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Development of a Performance-Based Industrial Energy Efficiency Indicator for Corn Refining Plants.
Organizations that implement strategic energy management programs have the potential to achieve sustained energy savings if the programs are carried out properly. A key opportunity for achieving energy savings that plant managers can take is to determine an appropriate level of energy performance by comparing their plant's performance with that of similar plants in the same industry. Manufacturing facilities can set energy efficiency targets by using performance-based indicators. The U.S. Environmental Protection Agency (EPA), through its ENERGY STAR{reg_sign} program, has been developing plant energy performance indicators (EPIs) to encourage a variety of U.S. industries to use energy more efficiently. This report describes work with the corn refining industry to provide a plant-level indicator of energy efficiency for facilities that produce a variety of products--including corn starch, corn oil, animal feed, corn sweeteners, and ethanol--for the paper, food, beverage, and other industries in the United States. Consideration is given to the role that performance-based indicators play in motivating change; the steps needed to develop indicators, including interacting with an industry to secure adequate data for an indicator; and the actual application and use of an indicator when complete. How indicators are employed in the EPA's efforts to encourage industries to voluntarily …
Date:
July 31, 2006
Creator:
Boyd, G. A. & Sciences, Decision and Information
Object Type:
Report
System:
The UNT Digital Library
Comparison groups on bills: Automated, personalized energy information
A program called ``Innovative Billing?? has been developed to provide individualized energy information for a mass audience?the entireresidential customer base of an electric or gas utility. Customers receive a graph on the bill that compares that customer?s consumption with othersimilar customers for the same month. The program aims to stimulate customers to make ef?ciency improvements. To group as many as severalmillion customers into small ``comparison groups??, an automated method must be developed drawing solely from the data available to the utility.This paper develops and applies methods to compare the quality of resulting comparison groups.A data base of 114,000 customers from a utility billing system was used to evaluate Innovative Billing comparison groups, comparing fouralternative criteria: house characteristics (?oor area, housing type, and heating fuel); street; meter read route; billing cycle. Also, customers wereinterviewed to see what forms of comparison graphs made most sense and led to fewest errors of interpretation. We ?nd that good qualitycomparison groups result from using street name, meter book, or multiple house characteristics. Other criteria we tested, such as entire cycle, entiremeter book, or single house characteristics such as ?oor area, resulted in poor quality comparison groups. This analysis provides a basis forchoosing comparison groups based …
Date:
July 1, 2006
Creator:
Iyer, Maithili; Kempton, Willett & Payne, Christopher
Object Type:
Article
System:
The UNT Digital Library
Genetic Diversity Among Botulinum Neurotoxin Producing Clostridial Strains
Clostridium botulinum is a taxonomic designation for many diverse anaerobic spore forming rod-shaped bacteria which have the common property of producing botulinum neurotoxins (BoNTs). The BoNTs are exoneurotoxins that can cause severe paralysis and even death in humans and various other animal species. A collection of 174 C. botulinum strains were examined by amplified fragment length polymorphism (AFLP) analysis and by sequencing of the 16S rRNA gene and BoNT genes to examine genetic diversity within this species. This collection contained representatives of each of the seven different serotypes of botulinum neurotoxins (BoNT A-G). Analysis of the16S rRNA sequences confirmed earlier reports of at least four distinct genomic backgrounds (Groups I-IV) each of which has independently acquired one or more BoNT serotypes through horizontal gene transfer. AFLP analysis provided higher resolution, and can be used to further subdivide the four groups into sub-groups. Sequencing of the BoNT genes from serotypes A, B and E in multiple strains confirmed significant sequence variation within each serotype. Four distinct lineages within each of the BoNT A and B serotypes, and five distinct lineages of serotype E strains were identified. The nucleotide sequences of the seven serotypes of BoNT were compared and show varying degrees …
Date:
July 6, 2006
Creator:
Hill, K K; Smith, T J; Helma, C H; Ticknor, L O; Foley, B T; Svennson, R T et al.
Object Type:
Article
System:
The UNT Digital Library
Avoiding the Haircut: Potential Ways to Enhance the Value of theUSDA's Section 9006 Program
Section 9006 of Title IX of The Farm Security and Rural Investment Act of 2002 (the '2002 Farm Bill') established the Renewable Energy Systems and Energy Efficiency Improvements Program (the 'Section 9006 program'). Administered by the United States Department of Agriculture (USDA), the Section 9006 program provides grants, loan guarantees, and - perhaps in the future - direct loans to farmers, ranchers, and rural small businesses for assistance with purchasing renewable energy systems and making energy efficiency improvements. In the three rounds of Section 9006 funding to date (FY03-FY05), roughly 40% of all grant dollars in aggregate have been awarded to 'large' (defined as > 100 kW) wind projects. Such projects are also typically eligible for the Federal Production Tax Credit (PTC) codified in Section 45 of the US tax code. Because the PTC provides a significant amount of value to a wind project, most 'large wind' applicants to the Section 9006 program have also tried to take advantage of the PTC. Through what are known as 'anti-double-dipping' or, more colloquially, 'haircut' provisions, however, the size of the PTC is reduced if a project receives certain other forms of governmental support. Specifically, Section 45(b)(3) of the US tax code reduces …
Date:
July 13, 2006
Creator:
Bolinger, Mark
Object Type:
Report
System:
The UNT Digital Library
SATB1 tethers multiple gene loci to reprogram expression profiledriving breast cancer metastasis
Global changes in gene expression occur during tumor progression, as indicated by expression profiling of metastatic tumors. How this occurs is poorly understood. SATB1 functions as a genome organizer by folding chromatin via tethering multiple genomic loci and recruiting chromatin remodeling enzymes to regulate chromatin structure and expression of a large number of genes. Here we show that SATB1 is expressed at high levels in aggressive breast cancer cells, and is undetectable in non-malignant breast epithelial cells. Importantly, RNAi-mediated removal of SATB1 from highly-aggressive MDA-MB-231 cells altered the expression levels of over 1200 genes, restored breast-like acinar polarity in three-dimensional cultures, and prevented the metastastic phenotype in vivo. Conversely, overexpression of SATB1 in the less-aggressive breast cancer cell line Hs578T altered the gene expression profile and increased metastasis dramatically in vivo. Thus, SATB1 is a global regulator of gene expression in breast cancer cells, directly regulating crucial metastasis-associated genes, including ERRB2 (HER2/NEU), TGF-{beta}1, matrix metalloproteinase 3, and metastasin. The identification of SATB1 as a protein that re-programs chromatin organization and transcription profiles to promote breast cancer metastasis suggests a new model for metastasis and may provide means of therapeutic intervention.
Date:
July 13, 2006
Creator:
Han, Hye-Jung; Kohwi, Yoshinori & Kohwi-Shigematsu, Terumi
Object Type:
Article
System:
The UNT Digital Library
A Variation of the F-Test for Determining Statistical Relevance ofParticular Parameters in EXAFS Fits
A general problem when fitting EXAFS data is determining whether particular parameters are statistically significant. The F-test is an excellent way of determining relevancy in EXAFS because it only relies on the ratio of the fit residual of two possible models, and therefore the data errors approximately cancel. Although this test is widely used in crystallography (there, it is often called a 'Hamilton test') and has been properly applied to EXAFS data in the past, it is very rarely applied in EXAFS analysis. We have implemented a variation of the F-test adapted for EXAFS data analysis in the RSXAP analysis package, and demonstrate its applicability with a few examples, including determining whether a particular scattering shell is warranted, and differentiating between two possible species or two possible structures in a given shell.
Date:
July 25, 2006
Creator:
Downward, L.; Booth, C.H.; Lukens, W.W. & Bridges, F.
Object Type:
Article
System:
The UNT Digital Library
Transmission Electron Microscopy Study of InN Nanorods
InN nanorods were grown on a, c-, and r-plane of sapphire and also on Si (111) and GaN (0001) by non-catalytic, template-free hydride metal-organic vapor phase epitaxy and studied by transmission electron microscopy, electron energy loss (EELS) and photoluminescence (PL) at room temperature. These nanocrystals have different shapes and different faceting depending on the substrate used and their crystallographic orientation. EELS measurements have confirmed the high purity of these crystals. The observed PL peak was in the range of 0.9-0.95 eV. The strongest PL intensity was observed for the nanocrystals with the larger diameters.
Date:
July 13, 2006
Creator:
Liliental-Weber, Z.; Li, X.; Kryliouk, Olga; Park, H.J.; Mangum,J. & Anderson, T.
Object Type:
Article
System:
The UNT Digital Library
MODELING OF NI-CR-MO BASED ALLOYS: PART II - KINETICS
The CALPHAD approach is applied to kinetic studies of phase transformations and aging of prototypes of Ni-Cr-Mo-based alloys selected for waste disposal canisters in the Yucca Mountain Project (YMP). Based on a previous study on alloy stability for several candidate alloys, the thermodynamic driving forces together with a newly developed mobility database have been used to analyze diffusion-controlled transformations in these Ni-based alloys. Results on precipitation of the Ni{sub 2}Cr-ordered phase in Ni-Cr and Ni-Cr-Mo alloys, and of the complex P- and {delta}-phases in a surrogate of Alloy 22 are presented, and the output from the modeling are compared with experimental data on aging.
Date:
July 7, 2006
Creator:
Turchi, P A; Kaufman, L & Liu, Z
Object Type:
Article
System:
The UNT Digital Library
Incorporation of aqueous reaction kinetics and biodegradation intoTOUGHREACT: Application of a multi-region model to hydrobiogeoChemicaltransport of denitrification and sulfate reduction
The need to consider aqueous and sorption kinetics andmicrobiological processes arises in many subsurface problems. Ageneral-rate expression has been implemented into the TOUGHREACTsimulator, which considers multiple mechanisms (pathways) and includesmultiple product, Monod, and inhibition terms. This paper presents aformulation for incorporating kinetic rates among primary species intomass-balance equations. The space discretization used is based on aflexible integral finite difference approach that uses irregular griddingto model bio-geologic structures. A general multi-region model forhydrological transport interacted with microbiological and geochemicalprocesses is proposed. A 1-D reactive transport problem with kineticbiodegradation and sorption was used to test the enhanced simulator,which involves the processes that occur when a pulse of water containingNTA (nitrylotriacetate) and cobalt is injected into a column. The currentsimulation results agree very well with those obtained with othersimulators. The applicability of this general multi-region model wasvalidated by results from a published column experiment ofdenitrification and sulfate reduction. The matches with measured nitrateand sulfate concentrations were adjusted with the interficial areabetween mobile hydrological and immobile biological regions. Resultssuggest that TOUGHREACT can not only be a useful interpretative tool forbiogeochemical experiments, but also can produce insight into processesand parameters of microscopic diffusion and their interplay withbiogeochemical reactions. The geometric- and process-based multi-regionmodel may provide …
Date:
July 13, 2006
Creator:
Xu, Tianfu
Object Type:
Article
System:
The UNT Digital Library
The Role of Demand Resources In Regional Transmission Expansion Planning and Reliable Operations
Investigating the role of demand resources in regional transmission planning has provided mixed results. On one hand there are only a few projects where demand response has been used as an explicit alternative to transmission enhancement. On the other hand there is a fair amount of demand response in the form of energy efficiency, peak reduction, emergency load shedding, and (recently) demand providing ancillary services. All of this demand response reduces the need for transmission enhancements. Demand response capability is typically (but not always) factored into transmission planning as a reduction in the load which must be served. In that sense demand response is utilized as an alternative to transmission expansion. Much more demand response is used (involuntarily) as load shedding under extreme conditions to prevent cascading blackouts. The amount of additional transmission and generation that would be required to provide the current level of reliability if load shedding were not available is difficult to imagine and would be impractical to build. In a very real sense demand response solutions are equitably treated in every region - when proposed, demand response projects are evaluated against existing reliability and economic criteria. The regional councils, RTOs, and ISOs identify needs. Others propose …
Date:
July 1, 2006
Creator:
Kirby, Brendan J.
Object Type:
Report
System:
The UNT Digital Library
Laser Fusion: The First Ten Years 1962-1972
This account of the beginning of the program on laser fusion at Livermore in 1962, and its subsequent development during the decade ending in 1972, was originally prepared as a contribution to the January 1991 symposium 'Achievements in Physics' honoring Professor Keith Brueckner upon his retirement from the University of San Diego at La Jolla. It is a personal recollection of work at Livermore from my vantage point as its scientific leader, and of events elsewhere that I thought significant. This period was one of rapid growth in which the technology of high-power short-pulse lasers needed to drive the implosion of thermonuclear fuel to the temperature and density needed for ignition was developed, and in which the physics of the interaction of intense light with plasmas was explored both theoretically and experimentally.
Date:
July 6, 2006
Creator:
Kidder, R. E.
Object Type:
Book
System:
The UNT Digital Library
Exploring Metric Symmetry
Relatively minor perturbations to a crystal structure can in some cases result in apparently large changes in symmetry. Changes in space group or even lattice can be induced by heavy metal or halide soaking (Dauter et al, 2001), flash freezing (Skrzypczak-Jankun et al, 1996), and Se-Met substitution (Poulsen et al, 2001). Relations between various space groups and lattices can provide insight in the underlying structural causes for the symmetry or lattice transformations. Furthermore, these relations can be useful in understanding twinning and how to efficiently solve two different but related crystal structures. Although (pseudo) symmetric properties of a certain combination of unit cell parameters and a space group are immediately obvious (such as a pseudo four-fold axis if a is approximately equal to b in an orthorhombic space group), other relations (e.g. Lehtio, et al, 2005) that are less obvious might be crucial to the understanding and detection of certain idiosyncrasies of experimental data. We have developed a set of tools that allows straightforward exploration of possible metric symmetry relations given unit cell parameters and a space group. The new iotbx.explore{_}metric{_}symmetry command produces an overview of the various relations between several possible point groups for a given lattice. Methods for …
Date:
July 31, 2006
Creator:
Zwart, P. H.; Grosse-Kunstleve, R. W. & Adams, P. D.
Object Type:
Report
System:
The UNT Digital Library
Probing Dark Energy via Neutrino and Supernova Observatories
A novel method for extracting cosmological evolution parameters is proposed, using a probe other than light: future observations of the diffuse anti-neutrino flux emitted from core-collapse supernovae (SNe), combined with the SN rate extracted from future SN surveys. The relic SN neutrino differential flux can be extracted by using future neutrino detectors such as Gadolinium-enriched, megaton, water detectors or 100-kiloton detectors of liquid Argon or liquid scintillator. The core-collapse SN rate can be reconstructed from direct observation of SN explosions using future precision observatories. Our method, by itself, cannot compete with the accuracy of the optical-based measurements but may serve as an important consistency check as well as a source of complementary information. The proposal does not require construction of a dedicated experiment, but rather relies on future experiments proposed for other purposes.
Date:
July 10, 2006
Creator:
Hall, Lawrence; Hall, Lawrence J.; Murayama, Hitoshi; Papucci, Michele & Perez, Gilad
Object Type:
Report
System:
The UNT Digital Library
Thermal Neutron Capture Cross Sections of the PalladiumIsotopes
Precise gamma-ray thermal neutron capture cross sectionshave been measured at the Budapest Reactor for all elements withZ=1-83,92 except for He and Pm. These measurements and additional datafrom the literature been compiled to generate the Evaluated Gamma-rayActivation File (EGAF), which is disseminated by LBNL and the IAEA. Thesedata are nearly complete for most isotopes with Z<20 so the totalradiative thermal neutron capture cross sections can be determineddirectly from the decay scheme. For light isotopes agreement with therecommended values is generally satisfactory although large discrepanciesexist for 11B, 12,13C, 15N, 28,30Si, 34S, 37Cl, and 40,41K. Neutroncapture decay data for heavier isotopes are typically incomplete due tothe contribution of unresolved continuum transitions so only partialradiative thermal neutron capture cross sections can be determined. Thecontribution of the continuum to theneutron capture decay scheme arisesfrom a large number of unresolved levels and transitions and can becalculated by assuming that the fluctuations in level densities andtransition probabilities are statistical. We have calculated thecontinuum contribution to neutron capture decay for the palladiumisotopes with the Monte Carlo code DICEBOX. These calculations werenormalized to the experimental cross sections deexciting low excitationlevels to determine the total radiative thermal neutron capture crosssection. The resulting palladium cross sections values were determinedwith a precision …
Date:
July 17, 2006
Creator:
Firestone, R.B.; Krticka, M.; McNabb, D.P.; Sleaford, B.; Agvaanluvsan, U.; Belgya, T. et al.
Object Type:
Article
System:
The UNT Digital Library
Random polycrystals of grains containing cracks: Model ofquasistatic elastic behavior for fractured systems
A model study on fractured systems was performed using aconcept that treats isotropic cracked systems as ensembles of crackedgrains by analogy to isotropic polycrystalline elastic media. Theapproach has two advantages: (a) Averaging performed is ensembleaveraging, thus avoiding the criticism legitimately leveled at mosteffective medium theories of quasistatic elastic behavior for crackedmedia based on volume concentrations of inclusions. Since crack effectsare largely independent of the volume they occupy in the composite, sucha non-volume-based method offers an appealingly simple modelingalternative. (b) The second advantage is that both polycrystals andfractured media are stiffer than might otherwise be expected, due tonatural bridging effects of the strong components. These same effectshave also often been interpreted as crack-crack screening inhigh-crack-density fractured media, but there is no inherent conflictbetween these two interpretations of this phenomenon. Results of thestudy are somewhat mixed. The spread in elastic constants observed in aset of numerical experiments is found to be very comparable to the spreadin values contained between the Reuss and Voigt bounds for thepolycrystal model. However, computed Hashin-Shtrikman bounds are much tootight to be in agreement with the numerical data, showing thatpolycrystals of cracked grains tend to violate some implicit assumptionsof the Hashin-Shtrikman bounding approach. However, the self-consistentestimates obtained for …
Date:
July 8, 2006
Creator:
Berryman, James G. & Grechka, Vladimir
Object Type:
Article
System:
The UNT Digital Library
Modeling geologic storage of carbon dioxide: Comparison of non-hysteretic and hysteretic characteristic curves
Numerical models of geologic storage of carbon dioxide (CO2)in brine-bearing formations use characteristic curves to represent theinteractions of non-wetting-phase CO2 and wetting-phase brine. When aproblem includes both injection of CO2 (a drainage process) and itssubsequent post-injection evolution (a combination of drainage andwetting), hysteretic characteristic curves are required to correctlycapture the behavior of the CO2 plume. In the hysteretic formulation,capillary pressure and relative permeability depend not only on thecurrent grid-block saturation, but also on the history of the saturationin the grid block. For a problem that involves only drainage or onlywetting, a non-hysteretic formulation, in which capillary pressure andrelative permeability depend only on the current value of the grid-blocksaturation, is adequate. For the hysteretic formulation to be robustcomputationally, care must be taken to ensure the differentiability ofthe characteristic curves both within and beyond the turning-pointsaturations where transitions between branches of the curves occur. Twoexample problems involving geologic CO2 storage are simulated withTOUGH2, a multiphase, multicomponent code for flow and transport codethrough geological media. Both non-hysteretic and hysteretic formulationsare used, to illustrate the applicability and limitations ofnon-hysteretic methods.The first application considers leakage of CO2from the storage formation to the ground surface, while the secondexamines the role of heterogeneity within the storageformation.
Date:
July 17, 2006
Creator:
Doughty, Christine
Object Type:
Article
System:
The UNT Digital Library
High Pressure Materials Research using Advanced Third-Generation Synchrotron X-ray
The recent discoveries of nonmolecular phases of simple molecular solids [1,2] demonstrate the proof-of-the-principles for producing exotic phases by application of high pressure. Modern advances in theoretical and computational methodologies now make possible to explain or even predict novel structures and properties in a relatively wide range of length scales on the basis of thermodynamic stability [3]. Equally important in materials research is the recent developments in advanced x-ray and laser diagnostics that enable in-situ observations at the formidable pressure-temperature conditions [4]. Having benefited by all these developments, we discuss the first principle of the pressure-induced chemistry, 'Mbar Chemistry', with a few examples that may have important implications in materials research.
Date:
July 7, 2006
Creator:
Yoo, C. S.; Iota, V.; Park, J.; Lee, G.; Evans, W.; Jenei, Z. et al.
Object Type:
Article
System:
The UNT Digital Library
An Aerial Radiological Survey of the Yucca Mountain Project Proposed Land Withdrawal and Adjacent Areas
An aerial radiological survey of the Yucca Mountain Project (YMP) proposed land withdrawal was conducted from January to April 2006, and encompassed a total area of approximately 284 square miles (73,556 hectares). The aerial radiological survey was conducted to provide a sound technical basis and rigorous statistical approach for determining the potential presence of radiological contaminants in the Yucca Mountain proposed Land withdrawal area. The survey site included land areas currently managed by the Bureau of Land Management, the U.S. Air Force as part of the Nevada Test and Training Range or the U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Site Office (NNSA/NSO) as part of the Nevada Test Site (NTS). The survey was flown at an approximate ground speed of 70 knots (36 meters per second), at a nominal altitude of 150 ft (46 m) above ground level, along a set of parallel flight lines spaced 250 ft (76 m) apart. The flight lines were oriented in a north-south trajectory. The survey was conducted by the DOE NNSA/NSO Remote Sensing Laboratory-Nellis, which is located in Las Vegas, Nevada. The aerial survey was conducted at the request of the DOE Office of Civilian Radioactive Waste Management. The …
Date:
July 1, 2006
Creator:
Craig Lyons, Thane Hendricks
Object Type:
Report
System:
The UNT Digital Library
Development of a performance-based industrial energy efficiency indicator for cement manufacturing plants.
Organizations that implement strategic energy management programs have the potential to achieve sustained energy savings if the programs are carried out properly. A key opportunity for achieving energy savings that plant managers can take is to determine an appropriate level of energy performance by comparing the plant performance with that of similar plants in the same industry. Manufacturing plants can set energy efficiency targets by using performance-based indicators. The U.S. Environmental Protection Agency (EPA), through its ENERGY STAR{reg_sign} program, has been developing plant energy performance indicators (EPIs) to encourage a variety of U.S. industries to use energy more efficiently. This report describes work with the cement manufacturing industry to provide a plant-level indicator of energy efficiency for assembly plants that produce a variety of products, including Portland cement and other specialty cement products, in the United States. Consideration is given to the role that performance-based indicators play in motivating change; the steps needed to develop indicators, including interacting with an industry to secure adequate data for an indicator; and the actual application and use of an indicator when complete. How indicators are employed in the EPA's efforts to encourage industries to voluntarily improve their use of energy is discussed as …
Date:
July 21, 2006
Creator:
Boyd, G. & Sciences, Decision and Information
Object Type:
Report
System:
The UNT Digital Library
X-ray survival characteristics and genetic analysis for nineSaccharomyces deletion mutants that affect radiation sensitivity
We examine ionizing radiation (IR) sensitivity and epistasisrelationships of several Saccharomyces mutants affectingpost-translational modifications of histones H2B and H3. Mutantsbre1delta, lge1delta, and rtf1delta, defective in histone H2B lysine 123ubiquitination, show IR sensitivity equivalent to that of the dot1deltamutant that we reported on earlier, consistent with published findingsthat Dot1p requires H2B K123 ubiquitination to fully methylate histone H3K79. This implicates progressive K79 methylation rather thanmono-methylation in IR resistance. The set2delta mutant, defective in H3K36 methylation, shows mild IR sensitivity whereas mutants that abolishH3 K4 methylation resemble wild type. The dot1delta, bre1delta, andlge1delta mutants show epistasis for IR sensitivity. The paf1deltamutant, also reportedly defective in H2B K123 ubiquitination, confers nosensitivity. The rad6delta, rad51null, rad50delta, and rad9deltamutations are epistatic to bre1? and dot1delta, but rad18delta andrad5delta show additivity with bre1delta, dot1delta, and each other. Thebre1delta rad18delta double mutant resembles rad6delta in sensitivity;thus the role of Rad6p in ubiquitinating H2B accounts for its extrasensitivity compared to rad18delta. We conclude that IR resistanceconferred by BRE1 and DOT1 is mediated through homologous recombinationalrepair, not postreplication repair, and confirm findings of a G1checkpoint role for the RAD6/BRE1/DOT1 pathway.
Date:
July 21, 2006
Creator:
Game, John C.; Williamson, Marsha S. & Baccari, Clelia
Object Type:
Article
System:
The UNT Digital Library
The Heavy-Ion Approximation for Ambipolar Diffusion Calcuations for Weakly Ionized Plasmas
Ambipolar diffusion redistributes magnetic flux in weakly ionized plasmas and plays a critical role in star formation. Simulations of ambipolar diffusion using explicit MHD codes are prohibitively expensive for the level of ionization observed in molecular clouds ({approx}< 10{sup -6}) since an enormous number of time steps is required to represent the dynamics of the dominant neutral component with a time step determined by the trace ion component. Here we show that ambipolar diffusion calculations can be significantly accelerated by the 'heavy-ion approximation', in which the mass density of the ions is increased and the collisional coupling constant with the neutrals decreased such that the product remains constant. In this approximation, the ambipolar diffusion time and the ambipolar magnetic Reynolds number remain unchanged. We present three tests of the heavy-ion approximation: C-type shocks, the Wardle instability, and the 1D collapse of a magnetized slab. We show that this approximation is quite accurate provided that (1) the square of the Alfven Mach number is small compared to the ambipolar diffusion Reynolds number for dynamical problems, and that (2) the ion mass density is negligible for quasi-static problems; a specific criterion is given for the magnetized slab problem. The first condition can …
Date:
July 27, 2006
Creator:
Li, P; McKee, C & Klein, R
Object Type:
Article
System:
The UNT Digital Library
Development of a 2D Vlasov Solver for Single-Pass Systems
Direct numerical methods for solving the Vlasov equationoffer some advantages over macroparticle simulations, as they do notsuffer from the numerical noise inherent in using a number ofmacroparticles smaller than the bunch population. Unfortunately thesemethods are more time-consuming and generally considered impractical in afull 6D phase space. However, in a lower-dimension phase space they maybecome attractive if the beam dynamics is sensitive to the presence ofsmall charge-density fluctuations and a high resolution is needed. Inthis paper we present a 2D Vlasov solver for studying the longitudinalbeam dynamics in single-pass systems of interest for X-FEL's, wherecharacterization of the microbunching instability is of particularrelevance. The solver includes a model to account for the smearing effectof a finite horizontal emittance on microbuncing. We explore the effectof space charge and coherent synchrotron radiation (CSR). The numericalsolutions are compared with results from linear theory and good agreementis found in the regime where linear theory applies.
Date:
July 31, 2006
Creator:
Venturini, Marco; Warnock, Robert & Zholents, Alexander
Object Type:
Report
System:
The UNT Digital Library
Epigenetic reversion of breast carcinoma phenotype is accompanied by DNA sequestration
The importance of microenvironment and context in regulation of tissue-specific genes is finally well established. DNA exposure to, or sequestration from, nucleases can be used to detect differences in higher order chromatin structure in intact cells without disturbing cellular or tissue architecture. To investigate the relationship between chromatin organization and tumor phenotype, we utilized an established 3-D assay where normal and malignant human breast cells can be easily distinguished by the morphology of the structures they make (acinus-like vs tumor-like, respectively). We show that these phenotypes can be distinguished also by sensitivity to AluI digestion where the malignant cells are resistant to digestion relative to non-malignant cells. Reversion of the T4-2 breast cancer cells by either cAMP analogs, or a phospatidylinositol 3-kinase (P13K) inhibitor not only reverted the phenotype, but also the chromatin sensitivity to AluI. By using different cAMP-analogs, we show that the cAMP-induced phenotypic reversion, polarization, and shift in DNA organization act through a cAMP-dependent-protein-kinase A-coupled signaling pathway. Importantly, inhibitory antibody to fibronectin also reverted the malignant phenotype, polarized the acini, and changed chromatin sequestration. These experiments show not only that modifying the tumor microenvironment can alter the organization of tumor cells but also that architecture of the …
Date:
July 19, 2006
Creator:
Sandal, Tone; Valyi-Nagy, Klara; Spencer, Virginia A.; Folberg,Robert; Bissell, Mina J. & Maniotis, Andrew J.
Object Type:
Article
System:
The UNT Digital Library
Sustainable Building Rating Systems Summary
The purpose of this document is to offer information that could be used to compare and contrast sustainable building rating systems.
Date:
July 1, 2006
Creator:
Fowler, Kimberly M. & Rauch, Emily M.
Object Type:
Report
System:
The UNT Digital Library