Carrier mounted bacterial consortium facilitates oil remediation in the marine environment.

PubMed

Simons, Keryn L; Sheppard, Petra J; Adetutu, Eric M; Kadali, Krishna; Juhasz, Albert L; Manefield, Mike; Sarma, Priyangshu M; Lal, Banwari; Ball, Andrew S

2013-04-01

Marine oil pollution can result in the persistent presence of weathered oil. Currently, removal of weathered oil is reliant on chemical dispersants and physical removal, causing further disruption. In contrast few studies have examined the potential of an environmentally sustainable method using a hydrocarbon degrading microbial community attached to a carrier. Here, we used a tank mesocosm system (50 l) to follow the degradation of weathered oil (10 g l(-1)) using a bacterial consortium mobilised onto different carrier materials (alginate or shell grit). GCMS analysis demonstrated that the extent of hydrocarbon degradation was dependent upon the carrier material. Augmentation of shell grit with nutrients and exogenous hydrocarbon degraders resulted in 75±14% removal of >C32 hydrocarbons after 12 weeks compared to 20±14% for the alginate carrier. This study demonstrated the effectiveness of a biostimulated and bioaugmented carrier material to degrade marine weathered oil. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells

PubMed Central

Willumeit-Römer, Regine; Laipple, Daniel; Luthringer, Bérengère; Feyerabend, Frank

2016-01-01

Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys) is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells) are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity. PMID:27327435

The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells.

PubMed

Ahmad Agha, Nezha; Willumeit-Römer, Regine; Laipple, Daniel; Luthringer, Bérengère; Feyerabend, Frank

2016-01-01

Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys) is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells) are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity.

Behavior of POP-calcium carbonate hydrogel as bone substitute with controlled release capability: a study in rat.

PubMed

Dewi, Anne Handrini; Ana, Ika Dewi; Wolke, Joop; Jansen, John

2015-10-01

Gypsum or calcium sulfate (CS) or plaster of Paris (POP) is considered as a fast degradable material that usually resorbs before the bone defect area is completely filled by new bone. In this study, the incorporation of CaCO3 hydrogel into POP in different compositions was proposed to enhance the bone biological activity of POP and to decrease its degradability. The mechanical and degradation properties of the various materials were characterized by in vitro analysis. Subsequently, the materials were inserted into cylindrically sized bone defects as created into the femoral condyle of rats and left in situ for 1, 4, and 8 weeks. Histological analysis of the retrieved specimens indicated that the addition of CaCO3 hydrogel into POP increased bone formation, angiogenesis and collagen density and resulted into faster bone formation and maturation. It was also confirmed that the degradation rate of the POP decreased by the addition of CaCO3 hydrogel. The in vivo findings did corroborate with the in vitro analysis. In conclusion, the incorporation of CaCO3 hydrogel provides a promising technology to improve the properties of POP, the oldest biomaterial used for bone grafting. © 2015 Wiley Periodicals, Inc.

The application of encapsulation material stability data to photovoltaic module life assessment

NASA Technical Reports Server (NTRS)

Coulbert, C. D.

1983-01-01

For any piece of hardware that degrades when subject to environmental and application stresses, the route or sequence that describes the degradation process may be summarized in terms of six key words: LOADS, RESPONSE, CHANGE, DAMAGE, FAILURE, and PENALTY. Applied to photovoltaic modules, these six factors form the core outline of an expanded failure analysis matrix for unifying and integrating relevant material degradation data and analyses. An important feature of this approach is the deliberate differentiation between factors such as CHANGE, DAMAGE, and FAILURE. The application of this outline to materials degradation research facilitates the distinction between quantifying material property changes and quantifying module damage or power loss with their economic consequences. The approach recommended for relating material stability data to photovoltaic module life is to use the degree of DAMAGE to (1) optical coupling, (2) encapsulant package integrity, (3) PV circuit integrity or (4) electrical isolation as the quantitative criterion for assessing module potential service life rather than simply using module power loss.

Infrared microspectroscopic study of the thermo-oxidative degradation of hydroxy-terminated polybutadiene/isophorone diisocyanate polyurethane rubber

DOE PAGES

Nagle, Dylan J.; Celina, Mathew; Rintoul, Llewellyn; ...

2007-05-21

In this work, hydroxy-terminated polybutadiene/isophorone diisocyanate (HTPB/IPDI) polyurethane rubber which was aged in air at elevated temperatures has been studied by infrared microspectroscopy. Spectra were collected in transmission mode on microtomed samples. Analysis of sets of spectra taken across the sectioned material showed that most of the degradation occurred in the polybutadiene part of the polymer and that the urethane linkage was essentially unchanged. The trans isomer of the polybutadiene appears to be preferentially degraded compared with the vinyl isomer. The IR technique does not provide significant information about the cis isomer. The IR spectra indicated that likely degradation productsmore » included acids, esters, alcohols, and small amounts of other products containing a carbonyl functional group. Band area ratios, supported by a principal components analysis, were used to derive degradation profiles for the material. Lastly, these profiles were steep-sided indicating an oxygen diffusion limited process.« less

Quantifying the degradation of TNT and RDX in a saline environment with and without UV-exposure.

PubMed

Sisco, Edward; Najarro, Marcela; Bridge, Candice; Aranda, Roman

2015-06-01

Terrorist attacks in a maritime setting, such as the bombing of the USS Cole in 2000, or the detection of underwater mines, require the development of proper protocols to collect and analyse explosive material from a marine environment. In addition to proper analysis of the explosive material, protocols must also consider the exposure of the material to potentially deleterious elements, such as UV light and salinity, time spent in the environment, and time between storage and analysis. To understand how traditional explosives would be affected by such conditions, saline solutions of explosives were exposed to natural and artificial sunlight. Degradation of the explosives over time was then quantified using negative chemical ionization gas chromatography mass spectrometry (GC/NCI-MS). Two explosives, trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX), were exposed to different aqueous environments and light exposures with salinities ranging from freshwater to twice the salinity of ocean water. Solutions were then aged for up to 6 months to simulate different conditions the explosives may be recovered from. Salinity was found to have a negligible impact on the degradation of both RDX and TNT. RDX was stable in solutions of all salinities while TNT solutions degraded regardless of salinity. Solutions of varying salinities were also exposed to UV light, where accelerated degradation was seen for both explosives. Potential degradation products of TNT were identified using electrospray ionization mass spectrometry (ESI-MS), and correspond to proposed degradation products discussed in previously published works [1]. Published by Elsevier Ireland Ltd.

Material degradation due to moisture and temperature. Part 1: mathematical model, analysis, and analytical solutions

NASA Astrophysics Data System (ADS)

Xu, C.; Mudunuru, M. K.; Nakshatrala, K. B.

2016-11-01

The mechanical response, serviceability, and load-bearing capacity of materials and structural components can be adversely affected due to external stimuli, which include exposure to a corrosive chemical species, high temperatures, temperature fluctuations (i.e., freezing-thawing), cyclic mechanical loading, just to name a few. It is, therefore, of paramount importance in several branches of engineering—ranging from aerospace engineering, civil engineering to biomedical engineering—to have a fundamental understanding of degradation of materials, as the materials in these applications are often subjected to adverse environments. As a result of recent advancements in material science, new materials such as fiber-reinforced polymers and multi-functional materials that exhibit high ductility have been developed and widely used, for example, as infrastructural materials or in medical devices (e.g., stents). The traditional small-strain approaches of modeling these materials will not be adequate. In this paper, we study degradation of materials due to an exposure to chemical species and temperature under large strain and large deformations. In the first part of our research work, we present a consistent mathematical model with firm thermodynamic underpinning. We then obtain semi-analytical solutions of several canonical problems to illustrate the nature of the quasi-static and unsteady behaviors of degrading hyperelastic solids.

In vitro and in vivo degradation of potential anti-adhesion materials: Electrospun membranes of poly(ester-amide) based on l-phenylalanine and p-(dioxanone).

PubMed

Wang, Bing; Dong, Jun; Niu, Lijing; Chen, Wenyan; Chen, Dongliang; Shen, Chengyi; Zhu, Jiang; Zhang, Xiaoming

2017-08-01

Electrospun membranes of poly(p-dioxanone-co-l-phenylalanine) (PDPA) hold potential as an anti-adhesion material. Since adjustable degradation properties are important for anti-adhesion materials, in this study, the in vitro and in vivo degradation processes of PDPA electrospun membranes were investigated in detail. The morphological analysis of these membranes revealed the main degradation conditions of PDPA membranes. The weight remaining and molecular weight variation showed that the overall degradation rate of the membranes could be adjusted by modulating the molecular structure of the PDPAs. Especially, α-chymotrypsin could catalyze the degradation process of PDPAs. Based on these results, the in vitro degradation mechanism was demonstrated, and confirmed by 1 H NMR of the hydrolysis products. Finally, the in vivo degradation and biocompatibility of different PDPAs were investigated. The kinetic study showed that the in vitro and in vivo molecular weight loss of PDPAs have the first-order characteristics. The in vivo degradation rate of the most Phe-containing PDPA-3 is the slowest, and this result relates to the biocompatibilities of PDPAs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1369-1378, 2017. © 2016 Wiley Periodicals, Inc.

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

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

A Column Experiment To Determine Black Shale Degradation And Colonization By Means of δ13C and 14C Analysis Of Phospholipid Fatty Acids And DNA Extraction

NASA Astrophysics Data System (ADS)

Seifert, A.; Gleixner, G.

2008-12-01

We investigated the degradation of black shale organic matter by microbial communities. We inoculated two columns respectively, with the fungi Schizophyllum commune, the gram-positive bacterium Pseudomonas putida and the gram-negative bacteria Streptomyces griseus and Streptomyces chartreusis. These microorganisms are known to degrade a wide variety of organic macromolecules. Additionally, we had two sets of control columns. To one set the same nutrient solution was added as to the inoculated columns and to the other set only sterile deionised water was supplied. All columns contained 1.5 kg of freshly crushed not autoclaved black shale material with a particle size of 0.63-2 mm. The columns were incubated at 28° C and 60% humidity in the dark. The aim was to investigate, which microorganisms live on black shales and if these microorganisms are able to degrade ancient organic matter. We used compound specific stable isotope measurement techniques and compound specific 14C-dating methods. After 183 days PLFAs were extracted from the columns to investigate the microbial community, furthermore we extracted on one hand total-DNA of column material and on the other hand DNA from pure cultures isolates which grew on Kinks-agar B, Starch-casein-nitrate-agar (SCN) and on complete-yeast-medium-agar (CYM). According to the PLFA analysis bacteria dominated in the columns, whereas in pure cultures more fungi were isolated. A principal component analysis revealed differences between the columns in accordance with the inoculation, but it seems that the inoculated microorganisms were replaced by the natural population. For AMS measurements palmitic acid (C 16:0) was re-isolated from total-PLFA-extract with a preparative fraction collector (PFC). Preliminary results of the study revealed that microorganisms are able to degrade black shale material and that PLFA analysis are useful methods to be combined with analysis of stable isotope and 14C measurements to study microbial degradation processes.

Surviving the space environment - An overview of advanced materials and structures development at the CWRU CCDS

NASA Technical Reports Server (NTRS)

Wallace, John F.; Zdankiewicz, Edward M.; Schmidt, Robert N.

1991-01-01

The development of advanced materials and structures for long-term use in space is described with specific reference given to applications to the Space Station Freedom and the lunar base. A flight-testing program is described which incorporates experiments regarding the passive effects of space travel such as material degradation with active materials experiments such as the Materials Exposure Flight Experiment. Also described is a research and development program for materials such as organic coatings and polymeric composites, and a simulation laboratory is described which permits the analysis of materials in the laboratory. The methods of investigation indicate that the NASA Center for the Commercial Development of Space facilitates the understanding of material degradation in space.

Magnesium degradation influenced by buffering salts in concentrations typical of in vitro and in vivo models.

PubMed

Agha, Nezha Ahmad; Feyerabend, Frank; Mihailova, Boriana; Heidrich, Stefanie; Bismayer, Ulrich; Willumeit-Römer, Regine

2016-01-01

Magnesium and its alloys have considerable potential for orthopedic applications. During the degradation process the interface between material and tissue is continuously changing. Moreover, too fast or uncontrolled degradation is detrimental for the outcome in vivo. Therefore in vitro setups utilizing physiological conditions are promising for the material/degradation analysis prior to animal experiments. The aim of this study is to elucidate the influence of inorganic salts contributing to the blood buffering capacity on degradation. Extruded pure magnesium samples were immersed under cell culture conditions for 3 and 10 days. Hank's balanced salt solution without calcium and magnesium (HBSS) plus 10% of fetal bovine serum (FBS) was used as the basic immersion medium. Additionally, different inorganic salts were added with respect to concentration in Dulbecco's modified Eagle's medium (DMEM, in vitro model) and human plasma (in vivo model) to form 12 different immersion media. Influences on the surrounding environment were observed by measuring pH and osmolality. The degradation interface was analyzed by electron-induced X-ray emission (EIXE) spectroscopy, including chemical-element mappings and electron microprobe analysis, as well as Fourier transform infrared reflection micro-spectroscopy (FTIR). Copyright © 2015 Elsevier B.V. All rights reserved.

Degradation and Deformation of Scarps and Slopes on Io: New Results

NASA Technical Reports Server (NTRS)

Moore, J. M.; Sullivan, R. J.; Pappalardo, R. T.; Turtle, E. P.

2000-01-01

Initial analysis of degradational processes on scarps and slopes on Io using just-acquired images by the Galileo SSI team. Among other results, is evidence for sublimation, sapping, and perhaps "glacial" flow of interstitial volatiles in relief-forming materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isanapong, Jantiya; Goodwin, Lynne A.; Bruce, David

Microbial communities in the termite hindgut are essential for degrading plant material. We present the high-quality draft genome sequence of the Opitutaceae bacterium strain TAV1, the first member of the phylum Verrucomicrobia to be isolated from wood-feeding termites. The genomic analysis reveals genes coding for lignocellulosic degradation and nitrogen fixation.

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

NASA Astrophysics Data System (ADS)

Reinitz, Steven D.

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

Effect of DMMP on the pyrolysis products of polyurethane foam materials in the gaseous phase

NASA Astrophysics Data System (ADS)

Liu, W.; Li, F.; Ge, X. G.; Zhang, Z. J.; He, J.; Gao, N.

2016-07-01

Dimethyl methylphosphonate (DMMP) has been used as a flame retardant containing phosphorus to decrease the flammability of the polyurethane foam material (PUF). Flame retardancy and thermal degradation of PUF samples have been investigated by the LOI tests and thermal analysis. The results show that LOI values of all PUF/DMMP samples are higher than that of the neat PUF sample and the LOI value of the samples increases with both DMMP concentration and the %P value. Thermal analysis indicates that flame retardant PUF shows a dominant condensed flame retardant activity during combustion. Thermogravimetric analysis-infrared spectrometry (TG-FTIR) has been used to study the influence of DMMP on the pyrolysis products in the gaseous phase during the thermal degradation of the PUF sample. Fourier transform infrared spectrometry (FTIR) spectra of the PUF sample at the maximum evolution rates and the generated trends of water and the products containing -NCO have been examined to obtain more information about the pyrolysis product evolutions of the samples at high temperature. These results reveal that although DMMP could improve the thermal stability of PUF samples through the formation of the residual char layer between fire and the decomposed materials, the influence of DMMP on the gaseous phase can be also observed during the thermal degradation process of materials.

Degradation Analysis of Field-Exposed Photovoltaic Modules with Non-Fluoropolymer-Based Backsheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kempe, Michael D; Fairbrother, Andrew; Julien, Scott

The selection of polymeric materials utilized in photovoltaic (PV) modules has changed relatively little since the inception of the PV industry, with ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), and fluoropolymer-based laminates being the most widely adopted primary components of the encapsulant and backsheet materials. The backsheet must serve to electrically insulate the solar cells and protect them from the effects of weathering. Due to continued downward pressure on cost, other polymeric materials are being formulated to withstand outdoor exposure for use in backsheets to replace either the PET film, the fluoropoymer film, or both. Because of their relatively recent deployment,more » less is known about their reliability and if they are durable enough to fulfill the greater than or equal to 25 year warranties of current PV modules. This work presents a degradation analysis of field-exposed modules with polyamide- and polyester-based backsheets. Modules were exposed for up to five years in different geographic locations: USA (Maryland, Ohio), China, and Italy. Surface and cross-sectional analysis included visual inspection, colorimetry, glossimetry, and Fourier-transform infrared spectroscopy. Each module experienced different types of degradation depending on the exposure site, even for the same material and module brand. For instance, the polyamide-based backsheet experienced hairline cracking and greater yellowing and chemical changes in China (Changsu, humid subtropical climate), while in Italy (Rome, hot-summer Mediterranean climate) it underwent macroscopic cracking and greater losses in gloss. Spectroscopic studies have permitted identification of degradation products and changes in polymer structure over time. Comparisons are made to fielded modules with fluoropolymer-based backsheets, as well as backsheet materials in accelerated laboratory exposures. Implications for qualification testing and service life prediction of the non-fluoropolymer-based backsheets are discussed.« less

Degradation analysis of field-exposed photovoltaic modules with non-fluoropolymer-based backsheets

NASA Astrophysics Data System (ADS)

Fairbrother, Andrew; Julien, Scott; Wan, Kai-Tak; Ji, Liang; Boyce, Kenneth; Merzlic, Sebastien; Lefebvre, Amy; O'Brien, Greg; Wang, Yu; Bruckman, Laura; French, Roger; Kempe, Michael; Gu, Xiaohong

2017-08-01

The selection of polymeric materials utilized in photovoltaic (PV) modules has changed relatively little since the inception of the PV industry, with ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), and fluoropolymer-based laminates being the most widely adopted primary components of the encapsulant and backsheet materials. The backsheet must serve to electrically insulate the solar cells and protect them from the effects of weathering. Due to continued downward pressure on cost, other polymeric materials are being formulated to withstand outdoor exposure for use in backsheets to replace either the PET film, the fluoropoymer film, or both. Because of their relatively recent deployment, less is known about their reliability and if they are durable enough to fulfill the >=25 year warranties of current PV modules. This work presents a degradation analysis of field-exposed modules with polyamide- and polyester-based backsheets. Modules were exposed for up to five years in different geographic locations: USA (Maryland, Ohio), China, and Italy. Surface and cross-sectional analysis included visual inspection, colorimetry, glossimetry, and Fourier-transform infrared spectroscopy. Each module experienced different types of degradation depending on the exposure site, even for the same material and module brand. For instance, the polyamide-based backsheet experienced hairline cracking and greater yellowing and chemical changes in China (Changsu, humid subtropical climate), while in Italy (Rome, hot-summer Mediterranean climate) it underwent macroscopic cracking and greater losses in gloss. Spectroscopic studies have permitted identification of degradation products and changes in polymer structure over time. Comparisons are made to fielded modules with fluoropolymer-based backsheets, as well as backsheet materials in accelerated laboratory exposures. Implications for qualification testing and service life prediction of the non-fluoropolymer-based backsheets are discussed.

Classifying Degraded Modern Polymeric Museum Artefacts by Their Smell.

PubMed

Curran, Katherine; Underhill, Mark; Grau-Bové, Josep; Fearn, Tom; Gibson, Lorraine T; Strlič, Matija

2018-02-05

The use of VOC analysis to diagnose degradation in modern polymeric museum artefacts is reported. Volatile organic compound (VOC) analysis is a successful method for diagnosing medical conditions but to date has found little application in museums. Modern polymers are increasingly found in museum collections but pose serious conservation difficulties owing to unstable and widely varying formulations. Solid-phase microextraction gas chromatography/mass spectrometry and linear discriminant analysis were used to classify samples according to the length of time they had been artificially degraded. Accuracies in classification of 50-83 % were obtained after validation with separate test sets. The method was applied to three artefacts from collections at Tate to detect evidence of degradation. This approach could be used for any material in heritage collections and more widely in the field of polymer degradation. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Electro-catalytic degradation of sulfisoxazole by using graphene anode.

PubMed

Wang, Yanyan; Liu, Shuan; Li, Ruiping; Huang, Yingping; Chen, Chuncheng

2016-05-01

Graphite and graphene electrodes were prepared by using pure graphite as precursor. The electrode materials were characterized by a scanning electron microscope (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV) measurements. The electro-catalytic activity for degradation of sulfisoxazole (SIZ) was investigated by using prepared graphene or graphite anode. The results showed that the degradation of SIZ was much more rapid on the graphene than that on the graphite electrode. Moreover, the graphene electrode exhibited good stability and recyclability. The analysis on the intermediate products and the measurement of active species during the SIZ degradation demonstrated that indirect oxidation is the dominant mechanism, involving the electro-catalytic generation of OH and O2(-) as the main active oxygen species. This study implies that graphene is a promising potential electrode material for long-term application to electro-catalytic degradation of organic pollutants. Copyright © 2015. Published by Elsevier B.V.

Computational Modelling of Materials for Wind Turbine Blades: Selected DTU Wind Energy Activities.

PubMed

Mikkelsen, Lars Pilgaard; Mishnaevsky, Leon

2017-11-08

Computational and analytical studies of degradation of wind turbine blade materials at the macro-, micro-, and nanoscale carried out by the modelling team of the Section Composites and Materials Mechanics, Department of Wind Energy, DTU, are reviewed. Examples of the analysis of the microstructural effects on the strength and fatigue life of composites are shown. Computational studies of degradation mechanisms of wind blade composites under tensile and compressive loading are presented. The effect of hybrid and nanoengineered structures on the performance of the composite was studied in computational experiments as well.

Computational Modelling of Materials for Wind Turbine Blades: Selected DTU Wind Energy Activities

PubMed Central

2017-01-01

Computational and analytical studies of degradation of wind turbine blade materials at the macro-, micro-, and nanoscale carried out by the modelling team of the Section Composites and Materials Mechanics, Department of Wind Energy, DTU, are reviewed. Examples of the analysis of the microstructural effects on the strength and fatigue life of composites are shown. Computational studies of degradation mechanisms of wind blade composites under tensile and compressive loading are presented. The effect of hybrid and nanoengineered structures on the performance of the composite was studied in computational experiments as well. PMID:29117138

Wavelet Analysis of Acoustic Emissions during Tensile Test of Carbon Fibre Reinforced Polymer Composites

NASA Astrophysics Data System (ADS)

Świt, Grzegorz; Adamczak, Anna; Krampikowska, Aleksandra

2017-10-01

The increase of the interest in polymer composites in technology and in people’s everyday lives has been noticed in the recent years. Producing new materials with polymer matrix of particular properties that cannot be achieved by traditional construction materials contributed to high interest in fibre composite materials. However, a wider use of these materials is limited because of the lack of detailed knowledge about their properties and behaviour in various conditions of exposure under load. Mechanical degradation of polymer composites, which is caused by prolonged permanent loads, is connected with the changes of the material structure that are local or that include the whole volume of the element’s body. These changes are in the form of various types of discontinuity, including: deboning, matrix and fibers cracks and delamination. The article presents the example of the application of acoustic emission method based on the analysis of the waves through the use of wavelet analysis for the evaluation of the progress of the destructive processes and the level of the degradation of composite tapes that were subject to tensile testing.

Numerical and experimental study of the thermal degradation process during the atmospheric re-entry of a TiAl6V4 tank

NASA Astrophysics Data System (ADS)

Prévereaud, Y.; Vérant, J.-L.; Balat-Pichelin, M.; Moschetta, J.-M.

2016-05-01

To answer the question of space debris survivability during atmospheric entry ONERA uses its software named MUSIC/FAST. So, the first part of this paper is dedicated to the presentation of the ONERA tool and its validation by comparison with flight data and CFD computations. However, the influence of oxidation on the thermal degradation process and material properties in atmospheric entry conditions is still unknown. A second step is then devoted to the presentation of an experimental campaign investigating TA6V oxidation in atmospheric entry conditions, as the most of the debris found on ground are made of this material. Experiments have been realized using the MESOX facility implemented at the 6 kW solar furnace in PROMES-CNRS laboratory. Finally, an application of MUSIC/FAST is proposed on the atmospheric re-entry of a generic TA6V tank. Aiming at degradation assessment, a sensitive study to initial conditions is conducted. To complete computational analysis regarding degradation process by melting, a numerical analysis of the influence of oxidation on the thermal wall degradation during the tank atmospheric re-entry is presented as well.

Degradation mechanisms of cable insulation materials during radiation-thermal ageing in radiation environment

NASA Astrophysics Data System (ADS)

Seguchi, Tadao; Tamura, Kiyotoshi; Ohshima, Takeshi; Shimada, Akihiko; Kudoh, Hisaaki

2011-02-01

Radiation and thermal degradation of ethylene-propylene rubber (EPR) and crosslinked polyethylene (XLPE) as cable insulation materials were investigated by evaluating tensile properties, gel-fraction, and swelling ratio, as well as by the infrared (FTIR) analysis. The activation energy of thermal oxidative degradation changed over the range 100-120 °C for both EPR and XLPE. This may be attributed to the fact that the content of an antioxidant used as the stabilizer for polymers decreases by evaporation during thermal ageing at high temperatures. The analysis of antioxidant content and oxidative products in XLPE as a model sample showed that a small amount of antioxidant significantly reduced the extent of thermal oxidation, but was not effective for radiation induced oxidation. The changes in mechanical properties were well reflected by the degree of oxidation. A new model of polymer degradation mechanisms was proposed where the degradation does not take place by chain reaction via peroxy radical and hydro-peroxide. The role of the antioxidant in the polymer is the reduction of free radical formation in the initiation step in thermal oxidation, and it could not stop radical reactions for either radiation or thermal oxidation.

Determination of the mechanism and extent of surface degradation in Ni-based cathode materials after repeated electrochemical cycling

NASA Astrophysics Data System (ADS)

Hwang, Sooyeon; Kim, Se Young; Chung, Kyung Yoon; Stach, Eric A.; Kim, Seung Min; Chang, Wonyoung

2016-09-01

We take advantage of scanning transmission electron microscopy and electron energy loss spectroscopy to investigate the changes in near-surface electronic structure and quantify the degree of local degradation of Ni-based cathode materials with the layered structure (LiNi0.8Mn0.1Co0.1O2 and LiNi0.4Mn0.3Co0.3O2) after 20 cycles of delithiation and lithiation. Reduction of transition metals occurs in the near-surface region of cathode materials: Mn is the major element to be reduced in the case of relatively Mn-rich composition, while reduction of Ni ions is dominant in Ni-rich materials. The valences of Ni and Mn ions are complementary, i.e., when one is reduced, the other is oxidized in order to maintain charge neutrality. The depth of degradation zone is found to be much deeper in Ni-rich materials. This comparative analysis provides important insights needed for the devising of new cathode materials with high capacity as well as long lifetime.

Use of different surface analysis techniques for the study of the photo-degradation of a polymeric matrix composite

NASA Astrophysics Data System (ADS)

Larena, A.; Ochoa, S. Jimenez de

2004-11-01

Polypropylene matrix composites, with different reinforcement degrees of long glass fibres, are usually used in different fields of the industry, like aeronautics or automotive. Owed to their huge application field, and work under diverse and severe conditions, samples of the materials were exposed to artificial accelerated photo ageing in UV chamber (Heraeus Xenotest 15OS). Although the oxidative mechanism of the PP is known enough, the fact that the material presents a high content of glass fibre, cause a surface degradation higher than that the case of no reinforced materials, owed to the presence of the fibres near the surface. In order to study this topographic modifications, the optical confocal microscopy is used that allows us the analysis of the material surface with more accuracy than a surface profiler, and with nanometric precision. We also want a correlation between surface degradation studied by confocal microscopy and reflectometer measurements. By this way, we can know the surface state, and the degradation evolution, by means of a set of easy measurements, taken with a portable reflectometer, in samples at work, without preparation. Since these materials shall fulfil some aesthetic requirements, we study also, by means of UV-vis spectroscopy, Yellow Index and White Index variations, trying to explain the photochemical processes causing these modifications. Also, the fact that these materials are usually subjected to surface treatments like adhesion or painting makes necessary the study of surface energy. We study the variation of this factor with exposing time and percentage of fibre, by means of contact angle measurements, with different liquids of known surface tensions.

Photodegradation of pharmaceutical persistent pollutants using hydroxyapatite-based materials.

PubMed

Márquez Brazón, E; Piccirillo, C; Moreira, I S; Castro, P M L

2016-11-01

Pharmaceutical persistent pollutants pose a serious threat to the environment. The aim of this study was to use, for the first time, hydroxyapatite-based biomaterials as photocatalysts to degrade micropollutants. Diclofenac and fluoxetine were selected for these initial tests. Hydroxyapatite (Ca10(PO4)(OH)2, HAp) is one of the most commonly used biomaterials/bioceramics, being a major constituent of bone. In this work sustainable HAp-based materials of marine origin, obtained from cod fish bones, were used; these photocatalysts were previously fully studied and characterised. Both single-phase HAp and HAp-titania multicomponent materials (1 wt% TiO2) were employed as UV light photocatalysts, the latter showing better performance, indicated by higher degradation rates of both compounds. The HAp-titania photocatalyst showed excellent degradation of both persistent pollutants, the maximum degradation performance being 100% for fluoxetine and 92% for diclofenac, with pollutant and photocatalyst concentrations of 2 ppm and 4 g/L, respectively. Variations in features such as pollutant and photocatalyst concentrations were investigated, and results showed that generally fluoxetine was degraded more easily than diclofenac. The photocatalyst's crystallinity was not affected by the photodegradation reaction; indeed the material exhibited good photostability, as the degradation rate did not decrease when the material was reused. Tests were also performed using actual treated wastewater; the photocatalyst was still effective, even if with lower efficiency (-20% and -4% for diclofenac and fluoxetine, respectively). TOC analysis showed high but incomplete mineralisation of the pollutants (maximum 60% and 80% for DCF and FXT, respectively). Copyright © 2016 Elsevier Ltd. All rights reserved.

Characterization, degradation, and mechanical strength of poly(D,L-lactide-co-epsilon-caprolactone)-poly(ethylene glycol)-poly(D,L-lactide-co-epsilon-caprolactone).

PubMed

Bramfeldt, Hanna; Sarazin, Pierre; Vermette, Patrick

2007-11-01

A series of three biocompatible P(CL-co-LA)-PEG-P(CL-co-LA) copolymers were synthesized using ring-opening polymerization and characterized by 1H-NMR, gel permeation chromatography, DSC, dynamic-mechanical analysis, and X-ray diffraction. The number of monomer units was kept constant, while the D,L-LA fraction was varied so as to constitute 0, 30, or 70% of the end segments. The molecular weights were sufficiently high to eventually permit 3D scaffold preparation. A degradation study was carried out over 26 weeks, and the effect of monomer composition on the rate of degradation as well as on changes in mechanical strength was investigated. Pure polycaprolactone (PCL)-poly(ethylene glycol) (PEG)-PCL copolymer, P(100/0), was a crystalline material displaying no measurable mass loss, a 30% reduction in mean molecular weight (Mn), and only very slight changes in tensile strength. The random incorporation of 30 and 70% D,L-LA into the end sections of the polymer chain, produced more and more amorphous materials, exhibiting increasingly high rates of degradation, mass loss, and loss of tensile strength. Compared with random P(CL-co-LA), the presence of the PEG block was found both to improve hydrophilicity and thus the rate of degradation and to infer a stabilizing quality, thereby pacing the decrease in tensile strength during degradation. The tested copolymers range from materials exhibiting low mechanical strength and high rate of degradation to slow-degrading materials with high mechanical strength suitable, e.g., for three-dimensional scaffolding. Copyright (c) 2007 Wiley Periodicals, Inc.

Degradation studies of transparent conductive electrodes on electroactive poly(vinylidene fluoride) for uric acid measurements

NASA Astrophysics Data System (ADS)

Cardoso, Vanessa F.; Martins, Pedro; Botelho, Gabriela; Rebouta, Luis; Lanceros-Méndez, Senentxu; Minas, Graca

2010-08-01

Biochemical analysis of physiological fluids using, for example, lab-on-a-chip devices requires accurate mixing of two or more fluids. This mixing can be assisted by acoustic microagitation using a piezoelectric material, such as the β-phase of poly(vinylidene fluoride) (β-PVDF). If the analysis is performed using optical absorption spectroscopy and β-PVDF is located in the optical path, the material and its conductive electrodes must be transparent. Moreover, if, to improve the transmission of the ultrasonic waves to the fluids, the piezoelectric transducer is placed inside the fluidic structures, its degradation must be assessed. In this paper, we report on the degradation properties of transparent conductive oxides, namely, indium tin oxide (ITO) and aluminum-doped zinc oxide, when they are used as electrodes for providing acoustic microagitation. The latter promotes mixing of chemicals involved in the measurement of uric acid concentration in physiological fluids. The results are compared with those for aluminum electrodes. We find that β-PVDF samples with ITO electrodes do not degrade either with or without acoustic microagitation.

High Temperature Degradation Mechanisms in Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Cunningham, Ronan A.

1996-01-01

Polymer matrix composites are increasingly used in demanding structural applications in which they may be exposed to harsh environments. The durability of such materials is a major concern, potentially limiting both the integrity of the structures and their useful lifetimes. The goal of the current investigation is to develop a mechanism-based model of the chemical degradation which occurs, such that given the external chemical environment and temperatures throughout the laminate, laminate geometry, and ply and/or constituent material properties, we can calculate the concentration of diffusing substances and extent of chemical degradation as functions of time and position throughout the laminate. This objective is met through the development and use of analytical models, coupled to an analysis-driven experimental program which offers both quantitative and qualitative information on the degradation mechanism. Preliminary analyses using a coupled diffusion/reaction model are used to gain insight into the physics of the degradation mechanisms and to identify crucial material parameters. An experimental program is defined based on the results of the preliminary analysis which allows the determination of the necessary material coefficients. Thermogravimetric analyses are carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. Powdered samples are used to eliminate diffusion effects. Tests in both inert and oxidative environments allow the separation of thermal and oxidative contributions to specimen mass loss. The concentration dependency of the oxidative reactions is determined from the tests in pure oxygen. Short term isothermal tests at different temperatures are carried out on neat resin and unidirectional macroscopic specimens to identify diffusion effects. Mass loss, specimen shrinkage, the formation of degraded surface layers and surface cracking are recorded as functions of exposure time. Geometry effects in the neat resin, and anisotropic diffusion effects in the composites, are identified through the use of specimens with different aspect ratios. The data is used with the model to determine reaction coefficients and effective diffusion coefficients. The empirical and analytical correlations confirm the preliminary model results which suggest that mass loss at lower temperatures is dominated by oxidative reactions and that these reaction are limited by diffusion of oxygen from the surface. The mechanism-based model is able to successfully capture the basic physics of the degradation phenomena under a wide range of test conditions. The analysis-based test design is successful in separating out oxidative, thermal, and diffusion effects to allow the determination of material coefficients. This success confirms the basic picture of the process; however, a more complete understanding of some aspects of the physics are required before truly predictive capability can be achieved.

Progressive Failure Analysis Methodology for Laminated Composite Structures

NASA Technical Reports Server (NTRS)

Sleight, David W.

1999-01-01

A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

Summary Report of Cable Aging and Performance Data for Fiscal Year 2014.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Celina, Mathias C.; Celina, Mathias C.; Redline, Erica Marie

2014-09-01

As part of the Light Water Reactor Sustainability Program, science - based engineering approaches were employed to address cable degradation behavior under a range of exposure environments. Experiments were conducted with the goal to provide best guidance for aged material states, remaining life and expected performance under specific conditions for a range of cable materials. Generic engineering tests , which focus on rapid accelerated aging and tensile elongation , were combined with complementar y methods from polymer degradation science. Sandia's approach, building on previous years' efforts, enabled the generation of some of the necessary data supporting the development of improvedmore » lifetime predictions models, which incorporate known material b ehaviors and feedback from field - returned 'aged' cable materials. Oxidation rate measurements have provided access to material behavior under low dose rate thermal conditions, where slow degradation is not apparent in mechanical property changes. Such da ta have shown aging kinetics consistent with established radiati on - thermal degradation models. ACKNOWLEDGEMENTS We gratefully acknowledge ongoing technical support at the LICA facility and extensive sample handling provided by Maryla Wasiolek and Don Hans on. Sam Durbin and Patrick Mattie are recognized for valuable guidance throughout the year and assistance in the preparation of the final report. Doug Brunson is appreciated for sample analysis, compilation and plotting of experimental data.« less

Carbon speciation in ash, residual waste and contaminated soil by thermal and chemical analyses.

PubMed

Kumpiene, Jurate; Robinson, Ryan; Brännvall, Evelina; Nordmark, Désirée; Bjurström, Henrik; Andreas, Lale; Lagerkvist, Anders; Ecke, Holger

2011-01-01

Carbon in waste can occur as inorganic (IC), organic (OC) and elemental carbon (EC) each having distinct chemical properties and possible environmental effects. In this study, carbon speciation was performed using thermogravimetric analysis (TGA), chemical degradation tests and the standard total organic carbon (TOC) measurement procedures in three types of waste materials (bottom ash, residual waste and contaminated soil). Over 50% of the total carbon (TC) in all studied materials (72% in ash and residual waste, and 59% in soil) was biologically non-reactive or EC as determined by thermogravimetric analyses. The speciation of TOC by chemical degradation also showed a presence of a non-degradable C fraction in all materials (60% of TOC in ash, 30% in residual waste and 13% in soil), though in smaller amounts than those determined by TGA. In principle, chemical degradation method can give an indication of the presence of potentially inert C in various waste materials, while TGA is a more precise technique for C speciation, given that waste-specific method adjustments are made. The standard TOC measurement yields exaggerated estimates of organic carbon and may therefore overestimate the potential environmental impacts (e.g. landfill gas generation) of waste materials in a landfill environment. Copyright © 2010 Elsevier Ltd. All rights reserved.

Facile Fabrication of 100% Bio-Based and Degradable Ternary Cellulose/PHBV/PLA Composites

PubMed Central

Wang, Jinwu

2018-01-01

Modifying bio-based degradable polymers such as polylactide (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with non-degradable agents will compromise the 100% degradability of their resultant composites. This work developed a facile and solvent-free route in order to fabricate 100% bio-based and degradable ternary cellulose/PHBV/PLA composite materials. The effects of ball milling on the physicochemical properties of pulp cellulose fibers, and the ball-milled cellulose particles on the morphology and mechanical properties of PHBV/PLA blends, were investigated experimentally and statistically. The results showed that more ball-milling time resulted in a smaller particle size and lower crystallinity by way of mechanical disintegration. Filling PHBV/PLA blends with the ball-milled celluloses dramatically increased the stiffness at all of the levels of particle size and filling content, and improved their elongation at the break and fracture work at certain levels of particle size and filling content. It was also found that the high filling content of the ball-milled cellulose particles was detrimental to the mechanical properties for the resultant composite materials. The ternary cellulose/PHBV/PLA composite materials have some potential applications, such as in packaging materials and automobile inner decoration parts. Furthermore, filling content contributes more to the variations of their mechanical properties than particle size does. Statistical analysis combined with experimental tests provide a new pathway to quantitatively evaluate the effects of multiple variables on a specific property, and figure out the dominant one for the resultant composite materials. PMID:29495315

Ultraviolet stability and contamination analysis of Spectralon diffuse reflectance material

NASA Technical Reports Server (NTRS)

Stiegman, Albert E.; Bruegge, Carol J.; Springsteen, Arthur W.

1993-01-01

A detailed chemical analysis was carried out on Spectralon, a highly Lambertian, diffuse reflectance material. Results of this investigation unambiguously identified the presence of an organic (hydrocarbon) impurity intrinsic to the commercial material. This impurity could be removed by a vacuum bake-out procedure and was identified as the cause of optical changes (degradation) that occur in the material when exposed to UV light. It was found that when this impurity was removed, the Spectralon material was photochemically stable and maintained its reflectance properties even after extensive solar UV exposure.

Water Vapor Corrosion in EBC Constituent Materials

NASA Technical Reports Server (NTRS)

Kowalski, Benjamin; Fox, Dennis; Jacobson, Nathan S.

2017-01-01

Environmental Barrier Coating (EBC) materials are sought after to protect ceramic matrix composites (CMC) in high temperature turbine engines. CMCs are particularly susceptible to degradation from oxidation, Ca-Al-Mg-Silicate (CMAS), and water vapor during high temperature operation which necessitates the use of EBCs. However, the work presented here focuses on water vapor induced recession in EBC constituent materials. For example, in the presence of water vapor, silica will react to form Si(OH)4 (g) which will eventually corrode the material away. To investigate the recession rate in EBC constituent materials under high temperature water vapor conditions, thermal gravimetric analysis (TGA) is employed. The degradation process can then be modeled through a simple boundary layer expression. Ultimately, comparisons are made between various single- and poly-crystalline materials (e.g. TiO2, SiO2) against those found in literature.

Lignin degradation: microorganisms, enzymes involved, genomes analysis and evolution.

PubMed

Janusz, Grzegorz; Pawlik, Anna; Sulej, Justyna; Swiderska-Burek, Urszula; Jarosz-Wilkolazka, Anna; Paszczynski, Andrzej

2017-11-01

Extensive research efforts have been dedicated to describing degradation of wood, which is a complex process; hence, microorganisms have evolved different enzymatic and non-enzymatic strategies to utilize this plentiful plant material. This review describes a number of fungal and bacterial organisms which have developed both competitive and mutualistic strategies for the decomposition of wood and to thrive in different ecological niches. Through the analysis of the enzymatic machinery engaged in wood degradation, it was possible to elucidate different strategies of wood decomposition which often depend on ecological niches inhabited by given organism. Moreover, a detailed description of low molecular weight compounds is presented, which gives these organisms not only an advantage in wood degradation processes, but seems rather to be a new evolutionatory alternative to enzymatic combustion. Through analysis of genomics and secretomic data, it was possible to underline the probable importance of certain wood-degrading enzymes produced by different fungal organisms, potentially giving them advantage in their ecological niches. The paper highlights different fungal strategies of wood degradation, which possibly correlates to the number of genes coding for secretory enzymes. Furthermore, investigation of the evolution of wood-degrading organisms has been described. © FEMS 2017.

Lignin degradation: microorganisms, enzymes involved, genomes analysis and evolution

PubMed Central

Pawlik, Anna; Sulej, Justyna; Świderska-Burek, Urszula; Jarosz-Wilkołazka, Anna; Paszczyński, Andrzej

2017-01-01

Abstract Extensive research efforts have been dedicated to describing degradation of wood, which is a complex process; hence, microorganisms have evolved different enzymatic and non-enzymatic strategies to utilize this plentiful plant material. This review describes a number of fungal and bacterial organisms which have developed both competitive and mutualistic strategies for the decomposition of wood and to thrive in different ecological niches. Through the analysis of the enzymatic machinery engaged in wood degradation, it was possible to elucidate different strategies of wood decomposition which often depend on ecological niches inhabited by given organism. Moreover, a detailed description of low molecular weight compounds is presented, which gives these organisms not only an advantage in wood degradation processes, but seems rather to be a new evolutionatory alternative to enzymatic combustion. Through analysis of genomics and secretomic data, it was possible to underline the probable importance of certain wood-degrading enzymes produced by different fungal organisms, potentially giving them advantage in their ecological niches. The paper highlights different fungal strategies of wood degradation, which possibly correlates to the number of genes coding for secretory enzymes. Furthermore, investigation of the evolution of wood-degrading organisms has been described. PMID:29088355

[Analysis of the character of film decomposition of methyl methacrylate (MMA) coated urea by infrared spectrum].

PubMed

Li, Dong-po; Wu, Zhi-jie; Liang, Cheng-hua; Chen, Li-jun; Zhang, Yu-lan; Nie, Yan-xi

2012-03-01

The degradability characteristics of film with 4 kinds of methyl methacrylate coated urea amended with inhibitors were analyzed by FITR, which was purposed to supply theoretical basis for applying the FITR analysis method to film decomposition and methyl methacrylate coated urea fertilizers on farming. The result showed that the chemical component, molecule structure and material form of the membrane were not changed because of adding different inhibitors to urea. the main peaks of expressing film degradation process were brought by the -C-H of CH3 & CH2, -OH, C-O, C-C, C-O-C, C=O, C=C flexing vibrancy in asymmetry and symmetry in 3 479-3 195, 2 993--2 873, 1 741-1 564, 1 461-925 and 850-650 cm(-1). The peak value changed from smooth to tip, and from width to narrow caused by chemical structural transform of film The infrared spectrum of 4 kinds of fertilizers was not different remarkably before 60 days, and the film was slowly degraded. But degradation of the film was expedited after 60 days, it was most quickened at 120 day, and the decomposition rate of film was decreased at 310 day. The substantiality change of film in main molecule structure of 4 kinds of fertilizers didn't happen in 310 days. The main component of film materials was degraded most slowly in brown soil. The speed of film degradation wasn't heavily impacted by different inhibitors. The characteristic of film degradation may be monitored entirely by infrared spectrum. The degradation dynamic, chemical structure change, degradation speed difference of the film could be represented through infrared spectrum.

Emergy Analysis of Biogas Systems Based on Different Raw Materials

PubMed Central

Wang, Yang; Lin, Cong; Li, Jing; Duan, Na; Li, Xue; Fu, Yanyan

2013-01-01

Environmental pollution and energy crisis restrict the development of China, and the utilization of renewable technology is an effective strategy to alleviate the damage. Biogas engineering has rapidly developed attributes to solve environmental problems and create a renewable energy product biogas. In this paper, two different biogas plants' materials were analyzed by emergy method. One of them is a biogas project whose degraded material is feces (BPF system), and the other is the one whose degraded material is corn straw (BPC system). As a result, the ecological-economic values of BPF and BPC are $28,300/yr and $8,100/yr, respectively. Considering currency, environment, and human inputs, both of the biogas projects have the ability of disposing waste and potential for development. The proportion of biogas output is much more than fertilizer output; so, fertilizer utilization should be emphasized in the future. In comparison, BPF is better than BPC in the aspects of ecological-economic benefits, environmental benefits, and sustainability. The reason is the difficulty of corn straw seasonal collection and degradation. Thus it is proposed that BPC should be combined with the other raw materials. PMID:23476134

Emergy analysis of biogas systems based on different raw materials.

PubMed

Wang, Yang; Lin, Cong; Li, Jing; Duan, Na; Li, Xue; Fu, Yanyan

2013-01-01

Environmental pollution and energy crisis restrict the development of China, and the utilization of renewable technology is an effective strategy to alleviate the damage. Biogas engineering has rapidly developed attributes to solve environmental problems and create a renewable energy product biogas. In this paper, two different biogas plants' materials were analyzed by emergy method. One of them is a biogas project whose degraded material is feces (BPF system), and the other is the one whose degraded material is corn straw (BPC system). As a result, the ecological-economic values of BPF and BPC are $28,300/yr and $8,100/yr, respectively. Considering currency, environment, and human inputs, both of the biogas projects have the ability of disposing waste and potential for development. The proportion of biogas output is much more than fertilizer output; so, fertilizer utilization should be emphasized in the future. In comparison, BPF is better than BPC in the aspects of ecological-economic benefits, environmental benefits, and sustainability. The reason is the difficulty of corn straw seasonal collection and degradation. Thus it is proposed that BPC should be combined with the other raw materials.

International Space Station External Contamination Status

NASA Technical Reports Server (NTRS)

Mikatarian, Ron; Soares, Carlos

2000-01-01

PResentation slides examine external contamination requirements; International Space Station (ISS) external contamination sources; ISS external contamination sensitive surfaces; external contamination control; external contamination control for pre-launch verification; flight experiments and observations; the Space Shuttle Orbiter waste water dump, materials outgassing, active vacuum vents; example of molecular column density profile, modeling and analysis tools; sources of outgassing induced contamination analyzed to date, quiescent sources, observations on optical degradation due to induced external contamination in LEO; examples of typical contaminant and depth profiles; and status of the ISS system, material outgassing, thruster plumes, and optical degradation.

Magnetic α-Fe2O3/MCM-41 nanocomposites: preparation, characterization, and catalytic activity for methylene blue degradation.

PubMed

Ursachi, Irina; Stancu, Alexandru; Vasile, Aurelia

2012-07-01

Catalysts based on nanosized magnetic iron oxide stabilized inside the pore system of ordered mesoporous silica MCM-41 have been prepared. The obtained materials were characterized by powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and N(2) adsorption-desorption isotherm. XRD analysis showed that the obtained materials consist from the pure hematite crystalline phase (α-Fe(2)O(3)) dispersed within ordered mesoporous silica MCM-41. Magnetic measurements show that the obtained nanocomposites exhibit at room temperature weak ferromagnetic behavior with slender hysteresis. The catalytic activity of the magnetic α-Fe(2)O(3)/MCM-41 nanocomposites was evaluated by the degradation of methylene blue (MB) aqueous solution. For this purpose, an ultrasound-assisted Fenton-like process was used. The effect of solution pH on degradation of MB was investigated. The results indicated that US-H(2)O(2)-α-Fe(2)O(3)/MCM-41 nanocomposite system is effective for the degradation of MB, suggesting its great potential in removal of dyes from wastewater. It was found that the degradation rate of MB increases with decrease in the pH value of the solution. Copyright © 2012 Elsevier Inc. All rights reserved.

Microbial degradation of high impact polystyrene (HIPS), an e-plastic with decabromodiphenyl oxide and antimony trioxide.

PubMed

Sekhar, Vini C; Nampoothiri, K Madhavan; Mohan, Arya J; Nair, Nimisha R; Bhaskar, Thallada; Pandey, Ashok

2016-11-15

Accumulation of electronic waste has increased catastrophically and out of that various plastic resins constitute one of the leading thrown out materials in the electronic machinery. Enrichment medium, containing high impact polystyrene (HIPS) with decabromodiphenyl oxide and antimony trioxide as sole carbon source, was used to isolate microbial cultures. The viability of these cultures in the e-plastic containing mineral medium was further confirmed by triphenyl tetrazolium chloride (TTC) reduction test. Four cultures were identified by 16S rRNA sequencing as Enterobacter sp., Citrobacter sedlakii, Alcaligenes sp. and Brevundimonas diminuta. Biodegradation experiments were carried out in flask level and gelatin supplementation (0.1% w/v) along with HIPS had increased the degradation rate to a maximum of 12.4% (w/w) within 30days. This is the first report for this kind of material. The comparison of FTIR, NMR, and TGA analysis of original and degraded e-plastic films revealed structural changes under microbial treatment. Polystyrene degradation intermediates in the culture supernatant were also detected using HPLC analysis. The gravity of biodegradation was validated by morphological changes under scanning electron microscope. All isolates displayed depolymerase activity to substantiate enzymatic degradation of e-plastic. Copyright © 2016 Elsevier B.V. All rights reserved.

Field-emission scanning electron microscopy and energy-dispersive x-ray analysis to understand the role of tannin-based dyes in the degradation of historical wool textiles.

PubMed

Restivo, Annalaura; Degano, Ilaria; Ribechini, Erika; Pérez-Arantegui, Josefina; Colombini, Maria Perla

2014-10-01

An innovative approach, combining field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX) analysis, is presented to investigate the degradation mechanisms affecting tannin-dyed wool. In fact, tannin-dyed textiles are more sensitive to degradation then those dyed with other dyestuffs, even in the same conservation conditions. FESEM-EDX was first used to study a set of 48 wool specimens (artificially aged) dyed with several raw materials and mordants, and prepared according to historical dyeing recipes. EDX analysis was performed on the surface of wool threads and on their cross-sections. In addition, in order to validate the model formulated by the analysis of reference materials, several samples collected from historical and archaeological textiles were subjected to FESEM-EDX analysis. FESEM-EDX investigations enabled us to reveal the correlation between elemental composition and morphological changes. In addition, aging processes were clarified by studying changes in the elemental composition of wool from the protective cuticle to the fiber core in cross-sections. Morphological and elemental analysis of wool specimens and of archaeological and historical textiles showed that the presence of tannins increases wool damage, primarily by causing a sulfur decrease and fiber oxidation.

Analytical Ultrasonics in Materials Research and Testing

NASA Technical Reports Server (NTRS)

Vary, A.

1986-01-01

Research results in analytical ultrasonics for characterizing structural materials from metals and ceramics to composites are presented. General topics covered by the conference included: status and advances in analytical ultrasonics for characterizing material microstructures and mechanical properties; status and prospects for ultrasonic measurements of microdamage, degradation, and underlying morphological factors; status and problems in precision measurements of frequency-dependent velocity and attenuation for materials analysis; procedures and requirements for automated, digital signal acquisition, processing, analysis, and interpretation; incentives for analytical ultrasonics in materials research and materials processing, testing, and inspection; and examples of progress in ultrasonics for interrelating microstructure, mechanical properites, and dynamic response.

Efficient photo-catalytic degradation of malachite green using nickel tungstate material as photo-catalyst.

PubMed

Helaïli, N; Boudjamaa, A; Kebir, M; Bachari, K

2017-03-01

The present study focused on the evaluation of photo-catalytic and photo-electrochemical properties of the photo-catalyst based on nickel tungstate material prepared by a nitrate method through the degradation of malachite green (MG) dye's. The effect of catalyst loading and dye concentration was examined. Physico-chemical, optical, electrical, electrochemical, and photo-electrochemical properties of the prepared material were analyzed by X-ray diffraction (XRD), fourier transform-infrared spectroscopy (FTIR), BET analysis, optical reflectance diffuse (DR), scanning electron microscopy (SEM/EDX), electrical conductivity, cyclic voltammetry (CV), current intensity, mott-shottky, and nyquist. XRD revealed the formation of monoclinic structure with a small particle size. BET surface area of the sample was around 10 m 2 /g. The results show that the degradation of MG was more than 80%, achieved after 3 h of irradiation at pH 4.6 and with a catalyst loading of 75 mg. Also, it was found that the dye photo-degradation obeyed the pseudo-first order kinetic via Langmuir Hinshelwood model.

Method for modeling the gradual physical degradation of a porous material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flach, Greg

Cementitious and other engineered porous materials encountered in waste disposals may degrade over time due to one or more mechanisms. Physical degradation may take the form of cracking (fracturing) and/or altered (e.g. increased) porosity, depending on the material and underlying degradation mechanism. In most cases, the hydraulic properties of degrading materials are expected to evolve due to physical changes occurring over roughly the pore to decimeter scale, which is conducive to calculating equivalent or effective material properties. The exact morphology of a degrading material in its end-state may or may not be known. In the latter case, the fully-degraded conditionmore » can be assumed to be similar to a more-permeable material in the surrounding environment, such as backfill soil. Then the fully-degraded waste form or barrier material is hydraulically neutral with respect to its surroundings, constituting neither a barrier to nor conduit for moisture flow and solute transport. Unless the degradation mechanism is abrupt, a gradual transition between the intact initial and fully-degraded final states is desired. Linear interpolation through time is one method for smoothly blending hydraulic properties between those of an intact matrix and those of a soil or other surrogate for the end-state.« less

Proteomic researches for lignocellulose-degrading enzymes: A mini-review.

PubMed

Guo, Hongliang; Wang, Xiao-Dong; Lee, Duu-Jong

2018-05-31

Protective action of lignin/hemicellulose networks and crystalline structures of embedded cellulose render lignocellulose material resistant to external enzymatic attack. To eliminate this bottleneck, research has been conducted in which advanced proteomic techniques are applied to identify effective commercial hydrolytic enzymes. This mini-review summarizes researches on lignocellulose-degrading enzymes, the mechanisms of the responses of various lignocellulose-degrading strains and microbial communities to various carbon sources and various biomass substrates, post-translational modifications of lignocellulose-degrading enzymes, new lignocellulose-degrading strains, new lignocellulose-degrading enzymes and a new method of secretome analysis. The challenges in the practical use of enzymatic hydrolysis process to realize lignocellulose biorefineries are discussed, along with the prospects for the same. Copyright © 2018 Elsevier Ltd. All rights reserved.

Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep and thermal fatigue

NASA Technical Reports Server (NTRS)

Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

1992-01-01

This report presents the results of a fourth year effort of a research program, conducted for NASA-LeRC by the University of Texas at San Antonio (UTSA). The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subject to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 has been analyzed using the developed methodology.

Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep, and thermal fatigue

NASA Technical Reports Server (NTRS)

Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

1992-01-01

The results of a fourth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA) are presented. The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue, or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation was randomized and is included in the computer program, PROMISC. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

Section 2: Corrosion and failure analysis studies in support of the pulp and paper industry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keiser, J.R.; Pawel, S.J.; Swindeman, R.W.

1997-04-01

Technical support is being provided to various pulp and paper companies and related industries to help determine the cause of material degradation problems and to identify alternate materials to prevent such degradation. During the past year, examinations have included parts from several sootblowers, two failed economizer tubes, and inspection of a continuous digester. The results of the analyses and inspections were communicated to the plant operators, and, in some cases, recommendations were made. This article discusses examination of sootblower nozzles, which evidenced intergranular cracking. Analysis indicated the presence of chromium carbide precipitates along the grain boundaries, which can cause themore » sample to be sensitized to grain boundary attack.« less

Mechanical behaviour of degradable phosphate glass fibres and composites-a review.

PubMed

Colquhoun, R; Tanner, K E

2015-12-23

Biodegradable materials are potentially an advantageous alternative to the traditional metallic fracture fixation devices used in the reconstruction of bone tissue defects. This is due to the occurrence of stress shielding in the surrounding bone tissue that arises from the absence of mechanical stimulus to the regenerating bone due to the mismatch between the elastic modulus of bone and the metal implant. However although degradable polymers may alleviate such issues, these inert materials possess insufficient mechanical properties to be considered as a suitable alternative to current metallic devices at sites of sufficient mechanical loading. Phosphate based glasses are an advantageous group of materials for tissue regenerative applications due to their ability to completely degrade in vivo at highly controllable rates based on the specific glass composition. Furthermore the release of the glass's constituent ions can evoke a therapeutic stimulus in vivo (i.e. osteoinduction) whilst also generating a bioactive response. The processing of these materials into fibres subsequently allows them to act as reinforcing agents in degradable polymers to simultaneously increase its mechanical properties and enhance its in vivo response. However despite the various review articles relating to the compositional influences of different phosphate glass systems, there has been limited work summarising the mechanical properties of different phosphate based glass fibres and their subsequent incorporation as a reinforcing agent in degradable composite materials. As a result, this review article examines the compositional influences behind the development of different phosphate based glass fibre compositions intended as composite reinforcing agents along with an analysis of different potential composite configurations. This includes variations in the fibre content, matrix material and fibre architecture as well as other novel composites designs.

A novel mechanistic modeling framework for analysis of electrode balancing and degradation modes in commercial lithium-ion cells

NASA Astrophysics Data System (ADS)

Schindler, Stefan; Danzer, Michael A.

2017-03-01

Aiming at a long-term stable and safe operation of rechargeable lithium-ion cells, elementary design aspects and degradation phenomena have to be considered depending on the specific application. Among the degrees of freedom in cell design, electrode balancing is of particular interest and has a distinct effect on useable capacity and voltage range. Concerning intrinsic degradation modes, understanding the underlying electrochemical processes and tracing the overall degradation history are the most crucial tasks. In this study, a model-based, minimal parameter framework for combined elucidation of electrode balancing and degradation pathways in commercial lithium-ion cells is introduced. The framework rests upon the simulation of full cell voltage profiles from the superposition of equivalent, artificially degraded half-cell profiles and allows to separate aging contributions from loss of available lithium and active materials in both electrodes. A physically meaningful coupling between thermodynamic and kinetic degradation modes based on the correlation between altered impedance features and loss of available lithium as well as loss of active material is proposed and validated by a low temperature degradation profile examined in one of our recent publications. The coupled framework is able to determine the electrode balancing within an error range of < 1% and the projected cell degradation is qualitatively and quantitatively in line with experimental observations.

Modelling of chemical degradation of blended cement-based materials by leaching cycles with Callovo-Oxfordian porewater

NASA Astrophysics Data System (ADS)

Olmeda, Javier; Henocq, Pierre; Giffaut, Eric; Grivé, Mireia

2017-06-01

The present work describes a thermodynamic model based on pore water replacement cycles to simulate the chemical evolution of blended cement (BFS + FA) by interaction with external Callovo-Oxfordian (COx) pore water. In the framework of the radioactive waste management, the characterization of the radionuclide behaviour (solubility/speciation, adsorption) in cementitious materials needs to be done for several chemical degradation states (I to IV). In particular, in the context of the deep geological radioactive waste disposal project (Cigéo), cement-based materials will be chemically evolved with time in contact with the host-rock (COx formation). The objective of this study is to provide an equilibrium solution composition for each degradation state for a CEM-V cement-based material to support the adsorption and diffusion experiments reproducing any state of degradation. Calculations have been performed at 25 °C using the geochemical code PhreeqC and an up-to-date thermodynamic database (ThermoChimie v.9.0.b) coupled to SIT approach for ionic strength correction. The model replicates experimental data with accuracy. The approach followed in this study eases the analysis of the chemical evolution in both aqueous and solid phase to obtain a fast assessment of the geochemical effects associated to an external water intrusion of variable composition on concrete structures.

Effect of TiO2-Crystal Forms on the Photo-Degradation of EVA/PLA Blend Under Accelerated Weather Testing

NASA Astrophysics Data System (ADS)

Van Cong, Do; Trang, Nguyen Thi Thu; Giang, Nguyen Vu; Lam, Tran Dai; Hoang, Thai

2016-05-01

Photo-degradation of poly (ethylene-co-vinyl acetate) (EVA)/poly (lactic acid) (PLA) blend and EVA/PLA/TiO2 nanocomposites was carried out under accelerated weather testing conditions by alternating cycles of ultraviolet (UV) light and moisture at controlled and elevated temperatures. The characters, properties, and morphology of these materials before and after accelerated weather testing were determined by Fourier transform infrared spectroscopy, colour changes, viscosity, tensile test, thermogravimetric analysis, and field emission scanning electron microscopy. The increases in the content of oxygen-containing groups, colour changes; the decreases in viscosity, tensile properties, and thermal stability of these materials after accelerated weather testing are the evidence for the photo-degradation of the blend and nanocomposites. After accelerated weather testing, the appearance of many micro-holes and micro-pores on the surface of the collected samples was observed. The photo-degradation degree of the nanocomposites depended on the TiO2-crystal form. Rutile TiO2 do not enhance the degradation, but anatase and mixed crystals TiO2 nanoparticles promoted the degradation of the nanocomposites. Particularly, the mixed crystals TiO2 nanoparticles showed the highest photo-catalytic activity of the nanocomposites.

Investigation of abrupt degradation of drain current caused by under-gate crack in AlGaN/GaN high electron mobility transistors during high temperature operation stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Chang; Liao, XueYang; Li, RuGuan

2015-09-28

In this paper, we investigate the degradation mode and mechanism of AlGaN/GaN based high electron mobility transistors (HEMTs) during high temperature operation (HTO) stress. It demonstrates that there was abrupt degradation mode of drain current during HTO stress. The abrupt degradation is ascribed to the formation of crack under the gate which was the result of the brittle fracture of epilayer based on failure analysis. The origin of the mechanical damage under the gate is further investigated and discussed based on top-down scanning electron microscope, cross section transmission electron microscope and energy dispersive x-ray spectroscopy analysis, and stress simulation. Basedmore » on the coupled analysis of the failure physical feature and stress simulation considering the coefficient of thermal expansion (CTE) mismatch in different materials in gate metals/semiconductor system, the mechanical damage under the gate is related to mechanical stress induced by CTE mismatch in Au/Ti/Mo/GaN system and stress concentration caused by the localized structural damage at the drain side of the gate edge. These results indicate that mechanical stress induced by CTE mismatch of materials inside the device plays great important role on the reliability of AlGaN/GaN HEMTs during HTO stress.« less

Optical properties of dissolved organic matter (DOM): Effects of biological and photolytic degradation

USGS Publications Warehouse

Hansen, Angela; Kraus, Tamara; Pellerin, Brian; Fleck, Jacob; Downing, Bryan D.; Bergamaschi, Brian

2016-01-01

Advances in spectroscopic techniques have led to an increase in the use of optical properties (absorbance and fluorescence) to assess dissolved organic matter (DOM) composition and infer sources and processing. However, little information is available to assess the impact of biological and photolytic processing on the optical properties of original DOM source materials. We measured changes in commonly used optical properties and indices in DOM leached from peat soil, plants, and algae following biological and photochemical degradation to determine whether they provide unique signatures that can be linked to original DOM source. Changes in individual optical parameters varied by source material and process, with biodegradation and photodegradation often causing values to shift in opposite directions. Although values for different source materials overlapped at the end of the 111-day lab experiment, multivariate statistical analyses showed that unique optical signatures could be linked to original DOM source material even after degradation, with 17 optical properties determined by discriminant analysis to be significant (p<0.05) in distinguishing between DOM source and environmental processing. These results demonstrate that inferring the source material from optical properties is possible when parameters are evaluated in combination even after extensive biological and photochemical alteration.

Thermal protection system (TPS) monitoring using acoustic emission

NASA Astrophysics Data System (ADS)

Hurley, D. A.; Huston, D. R.; Fletcher, D. G.; Owens, W. P.

2011-04-01

This project investigates acoustic emission (AE) as a tool for monitoring the degradation of thermal protection systems (TPS). The AE sensors are part of an array of instrumentation on an inductively coupled plasma (ICP) torch designed for testing advanced thermal protection aerospace materials used for hypervelocity vehicles. AE are generated by stresses within the material, propagate as elastic stress waves, and can be detected with sensitive instrumentation. Graphite (POCO DFP-2) is used to study gas-surface interaction during degradation of thermal protection materials. The plasma is produced by a RF magnetic field driven by a 30kW power supply at 3.5 MHz, which creates a noisy environment with large spikes when powered on or off. AE are waveguided from source to sensor by a liquid-cooled copper probe used to position the graphite sample in the plasma stream. Preliminary testing was used to set filters and thresholds on the AE detection system (Physical Acoustics PCI-2) to minimize the impact of considerable operating noise. Testing results show good correlation between AE data and testing environment, which dictates the physics and chemistry of the thermal breakdown of the sample. Current efforts for the project are expanding the dataset and developing statistical analysis tools. This study shows the potential of AE as a powerful tool for analysis of thermal protection material thermal degradations with the unique capability of real-time, in-situ monitoring.

Study on immobilization of marine oil-degrading bacteria by carrier of algae materials.

PubMed

Zhang, Yiran; Gao, Wei; Lin, Faxiang; Han, Bin; He, Changfei; Li, Qian; Gao, Xiangxing; Cui, Zhisong; Sun, Chengjun; Zheng, Li

2018-05-18

This study investigated the immobilizations with of bacteria two kinds of algal materials, Enteromorpha residue and kelp residue. The lipophilicity of them were compared by diesel absorption rates. The immobilization efficiency of Bacillus sp. E3 was measured to evaluate whether these carriers would satisfy the requirement for biodegradation of oil spills. The bacteria were immobilized through adsorption with the sterilized and non-sterilized carriers to compare the differences between the two treatments. Oil degradation rates were determined using gravimetric and GC-MS methods. Results showed the absorption rates of Enteromorpha residue and kelp residue for diesel were 411 and 273% respectively and remained approximately 105 and 120% after 2 h of erosion in simulated seawater system. After immobilized of Bacillus sp. E3, the oil degradation rates of them were higher than 65% after 21 days biodegradations. GC-MS analysis showed that two immobilizations degraded higher than 70% of the total alkane and the total PAHs, whereas the free bacteria degraded 63% of the total alkane and 66% the total PAHs. And the bacteria immobilized with the carriers degraded more HMW-alkanes and HMW-PAHs than the free bacteria. The bacteria immobilized by non-sterilized kelp residue showed a considerably higher degradation rate than that using sterilized kelp residue. A considerably higher cells absorption rate of immobilization was obtained when using kelp residue, and the preparation of immobilization was low cost and highly efficient. The experiments show the two algae materials, especially the kelp residue, present potential application in bioremediation of marine oil spills.

Plasma facing materials and components for future fusion devices—development, characterization and performance under fusion specific loading conditions

NASA Astrophysics Data System (ADS)

Linke, J.

2006-04-01

The plasma exposed components in existing and future fusion devices are strongly affected by the plasma material interaction processes. These mechanisms have a strong influence on the plasma performance; in addition they have major impact on the lifetime of the plasma facing armour and the joining interface between the plasma facing material (PFM) and the heat sink. Besides physical and chemical sputtering processes, high heat quasi-stationary fluxes during normal and intense thermal transients are of serious concern for the engineers who develop reliable wall components. In addition, the material and component degradation due to intense fluxes of energetic neutrons is another critical issue in D-T-burning fusion devices which requires extensive R&D. This paper presents an overview on the materials development and joining, the testing of PFMs and components, and the analysis of the neutron irradiation induced degradation.

Nanocrystalline ZnO as a Visible Active Photocatalyst for the Degradation of Benzene-1,4-diol

NASA Astrophysics Data System (ADS)

Ramachandran, Saranya; Sivasamy, A.

We have synthesized nanocrystalline ZnO by a simple precipitation method. The prepared ZnO was found to be highly phase pure and nanocrystalline hexagonal wurtzite structure. UV-Visible-DRS spectroscopy showed the material to have bandgap energy of 3.22eV. HR-SEM image revealed the material to be made up of distinct hexagonal particles with a highly porous surface. AFM analysis was employed to confirm the high surface roughness and porosity of the material. The photocatalytic activity of the prepared ZnO was evaluated by the degradation of benzene-1,4-diol (hydroquinone), under visible light irradiation. Preliminary experiments showed the catalyst to be effective at neutral pH with an optimum catalyst dosage of 4g/L. Kinetic studies showed the degradation reaction to follow pseudo-first-order kinetics. In the presence of commonly used industrial electrolytes, the catalyst exhibited a decrease in efficiency. Reusability studies showed the catalytic efficiency of ZnO to diminish marginally after the third cycle of reuse.

Intracisternal granules in the adipokinetic cells of locusts are not degraded and apparently function as supplementary stores of secretory material.

PubMed

Harthoorn, L F; Diederen, J H; Oudejans, R C; Verstegen, M M; Vullings, H G; Van der Horst, D J

2000-01-01

The intracisternal granules in locust adipokinetic cells appear to represent accumulations of secretory material within cisternae of the rough endoplasmic reticulum. An important question is whether these granules are destined for degradation or represent stores of (pro)hormones. Two strategies were used to answer this question. First, cytochemistry was applied to elucidate the properties of intracisternal granules. The endocytic tracers horseradish peroxidase and wheat-germ agglutinin-conjugated horseradish peroxidase were used to facilitate the identification of endocytic, autophagic, and lysosomal organelles, which may be involved in the degradation of intracisternal granules. No intracisternal granules could be found within autophagosomes, and granules fused with endocytic and lysosomal organelles were not observed, nor could tracer be found within the granules. The lysosomal enzyme acid phosphatase was absent from the granules. Second, biochemical analysis of the content of intracisternal granules revealed that these granules contain prohormones as well as hormones. Prohormones were present in relatively higher amounts compared with ordinary secretory granules. Since the intracisternal granules in locust adipokinetic cells are not degraded and contain intact (pro)hormones it is concluded that they function as supplementary stores of secretory material.

Reliability analysis of InGaN/GaN multi-quantum-well solar cells under thermal stress

NASA Astrophysics Data System (ADS)

Huang, Xuanqi; Fu, Houqiang; Chen, Hong; Lu, Zhijian; Baranowski, Izak; Montes, Jossue; Yang, Tsung-Han; Gunning, Brendan P.; Koleske, Dan; Zhao, Yuji

2017-12-01

We investigate the thermal stability of InGaN solar cells under thermal stress at elevated temperatures from 400 °C to 500 °C. High Resolution X-Ray Diffraction analysis reveals that material quality of InGaN/GaN did not degrade after thermal stress. The external quantum efficiency characteristics of solar cells were well-maintained at all temperatures, which demonstrates the thermal robustness of InGaN materials. Analysis of current density-voltage (J-V) curves shows that the degradation of conversion efficiency of solar cells is mainly caused by the decrease in open-circuit voltage (Voc), while short-circuit current (Jsc) and fill factor remain almost constant. The decrease in Voc after thermal stress is attributed to the compromised metal contacts. Transmission line method results further confirmed that p-type contacts became Schottky-like after thermal stress. The Arrhenius model was employed to estimate the failure lifetime of InGaN solar cells at different temperatures. These results suggest that while InGaN solar cells have high thermal stability, the degradation in the metal contact could be the major limiting factor for these devices under high temperature operation.

Multiple ion beam irradiation for the study of radiation damage in materials

NASA Astrophysics Data System (ADS)

Taller, Stephen; Woodley, David; Getto, Elizabeth; Monterrosa, Anthony M.; Jiao, Zhijie; Toader, Ovidiu; Naab, Fabian; Kubley, Thomas; Dwaraknath, Shyam; Was, Gary S.

2017-12-01

The effects of transmutation produced helium and hydrogen must be included in ion irradiation experiments to emulate the microstructure of reactor irradiated materials. Descriptions of the criteria and systems necessary for multiple ion beam irradiation are presented and validated experimentally. A calculation methodology was developed to quantify the spatial distribution, implantation depth and amount of energy-degraded and implanted light ions when using a thin foil rotating energy degrader during multi-ion beam irradiation. A dual ion implantation using 1.34 MeV Fe+ ions and energy-degraded D+ ions was conducted on single crystal silicon to benchmark the dosimetry used for multi-ion beam irradiations. Secondary Ion Mass Spectroscopy (SIMS) analysis showed good agreement with calculations of the peak implantation depth and the total amount of iron and deuterium implanted. The results establish the capability to quantify the ion fluence from both heavy ion beams and energy-degraded light ion beams for the purpose of using multi-ion beam irradiations to emulate reactor irradiated microstructures.

Static Corrosion Test of Porous Iron Material with Polymer Coating

NASA Astrophysics Data System (ADS)

Markušová-Bučková, Lucia; Oriňaková, Renáta; Oriňak, Andrej; Gorejová, Radka; Kupková, Miriam; Hrubovčáková, Monika; Baláž, Matej; Kováľ, Karol

2016-12-01

At present biodegradable implants received increased attention due to their use in various fields of medicine. This work is dedicated to testing of biodegradable materials which could be used as bone implants. The samples were prepared from the carbonyl iron powder by replication method and surface polymer film was produced through sol-gel process. Corrosion testing was carried out under static conditions during 12 weeks in Hank's solution. The quantity of corrosion products increased with prolonging time of static test as it can be concluded from the results of EDX analysis. The degradation of open cell materials with polyethylene glycol coating layer was faster compared to uncoated Fe sample. Also the mass losses were higher for samples with PEG coating. The polymer coating brought about the desired increase in degradation rate of porous iron material.

Cementitious Barriers Partnership FY2013 End-Year Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flach, G. P.; Langton, C. A.; Burns, H. H.

2013-11-01

In FY2013, the Cementitious Barriers Partnership (CBP) demonstrated continued tangible progress toward fulfilling the objective of developing a set of software tools to improve understanding and prediction of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. In November 2012, the CBP released “Version 1.0” of the CBP Software Toolbox, a suite of software for simulating reactive transport in cementitious materials and important degradation phenomena. In addition, the CBP completed development of new software for the “Version 2.0” Toolbox to be released in early FY2014 and demonstrated use of the Version 1.0 Toolbox on DOEmore » applications. The current primary software components in both Versions 1.0 and 2.0 are LeachXS/ORCHESTRA, STADIUM, and a GoldSim interface for probabilistic analysis of selected degradation scenarios. The CBP Software Toolbox Version 1.0 supports analysis of external sulfate attack (including damage mechanics), carbonation, and primary constituent leaching. Version 2.0 includes the additional analysis of chloride attack and dual regime flow and contaminant migration in fractured and non-fractured cementitious material. The LeachXS component embodies an extensive material property measurements database along with chemical speciation and reactive mass transport simulation cases with emphasis on leaching of major, trace and radionuclide constituents from cementitious materials used in DOE facilities, such as Saltstone (Savannah River) and Cast Stone (Hanford), tank closure grouts, and barrier concretes. STADIUM focuses on the physical and structural service life of materials and components based on chemical speciation and reactive mass transport of major cement constituents and aggressive species (e.g., chloride, sulfate, etc.). THAMES is a planned future CBP Toolbox component focused on simulation of the microstructure of cementitious materials and calculation of resultant hydraulic and constituent mass transfer parameters needed in modeling. Two CBP software demonstrations were conducted in FY2013, one to support the Saltstone Disposal Facility (SDF) at SRS and the other on a representative Hanford high-level waste tank. The CBP Toolbox demonstration on the SDF provided analysis on the most probable degradation mechanisms to the cementitious vault enclosure caused by sulfate and carbonation ingress. This analysis was documented and resulted in the issuance of a SDF Performance Assessment Special Analysis by Liquid Waste Operations this fiscal year. The two new software tools supporting chloride attack and dual-regime flow will provide additional degradation tools to better evaluate performance of DOE and commercial cementitious barriers. The CBP SRNL experimental program produced two patent applications and field data that will be used in the development and calibration of CBP software tools being developed in FY2014. The CBP software and simulation tools varies from other efforts in that all the tools are based upon specific and relevant experimental research of cementitious materials utilized in DOE applications. The CBP FY2013 program involved continuing research to improve and enhance the simulation tools as well as developing new tools that model other key degradation phenomena not addressed in Version 1.0. Also efforts to continue to verify the various simulation tools through laboratory experiments and analysis of field specimens are ongoing and will continue into FY2014 to quantify and reduce the uncertainty associated with performance assessments. This end-year report summarizes FY2013 software development efforts and the various experimental programs that are providing data for calibration and validation of the CBP developed software.« less

An efficient and environment-friendly method of removing graphene oxide in wastewater and its degradation mechanisms.

PubMed

Zhang, Chao-Zhi; Li, Ting; Yuan, Yang; Xu, Jianqiang

2016-06-01

Graphene and graphene oxide (GO) have already existed in air, water and soil due to their popular application in functional materials. However, degradation of graphene and GO in wastewater has not been reported. Degradation of GO plays a key role in the elimination of graphene and GO in wastewater due to graphene being easily oxidized to GO. In this paper, GO was completely degraded to give CO2 by Photo-Fenton. The degradation intermediates were determined by UV-vis absorption spectra, elemental analysis (EA), fourier transform infrared (FT-IR) and liquid chromatography-mass spectrometry (LC-MS). Experimental results showed that graphene oxide was completely degraded to give CO2 after 28 days. Based on UV, FT-IR, LC-MS spectra and EA data of these degradation intermediates, the degradation mechanisms of GO were supposed. This paper suggests an efficient and environment-friendly method to degrade GO and graphene. Copyright © 2016 Elsevier Ltd. All rights reserved.

Acousto-Ultrasonic analysis of failure in ceramic matrix composite tensile specimens

NASA Technical Reports Server (NTRS)

Kautz, Harold E.; Chulya, Abhisak

1993-01-01

Three types of acousto-ultrasonic (AU) measurements, stress-wave factor (SWF), lowest antisymmetric plate mode group velocity (VS), and lowest symmetric plate mode group velocity (VL), were performed on specimens before and after tensile failure. Three different Nicalon fiber architectures with ceramic matrices were tested. These composites were categorized as 1D (unidirectional fiber orientation) SiC/CAS glass ceramic, and 2D and 3D woven SiC/SiC ceramic matrix materials. SWF was found to be degraded after tensile failure in all three material categories. VS was found to be degraded only in the 1D SiC/CAS. VL was difficult to determine on the irregular specimen surfaces but appeared unchanged on all failed specimens. 3D woven specimens with heat-treatment at high temperature exhibited degradation only in SWF.

Micro- and nano-scale characterization to study the thermal degradation of cement-based materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Seungmin, E-mail: lim76@illinois.edu; Mondal, Paramita

2014-06-01

The degradation of hydration products of cement is known to cause changes in the micro- and nano-structure, which ultimately drive thermo-mechanical degradation of cement-based composite materials at elevated temperatures. However, a detailed characterization of these changes is still incomplete. This paper presents results of an extensive experimental study carried out to investigate micro- and nano-structural changes that occur due to exposure of cement paste to high temperatures. Following heat treatment of cement paste up to 1000 °C, damage states were studied by compressive strength test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) atomic force microscopy (AFM) and AFM image analysis.more » Using experimental results and research from existing literature, new degradation processes that drive the loss of mechanical properties of cement paste are proposed. The development of micro-cracks at the interface between unhydrated cement particles and paste matrix, a change in C–S–H nano-structure and shrinkage of C–S–H, are considered as important factors that cause the thermal degradation of cement paste. - Highlights: • The thermal degradation of hydration products of cement is characterized at micro- and nano-scale using scanning electron microscopy (SEM) and atomic force microscopy (AFM). • The interface between unhydrated cement particles and the paste matrix is considered the origin of micro-cracks. • When cement paste is exposed to temperatures above 300 ºC, the nano-structure of C-S-H becomes a more loosely packed globular structure, which could be indicative of C-S-H shrinkage.« less

Thermochemical Stability Study of Alkyl-Tethered Quaternary Ammonium Cations for Anion Exchange Membrane Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohanty, Angela D.; Tignor, Steven E.; Sturgeon, Matthew R.

2017-01-01

The increased interest in the use of anion exchange membranes (AEMs) for applications in electrochemical devices has prompted significant efforts in designing materials with robust stability in alkaline media. Most reported AEMs suffer from polymer backbone degradation as well as cation functional group degradation. In this report, we provide comprehensive experimental investigations for the analysis of cation functional group stability under alkaline media. A silver oxide-mediated ion exchange method and an accelerated stability test in aqueous KOH solutions at elevated temperatures using a Parr reactor were used to evaluate a broad scope of quaternary ammonium (QA) cationic model compound structures,more » particularly focusing on alkyl-tethered cations. Additionally, byproduct analysis was employed to gain better understanding of degradation pathways and trends of alkaline stability. Experimental results under different conditions gave consistent trends in the order of cation stability of various QA small molecule model compounds. Overall, cations that are benzyl-substituted or that are near to electronegative atoms (such as oxygen) degrade faster in alkaline media in comparison to alkyl-tethered QAs. These comprehensive model compound stability studies provide valuable information regarding the relative stability of various cation structures and can help guide researchers towards designing new and promising candidates for AEM materials.« less

Temperature Effects of Ultraviolet Irradiation on Material Degradation

NASA Astrophysics Data System (ADS)

Mori, Kazuyuki; Ishizawa, Junichiro

Ultraviolet rays (UV) cause organic materials to deteriorate. UV irradiation ground testing is therefore important to understand the “adequate lifetime assessment” and the “end-of-life (EOL) characteristic” of materials used in space. In previous experiments, high temperatures were found to accelerate the UV degradation of cross-linked ethylene tetrafluoroethylene (X-ETFE). This causes concern of potentially similar effects in other materials. In this study, we evaluated UV degradation at high temperatures and subsequently determined materials usable in space that had shown accelerated degradation due to UV irradiation at high temperatures.

Application of Ni-Oxide@TiO₂ Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors.

PubMed

Lee, Seungwon; Lee, Jisuk; Nam, Kyusuk; Shin, Weon Gyu; Sohn, Youngku

2016-12-20

Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO₂ core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue) degradation under ultraviolet (UV) and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO₂ overlayer coating.

Probabilistic sizing of laminates with uncertainties

NASA Technical Reports Server (NTRS)

Shah, A. R.; Liaw, D. G.; Chamis, C. C.

1993-01-01

A reliability based design methodology for laminate sizing and configuration for a special case of composite structures is described. The methodology combines probabilistic composite mechanics with probabilistic structural analysis. The uncertainties of constituent materials (fiber and matrix) to predict macroscopic behavior are simulated using probabilistic theory. Uncertainties in the degradation of composite material properties are included in this design methodology. A multi-factor interaction equation is used to evaluate load and environment dependent degradation of the composite material properties at the micromechanics level. The methodology is integrated into a computer code IPACS (Integrated Probabilistic Assessment of Composite Structures). Versatility of this design approach is demonstrated by performing a multi-level probabilistic analysis to size the laminates for design structural reliability of random type structures. The results show that laminate configurations can be selected to improve the structural reliability from three failures in 1000, to no failures in one million. Results also show that the laminates with the highest reliability are the least sensitive to the loading conditions.

Probabilistic analysis for fatigue strength degradation of materials

NASA Technical Reports Server (NTRS)

Royce, Lola

1989-01-01

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

Mechanisms Underpinning Degradation of Protective Oxides and Thermal Barrier Coatings in High Hydrogen Content (HHC) - Fueled Turbines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mumm, Daniel

2013-08-31

The overarching goal of this research program has been to evaluate the potential impacts of coal-derived syngas and high-hydrogen content fuels on the degradation of turbine hot-section components through attack of protective oxides and thermal barrier coatings. The primary focus of this research program has been to explore mechanisms underpinning the observed degradation processes, and connections to the combustion environments and characteristic non-combustible constituents. Based on the mechanistic understanding of how these emerging fuel streams affect materials degradation, the ultimate goal of the program is to advance the goals of the Advanced Turbine Program by developing materials design protocols leadingmore » to turbine hot-section components with improved resistance to service lifetime degradation under advanced fuels exposures. This research program has been focused on studying how: (1) differing combustion environments – relative to traditional natural gas fired systems – affect both the growth rate of thermally grown oxide (TGO) layers and the stability of these oxides and of protective thermal barrier coatings (TBCs); and (2) how low levels of fuel impurities and characteristic non-combustibles interact with surface oxides, for instance through the development of molten deposits that lead to hot corrosion of protective TBC coatings. The overall program has been comprised of six inter-related themes, each comprising a research thrust over the program period, including: (i) evaluating the role of syngas and high hydrogen content (HHC) combustion environments in modifying component surface temperatures, heat transfer to the TBC coatings, and thermal gradients within these coatings; (ii) understanding the instability of TBC coatings in the syngas and high hydrogen environment with regards to decomposition, phase changes and sintering; (iii) characterizing ash deposition, molten phase development and infiltration, and associated corrosive/thermo-chemical attack mechanisms; (iv) developing a mechanics-based analysis of the driving forces for crack growth and delamination, based on molten phase infiltration, misfit upon cooling, and loss of compliance; (v) understanding changes in TGO growth mechanisms associated with these emerging combustion product streams; and (vi) identifying degradation resistant alternative materials (including new compositions or bi-layer concepts) for use in mitigating the observed degradation modes. To address the materials stability concerns, this program integrated research thrusts aimed at: (1) Conducting tests in simulated syngas and HHC environments to evaluate materials evolution and degradation mechanisms; assessing thermally grown oxide development unique to HHC environmental exposures; carrying out high-resolution imaging and microanalysis to elucidate the evolution of surface deposits (molten phase formation and infiltration); exploring thermo-chemical instabilities; assessing thermo-mechanical drivers and thermal gradient effects on degradation; and quantitatively measuring stress evolution due to enhanced sintering and thermo-chemical instabilities induced in the coating. (2) Executing experiments to study the melting and infiltration of simulated ash deposits, and identifying reaction products and evolving phases associated with molten phase corrosion mechanisms; utilizing thermal spray techniques to fabricate test coupons with controlled microstructures to study mechanisms of instability and degradation; facilitating thermal gradient testing; and developing new materials systems for laboratory testing; (3) Correlating information on the resulting combustion environments to properly assess materials exposure conditions and guide the development of lab-scale simulations of material exposures; specification of representative syngas and high-hydrogen fuels with realistic levels of impurities and contaminants, to explore differences in heat transfer, surface degradation, and deposit formation; and facilitating combustion rig testing of materials test coupons.« less

Degradation of Degradable Starch-Polyethylene Plastics in a Compost Environment †

PubMed Central

Johnson, Kenneth E.; Pometto, Anthony L.; Nikolov, Zivko L.

1993-01-01

The degradation performance of 11 types of commercially produced degradable starch-polyethylene plastic compost bags was evaluated in municipal yard waste compost sites at Iowa State University (Ames) and in Carroll, Dubuque, and Grinnell, Iowa. Masterbatches for plastic production were provided by Archer Daniels Midland Co. (Decatur, Ill.), St. Lawrence Starch Co. Ltd. (Mississauga, Ontario, Canada), and Fully Compounded Plastics (Decatur, Ill.). Bags differed in starch content (5 to 9%) and prooxidant additives (transition metals and a type of unsaturated vegetable oil). Chemical and photodegradation properties of each material were evaluated. Materials from St. Lawrence Starch Co. Ltd. and Fully Compounded Plastics photodegraded faster than did materials from Archer Daniels Midland Co., whereas all materials containing transition metals demonstrated rapid thermal oxidative degradation in 70°C-oven (dry) and high-temperature, high-humidity (steam chamber) treatments. Each compost site was seeded with test strips (200 to 800 of each type) taped together, which were recovered periodically over an 8- to 12-month period. At each sampling date, the compost row temperature was measured (65 to 95°C), the location of the recovered test strip was recorded (interior or exterior), and at least four strips were recovered for evaluation. Degradation was followed by measuring the change in polyethylene molecular weight distribution via high-temperature gel permeation chromatography. Our initial 8-month study indicated that materials recovered from the interior of the compost row demonstrated very little degradation, whereas materials recovered from the exterior degraded well. In the second-year study, however, degradation was observed in several plastic materials recovered from the interior of the compost row by month 5 at the Carroll site and almost every material by month 12 at the Grinnell site. The plastic bags collected from each community followed a similar degradation pattern. To our knowledge, this is the first scientific study demonstrating significant polyethylene degradation by these materials in a compost environment. PMID:16348914

Degradation of degradable starch-polyethylene plastics in a compost environment.

PubMed

Johnson, K E; Pometto, A L; Nikolov, Z L

1993-04-01

The degradation performance of 11 types of commercially produced degradable starch-polyethylene plastic compost bags was evaluated in municipal yard waste compost sites at Iowa State University (Ames) and in Carroll, Dubuque, and Grinnell, Iowa. Masterbatches for plastic production were provided by Archer Daniels Midland Co. (Decatur, Ill.), St. Lawrence Starch Co. Ltd. (Mississauga, Ontario, Canada), and Fully Compounded Plastics (Decatur, Ill.). Bags differed in starch content (5 to 9%) and prooxidant additives (transition metals and a type of unsaturated vegetable oil). Chemical and photodegradation properties of each material were evaluated. Materials from St. Lawrence Starch Co. Ltd. and Fully Compounded Plastics photodegraded faster than did materials from Archer Daniels Midland Co., whereas all materials containing transition metals demonstrated rapid thermal oxidative degradation in 70 degrees C-oven (dry) and high-temperature, high-humidity (steam chamber) treatments. Each compost site was seeded with test strips (200 to 800 of each type) taped together, which were recovered periodically over an 8- to 12-month period. At each sampling date, the compost row temperature was measured (65 to 95 degrees C), the location of the recovered test strip was recorded (interior or exterior), and at least four strips were recovered for evaluation. Degradation was followed by measuring the change in polyethylene molecular weight distribution via high-temperature gel permeation chromatography. Our initial 8-month study indicated that materials recovered from the interior of the compost row demonstrated very little degradation, whereas materials recovered from the exterior degraded well. In the second-year study, however, degradation was observed in several plastic materials recovered from the interior of the compost row by month 5 at the Carroll site and almost every material by month 12 at the Grinnell site. The plastic bags collected from each community followed a similar degradation pattern. To our knowledge, this is the first scientific study demonstrating significant polyethylene degradation by these materials in a compost environment.

Bone-repair properties of biodegradable hydroxyapatite nano-rod superstructures

NASA Astrophysics Data System (ADS)

D'Elía, Noelia L.; Mathieu, Colleen; Hoemann, Caroline D.; Laiuppa, Juan A.; Santillán, Graciela E.; Messina, Paula V.

2015-11-01

Nano-hydroxyapatite (nano-HAp) materials show an analogous chemical composition to the biogenic mineral components of calcified tissues and depending on their topography they may mimic the specific arrangement of the crystals in bone. In this work, we have evaluated the potential of four synthesized nano-HAp superstructures for the in vitro conditions of bone-repair. Experiments are underway to investigate the effects of the material microstructure, surface roughness and hydrophilicity on their osseo-integration, osteo-conduction and osteo-induction abilities. Materials were tested in the presence of both, rat primary osteoblasts and rabbit mesenchymal stem cells. The following aspects are discussed: (i) cytotoxicity and material degradation; (ii) rat osteoblast spreading, proliferation and differentiation; and (iii) rabbit mesenchymal stem cell adhesion on nano-HAp and nano-HAp/collagen type I coatings. We effectively prepared a material based on biomimetic HAp nano-rods displaying the appropriate surface topography, hydrophilicity and degradation properties to induce the in vitro desired cellular responses for bone bonding and healing. Cells seeded on the selected material readily attached, proliferated and differentiated, as confirmed by cell viability, mitochondrial metabolic activity, alkaline phosphatase (ALP) activity and cytoskeletal integrity analysis by immunofluorescence localization of alpha-smooth muscle actin (α-SMA) protein. These results highlight the influence of material's surface characteristics to determine their tissue regeneration potential and their future use in engineering osteogenic scaffolds for orthopedic implants.Nano-hydroxyapatite (nano-HAp) materials show an analogous chemical composition to the biogenic mineral components of calcified tissues and depending on their topography they may mimic the specific arrangement of the crystals in bone. In this work, we have evaluated the potential of four synthesized nano-HAp superstructures for the in vitro conditions of bone-repair. Experiments are underway to investigate the effects of the material microstructure, surface roughness and hydrophilicity on their osseo-integration, osteo-conduction and osteo-induction abilities. Materials were tested in the presence of both, rat primary osteoblasts and rabbit mesenchymal stem cells. The following aspects are discussed: (i) cytotoxicity and material degradation; (ii) rat osteoblast spreading, proliferation and differentiation; and (iii) rabbit mesenchymal stem cell adhesion on nano-HAp and nano-HAp/collagen type I coatings. We effectively prepared a material based on biomimetic HAp nano-rods displaying the appropriate surface topography, hydrophilicity and degradation properties to induce the in vitro desired cellular responses for bone bonding and healing. Cells seeded on the selected material readily attached, proliferated and differentiated, as confirmed by cell viability, mitochondrial metabolic activity, alkaline phosphatase (ALP) activity and cytoskeletal integrity analysis by immunofluorescence localization of alpha-smooth muscle actin (α-SMA) protein. These results highlight the influence of material's surface characteristics to determine their tissue regeneration potential and their future use in engineering osteogenic scaffolds for orthopedic implants. Electronic supplementary information (ESI) available: Calculation of roughness parameters Rz, Rz,max, and Rz, prom. Nano-HAp powder degradation after immersion in phosphate buffer (pH = 7.4). Optical phase contrast microphotographs of MSC adhesion on nano-HAp and nano-HAp/Co I coatings at different concentrations. Laser scanning confocal microphotographs of MSCs' α-SMA expression spreading on large amounts of nano-HAp (MI) coatings. Immunofluorescence microphotograph analysis by image software. See DOI: 10.1039/c5nr04850h

New insight of hybrid membrane to degrade Congo red and Reactive yellow under sunlight.

PubMed

Rajeswari, A; Jackcina Stobel Christy, E; Pius, Anitha

2018-02-01

A study was carried out to investigate the degradation of organic contaminants (Congo red and Reactive yellow - 105) using cellulose acetate - polystyrene (CA-PS) membrane with and without ZnO impregnation. Scanning electron microscope (SEM), electron dispersive analysis of X-rays (EDAX), Fourier transform infrared spectrometer (FTIR), atomic force microscope (AFM) and thermogravimeric analysis (TG-DTA) analysis were carried out to characterize bare and ZnO impregnated CA-PS membranes. Membrane efficiency was also tested for pure water flux and antifouling performance. The modified membrane showed almost 85% water flux recovery. Blending of ZnO nanoparticles to CA-PS matrix could decrease membrane fouling and increase permeation quality of the membrane with above 90% of photocatalytic degradation efficiency for dyes. The rate of degradation of dyes was observed using UV-Vis spectrometer. Reusability of CA-PS-ZnO membrane was studied and no significant change was noted in the degradation efficiency until fourth cycle. Langmuir-Hinshelwood kinetic model well describes the photo degradation capacity and the degradation of dyes CR and RY - 105 exhibited pseudo-first order kinetics. The regression coefficient (R) of CR and RY - 105 found to be 0.99. The novelty of the prepared CA-PS-ZnO membrane is that it has better efficiency and high thermal stability than our previously reported material. Therefore, ZnO impregnated CA-PS membrane had proved to be an innovative alternative for the degradation of CR and RY - 105 dyes. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation of Carbon-Chitosan-Polyvinyl Chloride (CC-PVC) Material and its Application to Electrochemical Degradation of Methylene Blue in Sodium Chloride Solution

NASA Astrophysics Data System (ADS)

Riyanto; Prawidha, A. D.

2018-01-01

Electrochemical degradation of methylene blue using Carbon-Chitosan-Polyvinyl Chloride (CC-PVC) electrode in sodium chloride have been done. The aim of this work was to degradation of methylene blue using Carbon-Chitosan-Polyvinyl Chloride (CC-PVC). Carbon chitosan composite electrode was preparing by Carbon and Chitosan powder and PVC in 4 mL tetrahydrofuran (THF) solvent and swirled flatly to homogeneous followed by drying in an oven at 100 °C for 3 h. The mixture was placed in stainless steel mould and pressed at 10 ton/cm2. Sodium chloride was used electrolyte solution. The effects of the current and electrolysis time were investigated using spectrophotometer UV-Visible. The experimental results showed that the carbon-chitosan composite electrode have higher effect in the electrochemical degradation of methylene blue in sodium chloride. Based on UV-visible spectra analysis shows current and electrolysis time has high effect to degradation of methylene blue in sodium chloride. Chitosan and polyvinyl chloride can strengthen the bond between the carbons so that the material has the high stability and conductivity. As conclusions is Carbon-Chitosan-Polyvinyl Chloride (CC-PVC) electrode have a high electrochemical activity for degradation of methylene blue in sodium chloride.

Remote Determination of Time-Dependent Stiffness of Surface-Degrading-Polymer Scaffolds Via Synchrotron-Based Imaging.

PubMed

Bawolin, N K; Chen, X B

2017-04-01

Surface-degrading polymers have been widely used to fabricate scaffolds with the mechanical properties appropriate for tissue regeneration/repair. During their surface degradation, the material properties of polymers remain approximately unchanged, but the scaffold geometry and thus mechanical properties vary with time. This paper presents a novel method to determine the time-dependent mechanical properties, particularly stiffness, of scaffolds from the geometric changes captured by synchrotron-based imaging, with the help of finite element analysis (FEA). Three-dimensional (3D) tissue scaffolds were fabricated from surface-degrading polymers, and during their degradation, the tissue scaffolds were imaged via the synchrotron-based imaging to characterize their changing geometry. On this basis, the stiffness behavior of scaffolds was estimated from the FEA, and the results obtained were compared to the direct measurements of scaffold stiffness from the load-displacement material testing. The comparison illustrates that the Young's moduli estimated from the FEA and characterized geometry are in agreement with the ones of direct measurements. The developed method of estimating the mechanical behavior was also demonstrated effective with a nondegrading scaffold that displays the nonlinear stress-strain behavior. The in vivo monitoring of Young's modulus by morphology characterization also suggests the feasibility of characterizing experimentally the difference between in vivo and in vitro surface degradation of tissue engineering constructs.

Difficulties in Interpreting Ballast Degradation Level Estimates from Synthetic Ground-Penetrating Radar Data

NASA Astrophysics Data System (ADS)

Scanlan, K. M.; Hendry, M. T.; Martin, C. D.; Schmitt, D. R.

2016-12-01

As fine-grained particles accumulate within railway ballast, it becomes more susceptible to differential deformations, which leads to the loss of proper track alignment and an increased risk for car derailment. Methods for estimating the ballast degradation level from low-frequency (<1 GHz) ground-penetrating radar (GPR) measurements exist, but their applicability in a wide range of track foundation conditions has yet to be evaluated. This analysis, based on simulated GPR data, evaluates the sensitivity of these methods to changing ballast moisture contents, ballast thicknesses and subballast material types. The results highlight that small changes to the track foundation, indepedent of the concentration of degraded ballast, significantly alter the attenuation and reflectivity characteristics of the simualted GPR measurements. As such, ballast degraded to a certain level will manifest with different attenuation and reflectivity characteristics, limiting the ability to accurately and reliably detect these changes using GPR. Radar propagation velocities within the ballast are less influenced by changes in ballast depth and subballast material type. However, ambiguous propagation velocities are observed for certain ballast moisture contents and degradation levels; furthermore, velocities can only be calculated when the ballast thickness is known. These results suggest that while under certain circumstances, with additional information on the track foundation conditons, ballast degradation levels can be estimated from GPR data; in general, the complicated nature of GPR signals makes the quantificaion of ballast degradation levels difficult.

CdZnTe substrate impurities and their effects on liquid phase epitaxy HgCdTe

NASA Astrophysics Data System (ADS)

Tower, J. P.; Tobin, S. P.; Kestigian, M.; Norton, P. W.; Bollong, A. B.; Schaake, H. F.; Ard, C. K.

1995-05-01

Impurity levels were tracked through the stages of substrate and liquid phase epitaxy (LPE) layer processing to identify sources of elements which degrade infrared photodetector performance. Chemical analysis by glow discharge mass spectrometry and Zeeman corrected graphite furnace atomic absorption effectively showed the levels of impurities introduced into CdZnTe substrate material from the raw materials and the crystal growth processes. A new purification process (in situ distillation zone refining) for raw materials was developed, resulting in improved CdZnTe substrate purity. Substrate copper contamination was found to degrade the LPE layer and device electrical properties, in the case of lightly doped HgCdTe. Anomalous HgCdTe carrier type conversion was correlated to certain CdZnTe and CdTe substrate ingots.

In-Situ Strain Analysis of Potential Habitat Composites Exposed to a Simulated Long-Term Lunar Radiation Exposure

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; O'Rourke, Mary Jane; Hill, Charles; Nutt, Steven; Atwell, William

2010-01-01

NASA is studying the effects of long-term space radiation on potential multifunctional composite materials for habitats to better determine their characteristics in the harsh space environment. Two composite materials were selected for the study and were placed in a test stand that simulated the stresses of a pressure vessel wall on the material. The samples in the test stand were exposed to radiation at either a fast dose rate or a slow dose rate, and their strain and temperature was recorded during the exposure. It was found that during a fast dose rate exposure the materials saw a decreased strain with time, or a shrinking of the materials. Given previous radiation studies of polymers, this is believed to be a result of crosslinking occurring in the matrix material. However, with a slow dose rate, the materials saw an increase in strain with time, or a stretching of the materials. This result is consistent with scission or degradation of the matrix occurring, possibly due to oxidative degradation.

Zeolite Degradation: An Investigation of CO2 Capacity Loss of 13x Sorbent

NASA Technical Reports Server (NTRS)

Huang, Roger; Richardson, Tra-My Justine; Belancik, Grace; Jan, Darrell; Hogan, John; Knox, James C.

2017-01-01

System testing of the Carbon Dioxide Removal and Compression System (CRCS) has revealed that sufficient CO2 removal capability was not achieved with the designed system. Subsystem component analysis of the zeolite bed revealed that the sorbent material suffered significant degradation and CO2 loading capacity loss. In an effort to find the root cause of this degradation, various factors were investigated to try to reproduce the observed performance loss. These factors included contamination by vacuum pump oil, o-ring vacuum grease, loading/unloading procedures, and operations. This paper details the experiments that were performed and their results.

Immobilization of fungal laccase onto a nonionic surfactant-modified clay material: application to PAH degradation.

PubMed

Chang, Yi-Tang; Lee, Jiunn-Fwu; Liu, Keng-Hua; Liao, Yi-Fen; Yang, Vivian

2016-03-01

Nonionic surfactant-modified clay is a useful absorbent material that effectively removes hydrophobic organic compounds from soil/groundwater. We developed a novel material by applying an immobilized fungal laccase onto nonionic surfactant-modified clay. Low-water-solubility polycyclic aromatic hydrocarbons (PAHs) (naphthalene/phenanthrene) were degraded in the presence of this bioactive material. PAH degradation by free laccase was higher than degradation by immobilized laccase when the surfactant concentration was allowed to form micelles. PAH degradation by immobilized laccase on TX-100-modified clay was higher than on Brij35-modified clay. Strong laccase degradation of PAH can be maintained by adding surfactant monomers or micelles. The physical adsorption of nonionic surfactants onto clay plays an important role in PAH degradation by laccase, which can be explained by the structure and molecular interactions of the surfactant with the clay and enzyme. A system where laccase is immobilized onto TX-100-monomer-modified clay is a good candidate bioactive material for in situ PAHs bioremediation.

qPCR-based mitochondrial DNA quantification: Influence of template DNA fragmentation on accuracy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Christopher B., E-mail: Christopher.jackson@insel.ch; Gallati, Sabina, E-mail: sabina.gallati@insel.ch; Schaller, Andre, E-mail: andre.schaller@insel.ch

2012-07-06

Highlights: Black-Right-Pointing-Pointer Serial qPCR accurately determines fragmentation state of any given DNA sample. Black-Right-Pointing-Pointer Serial qPCR demonstrates different preservation of the nuclear and mitochondrial genome. Black-Right-Pointing-Pointer Serial qPCR provides a diagnostic tool to validate the integrity of bioptic material. Black-Right-Pointing-Pointer Serial qPCR excludes degradation-induced erroneous quantification. -- Abstract: Real-time PCR (qPCR) is the method of choice for quantification of mitochondrial DNA (mtDNA) by relative comparison of a nuclear to a mitochondrial locus. Quantitative abnormal mtDNA content is indicative of mitochondrial disorders and mostly confines in a tissue-specific manner. Thus handling of degradation-prone bioptic material is inevitable. We established a serialmore » qPCR assay based on increasing amplicon size to measure degradation status of any DNA sample. Using this approach we can exclude erroneous mtDNA quantification due to degraded samples (e.g. long post-exicision time, autolytic processus, freeze-thaw cycles) and ensure abnormal DNA content measurements (e.g. depletion) in non-degraded patient material. By preparation of degraded DNA under controlled conditions using sonification and DNaseI digestion we show that erroneous quantification is due to the different preservation qualities of the nuclear and the mitochondrial genome. This disparate degradation of the two genomes results in over- or underestimation of mtDNA copy number in degraded samples. Moreover, as analysis of defined archival tissue would allow to precise the molecular pathomechanism of mitochondrial disorders presenting with abnormal mtDNA content, we compared fresh frozen (FF) with formalin-fixed paraffin-embedded (FFPE) skeletal muscle tissue of the same sample. By extrapolation of measured decay constants for nuclear DNA ({lambda}{sub nDNA}) and mtDNA ({lambda}{sub mtDNA}) we present an approach to possibly correct measurements in degraded samples in the future. To our knowledge this is the first time different degradation impact of the two genomes is demonstrated and which evaluates systematically the impact of DNA degradation on quantification of mtDNA copy number.« less

Rotational molding of bio-polymers

NASA Astrophysics Data System (ADS)

Greco, Antonio; Maffezzoli, Alfonso; Forleo, Stefania

2014-05-01

This paper is aimed to study the suitability of bio-polymers, including poly-lactic acid (PLLA) and Mater-Bi, for the production of hollow components by rotational molding. In order to reduce the brittleness of PLLA, the material was mixed with two different plasticizers, bis-ethyl-hexyl-phthalate (DEHP) and poly-ethylene-glycol (PEG). The materials were characterized in terms of sinterability. To this purpose, thermomechanical (TMA) analysis was performed at different heating rates, in order to identify the endset temperatures of densification and the onset temperatures of degradation. Results obtained indicated that the materials are characterized by a very fast sintering process, occurring just above the melting temperature, and an adequately high onset of degradation. The difference between the onset of degradation and the endset of sintering, defined as the processing window of the polymer, is sufficiently wide, indicating that the polymers can be efficiently processed by rotational molding. Therefore, a laboratory scale apparatus was used for the production of PLLA and Mater-Bi prototypes. The materials were processed using very similar conditions to those used for LLDPE. The production of void-free samples of uniform wall thickness was considered as an indication of the potentiality of the process for the production of biodegradable containers.

Material Analysis and System Design for Exploration Life Support Systems 2017

NASA Technical Reports Server (NTRS)

Knox, Jim; Cmarik, Gregory E.

2017-01-01

Advanced Environmental Control and Life Support System (ECLSS) design is critical for manned space flight beyond Earth. Current systems enable extended missions in low-Earth orbit, but for deep-space missions, not only will astronauts be outside the reach of resupply operations from Earth but they will also need to handle malfunctions and compensate for the degradation of materials. These two daunting challenges must be overcome for long-term independent space flight. In order to solve the first, separation and recycling of onboard atmosphere is required. Current systems utilize space vacuum to fully regenerate CO2 sorbent beds, but this is not sustainable. The second challenge stems from material and performance degradation due to operational cycling and on-board contaminants. This report will review the recent work by the ECLSS team at Marshall Space Flight Center towards overcoming these challenges by characterizing materials via novel methods and by assessing new air revitalization systems.

Phosphorous-doped TiO2 nanoparticles: synthesis, characterization, and visible photocatalytic evaluation on sulfamethazine degradation.

PubMed

Mendiola-Alvarez, Sandra Yadira; Hernández-Ramírez, Ma Aracely; Guzmán-Mar, Jorge Luis; Garza-Tovar, Lorena Leticia; Hinojosa-Reyes, Laura

2018-05-24

Mesoporous phosphorous-doped TiO 2 (TP) with different wt% of P (0.5, 1.0, and 1.5) was synthetized by microwave-assisted sol-gel method. The obtained materials were characterized by XRD with cell parameters refinement approach, Raman, BET-specific surface area analysis, SEM, ICP-OES, UV-Vis with diffuse reflectance, photoluminescence, FTIR, and XPS. The photocatalytic activity under visible light was evaluated on the degradation of sulfamethazine (SMTZ) at pH 8. The characterization of the phosphorous materials (TP) showed that incorporation of P in the lattice of TiO 2 stabilizes the anatase crystalline phase, even increasing the annealing temperature. The mesoporous P-doped materials showed higher surface area and lower average crystallite size, band gap, and particle size; besides, more intense bands attributed to O-H bond were observed by FTIR analysis compared with bare TiO 2 . The P was substitutionally incorporated in the TiO 2 lattice network as P 5+ replacing Ti 4+ to form Ti-O-P bonds and additionally present as PO 4 3-  on the TiO 2 surface. All these characteristics explain the observed superior photocatalytic activity on degradation (100%) and mineralization (32%) of SMTZ under visible radiation by TP catalysts, especially for P-doped TiO 2 1.0 wt% calcined at 450 °C (TP1.0-450). Ammonium, nitrate, and sulfate ions released during the photocatalytic degradation were quantified by ion chromatography; the nitrogen and sulfur mass balance evidenced the partial mineralization of this recalcitrant molecule.

Green synthesis of ZnO nanoparticles via complex formation by using Curcuma longa extract

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fatimah, Is, E-mail: isfatimah@uii.ac.id; Yudha, Septian P.; Mutiara, Nur Afisa Lintang

Synthesis of ZnO nanoparticles(NPs) were conducted via Zn(II) complex formation by using Curcuma longa extract as template. Curcuma longa extract has the ability to form zinc ions complex with curcumin as ligating agent. Study on synthesis was conducted by monitoring thermal degradation of the material. Successful formation of zinc oxide nanoparticles was confirmed by employing x-ray diffraction, surface area analysis and transmission electron microscopy(TEM) studies. From the XRD analysis it is denoted that ZnO in hexagonal wurtzite phase was formed and particle size was varied as varied temperature. The data are also confirmed by TEM analysis which shows the particlemore » sie at the range 20-80nm. The NPs exhibited excelent photocatalytic activity for methylene blue degradation and also significant antibacterial activity for Eschericia coli. The activity in methylene blue degradation was also confirmed from fast chemical oxygen demand (COD) reduction.« less

Green synthesis of ZnO nanoparticles via complex formation by using Curcuma longa extract

NASA Astrophysics Data System (ADS)

Fatimah, Is; Yudha, Septian P.; Mutiara, Nur Afisa Lintang

2016-02-01

Synthesis of ZnO nanoparticles(NPs) were conducted via Zn(II) complex formation by using Curcuma longa extract as template. Curcuma longa extract has the ability to form zinc ions complex with curcumin as ligating agent. Study on synthesis was conducted by monitoring thermal degradation of the material. Successful formation of zinc oxide nanoparticles was confirmed by employing x-ray diffraction, surface area analysis and transmission electron microscopy(TEM) studies. From the XRD analysis it is denoted that ZnO in hexagonal wurtzite phase was formed and particle size was varied as varied temperature. The data are also confirmed by TEM analysis which shows the particle sie at the range 20-80nm. The NPs exhibited excelent photocatalytic activity for methylene blue degradation and also significant antibacterial activity for Eschericia coli. The activity in methylene blue degradation was also confirmed from fast chemical oxygen demand (COD) reduction.

Tri-Service Thermal Flash Test Facility. Summary Report.

DTIC Science & Technology

1980-01-15

degradation of materials exposed to the radiant heating generated by a nuclear blast can very enormously. The intense radiation needed to simulate a...Photography - Motion picture photo- graphy of surface degradation would be an asset to data analysis. Although this procedure is relatively straightforward...Polyvinylchloride 68 Rubber 69 Army Systems Camouflage MIL-E-52798A over TTP-636 primer 70 Army Systems Camouflage MIL-E-52835A over TTP-636 primer 71 Army

Long Duration Sorbent Testbed

NASA Technical Reports Server (NTRS)

Howard, David F.; Knox, James C.; Long, David A.; Miller, Lee; Cmaric, Gregory; Thomas, John

2016-01-01

The Long Duration Sorbent Testbed (LDST) is a flight experiment demonstration designed to expose current and future candidate carbon dioxide removal system sorbents to an actual crewed space cabin environment to assess and compare sorption working capacity degradation resulting from long term operation. An analysis of sorbent materials returned to Earth after approximately one year of operation in the International Space Station's (ISS) Carbon Dioxide Removal Assembly (CDRA) indicated as much as a 70% loss of working capacity of the silica gel desiccant material at the extreme system inlet location, with a gradient of capacity loss down the bed. The primary science objective is to assess the degradation of potential sorbents for exploration class missions and ISS upgrades when operated in a true crewed space cabin environment. A secondary objective is to compare degradation of flight test to a ground test unit with contaminant dosing to determine applicability of ground testing.

Raman spectroscopy and capillary zone electrophoresis for the analysis of degradation processes in commercial effervescent tablets containing acetylsalicylic acid and ascorbic acid.

PubMed

Neuberger, Sabine; Jooß, Kevin; Flottmann, Dirk; Scriba, Gerhard; Neusüß, Christian

2017-02-05

In order to ensure the stability of pharmaceutical products appropriate manufacturing and storage conditions are required. In general, the degradation of active pharmaceutical ingredients (APIs) and subsequent formation of degradation products affect the pharmaceutical quality. Thus, a fast and effective detection and characterization of these substances is mandatory. Here, the applicability of Raman spectroscopy and CZE for the characterization of the degradation of effervescent tablets containing acetylsalicylic acid (ASA) and ascorbic acid (AA) was evaluated. Therefore, a degradation study was performed analyzing tablets from two different manufacturers at varying conditions (relative humidity (RH) 33%, 52% and 75% at 30°C). Raman spectroscopy combined with principal component analysis could be successfully applied for the fast and easy discrimination of non-degraded and degraded effervescent tablets after a storage period of approximately 24h (RH 52%). Nevertheless, a clear identification or quantification of APIs and degradation products within the analyzed tablets was not possible, i.a. due to missing reference materials. CZE-UV enabled the quantification of the APIs (ASA, AA) and related degradation products (salicylic acid (SA); semi-quantitative also mono- and diacetylated AA) within the complex tablet mixtures. The higher the RH, the faster the degradation of ASA and AA as well as the formation of the degradation products. Mono- and diacetylated AA are major primary degradation products of AA for the applied effervescent tablets. A significant degradation of the APIs was detected earlier by CZE (6-12h, RH 52%) than by Raman spectroscopy. Summarized, Raman spectroscopy is well-suited as quick test to detect degradation of these tablets and CZE can be utilized for further detailed characterization and quantification of specific APIs and related degradation products. Copyright © 2016 Elsevier B.V. All rights reserved.

Material State Awareness for Composites Part II: Precursor Damage Analysis and Quantification of Degraded Material Properties Using Quantitative Ultrasonic Image Correlation (QUIC)

PubMed Central

Patra, Subir; Banerjee, Sourav

2017-01-01

Material state awareness of composites using conventional Nondestructive Evaluation (NDE) method is limited by finding the size and the locations of the cracks and the delamination in a composite structure. To aid the progressive failure models using the slow growth criteria, the awareness of the precursor damage state and quantification of the degraded material properties is necessary, which is challenging using the current NDE methods. To quantify the material state, a new offline NDE method is reported herein. The new method named Quantitative Ultrasonic Image Correlation (QUIC) is devised, where the concept of microcontinuum mechanics is hybrid with the experimentally measured Ultrasonic wave parameters. This unique combination resulted in a parameter called Nonlocal Damage Entropy for the precursor awareness. High frequency (more than 25 MHz) scanning acoustic microscopy is employed for the proposed QUIC. Eight woven carbon-fiber-reinforced-plastic composite specimens were tested under fatigue up to 70% of their remaining useful life. During the first 30% of the life, the proposed nonlocal damage entropy is plotted to demonstrate the degradation of the material properties via awareness of the precursor damage state. Visual proofs for the precursor damage states are provided with the digital images obtained from the micro-optical microscopy, the scanning acoustic microscopy and the scanning electron microscopy. PMID:29258256

In Vitro Biodegradation of Hepatotoxic Indospicine in Indigofera spicata and Its Degradation Derivatives by Camel Foregut and Cattle Rumen Fluids.

PubMed

Tan, Eddie T T; Al Jassim, Rafat; D'Arcy, Bruce R; Fletcher, Mary T

2017-08-30

The known accumulation of the hepatotoxin indospicine in tissues of camels and cattle grazing Indigofera pasture plants is unusual in that free amino acids would normally be expected to be degraded during the fermentation processes in these foregut fermenters. In this study, in vitro experiments were carried out to examine the degradability of indospicine of Indigofera spicata by camel and cattle foregut microbiota. In the first experiment, a 48 h in vitro incubation was carried out using foregut fluid samples that were collected from 15 feral camels and also a fistulated cow. Degradability of indospicine ranged between 97% and 99%, with the higher value of 99% for camels. A pooled sample of foregut fluids from three camels that were on a roughage diet was used in a second experiment to examine the time-dependent degradation of indospicine present in the plant materials. Results indicated that camels' foregut fluids have the ability to biodegrade ∼99% of the indospicine in I. spicata within 48 h of incubation and produced 2-aminopimelamic acid and 2-aminopimelic acid. The time-dependent degradation analysis showed rapid indospicine degradation (65 nmol/h) during the first 8-18 h of incubation followed by a slower degradation rate (12 nmol/h) between 18 and 48 h. Indospicine degradation products were also degraded toward the end of the experiment. The results of these in vitro degradation studies suggest that dietary indospicine may undergo extensive degradation in the foregut of the camel, resulting in trace levels after 48 h. The retention time for plant material in the camel foregut varies depending on feed quality, and the results of this study together with the observed accumulation of indospicine in camel tissues suggest that, although indospicine can be degraded by foregut fermentation, this degradation is not complete before the passage of the digesta into the intestine.

Degradable and porous Fe-Mn-C alloy for biomaterials candidate

NASA Astrophysics Data System (ADS)

Pratesa, Yudha; Harjanto, Sri; Larasati, Almira; Suharno, Bambang; Ariati, Myrna

2018-02-01

Nowadays, degradable implants attract attention to be developed because it can improve the quality of life of patients. The degradable implant is expected to degrade easily in the body until the bone healing process already achieved. However, there is limited material that could be used as a degradable implant, polymer, magnesium, and iron. In the previous study, Fe-Mn-C alloys had succesfully produced austenitic phase. However, the weakness of the alloy is degradation rate of materials was considered below the expectation. This study aimed to produce porous Fe-Mn-C materials to improve degradation rate and reduce the density of alloy without losing it non-magnetic properties. Potassium carbonate (K2CO3) were chosen as filler material to produce foam structure by sintering and dissolution process. Multisteps sintering process under argon gas environment was performed to generate austenite phase. The product showed an increment of the degradation rate of the foamed Fe-Mn-C alloy compared with the solid Fe-Mn-C alloy without losing the Austenitic Structure

Effects of the restoration mortar on chalk stone buildings

NASA Astrophysics Data System (ADS)

Ion, R. M.; Teodorescu, S.; Ştirbescu, R. M.; Dulamă, I. D.; Şuică-Bunghez, I. R.; Bucurică, I. A.; Fierăscu, R. C.; Fierscu, I.; Ion, M. L.

2016-06-01

The monument buildings as components of cultural heritage are exposed to degradation of surfaces and chemical and mechanical degradation, often associated to soiling and irreversible deterioration of the building. In many conservative and restorative works, a cement-based mortar was used without knowing all the adverse effects of this material on the building. This paper deals with the study of the effects of natural cement used in restorative works in the particular case of the Basarabi-Murfatlar Churches Ensemble. Cement-based materials exposed to sulfate present in the chalk stone - gypsum (CaSO4.2H2O), can induce signs of deterioration, due to ettringite ([Ca3Al (OH)612H2O]2(SO4)32H2O) or thaumasite (Ca3[Si(OH)612H2O](CO3)SO4) formation. These phases contribute to strain within the material, inducing expansion, strength loss, spalling and severe degradation. Several combined techniques (XRD, EDXRF, ICP-AES, SEM, EDS, sulphates content, FT-IR and Raman analysis were carried out to put into evidence the effects of them on the building walls.

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

DOEpatents

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

2012-03-20

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.

Building and degradation of secondary cell walls: are there common patterns of lamellar assembly of cellulose microfibrils and cell wall delamination?

PubMed

De Micco, Veronica; Ruel, Katia; Joseleau, Jean-Paul; Aronne, Giovanna

2010-08-01

During cell wall formation and degradation, it is possible to detect cellulose microfibrils assembled into thicker and thinner lamellar structures, respectively, following inverse parallel patterns. The aim of this study was to analyse such patterns of microfibril aggregation and cell wall delamination. The thickness of microfibrils and lamellae was measured on digital images of both growing and degrading cell walls viewed by means of transmission electron microscopy. To objectively detect, measure and classify microfibrils and lamellae into thickness classes, a method based on the application of computerized image analysis combined with graphical and statistical methods was developed. The method allowed common classes of microfibrils and lamellae in cell walls to be identified from different origins. During both the formation and degradation of cell walls, a preferential formation of structures with specific thickness was evidenced. The results obtained with the developed method allowed objective analysis of patterns of microfibril aggregation and evidenced a trend of doubling/halving lamellar structures, during cell wall formation/degradation in materials from different origin and which have undergone different treatments.

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid

NASA Astrophysics Data System (ADS)

Yusof, F. A. M.; Hashim, A. S.; Tajudin, Z.

2017-12-01

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid materials was investigated by thermogravimetric analysis (TGA). Model-free iso-conversion Flynn-Wall-Ozawa (FWO) and Coats-Redfern-modified (CRm) were chosen to evaluate the activation energy of the kenaf (KF) and kenaf/sol-gel silica (KFS) at heating rates (β) of 10, 20, 30 and 40 °C/min. The results shows that an apparent activation energy was increased for the kenaf/sol-gel silica hybrid (211.59 kJ/mol for FWO and 191.55 kJ/mol for CRm) as compared to kenaf fiber (202.84 kJ/mol for FWO and 186.20 kJ/mol for CRm). Other parameters such as integral procedure decomposition temperature (IPDT), final residual weight (Rf), temperature of maximum degradation rate (Tmax) and residual at maximum temperature (RTmax) were obtained from TGA curves, additionally confirmed the thermal stability of the kenaf/sol-gel silica hybrid. These activation energy values and other findings developed the simplified approach in order to understand the thermal stability and degradation kinetics behavior of kenaf/sol-gel silica hybrid materials.

Microbial degradation of low-density polyethylene (LDPE) by Aspergillus clavatus strain JASK1 isolated from landfill soil.

PubMed

Gajendiran, Anudurga; Krishnamoorthy, Sharmila; Abraham, Jayanthi

2016-06-01

Polythene and plastic waste are found to accumulate in the environment, posing a major ecological threat. They are found to be considered non-degradable, once it enters the environment it has been found to remain there indefinitely. However, significant attention has been placed on biodegradable polymer, identification of microbes with degradative potential on plastic material. The aim of the present investigation was to biodegrade low-density polyethylene (LDPE) using potential fungi isolated from landfill soil. Based on 18S rRNA analyses the isolated strain was identified as Aspergillus clavatus. LDPE degradation by A. clavatus was monitored for 90 days of incubation in aqueous medium. The degradation was confirmed by changes in polyethylene weight, CO 2 evolution by Strum test, infrared spectra and morphological changes by SEM and AFM analysis.

Material Life Cycle Analysis for the Reduction of Waste Generation at Military Installations

DTIC Science & Technology

2017-02-01

avoid the fossil fuel consumption and land degradation associated with transporting those materials to a landfill. Eco-LCA can also be used to calcu...Recycling Program RMRC Recycled Materials Resource Center SAR Same As Report SDD Sustainable Design and Development SF Standard Form SME Subject...Agency WWII World War II REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information

A General Accelerated Degradation Model Based on the Wiener Process.

PubMed

Liu, Le; Li, Xiaoyang; Sun, Fuqiang; Wang, Ning

2016-12-06

Accelerated degradation testing (ADT) is an efficient tool to conduct material service reliability and safety evaluations by analyzing performance degradation data. Traditional stochastic process models are mainly for linear or linearization degradation paths. However, those methods are not applicable for the situations where the degradation processes cannot be linearized. Hence, in this paper, a general ADT model based on the Wiener process is proposed to solve the problem for accelerated degradation data analysis. The general model can consider the unit-to-unit variation and temporal variation of the degradation process, and is suitable for both linear and nonlinear ADT analyses with single or multiple acceleration variables. The statistical inference is given to estimate the unknown parameters in both constant stress and step stress ADT. The simulation example and two real applications demonstrate that the proposed method can yield reliable lifetime evaluation results compared with the existing linear and time-scale transformation Wiener processes in both linear and nonlinear ADT analyses.

Rapid estimation of glucosinolate thermal degradation rate constants in leaves of Chinese kale and broccoli (Brassica oleracea) in two seasons.

PubMed

Hennig, Kristin; Verkerk, Ruud; Bonnema, Guusje; Dekker, Matthijs

2012-08-15

Kinetic modeling was used as a tool to quantitatively estimate glucosinolate thermal degradation rate constants. Literature shows that thermal degradation rates differ in different vegetables. Well-characterized plant material, leaves of broccoli and Chinese kale plants grown in two seasons, was used in the study. It was shown that a first-order reaction is appropriate to model glucosinolate degradation independent from the season. No difference in degradation rate constants of structurally identical glucosinolates was found between broccoli and Chinese kale leaves when grown in the same season. However, glucosinolate degradation rate constants were highly affected by the season (20-80% increase in spring compared to autumn). These results suggest that differences in glucosinolate degradation rate constants can be due to variation in environmental as well as genetic factors. Furthermore, a methodology to estimate rate constants rapidly is provided to enable the analysis of high sample numbers for future studies.

A General Accelerated Degradation Model Based on the Wiener Process

PubMed Central

Liu, Le; Li, Xiaoyang; Sun, Fuqiang; Wang, Ning

2016-01-01

Accelerated degradation testing (ADT) is an efficient tool to conduct material service reliability and safety evaluations by analyzing performance degradation data. Traditional stochastic process models are mainly for linear or linearization degradation paths. However, those methods are not applicable for the situations where the degradation processes cannot be linearized. Hence, in this paper, a general ADT model based on the Wiener process is proposed to solve the problem for accelerated degradation data analysis. The general model can consider the unit-to-unit variation and temporal variation of the degradation process, and is suitable for both linear and nonlinear ADT analyses with single or multiple acceleration variables. The statistical inference is given to estimate the unknown parameters in both constant stress and step stress ADT. The simulation example and two real applications demonstrate that the proposed method can yield reliable lifetime evaluation results compared with the existing linear and time-scale transformation Wiener processes in both linear and nonlinear ADT analyses. PMID:28774107

Application of Ni-Oxide@TiO2 Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors

PubMed Central

Lee, Seungwon; Lee, Jisuk; Nam, Kyusuk; Shin, Weon Gyu; Sohn, Youngku

2016-01-01

Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO2 core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue) degradation under ultraviolet (UV) and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO2 overlayer coating. PMID:28774145

Mitigation of Methane and Odor using a Pilot-Scale Engineered Biocover at a Landfill, South Korea

NASA Astrophysics Data System (ADS)

Bomin, K.; O, G. C.; Ryu, H. W.; Jeon, J. M.; Cho, K. S.

2016-12-01

Landfill is an important anthropogenic source of methane (CH4) and odorous gases. In South Korea, 37% (0.5 Tg/y) of annual anthropogenic CH4 emissions come from landfills, which represent the third largest source of anthropogenic CH4 emissions. Moreover, civil complaints on landfill odor have been gradually increased. Biocovers have been demonstrated as promising solutions to mitigate CH4 and odors from landfills. The pilot-scale biocover (10 m in length x 5 m in width x 1 m in depth) was constructed at a landfill, Gwangyang, South Korea. The mixture of soil and perlite was used as packing materials, and EG microbial agent was used as an inoculum source. Methane removal efficiencies were 21% 72% from Feburary to May. Based on the dilution-to-threshold ratios derived by the air dilution sensory test, the removal efficiencies for complex odor were ranged from 95% to 99%. The packing materials of biocover were sampled from each of the following depth intervals: 0-15 cm, 15-30 cm, and 30-50 cm, and CH4 and DMS degradation rates were measured in serum bottles experiment. CH4 and DMS average degradation rates were the fastest in the 15-30 cm depth. Average degradation rates of CH4 and DMS in the 15-30 cm depth were 208±2.68 and 82±3.04 μg·g dry soil-1·h-1, respectively. Specific degradation rate were calculated excluding the lag time. CH4 specific degradation rate was the fastest in the 0-15 cm depth (329±14.45 μg·g dry soil-1·h-1), while DMS specific degradation rate was the fastest in the 30-50 cm depth (106±6.93 μg·g dry soil-1·h-1). The filling materials of biocover were sampled during winter, spring and summer. And three samples were examined bacterial communities by 16S rRNA pyrosequencing analysis. In order to clarify the relationship between the community structures and CH4/odor concentration, network analysis using extended local similarity analysis (eLSA) was also conducted. According to a phylogenic analysis, Methylobacter (40.4 42.1%) and Flavobacterium (20.2 38.2%) were the most prevalent species in the pilot-scale biocover. Methylobacter (Methanotrophics of Type I) are responsible for methane oxidation and can be identified in the biocover.

Mapping the polysaccharide degradation potential of Aspergillus niger

PubMed Central

2012-01-01

Background The degradation of plant materials by enzymes is an industry of increasing importance. For sustainable production of second generation biofuels and other products of industrial biotechnology, efficient degradation of non-edible plant polysaccharides such as hemicellulose is required. For each type of hemicellulose, a complex mixture of enzymes is required for complete conversion to fermentable monosaccharides. In plant-biomass degrading fungi, these enzymes are regulated and released by complex regulatory structures. In this study, we present a methodology for evaluating the potential of a given fungus for polysaccharide degradation. Results Through the compilation of information from 203 articles, we have systematized knowledge on the structure and degradation of 16 major types of plant polysaccharides to form a graphical overview. As a case example, we have combined this with a list of 188 genes coding for carbohydrate-active enzymes from Aspergillus niger, thus forming an analysis framework, which can be queried. Combination of this information network with gene expression analysis on mono- and polysaccharide substrates has allowed elucidation of concerted gene expression from this organism. One such example is the identification of a full set of extracellular polysaccharide-acting genes for the degradation of oat spelt xylan. Conclusions The mapping of plant polysaccharide structures along with the corresponding enzymatic activities is a powerful framework for expression analysis of carbohydrate-active enzymes. Applying this network-based approach, we provide the first genome-scale characterization of all genes coding for carbohydrate-active enzymes identified in A. niger. PMID:22799883

Mapping the polysaccharide degradation potential of Aspergillus niger.

PubMed

Andersen, Mikael R; Giese, Malene; de Vries, Ronald P; Nielsen, Jens

2012-07-16

The degradation of plant materials by enzymes is an industry of increasing importance. For sustainable production of second generation biofuels and other products of industrial biotechnology, efficient degradation of non-edible plant polysaccharides such as hemicellulose is required. For each type of hemicellulose, a complex mixture of enzymes is required for complete conversion to fermentable monosaccharides. In plant-biomass degrading fungi, these enzymes are regulated and released by complex regulatory structures. In this study, we present a methodology for evaluating the potential of a given fungus for polysaccharide degradation. Through the compilation of information from 203 articles, we have systematized knowledge on the structure and degradation of 16 major types of plant polysaccharides to form a graphical overview. As a case example, we have combined this with a list of 188 genes coding for carbohydrate-active enzymes from Aspergillus niger, thus forming an analysis framework, which can be queried. Combination of this information network with gene expression analysis on mono- and polysaccharide substrates has allowed elucidation of concerted gene expression from this organism. One such example is the identification of a full set of extracellular polysaccharide-acting genes for the degradation of oat spelt xylan. The mapping of plant polysaccharide structures along with the corresponding enzymatic activities is a powerful framework for expression analysis of carbohydrate-active enzymes. Applying this network-based approach, we provide the first genome-scale characterization of all genes coding for carbohydrate-active enzymes identified in A. niger.

About microcracking due to leaching in cementitious composites: X-ray microtomography description and numerical approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rougelot, Thomas; Burlion, Nicolas, E-mail: nicolas.burlion@polytech-lille.f; Bernard, Dominique

2010-02-15

Chemical shock of cement based materials leads to significant degradation of their physical properties. A typical scenario is a calcium leaching due to water (water with very low pH compared with that of pore fluid). The main objective of this paper is to evaluate the evolution of microstructure induced by leaching of a cementitious composite using synchrotron X-ray micro tomography, mainly from an experimental point of view. In this particular case, it was possible to identify cracking induced by leaching. After a description of the degradation mechanism and the X-ray synchrotron microtomographic analysis, numerical simulations are performed in order tomore » show that cracking is induced by an initial pre-stressing of the composite, coupled with decalcification shrinkage and dramatic decrease in tensile strength during leaching. X-ray microtomography analysis allowed to make evidence of an induced microcracking in cementitious material submitted to leaching.« less

Oxidation Kinetics and Strength Degradation of Carbon Fibers in a Cracked Ceramic Matrix Composite

NASA Technical Reports Server (NTRS)

Halbig, Michael C.

2003-01-01

Experimental results and oxidation modeling will be presented to discuss carbon fiber susceptibility to oxidation, the oxidation kinetics regimes and composite strength degradation and failure due to oxidation. Thermogravimetric Analysis (TGA) was used to study the oxidation rates of carbon fiber and of a pyro-carbon interphase. The analysis was used to separately obtain activation energies for the carbon constituents within a C/SiC composite. TGA was also conducted on C/SiC composite material to study carbon oxidation and crack closure as a function of temperature. In order to more closely match applications conditions C/SiC tensile coupons were also tested under stressed oxidation conditions. The stressed oxidation tests show that C/SiC is much more susceptible to oxidation when the material is under an applied load where the cracks are open and allow for oxygen ingress. The results help correlate carbon oxidation with composite strength reduction and failure.

Wood products : thermal degradation and fire

Treesearch

R.H. White; M.A. Dietenberger

2001-01-01

Wood is a thermally degradable and combustible material. Applications range from a biomass providing useful energy to a building material with unique properties. Wood products can contribute to unwanted fires and be destroyed as well. Minor amounts of thermal degradation adversely affect structural properties. Therefore, knowledge of the thermal degradation and fire...

Thrombus organization and healing in an experimental aneurysm model. Part II. The effect of various types of bioactive bioabsorbable polymeric coils.

PubMed

Yuki, Ichiro; Lee, Daniel; Murayama, Yuichi; Chiang, Alexander; Vinters, Harry V; Nismmura, Ichiro; Wang, Chiachien J; Ishii, Akira; Wu, Benjamin M; Viñuela, Fernando

2007-07-01

Bioabsorbable polymeric material coils are being used in the endovascular treatment of aneurysms to achieve better thrombus organization than is possible using bare platinum coils. We used immunohistochemical and molecular biological analysis techniques in experimental aneurysms implanted with three different bioabsorbable polymer coils and platinum coils. The degradation kinetics of nine polymer candidates for further analysis were first analyzed in vitro, and three materials with different degradation rates were selected. Seventy-four aneurysms were created in 37 swine using the venous pouch technique. The aneurysms were surgically implanted with one of the materials as follows (time points = 3, 7, and 14 days): Group 1, Guglielmi detachable coils (platinum); Group 2, Polysorb (90:10 polyglycolic acid [PGA]/polylactic acid); Group 3, Maxon (PGA/trimethylene carbonate); and Group 4, poly-l-lactic acid. Histological, immunohistochemical, and cDNA microarray analyses were performed on tissue specimens. Groups 1 and 4 showed minimal inflammatory response adjacent to the coil mass. In Group 2, Polysorb elicited a unique, firm granulation tissue that accelerated intraaneurysmal thrombus organization. In Group 3 intermediate inflammatory reactions were seen. Microarray analysis with Expression Analysis Sytematic Explorer software showed functional-cluster-gene activation to be increased at Day 7, preceding the histologic manifestation of polymer-induced granulation tissue at Day 14. A profile of expression changes in cytokine-related and extracellular membrane-related genes was compiled. Degradation speed was not the only factor determining the strength of the biological response. Polysorb induced an early, unique granulation tissue that conferred greater mechanical strength to the intraaneurysmal coilthrombus complex. Enhancing the formation of this polymer-induced granulation tissue may provide a new direction for improving long-term anatomical outcomes in cases involving aneurysms embolized with detachable coils.

Blood compatibility of magnesium and its alloys.

PubMed

Feyerabend, Frank; Wendel, Hans-Peter; Mihailova, Boriana; Heidrich, Stefanie; Agha, Nezha Ahmad; Bismayer, Ulrich; Willumeit-Römer, Regine

2015-10-01

Blood compatibility analysis in the field of biomaterials is a highly controversial topic. Especially for degradable materials like magnesium and its alloys no established test methods are available. The purpose of this study was to apply advanced test methodology for the analysis of degrading materials to get a mechanistic insight into the corrosion process in contact with human blood and plasma. Pure magnesium and two magnesium alloys were analysed in a modified Chandler-Loop setup. Standard clinical parameters were determined, and a thorough analysis of the resulting implant surface chemistry was performed. The contact of the materials to blood evoked an accelerated inflammatory and cell-induced osteoconductive reaction. Corrosion products formed indicate a more realistic, in vivo like situation. The active regulation of corrosion mechanisms of magnesium alloys by different cell types should be more in the focus of research to bridge the gap between in vitro and in vivo observations and to understand the mechanism of action. This in turn could lead to a better acceptance of these materials for implant applications. The presented study deals with the first mechanistic insights during whole human blood contact and its influence on a degrading magnesium-based biomaterial. The combination of clinical parameters and corrosion layer analysis has been performed for the first time. It could be of interest due to the intended use of magnesium-based stents and for orthopaedic applications for clinical applications. An interest for the readers of Acta Biomaterialia may be given, as one of the first clinically approved magnesium-based devices is a wound-closure device, which is in direct contact with blood. Moreover, for orthopaedic applications also blood contact is of high interest. Although this is not the focus of the manuscript, it could help to rise awareness for potential future applications. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ground-based simulation of LEO environment: Investigations of a select LDEF material: FEP Teflon (trademark)

NASA Technical Reports Server (NTRS)

Cross, Jon B.; Koontz, Steven L.

1993-01-01

The Long Duration Exposure Facility (LDEF) has produced a wealth of data on materials degradation in the low earth orbit (LEO) space environment and has conclusively shown that surface chemistry (as opposed to surface physics-sputtering) is the key to understanding and predicting the degradation of materials in the LEO environment. It is also clear that materials degradation and spacecraft contamination are closely linked and that the fundamental mechanisms responsible for this linking are in general not well understood especially in the area of synergistic effects. The study of the fundamental mechanisms underlying materials degradation in LEO is hampered by the fact that the degradation process itself is not observed during the actual exposure to the environment. Rather the aftermath of the degradation process is studied, i.e., the material that remains after exposure is observed and mechanisms are proposed to explain the observed results. The EOIM-3 flight experiment is an attempt to bring sophisticated diagnostic equipment into the space environment and monitor the degradation process in real time through the use of mass spectrometry. More experiments of this nature which would include surface sensitive diagnostics (Auger and photoelectron spectroscopes) are needed to truly unravel the basic chemical mechanisms involved in the materials degradation process. Since these in-space capabilities will most likely not be available in the near future, ground-based LEO simulation facilities employing sophisticated diagnostics are needed to further advance the basic understanding of the materials degradation mechanisms. The LEO simulation facility developed at Los Alamos National Laboratory has been used to investigate the atomic oxygen/vacuum ultraviolet (AO/VUV) enhanced degradation of FEP Teflon. The results show that photo-ejection of polymer fragments occur at elevated temperature (200 C), that VUV synergistic rare gas sputtering of polymer fragments occur even at 25 C, and that combined OA/VUV interaction produces a wide variety of gas phase reaction products.

Numerical Modelling of Connections Between Stones in Foundations of Historical Buildings

NASA Astrophysics Data System (ADS)

Przewlocki, Jaroslaw; Zielinska, Monika; Grebowski, Karol

2017-12-01

The aim of this paper is to analyse the behaviour of old building foundations composed of stones (the main load-bearing elements) and mortar, based on numerical analysis. Some basic aspects of historical foundations are briefly discussed, with an emphasis on their development, techniques, and material. The behaviour of a foundation subjected to the loads transmitted from the upper parts of the structure is described using the finite element method (FEM). The main problems in analysing the foundations of historical buildings are determining the characteristics of the materials and the degree of degradation of the mortar, which is the weakest part of the foundation. Mortar is graded using the damaged-plastic model. In this model, exceeding the bearing capacity occurs due to the degradation of materials. The damaged-plastic model is the most accurate model describing the work and properties of mortar because it shows exactly what happens with this material throughout its total load history. For a uniformly loaded fragment of the foundation, both stresses and strains were analysed. The results of the analysis presented in this paper contribute to further research in the field of understanding both behaviour and modelling in historical buildings’ foundations.

Drug Release Kinetics and Transport Mechanisms of Non-degradable and Degradable Polymeric Delivery Systems

PubMed Central

Fu, Yao; Kao, Weiyuan John

2010-01-01

Importance of the field The advancement in material design and engineering has led to the rapid development of novel materials with increasing complexity and functions. Both non-degradable and degradable polymers have found wide applications in the controlled delivery field. Studies on drug release kinetics provide important information into the function of material systems. To elucidate the detailed transport mechanism and the structure-function relationship of a material system, it is critical to bridge the gap between the macroscopic data and the transport behavior at the molecular level. Areas covered in this review The structure and function information of selected non-degradable and degradable polymers have been collected and summarized from literatures published after 1990s. The release kinetics of selected drug compounds from various material systems will be discussed in case studies. Recent progresses in the mathematical models based on different transport mechanisms will be highlighted. What the reader will gain This article aims to provide an overview of structure-function relationships of selected non-degradable and degradable polymers as drug delivery matrices. Take home message Understanding the structure-function relationship of the material system is key to the successful design of a delivery system for a particular application. Moreover, developing complex polymeric matrices requires more robust mathematical models to elucidate the solute transport mechanisms. PMID:20331353

Insights into the Mechanism and Kinetics of Thermo-Oxidative Degradation of HFPE High Performance Polymer.

PubMed

Kunnikuruvan, Sooraj; Parandekar, Priya V; Prakash, Om; Tsotsis, Thomas K; Nair, Nisanth N

2016-06-02

The growing requisite for materials having high thermo-oxidative stability makes the design and development of high performance materials an active area of research. Fluorination of the polymer backbone is a widely applied strategy to improve various properties of the polymer, most importantly the thermo-oxidative stability. Many of these fluorinated polymers are known to have thermo-oxidative stability up to 700 K. However, for space and aerospace applications, it is important to improve its thermo-oxidative stability beyond 700 K. Molecular-level details of the thermo-oxidative degradation of such polymers can provide vital information to improve the polymer. In this spirit, we have applied quantum mechanical and microkinetic analysis to scrutinize the mechanism and kinetics of the thermo-oxidative degradation of a fluorinated polymer with phenylethenyl end-cap, HFPE. This study gives an insight into the thermo-oxidative degradation of HFPE and explains most of the experimental observations on the thermo-oxidative degradation of this polymer. Thermolysis of C-CF3 bond in the dianhydride component (6FDA) of HFPE is found to be the rate-determining step of the degradation. Reaction pathways that are responsible for the experimentally observed weight loss of the polymer is also scrutinized. On the basis of these results, we propose a modification of HFPE polymer to improve its thermo-oxidative stability.

Microstructural analysis of 800H steel exposed at test operation in HTHL by using FIB-SEM and HRTEM techniques

NASA Astrophysics Data System (ADS)

Marušáková, Daniela; Bublíková, Petra; Berka, Jan; Vávrovcová, Zuzana; Burda, Jaroslav

2017-09-01

To understand the degradation process of metal materials which are used in power engineering, appropriate evaluation procedure is necessary to ensure. In that order, the degradation of alloy 800H during the first period of test operation in High Temperature Helium Loop (HTHL) was tested. Experiment was carried out in atmosphere of pure technical helium with purity 4.6 containing only residual concentration of moisture up to 300 vppm. Parameters during the operation test were not constant, process was interrupted several times. The maximum temperature on specimens during this period was 750 °C, average temperature was 460 °C, gas pressure ranged from 3 to 6 MPa and gas flow from 3 to 9 gs-1. Total duration of the test was 264 h. After the exposure the degradation of specimens was investigated by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Using the technique of Focused Ion Beam (FIB) integrated within SEM the transparent samples with quality surface parameters were obtained for TEM analysis. FIB technique in combination with High Resolution TEM ensured the guaranteed methodology of exposed sample preparation and precise description of changes in this kind of material.

Synthesis and characterization of ferrite-semiconductor nano composite for photocatalytic degradation of aqueous nitrobenzene solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Modi, K. B.; Kathad, C. R.; Raval, P. Y.

2016-05-06

Nanoparticles of semiconductor TiO{sub 2}, zinc ferrite (ZnFe{sub 2}O{sub 4}) and ZnFe{sub 2}O{sub 4}-TiO{sub 2} composite, were synthesized by auto combustion route. Subsequent characterization of synthesized photocatalysts was carried out by X-ray powder diffractometry, transmission electron microscopy, UV-Vis-Diffuse Reflectance Spectroscopy to study the structural and textural properties. The specific surface area, pore diameter and pore volume of synthesized materials were investigated by N{sub 2} adsorption analysis while the presence of TiO{sub 2} in the composite material was verified by infrared spectral analysis. The photocatalytic activity of synthesized photocatalysts was evaluated by degradation of nitrobenzene (NB) in aqueous medium under irradiationmore » of ultraviolet light. The result revealed that 77, 73 and 70% of NB was degraded using TiO{sub 2}, ZnFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4}-TiO{sub 2} photocatalysts after 4h in the presence of UV irradiation. The composite photocatalyst was found easy to separate from the treated solution.« less

Hygrothermal behavior of polybenzimidazole

DOE PAGES

Liu, Peng; Mullins, Michael; Bremner, Tim; ...

2016-04-11

Poly[2,2’-(m-phenylene)-5,5’-bibenzimidazole] (PBI) is used in extremely high temperature harsh environment applications. It is a unique engineering material that is formed into parts by powder-sintering at temperatures as high as 500 °C. Recently, ever increasing demands for high temperature polymers have led to significant interest in PBI such that engineering guidelines could be established for its application in high temperature and highly humid environments. The goal of this work was to understand the material science of PBI in hot-wet environments at temperatures up to 288 °C. Thermal gravimetric analysis and mass spectrometry were employed to identify the degraded volatile products. Themore » molecular scale damping behavior of PBI was probed using dynamic mechanical analysis. The changes in tensile properties and fracture toughness due to environmental exposure were also characterized. Upon heating above 250 °C, moisture-containing PBI exhibits obvious molecular structure change. Evidence of crosslinking and degradation is observed. With 288 °C hot water treatment severe degradation of PBI is observed. As a result, fundamental structure-property relationships of PBI affected by these higher temperature, high moisture content environments are discussed.« less

Isotopic analysis for degradation diagnosis of calcite matrix in mortar.

PubMed

Dotsika, E; Psomiadis, D; Poutoukis, D; Raco, B; Gamaletsos, P

2009-12-01

Mortar that was used in building as well as in conservation and restoration works of wall paintings have been analysed isotopically (delta(13)C and delta(18)O) in order to evaluate the setting environments and secondary processes, to distinguish the structural components used and to determine the exact causes that incurred the degradation phenomena. The material undergoes weathering and decay on a large proportion of its surface and in depth, due to the infiltration of water through the structural blocks. Mineralogical analysis indicated signs of sulphation and dissolution/recrystallisation processes taking place on the material, whereas stable isotopes provided information relative to the origin of the CO(2) and water during calcite formation and degradation processes. Isotopic change of the initial delta(13)C and delta(18)O in carbonate matrix was caused by alteration of the primary source of CO(2) and H(2)O in mortar over time, particularly by recrystallisation of calcite with porewater, evaporated or re-condensed water, and CO(2) from various sources of atmospheric and biogenic origin. Human influence (surface treatment) and biological growth (e.g. fungus) are major exogenic processes which may alter delta(18)O and delta(13)C in lime mortar.

Skylab D024 thermal control coatings and polymeric films experiment

NASA Technical Reports Server (NTRS)

Lehn, William L.; Hurley, Charles J.

1992-01-01

The Skylab D024 Thermal Control Coatings and Polymeric Films Experiment was designed to determine the effects of the external Skylab space environment on the performance and properties of a wide variety of selected thermal control coatings and polymeric films. Three duplicate sets of thermal control coatings and polymeric films were exposed to the Skylab space environment for varying periods of time during the mission. The specimens were retrieved by the astronauts during extravehicular activities (EVA) and placed in hermetically sealed return containers, recovered, and returned to the Wright Laboratory/Materials Laboratory/WPAFB, Ohio for analysis and evaluation. Postflight analysis of the three sets of recovered thermal control coatings indicated that measured changes in specimen thermo-optical properties were due to a combination of excessive contamination and solar degradation of the contaminant layer. The degree of degradation experienced over-rode, obscured, and compromised the measurement of the degradation of the substrate coatings themselves. Results of the analysis of the effects of exposure on the polymeric films and the contamination observed are also presented. The D024 results were used in the design of the LDEF M0003-5 Thermal Control Materials Experiment. The results are presented here to call to the attention of the many other LDEF experimenters the wealth of directly related, low earth orbit, space environmental exposure data that is available from the ten or more separate experiments that were conducted during the Skylab mission. Results of these experiments offer data on the results of low altitude space exposure on materials recovered from space with exposure longer than typical STS experiments for comparison with the LDEF results.

Identification of three homologous latex-clearing protein (lcp) genes from the genome of Streptomyces sp. strain CFMR 7.

PubMed

Nanthini, Jayaram; Ong, Su Yean; Sudesh, Kumar

2017-09-10

Rubber materials have greatly contributed to human civilization. However, being a polymeric material does not decompose easily, it has caused huge environmental problems. On the other hand, only few bacteria are known to degrade rubber, with studies pertaining them being intensively focusing on the mechanism involved in microbial rubber degradation. The Streptomyces sp. strain CFMR 7, which was previously confirmed to possess rubber-degrading ability, was subjected to whole genome sequencing using the single molecule sequencing technology of the PacBio® RS II system. The genome was further analyzed and compared with previously reported rubber-degrading bacteria in order to identify the potential genes involved in rubber degradation. This led to the interesting discovery of three homologues of latex-clearing protein (Lcp) on the chromosome of this strain, which are probably responsible for rubber degrading activities. Genes encoding oxidoreductase α-subunit (oxiA) and oxidoreductase β-subunit (oxiB) were also found downstream of two lcp genes which are located adjacent to each other. In silico analysis reveals genes that have been identified to be involved in the microbial degradation of rubber in the Streptomyces sp. strain CFMR 7. This is the first whole genome sequence of a clear-zone-forming natural rubber- degrading Streptomyces sp., which harbours three Lcp homologous genes with the presence of oxiA and oxiB genes compared to the previously reported Gordonia polyisoprenivorans strain VH2 (with two Lcp homologous genes) and Nocardia nova SH22a (with only one Lcp gene). Copyright © 2017 Elsevier B.V. All rights reserved.

A distributed real-time model of degradation in a solid oxide fuel cell, part I: Model characterization

NASA Astrophysics Data System (ADS)

Zaccaria, V.; Tucker, D.; Traverso, A.

2016-04-01

Despite the high efficiency and flexibility of fuel cells, which make them an attractive technology for the future energy generation, their economic competitiveness is still penalized by their short lifetime, due to multiple degradation phenomena. As a matter of fact, electrochemical performance of solid oxide fuel cells (SOFCs) is reduced because of different degradation mechanisms, which depend on operating conditions, fuel and air contaminants, impurities in materials, and others. In this work, a real-time, one dimensional (1D) model of a SOFC is used to simulate the effects of voltage degradation in the cell. Different mechanisms are summarized in a simple empirical expression that relates degradation rate to cell operating parameters (current density, fuel utilization and temperature), on a localized basis. Profile distributions of different variables during cell degradation are analyzed. In particular, the effect of degradation on current density, temperature, and total resistance of the cell are investigated. An analysis of localized degradation effects shows how different parts of the cell degrade at a different time rate, and how the various profiles are redistributed along the cell as consequence of different degradation rates.

Development of a Predictive Corrosion Model Using Locality-Specific Corrosion Indices

DTIC Science & Technology

2017-09-12

6 3.2.1 Statistical data analysis methods ...6 3.2.2 Algorithm development method ...components, and method ) were compiled into an executable program that uses mathematical models of materials degradation, and statistical calcula- tions

How-To-Do-It: Glyphosate: Herbicidal Effects, Mode of Action and Degradation in Soil.

ERIC Educational Resources Information Center

Kafarski, Pawel; And Others

1988-01-01

Describes the usefulness of glyphosate for a demonstration of its herbicidal properties. Includes a list of the materials, preparation of solutions, procedures, data collection and analysis for three activities involving this chemical. (CW)

Forensic engineering of advanced polymeric materials Part IV: Case study of oxo-biodegradable polyethylene commercial bag - Aging in biotic and abiotic environment.

PubMed

Musioł, Marta; Rydz, Joanna; Janeczek, Henryk; Radecka, Iza; Jiang, Guozhan; Kowalczuk, Marek

2017-06-01

The public awareness of the quality of environment stimulates the endeavor to safe polymeric materials and their degradation products. The aim of the forensic engineering case study presented in this paper is to evaluate the aging process of commercial oxo-degradable polyethylene bag under real industrial composting conditions and in distilled water at 70°C, for comparison. Partial degradation of the investigated material was monitored by changes in molecular weight, thermal properties and Keto Carbonyl Bond Index and Vinyl Bond Index, which were calculated from the FTIR spectra. The results indicate that such an oxo-degradable product offered in markets degrades slowly under industrial composting conditions. Even fragmentation is slow, and it is dubious that biological mineralization of this material would occur within a year under industrial composting conditions. The slow degradation and fragmentation is most likely due to partially crosslinking after long time of degradation, which results in the limitation of low molecular weight residues for assimilation. The work suggests that these materials should not be labeled as biodegradable, and should be further analyzed in order to avoid the spread of persistent artificial materials in nature. Copyright © 2017 Elsevier Ltd. All rights reserved.

Transport and degradation of metalaxyl and isoproturon in biopurification columns inoculated with pesticide-primed material.

PubMed

De Wilde, Tineke; Spanoghe, Pieter; Sniegowksi, Kristel; Ryckeboer, Jaak; Jaeken, Peter; Springael, Dirk

2010-01-01

Laboratory column displacement experiments were performed to examine whether addition of pesticide-primed material to the matrix of an on-farm biopurification system (BPS), intended to remove pesticides from agricultural waste water, positively affects the degradation of mobile pesticides in the system. Percolated column microcosms with varying types and amounts of metalaxyl and/or isoproturon-primed material or non-primed material were irrigated with water artificially contaminated with isoproturon and/or metalaxyl. Transport of isoproturon was well described using the convection dispersion equation and no dissipation was observed, even in columns inoculated with isoproturon-primed material. On the other hand, delayed dissipation of metalaxyl, i.e., after an initial lag phase, was encountered in all columns receiving metalaxyl. In all systems, dissipation could be described using the Monod model indicating that a metalaxyl degrading population grew in the systems. There was a clear correlation between the lag phase and the amount of metalaxyl-primed material added to the system, i.e., increasing amounts of added material resulted into shorter lag phases and hence more rapid initiation of growth-associated metalaxyl degradation in the system. Our observations suggest that indeed pesticide-primed material can reduce the start-up phase of degradation of mobile pesticides in a BPS and as such can increase its efficiency. However, the primed material should be chosen carefully and preferentially beforehand tested for its capacity to degrade the pesticide.

Biological degradation of plastics: a comprehensive review.

PubMed

Shah, Aamer Ali; Hasan, Fariha; Hameed, Abdul; Ahmed, Safia

2008-01-01

Lack of degradability and the closing of landfill sites as well as growing water and land pollution problems have led to concern about plastics. With the excessive use of plastics and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. Awareness of the waste problem and its impact on the environment has awakened new interest in the area of degradable polymers. The interest in environmental issues is growing and there are increasing demands to develop material which do not burden the environment significantly. Biodegradation is necessary for water-soluble or water-immiscible polymers because they eventually enter streams which can neither be recycled nor incinerated. It is important to consider the microbial degradation of natural and synthetic polymers in order to understand what is necessary for biodegradation and the mechanisms involved. This requires understanding of the interactions between materials and microorganisms and the biochemical changes involved. Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. This paper reviews the current research on the biodegradation of biodegradable and also the conventional synthetic plastics and also use of various techniques for the analysis of degradation in vitro.

In vitro degradation behavior and cytocompatibility of Mg–Zn–Zr alloys

PubMed Central

Huan, Z. G.; Leeflang, M. A.; Fratila-Apachitei, L. E.; Duszczyk, J.

2010-01-01

Zinc and zirconium were selected as the alloying elements in biodegradable magnesium alloys, considering their strengthening effect and good biocompatibility. The degradation rate, hydrogen evolution, ion release, surface layer and in vitro cytotoxicity of two Mg–Zn–Zr alloys, i.e. ZK30 and ZK60, and a WE-type alloy (Mg–Y–RE–Zr) were investigated by means of long-term static immersion testing in Hank’s solution, non-static immersion testing in Hank’s solution and cell-material interaction analysis. It was found that, among these three magnesium alloys, ZK30 had the lowest degradation rate and the least hydrogen evolution. A magnesium calcium phosphate layer was formed on the surface of ZK30 sample during non-static immersion and its degradation caused minute changes in the ion concentrations and pH value of Hank’s solution. In addition, the ZK30 alloy showed insignificant cytotoxicity against bone marrow stromal cells as compared with biocompatible hydroxyapatite (HA) and the WE-type alloy. After prolonged incubation for 7 days, a stimulatory effect on cell proliferation was observed. The results of the present study suggested that ZK30 could be a promising material for biodegradable orthopedic implants and worth further investigation to evaluate its in vitro and in vivo degradation behavior. PMID:20532960

Long-Term In Vitro Degradation of a High-Strength Brushite Cement in Water, PBS, and Serum Solution

PubMed Central

Ajaxon, Ingrid; Öhman, Caroline; Persson, Cecilia

2015-01-01

Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for a bone fracture to heal. This study aimed at evaluating the long-term in vitro degradation properties of a high-strength brushite CPC in three different solutions: water, phosphate buffered saline, and a serum solution. Microcomputed tomography was used to evaluate the degradation nondestructively, complemented with gravimetric analysis. The compressive strength, chemical composition, and microstructure were also evaluated. Major changes from 10 weeks onwards were seen, in terms of formation of a porous outer layer of octacalcium phosphate on the specimens with a concomitant change in phase composition, increased porosity, decrease in object volume, and mechanical properties. This study illustrates the importance of long-term evaluation of similar cement compositions to be able to predict the material's physical changes over a relevant time frame. PMID:26587540

Stable-isotope-based labeling of styrene-degrading microorganisms in biofilters.

PubMed

Alexandrino, M; Knief, C; Lipski, A

2001-10-01

Deuterated styrene ([(2)H(8)]styrene) was used as a tracer in combination with phospholipid fatty acid (PLFA) analysis for characterization of styrene-degrading microbial populations of biofilters used for treatment of waste gases. Deuterated fatty acids were detected and quantified by gas chromatography-mass spectrometry. The method was evaluated with pure cultures of styrene-degrading bacteria and defined mixed cultures of styrene degraders and non-styrene-degrading organisms. Incubation of styrene degraders for 3 days with [(2)H(8)]styrene led to fatty acids consisting of up to 90% deuterated molecules. Mixed-culture experiments showed that specific labeling of styrene-degrading strains and only weak labeling of fatty acids of non-styrene-degrading organisms occurred after incubation with [(2)H(8)]styrene for up to 7 days. Analysis of actively degrading filter material from an experimental biofilter and a full-scale biofilter by this method showed that there were differences in the patterns of labeled fatty acids. For the experimental biofilter the fatty acids with largest amounts of labeled molecules were palmitic acid (16:0), 9,10-methylenehexadecanoic acid (17:0 cyclo9-10), and vaccenic acid (18:1 cis11). These lipid markers indicated that styrene was degraded by organisms with a Pseudomonas-like fatty acid profile. In contrast, the most intensively labeled fatty acids of the full-scale biofilter sample were palmitic acid and cis-11-hexadecenoic acid (16:1 cis11), indicating that an unknown styrene-degrading taxon was present. Iso-, anteiso-, and 10-methyl-branched fatty acids showed no or weak labeling. Therefore, we found no indication that styrene was degraded by organisms with methyl-branched fatty fatty acids, such as Xanthomonas, Bacillus, Streptomyces, or Gordonia spp.

Effects of prior information on decoding degraded speech: an fMRI study.

PubMed

Clos, Mareike; Langner, Robert; Meyer, Martin; Oechslin, Mathias S; Zilles, Karl; Eickhoff, Simon B

2014-01-01

Expectations and prior knowledge are thought to support the perceptual analysis of incoming sensory stimuli, as proposed by the predictive-coding framework. The current fMRI study investigated the effect of prior information on brain activity during the decoding of degraded speech stimuli. When prior information enabled the comprehension of the degraded sentences, the left middle temporal gyrus and the left angular gyrus were activated, highlighting a role of these areas in meaning extraction. In contrast, the activation of the left inferior frontal gyrus (area 44/45) appeared to reflect the search for meaningful information in degraded speech material that could not be decoded because of mismatches with the prior information. Our results show that degraded sentences evoke instantaneously different percepts and activation patterns depending on the type of prior information, in line with prediction-based accounts of perception. Copyright © 2012 Wiley Periodicals, Inc.

A Comparison of Atomic Oxygen Degradation in Low Earth Orbit and in a Plasma Etcher

NASA Technical Reports Server (NTRS)

Townsend, Jacqueline A.; Park, Gloria

1997-01-01

In low Earth orbit (LEO) significant degradation of certain materials occurs from exposure to atomic oxygen (AO). Orbital opportunities to study this degradation for specific materials are limited and expensive. While plasma etchers are commonly used in ground-based studies because of their low cost and convenience, the environment produced in an etcher chamber differs greatly from the LEO environment. Because of the differences in environment, the validity of using etcher data has remained an open question. In this paper, degradation data for 22 materials from the orbital experiment Evaluation of Oxygen Interaction with Materials (EOIM-3) are compared with data from EOIM-3 control specimens exposed in a typical plasma etcher. This comparison indicates that, when carefully considered, plasma etcher results can produce order-of-magnitude estimates of orbital degradation. This allows the etcher to be used to screen unacceptable materials from further, more expensive tests.

Isolation and characterization of an ether-type polyurethane-degrading micro-organism and analysis of degradation mechanism by Alternaria sp.

PubMed

Matsumiya, Y; Murata, N; Tanabe, E; Kubota, K; Kubo, M

2010-06-01

To degrade ether-type polyurethane (ether-PUR), ether-PUR-degrading micro-organism was isolated. Moreover, ether-PUR-degrading mechanisms were analysed using model compounds of ether-PUR. A fungus designated as strain PURDK2, capable of changing the configuration of ether-PUR, has been isolated. This isolated fungus was identified as Alternaria sp. Using a scanning electron microscope, the grid structure of ether-PUR was shown to be melted and disrupted by the fungus. The degradation of ether-PUR by the fungus was analysed, and the ether-PUR was degraded by the fungus by about 27.5%. To analyse the urethane-bond degradation by the fungus, a degraded product of ethylphenylcarbamate was analysed using GC/MS. Aniline and ethanol were detected by degradation with the supernatant, indicating that the fungus secreted urethane-bond-degrading enzyme(s). PURDK2 also degraded urea bonds when diphenylmethane-4,4'-dibutylurea was used as a substrate. The enzyme(s) from PURDK2 degraded urethane and urea bonds to convert the high molecular weight structure of ether-PUR to small molecules; and then the fungus seems to use the small molecules as an energy source. Ether-PUR-degrading fungus, strain PURDK2, was isolated, and the urethane- and urea-bonds-degrading enzymes from strain PURDK2 could contribute to the material recycling of ether-PUR.

The influence of fire exposure on austenitic stainless steel for pressure vessel fitness-for-service assessment: Experimental research

NASA Astrophysics Data System (ADS)

Li, Bo; Shu, Wenhua; Zuo, Yantian

2017-04-01

The austenitic stainless steels are widely applied to pressure vessel manufacturing. The fire accident risk exists in almost all the industrial chemical plants. It is necessary to make safety evaluation on the chemical equipment including pressure vessels after fire. Therefore, the present research was conducted on the influences of fire exposure testing under different thermal conditions on the mechanical performance evolution of S30408 austenitic stainless steel for pressure vessel equipment. The metallurgical analysis described typical appearances in micro-structure observed in the material suffered by fire exposure. Moreover, the quantitative degradation of mechanical properties was investigated. The material thermal degradation mechanism and fitness-for-service assessment process of fire damage were further discussed.

Pocketing mechanics of SRM nozzle liner

NASA Technical Reports Server (NTRS)

Verderaime, V. S.

1986-01-01

A systems approach was adopted to study the pocketing phenomena on a solid rocket nozzle liner. The classical thermoelastic analysis was used to identify marginally strained regions on the composite liner erosion surface and at a depth coincident with the peak value of the across ply coefficient of thermal expansion. A failure criterion was introduced which included a thermal term and permitted failure assessment over the charred liner. The method was verified by satisfactory application to a reported related experiment. Liner pocketing mechanism was attributed to very localized material degradation caused during manufacturing process either by reduction of fiber strength and/or by concentration of resin volume fraction. Pocketing scenario over the degraged material was constructed with supporting formulation to predict size of fissures with respect to degraded material size and location in the liner and with burn time. Sensitivities of liner material parameters were determined to influence test programs designed to update mechanical data base of carbon cloth phenolic over the char temperature range.

Documentation Protocols to Generate Risk Indicators Regarding Degradation Processes for Cultural Heritage Risk Evaluation

NASA Astrophysics Data System (ADS)

Kioussi, A.; Karoglou, M.; Bakolas, A.; Labropoulos, K.; Moropoulou, A.

2013-07-01

Sustainable maintenance and preservation of cultural heritage assets depends highly on its resilience to external or internal alterations and to various hazards. Risk assessment of a heritage asset's can be defined as the identification of all potential hazards affecting it and the evaluation of the asset's vulnerability (building materials and building structure conservation state).Potential hazards for cultural heritage are complex and varying. The risk of decay and damage associated with monuments is not limited to certain long term natural processes, sudden events and human impact (macroscale of the heritage asset) but is also a function of the degradation processes within materials and structural elements due to physical and chemical procedures. Obviously, these factors cover different scales of the problem. The deteriorating processes in materials may be triggered by external influences or caused because of internal chemical and/or physical variations of materials properties and characteristics. Therefore risk evaluation should be dealt in the direction of revealing the specific active decay and damage mechanism both in mesoscale [type of decay and damage] and microscale [decay phenomenon mechanism] level. A prerequisite for risk indicators identification and development is the existence of an organised source of comparable and interoperable data about heritage assets under observation. This unified source of information offers a knowledge based background of the asset's vulnerability through the diagnosis of building materials' and building structure's conservation state, through the identification of all potential hazards affecting these and through mapping of its possible alterations during its entire life-time. In this framework the identification and analysis of risks regarding degradation processes for the development of qualitative and quantitative indicators can be supported by documentation protocols. The data investigated by such protocols help identify the parameters needed for the assessment of the preservation state of a monument and its monitoring through its entire lifetime. The main tool for detecting these indicators is a diagnostic methodology based on appropriate standards that reveals the actual degradation processes responsible of the asset's vulnerability. It is very important that the integration between the material's diagnosis and the overall documentation is taken into consideration in order to identify the required levels of protection and preventive conservation for heritage assets depending on the most frequent local risks. The ranging of risks is therefore necessary according to their importance in each area. Documentation protocols provide with a specific diagnostic tool for materials characterization, decay diagnosis, evaluation process of former conservation materials and interventions, standard procedures for monitoring and control as well as data documentation based on specific guidelines and standards. Implementation and analysis of a "standardised" diagnostic study will reveal the main risks due to degradation processes affecting the heritage asset to be subsequently recorded in order to result into risk indicators. The development of risk indicators regarding degradation processes is the basic step towards uptaking efficient management, preventive conservation and strategic planning for heritage assets against various threats. These risk indicators could be further elaborated according to the activities of inspection, diagnosis and intervention works, offering scientific support to the decision making process for cultural heritage preventive conservation and overall protection.

The Behavior of Translucent Composite Laminates under Highly Energetic Laser Irradiations

NASA Astrophysics Data System (ADS)

Allheily, Vadim; Merlat, Lionel; Lacroix, Fabrice; Eichhorn, Alfred; L'Hostis, Gildas

With the emergence of composite materials in the last decades, the interaction between light and diffusive materials has become a challenging topic in many key manufacturing areas (laser welding, laser surface treatment, engraving, etc.). In this paper, the behavior of laminated glass fiber-reinforced plastic composites (GFRP) under 1.07 μm-wavelength irradiations is investigated. Optical parameters are first assessed to build up a basic analytical interaction model involving internal refraction and reflection. The scattering effect due to the presence of oriented glass fibers is also a topic of interest. A thermodynamic analysis is then carried out from the induced volume heat source until the degradation temperature of the material is reached out. The study finally results in a one-dimensional model describing the optical and thermo-dynamical behavior of GFRP under high-power laser irradiations up to ignition of the chemical degradation phenomena.

Atomic oxygen degradation of Intelsat 4-type solar array interconnects: Laboratory investigations

NASA Technical Reports Server (NTRS)

Koontz, S. L.; Cross, J. B.; Hoffbauer, M. A.; Kirkendahl, T. D.

1991-01-01

A Hughes 506 type communication satellite belonging to the Intelsat organization was marooned in low Earth orbit on March 14, 1990, following failure of the Titan third stage to separate properly. The satellite, Intelsat VI, was designed for service in geosynchronous orbit and contains several material configurations which are susceptible to attack by atomic oxygen. Analysis showed the silver foil interconnects in the satellite photovoltaic array to be the key materials issue because the silver is exposed directly to the atomic oxygen ram flux. The results are reported of atomic oxygen degradation testing of Intelsat VI type silver foil interconnects both as virgin material and in a configured solar cell element. Test results indicate that more than 80 pct. of the original thickness of silver in the Intelsat VI solar array interconnects should remain after completion of the proposed Space Shuttle rescue and/or reboost mission.

Physico-chemical behaviour of β irradiated plastic materials currently used as packagings and medical products

NASA Astrophysics Data System (ADS)

Yagoubi, N.; Baillet, A.; Pellerin, F.; Ferrier, D.

1995-11-01

The combined chromatographic technics and thermal analysis constitute an informative methodology for studying the modifications which could occur following a radiotreatment of plastic material at different doses (25 to 100 kGy). Several plastic materials used as packagings (PVC, PE, PS) were investigated. SEC method coupled with UV and DDL detections was applied to document any changes in molecular weight distribution. Reticulation and scission were the main observed degradation phenomena. These structural modifications were supported by TGA data, while the DSC provided information on modifications in crystallinity. In addition, RP-HPLC was carried out for the evaluation of the radiochemical behaviour of the additives and monomers. Firstly we demonstrated the degradation of high molecular weight phenolic antioxidants in BHT within the PEVA. Secondly, the modifications of amino 6 caproic acid and ɛ caprolactam, present in polyamid 6, depend on the irradiation doses.

A Time-Variant Reliability Model for Copper Bending Pipe under Seawater-Active Corrosion Based on the Stochastic Degradation Process

PubMed Central

Li, Mengmeng; Feng, Qiang; Yang, Dezhen

2018-01-01

In the degradation process, the randomness and multiplicity of variables are difficult to describe by mathematical models. However, they are common in engineering and cannot be neglected, so it is necessary to study this issue in depth. In this paper, the copper bending pipe in seawater piping systems is taken as the analysis object, and the time-variant reliability is calculated by solving the interference of limit strength and maximum stress. We did degradation experiments and tensile experiments on copper material, and obtained the limit strength at each time. In addition, degradation experiments on copper bending pipe were done and the thickness at each time has been obtained, then the response of maximum stress was calculated by simulation. Further, with the help of one kind of Monte Carlo method we propose, the time-variant reliability of copper bending pipe was calculated based on the stochastic degradation process and interference theory. Compared with traditional methods and verified by maintenance records, the results show that the time-variant reliability model based on the stochastic degradation process proposed in this paper has better applicability in the reliability analysis, and it can be more convenient and accurate to predict the replacement cycle of copper bending pipe under seawater-active corrosion. PMID:29584695

Enzymatic tranformations of lignin. Annual report 1 July 1980-30 June 1981

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glasser, W.G.; Hall, P.L.

1981-06-01

Research is summarized on biological approaches to the utilization of lignin degradation to raw material for the manufacture of chemicals and materials. This investigation studied the possible involvement of reduced oxygen species produced by the white-rot fungus, C. versicolor, in the initial breakdown of the lignin macromolecule during its biodegradation. This fungus was shown to be capable of exporting superoxide radical. While the degree to which this organism was responsible for actual lignin degradation is not clear, there were indications that a correlation may exist between the concentration of extracellular superoxide radical in the medium and the extent of ligninmore » degradation. Two different fermentation schemes were compared and several control fermentation experiments were made. Research dealing with improvements in lignin structure analysis, liquefaction of lignin preparations by reaction with propylene oxide, and solidification of liquified kraft lignin by crosslinking with diisocyanate compounds was explored. The use of scanning electron microscopy for revealing interaction between fiber and binder is noted.« less

Molecular Design and Evaluation of Biodegradable Polymers Using a Statistical Approach

PubMed Central

Lewitus, Dan; Rios, Fabian; Rojas, Ramiro; Kohn, Joachim

2013-01-01

The challenging paradigm of bioresorbable polymers, whether in drug delivery or tissue engineering, states that a fine-tuning of the interplay between polymer properties (e.g., thermal, degradation), and the degree of cell/tissue replacement and remodeling is required. In this paper we describe how changes in the molecular architecture of a series of terpolymers allow for the design of polymers with varying glass transition temperatures and degradation rates. The effect of each component in the terpolymers is quantified via design of experiment (DoE) analysis. A linear relationship between terpolymer components and resulting Tg (ranging from 34 to 86 °C) was demonstrated. These findings were further supported with mass-per-flexible-bond (MPFB) analysis. The effect of terpolymer composition on the in vitro degradation of these polymers revealed molecular weight loss ranging from 20 to 60% within the first 24 hours. DoE modeling further illustrated the linear (but reciprocal) relationship between structure elements and degradation for these polymers. Thus, we describe a simple technique to provide insight into the structure property relationship of degradable polymers, specifically applied using a new family of tyrosine-derived polycarbonates, allowing for optimal design of materials for specific applications. PMID:23888354

Characterization of mechanisms underlying degradation of sclerotia of Sclerotinia sclerotiorum by Aspergillus aculeatus Asp-4 using a combined qRT-PCR and proteomic approach.

PubMed

Hu, Xiaojia; Qin, Lu; Roberts, Daniel P; Lakshman, Dilip K; Gong, Yangmin; Maul, Jude E; Xie, Lihua; Yu, Changbing; Li, Yinshui; Hu, Lei; Liao, Xiangsheng; Liao, Xing

2017-08-31

The biological control agent Aspergillus aculeatus Asp-4 colonizes and degrades sclerotia of Sclerotinia sclerotiorum resulting in reduced germination and disease caused by this important plant pathogen. Molecular mechanisms of mycoparasites underlying colonization, degradation, and reduction of germination of sclerotia of this and other important plant pathogens remain poorly understood. An RNA-Seq screen of Asp-4 growing on autoclaved, ground sclerotia of S. sclerotiorum for 48 h identified 997 up-regulated and 777 down-regulated genes relative to this mycoparasite growing on potato dextrose agar (PDA) for 48 h. qRT-PCR time course experiments characterized expression dynamics of select genes encoding enzymes functioning in degradation of sclerotial components and management of environmental conditions, including environmental stress. This analysis suggested co-temporal up-regulation of genes functioning in these two processes. Proteomic analysis of Asp-4 growing on this sclerotial material for 48 h identified 26 up-regulated and 6 down-regulated proteins relative to the PDA control. Certain proteins with increased abundance had putative functions in degradation of polymeric components of sclerotia and the mitigation of environmental stress. Our results suggest co-temporal up-regulation of genes involved in degradation of sclerotial compounds and mitigation of environmental stress. This study furthers the analysis of mycoparasitism of sclerotial pathogens by providing the basis for molecular characterization of a previously uncharacterized mycoparasite-sclerotial interaction.

40 CFR 265.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2012 CFR

2012-07-01

... (iii) Mixtures of these non-bio-degrad-a-ble materials. (2) Tests for non-bio-degrad-a-ble sorbents. (i) The sorbent material is determined to be non-bio-degrad-a-ble under ASTM Method G21-70 (1984a...

40 CFR 265.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2013 CFR

2013-07-01

... (iii) Mixtures of these non-bio-degrad-a-ble materials. (2) Tests for non-bio-degrad-a-ble sorbents. (i) The sorbent material is determined to be non-bio-degrad-a-ble under ASTM Method G21-70 (1984a...

40 CFR 265.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2014 CFR

2014-07-01

... (iii) Mixtures of these non-bio-degrad-a-ble materials. (2) Tests for non-bio-degrad-a-ble sorbents. (i) The sorbent material is determined to be non-bio-degrad-a-ble under ASTM Method G21-70 (1984a...

40 CFR 265.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2010 CFR

2010-07-01

... (iii) Mixtures of these non-bio-degrad-a-ble materials. (2) Tests for non-bio-degrad-a-ble sorbents. (i) The sorbent material is determined to be non-bio-degrad-a-ble under ASTM Method G21-70 (1984a...

Surface protection coating material for controlling the decay of major construction stone

NASA Astrophysics Data System (ADS)

Arun, T.; Ray, D. K.; Gupta, V. P.; Panda, S. S.; Sahoo, P. K.; Ghosh, Jaydip; Sengupta, Pranesh; Satyam, P. V.

2017-05-01

Degradation of the building stones are creating instability in the old building and monuments which is to be protected. To investigate the characteristics of such a stones used for the construction in eastern India, we have collected the khondalite stones. The microstructural and elemental composition analysis of the khondalite stones are analyzed by using SEM, EDX and PIXE trace elemental analysis. We have prepared surface protection coating material with graphene oxide and cobalt ferrite as a base material along with other residuals. The prepared coating materials is coated on the galvanized iron substrate for further characterization. The surface morphology characteristics of the coating material is analyzed by SEM and AFM. The corrosion resistance characteristics of the prepared coating material is studied by the electrochemical impedance spectroscopy. The results suggests that the prepared coating material can be used as a surface protection materials to control the self-destruction of khondalite stones.

Solar Light Responsive Photocatalytic Activity of Reduced Graphene Oxide-Zinc Selenide Nanocomposite

NASA Astrophysics Data System (ADS)

Chakraborty, Koushik; Ibrahim, Sk; Das, Poulomi; Ghosh, Surajit; Pal, Tanusri

2017-10-01

Solution processable reduced graphene oxide-zinc selenide (RGO-ZnSe) nanocomposite has been successfully synthesized by an easy one-pot single-step solvothermal reaction. The RGO-ZnSe composite was characterized structurally and morphologically by the study of XRD analysis, SEM and TEM imaging. Reduction in graphene oxide was confirmed by FTIR spectroscopy analysis. Photocatalytic efficiency of RGO-ZnSe composite was investigated toward the degradation of Rhodamine B under solar light irradiation. Our study indicates that the RGO-ZnSe composite is catalytically more active compared to the controlled-ZnSe under the solar light illumination. Here, RGO plays an important role for photoinduced charge separation and subsequently hinders the electron-hole recombination probability that consequently enhances photocatalytic degradation efficiency. We expect that this type of RGO-based optoelectronics materials opens up a new avenue in the field of photocatalytic degradation of different organic water pollutants.

DNA Sequencing in Cultural Heritage.

PubMed

Vai, Stefania; Lari, Martina; Caramelli, David

2016-02-01

During the last three decades, DNA analysis on degraded samples revealed itself as an important research tool in anthropology, archaeozoology, molecular evolution, and population genetics. Application on topics such as determination of species origin of prehistoric and historic objects, individual identification of famous personalities, characterization of particular samples important for historical, archeological, or evolutionary reconstructions, confers to the paleogenetics an important role also for the enhancement of cultural heritage. A really fast improvement in methodologies in recent years led to a revolution that permitted recovering even complete genomes from highly degraded samples with the possibility to go back in time 400,000 years for samples from temperate regions and 700,000 years for permafrozen remains and to analyze even more recent material that has been subjected to hard biochemical treatments. Here we propose a review on the different methodological approaches used so far for the molecular analysis of degraded samples and their application on some case studies.

Characterization of biodegradable polymers irradiated with swift heavy ions

NASA Astrophysics Data System (ADS)

Salguero, N. G.; del Grosso, M. F.; Durán, H.; Peruzzo, P. J.; Amalvy, J. I.; Arbeitman, C. R.; García Bermúdez, G.

2012-02-01

In view of their application as biomaterials, there is an increasing interest in developing new methods to induce controlled cell adhesion onto polymeric materials. The critical step in all these methods involves the modification of polymer surfaces, to induce cell adhesion, without changing theirs degradation and biocompatibility properties. In this work two biodegradable polymers, polyhydroxybutyrate (PHB) and poly- L-lactide acid (PLLA) were irradiated using carbon and sulfur beams with different energies and fluences. Pristine and irradiated samples were degradated by immersion in a phosphate buffer at pH 7.0 and then characterized. The analysis after irradiation and degradation showed a decrease in the contact angle values and changes in their crystallinity properties.

FOREWORD: Focus on the Degradation and Stability of Polymers

NASA Astrophysics Data System (ADS)

Terano, Minoru

2008-06-01

Modern society is so reliant on polymers that products incorporating these macromolecules are almost 'invisible'. Polymers are indispensable materials used for manufacturing compact disks, clothes, lightweight airplanes, automobiles, footware and even the humble polystyrene boxes for packing our favorite hamburgers and fries. But, like many other materials, polymers degrade and become unstable, so a deeper understanding of the physical mechanisms responsible for degradation is necessary to address issues such as potential applications, recycling and the impact of polymer-products on the environment. In particular, polymers are highly vulnerable to oxidative degradation at elevated temperatures and in sunlight. Unfortunately, in spite of extensive research on polymer degradation, our knowledge is still incomplete. The analysis of polymer degradation and stability has recently become harder and more complicated because of the wider range of polymer applications, including blends and composites. Notably, composites with nanofillers are being studied for automotive, electrical and other industrial applications. With this background, the 1st International Symposium on Ultimate Stability of NanoStructured Polymers and Composites (NT2007) was held in October at the Japan Advanced Institute of Science and Technology in Ishikawa Prefecture. The meeting provided a forum to discuss advanced research achievements to resolve problems in this field of research. The papers selected for this focus issue describe recent discoveries on the stability, weatherability and flame retardancy of polymers, as well as providing an insight into degradation mechanisms of nanostructured polymers and composites. We hope that this focus issue will serve as a timely source of information about one of the most important topics in polymer science and related technologies.

Space simulation test for thermal control materials

NASA Technical Reports Server (NTRS)

Hardgrove, W. R.

1990-01-01

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.

Experimental analysis of the material degradation of PET on a co-rotating twin-screw extruder for varying vacuum pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herken, T.; Fecke, N.; Schöppner, V., E-mail: Tobias.Herken@ktp.uni-paderborn.de, E-mail: Nikolas.Fecke@ktp.uni-paderborn.de, E-mail: Volker.Schoeppner@ktp.uni-paderborn.de

Plastics, starting from inexpensive mass-produced articles to technical high-end applications, are being used in ever more areas of life. The main drivers are their flexible product properties and the resultant broad application possibilities. To be able to offer plastic products inexpensively and conserve the environment at the same time, more and more attention is being paid to plastics recycling. Polyethylene terephthalate – in short PET – is of particular significance here because of its frequent application in the film and packaging industry and its special material properties. The recycling of PET, however, can only be carried out a limited numbermore » of times because it’s processing necessarily results in both thermal and mechanical stresses on the material. This is the basis for the reactions at molecular level, which result in a shortening of the molecule chains (material degradation) and exert a negative effect on the product properties. The aim of this study is to identify the factors that influence the material degradation of PET in twin-screw extrusion. To do this, various screw configurations and different speed and throughput conditions are examined in a series of experiments. Furthermore, material specimens are removed along the length of the screw in order to evaluate the influence of individual screw sections. By determining the intrinsic viscosity of the specimens, it is possible to measure the mean molecular weight and thus the material damage. Based on the test results, guidelines are drawn up for the compounding of PET so as to ensure as little damage as possible to the material.« less

Characteristics of Impact Craters and Interior Deposits: Analysis of the Spatial and Temporal Distribution of Volatiles in the Highlands of Mars

NASA Technical Reports Server (NTRS)

Mest, S. C.

2005-01-01

The martian southern highlands contain impact craters that display pristine to degraded morphologies, and preserve a record of degradation that can be attributed to fluvial, eolian, mass wasting, volcanic and impact-related processes. However, the relative degree of modification by these processes and the amounts of material contributed to crater interiors are not well constrained. Impact craters (D>10 km) within Terra Cimmeria (0deg-60degS, 190deg-240degW), Terra Tyrrhena (0deg-30degS, 260deg-310degW) and Noachis Terra (20deg-50degS, 310deg-340degW) are being examined to better understand the degradational history and evolution of highland terrains. The following scientific objectives will be accomplished. 1) Determine the geologic processes that modified impact craters (and surrounding highland terrains). 2) Determine the sources (e.g. fluvial, lacustrine, eolian, mass wasting, volcanic, impact melt) and relative amounts of material composing crater interior deposits. 3) Document the relationships between impact crater degradation and highland fluvial systems. 4) Determine the spatial and temporal relationships between degradational processes on local and regional scales. And 5) develop models of impact crater (and highland) degradation that can be applied to these and other areas of the martian highlands. The results of this study will be used to constrain the geologic, hydrologic and climatic evolution of Mars and identify environments in which subsurface water might be present or evidence for biologic activity might be preserved.

Spin Transfer in Polymer Degradation of Abnormal Linkage

NASA Astrophysics Data System (ADS)

Yu, Tianrong; Tian, Chuanjin; Liu, Xizhe; Wang, Jia; Gao, Yang; Wang, Zhigang

2017-07-01

The degradation of polymer materials plays an important role in production and life. In this work, the degradation mechanism of poly-α-methylstyrene (PAMS) tetramers with abnormal linkage was investigated by using density functional theory (DFT). Calculated results indicate that the head-to-head and the tail-to-tail reactions needed to overcome the energy barriers are about 0.15 eV and about 1.26 eV, respectively. The broken C-C bond at the unsaturated end of the chain leads to the dissociation of alpha-methylstyrene (AMS) monomers one by one. Furthermore, the analyses of bond characteristics are in good agreement with the results of energy barriers. In addition, the spin population analysis presents an interesting net spin transfer process in depolymerization reactions. We hope that the current theoretical results provide useful help to understand the degradation mechanism of polymers.

Performance degradation of space Stirling cryocoolers due to gas contamination

NASA Astrophysics Data System (ADS)

Liu, Xin-guang; Wu, Yi-nong; Yang, Shao-hua; Zhang, Xiao-ming; Lu, Guo-hua; Zhang, Li

2011-08-01

With extensive application of infrared detective techniques, Stirling cryocoolers, used as an active cooling source, have been developed vigorously in China. After the cooler's cooling performance can satisfy the mission's request, its reliability level is crucial for its application. Among all the possible failure mechanisms, gas contamination has been found to be the most notorious cause of cooler's performance degradation by failure analyses. To analyze the characteristic of gas contamination, some experiments were designed and carried out to quantitatively analyze the relationship between failure and performance. Combined with the test results and the outgassing characteristic of non-metal materials in the cryocooler, a degradation model of cooling performance was given by T(t)=T0+A[1-exp(-t/B)] under some assumptions, where t is the running time, T is the Kelvin cooling temperature, and T0, A, B are model parameters, which can be given by the least square method. Here T0 is the fitting initial cooling temperature, A is the maximum range of performance degradation, and B is the time dependent constant of degradation. But the model parameters vary when a cryocooler is running at different cooling temperature ranges, or it is treated by different cleaning process. In order to verify the applicability of the degradation model, data fit analysis on eight groups of cooler's lifetime test was carried out. The final work indicated this model fit well with the performance degradation of space Stirling cryocoolers due to gas contamination and this model could be used to predict or evaluation the cooler's lifetime. Gaseous contamination will not arouse severe performance degradation until the contaminants accumulate to a certain amount, but it could be fatal when it works. So it is more serious to the coolers whose lifetime is more than 10,000 h. The measures taken to control or minimize its damage were discussed as well. To the long-life cryocooler, internal materials must be baked and organic/epoxy materials should be used as few as possible. Further more, pipeline for filling working fluid must have purifying facilities.

Degradation of strength properties of epoxy resin filled with natural-based particles

NASA Astrophysics Data System (ADS)

Valášek, Petr; Habrová, Karolína; Müller, Miroslav

2018-05-01

Degradation of polymeric materials can be considered as a limiting factor for their use. Mechanical characteristics of epoxy resins are reduced, for example, by the action and changes of temperature or humidity. Degradation also occurs in composite systems where the epoxy resins function as matrices, i.e. in polymer composite materials. If a natural filler is used together with the epoxy resin, we refer to these materials as biocomposites, where also the natural character of the filler material greatly affects the degradation process. The paper focuses on the description of the shear strength of the resin filled with particles prepared from the seeds of dates of Phoenix Dactylifera plant. The degradation was evaluated experimentally in laboratory conditions via the climatic chamber. The experiment describes composites with a particle size of filler 100-200 μm with a concentration of 5 - 10 wt%. As the number of degradation cycles increased, the tensile strength of both the unfilled and the filled epoxy resin decreased. After 5 weeks, the drop was up to 50%. The presence of the particles did not significantly affect the shear strength compared to the non-filled resin. The described way of utilization of the natural-based particles is the possibility of material utilization of secondary natural materials.

Magnetoelastic galfenol as a stent material for wirelessly controlled degradation rates.

PubMed

DeRouin, Andrew; Guillory, Roger; He, Weilue; Frost, Megan; Goldman, Jeremy; Ong, Keat Ghee

2018-03-23

The gold standard of care for coronary artery disease, a leading cause of death for in the world, is balloon angioplasty in conjunction with stent deployment. However, implantation injuries and long-term presence of foreign material often promotes significant luminal tissue growth, leading to a narrowing of the artery and severely restricted blood flow. A promising method to mitigate this process is the use of biodegradable metallic stents, but thus far they have either degraded too slowly (iron) or disappeared prematurely (magnesium). The present work investigates the use of a unique type of magnetic material, galfenol (iron-gallium), for postoperative wireless control of stent degradation rates. Due to its magnetoelastic property, galfenol experiences longitudinal micron-level elongations when exposed to applied magnetic fields, allowing generation of a microstirring effect that affect its degradation behavior. In vitro indirect cytotoxicity tests on primary rat aortic smooth muscle cells indicated that galfenol byproducts must be concentrated approximately seven times from collected 60 day degradation medium to cause ∼15% of death from all cells. Surface and cross-sectional characterization of the material indicate that galfenol (Fe 80 Ga 20 ) degradation rates (∼0.55% per month) are insufficient for stenting applications. While this material may not be ideal for comprising the entire stent, there is potential for use in combination with other materials. Furthermore, the ability to control degradation rates postimplantation opens new possibilities for biodegradable stents; additional magnetoelastic materials should be investigated for use in stenting applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Coercivity degradation caused by inhomogeneous grain boundaries in sintered Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Chen, Hansheng; Yun, Fan; Qu, Jiangtao; Li, Yingfei; Cheng, Zhenxiang; Fang, Ruhao; Ye, Zhixiao; Ringer, Simon P.; Zheng, Rongkun

2018-05-01

Quantitative correlation between intrinsic coercivity and grain boundaries in three dimensions is critical to further improve the performance of sintered Nd-Fe-B permanent magnets. Here, we quantitatively reveal the local composition variation across and especially along grain boundaries using the powerful atomic-scale analysis technique known as atom probe tomography. We also estimate the saturation magnetization, magnetocrystalline anisotropy constant, and exchange stiffness of the grain boundaries on the basis of the experimentally determined structure and composition. Finally, using micromagnetic simulations, we quantify the intrinsic coercivity degradation caused by inhomogeneous grain boundaries. This approach can be applied to other magnetic materials for the analysis and optimization of magnetic properties.

Histological and histomorphometrical analysis of a silica matrix embedded nanocrystalline hydroxyapatite bone substitute using the subcutaneous implantation model in Wistar rats.

PubMed

Ghanaati, Shahram; Orth, Carina; Barbeck, Mike; Willershausen, Ines; Thimm, Benjamin W; Booms, Patrick; Stübinger, Stefan; Landes, Constantin; Sader, Robert Anton; Kirkpatrick, Charles James

2010-06-01

The clinical suitability of a bone substitute material is determined by the ability to induce a tissue reaction specific to its composition. The aim of this in vivo study was to analyze the tissue reaction to a silica matrix-embedded, nanocrystalline hydroxyapatite bone substitute.The subcutaneous implantation model in Wistar rats was chosen to assess the effect of silica degradation on the vascularization of the biomaterial and its biodegradation within a time period of 6 months. Already at day 10 after implantation, histomorphometrical analysis showed that the vascularization of the implantation bed reached its peak value compared to all other time points. Both vessel density and vascularization significantly decreased until day 90 after implantation. In this time period, the bone substitute underwent a significant degradation initiated by TRAP-positive and TRAP-negative multinucleated giant cells together with macrophages and lymphocytes. Although no specific tissue reaction could be related to the described silica degradation, the biomaterial was close to being fully degraded without a severe inflammatory response. These characteristics are advantageous for bone regeneration and remodeling processes.

Cross-Discipline Bio-Nanostructured Enhanced Photonic Multimode-Sensor Science

DTIC Science & Technology

2017-05-23

experimental study aimed to combine soft material science with nanotechnology and multi-physics modeling to produce adaptable bio-nanostructure based on...degradation through optical analysis and tracking programs Protein and DNA engineering . - The properties of proteins to be used in sensors were studies

Volumetric analysis of bone substitute material performance within the human sinus cavity of former head and neck cancer patients: A prospective, randomized clinical trial.

PubMed

Lorenz, Jonas; Eichler, Kathrin; Barbeck, Mike; Lerner, Henriette; Stübinger, Stefan; Seipel, Catherine; Vogl, Thomas J; Kovács, Adorján F; Ghanaati, Shahram; Sader, Robert A

2016-01-01

In numerous animal and human studies, it could be detected that in bone augmentation procedures, material's physicochemical characteristics can influence the cellular inflammatory pattern and therefore the integration in the host tissue. Histological, histomorphometrical, and clinical analyses of the integration of the biomaterial in the surrounding tissue are well established methodologies; however, they do not make a statement on volume and density changes of the augmented biomaterial. The aim of the present study was to assess the volume and density of a xenogeneic (Bio-Oss ® , BO) and a synthetic (NanoBone ® , NB) bone substitute material in split-mouth sinus augmentations in former tumor patients to complete histological and histomorphometrical assessment. Immediately and 6 months after sinus augmentation computed tomography scans were recorded, bone grafts were marked, and the volume was calculated with radiologic RIS-PACS software (General Electric Healthcare, Chalfont St. Giles, Great Britain) to determine the integration and degradation behavior of both biomaterials. Radiographic analysis revealed a volume reduction of the initial augmented bone substitute material (i.e. 100%) to 77.36 (±11.68) % in the BO-group, respectively, 75.82 (±22.28) % in the NB-group six months after augmentation. In both materials, the volume reduction was not significant. Bone density significantly increased in both groups. The presented radiological investigation presents a favorable method to obtain clinically relevant information concerning the integration and degradation behavior of bone substitute materials.

Time-Variant Reliability Analysis for Rubber O-Ring Seal Considering Both Material Degradation and Random Load

PubMed Central

Liao, Baopeng; Yan, Meichen; Zhang, Weifang; Zhou, Kun

2017-01-01

Due to the increase in working hours, the reliability of rubber O-ring seals used in hydraulic systems of transfer machines will change. While traditional methods can only analyze one of the material properties or seal properties, the failure of the O-ring is caused by these two factors together. In this paper, two factors are mainly analyzed: the degradation of material properties and load randomization by processing technology. Firstly, the two factors are defined in terms of material failure and seal failure, before the experimental methods of rubber materials are studied. Following this, the time-variant material properties through experiments and load distribution by monitoring the processing can be obtained. Thirdly, compressive stress and contact stress have been calculated, which was combined with the reliability model to acquire the time-variant reliability for the O-ring. Finally, the life prediction and effect of oil pressure were discussed, then compared with the actual situation. The results show a lifetime of 12 months for the O-ring calculated in this paper, and compared with the replacement records from the maintenance workshop, the result is credible. PMID:29053597

Cometabolic degradation of trichloroethene by Rhodococcus sp. strain L4 immobilized on plant materials rich in essential oils.

PubMed

Suttinun, Oramas; Müller, Rudolf; Luepromchai, Ekawan

2010-07-01

The cometabolic degradation of trichloroethene (TCE) by Rhodococcus sp. L4 was limited by the loss of enzyme activity during TCE transformation. This problem was overcome by repeated addition of inducing substrates, such as cumene, limonene, or cumin aldehyde, to the cells. Alternatively, Rhodococcus sp. L4 was immobilized on plant materials which contain those inducers in their essential oils. Cumin seeds were the most suitable immobilizing material, and the immobilized cells tolerated up to 68 muM TCE and degraded TCE continuously. The activity of immobilized cells, which had been inactivated partially during TCE degradation, could be reactivated by incubation in mineral salts medium without TCE. These findings demonstrate that immobilization of Rhodococcus sp. L4 on plant materials rich in essential oils is a promising method for efficient cometabolic degradation of TCE.

Cometabolic Degradation of Trichloroethene by Rhodococcus sp. Strain L4 Immobilized on Plant Materials Rich in Essential Oils▿ †

PubMed Central

Suttinun, Oramas; Müller, Rudolf; Luepromchai, Ekawan

2010-01-01

The cometabolic degradation of trichloroethene (TCE) by Rhodococcus sp. L4 was limited by the loss of enzyme activity during TCE transformation. This problem was overcome by repeated addition of inducing substrates, such as cumene, limonene, or cumin aldehyde, to the cells. Alternatively, Rhodococcus sp. L4 was immobilized on plant materials which contain those inducers in their essential oils. Cumin seeds were the most suitable immobilizing material, and the immobilized cells tolerated up to 68 μM TCE and degraded TCE continuously. The activity of immobilized cells, which had been inactivated partially during TCE degradation, could be reactivated by incubation in mineral salts medium without TCE. These findings demonstrate that immobilization of Rhodococcus sp. L4 on plant materials rich in essential oils is a promising method for efficient cometabolic degradation of TCE. PMID:20472723

Overview of NRC Proactive Management of Materials Degradation (PMMD) Program

NASA Astrophysics Data System (ADS)

Carpenter, C. E. Gene; Hull, Amy; Oberson, Greg

Materials degradation phenomena, if not appropriately managed, have the potential to adversely impact the design functionality and safety margins of nuclear power plant (NPP) systems, structures and components (SSCs). Therefore, the U.S. Nuclear Regulatory Commission (NRC) has initiated an over-the-horizon multi-year research Proactive Management of Materials Degradation (PMMD) Research Program, which is presently evaluating longer time frames (i.e., 80 or more years) and including passive long-lived SSCs beyond the primary piping and core internals, such as concrete containment and cable insulation. This will allow the NRC to (1) identify significant knowledge gaps and new forms of degradation; (2) capture current knowledge base; and, (3) prioritize materials degradation research needs and directions for future efforts. This effort is being accomplished in collaboration with the U.S. Department of Energy's (DOE) LWR Sustainability (LWRS) program. This presentation will discuss the activities to date, including results, and the path forward.

Reactive Black 5 dye degradation using filters of smuggled cigarette modified with Fe3.

PubMed

Glugoski, Letícia Polli; de Jesus Cubas, Paloma; Fujiwara, Sérgio Toshio

2017-03-01

This study presents an attempt to solve two serious environmental problems: the generation of toxic effluents and solid waste disposal. The work proposes recycling cigarette filters with the purpose of degrading reactive dyes, which are used in the textile industry. Filters of smuggled cigarettes were recycled through Fe 3+ immobilization on their surface. The material obtained was characterized through Fourier transform infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and ultraviolet-visible spectroscopy (UV-vis). The factorial design revealed that the most suitable conditions for the degradation of Reactive Black 5 dye were obtained by using 1 g of material at pH 3.0 in a 100 mg L -1 hydrogen peroxide solution. The material showed excellent performance in the Reactive Black 5 dye degradation process; in 60 min, 99.09 % dye was removed. At pH 7.0, the dye degradation was 72.67 %, indicating that the material prepared can be used at pH values greater than 3.0 without the occurrence of hydrated Fe 3+ oxide precipitation. Furthermore, the material showed no loss of catalytic activity after three degradation studies.

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

NASA Technical Reports Server (NTRS)

Boyce, Lola; Bast, Callie C.

1992-01-01

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

The effects of acid erosion and remineralization on enamel and three different dental materials: FT-Raman spectroscopy and scanning electron microscopy analysis.

PubMed

Soares, Luís Eduardo Silva; Soares, Ana Lúcia Silva; De Oliveira, Rodrigo; Nahórny, Sidnei

2016-07-01

FT-Raman spectroscopy and scanning electron microscopy (SEM) were employed to test the hypothesis that the beverage consumption or mouthwash utilization would change the chemistry of dental materials and enamel inorganic content. Bovine enamel samples (n = 36) each received two cavity preparations (n = 72), each pair filled with one of three dental materials (R: nanofilled composite resin, GIC: glass-ionomer cement, RMGIC: resin-modified GIC). Furthermore, they were treated with three different solutions (S: artificial saliva, E: erosion/Pepsi Twist or EM: erosion + mouthwash/Colgate Plax). Reduction of carbonate content of enamel was greater in RE than RS (P < 0.01). Increment of carbonate was greater in GICEM than in GICE and GICS (P < 0.01; P < 0.001). Significant material degradation was found in RE, REM, GICE, and GICEM than in RS and GICS (P < 0.01; P < 0.001). SEM showed clear enamel demineralization after erosion. Material degradation was greater after E and EM than S. GIC and RMGIC materials had a positive effect against acid erosion in the adjacent enamel after remineralization with mouthwash. The beverage and mouthwash utilization would change R and GIC chemical properties. A professional should periodically monitor the glass-ionomer and resin restorations, as they degrade over time under erosive challenges and mouthwash utilization. Microsc. Res. Tech., 2016. © 2016 Wiley Periodicals, Inc. Microsc. Res. Tech. 79:646-656, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Methods for degrading lignocellulosic materials

DOEpatents

Vlasenko, Elena [Davis, CA; Cherry, Joel [Davis, CA; Xu, Feng [Davis, CA

2008-04-08

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

Methods for degrading lignocellulosic materials

DOEpatents

Vlasenko, Elena [Davis, CA; Cherry, Joel [Davis, CA; Xu, Feng [Davis, CA

2011-05-17

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

Methods for degrading lignocellulosic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlasenko, Elena; Cherry, Joel; Xu, Feng

2008-04-08

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

The Lone Ranger Mission: Understanding Synthetic Polymer Microbe Interactions In the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Mielke, R.; Neal, A.; Stam, C. N.; Ferry, J. G.; Schlegel, R.; Tsapin, A. I.; Park, S.; Bhartia, R.; Salas, E.; Hug, W.; Behar, A. E.; Nadeau, J.

2011-12-01

Pollution is one of the most ubiquitous and insidious problems currently facing the oceans. As synthetic polymer debris degrades, it becomes increasingly accessible to organisms that forage or absorb food particles. However, research on this significant environmental pollution problem has not been able to keep up with the scope of the issue, since some of the first studies published in 1972 by Edward Carpenter. In January 2011, The Lone Ranger Atlantic Expedition, a collaboration between Blue Ocean Sciences (BOS) and the Schmidt Ocean Institute (SOI) transected the Atlantic Ocean covering 3,100 nautical miles sampling the first 15cm of the water column to investigate microbial interactions with synthetic polymer marine debris. Using established and novel techniques of Fourier transform infrared spectroscopy (FT-IR), scanning transmission electron microscopy (STEM), environmental scanning electron microscopy (ESEM), and gas chromatography-mass spectrometry (GC-MS), we were able to image and locate material degradation of pre-production, association of microbial biofilms, and accumulation of persistent organic pollutants (POP's) on environmental microplastics. We then used Spectroscopic Organic Analysis and ArcGIS mapping systems to observe the material degradation and the associated biofilm lattice on the environmental microplastics. This data sheds light on possible mechanisms of material weathering of synthetic polymers in deep ocean environments and new methods for identifying POP's association with them. These new techniques are highly transferable to many studies on material biofilm interactions in the environment.

Environmental degradation of composites for marine structures: new materials and new applications

PubMed Central

2016-01-01

This paper describes the influence of seawater ageing on composites used in a range of marine structures, from boats to tidal turbines. Accounting for environmental degradation is an essential element in the multi-scale modelling of composite materials but it requires reliable test data input. The traditional approach to account for ageing effects, based on testing samples after immersion for different periods, is evolving towards coupled studies involving strong interactions between water diffusion and mechanical loading. These can provide a more realistic estimation of long-term behaviour but still require some form of acceleration if useful data, for 20 year lifetimes or more, are to be obtained in a reasonable time. In order to validate extrapolations from short to long times, it is essential to understand the degradation mechanisms, so both physico-chemical and mechanical test data are required. Examples of results from some current studies on more environmentally friendly materials including bio-sourced composites will be described first. Then a case study for renewable marine energy applications will be discussed. In both cases, studies were performed first on coupons at the material level, then during structural testing and analysis of large components, in order to evaluate their long-term behaviour. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242304

Stability of Materials in High Temperature Water Vapor: SOFC Applications

NASA Technical Reports Server (NTRS)

Opila, E. J.; Jacobson, N. S.

2010-01-01

Solid oxide fuel cell material systems require long term stability in environments containing high-temperature water vapor. Many materials in fuel cell systems react with high-temperature water vapor to form volatile hydroxides which can degrade cell performance. In this paper, experimental methods to characterize these volatility reactions including the transpiration technique, thermogravimetric analysis, and high pressure mass spectrometry are reviewed. Experimentally determined data for chromia, silica, and alumina volatility are presented. In addition, data from the literature for the stability of other materials important in fuel cell systems are reviewed. Finally, methods for predicting material recession due to volatilization reactions are described.

Enzymatic Formulation Capable of Degrading Scrapie Prion under Mild Digestion Conditions

PubMed Central

Okoroma, Emeka A.; Purchase, Diane; Garelick, Hemda; Morris, Roger; Neale, Michael H.; Windl, Otto; Abiola, Oduola O.

2013-01-01

The prion agent is notoriously resistant to common proteases and conventional sterilisation procedures. The current methods known to destroy prion infectivity such as incineration, alkaline and thermal hydrolysis are harsh, destructive, environmentally polluting and potentially hazardous, thus limit their applications for decontamination of delicate medical and laboratory devices, remediation of prion contaminated environment and for processing animal by-products including specified risk materials and carcases. Therefore, an environmentally friendly, non-destructive enzymatic degradation approach is highly desirable. A feather-degrading Bacillus licheniformis N22 keratinase has been isolated which degraded scrapie prion to undetectable level of PrPSc signals as determined by Western Blot analysis. Prion infectivity was verified by ex vivo cell-based assay. An enzymatic formulation combining N22 keratinase and biosurfactant derived from Pseudomonas aeruginosa degraded PrPSc at 65°C in 10 min to undetectable level -. A time-course degradation analysis carried out at 50°C over 2 h revealed the progressive attenuation of PrPSc intensity. Test of residual infectivity by standard cell culture assay confirmed that the enzymatic formulation reduced PrPSc infectivity to undetectable levels as compared to cells challenged with untreated standard scrapie sheep prion (SSBP/1) (p-value = 0.008 at 95% confidence interval). This novel enzymatic formulation has significant potential application for prion decontamination in various environmentally friendly systems under mild treatment conditions. PMID:23874511

A degradation function consistent with Cocks–Ashby porosity kinetics

DOE PAGES

Moore, John A.

2017-10-14

Here, the load carrying capacity of ductile materials degrades as a function of porosity, stress state and strain-rate. The effect of these variables on porosity kinetics is captured by the Cocks–Ashby model; however, the Cocks–Ashby model does not account for material degradation directly. This work uses a yield criteria to form a degradation function that is consistent with Cocks–Ashby porosity kinetics and is a function of porosity, stress state and strain-rate dependence. Approximations of this degradation function for pure hydrostatic stress states are also explored.

A degradation function consistent with Cocks–Ashby porosity kinetics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, John A.

Here, the load carrying capacity of ductile materials degrades as a function of porosity, stress state and strain-rate. The effect of these variables on porosity kinetics is captured by the Cocks–Ashby model; however, the Cocks–Ashby model does not account for material degradation directly. This work uses a yield criteria to form a degradation function that is consistent with Cocks–Ashby porosity kinetics and is a function of porosity, stress state and strain-rate dependence. Approximations of this degradation function for pure hydrostatic stress states are also explored.

The influence of hydroxyapatite particles on in vitro degradation behavior of poly epsilon-caprolactone-based composite scaffolds.

PubMed

Guarino, Vincenzo; Taddei, Paola; Di Foggia, Michele; Fagnano, Concezio; Ciapetti, Gabriela; Ambrosio, Luigi

2009-11-01

The design of composite scaffolds with slow degradation kinetics imposes the assessment of the time-course of degradation to predict the long-term in vitro behavior. In this work, the effect of hydroxyapatite (HA) particles on the hydrolytic degradation of poly epsilon-caprolactone composite scaffold was investigated. The study of accelerated degradation mechanisms in alkaline medium enabled analysing comparable degradation profiles at different times. The accurate qualitative and quantitative study of morphology by scanning electron microscopy supported by image analysis demonstrated only a negligible effect on the structural porosity, to be ascribed to the addition of micrometric HA as a filler. Moreover, by comparing the Raman spectra with thermal analysis(thermogravimetry and differential scanning calorimetry) the role of HA on the composite degradation mechanism was defined, by separately quantifying the contribution of HA particles in the bulk and on the surface, on the bone formation as a function of modifications induced in the pore morphology, as well as physical and chemical properties of the polymer matrix. Indeed, HA particles alter the poly epsilon-caprolactone crystallinity inducing a "shielding" effect of the polymer matrix. Meanwhile, the slight reduction of pore size as a function of the increasing HA content and the improvement of the effective hydrophilicity of the scaffolds also influence the degradation by faster mechanisms. Finally, it has been proven that the presence of HA enhances the scaffold bioactivity and human osteoblast cell response, remarking the active role of bioactive signals on the promotion of the surface mineralization and, as a consequence, on the cell-material interaction.

Final report for SERDP WP-2209 Replacement melt-castable formulations for Composition B

DTIC Science & Technology

2017-05-19

Chemical reaction of the materials in the melt ............................................................... 5 Thermal degradation of materials...reasons other than the hazard of explosion, these include: • Chemical reaction of the materials in the melt • Thermal degradation at low...temperature • Sublimation and condensation of explosive material on equipment and exposure to workers Chemical reaction of the materials in the melt

Bone regeneration capacity of magnesium phosphate cements in a large animal model.

PubMed

Kanter, Britta; Vikman, Anna; Brückner, Theresa; Schamel, Martha; Gbureck, Uwe; Ignatius, Anita

2018-03-15

Magnesium phosphate minerals have captured increasing attention during the past years as suitable alternatives for calcium phosphate bone replacement materials. Here, we investigated the degradation and bone regeneration capacity of experimental struvite (MgNH 4 PO 4 ·6H 2 O) forming magnesium phosphate cements in two different orthotopic ovine implantation models. Cements formed at powder to liquid ratios (PLR) of 2.0 and 3.0 g ml -1 were implanted into trabecular bone using a non-load-bearing femoral drill-hole model and a load-bearing tibial defect model. After 4, 7 and 10 months the implants were retrieved and cement degradation and new bone formation was analyzed by micro-computed tomography (µCT) and histomorphometry. The results showed cement degradation in concert with new bone formation at both defect locations. Both cements were almost completely degraded after 10 months. The struvite cement formed with a PLR of 2.0 g ml -1 exhibited a slightly accelerated degradation kinetics compared to the cement with a PLR of 3.0 g ml -1 . Tartrat-resistant acid phosphatase (TRAP) staining indicated osteoclastic resorption at the cement surface. Energy dispersive X-ray analysis (EDX) revealed that small residual cement particles were mostly accumulated in the bone marrow in between newly formed bone trabeculae. Mechanical loading did not significantly increase bone formation associated with cement degradation. Concluding, struvite-forming cements might be promising bone replacement materials due to their good degradation which is coupled with new bone formation. Recently, the interest in magnesium phosphate cements (MPC) for bone substitution increased, as they exhibit high initial strength, comparably elevated degradation potential and the release of valuable magnesium ions. However, only few in vivo studies, mostly including non-load-bearing defects in small animals, have been performed to analyze the degradation and regeneration capability of MPC derived compounds. The present study examined the in vivo behavior of magnesiumammoniumphosphate hexahydrate (struvite) implants with different porosity in both mechanically loaded and non-loaded defects of merino sheep. For the first time, the effect of mechanical stimuli on the biological outcome of this clinically relevant replacement material is shown and directly compared to the conventional unloaded defect situation in a large animal model. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Thermal Degradation Kinetics Modeling of Benzophenones and Xanthones during High-Temperature Oxidation of Cyclopia genistoides (L.) Vent. Plant Material.

PubMed

Beelders, Theresa; de Beer, Dalene; Joubert, Elizabeth

2015-06-10

Degradation of the major benzophenones, iriflophenone-3-C-glucoside-4-O-glucoside and iriflophenone-3-C-glucoside, and the major xanthones, mangiferin and isomangiferin, of Cyclopia genistoides followed first-order reaction kinetics during high-temperature oxidation of the plant material at 80 and 90 °C. Iriflophenone-3-C-glucoside-4-O-glucoside was shown to be the most thermally stable compound. Isomangiferin was the second most stable compound at 80 °C, while its degradation rate constant was influenced the most by increased temperature. Mangiferin and iriflophenone-3-C-glucoside had comparable degradation rate constants at 80 °C. The thermal degradation kinetic model was subsequently evaluated by subjecting different batches of plant material to oxidative conditions (90 °C/16 h). The model accurately predicted the individual contents of three of the compounds in aqueous extracts prepared from oxidized plant material. The impact of benzophenone and xanthone degradation was reflected in the decreased total antioxidant capacity of the aqueous extracts, as determined using the oxygen radical absorbance capacity and DPPH(•) scavenging assays.

Photocatalytic degradation of leather dye over ZnO catalyst supported on alumina and glass surfaces.

PubMed

Sakthivel, S; Neppoiian, B; Palanichamy, M; Arabindoo, B; Murugesan, V

2001-01-01

The photocatalytic degradation of leather dye, Acid green 16, has been investigated over a ZnO catalyst supported on two different materials, namely alumina and glass beads (3-5 mm diameter). Sunlight was used as the energy source. The alumina-supported ZnO outperformed the glass-supported ZnO under identical operational conditions suggesting that the dye molecules are adsorbed on the alumina supports to make a high concentration environment around the loaded ZnO. The degradation efficiency was greater at pH = 4 compared to other acidic and neutral pH. Also, the degradation efficiency was a little bit higher in alkaline medium, which correlates with the adsorption behaviour of acid green 16 on the alumina supported ZnO. The influence of inorganic oxidants like H2O2, FeCl3 and Fenton reagent on the degradation efficiency were systematically studied. The decolourisation and extent of degradation of the dye were determined by UV-VIS spectroscopy and COD reflux methods, respectively. Complete mineralisation of the dye was conformed by High performance liquid chromatography (HPLC) analysis.

Secretion of small proteins is species-specific within Aspergillus sp.

PubMed

Valette, Nicolas; Benoit-Gelber, Isabelle; Falco, Marcos Di; Wiebenga, Ad; de Vries, Ronald P; Gelhaye, Eric; Morel-Rouhier, Mélanie

2017-03-01

Small secreted proteins (SSP) have been defined as proteins containing a signal peptide and a sequence of less than 300 amino acids. In this analysis, we have compared the secretion pattern of SSPs among eight aspergilli species in the context of plant biomass degradation and have highlighted putative interesting candidates that could be involved in the degradative process or in the strategies developed by fungi to resist the associated stress that could be due to the toxicity of some aromatic compounds or reactive oxygen species released during degradation. Among these candidates, for example, some stress-related superoxide dismutases or some hydrophobic surface binding proteins (HsbA) are specifically secreted according to the species . Since these latter proteins are able to recruit lytic enzymes to the surface of hydrophobic solid materials and promote their degradation, a synergistic action of HsbA with the degradative system may be considered and need further investigations. These SSPs could have great applications in biotechnology by optimizing the efficiency of the enzymatic systems for biomass degradation. © 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

W. L. Poe, Jr.; P.F. Wise

The U.S. Department of Energy (DOE) is preparing a proposal to construct, operate 2nd monitor, and eventually close a repository at Yucca Mountain in Nye County, Nevada, for the geologic disposal of spent nuclear fuel (SNF) and high-level radioactive waste (HLW). As part of this effort, DOE has prepared a viability assessment and an assessment of potential consequences that may exist if the repository is not constructed. The assessment of potential consequences if the repository is not constructed assumes that all SNF and HLW would be left at the generator sites. These include 72 commercial generator sites (three commercial facilitymore » pairs--Salem and Hope Creek, Fitzpatrick and Nine Mile Point, and Dresden and Morris--would share common storage due to their close proximity to each other) and five DOE sites across the country. DOE analyzed the environmental consequences of the effects of the continued storage of these materials at these sites in a report titled Continued Storage Analysis Report (CSAR; Reference 1 ) . The CSAR analysis includes a discussion of the degradation of these materials when exposed to the environment. This document describes the environmental parameters that influence the degradation analyzed in the CSAR. These include temperature, relative humidity, precipitation chemistry (pH and chemical composition), annual precipitation rates, annual number of rain-days, and annual freeze/thaw cycles. The document also tabulates weather conditions for each storage site, evaluates the degradation of concrete storage modules and vaults in different regions of the country, and provides a thermal analysis of commercial SNF in storage.« less

Combined optical gain and degradation measurements in DCM2 doped Tris-(8-hydroxyquinoline)aluminum thin-films

NASA Astrophysics Data System (ADS)

Čehovski, Marko; Döring, Sebastian; Rabe, Torsten; Caspary, Reinhard; Kowalsky, Wolfgang

2016-04-01

Organic laser sources offer the opportunity to integrate flexible and widely tunable lasers in polymer waveguide circuits, e.g. for Lab-on-Foil applications. Therefore, it is necessary to understand gain and degradation processes for long-term operation. In this paper we address the challenge of life-time (degradation) measurements of photoluminescence (PL) and optical gain in thin-film lasers. The well known guest-host system of aluminum-chelate Alq3 (Tris-(8-hydroxyquinoline)aluminum) as host material and the laser dye DCM2 (4-(Dicyanomethylene)-2- methyl-6-julolidyl-9-enyl-4H-pyran) as guest material is employed as laser active material. Sample layers have been built up by co-evaporation in an ultrahigh (UHV) vacuum chamber. 200nm thick films of Alq3:DCM2 with different doping concentrations have been processed onto glass and thermally oxidized silicon substrates. The gain measurements have been performed by the variable stripe length (VSL) method. This measurement technique allows to determine the thin-film waveguide gain and loss, respectively. For the measurements the samples were excited with UV irradiation (ƛ = 355nm) under nitrogen atmosphere by a passively Q-switched laser source. PL degradation measurements with regard to the optical gain have been done at laser threshold (approximately 3 μJ/cm2), five times above laser threshold and 10 times above laser threshold. A t50-PL lifetime of > 107 pulses could be measured at a maximum excitation energy density of 32 μJ/cm2. This allows for a detailed analysis of the gain degradation mechanism and therefore of the stimulated cross section. Depending on the DCM2 doping concentration C the stimulated cross section was reduced by 35 %. Nevertheless, the results emphasizes the necessity of the investigation of degradation processes in organic laser sources for long-term applications.

Novel Zn-based alloys for biodegradable stent applications: Design, development and in vitro degradation.

PubMed

Mostaed, E; Sikora-Jasinska, M; Mostaed, A; Loffredo, S; Demir, A G; Previtali, B; Mantovani, D; Beanland, R; Vedani, M

2016-07-01

The search for a degradable metal simultaneously showing mechanical properties equal or higher to that of stainless steel and uniform degradation is still an open challenge. Several magnesium-based alloys have been studied, but their degradation rate has proved to be too fast and rarely homogeneous. Fe-based alloys show appropriate mechanical properties but very low degradation rate. In the present work, four novel Zn-Mg and two Zn-Al binary alloys were investigated as potential biodegradable materials for stent applications. The alloys were developed by casting process and homogenized at 350°C for 48h followed by hot extrusion at 250°C. Tube extrusion was performed at 300°C to produce tubes with outer/inner diameter of 4/1.5mm as precursors for biodegradable stents. Corrosion tests were performed using Hanks׳ modified solution. Extruded alloys exhibited slightly superior corrosion resistance and slower degradation rate than those of their cast counterparts, but all had corrosion rates roughly half that of a standard purity Mg control. Hot extrusion of Zn-Mg alloys shifted the corrosion regime from localized pitting to more uniform erosion, mainly due to the refinement of second phase particles. Zn-0.5Mg is the most promising material for stent applications with a good combination of strength, ductility, strain hardening exponent and an appropriate rate of loss of mechanical integrity during degradation. An EBSD analysis in the vicinity of the laser cut Zn-0.5Mg tube found no grain coarsening or texture modification confirming that, after laser cutting, the grain size and texture orientation of the final stent remains unchanged. This work shows the potential for Zn alloys to be considered for stent applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mechanical properties, morphology, and hydrolytic degradation behavior of polylactic acid / natural rubber blends

NASA Astrophysics Data System (ADS)

Buys, Y. F.; Aznan, A. N. A.; Anuar, H.

2018-01-01

Due to its biodegradability and renewability, polylactic acid (PLA) has been receiving enormous attention as a potential candidate to replace petroleum based polymers. However, PLA has limitation due to its inherent brittleness. In order to overcome this limitation, blending PLA with elastomeric materials such as natural rubber (NR) are commonly reported. In previous, several researches on PLA/NR blend had been reported, with most of them evaluated the mechanical properties. On the other hand, study of degradation behavior is significance of importance, as controlling materials degradation is required in some applications. This research studied the effect of blend composition on mechanical properties, morphology development, and hydrolytic degradation behavior of PLA/NR blends. Various compositions of PLA/NR blends were prepared by melt blending technique. Tensile test and impact test of the blends were performed to evaluate the mechanical properties. Addition of NR improved the elongation at break and impact strength of the blends, but reduced the tensile strength and stiffness of the specimens. Dynamic Mechanical Analysis (DMA) measurements of the blends displayed two peaks at temperature -70˚C which corresponded to T g of NR and 65˚C which corresponded to T g of PLA. Field Emission Scanning Electron Microscopy (FE-SEM) micrograph of 70/30 PLA/NR specimen also showed two distinct phases, which lead to indication that PLA/NR blends are immiscible. Hydrolytic degradation behavior was evaluated by measuring the remaining weight of the samples immersed in sodium hydroxide solution for a predetermined times. It was shown that the degradation behavior of PLA/NR blends is affected by composition of the blends, with 100 PLA and 70/30 PLA/NR blend showed the fastest degradation rate and 100 NR displayed the slowest one.

Materials interactions between the thermoelectric converter and the 5kwe reactor system

NASA Technical Reports Server (NTRS)

Ferry, P. B.

1973-01-01

The integration of a compact thermoelectric converter with a 5-kwe reactor system is described. Material interaction uncertainties study is also presented. This includes degradation of the required austenitic - refractory metal transition joint during operation at high temperatures; loss of corrosion resistance; embrittlement by the presence of hydrogen; and loss of design margin by transport of interstitial elements. Analysis and limited experimental evidence indicate that these potential materials interactions can be adequately controlled. Group 5-2 refractory metals can be utilized without unacceptable adverse effect on system reliability.

Characterisation of the biochemical methane potential (BMP) of individual material fractions in Danish source-separated organic household waste.

PubMed

Naroznova, Irina; Møller, Jacob; Scheutz, Charlotte

2016-04-01

This study is dedicated to characterising the chemical composition and biochemical methane potential (BMP) of individual material fractions in untreated Danish source-separated organic household waste (SSOHW). First, data on SSOHW in different countries, available in the literature, were evaluated and then, secondly, laboratory analyses for eight organic material fractions comprising Danish SSOHW were conducted. No data were found in the literature that fully covered the objectives of the present study. Based on laboratory analyses, all fractions were assigned according to their specific properties in relation to BMP, protein content, lipids, lignocellulose biofibres and easily degradable carbohydrates (carbohydrates other than lignocellulose biofibres). The three components in lignocellulose biofibres, i.e. lignin, cellulose and hemicellulose, were differentiated, and theoretical BMP (TBMP) and material degradability (BMP from laboratory incubation tests divided by TBMP) were expressed. Moreover, the degradability of lignocellulose biofibres (the share of volatile lignocellulose biofibre solids degraded in laboratory incubation tests) was calculated. Finally, BMP for average SSOHW composition in Denmark (untreated) was calculated, and the BMP contribution of the individual material fractions was then evaluated. Material fractions of the two general waste types, defined as "food waste" and "fibre-rich waste," were found to be anaerobically degradable with considerable BMP. Material degradability of material fractions such as vegetation waste, moulded fibres, animal straw, dirty paper and dirty cardboard, however, was constrained by lignin content. BMP for overall SSOHW (untreated) was 404 mL CH4 per g VS, which might increase if the relative content of material fractions, such as animal and vegetable food waste, kitchen tissue and dirty paper in the waste, becomes larger. Copyright © 2016 Elsevier Ltd. All rights reserved.

Specially designed B4C/SnO2 nanocomposite for photocatalysis: traditional ceramic with unique properties

NASA Astrophysics Data System (ADS)

Singh, Paviter; Kaur, Gurpreet; Singh, Kulwinder; Singh, Bikramjeet; Kaur, Manpreet; Kaur, Manjot; Krishnan, Unni; Kumar, Manjeet; Bala, Rajni; Kumar, Akshay

2018-02-01

Boron carbide: A traditional ceramic material shows unique properties when explored in nano-range. Specially designed boron-based nanocomposite has been synthesized by reflux method. The addition of SnO2 in base matrix increases the defect states in boron carbide and shows unique catalytic properties. The calculated texture coefficient and Nelson-Riley factor show that the synthesized nanocomposite has large number of defect states. Also this composite is explored for the first time for catalysis degradation of industrial used dyes. The degradation analysis of industrial pollutants such as Novacron red Huntsman (NRH) and methylene blue (MB) dye reveals that the composite is an efficient catalyst. Degradation study shows that 1 g/L catalyst concentration of B4C/SnO2 degrades NRH and MB dye up to approximately 97.38 and 79.41%, respectively, in 20 min under sunlight irradiation. This water-insoluble catalyst can be recovered and reused.

Sulphated Electric Arc Furnace Slag Asfenton-Like Catalyst for Degradation of Reactive Black 5

NASA Astrophysics Data System (ADS)

Zubir, N. A.; Nasuha, N.; Alrozi, R.

2018-06-01

Sulphated electric arc furnace slag (S-EAFS) was obtained through a facile chemical and thermal treatment method. The S-EAFS was evaluated as a Fenton-like catalyst for the oxidative degradation of reactive black 5 (RB5). The S-EAFS was characterized by XRD, SEM-EDX and nitrogen adsorption analysis. The highest RB5 degradation efficiency obtained in this study was above 90% which was maintained across seven successive cycles with minimum iron leaching. This was achieved at a RB5 concentration of 0.15 gL-1 (50 ppm) with 8 mM of H2O2 and a pH of 4.5. Characterization revealed that the presence of sulphated groups (SO4 2-) within the EAFS improved the surface acidity of the material and corresponded to an increase in the catalytic activity for the degradation of RB5 at mild pH.

Considerations for spectroscopy of liquid-exfoliated 2D materials: emerging photoluminescence of N-methyl-2-pyrrolidone.

PubMed

Ogilvie, Sean P; Large, Matthew J; Fratta, Giuseppe; Meloni, Manuela; Canton-Vitoria, Ruben; Tagmatarchis, Nikos; Massuyeau, Florian; Ewels, Christopher P; King, Alice A K; Dalton, Alan B

2017-12-01

N-methyl-2-pyrrolidone (NMP) has been shown to be the most effective solvent for liquid phase exfoliation and dispersion of a range of 2D materials including graphene, molybdenum disulphide (MoS 2 ) and black phosphorus. However, NMP is also known to be susceptible to sonochemical degradation during exfoliation. We report that this degradation gives rise to strong visible photoluminescence of NMP. Sonochemical modification is shown to influence exfoliation of layered materials in NMP and the optical absorbance of the solvent in the dispersion. The emerging optical properties of the degraded solvent present challenges for spectroscopy of nanomaterial dispersions; most notably the possibility of observing solvent photoluminescence in the spectra of 2D materials such as MoS 2 , highlighting the need for stable solvents and exfoliation processes to minimise the influence of solvent degradation on the properties of liquid-exfoliated 2D materials.

Techniques used for limiting degradation products of polymeric materials for use in the space environment

NASA Technical Reports Server (NTRS)

Vest, C. E.; Park, J. J.

1978-01-01

Techniques are discussed for limiting or controlling the degradation products (outgassing) of polymeric materials in the space environment. One technique, now ASTM E-595-77, is used to screen out those materials which lose greater than 1% Total Mass Loss when in vacuum for 24 hours at 125 C and which have more than 0.10% Collected Volatile Condensable Materials condensing on a collector surface at 25 C. Examples of silicone materials which are high and low in outgassing are given. The numerous mechanical motions in spacecraft experiments require liquid lubricants which also might degrade in space. Labyrinth seals and barrier films are utilized to limit the degradation of or from these lubricants. A recoverable in-flight experiment has been proposed for making definitive measurements of how effective these techniques are in limiting the amounts and escape paths of outgassed molecules.

Degradable vinyl polymers for biomedical applications.

PubMed

Delplace, Vianney; Nicolas, Julien

2015-10-01

Vinyl polymers have been the focus of intensive research over the past few decades and are attractive materials owing to their ease of synthesis and their broad diversity of architectures, compositions and functionalities. Their carbon-carbon backbones are extremely resistant to degradation, however, and this property limits their uses. Degradable polymers are an important field of research in polymer science and have been used in a wide range of applications spanning from (nano)medicine to microelectronics and environmental protection. The development of synthetic strategies to enable complete or partial degradation of vinyl polymers is, therefore, of great importance because it will offer new opportunities for the application of these materials. This Review captures the most recent and promising approaches to the design of degradable vinyl polymers and discusses the potential of these materials for biomedical applications.

Current Insights into the Modulation of Oral Bacterial Degradation of Dental Polymeric Restorative Materials

PubMed Central

Zhang, Ning; Ma, Yansong; Weir, Michael D.; Xu, Hockin H. K.; Bai, Yuxing; Melo, Mary Anne S.

2017-01-01

Dental polymeric composites have become the first choice for cavity restorations due to their esthetics and capacity to be bonded to the tooth. However, the oral cavity is considered to be harsh environment for a polymeric material. Oral biofilms can degrade the polymeric components, thus compromising the marginal integrity and leading to the recurrence of caries. Recurrent caries around restorations has been reported as the main reason for restoration failure. The degradation of materials greatly compromises the clinical longevity. This review focuses on the degradation process of resin composites by oral biofilms, the mechanisms of degradation and its consequences. In addition, potential future developments in the area of resin-based dental biomaterials with an emphasis on anti-biofilm strategies are also reviewed. PMID:28772863

Silk Fibroin Degradation Related to Rheological and Mechanical Properties.

PubMed

Partlow, Benjamin P; Tabatabai, A Pasha; Leisk, Gary G; Cebe, Peggy; Blair, Daniel L; Kaplan, David L

2016-05-01

Regenerated silk fibroin has been proposed as a material substrate for biomedical, optical, and electronic applications. Preparation of the silk fibroin solution requires extraction (degumming) to remove contaminants, but results in the degradation of the fibroin protein. Here, a mechanism of fibroin degradation is proposed and the molecular weight and polydispersity is characterized as a function of extraction time. Rheological analysis reveals significant changes in the viscosity of samples while mechanical characterization of cast and drawn films shows increased moduli, extensibility, and strength upon drawing. Fifteen minutes extraction time results in degraded fibroin that generates the strongest films. Structural analysis by wide angle X-ray scattering (WAXS) and Fourier transform infrared spectroscopy (FTIR) indicates molecular alignment in the drawn films and shows that the drawing process converts amorphous films into the crystalline, β-sheet, secondary structure. Most interesting, by using selected extraction times, films with near-native crystallinity, alignment, and molecular weight can be achieved; yet maximal mechanical properties for the films from regenerated silk fibroin solutions are found with solutions subjected to some degree of degradation. These results suggest that the regenerated solutions and the film casting and drawing processes introduce more complexity than native spinning processes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3D Progressive Damage Modeling for Laminated Composite Based on Crack Band Theory and Continuum Damage Mechanics

NASA Technical Reports Server (NTRS)

Wang, John T.; Pineda, Evan J.; Ranatunga, Vipul; Smeltzer, Stanley S.

2015-01-01

A simple continuum damage mechanics (CDM) based 3D progressive damage analysis (PDA) tool for laminated composites was developed and implemented as a user defined material subroutine to link with a commercially available explicit finite element code. This PDA tool uses linear lamina properties from standard tests, predicts damage initiation with an easy-to-implement Hashin-Rotem failure criteria, and in the damage evolution phase, evaluates the degradation of material properties based on the crack band theory and traction-separation cohesive laws. It follows Matzenmiller et al.'s formulation to incorporate the degrading material properties into the damaged stiffness matrix. Since nonlinear shear and matrix stress-strain relations are not implemented, correction factors are used for slowing the reduction of the damaged shear stiffness terms to reflect the effect of these nonlinearities on the laminate strength predictions. This CDM based PDA tool is implemented as a user defined material (VUMAT) to link with the Abaqus/Explicit code. Strength predictions obtained, using this VUMAT, are correlated with test data for a set of notched specimens under tension and compression loads.

Application of advanced oxidation processes for cleaning of industrial water generated in wet dedusting of shaft furnace gases.

PubMed

Czaplicka, Marianna; Kurowski, Ryszard; Jaworek, Katarzyna; Bratek, Łukasz

2013-01-01

The paper presents results of studies into advanced oxidation processes in 03 and 03/UV systems. An advanced oxidation process (AOP) was conducted to reduce the load of impurities in circulating waters from wet de-dusting of shaft furnace gases. Besides inorganic impurities, i.e. mainly arsenic compounds (16 g As L(-1) on average), lead, zinc, chlorides and sulphates, the waters also contain some organic material. The organic material is composed of a complex mixture that contains, amongst others, aliphatic compounds, phenol and its derivatives, pyridine bases, including pyridine, and its derivatives. The test results show degradation of organic and inorganic compounds during ozonation and photo-oxidation processes. Analysis of the solutions from the processes demonstrated that the complex organic material in the industrial water was oxidized in ozonation and in photo-oxidation, which resulted in formation of aldehydes and carboxylic acids. Kinetic degradation of selected pollutants is presented. Obtained results indicated that the O3/UV process is more effective in degradation of organic matter than ozonation. Depending on the process type, precipitation of the solid phase was observed. The efficiency of solid-phase formation was higher in photo-oxidation with ozone. It was found that the precipitated solid phase is composed mainly of arsenic, iron and oxygen.

Phytate degradation by fungi and bacteria that inhabit sawdust and coffee residue composts.

PubMed

Fathallh Eida, Mohamed; Nagaoka, Toshinori; Wasaki, Jun; Kouno, Kenji

2013-01-01

Phytate is the primary source of organic phosphorus, but it cannot be directly utilized by plants and is strongly adsorbed by the soil, reducing bioavailability. Composting is a process used to improve the bioavailability of phytate in organic wastes through degradation by microorganisms. In this study, we aimed to investigate the phytate-degrading ability of fungi and bacteria that inhabit sawdust compost and coffee residue compost, and their contribution to the composting process. In the plate assay, the fungi that formed clear zones around their colonies belonged to the genera Mucor, Penicillium, Galactomyces, Coniochaeta, Aspergillus, and Fusarium, while the bacteria belonged to the genera Pseudomonas, Enterobacter, Chitinophaga, and Rahnella. Eight fungal isolates (genera Mucor, Penicillium, Galactomyces, and Coniochaeta) and four bacterial isolates (genera Pseudomonas, Enterobacter, and Rahnella) were selected to evaluate phytase activity in their liquid culture and their ability to degrade phytate in organic materials composed of mushroom media residue and rice bran. The selected fungi degraded phytate in organic materials to varying degrees. Penicillium isolates showed the highest degradation ability and Coniochaeta isolate exhibited relatively high degradation ability. The clear zone diameters of these fungal isolates displayed significantly positive and negative correlations with inorganic and phytate phosphorus contents in the organic materials after incubation, respectively; however, none of the selected bacteria reduced phytate phosphorus in organic materials. It is therefore possible that fungi are major contributors to phytate degradation during composting.

Environmental isolation task

NASA Technical Reports Server (NTRS)

Coulbert, C. D.

1982-01-01

The failure-analysis process was organized into a more specific set of long-term degradation steps so that material property change can be differentiated from module damage and module failure. Increasing module performance and life are discussed. A polymeric aging computer model is discussed. Early detection of polymer surface reactions due to aging is reported.

High-accuracy phase-field models for brittle fracture based on a new family of degradation functions

NASA Astrophysics Data System (ADS)

Sargado, Juan Michael; Keilegavlen, Eirik; Berre, Inga; Nordbotten, Jan Martin

2018-02-01

Phase-field approaches to fracture based on energy minimization principles have been rapidly gaining popularity in recent years, and are particularly well-suited for simulating crack initiation and growth in complex fracture networks. In the phase-field framework, the surface energy associated with crack formation is calculated by evaluating a functional defined in terms of a scalar order parameter and its gradients. These in turn describe the fractures in a diffuse sense following a prescribed regularization length scale. Imposing stationarity of the total energy leads to a coupled system of partial differential equations that enforce stress equilibrium and govern phase-field evolution. These equations are coupled through an energy degradation function that models the loss of stiffness in the bulk material as it undergoes damage. In the present work, we introduce a new parametric family of degradation functions aimed at increasing the accuracy of phase-field models in predicting critical loads associated with crack nucleation as well as the propagation of existing fractures. An additional goal is the preservation of linear elastic response in the bulk material prior to fracture. Through the analysis of several numerical examples, we demonstrate the superiority of the proposed family of functions to the classical quadratic degradation function that is used most often in the literature.

High UV light performance for the degradation of Rhodamine B dye by synthesized Bi2S3ZnO nanocomposite

NASA Astrophysics Data System (ADS)

Sangareswari, M.; Meenakshi Sundaram, M.

2017-05-01

Heterogeneous photocatalytic degradation of organics in water and wastewater by large band gap semiconductors has offered an attractive alternative for environmental remediation. Zinc oxide is a very fast and efficient catalyst because of its wide band gap and large exciton binding energy. In this study, an efficient Bi2S3ZnO was synthesized by sonochemical method. The obtained product was further characterized by TEM, SEM, XRD, FT-IR and UV-DRS analysis. Scanning electron microscopy images revealed that Bi2S3ZnO has flower-like structure. The synthesized flower-like Bi2S3ZnO nanocomposites were more efficient than commercial ZnO for the degradation of organic contaminants under UV light irradiation. The prepared material shows enhanced photocatalytic activity on Rhodamine B dye solution under UV light irradiation. The percentage removal of dye was calculated by UV-Vis spectrophotometer. In addition, Bi2S3ZnO showed tremendous photocatalytic stability after seven cycles under UV light irradiation. A possible mechanism for the photocatalytic oxidative degradation was also discussed. It is concluded that the Bi2S3ZnO nanocomposite acts as an excellent photocatalyst for the decomposition of RhB and it could be a potential material for essential wastewater treatment.

Bacteria encapsulated in layered double hydroxides: towards an efficient bionanohybrid for pollutant degradation.

PubMed

Halma, Matilte; Mousty, Christine; Forano, Claude; Sancelme, Martine; Besse-Hoggan, Pascale; Prevot, Vanessa

2015-02-01

A soft chemical process was successfully used to immobilize Pseudomonas sp. strain ADP (ADP), a well-known atrazine (herbicide) degrading bacterium, within a Mg2Al-layered double hydroxide host matrix. This approach is based on a simple, quick and ecofriendly direct coprecipitation of metal salts in the presence of a colloidal suspension of bacteria in water. It must be stressed that by this process the mass ratio between inorganic and biological components was easily tuned ranging from 2 to 40. This ratio strongly influenced the biological activity of the bacteria towards atrazine degradation. The better results were obtained for ratios of 10 or lower, leading to an enhanced atrazine degradation rate and percentage compared to free cells. Moreover the biohybrid material maintained this biodegradative activity after four cycles of reutilization and 3 weeks storage at 4°C. The ADP@MgAl-LDH bionanohybrid materials were completely characterized by X-ray diffraction (XRD), FTIR spectroscopy, thermogravimetric analysis and scanning and transmission electronic microscopy (SEM and TEM) evidencing the successful immobilization of ADP within the inorganic matrix. This synthetic approach could be readily extended to other microbial whole-cell immobilization of interest for new developments in biotechnological systems. Copyright © 2014 Elsevier B.V. All rights reserved.

Elastomer degradation sensor using a piezoelectric material

DOEpatents

Olness, Dolores U.; Hirschfeld, deceased, Tomas B.

1990-01-01

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.

Thermophilic biofilter for SO2 removal: performance and microbial characteristics.

PubMed

Zhang, Jingying; Li, Lin; Liu, Junxin

2015-03-01

A bench-scale thermophilic biofilter was applied to remove SO2 at 60°C in the present study. The SO2 concentration in the inlet stream ranged from 100mg/m(3) to 200mg/m(3). An average SO2 removal efficiency of 93.10% was achieved after developing acclimated organisms that can degrade SO2. The thermophilic biofilter effectively reduced SO2, with a maximum elimination capacity of 50.67g/m(3)/h at a loading rate of 51.44g/m(3)/h. Removal efficiency of the thermophilic biofilter was largely influenced by the water containing rate of the packing materials. The SO2 transfer in the biofilter included adsorption by the packing materials, dissolution in liquid, and microbial degradation. The main product of SO2 degradation was SO4(2-). The temporal shifts in the bacterial community that formed in the biofilter were determined through polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequence analysis. These shifts revealed a correlation between biofilter performance and bacterial community structure. Copyright © 2014 Elsevier Ltd. All rights reserved.

The Mars oxidant experiment (MOx) for Mars '96

NASA Technical Reports Server (NTRS)

McKay, C. P.; Grunthaner, F. J.; Lane, A. L.; Herring, M.; Bartman, R. K.; Ksendzov, A.; Manning, C. M.; Lamb, J. L.; Williams, R. M.; Ricco, A. J.;

Long-life mission reliability for outer planet atmospheric entry probes

NASA Technical Reports Server (NTRS)

Mccall, M. T.; Rouch, L.; Maycock, J. N.

1976-01-01

The results of a literature analysis on the effects of prolonged exposure to deep space environment on the properties of outer planet atmospheric entry probe components are presented. Materials considered included elastomers and plastics, pyrotechnic devices, thermal control components, metal springs and electronic components. The rates of degradation of each component were determined and extrapolation techniques were used to predict the effects of exposure for up to eight years to deep space. Pyrotechnic devices were aged under accelerated conditions to an equivalent of eight years in space and functionally tested. Results of the literature analysis of the selected components and testing of the devices indicated that no severe degradation should be expected during an eight year space mission.

Modeling Natural Space Ionizing Radiation Effects on External Materials

NASA Technical Reports Server (NTRS)

Alstatt, Richard L.; Edwards, David L.; Parker, Nelson C. (Technical Monitor)

2000-01-01

Predicting the effective life of materials for space applications has become increasingly critical with the drive to reduce mission cost. Programs have considered many solutions to reduce launch costs including novel, low mass materials and thin thermal blankets to reduce spacecraft mass. Determining the long-term survivability of these materials before launch is critical for mission success. This presentation will describe an analysis performed on the outer layer of the passive thermal control blanket of the Hubble Space Telescope. This layer had degraded for unknown reasons during the mission, however ionizing radiation (IR) induced embrittlement was suspected. A methodology was developed which allowed direct comparison between the energy deposition of the natural environment and that of the laboratory generated environment. Commercial codes were used to predict the natural space IR environment model energy deposition in the material from both natural and laboratory IR sources, and design the most efficient test. Results were optimized for total and local energy deposition with an iterative spreadsheet. This method has been used successfully for several laboratory tests at the Marshall Space Flight Center. The study showed that the natural space IR environment, by itself, did not cause the premature degradation observed in the thermal blanket.

Modeling natural space ionizing radiation effects on external materials

NASA Astrophysics Data System (ADS)

Altstatt, Richard L.; Edwards, David L.

2000-10-01

Predicting the effective life of materials for space applications has become increasingly critical with the drive to reduce mission cost. Programs have considered many solutions to reduce launch costs including novel, low mass materials and thin thermal blankets to reduce spacecraft mass. Determining the long-term survivability of these materials before launch is critical for mission success. This presentation will describe an analysis performed on the outer layer of the passive thermal control blanket of the Hubble Space Telescope. This layer had degraded for unknown reasons during the mission, however ionizing radiation (IR) induced embrittlement was suspected. A methodology was developed which allowed direct comparison between the energy deposition of the natural environment and that of the laboratory generated environment. Commercial codes were used to predict the natural space IR environment, model energy deposition in the material from both natural and laboratory IR sources, and design the most efficient test. Results were optimized for total and local energy deposition with an iterative spreadsheet. This method has been used successfully for several laboratory tests at the Marshall Space Flight Center. The study showed that the natural space IR environment, by itself, did not cause the premature degradation observed in the thermal blanket.

Self-degradable Cementitious Sealing Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2010-10-01

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 silicatemore » 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.« less

Rock Failure Analysis Based on a Coupled Elastoplastic-Logarithmic Damage Model

NASA Astrophysics Data System (ADS)

Abdia, M.; Molladavoodi, H.; Salarirad, H.

2017-12-01

The rock materials surrounding the underground excavations typically demonstrate nonlinear mechanical response and irreversible behavior in particular under high in-situ stress states. The dominant causes of irreversible behavior are plastic flow and damage process. The plastic flow is controlled by the presence of local shear stresses which cause the frictional sliding. During this process, the net number of bonds remains unchanged practically. The overall macroscopic consequence of plastic flow is that the elastic properties (e.g. the stiffness of the material) are insensitive to this type of irreversible change. The main cause of irreversible changes in quasi-brittle materials such as rock is the damage process occurring within the material. From a microscopic viewpoint, damage initiates with the nucleation and growth of microcracks. When the microcracks length reaches a critical value, the coalescence of them occurs and finally, the localized meso-cracks appear. The macroscopic and phenomenological consequence of damage process is stiffness degradation, dilatation and softening response. In this paper, a coupled elastoplastic-logarithmic damage model was used to simulate the irreversible deformations and stiffness degradation of rock materials under loading. In this model, damage evolution & plastic flow rules were formulated in the framework of irreversible thermodynamics principles. To take into account the stiffness degradation and softening on post-peak region, logarithmic damage variable was implemented. Also, a plastic model with Drucker-Prager yield function was used to model plastic strains. Then, an algorithm was proposed to calculate the numerical steps based on the proposed coupled plastic and damage constitutive model. The developed model has been programmed in VC++ environment. Then, it was used as a separate and new constitutive model in DEM code (UDEC). Finally, the experimental Oolitic limestone rock behavior was simulated based on the developed model. The irreversible strains, softening and stiffness degradation were reproduced in the numerical results. Furthermore, the confinement pressure dependency of rock behavior was simulated in according to experimental observations.

A test and instrumentation system for the investigation of degradation of electrical insulating materials

NASA Technical Reports Server (NTRS)

1982-01-01

The basic test methods of aging and deterioration mechanisms of electrical insulating materials are discussed. A comprehensive test system developed to study the degradation process is described. This system is completely checked, and calibrated with a few insulating material samples.

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

ERIC Educational Resources Information Center

Technology Teacher, 1991

1991-01-01

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)

Non-destructive Moisture Content Measurement of Bioabsorbable Polymers Used in Medical Implants

NASA Astrophysics Data System (ADS)

Carroll, P. A.; Bell, S. A.; Maxwell, A. S.; Tomlins, P. E.

2012-09-01

Measurements have been made that link moisture content to the degradation of a bioabsorbable polymeric material, poly ( dl-lactide- co-glycolide) (PLGA). Bioabsorbable polymers used in medical implants degrade and are absorbed into the body. In the course of degradation, these polymers absorb water. Progressive non-destructive laboratory measurements of moisture content can be used as a means of tracking changes in these materials over the course of their degradation. Measurements of moisture content were made using a non-destructive microwave resonance instrument. The measurement approach, more usually applied to granular materials, was adapted to measure small, individual solid samples that do not fill the conventional sample volume of the resonator. Using the microwave resonance technique, gains in moisture content were measurable in increasingly degraded samples. The results were confirmed using alternative (destructive) measurements of sample moisture content. The microwave resonance technique offers a non-destructive measurement that can be used to study the degradation characteristics of PLGA. Better understanding of the degradation process can enable the polymer break-down rate to be tailored to match the healing rate of tissue. Non-destructive measurement allows effective study using single rather than multiple samples. This is a strong advantage when novel materials under study may be either expensive or in strictly limited availability.

Development of a novel high-entropy alloy with eminent efficiency of degrading azo dye solutions

PubMed Central

Lv, Z. Y.; Liu, X. J.; Jia, B.; Wang, H.; Wu, Y.; Lu, Z. P.

2016-01-01

In addition to its scientific importance, the degradation of azo dyes is of practical significance from the perspective of environmental protection. Although encouraging progress has been made on developing degradation approaches and materials, it is still challenging to fully resolve this long-standing problem. Herein, we report that high entropy alloys, which have been emerging as a new class of metallic materials in the last decade, have excellent performance in degradation of azo dyes. In particular, the newly developed AlCoCrTiZn high-entropy alloy synthesized by mechanical alloying exhibits a prominent efficiency in degradation of the azo dye (Direct Blue 6: DB6), as high as that of the best metallic glass reported so far. The newly developed AlCoCrTiZn HEA powder has low activation energy barrier, i.e., 30 kJ/mol, for the degrading reaction and thus make the occurrence of reaction easier as compared with other materials such as the glassy Fe-based powders. The excellent capability of our high-entropy alloys in degrading azo dye is attributed to their unique atomic structure with severe lattice distortion, chemical composition effect, residual stress and high specific surface area. Our findings have important implications in developing novel high-entropy alloys for functional applications as catalyst materials. PMID:27677462

Characteristics of proton beams and secondary neutrons arising from two different beam nozzles

NASA Astrophysics Data System (ADS)

Choi, Yeon-Gyeong; Kim, Yu-Seok

2015-10-01

A tandem or a Van de Graaff accelerator with an energy of 3 MeV is typically used for Proton Induced X-ray Emission (PIXE) analysis. In this study, the beam line design used in the PIXE analysis, instead of the typical low-energy accelerator, was used to increase the production of isotopes from a 13-MeV cyclotron. For the PIXE analysis, the proton beam should be focused at the target through a nozzle after degrading the proton beams energy from 13 MeV to 3 MeV by using an energy degrader. Previous studies have been conducted to determine the most appropriate material for and the thickness of the energy degrader. From the energy distribution of the degraded proton beam and the neutron occurrence rate at the degrader, an aluminum nozzle of X thickness was determined to be the most appropriate nozzle construction. Neutrons are created by the collision of 3-MeV protons in the nozzle after passage through the energy degrader. In addition, a proton beam of sufficient intensity is required for a non-destructive PIXE analysis. Therefore, if nozzle design is to be optimized, the number of neutrons that arise from the collision of protons inside the nozzle, as well as the track direction of the generated secondary neutrons, must be considered, with the primary aim of ensuring that a sufficient number of protons pass through the nozzle as a direct beam. A number of laboratories are currently conducting research related to the design of nozzles used in accelerator fields, mostly medical fields. This paper presents a comparative analysis of two typical nozzle shapes in order to minimize the loss of protons and the generation of secondary neutrons. The neutron occurrence rate and the number of protons that pass through the nozzle were analyzed by using a Particle and Heavy Ion Transport code System (PHITS) program in order to identify the nozzle that generated the strongest proton beam.

Comparative analysis of fungal genomes reveals different plant cell wall degrading capacity in fungi

PubMed Central

2013-01-01

Background Fungi produce a variety of carbohydrate activity enzymes (CAZymes) for the degradation of plant polysaccharide materials to facilitate infection and/or gain nutrition. Identifying and comparing CAZymes from fungi with different nutritional modes or infection mechanisms may provide information for better understanding of their life styles and infection models. To date, over hundreds of fungal genomes are publicly available. However, a systematic comparative analysis of fungal CAZymes across the entire fungal kingdom has not been reported. Results In this study, we systemically identified glycoside hydrolases (GHs), polysaccharide lyases (PLs), carbohydrate esterases (CEs), and glycosyltransferases (GTs) as well as carbohydrate-binding modules (CBMs) in the predicted proteomes of 103 representative fungi from Ascomycota, Basidiomycota, Chytridiomycota, and Zygomycota. Comparative analysis of these CAZymes that play major roles in plant polysaccharide degradation revealed that fungi exhibit tremendous diversity in the number and variety of CAZymes. Among them, some families of GHs and CEs are the most prevalent CAZymes that are distributed in all of the fungi analyzed. Importantly, cellulases of some GH families are present in fungi that are not known to have cellulose-degrading ability. In addition, our results also showed that in general, plant pathogenic fungi have the highest number of CAZymes. Biotrophic fungi tend to have fewer CAZymes than necrotrophic and hemibiotrophic fungi. Pathogens of dicots often contain more pectinases than fungi infecting monocots. Interestingly, besides yeasts, many saprophytic fungi that are highly active in degrading plant biomass contain fewer CAZymes than plant pathogenic fungi. Furthermore, analysis of the gene expression profile of the wheat scab fungus Fusarium graminearum revealed that most of the CAZyme genes related to cell wall degradation were up-regulated during plant infection. Phylogenetic analysis also revealed a complex history of lineage-specific expansions and attritions for the PL1 family. Conclusions Our study provides insights into the variety and expansion of fungal CAZyme classes and revealed the relationship of CAZyme size and diversity with their nutritional strategy and host specificity. PMID:23617724

Nonmetallic materials handbook. Volume 2: Epoxy and silicone materials

NASA Technical Reports Server (NTRS)

Podlaseck, S. E.

1982-01-01

Chemical and physical property test data obtained during qualification and receiving inspection testing of nonmetallic materials for the Viking Mars Lander program is presented. Thermochemical data showing degradation as a function of temperature from room temperature through 773 K is included. These data include activation energies for thermal degradation, rate constants, and exo- and/or endotherms. Thermal degradations carried out under vacuum include mass spectral data taken simultaneously during the decomposition. Many materials have supporting data such as condensation rates of degassed products and isothermal weight loss. Changes in mechanical, electrical, and thermal properties after exposure to 408 K in nitrogen for times ranging from 380 to 570 hours are included for many materials.

Microbial functional diversity plays an important role in the degradation of polyhydroxybutyrate (PHB) in soil.

PubMed

Dey, Samrat; Tribedi, Prosun

2018-03-01

Towards bioremediation of recalcitrant materials like synthetic polymer, soil has been recognized as a traditional site for disposal and subsequent degradation as some microorganisms in soil can degrade the polymer in a non-toxic, cost-effective, and environment friendly way. Microbial functional diversity is a constituent of biodiversity that includes wide range of metabolic activities that can influence numerous aspects of ecosystem functioning like ecosystem stability, nutrient availability, ecosystem dynamics, etc. Thus, in the current study, we assumed that microbial functional diversity could play an important role in polymer degradation in soil. To verify this hypothesis, we isolated soil from five different sites of landfill and examined several microbiological parameters wherein we observed a significant variation in heterotrophic microbial count as well as microbial activities among the soil microcosms tested. Multivariate analysis (principle component analysis) based on the carbon sources utilization pattern revealed that soil microcosms showed different metabolic patterns suggesting the variable distribution of microorganisms among the soil microcosms tested. Since microbial functional diversity depends on both microbial richness and evenness, Shannon diversity index was determined to measure microbial richness and Gini coefficient was determined to measure microbial evenness. The tested soil microcosms exhibited variation in both microbial richness and evenness suggesting the considerable difference in microbial functional diversity among the tested microcosms. We then measured polyhydroxybutyrate (PHB) degradation in soil microcosms after desired period of incubation of PHB in soil wherein we found that soil microcosms having higher functional diversity showed enhanced PHB degradation and soil microcosms having lower functional diversity showed reduced PHB degradation. We also noticed that all the tested soil microcosms showed similar pattern in both microbial functional diversity and PHB degradation suggesting a strong positive correlation ( r  = 0.95) between microbial functional diversity and PHB degradation. Thus, the results demonstrate that microbial functional diversity plays an important role in PHB degradation in soil by exhibiting versatile microbial metabolic potentials that lead to the enhanced degradation of PHB.

Establishment of a Methanogenic Benzene-Degrading Culture and its Implication in Bioremediation

NASA Astrophysics Data System (ADS)

Qiao, W.; Luo, F.; Bawa, N.; Guo, S.; Ye, S.; Edwards, E.

2017-12-01

Benzene is a known human carcinogen and it is a common pollutant in groundwater, mainly resulting from petrochemical industry. Anaerobic degradation of benzene has significant advantages over aerobic processes for in situ bioremediation. In this study, new methanogenic and sulfate-reducing benzene degrading cultures have been enriched. Microbial community composition was characterized with two other previously established benzene-degrading cultures, and their potential use in bioaugmentation is investigated. In this study, a lab microcosm study was conducted anaerobically with contaminated soil and groundwater from a former chemical plant. Benzene degradation was observed in the presence of co-contaminants and electron donor. Through repetitive amendment of benzene, two enrichment cultures have been developed under sulfate and methanogenic conditions. Results from DNA amplicon sequencing and qPCR analysis revealed that an organism similar to previously described benzene-degrading Deltaproteobacterium has been enriched. The microbial community of this culture was compared with other two methanogenic benzene-degrading enrichment cultures that were derived from an oil refinery and a decommissioned gasoline station, and have been maintained for decades. Deltaproteobacterium ORM2-like microbes were dominate in all enrichment cultures, which brought to light benzene-degrading microbes, ORM2 were enriched under different geological conditions distributed around the world. The relative abundance of methanogens was much lower compared to previously established cultures, although substantial amount of methane was produced. The peripheral organisms also vary. To investigate effectiveness of using ORM2-dominant enrichment cultures in bioremediation, microcosm studies were set up using contaminated materials, and a ORM2-dominating methanogenic benzene-degrading culture was used for bioaugmentation. Results revealed that benzene degradation was speeded up under methanogenic or sulfate-reducing condition, and the growth of ORM2 was observed via qPCR analysis. The treatability test is on-going to establish more reliable correspondence between the benzene degraders and natural attenuation potential, to provide more insights into contaminated site management.

Visible light photoactivity of Polypropylene coated Nano-TiO2 for dyes degradation in water

PubMed Central

Giovannetti, R.; Amato, C. A. D’; Zannotti, M.; Rommozzi, E.; Gunnella, R.; Minicucci, M.; Di Cicco, A.

2015-01-01

The use of Polypropylene as support material for nano-TiO2 photocatalyst in the photodegradation of Alizarin Red S in water solutions under the action of visible light was investigated. The optimization of TiO2 pastes preparation using two commercial TiO2, Aeroxide P-25 and Anatase, was performed and a green low-cost dip-coating procedure was developed. Scanning electron microscopy, Atomic Force Microscopy and X-Ray Diffraction analysis were used in order to obtain morphological and structural information of as-prepared TiO2 on support material. Equilibrium and kinetics aspects in the adsorption and successive photodegradation of Alizarin Red S, as reference dye, are described using polypropylene-TiO2 films in the Visible/TiO2/water reactor showing efficient dyes degradation. PMID:26627118

Effect of food processing on plant DNA degradation and PCR-based GMO analysis: a review.

PubMed

Gryson, Nicolas

2010-03-01

The applicability of a DNA-based method for GMO detection and quantification depends on the quality and quantity of the DNA. Important food-processing conditions, for example temperature and pH, may lead to degradation of the DNA, rendering PCR analysis impossible or GMO quantification unreliable. This review discusses the effect of several food processes on DNA degradation and subsequent GMO detection and quantification. The data show that, although many of these processes do indeed lead to the fragmentation of DNA, amplification of the DNA may still be possible. Length and composition of the amplicon may, however, affect the result, as also may the method of extraction used. Also, many techniques are used to describe the behaviour of DNA in food processing, which occasionally makes it difficult to compare research results. Further research should be aimed at defining ingredients in terms of their DNA quality and PCR amplification ability, and elaboration of matrix-specific certified reference materials.

Risk assessment associated to possible concrete degradation of a near surface disposal facility

NASA Astrophysics Data System (ADS)

Capra, B.; Billard, Y.; Wacquier, W.; Gens, R.

2013-07-01

This article outlines a risk analysis of possible concrete degradation performed in the framework of the preparation of the Safety Report of ONDRAF/NIRAS, the Belgian Agency for Radioactive Waste and Enriched Fissile Materials, for the construction and operation of a near surface disposal facility of category A waste - short-lived low and intermediate level waste - in Dessel. The main degradation mechanism considered is the carbonation of different concrete components over different periods (from the building phase up to 2000 years), which induces corrosion of the rebars. A dedicated methodology mixing risk analysis and numerical modeling of concrete carbonation has been developed to assess the critical risks of the disposal facility at different periods. According to the results obtained, risk mapping was used to assess the impact of carbonation of concrete on the different components at the different stages. The most important risk is related to an extreme situation with complete removal of the earth cover and side embankment.

Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, Mechanical Fatigue, Creep and Thermal Fatigue Effects

NASA Technical Reports Server (NTRS)

Bast, Callie Corinne Scheidt

1994-01-01

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.

Volumetric analysis of bone substitute material performance within the human sinus cavity of former head and neck cancer patients: A prospective, randomized clinical trial

PubMed Central

Lorenz, Jonas; Eichler, Kathrin; Barbeck, Mike; Lerner, Henriette; Stübinger, Stefan; Seipel, Catherine; Vogl, Thomas J.; Kovács, Adorján F.; Ghanaati, Shahram; Sader, Robert A.

2016-01-01

Background: In numerous animal and human studies, it could be detected that in bone augmentation procedures, material's physicochemical characteristics can influence the cellular inflammatory pattern and therefore the integration in the host tissue. Histological, histomorphometrical, and clinical analyses of the integration of the biomaterial in the surrounding tissue are well established methodologies; however, they do not make a statement on volume and density changes of the augmented biomaterial. Aims: The aim of the present study was to assess the volume and density of a xenogeneic (Bio-Oss®, BO) and a synthetic (NanoBone®, NB) bone substitute material in split-mouth sinus augmentations in former tumor patients to complete histological and histomorphometrical assessment. Methods: Immediately and 6 months after sinus augmentation computed tomography scans were recorded, bone grafts were marked, and the volume was calculated with radiologic RIS-PACS software (General Electric Healthcare, Chalfont St. Giles, Great Britain) to determine the integration and degradation behavior of both biomaterials. Results: Radiographic analysis revealed a volume reduction of the initial augmented bone substitute material (i.e. 100%) to 77.36 (±11.68) % in the BO-group, respectively, 75.82 (±22.28) % in the NB-group six months after augmentation. In both materials, the volume reduction was not significant. Bone density significantly increased in both groups. Conclusion: The presented radiological investigation presents a favorable method to obtain clinically relevant information concerning the integration and degradation behavior of bone substitute materials. PMID:28299254

Weathering of wood

Treesearch

R. Sam Williams

2005-01-01

Weathering is the general term used to define the slow degradation of materials exposed to the weather. The degradation mechanism depends on the type of material, but the cause is a combination of factors found in nature: moisture, sunlight, heat/cold, chemicals, abrasion by windblown materials, and biological agents. Tall mountains weather by the complex and...

Accelerated aging studies of UHMWPE. II. Virgin UHMWPE is not immune to oxidative degradation.

PubMed

Edidin, A A; Villarraga, M L; Herr, M P; Muth, J; Yau, S S; Kurtz, S M

2002-08-01

In Part I of this series, we showed that aging at elevated oxygen pressure is more successful at increasing the depth to which degradation occurs although it, too, generally causes greater degradation at the surface than at the subsurface. Therefore we hypothesized that thermal degradation alone, in the absence of free radicals, could be sufficient to artificially age UHMWPE in a manner analogous to natural aging. In the present study, virgin and air-irradiated UHMWPE (extruded GUR 1050 and compression-molded 1900) were aged up to 4 weeks at elevated oxygen pressure, and the mechanical behavior at the surface and subsurface was examined. All the materials were substantially degraded following 4 weeks of aging, but the spatial variations in the nonirradiated materials more closely mimicked the previously observed subsurface peak of degradation seen in naturally aged UHMWPE following irradiation in air. This aged material could provide a more realistic model for subsurface mechanical degradation, making it suitable for further mechanical testing in venues such as wear simulation. Copyright 2002 Wiley Periodicals, Inc.

Factors Associated With Exposure to Violent or Degrading Pornography Among High School Students.

PubMed

Romito, Patrizia; Beltramini, Lucia

2015-08-01

The purpose of this study was to analyze pornography exposure in a sample of 702 Italian adolescents (46% males; mean age = 18.2, SD = 0.8). Among male students, 11% were not exposed, 44.5% were exposed to nonviolent material, and 44.5% were exposed to violent/degrading material. Among female students, 60.8% were not exposed, 20.4% were exposed to nonviolent material, and 18.8% were exposed to violent/degrading material. Among males, adjusted odds ratio (AdjOR) of exposure to violent/degrading pornography were higher if using alcohol, having friends who sell/buy sex, and taking sexual pictures. Females who were victims of family violence, attending technical/vocational schools, and taking sexual pictures had higher AdjOR of watching violent pornography; smoking and having friends who sell/buy sex were associated with both nonviolent and violent/degrading exposure. Exposure to violent/degrading pornography is common among adolescents, associated with at-risk behaviors, and, for females, it correlates with a history of victimization. School nurses have a pivotal role in including discussions about pornography in interventions about relationships, sexuality, or violence. © The Author(s) 2015.

Environmental barrier coating (EBC) durability modeling using a progressive failure analysis approach

NASA Astrophysics Data System (ADS)

Abdul-Aziz, Ali; Abumeri, Galib; Troha, William; Bhatt, Ramakrishna T.; Grady, Joseph E.; Zhu, D.

2012-04-01

Ceramic matrix composites (CMCs) are getting the attention of most engine manufacturers and aerospace firms for turbine engine and other related applications. This is because of their potential weight advantage and performance benefits. As a protecting guard for these materials, a highly specialized form of environmental barrier coating (EBC) is being developed and explored for high temperature applications that are greater than 1100 °C1,2. The EBCs are typically a multilayer of coatings and are on the order of hundreds of microns thick. CMCs are generally porous materials and this feature is somewhat beneficial since it allows some desirable infiltration of the EBC. Their degradation usually includes coating interface oxidation as opposed to moisture induced matrix degradation which is generally seen at a higher temperature. A variety of factors such as residual stresses, coating process related flaws, and casting conditions may influence the strength of degradation. The cause of such defects which cause cracking and other damage is that not much energy is absorbed during fracture of these materials. Therefore, an understanding of the issues that control crack deflection and propagation along interfaces is needed to maximize the energy dissipation capabilities of layered ceramics. Thus, evaluating components and subcomponents made out of CMCs under gas turbine engine conditions is suggested to demonstrate that these material will perform as expected and required under these aggressive environmental circumstances. Progressive failure analysis (PFA) is applied to assess the damage growth of the coating under combined thermal and mechanical loading conditions. The PFA evaluation is carried out using a full-scale finite element model to account for the average material failure at the microscopic or macroscopic levels. The PFA life prediction evaluation identified the root cause for damage initiation and propagation. It indicated that delamination type damage initiated mainly in the bond and intermediate coating materials then propagated to the substrate. Results related to damage initiation and propagation; behavior and life assessment of the coating at the interface of the EBC/CMC are presented and discussed.

Degradation of thermal control materials under a simulated radiative space environment

NASA Astrophysics Data System (ADS)

Sharma, A. K.; Sridhara, N.

2012-11-01

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.

Tribological behaviour of orthodontic archwires under dry and wet sliding conditions in-vitro. II--Wear patterns.

PubMed

Berradja, Abdenacer; Willems, Guy; Celis, Jean-Pierre

2006-05-01

To evaluate the wear patterns of orthodontic archwires in dry and wet conditions in-vitro. The patterns of wear of stainless steel and NiTi orthodontic archwires were investigated with a fretting wear tribometer fitted with an alumina ball. The tribometer was operated at 23 degrees C in three different environments: ambient air with 50 per cent relative humidity (RH), 0.9 wt. per cent sodium chloride solution and deionised water. Differences in the wear characteristics of the archwires were investigated by scanning electron microscopy. Energy Dispersive X-ray Analysis and Inductively Coupled Plasma Analysis were used to investigate the surface composition of the wires, the wear debris generated during fretting and the corrosion products in the test solutions. Both archwire materials were degraded by oxidational wear in ambient air. The NiTi wires were more resistant to wear than the stainless steel wires. In the aqueous media the stainless steel wires were degraded by abrasive wear, while the NiTi wires were degraded by adhesive wear. In ambient air with 50 per cent RH, NiTi wires were more resistant to wear than stainless steel wires. Both archwire materials exhibited higher wear rates in the solutions than in air, indicating some synergism between the wear and corrosion processes. In the solutions the stainless steel archwires had a much lower corrosion-wear resistance than the NiTi archwires.

Time-frequency analysis of acoustic emission signals generated by the Glass Fibre Reinforced Polymer Composites during the tensile test

NASA Astrophysics Data System (ADS)

Świt, G.; Adamczak, A.; Krampikowska, A.

2017-10-01

Fibre reinforced polymer composites are currently dominating in the composite materials market. The lack of detailed knowledge about their properties and behaviour in various conditions of exposure under load significantly limits the broad possibilities of application of these materials. Occurring and accumulation of defects in material during the exploitation of the construction lead to the changes of its technical condition. The necessity to control the condition of the composite is therefore justified. For this purpose, non-destructive method of acoustic emission can be applied. This article presents an example of application of acoustic emission method based on time analysis and time-frequency analysis for the evaluation of the progress of the destructive processes and the level of degradation of glass fibre reinforced composite tapes that were subject to tensile testing.

Study of Aging-Induced Degradation of Fracture Resistance of Alloy 617 Toward High-Temperature Applications

NASA Astrophysics Data System (ADS)

Singh, Aditya Narayan; Moitra, A.; Bhaskar, Pragna; Sasikala, G.; Dasgupta, Arup; Bhaduri, A. K.

2017-07-01

For the Alloy 617, the effect of aging on the fracture energy degradation has been investigated after aging for different time periods at 1023 K (750 °C). A sharp reduction in impact energy (by 55 pct vis-à-vis the as-received material) after 1000 hours of aging, as evaluated from room-temperature Charpy impact tests, has been observed. Further aging up to 10,000 hours has led to a degradation of fracture energy up to 78 pct. Fractographic examinations using scanning electron microscopy (SEM) have revealed a change in fracture mode from fibrous-ductile for the un-aged material to intergranular mode for the aged one. The extent of intergranular fracture increases with the increasing aging time, indicating a tendency of the material to undergo grain boundary embrittlement over long-term aging. Analysis of the transmission electron microscopy (TEM) micrographs along with selected area diffraction (SAD) patterns for the samples aged at 10,000 hours revealed finely dispersed γ' precipitates of size 30 to 40 nm, rich in Al and Ti, along with extensive precipitation of M23C6 at the grain boundaries. In addition, the presence of Ni3Si of size in the range of 110 to 120 nm also has been noticed. The extensive precipitation of M23C6 at the grain boundaries have been considered as a major reason for aging-induced embrittlement of this material.

Catalyst Stability Benchmarking for the Oxygen Evolution Reaction: The Importance of Backing Electrode Material and Dissolution in Accelerated Aging Studies.

PubMed

Geiger, Simon; Kasian, Olga; Mingers, Andrea M; Nicley, Shannon S; Haenen, Ken; Mayrhofer, Karl J J; Cherevko, Serhiy

2017-09-18

In searching for alternative oxygen evolution reaction (OER) catalysts for acidic water splitting, fast screening of the material intrinsic activity and stability in half-cell tests is of vital importance. The screening process significantly accelerates the discovery of new promising materials without the need of time-consuming real-cell analysis. In commonly employed tests, a conclusion on the catalyst stability is drawn solely on the basis of electrochemical data, for example, by evaluating potential-versus-time profiles. Herein important limitations of such approaches, which are related to the degradation of the backing electrode material, are demonstrated. State-of-the-art Ir-black powder is investigated for OER activity and for dissolution as a function of the backing electrode material. Even at very short time intervals materials like glassy carbon passivate, increasing the contact resistance and concealing the degradation phenomena of the electrocatalyst itself. Alternative backing electrodes like gold and boron-doped diamond show better stability and are thus recommended for short accelerated aging investigations. Moreover, parallel quantification of dissolution products in the electrolyte is shown to be of great importance for comparing OER catalyst feasibility. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Methods for visualising active microbial benzene degraders in in situ microcosms.

PubMed

Schurig, Christian; Mueller, Carsten W; Höschen, Carmen; Prager, Andrea; Kothe, Erika; Beck, Henrike; Miltner, Anja; Kästner, Matthias

2015-01-01

Natural attenuation maybe a cost-efficient option for bioremediation of contaminated sites but requires knowledge about the activity of degrading microbes under in situ conditions. In order to link microbial activity to the spatial distribution of contaminant degraders, we combined the recently improved in situ microcosm approach, so-called 'direct-push bacterial trap' (DP-BACTRAP), with nano-scale secondary ion mass spectrometry (NanoSIMS) analysis on samples from contaminated constructed wetlands. This approach is based on initially sterile microcosms amended with (13)C-labelled benzene as a source of carbon and energy for microorganisms. The microcosms were introduced directly in the constructed wetland, where they were colonised by indigenous microorganisms from the sediment. After incubation in the field, the samples were analysed by NanoSIMS, scanning electron microscopy (SEM) and fluorescence microscopy in order to visualise (13)C-labelled microbial biomass on undisturbed samples from the microcosms. With the approach developed, we successfully visualised benzene-degrading microbes on solid materials with high surface area by means of NanoSIMS. Moreover, we could demonstrate the feasibility of NanoSIMS analysis of unembedded porous media with a highly complex topography, which was frequently reasoned to not lead to sufficient results.

Morphology analysis in middle-downstream area of Progo River due to the debris flow

NASA Astrophysics Data System (ADS)

Fitriadin, Ahmad Azmi; Ikhsan, Jaza'ul; Harsanto, Puji

2017-06-01

One of the problems that occur in Progo River is the formation of sediment in the downstream section. The sediment material in the upstream becomes the source of sediment at the downstream area. Excess sediment supply from the upstream causes morphological changes in a relatively short time. The morphological changes in riverbed will affect hydraulics conditions. Hydraulic has an important role in the process of aggradation and degradation in the riverbed. Furthermore, the process of erosion and sedimentation will affect the stability of the construction in the water. In Progo River, there are some buildings of infrastructure such as revetment, bridge, irrigation intake, groundsill, and weir. Based on the results of a numerical model of the hydraulic analysis system, there was approximately 87,000,000 m3 of sediment on Progo River in 2015. In fact, aggradation and degradation occurred very intensively in the middle-downstream area of Progo River. Sediment movement simulation also showed that the sediment supply of lava could prevent excessive bed degradation. Nevertheless, the absence of sediment supply will lead to bed degradation process. It indicates that the management of the sediment supply in the upstream area must be managed properly.

Biodegradable Polymeric Materials in Degradable Electronic Devices

PubMed Central

2018-01-01

Biodegradable electronics have great potential to reduce the environmental footprint of devices and enable advanced health monitoring and therapeutic technologies. Complex biodegradable electronics require biodegradable substrates, insulators, conductors, and semiconductors, all of which comprise the fundamental building blocks of devices. This review will survey recent trends in the strategies used to fabricate biodegradable forms of each of these components. Polymers that can disintegrate without full chemical breakdown (type I), as well as those that can be recycled into monomeric and oligomeric building blocks (type II), will be discussed. Type I degradation is typically achieved with engineering and material science based strategies, whereas type II degradation often requires deliberate synthetic approaches. Notably, unconventional degradable linkages capable of maintaining long-range conjugation have been relatively unexplored, yet may enable fully biodegradable conductors and semiconductors with uncompromised electrical properties. While substantial progress has been made in developing degradable device components, the electrical and mechanical properties of these materials must be improved before fully degradable complex electronics can be realized. PMID:29632879

Interpreting statistics of small lunar craters

NASA Technical Reports Server (NTRS)

Schultz, P. H.; Gault, D.; Greeley, R.

1977-01-01

Some of the wide variations in the crater-size distributions in lunar photography and in the resulting statistics were interpreted as different degradation rates on different surfaces, different scaling laws in different targets, and a possible population of endogenic craters. These possibilities are reexamined for statistics of 26 different regions. In contrast to most other studies, crater diameters as small as 5 m were measured from enlarged Lunar Orbiter framelets. According to the results of the reported analysis, the different crater distribution types appear to be most consistent with the hypotheses of differential degradation and a superposed crater population. Differential degradation can account for the low level of equilibrium in incompetent materials such as ejecta deposits, mantle deposits, and deep regoliths where scaling law changes and catastrophic processes introduce contradictions with other observations.

A thin film degradation study of a fluorinated polyether liquid lubricant using an HPLC method

NASA Technical Reports Server (NTRS)

Morales, W.

1986-01-01

A High Pressure Liquid Chromatography (HPLC) separation method was developed to study and analyze a fluorinated polyether fluid which is promising liquid lubricant for future applications. This HPLC separation method was used in a preliminary study investigating the catalytic effect of various metal, metal alloy, and ceramic engineering materials on the degradation of this fluid in a dry air atmosphere at 345 C. Using a 440 C stainless steel as a reference catalytic material it was found that a titanium alloy and a chromium plated material degraded the fluorinated polyether fluid substantially more than the reference material.

Characterization, performance and optimization of PVDF as a piezoelectric film for advanced space mirror concepts.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Gary D.; Assink, Roger Alan; Dargaville, Tim Richard

2005-11-01

Piezoelectric polymers based on polyvinylidene fluoride (PVDF) are of interest for large aperture space-based telescopes as adaptive or smart materials. Dimensional adjustments of adaptive polymer films depend on controlled charge deposition. Predicting their long-term performance requires a detailed understanding of the piezoelectric material features, expected to suffer due to space environmental degradation. Hence, the degradation and performance of PVDF and its copolymers under various stress environments expected in low Earth orbit has been reviewed and investigated. Various experiments were conducted to expose these polymers to elevated temperature, vacuum UV, {gamma}-radiation and atomic oxygen. The resulting degradative processes were evaluated. Themore » overall materials performance is governed by a combination of chemical and physical degradation processes. Molecular changes are primarily induced via radiative damage, and physical damage from temperature and atomic oxygen exposure is evident as depoling, loss of orientation and surface erosion. The effects of combined vacuum UV radiation and atomic oxygen resulted in expected surface erosion and pitting rates that determine the lifetime of thin films. Interestingly, the piezo responsiveness in the underlying bulk material remained largely unchanged. This study has delivered a comprehensive framework for material properties and degradation sensitivities with variations in individual polymer performances clearly apparent. The results provide guidance for material selection, qualification, optimization strategies, feedback for manufacturing and processing, or alternative materials. Further material qualification should be conducted via experiments under actual space conditions.« less

Multi-length-scale Material Model for SiC/SiC Ceramic-Matrix Composites (CMCs): Inclusion of In-Service Environmental Effects

NASA Astrophysics Data System (ADS)

Grujicic, M.; Galgalikar, R.; Snipes, J. S.; Ramaswami, S.

2016-01-01

In our recent work, a multi-length-scale room-temperature material model for SiC/SiC ceramic-matrix composites (CMCs) was derived and parameterized. The model was subsequently linked with a finite-element solver so that it could be used in a general room-temperature, structural/damage analysis of gas-turbine engine CMC components. Due to its multi-length-scale character, the material model enabled inclusion of the effects of fiber/tow (e.g., the volume fraction, size, and properties of the fibers; fiber-coating material/thickness; decohesion properties of the coating/matrix interfaces; etc.) and ply/lamina (e.g., the 0°/90° cross-ply versus plain-weave architectures, the extent of tow crimping in the case of the plain-weave plies, cohesive properties of the inter-ply boundaries, etc.) length-scale microstructural/architectural parameters on the mechanical response of the CMCs. One of the major limitations of the model is that it applies to the CMCs in their as-fabricated conditions (i.e., the effect of prolonged in-service environmental exposure and the associated material aging-degradation is not accounted for). In the present work, the model is upgraded to include such in-service environmental-exposure effects. To demonstrate the utility of the upgraded material model, it is used within a finite-element structural/failure analysis involving impact of a toboggan-shaped turbine shroud segment by a foreign object. The results obtained clearly revealed the effects that different aspects of the in-service environmental exposure have on the material degradation and the extent of damage suffered by the impacted CMC toboggan-shaped shroud segment.

Degradation of Methylammonium Lead Iodide Perovskite Structures through Light and Electron Beam Driven Ion Migration

PubMed Central

2016-01-01

Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques. PMID:26804213

Phytate Degradation by Fungi and Bacteria that Inhabit Sawdust and Coffee Residue Composts

PubMed Central

Eida, Mohamed Fathallh; Nagaoka, Toshinori; Wasaki, Jun; Kouno, Kenji

2013-01-01

Phytate is the primary source of organic phosphorus, but it cannot be directly utilized by plants and is strongly adsorbed by the soil, reducing bioavailability. Composting is a process used to improve the bioavailability of phytate in organic wastes through degradation by microorganisms. In this study, we aimed to investigate the phytate-degrading ability of fungi and bacteria that inhabit sawdust compost and coffee residue compost, and their contribution to the composting process. In the plate assay, the fungi that formed clear zones around their colonies belonged to the genera Mucor, Penicillium, Galactomyces, Coniochaeta, Aspergillus, and Fusarium, while the bacteria belonged to the genera Pseudomonas, Enterobacter, Chitinophaga, and Rahnella. Eight fungal isolates (genera Mucor, Penicillium, Galactomyces, and Coniochaeta) and four bacterial isolates (genera Pseudomonas, Enterobacter, and Rahnella) were selected to evaluate phytase activity in their liquid culture and their ability to degrade phytate in organic materials composed of mushroom media residue and rice bran. The selected fungi degraded phytate in organic materials to varying degrees. Penicillium isolates showed the highest degradation ability and Coniochaeta isolate exhibited relatively high degradation ability. The clear zone diameters of these fungal isolates displayed significantly positive and negative correlations with inorganic and phytate phosphorus contents in the organic materials after incubation, respectively; however, none of the selected bacteria reduced phytate phosphorus in organic materials. It is therefore possible that fungi are major contributors to phytate degradation during composting. PMID:23100024

Fragility Analysis Methodology for Degraded Structures and Passive Components in Nuclear Power Plants - Illustrated using a Condensate Storage Tank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie, J.; Braverman, J.; Hofmayer, C.

2010-06-30

The Korea Atomic Energy Research Institute (KAERI) is conducting a five-year research project to develop a realistic seismic risk evaluation system which includes the consideration of aging of structures and components in nuclear power plants (NPPs). The KAERI research project includes three specific areas that are essential to seismic probabilistic risk assessment (PRA): (1) probabilistic seismic hazard analysis, (2) seismic fragility analysis including the effects of aging, and (3) a plant seismic risk analysis. Since 2007, Brookhaven National Laboratory (BNL) has entered into a collaboration agreement with KAERI to support its development of seismic capability evaluation technology for degraded structuresmore » and components. The collaborative research effort is intended to continue over a five year period. The goal of this collaboration endeavor is to assist KAERI to develop seismic fragility analysis methods that consider the potential effects of age-related degradation of structures, systems, and components (SSCs). The research results of this multi-year collaboration will be utilized 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. 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. In the Year 2 scope of work, BNL carried out a research effort to identify and assess degradation models for the long-term behavior of dominant materials that are determined to be risk significant to NPPs. Multiple models have been identified for concrete, carbon and low-alloy steel, and stainless steel. These models are documented in the Annual Report for the Year 2 Task, identified as BNL Report-82249-2009 and also designated as KAERI/TR-3757/2009. This report describes the research effort performed by BNL for the Year 3 scope of work. The objective is for BNL to develop the seismic fragility capacity for a condensate storage tank with various degradation scenarios. The conservative deterministic failure margin method has been utilized for the undegraded case and has been modified to accommodate the degraded cases. A total of five seismic fragility analysis cases have been described: (1) undegraded case, (2) degraded stainless tank shell, (3) degraded anchor bolts, (4) anchorage concrete cracking, and (5)a perfect combination of the three degradation scenarios. Insights from these fragility analyses are also presented.« less

Development of a natural degradable polymer for orthopaedic use.

PubMed

Knowles, J C

1993-01-01

Currently, there are a large variety of degradable polymers available for use in surgery, which are generally based on blends and copolymers of poly(L-lactide) (PLLA) and poly(L-glycolide) (PGA). The major demand for these materials is for suturing of wounds, but the materials are also being developed for use in orthopaedic surgery for fracture reduction. The development of these materials is on two fronts, the first involving conventional fracture fixation design of plates. The second is to produce simple devices such as rods and to use the degradable materials for treatment of specific fracture types such as fractures of the olecranon. These materials have the advantage of possessing initially enhanced mechanical properties, although their relatively quick degradation profile diminishes these properties. As an alternative we are developing polyhydroxybutyrate (PHB) and its copolymers with polyhydroxyvalerate (PHV). This range of polymers mab be easily thermally processed, are very cheap and easily available. The polymer also has the significant advantage of being piezoelectric. This is discussed.

Compendium of information on identification and testing of materials for plastic solar thermal collectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGinniss, V.D.; Sliemers, F.A.; Landstrom, D.K.

1980-07-31

This report is intended to organize and summarize prior and current literature concerning the weathering, aging, durability, degradation, and testing methodologies as applied to materials for plastic solar thermal collectors. Topics covered include (1) rate of aging of polymeric materials; (2) environmental factors affecting performance; (3) evaluation and prediction of service life; (4) measurement of physical and chemical properties; (5) discussion of evaluation techniques and specific instrumentation; (6) degradation reactions and mechanisms; (7) weathering of specific polymeric materials; and (8) exposure testing methodology. Major emphasis has been placed on defining the current state of the art in plastics degradation andmore » on identifying information that can be utilized in applying appropriate and effective aging tests for use in projecting service life of plastic solar thermal collectors. This information will also be of value where polymeric components are utilized in the construction of conventional solar collectors or any application where plastic degradation and weathering are prime factors in material selection.« less

The Role of Deformation and Microchemistry in the Corrosion Processes of Type 304 Stainless Steel in Simulated Pressurized Water Reactor Environments

NASA Astrophysics Data System (ADS)

Fisher, Kevin B.

Degradation of structural components in nuclear environments is a limiting factor in the lifetime of nuclear power plants. Despite decades of research on the topic, there are still aspects of the degradation phenomena that are not well understood, leading to premature failure of components that can be both expensive to repair and potentially dangerous. The current work addresses the role of material deformation on the corrosion phenomena of 304 SS in a simulated nuclear reactor environment by studying the relationship of the material microstructure and microchemistry with the resulting corrosion products using a multiscale analysis approach. The general corrosion phenomenon was studied in relation to the surface deformation of the material, and it was determined that surface deformation not only increases the rate of oxidation, but also has a pronounced impact on the microchemical structure of the oxide film when compared to undeformed material. These findings were applied to understanding the role of deformation in the more complex corrosion phenomena of stress corrosion cracking (SCC) and corrosion fatigue cracking (CFC). In SCC experiments, material deformation in the form of cold work played a synergistic role with unique microchemical features of the materials studied to promote the cracking process under certain environmental and material heat treatment conditions. Despite the fact that the materials studied were low carbon heats of 304L SS thought to be immune to the sensitization and therefore resistant to SCC, elevated boron and delta ferrites in the material were implicated in the SCC susceptibility after heat treatment. On the other hand, low levels of residual deformation played only a minor role in the corrosion processes occurring during CFC experiments over a wide range of rise times. Instead, deformation was suspected to play a larger role in the mechanical cracking response of the material. By studying multiple corrosion processes of 304 SS a greater understanding of the role of deformation and microchemical factors in the related corrosion phenomena has been achieved, and provides evidence that material and component fabrication, in terms of surface and bulk deformation, material microchemistry, and heat treatment must be considered to avoid degradation issues.

Cause and Effects of Fluorocarbon Degradation in Electronics and Opto-Electronic Systems

NASA Technical Reports Server (NTRS)

Predmore, Roamer E.; Canham, John S.

2002-01-01

Trace degradation of fluorocarbon or halocarbon materials must be addressed in their application in sensitive systems. As the dimensions and/or tolerances of components in a system decrease, the sensitivity of the system to trace fluorocarbon or halocarbon degradation products increases. Trace quantities of highly reactive degradation products from fluorocarbons have caused a number of failures of flight hardware. It is of utmost importance that the risk of system failure, resulting from trace amounts of reactive fluorocarbon degradation products be addressed in designs containing fluorocarbon or halocarbon materials. Thermal, electrical, and mechanical energy input into the system can multiply the risk of failure.

Biological degradation of gas-filled composite materials on the base of polyethylene

NASA Astrophysics Data System (ADS)

Grigoreva, E. A.; Kolesnikova, N. N.; Popov, A. A.; Olkhov, A. A.

2017-12-01

Gas-filled composite materials based on polyethylene were obtained. It was assumed that introduction of porosity in polyethylene will improve the biodegradability of synthetic materials. The morphological and structural changes were estimated, physical and mechanical properties, stability in water and soil of these materials were determined. It is stated that filling the polymer matrix with pores increases the ability to degrade in nature.

Attitudinal effects of degrading themes and sexual explicitness in video materials.

PubMed

Golde, J A; Strassberg, D S; Turner, C M; Lowe, K

2000-07-01

This study examined the independent and interactive effects of sexual explicitness and degrading themes toward women on mens' attitudes following exposure to video presentations of male-female interactions. Subjects were 83 male college students who viewed video vignettes under one of four stimulus conditions: (a) sexually explicit/degrading, (b) sexually explicit/nondegrading, (c) nonexplicit/degrading, and (d) nonexplicit/nondegrading. Results revealed that men exposed to degrading material, regardless of explicitness, were significantly more likely to express attitudes supportive of rape, while explicitness had no significant main or interactive effect on these attitudes. Further, the interaction of explicitness with degradation was found to impact scores on a measure of sexual callousness. Theoretical and clinical implications of these findings are discussed.

Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning.

PubMed

Sivakumaran, Daryl; Bakaic, Emilia; Campbell, Scott B; Xu, Fei; Mueller, Eva; Hoare, Todd

2018-04-16

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), their ultimate clinical use has been hampered by the lack of biologically-relevant degradation observed for most smart materials. This is particularly true for temperature-responsive hydrogels, which are almost uniformly based on polymers that are functionally non-degradable (e.g., poly(N-isopropylacrylamide) (PNIPAM) or poly(oligoethylene glycol methacrylate) (POEGMA)). As such, to effectively translate the potential of thermoresponsive hydrogels to the challenges of remote-controlled or metabolism-regulated drug delivery, cell scaffolds with tunable cell-material interactions, theranostic materials with the potential for both imaging and drug delivery, and other such applications, a method is required to render the hydrogels (if not fully degradable) at least capable of renal clearance following the required lifetime of the material. To that end, this protocol describes the preparation of hydrolytically-degradable hydrazone-crosslinked hydrogels on multiple length scales based on the reaction between hydrazide and aldehyde-functionalized PNIPAM or POEGMA oligomers with molecular weights below the renal filtration limit. Specifically, methods to fabricate degradable thermoresponsive bulk hydrogels (using a double barrel syringe technique), hydrogel particles (on both the microscale through the use of a microfluidics platform facilitating simultaneous mixing and emulsification of the precursor polymers and the nanoscale through the use of a thermally-driven self-assembly and cross-linking method), and hydrogel nanofibers (using a reactive electrospinning strategy) are described. In each case, hydrogels with temperature-responsive properties similar to those achieved via conventional free radical cross-linking processes can be achieved, but the hydrazone cross-linked network can be degraded over time to re-form the oligomeric precursor polymers and enable clearance. As such, we anticipate these methods (which may be generically applied to any synthetic water-soluble polymer, not just smart materials) will enable easier translation of synthetic smart materials to clinical applications.

Time-Resolved Photoluminescence Spectroscopy and Imaging: New Approaches to the Analysis of Cultural Heritage and Its Degradation

PubMed Central

Nevin, Austin; Cesaratto, Anna; Bellei, Sara; D'Andrea, Cosimo; Toniolo, Lucia; Valentini, Gianluca; Comelli, Daniela

2014-01-01

Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested. PMID:24699285

Investigation of thermal degradation with extrusion-based dispensing modules for 3D bioprinting technology.

PubMed

Lee, Hyungseok; Yoo, James J; Kang, Hyun-Wook; Cho, Dong-Woo

2016-02-04

Recently, numerous three-dimensional (3D) bioprinting systems have been introduced for the artificial regeneration of tissues. Among them, the extrusion-based dispensing module is the most widely used because of the processability it gives various biomaterials. The module uses high forces and temperature to dispense materials through a micro-nozzle. Generally, the harsh conditions induce thermal degradation of the material in the dispensing procedure. The thermal degradation affects the properties of the materials, and the change of the properties should be carefully controlled, because it severely affects the regeneration of tissues. Therefore, in this research, the relationship between the dispensing module and the thermal degradation of material was investigated. Extrusion-based dispensing modules can be divided into the syringe type (ST) and filament type (FT) based on working principles. We prepared a poly lactic-co-glycolic acid (PLGA) scaffold with the two methods at various time points. Then, the characteristics of the printed scaffolds were assessed by measuring molecular weight (M w), glass transition temperature (T g), in vitro degradation, compressive modulus, and cytocompatibility. The results showed that the PLGA scaffold with the FT dispensing module maintained its properties regardless of printing time points. In contrast, severe thermal degradation was observed in the scaffold group prepared by the ST dispensing module. Consequentially, it was obvious that the FT dispensing module was more suitable for producing scaffolds without severe thermal degradation.

Monitoring trichloroethene remediation at an iron permeable reactive barrier using stable carbon isotopic analysis

NASA Astrophysics Data System (ADS)

VanStone, Nancy; Przepiora, Andrzej; Vogan, John; Lacrampe-Couloume, Georges; Powers, Brian; Perez, Ernesto; Mabury, Scott; Sherwood Lollar, Barbara

2005-08-01

Stable carbon isotopic analysis, in combination with compositional analysis, was used to evaluate the performance of an iron permeable reactive barrier (PRB) for the remediation of ground water contaminated with trichloroethene (TCE) at Spill Site 7 (SS7), F.E. Warren Air Force Base, Wyoming. Compositional data indicated that although the PRB appeared to be reducing TCE to concentrations below treatment goals within and immediately downgradient of the PRB, concentrations remained higher than expected at wells further downgradient (i.e. > 9 m) of the PRB. At two wells downgradient of the PRB, TCE concentrations were comparable to upgradient values, and δ13C values of TCE at these wells were not significantly different than upgradient values. Since the process of sorption/desorption does not significantly fractionate carbon isotope values, this suggests that the TCE observed at these wells is desorbing from local aquifer materials and was present before the PRB was installed. In contrast, three other downgradient wells show significantly more enriched δ13C values compared to the upgradient mean. In addition, δ13C values for the degradation products of TCE, cis-dichloroethene and vinyl chloride, show fractionation patterns expected for the products of the reductive dechlorination of TCE. Since concentrations of both TCE and degradation products drop to below detection limit in wells within the PRB and directly below it, these downgradient chlorinated hydrocarbon concentrations are attributed to desorption from local aquifer material. The carbon isotope values indicate that this dissolved contaminant is subject to local degradation, likely due to in situ microbial activity.

Monitoring trichloroethene remediation at an iron permeable reactive barrier using stable carbon isotopic analysis.

PubMed

VanStone, Nancy; Przepiora, Andrzej; Vogan, John; Lacrampe-Couloume, Georges; Powers, Brian; Perez, Ernesto; Mabury, Scott; Sherwood Lollar, Barbara

2005-08-01

Stable carbon isotopic analysis, in combination with compositional analysis, was used to evaluate the performance of an iron permeable reactive barrier (PRB) for the remediation of ground water contaminated with trichloroethene (TCE) at Spill Site 7 (SS7), F.E. Warren Air Force Base, Wyoming. Compositional data indicated that although the PRB appeared to be reducing TCE to concentrations below treatment goals within and immediately downgradient of the PRB, concentrations remained higher than expected at wells further downgradient (i.e. >9 m) of the PRB. At two wells downgradient of the PRB, TCE concentrations were comparable to upgradient values, and delta13C values of TCE at these wells were not significantly different than upgradient values. Since the process of sorption/desorption does not significantly fractionate carbon isotope values, this suggests that the TCE observed at these wells is desorbing from local aquifer materials and was present before the PRB was installed. In contrast, three other downgradient wells show significantly more enriched delta13C values compared to the upgradient mean. In addition, delta13C values for the degradation products of TCE, cis-dichloroethene and vinyl chloride, show fractionation patterns expected for the products of the reductive dechlorination of TCE. Since concentrations of both TCE and degradation products drop to below detection limit in wells within the PRB and directly below it, these downgradient chlorinated hydrocarbon concentrations are attributed to desorption from local aquifer material. The carbon isotope values indicate that this dissolved contaminant is subject to local degradation, likely due to in situ microbial activity.

Degradation of sustainable mulch materials in two types of soil under laboratory conditions

NASA Astrophysics Data System (ADS)

Villena, Jaime; González, Sara; Moreno, Carmen; Aceituno, Patricia; Campos, Juan; Meco, Ramón; María Moreno, Marta

2017-04-01

Mulching is a technique used in cultivation worldwide, especially for vegetable crops, for reducing weed growth, minimising or eliminating soil erosion, and often for enhancing total yields. Manufactured plastic films, mainly polyethylene (PE), have been widely used for this purpose due to their excellent mechanical properties, light weight and relatively low prices in recent years. However, the use of PE is associated with serious environmental problems related to its petrochemical origin and its long shelf-life, which causes a waste problem in our crop fields. For this reason, the use of biodegradable mulch materials (biopolymers and papers) as alternative to PE is increasing nowadays, especially in organic farming. However, these materials can suffer an undesirable early degradation (and therefore not fulfilling their function successfully), greatly resulting from the type of soil. For this reason, this study aimed to analyse the degradation pattern of different mulch materials buried in two types of soils, clay and sand, under laboratory conditions (25°C, dark surroundings, constant humidity). The mulch materials used were: 1) black polyethylene (15 µm); black biopolymers (15 µm): 2) maize starch-based, 3) potato starch-based, 4) polylactic acid-based, 5) black paper, 85 g/m2. Periodically (every 15-20 days), the weight and surface loss of the different materials were recorded. The results indicate that mulch degradation was earlier and higher in the clay soil, especially in the paper and in the potato starch-based materials, followed by the maize starch-based mulch, while polylactic acid-based suffered the least and the latest degradation. Keywords: mulch, biodegradable, biopolymer, paper, degradation. Acknowledgements: the research was funded by Project RTA2011-00104-C04-03 from the INIA (Spanish Ministry of Economy and Competitiveness).

Study of thermal stability and degradation of fire resistant candidate polymers for aircraft interiors

NASA Technical Reports Server (NTRS)

Hsu, M. T. S.

1976-01-01

The thermochemistry of bismaleimide resins and phenolphthalein polycarbonate was studied. Both materials are fire-resistant polymers and may be suitable for aircraft interiors. The chemical composition of the polymers has been determined by nuclear magnetic resonance and infrared spectroscopy and by elemental analysis. Thermal properties of these polymers have been characterized by thermogravimetric analyses. Qualitative evaluation of the volatile products formed in pyrolysis under oxidative and non-oxidative conditions has been made using infrared spectrometry. The residues after pyrolysis were analyzed by elemental analysis. The thermal stability of composite panel and thermoplastic materials for aircraft interiors was studied by thermogravimetric analyses.

Reliability Analysis of the Gradual Degradation of Semiconductor Devices.

DTIC Science & Technology

1983-07-20

under the heading of linear models or linear statistical models . 3 ,4 We have not used this material in this report. Assuming catastrophic failure when...assuming a catastrophic model . In this treatment we first modify our system loss formula and then proceed to the actual analysis. II. ANALYSIS OF...Failure Time 1 Ti Ti 2 T2 T2 n Tn n and are easily analyzed by simple linear regression. Since we have assumed a log normal/Arrhenius activation

Mechanical Properties of Degraded PMR-15 Resin

NASA Technical Reports Server (NTRS)

Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

1998-01-01

Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

The impact of shape memory test on degradation profile of a bioresorbable polymer.

PubMed

Musioł, Marta; Jurczyk, Sebastian; Kwiecień, Michał; Smola-Dmochowska, Anna; Domański, Marian; Janeczek, Henryk; Włodarczyk, Jakub; Klim, Magdalena; Rydz, Joanna; Kawalec, Michał; Sobota, Michał

2018-05-01

The semicrystalline poly(L-lactide) (PLLA) belongs to the materials with shape memory effect (SME) and as a bioresorbable and biocompatible polymer it have found many applications in medical and pharmaceutical field. Assessment of the SME impact on the polymer degradation profile plays crucial role in applications such as drug release systems or in regenerative medicine. Herein, the results of in vitro degradation studies of PLLA samples after SME full test cycle are presented. The samples were loaded and deformed in two manners: progressive and non-progressive. The performed experiments illustrate also influence of the material mechanical damages, caused e.g. during incorrect implantation of PLLA product, on hydrolytic degradation profile. Apparently, degradation profiles are significantly different for the material which was not subjected to the deformation and the deformed ones. The materials after deformation of 50% (in SME cycle) was characterized by non-reversible morphology changes. The effect was observed in deformed samples during the SME test which were carried out ten times. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthesis and Testing of Polymers Susceptible to Degradation by Proteolytic Enzymes

DTIC Science & Technology

1975-05-01

diisocyanatohexane, was biodegraded by the enzymes urease and rennin and also by two fungi. The tensile strength was greater than 10,000 psi, with high...Copolymer Degradation by Urease Enzyme Copolymer Degradation by Rennin Enzyme Degradation of Modified Gelatins: Undrawn Bulk Material Degradation of...bacteria. Results with urease enzyme did indicate significant degradation, as shown by the following tables: Table 1. Copolymer Degradation by

Pre-heating mitigates composite degradation

PubMed Central

da SILVA, Jessika Calixto; Rogério Vieira, REGES; REGE, Inara Carneiro Costa; CRUZ, Carlos Alberto dos Santos; VAZ, Luís Geraldo; ESTRELA, Carlos; de CASTRO, Fabrício Luscino Alves

2015-01-01

ABSTRACT Dental composites cured at high temperatures show improved properties and higher degrees of conversion; however, there is no information available about the effect of pre-heating on material degradation. Objectives This study evaluated the effect of pre-heating on the degradation of composites, based on the analysis of radiopacity and silver penetration using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Material and Methods Thirty specimens were fabricated using a metallic matrix (2x8 mm) and the composites Durafill VS (Heraeus Kulzer), Z-250 (3M/ESPE), and Z-350 (3M/ESPE), cured at 25°C (no pre-heating) or 60°C (pre-heating). Specimens were stored sequentially in the following solutions: 1) water for 7 days (60°C), plus 0.1 N sodium hydroxide (NaOH) for 14 days (60°C); 2) 50% silver nitrate (AgNO3) for 10 days (60°C). Specimens were radiographed at baseline and after each storage time, and the images were evaluated in gray scale. After the storage protocol, samples were analyzed using SEM/EDS to check the depth of silver penetration. Radiopacity and silver penetration data were analyzed using ANOVA and Tukey’s tests (α=5%). Results Radiopacity levels were as follows: Durafill VSZ-350>Z-250 (p<0.05). After storage in water/NaOH, pre-heated specimens presented higher radiopacity values than non-pre-heated specimens (p<0.05). There was a lower penetration of silver in pre-heated specimens (p<0.05). Conclusions Pre-heating at 60°C mitigated the degradation of composites based on analysis of radiopacity and silver penetration depth. PMID:26814459

Morphological features (defects) in fuel cell membrane electrode assemblies

NASA Astrophysics Data System (ADS)

Kundu, S.; Fowler, M. W.; Simon, L. C.; Grot, S.

Reliability and durability issues in fuel cells are becoming more important as the technology and the industry matures. Although research in this area has increased, systematic failure analysis, such as a failure modes and effects analysis (FMEA), are very limited in the literature. This paper presents a categorization scheme of causes, modes, and effects related to fuel cell degradation and failure, with particular focus on the role of component quality, that can be used in FMEAs for polymer electrolyte membrane (PEM) fuel cells. The work also identifies component defects imparted on catalyst-coated membranes (CCM) by manufacturing and proposes mechanisms by which they can influence overall degradation and reliability. Six major defects have been identified on fresh CCM materials, i.e., cracks, orientation, delamination, electrolyte clusters, platinum clusters, and thickness variations.

Research on the degradation mechanism of pyridine in drinking water by dielectric barrier discharge.

PubMed

Li, Yang; Yi, Rongjie; Yi, Chengwu; Zhou, Biyun; Wang, Huijuan

2017-03-01

Pyridine, an important chemical raw material, is widely used in industry, for example in textiles, leather, printing, dyeing, etc. In this research, a dielectric barrier discharge (DBD) system was developed to remove pyridine, as a representative type of nitrogen heterocyclic compound in drinking water. First, the influence of the active species inhibitors tertiary butanol alcohol (TBA), HCO 3 - , and CO 3 2- on the degradation rate of pyridine was investigated to verify the existence of active species produced by the strong ionization discharge in the system. The intermediate and final products generated in the degradation process of pyridine were confirmed and analyzed through a series of analytical techniques, including liquid chromatography-mass spectrometry (LC-MS), high performance liquid chromatography (HPLC), ion chromatography (IC), total organic carbon (TOC) analysis, ultraviolet (UV) spectroscopy, etc. The results showed that the degradation of pyridine was mainly due to the strong oxidizing power of ozone and hydroxyl radical produced by the DBD system. Several intermediate products including 3-hydroxyl pyridine, fumaric acid, 2, 3-dihydroxypyridine, and oxalic acid were detected. Nitrogen was removed from the pyridine molecule to form nitrate. Through analysis of the degradation mechanism of pyridine, the oxidation pathway was deduced. The study provided a theoretical and experimental basis for the application of DBD strong ionization discharge in treatment of nitrogen heterocyclic compounds in drinking water. Copyright © 2016. Published by Elsevier B.V.

An analysis of space environment effects on performance and missions of a Solar Electric Propulsion Stage (SEPS)

NASA Technical Reports Server (NTRS)

Mcglathery, D. M.

1975-01-01

The development of an analysis which addresses the problems of degrading space environmental effects on the performance and missions of a Solar Electric Propulsion Stage (SEPS) is reported. A detailed study concerning the degrading effects of the Van Allen Belt charged-particle radiation on specific spacecraft subsystems is included, along with some of the thermal problems caused by electromagnetic radiation from the sun. The analytical methods used require the integration of two distinct analyses. The first, is a low-thrust trajectory analysis which uses analytical approximations to optimum steering for orbit raising, including three-dimensional plane change cases. The second is the conversion of the Vette time-averaged differential energy spectra for protons and electrons into a 1-MeV electron equivalent environment as a function of spatial position and thickness of various shielding materials and solar-cell cover slides.

Uncovering the abilities of Agaricus bisporus to degrade plant biomass throughout its life cycle.

PubMed

Patyshakuliyeva, Aleksandrina; Post, Harm; Zhou, Miaomiao; Jurak, Edita; Heck, Albert J R; Hildén, Kristiina S; Kabel, Mirjam A; Mäkelä, Miia R; Altelaar, Maarten A F; de Vries, Ronald P

2015-08-01

The economically important edible basidiomycete mushroom Agaricus bisporus thrives on decaying plant material in forests and grasslands of North America and Europe. It degrades forest litter and contributes to global carbon recycling, depolymerizing (hemi-)cellulose and lignin in plant biomass. Relatively little is known about how A. bisporus grows in the controlled environment in commercial production facilities and utilizes its substrate. Using transcriptomics and proteomics, we showed that changes in plant biomass degradation by A. bisporus occur throughout its life cycle. Ligninolytic genes were only highly expressed during the spawning stage day 16. In contrast, (hemi-)cellulolytic genes were highly expressed at the first flush, whereas low expression was observed at the second flush. The essential role for many highly expressed plant biomass degrading genes was supported by exo-proteome analysis. Our data also support a model of sequential lignocellulose degradation by wood-decaying fungi proposed in previous studies, concluding that lignin is degraded at the initial stage of growth in compost and is not modified after the spawning stage. The observed differences in gene expression involved in (hemi-)cellulose degradation between the first and second flushes could partially explain the reduction in the number of mushrooms during the second flush. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Open circuit voltage durability study and model of catalyst coated membranes at different humidification levels

NASA Astrophysics Data System (ADS)

Kundu, Sumit; Fowler, Michael W.; Simon, Leonardo C.; Abouatallah, Rami; Beydokhti, Natasha

Fuel cell material durability is an area of extensive research today. Chemical degradation of the ionomer membrane is one important degradation mechanism leading to overall failure of fuel cells. This study examined the effects of relative humidity on the chemical degradation of the membrane during open circuit voltage testing. Five Gore™ PRIMEA ® series 5510 catalyst coated membranes were degraded at 100%, 75%, 50%, and 20% RH. Open circuit potential and cumulative fluoride release were monitored over time. Additionally scanning electron microscopy images were taken at end of the test. The results showed that with decreasing RH fluoride release rate increased as did performance degradation. This was attributed to an increase in gas crossover with a decrease in RH. Further, it is also shown that interruptions in testing may heavily influence cumulative fluoride release measurements where frequent stoppages in testing will cause fluoride release to be underestimated. SEM analysis shows that degradation occurred in the ionomer layer close to the cathode catalyst. A chemical degradation model of the ionomer membrane was used to model the results. The model was able to predict fluoride release trends, including the effects of interruptions, showing that changes in gas crossover with RH could explain the experimental results.

Forensic strategy to ensure the quality of sequencing data of mitochondrial DNA in highly degraded samples.

PubMed

Adachi, Noboru; Umetsu, Kazuo; Shojo, Hideki

2014-01-01

Mitochondrial DNA (mtDNA) is widely used for DNA analysis of highly degraded samples because of its polymorphic nature and high number of copies in a cell. However, as endogenous mtDNA in deteriorated samples is scarce and highly fragmented, it is not easy to obtain reliable data. In the current study, we report the risks of direct sequencing mtDNA in highly degraded material, and suggest a strategy to ensure the quality of sequencing data. It was observed that direct sequencing data of the hypervariable segment (HVS) 1 by using primer sets that generate an amplicon of 407 bp (long-primer sets) was different from results obtained by using newly designed primer sets that produce an amplicon of 120-139 bp (mini-primer sets). The data aligned with the results of mini-primer sets analysis in an amplicon length-dependent manner; the shorter the amplicon, the more evident the endogenous sequence became. Coding region analysis using multiplex amplified product-length polymorphisms revealed the incongruence of single nucleotide polymorphisms between the coding region and HVS 1 caused by contamination with exogenous mtDNA. Although the sequencing data obtained using long-primer sets turned out to be erroneous, it was unambiguous and reproducible. These findings suggest that PCR primers that produce amplicons shorter than those currently recognized should be used for mtDNA analysis in highly degraded samples. Haplogroup motif analysis of the coding region and HVS should also be performed to improve the reliability of forensic mtDNA data. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

On-Going International Research Program on Irradiated Concrete Conducted by DOE, EPRI and Japan Research Institutions. Roadmap, Achievements and Path Forward

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Pape, Yann; Rosseel, Thomas M.

The Joint Department of Energy (DOE)-Electric Power Research Institute (EPRI) Program (Light Water Reactor Sustainability (LWRS) Program–Material Pathway–Concrete and Long-Term Operation (LTO) Program) and US Nuclear Regulatory Commission (NRC) research studies aim at understanding the most prominent degradation modes and their effects on the long-term operation of concrete structures to nuclear power generation. Based on the results of the Expanded Materials Degradation Analysis (EMDA), (NUREG/CR-7153, ORNL/TM-2011/545), irradiated concrete and alkali-silica reaction (ASR)-affected concrete structures are the two prioritized topics of on-going research. This report focuses specifically on the topic of irradiated concrete and summarizes the main accomplishments obtained by thismore » joint program, but also provides an overview of current relevant activities domestically and internationally. Possible paths forward are also suggested to help near-future orientation of this program.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao Xia; Liu Bing; Hou Qian

A new route for the economic and efficient treatment of azo dye pollutants is reported, in which surface-modified organic-inorganic hybrid mesoporous silica (MS) spheres were chosen as microreactors for the accumulation and subsequent photodegradation of pollutants in defined regions. The surface-modified silica materials were prepared by anchoring the polycationic species such as poly(allylamine hydrochloride) on MS spheres via a simple wet impregnation method. The as-synthesized spheres with well-defined porous structures exhibited 15 times of accumulating capacity for orange II and Congo red compared to that of the pure MS spheres. Diffuse reflectance UV-vis spectroscopy and confocal laser scanning microscopy demonstratedmore » that the accumulated orange II and CR in defined MS spheres were rapidly degraded in the presence of Fenton reagent under visible radiation. Kinetics analysis in recycling degradation showed that the as-synthesized materials might be utilized as environment-friendly preconcentrators/microreactors for the remediation of dye wastewater.« less

Measurements and simulations of boron carbide as degrader material for proton therapy.

PubMed

Gerbershagen, Alexander; Baumgarten, Christian; Kiselev, Daniela; van der Meer, Robert; Risters, Yannic; Schippers, Marco

2016-07-21

We report on test measurements using boron carbide (B4C) as degrader material in comparison with the conventional graphite, which is currently used in many proton therapy degraders. Boron carbide is a material of lower average atomic weight and higher density than graphite. Calculations predict that, compared to graphite, the use of boron carbide results in a lower emittance behind the degrader due to the shorter degrader length. Downstream of the acceptance defining collimation system we expect a higher beam transmission, especially at low beam energies. This is of great interest in proton therapy applications as it allows either a reduction of the beam intensity extracted from the cyclotron leading to lower activation or a reduction of the treatment time. This paper summarizes the results of simulations and experiments carried out at the PROSCAN facility at the Paul Scherrer Institute(1). The simulations predict an increase in the transmitted beam current after the collimation system of approx. 30.5% for beam degradation from 250 to 84 MeV for a boron carbide degrader compared to graphite. The experiment carried out with a boron carbide block reducing the energy to 84 MeV yielded a transmission improvement of 37% compared with the graphite degrader set to that energy.

Site-specific variability in BTEX biodegradation under denitrifying conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kao, C.M.; Borden, R.C.

1997-03-01

Laboratory microcosm experiments were conducted to evaluate the feasibility of benzene, toluene, ethylbenzene, m-xylene, and o-xylene (BTEX) biodegradation under denitrifying conditions. Nine different sources of inocula, including contaminated and uncontaminated soil cores from four different sites and activated sludge, were used to establish microcosms. BTEX was not degraded under denitrifying conditions in microcosms inoculated with aquifer material from Rocky Point and Traverse City. However, rapid depletion of glucose under denitrifying conditions was observed in microcosms containing Rocky Point aquifer material. TEX degradation was observed in microcosms containing Rocky Point aquifer material. TEX degradation was observed in microcosms containing aquifer materialmore » from Fort Bragg and Sleeping Bear Dunes and sewage sludge. Benzene was recalcitrant in all microcosms tested. The degradation of o-xylene ceased after toluene, ethylbenzene, and m-xylene were depleted in the Fort Bragg and sludge microcosms, but o-xylene continued to degrade in microcosms with contaminated Sleeping Bear Dunes soil. The most probable number (MPN) of denitrifiers in these nine different inocula were measured using a microtiter technique. There was no correlation between the MPN of denitrifiers and the TEX degradation rate under denitrifying conditions. Experimental results indicate that the degradation sequence and TEX degradation rate under denitrifying conditions may differ among sites. Results also indicate that denitrification alone may not be a suitable bioremediation technology for gasoline-contaminated aquifers because of the inability of denitrifiers to degrade benzene.« less

Effects of cellulose degradation products on the mobility of Eu(III) in repositories for low and intermediate level radioactive waste.

PubMed

Diesen, Veronica; Forsberg, Kerstin; Jonsson, Mats

2017-10-15

The deep repository for low and intermediate level radioactive waste SFR in Sweden will contain large amounts of cellulosic waste materials contaminated with radionuclides. Over time the repository will be filled with water and alkaline conditions will prevail. In the present study degradation of cellulosic materials and the ability of cellulosic degradation products to solubilize and thereby mobilise Eu(III) under repository conditions has been investigated. Further, the possible immobilization of Eu(III) by sorption onto cement in the presence of degradation products has been investigated. The cellulosic material has been degraded under anaerobic and aerobic conditions in alkaline media (pH: 12.5) at ambient temperature. The degradation was followed by measuring the total organic carbon (TOC) content in the aqueous phase as a function of time. After 173days of degradation the TOC content is highest in the anaerobic artificial cement pore water (1547mg/L). The degradation products are capable of solubilising Eu(III) and the total europium concentration in the aqueous phase was 900μmol/L after 498h contact time under anaerobic conditions. Further it is shown that Eu(III) is adsorbed to the hydrated cement to a low extent (<9μmol Eu/g of cement) in the presence of degradation products. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of materials during outdoor testing using a computer-controlled test apparatus

Treesearch

R. Sam Williams; Steven Lacher; Corey Halpin; Christopher White

2006-01-01

Ultraviolet radiation, moisture, heat, and cyclic fatigue are some of the stressors that cause materials to degrade outdoors. Considerable research has addressed the effects of ultraviolet radiation and moisture on the rate of this degradation. An often overlooked stressor on materials, during outdoor testing, is the cyclic fatigue. Cyclic fatigue is caused by self-...

Use of Organic Substrates as a Best Management Practice for Active Ranges

DTIC Science & Technology

2011-11-30

is much more limited in high organic carbon soils due to a combination of enhanced sorption and degradation . Organic materials can enhance explosive... degradation by stimulating anaerobic biodegradation of the target contaminants and reducing naturally occurring Fe(III) to Fe(II), providing a reservoir...of reducing power to maintain anoxic conditions in the soil and enhance abiotic degradation . Humic materials slowly biodegrade, consuming oxygen

Novel biomixtures based on local Mediterranean lignocellulosic materials: evaluation for use in biobed systems.

PubMed

Karanasios, Evangelos; Tsiropoulos, Nikolaos G; Karpouzas, Dimitrios G; Menkissoglu-Spiroudi, Urania

2010-08-01

The composition of biomixtures strongly affect the efficacy of biobeds. Typically, biomixture consists of peat (or compost), straw (STR) and topsoil (1:2:1 by volume). Straw guarantees a continuous supply of nutrients and high microbial activity. However, in south Europe other lignocellulosic materials including sunflower crop residues (SFR), olive leaves, grape stalks (GS), orange peels, corn cobs (CC) and spent mushroom substrate (SMS) are also readily available at no cost. Their potential utilization in biomixtures instead of STR was tested in pesticide degradation and adsorption studies. The microbial activity in these biomixtures was also assessed. The GS-biomixture was the most efficient in pesticide degradation, while CC- and SFR-biomixtures showed comparable degrading efficacy with the STR-biomixture. The SMS-biomixture was also highly efficient in degrading the pesticide mixture with degradation rates being correlated with the proportion of SMS in the biomixture. Microbial respiration was positively correlated with the degradation rates of metalaxyl, azoxystrobin and chlorpyrifos, compared to phenoloxidase which showed no correlation. Biomixtures containing alternative lignocellulosic materials showed a higher adsorption affinity for terbuthylazine and metribuzin compared to the STR-biomixture. We provide first evidence that STR can be substituted in biomixtures by other lignocellulosic materials which are readily available in south Europe. (c) 2010 Elsevier Ltd. All rights reserved.

Graphene/TiO2/ZSM-5 composites synthesized by mixture design were used for photocatalytic degradation of oxytetracycline under visible light: Mechanism and biotoxicity

NASA Astrophysics Data System (ADS)

Hu, Xin-Yan; Zhou, Kefu; Chen, Bor-Yann; Chang, Chang-Tang

2016-01-01

This first-attempt study revealed mixture design of experiments to obtain the most promising composites of TiO2 loaded on zeolite and graphene for maximal photocatalytic degradation of oxytetracycline (OTC). The optimal weight ratio of graphene, titanium dioxide (TiO2), and zeolite was 1:8:1 determined via experimental design of simplex lattice mixture. The composite material was characterized by XRD, UV-vis, TEM and EDS analysis. The findings showed the composite material had a higher stability and a stronger absorption of the visible light. In addition, it was uniformly dispersed with promising adsorption characteristics. OTC was used as model toxicant to evaluate the photodegradation efficiency of the GTZ (1:8:1). At optimal operating conditions (i.e., pH 7 and 25 °C), complete degradation (ca. 100%) was achieved in 180 min. The biotoxicity of the degraded intermediates of OTC on cell growth of Escherichia coli DH5α were also assayed. After 180 min photocatalytic treatment, OTC solution treated by GTZ (1:8:1) showed insignificant biotoxicity to receptor DH5α cells. Furthermore, EDTA (hole scavengers) and t-BuOH (radical scavengers) were used to detect the main active oxidative species in the system. The results showed that the holes are the main oxidation species in the photocatalytic process.

Hygienic support of the ISS air quality (main achievements and prospects)

NASA Astrophysics Data System (ADS)

Moukhamedieva, Lana; Tsarkov, Dmitriy; Pakhomova, Anna

Hygienic preventive measures during pre-flight processing of manned spaceships, selection of polymeric materials, sanitary-hygienic evaluation of cargo and scientific hardware to be used on the ISS and life support systems allow to maintain air quality in limits of regulatory requirements. However, graduate increase of total air contamination by harmful chemicals is observed as service life of the ISS gets longer. It is caused by polymeric materials used on the station overall quantity rise, by additional contamination brought by cargo spacecrafts and modules docking to the ISS and by the cargo. At the same time the range of contaminants that are typical for off-gassing from polymeric materials where modern stabilizers, plasticizers, flame retarders and other additives are used gets wider. In resolving the matters of the ISS service life extension the main question of hygienic researches is to determine real safe operation life of the polymeric material used in structures and hardware of the station, including: begin{itemize} research of polymers degradation (ageing) and its effect on intensity of off gassing and its toxicity; begin{itemize} introduction of polymers with minimal volatile organic compounds off gassing under conditions of space flight and thermal-oxidative degradation. In order to ensure human safety during long-term flight it is important to develop: begin{itemize} real-time air quality monitoring systems, including on-line analysis of highly toxic contaminants evolving during thermo-oxidative degradation of polymer materials and during blowouts of toxic contaminants; begin{itemize} hygienic standards of contaminants level for extended duration of flight up to 3 years. It is essential to develop an automated control system for on-line monitoring of toxicological status and to develop hygienic and engineer measures of its management in order to ensure crew members safety during off-nominal situation.

Effect of food processing on degradation of hexachlorocyclohexane and its isomers in milk

PubMed Central

Singh, Sujatha; Nelapati, Krishnaiah

2017-01-01

Aim: To study the effect of different food processing techniques on the degradation of organochlorine compounds (α, β, ɣ and δ hexachlorocyclohexane isomers (HCH)) residues in both natural and fortified samples of milk. Materials and Methods: Raw milk samples are collected from the local areas of Hyderabad, India. Naturally and fortified milk samples (HCH) were subjected to various food processing techniques, pasteurization (63ºC for ½ h), sterilization (121ºC for 15 min) and boiling for 5 min and analyzed by gas chromatography with electron capture detector using quick, easy, cheap, effective, rugged and safe method for multiresidue analysis of pesticides in milk with slight modification. Results: The final mean residual concentration of pesticide in milk after heat processing and percentage of degradation were calculated with respective treatments. Conclusion: Heat treatments are highly effective on reduction of mean residual concentration of HCH in milk. In which Sterilization and boiling proved to be more effective in degradation of HCH isomers. PMID:28435187

Effect of filler loading and silane modification on the biodegradability of SBR composites reinforced with peanut shell powder

NASA Astrophysics Data System (ADS)

Shaniba, V.; Balan, Aparna K.; Sreejith, M. P.; Jinitha, T. V.; Subair, N.; Purushothaman, E.

2017-06-01

The development of biocomposites and their applications are important in material science due to environmental and sustainability issues. The extent of degradation depends on the nature of reinforcing filler, particle size and their modification. In this article, we tried to focus on the biodegradation of composites of Styrene Butadiene Rubber (SBR) reinforced with Peanut Shell Powder (PSP) by soil burial test. The composites of SBR with untreated PSP (UPSP) and silane modified PSP (SPSP) of 10 parts per hundred rubber (phr) and 20 phr filler loading in two particle size were buried in the garden soil for six months. The microbial degradation were assessed through the measurement of weight loss, tensile strength and hardness at definite period. The study shows that degradation increases with increase in filler loading and particle size. The chemical treatment of filler has been found to resist the degradation. The analysis of morphological properties by the SEM also confirmed biodegradation process by the microorganism in the soil.

Degradation of lignin in birch sawdust treated by a novel Myrothecium verrucaria coupled with ultrasound assistance.

PubMed

Wang, Qing-Fang; Niu, Li-Li; Jiao, Jiao; Guo, Na; Zang, Yu-Ping; Gai, Qing-Yan; Fu, Yu-Jie

2017-11-01

Combined treatment of a novel fungal endophyte Myrothecium verrucaria coupled with ultrasound assistance was conducted to enhance lignin degradation in birch sawdust. The optimum treatment conditions were confirmed as the materials to liquid ratio 1:20, temperature 30°C, time 4days and pH 7, respectively. The results showed that the combined treatment led to the lignin degradation reaching 67.95±2.14%, while the lignin degradation were 45.50±2.12% and 13.75±0.66% with separate fungal treatment and ultrasound treatment, respectively. Moreover, SEM and FTIR analysis indicated that combined treatment significantly altered surface morphology and chemical structure of birch sawdust. The combined treatment greatly increased lignin removal during short time in mild environment. Therefore, these results demonstrated that the combined treatment of fungal endophyte coupled with ultrasound assistance has the high potential for the removal lignin in lignocellulose. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of different sources of DNA for use in genome wide studies and forensic application.

PubMed

Al Safar, Habiba S; Abidi, Fatima H; Khazanehdari, Kamal A; Dadour, Ian R; Tay, Guan K

2011-02-01

In the field of epidemiology, Genome-Wide Association Studies (GWAS) are commonly used to identify genetic predispositions of many human diseases. Large repositories housing biological specimens for clinical and genetic investigations have been established to store material and data for these studies. The logistics of specimen collection and sample storage can be onerous, and new strategies have to be explored. This study examines three different DNA sources (namely, degraded genomic DNA, amplified degraded genomic DNA and amplified extracted DNA from FTA card) for GWAS using the Illumina platform. No significant difference in call rate was detected between amplified degraded genomic DNA extracted from whole blood and amplified DNA retrieved from FTA™ cards. However, using unamplified-degraded genomic DNA reduced the call rate to a mean of 42.6% compared to amplified DNA extracted from FTA card (mean of 96.6%). This study establishes the utility of FTA™ cards as a viable storage matrix for cells from which DNA can be extracted to perform GWAS analysis.

The Reduction of the Critical Currents in Nb3Sn Cables under Transverse Loads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Oort, J.M.; Scanlan, R.M.; Weijers, H.W.

1992-08-01

The degradation of the critical current of impregnated Rutherford type Nb{sub 3}Sn cables is investigated as a function of the applied transverse load and magnetic field. The cable is made of TWCA modified jelly-roll type strand material and has a keystone angle of 1.0 degree. The voltage-current characteristics are determined for the magnetic field ranging from 2 to 11 tesla and transverse pressure up to 250 MPa on the cable surface. It is found that the 48-strand cable, made of strands with 6 elements in the matrix, shows a larger critical current degradation than the 26-strand cable with 36 elementsmore » per strand. The global degradation of the 48-strand cable is 63% at 150 MPa, and 40% at 150 MPa for the 26-strand cable. Micro-analysis of the cross-section shows permanent damage to the sharp edge of the cable. The influence of the keystone angle on the critical-current degradation is currently under investigation.« less

Material properties and laser cutting of composites

NASA Astrophysics Data System (ADS)

Chen, Chia-Chieh; Cheng, Wing

Laser (Light Amplification by Stimulated Emission of Radiation) has been used successfully for many material cutting, drilling, metal welding and heat treating applications. However, laser cutting of polymer composites were attempted with varying degrees of success. Because composites are heterogeneous, the energy applied by laser could result in severe resin degradation before fibers were cut. In this study, cutting of glass, Kevlar, and graphite composites were evaluated based on their material properties and laser cutting parameters. A transient heat transfer analysis was used to determine the relative heat affected zones of these composites. Kevlar composites can be cut very well while graphite composites are difficult to cut. Though the cutting process is much more complicated in reality, the analysis provides a semi-quantitative perspective on the characteristics and limitations of laser cutting of different composites.

Analysis of polymer/oxide interfaces under ambient conditions - An experimental perspective

NASA Astrophysics Data System (ADS)

González-Orive, A.; Giner, I.; de los Arcos, T.; Keller, A.; Grundmeier, G.

2018-06-01

In many different hybrid materials and materials composites polymers adhere to bulk oxides or oxide covered metal. The formed polymer/oxide interfaces are of crucial importance for the functionality and durability of such complex materials. Especially, under humid and corrosive conditions such interfaces tend to degrade due to permeability of polymers for water, the high adsorption energy of water on oxide surfaces and even corrosion processes of the metal. Different experimental studies considered such interfaces ranging from spectroscopy to electrochemical analysis. However, it is still a challenge to understand the complex interaction especially under non-ideal ambient conditions. The perspective article presents an overview on the existing experimental approaches and considers most recent experimental developments with regard to their potential applications in the area of polymer/oxide interfaces in the future.

Adaptation of the biobed composition for chlorpyrifos degradation to Southern Europe conditions.

PubMed

Coppola, Laura; Castillo, Maria d P; Monaci, Elga; Vischetti, Costantino

2007-01-24

Biobeds developed in Sweden bind and degrade pesticides from point sources. The objective of this work was to adapt the biobed to Italian operating conditions, for example, to identify organic materials as effective as those in the original Swedish composition. The capacity of urban and garden composts alone or mixed with citrus peel or straw to degrade chlorpyrifos and its metabolite TCP was compared to the typical Swedish biomix consisting of straw, peat, and soil. A tendency for higher 14C-chlorpyrifos mineralization and lower TCP levels was observed in the biomixes with garden compost alone or amended with straw. In a second trial, a high correlation of lower TCP with increasing levels of straw in typical Swedish biomixes was observed. Straw stimulates production of lignin-degrading enzymes such as manganese peroxidase (MnP), and further trials with pure MnP showed that this enzyme degrades TCP. Materials with an active lignin-degrading microflora are a prerequisite for effective dissipation of chlorpyrifos and non-accumulation of TCP. Thus, lignocellulosic materials as straw and garden composts should be present in biomixes to be used under Italian conditions.

TCP is hardly resorbed and not osteoconductive in a non-loading calvarial model.

PubMed

Handschel, Jörg; Wiesmann, Hans Peter; Stratmann, Udo; Kleinheinz, Johannes; Meyer, Ulrich; Joos, Ulrich

2002-04-01

Tricalciumphosphate (TCP) has been used as a ceramic bone substitute material in the orthopedic field as well as in craniofacial surgery. Some controversies exist concerning the osteoconductive potential of this material in different implantation sites. This study was designed to evaluate the biological response of calvarial bone towards TCP granules under non-loading conditions to assess the potential of TCP as a biodegredable and osteoconductive bone substitue material for the cranial vault. Full-thickness non-critical size defects were made bilaterally in the calvaria of 21 adult Wistar rats. One side was filled by TCP granules, the contralateral side was left empty and used as a control. Animals were sacrified in defined time intervals up to 6 months. Bone regeneration was analyzed with special respect toward the micromorphological and microanalytical features of the material-bone interaction by electron microscopy and electron diffraction analysis. Histologic examination revealed no TCP degradation even after 6 months of implantation. In contrast, a nearly complete bone regeneration of control defects was found after 6 months. At all times TCP was surrounded by a thin fibrous layer without presence of osteoblasts and features of regular mineralization. As far as degradation and substitution are concerned, TCP is a less favourable material tinder conditions of non-loading.

Contact material optimization and contact physics in metal-contact microelectromechanical systems (MEMS) switches

NASA Astrophysics Data System (ADS)

Yang, Zhenyin

Metal-contact MEMS switches hold great promise for implementing agile radio frequency (RF) systems because of their small size, low fabrication cost, low power consumption, wide operational band, excellent isolation and exceptionally low signal insertion loss. Gold is often utilized as a contact material for metal-contact MEMS switches due to its excellent electrical conductivity and corrosion resistance. However contact wear and stiction are the two major failure modes for these switches due to its material softness and high surface adhesion energy. To strengthen the contact material, pure gold was alloyed with other metal elements. We designed and constructed a new micro-contacting test facility that closely mimic the typical MEMS operation and utilized this facility to efficiently evaluate optimized contact materials. Au-Ni binary alloy system as the candidate contact material for MEMS switches was systematically investigated. A correlation between contact material properties (etc. microstructure, micro-hardness, electrical resistivity, topology, surface structures and composition) and micro-contacting performance was established. It was demonstrated nano-scale graded two-phase Au-Ni film could possibly yield an improved device performance. Gold micro-contact degradation mechanisms were also systematically investigated by running the MEMS switching tests under a wide range of test conditions. According to our quantitative failure analysis, field evaporation could be the dominant failure mode for highfield (> critical threshold field) hot switching; transient thermal-assisted wear could be the dominant failure mode for low-field hot switching; on the other hand, pure mechanical wear and steady current heating (1 mA) caused much less contact degradation in cold switching tests. Results from low-force (50 muN/micro-contact), low current (0.1 mA) tests on real MEMS switches indicated that continuous adsorbed films from ambient air could degrade the switch contact resistance. Our work also contributes to the field of general nano-science and technology by resolving the transfer directionality of field evaporation of gold in atomic force microscope (AFM)/scanning tunneling microscope (STM).

Mechanical Properties of Degraded PMR-15 Resin

NASA Technical Reports Server (NTRS)

Tsuji, Luis C.

2000-01-01

Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

Biodegradation of polyether-polyol-based polyurethane elastomeric films: influence of partial replacement of polyether polyol by biopolymers of renewable origin.

PubMed

Obruca, Stanislav; Marova, Ivana; Vojtova, Lucy

2011-07-01

In this work we investigated the degradation process ofpolyether-polyol-based polyurethane (PUR) elastomeric films in the presence of a mixed thermophilic culture as a model of a natural bacterial consortium. The presence of PUR material in cultivation medium resulted in delayed but intensive growth of the bacterial culture. The unusually long lag phase was caused by the release of unreacted polyether polyol and tin catalyst from the material. The lag phase was significantly shortened and the biodegradability of PUR materials was enhanced by partial replacement (10%) of polyether polyol with biopolymers (carboxymethyl cellulose, hydroxyethyl cellulose, acetyl cellulose and actylated starch). The process of material degradation consisted of two steps. First, the materials were mechanically disrupted and, second, the bacterial culture was able to utilize abiotic degradation products, which resulted in supported bacterial growth. Direct utilization of PUR by the bacterial culture was observed as well, but the bacterial culture contributed only slightly to the total mass losses. The only exception was PUR material modified by acetyl cellulose. In this case, direct biodegradation represented the major mechanism of material decomposition. Moreover, PUR material modified by acetyl cellulose did not tend to undergo abiotic degradation. In conclusion, the modification of PUR by proper biopolymers is a promising strategy for reducing potential negative effects of waste PUR materials on the environment and enhancing their biodegradability.

Enhanced Photocatalytic Activity toward Organic Pollutants Degradation and Mechanism Insight of Novel CQDs/Bi₂O₂CO₃ Composite.

PubMed

Zhang, Zisheng; Lin, Shuanglong; Li, Xingang; Li, Hong; Zhang, Tong; Cui, Wenquan

2018-05-15

Novel carbon quantum dots (CQDs) modified with Bi₂O₂CO₃ (CQDs/Bi₂O₂CO₃) were prepared using a simple dynamic-adsorption precipitation method. X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) were used to test the material composition, structure, and band structures of the as-prepared samples. Methylene blue (MB) and colorless phenol, as target organic pollutants, were used to evaluate the photocatalytic performance of the CQDs/Bi₂O₂CO₃ hybrid materials under visible light irradiation. Experimental investigation shows that 2⁻5 nm CQDs were uniformly decorated on the surface of Bi₂O₂CO₃; CQDs/Bi₂O₂CO₃ possess an efficient photocatalytic performance, and the organic matter removal rate of methylene blue and phenol can reach up to 94.45% and 61.46% respectively, within 2 h. In addition, the degradation analysis of phenol by high performance liquid chromatography (HPLC) proved that there are no other impurities in the degradation process. Photoelectrochemical testing proved that the introduction of CQDs (electron acceptor) effectively suppresses the recombination of e - -h⁺, and promotes charge transfer. Quenching experiments and electron spin resonance (ESR) suggested that ·OH, h⁺, and ·O₂ - were involved in the photocatalytic degradation process. These results suggested that the up-conversion function of CQDs could improve the electron transfer and light absorption ability of photocatalysts and ·O₂ - formation. Furthermore, the up-conversion function of CQDs would help maintain photocatalytic stability. Finally, the photocatalytic degradation mechanism was proposed according to the above experimental result.

Experimental and computational studies of poly-L-lactic acid for cardiovascular applications: recent progress

NASA Astrophysics Data System (ADS)

Naseem, Raasti; Zhao, Liguo; Liu, Yang; Silberschmidt, Vadim V.

2017-12-01

Stents are commonly used in medical procedures to alleviate the symptoms of coronary heart disease, a prevalent modern society disease. These structures are employed to maintain vessel patency and restore blood flow. Traditionally stents are made of metals such as stainless steel or cobalt chromium; however, these scaffolds have known disadvantages. An emergence of transient scaffolds is gaining popularity, with the structure engaged for a required period whilst healing of the diseased arterial wall occurs. Polymers dominate a medical device sector, with incorporation in sutures, scaffolds and screws. Thanks to their good mechanical and biological properties and their ability to degrade naturally. Polylactic acid is an extremely versatile polymer, with its properties easily tailored to applications. Its dominance in the stenting field increases continually, with the first polymer scaffold gaining FDA approval in 2016. Still some challenges with PLLA bioresorbable materials remain, especially with regard to understanding their mechanical response, assessment of its changes with degradation and comparison of their performance with that of metallic drug-eluting stent. Currently, there is still a lack of works on evaluating both the pre-degradation properties and degradation performance of these scaffolds. Additionally, there are no established material models incorporating non-linear viscoelastic behaviour of PLLA and its evolution with in-service degradation. Assessing these features through experimental analysis accompanied by analytical and numerical studies will provide powerful tools for design and optimisation of these structures endorsing their broader use in stenting. This overview assesses the recent studies investigating mechanical and computational performance of poly(l-lactic) acid and its use in stenting applications.

UV and visible activation of Cr(III)-doped TiO2 catalyst prepared by a microwave-assisted sol-gel method during MCPA degradation.

PubMed

Mendiola-Alvarez, S Y; Guzmán-Mar, J L; Turnes-Palomino, G; Maya-Alejandro, F; Hernández-Ramírez, A; Hinojosa-Reyes, L

2017-05-01

Photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in aqueous solution using Cr(III)-doped TiO 2 under UV and visible light was investigated. The semiconductor material was synthesized by a microwave-assisted sol-gel method with Cr(III) doping contents of 0.02, 0.04, and 0.06 wt%. The catalyst was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption, UV-Vis diffuse reflectance spectroscopy (DRS), and atomic absorption spectroscopy (AAS). The photocatalytic activity for the photodegradation of MCPA was followed by reversed-phase high-performance liquid chromatography (HPLC) and total organic carbon (TOC) analysis. The intermediates formed during degradation were identified using gas chromatography-mass spectrometry (GC-MS). Chloride ion evolution was measured by ion chromatography. Characterization results showed that Cr(III)-doped TiO 2 materials possessed a small crystalline size, high surface area, and mesoporous structure. UV-Vis DRS showed enhanced absorption in the visible region as a function of the Cr(III) concentration. The Cr(III)-doped TiO 2 catalyst with 0.04 wt% of Cr(III) was more active than bare TiO 2 for the degradation of MCPA under both UV and visible light. The intermediates identified during MCPA degradation were 4-chloro-2-methylphenol (CMP), 2-(4-hydroxy-2-methylphenoxy) acetic acid (HMPA), and 2-hydroxybuta-1,3-diene-1,4-diyl-bis (oxy)dimethanol (HBDM); the formation of these intermediates depended on the radiation source.

High Temperature Degradation of Advanced Thermal and Environmental Barrier Coatings (TEBCs) by CaO-MgO-Al2O3-SiO2 (CMAS)

NASA Technical Reports Server (NTRS)

Costa, Gustavo; Zhu, Dongming

2017-01-01

There is increasing interest in the degradation studies of thermal and environmental barrier coatings (TEBCs) of gas turbines by molten CaO-MgO-Al2O3-SiO2 (CMAS). CMAS minerals are usually referred as silica-containing sand dust and volcano ash materials that are carried by the intake air into gas turbines, e.g. aircraft engines. The low-melting deposits react at high temperatures (1000C) with the coating materials. This causes degradation and accelerated coating failure of the static and rotating components of the turbine engines. We discuss some preliminary results of the reactions between CMAS and Rare-Earth (RE Y, Yb, Dy, Gd, Nd and Sm) oxide stabilized ZrO2 or HfO2 systems, and the stability of the resulting oxides and silicates. Plasma sprayed hollow tube samples (outer diameter 4.7 mm, wall thickness 0.76 mm and 26 mm height) were half filled with CMAS powder, wrapped and sealed with platinum foil, and heat- treated at 1310 C for 5h. Samples were characterized by differential scanning calorimetry, X-ray diffraction and cross section electron microscopy analysis.

Analysis of biodegradation performance of furfural and 5-hydroxymethylfurfural by Amorphotheca resinae ZN1

PubMed Central

2014-01-01

Background Furfural and 5-hydroxymethylfurfural (HMF) are the degradation products of lignocellulose during pretreatment operations and significantly inhibit the consequent enzymatic hydrolysis and fermentation processes. The biodetoxification fungus Amorphotheca resinae ZN1 had demonstrated its excellent capacity on degrading lignocellulose derived inhibitors and helped the fermentation processes to achieve high yield of ethanol and biochemicals. Analysis of the biological degradation performance of furfural and HMF by A. resinae ZN1 will provide essential information for their fast and complete removal from the pretreated lignocellulose materials and facilitate the consequent ethanol fermentation. Results The degradation performance of furfural and HMF by A. resinae ZN1 was investigated by capturing intermediate metabolic products at various culture conditions. A. resinae ZN1 converts furfural/HMF into furfuryl/HMF alcohols and furoic/HMF acids simultaneously at aerobic condition, and only the corresponding furfuryl/HMF alcohols are obtained at anaerobic condition. The existence of glucose accelerates the degradation rate of furfural and HMF by A. resinae ZN1 and the cell mass growth rate aerobically. Remarkably, glucose is not consumed before furfural or HMF is degraded to a low threshold concentration. The finding suggests that furfural or HMF has a substrate priority of utilization by A. resinae ZN1 than glucose. This property may help the detoxification of furfural and HMF to be operated without consuming glucose. Conclusions The biological degradation performance of furfural and HMF by A. resinae ZN1 was investigated experimentally. Oxygen supply is important on the complete biodegradation of furfural and HMF by A. resinae ZN1. Furfural or HMF has the priority of substrate utilization than glucose by A. resinae ZN1. This study provided important information for detoxification enhancement and strain modification. PMID:24708699

Subsystem radiation susceptibility analysis for deep-space missions

NASA Technical Reports Server (NTRS)

West, W. S.; Poch, W.; Holmes-Siedle, A.; Bilsky, H. W.; Carroll, D.

1971-01-01

Scientific, unmanned spacecraft on mission to Jupiter and beyond will be subjected to nuclear radiation from the natural environment and onboard nuclear power sources which may be harmful to subsystems. This report postulates these environments and discusses practical considerations to ensure confidence that the spacecraft's materials and subsystems will withstand the effects of anticipated radiation. Degradation mechanisms are discussed.

Cloning of the poly(ADP-ribose) Gene from Rat Liver.

DTIC Science & Technology

1986-09-24

Levinson, Ph.D. (Cetus Corp., Berkeley). 5. Amino acid analysis done in UCSF Bioanal. Lab. TABLE OF CONTENTS Page METHOD I...TABLE I ............. ............................... ... 12 Proteolytic degradation, isolation of peptide and amino acid sequences...technique developed for enzyme quantitation in biological materials. The amino- acid sequence of the enzyme has so far been determined because the amino

The development and characterization of degradable poly(vinyl ester) and poly(vinyl ester)/PEO block copolymers

NASA Astrophysics Data System (ADS)

Lipscomb, Corinne Elizabeth

The development of biodegradable materials is a challenging and important problem in polymer science. A review of the state of the art in degradable materials is presented, which reveals that current biodegradable materials do not exhibit the thermal or mechanical properties necessary for widespread applications. One strategy for toughening polymeric materials, which has previously been applied to non-degradable thermoplastics and thermoplastic elastomers, is the formation of block copolymers. Poly(vinyl esters) (PVE) homopolymers are known to have a wide range of properties, but PVE block copolymers comprise a class of inexpensive and (bio)degradable materials that were previously unknown. Therefore, the synthesis and properties of these block copolymers were explored in an effort to develop robust degradable materials. This thesis research probes the reaction conditions necessary for the reversible-addition fragmentation chain transfer (RAFT) polymerization and chain extension reactions of vinyl ester monomers. PVE di- and triblock copolymers are synthesized and studied, and the triblock copolymers display extremely poor toughness due to their relatively low molecular weights in light of the high entanglement molecular weight of the poly(vinyl acetate) center block. Attempts to improve the mechanical properties of these materials focus on the incorporation of poly(ethylene oxide) (PEO) as a low entanglement molecular weight and biocompatible center block in PVE-containing triblock copolymers. Depending on the choice of PVE endblocks and the overall polymer composition, crystallization of the PEO block can be controlled, confined, or inhibited. Polymers in which PEO crystallization is completely inhibited exhibit enhanced mechanical properties and behave as weak thermoplastics. In order to understand the relationship between the inhibition of PEO crystallization and the mechanical properties of PVE/PEO materials, these polymers were studied using dynamic mechanical spectroscopy, wide angle X-ray scattering, small angle X-ray scattering, differential scanning calorimetry, and uniaxial tensile tests. By combining insights gained from these techniques, a complex picture emerges that explains the enhanced mechanical properties of these materials based on the type and location of thermal transitions, amorphous PEO entanglements, and the strain-induced crystallization of PEO. This work represents an important step toward developing robust materials with tunable properties containing (bio)degradable components.

Thermal degradation and morphological studies on raw and reinforced polyacrylic rubbers

NASA Astrophysics Data System (ADS)

Sasikala, A.; Kala, A.

2017-05-01

Poly acrylate rubbers (ACM) of today are saturated copolymers of monomeric acrylic esters and reactive cure site monomers. ACM elastomer have also found use in vibration damping due to its excellent resilience. Other applications include textiles, adhesives, and coatings. Two state of Poly acrylic raw and reinforced Rubber are analyzed using FTIR spectroscopy, Optical Microscopy, DSC and TGA measurements. With the objective of determined the mechanical strength, Thermal analysis on TGA and DSC studies show that, the thermal degradation temperature Tg of the sample material is obtained and activation energy is also calaulated by Broido, Horowitz - Metzger, Piloyan-Novikova and Coats Redfern methods which are found.

Biodegradable Materials for Bone Repair and Tissue Engineering Applications

PubMed Central

Sheikh, Zeeshan; Najeeb, Shariq; Khurshid, Zohaib; Verma, Vivek; Rashid, Haroon; Glogauer, Michael

2015-01-01

This review discusses and summarizes the recent developments and advances in the use of biodegradable materials for bone repair purposes. The choice between using degradable and non-degradable devices for orthopedic and maxillofacial applications must be carefully weighed. Traditional biodegradable devices for osteosynthesis have been successful in low or mild load bearing applications. However, continuing research and recent developments in the field of material science has resulted in development of biomaterials with improved strength and mechanical properties. For this purpose, biodegradable materials, including polymers, ceramics and magnesium alloys have attracted much attention for osteologic repair and applications. The next generation of biodegradable materials would benefit from recent knowledge gained regarding cell material interactions, with better control of interfacing between the material and the surrounding bone tissue. The next generations of biodegradable materials for bone repair and regeneration applications require better control of interfacing between the material and the surrounding bone tissue. Also, the mechanical properties and degradation/resorption profiles of these materials require further improvement to broaden their use and achieve better clinical results. PMID:28793533

In vitro degradation and in vivo toxicity of NanoMatrix3D® polycaprolactone and poly(lactic acid) nanofibrous scaffolds.

PubMed

Pogorielov, Maksym; Hapchenko, Andrii; Deineka, Volodymyr; Rogulska, Larysa; Oleshko, Olexandr; Vodseďálková, Kateřina; Berezkinová, Liliana; Vysloužilová, Lucie; Klápšťová, Andrea; Erben, Jakub

2018-04-10

Nanofibrous materials present unique properties favorable in many biomedicine and industrial applications. In this research we evaluated biodegradation, tissue response and general toxicity of nanofibrous poly(lactic acid) (PLA) and polycaprolactone (PCL) scaffolds produced by conventional method of electrospinning and using NanoMatrix3D ® (NM3D ® ) technology. Mass density, scanning electron microscopy and in vitro degradation (static and dynamic) were used for material characterization, and subcutaneous, intramuscular and intraperitoneal implantation - for in vivo tests. Biochemical blood analysis and histology were used to assess toxicity and tissue response. Pore size and fiber diameter did not differ in conventional and NM3D ® PLA and PCL materials, but mass density was significantly lower in NM3D ® ones. Scaffolds made by conventional method showed toxic effect during the in-vivo tests due to residual concentration of chloroform that released with material degradation. NM3D ® method allowed cleaning scaffolds from residual solutions that made them nontoxic and biocompatible. Subcutaneous, intramuscular and intraperitoneal implantation of PCL and PLA NM3D ® electrospun nanofibrous scaffolds showed their appropriate cell conductive properties, tissue and vessels formation in all sites. Thus, NM3D ® PCL and PLA nanofibrous electrospun scaffolds can be used in the field of tissue engineering, surgery, wound healing, drug delivery, and so forth, due to their unique properties, nontoxicity and biocompatibility. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A:000-000, 2018. © 2018 Wiley Periodicals, Inc.

Intralaminar and Interlaminar Progressive Failure Analysis of Composite Panels with Circular Cutouts

NASA Technical Reports Server (NTRS)

Goyal, Vinay K.; Jaunky, Navin; Johnson, Eric R.; Ambur, Damodar

2002-01-01

A progressive failure methodology is developed and demonstrated to simulate the initiation and material degradation of a laminated panel due to intralaminar and interlaminar failures. Initiation of intralaminar failure can be by a matrix-cracking mode, a fiber-matrix shear mode, and a fiber failure mode. Subsequent material degradation is modeled using damage parameters for each mode to selectively reduce lamina material properties. The interlaminar failure mechanism such as delamination is simulated by positioning interface elements between adjacent sublaminates. A nonlinear constitutive law is postulated for the interface element that accounts for a multi-axial stress criteria to detect the initiation of delamination, a mixed-mode fracture criteria for delamination progression, and a damage parameter to prevent restoration of a previous cohesive state. The methodology is validated using experimental data available in the literature on the response and failure of quasi-isotropic panels with centrally located circular cutouts loaded into the postbuckling regime. Very good agreement between the progressive failure analyses and the experimental results is achieved if the failure analyses includes the interaction of intralaminar and interlaminar failures.

LONG TERM OPERATION ISSUES FOR ELECTRICAL CABLE SYSTEMS IN NUCLEAR POWER PLANTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fifield, Dr Leonard S; Duckworth, Robert C; Glass III, Dr. Samuel W.

Nuclear power plants contain hundreds of kilometers of electrical cables including cables used for power, for instrumentation, and for control. It is essential that safety-related cable systems continue to perform following a design-basis event. Wholesale replacement of electrical cables in existing plants facing licensing period renewal is both impractical and cost-prohibitive. It is therefore important to understand the long term aging of cable materials to have confidence that aged cables will perform when needed. It is equally important in support of cable aging management to develop methods to evaluate the health of installed cables and inform selective cable replacement decisions.more » The most common insulation materials for electrical cables in nuclear power plants are cross-linked polyethylene and ethylene-propylene rubber. The mechanical properties of these materials degrade over time in the presence of environmental stresses including heat, gamma irradiation, and moisture. Mechanical degradation of cable insulation beyond a certain threshold is unacceptable because it can lead to insulation cracking, exposure of energized conductors, arcing and burning or loss of the ability of the cable system to function during a design-basis accident. While thermal-, radiation-, and moisture-related degradation of polymer insulation materials has been extensively studied over the last few decades, questions remain regarding the long-term performance of cable materials in nuclear plant-specific environments. Identified knowledge gaps include an understanding of the temperature-dependence of activation energies for thermal damage and an understanding of the synergistic effects of radiation and thermal stress on polymer degradation. Many of the outstanding questions in the aging behavior of cable materials relate to the necessity of predicting long-term field degradation using accelerated aging results from the laboratory. Materials degrade faster under more extreme conditions, but extension of behavior to long term degradation under more mild conditions, such as those experienced by most installed cables in nuclear power plants, is complicated by the fact that different degradation mechanisms may be involved in extreme and mild scenarios. The discrepancy in predicted results from short term, more extreme exposure and actual results from longer term, more mild exposures can be counter intuitive. For instance, due to the attenuation of oxidation penetration in material samples rapidly aged through exposure to high temperatures, the bulk of the samples may be artificially protected from thermal aging. In another example, simultaneous exposure of cable insulation material to heat and radiation may actually lead to less damage at higher temperatures than may be observed at lower temperatures. The Light Water Reactor Sustainability program of the United States (US) Department of Energy Office (DOE) of Nuclear Energy is funding research to increase the predictive understanding of electrical cable material aging and degradation in existing nuclear power plants in support of continued safe operation of plants beyond their initial license periods. This research includes the evaluation and development of methods to assess installed cable condition.« less

Bacterial secondary production on vascular plant detritus: relationships to detritus composition and degradation rate.

PubMed Central

Moran, M A; Hodson, R E

1989-01-01

Bacterial production at the expense of vascular plant detritus was measured for three emergent plant species (Juncus effusus, Panicum hemitomon, and Typha latifolia) degrading in the littoral zone of a thermally impacted lake. Bacterial secondary production, measured as tritiated thymidine incorporation into DNA, ranged from 0.01 to 0.81 microgram of bacterial C mg of detritus-1 day-1. The three plant species differed with respect to the amount of bacterial productivity they supported per milligram of detritus, in accordance with the predicted biodegradability of the plant material based on initial nitrogen content, lignin content, and C/N ratio. Bacterial production also varied throughout the 22 weeks of in situ decomposition and was positively related to the nitrogen content and lignin content of the remaining detritus, as well as to the temperature of the lake water. Over time, production was negatively related to the C/N ratio and cellulose content of the degrading plant material. Bacterial production on degrading plant material was also calculated on the basis of plant surface area and ranged from 0.17 to 1.98 micrograms of bacterial C cm-2 day-1. Surface area-based calculations did not correlate well with either initial plant composition or changing composition of the remaining detritus during decomposition. The rate of bacterial detritus degradation, calculated from measured production of surface-attached bacteria, was much lower than the actual rate of weight loss of plant material. This discrepancy may be attributable to the importance of nonbacterial organisms in the degradation and loss of plant material from litterbags or to the microbially mediated solubilization of particulate material prior to bacterial utilization, or both. PMID:2802603

Mechanical stabilization of proteolytically degradable polyethylene glycol dimethacrylate hydrogels through peptide interaction.

PubMed

Lim, Hyun Ju; Khan, Zara; Lu, Xi; Perera, T Hiran; Wilems, Thomas S; Ravivarapu, Krishna T; Smith Callahan, Laura A

2018-04-15

Balancing enhancement of neurite extension against loss of matrix support in synthetic hydrogels containing proteolytically degradable and bioactive signaling peptides to optimize tissue formation is difficult. Using a systematic approach, polyethylene glycol hydrogels containing concurrent continuous concentration gradients of the laminin derived bioactive signaling peptide, Ile-Lys-Val-Ala-Val (IKVAV), and collagen derived matrix metalloprotease degradable peptide, GPQGIWGQ, were fabricated and characterized. During proteolytic degradation of the concentration gradient hydrogels, the IKVAV and IWGQ cleavage fragment from GPQGIWGQ were found to interact and stabilize the bulk Young's Modulus of the hydrogel. Further testing of discrete samples containing GPQGIWGQ or its cleavage fragments, GPQG and IWGQ, indicates hydrophobic interactions between the peptides are not necessary for mechanical stabilization of the hydrogel, but changes in the concentration ratio between the peptides tethered in the hydrogel and salts and ions in the swelling solution can affect the stabilization. Encapsulation of human induced pluripotent stem cell derived neural stem cells did not reduce the mechanical properties of the hydrogel over a 14 day neural differentiation culture period, and IKVAV was found to maintain concentration dependent effects on neurite extension and mRNA gene expression of neural cytoskeletal markers, similar to previous studies. As a result, this work has significant implications for the analysis of biological studies in matrices, as the material and mechanical properties of the hydrogel may be unexpectedly temporally changing during culture due to interactions between peptide signaling elements, underscoring the need for greater matrix characterization during the degradation and cell culture. Greater emulation of the native extracellular matrix is necessary for tissue formation. To achieve this, matrices are becoming more complex, often including multiple bioactive signaling elements. However, peptide signaling in polyethylene glycol matrices and amino acids interactions between peptides can affect hydrogel material and mechanical properties, but are rarely studied. The current study identifies such an interaction between laminin derived peptide, IKVAV, and collagen derived matrix metalloprotease degradable peptide, GPQGIWGQ. Previous studies using these peptides did not identify their interactions' ability to mechanically stabilize the hydrogel during degradation. This work underscores the need for greater matrix characterization and consideration of bioactive signaling element effects temporally on the matrix's material and mechanical properties, as they can contribute to cellular response. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Sustainability of transport structures - some aspects of the nonlinear reliability assessment

NASA Astrophysics Data System (ADS)

Pukl, Radomír; Sajdlová, Tereza; Strauss, Alfred; Lehký, David; Novák, Drahomír

2017-09-01

Efficient techniques for both nonlinear numerical analysis of concrete structures and advanced stochastic simulation methods have been combined in order to offer an advanced tool for assessment of realistic behaviour, failure and safety assessment of transport structures. The utilized approach is based on randomization of the non-linear finite element analysis of the structural models. Degradation aspects such as carbonation of concrete can be accounted in order predict durability of the investigated structure and its sustainability. Results can serve as a rational basis for the performance and sustainability assessment based on advanced nonlinear computer analysis of the structures of transport infrastructure such as bridges or tunnels. In the stochastic simulation the input material parameters obtained from material tests including their randomness and uncertainty are represented as random variables or fields. Appropriate identification of material parameters is crucial for the virtual failure modelling of structures and structural elements. Inverse analysis using artificial neural networks and virtual stochastic simulations approach is applied to determine the fracture mechanical parameters of the structural material and its numerical model. Structural response, reliability and sustainability have been investigated on different types of transport structures made from various materials using the above mentioned methodology and tools.

Investigation of Thermally Induced Degradation in CH3NH3PbI3 Perovskite Solar Cells using In-situ Synchrotron Radiation Analysis.

PubMed

Kim, Nam-Koo; Min, Young Hwan; Noh, Seokhwan; Cho, Eunkyung; Jeong, Gitaeg; Joo, Minho; Ahn, Seh-Won; Lee, Jeong Soo; Kim, Seongtak; Ihm, Kyuwook; Ahn, Hyungju; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan

2017-07-05

In this study, we employ a combination of various in-situ surface analysis techniques to investigate the thermally induced degradation processes in MAPbI 3 perovskite solar cells (PeSCs) as a function of temperature under air-free conditions (no moisture and oxygen). Through a comprehensive approach that combines in-situ grazing-incidence wide-angle X-ray diffraction (GIWAXD) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) measurements, we confirm that the surface structure of MAPbI 3 perovskite film changes to an intermediate phase and decomposes to CH 3 I, NH 3 , and PbI 2 after both a short (20 min) exposure to heat stress at 100 °C and a long exposure (>1 hour) at 80 °C. Moreover, we observe clearly the changes in the orientation of CH 3 NH 3 + organic cations with respect to the substrate in the intermediate phase, which might be linked directly to the thermal degradation processes in MAPbI 3 perovskites. These results provide important progress towards improved understanding of the thermal degradation mechanisms in perovskite materials and will facilitate improvements in the design and fabrication of perovskite solar cells with better thermal stability.

O-atom degradation mechanisms of materials

NASA Technical Reports Server (NTRS)

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

1987-01-01

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.

Impact damage in composite plates

NASA Technical Reports Server (NTRS)

Shahid, I.; Lee, S.; Chang, F. K.; Shah, B. M.

1995-01-01

The objective of this research paper was to link two computer codes, PDCOMP (for Progressive Damage Analysis for Laminated Composites) and 3DIMPACT (for the prediction of the extent of delaminations in laminated composites resulting from point impact loads), in order to predict impact damage by taking into account local damage and material degradation and to estimate residual stiffness of composites after impact. The resulting graphs and analysis versus test results are presented along with the conclusive results of the codes' performances.

N/Fe-TiO2 doped nanoparticles loaded on bentonite for increased photocatalytic activity for the degradation of organic pollutants

NASA Astrophysics Data System (ADS)

Espenilla, Mel Bryan L.; Magyaya, Ryan Carl S.; Conato, Marlon T.

2018-05-01

Photocatalyst materials based on Philippine bentonite-titanium oxide composites and their ability to degrade organic pollutants is reported. Nanosized-titanium dioxide (TiO2) was synthesized by sol-gel method from titanium tetraisopropoxide. This was then incorporated in the Philippine bentonite via hydrothermal methods. In order to shift the absorbance of the TiO2 to the visible region doping was done using iron and nitrogen ions. The hydrodynamic radius of the synthesized TiO2 was analyzed using a zeta-sizer and was found to be around 70 nm. The photocatalytic efficiency of the TiO2/bentonite, N-TiO2/bentonite, Fe-TiO2/bentonite and N-Fe-TiO2/bentonite was evaluated using a photocatalytic reactor. It was found out that the N-Fe-TiO2/bentonite to be the most efficient with 22% degradation of the model pollutant after 80 minutes. FT-IR analysis was done to determine the bonding of the different components. Scanning electron microscopy and atomic force microscopy analysis was also performed to characterize the products.

A study of the effects of solid phase reactions on the thermal degradation and ballistic properties of solid propellants

NASA Technical Reports Server (NTRS)

Schmidt, W. G.

1974-01-01

The thermal stability of perchlorate composite propellants was studied at 135 and 170 C. The experimental efforts were concentrated on determining the importance of heterogeneous oxidizer-fuel reactions in the thermal degradation process. The experimental approach used to elucidate the mechanisms by which the oxidizer fuel composites thermally degrade was divided into two parts: (1) keeping the fuel constant and varying the nature of the oxidizers, and (2) holding the oxidizer constant and varying the fuel components. The fuel component primarily utilized in the first phase was polyethylene. Oxidizers included KClO4, KClO3, NH4ClO4 and NH4ClO4 doped with materials such as chlorate, phosphate and arsenate. In the second phase the oxidizer used was primarily NH4ClO4 while the fuels included saturated and unsaturated polybutadiene prepolymers and a series of bonding agents. Techniques employed in the current study include thermogravimetric measurements, differential thermal analysis, infrared, mass spectrometry, electron microscopy, and appropriate wet chemical analysis.

Thermochemical properties of cellulose acetate blends with acetosolv and sawdust lignin: A comparative study.

PubMed

Peredo, Karol; Escobar, Danilo; Vega-Lara, Johana; Berg, Alex; Pereira, Miguel

2016-02-01

Sawdust (SD) and cotton-lignin blends (CLB) were acetylated and the effect of lignin type and content on thermoplastic properties of the acetate produced was studied. The lignin in samples did not significantly affect the degree of acetylation. An increase in acetyl groups of 1-3% was observed in acetylated SD (ASD) unlike acetylated CLB (ACLB). Thermogravimetric analysis showed two thermal degradation zones; one at 190-200°C and the other at 330-370°C. The early degradation in ASD corresponds to galactoglucomannans while that in ACLB corresponds to the low-molecular-weight lignin. The second degradation is due to decomposition of cellulose acetate and high-molecular-weight lignin. DSC analysis showed homogeneous behaviour in ASD with only one glass transition temperature (Tg) at 170-180°C, unlike ACLB that showed two Tgs at 170-180°C. Sawdust acetylation, taking advantage of its residual lignin, showed higher reactivity and miscibility as compared to the same material produced by adding previously extracted lignin on cotton. Copyright © 2015 Elsevier B.V. All rights reserved.

Enhanced tolerance to stretch-induced performance degradation of stretchable MnO2-based supercapacitors.

PubMed

Huang, Yan; Huang, Yang; Meng, Wenjun; Zhu, Minshen; Xue, Hongtao; Lee, Chun-Sing; Zhi, Chunyi

2015-02-04

The performance of many stretchable electronics, such as energy storage devices and strain sensors, is highly limited by the structural breakdown arising from the stretch imposed. In this article, we focus on a detailed study on materials matching between functional materials and their conductive substrate, as well as enhancement of the tolerance to stretch-induced performance degradation of stretchable supercapacitors, which are essential for the design of a stretchable device. It is revealed that, being widely utilized as the electrode material of the stretchable supercapacitor, metal oxides such as MnO2 nanosheets have serious strain-induced performance degradation due to their rigid structure. In comparison, with conducting polymers like a polypyrrole (PPy) film as the electrochemically active material, the performance of stretchable supercapacitors can be well preserved under strain. Therefore, a smart design is to combine PPy with MnO2 nanosheets to achieve enhanced tolerance to strain-induced performance degradation of MnO2-based supercapacitors, which is realized by fabricating an electrode of PPy-penetrated MnO2 nanosheets. The composite electrodes exhibit a remarkable enhanced tolerance to strain-induced performance degradation with well-preserved performance over 93% under strain. The detailed morphology and electrochemical impedance variations are investigated for the mechanism analyses. Our work presents a systematic investigation on the selection and matching of electrode materials for stretchable supercapacitors to achieve high performance and great tolerance to strain, which may guide the selection of functional materials and their substrate materials for the next-generation of stretchable electronics.

A laboratory and field study of composite piles for bridge substructures

DOT National Transportation Integrated Search

2006-03-01

The most commonly used pile materials are steel, concrete, and wood. These materials can degrade, and the degradation rate can be relatively rapid in harsh marine environments. It has been estimated that the U.S. spends over $1 billion annually for r...

Effect of biodegradation on the consolidation properties of a dewatered municipal sewage sludge.

PubMed

O'Kelly, Brendan C

2008-01-01

The effect of biodegradation on the consolidation characteristics of an anaerobically digested, dewatered municipal sewage sludge was studied. Maintained-load oedometer consolidation tests that included measurement of the pore fluid pressure response were conducted on moderately degraded sludge material and saturated bulk samples that had been stored under static conditions and allowed to anaerobically biodegrade further (simulating what would happen in an actual sewage sludge monofill or lagoon condition). Strongly degraded sludge material was produced after a storage period of 13 years at ambient temperatures of 5-15 degrees C, with the total volatile solids reducing from initially 70% to 55%. The sludge materials were highly compressible, although impermeable for practical purposes. Primary consolidation generally occurred very slowly, which was attributed to the microstructure of the solid phase, the composition and viscosity of the pore fluid, ongoing biodegradation and the high organic contents. The coefficient of primary consolidation values decreased from initially about 0.35m2/yr to 0.003-0.03m2/yr with increasing effective stress (sigmav'=3-100kPa). Initially, the strongly degraded sludge material was slightly more permeable, although both the moderately and strongly degraded materials became impermeable for practical purposes (k=10(-9)-10(-12)m/s) below about 650% and 450% water contents, respectively. Secondary compression became more dominant with increasing effective stress with a mean secondary compression index (Calphae) value of 0.9 measured for both the moderately and strongly degraded materials.

Aerobic Degradation of N-Methyl-4-Nitroaniline (MNA) by Pseudomonas sp. Strain FK357 Isolated from Soil

PubMed Central

Khan, Fazlurrahman; Vyas, Bhawna; Pal, Deepika; Cameotra, Swaranjit Singh

2013-01-01

N-Methyl-4-nitroaniline (MNA) is used as an additive to lower the melting temperature of energetic materials in the synthesis of insensitive explosives. Although the biotransformation of MNA under anaerobic condition has been reported, its aerobic microbial degradation has not been documented yet. A soil microcosms study showed the efficient aerobic degradation of MNA by the inhabitant soil microorganisms. An aerobic bacterium, Pseudomonas sp. strain FK357, able to utilize MNA as the sole carbon, nitrogen, and energy source, was isolated from soil microcosms. HPLC and GC-MS analysis of the samples obtained from growth and resting cell studies showed the formation of 4-nitroaniline (4-NA), 4-aminophenol (4-AP), and 1, 2, 4-benzenetriol (BT) as major metabolic intermediates in the MNA degradation pathway. Enzymatic assay carried out on cell-free lysates of MNA grown cells confirmed N-demethylation reaction is the first step of MNA degradation with the formation of 4-NA and formaldehyde products. Flavin-dependent transformation of 4-NA to 4-AP in cell extracts demonstrated that the second step of MNA degradation is a monooxygenation. Furthermore, conversion of 4-AP to BT by MNA grown cells indicates the involvement of oxidative deamination (release of NH2 substituent) reaction in third step of MNA degradation. Subsequent degradation of BT occurs by the action of benzenetriol 1, 2-dioxygenase as reported for the degradation of 4-nitrophenol. This is the first report on aerobic degradation of MNA by a single bacterium along with elucidation of metabolic pathway. PMID:24116023

Aerobic degradation of N-methyl-4-nitroaniline (MNA) by Pseudomonas sp. strain FK357 isolated from soil.

PubMed

Khan, Fazlurrahman; Vyas, Bhawna; Pal, Deepika; Cameotra, Swaranjit Singh

2013-01-01

N-Methyl-4-nitroaniline (MNA) is used as an additive to lower the melting temperature of energetic materials in the synthesis of insensitive explosives. Although the biotransformation of MNA under anaerobic condition has been reported, its aerobic microbial degradation has not been documented yet. A soil microcosms study showed the efficient aerobic degradation of MNA by the inhabitant soil microorganisms. An aerobic bacterium, Pseudomonas sp. strain FK357, able to utilize MNA as the sole carbon, nitrogen, and energy source, was isolated from soil microcosms. HPLC and GC-MS analysis of the samples obtained from growth and resting cell studies showed the formation of 4-nitroaniline (4-NA), 4-aminophenol (4-AP), and 1, 2, 4-benzenetriol (BT) as major metabolic intermediates in the MNA degradation pathway. Enzymatic assay carried out on cell-free lysates of MNA grown cells confirmed N-demethylation reaction is the first step of MNA degradation with the formation of 4-NA and formaldehyde products. Flavin-dependent transformation of 4-NA to 4-AP in cell extracts demonstrated that the second step of MNA degradation is a monooxygenation. Furthermore, conversion of 4-AP to BT by MNA grown cells indicates the involvement of oxidative deamination (release of NH2 substituent) reaction in third step of MNA degradation. Subsequent degradation of BT occurs by the action of benzenetriol 1, 2-dioxygenase as reported for the degradation of 4-nitrophenol. This is the first report on aerobic degradation of MNA by a single bacterium along with elucidation of metabolic pathway.

Degradation of experimental composite materials and in vitro wear simulation

NASA Astrophysics Data System (ADS)

Givan, Daniel Allen

2001-12-01

The material, mechanical, and clinical aspects of surface degradation of resin composite dental restorative materials by in vitro wear simulation continues to be an area of active research. To investigate wear mechanisms, a series of experimental resin composites with variable and controlled filler particle shape and loading were studied by in vitro wear simulation. The current investigation utilized a simulation that isolated the wear environment, entrapped high and low modulus debris, and evaluated the process including machine and fluid flow dynamics. The degradation was significantly affected by filler particle shape and less by particle loading. The spherical particle composites demonstrated wear loss profiles suggesting an optimized filler loading may exist. This was also demonstrated by the trends in the mechanical properties. Very little difference in magnitude was noted for the wear of irregular particle composites as a function of particulate size; and as a group they were more wear resistant than spherical particle composites. This was the result of different mechanisms of wear that were correlated with the three-dimensional particle shape. The abrasive effects of the aggregate particles and the polymeric stabilization of the irregular shape versus the destabilization and "plucking" of the spherical particles resulted in an unprotected matrix that accounted for significantly greater wear of spherical composite. A model and analysis was developed to explain the events associated with the progressive material wear loss. The initial phase was explained by fatigue-assisted microcracking and loss of material segments in a zone of high stress immediately beneath a point of high stress contact. The early phase was characterized by the development of a small facet primarily by fatigue-assisted microcracking. Although the translation effects were minimal, some three-body and initial two-body wear events were also present. In the late phases, the abrasive effects of the debris aggregate predominated the wear process. The non-linear rate of wear loss was accelerated as the facet deepened. Physical effects, such as thermal fatigue, and chemical effects were less important but contributed to the degradation process. This study provides new insight into the role(s) of high modulus third body debris in the wear of dental composites.

Triggerable Degradation of Polyurethanes for Tissue Engineering Applications.

PubMed

Xu, Cancan; Huang, Yihui; Wu, Jinglei; Tang, Liping; Hong, Yi

2015-09-16

Tissue engineered and bioactive scaffolds with different degradation rates are required for the regeneration of diverse tissues/organs. To optimize tissue regeneration in different tissues, it is desirable that the degradation rate of scaffolds can be manipulated to comply with various stages of tissue regeneration. Unfortunately, the degradation of most degradable polymers relies solely on passive controlled degradation mechanisms. To overcome this challenge, we report a new family of reduction-sensitive biodegradable elastomeric polyurethanes containing various amounts of disulfide bonds (PU-SS), in which degradation can be initiated and accelerated with the supplement of a biological product: antioxidant-glutathione (GSH). The polyurethanes can be processed into films and electrospun fibrous scaffolds. Synthesized materials exhibited robust mechanical properties and high elasticity. Accelerated degradation of the materials was observed in the presence of GSH, and the rate of such degradation depends on the amount of disulfide present in the polymer backbone. The polymers and their degradation products exhibited no apparent cell toxicity while the electrospun scaffolds supported fibroblast growth in vitro. The in vivo subcutaneous implantation model showed that the polymers prompt minimal inflammatory responses, and as anticipated, the polymer with the higher disulfide bond amount had faster degradation in vivo. This new family of polyurethanes offers tremendous potential for directed scaffold degradation to promote maximal tissue regeneration.

LC3- and p62-based biochemical methods for the analysis of autophagy progression in mammalian cells.

PubMed

Jiang, Peidu; Mizushima, Noboru

2015-03-01

Autophagy is an intracellular degradation system that delivers cytoplasmic materials to the lysosome or vacuole. This system plays a crucial role in various physiological and pathological processes in living organisms ranging from yeast to mammals. Thus, an accurate and reliable measure of autophagic activity is necessary. However, autophagy involves dynamic and complicated processes that make it difficult to analyze. The term "autophagic flux" is used to denote overall autophagic degradation (i.e., delivery of autophagic cargo to the lysosome) rather than autophagosome formation. Immunoblot analysis of LC3 and p62/SQSTM1, among other proteins, has been widely used to monitor autophagic flux. Here, we describe basic protocols to measure the levels of endogenous LC3 and p62 by immunoblotting in cultured mammalian cells. Copyright © 2014 Elsevier Inc. All rights reserved.

Degradation Mechanisms of Poly(ester urethane) Elastomer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edgar, Alexander S.

This report describes literature regarding the degradation mechanisms associated with a poly(ester urethane) block copolymer, Estane® 5703 (Estane), used in conjunction with Nitroplasticizer (NP), and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, also known as high molecular weight explosive (HMX) to produce polymer bonded explosive PBX 9501. Two principal degradation mechanisms are reported: NO2 oxidative reaction with the urethane linkage resulting in crosslinking and chain scission events, and acid catalyzed hydrolysis of the ester linkage. This report details future work regarding this PBX support system, to be conducted in late 2017 and 2018 at Engineered Materials Group (MST-7), Materials Science and Technology Division, Los Alamos Nationalmore » Laboratory. This is the first of a series of three reports on the degradation processes and trends of the support materials of PBX 9501.« less

Solar concentrator materials development

NASA Technical Reports Server (NTRS)

Morel, D. E.; Ayers, S. R.; Gulino, D. A.; Tennyson, R. C.; Egger, R. A.

1986-01-01

Materials with potential applications in reflective and refractive solar dynamic concentrators are tested for resistance to atomic oxygen degradation. It is found that inorganic coatings such as MgF2, SiO(x), and ITO provide excellent protection for reflective surfaces while organic materials are much more susceptible to erosion and mass loss. Of the organic polymers tested, the silicones have the highest intrinsic resistance to atomic oxygen degradation.

Formation of free radicals during mechanical degradation of elastomers.

NASA Technical Reports Server (NTRS)

Devries, K. L.; Williams, M. L.; Roylance, D. K.

1971-01-01

Solithane 113 (an amorphous polyurethane elastomer) was prepared by curing equal proportions of castor oil and trifunctional isocyanate for 6 hr 45 min at 170 F. The sample material was mechanically degraded by grinding below and above its glass transition point at liquid nitrogen and room temperatures. The EPR spectra of ground samples were recorded and the number of free radicals were determined by a computer double-integration of the recorded spectra and by a comparison of the values with those of a standard material. Curves of EPR spectra suggest that different molecular mechanisms may be active in degradation of this material below and above its glass transition temperature.

Atomic oxygen interaction with spacecraft materials: Relationship between orbital and ground-based testing for materials certification

NASA Technical Reports Server (NTRS)

Cross, Jon B.; Koontz, Steven L.; Lan, Esther H.

1993-01-01

The effects of atomic oxygen on boron nitride (BN), silicon nitride (Si3N4), Intelsat 6 solar cell interconnects, organic polymers, and MoS2 and WS2 dry lubricant, were studied in Low Earth Orbit (LEO) flight experiments and in a ground based simulation facility. Both the inflight and ground based experiments employed in situ electrical resistance measurements to detect penetration of atomic oxygen through materials and Electron Spectroscopy for Chemical Analysis (ESCA) analysis to measure chemical composition changes. Results are given. The ground based results on the materials studied to date show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground based facility in terms of reproducing LEO flight results. In addition it was demonstrated that ground based simulation is capable of performing more detailed experiments than orbital exposures can presently perform. This allows the development of a fundamental understanding of the mechanisms involved in the LEO environment degradation of materials.

Non-targeted multi-component analytical surveillance of plastic food contact materials: Identification of substances not included in EU positive lists and their risk assessment.

PubMed

Skjevrak, Ingun; Brede, Cato; Steffensen, Inger-Lise; Mikalsen, Arne; Alexander, Jan; Fjeldal, Per; Herikstad, Hallgeir

2005-10-01

A procedure used by the Norwegian Food Safety Authority for surveillance of contaminants from plastic food contact materials (polyolefin drinking bottles, water boilers, polyamide cooking utensils and plastic multi-layer materials) is described. It is based on gas chromatographic-mass spectrometric (GC/MS) analysis of food simulants exposed to plastic materials. Most migrants were substances not-intentionally added to the plastic (degradation products, impurities) or originated from non-plastic components, such as printing inks, adhesives, not-listed additives, solvents and coatings. Hence, the majority of the identified migrants were regulated by the general statements in the EU Framework Regulation, which neither specify limits nor requirements regarding risk assessment, rather than by specific migration controls. Risk assessment has been carried out for selected non-authorized substances. The analysis and the management of these substances and materials with respect to safety represents a challenge to the food authorities.

TG-FTIR characterization of flame retardant polyurethane foams materials

NASA Astrophysics Data System (ADS)

Liu, W.; Tang, Y.; Li, F.; Ge, X. G.; Zhang, Z. J.

2016-07-01

Dimethyl methylphosphonate (DMMP) and trichloroethyl phosphtate (TCEP) have been used to enhance the flame retardancy of polyurethane foams materials (PUF). Flame retardancy and thermal degradation of PUF samples have been investigated by the LOI tests and thermal analysis. The results indicate that the excellent flame retardancy can be achieved due to the presence of the flame retardant system containing DMMP and TCEP. TG-FTIR reveals that the addition of DMMP/TCEP can not only improve the thermal stability of PUF samples but can also affect the gaseous phase at high temperature.

Dielectric Spectroscopy Analysis of Aged EVOH films with Application to Deterioration of Food Packaging Materials

NASA Astrophysics Data System (ADS)

Hoeller, Timothy

2007-06-01

Samples of EVOH films from compositions of 29 - 44 mol% ethylene content were exposed to thermal aging with and without light exposure. The results of Dielectric Spectroscopy on select samples showed Cole-Cole plots of skewed dielectric constant indicating multiple distributions of dipole relaxation times. The onset for decreases in dielectric response occurs earlier in samples exposed to elevated temperature under light exposure. Lower permittivity is exhibited in samples of higher ethylene content. Results from heat exposed samples are presented. Colorimetric analysis indicates only a slight film yellowing in one case. Raman spectroscopy on untreated films discerns changes in the C-C-O stretch associated with the alcohol. The effects of aging on microstructure may cause hindrance of molecular motion from moisture desorption. Slight material degradation occurs from film hardening presumably due to crosslinking. An electrical circuit model of the conduction processes associated with the EVOH films is presented. Dielectric analysis shows promise for monitoring material changes related to deterioration. We are also using these methods to understand Fluorescence Imaging which has been recently released for paper and plastic materials analysis. Future work may include refinement of these techniques for identification of changes in material properties correlated to packaging material barrier resistance.

Detection of local chemical states of lithium and their spatial mapping by scanning transmission electron microscopy, electron energy-loss spectroscopy and hyperspectral image analysis.

PubMed

Muto, Shunsuke; Tatsumi, Kazuyoshi

2017-02-08

Advancements in the field of renewable energy resources have led to a growing demand for the analysis of light elements at the nanometer scale. Detection of lithium is one of the key issues to be resolved for providing guiding principles for the synthesis of cathode active materials, and degradation analysis after repeated use of those materials. We have reviewed the different techniques currently used for the characterization of light elements such as high-resolution transmission electron microscopy, scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). In the present study, we have introduced a methodology to detect lithium in solid materials, particularly for cathode active materials used in lithium-ion battery. The chemical states of lithium were isolated and analyzed from the overlapping multiple spectral profiles, using a suite of STEM, EELS and hyperspectral image analysis. The method was successfully applied in the chemical state analyses of hetero-phases near the surface and grain boundary regions of the active material particles formed by chemical reactions between the electrolyte and the active materials. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Elasticity and breaking strength of synthetic suture materials incubated in various equine physiological and pathological solutions.

PubMed

Kearney, C M; Buckley, C T; Jenner, F; Moissonnier, P; Brama, P A J

2014-07-01

Selection of suture material in equine surgery is often based on costs or subjective factors, such as the surgeon's personal experience, rather than objective facts. The amount of objective data available on durability of suture materials with regard to specific equine physiological conditions is limited. To evaluate the effect of various equine physiological and pathological fluids on the rate of degradation of a number of commonly used suture materials. In vitro material testing. Suture materials were exposed in vitro to physiological fluid, followed by biomechanical analysis. Three absorbable suture materials, glycolide/lactide copolymer, polyglactin 910 and polydioxanone were incubated at 37°C for 7, 14 or 28 days in phosphate-buffered saline, equine serum, equine urine and equine peritoneal fluid from an animal with peritonitis. Five strands of each suture material type were tested to failure in a materials testing machine for each time point and each incubation medium. Yield strength, strain and Young's modulus were calculated, analysed and reported. For all suture types, the incubation time had a significant effect on yield strength, percentage elongation and Young's modulus in all culture media (P<0.0001). Suture type was also shown significantly to influence changes in each of yield strength, percentage elongation and Young's modulus in all culture media (P<0.0001). While the glycolide/lactide copolymer demonstrated the highest Day 0 yield strength, it showed the most rapid degradation in all culture media. For each of the 3 material characteristics tested, polydioxanone showed the least variation across the incubation period in each culture medium. The duration of incubation and the type of fluid have significant effects on the biomechanical properties of various suture materials. These findings are important for evidence-based selection of suture material in clinical cases. © 2013 EVJ Ltd.

Probabilistic material degradation model for aerospace materials subjected to high temperature, mechanical and thermal fatigue, and creep

NASA Technical Reports Server (NTRS)

Boyce, L.

1992-01-01

A probabilistic general material strength degradation model has been developed for structural components of aerospace propulsion systems subjected to diverse random effects. The model has been implemented in two FORTRAN programs, PROMISS (Probabilistic Material Strength Simulator) and PROMISC (Probabilistic Material Strength Calibrator). PROMISS calculates the random lifetime strength of an aerospace propulsion component due to as many as eighteen diverse random effects. Results are presented in the form of probability density functions and cumulative distribution functions of lifetime strength. PROMISC calibrates the model by calculating the values of empirical material constants.

Rapid, direct extraction of DNA from soils for PCR analysis using polyvinylpolypyrrolidone spin columns.

PubMed

Berthelet, M; Whyte, L G; Greer, C W

1996-04-15

Polyvinylpolypyrrolidone spin columns were used to rapidly purify crude soil DNA extracts from humic materials for polymerase chain reaction (PCR) analysis. The PCR detection limit for the tfdC gene, encoding chlorocatechol dioxygenase from the 2,4-dichlorophenoxyacetic acid degradation pathway, was 10(1)-10(2) cells/g soil in inoculated soils. The procedure could be applied to the amplification of biodegradative genes from indigenous microbial populations from a wide variety of soil types, and the entire analysis could be performed within 8 h.

In-situ multianalytical approach to analyze and compare the degradation pathways jeopardizing two murals exposed to different environments (Ariadne House, Pompeii, Italy).

PubMed

Veneranda, M; Prieto-Taboada, N; Fdez-Ortiz de Vallejuelo, S; Maguregui, M; Morillas, H; Marcaida, I; Castro, K; Garcia-Diego, F-J; Osanna, M; Madariaga, J M

2018-05-29

This study aimed at using portable analytical techniques to characterize original and decayed materials from two murals paintings of Ariadne House (archaeological site of Pompeii, Italy) and define the degradation pathways threatening their conservation. The first wall, located in an outdoor environment, has been directly exposed to degradation processes triggered by weathering and atmospheric pollution. The second wall, placed in a basement under the ground floor, has been constantly sheltered from sunlight exposure and drastic temperature fluctuations. The analytical data obtained in-situ by using Raman spectroscopy and Laser Induced Breakdown Spectroscopy (LIBS) correlates the degradation patterns affecting the two surfaces to their environmental context. The deterioration processes detected on the outdoor wall, which entailed the complete loss of the paint layer, were mostly related to leaching and thermal fluctuation phenomena. The mural painting from the basement instead, showed deep degradation issues due to soluble salt infiltration and biological colonization. The results obtained from this unique case of study highlight the indispensable role of in-situ spectroscopic analysis to understand and predict the degradation pathways jeopardizing the cultural heritage and provide to the Archaeological Park of Pompeii important inference to consider in future conservation projects. Copyright © 2018. Published by Elsevier B.V.

Winery biomass waste degradation by sequential sonication and mixed fungal enzyme treatments.

PubMed

Karpe, Avinash V; Dhamale, Vijay V; Morrison, Paul D; Beale, David J; Harding, Ian H; Palombo, Enzo A

2017-05-01

To increase the efficiency of winery-derived biomass biodegradation, grape pomace was ultrasonicated for 20min in the presence of 0.25M, 0.5Mand1.0MKOH and 1.0MNaOH. This was followed by treatment with a 1:1 (v/v) mix of crude enzyme preparation derived from Phanerochaete chrysosporium and Trametes versicolor for 18h and a further 18h treatment with a 60:14:4:2 percent ratio combination of enzymes derived from Aspergillus niger: Penicillium chrysogenum: Trichoderma harzianum: P. citrinum, repsectively. Process efficiency was evaluated by its comparison to biological only mixed fungal degradation over 16days. Ultrasonication treatment with 0.5MKOH followed by mixed enzyme treatment yielded the highest lignin degradation of about 13%. Cellulase, β-glucosidase, xylanase, laccase and lignin peroxidase activities of 77.9, 476, 5,390.5, 66.7 and 29,230.7U/mL, respectively, were observed during biomass degradation. Gas chromatography-mass spectrometry (GC-MS) analysis of the degraded material identified commercially important compounds such as gallic acid, lithocholic acid, glycolic acid and lactic acid which were generated in considerable quantities. Thus, the combination of sonication pre-treatment and enzymatic degradation has the potential to considerably improve the breakdown of agricultural biomass and produce commercially useful compounds in markedly less time (<40h) with respect to biological only degradation (16days). Copyright © 2016 Elsevier Inc. All rights reserved.

Quantitative Hyperspectral Reflectance Imaging

PubMed Central

Klein, Marvin E.; Aalderink, Bernard J.; Padoan, Roberto; de Bruin, Gerrit; Steemers, Ted A.G.

2008-01-01

Hyperspectral imaging is a non-destructive optical analysis technique that can for instance be used to obtain information from cultural heritage objects unavailable with conventional colour or multi-spectral photography. This technique can be used to distinguish and recognize materials, to enhance the visibility of faint or obscured features, to detect signs of degradation and study the effect of environmental conditions on the object. We describe the basic concept, working principles, construction and performance of a laboratory instrument specifically developed for the analysis of historical documents. The instrument measures calibrated spectral reflectance images at 70 wavelengths ranging from 365 to 1100 nm (near-ultraviolet, visible and near-infrared). By using a wavelength tunable narrow-bandwidth light-source, the light energy used to illuminate the measured object is minimal, so that any light-induced degradation can be excluded. Basic analysis of the hyperspectral data includes a qualitative comparison of the spectral images and the extraction of quantitative data such as mean spectral reflectance curves and statistical information from user-defined regions-of-interest. More sophisticated mathematical feature extraction and classification techniques can be used to map areas on the document, where different types of ink had been applied or where one ink shows various degrees of degradation. The developed quantitative hyperspectral imager is currently in use by the Nationaal Archief (National Archives of The Netherlands) to study degradation effects of artificial samples and original documents, exposed in their permanent exhibition area or stored in their deposit rooms. PMID:27873831

The effect of soil texture on the degradation of textiles associated with buried bodies.

PubMed

Lowe, A C; Beresford, D V; Carter, D O; Gaspari, F; O'Brien, R C; Stuart, B H; Forbes, S L

2013-09-10

There are many factors which affect the rate of decomposition in a grave site including; the depth of burial, climatic conditions, physical conditions of the soil (e.g. texture, pH, moisture), and method of burial (e.g. clothing, wrappings). Clothing is often studied as a factor that can slow the rate of soft tissue decomposition. In contrast, the effect of soft tissue decomposition on the rate of textile degradation is usually reported as anecdotal evidence rather than being studied under controlled conditions. The majority of studies in this area have focused on the degradation of textiles buried directly in soil. The purpose of this study was to investigate the effect of soil texture on the degradation and/or preservation of textile materials associated with buried bodies. The study involved the burial of clothed domestic pig carcasses and control clothing in contrasting soil textures (silty clay loam, fine sand and fine sandy loam) at three field sites in southern Ontario, Canada. Graves were exhumed after 2, 12 and 14 months burial to observe the degree of degradation for both natural and synthetic textiles. Recovered textile samples were chemically analyzed using infrared (IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) to investigate the lipid decomposition by-products retained in the textiles. The findings of this study demonstrate that natural textile in contact with a buried decomposing body will be preserved for longer periods of time when compared to the same textile buried directly in soil and not in contact with a body. The soil texture did not visually impact the degree of degradation or preservation. Furthermore, the natural-synthetic textile blend was resistant to degradation, regardless of soil texture, contact with the body or time since deposition. Chemical analysis of the textiles using GC-MS correctly identified a lipid degradation profile consistent with the degree of soft tissue decomposition. Such information may be important for estimating time since deposition in instances where only grave goods and associated materials are recovered from a burial site. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Microbial Degradation of Forensic Samples of Biological Origin: Potential Threat to Human DNA Typing.

PubMed

Dash, Hirak Ranjan; Das, Surajit

2018-02-01

Forensic biology is a sub-discipline of biological science with an amalgam of other branches of science used in the criminal justice system. Any nucleated cell/tissue harbouring DNA, either live or dead, can be used as forensic exhibits, a source of investigation through DNA typing. These biological materials of human origin are rich source of proteins, carbohydrates, lipids, trace elements as well as water and, thus, provide a virtuous milieu for the growth of microbes. The obstinate microbial growth augments the degradation process and is amplified with the passage of time and improper storage of the biological materials. Degradation of these biological materials carriages a huge challenge in the downstream processes of forensic DNA typing technique, such as short tandem repeats (STR) DNA typing. Microbial degradation yields improper or no PCR amplification, heterozygous peak imbalance, DNA contamination from non-human sources, degradation of DNA by microbial by-products, etc. Consequently, the most precise STR DNA typing technique is nullified and definite opinion can be hardly given with degraded forensic exhibits. Thus, suitable precautionary measures should be taken for proper storage and processing of the biological exhibits to minimize their decaying process by micro-organisms.

Influences of specific ions in groundwater on concrete degradation in subsurface engineered barrier system.

PubMed

Lin, Wen-Sheng; Liu, Chen-Wuing; Li, Ming-Hsu

2016-01-01

Many disposal concepts currently show that concrete is an effective confinement material used in engineered barrier systems (EBS) at a number of low-level radioactive waste (LLW) disposal sites. Cement-based materials have properties for the encapsulation, isolation, or retardation of a variety of hazardous contaminants. The reactive chemical transport model of HYDROGEOCHEM 5.0 was applied to simulate the effect of hydrogeochemical processes on concrete barrier degradation in an EBS which has been proposed to use in the LLW disposal site in Taiwan. The simulated results indicated that the main processes that are responsible for concrete degradation are the species induced from hydrogen ion, sulfate, and chloride. The EBS with the side ditch drainage system effectively discharges the infiltrated water and lowers the solute concentrations that may induce concrete degradation. The redox processes markedly influence the formations of the degradation materials. The reductive environment in the EBS reduces the formation of ettringite in concrete degradation processes. Moreover, the chemical conditions in the concrete barriers maintain an alkaline condition after 300 years in the proposed LLW repository. This study provides a detailed picture of the long-term evolution of the hydrogeochemical environment in the proposed LLW disposal site in Taiwan.

The DTIC Review: Volume 2, Number 4, Surviving Chemical and Biological Warfare

DTIC Science & Technology

1996-12-01

CHROMATOGRAPHIC ANALYSIS, NUCLEAR MAGNETIC RESONANCE, INFRARED SPECTROSCOPY , ARMY RESEARCH, DEGRADATION, VERIFICATION, MASS SPECTROSCOPY , LIQUID... mycotoxins . Such materials are not attractive as weapons of mass destruction however, as large amounts are required to produce lethal effects. In...VERIFICATION, ATOMIC ABSORPTION SPECTROSCOPY , ATOMIC ABSORPTION. AL The DTIC Review Defense Technical Information Center AD-A285 242 AD-A283 754 EDGEWOOO

Post-test analysis of lithium-ion battery materials at Argonne National Laboratory

NASA Astrophysics Data System (ADS)

Bareno, Javier; Dietz-Rago, Nancy; Bloom, Ira

2014-03-01

Electrochemical performance is often limited by surface and interfacial reactions at the electrodes. However, routine handling of samples can alter the very surfaces that are the object of study. Our approach combines standardized testing of batteries with sample harvesting under inert atmosphere conditions. Cells of different formats are disassembled inside an Argon glove box with controlled water and oxygen concentrations below 2 ppm. Cell components are characterized in situ, guaranteeing that observed changes in physicochemical state are due to electrochemical operation, rather than sample manipulation. We employ a complementary set of spectroscopic, microscopic, electrochemical and metallographic characterization to obtain a complete picture of cell degradation mechanisms. The resulting information about observed degradation mechanisms is provided to materials developers, both academic and industrial, to suggest new strategies and speed up the Research & Development cycle of Li-ion and related technologies. This talk will describe Argonne's post-test analysis laboratory, with an emphasis on capabilities and opportunities for collaboration. Cell disassembly, sample harvesting procedures and recent results will be discussed. This work was performed under the auspices of the U.S. Department of Energy, Office of Vehicle Technologies, Hybrid and Electric Systems, under Contract No. DE-AC02-06CH11357.

Thermophilic molds: Biology and applications.

PubMed

Singh, Bijender; Poças-Fonseca, Marcio J; Johri, B N; Satyanarayana, Tulasi

2016-11-01

Thermophilic molds thrive in a variety of natural habitats including soils, composts, wood chip piles, nesting materials of birds and other animals, municipal refuse and others, and ubiquitous in their distribution. These molds grow in simple media containing carbon and nitrogen sources and mineral salts. Polyamines are synthesized in these molds and the composition of lipids varies considerably, predominantly containing palmitic, oleic and linoleic acids with low levels of lauric, palmiotoleic and stearic acids. Thermophilic molds are capable of efficiently degrading organic materials by secreting thermostable enzymes, which are useful in the bioremediation of industrial wastes and effluents that are rich in oil, heavy metals, anti-nutritional factors such as phytic acid and polysaccharides. Thermophilic molds synthesize several antimicrobial substances and biotechnologically useful miscellaneous enzymes. The analysis of genomes of thermophilic molds reveals high G:C contents, shorter introns and intergenic regions with lesser repetitive sequences, and further confirms their ability to degrade agro-residues efficiently. Genetic engineering has aided in ameliorating the characteristics of the enzymes of thermophilic molds. This review is aimed at focusing on the biology of thermophilic molds with emphasis on recent developments in the analysis of genomes, genetic engineering and potential applications.

In vivo corrosion of four magnesium alloys and the associated bone response.

PubMed

Witte, F; Kaese, V; Haferkamp, H; Switzer, E; Meyer-Lindenberg, A; Wirth, C J; Windhagen, H

2005-06-01

Degrading metal alloys are a new class of implant materials suitable for bone surgery. The aim of this study was to investigate the degradation mechanism at the bone-implant interface of different degrading magnesium alloys in bone and to determine their effect on the surrounding bone. Sample rods of four different magnesium alloys and a degradable polymer as a control were implanted intramedullary into the femora of guinea pigs. After 6 and 18 weeks, uncalcified sections were generated for histomorphologic analysis. The bone-implant interface was characterized in uncalcified sections by scanning electron microscopy (SEM), element mapping and X-ray diffraction. Results showed that metallic implants made of magnesium alloys degrade in vivo depending on the composition of the alloying elements. While the corrosion layer of all magnesium alloys accumulated with biological calcium phosphates, the corrosion layer was in direct contact with the surrounding bone. The results further showed high mineral apposition rates and an increased bone mass around the magnesium rods, while no bone was induced in the surrounding soft tissue. From the results of this study, there is a strong rationale that in this research model, high magnesium ion concentration could lead to bone cell activation.

WEATHERABILITY OF ENHANCED DEGRADABLE PLASTICS

EPA Science Inventory

The main objective of this study was to assess the performance and the asociated variability of several selected enhanced degradable plastic materials under a variety of different exposure conditions. Other objectives were to identify the major products formed during degradation ...

Investigation of degradation mechanisms in composite matrices

NASA Technical Reports Server (NTRS)

Giori, C.; Yamauchi, T.

1982-01-01

Degradation mechanisms were investigated for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiations in vacuum up to 960 equivalent sun hours and 10 to the ninth power rads respectively. Based on GC and combined GC/MS analysis of volatile by-products evolved during irradiation, several free radical mechanisms of composite degradation were identified. The radiation resistance of different matrices was compared in terms of G values and quantum yields for gas formation. All the composite materials evaluated show high electron radiation stability and relatively low ultraviolet stability as indicated by low G values and high quantum for gas formation. Mechanical property measurements of irradiated samples did not reveal significant changes, with the possible exception of UV exposed polysulfone laminates. Hydrogen and methane were identified as the main by-products of irradiation, along with unexpectedly high levels of CO and CO2.

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

EPA Science Inventory

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

Biocide Runoff from Building Facades: Degradation Kinetics in Soil.

PubMed

Bollmann, Ulla E; Fernández-Calviño, David; Brandt, Kristian K; Storgaard, Morten S; Sanderson, Hans; Bester, Kai

2017-04-04

Biocides are common additives in building materials. In-can and film preservatives in polymer-resin render and paint, as well as wood preservatives are used to protect facade materials from microbial spoilage. Biocides leach from the facade material with driving rain, leading to highly polluted runoff water (up to several mg L -1 biocides) being infiltrated into the soil surrounding houses. In the present study the degradation rates in soil of 11 biocides used for the protection of building materials were determined in laboratory microcosms. The results show that some biocides are degraded rapidly in soil (e.g., isothiazolinones: T 1/2 < 10 days) while others displayed higher persistence (e.g., terbutryn, triazoles: T 1/2 ≫ 120 days). In addition, mass balances of terbutryn and octylisothiazolinone were determined, including nine (terbutryn) and seven (octylisothiazolinone) degradation products, respectively. The terbutryn mass balance could be closed over the entire study period of 120 days and showed that relative persistent metabolites were formed, while the mass balances for octylisothiazolinone could not be closed. Octylisothiazolinone degradation products did not accumulate over time suggesting that the missing fraction was mineralized. Microtox-tests revealed that degradation products were less toxic toward the bacterium Aliivibrio fischeri than their parent compounds. Rain is mobilizing these biocides from the facades and transports them to the surrounding soils; thus, rainfall events control how often new input to the soil occurs. Time intervals between rainfall events in Northern Europe are shorter than degradation half-lives even for many rapidly degraded biocides. Consequently, residues of some biocides are likely to be continuously present due to repeated input and most biocides can be considered as "pseudo-persistent"-contaminants in this context. This was verified by (sub)urban soil screening, where concentrations of up to 0.1 μg g -1 were detected for parent compounds as well as terbutryn degradation products in soils below biocide treated facades.

Solar UV Degradation Patterns in Photodegradable Ldpe

NASA Astrophysics Data System (ADS)

Andrady, A. L.

2016-02-01

"Degradable" polymers have been proposed as an alternative to traditional polymers as a means to potentially reduce the amount and impacts of plastic marine debris, yet the degradation of these materials in seawater is typically unknown. The light-induced degradation of a copolymer of ethylene - carbon monoxide {1%} was studied under accelerated laboratory exposure conditions. The copolymer, used as a substitute for LDPE in some applications where rapid photodegradation is desirable, loses mechanical integrity and embrittles rapidly under outdoor exposure. A laboratory weathering study of these laminates was carried out to compare the kinetics of degradation on sand to those in seawater at ambient temperature, based on the rate of change in tensile properties of the material. Virgin resin pellets of the copolymer were also exposed to laboratory weathering to detect the generation of microparticles at their surface during extensive degradation. Microparticle generation, detected by laser light scattering, as a function of the exposure duration will also be discussed.

Nanotransforming Assemblies

NASA Astrophysics Data System (ADS)

Discher, Dennis

2005-03-01

Degradable polymeric materials with hydrolysable backbones have attracted much attention because they break down to non-toxic metabolites. They are the key solutions to many environmental problems, and are particularly useful for various biomedical applications. Much work has been focused on degradable polymers and their co-polymers as bulk, or films and monolayers.^2 Only limited work has explored the degradable amphiphilic copolymer self-assemblies (spherical micelles, worm micelles and vesicles) in solutions, which are quite important for soft-material engineering. Mostly spherical micelles, and in rare cases, vesicles, have been reported made from copolymers with degradable polyester, typically polylactide or polycaprolactone, as the hydrophobic block, connected to biocompatible, stealthy poly (ethylene oxide) as hydrophilic block. Morphological change of such spherical micelles induced by degradation is subtle, and the degradation kinetics and mechanism in assemblies, which can be quite different from that in bulk or film, are not well understood. Here we will describe the phase transformations of worm micelles and vesicles as they degrade and also highlight how these polymeric self-assemblies interact with lipid membranes.

The role of microbial biofilms in deterioration of space station candidate materials.

PubMed

Gu, J D; Roman, M; Esselman, T; Mitchell, R

1998-01-01

Formation of microbial biofilms on surfaces of a wide range of materials being considered as candidates for use on the International Space Station was investigated. The materials included a fibre-reinforced polymeric composite, an adhesive sealant, a polyimide insulation foam, teflon cable insulation, titanium, and an aliphatic polyurethane coating. They were exposed to a natural mixed population of bacteria under controlled conditions of temperature and relative humidity (RH). Biofilms formed on the surfaces of the materials at a wide range of temperatures and RHs. The biofilm population was dominated by Pseudomonas aeruginosa, Ochrobactrum anthropi, Alcaligenes denitrificans, Xanthomonas maltophila, and Vibrio harveyi. The biocide, diiodomethyl-p-tolyl sulfone, impregnated in the polyurethane coating, was ineffective against microbial colonization and growth. Degradation of the polyurethane coatings was monitored with electrochemical impedance spectroscopy (EIS). The impedance spectra indicated that microbial degradation of the coating occurred in several stages. The initial decreases in impedance were due to the transport of water and solutes into the polymeric matrices. Further decreases were a result of polymer degradation by microorganisms. Our data showed that these candidate materials for space application are susceptible to biofilm formation and subsequent degradation. Our study suggests that candidate materials for use in space missions need to be carefully evaluated for their susceptibility to microbial biofilm formation and biodegradation.

Evaluation of SnO2 for sunlight photocatalytic decontamination of water.

PubMed

Aslam, M; Qamar, M Tariq; Ali, Shahid; Rehman, Ateeq Ur; Soomro, M T; Ahmed, Ikram; Ismail, I M I; Hameed, A

2018-07-01

The broad bandgap tin (IV) oxide (SnO 2 ) is the least investigated semiconductor material for photocatalytic water decontamination in sunlight exposure. A detailed study covering the synthesis, characterization and the evaluation of photocatalytic activity of SnO 2 , in the natural sunlight exposure, is presented. The structural characterization by XRD revealed the formation of phase pure tetragonal SnO 2 with the average crystallite size of ∼41.5 nm whereas minor Sn 2+ states in the material were identified by XPS analysis. As explored by diffuse reflectance (DR) and photoluminescence (PL) spectroscopy, the material exhibited a distinct absorption edge at ∼3.4 eV. The morphological and microstructure analysis of the synthesized SnO 2 was carried out by FESEM and HRTEM. The electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP) predicted the better charge transport and retention ability of the material under illumination whereas the Mott-Schottky extrapolation prophesied the n-type behavior with the flat-band potential of -0.60 V. The photocatalytic activity of SnO 2 was assessed in the exposure of complete spectrum natural sunlight for the removal of 2,4,6-trichlorophenol. The HPLC and TOC analysis monitored the progress of degradation and mineralization whereas the released chloride ions were evaluated by ion chromatography. The effect of the transition metal ions (Fe 3+ , Cu 2+ , Ni 2+, and Zn 2+ ) as electron capture agents and H 2 O 2 as ROS generator was explored during the degradation process. The utility of the material for the simultaneous removal of chlorophenols in the mixture was also investigated. The SnO 2 exhibited sustained activity in the repeated use. Based on experimental evidence congregated, the mechanism of the removal process and the efficacy of SnO 2 for sunlight photocatalytic decontamination of water was established. Copyright © 2018 Elsevier Ltd. All rights reserved.

A new iron calcium phosphate material to improve the osteoconductive properties of a biodegradable ceramic: a study in rabbit calvaria.

PubMed

Manchón, Angel; Hamdan Alkhraisat, Mohammad; Rueda-Rodriguez, Carmen; Prados-Frutos, Juan Carlos; Torres, Jesús; Lucas-Aparicio, Julia; Ewald, Andrea; Gbureck, Uwe; López-Cabarcos, Enrique

2015-10-20

β-tricalcium phosphate (β-TCP) is an osteoconductive and biodegradable material used in bone regeneration procedures, while iron has been suggested as a tool to improve the biological performance of calcium phosphate-based materials. However, the mechanisms of interaction between these materials and human cells are not fully understood. In order to clarify this relationship, we have studied the iron role in β-TCP ceramics. Iron-containing β-TCPs were prepared by replacing CaCO3 with C6H5FeO7 at different molar ratios. X-ray diffraction analysis indicated the occurrence of β-TCP as the sole phase in the pure β-TCP and iron-containing ceramics. The incorporation of iron ions in the β-TCP lattice decreased the specific surface area as the pore size was shifted toward meso- and/or macropores. Furthermore, the human osteoblastlike cell line MG-63 was cultured onto the ceramics to determine cell proliferation and viability, and it was observed that the iron-β-TCP ceramics have better cytocompatibility than pure β-TCP. Finally, in vivo assays were performed using rabbit calvaria as a bone model. The scaffolds were implanted for 8 and 12 weeks in the defects created in the skullcap with pure β-TCP as the control. The in vivo behavior, in terms of new bone formed, degradation, and residual graft material were investigated using sequential histological evaluations and histomorphometric analysis. The in vivo implantation of the ceramics showed enhanced bone tissue formation and scaffold degradation for iron-β-TCPs. Thus, iron appears to be a useful tool to enhance the osteoconductive properties of calcium phosphate ceramics.

Thermal degradation of the tensile strength of unidirectional boron/aluminum composites

NASA Technical Reports Server (NTRS)

Grimes, H. H.; Lad, R. A.; Maisel, J. E.

1977-01-01

The variation of ultimate tensile strength with thermal treatment of B-Al composite materials and of boron fibers chemically removed from these composites in an attempt to determine the mechanism of the resulting strength degradation was studied. Findings indicate that thermally cycling B-Al represents a more severe condition than equivalent time at temperature. Degradation of composite tensile strength from about 1.3 GN/m squared to as low as 0.34 GN/m squared was observed after 3,000 cycles to 420 C for 203 micrometers B-1100 Al composite. In general, the 1100 Al matrix composites degraded somewhat more than the 6061 matrix material studied. Measurement of fiber strengths confirmed a composite strength loss due to the degradation of fiber strength. Microscopy indicated a highly flawed fiber surface.

Solid-state 13C NMR studies of dissolved organic matter in pore waters from different depositional environments

USGS Publications Warehouse

Orem, W.H.; Hatcher, P.G.

1987-01-01

Dissolved organic matter (DOM) in pore waters from sediments of a number of different depositional environments was isolated by ultrafiltration using membranes with a nominal molecular weight cutoff of 500. This > 500 molecular weight DOM represents 70-98% of the total DOM in these pore waters. We determined the gross chemical structure of this material using both solid-state 13C nuclear magnetic resonance spectroscopy and elemental analysis. Our results show that the DOM in these pore waters appears to exist as two major types: one type dominated by carbohydrates and paraffinic structures and the second dominated by paraffinic and aromatic structures. We suggest that the dominance of one or the other structural type of DOM in the pore water depends on the relative oxidizing/reducing nature of the sediments as well as the source of the detrital organic matter. Under dominantly anaerobic conditions carbohydrates in the sediments are degraded by bacteria and accumulate in the pore water as DOM. However, little or no degradation of lignin occurs under these conditions. In contrast, sediments thought to be predominantly aerobic in character have DOM with diminished carbohydrate and enhanced aromatic character. The aromatic structures in the DOM from these sediments are thought to arise from the degradation of lignin. The large amounts of paraffinic structures in both types of DOM may be due to the degradation of unidentified paraffinic materials in algal or bacterial remains. ?? 1987.

Structural Characteristics and Corrosion Behavior of Bio-Degradable Zn-Li Alloys in Stent Application

NASA Astrophysics Data System (ADS)

Zhao, Shan

Zinc has begun to be studied as a bio-degradable material in recent years due to its excellent corrosion rate and optimal biocompatibility. Unfortunately, pure Zn's intrinsic ultimate tensile strength (UTS; below 120 MPa) is lower than the benchmark (about 300 MPa) for cardiovascular stent materials, raising concerns about sufficient strength to support the blood vessel. Thus, modifying pure Zn to improve its mechanical properties is an important research topic. In this dissertation project, a new Zn-Li alloy has been developed to retain the outstanding corrosion behavior from Zn while improving the mechanical characteristics and uniform biodegradation once it is implanted into the artery of Sprague-Dawley rats. The completed work includes: Manufactured Zn-Li alloy ingots and sheets via induction vacuum casting, melt spinning, hot rolling deformation, and wire electro discharge machining (wire EDM) technique; processed alloy samples using cross sectioning, mounting, etching and polishing technique; • Characterized alloy ingots, sheets and wires using hardness and tensile test, XRD, BEI imaging, SEM, ESEM, FTIR, ICP-OES and electrochemical test; then selected the optimum composition for in vitro and in vivo experiments; • Mimicked the degradation behavior of the Zn-Li alloy in vitro using simulated body fluid (SBF) and explored the relations between corrosion rate, corrosion products and surface morphology with changing compositions; • Explanted the Zn-Li alloy wire in abdominal aorta of rat over 12 months and studied its degradation mechanism, rate of bioabsorption, cytotoxicity and corrosion product migration from histological analysis.

Thermal degradation of polybrominated diphenyl ethers over as-prepared Fe3O4 micro/nano-material and hypothesized mechanism.

PubMed

Li, Qianqian; Yang, Fan; Su, Guijin; Huang, Linyan; Lu, Huijie; Zhao, Yuyang; Zheng, Minghui

2016-01-01

The thermal degradation of decabromodiphenyl ether (BDE-209) featuring fully substituted bromines was investigated over an as-prepared Fe3O4 micro/nano-material at 300 °C. Degradation followed pseudo-first-order kinetics with kobs = 0.15 min(-1) higher than that for decachlorobiphenyl (CB-209). Twenty-six newly produced polybrominated diphenyl ether (PBDE) congeners were identified using the available PBDE standards, while four PBDE congener products were predicted using third-order polynomial regression equation. Analysis of the products indicated that BDE-209 underwent stepwise hydrodebromination over as-prepared Fe3O4. Similar to the case for CB-209, two initial hydrodebromination steps are favored at the BDE-209 meta-positions, giving the major products BDE-207 and BDE-197. However, the variance about the preferred products began to emerge from the start of heptabromodiphenyl ethers (hepta-BDEs). The majorly produced hepta-BDE isomer with BDE-183 is unbrominated at one ortho-position. However, this is different from the reported degradation of CB-209, which always produced the products chlorinated at all four ortho-positions until the ortho-position had to be removed for the formation of trichlorobiphenyls and dichlorobiphenyl still majorly chlorinated at three or two ortho-positions. The early BDE-209 hydrodebromination steps appear to be strongly influenced by steric effects, whereas subsequent hydrodebromination steps, as more bromine atoms are removed, will be gradually governed more by thermodynamics.

Improved photocatalytic degradation rates of phenol achieved using novel porous ZrO2-doped TiO2 nanoparticulate powders.

PubMed

McManamon, Colm; Holmes, Justin D; Morris, Michael A

2011-10-15

This paper studies the photocatalytic degradation of phenol using zirconia-doped TiO(2) nanoparticles. ZrO(2) was chosen due to its promising results during preliminary studies. Particles smaller than 10nm were synthesised and doped with quantities of ZrO(2) ranging from 0.5 to 4% (molar metal content). Particles were calcined at different temperatures to alter the TiO(2) structure, from anatase to rutile, in order to provide an ideal ratio of the two phases. Powder X-ray diffraction (PXRD) analysis was used to examine the transformation between anatase and rutile. Degradation of phenol was carried out using a 40 W UV bulb at 365 nm and results were measured by UV-vis spectrometry. TEM images were obtained and show the particles exhibit a highly ordered structure. TiO(2) doped with 1% ZrO(2) (molar metal content) calcined at 700 °C proved to be the most efficient catalyst. This is due to an ideal anatase:rutlie ratio of 80:20, a large surface area and the existence of stable electron-hole pairs. ZrO(2) doping above the optimum loading acted as an electron-hole recombination centre for electron-hole pairs and reduced photocatalytic degradation. Synthesised photocatalysts compared favourably to the commercially available photocatalyst P25. The materials also demonstrated the ability to be recycled with similar results to those achieved on fresh material after 5 uses. Copyright © 2011 Elsevier B.V. All rights reserved.

Critical analysis of industrial electron accelerators

NASA Astrophysics Data System (ADS)

Korenev, S.

2004-09-01

The critical analysis of electron linacs for industrial applications (degradation of PTFE, curing of composites, modification of materials, sterlization and others) is considered in this report. Main physical requirements for industrial electron accelerators consist in the variations of beam parameters, such as kinetic energy and beam power. Questions for regulation of these beam parameters are considered. The level of absorbed dose in the irradiated product and throughput determines the main parameters of electron accelerator. The type of ideal electron linac for industrial applications is discussed.

Projections of limiting states for load-bearing structures of reflectors made of polymer composites

NASA Astrophysics Data System (ADS)

Doronin, S. V.

2017-12-01

This paper deals with limiting states typical for reflector antennas for terrestrial satellite communication systems. Reflectors made of polymer composites are studied. These limiting states are projected by results of the numerical analysis of the stress and strain states. The analysis is executed for reflectors under conditions of static and dynamic loading. It takes into account both overshoot of the state variables of allowed level and the processes of long-term structural material degradation.

Analysis of the eukaryotic community and metabolites found in clay wall material used in the construction of traditional Japanese buildings.

PubMed

Kitajima, Sakihito; Kamei, Kaeko; Nishitani, Maiko; Sato, Hiroyuki

2010-01-01

Clay wall (tsuchikabe in Japanese) material for Japanese traditional buildings is manufactured by fermenting a mixture of clay, sand, and rice straw. The aim of this study was to understand the fermentation process in order to gain insight into the ways waste biomass can be used to produce useful materials. In this study, in addition to Clostridium, we suggested that the family Nectriaceae and the Scutellinia sp. of fungi were important in degrading cell wall materials of rice straw, such as cellulose and/or lignin. The microorganisms in the clay wall material produced sulfur-containing inorganic compounds that may sulfurate minerals in clay particles, and polysaccharides that give viscosity to clay wall material, thus increasing workability for plastering, and possibly giving water-resistance to the dried clay wall.

Fungal degradation of fiber-reinforced composite materials

NASA Technical Reports Server (NTRS)

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

1997-01-01

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

Stability control of senna leaves and senna extracts.

PubMed

Goppel, Martin; Franz, Gerhard

2004-05-01

Powdered senna leaves and a commercial methanolic senna leaf extract were investigated for apparent degradation pathways of known constituents. Different defined storage conditions were chosen according to the guidelines of the international conference on harmonization. Analytical fingerprinting was carried out by HPLC with photodiode array detection. Differences in degradation pathways were observed between the powdered herbal drug material and the extract, depending on storage conditions and packaging materials. Within the crude plant material sennosides were shown to be degraded to sennidine monoglycosides, while rhein 8-O-glucoside was hydrolysed to rhein by enzymatic processes. Degradation of the anthranoid compounds was not due to the same pathways in the investigated commercial extracts. Only unspecific alterations of all compounds were observed. Forced decomposition of this herbal drug preparation under high temperature caused oxidative decomposition of the sennosides to rhein 8-O-glucoside. Furthermore flavonoid glycosides decomposition were observed with an apparent increase in the content of flavone aglyca.

Characterization of SiCSiC Composites in Support of Environmental Degradation Modeling

NASA Technical Reports Server (NTRS)

Kiser, Doug; Sullivan, Roy; Bhatt, Ram; Smith, Craig; Zima, John; McCue, Terry

2016-01-01

SiCSiC (silicon carbide fiber reinforced silicon carbide) composites are candidate materials for various turbine engine applications because of their high specific strength and good creep and oxidation resistance at elevated temperatures. This study was performed to characterize the microstructure of a melt infiltrated (MI) SiCSiC, and to examine environmental degradation mechanisms occurring in precracked MI SiCSiC CMC specimens under tensile stresses of 30 ksi or less at 815C in dry air or argon. In addition, the oxidation of the BN interface was characterized at815C, and crack opening displacement as a function of stress measurements were made. This material characterization is being performed to obtain data to support NASA GRC modeling of SiCSiC environmental degradation. The comparison of experimentally-observed phenomena with model predictions can lead to improved understanding of material degradation mechanisms.

Biodegradability of Plastics: Challenges and Misconceptions.

PubMed

Kubowicz, Stephan; Booth, Andy M

2017-11-07

Plastics are one of the most widely used materials and, in most cases, they are designed to have long life times. Thus, plastics contain a complex blend of stabilizers that prevent them from degrading too quickly. Unfortunately, many of the most advantageous properties of plastics such as their chemical, physical and biological inertness and durability present challenges when plastic is released into the environment. Common plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) are extremely persistent in the environment, where they undergo very slow fragmentation (projected to take centuries) into small particles through photo-, physical, and biological degradation processes 1 . The fragmentation of the material into increasingly smaller pieces is an unavoidable stage of the degradation process. Ultimately, plastic materials degrade to micron-sized particles (microplastics), which are persistent in the environment and present a potential source of harm for organisms.

Accelerated degradation and durability of concrete in cold climates.

DOT National Transportation Integrated Search

2011-08-01

Degradation of aggregate in concrete can be caused by erosion or fracture, and both cementitious materials and aggregate age over time. : The specification requirements for the degradation of aggregates have been established for hot mix asphalt and f...

Ureteral Stents. New Materials and Designs

NASA Astrophysics Data System (ADS)

Monga, Manoj

2008-09-01

Issues of stent migration and challenges of stent placement can be addressed adequately with current stent designs and materials, and an emphasis on precision in technique. Future changes in ureteral stents will need to maintain the current standard that has been set with existing devices in these regards. In contrast, new advances are sorely needed in encrustation and infection associated with ureteral stents. The main target for future development in ureteral stent materials lies in a biodegradable stent that degrades either on demand or degrades reliably within one-month with predictable degradation patterns that do not predispose to urinary obstruction, discomfort or need for secondary procedures. The main target for future development in ureteral stent design is improved patient comfort.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCloy, John S.; Montgomery, Robert O.; Ramuhalli, Pradeep

2013-02-01

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 ismore » discussed in the paper.« less

Performance degradation mechanisms and modes in terrestrial photovoltaic arrays and technology for their diagnosis

NASA Technical Reports Server (NTRS)

Noel, G. T.; Sliemers, F. A.; Derringer, G. C.; Wood, V. E.; Wilkes, K. E.; Gaines, G. B.; Carmichael, D. C.

1978-01-01

Accelerated life-prediction test methodologies have been developed for the validation of a 20-year service life for low-cost photovoltaic arrays. Array failure modes, relevant materials property changes, and primary degradation mechanisms are discussed as a prerequisite to identifying suitable measurement techniques and instruments. Measurements must provide sufficient confidence to permit selection among alternative designs and materials and to stimulate widespread deployment of such arrays. Furthermore, the diversity of candidate materials and designs, and the variety of potential environmental stress combinations, degradation mechanisms and failure modes require that combinations of measurement techniques be identified which are suitable for the characterization of various encapsulation system-cell structure-environment combinations.

Thermochemistry of CaO-MgO-Al2O3-SiO2 (CMAS) and Advanced Thermal and Environmental Barrier Coating Systems

NASA Technical Reports Server (NTRS)

Costa, Gustavo; Zhu, Dongming

2017-01-01

CaO-MgO-Al2O3-SiO2 (CMAS) oxides are constituents in a broad number of materials and minerals which have recently inferred to discussions in materials science, planetary science, geochemistry and cosmochemistry communities. In materials science, there is increasing interest in the degradation studies of thermal (TBC) and environmental (EBC) barrier coatings of gas turbines by molten CMAS. CMAS minerals usually are carried by the intake air into gas turbines, e.g. in aircraft engines, and their deposits react at high temperatures (1000C) with the coating materials. This causes degradation and accelerated failure of the static and rotating components of the turbine engines. We discuss some preliminary results of the reactions between CMAS and Rare-Earth (RE Y, Yb, Dy, Gd, Nd and Sm) oxide stabilized ZrO2 or HfO2 systems, and the stability of the resulting oxides and silicates. Plasma sprayed hollow tube samples ( 2.2 mm and 26 mm height) were half filled with CMAS powder, wrapped and sealed with platinum foil, and heat treated at 1310 C for 5h. Samples were characterized by differential scanning calorimetry, X-ray diffraction and cross section electron microscopy analysis.

Hot hydrogen testing of metallic turbo pump materials

NASA Technical Reports Server (NTRS)

Zee, Ralph; Chin, Bryan; Inamdar, Rohit

1993-01-01

The objectives of this investigation are to expose heat resistant alloys to hydrogen at elevated temperatures and to use various microstructural and analytical techniques to determine the chemical and rate process involved in degradation of these materials due to hydrogen environment. Inconel 718 and NASA-23 (wrought and cast) are candidate materials. The degradation of these materials in the presence of 1 to 5 atmospheric pressure of hydrogen from 450 C to 1100 C was examined. The hydrogen facility at Auburn University was used for this purpose. Control experiments were also conducted wherein the samples were exposed to vacuum so that a direct comparison of the results would separate the thermal contribution from the hydrogen effects. The samples were analyzed prior to and after exposure. A residual gas collection system was used to determine the gaseous species produced by any chemical reaction that may have occurred during the exposure. Analysis of this gas sample shows only the presence of H2 as expected. Analyses of the samples were conducted using optical microscopy, x-ray diffraction, scanning electron microscopy, and weight change. There appears to be no change in weight of the samples as a result of hydrogen exposure. In addition no visible change on the surface structure was detected. This indicates that the materials of interest do not have strong interaction with hot hydrogen. This is consistent with the microstructure results.

Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic.

PubMed

He, Fupo; Ren, Weiwei; Tian, Xiumei; Liu, Wei; Wu, Shanghua; Chen, Xiaoming

2016-07-01

In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones. Copyright © 2016 Elsevier B.V. All rights reserved.

Mechanical degradation temperature of waste storage materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1993-05-13

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-densitymore » 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.« less

An efficient method to predict and include Bragg curve degradation due to lung-equivalent materials in Monte Carlo codes by applying a density modulation

NASA Astrophysics Data System (ADS)

Baumann, Kilian-Simon; Witt, Matthias; Weber, Uli; Engenhart-Cabillic, Rita; Zink, Klemens

2017-05-01

Sub-millimetre-sized heterogeneities such as lung parenchyma cause Bragg peak degradation which can lead to an underdose of the tumor and an overdose of healthy tissue when not accounted for in treatment planning. Since commonly used treatment-planning CTs do not resolve the fine structure of lungs, this degradation can hardly be considered. We present a mathematical model capable of predicting and describing Bragg peak degradation due to a lung-equivalent geometry consisting of sub-millimetre voxels filled with either lung tissue or air. The material characteristic ‘modulation power’ is introduced to quantify the Bragg peak degradation. A strategy was developed to transfer the modulating effects of such fine structures to rougher structures such as 2 mm thick CT voxels, which is the resolution of typically used CTs. This is done by using the modulation power to derive a density distribution applicable to these voxels. By replacing the previously used sub-millimetre voxels by 2 mm thick voxels filled with lung tissue and modulating the lung tissue’s density in each voxel individually, we were able to reproduce the Bragg peak degradation. Hence a solution is found to include Bragg curve degradation due to lung-equivalent materials in Monte Carlo-based treatment-planning systems.

Fatigue strength degradation of metals in corrosive environments

NASA Astrophysics Data System (ADS)

Adasooriya, N. D.; Hemmingsen, T.; Pavlou, D.

2017-12-01

Structures exposed to aggressive environmental conditions are often subjected to time-dependent loss of coating and loss of material due to corrosion; this causes reduction in the cross-sectional properties of the members, increased surface roughness, surface irregularities and corrosion pits, and degradation of material strengths. These effects have been identified and simulated in different research studies. However, time and corrosive media dependent fatigue strength curves for materials have not been discussed in the design or assessment guidelines for structures. This paper attempts to review the corrosion degradation process and available approaches/models used to determine the fatigue strength of corroded materials and to interpolate corrosion deterioration data. High cycle fatigue and full range fatigue life formulae for fatigue strength of corroded materials are proposed. The above formulae depend on the endurance limit of corroded material, in addition to the stress-life fatigue curve parameters of the uncorroded material. The endurance limit of corroded material can either be determined by a limited number of tests in the very high-cycle fatigue region or predicted by an analytical approach. Comparison with experimentally measured corrosion fatigue behavior of several materials is provided and discussed.

PROGRAM ASTEC (ADVANCED SOLAR TURBO ELECTRIC CONCEPT). PART III CANDIDATE MATERIALS ORBITAL EVALUATION.

DTIC Science & Technology

by the solar-collector industry for use in the ASTEC Program, and to test the degrading effects of various segregated and combined elements of the...elements which may be causative to material surface degradation can be determined. The ASTEC scientific space experiment was developed and qualified, and

Degradable phosphate glass fiber reinforced polymer matrices: mechanical properties and cell response.

PubMed

Brauer, Delia S; Rüssel, Christian; Vogt, Sebastian; Weisser, Jürgen; Schnabelrauch, Matthias

2008-01-01

The development of biodegradable materials for internal fracture fixation is of great interest, as they would both eliminate the problem of stress shielding and obviate the need for a second operation to remove fixation devices. Preliminary investigations for the production of degradable fiber reinforced polymer composite materials are detailed. Composites were produced of phosphate invert glass fibers of the glass system P(2)O(5)-CaO-MgO-Na(2)O-TiO(2), which showed a low solubility in previous work. The fibers were embedded into a matrix of a degradable organic polymer network based on methacrylate-modified oligolactide. Fracture behavior, bending strength and elastic modulus were evaluated during 3-point bending tests and the fracture surface of the composites was investigated using a scanning electron microscope. Short-term biocompatibility was tested in an FDA/EtBr viability assay using MC3T3-E1 murine pre-osteoblast cells and showed a good cell compatibility of the composite materials. Results suggested that these composite materials are biocompatible and show mechanical properties which are of interest for the production of degradable bone fixation devices.

Results from testing and analysis of solar cells flown on LDEF

NASA Technical Reports Server (NTRS)

Dursch, Harry

1992-01-01

A brief discussion of the solar cell experiments flown on the Long Duration Exposure Facility (LDEF) is provided. The information presented is a collation of results published by the various experimenters. This process of collation and documentation is an ongoing Systems Special Investigation Group (SIG) effort. There are four LEO environments, operating individually and/or synergistically, that cause performance loss in solar cells: meteoroid and space debris, atomic oxygen, ultraviolet radiation, and charged particle radiation. In addition, the effects of contamination caused by outgassing of materials used on the specific spacecraft play a role in decreasing the light being transmitted through the coverglass and adhesive to the solar cell. From the results presented on the solar cells aboard LDEF, the most extensive degradation of the solar cells came from impacts and the resulting cratering. The extent of the damage to the solar cells was largely dependent upon the size and energy of the meteoroids or space debris. The other cause of degradation was reduced light reaching the solar cell. This was caused by contamination, UV degradation of coverglass adhesive, and/or atomic oxygen/UV degradation of antireflection coatings.

Improving quality and digestibility of cocoa pod with white rot fungi

NASA Astrophysics Data System (ADS)

Mustabi, J.; Wedawati; Armayanti, A. K.

2018-05-01

White rot fungi is a type of fungus that is able to degrade lignin in the feed material from waste, so it can be used to increase the added value of cocoa pod as alternative feed ingredients to meet the nutritional needs of cattle. The purpose of this study is to investigate the use of white rot fungi in improving the quality and digestibility cocoa pod as feed. The study consisted of two phases, namely fermentation using three isolates of white rot fungi (Coprinus comatus, Corilopsis polyzona and Lentinus torulosus) on pod husks and quality testing in vitro digestibility of fermented. Results of analysis of variance show that the treatment was highly significant on the content of lignin, cellulose and hemicellulose pod husks. Fermented cocoa husks with white rot fungi can degrade lignin content of 1.42% - 12.28% and highly significant improved on in vitro digestibility of dry matter and organic matter. The conclusion, isolates of white rot fungi most active in degrading lignin was Lentinus torulosus isolates and less ability to degrade cellulose and hemicellulose.

In vitro degradation kinetics of pure PLA and Mg/PLA composite: Effects of immersion temperature and compression stress.

PubMed

Li, Xuan; Chu, Chenglin; Wei, Yalin; Qi, Chenxi; Bai, Jing; Guo, Chao; Xue, Feng; Lin, Pinghua; Chu, Paul K

2017-01-15

The effects of the immersion temperature and compression stress on the in vitro degradation behavior of pure poly-lactic acid (pure-PLA) and PLA-based composite unidirectionally reinforced with micro-arc oxidized magnesium alloy wires (Mg/PLA or MAO-MAWs/PLA) are investigated. The degradation kinetics of pure-PLA and the PLA matrix in MAO-MAWs/PLA exhibit an Arrhenius-type behavior. For the composite, the synergic degradation of MAO-MAWs maintains a steady pH and mitigates the degradation of PLA matrix during immersion. However, the external compression stress decreases the activation energy (E a ) and pre-exponential factor (k 0 ) consequently increasing the degradation rate of PLA. Under a compression stress of 1MPa, E a and k 0 of pure PLA are 57.54kJ/mol and 9.74×10 7 day -1 , respectively, but 65.5kJ/mol and 9.81×10 8 day -1 for the PLA matrix in the composite. Accelerated tests are conducted in rising immersion temperature in order to shorten the experimental time. Our analysis indicates there are well-defined relationships between the bending strength of the specimens and the PLA molecular weight during immersion, which are independent of the degradation temperature and external compression stress. Finally, a numerical model is established to elucidate the relationship of bending strength, the PLA molecular weight, activation energy, immersion time and temperature. We systematically evaluate the effects of compression stress and temperature on the degradation properties of two materials: (pure-PLA) and MAO-MAWs/PLA (or Mg/PLA). The initial in vitro degradation kinetics of the unstressed or stressed pure-PLA and MAO-MAWs/PLA composite is confirmed to be Arrhenius-like. MAO-MAWs and external compression stress would influence the degradation activation energy (E a ) and pre-exponential factor (k 0 ) of PLA, and we noticed there is a linear relationship between E a and ln k 0 . Thereafter, we noticed that Mg 2+ , not H + , plays a significant role on the mitigation of the PLA degradation and external compression stress brings the molecular structure change of PLA. Finally, we proposed a model to predict the bending strength of the specimens versus immersion time at different immersion temperatures. This fundamental study could provide some scientific basis in our understanding for the evaluations and biomedical applications of these biodegradable materials. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F. J.; Noufi, R.

A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15oC and then a 15% relative humidity (RH) increment step, beginning from 40oC/40%RH (T/RH = 40/40) to 85oC/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. Themore » 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 μm to 0.50 μm 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.« less

3D Nanostructured materials: TiO2 nanoparticles incorporated gellan gum scaffold for photocatalyst and biomedical Applications

NASA Astrophysics Data System (ADS)

Hasmizam Razali, Mohd; Arifah Ismail, Nur; Zulkafli, Mohd Farhan Azly Mohd; Anuar Mat Amin, Khairul

2018-03-01

A unique three-dimensional (3D) nanostructured gellan gum (GG) is fabricated by incorporating TiO2 nanoparticles (GG + TiO2NPs) scaffold by freeze-drying. The fabricated GG + TiO2NPs were characterized using Fourier transform infrared (FTIR), x-ray diffraction (XRD), and scanning electron microscopy (SEM) to study their physiochemical properties. FTIR was used to investigate the intermolecular interactions in the scaffolds. The crystal structure was determined by bulk analysis using XRD and SEM for microstructure observation of scaffold surfaces. The performance of synthesized GG + TiO2NPs scaffold 3D nanostructured materials was evaluated as a photocatalyst for methyl orange (MO) degradation and for biomedical applications. The results showed that the scaffold possessed good photocatalytic activity for removal of methyl orange with 88.24% degradation after 3 h of UV irradiation. The scaffold also induces the cell growth, thus offering a good candidate for biomedical applications.

Corrosion assessment and enhanced biocompatibility analysis of biodegradable magnesium-based alloys

NASA Astrophysics Data System (ADS)

Pompa, Luis Enrique

Magnesium alloys have raised immense interest to many researchers because of its evolution as a new third generation material. Due to their biocompatibility, density, and mechanical properties, magnesium alloys are frequently reported as prospective biodegradable implant materials. Moreover, magnesium based alloys experience a natural phenomena to biodegrade in aqueous solutions due to its corrosive activity, which is excellent for orthopedic and cardiovascular applications. However, major concerns with such alloys are fast and non-uniform corrosion degradation. Controlling the degradation rate in the physiological environment determines the success of an implant. In this investigation, three grades of magnesium alloys: AZ31B, AZ91E and ZK60A were studied for their corrosion resistance and biocompatibility. Scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy and contact angle meter are used to study surface morphology, chemistry, roughness and wettability, respectively. Additionally, the cytotoxicity of the leached metal ions was evaluated by a tetrazolium based bio-assay, MTS.

Durability of symmetric-structured metal-supported solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Tucker, Michael C.

2017-11-01

Symmetric-structure metal-supported solid oxide fuel cells (MS-SOFC) with YSZ electrolyte are fabricated with porous YSZ backbone electrodes, stainless steel supports, and infiltrated catalysts on both anode and cathode side. Durability towards aggressive thermal and redox cycling, and long-term operation is assessed. Many sealing material candidates are screened for compatibility with the cell materials and operating conditions, and a commercial sealing glass, GM31107, is selected. LSM/SDCN cells are then subjected to 200 very fast thermal cycles and 20 complete redox cycles, with minimal impact to cell performance. LSM/SDCN and SDCN/SDCN cells are operated for more than 1200 h at 700 °C. The seal and cell hermeticity is maintained, and cell ohmic impedance does not change significantly during operation. Electrode polarization increases during operation, leading to significant degradation of the cell performance. In-operando EIS and post-mortem SEM/EDS analysis suggest that catalyst coarsening and cathode Cr deposition are the dominant degradation modes.

Thermal control system corrosion study

NASA Technical Reports Server (NTRS)

Yee, Robert; Folsom, Rolfe A.; Mucha, Phillip E.

1990-01-01

During the development of an expert system for autonomous control of the Space Station Thermal Control System (TCS), the thermal performance of the Brassboard TCS began to gradually degrade. This degradation was due to filter clogging by metallic residue. A study was initiated to determine the source of the residue and the basic cause of the corrosion. The investigation focused on the TCS design, materials compatibility, Ames operating and maintenance procedures, and chemical analysis of the residue and of the anhydrous ammonia used as the principal refrigerant. It was concluded that the corrosion mechanisms involved two processes: the reaction of water alone with large, untreated aluminum parts in a high pH environment and the presence of chlorides and chloride salts. These salts will attack the aluminum oxide layer and may enable galvanic corrosion between the aluminum and the more noble stainless steel and other metallic elements present. Recommendations are made for modifications to the system design, the materials used, and the operating and maintenance procedures, which should largely prevent the recurrence of these corrosion mechanisms.

An optimized transversely isotropic, hyper-poro-viscoelastic finite element model of the meniscus to evaluate mechanical degradation following traumatic loading

PubMed Central

Wheatley, Benjamin B.; Fischenich, Kristine M.; Button, Keith D.; Haut, Roger C.; Haut Donahue, Tammy L.

2015-01-01

Inverse finite element (FE) analysis is an effective method to predict material behavior, evaluate mechanical properties, and study differences in biological tissue function. The meniscus plays a key role in load distribution within the knee joint and meniscal degradation is commonly associated with the onset of osteoarthritis. In the current study, a novel transversely isotropic hyper-poro-viscoelastic constitutive formulation was incorporated in a FE model to evaluate changes in meniscal material properties following tibiofemoral joint impact. A non-linear optimization scheme was used to fit the model output to indentation relaxation experimental data. This study is the first to investigate rate of relaxation in healthy versus impacted menisci. Stiffness was found to be decreased (p=0.003), while the rate of tissue relaxation increased (p=0.010) at twelve weeks post impact. Total amount of relaxation, however, did not change in the impacted tissue (p=0.513). PMID:25776872

Coating effects on thermal properties of carbon carbon and carbon silicon carbide composites for space thermal protection systems

NASA Astrophysics Data System (ADS)

Albano, M.; Morles, R. B.; Cioeta, F.; Marchetti, M.

2014-06-01

Many are the materials for hot structures, but the most promising one are the carbon based composites nowadays. This is because they have good characteristics with a high stability at high temperatures, preserving their mechanical properties. Unfortunately, carbon reacts rapidly with oxygen and the composites are subjected to oxidation degradation. From this point of view CC has to be modified in order to improve its thermal and oxidative resistance. The most common solutions are the use of silicon carbide into the carbon composites matrix (SiC composites) to make the thermal properties increase and the use of coating on the surface in order to protect the composite from the space plasma effects. Here is presented an experimental study on coating effects on these composites. Thermal properties of coated and non coated materials have been studied and the thermal impact on the matrix and surface degradation is analyzed by a SEM analysis.

Designing degradable hydrogels for orthogonal control of cell microenvironments

PubMed Central

Kharkar, Prathamesh M.

2013-01-01

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

Damage tolerance in filament-wound graphite/epoxy pressure vessels

NASA Technical Reports Server (NTRS)

Simon, William E.; Ngueyen, Vinh D.; Chenna, Ravi K.

1995-01-01

Graphite/epoxy composites are extensively used in the aerospace and sporting goods industries due to their superior engineering properties compared to those of metals. However, graphite/epoxy is extremely susceptible to impact damage which can cause considerable and sometimes undetected reduction in strength. An inelastic impact model was developed to predict damage due to low-velocity impact. A transient dynamic finite element formulation was used in conjunction with the 3D Tsai-Wu failure criterion to determine and incorporate failure in the materials during impact. Material degradation can be adjusted from no degradation to partial degradation to full degradation. The developed software is based on an object-oriented implementation framework called Extensible Implementation Framework for Finite Elements (EIFFE).

Liquid chromatographic analysis of a formulated ester from a gas-turbine engine test

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Morales, W.

1983-01-01

Size exclusion chromatography (SEC) utilizing mu-Bondagel and mu-Styragel columns with a tetrahydrofuran mobile phase was used to determine the chemical degradation of lubricant samples from a gas-turbine engine test. A MIL-L-27502 candidate, ester-based lubricant was run in a J57-29 engine at a bulk oil temperature of 216 C. In general, the analyses indicated a progressive loss of primary ester, additive depletion, and formation of higher molecular weight material. An oil sample taken at the conclusion of the test showed a reversal of this trend because of large additions of new oil. The high-molecular-weight product from the degraded ester absorbed strongly in the ultraviolet region at 254 nanometers. This would indicate the presence of chromophoric groups. An analysis of a similar ester lubricant from a separate high-temperature bearing test yielded qualitatively similar results.

Effect of Boric Acid on Volatile Products of Thermooxidative Degradation of Epoxy Polymers

NASA Astrophysics Data System (ADS)

Nazarenko, O. B.; Bukhareva, P. B.; Melnikova, T. V.; Visakh, P. M.

2016-01-01

The polymeric materials are characterized by high flammability. The use of flame retardants in order to reduce the flammability of polymers can lead to the formation of toxic gaseous products under fire conditions. In this work we studied the effect of boric acid on the volatile products of thermooxidative degradation of epoxy polymers. The comparative investigations were carried out on the samples of the unfilled epoxy resin and epoxy resin filled with a boric acid at percentage 10 wt. %. The analysis of the volatile decomposition products and thermal stability of the samples under heating in an oxidizing medium was performed using a thermal mass-spectrometric analysis. It is found that the incorporation of boric acid into the polymer matrix increases the thermal stability of epoxy composites and leads to a reduction in the 2-2.7 times of toxic gaseous products

Quantification of the Barkhausen noise method for the evaluation of time-dependent degradation

NASA Astrophysics Data System (ADS)

Kim, Dong-Won; Kwon, Dongil

2003-02-01

The Barkhausen noise (BN) method has long been applied to measure the bulk magnetic properties of magnetic materials. Recently, this important nondestructive testing (NDT) method has been applied to evaluate microstructure, stress distribution analysis, fatigue, creep and fracture characteristics. Until now the BN method has been used only qualitatively in evaluating the variation of BN with variations in material properties. For this reason, few NDT methods have been applied in industrial plants and laboratories. The present investigation studied the coercive force and BN while varying the microstructure of ultrafine-grained steels and SA508 cl.3 steels. This variation was carried out according to the second heat-treatment condition with rolling of ultrafine-grained steels and the simulated time-dependent degradation of SA 508 cl.3 steels. An attempt was also made to quantify BN from the relationship between the velocity of magnetic domain walls and the retarding force, using the coercive force of the domain wall movement. The microstructure variation was analyzed according to time-dependent degradation. Fracture toughness was evaluated quantitatively by measuring the BN from two intermediary parameters; grain size and distribution of nonmagnetic particles. From these measurements, the variation of microstructure and fracture toughness can be directly evaluated by the BN method as an accurate in situ NDT method.

Polyacylurethanes as Novel Degradable Cell Carrier Materials for Tissue Engineering

PubMed Central

Jovanovic, Danijela; Roukes, Frans V.; Löber, Andrea; Engels, Gerwin E.; van Oeveren, Willem; van Seijen, Xavier J. Gallego; van Luyn, Marja J.A.; Harmsen, Martin C.; Schouten, Arend Jan

2011-01-01

Polycaprolactone (PCL) polyester and segmented aliphatic polyester urethanes based on PCL soft segment have been thoroughly investigated as biodegradable scaffolds for tissue engineering. Although proven beneficial as long term implants, these materials degrade very slowly and are therefore not suitable in applications in which scaffold support is needed for a shorter time. A recently developed class of polyacylurethanes (PAUs) is expected to fulfill such requirements. Our aim was to assess in vitro the degradation of PAUs and evaluate their suitability as temporary scaffold materials to support soft tissue repair. With both a mass loss of 2.5–3.0% and a decrease in molar mass of approx. 35% over a period of 80 days, PAUs were shown to degrade via both bulk and surface erosion mechanisms. Fourier Transform Infra Red (FTIR) spectroscopy was successfully applied to study the extent of PAUs microphase separation during in vitro degradation. The microphase separated morphology of PAU1000 (molar mass of the oligocaprolactone soft segment = 1000 g/mol) provided this polymer with mechano-physical characteristics that would render it a suitable material for constructs and devices. PAU1000 exhibited excellent haemocompatibility in vitro. In addition, PAU1000 supported both adhesion and proliferation of vascular endothelial cells and this could be further enhanced by pre-coating of PAU1000 with fibronectin (Fn). The contact angle of PAU1000 decreased both with in vitro degradation and by incubation in biological fluids. In endothelial cell culture medium the contact angle reached 60°, which is optimal for cell adhesion. Taken together, these results support the application of PAU1000 in the field of soft tissue repair as a temporary degradable scaffold. PMID:28824103

MaTrace: tracing the fate of materials over time and across products in open-loop recycling.

PubMed

Nakamura, Shinichiro; Kondo, Yasushi; Kagawa, Shigemi; Matsubae, Kazuyo; Nakajima, Kenichi; Nagasaka, Tetsuya

2014-07-01

Even for metals, open-loop recycling is more common than closed-loop recycling due, among other factors, to the degradation of quality in the end-of-life (EoL) phase. Open-loop recycling is subject to loss of functionality of original materials, dissipation in forms that are difficult to recover, and recovered metals might need dilution with primary metals to meet quality requirements. Sustainable management of metal resources calls for the minimization of these losses. Imperative to this is quantitative tracking of the fate of materials across different stages, products, and losses. A new input-output analysis (IO) based model of dynamic material flow analysis (MFA) is presented that can trace the fate of materials over time and across products in open-loop recycling taking explicit consideration of losses and the quality of scrap into account. Application to car steel recovered from EoL vehicles (ELV) showed that after 50 years around 80% of the steel is used in products, mostly buildings and civil engineering (infrastructure), with the rest mostly resided in unrecovered obsolete infrastructure and refinery losses. Sensitivity analysis was conducted to evaluate the effects of changes in product lifespan, and the quality of scrap.

Predicted reliability of aerospace electronics: Application of two advanced probabilistic concepts

NASA Astrophysics Data System (ADS)

Suhir, E.

Two advanced probabilistic design-for-reliability (PDfR) concepts are addressed and discussed in application to the prediction, quantification and assurance of the aerospace electronics reliability: 1) Boltzmann-Arrhenius-Zhurkov (BAZ) model, which is an extension of the currently widely used Arrhenius model and, in combination with the exponential law of reliability, enables one to obtain a simple, easy-to-use and physically meaningful formula for the evaluation of the probability of failure (PoF) of a material or a device after the given time in operation at the given temperature and under the given stress (not necessarily mechanical), and 2) Extreme Value Distribution (EVD) technique that can be used to assess the number of repetitive loadings that result in the material/device degradation and eventually lead to its failure by closing, in a step-wise fashion, the gap between the bearing capacity (stress-free activation energy) of the material or the device and the demand (loading). It is shown that the material degradation (aging, damage accumulation, flaw propagation, etc.) can be viewed, when BAZ model is considered, as a Markovian process, and that the BAZ model can be obtained as the ultimate steady-state solution to the well-known Fokker-Planck equation in the theory of Markovian processes. It is shown also that the BAZ model addresses the worst, but a reasonably conservative, situation. It is suggested therefore that the transient period preceding the condition addressed by the steady-state BAZ model need not be accounted for in engineering evaluations. However, when there is an interest in understanding the transient degradation process, the obtained solution to the Fokker-Planck equation can be used for this purpose. As to the EVD concept, it attributes the degradation process to the accumulation of damages caused by a train of repetitive high-level loadings, while loadings of levels that are considerably lower than their extreme values do not contribute- appreciably to the finite lifetime of a material or a device. In our probabilistic risk management (PRM) based analysis we treat the stress-free activation energy (capacity) as a normally distributed random variable, and choose, for the sake of simplicity, the (single-parametric) Rayleigh law as the basic distribution underlying the EVD. The general concepts addressed and discussed are illustrated by numerical examples. It is concluded that the application of the PDfR approach and particularly the above two advanced models should be considered as a natural, physically meaningful, informative, comprehensive, and insightful technique that reflects well the physics underlying the degradation processes in materials, devices and systems. It is the author's belief that they will be widely used in engineering practice, when high reliability is imperative, and the ability to quantify it is highly desirable.

Characterization of Thin Film Polymers Through Dynamic Mechanical Analysis and Permeation

NASA Technical Reports Server (NTRS)

Herring, Helen

2003-01-01

Thin polymer films are being considered, as candidate materials to augment the permeation resistance of cryogenic hydrogen fuel tanks such as would be required for future reusable launch vehicles. To evaluate performance of candidate films after environmental exposure, an experimental study was performed to measure the thermal/mechanical and permeation performance of six, commercial-grade materials. Dynamic storage modulus, as measured by Dynamic Mechanical Analysis, was found over a range of temperatures. Permeability, as measured by helium gas diffusion, was found at room temperature. Test data was correlated with respect to film type and pre-test exposure to moisture, elevated temperature, and cryogenic temperature. Results indicated that the six films were comparable in performance and their resistance to environmental degradation.

Comments on the interaction of materials with atomic oxygen

NASA Technical Reports Server (NTRS)

Torre, Larry P.; Pippin, H. Gary

1987-01-01

An explanation of the relative resistance of various materials to attack by atomic oxygen is presented. Data from both ground based and on-orbit experiments is interpreted. The results indicate the importance of bond strengths, size and structure of pendant groups, and fluorination to the resistance of certain polymers to atomic oxygen. A theory which provides a partial explanation of the degradation of materials in low Earth orbit due to surface recombination of oxygen atoms is also included. Finally, a section commenting on mechanisms of material degradation is provided.

Analysis of optical properties behaviour of CLEARCERAM, fused silica and CaF2 glasses exposed to simulated space conditions

NASA Astrophysics Data System (ADS)

Fernández-Rodríguez, M.; Alvarado, C. G.; Núñez, A.; Álvarez-Herrero, A.

2017-11-01

Optical instrumentation on-board satellites suffer degradation due to the hostile conditions of space environment. Space conditions produce instrumentation performances changes causing a decrease or a cancellation of their features. Particularly, space environment conditions have a significant influence on the optical properties of glasses which are part of space optical systems. Space environment characteristics which effects on the optical system have to be taken into account are: outgassing, volatile components, gas or water vapor which form part of the spacecraft materials, vacuum, microgravity, micrometeorites, space debris, thermal, mechanical and radiation environment and effects of the high atmosphere [1]. This work is focused on analyzing temperature variations and ultraviolet (UV) and gamma radiation effects on the optical properties of several glasses used on space applications. Thermal environment is composed of radiation from the Sun, the albedo and the Earth radiation and the radiation from the spacecraft to deep space. Flux and influence of temperature on satellite materials depend on factors as the period of year or the position of them on the space system. Taking into account that the transfer mechanisms of heat are limited by the conduction and the radiation, high gradients of temperature are obtained in system elements which can cause changes of their optical properties, birefringence… Also, these thermal cycles can introduce mechanical loads into material structure due to the expansion and the contraction of the material leading to mechanical performances degradation [2]. However, it is the radiation environment the main cause of damage on optical properties of materials used on space instrumentation. This environment consists of a wide range of energetic particles between keV and MeV which are trapped by the geomagnetic field or are flux of particles that cross the Earth environment from the external of the Solar System [3]. The damage produced by the radiation environment on the optical materials can be classified in two types: ionizing or non-ionizing. This damage may produce continual or accumulative (dose) alterations on the optical material performances, or may produce alterations which not remain along the time (transitory effects). The effects of the radiation on optical materials can be summarized on changes of optical transmission and refractive index, variation of density and superficial degradation [4-6]. Two non-invasive and non-destructive techniques such as Optical Spectrum Analyzer and Spectroscopic Ellipsometry [7] have been used to characterize optically the three kinds of studied glasses, CaF2, Fused Silica and Clearceram. The study of the temperature and radiation effects on the glasses optical properties showed that the gamma radiation is the principal responsible of glasses optical degradation. The optical properties of the Clearceram glass have been affected by the gamma irradiation due to the absorption bands induced by the radiation in the visible spectral range (color centers). Therefore, an analysis about the behavior of these color centers with the gamma radiation total dose and with the time after the irradiation has been carried out in the same way that it is performed in [8].

Progressive Damage Analyses of Skin/Stringer Debonding

NASA Technical Reports Server (NTRS)

Daville, Carlos G.; Camanho, Pedro P.; deMoura, Marcelo F.

2004-01-01

The debonding of skin/stringer constructions is analyzed using a step-by-step simulation of material degradation based on strain softening decohesion elements and a ply degradation procedure. Decohesion elements with mixed-mode capability are placed at the interface between the skin and the flange to simulate the initiation and propagation of the delamination. In addition, the initiation and accumulation of fiber failure and matrix damage is modeled using Hashin-type failure criteria and their corresponding material degradation schedules. The debonding predictions using simplified three-dimensional models correlate well with test results.

Gradual pore formation in natural origin scaffolds throughout subcutaneous implantation

PubMed Central

Martins, Ana M.; Kretlow, James D.; Costa-Pinto, Ana R.; Malafaya, Patrícia B.; Fernandes, Emanuel M.; Neves, Nuno M.; Alves, Catarina M.; Mikos, Antonios G.; Kasper, F. Kurtis; Reis, Rui L.

2012-01-01

The present study employed a rat subcutaneous implantation model to investigate gradual in situ pore formation in a self-regulating degradable chitosan-based material, which comprises lysozyme incorporated into biomimetic calcium phosphate (CaP) coatings at the surface in order to control the scaffold degradation and subsequent pore formation. Specifically, the in vivo degradation of the scaffolds, the in situ pore formation and the tissue response were investigated. Chitosan or chitosan/starch scaffolds were studied with and without a CaP coating in the presence or absence of lysozyme for a total of 6 experimental groups. Twenty-four scaffolds per group were implanted, and eight scaffolds were retrieved at each of three time points (3, 6 and 12 weeks). Harvested samples were analyzed for weight loss, micro-computed tomography, and histological analysis. All scaffolds showed pronounced weight loss and pore formation as a function of time. The highest weight loss was 29.8 ± 1.5%, obtained at week 12 for CaP chitosan/starch scaffolds with lysozyme incorporated. Moreover, all experimental groups showed a significant increase in porosity after 12 weeks. At all time points no adverse tissue reaction was observed, and as degradation increased, histological analysis showed cellular ingrowth throughout the implants. Using this innovative methodology, the ability to gradually generate pores in situ was clearly demonstrated in vivo. PMID:22213676

Tortoiseshell or Polymer? Spectroscopic Analysis to Redefine a Purported Tortoiseshell Box with Gold Decorations as a Plastic Box with Brass.

PubMed

Pereira, António; Caldeira, Ana Teresa; Maduro, Belmira; Vandenabeele, Peter; Candeias, António

2016-01-01

The study and preservation of museum collections requires complete knowledge and understanding of constituent materials that can be natural, synthetic, or semi-synthetic polymers. In former times, objects were incorporated in museum collections and classified solely by their appearance. New studies, prompted by severe degradation processes or conservation-restoration actions, help shed light on the materiality of objects that can contradict the original information or assumptions. The selected case study presented here is of a box dating from the beginning of the 20th century that belongs to the Portuguese National Ancient Art Museum. Museum curators classified it as a tortoiseshell box decorated with gold applications solely on the basis of visual inspection and the information provided by the donor. This box has visible signs of degradation with white veils, initially assumed to be the result of biological degradation of a proteinaceous matrix. This paper presents the methodological rationale behind this study and proposes a totally non-invasive methodology for the identification of polymeric materials in museum artifacts. The analysis of surface leachates using (1)H and (13)C nuclear magnetic resonance (NMR) complemented by in situ attenuated total reflection infrared spectroscopy (ATR FT-IR) allowed for full characterization of the object s substratum. The NMR technique unequivocally identified a great number of additives and ATR FT-IR provided information about the polymer structure and while also confirming the presence of additives. The pressure applied during ATR FT-IR spectroscopy did not cause any physical change in the structure of the material at the level of the surface (e.g., color, texture, brightness, etc.). In this study, variable pressure scanning electron microscopy (VP-SEM-EDS) was also used to obtain the elemental composition of the metallic decorations. Additionally, microbiologic and enzymatic assays were performed in order to identify the possible biofilm composition and understand the role of microorganisms in the biodeterioration process. Using these methodologies, the box was correctly identified as being made of cellulose acetate plastic with brass decorations and the white film was identified as being composed mainly of polymer exudates, namely sulphonamides and triphenyl phosphate. © The Author(s) 2015.

Analysis of the degradation of biodegradable mulches in a pepper crop under organic management

NASA Astrophysics Data System (ADS)

Moreno, Carmen; González, Sara; Villena, Jaime; Meco, Ramón; María Moreno, Marta

2016-04-01

The use of biodegradable mulch materials (biopolymers and papers) as an alternative to polyethylene is increasing nowadays, particularly in organic farming, due to environmental factors. It is necessary to test their functionality under field conditions by identifying, for example, the undesirable early degradation which commonly takes place in some of these biodegradable materials. In this sense, it is quite common and easy to apply the use of visual scales to estimate the level of deterioration of mulches, which can be subjective. Therefore, the objectives of this work are: i) To study the degradation of different mulch materials under field conditions by measuring the soil surface they covered. ii) To compare these soil surface values with the overall assessment of their functionality obtained by visual scales. The trial was performed in an organically grown pepper crop in Ciudad Real (Central Spain) in the 2014 spring-summer season. The mulch materials used were: 1) black polyethylene (15 μm); black biopolymers (15 μm): 2) Mater-Bi® (corn starch based), 3) Sphere 4® (potato starch based), 4) Sphere 6® (potato starch based), 5) Bioflex® (polylactic acid based), 6) Ecovio® (polylactic acid based), 7) Mimgreen® (black paper, 85 g/m2). A randomized complete block design with four replications was adopted. The crop was drip irrigated following the water demand of each treatment. To assess the evolution of the soil surface covered by the mulches, a total of 560 photographs of the superficial (exposed) part and 196 photographs of the buried part of the materials (1415x2831 pixels, 28 pixels/cm) were analyzed by using Adobe Photoshop CS at 15, 30, 45, 60, 90,120, 145 days after transplanting. Additionally, four experts evaluated the functionality of these materials based on the photographs according to a scale from 1 (completely deteriorated material) to 9 (intact material). The results show: i) The superficial part corresponding to the polyethylene and the Mimgreen® paper remained practically intact or with little damaged until the end of the crop season, while biopolymers suffered further deterioration, especially Bioflex®. ii) The buried part of the Mimgreen® paper underwent a rapid and complete degradation, while biopolymers presented a variable behavior, from practically intact, similar to polyethylene (Ecovio®), to an important decrease of the soil covered (Mater-Bi® and Sphere 4®). iii) A visual understatement of the functionality of the material (subjective scales) was observed when compared with the numerical value of the percentage of the soil covered by the mulch. Acknowledgements: the research was funded by Project RTA2011-00104-C04-03 from the INIA (Spanish Ministry of Economy and Competitiveness).

Dynamic mechanical properties of hydroxyapatite-reinforced and porous starch-based degradable biomaterials.

PubMed

Mano, J F; Vaz, C M; Mendes, S C; Reis, R L; Cunha, A M

1999-12-01

It has been shown that blends of starch with a poly(ethylene-vinyl-alcohol) copolymer, EVOH, designated as SEVA-C, present an interesting combination of mechanical, degradation and biocompatible properties, specially when filled with hydroxyapatite (HA). Consequently, they may find a range of applications in the biomaterials field. This work evaluated the influence of HA fillers and of blowing agents (used to produce porous architectures) over the viscoelastic properties of SEVA-C polymers, as seen by dynamic mechanical analysis (DMA), in order to speculate on their performances when withstanding cyclic loading in the body. The composite materials presented a promising performance under dynamic mechanical solicitation conditions. Two relaxations were found being attributed to the starch and EVOH phases. The EVOH relaxation process may be very useful in vivo improving the implants performance under cyclic loading. DMA results also showed that it is possible to produce SEVA-C compact surface/porous core architectures with a mechanical performance similar to that of SEVA-C dense materials. This may allow for the use of these materials as bone replacements or scaffolds that must withstand loads when implanted. Copyright 1999 Kluwer Academic Publishers

Analysis of the Osteogenic Effects of Biomaterials Using Numerical Simulation

PubMed Central

Zhang, Jie; Zhang, Wen; Yang, Hui-Lin

2017-01-01

We describe the development of an optimization algorithm for determining the effects of different properties of implanted biomaterials on bone growth, based on the finite element method and bone self-optimization theory. The rate of osteogenesis and the bone density distribution of the implanted biomaterials were quantitatively analyzed. Using the proposed algorithm, a femur with implanted biodegradable biomaterials was simulated, and the osteogenic effects of different materials were measured. Simulation experiments mainly considered variations in the elastic modulus (20–3000 MPa) and degradation period (10, 20, and 30 days) for the implanted biodegradable biomaterials. Based on our algorithm, the osteogenic effects of the materials were optimal when the elastic modulus was 1000 MPa and the degradation period was 20 days. The simulation results for the metaphyseal bone of the left femur were compared with micro-CT images from rats with defective femurs, which demonstrated the effectiveness of the algorithm. The proposed method was effective for optimization of the bone structure and is expected to have applications in matching appropriate bones and biomaterials. These results provide important insights into the development of implanted biomaterials for both clinical medicine and materials science. PMID:28116309

Analysis of the Osteogenic Effects of Biomaterials Using Numerical Simulation.

PubMed

Wang, Lan; Zhang, Jie; Zhang, Wen; Yang, Hui-Lin; Luo, Zong-Ping

2017-01-01

We describe the development of an optimization algorithm for determining the effects of different properties of implanted biomaterials on bone growth, based on the finite element method and bone self-optimization theory. The rate of osteogenesis and the bone density distribution of the implanted biomaterials were quantitatively analyzed. Using the proposed algorithm, a femur with implanted biodegradable biomaterials was simulated, and the osteogenic effects of different materials were measured. Simulation experiments mainly considered variations in the elastic modulus (20-3000 MPa) and degradation period (10, 20, and 30 days) for the implanted biodegradable biomaterials. Based on our algorithm, the osteogenic effects of the materials were optimal when the elastic modulus was 1000 MPa and the degradation period was 20 days. The simulation results for the metaphyseal bone of the left femur were compared with micro-CT images from rats with defective femurs, which demonstrated the effectiveness of the algorithm. The proposed method was effective for optimization of the bone structure and is expected to have applications in matching appropriate bones and biomaterials. These results provide important insights into the development of implanted biomaterials for both clinical medicine and materials science.

Conversion of borate-based glass scaffold to hydroxyapatite in a dilute phosphate solution.

PubMed

Liu, Xin; Pan, Haobo; Fu, Hailuo; Fu, Qiang; Rahaman, Mohamed N; Huang, Wenhai

2010-02-01

Porous scaffolds of a borate-based glass (composition in mol%: 6Na2O, 8K2O, 8MgO, 22CaO, 36B2O3, 18SiO2, 2P2O5), with interconnected porosity of approximately 70% and pores of size 200-500 microm, were prepared by a polymer foam replication technique. The degradation of the scaffolds and conversion to a hydroxyapatite-type material in a 0.02 M K2HPO4 solution (starting pH = 7.0) at 37 degrees C were studied by measuring the weight loss of the scaffolds, as well as the pH and the boron concentration of the solution. X-ray diffraction, scanning electronic microscopy and energy dispersive x-ray analysis showed that a hydroxyapatite-type material was formed on the glass surface within 7 days of immersion in the phosphate solution. Cellular response to the scaffolds was assessed using murine MLO-A5 cells, an osteogenic cell line. Scanning electron microscopy showed that the scaffolds supported cell attachment and proliferation during the 6 day incubation. The results indicate that this borate-based glass could provide a promising degradable scaffold material for bone tissue engineering applications.

Studies on the injection molding of polyvinyl chloride: Analysis of viscous heating and degradation in simple geometries

NASA Astrophysics Data System (ADS)

Garcia, Jose Luis

2000-10-01

In injection molding processes, computer aided engineering (CAE) allows processors to evaluate different process parameters in order to achieve complete filling of a cavity and, in some cases, it predicts shrinkage and warpage. However, because commercial computational packages are used to design complex geometries, detail in the thickness direction is limited. Approximations in the thickness direction lead to the solution of a 2½-D problem instead of a 3-D problem. These simplifications drastically reduce computational times and memory requirements. However, these approximations hinder the ability to predict thermal and/or mechanical degradation. The goal of this study was to determine the degree of degradation during PVC injection molding and to compare the results with a computational model. Instead of analyzing degradation in complex geometries, the computational analysis and injection molding trials were performed on typical sections found in complex geometries, such as flow in a tube, flow in a rectangular channel, and radial flow. This simplification reduces the flow problem to a 1-D problem and allows one to develop a computational model with a higher level of detail in the thickness direction, essential for the determination of degradation. Two different geometries were examined in this study: a spiral mold, in order to approximate the rectangular channel, and a center gated plate for the radial flow. Injection speed, melt temperature, and shot size were varied. Parts varying in degree of degradation, from no to severe degradation, were produced to determine possible transition points. Furthermore, two different PVC materials were used, low and high viscosity, M3800 and M4200, respectively (The Geon Company, Avon Lake, OH), to correlate the degree of degradation with the viscous heating observed during injection. It was found that a good agreement between experimental and computational results was obtained only if the reaction was assumed to be more thermally sensitive than found in literature. The results from this study show that, during injection, the activation energy for degradation was 65 kcal/mol, compared to 17--30 kcal/mol found in literature for quiescent systems.

Molecular imprinted hydrogel polymer (MIHP) as microbial immobilization media in artificial produced water treatment

NASA Astrophysics Data System (ADS)

Kardena, E.; Ridhati, S. L.; Helmy, Q.

2018-01-01

Produced water generated during oil and gas exploration and drilling, consists of many chemicals which used in drilling process. The production of produced water is over three fold of the oil production. The water-cut has increased over time and continues to do so because the fraction of oil in the reservoir decreases and it is more difficult to get the oil out from an old oil-field. It therefore requires more sea water to be injected in order to force the oil out; hence more produced water is generated. Produced water can pollute the environment if it is not treated properly. In this research, produced water will be treated biologically using bacterial consortium which is isolated from petroleum processing facility with Molecular Imprinted Hydrogel Polymer (MIHP) for microbial immobilization media. Microbial growth rate is determined by measuring the MLVSS and hydrogel mass, also by SEM-EDS analysis. SEM-EDS analysis is an analysis to evidence the presence of microbe trapped in hydrogel, and also to determine the types and weight of the molecules of hydrogel. From this research, suspended microbial growth rate was found at 0.1532/days and attached microbial growth rate was 0.3322/days. Furthermore, based on SEM analysis, microbe is entrapped inside the hydrogel. Effectiveness of microbial degradation activity was determined by measuring organic materials as COD. Based on COD measurement, degradation rate of organic materials in wastewater is 0.3089/days, with maximum COD removal efficiency of 76.67%.

Advanced composites structural concepts and materials technologies for primary aircraft structures: Structural response and failure analysis

NASA Technical Reports Server (NTRS)

Dorris, William J.; Hairr, John W.; Huang, Jui-Tien; Ingram, J. Edward; Shah, Bharat M.

1992-01-01

Non-linear analysis methods were adapted and incorporated in a finite element based DIAL code. These methods are necessary to evaluate the global response of a stiffened structure under combined in-plane and out-of-plane loading. These methods include the Arc Length method and target point analysis procedure. A new interface material model was implemented that can model elastic-plastic behavior of the bond adhesive. Direct application of this method is in skin/stiffener interface failure assessment. Addition of the AML (angle minus longitudinal or load) failure procedure and Hasin's failure criteria provides added capability in the failure predictions. Interactive Stiffened Panel Analysis modules were developed as interactive pre-and post-processors. Each module provides the means of performing self-initiated finite elements based analysis of primary structures such as a flat or curved stiffened panel; a corrugated flat sandwich panel; and a curved geodesic fuselage panel. This module brings finite element analysis into the design of composite structures without the requirement for the user to know much about the techniques and procedures needed to actually perform a finite element analysis from scratch. An interactive finite element code was developed to predict bolted joint strength considering material and geometrical non-linearity. The developed method conducts an ultimate strength failure analysis using a set of material degradation models.

Facile sonochemical synthesis of Ag modified Bi{sub 4}Ti{sub 3}O{sub 12} nanoparticles with enhanced photocatalytic activity under visible light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, Dimple P., E-mail: dimpled@barc.gov.in; Tyagi, A.K.

2016-02-15

Highlights: • Ag doped/dispersed Bi{sub 4}Ti{sub 3}O{sub 12} nanoparticles synthesized sonochemically. • Undoped Bi{sub 4}Ti{sub 3}O{sub 12} exhibited 100% RhB degradation in 45 min under UV light. • Under visible light 100% RhB degradation occured with Bi{sub 4}Ti{sub 3}O{sub 12} in 150 min. • Improved photodegradation of RhB by Ag doped Bi{sub 4}Ti{sub 3}O{sub 12} in visible light. • The Bi{sub 4}Ti{sub 3}O{sub 12}:Ag(5%) sample photodegrades RhB from wastewater under sunlight. - Abstract: Unmodified and Ag modified Bi{sub 4}Ti{sub 3}O{sub 12}:Ag(x%) (x = 2 and 5) nanoparticles have been synthesized sonochemically and characterized using X-ray diffraction, X-ray photoelectron spectroscopy (XPS),more » Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy (SEM), energy dispersion X-ray spectrum (EDS) analysis, transmission electron microscopy (TEM) and UV–vis diffuse reflectance spectroscopy. In the presence of unmodified Bi{sub 4}Ti{sub 3}O{sub 12} nanoparticles, complete photocatalytic degradation of Rhodamine B (RhB) was observed under UV light within 45 min. However, the response of this material for photodegradation of RhB under visible light was poor and could be greatly enhanced with Ag modification. A possible mechanism for this observation has been discussed in detail. The reusability of the material has also been tested and it has been found to have favorable recycling capability. Moreover, the Ag- modified Bi{sub 4}Ti{sub 3}O{sub 12} has been tested for RhB degradation from a wastewater sample under sunlight and promising results have been obtained.« less

Rescue of compromised lysosomes enhances degradation of photoreceptor outer segments and reduces lipofuscin-like autofluorescence in retinal pigmented epithelial cells.

PubMed

Guha, Sonia; Liu, Ji; Baltazar, Gabe; Laties, Alan M; Mitchell, Claire H

2014-01-01

Healthful cell maintenance requires the efficient degradative processing and removal of waste material. Retinal pigmented epithelial (RPE) cells have the onerous task of degrading both internal cellular debris generated through autophagy as well as phagocytosed photoreceptor outer segments. We propose that the inadequate processing material with the resulting accumulation of cellular waste contributes to the downstream pathologies characterized as age-related macular degeneration (AMD). The lysosomal enzymes responsible for clearance function optimally over a narrow range of acidic pH values; elevation of lysosomal pH by compounds like chloroquine or A2E can impair degradative enzyme activity and lead to a lipofuscin-like autofluorescence. Restoring acidity to the lysosomes of RPE cells can enhance activity of multiple degradative enzymes and is therefore a logical target in early AMD. We have identified several approaches to reacidify lysosomes of compromised RPE cells; stimulation of beta-adrenergic, A2A adenosine and D5 dopamine receptors each lowers lysosomal pH and improves degradation of outer segments. Activation of the CFTR chloride channel also reacidifies lysosomes and increases degradation. These approaches also restore the lysosomal pH of RPE cells from aged ABCA4(-/-) mice with chronically high levels of A2E, suggesting that functional signaling pathways to reacidify lysosomes are retained in aged cells like those in patients with AMD. Acidic nanoparticles transported to RPE lysosomes also lower pH and improve degradation of outer segments. In summary, the ability of diverse approaches to lower lysosomal pH and enhance outer segment degradation support the proposal that lysosomal acidification can prevent the accumulation of lipofuscin-like material in RPE cells.

Characterization of bioplastic based from cassava crisp home industrial waste incorporated with chitosan and liquid smoke

NASA Astrophysics Data System (ADS)

Fathanah, U.; Lubis, M. R.; Nasution, F.; Masyawi, M. S.

2018-03-01

Cassava peel (Manihot utilissima) is waste of agricultural result that is much potential as raw material of bioplastic making. This research focuses on bioplastic making from cassava peel. It aims to characterize the resulted bioplastic (mechanical and physical properties, SEM analysis, FTIR analysis and time test of bioplastic degradation). The bioplastic preparation takes place by mixing starch of cassava peel and chitosan (20, 30, 40 and 50% w/w), glycerol 30% w/w as plasticizer, and liquid smoke (0, 1 and 2 mL) as antimicrobial agent. The research result shows the highest value of tensile strength is 96.04 MPa, the highest elongation at break is 52.27%, and the value of water-resistant test is 22.68%. Morphology analysis by using SEM shows uneven surface and there is fracture in its cross-section. The analysis of functional group by FTIR shows the presence of functional groups of O–H (hydroxyl), N–H (amine), dan CH3–O (ether). The fastest complete degradation of bioplastic occurs in 45 days, and the longest occurs in 57 days.

Bio and nanomaterials in tribocorrosion systems

NASA Astrophysics Data System (ADS)

Benea, Lidia

2017-02-01

The growing attention that the scientific community has paid in the last decades to the corrosion phenomena, including tribocorrosion is related to the huge economic, social and environmental losses (3,5 % GDP in industrialized countries as USA, UK, Japan and Germany), that result from the spread of damage of several metal constructions and devices. Tribocorrosion is defined as the chemical-electrochemical-mechanical process leading to a degradation of materials in sliding, rolling or erosion contacts immersed in a corrosive environment or even in water. That degradation results from the combined action of corrosion and wear are higher compared with addition of corrosion and wear degradation separately. This synergism between chemical, electrochemical, and mechanical processes on materials in sliding, abrasive or erosive contacts immersed in a liquid requires a multi-disciplinary approach (material science, electrochemistry, tribology, mechanics, and surface engineering). This paper presents few summary results obtained by studying the materials degradation by complex tribocorrosion processes in terms of two broad categories of applications: tribocorrosion in industrial systems with improved behaviour of nanomaterials as hybrid and nanocomposite layers and tribocorrosion in living systems with improved behaviour by surface modifications of biomaterials applying electrochemical techniques. The purpose of this paper is to provide information on the surface conditions of materials in sliding contacts and also on the kinetics of reactions that control the corrosion component in the material loss during tribocorrosion tests.

Quick photo-Fenton degradation of phenolic compounds by Cu/Al2O3-MCM-41 under visible light irradiation: small particle size, stabilization of copper, easy reducibility of Cu and visible light active material.

PubMed

Pradhan, Amaresh C; Nanda, Binita; Parida, K M; Das, Mira

2013-01-14

The present study reports the photo-Fenton degradation of phenolic compounds (phenol, 2-chloro-4-nitrophenol and 4-chloro-2-nitrophenol) in aqueous solution using mesoporous Cu/Al(2)O(3)-MCM-41 nanocomposite as a heterogeneous photo-Fenton-like catalyst. The in situ incorporation of mesoporous Al(2)O(3) (MA) into the framework of MCM-41 (sol-gel method) forms Al(2)O(3)-MCM-41 and wetness impregnation of Cu(II) on Al(2)O(3)-MCM-41 generates mesoporous Cu/Al(2)O(3)-MCM-41 composite. The effects of pH and H(2)O(2) concentration on degradation of phenol, 2-chloro-4-nitrophenol and 4-chloro-2-nitrophenol are studied. Kinetics analysis shows that the photocatalytic degradation reaction follows a first-order rate equation. Mesoporous 5 Cu/Al(2)O(3)-MCM-41 is found to be an efficient photo-Fenton-like catalyst for the degradation of phenolic compounds. It shows nearly 100% degradation in 45 min at pH 4. The combined effect of small particle size, stabilization of Cu(2+) on the support Al(2)O(3)-MCM-41, ease reducibility of Cu(2+) and visible light activeness are the key factors for quick degradation of phenolic compounds by Cu/Al(2)O(3)-MCM-41.

Leucoagaricus gongylophorus Produces Diverse Enzymes for the Degradation of Recalcitrant Plant Polymers in Leaf-Cutter Ant Fungus Gardens

PubMed Central

Aylward, Frank O.; Burnum-Johnson, Kristin E.; Tringe, Susannah G.; Teiling, Clotilde; Tremmel, Daniel M.; Moeller, Joseph A.; Scott, Jarrod J.; Barry, Kerrie W.; Piehowski, Paul D.; Nicora, Carrie D.; Malfatti, Stephanie A.; Monroe, Matthew E.; Purvine, Samuel O.; Goodwin, Lynne A.; Smith, Richard D.; Weinstock, George M.; Gerardo, Nicole M.; Suen, Garret; Lipton, Mary S.

2013-01-01

Plants represent a large reservoir of organic carbon comprised primarily of recalcitrant polymers that most metazoans are unable to deconstruct. Many herbivores gain access to nutrients in this material indirectly by associating with microbial symbionts, and leaf-cutter ants are a paradigmatic example. These ants use fresh foliar biomass as manure to cultivate gardens composed primarily of Leucoagaricus gongylophorus, a basidiomycetous fungus that produces specialized hyphal swellings that serve as a food source for the host ant colony. Although leaf-cutter ants are conspicuous herbivores that contribute substantially to carbon turnover in Neotropical ecosystems, the process through which plant biomass is degraded in their fungus gardens is not well understood. Here we present the first draft genome of L. gongylophorus, and, using genomic and metaproteomic tools, we investigate its role in lignocellulose degradation in the gardens of both Atta cephalotes and Acromyrmex echinatior leaf-cutter ants. We show that L. gongylophorus produces a diversity of lignocellulases in ant gardens and is likely the primary driver of plant biomass degradation in these ecosystems. We also show that this fungus produces distinct sets of lignocellulases throughout the different stages of biomass degradation, including numerous cellulases and laccases that likely play an important role in lignocellulose degradation. Our study provides a detailed analysis of plant biomass degradation in leaf-cutter ant fungus gardens and insight into the enzymes underlying the symbiosis between these dominant herbivores and their obligate fungal cultivar. PMID:23584789

Kinetic study of photocatalytic degradation of carbamazepine, clofibric acid, iomeprol and iopromide assisted by different TiO2 materials--determination of intermediates and reaction pathways.

PubMed

Doll, Tusnelda E; Frimmel, Fritz H

2004-02-01

The light-induced degradation of clofibric acid, carbamazepine, iomeprol and iopromide under simulated solar irradiation has been investigated in aqueous solutions suspended with different TiO2 materials (P25 and Hombikat UV100). Kinetic studies showed that P25 had a better photocatalytic activity for clofibric acid and carbamazepine than Hombikat UV100. For photocatalytic degradation of iomeprol Hombikat UV100 was more suitable than P25. The results can be explained by the higher adsorption capacity of Hombikat UV100 for iomeprol. The study also focuses on the identification and quantification of possible degradation products. The degradation process was monitored by determination of sum parameters and inorganic ions. In case of clofibric acid various aromatic and aliphatic degradation products have been identified and quantified. A possible multi-step degradation scheme for clofibric acid is proposed. This study proves the high potential of the photocatalytic oxidation process to transform and mineralize environmentally relevant pharmaceuticals and contrast media in water.

Observation of Nanoscale Morphological and Structural Degradation in Perovskite Solar Cells by In-Situ TEM

DOE PAGES

Yang, Bin; Dyck, Ondrej K.; Univ. of Tennessee, Knoxville, TN; ...

2016-11-04

The chemical stability of organometallic halide perovskites is a major barrier facing their application in the fast rising field of next generation photovoltaics. These materials were shown to undergo degradation due to the influence of heat or moisture, significantly limiting the lifetime of associated devices. To overcome this stability issue, a fundamental understanding of degradation mechanisms is of foremost importance. Here, high resolution in situ transmission electron microscopy and electron energy loss spectroscopy elemental mapping were applied to probe morphological and structural changes in perovskite films during controlled environmental exposure treatments. Both moisture and oxygen in ambient air are revealedmore » to facilitate degradation in CH 3NH 3PbI 3 perovskites through decomposition and oxidation pathways, respectively. In addition, even in moisture- and oxygen-free environment evident degradation could be induced by heating at the solar cell s real-field operating temperature and the degradation was found to originate from defect sites. These findings provide fundamental insight to prevent degradation of perovskite materials and associated devices for realistic applications.« less

Observation of Nanoscale Morphological and Structural Degradation in Perovskite Solar Cells by In-Situ TEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Bin; Dyck, Ondrej K.; Univ. of Tennessee, Knoxville, TN

The chemical stability of organometallic halide perovskites is a major barrier facing their application in the fast rising field of next generation photovoltaics. These materials were shown to undergo degradation due to the influence of heat or moisture, significantly limiting the lifetime of associated devices. To overcome this stability issue, a fundamental understanding of degradation mechanisms is of foremost importance. Here, high resolution in situ transmission electron microscopy and electron energy loss spectroscopy elemental mapping were applied to probe morphological and structural changes in perovskite films during controlled environmental exposure treatments. Both moisture and oxygen in ambient air are revealedmore » to facilitate degradation in CH 3NH 3PbI 3 perovskites through decomposition and oxidation pathways, respectively. In addition, even in moisture- and oxygen-free environment evident degradation could be induced by heating at the solar cell s real-field operating temperature and the degradation was found to originate from defect sites. These findings provide fundamental insight to prevent degradation of perovskite materials and associated devices for realistic applications.« less

Recommendations for Exploring the Disfluency Hypothesis for Establishing Whether Perceptually Degrading Materials Impacts Performance

ERIC Educational Resources Information Center

Dunlosky, John; Mueller, Michael L.

2016-01-01

The target articles explore a common hypothesis pertaining to whether perceptually degrading materials will improve reasoning, memory, and metamemory. Outcomes are mixed, yet some evidence was garnered in support of a version of the disfluency hypothesis that includes moderators, and along with evidence from prior research, researchers will likely…

Simulation of Delamination Under High Cycle Fatigue in Composite Materials Using Cohesive Models

NASA Technical Reports Server (NTRS)

Camanho, Pedro P.; Turon, Albert; Costa, Josep; Davila, Carlos G.

2006-01-01

A new thermodynamically consistent damage model is proposed for the simulation of high-cycle fatigue crack growth. The basis for the formulation is an interfacial degradation law that links Fracture Mechanics and Damage Mechanics to relate the evolution of the damage variable, d, with the crack growth rate da/dN. The damage state is a function of the loading conditions (R and (Delta)G) as well as the experimentally-determined crack growth rates for the material. The formulation ensures that the experimental results can be reproduced by the analysis without the need of additional adjustment parameters.

Simulating Initial and Progressive Failure of Open-Hole Composite Laminates under Tension

NASA Astrophysics Data System (ADS)

Guo, Zhangxin; Zhu, Hao; Li, Yongcun; Han, Xiaoping; Wang, Zhihua

2016-12-01

A finite element (FE) model is developed for the progressive failure analysis of fiber reinforced polymer laminates. The failure criterion for fiber and matrix failure is implemented in the FE code Abaqus using user-defined material subroutine UMAT. The gradual degradation of the material properties is controlled by the individual fracture energies of fiber and matrix. The failure and damage in composite laminates containing a central hole subjected to uniaxial tension are simulated. The numerical results show that the damage model can be used to accurately predicte the progressive failure behaviour both qualitatively and quantitatively.

Multi-time series RNA-seq analysis of Enterobacter lignolyticus SCF1 during growth in lignin-amended medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orellana, Roberto; Chaput, Gina; Markillie, Lye Meng

The production of lignocellulosic-derived biofuels is a highly promising source of alternative energy, but it has been constrained by the lack of a microbial platform capable to efficiently degrade this recalcitrant material and cope with by-products that can be toxic to cells. Species that naturally grow in environments where carbon is mainly available as lignin are promising for finding new ways of removing the lignin that protects cellulose for improved conversion of lignin to fuel precursors. Enterobacter lignolyticus SCF1 is a facultative anaerobic Gammaproteobacteria isolated from tropical rain forest soil collected in El Yunque forest, Puerto Rico under anoxic growthmore » conditions with lignin as sole carbon source. Whole transcriptome analysis of SCF1 during E.lignolyticus SCF1 lignin degradation was conducted on cells grown in the presence (0.1%, w/w) and the absence of lignin, where samples were taken at three different times during growth, beginning of exponential phase, mid-exponential phase and beginning of stationary phase. Lignin-amended cultures achieved twice the cell biomass as unamended cultures over three days, and in this time degraded 60% of lignin. Transcripts in early exponential phase reflected this accelerated growth. A complement of laccases, aryl-alcohol dehydrogenases, and peroxidases were most up-regulated in lignin amended conditions in mid-exponential and early stationary phases compared to unamended growth. The association of hydrogen production by way of the formate hydrogenlyase complex with lignin degradation suggests a possible value added to lignin degradation in the future.« less

Multi-time series RNA-seq analysis of Enterobacter lignolyticus SCF1 during growth in lignin-amended medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orellana, Roberto; Chaput, Gina; Markillie, Lye Meng

The production of lignocellulosic-derived biofuels is a highly promising source of alternative energy, but it has been constrained by the lack of a microbial platform capable to efficiently degrade this recalcitrant material and cope with by-products that can be toxic to cells. Species that naturally grow in environments where carbon is mainly available as lignin are promising for finding new ways of removing the lignin that protects cellulose for improved conversion of lignin to fuel precursors. Enterobacter lignolyticus SCF1 is a facultative anaerobic Gammaproteobacteria isolated from tropical rain forest soil collected in El Yunque forest, Puerto Rico under anoxic growthmore » conditions with lignin as sole carbon source. Whole transcriptome analysis of SCF1 during E.lignolyticus SCF1 lignin degradation was conducted on cells grown in the presence (0.1%, w/w) and the absence of lignin, where samples were taken at three different times during growth, beginning of exponential phase, midexponential phase and beginning of stationary phase. Lignin-amended cultures achieved twice the cell biomass as unamended cultures over three days, and in this time degraded 60% of lignin. Transcripts in early exponential phase reflected this accelerated growth. A complement of laccases, aryl-alcohol dehydrogenases, and peroxidases were most up-regulated in lignin amended conditions in mid-exponential and early stationary phases compared to unamended growth. The association of hydrogen production by way of the formate hydrogenlyase complex with lignin degradation suggests a possible value added to lignin degradation in the future.« less

Multi-time series RNA-seq analysis of Enterobacter lignolyticus SCF1 during growth in lignin-amended medium.

PubMed

Orellana, Roberto; Chaput, Gina; Markillie, Lye Meng; Mitchell, Hugh; Gaffrey, Matt; Orr, Galya; DeAngelis, Kristen M

2017-01-01

The production of lignocellulosic-derived biofuels is a highly promising source of alternative energy, but it has been constrained by the lack of a microbial platform capable to efficiently degrade this recalcitrant material and cope with by-products that can be toxic to cells. Species that naturally grow in environments where carbon is mainly available as lignin are promising for finding new ways of removing the lignin that protects cellulose for improved conversion of lignin to fuel precursors. Enterobacter lignolyticus SCF1 is a facultative anaerobic Gammaproteobacteria isolated from tropical rain forest soil collected in El Yunque forest, Puerto Rico under anoxic growth conditions with lignin as sole carbon source. Whole transcriptome analysis of SCF1 during E.lignolyticus SCF1 lignin degradation was conducted on cells grown in the presence (0.1%, w/w) and the absence of lignin, where samples were taken at three different times during growth, beginning of exponential phase, mid-exponential phase and beginning of stationary phase. Lignin-amended cultures achieved twice the cell biomass as unamended cultures over three days, and in this time degraded 60% of lignin. Transcripts in early exponential phase reflected this accelerated growth. A complement of laccases, aryl-alcohol dehydrogenases, and peroxidases were most up-regulated in lignin amended conditions in mid-exponential and early stationary phases compared to unamended growth. The association of hydrogen production by way of the formate hydrogenlyase complex with lignin degradation suggests a possible value added to lignin degradation in the future.

Multi-time series RNA-seq analysis of Enterobacter lignolyticus SCF1 during growth in lignin-amended medium

PubMed Central

Chaput, Gina; Markillie, Lye Meng; Mitchell, Hugh; Gaffrey, Matt; Orr, Galya; DeAngelis, Kristen M.

2017-01-01

The production of lignocellulosic-derived biofuels is a highly promising source of alternative energy, but it has been constrained by the lack of a microbial platform capable to efficiently degrade this recalcitrant material and cope with by-products that can be toxic to cells. Species that naturally grow in environments where carbon is mainly available as lignin are promising for finding new ways of removing the lignin that protects cellulose for improved conversion of lignin to fuel precursors. Enterobacter lignolyticus SCF1 is a facultative anaerobic Gammaproteobacteria isolated from tropical rain forest soil collected in El Yunque forest, Puerto Rico under anoxic growth conditions with lignin as sole carbon source. Whole transcriptome analysis of SCF1 during E.lignolyticus SCF1 lignin degradation was conducted on cells grown in the presence (0.1%, w/w) and the absence of lignin, where samples were taken at three different times during growth, beginning of exponential phase, mid-exponential phase and beginning of stationary phase. Lignin-amended cultures achieved twice the cell biomass as unamended cultures over three days, and in this time degraded 60% of lignin. Transcripts in early exponential phase reflected this accelerated growth. A complement of laccases, aryl-alcohol dehydrogenases, and peroxidases were most up-regulated in lignin amended conditions in mid-exponential and early stationary phases compared to unamended growth. The association of hydrogen production by way of the formate hydrogenlyase complex with lignin degradation suggests a possible value added to lignin degradation in the future. PMID:29049419

Multi-time series RNA-seq analysis of Enterobacter lignolyticus SCF1 during growth in lignin-amended medium

DOE PAGES

Orellana, Roberto; Chaput, Gina; Markillie, Lye Meng; ...

2017-10-19

The production of lignocellulosic-derived biofuels is a highly promising source of alternative energy, but it has been constrained by the lack of a microbial platform capable to efficiently degrade this recalcitrant material and cope with by-products that can be toxic to cells. Species that naturally grow in environments where carbon is mainly available as lignin are promising for finding new ways of removing the lignin that protects cellulose for improved conversion of lignin to fuel precursors. Enterobacter lignolyticus SCF1 is a facultative anaerobic Gammaproteobacteria isolated from tropical rain forest soil collected in El Yunque forest, Puerto Rico under anoxic growthmore » conditions with lignin as sole carbon source. Whole transcriptome analysis of SCF1 during E.lignolyticus SCF1 lignin degradation was conducted on cells grown in the presence (0.1%, w/w) and the absence of lignin, where samples were taken at three different times during growth, beginning of exponential phase, mid-exponential phase and beginning of stationary phase. Lignin-amended cultures achieved twice the cell biomass as unamended cultures over three days, and in this time degraded 60% of lignin. Transcripts in early exponential phase reflected this accelerated growth. A complement of laccases, aryl-alcohol dehydrogenases, and peroxidases were most up-regulated in lignin amended conditions in mid-exponential and early stationary phases compared to unamended growth. The association of hydrogen production by way of the formate hydrogenlyase complex with lignin degradation suggests a possible value added to lignin degradation in the future.« less

Micro-thermal analysis of polyester coatings

NASA Astrophysics Data System (ADS)

Fischer, Hartmut R.

2010-04-01

The application and suitability of micro-thermal analysis to detect changes in the chemical and physical properties of coating due to ageing and especially photo-degradation is demonstrated using a model polyester coating based on neopentyl glycol isophthalic acid. The changes in chemical structure like chain scission and cross-linking are manifested by a shift of the LTA detectable Tg and by a change of the slope of the part of the LTA graph responsible for the penetration of the hot sensor into the material after passing the glass transition temperature. As such LTA is a valuable tool to have a quick look into coating surfaces and especially their ageing. The photo-degradation of polyester in air leads to the formation of a cross-linked network at a surface layer of about 3-4 μm coupled with an increase in hardness and of the glass transition temperature by ˜90 K, the effect is less drastic for a photo-degradation in a nitrogen environment. Moreover, the presence of a non-equilibrium dense surface layer with a higher Tg formed during the drying of the coating formulation and the film solidification can be shown.

Fast charging technique for high power LiFePO4 batteries: A mechanistic analysis of aging

NASA Astrophysics Data System (ADS)

Anseán, D.; Dubarry, M.; Devie, A.; Liaw, B. Y.; García, V. M.; Viera, J. C.; González, M.

2016-07-01

One of the major issues hampering the acceptance of electric vehicles (EVs) is the anxiety associated with long charging time. Hence, the ability to fast charging lithium-ion battery (LIB) systems is gaining notable interest. However, fast charging is not tolerated by all LIB chemistries because it affects battery functionality and accelerates its aging processes. Here, we investigate the long-term effects of multistage fast charging on a commercial high power LiFePO4-based cell and compare it to another cell tested under standard charging. Coupling incremental capacity (IC) and IC peak area analysis together with mechanistic model simulations ('Alawa' toolbox with harvested half-cell data), we quantify the degradation modes that cause aging of the tested cells. The results show that the proposed fast charging technique caused similar aging effects as standard charging. The degradation is caused by a linear loss of lithium inventory, coupled with a less degree of linear loss of active material on the negative electrode. This study validates fast charging as a feasible mean of operation for this particular LIB chemistry and cell architecture. It also illustrates the benefits of a mechanistic approach to understand cell degradation on commercial cells.

Degradation and recovery of iron doped barium titanate single crystals via modulus spectroscopy and thermally stimulated depolarization current

NASA Astrophysics Data System (ADS)

Carter, J. J.; Bayer, T. J. M.; Randall, C. A.

2017-04-01

Understanding resistance degradation during the application of DC bias and recovery after removing the DC bias provides insight into failure mechanisms and defects in dielectric materials. In this experiment, modulus spectroscopy and thermally stimulated depolarization current (TSDC) techniques were used to characterize the degradation and recovery of iron-doped barium titanate single crystals. Modulus spectroscopy is a very powerful analytical tool applied during degradation and recovery to observe changes in the local conductivity distribution. During degradation, oxygen vacancies migrate to the cathode region, and a counter flow of oxygen anions migrates towards the anode. With increasing time during degradation, the distribution of conductivity broadens only slightly exhibiting crucial differences to iron doped strontium titanate. After removing the DC bias, the recovery shows that a second previously unobserved and distinct conductivity maximum arises in the modulus data. This characteristic with two maxima related to different conductivities in the anode and cathode region is what can be expected from the published defect chemistry. It will be concluded that only the absence of an external electric field during recovery measurements permits the observation of local conductivity measurements without the presence of non-equilibrium conditions such as charge injection. Equilibrium conductivity as a function of oxygen vacancy concentration is described schematically. Oxygen vacancy migration during degradation and recovery is verified by TSDC analysis. We establish a self-consistent rationale of the transient changes in the modulus and TSDC for the iron doped barium titanate single crystal system including electron, hole and oxygen vacancy conductivity. During degradation, the sample fractured.

Energy balance associated with the degradation of lignocellulosic material by white-rot and brown-rot fungi.

NASA Astrophysics Data System (ADS)

Derrien, Delphine; Bédu, Hélène; Buée, Marc; Kohler, Annegret; Goodell, Barry; Gelhaye, Eric

2017-04-01

Forest soils cover about 30% of terrestrial area and comprise between 50 and 80% of the global stock of soil organic carbon (SOC). The major precursor for this forest SOC is lignocellulosic material, which is made of polysaccharides and lignin. Lignin has traditionally been considered as a recalcitrant polymer that hinders access to the much more labile structural polysaccharides. This view appears to be partly incorrect from a microbiology perspective yet, as substrate alteration depends on the metabolic potential of decomposers. In forest ecosystems the wood-rotting Basidiomycota fungi have developed two different strategies to attack the structure of lignin and gain access to structural polysaccharides. White-rot fungi degrade all components of plant cell walls, including lignin, using enzymatic systems. Brown-rot fungi do not remove lignin. They generate oxygen-derived free radicals, such as the hydroxyl radical produced by the Fenton reaction, that disrupt the lignin polymer and depolymerize polysaccharides which then diffuse out to where the enzymes are located The objective of this study was to develop a model to investigate whether the lignin relative persistence could be related to the energetic advantage of brown-rot degradative pathway in comparison to white-rot degradative pathway. The model simulates the changes in substrate composition over time, and determines the energy gained from the conversion of the lost substrate into CO2. The energy cost for the production of enzymes involved in substrate alteration is assessed using information derived from genome and secretome analysis. For brown-rot fungus specifically, the energy cost related to the production of OH radicals is also included. The model was run, using data from the literature on populous wood degradation by Trametes versicolor, a white-rot fungus, and Gloeophyllum trabeum, a brown-rot fungus. It demonstrates that the brown-rot fungus (Gloeophyllum trabeum) was more efficient than the white-rot fungus (Trametes versicolor). The energy advantage could explain the emergence of the brown-rot degradative pathway from a white-rot degradative pathway and subsequently, the relative persistence of lignin in soil.

Screening of Biodegradable Function of Indigenous Ligno-degrading Mushroom Using Dyes

PubMed Central

Cho, Soo-Muk; Seok, Soon-Ja; Kong, Won-Sik; Kim, Gyu-Hyun; Sung, Jae-Mo

2009-01-01

The process of biodegradation in lingo-cellulosic materials is critically relevant to biospheric carbon. The study of this natural process has largely involved laboratory investigations, focused primarily on the biodegradation and recycling of agricultural by-products, generally using basidiomycetes species. In order to collect super white rot fungi and evaluate its ability to degrade lingo-cellulosic material, 35 fungal strains, collected from forests, humus soil, livestock manure, and dead trees, were screened for enzyme activities and their potential to decolorize the commercially used Poly-R 478 dye. In the laccase enzymatic analysis chemical test, 33 white rot fungi and 2 brown rot fungi were identified. The degradation ability of polycyclic aromatic hydrocarbons (PAHs) according to the utilized environmental conditions was higher in the mushrooms grown in dead trees and fallen leaves than in the mushrooms grown in humus soil and livestock manure. Using Poly-R 478 dye to assess the PAH-degradation activity of the identified strains, four strains, including Agrocybe pediades, were selected. The activities of laccase, MnP, and Lip of the four strains with PAH-degrading ability were highest in Pleurotus incarnates. 87 fungal strains, collected from forests, humus soil, livestock manure, and dead trees, were screened for enzyme activities and their potential to decolorize the commercially used Poly-R 478 dye on solid media. Using Poly-R 478 dye to assess the PAHdegrading activity of the identified strains, it was determined that MKACC 51632 and 52492 strains evidenced superior activity in static and shaken liquid cultures. Subsequent screening on plates containing the polymeric dye poly R-478, the decolorization of which is correlated with lignin degradation, resulted in the selection of a strain of Coriolus versicolor, MKACC52492, for further study, primarily due to its rapid growth rate and profound ability to decolorize poly R-478 on solid media. Considering our findings using Poly-R 478 dye to evaluate the PAH-degrading activity of the identified strains, Coriolus versicolor, MKACC 52492 was selected as a favorable strain. Coriolus versicolor, which was collected from Mt. Yeogi in Suwon, was studied for the production of the lignin-modifying enzymes laccase, manganese-dependent peroxidase (MnP), and lignin peroxidase (LiP). PMID:23983508

A review on biodegradable materials for cardiovascular stent application

NASA Astrophysics Data System (ADS)

Hou, Li-Da; Li, Zhen; Pan, Yu; Sabir, MuhammadIqbal; Zheng, Yu-Feng; Li, Li

2016-09-01

A stent is a medical device designed to serve as a temporary or permanent internal scaffold to maintain or increase the lumen of a body conduit. The researchers and engineers diverted to investigate biodegradable materials due to the limitation of metallic materials in stent application such as stent restenosis which requires prolonged anti platelet therapy, often result in smaller lumen after implantation and obstruct re-stenting treatments. Biomedical implants with temporary function for the vascular intervention are extensively studied in recent years. The rationale for biodegradable stent is to provide the support for the vessel in predicted period of time and then degrading into biocompatible constituent. The degradation of stent makes the re-stenting possible after several months and also ameliorates the vessel wall quality. The present article focuses on the biodegradable materials for the cardiovascular stent. The objective of this review is to describe the possible biodegradable materials for stent and their properties such as design criteria, degradation behavior, drawbacks and advantages with their recent clinical and preclinical trials.

Porous Biodegradable Metals for Hard Tissue Scaffolds: A Review

PubMed Central

Yusop, A. H.; Bakir, A. A.; Shaharom, N. A.; Abdul Kadir, M. R.; Hermawan, H.

2012-01-01

Scaffolds have been utilized in tissue regeneration to facilitate the formation and maturation of new tissues or organs where a balance between temporary mechanical support and mass transport (degradation and cell growth) is ideally achieved. Polymers have been widely chosen as tissue scaffolding material having a good combination of biodegradability, biocompatibility, and porous structure. Metals that can degrade in physiological environment, namely, biodegradable metals, are proposed as potential materials for hard tissue scaffolding where biodegradable polymers are often considered as having poor mechanical properties. Biodegradable metal scaffolds have showed interesting mechanical property that was close to that of human bone with tailored degradation behaviour. The current promising fabrication technique for making scaffolds, such as computation-aided solid free-form method, can be easily applied to metals. With further optimization in topologically ordered porosity design exploiting material property and fabrication technique, porous biodegradable metals could be the potential materials for making hard tissue scaffolds. PMID:22919393

Sustainability of Metal Structures via Spray-Clad Remanufacturing

NASA Astrophysics Data System (ADS)

Smith, Gregory M.; Sampath, Sanjay

2018-04-01

Structural reclamation and remanufacturing is an important future design consideration to allow sustainable recovery of degraded structural metals. Heavy machinery and infrastructure components subjected to extended use and/or environment induced degradation require costly and time-consuming replacement. If these parts can be remanufactured to original tolerances, and returned to service with "as good or better" performance, significant reductions in materials, cost, and environmental impact can be achieved. Localized additive restoration via thermal or cold spray methods is a promising approach in recovering and restoring original design strength of degraded metals. The advent of high velocity spray deposition technologies has allowed deposition of near full density materials. In this review, the fundamental scientific and technological elements of such local additive restoration is contemplated including materials, processes, and methodologies to assess the capabilities of such remanufactured systems. This points to sustainable material reclamation, as well as a route toward resource and process sustainability.

Trends in biomedical engineering: focus on Smart Bio-Materials and Drug Delivery.

PubMed

Tanzi, Maria Cristina; Bozzini, Sabrina; Candiani, Gabriele; Cigada, Alberto; De Nardo, Luigi; Farè, Silvia; Ganazzoli, Fabio; Gastaldi, Dario; Levi, Marinella; Metrangolo, Pierangelo; Migliavacca, Francesco; Osellame, Roberto; Petrini, Paola; Raffaini, Giuseppina; Resnati, Giuseppe; Vena, Pasquale; Vesentini, Simone; Zunino, Paolo

2011-01-01

The present article reviews on different research lines, namely: drug and gene delivery, surface modification/modeling, design of advanced materials (shape memory polymers and biodegradable stents), presently developed at Politecnico di Milano, Italy. For gene delivery, non-viral polycationic-branched polyethylenimine (b-PEI) polyplexes are coated with pectin, an anionic polysaccharide, to enhance the polyplex stability and decrease b-PEI cytotoxicity. Perfluorinated materials, specifically perfluoroether, and perfluoro-polyether fluids are proposed as ultrasound contrast agents and smart agents for drug delivery. Non-fouling, self-assembled PEG-based monolayers are developed on titanium surfaces with the aim of drastically reducing cariogenic bacteria adhesion on dental implants. Femtosecond laser microfabrication is used for selectively and spatially tuning the wettability of polymeric biomaterials and the effects of femtosecond laser ablation on the surface properties of polymethylmethacrylate are studied. Innovative functionally graded Alumina-Ti coatings for wear resistant articulating surfaces are deposited with PLD and characterized by means of a combined experimental and computational approach. Protein adsorption on biomaterials surfaces with an unlike wettability and surface-modification induced by pre-adsorbed proteins are studied by atomistic computer simulations. A study was performed on the fabrication of porous Shape Memory Polymeric structures and on the assessment of their potential application in minimally invasive surgical procedures. A model of magnesium (alloys) degradation, in a finite element framework analysis, and a bottom-up multiscale analysis for modeling the degradation mechanism of PLA matrices was developed, with the aim of providing valuable tools for the design of bioresorbable stents.

Polymer materials and component evaluation in acidic-radiation environments

NASA Astrophysics Data System (ADS)

Celina, M.; Gillen, K. T.; Malone, G. M.; Clough, R. L.; Nelson, W. H.

2001-07-01

Polymeric materials used for cable/wire insulation, electrical connectors, O-rings, seals, and in critical components such as motors, level switches and resistive thermo-devices were evaluated under accelerated degradation conditions in combined radiation-oxidative elevated-temperature acidic-vapor (nitric/oxalic) environments relevant to conditions in isotope processing facilities. Experiments included the assessment of individual materials such as PEEK, polyimides, polyolefin based cable insulation, EPDM rubbers, various epoxy systems, commercial caulking materials as well as some functional testing of components. We discuss how to conduct laboratory experiments to simulate such complex hostile environments, describe some degradation effects encountered, and evaluate the impact on appropriate material and component selection.

Steve P. Harvey | NREL

Science.gov Websites

photoemission measurements to better understand materials fundamentals and degradation in semiconductor, organic , investigating root-cause mechanisms of degradation in photovoltaic modules, investigating organic-inorganic

Investigation of the persistence of nerve agent degradation analytes on surfaces through wipe sampling and detection with ultrahigh performance liquid chromatography-tandem mass spectrometry.

PubMed

Willison, Stuart A

2015-01-20

The persistence of chemical warfare nerve agent degradation analytes on surfaces is important, from indicating the presence of nerve agent on a surface to guiding environmental restoration of a site after a release. Persistence was investigated for several chemical warfare nerve agent degradation analytes on indoor surfaces and presents an approach for wipe sampling of surfaces, followed by wipe extraction and liquid chromatography-tandem mass spectrometry detection. Commercially available wipe materials were investigated to determine optimal wipe recoveries. Tested surfaces included porous/permeable (vinyl tile, painted drywall, and wood) and largely nonporous/impermeable (laminate, galvanized steel, and glass) surfaces. Wipe extracts were analyzed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). UPLC provides a separation of targeted degradation analytes in addition to being nearly four times faster than high-performance liquid chromatography, allowing for greater throughput after a large-scale contamination incident and subsequent remediation events. Percent recoveries from nonporous/impermeable surfaces were 60-103% for isopropyl methylphosphonate (IMPA), GB degradate; 61-91% for ethyl methylphosphonate (EMPA), VX degradate; and 60-98% for pinacolyl methylphosphonate (PMPA), GD degradate. Recovery efficiencies for methyl phosphonate (MPA), nerve agent degradate, and ethylhydrogen dimethylphosphonate (EHDMAP), GA degradate, were lower, perhaps due to matrix effects. Diisopropyl methylphosphonate, GB impurity, was not recovered from surfaces. The resulting detection limits for wipe extracts were 0.065 ng/cm(2) for IMPA, 0.079 ng/cm(2) for MPA, 0.040 ng/cm(2) for EMPA, 0.078 ng/cm(2) for EHDMAP, and 0.013 ng/cm(2) for PMPA. The data indicate that laboratories may hold wipe samples for up to 30 days prior to analysis. Target analytes were observed to persist on surfaces for at least 6 weeks.

Fungal degradation of polyhydroxyalkanoates and a semiquantitative assay for screening their degradation by terrestrial fungi.

PubMed

Matavulj, M; Molitoris, H P

1992-12-01

The current problems with decreasing fossile resources and increasing environmental pollution by petrochemical-based plastics have stimulated investigations to find biosynthetic materials which are also biodegradable. Bacterial reserve materials such as polyhydroxyalkanoates (PHA) have been discovered to possess thermoplastic properties and can be synthesized from renewable resources. Poly-beta-hydroxybutyric acid (PHB) is at present the most promising PHA; and BIOPOL, its copolymer with poly-beta-hydroxy-valerate (PHV), is already industrially produced (ICI, UK), and used as packaging material (WELLA, FRG). According to the literature, PHA degradation has so far mainly been observed in bacteria; only under certain environmental conditions has fungal degradation of PHAs been indicated. Since fungi constitute an important part of microbial populations participating in degradation processes, a simple screening method for fungal degradation of BIOPOL, a PHA-based plastic, was developed. Several media with about 150 fungal strains from different terrestrial environments and belonging to different systematic and ecological groups were used. PHA depolymerization was tested on three PHB-based media, each with 0.1% BIOPOL or PHB homopolymer causing turbidity of the medium. The media contained either a comparatively low or high content of organic carbon (beside PHA) or were based on mineral medium with PHA as the principal source of carbon. The degradation activity was detectable due to formation of a clear halo around the colony (Petri plates) or a clear zone under the colony (test tubes).(ABSTRACT TRUNCATED AT 250 WORDS)

Holistic assessment of covalently-labelled core-shell polymeric nanoparticles with fluorescent contrast agents towards theranostic applications

PubMed Central

Gustafson, Tiffany P.; Lim, Young H.; Flores, Jeniree A.; Heo, Gyu Seong; Zhang, Fuwu; Zhang, Shiyi; Samarajeewa, Sandani; Raymond, Jeffery E.; Wooley, Karen L.

2014-01-01

The successful development of degradable polymeric nanostructures as optical probes for use in nanotheranostic applications requires the intelligent design of materials such that their surface response, degradation, drug delivery and imaging properties are all optimized. In the case of imaging, optimization must result in materials that allow differentiation between unbound optical contrast agents and labeled polymeric materials as they undergo degradation. In this study, we have shown that use of traditional electrophoretic gel-plate assays for determination of the purity of dye-conjugated degradable nanoparticles is limited, due to polymer degradation characteristics. To overcome these limitations, we have outlined a holistic approach to evaluating dye-and peptide-polymer nanoparticle conjugation by utilizing steady-state fluorescence, anisotropy, and emission and anisotropy life-time decay profiles, through which nanoparticle-dye binding can be assessed independent of perturbations, such as those presented during the execution of electrolyte gel-based assays. This approach has been demonstrated to provide an overall understanding of the spectral signature-structure-function relationship, ascertaining key information on interactions between the fluorophore, polymer and solvent components that have a direct and measurable impact on the emissive properties of the optical probe. The use of these powerful techniques provides feedback that can be utilized to improve nanotheranostics by evaluating dye emissivity in degradable nanotheranostic systems, which has become increasingly important as modern platforms transition to architectures intentionally reliant on degradation and built-in environmental responses. PMID:24392760

Degradation of atrazine and isoproturon in surface and sub-surface soil materials undergoing different moisture and aeration conditions.

PubMed

Issa, Salah; Wood, Martin

2005-02-01

The influence of different moisture and aeration conditions on the degradation of atrazine and isoproturon was investigated in environmental samples aseptically collected from surface and sub-surface zones of agricultural land. The materials were maintained at two moisture contents corresponding to just above field capacity or 90% of field capacity. Another two groups of samples were adjusted with water to above field capacity, and, at zero time, exposed to drying-rewetting cycles. Atrazine was more persistent (t(1/2) = 22-35 days) than isoproturon (t(1/2) = 5-17 days) in samples maintained at constant moisture conditions. The rate of degradation for both herbicides was higher in samples maintained at a moisture content of 90% of field capacity than in samples with higher moisture contents. The reduction in moisture content in samples undergoing desiccation from above field capacity to much lower than field capacity enhanced the degradation of isoproturon (t(1/2) = 9-12 days) but reduced the rate of atrazine degradation (t(1/2) = 23-35 days). This demonstrates the variability between different micro-organisms in their susceptibility to desiccation. Under anaerobic conditions generated in anaerobic jars, atrazine degraded much more rapidly than isoproturon in materials taken from three soil profiles (0-250 cm depth). It is suggested that some specific micro-organisms are able to survive and degrade herbicide under severe conditions of desiccation. Copyright (c) 2005 Society of Chemical Industry.

Degradation of Silicone Encapsulants in CPV Optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Can; Miller, David C.; Tappan, Ian A.

High efficiency multijunction solar cells in terrestrial concentrator photovoltaic (CPV) modules are becoming an increasingly cost effective and viable option in utility scale power generation. As with other utility scale photovoltaics, CPV modules need to guarantee operational lifetimes of at least 25 years. The reliability of optical elements in CPV modules poses a unique materials challenge due to the increased UV irradiance and enhanced temperature cycling associated with concentrated solar flux. The polymeric and thin film materials used in the optical elements are especially susceptible to UV damage, diurnal temperature cycling and active chemical species from the environment. We usedmore » fracture mechanics approaches to study the degradation modes including: the adhesion between the encapsulant and the cell or secondary optical element; and the cohesion of the encapsulant itself. Understanding the underlying mechanisms of materials degradation under elevated stress conditions is critical for commercialization of CPV technology and can offer unique insights into degradation modes in similar encapsulants used in other photovoltaic modules.« less

Degradation of Silicone Encapsulants in CPV Optics: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, David C.; Tappan, Ian A.; Cai, Can

High efficiency multijunction solar cells in terrestrial concentrator photovoltaic (CPV) modules are becoming an increasingly cost effective and viable option in utility scale power generation. As with other utility scale photovoltaics, CPV modules need to guarantee operational lifetimes of at least 25 years. The reliability of optical elements in CPV modules poses a unique materials challenge due to the increased UV irradiance and enhanced temperature cycling associated with concentrated solar flux. The polymeric and thin film materials used in the optical elements are especially susceptible to UV damage, diurnal temperature cycling and active chemical species from the environment. We usedmore » fracture mechanics approaches to study the degradation modes including: the adhesion between the encapsulant and the cell or secondary optical element; and the cohesion of the encapsulant itself. Understanding the underlying mechanisms of materials degradation under elevated stress conditions is critical for commercialization of CPV technology and can offer unique insights into degradation modes in similar encapsulants used in other photovoltaic modules.« less

Development and Utilization of Host Materials for White Phosphorescent Organic Light-Emitting Diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Ching; Chen, Shaw

Our project was primarily focused on the MYPP 2015 goal for white phosphorescent organic devices (PhOLEDs or phosphorescent organic light-emitting diodes) for solid-state lighting with long lifetimes and high efficiencies. Our central activity was to synthesize and evaluate a new class of host materials for blue phosphors in the PhOLEDs, known to be a weak link in the device operating lifetime. The work was a collaborative effort between three groups, one primarily responsible for chemical design and characterization (Chen), one primarily responsible for device development (Tang) and one primarily responsible for mechanistic studies and degradation analysis (Rothberg). The host materialsmore » were designed with a novel architecture that chemically links groups with good ability to move electrons with those having good ability to move “holes” (positive charges), the main premise being that we could suppress the instability associated with physical separation and crystallization of the electron conducting and hole conducting materials that might cause the devices to fail. We found that these materials do prevent crystallization and that this will increase device lifetimes but that efficiencies were reduced substantially due to interactions between the materials creating new low energy “charge transfer” states that are non-luminescent. Therefore, while our proposed strategy could in principle improve device lifetimes, we were unable to find a materials combination where the efficiency was not substantially compromised. In the course of our project, we made several important contributions that are peripherally related to the main project goal. First, we were able to prepare the proposed new family of materials and develop synthetic routes to make them efficiently. These types of materials that can transport both electrons and holes may yet have important roles to play in organic device technology. Second we developed an important new method for controlling the deposition profile of material so that arbitrary concentration gradients can be implemented in layers with mixed composition. These concentration profiles are known to increase device efficiency and longevity and we confirmed that experimentally. Third, we investigated a new method for analyzing degradation in devices using mass spectrometry to look for degradation products. We showed that these methods are not simple to interpret unambiguously and need to be used with caution.« less

A process for complete biodegradation of shrimp waste by a novel marine isolate Paenibacillus sp. AD with simultaneous production of chitinase and chitin oligosaccharides.

PubMed

Kumar, Aditya; Kumar, Deepak; George, Nancy; Sharma, Prince; Gupta, Naveen

2018-04-01

Disposal of chitinaceous waste is a major problem of seafood industry. Most of the known chitinolytic organisms have been studied with respect to pure chitin as substrate. Use of these organisms for degradation of seafood waste has not been explored much. In present study a marine bacterium capable of proficiently degrading shrimp waste with co-production of value added products like chitinase and chitin oligosaccharides was isolated from seafood waste dumping sites. On 16s rRNA and biochemical analysis bacterium was found to be a novel species of genus Paenibacillus.Under optimized condition complete shrimp waste degradation (99%) was achieved along with chitinase yield of 20.01 IUml -1 . SEM and FTIR showed the structural changes and breakage of bonds typical to that of chitin, which indicated that this process can be used for the degradation of other chitinaceous material also. Thin layer chromatography revealed the presence of chitin oligosaccharides of various degree of polymerization in the hydrolysate. Complete degradation of shrimp waste by Paenibacillus sp. AD makes it a potential candidate for the bioremediation of seafood waste at large scale. Concomitant production of chitinase and chitin oligosaccharides further makes the process economical and commercially viable. Copyright © 2017 Elsevier B.V. All rights reserved.

Hydrothermal degradation of lignin: products analysis for phenol formaldehyde adhesive synthesis.

PubMed

Yang, Sheng; Yuan, Tong-Qi; Li, Ming-Fei; Sun, Run-Cang

2015-01-01

Corncob lignin was treated with pressurized hot water in a cylindrical autoclave in current investigation. With the aim of investigating the effect of reaction temperature and retention time on the distribution of degradation products, the products were divided into five fractions including gas, volatile organic compounds, water-soluble oil, heavy oil, and solid residue. It was found that hydrothermal degradation of corncob lignin in pressurized hot water produced a large amount of phenolic compounds with lower molecular weight than the raw lignin. Some phenolic and benzene derivatives monomers such as vanillin, 2-methoxy-phenol, 2-ethyl-phenol, p-xylene, and 1, 3-dimethyl-benzene were also identified in the degradation products. The products were further analyzed by GC-MS, GPC, 2D-HSQC, and (31)P-NMR to investigate their suitability for partial incorporation into phenol formaldehyde adhesive as a substitution of phenol. The results indicated that the reaction temperature had more effect on the products distribution than the retention time. The optimal condition for heavy oil production appeared at 290 °C with retention time 0 min. The compounds of heavy oil had more active sites than the raw lignin, suggesting that the heavy oil obtained from hydrothermal degradation of lignin is a promising material for phenol formaldehyde adhesive synthesis. Copyright © 2014 Elsevier B.V. All rights reserved.

Biodegradation of polystyrene-graft-starch copolymers in three different types of soil.

PubMed

Nikolic, Vladimir; Velickovic, Sava; Popovic, Aleksandar

2014-01-01

Materials based on polystyrene and starch copolymers are used in food packaging, water pollution treatment, and textile industry, and their biodegradability is a desired characteristic. In order to examine the degradation patterns of modified, biodegradable derivates of polystyrene, which may keep its excellent technical features but be more environmentally friendly at the same time, polystyrene-graft-starch biomaterials obtained by emulsion polymerization in the presence of new type of initiator/activator pair (potassium persulfate/different amines) were subjected to 6-month biodegradation by burial method in three different types of commercially available soils: soil rich in humus and soil for cactus and orchid growing. Biodegradation was monitored by mass decrease, and the highest degradation rate was achieved in soil for cactus growing (81.30%). Statistical analysis proved that microorganisms in different soil samples have different ability of biodegradation, and there is a significant negative correlation between the share of polystyrene in copolymer and degree of biodegradation. Grafting of polystyrene on starch on one hand prevents complete degradation of starch that is present (with maximal percentage of degraded starch ranging from 55 to 93%), while on the other hand there is an upper limit of share of polystyrene in the copolymer (ranging from 37 to 77%) that is preventing biodegradation of degradable part of copolymers.

The effects of 1 kW class arcjet thruster plumes on spacecraft charging and spacecraft thermal control materials

NASA Technical Reports Server (NTRS)

Bogorad, A.; Lichtin, D. A.; Bowman, C.; Armenti, J.; Pencil, E.; Sarmiento, C.

1992-01-01

Arcjet thrusters are soon to be used for north/south stationkeeping on commercial communications satellites. A series of tests was performed to evaluate the possible effects of these thrusters on spacecraft charging and the degradation of thermal control material. During the tests the interaction between arcjet plumes and both charged and uncharged surfaces did not cause any significant material degradation. In addition, firing an arcjet thruster benignly reduced the potential of charged surfaces to near zero.

Environmental effects on composite airframes: A study conducted for the ARM UAV Program (Atmospheric Radiation Measurement Unmanned Aerospace Vehicle)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noguchi, R.A.

1994-06-01

Composite materials are affected by environments differently than conventional airframe structural materials are. This study identifies the environmental conditions which the composite-airframe ARM UAV may encounter, and discusses the potential degradation processes composite materials may undergo when subjected to those environments. This information is intended to be useful in a follow-on program to develop equipment and procedures to prevent, detect, or otherwise mitigate significant degradation with the ultimate goal of preventing catastrophic aircraft failure.

Synthetic and degradable patches: an emerging solution for rotator cuff repair

PubMed Central

Hakimi, Osnat; Mouthuy, Pierre-Alexis; Carr, Andrew

2013-01-01

The use of rotator cuff augmentation has increased dramatically over the last 10 years in response to the high rate of failure observed after non-augmented surgery. However, although augmentations have been shown to reduce shoulder pain, there is no consensus or clear guideline as to what is the safest or most efficacious material. Current augmentations, either available commercially or in development, can be classified into three categories: non-degradable structures, extra cellular matrix (ECM)-based patches and degradable synthetic scaffolds. Non-degradable structures have excellent mechanical properties, but can cause problems of infection and loss of integrity in the long-term. ECM-based patches usually demonstrate excellent biological properties in vitro, but studies have highlighted complications in vivo due to poor mechanical support and to infection or inflammation. Degradable synthetic scaffolds represent the new generation of implants. It is proposed that a combination of good mechanical properties, active promotion of biological healing, low infection risk and bio-absorption are the ideal characteristics of an augmentation material. Among the materials with these features, those processed by electrospinning have shown great promis. However, their clinical effectiveness has yet to be proven and well conducted clinical trials are urgently required. PMID:23837794

Potential of bacteria isolated from landfill soil in degrading low density polyethylene plastic

NASA Astrophysics Data System (ADS)

Munir, E.; Sipayung, F. C.; Priyani, N.; Suryanto, D.

2018-03-01

Plastic is an important material and used for many purposes. It is returned to the environment as a waste which is recently considered as the second largest solid waste. The persistency of plastic in the environment has been attracted researchers from a different point of view. The study of the degradation of plastic using bacteria isolated from local landfill soil was conducted. Low density polyethylene (LDPE) plastic was used as tested material. Potential isolates were obtained by culturing the candidates in mineral salt medium broth containing LDPE powder. Two of ten exhibited better growth response in the selection media and were used in degradation study. Results showed that isolate SP2 and SP4 reduced the weight of LDPE film significantly to a weight loss of 10.16% and 12.06%, respectively after four weeks of incubation. Scanning electron micrograph analyses showed the surface of LDPE changed compared to the untreated film. It looked rough and cracked, and bacteria cells attached to the surface was also noticed. Fourier transform infrared spectroscopy analyses confirmed the degradation of LDPE film. These results indicated that bacteria isolated from landfill might play an important role in degrading plastic material in the landfill.

Effect of the Addition of a Labile Gelatin Component on the Degradation and Solute Release Kinetics of a Stable PEG Hydrogel

PubMed Central

Waldeck, H.; Kao, W. J.

2013-01-01

Characterization of the degradation mechanisms and resulting products of biodegradable materials is critical in understanding the behavior of the material including solute transport and biological response. Previous mathematical analyses of a semi-interpenetrating network (sIPN) containing both labile gelatin and a stable cross-linked poly(ethylene glycol) (PEG) network found that diffusion-based models alone were unable to explain the release kinetics of solutes from the system. In this study, degradation of the sIPN and its effect on solute release and swelling kinetics were investigated. The kinetics of the primary mode of degradation, gelatin dissolution, was dependent on temperature, preparation methods, PEGdA and gelatin concentration, and the weight ratio between the gelatin and PEG. The gelatin dissolution rate positively correlated with both matrix swelling and the release kinetics of high-molecular-weight model compound, FITC-dextran. Coupled with previous in vitro studies, the kinetics of sIPN degradation provided insights into the time-dependent changes in cellular response including adhesion and protein expression. These results provide a facile guide in material formulation to control the delivery of high-molecular-weight compounds with concomitant modulation of cellular behavior. PMID:21801489

[Biodegradable synthetic implant materials : clinical applications and immunological aspects].

PubMed

Witte, F; Calliess, T; Windhagen, H

2008-02-01

In the last decade biodegradable synthetic implant materials have been established for various clinical applications. Ceramic materials such as calcium phosphate, bioglass and polymers are now routinely used as degradable implants in the clinical practice. Additionally these materials are now also used as coating materials or as microspheres for controlled drug release and belong to a series of examples for applications as scaffolds for tissue engineering. Because immense local concentrations of degradation products are produced during biodegradation, this review deals with the question whether allergic immune reactions, which have been reported for classical metallic and organic implant materials, also play a role in the clinical routine for synthetic biodegradable materials. Furthermore, possible explanatory theories will be developed to clarify the lack of clinical reports on allergy or sensitization to biodegradable synthetic materials.

Exploring the mechanical behavior of degrading swine neural tissue at low strain rates via the fractional Zener constitutive model.

PubMed

Bentil, Sarah A; Dupaix, Rebecca B

2014-02-01

The ability of the fractional Zener constitutive model to predict the behavior of postmortem swine brain tissue was examined in this work. Understanding tissue behavior attributed to degradation is invaluable in many fields such as the forensic sciences or cases where only cadaveric tissue is available. To understand how material properties change with postmortem age, the fractional Zener model was considered as it includes parameters to describe brain stiffness and also the parameter α, which quantifies the viscoelasticity of a material. The relationship between the viscoelasticity described by α and tissue degradation was examined by fitting the model to data collected in a previous study (Bentil, 2013). This previous study subjected swine neural tissue to in vitro unconfined compression tests using four postmortem age groups (<6h, 24h, 3 days, and 1 week). All samples were compressed to a strain level of 10% using two compressive rates: 1mm/min and 5mm/min. Statistical analysis was used as a tool to study the influence of the fractional Zener constants on factors such as tissue degradation and compressive rate. Application of the fractional Zener constitutive model to the experimental data showed that swine neural tissue becomes less stiff with increased postmortem age. The fractional Zener model was also able to capture the nonlinear viscoelastic features of the brain tissue at low strain rates. The results showed that the parameter α was better correlated with compressive rate than with postmortem age. © 2013 Published by Elsevier Ltd.

Dissolution and degradation of Fmoc-diphenylalanine self-assembled gels results in necrosis at high concentrations in vitro.

PubMed

Truong, Warren Ty; Su, Yingying; Gloria, Danmar; Braet, Filip; Thordarson, Pall

2015-02-01

Herein we report an approach to assess in vitro cellular responses to the dissolution or degradation products from Fmoc-diphenylalanine (Fmoc-FF) self-assembled hydrogels. Three cell lines were used in these studies and two-way ANOVA was used to assess (i) the age of gel dissolution and degradation products and (ii) exposure time on cell fate and state, using viability assays in conjunction with time-lapse fluorescence and high-resolution scanning electron microscopy investigation. The studies show that leaching time but not the exposure time affects the overall cell viability. The cytotoxic effect was only observed once the gel is completely dissolved. Further analysis revealed that the principal mechanism of cell death is necrosis. In addition, the effect of chemotherapeutics (5-fluorouracil and paclitaxel) released from the Fmoc-FF gel (with addition before and after gelation) on colorectal cancer cells were investigated using this methodology, demonstrating enhanced activity of these drugs compared to bulk control. This enhanced activity, however, appears to be a combination of the apoptosis caused by the cancer drugs and necrosis caused by gel dissolution and degradation products. Given that in vivo studies by others on Fmoc-peptides that this material is not harmful to animals, our work highlights that conventional in vitro cellular assays may yield conflicting messages when used for the evaluation of cytotoxicity and drug release from self-assembled gels such as Fmoc-FF and that better in vitro models, (e.g. 3D cell culture systems) need to be developed to evaluate these materials for biomedical applications.

Catabolism and biotechnological applications of cholesterol degrading bacteria

PubMed Central

García, J. L.; Uhía, I.; Galán, B.

2012-01-01

Summary Cholesterol is a steroid commonly found in nature with a great relevance in biology, medicine and chemistry, playing an essential role as a structural component of animal cell membranes. The ubiquity of cholesterol in the environment has made it a reference biomarker for environmental pollution analysis and a common carbon source for different microorganisms, some of them being important pathogens such as Mycobacterium tuberculosis. This work revises the accumulated biochemical and genetic knowledge on the bacterial pathways that degrade or transform this molecule, given that the characterization of cholesterol metabolism would contribute not only to understand its role in tuberculosis but also to develop new biotechnological processes that use this and other related molecules as starting or target materials. PMID:22309478

Quantifying the degradation of degradable implants and bone formation in the femoral condyle using micro-CT 3D reconstruction

PubMed Central

Xu, Yichi; Meng, Haoye; Yin, Heyong; Sun, Zhen; Peng, Jiang; Xu, Xiaolong; Guo, Quanyi; Xu, Wenjing; Yu, Xiaoming; Yuan, Zhiguo; Xiao, Bo; Wang, Cheng; Wang, Yu; Liu, Shuyun; Lu, Shibi; Wang, Zhaoxu; Wang, Aiyuan

2018-01-01

Degradation limits the application of magnesium alloys, and evaluation methods for non-traumatic in vivo quantification of implant degradation and bone formation are imperfect. In the present study, a micro-arc-oxidized AZ31 magnesium alloy was used to evaluate the degradation of implants and new bone formation in 60 male New Zealand white rabbits. Degradation was monitored by weighing the implants prior to and following implantation, and by performing micro-computed tomography (CT) scans and histological analysis after 1, 4, 12, 24, 36, and 48 weeks of implantation. The results indicated that the implants underwent slow degradation in the first 4 weeks, with negligible degradation in the first week, followed by significantly increased degradation during weeks 12–24 (P<0.05), and continued degradation until the end of the 48-week experimental period. The magnesium content decreased as the implant degraded (P<0.05); however, the density of the material exhibited almost no change. Micro-CT results also demonstrated that pin volume, pin mineral density, mean ‘pin thickness’, bone surface/bone volume and trabecular separation decreased over time (P<0.05), and that the pin surface area/pin volume, bone volume fraction, trabecular thickness, trabecular number and tissue mineral density increased over time (P<0.05), indicating that the number of bones and density of new bone increased as magnesium degraded. These results support the positive effect of magnesium on osteogenesis. However, from the maximum inner diameter of the new bone loop and diameter of the pin in the same position, the magnesium alloy was not capable of creating sufficient bridges between the bones and biomaterials when there were preexisting gaps. Histological analyses indicated that there were no inflammatory responses around the implants. The results of the present study indicate that a micro-arc-oxidized AZ31 magnesium alloy is safe in vivo and efficiently degraded. Furthermore, the novel bone formation increased as the implant degraded. The findings concluded that micro-CT, which is useful for providing non-traumatic, in vivo, quantitative and precise data, has great value for exploring the degradation of implants and novel bone formation. PMID:29375677

Quantifying the degradation of degradable implants and bone formation in the femoral condyle using micro-CT 3D reconstruction.

PubMed

Xu, Yichi; Meng, Haoye; Yin, Heyong; Sun, Zhen; Peng, Jiang; Xu, Xiaolong; Guo, Quanyi; Xu, Wenjing; Yu, Xiaoming; Yuan, Zhiguo; Xiao, Bo; Wang, Cheng; Wang, Yu; Liu, Shuyun; Lu, Shibi; Wang, Zhaoxu; Wang, Aiyuan

2018-01-01

Degradation limits the application of magnesium alloys, and evaluation methods for non-traumatic in vivo quantification of implant degradation and bone formation are imperfect. In the present study, a micro-arc-oxidized AZ31 magnesium alloy was used to evaluate the degradation of implants and new bone formation in 60 male New Zealand white rabbits. Degradation was monitored by weighing the implants prior to and following implantation, and by performing micro-computed tomography (CT) scans and histological analysis after 1, 4, 12, 24, 36, and 48 weeks of implantation. The results indicated that the implants underwent slow degradation in the first 4 weeks, with negligible degradation in the first week, followed by significantly increased degradation during weeks 12-24 (P<0.05), and continued degradation until the end of the 48-week experimental period. The magnesium content decreased as the implant degraded (P<0.05); however, the density of the material exhibited almost no change. Micro-CT results also demonstrated that pin volume, pin mineral density, mean 'pin thickness', bone surface/bone volume and trabecular separation decreased over time (P<0.05), and that the pin surface area/pin volume, bone volume fraction, trabecular thickness, trabecular number and tissue mineral density increased over time (P<0.05), indicating that the number of bones and density of new bone increased as magnesium degraded. These results support the positive effect of magnesium on osteogenesis. However, from the maximum inner diameter of the new bone loop and diameter of the pin in the same position, the magnesium alloy was not capable of creating sufficient bridges between the bones and biomaterials when there were preexisting gaps. Histological analyses indicated that there were no inflammatory responses around the implants. The results of the present study indicate that a micro-arc-oxidized AZ31 magnesium alloy is safe in vivo and efficiently degraded. Furthermore, the novel bone formation increased as the implant degraded. The findings concluded that micro-CT, which is useful for providing non-traumatic, in vivo , quantitative and precise data, has great value for exploring the degradation of implants and novel bone formation.

Early detection of materials degradation

NASA Astrophysics Data System (ADS)

Meyendorf, Norbert

2017-02-01

Lightweight components for transportation and aerospace applications are designed for an estimated lifecycle, taking expected mechanical and environmental loads into account. The main reason for catastrophic failure of components within the expected lifecycle are material inhomogeneities, like pores and inclusions as origin for fatigue cracks, that have not been detected by NDE. However, material degradation by designed or unexpected loading conditions or environmental impacts can accelerate the crack initiation or growth. Conventional NDE methods are usually able to detect cracks that are formed at the end of the degradation process, but methods for early detection of fatigue, creep, and corrosion are still a matter of research. For conventional materials ultrasonic, electromagnetic, or thermographic methods have been demonstrated as promising. Other approaches are focused to surface damage by using optical methods or characterization of the residual surface stresses that can significantly affect the creation of fatigue cracks. For conventional metallic materials, material models for nucleation and propagation of damage have been successfully applied for several years. Material microstructure/property relations are well established and the effect of loading conditions on the component life can be simulated. For advanced materials, for example carbon matrix composites or ceramic matrix composites, the processes of nucleation and propagation of damage is still not fully understood. For these materials NDE methods can not only be used for the periodic inspections, but can significantly contribute to the material scientific knowledge to understand and model the behavior of composite materials.

Degradability of Polymers for Implantable Biomedical Devices

PubMed Central

Lyu, SuPing; Untereker, Darrel

2009-01-01

Many key components of implantable medical devices are made from polymeric materials. The functions of these materials include structural support, electrical insulation, protection of other materials from the environment of the body, and biocompatibility, as well as other things such as delivery of a therapeutic drug. In such roles, the stability and integrity of the polymer, over what can be a very long period of time, is very important. For most of these functions, stability over time is desired, but in other cases, the opposite–the degradation and disappearance of the polymer over time is required. In either case, it is important to understand both the chemistry that can lead to the degradation of polymers as well as the kinetics that controls these reactions. Hydrolysis and oxidation are the two classes of reactions that lead to the breaking down of polymers. Both are discussed in detail in the context of the environmental factors that impact the utility of various polymers for medical device applications. Understanding the chemistry and kinetics allows prediction of stability as well as explanations for observations such as porosity and the unexpected behavior of polymeric composite materials in some situations. In the last part, physical degradation such interfacial delamination in composites is discussed. PMID:19865531

Pollen tube reuses intracellular components of nucellar cells undergoing programmed cell death in Pinus densiflora.

PubMed

Hiratsuka, Rie; Terasaka, Osamu

2011-04-01

Through the process known as programmed cell death (PCD), nucelli of Pinus densiflora serve as the transmitting tissue for growth of the pollen tube. We sought to clarify the processes of degradation of nucellar cell components and their transport to the pollen tube during PCD in response to pollen tube penetration of such nucelli. Stimulated by pollination, synthesis of large amounts of starch grains occurred in cells in a wide region of the nucellus, but as the pollen tube penetrated the nucellus, starch grains were degraded in amyloplasts of nucellar cells. In cells undergoing PCD, electron-dense vacuoles with high membrane contrast appeared, assumed a variety of autophagic structures, expanded, and ultimately collapsed and disappeared. Vesicles and electron-dense amorphous materials were released inside the thickened walls of cells undergoing PCD, and those vesicles and materials reaching the pollen tube after passing through the extracellular matrix were taken into the tube by endocytosis. These results show that in PCD of nucellar cells, intracellular materials are degraded in amyloplasts and vacuoles, and some of the degraded material is supplied to the pollen tube by vesicular transport to support tube growth.

Impact of polymer structure and composition on fully resorbable endovascular scaffold performance

PubMed Central

Ferdous, Jahid; Kolachalama, Vijaya B.; Shazly, Tarek

2014-01-01

Fully erodible endovascular scaffolds are being increasingly considered for the treatment of obstructive arterial disease owing to their potential to mitigate long-term risks associated with permanent alternatives. While complete scaffold erosion facilitates vessel healing, generation and release of material degradation by-products from candidate materials such as poly-l-lactide (PLLA) may elicit local inflammatory responses that limit implant efficacy. We developed a computational framework to quantify how the compositional and structural parameters of PLLA-based fully erodible endovascular scaffolds affect degradation kinetics, erosion kinetics and the transient accumulation of material by-products within the arterial wall. Parametric studies reveal that, while some material properties have similar effects on these critical processes, others induce qualitatively opposing responses. For example, scaffold degradation is only mildly responsive to changes in either PLLA polydispersity or the initial degree of crystallinity, while the erosion kinetics is comparatively sensitive to crystallinity. Moreover, lactide doping can effectively tune both scaffold degradation and erosion, but a concomitant increase in local byproduct accumulation raises concerns about implant safety. Optimized erodible endovascular scaffolds must precisely balance therapeutic function and biological response over the implant lifetime, where compositional and structural parameters will have differential effects on implant performance. PMID:23261926

Development of spectral indices for roofing material condition status detection using field spectroscopy and WorldView-3 data

NASA Astrophysics Data System (ADS)

Samsudin, Sarah Hanim; Shafri, Helmi Z. M.; Hamedianfar, Alireza

2016-04-01

Status observations of roofing material degradation are constantly evolving due to urban feature heterogeneities. Although advanced classification techniques have been introduced to improve within-class impervious surface classifications, these techniques involve complex processing and high computation times. This study integrates field spectroscopy and satellite multispectral remote sensing data to generate degradation status maps of concrete and metal roofing materials. Field spectroscopy data were used as bases for selecting suitable bands for spectral index development because of the limited number of multispectral bands. Mapping methods for roof degradation status were established for metal and concrete roofing materials by developing the normalized difference concrete condition index (NDCCI) and the normalized difference metal condition index (NDMCI). Results indicate that the accuracies achieved using the spectral indices are higher than those obtained using supervised pixel-based classification. The NDCCI generated an accuracy of 84.44%, whereas the support vector machine (SVM) approach yielded an accuracy of 73.06%. The NDMCI obtained an accuracy of 94.17% compared with 62.5% for the SVM approach. These findings support the suitability of the developed spectral index methods for determining roof degradation statuses from satellite observations in heterogeneous urban environments.

In vivo degradation of polyurethane foam with 55 wt % polyethylene glycol.

PubMed

Broekema, Ferdinand I; Van Leeuwen, M Barbara M; Van Minnen, Baucke; Bos, Rudolf R M

2015-11-01

Most topical hemostatic agents are based on animal-derived products like collagen and gelatin. They carry the potential risk of pathogen transmission while adjustments in the production process of these materials are limited. A synthetic hemostatic agent based on polyurethane (PU) and polyethylene glycol (PEG) was developed to overcome these disadvantages. The goal of this study was to compare the degradation process of this biomaterial to collagen and gelatin hemostatic agents. Samples of the test materials were implanted subcutaneously in both rats and rabbits. The animals were sacrificed at certain time intervals up to three years and the explanted samples were microscopically assessed. The histological examination showed a comparable pattern of degradation for the different test materials. Remnants of gelatin and collagen were seen up to 26 and 39 weeks, respectively. For PU, it took up to three years before micro-particles of the material were no longer detected. All biomaterials showed a good biocompatibility and no severe foreign body reactions occurred. The good biocompatibility and predictable pattern of resorption indicate that PU can be used as a topical hemostatic agent. However, a degradation time comparable to collagen and gelatin would be favorable. © 2015 Wiley Periodicals, Inc.

SYNERGISTIC DEGRADATION OF DENTIN BY CYCLIC STRESS AND BUFFER AGITATION

PubMed Central

Orrego, Santiago; Romberg, Elaine; Arola, Dwayne

2015-01-01

Secondary caries and non-carious lesions develop in regions of stress concentrations and oral fluid movement. The objective of this study was to evaluate the influence of cyclic stress and fluid movement on material loss and subsurface degradation of dentin within an acidic environment. Rectangular specimens of radicular dentin were prepared from caries-free unrestored 3rd molars. Two groups were subjected to cyclic cantilever loading within a lactic acid solution (pH=5) to achieve compressive stresses on the inner (pulpal) or outer sides of the specimens. Two additional groups were evaluated in the same solution, one subjected to movement only (no stress) and the second held stagnant (control: no stress or movement). Exterior material loss profiles and subsurface degradation were quantified on the two sides of the specimens. Results showed that under cyclic stress material loss was significantly greater (p≤0.0005) on the pulpal side than on the outer side and significantly greater (p≤0.05) under compression than tension. However, movement only caused significantly greater material loss (p≤0.0005) than cyclic stress. Subsurface degradation was greatest at the location of highest stress, but was not influenced by stress state or movement. PMID:25637823

N, S co-doped-TiO2/fly ash beads composite material and visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Lv, Jun; Sheng, Tong; Su, Lili; Xu, Guangqing; Wang, Dongmei; Zheng, Zhixiang; Wu, Yucheng

2013-11-01

Using TiCl4 as the titanium source, urea as the precipitating agent, nano-TiO2/fly ash beads composite materials were prepared by hydrolysis-precipitation method. Using (NH2)2CO and (NH2)2SC as the N and S source respectively, N and S co-doped TiO2/fly ash beads composite materials were prepared by grinding them together according to a certain proportion and calcined at 500 °C for 2 h. The composite materials were characterized by SEM, EDS, XPS, and UV-vis spectrophotometer methods. The UV-vis absorption spectra results show that the absorption edge of un-doped composites is 390 nm while that of doped composites red-shifts to 500 nm. The photocatalytic activity of composite materials was evaluated by degradation of methyl orange under visible light irradiation (halogen lamp, 250 W). The results showed that after irradiation for 1 h, degradation rate of N, S co-doped-TiO2/fly ash beads composite material can reach 65%, while the degradation rate of un-doped sample and P25 were just 10% and 6%, respectively. The composite material also showed excellent recycling properties.

Photocatalytic activity of undoped and Ag-doped TiO{sub 2}-supported zeolite for humic acid degradation and mineralization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lazau, C.; Ratiu, C.; National Institute for Research and Development in Microtechnologies, Erou Iancu Nicolae Street, 077190 Bucharest

2011-11-15

Highlights: {yields} Hybrid materials based on natural zeolite and TiO{sub 2} obtained by solid-state reaction. {yields} XRD proved the presence of anatase form of undoped and Ag-doped TiO{sub 2} onto zeolite. {yields} FT-IR spectra evidenced the presence on TiO{sub 2} bounded at the zeolite network. {yields} Ag-doped TiO{sub 2} onto zeolitic matrix exhibited an enhanced photocatalytic activity. -- Abstract: The hybrid materials based on natural zeolite and undoped and Ag-doped TiO{sub 2}, i.e., Z-Na-TiO{sub 2} and Z-Na-TiO{sub 2}-Ag, were successfully synthesized by solid-state reaction in microwave-assisted hydrothermal conditions. Undoped TiO{sub 2} and Ag-doped TiO{sub 2} nanocrystals were previously synthesized bymore » sol-gel method. The surface characterization of undoped TiO{sub 2}/Ag-doped TiO{sub 2} and natural zeolite hybrid materials has been investigated by X-ray diffraction, DRUV-VIS spectroscopy, FT-IR spectroscopy, BET analysis, SEM microscopy and EDX analysis. The results indicated that anatase TiO{sub 2} is the dominant crystalline type as spherical form onto zeolitic matrix. The presence of Ag into Z-Na-TiO{sub 2}-Ag was confirmed by EDX analysis. The DRUV-VIS spectra showed that Z-Na-TiO{sub 2}-Ag exhibited absorption within the range of 400-500 nm in comparison with Z-Na-TiO{sub 2} catalyst. The enhanced photocatalytic activity of Z-Na-TiO{sub 2}-Ag catalyst is proved through the degradation and mineralization of humic acid under ultraviolet and visible irradiation.« less

Methods for cellobiosan utilization

DOEpatents

Linger, Jeffrey; Beckham, Gregg T.

2017-07-11

Disclosed herein are enzymes useful for the degradation of cellobiosan in materials such a pyrolysis oils. Methods of degrading cellobiosan using enzymes or organisms expressing the same are also disclosed.

Comparison of bacterial community structure and dynamics during the thermophilic composting of different types of solid wastes: anaerobic digestion residue, pig manure and chicken manure

PubMed Central

Song, Caihong; Li, Mingxiao; Jia, Xuan; Wei, Zimin; Zhao, Yue; Xi, Beidou; Zhu, Chaowei; Liu, Dongming

2014-01-01

This study investigated the impact of composting substrate types on the bacterial community structure and dynamics during composting processes. To this end, pig manure (PM), chicken manure (CM), a mixture of PM and CM (PM + CM), and a mixture of PM, CM and anaerobic digestion residue (ADR) (PM + CM + ADR) were selected for thermophilic composting. The bacterial community structure and dynamics during the composting process were detected and analysed by polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) coupled with a statistic analysis. The physical-chemical analyses indicated that compared to single-material composting (PM, CM), co-composting (PM + CM, PM + CM + ADR) could promote the degradation of organic matter and strengthen the ability of conserving nitrogen. A DGGE profile and statistical analysis demonstrated that co-composting, especially PM + CM + ADR, could improve the bacterial community structure and functional diversity, even in the thermophilic stage. Therefore, co-composting could weaken the screening effect of high temperature on bacterial communities. Dominant sequencing analyses indicated a dramatic shift in the dominant bacterial communities from single-material composting to co-composting. Notably, compared with PM, PM + CM increased the quantity of xylan-degrading bacteria and reduced the quantity of human pathogens. PMID:24963997

Tracers and constituents indicating the nature of organic fluxes, their origin and the effect of environmental conditions

NASA Astrophysics Data System (ADS)

Gadel, F.; Puigbó, A.; Alcan˜iz, J. M.; Charrière, B.; Serve, L.

1990-09-01

The nature of particulate organic matter was studied in suspended material sampled by bottles, particles collected by sediment traps and deposits from deltaic and open sea ecosystems of the northwestern Mediterranean. Elemental analyses were combined with pyrolysis-gas chromatography-mass spectrometry and with analysis of individual compounds such as phenols separated by high-performance liquid chromatography. In the Rhoˆne delta, a multilayered system was observed. The surficial turbid layer was enriched with fresh material of river origin. Organic matter was more altered and richer in phenols in the bottom nepheloid layer. The river regime determined the nature and quantity of suspended material: when in spate, degraded organic matter previously deposited in the river bed was transported to the sea, thereby inducing an increase of pyrolysis derived aromatic hydrocarbons. On the other hand, phenolic aldehydes increased in the bottom nepheloid layer. When water level was low, organic matter seemed to be of more local origin. The content of phenols and nitrogen-containing compounds increased. The influence of the Rhoˆne River decreased off the mouth, when terrestrial markers were diluted by products deriving from phytoplanktonic activity. Compared with suspended material, trapped organic matter was coarser, more degraded and contained more aromatic hydrocarbons. It was different in nature and size, indicating that it was trapped over a longer period. Deposits contained altered organic matter resulting from degrading processes in the water column. Sediments showed a double trend off the mouth of the river; an increase in nitrogen-containing compounds, indicating a more marine character, and a decrease in phenols and carbohydrates deriving from the terrestrial ligno-cellulosic complex. In the southwestern part of the Gulf of Lions, in the Teˆt prodelta, organic matter from sediment traps was fresher than in the Rhoˆne delta. Phenols and some carbohydrates rapidly decreased from the prodelta due to a lower runoff. During the spate, suspended material was rapidly deposited and sediments were enriched in terrestrial phenols. In the open sea environment, in the Lacaze-Duthiers Canyon at 645 m, in summer, the euphotic zone was rich in amino-sugars and contained a large diversity of phenols deriving from fish fecal pellets. In winter/spring, the development of phytoplanktonic blooms in surficial layers led to high contents of nitrogenous compounds. In deeper layers, the nature of organic matter was different from surficial layers in summer and more homogeneous in winter, although a flux of degraded material rich in pyrolysis-derived aromatic hydrocarbons and poor in nitrogenous compounds progressively sank towards the bottom. The two marine prodeltas were compared: organic matter was more degraded in suspended material and sediments collected in the submarine delta of the Rhoˆne River. Organic material originating from the river was transported further offshore, as indicated by a higher content of aromatic hydrocarbons and phenols. In the southwestern part of the Gulf of Lions, the prodelta reflected the influence of local rivers, with lower discharges.

Histomorphometric Study of New Bone Formation Comparing Defect Healing with Three Bone Grafting Materials: The Effect of Osteoporosis on Graft Consolidation.

PubMed

Zhang, Qiao; Jing, Dai; Zhang, Yufeng; Miron, Richard J

Bone grafting materials are frequently utilized in oral surgery and periodontology to fill bone defects and augment lost or missing bone. The purpose of this study was to compare new bone formation in bone defects created in both normal and osteoporotic animals loaded with three types of bone grafts from different origins. Forty-eight female Wistar rats were equally divided into control normal and ovariectomized animals. Bilateral 2.5-mm femur defects were created and filled with an equal weight of (1) natural bone mineral (NBM, BioOss) of bovine origin, (2) demineralized freeze-dried bone allograft (DFDBA, LifeNet), or (3) biphasic calcium phosphate (BCP, Vivoss). Following 3 and 6 weeks of healing, hematoxylin and eosin and TRAP staining was performed to determine new bone formation, material degradation, and osteoclast activity. All bone substitutes demonstrated osteoconductive potential at 3 and 6 weeks with higher osteoclast numbers observed in all ovariectomized animals. NBM displayed continual new bone formation with little to no sign of particle degradation, even in osteoporotic animals. DFDBA particles showed similar levels of new bone formation but rapid particle degradation rates with lower levels of mineralized tissue. BCP bone grafts demonstrated significantly higher new bone formation when compared with both NBM and DFDBA particles; however, the material was associated with higher osteoclast activity and particle degradation. Interestingly, in osteoporotic animals, BCP displayed synergistically and markedly more rapid rates of particle degradation. Recent modifications to synthetically fabricated materials were shown to be equally or more osteopromotive than NBM and DFDBA. However, the current BCP utilized demonstrated much faster resorption properties in osteoporotic animals associated with a decrease in total bone volume when compared with the slowly/nonresorbing NBM. The results from this study point to the clinical relevance of minimizing fast-resorbing bone grafting materials in osteoporotic phenotypes due to the higher osteoclastic activity and greater material resorption.

Silver nanowires network encapsulated by low temperature sol-gel ZnO for transparent flexible electrodes with ambient stability

NASA Astrophysics Data System (ADS)

Shin, Wonjung; Cho, Wonki; Baik, Seung Jae

2018-01-01

As a geometrically engineered realization of transparent electrode, Ag nanowires network is promising for its superior characteristics both on electrical conductivity and optical transmittance. However, for a potential commercialization of Ag nanowires network, further investigations on encapsulation materials are necessary to prevent degradation caused by ambient aging. In addition, the temperature range of the coating process for the encapsulation material needs to be low enough to prevent degradation of polymer substrates during the film coating processes, when considering emerging flexible device application of transparent electrodes. We present experimental results showing that low temperature sol-gel ZnO processed under 130 °C is an effective encapsulation material preventing ambient oxidation of Ag nanowires network without degrading electrical, optical, and mechanical properties.

Biodegradation of polyester polyurethane by Aspergillus tubingensis.

PubMed

Khan, Sehroon; Nadir, Sadia; Shah, Zia Ullah; Shah, Aamer Ali; Karunarathna, Samantha C; Xu, Jianchu; Khan, Afsar; Munir, Shahzad; Hasan, Fariha

2017-06-01

The xenobiotic nature and lack of degradability of polymeric materials has resulted in vast levels of environmental pollution and numerous health hazards. Different strategies have been developed and still more research is being in progress to reduce the impact of these polymeric materials. This work aimed to isolate and characterize polyester polyurethane (PU) degrading fungi from the soil of a general city waste disposal site in Islamabad, Pakistan. A novel PU degrading fungus was isolated from soil and identified as Aspergillus tubingensis on the basis of colony morphology, macro- and micro-morphology, molecular and phylogenetic analyses. The PU degrading ability of the fungus was tested in three different ways in the presence of 2% glucose: (a) on SDA agar plate, (b) in liquid MSM, and (c) after burial in soil. Our results indicated that this strain of A. tubingensis was capable of degrading PU. Using scanning electron microscopy (SEM), we were able to visually confirm that the mycelium of A. tubingensis colonized the PU material, causing surface degradation and scarring. The formation or breakage of chemical bonds during the biodegradation process of PU was confirmed using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy. The biodegradation of PU was higher when plate culture method was employed, followed by the liquid culture method and soil burial technique. Notably, after two months in liquid medium, the PU film was totally degraded into smaller pieces. Based on a comprehensive literature search, it can be stated that this is the first report showing A. tubingensis capable of degrading PU. This work provides insight into the role of A. tubingensis towards solving the dilemma of PU wastes through biodegradation. Copyright © 2017 Elsevier Ltd. All rights reserved.