due to partially filled d-bands that allow for a lowering of liquid phase energy through s-d electron transfer and the formation of local structures. In the case of bcc transition metals we show the apparent discrepancy of DAC melting measurements with shock melting of Mo can be understood by reexamining the shock data for V and Ta and introducing the presence of an icosahedral short range order (ISRO) melt phase.
Date: May 26, 2006
Creator: Ross, M; Boehler, R & Japel, S
System: The UNT Digital Library
Towards an Accurate Performance Modeling of Parallel SparseFactorization (open access)

Towards an Accurate Performance Modeling of Parallel SparseFactorization

We present a performance model to analyze a parallel sparseLU factorization algorithm on modern cached-based, high-end parallelarchitectures. Our model characterizes the algorithmic behavior bytakingaccount the underlying processor speed, memory system performance, aswell as the interconnect speed. The model is validated using theSuperLU_DIST linear system solver, the sparse matrices from realapplications, and an IBM POWER3 parallel machine. Our modelingmethodology can be easily adapted to study performance of other types ofsparse factorizations, such as Cholesky or QR.
Date: May 26, 2006
Creator: Grigori, Laura & Li, Xiaoye S.
System: The UNT Digital Library
EUV mask reflectivity measurements with micron-scale spatial resolution (open access)

EUV mask reflectivity measurements with micron-scale spatial resolution

The effort to produce defect-free mask blanks for EUV lithography relies on increasing the detection sensitivity of advanced mask inspection tools, operating at several wavelengths. We describe the unique measurement capabilities of a prototype actinic (EUV wavelength) microscope that is capable of detecting small defects and reflectivity changes that occur on the scale of microns to nanometers. Types of defects: (a) Buried Substrate Defects: particles & pits (causes amplitude and/or phase variations); (b) Surface Contamination (reduces reflectivity and (possibly) contrast); (c) Damage from Inspection and Use (reduces the reflectivity of the multilayer coating). This paper presents an overview of several topics where scanning actinic inspection makes a unique contribution to EUVL research. We describe the role of actinic scanning inspection in four cases: defect repair studies; observations of laser damage; after scanning electron microscopy; and native and programmed defects.
Date: May 26, 2008
Creator: Goldberg, Kenneth A.; Rekawa, S. B.; Kemp, C. D.; Barty, A.; Anderson, E. H.; Kearney, Patrick et al.
System: The UNT Digital Library
Visualization of Excitonic Structure in the Fenna-Matthews-OlsonPhotosynthetic Complex by Polarization-Dependent Two-DimensionalElectronic Spectroscopy (open access)

Visualization of Excitonic Structure in the Fenna-Matthews-OlsonPhotosynthetic Complex by Polarization-Dependent Two-DimensionalElectronic Spectroscopy

Photosynthetic light-harvesting proceeds by the collection and highly efficient transfer of energy through a network of pigment-protein complexes. Inter-chromophore electronic couplings and interactions between pigments and the surrounding protein determine energy levels of excitonic states and dictate the mechanism of energy flow. The excitonic structure (orientation of excitonic transition dipoles) of pigment-protein complexes is generally deduced indirectly from x-ray crystallography in combination with predictions of transition energies and couplings in the chromophore site basis. Here, we demonstrate that coarse-grained excitonic structural information in the form of projection angles between transition dipole moments can be obtained from polarization-dependent two-dimensional electronic spectroscopy of an isotropic sample, particularly when the nonrephasing or free polarization decay signal rather than the photon echo signal is considered. The method provides an experimental link between atomic and electronic structure and accesses dynamical information with femtosecond time resolution. In an investigation of the Fenna-Matthews-Olson complex from green sulfur bacteria, energy transfer connecting two particular exciton states in the protein is isolated as being the primary contributor to a cross peak in the nonrephasing 2D spectrum at 400 fs under a specific sequence of polarized excitation pulses. The results suggest the possibility of designing experiments using combinations of tailored …
Date: May 26, 2008
Creator: Department of Chemistry, The University of Chicago; Department of Biology, Department of Chemistry, Washington University; Fleming, Graham; Read, Elizabeth L.; Schlau-Cohen, Gabriela S.; Engel, Gregory S. et al.
System: The UNT Digital Library
Proteomic Analysis of Calcium- and Phosphorylation-dependentCalmodulin Complexes in Mammalian Cells (open access)

Proteomic Analysis of Calcium- and Phosphorylation-dependentCalmodulin Complexes in Mammalian Cells

Protein conformational changes due to cofactor binding (e.g. metal ions, heme) and/or posttranslational modifications (e.g. phosphorylation) modulate dynamic protein complexes. Calmodulin (CaM) plays an essential role in regulating calcium (Ca{sup 2+}) signaling and homeostasis. No systematic approach on the identification of phosphorylation-dependent Ca{sup 2+}/CaM binding proteins has been published. Herein, we report a proteome-wide study of phosphorylation-dependent CaM binding proteins from mammalian cells. This method, termed 'Dynamic Phosphoprotein Complex Trapping', 'DPPC Trapping' for short, utilizes a combination of in vivo and in vitro assays. The basic strategy is to drastically shift the equilibrium towards endogenous phosphorylation of Ser, Thr, and Tyr at the global scale by inhibiting corresponding phosphatases in vivo. The phosphorylation-dependent calmodulin-binding proteins are then trapped in vitro in a Ca{sup 2+}-dependent manner by CaM-Sepharose chromatography. Finally, the isolated calmodulin-binding proteins are separated by SDS-PAGE and identified by LC/MS/MS. In parallel, the phosphorylation-dependent binding is visualized by silver staining and/or Western blotting. Using this method, we selectively identified over 120 CaM-associated proteins including many previously uncharacterized. We verified ubiquitin-protein ligase EDD1, inositol 1, 4, 5-triphosphate receptor type 1 (IP{sub 3}R1), and ATP-dependent RNA helicase DEAD box protein 3 (DDX3), as phosphorylation-dependent CaM binding proteins. To demonstrate the utilities …
Date: May 26, 2006
Creator: Jang, Deok-Jin & Wang, Daojing
System: The UNT Digital Library
Abrupt onset of a second energy gap at the superconducting transition of underdoped Bi2212 (open access)

Abrupt onset of a second energy gap at the superconducting transition of underdoped Bi2212

he superconducting gap--an energy scale tied to the superconducting phenomena--opens on the Fermi surface at the superconducting transition temperature (Tc) in conventional BCS superconductors. In underdoped high-Tc superconducting copper oxides, a pseudogap (whose relation to the superconducting gap remains a mystery) develops well above Tc (refs 1, 2). Whether the pseudogap is a distinct phenomenon or the incoherent continuation of the superconducting gap above Tc is one of the central questions in high-Tc research3, 4, 5, 6, 7, 8. Although some experimental evidence suggests that the two gaps are distinct9, 10, 11, 12, 13, 14, 15, 16, 17, 18, this issue is still under intense debate. A crucial piece of evidence to firmly establish this two-gap picture is still missing: a direct and unambiguous observation of a single-particle gap tied to the superconducting transition as function of temperature. Here we report the discovery of such an energy gap in underdoped Bi2Sr2CaCu2O8+delta in the momentum space region overlooked in previous measurements. Near the diagonal of Cu?O bond direction (nodal direction), we found a gap that opens at Tc and has a canonical (BCS-like) temperature dependence accompanied by the appearance of the so-called Bogoliubov quasi-particles, a classical signature of superconductivity. This is …
Date: May 26, 2007
Creator: Hussain, Zahid; Lee, W. S.; Vishik, I. M.; Tanaka, K.; Lu, D. H.; Sasagawa, T. et al.
System: The UNT Digital Library
Detection of Ultra High Energy Neutrinos via Coherent Radio Emission (open access)

Detection of Ultra High Energy Neutrinos via Coherent Radio Emission

None
Date: May 26, 2006
Creator: Varner, G.; Gorham, P. W.; Kowalski, R. J.; Learned, J. G.; Link, J. T.; Matsuno, S. et al.
System: The UNT Digital Library
Determining the critical size of EUV mask substrate defects (open access)

Determining the critical size of EUV mask substrate defects

Determining the printability of substrate defects beneath the extreme ultraviolet (EUV) reflecting multilayer stack is an important issue in EUVL lithography. Several simulation studies have been performed in the past to determine the tolerable defect size on EUV mask blank substrates but the industry still has no exact specification based on real printability tests. Therefore, it is imperative to experimentally determine the printability of small defects on a mask blanks that are caused by substrate defects using direct printing of programmed substrate defect in an EUV exposure tools. SEMATECH fabricated bump type program defect masks using standard electron beam lithography and performed printing tests with the masks using an EUV exposure tool. Defect images were also captured using SEMATECH's Berkeley Actinic Imaging Tool in order to compare aerial defect images with secondary electron microscope images from exposed wafers. In this paper, a comprehensive understanding of substrate defect printability will be presented and printability specifications of EUV mask substrate defects will be discussed.
Date: May 26, 2008
Creator: Goldberg, Kenneth A.; Gullikson, Eric M.; Han, Hakseung; Cho, Wonil; Jeon, Chan-Uk & Wurm, Stefan
System: The UNT Digital Library
Microprocessor control and data acquisition at the LLNL 100-MeV accelerator (open access)

Microprocessor control and data acquisition at the LLNL 100-MeV accelerator

A distributed microprocessor control and data acquisition network has been designed for implementation on the Lawrence Livermore National Laboratory 100 MeV electron/positron accelerator (LINAC). The system has been designed to be as transparent to the user as possible by stressing responsiveness, reliability, and relevance of data presented to the user. Implementation of the network will take place in modular fashion in three stages, so as to minimize disruption of normal operations. The first elements to be installed will be the beam transport system controls, beam set-up time. Beam diagnostic equipment is now being position monitors, and accelerator operating status monitors. These units will reduce beam set-up time. Beam diagnostic equipment is now being designed that will be used in a second stage implementation. This stage will concentrate on determining beam parameters and allowing the user to optimize the beam for a given parameter. The final stage will be to install experimenter data acquisition equipment. The equipment will augment the presently existing data acquisition system. The completed network will allow a more efficient operation of the LINAC, resulting in reduced experiment costs, and more controllable beam parameters, both of which are major concerns of experimenters.
Date: May 26, 1981
Creator: Mendonca, M.L.
System: The UNT Digital Library
Nuclear design of the LLL-GA U/sub 3/Si blanket (open access)

Nuclear design of the LLL-GA U/sub 3/Si blanket

The nuclear design analysis and performance of the blanket for the Pu/sup 239/ producing standard mirror hybrid is discussed. The blanket is based on present day materials and technology. It is designed for peak power density and burnup in the uranium fuel of 500 W/cc and 3 atom percent. The blanket produces 2.0 Mg/yr of Pu-239 (net) from 400 MW fusion (D-T) and depleted uranium and has an average energy multiplication of 11.
Date: May 26, 1978
Creator: Lee, J. D.
System: The UNT Digital Library
A new glove-box system for a high-pressure tritium pump (open access)

A new glove-box system for a high-pressure tritium pump

A new glove-box system that was designed around a high-pressure tritium pump is described. The system incorporates new containment ideas such as ''burpler'' passive pressure controls, valves that can be turned from outside the box, inflatable door seals, ferro-fluidic motor-shaft seals, and rapid box-to-hood conversion during cryostaging. Currently under construction, the system will contain nine separate sections with automatic pressure-balancing and venting systems. 3 refs., 5 figs.
Date: May 26, 1988
Creator: Wilson, S. W.; Borree, R. J.; Chambers, D. I.; Chang, Y.; Merrill, J. T.; Souers, P. C. et al.
System: The UNT Digital Library
Tandem Mirror Reactor (open access)

Tandem Mirror Reactor

A reactor based on this concept that produces 1000 MWe consists of a solenoidal magnet about 50 to 100 m long. A cylindrical blanket is used for energy recovery and tritium breeding. Thus the reactor itself is simple and of low technology. The end plugs, however, are of high technology, having the high magnetic fields needed to confine the high-pressure plasma and the high injection energy (0.6 to 1.2 MeV) needed to achieve good magnetic confinement. A low technology, compact, economical hybrid fusion-fission reactor results from injection in the central cell as well as the ends, provided a means can be found to stabilize the end plugs against microinstabilities, particularly in small sizes (plug radius divided by ion gyroradius less than or equal to 10). The Q value is 1.8 and the power is 500 MWe, with 1000 kG of /sup 233/U produced per year. If, on the other hand, the tandem is operated in the two-component mode (i.e., cold tritium plasma electrostatically contained into which a 100-200 keV D/sup 0/ beam is injected), then the end plugs can be stabilized by the outward flowing tritium plasma. Finally, we show that D-D burning tandem reactors appear feasible in large sizes …
Date: May 26, 1978
Creator: Moir, R.W.; Barr, W.L. & Bender, D.J.
System: The UNT Digital Library
Effects of local mass anomalies in Eoetvoes-like experiments (open access)

Effects of local mass anomalies in Eoetvoes-like experiments

We consider in detail the effects of local mass anomalies in Eoetvoes-like experiments. It is shown that in the presence of an intermediate-range non-gravitational force, the dominant contributions to both the sign and magnitude of the Eoetvoes anomaly may come from nearby masses and not from the earth as a whole. This observation has important implications in the design and interpretation of future experiments, and in the formulation of unified theories incorporating new intermediate-range forces.
Date: May 26, 1986
Creator: Talmadge, C.; Aronson, S.H. & Fischbach, E.
System: The UNT Digital Library
Charge exchange losses during cyclotron acceleration: experiment and theory (open access)

Charge exchange losses during cyclotron acceleration: experiment and theory

Quantitative estimates of charge exchange (CE) losses during acceleration are very important in the design and operation of heavy ion cyclotrons. Such estimates have been made using a vacuum model computer code which was developed to establish vacuum requirements for the MSU superconducting heavy ion cyclotron. This code uses pressure and cross-section data to calculate the radial loss of beam due to charge exchange. Since CE cross sections and radial pressure profiles are not always well known, certain specific measurements have been made using the LBL 88-Inch Cyclotron to provide experimental data needed to test the code. These include measurements of pressure versus radius under vacuum conditions closely approximating those existing during acceleration of /sup 14/N/sup 4 -/ and /sup 40/Ar/sup 8 -/ beams. Beam intensity versus radius data demonstrating transmission losses for three beams are presented. Comparisons with theoretical predictions are given.
Date: May 26, 1978
Creator: Gough, R.A. & Mallory, M.L.
System: The UNT Digital Library
A Structural Determination Using Magnetic X-Ray Circular Dichroism in Spin-Polarized Photoelectron Diffraction (open access)

A Structural Determination Using Magnetic X-Ray Circular Dichroism in Spin-Polarized Photoelectron Diffraction

The first structural determination with spin-polarized, energy-dependent photoelectron diffraction using circularly-polarized x-rays is reported for Fe films on Cu(001). Circularly-polarized x-rays produce spin-polarized photoelectrons from the Fe 2p doublet, and intensity asymmetries in the 2p{sup 3/2} level are observed. . Fully spin-specific multiple scattering calculations reproduce the experimentally determined energy and angular dependences. A new analytical procedure which focuses upon intensity variations due to spin-dependent diffraction is introduced.
Date: May 26, 1994
Creator: Waddill, G. D.; Tobin, J. G.; Guo, X. & Tong, S. Y.
System: The UNT Digital Library
Measurement of the polarization in the decay B{sup 0} {yields} J/{psi}K{sup *0} in {bar p}p collisions at {radical}s = 1.8 TeV (open access)

Measurement of the polarization in the decay B{sup 0} {yields} J/{psi}K{sup *0} in {bar p}p collisions at {radical}s = 1.8 TeV

This paper reports on the measurement of the polarization in the decay B{sup o} {yields} J/{psi}K{sup *o} using data collected at the collider Detector at Fermilab in {bar p}p collisions at {radical}s = 1.8 TeV. B{sup O} mesons were reconstructed through the decay chain B{sup o} {yields} J/{psi}K{sup *o}, J/{psi} {yields} {mu}{sup +}{mu}{sup {minus}}, K{sup *o} {yields} K{sup +}{pi}{sup {minus}}. A sample of 50 {plus_minus} 11 events was used in the measurement, yielding the result {Gamma}{sub L}/{Gamma} = 0.66 {plus_minus} 0.10 (stat) {sub {minus}}0.10 {sup +0.08} (sys).
Date: May 26, 1994
Creator: CDF Collaboration
System: The UNT Digital Library
Beryllium based multilayers for normal incidence extreme ultraviolet reflectivity (open access)

Beryllium based multilayers for normal incidence extreme ultraviolet reflectivity

The need for normal incidence mirrors maintaining reflectivity greater than 60% for an industrially competitive Extreme Ultraviolet Lithography (EUV) system has been well documented. The Molybdenum/Silicon system has emerged as the de-facto standard, where researchers are now routinely fabricating mirrors demonstrating 63% reflectivity near 130 Angstroms. However, multilayer mirrors using beryllium as the low atomic number (low-Z) spacer could potentially show similar or better reflectivity, and operate at wavelengths down to the beryllium K-edge at 111 Angstroms. Besides offering potentially greater reflectivity, the shorter wavelength light offers increased dissolution depth in photoresists, and offers potentially better resolution and depth of focus. We will report our latest results from beryllium based multilayers. The mirrors were fabricated at the Lawrence Livermore National Laboratory (LLNL) and tested at the Center for X-Ray Optics at Lawrence Berkeley Laboratory (CXRO/LBL).
Date: May 26, 1994
Creator: Skulina, K. M.; Alford, C.; Bionta, R. M.; Makowiecki, D. M.; Kortright, J.; Soufli, R. et al.
System: The UNT Digital Library
Power conditioning for the National Ignition Facility (open access)

Power conditioning for the National Ignition Facility

A cost-effective, 320-MJ power-conditioning system has been completed for the proposed National Ignition Facility (NIF). The design features include metallized dielectric capacitors, a simple topology, and large (1.6-MJ) module size. Experimental results address the technical risks associated with the design.
Date: May 26, 1994
Creator: Larson, D. W.; Anderson, R. & Boyes, J.
System: The UNT Digital Library
RECENT TEST RESULTS OF THE FAST-PULSED 4 T COS DIPOLE GSI 001. (open access)

RECENT TEST RESULTS OF THE FAST-PULSED 4 T COS DIPOLE GSI 001.

For the FAIR-project at GSI a model dipole was built at BNL with the nominal field of 4 T and a nominal ramp rate of 1 T/S. The magnet design was similar to the RHIC dipole, with some changes for loss reduction and better cooling. The magnet was already successfully tested in a vertical cryostat, with good training behavior. Cryogenic losses were measured and first results of field harmonics were published. However, for a better understanding of the cooling process, quench currents at several ramp rates were investigated. Detailed measurements of the field harmonics at 2 T/S between 0 and 4 T were performed.
Date: May 26, 2005
Creator: Moritz, G.; Kaugerts, J.; Escallier, J.; Ganetis, G.; Jain, A.; Marone, A. et al.
System: The UNT Digital Library
Massive-scale RDF Processing Using Compressed Bitmap Indexes (open access)

Massive-scale RDF Processing Using Compressed Bitmap Indexes

The Resource Description Framework (RDF) is a popular data model for representing linked data sets arising from the web, as well as large scienti#12;c data repositories such as UniProt. RDF data intrinsically represents a labeled and directed multi-graph. SPARQL is a query language for RDF that expresses subgraph pattern-#12;nding queries on this implicit multigraph in a SQL- like syntax. SPARQL queries generate complex intermediate join queries; to compute these joins e#14;ciently, we propose a new strategy based on bitmap indexes. We store the RDF data in column-oriented structures as compressed bitmaps along with two dictionaries. This paper makes three new contributions. (i) We present an e#14;cient parallel strategy for parsing the raw RDF data, building dictionaries of unique entities, and creating compressed bitmap indexes of the data. (ii) We utilize the constructed bitmap indexes to e#14;ciently answer SPARQL queries, simplifying the join evaluations. (iii) To quantify the performance impact of using bitmap indexes, we compare our approach to the state-of-the-art triple-store RDF-3X. We #12;nd that our bitmap index-based approach to answering queries is up to an order of magnitude faster for a variety of SPARQL queries, on gigascale RDF data sets.
Date: May 26, 2011
Creator: Madduri, Kamesh & Wu, Kesheng
System: The UNT Digital Library
Raman Spectroscopy of Lithium Hydride Corrosion: Selection of an Appropriate Excitation Wavelength to Minimize Fluorescence (open access)

Raman Spectroscopy of Lithium Hydride Corrosion: Selection of an Appropriate Excitation Wavelength to Minimize Fluorescence

The recent interest in a hydrogen-based fuel economy has renewed research into metal hydride chemistry. Many of these compounds react readily with water to release hydrogen gas and form a caustic. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) has been used to study the hydrolysis reaction. The LiOH stretch appears at 3670 cm{sup -1}. Raman spectroscopy is a complementary technique that employs monochromatic excitation (laser) allowing access to the low energy region of the vibrational spectrum (<600 cm{sup -1}). Weak scattering and fluorescence typically prevent Raman from being used for many compounds. The role of Li{sub 2}O in the moisture reaction has not been fully studied for LiH. Li{sub 2}O can be observed by Raman while being hidden in the Infrared spectrum.
Date: May 26, 2011
Creator: Stowe, A. C. & Smyrl, N. R.
System: The UNT Digital Library
Phase Transition in BCx system under High-Pressure and High-Temperature: Synthesis of Cubic Dense BC3 Nanostructured Phase (open access)

Phase Transition in BCx system under High-Pressure and High-Temperature: Synthesis of Cubic Dense BC3 Nanostructured Phase

None
Date: May 26, 2012
Creator: Zinin, P. V.; Ming, L. C.; Ishii, H. A.; Jia, R.; Acosta, T. & Hellebrand, E.
System: The UNT Digital Library
Scoping economics for the commercial manufacture of metallocene catalysts (open access)

Scoping economics for the commercial manufacture of metallocene catalysts

This study assumes that commercial-scale production of propylene-based isotactic polymers with metallocene catalyst systems will become a reality. The challenge that must be overcome for commercial success with these propylene polymers is to discover a metallocene system recipe that will give sufficient catalyst activity along with the requisite stereo-selectivity at reasonable cost. Anticipating such a discovery, it is assumed here that the economics are well-represented by a catalyst system that consists in part of a silylene-bridged cyclopentadienyl zirconocene made in a batchwise process having an annual capacity of 15,000 pounds. Activation will be achieved with a cocatalyst such as methylaluminoxane (MAO), coated in conjunction with the catalyst on a support such as silica. The MAO at an estimated $100/lb contributes $1800/lb cost to the finished catalyst with an assumed recipe of 18:1 mass ratio of MAO to zirconocene. Based on a 20% return on investment, the selling price for the supported zirconocene system is estimated to be $2915/lb. The required capital investment to make 735,000 lb/yr of the total supported system is 9 million dollars. These estimates have {plus_minus}50% range of uncertainty. Payback period for this plant in a sold-out condition is three years. The catalyst system cost in ethylene-propylene …
Date: May 26, 1994
Creator: Brockmeier, N. F.
System: The UNT Digital Library
Simulation Results for the New NSTX HHFW Antenna Straps Design by Using Microwave Studio (open access)

Simulation Results for the New NSTX HHFW Antenna Straps Design by Using Microwave Studio

Experimental results have shown that the high harmonic fast wave (HHFW) at 30 MHz can provide substantial plasma heating and current drive for the NSTX spherical tokamak operation. However, the present antenna strap design rarely achieves the design goal of delivering the full transmitter capability of 6 MW to the plasma. In order to deliver more power to the plasma, a new antenna strap design and the associated coaxial line feeds are being constructed. This new antenna strap design features two feedthroughs to replace the old single feed-through design. In the design process, CST Microwave Studio has been used to simulate the entire new antenna strap structure including the enclosure and the Faraday shield. In this paper, the antenna strap model and the simulation results will be discussed in detail. The test results from the new antenna straps with their associated resonant loops will be presented as well.
Date: May 26, 2009
Creator: Kung, C. C.; Brunkhorst, C.; Greenough, N.; Fredd, E.; Castano, A.; Miller, D. et al.
System: The UNT Digital Library