Note: This page contains sample records for the topic control materials degradation from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

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

2

Improved water chemistry controls for minimizing degradation of materials  

Microsoft Academic Search

The Electric Power Research Institute and the Steam Generator Owners Group have sponsored several efforts to develop secondary water chemistry guidelines to minimize pressurized water reactor (PWR) steam generator tubing degradation. To develop these guidelines, chemical species known to accelerate corrosion of Alloy 600 were identified, and values for normal and abnormal chemistry situations were established. For example, sodium hydroxide

Sawochka

1986-01-01

3

Degradation of thermal control materials under a simulated radiative space environment  

NASA Astrophysics Data System (ADS)

A spacecraft with a passive thermal control system utilizes various thermal control materials to maintain temperatures within safe operating limits. Materials used for spacecraft applications are exposed to harsh space environments such as ultraviolet (UV) and particle (electron, proton) irradiation and atomic oxygen (AO), undergo physical damage and thermal degradation, which must be considered for spacecraft thermal design optimization and cost effectiveness. This paper describes the effect of synergistic radiation on some of the important thermal control materials to verify the assumptions of beginning-of-life (BOL) and end-of-life (EOL) properties. Studies on the degradation in the optical properties (solar absorptance and infrared emittance) of some important thermal control materials exposed to simulated radiative geostationary space environment are discussed. The current studies are purely related to the influence of radiation on the degradation of the materials; other environmental aspects (e.g., thermal cycling) are not discussed. The thermal control materials investigated herein include different kind of second-surface mirrors, white anodizing, white paints, black paints, multilayer insulation materials, varnish coated aluminized polyimide, germanium coated polyimide, polyether ether ketone (PEEK) and poly tetra fluoro ethylene (PTFE). For this purpose, a test in the constant vacuum was performed reproducing a three year radiative space environment exposure, including ultraviolet and charged particle effects on North/South panels of a geostationary three-axis stabilized spacecraft. Reflectance spectra were measured in situ in the solar range (250-2500 nm) and the corresponding solar absorptance values were calculated. The test methodology and the degradations of the materials are discussed. The most important degradations among the low solar absorptance materials were found in the white paints whereas the rigid optical solar reflectors remained quite stable. Among the high solar absorptance elements, as such the change in the solar absorptance was very low, in particular the germanium coated polyimide was found highly stable.

Sharma, A. K.; Sridhara, N.

2012-11-01

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

Comparison Study of Combined and Single Space Environmental Degradation Effects on Thermal Control Materials  

NASA Astrophysics Data System (ADS)

This paper presents a comparison study of single and combined space environmental effects by electrons, protons and near ultraviolet (NUV) radiation on thermal control coatings. The space environment includes many hazardous factors. Because of synergistic effects among different environmental factors and the expensive nature of the open space experiments, ground-based combined environmental test methods are necessary to simulate orbital environmental effects. In many cases, the combined environmental effect from two or more factors is not equal to the sum of single environmental effects. By studying the effects from single environmental factors, a better knowledge of their influence on the degradation of materials could be acquired. Space environmental degradation of thermal control coatings of S781 white paint, SR107-ZK white paint, silvered FEP, and OSR used on the outer satellite surfaces was simulated by exposing them to combined irradiation with electrons, protons and NUV. In addition, irradiation with single factors with the same parameters was performed for comparison studies. Low energy proton irradiation has been found to affect the thermal control coatings the most. The effects from combined irradiation were found to be lower than from the sum of single environmental factors.

Feng, Weiquan; Ding, Yigang; Yan, Dekui; Liu, Xuechao; Wang, Wei; Li, Dongmei

2009-01-01

6

Study of Degradation Processes in Dielectric Materials Used in Electronic Control Equipment Operated in 'Kozloduy' NPP  

SciTech Connect

The electronic equipment for control of different systems of Units 5 and 6 is studied for presence of degradation processes occurring in result of continuous usage in conditions of controlled radiation background in compliance with 'Kozloduy' NPP safety codes. Systems, operated in a continuous mode in the course of about 10 years were chosen - separate units containing different dielectric materials (varnish coating, circuit board bases, cable insulations, electro protective elements, etc.) were extrapolated. Series of test samples were prepared which were connected with flat or coaxial condensers and their characteristic parameters were measured: tg{delta}, {epsilon}, low voltage conductivity and leak currents at voltages that exceed the working ones several times. When comparing the obtained data with the reference ones, a conclusion is made about the effectiveness of electric ageing during operation in the course of time.

Naydenov, Nayden ['Kozloduy' NPP, Kozloduy (Bulgaria); Popov, Angel [Department of Semiconductor Physics, Faculty of Physics, University of Sofia 'St. Kliment Ohridski', 5 J. Bourchier Blvd., 1164 Sofia (Bulgaria)

2007-04-23

7

LWR Aging Management Using a Proactive Approach to Control Materials Degradation  

SciTech Connect

Material issues can be the limiting factor for the operation of nuclear power plants. There is growing interest in new and improved philosophies and methodolgies for plant life management, which include the migration from reliance on periodic inservice inspection to include condition-based maintenance. A further step in the development of plant management is the move from proactive responses based on ISI to become proactive, through the investigation of the potential for implementation of a proactive management of materials degradation program and its potential impact on the managements of LWRs

Bond, Leonard J.; Doctor, Steven R.; Cumblidge, Stephen E.; Bruemmer, Stephen M.; Taylor, W Boyd; Hull, Amy; Malik, Shah

2009-05-12

8

Surface Degradation of Polymeric Materials.  

National Technical Information Service (NTIS)

A review of surface degradation of polymeric materials exposed to natural and artificial weathering environments has been carried out. Mechanisms of degradation are discussed, the role of different environmental variables is evaluated, and methods of char...

J. White A. Turnbull

1992-01-01

9

Methods for Degrading Lignocellulosic Materials.  

National Technical Information Service (NTIS)

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 ...

E. Vlasenko F. Xu J. Cherry

2005-01-01

10

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

11

Characterization of Thermally Degraded Energetic Materials: Mechanical and Chemical Behavior  

SciTech Connect

We report the results of recent experiments on thermally degraded HMX and HMX/binder materials. Small-scale samples were heated confined in either constant-volume or load- controlled configurations. A main emphasis of the work reported here is developing an understanding of the complex coupling of the mechanical and chemical responses during thermal degradation.

Miller, J.C.; Renlund, A.M.; Schmitt, R.G.; Wellman, G.W.

1998-12-04

12

Hyperbranched Polymers - Engineering Materials and Degradation Behavior.  

National Technical Information Service (NTIS)

Hyperbranched polymers of unique compositions were studied for their mechanical properties and degradation behaviors. Highly branched polymeric architectures have been shown to exhibit properties that are unique to those of linear polymer materials. In th...

K. L. Wooley

2000-01-01

13

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

14

Mechanical degradation temperature of waste storage materials  

SciTech Connect

Heat loading analysis of the Solid Waste Disposal Facility (SWDF) waste storage configurations show the containers may exceed 90{degrees}C without any radioactive decay heat contribution. Contamination containment is primarily controlled in TRU waste packaging by using multiple bag layers of polyvinyl chloride and polyethylene. Since literature values indicate that these thermoplastic materials can begin mechanical degradation at 66{degrees}C, there was concern that the containment layers could be breached by heating. To better define the mechanical degradation temperature limits for the materials, a series of heating tests were conducted over a fifteen and thirty minute time interval. Samples of a low-density polyethylene (LDPE) bag, a high-density polyethylene (HDPE) high efficiency particulate air filter (HEPA) container, PVC bag and sealing tape were heated in a convection oven to temperatures ranging from 90 to 185{degrees}C. The following temperature limits are recommended for each of the tested materials: (1) low-density polyethylene -- 110{degrees}C; (2) polyvinyl chloride -- 130{degrees}C; (3) high-density polyethylene -- 140{degrees}C; (4) sealing tape -- 140{degrees}C. Testing with LDPE and PVC at temperatures ranging from 110 to 130{degrees}C for 60 and 120 minutes also showed no observable differences between the samples exposed at 15 and 30 minute intervals. Although these observed temperature limits differ from the literature values, the trend of HDPE having a higher temperature than LDPE is consistent with the reference literature. Experimental observations indicate that the HDPE softens at elevated temperatures, but will retain its shape upon cooling. In SWDF storage practices, this might indicate some distortion of the waste container, but catastrophic failure of the liner due to elevated temperatures (<185{degrees}C) is not anticipated.

Fink, M.C.; Meyer, M.L.

1993-05-13

15

Degradation of materials in the atmosphere  

SciTech Connect

This paper provides a perspective on the potential for materials degradation as a consequence of atmospheric exposure. Ferrous metals, masonry, zinc, copper, and perhaps some paints appear most likely to be degraded. The regimes of greatest concern vary with different materials, but they include dew, fog, airborne particles, and indoor air. The results, however, rest on a rather sparse data base and take no account of synergistic deterioration effects of corrodents; thus, the presentation should be considered a starting point for discussion and experimentation.

Graedel, T.E.; R. McGill

1986-11-01

16

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

17

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

18

Characterization of thermally degraded energetic materials  

Microsoft Academic Search

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.

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

1997-01-01

19

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

20

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

21

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

22

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

23

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

24

Materials degradation caused by acid rain  

Microsoft Academic Search

This book presents the papers given at a symposium on acid rain. Topics considered at the symposium included acidification, wet deposition, dry deposition, the corrosion of metals, corrosion products, the weathering of steel, environmental effects, automotive corrosion, effects on indoor surfaces, the degradation of organics, effects on wood surfaces, effects on plants, the acid rain degradation of nylon, the legal

Baboian

1986-01-01

25

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

26

Materials Degradation in Light Water Reactors: Life After 60.  

National Technical Information Service (NTIS)

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 redu...

D. J. Naus J. T. Busby R. E. Stoller R. K. Nanstad Z. Feng

2008-01-01

27

AGING MANAGEMENT USING PROACTIVE MANAGEMENT OF MATERIALS DEGRADATION  

SciTech Connect

The U.S. Nuclear Regulatory Commission (NRC) has undertaken a program to lay the technical foundations for defining proactive actions to manage degradation of materials in light water reactors. The current focus is existing plants; however, if applied to new construction, there is potential to better monitor and manage plants throughout their life cycle. This paper discusses the NRC's Proactive Management of Materials Degradation program and its application to nuclear power plant structures, systems, and components.

Doctor, S. R.; Bond, L. J.; Cumblidge, S. E.; Bruemmer, S. M.; Taylor, W. B. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Carpenter, C. E.; Hull, A. B.; Malik, S. N. [U.S. Nuclear Regulatory Commission, Washington D.C. 20555-0001 (United States)

2010-02-22

28

Aging Management using Proactive Management of Materials Degradation  

SciTech Connect

The U.S. Nuclear Regulatory Commission (NRC) has undertaken a program to lay the technical foundations for defining proactive actions to manage degradation of materials in light water reactors (LWRs). The current focus is existing plants; however, if applied to new construction, there is potential to better monitor and manage plants throughout their life cycle. This paper discusses the NRC’s Proactive Management of Materials Degradation (PMMD) program and its application to nuclear power plant structures, systems, and components (SSC).

Doctor, Steven R.; Bond, Leonard J.; Cumblidge, Stephen E.; Bruemmer, Stephen M.; Taylor, W Boyd; Carpenter, C. E. (Gene); Hull, Amy B.; Malik, Shah

2010-10-01

29

External Building Materials: Quantities and Degradation.  

National Technical Information Service (NTIS)

The report presents an investigation of external materials on buildings in the greater Stockholm area. The investigation had two main goals: to make an inventory of the amount of different exterior building materials and to inspect and account for the obs...

N. Tolstoy G. Andersson C. Sjoestroem V. Kucera

1990-01-01

30

OXIDATIVE DEGRADATION OF AQUATIC HUMIC MATERIAL  

EPA Science Inventory

Experimental research on the chemical structure of aquatic humic material has been stimulated in the last decade by public health interest in possible adverse human health effects of reaction by-products of humic materials with chlorine. The purpose of the paper is to describe th...

31

Oxidative Degradation of Aquatic Humic Material.  

National Technical Information Service (NTIS)

Experimental research on the chemical structure of aquatic humic material has been stimulated in the last decade by public health interest in possible adverse human health effects of reaction by-products of humic materials with chlorine. The purpose of th...

R. F. Christman D. L. Norwood Y. Seo F. H. Frimmel

1987-01-01

32

Material degradation under DEMO relevant neutron fluences  

NASA Astrophysics Data System (ADS)

In fusion power reactors, the plasma facing and breeding-blanket components will suffer intense irradiation by 14 MeV neutrons. These high-energy fusion neutrons will produce atomic displacement cascades and nuclear transmutation reactions inside the irradiated materials, and these will result in important radiation damage and effects. In the present paper, typical examples of radiation damage and effects on candidate materials for plasma facing components in fusion power reactors are presented and discussed.

Baluc, N.

2009-12-01

33

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

34

Design of mesostructured H 3PW 12O 40–titania materials with controllable structural orderings and pore geometries and their simulated sunlight photocatalytic activity towards diethyl phthalate degradation  

Microsoft Academic Search

A series of mesostructured H3PW12O40–titania materials with two-dimensional hexagonal, three-dimensional cubic, and three-dimensional interconnected sponge-like pore geometries were developed by using a single step nonionic-surfactant-templating strategy combined with evaporation-induced self-assembly (EISA) or hydrothermal treatment technique. The mesostructure, morphology, porosity, optical absorption property as well as composition and structure of as-prepared materials were well-characterized. Subsequently, the materials were successfully applied to

Kexin Li; Xia Yang; Yingna Guo; Fengyan Ma; Huichao Li; Ling Chen; Yihang Guo

2010-01-01

35

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

36

DERIVATION OF DAMAGE FUNCTIONS FOR ATMOSPHERIC DEGRADATION OF MATERIALS  

EPA Science Inventory

The information in the pape is directed to those who develop and use damage functions which relate atmospheric degradation of materials to various causal agents in the atmosphere. Such relationships must be quantified mathematically as part of the overall cost-benefit considerati...

37

Speckle interferometry to investigate degradation processes of stressed solid materials  

Microsoft Academic Search

Degradation processes of stressed solid materials was investigated by newly developed speckle interferometry. Sequence of speckle correlation fringes were obtained by subtracting couples of interfering speckle patterns successively acquired. The behavior of plastic deformation and fracture were observed on a video monitor as moving fringe patterns of in-plane deformation components. In experiments of a specimen of carbon steel S45C, we

Satoru Toyooka; Suprapedi; Qinchuan Zhang

1998-01-01

38

Material degradation assessment for stiffened composite shells using metamodelling approach  

Microsoft Academic Search

The intense interest coming from the aerospace industry indicates the need of safe exploitation of composite materials in\\u000a stiffened shell structures. Since stiffened shells are far most consumed structural component, it is important to study the\\u000a behaviour of material degradation to evaluate the safe design guidelines. Moreover, current numerical procedures cannot simulate\\u000a the collapse of stiffened shells with sufficient reliability

Kaspars Kalnins; Rolands Rikards; Janis Auzins

39

Physical and mechanical properties of degraded waste surrogate material  

SciTech Connect

This paper discusses rock mechanics testing of surrogate materials to provide failure criteria for compacted, degraded nuclear waste. This daunting proposition was approached by first assembling all known parameters such as the initial waste inventory and rock mechanics response of the underground setting after the waste is stored. Conservative assumptions allowing for extensive degradation processes helped quantify the lowest possible strength conditions of the future state of the waste. In the larger conceptual setting, computations involve degraded waste behavior in transient pressure gradients as gas exits the waste horizon into a wellbore. Therefore, a defensible evaluation of tensile strength is paramount for successful analyses and intentionally provided maximal failed volumes. The very conservative approach assumes rampant degradation to define waste surrogate composition. Specimens prepared from derivative degradation product were consolidated into simple geometries for rock mechanics testing. Tensile strength thus derived helped convince a skeptical peer review panel that drilling into the Waste Isolation Pilot Plant (WIPP) would not likely expel appreciable solids via the drill string.

Hansen, F.D. [Sandia National Labs., Carlsbad, NM (United States); Mellegard, K.D. [RE/SPEC Inc., Rapid City, SD (United States)

1998-03-01

40

Degradation of bifenthrin, chlorpyrifos and imidacloprid in soil and bedding materials at termiticidal application rates  

Microsoft Academic Search

Organophosphorus, pyrethroid and chloronicotinyl insecticides have been used to control termites in building structures in recent years. We investigated the degradation behaviour of three insecticides (bifenthrin, chlorpyrifos and imidacloprid) at termiticidal application rates under standard laboratory conditions (25 °C, 60% field moisture capacity and darkness) for 24 months. The study was carried out on one soil and two bedding materials

Sundaram Baskaran; Rai S Kookana; Ravendra Naidu

1999-01-01

41

Gamma-ray-induced degradation of lignocellulosic materials  

SciTech Connect

Lignocellulosic plant materials were treated with various swelling agents and exposed to gamma radiation from 60Co or 137Cs. At dosages of 50 Mrad or above, lignocellulosic materials were extensively degraded and solubilized in water. Addition of water, NaOH, or H2SO4 to the substrate increased the degree of solubilization. Complete solubilization was achieved for samples of sugarcane bagasse, newspaper, cotton linters, cotton cloth, sawdust, and alpha-cellulose powder. About 35% total sugar and 5% reducing sugar per dry weight of sugarcane bagasse could be obtained by this method. Most of the soluble carbohydrates seemed to be disaccharides or larger molecules and glucose degradation products. Solubilization of cellulose was dosage dependent and although the rate of solubilization was increased by adding alkali, released sugar was further decomposed by the alkali and by high dosages of radiation. (Refs. 14).

Han, Y.W.; Timpa, J.; Ciegler, A.; Courtney, J.; Curry, W.F.; Lambremont, E.N.

1981-11-01

42

Recyclability Evaluation Method Considering Material Combination and Degradation  

NASA Astrophysics Data System (ADS)

A new method of recyclability evaluation is proposed. The recyclability of a product is given by summing up recyclability of all units to which the product is manually disassembled. The recyclability of a unit is calculated if all names and amounts of materials of which the unit is composed are known. The recyclability of a disassembled unit consisting of multiple materials is judged on the grounds of removability of impurities, miscibility and marketability of polymer blends. Recyclability of a long-lifetime product can be estimated from recyclability of units, which are modeled as probabilistically distributed degradation of materials. The proposed method is applied to recyclability evaluation for a refrigerator with several scenarios of disassembly levels. The practical disassembly scenarios limit the maximum recyclability rate of the product. Therefore, recyclability rates calculated based on the proposed method are considerably lower than those of the recyclable materials of which the product consisted.

Oyasato, Naohiko; Kobayashi, Hideki

43

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

44

Proactive Management of Materials Degradation (PMMD) and Enhanced Structural Reliability  

SciTech Connect

This paper discusses the U.S. Nuclear Regulatory Commission’s (NRC) activities to further the Proactive Management of Materials Degradation (PMMD), including those to determine the effectiveness of emerging NDE techniques. The paper discusses the first part of the development of a methodology to determine the effectiveness of these emerging NDE techniques for managing metallic degradation. This methodology draws on experience derived from evaluating techniques that have ‘emerged’ in the past. The methodology will follow five stages: a definition of inspection parameters, a technical evaluation, laboratory testing, round-robin testing, and the design of a performance demonstration program. This methodology will document the path taken for previous techniques and set a standardized course for future NDE techniques.

Doctor, Steven R.; Bond, Leonard J.; Cumblidge, Stephen E.; Hull, Amy; Malik, Shah

2009-09-01

45

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

46

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

47

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

48

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

49

Speckle interferometry to investigate degradation processes of stressed solid materials  

NASA Astrophysics Data System (ADS)

Degradation processes of stressed solid materials was investigated by newly developed speckle interferometry. Sequence of speckle correlation fringes were obtained by subtracting couples of interfering speckle patterns successively acquired. The behavior of plastic deformation and fracture were observed on a video monitor as moving fringe patterns of in-plane deformation components. In experiments of a specimen of carbon steel S45C, we observed a characteristic white band which can be interpreted as a Luder's band sweeping over the specimen in the yielding state of the loading test. In experiments of an aluminum alloy specimen, complicated movement of a white and was found corresponding to load serration.

Toyooka, Satoru; Suprapedi; Zhang, Qinchuan

1998-09-01

50

Global nuclear material control model  

SciTech Connect

The nuclear danger can be reduced by a system for global management, protection, control, and accounting as part of a disposition program for special nuclear materials. The development of an international fissile material management and control regime requires conceptual research supported by an analytical and modeling tool that treats the nuclear fuel cycle as a complete system. Such a tool must represent the fundamental data, information, and capabilities of the fuel cycle including an assessment of the global distribution of military and civilian fissile material inventories, a representation of the proliferation pertinent physical processes, and a framework supportive of national or international perspective. They have developed a prototype global nuclear material management and control systems analysis capability, the Global Nuclear Material Control (GNMC) model. The GNMC model establishes the framework for evaluating the global production, disposition, and safeguards and security requirements for fissile nuclear material.

Dreicer, J.S.; Rutherford, D.A.

1996-05-01

51

Material degradation analysis and maintenance decisions based on material condition monitoring during in-service inspections  

SciTech Connect

The degradation of the material in critical components is shown to be an effective measure which can be used to compute the risk adjusted economic penalty associated with different maintenance decisions. The approach of estimating the probability, with confidence interval, of the time that a prescribed degradation level is exceeded is shown to be practical, as demonstrated in the analysis of irradiated fuel cladding. The methodology for the estimation of the probability is predicated on the existence of a parsimonious and robust mixed-effects model of the evolution of the degradation. This model, in general, relates measured surrogates of the degradation level to computed or measured variables, which characterize the environment during the operating history of the component. We propose and demonstrate the efficacy of using an artificial neural network, constructed via a genetic supervisor, as an aid in developing the requisite mixed-effects model and testing its continued validity as new data are obtained.

Yacout, A.M.; Orechwa, Y.

1996-03-01

52

Degradation study on optical materials for concentrator photovoltaics  

NASA Astrophysics Data System (ADS)

In this work the impact of accelerated aging on the spectral transmission and the mechanical robustness of silicone elastomers for concentrator photovoltaic applications was investigated. Therefore, specific test samples were manufactured. The samples were annealed at 150 °C to assure a complete cross-linking. These samples were exposed to humidity freeze, to a pressure cooker test, and to UV light. To investigate optical materials under UVA intensity up to 10 W/cm2 a test setup was developed. Thus, a UV dosage of 10000 kWh/m2 was applied to the silicone samples after thermal treatment. The mean transmission was used as a measure to identify changes in the spectral behavior and was, therefore, compared after the stress tests with the initial value. No total failures but rather degradation was observed, mainly in the range of ultraviolet and visible light. In addition, the shear strengths for the silicone elastomers were compared before and after stress.

Eltermann, Fabian; Roeder, Kerstin; Wiesenfarth, Maike; Wilde, Juergen; Bett, Andreas W.

2012-10-01

53

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

54

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

55

Integrated control of protein degradation in C. elegans muscle.  

PubMed

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

2012-07-01

56

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

57

Analysis of the Local Material Degradation Near Cutting Edges of Electrical Steel Sheets  

Microsoft Academic Search

Cutting leads to a certain local magnetic material degradation of the electrical steel sheet. Moreover, the material properties near the cutting edge contribute significantly to the global performance. This material degradation mostly occurs in the vicinity of critical parts of electromagnetic devices, such as stator and rotor teeth. Therefore, the need exists to characterize the local magnetic hysteresis properties due

Guillaume Crevecoeur; Peter Sergeant; Luc Dupre; Lode Vandenbossche; Rik Van de Walle

2008-01-01

58

Finite Difference Method Analysis of Ultrasonic Nonlinearity in Partially Degraded Material  

Microsoft Academic Search

In recent years, the fact that the nonlinear acoustic effect has a strong correlation to the microdeformation of materials has been considered to be useful for non-destructive evaluation (NDE) of material degradation. However, in the past, most research considered only the case in which the material degradation was distributed evenly along the path of the probing wave. In contrast, in

Kyung-Cho Kim; Kyung Young Jhang; Hisashi Yamawaki; Tetsuya Saito

2001-01-01

59

Counteracting the dynamical degradation of digital chaos via hybrid control  

NASA Astrophysics Data System (ADS)

Chaotic systems would degrade owing to finite computing precisions, and such degradation often seriously affects the performance of digital chaos-based applications. In this paper, a chaotification method is proposed to solve the dynamical degradation of digital chaotic systems based on a hybrid structure, where a continuous chaotic system is applied to control the digital chaotic system, and a unidirectional coupling controller that combines a linear external state control with a modular function is designed. Moreover, we proof rigorously that a class of digital chaotic systems can be driven to be chaotic in the sense that the system is sensitive to initial conditions. Different from the existing remedies, this method can recover the dynamical properties of system, and even make some properties better than those of the original chaotic system. Thus, this new approach can be applied to the fields of chaotic cryptography and secure communication.

Hu, Hanping; Deng, Yashuang; Liu, Lingfeng

2014-06-01

60

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

61

Degradation of apple cell wall material by commercial enzyme preparations.  

PubMed

The action of commercial enzyme preparations on the release of cell wall constituents from alcohol-insoluble substance prepared from apples without skins and cores as well as their influence on the water binding of remaining residues is described as a model for the enzymatic cell wall destruction during production of liquid fruit products. Besides 'normal' enzyme concentrations adapted from the usual industrial dosage, 'tenfold' enzyme concentrations were applied. Dependent on enzyme spectrum and activities, concentrations of dietary fibre, e.g., pectin, increased in the soluble fractions using conditions of enzymatic 'mash treatment'. A further release of these cell wall constituents occurred when cellulase containing enzyme preparations were used under conditions of 'pomace treatment', especially with the 'tenfold' enzyme dosage. The partial enzymatic degradation of the cell wall material is connected with a decrease in water binding of the remaining residues during both simulated mash treatment of pomace treatment. Alcohol-insoluble substance from apples is a suitable model for the determination of complex enzymatic actions of enzyme preparations containing pectolytic, hemicellulolytic, and/or cellulolytic activities under standardised conditions. PMID:12017986

Dongowski, G; Sembries, S; Bauckhage, K; Will, F; Dietrich, H

2002-04-01

62

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

63

CERAMIC MATERIALS WITH CONTROLLED POROSITY  

Microsoft Academic Search

The precursors for magnesium aluminate spinel were synthesized by the method of joint crystallization from mixed solutions of magnesium and aluminum salts. The sequence of the MgAl 2 O 4 phase formation vs starting reagents was studied. Spinel materials with controlled porosity were obtained using the variation of the Al source at nano-sized precursors synthesis, the changes of the sintering

E. A. Vasilyeva; L. V. Morozova; A. E. Lapshin; V. G. Konakov

2002-01-01

64

Accepting performance degradation in fault-tolerant control system design  

Microsoft Academic Search

A novel fault-tolerant control system design technique has been proposed in this paper, which blends the multiple-model principle with the unavoidable performance degradation due to faults in actuators, sensors or system dynamics. The number of models employed depends on the characteristics of the system, the nature of the failures considered, and the physical limits of system variables. The achievable performance

Jin Jiang; Youmin Zhang

2006-01-01

65

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

SciTech Connect

Summary for Special Session Invited paper "The Best of NPIC&HMIT 2009" The Nuclear Regulatory Commission has undertaken the Proactive Management of Materials Degradation (PMMD) program to lay the groundwork for defining proactive actions to manage degradation of materials in light water reactors (LWRs) including 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.

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

2009-04-17

66

Modeling and simulation of material degradation in biodegradable wound closure devices.  

PubMed

Biodegradable materials have been used as wound closure materials. It is important for these materials to enhance wound healing when the wound is vulnerable, and maintain wound closure until the wound is heal. This article studies the degradation process of bioresorbable magnesium micro-clips for wound closure in voice/laryngeal microsurgery. A novel computational approach is proposed to model degradation of the biodegradable micro-clips. The degradation process that considers both material and geometry of the device as well as its deployment is modeled as an energy minimization problem that is iteratively solved using active contour and incremental finite element methods. Strain energy of the micro-clip during degradation is calculated with the stretching and bending functions in the active contour formulation. The degradation rate is computed from strain energy using a transformation formulation. By relating strain energy to material degradation, the degradation rates and geometries of the micro-clip during degradation can be represented using a simulated degradation map. Computer simulation of the degradation of the micro-clip presented in the study is validated by in vivo and in vitro experiments. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1181-1189, 2014. PMID:24425148

Xiong, Linfei; Chui, Chee-Kong; Teo, Chee-Leong; Lau, David P C

2014-08-01

67

Heat and mass transport from thermally degrading thin cellulosic materials in a microgravity environment  

NASA Technical Reports Server (NTRS)

Attention is given to a theoretical model describing the behavior of a thermally thin cellulosic sheet heated by external thermal radiation in a quiescent microgravity environment. This model describes thermal and oxidative degradation of the sheet and the heat and mass transfer of evolved degradation products from the heated cellulosic surface into the gas phase. Two calculations are carried out: heating without thermal degradation, and heating with thermal degradation of the sheet with endothermic pyrolysis, exothermic thermal oxidative degradation, and highly exothermic char oxidation. It is shown that pyrolysis is the main degradation reaction. Self-sustained smoldering is controlled and severely limited by the reduced oxygen supply.

Kushida, G.; Baum, H. R.; Kashiwagi, T.; Di Blasi, C.

1992-01-01

68

The first word in material control is material  

Microsoft Academic Search

Material control has tended to rely on containment and access control, augmented by physical inventories, to meet the material control and accounting (MC A) goals of detecting theft\\/diversion and providing assurance that all nuclear material (NM) is present. Such systems have significant deficiencies. Material containment strategies are generally based on protection provided at boundaries around the NM and rely on

H. R. Martin; D. D. Wilkey

1989-01-01

69

Control of MCAK Degradation and Removal from Centromeres  

PubMed Central

Mitotic centromere associated kinesin (MCAK) is a kinesin related protein with the ability to stimulate microtubule depolymerization. It is found at spindle poles, where it may be involved in poleward microtubule flux, and at kinetochores and centromeres where it plays a role in correcting chromosome alignment errors. Its microtubule depolymerase activity and recruitment to centromeres is regulated by phosphorylation, but little is known about how MCAK is maintained at appropriate levels. We previously reported that MCAK accumulates during the cell cycle and is then degraded during mitosis. Using proteomic analysis, we have now identified a new phosphorylation site on MCAK that is responsible for its degradation. Mutation of the site to prevent phosphorylation prolonged the stability of the protein beyond the metaphase to anaphase transition and into the subsequent cell cycle whereas a phosphomimetic mutation accelerated degradation. Unexpectedly, the mutation that prevented phosphorylation also inhibited the removal of MCAK from centromeres causing it to remain attached throughout the cell cycle. Even low expression of phosphorylation-resistant MCAK delayed mitosis and interfered with cell division. Mitotic defects were also observed by overexpressing a GFP-tagged version of wild-type MCAK that similarly escaped degradation and accumulated to toxic levels, but didn't remain associated with kinetochores during interphase. The results demonstrate that degradation is an important mechanism for controlling the activity of MCAK.

Ganguly, Anutosh; Bhattacharya, Rajat; Cabral, Fernando

2012-01-01

70

Torso RTK controls Capicua degradation by changing its subcellular localization  

PubMed Central

The transcriptional repressor Capicua (Cic) controls multiple aspects of Drosophila embryogenesis and has been implicated in vertebrate development and human diseases. Receptor tyrosine kinases (RTKs) can antagonize Cic-dependent gene repression, but the mechanisms responsible for this effect are not fully understood. Based on genetic and imaging studies in the early Drosophila embryo, we found that Torso RTK signaling can increase the rate of Cic degradation by changing its subcellular localization. We propose that Cic is degraded predominantly in the cytoplasm and show that Torso reduces the stability of Cic by controlling the rates of its nucleocytoplasmic transport. This model accounts for the experimentally observed spatiotemporal dynamics of Cic in the early embryo and might explain RTK-dependent control of Cic in other developmental contexts.

Grimm, Oliver; Zini, Victoria Sanchez; Kim, Yoosik; Casanova, Jordi; Shvartsman, Stanislav Y.; Wieschaus, Eric

2012-01-01

71

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, such as stress corrosion cracking, are characterized by a long initiation time followed by a rapid growth phase. Monitoring such long-term degradation will require new 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; Malik, Shah

2011-02-26

72

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

73

The effect of different organic solvents on the degradation of restorative materials  

PubMed Central

Objective: To evaluate the solubility of three restorative materials exposed to the different endodontic solvents. Materials and Methods: The organic solvents eucalyptus oil, xylol, chloroform, and orange oil, with distilled water as the control group was utilized. The restorative materials light-cured resin (Filtek Z250/3M ESPE), light-cured-resin-reinforced glass ionomer (Riva Light Cure LC/Southern Dental Industries SDI]) and resin-modified glass ionomer (Vitremer/3M ESPE) were analyzed. A total of 50 disks containing specimens (2 mm × 8 mm Ø) were prepared for each of the three classes of restorative materials, which were divided into 10 groups (n = 5) for immersion in eucalyptus oil, xylol, chloroform, orange oil or distilled water for periods of either 2 min or 10 min. The means of restorative material disintegration in solvents were obtained by the difference between the original preimmersion weight and the postimmersion weight in a digital analytical scale. Data were statistically analyzed by two-way analysis of variance while the difference between the materials was analyzed by Student-Newman-Keuls test. The significance level set at 0.05. Results: Vitremer showed the highest solubility, followed by Riva LC, and these were statistically different from eucalyptus oil, xylol, chloroform, and distilled water (P < 0.05). Regarding the immersion time in solvents, there were no significant differences between the two tested periods (P > 0.05). Conclusions: The solvents minimally degraded the composite resin, although they did influence the degradation of both resin-modified glass ionomer resin and resin reinforced with glass ionomer.

Martos, Josue; Silveira, Luiz Fernando Machado; Silveira, Carina Folgearini; de Castro, Luis Antonio Suita; Ferrer-Luque, Carmen Maria

2013-01-01

74

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

75

Study on surface degradation of polymer insulating materials caused by leakage current  

Microsoft Academic Search

Some artificial aging tests were performed using test rods made of Silicone Rubber (SR) and Ethylene Propylene Rubber (EPDM), based on the Rotating Wheel Dip Test (RWDT) method and the Salt Fog Chamber Test (SFCT) method, and aspects of the surface degradation were evaluated. Following the tests, it was concluded that the surface degradation of polymer insulating materials is directly

H. Homma; T. Takahashi; T. Taniguchi; K. Izumi

1994-01-01

76

Degradation Product Analysis for Polymeric Dielectric Materials Exposed to Partial Discharges  

Microsoft Academic Search

Partial discharge phenomena appear to play an important role in insulation failure, and thus the analysis of products resulting from such degradation may lead to an understanding of insulation breakdown mechanisms and more accurate determination of insulation lifetimes. Progress in the area of degradation product analysis is reviewed for solid and liquid insulating materials.

Kevin D. Wolter; Julian F. Johnson; John Tanaka

1978-01-01

77

Photoconversion of gasified organic materials into biologically-degradable plastics  

Microsoft Academic Search

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

P. F. Weaver; Pinching Maness

1993-01-01

78

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

79

The History and Future of NDE in the Management of Nuclear Power Plant Materials Degradation  

SciTech Connect

The author has spent more than 25 years conducting engineering and research studies to quantify the performance of nondestructive evaluation (NDE) in nuclear power plant (NPP) applications and identifying improvements to codes and standards for NDE to manage materials degradation. This paper will review this fundamental NDE engineering/research work and then look to the future on how NDE can be optimized for proactively managing materials degradation in NPP components.

Doctor, Steven R.

2009-04-01

80

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

81

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

82

Ground and space based optical analysis of materials degradation in low-Earth-orbit  

NASA Technical Reports Server (NTRS)

There is strong interest in being able to accurately and sensitively monitor materials degradation in both ground-based and space-based environments. Two optical techniques for sensitive degradation monitoring are reviewed: spectroscopic ellipsometry and photothermal spectroscopy. These techniques complement each other in that ellipsometry is sensitive to atomically thin surface and subsurface changes, and photothermal spectroscopy is sensitive to local defects, pin-holes, subsurface defects, and delamination. Progress in applying these spectroscopies (both ex situ and in situ) to atomic oxygen degradation of space materials is reviewed.

Woollam, John A.; Synowicki, Ron; Hale, Jeffrey S.; Peterkin, Jane; Machlab, Hassanayn; De, Bhola N.; Johs, Blaine

1991-01-01

83

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 10months. While the higher-porosity brushite cement quantitatively transformed into crystalline octacalcium phosphate after 10months, 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 10months of implantation. PMID:24769112

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

2014-07-01

84

Phosphate Ions - Does Exposure Lead to Degradation of Cementitious Materials?  

SciTech Connect

An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a "bench-scale" laboratory investigation. Results indicate that no harmful interactions occur between phosphate ions and cememtitious materials unless phosphates are present in form of phosphoric acid.

Naus, Dan J [ORNL; Mattus, Catherine H [ORNL; Dole, Leslie Robert [ORNL

2008-01-01

85

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

86

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

87

Corrosion degradation and prevention by surface modification of biometallic materials.  

PubMed

Metals, in addition to ceramics and polymers, are important class of materials considered for replacement of non-functional parts in the body. Stainless steel 316, titanium and titanium alloys, Co-Cr, and nitinol shape memory alloys are the most frequently used metallic materials. These alloys are prone to corrosion in various extents. This review briefly discusses the important biomaterials, their properties, and the physiological environment to which these materials are exposed. Corrosion performance of currently used metallic materials has been assessed and threat to the biocompatibility from corrosion products/metal ions is discussed. The possible preventive measures to improve corrosion resistance by surface modification and to increase the bioactivity of the metallic surfaces have also been discussed. Importance of the formation of oxide layers on the metal surface, another aspect of corrosion process, has been correlated with the host response. The gap areas and future direction of research are also outlined in the paper. PMID:17143737

Singh, Raghuvir; Dahotre, Narendra B

2007-05-01

88

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

89

Toxicity of thermal degradation products of spacecraft materials  

NASA Technical Reports Server (NTRS)

Three polymeric materials were evaluated for relative toxicity of their pyrolysis products to rats by inhalation: Y-7683 (LS 200), Y-7684 (Vonar 3 on Fiberglass), and Y-7685 (Vonar 3 on N W Polyester). Criteria employed for assessing relative toxicity were (1) lethality from in-chamber pyrolysis, (2) lethality from an outside-of-chamber pyrolysis MSTL Procedure, and (3) disruption of trained rats' shock-avoidance performance during sub-lethal exposures to in-chamber pyrolysis of the materials.

Lawrence, W. H.; Turner, J. E.; Sanford, C.; Foster, S.; Baldwin, E.; Oconnor, J.

1982-01-01

90

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

91

Nuclear material control in the United States  

SciTech Connect

The Department of Energy has defined a safeguards system to be an integrated system of physical protection, material accounting and material control subsystems designed to deter, prevent, detect, and respond to unauthorized possession, use, or sabotage of SNM. In practice, safeguards involve the development and application of techniques and procedures dealing with the establishment and continued maintenance of a system of activities. The system must also include administrative controls and surveillance to assure that the procedures and techniques of the system are effective and are being carried out. The control of nuclear material is critical to the safeguarding of nuclear materials within the United States. The U.S. Department of Energy includes as part of material control four functional performance areas. They include access controls, material surveillance, material containment and detection/assessment. This paper will address not only these areas but also the relationship between material control and other safeguards and security functions.

Jaeger, C.; Waddoups, I.

1995-09-01

92

Weld repair of helium degraded reactor vessel material  

SciTech Connect

Welding methods for modification or repair of irradiated nuclear reactor vessels are being evaluated at the Savannah River Site. A low-penetration weld overlay technique has been developed to minimize the adverse effects of irradiation induced helium on the weldability of metals and alloys. This technique was successfully applied to Type 304 stainless steel test plates that contained 3 to 220 appm helium from tritium decay. Conventional welding practices caused significant cracking and degradation in the test plates. Optical microscopy of weld surfaces and cross sections showed that large surface toe cracks formed around conventional welds in the test plates but did not form around overlay welds. Scattered incipient underbead cracks (grain boundary separations) were associated with both conventional and overlay test welds. Tensile and bend tests were used to assess the effect of base metal helium content on the mechanical integrity of the low-penetration overlay welds. The axis of tensile specimens was perpendicular to the weld-base metal interface. Tensile specimens were machined after studs were resistance welded to overlay surfaces.

Kanne, W.R. Jr.; Lohmeier, D.A.; Louthan, M.R. Jr.; Rankin, D.T.; Franco-Ferreira, E.A. [Westinghouse Savannah River Co., Aiken, SC (United States); Bruck, G.J.; Madeyski, A.; Shogan, R.P.; Lessmann, G.G. [Westinghouse Electric Corp., Pittsburgh, PA (United States). Science and Technology Center

1990-12-31

93

Weld repair of helium degraded reactor vessel material  

SciTech Connect

Welding methods for modification or repair of irradiated nuclear reactor vessels are being evaluated at the Savannah River Site. A low-penetration weld overlay technique has been developed to minimize the adverse effects of irradiation induced helium on the weldability of metals and alloys. This technique was successfully applied to Type 304 stainless steel test plates that contained 3 to 220 appm helium from tritium decay. Conventional welding practices caused significant cracking and degradation in the test plates. Optical microscopy of weld surfaces and cross sections showed that large surface toe cracks formed around conventional welds in the test plates but did not form around overlay welds. Scattered incipient underbead cracks (grain boundary separations) were associated with both conventional and overlay test welds. Tensile and bend tests were used to assess the effect of base metal helium content on the mechanical integrity of the low-penetration overlay welds. The axis of tensile specimens was perpendicular to the weld-base metal interface. Tensile specimens were machined after studs were resistance welded to overlay surfaces.

Kanne, W.R. Jr.; Lohmeier, D.A.; Louthan, M.R. Jr.; Rankin, D.T.; Franco-Ferreira, E.A. (Westinghouse Savannah River Co., Aiken, SC (United States)); Bruck, G.J.; Madeyski, A.; Shogan, R.P.; Lessmann, G.G. (Westinghouse Electric Corp., Pittsburgh, PA (United States). Science and Technology Center)

1990-01-01

94

Correlation of electrical reactor cable failure with materials degradation  

Microsoft Academic Search

Complete circuit failure (shortout) of electrical cables typically used in nuclear power plant containments is investigated. Failure modes are correlated with the mechanical deterioration of the elastomeric cable materials. It is found that for normal reactor operation, electrical cables are reliable and safe over very long periods. During high temperature excursions, however, cables pulled across corners under high stress may

Stuetzer

1986-01-01

95

Reliability and surface degradation aspects of synthetic insulator materials for hv application  

Microsoft Academic Search

This study is a theoretical and experimental investigation on the state of the art of synthetic insulators for outdoor high voltage transmission systems. The surface of a polymeric material is known to be degraded by, among other things, environmental stresses such as UV, air pollutants, etc. The reliability of an insulator material is governed by the surface and other characteristics

Bhatia

1977-01-01

96

Controlling panel flutter using adaptive materials  

NASA Technical Reports Server (NTRS)

The effectiveness of using adaptive materials to control panel flutter is examined. Adaptive materials are those whose strain or mechanical properties can be controlled by the application of an external stimulus. Two such material types are piezoelectric (ceramics or polymers) and shape memory alloys. These materials experience controllable strain when subjected to applied voltage and heat, respectively. The present study investigates the use of both material types to modify the flutter characteristics of a simply supported panel in supersonic flow. Piezoelectric materials respond quickly to applied voltages and can be used with feedback control for active vibration suppression. The adaptive process of the shape memory alloy used in this study (geometry and stiffness change) is a relatively low frequency phenomenon; therefore, it is considered for passive (on/off) control schemes only. Nondimensional parameters for these adaptive materials are used with linear panel models, yielding results which allow for a better understanding of their capabilities in controlling aeroelastic responses.

Scott, R. C.; Weisshaar, T. A.

1991-01-01

97

Chlorine related degradation of materials in coal liquefaction  

SciTech Connect

During the 1970's, a concentrated effort was directed toward development of coal liquefaction in the United States, at least in part, because of the demonstrated vulnerability of this country during the oil embargoes. A number of pilot plants were operated to evaluate different liquefaction processes, and the performance of structural materials was assessed in these plants. Although material performance in coal liquefaction plants had many similarities with performance in petrochemical plants, the presence of significant amounts of chlorine in some coals caused serious problems. Severe localized corrosion that was related to amine hydrochlorides was encountered in fractionation columns, and chloride stress corrosion cracking was found in many pipes and vessels. 12 refs., 5 figs.

Keiser, J.R.; Judkins, R.R.

1989-01-01

98

Degradation mode surveys of high performance candidate container materials  

SciTech Connect

Corrosion resistant materials are being considered for the metallic barrier of the Yucca Mountain Project`s high-level radioactive waste disposal containers. Nickel-chromium-molybdenum alloys and titanium alloys have good corrosion resistance properties and are considered good candidates for the metallic barrier. The localized corrosion phenomena, pitting and crevice corrosion, are considered as potentially limiting for the barrier lifetime. An understanding of the mechanisms of localized corrosion and of how various parameters affect it will be necessary for adequate performance assessment of candidate container materials. Examples of some of the concerns involving localized corrosion are discussed. The effects of various parameters, such as temperature and concentration of halide species, on localized corrosion are given. In addition, concerns about aging of the protective oxide layer in the expected service temperature range (50 to 250{degree}C) are presented. Also some mechanistic considerations of localized corrosion are given. 45 refs., 1 tab.

Gdowski, G.E.; McCright, R.D.

1990-12-01

99

Use of degradable and nondegradable nanomaterials for controlled release.  

PubMed

Drug-delivery devices are fundamentally important in improving the pharmacological profiles of therapeutic molecules. Nanocontrolled-release systems are attracting a lot of attention currently owing to their large surface area and their ability to target delivery to specific sites in the human body. In addition, they can penetrate the cell membrane for gene, nucleic acid and bioactive peptide/protein delivery. Representative applications of nanodrug-delivery systems include controlled-release wound dressings, controlled-release scaffolds for tissue regeneration and implantable biodegradable nanomaterial-based medical devices integrated with drug-delivery functions. We review the present status and future perspectives of various types of nanocontrolled-release systems. Although many of the well-established degradable and nondegradable controlled-release vehicles are being investigated for their processing into nanocarriers, several new emerging nanomaterials are being studied for their controlled-release properties. The release of multiple bioactive agents, each with its own kinetic profile, is becoming possible. In addition, integration of the nanocontrolled-release systems with other desirable functions to create new, cross-discipline applications can also be realized. PMID:17716133

Wan, W K; Yang, Lifang; Padavan, Donna T

2007-08-01

100

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

101

Correlation of electrical reactor cable failure with materials degradation  

SciTech Connect

Complete circuit failure (shortout) of electrical cables typically used in nuclear power plant containments is investigated. Failure modes are correlated with the mechanical deterioration of the elastomeric cable materials. It is found that for normal reactor operation, electrical cables are reliable and safe over very long periods. During high temperature excursions, however, cables pulled across corners under high stress may short out due to conductor creep. Severe cracking will occur in short times during high temperatures (>150/sup 0/C) and in times of the order of years at elevated temperatures (100/sup 0/C to 140/sup 0/C). A theoretical treatment of stress distribution responsible for creep and for cracking by J.E. Reaugh of Science Applications, Inc. is contained in the Appendix. 29 refs., 32 figs.

Stuetzer, O.M.

1986-03-01

102

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

103

Report of the Material Control and Material Accounting Task Force. Volume 2. The Role of Material Control and Material Accounting in the Safeguards Program.  

National Technical Information Service (NTIS)

The Material Control and Material Accounting Task Force defined the roles, objectives, and goals of material control and material accounting within the domestic Safeguards Program for licensed strategic special nuclear material (SSNM). The Task Force then...

F. L. Crane W. D. Altman W. B. Brown R. J. Dube J. W. Hockert

1978-01-01

104

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

105

Materials and degradation modes in an alternative LLW (low-level waste) disposal facility  

SciTech Connect

The materials used in the construction of alternative low-level waste disposal facilities will be subject to interaction with both the internal and the external environments associated with the facilities and unless precautions are taken, may degrade, leading to structural failure. This paper reviews the characteristics of both environments with respect to three alternative disposal concepts, then assesses how reaction with them might affect the properties of the materials, which include concrete, steel-reinforced concrete, structural steel, and various protective coatings and membranes. It identifies and evaluates the probability of reactions occurring which might lead to degradation of the materials and so compromise the structure. The probability of failure (interpreted relative to the ability of the structure to restrict ingress and egress of water) is assessed for each material and precautionary measures, intended to maximize the durability of the facility, are reviewed. 19 refs., 2 tabs.

Cowgill, M.G.; MacKenzie, D.R.

1989-01-01

106

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

107

Adiabatic shear banding-induced degradation in a thermo-elastic\\/viscoplastic material under dynamic loading  

Microsoft Academic Search

In the approach presented, adiabatic shear banding (ASB) is considered as a form of anisotropic deterioration. The anisotropic mechanical degradation induced in the structural material by the bands is dealt with by using a second-order tensor internal variable. The kinematical consequences of the presence of the bands are described by means of the corresponding part (deterioration-induced part in addition to

Patrice Longère; André Dragon; Hervé Trumel; Xavier Deprince

2005-01-01

108

Space Mapping Optimization of the Magnetic Circuit of Electrical Machines Including Local Material Degradation  

Microsoft Academic Search

Production processes like cutting, performed on electrical steel laminations, influence their magnetic properties locally. Since the magnetic design of electrical machines does not take this effect into account accurately, the design may be suboptimal. Therefore, the need exists to develop a numerical procedure which is capable of optimizing electrical devices, taking into account the local material degradation and featuring high

Guillaume Crevecoeur; Luc Dupr; Rik Van de Walle

2007-01-01

109

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

110

Role of synergy between wear and corrosion in degradation of materials  

NASA Astrophysics Data System (ADS)

Tribocorrosion is a term used to describe the material degradation due to the combination of electrochemical and tribological processes. Due to a synergetic effect, the material loss can be larger than the sum of the losses due to wear and corrosion acting separately. In this thesis, the synergy of wear and corrosion was investigated for different types of material, namely the Ti-6Al-4V alloy, the SS316L stainless steel coated with a thin film of Diamond Like Carbon (DLC), and the SS301 stainless steel coated with a thin film of chromium silicon nitride (CrSiN). A tribocorrosion apparatus was designed and constructed to conduct wear experiments in corrosive media. Sliding ball-on-plate configuration was used in this design, where the contact between the ball and the specimen is totally immersed in the test electrolyte. The specimen was connected to a potentiostat to control its electrochemical parameters, namely the potential and the current. Electrochemical techniques were used to control the kinetics of corrosion reactions, and therefore it was possible to assess separately the role of corrosion and wear in the total degradation of material, and to evaluate the synergy between them. For Ti-6Al-4V, it was found that the corrosion and tribocorrosion depend strongly on the structure of the material. The alpha-equiaxed microstructure with fine dispersed beta-phase exhibited the best corrosion resistance. The corrosion resistance was found to decrease when the basal plane was preferentially aligned parallel to the surface, which is attributed to a low resistance to charge transfer in the oxide films formed on this plane. On the other hand, when wear and corrosion were involved simultaneously, the oxide layer protecting the substrate against dissolution was mechanically destroyed leading to a high corrosion rate. It was found that the hardness was the most important factor determining the tribocorrosion behavior of the Ti-6Al-4V alloy; samples with high hardness exhibited less mechanical wear, less wear-enhanced corrosion, and less corrosion-enhanced wear. For DLC coatings, it was found that interface engineering plays a crucial role in the tribocorrosion behavior of DLC films. DLC films with nitrided interface layer (SSN3hDLC) were shown to have very poor tribocorrosion resistance; the DLC film delaminated from the substrate after 50 cycles of sliding wear at 9 N load in Ringer's solution. It should be mentioned that a previous study performed at Ecole Polytechnique de Montreal [4] has shown that the same coating resisted 1800 cycles of dry wear at 22 N without delamination. This demonstrates clearly the effect of corrosion on the wear resistance of DLC films. The use of a-SiN:H bond layer between the SS316L substrate and the DLC film improved significantly the tribocorrosion behavior of the coating. This layer acts as a barrier against corrosion reaction; the polarization resistance was 5.76 GO.cm2 compared to 27.5 MO.cm2 and 1.81 MO.cm2 for the DLC-coated SS316L with nitrided interface layer and the bare substrate, respectively. For CrSiN coatings, it was also shown that nitriding treatment of the substrate prior to deposition reduces significantly the tribocorosion resistance of the CrSiN-coated SS301 substrates. This is attributed to the peculiar morphology of the nitrided surface prior to deposition. The high relives at the grain boundaries of the substrate may be the reason for the generation, during sliding wear, of defects in the film, which makes the infiltration of the liquid easier, and consequently leads to the destruction of the CrSiN film.

Azzi, Marwan

111

Strukturnye perestrojki i degradatsiya svojstv diehlektricheskikh materialov pod oblucheniem. (Structure rearrangement and degradation of properties in dielectric materials under irradiation).  

National Technical Information Service (NTIS)

Results of optical, electrical and structural investigation of BN and Al(sub 2)O(sub 3) materials which allow one to determine the peculiarities of radiation induced degradation (RID) concerning electrical and optical properties of dielectric materials wi...

O. A. Plaksin V. A. Stepanov P. A. Stepanov L. M. Kryukova A. M. Polyakov

1994-01-01

112

Applied physics: Materials scientists take control  

NASA Astrophysics Data System (ADS)

The discovery of a new way of controlling a class of complex-oxide materials, known as the Ruddlesden-Popper series of structures, may lead the way to making electronically tunable microwave devices. See Letter p.532

Cole, Melanie W.

2013-10-01

113

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

114

Study of the degradation of mulch materials in vegetable crops for organic farming  

NASA Astrophysics Data System (ADS)

Mulching is the most common technique used worldwide by vegetable growers in protected cultivation. For this purpose, several plastic materials have been used, with polyethylene (PE) being the most widespread. However, PE is produced from petroleum derivatives, it is not degradable, and thus pollutes the environment for periods much longer than the crop duration (Martín-Closas and Pelacho, 2011), which are very important negative aspects especially for organic farmers. A large portion of plastic films is left on the field or burnt uncontrollably by the farmers, with the associated negative consequences to the environment (Moreno and Moreno, 2008). Therefore, the best solution is to find a material with a lifetime similar to the crop duration time that can be later incorporated by the agricultural system through a biodegradation process (Martín-Closas and Pelacho, 2011). In this context, various biodegradable materials have been considered as alternatives in the last few years, including oxo-biodegradable films, biopolymer mulches, different types of papers, and crop residues (Kasirajan and Ngouajio, 2012). In this work we evaluate the evolution of different properties related to mulch degradation in both the buried and the superficial (exposed) part of mulch materials of different composition (standard black PE, papers and black biodegradable plastics) in summer vegetable crops under organic management in Castilla-La Mancha (Central Spain). As results, it is remarkable the early deterioration suffered by the buried part of the papers, disappearing completely in the soil at the end of the crop cycles and therefore indicating the total incorporation of these materials to the soil once the crop has finished. In the case of the degradation of the exposed mulch, small differences between crops were observed. In general, all the materials were less degraded under the plants than when receiving directly the solar radiation. As conclusion, biodegradable mulches degrade early but once they have fulfilled their functions, appearing as a good alternative to PE, especially in organic farming. Project INIA RTA2011-00104-C04-03. References: Kasirajan, S.; Ngouajio, M. 2012. Polyethylene and biodegradable mulches for agricultural applications: a review. Agron. Sustain. Dev. 32: 501-529. Martín-Closas, L.; Pelacho, A.M. 2011. Agronomic potential of biopolymer films. p. 277-299. In: Biopolymers. New materials for sustainable films and coating. John Wiley & Sons, New York. Moreno, M.M.; Moreno A. 2008. Effect of different biodegradable and polyethylene mulches on productivity and soil thermal and biological properties in a tomato crop. Sci. Hort. 116(3): 256-263.

María Moreno, Marta; Mancebo, Ignacio; Moreno, Carmen; Villena, Jaime; Meco, Ramón

2014-05-01

115

Semi-degradable poly(?-amino ester) networks with temporally controlled enhancement of mechanical properties.  

PubMed

Biodegradable polymers are clinically used in numerous biomedical applications, and classically show a loss of mechanical properties within weeks of implantation. This work demonstrates a new class of semi-degradable polymers that show an increase in mechanical properties through degradation via a controlled shift in a thermal transition. Semi-degradable polymer networks, poly(?-amino ester)-co-methyl methacrylate, were formed from a low glass transition temperature crosslinker, poly(?-amino ester), and high glass transition temperature monomer, methyl methacrylate, which degraded in a manner dependent upon the crosslinker chemical structure. In vitro and in vivo degradation revealed changes in mechanical behavior due to the degradation of the crosslinker from the polymer network. This novel polymer system demonstrates a strategy to temporally control the mechanical behavior of polymers and to enhance the initial performance of smart biomedical devices. PMID:24769113

Safranski, David L; Weiss, Daiana; Clark, J Brian; Taylor, W Robert; Gall, Ken

2014-08-01

116

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

117

Downhole material injector for lost circulation control  

DOEpatents

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, David A. (Tijeras, NM)

1994-01-01

118

Thermal degradation of nano-cellulose hybrid materials containing reactive polyhedral oligomeric silsesquioxane  

Microsoft Academic Search

Nano-cellulose hybrids containing reactive polyhedral oligomeric silsesquioxane (R-POSS) were synthesized by staring crosslinking reaction using reactive polyhedral oligomeric silsesquioxane containing multi-N-methylol groups. Thermal degradation properties of nano-cellulose hybrid materials containing R-POSS were investigated by TGA and DSC. Surface chemical ingredients of the nano-cellulose hybrids were analyzed by X-ray photoelectron spectroscopy (XPS). Chemical structure and morphology of charred residue were analyzed

Kongliang Xie; Xiuriu Gao; Weiguo Zhao

2010-01-01

119

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

120

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

121

Report of the Material Control and Material Accounting Task Force. Executive Summary.  

National Technical Information Service (NTIS)

The Material Control and Material Accounting Task Force defined the roles, objectives, and goals of material control and material accounting within the domestic Safeguards Program for licensed strategic special nuclear material (SSNM). The Task Force then...

F. L. Crane W. D. Altman W. B. Brown R. J. Dube J. W. Hockert

1978-01-01

122

Report of the Material Control and Material Accounting Task Force. Volume 1. Summary.  

National Technical Information Service (NTIS)

The Material Control and Material Accounting Task Force defined the roles, objectives, and goals of material control and material accounting within the domestic Safeguards Program for licensed strategic special nuclear material (SSNM). The Task Force then...

F. L. Crane W. D. Altman W. B. Brown R. J. Dube J. W. Hockert

1978-01-01

123

Thermal control materials in Mercury environment  

NASA Astrophysics Data System (ADS)

Thermal control materials are under development concerning the BepiColombo mission to the planet Mercury. The vicinity to the sun creates extreme heat and radiation fluxes and, advanced materials are needed. A Multi-Layer Insulation has been developed able to withstand the high temperatures and particle fluxes. Upilex has been preferred to Kapton for the reflective screens of the MLI and Tissue Glass is used as a spacer. On sunlit surfaces a sun shield will be added to the MLI employing a ceramic fabric. Further developments for application on external surfaces are a Solar Reflector Coating and an Optical Surface Reflector. An Infrared Rejection Device will be applied within the entrance port of nadir pointing instruments and serve as a protective element to reflect or absorb the planetary infra-red radiation. This paper presents the current status in the development of the thermal insulation and the other thermal control materials. The materials selection and available test results are presented.

Antonenko, J.

2003-09-01

124

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

125

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.

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

2014-01-01

126

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

127

Influence of chemical degradation on the surface properties of nano restorative materials.  

PubMed

SUMMARY Objectives : The aim of this in vitro study was to investigate the effect of chemical degradation on the surface roughness (Ra) and hardness (Knoop hardness number [KHN]) of nano restorative materials. Methods : Disc-shaped specimens (5-mm diameter; 2-mm thick) of Filtek Z350 and TPH Spectrum composites and the Vitremer and Ketac Nano light-curing glass ionomer cements were prepared according to the manufacturers' instructions. After 24 hours, polishing procedures were performed and initial measurements of Ra and KHN were taken. The specimens were divided into 12 groups (n=10) according to material and storage media: artificial saliva, orange juice, and Coca-Cola. After 30 days of storage, the specimens were reevaluated for Ra and KHN. The pH values of the storage media were measured weekly. Data were tested for significant differences by repeated-measures three-way analysis of variance and Tukey tests (p<0.05). Results : Composites were found to present lower roughness values and higher hardness values than the ionomeric materials under all storage conditions. After degradation, the KHN of all experimental samples decreased significantly, while the Ra of the ionomeric materials increased, depending on the media, with a markedly negative impact of Coca-Cola and orange juice. There was no difference among the storage media for Filtek Z350 with regard to the KHN values. Nanofillers did not show any influence on the roughness and hardness of resin-modified glass ionomer cements and resin composites concerning their degradation resistance. PMID:24289802

de Paula, Ab; de Fúcio, Sbp; Alonso, Rcb; Ambrosano, Gmb; Puppin-Rontani, Rm

2014-01-01

128

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

129

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.

2012-11-14

130

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

NASA Technical Reports Server (NTRS)

An atomic oxygen exposure facility was 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 materials for use in low Earth orbit. The studies that are being undertaken will provide: (1) absolute reaction cross sections for the engineering design problems, (2) formulations of reaction mechanisms for use in the selection of suitable existing materials and the design of new more resistant ones, and (3) the 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 a CW laser sustained discharge source of O-atoms, an atomic beam formation and diagnostics system, a spinning rotor viscometer, and provision for using the system for calibration of actual flight instruments.

Cross, J. B.; Spangler, L. H.; Hoffbauer, M. A.; Archuleta, F. A.; Leger, Lubert; Visentine, James; Hunton, Don E.; Cross, J. B.

1986-01-01

131

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

132

Computerized materials protection, control, and accountability  

Microsoft Academic Search

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

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

1997-01-01

133

Degradable hydrogels for spatiotemporal control of mesenchymal stem cells localized at decellularized bone allografts.  

PubMed

The transplantation of cells, such as mesenchymal stem cells (MSCs), has numerous applications in the field of regenerative medicine. For cell transplantation strategies to be successful therapeutically, cellular localization and persistence must be controlled to maximize cell-mediated contributions to healing. Herein, we demonstrate that hydrolytic degradation of poly(ethylene glycol) (PEG) hydrogels can be used to spatiotemporally control encapsulated MSC localization to decellularized bone allografts, both in vitro and in vivo. By altering the number of hydrolytically degradable lactide repeat units within PEG-d,l-lactide-methacrylate macromers, a series of hydrogels was synthesized that degraded over ?1, 2 and 3weeks. MSCs were encapsulated within these hydrogels formed around decellularized bone allografts, and non-invasive, longitudinal fluorescence imaging was used to track cell persistence both in vitro and in vivo. Spatiotemporal localization of MSCs to the exterior of bone allograft surfaces was similar to in vitro hydrogel degradation kinetics despite hydrogel mesh sizes being ?2-3 orders of magnitude smaller than MSC size throughout the degradation process. Thus, localized, cell-mediated degradation and MSC migration from the hydrogels are suspected, particularly as ?10% of the total transplanted MSC population was shown to persist in close proximity (within ?650?m) to grafts 7weeks after complete hydrogel degradation. This work demonstrates the therapeutic utility of PEG-based hydrogels for controlling spatiotemporal cell transplantation for a myriad of regenerative medicine strategies. PMID:24751534

Hoffman, Michael D; Van Hove, Amy H; Benoit, Danielle S W

2014-08-01

134

Smart Control Systems for Smart Materials  

NASA Astrophysics Data System (ADS)

Shape memory alloys (SMAs) are thermally activated smart materials. Due to their ability to change into a previously imprinted shape by the means of thermal activation, they are suitable as actuators for microsystems and, within certain limitations for macroscopic systems. Most commonly used SMAs for actuators are binary nickel-titanium alloys (NiTi). The shape memory effect relies on the martensitic phase transformation. On heating the material from the low temperature phase (martensite) the material starts to transform into the high temperature phase (austenite) at the austenite start temperature ( A s). The reverse transformation starts at the martensite start temperature after passing a hysteresis cycle. To apply these materials to a wide range of industrial applications, a simple method for controlling the actuator effect is required. Today's control concepts for shape memory actuators, in applications as well as in test stands, are time-based. This often leads to overheating after transformation into the high temperature phase which results in early fatigue. Besides, the dynamic behavior of such systems is influenced by unnecessary heating, resulting in a poor time performance. To minimize these effects, a controller system with resistance feedback is required to hold the energy input on specific keypoints. These two key points are directly before transformation ( A s) and shortly before retransformation ( M s). This allows triggering of fast and energy-efficient transformation cycles. Both experimental results and a mechatronical demonstrator system, exhibit the advantages of systems concerning efficiency, dynamics, and reliability.

Meier, Horst; Czechowicz, Alexander; Haberland, Christoph; Langbein, Sven

2011-07-01

135

Materials and techniques for controllable microwave surfaces  

NASA Astrophysics Data System (ADS)

Discs and waveguide samples of polymeric mixed conductor nanocomposite materials comprising a conducting polymer and redox active switching agent in a polymer electrolyte have been prepared and studied. These novel materials have been shown to exhibit large, rapid and reversible changes in their microwave impedance when small d.c. electric fields are applied across them from the edges. The results of simultaneous cyclic voltammetry or potential square waves and microwave transmission measurements have shown that the changes are apparantly instantaneous with the application or removal of the applied field. Analysis of the microwave results has shown that the impedance of the materials changes by a factor of up to almost 50 with the imposition or removal of the fields. Nanocomposite materials having either poly(pyrrole) or poly(aniline) as the conducting polymer component and either silver/silver tetrafluoroborate or copper/copper(II) tetrafluoroborate as the redox active components have been investigated. The results of the nanocomposite materials are compared with those of microparticulate composities of similar composition. A new configuration of single layer tunable microwave absorber using only resistive control has been investigated and shown to exhibit wideband, low reflectivity performance combined with reduced thickness. A major advantage of the new topology is the requirement for only a 3:1 change in controllable resistance.

Barnes, Alan; Ford, Kenneth L.; Wright, Peter V.; Chambers, Barry; Smith, Christopher D.; Thompson, Denise A.; Pavri, Francis

2000-08-01

136

Fuzzy controllers in nuclear material accounting  

SciTech Connect

Fuzzy controllers are applied to predicting and modeling a time series, with particular emphasis on anomaly detection in nuclear material inventory differences. As compared to neural networks, the fuzzy controllers can operate in real time; their learning process does not require many iterations to converge. For this reason fuzzy controllers are potentially useful in time series forecasting, where the authors want to detect and identify trends in real time. They describe an object-oriented implementation of the algorithm advanced by Wang and Mendel. Numerical results are presented both for inventory data and time series corresponding to chaotic situations, such as encountered in the context of strange attractors. In the latter case, the effects of noise on the predictive power of the fuzzy controller are explored.

Zardecki, A.

1994-10-01

137

Degradation of TAUVEX optical system performance due to contamination by outgassed spacecraft materials  

NASA Astrophysics Data System (ADS)

The space ultrahigh vacuum environment induces outgassing of spacecraft organic materials which may condense on optical surfaces and degrade the performance of optical systems. Lab simulation outgassing tests show transmission and/or reflection losses of optical components (i.e., optically polished plates and mirrors) measured at the wavelength range of 200 - 800 nm. The losses caused by deposition of outgassed products on the optical surfaces at the amount of 10-6 - X10-4 g/cm2 were measured. The loss mechanism is most likely scattering of light. This experimental data was combined with a computerized ab-initio model which calculated the contamination developed in a simulated preliminary design of the TAUVEX astronomical UV research telescope. This enabled us to estimate the performance of TAUVEX's optical system as a function of mission time, and served as a guideline for selection of materials, cleanliness requirements, thermal conditions and bakeout processes.

Nahor, Gad; Baer, Michael; Anholt, Micha; Murat, Michael; Noter, Yoram; Lifshitz, Yeshayahu; Saar, Nachman; Braun, Ofer

1993-08-01

138

Deterioration of slot stress control materials on generator stator conductors by non-mechanical mechanisms  

Microsoft Academic Search

Long-term aging experiments conducted to examine mechanisms which could degrade a stator conductor slot stress control system are described. Models consisting of two conductor bars in a short length of core, single conductor bars, and other arrangements were used to investigate the development of slot discharge and compare the performances of various materials. Damage was found to start in the

J. W. Wood; R. T. Hindmarch

1990-01-01

139

Report of the Material Control and Material Accounting Task Force. Volume 4. Appendices.  

National Technical Information Service (NTIS)

Contents: Chronological development of material control and material accounting requirements; Current requirements and practices; Measurement and measurement quality control programs; Special inventory difference considerations; Evaluation methodologies.

F. L. Crane W. D. Altman W. B. Brown R. J. Dube J. W. Hockert

1978-01-01

140

Insider Threat - Material Control and Accountability Mitigation  

SciTech Connect

The technical objectives of nuclear safeguards are (1) the timely detection of diversion of significant quantities of nuclear material from peaceful uses to the manufacture of nuclear weapons or other nuclear explosive devices or for purposes unknown and (2) the deterrence of such diversion by the risk of early detection. The safeguards and security program must address both outsider threats and insider threats. Outsider threats are primarily addressed by the physical protection system. Insider threats can be any level of personnel at the site including passive or active insiders that could attempt protracted or abrupt diversion. This could occur by an individual acting alone or by collusion between an individual with material control and accountability (MC&A) responsibilities and another individual who has responsibility or control within both the physical protection and the MC&A systems. The insider threat is one that must be understood and incorporated into the safeguards posture. There have been more than 18 documented cases of theft or loss of plutonium or highly enriched uranium. The insider has access, authority, and knowledge, as well as a set of attributes, that make him/her difficult to detect. An integrated safeguards program is designed as a defense-in-depth system that seeks to prevent the unauthorized removal of nuclear material, to provide early detection of any unauthorized attempt to remove nuclear material, and to rapidly respond to any attempted removal of nuclear material. The program is also designed to support protection against sabotage, espionage, unauthorized access, compromise, and other hostile acts that may cause unacceptable adverse impacts on national security, program continuity, the health and safety of employees, the public, or the environment. Nuclear MC&A play an essential role in the capabilities of an integrated safeguards system to deter and detect theft or diversion of nuclear material. An integrated safeguards system with compensating mitigation can decrease the risk of an insider performing a malicious act without detection.

Powell, Danny H [ORNL] [ORNL; Elwood Jr, Robert H [ORNL] [ORNL; Roche, Charles T [ORNL] [ORNL

2011-01-01

141

Degradation in steam of 60 cm-long B4C control rods  

NASA Astrophysics Data System (ADS)

In the framework of nuclear reactor core meltdown accident studies, the degradation of boron carbide control rod segments exposed to argon/steam atmospheres was investigated up to about 2000 °C in IRSN laboratories. The sequence of the phenomena involved in the degradation has been found to take place as expected. Nevertheless, the ZrO2 oxide layer formed on the outer surface of the guide tube was very protective, significantly delaying and limiting the guide tube failure and therefore the boron carbide pellet oxidation. Contrary to what was expected, the presence of the control rod decreases the hydrogen release instead of increasing it by additional oxidation of boron compounds. Boron contents up to 20 wt.% were measured in metallic mixtures formed during degradation. It was observed that these metallic melts are able to attack the surrounding fuel rods, which could have consequences on fuel degradation and fission product release kinetics during severe accidents.

Dominguez, C.; Drouan, D.

2014-08-01

142

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

143

Integrated design of structures, controls, and materials  

NASA Technical Reports Server (NTRS)

In this talk we shall discuss algorithms and CAD tools for the design and analysis of structures for high performance applications using advanced composite materials. An extensive mathematical theory for optimal structural (e.g., shape) design was developed over the past thirty years. Aspects of this theory have been used in the design of components for hypersonic vehicles and thermal diffusion systems based on homogeneous materials. Enhancement of the design methods to include optimization of the microstructure of the component is a significant innovation which can lead to major enhancements in component performance. Our work is focused on the adaptation of existing theories of optimal structural design (e.g., optimal shape design) to treat the design of structures using advanced composite materials (e.g., fiber reinforced, resin matrix materials). In this talk we shall discuss models and algorithms for the design of simple structures from composite materials, focussing on a problem in thermal management. We shall also discuss methods for the integration of active structural controls into the design process.

Blankenship, G. L.

1994-01-01

144

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.

145

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.

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

2013-01-01

146

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

147

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

148

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); Michael Maurizi (National Cancer Institute;Laboratory of Cell Biology); Susan Gottesman (National Cancer Institute;Laboratory of Molecular Biology)

1999-12-03

149

Opposed growth factor signals control protein degradation in muscles of Caenorhabditis elegans  

PubMed Central

In addition to contractile function, muscle provides a metabolic buffer by degrading protein in times of organismal need. Protein is also degraded during adaptive muscle remodeling upon exercise, but extreme degradation in diverse clinical conditions can compromise function(s) and threaten life. Here, we show how two independent signals interact to control protein degradation. In striated muscles of Caenorhabditis elegans, reduction of insulin-like signaling via DAF-2 insulin/IGF receptor or its intramuscular effector PtdIns-3-kinase (PI3K) causes unexpected activation of MAP kinase (MAPK), consequent activation of pre-existing systems for protein degradation, and progressive impairment of mobility. Degradation is prevented by mutations that increase signal downstream of PI3K or by disruption of autocrine signal from fibroblast growth factor (FGF) via the FGF receptor and its effectors in the Ras–MAPK pathway. Thus, the activity of constitutive protein degradation systems in normal muscle is minimized by a balance between directly interacting signaling pathways, implying that physiological, pathological, or therapeutic alteration of this balance may contribute to muscle remodeling or wasting.

Szewczyk, Nathaniel J; Peterson, Brant K; Barmada, Sami J; Parkinson, Leah P; Jacobson, Lewis A

2007-01-01

150

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

151

Report of the Material Control and Material Accounting Task Force. Volume 3. Blueprint for the Future.  

National Technical Information Service (NTIS)

Contents: Proposed regulatory upgrades and supporting programs; Special issues-(Action criteria for inventory differences, Material balance area accounting, The analysis of inventory differences, Rapid material control, Collusion and material control and ...

F. L. Crane W. D. Altman W. B. Brown D. J. Dube J. W. Hockert

1978-01-01

152

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

153

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

154

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

155

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

156

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

NASA Astrophysics Data System (ADS)

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; Seiler, Georg; Altpeter, Iris; Dobmann, Gerd; Herrmann, Hans-Georg; Boller, Christian

2014-02-01

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

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-vacuo reflectance technique. The dose applied to the paints was approximately equivalent to 5 yr 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-vacuo reflectance technique to investigate UV activated reflectance recovery. Both samples showed minimal UV activated reflectance 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, Jason A.; Kamenetzky, Rachel R.; Finckenor, M. M.; Meshishnek, M. J.

1998-01-01

159

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-vacuo reflectance technique. The dose applied to the paints was approximately equivalent to 5 yr 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-vacuo reflectance technique to investigate UV activated reflectance recovery. Both samples showed minimal UV activated reflectance 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, Jason A.; Kamenetzky, Rachel R.; Finckenor, M. M.; Meshishnek, M. J.

1999-01-01

160

Controlled degradation of hydrogels using multi-functional cross-linking molecules.  

PubMed

Hydrogels, chemically cross-linked or physically entangled, have found a number of applications as novel delivery vehicles of drugs and cells. However, the narrow ranges of degradation rates and mechanical strength currently available from many hydrogels limits their applications. We have hypothesized that utilization of multi-functional cross-linking molecules to form hydrogels could provide a wider range and tighter control over the degradation rates and mechanical stiffness of gels than bi-functional cross-linking molecules. To address the possibility, we isolated alpha-L-guluronate residues of sodium alginate, and oxidized them to prepare poly(aldehyde guluronate) (PAG). Hydrogels were formed with either poly(acrylamide-co-hydrazide) (PAH) as a multi-functional cross-linking molecule or adipic acid dihydrazide (AAD) as a bi-functional cross-linking molecule. The initial properties and degradation behavior of both PAG gel types were monitored. PAG/PAH hydrogels showed higher mechanical stiffness before degradation and degraded more slowly than PAG/AAD gels, at the same concentration of cross-linking functional groups. The enhanced mechanical stiffness and prolonged degradation behavior could be attributed to the multiple attachment points of PAH in the gel at the same concentration of functional groups. This approach to regulating gel properties with multifunctional cross-linking molecules could be broadly used in hydrogels. PMID:14751730

Lee, Kuen Yong; Bouhadir, Kamal H; Mooney, David J

2004-06-01

161

PAH degradation and redox control in an electrode enhanced sediment cap  

PubMed Central

Capping is typically used to control contaminant release from the underlying sediments. However, the presence of conventional sediment caps will often eliminate or slow natural degradation that might otherwise occur at the surface sediment. The objective of this study was to explore the potential of a novel reactive capping, an electrode enhanced cap for the remediation of PAH contaminated sediment. The study on electrode enhanced biodegradation of PAH in slurries showed that naphthalene concentration decreased from ~1000 ?g/L to ~50 ?g/L, and phenanthrene decreased from ~150 ?g/L to ~30 ?g/L in ElectroBioReactor within 4 days, and the copy numbers of PAH degrading genes increased by almost 2 orders of magnitude. In a cap microcosm, two carbon electrodes were emplaced within a sediment cap with an applied potential of 2 V. The anode was placed at the sediment-cap interface encouraging oxidizing conditions. Oxidation and Reduction Potential (ORP) profiles showed redox potential approximately 60-100 mV higher at the sediment-cap interface with the application of voltage than in controls. Vertical profiles of phenanthrene porewater concentration were obtained by PDMS-coated fiber, and results showed that phenanthrene at the depth of 0-0.5 cm below the anode was degraded to ~70% of the initial concentration within 10 weeks. PAH degrading genes showed an increase of approximately 1 order of magnitude at the same depth. The no power controls showed no degradation of PAH. These findings suggest that electrode enhanced capping can be used to control redox potential, provide microbial electron acceptor, and stimulate PAH degradation.

Yan, Fei; Reible, Danny D.

2012-01-01

162

Bioactive, degradable composite microspheres: effect of filler material on surface reactivity.  

PubMed

Composite microspheres with two different fillers were developed using a solid-in-oil-in-water (s/o/w) emulsion solvent removal method. Two types of bioactive ceramic powders, specifically calcium hydroxyapatite (HA) and modified bioactive glass (MBG), were incorporated into degradable poly(lactic acid) (PLA) polymer matrix to form composite microspheres. For each filler material, microspheres with three different weight ratios of filler material to polymer, namely, 1: 1, 1: 3, and 1: 9, were synthesized. In vitro immersion using simulated physiological fluid (SPF) was employed to evaluate the surface reactivity of the microspheres. SEM analysis revealed that after a 14-day immersion the surface of the microspheres containing 50% MBG was fully transformed into a bone-like apatite. In contrast, a limited number of mineral nodules were present on the surface of microspheres containing HA. The solution chemical analyses performed to determine changes of Ca, P, and Si concentrations as a function of the immersion time showed that the ion concentration profiles were similar for all microspheres, except the [Si] profile. A higher Si concentration was detected in the SPF immersed with MBG-containing microspheres. These data show that the MBG filler significantly enhances the surface reactivity of the composite microspheres. This observation enables us to conclude that the composite MBG-containing microspheres are the preferable microspheres for three-dimensional bone tissue engineering. PMID:12446347

Qiu, Qing-Qing; Ducheyne, Paul; Ayyaswamy, Portonovo S

2002-10-01

163

Effect of enzymatic degradation on the mechanical properties of biological scaffold materials  

PubMed Central

Background Biological scaffolds must support a complex balance of resisting enzymatic degradation while promoting tissue remodeling. Thus, the purpose of this study was to evaluate the effects of in vitro enzymatic exposure on the mechanical properties of biological scaffolds. It was hypothesized that exposure to an enzyme solution would result in decreased tensile strength and that crosslinked scaffolds would resist enzymatic degradation more effectively than noncrosslinked scaffolds. Methods Nine scaffolds were evaluated (four porcine dermis: Permacol™, CollaMend™, Strattice™, XenMatrix™; two human dermis: AlloMax™, FlexHD®; two bovine pericardium: Veritas®, PeriGuard®; and one porcine small intestine submucosa: Surgisis™). Ten specimens (n = 10) were hydrated in saline at 37 °C and subjected to uniaxial testing to establish baseline properties. 50 specimens (n = 50) were incubated in collagenase solution at 37 °C for 2, 6, 12, 24, or 30 h (n = 10 each group) followed by uniaxial tensile testing. Results Tensile strength was significantly reduced after 30 h for CollaMend™, AlloMax™, Veritas®, Strattice™, XenMatrix™, Permacol™, and FlexHD® (p < 0.01), while PeriGuard® demonstrated a slight increase in tensile strength (p = 0.0188). Crosslinked bovine pericardium (PeriGuard®) maintained greater tensile strength than noncrosslinked bovine pericardium (Veritas®) throughout all exposure periods (p < 0.0001). Similarly, crosslinked porcine dermis (Permacol™) maintained greater tensile strength than non-crosslinked porcine dermis (Strattice™ and XenMatrix™) throughout all exposure periods (p < 0.0001). Conclusions Materials that deteriorate rapidly after in vitro enzymatic exposure may also deteriorate rapidly in vivo, particularly when exposed to a wound environment with elevated levels of matrix metalloproteinases. Permacol™, CollaMend™, Strattice™, FlexHD®, and Peri-Guard® survived the longest incubation period (30 h) and withstood mechanical testing. XenMatrix™, AlloMax™, Veritas®, and Surgisis™ degraded more quickly and did not survive the longer exposure periods. Scaffolds that maintain strength characteristics after in vitro collagenase exposure may be advantageous for long-term hernia repair scenarios where elevated enzyme levels are expected.

Annor, Afua H.; Tang, Michael E.; Pui, Chi Lun; Ebersole, Gregory C.; Frisella, Margaret M.; Matthews, Brent D.

2013-01-01

164

Control of the molecular degradation of hyaluronic acid hydrogels for tissue augmentation.  

PubMed

A novel protocol to control the molecular degradation of hyaluronic acid (HA) hydrogels was successfully developed for tissue augmentation applications. HA has a different conformational structure in water and organic solvent, and the carboxyl group of HA is known to be the recognition site of hyaluronidase and HA receptors. Based on these findings, HA was chemically modified by grafting adipic acid dihydrazide (ADH) to the carboxyl group of HA in the water to prepare HA-ADH(WATER) and in the mixed solvent of water and ethanol to prepare degradation-controlled HA-ADH(WATER/ETHANOL). Three kinds of HA hydrogels were prepared by the crosslinking of HA-ADH(WATER) or HA-ADH(WATER/ETHANOL) with bis(sulfosuccinimidyl) suberate, and by the crosslinking of HA-OH with divinyl sulfone (DVS). In vitro and in vivo degradation tests showed that HA-DVS hydrogels were degraded most rapidly, followed by HA-ADH(WATER) hydrogels and HA-ADH(WATER/ETHANOL) hydrogels. There was no adverse effect during and after in vivo degradation tests. All of the HA hydrogel samples appeared to be biocompatible, according to the histological analysis with hematoxylin-eosin and Alcian blue. PMID:18022803

Oh, Eun Ju; Kang, Sun-Woong; Kim, Byung-Soo; Jiang, Ge; Cho, Il Hwan; Hahn, Sei Kwang

2008-09-01

165

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

Microsoft Academic Search

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

Phifer

2004-01-01

166

Controlled degradation of polyhydroxybutyrate via alcoholysis with ethylene glycol or glycerol  

Microsoft Academic Search

It was shown that controlled degradation of poly-[(R)-3-hydroxybutyrate] (PHB) can be achieved by alcoholysis with two types of alcohol in the presence of a catalyst. PHB oligomers terminated with free hydroxyl groups were prepared in this way. Molecular weight of the prepared samples was studied with three methods: SEC analysis with polystyrene calibration, SEC analysis using universal calibration, and viscometry.

Zdeno Špitalský; Igor Lacík; Elena Lathová; Ivica Janigová; Ivan Chodák

2006-01-01

167

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 κB (NF-κB) family of transcription factors. Stimulation and termination of NF-κB activity are subject to stringent spatiotemporal control. According to the classical model of NF-κB regulation, both activation and termination mechanisms are centered on inhibitor of NF-κB (IκB) proteins. Whereas activation of NF-κB requires degradation of the IκBs, the main mechanism responsible for termination of NF-κB activity is the resynthesis of a specific IκB, IκBα, which sequesters NF-κB 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-κB proteins is their nuclear degradation. At least two E3 ubiquitin ligases, one of which seems to be essential for control of nuclear NF-κB p65 (also known as RelA) in myeloid cells, have been identified. Moreover, additional evidence indicates that individual NF-κB dimers with particular activating or repressive properties may be differentially controlled by nuclear degradation, thus paving the way for the exploitation of NF-κB degradation pathways for therapeutic purposes.

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

2008-01-08

168

Handling Qualities Degradation in Tilt-Rotor Aircraft Following Flight Control System Failures  

Microsoft Academic Search

Handling Qualities are critical in terms of performance and flight safety and will have a strong influence on the design of a future Civil Tilt-Rotor. As with all civil aircraft, the design must comply with civil aviation airworthiness regulations within which safety standards play a major role, thus any handling qualities degradations caused by a flight control system component failure

Neil Cameron; Gareth D Padfield

169

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

SciTech Connect

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 copper-based alloys discussed here are being considered in addition to the iron- to nickel-based austenitic materials discussed in Volume 3. The decay of radionuclides will result in substantial heat generation and in fluxes of gamma radiation. In this environment, container materials may degrade by atmospheric oxidation, uniform aqueous phase corrosion, pitting, crevice corrosion, transgranular stress corrosion cracking (TGSCC) in tarnishing environments, or intergranular stress corrosion cracking (IGSCC) in nontarnishing environments. This report is a critical survey of available data on the stress corrosion cracking (SCC) of the three copper-based alloys. The requisite conditions for TGSCC and IGSCC include combinations of stress, oxygen, ammonia or nitrite, and water. Note that nitrite is generated by gamma radiolysis of moisture films in air but that ammonia is not. TGSCC has been observed in CDA 102 and CDA 613 exposed to moist ammonia-containing environments whereas SCC has not been documented for CDA 715 under similar conditions. SCC is also promoted in copper by nitrite ions. Furthermore, phosphorus-deoxidized copper is unusually susceptible to embrittlement in such environments. The presence of tin in CDA 613 prevents IGSCC. It is believed that tin segregates to grain boundaries, where it oxidizes very slowly, thereby inhibiting the oxidation of aluminum. 117 refs., 27 figs., 9 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))

1988-05-01

170

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

171

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...

172

Degradation of the elastomeric gasket material in a simulated and four accelerated proton exchange membrane fuel cell environments  

Microsoft Academic Search

Long-term stability and durability of gaskets in Proton Exchange Membrane (PEM) fuel cell are critical to both sealing and the electrochemical performance of the PEM fuel cell. In this paper, the time-dependent chemical degradation of the silicone rubber, which is one of the potential gasket materials for PEM fuel cells, is studied in a simulated PEM fuel cell environment and

Guo Li; Jinzhu Tan; Jianming Gong

173

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

174

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

175

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

176

Materials degradation in PVC medical devices, DEHP leaching and neonatal outcomes.  

PubMed

Polymeric materials play a key role in the production of medical and clinical devices thanks to their special features such as flexibility, easy processing and good price/performance ratio. Among the different polymeric matrixes, one of the most used is Poly(vinyl chloride) (PVC). At room temperature PVC is hard and brittle, thus great amounts (40-50%) of phthalate esters that act as plasticizers are added to the polymer to make it flexible and appropriate for medical use. Di-(2-ethylhexyl)-phthalate (DEHP) is the most widely used plasticizer in PVC medical devices. However, DEHP is not chemically bound to PVC and migrates from medical devices with time and use. The potential for DEHP to produce adverse effects in humans has been the subject of considerable discussion and debate in the scientific community. In particular, newborns in the new environment have to be considered at particularly increased risk, because of their small body size and the multiple medical device-related to the DEHP exposure. The major factors determining the degree to which DEHP migrates from medical devices are temperature, amount of DEHP in the device, storage time, shaking of the device while in contact with the medical solutions and degree of PVC degradation. PMID:20858177

Latini, G; Ferri, M; Chiellini, F

2010-01-01

177

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

178

Nuclear Material Control and Accountability System Effectiveness Tool (MSET)  

SciTech Connect

A nuclear material control and accountability (MC&A) system effectiveness tool (MSET) has been developed in the United States for use in evaluating material protection, control, and accountability (MPC&A) systems in nuclear facilities. The project was commissioned by the National Nuclear Security Administration's Office of International Material Protection and Cooperation. MSET was developed by personnel with experience spanning more than six decades in both the U.S. and international nuclear programs and with experience in probabilistic risk assessment (PRA) in the nuclear power industry. MSET offers significant potential benefits for improving nuclear safeguards and security in any nation with a nuclear program. MSET provides a design basis for developing an MC&A system at a nuclear facility that functions to protect against insider theft or diversion of nuclear materials. MSET analyzes the system and identifies several risk importance factors that show where sustainability is essential for optimal performance and where performance degradation has the greatest impact on total system risk. MSET contains five major components: (1) A functional model that shows how to design, build, implement, and operate a robust nuclear MC&A system (2) A fault tree of the operating MC&A system that adapts PRA methodology to analyze system effectiveness and give a relative risk of failure assessment of the system (3) A questionnaire used to document the facility's current MPC&A system (provides data to evaluate the quality of the system and the level of performance of each basic task performed throughout the material balance area [MBA]) (4) A formal process of applying expert judgment to convert the facility questionnaire data into numeric values representing the performance level of each basic event for use in the fault tree risk assessment calculations (5) PRA software that performs the fault tree risk assessment calculations and produces risk importance factor reports on the facility's MC&A (software widely used in the aerospace, chemical, and nuclear power industries) MSET was peer reviewed in 2007 and validated in 2008 by benchmark testing at the Idaho National Laboratory in the United States. The MSET documents were translated into Russian and provided to Rosatom in July of 2008, and MSET is currently being evaluated for potential application in Russian Nuclear Facilities.

Powell, Danny H [ORNL] [ORNL; Elwood Jr, Robert H [ORNL] [ORNL; Roche, Charles T [ORNL] [ORNL; Campbell, Billy J [ORNL] [ORNL; Hammond, Glenn A [ORNL] [ORNL; Meppen, Bruce W [ORNL] [ORNL; Brown, Richard F [ORNL] [ORNL

2011-01-01

179

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

180

Corrosion and degradation of test materials in the IGT HYGAS coal-gasification pilot plant  

SciTech Connect

Corrosion monitoring of test materials was conducted in the operating environment of the IGT HYGAS pilot plant between 1974 and 1980. Metals were exposed in the coal pretreater, pretreater quench system, coal slurry mix tank, multistage gasifier, gasifier quench system, and spent char mix tank. Austenitic alloy Types 304 and 316 were found to be superior in corrosion performance compared to Type 410 and carbon steel in the coal pretreater environment. Pack aluminized coatings on carbon steel A-515 prevented attack of the substrate; hairline cracks were always observed in the coating but never penetrating the diffusion zone. Throughout the HYGAS quench systems (gasifier and coal pretreater), the 300 series austenitic stainless steels showed consistently better corrosion resistance than other test materials in all test locations. This was also true in the slurry and char mix tanks. Equivalent linear corrosion rates were less than 1 mpy (0.03 mm/y); mild pitting was encountered in some cases. Of the alloys tested in the lower gasifier stages, alloys IN-671, IN-800, and Types 310, 309, and 446 were consistently better performers. Pack aluminized alloys (Type 310, IN-800) showed no improved corrosion resistance. All refractories were exposed as 9 in. (228.6 mm) straight bricks and used as headers to brick up a manway with only their ends exposed to the gasifier environment. Dense refractories were little affected by exposure, but lightweight refractories deteriorated. In general, the physical properties and abrasion resistance of the high-alumina (90% or greater) dense refractories were degraded by exposure while those of medium-alumina (50 to 60%) dense refractories were enhanced. Any of the dense refractories would have been suitable for lining the gasifier, but a medium-alumina castable would have been the optimum selection because of its lower cost.

Schaefer, A.O.

1981-12-01

181

Corrosion and degradation of materials in the Synthane coal-gasification pilot plant  

SciTech Connect

Corrosion monitoring of materials was conducted in the operating environments of the Synthane coal gasification pilot plant between 1976 and 1978. Metal and refractory specimens were exposed in the gasifier vessel in two test locations (fluidized bed, freeboard). Metal coupons only were exposed in the gasifier char cooler (freeboard) and four test locations in the quench system (vapor and liquid phases). Exposure times under operating conditions were 181 to 782 h. In two gasifier test locations (600 psig, 1284/sup 0/F and 1434/sup 0/F), the performance of nickel-base alloys with >20 wt % Cr, 40 to 46 wt % Ni, and 3 to 9.1 wt % Mo was consistently better than for other test alloys. Equivalent linear corrosion rates for these better alloys were < 20 mpy (782 h) with Montana Rosebud coal as feedstock; however, with Illinois No. 6 coal the linear rates were >20 mpy but <75 mpy (181 h). IN-600 (76.5 wt % Ni, 15.8 wt % Cr) was found unsuitable for gasifier internal application. All refractories tested in the two gasifier test locations (600 psig, 1284/sup 0/F and 1434/sup 0/F), with the exception of silicon nitride, were not greatly affected during either exposure period. The better materials were monolithic refractories with 5 to 30% porosity and 50 to 60% alumina content. Corrosion monitoring of metals in the gasifier char cooler freeboard (600 psig, 800/sup 0/F) showed that Type 304 was more resistant to corrosion attack than Type 410 and carbon steel (A-515).During exposure in the product gas quench system (5 to 600 psig, 200/sup 0/ to 445/sup 0/F), austenitic stainless steels, IN-600, and Type 430 experienced only limited corrosion loss and slight to moderate pitting attack (maximum pit depth <7 mils). Monel 400 and carbon steel specimens incurred unacceptable levels of degradation.

Yurkewycz, R.; Firestone, R.F.

1981-09-01

182

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

183

MISSE Thermal Control Materials with Comparison to Previous Flight Experiments  

Microsoft Academic Search

Many different passive thermal control materials were flown as part of the Materials on International Space Station Experiment, including inorganic coatings, anodized aluminum, and multi-layer insulation materials. These and other material samples were exposed to the low Earth orbital environment of atomic oxygen, ultraviolet radiation, thermal cycling, and hard vacuum, though atomic oxygen exposure was limited for some samples. Materials

Miria Finckenor

2009-01-01

184

Ag2S nanoparticle encapsulated in mesoporous material nanoparticles and its application for photocatalytic degradation of dye in aqueous solution  

NASA Astrophysics Data System (ADS)

Semiconductor loaded mesoporous materials in general possess greater photocatalytic activity than pure semiconductors. Hence, with an attempt to achieve higher photocatalytic activity, Ag2S/MCM-41 photocatalysts were prepared by ion exchange method and used for the photocatalytic degradation of methylene blue. The materials were characterized by different analytical techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and BET (Brunauer-Emmert-Teller) experiments. The effect of Ag2S, MCM-41 support and different wt% of Ag2S over the support on the photocatalytic degradation and influence of parameters such as Ag2S loading, catalyst a mount, pH and initial concentration of dye on degradation are evaluated. The degradation reaction follows pseudo-first order kinetics. It was seen that 0.6 g/L of photocatalyst is an optimum value for the dosage of photocatalyst. The degradation efficiency was decreased in dye concentration above 3.2 ppm for dye.

Pourahmad, A.

2012-08-01

185

Regulation of Silk Material Structure by Temperature-Controlled Water Vapor Annealing  

PubMed Central

We present a simple and effective method to obtain refined control of the molecular structure of silk biomaterials through physical temperature-controlled water vapor annealing (TCWVA). The silk materials can be prepared with control of crystallinity, from a low content using conditions at 4°C (alpha-helix dominated silk I structure), to highest content of ~60% crystallinity at 100°C (beta-sheet dominated silk II structure). This new physical approach covers the range of structures previously reported to govern crystallization during the fabrication of silk materials, yet offers a simpler, green chemistry, approach with tight control of reproducibility. The transition kinetics, thermal, mechanical, and biodegradation properties of the silk films prepared at different temperatures were investigated and compared by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), uniaxial tensile studies, and enzymatic degradation studies. The results revealed that this new physical processing method accurately controls structure, in turn providing control of mechanical properties, thermal stability, enzyme degradation rate, and human mesenchymal stem cell interactions. The mechanistic basis for the control is through the temperature controlled regulation of water vapor, to control crystallization. Control of silk structure via TCWVA represents a significant improvement in the fabrication of silk-based biomaterials, where control of structure-property relationships is key to regulating material properties. This new approach to control crystallization also provides an entirely new green approach, avoiding common methods which use organic solvents (methanol, ethanol) or organic acids. The method described here for silk proteins would also be universal for many other structural proteins (and likely other biopolymers), where water controls chain interactions related to material properties.

Hu, Xiao; Shmelev, Karen; Sun, Lin; Gil, Eun-Seok; Park, Sang-Hyug; Cebe, Peggy; Kaplan, David L.

2011-01-01

186

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>ilim, 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

187

Defective in Mitotic Arrest 1 (Dma1) Ubiquitin Ligase Controls G1 Cyclin Degradation*  

PubMed Central

Progression through the G1 phase of the cell cycle is controlled by diverse cyclin-dependent kinases (CDKs) that might be associated to numerous cyclin isoforms. Given such complexity, regulation of cyclin degradation should be crucial for coordinating progression through the cell cycle. In Saccharomyces cerevisiae, SCF is the only E3 ligase known to date to be involved in G1 cyclin degradation. Here, we report the design of a genetic screening that uncovered Dma1 as another E3 ligase that targets G1 cyclins in yeast. We show that the cyclin Pcl1 is ubiquitinated in vitro and in vivo by Dma1, and accordingly, is stabilized in dma1 mutants. We demonstrate that Pcl1 must be phosphorylated by its own CDK to efficiently interact with Dma1 and undergo degradation. A nonphosphorylatable version of Pcl1 accumulates throughout the cell cycle, demonstrating the physiological relevance of the proposed mechanism. Finally, we present evidence that the levels of Pcl1 and Cln2 are independently controlled in response to nutrient availability. This new previously unknown mechanism for G1 cyclin degradation that we report here could help elucidate the specific roles of the redundant CDK-cyclin complexes in G1.

Hernandez-Ortega, Sara; Bru, Samuel; Ricco, Natalia; Ramirez, Sara; Casals, Nuria; Jimenez, Javier; Isasa, Marta; Crosas, Bernat; Clotet, Josep

2013-01-01

188

Integrated Naval Shipyard Material Control System.  

National Technical Information Service (NTIS)

This thesis explores the possibility of establishing a centrally managed redistribution system for material located in naval shipyards employing the techniques of rapid communications and automatic data processing systems. The area of direct material inve...

D. R. Jahn C. E. Sojka

1965-01-01

189

On the degraded effectiveness of diffusion synthetic acceleration for multidimensional sn calculations in the presence of material discontinuities  

SciTech Connect

We investigate the degradation in performance of diffusion synthetic acceleration (DSA) methods in problems with discontinuities in material properties. A loss in the effectiveness of DSA schemes has been Observed before with other discretizations in two dimensions under certain conditions. We present more evidence in support of the conjecture that DSA effectiveness can degrade in multidimensional problems with discontinuities in total cross section, regardless of the particular physical configuration or spatial discretization. Through Fourier analysis and numerical experiments, we identify a set of representative problems for which established DSA schemes are ineffective, focusing on highly diffusive problems for which DSA is most needed. We consider a lumped, linear discontinuous spatial discretization of the S N transport equation on three-dimensional, unstructured tetrahedral meshes and look ata fully consistent and a 'partially consistent' DSA method for this discretization. We find that the effectiveness of both methods can be significantly degraded in the presence of material discontinuities. A Fourier analysis in the limit of decreasing cell optical thickness is shown that supports the view that the degraded effectiveness of a fully consistent DSA scheme simply reflects the failure of the spatially continuous DSA method in problems where material discontinuities are present. Key Words: diffusion synthetic acceleration, discrete ordinates, deterministic transport methods, unstructured meshes

Warsa, J. S. (James S.); Wareing, T. A. (Todd A.); Morel, J. E.

2002-01-01

190

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

191

Regulation of ubiquitin chain initiation to control the timing of substrate degradation  

PubMed Central

Processive reactions, such as transcription or translation, often proceed through distinct initiation and elongation phases. The processive formation of polymeric ubiquitin chains can accordingly be catalyzed by specialized initiating and elongating E2 enzymes, but the functional significance for this division of labor has remained unclear. Here, we have identified sequence motifs in several substrates of the anaphase-promoting complex (APC/C) that are required for efficient chain initiation by its E2 Ube2C. Differences in the quality and accessibility of these chain initiation motifs can determine the rate of a substrate’s degradation without affecting its affinity for the APC/C, a mechanism used by the APC/C to control the timing of substrate proteolysis during the cell cycle. Based on our results, we propose that initiation motifs and their cognate E2s allow E3 enzymes to exert precise temporal control over substrate degradation.

Williamson, Adam; Banerjee, Sudeep; Zhu, Xining; Philipp, Isabelle; Iavarone, Anthony T.; Rape, Michael

2011-01-01

192

Controlled release of proteins from degradable poly(ether-ester) multiblock copolymers  

Microsoft Academic Search

A new series of multiblock poly(ether-ester)s based on poly(ethylene glycol) (PEG), butylene terephthalate (BT) and butylene succinate (BS) segments were introduced as matrices for controlled release applications. The release of two model proteins, lysozyme and bovine serum albumin (BSA), from poly(ether-ester) films were evaluated and correlated to the swelling and degradation characteristics of the polymer matrices. First- and zero-order profiles

R. van Dijkhuizen-Radersma; S. Métairie; J. R. Roosma; K. de Groot; J. M. Bezemer

2005-01-01

193

Controlled degradation of hydrogels using multi-functional cross-linking molecules  

Microsoft Academic Search

Hydrogels, chemically cross-linked or physically entangled, have found a number of applications as novel delivery vehicles of drugs and cells. However, the narrow ranges of degradation rates and mechanical strength currently available from many hydrogels limits their applications. We have hypothesized that utilization of multi-functional cross-linking molecules to form hydrogels could provide a wider range and tighter control over the

Kuen Yong Lee; Kamal H. Bouhadir; David J. Mooney

2004-01-01

194

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

195

Anomaly and error detection in computerized materials control & accountability databases  

Microsoft Academic Search

Unites States Department of Energy sites use computerized material control and accountability (MC&A) systems to manage the large amounts of data necessary to control and account for their nuclear materials. Theft or diversion of materials from these sites would likely result in anomalies in the data, and erroneous information greatly reduces the value of the information to its users. Therefore,

R. Whiteson; B. Hoffbauer; T. F. Yarbro

1997-01-01

196

On Social and Material Aspects of Technological Control  

Microsoft Academic Search

This commentary on Hugh Lacey's paper emphasises the material aspects of the social structure within which technological control takes place. It is suggested here that when the example of the Green Revolution is examined in detail a clear-cut distinction between material and social constraints\\/possibilities is misleading. I propose a material analysis of the control situation. This analysis is placed within

William E. Herfel

1999-01-01

197

Degradation of heat exchanger materials under biomass co-firing conditions  

SciTech Connect

Co-firing biomass in conventional pulverised coal fired power stations offers a means to rapidly introduce renewable and CO{sub 2} neutral biomass fuels into the power generation market. This paper reports the results of assessments carried out to evaluate the potential operating conditions of heat exchangers in combustion systems with biomass (wood or straw) and coal co-firing, as well as laboratory corrosion tests that have been carried out to give an initial assessment of potential effects of biomass co-firing. The corrosion tests have been carried out using the deposit recoat method in controlled atmosphere furnaces. A series of 1000 hour tests have been carried out at typical superheater and evaporator metal temperatures using simulated deposit compositions and gaseous environments (selected on the basis of plant experience and potential fuel compositions). Five materials were exposed in these tests: 1Cr steel, T22 steel, X20CrMoV121, TP347HFG and alloy 625. In order to produce statistically valid data on the actual metal loss from the materials, the performance of the materials in these tests was determined from dimensional metrology before and after exposure. For each material, these data have been used to determine the sensitivity of the corrosion damage to changes in the exposure conditions (e.g. deposit composition, gas composition) thereby producing initial models of the corrosion performance of the materials. The corrosion data and model outputs have been compared with data available from power plants operating on coal, straw or wood fuels.

Simms, N.J.; Kilgallon, P.J.; Oakey, J.E. [Cranfield University, Cranfield (United Kingdom). Energy Technology Centre

2007-07-01

198

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

PubMed

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 depending on the application site. Over the past decades, a wide-ranging and comprehensive set of in vitro, in vivo and for some cases also ex vivo tests have been proposed and exhaustively investigated for conventional corrosion-resistant metallic biomaterials. Standardization and regulatory bodies in the United States, Japan and Europe have therefore developed tests to license corrosion-resistant metals for use as "biomaterials". This is not the case for DMMs. Once implanted, this new class of biomaterials is expected to support the healing process of a diseased tissue or organ while degrading at a potentially adjustable degradation rate. The tests developed for corrosion-resistant metals cannot simply be transposed to DMMs. These tests can in some cases be adapted, but the expected unique properties of DMMs should also inspire and lead to the design and the development of new specific tests. The current challenge is how to assess the tolerance of surrounding tissues and organs to the presence of degradation products. This work precisely focuses on this topic. The tests usually used to assess the biocompatibility of conventional corrosion-resistant metals are briefly reviewed. Then, genetic regulation is proposed as an original and novel approach to assess the biocompatibility of DMMs. This method appears to predict cell behaviour in the presence of degradation products that are closely related to DNA damage. Various genes have been related to the toxicity and inflammatory responses, indicating their role as biomarkers to assess the toxicity of degradation products. Finally, some gene families that have the potential to be applied as biomarkers of degradation product toxicity are summarized. PMID:20176149

Purnama, Agung; Hermawan, Hendra; Couet, Jacques; Mantovani, Diego

2010-05-01

199

Quality by design development of brivanib alaninate tablets: degradant and moisture control strategy.  

PubMed

A quality by design approach was applied to the development of brivanib alaninate tablets. Brivanib alaninate, an ester pro-drug, undergoes hydrolysis to its parent compound, BMS-540215. The shelf-life of the tablets is determined by the rate of the hydrolysis reaction. Hydrolysis kinetics in the tablets was studied to understand its dependence on temperature and humidity. The BMS-540215 amount versus time profile was simulated using a kinetic model for the formation of BMS-540215 as function of relative humidity in the environment and a sorption-desorptiom moisture transfer model for the relative humidity inside the package. The combined model was used to study the effect of initial tablet water content on the rate of degradation and to identify a limit for initial tablet water content that results in acceptable level of the degradant at the end of shelf-life. A strategy was established for the moisture and degradant control in the tablet based on the understanding of its stability behavior and mathematical models. The control strategy includes a specification limit on the tablet water content and manufacturing process controls that achieve this limit at the time of tablet release testing. PMID:24780101

Badawy, Sherif I F; Lin, Judy; Gokhale, Madhushree; Desai, Sachin; Nesarikar, Vishwas V; LaMarche, Keirnan R; Subramanian, Ganeshkumar A; Narang, Ajit S

2014-07-20

200

Performance of Flexible Erosion Control Materials.  

National Technical Information Service (NTIS)

The objectives of the study were to determine the effect of flexible materials on the germination and growth of native grasses, as well as to determine the effectiveness of the materials to prevent erosion on typical, steep, roadside slopes before the est...

H. C. Landphair J. A. McFalls J. P. Long S. H. Godfrey

1993-01-01

201

Smart Materials for Helicopter Rotor Active Control.  

National Technical Information Service (NTIS)

A major improvement of helicopter performance and comfort can be achieved by the implementation of rotor active control technology (RACT). The introduction of individual blade control (IBC) is a subject of current research activities. But the breakthrough...

H. Strehlow H. Rapp

1993-01-01

202

Nanostructured Solar Irradiation Control Materials for Solar Energy Conversion.  

National Technical Information Service (NTIS)

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 sola...

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

2012-01-01

203

Materials for Adaptive Structural Acoustic Control. Volume 2.  

National Technical Information Service (NTIS)

This report documents work carried out in the Materials Research Laboratory of the Pennsylvania State University over the first year of a new ONR sponsored University Research Initiative (URI) entitled Materials for Adaptive Structural Acoustic Control. F...

L. E. Cross

1993-01-01

204

Materials for Adaptive Structural Acoustic Control. Volume 1.  

National Technical Information Service (NTIS)

This report documents work carried out in the Materials Research Laboratory of the Pennsylvania State University over the first year of a new ONR sponsored University Research Initiative (URI) entitled Materials for Adaptive Structural Acoustic Control. F...

L. E. Cross

1993-01-01

205

Materials for Adaptive Structural Acoustic Control. Volume 4.  

National Technical Information Service (NTIS)

This report documents work carried out in the Materials Research Laboratory of the Pennsylvania State University over the first year of a new ONR sponsored University Research Initiative (URI) entitled Materials for Adaptive Structural Acoustic Control. F...

L. E. Cross

1993-01-01

206

Materials for Adaptive Structural Acoustic Control. Volume 3.  

National Technical Information Service (NTIS)

This report documents work carried out in the Materials Research Laboratory of the Pennsylvania State University over the first year of a new ONR sponsored University Research Initiative (URI) entitled Materials for Adaptive Structural Acoustic Control. F...

L. E. Cross

1993-01-01

207

Behavior of control rods during core degradation: pressurization of silver-indium-cadmium control rods  

SciTech Connect

Activity data for the liquid binary systems Ag-Cd, Ag-In, and In-Cd are correlated in terms of the Wilson equation. These correlations are used to construct a model of the ternary system Ag-In-Cd. Spectroscopic data for the vapor species Ag(g), Ag/sub 2/(g), Ag/sub 3/(g), Ag/sup +/(g), In(g), In/sub 2/(g), In/sup +/(g), Cd(g), Cd/sub 2/(g), Cd/sup +/(g), AgIn(g), and CdIn(g) are reviewed and are used to define thermodynamic functions for these species for temperatures between 298 and 3500/sup 0/K. Vapor pressures for the liquid phase pure elements, liquid binary alloys, and the liquid ternary alloy are calculated using the Wilson equation model and using the assumption that the condensed phase is an ideal mixture. An azeotrope is predicted for the Ag-In system. Predictions are made of the vaporization of alloys of 80% Ag, 15% In, and 5% Cd used as control materials in some pressurized water reactors. 92 refs., 58 figs., 45 tabs.

Powers, D.A.

1985-09-01

208

INrf2 (Keap1) targets Bcl-2 degradation and controls cellular apoptosis  

PubMed Central

Cytosolic inhibitor of Nrf2 (INrf2) is an adaptor protein that mediates ubiquitination/degradation of NF-E2-related factor 2 (Nrf2), a master regulator of cytoprotective gene expression. In this paper, we demonstrate that INrf2 degrades endogenous antiapoptotic B-cell CLL/lymphoma 2 (Bcl-2) protein and controls cellular apoptosis. The DGR domain of INrf2 interacts with the BH2 domain of Bcl-2 and facilitates INrf2:Cul3–Rbx1-mediated ubiquitination of Bcl-2 by the conjugation of ubiquitin molecules to lysine17 of Bcl-2. Further studies showed that INrf2 enhanced etoposide-mediated accumulation of Bax, increased release of cytochrome c from mitochondria, activated caspase-3/7, and enhanced DNA fragmentation and apoptosis. Antioxidants antagonized Bcl-2:INrf2 interaction, led to the release and stabilization of Bcl-2, increased Bcl-2:Bax heterodimers and reduced apoptosis. Moreover, dysfunctional/mutant INrf2 in human lung cancer cells failed to degrade Bcl-2, resulting in decreased etoposide and UV/? radiation-mediated DNA fragmentation. These data provide the first evidence of INrf2 control of Bcl-2 and apoptotic cell death, with implications in antioxidant protection, survival of cancer cells containing dysfunctional INrf2, and drug resistance.

Niture, S K; Jaiswal, A K

2011-01-01

209

Thermochromic Indicator Materials with Controlled Reversibility.  

National Technical Information Service (NTIS)

A thermal indicator material which comprises a plurality of polythiophenes having a second low temperature color and a high temperature color. The polythiophenes are structured and arranged to exhibit a color change from the second low temperature color t...

B. Lucht W. B. Euler Y. Wang

2004-01-01

210

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

211

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

212

Control of Cartographic Materials in Archives.  

ERIC Educational Resources Information Center

Discusses differences in archival and bibliographic description of maps and suggests options for developing standards in the control of cartographic archives. The automation of archival access using the MARC format for Archival and Manuscripts Control (AMC) is described, and examples of bibliographic records for maps are given. (11 references)…

Corsaro, James

1990-01-01

213

Degradable magnesium-based implant materials with anti-inflammatory activity.  

PubMed

The objective of this study was to prepare a new biodegradable Mg-based biomaterial, which provides good mechanical integrity in combination with anti-inflammatory function during the degradation process. The silver element was used, because it improved the mechanical properties as an effective grain refiner and it is also treated as a potential anti-inflammatory core. The new degradable Mg-Zn-Ag biomaterial was prepared by zone solidification technology and extrusion. The mechanical properties were mostly enhanced by fine grain strengthening. In addition, the alloys exhibited good cytocompatibility. The anti-inflammatory function of degradation products was identified by both interleukin-1? and nitric oxide modes. The anti-inflammatory impact was significantly associated with the concentration of silver ion. It was demonstrated that Mg-Zn-Ag system was a potential metallic stent with anti-inflammatory function, which can reduce the long-term dependence of anti-inflammatory drug after coronary stent implantation. PMID:23203562

Peng, Qiuming; Li, Kun; Han, Zengsheng; Wang, Erde; Xu, Zhigang; Liu, Riping; Tian, Yongjun

2013-07-01

214

Effects of cesium ions and cesium vapor on selected ATS-F samples. [thermal control coating degradation  

NASA Technical Reports Server (NTRS)

Thermal control coating samples were subjected to cesium ion beam and vapor exposures. Degradation of solar absorptance and infrared emittance were measured. Solar cells and samples selected from surfaces on the ATS-F spacecraft likely to experience ion or vapor impingement were bombarded by 10-volt cesium ions. Other samples were subjected to high levels of cesium vapor. Aluminum and white paint were backsputtered by 550-volt cesium ions onto selected samples. For direct bombardment, the threshold for ion-induced property changes was above five-thousand trillion ions/sq cm. With material sputtered from a 450-sq cm target onto samples 36 cm distant, the threshold for noticeable effects was above 5 times 10 to the 17-th power ions/sq cm.

Kemp, R. F.; Beynon, J. C.; Hall, D. F.; Luedke, E. E.

1973-01-01

215

Environmental degradation of materials: Surface chemistry related to stress corrosion cracking  

NASA Technical Reports Server (NTRS)

Parallel experiments have been performed in order to develop a comprehensive model for stress cracking (SCC) in structural materials. The central objective is to determine the relationship between the activity and selectivity of the microstructure of structural materials to their dissolution kinetics and experimentally measured SCC kinetics. Zinc was chosen as a prototype metal system. The SCC behavior of two oriented single-crystal disks of zinc in a chromic oxide/sodium sulfate solution (Palmerton solution) were determined. It was found that: (1) the dissolution rate is strongly (hkil)-dependent and proportional to the exposure time in the aggressive environment; and (2) a specific slip system is selectively active to dissolution under applied stress and this slip line controls crack initiation and propagation. As a precursor to potential microgrvity experiments, electrophoretic mobility measurements of zinc particles were obtained in solutions of sodium sulfate (0.0033 M) with concentrations of dissolved oxygen from 2 to 8 ppm. The equilibrium distribution of exposed oriented planes as well as their correlation will determine the particle mobility.

Schwarz, J. A.

1985-01-01

216

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

217

Insider Threat - Material Control and Accountability Mitigation  

Microsoft Academic Search

The technical objectives of nuclear safeguards are (1) the timely detection of diversion of significant quantities of nuclear material from peaceful uses to the manufacture of nuclear weapons or other nuclear explosive devices or for purposes unknown and (2) the deterrence of such diversion by the risk of early detection. The safeguards and security program must address both outsider threats

Danny H Powell; Robert H Elwood Jr; Charles T Roche

2011-01-01

218

Composition stability and degradation products of selected materials for solar heating and cooling  

Microsoft Academic Search

The composition, stability and thermal degradation products of a variety of structural plastics, heat transfer fluids, thermal storage media and sealants, which have been proposed for use in solar heating and cooling applications, were either defined generically by analysis or obtained by surveying the literature. This information will be used to aid in the assessment of the environmental impact of

C. Arnold Jr.; R. E. Trujillo

1979-01-01

219

Systematic control of nonmetallic materials for improved fire safety  

NASA Technical Reports Server (NTRS)

The elements of a systematic fire safety program are summarized and consist of fire safety criteria, design considerations, testing of materials, development of nonmetallic materials, nonmetallic materials information systems, design reviews, and change control. The system described in this report was developed for the Apollo spacecraft. The system can, however, be tailored to many industrial, commercial, and military activities.

1972-01-01

220

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

221

A tuneable switch for controlling environmental degradation of bioplastics: addition of isothiazolinone to polyhydroxyalkanoates.  

PubMed

Controlling the environmental degradation of polyhydroxybutyrate (PHB) and polyhydroxyvalerate (P(HB-co-HV)) bioplastics would expand the range of their potential applications. Combining PHB and P(HB-co-HV) films with the anti-fouling agent 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOI, <10% w/w) restricted microbial colonisation in soil, but did not significantly affect melting temperature or the tensile strength of films. DCOI films showed reduced biofouling and postponed the onset of weight loss by up to 100 days, a 10-fold increase compared to unmodified films where the microbial coverage was significant. In addition, the rate of PHA-DCOI weight loss, post-onset, reduced by about 150%; in contrast a recorded weight loss of only 0.05% per day for P(HB-co-HV) with a 10% DCOI loading was observed. This is in stark contrast to the unmodified PHB film, where a recorded weight loss of only 0.75% per day was made. The 'switch' that initiates film weight loss, and its subsequent reduced rate, depended on the DCOI loading to control biofouling. The control of biofouling and environmental degradation for these DCOI modified bioplastics increases their potential use in biodegradable applications. PMID:24146779

Woolnough, Catherine Anne; Yee, Lachlan Hartley; Charlton, Timothy Stuart; Foster, Leslie John Ray

2013-01-01

222

Additive-free controllable fabrication of bismuth vanadates and their photocatalytic activity toward dye degradation  

NASA Astrophysics Data System (ADS)

Bismuth vanadates (BiVO 4) with various crystal structures (tetragonal scheelite, monoclinic scheelite, and tetragonal zircon) and morphologies (sphere-, nanosheet-, dendrite-, and flower-like) were controllably fabricated by using a mild additive-free hydrothermal treatment process under the different preparation conditions. The crystal structures, morphologies, and photophysical properties of the products were well-characterized. Subsequently, their UV- as well as visible-light photocatalytic performance was evaluated via dyes rhodamine B (RB) and methylene blue (MB) degradation. Special attention was paid to evaluate the correlation of the reactivity with crystal structure, morphology, and electronic structure of as-prepared BiVO 4 samples.

Guo, Yingna; Yang, Xia; Ma, Fengyan; Li, Kexin; Xu, Lei; Yuan, Xing; Guo, Yihang

2010-01-01

223

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

224

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

225

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.

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

2014-01-01

226

Influence of surface printing materials on the degradability of biodegradable plastic films in soil  

Microsoft Academic Search

Effect of surface printing on the biodegradability of plastic films was studied. Biodegradable films (polybutylene-succinate (PBS)) printed with four kinds of gravure inks were placed in soil for 1 year. The inks consisted of carbon black-pigment with four kinds of resins: poly-(?-caprolactone) (PCL), nitrocellulose-polyamide blended resin (NT), polyvinyl chloride-vinyl acetate copolymer (V), and nitrocellulose (NC). Degradation of film specimens printed

Akira Hoshino; Shinzou Kanao; Kenji Fukushima; Shigeichi Sakai; Makoto Kimura

2003-01-01

227

Thermal degradation of collagen-based materials that are supports of cultural and historical objects  

Microsoft Academic Search

The thermal analysis methods (TG, DTG and DTA) were used for the investigation of the thermal degradation of some recent manufactured\\u000a tanned leathers, leathers that are supports of cultural or historical objects (leather from book covers (XVII-XIX centuries);\\u000a leather from an Austrian belt (Franz Joseph period), Cordoba leather (XVII century), lining leathers), recent and patrimonial\\u000a parchments and recent extracted collagen

P. Budrugeac; L. Miu; V. Bocu; F. J. Wortman; C. Popescu

2003-01-01

228

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

Microsoft Academic Search

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,

A. N. Roumiantsev; Y. A. Ostroumov; R. Whiteson; S. L. Seitz; R. P. Landry; B. J. Martinez; M. G. Boor; L. K. Anderson; S. P. Gary

1997-01-01

229

Comparison of gamma-ray and Electron Beam Induced Degradation of Polymer Insulating Materials.  

National Technical Information Service (NTIS)

In the radiation environments of nuclear reactors and high power particle accelerators, large amounts of organic polymer materials are used as electric insulator, lubricant, sealant, etc. The mechanical and electrical properties of these materials are gra...

Y. Haruyama Y. Morita T. Seguchi R. Tanaka T. Kanazawa

1988-01-01

230

Wear-Out Approach for Predicting the Remaining Lifetime of Materials; Polymer Degradation and Stability.  

National Technical Information Service (NTIS)

Failure models based on the Palmgren-Miner concept that material damage is cumulative have been derived and used mainly for fatigue life predictions for metals and composite materials. The authors review the principles underlying such models and suggest w...

Gillen Celina

2000-01-01

231

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

232

U.S. national nuclear material control and accounting system  

SciTech Connect

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 materials. The Russian delegation at this meeting stated that ''the creation of a nuclear materials accounting, control, and physical protection system has become a government priority''. Therefore, in order to create a government nuclear material control and accounting system for the Russian Federation, it is critical to study the structure, operating principles, and regulations supporting the control and accounting of nuclear materials in the national systems of nuclear powers. In particular, Russian specialists have a definite interest in learning about the National Nuclear Material Control and Accounting System of the US, which has been operating successfully as an automated system since 1968.

Taylor, S; Terentiev, V G

1998-12-01

233

Arabidopsis DELLA Protein Degradation Is Controlled by a Type-One Protein Phosphatase, TOPP4  

PubMed Central

Gibberellins (GAs) are a class of important phytohormones regulating a variety of physiological processes during normal plant growth and development. One of the major events during GA-mediated growth is the degradation of DELLA proteins, key negative regulators of GA signaling pathway. The stability of DELLA proteins is thought to be controlled by protein phosphorylation and dephosphorylation. Up to date, no phosphatase involved in this process has been identified. We have identified a dwarfed dominant-negative Arabidopsis mutant, named topp4-1. Reduced expression of TOPP4 using an artificial microRNA strategy also resulted in a dwarfed phenotype. Genetic and biochemical analyses indicated that TOPP4 regulates GA signal transduction mainly via promoting DELLA protein degradation. The severely dwarfed topp4-1 phenotypes were partially rescued by the DELLA deficient mutants rga-t2 and gai-t6, suggesting that the DELLA proteins RGA and GAI are required for the biological function of TOPP4. Both RGA and GAI were greatly accumulated in topp4-1 but significantly decreased in 35S-TOPP4 transgenic plants compared to wild-type plants. Further analyses demonstrated that TOPP4 is able to directly bind and dephosphorylate RGA and GAI, confirming that the TOPP4-controlled phosphorylation status of DELLAs is associated with their stability. These studies provide direct evidence for a crucial role of protein dephosphorylation mediated by TOPP4 in the GA signaling pathway.

Qin, Qianqian; Wang, Wei; Guo, Xiaola; Yue, Jing; Huang, Yan; Xu, Xiufei; Li, Jia; Hou, Suiwen

2014-01-01

234

Gammaherpesviral gene expression and virion composition are broadly controlled by accelerated mRNA degradation.  

PubMed

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

235

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

236

Materials for Adaptive Structural Acoustic Control. Volume 5.  

National Technical Information Service (NTIS)

This report documents work carried forward over the fourth year of a five year ONR sponsored University Research initiative (URI) entitled 'Materials for Adaptive Structural Acoustic Control.' The program has continued to underpin the development of new e...

L. E. Cross

1996-01-01

237

Testing of Aircraft Runway Ice Control Products. Materials Compatibility.  

National Technical Information Service (NTIS)

New commercial formulations of runway ice control products have recently made their way onto military and commercial aircraft runways. These products have not been tested for compatibility with a number of aircraft materials, many of which are common to b...

L. Gulley

1998-01-01

238

Methods of Measurement for Semiconductor Materials, Process Control, and Devices.  

National Technical Information Service (NTIS)

The report, describes NBS activities directed toward the development of methods of measurement for semiconductor materials, process control, and devices. Significant accomplishments include development of a procedure to correct for the substantial differe...

W. M. Bullis

1972-01-01

239

Methods of Measurement for Semiconductor Materials, Process Control, and Devices.  

National Technical Information Service (NTIS)

The report describes NBS activities directed toward the development of methods of measurement for semiconductor materials, process control, and devices. Significant accomplishments during this reporting period include design of a plan to provide standard ...

W. M. Bullis

1973-01-01

240

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

241

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

242

MSFC Analysis of Thermal Control Materials on MISSE  

NASA Technical Reports Server (NTRS)

Many different passive thermal control materials were flown as part of the Materials on International Space Station Experiment, including coatings, anodizes, and multi-layer insulation materials. Engineers and scientists at the Marshall Space Flight Center have analyzed a number of these materials, including: Zinc oxide/potassium silicate coating, Zinc orthotitanate/potassium silicate coating, Sulfuric acid anodized aluminum, Various coatings for part marking, automated rendezvous and capture, and astronaut visual aids, FEP Teflon with silver/Inconel backing, and Beta cloth with and without aluminization. These and other material samples were exposed to the low Earth orbital environment of atomic oxygen, ultraviolet radiation, thermal cycling, and hard vacuum, though atomic oxygen exposure was very limited for some samples. Solar absorptance, infrared emittance, and mass measurements indicate the durability of these materials to withstand the space environment. The effect of contamination from an active space station on the performance of white thermal control coatings is discussed.

Finckenor, Miria

2006-01-01

243

Molecular chaperones and substrate ubiquitination control the efficiency of endoplasmic reticulum-associated degradation.  

PubMed

The endoplasmic reticulum (ER) must contend with a large protein flux, which is especially notable in cells dedicated to secreting hormone-regulated gene products. Because of the complexity of the protein folding pathway and the potential for genetic or stochastic errors, a significant percentage of these nascent secreted proteins fail to acquire their native conformations. If these species cannot be cleared from the ER, they may aggregate, which leads to cell death. To lessen the effects of potentially toxic polypeptides, aberrant ER proteins are destroyed via a process known as ER-associated degradation (ERAD). ERAD substrates are selected by molecular chaperones and chaperone-like proteins, and prior to degradation most substrates are ubiquitin-modified. Together with the unfolded protein response, the ERAD pathway is a critical component of the protein quality control machinery in the ER. Although emerging data continue to link ERAD with human diseases, most of our knowledge of this pathway arose from studies using a model eukaryote, the yeast Saccharomyces cerevisiae. In this review, we will summarize the discoveries that led to our current understanding of this pathway, focusing primarily on experiments in yeast. We will also indicate links between ERAD and disease and emphasize future research avenues. PMID:21029298

Goeckeler, J L; Brodsky, J L

2010-10-01

244

Durability of thermal control and environmental protective materials for the SSRMS in simulated LEO environment  

NASA Astrophysics Data System (ADS)

Nine thermal control and environmental protection materials, selected on the basis of their space pedigree, thermal vacuum stability, and thermo-optical properties, were tested to determine their suitability for the Space Station Remote Manipulator System (SSRMS). The ground based testing was carried out to simulate the effects of atomic oxygen and thermal cycling in the Low Earth Orbit (LEO) environment. These factors are deemed most likely to cause degradation to the selected materials. With the exception of the urethane based coatings, the materials tested demonstrate sufficient resistance to atomic oxygen. The detrimental effect of thermal cycling on the adhesion of the silicate based coatings to aluminum substrate was found to depend on the pigment. A separate experiment on Beta-Cloth showed that its thermo-optical properties remained substantially unchanged as the Teflon coating was progressively removed in a plasma asher.

Chang, S. K.

1993-06-01

245

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

246

SUSTAINABLE DEVELOPMENT USING CONTROLLED LOW-STRENGTH MATERIAL  

Microsoft Academic Search

This paper describes the use of controlled low-strength material (CLSM) in the United States, with an emphasis on the use of by-product and waste materials CLSM for infrastructure applications. CLSM is a self-leveling, cementitious material used as an alternative to compacted fill in applications including backfill, utility bedding, void fill, and bridge approaches. A general overview of the technology is

David Trejo; Kevin J. Folliard; Lianxiang Du

247

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

248

Strength properties of fly ash based controlled low strength materials  

Microsoft Academic Search

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

S. Türkel

2007-01-01

249

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

250

Laboratory tests on the role of impurities in semiconducting shield materials on the degradation of XLPE cable insulation  

SciTech Connect

Analyses of field-aged and failed cables recovered from the field over the past fifteen years have contributed a great deal of information that has been compiled to gain a better understanding of failure mechanisms is direct buried (URD), medium voltage cables. The experience gained through these analyses strongly suggested that water and ions, acting with the applied electric field, were responsible for a large number of premature failures of URD cables. The type of cable construction, cleanliness of the raw materials, extrusion practices, and nature of the operating environment were shown to influence the rate of degradation. Experience gained through analysis of field aged cables, combined with laboratory tests, has resulted in significant and ongoing technology transfer to the electric utilities, cable materials suppliers, and cable manufacturers. 11 refs.

Groeger, J.H.; Mashikian, M.S.; Dale, S.

1989-01-01

251

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

252

Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, mechanical fatigue, creep and thermal fatigue effects  

NASA Astrophysics Data System (ADS)

This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.

Bast, Callie Corinne Scheidt

1994-03-01

253

MISSE Thermal Control Materials with Comparison to Previous Flight Experiments  

NASA Astrophysics Data System (ADS)

Many different passive thermal control materials were flown as part of the Materials on International Space Station Experiment, including inorganic coatings, anodized aluminum, and multi-layer insulation materials. These and other material samples were exposed to the low Earth orbital environment of atomic oxygen, ultraviolet radiation, thermal cycling, and hard vacuum, though atomic oxygen exposure was limited for some samples. Materials flown on MISSE-1 and MISSE-2 were exposed to the space environment for nearly four years. Materials flown on MISSE-3, MISSE-4, and MISSE-5 were exposed to the space environment for one year. Solar absorptance, infrared emittance, and mass measurements indicate the durability of these materials to withstand the space environment. Effects of short duration versus long duration exposure on ISS are explored, as well as comparable data from previous flight experiments, such as the Passive Optical Sample Assembly (POSA), Optical Properties Monitor (OPM), and Long Duration Exposure Facility (LDEF).

Finckenor, Miria

2009-01-01

254

MISSE Thermal Control Materials with Comparison to Previous Flight Experiments  

NASA Technical Reports Server (NTRS)

Many different passive thermal control materials were flown as part of the Materials on International Space Station Experiment (MISSE), including inorganic coatings, anodized aluminum, and multi-layer insulation materials. These and other material samples were exposed to the low Earth orbital environment of atomic oxygen, ultraviolet radiation, thermal cycling, and hard vacuum, though atomic oxygen exposure was limited for some samples. Materials flown on MISSE-1 and MISSE-2 were exposed to the space environment for nearly four years. Materials flown on MISSE-3, MISSE-4, and MISSE-5 were exposed to the space environment for one year. Solar absorptance, infrared emittance, and mass measurements indicate the durability of these materials to withstand the space environment. Effects of short duration versus long duration exposure on ISS are explored, as well as comparable data from previous flight experiments, such as the Passive Optical Sample Assembly (POSA), Optical Properties Monitor (OPM), and Long Duration Exposure Facility (LDEF).

Finckenor, Miria; Pippin, H. Gary; Frey, George

2008-01-01

255

Friction stir processing of magnesium-nanohydroxyapatite composites with controlled in vitro degradation behavior.  

PubMed

Nano-hydroxyapatite (nHA) reinforced magnesium composite (Mg-nHA) was fabricated by friction stir processing (FSP). The effect of smaller grain size and the presence of nHA particles on controlling the degradation of magnesium were investigated. Grain refinement from 1500?m to ?3.5?m was observed after FSP. In vitro bioactivity studies by immersing the samples in supersaturated simulated body fluid (SBF 5×) indicate that the increased hydrophilicity and pronounced biomineralization are due to grain refinement and the presence of nHA in the composite respectively. Electrochemical test to assess the corrosion behavior also clearly showed the improved corrosion resistance due to grain refinement and enhanced biomineralization. Using MTT colorimetric assay, cytotoxicity study of the samples with rat skeletal muscle (L6) cells indicate marginal increase in cell viability of the FSP-Mg-nHA sample. The composite also showed good cell adhesion. PMID:24863230

Ratna Sunil, B; Sampath Kumar, T S; Chakkingal, Uday; Nandakumar, V; Doble, Mukesh

2014-06-01

256

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.

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

2007-01-01

257

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...

258

Control of radioactive material transport in sodium-cooled reactors  

Microsoft Academic Search

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

Brehm

2008-01-01

259

State of composite material structure control in situ  

NASA Astrophysics Data System (ADS)

A review is given of methods available for the metallurgical control and NDT evaluations of composite materials with attention given to their limitations. Among the techniques examined are holography, acoustic emission, and extensometry. The development of automated ultrasonic control techniques is leading to more routine use in such industrial applications as aircraft fabrication.

Huther, M.; Jouan, M.

260

Compatibility of Refractory Materials for Nuclear Reactor Poison Control Systems.  

National Technical Information Service (NTIS)

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 material...

J. H. Sinclair

1974-01-01

261

On Social and Material Aspects of Technological Control  

NASA Astrophysics Data System (ADS)

This commentary on Hugh Lacey's paper emphasises the material aspects of the social structure within which technological control takes place. It is suggested here that when the example of the Green Revolution is examined in detail a clear-cut distinction between material and social constraints/possibilities is misleading. I propose a material analysis of the control situation. This analysis is placed within the material framework of the social structure within which the control system is employed. By widening of the analysis even further it is hoped that the environmental issues of the Green Revolution that concern Vandana Shiva can be addressed. I provide a glimpse of how such an account should proceed.

Herfel, William E.

262

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

263

Application of magnetostrictive smart materials in rotor servoflap control  

Microsoft Academic Search

The main theme of this research project has been to analytically develop a proof-of-concept design to demonstrate the effectiveness of a smart material actuator employing ETREMA TERFENOL-DTM for helicopter rotor servoflap control. This design enables the control of the rotor blade flap with an actuator embedded in the blade itself. By moving the control to the rotor blades, the swashplate

Solomon R. Ghorayeb; T. Toby Hansen; Friedrich K. Straub

1995-01-01

264

Distribution of electrical energy consumption for the efficient degradation control of THMs mixture in sonophotolytic process.  

PubMed

Sonophotolytic degradation of THMs mixture with different electrical energy ratio was carried out for efficient design of process. The total consumed electrical energy was fixed around 50W, and five different energy conditions were applied. The maximum degradation rate showed in conditions of US:UV=1:3 and US:UV=0:4. This is because the photolytic degradation of bromate compounds is dominant degradation mechanism for THMs removal. However, the fastest degradation of total organic carbon was observed in a condition of US:UV=1:3. Because hydrogen peroxide generated by sonication was effectively dissociated to hydroxyl radicals by ultraviolet, the concentration of hydroxyl radical was maintained high. This mechanism provided additional degradation of organics. This result was supported by comparison between the concentration of hydrogen peroxide sole and combined process. Consequently, the optimal energy ratio was US:UV=1:3 for degradation of THMs in sonophotolytic process. PMID:24798228

Park, Beomguk; Cho, Eunju; Son, Younggyu; Khim, Jeehyeong

2014-11-01

265

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

266

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

267

Development of Materials Resistant to Metal Dusting Degradation Annual Report for Calendar Year 2005.  

National Technical Information Service (NTIS)

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 hav...

K. Natesan Z. Zeng

2006-01-01

268

Real-Time Characterization of Materials Degradation Using Leaky Lamb Wave  

NASA Technical Reports Server (NTRS)

Leaky Lamb wave (LLW) propagation in composite materials has been studied extensively since it was first observed in 1982. The wave is induced using a pitch-catch arrangement and the plate wave modes are detected by searching minima in the reflected spectra.

Shiuh, S.; Bar-Cohen, Y.

1997-01-01

269

Mechanical Response and Decomposition of Thermally Degraded Energetic Materials: Experiments and Model Simulations  

Microsoft Academic Search

We report progress of a continuing effort to characterize and simulate the response of energetic materials (EMs), primarily HMX-based, under conditions leading to cookoff. Our experiments include mechanical-effects testing of HMX and FIMX with binder at temperatures nearing decomposition thresholds. Additional experiments have focused on decomposition of these EMs under confinement, measuring evolution of gas products and observing the effect

MICHAEL J. KANESHIGE; ANITA M. RENLUND; ROBERT G. SCHMITT; GERALD W. WELLMAN

1999-01-01

270

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

271

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...

272

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

273

Material Control and Accountability Experience at the Fuel Conditioning Facility  

SciTech Connect

The Fuel Conditioning Facility (FCF) at the Idaho National Laboratory (INL) treats spent nuclear fuel using an electrometallurgical process that separates the uranium from the fission products, sodium thermal bond, and cladding materials. Material accountancy is necessary at FCF for two reasons: 1) it provides a mechanism for detecting a potential loss of nuclear material for safeguards and security, and 2) it provides a periodic check of inventories to ensure that processes and materials are within control limits. Material Control and Accountability is also a Department of Energy (DOE) requirement (DOE Order 474.1). The FCF employs a computer based Mass Tracking (MTG) System to collect, store, retrieve, and process data on all operations that directly affect the flow of materials through the FCF. The MTG System is important for the operations of the FCF because it supports activities such as material control and accountability, criticality safety, and process modeling. To conduct material control and accountability checks and to monitor process performance, mass balances are routinely performed around the process equipment. The equipment used in FCF for pyro-processing consists of two mechanical choppers and two electro-refiners (the Mark-IV with the accompanying element chopper and Mark-V with the accompanying blanket chopper for processing driver fuel and blanket, respectively), and a cathode processor (used for processing both driver fuel and blanket) and casting furnace (mostly used for processing driver fuel). Performing mass balances requires the measurement of the masses and compositions of several process streams and equipment inventories. The masses of process streams are obtained via in-cell balances (i.e., load cells) that weigh containers entering and leaving the process equipment. Samples taken at key locations are analyzed to determine the composition of process streams and equipment inventories. In cases where equipment or containers cannot be placed on a balance, others methods (e.g., level measurements, volume calibration equations, calculated density via additive volumes) are utilized to measure the inventory mass. This paper will discuss the material control and accountability experience at the FCF after ten-plus years of processing spent nuclear fuel. A particular area of discussion is the calculated electrolyte density via additive volumes and its importance in determining the mass and composition in the FCF electro-refiners for material control and accountability of special nuclear material. (authors)

Vaden, D.; Fredrickson, G.L. [Idaho National Laboratory, Idaho Falls ID 83415 (United States)

2007-07-01

274

Migration of volatile degradation products into ozonated water from plastic packaging materials.  

PubMed

Migration of volatile degradation products from poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE) bottles, polypropylene (PP) caps and ethyl vinyl acetate (EVA) liners into ozonated water was measured. Polymer strips were immersed in deionized and distilled water with ozone concentrations of 0.5, 2.5 and/or 5 mg kg(-1) inside 35-ml vials, which were clamp-sealed and stored at 40 degrees C for 10 days. A purge-and-trap unit was developed to extract volatile products from the ozonated water in vials. The extractables were trapped in an adsorbent tube and analysed using a GC-MS coupled with an automated thermal desorber (ATD). Mass spectra were interpreted by comparison with a NIST mass spectral library, and an internal standard method was used to quantify the extractables of interest. Several volatile compounds found in ozonated water that had been in contact with PP, EVA and HDPE polymers included butanal, pentanal, hexanal, heptanal, octanal, nonanal, 2,2-dimethyl propanal, 3-hexanone, 2-hexanone and heptanone. These compounds could cause off-taste and off-odour with a low organoleptic threshold. In general, the concentrations of these volatile compounds increased with an increased exposure to ozone. The highest concentration found was 14.1 +/- 0.6 microg kg(-1) for hexanal with a 5 mg kg(-1) ozone treatment of PP caps. Even at a treatment level of 5 mg kg(-1) ozone, which is greater than 10 times the current regulatory limits for bottled water, the extractables migrating from those polymers were within the levels permitted by the FDA. For the PET sample, no significant peaks were observed before or after ozonation. These results imply that PP caps containing EVA liners may be major sources of off-odour and taste in ozonated bottled water. PMID:14594682

Song, Y S; Al-Taher, F; Sadler, G

2003-10-01

275

Degradation of optical reflectivity of in-vessel mirror materials by helium bombardment  

NASA Astrophysics Data System (ADS)

The effect of helium irradiation on in-vessel mirror materials, i.e. molybdenum and rhodium, are investigated experimentally. By the exposure to helium plasmas with low incident ion energy (˜50 eV) at different surface temperatures, the optical reflectivity of molybdenum and rhodium decreases significantly. From the surface analysis, it is shown that fiberlike nanostructure is formed on molybdenum surface when the surface temperature is high (at 1500 K), while rough surface is observed when the surface temperature is low (<1000 K). The decrease in the optical reflectivity is significant particularly for short wavelength ranges, typically, less than 300 nm. The results indicate that the helium irradiation should be taken into account for in-vessel mirror materials for the optical diagnostics in ITER.

Kajita, Shin; Saeki, Tsubasa; Ohno, Noriyasu; Tokitani, Masayuki; Hatae, Takaki; Sakaguchi, Wataru

2011-10-01

276

Time-dependent degradation of titanium osteoconductivity: An implication of biological aging of implant materials  

Microsoft Academic Search

The shelf life of implantable materials has rarely been addressed. We determined whether osteoconductivity of titanium is stable over time. Rat bone marrow-derived osteoblasts were cultured on new titanium disks (immediately after acid-etching), 3-day-old (stored after acid-etching for 3 days in dark ambient conditions), 2-week-old, and 4-week-old disks. Protein adsorption capacity, and osteoblast migration, attachment, spread, proliferation and mineralization decreased

Wael Att; Norio Hori; Masato Takeuchi; Jianyong Ouyang; Yang Yang; Masakazu Anpo; Takahiro Ogawa

2009-01-01

277

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

278

Partial discharge-induced degradation characteristics of insulating materials of gas-filled power transformers  

Microsoft Academic Search

The soundness of a transformer under an operating voltage is evaluated in partial discharge (PD) test of long-duration ac withstand voltage test. At present, the same criteria for evaluating oil-filled transformers are adopted as those for evaluating gas-filled transformers in this PD test. However, gas-filled transformers are made of different insulating materials than those for oil-filled transformers, and therefore they

Shigemitsu Okabe; Genyo Ueta; Haruhisa Wada; Hitoshi Okubo

2010-01-01

279

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

280

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.

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

281

SCF(KMD) controls cytokinin signaling by regulating the degradation of type-B response regulators.  

PubMed

Cytokinins are plant hormones that play critical roles in growth and development. In Arabidopsis, the transcriptional response to cytokinin is regulated by action of type-B Arabidopsis response regulators (ARRs). Although central elements in the cytokinin signal transduction pathway have been identified, mechanisms controlling output remain to be elucidated. Here we demonstrate that a family of F-box proteins, called the kiss me deadly (KMD) family, targets type-B ARR proteins for degradation. KMD proteins form an S-phase kinase-associated PROTEIN1 (SKP1)/Cullin/F-box protein (SCF) E3 ubiquitin ligase complex and directly interact with type-B ARR proteins. Loss-of-function KMD mutants stabilize type-B ARRs and exhibit an enhanced cytokinin response. In contrast, plants with elevated KMD expression destabilize type-B ARR proteins leading to cytokinin insensitivity. Our results support a model in which an SCF(KMD) complex negatively regulates cytokinin responses by controlling levels of a key family of transcription factors. PMID:23720308

Kim, Hyo Jung; Chiang, Yi-Hsuan; Kieber, Joseph J; Schaller, G Eric

2013-06-11

282

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

283

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

284

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

285

Maximising municipal solid waste--legume trimming residue mixture degradation in composting by control parameters optimization.  

PubMed

Composting is one of the most successful biological processes for the treatment of the residues enriched in putrescible materials. The optimization of parameters which have an influence on the stability of the products is necessary in order to maximize recycling and recovery of waste components. The influence of the composting process parameters (aeration, moisture, C/N ratio, and time) on the stability parameters (organic matter, N-losses, chemical oxygen demand, nitrate, biodegradability coefficient) of the compost was studied. The composting experiment was carried out using Municipal Solid Waste (MSW) and Legume Trimming Residues (LTR) in 200 L isolated acrylic barrels following a Box-Behnken central composite experimental design. Second-order polynomial models were found for each of the studied compost stability parameter, which accurately described the relationship between the parameters. The differences among the experimental values and those estimated by using the equations never exceeded 10% of the former. Results of the modelling showed that excluding the time, the C/N ratio is the strongest variable influencing almost all the stability parameters studied in this case, with the exception of N-losses which is strongly dependent on moisture. Moreover, an optimized ratio MSW/LTR of 1/1 (w/w), moisture content in the range of 40-55% and moderate to low aeration rate (0.05-0.175 Lair kg(-)(1) min(-1)) is recommended to maximise degradation and to obtain a stable product during co-composting of MSW and LTR. PMID:23764508

Cabeza, I O; López, R; Ruiz-Montoya, M; Díaz, M J

2013-10-15

286

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

287

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

288

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

289

Tracing and control of raw materials sourcing for vaccine manufacturers.  

PubMed

The control of the raw materials used to manufacture vaccines is mandatory; therefore, a very clear process must be in place to guarantee that raw materials are traced. Those who make products or supplies used in vaccine manufacture (suppliers of culture media, diagnostic tests, etc.) must apply quality systems proving that they adhere to certain standards. ISO certification, Good Manufacturing Practices for production sites and the registration of culture media with a 'Certificate of Suitability' from the European Directorate for the Quality of Medicines and Healthcare are reliable quality systems pertaining to vaccine production. Suppliers must assure that each lot of raw materials used in a product that will be used in vaccine manufacture adheres to the level of safety and traceability required. Incoming materials must be controlled in a single 'Enterprise Resource Planning' system which is used to document important information, such as the assignment of lot number, expiration date, etc. Ingredients for culture media in particular must conform to certain specifications. The specifications that need to be checked vary according to the ingredient, based on the level of risk. The way a raw material is produced is also important, and any aspect relative to cross-contamination, such as the sanitary measures used in producing and storing the raw material must be checked as well. In addition, suppliers can reduce the risk of viral contamination of raw materials by avoiding purchases in countries where a relevant outbreak is currently declared. PMID:20335052

Faretra Peysson, Laurence

2010-05-01

290

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

Microsoft Academic Search

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)

Phifer

2004-01-01

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

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

293

Erosion kinetics of hydrolytically degradable polymers.  

PubMed Central

Degradable polymers are beginning to play an increasing role as materials for environmental and medical applications. Understanding factors that control erosion, such as bond cleavage and the dissolution and diffusion of degradation products, will be critical to the future development of these materials. Erosion kinetics, photomicroscopy, and infrared spectroscopy were used to understand the erosion mechanism of two families of degradable polymers, polyanhydrides and polyesters. Polyanhydrides exhibit behavior more characteristic of surface erosion, whereas the polyesters exhibit bulk erosion patterns. Control of erosion times from a few days to several years can be achieved by a judicious choice of monomer units and bond selection. Images

Tamada, J A; Langer, R

1993-01-01

294

Antimicrobial Materials for Advanced Microbial Control in Spacecraft Water Systems  

NASA Technical Reports Server (NTRS)

Microbial detection, identification, and control are essential for the maintenance and preservation of spacecraft water systems. Requirements set by NASA put limitations on the energy, mass, materials, noise, cost, and crew time that can be devoted to microbial control. Efforts are being made to attain real-time detection and identification of microbial contamination in microgravity environments. Research for evaluating technologies for capability enhancement on-orbit is currently focused on the use of adenosine triphosphate (ATP) analysis for detection purposes and polymerase chain reaction (peR) for microbial identification. Additional research is being conducted on how to control for microbial contamination on a continual basis. Existing microbial control methods in spacecraft utilize iodine or ionic silver biocides, physical disinfection, and point-of-use sterilization filters. Although these methods are effective, they require re-dosing due to loss of efficacy, have low human toxicity thresholds, produce poor taste, and consume valuable mass and crew time. Thus, alternative methods for microbial control are needed. This project also explores ultraviolet light-emitting diodes (UV-LEDs), surface passivation methods for maintaining residual biocide levels, and several antimicrobial materials aimed at improving current microbial control techniques, as well as addressing other materials presently under analysis and future directions to be pursued.

Birmele, Michele; Caro, Janicce; Newsham, Gerard; Roberts, Michael; Morford, Megan; Wheeler, Ray

2012-01-01

295

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

296

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

297

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

298

Material control and accounting requirements for uranium enrichment facilities  

SciTech Connect

This paper reports that the U.S. Nuclear Regulatory Commission has defined material control and accounting (MC and A) requirement for low-enriched uranium enrichment plants licensed under 10 CFR parts 40 and 70. Following detailed assessment of potential safeguards issues relevant to these facilities, a new MC and A rule was developed. The primary safeguards considerations are detection of the loss of special nuclear material, detection of clandestine production of special nuclear material of low strategic significance for unauthorized use or distribution, and detection of unauthorized production of uranium enriched to {ge}10 wt % U-235. The primary safeguards concerns identified were the large absolute limit of error associated with the material balance closing, the inability to shutdown some uranium enrichment technologies to perform a cleanout inventory of the process system, and the flexibility of some of these technologies to produce higher enrichments. Unauthorized production scenarios were identified for some technologies that could circumvent the detection of the production and removal of 5 kilograms of U-235 as high-enriched uranium through conventional material control and accounting programs. Safeguards techniques, including the use of production and process control information, measurements, and technical surveillance, were identified to compensate for these concerns.

Ting, P. (Nuclear Regulatory Commission, Washington, DC (United States). Office of Nuclear Material Safety and Safeguards); Moran, B.W. (International Technology Programs Div., Martin Marietta Energy Systems, Inc., Oak Ridge, TN (US))

1991-01-01

299

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

300

10 CFR 76.111 - Physical security, material control and accounting, and protection of certain information.  

...2014-01-01 2014-01-01 false Physical security, material control and accounting...Safeguards and Security § 76.111 Physical security, material control and accounting...certification of the Corporation 2 for physical security and material control...

2014-01-01

301

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

302

Computer Simulation of Scaffold Degradation  

NASA Astrophysics Data System (ADS)

Scaffolds are porous biocompatible materials with suitable microarchitectures that are designed to allow for cell adhesion, growth and proliferation. They are used in combination with cells in regenerative medicine to promote tissue regeneration by means of a controlled deposition of natural extracellular matrix by the hosted cells therein. This healing process is in many cases accompanied by scaffold degradation up to its total disappearance when the scaffold is made of a biodegradable material. This work presents a computational model that simulates the degradation of scaffolds. The model works with three-dimensional microstructures, which have been previously discretised into small cubic homogeneous elements, called voxels. The model simulates the evolution of the degradation of the scaffold using a Monte Carlo algorithm, which takes into account the curvature of the surface of the fibres. The simulation results obtained in this study are in good agreement with empirical degradation measurements performed by mass loss on scaffolds after exposure to an etching alkaline solution.

Erkizia, G.; Rainer, A.; De Juan-Pardo, E. M.; Aldazabal, J.

2010-11-01

303

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

304

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.

2013-07-01

305

Material control and accounting requirements for uranium enrichment facilities  

Microsoft Academic Search

This paper reports that the U.S. Nuclear Regulatory Commission has defined material control and accounting (MC and A) requirement for low-enriched uranium enrichment plants licensed under 10 CFR parts 40 and 70. Following detailed assessment of potential safeguards issues relevant to these facilities, a new MC and A rule was developed. The primary safeguards considerations are detection of the loss

P. Ting; B. W. Moran

1991-01-01

306

MEASUREMENT TECHNIQUES FOR INORGANIC TRACE MATERIALS IN CONTROL SYSTEM STREAMS  

EPA Science Inventory

The report gives results of a study showing that inorganic materials in control process streams at trace levels can be determined using modified, commercially available sampling equipment and atomic absorption analysis procedures; however, special care must be taken to attain hig...

307

Controlled Release of Bioactive Materials Using Alginate Gel Beads.  

National Technical Information Service (NTIS)

Alginate gel beads containing bioactive materials dispersed therein are the product and the process of this invention. These beads can be made to either float or sink in aqueous environments, and are capable of providing the controlled release of their bi...

W. J. Connick

1980-01-01

308

EVALUATION OF CONTROL ROD MATERIALS CVTR PROJECT. Terminal Report  

Microsoft Academic Search

Mechanical and corrosion tests were performed on various control rod ; materials for CVTR application. The corrosion tests were carried out in ; demineralized static-water at 190 deg F and in a helium-water vapor atmosphere at ; 530 deg F. The mechanical tests were carried out at room temperature and at 250 ; deg F. The tests indicated that either

L. Marti-Balaguer; W. R. Smalley

1960-01-01

309

Controlled extracellular matrix degradation in breast cancer tumors improves therapy by trastuzumab.  

PubMed

Extracellular matrix (ECM) in solid tumors affects the effectiveness of therapeutics through blocking of intratumoral diffusion and/or physical masking of target receptors on malignant cells. In immunohistochemical studies of tumor sections from breast cancer patients and xenografts, we observed colocalization of ECM proteins and Her2/neu, a tumor-associated antigen that is the target for the widely used monoclonal antibody trastuzumab (Herceptin). We tested whether intratumoral expression of the peptide hormone relaxin (Rlx) would result in ECM degradation and the improvement of trastuzumab therapy. As viral gene delivery into epithelial tumors with extensive tumor ECM is inefficient, we used a hematopoietic stem cell (HSC)-based approach to deliver the Rlx gene to the tumor. In mouse models with syngeneic breast cancer tumors, HSC-mediated intratumoral Rlx expression resulted in a decrease of ECM proteins and enabled control of tumor growth. Moreover, in a model with Her2/neu-positive BT474-M1 tumors and more treatment-refractory tumors derived from HCC1954 cells, we observed a significant delay of tumor growth when trastuzumab therapy was combined with Rlx expression. Our results have implications for antibody therapy of cancer as well as for other anticancer treatment approaches that are based on T-cells or encapsulated chemotherapy drugs. PMID:21081901

Beyer, Ines; Li, Zongyi; Persson, Jonas; Liu, Ying; van Rensburg, Ruan; Yumul, Roma; Zhang, Xiao-Bing; Hung, Mien-Chie; Lieber, André

2011-03-01

310

Control of vacuole permeability and protein degradation by the cell cycle arrest signal in Saccharomyces cerevisiae.  

PubMed Central

Saccharomyces cerevisiae responds to deperivation of nutrients by arresting cell division at the unbudded G1 stage. Cells situated outside of G1 at the time of deperivation complete the cell cycle before arresting. This prompted an investigation of the source of nutrients used by these cells to complete division and the mechanisms controlling their availability. We found a close correlation between accumulation of unbudded cells and loss of previously formed allophanate hydrolase activity after nutrient starvation. These losses were not specific to the allantoin, system since they have been observed for a number of other enzymes and also when cellular protein levels were monitored with [3H]leucine. Loss of hydrolase activity was also observed when protein synthesis was inhibited either by addition of inhibitors or loss of the prtl gene product. We found that onset of nutrient starvation brought about release of large quantities of arginine and allantoin normally sequestered in the cell vacuole. Treatment of a cells with alpha-factor resulted in both the release of allantoin and arginine from the cell vacuole and the onset of intracellular protein degradation. These effects were not observed when either alpha cells or a/alpha diploid strains were treated with alpha-factor. These data suggest that release of vacuolar constitutents and protein turnover may be regulated by the G1 arrest signal.

Sumrada, R; Cooper, T G

1978-01-01

311

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

312

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

313

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

314

Mechanical Response and Decomposition of Thermally Degraded Energetic Materials: Experiments and Model Simulations  

SciTech Connect

We report progress of a continuing effort to characterize and simulate the response of energetic materials (EMs), primarily HMX-based, under conditions leading to cookoff. Our experiments include mechanical-effects testing of HMX and FIMX with binder at temperatures nearing decomposition thresholds. Additional experiments have focused on decomposition of these EMs under confinement, measuring evolution of gas products and observing the effect of pressurization on the solid. Real-time measurements on HMX show abrupt changes that maybe due to sudden void collapse under increasing load. Postmortem examination shows significant internal damage to the pellets, including voids and cracks. These experiments have been used to help develop a constitutive model for pure HMX. Unconfined uniaxial compression tests were performed on HMX and LX-14 to examine the effect of binders on the deviatoric strength of EM pellets, and to assess the need of including deviatoric terms in the model. A scale-up experiment will be described that is being developed to validate the model and provide additional diagnostics.

KANESHIGE,MICHAEL J.; RENLUND,ANITA M.; SCHMITT,ROBERT G.; WELLMAN,GERALD W.

1999-10-14

315

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.

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

2010-01-01

316

Degradable, thermo-sensitive poly(N-isopropyl acrylamide)-based scaffolds with controlled porosity for tissue engineering applications.  

PubMed

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 photocopolymerization 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

2010-10-11

317

An application of neural networks to process and materials control  

SciTech Connect

Process control consists of two basic elements: a model of the process and knowledge of the desired control algorithm. In some cases the level of the control algorithm is merely supervisory, as in an alarm-reporting or anomaly-detection system. If the model of the process is known, then a set of equations may often be solved explicitly to provide the control algorithm. Otherwise, the model has to be discovered through empirical studies. Neural networks have properties that make them useful in this application. They can learn (make internal models from experience or observations). The problem of anomaly detection in materials control systems fits well into this general control framework. To successfully model a process with a neutral network, a good set of observables must be chosen. These observables must in some sense adequately span the space of representable events, so that a signature metric can be built for normal operation. In this way, a non-normal event, one that does not fit within the signature, can be detected. In this paper, we discuss the issues involved in applying a neural network model to anomaly detection in materials control systems. These issues include data selection and representation, network architecture, prediction of events, the use of simulated data, and software tools. 10 refs., 4 figs., 1 tab.

Howell, J.A.; Whiteson, R.

1991-01-01

318

Systems analysis for materials control and accountancy technology  

SciTech Connect

The objective is to upgrade Materials Control and Accountancy (MCandA) technology over the flows of special nuclear materials throughout the DOE complex of fuel cycles. The program focus is to develop a ''Management Tool'' for decision support in evaluating MCandA upgrades, and invalidating the MCandA aspects of the Master Safeguards and Security Agreements (MSSA) effectiveness. The approach is the computerization of the nuclear materials flow charts, identification of key measurement locations in the production and product fuel cycle, and construct data information processing at each measurement location. The program is to provide the Office of Safeguards and Security (OSS) with a timely management decision support system in planning MCandA safeguards technology upgrades over the nuclear materials production and product cycles.

Daly, T.A.; Bucher, R.G.; Rothman, A.B.; Charak, I.; Persiani, P.J.

1987-07-01

319

Systems analysis for materials control and accountancy technology  

SciTech Connect

The objective of this study is to upgrade Materials Control and Accountancy (MC and A) technology over the flows of special nuclear materials throughout the DOE complex of fuel cycles. The program focus is to develop a ''Management Tool'' for decision support in evaluating MC and A upgrades, and in validating the MC and A aspects of the Master Safeguards and Security Agreements (MSSA) effectiveness. The approach is the computerization of the nuclear materials flow charts, identification of key measurement locations in the production and product fuel cycle, and construct data information processing at each measurement location. The program is to provide the Office of Safeguards and Security (OSS) with a timely management decision support system in planning MC and A safeguards technology upgrades over the nuclear materials production and product cycles.

Daly, T.A.; Bucher, R.G.; Rothman, A.B.; Charak, I.; Persiani, P.J.

1987-01-01

320

Materials for adaptive structural acoustic control, volume 1  

NASA Astrophysics Data System (ADS)

This report documents work carried out in the Materials Research Laboratory of the Pennsylvania State University over the first year of a new ONR sponsored University Research Initiative (URI) entitled Materials for Adaptive Structural Acoustic Control. For this report the activities have been grouped under the following topic headings: (1) General Summary Papers; (2) Materials Studies; (3) Composite Sensors; (4) Actuator Studies; (5) Integration Issues; (6) Processing Studies; and (7) Thin Film Ferroelectrics. In material studies important advances have been made in the understanding of the evaluation of relaxor behavior in the PLZT's and of the order disorder behavior in lead scandium tantalate:lead titanate solid solutions and of the Morphotropic Phase Boundary in this system.

Cross, L. E.

1993-04-01

321

Control of epithelial cell migration and invasion by the IKK?- and CK1?-mediated degradation of RAPGEF2.  

PubMed

Epithelial cell migration is crucial for the development and regeneration of epithelial tissues. Aberrant regulation of epithelial cell migration has a major role in pathological processes such as the development of cancer metastasis and tissue fibrosis. Here, we report that in response to factors that promote cell motility, the Rap guanine exchange factor RAPGEF2 is rapidly phosphorylated by I-kappa-B-kinase-? and casein kinase-1? and consequently degraded by the proteasome via the SCF(?TrCP) ubiquitin ligase. Failure to degrade RAPGEF2 in epithelial cells results in sustained activity of Rap1 and inhibition of cell migration induced by HGF, a potent metastatic factor. Furthermore, expression of a degradation-resistant RAPGEF2 mutant greatly suppresses dissemination and metastasis of human breast cancer cells. These findings reveal a molecular mechanism regulating migration and invasion of epithelial cells and establish a key direct link between IKK? and cell motility controlled by Rap-integrin signaling. PMID:24290981

Magliozzi, Roberto; Low, Teck Yew; Weijts, Bart G M W; Cheng, Tianhong; Spanjaard, Emma; Mohammed, Shabaz; van Veen, Anouk; Ovaa, Huib; de Rooij, Johan; Zwartkruis, Fried J T; Bos, Johannes L; de Bruin, Alain; Heck, Albert J R; Guardavaccaro, Daniele

2013-12-01

322

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

323

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

324

Radioactive material inventory control at a waste characterization facility  

SciTech Connect

Due to the recent introduction of more stringent Department of Energy (DOE) regulations and requirements pertaining to nuclear and criticality safety, the control of radioactive material inventory has emerged as an important facet of operations at DOE nuclear facilities. In order to comply with nuclear safety regulations and nuclear criticality requirements, radioactive material inventories at each nuclear facility have to be maintained below limits specified for the facility in its safety authorization basis documentation. Exceeding these radioactive material limits constitutes a breach of the facility`s nuclear and criticality safety envelope and could potentially result in an accident, cause a shut-down of the facility, and bring about imminent regulatory repercussions. The practice of maintaining control of radioactive material, especially sealed and unsealed sources, is commonplace and widely implemented; however, the requirement to track the entire radioactivity inventory at each nuclear facility for the purpose of ensuring nuclear safety is a new development. To meet the new requirements, the Applied Radiation Measurements Department at Oak Ridge National Laboratory (ORNL) has developed an information system, called the {open_quotes}Radioactive Material Inventory System{close_quotes} (RMIS), to track the radioactive material inventory at an ORNL facility, the Waste Examination and Assay Facility (WEAF). The operations at WEAF, which revolve around the nondestructive assay and nondestructive examination of waste and related research and development activities, results in an ever-changing radioactive material inventory. Waste packages and radioactive sources are constantly being brought in or taken out of the facility; hence, use of the RMIS is necessary to ensure that the radioactive material inventory limits are not exceeded.

Yong, L.K.; Chapman, J.A.; Schultz, F.J. [Oak Ridge National Laboratory, TN (United States)

1996-06-01

325

Legumain/asparaginyl endopeptidase controls extracellular matrix remodeling through the degradation of fibronectin in mouse renal proximal tubular cells.  

PubMed

Legumain/asparaginyl endopeptidase (EC 3.4.22.34) is a novel cysteine protease that is abundantly expressed in the late endosomes and lysosomes of renal proximal tubular cells. Recently, emerging evidence has indicated that legumain might play an important role in control of extracellular matrix turnover in various pathological conditions such as tumor growth/metastasis and progression of atherosclerosis. We initially found that purified legumain can directly degrade fibronectin, one of the main components of the extracellular matrix, in vitro. Therefore, we examined the effect of legumain on fibronectin degradation in cultured mouse renal proximal tubular cells. Fibronectin processing can be inhibited by chloroquine, an inhibitor of lysosomal degradation, and can be enhanced by the overexpression of legumain, indicating that fibronectin degradation occurs in the presence of legumain in lysosomes from renal proximal tubular cells. Furthermore, in legumain-deficient mice, unilateral ureteral obstruction (UUO)-induced renal interstitial protein accumulation of fibronectin and renal interstitial fibrosis were markedly enhanced. These findings indicate that legumain might have an important role in extracellular matrix remodeling via the degradation of fibronectin in renal proximal tubular cells. PMID:17350006

Morita, Yoshikata; Araki, Hisazumi; Sugimoto, Toshiro; Takeuchi, Keisuke; Yamane, Takuya; Maeda, Toshinaga; Yamamoto, Yoshio; Nishi, Katsuji; Asano, Masahide; Shirahama-Noda, Kanae; Nishimura, Mikio; Uzu, Takashi; Hara-Nishimura, Ikuko; Koya, Daisuke; Kashiwagi, Atsunori; Ohkubo, Iwao

2007-04-01

326

Degradation of pathogen quorum-sensing molecules by soil bacteria: a preventive and curative biological control mechanism.  

PubMed

Abstract The plasmid pME6863, carrying the aiiA gene from the soil bacterium Bacillus sp. A24 that encodes a lactonase enzyme able to degrade N-acyl-homoserine lactones (AHLs), was introduced into the rhizosphere isolate Pseudomonas fluorescens P3. This strain is not an effective biological control agent against plant pathogens. The transformant P. fluorescens P3/pME6863 acquired the ability to degrade AHLs. In planta, P. fluorescens P3/pME6863 significantly reduced potato soft rot caused by Erwinia carotovora and crown gall of tomato caused by Agrobacterium tumefaciens to a similar level as Bacillus sp. A24. Little or no disease reduction was observed for the wild-type strain P3 carrying the vector plasmid without aiiA. Suppression of potato soft rot was observed even when the AHL-degrading P. fluorescens P3/pME6863 was applied to tubers 2 days after the pathogen, indicating that biocontrol was not only preventive but also curative. When antagonists were applied individually with the bacterial plant pathogens, biocontrol activity of the AHL degraders was greater than that observed with several Pseudomonas 2,4-diacetylphloroglucinol-producing strains and with Pseudomonas chlororaphis PCL1391, which relies on production of phenazine antibiotic for disease suppression. Phenazine production by this well characterized biological control strain P. chlororaphis PCL1391 is regulated by AHL-mediated quorum sensing. When P. chlororaphis PCL1391 was co-inoculated with P. fluorescens P3/pME6863 in a strain mixture, the AHL degrader interfered with the normally excellent ability of the antibiotic producer to suppress tomato vascular wilt caused by Fusarium oxysporum f. sp. lycopersici. Our results demonstrate AHL degradation as a novel biocontrol mechanism, but also demonstrate the potential for non-target interactions that can interfere with the biocontrol efficacy of other strains. PMID:19719608

Molina, Lázaro; Constantinescu, Florica; Michel, Laurent; Reimmann, Cornelia; Duffy, Brion; Défago, Geneviève

2003-07-01

327

Corrosion and degradation of test materials in the BI-GAS coal-gasification pilot plant  

SciTech Connect

Corrosion monitoring of test materials was conducted in the BI-GAS coal gasification pilot plant from 1976 through 1981. Montana Rosebud subbituminous coal was processed at pressures of 750 psia (5175 kPa). Metals were exposed at low to moderate temperatures (700/sup 0/F (371/sup 0/C)) in the coal preparation area, gasifier slag quench, and the product gas scrubbing system. Refractories and metals were evaluated in the gasifier high temperature (1372/sup 0/F (744/sup 0/C)-1915/sup 0/F (1046/sup 0/C)) test sites at the top of stage II. In the moderate temperature aqueous environments, alloys 26-1, Types 329, 304, 316, 405, and IN-825 were superior in performance to Monel 400, carbon steel A515, and 2-1/4Cr-1Mo. Stress corrosion cracking was not observed in welded U-bend samples (A515, 304, 316, 329, 26-1). First-exposure gasifier corrosion test results generally indicated that uncoated alloys with 23.0 to 26.2 wt % Cr and less than 30 wt % Ni exhibited the best performance. Alloy Types 446 and 310 experienced the least corrosion attack with linear corrosion rates less than 20 mpy (0.51 mm/y); marginal performing alloys were Type 314, 22-13-5, and RA-333. During the second exposure, all uncoated alloys incurred acceptable corrosion losses. Alloys with Co, Cr, and Ni (N155, 556) in approximately equal proportions, at concentrations of approx. 20 wt %, ranked higher in performance than alloys such as Type 310, IN-800, Cru-25, and RA-333. Gasifier exposure of pack-aluminized alloys IN-800(A1) and Type 310(A1)showed that the coating provided corrosion protection. Cracks in the bulk coating were filled with Fe-Al rich oxides. The refractories were changed very little by exposure with two exceptions: tar was removed from a tar-impregnated brick, and a lightweight insulating castable deteriorated greatly.

Yurkewycz, R.; Firestone, R.F.

1982-02-01

328

Materials for adaptive structural acoustic control, volume 2  

NASA Astrophysics Data System (ADS)

This report documents work carried out in the Materials Research Laboratory of the Pennsylvania State University over the first year of a new ONR sponsored University Research Initiative (URI) entitled Materials for Adaptive Structural Acoustic Control. For this report the activities have been grouped under the following topic headings: (1) General Summary Papers; (2) Materials Studies; (3) Composite Sensors; (4) Actuator Studies; (5) Integration Issues; (6) Processing Studies; (7) Thin Film Ferroelectrics. In material studies important advances have been made in the understanding of the evaluation of relaxor behavior in the PLZT's and of the order disorder behavior in lead scandium tantalate:lead titanate solid solutions and of the Morphotropic Phase Boundary in this system. For both composite sensors and actuators we have continued to explore and exploit the remarkable versatility of the flextensional moonie type structure. Finite element (FEA) calculations have given a clear picture of the lower order resonant modes and permitted the evaluation of various end cap metals, cap geometries and load conditions. In actuator studies multilayer structures have been combined with flextensional moonie endcaps to yield high displacement (50 micrometers) compact structures. Electrically controlled shape memory has been demonstrated in lead zirconate stannate titanate compositions, and used for controlling a simple latching relay.

Cross, L. E.

1993-04-01

329

Materials for adaptive structural acoustic control, volume 3  

NASA Astrophysics Data System (ADS)

This report documents work carried out in the Materials Research Laboratory of the Pennsylvania State University over the first year of a new ONR sponsored University Research Initiative (URI) entitled Materials for Adaptive Structural Acoustic Control. For this report the activities have been grouped under the following topic headings: (1) General Summary Papers; (2) Materials Studies; (3) Composite Sensors; (4) Actuator Studies; (5) Integration Issues; (6) Processing Studies; and (7) Thin Film Ferroelectrics. In material studies important advances have been made in the understanding of the evaluation of relaxor behavior in the PLZT's and of the order-disorder behavior in lead scandium tantalate:lead titanate solid solutions and of the Morphotropic Phase Boundary in this system. For both composite sensors and actuators, we have continued to explore and exploit the remarkable versatility of the flextensional moonie type structure. Finite element (FEA) calculations have given a clear picture of the lower order resonant modes and permitted the evaluation of various end cap metals, cap geometries, and load conditions. In actuator studies multilayer structures have been combined with flextensional moonie endcaps to yield high displacement (50 micrometers) compact structures. Electrically controlled shape memory has been demonstrated in lead zirconate stannate titanate compositions, and used for controlling a simple latching relay.

Cross, L. E.

1993-04-01

330

Agricultural biological reference materials for analytical quality control  

SciTech Connect

Cooperative work is under way at Agriculture Canada, US Department of Agriculture, and US National Bureau of Standards in an attempt to fill some of the gaps in the world repertoire of reference materials and to provide much needed control materials for laboratories' day to day operations. This undertaking involves the preparation and characterization of a number of agricultural and food materials for data quality control for inorganic constituents. Parameters considered in the development of these materials were material selection based on importance in commerce and analysis; techniques of preparation, processing, and packaging; physical and chemical characterization; homogeneity testing and quantitation (certification). A large number of agricultural/food products have been selected to represent a wide range of not only levels of sought-for constituents (elements) but also a wide range of matrix components such as protein, carbohydrate, dietary fiber, fat, and ash. Elements whose concentrations are being certified cover some two dozen major, minor, and trace elements of nutritional, toxicological, and environmental significance.

Ihnat, M.

1986-01-01

331

Anomaly and error detection in computerized materials control & accountability databases  

SciTech Connect

Unites States Department of Energy sites use computerized material control and accountability (MC&A) systems to manage the large amounts of data necessary to control and account for their nuclear materials. Theft or diversion of materials from these sites would likely result in anomalies in the data, and erroneous information greatly reduces the value of the information to its users. Therefore, it is essential that MC&A data be periodically assessed for anomalies or errors. At Los Alamos National Laboratory, we have been developing expert systems to provide efficient, cost-effective, automated error and anomaly detection. Automated anomaly detection can provide assurance of the integrity of data, reduce inventory frequency, enhance assurance of physical inventory, detect errors in databases, and gain a better perspective on overall facility operations. The Automated MC&A Database Assessment Project is aimed at improving anomaly and error detection in MC&A databases and increasing confidence in the data. We are working with data from the Los Alamos Plutonium Facility and the Material Accountability and Safeguards System, the Facility`s near-real-time computerized nuclear material accountability and safeguards system. This paper describes progress in customizing the expert systems to the needs of the users of the data and reports on our results.

Whiteson, R.; Hoffbauer, B.; Yarbro, T.F. [and others

1997-09-01

332

Material and method to dissociate water at controlled rates  

SciTech Connect

A material and method for the decomposition/dissociation of water into hydrogen and oxygen is disclosed. The material comprises an amalgam of an alkali metal, mercury, and aluminum combined with a catalytically effective amount of an alloy comprising platinum and at least one metal selected from the group consisting of germanium, antimony, gallium, thallium, indium, cadmium, bismuth, lead, zinc and tin, and with an extender metal to control the rate of dissociation of the water while being non-reactive with the amalgam during dissociation.

Anderson, E.R.

1982-04-13

333

Ferromagnetic nanocomposites as spintronic materials with controlled magnetic structure  

NASA Astrophysics Data System (ADS)

The physical properties of ferromagnetic dilute magnetic semiconductors and nanocomposites are considered in a wide range of temperatures from 5 to 300 K. The latter have several advantages as spintronic materials with a controlled magnetic structure for weak magnetic field sensors. A characteristic feature of ferromagnetic nanocomposites is the spin-dependent tunneling conductance, which is responsible for the negative and positive magnetoresistance. The magnetoresistive effects have a wide range of applications. In particular, materials with such effects may be used in the development of magnetoresistive memory devices, weak magnetic field sensors, medical diagnostic devices, and other items of electronic equipment.

Lashkarev, G. V.; Radchenko, M. V.; Bugaiova, M. E.; Dmitriev, A. I.; Lazorenko, V. I.; Sichkovskyi, V. I.; Knoff, W.; Story, T.; Stelmakh, Y. A.; Krushynskaya, L. A.

2013-01-01

334

Degradation of ZrN films at high temperature under controlled atmosphere  

Microsoft Academic Search

The degradation of ZrN films deposited onto Si substrates by unbalanced magnetron sputtering was investigated over temperatures of 300-1200 °C in different atmospheres by analyzing changes in color and appearance, as well as microstructures. The atmospheres contained air, nitrogen, and forming gas (N2\\/H2=9), which exhibited drastically different oxygen\\/nitrogen partial pressure ratios. The resultant degradation included mainly color changes and formation

Fu-Hsing Lu; Wen-Zheng Lo

2004-01-01

335

Constitutive and UV-induced fibronectin degradation is a ubiquitination-dependent process controlled by beta-TrCP.  

PubMed

Loss of fibronectin (FN) assembly in the extracellular matrix has long been recognized as a feature of cellular transformation. However, such assembly is regulated not only by FN synthesis but also by its post-translational modifications. The mechanism controlling FN protein stability has remained unclear so far. Recently it was demonstrated that FN matrix turnover occurs intracellularly at the lysosome following caveolin-1-dependent endocytosis. Although FN was reported to undergo ubiquitindependent degradation, the ubiquitin ligase responsible for FN ubiquitination is unknown. In this study, we have identified beta-TrCP as the ubiquitin ligase for lysosomal degradation of FN. We found two conserved beta-TrCP recognition motif (DSGVVYS and DSGSIVVS) in the primary amino acid sequence of human, mouse, and rat FN. Down-regulation of either beta-TrCP1 or beta-TrCP2 by small interference (siRNA) caused significant accumulation of FN. Immunolocalization studies showed intracellular accumulation of FN in beta-TrCP siRNA-treated cells without showing much alteration in its matrix association. We also observed that exposure of cells to UV irradiation effectively down-regulated FN following increased ubiquitination, which was significantly inhibited either by lysosomal inhibitor or by siRNA-mediated down-regulation of beta-TrCP. Taken together, constitutive FN degradation, as well as UV-induced degradation, is ubiquitination dependent and controlled by beta-TrCP. PMID:16757476

Ray, Dipankar; Osmundson, Evan C; Kiyokawa, Hiroaki

2006-08-11

336

Pretreatment of lignocellulosic material with fungi capable of higher lignin degradation and lower carbohydrate degradation improves substrate acid hydrolysis and the eventual conversion to ethanol.  

PubMed

Phanerochaete chrysosporium, Pycnoporus cinnabarinus,and fungal isolates RCK-1 and RCK-3 were tested for their lignin degradation abilities when grown on wheat straw (WS) and Prosopis juliflora (PJ) under solid-state cultivation conditions. Fungal isolate RCK-1 degraded more lignin in WS (12.26% and 22.64%) and PJ (19.30% and 21.97%) and less holocellulose in WS (6.27% and 9.39%) and PJ (3.01% and 4.58%) after 10 and 20 days, respectively, than other fungi tested. Phanerochaete chrysosporium caused higher substrate mass loss and degraded more of holocellulosic content (WS: 55.67%; PJ: 48.89%) than lignin (WS: 18.89%; PJ: 20.20%) after 20 days. The fungal pretreatment of WS and PJ with a high-lignin-degrading and low-holocellulose-degrading fungus (fungal isolate RCK-1) for 10 days resulted in (i) reduction in acid load for hydrolysis of structural polysaccharides (from 3.5% to 2.5% in WS and from 4.5% to 2.5% in PJ), (ii) an increase in the release of fermentable sugars (from 30.27 to 40.82 g L(-1) in WS and from 18.18 to 26.00 g L(-1) in PJ), and (iii) a reduction in fermentation inhibitors (total phenolics) in acid hydrolysate of WS (from 1.31 to 0.63 g L(-1)) and PJ (from 2.05 to 0.80 g L(-1)). Ethanol yield and volumetric productivity from RCK-1-treated WS (0.48 g g(-1) and 0.54 g L(-1) h(-1), respectively) and PJ (0.46 g g(-1) and 0.33 g L(-1) h(-1), respectively) were higher than untreated WS (0.36 g g(-1) and 0.30 g L(-1) h(-1), respectively) and untreated PJ (0.42 g g(-1) and 0.21 g L(-1) h(-1), respectively). PMID:18389003

Kuhar, Sarika; Nair, Lavanya M; Kuhad, Ramesh Chander

2008-04-01

337

A nuclear degradation pathway controls the abundance of normal mRNAs in Saccharomyces cerevisiae  

PubMed Central

We previously demonstrated an increased degradation of mRNAs in mutants of Saccharomyces cerevisiae having blocks in nuclear export. The degradation activity, designated DRN (degradation of mRNA in the nucleus), requires Cbc1p, a nuclear cap-binding protein, and Rrp6p, a nuclear exosome component. Microarray procedures were used to determine the half-lives of mRNAs from normal and mutant strains, leading to the tentative identification of hundreds of normal mRNAs that were notably stabilized when either CBC1 or RRP6 were deleted. Northern blot analysis of representative mRNAs confirmed the diminished degradation. One representative of this group, SKS1 mRNA, was also shown by a cytological procedure to be preferentially retained in the nucleus compared with typical mRNAs. We suggest that all normal mRNAs are subjected to degradation by DRN, but the degree of degradation is determined by the degree of nuclear retention. Furthermore, these mRNAs particularly susceptible to DRN were also diminished by overproduction of Cbc1p, demonstrating a regulatory role for CBC1. This conclusion was corroborated by finding an inverse relationship of the CBC1 and SKS1 mRNA levels in normal strains grown under different conditions.

Kuai, Letian; Das, Biswadip; Sherman, Fred

2005-01-01

338

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

339

Amoxicillin-degradation products formed under controlled environmental conditions: identification and determination in the aquatic environment.  

PubMed

Amoxicillin (AMX) is a widely used penicillin-type antibiotic whose presence in the environment has been widely investigated, despite its rapid hydrolysis to various degradation products (DPs). In this work, the formation of AMX DPs was studied in various aqueous solutions containing 100?gmL(-1) AMX. Three phosphate buffer solutions, at pH 5, pH 7 and pH 8, and a fourth buffer solution at pH 7 with the addition of the bivalent ions Mg(2+)and Ca(2) as chelating agents, were examined under controlled environmental conditions. In addition, two solutions from natural sources were examined secondary effluents and tap water. The obtained DPs were identified by their MS/MS, UV and NMR spectra (obtained from pure compounds isolated by preparative HPLC) as: AMX penicilloic acid (ADP1/2), AMX penilloic acid (ADP4/5) and phenol hydroxypyrazine (ADP6). Two additional detected DPs AMX 2',5'-diketopiperazine (ADP8/9), and AMX-S-oxide (ADP3) were reported and discussed in our previous publications. These DPs were then detected in secondary effluent and groundwater from a well located beneath agricultural fields continuously irrigated with secondary effluent. Concentrations in the secondary effluent were: ADP1/2, several micrograms per liter; ADP4/5, 0.15?gL(-1), and ADP8/9, 0.5?gL(-1). ADP6 were detected but not quantified. In the groundwater, only ADP8/9 was detected, at a concentration of 0.03?gL(-1). The detection and quantification of DPs of other investigated drugs is recommended as an integral part of any study, method or technique dealing with pharmaceutical residues in aquatic environments. PMID:23466086

Gozlan, Igal; Rotstein, Adi; Avisar, Dror

2013-05-01

340

Materials and techniques for spacecraft static charge control 2  

NASA Technical Reports Server (NTRS)

Results of exploratory development on the design, fabrication and testing of transparent conductive coatings, conductive bulk materials and grounding techniques for application to high resistivity spacecraft dielectric materials to obtain control of static charge buildup are presented. Deposition techniques for application of indium oxide, indium/tin oxide and other metal oxide films on Kapton, FEP Teflon, OSR and solar cell coverglasses discussed include RF and Magnetron sputtering and vapor deposition. Development, fabrication and testing of conductive glass tiles for OSR and solar cell coverglass applications is discussed. Several grounding techniques for rapid charge dissipation from the conductively coated polymer and glass dielectrics which were developed and tested in thermal cycled and electron plasma environments are described. The optical and electrical characterization and aging effects of these coatings, bulk materials and grounding techniques are reviewed as they apply to the performance of their design functions in a geosynchronous orbit environment.

Schmidt, R. E.; Eagles, A. E.

1979-01-01

341

Controllable jamming of amorphous granular materials applied to robotics  

NASA Astrophysics Data System (ADS)

We demonstrate the practicality of using a controlled jamming transition in an amorphous mass of granular material for applications to robotic gripping, and how the gripping capabilities depend on the properties of the jammed state. A mass of granular material contained in a flexible membrane in an unjammed state flows and conforms to almost any object it is pressed against. Upon application of a vacuum, the external pressure on the membrane jams the granular mass with a volumetric contraction < 1%, allowing it to pinch the object. By measuring the holding force on a test sphere at different levels of envelopment, we show that three mechanisms contribute to the holding force: friction, suction, and interlocking. We use a solid mechanics model to relate the holding force from each mechanism to the measured stress response of jammed granular materials to compressional, extensional, and bending strains. This opens up new possibilities for the design of simple systems that excel at gripping objects of arbitrary shape.

Brown, Eric; Rodenberg, Rodenberg; Amend, John; Lipson, Hod; Mozeika, Annan; Steltz, Erik; Zakin, Mitchell; Jaeger, Heinrich

2011-03-01

342

Preparation of porous materials with controlled pore size and porosity  

Microsoft Academic Search

Well-defined porous ceramics with controllable pore size and porosity were fabricated via a hetero-coagulation of template\\/ceramic particle colloidal processing. Monodispersed polymer spheres were used as template and ceramic nanoparticles as inorganic building blocks to create porous structures. The preparation of well-dispersed suspensions of polymers and ceramics is essential for the fabrication of uniformly porous materials. Core–shell composites of polymer\\/ceramic could

Fengqiu Tang; Hiroshi Fudouzi; Tetsuo Uchikoshi; Yoshio Sakka

2004-01-01

343

Control of textural properties of ordered mesoporous materials  

Microsoft Academic Search

Two different types of ordered mesoporous materials have been synthesized. On one hand, SBA-15 silicas with different textural properties were prepared using tetraethyl orthosilicate (TEOS) as silica source and a triblock copolymer (P123) as template. Their textural properties were controlled by using different TEOS\\/P123 mass ratios. On the other hand, mesoporous carbons were synthesised by incipient wetness impregnation of the

L. Calvillo; V. Celorrio; R. Moliner; P. L. Cabot; I. Esparbé; M. J. Lázaro

2008-01-01

344

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

345

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

346

Insider Threat - Material Control and Accountability Mitigation (Presentation)  

SciTech Connect

Why is the insider a concern? There are many documented cases of nuclear material available for sale - there are more insider diversions than outsider attacks and more than 18 documented cases of theft or loss of plutonium or highly enriched uranium. Insider attributes are: have access, has authority, possesses knowledge, works with absence of timeline, can test system, and may act alone or support a team. Material control and accountability (MC&A) is an essential part of an integrated safeguards system. Objectives of MC&A are: (1) Ongoing confirmation of the presence of special nuclear material (SNM) in assigned locations; (2) Prompt investigation of anomalies that may indicate a loss of SNM; (3) Timely and localized detection of loss, diversion, or theft of a goal quantity; (4) Rapid assessment and response to detection alarms; and (5) Timely generation of information to aid in the recovery of SNM in the event of an actual loss, diversion, or theft from the purview of the MC&A system. Control and accountability of material, equipment, and data are essential to minimizing insider threats.

Powell, Danny H [ORNL] [ORNL; Elwood Jr, Robert H [ORNL] [ORNL

2011-01-01

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

Growth and enrichment of pentachlorophenol-degrading microorganisms in the nutristat, a substrate concentration-controlled continuous culture  

SciTech Connect

The nutristat, a substrate concentration-controlled continuous culture, was used to grow pentachlorophenol (PCP)-degrading microorganisms. The PCP concentration control system consisted of on-line measurement of the PCP concentration in the culture vessel with a tangential filter and a flowthrough spectrophotometer. With PCP concentrations between 45 and 77 [mu]M, a stable situation was established in the nutristat, with an average dilution rate of 0.035 [+-] 0.003 h[sup [minus]1]. Compared with those of fed-batch cultures and chemostat cultures, the growth rates of microorganisms in the PCP nutristat were significantly higher, leading to considerable time savings in the enrichment procedure. In addition, PCP accumulation to severe inhibitory levels in the culture is prevented because the set point determines the (maximum) PCP concentration in the culture. The use of the nutristat as a tool for the growth of bacteria that degrade toxic compounds is discussed.

Rutgers, M.; Bogte, J.J.; Breure, A.M.; Van Andel, J.G. (National Institute of Public Health and Environmental Protection, Bilthoven (Netherlands))

1993-10-01

349

p34Cdc28-mediated control of Cln3 cyclin degradation.  

PubMed Central

Cln3 cyclin of the budding yeast Saccharomyces cerevisiae is a key regulator of Start, a cell cycle event in G1 phase at which cells become committed to division. The time of Start is sensitive to Cln3 levels, which in turn depend on the balance between synthesis and rapid degradation. Here we report that the breakdown of Cln3 is ubiquitin dependent and involves the ubiquitin-conjugating enzyme Cdc34 (Ubc3). The C-terminal tail of Cln3 functions as a transferable signal for degradation. Sequences important for Cln3 degradation are spread throughout the tail and consist largely of PEST elements, which have been previously suggested to target certain proteins for rapid turnover. The Cln3 tail also appears to contain multiple phosphorylation sites, and both phosphorylation and degradation of Cln3 are deficient in a cdc28ts mutant at the nonpermissive temperature. A point mutation at Ser-468, which lies within a Cdc28 kinase consensus site, causes approximately fivefold stabilization of a Cln3-beta-galactosidase fusion protein that contains a portion of the Cln3 tail and strongly reduces the phosphorylation of this protein. These data indicate that the degradation of Cln3 involves CDC28-dependent phosphorylation events.

Yaglom, J; Linskens, M H; Sadis, S; Rubin, D M; Futcher, B; Finley, D

1995-01-01

350

Control and accountancy of nuclear materials in a uranium enrichment plant  

SciTech Connect

A nuclear material control and accountancy system has been developed by Goodyear Atomic Corporation to meet safeguards and security requirements. It comprises three major elements: physical security, nuclear material control, and nuclear material accounting. This safeguards system is called Dynamic Material Control and Accountancy System (DYMCAS). The system approaches real-time computer control on a transaction-by-transaction basis.

Hurt, N.H.

1985-05-21

351

Issues related to regulatory control of naturally occurring radioactive materials  

SciTech Connect

Nearly 80% of human radiation exposure is from naturally occurring radioactive materials (NORM). While exposure from man-made sources of radiation has been well regulated, no consistent regulatory controls exist for NORM. Because elevated radiation levels have resulted from NORM enhancement activities such as occur in the petroleum, fertilizer, mining, and processing industries, some form of regulatory control is in order. In the US, regulation of NORM by federal agencies such as the Nuclear Regulatory Commission or the Environmental Protection Agency is not anticipated in the near future because there are no authorizing federal statutes. Important issues for addressing the control of NORM include source characterization and generation, radiation protection concerns, waste management and disposition, and the regulatory framework.

Chen, S.Y.

1997-04-01

352

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

PubMed

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

2013-07-15

353

Substrate Recognition in Nuclear Protein Quality Control Degradation Is Governed by Exposed Hydrophobicity That Correlates with Aggregation and Insolubility*  

PubMed Central

Misfolded proteins present an escalating deleterious challenge to cells over the course of their lifetime. One mechanism the cell possesses to prevent misfolded protein accumulation is their destruction by protein quality control (PQC) degradation systems. In eukaryotes, PQC degradation typically proceeds via multiple ubiquitin-protein ligases that act throughout the cell to ubiquitinate misfolded proteins for proteasome degradation. What the exact feature of misfolding that each PQC ubiquitin-protein ligase recognizes in their substrates remains an open question. Our previous studies of the budding yeast nuclear ubiquitin-protein ligase San1 indicated that it recognizes exposed hydrophobicity within its substrates, with the threshold of hydrophobicity equivalent to that of 5 contiguous hydrophobic residues. Here, we uncover an additional parameter: the nature of the exposed hydrophobicity that confers San1-mediated degradation correlates with significant protein insolubility. San1 particularly targets exposed hydrophobicity that leads to insolubility and aggregation above a certain threshold. Our studies presented here provide additional insight into the details of misfolded nuclear protein recognition and demonstrate that there is selectivity for the type of exposed hydrophobicity.

Fredrickson, Eric K.; Gallagher, Pamela S.; Clowes Candadai, Sarah V.; Gardner, Richard G.

2013-01-01

354

Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue effects  

NASA Astrophysics Data System (ADS)

The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

Bast, Callie C.; Boyce, Lola

1995-11-01

355

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

356

36 CFR 401.5 - Control and supervision of materials, design, and building.  

Code of Federal Regulations, 2013 CFR

...Control and supervision of materials, design, and building. 401.5 Section 401.5 Parks...Control and supervision of materials, design, and building. The Commission controls the design and prescribes regulations for the...

2013-07-01

357

A Strategic Analysis of Product Recalls: The Role of Moral Degradation and Organizational Control  

Microsoft Academic Search

abstract? Although product recalls are neither new nor unique to China, China bears much of the bitter criticism from the media and negative reactions from the public. This essay discusses the reasons behind recalls from a moral degradation perspective, grounded in the larger framework of anomie theory. While making remarkable economic progress, China is also moving toward a society with

Yadong Luo

2008-01-01

358

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

359

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

360

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.

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

2014-01-01

361

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

PubMed

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

2014-02-01

362

Investigation of the mechanical and degradation properties of Mg-Sr and Mg-Zn-Sr alloys for use as potential biodegradable implant materials.  

PubMed

Magnesium (Mg) has garnered significant interest for its potential use as a biodegradable implant material. Of specific interest in this study is the effect of zinc (Zn) and strontium (Sr) additions on both the mechanical and degradation behaviors in Mg due to their established beneficial effect on strength and microstructural grain refinement while being biocompatible. Three binary Mg-x wt% Sr (x=0.5, 1.0, 1.5) alloys and three ternary Mg-x wt%Zn-0.5 wt% Sr (x=2.0, 4.0, 6.0) were studied to evaluate their mechanical and degradation behavior. Mechanical testing was performed at room temperature on solution-treated and peak aged alloys using microhardness and tensile tests. Degradation was studied using immersion tests in Hanks' solution. Results indicate a decrease in grain size and an increase in strength with increasing Sr and Zn content. When considering degradation behavior Mg-0.5 wt%Sr demonstrated the lowest degradation rate among binary alloys. At constant Sr content at 0.5 wt%, the addition of Zn increased the corrosion rate, with the highest rate for the Mg-6.0 wt%Zn-0.5 wt%Sr. The alloys which best optimized both mechanical and degradation behaviors were Mg-2.0 wt%Zn-0.5 wt%Sr and Mg-4.0 wt%Zn-0.5 wt%Sr. Finally, microstructure and property relationships were evaluated and discussed in reference to each alloy's potential use as a biodegradable implant material. PMID:22340688

Brar, Harpreet S; Wong, Joey; Manuel, Michele V

2012-03-01

363

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

364

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

365

Hexapartite safeguards project team 3: material accounting and control questionnaire  

SciTech Connect

Information provided in this report reflects the current design and operating procedures for the GCEP. However, since the installation is currently under construction, facility design and operating procedures discussed in this report are subject to change. Where applicable, the responses are based on material control and accounting practices of the Portsmouth Gaseous Diffusion Plant's (GDP) operating contractor (Goodyear Atomic Corporation). These practices meet US Department of Energy (DOE) standards and are assumed to be the reference practices for the GCEP. This report covers data collection and record keeping actions of the operator.

Swindle, D.W. Jr.

1981-06-16

366

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 reported. Significant accomplishments include: (1) Completion of an initial identification of the more important problems in process control for integrated circuit fabrication and assembly; (2) preparations for making silicon bulk resistivity wafer standards available to the industry; and (3) establishment of the relationship between carrier mobility and impurity density in silicon. Work is continuing on measurement of resistivity of semiconductor crystals; characterization of generation-recombination-trapping centers, including gold, in silicon; evaluation of wire bonds and die attachment; study of scanning electron microscopy for wafer inspection and test; measurement of thermal properties of semiconductor devices; determination of S-parameters and delay time in junction devices; and characterization of noise and conversion loss of microwave detector diodes.

Bullis, W. M. (ed)

1973-01-01

367

Controlling the porosity and density of silicone rubber prosthetic materials.  

PubMed

The chemical components of the four silicone rubber polymers were reviewed. Methods of controlling the porosity and density of both the one-component semisolid prepolymer and the two-component fluid prepolymer systems were evaluated. The variables examined were deairing of the fluid systems; trial packing, pressure sealing, and processing of the semisolid materials; injection versus hand packing of the mold; the effects of moist-heat versus dry-heat application during processing; and the need for investment of the mold within the confines of a closed flask. It can be concluded that porosity of medical-grade silicone rubber polymers may be totally prevented, or accurately controlled, by proper handling techniques. PMID:6578331

Kent, K; Zeigel, R F; Kent, K; Frost, A L; Schaaf, N G

1983-08-01

368

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

369

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

370

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

371

Osmotic control of glycine betaine biosynthesis and degradation in Rhizobium meliloti.  

PubMed Central

Intracellular accumulation of glycine betaine has been shown to confer an enhanced level of osmotic stress tolerance in Rhizobium meliloti. In this study, we used a physiological approach to investigate the mechanism by which glycine betaine is accumulated in osmotically stressed R. meliloti. Results from growth experiments, 14C 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

1988-01-01

372

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.

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

2014-01-01

373

Anaerobic degradation of inedible crop residues produced in a controlled ecological life support system  

NASA Astrophysics Data System (ADS)

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

374

Reactive extrusion of polypropylene: production of controlled-rheology polypropylene (CRPP) by peroxide-promoted degradation  

Microsoft Academic Search

Results of experimental studies of free-radical-induced degradation of polypropylene (PP) in the melt phase are presented. Experiments were carried out in a co-rotating twin-screw extruder. The initiator, dicumyl peroxide (DCP) was used as a radical generator. Concentration of the peroxide was in the range 0.02–0.6 %wt. Melt flow index, mechanical, thermal and rheological properties were measured to see the effect

Hamed Azizi; Ismaiel Ghasemi

2004-01-01

375

Desertification Control and Management of Land Degradation in the Thar Desert of India  

Microsoft Academic Search

India has 2.34 million km2 of hot desert called Thar located in the north-western part of Rajasthan between latitudes 23°3' and 30°12' North and longitudes 63°30' and 70°18' East. The Indian desert is spreading annually over 12000 ha of productive land degrading it and slowly advancing towards the national capital New Delhi at the rate of 0.5 km per year.

Surendra Singh Chauhan

2003-01-01

376

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

377

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.

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

378

Bioactive inorganic-materials/alginate composite microspheres with controllable drug-delivery ability.  

PubMed

Alginate microspheres are considered a promising material as a drug carrier in bone repair because of excellent biocompatibility, but their main disadvantage is low drug entrapment efficiency and noncontrollable release. The aim of this study was to investigate the effect of incorporating mesoporous bioglass (MBG), nonmesoporous bioglass (BG), or hydroxyapatite (HAp) into alginate microspheres on their drug-loading and release properties. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and atomic emission spectroscopy (AES) were used to analyze the composition, structure, and dissolution of bioactive inorganic materials and their microspheres. Dexamethasone (DEX)-loading and release ability of four microspheres were tested in phosphate buffered saline with varying pH. Results showed that the drug-loading capacity was enhanced with the incorporation of bioactive inorganic materials into alginate microspheres. The MBG/alginate microspheres had the highest drug loading ability. DEX release from alginate microspheres correlated to the dissolution of MBG, BG, and HAp in PBS, and that the pH was an efficient factor in controlling the DEX release; a high pH resulted in greater DEX release, whereas a low pH delayed DEX release. In addition, MBG/alginate, BG/alginate, and HAp/alginate microspheres had varying apatite-formation and dissolution abilities, which indicate that the composites would behave differently with respect to bioactivity. The study suggests that microspheres made of a composite of bioactive inorganic materials and alginate have a bioactivity and degradation profile which greatly improves their drug delivery capacity, thus enhancing their potential applications as bioactive filler materials for bone tissue regeneration. PMID:20225253

Wu, Chengtie; Zhu, Yufang; Chang, Jiang; Zhang, Yufeng; Xiao, Yin

2010-07-01

379

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.

2010-03-01

380

The melanoma-associated transmembrane glycoprotein Gpnmb controls trafficking of cellular debris for degradation and is essential for tissue repair  

PubMed Central

Kidney damage due to injury rarely resolves completely, and there are currently no therapies capable of promoting repair. In addition to understanding mechanisms by which tissues are damaged, illuminating mechanisms of repair and regeneration is also of great importance. Here we show that the melanoma-associated, transmembrane glycoprotein, Gpnmb, is up-regulated 15-fold following ischemic damage in kidney tissue and by more than 10-fold in macrophages and 3-fold in surviving epithelial cells. Gpnmb-expressing macrophages and epithelial cells were found to contain apoptotic bodies at 3 times the rate of nonexpressing cells. Either mutation of Gpnmb or ablation of inflammatory macrophages prevents normal repair of the kidney. Significantly, the kidneys from postischemic Gpnmb mutant mice exhibited a 5-fold increase in apoptotic cellular debris compared to wild-type mice. These mice also experienced an 85% increase in mortality following bilateral ischemic kidney. Finally, we demonstrate that Gpnmb is a phagocytic protein that is necessary for recruitment of the autophagy protein LC3 to the phagosome where these proteins are colocalized and for lysosomal fusion with the phagosome and hence bulk degradation of their content. Therefore, Gpnmb is a novel prorepair gene that is necessary for crosstalk between the macroautophagic degradation pathway and phagocytosis.—Li, B., Castano, A. P., Hudson, T. E., Nowlin, B. T., Lin, S.-L., Bonventre, J. V., Swanson, K. D., Duffield, J. S. The melanoma-associated transmembrane glycoprotein Gpnmb controls trafficking of cellular debris for degradation and is essential for tissue repair.

Li, Bing; Castano, Ana P.; Hudson, Thomas E.; Nowlin, Brian T.; Lin, Shuei-Liong; Bonventre, Joseph V.; Swanson, Kenneth D.; Duffield, Jeremy S.

2010-01-01

381

In vitro degradation and cytotoxicity response of Mg-4% Zn-0.5% Zr (ZK40) alloy as a potential biodegradable material.  

PubMed

Mg-4 wt.% Zn-0.5 wt.% Zr (ZK40) alloy was studied as a candidate material for biodegradable metallic implants in terms of its biocorrosion resistance, mechanical properties and cytocompatibility. The corrosion characteristics of ZK40 alloy were assessed by potentiodynamic polarization and immersion testing in DMEM+10% FBS solution. Analysis of the degradation characteristics by potentiodynamic polarization measurements shows the corrosion rates of ZK40 alloy in as-cast and solution treatment (T4) condition were slightly higher than those of pure Mg or as-drawn AZ31. Determination of the corrosion rate by the weight loss technique reveals that the as-cast ZK40 resulted in slower degradation than other alloy specimens after 7 days of immersion but exhibited accelerated degradation after 14 and 21 days, respectively. T4-treated ZK40 exhibited stable degradation rates compared to as-cast ZK40 and close to those of pure Mg and AZ31 during immersion testing for 14 and 21 days. In order to examine the in vitro cytocompatibility of ZK40 alloy, live/dead cell viability assay and indirect MTT assay were performed using a murine osteoblast-like cell line (MC3T3). After 3 days of direct culture of MC3T3 on ZK40 alloys the live/dead assay indicated favorable cell viability and attachment. The degradation product of ZK40 also showed minimal cytotoxicity when assessed in indirect MTT assay. The mechanical properties of the as-cast and T4-treated ZK40 alloy were superior to those of pure Mg and comparable to as-drawn AZ31. Solution treatment did not significantly enhance the cytocompatibility and mechanical properties of ZK40 alloy. Overall, the ZK40 alloy exhibited favorable cytocompatibility, biocorrosion, and mechanical properties rendering it a potential candidate for degradable implant applications. PMID:23851175

Hong, Daeho; Saha, Partha; Chou, Da-Tren; Lee, Boeun; Collins, Boyce E; Tan, Zongqing; Dong, Zhongyun; Kumta, Prashant N

2013-11-01

382

The evolution of N-glycan-dependent endoplasmic reticulum quality control factors for glycoprotein folding and degradation.  

PubMed

Asn-linked glycans (N-glycans) play important roles in the quality control (QC) of glycoprotein folding in the endoplasmic reticulum (ER) lumen and in ER-associated degradation (ERAD) of proteins by cytosolic proteasomes. A UDP-Glc:glycoprotein glucosyltransferase glucosylates N-glycans of misfolded proteins, which are then bound and refolded by calreticulin and/or calnexin in association with a protein disulfide isomerase. Alternatively, an alpha-1,2-mannosidase (Mns1) and mannosidase-like proteins (ER degradation-enhancing alpha-mannosidase-like proteins 1, 2, and 3) are part of a process that results in the dislocation of misfolded glycoproteins into the cytosol, where proteins are degraded in the proteasome. Recently we found that numerous protists and fungi contain 0-11 sugars in their N-glycan precursors versus 14 sugars in those of animals, plants, fungi, and Dictyostelium. Our goal here was to determine what effect N-glycan precursor diversity has on N-glycan-dependent QC systems of glycoprotein folding and ERAD. N-glycan-dependent QC of folding (UDP-Glc:glycoprotein glucosyltransferase, calreticulin, and/or calnexin) was present and active in some but not all protists containing at least five mannose residues in their N-glycans and was absent in protists lacking Man. In contrast, N-glycan-dependent ERAD appeared to be absent from the majority of protists. However, Trypanosoma and Trichomonas genomes predicted ER degradation-enhancing alpha-mannosidase-like protein and Mns1 orthologs, respectively, each of which had alpha-mannosidase activity in vitro. Phylogenetic analyses suggested that the diversity of N-glycan-dependent QC of glycoprotein folding (and possibly that of ERAD) was best explained by secondary loss. We conclude that N-glycan precursor length has profound effects on N-glycan-dependent QC of glycoprotein folding and ERAD. PMID:17606910

Banerjee, Sulagna; Vishwanath, Prashanth; Cui, Jike; Kelleher, Daniel J; Gilmore, Reid; Robbins, Phillips W; Samuelson, John

2007-07-10

383

Preprocessing and Quality Control Strategies for Illumina DASL Assay-Based Brain Gene Expression Studies with Semi-Degraded Samples.  

PubMed

Available statistical preprocessing or quality control analysis tools for gene expression microarray datasets are known to greatly affect downstream data analysis, especially when degraded samples, unique tissue samples, or novel expression assays are used. It is therefore important to assess the validity and impact of the assumptions built in to preprocessing schemes for a dataset. We developed and assessed a data preprocessing strategy for use with the Illumina DASL-based gene expression assay with partially degraded postmortem prefrontal cortex samples. The samples were obtained from individuals with autism as part of an investigation of the pathogenic factors contributing to autism. Using statistical analysis methods and metrics such as those associated with multivariate distance matrix regression and mean inter-array correlation, we developed a DASL-based assay gene expression preprocessing pipeline to accommodate and detect problems with microarray-based gene expression values obtained with degraded brain samples. Key steps in the pipeline included outlier exclusion, data transformation and normalization, and batch effect and covariate corrections. Our goal was to produce a clean dataset for subsequent downstream differential expression analysis. We ultimately settled on available transformation and normalization algorithms in the R/Bioconductor package lumi based on an assessment of their use in various combinations. A log2-transformed, quantile-normalized, and batch and seizure-corrected procedure was likely the most appropriate for our data. We empirically tested different components of our proposed preprocessing strategy and believe that our results suggest that a preprocessing strategy that effectively identifies outliers, normalizes the data, and corrects for batch effects can be applied to all studies, even those pursued with degraded samples. PMID:22375143

Chow, Maggie L; Winn, Mary E; Li, Hai-Ri; April, Craig; Wynshaw-Boris, Anthony; Fan, Jian-Bing; Fu, Xiang-Dong; Courchesne, Eric; Schork, Nicholas J

2012-01-01

384

Purification and characterization of keratinase from feather degrading bacterium useful for mosquito control - A new report.  

PubMed

Every day, food processing industries release wastes, which are environmental menance. Chicken feathers have been discarded in bulk as waste from poultry industries, globally. Degrading these wastes, as unused disposals, without acquiring any additional benefits has led to an idea to develop a new technology. We have reported earlier that Bacillus thuringiensis serovar israelensis (Bti) can be used for biodegradation of feather waste for biopesticide production. In the present study, purification and characterization of keratinase from feather degrading bacterium (Bti) is reported. Protein precipitate obtained at Ammonium sulphate saturation at 60% level and Sephacryl S-200 column chromatography resulted in 2.3 and 11.68 fold purification of the enzyme respectively. The purity was revealed in SDS-PAGE by a single band of molecular weight of 40 kDa and it was characterized. The optimum pH of the enzyme shifted to a more neutral range (6.0-8.0) with the highest activity (7.0). The optimum temperature of the reaction was determined to be 30ºC. The keratinase enzyme retained 51% residual activity (303 U/mg protein) at 70ºC (60 min) and the half-lives of the enzyme were 130 minutes at 40ºC, 90 min at 50ºC and of 60 min at 70ºC, respectively. Keratinase activity was enhanced by calcium and magnesium ions while EDTA, PMSF, ?- mercaptoethanol and manganese inhibited the activity. This is the first report investigating the keratinase from Bti degraded chicken feathers for the bio-synthesis of mosquitocidal toxins. PMID:24862049

Poopathi, S; Thirugnanasambantham, K; Mani, C; Lakshmi, P V; Ragul, K

2014-03-01

385

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

386

Urban-rural mortality differentials: controlling for material deprivation.  

PubMed

This paper investigates the relationship between premature mortality and material deprivation, and the differences in this relationship between urban and rural areas. We examine, given comparable measures of affluence or deprivation, whether residual differences exist between urban and rural areas for all-causes of death and, separately, for cancers, circulatory and respiratory diseases. Using 1990-92 mortality data for the 908 wards of Wales we apply statistical analyses based on tabular data and parametric Poisson regression models. Contrasts are sought between six urban and rural categories defined in terms of settlement sizes and the employment structure of rural areas. Inequalities in all-cause premature mortality are widest in the cities, narrowest in the deeper rural areas, and of intermediate and comparable value in other areas of Wales. This is largely a reflection of the different distributions of material deprivation in these areas. After controlling for differences in socio-economic characteristics, using deprivation measures, the tendency for lower mortality in deeper rural areas is substantially reduced. Residual mortality differences between urban and rural areas are shown to be dependent on the way deprivation is measured and the disease group under study. For cancers there are no residual mortality differences, while for respiratory and circulatory diseases some of the residual variation can be accounted for by employment variables, particularly previous employment in the coal mining industry. PMID:10832575

Senior, M; Williams, H; Higgs, G

2000-07-01

387

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

388

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

389

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

390

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

391

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

392

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

393

Degradation of ZrN films at high temperature under controlled atmosphere  

SciTech Connect

The degradation of ZrN films deposited onto Si substrates by unbalanced magnetron sputtering was investigated over temperatures of 300-1200 deg. C in different atmospheres by analyzing changes in color and appearance, as well as microstructures. The atmospheres contained air, nitrogen, and forming gas (N{sub 2}/H{sub 2}=9), which exhibited drastically different oxygen/nitrogen partial pressure ratios. The resultant degradation included mainly color changes and formation of blisters on the film surface. Color change was associated with the oxidation of the nitride film, which was analyzed by looking into the Gibbs free-energy changes at various temperatures and oxygen partial pressures. Two types of blisters occurred at different temperature ranges. Several large round blisters, denoted as A-type blisters, occurring at low temperatures originated from the large residual stress in the films. Many small irregular blisters, denoted as B-type blisters, appearing at relatively high temperatures resulted from the oxidation of the film.

Lu, F.-H.; Lo, W.-Z. [Department of Materials Engineering, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 402, Taiwan (China)

2004-09-01

394

Effects of materials parameters on mineralization and degradation of sol-gel bioactive glasses with 3D-ordered macroporous structures.  

PubMed

Bioactive glasses (BGs) with three-dimensionally ordered macroporous (3DOM) structures were prepared by combining a sol-gel synthesis with colloidal crystal templating. 3DOM sol-gel BGs with two compositions (20 mol % CaO-80% SiO2 and 20 mol % CaO-4% P2O5-76% SiO2) and three macropore sizes (average: 345, 440, and 790 nm) were prepared. Glasses were separated into two particle sizes (212 microm< small < 355 microm and 600 microm < large < 1000 microm). The glasses were soaked in simulated body fluid at 37 degrees C for 2 or 4 days and the effects of composition, particle size, and macropore size on the formation of apatite and glass degradation were characterized. Within the parameter range of the experiments, several comparisons could be made. First, the formation of apatite and degradation of the glass were slightly enhanced for the phosphate containing composition. Second, large particles formed less apatite and degraded less completely compared with small particles. Lastly, an increase in macropore size slowed down the glass degradation and apatite formation processes, an effect related to the decreased internal surface area of the larger pore materials. PMID:12926039

Zhang, Kai; Yan, Hongwei; Bell, David C; Stein, Andreas; Francis, Lorraine F

2003-09-15

395

Engineer Design Tests of Modified Dust-Control Materials and Prototype Equipment.  

National Technical Information Service (NTIS)

Engineer design tests were performed on a dust-control system, i.e. materials and prototype emplacement equipment. The performance of the dust-control material exceeded the criteria of the currently existent Qualitative Materiel Requirement. The liquid di...

M. M. Culpepper R. Osmond

1973-01-01

396

Federal Automated Information System of Nuclear Material Control and Accounting: Uniform System of Reporting Documents.  

National Technical Information Service (NTIS)

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 SS...

V. P. Martyanov L. Kasumova R. A. Babcock C. Heinberg

2003-01-01

397

A Digraph-Fault Tree Methodology for the Assessment of Material Control Systems.  

National Technical Information Service (NTIS)

The Lawrence Livermore Laboratory is developing a procedure to assess the effectiveness of material control and accounting systems at nuclear fuel cycle facilities. The purpose of a material control and accounting system is to prevent the theft of special...

H. E. Lambert J. J. Lim F. M. Gilman

1979-01-01

398

Cell Wall Degrading Enzymes: An Approach to the Control of Fungal Infection of Human Burns.  

National Technical Information Service (NTIS)

The increased occurence of invasive fungal infections in burn wounds is probably a direct result of the more effective bacterial control measures recently introduced. Systemic and topical chemotherapy have failed to control zygomycetes in burns, and frequ...

D. E. Eveleigh R. P. Tewari R. L. Monaghan G. L. Cuffari R. D. Baker

1973-01-01

399

Enzymatic degradation of starch-based thermoplastic compounds used in protheses: identification of the degradation products in solution  

Microsoft Academic Search

Apart from favourable physico-chemical and mechanical properties, the most important requirement for a biodegradable polymer to be used in medical applications is its biocompatibility and the non-cytotoxicity of its degradation products. Their combined effect should assure the safe material degradation under controlled kinetics. The present work analyses the degradation behaviour of blends of corn starch with poly(ethylene-vinyl alcohol) copolymer (SEVA-C).

M Alberta Araújo; António M Cunha; Manuel Mota

2004-01-01

400

Review of selected dynamic material control functions for international safeguards  

SciTech Connect

With the development of Dynamic Special Nuclear Material Accounting and Control systems used in nuclear manufacturing and reprocessing plants, there arises the question as to how these systems affect the IAEA inspection capabilities. The systems in being and under development provide information and control for a variety of purposes important to the plant operator, the safeguards purpose being one of them. This report attempts to judge the usefulness of these dynamic systems to the IAEA and have defined 12 functions that provide essential information to it. If the information acquired by these dynamic systems is to be useful to the IAEA, the inspectors must be able to independently verify it. Some suggestions are made as to how this might be done. But, even if it should not be possible to verify all the data, the availability to the IAEA of detailed, simultaneous, and plant-wide information would tend to inhibit a plant operator from attempting to generate a floating or fictitious inventory. Suggestions are made that might be helpful in the design of future software systems, an area which has proved to be fatally deficient in some systems and difficult in all.

Lowry, L.L.

1980-09-01

401

Controls of soil organic material stability in coastal wetland soils  

NASA Astrophysics Data System (ADS)

In this study, we utilize ramped pyrolysis to identify relative stability differences in bulk soil organic material (SOM) from three wetland types (fresh, brackish, and salt marshes). Wetland soils are responsible for the storage of 500-700 Pg of carbon, globally. Understanding the stability of this carbon is important for predicting its role as source or sink in the global carbon cycle and with various changes in climate. By comparing and relating our ramped pyrolysis stability index to the SOM depth, TOC, composition, and source, we are able to determine which of these factors plays the larger role in controlling its stability. Preliminary results indicate that, of these factors, the source of OM has the most control over SOM stability in these wetland environments, with fresh marsh SOM being more stable than salt and brackish marsh SOM. As fresh marshes are replaced by salt marshes accompanying sea-level rise, our results imply that this will initiate the accumulation of less stable OM in these soils.

Williams, Elizabeth; Rosenheim, Brad

2014-05-01

402

Hands-free mobile phone speech while driving degrades coordination and control  

Microsoft Academic Search

Using a closed-circuit driving track environment, we investigated the influence of using a hands-free mobile (or cell) phone on various biomechanical and perceptual factors that underlie the control of driving. Results showed that in three tasks representative of everyday driving conditions, the perceptual control of action was compromised when compared to a control condition where no mobile phone conversation was

Paul J. Treffner; Rod Barrett

2004-01-01

403

Influence of support material on the immobilization of biomass for the degradation of linear alkylbenzene sulfonate in anaerobic reactors.  

PubMed

Two horizontal-flow anaerobic immobilized biomass reactors (HAIB) were used to study the degradation of the LAS surfactant: one filled with charcoal (HAIB1) and the other with a mixed bed of expanded clay and polyurethane foam (HAIB2). The reactors were fed with synthetic substrate supplemented with 14 mg l(-1)of LAS, kept at 30+/-2 degrees C and operated with a hydraulic retention time (HRT) of 12h. The surfactant was quantified by HPLC. Spatial variation analyses were done to quantify organic matter and LAS consumption along the reactor length. The presence of the surfactant in the load did not affect the removal of organic matter (COD), which was close to 90% in both reactors for an influent COD of 550 mg l(-1). The results of a mass balance indicated that 28% of all LAS added to HAIB1 was removed by degradation. HAIB2 presented 27% degradation. Molecular biology techniques revealed microorganisms belonging the uncultured Holophaga sp., uncultured delta Proteobacterium, uncultured Verrucomicrobium sp., Bacteroides sp. and uncultured gamma Proteobacterium sp. The reactor with biomass immobilized on charcoal presented lower adsorption and a higher kinetic degradation coefficient. So, it was the most suitable support for LAS anaerobic treatment. PMID:18814953

Lima de Oliveira, Lorena; Silveira Duarte, Iolanda Cristina; Sakamoto, Isabel Kimiko; Amâncio Varesche, Maria Bernadete

2009-02-01

404

ReflectoActive{trademark} Seals for Materials Control and Accountability  

SciTech Connect

The ReflectoActive{trademark} Seals system, a continuously monitored fiber optic, active seal technology, provides real-time tamper indication for large arrays of storage containers. The system includes a PC running the RFAS software, an Immediate Detection Unit (IDU), an Optical Time Domain Reflectometer (OTDR), links of fiber optic cable, and the methods and devices used to attach the fiber optic cable to the containers. When a breach on any of the attached fiber optic cable loops occurs, the IDU immediately signals the connected computer to control the operations of an OTDR to seek the breach location. The ReflectoActive{trademark} Seals System can be adapted for various types of container closure designs and implemented in almost any container configuration. This automatic protection of valued assets can significantly decrease the time and money required for surveillance. The RFAS software is the multi-threaded, client-server application that monitors and controls the components of the system. The software administers the security measures such as a two-person rule as well as continuous event logging. Additionally the software's architecture provides a secure method by which local or remote clients monitor the system and perform administrative tasks. These features provide the user with a robust system to meet today's material control and accountability needs. A brief overview of the hardware, and different hardware configurations will be given. The architecture of the system software, and its benefits will then be discussed. Finally, the features to be implemented in future versions of the system will be presented.

Richardson, G.D.; Younkin, J.R.; Bell, Z.W.

2002-01-01

405

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

406

Retinoblastoma protein co-purifies with proteasomal insulin-degrading enzyme: Implications for cell proliferation control  

SciTech Connect

Previous investigations on proteasomal preparations containing insulin-degrading enzyme (IDE; EC 3.4.24.56) have invariably yielded a co-purifying protein with a molecular weight of about 110 kDa. We have now found both in MCF-7 breast cancer and HepG2 hepatoma cells that this associated molecule is the retinoblastoma tumor suppressor protein (RB). Interestingly, the amount of RB in this protein complex seemed to be lower in HepG2 vs. MCF-7 cells, indicating a higher (cytoplasmic) protein turnover in the former vs. the latter cells. Moreover, immunofluorescence showed increased nuclear localization of RB in HepG2 vs. MCF-7 cells. Beyond these subtle differences between these distinct tumor cell types, our present study more generally suggests an interplay between RB and IDE within the proteasome that may have important growth-regulatory consequences.

Radulescu, Razvan T., E-mail: ratura@gmx.net [Molecular Concepts Research (MCR), Muenster (Germany); Duckworth, William C. [Department of Medicine, Phoenix VA Health Care System, Phoenix, AZ (United States)] [Department of Medicine, Phoenix VA Health Care System, Phoenix, AZ (United States); Levy, Jennifer L. [Research Service, Phoenix VA Health Care System, Phoenix, AZ (United States)] [Research Service, Phoenix VA Health Care System, Phoenix, AZ (United States); Fawcett, Janet, E-mail: janet.fawcett@va.gov [Research Service, Phoenix VA Health Care System, Phoenix, AZ (United States)] [Research Service, Phoenix VA Health Care System, Phoenix, AZ (United States)

2010-04-30

407

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.

Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu

2014-01-01

408

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

409

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

410

Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique.  

PubMed

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

411

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

412

Tailoring the nano-channel of ZrO 2/SBA-15 mesoporous materials for efficiently trapping and degradation volatile nitrosamines  

NASA Astrophysics Data System (ADS)

This article reports a bifunctionalized mesoporous ZrO 2/SBA-15 materials prepared through a simplified one-pot synthesis, in which the aged sample was evaporated with mother solution under the self-adjusted pH condition. The results of low-angle XRD, HRTEM, nitrogen adsorption-desorption, in-situ 1H NMR and NH 3-TPD tests confirmed the well-ordered hexagonal structure and large pore size of these composites along with the newly formed acidity and basicity. Temperature programmed surface reaction (TPSR) was employed to assess the catalytic function of ZrO 2/SBA-15 composites on the degradation of carcinogenic volatile nitrosamines such as N-nitrosopyrrolidine (NPYR). Due to the special interaction between the N-NO group of nitrosamines and the acidic site of mesop