Pathway confirmation and flux analysis of central metabolicpathways in Desulfovibrio vulgaris Hildenborough using gaschromatography-mass spectrometry and fourier transform-ion cyclotronresonance mass spectrometry (open access)

Pathway confirmation and flux analysis of central metabolicpathways in Desulfovibrio vulgaris Hildenborough using gaschromatography-mass spectrometry and fourier transform-ion cyclotronresonance mass spectrometry

It has been proposed that during growth under anaerobic oroxygen-limited conditions Shewanella oneidensis MR-1 uses theserine-isocitrate lyase pathway common to many methylotrophic anaerobes,in which formaldehyde produced from pyruvate is condensed with glycine toform serine. The serine is then transformed through hydroxypyruvate andglycerate to enter central metabolism at phosphoglycerate. To examine itsuse of the serine-isocitrate lyase pathway under anaerobic conditions, wegrew S. oneidensis MR-1 on [1-13C]lactate as the sole carbon source witheither trimethylamine N-oxide (TMAO) or fumarate as an electron acceptor.Analysis of cellular metabolites indicates that a large percentage(>75 percent) of lactate was partially oxidized to either acetate orpyruvate. The 13C isotope distributions in amino acids and other keymetabolites indicate that, under anaerobic conditions, a complete serinepathway is not present, and lactate is oxidized via a highly reversibleserine degradation pathway. The labeling data also suggest significantactivity in the anaplerotic (malic enzyme and phosphoenolpyruvatecarboxylase) and glyoxylate shunt (isocitrate lyase and malate synthase)reactions. Although the tricarboxylic acid (TCA) cycle is often observedto be incomplete in many other anaerobes (absence of 2-oxoglutaratedehydrogenase activity), isotopic labeling supports the existence of acomplete TCA cycle in S. oneidensis MR-1 under TMAO reductioncondition.
Date: July 11, 2006
Creator: Tang, Yinjie; Pingitore, Francesco; Mukhopadhyay, Aindrila; Phan,Richard; Hazen, Terry C. & Keasling, Jay D.
System: The UNT Digital Library
U.S. Aims for Zero-Energy: Support for PV on New Homes (open access)

U.S. Aims for Zero-Energy: Support for PV on New Homes

As a market segment for solar photovoltaic (PV) adoption, new homes have a number of attractive attributes. Homebuyers can easily roll the cost of the PV system into their mortgage and, with rebates or other financial incentives, potentially realize an immediate net positive cash flow from the investment. PV system performance can be optimized by taking roof orientation, shading, and other structural factors into account in the design of new homes. Building-integrated photovoltaics (BIPV), which are subject to fewer aesthetic concerns than traditional, rack-mounted systems, are well-suited to new construction applications. In large new residential developments, costs can be reduced through bulk purchases and scale economies in system design and installation. Finally, the ability to install PV as a standard feature in new developments - like common household appliances - creates an opportunity to circumvent the high transaction costs and other barriers typically confronted when each individual homeowner must make a distinct PV purchase decision.
Date: May 11, 2006
Creator: Barbose, Galen; Wiser, Ryan & Bolinger, Mark
System: The UNT Digital Library
On the electronic configuration in Pu: spectroscopy and theory (open access)

On the electronic configuration in Pu: spectroscopy and theory

Photoelectron spectroscopy, synchrotron-radiation-based x-ray absorption, electron energy-loss spectroscopy, and density-functional calculations within the mixed-level and magnetic models, together with canonical band theory have been used to study the electron configuration in Pu. These methods suggest a 5f{sup n} configuration for Pu of 5 {le} n < 6, with n {ne} 6, contrary to what has recently been suggested in several publications. We show that the n = 6 picture is inconsistent with the usual interpretation of photoemission and x-ray absorption spectra. Instead, these spectra support the traditional conjecture of a 5f{sup 5} configuration in Pu as is obtained by density-functional theory. We further argue, based on 5f-band filling, that an n = 6 hypothesis is incompatible with the position of Pu in the actinide series and its monoclinic ground-state phase.
Date: October 11, 2006
Creator: Tobin, J G; Soderlind, P; Landa, A; Moore, K T; Schwartz, A J; Chung, B W et al.
System: The UNT Digital Library
Study of Bunch Instabilities By the Nonlinear Vlasov-Fokker-Planck Equation (open access)

Study of Bunch Instabilities By the Nonlinear Vlasov-Fokker-Planck Equation

Instabilities of the bunch form in storage rings may be induced through the wake field arising from corrugations in the vacuum chamber, or from the wake and precursor fields due to coherent synchrotron radiation (CSR). For over forty years the linearized Vlasov equation has been applied to calculate the threshold in current for an instability, and the initial growth rate. Increasing interest in nonlinear aspects of the motion has led to numerical solutions of the nonlinear Vlasov equation, augmented with Fokker-Planck terms to describe incoherent synchrotron radiation in the case of electron storage rings. This opens the door to much deeper studies of coherent instabilities, revealing a rich variety of nonlinear phenomena. Recent work on this topic by the author and collaborators is reviewed.
Date: July 11, 2006
Creator: Warnock, Robert L.
System: The UNT Digital Library
Transverse momentum and centrality dependence of high-ptnon-photonic electron suppression in Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV (open access)

Transverse momentum and centrality dependence of high-ptnon-photonic electron suppression in Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV

The STAR collaboration at RHIC reports measurements of theinclusive yield of non-photonic electrons, which arise dominantly fromsemi-leptonic decays of heavy flavor mesons, over a broad range oftransverse momenta (1.2<pt<10 gevc) in pp, dAu, and AuAucollisions at sqrt sNN = 200 GeV. The non-photonic electron yieldexhibits unexpectedly large suppression in central AuAu collisions athigh pt, suggesting substantial heavy quark energy loss at RHIC. Thecentrality and \pt dependences of the suppression provide constraints ontheoretical models of suppression.
Date: July 11, 2006
Creator: Abelev, B. I.; Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D. et al.
System: The UNT Digital Library
Supersymmetry with Small mu: Connections between Naturalness, DarkMatter, and (Possibly) Flavor (open access)

Supersymmetry with Small mu: Connections between Naturalness, DarkMatter, and (Possibly) Flavor

Weak scale supersymmetric theories often suffer from several naturalness problems: the problems of reproducing the correct scale for electroweak symmetry breaking, the correct abundance for dark matter, and small rates for flavor violating processes. We argue that the first two problems point to particular regions of parameter space in models with weak scale supersymmetry: those with a small {mu} term. This has an interesting implication on direct dark matter detection experiments. We find that, if the signs of the three gaugino mass parameters are all equal, we can obtain a solid lower bound on the spin-independent neutralino-nucleon cross section, {sigma}{sub SI}. In the case that the gaugino masses satisfy the unified mass relations, we obtain {sigma}{sub SI} {approx}&gt; 4 x 10{sup -46} cm{sup 2} (1 x 10{sup -46} cm{sup 2}) for fine-tuning in electroweak symmetry breaking no worse than 10% (5%). We also discuss a possibility that the three problems listed above are all connected to the hierarchy of fermion masses. This occurs if supersymmetry breaking and electroweak symmetry breaking (the Higgs fields) are coupled to matter fields with similar hierarchical structures. The discovery of {mu} {yields} e transition processes in near future experiments is predicted in such a framework.
Date: June 11, 2006
Creator: Kitano, Ryuichiro Kitano & Nomura, Yasunori
System: The UNT Digital Library
Zinc Single Crystal Deformation Experiments using a "6 Degrees of Freedom" Apparatus (open access)

Zinc Single Crystal Deformation Experiments using a "6 Degrees of Freedom" Apparatus

A new experimental technique to study crystallographic slip system activity in metallic single crystals deformed under a condition of uniaxial stress is applied to study the behavior of Zn single crystals. The experimental apparatus allows essentially unconstrained shape change of inherently anisotropic materials under a condition of uniaxial stress by allowing 3 translational and 3 rotational degrees of freedom during compression; hence we have named the experiment 6 degrees of freedom (6DOF). The experiments also utilize a 3-D digital image correlation system to measure full-field displacement fields, which are used to calculate strain and make direct observations of slip system activity. We show that the experimental results associated with a pristine zinc single crystal are precisely consistent with the theoretical predicted shape change (sample distortion) assuming that the most favored slip system on the basal plane is the only one that is active. Another experiment was performed on a processed and annealed Zn single crystal to investigate slip that is inconsistent with the critical resolved shear stress (CRSS) theory. These experiments on zinc illustrate the ability of the 6DOF experiment, together with image correlation (IC) data, to measure slip system activity with a high degree of fidelity.
Date: May 11, 2006
Creator: Lassila, D. H.; LeBlanc, M. M. & Florando, J. N.
System: The UNT Digital Library
Half-life of 14O (open access)

Half-life of 14O

We have measured the half-life of 14O, a superallowed (0+\rightarrow 0+) \beta decay isotope. The 14O was produced by the12C(3He,n)14O reaction using a carbon aerogel target. A low-energy ionbeam of 14O was mass separated and implanted in a thin beryllium foil.The beta particles were counted with plastic scintillator detectors. Wefind \tau 1/2 = 70.696 +- 0.037\sigma. This result is 2.0\sigma higherthan an average value from six earlier experiments, but agrees moreclosely with the most recent previous measurment.
Date: January 11, 2006
Creator: Burke, Jason T.; Vetter, Paul A.; Freedman, Stuart J.; Fujikawa,Brian K. & Winter, Wesley T.
System: The UNT Digital Library
Real-Time Quadrupole Mass Spectrometer Analysis of Gas in Borehole Fluid Samples Acquired Using the U-Tube Sampling Methodology (open access)

Real-Time Quadrupole Mass Spectrometer Analysis of Gas in Borehole Fluid Samples Acquired Using the U-Tube Sampling Methodology

Sampling of fluids in deep boreholes is challenging becauseof the necessity to minimize external contamination and maintain sampleintegrity during recovery. The U-tube sampling methodology was developedto collect large volume, multiphase samples at in situ pressures. As apermanent or semi-permanent installation, the U-tube can be used forrapidly acquiring multiple samples or it may be installed for long-termmonitoring applications. The U-tube was first deployed in Liberty County,TX to monitor crosswell CO2 injection as part of the Frio CO2sequestration experiment. Analysis of gases (dissolved or separate phase)was performed in the field using a quadrupole mass spectrometer, whichserved as the basis for determining the arrival of the CO2 plume. Thepresence of oxygen and argon in elevated concentrations, along withreduced methane concentration, indicate sample alteration caused by theintroduction of surface fluids during borehole completion. Despiteproducing the well to eliminate non-native fluids, measurementsdemonstrate that contamination persists until the immiscible CO2injection swept formation fluid into the observationwellbore.
Date: January 11, 2006
Creator: Freifeld, Barry M. & Trautz, Robert C.
System: The UNT Digital Library
Rhamm-/- mice are defective in skin wound repair due to aberrantERK1,2 signaling in fibroblast migration (open access)

Rhamm-/- mice are defective in skin wound repair due to aberrantERK1,2 signaling in fibroblast migration

None
Date: September 11, 2006
Creator: Tolg, Cornelia; Hamilton, Sara R.; Nakrieko, Kari-Anne; Walton, Paul; McCarthy, James B.; Bissell, Mina J. et al.
System: The UNT Digital Library
High-Performance Corrosion-Resistant Iron-Based Amorphous Metals: The Effects of Composition, Structure and Environment on Corrosion Resistance (open access)

High-Performance Corrosion-Resistant Iron-Based Amorphous Metals: The Effects of Composition, Structure and Environment on Corrosion Resistance

New corrosion-resistant, iron-based amorphous metals have been identified from published data or developed through combinatorial synthesis, and tested to determine their relative thermal phase stability, microstructure, mechanical properties, damage tolerance, and corrosion resistance. Some alloy additions are known to promote glass formation and to lower the critical cooling rate [F. Guo, S. J. Poon, Applied Physics Letters, 83 (13) 2575-2577, 2003]. Other elements are known to enhance the corrosion resistance of conventional stainless steels and nickel-based alloys [A. I. Asphahani, Materials Performance, Vol. 19, No. 12, pp. 33-43, 1980] and have been found to provide similar benefits to iron-based amorphous metals. Many of these materials can be cast as relatively thick ingots, or applied as coatings with advanced thermal spray technology. A wide variety of thermal spray processes have been developed by industry, and can be used to apply these new materials as coatings. Any of these can be used for the deposition of the formulations discussed here, with varying degrees of residual porosity and crystalline structure. Thick protective coatings have now been made that are fully dense and completely amorphous in the as-sprayed condition. An overview of the High-Performance Corrosion Resistant Materials (HPCRM) Project will be given, with particular …
Date: April 11, 2006
Creator: Farmer, J; Choi, J S; Haslam, J; Lian, T; Day, S; Yang, N et al.
System: The UNT Digital Library
Dark Energy in the Dark Ages (open access)

Dark Energy in the Dark Ages

Non-negligible dark energy density at high redshifts would indicate dark energy physics distinct from a cosmological constant or&quot;reasonable'&quot; canonical scalar fields. Such dark energy can be constrained tightly through investigation of the growth of structure, with limits of&lt;~;;2percent of total energy density at z&gt;&gt; 1 for many models. Intermediate dark energy can have effects distinct from its energy density; the dark ages acceleration can be constrained to last less than 5percent of a Hubble e-fold time, exacerbating the coincidence problem. Both the total linear growth, or equivalently sigma 8, and the shape and evolution of the nonlinear mass power spectrum for z&lt;2 (using the Linder-White nonlinear mapping prescription) provide important windows. Probes of growth, such as weak gravitational lensing, can interact with supernovae and CMB distance measurements to scan dark energy behavior over the entire range z=0-1100.
Date: April 11, 2006
Creator: Linder, Eric V.
System: The UNT Digital Library
From Question Answering to Visual Exploration (open access)

From Question Answering to Visual Exploration

Research in Question Answering has focused on the quality of information retrieval or extraction using the metrics of precision and recall to judge success; these metrics drive toward finding the specific best answer(s) and are best supportive of a lookup type of search. These do not address the opportunity that users? natural language questions present for exploratory interactions. In this paper, we present an integrated Question Answering environment that combines a visual analytics tool for unstructured text and a state-of-the-art query expansion tool designed to compliment the cognitive processes associated with an information analysts work flow. Analysts are seldom looking for factoid answers to simple questions; their information needs are much more complex in that they may be interested in patterns of answers over time, conflicting information, and even related non-answer data may be critical to learning about a problem or reaching prudent conclusions. In our visual analytics tool, questions result in a comprehensive answer space that allows users to explore the variety within the answers and spot related information in the rest of the data. The exploratory nature of the dialog between the user and this system requires tailored evaluation methods that better address the evolving user goals and …
Date: August 11, 2006
Creator: McColgin, Dave W.; Gregory, Michelle L.; Hetzler, Elizabeth G. & Turner, Alan E.
System: The UNT Digital Library
The Dark Matter Halos of Massive, Relaxed Galaxy Clusters Observed With Chandra (open access)

The Dark Matter Halos of Massive, Relaxed Galaxy Clusters Observed With Chandra

We use the Chandra X-ray Observatory to study the dark matter halos of 34 massive, dynamically relaxed galaxy clusters, spanning the redshift range 0.06 &lt; z &lt; 0.7. The observed dark matter and total mass (dark-plus-luminous matter) profiles can be approximated by the Navarro Frenk & White (hereafter NFW) model for cold dark matter (CDM) halos; for {approx} 80 percent of the clusters, the NFW model provides a statistically acceptable fit. In contrast, the singular isothermal sphere model can, in almost every case, be completely ruled out. We observe a well-defined mass-concentration relation for the clusters with a normalization and intrinsic scatter in good agreement with the predictions from simulations. The slope of the mass-concentration relation, c {infinity} M{sub vir}{sup a}/(1 + z){sup b} with a = -0.41 {+-} 0.11 at 95 percent confidence, is steeper than the value a {approx} -0.1 predicted by CDM simulations for lower mass halos. With the slope a included as a free fit parameter, the redshift evolution of the concentration parameter, b = 0.54 {+-} 0.47 at 95 percent confidence, is also slower than, but marginally consistent with, the same simulations (b {approx} 1). Fixing a {approx} -0.1 leads to an apparent evolution that …
Date: October 11, 2006
Creator: Schmidt, Robert W.; /Heidelberg, Astron. Rechen Inst.; Allen, S.W. & /KIPAC, Menlo Park
System: The UNT Digital Library
2005 Quantum Control of Light and Matter - Conference July 31 - August 5, 2005 (open access)

2005 Quantum Control of Light and Matter - Conference July 31 - August 5, 2005

This report is about Quantum Control of Light and Matter Gordon Research Conference
Date: September 11, 2006
Creator: Corkum, Paul B.
System: The UNT Digital Library
An Analysis of Shot Noise Propagation and Amplificationin Harmonic Cascade FELs (open access)

An Analysis of Shot Noise Propagation and Amplificationin Harmonic Cascade FELs

The harmonic generation process in a harmonic cascade (HC) FEL is subject to noise degradation which is proportional to the square of the total harmonic order. In this paper, we study the shot noise evolution in the first-stage modulator and radiator of a HC FEL that produces the dominant noise contributions. We derive the effective input noise for a modulator operating in the low-gain regime, and analyze the radiator noise for a density-modulated beam. The significance of these noise sources in different harmonic cascade designs is also discussed.
Date: December 11, 2006
Creator: Huang, Z.
System: The UNT Digital Library
2006 Multiphoton Processes Gordon Conference - June 11-16 (open access)

2006 Multiphoton Processes Gordon Conference - June 11-16

The first Gordon Research Conference on Multiphoton Processes, was held in 1982. The meeting continues to evolve as it embraces both the rapid technological and intellectual growth in the field as well as the multi-disciplinary expertise of the participants. Current areas of interest include: (1) Ionization/Dissociation of Atoms and Molecules in Intense Laser Fields; (2) Frequency Domain Multi-Photon and Multiple-Resonance Spectroscopies of Molecules; (3) Time-Resolved Photoelectron Spectroscopy; (4) Ultrafast Pump-Probe Spectroscopy; (5) Coherent Strong-Field Manipulation of Atoms and Molecules; (6) High-Harmonic Generation; (7) Attosecond Pulse Generation and Measurement; and (8) Super-Intense Laser-Matter Interactions. In developing the program, the conference organizers will strive to blur traditional disciplinary boundaries, involving chemists, physicists, and optical engineers, representing both experiment and theory, as presenters and discussion leaders. The broad range of expertise and different perspectives of attendees should provide a stimulating and unique environment for solving problems and developing new ideas in this rapidly evolving field.
Date: June 11, 2006
Creator: Jones, Robert Rivers
System: The UNT Digital Library
IN SITU INVESTIGATION OF THE PASSIVATION OF ALLOY C22 AND OF THE PASSIVE FILMS FORMED ON ALLOY C22 IN ACIDIC ELECTROLYTES AT ROOM TEMPERATURE AND AT 90 DEGREES C (open access)

IN SITU INVESTIGATION OF THE PASSIVATION OF ALLOY C22 AND OF THE PASSIVE FILMS FORMED ON ALLOY C22 IN ACIDIC ELECTROLYTES AT ROOM TEMPERATURE AND AT 90 DEGREES C

The passive films formed on Alloy C22 in several acidic solutions were investigated by a combination of five in situ techniques: cyclic polarization, electrochemical impedance spectroscopy, Mott-Schottky analyses, electrochemical quartz crystal microbalance measurements, and surface enhanced Raman spectroscopy. Similar tests were conducted on unalloyed samples of nickel, chromium and molybdenum, which are the main alloying elements of Alloy C22. The results of the tests conducted on nickel, chromium, and molybdenum helped to determine the roles of these elements in the passivation of Alloy C22. In general, the corrosion resistance of C22 was superior to that of unalloyed chromium. Although chromium is an important component of the passive film on Alloy C22, the other elements figure prominently in the corrosion resistance of C22 in acidic solutions. The passivity of Alloy C22 was detrimentally affected by increasing concentrations of hydrogen ions, chloride ions, and increasing temperature. The results of this study provide understanding of the resistance/susceptibility of Alloy C22 to corrosion by the aggressive solutions that can develop inside pits and crevices.
Date: March 11, 2006
Creator: M. Miyagusuku, S. Harrington, and T. M. Devine
System: The UNT Digital Library
Blind Analysis in Nuclear and Particle Physics (open access)

Blind Analysis in Nuclear and Particle Physics

None
Date: August 11, 2006
Creator: Klein, J.R.; U., /Texas & Roodman, A.
System: The UNT Digital Library
Comparison of the Acceptability of Various Oil Shale Processes (open access)

Comparison of the Acceptability of Various Oil Shale Processes

While oil shale has the potential to provide a substantial fraction of our nation's liquid fuels for many decades, cost and environmental acceptability are significant issues to be addressed. Lawrence Livermore National Laboratory (LLNL) examined a variety of oil shale processes between the mid 1960s and the mid 1990s, starting with retorting of rubble chimneys created from nuclear explosions [1] and ending with in-situ retorting of deep, large volumes of oil shale [2]. In between, it examined modified-in-situ combustion retorting of rubble blocks created by conventional mining and blasting [3,4], in-situ retorting by radio-frequency energy [5], aboveground combustion retorting [6], and aboveground processing by hot-solids recycle (HRS) [7,8]. This paper reviews various types of processes in both generic and specific forms and outlines some of the tradeoffs for large-scale development activities. Particular attention is given to hot-recycled-solids processes that maximize yield and minimize oil shale residence time during processing and true in-situ processes that generate oil over several years that is more similar to natural petroleum.
Date: March 11, 2006
Creator: Burnham, A K & McConaghy, J R
System: The UNT Digital Library
An improved strategy to detect CO2 leakage for verification ofgeologic carbon sequestration (open access)

An improved strategy to detect CO2 leakage for verification ofgeologic carbon sequestration

To detect and quantify subtle surface CO2 leakage signals, we present a strategy that combines measurements of CO2 fluxes or concentrations in the near-surface environment with an algorithm that enhances temporally- and spatially-correlated leakage signals while suppressing random background noise. The algorithm consists of a filter that highlights spatial coherence in the leakage signal, and temporal stacking (averaging) that reduces noise from temporally uncorrelated background fluxes/concentrations. We assess the performance of our strategy using synthetic data sets in which the surface leakage signal is either specified directly or calculated using flow and transport simulations of leakage source geometries one might expect to be present at sequestration sites. We estimate the number of measurements required to detect a potential CO2 leakage signal of given magnitude and area. Results show that given a rigorous field-sampling program, subtle CO2 leakage may be detected using the algorithm; however, leakage of very limited spatial extent or exceedingly small magnitude may be difficult to detect with a reasonable set of monitoring resources.
Date: May 11, 2006
Creator: Lewicki, Jennifer L.; Hilley, George E. & Oldenburg, Curtis M.
System: The UNT Digital Library
Beam Interaction Measurements with a Retarding Field Analyzer in a High-Current High-Vacuum Positively-Charged Particle Accelerator (open access)

Beam Interaction Measurements with a Retarding Field Analyzer in a High-Current High-Vacuum Positively-Charged Particle Accelerator

A Retarding Field Analyzer (RFA) was inserted in a drift region of a magnetic transport section of the high-current experiment (HCX) that is at high-vacuum to measure ions and electrons resulting from beam interaction with background gas and walls. The ions are expelled during the beam by the space-charge potential and the electrons are expelled mainly at the end of the beam, when the beam potential decays. The ion energy distribution shows the beam potential of {approx} 2100 V and the beam-background gas total cross-section of 1.6x10{sup -20} m{sup 2}. The electron energy distribution reveals that the expelled electrons are mainly desorbed from the walls and gain {approx} 22 eV from the beam potential decaying with time before entering the RFA. Details of the RFA design and of the measured energy distributions are presented and discussed.
Date: July 11, 2006
Creator: Covo, M. K.; Molvik, A. W.; Friedman, A.; Barnard, J. J.; Seidl, P. A.; Logan, B. G. et al.
System: The UNT Digital Library
Kinetics of PBX9404 Aging (open access)

Kinetics of PBX9404 Aging

PBX 9404 is an early formulation of HMX from which we can learn about the effects of aging in the weapons stockpile. Of particular interest is the presence of 3% nitrocellulose in PBX 9404 as an energetic binder. Nitrocellulose is used pervasively in smokeless gunpowders and was formerly used extensively in the film and art preservation industries. It is well known that nitrocellulose decomposes autocatalytically, and stabilizers, such as the diphenylamine used in PBX 9404, are used to retard its decomposition. Even so, its lifetime is still limited, and the reactions eventually leading to catastrophic autocatalysis are still not understood well despite years of work. In addition to reducing the available energy in the explosive, degradation of nitrocellulose affects the mechanical properties of the pressed PBX 9404 parts by the associated reduction in molecular weight, which reduces the strength of the binder. A structural formula for a monomer of the nitrocellulose used in PBX 9404 is shown. The initial nitration level is 2.3 of 3.0 possible sites, and they have different reactivities. Degradation of nitrocellulose affects many properties. As an aid in examining historical chemical analysis data, several measures of degradation are given for the simple replacement of a nitro …
Date: September 11, 2006
Creator: Burnham, A K & Fried, L E
System: The UNT Digital Library
State Compensation: A No-cost Scheme for Scalable Failure Recovery in Tree-based Overlay Networks (open access)

State Compensation: A No-cost Scheme for Scalable Failure Recovery in Tree-based Overlay Networks

Tree-based overlay networks (TB{bar O}Ns) have become important for scalable data multicast and aggregation. This infrastructure's generality has lead to widespread usage in large scale and widely distributed environments--environments in which reliability must be addressed. This paper presents state compensation, a novel reliability concept for TB{bar O}N environments that avoids explicit state replication (such as checkpoints) for failure recovery by leveraging general properties of TB{bar O}N computations that allow computational state from non-failed processes to compensate for state lost from failed ones. In this paper, we present our state compensation mechanisms, prove sufficient properties of distributed computations that make these mechanisms feasible and show how to derive computation-specific recovery primitives from these properties. We also present a case study of the recovery process. The result is a general TB{bar O}N recovery model that requires no additional storage, network, or computational resources during normal operation.
Date: July 11, 2006
Creator: Arnold, D C & Miller, B P
System: The UNT Digital Library