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1

Evaluation of thermal control materials degradation in simulated space environment  

NASA Astrophysics Data System (ADS)

Indian Space Research Organisation (ISRO) has been actively pursuing research and development of a host of materials to be used for its satellite and launch vehicle programs. A variety of thermal control materials have been developed in-house for use in 10-15 years in the LEO and GEO orbits. The present study was carried out [1] to evaluate the effect of synergistic radiation on the thermal control materials and verify the assumptions of BOL and EOL values of materials including White paints, second-surface mirrors, aluminized films of polyimide and polyester, White anodisation and Germanium tapes. The space environment simulation using UV, protons and electrons was carried out at ONERA using a combined radiation test facility. A long term test extending to over three months in vacuum was performed to simulate a three years exposure on the N-S panels in the geostationary orbit for a three axis stabilized spacecraft. Reflectance spectra were measured in-situ in the solar range (250-2500 nm) enabling the evaluation of initial air to vacuum transition effects and the final transition (nitrogen and air exposure effects). This is in addition to the investigation of the UV and particulate radiation induced degradation over three years, measured by steps of 0.5 year. Little spectral water desorption effect occurred during initial transition whereas large bleaching of degradation happened (e.g. in white paint) when the first nitrogen inlet was permitted during return to ambient atmospheric pressure. This bleaching effect increased on exposure to air and continued for one week. Specific spectral bleaching of degradations were observed in the infrared on some samples where UV provoked bleaching of previous step particles degradation. The solar absorptance values were deduced from the reflectance data. The degradation has been observed most in white paints and white anodisation while the second surface mirrors and aluminium paint have been quite stable. Empiric degradation models have been applied on the most degraded materials to extrapolate the degradation for long duration exposure. To complete the thermo-optical properties investigations, infrared emissivity measurements were performed in air at the beginning and end of test showing a good stability, except in the case of polyimide and FEP based thermal control materials.

Marco, J.; Bhojaraj, H.; Hulyal, R.

2003-09-01

2

Study of balloon and thermal control material degradation aboard LDEF  

NASA Technical Reports Server (NTRS)

The initial results of analysis performed on a number of polymeric materials which were exposed aboard the Long Duration Exposure Facility (LDEF) are discussed. These materials include two typical high altitude balloon films (a polyester and a polyethylene) and silver-backed Teflon from thermal control blanket samples. The techniques used for characterizing changes in mechanical properties, chemical structure and surface morphology include Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy, and dynamic mechanical analysis.

Letton, Alan; Rock, Neil I.; Williams, Kevin D.; Strganac, Thomas

1991-01-01

3

Semiconductor CMP Process Control Predicting Degradation Effect of Consumed Materials  

NASA Astrophysics Data System (ADS)

This paper describes a methodology to build a virtual metrology (VM) model for semiconductor chemical mechanical polishing (CMP) process control. The VM model predicts the polishing rate based on equipment-derived data as soon as allowed, and immediately applies the results to advanced process control (APC). The proposed methodology uses Markov chain Monte Carlo (MCMC) methods to build an analytical model with many parameters for individual consumed materials from historical data in small quantities. The mutual interference of two kinds of consumed materials: dresser and pad are modeled in a form of multilevel predictive model. The methodology uses MCMC methods again to identify the multilevel predictive model taking into account the assumed operation of an actual manufacturing line, for instance, using preliminary test result, learning a model parameter online, and being affected by metrology lag as disturbance. The simulation results show the APC with the proposed VM model is low sensitivity to metrology lag and high precision on polishing amount control.

Tamaki, Kenji; Kaneko, Shun'ichi

4

Degradation of Hubble Space Telescope Metallized Teflon(trademark) FEP Thermal Control Materials  

NASA Technical Reports Server (NTRS)

The mechanical and optical properties of the metallized Teflon Fluorinated Ethylene Propylene (FEP) thermal control materials on the Hubble Space Telescope (HST) have degraded over the seven years the telescope has been in orbit. Astronaut observations and photographic documentation from the Second Servicing Mission revealed severe cracks of the multi-layer insulation (MLI) blanket outer layer in many locations around the telescope, particularly on solar facing surfaces. Two samples, the outer Teflon FEP MLI layer and radiator surfaces, were characterized post- mission through exhaustive mechanical, thermal, chemical, and optical testing. The observed damage to the thermal control materials, the sample retrieval and handling, and the significant changes to the radiator surfaces of HST will be discussed. Each of these issues is addressed with respect to current and future mission requirements.

Hansen, Patricia A.; Townsend, Jacqueline A.; Yoshikawa, Yukio; Castro, J. David; Triolo, Jack J.; Peters, Wanda C.

1998-01-01

5

Final report for the designed synthesis of controlled degradative materials LDRD  

SciTech Connect

The main goal of this research was to develop degradable systems either by developing weaklink-containing polymers or identifying commercial polymeric systems which are easily degraded. In both cases, the degradation method involves environmentally friendly chemistries. The weaklinks are easily degradable fragments which are introduced either randomly or regularly in the polymer backbone or as crosslinking sites to make high molecular weight systems via branching. The authors targeted three general application areas: (1) non-lethal deterrents, (2) removable encapsulants, and (3) readily recyclable/environmentally friendly polymers for structural and thin film applications.

LOY,DOUGLAS A.; ULIBARRI,TAMARA A.; CURRO,JOHN G.; SAUNDERS,R.; DERZON,DORA K.; GUESS,TOMMY R.; BAUGHER,B.M.

2000-02-01

6

Balloon materials degradation (S1006)  

NASA Technical Reports Server (NTRS)

The objective of this experiment is to assess the effects of long-term exposure of candidate balloon films, tapes, and lines to the hostile environment above the Earth's atmosphere. Degradation of mechanical and radiometric properties will be observed by a series of tests on exposed materials. The experiment is passive and will test candidate balloon films, tapes, and lines. The experiment will occupy one-third of a 3-in.-deep peripheral tray. Two additional identical sets of material will be prepared. The first set will be tested immediately and the second will be held in a controlled environment until the recovery of the samples placed on orbit. Tests will then be performed on this second set to determine any effects of aging. The specimens that are recovered from the Long Duration Exposure Facility will also be tested and the effects of long-duration exposure noted. In addition to these specimens, another set of specimens will be exposed at an accelerated exposure facility and the results will be compared with those of specimens exposed in situ.

Allen, D. H.

1984-01-01

7

Methods for degrading lignocellulosic materials  

DOEpatents

The present invention relates to methods for degrading a lignocellulosic material, comprising: treating the lignocellulosic material with an effective amount of one or more cellulolytic enzymes in the presence of at least one surfactant selected from the group consisting of a secondary alcohol ethoxylate, fatty alcohol ethoxylate, nonylphenol ethoxylate, tridecyl ethoxylate, and polyoxyethylene ether, wherein the presence of the surfactant increases the degradation of lignocellulosic material compared to the absence of the surfactant. The present invention also relates to methods for producing an organic substance, comprising: (a) saccharifying a lignocellulosic material with an effective amount of one or more cellulolytic enzymes in the presence of at least one surfactant selected from the group consisting of a secondary alcohol ethoxylate, fatty alcohol ethoxylate, nonylphenol ethoxylate, tridecyl ethoxylate, and polyoxyethylene ether, wherein the presence of the surfactant increases the degradation of lignocellulosic material compared to the absence of the surfactant; (b) fermenting the saccharified lignocellulosic material of step (a) with one or more fermenting microorganisms; and (c) recovering the organic substance from the fermentation.

Vlasenko, Elena (Davis, CA); Cherry, Joel (Davis, CA); Xu, Feng (Davis, CA)

2011-05-17

8

Methods for degrading lignocellulosic materials  

DOEpatents

The present invention relates to methods for degrading a lignocellulosic material, comprising: treating the lignocellulosic material with an effective amount of one or more cellulolytic enzymes in the presence of at least one surfactant selected from the group consisting of a secondary alcohol ethoxylate, fatty alcohol ethoxylate, nonylphenol ethoxylate, tridecyl ethoxylate, and polyoxyethylene ether, wherein the presence of the surfactant increases the degradation of lignocellulosic material compared to the absence of the surfactant. The present invention also relates to methods for producing an organic substance, comprising: (a) saccharifying a lignocellulosic material with an effective amount of one or more cellulolytic enzymes in the presence of at least one surfactant selected from the group consisting of a secondary alcohol ethoxylate, fatty alcohol ethoxylate, nonylphenol ethoxylate, tridecyl ethoxylate, and polyoxyethylene ether, wherein the presence of the surfactant increases the degradation of lignocellulosic material compared to the absence of the surfactant; (b) fermenting the saccharified lignocellulosic material of step (a) with one or more fermentating microoganisms; and (c) recovering the organic substance from the fermentation.

Vlasenko, Elena (Davis, CA); Cherry, Joel (Davis, CA); Xu, Feng (Davis, CA)

2008-04-08

9

Degradation of FEP thermal control materials returned from the Hubble Space Telescope  

NASA Technical Reports Server (NTRS)

After an initial 3.6 years of space flight, the Hubble Space Telescope was serviced through a joint effort with the NASA and the European Space Agency. Multi-layer insulation (MLI) was retrieved from the electronics boxes of the two magnetic sensing systems (MSS), also called the magnetometers, and from the returned solar array (SA-I) drive arm assembly. The top layer of each MLI assembly is fluorinated ethylene propylene (FEP, a type of Teflon). Dramatic changes in material properties were observed when comparing areas of high solar fluence to areas of low solar fluence. Cross sectional analysis shows atomic oxygen (AO) erosion values up to 25.4 mu m (1 mil). Greater occurrences of through-thickness cracking and surface microcracking were observed in areas of high solar exposure. Atomic force microscopy (AFM) showed increases in surface microhardness measurements with increasing solar exposure. Decreases in FEP tensile strength and elongation were measured when compared to non-flight material. Erosion yield and tensile results are compared with FEP data from the Long Duration Exposure Facility. AO erosion yield data, solar fluence values, contamination, micrometeoroid or debris impact sites, and optical properties are presented.

Zuby, Thomas M.; Degroh, Kim K.; Smith, Daniela C.

1995-01-01

10

Material Corrion/Degradation Database  

SciTech Connect

The corrosion of a variety of structural metals and materials is presented. Data on specific material--and for well-studied agents--has been abstracted from the corrosion literature. In addition, limited data on one superacid (so-called ''Magic Acid,'' a mixture of 100% fluorosulfonic acid, HSO{sub 3}F, with 25% (w/w) of antimony pentafluoride (SbF{sub 5}) added) is tabulated.

Kinkead, S.A.

1999-07-08

11

Elastomer degradation sensor using a piezoelectric material  

DOEpatents

A method and apparatus for monitoring the degradation of elastomeric materials is provided. Piezoelectric oscillators are placed in contact with the elastomeric material so that a forced harmonic oscillator with damping is formed. The piezoelectric material is connected to an oscillator circuit,. A parameter such as the resonant frequency, amplitude or Q value of the oscillating system is related to the elasticity of the elastomeric material. Degradation of the elastomeric material causes changes in its elasticity which, in turn, causes the resonant frequency, amplitude or Q of the oscillator to change. These changes are monitored with a peak height monitor, frequency counter, Q-meter, spectrum analyzer, or other measurement circuit. Elasticity of elastomers can be monitored in situ, using miniaturized sensors.

Olness, Dolores U. (Livermore, CA); Hirschfeld, deceased, Tomas B. (late of Livermore, CA)

1990-01-01

12

Self-degradable Cementitious Sealing Materials  

SciTech Connect

A self-degradable alkali-activated cementitious material consisting of a sodium silicate activator, slag, Class C fly ash, and sodium carboxymethyl cellulose (CMC) additive was formulated as one dry mix component, and we evaluated its potential in laboratory for use as a temporary sealing material for Enhanced Geothermal System (EGS) wells. The self-degradation of alkali-activated cementitious material (AACM) occurred, when AACM heated at temperatures of {ge}200 C came in contact with water. We interpreted the mechanism of this water-initiated self-degradation as resulting from the in-situ exothermic reactions between the reactants yielded from the dissolution of the non-reacted or partially reacted sodium silicate activator and the thermal degradation of the CMC. The magnitude of self-degradation depended on the CMC content; its effective content in promoting degradation was {ge}0.7%. In contrast, no self-degradation was observed from CMC-modified Class G well cement. For 200 C-autoclaved AACMs without CMC, followed by heating at temperatures up to 300 C, they had a compressive strength ranging from 5982 to 4945 psi, which is {approx}3.5-fold higher than that of the commercial Class G well cement; the initial- and final-setting times of this AACM slurry at 85 C were {approx}60 and {approx}90 min. Two well-formed crystalline hydration phases, 1.1 nm tobermorite and calcium silicate hydrate (I), were responsible for developing this excellent high compressive strength. Although CMC is an attractive, as a degradation-promoting additive, its addition to both the AACM and the Class G well cement altered some properties of original cementitious materials; among those were an extending their setting times, an increasing their porosity, and lowering their compressive strength. Nevertheless, a 0.7% CMC-modified AACM as self-degradable cementitious material displayed the following properties before its breakdown by water; {approx}120 min initial- and {approx}180 min final-setting times at 85 C, and 1825 to 1375 psi compressive strength with 51.2 to 55.0% porosity up to 300 C.

Sugama, T.; Butcher, T., Lance Brothers, Bour, D.

2010-10-01

13

Designing degradable hydrogels for orthogonal control of cell microenvironments  

PubMed Central

Degradable and cell-compatible hydrogels can be designed to mimic the physical and biochemical characteristics of native extracellular matrices and provide tunability of degradation rates and related properties under physiological conditions. Hence, such hydrogels are finding widespread application in many bioengineering fields, including controlled bioactive molecule delivery, cell encapsulation for controlled three-dimensional culture, and tissue engineering. Cellular processes, such as adhesion, proliferation, spreading, migration, and differentiation, can be controlled within degradable, cell-compatible hydrogels with temporal tuning of biochemical or biophysical cues, such as growth factor presentation or hydrogel stiffness. However, thoughtful selection of hydrogel base materials, formation chemistries, and degradable moieties is necessary to achieve the appropriate level of property control and desired cellular response. In this review, hydrogel design considerations and materials for hydrogel preparation, ranging from natural polymers to synthetic polymers, are overviewed. Recent advances in chemical and physical methods to crosslink hydrogels are highlighted, as well as recent developments in controlling hydrogel degradation rates and modes of degradation. Special attention is given to spatial or temporal presentation of various biochemical and biophysical cues to modulate cell response in static (i.e., non-degradable) or dynamic (i.e., degradable) microenvironments. This review provides insight into the design of new cell-compatible, degradable hydrogels to understand and modulate cellular processes for various biomedical applications. PMID:23609001

Kharkar, Prathamesh M.

2013-01-01

14

Materials Degradation in Light Water Reactors: Life After 60,???  

SciTech Connect

Nuclear reactors present a very harsh environment for components service. Components within a reactor core must tolerate high temperature water, stress, vibration, and an intense neutron field. Degradation of materials in this environment can lead to reduced performance, and in some cases, sudden failure. A recent EPRI-led study interviewed 47 US nuclear utility executives to gauge perspectives on long-term operation of nuclear reactors. Nearly 90% indicated that extensions of reactor lifetimes to beyond 60 years were likely. When polled on the most challenging issues facing further life extension, two-thirds cited plant reliability as the key issue with materials aging and cable/piping as the top concerns for plant reliability. Materials degradation within a nuclear power plant is very complex. There are many different types of materials within the reactor itself: over 25 different metal alloys can be found with can be found within the primary and secondary systems, not to mention the concrete containment vessel, instrumentation and control, and other support facilities. When this diverse set of materials is placed in the complex and harsh environment coupled with load, degradation over an extended life is indeed quite complicated. To address this issue, the USNRC has developed a Progressive Materials Degradation Approach (NUREG/CR-6923). This approach is intended to develop a foundation for appropriate actions to keep materials degradation from adversely impacting component integrity and safety and identify materials and locations where degradation can reasonably be expected in the future. Clearly, materials degradation will impact reactor reliability, availability, and potentially, safe operation. Routine surveillance and component replacement can mitigate these factors, although failures still occur. With reactor life extensions to 60 years or beyond or power uprates, many components must tolerate the reactor environment for even longer times. This may increase susceptibility for most components and may introduce new degradation modes. While all components (except perhaps the reactor vessel) can be replaced, it may not be economically favorable. Therefore, understanding, controlling, and mitigating materials degradation processes are key priorities for reactor operation, power uprate considerations, and life extensions. This document is written to give an overview of some of the materials degradation issues that may be key for extend reactor service life. A detailed description of all the possible forms of degradation is beyond the scope of this short paper and has already been described in other documents (for example, the NUREG/CR-6923). The intent of this document is to present an overview of current materials issues in the existing reactor fleet and a brief analysis of the potential impact of extending life beyond 60 years. Discussion is presented in six distinct areas: (1) Reactor pressure vessel; (2) Reactor core and primary systems; (3) Reactor secondary systems; (4) Weldments; (5) Concrete; and (6) Modeling and simulations. Following each of these areas, some research thrust directions to help identify and mitigate lifetime extension issues are proposed. Note that while piping and cabling are important for extended service, these components are discussed in more depth in a separate paper. Further, the materials degradation issues associated with fuel cladding and fuel assemblies are not discussed in this section as these components are replaced periodically and will not influence the overall lifetime of the reactor.

Busby, Jeremy T [ORNL; Nanstad, Randy K [ORNL; Stoller, Roger E [ORNL; Feng, Zhili [ORNL; Naus, Dan J [ORNL

2008-04-01

15

Dedication to Degradation: The Beauty of Materials Designed to Lay in Ruin  

NASA Astrophysics Data System (ADS)

Degradation of materials is typically perceived to be a negative response in service. Many designs, and materials, have been and are ruined due to corrosion, fatigue, weathering, ultraviolet light, fungal attack, bacterial attack, erosion, wear, electromigration… and on the list goes. However, the carefully controlled and purposeful degradation of materials is a prerequisite for success for some designs—and such ability is a beautiful necessity when it comes to many regenerative biomaterials. In other instances, we must seek first to understand the degradation mechanisms before we can achieve degradation prevention—and the resistance of some materials to degradation is also beautiful. Regardless of whether we try to prevent or elicit degradation, our dedication to degradation of materials is ever present in materials design.

Nychka, John A.; Kruzic, Jaime

2014-04-01

16

Characterization of thermally degraded energetic materials  

SciTech Connect

Characterization of the damage state of a thermally degraded energetic material (EM) is a critical first step in understanding and predicting cookoff behavior. Unfortunately, the chemical and mechanical responses of heated EMs are closely coupled, especially if the EM is confined. The authors have examined several EMs in small-scale experiments (typically 200 mg) heated in both constant-volume and constant-load configurations. Fixtures were designed to minimize free volume and to contain gas pressures to several thousand psi. The authors measured mechanical forces or displacements that correlated to thermal expansion, phase transitions, material creep and gas pressurization as functions of temperature and soak time. In addition to these real-time measurements, samples were recovered for postmortem examination, usually with scanning electron microscopy (SEM) and chemical analysis. The authors present results on EMs (HMX and TATB), with binders (e.g., PBX 9501, PBX 9502, LX-14) and propellants (Al/AP/HTPB).

Renlund, A.M.; Miller, J.C.; Trott, W.M.; Erickson, K.L.; Hobbs, M.L.; Schmitt, R.G.; Wellman, G.W.; Baer, M.R.

1997-12-31

17

Tuning the Degradation Profiles of Poly(l-lactide)-Based Materials through Miscibility  

PubMed Central

The effective use of biodegradable polymers relies on the ability to control the onset of and time needed for degradation. Preferably, the material properties should be retained throughout the intended time frame, and the material should degrade in a rapid and controlled manner afterward. The degradation profiles of polyester materials were controlled through their miscibility. Systems composed of PLLA blended with poly[(R,S)-3-hydroxybutyrate] (a-PHB) and polypropylene adipate (PPA) with various molar masses were prepared through extrusion. Three different systems were used: miscible (PLLA/a-PHB5 and PLLA/a-PHB20), partially miscible (PLLA/PPA5/comp and PLLA/PPA20/comp), and immiscible (PLLA/PPA5 and PLLA/PPA20) blends. These blends and their respective homopolymers were hydrolytically degraded in water at 37 °C for up to 1 year. The blends exhibited entirely different degradation profiles but showed no diversity between the total degradation times of the materials. PLLA presented a two-stage degradation profile with a rapid decrease in molar mass during the early stages of degradation, similar to the profile of PLLA/a-PHB5. PLLA/a-PHB20 presented a single, constant linear degradation profile. PLLA/PPA5 and PLLA/PPA20 showed completely opposing degradation profiles relative to PLLA, exhibiting a slow initial phase and a rapid decrease after a prolonged degradation time. PLLA/PPA5/comp and PLLA/PPA20/comp had degradation profiles between those of the miscible and the immiscible blends. The molar masses of the materials were approximately the same after 1 year of degradation despite their different profiles. The blend composition and topographical images captured at the last degradation time point demonstrate that the blending component was not leached out during the period of study. The hydrolytic stability of degradable polyester materials can be tailored to obtain different and predetermined degradation profiles for future applications. PMID:24279455

2013-01-01

18

Controlling the radiation degradation of carboxymethylcellulose solution  

Microsoft Academic Search

In this study, the effects of an irradiation on the viscosity of the carboxymethylcellulose (CMC) solution were investigated, and the methods to control the degradation of the CMC caused by an irradiation were developed. The viscosity of the CMC solution was decreased with an increase in the irradiation dose, but the extent of the degradation by an irradiation was found

Jong-il Choi; Hee Sub Lee; Jae-Hun Kim; Kwang-Won Lee; Ju-Woon Lee; Seog-jin Seo; Ke Won Kang; Myung-Woo Byun

2008-01-01

19

O-atom degradation mechanisms of materials  

NASA Technical Reports Server (NTRS)

The low Earth orbit environment is described and the critical issues relating to oxygen atom degradation are discussed. Some analytic techniques for studying the problem and preliminary results on the underlying degradation mechanisms are presented.

Coulter, Daniel R.; Liang, Ranty H.; Chung, Shirley Y.; Smith, Keri Oda; Gupta, Amitava

1987-01-01

20

Degradation and acute toxicity studies of degradable implant materials  

NASA Astrophysics Data System (ADS)

The present study investigated the acute toxicities of the degradation product components of six degradable polymers, the acute toxicities of nine metallic ions and accelerated degradation of one degradable polymer. Prior to these studies, the effect of the anticipated test conditions on the Microtox acute toxicity assay was determined. It was shown that the Microtox is unaffected by pH of water within the range of 5 to 10 and that the test is unaffected by tris buffer at physiologic pH and concentration. The toxicity and rates of degradation of poly(glycolic acid), PGA; two samples of poly(L-lactic acid), PLLA; samples of different molecular weights, poly(caprolactone), PCL; poly(ortho ester), POE; and poly(hydroxybutyrate-cohydroxyvalerate), PHBV, were compared, along with the toxicity of their degradation product components. The toxic concentrations ranged from 100 muM (lactic acid) to 125,000 muM (pentaerythritol). The degradation product components in order of most toxic to least toxic are lactic acid, caproic acid, glycolic acid, cyclohexanedimethanol, propionic acid, hydroxybutyric acid, 1,6-hexanediol, pentaerythritol dipropionate, pentaerythritol and hydroxyvaleric acid. Acute toxicity was determined for metallic ions in water and buffer. The toxic concentrations ranged from 33 muM (Tisp{4+} in water) to 3,580 muM (Wsp{6+} in buffer). The four most toxic ions in water (Tisp{4+}, Mosp{5+}, Fesp{3+}, Crsp{3+}) caused solution pH to decrease markedly. The six other ions (Vasp{3+}, Cosp{3+}, Alsp{3+,} Tisp{4+} adjusted to pH 6.1, Nisp{2+} and Wsp{6+}) markedly. The six other ions (Vasp{3+}, Cosp{3+}, Alsp{3+}, Tisp{4+} adjusted to pH 6.1, Nisp{2+} and Wsp{6+}) did not appreciably affect pH. In buffer, Alsp{3+}, Nisp{2+}, Wsp{6+} and Vsp{3+} became much less toxic, suggesting formation of complexes. In general the least toxic ions do not create an acid environment and/or do form protective complexes. PHBV has good mechanical properties and, compared with the other polymers studied, relatively little is known about it. So PHBV was selected for further investigation. Polymer specimens were incubated at 37sp°C, 55sp°C and 70sp°C for time periods up to 1 year. Samples incubated at 37sp°C retained 90% of initial flexural yield strength for 5.5 months. Differential scanning calorimetry indicated changes to the bulk morphology during the exposure intervals for samples incubated at 70sp°C and 55sp°C.

Taylor, Michelle Suzette

21

Space simulation test for thermal control materials  

NASA Technical Reports Server (NTRS)

Tests were run in TRW's Combined Environment Facility to examine the degradation of thermal control materials in a simulated space environment. Thermal control materials selected for the test were those presently being used on spacecraft or predicted to be used within the next few years. The geosynchronous orbit environment was selected as the most interesting. One of the goals was to match degradation of those materials with available flight data. Another aim was to determine if degradation can adequately be determined with accelerated or short term ground tests.

Hardgrove, W. R.

1990-01-01

22

Geochemistry Model Validation Report: Material Degradation and Release Model  

SciTech Connect

The purpose of this Analysis and Modeling Report (AMR) is to validate the Material Degradation and Release (MDR) model that predicts degradation and release of radionuclides from a degrading waste package (WP) in the potential monitored geologic repository at Yucca Mountain. This AMR is prepared according to ''Technical Work Plan for: Waste Package Design Description for LA'' (Ref. 17). The intended use of the MDR model is to estimate the long-term geochemical behavior of waste packages (WPs) containing U. S . Department of Energy (DOE) Spent Nuclear Fuel (SNF) codisposed with High Level Waste (HLW) glass, commercial SNF, and Immobilized Plutonium Ceramic (Pu-ceramic) codisposed with HLW glass. The model is intended to predict (1) the extent to which criticality control material, such as gadolinium (Gd), will remain in the WP after corrosion of the initial WP, (2) the extent to which fissile Pu and uranium (U) will be carried out of the degraded WP by infiltrating water, and (3) the chemical composition and amounts of minerals and other solids left in the WP. The results of the model are intended for use in criticality calculations. The scope of the model validation report is to (1) describe the MDR model, and (2) compare the modeling results with experimental studies. A test case based on a degrading Pu-ceramic WP is provided to help explain the model. This model does not directly feed the assessment of system performance. The output from this model is used by several other models, such as the configuration generator, criticality, and criticality consequence models, prior to the evaluation of system performance. This document has been prepared according to AP-3.10Q, ''Analyses and Models'' (Ref. 2), and prepared in accordance with the technical work plan (Ref. 17).

H. Stockman

2001-09-28

23

Degradation of Spacecraft Materials in the Space Environment  

NASA Technical Reports Server (NTRS)

When we think of space, we typically think of a vacuum containing very little matter that lies between the Earth and other planetary and stellar bodies. However, the space above Earth's breathable atmosphere and beyond contains many things that make designing durable spacecraft a challenge. Depending on where the spacecraft is flyng, it may encounter atomic oxygen, ultraviolet and other forms of radiation, charged particles, micrormeteoroids and debris, and temperature extremes. These environments on their own and in combination can cause degradation and failure of polymers, composites, paints and other materials used on the exterior of spacecraft for thermal control, structure, and power generation. This article briefly discusses and gives examples of some of the degradation experienced on spacecraft and night experiments as a result of the space environment and the use of ground and space data to predict durability.

Miller, Sharon K. R.; Banks, Bruce A.

2010-01-01

24

Adjustable degradation properties and biocompatibility of amorphous and functional poly(ester-acrylate)-based materials.  

PubMed

Tuning the properties of materials toward a special application is crucial in the area of tissue engineering. The design of materials with predetermined degradation rates and controlled release of degradation products is therefore vital. Providing a material with various functional groups is one of the best ways to address this issue because alterations and modifications of the polymer backbone can be performed easily. Two different 2-methylene-1,3-dioxepane/glycidyl methacrylate-based (MDO/GMA) copolymers were synthesized with different feed ratios and immersed into a phosphate buffer solution at pH 7.4 and in deionized water at 37 °C for up to 133 days. After different time intervals, the molecular weight changes, mass loss, pH, and degradation products were determined. By increasing the amount of GMA functional groups in the material, the degradation rate and the amount of acidic degradation products released from the material were decreased. As a result, the composition of the copolymers greatly affected the degradation rate. A rapid release of acidic degradation products during the degradation process could be an important issue for biomedical applications because it might affect the biocompatibility of the material. The cytotoxicity of the materials was evaluated using a MTT assay. These tests indicated that none of the materials demonstrated any obvious cytotoxicity, and the materials could therefore be considered biocompatible. PMID:24915542

Undin, Jenny; Finne-Wistrand, Anna; Albertsson, Ann-Christine

2014-07-14

25

Ability of Fungal Strains to Degrade PVA Based Materials  

Microsoft Academic Search

The aim of this work was to select a fungal strain with degradative potential upon PVA based materials. The polymeric materials\\u000a tested were PVA films which contain different percentages of PVA, starch and glycerol. These materials are of interest for\\u000a food packaging applications, which presume to solve the problems concerning accumulation, disposal and degradation. Eleven\\u000a strains were tested in solid

L. Jecu; A. Gheorghe; A. Rosu; I. Raut; E. Grosu; M. Ghiurea

2010-01-01

26

Material degradation detection by magnetic method  

SciTech Connect

To be able to evaluate the life of nuclear power plant becomes inevitable as the plant operating period extends. So, magnetic methods using Barkhausen noise (BHN) and B-H curve were applied to detect the degradation by fatigue and thermal aging. Low alloy steel (SA 508 cl.2) was fatigued, and duplex stainless steel (SCS 14A) was aged at 400 C. For the degradation by thermal aging, BHN and B-H curve were measured and good correlations between magnetic properties and aging time were obtained. For fatigue, BHN was measured at predetermined loading cycles and, at each predetermined cycle, the effect of stress or strain condition in the measurement was evaluated. The results showed that BHN was affected by the stress or strain condition in the measurement, the cause of which seemed to be the change of internal stress condition, and by identifying the measuring condition, good correlation between BHN and fatigue damage was obtained.

Yamaguchi, A.; Maeda, N.; Sugibayashi, T. [Japan Power Engineering and Inspection Corp., Yokohama (Japan)

1995-08-01

27

Material degradation detection by ultrasonic decay constant measurement  

SciTech Connect

Structural materials used in a nuclear power plant may be degraded mainly by fatigue, neutron irradiation embrittlement or thermal embrittlement in case of duplex stainless steel. In order to improve the availability and reliability off a nuclear power plant, it is especially advantageous to detect the degradation as early as possible and to prevent possible failures. Measurement of change of ultrasonic velocity, decay constant or scattering characteristics have been proposed as degradation detection method using ultrasonic wave. In this study, measurement of frequency dependence of decay constant of ultrasonic wave during propagation in materials is introduced. By exiting an EMAT (electromagnetic ultrasonic transducers) with sine burst wave and processing the ringing signals with a superheterodyne phase sensitive detector, decay constant is measured at the resonance frequency for platetype test piece. Based on this results, it was confirmed that the relation between frequency and decay constant varied with the degree of material degradation.

Maeda, N.; Sugibayashi, T.; Yamaguchi, A. [Japan Power Engineering and Inspection Corp., Yokohama (Japan)

1995-08-01

28

Storage life of parachutes -- long time material degradation  

SciTech Connect

This study considers the long-time storage of single-use nylon and Kevlar{reg_sign} parachutes. The authors present data from a 29-year-old nylon parachute, and nylon and Kevlar{reg_sign} test samples stored 14 years under ambient conditions in the absence of sunlight. They compare the results with existing predictions of parachute material degradation and other aging data. X-ray photoelectron spectroscopy analyses were preformed on Nylon and Kevlar{reg_sign} fabrics that were degraded by elevated temperature aging. The results suggest that this technique should be further examined as a {open_quotes}non-destructive{close_quotes} method of detecting degradation.

Ericksen, R.H.; Whinery, L.D.

1995-04-01

29

Hubble Space Telescope Metallized Teflon(registered trademark) FEP Thermal Control Materials: On-Orbit Degradation and Post-Retrieval Analysis  

NASA Technical Reports Server (NTRS)

During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon(Registered Trademark) FEP (fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(Registered Trademark) FEP sample evaluation and additional testing of pristine Teflon(Registered Trademark) FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations , and that the damage increased with the combined total dose of electrons, protons, UV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the retrieved Teflon(Registered Trademark) FEP.

Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, J. A.; deGroh, K. K.; Banks, B.; Wang, L.; He, C.

1988-01-01

30

Materials Degradation and Detection (MD2): Deep Dive Final Report  

SciTech Connect

An effort is underway at Pacific Northwest National Laboratory (PNNL) to develop a fundamental and general framework to foster the science and technology needed to support real-time monitoring of early degradation in materials used in the production of nuclear power. The development of such a capability would represent a timely solution to the mounting issues operators face with materials degradation in nuclear power plants. The envisioned framework consists of three primary and interconnected “thrust” areas including 1) microstructural science, 2) behavior assessment, and 3) monitoring and predictive capabilities. A brief state-of-the-art assessment for each of these core technology areas is discussed in the paper.

McCloy, John S.; Montgomery, Robert O.; Ramuhalli, Pradeep; Meyer, Ryan M.; Hu, Shenyang Y.; Li, Yulan; Henager, Charles H.; Johnson, Bradley R.

2013-02-01

31

MATERIAL CONTROL ACCOUNTING INMM  

SciTech Connect

Since 1996, the Mining and Chemical Combine (MCC - formerly known as K-26), and the United States Department of Energy (DOE) have been cooperating under the cooperative Nuclear Material Protection, Control and Accounting (MPC&A) Program between the Russian Federation and the U.S. Governments. Since MCC continues to operate a reactor for steam and electricity production for the site and city of Zheleznogorsk which results in production of the weapons grade plutonium, one of the goals of the MPC&A program is to support implementation of an expanded comprehensive nuclear material control and accounting (MC&A) program. To date MCC has completed upgrades identified in the initial gap analysis and documented in the site MC&A Plan and is implementing additional upgrades identified during an update to the gap analysis. The scope of these upgrades includes implementation of MCC organization structure relating to MC&A, establishing material balance area structure for special nuclear materials (SNM) storage and bulk processing areas, and material control functions including SNM portal monitors at target locations. Material accounting function upgrades include enhancements in the conduct of physical inventories, limit of error inventory difference procedure enhancements, implementation of basic computerized accounting system for four SNM storage areas, implementation of measurement equipment for improved accountability reporting, and both new and revised site-level MC&A procedures. This paper will discuss the implementation of MC&A upgrades at MCC based on the requirements established in the comprehensive MC&A plan developed by the Mining and Chemical Combine as part of the MPC&A Program.

Hasty, T.

2009-06-14

32

Materials Degradation Studies for High Temperature Steam Electrolysis Systems  

SciTech Connect

Experiments are currently in progress to assess the high temperature degradation behavior of materials in solid oxide electrolysis systems. This research includes the investigation of various electrolysis cell components and balance of plant materials under both anodic and cathodic gas atmospheres at temperatures up to 850°C. Current results include corrosion data for a high temperature nickel alloy used for the air-side flow field in electrolysis cells and a commercial ferritic stainless steel used as the metallic interconnect. Three different corrosion inhibiting coatings were also tested on the steel material. The samples were tested at 850ºC for 500 h in both air and H2O/H2 atmospheres. The results of this research will be used to identify degradation mechanisms and demonstrate the suitability of candidate materials for long-term operation in electrolysis cells.

Paul Demkowicz; Pavel Medvedev; Kevin DeWall; Paul Lessing

2007-06-01

33

MATERIALS MANAGEMENT MATERIALS MANAGEMENT -INVENTORY CONTROL  

E-print Network

MATERIALS MANAGEMENT MATERIALS MANAGEMENT - INVENTORY CONTROL NOTICE OF DESIGNATED DEPARTMENTAL directly delivered to the department (i.e. vendor deliveries) See the Inventory Control Manual for More will be communicated to Inventory Control via this form. Subsequent changes of the DMC will also be communicated via

Oliver, Douglas L.

34

Numerical simulation of cementitious materials degradation under external sulfate attack  

Microsoft Academic Search

A numerical methodology is proposed in this paper to simulate the degradation of cementitious materials under external sulfate attack. The methodology includes diffusion of ions in and out of the structure, chemical reactions which lead to dissolution and precipitation of solids, and mechanical damage accumulation using a continuum damage mechanics approach. Diffusion of ions is assumed to occur under a

S. Sarkar; S. Mahadevan; J. C. L. Meeussen; H. van der Sloot; D. S. Kosson

2010-01-01

35

Degradation Of Cementitious Materials Associated With Saltstone Disposal Units  

SciTech Connect

The Saltstone facilities at the DOE Savannah River Site (SRS) stabilize and dispose of low-level radioactive salt solution originating from liquid waste storage tanks at the site. The Saltstone Production Facility (SPF) receives treated salt solution and mixes the aqueous waste with dry cement, blast furnace slag, and fly ash to form a grout slurry which is mechanically pumped into concrete disposal cells that compose the Saltstone Disposal Facility (SDF). The solidified grout is termed “saltstone”. Cementitious materials play a prominent role in the design and long-term performance of the SDF. The saltstone grout exhibits low permeability and diffusivity, and thus represents a physical barrier to waste release. The waste form is also reducing, which creates a chemical barrier to waste release for certain key radionuclides, notably Tc-99. Similarly, the concrete shell of an SDF disposal unit (SDU) represents an additional physical and chemical barrier to radionuclide release to the environment. Together the waste form and the SDU compose a robust containment structure at the time of facility closure. However, the physical and chemical state of cementitious materials will evolve over time through a variety of phenomena, leading to degraded barrier performance over Performance Assessment (PA) timescales of thousands to tens of thousands of years. Previous studies of cementitious material degradation in the context of low-level waste disposal have identified sulfate attack, carbonation influenced steel corrosion, and decalcification (primary constituent leaching) as the primary chemical degradation phenomena of most relevance to SRS exposure conditions. In this study, degradation time scales for each of these three degradation phenomena are estimated for saltstone and concrete associated with each SDU type under conservative, nominal, and best estimate assumptions. The nominal value (NV) is an intermediate result that is more probable than the conservative estimate (CE) and more defensible than the best estimate (BE). The combined effects of multiple phenomena are then considered to determine the most limiting degradation time scale for each cementitious material. Degradation times are estimated using a combination of analytic solutions from literature and numerical simulation codes provided through the DOE Cementitious Barriers Partnership (CBP) Software Toolbox (http://cementbarriers.org). For the SDU 2 design, the roof, wall, and floor components are projected to become fully degraded under Nominal conditions at 3866, 923, and 1413 years, respectively. For SDU 4 the roof and floor are estimated to be fully degraded under Nominal conditions after 1137 and 1407 years, respectively; the wall is assumed to be fully degraded at time zero in the most recent PA simulations. Degradation of these concrete barriers generally occurs from combined sulfate attack and corrosion of embedded steel following carbonation. Saltstone is projected to degrade very slowly by decalcification, with complete degradation occurring in excess of 200,000 years for any SDU type. Complete results are provided.

Flach, G. P; Smith, F. G. III

2013-03-19

36

Dielectric material degradation monitoring of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

It is a known phenomenon that some dielectric materials used to construct plasma actuators degrade during operation. However, the rate at which this process occurs, to what extent, as well as a method to monitor is yet to be established. In this experimental study, it is shown that electrical measurements can be used to monitor changes in the material of the plasma actuators. The procedure we introduce for monitoring the actuators follows from the work of Kriegseis, Grundmann, and Tropea [Kriegseis et al., J. Appl. Phys. 110, 013305 (2011)], who used Lissajous figures to measure actuator power consumption and capacitance. In the present study, we quantify changes in both the power consumption and capacitance of the actuators over long operating durations. It is shown that the increase in the effective capacitance of the actuator is related to degradation (thinning) of the dielectric layer, which is accompanied by an increase in actuator power consumption. For actuators constructed from layers of Kapton® polyimide tape, these changes are self-limiting. Although the polyimide film degrades relatively quickly, the underlying adhesive layer appears to remain intact. Over time, the effective capacitance was found to increase by up to 36%, 25%, and 11% for actuators constructed with 2, 3, and 4 layers of Kapton tape, respectively. A method is presented to prevent erosion of the Kapton dielectric layer using a coating of Polydimethylsiloxane oil. It is shown the application of this treatment can delay the onset of degradation of the Kapton dielectric material.

Hanson, Ronald E.; Houser, Nicole M.; Lavoie, Philippe

2014-01-01

37

Fungal degradation of fiber-reinforced composite materials  

NASA Technical Reports Server (NTRS)

As described in a previous report, a fungal consortium isolated from degraded polymeric materials was capable of growth on presterilized coupons of five composites, resulting in deep penetration into the interior of all materials within five weeks. Data describing the utilization of composite constituents as nutrients for the microflora are described in this article. Increased microbial growth was observed when composite extract was incubated with the fungal inoculum at ambient temperatures. Scanning electron microscopic observation of carbon fibers incubated with a naturally developed population of microorganisms showed the formation of bacterial biofilms on the fiber surfaces, suggesting possible utilization of the fiber chemical sizing as carbon and energy sources. Electrochemical impedance spectroscopy was used to monitor the phenomena occurring at the fiber-matrix interfaces. Significant differences were observed between inoculated and sterile panels of the composite materials. A progressive decline in impedance was detected in the inoculated panels. Several reaction steps may be involved in the degradation process. Initial ingress of water into the resin matrix appeared to be followed by degradation of fiber surfaces, and separation of fibers from the resin matrix. This investigation suggested that composite materials are susceptible to microbial attack by providing nutrients for growth.

Gu, J. D.; Lu, C.; Mitchell, R.; Thorp, K.; Crasto, A.

1997-01-01

38

Stress and Damage in Polymer Matrix Composite Materials Due to Material Degradation at High Temperatures  

NASA Technical Reports Server (NTRS)

This report describes analytical methods for calculating stresses and damage caused by degradation of the matrix constituent in polymer matrix composite materials. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. The model is incorporated into an existing composite mechanics computer code. Stresses, strains, and deformations at the laminate, ply, and micro levels are calculated, and from these calculations it is determined if there is failure of any kind. The rationale for the model (based on published experimental work) is presented, its integration into the laminate analysis code is outlined, and example results are given, with comparisons to existing material and structural data. The mechanisms behind the changes in properties and in surface cracking during long-term aging of polyimide matrix composites are clarified. High-temperature-material test methods are also evaluated.

McManus, Hugh L.; Chamis, Christos C.

1996-01-01

39

Moving Beyond NDE to Proactive Management of Materials Degradation  

SciTech Connect

There is growing interest in life extensions to enable longer term operation (LTO) for both existing nuclear power plants (NPPs) and proposed new NPPs. In order to justify an initial license extension for the 40-60 year period, new non-destructive examination (NDE) approaches have been developed and deployed by NPP operators in their Aging Management Programs (AMPs). However, to achieve the goals of even longer term operation, and specifically for the USA in looking at methodologies to support subsequent license renewal periods (i.e., 60-80 years, and beyond), it is necessary to understand the capabilities of current NDE methods to detect, monitor and trend degradation and hence enable timely implementation of appropriate corrective actions. This paper discusses insights from past experience, the state-of-the-art, and current activities in the move towards providing a capacity for proactive management of materials degradation (PMMD) to support NPP LTO.

Bond, Leonard J.

2010-07-20

40

Moving Beyond Nondestructive Examination to Proactive Management of Materials Degradation  

SciTech Connect

There is growing interest in life extensions to enable longer term operation (LTO) for both existing nuclear power plants (NPPs) and proposed new NPPs. In order to justify an initial license extension for the 40-60 year period, new non-destructive examination (NDE) approaches have been developed and deployed by NPP operators in their Aging Management Programs (AMPs). However, to achieve the goals of even longer term operation, and specifically for the USA in looking at methodologies to support subsequent license renewal periods (i.e., 60-80 years, and beyond), it is necessary to understand the capabilities of current NDE methods to detect, monitor and trend degradation and hence enable timely implementation of appropriate corrective actions. This paper discusses insights from past experience, the state-of-the-art, and current activities in the move towards providing a capacity for proactive management of materials degradation (PMMD) to support NPP LTO.

Bond, Leonard J.

2010-07-01

41

Conduction degradation in anisotropic multi-cracked materials  

NASA Astrophysics Data System (ADS)

The electrical and thermal conduction properties of disordered solids and the possible degradation processes induced by the generation of cracks are central issues in the field of the heterogeneous materials. However, most of the existing theories are unable to consider an arbitrary density of cracks. We obtained an exact result for the fields induced within an elliptic anisotropic inhomogeneity embedded in a different anisotropic (two-dimensional) conductor. Then, we applied it to show that the degradation process strongly depends on the statistical orientational distribution of defects: in particular we theoretically prove that parallel cracks lead to the power law decay log ? ˜ - log N while random oriented cracks lead to the exponential law decay log ? ˜ - N (where ? is the effective conductivity of a region with a large number N of defects), as recently predicted by numerical findings.

Giordano, S.; Palla, P. L.

2012-02-01

42

Electrochemical Shock: Mechanical Degradation of Ion-Intercalation Materials  

NASA Astrophysics Data System (ADS)

The ion-intercalation materials used in high-energy batteries such as lithium-ion undergo large composition changes-which correlate to high storage capacity---but which also induce structural changes and stresses that can cause performance metrics such as power, achievable storage capacity, and life to degrade. "Electrochemical shock"---the electrochemical cyclinginduced fracture of materials-contributes to impedance growth and performance degradation in ion-intercalation batteries. Using a combination of micromechanical models and in operando acoustic emission experiments, the mechanisms of electrochemical shock are identified, classified, and modeled in targeted model systems with different composition and microstructure. Three distinct mechanisms of electrochemical shock in ion-intercalation materials are identified: 1) concentration-gradient stresses which arise during fast cycling, 2) two-phase coherency stresses which arise during first-order phase-transformations, and 3) intergranular compatibility stresses in anisotropic polycrystalline materials. While concentration-gradient stresses develop in proportion to the electrochemical cycling rate, two-phase coherency stresses and intergranular compatibility stresses develop independent of the electrochemical cycling rate and persist to arbitrarily low rates. For each mechanism, a micromechanical model with a fracture mechanics failure criterion is developed. This fundamental understanding of electrochemical shock leads naturally to microstructure design criteria and materials selection criteria for ion-intercalation materials with improved life and energy storage efficiency. In a given material system, crystal symmetry and phase-behavior determine the active mechanisms. Layered materials, as exemplified by LiCoO2, are dominated by intergranular compatibility stresses when prepared in polycrystalline form, and two-phase coherency when prepared as single crystal powders. Spinel materials such as LiMn2O4, and LiMn1.5Ni0.5O 4 undergo first-order cubic-to-cubic phasetransformations, and are subject to two-phase coherency stresses even during low-rate electrochemical cycling. This low-rate electrochemical shock is averted in iron-doped material, LiMn 1.5Ni0.42Fe0.08O4, which has continuous solid solubility and is therefore not subject to two-phase coherency stresses; this enables a wider range of particle sizes and duty cycles to be used without electrochemical shock. While lithium-storage materials are used as model systems, the physical phenomena are common to other ion-intercalation systems, including sodium-, magnesium-, and aluminum-storage compounds. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

Woodford, William Henry, IV

43

Novel oxygen atom source for material degradation studies  

NASA Technical Reports Server (NTRS)

Physical Sciences Inc. (PSI) has developed a high flux pulsed source of energetic (8 km/s) atomic oxygen to bombard specimens in experiments on the aging and degradation of materials in a low earth orbit environment. The proof-of-concept of the PSI approach was demonstrated in a Phase 1 effort. In Phase 2 a large O-atom testing device (FAST-2) has been developed and characterized. Quantitative erosion testing of materials, components, and even small assemblies (such as solar cell arrays) can be performed with this source to determine which materials and/or components are most vulnerable to atomic oxygen degradation. The source is conservatively rated to irradiate a 100 sq cm area sample at greater than 10(exp 17) atoms/s, at a 10 Hz pulse rate. Samples can be exposed to an atomic oxygen fluence equivalent to the on-orbit ram direction exposure levels incident on Shuttle surfaces at 250 km during a week-long mission in a few hours.

Krech, R. H.; Caledonia, G. E.

1988-01-01

44

Degradability of injectable calcium sulfate/mineralized collagen-based bone repair material and its effect on bone tissue regeneration.  

PubMed

The nHAC/CSH composite is an injectable bone repair material with controllable injectability and self-setting properties prepared by introducing calcium sulfate hemihydrate (CSH) into mineralized collagen (nHAC). When mixed with water, the nHAC/CSH composites can be transformed into mineralized collagen/calcium sulfate dihydrate (nHAC/CSD) composites. The nHAC/CSD composites have good biocompatibility and osteogenic capability. Considering that the degradation behavior of bone repair material is another important factor for its clinical applications, the degradability of nHAC/CSD composites was studied. The results showed that the degradation ratio of the nHAC/CSD composites with lower nHAC content increased with the L/S ratio increase of injectable materials, but the variety of L/S ratio had no significant effect on the degradation ratio of the nHAC/CSD composites with higher nHAC content. Increasing nHAC content in the composites could slow down the degradation of nHAC/CSD composite. Setting accelerator had no significant effect on the degradability of nHAC/CSD composites. In vivo histological analysis suggests that the degradation rate of materials can match the growth rate of new mandibular bone tissues in the implanted site of rabbit. The regulable degradability of materials resulting from the special prescriptions of injectable nHAC/CSH composites will further improve the workability of nHAC/CSD composites. PMID:25491806

Chen, Zonggang; Kang, Lingzhi; Meng, Qing-Yuan; Liu, Huanye; Wang, Zhaoliang; Guo, Zhongwu; Cui, Fu-Zhai

2014-12-01

45

Degradable hybrid materials based on cationic acylhydrazone dynamic covalent polymers promote DNA complexation through multivalent interactions.  

PubMed

The design of smart nonviral vectors for gene delivery is of prime importance for the successful implementation of gene therapies. In particular, degradable analogues of macromolecules represent promising targets as they would combine the multivalent presentation of multiple binding units that is necessary for achieving effective complexation of therapeutic oligonucleotides with the controlled degradation of the vector that would in turn trigger drug release. Toward this end, we have designed and synthesized hybrid polyacylhydrazone-based dynamic materials that combine bis-functionalized cationic monomers with ethylene oxide containing monomers. Polymer formation was characterized by (1) H and DOSY NMR spectroscopy and was found to take place at high concentration, whereas macrocycles were predominantly formed at low concentration. HPLC monitoring of solutions of these materials in aqueous buffers at pH values ranging from 5.0 to 7.0 revealed their acid-catalyzed degradation. An ethidium bromide displacement assay and gel electrophoresis clearly demonstrated that, despite being dynamic, these materials are capable of effectively complexing dsDNA in aqueous buffer and biological serum at N/P ratios comparable to polyethyleneimine polymers. The self-assembly of dynamic covalent polymers through the incorporation of a reversible covalent bond within their main chain is therefore a promising strategy for generating degradable materials that are capable of establishing multivalent interactions and effectively complexing dsDNA in biological media. PMID:25251569

Bouillon, Camille; Paolantoni, Delphine; Rote, Jennifer C; Bessin, Yannick; Peterson, Larryn W; Dumy, Pascal; Ulrich, Sébastien

2014-11-01

46

Degradation, Fatigue, and Failure of Resin Dental Composite Materials  

SciTech Connect

The intent of this article is to review the numerous factors that affect the mechanical properties of particle- or fiber-filler-containing indirect dental resin composite materials. The focus will be on the effects of degradation due to aging in different media, mainly water and water and ethanol, cyclic loading, and mixed-mode loading on flexure strength and fracture toughness. Several selected papers will be examined in detail with respect to mixed and cyclic loading, and 3D tomography with multi-axial compression specimens. The main cause of failure, for most dental resin composites, is the breakdown of the resin matrix and/or the interface between the filler and the resin matrix. In clinical studies, it appears that failure in the first 5 years is a restoration issue (technique or material selection); after that time period, failure most often results from secondary decay.

Drummond, J.L. (UIC)

2008-11-03

47

Degradation, fatigue and failure of resin dental composite materials  

PubMed Central

The intent of this article is to review the numerous factors that affect the mechanical properties of particle or fiber filler containing, indirect dental resin composite materials. The focus will be on degradation due to aging in different media, mainly water and water and ethanol, cyclic loading, and mixed mode loading on the flexure strength and fracture toughness. Next several selected papers will be examined in detail with respect to mixed and cyclic loading and then an examination of 3D tomography using multiaxial compression specimens. The main cause of failure, for most dental resin composites, is the breakdown of the resin matrix and or the interface between the filler and the resin matrix. In clinical studies, it appears that failure in the first 5 years is a restoration issue (technique or material selection) and after that time period from secondary decay. PMID:18650540

Drummond, James L.

2008-01-01

48

Computational simulation of coupled material degradation processes for probabilistic lifetime strength of aerospace materials  

NASA Technical Reports Server (NTRS)

The research included ongoing development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primative variables. These primative variable may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above described constitutive equation using actual experimental materials data together with linear regression of that data, thereby predicting values for the empirical material constraints for each effect or primative variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from the open literature for materials typically of interest to those studying aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

Boyce, Lola; Bast, Callie C.

1992-01-01

49

Material Aging and Degradation Detection and Remaining Life Assessment for Plant Life Management  

SciTech Connect

One of the major factors that may impact long term operations is structural material degradation, Detecting materials degradation, estimating the remaining useful life (RUL) of the component, and determining approaches to mitigating the degradation are important from the perspective of long term operations. In this study, multiple nondestructive measurement and monitoring methods were evaluated for their ability to assess the material degradation state. Metrics quantifying the level of damage from these measurements were defined, and evaluated for their ability to provide estimates of remaining life of the component. An example of estimating the RUL from nondestructive measurements of material degradation condition is provided.

Ramuhalli, Pradeep; Henager, Charles H.; Griffin, Jeffrey W.; Meyer, Ryan M.; Coble, Jamie B.; Pitman, Stan G.; Bond, Leonard J.

2012-12-31

50

Common causes of material degradation in buried piping  

SciTech Connect

Buried pipe may fail for innumerable reasons. Causes can be mechanical damage/breakage, chemically initiated corrosion, or a combination. Failures may originate either internally or externally on the pipe. They may be related to flaws in the design, to excessive or unanticipated internal pressure or ground level loading, and/or to poor or uncertain installation practice. Or the pipe may simply ``wear out`` in service. Steel is strong and very forgiving in underground applications, especially with regard to backfill. However, soil support developed through densification or compaction is critical for brittle concrete and vitrified clay tile pipe, and is very important for cast iron and plastic pipe. Chemistry of the soil determines whether or not it will enhance corrosion or other types of degradation. Various causes and mechanisms for deterioration of buried pipe are indicated. Some peculiarities of the different materials of construction are characterized. Repair methods and means to circumvent special problems are described.

Jenkins, C.F.

1997-01-20

51

Integrated control of protein degradation in C. elegans muscle  

PubMed Central

Protein degradation is a fundamental cellular process, the genomic control of which is incompletely understood. The advent of transgene-coded reporter proteins has enabled the development of C. elegans into a model for studying this problem. The regulation of muscle protein degradation is surprisingly complex, integrating multiple signals from hypodermis, intestine, neurons and muscle itself. Within the muscle, degradation is executed by separately regulated autophagy-lysosomal, ubiquitin-proteasome and calpain-mediated systems. The signal-transduction mechanisms, in some instances, involve modules previously identified for their roles in developmental processes, repurposed in terminally differentiated muscle to regulate the activities of pre-formed proteins. Here we review the genes, and mechanisms, which appear to coordinately control protein degradation within C. elegans muscle. We also consider these mechanisms in the context of development, physiology, pathophysiology and disease models. PMID:23457662

Lehmann, Susann; Shephard, Freya; Jacobson, Lewis A.; Szewczyk, Nathaniel J.

2012-01-01

52

Degradation behavior of Ca-Mg-Zn intermetallic compounds for use as biodegradable implant materials.  

PubMed

With the goal of developing new biodegradable implant materials, we have investigated the degradation behavior of (Ca, Mg)-based intermetallic compounds. The degradation behavior of the compounds within the Ca-Mg-Zn system was roughly classified into four groups, and their behaviors were strongly influenced by the compositions of the compounds. For example, the Ca3MgxZn(15-x) compound exhibited a large solubility region with varying the Mg/Zn ratio, and the Ca3Mg12Zn3 phase alloy with the lowest Zn content was rapidly broken apart within 6h of immersion. Alternatively, the Ca3Mg4.6Zn10.4 phase alloy with the highest Zn content retained the bulk shape even after 250 h of immersion. These varying degradation behaviors were ascribed to the difference in the formability of Zn oxide as a protective layer against corrosion on the specimen surfaces, depending on the Zn content. The gained results suggest that there is a feasibility on developing new biodegradable materials based on intermetallic compounds in which the degradation rate can be controlled by their compositions. PMID:25280708

Hagihara, Koji; Shakudo, Shuhei; Fujii, Kenta; Nakano, Takayoshi

2014-11-01

53

Three-dimensional biomaterial degradation - Material choice, design and extrinsic factor considerations.  

PubMed

The apparent difficulty to precisely control fine-tuning of biomaterial degradation has initiated the recent paradigm shift from conventional top-down fabrication methods to more nature-inspired bottom-up assemblies. Sophistication of material fabrication techniques allows today's scientists to reach beyond conventional natural materials in order to synthesise tomorrow's 'designer material'. Material degradation into smaller components and subsequent release of encapsulated cells or cell-signalling agents have opened medically exploitable avenues, transforming the area of regenerative medicine into a dynamic and self-propagating branch of modern medicine. The aim to synthesise ever more refined scaffolding structures in order to create micro- and nanoenvironments resembling those found in natural tissues now represents an ever growing niche in the materials sciences. Recently, we have developed and conducted the world's first in-human tracheal transplantation using a non-degradable completely synthetic biomaterial. Fuelled by such clinical potential, we are currently developing a biodegradable version suitable for skin tissue engineering and paediatric applications. However, despite enormous efforts, current, as yet insurmountable challenges include precise biomaterial degradation within pre-determined spatial and temporal confines in an effort to release bio-signalling agents in such orchestrated fashion as to fully regenerate functioning tissues. In this review, the authors, almost anti-climactically, ask the readers to step out of the artificially over-constructed spiral of ever more convoluted scaffold fabrication techniques and consider the benefits of controllable bottom-up scaffold fabrication methods. It will further be investigated how scaffold designs and fabrication methods may influence degradation and subsequent release of incorporated elements. A focus will be placed on the delivery of growth factors, stem cells and therapeutic agents alone or in parallel. The difficulties of designing a delivery vehicle capable of delivering multiple factors whilst maintaining distinct release kinetics will be highlighted. Finally, this review will be rounded off with an insight into current literature addressing the recurring issues of degradation product toxicities and suggests means of overcoming those. PMID:24858478

Yildirimer, Lara; Seifalian, Alexander M

2014-01-01

54

Control of Several Emissions during Olive Pomace Thermal Degradation  

PubMed Central

Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25–750 °C and a heating rate of 20 °C·min?1. The following species were analysed: aromatic compounds (benzene and toluene), sulphur emissions (sulphur dioxide), 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor. PMID:25314298

Miranda, Teresa; Nogales, Sergio; Román, Silvia; Montero, Irene; Arranz, José Ignacio; Sepúlveda, Francisco José

2014-01-01

55

Control of several emissions during olive pomace thermal degradation.  

PubMed

Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25-750 °C and a heating rate of 20 °C·min?¹. The following species were analysed: aromatic compounds (benzene and toluene), sulphur emissions (sulphur dioxide), 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor. PMID:25314298

Miranda, Teresa; Nogales, Sergio; Román, Silvia; Montero, Irene; Arranz, José Ignacio; Sepúlveda, Francisco José

2014-01-01

56

Probabilistic analysis for fatigue strength degradation of materials  

NASA Technical Reports Server (NTRS)

This report presents the results of the first year of a research program conducted for NASA-LeRC by the University of Texas at San Antonio. The research included development of methodology that provides a probabilistic treatment of lifetime prediction of structural components of aerospace propulsion systems subjected to fatigue. Material strength degradation models, based on primitive variables, include both a fatigue strength reduction model and a fatigue crack growth model. Linear elastic fracture mechanics is utilized in the latter model. Probabilistic analysis is based on simulation, and both maximum entropy and maximum penalized likelihood methods are used for the generation of probability density functions. The resulting constitutive relationships are included in several computer programs, RANDOM2, RANDOM3, and RANDOM4. These programs determine the random lifetime of an engine component, in mechanical load cycles, to reach a critical fatigue strength or crack size. The material considered was a cast nickel base superalloy, one typical of those used in the Space Shuttle Main Engine.

Royce, Lola

1989-01-01

57

Materials Degradation & Failure: Assessment of Structure and Properties. Resources in Technology.  

ERIC Educational Resources Information Center

This module provides information on materials destruction (through corrosion, oxidation, and degradation) and failure. A design brief includes objective, student challenge, resources, student outcomes, and quiz. (SK)

Technology Teacher, 1991

1991-01-01

58

Material control and accountability alternatives  

SciTech Connect

Department of Energy and Nuclear Regulatory Commission regulations governing material control and accountability in nuclear facilities have become more restrictive in the past decade, especially in areas that address the insider threat. As the insider threat receives greater credibility, regulations have been strengthened to increase the probability of detecting insider activity and to prevent removal of a significant quantity of Special Nuclear Material (SNM) from areas under control of the protective force.

NONE

1991-08-12

59

Aerospace Materials Quality Control Presentation  

NSDL National Science Digital Library

This PowerPoint document from the Aerospace Manufacturing Education Project looks into the topic of quality control of materials used in the aerospace industry. The presentation includes 27 slides and covers why quality control is important in this field. It also includes details about aerospace QC teams and techniques, including non-destructive testing.

60

Thermal and chemical degradation of inorganic membrane materials. Topical report  

SciTech Connect

This report describes the results of a literature review to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate gaseous products produced by the gasification or combustion of coal in fixed-, fluidized-, and entrained-bed gasifiers, direct coal-fired turbines, and pressurized-fluidized-bed combustors. Several impurities, such as H{sub 2}S, NH{sub 3}, SO{sub 2}, NO{sub x}, and trace metal compounds are generated during coal conversion, and they must be removed from the coal gas or the combustor flue gas to meet environmental standards. The use of membranes to separate these noxious gases is an attractive alternative to their removal by sorbents such as zinc titanate or calcium oxide. Inorganic membranes that have a high separation efficiency and exhibit both thermal and chemical stability would improve the economics of power generation from coal. The U.S. Department of Energy is supporting investigations to develop inorganic membranes for separating hydrogen from coal gas streams and noxious impurities from hot coal- and flue-gas streams. Membrane materials that have been investigated in the past include glass (silica), alumina, zirconia, carbon, and metals (Pd and Pt).

Krishnan, G.N.; Sanjurjo, A.; Wood, B.J.; Lau, K.H.

1994-04-01

61

Thermal Control Surfaces Experiment (TCSE) materials analysis  

NASA Technical Reports Server (NTRS)

Materials on the Thermal Control Surfaces Experiment (TCSE) underwent changes in their properties during the 5.8 years of exposure to the combined space environment. The analysis of these materials is continuing and current results are discussed. Some materials were significantly degraded such as silver Teflon, S13GLO, and Z302; while others such as Z93 and YB71 were stable. Time dependent flight data is provided, along with preflight and postflight measurements. Results are compared with other experiments, demonstrating the atomic oxygen (AO) ram effect. Atomic oxygen texturing of silver Teflon varies with incident angle. Even indirect exposure to atomic oxygen appears to be involved with surface texturing on the interior of the TCSE. Localized contamination occurred at discrete locations both inside and on exterior surfaces. Most of the visible deposits were the result of the classical photo-enhanced contamination deposition. The synergism of combined space environmental effects is demonstrated by the specific localization of contamination caused by photo-enhanced deposition versus AO removal. Optical degradation measurements of these contaminated areas, utilizing a new portable reflectometer, are presented.

Wilkes, Donald R.; Miller, Edgar R.; Zwiener, James M.; Mell, Richard J.

1992-01-01

62

Materials Control for Aerospace Applications  

NASA Technical Reports Server (NTRS)

The distant future of mankind and the ultimate survivability of the human race, as it is known today, will depend on mans' ability to break earthly bonds and establish new territorial positions throughout the universe. Man must therefore be positioned to not only travel to, but also, to readily adapt to numerous and varying environments. For this mass migration across the galaxies nothing is as import to the human race as is NASA's future missions into Low Earth Orbit (LEO), to the moon, and/or Mars. These missions will form the building blocks to eternity for mankind. From these missions, NASA will develop the foundations for these building blocks based on sound engineering and scientific principles, both known and yet to be discovered. The integrity of the program will lead to development, tracking and control of the most basic elements of hardware production: That being development and control of applications of space flight materials. Choosing the right material for design purposes involves many considerations, such as governmental regulations associated with manufacturing operations, both safety of usage and of manufacturing, general material usage requirements, material longevity and performance requirements, material interfacing compatibility and material usage environments. Material performance is subject to environmental considerations in as much as a given material may perform exceptionally well at standard temperatures and pressures while performing poorly under non-standard conditions. These concerns may be found true for materials relative to the extreme temperatures and vacuum gradients of high altitude usage. The only way to assure that flight worthy materials are used in design is through testing. However, as with all testing, it requires both time on schedule and cost to the operation. One alternative to this high cost testing approach is to rely on a materials control system established by NASA. The NASA community relies on the MAPTIS materials control system founded at MSFC and supported by the other NASA Centers. This system is a data bank of all materials used in space flight operations. These materials are rated for several characteristics that are common concerns in high altitude or deep space usage: Odor, off gassing, material fluid compatibility, toxicity, corrosion susceptibility, stress corrosion susceptibility, etc.

Ferguson, Michael

2005-01-01

63

Hydrolytically Degradable Hyaluronic Acid Hydrogels with Controlled Temporal Structures  

PubMed Central

Polysaccharides are being processed into biomaterials for numerous biological applications due to their native source in numerous tissues and biological functions. For instance, hyaluronic acid (HA) is found abundantly in the body, interacts with cells through surface receptors, and can regulate cellular behavior (e.g., proliferation, migration). HA was previously modified with reactive groups to form hydrogels that are degraded by hyaluronidases, either added exogenously or produced by cells. However, these hydrogels may be inhibitory and their applications are limited if the appropriate enzymes are not present. Here, for the first time, we synthesized HA macromers and hydrogels that are both hydrolytically (via ester group hydrolysis) and enzymatically degradable. The hydrogel degradation and growth factor release was tailored through the hydrogel cross-linking density (i.e., macromer concentration) and copolymerization with purely enzymatically degradable macromers. When mesenchymal stem cells (MSCs) were encapsulated in the hydrogels, cellular organization and tissue distribution was influenced by the copolymer concentration. Importantly, the distribution of released extracellular matrix molecules (e.g., chondroitin sulfate) was improved with increasing amounts of the hydrolytically degradable component. Overall, this new macromer allows for enhanced control over the structural evolution of the HA hydrogels toward applications as biomaterials. PMID:18324776

Sahoo, Sujata; Chung, Cindy; Khetan, Sudhir; Burdick, Jason A.

2009-01-01

64

Kinetics for the degradation of nylon and Kevlar parachute materials  

SciTech Connect

The degradation of nylon 66 and Kevlar 29 yarns at elevated temperatures and over a broad range of humidities was studied and a rate relationship developed which models the degradation and permits computation of rate constants. The degradation rates are slow initially due to the presence of an inhibitor but increase rapidly as the inhibitor is depleted. The effect of relative humidity (RH) can be very large especially at values in the 100% range. An exponential relationship exists for nylon between the rate constant and RH. Kinetic parameters were evaluated and the rate constants at 25/sup 0/C calculated. These values showed that the tensile strength of nylon 66 will remain at a safe level over a 25-year period if the humidity is maintained at the 10% range or less. Kevlar 29 is more resistant and can tolerate humidity levels in the range of 90% or less. Degradation is governed by thermal-oxidative and moisture induced mechanisms. At the very high humidities the moisture induced degradation predominates. A relationship is developed which predicts the degradation rate over a very broad range of temperatures and humidities.

Auerbach, I.

1986-01-01

65

Expert system for evaluation of material degradation in a nuclear power plant with the data of material condition monitoring  

SciTech Connect

In nuclear power plant components, there is the possibility that the material could be degraded due to the operation for many years, that is fatigue damage, irradiated embrittlement and thermal embrittlement. When intending to improve the availability of the plant and to extend the plant life, it is important to identify those material degradations which may cause a component to deteriorate its structure integrity. On this account, many Material Condition Monitoring (MCM) techniques are under development in these days. But no single device is considered to be a perfect candidate to assess the degradation, and one needs to think collectively about the data from two or more examination devices. Thus, the authors are developing a computer system to read data obtained from the devices and to assess the material degradation. This computer system is to assess material degradation with its mode and level using the MCM data and plant information such as operating record. This paper describes an outline of the evaluation system of material degradation, and shows some evaluation results using the neural network inference, which is adopted in the system as a tool to evaluate the degradation quantitatively.

Araki, K.; Yoshida, K. [Ishikawajima-Harima Heavy Industries Co., Ltd., Yokohama (Japan)

1995-08-01

66

Damage Assessment Technologies for Prognostics and Proactive Management of Materials Degradation  

SciTech Connect

The Nuclear Regulatory Commission has undertaken a program to lay the groundwork for defining proactive actions to manage degradation of materials in light water reactors (LWRs). This paper discusses the U.S. Nuclear Regulatory Commission’s Proactive Management of Materials Degradation (PMMD) program and its application to nuclear power plant structures, systems and components. The PMMD program is examining LWR component materials and the degradation phenomena that affect them. Of particular interest is how such phenomena can be monitored to predict degradation and prevent component failure. Some forms of degradation, including some modes of stress corrosion cracking, are characterized by a long initiation time followed by a rapid growth phase. Monitoring such long-term degradation will require new non-destructive evaluation (NDE) methods and measurement procedures. A critical analysis of all reactor components is required to determine if new inspection strategies are required to effectively manage slow degradation mechanisms that may lead to component failure. As reactor lifetimes are extended, degradation mechanisms previously considered too long-term to be of consequence (such as concrete and wiring insulation degradation) may become more important. This paper includes a review of techniques with potential for sensing and monitoring degradation in its early stages and will concisely explain the basic principles of PMMD and its relationship to in-service inspection, condition based maintenance, and advanced diagnostics and prognostics.

Bond, Leonard J.; Doctor, Steven R.; Griffin, Jeffrey W.; Hull, Amy B.; Malik, Shah

2011-01-01

67

Electrochemical degradation of trichloroacetic acid in aqueous media: influence of the electrode material.  

PubMed

The electrochemical degradation of trichloroacetic acid (TCAA) in water has been analysed through voltammetric studies with a rotating disc electrode and controlled-potential bulk electrolyses. The influence of the mass-transport conditions and initial concentration of TCAA for titanium, stainless steel and carbon electrodes has been studied. It is shown that the electrochemical reduction of TCAA takes place prior to the massive hydrogen evolution in the potential window for all electrode materials studied. The current efficiency is high (> 18%) compared with those normally reported in the literature, and the fractional conversion is above 50% for all the electrodes studied. Only dichloroacetic acid (DCAA) and chloride anions were routinely detected as reduction products for any of the electrodes, and reasonable values of mass balance error were obtained. Of the three materials studied, the titanium cathode gave the best results. PMID:23530352

Esclapez, M D; Díez-García, M I; Sàez, V; Bonete, P; González-García, José

2013-01-01

68

Developing a Software Architecture for Graceful Degradation in an Elevator Control System  

E-print Network

Developing a Software Architecture for Graceful Degradation in an Elevator Control System Abstract that may enhance graceful degradation for an example elevator control system, and discussion about Many embedded systems have high safety and dependability requirements, which makes ensuring software

Koopman, Philip

69

Methods Currently Used in Testing Microbiological Degradation and Deterioration of a Wide Range of Polymeric Materials with Various Degree of Degradability: A Review  

Microsoft Academic Search

Biodegradation of polymeric materials affect a wide range of industries, information on degradability can provide fundamental information facilitating design and life-time analysis of materials. Among the methods currently used in testing, traditional gravimetric and respirometric techniques are tailored to readily degradable polymeric materials mostly and polymer blends with biodegradable components, but they are not applicable to the new generation of

Ji-Guang Gu; Ji-Dong Gu

2005-01-01

70

Thermomechanical Constitutive Modeling of Viscoelastic Materials undergoing Degradation  

E-print Network

of moisture and chemical reactions (for instance, oxidation) and there is need for a good understanding of the various degradation mechanisms. This work focuses on: 1) some topics related to development of viscoelastic fluid models that can be used to predict...

Karra, Satish

2012-07-16

71

Sources of high temperature degradation of cement-based materials : nanoindentation and microporoelastic analysis  

E-print Network

The effects of high temperature exposure on cement-based materials have been under investigation for quite some time, but a fundamental understanding of the sources of high temperature degradation has been limited by ...

DeJong, Matthew J. (Matthew Justin)

2005-01-01

72

Main chain acid-degradable polymers for the delivery of bioactive materials  

DOEpatents

Novel main chain acid degradable polymer backbones and drug delivery systems comprised of materials capable of delivering bioactive materials to cells for use as vaccines or other therapeutic agents are described. The polymers are synthesized using monomers that contain acid-degradable linkages cleavable under mild acidic conditions. The main chain of the resulting polymers readily degrade into many small molecules at low pH, but remain relatively stable and intact at physiological pH. The new materials have the common characteristic of being able to degrade by acid hydrolysis under conditions commonly found within the endosomal or lysosomal compartments of cells thereby releasing their payload within the cell. The materials can also be used for the delivery of therapeutics to the acidic regions of tumors and other sites of inflammation.

Frechet, Jean M. J. (Oakland, CA); Standley, Stephany M. (Evanston, IL); Jain, Rachna (Milpitas, CA); Lee, Cameron C. (Cambridge, MA)

2012-03-20

73

Control of in vivo mineral bone cement degradation.  

PubMed

The current study aimed to prevent the formation of hydroxyapatite reprecipitates in brushite-forming biocements by minimizing the availability of free Ca(2+) ions in the cement matrix. This was achieved by both maximizing the degree of cement setting to avoid unreacted, calcium-rich cement raw materials which can deliver Ca(2+) directly to the cement matrix after dissolution, and by a reduction in porosity to reduce Ca(2+) diffusion into the set cement matrix. In addition, a biocement based on the formation of the magnesium phosphate mineral struvite (MgNH4PO4·6H2O) was tested, which should prevent the formation of low-solubility hydroxyapatite reprecipitates due to the high magnesium content. Different porosity levels were fabricated by altering the powder-to-liquid ratio at which the cements were mixed and the materials were implanted into mechanically unloaded femoral defects in sheep for up to 10 months. While the higher-porosity brushite cement quantitatively transformed into crystalline octacalcium phosphate after 10 months, slowing down cement resorption, a lower-porosity brushite cement modification was found to be chemically stable with the absence of reprecipitate formation and minor cement resorption from the implant surface. In contrast, struvite-forming cements were much more degradable due to the absence of mineral reprecipitates and a nearly quantitative cement degradation was found after 10 months of implantation. PMID:24769112

Kanter, Britta; Geffers, Martha; Ignatius, Anita; Gbureck, Uwe

2014-07-01

74

Probabilistic constitutive relationships for material strength degradation models  

NASA Technical Reports Server (NTRS)

In the present probabilistic methodology for the strength of aerospace propulsion system structural components subjected to such environmentally-induced primitive variables as loading stresses, high temperature, chemical corrosion, and radiation, time is encompassed as an interacting element, allowing the projection of creep and fatigue effects. A probabilistic constitutive equation is postulated to account for the degradation of strength due to these primitive variables which may be calibrated by an appropriately curve-fitted least-squares multiple regression of experimental data. The resulting probabilistic constitutive equation is embodied in the PROMISS code for aerospace propulsion component random strength determination.

Boyce, L.; Chamis, C. C.

1989-01-01

75

Advanced Materials for RSOFC Dual Operation with Low Degradation  

SciTech Connect

Reversible solid oxide fuel cells (RSOFCs) are energy conversion devices. They are capable of operating in both power generation mode (SOFC) and electrolysis modes (SOEC). RSOFC can integrate renewable production of electricity and hydrogen when power generation and steam electrolysis are coupled in a system, which can turn intermittent solar and wind energy into "firm power." In this DOE EERE project, VPS continuously advanced RSOFC cell stack technology in the areas of endurance and performance. Over 20 types of RSOFC cells were developed in the project. Many of those exceeded performance (area specific resistance less than 300 mohmcm2) and endurance (degradation rate less than 4% per 1000 hours) targets in both fuel cell and electrolysis modes at 750C. One of those cells, RSOFC-7, further demonstrated the following: Steady-state electrolysis with a degradation rate of 1.5% per 1000 hours. Ultra high current electrolysis over 3 A/cm2 at 75% water electrolysis efficiency voltage of 1.67 V. Daily SOFC/SOEC cyclic test of over 600 days with a degradation rate of 1.5% per 1000 hours. Over 6000 SOFC/SOEC cycles in an accelerated 20-minute cycling with degradation less than 3% per 1000 cycles. In RSOFC stack development, a number of kW-class RSOFC stacks were developed and demonstrated the following: Steady-state electrolysis operation of over 5000 hours. Daily SOFC/SOEC cyclic test of 100 cycles. Scale up capability of using large area cells with 550 cm2 active area showing the potential for large-scale RSOFC stack development in the future. Although this project is an open-ended development project, this effort, leveraging Versa Power Systems' years of development experience, has the potential to bring renewable energy RSOFC storage systems significantly closer to commercial viability through improvements in RSOFC durability, performance, and cost. When unitized and deployed in renewable solar and wind installations, an RSOFC system can enable higher availability for intermittent renewable resources, thereby improving the commercial viability of these types of energy resources.

Eric, Tang; Tony, Wood; Sofiane, Benhaddad; Casey, Brown; Hongpeng, He; Jeff, Nelson; Oliver, Grande; Ben, Nuttall; Mark, Richards; Randy, Petri

2012-12-27

76

Photoconversion of gasified organic materials into biologically-degradable plastics  

DOEpatents

A process is described for converting organic materials (such as biomass wastes) into a bioplastic suitable for use as a biodegradable plastic. In a preferred embodiment the process involves thermally gasifying the organic material into primarily carbon monoxide and hydrogen, followed by photosynthetic bacterial assimilation of the gases into cell material. The process is ideally suited for waste recycling and for production of useful biodegradable plastic polymer. 3 figures.

Weaver, P.F.; Pinching Maness.

1993-10-05

77

Photoconversion of gasified organic materials into biologically-degradable plastics  

DOEpatents

A process is described for converting organic materials (such as biomass wastes) into a bioplastic suitable for use as a biodegradable plastic. In a preferred embodiment the process involves thermally gasifying the organic material into primarily carbon monoxide and hydrogen, followed by photosynthetic bacterial assimilation of the gases into cell material. The process is ideally suited for waste recycling and for production of useful biodegradable plastic polymer.

Weaver, Paul F. (Golden, CO); Maness, Pin-Ching (Golden, CO)

1993-01-01

78

A novel method for on-orbit measurement of space materials degradation  

SciTech Connect

The low Earth orbit (LEO) environment is considered hazardous to spacecraft, resulting in materials degradation. Currently, in order to evaluate the degradation of materials in LEO, a retrieval of space exposed samples is required. In this study, a novel approach is proposed to evaluate degradation of materials in LEO without the need of retrieval. The method is utilizing photovoltaic cells (PVCs), an existing component onboard of any satellite. The PVCs are coated by various materials which are sensitive to different LEO constituents, such as atomic oxygen (AO) or ultra-violet (UV) radiation. The method's acronym is ORMADD (on-ORbit MAterials Degradation Detector). The ORMADD's principle of operation is based on measuring the PVC output power which depends on the cell coating material's optical transmission. Erosion of the coating by AO or coloring due to UV radiation affects its optical transmission and, accordingly, the PVC output. The ORMADD performance was tested using different coatings, such as polyimide and amorphous carbon (sensitive to AO), and siloxane based coating which is sensitive to UV radiation. The proposed ORMADD reveals sensitivity to different LEO components and can be used either as material degradation detector or as an AO monitor.

Verker, Ronen; Grossman, Eitan; Gouzman, Irina [Space Environment Department, Soreq NRC, Yavne 81800 (Israel)

2011-02-15

79

A novel method for on-orbit measurement of space materials degradation.  

PubMed

The low Earth orbit (LEO) environment is considered hazardous to spacecraft, resulting in materials degradation. Currently, in order to evaluate the degradation of materials in LEO, a retrieval of space exposed samples is required. In this study, a novel approach is proposed to evaluate degradation of materials in LEO without the need of retrieval. The method is utilizing photovoltaic cells (PVCs), an existing component onboard of any satellite. The PVCs are coated by various materials which are sensitive to different LEO constituents, such as atomic oxygen (AO) or ultra-violet (UV) radiation. The method's acronym is ORMADD (on-ORbit MAterials Degradation Detector). The ORMADD's principle of operation is based on measuring the PVC output power which depends on the cell coating material's optical transmission. Erosion of the coating by AO or coloring due to UV radiation affects its optical transmission and, accordingly, the PVC output. The ORMADD performance was tested using different coatings, such as polyimide and amorphous carbon (sensitive to AO), and siloxane based coating which is sensitive to UV radiation. The proposed ORMADD reveals sensitivity to different LEO components and can be used either as material degradation detector or as an AO monitor. PMID:21361605

Verker, Ronen; Grossman, Eitan; Gouzman, Irina

2011-02-01

80

On the degradation of insulating materials withstanding electrical stress  

Microsoft Academic Search

An avalanche of physical and physico-chemical phenomena, often self-sustained, lead to the end of life of an insulating material. The collapse of the insulating role of a material is greatly due to the electrical field stress. The path leading from the catastrophic situation, the breakdown, to its origin is followed in the present report. A defect, preexisting or created by

Christian Mayoux

2000-01-01

81

Caveolin: a possible biomarker of degradable metallic materials toxicity in vascular cells.  

PubMed

Iron-based materials could constitute an interesting option for cardiovascular biodegradable stent applications due to their appropriate ductility compared with their counterparts, magnesium alloys. However, the predicted degradation rate of pure iron is considered to be too slow for such applications. We explored manganese (35 wt.%) as an alloying element in combination with iron to circumvent this problem through powder metallurgical processing (Fe-35Mn). Manganese, on the other hand, is highly cytotoxic. We recently explored a new method to better characterize the safety of degradable metallic materials (DMMs) by establishing the gene expression profile (GEP) of cells (mouse 3T3 fibroblasts) exposed to Fe-35Mn degradation products in order to better understand their global response to a potentially cytotoxic DMM. We identified a number of up- and down-regulated genes and confirmed the regulation of a subset of them by quantitative real time polymerase chain reaction. Caveolin-1 (cav1), the structural protein of caveolae, small, smooth plasma membrane invaginations present in various differentiated cell types, was one of the most down-regulated genes in our GEPs. In the present study we further studied the potential of this 22 kDa protein to become a biomarker for cytotoxicity after exposure to degradable metallic elements. In order to better characterize cav1 expression in this context 3T3 mouse fibroblasts were exposed to either ferrous and manganese ions at cytostatic concentrations for 24 or 48 h. cav1 gene expression was not influenced by exposure to ferrous ions. On the other hand, exposure to manganese for 24h reduced cav1 gene expression by about 30% and by >65% after 48 h compared with control 3T3 cells. The cav1 cellular protein content was reduced to the same extent. The same pattern of expression of cav3 (the muscle-specific caveolin subtype) was also observed in this study. This strong and reproducible pattern of regulation of caveolins thus indicates potential as a biomarker for the toxicity of DMM elements. PMID:23597857

Purnama, Agung; Mantovani, Diego; Couet, Jacques

2013-11-01

82

Long-Term Lunar Radiation Degradation Effects on Materials  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration (NASA) is focused on developing technologies for extending human presence beyond low Earth orbit. These technologies are to advance the state-of-the-art and provide for longer duration missions outside the protection of Earth's magnetosphere. One technology of great interest for large structures is advanced composite materials, due to their weight and cost savings, enhanced radiation protection for the crew, and potential for performance improvements when compared with existing metals. However, these materials have not been characterized for the interplanetary space environment, and particularly the effects of high energy radiation, which is known to cause damage to polymeric materials. Therefore, a study focusing on a lunar habitation element was undertaken to investigate the integrity of potential structural composite materials after exposure to a long-term lunar radiation environment. An overview of the study results are presented, along with a discussion of recommended future work.

Rojdev, Kristina; ORourke, Mary Jane; Koontz, Steve; Alred, John; Hill, Charles; Devivar, Rodrigo; Morera-Felix, Shakira; Atwell, William; Nutt, Steve; Sabbann, Leslie

2010-01-01

83

Electrochemical shock : mechanical degradation of ion-intercalation materials  

E-print Network

The ion-intercalation materials used in high-energy batteries such as lithium-ion undergo large composition changes-which correlate to high storage capacity-but which also induce structural changes and stresses that can ...

Woodford, William Henry, IV

2013-01-01

84

Understanding and harnessing energy-dependent proteolysis for controlled protein degradation in bacteria  

E-print Network

Regulated intracellular protein degradation is critical for cellular viability. In many organisms, degradation controls cell-cycle progression, executes responses to stress-inducing environmental changes, and enables the ...

Davis, Joseph H. (Joseph Harry), III

2010-01-01

85

ADAPTIVE OPTICS CONTROL FOR LASER MATERIAL PROCESSING  

E-print Network

ADAPTIVE OPTICS CONTROL FOR LASER MATERIAL PROCESSING S. Mauch , J. Reger , E. Beckert Control-mail: erik.beckert@iof.fraunhofer.de) Abstract: An adaptive optics system is used for correcting tip: adaptive optics, tip-tilt control, Kalman-filtering, material processing 1. INTRODUCTION In laser material

Knobloch,Jürgen

86

Degradable polyester scaffolds with controlled surface chemistry combining minimal protein adsorption with specific bioactivation  

NASA Astrophysics Data System (ADS)

Advanced biomaterials and scaffolds for tissue engineering place high demands on materials and exceed the passive biocompatibility requirements previously considered acceptable for biomedical implants. Together with degradability, the activation of specific cell-material interactions and a three-dimensional environment that mimics the extracellular matrix are core challenges and prerequisites for the organization of living cells to functional tissue. Moreover, although bioactive signalling combined with minimization of non-specific protein adsorption is an advanced modification technique for flat surfaces, it is usually not accomplished for three-dimensional fibrous scaffolds used in tissue engineering. Here, we present a one-step preparation of fully synthetic, bioactive and degradable extracellular matrix-mimetic scaffolds by electrospinning, using poly(D,L-lactide-co-glycolide) as the matrix polymer. Addition of a functional, amphiphilic macromolecule based on star-shaped poly(ethylene oxide) transforms current biomedically used degradable polyesters into hydrophilic fibres, which causes the suppression of non-specific protein adsorption on the fibres’ surface. The subsequent covalent attachment of cell-adhesion-mediating peptides to the hydrophilic fibres promotes specific bioactivation and enables adhesion of cells through exclusive recognition of the immobilized binding motifs. This approach permits synthetic materials to directly control cell behaviour, for example, resembling the binding of cells to fibronectin immobilized on collagen fibres in the extracellular matrix of connective tissue.

Grafahrend, Dirk; Heffels, Karl-Heinz; Beer, Meike V.; Gasteier, Peter; Möller, Martin; Boehm, Gabriele; Dalton, Paul D.; Groll, Jürgen

2011-01-01

87

Characterization of thermal conductivity degradation induced by heavy ion irradiation in ceramic materials  

NASA Astrophysics Data System (ADS)

Thermal conductivity degradation of three semi-metallic ceramics: titanium carbide, zirconium carbide and titanium nitride, and a covalent compound: 6H silicon carbide, induced by irradiation with energetic heavy ions at room temperature, is studied and quantified. Irradiations by 25.8 MeV krypton ions at 1016 and 6 × 1016 ions cm-2 doses were used to produce defects in the considered materials. Modulated thermoreflectance microscopy measurements were performed to characterize the resulting subsurfasic degradation of the thermal conductivity for each of the investigated materials. The study considers the two collision domains produced by the inelastic collisions and the elastic collisions that occur during an ion irradiation. A significant thermal conductivity degradation in the two collision domains for all materials is obtained. Elastic collisions are shown to degrade the thermal properties more strongly than the inelastic ones. The scattering of thermal energy carriers is larger in the elastic collision domain because displacement cascades produce a very high concentration of point defects. The degradation coming from electronic interactions is found to be more important in SiC, which can be explained by the presence of large populations of generated extended defects, facing generated individual point defects in the studied semi-metallic materials.

David, L.; Gomès, S.; Carlot, G.; Roger, J.-P.; Fournier, D.; Valot, C.; Raynaud, M.

2008-02-01

88

New Evaluation Method of Material Degradation Considering Synergistic Effects of Radiation Damage  

NASA Astrophysics Data System (ADS)

In core structural materials of next generation reactors such as a liquid-metal cooled fast breeding reactor and a supercritical-water cooled thermal or first reactor, materials' degradation behavior by neutron irradiation damage and thermal (cyclic) stress should be considered with fair accuracy in design process (including maintenance and repair plans), because the materials are used under higher temperature gradients and higher neutron flux fields than those in the present light water reactors. In the current experiential design rules, service lives of core structural components were determined by the materials degradation such as the increase of ductile-to-brittle transition temperature after post irradiation examination data. However, other materials degradations such as irradiation-assisted stress corrosion cracking (IASCC), which occurs by the degradation synergistically interacting with radiation hardening, local chemical composition change, swelling and radiation creep, should be considered reasonably in the design process of the next generation reactors, because of the anticipation of the beneficial effects by synergy of radiation damage. The radiation hardening and local chemical composition change at grain boundaries due to radiation-induced segregation increased with increasing dose. Above some threshold dose, swelling increased rapidly with increasing dose. Residual stress due to thermal stress and welding procedure decreased with increasing dose. To predict material failure by IASCC with reasonable accuracy, in this study, each material degradation phenomenon with different dose dependence was modeled with consideration of radiation induced stress relaxation. And then the models were integrated to simulate the failure behavior for the duration of reactor operation period. In this paper, the models obtained by ion-irradiation experiments and compared by data from neutron irradiation experiments were presented, and the concept of our new evaluation method and the programming code for the failure simulation were outlined.

Miwa, Yukio; Kaji, Yoshiyuki; Okubo, Nariaki; Kondo, Keietsu; Tsukada, Takashi

89

Thermal conductivity degradation induced by heavy ion irradiation at room temperature in ceramic materials  

NASA Astrophysics Data System (ADS)

The thermal conductivity degradation induced by irradiation with energetic heavy ions at room temperature is studied and quantified. Three semi-metallic systems: titanium and zirconium carbides, titanium nitride, as well as a covalent compound: 6H silicon carbide were irradiated by 25.8 MeV krypton ions at 1016 and 6 \\cdot 1016 ions.cm-2 doses to produce defects. During ion irradiation, inelastic collisions and elastic collisions occur at a different depth in a material. Two collision domains can be defined. Modulated thermoreflectance microscopy measurements were performed at differing frequencies to characterize the thermal conductivity degradation in these two domains for each of the investigated materials. Our results reveal a significant thermal conductivity degradation in the two collision domains for all materials. Elastic collisions are shown to degrade more strongly the thermal properties than inelastic ones. Scattering of thermal energy carriers is larger in elastic collision domain because displacement cascades produce a very high concentration of point defects: vacancies, interstitials and implanted Kr ions. The degradation coming from electronic interactions that seems to be more important in SiC can be explained by the presence of large populations of generated extended defects, facing to generated individual point defects in TiC, TiN or ZrC.

Gomès, S.; David, L.; Roger, J.-P.; Carlot, G.; Fournier, D.; Valot, C.; Raynaud, M.

2008-01-01

90

Development of materials resistant to metal dusting degradation.  

SciTech Connect

Metal dusting corrosion has been a serious problem in the petroleum and petrochemical industries, such as reforming and syngas production systems. This form of deterioration has led to worldwide material loss for 50 years. For the past three years, we have studied the mechanism of metal dusting for Fe- and Ni-base alloys. In this report, we present a correlation between the weight loss and depth of pits that form in Ni-base alloys. Nickel-base alloys were also tested at 1 and 14.8 atm (210 psi), in a high carbon activity environment. Higher system pressure was found to accelerate corrosion in most Ni-base alloys. To reduce testing time, a pre-pitting method was developed. Mechanical scratches on the alloy surface led to fast metal dusting corrosion. We have also developed preliminary data on the performance of weldments of several Ni-base alloys in a metal dusting environment. Finally, Alloy 800 tubes and plates used in a reformer plant were examined by scanning electron microscopy, energy dispersive X-ray, and Raman spectroscopy. The oxide scale on the surface of the Alloy 800 primarily consists of Fe{sub 1+x}Cr{sub 2-X}O{sub 4} spinel phase with high Fe content. Carbon can diffuse through this oxide scale. It was discovered that the growth of metal dusting pits could be stopped by means of a slightly oxidized alloy surface. This leads to a new way to solve metal dusting problem.

Natesan, K.; Zeng, Z.

2006-04-24

91

Material Recycling and Waste Disposal Document Control  

E-print Network

1 Material Recycling and Waste Disposal Procedure Document Control Document Created by 23, treatment, handling, transport and disposal of recyclable materials and residual wastes so as to maximise the opportunity and value for the recyclable materials and to minimise the quantity of residual materials

Guillas, Serge

92

Controlling Weapons-Grade Fissile Material  

ERIC Educational Resources Information Center

Discusses the problems of controlling weapons-grade fissionable material. Projections of the growth of fission nuclear reactors indicates sufficient materials will be available to construct 300,000 atomic bombs each containing 10 kilograms of plutonium by 1990. (SL)

Rotblat, J.

1977-01-01

93

Sonolytic degradation of dimethoate: Kinetics, mechanisms and toxic intermediates controlling  

Microsoft Academic Search

The sonolytic degradation of aqueous solutions of dimethoate, O,O-dimethyl S-[2-(methylamino)-2-oxoethyl]dithiophosphate, was examined. Optimal degradation rates were obtained at 619kHz for continuous sonolysis and 406kHz for pulse sonolysis. The primary pathways for degradation include hydroxyl radical oxidation, hydrolysis and pyrolysis on collapsing cavitation bubble interfaces. Reaction mechanisms coupled with the corresponding kinetic models are proposed to reproduce the observed concentration versus

Juan-Juan Yao; Michael R. Hoffmann; Nai-Yun Gao; Zhi Zhang; Lei Li

2011-01-01

94

Integrin expression by human osteoblasts cultured on degradable polymeric materials applicable for tissue engineered bone  

E-print Network

Integrin expression by human osteoblasts cultured on degradable polymeric materials applicable was to evaluate human osteoblastic cell adherence and growth on PLAGA and PLA scaffolds by examining integrin composites. Interestingly, the integrin subunits, a2; a3; a4; a5; a6 and b1 were all expressed at higher

Lu, Helen H.

95

SCAPS Modeling for Degradation of Ultrathin CdTe Films: Materials Interdiffusion  

NASA Astrophysics Data System (ADS)

Ultrathin film solar cells based on CdS/CdTe (d CdTe ? 1 µm) suffer from two main issues: incomplete photo absorption and high degradation rate. The former is cured by light-trapping techniques, whereas the latter is a matter of fabrication details. Interdiffusion of the material components and formation of subsequent interlayers at the front/back region can change the optical/electrical properties and performance/stability of the device. We model the degradation of the ultrathin CdTe film devices considering the material interdiffusion and interlayers formation: CdTeS, CdZnTe, Cu x Te (i.e., Te/Cu bilayer), and oxide interlayers (i.e., CdTeO3). The diffusion rate of the materials is considered separately and the reactions that change the interlayer's properties are studied. Additionally, a back contact of single-walled carbon nanotube showed a higher stability than the metallic contacts. A new time-dependent approach is applied to simulate the degradation rate due to formation of any interlayer. It is shown that the materials interdiffusion causes a defect increment under thermal stress and illumination. The metallic back contact accelerates the degradation, whereas single-walled carbon nanotubes show the highest stability. A SCAPS simulator was used because of its ability in defining the properties of the back contact and metastabilities at the interface layers. The properties of the layers were taken from the experimental data reported in the literature.

Houshmand, Mohammad; Zandi, M. Hossein; Gorji, Nima E.

2015-01-01

96

An analytical approach toward monitoring degradation in engineering thermoplastic materials used for electrical applications  

Microsoft Academic Search

Engineering thermoplastics are being used in a broad array of applications throughout the electrical industry. Polyester thermoplastics offer desirable electrical and mechanical properties; but when used in the wrong environments, they can be susceptible to hydrolysis. Size exclusion chromatography (SEC) can be used as an analytical tool for monitoring the degree of hydrolytic degradation occurring to engineering thermoplastic materials. By

Sam J. Ferrito; Thomas A. Edison

1996-01-01

97

Materials Degradation Issues in the U.S. High-Level Nuclear Waste Repository  

SciTech Connect

This paper reviews the state-of-the-art understanding of the degradation processes by the Yucca Mountain Project (YMP) with focus on interaction between the in-drift environmental conditions and long-term materials degradation of waste packages and drip shields within the repository system during the first 10,000-years after repository closure. This paper provides an overview of the degradation of the waste packages and drip shields in the repository after permanent closure of the facility. The degradation modes discussed in this paper include aging and phase instability, dry oxidation, general and localized corrosion, stress corrosion cracking, and hydrogen induced cracking of Alloy 22 and titanium alloys. The effects of microbial activity and radiation on the degradation of Alloy 22 and titanium alloys are also discussed. Further, for titanium alloys, the effects of fluorides, bromides, and galvanic coupling to less noble metals are considered. It is concluded that the materials and design adopted will provide sufficient safety margins for at least 10,000-years after repository closure.

K.G. Mon; F. Hua

2005-04-12

98

Carbon Nanotube Materials for Substrate Enhanced Control of Catalytic Activity  

SciTech Connect

Carbon SWNTs are attractive materials for supporting electrocatalysts. The properties of SWNTs are highly tunable and controlled by the nanotube's circumferential periodicity and their surface chemistry. These unique characteristics suggest that architectures constructed from these types of carbon support materials would exhibit interesting and useful properties. Here, we expect that the structure of the carbon nanotube support will play a major role in stabilizing metal electrocatalysts under extreme operating conditions and suppress both catalyst and support degradation. Furthermore, the chemical modification of the carbon nanotube surfaces can be expected to alter the interface between the catalyst and support, thus, enhancing the activity and utilization of the electrocatalysts. We plan to incorporate discrete reaction sites into the carbon nanotube lattice to create intimate electrical contacts with the catalyst particles to increase the metal catalyst activity and utilization. The work involves materials synthesis, design of electrode architectures on the nanoscale, control of the electronic, ionic, and mass fluxes, and use of advanced optical spectroscopy techniques.

Heben, M.; Dillon, A. C.; Engtrakul, C.; Lee, S.-H.; Kelley, R. D.; Kini, A. M.

2007-05-01

99

Sonolytic degradation of dimethoate: kinetics, mechanisms and toxic intermediates controlling.  

PubMed

The sonolytic degradation of aqueous solutions of dimethoate, O,O-dimethyl S-[2-(methylamino)-2-oxoethyl]dithiophosphate, was examined. Optimal degradation rates were obtained at 619 kHz for continuous sonolysis and 406 kHz for pulse sonolysis. The primary pathways for degradation include hydroxyl radical oxidation, hydrolysis and pyrolysis on collapsing cavitation bubble interfaces. Reaction mechanisms coupled with the corresponding kinetic models are proposed to reproduce the observed concentration versus time profiles for dimethoate, omethoate and N-(methyl) mercaptoacetamide during sonolysis. The oxidation and hydrolysis of dimethoate and omethoate occurred at the water-bubble interface was the rate-determining step for sonolytic overall degradation of dimethoate. More than 90% toxicity of dimethoate was reduced within 45 min ultrasonic irradiation. Ferrous ion at micro molar level can significantly enhance the sonolytic degradation of dimethoate and effectively reduce the yields of toxic intermediate omethoate. PMID:21962849

Yao, Juan-Juan; Hoffmann, Michael R; Gao, Nai-Yun; Zhang, Zhi; Li, Lei

2011-11-15

100

Thermal/chemical degradation of ceramic cross-flow filter materials  

SciTech Connect

This report summarizes the 14-month, Phase 1 effort conducted by Westinghouse on the Thermal/Chemical Degradation of Ceramic Cross-Flow Filter Materials program. In Phase 1 expected filter process conditions were identified for a fixed-bed, fluid-bed, and entrained-bed gasification, direct coal fired turbine, and pressurized fluidized-bed combustion system. Ceramic cross-flow filter materials were also selected, procured, and subjected to chemical and physical characterization. The stability of each of the ceramic cross-flow materials was assessed in terms of potential reactions or phase change as a result of process temperature, and effluent gas compositions containing alkali and fines. In addition chemical and physical characterization was conducted on cross-flow filters that were exposed to the METC fluid-bed gasifier and the New York University pressurized fluidized-bed combustor. Long-term high temperature degradation mechanisms were proposed for each ceramic cross-flow material at process operating conditions. An experimental bench-scale test program is recommended to be conducted in Phase 2, generating data that support the proposed cross-flow filter material thermal/chemical degradation mechanisms. Papers on the individual subtasks have been processed separately for inclusion on the data base.

Alvin, M.A.; Lane, J.E.; Lippert, T.E.

1989-11-01

101

LANL material control indicator analysis program  

SciTech Connect

The possibility of SNM diversion/theft is a major concern to organizations charged with control of Special Nuclear Material (SNM). Several methods have been put in place to deter and or detect losses of SNM. These include inventory, material control physical barriers and the use of material control indicators (MCI). This paper will discuss the multi-tier LANL review mechanism for detecting and isolating missing SNM by the use of Material Control Indicators. Los Alamos MCI include daily analysis and review of item adjustments, weekly review of item adjustments, monthly analysis and review of inventory differences by Process Status and by Material Balance Areas, and quarterly analysis and review of Propagation of Variance. This paper, by providing an introduction to a site-specific application of MCI's, assists safeguards professionals in understanding the importance of an MCI Program in detecting accumulation for subsequent diversion/theft of special nuclear material.

Roybal, G. S. (Gilbert S.)

2001-01-01

102

Small-Molecule Control of Protein Degradation Using Split Adaptors  

E-print Network

Targeted intracellular degradation provides a method to study the biological function of proteins and has numerous applications in biotechnology. One promising approach uses adaptor proteins to target substrates with ...

Davis, Joseph H.

103

Damage Assessment Technologies for Prognostics and Proactive Management of Materials Degradation (PMMD)  

SciTech Connect

There are approximately 440 operating reactors in the global nuclear power plant (NPP) fleet with an average age greater than 20 years and design lives of 30 or 40 years. The United States is currently implementing license extensions of 20 years on many plants, and consideration is now being given to the concept of "life-beyond-60", license extension from 60 to 80 years and potentially longer. In almost all countries with NPPs, authorities are looking at some form of license renewal program. In support of NPP license renewal over the past decade, various national and international programs have been initiated. This paper discusses stressor-based prognostics and its role as part of emerging trends in Proactive Management of Materials Degradation (PMMD) applied to nuclear power plant structures, systems and components (SSC). The paper concisely explains the US Nuclear Regulatory Commission’s (NRC) program in PMMD, the basic principles of PMMD and its relationship to advanced diagnostics and prognostics. It then provides an assessment of the state of maturity for diagnostic and prognostic technologies, including NDE and related technologies for damage assessment, and the current trend to move from condition-based maintenance to on-line monitoring for advanced diagnostics and stressor-based prognostics. This development in technology requires advances in sensors; better understanding of what and how to measure within a nuclear power plant; enhanced data interrogation, communication and integration; new prediction models for damage/aging evolution; system integration for real-world deployments and quantification of uncertainties in what are inherently ill-posed problems. Stressor-based analysis is based upon understanding which stressor characteristics (e.g., pressure transients) provide a percussive indication that can be used for mapping subsequent damage due to a specific degradation mechanism. The resulting physical damage and the associated decrease in asset performance start with the application of a stressor to the component. The design engineer sets the desired operational stressor intensity level so that the degradation in the physical state of the component occurs slowly enough for the equipment to last for its required design life. In general, when the design limit of a stressor is exceeded (during operation), the component life expectancy starts to shorten. Conversely, careful control of operational parameters can enable extension of component life beyond that normally expected. For systems which were conservatively designed (such as nuclear power plants), the premise of the prognostic methodology is that a relationship can be derived that will allow a much more accurate projection of the remaining useful life. This is achieved by focusing on trending the stressor characterics rather than trending a performance metric. In this trend analysis example, the slope of the trended parameter is thought to give a measure of the degradation rate of the component performance. This is assumed to be a function of the rate of decline in the physical integrity of the equipment. Experience from measurements has shown this assumption to be true if one accounts for the nonlinearity which can occur between physical attributes and their effects on performance.

Bond, Leonard J.; Doctor, Steven R.; Griffin, Jeffrey W.; Hull, Amy B.; Malik, Shah

2009-01-16

104

Degradation mechanisms of materials for large space systems in low Earth orbit  

NASA Technical Reports Server (NTRS)

Degradation was explored of various materials used in aerospace vehicles after severe loss of polymeric material coatings (Kapton) was observed on an early shuttle flight in low Earth orbit. Since atomic oxygen is the major component of the atmosphere at 300 km, and the shuttle's orbital velocity produced relative motion corresponding to approx. 5 eV of oxygen energy, it was natural to attribute much of this degradation to oxygen interaction. This assumption was tested using large volume vacuum systems and ion beam sources, in an exploratory effort to produce atomic oxygen of the appropriate energy, and to observe mass loss from various samples as well as optical radiation. Several investigations were initiated and the results of these investigations are presented in four papers. These papers are summarized. They are entitled: (1) The Space Shuttle Glow; (2) Laboratory Degradation of Kapton in a Low Energy Oxygen Ion Beam; (3) The Energy Dependence and Surface Morphology of Kapton Degradation Under Atomic Oxygen Bombardment; and (4) Surface Analysis of STS 8 Samples.

Gordon, William L.; Hoffman, R. W.

1987-01-01

105

Understanding Fundamental Material Degradation Processes in High Temperature Aggressive Chemomechanical Environments  

SciTech Connect

The objective of this project is to develop a fundamental understanding of the mechanisms that limit materials durability for very high-temperature applications. Current design limitations are based on material strength and corrosion resistance. This project will characterize the interactions of high-temperature creep, fatigue, and environmental attack in structural metallic alloys of interest for the very high-temperature gas-cooled reactor (VHTR) or Next–Generation Nuclear Plant (NGNP) and for the associated thermo-chemical processing systems for hydrogen generation. Each of these degradation processes presents a major materials design challenge on its own, but in combination, they can act synergistically to rapidly degrade materials and limit component lives. This research and development effort will provide experimental results to characterize creep-fatigue-environment interactions and develop predictive models to define operation limits for high-temperature structural material applications. Researchers will study individually and in combination creep-fatigue-environmental attack processes in Alloys 617, 230, and 800H, as well as in an advanced Ni-Cr oxide dispersion strengthened steel (ODS) system. For comparison, the study will also examine basic degradation processes in nichrome (Ni-20Cr), which is a basis for most high-temperature structural materials, as well as many of the superalloys. These materials are selected to represent primary candidate alloys, one advanced developmental alloy that may have superior high-temperature durability, and one model system on which basic performance and modeling efforts can be based. The research program is presented in four parts, which all complement each other. The first three are primarily experimental in nature, and the last will tie the work together in a coordinated modeling effort. The sections are 1) dynamic creep-fatigue-environment process, 2) subcritical crack processes, 3) dynamic corrosion – crack initiation processes, and 4) modeling.

Stubbins, James; Gewirth, Andrew; Sehitoglu, Huseyin; Sofronis, Petros; Robertson, Ian

2014-01-16

106

Degradation of the materials of construction in Li-ion batteries  

Microsoft Academic Search

The primary current-collector materials being used in lithium-ion cells are susceptible to environmental degradation: aluminum to pitting corrosion and copper to environmentally assisted cracking. Pitting occurs at the highly oxidizing potentials associated with the positive-electrode charge condition. However, the pitting mechanism is more complex than that typically observed in aqueous systems in that the pits are filled with a mixed

Jeffrey W. Braithwaite; Angelo Gonzales; Samuel J. Lucero

1997-01-01

107

Development of advanced SQUID system for nondestructive evaluation of material degradation in power plants  

SciTech Connect

A newer and more advanced version of the SQUID sensor system for estimating the degradation of materials in power plants have been developed. The miniaturized SQUID sensor developed for nondestructive measurement is 262 mm high, 152 mm in diameter, and 5 kg in weight, making it only one-twelfth the size and one-tenth the weight of a conventional SQUID sensor. Tests have demonstrated that the new SQUID sensor can successfully estimate fatigue damage in Type 316 stainless steel.

Otaka, M.; Hayashi, E. [Hitachi, Ltd., Ibaraki (Japan)

1995-08-01

108

Degradation mechanisms of nylon separator materials for a nickel-cadmium cell in KOH electrolytes  

NASA Astrophysics Data System (ADS)

Degradation reactions of a nylon-6 battery separator material have been studied in 4-34-percent aqueous KOH electrolytes at 35-110 C. In a Ni/Cd cell, this degradation involves a slow hydrolysis reaction followed by fast electrochemical oxidations of the hydrolysis reaction products. Arrhenius activation energy of the hydrolysis reaction in 34-percent KOH was 20.0 + or - 0.3 kcal/mole. A plot of the hydrolysis rate at 100 C vs hydroxyl ion concentration gave a rate maximum at about 16-percent KOH, and the mechanism for this effect is discussed. Electrochemical oxidations of the hydrolysis product, 6-aminocaproate ion, appear to proceed rapidly in several sequential steps at a nickel oxide electrode. In a Ni/Cd cell, the combination of nylon separator hydrolysis followed by electrochemical oxidation of the products can seriously degrade the battery life-time. The rate of the hydrolysis of nylon-66 separator material was approximately one half of that of the nylon-6 material.

Lim, H. S.; Margerum, J. D.; Verzwyvelt, S. A.; Lackner, A. M.; Knechtli, R. C.

1989-03-01

109

Degradation mechanisms of nylon separator materials for a nickel-cadmium cell in KOH electrolytes  

SciTech Connect

Degradation reactions of a nylon 6 battery separator material have been studied in 4-34% aqueous KOH electrolytes at 35/sup 0/-110/sup 0/C. In a Ni/Cd cell, this degradation involves a slow hydrolysis reaction followed by fast electrochemical oxidations of the hydrolysis reaction products. Arrhenius activation energy of the hydrolysis reaction in 34% KOH was 20.0 +- 0.3 kcal/mole. A plot of the hydrolysis rate at 100/sup 0/C vs. hydroxyl ion concentration gave a rate maximum at about 16% KOH, and the mechanism for this effect is discussed. Electrochemical oxidations of the hydrolysis product, 6-aminocaproate ion, appear to proceed rapidly in several sequential steps at a nickel oxide electrode. In a Ni/Cd cell, the combination of nylon separator hydrolysis followed by electrochemical oxidation of the products can seriously degrade the battery lifetime. The rate of the hydrolysis of nylon 66 separator material was approximately one half of that of the nylon 6 material.

Lim, H.S.; Margerum, J.D.; Verzwyvelt, S.A.; Lackner, A.M.; Knechtli, R.C.

1989-03-01

110

Proactive Management of Materials Degradation - A Review of Principles and Programs  

SciTech Connect

The U.S. Nuclear Regulatory Commission (NRC) has undertaken a program to lay the technical foundation for defining proactive actions so that future degradation of materials in light water reactors (LWRs) is limited and, thereby, does not diminish either the integrity of important LWR components or the safety of operating plants. This technical letter report was prepared by staff at Pacific Northwest National Laboratory in support of the NRC Proactive Management of Materials Degradation (PMMD) program and relies heavily on work that was completed by Dr. Joseph Muscara and documented in NUREG/CR-6923. This report concisely explains the basic principles of PMMD and its relationship to prognostics, provides a review of programs related to PMMD being conducted worldwide, and provides an assessment of the technical gaps in PMMD and prognostics that need to be addressed. This technical letter report is timely because the majority of the U.S. reactor fleet is applying for license renewal, and many plants are also applying for increases in power rating. Both of these changes could increase the likelihood of materials degradation and underline, therefore, the interest in proactive management in the future.

Bond, Leonard J.; Doctor, Steven R.; Taylor, Theodore T.

2008-08-28

111

High-Resolution Crack Imaging Reveals Degradation Processes in Nuclear Reactor Structural Materials  

SciTech Connect

Corrosion and cracking represent critical failure mechanisms for structural materials in many applications. Although a crack can often be seen with the unaided eye, higher resolution imaging techniques are required to understand the nature of the crack tips and underlying degradation processes. Researchers at Pacific Northwest National Laboratory (PNNL) employ a suite of microscopy techniques and site-specific material sampling to analyze corrosion and crack structures, producing images and compositional analyses with near-atomic spatial resolution. The samples are cracked components removed from commercial light-water reactor service or laboratory samples tested in simulated reactor environments.

Olszta, Matthew J.; Schreiber, Daniel K.; Thomas, Larry E.; Bruemmer, Stephen M.

2012-04-01

112

Enhanced s-triazine Degradation and Sugar Cane Weed Control Options  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil borne bacteria on all continents except Antarctica have developed the ability to rapidly degrade the herbicide atrazine. Reduced residual weed control with atrazine in soils exhibiting enhanced degradation was confirmed under Mississippi Delta corn production and is expected to be occurring in...

113

Comparison of amorphous silicon absorber materials: Light-induced degradation and solar cell efficiency  

NASA Astrophysics Data System (ADS)

Several amorphous silicon (a-Si:H) deposition conditions have been reported to produce films that degrade least under light soaking when incorporated into a-Si:H solar cells. However, a systematic comparison of these a-Si:H materials has never been presented. In the present study, different plasma-enhanced chemical vapor deposition conditions, yielding standard low-pressure VHF a-Si:H, protocrystalline, polymorphous, and high-pressure RF a-Si:H materials, are compared with respect to their optical properties and their behavior when incorporated into single-junction solar cells. A wide deposition parameter space has been explored in the same deposition system varying hydrogen dilution, deposition pressure, temperature, frequency, and power. From the physics of layer growth, to layer properties, to solar cell performance and light-induced degradation, a consistent picture of a-Si:H materials that are currently used for a-Si:H solar cells emerges. The applications of these materials in single-junction, tandem, and triple-junction solar cells are discussed, as well as their deposition compatibility with rough substrates, taking into account aspects of voltage, current, and charge collection. In sum, this contributes to answering the question, "Which material is best for which type of solar cell?"

Stuckelberger, M.; Despeisse, M.; Bugnon, G.; Schüttauf, J.-W.; Haug, F.-J.; Ballif, C.

2013-10-01

114

Characterization of Material Degradation in Ceramic Matrix Composites Using Infrared Reflectance Spectroscopy  

NASA Astrophysics Data System (ADS)

Ceramic matrix composite materials for thermal protection systems are required to maintain operational performance in extreme thermal and mechanical environments. In-service inspection of materials capable of assessing the degree and extent of damage and degradation will be required to ensure the safety and readiness of future air vehicles. Infrared reflectance spectroscopy is an established material characterization technique capable of extracting information regarding the chemical composition of substances. The viability of this technique as a potentially powerful nondestructive evaluation method capable of monitoring degradation in thermal protection system materials subjected to extreme mechanical and thermal environments is analyzed. Several oxide-based and non-oxide-based ceramic matrix composite materials were stressed to failure in a high temperature environment and subsequently measured using infrared reflectance spectroscopy. Spectral signatures at locations along the length of the samples were compared resulting in distinct and monotonic reflectance peak changes while approaching the fracture point. The chemical significance of the observed signatures and the feasibility of infrared reflectance nondestructive evaluation techniques are discussed.

Cooney, Adam T.; Flattum-Riemers, Richard Y.; Scott, Benjamin J.

2011-06-01

115

Characterization of material degradation in ceramic matrix composites using infrared reflectance spectroscopy  

SciTech Connect

Ceramic matrix composite materials for thermal protection systems are required to maintain operational performance in extreme thermal and mechanical environments. In-service inspection of materials capable of assessing the degree and extent of damage and degradation will be required to ensure the safety and readiness of future air vehicles. Infrared reflectance spectroscopy is an established material characterization technique capable of extracting information regarding the chemical composition of substances. The viability of this technique as a potentially powerful nondestructive evaluation method capable of monitoring degradation in thermal protection system materials subjected to extreme mechanical and thermal environments is analyzed. Several oxide-based and non-oxide-based ceramic matrix composite materials were stressed to failure in a high temperature environment and subsequently measured using infrared reflectance spectroscopy. Spectral signatures at locations along the length of the samples were compared resulting in distinct and monotonic reflectance peak changes while approaching the fracture point. The chemical significance of the observed signatures and the feasibility of infrared reflectance nondestructive evaluation techniques are discussed.

Cooney, Adam T.; Flattum-Riemers, Richard Y. [Air Force Research Laboratory, Materials and Manufacturing Directorate, NonDestructive Evaluation Branch, Wright-Patterson AFB, OH (United States); Scott, Benjamin J. [Universal Technology Corporation, Dayton, OH (United States)

2011-06-23

116

Engineering hyaluronic acid hydrogel degradation to control cellular interactions and adult stem cell fate in 3D  

NASA Astrophysics Data System (ADS)

The design and implementation of extracellular matrix (ECM)-mimetic hydrogels for tissue engineering (TE) applications requires an intensive understanding of cell-material interactions, including matrix remodeling and stem cell differentiation. However, the influence of microenvironmental cues, e.g., matrix biodegradability, on cell behavior in vitro has not been well studied in the case of direct cell encapsulation within 3-dimensional (3D) hydrogels. To address these issues, a facile sequential crosslinking technique was developed that provides spatial and temporal control of 3D hydrogel degradability to investigate the importance of material design on cell behavior. Specifically, hydrogels were synthesized from hyaluronic acid (HA) macromers in a sequential process: (1) a primary Michael-type addition crosslinking using cell adhesive and matrix metalloprotease (MMP)-degradable oligopeptides to consume a portion of total reactive groups and resulting in "-UV" hydrogels permissive to cell-mediated degradation, followed by (2) a secondary, light initiated free-radical crosslinking to consume remaining reactive groups and "switch" the network to a non-degradable structure ("+UV") via the addition of non-degradable kinetic chains. Using this approach, we demonstrated control of encapsulated hMSC spreading by varying the crosslink type (i.e., the relative hydrogel biodegradability), including with spatial control. Upon incubation with bipotential soluble differentiation factors, these same degradation-mediated spreading cues resulted in an hMSC differentiation fate switch within -UV versus +UV environments. Follow-up studies demonstrated that degradation-mediated traction generation, rather than matrix mechanics or cell morphology, is the critical biophysical signal determining hMSC fate. Sequentially crosslinked HA hydrogels were also studied for the capacity to support remodeling by in vivo and ex vivo tissues, including with spatial control, toward tissue engineering (e.g., neovascularization) applications. In total, the work presented here highlights sequential crosslinking as a versatile platform technology affording processing capabilities to better mimic dynamic features of native microenvironments, including spatial patterning and temporal alteration of hydrogel degradability, toward both basic studies of cell behavior and TE applications.

Khetan, Sudhir

117

Enhanced Atrazine Degradation and Implications for Weed Control in Corn  

Technology Transfer Automated Retrieval System (TEKTRAN)

Enhanced atrazine degradation is the phenomenon whereby the herbicide is rapidly biodegraded by a population of soil bacteria that has developed the ability to use the pesticide as a nutrient source because of previous exposure to it or other s-triazine herbicides. This phenomenon has been reported...

118

Water-Soluble, Biocompatible Polyphosphazenes with Controllable and pH-Promoted Degradation Behavior  

PubMed Central

The synthesis of a series of novel, water-soluble poly(organophosphazenes) prepared via living cationic polymerization is presented. The degradation profiles of the polyphosphazenes prepared are analyzed by GPC, 31P NMR spectroscopy, and UV–Vis spectroscopy in aqueous media and show tunable degradation rates ranging from days to months, adjusted by subtle changes to the chemical structure of the polyphosphazene. Furthermore, it is observed that these polymers demonstrate a pH-promoted hydrolytic degradation behavior, with a remarkably faster rate of degradation at lower pH values. These degradable, water soluble polymers with controlled molecular weights and structures could be of significant interest for use in aqueous biomedical applications, such as polymer therapeutics, in which biological clearance is a requirement and in this context cell viability tests are described which show the non-toxic nature of the polymers as well as their degradation intermediates and products. PMID:24729657

Wilfert, Sandra; Iturmendi, Aitziber; Schoefberger, Wolfgang; Kryeziu, Kushtrim; Heffeter, Petra; Berger, Walter; Brüggemann, Oliver; Teasdale, Ian

2014-01-01

119

Stability of CIGS Solar Cells and Component Materials Evaluated by a Step-Stress Accelerated Degradation Test Method: Preprint  

SciTech Connect

A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15oC and then a 15% relative humidity (RH) increment step, beginning from 40oC/40%RH (T/RH = 40/40) to 85oC/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. The best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 ?m to 0.50 ?m on the cells. No clear 'stepwise' feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH ? 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and 'capacitor quality' factor (CPE-P), which were related to the cells? p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH ? 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS cell pieces was observed that was not seen on BZO/glass, and a CdS/CIGS sample displayed a small darkening and then flaking feature. Additionally, standard AlNi grid contact was less stable than thin Ni grid contact at T/RH ? 70/70. The edge sealant and moisture-blocking films were effective to block moisture ingress, as evidenced by the good stability of most CIGS solar cells and device components at T/RH = 85/70 for 704 h, and by preservation of the initial blue color on the RH indicator strips. The SSADT experiment is ongoing to be completed at T/RH = 85/85.

Pern, F. J.; Noufi, R.

2012-10-01

120

Stability of CIGS solar cells and component materials evaluated by a step-stress accelerated degradation test method  

NASA Astrophysics Data System (ADS)

A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15°C and then a 15% relative humidity (RH) increment step, beginning from 40°C/40%RH (T/RH = 40/40) to 85°C/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. The best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 ?m to 0.50 ?m on the cells. No clear "stepwise" feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH >= 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and "capacitor quality" factor (CPE-P), which were related to the cells' p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH >= 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS cell pieces was observed that was not seen on BZO/glass, and a CdS/CIGS sample displayed a small darkening and then flaking feature. Additionally, standard AlNi grid contact was less stable than thin Ni grid contact at T/RH >= 70/70. The edge sealant and moisture-blocking films were effective to block moisture ingress, as evidenced by the good stability of most CIGS solar cells and device components at T/RH = 85/70 for 704 h, and by preservation of the initial blue color on the RH indicator strips. The SSADT experiment is ongoing to be completed at T/RH = 85/85.

Pern, F. J.; Noufi, R.

2012-10-01

121

Downhole material injector for lost circulation control  

DOEpatents

This invention is comprised of an apparatus and method for simultaneously and separately emplacing two streams of different materials through a drillstring in a borehole to a downhole location for lost circulation control. The two streams are mixed outside the drillstring at the desired downhole location and harden only after mixing for control of a lost circulation zone.

Glowka, D.A.

1991-01-01

122

Downhole material injector for lost circulation control  

DOEpatents

Apparatus and method are disclosed for simultaneously and separately emplacing two streams of different materials through a drill string in a borehole to a downhole location for lost circulation control. The two streams are mixed outside the drill string at the desired downhole location and harden only after mixing for control of a lost circulation zone. 6 figs.

Glowka, D.A.

1994-09-06

123

A study of the controlled degradation of polypropylene containing pro-oxidant agents.  

PubMed

Intentional degradation by pro-oxidant agents, many of which are metal-based, can result in uncertainty as to the time of biodegradation. Polyacetal (POM) is a thermoplastic polymer commercially classified as an engineering polymer and contains carbon, hydrogen and oxygen. The depolymerization of POM during processing can enhance thermal decomposition. The aim of this study was to investigate the controlled degradation of polypropylene induced by the degradation of POM or d2w®. Mixtures of polypropylene containing different concentrations of POM or d2w® were prepared by extrusion. The properties of the mixtures (blends) were evaluated based on the melt index (MFI), tensile properties, Fourier transform infrared spectroscopy (FTIR), Time inductive oxidation (OIT) and Thermogravimetric analysis (TGA). The two additives (POM and d2w®) enhanced the oxidative thermal degradation of polypropylene and the degradation of the polypropylene/POM mixture could be controlled by altering the POM concentration. PMID:24340244

de Carvalho, Celso Luis; Silveira, Alexandre F; Rosa, Derval Dos Santos

2013-01-01

124

Distinct quaternary structures of the AAA+ Lon protease control substrate degradation  

E-print Network

Lon is an ATPase associated with cellular activities (AAA+) protease that controls cell division in response to stress and also degrades misfolded and damaged proteins. Subunits of Lon are known to assemble into ring-shaped ...

Vieux (Kloss), Ellen

125

Towards coherent control of energetic material initiation  

SciTech Connect

Direct optical initiation (DOI) of energetic materials using coherent control of localized energy deposition requires depositing energy into the material to produce a critical size hot spot, which allows propagation of the reaction and thereby initiation, The hot spot characteristics needed for growth to initiation can be studied using quantum controlled initiation (QCI). Achieving direct quantum controlled initiation (QCI) in condensed phase systems requires optimally shaped ultrafast laser pulses to coherently guide the energy flow along the desired paths. As a test of our quantum control capabilities we have successfully demonstrated our ability to control the reaction pathway of the chemical system stilbene. An acousto-optical modulator based pulse shaper was used at 266 nm, in a shaped pump/supercontinuum probe technique, to enhance and suppress th relative yields of the cis- to trans-stilbene isomerization. The quantum control techniques tested in the stilbene experiments are currently being used to investigate QCI of the explosive hexanitroazobenzene (HNAB).

Greenfield, Margo T [Los Alamos National Laboratory; Mcgrane, Shawn D [Los Alamos National Laboratory; Scharff, R Jason [Los Alamos National Laboratory; Moore, David S [Los Alamos National Laboratory

2009-01-01

126

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers  

SciTech Connect

This volume surveys the effects of welding on the degradation modes of three austenitic alloys: Types 304L and 316L stainless steels and Alloy 825. These materials are candidates for the fabrication of containers for the long-term storage of high-level nuclear waste. The metallurgical characteristics of fusion welds are reviewed here and related to potential degradation modes of the containers. Three specific areas are discussed in depth: (1) decreased resistance to corrosion in the forms of preferential corrosion, sensitization, and susceptibility to stress corrosion cracking, (2) hot cracking in the heat-affected zone and the weld zone, and (3) formation of intermetallic phases. The austenitic alloys are ranked as follows in terms of overall weldability: Alloy 825 (best) > Type 316L stainless steel > Type 304L stainless steel (worst). 108 refs., 31 figs., 7 tabs.

Strum, M.J.; Weiss, H.; Farmer, J.C. (Lawrence Livermore National Lab., CA (USA)); Bullen, D.B. (Science and Engineering Associates, Inc., Pleasanton, CA (USA))

1988-06-01

127

Controlling dynamic mechanical properties and degradation of composites for bone regeneration by means of filler content.  

PubMed

Bone tissue is a dynamic composite system that adapts itself, in response to the surrounding daily (cyclic) mechanical stimuli, through an equilibrium between growth and resorption processes. When there is need of synthetic bone grafts, the biggest issue is to support bone regeneration without causing mechanically-induced bone resorption. Apart from biological properties, such degradable materials should initially support and later leave room to bone formation. Further, dynamic mechanical properties comparable to those of bone are required. In this study we prepared composites comprising calcium phosphate and L-lactide/D-lactide copolymer in various content ratios using the extrusion method. We evaluated the effect of the inorganic filler amount on the polymer phase (i.e. on the post-extrusion intrinsic viscosity). We then studied their in vitro degradation and dynamic mechanical properties (in dry and humid conditions). By increasing the filler content, we observed significant decrease of the intrinsic viscosity of the polymer phase during the extrusion process. Composites containing higher amounts of apatite had faster degradation, and were also mechanically stiffer. But, due to the lower intrinsic viscosity of their polymer phase, they had larger damping properties. Besides this, higher amounts of apatite also rendered the composites more hydrophilic letting them absorb more water and causing them the largest decrease in stiffness. These results show the importance of filler content in controlling the properties of such composites. Further, in this study we observed that the viscoelastic properties of the composite containing 50wt% apatite were comparable to those of dry human cortical bone. PMID:23455172

Barbieri, Davide; de Bruijn, Joost D; Luo, Xiaoman; Farè, Silvia; Grijpma, Dirk W; Yuan, Huipin

2013-04-01

128

Constitutive Photomorphogenesis 1 and Multiple Photoreceptors Control Degradation of Phytochrome  

E-print Network

import of the plant photoreceptors phytochrome, promotes interaction of phytochrome A (phyA) and phyBA, phyB, and phyD photoreceptors, and it is not affected by COP1. Rapid light-induced degradation of PIF3 irradiations with continuous far-red light (cFR). In contrast with phyA, phyB to phyE mediate responses

Schäfer, Eberhard

129

Gas chromatographic study of degradation phenomena concerning building and cultural heritage materials.  

PubMed

Air pollution influences all aspects of social and economical life nowadays. In order to investigate the impact of air pollution on materials of works of art, the method of Reversed Flow-Inverse Gas Chromatography has been selected. The presence of various atmospheric pollutants is studied on marbles, oxides--building materials and samples of authentic statues from the Greek Archaeological Museums of Kavala and of Philippi. The method leads to the determination of several physicochemical quantities and the characterization of the heterogeneous surfaces of these solids. Moreover, the influence of a second pollutant (synergistic effect) is examined. The structure, the properties and the behavior of the materials are examined by X-Ray Diffraction, Scanning Electron Microscopy and Raman Spectroscopy. Therefore, the precise measurement of the above mentioned quantities form the scientific basis for elucidation of the mechanism of the whole phenomenon of the degradation, thus providing a scientific platform to conservation procedures. PMID:19022569

Metaxa, E; Agelakopoulou, T; Bassiotis, I; Karagianni, Ch; Roubani-Kalantzopoulou, F

2009-05-30

130

Occurrence, degradation, and effect of polymer-based materials in the environment.  

PubMed

There is now a plethora of polymer-based materials (PBMs) on the market, because of the increasing demand for cheaper consumable goods, and light-weight industrial materials. Each PBM constitutes a mixture of their representative polymer/sand their various chemical additives. The major polymer types are polyethylene, polypropylene,and polyvinyl chloride, with natural rubber and biodegradable polymers becoming increasingly more important. The most important additives are those that are biologically active, because to be effective such chemicals often have properties that make them resistant to photo-degradation and biodegradation. During their lifecycle,PBMs can be released into the environment form a variety of sources. The principal introduction routes being general littering, dumping of unwanted waste materials,migration from landfills and emission during refuse collection. Once in the environment,PBMs are primarily broken down by photo-degradation processes, but due to the complex chemical makeup of PBMs, receiving environments are potentially exposed to a mixture of macro-, meso-, and micro-size polymer fragments, leached additives, and subsequent degradation products. In environments where sunlight is absent (i.e., soils and the deep sea) degradation for most PBMs is minimal .The majority of literature to date that has addressed the environmental contamination or disposition of PBMs has focused on the marine environment. This is because the oceans are identified as the major sink for macro PBMs, where they are known to present a hazard to wildlife via entanglement and ingestion. The published literature has established the occurrence of microplastics in marine environment and beach sediments, but is inadequate as regards contamination of soils and freshwater sediments. The uptake of microplastics for a limited range of aquatic organisms has also been established, but there is a lack of information regarding soil organisms, and the long-term effects of microplastic uptake are also less well understood.There is currently a need to establish appropriate degradation test strategies consistent with realistic environmental conditions, because the complexity of environmental systems is lost when only one process (e.g., hydrolysis) is assessed in isolation. Enhanced methodologies are also needed to evaluate the impact of PBMs to soil and freshwater environments. PMID:24158578

Lambert, Scott; Sinclair, Chris; Boxall, Alistair

2014-01-01

131

Hyaluronic Acid Hydrogels with Controlled Degradation Properties for Oriented Bone Regeneration  

PubMed Central

Non-healing fractures can result from trauma, disease, or age-related bone loss. While many treatments focus on restoring bone volume, few try to recapitulate bone organization. However, the native architecture of bone is optimized to provide its necessary mechanical properties. Hyaluronic acid (HA) hydrogel scaffold systems with tunable degradation properties were developed for the controlled delivery of osteoinductive and angiogenic growth factors, thus affecting the quantity and quality of regenerated tissue. HA hydrogels were designed to degrade at fast, intermediate, and slow rates due to hydrolysis and further provided controlled release of cationic proteins due to electrostatic interactions. Scaffolds delivering bone morphogenetic protein-2 (BMP-2) were evaluated in a rat calvarial bone critical size defect model. BMP-2 delivery from the HA hydrogels had a clear osteoinductive effect in vivo and, for all hydrogel types, BMP-2 delivery resulted in significant mineralization compared to control hydrogels. The temporal progression of this effect could be modulated by altering the degradation rate of the scaffold. All three degradation rates tested resulted in similar amounts of mineral formation at the latest (six week) time point examined. Interestingly, however, the fastest and slowest degrading scaffolds seemed to result in more organized bone than the intermediate degrading scaffold, which was designed to degrade in 6–8 weeks to match the healing time. Additionally, healing could be enhanced by co-delivery of vascular endothelial growth factor along with BMP-2. PMID:20573393

Patterson, J; Siew, R; Herring, SW; Lin, ASP; Guldberg, R; Stayton, PS

2010-01-01

132

The nuclear materials control technology briefing book  

SciTech Connect

As national and international interests in nuclear arms control and non-proliferation of nuclear weapons, intensify, it becomes ever more important that contributors be aware of the technologies available for the measurement and control of the nuclear materials important to nuclear weapons development. This briefing book presents concise, nontechnical summaries of various special nuclear material (SNM) and tritium production monitoring technologies applicable to the control of nuclear materials and their production. Since the International Atomic Energy Agency (IAEA) operates a multinational, on-site-inspector-based safeguards program in support of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), many (but not all) of the technologies reported in this document are in routine use or under development for IAEA safeguards.

Hartwell, J.K.; Fernandez, S.J.

1992-03-01

133

Aerospace Materials Quality Control: Instructor Notes  

NSDL National Science Digital Library

This document from the Aerospace Manufacturing Education Project is intended to accompany a PowerPoint presentation on the topic of quality control of materials used in the aerospace industry. That presentation is available for download here. The presentation and notes will help students understand why quality control is important in this field. They also include details about aerospace QC teams and techniques, including non-destructive testing. These instructor notes also include links to a number of useful online references.

134

Thermal/chemical degradation of ceramic candle filter materials. Final report, September 1988--October 1994  

SciTech Connect

High-temperature ceramic candle filters are being developed for use in advanced power generation systems such as the Integrated Gasification Combined Cycle (IGCC), Pressurized Fluidized-Bed Combustor (PFBC), and Direct Coal-Fired Turbine (DCFT). The direct firing of coal produces particulate matter which must be removed to meet both environmental and process limitations. The ceramic candles increase the efficiency of the advanced power generation systems and protect downstream equipment from erosion and impingement of particulate matter in the hot exhaust gases. Ceramic candle filters are rigid, closed-ended (capped on one side) porous cylinders which generally have a flange on the open-ended side. The flange at the open end allows the candle to be suspended by a tubesheet in the filter vessel. Candle filters have shown promise, but have also encountered durability problems during use in hostile, high-temperature environments. Limitations in the candle lifetime lower the economic advantages of using candle filters for this application. Candles typically fail by cracking at the flange or in the body of the candle. The objective of this project was to test and analyze ceramic candle filter materials and to evaluate the degradation mechanisms. The tests were conducted such that the effects of each degradation mechanism could be examined. Separately. The overall objective of the project was to: (a) develop a better understanding of the thermal and chemical degradation mechanisms of ceramic candle filter materials in advanced coal utilization projects, (b) develop test procedures, and (c) recommend changes to increase filter lifetime. 15 refs., 67 figs., 17 tabs.

NONE

1995-01-01

135

Experimental simulation of materials degradation of plasma-facing components using lasers  

NASA Astrophysics Data System (ADS)

The damage and erosion of plasma-facing components (PFCs) due to extremely high heat loads and particle bombardment is a key issue for the nuclear fusion community. Currently high current ion and electron beams are used in laboratories for simulating the behaviour of PFC materials under ITER-like conditions. Our results indicate that high-power nanosecond lasers can be used for laboratory simulation of high heat flux PFC material degradation. We exposed tungsten (W) surfaces with repetitive laser pulses from a nanosecond laser with a power density ˜ a few GW cm-2. Emission spectroscopic analysis showed that plasma features at early times followed by intense particle emission at later times. Analysis of laser-exposed W surface demonstrated cracks and grain structures. Our results indicate that the typical particle emission features from laser-irradiated tungsten are consistent with high-power particle beam simulation results.

Farid, N.; Harilal, S. S.; El-Atwani, O.; Ding, H.; Hassanein, A.

2014-01-01

136

NON-THERMAL PLASMA TECHNOLOGY FOR DEGRADATION OF ORGANIC COMPOUNDS IN WASTEWATER CONTROL: A CRITICAL REVIEW  

Microsoft Academic Search

Non-thermal plasma is an emerging technique in environmental pollution control technology, produced by the high-voltage discharge processes and therefore a large amount of high energy electrons and active species are generated. The degradation of difficult-degraded organic pollutions will be greatly enhanced by the active species generated from non-thermal plasma process. However, research on non-thermal plasma technology on organic wastewater cleaning

Hsu-Hui Cheng; Shiao-Shing Chen; Yu-Chi Wu; Din-Lit Ho

137

In and Out of the ER: Protein Folding, Quality Control, Degradation, and Related Human Diseases  

E-print Network

In and Out of the ER: Protein Folding, Quality Control, Degradation, and Related Human Diseases 1377 C. Protein folding 1378 II. Protein Translocation, Folding, and Quality Control in the Endoplasmic Reticulum 1379 A. Protein targeting to the ER 1379 B. Chaperone-assisted protein folding in the ER 1379 C

Hebert, Daniel N.

138

Post-translational control of Cdc25 degradation terminates Drosophila’s early cell cycle program  

PubMed Central

SUMMARY In most metazoans, early embryonic development is characterized by rapid mitotic divisions that are controlled by maternal mRNAs and proteins that accumulate during oogenesis [1]. These rapid divisions pause at the Mid-Blastula Transition (MBT), coinciding with a dramatic increase in gene transcription and the degradation of a subset of maternal mRNAs [2, 3]. In Drosophila, the cell cycle pause is controlled by inhibitory phosphorylation of Cdk1, which in turn is driven by down-regulation of the activating Cdc25 phosphatases [4, 5]. Here, we show that the two Drosophila Cdc25 homologues, String and Twine, differ in their dynamics and that, contrary to current models [4], their down-regulations are not controlled by mRNA degradation but through different post-translational mechanisms. The degradation rate of String protein gradually increases during the late syncytial cycles in a manner dependent on the nuclear-to-cytoplasmic ratio and on the DNA replication checkpoints. Twine, on the other hand, is targeted for degradation at the onset of the MBT through a switch-like mechanism controlled like String by the nuclear-to-cytoplasmic ratio, but not requiring the DNA replication checkpoints. We demonstrate that post-translational control of Twine degradation ensures that the proper number of mitoses precede the MBT. PMID:23290553

Talia, Stefano Di; She, Richard; Blythe, Shelby A.; Lu, Xuemin; Zhang, Qi Fan; Wieschaus, Eric F.

2013-01-01

139

Bio-inspired Supramolecular Assemblies and Porous Materials for the Degradation of Organophosphate Nerve Agents  

NASA Astrophysics Data System (ADS)

This thesis reports the synthesis of bio-inspired supramolecular assemblies and porous materials that are catalytically active in the degradation of organophosphate nerve agents. The first catalysts described are a series of cofacial metalloporphyrin dimers modeled after the active site of phosphotriesterase that were modularly prepared from a single porphyrin building block and shown to catalyze the methanolysis of p-nitrophenyl diphenyl phosphate (PNPDPP), a simulant for nerve agents. Notably, tuning the active sites inside the cavities of these dimers, from ZnII metal centers to Al-OMe moieties, affords an enhanced nucleophilic environment where a high concentration of methoxy ligands becomes available for reaction with encapsulated phosphate triesters. Up to a 1300-fold rate acceleration over the uncatalyzed reaction can be achieved via a combination of cavity-localized Lewis-acid activation and methoxide-induced methanolysis. Based on the design principles learned from the aforementioned solution-phase Al(porphyrin) dimers, a heterogeneous porous organic polymer (POP) catalyst was synthesized by incorporating an Al(porphyrin) functionalized with a large axial ligand into a POP using a cobalt-catalyzed acetylene trimerization strategy. Removal of the axial ligand afforded a microporous material that is capable of encapsulating and solvolytically degrading PNPDPP. Supercritical CO 2 processing of the Al(porphyrin)-based POP dramatically increased the pore size and volume, allowing for significantly higher catalytic activities. The syntheses of porphyrin-based POPs with tunable pore diameters and volumes have also been attempted. SnIV(porphyrins) functionalized with bulky trans-diaxial ligands can be incorporated into POPs. Post-synthesis removal of the ligands reveal POPs with a tunable range of micro- and mesopores as well as tunable pore volumes. Expanding upon the idea that active sites that can both bind substrates and deliver nucleophiles should be active catalysts for the degradation of organophosphates, metal catecholate POPs were also explored. Metallation of catechol POPs with La(acac)3 affords a catalytically active microporous network for the solvolytic and hydrolytic degradation of the toxic organophosphate compound methyl paraoxon. As the Lewis-acidic LaIII metal ion can bind up to 9 substrates, its incorporation into a catechol-decorated POP affords a microporous environment capable of pre-concentrating methyl paraoxon in the presence of a large number of hydroxylated nucleophiles for enhanced catalysis.

Totten, Ryan K.

140

A Golgi-based KDELR-dependent signalling pathway controls extracellular matrix degradation.  

PubMed

We recently identified an endomembrane-based signalling cascade that is activated by the KDEL receptor (KDELR) on the Golgi complex. At the Golgi, the KDELR acts as a traffic sensor (presumably via binding to chaperones that leave the ER) and triggers signalling pathways that balance membrane fluxes between ER and Golgi. One such pathway relies on Gq and Src. Here, we examine if KDELR might control other cellular modules through this pathway. Given the central role of Src in extracellular matrix (ECM) degradation, we investigated the impact of the KDELR-Src pathway on the ability of cancer cells to degrade the ECM. We find that activation of the KDELR controls ECM degradation by increasing the number of the degradative structures known as invadopodia. The KDELR induces Src activation at the invadopodia and leads to phosphorylation of the Src substrates cortactin and ASAP1, which are required for basal and KDELR-stimulated ECM degradation. This study furthers our understanding of the regulatory circuitry underlying invadopodia-dependent ECM degradation, a key phase in metastases formation and invasive growth. PMID:25682866

Ruggiero, Carmen; Fragassi, Giorgia; Grossi, Mauro; Picciani, Benedetta; Di Martino, Rosaria; Capitani, Mirco; Buccione, Roberto; Luini, Alberto; Sallese, Michele

2015-02-20

141

The effect of the memristor electrode material on its resistance to degradation under conditions of cyclic switching  

NASA Astrophysics Data System (ADS)

The stability of titanium oxide memristors with gold and platinum electrodes with respect to switching-induced degradation has been studied. It is established that the use of gold instead of platinum as the electrode material significantly increases the resistance of a memristor to degradation in the course of repeated resistance read-write(erase) cycles. The first Russian high-endurance memristor based on titanium oxide has been obtained, which can withstand up to 3000 resistive switching cycles.

Khrapovitskaya, Yu. V.; Maslova, N. E.; Grishchenko, Yu. V.; Demin, V. A.; Zanaveskin, M. L.

2014-04-01

142

Factors Controlling Elevated Temperature Strength Degradation of Silicon Carbide Composites  

NASA Technical Reports Server (NTRS)

For 5 years, the cooperative agreement NCC3-763 has focused on the development and understanding of Sic-based composites. Most of the work was performed in the area of SiC fiber-reinforced composites for UEET and NGLT and in collaboration with Goodrich Corporation under a partially reimbursable Space Act Agreement. A smaller amount of work was performed on C fiber-reinforced SiC matrix composites for NGLT. Major accomplishments during this agreement included: Improvements to the interphase used in melt-infiltrated (MI) SiC/SiC composites which increases the life under stressed-oxidation at intermediate temperatures referred to as "outside-debonding". This concept is currently in the patent process and received a Space Act Award. Mechanistic-based models of intermediate temperature degradation for MI SiC/SiC Quantification and relatively robust relationships for matrix crack evolution under stress in SiC/SiC composites which serve as the basis for stress-strain and elevated temperature life models The furthering of acoustic emission as a useful tool in composite damage evolution and the extension of the technique to other composite systems Development of hybrid C-SiC fiber-reinforced SiC matrix composites Numerous presentations at conferences, industry partners, and government centers and publications in recognized proceedings and journals. Other recognition of the author's accomplishments by NASA with a TGIR award (2004), NASA's Medal for Public Service (2004), and The American Ceramic Society s Richard M. Fulrath Award (2005). The following will briefly describe the work of the past five years in the three areas of interest: SiC/SiC composite development, mechanistic understanding and modeling of SiC/SiC composites, and environmental durability of C/SiC composites. More detail can be found in the publications cited at the end of this report.

2005-01-01

143

Distinct quaternary structures of the AAA+ Lon protease control substrate degradation.  

PubMed

Lon is an ATPase associated with cellular activities (AAA+) protease that controls cell division in response to stress and also degrades misfolded and damaged proteins. Subunits of Lon are known to assemble into ring-shaped homohexamers that enclose an internal degradation chamber. Here, we demonstrate that hexamers of Escherichia coli Lon also interact to form a dodecamer at physiological protein concentrations. Electron microscopy of this dodecamer reveals a prolate structure with the protease chambers at the distal ends and a matrix of N domains forming an equatorial hexamer-hexamer interface, with portals of ?45 Å providing access to the enzyme lumen. Compared with hexamers, Lon dodecamers are much less active in degrading large substrates but equally active in degrading small substrates. Our results support a unique gating mechanism that allows the repertoire of Lon substrates to be tuned by its assembly state. PMID:23674680

Vieux, Ellen F; Wohlever, Matthew L; Chen, James Z; Sauer, Robert T; Baker, Tania A

2013-05-28

144

Atomic force microscopy imaging directly on paper: a study of library materials degradation  

NASA Astrophysics Data System (ADS)

Atomic Force Microscopy (AFM) has been used to study fiber degradations, as they appear on paper surface, aiming -in the mid term- at assessment of a micro-destructive technique capable of providing qualitative and semi-quantitative information on deterioration and ageing. AFM topographies of pure cellulose paper samples artificially aged were considered as well as topographies of original paper samples naturally aged showing different kind of deterioration. Whatman N.1 chromatography paper was used as a model system to study ageing effect on sub-micron structures on cellulose fibers. Chemical and biological deterioration processes were modeled, as well, by mean of artificial degradation treatments, following the criteria of reproducing effects frequently isolated from library materials. The effects of chemical reaction induced by accelerated ageing in climatic chamber (80°C, R.H. 65%) on paper surface, and the effects of a fungal attack reproduced in vitro inoculating paper samples with Aspergillus terreus Thom (6000spores/100?l, 27°C, R.H. 100%) were evaluated by means of Atomic Force Microscopy imaging, and spectrophotometric measurement in the UV-Vis-NIR. In order to map structure local properties, morphological variations repeated with statistical relevance were correlated to chemical, biological and spectroscopic characterization. Information achieved from such analysis is then used for a comparison with measurements of naturally aged paper, providing insight in analysis and classification of typical phenomena, like yellowing and foxing stains, usually affecting valuables in libraries.

Piantanida, Giovanna; Bicchieri, Marina; Pinzari, Flavia; Coluzza, Carlo

2005-06-01

145

Posttranslational Quality Control: Folding, Refolding, and Degrading Proteins  

NSDL National Science Digital Library

Polypeptides emerging from the ribosome must fold into stable three-dimensional structures and maintain that structure throughout their functional lifetimes. Maintaining quality control over protein structure and function depends on molecular chaperones and proteases, both of which can recognize hydrophobic regions exposed on unfolded polypeptides. Molecular chaperones promote proper protein folding and prevent aggregation, and energy-dependent proteases eliminate irreversibly damaged proteins. The kinetics of partitioning between chaperones and proteases determines whether a protein will be destroyed before it folds properly. When both quality control options fail, damaged proteins accumulate as aggregates, a process associated with amyloid diseases.

Sue Wickner (National Cancer Institute; Laboratory of Molecular Biology)

1999-12-03

146

Environmental degradation of materials during wet storage of spent nuclear fuels  

NASA Astrophysics Data System (ADS)

Wet storage is the predominant mode of storage of spent nuclear fuels. Due to legislation and other constraints, many countries do not reprocess spent fuels and have to store these for extended periods in spent fuel storage pools (SFSPs). Although the water chemistry of the pool is benign, certain factors such as stagnancy of water, crevices, and galvanic contacts between various materials of the fuel clad and the lining of the pools can result in unexpected localized corrosion. In this study, the susceptibility to localized corrosion of aluminum-1S (Al-1S), Zircaloy-2, and type 304 stainless steel (SS) has been assessed using accelerated tests with crevice bent beam (CBB) assemblies. The pool water constituents have been analyzed and electrochemical potentials (ECPs) measured in water samples drawn from different locations of the pool. The ECP has also been measured in situ, in the pools. It has been demonstrated that under conditions of crevice and galvanic contact, aluminum clad fuels from research reactors are prone to localized corrosion even in the benign environments of a SFSP. The ECP experiments indicate the importance of surface condition of the material and irradiation on degradation of various materials due to corrosion.

Kain, Vivekanand; de, P. K.; Agarwal, K.; Seetharamaih, P.

2000-06-01

147

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers  

SciTech Connect

Three copper-based alloys, CDA 102 (oxygen-free, high-purity copper), CDA 613 (aluminum bronze), and CDA 715 (Cu-30Ni), are candidates for the fabrication of high-level radioactive-waste disposal containers. Waste will include spent fuel assemblies from reactors as well as borosilicate glass, and will be sent to the prospective repository site at Yucca Mountain in Nye County, Nevada. The decay of radionuclides will result in the generation of substantial heat and in fluxes of gamma radiation outside the containers. In this environment, container materials might degrade by atmospheric oxidation, general aqueous phase corrosion, localized corrosion (LC), and stress corrosion cracking (SCC). This volume is a critical survey of available data on pitting and crevice corrosion of the copper-based candidates. Pitting and crevice corrosion are two of the most common forms of LC of these materials. Data on the SCC of these alloys is surveyed in Volume 4. Pitting usually occurs in water that contains low concentrations of bicarbonate and chloride anions, such as water from Well J-13 at the Nevada Test Site. Consequently, this mode of degradation might occur in the repository environment. Though few quantitative data on LC were found, a tentative ranking based on pitting corrosion, local dealloying, crevice corrosion, and biofouling is presented. CDA 102 performs well in the categories of pitting corrosion, local dealloying, and biofouling, but susceptibility to crevice corrosion diminishes its attractiveness as a candidate. The cupronickel alloy, CDA 715, probably has the best overall resistance to such localized forms of attack. 123 refs., 11 figs., 3 tabs.

Farmer, J.C.; Van Konynenburg, R.A.; McCright, R.D. (Lawrence Livermore National Lab., CA (USA)); Gdowski, G.E. (Science and Engineering Associates, Inc., Pleasanton, CA (USA))

1988-06-01

148

Early detection of critical material degradation by means of electromagnetic multi-parametric NDE  

SciTech Connect

With an increasing number of power plants operated in excess of their original design service life an early recognition of critical material degradation in components will gain importance. Many years of reactor safety research allowed for the identification and development of electromagnetic NDE methods which detect precursors of imminent damage with high sensitivity, at elevated temperatures and in a radiation environment. Regarding low-alloy heat-resistant steel grade WB 36 (1.6368, 15NiCuMoNb5), effects of thermal and thermo-mechanical aging on mechanical-technological properties and several micromagnetic parameters have been thoroughly studied. In particular knowledge regarding the process of copper precipitation and its acceleration under thermo-mechanical load has been enhanced. Whilst the Cu-rich WB 36 steel is an excellent model material to study and understand aging effects related to neutron radiation without the challenge of handling radioactive specimens in a hot cell, actually neutron-irradiated reactor pressure vessel materials were investigated as well. The neutron fluence experienced and the resulting shift of the ductile-brittle transition temperature were determined electromagnetically, and it was shown that weld and base material can be distinguished from the cladded side of the RPV wall. Low-cycle fatigue of the austenitic stainless steel AISI 347 (1.4550, X6CrNiNb18-10) has been characterized with electromagnetic acoustic transducers (EMATs) at temperatures of up to 300 °C. Time-of-flight and amplitude of the transmitted ultrasound signal were evaluated against the number of load cycles applied and observed as an indication of the imminent material failure significantly earlier than monitoring stresses or strains.

Szielasko, Klaus; Tschuncky, Ralf; Rabung, Madalina; Altpeter, Iris; Dobmann, Gerd [Fraunhofer Institute for Nondestructive Testing (IZFP), Campus E3 1, 66123 Saarbrücken (Germany); Seiler, Georg; Herrmann, Hans-Georg; Boller, Christian [Fraunhofer Institute for Nondestructive Testing (IZFP), Campus E3 1, 66123 Saarbrücken, Germany and Saarland University, Chair of NDT and Quality Assurance, Campus E3 1, 66123 Saarbrücken (Germany)

2014-02-18

149

Synthesis and biological evaluation of a polysialic acid-based hydrogel as enzymatically degradable scaffold material for tissue engineering.  

PubMed

Restorative medicine has a constant need for improved scaffold materials. Degradable biopolymers often suffer from uncontrolled chemical or enzymatic hydrolysis by the host. The need for a second surgery on the other hand is a major drawback for nondegradable scaffold materials. In this paper we report the design and synthesis of a novel polysialic acid-based hydrogel with promising properties. Hydrogel synthesis was optimized and enzymatic degradation was studied using a phage-born endosialidase. After addition of endosialidase, hydrogels readily degraded depending on the amount of initially used cross-linker within 2 to 11 days. This polysialic acid hydrogel is not cytotoxic, completely stable under physiological conditions, and could be evaluated as growth support for PC12 cells. Here, additional coating with collagen I, poly-L-lysine or matrigel is mandatory to improve the properties of the material. PMID:18690740

Berski, Silke; van Bergeijk, Jeroen; Schwarzer, David; Stark, Yvonne; Kasper, Cornelia; Scheper, Thomas; Grothe, Claudia; Gerardy-Schahn, Rita; Kirschning, Andreas; Dräger, Gerald

2008-09-01

150

10 CFR 74.51 - Nuclear material control and accounting for strategic special nuclear material.  

Code of Federal Regulations, 2014 CFR

...10 Energy 2 2014-01-01 2014-01-01 false Nuclear material control and accounting for strategic special nuclear material. 74.51 Section 74.51 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) MATERIAL CONTROL...

2014-01-01

151

10 CFR 74.51 - Nuclear material control and accounting for strategic special nuclear material.  

Code of Federal Regulations, 2013 CFR

...10 Energy 2 2013-01-01 2013-01-01 false Nuclear material control and accounting for strategic special nuclear material. 74.51 Section 74.51 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) MATERIAL CONTROL...

2013-01-01

152

10 CFR 74.51 - Nuclear material control and accounting for strategic special nuclear material.  

Code of Federal Regulations, 2011 CFR

...10 Energy 2 2011-01-01 2011-01-01 false Nuclear material control and accounting for strategic special nuclear material. 74.51 Section 74.51 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) MATERIAL CONTROL...

2011-01-01

153

10 CFR 74.51 - Nuclear material control and accounting for strategic special nuclear material.  

Code of Federal Regulations, 2012 CFR

...10 Energy 2 2012-01-01 2012-01-01 false Nuclear material control and accounting for strategic special nuclear material. 74.51 Section 74.51 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) MATERIAL CONTROL...

2012-01-01

154

10 CFR 74.51 - Nuclear material control and accounting for strategic special nuclear material.  

Code of Federal Regulations, 2010 CFR

...10 Energy 2 2010-01-01 2010-01-01 false Nuclear material control and accounting for strategic special nuclear material. 74.51 Section 74.51 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) MATERIAL CONTROL...

2010-01-01

155

Peptide assembly for nanoscale control of materials  

NASA Astrophysics Data System (ADS)

Self-assembly of molecules is an attractive materials construction strategy due to its simplicity in application. By considering peptidic, charged synthetic molecules in the bottom-up materials self-assembly design process, one can take advantage of inherently biomolecular attributes; intramolecular folding events, secondary structure, and electrostatic interactions; in addition to more traditional self-assembling molecular attributes such as amphiphilicty, to define hierarchical material structure and consequent properties. Design strategies for materials self-assembly based on small (less than 24 amino acids) beta-hairpin peptides will be discussed. Self-assembly of the peptides is predicated on an intramolecular folding event caused by desired solution properties. Importantly, kinetics of self-assembly can be tuned in order to control gelation time. The final gel behaves as a shear thinning, but immediately rehealing, solid that is potentially useful for cell injection therapies. The morphological, and viscoelastic properties of these peptide hydrogels will be discussed. In addition, slight changes in peptide primary sequence can have drastic effects on the self-assembled morphology. Additional sequences will be discussed that do not form hydrogels but rather form nanoscale templates for inorganic material assembly.

Pochan, Darrin

2011-03-01

156

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers  

SciTech Connect

Six alloys are being considered as possible materials for the fabrication of containers for the disposal of high-level radioactive waste. Three of these candidate materials are copper-based alloys: CDA 102 (oxygen-free copper), CDA 613 (Cu-7Al), and CDA 715 (Cu-30Ni). The other three are iron- to nickel-based austenitic materials: Types 304L and 316L stainless steels and Alloy 825. Radioactive waste will include spent-fuel assemblies from reactors as well as waste in borosilicate glass and will be sent to the prospective site at Yucca Mountain, Nevada, for disposal. The waste-package containers must maintain substantially complete containment for at least 300 yr and perhaps as long as 1000 yr. During the first 50 yr after emplacement, the containers must be retrievable from the disposal site. Shortly after emplacement of the containers in the repository, they will be exposed to high temperatures and high gamma radiation fields from the decay of high-level waste. This radiation will promote the radiolytic decomposition of moist air to hydrogen. This volume surveys the available data on the effects of hydrogen on the six candidate alloys for fabrication of the containers. For copper, the mechanism of hydrogen embrittlement is discussed, and the effects of hydrogen on the mechanical properties of the copper-based alloys are reviewed. The solubilities and diffusivities of hydrogen are documented for these alloys. For the austenitic materials, the degradation of mechanical properties by hydrogen is documented. The diffusivity and solubility of hydrogen in these alloys are also presented. For the copper-based alloys, the ranking according to resistance to detrimental effects of hydrogen is: CDA 715 (best) > CDA 613 > CDA 102 (worst). For the austenitic alloys, the ranking is: Type 316L stainless steel {approx} Alloy 825 > Type 304L stainless steel (worst). 87 refs., 19 figs., 8 tabs.

Gdowski, G.E.; Bullen, D.B. (Science and Engineering Associates, Inc., Pleasanton, CA (USA))

1988-08-01

157

Radiation Induced Degradation of White Thermal Control Paint  

NASA Technical Reports Server (NTRS)

This paper details a comparison analysis of the Zinc Oxide pigmented white thermal control paints Z-93 and Z-93P. Both paints were simultaneously exposed to combined space environmental effects and analyzed using an in-vacuum reflectance technique. The dose applied to the paints was approximately equivalent to 5 years in a geosynchronous orbit. This comparison analysis showed that Z-93P is an acceptable substitute for Z-93. Irradiated samples of Z-93 and Z-93P were subjected to additional exposures of ultraviolet (UV) radiation and analyzed using the in-vacuum reflectance technique to investigate UV activated reflectance recovery. Both samples showed minimal UV activated reflectanc6 recovery after an additional 190 Equivalent Sun Hour (ESH) exposure. Reflectance response utilizing nitrogen as a repressurizing gas instead of air was also investigated. This investigation found the rates of reflectance recovery when repressurized with nitrogen are slower than when repressurized with air.

Edwards, D. L.; Zwiener, J. M.; Wertz, G. E.; Vaughn, J. A.; Kamenetzky, R. R.; Finckenor, M. M.; Meshishnek, M. J.

1998-01-01

158

Computerized materials protection, control, and accountability  

SciTech Connect

The proliferation of nuclear weapons, along with the technical knowledge and materials needed to make these weapons, is an enduring problem of international urgency. Current international nuclear nonproliferation efforts are aimed at deterring, detecting, and responding to proliferation of weapons of mass destruction. These safeguards efforts are being implemented by applying preeminent science and technology to the management and control of nuclear materials. By strengthening systems of nuclear material protection, control, and accountability (MPC and A), one can reduce the threat of nuclear weapons proliferation. Two major programs of international cooperation are now underway to achieve this goal. The first is between the US Department of Energy (DOE) and the Institutes of the Russian Federation (Laboratory-to-Laboratory Program), and the second is between the US Government and Governments of the former Soviet Republics (Government-to-Government Program). As part of these programs, the DOE is working with facilities to assist them in implementing computerized MPC and A systems. This work is a collaboration between computer scientists and safeguards experts in both the US and the new Republics. The US is making available technology and expertise to enable Russian experts to build on computerized MPC and A software developed in the US. This paper describes the joint efforts of these international teams to develop sophisticated computerized MPC and A systems using modern computer hardware and software technology. These systems are being customized to meet the site-specific needs of each facility.

Whiteson, R.; Seitz, S.; Landry, R.P.; Hadden, M.L.; Painter, J.A.

1997-05-01

159

Epidermal Growth Factor Receptor Fate Is Controlled by Hrs Tyrosine Phosphorylation Sites That Regulate Hrs Degradation?  

PubMed Central

Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is an endosomal protein essential for the efficient sorting of activated growth factor receptors into the lysosomal degradation pathway. Hrs undergoes ligand-induced tyrosine phosphorylation on residues Y329 and Y334 downstream of epidermal growth factor receptor (EGFR) activation. It has been difficult to investigate the functional roles of phosphoHrs, as only a small proportion of the cellular Hrs pool is detectably phosphorylated. Using an HEK 293 model system, we found that ectopic expression of the protein Cbl enhances Hrs ubiquitination and increases Hrs phosphorylation following cell stimulation with EGF. We exploited Cbl's expansion of the phosphoHrs pool to determine whether Hrs tyrosine phosphorylation controls EGFR fate. In structure-function studies of Cbl and EGFR mutants, the level of Hrs phosphorylation and rapidity of apparent Hrs dephosphorylation correlated directly with EGFR degradation. Differential expression of wild-type versus Y329,334F mutant Hrs in Hrs-depleted cells revealed that one or both tyrosines regulate ligand-dependent Hrs degradation, as well as EGFR degradation. By modulating Hrs ubiquitination, phosphorylation, and protein levels, Cbl may control the composition of the endosomal sorting machinery and its ability to target EGFR for lysosomal degradation. PMID:17101784

Stern, Kathryn A.; Visser Smit, Gina D.; Place, Trenton L.; Winistorfer, Stanley; Piper, Robert C.; Lill, Nancy L.

2007-01-01

160

Control of Xanthan-Degrading Organisms in the Loudon Pilot: Approach, Methodology, and Results  

Microsoft Academic Search

An investigation of loss of mobility control in Exxon's Loudon micellar\\/polymer pilot test has confirmed that loss was caused by microbial degradation of the xanthan biopolymer used to viscosify the microemulsion and polymer drive banks. This study describes techniques which were used to sample and culture bacteria from the Loudon pilot and demonstrate that these mixed cultures are able to

J. R. Bragg; S. D. Maruca; W. W. Gale; L. S. Gall; W. C. Wernau; D. Beck; I. M. Goldman; A. I. Laskin; L. A. Naslund

1983-01-01

161

Nuclear Ubiquitin Ligases, NF-{kappa}B Degradation, and the Control of Inflammation  

NSDL National Science Digital Library

Transcriptional control of the vast majority of genes involved in the inflammatory response requires the nuclear factor ?B (NF-?B) family of transcription factors. Stimulation and termination of NF-?B activity are subject to stringent spatiotemporal control. According to the classical model of NF-?B regulation, both activation and termination mechanisms are centered on inhibitor of NF-?B (I?B) proteins. Whereas activation of NF-?B requires degradation of the I?Bs, the main mechanism responsible for termination of NF-?B activity is the resynthesis of a specific I?B, I?B?, which sequesters NF-?B dimers in the nucleus and translocates them to the cytoplasm in an inactive form. Studies now show that an additional mechanism that is required to prevent the uncontrolled activity of NF-?B proteins is their nuclear degradation. At least two E3 ubiquitin ligases, one of which seems to be essential for control of nuclear NF-?B p65 (also known as RelA) in myeloid cells, have been identified. Moreover, additional evidence indicates that individual NF-?B dimers with particular activating or repressive properties may be differentially controlled by nuclear degradation, thus paving the way for the exploitation of NF-?B degradation pathways for therapeutic purposes.

Gioacchino Natoli (Milan; European Institute of Oncology (IEO) REV)

2008-01-08

162

In vivo degradation in modern orthopaedic UHMWPE bearings and structural characterization of a novel alternative UHMWPE material  

NASA Astrophysics Data System (ADS)

Ultra-high molecular weight polyethylene (UHMWPE) remains the most common bearing material for total joint arthroplasty. Advances in radiation cross-linking and other post-consolidation treatments have led to a rapid differentiation of polyethylene products on the market, with more than twenty unique materials currently being sold by the five largest orthopaedic manufacturers alone. Through oxidation, cross-link density, and free radical measurements, this work demonstrates for the first time that in vivo material degradation is occurring in cross-linked UHMWPE materials. Based on the rate of the reaction in certain materials, it is concluded that oxidative degradation may compromise the mechanical properties of the bearings in as few as ten years, potentially leading to early clinical failure of the devices. Using the knowledge gained from this work as well as previously published observations about UHMWPE oxidation, a two-mechanism model of oxidation is proposed that offers an explanation for the observed in vivo changes. From this model it is concluded that oxidative degradation is in part the result of in vivo chemical species. The two-mechanism model of oxidation suggests that different processing techniques for UHMWPE may reduce the risk of oxidative degradation. It is concluded that by avoiding any radiation cross-linking step, Equal Channel Angular Processing (ECAP) can produce UHMWPE materials with a reduced risk for in vivo oxidation while at the same time offering superior mechanical properties compared to commercially available UHMWPE materials, as well as similar wear behavior. Using dynamic mechanical analysis, the entanglement density in ECAP materials is quantified, and is related back to the ECAP processing parameters. The relationship between entanglement density and resultant material properties is established. The results will allow informed processing parameter selection for producing optimized materials for orthopaedics and other applications.

Reinitz, Steven D.

163

Evaluation of near surface material degradation in concrete using nonlinear Rayleigh surface waves  

NASA Astrophysics Data System (ADS)

Comparative studies of nondestructive evaluation methods have shown that nonlinear ultrasonic techniques are more sensitive than conventional linear methods to changes in material microstructure and the associated small-scale damage. Many of the material degradation processes such as carbonation in concrete, corrosion in metals, etc., initiate at the surface. In such cases, ultrasonic Rayleigh surface waves are especially appropriate for detection and characterization of damage since their energy is concentrated in the top layer of the test object. For the civil engineering infrastructure, only a limited number of field applicable nonlinear ultrasonic techniques have been introduced. In this paper a nonlinear ultrasonic measurement technique based on the use of Rayleigh waves is developed and used to characterize carbonation in concrete samples. This work develops a collinear mixing technique for concrete structures. Wedge transducer is used for the generation and an accelerometer for the detection of the fundamental and nonlinearity modulated ultrasonic signal components. The measurements are made by varying the input voltage and along the propagation distance. The slope of the normalized modulation amplitudes is taken as the nonlinearity parameter. Concrete samples with two different levels of damage are examined, and the difference of the two fundamental frequencies is used to quantify damage state.

Gross, J.; Kim, J.-Y.; Jacobs, L. J.; Kurtis, K. E.; Qu, J.

2013-01-01

164

Thermal control materials on EOIM-3  

NASA Technical Reports Server (NTRS)

Thermal control paints, anodized aluminum, and beta cloth samples were flown on STS-46 as part of the Evaluation of Oxygen Interaction with Materials Experiment (EOIM-3). The thermal control paints flown on EOIM-3 include ceramic and polyurethane-based paints. Passively exposed samples are compared to actively heated samples and controlled exposure samples. Optical property measurements of absorptivity, emissivity, and spectrofluorescence are presented for each paint. Several variations of anodized aluminum, including chromic acid anodize, sulfuric acid anodize, and boric/sulfuric acid anodize were flown on the actively heated trays and the passive exposure trays. The post-flight optical properties are within tolerances for these materials. Also flown were two samples of yellow anodized aluminum. The yellow anodized aluminum samples darkened noticeably. Samples of aluminized and unaluminized beta cloth, a fiberglass woven mat impregnated with TFE Teflon, were flown with passive exposure to the space environment. Data from this part of the experiment is correlated to observations from LDEF and erosion of the Teflon thin film samples also flown on EOIM-3 and LDEF.

Finckenor, Miria M.; Linton, Roger C.; Kamenetzky, Rachel R.; Vaughn, Jason A.

1995-01-01

165

Multiple phosphorylation events control mitotic degradation of the muscle transcription factor Myf5  

E-print Network

, and is inhibited by Myf5 mitotic degradation is conserved in non-muscle cellsFigure 1 Myf5 mitotic degradation is conserved in non-muscle cells. HeLa-S3 cells expressing Myf5 under an inducible pro- motor (tetoff) were treated (lanes 2, 3, 4) or not (AS, lane 1... ) for 30 min at 30°C. 25 µg of each extract were resolved by 10% SDS-PAGE and immuno- blotted with anti-Myf5 antibodies. AS: asynchronous cells; * indicates a non specific band recognized by the antibodies that can be used as a loading control. Myf5 MG...

Doucet, Christine; Gutierrez, Gustavo J; Lindon, Catherine; Lorca, Thierry; Lledo, Gwendaline; Pinset, Christian; Coux, Olivier

2005-12-01

166

Podoplanin mediates ECM degradation by squamous carcinoma cells through control of invadopodia stability.  

PubMed

Invadopodia are actin-rich cell membrane projections used by invasive cells to penetrate the basement membrane. Control of invadopodia stability is critical for efficient degradation of the extracellular matrix (ECM); however, the underlying molecular mechanisms remain poorly understood. Here, we uncover a new role for podoplanin, a transmembrane glycoprotein closely associated with malignant progression of squamous cell carcinomas (SCCs), in the regulation of invadopodia-mediated matrix degradation. Podoplanin downregulation in SCC cells impairs invadopodia stability, thereby reducing the efficiency of ECM degradation. We report podoplanin as a novel component of invadopodia-associated adhesion rings, where it clusters prior to matrix degradation. Early podoplanin recruitment to invadopodia is dependent on lipid rafts, whereas ezrin/moesin proteins mediate podoplanin ring assembly. Finally, we demonstrate that podoplanin regulates invadopodia maturation by acting upstream of the ROCK-LIMK-Cofilin pathway through the control of RhoC GTPase activity. Thus, podoplanin has a key role in the regulation of invadopodia function in SCC cells, controlling the initial steps of cancer cell invasion.Oncogene advance online publication, 8 December 2014; doi:10.1038/onc.2014.388. PMID:25486435

Martín-Villar, E; Borda-d'Agua, B; Carrasco-Ramirez, P; Renart, J; Parsons, M; Quintanilla, M; Jones, G E

2014-12-01

167

Enhanced Atrazine Degradation: Evidence for Reduced Residual Weed Control and A Method for Identifying Adapted Soils and Predicting Herbicide Persistence  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soilborn bacteria with novel metabolic abilities have been linked with enhanced atrazine degradation and complaints of reduced residual weed control in soils with an s-triazine use history. However, no field study has verified that enhanced degradation reduces atrazine’s residual weed control. The...

168

EVALUATION OF THE RESISTANCE OF A CHLORINATED POLYETHYLENE PROTECTIVE GARMENT MATERIAL TO PERMEATION AND DEGRADATION BY LIQUID CHEMICALS  

EPA Science Inventory

The objectives of the project was to investigate existing permeation and degradation resistance data for chlorinated polyethylene (CPE); to develop a laboratory test plan consistent with American Society for Testing and Materials (ASTM) Standard Test Methods F739-81 and D471-79 r...

169

Assessing the biocompatibility of degradable metallic materials: State-of-the-art and focus on the potential of genetic regulation  

Microsoft Academic Search

For decades, the design, development and use of metallic biomaterials has focused on the corrosion resistance of these materials once implanted in the human body. Recently, degradable metallic biomaterials (DMMs) have been proposed for some specific applications, including paediatric, orthopaedic and cardiovascular applications. DMMs are expected to disappear via corrosion after providing structural support for a certain period of time

Agung Purnama; Hendra Hermawan; Jacques Couet; Diego Mantovani

2010-01-01

170

Novel Fe-Pd/SiO2 catalytic materials for degradation of chlorinated organic compounds in water  

EPA Science Inventory

Novel reactive materials for catalytic degradation of chlorinated organic compounds in water at ambient conditions have been prepared on the basis of silica-supported Pd-Fe nanoparticles. Nanoscale Fe-Pd particles were synthesized inside porous silica supports using (NH4...

171

Material control for a reprocessing plant  

SciTech Connect

Adequate control of special nuclear material (SNM) implies a basic knowledge of the quantities of SNM processed through or contained within a fuels processing facility with sufficient accuracy that diversion of the SNM for deleterious purposes can be detected in a timely manner. This report to the Lawrence Livermore Laboratory (LLL) describes the primary process streams containing plutonium that are handled routinely within a spent fuel reprocessing plant and conversion facility. As an aid in implementing the objectives of the accountability system in a realistic situation, the Allied General Nuclear Services (AGNS) reprocessing plant now under construction near Barnwell, South Carolina, was chosen as the study model. The AGNS plant processes are discussed in detail emphasizing those portions of the process that contain significant quantities of plutonium. The unit processes within the separations plant, nitrate storage, plutonium product facility and the analytical laboratory are described with regard to the SNM control system currently planned for use in the facilities. A general discussion of laboratory techniques, nondestructive assay and process instrumentation for plutonium process and product material from a reprocessing plant is included. A comprehensive discussion is given of holdup measurements in plutonium recycle facilities. A brief preliminary overview is presented of alternative processing strategies for LWR fuel. An extensive review and summary of modeling efforts for liquid-liquid extraction cycles is included. A comprehensive bibliography of previous modeling efforts is covered.

Rundquist, D.; Bray, G.; Donelson, S.; Glancy, J.; Gozani, T.; Harris, L.; McNamera, R.; Pence, D.; Ringham, M.

1976-08-15

172

Enzymes for Degradation of Energetic Materials and Demilitarization of Explosives Stockpiles - SERDP Annual (Interim) Report, 12/98  

SciTech Connect

The current stockpile of energetic materials requiring disposal contains about half a million tons. Through 2001, over 2.1 million tons are expected to pass through the stockpile for disposal. Safe and environmentally acceptable methods for disposing of these materials are needed. This project is developing safe, economical, and environmentally sound processes using biocatalyst (enzymes) to degrade energetic materials and to convert them into economically valuable products. Alternative methods for destroying these materials are hazardous, environmentally unacceptable, and expensive. These methods include burning, detonation, land and sea burial, treatment at high temperature and pressure, and treatment with harsh chemicals. Enzyme treatment operates at room temperature and atmospheric pressure in a water solution.

Shah, M.M.

1999-01-18

173

Material layer control based on slag vertical mill's steady conditions  

Microsoft Academic Search

The slag grinding process is introduced. The basic control forms of vertical mill are presented by analyzing the dynamic characteristics of material layer in slag vertical mill. Simulation results show that, in steady conditions, self-tuned scaling factors fuzzy controller performs better than basic fuzzy controller in material layer control. Self-tuned scaling factors fuzzy controller was applied in one slag vertical

Zhao Liu; Xiaohong Wang

2011-01-01

174

Controlled thermal degradation for the identification and quantification of amine N-oxides in urine.  

PubMed

Studies of amine N-oxides in urine are important for the evaluation of occupational exposure to amines. These thermolabile compounds are difficult to handle by either gas or liquid chromatography, so a device for controlled thermal degradation has therefore been developed. It consists of a short precolumn with shut-off valves at both ends and an aluminum block for heating, and it was connected to the injection port of a gas chromatograph. After injection of amine N-oxides onto the precolumn and thermal degradation, the degradation products were allowed to enter the analytical column. Trimethylamine N-oxide (TMAO) and triethylamine N-oxide (TEAO) were investigated. Their thermal degradation patterns could be used for identification and quantification in aqueous solutions and in urine. Linear calibration graphs based on degradation product peaks (trimethylamine and O,N,N-trimethylhydroxylamine from TMAO and diethylamine and triethylamine from TEAO) were obtained for concentrations up to 500 ppm. Detection limits in aqueous solutions were 0.2 ppm (ca. 1 ng) for TMAO and 1 ppm for TEAO and the precisions were 6% and 9%, respectively. In urine, similar values were obtained for TEAO. The detection limit for TEAO corresponds to the expected concentration in urine after an 8-h exposure to air containing 0.8 mg/m3 of triethylamine. PMID:2258398

Lindegård, B; Mathiasson, L; Jönsson, J A; Akesson, B

1990-08-29

175

Some Materials Degradation Issues in the U.S. High-Level Nuclear Waste Repository Study (The Yucca Mountain Project)  

SciTech Connect

The safe disposal of radioactive waste requires that the waste be isolated from the environment until radioactive decay has reduced its toxicity to innocuous levels for plants, animals, and humans. All of the countries currently studying the options for disposing of high-level nuclear waste (HLW) have selected deep geologic formations to be the primary barrier for accomplishing this isolation. In U.S.A., the Nuclear Waste Policy Act of 1982 (as amended in 1987) designated Yucca Mountain in Nevada as the potential site to be characterized for high-level nuclear waste (HLW) disposal. Long-term containment of waste and subsequent slow release of radionuclides into the geosphere will rely on a system of natural and engineered barriers including a robust waste containment design. The waste package design consists of a highly corrosion resistant Ni-based Alloy 22 cylindrical barrier surrounding a Type 316 stainless steel inner structural vessel. The waste package is covered by a mailbox-shaped drip shield composed primarily of Ti Grade 7 with Ti Grade 24 structural support members. The U.S. Yucca Mountain Project has been studying and modeling the degradation issues of the relevant materials for some 20 years. This paper reviews the state-of-the-art understanding of the degradation processes based on the past 20 years studies on Yucca Mountain Project (YMP) materials degradation issues with focus on interaction between the in-drift environmental conditions and long-term materials degradation of waste packages and drip shields within the repository system during the 10,000 years regulatory period. This paper provides an overview of the current understanding of the likely degradation behavior of the waste package and drip shield in the repository after the permanent closure of the facility. The degradation scenario discussed in this paper include aging and phase instability, dry oxidation, general and localized corrosion, stress corrosion cracking and hydrogen induced cracking of Alloy 22 and titanium alloys. The effects of microbial activity and radiation on degradation of Alloy 22 and titanium alloys are also discussed. Further, for titanium alloys, the effects of fluorides, bromides, calcium ions, and galvanic coupling to less noble metals are further considered. It is concluded that, as far as materials degradation is concerned, the materials and design adopted in the U.S. Yucca Mountain Project will provide sufficient safety margins within the 10,000-years regulatory period.

F. Hua; P. Pasupathi; N. Brown; K. Mon

2005-09-19

176

76 FR 28193 - Amendments to Material Control and Accounting Regulations  

Federal Register 2010, 2011, 2012, 2013, 2014

...Amendments to Material Control and Accounting Regulations AGENCY: Nuclear Regulatory...amendments to the material control and accounting (MC&A) regulations. These regulations...outdated term, as it does not include ``accounting,'' and thus does not fully...

2011-05-16

177

In vitro degradation and cell response of calcium carbonate composite ceramic in comparison with other synthetic bone substitute materials.  

PubMed

The robust calcium carbonate composite ceramics (CC/PG) can be acquired by fast sintering calcium carbonate at a low temperature (650°C) using a biocompatible, degradable phosphate-based glass (PG) as sintering agent. In the present study, the in vitro degradation and cell response of CC/PG were assessed and compared with 4 synthetic bone substitute materials, calcium carbonate ceramic (CC), PG, hydroxyapatite (HA) and ?-tricalcium phosphate (?-TCP) ceramics. The degradation rates in decreasing order were as follows: PG, CC, CC/PG, ?-TCP, and HA. The proliferation of rat bone mesenchymal stem cells (rMSCs) cultured on the CC/PG was comparable with that on CC and PG, but inferior to HA and ?-TCP. The alkaline phosphatase (ALP) activity of rMSCs on CC/PG was lower than PG, comparable with ?-TCP, but higher than HA. The rMSCs on CC/PG and PG had enhanced gene expression in specific osteogenic markers, respectively. Compared to HA and ?-TCP, the rMSCs on the CC/PG expressed relatively lower level of collagen I and runt-related transcription factor 2, but showed more considerable expression of osteopontin. Although CC, PG, HA, and ?-TCP possessed impressive performances in some specific aspects, they faced extant intrinsic drawbacks in either degradation rate or mechanical strength. Based on considerable compressive strength, moderate degradation rate, good cell response, and being free of obvious shortcoming, the CC/PG is promising as another choice for bone substitute materials. PMID:25746269

He, Fupo; Zhang, Jing; Yang, Fanwen; Zhu, Jixiang; Tian, Xiumei; Chen, Xiaoming

2015-05-01

178

Analysis of Retrieved Hubble Space Telescope Thermal Control Materials  

NASA Technical Reports Server (NTRS)

The mechanical and optical properties of the thermal control materials on the Hubble Space Telescope (HST) have degraded over the nearly seven years the telescope has been in orbit. Astronaut observations and photographs from the Second Servicing Mission (SM2) revealed large cracks in the metallized Teflon FEP, the outer-layer of the multi-layer insulation (MLI), in many locations around the telescope. Also, the emissivity of the bonded metallized Teflon FEP radiator surfaces of the telescope has increased over time. Samples of the top layer of the MLI and radiator material were retrieved during SM2, and a thorough investigation into the de-radiation followed in order to determine the primary cause of the damage. Mapping of the cracks on HST and the ground testing showed that thermal cycling with deep-layer damage from electron and proton radiation are necessary to cause the observed embrittlement. Further, strong, evidence was found indicating that chain scission (reduced molecular weight) is the dominant form of damage to the metallized Teflon FEP.

Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, Joyce A.; Triolo, Jack J.

1998-01-01

179

Degradation of the materials of construction in Li-ion batteries  

SciTech Connect

The primary current-collector materials being used in lithium-ion cells are susceptible to environmental degradation: aluminum to pitting corrosion and copper to environmentally assisted cracking. Pitting occurs at the highly oxidizing potentials associated with the positive-electrode charge condition. However, the pitting mechanism is more complex than that typically observed in aqueous systems in that the pits are filled with a mixed metal/oxide product and exist as mounds or nodules on the surface. Electrochemical impedance spectroscopy was shown to be an effective analytical tool for quantifying and verifying aluminum corrosion behavior. Two fluorocarbon-based coatings were shown to improve the resistance of Al to pitting attack. Detailed x-ray photoelectron spectroscopy (XPS) surface analyses showed that there was very little difference in the films observed after simple immersion in either PC:DEC or EC:DMC electrolytes versus those following electrical cycling. Li and P are the predominant surface species. Finally, environmental cracking of copper can occur at or near the lithium potential and only if specific metallurgical conditions exist (work-hardening and large grain size).

Braithwaite, J.W.; Gonzales, A.; Lucero, S.J. [and others

1997-03-01

180

UV Induced Degradation of Polycarbonate-Based Lens Materials and Implications for the Heath Care Field  

NASA Astrophysics Data System (ADS)

Experimental undergraduate research at Keene State College has utilized facilities in physics and chemistry and at Polyonics, a local firm to study the effects of mono- and polychromatic UV radiation from various sources, including a Deuterium lamp, a solarization unit, a monochromator, and natural sunlight to study the photodegradation of polycarbonate-based lens materials used to produce eyewear using spectrophotometry and FTIR analysis. Ophthalmologic literature indicates a correlation between exposure to the UVB band of sunlight and the onset of cataract formation and macular degeneration. It is well known that polycarbonate plastic ``yellows'' when exposed to intense sunlight and, particularly, UV light either via photo-Fries rearrangement or by a photo oxidative process, forming polyconjugated systems and is a concern primarily for cosmetic reasons. Our data indicates that the ``yellowing'' is an indication of a more sinister problem in the case of eyeglasses in that spectrophotometric comparison shows it is accompanied by an increase in transmissivity in the UVB band where the wearer expects and needs protection. FTIR results indicate a degradation of molecular stabilizers and the appearance of free radicals that indicate a breakdown of the resin's chemical structure. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NES07.B1.4

Harkay, J. Russell; Henry, Jerry

2007-04-01

181

Programmable temperature control system for biological materials  

NASA Technical Reports Server (NTRS)

A system was constructed which allows programmable temperature-time control for a 5 cu cm sample volume of arbitrary biological material. The system also measures the parameters necessary for the determination of the sample volume specific heat and thermal conductivity as a function of temperature, and provides a detailed measurement of the temperature during phase change and a means of calculating the heat of the phase change. Steady-state and dynamic temperature control is obtained by supplying heat to the sample volume through resistive elements constructed as an integral part of the sample container. For cooling purposes, this container is totally immersed into a cold heat sink. Using a mixture of dry ice and alcohol at 79 C, the sample volume can be controlled from +40 to -60 C at rates from steady state to + or - 65 C/min. Steady-state temperature precision is better than 0.2 C, while the dynamic capability depends on the temperature rate of change as well as the mass of both the sample and the container.

Anselmo, V. J.; Harrison, R. G.; Rinfret, A. P.

1982-01-01

182

Probabilistic Structural Analysis and Reliability Using NESSUS With Implemented Material Strength Degradation Model  

NASA Technical Reports Server (NTRS)

This project included both research and education objectives. The goal of this project was to advance innovative research and education objectives in theoretical and computational probabilistic structural analysis, reliability, and life prediction for improved reliability and safety of structural components of aerospace and aircraft propulsion systems. Research and education partners included Glenn Research Center (GRC) and Southwest Research Institute (SwRI) along with the University of Texas at San Antonio (UTSA). SwRI enhanced the NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) code and provided consulting support for NESSUS-related activities at UTSA. NASA funding supported three undergraduate students, two graduate students, a summer course instructor and the Principal Investigator. Matching funds from UTSA provided for the purchase of additional equipment for the enhancement of the Advanced Interactive Computational SGI Lab established during the first year of this Partnership Award to conduct the probabilistic finite element summer courses. The research portion of this report presents the cumulation of work performed through the use of the probabilistic finite element program, NESSUS, Numerical Evaluation and Structures Under Stress, and an embedded Material Strength Degradation (MSD) model. Probabilistic structural analysis provided for quantification of uncertainties associated with the design, thus enabling increased system performance and reliability. The structure examined was a Space Shuttle Main Engine (SSME) fuel turbopump blade. The blade material analyzed was Inconel 718, since the MSD model was previously calibrated for this material. Reliability analysis encompassing the effects of high temperature and high cycle fatigue, yielded a reliability value of 0.99978 using a fully correlated random field for the blade thickness. The reliability did not change significantly for a change in distribution type except for a change in distribution from Gaussian to Weibull for the centrifugal load. The sensitivity factors determined to be most dominant were the centrifugal loading and the initial strength of the material. These two sensitivity factors were influenced most by a change in distribution type from Gaussian to Weibull. The education portion of this report describes short-term and long-term educational objectives. Such objectives serve to integrate research and education components of this project resulting in opportunities for ethnic minority students, principally Hispanic. The primary vehicle to facilitate such integration was the teaching of two probabilistic finite element method courses to undergraduate engineering students in the summers of 1998 and 1999.

Bast, Callie C.; Jurena, Mark T.; Godines, Cody R.; Chamis, Christos C. (Technical Monitor)

2001-01-01

183

Relationship between anode material, supporting electrolyte and current density during electrochemical degradation of organic compounds in water.  

PubMed

Taking crystal violet (CV) dye as pollutant model, the electrode, electrolyte and current density (i) relationship for electro-degrading organic molecules is discussed. Boron-doped diamond (BDD) or Iridium dioxide (IrO2) used as anode materials were tested with Na2SO4 or NaCl as electrolytes. CV degradation and generated oxidants showed that degradation pathways and efficiency are strongly linked to the current density-electrode-electrolyte interaction. With BDD, the degradation pathway depends on i: If idegraded by OH radicals, whereas if i>i(lim), generated oxidants play a major role in the CV elimination. When IrO2 was used, CV removal was not dependent on i, but on the electrolyte. Pollutant degradation in Na2SO4 on IrO2 seems to occur via IrO3; however, in the presence of NaCl, degradation was dependent on the chlorinated oxidative species generated. In terms of efficiency, the Na2SO4 electrolyte showed better results than NaCl when BDD anodes were employed. On the contrary, NaCl was superior when combined with IrO2. Thus, the IrO2/Cl(-) and BDD/SO4(2-) systems were better at removing the pollutant, being the former the most effective. On the other hand, pollutant degradation with the BDD/SO4(2-) and IrO2/Cl(-) systems is favored at low and high current densities, respectively. PMID:24981674

Guzmán-Duque, Fernando L; Palma-Goyes, Ricardo E; González, Ignacio; Peñuela, Gustavo; Torres-Palma, Ricardo A

2014-08-15

184

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers  

SciTech Connect

Three iron- to nickel-based austenitic alloys (Types 304L and 316L stainless steels and Alloy 825) are being considered as candidate materials for the fabrication of high-level radioactive-waste containers. Waste will include fuel assemblies from reactors as well as high-level waste in borosilicate glass forms, and will be sent to the prospective repository at Yucca Mountain, Nevada. The decay of radionuclides in the repository will result in the generation of substantial heat and in fluences of gamma radiation. Container materials may undergo any of several modes of degradation in this environment, including atmospheric oxidation; uniform aqueous phase corrosion; pitting; crevice corrosion; sensitization and intergranular stress corrosion cracking (IGSCC); and transgranular stress corrosion cracking (TGSCC). This report is an analysis of data relevant to the pitting, crevice corrosion, and stress corrosion cracking (SCC) of the three austenitic candidate alloys. The candidates are compared in terms of their susceptibilities to these forms of corrosion. Although all three candidates have demonstrated pitting and crevice corrosion in chloride-containing environments, Alloy 825 has the greatest resistance to these types of localized corrosion (LC); such resistance is important because pits can penetrate the metal and serve as crack initiation sites. Both Types 304L and 316L stainless steels are susceptible to SCC in acidic chloride media. In contrast, SCC has not been documented in Alloy 825 under comparable conditions. Gamma radiation has been found to enhance SCC in Types 304 and 304L stainless steels, but it has no detectable effect on the resistance of Alloy 825 to SCC. Furthermore, while the effects of microbiologically induced corrosion have been observed for 300-series stainless steels, nickel-based alloys such as Alloy 825 seem to be immune to such problems. 211 refs., 49 figs., 10 tabs.

Farmer, J.C.; Van Konynenburg, R.A.; McCright, R.D. (Lawrence Livermore National Lab., CA (USA)); Bullen, D.B. (Science and Engineering Associates, Inc., Pleasanton, CA (USA))

1988-04-01

185

Selenoprotein W controls epidermal growth factor receptor surface expression, activation and degradation via receptor ubiquitination.  

PubMed

Epidermal growth factor (EGF) receptor (EGFR) is the founding member of the ErbB family of growth factor receptors that modulate a complex network of intracellular signaling pathways controlling growth, proliferation, differentiation, and motility. Selenoprotein W (SEPW1) is a highly conserved, diet-regulated 9kDa thioredoxin-like protein required for normal cell cycle progression. We report here that SEPW1 is required for EGF-induced EGFR activation and that it functions by suppressing EGFR ubiquitination and receptor degradation. SEPW1 depletion inhibited EGF-dependent cell cycle entry in breast and prostate epithelial cells. In prostate cells, SEPW1 depletion decreased EGFR auto-phosphorylation, while SEPW1 overexpression increased EGFR auto-phosphorylation. SEPW1 depletion increased the rate of EGFR degradation, which decreased total and surface EGFR and suppressed EGF-dependent EGFR endocytosis, EGFR dimer formation, and activation of EGF-dependent pathways. EGFR ubiquitination was increased in SEPW1-depleted cells - in agreement with the increased rate of EGFR degradation, and suggests that SEPW1 suppresses EGFR ubiquitination. Ubiquitination-directed lysozomal degradation controls post-translational EGFR expression and is dysregulated in many cancers. Thus, suppression of EGFR ubiquitination by SEPW1 may be related to the putative increase in cancer risk associated with high selenium intakes. Knowledge of the mechanisms underlying SEPW1's regulation of EGFR ubiquitination may reveal new opportunities for nutritional cancer prevention or cancer drug development. PMID:25721765

Alkan, Zeynep; Duong, Frank L; Hawkes, Wayne C

2015-05-01

186

Compartmentalization of endoplasmic reticulum quality control and ER-associated degradation factors.  

PubMed

Recent studies are delineating a detailed picture of the architecture and function of the endoplasmic reticulum (ER) and the early secretory pathway, showing the existence of dynamic compartmentalization of ER quality control and ER-associated degradation (ERAD) factors. The compartmentalization is regulated by ER protein load and in turn regulates protein processing and cell fate. This compartmentalization is intimately linked to the protein quality control processes, protein disposal through ERAD, the unfolded protein response, and the initiation of apoptosis. It includes novel compartments, the ER-derived quality control compartment (ERQC), vesicles implicated in "ERAD-tuning," and the mitochondria-associated membranes (MAMs). PMID:23194074

Leitman, Julia; Ron, Efrat; Ogen-Shtern, Navit; Lederkremer, Gerardo Z

2013-01-01

187

Materials Science and Engineering A 445446 (2007) 669675 Degradation of elastomeric gasket materials in PEM fuel cells  

E-print Network

­20]. For instance, Gustavsson et al. [14] showed the aging of Silicone rubber under ac and dc voltages in a coastal and Huh [18] reported the surface degradation of HTV Sili- cone rubber and EPDM under accelerated

Van Zee, John W.

188

An investigation of the degradation of Fluorinated Ethylene Propylene (FEP) copolymer thermal blanketing materials aboard LDEF in the laboratory  

NASA Technical Reports Server (NTRS)

Samples of fluorinated ethylene propylene copolymer thermal blanketing material, recovered from the Long Duration Exposure Facility (LDEF), were investigated to determine the nature and the extent of degradation due to exposure to the low-Earth-orbit environment. Samples recovered from the ram-facing direction of LDEF, which received vacuum-ultraviolet (VUV) radiation and atomic-oxygen impingement, and samples from the trailing edge, which received almost exclusively VUV exposure, were investigated by scanning electron microscopy and atomic force microscopy. The most significant result of this investigation was found on samples that received only VUV exposure. These samples possessed a hard, embrittled surface layer that was absent from the atomic-oxygen exposed sample and from unexposed control samples. This surface layer is believed to be responsible for the 'synergistic' effect between VUV and atomic oxygen. Overall, the investigation revealed dramatically different morphologies for the two samples. The sample receiving both atomic-oxygen and VUV exposure was deeply eroded and had a characteristic 'rolling' surface morphology, while the sample that received only VUV exposure showed mild erosion and a surface morphology characterized by sharp high-frequency peaks. The morphologies observed in the LDEF samples, including the embrittled surface layer, were successfully duplicated in the laboratory.

Stiegman, A. E.; Brinza, David E.; Anderson, Mark S.; Minton, Timothy K.; Laue, Eric G.; Liang, Ranty H.

1991-01-01

189

Degradation of stone materials in the archaeological context of the Greek-Roman Theatre in Taormina (Sicily, Italy)  

NASA Astrophysics Data System (ADS)

In the present work results on the degradation phenomena of stone materials in the Ancient Theatre of Taormina, one of the most important Greek-Roman monuments of Sicily, are reported. Artificial stone materials in different conservation conditions were investigated. Samples of salt efflorescences from brick walls and degraded setting mortars were taken from the open gallery in “ summa cavea”. The chemical, physical and structural characterization was performed by means of X-Ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF), both in situ and ex situ. Results showed that the deterioration of stone materials is due to the aggressive action of the environment agents. Soluble salts, such as chlorides, sulphates and nitrates, were found in efflorescence samples. Mortars were affected by a decomposition process induced by sulphates’ attack.

Brai, M.; Casaletto, M. P.; Gennaro, G.; Marrale, M.; Schillaci, T.; Tranchina, L.

2010-09-01

190

MATERIALS DEGRADATION ANALYSIS AND DEVELOPMENT TO ENABLE ULTRA LOW COST, WEB-PROCESSED WHITE P-OLED FOR SSL  

SciTech Connect

Progress over Phase II of DE-FG02-07ER86293 'Materials Degradation Analysis and Development to Enable Ultra Low Cost, Web-Processed White P-OLED for SSL' was initially rapid in terms of device performance improvements. We exceeded our device luminance lifetime goals for printed flexible white OLEDs as laid out in our project proposal. Our Phase II performance target was to demonstrate >1500 hours luminance lifetime at 100 Cd/m2 from a printed flexible device. We now have R&D devices well in excess of 8000 hrs lifetime at 100 Cd/m2, tested in air. We also were able to produce devices which met the voltage target of >1500 hours below 15V operation. After completing the initial performance milestones, we went on to focus on color-related degradation issues which were cited as important to commercialization of the technology by our manufacturing partners. We also put additional focus on cathode work as the active material development that occurred over the STTR time period required an adaptation of the cathode from the original cathode formulations which were developed based on previous generation active layer materials. We were able to improve compatibility of the cathode with some of the newer generation active layer materials and improve device yield and voltage behavior. An additional objective of the initial Phase II was to further develop the underlying manufacturing technology and real-life product specifications. This is a key requirement that must be met to ensure eventual commercialization of this DOE-funded technology. The link between commercial investment for full commercialization and R&D efforts in OLED solid State Lighting is often a large one. Add-Vision's lower cost, printed OLED manufacturing approach is an attraction, but close engagement with manufacturing partners and addressing customer specifications is a very important link. Manufacturing technology encompasses development of moisture reduction encapsulation technology, improved cost performance, and reductions in operating voltage through thinner and higher uniformity active device layers. We have now installed a pilot encapsulation system at AVI for controlled, high throughput lamination encapsulation of flexible OLEDs in a novel process. Along with this, we have developed, with our materials supply partners, adhesives, barrier films and other encapsulation materials and we are showing total air product lifetimes in the 2-4 years range from a process consistent with our throughput goals of {approx}1M device per month ({approx}30,000 sq. ft. of processed OLEDs). Within the last year of the project, we have been working to introduce the manufacturing improvements made in our LEP deposition and annealing process to our commercial partners. Based on the success of this, a pilot scale-up program was begun. During this process, Add-Vision was acquired by a strategic partner, in no small part, because of the promise of future success of the technology as evidenced by our commercial partners pilot scale-up plans. Overall, the performance, manufacturing and product work in this project has been successful. Additional analysis and device work at LBL has also shown a unique adhesion change with device bias stressing which may result from active layer polymer cross-linking during bias stressing of device. It was shown that even small bias stresses, as a fraction of a full device lifetime stress period, result in measurable chemical change in the device. Further work needs to be conducted to fully understand the chemical nature of this interaction. Elucidation of this effect would enable doped OLED formulation to be engineered to suppress this effect and further extend lifetimes and reduce voltage climb.

DR. DEVIN MACKENZIE

2011-12-13

191

RELIABILITY MODELS OF AGING PASSIVE COMPONENTS INFORMED BY MATERIALS DEGRADATION METRICS TO SUPPORT LONG-TERM REACTOR OPERATIONS  

SciTech Connect

Paper describes a methodology for the synthesis of nuclear power plant service data with expert-elicited materials degradation information to estimate the future failure rates of passive components. This method should be an important resource to long-term plant operations and reactor life extension. Conventional probabilistic risk assessments (PRAs) are not well suited to addressing long-term reactor operations. Since passive structures and components are among those for which replacement can be least practical, they might be expected to contribute increasingly to risk in an aging plant; yet, passives receive limited treatment in PRAs. Furthermore, PRAs produce only snapshots of risk based on the assumption of time-independent component failure rates. This assumption is unlikely to be valid in aging systems. The treatment of aging passive components in PRA presents challenges. Service data to quantify component reliability models are sparse, and this is exacerbated by the greater data demands of age-dependent reliability models. Another factor is that there can be numerous potential degradation mechanisms associated with the materials and operating environment of a given component. This deepens the data problem since risk-informed management of component aging will demand an understanding of the long-term risk significance of individual degradation mechanisms. In this paper we describe a Bayesian methodology that integrates metrics of materials degradation susceptibility with available plant service data to estimate age-dependent passive component reliabilities. Integration of these models into conventional PRA will provide a basis for materials degradation management informed by predicted long-term operational risk.

Unwin, Stephen D.; Lowry, Peter P.; Toyooka, Michael Y.

2012-05-01

192

Identification and Assessment of Material Models for Age-Related Degradation of Structures and Passive Components in Nuclear Power Plants  

SciTech Connect

When performing seismic safety assessments of nuclear power plants (NPPs), the potential effects of age-related degradation on structures, systems, and components (SSCs) should be considered. To address the issue of aging degradation, the Korea Atomic Energy Research Institute (KAERI) has embarked on a five-year research project to develop a realistic seismic risk evaluation system which will include the consideration of aging of structures and components in NPPs. Three specific areas that are included in the KAERI research project, related to seismic probabilistic risk assessment (PRA), are probabilistic seismic hazard analysis, seismic fragility analysis including the effects of aging, and a plant seismic risk analysis. To support the development of seismic capability evaluation technology for degraded structures and components, KAERI entered into a collaboration agreement with Brookhaven National Laboratory (BNL) in 2007. The collaborative research effort is intended to continue over a five year period with the goal of developing seismic fragility analysis methods that consider the potential effects of age-related degradation of SSCs, and using these results as input to seismic PRAs. In the Year 1 scope of work BNL collected and reviewed degradation occurrences in US NPPs and identified important aging characteristics needed for the seismic capability evaluations that will be performed in the subsequent evaluations in the years that follow. This information is presented in the Annual Report for the Year 1 Task, identified as BNL Report-81741-2008 and also designated as KAERI/RR-2931/2008. The report presents results of the statistical and trending analysis of this data and compares the results to prior aging studies. In addition, the report provides a description of U.S. current regulatory requirements, regulatory guidance documents, generic communications, industry standards and guidance, and past research related to aging degradation of SSCs. This report describes the research effort performed by BNL for the Year 2 scope of work. This research focused on methods that could be used to represent the long-term behavior of materials used at NPPs. To achieve this BNL reviewed time-dependent models which can approximate the degradation effects of the key materials used in the construction of structures and passive components determined to be of interest in the Year 1 effort. The intent was to review the degradation models that would cover the most common time-dependent changes in material properties for concrete and steel components.

Nie,J.; Braverman, J.; Hofmayer, C.; Kim, M. K.; Choi, I-K.

2009-04-27

193

Spatial Control of Cell-Mediated Degradation to Regulate Vasculogenesis and Angiogenesis in Hyaluronan Hydrogels  

PubMed Central

Matrix remodeling is crucial for neovascularization, however its utilization to control this process in synthetic biomaterials has been limited. Here, we utilized hyaluronic acid (HA) hydrogels to spatially control cellular remodeling during vascular network formation. Specifically, we exploited a secondary radical polymerization to alter the ability of cells to degrade the hydrogel and utilized it to create spatial patterning using light initiation. We first demonstrated the ability of the hydrogel to either support or inhibit in vitro vasculogenesis of endothelial colony-forming cells (ECFCs) or angiogenesis from ex ovo chorioallantoic membranes. We showed that vascular tube branching and sprouting, which required matrix metalloproteinases (MMPs)-dependent remodeling, could be achieved in hydrogels formed by primary addition-crosslinking only. Although ECFCs expressed higher levels of MMPs in the hydrogels with the secondary radical-crosslinking, the generated kinetic chains disabled cell-mediated remodeling and therefore vascular formation was arrested at the vacuole and lumen stage. We then patterned hydrogels to have regions that either permitted or inhibited cell-mediated degradation during in vitro vasculogenesis or angiogenesis. Our ability to control degradation cues that regulate vascular tube formation is important for the study of vascular biology and the application of synthetic biomaterials in tissue regeneration. PMID:22672833

Hanjaya-Putra, Donny; Wong, Kyle T.; Hirotsu, Kelsey; Khetan, Sudhir; Burdick, Jason A.; Gerecht, Sharon

2012-01-01

194

Multilayer Films Assembled from Naturally-Derived Materials for Controlled Protein Release  

PubMed Central

Herein we designed and characterized films composed of naturally derived materials for controlled release of proteins. Traditional drug delivery strategies rely on synthetic or semi-synthetic materials, or utilize potentially denaturing assembly conditions that are not optimal for sensitive biologics. Layer-by-Layer (LbL) assembly of films uses benign conditions and can generate films with various release mechanisms including hydrolysis-facilitated degradation. These use components such as synthetic polycations that degrade into non-natural products. Herein we report the use of a naturally-derived, biocompatible and degradable polyanion, poly(?-l-malic acid), alone and in combination with chitosan in an LbL film, whose degradation products of malic acid and chitosan are both generally recognized as safe (GRAS) by the FDA. We have found that films based on this polyanion have shown sustained release of a model protein, lysozyme that can be timed from tens of minutes to multiple days through different film architectures. We also report the incorporation and release of a clinically used biologic, basic fibroblast growth factor (bFGF), which demonstrates the use of this strategy as a platform for controlled release of various biologics. PMID:24825478

Hsu, Bryan B.; Hagerman, Samantha R; Jamieson, Kelsey; Veselinovic, Jovana; O’Neill, Nicholas; Holler, Eggehard; Ljubimova, Julia Y.; Hammond, Paula T.

2014-01-01

195

Imprinted sol-gel materials for monitoring degradation products in automotive oils by shear transverse wave.  

PubMed

Titania sol-gel layers imprinted with capric acid have been used as synthetic receptors for highly sensitive detection of oxidized products resulting from degradation of automotive engine oil. These layers have been applied as sensitive coating material on shear transverse wave (STW) resonators of frequencies ranging from 100 MHz to 430 MHz. A relatively small size of STW resonators, i.e. about 2 mm for 430 MHz makes these devices extremely useful while considering the concept of miniaturization. It has been proved experimentally that by increasing fundamental resonance frequency of these devices, a very high sensor response i.e. 22 kHz up to 460 kHz can be generated. The geometry of long chain capric acid fits best as recognition element in the synthesis of imprinted TiO(2) network. The thin titania layers coated on transducer surface provide excellent diffusion pathways to oxidized products of waste engine oil for selective and reversible re-inclusion i.e. recovery time of 30 min. Viscosity effects of oxidized engine oil can be minimized by shear waves which do not dissipate considerable amount of energy that ensure smooth liquid phase operation. Different oxidized products i.e. carbonic acids and esters can be characterized in lubricant via infra-red (IR) spectroscopy. The increasing IR absorbance of different waste oil samples is a clear indication of increasing concentration of carbonyl group. The IR absorbance of carbonyl groups is directly correlated to the age of respective waste engine oil samples and a quantitative relationship between sensor responses from STWs and IR absorbance was also developed. PMID:20708116

Mujahid, Adnan; Afzal, Adeel; Glanzing, Gerd; Leidl, Anton; Lieberzeit, Peter A; Dickert, Franz L

2010-08-18

196

Use of lateral structures to monitor and evaluate degradation of key photovoltaic parameters in an organic bulk heterojunction material  

NASA Astrophysics Data System (ADS)

Charge transport and recombination mechanisms within organic bulk heterojunction (BHJ) systems have been studied using lateral devices to perform in situ potentiometry. We have developed a simplified measurement technique using two types of lateral structures to elicit key charge transport parameters and study the time and process dependence of the carrier mobilities and their ratio. Small geometry lateral devices are used to evaluate the mobility of the slower carrier within the P3HT:PCBM material system. Larger structures with 5 in situ voltage probes are used to construct a simple potential profile of the device channel and accurately determine the carrier mobility ratio. These two measurements enable the calculation of carrier densities and the recombination coefficient. We monitor the change in these parameters as the P3HT:PCBM film degrades in the presence of oxygen and also examine the effect of the solvent additive 1,8-diiodooctane on this degradation mechanism. By exposing ethanol vapor to the BHJ film, we induce traps in the material and monitor the shift in dominant nongeminate recombination mechanism to a more unimolecular type. We are also able to measure the resulting decrease in carrier mobilities due to the presence of dipole-induced traps. Lateral devices are useful material diagnostic structures for studying degradation in BHJ materials.

Danielson, Eric; Ooi, Zi-En; Dodabalapur, Ananth

2014-12-01

197

Phase change material for temperature control and material storage  

NASA Technical Reports Server (NTRS)

A phase change material comprising a mixture of water and deuterium oxide is described, wherein the mole fraction of deuterium oxide is selected so that the mixture has a selected phase change temperature within a range between 0.degree. C. and 4.degree. C. The mixture is placed in a container and used for passive storage and transport of biomaterials and other temperature sensitive materials. Gels, nucleating agents, freezing point depression materials and colorants may be added to enhance the characteristics of the mixture.

Wessling, Jr., Francis C. (Inventor); Blackwood, James M. (Inventor)

2011-01-01

198

Virtual earthquake engineering laboratory with physics-based degrading materials on parallel computers  

NASA Astrophysics Data System (ADS)

For the last few decades, we have obtained tremendous insight into underlying microscopic mechanisms of degrading quasi-brittle materials from persistent and near-saintly efforts in laboratories, and at the same time we have seen unprecedented evolution in computational technology such as massively parallel computers. Thus, time is ripe to embark on a novel approach to settle unanswered questions, especially for the earthquake engineering community, by harmoniously combining the microphysics mechanisms with advanced parallel computing technology. To begin with, it should be stressed that we placed a great deal of emphasis on preserving clear meaning and physical counterparts of all the microscopic material models proposed herein, since it is directly tied to the belief that by doing so, the more physical mechanisms we incorporate, the better prediction we can obtain. We departed from reviewing representative microscopic analysis methodologies, selecting out "fixed-type" multidirectional smeared crack model as the base framework for nonlinear quasi-brittle materials, since it is widely believed to best retain the physical nature of actual cracks. Microscopic stress functions are proposed by integrating well-received existing models to update normal stresses on the crack surfaces (three orthogonal surfaces are allowed to initiate herein) under cyclic loading. Unlike the normal stress update, special attention had to be paid to the shear stress update on the crack surfaces, due primarily to the well-known pathological nature of the fixed-type smeared crack model---spurious large stress transfer over the open crack under nonproportional loading. In hopes of exploiting physical mechanism to resolve this deleterious nature of the fixed crack model, a tribology-inspired three-dimensional (3d) interlocking mechanism has been proposed. Following the main trend of tribology (i.e., the science and engineering of interacting surfaces), we introduced the base fabric of solid particle-soft matrix to explain realistic interlocking over rough crack surfaces, and the adopted Gaussian distribution feeds random particle sizes to the entire domain. Validation against a well-documented rough crack experiment reveals promising accuracy of the proposed 3d interlocking model. A consumed energy-based damage model has been proposed for the weak correlation between the normal and shear stresses on the crack surfaces, and also for describing the nature of irrecoverable damage. Since the evaluation of the consumed energy is directly linked to the microscopic deformation, which can be efficiently tracked on the crack surfaces, the proposed damage model is believed to provide a more physical interpretation than existing damage mechanics, which fundamentally stem from mathematical derivation with few physical counterparts. Another novel point of the present work lies in the topological transition-based "smart" steel bar model, notably with evolving compressive buckling length. We presented a systematic framework of information flow between the key ingredients of composite materials (i.e., steel bar and its surrounding concrete elements). The smart steel model suggested can incorporate smooth transition during reversal loading, tensile rupture, early buckling after reversal from excessive tensile loading, and even compressive buckling. Especially, the buckling length is made to evolve according to the damage states of the surrounding elements of each bar, while all other dominant models leave the length unchanged. What lies behind all the aforementioned novel attempts is, of course, the problem-optimized parallel platform. In fact, the parallel computing in our field has been restricted to monotonic shock or blast loading with explicit algorithm which is characteristically feasible to be parallelized. In the present study, efficient parallelization strategies for the highly demanding implicit nonlinear finite element analysis (FEA) program for real-scale reinforced concrete (RC) structures under cyclic loading are proposed. Quantitat

Cho, In Ho

199

Polyester-Based (Bio)degradable Polymers as Environmentally Friendly Materials for Sustainable Development  

PubMed Central

This review focuses on the polyesters such as polylactide and polyhydroxyalkonoates, as well as polyamides produced from renewable resources, which are currently among the most promising (bio)degradable polymers. Synthetic pathways, favourable properties and utilisation (most important applications) of these attractive polymer families are outlined. Environmental impact and in particular (bio)degradation of aliphatic polyesters, polyamides and related copolymer structures are described in view of the potential applications in various fields. PMID:25551604

Rydz, Joanna; Sikorska, Wanda; Kyulavska, Mariya; Christova, Darinka

2014-01-01

200

U.S. national nuclear material control and accounting system  

Microsoft Academic Search

Issues related to nuclear material control and accounting and illegal dealing in these materials were discussed at the April 19--20, 1996 Moscow summit meeting (G7 + Russia). The declaration from this meeting reaffirmed that governments are responsible for the safety of all nuclear materials in their possession and for the effectiveness of the national control and accounting system for these

S Taylor; V G Terentiev

1998-01-01

201

Evaluation of Ultrasonic and Thermal Nondestructive Evaluation for the Characterization of Aging Degradation in Braided Composite Materials  

NASA Technical Reports Server (NTRS)

This paper examines the ability of traditional nondestructive evaluation (NDE) techniques to measure the degradation of braided polymer composite materials subjected to thermal-humidity cycling to simulate aging. A series of braided composite coupons were examined using immersion ultrasonic and pulsed thermography techniques in the as received condition. These same specimens were then examined following extended thermal-humidity cycling. Results of this examination did not show a significant change in the resulting (NDE) signals.

Martin, Richard E.

2010-01-01

202

The effect of visual degradation on anticipatory and compensatory steering control.  

PubMed

It has long been held that steering a vehicle is subserved by two distinct visual processes, a compensatory one for maintaining lane position and an anticipatory one for previewing the curvature of the upcoming road. In this study, we investigated the robustness of these two steering control processes by systematically degrading their visual inputs. Performance was measured at the level of vehicle position and at the level of the actions on the steering wheel. The results show that the compensatory process is more robust to visual degradation than the anticipatory process. The results are also consistent with the idea that steering is under the supervision of a combination of compensatory and anticipatory mechanisms, although they suggest that the quality of the sensory information will determine how information is combined. PMID:23915269

Frissen, Ilja; Mars, Franck

2014-01-01

203

Control of xanthan-degrading organisms in the Loudon pilot: approach, methodology, and results  

SciTech Connect

An investigation of loss of mobility control in Exxon's Loudon micellar/polymer pilot test has confirmed that loss was caused by microbial degradation of the xanthan biopolymer used to viscosify the microemulsion and polymer drive banks. This study describes techniques which were used to sample and culture bacteria from the Loudon pilot and demonstrate that these mixed cultures are able to degrade xanthan rapidly under reservoir conditions. Laboratory studies show that, under anaerobic conditions, bacteria cultured from the Loudon pilot can cause over 90% loss of xanthan viscosity in micellar/polymer fluids within 7 days. An extensive laboratory screening program was conducted to identify biocides that are effective against the offending organisms. Complete kill of the organisms, biocide compatibility (with biopolymer, formation rock, field brines, and microemulsion), cost effectiveness, and chemical stability were key parameters. Of the biocides tested, formaldehyde was found to be the most consistently effective.

Bragg, J.R.; Maruca, S.D.; Gale, W.W.; Gall, L.S.; Wernau, W.C.

1983-01-01

204

Degraded Litter Leachates as a Potential Control on Streamwater Nitrogen Dynamics  

NASA Astrophysics Data System (ADS)

Dissolved organic nitrogen (DON) export from catchments is a critical element of overall nutrient cycling. An underlying assumption in most studies investigating DON export is that the source of this DON is from an aged soil organic matter (SOM) pool. However, recent investigations of dissolved organic carbon (DOC) have called into question the idea that dissolved organic matter (DOM) in streams is derived primarily from aged SOM. Evidence includes riverine DOC 14C ages (~5 years) that are much younger than SOM within the catchment as well as the riverine particulate organic matter (POM) pool (decades to 100s of years). Molecular fractionation due to litter leaching and sorption to mineral surfaces can completely account for the degraded molecular signatures observed in dissolved amino acid and dissolved lignin compositions within the DOM pool. Thus it is feasible that a significant portion of exported DON from catchments could come from a younger, less degraded organic matter pool such as litters. To evaluate this potential, we conducted a leaching incubation experiment using litters and degraded "duff" litters (estimated 2-5 yrs of degradation) from four vegetation types (live and blue oak leaves, foothill pine needles, and mixed annual grasses) in an oak woodland ecosystem in the foothills of the Sierra mountains of California. Litters and duffs were placed on sieves within funnels throughout the catchment, and leachates were collected during each rainfall event from Dec. 1, 2006 through May 31, 2007. DON accounted for 50-70% of nitrogen released from litters and DON plus particulate organic nitrogen (PON) constituted >90% of released nitrogen. In contrast, dissolved inorganic nitrogen (DIN) made up 60-80% of released nitrogen in the duff materials with the majority as ammonia. When scaled to the entire watershed, overall yields of dissolved nitrogen in leachates was estimated at 6.0 kg ha-1 for DON, 7.3 kg ha-1 for NH4-N, and 8.8 kg ha-1 for NO3-N, with 90% of the DON and 99% of the DIN derived from the duff materials. Areal yields are up to an order of magnitude greater than reported stream/riverine exports from catchments, indicating that much of this leachate must be degraded or sorbed along hydrologic flowpaths to streams, but that leachates could constitute a significant component of the DON/DOM pool within streams.

Hernes, P. J.; O'Geen, A. T.; Dahlgren, R. A.

2008-12-01

205

Quality control material for plasma fibrinogen test produced from purified human fibrinogen  

PubMed Central

Plasma fibrinogen measurement is a routine laboratory procedure commonly performed on automated coagulation analysers. Its determination is quantitative, not quantitative. Yet, a lack of precision has been an issue for fibrinogen measurement. A control material derived from plasma comprises many proteins, inhibitors and fatty acids, any or all of which can interfere in the fibrinogen assay. This study has attempted to develop a quality control material using purified human fibrinogen and has compared measurement precision between both purified and plasma materials. Purified fibrinogen was prepared using Cohn fraction 1 and glycine precipitation. Purified fibrinogen clottability was greater than 95%, with no main plasma proteins, lipids or fibrinogen degradation products observed. Two purified control materials were lyophilized at normal (2.30 g lm1) and abnormal (1.20 g lm1) levels of fibrinogen concentration. Precision was evaluated using a liquid-type reagent, Thrombocheck Fib(L), on automated coagulation analysers. Coefficient of variation for within-run, intraday and between-day precision of the purified materials was 0.7-3.5%. In comparison, the coefficient of variation for plasma materials ranged from 1.2 to 5.3%. These results suggest that materials prepared from purified fibrinogen can be useful to laboratory quality control by improving overall precision of fibrinogen measurement and are applicable to automated coagulation analysers. PMID:18924717

Uemura, Yahiro; Tatsumi, Noriyuki

2003-01-01

206

Degradation of insecticides used for indoor spraying in malaria control and possible solutions  

PubMed Central

Background The insecticide dichloro-diphenyl-trichloroethane (DDT) is widely used in indoor residual spraying (IRS) for malaria control owing to its longer residual efficacy in the field compared to other World Health Organization (WHO) alternatives. Suitable stabilization to render these alternative insecticides longer lasting could provide a less controversial and more acceptable and effective alternative insecticide formulations than DDT. Methods This study sought to investigate the reasons behind the often reported longer lasting behaviour of DDT by exposing all the WHO approved insecticides to high temperature, high humidity and ultra-violet light. Interactions between the insecticides and some mineral powders in the presence of an aqueous medium were also tested. Simple insecticidal paints were made using slurries of these mineral powders whilst some insecticides were dispersed into a conventional acrylic paint binder. These formulations were then spray painted on neat and manure coated mud plaques, representative of the material typically used in rural mud houses, at twice the upper limit of the WHO recommended dosage range. DDT was applied directly onto mud plaques at four times the WHO recommended concentration and on manure plaques at twice WHO recommended concentration. All plaques were subjected to accelerated ageing conditions of 40°C and a relative humidity of 90%. Results The pyrethroids insecticides outperformed the carbamates and DDT in the accelerated ageing tests. Thus UV exposure, high temperature oxidation and high humidity per se were ruled out as the main causes of failure of the alternative insecticides. Gas chromatography (GC) spectrograms showed that phosphogypsum stabilised the insecticides the most against alkaline degradation (i.e., hydrolysis). Bioassay testing showed that the period of efficacy of some of these formulations was comparable to that of DDT when sprayed on mud surfaces or cattle manure coated surfaces. Conclusions Bioassay experiments indicated that incorporating insecticides into a conventional paint binder or adsorbing them onto phosphogypsum can provide for extended effective life spans that compare favourably with DDT's performance under accelerated ageing conditions. Best results were obtained with propoxur in standard acrylic emulsion paint. Similarly, insecticides adsorbed on phosphogypsum and sprayed on cattle manure coated surfaces provided superior lifespans compared with DDT sprayed directly on a similar surface. PMID:22008292

2011-01-01

207

Evidence of widespread degraded Amazonian-aged ice-rich deposits in the transition between Elysium Rise and Utopia Planitia, Mars: Guidelines for the recognition of degraded ice-rich materials  

NASA Astrophysics Data System (ADS)

Widespread deposits surrounding mesas, in craters and in valley systems are observed in the transition zone between the Elysium Rise and the Utopia Planitia Basin. They are characterized by their relatively high albedo, the presence of ring-mold crater (RMC) morphologies and their pitted surfaces, with textures ranging from lineations and fish-scale-patterns to widely distributed knobs. These deposits are interpreted to be modified ice-rich material in the form of degraded deposits of concentric crater fill (CCF), lineated valley fill (LVF) and lobate debris aprons (LDA). The degraded CCF deposits are observed from 31.2-40°N, 138-150°E over an elevation range of almost 9 km. This wide-ranging distribution demonstrates that degraded ice-rich deposits exist at every altitude and latitude in the study area, indicating that icy mantle materials were initially deposited over extensive areas and were stable over a long time period, allowing the deposits to coexist and interact with different processes under very different conditions. The degraded LDA deposits represent the largest unit of modified ice-rich material, with an area of ˜15,700 km 2, and are populated with a range of ring-mold crater morphologies that is interpreted to be related to a degradational sequence between previously described RMC and newly observed RMCs that appear to be more degraded. A distinctive frequency difference in the distribution of normal and degraded RMCs permits an evaluation of different degradation stages of the LDA deposits; we show how an RMC distribution can be used as a key tool for evaluation of altered LDA, LVF and CCF deposits. Taken together, these observations suggest that ice-rich material has played a major role in shaping the present-day landscape in the transition zone between the Elysium Rise and the Utopia Planitia Basin, and they provide a link for understanding Amazonian-aged degradation processes of ice-rich deposits in an area with no significant topographic relief.

Pedersen, G. B. M.; Head, J. W.

2010-12-01

208

Towards programmable materials : tunable material properties through feedback control of conducting polymers  

E-print Network

Mammalian skeletal muscle is an amazing actuation technology that can controllably modify its force and position outputs as well as its material properties such as stiffness. Unlike muscle, current engineering materials ...

Wiedenman, Nathan Scott

2008-01-01

209

A Measurement Control Program for Nuclear Material Accounting  

SciTech Connect

A measurement control program for nuclear material accounting monitors and controls the quality of the measurements of special nuclear material that are involved in material balances. The quality is monitored by collecting data from which the current precision and accuracy of measurements can be evaluated. The quality is controlled by evaluations, reviews, and other administrative measures for control of selection or design of facilities. equipment and measurement methods and the training and qualification of personnel who perform SNM measurements. This report describes the most important elements of a program by which management can monitor and control measurement quality.

,

1980-06-01

210

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers; Overview  

SciTech Connect

Three iron- to nickel-based austenitic alloys and three copper-based alloys are being considered as candidate materials for the fabrication of high-level radioactive-waste disposal containers. The austenitic alloys are Types 304L and 316L stainless steels and the high-nickel material Alloy 825. The copper-based alloys are CDA 102 (oxygen-free copper), CDA 613 (Cu-7Al), and CDA 715 (Cu-30Ni). Waste in the forms of both spent fuel assemblies from reactors and borosilicate glass will be sent to the prospective repository at Yucca Mountain, Nevada. The decay of radionuclides will result in the generation of substantial heat and gamma radiation. Container materials may undergo any of several modes of degradation in this environment, including undesirable phase transformations due to a lack of phase stability; atmospheric oxidation; general aqueous corrosion; pitting; crevice corrosion; intergranular stress corrosion cracking; and transgranular stress corrosion cracking. Problems specific to welds, such as hot cracking, may also occur. A survey of the literature has been prepared as part of the process of selecting, from among the candidates, a material that is adequate for repository conditions. The modes of degradation are discussed in detail in the survey to determine which apply to the candidate alloys and the extent to which they may actually occur. The eight volumes of the survey are summarized in Sections 1 through 8 of this overview. The conclusions drawn from the survey are also given in this overview.

Farmer, J.C.; McCright, R.D.; Kass, J.N.

1988-06-01

211

Glucan, Water Dikinase Exerts Little Control over Starch Degradation in Arabidopsis Leaves at Night1[W][OPEN  

PubMed Central

The first step on the pathway of starch degradation in Arabidopsis (Arabidopsis thaliana) leaves at night is the phosphorylation of starch polymers, catalyzed by glucan, water dikinase (GWD). It has been suggested that GWD is important for the control of starch degradation, because its transcript levels undergo strong diel fluctuations, its activity is subject to redox regulation in vitro, and starch degradation is strongly decreased in gwd mutant plants. To test this suggestion, we analyzed changes in GWD protein abundance in relation to starch levels in wild-type plants, in transgenic plants in which GWD transcripts were strongly reduced by induction of RNA interference, and in transgenic plants overexpressing GWD. We found that GWD protein levels do not vary over the diel cycle and that the protein has a half-life of 2 d. Overexpression of GWD does not accelerate starch degradation in leaves, and starch degradation is not inhibited until GWD levels are reduced by 70%. Surprisingly, this degree of reduction also inhibits starch synthesis in the light. To discover the importance of redox regulation, we generated transgenic plants expressing constitutively active GWD. These plants retained normal control of degradation. We conclude that GWD exerts only a low level of control over starch degradation in Arabidopsis leaves. PMID:24781197

Skeffington, Alastair W.; Graf, Alexander; Duxbury, Zane; Gruissem, Wilhelm; Smith, Alison M.

2014-01-01

212

Remote inhibition of polymer degradation.  

SciTech Connect

Polymer degradation has been explored on the basis of synergistic infectious and inhibitive interaction between separate materials. A dual stage chemiluminescence detection system with individually controlled hot stages was applied to probe for interaction effects during polymer degradation in an oxidizing environment. Experimental confirmation was obtained that volatile antioxidants can be transferred over a relatively large distance. The thermal degradation of a polypropylene (PP) sample receiving traces of inhibitive antioxidants from a remote source is delayed. Similarly, volatiles from two stabilized elastomers were also capable of retarding a degradation process remotely. This observation demonstrates inhibitive cross-talk as a novel interactive phenomenon between different polymers and is consequential for understanding general polymer interactions, fundamental degradation processes and long-term aging effects of multiple materials in a single environment.

Clough, Roger Lee; Celina, Mathias Christopher

2005-08-01

213

Advanced diffusion studies with isotopically controlled materials  

SciTech Connect

The use of enriched stable isotopes combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self- and foreign-atom diffusion experiments. Over the past decade we have performed diffusion studies with isotopically enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of isotopically enriched materials ushered in a new era in the study of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of studying atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses.

Bracht, Hartmut A.; Silvestri, Hughes H.; Haller, Eugene E.

2004-11-14

214

7 CFR 3201.68 - Erosion control materials.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Erosion control materials. 3201.68 Section...PROCUREMENT Designated Items § 3201.68 Erosion control materials. (a) Definition...or other sites to prevent wind or water erosion of loose earth surfaces, which may...

2013-01-01

215

7 CFR 3201.68 - Erosion control materials.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Erosion control materials. 3201.68 Section...PROCUREMENT Designated Items § 3201.68 Erosion control materials. (a) Definition...or other sites to prevent wind or water erosion of loose earth surfaces, which may...

2012-01-01

216

7 CFR 3201.68 - Erosion control materials.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Erosion control materials. 3201.68 Section...PROCUREMENT Designated Items § 3201.68 Erosion control materials. (a) Definition...or other sites to prevent wind or water erosion of loose earth surfaces, which may...

2014-01-01

217

Materials control and accounting (MC and A): the evolutionary pressures  

SciTech Connect

Nuclear materials control and accounting systems are subject to pressures of both regulatory and institutional natures. This fact, coupled with the emergence of new technology, is causing evolutionary changes in materials control and accounting systems. These changes are the subject of this paper.

Shipley, J.P.

1983-01-01

218

Gammaherpesviral Gene Expression and Virion Composition Are Broadly Controlled by Accelerated mRNA Degradation  

PubMed Central

Lytic gammaherpesvirus infection restricts host gene expression by promoting widespread degradation of cytoplasmic mRNA through the activity of the viral endonuclease SOX. Though generally assumed to be selective for cellular transcripts, the extent to which SOX impacts viral mRNA stability has remained unknown. We addressed this issue using the model murine gammaherpesvirus MHV68 and, unexpectedly, found that all stages of viral gene expression are controlled through mRNA degradation. Using both comprehensive RNA expression profiling and half-life studies we reveal that the levels of the majority of viral mRNAs but not noncoding RNAs are tempered by MHV68 SOX (muSOX) activity. The targeting of viral mRNA by muSOX is functionally significant, as it impacts intracellular viral protein abundance and progeny virion composition. In the absence of muSOX-imposed gene expression control the viral particles display increased cell surface binding and entry as well as enhanced immediate early gene expression. These phenotypes culminate in a viral replication defect in multiple cell types as well as in vivo, highlighting the importance of maintaining the appropriate balance of viral RNA during gammaherpesviral infection. This is the first example of a virus that fails to broadly discriminate between cellular and viral transcripts during host shutoff and instead uses the targeting of viral messages to fine-tune overall gene expression. PMID:24453974

Abernathy, Emma; Clyde, Karen; Yeasmin, Rukhsana; Krug, Laurie T.; Burlingame, Al; Coscoy, Laurent; Glaunsinger, Britt

2014-01-01

219

Aquatic degradation of Cry1Ab protein and decomposition dynamics of transgenic corn leaves under controlled conditions.  

PubMed

The increasing cultivation of genetically modified corn plants (Zea mays) during the last decades is suggested as a potential risk to the environment. One of these genetically modified variety expressed the insecticidal Cry1Ab protein originating from Bacillus thuringiensis (Bt), resulting in resistance against Ostrinia nubilalis, the European corn borer. Transgenic litter material is extensively studied regarding the decomposition in soils. However, only a few field studies analyzed the fate of the Cry1Ab protein and the impact of green and senescent leaf litter from corn on the decomposition rate and related ecosystem functions in aquatic environments. Consequently, a microbial litter decomposition experiment was conducted under controlled semi-natural conditions in batch culture using two maize varieties: one variety with Cry1Ab and another one with the appertaining Iso-line as control treatment. The results showed no significant differences between the treatment with Cry1Ab and the Iso-line regarding loss of total mass in dry weight of 43% for Iso-line and 45% for Bt-corn litter, lignin content increased to 137.5% (Iso-line) and 115.7% (Bt-corn), and phenol loss decreased by 53.6% (Iso-line), 62.2% (Bt-corn) during three weeks of the experiment. At the end of the experiment Cry1Ab protein was still detected with 6% of the initial concentration. A slightly but significant lower cellulose content was found for the Cry1Ab treatment compared to the Iso-line litter at the end of the experiment. The significant higher total protein (25%) and nitrogen (25%) content in Bt corn, most likely due to the additionally expression of the transgenic protein, may increase the microbial cellulose degradation and decrease microbial lignin degradation. In conclusion a relevant year by year input of protein and therefore nitrogen rich Bt corn litter into aquatic environments may affect the balanced nutrient turnover in aquatic ecosystems. PMID:25553417

Böttger, Rita; Schaller, Jörg; Lintow, Sven; Gert Dudel, E

2015-03-01

220

FastTrack 8800 Materials Test Control System  

E-print Network

to stop the test and isolate the testing system from hydraulic or electrical power. Carefully read allInstron FastTrack 8800 Materials Test Control System Reference Manual - Configuration M21-10011-EN Materials testing systems are potentially hazardous. Materials testing involves inherent hazards from high

Adams, Mark

221

Recent Insights into the Control of Human Papillomavirus (HPV) Genome Stability, Loss, and Degradation  

PubMed Central

Most human papillomavirus (HPV) antiviral strategies have focused upon inhibiting viral DNA replication, but it is increasingly apparent that viral DNA levels can be chemically controlled by approaches that promote its instability. HPVs and other DNA viruses have a tenuous relationship with their hosts. They must replicate and hide from the DNA damage response (DDR) and innate immune systems, which serve to protect cells from foreign or “non-self” DNA, and yet they draft these same systems to support their life cycles. DNA binding antiviral agents promoting massive viral DNA instability and elimination are reviewed. Mechanistic studies of these agents have identified genetic antiviral enhancers and repressors, antiviral sensitizers, and host cell elements that protect and stabilize HPV genomes. Viral DNA degradation appears to be an important means of controlling HPV DNA levels in some cases, but the underlying mechanisms remain poorly understood. These findings may prove useful not only for understanding viral DNA persistence but also in devising future antiviral strategies.

Fisher, Chris

2015-01-01

222

Protein capsules with cross-linked, semipermeable, and enzyme-degradable surface barriers for controlled release.  

PubMed

This paper describes a method for fabricating protein-based capsules with semipermeable and enzyme-degradable surface barriers. It involves the use of a simple fluidic device to generate water-in-oil emulsion droplets, followed by cross-linking of proteins at the water-oil interface to generate a semipermeable surface barrier. The capsules can be readily fabricated with uniform and controllable sizes and, more importantly, show selective permeability toward molecules with different molecular weights: small molecules like fluorescein sodium salt can freely diffuse through the surface barrier while macromolecules such as proteins can not. The proteins, however, can be released by digesting the surface barrier with an enzyme such as pepsin. Taken together, the capsules hold great potential for applications in controlled release, in particular, for the delivery of protein drugs. PMID:24957975

Zhou, Jianhua; Hyun, Dong Choon; Liu, Hang; Wu, Hongkai; Xia, Younan

2014-08-01

223

E-Area Vault Concrete Material Property And Vault Durability/Degradation Projection Recommendations  

SciTech Connect

Subsequent to the 2008 E-Area Low-Level Waste Facility (ELLWF) Performance Assessment (PA) (WSRC 2008), two additional E-Area vault concrete property testing programs have been conducted (Dixon and Phifer 2010 and SIMCO 2011a) and two additional E-Area vault concrete durability modeling projections have been made (Langton 2009 and SIMCO 2012). All the information/data from these reports has been evaluated and consolidated herein by the Savannah River National Laboratory (SRNL) at the request of Solid Waste Management (SWM) to produce E-Area vault concrete hydraulic and physical property data and vault durability/degradation projection recommendations that are adequately justified for use within associated Special Analyses (SAs) and future PA updates. The Low Activity Waste (LAW) and Intermediate Level (IL) Vaults structural degradation predictions produced by Carey 2006 and Peregoy 2006, respectively, which were used as the basis for the 2008 ELLWF PA, remain valid based upon the results of the E-Area vault concrete durability simulations reported by Langton 2009 and those reported by SIMCO 2012. Therefore revised structural degradation predictions are not required so long as the mean thickness of the closure cap overlying the vaults is no greater than that assumed within Carey 2006 and Peregoy 2006. For the LAW Vault structural degradation prediction (Carey 2006), the mean thickness of the overlying closure cap was taken as nine feet. For the IL Vault structural degradation prediction (Peregoy 2006), the mean thickness of the overlying closure cap was taken as eight feet. The mean closure cap thicknesses as described here for both E-Area Vaults will be included as a key input and assumption (I&A) in the next revision to the closure plan for the ELLWF (Phifer et al. 2009). In addition, it has been identified as new input to the PA model to be assessed in the ongoing update to the new PA Information UDQE (Flach 2013). Once the UDQE is approved, the SWM Key I&A database will be updated with this new information.

Phifer, M. A.

2014-03-11

224

Determination of load sequence effects on the degradation and failure of composite materials. [Graphite-epoxy composites  

NASA Technical Reports Server (NTRS)

A theoretical model was established to predict the fatigue behavior of composite materials, with emphasis placed on predictions of the degradation of residual strength and residual stiffness during fatigue cycling. The model parameters were evaluated from three test series including static strength fatigue life and residual strength tests. The tests were applied to two graphite/epoxy laminates. Load sequence effects were emphasized for both laminates and the predicted results agreed quite well with subsequent verification tests. Dynamic as well as static stiffness reduction data were collected by use of a PDP11-03 computer, which performed quite satisfactorily and permitted the recording of a substantial amount of dynamic stiffness reduction data.

Yang, J. N.; Jones, D. L.

1981-01-01

225

Saltstone Disposal Facility Closure Cap Configuration and Degradation Base Case: Institutional Control to Pine Forest Scenario  

SciTech Connect

The Performance Assessment (PA) for the Saltstone Disposal Facility (SDF) is currently under revision. As part of the PA revision and as documented herein, the closure cap configuration has been reevaluated and closure cap degradation mechanisms and their impact upon infiltration through the closure cap have been evaluated for the institutional control to pine forest, land use scenario. This land use scenario is considered the base case land use scenario. This scenario assumes a 100-year institutional control period following final SDF closure during which the closure cap is maintained. At the end of institutional control, it is assumed that a pine forest succeeds the cap's original bamboo cover. Infiltration through the upper hydraulic barrier layer of the closure cap as determined by this evaluation will be utilized as the infiltration input to subsequent PORFLOW vadose zone contaminant transport modeling, which will also be performed as part of the PA revision. The impacts of pine forest succession, erosion, and colloidal clay migration as degradation mechanisms on the hydraulic properties of the closure cap layers over time have been estimated and the resulting infiltration through the closure cap has been evaluated. The primary changes caused by the degradation mechanisms that result in increased infiltration are the formation of holes in the upper GCL by pine forest succession and the reduction in the saturated hydraulic conductivity of the drainage layers due to colloidal clay migration into the layers. Erosion can also result in significant increases in infiltration if it causes the removal of soil layers, which provide water storage for the promotion of evapotranspiration. For this scenario, infiltration through the upper GCL was estimated at approximately 0.29 inches/year under initial intact conditions, it increased to approximately 11.6 inches/year at year 1000 in nearly a linear fashion, and it approached an asymptote of around 14.1 inches/year at year 1800 and thereafter. At year 1800, it was estimated that holes covered approximately 0.3 percent of the GCL due to root penetration, and that this resulted in an infiltration near that of typical background infiltration (i.e. as though the GCL were not there at all). This demonstrated that a very small area of holes essentially controlled the hydraulic performance of the GCL.

Phifer, M.A.

2004-03-19

226

Study of Micro and Nano Scale Features in the Fabrication, Performance, and Degradation of Advanced Engineering Materials  

NASA Astrophysics Data System (ADS)

Increasingly, modern engineering materials are designed on a micron or nano scale to fulfill a given set of requirements or to enhance the material's performance. In this dissertation several such materials will be studied including catalyst particles for carbon nanotube (CNT) growth by use of atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS), multi walled carbon nanotubes (MWNTs) by reactor scale modeling, hermetic carbon coatings by focused ion beam/ scanning electron microscopy (FIB/SEM) and Fourier transform infrared spectroscopy (FTIR) the latter of which was performed by Andrei Stolov at OFS Specialty Photonics Division (Avon, CT), and Ni/Yttria stabilized zirconia (YSZ) solid oxide fuel cell (SOFC) anodes using X-ray nanotomography (XNT) and X-ray fluorescence (XRF) the second of which was performed by Barry Lai at APS (Argonne National Lab, IL). For each material, a subset of the material properties will be looked at to determine how the selected property affects either the fabrication, performance, or degradation of the material. Following the analysis of these materials, it was found that although the materials are different, the study of micron and nano scale features has many related traits. X-rays and electrons are frequently used to examine nanoscale structures, numerical study can be exploited to expedite measurements and extract additional information from experiments, and the study of these requires knowledge across many scientific fields. As a product of this research, detailed information about all of the materials studied has been contributed to the scientific literature including size dependance information about the oxidation states of nanometer size iron particles, optimal CVD reactor growth conditions for different CNT catalyst particle sizes and number of walls, a technique for rapid measurement of hermetic carbon film thickness, and detailed microstructural detail and sulfur poisoning mapping for Ni/YSZ SOFC anodes.

Lombardo, Jeffrey John

227

Controlled low strength materials (CLSM), reported by ACI Committee 229  

SciTech Connect

Controlled low-strength material (CLSM) is a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. Many terms are currently used to describe this material including flowable fill, unshrinkable fill, controlled density fill, flowable mortar, flowable fly ash, fly ash slurry, plastic soil-cement, soil-cement slurry, K-Krete and other various names. This report contains information on applications, material properties, mix proportioning, construction and quality-control procedures. This report`s intent is to provide basic information on CLSM technology, with emphasis on CLSM material characteristics and advantages over conventional compacted fill. Applications include backfills, structural fills, insulating and isolation fills, pavement bases, conduit bedding, erosion control, void filling, and radioactive waste management.

Rajendran, N.

1997-07-01

228

Preliminary investigations into UHCRE thermal control materials  

NASA Technical Reports Server (NTRS)

An overview is given of the initial work which has been done in the European Space Research and Technology Center (ESTEC) Materials and Processes Division to evaluate the effect of space environment on the thermal blankets of the Ultra-Heavy Cosmic Ray Nuclei Experiment (UHCRE). Also, an account is given of the simulation of the impacts of micrometeoroids and space debris in a spare flight thermal blanket by means of plasma gun and light gas gun acceleration facilities.

Levadou, Francois; Froggatt, Mike; Rott, Martin; Schneider, Eberhard

1991-01-01

229

RNF41 (Nrdp1) controls type 1 cytokine receptor degradation and ectodomain shedding  

PubMed Central

Cytokines, such as interferons, erythropoietin, leptin and most interleukins, signal through type 1 cytokine receptors and activate the canonical JAK–STAT pathway. Aberrant cytokine signalling underlies numerous pathologies and adequate, temporary receptor activation is therefore under tight control. Negative-feedback mechanisms are very well studied, but cellular sensitivity also depends on the number of receptors exposed at the cell surface. This is determined by the equilibrium between receptor synthesis and transport to the plasma membrane, internalisation and recycling, degradation and ectodomain shedding, but the molecular basis of how cells establish steady state receptor levels is poorly understood. Here, we report that ring finger protein 41 (RNF41, also known as E3 ubiquitin-protein ligase Nrdp1) interacts with JAK2-associated cytokine receptor complexes and modulates their cell surface exposure and signalling. Moreover, ectopic expression of RNF41 affected turnover of leptin, leukaemia inhibitory factor and interleukin-6 receptor in a dual way: it blocked intracellular cathepsin-L-dependent receptor cleavage and concomitantly enhanced receptor shedding by metalloproteases of the ADAM family. Receptor degradation and shedding are thus interconnected phenomena with a single protein, RNF41, determining the balance. PMID:21378310

Wauman, Joris; De Ceuninck, Leentje; Vanderroost, Nele; Lievens, Sam; Tavernier, Jan

2011-01-01

230

Contrasting controls on arsenic and lead budgets for a degraded peatland catchment in Northern England.  

PubMed

Atmospheric deposition of trace metals and metalloids from anthropogenic sources has led to the contamination of many European peatlands. To assess the fate and behaviour of previously deposited arsenic and lead, we constructed catchment-scale mass budgets for a degraded peatland in Northern England. Our results show a large net export of both lead and arsenic via runoff (282 ± 21.3 gPb ha(-1) y(-1) and 60.4 ± 10.5 gAs ha(-1) y(-1)), but contrasting controls on this release. Suspended particulates account for the majority of lead export, whereas the aqueous phase dominates arsenic export. Lead release is driven by geomorphological processes and is a primary effect of erosion. Arsenic release is driven by the formation of a redox-dynamic zone in the peat associated with water table drawdown, a secondary effect of gully erosion. Degradation of peatland environments by natural and anthropogenic processes has the potential to release the accumulated pool of legacy contaminants to surface waters. PMID:21683489

Rothwell, James J; Taylor, Kevin G; Evans, Martin G; Allott, Timothy E H

2011-10-01

231

Control of xanthan-degrading organisms in the Loudon pilot: Approach, methodology, and results  

SciTech Connect

An investigation of loss of mobility control in Exxon's Loudon micellar/polymer pilot test has confirmed that loss was caused by microbial degradation of the xanthan biopolymer used to viscosify the microemulsion and polymer drive banks. This paper describes techniques which were used to sample and culture bacteria from the Loudon pilot and demonstrate that these mixed cultures are able to degrade xanthan rapidly under reservoir conditions. Laboratory studies show that, under anaerobic conditions, bacteria cultured from the Loudon pilot can cause over 90% loss of xanthan viscosity in micellar/polymer fluids within seven days. To remedy this problem, an extensive laboratory screening program was conducted to identify biocides that are effective against the offending organisms. Complete kill of the organisms under repeated laboratory challenge tests was the chief screening criterion. Biocide compatibility (with biopolymer, formation rock, field brines, and microemulsion), cost effectiveness, and chemical stability were also judged key parameters for effectiveness in field applications. Of the biocides tested against the Loudon organisms, formaldehyde was found to be the most consistently effective, providing complete kill and persistence at levels of 500 to 2000 ppm. Formaldehyde was shown to reduce bacteria below detectable levels in the formation and permit propagation of xanthan in a follow-up test conducted within the highly contaminated pilot zone. Therefore, formaldehyde should be an effective biocide for future floods at Loudon.

Bragg, J.R.; Beck, D.; Gale, W.W.; Gall, L.S.; Goldman, I.M.; Laskin, A.I.; Maruca, S.D.; Naslund, L.A.; Wernau, W.C.

1983-10-01

232

Cyclin-dependent kinase 5 governs learning and synaptic plasticity via control of NMDAR degradation  

PubMed Central

Learning is accompanied by modulation of postsynaptic signal transduction pathways in neurons. Although the neuronal protein kinase cyclin-dependent kinase 5 (Cdk5) has been implicated in cognitive disorders, its role in learning has been obscured by the perinatal lethality of constitutive knockout mice. Here we report that conditional knockout of Cdk5 in the adult mouse brain improved performance in spatial learning tasks and enhanced hippocampal long-term potentiation and NMDA receptor (NMDAR)-mediated excitatory postsynaptic currents. Enhanced synaptic plasticity in Cdk5 knockout mice was attributed to reduced NR2B degradation, which caused elevations in total, surface and synaptic NR2B subunit levels and current through NR2B-containing NMDARs. Cdk5 facilitated the degradation of NR2B by directly interacting with both it and its protease, calpain. These findings reveal a previously unknown mechanism by which Cdk5 facilitates calpain-mediated proteolysis of NR2B and may control synaptic plasticity and learning. PMID:17529984

Nguyen, Chan; Kansy, Janice W; Hayashi, Kanehiro; Chambon, Pierre; Greengard, Paul; Powell, Craig M; Cooper, Donald C; Bibb, James A

2014-01-01

233

Cyclin-dependent kinase 5 governs learning and synaptic plasticity via control of NMDAR degradation.  

PubMed

Learning is accompanied by modulation of postsynaptic signal transduction pathways in neurons. Although the neuronal protein kinase cyclin-dependent kinase 5 (Cdk5) has been implicated in cognitive disorders, its role in learning has been obscured by the perinatal lethality of constitutive knockout mice. Here we report that conditional knockout of Cdk5 in the adult mouse brain improved performance in spatial learning tasks and enhanced hippocampal long-term potentiation and NMDA receptor (NMDAR)-mediated excitatory postsynaptic currents. Enhanced synaptic plasticity in Cdk5 knockout mice was attributed to reduced NR2B degradation, which caused elevations in total, surface and synaptic NR2B subunit levels and current through NR2B-containing NMDARs. Cdk5 facilitated the degradation of NR2B by directly interacting with both it and its protease, calpain. These findings reveal a previously unknown mechanism by which Cdk5 facilitates calpain-mediated proteolysis of NR2B and may control synaptic plasticity and learning. PMID:17529984

Hawasli, Ammar H; Benavides, David R; Nguyen, Chan; Kansy, Janice W; Hayashi, Kanehiro; Chambon, Pierre; Greengard, Paul; Powell, Craig M; Cooper, Donald C; Bibb, James A

2007-07-01

234

Modeling and control of microelectronics materials processing  

Microsoft Academic Search

Major advances in modeling and control will be required to meet future technical challenges in microelectronics manufacturing. This paper reviews the recent applications of fundamental mathematical modeling to unit operations such as crystal growth, lithography, chemical vapor deposition and plasma etching, where there have been some notable successes. Important characteristics of these processes are identified, and the evolution of the

T. A. Badgwell; T. Breedijk; S. G. Bushman; S. W. Butler; S. Chatterjee; T. F. Edgar; A. J. Toprac; I. Trachtenberg

1995-01-01

235

INTERACTION OF TIME AND LOAD HISTORY-DEPENDENT DEGRADATION OF MULTILAYERED MATERIALS  

E-print Network

and material properties) · Material behavior of the mixed zone and pure alumina layer Purpose: · To show that tensile stresses can develop in the TGO (aged specimens only) Component Thickness Function Top Coat 100 Alumina) Bond Coat 75-150 m Al Reservoir that provides oxidation protection (NiCoCrAlY) Superalloy

Karlsson, Anette M.

236

Understanding local degradation of cycled Ni-rich cathode materials at high operating temperature for Li-ion batteries  

SciTech Connect

We utilize transmission electron microscopy in conjunction with electron energy loss spectroscopy to investigate local degradation that occurs in Li{sub x}Ni{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} cathode materials (NCA) after 30 cycles with cutoff voltages of 4.3?V and 4.8?V at 55?°C. NCA has a homogeneous crystallographic structure before electrochemical reactions; however, we observed that 30 cycles of charge/discharge reactions induced inhomogeneity in the crystallographic and electronic structures and also introduced porosity particularly at surface area. These changes were more noticeable in samples cycled with higher cutoff voltage of 4.8?V. Effect of operating temperature was further examined by comparing electronic structures of oxygen of the NCA particles cycled at both room temperature and 55?°C. The working temperature has a greater impact on the NCA cathode materials at a cutoff voltage of 4.3?V that is the practical the upper limit voltage in most applications, while a cutoff voltage of 4.8?V is high enough to cause surface degradation even at room temperature.

Hwang, Sooyeon; Kim, Dong Hyun; Chung, Kyung Yoon; Chang, Wonyoung, E-mail: cwy@kist.re.kr [Center for Energy Convergence, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)

2014-09-08

237

A New Class of Risk-Importance Measures to Support Reactor Aging Management and the Prioritization of Materials Degradation Research  

SciTech Connect

As the US fleet of light water reactors ages, the risks of operation might be expected to increase. Although probabilistic risk assessment has proven a critical resource in risk-informed regulatory decision-making, limitations in current methods and models have constrained their prospective value in reactor aging management. These limitations stem principally from the use of static component failure rate models (which do not allow the impact of component aging on failure rates to be represented) and a very limited treatment of passive components (which would be expected to have an increasingly significant risk contribution in an aging system). Yet, a PRA captures a substantial knowledge base that could be of significant value in addressing plant aging. In this paper we will describe a methodology and a new class of risk importance measures that allow the use of an existing PRA model to support the management of plant aging, the prioritization of improvements to non-destructive examination and monitoring techniques, and the establishment of research emphases in materials science. This methodology makes use of data resources generated under the USNRC Proactive Management of Materials Degradation program which addresses the anticipated effects of numerous aging degradation mechanisms on a wide variety of component types.

Unwin, Stephen D.; Lowry, Peter P.; Toyooka, Michael Y.

2010-06-07

238

Survey of the degradation modes of candidate materials for high-level radioactive waste disposal containers. Final report  

SciTech Connect

One of the most significant factors impacting the performance of waste package container materials under repository relevant conditions is the thermal environment. This environment will be affected by the areal power density of the repository, which is dictated by facility design, and the dominant heat transfer mechanism at the site. The near-field environment will evolve as radioactive decay decreases the thermal output of each waste package. Recent calculations (Buscheck and Nitao, 1994) have addressed the importance of thermal loading conditions on waste package performance at the Yucca Mountain site. If a relatively low repository thermal loading design is employed, the temperature and relative humidity near the waste package may significantly affect the degradation of corrosion allowance barriers due to moist air oxidation and radiolytically enhanced corrosion. The purpose this report is to present a literature review of the potential degradation modes for moderately corrosion resistant nickel copper and nickel based candidate materials that may be applicable as alternate barriers for the ACD systems in the Yucca Mountain environment. This report presents a review of the corrosion of nickel-copper alloys, summaries of experimental evaluations of oxidation and atmospheric corrosion in nickel-copper alloys, views of experimental studies of aqueous corrosion in nickel copper alloys, a brief review of galvanic corrosion effects and a summary of stress corrosion cracking in these alloys.

Vinson, D.W.; Bullen, D.B. [Iowa State Univ. of Science and Technology, Ames, IA (United States)

1995-09-22

239

Fabrication of Biocompatible, Vibrational Magnetoelastic Materials for Controlling Cellular Adhesion  

PubMed Central

This paper describes the functionalization of magnetoelastic (ME) materials with Parylene-C coating to improve the surface reactivity to cellular response. Previous study has demonstrated that vibrating ME materials were capable of modulating cellular adhesion when activated by an externally applied AC magnetic field. However, since ME materials are not inherently biocompatible, surface modifications are needed for their implementation in biological settings. Here, the long-term stability of the ME material in an aqueous and biological environment is achieved by chemical-vapor deposition of a conformal Parylene-C layer, and further functionalized by methods of oxygen plasma etching and protein adsorption. In vitro cytotoxicity measurement and characterization of the vibrational behavior of the ME materials showed that Parylene-C coatings of 10 µm or greater could prevent hydrolytic degradation without sacrificing the vibrational behavior of the ME material. This work allows for long-term durability and functionality of ME materials in an aqueous and biological environment and makes the potential use of this technology in monitoring and modulating cellular behavior at the surface of implantable devices feasible. PMID:25585632

Holmes, Hal R.; Tan, Ee Lim; Ong, Keat Ghee; Rajachar, Rupak M.

2012-01-01

240

The Effect of Degraded Digital Instrumentation and Control systems on Human-system Interfaces and Operator Performance  

SciTech Connect

Integrated digital instrumentation and control (I&C) systems in new and advanced nuclear power plants (NPPs) will support operators in monitoring and controlling the plants. Even though digital systems typically are expected to be reliable, their potential for degradation or failure significantly could affect the operators performance and, consequently, jeopardize plant safety. This U.S. Nuclear Regulatory Commission (NRC) research investigated the effects of degraded I&C systems on human performance and on plant operations. The objective was to develop technical basis and guidance for human factors engineering (HFE) reviews addressing the operator's ability to detect and manage degraded digital I&C conditions. We reviewed pertinent standards and guidelines, empirical studies, and plant operating experience. In addition, we evaluated the potential effects of selected failure modes of the digital feedwater control system of a currently operating pressurized water reactor (PWR) on human-system interfaces (HSIs) and the operators performance. Our findings indicated that I&C degradations are prevalent in plants employing digital systems, and the overall effects on the plant's behavior can be significant, such as causing a reactor trip or equipment to operate unexpectedly. I&C degradations may affect the HSIs used by operators to monitor and control the plant. For example, deterioration of the sensors can complicate the operators interpretation of displays, and sometimes may mislead them by making it appear that a process disturbance has occurred. We used the findings as the technical basis upon which to develop HFE review guidance.

OHara, J.M.; Gunther, B.; Martinez-Guridi, G. (BNL); Xing, J.; Barnes, V. (NRC)

2010-11-07

241

Methylation-Controlled J Protein Promotes c-Jun Degradation To Prevent ABCB1 Transporter Expression? †  

PubMed Central

Methylation-controlled J protein (MCJ) is a newly identified member of the DnaJ family of cochaperones. Hypermethylation-mediated transcriptional silencing of the MCJ gene has been associated with increased chemotherapeutic resistance in ovarian cancer. However, the biology and function of MCJ remain unknown. Here we show that MCJ is a type II transmembrane cochaperone localized in the Golgi network and present only in vertebrates. MCJ is expressed in drug-sensitive breast cancer cells but not in multidrug-resistant cells. The inhibition of MCJ expression increases resistance to specific drugs by inducing expression of the ABCB1 drug transporter that prevents intracellular drug accumulation. The induction of ABCB1 gene expression is mediated by increased levels of c-Jun due to an impaired degradation of this transcription factor in the absence of MCJ. Thus, MCJ is required in these cells to prevent c-Jun-mediated expression of ABCB1 and maintain drug response. PMID:17283040

Hatle, Ketki M.; Neveu, Wendy; Dienz, Oliver; Rymarchyk, Stacia; Barrantes, Ramiro; Hale, Sarah; Farley, Nicholas; Lounsbury, Karen M.; Bond, Jeffrey P.; Taatjes, Douglas; Rincón, Mercedes

2007-01-01

242

Ubiquitin Ligase Smurf1 Controls Osteoblast Activity and Bone Homeostasis by Targeting MEKK2 for Degradation  

PubMed Central

Summary Bone is constantly resorbed and formed throughout life by coordinated actions of osteoclasts and osteoblasts. Here we show that Smurf1, a HECT domain ubiquitin ligase, has a specific physiological role in suppressing the osteogenic activity of osteoblasts. Smurf1-deficient mice are born normal but exhibit an age-dependent increase of bone mass. The cause of this increase can be traced to enhanced activities of osteoblasts, which become sensitized to bone morphogenesis protein (BMP) in the absence of Smurf1. However, loss of Smurf1 does not affect the canonical Smad-mediated intracellular TGF? or BMP signaling; instead, it leads to accumulation of phosphorylated MEKK2 and activation of the downstream JNK signaling cascade. We demonstrate that Smurf1 physically interacts with MEKK2 and promotes the ubiquitination and turnover of MEKK2. These results indicate that Smurf1 negatively regulates osteoblast activity and response to BMP through controlling MEKK2 degradation. PMID:15820682

Yamashita, Motozo; Ying, Sai-Xia; Zhang, Gen-mu; Li, Cuiling; Cheng, Steven Y.; Deng, Chu-xia; Zhang, Ying E.

2012-01-01

243

Analysis of Phase Noise Degradation Considering Switch Transistor Capacitances for CMOS Voltage Controlled Oscillators  

NASA Astrophysics Data System (ADS)

In this paper we present a study on the design optimization of voltage-controlled oscillators. The phase noise of LC-type oscillators is basically limited by the quality factor of inductors. It has been experimentally shown that higher-Q inductors can be achieved at higher frequencies while the oscillation frequency is limited by parasitic capacitances. In this paper, the minimum transistor size and the degradation of the quality factor caused by a switched-capacitor array are analytically estimated, and the maximum oscillation frequency of VCOs is also derived from an equivalent circuit by considering parasitic capacitances. According to the analytical evaluation, the phase noise of a VCO using a 65nm CMOS is 2dB better than that of a 180nm CMOS.

Murakami, Rui; Hara, Shoichi; Okada, Kenichi; Matsuzawa, Akira

244

Controls on the width of aggrading and degrading braided rivers: A micro-scale flume experiment  

NASA Astrophysics Data System (ADS)

Feedbacks between river width, sediment transport and morphological change are understood and represented poorly by existing theory, particularly in the case of multithread channel systems. Micro-scale experimental rivers (with flow depths in the order of few millimetres) have become increasingly popular in recent years and provide a means of quantifying these feedbacks. We present preliminary results from the application of micro-scale modelling to investigate changes in the hydraulic geometry and sediment transport capacity of braided channels subject to a series of aggradation and degradation events. Our experimental model is generic and is not scaled to a real world prototype. The laboratory flume tank used is 5 m long and 2.7 m wide, hence we consider situations where channel width is unrestricted by our experimental setup. River morphology was measured using high resolution laser profiling to quantify channel changes (fill, incision and lateral erosion) and section geometry. During all the runs, the evolution of the channel was recorded continuously using a Canon HG10 digital video camera and still imagery was collected at 5 minute intervals using Canon EOS10d digital cameras. All cameras were mounted overhead. The resulting data time series are used to elucidate controls on channel width evolution during aggradation and degradation. Topographic data are analysed to quantify changes in section shape and lateral flow variability that are known to represent a first order control on total sediment transport rate (Ferguson, 2003, Geomorphology, vol 56, 1-14). The purpose of this analysis is to develop simple statistical relationships that can act as width closures in models of braided river long profile evolution under non-equilibrium conditions.

Moges, M. M.; Nicholas, A. P.; Quine, T. A.

2010-05-01

245

An overview of environmental degradation of materials in nuclear power plant piping systems  

SciTech Connect

Piping in light water reactor (LWR) power systems is affected by several types of environmental degradation: intergranular stress corrosion cracking (IGSCC) of austenitic stainless steel piping in boiling water reactors (BWRs) has required research, inspection, and mitigation programs that will ultimately cost several billion dollars; erosion-corrosion of carbon steel piping has been observed frequently in the secondary systems of both BWRs and pressurized water reactors (PWRs); the effect of the BWR environment can greatly diminish the design margin inherent in the ASME Section III fatigue design curves for carbon steel piping; and cast stainless steels are subject to embrittlement after extended thermal aging at reactor operating temperatures. These problems are being addressed by wide-ranging research programs in this country and abroad. The purpose of this review is to highlight some of the accomplishments of these programs and to note some of the remaining unanswered questions.

Shack, W.J.

1987-08-01

246

Process of making porous ceramic materials with controlled porosity  

DOEpatents

A method of making metal oxide ceramic material is disclosed by which the porosity of the resulting material can be selectively controlled by manipulating the sol used to make the material. The method can be used to make a variety of metal oxide ceramic bodies, including membranes, but also pellets, plugs or other bodies. It has also been found that viscous sol materials can readily be shaped by extrusion into shapes typical of catalytic or adsorbent bodies used in industry, to facilitate the application of such materials for catalytic and adsorbent applications.

Anderson, Marc A. (Madison, WI); Ku, Qunyin (Madison, WI)

1993-01-01

247

MICROBIAL DEGRADATION OF SELECTED HAZARDOUS MATERIALS: PENTACHLOROPHENOL, HEXACHLOROCYCLOPENTADIENE, AND METHYL PARATHION  

EPA Science Inventory

This program evaluated the use of selected pure culture microrganisms for potential in biodegrading the hazardous materials pentachlorophenol (PCP), hexachlorocyclopentadiene (HCCP), and methyl parathion (MP). Each chemical was separately challenged by each of 24 organisms in aqu...

248

BIFUNCTIONAL ALUMINUN: A PERMEABLE BARRIER MATERIAL FOR THE DEGRADATION OF MTBE  

EPA Science Inventory

Bifunctional aluminum is an innovative remedial material for the treatment of gasoline oxygenates in permeable reactive barriers (PRBs). PRBs represent a promising environmental technology for remediation of groundwater contamination. Although zero-valent metals (ZVM) have been...

249

Chromium vapor species over solid oxide fuel cell interconnect materials and their potential for degradation processes  

Microsoft Academic Search

Alloys protected from corrosion by a chromia scale and LaCrOâ-based perovskites are used as materials for the interconnect of solid oxide fuel cells (SOFCs). The chromium vaporization of these materials was studied by thermochemical modeling. Partial pressures of the vaporizing species were determined for different Oâ and HâO concentrations in the oxidizing gas. CrOâ(OH)â(g) and CrOâ(g) are the most abundant

K. Hilpert; D. Das; M. Miller; D. H. Peck; R. Weiss

1996-01-01

250

21 CFR 862.3280 - Clinical toxicology control material.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Clinical toxicology control material. 862.3280 Section 862...MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Toxicology Test Systems § 862.3280 Clinical...

2010-04-01

251

Fuzzy control of vibration on smart materials incorporating electrorheological fluids  

NASA Astrophysics Data System (ADS)

The smart composite beam featuring the electrorheological (ER) fluids which is designed in this paper is composed of three kinds of materials that are structural material, damping material and sealant material. The elastodynamic frequency response characteristics of smart beam are studied in details by using experimental method. The results demonstrate clearly the ability to significantly change the vibration characteristics of beam fabricated in smart composite by changing the electric field intensity imposed on the fluid domains. Meantime, a control algorithm based on fuzzy-like logic are employed in the active vibration control of cantilevered beam featuring electrorheological fluids. The study results are shown that the beam's structural vibration can be controlled more effectively using the proposed active control rule.

Leng, Jinsong; Liu, Yanju; Du, Shanyi; Li, Q. L.; Wang, Duo

1997-03-01

252

10 CFR 835.1101 - Control of material and equipment.  

Code of Federal Regulations, 2013 CFR

...paragraphs (b) and (c) of this section, material and equipment in contamination areas, high contamination areas, and airborne radioactivity areas shall not be released to a controlled area if: (1) Removable surface contamination levels on accessible...

2013-01-01

253

Possible Responsibility of Silicone Materials for Degradation of the CO2 Removal System in the International Space Station  

NASA Technical Reports Server (NTRS)

From data concerning the degradation of the CO2 removal system in the International Space Station (ISS) two important features were apparent: (1) The atmosphere within the International Space Station (ISS) contained many organic compounds including alcohols, halocarbons, aldehydes, esters, and ketones, inter alia. Various cyclosiloxanes Dn, hexamethylcyclotrisiloxane (D3) and its higher homologs (D4) and (D5) are also present presumably due to offgassing. (2) Screens within the zeolite-containing canisters, used for the removal of CO2, exhibited partial clogging due to zeolitic fragments (dust) along with "sticky" residues, that in toto significantly reduced the efficiency of the CO2 removal process. Samples of the ISS fresh zeolite, used zeolite, filter clogging zeolite particles and residual polymeric materials were examined using, inter alia, NMR, EM and HRSEM. These data were compared to equivalent samples obtained prior and subsequent to Dn polymerization experiments performed in our laboratories using the clean ISS zeolite samples as catalyst. Polysiloxane materials produced were essentially equivalent in the two cases and the EM images demonstrate a remarkable similarity between the ISS filter zeolite samples and the post-polymerization zeolite material from our experiments. In this regard even the changes in the Al/Si ratio from the virgin zeolite material to the filter samples and the post-polymerization laboratory samples samples is noteworthy. This research was supported by a contract from the Boeing Company

Baeza, Mario; Sharma, Hemant; Borrok, David; Ren, Mingua; Pannell, Keith

2011-01-01

254

PREDICTING BIOTRANSFORMATIONS IN THE SUBSURFACE: RELATIONSHIP BETWEEN THE ATP (ADENOSINE TRIPHOSPHATE) CONTENT OF SUBSURFACE MATERIAL AND THE CAPACITY OF SUBSURFACE ORGANISMS TO DEGRADE TOLUENE  

EPA Science Inventory

Deeper subsurface material was collected in a manner that prevented contamination by surface microorganisms. This material was analyzed for ATP content, and for its capacity to degrade toluene, a common organic contaminant of ground water originating from release of petroleum pro...

255

An automated model for materials management and control  

Microsoft Academic Search

Current, manual, materials management and control procedures are unsatisfactory: they are labour intensive, inaccurate and error prone. The result is waste and surplus of materials, delays, decrease in productivity and lack of up?to?date, real?time information regarding the status of purchase orders (PO), the levels of inventory, the actual vs. planned usage of materials, and others. The purpose of the present

R. Navon; O. Berkovich

2006-01-01

256

Temperature control of a solar furnace for material testing  

Microsoft Academic Search

A solar furnace is a thermodynamic device that concentrates sun radiation in order to achieve high-temperatures at a focus, where a sample of the material to be tested is located. This article address the problem of designing a control architecture for solar furnaces. It is motivated by the use of a solar furnace as an instrument in material science research

B. Andrade Costa; J. M. Lemos; L. G. Rosa

2011-01-01

257

Materials of Controlled Shape and Stiffness with Photocurable Microfluidic Endoskeleton  

E-print Network

demonstrated the use of 3D microvascular networks in a self-healing material, which is inspired by the functionality of natural skin derived from its vesicular blood network.[30] Their self-healing compositeMaterials of Controlled Shape and Stiffness with Photocurable Microfluidic Endoskeleton By Suk Tai

Velev, Orlin D.

258

Application of porous materials for laminar flow control  

NASA Technical Reports Server (NTRS)

Fairly smooth porous materials were elected for study Doweave; Fibermetal; Dynapore; and perforated titanium sheet. Factors examined include: surface smoothness; suction characteristics; porosity; surface impact resistance; and strain compatibility. A laminar flow control suction glove arrangement was identified with material combinations compatible with thermal expansion and structural strain.

Pearce, W. E.

1978-01-01

259

The Study of Logistics Management Theory in Material Cost Control  

Microsoft Academic Search

In this paper, the project cost control was discussed by logistics. And the constructing corporation costing management is running through the whole process of the project constructing. The project cost is composed of labor cost, material cost, mechanical cost and other cost. Among these costs, the material cost which is occupied the whole cost's 70% is affecting the integral engineering

Fei Wang; Lihuan Ma; Weijian Huang; Juwei Yan

2008-01-01

260

Incorporation of Proteinase Inhibitors into Silk-Based Delivery Devices for Enhanced Control of Degradation and Drug Release  

PubMed Central

Controlling the rate of silk degradation is critical to its potential use in biomedical applications, including drug delivery and tissue engineering. The effect of protease concentration on accelerating degradation, and the use of ethylenediamine tetraacetic acid (EDTA) on reducing rates of degradation and on drug release from silk-based drug carriers was studied. Increased rates of proteolysis resulted in increased dye release from silk carriers, while EDTA release from the silk carriers inhibited proteolysis. The sustained release of EDTA from silk carriers in combination with the release of the small molecule anticonvulsant adenosine was investigated in vitro. This combination of factors resulted in delayed release of adenosine by inhibiting proteolytic activity. These results introduce a promising strategy to control drug delivery through the regulation of silk degradation rate, achieved via manipulation of local proteolytic activity. This ability to modulate enzyme function could be applicable to a range of silk biomaterial formats as well as other biodegradable polymers where enzymatic functions control biomaterial degradation and drug release rates. PMID:20950854

Pritchard, Eleanor M.; Valentin, Thomas; Boison, Detlev; Kaplan, David L.

2010-01-01

261

Evaluation of Low-Earth-Orbit Environmental Effects on International Space Station Thermal Control Materials  

NASA Technical Reports Server (NTRS)

Many spacecraft thermal control coatings in low Earth orbit (LEO) can be affected by solar ultraviolet radiation and atomic oxygen. Ultraviolet radiation can darken some polymers and oxides commonly used in thermal control materials. Atomic oxygen can erode polymer materials, but it may reverse the ultraviolet-darkening effect on oxides. Maintaining the desired solar absorptance for thermal control coatings is important to assure the proper operating temperature of the spacecraft. Thermal control coatings to be used on the International Space Station (ISS) were evaluated for their performance after exposure in the NASA Lewis Research Center's Atomic Oxygen-Vacuum Ultraviolet Exposure (AO-VUV) facility. This facility simulated the LEO environments of solar vacuum ultraviolet (VUV) radiation (wavelength range, 115 to 200 nanometers (nm)) and VUV combined with atomic oxygen. Solar absorptance was measured in vacuo to eliminate the "bleaching" effects of ambient oxygen on VUV-induced degradation. The objective of these experiments was to determine solar absorptance increases of various thermal control materials due to exposure to simulated LEO conditions similar to those expected for ISS. Work was done in support of ISS efforts at the requests of Boeing Space and Defense Systems and Lockheed Martin Vought Systems.

Dever, Joyce A.

1998-01-01

262

Initiation of polymer degradation via transfer of infectious species.  

SciTech Connect

A novel dual stage chemiluminescence detection system incorporating individually controlled hot stages has been developed and applied to probe for material interaction effects during polymer degradation. Utilization of this system has resulted in experimental confirmation for the first time that in an oxidizing environment a degrading polymer A (in this case polypropylene, PP) is capable of infecting a different polymer B (in this case polybutadiene, HTPB) over a relatively large distance. In the presence of the infectious degrading polymer A, the thermal degradation of polymer B is observed over a significantly shorter time period. Consistent with infectious volatiles from material A initiating the degradation process in material B it was demonstrated that traces (micrograms) of a thermally sensitive peroxide in the vicinity of PP could induce degradation remotely. This observation documents cross-infectious phenomena between different polymers and has major consequences for polymer interactions, understanding fundamental degradation processes and long-term aging effects under combined material exposures.

Clough, Roger Lee; Jones, Gary D.; Celina, Mathias Christopher

2005-02-01

263

Initiation of polymer degradation via transfer of infectious species.  

SciTech Connect

A novel dual stage chemiluminescence detection system incorporating individually controlled hot stages has been developed and applied to probe for material interaction effects during polymer degradation. Utilization of this system has resulted in experimental confirmation for the first time that in an oxidizing environment a degrading polymer A (in this case polypropylene, PP) is capable of infecting a different polymer B (in this case polybutadiene, HTPB) over a relatively large distance. In the presence of the infectious degrading polymer A, the thermal degradation of polymer B is observed over a significantly shorter time period. Consistent with infectious volatiles from material A initiating the degradation process in material B it was demonstrated that traces (micrograms) of a thermally sensitive peroxide in the vicinity of PP could induce degradation remotely. This observation documents cross-infectious phenomena between different polymers and has major consequences for polymer interactions, understanding fundamental degradation processes and long-term aging effects under combined material exposures.

Clough, Roger Lee; Jones, Gary Dunn; Celina, Mathias Christopher

2005-06-01

264

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers  

SciTech Connect

Three copper-based alloys and three iron- to nickel-based austenitic alloys are being considered as possible materials for fabrication of containers for disposal of high-level radioactive waste. This waste will include spent fuel assemblies from reactors as well as high-level waste in borosilicate glass and will be sent to the prospective site at Yucca Mountain, Nevada, for disposal. The containers must maintain substantially complete containment for at least 300 yr and perhaps as long as 1000 yr. During the first 50 yr after emplacement, they must be retrievable from the disposal site. Shortly after the containers are emplaced in the repository, they will be exposed to high temperatures and high gamma radiation fields from the decay of the high-level waste. This volume surveys the available data on oxidation and corrosion of the iron- to nickel-based austenitic materials (Types 304L and 316L stainless steels and Alloy 825) and the copper-based alloy materials (CDA 102 (oxygen-free copper), CDA 613 (Cu-7Al), and CDA 715 (Cu-30Ni)), which are the present candidates for fabrication of the containers. Studies that provided a large amount of data are highlighted, and those areas in which little data exists are identified. Examples of successful applications of these materials are given. On the basis of resistance to oxidation and general corrosion, the austenitic materials are ranked as follows: Alloy 825 (best), Type 316L stainless steel, and then Type 304L stainless steel (worst). For the copper-based materials, the ranking is as follows: CDA 715 and CDA 613 (both best), and CDA 102 (worst). 110 refs., 30 figs., 13 tabs.

Gdowski, G.E.; Bullen, D.B. (Science and Engineering Associates, Inc., Pleasanton, CA (USA))

1988-08-01

265

Material-controlled dynamic vacuum insulation  

DOEpatents

A compact vacuum insulation panel comprising a chamber enclosed by two sheets of metal, glass-like spaces disposed in the chamber between the sidewalls, and a high-grade vacuum in the chamber includes apparatus and methods for enabling and disabling, or turning "on" and "off" the thermal insulating capability of the panel. One type of enabling and disabling apparatus and method includes a metal hydride for releasing hydrogen gas into the chamber in response to heat, and a hydrogen grate between the metal hydride and the chamber for selectively preventing and allowing return of the hydrogen gas to the metal hydride. Another type of enabling and disabling apparatus and method includes a variable emissivity coating on the sheets of metal in which the emissivity is controllably variable by heat or electricity. Still another type of enabling and disabling apparatus and method includes metal-to-metal contact devices that can be actuated to establish or break metal-to-metal heat paths or thermal short circuits between the metal sidewalls.

Benson, David K. (14154 W. First Dr., Golden, CO 80401); Potter, Thomas F. (515 S. Magnolia La., Denver, CO 80224)

1996-10-08

266

Material-controlled dynamic vacuum insulation  

DOEpatents

A compact vacuum insulation panel is described comprising a chamber enclosed by two sheets of metal, glass-like spaces disposed in the chamber between the sidewalls, and a high-grade vacuum in the chamber includes apparatus and methods for enabling and disabling, or turning ``on`` and ``off`` the thermal insulating capability of the panel. One type of enabling and disabling apparatus and method includes a metal hydride for releasing hydrogen gas into the chamber in response to heat, and a hydrogen grate between the metal hydride and the chamber for selectively preventing and allowing return of the hydrogen gas to the metal hydride. Another type of enabling and disabling apparatus and method includes a variable emissivity coating on the sheets of metal in which the emissivity is controllably variable by heat or electricity. Still another type of enabling and disabling apparatus and method includes metal-to-metal contact devices that can be actuated to establish or break metal-to-metal heat paths or thermal short circuits between the metal sidewalls. 25 figs.

Benson, D.K.; Potter, T.F.

1996-10-08

267

Accounting systems for special nuclear material control. Technical report  

SciTech Connect

Nuclear material accounting systems were examined and compared to financial double-entry accounting systems. Effective nuclear material accounting systems have been designed using the principles of double-entry financial accounting. The modified double-entry systems presently employed are acceptable if they provide adequate control over the recording and summarizing of transactions. Strong internal controls, based on principles of financial accounting, can help protect nuclear materials and produce accurate, reliable accounting data. An electronic data processing system can more accurately maintain large volumes of data and provide management with more current, reliable information.

Korstad, P.A.

1980-05-01

268

JOURNAL OF MATERIALS SCIENCE 36 (2001) 4345 4349 Cementitious bond degradation during cyclic  

E-print Network

Materials Research Laboratory, University at Buffalo, The State University of New York, Buffalo, NY 14260- sistivity of the bond interface has recently been used to investigate the effects of admixtures, water. The ratio of cement to fine aggregate to coarse aggre- gate was 1 : 1.5 : 2.5. The water-cement ratio was 0

Chung, Deborah D.L.

269

Biodegradability of biodegradable\\/degradable plastic materials under aerobic and anaerobic conditions  

Microsoft Academic Search

A study was conducted on two types of plastic materials, Mater-Bi Novamont (MB) and Environmental Product Inc. (EPI), to assess their biodegradability under aerobic and anaerobic conditions. For aerobic conditions, organic fractions of municipal solid wastes were composted. For the anaerobic process, anaerobic inoculum from a wastewater treatment plant was used. Cellulose filter papers (CFP) were used as a positive

R. Mohee; G. D. Unmar; A. Mudhoo; P. Khadoo

2008-01-01

270

Parameters Affecting the Loading Behavior and Degradation of Electrically Active Filter Materials  

Microsoft Academic Search

Electrically active fibrous filters, that is fibrous filters whose fibers carry a permanent electric charge, are a popular alternative to conventional fibrous filters in applications where low pressure drop and high collection efficiencies are critical. The advantage of these materials is the additional collection efficiency, due to electrostatic mechanisms, that can be achieved without pressure drop increase. Although the efficiency

D. C. Walsh; J. I. T. Stenhouse

1998-01-01

271

Degradation of space exposed surfaces by hypervelocity dust bombardment, and refractory materials for space  

Microsoft Academic Search

Dust particles with diameters below 100?m represent an important part of the space environment. Objects like satellites or spacecrafts, are constantly bombarded with particles of cosmic velocities of 10km\\/s and more. These hypervelocity impacts lead to evaporation of a large fraction of these particles and to the formation of craters on the material surfaces which exhibit diameters which are up

H. M. Ortner; F. J. Stadermann

2009-01-01

272

TRUE COLORS: LEDS AND THE RELATIONSHIP BETWEEN CCT, CRI, OPTICAL SAFETY, MATERIAL DEGRADATION, AND PHOTOBIOLOGICAL STIMULATION  

SciTech Connect

This document analyzes the optical, material, and photobiological hazards of LED light sources compared to conventional light sources. It documents that LEDs generally produce the same amount of blue light, which is the primary contributor to the risks, as other sources at the same CCT. Duv may have some effect on the amount of blue light, but CRI does not.

Royer, Michael P.

2014-08-30

273

Materials Process Design and Control Laboratory Cornell University  

E-print Network

remediation, nuclear contamination and enhanced oil recovery Availability of enough input data and comparative results Pose and solve questions that provide some insight Ground water remediation and contamination control Oil recovery #12;Materials Process Design and Control Laboratory Cornell University Proposed

Zabaras, Nicholas J.

274

The ER quality control and ER associated degradation machineries are vital for viral pathogenesis  

PubMed Central

The endoplasmic reticulum (ER) is central to protein production and membrane lipid synthesis. The unfolded protein response (UPR) supports cellular metabolism by ensuring protein quality control in the ER. Most positive strand RNA viruses cause extensive remodeling of membranes and require active membrane synthesis to promote infection. How viruses interact with the cellular machinery controlling membrane metabolism is largely unknown. Furthermore, there is mounting data pointing to the importance of the UPR and ER associated degradation (ERAD) machineries in viral pathogenesis in eukaryotes emerging topic. For many viruses, the UPR is an early event that is essential for persistent infection and benefits virus replication. In addition, many viruses are reported to commandeer ER resident chaperones to contribute to virus replication and intercellular movement. In particular, calreticulin, the ubiquitin machinery, and the 26S proteasome are most commonly identified components of the UPR and ERAD machinery that also regulate virus infection. In addition, researchers have noted a link between UPR and autophagy. It is well accepted that positive strand RNA viruses use autophagic membranes as scaffolds to support replication and assembly. However this topic has yet to be explored using plant viruses. The goal of research on this topic is to uncover how viruses interact with this ER-related machinery and to use this information for designing novel strategies to boost immune responses to virus infection. PMID:24653727

Verchot, Jeanmarie

2014-01-01

275

Interstitial ATP level and degradation in control and postmyocardial infarcted rats.  

PubMed

With the aim of estimating interstitial levels and the breakdown process of ATP, cardiac microdialysis was performed in the left ventricular wall of in situ control and postinfarcted as well as of isolated, Langendorff-perfused rat hearts. With the use of a bioluminescence technique for dialysate ATP measurement, the baseline interstitial fluid ATP concentration in in situ hearts was estimated to be 38 +/- 8 nM. Regional ischemia induced an early peak increase in interstitial fluid ATP to 373 +/- 73 nM that correlates with the maximal incidence of ventricular arrhythmias. During continuous infusion of individual adenine nucleotides (50 microM ATP, ADP, or AMP), the dialysate samples were analyzed for adenine nucleotides, nucleosides, and bases using HPLC with ultraviolet detection. The patterns of catabolites were consistent with the major pathway of metabolism, that is, sequential dephosphorylation catalyzed by a chain of separate ecto-nucleotidases. In in situ postinfarcted hearts as well as in perfused hearts, a reduced catabolism rate of extracellular adenine nucleotides was observed. In conclusion, in in situ rat hearts, ATP can be released in substantial amounts in the interstitium where it readily undergoes enzymatic degradation. Dephosphorylation occurs sequentially and faster in in situ control hearts than in in situ postinfarcted or in perfused hearts. PMID:9730960

Kuzmin, A I; Lakomkin, V L; Kapelko, V I; Vassort, G

1998-09-01

276

A Ribosome-Bound Quality Control Complex Triggers Degradation of Nascent Peptides and Signals Translation Stress  

PubMed Central

Summary The conserved transcriptional regulator Heat Shock Factor 1 (Hsf1) is a key sensor of proteotoxic and other stress in the eukaryotic cytosol, yet its regulation is poorly understood. We surveyed Hsf1 activity in a genome-wide loss-of-function library in Saccaromyces cerevisiae as well as ~78,000 double mutants and found Hsf1 activity to be modulated by highly diverse stresses. These included disruption of a ribosome-bound complex we named the Ribosome Quality Control Complex (RQC) comprising the Ltn1 E3 ubiquitin ligase, two highly conserved but poorly characterized proteins (Tae2 and Rqc1), and Cdc48 and its cofactors. Electron microscopy and biochemical analyses revealed that the RQC forms a stable complex with 60S ribosomal subunits containing stalled polypeptides and triggers their degradation. A negative feedback loop regulates the RQC and Hsf1 senses an RQC-mediated translation stress signal distinctly from other stresses. Our work reveals the range of stresses Hsf1 monitors and elucidates a conserved cotranslational protein quality control mechanism. PMID:23178123

Brandman, Onn; Stewart-Ornstein, Jacob; Wong, Daisy; Larson, Adam; Williams, Christopher C.; Li, Gene-Wei; Zhou, Sharleen; King, David; Shen, Peter S.; Weibezahn, Jimena; Dunn, Joshua G.; Rouskin, Silvi; Inada, Toshifumi; Frost, Adam; Weissman, Jonathan S.

2012-01-01

277

Electrical characterization and analysis of the degradation of electrode Schottky barriers in BaTiO3 dielectric materials due to hydrogen exposure  

NASA Astrophysics Data System (ADS)

Hydrogen gas creates a highly damaging environment that degrades electrical properties in oxide based dielectrics and piezoelectrics. In this study, the degradation resistivity due to hydrogen gas in a barium titanate X7R dielectric is designed and processed for base metal electrode capacitors. The present paper is devoted to I-V measurements and the loss of resistivity in the electrode Schottky barriers. The DC degradation and asymmetries noted in I-V forward and reverse biasing conditions were assumed to be hydrogen ion interstitials, locally creating donor substitutions. Thermionic and field emission conductivity mechanisms are applied to model the I-V data; the conductivity is controlled by the Schottky barrier heights and hydrogen ions localizing at the interfaces. Finally, a mechanism was proposed for resistivity degradation due to exposure to hydrogen gas. The proposed mechanism predicts the degradation should be reversible, and its validity was examined by recovery tests.

Heidary, Damoon Sohrabi Baba; Qu, Weiguo; Randall, Clive A.

2015-03-01

278

Hydrophobic and hydrophilic control in polyphosphazene materials  

NASA Astrophysics Data System (ADS)

This thesis is the culmination of several recent studies focused on the surface characterization of polyphosphazenes specifically the properties of water repellency or hydrophobicity. Chapter 1 is a background account of polyphosphazene chemistry and the hydrophobicity of polyphosphazenes. Chapter 2 provides an examination of the role of surface morphology on hydrophobicity. This study deals in depth with the electrospinning of poly[bis(2,2,2-trifluoroethoxy)phosphazene] in tetrahydrofuran. This process yields fiber mats or bead and fiber mats which exhibit roughness in continuous contact with the water droplet (fiber mats) or discontinuous contact (bead and fiber mats). These surface roughness types are compared to spun cast films using water contact angles to measure the air-water-polymer interface. The influence of aromatic moieties and fluorine content on the air-water-polymer interface is examined in Chapter 3. This study examines the influence of fluorine content and aryloxy groups on the hydrophobicity of a polyphosphazene surface via static water contact angle measurements on a goniometer. Polymer surfaces of spun cast and electrospun mats were probed with advancing, receeding, and static water contact angle and dip coated slides of the same materials were also examined with a Langmuir-Blogett trough. Chapter 4 is a description of the environmental plasma surface treatments of polyphosphazenes as a method of functionalizing solid polymer surfaces. The treatment procedure of functionalizing spun cast and electrospun poly[bis(2,2,2-trifluoroethoxy)phosphazene] surfaces with plasma gases of oxygen, nitrogen, methane, and tetrafluoromethane is detailed. The resulting functionalization of the surface is examined with XPS and water contact angle data. In Chapter 5 fluoroalkoxy polyphosphazenes were processed with liquid carbon dioxide into foams. The foams were then tested for flame retardance and hydrophobicity. Appendixes A-C contain studies on moisture sensitive phosphoranimine monomer storage, micelle formation in water from triblock copolymers, and single ion conductive membranes with increased hydrophobicity respectively. Although the appendixes examine polyphosphazene hydrophobic relationships they are not specific to surface hydrophobicity of solids and were not placed in the main text. Appendix A involves the optimization of storage conditions for a phosphoranimine monomer. Conditions examined include room temperature to -80 ºC and dilution with a variety of organic solvents. The micelle formation of A-B-A triblock copolymer of poly[bis(2,2,2-trifluoroethoxy)phosphazene]-poly(propylene-glycol)-poly[bis(2,2,2-trifluoroethoxy)phosphazene] was explored in appendix B. It was determined with light scattering and TEM that hairpin folding of our triblock copolymer allowed micelle formation with the two hydrophobic poly[bis(2,2,2-trifluoroethoxy)phosphazene] blocks facing the hydrophobic core of the micelle. Appendix C details the lithium ion conductivity of poly[norbornene-pendent-cyclotriphosphazene] with sulfonimide and methoxyethoxyethoxy groups attached. These results are then compared with unbound lithium counter ion systems.

Steely, Lee Brent

279

Novel Na?Mo?O??/?-MoO? hybrid material as highly efficient CWAO catalyst for dye degradation at ambient conditions.  

PubMed

We report a novel hybrid material Na2Mo4O13/?-MoO3 as highly efficient catalytic wet air oxidation (CWAO) catalyst, which showed the highest ever activity at room temperature and atmosphere pressure for the degradation of cationic red GTL. SEM and TEM analyses indicated that this hybrid catalyst has bamboo-shaped nanofiber morphology. In view of practical applications, the influence of some key parameters including operation temperature, catalyst calcination temperature, and the volume of dye wastewater have been optimized. The mechanism for the superior catalytic performance was investigated. XRD, XPS, and ESR suggested the Na2Mo4O13/?-MoO3 hybrid catalyst possesses more O(2-) ions in the oxygen deficient regions than neat ?-MoO3, promoting the formation of active ·OH radicals and resulting in a higher activity. Considering the facile preparation and its superior activity, this novel catalyst is promising for practical dye wastewater treatment. PMID:25348943

Zhang, Zhang; Yang, Ruoyan; Gao, Yanshan; Zhao, Yufei; Wang, Junyang; Huang, Liang; Guo, Jiang; Zhou, Tuantuan; Lu, Peng; Guo, Zhanhu; Wang, Qiang

2014-01-01

280

Role of chemical reactions of arylamine hole transport materials in operational degradation of organic light-emitting diodes  

SciTech Connect

We report that the representative arylamine hole transport materials undergo chemical transformations in operating organic light-emitting diode (OLED) devices. Although the underlying chemical mechanisms are too complex to be completely elucidated, structures of several identified degradation products point at dissociations of relatively weak carbon-nitrogen and carbon-carbon bonds in arylamine molecules as the initiating step. Considering the photochemical reactivities, the bond dissociation reactions of arylamines occur by the homolysis of the lowest singlet excited states formed by recombining charge carriers in the operating OLED device. The subsequent chemical reactions are likely to yield long-lived, stabilized free radicals capable of acting as deep traps--nonradiative recombination centers and fluorescence quenchers. Their presence in the hole transport layer results in irreversible hole trapping and manifests as a positive fixed charge. The extent and localization of chemical transformations in several exemplary devices suggest that the free radical reactions of hole transporting materials, arylamines, can be sufficient to account for the observed luminance efficiency loss and voltage rise in operating OLEDs. The relative bond strengths and excited state energies of OLED materials appear to have a determining effect on the operational stability of OLED devices.

Kondakov, Denis Y. [Eastman Kodak Company, Rochester, New York 14650-2103 (United States)

2008-10-15

281

High intensity 5 eV cw laser substained O-atom exposure facility for material degradation studies  

SciTech Connect

An atomic oxygen exposure facility has been developed for studies of material degradation. The goal of these studies is to provide design criteria and information for the manufacture of long life (20 to 30 years) construction material for use in low earth orbit. The studies that are being undertaken using the facility will provide (1) absolute reaction cross sections for use in engineering design problems, (2) formulations of reaction mechanisms for use in selection of suitable existing materials and design of new more resistant ones, and (3) calibration of flight hardware (mass spectrometers, etc.) in order to directly relate experiments performed in low earth orbit to ground based investigations. The facility consists of (1) a cw laser sustained discharge source of O-atoms having a variable energy up to 5 eV and an intensity of between 10/sup 15/-10/sup 17/ O-atoms s/sup -1/ cm/sup -2/, (2) an atomic beam formation and diagnostics system consisting of various stages of differential pumping, mass spectrometer detector and time-of-flight analysis, (3) a spinning rotor viscometer for absolute O-atom flux measurements, and (4) provision for using the system for calibration of flight instruments. 15 refs., 10 figs.

Cross, J.B.; Spangler, L.H.; Hoffbauer, M.A.; Archuleta, F.A.

1986-01-01

282

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers  

Microsoft Academic Search

Three copper-based alloys --- CDA 102 (OFHC copper), CDA 613 (aluminum bronze), and CDA 715 (Cu-30Ni) --- are being considered as possible materials for the fabrication of high-level radioactive-waste disposal containers. Waste will include fuel assemblies from reactors as well as borosilicate glass forms, and will be sent to the prospective repository at Yucca Mountain, Nevada, for emplacement. The three

J. C. Farmer; R. A. Van Konynenburg; R. D. McCright; G. E. Gdowski

1988-01-01

283

Survey of the degradation modes of candidate materials for high-level radioactive waste disposal containers  

SciTech Connect

Oxidation and atmospheric corrosion data suggest that addition of Cr provides the greatest improvement in oxidation resistance. Cr-bearing cast irons are resistant to chloride environments and solutions containing strongly oxidizing constituents. Weathering steels, including high content and at least 0.04% Cu, appear to provide adequate resistance to oxidation under temperate conditions. However, data from long-term, high-temperature oxidation studies on weathering steels were not available. From the literature, it appears that the low alloy steels, plain carbon steels, cast steels, and cast irons con-ode at similar rates in an aqueous environment. Alloys containing more than 12% Cr or 36% Ni corrode at a lower rate than plain carbon steels, but pitting may be worse. Short term tests indicate that an alloy of 9Cr-1Mo may result in increased corrosion resistance, however long term data are not available. Austenitic cast irons show the best corrosion resistance. A ranking of total corrosion performance of the materials from most corrosion resistant to least corrosion resistant is: Austenitic Cast Iron; 12% Cr = 36% Ni = 9Cr-1Mo; Carbon Steel = Low Alloy Steels; and Cast Iron. Since the materials to be employed in the Advanced Conceptual Design (ACD) waste package are considered to be corrosion allowance materials, the austenitic cast irons, high Cr steels, high Ni steels and the high Cr-Mo steels should not be considered as candidates for the outer containment barrier. Based upon the oxidation and corrosion data available for carbon steels, low alloy steels, and cast irons, a suitable list of candidate materials for a corrosion allowance outer barrier for an ACD waste package could include, A516, 2.25%Cr -- 1%Mo Steel, and A27.

Vinson, D.W.; Nutt, W.M.; Bullen, D.B. [Iowa State Univ. of Science and Technology, Ames, IA (United States)

1995-06-01

284

Gamma and Proton Induced Degradation in Ceramics Materials-a Proposal  

Microsoft Academic Search

Ceramic materials will play very important roles in developing fusion reactors, where they will be used under heavy irradiation environments (neutrons, gamma-rays, protons, helium and other ions) for substantial periods for the first time. The programme at the Institute of Atomic Physics in Bucharest forms a part of the on going ceramics programmes to assess the suitability of SiO2 based

B. Constantinescu

285

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers  

Microsoft Academic Search

Three copper-based alloys, CDA 102 (oxygen-free copper), CDA 613 (Cu-7Al), and CDA 715 (Cu-30Ni), are being considered along with three austenitic candidates as possible materials for fabrication of containers for disposal of high-level radioactive waste. The waste will include spent fuel assemblies from reactors as well as high-level reprocessing wastes in borosilicate glass and will be sent to the prospective

D. B. Bullen; G. E. Gdowski; H. Weiss

1988-01-01

286

ENHANCED DEGRADATION OF ATRAZINE UNDER FIELD CONDITIONS CORRELATES WITH A LOSS OF WEED CONTROL IN THE GLASSHOUSE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Enhanced degradation of atrazine has been reported in the literature indicating the potential for reduced residual weed control with this herbicide. Experiments were conducted to determine the field dissipation of atrazine in three cropping systems: continuous Zea mays L. (CC) receiving atrazine a...

287

Optical response of strongly absorbing inhomogeneous materials: Application to paper degradation  

NASA Astrophysics Data System (ADS)

In this paper, we present a new noninvasive and nondestructive approach to recover scattering and absorption coefficients from reflectance measurements of highly absorbing and optically inhomogeneous media. Our approach is based on the Yang and Miklavcic theoretical model of light propagation through turbid media, which is a generalization of the Kubelka-Munk theory, extended to accommodate optically thick samples. We show its applications to paper, a material primarily composed of a web of fibers of cellulose, whose optical properties are strongly governed by light scattering effects. Samples studied were ancient and industrial paper sheets, aged in different conditions and highly absorbing in the ultraviolet region. The recovered experimental absorptions of cellulose fibers have been compared to theoretical ab initio quantum-mechanical computational simulations carried out within time-dependent density functional theory. In this way, for each sample, we evaluate the absolute concentration of different kinds of oxidized groups formed upon aging and acting as chromophores causing paper discoloration. We found that the relative concentration of different chromophores in cellulose fibers depends on the aging temperature endured by samples. This clearly indicates that the oxidation of cellulose follows temperature-dependent reaction pathways. Our approach has a wide range of applications for cellulose-based materials, like paper, textiles, and other manufactured products of great industrial and cultural interest, and can potentially be extended to other strongly absorbing inhomogeneous materials.

Missori, M.; Pulci, O.; Teodonio, L.; Violante, C.; Kupchak, I.; Bagniuk, J.; ?ojewska, J.; Conte, A. Mosca

2014-02-01

288

Photocatalytic degradation of an azo-dye on TiO2/activated carbon composite material.  

PubMed

A sequential adsorption/photocatalytic regeneration process to remove tartrazine, an azo-dye in aqueous solution, has been investigated. The aim ofthis work was to compare the effectiveness of an adsorbent/photocatalyst composite-TiO2 deposited onto activated carbon (AC) - and a simple mixture of powders of TiO2 and AC in same proportion. The composite was an innovative material as the photocatalyst, TiO2, was deposited on the porous surface ofa microporous-AC using metal-organic chemical vapour deposition in fluidized bed. The sequential process was composed of two-batch step cycles: every cycle alternated a step of adsorption and a step of photocatalytic oxidation under ultra-violet (365 nm), at 25 degreeC and atmospheric pressure. Both steps, adsorption and photocatalytic oxidation, have been investigated during four cycles. For both materials, the cumulated amounts adsorbed during four cycles corresponded to nearly twice the maximum adsorption capacities qmax proving the photocatalytic oxidation to regenerate the adsorbent. Concerning photocatalytic oxidation, the degree of mineralization was higher with the TiO2/AC composite: for each cycle, the value of the total organic carbon removal was 25% higher than that obtained with the mixture powder. These better photocatalytic performances involved better regeneration than higher adsorbed amounts for cycles 2, 3 and 4. Better performances with this promising material - TiO2 deposited onto AC - compared with TiO2 powder could be explained by the vicinity of photocatalytic and AC adsorption sites. PMID:24600875

Andriantsiferana, C; Mohamed, E F; Delmas, H

2014-01-01

289

The influence of Lemna gibba L. on the degradation of organic material in duckweed-covered domestic wastewater  

Microsoft Academic Search

Laboratory scale experiments on duckweed-covered domestic sewage were carried out to determine whether removal of organic material is faster in the presence of duckweed. Performance of systems containing axenic and non-axenic Lemna gibba L., artificial plastic duckweed, air bubbling pumps and a combination of the latter two were compared with a control system without duckweed to find out which role

S Körner; G. B Lyatuu; J. E Vermaat

1998-01-01

290

Control of radioactive material transport in sodium-cooled reactors  

SciTech Connect

The Radioactivity Control Technology (RCT) program was established by the Department of Energy to develop and demonstrate methods to control radionuclide transport to ex-core regions of sodium-cooled reactors. This radioactive material is contained within the reactor heat transport system with any release to the environment well below limits established by regulations. However, maintenance, repair, decontamination, and disposal operations potentially expose plant workers to radiation fields arising from radionuclides transported to primary system components. This paper deals with radioactive material generated and transported during steady-state operation, which remains after /sup 24/Na decay. Potential release of radioactivity during postulated accident conditions is not discussed. The control methods for radionuclide transport, with emphasis on new information obtained since the last Environmental Control Symposium, are described. Development of control methods is an achievable goal.

Brehm, W.F.

1980-03-17

291

Susceptibility of a Polycaprolactone-Based Root Canal Filling Material to Degradation. I. Alkaline Hydrolysis  

Microsoft Academic Search

Polycaprolactone, a thermoplastic aliphatic polyester, is reportedly susceptible to both alkaline and enzymatic hydrolyzes. This screening study examined the susceptibility of Resilon, a polycaprolactone-based root filling composite, to alkaline hydrolysis. There were 15-mm diameter disks of Resilon and Obtura gutta-percha prepared by compressive molding and immersed in 20% sodium ethoxide for 20 or 60 min. Control disks were immersed in

Franklin R. Tay; David H. Pashley; M. Chad Williams; Rakesh Raina; Robert J. Loushine; R. Norman Weller; W. Frank Kimbrough; Nigel M. King

2005-01-01

292

Predictive modeling of composite material degradation using piezoelectric wafer sensors electromechanical impedance spectroscopy  

NASA Astrophysics Data System (ADS)

The advancement of composite materials in aircraft structures has led to on increased need for effective structural health monitoring (SHM) technologies that are able to detect and assess damage present in composites structures. The work presented in this paper is interested in understanding using self-sensing piezoelectric wafer active sensors (PWAS) to conduct electromechanical impedance spectroscopy (EMIS) in glass fiber reinforced plastic (GFRP) to perform structures health monitoring. PWAS are bonded to the composite material and the EMIS method is used to analyze the changes in the structural resonance and anti-resonance. As the damage progresses in the specimen, the impedance spectrum will change. In addition, multi-physics based finite element method (MP-FEM) is used to model the electromechanical behavior of a free PWAS and its interaction with the host structure on which it is bonded. The MPFEM permits the input and the output variables to be expressed directly in electric terms while the two way electromechanical conversion is done internally in the MP_FEM formulation. To reach the goal of using the EMIS approach to detect damage, several damages models are generated on laminated GFRP structures. The effects of the modeling are carefully studied through experimental validation. A good match has been observed for low and very high frequencies.

Gresil, Matthieu; Yu, Lingyu; Sutton, Mike; Guo, Siming; Pollock, Patrick

2012-04-01

293

Developing a Software Architecture for Graceful Degradation in an Elevator Control System  

Microsoft Academic Search

Many embedded systems have high safety and dependability requirements, which makes ensuring software robustness a top priority in these systems. As embedded computer systems become more complex and incorporate increasing functionality, their software systems become increasingly more difficult to design, build, and maintain. One approach to achieving software robustness is graceful degradation. However, graceful degradation is a difficult property to

Charles P. Shelton; Philip Koopman

294

A Degradable, Thermo-sensitive Poly(N-isopropyl acrylamide)-Based Scaffold with Controlled Porosity for Tissue Engineering Applications  

PubMed Central

We have developed a thermoresponsive poly(N-isopropyl acrylamide)-based scaffold with degradability and controlled porosity. Biodegradable poly(N-isopropyl acrylamide) hydrogels were synthesized by photo-copolymerization of N-isopropylacrylamide with 2-methylene-1,3-dioxepane and polycaprolactone dimethacrylate. The hydrogels’ phase transition temperature, swelling and viscoelastic properties, as well as hydrolytic degradability at 25 and 37°C, were explored. A sphere-templating technique was applied to fabricate hydrogel scaffolds with controllable pore size and a highly interconnected porous structure. The scaffold pore diameter change as a function of temperature was evaluated and, as expected, pores decreased in diameter when the temperature was raised to 37°C. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test results suggested neither the scaffolds nor their degradation products were cytotoxic to NIH3T3 cells. Scaffolds with 55±5 ?m pore diameter were loaded with NIH3T3 cells and then were warmed to 37°C entrapping cells in pores approximately 39 ?m in diameter, a size range we have found to be optimal for angiogenesis and biointegration. Cells showed uniform infiltration and an elongated morphology after 7 days of culture. Due to the controlled monodisperse pore diameter, highly interconnected architecture, fully degradable chemistry and thermoresponsive properties, the polyNIPAM-based scaffolds developed here are attractive for applications in tissue engineering. PMID:20836521

Galperin, Anna; Long, Thomas J.; Ratner, Buddy D.

2010-01-01

295

Fine structure of the vaccinia virion determined by controlled degradation and immunolocalization.  

PubMed

The vaccinia virion is a membraned, slightly flattened, barrel-shaped particle, with a complex internal structure featuring a biconcave core flanked by lateral bodies. Although the architecture of the purified mature virion has been intensely characterized by electron microscopy, the distribution of the proteins within the virion has been examined primarily using biochemical procedures. Thus, it has been shown that non-ionic and ionic detergents combined or not with a sulfhydryl reagent can be used to disrupt virions and, to a limited degree, separate the constituent proteins in different fractions. Applying a controlled degradation technique to virions adsorbed on EM grids, we were able to immuno-localize viral proteins within the virion particle. Our results show after NP40 and DTT treatment, membrane proteins are removed from the virion surface revealing proteins that are associated with the lateral bodies and the outer layer of the core wall. Combined treatment using high salt and high DTT removed lateral body proteins and exposed proteins of the internal core wall. Cores treated with proteases could be disrupted and the internal components were exposed. Cts8, a mutant in the A3 protein, produces aberrant virus that, when treated with NP-40 and DTT, releases to the exterior the virus DNA associated with other internal core proteins. With these results, we are able to propose a model for the structure the vaccinia virion. PMID:25486587

Moussatche, Nissin; Condit, Richard C

2015-01-15

296

Systems Analysis for Material Control and Accountancy Technology (SAMCAT)  

SciTech Connect

The Systems Analysis for Material Control and Accountancy Technology (SAMCAT) is an interactive computer-based management system developed for the Department of Energy Office of Safeguards and Security, to assist in defining and prioritizing measurement upgrades programs for Material Control and Accountancy (MC A). The accountancy upgrades options evaluated by SAMCAT in this study are: (1) improvement of the uncertainties in the SNM measurement methods, (2) reduction of throughputs and/or inventories of SNM, and (3) reduction of the material balance accounting period. The goals of the MC A upgrades program are reduced inventory differences and associated uncertainties, improved detection probabilities for theft/diversion, decreased operating costs, and enhanced material traceability. 6 refs., 3 figs., 2 tabs.

Persiani, P.J., Bucher, R.G.; Rothman, A.B.; Cha, B.K.

1990-01-01

297

Controllable optical black hole in left-handed materials.  

PubMed

Halting and storing light by infinitely decelerating its speed, in the absence of any form of external control, is extremely di+/-cult to imagine. Here we present a theoretical prediction of a controllable optical black hole composed of a planar left-handed material slab. We reveal a criterion that the effective round-trip propagation length in one zigzag path is zero, which brings light to a complete standstill. Both theory and ab initio simulation demonstrate that this optical black hole has degrees flexible controllability for the speed of light. Surprisingly, the ab initio simulations reveal that our scheme has degrees flexible controllability for swallowing, holding, and releasing light. PMID:20174039

Bai, Qiang; Chen, Jing; Shen, Nian-Hai; Cheng, Chen; Wang, Hui-Tian

2010-02-01

298

Degradation and reuse of radiative thermal protection system materials for the space shuttle  

NASA Technical Reports Server (NTRS)

Three silicide coated columbium alloys and two cobalt alloys were subjected to identical simulated reentry profiling exposures in both static (controlled vacuum leak) and dynamic (hypersonic plasma shear) environments. Primary emphasis in the columbium alloy evaluation was on the Cb752 and C129Y alloys with a lesser amount on FS85. Commercial silicide coatings of the R512E and VH109 formulations were used. The coated specimens were intentionally defected to provide the types of coating flaws that are expected in service. Temperatures were profiled up to peak temperatures of either 2350 F or 2500 F for 15 minutes in each cycle.

Bartlett, E. S.; Maykuth, D. J.; Grinberg, I. M.; Luce, R. G.

1971-01-01

299

Saltstone Disposal Facility Mechanically Stabilized Earth Vault Closure Cap Degradation Base Case: Institutional Control To Pine Forest Scenario  

SciTech Connect

As part of the current Saltstone Disposal Facility (SDF) Performance Assessment (PA) revision, the closure cap configuration was reevaluated and closure cap degradation mechanisms and their impact upon infiltration through the closure cap was evaluated for the existing SDF concrete vaults (i.e. vaults 1 and 4) for the base case land use scenario (i.e. institutional control to pine forest scenario) and documented in Phifer and Nelson (2003). The closure cap configuration was modified from a compacted kaolin barrier layer concept to a geosynthetic clay layer (GCL) barrier layer concept. The degradation mechanisms developed included pine forest succession, erosion, and colloidal clay migration. These degradation mechanisms resulted in changes in the hydraulic properties of the closure cap layers and resulting increases in infiltration through the closure cap over time.

Phifer, MA

2004-03-19

300

21 CFR 866.5910 - Quality control material for cystic fibrosis nucleic acid assays.  

Code of Federal Regulations, 2011 CFR

... Quality control material for cystic fibrosis nucleic acid assays. 866... Quality control material for cystic fibrosis nucleic acid assays. (a...Quality control material for cystic fibrosis nucleic acid assays. A...

2011-04-01

301

78 FR 67223 - Proposed Guidance for Fuel Cycle Facility; Material Control and Accounting Plans and Completing...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Facility; Material Control and Accounting Plans and Completing NRC Form 327...Amendments to Material Control and Accounting Regulations; Proposed Rules Federal...Facility; Material Control and Accounting Plans and Completing NRC Form...

2013-11-08

302

78 FR 71532 - Amendments to Material Control and Accounting Regulations and Proposed Guidance for Fuel Cycle...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Amendments to Material Control and Accounting Regulations and Proposed Guidance...Facility Material Control and Accounting Plans and Completing the U...regulations for material control and accounting (MC&A) of special...

2013-11-29

303

21 CFR 866.5910 - Quality control material for cystic fibrosis nucleic acid assays.  

Code of Federal Regulations, 2012 CFR

... Quality control material for cystic fibrosis nucleic acid assays. 866.5910 ...Quality control material for cystic fibrosis nucleic acid assays. (a) Identification...Quality control material for cystic fibrosis nucleic acid assays. A quality...

2012-04-01

304

21 CFR 866.5910 - Quality control material for cystic fibrosis nucleic acid assays.  

Code of Federal Regulations, 2014 CFR

... Quality control material for cystic fibrosis nucleic acid assays. 866.5910 ...Quality control material for cystic fibrosis nucleic acid assays. (a) Identification... Quality control material for cystic fibrosis nucleic acid assays. A quality...

2014-04-01

305

49 CFR 195.559 - What coating material may I use for external corrosion control?  

Code of Federal Regulations, 2010 CFR

...coating material may I use for external corrosion control? 195.559 Section 195...OF HAZARDOUS LIQUIDS BY PIPELINE Corrosion Control § 195.559 What coating material may I use for external corrosion control? Coating material...

2010-10-01

306

Fine scale spatial variability of microbial pesticide degradation in soil: scales, controlling factors, and implications  

PubMed Central

Pesticide biodegradation is a soil microbial function of critical importance for modern agriculture and its environmental impact. While it was once assumed that this activity was homogeneously distributed at the field scale, mounting evidence indicates that this is rarely the case. Here, we critically examine the literature on spatial variability of pesticide biodegradation in agricultural soil. We discuss the motivations, methods, and main findings of the primary literature. We found significant diversity in the approaches used to describe and quantify spatial heterogeneity, which complicates inter-studies comparisons. However, it is clear that the presence and activity of pesticide degraders is often highly spatially variable with coefficients of variation often exceeding 50% and frequently displays non-random spatial patterns. A few controlling factors have tentatively been identified across pesticide classes: they include some soil characteristics (pH) and some agricultural management practices (pesticide application, tillage), while other potential controlling factors have more conflicting effects depending on the site or the pesticide. Evidence demonstrating the importance of spatial heterogeneity on the fate of pesticides in soil has been difficult to obtain but modeling and experimental systems that do not include soil's full complexity reveal that this heterogeneity must be considered to improve prediction of pesticide biodegradation rates or of leaching risks. Overall, studying the spatial heterogeneity of pesticide biodegradation is a relatively new field at the interface of agronomy, microbial ecology, and geosciences and a wealth of novel data is being collected from these different disciplinary perspectives. We make suggestions on possible avenues to take full advantage of these investigations for a better understanding and prediction of the fate of pesticides in soil. PMID:25538691

Dechesne, Arnaud; Badawi, Nora; Aamand, Jens; Smets, Barth F.

2014-01-01

307

?TrCP controls the lysosome-mediated degradation of CDK1, whose accumulation correlates with tumor malignancy  

PubMed Central

In mammals, cell cycle progression is controlled by cyclin-dependent kinases, among which CDK1 plays important roles in the regulation of the G2/M transition, G1 progression and G1/S transition. CDK1 is highly regulated by its association to cyclins, phosphorylation and dephosphorylation, changes in subcellular localization, and by direct binding of CDK inhibitor proteins. CDK1 steady-state protein levels are held constant throughout the cell cycle by a coordinated regulation of protein synthesis and degradation. We show that CDK1 is ubiquitinated by the E3 ubiquitin ligase SCF?TrCP and degraded by the lysosome. Furthermore, we found that DNA damage not only triggers the stabilization of inhibitory phosphorylation sites on CDK1 and repression of CDK1 gene expression, but also regulates ?TrCP-induced CDK1 degradation in a cell type-dependent manner. Specifically, treatment with the chemotherapeutic agent doxorubicin in certain cell lines provokes CDK1 degradation and induces apoptosis, whereas in others it inhibits destruction of the protein. These observations raise the possibility that different tumor types, depending on their pathogenic spectrum mutations, may display different sensitivity to ?TrCP-induced CDK1 degradation after DNA damage. Finally, we found that CDK1 accumulation in patients’ tumors shows a negative correlation with ?TrCP and a positive correlation with the degree of tumor malignancy. PMID:25149538

Herrero-Ruiz, Joaquín; Mora-Santos, Mar; Giráldez, Servando; Sáez, Carmen; Japón, Miguel Á.; Tortolero, Maria; Romero, Francisco

2014-01-01

308

Performance of thermal control tape in the protection of composite materials  

NASA Technical Reports Server (NTRS)

The selection of materials for construction of long duration mission spacecraft has presented many challenges to the aerospace design community. After nearly six years in low earth orbit, NASA's Long duration Exposure Facility (LDEF), retrieved in January of 1990, has provided valuable information on both the nature of the space environment as well as the effects of the space environment on potential spacecraft materials. Composites, long a favorite of the design community because of a high strength-to-weight ratio, were flown in various configurations on LDEF in order to evaluate the effects of radiation, atomic oxygen, vacuum, micrometeoroid debris, and thermal variation on their performance. Fiberglass composite samples covered with an aluminum thermal control tape were flown as part of the flight experiment A0171, the Solar Array Materials Passive LDEF Experiment (SAMPLE). Visual observations and test results indicate that the thermal control tape suffered little degradation from the space exposure and proved to be a reliable source of protection from atomic oxygen erosion and UV radiation for the underlying composite material.

Kamenetzky, Rachel R.; Whitaker, Ann F.

1992-01-01

309

Dynamic and structural control utilizing smart materials and structures  

NASA Technical Reports Server (NTRS)

An account is given of several novel 'smart material' structural control concepts that are currently under development. The thrust of these investigations is the evolution of intelligent materials and structures superceding the recently defined variable-geometry trusses and shape memory alloy-reinforced composites; the substances envisioned will be able to autonomously evaluate emergent environmental conditions and adapt to them, and even change their operational objectives. While until now the primary objective of the developmental efforts presently discussed has been materials that mimic biological functions, entirely novel concepts may be formulated in due course.

Rogers, C. A.; Robertshaw, H. H.

1989-01-01

310

UV Induced Degradation of Polycarbonate-Based Lens Materials and Implications for the Heath Care Field  

NASA Astrophysics Data System (ADS)

Experimental research is being carried out at Keene State at the undergraduate level that utilizes facilities in both physics and chemistry to study the effects of mono- and polychromatic UV radiation from various sources, including a Deuterium lamp, a solarization unit (at Polyonics, a local industry), and the Sun, to study the photodegradation of polycarbonate-based lens materials used to produce eyewear. Literature in the field of optometry and ophthalmology indicates a correlation between exposure to the UVB band of natural sunlight and the onset of cataract formation, as well as other eye disorders. The public is usually advised that plastic eyeglass lenses will provide protection from this damaging radiation. It is well known that polycarbonate plastic ``yellows'' when exposed to intense sunlight and, particularly, UV light^1,2, either via photo-Fries rearrangement or by a photooxidative process, forming polyconjugated systems and is an industrial concern primarily for cosmetic reasons. We have preliminary data, however, that indicates that the yellowing'' is an indication of a more sinister problem in the case of eyeglasses in that it is accompanied by an increase in transmissivity in the UVB band where the wearer expects and needs protection. Our group includes a local optometrist who will share results with peers in his field. [1] A. Andrady, J. Polymer Sci., 42, 1991 [2] E. P. Gorelov, Inst. Khim. Fiz., Russian Federation

Harkay, J. R.; Henry, Jerry

2006-10-01

311

Electromagnetic valve for controlling the flow of molten, magnetic material  

DOEpatents

An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell. 5 figs.

Richter, T.

1998-06-16

312

Electromagnetic valve for controlling the flow of molten, magnetic material  

DOEpatents

An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell.

Richter, Tomas (State College, PA)

1998-01-01

313

IMPORTANCE OF MATERIAL BALANCES AND THEIR STATISTICAL EVALUATION IN RUSSIAN MATERIAL, PROTECTION, CONTROL AND ACCOUNTING  

SciTech Connect

While substantial work has been performed in the Russian MPC&A Program, much more needs to be done at Russian nuclear facilities to complete four necessary steps. These are (1) periodically measuring the physical inventory of nuclear material, (2) continuously measuring the flows of nuclear material, (3) using the results to close the material balance, particularly at bulk processing facilities, and (4) statistically evaluating any apparent loss of nuclear material. The periodic closing of material balances provides an objective test of the facility's system of nuclear material protection, control and accounting. The statistical evaluation using the uncertainties associated with individual measurement systems involved in the calculation of the material balance provides a fair standard for concluding whether the apparent loss of nuclear material means a diversion or whether the facility's accounting system needs improvement. In particular, if unattractive flow material at a facility is not measured well, the accounting system cannot readily detect the loss of attractive material if the latter substantially derives from the former.

FISHBONE,L.G.

1999-07-25

314

Development of a murre (Uria spp.) egg control material  

USGS Publications Warehouse

The Seabird Tissue Archival and Monitoring Project (STAMP) is a collaborative Alaska-wide effort by the US Fish and Wildlife Service's Alaska Maritime National Wildlife Refuge (USFWS/AMNWR), the US Geological Survey's Biological Resources Division (USGS/BRD), the Bureau of Indian Affairs Alaska Region Subsistence Branch (BIA/ARSB), and the National Institute of Standards and Technology (NIST) to monitor long-term (decadal) trends in environmental contaminants using seabird eggs. To support this effort, a matrix- (seabird egg) and concentration-specific control material was needed to ensure quality during analytical work. Although a herring gull egg quality assurance (HGQA) material is available from Environment Canada (EC), contaminant concentrations in this material tended to be higher than those observed in Alaskan murre (Uria spp.) eggs. Therefore, to prepare a more appropriate control material, a total of 12 common murre (U. aalge) and thick-billed murre (U. lomvia) eggs from four Bering Sea and Gulf of Alaska nesting locations were cryohomogenized to create 190 aliquots each containing approximately 6 g. This new control material was analyzed by different methods at NIST and EC facilities for the determination of concentrations and value assignment of 63 polychlorinated biphenyl (PCB) congeners, 20 organochlorine pesticides, and 11 polybrominated diphenyl ether (PBDE) congeners. The total PCB concentration is approximately 58 ng g -1 wet mass. Results obtained for analytes not listed on the certificates of analysis of the previously used control materials, HGQA and NIST's Standard Reference Material (SRM) 1946 Lake Superior Fish Tissue, are also presented. [Figure not available: see fulltext.]. ?? Springer-Verlag 2007.

Vander Pol, S. S.; Ellisor, M.B.; Pugh, R.S.; Becker, P.R.; Poster, D.L.; Schantz, M.M.; Leigh, S.D.; Wakeford, B.J.; Roseneau, D.G.; Simac, K.S.

2007-01-01

315

Development of a murre (Uria spp.) egg control material.  

PubMed

The Seabird Tissue Archival and Monitoring Project (STAMP) is a collaborative Alaska-wide effort by the US Fish and Wildlife Service's Alaska Maritime National Wildlife Refuge (USFWS/AMNWR), the US Geological Survey's Biological Resources Division (USGS/BRD), the Bureau of Indian Affairs Alaska Region Subsistence Branch (BIA/ARSB), and the National Institute of Standards and Technology (NIST) to monitor long-term (decadal) trends in environmental contaminants using seabird eggs. To support this effort, a matrix- (seabird egg) and concentration-specific control material was needed to ensure quality during analytical work. Although a herring gull egg quality assurance (HGQA) material is available from Environment Canada (EC), contaminant concentrations in this material tended to be higher than those observed in Alaskan murre (Uria spp.) eggs. Therefore, to prepare a more appropriate control material, a total of 12 common murre (U. aalge) and thick-billed murre (U. lomvia) eggs from four Bering Sea and Gulf of Alaska nesting locations were cryohomogenized to create 190 aliquots each containing approximately 6 g. This new control material was analyzed by different methods at NIST and EC facilities for the determination of concentrations and value assignment of 63 polychlorinated biphenyl (PCB) congeners, 20 organochlorine pesticides, and 11 polybrominated diphenyl ether (PBDE) congeners. The total PCB concentration is approximately 58 ng g(-1) wet mass. Results obtained for analytes not listed on the certificates of analysis of the previously used control materials, HGQA and NIST's Standard Reference Material (SRM) 1946 Lake Superior Fish Tissue, are also presented. PMID:17103152

Vander Pol, Stacy S; Ellisor, Michael B; Pugh, Rebecca S; Becker, Paul R; Poster, Dianne L; Schantz, Michele M; Leigh, Stefan D; Wakeford, Bryan J; Roseneau, David G; Simac, Kristin S

2007-04-01

316

Nanostructured solar irradiation control materials for solar energy conversion  

NASA Astrophysics Data System (ADS)

Tailoring the solar absorptivity (?s) and thermal emissivity (?T) of materials constitutes an innovative approach to solar energy control and energy conversion. Numerous ceramic and metallic materials are currently available for solar absorbance/thermal emittance control. However, conventional metal oxides and dielectric/metal/dielectric multi-coatings have limited utility due to residual shear stresses resulting from the different coefficient of thermal expansion of the layered materials. This research presents an alternate approach based on nanoparticle-filled polymers to afford mechanically durable solar-absorptive and thermally-emissive polymer nanocomposites. The ?s and ?T were measured with various nano inclusions, such as carbon nanophase particles (CNPs), at different concentrations. Research has shown that adding only 5 wt% CNPs increased the ?s and ?T by a factor of about 47 and 2, respectively, compared to the pristine polymer. The effect of solar irradiation control of the nanocomposite on solar energy conversion was studied. The solar irradiation control coatings increased the power generation of solar thermoelectric cells by more than 380% compared to that of a control power cell without solar irradiation control coatings.

Kang, Jin Ho; Marshall, Iseley A.; Torrico, Mattew N.; Taylor, Chase R.; Ely, Jeffry; Henderson, Angel; Sauti, Godfrey; Gibbons, Luke J.; Kim, Jae-Woo; Park, Cheol; Lowther, Sharon E.; Lillehei, Peter T.; Bryant, Robert G.

2012-10-01

317

Nanostructured Solar Irradiation Control Materials for Solar Energy Conversion  

NASA Technical Reports Server (NTRS)

Tailoring the solar absorptivity (alpha(sub s)) and thermal emissivity (epsilon(sub T)) of materials constitutes an innovative approach to solar energy control and energy conversion. Numerous ceramic and metallic materials are currently available for solar absorbance/thermal emittance control. However, conventional metal oxides and dielectric/metal/dielectric multi-coatings have limited utility due to residual shear stresses resulting from the different coefficient of thermal expansion of the layered materials. This research presents an alternate approach based on nanoparticle-filled polymers to afford mechanically durable solar-absorptive and thermally-emissive polymer nanocomposites. The alpha(sub s) and epsilon(sub T) were measured with various nano inclusions, such as carbon nanophase particles (CNPs), at different concentrations. Research has shown that adding only 5 wt% CNPs increased the alpha(sub s) and epsilon(sub T) by a factor of about 47 and 2, respectively, compared to the pristine polymer. The effect of solar irradiation control of the nanocomposite on solar energy conversion was studied. The solar irradiation control coatings increased the power generation of solar thermoelectric cells by more than 380% compared to that of a control power cell without solar irradiation control coatings.

Kang, Jinho; Marshall, I. A.; Torrico, M. N.; Taylor, C. R.; Ely, Jeffry; Henderson, Angel Z.; Kim, J.-W.; Sauti, G.; Gibbons, L. J.; Park, C.; Lowther, S. E.; Lillehei, P. T.; Bryant, R. G.

2012-01-01

318

Ground-Based Testing of Replacement Thermal Control Materials for the Hubble Space Telescope  

NASA Technical Reports Server (NTRS)

The mechanical and optical properties of the metallized Teflon FEP thermal control materials on the Hubble Space Telescope (HST) have degraded over the nearly seven years the telescope has been in orbit. Given the damage to the outer layer of the multi-layer insulation (MLI) that was apparent during the second servicing mission (SM2), the decision was made to replace the outer layer during subsequent servicing missions. A Failure Review Board was established to investigate the damage to the MLI and identify a replacement material. The replacement material had to meet the stringent thermal requirements of the spacecraft and maintain mechanical integrity for at least ten years. Ten candidate materials were selected and exposed to ten-year HST-equivalent doses of simulated orbital environments. Samples of the candidates were exposed sequentially to low and high energy electrons and protons, atomic oxygen, x-ray radiation, ultraviolet radiation and thermal cycling. Following the exposures, the mechanical integrity and optical properties of the candidates were investigated using Optical Microscopy, Scanning Electron Microscopy (SEM), a Laboratory Portable Spectroreflectometer (LPSR) and a Lambda 9 Spectroreflectometer. Based on the results of these simulations and analyses, the Failure Review Board selected a replacement material and two alternates that showed the highest likelihood of providing the requisite thermal properties and surviving for ten years in orbit.

Townsend, Jacqueline A.; Hansen, Patricia A.; McClendon, Mark W.; deGroh, Kim K.; Banks, Bruce A.; Triolo, Jack J.

1998-01-01

319

Evaluation and Selection of Replacement Thermal Control Materials for the Hubble Space Telescope  

NASA Technical Reports Server (NTRS)

The mechanical and optical properties of the metallized Teflon(Registered Trademark) FEP thermal control materials on the Hubble Space Telescope (HST) have degraded over the nearly seven years the telescope has been in orbit. Given the damage to the outer layer of the multi-layer insulation (MLI) that was apparent during the second servicing mission (SM2), the decision was made to replace the outer layer during subsequent servicing missions. A Failure Review Board was established to investigate the damage to the MLI and identify a replacement material. The replacement material had to meet the stringent thermal requirements of the spacecraft and maintain structural integrity for at least ten years. Ten candidate materials were selected and exposed to ten-year HST-equivalent doses of simulated orbital environments. Samples of the candidates were exposed sequentially to low and high energy electrons and protons, atomic oxygen, x-ray radiation, ultraviolet radiation and thermal cycling. Following the exposures, the mechanical integrity and optical properties of the candidates were investigated using Optical Microscopy, Scanning Electron Microscopy (SEM), and a Laboratory Portable Spectroreflectometer (LPSR). Based on the results of these simulations and analyses, the FRB selected a replacement material and two alternates that showed the highest likelihood of providing the requisite thermal properties and surviving for ten years in orbit.q

Townsend, Jacqueline A.; Hansen, Patricia A.; McClendon, Mark W.; Dever, Joyce A.; Triolo, Jack J.

1998-01-01

320

Enhanced degradation of atrazine under field conditions correlates with a loss of weed control in the glasshouse.  

PubMed

Enhanced degradation of atrazine has been reported in the literature, indicating the potential for reduced residual weed control with this herbicide. Experiments were conducted to determine the field dissipation of atrazine in three cropping systems: continuous Zea mays L. (CC) receiving atrazine applications each year, Gossypium hirsutum L.-Z. mays rotation (CCR) receiving applications of atrazine once every 2 years and a no atrazine history soil (NAH). Subsequent laboratory and greenhouse experiments were conducted with soil collected from these cropping systems to determine atrazine degradation, mineralization and residual weed control. Field dissipation of atrazine followed first-order kinetics, and calculated half-life values for atrazine combined over 2003 and 2005 increased in the order of CC (9 d) = CCR (10 d) < NAH (17 d). Greenhouse studies confirmed that the persistence of atrazine was approximately twofold greater in NAH soil than in CC or CCR soil. Biometer flask mineralization studies suggested that enhanced degradation of atrazine was due to rapid catabolism of the s-triazine ring. Glasshouse efficacy studies revealed a loss of residual weed control in CC and CCR soil compared with NAH soil. These data indicate that, under typical Mississippi Delta field conditions and agronomic practices, the persistence of atrazine may be reduced by at least 50% if the herbicide is applied more than once every 24 months. Glasshouse studies suggest that under these conditions a loss of residual weed control is possible. PMID:17115404

Krutz, L Jason; Zablotowicz, Robert M; Reddy, Krishna N; Koger, Clifford H; Weaver, Mark A

2007-01-01

321

Quality control of MATa1 splicing and exon skipping by nuclear RNA degradation  

E-print Network

, the nuclear exosome and by the nuclear RNase III endonuclease Rnt1p to prevent undesired expression of non Rat1p and by the nuclear exosome. This function for Rat1p and the nuclear exosome in the degradation

Chanfreau, Guillaume

322

FINAL REPORT. CONTROL OF BIOLOGICALLY ACTIVE DEGRADATION ZONES BY VERTICAL HETEROGENEITY: APPLICATIONS IN FRACTURED MEDIA  

EPA Science Inventory

The key objective of this research was to determine the distribution of biologically active contaminant degradation zones in a fractured, subsurface medium with respect to vertical heterogeneities. Our expectation was that hydrogeological properties would determine the size, d...

323

Adaptable and adaptive materials for light flux control  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to describe and examine properties of light flux control materials. Indeed, intelligent light flux control is necessary not only to improve everyday visual convenience but also in an economical point of view in order to reduce global home energetic cost. Several types of materials are good potential candidates for such functions: (1) The most well-known investigations concern inorganic materials such as tungsten or molybdenum oxides in which an electrochrom layer darkens when enriched in ions, and looses its color when impoverished. Unfortunately, at the moment, there is no convenient way to realize correct ions suppliers. Moreover, other drawbacks arise, such as poor reversibility, reactive interferences or a sensitivity of the material to its environment. These systems only need a low voltage level to work. But, their dynamic response, which is correlated to the component surface, is quite long. (2) At the present time, another attractive issue seems promising. More and more studies concern micro-composite liquid crystal films. For first, we shall remind their principles as well as their way of preparation. After having talked about their main advantages as intelligent materials, we shall discuss their control, their light flux adaptability, or their memory capabilities.

Sixou, Pierre; Magnaldo, A.; Nourry, J.; Laye, C.

1996-04-01

324

Strength properties of fly ash based controlled low strength materials.  

PubMed

Controlled low strength material (CLSM) is a flowable mixture that can be used as a backfill material in place of compacted soils. Flowable fill requires no tamping or compaction to achieve its strength and typically has a load carrying capacity much higher than compacted soils, but it can still be excavated easily. The selection of CLSM type should be based on technical and economical considerations for specific applications. In this study, a mixture of high volume fly ash (FA), crushed limestone powder (filler) and a low percentage of pozzolana cement have been tried in different compositions. The amount of pozzolana cement was kept constant for all mixes as, 5% of fly ash weight. The amount of mixing water was chosen in order to provide optimum pumpability by determining the spreading ratio of CLSM mixtures using flow table method. The shear strength of the material is a measure of the materials ability to support imposed stresses on the material. The shear strength properties of CLSM mixtures have been investigated by a series of laboratory tests. The direct shear test procedure was applied for determining the strength parameters Phi (angle of shearing resistance) and C(h) (cohesion intercept) of the material. The test results indicated that CLSM mixtures have superior shear strength properties compared to compacted soils. Shear strength, cohesion intercept and angle of shearing resistance values of CLSM mixtures exceeded conventional soil materials' similar properties at 7 days. These parameters proved that CLSM mixtures are suitable materials for backfill applications. PMID:17331642

Türkel, S

2007-08-25

325

ESR spectroscopy for monitoring the photochemical and thermal degradation of conjugated polymers used as electron donor materials in organic bulk heterojunction solar cells.  

PubMed

It was shown that ESR spectroscopy is a very useful technique for monitoring the photochemical and thermal degradation of conjugated polymers commonly used in organic solar cells. The relative stability of materials can be quantified by comparing the rates of trap accumulation (dC(R)/dt) estimated from their ESR profiles. PMID:25435101

Frolova, Lyubov A; Piven, Natalia P; Susarova, Diana K; Akkuratov, Alexander V; Babenko, Sergey D; Troshin, Pavel A

2015-02-11

326

Total Quality development of Material Control Accountability software: LANMAS  

Microsoft Academic Search

Changing US Department of Energy (DOE) guidelines require Material Control & Accountability (MC&A) software to meet Total Quality certification requirements. Some MC&A software has met site quality standards, but only after extensive documentation rework. Mandating Total Quality methods during development virtually guarantees MC&A software certification.

M. R. Woychick; D. Yearsley; L. P. McRae

1993-01-01

327

Human performance: An essential element in materials control and accountability  

SciTech Connect

The importance of the role of human performance in the successful and effective operation of many activities throughout many industries has been well documented. Most closely related to the materials control and accountability area is the work in human factors that has been ongoing in the U.S. nuclear industry since the Three Mile Island Nuclear Power Plant accident in 1979. Research related to the role of human reliability, human-system interface, and organization and management influences has been and is still being conducted to identify ways to enhance the safe and effective operation of nuclear facilities. This paper will discuss these human performance areas and how they relate to the materials control and accountability area. Particular attention will be focussed on the notion of {open_quotes}safety culture{close_quotes} and how it can be defined and measured for understanding the values and attitudes held by individuals working in the materials control area. It is widely believed that the culture of an organization, which reflects the expectations and values of the management of an organization, is a key element to the operation of that organization. The human performance element is one which has not received a great deal of consideration in the materials control and accountability area and yet it will be demonstrated that it is an essential component to ensure the success of safeguards activities.

Haber, S.B.; Allentuck, J.

1996-10-01

328

Methods of Verification, Accountability and Control of Special Nuclear Material  

Microsoft Academic Search

This session demonstrates nondestructive assay (NDA) measurement, surveillance and analysis technology required to protect, control and account (MPC and A) for special nuclear materials (SNM) in sealed containers. These measurements, observations and analyses comprise state-of-the art, strengthened, SNM safeguards systems. Staff member specialists, actively involved in research, development, training and implementation worldwide, will present six NDA verification systems and two

1999-01-01

329

MATERIALS MANAGEMENT -INVENTORY CONTROL PROPERTY EQUIPMENT LOAN FORM -IC-5  

E-print Network

MATERIALS MANAGEMENT - INVENTORY CONTROL PROPERTY EQUIPMENT LOAN FORM - IC-5 Mail or PDF the entire. YOUR SIGNATURE ALSO CONFIRMS THAT ALL EQUIPMENT & ACCESSORIES USED WITH/OR HAVING CONTAINED RADIOACTIVE & RADIATION SAFETY. 2. YOUR SIGNATURE ALSO CONFIRMS THAT ALL ELECTRONIC STORAGE EQUIPMENT & DEVICES HAVE BEEN

Oliver, Douglas L.

330

PERFORMANCE TESTING OF SPILL CONTROL DEVICES ON FLOATABLE HAZARDOUS MATERIALS  

EPA Science Inventory

At the U.S. EPA's Oil and Hazardous Materials Simulated Environmental Test Tank (OHMSETT) in Leonardo, New Jersey, from September 1975 through November 1975, the U.S. Environmental Protection Agency (US EPA) and the U.S. Coast Guard evaluated selected oil-spill control equipment ...

331

WindTech TV: Bonus Materials- Machine Control Circuits  

NSDL National Science Digital Library

This section of the Wind Technician TV website provides bonus materials pertaining to machine control circuits. Users can review content on topics like electrical theory, magnetics, ladder diagrams and start-stop interlock example. Clicking on a subtopic will launch a pop up window demonstrating the concept.

332

Compatibility of refractory materials for nuclear reactor poison control systems  

NASA Technical Reports Server (NTRS)

Metal-clad poison rods have been considered for the control system of an advanced space power reactor concept studied at the NASA Lewis Research Center. Such control rods may be required to operate at temperatures of about 140O C. Selected poison materials (including boron carbide and the diborides of zirconium, hafnium, and tantalum) were subjected to 1000-hour screening tests in contact with candidate refractory metal cladding materials (including tungsten and alloys of tantalum, niobium, and molybdenum) to assess the compatibility of these materials combinations at the temperatures of interest. Zirconium and hafnium diborides were compatible with refractory metals at 1400 C, but boron carbide and tantalum diboride reacted with the refractory metals at this temperature. Zirconium diboride also showed promise as a reaction barrier between boron carbide and tungsten.

Sinclair, J. H.

1974-01-01

333

Phase change thermal control materials, method and apparatus  

NASA Technical Reports Server (NTRS)

An apparatus and method for metabolic cooling and insulation of a user in a cold environment. In its preferred embodiment the apparatus is a highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The apparatus can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The apparatus may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the apparatus also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Buckley, Theresa M. (Inventor)

2001-01-01

334

Biodegradable ferulic acid-containing poly(anhydride-ester): degradation products with controlled release and sustained antioxidant activity.  

PubMed

Ferulic acid (FA) is an antioxidant and photoprotective agent used in biomedical and cosmetic formulations to prevent skin cancer and senescence. Although FA exhibits numerous health benefits, physicochemical instability leading to decomposition hinders its efficacy. To minimize inherent decomposition, a FA-containing biodegradable polymer was prepared via solution polymerization to chemically incorporate FA into a poly(anhydride-ester). The polymer was characterized using nuclear magnetic resonance and infrared spectroscopies. The molecular weight and thermal properties were also determined. In vitro studies demonstrated that the polymer was hydrolytically degradable, thus providing controlled release of the chemically incorporated bioactive with no detectable decomposition. The polymer degradation products were found to exhibit antioxidant and antibacterial activity comparable to that of free FA, and in vitro cell viability studies demonstrated that the polymer is noncytotoxic toward fibroblasts. This renders the polymer a potential candidate for use as a controlled release system for skin care formulations. PMID:23327626

Ouimet, Michelle A; Griffin, Jeremy; Carbone-Howell, Ashley L; Wu, Wen-Hsuan; Stebbins, Nicholas D; Di, Rong; Uhrich, Kathryn E

2013-03-11

335

Spoken commands control robot that handles radioactive materials  

SciTech Connect

Several robotic systems have been developed by Los Alamos National Laboratory to handle radioactive material. Because of safety considerations, the robotic system must be under direct human supervision and interactive control continuously. In this paper, we describe the implementation of a voice-recognition system that permits this control, yet allows the robot to perform complex preprogrammed manipulations without the operator's intervention. To provide better interactive control, we connected to the robot's control computer, a speech synthesis unit, which provides audible feedback to the operator. Thus upon completion of a task or if an emergency arises, an appropriate spoken message can be reported by the control computer. The training programming and operation of this commercially available system are discussed, as are the practical problems encountered during operations.

Phelan, P.F.; Keddy, C.; Beugelsdojk. T.J.

1989-01-01

336

Stimuli-Responsive Materials for Controlled Release of Theranostic Agents.  

PubMed

Stimuli-responsive materials are so named because they can alter their physicochemical properties and/or structural conformations in response to specific stimuli. The stimuli can be internal, such as physiological or pathological variations in the target cells/tissues, or external, such as optical and ultrasound radiations. In recent years, these materials have gained increasing interest in biomedical applications due to their potential for spatially and temporally controlled release of theranostic agents in response to the specific stimuli. This article highlights several recent advances in the development of such materials, with a focus on their molecular designs and formulations. The future of stimuli-responsive materials will also be explored, including combination with molecular imaging probes and targeting moieties, which could enable simultaneous diagnosis and treatment of a specific disease, as well as multi-functionality and responsiveness to multiple stimuli, all important in overcoming intrinsic biological barriers and increasing clinical viability. PMID:25477774

Wang, Yucai; Shim, Min Suk; Levinson, Nathanael S; Sung, Hsing-Wen; Xia, Younan

2014-07-16

337

Teardown analysis for detecting shelf-life degradation  

NASA Technical Reports Server (NTRS)

Analysis is guideline in examining component materials, analytically determining physical properties and chemical compositions, and developing control data necessary for ascertaining effects of environments and their influence on deterioration and degradation mechanisms.

Eckstein, A. S.

1971-01-01

338

NRC Effort on Regulatory Approaches for Control of Solid Materials  

SciTech Connect

The U.S. Nuclear Regulatory Commission's (NRC's) regulations that set standards for protection of the public against radiation do not currently contain specific requirements for the control of solid materials with small or no amounts of radioactivity. Absent a National standard, NRC routinely evaluates, on a case-by-case basis, licensee requests to release solid materials when they are obsolete or no longer useful during operations, or when the facility is being shut down during decommissioning. As part of its continuing examination regarding the control of solid materials, NRC sponsored and received a report from the National Academies' (NA's) National Research Council that reviewed technical bases, policies, and precedents, and made several recommendations for moving forward on this issue. NRC evaluated the NA report and developed a set of options for proceeding with a process for examining approaches for control of solid materials. This paper explains the option that NRC chose and summarizes NRC's technical basis development and related National and international activities.

Huffert, A. M.

2003-02-27

339

Autophagy plays a critical role in the degradation of active RHOA, the control of cell cytokinesis and genomic stability  

PubMed Central

Degradation of signaling proteins is one of the most powerful tumor suppressive mechanisms by which a cell can control its own growth. Here, we identify RHOA as the molecular target by which autophagy maintains genomic stability. Specifically, inhibition of autophagosome degradation by the loss of the v-ATPase a3 (TCIRG1) subunit is sufficient to induce aneuploidy. Underlying this phenotype, active RHOA is sequestered via p62 (SQSTM1) within autolysosomes, and fails to localize to the plasma membrane or to the spindle midbody. Conversely, inhibition of autophagosome formation by ATG5 shRNA dramatically increases localization of active RHOA at the midbody, followed by diffusion to the flanking zones. As a result, all of the approaches we examined that compromise autophagy (irrespective of the defect: autophagosome formation, sequestration or degradation) drive cytokinesis failure, multinucleation, and aneuploidy, processes that directly have an impact upon cancer progression. Consistently, we report a positive correlation between autophagy defects and the higher expression of RHOA in human lung carcinoma. We therefore propose that autophagy may act in part as a safeguard mechanism that degrades and thereby maintains the appropriate level of active RHOA at the midbody for faithful completion of cytokinesis and genome inheritance. PMID:23704209

Belaid, Amine; Cerezo, Michaël; Chargui, Abderrahman; Corcelle–Termeau, Elisabeth; Pedeutour, Florence; Giuliano, Sandy; Ilie, Marius; Rubera, Isabelle; Tauc, Michel; Barale, Sophie; Bertolotto, Corinne; Brest, Patrick; Vouret-Craviari, Valérie; Klionsky, Daniel J.; Carle, Georges F.; Hofman, Paul; Mograbi, Baharia

2013-01-01

340

Nuclear materials control and accountability criteria for upgrades measures  

SciTech Connect

As a result of major political and societal changes in the past several years, methods of nuclear material control may no longer be as effective as in the past in Russia, the Newly Independent States (NIS), and the Baltic States (BS). The objective of the Department of Energy (DOE) Material Protection, Control, and Accounting Program (MPC and A) is to reduce the threat of nuclear proliferation by collaborating with Russia, NIS, and BS governments to promote western-style MPC and A. This cooperation will improve the MPC and A on all weapons useable nuclear materials and will establish a sustainable infrastructure to provide future support and maintenance for these technology-based improvements. Nuclear materials of proliferation concern include materials of the types and quantities that can be most easily and directly used in a nuclear weapon. Sabotage of nuclear material is an event of great concern and potentially disastrous consequences to both the US and the host country. However, sabotage is currently beyond the scope of program direction and cannot be used to justify US-funded MPC and A upgrades. Judicious MPC and A upgrades designed to protect against insider and outsider theft scenarios would also provide addition, although not comprehensive, protection against saboteurs. This paper provides some suggestions to establish consistency in prioritizing system-enhancement efforts at nuclear material facilities. The suggestions in this paper are consistent with DOE policy and directions and should be used as a supplement to any policy directives issued by NN-40, DOE Russia/NIS Task Force.

Erkkila, B.H.; Hatcher, C.R.

1998-11-01

341

Controlling Beryllium Contaminated Material And Equipment For The Building 9201-5 Legacy Material Disposition Project  

SciTech Connect

This position paper addresses the management of beryllium contamination on legacy waste. The goal of the beryllium management program is to protect human health and the environment by preventing the release of beryllium through controlling surface contamination. Studies have shown by controlling beryllium surface contamination, potential airborne contamination is reduced or eliminated. Although there are areas in Building 9201-5 that are contaminated with radioactive materials and mercury, only beryllium contamination is addressed in this management plan. The overall goal of this initiative is the compliant packaging and disposal of beryllium waste from the 9201-5 Legacy Material Removal (LMR) Project to ensure that beryllium surface contamination and any potential airborne release of beryllium is controlled to levels as low as practicable in accordance with 10 CFR 850.25.

Reynolds, T. D.; Easterling, S. D.

2010-10-01

342

Development of Tailorable Electrically Conductive Thermal Control Material Systems  

NASA Technical Reports Server (NTRS)

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has already added to the existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The object of this program was to develop two types of passive electrically conductive TCMS.

Deshpande, M. S.; Harada, Y.

1998-01-01

343

A Highly Conserved Signal Controls Degradation of 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) Reductase in Eukaryotes*  

E-print Network

A Highly Conserved Signal Controls Degradation of 3-Hydroxy-3- methylglutaryl-coenzyme A (HMG, through feedback-regulated degradation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR). In both groups, co- enzyme Q, dolichol, and sterols such as cholesterol (1). 3-Hy- droxy-3-methylglutaryl-coenzyme

Gardner, Rich

344

Thermally Controlled Hydrogen Storage System Using Novel Carbon Materials  

Microsoft Academic Search

Successful development of sorption storage technologies for hydrogen assumes an active temperature control and special properties\\u000a of the materials, capable to adsorb hydrogen in a reversible way.\\u000a \\u000a The goal of this paper is the development of the sectional vessel with heat pipe (HP) for hydrogen sorption storage at average\\u000a pressures 3.5–6 MPa, every separate section of which has the case

L. L. Vasiliev; L. E. Kanonchik; V. A. Babenko

345

Methods of Verification, Accountability and Control of Special Nuclear Material  

SciTech Connect

This session demonstrates nondestructive assay (NDA) measurement, surveillance and analysis technology required to protect, control and account (MPC and A) for special nuclear materials (SNM) in sealed containers. These measurements, observations and analyses comprise state-of-the art, strengthened, SNM safeguards systems. Staff member specialists, actively involved in research, development, training and implementation worldwide, will present six NDA verification systems and two software tools for integration and analysis of facility MPC and A data.

Stewart, J.E.

1999-05-03

346

Robotic control architecture development for automated nuclear material handling systems  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) is engaged in developing automated systems for handling materials for mixed waste treatment, nuclear pyrochemical processing, and weapon components disassembly. In support of these application areas there is an extensive robotic development program. This paper will describe the portion of this effort at LLNL devoted to control system architecture development, and review two applications currently being implemented which incorporate these technologies.

Merrill, R.D.; Hurd, R.; Couture, S.; Wilhelmsen, K.

1995-02-01

347

Safeguarding nuclear materials in the former Soviet Republics through computerized materials protection, control and accountability  

SciTech Connect

The threat of nuclear weapons proliferation is a problem of global concern. International efforts at nonproliferation focus on preventing acquisition of weapons-grade nuclear materials by unauthorized states, organizations, or individuals. Nonproliferation can best be accomplished through international cooperation in the application of advanced science and technology to the management and control of nuclear materials. Computerized systems for nuclear material protection, control, and accountability (MPC and A) are a vital component of integrated nuclear safeguards programs. This paper describes the progress of scientists in the United States and former Soviet Republics in creating customized, computerized MPC and A systems. The authors discuss implementation of the Core Material Accountability System (CoreMAS), which was developed at Los Alamos National Laboratory by the US Department of Energy and incorporates, in condensed and integrated form, the most valuable experience gained by US nuclear enterprises in accounting for and controlling nuclear materials. The CoreMAS approach and corresponding software package have been made available to sites internationally. CoreMAS provides methods to evaluate their existing systems and to examine advantages and disadvantages of customizing CoreMAS or improving their own existing systems. The sites can also address crucial issues of software assurance, data security, and system performance; compare operational experiences at sites with functioning computerized systems; and reasonably evaluate future efforts. The goal of the CoreMAS project is to introduce facilities at sites all over the world to modern international MPC and A practices and to help them implement effective, modern, computerized MPC and A systems to account for their nuclear materials, and thus reduce the likelihood of theft or diversion. Sites are assisted with MPC and A concepts and the implementation of an effective computerized MPC and A system.

Roumiantsev, A.N.; Ostroumov, Y.A. [Kurchatov Inst. Russian Research Center, Moscow (Russian Federation); Whiteson, R.; Seitz, S.L.; Landry, R.P.; Martinez, B.J.; Boor, M.G.; Anderson, L.K.; Gary, S.P. [Los Alamos National Lab., NM (United States)

1997-11-01

348

CONTROL OF BIOLOGICALLY ACTIVE DEGRADATION ZONES BY VERTICAL HETEROGENEITY: APPLICATIONS IN FRACTURED MEDIA  

EPA Science Inventory

The U.S. Department of Energy (DOE) is faced with cleaning up wastes from reactor and weapons production activities during the latter half of this century. Many DOE sites have contaminants that are difficult to access due to depth and complex geology and are challenging to degrad...

349

Materials and actuators for the shape control of structures  

NASA Astrophysics Data System (ADS)

Smart materials and actuators meet a noticeable infatuation for the shape control of aerodynamic surfaces. This interest is borne as well to reduced scale where space is limited for the machining of models allowing to demonstrate the merits of some advanced concepts as to full scale prototypes, where these novative mechanisms are supposed to replace advantageously hydraulic or classical electro-magnetic solutions. These new devices are even supposed to provide in some cases several benefits for integrity improvement of the structure itself. The extrapolation from one to the other is nevertheless not straight forward and must take into account the distinct specifications if only the avionability constraints and the cost. If bulk and multilayered electro-active materials and integrated adaptive systems issued from them are convenient for dynamic control, shape memory alloys are only suitable for slow but quite significant geometry changes. After a brief survey of the most outstanding properties, the availability and the limitations of usual materials, actuators and electronic controllers, easily provisionable on the market, the paper deals with some technological applications experimented on models. The subjects investigated concern the flap deflection, the twist of rotor blades and the swelling of a wing profile. The last part of presentation points out some fast started-up and economical developments, to promote these actuators in the near term in order to compensate topical deficiencies, and first actions already undertaken to this end.

Mercier des Rochettes, Hugues; Petitniot, Jean-Luc

2001-08-01

350

Quorum sensing controls hyphal initiation in Candida albicans through Ubr1-mediated protein degradation  

PubMed Central

Candida albicans is the most common cause of invasive fungal infections in humans. Its ability to undergo the morphological transition from yeast to hyphal growth forms is critical for its pathogenesis. Hyphal initiation requires the activation of the cAMP-PKA pathway, which down-regulates the expression of NRG1, the major repressor of hyphal development. Hyphal initiation also requires inoculation of a small amount of C. albicans cells from overnight culture to fresh medium. This inoculation releases the inhibition from farnesol, a quorum-sensing molecule of C. albicans, that accumulated in the spent medium. Here, we show that farnesol inhibits hyphal initiation mainly through blocking the protein degradation of Nrg1. Through screening a kinase mutant library, we identified Sok1 as the kinase required for Nrg1 degradation during inoculation. SOK1 expression is transiently activated on inoculation during hyphal initiation, and overexpression of SOK1 overcomes the farnesol-mediated inhibition of hyphal initiation. Screening a collection of transcription factor mutants, the homeodomain-containing transcription repressor Cup9 is found to be responsible for the repression of SOK1 expression in response to farnesol inhibition. Interestingly, farnesol inhibits Cup9 degradation mediated by the N-end rule E3 ubiquitin ligase, Ubr1. Therefore, hyphal initiation requires both the cAMP-PKA pathway-dependent transcriptional down-regulation of NRG1 and Sok1-mediated degradation of Nrg1 protein. The latter is triggered by the release from farnesol inhibition of Cup9 degradation and consequently, derepression of SOK1 transcription. Neither pathway alone is sufficient for hyphal initiation. PMID:24449897

Lu, Yang; Su, Chang; Unoje, Ohimai; Liu, Haoping

2014-01-01

351

Influence of the Piping-material-originated Metal-ion on Cell Degradation of Polymer Electrolyte Fuel Cell  

NASA Astrophysics Data System (ADS)

Influences of metal-ion adulterations into Polymer Electrolyte Fuel Cells (PEFC) were examined on PEFC generation characteristics and structural changes. Cupper and aluminun, novel candidate materials for forthcoming PEFC system, were introduced into polymer electrolyte membranes (PEM) by ion-exchange method as contaminants, and ca. 500-hour generation tests of PEFC cells with these PEMs were conducted in this study. Introduced metal ions were to be combined to sulfonic acid groups in PEMs by electrostatic forces. For the cell containing cupric ions (Cu2+) equivalent to 1000 pmm of supfonic acid groups in PEM, a decrease in deteriorating rate of cell voltage was observed to be 83 mV/kh during 500-hour generation, in comparison with the cell without metal-ion comtamination showing 154 mV/kh. On the other hand, an increase in deteriorating rates were observed for the cells containing 10 % Cu2+ or 1000 ppm aluminum ions (Al3+). Al3+ adulteration in PEFC set off increases in activation overpotential and fluoride ion release rate (FRR) with proceeding genaration test. An increase in activation overpotentials was supressed in 1000 ppm Cu2+-adulterated cell and the reverse was observed in 10 % Cu2+-adulterated one, though Cu2+ adulterations suppressed growths of platinum catalyst particles in size and FRR regardless of Cu2+ concentration. Restriction effect of 1000 ppm Cu2+-adulteration into PEM on PEFC voltage deterioration has found to be the unprecedented knoledge with respect to PEFC degradation phenomena. Mechanisms of those influences were also discussed.

Amitani, Chieko; Ishikawa, Masahiko; Mori, Kouya; Tanaka, Kenji; Hori, Michio

352

Biologically engineered protein-graft-poly(ethylene glycol) hydrogels: A cell-adhesive and plasmin-degradable biosynthetic material for tissue repair  

NASA Astrophysics Data System (ADS)

The goal of the research presented in this dissertation was to create a biomimetic artificial material that exhibits functions of extracellular matrix relevant for improved nerve regeneration. Neural adhesion peptides were photoimmobilized on highly crosslinked poly(ethylene glycol)-based substrates that were otherwise non-adhesive. Neurons adhered in two-dimensional patterns for eleven hours, but no neurites extended. To enable neurite extension and nerve regeneration in three dimensions, and to address the need for specifically cell adhesive and cell degradable materials for clinical applications in tissue repair in general, an artificial protein was recombinantly expressed and purified that consisted of a repeating amino acid sequence based on fibrinogen and anti-thrombin III. The recombinant protein contained integrin-binding RGD sites, plasmin degradation sites, heparin binding sites, and six thiol-containing cysteine residues as grafting sites for poly(ethylene glycol) diacrylate via Michael-type conjugate addition. The resulting protein-graft-poly(ethylene glycol)acrylates were crosslinked by photopolymerization to form hydrogels. Although three-dimensional, RGD mediated and serine protease-dependent ingrowth of human fibroblasts into protein-graft-poly(ethylene glycol) hydrogels occurred, only surface neurite outgrowth was observed from chick dorsal root ganglia. Axonal outgrowth depended on the concentration of matrix-bound heparin, suggesting that improved mechanical strength of the hydrogels and possible immobilization of neuroactive factors due to the presence of heparin promoted neurite outgrowth. Together, the above results show that specific biological functions can be harnessed by protein-graft-poly(ethylene glycol) hydrogels to serve as matrices for tissue repair and regeneration. In particular, the two design objectives, specific cell adhesion and degradability by cell-associated proteases, were fulfilled by the material. In the future, this and similar artificial protein-graft-poly(ethylene glycol) materials with varying protein elements for improved wound healing might serve as biosynthetic implant materials or wound dressings that degrade in synchrony with the formation of a variety of target tissues.

Halstenberg, Sven

2002-01-01

353

Influence of Air Pollution and Humidity on Limestone Materials Degradation in Historical Buildings Located in Cities Under Tropical Coastal Climates  

Microsoft Academic Search

Climatic changes and the increased air pollution intensify the atmospheric degradation of stone, affecting the aspect and\\u000a integrity of valuable historical buildings constructed using limestone and located in tropical coastal sites. This paper analyzes\\u000a limestone degradation process due to air pollution and humidity in tropical humid conditions in historical buildings located\\u000a in the cities of Havana, Cuba and San Francisco

F. Corvo; J. Reyes; C. Valdes; F. Villaseñor; O. Cuesta; D. Aguilar; P. Quintana

2010-01-01

354

A Novel Photocatalytic Material for Removing Microcystin-LR under Visible Light Irradiation: Degradation Characteristics and Mechanisms  

PubMed Central

Background and Purpose Microcystin-LR (MC-LR), a common toxic species in contaminated aquatic systems, persists for long periods because of its cyclic structure. Ag3PO4 is an environment-friendly photocatalyst with relatively good degradation capacity for hazardous organic pollutants. This study aimed to investigate the degradation capacity of Ag3PO4 for MC-LR under visible light. Methods An Ag3PO4 photocatalyst was synthesized by the ion-exchange method and characterized by X-ray diffraction, field-emission scanning electron microscope, and UV-Vis spectrophotometer. MC-LR was quantified in each sample through high-performance liquid chromatograph. The degradation efficiency of MC-LR was affected by initial pH, initial Ag3PO4 concentration, initial MC-LR concentration, and recycle experiments. The degradation intermediates of MC-LR were examined by liquid chromatography-mass spectrometry (LC/MS). Results The degradation process can be well fitted with the pseudo-first-order kinetic model. The maximum MC-LR degradation rate of 99.98% can be obtained within 5 h under the following optimum conditions: pH of 5.01, Ag3PO4 concentration of 26.67 g/L, and MC-LR concentration of 9.06 mg/L. Nine intermediates were detected and analyzed by LC/MS. Three main degradation pathways were proposed based on the molecular weight of the intermediates and the reaction mechanism: (1) hydroxylation on the aromatic ring of Adda, (2) hydroxylation on the diene bonds of Adda, and (3) internal interactions on the cyclic structure of MC-LR. Conclusion Ag3PO4 is a highly efficient catalyst for MC-LR degradation in aqueous solutions. PMID:24755986

Sui, Xin; Wang, Xiangrong; Huang, Honghui; Peng, Guotao; Wang, Shoubing; Fan, Zhengqiu

2014-01-01

355

10 CFR 74.31 - Nuclear material control and accounting for special nuclear material of low strategic significance.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Nuclear material control and accounting for special nuclear material of low strategic significance. 74.31 Section 74.31 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

2011-01-01

356

10 CFR 74.41 - Nuclear material control and accounting for special nuclear material of moderate strategic...  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Nuclear material control and accounting for special nuclear material of moderate strategic significance. 74.41 Section 74.41 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

2012-01-01

357

10 CFR 74.41 - Nuclear material control and accounting for special nuclear material of moderate strategic...  

Code of Federal Regulations, 2011 CFR

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2011-01-01

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10 CFR 74.41 - Nuclear material control and accounting for special nuclear material of moderate strategic...  

Code of Federal Regulations, 2010 CFR

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2010-01-01

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10 CFR 74.31 - Nuclear material control and accounting for special nuclear material of low strategic significance.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Nuclear material control and accounting for special nuclear material of low strategic significance. 74.31 Section 74.31 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

2013-01-01

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10 CFR 74.31 - Nuclear material control and accounting for special nuclear material of low strategic significance.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Nuclear material control and accounting for special nuclear material of low strategic significance. 74.31 Section 74.31 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

2014-01-01

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10 CFR 74.31 - Nuclear material control and accounting for special nuclear material of low strategic significance.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Nuclear material control and accounting for special nuclear material of low strategic significance. 74.31 Section 74.31 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

2010-01-01

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10 CFR 74.41 - Nuclear material control and accounting for special nuclear material of moderate strategic...  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Nuclear material control and accounting for special nuclear material of moderate strategic significance. 74.41 Section 74.41 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

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363

10 CFR 74.31 - Nuclear material control and accounting for special nuclear material of low strategic significance.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Nuclear material control and accounting for special nuclear material of low strategic significance. 74.31 Section 74.31 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

2012-01-01

364

10 CFR 74.41 - Nuclear material control and accounting for special nuclear material of moderate strategic...  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Nuclear material control and accounting for special nuclear material of moderate strategic significance. 74.41 Section 74.41 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED)...

2014-01-01

365

Anaerobic degradation of inedible crop residues produced in a Controlled Ecological Life Support System  

NASA Technical Reports Server (NTRS)

An anaerobic reactor seeded with organisms from an anaerobic lagoon was used to study the degradation of inedible crop residues from potato and wheat crops grown in a closed environment. Conversion of this biomass into other products was also evaluated. Degradation of wheat volatile solids was about 25% where that of potato was about 50%. The main product of the anaerobic fermentation of both crops was acetic acid with smaller quantities of propionate and butyrate produced. Nitrate, known to be high in concentration in inedible potato and wheat biomass grown hydroponically, was converted to ammonia in the anaerobic reactor. Both volatile fatty acid and ammonia production may have implications in a crop production system.

Schwingel, W. R.; Sager, J. C.

1996-01-01

366

Multiple Sclerosis Autoantigen Myelin Basic Protein Escapes Control by Ubiquitination during Proteasomal Degradation*  

PubMed Central

The vast majority of cellular proteins are degraded by the 26S proteasome after their ubiquitination. Here, we report that the major component of the myelin multilayered membrane sheath, myelin basic protein (MBP), is hydrolyzed by the 26S proteasome in a ubiquitin-independent manner both in vitro and in mammalian cells. As a proteasomal substrate, MBP reveals a distinct and physiologically relevant concentration range for ubiquitin-independent proteolysis. Enzymatic deimination prevents hydrolysis of MBP by the proteasome, suggesting that an abnormally basic charge contributes to its susceptibility toward proteasome-mediated degradation. To our knowledge, our data reveal the first case of a pathophysiologically important autoantigen as a ubiquitin-independent substrate of the 26S proteasome. PMID:24739384

Belogurov, Alexey; Kudriaeva, Anna; Kuzina, Ekaterina; Smirnov, Ivan; Bobik, Tatyana; Ponomarenko, Natalia; Kravtsova-Ivantsiv, Yelena; Ciechanover, Aaron; Gabibov, Alexander

2014-01-01

367

Control of spoT -dependent ppGpp Synthesis and Degradation in Escherichia coli  

Microsoft Academic Search

Escherichia colihas two ppGpp synthetases, PSI and PSII, encoded by therelAandspoTgenes. The spoT gene also encodes a ppGpp hydrolase. During exponential growth and under various starvation conditions, the level of ppGpp depends on the balance of ppGpp synthetic and degradative activities ofspoTgene products. To find out how these two activities respond to different physiological conditions and to learn about the

Daniel K. Murray; Hans Bremer

1996-01-01

368

A new neutron absorber material for criticality control  

SciTech Connect

A new neutron absorber material based on a nickel metal matrix composite has been developed for applications such as the Transport, Aging, and Disposal (TAD) canister for the Yucca Mountain Project. This new material offers superior corrosion resistance to withstand the more demanding geochemical environments found in a 300,000 year to a million year repository. The lifetime of the TAD canister is currently limited to 10,000 years, reflecting the focus of current regulations embodied in 10 CFR 63. The use of DOE-owned nickel stocks from decommissioned enrichment facilities could reduce the cost compared to stainless steel/boron alloy. The metal matrix composite allows the inclusion of more than one neutron absorber compound, so that the exact composition may be adjusted as needed. The new neutron absorber material may also be used for supplementary criticality control of stored or transported PWR spent fuel by forming it into cylindrical pellets that can be inserted into a surrogate control rod. (authors)

Wells, Alan H. [PhD Consultant, 2846 Peachtree Walk, Duluth, GA 30096 (United States)

2007-07-01

369

[Heavy metal]-Chlorophylls Formed in Vivo During Heavy Metal Stress and Degradation Products Formed During Digestion, Extraction and Storage of Plant Material  

Microsoft Academic Search

This chapter discusses the occurrence, properties and relevance of chlorophyll (Chl) degradation products that are formed\\u000a either in vivo in heavy metal-stressed plants or by digestion of algae in marine invertebrates, or that are formed during extraction or processing of dead plant material. The in vivo substitution of the central Mg2+ ion of chlorophyll by heavy metals constitutes an important

Hendrik Küpper; Frithjof C. Küpper; Martin Spiller

370

Control of Cellular Bcl-xL Levels by Deamidation-Regulated Degradation  

PubMed Central

The cellular concentration of Bcl-xL is among the most important determinants of treatment response and overall prognosis in a broad range of tumors as well as an important determinant of the cellular response to several forms of tissue injury. We and others have previously shown that human Bcl-xL undergoes deamidation at two asparaginyl residues and that DNA-damaging antineoplastic agents as well as other stimuli can increase the rate of deamidation. Deamidation results in the replacement of asparginyl residues with aspartyl or isoaspartyl residues. Thus deamidation, like phosphorylation, introduces a negative charge into proteins. Here we show that the level of human Bcl-xL is constantly modulated by deamidation because deamidation, like phosphorylation in other proteins, activates a conditional PEST sequence to target Bcl-xL for degradation. Additionally, we show that degradation of deamidated Bcl-xL is mediated at least in part by calpain. Notably, we present sequence and biochemical data that suggest that deamidation has been conserved from the simplest extant metazoans through the human form of Bcl-xL, underscoring its importance in Bcl-xL regulation. Our findings strongly suggest that deamidation-regulated Bcl-xL degradation is an important component of the cellular rheostat that determines susceptibility to DNA-damaging agents and other death stimuli. PMID:23823868

Dho, So Hee; Deverman, Benjamin E.; Lapid, Carlo; Manson, Scott R.; Gan, Lu; Riehm, Jacob J.; Aurora, Rajeev; Kwon, Ki-Sun; Weintraub, Steven J.

2013-01-01

371

Effects of Contamination, UV Radiation, and Atomic Oxygen on ISS Thermal Control Materials  

NASA Technical Reports Server (NTRS)

Thermal control surfaces on the International Space Station (ISS) have been tailored for optimum optical properties. The space environment, particularly contamination, ultraviolet (UV) radiation, and atomic oxygen (AO) may have a detrimental effect on these optical properties. These effects must be quantified for modeling and planning. Also of interest was the effect of porosity on the reaction to simulated space environment. Five materials were chosen for this study based on their use on ISS. The thermal control materials were Z-93 white coating, silverized Teflon, chromic acid anodized aluminum, sulfuric acid anodized aluminum, and 7075-T6 aluminum. Some of the samples were exposed to RTV 560 silicone; others were exposed to Tefzel offgassing products. Two samples of Z-93 were not exposed to contamination as clean "controls". VUV radiation was used to photo-fix the contaminant to the material surface, then the samples were exposed to AO. All samples were exposed to 1000 equivalent sun-hours (ESH) of vacuum ultraviolet radiation (VUV) at the AZ Technology facility and a minimum of 1.5 x 10(exp 20) atoms/sq cm of AO at Marshall Space Flight Center. Half of the samples were exposed to an additional 2000 ESH of VUV at Huntington Beach prior to sent to AZ Technology. Darkening of the Z-93 white coating was noted after VUV exposure. AO exposure did bleach the Z-93 but not back to its original brightness. Solar absorptance curves show the degradation due to contamination and VUV and the recovery with AO exposure. More bleaching was noted on the Tefzel-contaminated samples than with the RTV-contaminated samples.

Visentine, Jim; Finckenor, Miria; Zwiener, Jim; Munafo, Paul (Technical Monitor)

2001-01-01

372

Control of degradation of spent LWR (light-water reactor) fuel during dry storage in an inert atmosphere  

SciTech Connect

Dry storage of Zircaloy-clad spent fuel in inert gas (referred to as inerted dry storage or IDS) is being developed as an alternative to water pool storage of spent fuel. The objectives of the activities described in this report are to identify potential Zircaloy degradation mechanisms and evaluate their applicability to cladding breach during IDS, develop models of the dominant Zircaloy degradation mechanisms, and recommend cladding temperature limits during IDS to control Zircaloy degradation. The principal potential Zircaloy cladding breach mechanisms during IDS have been identified as creep rupture, stress corrosion cracking (SCC), and delayed hydride cracking (DHC). Creep rupture is concluded to be the primary cladding breach mechanism during IDS. Deformation and fracture maps based on creep rupture were developed for Zircaloy. These maps were then used as the basis for developing spent fuel cladding temperature limits that would prevent cladding breach during a 40-year IDS period. The probability of cladding breach for spent fuel stored at the temperature limit is less than 0.5% per spent fuel rod. 52 refs., 7 figs., 1 tab.

Cunningham, M.E.; Simonen, E.P.; Allemann, R.T.; Levy, I.S.; Hazelton, R.F.

1987-10-01

373

Dysprosium titanate as an absorber material for control rods  

NASA Astrophysics Data System (ADS)

Disprosium titanate is an attractive control rod material for the thermal neutron reactors. Its main advantages are: insignificant swelling, no out-gassing under neutron irradiation, rather high neutron efficiency, a high melting point (˜1870°C), non-interaction with the cladding at temperatures above 1000°C, simple fabrication and easily reprocessed non-radioactive waste. It can be used in control rods as pellets and powder. The disprosium titanate control rods have worked off in the MIR reactor for 17 years, in VVER-1000 - for 4 years without any operating problems. After post-irradiation examinations this type of control rod having high lifetime was recommended for the VVER and RBMK. The paper presents the examination results of absorber element dummies containing dysprosium titanate, irradiated in the SM reactor to the neutron fluence of 3.4×10 22 cm -2 ( E>0.1 MeV) and, also, the data on structure, thermal-physical properties of dysprosium titanate, efficiency of dysprosium titanate control rods.

Risovany, V. D.; Varlashova, E. E.; Suslov, D. N.

2000-09-01

374

Selection of optimal composition-control parameters for friable materials  

SciTech Connect

A method for composition analysis of coal and minerals is proposed which uses scattered gamma radiation and does away with preliminary sample preparation to ensure homogeneous particle density, surface area, and size. Reduction of the error induced by material heterogeneity has previously been achieved by rotation of the control object during analysis. A further refinement is proposed which addresses the necessity that the contribution of the radiation scattered from each individual surface to the total intensity be the same. This is achieved by providing a constant linear rate of travel for the irradiated spot through back-and-forth motion of the sensor. An analytical expression is given for the laws of motion for the sensor and test tube which provides for uniform irradiated area movement along a path analogous to the Archimedes spiral. The relationships obtained permit optimization of measurement parameters in analyzing friable materials which are not uniform in grain size.

Pak, Yu.N.; Vdovkin, A.V.

1988-05-01

375

Methodology for materials control and accounting information systems  

SciTech Connect

Modern approaches to nuclear materials safeguards have significantly increased the data processing needs of safeguards information systems. Implementing these approaches will require developing efficient, cost-effective designs. Guided by database design research, we are developing a design methodology for distributed materials control and accounting (MC and A) information systems. The methodology considers four design parameters: network topology, allocation of data to nodes, high-level global processing strategy, and local file structures to optimize system performance. Characteristics of system performance that are optimized are response time for an operation, timeliness of data, validity of data, and reliability. The ultimate goal of the research is to develop a comprehensive computerized design tool specifically tailored to the design of MC and A systems.

Helman, P.; Strittmatter, R.B.

1987-01-01

376

PEM fuel cell degradation  

SciTech Connect

The durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. While significant progress has been made in understanding degradation mechanisms and improving materials, further improvements in durability are required to meet commercialization targets. Catalyst and electrode durability remains a primary degradation mode, with much work reported on understanding how the catalyst and electrode structure degrades. Accelerated Stress Tests (ASTs) are used to rapidly evaluate component degradation, however the results are sometimes easy, and other times difficult to correlate. Tests that were developed to accelerate degradation of single components are shown to also affect other component's degradation modes. Non-ideal examples of this include ASTs examining catalyst degradation performances losses due to catalyst degradation do not always well correlate with catalyst surface area and also lead to losses in mass transport.

Borup, Rodney L [Los Alamos National Laboratory; Mukundan, Rangachary [Los Alamos National Laboratory

2010-01-01

377

Development of Tailorable Electrically Conductive Thermal Control Material Systems  

NASA Technical Reports Server (NTRS)

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and have been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties as well as mechanical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has added to already existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The objective of this program was to develop two types of passive electrically conductive TCMS. The first was a highly absorbing/emitting black surface and the second was a low (alpha(sub s)/epsilon(sub N)) type white surface. The surface resistance goals for the black absorber was 10(exp 4) to 10(exp 9) Omega/square, and for the white surfaces it was 10(exp 6) to 10(exp 10) Omega/square. Several material system concepts were suggested and evaluated for space environment stability and electrical performance characterization. Our efforts in designing and evaluating these material systems have resulted in several developments. New concepts, pigments and binders have been developed to provide new engineering quality TCMS. Some of these have already found application on space hardware, some are waiting to be recognized by thermal designers, and some require further detailed studies to become state-of-the-art for future space hardware and space structures. Our studies on baseline state-of-the-art materials and conductive concepts have resulted in several important findings that are of interest to all thermal designers and systems integrators.

Deshpande, M. S.; Harada, Y.

1997-01-01

378

Methods of measurement for semiconductor materials, process control, and devices  

NASA Technical Reports Server (NTRS)

Activities directed toward the development of methods of measurement for semiconductor materials, process control, and devices are described. Topics investigated include: measurements of transistor delay time; application of the infrared response technique to the study of radiation-damaged, lithium-drifted silicon detectors; and identification of a condition that minimizes wire flexure and reduces the failure rate of wire bonds in transistors and integrated circuits under slow thermal cycling conditions. Supplementary data concerning staff, standards committee activities, technical services, and publications are included as appendixes.

Bullis, W. M. (editor)

1972-01-01

379

Methods of measurement for semiconductor materials, process control, and devices  

NASA Technical Reports Server (NTRS)

The development of methods of measurement for semiconductor materials, process control, and devices is discussed. The following subjects are also presented: (1) demonstration of the high sensitivity of the infrared response technique by the identification of gold in a germanium diode, (2) verification that transient thermal response is significantly more sensitive to the presence of voids in die attachment than steady-state thermal resistance, and (3) development of equipment for determining susceptibility of transistors to hot spot formation by the current-gain technique.

Bullis, W. M. (editor)

1971-01-01

380

Controlled Chemistry Helium High Temperature Materials Test Loop  

SciTech Connect

A system to test aging and environmental effects in flowing helium with impurity content representative of the Next Generation Nuclear Plant (NGNP) has been designed and assembled. The system will be used to expose microstructure analysis coupons and mechanical test specimens for up to 5,000 hours in helium containing potentially oxidizing or carburizing impurities controlled to parts per million levels. Impurity levels in the flowing helium are controlled through a feedback mechanism based on gas chromatography measurements of the gas chemistry at the inlet and exit from a high temperature retort containing the test materials. Initial testing will focus on determining the nature and extent of combined aging and environmental effects on microstructure and elevated temperature mechanical properties of alloys proposed for structural applications in the NGNP, including Inconel 617 and Haynes 230.

Richard N. WRight

2005-08-01

381

Degradation Scheme graceful degradation  

E-print Network

degradation scheme OS degradation scheme OS Solaris Linux FreeBSD Windows Server Linux 3 OS Tomcat Solaris OS # of concurrent requests (Heavy) 0 1 2 3 4 Requests/sec(Heavy) (a) Solaris 9 (b) FreeBSD 5.2.1 (c) Windows 2003 Tomcat Solaris 9 Linux 2.6.7 2.6.5 2.4.18 FreeBSD 5.2.1 Windows 2003 Server Enterprise Edition Xeon 3

Chiba, Shigeru

382

Controlling the band gap energy of cluster-assembled materials.  

PubMed

Cluster-assembled materials combine the nanoscale size and composition-dependent properties of clusters, which have highly tunable magnetic and electronic properties useful for a great variety of potential technologies. To understand the emergent properties as clusters are assembled into hierarchical materials, we have synthesized 23 cluster-assembled materials composed of As7(3-)-based motifs and different countercations and measured their band gap energies. We found that the band gap energy varies from 1.09 to 2.21 eV. In addition, we have carried out first principles electronic structure studies to identify the physical mechanisms that enable control of the band gap edges of the cluster assemblies. The choice of counterion has a profound effect on the band gap energy in ionic cluster assemblies. The top of the valence band is localized on the arsenic cluster, while the conduction band edge is located on the alkali metal counterions. Changing the counterion changes the position of the conduction band edge, enabling control of the band gap energy. We can also vary the architecture of the ionic solid by incorporating cryptates as counterions, which provide charge but are separated from the clusters by bulky ligands. Higher dimensionality typically decreases the band gap energy through band broadening; however band gap energies increased upon moving from zero-dimensional (0D) to two-dimensional (2D) assemblies. This is because internal electric fields generated by the counterion preferentially stabilize the adjacent lone pair orbitals that mark the top of the valence band. Thus, the choice of the counterion can control the position of the conduction band edge of ionic cluster assemblies. In addition, the dimensionality of the solid via internal electric fields can control the valence band edge. Through covalently linking arsenic clusters into composite building blocks, we have also been able to tune the band gap energy. We used a theoretical description based on cluster orbital theory to provide microscopic understanding of the electronic character of the composite building blocks and the observed variations in the band gap energy. Also, we have shown how dimeric linkers can be used to control the band gap energy. Lastly, we also investigated the effects of charge transfer complexes of M(CO)3 on the band gap energy. PMID:23734558

Mandal, Sukhendu; Reber, Arthur C; Qian, Meichun; Weiss, Paul S; Khanna, Shiv N; Sen, Ayusman

2013-11-19

383

Bacterial populations and environmental factors controlling cellulose degradation in an acidic Sphagnum peat.  

PubMed

Northern peatlands represent a major global carbon store harbouring approximately one-third of the global reserves of soil organic carbon. A large proportion of these peatlands consists of acidic Sphagnum-dominated ombrotrophic bogs, which are characterized by extremely low rates of plant debris decomposition. The degradation of cellulose, the major component of Sphagnum-derived litter, was monitored in long-term incubation experiments with acidic (pH 4.0) peat extracts. This process was almost undetectable at 10°C and occurred at low rates at 20°C, while it was significantly accelerated at both temperature regimes by the addition of available nitrogen. Cellulose breakdown was only partially inhibited in the presence of cycloheximide, suggesting that bacteria participated in this process. We aimed to identify these bacteria by a combination of molecular and cultivation approaches and to determine the factors that limit their activity in situ. The indigenous bacterial community in peat was dominated by Alphaproteobacteria and Acidobacteria. The addition of cellulose induced a clear shift in the community structure towards an increase in the relative abundance of the Bacteroidetes. Increasing temperature and nitrogen availability resulted in a selective development of bacteria phylogenetically related to Cytophaga hutchinsonii (94-95% 16S rRNA gene sequence similarity), which densely colonized microfibrils of cellulose. Among isolates obtained from this community only some subdivision 1 Acidobacteria were capable of degrading cellulose, albeit at a very slow rate. These Acidobacteria represent indigenous cellulolytic members of the microbial community in acidic peat and are easily out-competed by Cytophaga-like bacteria under conditions of increased nitrogen availability. Members of the phylum Firmicutes, known to be key players in cellulose degradation in neutral habitats, were not detected in the cellulolytic community enriched at low pH. PMID:21564458

Pankratov, Timofey A; Ivanova, Anastasia O; Dedysh, Svetlana N; Liesack, Werner

2011-07-01

384

Exposure of Polymer Film Thermal Control Materials on the Materials International Space Station Experiment (MISSE)  

NASA Technical Reports Server (NTRS)

Seventy-nine samples of polymer film thermal control (PFTC) materials have been provided by the National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) for exposure to the low Earth orbit environment on the exterior of the International Space Station (ISS) as part of the Materials International Space Station Experiment (MISSE). MISSE is a materials flight experiment sponsored by the Air Force Research Lab/Materials Lab and NASA. This paper will describe background, objectives, and configurations for the GRC PFTC samples for MISSE. These samples include polyimides, fluorinated polyimides, and Teflon fluorinated ethylene propylene (FEP) with and without second-surface metallizing layers and/or surface coatings. Also included are polyphenylene benzobisoxazole (PBO) and a polyarylene ether benzimidazole (TOR-LM). On August 16, 2001, astronauts installed passive experiment carriers (PECs) on the exterior of the ISS in which were located twenty-eight of the GRC PFTC samples for 1-year space exposure. MISSE PECs for 3-year exposure, which will contain fifty-one GRC PFTC samples, will be installed on the ISS at a later date. Once returned from the ISS, MISSE GRC PFTC samples will be examined for changes in optical and mechanical properties and atomic oxygen (AO) erosion. Additional sapphire witness samples located on the AO exposed trays will be examined for deposition of contaminants.

Dever, Joyce; Miller, Sharon; Messer, Russell; Sechkar, Edward; Tollis, Greg

2002-01-01

385

Drug Release Kinetics and Transport Mechanisms of Non-degradable and Degradable Polymeric Delivery Systems  

PubMed Central

Importance of the field The advancement in material design and engineering has led to the rapid development of novel materials with increasing complexity and functions. Both non-degradable and degradable polymers have found wide applications in the controlled delivery field. Studies on drug release kinetics provide important information into the function of material systems. To elucidate the detailed transport mechanism and the structure-function relationship of a material system, it is critical to bridge the gap between the macroscopic data and the transport behavior at the molecular level. Areas covered in this review The structure and function information of selected non-degradable and degradable polymers have been collected and summarized from literatures published after 1990s. The release kinetics of selected drug compounds from various material systems will be discussed in case studies. Recent progresses in the mathematical models based on different transport mechanisms will be highlighted. What the reader will gain This article aims to provide an overview of structure-function relationships of selected non-degradable and degradable polymers as drug delivery matrices. Take home message Understanding the structure-function relationship of the material system is key to the successful design of a delivery system for a particular application. Moreover, developing complex polymeric matrices requires more robust mathematical models to elucidate the solute transport mechanisms. PMID:20331353

Fu, Yao; Kao, Weiyuan John

2010-01-01

386

The F-BAR protein PSTPIP1 controls extracellular matrix degradation and filopodia formation in macrophages.  

PubMed

PSTPIP1 is a cytoskeletal adaptor and F-BAR protein that has been implicated in autoinflammatory disease, most notably in the PAPA syndrome: pyogenic sterile arthritis, pyoderma gangrenosum, and acne. However, the mechanism by which PSTPIP1 regulates the actin cytoskeleton and contributes to disease pathogenesis remains elusive. Here, we show that endogenous PSTPIP1 negatively regulates macrophage podosome organization and matrix degradation. We identify a novel PSTPIP1-R405C mutation in a patient presenting with aggressive pyoderma gangrenosum. Identification of this mutation reveals that PSTPIP1 regulates the balance of podosomes and filopodia in macrophages. The PSTPIP1-R405C mutation is in the SRC homology 3 (SH3) domain and impairs Wiskott-Aldrich syndrome protein (WASP) binding, but it does not affect interaction with protein-tyrosine phosphatase (PTP)-PEST. Accordingly, WASP inhibition reverses the elevated F-actin content, filopodia formation, and matrix degradation induced by PSTPIP1-R405C. Our results uncover a novel role for PSTPIP1 and WASP in orchestrating different types of actin-based protrusions. Our findings implicate the cytoskeletal regulatory functions of PSTPIP1 in the pathogenesis of pyoderma gangrenosum and suggest that the cytoskeleton is a rational target for therapeutic intervention in autoinflammatory disease. PMID:24421327

Starnes, Taylor W; Bennin, David A; Bing, Xinyu; Eickhoff, Jens C; Grahf, Daniel C; Bellak, Jason M; Seroogy, Christine M; Ferguson, Polly J; Huttenlocher, Anna

2014-04-24

387

Osmotic control of glycine betaine biosynthesis and degradation in Rhizobium meliloti  

SciTech Connect

Intracellular accumulation of glycine betaine has been shown to confer an enhanced level of osmotic stress tolerance in Rhizobium meliloti. In this study, the authors used a physiological approach to investigate the mechanism by which glycine betaine is accumulated in osmotically stressed R. meliloti. Results from growth experiments, /sup 14/C labeling of intermediates, and enzyme activity assays are presented. The results provide evidence for the pathway of biosynthesis and degradation of glycine betaine and the osmotic effects on this pathway. High osmolarity in the medium decreased the activities of the enzymes involved in the degradation of glycine betaine but not those of enzymes that lead to its biosynthesis from choline. Thus, the concentration of the osmoprotectant glycine betaine is increased in stressed cells. This report demonstrates the ability of the osmolarity of the growth medium to regulate the use of glycine betaine as a carbon and nitrogen source or as an osmoprotectant. The mechanisms of osmoregulation in R. meliloti and Escherichia coli are compared.

Smith, L.T.; Pocard, J.A.; Bernard, T.; Le Rudulier, D.

1988-07-01

388

Serum amyloid P component controls chromatin degradation and prevents antinuclear autoimmunity.  

PubMed

Serum amyloid P component (SAP), a highly conserved plasma protein named for its universal presence in amyloid deposits, is the single normal circulating protein that shows specific calcium-dependent binding to DNA and chromatin in physiological conditions. The avid binding of SAP displaces H1-type histones and thereby solubilizes native long chromatin, which is otherwise profoundly insoluble at the physiological ionic strength of extracellular fluids. Furthermore, SAP binds in vivo both to apoptotic cells, the surface blebs of which bear chromatin fragments, and to nuclear debris released by necrosis. SAP may therefore participate in handling of chromatin exposed by cell death. Here we show that mice with targeted deletion of the SAP gene spontaneously develop antinuclear autoimmunity and severe glomerulonephritis, a phenotype resembling human systemic lupus erythematosus, a serious autoimmune disease. The SAP-/- mice also have enhanced anti-DNA responses to immunization with extrinsic chromatin, and we demonstrate that degradation of long chromatin is retarded in the presence of SAP both in vitro and in vivo. These findings indicate that SAP has an important physiological role, inhibiting the formation of pathogenic autoantibodies against chromatin and DNA, probably by binding to chromatin and regulating its degradation. PMID:10371509

Bickerstaff, M C; Botto, M; Hutchinson, W L; Herbert, J; Tennent, G A; Bybee, A; Mitchell, D A; Cook, H T; Butler, P J; Walport, M J; Pepys, M B

1999-06-01

389

Signal Transducer and Activator of Transcription 3 (STAT3) Degradation by Proteasome Controls a Developmental Switch in Neurotrophin Dependence*  

PubMed Central

Neonatal brains develop through a program that eliminates about half of the neurons. During this period, neurons depend on neurotrophins for their survival. Recently, we reported that, at the conclusion of the naturally occurring death period, neurons become neurotrophin-independent and, further, that this developmental switch is achieved by the emergence of a second survival pathway mediated by signal transducer and activator of transcription 3 (STAT3). Here I show that calcineurin plays a key role in controlling the developmental switch in mouse hippocampal neurons. Calcineurin promotes the degradation of STAT3 via the ubiquitin-proteasome pathway. Inhibition of calcineurin acutely increases total levels of STAT3 as well as its activated forms, resulting in decreased levels of the tumor suppressor p53 and its proapoptotic target, Bax. In vivo and in vitro, calcineurin regulates levels of STAT3 and neurotrophin dependence. TMF/ARA 160 (TATA element modulatory factor/androgen receptor co-activator 160), the key mediator of STAT3 ubiquitination, is required for calcineurin-dependent STAT3 degradation. Thus, these results show that the ubiquitin-proteasome pathway controls the critical developmental switch of neurotrophin dependence in the newborn hippocampus. PMID:23733189

Murase, Sachiko

2013-01-01

390

Controlled doping of semiconducting titania nanosheets for tailored spinelectronic materials  

NASA Astrophysics Data System (ADS)

Ti1-x-yFexCoyO2 nanosheets are synthesized in which the (Fe/Co) content is systematically controlled in the range of 0 <= x <= 0.4 and 0 <= y <= 0.2. A key feature of this new preparation is the use of (Li/Fe)-, (Fe/Co)- and (Li/Co)-co-substituted layered titanates as starting materials. In exfoliated nanosheets, the composition can be intentionally modified by controlled Fe/Co substitution into Ti sites during the solid-state synthesis of the starting layered compounds. The composition of the host layers is maintained in the subsequent exfoliation process, which is very helpful in the rational design of nanosheets through the use of controlled doping. Through this controlled doping, we achieve exquisite control of the electronic properties of Ti1-?O2 nanosheets, including the position of impurity bands, the Fermi energy and ferromagnetic properties. From photoelectron spectroscopy and first-principles studies, we have observed that the use of Fe/Co co-doping with higher Fe and Co oxidation states is necessary to bring the highest occupied Fe/Co impurity states to the Fermi level. This band engineering transforms the Ti1-x-yFexCoyO2 nanosheet into a room-temperature half-metallic ferromagnet, thus accomplishing the main requirements of future spinelectronics.Ti1-x-yFexCoyO2 nanosheets are synthesized in which the (Fe/Co) content is systematically controlled in the range of 0 <= x <= 0.4 and 0 <= y <= 0.2. A key feature of this new preparation is the use of (Li/Fe)-, (Fe/Co)- and (Li/Co)-co-substituted layered titanates as starting materials. In exfoliated nanosheets, the composition can be intentionally modified by controlled Fe/Co substitution into Ti sites during the solid-state synthesis of the starting layered compounds. The composition of the host layers is maintained in the subsequent exfoliation process, which is very helpful in the rational design of nanosheets through the use of controlled doping. Through this controlled doping, we achieve exquisite control of the electronic properties of Ti1-?O2 nanosheets, including the position of impurity bands, the Fermi energy and ferromagnetic properties. From photoelectron spectroscopy and first-principles studies, we have observed that the use of Fe/Co co-doping with higher Fe and Co oxidation states is necessary to bring the highest occupied Fe/Co impurity states to the Fermi level. This band engineering transforms the Ti1-x-yFexCoyO2 nanosheet into a room-temperature half-metallic ferromagnet, thus accomplishing the main requirements of future spinelectronics. Electronic supplementary information (ESI) available: Details on XRD data, chemical analysis results, Raman spectra, UV-Visible absorption spectra for multilayer films, first-principles DFT calculations on the magnetic properties, resistivity vs. the reciprocal temperature of Ti0.75Fe0.1Co0.15O2. See DOI: 10.1039/c4nr04465g

Osada, Minoru; Yoguchi, Satoshi; Itose, Masayuki; Li, Bao-Wen; Ebina, Yasuo; Fukuda, Katsutoshi; Kotani, Yoshinori; Ono, Kanta; Ueda, Shigenori; Sasaki, Takayoshi

2014-11-01

391

Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique  

NASA Astrophysics Data System (ADS)

Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin-avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin-biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area.

Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu

2014-04-01

392

Helicopter control response types for hover and low-speed near-earth tasks in degraded visual conditions  

NASA Technical Reports Server (NTRS)

The NASA-Ames Vertical Motion Simulator and Dig 1 Computer Image Generator (CIG) have been used to simulate a helicopter cockpit in a degraded visual environment in order to assess several control-response types during low-level flight. CIG visibility was reduced to the point where the horizon and other far-field cues were indiscernible. The control-response types encompassed a rate command, an attitude command/hold, and a translational rate command; piloting tasks were hover, vertical landing, a pirouette, acceleration/deceleration, and a sidestep maneuver. Visual cue ratings with a rate-command response type were initially collected to set the usable cue environment at 3. A rate-command response type provided poor Level 2 handling qualities.

Blanken, Christopher L.; Hart, Daniel C.; Hoh, Roger H.

1991-01-01

393

Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique  

PubMed Central

Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin–avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin–biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area. PMID:24770668

Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu

2014-01-01

394

77 FR 60482 - Regulatory Guide 5.67, Material Control and Accounting for Uranium Enrichment Facilities...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Material Control and Accounting for Uranium Enrichment Facilities Authorized To Produce...Material Control and Accounting for Uranium Enrichment Facilities Authorized to Produce...FNMC) Plan Required for Low-Enriched Uranium Facilities'' which was issued in...

2012-10-03

395

A preliminary study of the degradation of cyanoacrylate adhesives in the presence and absence of fossil material  

Microsoft Academic Search

Fossils are frequently conserved with cyanoacrylate (CA) adhesives, which have never been scientifically assessed for their long-term stability and suitability for this application. The degradation of three types of CA adhesives were studied: an ethyl CA, an ethyl CA with added poly(methyl methacrylate) (PMMA), and a butyl CA, in the presence and absence of five different fossils obtained from various

Jane L. Down; Elzbieta Kaminska

2006-01-01

396

Biologically inspired autonomous structural materials with controlled toughening and healing  

NASA Astrophysics Data System (ADS)

The field of structural health monitoring (SHM) has made significant contributions in the field of prognosis and damage detection in the past decade. The advantageous use of this technology has not been integrated into operational structures to prevent damage from propagating or to heal injured regions under real time loading conditions. Rather, current systems relay this information to a central processor or human operator, who then determines a course of action such as altering the mission or scheduling repair maintenance. Biological systems exhibit advanced sensory and healing traits that can be applied to the design of material systems. For instance, bone is the major structural component in vertebrates; however, unlike modern structural materials, bone has many properties that make it effective for arresting the propagation of cracks and subsequent healing of the fractured area. The foremost goal for the development of future adaptive structures is to mimic biological systems, similar to bone, such that the material system can detect damage and deploy defensive traits to impede damage from propagating, thus preventing catastrophic failure while in operation. After sensing and stalling the propagation of damage, the structure must then be repaired autonomously using self healing mechanisms motivated by biological systems. Here a novel autonomous system is developed using shape memory polymers (SMPs), that employs an optical fiber network as both a damage detection sensor and a network to deliver stimulus to the damage site initiating adaptation and healing. In the presence of damage the fiber optic fractures allowing a high power laser diode to deposit a controlled level of thermal energy at the fractured sight locally reducing the modulus and blunting the crack tip, which significantly slows the crack growth rate. By applying a pre-induced strain field and utilizing the shape memory recovery effect, thermal energy can be deployed to close the crack and return the system to its original operating state. The entire system will effectively detect, self toughen, and subsequently heal damage as biological materials such as bone does.

Garcia, Michael E.; Sodano, Henry A.

2010-04-01

397

Creep loading during degradation attenuates mechanical property loss in PLGA.  

PubMed

While absorbable materials and medical devices primarily degrade through hydrolysis, their degradation kinetics are sensitive to environmental conditions, including temperature, pH, and mechanical loading. While there is some consistent information in the literature suggesting that strain controlled loading accelerates strength loss, there is much more limited information on the interaction between degradation and mechanical load applied under force control. Force control conditions impose a different stress state on the material and therefore, may exhibit different effects on degradation. In this study, the interaction between loading and degradation rate for an exemplary absorbable polymer, poly(l-lactide-co-glycolide), was investigated. The results indicated that load during degradation results in significant polymer creep, which is associated with increased force loss, but decreased strength loss (i.e., stress based parameters such as ultimate stress). This study further identified that changes to the degradation kinetics from exposure to loading were not associated with alterations to polymer crystallinity but were associated with delayed loss of molecular weight. Overall, these results demonstrate the importance of investigating the interaction between loading and degradation and that physical changes, such as those induced by creep, rather than chemical changes offer the strongest explanation for alteration of degradation kinetics. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 700-708, 2015. PMID:25052133

Dreher, Maureen L; Nagaraja, Srinidhi; Li, Jian

2015-04-01

398

Location of the Genes That Control Induction of the Allantoin-Degrading Enzymes in SACCHAROMYCES CEREVISIAE  

PubMed Central

In an effort to understand the regulation of allantoin degradation in Saccharomyces cerevisiae, we isolated two classes of mutants, each defective in the induction process associated with production of the pathway enzymes. Mutation at one locus (DAL80) results in constitutive expression of the genes involved in allantoin catabolism. Mutation at the second locus (DAL-81) results in the loss of ability to induce these enzymes. This report describes genetic data indicating that the DAL80 and DAL81 loci are situated approximately 13 cM from the centromere on the right arm of chromosome XI and 9 cM proximal to the DAL1 locus on chromosome IX, respectively. PMID:6392015

Turoscy, Vanessa; Chisholm, George; Cooper, Terrance G.

1984-01-01

399

46 CFR 128.240 - Hydraulic or pneumatic power and control-materials and pressure design.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Hydraulic or pneumatic power and control-materials...Materials and Pressure Design § 128.240 Hydraulic or pneumatic power and control—materials...flanges, and standard valves) for hydraulic or pneumatic power and control...

2010-10-01

400

Federal Automated Information System of Nuclear Material Control and Accounting: Uniform System of Reporting Documents  

Microsoft Academic Search

One of the fundamental regulations of the Russian State System for Nuclear Material Accounting and Control (SSAC), ''Basic Nuclear Material Control and Accounting Rules,'' directed that a uniform report system be developed to support the operation of the SSAC. According to the ''Regulation on State Nuclear Material Control and Accounting,'' adopted by the Russian Federation Government, Minatom of Russia is

M V Pitel; L Kasumova; R A Babcock; C Heinberg

2003-01-01

401

Degradation mechanisms of carbon-based electrocatalyst support materials and development of an advanced support based on electrically conducting diamond  

NASA Astrophysics Data System (ADS)

In this dissertation, the degradation mechanisms of sp 2-bonded carbon electrocatalyst supports were studied under potential and temperature conditions relevant to the polymer electrolyte membrane fuel cell (PEMFC). In addition, an alternative support was fabricated in two forms: electrically conducting diamond powder and paper to overcome current material stability issues in the PEMFC. Two structurally well-characterized sp2-bonded carbon powders, graphite (structurally well-ordered) and glassy carbon (GC, structurally disordered) were studied under potentiostatic polarization from 1.0 to 1.6 V vs. Ag/AgCl at 25, 50, and 80°C. Characterization of the surface oxidation and microstructural changes (i.e., increase in the exposed edge plane density) provided evidence for the so-called order/disorder mechanism where structurally disordered carbons corrode more severely because of oxidation and gasification of the exposed edge plane. Microstructural changes for graphite were heterogeneously distributed across the electrode surface. This is indicative of a nucleation and growth process, where disordered regions and defects serve as active sites for electrochemical corrosion, while other, more structurally ordered regions do not corrode. Preliminary results for a high-surface-area carbon black, Vulcan XC-72, are presented that show changes in the surface oxide content and also discuss the effect of polarization potential on Pt activity. The physical and electrochemical properties of two commercial boron-doped diamond thin-film electrodes were compared with microcrystalline and nanocrystalline boron-doped diamond thin film deposited in our laboratory. The electrochemical response for Fe(CN)63-/4-, Ru(NH3)6 3+/2+, IrCl62-/3-, 4-methylcatechol, and Fe3+/2+ was quite reproducible from electrode type-to-type and from film-to-film for a given type. DeltaEp, ipox, and ip red values for Fe(CN)63-/4-, Ru(NH 3)63+/2+ on all electrodes were relatively unaffected by pH. Electrically conducting diamond powder was prepared by coating insulating diamond powder (8-12 mum diam) with a thin boron-doped diamond layer using microwave-assisted chemical vapor deposition (CVD). Increases in the electrical conductivity after growth confirmed that a conductive diamond overlayer formed. The charge passed during anodic polarization at 1.6 V vs. Ag/AgCl and 25°C for 1 h was largest for GC powder (0.88 C/cm2) and smallest for conductive diamond powder (0.18 C/cm2), illustrating the dimensional stability of diamond powder compared to sp2-bonded carbon powder. Boron-doped nanocrystalline diamond (BND) was coated on Toray RTM carbon paper (TCP) via microwave-assisted CVD. Pt nanoparticles were deposited on TCP and BND using a pulsed galvanostatic method. The stability of the bare TCP and BND substrates and the composite Pt/TCP and Pt/BND electrodes were studied using potentiostatic polarization in 0.1 M HClO4. The BND electrode exhibited superior morphological and microstructural stability over TCP at 1.6 V vs. Ag/AgCl. Evidence was found for dissolution and redeposition of Pt on composite electrodes, particularly for Pt/TCP.

Fischer, Anne Elizabeth

2005-11-01

402

WEATHERABILITY OF ENHANCED DEGRADABLE PLASTICS  

EPA Science Inventory

The main objective of this study was to assess the performance and the associated variability of several selected enhanced degradable plastic materials under a variety of different exposure conditions. ther objectives were to identify the major products formed during degradation ...

403

Radiological control criteria for materials considered for recycle and reuse  

SciTech Connect

Pacific Northwest Laboratory (PNL) is conducting technical analyses to support the US Department of Energy (DOE), Office of Environmental Guidance, Air, Water, and Radiation Division (DOE/EH-232) in developing radiological control criteria for recycling or reuse of metals or equipment containing residual radioactive contamination from DOE operations. The criteria, framed as acceptable concentrations for release of materials for recycling or reuse, are risk-based and were developed through analysis of generic radiation exposure scenarios and pathways. The analysis includes evaluation of relevant radionuclides, potential mechanisms of exposure, and non-health-related impacts of residual radioactivity on electronics and film. The analysis considers 42 key radionuclides that DOE operations are known to generate and that may be contained in recycled or reused metals or equipment. Preliminary results are compared with similar results reported by the International Atomic Energy Agency, by radionuclide grouping.

Kennedy, W.E. Jr.; Hill, R.L.; Aaberg, R.L. [Pacific Northwest Lab., Richland, WA (United States); Wallo, A. III [USDOE Assistant Secretary for Environment, Safety, and Health, Washington, DC (United States). Office of Environmental Guidance

1994-11-01

404

Dysprosium hafnate as absorbing material for control rods  

NASA Astrophysics Data System (ADS)

Dysprosium hafnate is proposed as a promising absorbing material for control rods of thermal nuclear reactors. The properties of dysprosium hafnate pellets with different Dy and Hf contents are presented in this article. The fluorite phase is characterized by the density range 6.8-7.8 g/cm 3 and; the thermal diffusivity achieves 0.58-0.83 mm 2/s at 20 °C, thermal conductivity of 1.5-2.0 W/(K m) and TLEC of (8.4-8.6) × 10 -6 K -1 at 20 °C. The temperature dependence of the thermophysical properties of dysprosium hafnate are presented. The neutron absorption efficiency of dysprosium hafnate was estimated in comparison with boron carbide. The radiation resistance of pellets after irradiation in the BOR-60 reactor is presented as well.

Risovany, V. D.; Zakharov, A. V.; Muraleva, E. M.; Kosenkov, V. M.; Latypov, R. N.

2006-09-01

405

Controlling the Casimir force via the electromagnetic properties of materials  

SciTech Connect

The control of the Casimir force between two parallel plates can be achieved through adjusting the frequency-dependent electromagnetic properties of materials of the two plates. We show that, for different plate separations, the main contribution to the Casimir force comes from different frequency regions: For smaller (larger) separation, it comes from the higher (lower) frequency region. When the separation of the plates increases, the Casimir force can vary from attractive to repulsive and/or vice versa, by selecting the two plates with suitable electromagnetic properties. We discuss how a restoring Casimir force, which varies from repulsive to attractive by increasing the separation, can be realized and that the stable equilibrium is formed at zero Casimir force.

Yang Yaping; Chen Hong [Department of Physics, Tongji University, Shanghai 200092 (China); Zeng Ran [Department of Physics, Tongji University, Shanghai 200092 (China); School of Telecommunication, Hangzhou Dianzi University, Hangzhou 300018 (China); Zhu Shiyao [Department of Physics, Hong Kong Baptist University (Hong Kong); Zubairy, M. Suhail [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States)

2010-02-15

406

Novel cost controlled materials and processing for primary structures  

NASA Technical Reports Server (NTRS)

Textile laminates, developed a number of years ago, have recently been shown to be applicable to primary aircraft structures for both small and large components. Such structures have the potential to reduce acquisition costs but require advanced automated processing to keep costs controlled while verifying product reliability and assuring structural integrity, durability and affordable life-cycle costs. Recently, resin systems and graphite-reinforced woven shapes have been developed that have the potential for improved RTM processes for aircraft structures. Ciba-Geigy, Brochier Division has registered an RTM prepreg reinforcement called 'Injectex' that has shown effectivity for aircraft components. Other novel approaches discussed are thermotropic resins producing components by injection molding and ceramic polymers for long-duration hot structures. The potential of such materials and processing will be reviewed along with initial information/data available to date.

Dastin, S. J.

1993-01-01

407

Integrated safeguards & security for material protection, accounting, and control.  

SciTech Connect

Traditional safeguards and security design for fuel cycle facilities is done separately and after the facility design is near completion. This can result in higher costs due to retrofits and redundant use of data. Future facilities will incorporate safeguards and security early in the design process and integrate the systems to make better use of plant data and strengthen both systems. The purpose of this project was to evaluate the integration of materials control and accounting (MC&A) measurements with physical security design for a nuclear reprocessing plant. Locations throughout the plant where data overlap occurs or where MC&A data could be a benefit were identified. This mapping is presented along with the methodology for including the additional data in existing probabilistic assessments to evaluate safeguards and security systems designs.

Duran, Felicia Angelica; Cipiti, Benjamin B.

2009-10-01

408

Microdielectric sensors for cure control and materials evaluation  

NASA Astrophysics Data System (ADS)

The principles involved in the use of dielectric measurements for monitoring cure processes and for material evaluation are presented. The methods used in the dielectric measurements are described, including the parallel plate technique and the microdielectric sensing technique, with special attention given to dielectric sensors. The process of collecting data and the methods of correlating the measurements with the mechanical viscosity of cured specimens are discussed. The examples presented include the results for a simple cure of a 5-min epoxy and those for an autoclave-cured graphite-epoxy laminate structure. The use of multiple sensors placed in contact with a few key parts (such as the thickest and the thinnest regions) of the autoclaved specimen is considered necessary for optimal control.

Day, D. R.

409

Accelerated degradation of metam-sodium and dazomet in soil: characterization and consequences for pathogen control  

Microsoft Academic Search

Metam-sodium (MS) and dazomet (DAZ) are soil fumigants that generate methyl-isothiocyanate (MITC) in soil. The latter effectively controls soilborne plant pathogens. Recently, we have found that repeated applications of MS yield less effective pathogen control. Soil samples collected from 12 field sites in Israel without (nonhistory) or with (history) previous applications of MS or DAZ were tested for MITC generation

Pietro Di Primo; Abraham Gamliel; Miriam Austerweil; Bracha Steiner; Marina Beniches; Itzik Peretz-Alon; Jaacov Katan

2003-01-01

410

Device for controlling the pouring of molten materials  

DOEpatents

A device for controlling the pouring of a molten material from a crucible or other container. The device (10) includes an annular retainer ring (12) for mounting in the drain opening in the bottom of a conventional crucible (16), the retainer ring defining a opening (14) therethrough. The device (10) also includes a plug member (22) having an annular forward end portion (24) for force-fit reception in the opening (14) of the retainer ring (12) to selectively seal the opening (14) and for being selectively forced through the opening (14). The plug member (22) has a rear end portion (26) for being positioned within the crucible (16), the rear end portion (26) including stop means for prohibiting the rear end portion from passing through the opening (14) in the retainer ring (12) when the forward end portion (24) is selectively forced through the opening. The plug member (22) defines at least one, and preferably a plurality of flutes (32), each extending from a point rearward the annular forward end portion (24) of the plug member (22), and forward the stop means, to a point rearward of the stop means. The flutes (32) permit fluid communication between the interior and exterior of the crucible (16) when the forward end portion (24) of the plug member (22) is forced through the opening (14) in the retaining ring (12) such that the molten material is allowed to flow from the crucible (16).

Moore, Alan F. (Knoxville, TN); Duncan, Alfred L. (Clinton, TN)

1994-01-01

411

Device for controlling the pouring of molten materials  

DOEpatents

A device is described for controlling the pouring of a molten material from a crucible or other container. The device includes an annular retainer ring for mounting in the drain opening in the bottom of a conventional crucible, the retainer ring defining a opening there through. The device also includes a plug member having an annular forward end portion for force-fit reception in the opening of the retainer ring to selectively seal the opening and for being selectively forced through the opening. The plug member has a rear end portion for being positioned within the crucible, the rear end portion including stop means for prohibiting the rear end portion from passing through the opening in the retainer ring when the forward end portion is selectively forced through the opening. The plug member defines at least one, and preferably a plurality of flutes, each extending from a point rearward the annular forward end portion of the plug member, and forward the stop means, to a point rearward of the stop means. The flutes permit fluid communication between the interior and exterior of the crucible when the forward end portion of the plug member is forced through the opening in the retaining ring such that the molten material is allowed to flow from the crucible. 5 figures.

Moore, A.F.; Duncan, A.L.

1994-02-15

412

Understanding and control of optical performance from ceramic materials  

SciTech Connect

This report summarizes a two-year Laboratory-Directed Research and Development (LDRD) program to gain understanding and control of the important parameters which govern the optical performance of rare-earth (RE) doped ceramics. This LDRD developed the capability to determine stable atomic arrangements in RE doped alumina using local density functional theory, and to model the luminescence from RE-doped alumina using molecular dynamic simulations combined with crystal-field calculations. Local structural features for different phases of alumina were examined experimentally by comparing their photoluminescence spectra and the atomic arrangement of the amorphous phase was determined to be similar to that of the gamma phase. The luminescence lifetimes were correlated to these differences in the local structure. The design of both high and low-phonon energy host materials was demonstrated through the growth of Er-doped aluminum oxide and lanthanum oxide. Multicomponent structures of rare-earth doped telluride glass in an alumina and silica matrix were also prepared. Finally, the optical performance of Er-doped alumina was determined as a function of hydrogen content in the host matrix. This LDRD is the groundwork for future experimentation to understand the effects of ionizing radiation on the optical properties of RE-doped ceramic materials used in space and other radiation environments.

Barbour, J.C.; Knapp, J.A.; Potter, B.G.; Jennison, D.R.; Verdozzi, C.A.; Follstaedt, D.M. [Sandia National Labs., Albuquerque, NM (United States); Bendale, R.D.; Simmons, J.H. [Univ. of Florida, Gainesville, FL (United States). Materials Science and Engineering Dept.

1998-06-01

413

Controllable biomimetic adhesion using embedded phase change material  

NASA Astrophysics Data System (ADS)

In many cases, such as in the instance of climbing robots or temporary adhesives, there is the need to be able to dynamically control the level of adhesion a biomimetic dry adhesive can provide. In this study, the effect of changing the backing layer stiffness of a dry adhesive is examined. Embedding a phase change material within the backing of a synthetic dry adhesive sheet allows the stiffness to be tailored at different points of a preload and adhesion cycle. Larger contact areas and more equal load sharing between adhesive fibres can be achieved by increasing the backing layer stiffness after initial deformation when the adhesive backing is loaded in its softened state. Adhesion behaviour is examined when the backing layer is maintained in solid and softened phases during complete load cycles and for load cycles under the condition of contact with the softened phase backing followed by pull-off during the solid phase. Absolute adhesion force is increased for trials in which a soft backing layer hardens prior to pull-off. This effect is due to the increased contact area made between the rounded probe and the softened material during preloading and the more equal load sharing condition during pull-off when the backing layer becomes stiff again.

Krahn, J.; Sameoto, D.; Menon, C.

2011-01-01

414

Nanostructured hydroxyapatite/poly(lactic-co-glycolic acid) composite coating for controlling magnesium degradation in simulated body fluid  

NASA Astrophysics Data System (ADS)

Biodegradable magnesium (Mg) and its alloys have many attractive properties (e.g. comparable mechanical properties to cortical bone) for orthopedic implant applications, but they degrade too rapidly in the human body to meet clinical requirements. Nanostructured hydroxyapatite (nHA)/poly(lactic-co-glycolic acid) (PLGA) composite coatings provide synergistic properties for controlling degradation of Mg-based substrates and improving bone-implant integration. In this study, nHA/PLGA composites were spin coated onto Mg-based substrates and the results showed that the nHA/PLGA coatings retained nano-scale features with nHA dispersed in PLGA matrix. In comparison with non-coated Mg, the nHA/PLGA composite coated Mg increased the corrosion potential and decreased the corrosion current in revised simulated body fluid (rSBF). After 24 h of immersion in rSBF, increased calcium phosphate (CaP) deposition and formation of Mg-substituted CaP rosettes were observed on the surface of the nHA/PLGA coated Mg, indicating greater bioactivity. In contrast, no significant CaP was deposited on the PLGA coated Mg. Since both PLGA coating and nHA/PLGA coating showed some degree of delamination from Mg-based substrates during extended immersion in rSBF, the coating processing and properties should be further optimized in order to take full advantage of biodegradable Mg and nHA/PLGA nanocomposites for orthopedic applications.

Johnson, Ian; Akari, Khalid; Liu, Huinan

2013-09-01

415

The Effects of Degraded Digital Instrumentation and Control Systems on Human-system Interfaces and Operator Performance: HFE Review Guidance and Technical Basis  

SciTech Connect

New and advanced reactors will use integrated digital instrumentation and control (I&C) systems to support operators in their monitoring and control functions. Even though digital systems are typically highly reliable, their potential for degradation or failure could significantly affect operator performance and, consequently, impact plant safety. The U.S. Nuclear Regulatory Commission (NRC) supported this research project to investigate the effects of degraded I&C systems on human performance and plant operations. The objective was to develop human factors engineering (HFE) review guidance addressing the detection and management of degraded digital I&C conditions by plant operators. We reviewed pertinent standards and guidelines, empirical studies, and plant operating experience. In addition, we conducted an evaluation of the potential effects of selected failure modes of the digital feedwater system on human-system interfaces (HSIs) and operator performance. The results indicated that I&C degradations are prevalent in plants employing digital systems and the overall effects on plant behavior can be significant, such as causing a reactor trip or causing equipment to operate unexpectedly. I&C degradations can impact the HSIs used by operators to monitor and control the plant. For example, sensor degradations can make displays difficult to interpret and can sometimes mislead operators by making it appear that a process disturbance has occurred. We used the information obtained as the technical basis upon which to develop HFE review guidance. The guidance addresses the treatment of degraded I&C conditions as part of the design process and the HSI features and functions that support operators to monitor I&C performance and manage I&C degradations when they occur. In addition, we identified topics for future research.

O'Hara, J.M.; W. Gunther, G. Martinez-Guridi

2010-02-26

416

Controlling the enzymatic digestion of lipids using hybrid nanostructured materials.  

PubMed

Solid nanoparticle-lipid hybrids have been engineered by using spray drying to assemble monodisperse hydrophilic silica nanoparticles and submicron lipid (triglyceride) emulsions together into composite microparticles, which have specific activity toward enzymes. The influence of silica particle size (100-1000 nm) and emulsifier type (anionic and cationic) on the three-dimensional structure of the composite particles was investigated. The nanostructure of the hybrid particles, which is controlled by the size of the voids between the closely packed silica particles, plays a critical role in lipase action and hence lipid digestion kinetics. Confining lipid droplets within the nanostructured silica aggregates led to 2- to 15-fold enhanced rate of lipolysis in comparison with dispersed coarse oil droplets. The composite particles were tailored to enhance, retain or sustain the lipolysis kinetics of submicron lipid emulsions. The presence of repulsive nanoparticle-droplet interactions favored aqueous redispersion and fast lipolysis of the hybrid composite materials, while attractive interactions hindered redispersion and delayed lipolysis of the confined lipid droplets. Such hybrid nanomaterials can be exploited to control the gastrointestinal enzymatic action and promisingly form the basis for the next generation of foods and medicines. PMID:25116477

Tan, Angel; Colliat-Dangus, Perrine; Whitby, Catherine P; Prestidge, Clive A

2014-09-10

417

Prescriptive concepts for advanced nuclear materials control and accountability systems  

SciTech Connect

Networking- and distributed-processing hardware and software have the potential of greatly enhancing nuclear materials control and accountability (MC and A) systems, from both safeguards and process operations perspectives, while allowing timely integrated safeguards activities and enhanced computer s