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First-principles investigations of the dielectric properties of polypropylene/metal-oxide interfaces (open access)

First-principles investigations of the dielectric properties of polypropylene/metal-oxide interfaces

Article on first-principles investigations of the dielectric properties of polypropylene/metal-oxide interfaces. Nanoscale-resolved dielectric properties of polypropylene/metal-oxide (alumina, PbTiO₃) interfaces and of the corresponding surfaces are investigated via first-principles calculations.
Date: October 30, 2009
Creator: Yu, Liping; Ranjan, Vivek; Buongiorno Nardelli, Marco & Bernholc, Jerry
System: The UNT Digital Library
Plasma"anti-assistance" and"self-assistance" to high power impulse magnetron sputtering (open access)

Plasma"anti-assistance" and"self-assistance" to high power impulse magnetron sputtering

A plasma assistance system was investigated with the goal to operate high power impulse magnetron sputtering (HiPIMS) at lower pressure than usual, thereby to enhance the utilization of the ballistic atoms and ions with high kinetic energy in the film growth process. Gas plasma flow from a constricted plasma source was aimed at the magnetron target. Contrary to initial expectations, such plasma assistance turned out to be contra-productive because it led to the extinction of the magnetron discharge. The effect can be explained by gas rarefaction. A better method of reducing the necessary gas pressure is operation at relatively high pulse repetition rates where the afterglow plasma of one pulse assists in the development of the next pulse. Here we show that this method, known from medium-frequency (MF) pulsed sputtering, is also very important at the much lower pulse repetition rates of HiPIMS. A minimum in the possible operational pressure is found in the frequency region between HiPIMS and MF pulsed sputtering.
Date: January 30, 2009
Creator: Anders, Andre & Yushkov, Georgy Yu.
System: The UNT Digital Library
How did matter gain the upper hand over antimatter? (open access)

How did matter gain the upper hand over antimatter?

Antimatter exists! We routinely make it in laboratories. For every familiar particle type we find a matching antiparticle with opposite charge, but exactly the same mass. For example, a positron with positive charge has the same mass as an electron; an antiproton with negative charge has the same mass as a proton. Antimatter occurs naturally all over the universe wherever high-energy particles collide. The laws of physics for antimatter are very, very similar to those for antimatter--so far we know only one tiny difference in them, a detail of the weak interactions of quarks that earned Makoto Kobayashi and Toshihide Maskawa a share of the 2008 Nobel Prize for Physics. Our understanding of the early Universe also tells us that after inflation ended equal amounts of matter and antimatter were produced. Today there's a lot of matter in the universe, but very little antimatter. This leaves a big question for cosmology. How did matter gain the upper hand over antimatter? It's a question at the root of our existence. Without this excess, there would be no stars, no Earth, and no us! When a particle meets its antiparticle, they annihilate each other in a flash of radiation. This process removed …
Date: January 30, 2009
Creator: Quinn, Helen
System: The UNT Digital Library
Analysis of Voltage Signals from Superconducting Accelerator Magnets (open access)

Analysis of Voltage Signals from Superconducting Accelerator Magnets

We present two techniques used in the analysis of voltage tap data collected during recent tests of superconducting magnets developed by the Superconducting Magnet Program at Lawrence Berkeley National Laboratory. The first technique was used on a quadrupole to provide information about quench origins that could not be obtained using the time-of-flight method. The second technique illustrates the use of data from transient flux imbalances occurring during magnet ramping to diagnose changes in the current-temperature margin of a superconducting cable. In both cases, the results of this analysis contributed to make improvements on subsequent magnets.
Date: October 30, 2009
Creator: Lizarazo, J.; Caspi, S.; Ferracin, P.; Joseph, J.; Lietzke, A. F.; Sabbi, G. L. et al.
System: The UNT Digital Library
Lattice super-Yang-Mills using domain wall fermions in the chiral limit (open access)

Lattice super-Yang-Mills using domain wall fermions in the chiral limit

None
Date: November 30, 2009
Creator: Giedt, J.; Brower, R.; Catterall, S.; Fleming, G. & Vranas, P.
System: The UNT Digital Library
Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica (open access)

Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica

Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to map the transient temperature field across the heated region, allowing assessment of the T-dependent mass transport mechanisms under different laser-heating conditions. Computational fluid dynamics simulations correlated well with experimental results, and showed that for large effective capillary numbers (N{sub c} > 2), surface diffusion is negligible and smoothing is dictated by capillary action, despite the relatively small spatial scales studied here. Extracted viscosity values over 1700-2000K were higher than the predicted bulk values, but were consistent with the surface depletion of OH groups, which was confirmed using confocal Raman microscopy.
Date: October 30, 2009
Creator: Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D et al.
System: The UNT Digital Library
Progress towards Managing Residential Electricity Demand: Impacts of Standards and Labeling for Refrigerators and Air Conditioners in India (open access)

Progress towards Managing Residential Electricity Demand: Impacts of Standards and Labeling for Refrigerators and Air Conditioners in India

The development of Energy Efficiency Standards and Labeling (EES&L) began in earnest in India in 2001 with the Energy Conservation Act and the establishment of the Indian Bureau of Energy Efficiency (BEE). The first main residential appliance to be targeted was refrigerators, soon to be followed by room air conditioners. Both of these appliances are of critical importance to India's residential electricity demand. About 15percent of Indian households own a refrigerator, and sales total about 4 million per year, but are growing. At the same time, the Indian refrigerator market has seen a strong trend towards larger and more consumptive frost-free units. Room air conditioners in India have traditionally been sold to commercial sector customers, but an increasing number are going to the residential sector. Room air conditioner sales growth in India peaked in the last few years at 20percent per year. In this paper, we perform an engineering-based analysis using data specific to Indian appliances. We evaluate costs and benefits to residential and commercial sector consumers from increased equipment costs and utility bill savings. The analysis finds that, while the BEE scheme presents net benefits to consumers, there remain opportunities for efficiency improvement that would optimize consumer benefits, according …
Date: May 30, 2009
Creator: McNeil, Michael A. & Iyer, Maithili
System: The UNT Digital Library
ENVIRONMENTAL PROBLEMS ASSOCIATED WITH DECOMMISSIONING THE CHERNOBYL NUCLEAR POWER PLANT COOLING POND (open access)

ENVIRONMENTAL PROBLEMS ASSOCIATED WITH DECOMMISSIONING THE CHERNOBYL NUCLEAR POWER PLANT COOLING POND

Decommissioning of nuclear power plants and other nuclear fuel cycle facilities has been an imperative issue lately. There exist significant experience and generally accepted recommendations on remediation of lands with residual radioactive contamination; however, there are hardly any such recommendations on remediation of cooling ponds that, in most cases, are fairly large water reservoirs. The literature only describes remediation of minor reservoirs containing radioactive silt (a complete closure followed by preservation) or small water reservoirs resulting in reestablishing natural water flows. Problems associated with remediation of river reservoirs resulting in flooding of vast agricultural areas also have been described. In addition, the severity of environmental and economic problems related to the remedial activities is shown to exceed any potential benefits of these activities. One of the large, highly contaminated water reservoirs that require either remediation or closure is Karachay Lake near the MAYAK Production Association in the Chelyabinsk Region of Russia where liquid radioactive waste had been deep well injected for a long period of time. Backfilling of Karachay Lake is currently in progress. It should be noted that secondary environmental problems associated with its closure are considered to be of less importance since sustaining Karachay Lake would have presented …
Date: September 30, 2009
Creator: Farfan, E.
System: The UNT Digital Library
Linear pi-Acceptor-Templated Dynamic Clipping to Macrobicycles and[2]Rotaxanes (open access)

Linear pi-Acceptor-Templated Dynamic Clipping to Macrobicycles and[2]Rotaxanes

Functional rotaxanes are one of the representative nanoscale molecular machines that have found applications in many areas, including molecular electronics, nanoelectromechanical systems (NEMS), photo controllable smart surfaces, and nanovalves. With the advent of molecular recognition and self-assembly, such molecular compounds can now be obtained efficiently through template-directed synthesis. One of the common strategies of making [2]rotaxanes involves the clipping of a macrocycle around a preformed dumbbell-shaped template in a [1+1] or [2+2] manner. While early examples were based on irreversible kinetic pathway through covalent bond formation, recent advances on reversible dynamic covalent chemistry (DCC) has attracted great attention to this field. By virtue of thermodynamically controlled equilibria, DCC has provided highly efficient and versatile synthetic routes in the selection of specific products from a complex system. Among the several reversible reactions in the category of DCC reactions, the imine formation has proven to be very versatile in macrocyclization to give complex interlocked molecular compounds. Cryptands are three dimensional bicyclic hosts with preorganized cavities capable of inclusion of ions and small molecules. Replacing the nitrogen bridgeheads in common cryptands with aromatic ring systems gives cyclophane-based macrobicycles. The introduction of aromatic ring systems into a preorganized cage-like geometry facilitates ion-{pi} interactions and …
Date: April 30, 2009
Creator: Klivansky, Liana M.; Koshkakaryan, Gayane; Cao, Dennis & Liu, Yi
System: The UNT Digital Library
BENCHMARKING UPGRADED HOTSPOT DOSE CALCULATIONS AGAINST MACCS2 RESULTS (open access)

BENCHMARKING UPGRADED HOTSPOT DOSE CALCULATIONS AGAINST MACCS2 RESULTS

The radiological consequence of interest for a documented safety analysis (DSA) is the centerline Total Effective Dose Equivalent (TEDE) incurred by the Maximally Exposed Offsite Individual (MOI) evaluated at the 95th percentile consequence level. An upgraded version of HotSpot (Version 2.07) has been developed with the capabilities to read site meteorological data and perform the necessary statistical calculations to determine the 95th percentile consequence result. These capabilities should allow HotSpot to join MACCS2 (Version 1.13.1) and GENII (Version 1.485) as radiological consequence toolbox codes in the Department of Energy (DOE) Safety Software Central Registry. Using the same meteorological data file, scenarios involving a one curie release of {sup 239}Pu were modeled in both HotSpot and MACCS2. Several sets of release conditions were modeled, and the results compared. In each case, input parameter specifications for each code were chosen to match one another as much as the codes would allow. The results from the two codes are in excellent agreement. Slight differences observed in results are explained by algorithm differences.
Date: April 30, 2009
Creator: Brotherton, Kevin
System: The UNT Digital Library
LCLS Undulator Commissioning, Alignment, and Performance (open access)

LCLS Undulator Commissioning, Alignment, and Performance

The LCLS x-ray FEL has recently achieved its 1.5-Angstrom lasing and saturation goals upon first trial. This was achieved as a result of a thorough pre-beam checkout, both traditional and beam-based component alignment techniques, and high electron beam brightness. The x-ray FEL process demands very tight tolerances on the straightness of the electron beam trajectory (<5 {micro}m) through the LCLS undulator system. Tight, but less stringent tolerances of {approx}100 {micro}m rms were met for the transverse placement of the individual undulator segments with respect to the beam axis. The tolerances for electron beam straightness can only be met through a beam-based alignment (BBA) method, which is implemented using large electron energy variations and sub-micron resolution cavity beam position monitors (BPM), with precise conventional alignment used to set the starting conditions. Precision-fiducialization of components mounted on remotely adjustable girders, and special beam-finder wires (BFW) at each girder have been used to meet these challenging alignment tolerances. Longer-term girder movement due to ground motion and temperature changes are being monitored, continuously, by a unique stretched wire and hydrostatic level Alignment Diagnostics System (ADS).
Date: October 30, 2009
Creator: Nuhn, Heinz-Dieter
System: The UNT Digital Library
Multidimensional profiling of cell surface proteins and nuclear markers (open access)

Multidimensional profiling of cell surface proteins and nuclear markers

Cell membrane proteins play an important role in tissue architecture and cell-cell communication. We hypothesize that segmentation and multidimensional characterization of the distribution of cell membrane proteins, on a cell-by-cell basis, enable improved classification of treatment groups and identify important characteristics that can otherwise be hidden. We have developed a series of computational steps to (i) delineate cell membrane protein signals and associate them with a specific nucleus; (ii) compute a coupled representation of the multiplexed DNA content with membrane proteins; (iii) rank computed features associated with such a multidimensional representation; (iv) visualize selected features for comparative evaluation through heatmaps; and (v) discriminate between treatment groups in an optimal fashion. The novelty of our method is in the segmentation of the membrane signal and the multidimensional representation of phenotypic signature on a cell-by-cell basis. To test the utility of this method, the proposed computational steps were applied to images of cells that have been irradiated with different radiation qualities in the presence and absence of other small molecules. These samples are labeled for their DNA content and E-cadherin membrane proteins. We demonstrate that multidimensional representations of cell-by-cell phenotypes improve predictive and visualization capabilities among different treatment groups, and identify hidden …
Date: January 30, 2009
Creator: Han, Ju; Chang, Hang; Andarawewa, Kumari; Yaswen, Paul; Helen Barcellos-Hoff, Mary & Parvin, Bahram
System: The UNT Digital Library
IMPACT OF TARGET MATERIAL ACTIVATION ON PERSONNEL EXPOSURE AND RADIOACTIVE CONTAMINATION IN THE NATIONAL IGNITION FACILITY (open access)

IMPACT OF TARGET MATERIAL ACTIVATION ON PERSONNEL EXPOSURE AND RADIOACTIVE CONTAMINATION IN THE NATIONAL IGNITION FACILITY

Detailed activation analyses are performed for the different materials under consideration for use in the target capsules and hohlraums used during the ignition campaign on the National Ignition Facility. Results of the target material activation were additionally used to estimate the levels of contamination within the NIF target chamber and the workplace controls necessary for safe operation. The analysis examined the impact of using Be-Cu and Ge-doped CH capsules on the external dose received by workers during maintenance activities. Five days following a 20 MJ shot, dose rates inside the Target Chamber (TC) due to the two proposed capsule materials are small ({approx} 1 {micro}rem/h). Gold and depleted-uranium (DU) are considered as potential hohlraum materials. Following a shot, gold will most probably get deposited on the TC first wall. On the other hand, while noble-gas precursors from the DU are expected to stay in the TC, most of the noble gases are pumped out of the chamber and end up on the cryopumps. The dose rates inside the TC due to activated gold or DU, at 5 days following a 20 MJ shot, are about 1 mrem/h. Dose rates in the vicinity of the cryo-pumps (containing noble 'fission' gases) drop-off …
Date: June 30, 2009
Creator: Khater, H; Epperson, P; Thacker, R; Beale, R; Kohut, T & Brereton, S
System: The UNT Digital Library
ATF2 Commissioning (open access)

ATF2 Commissioning

ATF2 is a final-focus test beam line that aims to focus the low-emittance beam from the ATF damping ring to a beam size of about 37 nm, and at the same time to demonstrate nm beam stability, using numerous advanced beam diagnostics and feedback tools. The construction has been finished at the end of 2008 and the beam commissioning of ATF2 has started in December of 2008. ATF2 is constructed and commissioned by ATF international collaborations with strong US, Asian and European participation.
Date: October 30, 2009
Creator: Seryi, A.; Christian, G.; Parker, B.; Schulte, D.; Delahaye, J. -P.; Tomas, R. et al.
System: The UNT Digital Library
Physics with tagged forward protons at RHIC (open access)

Physics with tagged forward protons at RHIC

The physics reach of the STAR detector at RHIC has been extended to include elastic and inelastic diffraction measurements with tagged forward protons. This program has started at RHIC in p+p collisions with a special optics run of {beta}* {approx} 21 m at STAR, at the center-of-mass energy {radical}s = 200 GeV during the last week of the RHIC 2009 run.
Date: August 30, 2009
Creator: Yip,K.
System: The UNT Digital Library
A Concept of Plasma Wake Field Acceleration Linear Collider (PWFA-LC) (open access)

A Concept of Plasma Wake Field Acceleration Linear Collider (PWFA-LC)

Plasma Wake-Field Acceleration (PWFA) has demonstrated acceleration gradients above 50 GeV/m. Simulations have shown drive/witness bunch configurations that yield small energy spreads in the accelerated witness bunch and high energy transfer efficiency from the drive bunch to the witness bunch, ranging from 30% for a Gaussian drive bunch to 95% for a shaped longitudinal profile. These results open the opportunity for a linear collider that could be compact, efficient and more cost effective that the present microwave technologies. A concept of a PWFA-based Linear Collider (PWFA-LC) has been developed and is described in this paper. The drive beam generation and distribution, requirements on the plasma cells, and optimization of the interaction region parameters are described in detail. The R&D steps needed for further development of the concept are also outlined.
Date: October 30, 2009
Creator: Seryi, Andrei; Hogan, Mark; Pei, Shilun; Raubenheimer, Tor; Tenenbaum, Peter; Katsouleas, Tom et al.
System: The UNT Digital Library
Approach to a Fully Integrated Performance Assurance System, 2009, July (open access)

Approach to a Fully Integrated Performance Assurance System, 2009, July

This report talks about Approach to a Fully Integrated Performance Assurance System.
Date: July 30, 2009
Creator: Grant, G. M.
System: The UNT Digital Library
Evidence for residual elastic strain in deformed natural quartz (open access)

Evidence for residual elastic strain in deformed natural quartz

Residual elastic strain in naturally deformed, quartz-containing rocks can be measured quantitatively in a petrographic thin section with high spatial resolution using Laue microdiffraction with white synchrotron x-rays. The measurements with a resolution of one micrometer allow the quantitative determination of the deviatoric strain tensor as a function of position within the crystal investigated. The observed equivalent strain values of 800-1200 microstrains represent a lower bound of the actual preserved residual strain in the rock, since the stress component perpendicular to the cut sample surface plane is released. The measured equivalent strain translates into an equivalent stress in the order of {approx} 50 MPa.
Date: January 30, 2009
Creator: Kunz, Martin; Chen, Kai; Tamura,Nobumichi & Wenk, Hans-Rudolf
System: The UNT Digital Library
IN-SITU ASSAY OF TRANSURANIC RADIONUCLIDES IN THE VADOSE ZONE USING HIGH-RESOLUTION SPECTRAL GAMMA LOGGING - A HANFORD CASE STUDY (open access)

IN-SITU ASSAY OF TRANSURANIC RADIONUCLIDES IN THE VADOSE ZONE USING HIGH-RESOLUTION SPECTRAL GAMMA LOGGING - A HANFORD CASE STUDY

High-resolution spectral gamma logging in steel-cased boreholes is used to detect and quantify transuranic radionuclides in the subsurface. Pu-239, Pu-241, Am-241, and Np-237 are identified based on characteristic decay gammas. Typical minimum detectable levels are on the order of 20 to 40 nCi/g. In intervals of high transuranic concentrations, gamma rays from other sources may complicate analysis and interpretation. Gamma rays detected in the borehole may originate from three sources: decay of the parent transuranic radionuclide or a daughter; alpha interactions; and interactions with neutrons resulting from either spontaneous fission or alpha particle interactions.
Date: November 30, 2009
Creator: VJ, ROHAY; P, HENWOOD & R, MCCAIN
System: The UNT Digital Library
Looking for Darwin's footprints in the microbial world (open access)

Looking for Darwin's footprints in the microbial world

As we observe the 200th anniversary of Charles Darwin's birthday, microbiologists interested in the application of Darwin's ideas to the microscopic world have a lot to celebrate: an emerging picture of the (mostly microbial) Tree of Life at ever-increasing resolution, an understanding of horizontal gene transfer as a driving force in the evolution of microbes, and thousands of complete genome sequences to help formulate and refine our theories. At the same time, quantitative models of the microevolutionary processes shaping microbial populations remain just out of reach, a point that is perhaps most dramatically illustrated by the lack of consensus on how (or even whether) to define bacterial species. We summarize progress and prospects in bacterial population genetics, with an emphasis on detecting the footprint of positive Darwinian selection in microbial genomes.
Date: March 30, 2009
Creator: Shapiro, B. Jesse; David, Lawrence A.; Friedman, Jonathan & Alm, Eric J.
System: The UNT Digital Library
Branching fractions and charge asymmetries in charmless hadronic decays at BABAR (open access)

Branching fractions and charge asymmetries in charmless hadronic decays at BABAR

We present measurements of branching fraction, polarization and charge asymmetry in charmless hadronic B decays with {eta}, {eta}{prime}, {omega}, and b{sub 1} in the final state. All the results use the final BABAR dataset.
Date: October 30, 2009
Creator: Biassoni, Pietro
System: The UNT Digital Library
Pyramidal and Chiral Groupings of Gold Nanocrystals Assembled Using DNA Scaffolds (open access)

Pyramidal and Chiral Groupings of Gold Nanocrystals Assembled Using DNA Scaffolds

Nanostructures constructed from metal and semiconductor nanocrystals conjugated to, and organized by DNA are an emerging class of material with collective optical properties. We created discrete pyramids of DNA with gold nanocrystals at the tips. By taking small angle X-ray scattering (SAXS) measurments from solutions of these pyramids we confirmed that this pyramidal geometry creates structures which are more rigid in solution than linear DNA. We then took advantage of the tetrahedral symmetry to demonstrate construction of chiral nanostructures.
Date: March 30, 2009
Creator: Mastroianni, Alexander; Claridge, Shelley & Alivisatos, A. Paul
System: The UNT Digital Library
A Vernier Regulator for ILC Marx Droop Compensation (open access)

A Vernier Regulator for ILC Marx Droop Compensation

A two-part compensation scheme, Vernier Regulation, has been applied to offset the voltage droop (40% without correction) in a Marx-topology klystron modulator developed for the International Linear Collider (ILC). Coarse regulation, {+-}5%, is achieved by turning on additional Main Marx cells (Delayed Cells) sequentially as the droop reaches the cell voltage (11 kV). Further regulation to {+-}0.5% is achieved by adding a small Marx in series with the Main Marx. This Vernier Marx is composed of sixteen, 1.2 kV cells that are assembled as a seventeenth cell in the Main Marx. These Vernier Cells are turned on sequentially to generate a series of discrete corrections to the droop in the Main Marx cells with a step size {le}1% of the output voltage. As the required correction reaches 11 kV, all Vernier Cells are turned off synchronously with the turn on of a Delayed Cell. There are up to five Delayed Cells and six Vernier Marx cycles during each ILC Marx output pulse. The Vernier Marx has a local control system that will detect and respond to over-voltage and over-current errors. In this paper, a detailed description of the design, implementation and testing of the Vernier Marx is presented.
Date: October 30, 2009
Creator: Tang, Tao
System: The UNT Digital Library
Laser Timing Jitter Measurements using a Dual-Sweep Streak Camera at the A0 Photoinjector (open access)

Laser Timing Jitter Measurements using a Dual-Sweep Streak Camera at the A0 Photoinjector

Excellent phase stability of the drive laser is a critical performance specification of photoinjectors such as Fermilab's A0 photoinjector (A0PI). Previous efforts based on the measurement of the power spectrum of the signal of a fast photodiode illuminated by the mode locked infrared laser pulse component indicated a phase jitter of less than 1.4 ps (technique limited). A recently procured dual sweep plugin unit and existing Hamamatsu C5680 streak camera were used to study the phase stability of the UV laser pulse component. Initial measurements with the synchroscan vertical sweep unit locked to 81.25 MHz showed that the phase slew through the micropulse train and the phase jitter micropulse to micropulse were two key aspects that could be evaluated. The phase slew was much less than 100 fs per micropulse, and the total phase jitter (camera, trigger, and laser) was approximately 300 fs RMS for measurements of 50-micropulse trains. Data on the macropulse phase stability were also obtained. A possible upgrade to achieve better phase stability will be also discussed.
Date: April 30, 2009
Creator: Ruan, J.; Lumpkin, A. H. & Santucci, J. K.
System: The UNT Digital Library